JP2015021043A - Polypropylene-based biaxially-stretched film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polypropylene-based biaxially-stretched film having both of the flexible characteristics of a polypropylene-based film, that has both of flexibility and an anti-sticking property, and low elongation characteristics while keeping excellent external appearance such as transparency and glossiness and anti-stretchability.SOLUTION: A propylene-ethylene random block copolymer (A) is prepared, which is obtained by using a metallocene catalyst, and successively producing 30-80 wt.% of a propylene-ethylene random copolymer (A1) having 0.1-7 wt.% ethylene content at a first step, and producing 20-70 wt.% of another propylene-ethylene random copolymer (A2) having the ethylene content higher than that of the propylene-ethylene random copolymer (A1) by 6-15 wt.% at a second step, and which is characterized in that the melt flow rate (2.16 kg, 230°C) thereof is 0.1-10 g/10 minutes and a single peak exists in a temperature-loss modulus (tan δ) curve, that is obtained by measuring the solid viscoelasticity thereof, at the temperature equal to or lower than 0°C. The polypropylene-based biaxially-stretched film is obtained by stretching a film of the propylene-ethylene random block copolymer (A) to the flowing direction of the film and to the direction perpendicular to the flowing direction.

Description

  The present invention relates to a polypropylene-based biaxially stretched film, and in particular, has both flexibility and stickiness resistance performance while maintaining the characteristics of a propylene-based stretched film that is excellent in the appearance of the film such as transparency and glossiness and hardly stretched. The present invention relates to a biaxially stretched film having both polypropylene-based flexibility characteristics and low elongation characteristics.

  Stretched flexible films represented by stretched vinylon film (PVA film) and wrap film (PE-based multilayer film) have excellent characteristics of transparency, flexibility, and low elongation. Widely used. However, PVA has a problem of being easily decomposed during molding and inferior in productivity, and a wrap film has a problem of inferior heat resistance due to the use of a PE-based resin. There is a demand for a polypropylene-based flexible stretched film (hereinafter also referred to as “polypropylene-based stretched flexible film”).

The polypropylene-based stretched film is obtained by stretching at a temperature below the melting point of the resin used. As a result of the polypropylene molecular chains being strongly oriented in the stretching direction by the above stretching process, the polypropylene-based stretched film is imparted with characteristics such as transparency and low elongation properties, but at the same time the rigidity is increased, so that the stretched vinylon film (PVA) Film) and wrap film (PE multilayer film), it was difficult to impart the same flexibility.
For imparting flexibility to a polypropylene-based stretched film, a technique is generally used in which a polypropylene resin is blended with a resin having excellent flexibility such as an elastomer. Flexible resin blends include those that are added during molding and those that are melt-kneaded in an extruder. Most of these blends are whitened due to the phase separation of the polypropylene resin and elastomer resin, making it extremely transparent. Or tearing at the phase interface during the stretching process, which impairs productivity.

  As an improvement in the resin raw material, in order to improve flexibility and solve the deterioration of transparency, the propylene-ethylene random copolymer having a low ethylene content in the first step is more than the first step in the second step. In order to suppress the formation of low molecular weight components having an ethylene content, a reactor TPO obtained by continuously polymerizing a propylene-ethylene copolymer elastomer having an intrinsic viscosity, that is, a molecular weight somewhat high, using a Ziegler-Natta catalyst. The stretched film used has been proposed (Patent Document 1). However, since Ziegler-Natta catalysts have multiple types of active sites, they have low crystallinity and many low molecular weight components, so even if the molecular weight is increased, the improvement effect is thin, and the improvement of stickiness and bleed out is insufficient. For this reason, it has many problems such as poor transparency and easy appearance of defective appearance such as fish eyes and butts derived from the high molecular weight of the elastomer.

A stretched film using a reactor TPO using a metallocene catalyst has been developed in contrast to such a reactor TPO using a Ziegler-Natta catalyst (Patent Document 2). In Patent Document 2, an isotactic propylene polymer and an isotactic propylene-α-olefin random copolymer having an α-olefin content other than propylene of 5 to 20 wt% are polymerized with a metallocene catalyst. To produce a propylene-based resin composition exhibiting a specific elution pattern in temperature rising elution fractionation by temperature rising temperature elution fractionation method (TREF), and forming a stretched film using the obtained composition, It is disclosed that the problem is improved.
However, this method has a drawback that the flexibility is insufficient due to the high crystallinity of the propylene-based resin composition, and there is a problem that the heat resistance is remarkably deteriorated in a region where the flexibility is further improved.

Japanese Patent No. 3769886 JP 2001-171001 A

  As described above, the polypropylene-based stretched flexible film has not yet been achieved to satisfy all of transparency, gloss, flexibility, heat resistance, low elongation characteristics, and stickiness resistance performance. Therefore, the object of the present invention is to maintain the characteristics of a polypropylene-based resin that is excellent in film appearance such as transparency and glossiness and has high heat resistance, and has flexibility, less stickiness, bleedout, blocking, etc. The object is to develop a polypropylene-based stretched flexible film which is excellent in handling and excellent in low elongation properties.

The inventors of the present invention have flexibility while maintaining the characteristics of a polypropylene-based resin, such as excellent transparency and glossy film appearance and high heat resistance, and handling with less stickiness, bleedout, blocking, etc. Propylene-ethylene random copolymer containing a small amount of ethylene in the first step using a metallocene catalyst as a result of earnest research to realize a polypropylene-based stretched flexible film that is excellent in low elongation properties. Component composition of each copolymer in a propylene-ethylene block copolymer obtained by sequentially polymerizing a component in a second step, a propylene-ethylene random copolymer component containing more ethylene than in the first step The ethylene content is specified and combined with the propylene-ethylene block copolymer melt. -Tan δ curve is characterized as a rate and solid viscoelastic property, and by using such a copolymer as a raw material for a polypropylene-based stretched flexible film, a polypropylene-based film having excellent film appearance such as transparency and glossiness and high heat resistance The present invention is completed by finding that a polypropylene-based stretched flexible film having flexibility while maintaining the characteristics of the resin, having less stickiness, bleed out, blocking, etc., excellent in handling, and excellent in low elongation properties can be obtained. It came to.
The present invention provides the following polypropylene biaxially stretched films.

[1] Using a metallocene catalyst, 30 to 80 wt% of a propylene-ethylene random copolymer (A1) having an ethylene content of 0.1 to 7 wt% in the first step, and from the copolymer (A1) in the second step Is a propylene-ethylene random block copolymer obtained by sequential polymerization of 20 to 70 wt% of a propylene-ethylene random copolymer (A2) containing 6 to 15 wt% of ethylene, and a melt flow rate ( 2.16 kg, 230 ° C.) is in the range of 0.1-10 g / 10 min, and in the temperature-loss elastic modulus (tan δ) curve obtained by solid viscoelasticity measurement, propylene-ethylene having a single peak below 0 ° C. A block copolymer (A) is formed by stretching a film in the flow direction of the film and in a direction perpendicular to the flow direction of the film. Pyrene-based biaxially oriented film.
[2] The polypropylene biaxially stretched film according to the above [1], which is stretched by a sequential biaxial stretching method.
[3] The polypropylene biaxially stretched film according to the above [1], which is stretched by a simultaneous biaxial stretching method.

[4] Elution amount (dwt) of propylene-ethylene block copolymer (A) by temperature rising elution fractionation method (TREF) in a temperature range of −15 ° C. to 140 ° C. using an o-dichlorobenzene solvent. % / DT) In the TREF elution curve obtained as a plot, the peak observed on the high temperature side is in the range of 65 ° C. to 96 ° C., and the peak observed on the low temperature side is below 45 ° C. or not observed The temperature at which 99 wt% elutes is 98 ° C. or lower, and the difference between the peak temperature observed on the high temperature side and the temperature at which 99 wt% elutes is 5 ° C. or lower is any one of the above [1] to [3] The polypropylene biaxially stretched film as described.
[5] The peak observed on the high temperature side is in the range of 65 ° C. to 88 ° C., and the peak observed on the low temperature side is 40 ° C. or lower or is not observed, and the 99 wt% elution temperature is 90 ° C. or lower. The polypropylene biaxially stretched film according to the above [4].
[6] The propylene-ethylene block copolymer (A) has a weight average molecular weight obtained by GPC measurement in the range of 100,000 to 400,000, and the total amount of components having a weight average molecular weight of 5,000 or less. The polypropylene-based biaxially stretched film according to any one of the above [1] to [5], which is 0.8 wt% or less.
[7] The propylene-ethylene block copolymer (A) has an intrinsic viscosity of 23 ° C. xylene solubles measured in decalin at 135 ° C. in the range of 1 to 2 dl / g [1] to [6] A polypropylene-based biaxially stretched film according to any one of the above.

  The polypropylene-based biaxially stretched film of the present invention has flexibility while maintaining the characteristics of a polypropylene-based resin that has excellent film appearance such as transparency and glossiness and high heat resistance, and is derived from stickiness and bleed-out. Excellent adhesion with little adhesion, and excellent low elongation properties.

It is a graph which shows the chart of the solid viscoelasticity measurement of superposition | polymerization manufacture example PP-1. It is a graph which shows the chart of the solid viscoelasticity measurement of superposition | polymerization manufacture example PP-5. It is a graph which shows the TREF elution curve of polymerization manufacture example PP-1. It is explanatory drawing which shows the adjustment state of the sample for performing peel strength measurement.

[Propylene-ethylene block copolymer (A)]
The propylene-ethylene block copolymer (A) used as a raw material for the polypropylene-based biaxially stretched film of the present invention uses a metallocene catalyst, and propylene-ethylene random having an ethylene content of 0.1 to 7 wt% in the first step. 30 to 80 wt% of copolymer (A1) and 20 to 70 wt% of propylene-ethylene random copolymer (A2) containing 6 to 15 wt% more ethylene than copolymer (A1) in the second step. Propylene-ethylene random block copolymer obtained by polymerization, having a melt flow rate (2.16 kg, 230 ° C.) in the range of 0.1 to 10 g / 10 min, and obtained by solid viscoelasticity measurement. A temperature-loss elastic modulus (tan δ) curve has a single peak at 0 ° C. or lower.
Such a propylene-ethylene block copolymer is commonly referred to as a so-called block copolymer, but the propylene-ethylene random copolymer (A1) and the propylene-ethylene random copolymer (A2). The two are not in a blended state and are not bonded by polymerization.
Hereinafter, the propylene-ethylene random copolymer (A1) is also referred to as “component (A1)”, and the propylene-ethylene random copolymer (A2) is also referred to as “component (A2)”.

・ Propylene-ethylene random copolymer (A1)
The propylene-ethylene random copolymer (A1) produced in the first step has a relatively high melting point and a crystalline ethylene content of 0.1 to 0.1 in order to suppress stickiness and develop heat resistance. It must be 7 wt% propylene-ethylene random copolymer. When the ethylene content is less than 0.1 wt%, the crystallinity of the component (A1) is increased, so that the crystal orientation after the stretching process is remarkably increased, and the rigidity of the stretched film is significantly increased, thereby imparting flexibility. Therefore, it is necessary to extremely increase the amount of the component (A2). However, since the heat resistance is remarkably impaired, the ethylene content in the component (A1) for obtaining a stretched flexible film is 0.1 wt% or more, preferably 1.0 wt% or more. On the other hand, if the ethylene content exceeds 7 wt%, the melting point becomes too low to deteriorate the heat resistance, so the ethylene content is 7 wt% or less, preferably 6 wt% or less.

If the proportion of the component (A1) in the propylene-ethylene block copolymer (A) is too large, the effect of improving the flexibility, impact resistance and transparency of the propylene-ethylene block copolymer may be sufficiently exhibited. Can not. Therefore, the proportion of the component (A1) in the propylene-ethylene block copolymer (A) is 80 wt% or less, preferably 75 wt% or less, more preferably 70 wt% or less.
On the other hand, if the proportion of the component (A1) becomes too small, the stickiness increases and the heat resistance is remarkably deteriorated. Therefore, the proportion of the component (A1) is 30 wt% or more, preferably 40 wt% or more.

・ Propylene-ethylene random copolymer (A2)
The propylene-ethylene random copolymer (A2) produced in the second step is a component necessary for improving the flexibility and transparency of the propylene-ethylene block copolymer (A). The component (A2) needs to have an ethylene content in a specific range in order to sufficiently exhibit the above effects. That is, in the propylene-ethylene block copolymer (A), the lower the crystallinity of the component (A2) with respect to the component (A1), the greater the flexibility improvement effect, and the crystallinity in the propylene-ethylene random copolymer Since it is controlled by the ethylene content, the ethylene content E (A2) in the component (A2) can exert its effect unless it is 6 wt% or more higher than the ethylene content E (A1) in the component (A1). Preferably, it is necessary to contain more ethylene than component (A1), preferably 6.5 wt% or more, more preferably 7 wt% or more.

  On the other hand, if the ethylene content is excessively increased to lower the crystallinity of the component (A2), the difference in the ethylene content between the component (A1) and the component (A2) (hereinafter also referred to as “E (gap)”). Becomes larger and takes a phase separation structure divided into a matrix and a domain, and the transparency is lowered. This is because polypropylene originally has low compatibility with polyethylene, and even in the propylene-ethylene random copolymer, although the ethylene content is different, the mutual compatibility decreases as the difference in ethylene content increases. . The upper limit of E (gap) may be within a range in which the peak of tan δ becomes single by solid viscoelasticity measurement described later. For that purpose, E (gap) is 15 wt% or less, preferably 13 wt% or less. Range.

If the proportion of the component (A2) in the propylene-ethylene block copolymer (A) is too large, stickiness increases, deterioration in blocking occurs, and the heat resistance decreases significantly, so the proportion of the component (A2) is It is necessary to suppress it to 70 wt% or less.
On the other hand, if the proportion of component (A2) is too small, the effect of improving flexibility cannot be obtained. Therefore, the proportion of (A2) needs to be 20 wt% or more, preferably 25 wt% or more, more preferably It is 30 wt% or more.

-MFR of propylene-ethylene block copolymer (A)
The MFR of the propylene-ethylene block copolymer (A) needs to be in the range of 0.1 to 10 g / 10 min. If the MFR of the propylene-ethylene block copolymer (A) is too low, surface roughness called shark skin or melt fracture occurs on the surface of the film, which not only significantly impairs transparency and appearance but also makes stretch molding difficult. . On the other hand, if the MFR is too high, it is preferable because film breakage occurs in the stretching process in the direction perpendicular to the film flow direction (MD direction) (TD direction) and the operability is remarkably impaired. Absent.
Therefore, the MFR of the propylene-ethylene block copolymer (A) must be in the range of 0.1 to 10 g / 10 min, and the range of 0.5 to 8 g / 10 min is the molding stability, film appearance, and physical properties. It is preferable from the viewpoint of balance.

  The melt flow rate (MFR) in the present invention is in accordance with JIS K7210 A method condition M, under conditions of test temperature: 230 ° C., nominal load: 2.16 kg, die shape: diameter 2.095 mm, length 8.00 mm. It is measured.

-Peak of tan δ curve of propylene-ethylene block copolymer (A) Propylene-ethylene block copolymer (A) is a tan δ curve in a temperature-loss tangent (tan δ) curve obtained by solid viscoelasticity measurement (DMA). Must have a single peak below 0 ° C.
When the propylene-ethylene block copolymer has a phase separation structure, the glass transition temperature of the amorphous part contained in the component (A1) is different from the glass transition temperature of the amorphous part contained in the component (A2). , There will be multiple peaks. In this case, there arises a problem that the transparency is remarkably deteriorated. Whether or not the phase separation structure is taken can be discriminated in the tan δ curve in the measurement of solid viscoelasticity, and the avoidance of the phase separation structure that affects the transparency of the molded article is that the tan δ curve has a single peak below 0 ° C. Is brought about by having.
In the present invention, it is necessary that the tan δ curve in the solid viscoelasticity measurement has a single peak in order to exhibit transparency.

  As an example having a single peak at 0 ° C. or lower of the tan δ curve, FIG. 1 shows a chart of the solid viscoelasticity measurement of Polymerization Production Example PP-1 described later, and also has a single peak for comparison. As an example of the tan δ curve in the case of not performing, the chart diagram of the solid viscoelasticity measurement of the post-polymerization production example PP-5 is shown in FIG.

  Specifically, solid viscoelasticity measurement is performed by applying a sinusoidal strain of a specific frequency to a strip-shaped sample piece and detecting the generated stress. Here, the frequency is 1 Hz, and the measurement temperature is raised stepwise from −60 ° C. until the sample is melted and cannot be measured. Further, it is recommended that the magnitude of distortion is about 0.1 to 0.5%. From the obtained stress, the storage elastic modulus and the loss elastic modulus are obtained by a known method, and the loss tangent (= loss elastic modulus G ″ / storage elastic modulus G ′) defined by the ratio thereof is plotted against the temperature. A tan δ curve is obtained, and the propylene-ethylene block copolymer (A) of the present invention shows a sharp peak in the temperature range of 0 ° C. or lower, and generally the peak of the tan δ curve at 0 ° C. or lower is a glass of an amorphous part. Transition is observed, and this peak temperature is defined as the glass transition temperature Tg (° C.).

・ Specification of ethylene content of component (A1) and component (A2) and the amount of each component The ethylene content and component amount of component (A1) and component (A2) depend on the material balance at the time of polymerization (material balance) Although it is possible to specify, it is preferable to use a temperature rising elution fractionation method (TREF) in order to specify these more accurately.

..Temperature elution fractionation method (TREF)
A technique for evaluating the crystallinity distribution of a propylene-ethylene random copolymer by temperature-elevated elution fractionation (TREF) is well known to those skilled in the art. It is shown.
G. Glockner, J. et al. Appl. Polym. Sci. : Appl. Polym. Symp. 45, 1-24 (1990)
L. Wild, Adv. Polym. Sci. 98, 1-47 (1990)
J. et al. B. P. Soares, A .; E. Hamielec, Polymer; 36, 8, 1639-1654 (1995)

The propylene-ethylene block copolymer (A) in the present invention has a large difference in crystallinity between the components (A1) and (A2), and each crystallinity is produced by using a metallocene catalyst. Since the distribution is narrow, there are very few intermediate components between the two, and both can be accurately separated by TREF.
An example of the TREF elution curve is shown in FIG. 3 which is a graph showing the TREF elution curve of Polymerization Production Example PP-1 described later.
In the TREF elution curve obtained as a plot of elution amount (dWt% / dT) against temperature by the temperature rising elution fractionation method (TREF) in the temperature range of −15 ° C. to 140 ° C. using o-dichlorobenzene solvent, (A1) and component (A2) show their elution peaks at the respective temperatures T (A1) and T (A2) due to the difference in crystallinity, and since the difference is sufficiently large, the intermediate temperature T (A3) (= { Separation is possible almost at T (A1) + T (A2)} / 2).

  In addition, the lower limit of the TREF measurement temperature is −15 ° C. in the apparatus used for this measurement, but in the case where the crystallinity of the component (A2) is very low or an amorphous component, There may be no peak within the range (at this time, the concentration of the component (A2) dissolved in the solvent is detected at the lower limit of the measurement temperature (ie, −15 ° C.)). In this case, T (A2) is considered to exist below the lower limit of the measurement temperature, but the value cannot be measured. In such a case, T (A2) is the lower limit of the measurement temperature − It is defined as 15 ° C.

  Here, if the integrated amount of the component eluted before T (A3) is defined as W (A2) wt%, and the integrated amount of the component eluted at T (A3) or higher is defined as W (A1) wt%, W (A2) Almost corresponds to the amount of the low-crystalline or amorphous component (A2), and the integrated amount W (A1) of the component eluted at T (A3) or higher is the component (A1) having a relatively high crystallinity. Almost corresponds to the amount of.

In the present invention, the TREF measurement is specifically performed as follows.
A sample is dissolved in o-dichlorobenzene (containing 0.5 mg / ml BHT) at 140 ° C. to obtain a solution. This is introduced into a 140 ° C. TREF column, cooled to 100 ° C. at a rate of 8 ° C./min, subsequently cooled to −15 ° C. at a rate of 4 ° C./min, and held for 60 minutes. Then, a component of -15 ° C o-dichlorobenzene (containing 0.5 mg / ml BHT), which is a solvent, flows through the column at a flow rate of 1 ml / min, and is dissolved in -15 ° C o-dichlorobenzene in the TREF column. Is eluted for 10 minutes, and then the column is linearly heated to 140 ° C. at a heating rate of 100 ° C./hour to obtain an elution curve.

-Identification of ethylene content in each component-Separation of components (A1) and (A2) Based on T (A3) determined by the previous TREF measurement, using a preparative type fractionation device by a temperature rising column fractionation method The component (A2) of the soluble component in T (A3) and the component (A1) of the insoluble component in T (A3) are fractionated, and the ethylene content of each component is determined by NMR.
The temperature rising column fractionation method is a measurement method disclosed in, for example, Macromolecules 21 314-319 (1988). Specifically, the following method was used in the present invention.

.. Fractionation condition A cylindrical column having a diameter of 50 mm and a height of 500 mm is filled with a glass bead carrier (80 to 100 mesh) and maintained at 140 ° C. Next, 200 ml of a sample o-dichlorobenzene solution (10 mg / ml) dissolved at 140 ° C. is introduced into the column. Thereafter, the temperature of the column is cooled to 0 ° C. at a rate of temperature decrease of 10 ° C./hour. After holding at 0 ° C. for 1 hour, the column temperature is heated to T (A3) at a heating rate of 10 ° C./hour and held for 1 hour. Note that the temperature control accuracy of the column through a series of operations is ± 1 ° C.
Next, while maintaining the column temperature at T (A3), 800 ml of o-dichlorobenzene of T (A3) is allowed to flow at a flow rate of 20 ml / min, whereby components soluble in T (A3) present in the column are obtained. Elute and collect.
Next, the column temperature is increased to 140 ° C. at a rate of temperature increase of 10 ° C./min, left at 140 ° C. for 1 hour, and then 800 ml of o-dichlorobenzene as a solvent at 140 ° C. is flowed at a flow rate of 20 ml / min. , T (A3) is eluted and recovered.
The polymer-containing solution obtained by fractionation is concentrated to 20 ml using an evaporator and then precipitated in 5 times the amount of methanol. The precipitated polymer is collected by filtration and dried overnight in a vacuum dryer.

.. Measurement of ethylene content by ¹³ C-NMR The ethylene contents E (A1) and E (A2) for each of the components (A1) and (A2) obtained by the above fractionation are as follows according to the proton complete decoupling method: It calculates | requires by analyzing the < ¹³ > C-NMR spectrum measured according to these conditions.
Model: GSX-400 manufactured by JEOL Ltd. or equivalent device (carbon nuclear resonance frequency of 100 MHz or more)
Solvent: o-dichlorobenzene / heavy benzene = 4/1 (volume ratio)
Concentration: 100 mg / ml
Temperature: 130 ° C
Pulse angle: 90 °
Pulse interval: 15 seconds Integration count: 5,000 times or more

Spectral assignment may be performed with reference to Macromolecules 17 1950 (1984), for example. The spectral attributions measured under the above conditions are shown in Table 1. In the table, symbols such as S _αα follow the notation of Carman et al. (Macromolecules 10 536 (1977)), P represents a methyl carbon, S represents a methylene carbon, and T represents a methine carbon.

Hereinafter, when “P” is a propylene unit in a copolymer chain and “E” is an ethylene unit, six types of triads of PPP, PPE, EPE, PEP, PEE and EEE may exist in the chain. As described in Macromolecules 15 1150 (1982) and the like, the concentration of these triads and the peak intensity of the spectrum are linked by the following relational expressions (1) to (6).
[PPP] = k × I (T _ββ ) (1)
[PPE] = k × I (T _βδ ) (2)
[EPE] = k × I (T _δδ ) (3)
[PEP] = k × I (S _ββ ) (4)
[PEE] = k × I (S _βδ ) (5)
[EEE] = k × {I (S _δδ ) / 2 + I (S _γδ ) / 4} (6)
Here, [] indicates the fraction of triads, for example, [PPP] is the fraction of PPP triads in all triads.
Therefore, [PPP] + [PPE] + [EPE] + [PEP] + [PEE] + [EEE] = 1 (7)
It is. Further, k is a constant, I indicates the spectral intensity, and for example, I (T _ββ ) means the intensity of the peak at 28.7 ppm attributed to T _ββ .

By using the relational expressions (1) to (7) above, the fraction of each triad is obtained, and the ethylene content is obtained from the following expression.
Ethylene content (mol%) = ([PEP] + [PEE] + [EEE]) × 100
Note that the propylene-ethylene random copolymer used in the present invention contains a small amount of propylene heterogeneous bonds (2,1-bonds and / or 1,3-bonds), thereby causing the minute peaks shown in Table 2 below. Produce.

In order to obtain an accurate ethylene content, it is necessary to include these peaks derived from heterogeneous bonds in the calculation, but it is difficult to completely separate and identify the peaks derived from heterogeneous bonds, and the amount of heterogeneous bonds is small. Therefore, the ethylene content of the present invention is obtained by using the relational expressions (1) to (7) as in the analysis of the copolymer produced with a Ziegler-Natta catalyst that does not substantially contain a heterogeneous bond. I will do it.
Conversion from mol% to wt% of ethylene content is performed using the following formula.
Ethylene content (wt%) =
(28 * X / 100) / {28 * X / 100 + 42 * (1-X / 100)} * 100
Here, X is the ethylene content in mol%.

In addition, the ethylene content E (W) of the entire propylene-ethylene block copolymer (A) is the ethylene content E (A1) and E (A2) of the components (A1) and (A2) measured above. And the weight ratio W (A1) and W (A2) wt% of each component calculated from TREF, and is calculated by the following formula.
E (W) =
{E (A1) × W (A1) + E (A2) × W (A2)} / 100 (wt%)

-Additional requirement of crystallinity distribution by TREF elution curve Propylene-ethylene block copolymer (A) is a temperature rising elution fractionation method in a temperature range of -15 ° C to 140 ° C using an o-dichlorobenzene solvent ( In the TREF elution curve obtained as a plot of elution amount (dwt% / dT) against temperature by TREF), the peak (T (A1)) observed on the high temperature side is in the range of 65 ° C. to 96 ° C., and on the low temperature side The observed peak (T (A2)) is 45 ° C. or lower or not observed, and the temperature at which 99 wt% elutes (T (A4)) is 98 ° C. or lower, and the peak temperature observed on the high temperature side ( The temperature difference (T (A4) -T (A1)) between T (A1)) and the temperature at which 99 wt% elutes (T (A4)) is preferably 5 ° C. or less.

..High temperature side elution peak temperature T (A1)
In the TREF elution curve of the propylene-ethylene block copolymer (A), the higher the elution peak temperature T (A1) of the component (A1), the higher the crystallinity of the component (A1). When the crystallinity of () increases, the component (A2) necessary for improving the flexibility and transparency of the stretched film of the propylene-ethylene block copolymer (A) must be increased.
On the other hand, if the proportion of the component (A2) is too large, stickiness, deterioration of blocking and heat resistance are reduced, so that the above-mentioned problems are not caused while improving the flexibility and transparency of the stretched film. T (A1) should not be too high.
In the present invention, the component (A1) is a propylene-ethylene random copolymer having an ethylene content of 0.1 to 7 wt%, but T (A1) can be decreased by increasing the ethylene content.
At this time, in order to exhibit a sufficient balance of flexibility, transparency, and heat resistance, the peak temperature T (A1) observed on the high temperature side is preferably 96 ° C. or less, and the most preferable range is 88 ° C. The following is preferable.
On the other hand, when the peak temperature T (A1) is less than 65 ° C., the temperature at which the component (A1) crystals melt is low and the propylene-ethylene block copolymer (A) exhibits sufficient heat resistance. The peak temperature T (A1) is preferably 65 ° C. or higher because blocking tends to be worsened.

..Elution end temperature Even if T (A1) is low, transparency is deteriorated when the crystalline distribution is present on the high crystal side. Therefore, it is preferable that the crystallinity spread to the high temperature side is suppressed in the TREF elution curve. The spread of crystallinity toward the high crystal side can be evaluated by TREF measurement, and the elution end temperature of the entire component propylene-ethylene block copolymer is preferably not higher than the peak temperature T (A1). However, since it is difficult to define the temperature at which elution is completed, considering the error in TREF measurement, it is difficult to define the temperature at which 99% by weight of the total elution is defined as the elution end temperature T (A4). To do. The 99 wt% elution temperature T (A4) is preferably 98 ° C. or less, more preferably 90 ° C. or less, because if the elution component is present on the high temperature side, the crystallinity of the component increases.

  Furthermore, the temperature difference (T (A4) −T (A1)) between the peak temperature (T (A1)) observed on the high temperature side and the temperature (T (A4)) at which 99 wt% is eluted, that is, T (A4) -T (A1) is preferably 5 ° C or lower, more preferably 4 ° C or lower, and even more preferably 3 ° C or lower.

..Low temperature elution peak temperature T (A2)
Since the flexibility and transparency of the propylene-ethylene block copolymer (A) cannot be ensured unless the crystallinity of the component (A2) is sufficiently lowered, the propylene-ethylene block copolymer (A) The peak temperature T (A2) observed on the low temperature side is preferably 45 ° C. or lower, more preferably 40 ° C. or lower.

-Molecular weight The propylene-ethylene block copolymer component (A) is additionally characterized by a low low molecular weight component.
It is considered that a low molecular weight component, particularly a component whose molecular weight is less than the molecular weight between the entanglement points, bleeds out to the surface of the molded body and deteriorates stickiness and transparency.
The molecular weight between the entanglement points of polypropylene is about 5,000, as described in Journal of Polymer Science: Part B: Polymer Physics; 37 1023-1103 (1999).
Accordingly, the propylene-ethylene block copolymer component (A) has few low molecular weight components, and the amount of components having a weight average molecular weight of 5,000 or less is preferably 0.8 wt% or less, more preferably 0.8. 6 wt% or less.
The propylene-ethylene block copolymer (A) preferably has a weight average molecular weight Mw obtained by GPC measurement in the range of 100,000 to 400,000.

-Molecular weight measurement In this invention, a weight average molecular weight (Mw) and a number average molecular weight (Mn) mean what was measured by the gel permeation chromatography (GPC) method.
Conversion from the retention volume to the molecular weight is performed using a calibration curve prepared in advance with standard polystyrene.
Standard polystyrenes used are the following brands manufactured by Tosoh Corporation. F380, F288, F128, F80, F40, F20, F10, F4, F1, A5000, A2500, A1000
A calibration curve is prepared by injecting 0.2 ml of a solution dissolved in o-dichlorobenzene (containing 0.5 mg / ml BHT) so that each is 0.5 mg / ml.
The calibration curve uses a cubic equation obtained by approximation by the least square method. The following numerical value is used for [η] = K × M ^α in the viscosity formula used for conversion to molecular weight.
PS: K = 1.38 × 10 ⁻⁴ , α = 0.7
PE: K = 3.92 × 10 ⁻⁴ , α = 0.733
PP: K = 1.03 × 10 ⁻⁴ , α = 0.78

The measurement conditions for GPC are as follows.
Apparatus: GPC (ALC / GPC 150C) manufactured by WATERS
Detector: MIRAN 1A IR detector manufactured by FOXBORO (measurement wavelength: 3.42 μm)
Column: AD806M / S (3 pieces) manufactured by Showa Denko KK
Mobile phase solvent: o-dichlorobenzene Measurement temperature: 140 ° C
Flow rate: 1.0 ml / min
Injection volume: 0.2ml
Sample Preparation Prepare a 1 mg / ml solution using o-dichlorobenzene (containing 0.5 mg / ml BHT) and dissolve it at 140 ° C. for about 1 hour.
The amount of the component having a molecular weight of 5,000 or less can also be determined from a plot of the elution ratio with respect to the molecular weight obtained by GPC measurement.

Intrinsic viscosity [η] cxs
In the propylene-ethylene block copolymer component (A), stickiness and bleed-out are particularly problematic because it is a component soluble in xylene at room temperature (CXS component), so that the intrinsic viscosity [η] (dl / g ) Is preferably performed on the CXS component.
Here, the CXS component was prepared by dissolving a propylene-ethylene block copolymer in p-xylene at 130 ° C. to obtain a solution, and then leaving it at 23 ° C. for 12 hours. The precipitated polymer was separated by filtration, and p-xylene was removed from the filtrate. The intrinsic viscosity [η] cxs of the obtained CXS component can be measured using a Ubbelohde viscometer at a temperature of 135 ° C. using decalin as a solvent.
The propylene-ethylene block copolymer (A) preferably has an intrinsic viscosity of 23 ° C. xylene solubles measured in 135 ° C. decalin in the range of 1 to 2 dl / g. At this time, since the propylene-ethylene block copolymer (A) does not increase the generation of a component having a molecular weight of 5,000 or less that is likely to bleed out, the conventional Ziegler-Natta catalyst has problems in production. Even if the intrinsic viscosity [η] cxs of the CXS component has a problem of practical use due to deterioration such as blocking, it can be produced and used without causing any particular deterioration in physical properties. .
The propylene-ethylene block copolymer that does not increase the component having a molecular weight of 5,000 or less while lowering the intrinsic viscosity of the CXS component has characteristics in terms of physical properties such as high tensile elongation at break and high tensile strength at break. Stretching is easy, and further, there is an effect that appearance defects called “butsu” and “fisheye” are less likely to occur.

[Producing method of propylene-ethylene block copolymer (A)]
-Metallocene catalyst The type of the metallocene catalyst used in the production of the propylene-ethylene copolymer (A) of the present invention is not particularly limited.

As a typical example of the metallocene catalyst that can be used in the present invention, a metallocene catalyst comprising the following components (a) and (b) and an optional component (c) can be mentioned.
Component (a): At least one metallocene transition metal compound selected from transition metal compounds represented by the following general formula (1) Component (b): At least selected from the following (b-1) to (b-4) One solid component (b-1) A particulate carrier on which an organoaluminum compound is supported (b-2) An ionic compound capable of reacting with component (a) to convert component (a) into a cation Or a particulate carrier on which a Lewis acid is supported (b-3) a solid acid particulate (b-4) an ion-exchange layered silicate Component (c): an organoaluminum compound

・ Ingredient (a)
Component (a) is at least one metallocene transition metal compound selected from transition metal compounds represented by the following general formula (1).

（式中、ＡおよびＡ’は、置換基を有していてもよい共役五員環配位子、Ｑは、二つの共役五員環配位子間を任意の位置で架橋する結合性基、Ｘ及びＹは、成分（ｂ）と反応してオレフィン重合能を発現させるσ共有結合性補助配位子、Ｍは、周期律表第４族の遷移金属である。）

(In the formula, A and A ′ are conjugated five-membered ring ligands that may have a substituent, and Q is a binding group that bridges two conjugated five-membered ring ligands at an arbitrary position. , X and Y are σ covalent bond ligands that react with the component (b) to develop olefin polymerization ability, and M is a transition metal of Group 4 of the periodic table.)

In the general formula (1), the conjugated five-membered ring ligand is a cyclopentadienyl group derivative that may have a substituent. When it has a substituent, examples of the substituent include a hydrocarbon group having 1 to 30 carbon atoms (which may contain a heteroatom such as halogen, silicon, oxygen, sulfur, etc.), and this hydrocarbon. Even if the group is bonded to the cyclopentadienyl group as a monovalent group, when two or more of them are present, two of them are bonded at the other end (ω-end) to form a cyclopentadienyl group. A ring may be formed together with a part.
Examples of such a conjugated five-membered ring ligand include an indenyl group, a fluorenyl group, or a hydroazurenyl group, and these groups may further have a substituent, and among them, an indenyl group or a hydroazurenyl group. Groups are preferred. These groups may further have a substituent.

Q is preferably a methylene group, an ethylene group, a silylene group, a germylene group, a group in which these are substituted with a hydrocarbon group, a silafluorene group, or the like.
The auxiliary ligands X and Y are those which react with a cocatalyst such as component (b) to produce an active metallocene having olefin polymerization ability, and each of them is a hydrogen atom, a halogen atom, a hydrocarbon group, or The hydrocarbon group which may have hetero atoms, such as oxygen, nitrogen, and silicon, can be illustrated. Among these, a hydrocarbon group having 1 to 10 carbon atoms or a halogen atom is preferable.
M is a transition metal of Group 4 of the periodic table, preferably titanium, zirconium or hafnium. In particular, zirconium and hafnium are preferable.

  Further, among the above transition metal compounds, those in which stereoregular polymerization of propylene proceeds and the obtained propylene polymer has a high molecular weight are preferable. Specifically, JP-A-1-301704, JP-A-4-221694, JP-A-6-1005909, JP-T 2002-535339, JP-A-6-239914, JP-A-10-226712. Preferably, transition metal compounds described in JP-A No. 3-193396 and JP-A No. 2001-504824 are listed.

Non-limiting examples of the transition metal compound include the following.
(1) Dichloro [1,1′-dimethylsilylenebis (2-methylcyclopentadienyl)] zirconium (2) Dichloro [1,1′-dimethylsilylenebis (2-methyl-4-phenylcyclopentadienyl) Zirconium (3) Dichloro [1,1′-dimethylsilylenebis (2,4,5-trimethylcyclopentadienyl)] zirconium (4) Dichloro [1,1′-dimethylsilylenebis (2-methyl-4-) Phenyl-indenyl)] zirconium (5) dichloro [1,1′-dimethylsilylenebis (2-ethyl-4-phenyl-indenyl)] zirconium (6) dichloro [1,1′-dimethylsilylene (2-methyl-4) -Phenyl-indenyl) (2-isopropyl-4-phenyl-indenyl)] zirconium (7) dichloro [1,1'- Dimethylsilylene (2-methyl-4-t-butylphenyl-indenyl) (2-isopropyl-4-t-butylphenyl-indenyl)] zirconium (8) dichloro [1,1′-dimethylsilylenebis {2- (5 -Methyl-2-furyl) -4-phenyl-indenyl}] zirconium (9) dichloro [1,1′-dimethylsilylenebis {2- (5-methyl-2-thienyl) -4-phenyl-indenyl}] zirconium (10) Dichloro [1,1′-dimethylsilylenebis {2- (5-methyl-2-furyl) -4- (2-naphthyl) -indenyl}] zirconium (11) dichloro [1,1′-dimethylsilylene Bis {2- (5-methyl-2-furyl) -4- (4-t-butylphenyl) -indenyl}] zirconium (12) dichloro {1,1 '-Dimethylsilylenebis (2-methyl-4-phenyl-4H-azurenyl)} zirconium (13) dichloro [1,1'-dimethylsilylenebis {2-methyl-4- (4-chlorophenyl) -4H-azurenyl} ] Zirconium (14) dichloro [1,1'-dimethylsilylenebis {2-methyl-4- (4-t-butylphenyl) -4H-azulenyl}] zirconium (15) dichloro [1,1'-dimethylsilylenebis] {2-Ethyl-4- (2-fluoro-4-biphenyl) -4H-azurenyl}] zirconium (16) dichloro [1,1′-dimethylsilylenebis {2-methyl-4- (4-chlorophenyl) -4H -5,6,7,8-tetrahydroazurenyl}] zirconium (17) dichloro {1,1'-dimethylsilylene (2,3-dimethyl) Cyclopentadienyl) (2-methyl-4-phenyl-4H-azulenyl)} zirconium (18) dichloro {1,1′-dimethylsilylene (2-methyl-4-phenylcyclopentadienyl) (2-methyl- 4-phenyl-4H-azurenyl)} zirconium (19) dichloro {1,1′-dimethylsilylene (2,3,4-trimethylcyclopentadienyl) (2-methyl-4-phenyl-4H-azurenyl)} zirconium (20) dichlorodimethylmethylene (3-t-butyl-5-methylcyclopentadienyl) fluorenyl) zirconium (21) dichlorodimethylmethylene (3-t-butyl-5-methylcyclopentadienyl) (2,7- Di-t-butylfluorenyl) zirconium (22) dichlorodimethylmethylene (3-t-butyl) 5-methylcyclopentadienyl) (1,1,4,4,7,7,10,10-octamethyl-1,2,3,4,7,8,9,10-octahydrodibenzofluorene Nyl) zirconium

  For the preferred compounds represented above, only representative exemplary compounds are described avoiding many complicated examples. Although a compound in which the central metal is zirconium has been described, it goes without saying that the same hafnium compound can also be used, and various conjugated five-membered ring ligands, binding groups or auxiliary ligands are optionally used. It is self-evident.

・ Ingredient (b)
As the component (b), at least one solid component selected from the components (b-1) to (b-4) described above is used. Each of these components is a known component, and can be appropriately selected from known technologies and used. Specific examples and manufacturing methods thereof are described in detail in JP-A No. 2002-284808, JP-A No. 2002-53609, JP-A No. 2002-69116, and the like.

  Examples of the particulate carrier used for the component (b-1) and the component (b-2) include inorganic oxides such as silica, alumina, magnesia, silica alumina, and silica magnesia, magnesium chloride, magnesium oxychloride, aluminum chloride, and chloride. Examples thereof include inorganic halides such as lanthanum, and porous organic carriers such as polypropylene, polyethylene, polystyrene, styrene divinyl benzene copolymer, and acrylic acid copolymer.

  Further, as a non-limiting specific example of the component (b), as the component (b-1), a particulate carrier on which methylalumoxane, isobutylalumoxane, methylisobutylalumoxane, aluminum butylboronate tetraisobutyl and the like are supported As component (b-2), triphenylborane, tris (3,5-difluorophenyl) borane, tris (pentafluorophenyl) borane, triphenylcarbonium tetrakis (pentafluorophenyl) borate, N, N-dimethyl Silica alumina and pentafluorophenol calcined after treating a particulate carrier carrying anilinium tetrakis (pentafluorophenyl) borate or the like as component (b-3) with alumina, silica alumina, magnesium chloride or fluorine compound And diethyl sub After reacting with an organometallic compound such as, and further reacting with water, silica carrying the product is used as component (b-4) as montmorillonite, zakonite, beidellite, nontronite, saponite, hectorite, stevensite. , Bentonite, teniolite and other smectites, vermiculite, mica and the like. These may form a mixed layer.

  Particularly preferred among the above components (b) is the ion-exchange layered silicate of component (b-4), and more preferred are chemical treatments such as acid treatment, alkali treatment, salt treatment, and organic matter treatment. It is an ion exchange layered silicate applied.

・ Ingredient (c)
The organoaluminum compound used as component (c) as required is
General formula AlR _a X _3-a
(Wherein R is a hydrocarbon group having 1 to 20 carbon atoms, X is hydrogen, halogen, alkoxy group, a is a number of 0 <a ≦ 3)
Preferred is an organoaluminum compound represented by the formula: trialkylaluminum such as trimethylaluminum, triethylaluminum, tripropylaluminum, triisobutylaluminum, trioctylaluminum, or halogen or alkoxy-containing alkylaluminum such as diethylaluminum monochloride or diethylaluminum monomethoxide Can be preferably exemplified.
In addition, aluminoxanes such as methylaluminoxane can also be used.
Of these, trialkylaluminum is particularly preferable as component (c).

-Formation of a catalyst A component (a), a component (b), and the component (c) as needed are made to contact, and it is set as a catalyst. The contact method is not particularly limited, but the contact can be made in the following order. Further, this contact may be performed not only at the time of catalyst preparation but also at the time of preliminary polymerization with olefin described later.
1) Contact component (a) and component (b) 2) Add component (c) after contacting component (a) and component (b) 3) Contact component (a) and component (c) 4) Add component (a) after contacting component (b) and component (c) 5) Contact three components simultaneously.

The amount of components (a), (b) and (c) used is arbitrary. For example, the amount of component (a) used relative to component (b) is preferably in the range of 0.1 μmol to 500 μmol, particularly preferably 0.5 μmol to 100 μmol, relative to 1 g of component (b). The amount of component (c) used relative to component (b) is preferably in the range of 0.001 mmol to 100 mmol, particularly preferably 0.005 mmol to 50 mmol, with respect to 1 g of component (b). It is. Accordingly, the amount of component (c) to component (a) is 0.002 to ⁶ in a molar ratio of transition metal, preferably 0.02 to 10 ^5, particularly preferably in the range of 0.2 to 10 ⁴ is there.

It is preferable to subject the metallocene catalyst to a prepolymerization treatment consisting of preliminarily contacting an olefin and polymerizing a small amount.
The olefin to be used is not particularly limited, but ethylene, propylene, 1-butene, 1-hexene, 1-octene, 4-methyl-1-pentene, 3-methyl-1-butene, vinylcycloalkane, styrene and the like can be used. It is possible to use, and it is particularly preferable to use propylene.

In the prepolymerization treatment, any method can be used for supplying the olefin, such as a supply method for maintaining the olefin at a constant speed or in a constant pressure state, a combination thereof, or a stepwise change. . The temperature and time of the prepolymerization are not particularly limited, but are preferably in the range of −20 ° C. to 100 ° C. and 5 minutes to 24 hours, respectively. The amount of prepolymerization is preferably 0.01 to 100 g / g, more preferably 0.1 to 50 g / g, based on 1 gram of the component (b). After completion of the prepolymerization, the catalyst can be used as it is, depending on the usage form of the catalyst. However, if necessary, drying can be performed.
Furthermore, a polymer such as polyethylene, polypropylene, or polystyrene, or an inorganic oxide solid such as silica or titania can be allowed to coexist during or after the contact of the above components.

-Propylene-ethylene block copolymer (A) production method-Sequential polymerization In producing the propylene-ethylene block copolymer (A) of the present invention, a crystalline propylene-ethylene random copolymer component (A1 ) And a low crystalline or amorphous propylene-ethylene random copolymer component (A2) are sequentially polymerized for the reasons described above.
When performing sequential polymerization, either a batch method or a continuous method can be used, but it is generally desirable to use a continuous method from the viewpoint of productivity.
In the case of a batch method, it is possible to polymerize component (A1) and component (A2) separately using a single reactor by changing the polymerization conditions with time. As long as the effects of the present invention are not impaired, a plurality of reactors may be connected in parallel.
In the case of the continuous method, it is necessary to use a production facility in which two or more reactors are connected in series because it is necessary to individually polymerize the component (A1) and the component (A2). A plurality of reactors may be connected in series and / or in parallel for each of component (A1) and component (A2).

.. Polymerization process As the polymerization process (polymerization method), any polymerization method such as a slurry method, a bulk method, or a gas phase method can be used. Although supercritical conditions can be used as intermediate conditions between the bulk method and the gas phase method, they are substantially the same as the gas phase method, and are therefore included in the gas phase method without particular distinction.
Since the low crystalline or amorphous propylene-ethylene random copolymer component (A2) is easily soluble in organic solvents such as hydrocarbons and liquefied propylene, it is desirable to use a gas phase method for the production of the component (A2).
Any process may be used for the production of the crystalline propylene-ethylene random copolymer component (A1), but in the case of producing the component (A1) having a relatively low crystallinity, adhesion, etc. In order to avoid this problem, it is desirable to use a vapor phase method.
Therefore, the crystalline propylene-ethylene random copolymer component (A1) is first polymerized by a bulk method or a gas phase method using a continuous method, followed by a low crystalline or amorphous propylene-ethylene random copolymer elastomer. It is most desirable to polymerize component (A2) by a gas phase method.

..Polymerization conditions The polymerization temperature can be used without any particular problem as long as it is in a commonly used temperature range. Specifically, a range of 0 ° C. to 200 ° C., more preferably 40 ° C. to 100 ° C. can be used.
Although the polymerization pressure varies depending on the process to be selected, it can be used without any problem as long as it is in a pressure range usually used. Specifically, a range of greater than 0 to 200 MPa, more preferably 0.1 MPa to 50 MPa can be used. At this time, an inert gas such as nitrogen can be coexisted.

  In the case where the sequential polymerization of the component (A1) in the first step and the component (A2) in the second step is performed, it is desirable to add a polymerization inhibitor into the system in the second step. In the case of producing a propylene-ethylene block copolymer, if a polymerization inhibitor is added to a reactor that performs ethylene-propylene random copolymerization in the second step, the particle properties (fluidity, etc.) of the resulting powder, gel, etc. Product quality can be improved. Various technical studies have been made on this technique, and examples thereof include Japanese Patent Publication Nos. 63-54296, 7-25960, and 2003-2939. It is desirable to apply the method to the present invention.

-Control method of each characteristic of a propylene-ethylene block copolymer Each characteristic of the propylene-ethylene block copolymer (A) used for the polypropylene-type biaxially stretched film of this invention is controlled as follows, and propylene- It can manufacture so that the structural requirements required for an ethylene block copolymer (A) may be satisfy | filled.

..Propylene-ethylene random copolymer (A1)
For the propylene-ethylene random copolymer component (A1) that is crystalline, the ethylene content E (A1) and the peak temperature T (A1) are controlled.
In the present invention, in order to control E (A1) within a predetermined range, the amount ratio of propylene and ethylene supplied to the polymerization tank in the first step may be appropriately adjusted. The relationship between the supply ratio and the ethylene content in the resulting propylene-ethylene random copolymer varies depending on the type of metallocene catalyst used, but the component (A1) having the ethylene content E (A1) required by adjusting the supply ratio ) Can be manufactured. When controlling E (A1) to 0.1 to 7 wt%, the supply weight ratio of ethylene to propylene is in the range of 0.001 to 0.3, preferably in the range of 0.001 to 0.2. Good.
At this time, the component (A1) has a narrow crystallinity distribution, and T (A1) decreases as E (A1) increases.
Therefore, in order to satisfy T (A1) within a predetermined range, the relationship between E (A1) and these is grasped and adjusted so as to take a target range.

..Propylene-ethylene random copolymer (A2)
For the propylene-ethylene random copolymer component (A2) that is low crystalline or amorphous, the ethylene content E (A2) and T (A2) are controlled.
In order to control E (A2) within a predetermined range, the ratio of ethylene supply to propylene in the second step may be controlled as in E (A1).
For example, when E (A2) is controlled to 5 to 20 wt%, the supply weight ratio of ethylene to propylene may be in the range of 0.01 to 5, preferably in the range of 0.05 to 2. At this time, the component (A2) also shows a slight increase in crystallinity distribution as the ethylene content increases, but T (A2) decreases as E (A2) increases, as in the component (A1).
Therefore, in order for T (A2) to satisfy the scope of the present invention, the relationship between E (A2) and T (A2) is grasped, and E (A2) is controlled to be within a predetermined range. Good.

..Weight ratio W (A1) and W (A2) of component (A1) and component (A2)
The amount W (A1) of the component (A1) and the amount W (A2) of the component (A2) change the ratio of the production amount of the first step for producing the component (A1) and the production amount of the component (A2). Can be controlled. For example, in order to increase W (A1) and decrease W (A2), the production amount of the second step may be reduced while maintaining the production amount of the first step, which shortens the residence time of the second step. It can be easily controlled by lowering the polymerization temperature or increasing the amount of the polymerization inhibitor. The reverse is also true.

  When actually setting the conditions, it is necessary to consider the activity decay. That is, in the range of the ethylene content E (A1) and E (A2) carried out in the present invention, generally, the polymerization activity increases when the ratio of ethylene supply to propylene is increased in order to increase the ethylene content. The activity decay tends to increase. Therefore, in order to maintain the activity of the second step, it is necessary to suppress the polymerization activity of the first step. Specifically, the production amount W (A1) is lowered in the first step, and the polymerization is performed as necessary. Lower the temperature and / or shorten the polymerization time (residence time), or increase the ethylene content E (A2) in the second step, increase the production W (A2), and raise the polymerization temperature as necessary And / or conditions may be set in such a way as to increase the polymerization time (residence time).

..Propylene-ethylene block copolymer (A) Method for controlling so as to have a single peak at 0 ° C. or lower in the temperature-loss tangent (tan δ) curve Propylene-ethylene block copolymer (A As described above, when the solid viscoelasticity is measured, the peak of the temperature-loss tangent (tan δ) curve defined as the glass transition point Tg needs to have a single peak at 0 ° C. or less. In order to have a single peak below 0 ° C., the difference [E] gap between the ethylene content E (A1) in component (A1) and the ethylene content E (A2) in component (A2), E (A2) -E (A1) is 20 wt% or less, preferably 18 wt% or less, more preferably 16 wt% or less, and E (gap) is reduced to a range where Tg becomes a single peak in actual measurement. Good.

  Depending on the ethylene content E (A1) of the crystalline copolymer component (A1), the ethylene content E (A2) of the low crystalline or amorphous copolymer component (A2) falls within an appropriate range. Thus, it is possible to obtain a polymer having a predetermined [E] gap by setting the supply weight ratio of ethylene to propylene during the polymerization of component (A2).

The Tg of the block copolymer that does not take a phase separation structure as in the present invention is the ethylene content E (A1) in the component (A1), the ethylene content E (A2) in the component (A2), and It is affected by the ratio of both components. In the present invention, the amount of the component (A2) is 20 to 70 wt%, but in this range, Tg is more strongly affected by the ethylene content E (A2) in the component (A2).
That is, Tg reflects the glass transition of the amorphous part. In the block copolymer (A) of the present invention, the component (A1) has crystallinity and relatively few amorphous parts. This is because the component (A2) is low crystalline or amorphous and most of it is an amorphous part.

..Melt flow rate (MFR)
In order to maintain transparency, the propylene-ethylene block copolymer (A) of the present invention comprises a crystalline copolymer component (A1) and a low crystalline or amorphous copolymer elastomer component (A2). Since compatibilization is essential, the viscosity [η] A1 of the component (A1), the viscosity [η] A2 of the component (A2), the viscosity [η] of the entire propylene-ethylene block copolymer (A) Between W, the apparent viscosity mixing rule is generally established. That is,
Log [η] W =
{W (A1) × Log [η] A1 + W (A2) × Log [η] A2} / 100
Is generally established. In general, there is a certain correlation between MFR and [η], so from the viewpoint of flexibility and heat resistance, [η] A2, W (A1), and W (A2) are set first. The MFR can be freely controlled by changing [η] A1 according to the above equation.

..99wt% elution temperature T (C)
T (C) is an index indicating the crystallinity distribution, and T (C) becomes closer to T (A1) as the crystallinity distribution of the component (A1) is narrower. The crystallinity distribution of component (A1) and component (A2) is none other than narrow control.
In general, by using a metallocene catalyst, a polymer having a narrower crystallinity distribution can be obtained than when using a Ziegler-Natta catalyst. It is not necessary and sufficient to use a metallocene catalyst in order to narrow the sex distribution.

  In order to adjust the final propylene-ethylene block copolymer to those having desirable physical properties, the component (A1) and the component (A2) need to have different specific polymer compositions. That is, in the first step and the second step, it is necessary to keep the polymerization conditions corresponding to the respective polymer compositions, particularly the monomer gas composition, at different specific values. Therefore, when the crystallinity distribution of the component (A2) is wide in the adopted process, the transfer step is adjusted so that the specific monomer gas mixture corresponding to the first step is not brought into the second step from the first step. It is necessary to devise such as. Specifically, the crystallinity distribution of the component (A2) can be narrowed by increasing the purge amount in the transfer step, or by diluting or substituting with an inert gas such as nitrogen. That is, T (C) can be controlled to be low by adjusting the transfer process.

..Amount of component having a weight average molecular weight of 5,000 or less Generally, a polymer having a narrower molecular weight distribution than that of a Ziegler-Natta catalyst can be obtained by using a metallocene catalyst. However, in a system that performs sequential polymerization as in the present invention, it is not always sufficient to use a metallocene catalyst in order to narrow the molecular weight distribution. In particular, in order to prevent the formation of low molecular weight components, the time for transferring from the first step to the second step can be shortened, or the monomer gas mixture corresponding to the first step in the transfer step can be replaced with an inert gas such as nitrogen. By completely substituting, the amount of the component having a weight average molecular weight of 5,000 or less can be controlled to be small independently of the polymerization conditions.

.. Intrinsic viscosity measured in 135 ° C decalin at 23 ° C xylene solubles ([η] cxs)
Regarding [η] cxs, the propylene-ethylene block copolymer (A) uses a metallocene catalyst, so that the component (A1) contains almost no CXS component, so the molecular weight of the component (A2) is changed. Can be controlled.
Therefore, in order to control [η] cxs, the ratio of hydrogen supply to the monomer in the second step may be controlled as usual. In general, a metallocene catalyst tends to have a lower molecular weight of the polymer as the polymerization temperature is higher. Therefore, [η] cxs can be controlled by changing the polymerization temperature. [Η] cxs can also be controlled by combining both the hydrogen supply ratio and the polymerization temperature.

[Other additive components]
Various additives that can be added to the propylene-based resin can be appropriately blended in the polypropylene-based biaxially stretched film resin composition of the present invention within a range that does not hinder the effects of the present invention. Additives include phenolic antioxidants, phosphorus antioxidants, sulfur antioxidants, neutralizers, nucleating agents, light stabilizers, UV absorbers, lubricants, antistatic agents, metal deactivators, peroxides. Oxides, anti-blocking agents, fillers, etc., and polyethylene-based resins, petroleum resins, terpene resins, rosin-based resins, coumarone represented by ethylene-α-olefin copolymers, low-density polyethylene, high-density polyethylene, etc. Indene resins and alicyclic hydrocarbon resins represented by hydrogenated derivatives thereof may be added.

[Polypropylene-based biaxially stretched film]
The polypropylene biaxially stretched film of the present invention is a biaxially stretched unstretched sheet of propylene-ethylene block copolymer in the film flow direction (MD direction) and in the direction perpendicular to the film flow direction (TD direction). Is done. The stretching method may be either a sequential biaxial stretching method or a simultaneous biaxial stretching method.
In the case of sequential biaxial stretching, the stretching ratio is preferably 3 to 6 times in the MD direction and 8 to 12 times in the TD direction. If the draw ratio is 3 times in the MD direction and less than 8 times in the TD direction, the tensile elastic modulus of the film becomes small, and if the draw ratio is 6 times in the MD direction and more than 12 times in the TD direction, the heat shrinkage rate becomes large. . In the case of simultaneous biaxial stretching, stretching in the range of 2 times x 2 times to 12 times x 12 times is preferable. If the magnification is less than 2 × 2 times, the stretched film tends to stretch, which is not preferable. If it is larger than 12 times × 12 times, the rigidity of the stretched film is increased, and the flexibility is impaired.

-Manufacture of an unstretched sheet For manufacture of an unstretched sheet, a well-known film or sheet forming method can be used. As a specific example, a casting method in which a raw material is plasticized by an extruder, and a resin melt-extruded from a T-die is cooled and solidified using an air knife and a cooling roll, and niped by two or more cooling rolls and then cooled and solidified. Examples thereof include sheet molding and inflation molding in which a resin melt-extruded from an annular die is cooled and solidified by air cooling or water cooling.

-Stretching method As the stretching method, a known method can be used, and examples thereof include a tubular method, a tenter-type stretching method, a pantograph-type batch stretching method, and the like.
An example of the stretching method is a method in which a sheet obtained by the T-die method is roll-stretched about 1.0 to 5.0 times and then stretched about 4.0 to 10.0 times by the tenter method.
As another example of the stretching method, a tube-shaped unstretched sheet obtained from an annular die by air cooling or water cooling is heated to a melting temperature or lower, and then in a bubble direction by air in the longitudinal direction of 3.0 to 7 Examples of the stretching method include a so-called tubular method that stretches about 3.0 times to about 7.0 times in the lateral direction.

  The polypropylene biaxially stretched film of the present invention can be subjected to a surface treatment in order to improve printability, laminating properties and the like. Examples of the surface treatment method include corona discharge treatment, plasma treatment, flame treatment, and acid treatment, and are not particularly limited. It is preferable to perform a corona discharge treatment, a plasma treatment, and a flame treatment that can be carried out continuously and can be easily carried out before the winding step of the film production process.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.
The evaluation methods and resins used in the examples and comparative examples are as follows.

[Method for measuring physical properties of propylene-ethylene block copolymer (A)]
1) Melt flow rate (MFR)
According to JIS K7210 A method condition M, it measured on condition of the following.
Test temperature: 230 ° C
Nominal weight: 2.16kg
Die shape: Diameter 2.095mm Length 8.00mm

2) TREF
A sample is dissolved in o-dichlorobenzene (containing 0.5 mg / ml BHT) at 140 ° C. to prepare a solution. This is introduced into a 140 ° C. TREF column, cooled to 100 ° C. at a rate of 8 ° C./min, subsequently cooled to −15 ° C. at a rate of 4 ° C./min, and held for 60 minutes. Thereafter, o-dichlorobenzene (containing 0.5 mg / ml BHT) as a solvent is caused to flow through the column at a flow rate of 1 ml / min, and components dissolved in o-dichlorobenzene at −15 ° C. in the TREF column. Elution is performed for 10 minutes, and then the column is linearly heated to 140 ° C. at a heating rate of 100 ° C./hour to obtain an elution curve.

〔apparatus〕
(TREF part)
TREF column: 4.3 mmφ × 150 mm Stainless steel column Column filler: 100 μm Surface inactive glass beads Heating method: Aluminum heat block Cooling method: Peltier element (Peltier element cooling is water-cooled)
Temperature distribution: ± 0.5 ° C
Temperature controller: manufactured by Chino Co., Ltd., digital program controller KP1000 (valve oven)
Heating method: Air bath oven Measurement temperature: 140 ° C
Temperature distribution: ± 1 ° C
Valve: 6-way valve 4-way valve (sample injection part)
Injection method: Loop injection method Injection amount: Loop size 0.1ml
Inlet heating method: Aluminum heat block Measurement temperature: 140 ° C
(Detection unit)
Detector: Fixed wavelength infrared detector FOXBORO MIRAN 1A
Detection wavelength: 3.42 μm
High-temperature flow cell: LC-IR micro flow cell Optical path length 1.5mm
Window shape 2φ × 4mm oval synthetic sapphire window Measurement temperature: 140 ° C
(Pump part)
Liquid feed pump: SSC-3461 pump manufactured by Senshu Kagaku Co. [Measurement conditions]
Solvent: o-dichlorobenzene (containing 0.5 mg / ml BHT)
Sample concentration: 5 mg / ml
Sample injection volume: 0.1 ml
Solvent flow rate: 1 ml / min

3) Measurement of solid viscoelasticity A sample cut into a strip of 10 mm width × 18 mm length × 2 mm thickness from a 2 mm thick sheet injection-molded under the following conditions was used. The apparatus used was ARES manufactured by Rheometric Scientific. The frequency is 1 Hz. The measurement temperature was raised stepwise from −60 ° C., and the measurement was performed until the sample melted and became impossible to measure. The strain was performed in the range of 0.1 to 0.5%.

[Preparation of specimen]
Standard number: JIS 7152 (ISO294-1)
Molding machine: TU-15 injection molding machine manufactured by Toyo Machine Metal Co., Ltd. Molding machine set temperature: 80, 80, 160, 200, 200, 200 ° C. from below the hopper
Mold temperature: 40 ℃
Injection speed: 200 mm / sec (speed in the mold cavity)
Injection pressure: 800 kgf / cm ²
Holding pressure: 800 kgf / cm ²
Holding time: 40 seconds Mold shape: Flat plate (thickness 2 mm, width 30 mm, length 90 mm)

4) DSC
Using a Seiko DSC, take 5.0 mg of sample, hold at 200 ° C. for 5 minutes, crystallize to 40 ° C. at a rate of temperature decrease of 10 ° C./min, and further melt at a rate of temperature increase of 10 ° C./min. The melting peak temperature was Tm (unit: ° C.). The melting enthalpy dHm was determined from the area of the endothermic curve at the time of temperature increase.

5) GPC
The weight average molecular weight (Mw) and the number average molecular weight (Mn) were measured by gel permeation chromatography (GPC).
Conversion from the retention volume to the molecular weight is performed using a calibration curve prepared in advance with standard polystyrene. The measurement method is as described above.

6) Calculation of ethylene content Using NMR, as described above.

7) Extraction of room temperature xylene soluble component (CXS) 2 g of sample was dissolved in 300 ml of p-xylene (containing 0.5 mg / ml BHT) at 130 ° C. to make a solution, and then left at 23 ° C. for 12 hours. . Thereafter, the precipitated polymer is filtered off, p-xylene is evaporated from the filtrate, and further dried under reduced pressure at 100 ° C. for 12 hours to recover CXS.

8) Intrinsic viscosity (Intrinsic viscosity is also synonymous)
Using an Ubbelohde viscometer, measurement was performed at a temperature of 135 ° C. as described above using decalin as a solvent.

9) Haze (Unit:%)
The transparency of the obtained stretched film was evaluated by haze measurement. The measuring method was based on JIS K7105-1981.

10) Glossiness (Gs (20 °), unit:%)
The surface glossiness of the obtained stretched film was evaluated by measuring 20 ° specular gloss (Gs (20 °)). The measuring method was based on JIS K7105-1981.

11) Tensile modulus (unit: MPa)
Under the following conditions, tensile measurement was carried out for each of the film flow direction (MD) and the flow direction perpendicular to the flow direction (TD) to obtain a measure of film flexibility. In addition, the calculation method of the tensile elasticity modulus was based on JISK7161-1994.
Sample length: 150mm
Sample width: 15mm
Distance between chucks: 100mm
Crosshead speed: 1mm / min

12) Tensile breaking strain (unit:%)
Tensile measurement was performed on the flow direction (MD) of the obtained stretched film, and used as a measure of elongation resistance. The measuring method was based on JIS K7127-1999, the test piece used the test piece type 5, and the test speed was 500 mm / min. The calculation method of the tensile breaking strain was based on JIS K7161-1994.

13) 180 ° peel strength (g / 10 cm ² )
Two pieces of stretched film are cut out into 200 mm × 200 mm, and as shown in FIG. 4, glass having a thickness of 2 mm so that both surfaces of the laminate obtained by stacking in the order of film, sulfuric acid paper, and film are in contact with the glass plate. The plate was pinched, and after applying a load of 15 kgf, the condition was adjusted for 7 days in a temperature atmosphere of 40 ° C. Thereafter, the laminate was cut out with a width of 20 mm in parallel with the film flow direction (MD) to obtain a strip-shaped test piece. The obtained test piece was subjected to a 180 ° peel test at a crosshead speed of 500 mm / min to obtain a measure of adhesion.
The smaller this value, the less the sticking between the films derived from stickiness and bleed out, and the better the handling.

(Production Example 1)
(1) Production of solid components Chemical treatment of silicate:
To a glass separable flask equipped with a 10 L stirring blade, 3.75 L of distilled water was added slowly, followed by 2.5 kg of concentrated sulfuric acid (96%). At 50 ° C., 1 kg of montmorillonite (“Benclay SL” manufactured by Mizusawa Chemical Co., Ltd., average particle size 50 μm) was further dispersed, heated to 90 ° C., and maintained at that temperature for 6.5 hours. After cooling to 50 ° C., the slurry was filtered under reduced pressure to recover the cake. 7 L of distilled water was added to the cake and reslurried, followed by filtration. This washing operation was performed until the pH of the washing solution (filtrate) exceeded 3.5. The collected cake was dried at 110 ° C. overnight under a nitrogen atmosphere. The mass after drying was 707 g. The chemically treated silicate was dried in a kiln dryer.

Catalyst preparation:
200 g of the dried silicate obtained above was introduced into a glass reactor equipped with a stirring blade with an internal volume of 3 L, 1,160 ml of mixed heptane and 840 ml of a heptane solution of triethylaluminum (0.60 M) were added, and the mixture was stirred at room temperature. did. After 1 hour, the mixture was washed with mixed heptane to prepare a silicate slurry at 2.0 L. Next, 9.6 ml of a heptane solution of triisobutylaluminum (0.71 M / L) was added to the prepared silicate slurry and reacted at 25 ° C. for 1 hour. In parallel, (r) -dichloro [1,1′-dimethylsilylenebis {2-methyl-4- (4-chlorophenyl) -4H-azulenyl}] zirconium (synthesizing is an example of JP-A-10-226712). 33.1 ml of a heptane solution of triisobutylaluminum (0.71 M) was added to 870 ml of 2,180 mg (3 mmol) and mixed heptane, and the mixture reacted at room temperature for 1 hour was added to a silicate slurry. In addition, the mixture was stirred for 1 hour to obtain a catalyst component (a1) of a silicate / metallocene complex slurry.

(2) Prepolymerization Subsequently, 2.1 L of n-heptane was introduced into a stirring autoclave having an internal volume of 10 L that had been sufficiently substituted with nitrogen, and maintained at 40 ° C. The silicate / metallocene complex slurry of the catalyst component (a1) prepared above was introduced there. When the temperature was stabilized at 40 ° C., propylene was supplied at a rate of 100 g / hour to maintain the temperature. After 4 hours, the supply of propylene was stopped and maintained for another 2 hours. After completion of the prepolymerization, the remaining monomer was purged, stirring was stopped, and the mixture was allowed to stand for about 10 minutes, and then about 3 L of the supernatant was decanted. Subsequently, 9.5 ml of a heptane solution of triisobutylaluminum (TIBA, 0.71 M / L) and 5.6 L of mixed heptane were added, and the mixture was stirred at 40 ° C. for 30 minutes and allowed to stand for 10 minutes. 6 L was removed. This operation was further repeated 3 times.
When the component analysis of the final supernatant was conducted, the concentration of the organoaluminum component was 1.23 mmol / L, the Zr concentration was 8.6 × 10 ⁻⁶ g / L, and the presence in the supernatant with respect to the charged amount The amount was 0.016%. Subsequently, 17.0 ml of a heptane solution of triisobutylaluminum (0.71 M / L) was added, followed by drying at 45 ° C. under reduced pressure. By this operation, a prepolymerized catalyst (a) containing 2.2 g of polypropylene per 1 g of catalyst was obtained.

(3) Production of propylene-ethylene block copolymer (PP-1) Two horizontal reactors (L / D = 5.2, internal volume 100 liters) having stirring blades (polymerizers 1, 2) in series Propylene-ethylene block copolymer was produced in the arranged polymerization apparatus.
After replacing the inside of the polymerization reactor with nitrogen gas, 25 kg of polypropylene powder having an MFR of 8 g / 10 min measured at 160 ° C. and 230 ° C. obtained by DSC measurement was introduced, and then propylene, ethylene and hydrogen were introduced. The temperature was raised while the polymerization conditions were satisfied, and the pre-polymerized hexane slurry of the catalyst was 0.40 g / hr as the catalyst component not containing the pre-polymerized polymer, and 15 mmol / hr of triisobutylaluminum as the organoaluminum compound. It was supplied to become.
The region is controlled in three sections, each temperature is 55, 58, 61 ° C. from the upstream, the pressure in the polymerization vessel is 2.0 MPa, the ethylene / propylene mixed gas molar ratio in the gas phase of the reactor is 0.05, Ethylene gas and hydrogen gas were continuously fed so as to maintain the hydrogen / propylene molar ratio at 0.00009. The propylene-ethylene random copolymer (component A1) produced in the polymerization vessel was continuously extracted from the first-stage polymerization vessel through the polymer extraction pipe so that the retained level of the propylene-ethylene random copolymer (component A1) was 50% by volume of the reaction volume. It supplied to the superposition | polymerization device of 2 superposition | polymerization processes.

Next, the propylene-ethylene random copolymer (component A1), propylene, ethylene, and hydrogen gas from the first polymerization step are continuously supplied into the polymerization vessel of the second polymerization step, and propylene-ethylene random copolymerization is performed. (Component A2) was performed. The reaction conditions were a temperature of 70 ° C. and a pressure of 1.9 MPa. In the second polymerization vessel, the mixed gas molar ratio of ethylene / propylene was 0.5, and the hydrogen / propylene molar ratio was continuously supplied while maintaining the MFR of component A2 to be the same as that of component A1. Furthermore, oxygen was supplied as an activity inhibitor so that the production amount to be polymerized in the polymerization vessel 2 was 40% by weight based on the whole.
The propylene block copolymer produced in the second polymerization step was continuously extracted so that the retained level of the polymer was 60% by volume of the reaction volume.
When a part of the sample taken out from the first polymerization vessel was analyzed, the MFR was 5 g / 10 min and the ethylene content was 1.7% by weight. When the finally obtained propylene-ethylene block copolymer (PP-1) was analyzed, the MFR was 5 g / 10 min, and the ethylene content in Component A2 was 11.7% by weight. The results are shown in Table 3.

(Production Examples 2 to 5): Production of PP-2 to PP-5 Polymerization was conducted in the same manner as in Example 1 except that the prepolymerization catalyst (a) of Example 1 was used and the polymerization conditions shown in Table 1 were used. And propylene-ethylene block copolymers (PP-2 to PP-5) were obtained. The results are shown in Table 3.

(Production Example 6): Production of PP-6 (1) Preparation of solid component A 10-L autoclave equipped with a stirrer was sufficiently substituted with nitrogen, and 2 L of purified toluene was introduced. To this, 200 g of Mg (OEt) ₂ and 1 L of TiCl ₄ were added at room temperature. The temperature was raised to 90 ° C. and 50 ml of di-n-butyl phthalate was introduced. Thereafter, the temperature was raised to 110 ° C. to carry out a reaction for 3 hours. The reaction product was thoroughly washed with purified toluene. Subsequently, the refined toluene was introduce | transduced and the whole liquid quantity was adjusted to 2L. 1 L of TiCl ₄ was added at room temperature, the temperature was raised to 110 ° C., and the reaction was performed for 2 hours. The reaction product was thoroughly washed with purified toluene. Subsequently, the refined toluene was introduce | transduced and the whole liquid quantity was adjusted to 2L. 1 L of TiCl ₄ was added at room temperature, the temperature was raised to 110 ° C., and the reaction was performed for 2 hours. The reaction product was thoroughly washed with purified toluene. Further, using purified n-heptane, toluene was replaced with n-heptane to obtain a slurry of the solid component (b1). A portion of this slurry was sampled and dried. As a result of analysis, the Ti content of the solid component (b1) was 2.7% by mass.
Next, a 20 L autoclave equipped with a stirring device was sufficiently substituted with nitrogen, and 100 g of the slurry of the solid component (b1) was introduced as the solid component (b1). Purified n-heptane was introduced to adjust the concentration of the solid component (b1) to 25 g / L. 50 ml of SiCl ₄ was added and a reaction was performed at 90 ° C. for 1 hr. The reaction product was thoroughly washed with purified n-heptane.
Thereafter, purified n-heptane was introduced to adjust the liquid level to 4 L. To this, 30 ml of dimethyldivinylsilane, 30 ml of (i-Pr) ₂ Si (OMe) ₂ and 80 g of Et ₃ Al in an n-heptane diluted solution were added as Et ₃ Al, and a reaction was carried out at 40 ° C. for 2 hours. The reaction product was thoroughly washed with purified n-heptane, and a portion of the resulting slurry was sampled and dried. As a result of analysis, the solid component contained 1.2% by mass of Ti and 8.8% by mass of (i-Pr) ₂ Si (OMe) ₂ .

(2) Prepolymerization Using the solid component obtained above, prepolymerization was performed by the following procedure. Purified n-heptane was introduced into the slurry, and the solid component concentration was adjusted to 20 g / L. After cooling the slurry to 10 ° C., 10 g was added n- heptane dilution of _Et 3 Al as _Et 3 Al, were fed over 4hr of propylene 280 g. After the supply of propylene was completed, the reaction was further continued for 30 minutes. Next, the gas phase was sufficiently replaced with nitrogen, and the reaction product was thoroughly washed with purified n-heptane. The obtained slurry was extracted from the autoclave and vacuum dried to obtain a solid catalyst component (b). This solid catalyst component (b) contained 2.5 g of polypropylene per 1 g of the solid component. As a result of analysis, the portion of the solid catalyst component (b) excluding polypropylene contained 1.0% by mass of Ti and 8.2% by mass of (i-Pr) ₂ Si (OMe) ₂ .

(3) Production of propylene-ethylene block copolymer Polymerization was carried out using a continuous reaction apparatus formed by connecting two fluidized bed reactors having an internal volume of 2000 liters. First, in the first reactor, the polymerization temperature is 55 ° C., the propylene partial pressure is 1.8 MPa, and the hydrogen as the molecular weight control agent is 0.004 in the hydrogen / propylene molar ratio and 0.0131 in the ethylene / propylene molar ratio. In this manner, triethylaluminum was continuously supplied as an organoaluminum compound at 88 mmol / hr. As a result of analysis by sampling the copolymer (copolymer A1) polymerized in the first stage polymerization step, the MFR was 2 g / 10 min and the ethylene content was 3% by weight.
Subsequent to the first stage polymerization step, polymerization (copolymer A2) in the second stage polymerization step was carried out in a fluidized bed reactor having an internal volume of 2000 liters. In the second reaction vessel, propylene and ethylene are continuously supplied at a polymerization temperature of 80 ° C. and a pressure of 1.5 MPa so that the molar ratio of ethylene / propylene is 0.1039, and further a molecular weight control agent. And continuously supplying hydrogen / propylene molar ratio so that the MFR of the product is the same as that of the first stage polymerization process product, and ethyl alcohol as an activity inhibitor of the copolymer A2. It supplied so that a ratio might be 40% with respect to the whole product. Finally, it was transferred to a downstream vessel where nitrogen gas containing moisture was supplied to stop the reaction and purge the residual gas to obtain a propylene-ethylene block copolymer (PP-6). The overall product obtained had an MFR of 2 g / 10 min, and the ethylene content in copolymer B was 13.7%. The results are shown in Table 3.

[Example 1]
(Granulation of propylene resin composition)
The following antioxidant and neutralizing agent were added to the block copolymer powder (PP-1) obtained in the production example so as to have the following contents, followed by stirring and mixing.
(Additive compounding)
Antioxidant:
Tetrakis [methylene-3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate] methane 500 ppm, tris (2,4-di-t-butylphenyl) phosphite 500 wtppm
Neutralizer: calcium stearate 500wtppm

(Granulation)
The block copolymer powder to which the additive has been added is melt-kneaded using a twin screw extruder with a 35 mm diameter at a screw rotation speed of 300 rpm and a molten resin temperature of 200 ° C., and the molten resin extruded from the strand die is cooled. The material pellets were obtained by taking out while cooling and solidifying in a water tank, and cutting the strands using a strand cutter.
[Η] of TREF, GPC, DSC, CXS, and CXS was measured using the obtained pellets. Table 4 shows the results obtained by the measurement. Moreover, injection molding was performed using this pellet, and DMA measurement was performed using the obtained test piece. The results are shown in Table 4.

(Manufacture of biaxially stretched film)
(1) Molding method of unstretched sheet Die to which a 30 mm diameter surface layer extruder-1, a 30 mm diameter surface layer extruder-2, and a 75 mm diameter intermediate layer extruder-3 were connected for molding. A three-layer T die with a width of 265 mm was used. All the extruders were charged with the pellets obtained by the above method, melt-extruded at 240 ° C., and cooled and solidified with a cooling roll at 30 ° C. to obtain an unstretched sheet of 1 type and 3 layers having a thickness of about 1 mm. .
(2) Forming method of stretched film Next, the obtained unstretched sheet was melted in the tenter furnace at a temperature of (melting point −40 ° C.) 5 times in the tenter type sequential biaxial stretching apparatus, After preheating at the same temperature, the film was stretched at a draw ratio of 9 times in the TD direction at (melting point-2 ° C.), and heat-set while being relaxed by 5% (melting point-2 ° C.), and the total film thickness A 20 μm monolayer polypropylene biaxially stretched film was obtained. Table 5 shows the evaluation results of the obtained polypropylene-based biaxially stretched film.

[Examples 2-3]
It implemented like Example 1 except having changed block copolymer powder into PP-2-3.
Table 4 shows the results of [η] measurement and DMA measurement of TREF, GPC, DSC, CXS, and CXS.
Table 5 shows the evaluation results of the obtained polypropylene-based biaxially stretched film.

[Comparative Examples 1-3]
The same operation as in Example 1 was carried out except that the block copolymer powder was changed to PP-4 to 6.
Table 4 shows the results of measurement of [η] and DMA measurement of TREF, GPC, DSC, CXS, and CXS, and Table 5 shows the evaluation results of the obtained polypropylene biaxially stretched film.

[Comparative Example 4]
Using the block copolymer powder PP-1, pellets obtained in the same manner as in Example 1 were extruded from a T-die of an extruder heated to 230 ° C., cooled and solidified with a cooling roll at 30 ° C., and the thickness A 20 μm unstretched film was obtained.
Table 4 shows the results of TREF, GPC, DSC, CXS, CXS [η] measurement and DMA measurement, and Table 5 shows the evaluation results of the obtained polypropylene-based laminated film.

Since the films obtained in Examples 1 to 3 satisfy all of the specific physical properties of the present application, they are excellent in flexibility, transparency, surface glossiness, hardly stretched, and are bonded to each other due to stickiness or the like. Did not occur.
In Comparative Example 1, since the amorphous propylene-ethylene random copolymer component (A2) which is a softening component was not contained, the softness was inferior. In Comparative Example 2, the tan δ peak of the amorphous propylene-ethylene random copolymer component (A2) is not single, so that it has a phase separation structure, transparency and surface gloss deteriorate, and 180 ° Peel strength has also increased.
In Comparative Example 3, since the amorphous propylene-ethylene random copolymer component (A2) was not polymerized by the metallocene catalyst, the 180 ° peel strength was increased, and the transparency and the surface gloss were inferior. . In Comparative Example 4, since the film was not stretched, the breaking strain was 600% and the low elongation characteristics were inferior.
As described above, the stretched flexible film made of the propylene-ethylene block copolymer of the present invention is superior to the comparative example in terms of performance such as transparency, gloss, flexibility, low elongation characteristics, and stickiness resistance, and is superior. It is the result that makes the sex stand out.

  Since the polypropylene-based biaxially stretched film of the present invention is excellent in transparency, gloss, flexibility, heat resistance, and low elongation properties, it can be used as a stretched vinylon film (PVA film) or a wrap film (PE multilayer film). Since it can be used as a packaged body such as a representative stretched flexible film, and further has excellent anti-sticking performance, it is excellent in secondary processing suitability typified by a bag-making process.

Claims (7)

  Using a metallocene catalyst, 30 to 80 wt% of propylene-ethylene random copolymer (A1) having an ethylene content of 0.1 to 7 wt% in the first step, and 6 to 15 wt% of the copolymer (A1) in the second step % Propylene-ethylene random block copolymer (A2) containing 20% to 70% by weight of ethylene-containing propylene-ethylene random copolymer (A2), comprising a melt flow rate (2.16 kg, 230 ° C.) in the range of 0.1 to 10 g / 10 min, and a propylene-ethylene block copolymer having a single peak at 0 ° C. or lower in a temperature-loss elastic modulus (tan δ) curve obtained by solid viscoelasticity measurement Polypropylene obtained by stretching (A) in the film flow direction and in a direction perpendicular to the film flow direction. Biaxially oriented film.   The polypropylene biaxially stretched film according to claim 1, which is stretched by a sequential biaxial stretching method.   The polypropylene biaxially stretched film according to claim 1, which is stretched by a simultaneous biaxial stretching method.   Elution amount (dwt% / dT) of propylene-ethylene block copolymer (A) with respect to temperature by temperature rising elution fractionation method (TREF) in a temperature range of −15 ° C. to 140 ° C. using an o-dichlorobenzene solvent. In the TREF elution curve obtained as a plot of), the peak observed on the high temperature side is in the range of 65 ° C. to 96 ° C., and the peak observed on the low temperature side is below 45 ° C. or not observed, and 99 wt% The polypropylene-based biaxial structure according to any one of claims 1 to 3, wherein the temperature at which elution is 98 ° C or less, and the difference between the peak temperature observed on the high temperature side and the temperature at which 99 wt% is eluted is 5 ° C or less. Stretched film.   5. The peak observed on the high temperature side is in the range of 65 ° C. to 88 ° C., and the peak observed on the low temperature side is 40 ° C. or lower or is not observed, and the 99 wt% elution temperature is 90 ° C. or lower. 2. A polypropylene-based biaxially stretched film.   The propylene-ethylene block copolymer (A) has a weight average molecular weight obtained by GPC measurement in the range of 100,000 to 400,000, and the amount of components having a weight average molecular weight of 5,000 or less is 0. It is 8 wt% or less, The polypropylene type biaxially stretched film in any one of Claims 1-5.   The propylene-ethylene block copolymer (A) has an intrinsic viscosity in a range of 1 to 2 dl / g of a 23 ° C xylene soluble component measured in decalin at 135 ° C. Polypropylene biaxially stretched film.

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