JPH01171834A - Manufacture of polypropylene resin sheet - Google Patents

Abstract

PURPOSE:To form a sheet of superior rigidity and strength and with high transparency and gloss by blending given polypropylene resin and aliphatic or alicyclic petroleum resin or hydrogenated terpene resin and a core making agent at a given blending formation, melting, kneading, extrusion molding and quenching by a given water cooling method. CONSTITUTION:A formation, composed of a blend in which 97-70 part by weight of polypropylene resin or 3-30 part by weight of aliphatic or alicyclic petroleum resin or hydrogenated terpene and a core making agent in a ratio of 0.001-2wt.% of the core making agent to the total 100wt.% of the resin, is melted, kneaded, extruded from a die, introduced in the downstream direction into a water cooling section where cooling water is flowed down and quenched. As for the polypropylene resin, a mixture containing 50wt.% or less of homopolypropylene and random polypropylene is used. For example, silica, talc or the like is used as the nucleating agent. The molten resin formation, extruded from a die outlet of an extrusion device, is extruded in the form of a film in the downstream direction of cooling water flowing down, and the extruded resin formation film-like material is quenched while being in contact with the cooling water flowing down, and then, if necessary, introduced into a cooling water tank to complete the cooling process.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing polypropylene resin sheets, and more particularly, to a method for manufacturing polypropylene resin sheets that can be suitably used for molding various packaging containers, etc. .

[Conventional technology]

Polystyrene and polyvinyl chloride resins are used as materials for highly transparent packaging containers, but these have insufficient strength and heat resistance, and their use in the urinal field is limited due to the toxicity of their monomers.

On the other hand, polypropylene has excellent strength, heat resistance, and moisture permeability, so it is molded by thermoforming methods such as vacuum forming and pressure forming and is used for various lightweight containers.However, it is usually The polypropylene sheet obtained by this molding method is inferior to polystyrene, polyvinyl chloride resin, etc. in terms of transparency, rigidity, thermoformability, etc., so its use is severely limited.In particular, its use is significantly limited compared to competing products whose transparency is even lower. It has not yet been replaced.

A commonly known method for making polypropylene transparent is to add a nucleating agent to polypropylene and make the spherulites that are formed during molding sufficiently fine to obtain a certain degree of transparency. When a rapid cooling method such as a water cooling method is applied, especially in the T-die method, crystallization differs due to slight cooling differences, wrinkles tend to occur at the sheet edges, and it is impossible to obtain an industrially uniform sheet. .

Attempts to obtain a polypropylene resin sheet with excellent transparency have conventionally been made by melting a composition of polypropylene and aliphatic or alicyclic petroleum resin at a temperature 40°C or more higher than the melting point of polypropylene. , A method of obtaining a sheet by rapidly cooling to a temperature of 60°C or less by a chill roll method, a submersion method, etc. (Kibun Showa No. 15894), ■
A method in which a nucleating agent is further added to a composition obtained by thermally decomposing a composition consisting of polypropylene and an aliphatic or alicyclic petroleum resin in the presence of an organic peroxide, and the mixture is extruded and sheeted using a chill roll method. (Unexamined Japanese Patent Publication No. 62-13
5551), but in the method (2) above, the level of transparency of the resulting polypropylene sheet is still insufficient, and the surface condition cannot be made uniform, or the surface condition cannot be made uniform. When forming containers by thermoforming from such sheets, there are problems such as a narrow thermoforming temperature range. On the other hand, in the method (2) above, the permeability level of the sheet obtained is low, as can be judged from the example in which the chill roll method with a chill roll temperature of 35°C was used in combination, and the permeability level of the sheet obtained is low. The process is complicated because it requires the use of materials and a decomposition process, and the resulting sheet has an odor, and the molecular weight distribution of the resin becomes narrow, resulting in poor thermoformability. There were serious problems such as:

[Problem that the invention seeks to solve]

The present invention has been made based on the above circumstances.

The purpose of the present invention is to obtain a container that has excellent rigidity and strength, uses a small amount of petroleum resin additives, has very high transparency and gloss, and has a uniform wall thickness under normal vacuum forming conditions. An object of the present invention is to provide a method for producing a polypropylene resin sheet that is extremely advantageous in practice.

[Means for solving problems]

As a result of extensive research to solve the above problems, the present inventors have identified a specific polypropylene resin, an aliphatic or alicyclic petroleum resin, or a hydrogenated terpene resin, and a nucleating agent. A method of melt-kneading a composition blended as a blending composition, extrusion molding as a film-like body, and rapidly cooling the film-like body using a specific water cooling method to form sheets is provided. The present invention was completed based on this finding.

That is, the present invention provides (A) polypropylene resin 97-
70 parts by weight, (B) 3 to 30 parts by weight of an aliphatic or alicyclic petroleum resin or hydrogenated terpene resin, and (C) a nucleating agent. ) O,OO 1-2% by weight when the total of the components is 100% by weight
The composition is melt-kneaded, extruded from a die, and introduced in the downstream direction into a water cooling section where cooling water flows down.

The present invention provides a method for manufacturing a polypropylene resin sheet that is cooled.

Polypropylene resin used in the present invention [(A)
The content of homopolypropylene ((AI) or random polypropylene (A2) is 50% by weight)
The following mixture of homopolypropylene (AI) and random polypropylene (A2) is used. As this homopolypropylene (AI), crystalline polypropylene is usually used. As the random polypropylene used, a copolymer of propylene and other α-olefins of 20% by weight or less, preferably 15% by weight or less can be used. Other α-olefins include
And α-olefins having about 4 to 10 carbon atoms can be suitably used, and these may be linear or branched. Specifically, for example, ethylene, 1-butene, isobutene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, neohexene, ■-heptene, 1-octene, 1 -decene, among others, ethylene, 1-butene, etc. are particularly preferred.

The random polypropylene may be a copolymer of propylene and one of the above α-olefins, or a copolymer of propylene and one of the above α-olefins.
It may be a copolymer with more than one species, or a combination of these may be used.

The above (AI) and (AI) used as the above (A) component
) and (A2) have a melt index (MI
>value is usually 0.3 to 20 g/min, preferably 0.
5 to 15 g/min can be suitably used.

However, when using a mixture of (A1) and (A2) as component (A), these may be separately blended into component (B) and component (C).

In the present invention, as component (B), an aliphatic petroleum resin (B1), an alicyclic petroleum resin (B2), a hydrogenated terpene resin (B, ), or these (B, "
), (B2) and (B3).

This aliphatic petroleum resin (Bl), alicyclic petroleum resin (B
2) and the hydrogenated terpene resin (B3) or a mixture thereof, known ones can be used. Normally each has a molecular weight of 400-5000 and a softening point of 50-50.
Those having a hydrogenation rate of 80% or more at 150°C can be preferably used. Specifically, as (B1), for example, a hydrogenated hydrocarbon resin with a degree of polymerization of about 5 to 20 obtained by polymerizing olefin and diene hydrocarbons obtained by high-temperature decomposition of petroleum, ( As B2), for example, aromatic petroleum resin obtained by polymerizing uniters such as vinyltoluene, vinylxylene, propenylbenzene, styrene, α-methylstyrene, indene, methylindene, ethylindene, etc. is hydrogenated. What I did, (
Examples of B3) include arrow ocimene, karen,
Polymerize acyclic, monocyclic or bicyclic monoterpenes, including pinene or its isomers, dipentine, terpinene, terbirun, limonene, turpentine, cuts or fractions of terpenes or various other terpenes. and hydrogenated products thereof. For any resin produced by hydrogenation, the hydrogenation rate is preferably 80% or more, preferably 90% or more, even if some lower saturated bonds and aromatic rings remain. Available for use.

Note that these may be used alone or in combination of two or more.

As the nucleating agent (C), known ones can be used, and specifically, for example, silica, talc, sodium benzoate, para-tertiary butylbenzoic acid aluminum salt, para-tertiary butyl phosphate. Examples include sodium salts, polyvinylcycloalkanes, dihenzylidene sorbitol derivatives, and sodium methylenebisacid phosphate.

Note that these may be used alone or in combination of two or more.

In the method of the present invention, a polypropylene resin composition prepared by blending the components (A), (B), and (C) in the following proportions is melt-kneaded, extruded as a film, and then The desired polypropylene resin sheets are manufactured by rapid cooling using a specific water cooling method.

As for the usage ratio of component (A), component (B) and component (C), the total amount of component (A) and component (B) used should be 1
The amount of component (A) used is 97 to 00 parts by weight.
70 parts by weight [i.e., the amount used of component (B) is 3 to 30 parts by weight], preferably 95 to 80 parts by weight [i.e., (B)
When the amount of the component used is within the range of 5 to 20 parts by weight], and the total amount of component (A), component (B), and component (C) used is 100% by weight, ( C) The amount of component used is 1 to 2% by weight of O,OO, preferably 0.01 to 2% by weight.
1% by weight, more preferably within the range of 0.02 to 0.5% by weight.

If the amount of the Bl component used is less than 3 parts by weight as defined above, there will be no effect of improving the transparency and moldability of the sheet, and even the thermoformability from the sheet to the container, while the amount of the CB component used. If it exceeds 30 parts by weight as defined above, the properties of the polypropylene resin such as impact strength, heat resistance, and hygiene will deteriorate, and the sheet will become sticky, resulting in a decrease in moldability and secondary processability.

In addition, the amount of component (C) used is 0°001 according to the above definition.
If the amount is less than 2% by weight, there will be no effect of improving transparency or thermoformability, while if it exceeds 2% by weight, the effect of the additive will not be particularly improved and will not be necessary.

Blending order of component (A), component (B), and component (C)
When using a mixture, the above (AI).

(A2), (Bl), (B, ), (B3) and (C) components] is not particularly limited, and they may be added at the same time, or ') or a blended composition of (A,) and (A2), (B+), (B2) or (B,),
Alternatively, any method may be used, such as a stepwise method of blending these mixtures and component (C) to form a composition.

In addition, the above-mentioned components are mixed in advance by a known method, such as a method using a Banbury mixer, etc.
A pellet containing B) or (C) or both of these components at a high concentration may be molded, and this may be mixed with component (A) and melt-kneaded at a predetermined blending ratio (or each of the above components may be mixed). may be put into a melt-kneading apparatus at the predetermined ratio and melt-kneaded.

Although this melt-kneading can be carried out separately in advance using a normal melt-kneading machine, it is usually preferable to carry out the melt-kneading using a melt-extrusion device having a melt-kneading section. In any case, after melt-kneading, the molten polypropylene resin composition is extruded from a die of a melt extrusion device as a molten resin film having a desired shape.

If desired, the polypropylene resin composition may further contain commonly used additives, such as heat stabilizers, ultraviolet absorbers, and antioxidants, in addition to the components (A), (B), and (C). It is also possible to add stabilizers such as antistatic agents and antistatic agents such as various surfactants.

The temperature of the resin composition is usually 200 to 300 degrees Celsius, preferably 210 degrees Celsius.
It is suitable to carry out within the range of ~280°C. When performing melt extrusion, the melting (kneading) temperature of the resin composition is set to the above temperature range, and the temperature at the outlet of the negative die is heated using a die lip heater or the like to be slightly higher than the temperature of the molten resin composition. It is desirable to keep it. For example, the die exit temperature is usually 10 to 60"C higher than the temperature of the molten resin composition.
It is preferable to do this at a higher level.

By setting the die exit temperature to be slightly higher than the temperature of the molten resin composition in this manner, the surface condition of the extruded resin film can be maintained in an extremely good condition. The present invention has a feature that, depending on the arrangement of the component (CB), a film with an extremely excellent surface condition can be extruded even if the extrusion speed of the resin is increased. Thereafter, by rapidly cooling this film-like body, the external haze degree and the total haze degree (total of the external haze degree and the internal haze degree) can be further reduced, and the gloss can be further improved.

As a method for film-forming by melt extrusion, known methods such as the usual T-die method and annular die method can be used.

In the method of the present invention, the film-like body, such as a sheet or hollow film, melt-extruded as described above is rapidly cooled by a water cooling method.

Note that one of the important points in the method of the present invention is to extrude the molten resin composition as a film from the die exit of the extrusion device in the direction of the cooling water flowing down, and to collect the extruded resin composition film. It is cooled while being brought into contact with the flowing cooling water, and then, if necessary, guided to a cooling water tank to complete cooling.

As this cooling water, water alone or an aqueous solution of water with an organic or inorganic thickener added is used, but an aqueous solution with a thickener added is preferable in terms of uniform cooling and a smooth surface. . Here, various organic thickeners can be used, such as natural polymer substances, semi-synthetic products, and synthetic products.

Natural polymer substances include starches such as Japanese starch, potato starch, and wheat starch; mannans such as konjac; seaweeds such as agar and sodium alginate; plant mucilages such as gum tragacanth and gum arabic; microbial slimes such as dextran and levan. Substances: Proteins such as garlic, gelatin, casein, and collagen. Semi-synthetic products include cellulose-based substances such as viscose, methylcellulose, and carboxymethylcellulose; starch-based substances such as soluble starch, carboxymethyl starch, and dialdehyde starch. In addition, synthetic products include polyvinyl alcohol, sodium polyacrylate, polyethylene oxide, and the like.

On the other hand, inorganic thickeners include silica sol, alumina sol,
These include clay, water glass, and various metal salts.

In addition to aqueous solutions prepared by adding these thickeners to water, viscous substances such as polyethylene glycol, polypropylene glycol, and silicone oil can also be used alone.

The viscosity of the aqueous solution containing the thickener is usually 2 to 3000 centipoise (cp), preferably 3 to 1000 cp.

In addition, the temperature of the cooling water is preferably -10°C to +50"C. Particularly in the production of sheets with a thickness of 200 μm or more, it is effective for rapid cooling to keep the liquid temperature below 20"C, particularly preferably below 10'C. It is true.

In this way, the molten resin composition film is heated to 100°C.
Hereinafter, polypropylene resin sheets are produced by rapidly cooling, preferably to 60°C or less.

Here, as the cooling device used, for example,
Disclosed in Publication No. 0-236719, JP-A-61
The cooling device shown in FIG. 1 of Japanese Patent Publication No.-130018 or the cooling device shown in FIG. 1 described later (cooling water flowing down type water level setting type cooling device) can be suitably used. An example of the rapid cooling method using the water cooling method used in the method of the present invention is as follows:
A more detailed explanation will be given below with reference to FIG. 1, which will be described later.

FIG. 1 is a cross-sectional view conceptually showing an example of a cooling device used in the method of the present invention. In the figure, 1 and 2 each indicate a water tank for introducing cooling water downstream, and 3 and 4 each indicate a cooling water tank. A lower slit for water flow is shown, and 5 represents a cooling water tank. The resin composition film 9 extruded in a molten state from the extrusion T-die 6 is introduced into the cooling water tank 5 by guide rolls 10 to 13 while being rapidly cooled. is introduced into the cooling water 14, and after cooling is completed, it is recovered. The temperature of the cooling water in the cooling water tank 5 is appropriately adjusted to a predetermined temperature by a temperature control mechanism 15 or the like, and can be circulated to the cooling water downstream tanks 1 and 2 by the pump 15 as appropriate.

Note that the cooling water flow down slit is preferably of the two-stage type shown in FIG. 1, and it is preferable to use a porous flow regulator for the flow path in the water tank. Furthermore, it is particularly preferable that the cooling water flow rate is faster than the introduction speed of the membrane-like body and that the cooling water does not stagnate at the slit entrance.

Next, when molding the resin composition into an annular film-like object, an annular resin film-like object is extruded using an annular die having a desired shape as an extrusion die, and cooling water is caused to flow down at least on the outer periphery; A cooling method should be used.

Note that the shape of the obtained polypropylene resin composition sheets is not particularly limited, and may be formed into a single layer sheet, multilayer sheet, hollow sheet, etc. having a desired size (width) and (film thickness). Can be done. However, from the viewpoint of transparency, strength, etc., the thickness of the resin composition sheets is usually in the range of 100 to 3000 μm, preferably 150 to 2000 μm, and the method of the present invention In particular, it is effective in that high transparency can be maintained even on sheets having a film thickness of 300 μm or more. Further, according to the method of the present invention, the sheets obtained can have significantly improved surface conditions such as gloss and other appearance in addition to transparency. In order to keep this gloss and appearance suitable, in addition to setting the die exit temperature slightly higher than the melting (kneading) temperature of the resin composition during melt extrusion as described above, it is also necessary to It is desirable to use a die that is

The resin sheets manufactured as described above may be subjected to heat treatment as desired.

This optional heat treatment is carried out at a temperature range of usually 70°C or higher and below the melting point of the resulting resin composition sheet, preferably 80°C or higher and 10°C lower than the melting point of the resin composition sheet. , for example heated rolls,
This can be done by heating using heated air, an inert liquid, or the like.

In addition, during the above heat treatment or before and after the heat treatment, the shrinkage stress is 5 kg at a stretching ratio of 1.02 to 1.50.
/c+Il or less may be moderately stretched or rolled.

This stretching or rolling is usually carried out at a temperature lower than the melting point of the resin composition sheets, preferably 5 to 70°C lower than the melting point.
More preferably, it can be carried out by heating to a temperature 5 to 50°C lower than the melting point and by roll stretching or roll rolling. Note that the stretching may be performed by uniaxial stretching or biaxial stretching. Slight orientation is imparted to the resin composition sheets obtained by this moderate stretching or rolling, and while maintaining good thermoformability during thermoforming, the sheet 1-IN is heated to cause lumes and wrinkles. can be reduced.

In the manner described above, desired polypropylene resin sheets can be obtained.

The sheet-shaped, hollow polypropylene resin sheet obtained by the method of the present invention has excellent strength, heat resistance, moisture permeability, etc. possessed by original polypropylene resin, and
It is an excellent polypropylene resin sheet that has excellent rigidity, very high transparency, and good gloss.Moreover, it can be easily molded into a well-shaped shape even under vacuum molding conditions, and the molding temperature range is particularly low due to the addition of component (C). There is a major characteristic that it becomes wider on the high temperature side. Furthermore, since a container with a uniform wall thickness is obtained, it can be widely and suitably used for various packaging containers and the like. In addition, these sheets can be used not only for thermoforming containers, but also for manufacturing cases by folding, and because of their excellent stretchability, they can also be used as raw materials for stretched films.

〔Example〕

(Examples 1 to 9, Comparative Examples 1 to 3) The blended composition polypropylene resin composition shown in Table 1 was extruded using a T-die extrusion device (extruder 65 mmφ, L/D=28,
The mixture was melt-kneaded using a die width of 550 mm and a die lip opening of 2 mm under conditions of a resin temperature of 250°C and a die temperature of 280°C, and a transparent resin film was extruded. Next, the membrane-like body was placed in a two-stage slit type water cooling device as shown in Fig. 1 (first stage slit: height 50 mm, width 2.5 mm, water level 4 mm, cooling water temperature 4°C. ;2nd stage slit: height 10mm, width 5mm, water level 10 marks, cooling water temperature 4
°C) and rapidly cooled to a thickness of 0.3 mm and 0.6
A sheet of mm was obtained. This sheet was heat-treated using a roll (145° C.) with a diameter of 300 φ. Table 1 shows the results of measuring the physical properties of this sheet.

Furthermore, using the sheet obtained in Example 5, opening diameter =
A container with a diameter of 100 mm, a bottom diameter of 85 mm, and a height of 40 mm was molded. The wall thickness of the container from the 0.6 trunk sheet is 0.6 on the side wall.
36 mm, 0.35 mm at the center of the lower part, and there is almost no thickness deviation in the circumferential direction, and the container molding range is 15 to 2.
1 second, and the moldable time was also long, 6 seconds.

In the case of Comparative Example 1, not only is the side wall -0.52 mm and the center of the lower part 0.21 mm, but the moldable range of the container is 18 to 19 seconds, and the moldable time is very narrow at 1 second. Not only was it difficult to do so, but transparency was also very low.

Furthermore, in the case of Comparative Example 2, wrinkles occurred at both ends of the sheet, making it impossible to obtain a good sheet, and the transparency was also insufficient.

Furthermore, the moldable range in Comparative Example 3 was 7 to 10 seconds, which was lower than 7 to 13 seconds in Example 3. On the other hand, in the case of Example 3, the range was very wide, the transparency did not decrease even when heated above the melting point of polypropylene, and the moldability, formability, and thickness uniformity were excellent.

The range in which containers can be formed is determined by the minimum time (seconds) that can be formed with good mold reproducibility by heating the sheet under the same conditions, and the time (seconds) until a part of the sheet turns white and a transparent container cannot be formed. means between.

〔Effect of the invention〕

The polypropylene resin sheets obtained by the present invention have excellent strength, heat resistance, moisture permeability, etc. inherent to polypropylene resin, as well as excellent rigidity, very high transparency, good gloss, and It can be easily molded with good formability over a wide temperature range depending on the molding conditions, etc., and has good elongation during molding, so containers with uniform wall thickness can be obtained, making it suitable for various packaging containers. It can be suitably used in a wide range of fields such as manufacturing.

That is, according to the present invention, polypropylene resin sheets having the above-mentioned excellent properties and a wide range of applications can be obtained easily and with high productivity, and the method for producing polypropylene resin sheets is extremely advantageous in practice. can be provided.

[Brief explanation of the drawing]

FIG. 1 is a sectional view conceptually showing an example of a cooling device used in the method of the present invention. In the figure, 1 and 2 cooling water flowing down introduction tank, 3 and 4 cooling water flowing down slit, 5 cooling water tank, 6 T-extrusion die, 7 and 8 flowing cooling water, 9 resin film-like body, 10-13 induction roll, 14
Cooling water, 15 temperature control mechanism, 16 pump

Claims (1)

[Scope of Claims] 1. (A) 97 to 70 parts by weight of polypropylene resin and (
B) 3 to 30 parts by weight of aliphatic or alicyclic petroleum resin or hydrogenated terpene resin and (C) nucleating agent as described in (A)
A composition formed by blending the components in an amount of 0.001 to 2% by weight when the total of the components (B) and (C) is 100% by weight is melt-kneaded, extruded through a die, and cooled. A method for producing polypropylene resin sheets, which comprises introducing water in a downstream direction into a water-cooling section for rapid cooling. 2. Polypropylene resin is homopolypropylene and 5
The method for producing polypropylene resin sheets according to claim 1, which is a mixture with 0% by weight or less of random polypropylene.