JP5047994B2 - Biaxially oriented laminated film - Google Patents

Description

  The present invention relates to a laminated film in which a base material layer is made of a biaxially oriented film made of an ethylene copolymer, and a release layer or an adhesive layer is laminated thereon.

  Using a random copolymer of ethylene and α-olefin such as linear low-density polyethylene (LLDPE), a film obtained by inflation molding or non-stretching molding by a T-die is used as a release film or adhesive film substrate. It has already been proposed for use in films.

  However, in a release film or a protective film, a film obtained by inflation molding or non-stretching molding by a T die does not have sufficient strength.

  Further, it has already been proposed to biaxially stretch an ethylene / α-olefin random copolymer as a method for improving the transparency and mechanical strength of a random copolymer film of ethylene and α-olefin. However, it is not known that these are used for a base layer of a release film or an adhesive film.

  The present invention is based on the finding that a biaxially oriented film made of an ethylene copolymer is suitable as a base material for a protective film such as a release film and an adhesive film.

That is, in the present invention, a base material layer made of an ethylene copolymer (A) having a density in the range of 910 to 940 Kg / m ³ is biaxially oriented, and a release layer or an adhesive layer is provided on the base material layer. It is related with the laminated | multilayer film characterized by being laminated | stacked.

According to the present invention, by using a biaxially oriented film made of an ethylene copolymer (A) having a density in the range of 910 to 940 Kg / m ³ as the base material layer, A laminated film with excellent dimensional stability and shrinkage at a temperature of 100 ° C. of less than 5% in the machine direction (MD) and less than 5% in the transverse direction (TD) can be obtained. Various release films, adhesive films, and protective films It can be used as a film.

  Hereinafter, the laminated film of the present invention will be described.

[Ethylene polymer (A)]
The ethylene copolymer (A) used in the present invention is an ethylene copolymer having a density of 910 to 940 Kg / m ³ , preferably 915 to 935 Kg / m ³ .

  When the density is outside the above range, it may be difficult to form a biaxially stretched film.

As long as the ethylene copolymer (A) can be formed into a film, the melt flow rate (MF)
R: ASTM D1238 (load 2160 g, temperature 190 ° C.) is not particularly limited, but is usually in the range of 0.5 to 10 g / 10 minutes, preferably 0.8 to 5 g / 10 minutes.

  The density of the ethylene polymer (A) used in the present invention is measured by a density gradient tube.

  The ethylene-based copolymer (A) in the present invention includes ethylene and an α-olefin having 4 to 10 carbon atoms, such as 1-butene, 1-heptene, 1-hexene, 1-octene, 4-methyl-1-pentene. And a random copolymer with at least one α-olefin selected from α-olefins such as.

The ethylene copolymer (A) may be one type or a mixture of two or more types as long as it is within the above-mentioned density range. In particular, density 895~925Kg / m ^3, preferably an ethylene · alpha-olefin copolymer (A1) component and density 925~950Kg / m ³ in the range of 900~920Kg / m ^3, preferably 930~940Kg An ethylene copolymer (A) comprising an ethylene / α-olefin random copolymer (A2) component in the range of / m ³ is preferable, and the ratio thereof is (A1) 20 to 80% by weight and (A2). 80 to 20% by weight, preferably (A1) 30 to 70% by weight and (A2) 70 to 30% by weight (note that the total of (A1) + (A2) is 100% by weight).

  Such an ethylene-based copolymer (A) has a molecular weight distribution (weight average molecular weight: Mw, number average molecular weight: Mn, ratio: expressed as Mw / Mn) is usually 1.5 to 4.0, preferably Is preferably in the range of 1.8 to 3.5. This Mw / Mn can be measured by gel permeation chromatography (GPC). In addition, when an ethylene-type copolymer (A) consists of two components as mentioned above, it is desirable to have said molecular weight distribution about each component.

  These ethylene / α-olefin copolymers (A1) can be produced by a conventionally known production method using a Ziegler catalyst, a single site catalyst or the like. Among these, a copolymer obtained by a single site catalyst (metallocene catalyst) is particularly preferable. The catalyst containing the metallocene compound is preferably formed from (a) a transition metal metallocene compound, (b) an organoaluminum oxy compound, and (c) a carrier, and if necessary, these components and (D) It may be formed from an organoaluminum compound and / or an organoboron compound.

  An olefin polymerization catalyst containing such a metallocene compound and a method for preparing an ethylene / α-olefin copolymer (A1) using the catalyst are described in, for example, JP-A-8-269270.

  The ethylene copolymer (A) may be blended with a high-pressure method low-density polyethylene, a medium-density polyethylene resin, or the like, if necessary. When mix | blending these, 10-100 weight part with respect to 100 weight part of ethylene-type copolymers (A), 30-90 weight part is suitable especially.

  Another component that is particularly desirable to be blended in the ethylene copolymer (A) of the present invention is high-pressure low-density polyethylene.

The high-pressure low-density polyethylene usually has a density in the range of 910 to 935 Kg / m ³ , preferably 915 to 930 Kg / m ³ . These high-pressure low-density polyethylenes are generally ethylene homopolymers polymerized under high pressure, but examples include copolymers with other α-olefins less than 5% by weight or vinyl compounds such as vinyl acetate. can do.

  The melt flow rate (MFR: ASTM D1238 load 2160 g, temperature 190 ° C.) of the high-pressure low-density polyethylene is not particularly limited as long as it has the ability to form a composition with the above-mentioned ethylene copolymer (A) into a film. However, it is usually 0.1 to 30 g / 10 min, preferably 0.1 to 10 g / 10 min.

  As long as the object of the present invention is not impaired in the composition with the ethylene polymer (A) or the high-pressure method low-density polyethylene, the antioxidant, weathering stabilizer, antistatic agent, antifogging agent, Additives such as antiblocking agents, lubricants, nucleating agents, pigments, or other polymers can be blended as necessary.

[Biaxially oriented substrate layer]
The base material layer in this invention consists of said ethylene-type copolymer (A) or a base material layer which has it as a main component, and is biaxially oriented.

  The thickness of a base material layer is 5-150 micrometers normally, Preferably it is 15-80 micrometers.

  In addition to a single layer, the base material layer may be a composite film comprising a surface layer / intermediate layer / surface layer. The resin composition of the surface layer and the intermediate layer on both sides may be the same or different. For example, as a composition of the surface layer, 10 to 30 parts by weight of high density polyethylene is further blended with respect to 100 parts by weight of the composition of the above-mentioned ethylene copolymer (A) to improve the releasability of the layer. .

  Furthermore, in order to improve the adhesion with the release layer or the adhesive layer, the surface of the surface of the base material layer to be bonded to the release layer or the adhesive layer is treated with, for example, a corona treatment. Surface activation treatment such as flame treatment, plasma treatment, and undercoat treatment may be performed.

[Manufacturing method of base material layer]
The biaxially oriented base material layer can be formed by successively biaxially or simultaneously biaxially stretching an unstretched film.

  The unstretched film used is formed by a normal extrusion method. In the case of a multilayer film, it is formed by coextrusion.

A flat system (tenter system) is exemplified for the sequential biaxial stretching.
In these biaxial stretching, the stretching ratio in one direction is 3 to 14 times, preferably 5 to 10 times, and the stretching ratio in the other direction is 3 to 14 times, preferably 5 to 10 times in the longitudinal (MD) direction and Biaxially stretched in the transverse (TD) direction.

  In the case of biaxial stretching by the flat method, usually, a sheet obtained by extrusion molding is stretched in the longitudinal direction at a temperature range of 90 to 125 ° C, and then stretched in the transverse direction at a temperature range of 90 to 130 ° C. can get. After biaxial stretching, it is desirable to perform heat setting in the temperature range of 80 to 150 ° C. depending on the application. The heat set may be either online or offline. The temperature of the heat setting is appropriately changed according to the target heat shrinkage rate.

  Especially in applications where dimensional stability is required, the shrinkage rate of the base material layer at 100 ° C. is usually less than 5%, preferably less than 4%, more preferably 3 by performing heat treatment in the machine direction (MD). % And in the transverse direction (TD) usually less than 5%, preferably less than 4%, more preferably less than 3%. Furthermore, the shrinkage ratio of the base material layer at 60 ° C. can be 0% of the base material layer in both the vertical direction (MD) and the horizontal direction (TD).

  Here, the shrinkage rate (%) of the film is determined by measuring a strip-shaped test piece having a width of 15 mm and a length of 200 mm so that the length direction from the sample film is the film flow direction (MD) and the width direction (TD). This is a value obtained by cutting out and opening holes at intervals of 150 mm, leaving them in an oven at a predetermined temperature for 15 minutes, taking them out and allowing them to cool to room temperature, then measuring the distance between the holes and determining the shrinkage.

Further, the tensile modulus (MPa) of the base material layer is 350 to 600 MPa in the machine direction (MD), particularly 440 to 550 MPa, 400 to 1200 MPa in the transverse direction, preferably 600 to 1100 MPa, more preferably 800 to 1000 MPa. is there. If the tensile modulus (MPa) of the base material layer is in such a range, it is desirable in that it can be a base material layer exhibiting an excellent shrinkage rate (%). Further, the strength at break of the base material layer is preferably in the range of 70 to 200 MPa in the machine direction (MD), particularly 100 to 150 MPa, and 100 to 200 MPa in the transverse direction (TD), particularly 140 to 180 MPa. When the strength at break (MPa) of the base material layer is in such a range, it is desirable in that it can be a base material layer exhibiting an excellent shrinkage rate (%). Further, the elongation at break (%) of the base material layer is preferably 250% or less in the machine direction (MD), preferably 230% or less, and 100% or less in the transverse direction (TD), particularly 80% or less. When the elongation at break (%) of the base material layer is in such a range, it is desirable in that the base material layer can exhibit an excellent shrinkage rate (%).
Examples of the method for forming the release layer or the adhesive layer on the base material layer include a dry laminating method, a solventless laminating method, an extrusion laminating method, and a coextrusion molding method.
[Release layer]
Various conventionally well-known things are illustrated by the release layer laminated | stacked on a base material layer. The material for forming the release layer is not particularly limited as long as it has releasability, such as a curable silicone resin, a silicone resin modified by graft polymerization with a urethane resin, an epoxy resin, or the like. Is exemplified. Among these, what has a curable silicone resin as a main component is preferable.

  For curable silicone resin, any curing reaction type such as solvent addition type, solvent condensation type, solvent ultraviolet curing type, solventless addition type, solventless condensation type, solventless ultraviolet curing type, solventless electron beam curing type, etc. can do. For example, KS-774, KS-775, KS-778, KS-779H, KS-856, X-62-2422, X-62-2461, KNS-305, KNS-3000, manufactured by Shin-Etsu Chemical Co., Ltd. Examples include X-62-1256, LTC750A, LTC300B, SD7223, SD7226, SD7229, SRX-210 and the like manufactured by Toray Dow Corning Silicone.

The coating amount of the release layer is usually 0.01 to 10 g / m ^2, is preferably in a range among them of 0.05-5 g / m ^2.

These release layers can be formed on only one side or both sides of the base material layer.
[Adhesive layer]
Various conventionally well-known things are illustrated by the adhesion layer laminated | stacked on a base material layer.

  As the pressure-sensitive adhesive, generally known acrylic, rubber-based, silicone-based and the like can be used without limitation. Furthermore, when it is set as a slightly adhesion layer, the composition which mix | blended petroleum resin etc. with the ethylene-alpha-olefin copolymer is illustrated. For example, an acrylic type is exemplified by an emulsion type, a solvent type, a rubber type is exemplified by an emulsion type, a solvent type, a hot melt type, and a silicone type is exemplified by a solvent type. These pressure-sensitive adhesives can be applied by various methods.

  For example, when applying a solvent-type pressure-sensitive adhesive, these pressure-sensitive adhesives are applied to the base material layer using a knife coater or a reverse coater. If necessary, release paper is temporarily laminated on the adhesive layer.

  Moreover, when using resin, such as an ethylene-alpha-olefin copolymer which mix | blended petroleum resin etc., as an adhesion layer, it shape | molds by dry lamination, extrusion coating, etc. to a base material layer.

  These adhesive layers can be formed on one side or both sides of the base material layer.

Next, the present invention will be described by way of examples.
(1) Melt flow rate (g / 10 min)
In accordance with ASTM D 1238, the measurement was performed under the conditions of a load of 2160 g and a temperature of 190 ° C.
(2) Density (Kg / m ³ )
The polymer strand obtained by measuring MFR was treated at 120 ° C. for 2 hours, slowly cooled to room temperature (23 ° C.) over 1 hour, and then measured by the D method (density gradient tube) according to JIS K 7112. did.
(3) Thermal contraction rate (%)
Cut out strip-shaped test pieces having a width of 15 mm and a length of 200 mm so that the length direction of the film is the film flow direction (MD) and the width direction (TD), and holes are formed at intervals of 150 mm. After leaving it in the oven for 15 minutes, it was taken out and allowed to cool to room temperature, and then the distance between the holes was measured to measure the shrinkage.
(4) Tensile modulus (MPa)
Based on JIS K7127, the tensile modulus in the machine direction (MD) and the transverse direction (TD) was measured using model RTC-1225 manufactured by Orientec Co., Ltd.
(5) Strength at break (MPa)
Based on JIS K7127, the strength at break in the machine direction (MD) and the transverse direction (TD) was measured using model RTC-1225 manufactured by Orientec Corporation.
(6) Elongation at break (MPa)
In accordance with JIS K 7127, the elongation at break in the machine direction (MD) and the transverse direction (TD) was measured using model RTC-1225 manufactured by Orientec Corporation.
Example 1
A composition comprising the following polymers (1), (2), and (3) (weight ratio 35:50:15 of (1) :( 2) :( 3)) was made into a twin-screw extruder manufactured by Ikegai Iron Works A composition was obtained using (46 mmφ).
(1) Polymer using ethylene-1-hexene random copolymer metallocene catalyst, density 905 Kg / m ³ , MFR; 0.5 g / 10 min.
(2) Ethylene-1-hexene random copolymer Polymer using metallocene catalyst, density: 915 Kg / m ³ , MFR: 0.5 g / 10 min.
(3) High pressure low density polyethylene density: 921 Kg / m ³ , MFR: 0.6 g / 10 min.

This composition was melt-extruded using a biaxially stretched film molding machine, shaped with a T-die, and then rapidly cooled on a cooling roll to obtain a sheet having a thickness of about 1.3 mm. This sheet was heated at 112 ° C. and stretched 5 times in the film flow direction (longitudinal direction). The 5-fold stretched sheet was heated at 116 ° C. and stretched 10 times in the direction perpendicular to the flow direction (lateral direction) to obtain a biaxially stretched ethylene copolymer film having a thickness of 40 μm.
The biaxially stretched ethylene copolymer film was used as a base material layer, and a silicone release agent was applied to one side of the film to form a release film. Also, an acrylic emulsion-type adhesive material was applied to form an adhesive film. These can be used as a release film or an adhesive film.
The shrinkage ratio of this base material layer was as follows.

Heating temperature (° C) Shrinkage rate (%)
Vertical direction (MD) Horizontal direction (TD)
50 0 0
60 0 0
70 0.5 0.1
80 0.8 0.1
90 1.5 0.4
100 2.6 1.6
110 3.8 3.8
120 4.8 6.2
Moreover, the physical property value of this base material layer was as follows.

Tensile modulus Tensile strength at break Elongation at break
(MPa) (MPa) (%)
MD TD MD TD MD TD
440 800 100 140 230 80

  The laminated film of the present invention can be widely used as various protective films in applications of release films and adhesive films. In particular, it can be used as an industrial material as a packaging material for applications requiring dimensional stability.

Claims (4)

Ethylene copolymer having a density in the range of 910~940Kg / m ³ (A) 100 parts by weight, and density composition including a high-pressure low density polyethylene 10 to 100 parts by weight in the range of 910~935Kg / m ³ base layer made of the object is oriented biaxially, and Ri release layer or an adhesive layer to the substrate layer name are stacked,
The said ethylene-type copolymer (A) is a copolymer of ethylene and a C4-C10 alpha olefin, The laminated film characterized by the above-mentioned . The laminated film according to claim 1, wherein the base material layer is a film stretched biaxially by sequential biaxial stretching or simultaneous biaxial stretching. 3. The laminated film according to claim 1, wherein the shrinkage rate at a temperature of 100 ° C. is less than 5% in the machine direction (MD) and less than 5% in the transverse direction (TD). The release film or adhesive film in any one of Claims 1-3 .