JPH07299853A - Easy tearing film and production thereof - Google Patents

Abstract

PURPOSE:To obtain an easy tearing film free from thickness irregularity and high in surface smoothness and uniformity by subjecting a non-compatible resin compsn. to extrusion molding. CONSTITUTION:A resin compsn. containing a propylene type polymer (A) such as polypropylene and a styrenic polymer (B) such as polystyrene in an A/B wt. ratio of 50/50-98/2 is subjected to extrusion molding. At this time, when the common logarithm value [log (MIA/MIB) of the ratio of the melt index MIA (g/10min) of the propylene type polymer at 230 deg.C under load of 2.16kg and the melt index MIB (g/10min) of the styrenic polymer at 200 deg.C under load of 5kg is X and the shearing speed at a die lip is r (sec<-1>), the resin compsn. is subjected to extrusion molding under conditions such that r is r>=(160-l35X) (1) when S is X>=0 and r is r>=(160--63X) (2) at the time of X<0 without being stretched.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an easily tearable film containing a propylene-based polymer and a styrene-based polymer as main components, which can be used as a packaging material having a high opening property, and a method for producing the film.

[0002]

2. Description of the Related Art As a film packaging material, various polymers such as polypropylene, polyethylene terephthalate, nylon, etc. are used, and the film is provided with a characteristic according to each polymer. However, since there is a limit to the properties that can be imparted by the polymer alone, a stretching treatment, a corona discharge treatment, and a composite by laminating and coating a plurality of polymer layers are being studied. For example, polypropylene or polyethylene is stretched to impart tearability to the film. However, when imparting tearability to the film by stretching, not only the stretching device and the work involved in the stretching operation are required, but also the cost becomes high, and the configuration of the stretching device (for example, stretching roll width) and its operability From the point of
When manufacturing films with different widths, it is necessary to change the configuration of the apparatus, etc., and thus the width of the film is limited. In addition, the stretched film is heat-sealed by heat sealing to generate wrinkles, which impairs the appearance.

On the other hand, if a technique of alloying a plurality of incompatible or low-affinity resins is used, the vapor barrier property, strength and heat resistance of the polymer alloy film are higher than those of a single polymer film. In many cases, properties such as tearability can be improved. Therefore, various studies have been made on the formation of composites using polymer alloys. For example, in Japanese Patent Laid-Open No. 1-153733,
A resin composition containing linear low-density polyethylene (LLDPE) and a thermoplastic resin that is incompatible with the linear low-density polyethylene and has a solubility coefficient of 9.0 or more in a specific ratio, A method of making a film that is easy to tear by hot melt extrusion is disclosed. Further, in JP-A-4-19137, two or more resin compositions which are incompatible with each other and have a large melting point difference, for example, a composition containing a high melting point nylon and a low melting point polyolefin is extruded and molded. It is disclosed to obtain a tearable laminated film by laminating with a base material.

The polymer alloy film as described above is
Although it has high tearability, when it is attempted to form a thin film, the film formation stability is low, and holes are easily formed in the film during film formation, and periodic streak-like thickness unevenness easily occurs, resulting in a smooth surface of the film. And the uniformity is reduced. In particular, when a film having a practical thickness of 50 μm or less (for example, about 10 to 30 μm) is formed, the above phenomenon appears remarkably. In order to suppress the thickness unevenness and obtain a film having high surface smoothness, the ratio of LLDPE and thermoplastic resin is set to the former / the latter as described in JP-A-1-153733.
It is considered that the latter is set to 99/1 to 80/20 and the amount of the thermoplastic resin used is greatly limited. However, when the surface smoothness is increased with such a composition ratio, not only the tearability of the film is lowered, but also when the film thickness is reduced, the thickness unevenness is still increased and the surface smoothness is lowered. Therefore, the application of the film using the polymer alloy is greatly limited.

The periodic thickness unevenness occurs in a long cycle of several seconds, and is not due to external factors such as mechanical vibrations caused by an extruder or a take-up machine, but the flow characteristics of the resin composition. It is presumed to be derived. That is, when a film is formed using a resin simple substance such as polypropylene, nylon, polyethylene, or polystyrene, even a thin film can be formed without any trouble. On the other hand, when trying to form a film by adding a small amount of an incompatible resin to the resin, the draft ratio (the take-up speed of the film and the extrusion of the resin at the die lip part) which was possible to form with the resin alone was formed. Periodic thickness unevenness also occurs in the speed ratio region. This cyclic thickness unevenness occurs when the draft ratio becomes large. For example, when an attempt is made to increase the draft ratio to increase the draft ratio to form a thin film of about 20 μm, the cyclic thickness unevenness occurs. It occurs remarkably. Then, in a film having periodic thickness unevenness, the thin portion has a thickness of about 10 μm and the thick portion has a thickness of 1 μm.
It will be more than 00 μm.

[0006]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an easily tearable film having a small thickness unevenness even if it is thin and having excellent tearability, and a method for producing the same.

Another object of the present invention is to provide an easily tearable film having a high surface smoothness and uniformity and suppressing the generation of wrinkles due to heat shrinkage, and a method for producing the film.

Still another object of the present invention is to provide a method capable of producing a film having the above-mentioned excellent properties in a stable, efficient and highly productive manner.

[0009]

Means for Solving the Problems As a result of intensive studies for achieving the above object, the present inventors have found that the shear rate during film formation has a great influence on the surface smoothness and film formation stability of the film. The present invention was completed.

That is, the method of the present invention is a method for producing a film by extruding a resin composition containing a propylene polymer (A) and a styrene polymer (B) as main components from a die. 230 ° C. and load 2.
The ratio of the melt index MI _A (g / 10 min) propylene-based polymer (A) at 16 kg, and the melt index MI _B of styrene polymer at 200 ° C. and a load 5kg (B) (g / 10 min) Common logarithm of [log
(MI _A / MI _B )] is X, and the shear rate at the die lip is r (sec ⁻¹ ), an easily tearable film is produced by extrusion molding under the following conditions.

(1) When X ≧ 0, r ≧ (160-135X) (2) When X <0, r ≧ (160-63X) The propylene-based polymer (A) such as polypropylene.
The melt index MI _A 0.5~30 (g / 10
Min) may be about, melt index MI _B of styrenic polymers such as polystyrene (B) is 0.5
It may be about 40 (g / 10 minutes). The melt index ratio MI _A / MI _B is 0.05 to 60.
It is often a degree. In the above method, in extrusion molding, a film-shaped or sheet-shaped molten resin composition,
For example, the film can be formed while taking it off at a draw ratio of about 5 to 70. The ratio of the propylene polymer (A) and the styrene polymer (B) can be selected within a wide range, and for example, the former (A) / (B) = 50/50 to 98 /
It may be about 2 (weight ratio). The resin composition,
Further, a compatibilizing agent such as hydrogenated styrene-based monomer-conjugated diene-based copolymer may be included.

The easily tearable film of the present invention thus obtained does not have thickness unevenness even if the thickness is small, and has high surface smoothness. That is, even for a film having an average thickness of about 3 to 35 μm, the thickness unevenness per 5 m in the film-drawing direction is within ± 100% of the average thickness. The easily tearable film may be laminated on a substrate and used as an easily tearable laminated film.

The shear rate r (sec.
^-1 ) is the flow rate of the resin composition at the die lip Q (c
m ³ / min), the die lip width is W (mm), and the die lip opening is H (mm).

R = [10 ² × Q] / [WH ² ] The present invention will be described in detail below.

The propylene-based polymer (A) includes a propylene homopolymer and a copolymer of propylene and another olefin. Such olefins include ethylene; 1-butene, 4-methyl-1-butene, 1-pentene, 3-methyl-1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1
Other olefins such as -decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene and the like having 4 to 20 carbon atoms: isobutene.

The propylene-based polymer may be a copolymer with another monomer copolymerizable with propylene.
Examples of the copolymerizable monomer include acrylic acid,
Ethylenically unsaturated carboxylic acids such as methacrylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, crotonic acid, isocrotonic acid, mesaconic acid, angelic acid;
Ethylenically unsaturated polycarboxylic acids such as maleic anhydride, citraconic anhydride, and itaconic anhydride, and acid anhydrides thereof;
Acrylic acid esters and methacrylic acid esters; ethylenically unsaturated carboxylic acid esters such as vinyl esters of carboxylic acids (eg vinyl acetate, vinyl propionate etc.); cyclic olefins such as norbornene, ethylidene norbornene and cyclopentadiene; and dienes etc. It is illustrated. The copolymerizable monomer may be used alone or in combination of two or more.

As the diene component, chain conjugated dienes such as 1,3-butadiene and isoprene; 1,4-hexadiene, 1,6-octadiene, 2-methyl-1,5-
Hexadiene, 6-methyl-1,5-heptadiene, 7
Chain non-conjugated dienes such as -methyl-1,6-octadiene; cyclohexadiene, dicyclopentadiene, methyltetrahydroindene, 5-vinylnorbornene, 5
-Ethylidene-2-norbornene, 5-methylene-2-
Cyclic non-conjugated dienes such as norbornene, 5-isopropylidene-2-norbornene, 6-chloromethyl-5-isopropylenyl-2-norbornene; 2,3-diisopropylidene-5-norbornene, 2-ethylidene-3-isopropylidene Ridene-5-norbornene, 2-propenyl-
Examples include cyclic conjugated dienes such as 2,2-norbornadiene.

Preferred propylene-based polymers include polypropylene; propylene and ethylene or C4-6.
Included are copolymers with some α-olefins. The propylene-based copolymer may be a block copolymer, but a preferable propylene-based copolymer includes a random copolymer. In the propylene-based copolymer,
The propylene content is 65% by weight or more. More preferable propylene-based polymers include polypropylene (for example, crystalline polypropylene such as isotactic polypropylene) and ethylene-based propylene.
A propylene copolymer (for example, a crystalline ethylene-propylene copolymer), particularly a crystalline polypropylene is preferable. When such a propylene-based polymer is combined with a styrene-based polymer, the easy tearability of the film can be enhanced. These propylene-based polymers can be used alone or in combination of two or more.

The molecular weight of the (A) propylene-based polymer is
For example, a weight average molecular weight of 1 × 10 ^{4 to} 100 × 10 ⁴ ,
It is preferably about 5 × 10 ⁴ to 50 × 10 ⁴ .

The styrene-based polymer (B) includes a homopolymer or a copolymer containing a styrene-based monomer as a main component. Polymerization methods for obtaining the styrene-based polymer include bulk polymerization, solution polymerization, Either suspension polymerization or emulsion polymerization may be used.

The styrene-based polymers include homopolymers or copolymers of styrene-based monomers such as styrene, α-methylstyrene and chlorostyrene; styrene-based monomers and vinyl monomers (eg acrylonitrile). Copolymers with unsaturated nitriles such as (meth) acrylic acid, (meth) acrylic acid esters, α, β-monoolefinically unsaturated carboxylic acids such as maleic anhydride or acid anhydrides or esters thereof); A copolymer of a styrene-based monomer and a diene (for example, butadiene, isoprene, etc.); a rubber-modified styrene-based resin obtained by polymerizing at least a styrene-based monomer in a rubber component, and the like are included. These styrene polymers can be used alone or in combination of two or more.

The rubber-modified styrene resin is, for example, an ABS resin obtained by graft-polymerizing a styrene monomer and acrylonitrile onto a diene rubber elastomer such as high impact polystyrene (HIPS) and polybutadiene.
AAS resin obtained by graft-polymerizing styrene-based monomer and acrylonitrile on acrylic rubber, ACS resin obtained by graft-polymerizing styrene-based monomer and acrylonitrile on chlorinated polyethylene, styrene-based monomer and acrylonitrile on ethylene-vinyl acetate copolymer Graft-polymerized polymer, ethylene-propylene rubber styrene-based monomer and vinyl monomer (eg, acrylonitrile or methyl methacrylate) Acrylonitrile-grafted polymer, polybutadiene with styrene-based monomer and methyl methacrylate Graft-polymerized MBS resin and the like are included.

Preferred styrenic polymers include, for example:
Styrene- (meth) acrylic acid ester copolymers such as polystyrene (GPPS), styrene- (meth) acrylic acid copolymer, styrene-methyl methacrylate copolymer (MAS resin), styrene-maleic anhydride copolymer ,
A styrene-acrylonitrile copolymer (AS resin) and a rubber-modified styrene resin are included. Particularly preferred styrene-based polymers include highly transparent styrene-based polymers (for example, polystyrene, styrene- (meth) acrylic acid copolymer, styrene-maleic anhydride copolymer methyl methacrylate-styrene copolymer, etc. Styrene- (meth) acrylic acid ester copolymer, styrene-acrylonitrile copolymer, etc.) are included.

The molecular weight of the styrene polymer (B) is, for example, about 1 × 10 ^{4 to} 100 × 10 ⁴ , preferably about 2 × 10 ⁴ to 50 × 10 ⁴ , the weight average molecular weight. In the case of rubber-modified styrenic resin, the molecular weight of the polystyrene part is, for example, weight average molecular weight 3 × 10 ^{3 to} 100 × 1.
It is often 0 ⁴ , preferably about 5 × 10 ³ to 50 × 10 ⁴ .

When a styrene-based polymer, particularly a highly transparent styrene-based polymer such as polystyrene, is used in combination with a propylene-based polymer, the tearability is excellent and
Despite the fact that both are incompatible with each other, a highly transparent film can be obtained.

The ratio of the propylene-based polymer (A) and the styrene-based polymer (B) is not particularly limited and can be selected within a range in which tearability can be imparted. For example, the former (A) / the latter (B) (weight) Ratio) = 50/50 to 98/2, preferably 50/50 to 90/10, more preferably 55/45
It is about 85/15 and often 55/45 to 80/20. In the film obtained by using such a resin composition, the dispersed phase of the styrene-based polymer seems to be dispersed in the continuous phase of the propylene-based polymer. If the proportion of the propylene-based polymer is less than 50% by weight, the styrene-based polymer forms a continuous phase of the film, and the film strength is likely to decrease, and the processability of the film and the smoothness of the film surface are likely to decrease. If the proportion of the propylene-based polymer exceeds 98% by weight, the tearing property tends to deteriorate.

The melt index MI _A propylene-based polymer at 230 ° C. and a load 2.16 kg, typically 0.5 (g / 10 min) or more (e.g., 0.5 to 30 (g
/ 10 min)), preferably 1 to 25 (g / 10 min), more preferably 1.5 to 20 (g / 10 min), and the melt index of the styrene polymer at 200 ° C. and a load of 5 kg. MI _B is, for example 0.5~40 (g
/ 10 minutes), preferably 1 to 20 (g / 10 minutes), and more preferably 2 to 15 (g / 10 minutes). When the melt index of the component (A) and / or the component (B) is out of the above range, film moldability, film formation stability, film strength, etc. may be reduced.

[0028] The ratio MI _A / MI _B with a melt index MI _B of the propylene polymer melt index MI _A and a styrene-based polymer, for example, 0.05 to 6
0, preferably 0.1-30, more preferably 0.1
It is about 5 to 10. The ratio MI _A / MI _B is 0.0
If it is less than 5, the processability of the film may be lowered, and if it exceeds 60, the melt viscosity of the propylene-based polymer may be small, and the tearability of the film may be lowered. In addition,
The melt index ratio MI _A / MI _B is 1 or more, preferably 1.1 to 60, more preferably 1.5 to 3
When it is 0, especially about 2 to 10, the film formation stability during film formation can be enhanced.

The propylene polymer and the styrene polymer are incompatible with each other. Therefore, the strength of the film may decrease, peeling may occur at the surface layer of the film, and the appearance may be impaired. In such a case, it is effective to add the compatibilizer (C) to the resin composition.

The compatibilizing agent (C) is not particularly limited as long as it is a compound having compatibility or affinity with the incompatible polymer. Preferred compatibilizers include, for example, styrene-based monomer-conjugated diene-based copolymers such as random copolymers of styrene-based monomers and conjugated dienes, block copolymers or hydrogenated copolymers thereof. . More preferable compatibilizers include hydrogenated styrene-based monomer-conjugated diene-based copolymers and the like.

The hydrogenated styrenic monomer-conjugated diene copolymer is (a) a hydrogenated copolymer obtained by hydrogenating a random or block copolymer of a styrene monomer and a conjugated diene. In addition, (b) a random or block copolymer of a styrene monomer and one or more α-olefins is also included.

The styrene-based monomer includes the above-exemplified monomers. The conjugated diene includes, for example, butadiene, isoprene, 2-ethylbutadiene and the like having 4 carbon atoms.
-10 conjugated dienes and the like are included. The α-olefin has 2 carbon atoms such as ethylene, propylene and butylene.
.About.6 .alpha.-olefins and the like are included.

The hydrogenated styrenic monomer
The conjugated diene-based copolymer may be modified with maleic anhydride, (meth) acrylic acid, (meth) acrylic acid ester, glycidyl (meth) acrylate or the like.

Preferred hydrogenated styrenic monomer-conjugated diene copolymers include styrene-based monomers such as hydrogenated styrene-butadiene random or block copolymers, hydrogenated styrene-isoprene random or block copolymers. Hydrogenated product of copolymer with conjugated diene having 4 to 6 carbon atoms; and styrene-ethylene / butylene copolymer (SEB), styrene-ethylene.
Styrene-based monomers such as butylene-styrene block copolymer (SEBS), styrene-ethylene / propylene block copolymer (SEP), styrene-ethylene / propylene-styrene block copolymer (SEPS), and carbon number 2
The copolymer with 2 or more types (for example, 2-3 types) of (alpha) -olefin of 4-4 etc. can be illustrated.

The hydrogenated styrenic monomer
The content of styrene units in the conjugated diene-based copolymer can be selected within a range that does not impair tearability, etc., but is usually 20-75.
It is about 20% by weight, preferably about 22 to 50% by weight.
When the content of the styrene unit is within the above range, the strength of the film is improved, and the fuzz at the cut end when the film is slit can be significantly suppressed.

The above-mentioned (a) hydrogenated copolymer is prepared by a conventional method, for example, by copolymerizing styrene and a conjugated diene, and a part of the aliphatic double bond contained in the obtained copolymer or It can be obtained by hydrogenating the whole (see, for example, US Pat. No. 3,595,942). By hydrogenation, the benzene ring derived from the styrene-based monomer may also be hydrogenated to form a cyclohexane ring,
Usually, double bonds derived from conjugated dienes are often hydrogenated. The hydrogenation rate of the double bond derived from the conjugated diene is usually 50% or more, preferably 70% or more.

The copolymer (b) can be obtained by polymerizing a styrene-based monomer and one or more α-olefins by a conventional method.

The amount of the compatibilizing agent (C) used is within a range capable of improving characteristics such as appearance of the film, peeling of the surface layer of the film, and piercing strength of the film. For example, the propylene polymer (A) and the styrene polymer (B) are used. 30 parts by weight or less (for example, 0.1 to 30 parts by weight), preferably 0.5 to 20 parts by weight, more preferably 1 to 10 parts by weight, and particularly about 100 parts by weight with 2 to 10 parts by weight,
In most cases, about 2.5 to 7.5 parts by weight is used. When the amount of the compatibilizer used exceeds 30 parts by weight with respect to 100 parts by weight of the total amount of (A) and (B), the rigidity of the obtained film is lowered, the flexibility is increased, and the tearability is increased. It tends to decrease.

The above-mentioned resin composition for obtaining the easily tearable film may contain other thermoplastic resins and various additives such as heat resistance and light resistance stability such as antioxidants and ultraviolet absorbers, if necessary. Agent, chlorine scavenger, plasticizer, antistatic agent,
It may contain organic or inorganic lubricants, dyes and pigments, fillers and the like.

The easily tearable film of the present invention is characterized by high surface smoothness and uniformity even if the film is thin.
The thickness of the film is not particularly limited and is, for example, 5 to 10
Although it can be selected in the range of 0 μm, preferably about 8 to 50 μm, the present invention is suitably applied to a thin film, for example, a film having an average thickness of 5 to 35 μm, preferably 10 to 30 μm, more preferably 15 to 30 μm. To be done. In addition, the thickness unevenness of the film is, for example, within ± 100%, preferably within ± 50%, and more preferably within ± 30% with respect to the average thickness per 5 m in the MD direction (drawing direction of the film), ± It is often within 20%.

The easily tearable film of the present invention may be coated with a coating layer such as a slipping layer or a gas barrier layer or a laminate layer as long as the tearability is not impaired. Further, the film may be subjected to surface treatment such as corona discharge treatment, flame treatment, ultrasonic treatment, and plasma treatment. If necessary, characteristics such as tear strength and breaking strength of the tearable film may be adjusted by uniaxial or biaxial stretching treatment. The draw ratio in at least one direction can be appropriately selected within a range of, for example, about 1.1 to 2.5 times.

The easily tearable film of the present invention can be used not only as a monolayer film but also as an easily tearable laminated body (easily tearable laminated film) by laminating it with a base material layer. That is, when an easily tearable film is laminated on an aluminum foil or the like used as a lid material in PTP (Press Through Pack) packaging or the like, by pressing the bottom of the container without significantly increasing the burst strength of the lid material, The lid material or film can be easily ruptured, and the contents such as tablets can be easily taken out. In addition, when an easily tearable film is laminated on paper such as kraft paper to form a sealed package, it can be easily torn along the tearing direction of the paper without significantly increasing the tear resistance of the paper. . Furthermore, when it is used as a sealing film for a liquid outlet such as brick packaging, it can be easily broken through with a straw or the like.

As the base material layer, an easily rupturable base material, for example, an olefin polymer such as polyethylene and polypropylene, a polyester such as polyvinyl chloride and polyethylene terephthalate, or a uniaxially or biaxially stretched polymer such as a styrene polymer. Film; glassine paper,
Paper such as imitation paper and white cardboard; metal foil such as aluminum.

Such a laminate is obtained, for example, by laminating the easily breakable base material layer and the easily tearable film by a conventional method such as adhesion, extrusion lamination, thermocompression bonding (thermal adhesion) or the like. You can

The film of the present invention is used in various applications such as packaging bags, adhesive tape substrates, brick packaging substrates, PTP (Press Through Pack) packaging substrates used for individual packaging of tablets and the like. Available.

The film of the present invention is easy to tear in the take-up direction of the film without forming perforations or notches or highly stretched, and can be torn linearly very easily. That is, when tearing in one direction by hand, not only the initial tear resistance (tearing resistance) but also the subsequent tear propagation resistance is extremely small, and whiskers do not occur at the cut end. Therefore, although it is easy to tear linearly in a specific direction, it is hard to tear in other directions. Further, not only the surface smoothness and uniformity are high, but also the heat shrinkage and the generation of wrinkles due to heat sealing and the like can be suppressed, so that it can be suitably used for pouch packaging and container packaging.

The easily tearable film of the present invention can be produced by extruding the resin composition by a conventional method such as a T-die molding method or an inflation molding method.

The feature of the present invention is that a molten resin composition is extruded from a die at a specific shear rate in association with the melt index of the propylene polymer (A) and the styrene polymer (B) to form a film. There is a point to gain. That is, the melt index MI _A (g / g) of the propylene-based polymer (A) at 230 ° C. and a load of 2.16 kg.
10 minutes), melt index MI _B of styrene polymer at 200 ° C. and a load 5kg (B) (g / 10
Min) Ratio of common logarithm [log (MI _A / MI _B )]
Is X and the shear rate at the die lip is r (sec ^-1 ), a film is obtained by extrusion molding under the following conditions.

(1) When X ≧ 0, r ≧ (160-135X) (2) When X <0, r ≧ (160-63X) In addition, in order to obtain a high-quality film having high surface smoothness. The preferred shear rate r (sec ^-1 ) is as follows.

(1) When X ≧ 0, (165-135X) ≦ r, preferably (165-135X) ≦ r ≦ (410-135X), more preferably (167-135X) ≦ r ≦ (360- 135X), especially (170-135X) ≦ r ≦ (310-135X) in many cases.

(2) When X <0, (165-63X) ≦ r, preferably (165-63X) ≦ r ≦ (410-63X), more preferably (167-63X) ≦ r ≦ (360- 63X), especially (170−63X) ≦ r ≦ (310−63X).

When extruded at the shear rate in association with the melt index of the components (A) and (B),
It is possible to stably obtain a film which has little unevenness in thickness regardless of the thickness and has not only tearability but also surface smoothness and uniformity. In particular, even if the film has a practical thickness of 50 μm or less, for example, about 10 to 30 μm, it is possible to form an easily tearable film with high surface smoothness and uniformity without periodic thickness unevenness or perforation. it can.

In forming the film, the molten film or sheet resin composition discharged from the die is
Even if it is cooled and formed into a film without stretching, high tearability is exhibited. Therefore, not only a stretching device is not required, but also the time, work and cost required for the stretching process can be saved and the productivity of the film can be remarkably improved.
Moreover, since the film width is not restricted by the stretching process, a wide film can be easily obtained. Furthermore, since the stretching treatment is not necessary, even if the obtained film is subjected to heat sealing, it does not shrink due to heat. Therefore, even when subjected to heat sealing, the appearance is impaired in pouch packaging for storing contents in bag-shaped packaging materials, container packaging for sealing the opening of the container for storing contents with a lid material, etc. There is no.

In the T-die molding method, the resin composition containing the propylene-based polymer (A) and the styrene-based polymer (B) as the main components is melted by an extrusion molding machine and extruded from the T-die and taken up. Meanwhile, the film may be formed without stretching. In the T-die molding method, the draw ratio (the speed V at which the molten resin is discharged from the die lip
The ratio of 1 to the winding speed V2 of the formed film V1 / V
In 2), for example, the film formation is often carried out while taking it off at 5 to 70, preferably 10 to 60, and more preferably 20 to 50.

Further, in the inflation molding method, when the molten resin composition is extruded from a circular die, it may be formed into a film by expanding the resin composition into a baffle and taking it out. In the inflation molding method, the ratio (deformation ratio) of the draw ratio (melt expansion ratio) V to the blow ratio (expansion ratio) D (deformation ratio) V / D = 0.5 to 8, preferably 0.5 to 5, and more preferably 0. The draw ratio and the blow ratio are, for example, 1 to 2 for the draw ratio.
0 and a blow ratio of about 1 to 10. The "draw ratio" and the "blow ratio" for a resin melt melted at a temperature higher than the melting point are distinguished from "stretching" performed at a temperature equal to or lower than the melting point of the polymer.

A preferred method uses the T-die molding method. In film forming, the distance from die to chill roll (cooling roll) (ie air gap)
It is also possible to obtain a film having a high surface smoothness by adjusting.

[0057] In the film forming, a melt index MI _A propylene-based polymer is higher than the melt index MI _B of styrene polymer (i.e., low melt viscosity) as a tendency to formability stabilization of the film. However, even when the MI _B of styrene polymer than MI _A propylene-based polymer is large, in the present invention, by increasing the shear rate, it can improve the uniformity and surface smoothness of the film. In order to increase the shear rate, the discharge amount of the resin may be increased, or if the discharge amount is the same, the width of the die lip and / or the die lip opening may be reduced.

The film forming temperature can be selected according to the kinds of the components (A) and (B), and is, for example, 300 ° C. or lower, preferably 170 to 270 ° C., more preferably 200 to 26.
It is about 0 ° C.

The resin composition containing the propylene polymer (A) and the styrene polymer (B) may be mixed and supplied to an extruder, and melt-kneaded in the extruder to disperse the resin. Pellets obtained by previously melt-kneading the resin composition may be supplied to an extruder. The resin composition can be prepared by a conventional method, for example, using a mixer such as a ribbon blender, a tumble mixer or a Henschel mixer. In addition, the pellets include an open roll, a Banbury mixer, a single screw extruder, a twin screw extruder,
It can be prepared using a single screw reciprocating screw kneader.

The easily tearable film and the laminated film using the same of the present invention are used for individual packaging such as packaging bags, adhesive tape substrates, flick packaging substrates and tablets.
It can be used for various applications such as TP (Press Through Pack) packaging base materials.

[0061]

EFFECTS OF THE INVENTION The easily tearable film of the present invention has a small thickness unevenness even if it is thin, and has high surface smoothness and uniformity.

In the method of the present invention, by adjusting the shear rate in relation to the melt index of the propylene-based polymer (A) and the styrene-based polymer (B), even if the thickness is thin, the thickness unevenness is small and excellent. An easily tearable film having tearability can be produced. In addition, the obtained film has high surface smoothness and uniformity, and since it does not need to be stretched, wrinkles due to heat shrinkage can be suppressed. Furthermore, since the film can be formed while being taken up without stretching, a film having the above-mentioned excellent properties can be produced stably and efficiently with high productivity.

[0063]

The present invention will be described in more detail based on the following examples, but the invention is not intended to be limited by these examples.

The polymers used in the examples and comparative examples and their abbreviations are as follows. MI indicates a melt index (unit: g / 10 minutes).

[Polypropylene (PP)] Polypropylene (PP-1): YK manufactured by Ube Industries, Ltd.
121 [MI: 3 (230 ° C., load 2.16 kg)] Polypropylene (PP-2): FM manufactured by Ube Industries, Ltd.
101A [MI: 9 (230 ° C, load 2.16 kg)] Polypropylene (PP-3): S1 manufactured by Ube Industries, Ltd.
15M [MI: 15 (230 ° C., load 2.16 kg)] [Polystyrene (PS)] Polystyrene (PS-1): M manufactured by Sumitomo Chemical Co., Ltd.
140 [MI: 10 (200 ° C., load 5 kg)] Polystyrene (PS-2): M manufactured by Sumitomo Chemical Co., Ltd.
183 [MI: 4 (200 ° C, load 5 kg)] Polystyrene (PS-3): G1 manufactured by Nippon Steel Chemical Co., Ltd.
2-55 [MI: 2.2 (200 ° C, load 5 kg)] [Styrene-ethylene / butylene-styrene block copolymer (SEBS)]: Asahi Kasei Corporation H1061 [MI: 0.1 (230
C, load 2.16 kg)] Examples 1-5, Comparative Examples 1-3 Polypropylene (PP-1 to 3), polystyrene (PS-1 to 3) and styrene-ethylene / butylene-styrene blocks in the proportions shown below. Copolymer (SEBS)
Was previously kneaded with a Henschel mixer, and the obtained resin composition was supplied to a uniaxial extruder (L / D = 26) of 65 mmφ and melt-kneaded, and a film (average thickness 20 μm was obtained by a T-die method under the following conditions. ) Got. As a T-die,
The one provided with a coat hanger manifold was used. Further, the shear rate at the die lip was adjusted by changing the screw rotation speed and adjusting the discharge amount of the resin composition.

[Resin composition (weight ratio)] Example 1: PP-1 / PS-2 / SEBS =
75/25/5 Example 2, Comparative Example 1: PP-1 / PS-1 / SEBS =
75/25/5 Example 3, Comparative Example 2: PP-2 / PS-3 / SEBS =
75/25/5 Example 4, Comparative Example 3: PP-2 / PS-2 = 75/25 Example 5: PP-3 / PS-3 / SEBS =
75/25/5 [Molding conditions] Cylinder and die temperature 250 ° C or less T-die die lip width 1500 mm Die lip opening 600 μm Draw ratio about 30 In addition, the thickness unevenness (μm) of the film is 5 m long in the take-up direction. The thickness was measured in the (MD direction) at a pitch of 50 mm, and the difference between the maximum value and the minimum value was evaluated by the following formula.

Δt = [maximum thickness (μm) −minimum thickness (μm)] Further, the thickness unevenness (±%) is calculated from the maximum thickness and the minimum thickness by the following formula, and the surface smoothness of the film is calculated according to the following criteria. The sex was evaluated.

Thickness unevenness (±%) = [Δt / average thickness (μm)] / 2 ×
100 ◯: Thickness unevenness is ± 100% with respect to the average thickness of the film
Within x: Thickness unevenness exceeds the above range. The results are shown in Table 1. In the table, the melt indexes of polypropylene and polystyrene measured under the above conditions are shown as MI _A (g / 10 minutes) and MI _B , respectively.
(G / 10 minutes), the common logarithm of the ratio of these melt indexes MI _A and MI _B [log (MI _A / MI _B )]
Is represented by X, the calculated value by the following formula regarding the minimum value (reference value) of the shear rate for obtaining a good quality film is represented by Y _s , and the shear rate at the die lip is represented by r (sec ⁻¹ ).

(1) When X ≧ 0, Y _s = (160−135X) (2) When X <0, Y _s = (160−63X)

[0070]

[Table 1] As is clear from Table 1, in each of the films of Comparative Examples, periodic thickness unevenness occurs in the range of ± 150% to ± 300%, and the surface smoothness is remarkably inferior. The obtained films all have thickness unevenness within ± 20%, and have high surface smoothness and uniformity. Each of the films of the examples could be easily torn linearly in the film-drawing direction.

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Claims (10)

[Claims] 1. A method for producing a film by extruding a resin composition containing a propylene-based polymer (A) and a styrene-based polymer (B) as main components from a die at 230 ° C. and a load of 2. Melt index MI _A of propylene-based polymer (A) at 16 kg (g / 10
Min) and the melt index MI _B (g / 10 min) of the styrenic polymer (B) at 200 ° C. and a load of 5 kg, where X is a common logarithmic value [log (MI _A / MI _B )], A method for producing an easily tearable film, which is extruded under the following conditions, where the shear rate at the die lip is r (sec ^-1 ). (1) When X ≧ 0, r ≧ (160-135X) (2) When X <0, r ≧ (160-63X) 2. A propylene-based polymer (A) having a melt index MI _A of 0.5 to 30 (g / 10 minutes) and a styrene-based polymer (B) having a melt index MI _B of 0.
It is 5-40 (g / 10 minutes), and the ratio MI _A / MI _{B of the} melt index is 0.05-60.
A method for producing the easily tearable film described. 3. The method for producing an easily tearable film according to claim 1, wherein the film is formed while the film is drawn at a draw ratio of 5 to 70. 4. A propylene-based polymer (A) and a styrene-based polymer (B), the former (A) / the latter (B) = 50/5.
The method for producing an easily tearable film according to claim 1, wherein a resin composition containing 0 to 98/2 (weight ratio) is extruded. 5. The method for producing an easily tearable film according to claim 4, wherein the resin composition further contains a compatibilizing agent (C). 6. The method for producing an easily tearable film according to claim 5, wherein the compatibilizing agent (C) is a hydrogenated styrene monomer-conjugated diene copolymer. 7. The resin composition contains 0.1 to 30 parts by weight of a compatibilizer (C) based on 100 parts by weight of the total amount of the propylene polymer (A) and the styrene polymer (B). Item 3. A method for producing an easily tearable film according to Item 1. 8. A polypropylene (A) and a polystyrene (B), the former (A) / the latter (B) = 50/50 to 90.
Included in the ratio of / 10 (weight ratio), 230 ° C, load 2.1
The melt index MI _A polypropylene (A) at 6kg is 1 to 25 (g / 10 min), 200 ° C., load 5k
Melt index MI _B of polystyrene (B) in g
Of 1 to 20 (g / 10 minutes) and the melt index ratio MI _A / MI _B of 0.1 to 30 is extruded from a die to produce a film. When the common logarithm of the melt index ratio [log (MI _A / MI _B )] is X and the shear rate at the die lip is r (sec ⁻¹ ), extrusion is performed under the following conditions without stretching. A method for producing an easily tearable film to be molded. (1) When X ≧ 0, (165-135X) ≦ r ≦ (4
10-135X) (2) When X <0, (165-63X) ≦ r ≦ (41
0-63X) 9. The film obtained by the method according to claim 1, wherein the average thickness is 5 to 35 μm, and the thickness unevenness per 5 m in the take-up direction of the film is within ± 100% of the average thickness. Easy tear film. 10. An easily tearable film having an average thickness of 10 to 30 μm and a thickness unevenness per 5 m in the take-up direction of ± 50% or less of the average thickness is laminated on a substrate. Easily tearable laminated film.