JPH07292130A - Film and its production - Google Patents

Abstract

PURPOSE:To obtain a film having slight unevenness of thickness even in the case of (A) an olefin-based polymer and (B) a styrenic polymer at (50050) to (98/2) composition weight ratio of the polymers (A)/ (B). CONSTITUTION:This film consists essentially of (A) an olefin-based polymer and (B) a styrenic polymer at (50/50) to (98/2) composition weight ratio of the polymers (A)/(B). Polypropylene having >=4g/10min melt index (MIA1) measured under conditions of 230 deg.C and 2.16 kg load or polyethylene, etc., having >=0.1g/10 min (MIA2) measured under conditions of 190 deg.C and 2.16kg load are used as the olefin-based polymer (A) and polystyrene, etc., having <=8g/10 min melt index (MIB) measured under conditions of 200 deg.C and 5kg load are used as the styrenic polymer (B). The ratio of the melt indexes (MIA1/MIB) is >=2 and the ratio of the melt indexes (MIA2/MIB) is >=0.008.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an easily tearable packaging material, a film useful as a material for ultrafine fibers, a nonwoven fabric thereof, a filter and the like, and a method for producing the film.

[0002]

2. Description of the Related Art Films obtained by blending polyolefin and polystyrene have the property of being easily tearable, and are therefore used as packaging materials, or by tearing the film to prepare ultrafine fibers for processing nonwoven fabrics and filters. Used. Also, depending on the composition ratio of polyolefin and polystyrene, gas permeability (or barrier) of water vapor etc.
Since the property can be adjusted, a film having a desired gas permeability can be obtained depending on the application.

For example, in JP-A-64-56740, a resin mixture comprising 50 to 95% by weight of a propylene (co) polymer and 5 to 50% by weight of a styrene (co) polymer is molded. An easily tearable heat-sealing film is disclosed.

However, as in this example, in general, (A)
In the film in which the composition ratio of the olefin polymer and the (B) styrene polymer is in the range of (A) / (B) = 50/50 to 98/2 (weight ratio), a polyolefin film or polystyrene is contained. Unlike a film whose amount is larger than that of polyolefin, the film formation stability is extremely low. That is, when polyolefin is used alone or when the content of polystyrene is high, even if a film is formed with a draft ratio that allows stable production, holes are formed in the film and periodic thickness unevenness occurs. This phenomenon is remarkable especially when a thin film is formed (when the draw ratio is high). The thickness unevenness is not caused by the rotation unevenness of the machine at the time of extrusion or the pressure fluctuation accompanying it, but is caused by the properties of the resin. The thickness unevenness can be reduced to some extent by increasing the temperature of the die or the cylinder, but cannot be sufficiently improved. Even if a thin film is formed by using polyolefin or polystyrene alone, such a phenomenon is not observed.Therefore, the above phenomenon is a peculiar phenomenon when preparing a blend or alloy film, and is generally observed during melt spinning. It is considered to be similar to the resonance or melt resonance phenomenon.

[0005]

Therefore, an object of the present invention is to make the composition ratio of (A) olefin polymer and (B) styrene polymer (A) / (B) = 50 / 50- 9
Even if it is 8/2 (weight ratio), it is to provide a film having small thickness unevenness and high surface smoothness, and a method for producing the film.

[0006] Another object of the present invention is to provide a film having a small thickness unevenness even if it is thin, and a method for producing the film.

[0007]

Means for Solving the Problems As a result of intensive studies for achieving the above object, the present inventors have found that a film is formed by using an olefin polymer and a styrene polymer having a melt index ratio within a specific range. Then, the composition ratio of the olefin-based polymer and the styrene-based polymer is the former / the latter = 50 / 50-
The inventors have found that even in the range of 98/2 (weight ratio), the film formation stability is remarkably improved and a film having a small thickness unevenness can be obtained, and the present invention has been completed.

That is, in the present invention, (A) an olefin polymer and (B) a styrene polymer are used, the former / the latter = 5.
A film formed of a resin composition containing a ratio of 0/50 to 98/2 (weight ratio), wherein the ratio of the melt index of the (A) olefin polymer and the (B) styrene polymer is as follows ( A film (1) which is either a) or (b) is provided.

(A) Melt index MI _A1 of the olefin polymer (A) measured at 230 ° C. and a load of 2.16 kg and (B) styrene polymer melt index M _A1 measured at 200 ° C. and a load of 5 kg. the ratio MI _A1 / MI _B with a melt index MI _B is two or more (b) 190 ℃, melt index was measured under a load of 2.16 kg (a) an olefin polymer MI _A2
And the melt index MI _B of the (B) styrene-based polymer measured under the conditions of 200 ° C. and a load of 5 kg, MI _A2
/ MI _B is 0.008 or more, in this film, the melt index MI _A1 of the (A) olefin-based polymer is 4 g / 10 minutes or more, or the melt index MI _A2 is 0.1 g / 10 minutes or more, (B) Melt index MI of styrene polymer
_B may be 8 g / 10 minutes or less. (A) The olefin polymer has a melt index MI _A1 of 4 g / 1.
Polypropylene having a melt index MI _A2 of 0.1 g / 10 min or more and the like are included. The (B) styrenic polymer, a melt index MI _B is included like 0.5 to 8 g / 10 minutes to polystyrene.

The film may further contain (C) a styrene monomer-conjugated diene copolymer.

In another film (2) of the present invention, 230
Polypropylene having a melt index of 7 to 20 g / 10 min under conditions of ℃ and load of 2.16 kg, and 190
(A) an olefin polymer selected from polyethylene having a melt index of 0.1 to 0.5 g / 10 min at a temperature of 2.16 kg and a melt index of 200 ° C. and a load of 5 kg. It contains 2 to 5 g / 10 minutes of (B) a styrene-based polymer as a main component, and the composition ratio of (A) and (B) is (A) / (B) = 55/45.
A film obtained by extruding a resin composition having a weight ratio of ~ 85/15 (weight ratio), having an average thickness of 10 to 30 µm, and a thickness unevenness per 5 m of the film take-up direction within ± 25% of the average thickness. is there.

The method for producing a film according to the present invention is a method for producing a film by extruding the resin composition, wherein the (A) olefin polymer and (B) of (a) or (b) above are used. ) Use a styrenic polymer.

In the present specification, MI _A1 is 23
The melt index of the olefin polymer under the conditions of 0 ° C. and a load of 2.16 kg, MI _A2 is the melt index of the olefin polymer under the conditions of 190 ° C. and a load of 2.16 kg, and MI _B is 200 ℃, load 5kg
Shows the melt index of the styrene polymer under the conditions of.

The (A) olefin polymer includes olefin homopolymers or copolymers. Examples of the olefin include ethylene, propylene, 1-butene, and 4
-Methyl-1-butene, 1-pentene, 3-methyl-1
Α-olefins such as -pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene and 1-eicosene: 2- Other olefins such as butene are included.

The olefin polymer may be a copolymer of an olefin and a copolymerizable monomer. Examples of the copolymerizable monomers include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, crotonic acid, isocrotonic acid, mesaconic acid, angelic acid, and other ethylenically unsaturated carboxylic acids; maleic anhydride. Ethylenically unsaturated polycarboxylic acids such as acids, citraconic anhydride, itaconic anhydride and their acid anhydrides; acrylic acid esters and methacrylic acid esters; vinyl esters of carboxylic acids (eg vinyl acetate, vinyl propionate, etc.) An ethylenically unsaturated carboxylic acid ester of
Examples thereof include cyclic olefins such as norbornene, ethylidene norbornene and cyclopentadiene; and dienes. 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 olefin polymers include polyethylene such as low density polyethylene, medium density polyethylene, high density polyethylene and linear low density polyethylene; ethylene-vinyl acetate copolymer; ethylene- (meth) acrylate acrylate copolymer. Ethylene; (meth) acrylic acid copolymer; polypropylene; propylene- (meth) acrylic acid copolymer; epoxy-modified polyolefin [eg,
Ethylene-glycidyl (meth) acrylate copolymer (for example, Sumitomo Chemical Co., Ltd., Bondfast E, etc.)], carboxyl-modified polyolefin [for example, ethylene-maleic anhydride copolymer (for example, Mitsui Petrochemical Co., Ltd.) , Admer NF series, etc.), and modified epoxy and carboxy modified polyolefin [eg, ethylene- (meth) acrylate-maleic anhydride copolymer (eg, Nisseki Chemical Co., Ltd., N polymer A1600)] Polyolefins; ethylene-propylene copolymers; olefin elastomers (for example, Mitsui Petrochemical Co., Ltd., Tuffmer, etc.); ethylene propylene rubber and the like.

The more preferable olefin polymer includes a homopolymer or a copolymer containing ethylene and propylene as main components. As such an olefin polymer, polyethylene, polypropylene, an ethylene-propylene copolymer, a copolymer of ethylene and / or propylene and a linear or branched α-olefin having about 4 to 6 carbon atoms. Is included. The content of ethylene and / or propylene in the olefin-based copolymer is 65% by weight or more. More specifically, polyethylene, polypropylene and ethylene-propylene copolymers, particularly polyethylene and polypropylene are preferred. Among polyethylene, low density polyethylene, medium density polyethylene, linear low density polyethylene and the like are preferable.

The olefin-based copolymer is usually a random copolymer in many cases. The homopolymer and / or copolymer may be used as a mixture of two or more kinds.

The molecular weight of the (A) olefin polymer is, for example, 1 × 10 ⁴ to 1 × 10 ⁶ , preferably 5 × 10.
It is about ^{4 to} 5 × 10 ⁵ .

The melt index MI _A1 of the olefin polymer is usually 4 g / 10 minutes or more (for example, 4 to 30 g /
10 minutes), preferably 5 to 25 g / 10 minutes, more preferably 7 to 20 g / 10 minutes. The melt index MI _A2 of an olefin polymer is usually 0.1 g / 1.
It is 0 minutes or more (for example, 0.1 to 1 g / 10 minutes), preferably about 0.1 to 0.5 g / 10 minutes. In the film using the olefin polymer having a melt index in the above range, the thickness unevenness can be particularly reduced.

The preferred (A) olefin polymer is
Polypropylene having a melt index MI _A1 in the above range or a copolymer of a linear or branched α-olefin having 2 to 6 carbon atoms and having propylene as a main component, and particularly having polypropylene or propylene as a main component Propylene-ethylene copolymers and the like, especially polypropylene and the like are included. Other preferred (A) olefin-based polymers include polyethylene having a melt index MI _A2 in the above range or 2 to 6 carbon atoms containing ethylene as a main component.
Included are straight chain or branched chain α-olefin copolymers, and the like, especially polyethylene and the like.

The (B) styrene-based polymer includes homopolymers or copolymers of styrene-based monomers such as styrene, α-methylstyrene and chlorostyrene, styrene-based monomers, and vinyl monomers (eg, acrylonitrile). Unsaturated nitrile, (meth) acrylic acid, (meth)
Copolymer with acrylic acid ester, α, β-monoolefinic unsaturated carboxylic acid such as maleic anhydride or acid anhydride or its ester), high impact polystyrene (high impact polystyrene HIPS), and high impact resistance Examples thereof include styrene resins.

The impact-resistant polystyrene can be obtained by mixing polystyrene with a diene rubber elastomer or by graft-polymerizing a styrene monomer onto the diene rubber elastomer. Further, the impact-resistant styrene resin is a diene rubber elastomer such as polybutadiene, an acrylic rubber containing an unsaturated group, a chlorinated polyethylene, an ethylene-vinyl acetate copolymer, a polymer such as ethylene-propylene rubber, a vinyl monomer ( For example,
It can also be obtained by graft-copolymerizing a styrene-based monomer with acrylonitrile or methyl methacrylate).

Preferred styrenic polymers include, for example:
Styrene- (meth) acrylic acid ester copolymers such as polystyrene (GPPS), styrene- (meth) acrylic acid copolymer, methyl methacrylate-styrene copolymer (MAS resin), styrene-maleic anhydride copolymer ,
Styrene-acrylonitrile copolymer (AS resin), impact-resistant polystyrene, impact-resistant styrene-based resin (for example, ABS resin obtained by graft-polymerizing styrene and acrylonitrile onto polybutadiene, AAS resin obtained by graft-polymerizing styrene and acrylonitrile onto acrylic rubber,
ACS resin obtained by graft-polymerizing styrene and acrylonitrile on chlorinated polyethylene, polymer obtained by graft-polymerizing styrene and acrylonitrile on ethylene-vinyl acetate copolymer, polymer obtained by graft-polymerizing styrene and acrylonitrile on ethylene-propylene rubber, styrene on polybutadiene And MBS resin obtained by graft-polymerizing methyl methacrylate). These styrene-based polymers can be used alone or in combination of two or more.

Particularly preferred styrenic polymers include highly transparent styrenic polymers [eg polystyrene, styrene- (meth) acrylic acid copolymers (eg Dainippon Ink and Rurex), Styrene- (meth) acrylic acid ester copolymers such as methyl methacrylate-styrene copolymer (for example, Nippon Steel Chemical Co., Ltd.,
MS resin, etc.), styrene-acrylonitrile copolymer, etc.], impact-resistant polystyrene, impact-resistant styrene-based resin, styrene-maleic anhydride copolymer (for example, Sekisui Plastics Co., Ltd., Dailark, etc.) and the like. Be done.

The molecular weight of the styrene-based polymer (B) is, for example, 1 × 10 ^{4 to} 5 × 10 ⁵ , preferably 5 × 10 ⁴ to 4.
× 10 ⁵ , and more preferably about 1 × 10 ^{5 to} 3 × 10 ⁵ .

In the film (1) of the present invention, (B)
The melt index MI _B styrenic polymer, 8g
/ 10 minutes or less, for example, 0.5 to 8 g / 10 minutes, preferably 1 to 6 g / 10 minutes, more preferably 2 to 5 g / 10.
It's about a minute.

In the film (1) of the present invention, the ratio MI _A1 / M of the melt index MI _A1 of the olefin polymer and the melt index MI _B of the styrene polymer.
I _B is 2 or more (e.g. 2 to 60), preferably 2 to 3
It is 0, more preferably about 2.1 to 20, and most often in the range of 2.2 to 10. Further, the ratio MI _A2 / MI of the melt index MI _A2 of the olefin polymer and the melt index MI _B of the styrene polymer.
_B is 0.008 or more (for example, 0.008 to 1), preferably 0.01 to 0.5, and more preferably 0.02.
It is about 0.2. Melt index ratio MI _A1 / MI
_{When B} is less than 2, and melt index MI _A2 /
If MI _B is less than 0.008, the film occurs uneven thickness, surface not high smoothness film is obtained.

The composition ratio [(A) / (B) (weight ratio)] of the (A) olefin polymer and the (B) styrene polymer is
50/50 to 98/2, preferably 50/50 to 90 /
10, more preferably about 55/45 to 85/15. The composition ratio (A) / (B) (weight ratio) is 55 /
It is often about 45 to 80/20. Even when the composition ratio of the olefin-based polymer and the styrene-based polymer is in the above range, the uneven thickness of the film is small and the surface smoothness is high.

The total content of (A) olefin polymer and (B) styrene polymer in the resin composition is, for example, 80 to 100% by weight, preferably 90 to 100% by weight, and more preferably 92 to 100% by weight. %.

In the present invention, the resin composition may further contain (C) a compatibilizing agent. In the film formed of the resin composition containing the compatibilizer, the film strength is improved and the peeling of the surface layer of the film can be suppressed.

Examples of the compatibilizer include styrene-based monomer-conjugated diene-based copolymers such as random copolymers of styrene-based monomers and conjugated dienes, block copolymers or hydrogenated copolymers thereof. included.

Examples of such a copolymer include styrene-
Butadiene copolymer, styrene-butadiene-styrene (SBS) block copolymer, styrene-isoprene block copolymer, styrene-isoprene-styrene (S
IS) block copolymer, styrene-ethylene / butylene-styrene block copolymer, styrene-ethylene
Propylene copolymer, hydrogenated styrene-butadiene-
Examples thereof include a styrene block copolymer, a hydrogenated styrene-isoprene-styrene block copolymer, and a styrene-butadiene random copolymer.

The hydrogenated copolymer is a copolymer obtained by hydrogenating some or all of the double bonds present in the above copolymer. The benzene ring may also be hydrogenated by hydrogenation to form a cyclohexane ring, but usually, a double bond derived from a conjugated diene is often hydrogenated. The hydrogenation rate is usually 50% or more, preferably 70% or more. Preferred hydrogenated copolymers include hydrogenated styrene-butadiene-styrene block copolymers, hydrogenated styrene-isoprene-styrene block copolymers and the like.

The copolymer may be modified with maleic anhydride, (meth) acrylic acid, (meth) acrylic acid ester, glycidyl (meth) acrylate or the like.

The amount of the compatibilizing agent such as these (C) styrene-based monomer-conjugated diene-based copolymer is such that the total amount of the (A) olefin polymer and (B) styrene-based polymer is 10
About 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 2.5 to 7.5 parts by weight.

In the present invention, the resin composition may contain a polymer other than the above. Other polymers include halogen-containing vinyl polymers (for example, polyvinyl chloride, polyvinylidene chloride, polyvinyl fluoride, polychloroprene, vinyl chloride-vinyl acetate copolymers, vinylidene chloride-vinyl acetate copolymers, etc.), Acrylic polymers (for example, homopolymers or copolymers of acrylic monomers such as acrylic acid, methacrylic acid, acrylic acid esters, methacrylic acid esters, acrylamide, and acrylonitrile; acrylic monomers, copolymers with other monomers, etc.) ), Polycarbonate (for example, a polymer obtained by reacting a dihydroxy compound such as bisphenol A with a carbonic acid ester such as phosgene or diphenyl carbonate), polyester (for example, polyethylene terephthalate, polybutylene terephthalate, etc.) Polyamides (e.g., nylon 6, nylon 6
6, nylon 610, nylon 612, nylon 11,
Nylon 12 etc.), polymers derived from epoxides (for example, homo- or copolymers of alkylene oxides such as ethylene oxide and propylene oxide), polyacetals (for example, homopolymers of aldehydes such as formaldehyde and trioxane or the above). Copolymers containing monomers as the main component), polyphenylene oxide (for example, poly (2,6-dimethyl-1,4-)
Phenylene) oxide, etc.), polysulfone (eg,
Examples thereof include polyether sulfone), polyurethane, and other thermoplastic resins.

The thickness of the film (1) of the present invention can be selected in the range of, for example, 5 to 100 μm, preferably 8 to 50 μm. A preferred film is a thin film, for example, an average thickness of 5 to 35 μm, preferably 1
A film having a thickness of 0 to 30 μm, more preferably about 15 to 30 μm is included. The present invention is characterized in that even if the film is thin, the thickness unevenness is extremely small.

In a preferred film, the thickness unevenness per 5 m in the MD direction (film take-up direction) is within ± 25%, particularly within ± 22%, and especially within ± 2% of the average thickness.
Includes films that are within 0%. Also, MD direction 5
The difference between the maximum thickness and the minimum thickness of the film per m is preferably 50% or less, particularly 44% or less, and particularly 40% or less with respect to the average thickness.

The film of the present invention may be coated with a coating layer such as a slipping layer or a gas barrier layer or a laminating layer as long as the tearability is not impaired. In addition, the film is subjected to surface oxidation treatment such as corona discharge treatment, flame treatment, hot air treatment, ozone treatment, and ultraviolet treatment; ultrasonic treatment; plasma treatment; surface roughening treatment such as sandblasting and solvent treatment. It may have been done. Corona discharge treatment or the like is often performed as the surface treatment.
Further, the film contains various additives such as antioxidants, heat and light resistance stabilizers such as ultraviolet absorbers, chlorine scavengers, plasticizers, antistatic agents, organic or inorganic lubricants, dyes and pigments, and fillers. You may stay.

The film of the present invention can be produced by a conventional method such as an extrusion molding method using a T die and an inflation molding method using a circular die.

In the T-die molding method, a resin composition containing (A) an olefin polymer and (B) a styrene polymer as main components is melted by an extrusion molding machine and extruded from a T-die to form a film. Can be molded. In addition, in the inflation molding method, a film can be formed by extruding the molten resin composition from a circular die.

In the method of the present invention, since the olefin polymer (A) and the styrene polymer (B) having a specific melt index ratio are combined and melt-extruded, the polymers (A) and (B) are used. ) Composition ratio is (A) / (B)
= 50/50 to 98/2 (weight ratio), the film-forming stability is remarkably improved, and a film with small thickness unevenness can be obtained. Moreover, even when a thin film is produced, a film with small thickness unevenness can be obtained.

The resin composition containing (A) an olefin polymer and (B) a styrene polymer as main components is mixed and supplied to an extruder, and melt-kneaded in the extruder to disperse the resin. Well, pellets obtained by previously melt-kneading the resin composition may be supplied to the 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. The pellets can be prepared using an open roll, Banbury mixer, single screw extruder, twin screw extruder, single screw reciprocating screw kneader, or the like.

The film forming temperature can be selected according to the type of resin, but is usually 270 ° C. or lower, for example, 150 to 270 ° C., preferably about 200 to 260 ° C.

The discharge amount of the resin composition, the die width, the lip opening, and the shear rate applied to the die lip portion are, for example, 6
You may adjust so that it may be 00 second ^-1 or more, preferably 600 to 2000 second ^-1 .

The draw ratio (melt stretching ratio: ratio V2 / V1 of speed V1 at which molten resin is discharged from the die lip and speed V2 at which the formed film is wound up) is determined by the desired film thickness. It can be appropriately selected within a range of about 1 to 70 (eg, 5 to 70). In the method of the present invention, the draw ratio is 1
Even if it takes a large value of about 0 to 60, it is possible to stably manufacture a thin film while suppressing unevenness in thickness.

In the inflation molding method,
The blow ratio (swelling ratio: the ratio d2 / d1 of the diameter d1 of the annular die lip to the diameter d2 of the film to be wound) can be appropriately selected within the range where the characteristics of the film are not impaired, for example, within the range of about 1 to 30. .

The film of the present invention can be used not only as a monolayer film, but also from a base material layer (for example, olefin polymers such as polyethylene and polypropylene, polyvinyl chloride, polyesters such as polyethylene terephthalate, and polymers such as styrene polymers). Uniaxially or biaxially stretched film, such as: glassine paper, imitation paper, white cardboard, etc .; easily breakable substrate such as metal foil such as aluminum, etc.), and can also be used as an easily tearable laminate.

The film of the present invention is an easily tearable packaging material (for example, PTP (Press Through Pack) used for individual packaging of packaging bags, base materials for brick packaging, tablets and the like.
It can be used for various applications such as packaging base materials) and raw materials for non-woven fabrics and ultrafine fibers for filters.

[0052]

Since the film of the present invention contains (A) an olefin polymer showing a specific melt index ratio and (B) a styrene polymer resin, the thickness unevenness of the film can be made extremely small. Further, even if it is thin, it can be used as a high-quality film because the thickness unevenness can be reduced.

According to the production method of the present invention, a film having the above-mentioned excellent properties can be produced simply and stably.

[0054]

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 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): YK manufactured by Ube Industries, Ltd.
105 [MI: 5 (230 ° C, load 2.16 kg)] Polypropylene (PP-3): FM manufactured by Ube Industries, Ltd.
101A [MI: 9 (230 ° C, load 2.16 kg)] Polypropylene (PP-4): S1 manufactured by Ube Industries, Ltd.
15M [MI: 15 (230 ° C, load 2.16 kg)] [Polyethylene (PE)] Low-density polyethylene (PE-1): Nippon Petrochemical Co., Ltd.
Rexron F12S [MI: 0.15 (190 ° C,
Load 2.16 kg)] [Polystyrene (PS)] Polystyrene (PS-1): M manufactured by Sumitomo Chemical Co., Ltd.
121 [MI: 32 (200 ° C., load 5 kg)] Polystyrene (PS-2): M manufactured by Sumitomo Chemical Co., Ltd.
140 [MI: 10 (200 ° C., load 5 kg)] Polystyrene (PS-3): M manufactured by Sumitomo Chemical Co., Ltd.
183 [MI: 4 (200 ° C., load 5 kg)] Polystyrene (PS-4): Nippon Steel Chemical Co., Ltd. G1
2-55 [MI: 2.5 (200 ° C., load 5 kg)] [Styrene-ethylene / butylene-styrene block copolymer (SEBS)] SEBS-1: Asahi Kasei Corporation H1061 [MI:
0.1 (230 ° C., load 2.16 kg)] SEBS-2: Asahi Kasei Corporation H1031 [MI: 1
60 (230 ° C., load 2.16 kg)] Example 1 The polypropylene (PP-1 to PP-4) and the polystyrene (PS-2 to PS-4) were combined with polypropylene / polystyrene = 75/25 (weight ratio). ) And were melt-kneaded using a twin-screw extruder to obtain pellets.
Using the obtained pellets, a film (average thickness 20 μm) was produced by a T-die method under the following conditions using a 40 mmφ uniaxial extruder. A T-die provided with a coat hanger type manifold was used.

Screw rotation speed 35 rpm Cylinder and die temperature 200 to 260 ° C. T die width 40 mm Lip opening about 600 μm Chill roll temperature 50 to 60 ° C. Discharge rate 6.5 to 7.5 kg /
Hour draw ratio: about 30 The thickness of the central portion of the obtained film in the TD direction (direction orthogonal to the film taking direction) was measured in the MD direction (film taking direction) at intervals of 5 cm over 5 m. . From the maximum thickness and the minimum thickness, the thickness unevenness (±
%) Was obtained, and the thickness unevenness of the film was evaluated according to the following criteria.

Thickness unevenness (±%) = {maximum thickness (μm) −
Minimum thickness (μm)} ÷ {Average thickness (μm)} ÷ 2 × 10
0: Thickness unevenness is within ± 25% of the average thickness of the film. X: Thickness unevenness exceeds the above range. Table 1 shows the results. The numbers in the table represent the melt indexes of polypropylene and polystyrene (see the above for measurement conditions). Note that "-" indicates that there is no data.

[0059]

[Table 1] As is clear from Table 1, 230 ° C., load 2.16 kg
Melt index MI _A1 measured under the conditions
Melt index M measured under conditions of ℃ and load of 5 kg
If the ratio MI _A1 / MI _B with I _B is 2 or more, a small film of uneven thickness was obtained.

Examples 2-8, Comparative Examples 1-10 Films were prepared in the same manner as in Example 1 except that the resins shown in Tables 2 and 3 were used in the proportions shown in the tables. The thickness of the film was measured by the same method as in Example 1,
The thickness unevenness (±%) was obtained. The results are shown in Table 2 and Table 3.
Shown in. In the table, "%" indicates the amount of each resin used (% by weight), and MI indicates the melt index of each resin (see the above for measurement conditions).

[0061]

[Table 2]

[0062]

[Table 3] As is clear from Tables 2 and 3, the films of Examples 2 to 8 have significantly smaller thickness unevenness than the films of Comparative Examples. Further, even if the wall thickness is thin, it is possible to stably manufacture a film with small thickness unevenness.

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Claims (9)

[Claims] 1. An (A) olefin polymer and a (B) styrene polymer, the former / the latter = 50/50 to 98/2.
A film formed of a resin composition containing (weight ratio), wherein the melt index ratio of (A) an olefin polymer and (B) a styrene polymer is the following (a) or (b): A film that is either. (A) Melt index MI _A1 of olefin polymer (A) measured under conditions of 230 ° C. and a load of 2.16 kg
And the melt index MI _B of the (B) styrene-based polymer measured under the conditions of 200 ° C. and a load of 5 kg, MI _A1
/ MI _B is 2 or more. (B) Melt index MI _A2 of olefin polymer (A) measured under conditions of 190 ° C. and load of 2.16 kg.
And the melt index MI _B of the (B) styrene-based polymer measured under the conditions of 200 ° C. and a load of 5 kg, MI _A2
/ MI _B is 0.008 or more 2. The melt index MI _A1 of the olefin polymer (A) is 4 g / 10 minutes or more, or MI _A2 is 0.1 g / 10 minutes or more, and the melt index MI of the styrene polymer (B) is The film according to claim 1, wherein _B is 8 g / 10 minutes or less. 3. The (A) olefin polymer is polypropylene having a melt index MI _A1 of 4 g / 10 minutes or more, or a melt index MI _A2 of 0.1 g / 10.
The film according to claim 1, which is a polyethylene having a length of at least one minute. Wherein (B) film of claim 1 wherein the melt index MI _B of the styrene polymer is 0.5 to 8 g / 10 min. 5. The compositional ratio of (A) olefin polymer to (B) styrene polymer is (A) / (B) = 50/50.
90/10 (weight ratio), the (A) olefin polymer has a melt index MI _{A1 of 5} to 25 g / 10.
Minute polypropylene or MI _A2 0.1-0.5g
/ 10 min are polyethylene, (B) a styrene-based polymer, the film of claim 1, wherein the MI _B is 1 to 6 g / 10 min polystyrene. 6. The average thickness is 5 to 35 μm, and the thickness unevenness per 5 m in the film taking direction is ± 2 with respect to the average thickness.
The film according to claim 1, which is within 5%. 7. A polypropylene having a melt index of 7 to 20 g / 10 min at 230 ° C. and a load of 2.16 kg, and a melt index of 0.1 to 0.5 g at 190 ° C. and a load of 2.16 kg. (A) an olefin-based polymer selected from polyethylene for 10 minutes, and 20
The melt index is 2 at 0 ° C and a load of 5 kg.
It contains 5 g / 10 minutes of (B) a styrene polymer as a main component, and the composition ratio of (A) and (B) is (A) /
(B) = 55/45 to 85/15 (weight ratio), which is a film obtained by extrusion-molding a resin composition, having an average thickness of 10 to 30 μm, and the thickness unevenness per 5 m of the film take-up direction is the average thickness. On the other hand, the film is within ± 25%. 8. The (A) olefin-based polymer and the (B) styrene-based polymer, the former / the latter = 50/50 to 98/2.
A method for producing a film, which comprises extruding a resin composition containing a (weight ratio), the method comprising the following (a) or (b): (A) olefin polymer and (B) styrene polymer. A method for producing a film using. (A) Melt index MI _A1 of olefin polymer (A) measured under conditions of 230 ° C. and a load of 2.16 kg
And the melt index MI _B of the (B) styrene-based polymer measured under the conditions of 200 ° C. and a load of 5 kg, MI _A1
/ MI _B is 2 or more. (B) Melt index MI _A2 of olefin polymer (A) measured under conditions of 190 ° C. and load of 2.16 kg.
And the melt index MI _B of the (B) styrene-based polymer measured under the conditions of 200 ° C. and a load of 5 kg, MI _A2
/ MI _B is 0.008 or more 9. The method for producing a film according to claim 8, wherein the film is extruded at a draw ratio of 10 to 60.