JPH1053674A - Stretched film - Google Patents

Abstract

(57) Abstract: The present invention provides optical properties such as transparency and haze,
An object of the present invention is to provide a stretched film which is excellent in flexibility, heat resistance and the like, and which can maintain high transparency for a long time by suppressing bleed out of an amorphous polyolefin contained therein during storage. SOLUTION: The present invention relates to (A) 20 to 100% by weight of an amorphous polyolefin having a propylene and / or butene-1 component content of 50% by weight or more, and (B) 80 to 0% by weight of a crystalline polypropylene. (However, the total of the amorphous polyolefin (A) and the crystalline polyolefin (B) is 1
(Which is 00% by weight).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a stretched film. More specifically, as a soft film comparable to soft vinyl chloride film and vinylon film, flexibility,
The present invention relates to a stretched film obtained by biaxially stretching a polyolefin-based resin composition having heat resistance, transparency, and the like. The stretched film of the present invention can be suitably used as a film that can be substituted for stretch packaging, stretch shrink packaging, shrink packaging, and the like of a soft vinyl chloride film.

[0002]

2. Description of the Related Art In recent years, soft vinyl chloride films containing a plasticizer have been widely used as soft films. However, the soft vinyl chloride resin has social factors such as toxicity and transfer problems due to bleed out of plasticizers and monomers, and acid rain problems due to generation of hydrogen chloride during incineration.

On the other hand, as a soft film similar to the above-mentioned soft vinyl chloride film, there is a film mainly composed of ethylene such as an ethylene-vinyl acetate copolymer, a low-density polyethylene, and an ionomer. However, these ethylene-based soft films are inferior to soft vinyl chloride films in terms of transparency, haze, gloss, and the like, and also have drawbacks in that they are inferior in heat resistance and stiffness. Also, a soft film obtained from a low-crystalline propylene-based polymer is already known (Japanese Patent Application Laid-Open Nos.
No. 7-47371). Low-crystallinity propylene-based polymers can be made into transparent and flexible films by water-cooled inflation and casting, which are common methods of forming commercially available high-crystalline propylene-based polymers into films. Only a translucent film can be obtained from air-cooled inflation processing, which is a typical film forming method, and there are limitations in practical applications.

Japanese Patent Application Laid-Open No. 60-118727 discloses a low-crystalline propylene polymer and a dibenzylidene sorbitol derivative as a polypropylene resin composition for obtaining a soft film having good transparency when subjected to air-cooling inflation. And a soft polypropylene composition for films comprising zeolite. But,
In this composition, in order to maintain good transparency when air-cooled inflation processing, the dibenzylidene sorbitol derivative and zeolite used in combination as the clarifying compounding agent are each in a specific range relative to the low-crystalline propylene polymer. In addition to the difficulty in controlling the amount of these transparent compounding agents, it is difficult to uniformly disperse them, and the transparent compounding agents easily bleed out to the film surface. Was.

Further, as a solution to the above-mentioned drawbacks of the soft film mainly composed of ethylene, transparency, haze, gloss and the like are good, and flexibility, heat resistance, strength of the waist and the like are also excellent. Polypropylene-based flexible films have already been proposed. For example, JP-A-6-927 discloses that an amorphous polyolefin having a propylene and / or butene-1 component content of 50% by weight or more is used in an amount of 20 to 10%.
(A) a layer composed of a resin composition containing 0% by weight and 80 to 0% by weight of a crystalline polypropylene, and a layer (B) composed of an ethylene-based resin, a film in which at least two layers are laminated, Further, a laminated film in which at least one of both outer surface layers is constituted by the layer (B) is disclosed. However, in this laminated film, a layer composed of an amorphous polyolefin and a crystalline polypropylene and a layer composed of an ethylene-based resin need to be laminated and complexed by a method such as a coextrusion lamination method, a lamination method, or a dry lamination method. However, since the manufacturing process is complicated, there remain problems such as being economically disadvantageous.

[0006] On the other hand, an amorphous polyolefin having a propylene and / or butene-1 component content of 50% by weight or more, which is proposed in Japanese Patent Application Laid-Open No. 5-194802, is 20-80% by weight and a crystalline polypropylene. 80 to
The soft polyolefin resin composition itself containing 20% by weight has the same moldability as the thermoplastic resin in the molding machine used for the thermoplastic resin, and has high transparency, high gloss, and flexibility. It is used in many fields because a film or sheet having heat resistance can be obtained.

[0007]

However, films and sheets obtained by molding the above soft polyolefin resin composition have poor storage characteristics, and some of the amorphous polyolefin contained therein is stored. It has the disadvantage that it oozes (bleed out) into the surface of the film or sheet inside, and the surface of the film or sheet becomes sticky and the transparency of the film or sheet decreases. Therefore, an object of the present invention is to provide a soft film comparable to a soft vinyl chloride film or a vinylon film, having flexibility, heat resistance, transparency, and the like, and at the time of storage, bleed out the amorphous polyolefin contained therein. And to provide a stretched film that can maintain high transparency for a long time.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that amorphous polyolefin having specific properties and crystalline polypropylene are contained in a specific ratio. The polyolefin-based resin composition is stretched at a specific stretching ratio, in particular, by successively or simultaneously biaxially stretching, so that transparency, optical properties such as haze, flexibility, heat resistance and the like are excellent, and upon storage. Also, it is possible to provide a stretched film capable of delaying bleed-out of the amorphous polyolefin contained therein to the surface and maintaining high transparency for a long time.
The inventors have found that the above objects can be achieved, and have completed the present invention.

That is, the first invention in the present invention is:
(A) An amorphous polyolefin having a propylene and / or butene-1 component content of 50% by weight or more is used in an amount of 20 to 10%.
Polyolefin resin containing 0% by weight and (B) 80 to 0% by weight of crystalline polypropylene (however, the total of amorphous polyolefin (A) and crystalline polypropylene (B) is 100% by weight) This can be achieved by providing a stretched film obtained by stretching the composition at least twice in area ratio.

A second invention according to the present invention relates to the stretched film according to the first invention, wherein the stretching is sequential biaxial stretching, and a third invention according to the present invention, wherein the stretching is simultaneous biaxial stretching. This can be achieved by providing the stretched films according to the first aspect of the invention.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. Amorphous polyolefin (A) used in the present invention
May be any amorphous polyolefin having a propylene component and / or butene-1 component content of 50% by weight or more. For example, amorphous polypropylene or polybutene-1, or propylene or butene-1 and other α-
Copolymers with olefins can be used. When the content of the propylene component and / or the butene-1 component in the amorphous polyolefin is less than 50% by weight, the content of the non-crystalline polyolefin with the crystalline polypropylene (B), which is another component constituting the polyolefin resin composition, It is not preferable because the compatibility is lowered.

The amorphous polyolefin (A) of the present invention comprises:
It satisfies the following conditions at the same time. The amorphous polyolefin (A) is one having a boiling n-heptane insoluble content, that is, a Soxhlet extraction insoluble content with boiling n-heptane of 70% by weight or less, preferably 60% by weight or less. If the boiling n-heptane insoluble content is more than 70% by weight, the ratio of the amorphous portion becomes small, and it is not possible to impart the intended flexibility to the finally obtained stretched film. The melt viscosity of the amorphous polyolefin (A) is 100 to 100,000 at 190 ° C.
0 cps, preferably 400 to 50,000 cps. When the melt viscosity is less than 100 cps, when forming a film or sheet from the obtained polyolefin-based resin composition, for example, extrusion molding is not stable, and when a film is produced by stretching such as sequential biaxial stretching or simultaneous biaxial stretching. , The film breaks often. On the other hand, when the melt viscosity is 10
If it exceeds 000 cps, it is difficult to form a film or sheet from the obtained polyolefin resin composition, which is not preferable. The amorphous polyolefin (A) preferably has a number average molecular weight of 1,000 to 20.
0000, more preferably 1,500 to 100,0
00. If the number average molecular weight exceeds 200,000, it is difficult to form a film or sheet from the obtained polyolefin-based resin composition, and if it is less than 1,000, the mechanical strength of the finally obtained stretched film decreases. Furthermore, the cold xylene solubles are at least 80% by weight, preferably at least 90% by weight. Cold soluble xylene content is 80
If less than 10% by weight, the amorphous polyolefin (A)
Of the polyolefin resin composition, the elastic modulus and shrinkage stress of the polyolefin resin composition increase, and the flexibility of a stretched film obtained from the resin composition decreases. In order to reliably suppress the occurrence of the above-described undesired phenomena in a finally obtained stretched film or the like, it is necessary to adjust the boiling n-heptane insoluble content, melt viscosity, number average molecular weight, and the like of the amorphous polyolefin (A). The cold xylene solubles and the like should each fall within the preferred ranges described above. In the present invention, the above-mentioned amorphous polyolefin (A) includes the above-mentioned amorphous polypropylene, amorphous polybutene-1, an amorphous copolymer of propylene and another α-olefin, and butene-1 and other One kind or a combination of two or more kinds such as an amorphous copolymer with an α-olefin can be used.

As the amorphous polypropylene, atactic polypropylene produced as a by-product during the production of the crystalline polypropylene (B) may be used, or it may be used as it is produced from raw materials. At this time, propylene or butene
The copolymer of 1 and another α-olefin can be produced from a raw material so as to contain a predetermined propylene component or a butene-1 component and used. In the case of target production, for example, using a titanium-supported catalyst supported on magnesium chloride and triethylaluminum in the presence of hydrogen /
Alternatively, it can be obtained by polymerizing a raw material monomer in the absence of hydrogen. From the viewpoint of the stability of raw material supply and the stability of quality, it is preferable to use a predetermined amorphous polyolefin produced for the purpose. In addition, if there is a corresponding suitable commercial product, a commercial product can be appropriately selected and used.

As the amorphous polyolefin (A) used for preparing the polyolefin resin composition of the present invention, specifically, polypropylene, propylene / ethylene copolymer having predetermined characteristics such as the content of the propylene component, Propylene / butene-1 copolymer, propylene / butene-1 / ethylene terpolymer, propylene / hexene-1 / octene-1 terpolymer, propylene / hexene-1 / 4-methylpentene-13 Amorphous polyolefins having a propylene component as a main component such as a main copolymer are exemplified. Also, polybutene-1, butene-1 · ethylene copolymer, butene-1 · propylene copolymer, butene-1 having predetermined properties such as the butene-1 component content.
1. Propylene-ethylene terpolymer, butene-1
Hexene-1 / octene-1 terpolymer, butene-1
Amorphous polyolefins containing butene-1 as a main component, such as hexene-1,4-methylpentene-1 terpolymer, are also included.

When the amorphous polyolefin (A) is a propylene / ethylene copolymer, the content of the ethylene component is preferably 30% by weight or less, more preferably 1 to 20% by weight. When the content of the ethylene component is more than 30% by weight, the obtained resin composition becomes too soft.

When the amorphous polyolefin (A) used in the preparation of the polyolefin resin composition of the present invention is a propylene / butene-1 copolymer, the copolymer containing propylene as a main component and the butene-1 Is a main component, but all have large tensile elongation and cohesive force, and are suitably used as an amorphous polyolefin (A) constituting the obtained polyolefin-based resin composition. Specifically, for example, a commercially available product such as REXTAC of Rexene of the United States can be used.

Next, crystalline polypropylene (B), another component of the polyolefin resin composition of the present invention, is a commercially available polypropylene for extrusion molding, injection molding, blow molding and the like. ,
Refers to boiling n-heptane insoluble isotactic polypropylene. In this case, a propylene homopolymer may be used, or a copolymer of isotactic polypropylene having stereoregularity and another α-olefin may be used. As the crystalline polypropylene (B), a commercially available product may be used, or it may be produced at the time of preparing the polyolefin-based resin composition. The method for producing the crystalline polypropylene is not particularly limited. For example, a solid titanium catalyst component in which titanium trichloride or a titanium trichloride composition is supported on magnesium chloride or the like and an organometallic compound (for example, trialkylaluminum, Combination of a catalyst component such as an organoaluminum compound such as an alkylaluminum halide) and, if necessary, an electron donor (such as an ester compound or an ether compound having a nitrogen atom, a phosphorus atom, a sulfur atom, a silicon atom, or a boron atom). A suitable method can be selected from conventional methods for producing crystalline polypropylene, such as a method of polymerizing using a catalyst (so-called stereoregular Ziegler-Natta catalyst).

The α-olefin used for the copolymerization with the crystalline polypropylene (B) is preferably a compound having 2 to 2 carbon atoms.
8, α-olefins, for example, ethylene, butene-1,
Pentene-1, hexene-1, heptene-1, octene-1 and the like are preferred. Among these, ethylene or butene-1 is particularly preferred.

In the present invention, the crystalline polypropylene (B) preferably contains a propylene homopolymer and an ethylene component in an amount of 30% by weight or less, preferably 1-2% by weight.
20% by weight of butene-1 random copolymer or block copolymer of propylene / ethylene containing 5% by weight
Examples thereof include a propylene / butene-1 random copolymer or a block copolymer contained below. Among them, a copolymer of ethylene or butene-1 and propylene is particularly preferred from the viewpoint of applications such as a film obtained by stretching the polyolefin resin composition of the present invention. The crystalline polypropylene (B) used for preparing the polyolefin resin composition of the present invention can be used alone or in combination of two or more.

Further, the amorphous polyolefin (A) and / or the crystalline polypropylene (B) constituting the polyolefin resin composition of the present invention may be modified. In this case, the modification may be performed by various known methods such as a method of heating and stirring the amorphous polyolefin (A) and / or the crystalline polypropylene (B) and the modifier together with a radical initiator in a molten state or a solution state. Can be done in a way.

The modifier includes acrylic acid, methacrylic acid, methyl methacrylic acid, crotonic acid, isocrotonic acid, α-ethylacrylic acid, β-ethylacrylic acid,
Furanic acid, pentenoic acid, angelic acid, maleic acid, fumaric acid, tetrahydrophthalic acid, itaconic acid, citraconic acid, endocis-bicyclo [2,2,1] hept-5
Α, β-unsaturated carboxylic acids such as ene-2,3-dicarboxylic acid (trade name: nadic acid), citric acid, aconitic acid and / or derivatives thereof, for example, acid halides, amides, imides, acid anhydrides , Metal salts (sodium salts, zinc salts, etc.) and esters. Specific examples of these α, β-unsaturated carboxylic acid derivatives include malonyl chloride, acrylamide, maleimide, N-
Phenylmaleimide, N-methylmaleimide, N-ethylmaleimide, maleic anhydride, itaconic anhydride, glutaconic anhydride, citraconic anhydride, endocis-bicyclo [2,2,1] hept-5-ene-2,3-dicarboxylic Acid anhydrides (trade name: nadic anhydride), aconitic anhydride, sodium acrylate, zinc acrylate, monomethyl maleate, dimethyl maleate, glycidyl acrylate, glycidyl methacrylate, glycidyl maleate, hydroxy methacrylate, and the like.
Among these, maleic anhydride and itaconic anhydride are preferably used, and more preferably, maleic anhydride is used.

The amount of the modifier, that is, the α, β-unsaturated carboxylic acid and / or a derivative thereof is used in an amount of 100 parts by weight of the amorphous polyolefin (A) and / or the crystalline polypropylene (B). On the other hand, 0.1
It is preferably from 5 to 5 parts by weight. When the amount is less than 0.1 part by weight based on 100 parts by weight of the amorphous polyolefin (A) and / or the crystalline polypropylene (B), the modifying effect is not sufficient, and exceeds 5 parts by weight. In each case, the unreacted monomer increases with a decrease in the modification efficiency (that is, the reaction rate of the α, β-unsaturated carboxylic acid and / or a derivative thereof).

The α, β of the amorphous polyolefin (A) and / or the crystalline polypropylene (B)
-For the modification reaction with unsaturated carboxylic acids and / or their derivatives, radical initiators such as organic peroxides and azo compounds are generally used. Representative examples of organic peroxides include t-butylperoxybenzoate, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, and 2,5-dimethyl-2,5-di (benzoylperoxide). Oxy) hexyne-3, benzoyl peroxide, dichlorobenzoyl peroxide, dicumyl peroxide, cyclohexanone peroxide, lauroyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, , 5-dimethyl-2,5
-Di (t-butylperoxy) hexine-3, t-butylperoxyacetate, methyl ethyl ketone peroxide and the like. Specific examples of the azo compound include azobisisobutyronitrile and dimethylazoisobutyrate. The amount of the radical initiator to be added is preferably 0.05 to 1 part by weight based on 100 parts by weight of the amorphous polyolefin and / or the crystalline polypropylene. If the addition amount is less than 0.05 part by weight based on 100 parts by weight of the amorphous polyolefin (A) and / or the crystalline polypropylene (B), the modification efficiency cannot be sufficiently expected, which is not preferable. Also, 1
If the amount exceeds the weight part, the amorphous polyolefin (A) and / or the crystalline polypropylene (B) are significantly deteriorated and colored, which is not preferable.

The modified product of the amorphous polyolefin and / or the crystalline polypropylene is the above-mentioned amorphous polyolefin (A) and / or crystalline polypropylene (B),
The α, β-unsaturated carboxylic acid and / or a derivative thereof and the radical initiator are mixed in the above-mentioned predetermined ratio, and the mixture is mixed at a temperature of 180 to 250 ° C. using an extruder or a Banbury mixer. Melt kneading for about 20 minutes, or after heating and dissolving the predetermined amount of amorphous polyolefin (A) and / or crystalline polypropylene (B) in a reaction vessel in a solvent such as toluene or xylene, Α, β-unsaturated carboxylic acids and / or their derivatives and a radical initiator are added at predetermined ratios, and the mixture is reacted under stirring, or the like. In particular, the former method is simple and suitable as an industrial process.

The content of the amorphous polyolefin (A) in the polyolefin resin composition of the present invention is from 20 to 1
00% by weight, preferably 20-80% by weight, so that the content of the crystalline polypropylene (B) is
It is 80 to 0% by weight, preferably 80 to 20% by weight.
The content of the amorphous polyolefin (A) is 20% by weight.
If it is less than 1, sufficient flexibility cannot be imparted to the finally obtained stretched film. Further, when the content of the amorphous polyolefin (A) exceeds 80% by weight, the melt viscosity of the polyolefin resin composition obtained by blending with the crystalline polypropylene (B) becomes extremely small, Problems such as deterioration of molding stability and insufficient heat resistance may occur.

The polyolefin resin composition of the present invention comprises:
The resin composition is usually contained in an amount not to impair the purpose of the present invention, depending on the application other than the amorphous polyolefin (A) or the amorphous polyolefin (A) and the crystalline polypropylene (B). Various additives, modifiers and fillers to be blended in, for example, heat stabilizers, ultraviolet absorbers, light stabilizers, antioxidants, antistatic agents, lubricants, antiblocking agents, tackifiers, seals Add a property improver, anti-fogging agent, crystal nucleating agent, mold release agent, plasticizer, cross-linking agent, foaming agent, flame retardant, calcium carbonate, mica, talc, glass fiber, colorant (pigment, dye, etc.) You can also. In particular, nonionic surfactants such as polyglycerin fatty acid ester, sorbitan fatty acid ester, polyethylene glycol fatty acid ester, polyoxyethylene fatty acid amide, and fatty acid alkanolamide can be used alone or in combination as the antifogging agent. Also,
When weather resistance is required, it is desirable to mix an ultraviolet absorber, a light stabilizer or a combination thereof with an antioxidant. In this case, as the ultraviolet absorber, light stabilizer and antioxidant to be used, known ones usually used for polyolefins are suitable. Furthermore, if necessary, the amorphous polyolefin (A) or a thermoplastic resin, a thermoplastic elastomer, rubbers, etc. other than the amorphous polyolefin (A) and the crystalline polypropylene (B) may be used. They can be blended in amounts that do not impair the objects of the invention, and they can also be crosslinked.

In the present invention, the method for preparing the polyolefin-based resin composition containing the amorphous polyolefin (A) and the crystalline polypropylene (B) is not particularly limited. It is prepared by a method commonly used in the production method of For example, the two essential main resin components supplied in the above-described mixing ratio, that is, the amorphous polyolefin (A) and the crystalline polypropylene (B), and the above-described additives that are added as necessary, A method of preparing from a modifier and a filler (hereinafter simply referred to as “additive”) by premixing (dry blending) and subsequent melt kneading can be applied. In this case, the preliminary mixing can be performed at room temperature using a high-speed rotary mixer such as a Henschel mixer or a low-speed rotary mixer such as a cone blender or a tumbler, which is used for ordinary mixing. In addition, melt kneading includes Banbury mixer, super mixer, mixing roll, twin-screw continuous mixer, Brabender plastograph,
Using a device such as a kneader, a single-screw extruder, a twin-screw extruder or the like, the melting of each of the components can be carried out at a temperature at which the melting proceeds sufficiently and does not decompose. Specifically, the melt-kneading temperature is 1
It is 50-250 ° C, preferably 170-230 ° C.
When the melt-kneading temperature is lower than 150 ° C., the melt viscosity of the amorphous polyolefin (A) and the crystalline polypropylene (B) becomes too high in the melt-kneading apparatus, and the polyolefin, that is, the amorphous The kneading of the respective components is not sufficiently performed due to solidification of a part of the polyolefin (A) and / or the crystalline polypropylene (B). On the other hand, if the temperature is higher than 250 ° C., thermal decomposition or thermal degradation of the polyolefin occurs, which results in discoloration or deterioration of physical properties of the obtained polyolefin resin composition, which is not preferable. In order to surely prevent the occurrence of these undesirable phenomena, the melt-kneading temperature should be within the above-mentioned preferable range.

In the present invention, in the premixing and the subsequent melt-kneading, there are no particular restrictions on the order in which the two essential resin components and the additives to be added as necessary are added. At the time of pre-mixing, the essential main resin component and an additive to be added as necessary may be simultaneously compounded, or one of the two essential main resin components and, if necessary, After the additive and the additive to be added are first blended to produce a premix, for example, in a melt kneader such as a single-screw extruder or a twin-screw extruder, the premix is supplied from a raw material supply port while the remaining essential mixture is supplied. The main resin component may be supplied from the middle of the cylinder, and these components may be melt-kneaded. Alternatively, one of the essential main resin components, for example, in a melt kneader such as a single-screw extruder or a twin-screw extruder, while supplying from the raw material supply port, the remaining essential main resin component And an additive to be added as necessary may be supplied from the middle of the cylinder, and these components may be melt-kneaded.

Incidentally, the present invention is characterized in that the polyolefin-based resin composition obtained as described above is stretched at a specific stretching ratio described below to obtain a stretched film. That is, the film obtained by this stretching can delay the bleed-out of the amorphous polyolefin (B) contained therein during storage, maintain high transparency for a long time, and be put to practical use. It becomes something.

The method for producing the stretched film of the present invention is not particularly limited, and it is produced by a known method. For example, the unstretched raw material of the polyolefin resin composition is obtained by a T-die method using an extruder and a T-die connected to the extruder or an inflation method using an extruder and a circular die for inflation connected thereto. After the sheet is melt-extruded and solidified by cooling, it may be stretched by reheating to a temperature at which stretching is possible. As the stretching method, the unstretched raw sheet may be successively biaxially or simultaneously biaxially stretched by a tenter method, or may be uniaxially stretched in a fixed width in a longitudinal or transverse direction. Moreover, it can also be performed by simultaneous biaxial stretching by the inflation method. Furthermore, a sequential biaxial stretching method in which after stretching in the longitudinal direction between two sets of pinch rolls having a speed difference, stretching in the transverse direction by a tenter stretching machine can be employed. Among these stretching methods, in order to reduce the anisotropy of various physical properties of the stretched film, sequential biaxial stretching and simultaneous biaxial stretching are preferable, and sequential biaxial stretching is more preferable.

The stretching temperature range is not particularly limited as long as it is a temperature range in which uniform stretching can be performed. Therefore, a suitable stretching temperature range varies depending on the composition ratio of the amorphous polyolefin (A) and the crystalline polypropylene (B) constituting the polyolefin-based resin composition, and cannot be unconditionally described. However, the content of the amorphous polyolefin (A), which is a preferable range of the composition ratio in the present invention, is 20 to
80% by weight, that is, the crystalline polypropylene (B)
At a room temperature (20% by weight) when the content of
° C) to 5 from the melting point of the crystalline polypropylene (B).
It is desirably in the range of a temperature lower by 10 ° C, preferably in the range of 60 ° C to a temperature lower by 10 ° C than the melting point of the crystalline polypropylene (B). When the stretching temperature is lower than room temperature, the polyolefin resin composition is insufficiently softened, so that uniform stretching cannot be performed. On the other hand, when the stretching temperature is higher than a temperature lower by 5 ° C. than the melting point of the crystalline polypropylene (B), the stretching is performed uniformly, but the molecular orientation of the film is insufficient or the film frequently breaks during the stretching. Or On the other hand, in the present invention, the stretching ratio of the unstretched raw sheet is required to be not less than 2 times, preferably not less than 4 times, more preferably not less than 8 times in terms of area ratio in one direction or longitudinal and transverse directions. is there. If the stretching ratio is less than 2 times in area ratio, the effect of retarding the bleed-out of the amorphous polyolefin (A) contained therein during storage of the stretched film becomes insufficient. It is not preferable because it is difficult to maintain the transparency for a long time. Then, in order to surely prevent the occurrence of these undesirable phenomena, the stretching ratio of the unstretched raw sheet should be within the above-mentioned preferable range, and more preferably, within the above-mentioned more preferable range. The upper limit of the stretching ratio of the unstretched raw sheet is not particularly limited, but is preferably 70 times or less in terms of area ratio in consideration of the breaking of the stretched film and the ease of the stretching operation. In the case of sequential biaxial stretching or simultaneous biaxial stretching,
The stretching ratios may not be the same in the vertical and horizontal directions, but are preferably the same in the vertical and horizontal directions in order to obtain physical properties such as good strength in the obtained stretched film.

In the present invention, the film taken out of the stretching device may be, if necessary, at a temperature not lower than the above-mentioned stretching temperature.
5 ° C. from the melting point of the crystalline polypropylene (B)
It is also possible to heat set at a temperature in the range of low temperature or lower for 1 minute or more. By this heat setting, natural shrinkage of the obtained film can be suppressed.

The mechanical properties of the stretched film obtained as described above are not particularly limited, but the tensile strength is 4.0.
kgf / mm ² or more, preferably 5.0 kgf / mm ²
As described above, the tensile elongation is in the range of 40 to 400%, and the tensile modulus is preferably in the range of 10 to 120 kgf / mm ² at 23 ° C., and more preferably in the range of 12 to 70 kgf / mm ² . The tensile modulus at 80 ° C. is preferably 5 kgf / mm ² or more. When the tensile strength of the stretched film is smaller than 4.0 kgf / mm ² ,
The film is easily torn. Therefore, in the case of stretch packaging, it is necessary to increase the thickness of the film so as not to break the film. On the other hand, when the tensile elastic modulus at 23 ° C. of the stretched film is less than 10 kgf / mm ² , the film has no rigidity, so that the packaging operation is difficult, and there is a problem that the automatic packaging machine is not particularly required. On the other hand, when the tensile modulus at 23 ° C. of the stretched film is larger than 120 kgf / mm ² , the film becomes hard and the elongation of the film becomes small. Further, when shrink-wrapping fresh foods and the like, the shrinkage stress increases, and it becomes difficult to maintain the shape of soft food. And, the tensile elastic modulus at 80 ° C. of the stretched film is 5 kgf / m
When it is smaller than m ² , the film is easily deformed. In addition, the thickness of the stretched film of the present invention varies depending on the packaging use and is not particularly limited.
μm, preferably 10 to 200 μm.

[0034]

The present invention will be described in more detail with reference to the following Examples and Comparative Examples, which do not limit the present invention in any way. In the following Examples and Comparative Examples, haze (%) of the stretched film and the raw sheet is
The measurement was performed according to ASTM D1003.

Examples 1 to 7 [Preparation of polyolefin resin composition] Density 0.86 g
/ Cm ³ , propylene content 65% by weight, butene-1 content 35% by weight and melt viscosity 10,000 cps (1
90 ° C) amorphous polyolefin (manufactured by Ube Lexen)
Product name: UBETAC APAO UT2780)
Density 0.90 g / cm ³ and melt flow rate (M
FR) (230 ° C.) = 1.0 g / 10 min crystalline polypropylene (G221, trade name: F221)
Are mixed at a weight ratio of 50/50, and a 30 mmφ twin screw extruder (manufactured by Ikegai Iron Works Co., Ltd., model: PCM30 / 3-40-)
4V), melt-kneaded at a temperature of 200 ° C., extruded into strands, introduced into a water bath, cooled, cut,
After drying, pellets of the polyolefin-based resin composition were prepared.

[Forming of raw sheet] Subsequently, pellets of the polyolefin resin composition prepared as described above were subjected to a 30 mmφ twin-screw extruder (manufactured by Ikegai Iron Works Co., Ltd., model:
PCM30 / 3-40-4V) and melt-extruded using the extruder and a T-die connected to the extruder. Next, the obtained molten resin was cooled and solidified by a cooling roll and air cooling to form a raw sheet having a thickness of 0.3 mm.

[Stretching and heat fixation] Then, a tenter type biaxial stretching apparatus (manufactured by Iwamoto Seisakusho Co., Ltd., model: BIX-7)
03), the raw sheet was preheated at 100 ° C. for about 2 minutes, and then biaxially stretched sequentially to the magnification shown in Table 1. Thereafter, each was heat-set at 100 ° C. for the time shown in Table 1 to obtain a stretched film. The time change of the transparency of the obtained stretched film (that is, the haze (%) of the film immediately after stretching and after standing at room temperature for 14 days after stretching) was as shown in Table 1, respectively.

[0038]

[Table 1]

Examples 8 to 10 In stretching the raw sheet, the stretching ratio was changed from 5 times in the machine direction and the transverse direction, that is, from 25 times in the area ratio, to the ratios shown in Table 2, respectively. and,
Except that the stretching method was simultaneous biaxial stretching instead of sequential biaxial stretching, the same operation as in Example 1 was performed to obtain a stretched film. The time change of the transparency of the obtained stretched film (that is, the haze (%) of the film immediately after stretching and after standing at room temperature for 14 days after stretching) was as shown in Table 2.

Examples 11 and 12 In stretching the raw sheet, the stretching ratio was changed from 5 times in the machine direction and the transverse direction, that is, from 25 times in the area ratio, to the ratios shown in Table 2, respectively. and,
A completely stretched film was obtained by performing exactly the same operation as in Example 1 except that the stretching method was changed to sequential fixed biaxial stretching instead of biaxial stretching. Table 2 shows the time change of the transparency of the obtained stretched film (that is, the haze (%) of the film immediately after stretching and after standing at room temperature for 14 days after stretching).
As shown in FIG.

[0041]

[Table 2]

Comparative Example 1 [Preparation of Polyolefin Resin Composition] Density 0.86 g
/ Cm ³ , propylene content 65% by weight, butene-1 content 35% by weight and melt viscosity 10,000 cps (1
90 ° C) amorphous polyolefin (manufactured by Ube Lexen)
Product name: UBETAC APAO UT2780)
Density 0.90 g / cm ³ and melt flow rate (M
FR) (230 ° C.) = 1.0 g / 10 min crystalline polypropylene (G221, trade name: F221)
Are mixed at a weight ratio of 50/50, and a 30 mmφ twin screw extruder (manufactured by Ikegai Iron Works Co., Ltd., model: PCM30 / 3-40-)
4V), melt-kneaded at a temperature of 200 ° C., extruded into strands, introduced into a water bath, cooled, cut,
After drying, pellets of the polyolefin-based resin composition were prepared.

[Forming of Raw Sheet] Subsequently, the pellets of the polyolefin resin composition prepared as described above were subjected to a 30 mmφ twin screw extruder (manufactured by Ikegai Iron Works Co., Ltd., model:
PCM30 / 3-40-4V) and melt-extruded using the extruder and a T-die connected to the extruder. Next, the obtained molten resin was cooled and solidified by a cooling roll and air cooling to form a raw sheet having a thickness of 0.3 mm. After leaving the obtained raw sheet at room temperature for 3 days, the haze was measured. As a result, the haze was 60%, which was inferior in transparency.

[0044]

As is clear from the examples and comparative examples described above, an amorphous polyolefin having a propylene and / or butene-1 component content of not less than 50% by weight is used.
0 to 100% by weight and 80 to 0% of crystalline polypropylene.
% By weight (however, the sum of the amorphous polyolefin and the crystalline polypropylene is 100% by weight), whereas the unstretched product of the polyolefin-based resin composition has a relatively low transparency in a relatively short time. It can be seen that a stretched film obtained by stretching the polyolefin-based resin composition, in particular, sequential biaxial stretching or simultaneous biaxial stretching, can maintain high transparency for a long time. Thus, the stretched film of the present invention is excellent in transparency, optical properties such as haze, flexibility, heat resistance, and the like, and upon storage, bleed out to the surface of the amorphous polyolefin contained therein. And can maintain high transparency for a long time, and can be suitably used as a packaging film material such as a stretch packaging, a stretch shrink packaging and a shrink packaging as a soft film comparable to a soft vinyl chloride film or a vinylon film. .

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location B29L 7:00

Claims (3)

[Claims] 1. An amorphous polyolefin having a content of (A) propylene and / or butene-1 of 50% by weight or more is 20 to 100% by weight, and (B) a crystalline polypropylene is 80 to 0% by weight (provided that And the total amount of the amorphous polyolefin (A) and the crystalline polypropylene (B) is 100% by weight). 2. The stretched film according to claim 1, wherein the stretching is sequential biaxial stretching. 3. The stretched film according to claim 1, wherein the stretching is simultaneous biaxial stretching.