JP2003039608A - Packaging stretch film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a well-balanced stretch packaging laminated film comprising a non-vinyl chloride type resin and excellent in packaging properties, automatic packaging machine aptitude, packaging workability, packaging finish properties, bottom sealability, film tension, elongation, strain restoring properties, appearance, steam barrier properties, gas barrier properties or the like. SOLUTION: The stretch packaging film has at least one layer mainly comprising an isobutylene type block copolymer composed of a polymer block containing isobutylene as a monomer main component and a polymer block containing an aromatic vinyl compound as a monomer main component.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stretch film for packaging food, and more particularly to a stretch packaging film which is chlorine-free and has excellent packaging suitability, appearance, water vapor barrier property, gas barrier property and the like.

[0002]

2. Description of the Related Art Conventionally, fruits and vegetables, meat, side dishes, fresh fish, etc. are placed on a lightweight tray and overlapped with a film,
As a so-called pre-package stretch film, a polyvinyl chloride type has been mainly used. It has good packaging efficiency and good packaging finish, and also has excellent elastic recovery to return to its original shape when the film after packing is deformed by pushing with a finger, and also has a good bottom sealing property. This is because it has the quality superiority recognized by both sellers and consumers that the product value does not decrease, such as the film does not easily peel off during transportation display. However, in recent years, problems such as hydrogen chloride gas generated during incineration and elution of a plasticizer contained in a large amount have been regarded as problems with polyvinyl chloride films. For this reason, various materials have been studied as alternatives to the polyvinyl chloride film, and in particular, various stretch films having a structure using a polyolefin resin have been proposed. Not only various laminated films of polyethylene, but also ethylene-vinyl acetate copolymer (EVA), EVA / polybutene-1 / EV
A, a stretch film having a constitution of EVA / linear ethylene-α-olefin copolymer / EVA, and the like have been proposed. However, like PVC, packaging workability,
Packaging finish, elastic recovery, strain recovery, bottom sealability, sealability at or in contact with the tray, sealability with glued tray, direct heat sealability with glueless tray, film tension, elongation, It is difficult to satisfy all the packaging suitability and appearance such as flexibility, appropriate slipperiness, self-adhesiveness, resistance to peeling, water vapor barrier property and gas barrier property.

[0003]

SUMMARY OF THE INVENTION An object of the present inventor is to provide a non-vinyl chloride type stretch film excellent in the above-mentioned various properties.

[0004]

Means for Solving the Problems That is, the present invention provides a stretch packaging film comprising a laminated film,
Characterized by having at least one layer containing an isobutylene-based block copolymer as a main component, which is composed of a polymer block containing isobutylene as a main monomer component and a polymer block containing an aromatic vinyl compound as a main monomer component. It is a stretch wrapping film. The present invention also provides a mixed layer comprising at least one selected from the group consisting of a tackifier resin, a polyolefin-based polymer, and a mixture of a tackifier resin and a polyolefin-based polymer, and the isobutylene block copolymer. A stretch packaging film having at least one layer can also be used. Further, it may be a laminated film having a layer containing a polyolefin-based polymer as a main component. The polyolefin-based polymer is preferably at least one selected from a propylene polymer, a butene-1 polymer, an ethylene-α-olefin copolymer, and an ethylene-vinyl acetate copolymer. The stretch packaging film described above, which may have a layer containing an aromatic vinyl-conjugated diene block copolymer or a hydrogenated product thereof, has a loss measured by dynamic viscoelasticity measurement at a frequency of 10 Hz and a temperature of 20 ° C. Tangent (ta
nδ) is preferably in the range of 0.2 to 0.8.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is described in detail below.
The stretch film of the present invention comprises a layer having an isobutylene-based block copolymer as a main component, which is composed of a polymer block having isobutylene as a main monomer component and a polymer block having an aromatic vinyl compound as a main monomer component. Those having at least one layer are preferable.

The isobutylene block copolymer generally has rubber elasticity, flexibility, resistance to breakage, and good transparency. Heretofore, styrene-butadiene block copolymers, styrene-isoprene block copolymers or hydrogenated products thereof have been known as this type of copolymer, and some of them are used for film applications. The part is viscoelastic and is not suitable for the present invention. That is, this type of copolymer conventionally used conventionally has a small loss tangent (tan δ) at room temperature, which will be described later.
Further, as compared with the conventional conjugated diene type, the isobutylene type can not have a C = C unsaturated bond, and therefore is superior in thermal stability, heat aging resistance and color tone. Furthermore, the water vapor barrier property, the gas barrier property, and the viscoelasticity (ta
n δ), is also characterized. Of the present invention, the one that can satisfy the viscoelastic properties described later and has a high tan δ at room temperature is preferable. If necessary,
Isobutylene-based block copolymers having different aromatic vinyl-based monomer contents may be mixed, and a block copolymer of another styrene and a conjugated diene or a hydrogenated product thereof, for example, a styrene-butadiene block. Copolymer, styrene-butadiene-styrene block copolymer or hydrogenated product thereof, styrene-isoprene block copolymer, styrene-isoprene-styrene block copolymer or hydrogenated product thereof, styrene-vinylisoprene block copolymer A polymer, a styrene-vinylisoprene-styrene block copolymer, a hydrogenated product thereof, or the like may be used alone or in combination of two or more.

The isobutylene block has a block obtained by randomly copolymerizing an aromatic vinyl monomer with isobutylene, or an isobutylene block is copolymerized with an aromatic vinyl monomer with a certain concentration gradient. It may be a tapered block. In the present invention, it is also possible to use a random copolymer of an aromatic vinyl monomer and isobutylene.

Further, a copolymer of an aromatic vinyl monomer and isobutylene may be blended with another polymer or other material having good compatibility. The isobutylene block copolymer that can be used in the present invention has a polymer block containing isobutylene as a monomer main component and a polymer block containing an aromatic vinyl compound as a monomer main component. There is no particular limitation as long as it is, for example, any of block copolymers having a linear, branched, star-shaped structure, diblock copolymer, triblock copolymer, multiblock copolymer, etc. can be selected. It is possible to select a material that meets each physical property and workability requirement.

The aromatic vinyl-based compound-containing monomer component of the present invention has an aromatic vinyl-based compound content of 6%.
The monomer component is 0% by weight or more, preferably 8
It is preferably 0% by weight or more, and more preferably 90% by weight or more.

As the aromatic vinyl compound, styrene, o-, m- or p-methylstyrene, α-methylstyrene, β-methylstyrene, 2,6-dimethylstyrene, 2,4-dimethylstyrene, α- Methyl-o-methylstyrene, α-methyl-m-methylstyrene, α-methyl-p-methylstyrene, β-methyl-o-methylstyrene, β-methyl-m-methylstyrene, β-methyl-p-methyl Styrene, 2,4,6-trimethylstyrene, α-methyl-2,6-dimethylstyrene, α-methyl-2,4-dimethylstyrene, β-methyl-2,6-
Dimethylstyrene, β-methyl-2,4-dimethylstyrene, o-, m- or p-chlorostyrene, 2,6-dichlorostyrene, 2,4-dichlorostyrene, α-chloro-o-chlorostyrene, α- Chloro-m-chlorostyrene, α-chloro-p-chlorostyrene, β-chloro-
o-chlorostyrene, β-chloro-m-chlorostyrene, β-chloro-p-chlorostyrene, 2,4,6-trichlorostyrene, α-chloro-2,6-dichlorostyrene, α-chloro-2,4 -Dichlorostyrene, β-chloro-2,6-dichlorostyrene, β-chloro-2,4
-Dichlorostyrene, o-, m- or p-t-butylstyrene, o-, m- or p-methoxystyrene, o-,
m- or p-chloromethylstyrene, o-, m- or p
-Bromomethylstyrene, styrene derivatives substituted with a silyl group, indene, vinylnaphthalene and the like. These may be used alone or in combination of two or more. Among them, it is preferable to use one or more kinds of monomers selected from the group consisting of styrene, α-methylstyrene, p-methylstyrene and indene. From the viewpoint of cost, styrene, α-methylstyrene, or these It is particularly preferred to use a mixture of

The monomer other than the aromatic vinyl compound in the monomer component containing the aromatic vinyl compound of the present invention as a main component is not particularly limited as long as it is a cationically polymerizable monomer component. Examples thereof include aliphatic olefins, dienes, vinyl ethers, silanes, vinylcarbazole, β-pinene, and acenaphthylene. These may be used alone or in combination of two or more.

Examples of the aliphatic olefinic monomer include ethylene, propylene, 1-butene, 2-methyl-1-butene, 3-methyl-1-butene, pentene, hexene, cyclohexene and 4-methyl-1-pentene. , Vinylcyclohexane, octene, norbornene and the like.
These may be used alone or in combination of two or more.

Examples of the diene monomer include butadiene, isoprene, hexadiene, cyclopentadiene, cyclohexadiene, dicyclopentadiene, divinylbenzene, ethylidene norbornene and the like. These may be used alone or in combination of two or more.

The vinyl ether type monomers include methyl vinyl ether, ethyl vinyl ether, (n-, iso) propyl vinyl ether, (n-, sec-, te).
Examples include rt-, iso) butyl vinyl ether, methyl propenyl ether, ethyl propenyl ether and the like. These may be used alone or in combination of two or more.

As the silane compound, vinyltrichlorosilane, vinylmethyldichlorosilane, vinyldimethylchlorosilane, vinyldimethylmethoxysilane, vinyltrimethylsilane, divinyldichlorosilane, divinyldimethoxysilane, divinyldimethylsilane, 1,3-
Examples thereof include divinyl-1,1,3,3-tetramethyldisiloxane, trivinylmethylsilane, γ-methacryloyloxypropyltrimethoxysilane, γ-methacryloyloxypropylmethyldimethoxysilane and the like.
These may be used alone or in combination of two or more.

The isobutylene-based monomer component of the present invention may or may not contain a monomer other than isobutylene, and generally contains 60% by weight or more of isobutylene, preferably 80%. It is a monomer component containing at least wt%. The monomer other than isobutylene is not particularly limited as long as it is a cationically polymerizable monomer, and examples thereof include the above monomers.

The ratio of the polymer block containing isobutylene as the main monomer component and the polymer block containing no isobutylene as the main monomer component is not particularly limited and may be selected from the balance of physical properties and processability. For example, from the viewpoint of the sealing property with the glued tray and the peeling property of the film wound into a roll, the polymer block containing isobutylene as a monomer main component is preferably 10 to 50% by weight, and 10 to 50% by weight. 30% by weight is preferred.

The preferred structure of the isobutylene block copolymer of the present invention is a polymer block-isobutylene containing an aromatic vinyl compound as a monomer main component from the viewpoint of physical properties and processability of the resulting composition. A polymer block containing monomer as a main component-a triblock copolymer having a structure of a polymer block containing an aromatic vinyl compound as a main component, and a polymer block containing isobutylene as a main component -Polymer block containing an aromatic vinyl compound as a monomer main component, a triblock copolymer formed from a polymer block containing isobutylene as a monomer main component, and a polymer containing styrene as a monomer main component. Diblock copolymer formed from a polymer block containing block isobutylene as a monomer main component, and polymer containing an aromatic vinyl compound as a main component Rock - preferably be at least one diblock copolymer formed isobutylene from the polymer block whose monomer major component is selected from the group consisting of star-shaped polymer to be the arm.

The weight average molecular weight of the isobutylene block copolymer is not particularly limited, but from the viewpoint of physical properties and processability, it is 3,000 to 1,500,000,
It is preferably from 000 to 550,000, and 20,
Particularly preferably 000 to 400,000,
It is particularly preferably 50,000 to 250,000. When the weight average molecular weight of the isobutylene-based block copolymer is lower than the above range, the physical properties of the composition are not sufficiently expressed, while when it exceeds the above range, it is disadvantageous in terms of processability. In particular, when a film of the viscoelastic composition is prepared by extrusion molding, the weight average molecular weight of the isobutylene block copolymer is 20,000 to 400,000.
By this, the surface property of the film is improved, and it is most preferable in terms of processability. The molecular weight distribution is 10 or less, preferably 3 or less, more preferably 2 or less. Melt flow rate of isobutylene block copolymer (200 ° C,
5000 g) is preferably 1.0 to 20 g / 10 minutes. This value differs depending on the molding method. For example, in inflation molding, 2.0 to 15 g / 10 minutes, T
In die molding, it is 3.0 to 20 g / 10 minutes. Generally, when the melt flow rate is high, the strength of the film becomes weak, and when it is low, the extrudability becomes poor. Further, for the purpose of improving the adhesion of the composition used in the present invention to the heat-sealing adhesive layer, an isobutylene block copolymer having various functional groups in the molecular chain or at the terminal of the molecular chain is used. be able to. Examples of the functional group include an ether group such as an epoxy group, a hydroxyl group, an amino group, an alkylamino group and an alkoxyl group, a carboxyl group, an alkoxycarbonyl group, an ester group such as an acyloxyl group, a carbamoyl group, an alkylcarbamoyl group and an acylamino group. Amide group, acid anhydride group such as maleic anhydride, silyl group,
Examples thereof include allyl group and vinyl group. The isobutylene-based block copolymer may have only one type of these functional groups, or may have two or more types. Preferred functional groups in terms of physical property balance and the like include an epoxy group, an amino group, an ether group, an ester group, an amide group, a silyl group, an allyl group, and a vinyl group.

The method for producing the isobutylene-based block copolymer is not particularly limited, and a known polymerization method can be used. In order to obtain a block copolymer having a controlled structure, the following general formula ( It is preferable to polymerize a monomer containing isobutylene as a main component and a monomer component containing no isobutylene as a main component such as an aromatic vinyl-based monomer in the presence of the compound represented by 1). (CR ₁ R ₂ X) nR ₃ (1) [In the formula, X represents a substituent selected from the group consisting of a halogen atom, an alkoxyl group having 1 to 6 carbon atoms and an acyloxyl group having 1 to 6 carbon atoms. . R1 and R2 each represent a hydrogen atom or a monovalent hydrocarbon group having 1 to 6 carbon atoms. R1 and R2 may be the same or different. In addition, a plurality of R1 and R2 that are present may be the same or different. R3 represents a polyvalent aromatic hydrocarbon group or a polyvalent aliphatic hydrocarbon group which can have n substituents. n represents a natural number of 1 to 6. Examples of the halogen atom include chlorine, fluorine, bromine, iodine and the like. The alkoxyl group having 1 to 6 carbon atoms is not particularly limited, and examples thereof include a methoxy group, an ethoxy group, an n- or isopropoxy group, and the like. The acyloxyl group having 1 to 6 carbon atoms is not particularly limited, and examples thereof include an acetyloxy group and a propionyloxy group. The hydrocarbon group having 1 to 6 carbon atoms is not particularly limited, and examples thereof include a methyl group, an ethyl group and n-
Alternatively, an isopropyl group and the like can be mentioned.

The compound represented by the above general formula (1) serves as an initiator and is considered to generate a carbon cation in the presence of a Lewis acid or the like and serve as a starting point of cationic polymerization. Examples of the compound represented by the general formula (1) used in the present invention include the following compounds. (1-Chloro-1-methylethyl) benzene [C ₆ H ₅ C
(CH _{3) 2} Cl] 1,4- bis (1-chloro-1-methylethyl) benzene _{[1,4-Cl (CH 3)} 2 CC 6 H 4 C (CH 3) 2 Cl] 1,3- bis (1-chloro-1-methylethyl) benzene _{[1,3-Cl (CH 3)} 2 CC 6 H 4 C (CH 3) 2 Cl] 1,3,5- tris (1-chloro-1-methyl ethyl)
Benzene _{[1,3,5- (ClC (CH 3)} 2) 3 C 6 H 3] 1,3- bis (1-chloro-1-methylethyl) -5-
(Tert-Butyl) benzene [1,3- (C (C
_{H 3) 2 Cl) 2 -5-} (C (CH 3) 3) C 6 H 3] Especially preferred are bis Among these (1-chloro -1
- methylethyl) benzene _{[C 6 H 4 (C (} CH 3) 2 C
1) ₂ ] and tris (1-chloro-1-methylethyl) benzene [(ClC (CH ₃ ) ₂ ) ₃ C ₆ H ₃ ]. Bis (1-chloro-1-methylethyl) benzene is also called bis (α-chloroisopropyl) benzene, bis (2-chloro-2-propyl) benzene or dicumyl chloride, and tris (1-chloro-benzene). 1-methylethyl) benzene is tris (α-chloroisopropyl) benzene, tris (2-chloro-2-propyl).
Also called benzene or tricumyl chloride. In _{2-5- (C (CH 3) 3} ) C 6 H 3 The polymerization reaction can coexist Lewis acid catalyst. Any Lewis acid may be used as long as it can be used for cationic polymerization, and TiCl ₄ , TiBr ₄ , BCl ₃ , B
F ₃ , BF ₃ · OEt ₂ , SnCl ₄ , SbCl ₅ , SbF ₅ , WC
l ₆ , TaCl ₅ , VCl ₅ , FeCl ₃ , ZnBr ₂ , AlCl
₃ , metal halides such as AlBr ₃ ; Et ₂ AlCl, E
Organometallic halides such as tAlCl ₂ can be preferably used. Considering the catalytic ability and industrial availability, TiCl ₄ , BCl ₃ , SnCl
₄ is preferred.

The amount of the Lewis acid catalyst used is not particularly limited and can be set in consideration of the polymerization characteristics or the polymerization concentration of the monomers used.

In the above polymerization reaction, if necessary, an electron donor component may coexist. This electron donor component is believed to have the effect of stabilizing the growing carbocation during cationic polymerization.
The addition of an electron donor produces a polymer with a controlled structure with a narrow molecular weight distribution. The electron donor component that can be used is not particularly limited, and examples thereof include pyridines, amines, amides, sulfoxides, esters, and metal compounds having an oxygen atom bonded to a metal atom.

The above polymerization reaction can be carried out in an organic solvent, if necessary, and the organic solvent can be used without particular limitation as long as it does not substantially inhibit the cationic polymerization. Specifically, halogenated hydrocarbons such as methyl chloride, dichloromethane, chloroform, ethyl chloride, dichloroethane, n-propyl chloride, n-butyl chloride and chlorobenzene; benzene, toluene, xylene,
Alkylbenzenes such as ethylbenzene, propylbenzene and butylbenzene; linear aliphatic hydrocarbons such as ethane, propane, butane, pentane, hexane, heptane, octane, nonane and decane; 2-methylpropane,
2-methylbutane, 2,3,3-trimethylpentane,
Branched aliphatic hydrocarbons such as 2,2,5-trimethylhexane; cycloaliphatic hydrocarbons such as cyclohexane, methylcyclohexane, ethylcyclohexane; paraffin oil obtained by hydrogenating and refining petroleum fractions. it can.

These solvents are used alone or in combination of two or more in consideration of the balance between the polymerization characteristics of the monomers constituting the block copolymer and the solubility of the resulting polymer.

The amount of the above-mentioned solvent used is 1 to 1 in consideration of the viscosity of the obtained polymer solution and the ease of heat removal.
It is determined to be 50 wt%, preferably 3 to 35 wt%.

In carrying out the actual polymerization, the respective components are mixed under cooling, for example, at a temperature of -100 ° C or higher and lower than 0 ° C. In order to balance the energy cost and the stability of polymerization, a particularly preferable temperature range is -30 ° C to -80 ° C.

The above-mentioned polymerization reaction may be carried out in a batch system (batch system or semi-batch system) or in a continuous system in which each component necessary for the polymerization reaction is continuously added into the polymerization vessel.

Further, as a method for producing a star-shaped polymer having a diblock copolymer formed from a polymer block containing styrene as a monomer main component and a polymer block containing isobutylene as a monomer main component as an arm, Although not particularly limited, for example, a method of polymerizing a monomer having styrene as a main component and a monomer component having isobutylene as a main component in the presence of a compound having three or more cationic polymerization initiation points, styrene A diblock copolymer is produced by polymerizing a monomer having a main component and a monomer component having isobutylene as a main component, and thereafter, using a polyfunctional compound as a coupling agent (binder), Examples thereof include a method of coupling the diblock copolymer.

As the polyfunctional compound, a compound having three or more reaction points (functional groups) capable of coupling per molecule can be used. 2 per molecule
When a compound having three reaction points can be polymerized or reacted to form a polymer and have three or more reaction points (functional groups), it does not prevent use.

Examples of such polyfunctional compounds include 1,3-divinylbenzene, 1,4-divinylbenzene, 1,2-diisopropenylbenzene, 1,3-diisopropenylbenzene and 1,4. -Diisopropenylbenzene, 1,3-divinylnaphthalene, 1,8-divinylnaphthalene, 2,4-divinylbiphenyl, 1,2-
Divinyl aromatic compounds such as divinyl-3,4-dimethylbenzene, 1,3-divinyl-4,5,8-tributylnaphthalene and 2,2'-divinyl-4-ethyl-4'-propylbiphenyl; 2,4-trivinylbenzene, 1,3,5-trivinylnaphthalene, 3,5
Trivinyl aromatic compounds such as 4'-trivinylbiphenyl and 1,5,6-trivinyl-3,7-diethylnaphthalene; cyclohexane diepoxide, 1,4-pentane diepoxide, 1,5-hexane diepoxide, etc. Diepoxide; 2,4-hexane-dione, 2,5-hexane-dione, diketone such as 2,6-heptane-dione; 1,4-butanedial, 1,5-pentanedial, 1,6-hexanedial Dialdehydes such as;
Examples thereof include siloxane compounds and calixarene. These may be used alone or in combination of two or more.

Among these, divinyl aromatic compounds are preferably used from the viewpoints of reactivity, physical properties of the resulting star polymer, and particularly preferred are 1,3-divinylbenzene, 1,4-divinylbenzene, 1, It is at least one selected from the group consisting of 3-diisopropenylbenzene and 1,4-diproisopenylbenzene. The above-mentioned compound is usually commercially available as a mixture with, for example, ethylvinylbenzene, and can be used as it is if the above-mentioned divinylaromatic compound is the main component, and if necessary, purified to increase the purity. You may use. The film of the present invention has a frequency of 10H as measured by dynamic viscoelasticity.
z, the loss tangent (tan δ) measured at a temperature of 20 ° C. is 0.
It is in the range of 2 to 0.8. If tan δ is less than 0.2, the restoring behavior with respect to the elongation of the film is instantaneous, so the film is restored in a short time before the film is folded into the bottom of the tray, and the film cannot be stretched well. Wrinkles easily occur. Also in the heat-sealed state of the bottom portion, in the case of stretch packaging, it is difficult to perform sufficient fusion bonding due to heat, so that the bottom seal is likely to be peeled off gradually during transportation or display after packaging. Further, if tan δ exceeds 0.8, the packaging finish is good, but plastic deformation is exhibited and the tension of the packed product against the external force is too weak, and the tray top surface is stuck due to stacking during transportation or display. The film tends to sag and the commercial value tends to decrease. Further, in the case of automatic packaging, problems such as a defective check are likely to occur because it tends to stretch vertically. ta
A particularly preferable range of nδ is 0.3 to 0.6.

The stretch packaging film having at least one layer of the isobutylene block copolymer of the present invention has relatively excellent packing suitability such as adhesiveness and flexibility, but is preferably a tackifier. (Petroleum resin, terpene resin, coumarone-indene resin, rosin-based resin, hydrogenated derivatives thereof, etc.) and / or polyolefin-based polymer may be mixed. Tackifiers and the like increase the glass transition temperature of the composition to achieve desired viscoelastic properties, and the polyolefin-based polymer enhances the strength of the mixture without significantly impairing the transparency and the viscosity of the mixture. It adjusts the elastic characteristics. Here, as the tackifier, there are alicyclic petroleum resin from polybutene, cyclopentadiene or a dimer thereof and aromatic petroleum resin from C9 component, and the terpene resin is terpene resin or terpene from β-pinene. -Phenol resins and aromatic modified terpene resins, and as rosin-based resins, rosin resins such as gum rosin and utudrosine,
Esterified rosin resin modified with glycerin, pentaerythritol, etc., coumarone-indene resin, aliphatic petroleum resin, alicyclic petroleum resin, aliphatic aromatic copolymer petroleum resin, low molecular weight polymer of styrene or substituted styrene Can be exemplified. It is known that this component shows a relatively good compatibility when mixed with the above-mentioned styrene-isobutylene block copolymer component, etc., however, from the viewpoint of color tone, thermal stability and compatibility, a hydrogenated derivative is recommended. It is preferable to use. These can be used alone or in combination of two or more. It should be noted that this component can be obtained mainly having various glass transition temperatures depending on the molecular weight, but the glass transition temperature of 50 to 130 is applicable to the present invention.
C., preferably 70 to 90.degree. When the glass transition temperature is less than 50 ° C., a large amount must be contained in order to obtain the viscoelastic properties described below when mixed with the above-mentioned styrene-isobutylene block copolymer component, and the material by bleeding to the surface It is easy to cause blocking of film and film. In addition, the mechanical strength of the film as a whole is insufficient and the film tends to be broken, which may cause a problem in practical use. On the other hand, when the glass transition temperature exceeds 130 ° C., the compatibility with the styrene-isobutylene block copolymer component is deteriorated, and bleeding may occur on the film surface over time, leading to blocking and deterioration of transparency.

For the above reasons, it is preferable that the content of this component is as small as possible within the range where the viscoelastic properties described later can be achieved.
By the way, when a desired viscoelastic property (tan δ value) cannot be obtained with only two components of an aromatic vinyl monomer-isobutylene block copolymer and a tackifier,
When sufficient strength cannot be obtained as a stretch film, in the present invention, a propylene polymer, butene-1
Polymers, ethylene polymers, ethylene-α-olefin copolymers, modified ethylene polymers, polyolefin polymers such as ethylene-vinyl acetate copolymer, preferably,
Propylene polymer, butene-1 polymer, ethylene-α-
At least one selected from an olefin copolymer and an ethylene-vinyl acetate copolymer may be mixed with the above two components. In the case of a particularly preferred propylene polymer, a resin containing 70 mol% or more of propylene, which is a homopolymer of polypropylene, a copolymer of propylene and ethylene or α-olefin having 4 to 12 carbon atoms, or a mixture thereof. Can be illustrated. If the propylene content is less than 70%, the crystallinity is too low to control the viscoelastic properties of the film or increase the strength. It also lacks stability during film formation. Propylene-based polymers generally have high crystallinity and high strength. Among polyolefin polymers, they have relatively high melting points and good heat resistance, but due to their high crystallinity, they require a large force during stretching and It exhibits only uniform elongation and these properties remain in the mixture.

Therefore, in the present invention, in order to obtain a film having good elongation, it is preferable to use a relatively low crystalline propylene-based copolymer as at least a part of the propylene-based polymer. As the copolymer in this case, a copolymer obtained by copolymerizing propylene with ethylene and α-olefin having 4 to 12 carbon atoms, such as butene, in an amount of about 3 to 30 mol% is preferable. Alternatively, EVA may be added.
Further, in order to set the tan δ of the mixed layer containing the styrene-isobutylene block copolymer, the polyolefin-based polymer and the tackifier resin of the present invention as the main components within the above range, it is most preferable to adjust the mixing ratio of the three components. It is effective. In order to have a tan δ in the range of 0.2 to 0.8 as a mixture, a styrene-isobutylene block copolymer component 20 to 60% by weight, a tackifier resin component 10 to 40% by weight, a polyolefin-based polymer. The component may be 20 to 70% by weight. If the content of the styrene-isobutylene block copolymer component is less than 20% by weight and the content of the polyolefin polymer component exceeds 70% by weight, the elastomer component will be insufficient, causing problems such as film breakage during stretch packaging. . Further, if the blending amount of the styrene-isobutylene block copolymer component exceeds 60% by weight and the blending amount of the polyolefin polymer component is less than 20% by weight, the film becomes stiff and difficult to handle and is not put to practical use. . When the compounding amount of the tackifier resin is less than 10% by weight, the self-adhesiveness of the film is inferior, and when it exceeds 40% by weight, the self-adhesiveness of the film is excellent, but the bleed-out on the film surface is severely sticky. There is a problem.

As another method for controlling the tan δ of the film of the present invention within the above range, it may be laminated with another non-vinyl chloride material layer. As the other resin layer, a polyolefin polymer described later (preferably a propylene polymer,
Butene-1 polymer, ethylene-α-olefin copolymer, ethylene-vinyl acetate copolymer) and the like,
By adjusting the viscoelastic characteristics of the film by laminating with these, the strength, softness, elongation, blocking resistance, adhesion between the adhesive films of the film,
The sealability with the tray (with glue) can be improved.

When a polyolefin polymer is selected as the other material layer of the laminated film, good interlayer adhesion can be obtained without interposing an adhesive layer. In the film of the present invention, of both outermost layers, one is a layer containing an isobutylene-based block copolymer as a main component, and the other is a layer containing a polyolefin-based polymer as a main component. A film with a well-balanced sealability with the tray (with glue), softness, and transparency.

As the polyolefin polymer of the layer containing the polyolefin polymer as a main component used in the present invention, low density polyethylene, linear low density polyethylene (copolymer of ethylene and α-olefin, preferably α -Olefin having 4 to 8 carbon atoms, for example, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene), ethylene-vinyl acetate copolymer (EVA), ethylene-alkyl acrylate copolymer, Ethylene-alkyl methacrylate copolymer, ethylene-acrylic acid copolymer (preferably acrylic acid content 5 to 20% by weight), ethylene-methacrylic acid copolymer, ethylene-maleic acid copolymer, ethylene-based ionomer (metal Zn as the salt,
Na, K, Li, Mg, etc.), polypropylene, propylene-ethylene copolymer, propylene-ethylene-α-olefin copolymer, propylene-based elastomer material, butene-1 polymer and the like are preferable. The butene-1 polymer can also be used for the purpose of improving the transparency of the propylene polymer and the ethylene polymer. Where α
-The content of olefin is preferably 6 to 20% by weight, more preferably 10 to 15% by weight. 6% by weight
If it is less than 1, the film becomes too hard. If it exceeds 20% by weight, the film becomes too soft and the releasability deteriorates.

The melt flow rate (190 ° C., 2160 g) of the polyolefin polymer is 0.1 to 5.0 g /
It is preferably 10 minutes. This value varies depending on the molding method. For example, in inflation molding, 0.5 to
3.0 g / 10 minutes, 1.5-5.0 g for T-die molding
/ 10 minutes. Generally, when the melt flow rate is high, the strength of the film is low, and when it is low,
The film stretches poorly.

Among these, from the viewpoint of packaging suitability, polypropylene, a propylene polymer such as propylene-ethylene copolymer or propylene-ethylene-butene-1 copolymer, butene-1 polymer, ethylene-α-olefin copolymer. Copolymers and ethylene-vinyl acetate copolymers are preferred.
These can be used alone or in combination of two or more. In particular, when an ethylene-vinyl acetate copolymer is preferably used, the vinyl acetate content is 3 to 40% by weight, preferably 5 to 20% by weight, more preferably 10 to 15% by weight.
% By weight, melt flow rate (190 ° C, 2160g)
Is 0.1 to 10 g / 10 minutes, preferably 0.2 to 5 g
/ 10 minutes is preferable in terms of strength, wrapping suitability, appearance and the like. If the content of vinyl acetate is less than 3% by weight, the film may have poor elongation, causing wrinkles and tears. If it exceeds 40% by weight, the adhesive strength of the film becomes too strong and the peeling of the film becomes poor, resulting in stickiness or blocking. In this case, the addition of a large amount of lubricant becomes a problem. Melt flow rate is 0.1g
If it is less than / 10 minutes, the elongation of the film becomes poor. When the melt flow rate exceeds 10 g / 10 minutes, the strength of the film becomes low. Although these polymers do not have the viscoelastic property (tan δ value) of the present invention as such, by combining them with an aromatic vinyl-isobutylene copolymer layer in an appropriate thickness ratio, the whole laminated film can be obtained. It is possible to obtain preferable viscoelastic properties. The thickness ratio may be determined according to the balance between the sealing property and the packaging suitability.

In general, a polyolefin polymer which can be used as a film for packaging has a tan δ of less than 0.2. Therefore, the aromatic vinyl-isobutylene copolymer has a tan δ of 0.25 or more, preferably 0. It is preferably 0.5 or more. By properly setting the thickness ratio of each layer, the above properties can be obtained as the entire laminated film.
The thickness of the film of the present invention is generally in the range used for ordinary stretch packaging, that is, about 5 to 30 μm, typically about 10 to 20 μm. The film of the present invention can be obtained by melt-extruding a material from one or a plurality of extruders and forming it into a film by inflation molding or T-die molding. In the case of a laminated film, it is preferable to coextrude with a multilayer die.
Alternatively, they are laminated and formed by a known method such as a coextrusion laminating method. You may stretch. Among these, the coextrusion inflation method is preferable because it is easy to balance the characteristics and the strength.

In the present invention, if necessary, a block copolymer of another aromatic vinyl monomer and a conjugated diene or a hydrogenated product thereof, for example, a styrene-butadiene block copolymer and a styrene. -Butadiene-styrene block copolymer or hydrogenated product thereof, styrene-isoprene block copolymer, styrene-isoprene-styrene block copolymer or hydrogenated product thereof, styrene-vinylisoprene block copolymer, styrene- The vinyl isoprene-styrene block copolymers or hydrogenated products thereof may be used alone or in combination of two or more. Furthermore, a block copolymer of an aromatic vinyl monomer and isobutylene, another polymer having good compatibility,
Other materials such as liquid polybutene, polyolefin (polyethylene, polypropylene, etc.), polystyrene, etc. may be blended. Specific examples of the block copolymer of the polymer block of the aromatic vinyl monomer and the polymer block of the conjugated diene or the hydrogenated product thereof,
Styrene-butadiene block copolymer, styrene-butadiene-styrene block copolymer or hydrogenated products thereof, styrene-isoprene block copolymer, styrene-isoprene-styrene block copolymer or hydrogenated products thereof, styrene- Examples thereof include vinyl isoprene block copolymers, styrene-vinyl isoprene-styrene block copolymers and hydrogenated products thereof, and these can be used alone or in admixture of two or more. Further, polystyrene may be mixed and used.

In each layer, in addition to the stabilizer, a surfactant,
If necessary, one or more kinds of lubricants, plasticizers, etc. may be added, for example, in order to adjust the slidability of the film.
Examples of the surfactant include alkyl fatty acid ester, glycerin fatty acid ester compound, sorbitan fatty acid ester compound, ethylene oxide adduct, propylene glycol fatty acid ester, polyalkylene ether polyol, dialkyl dibasic acid and the like. As the lubricant, oleic acid amide, stearic acid amide, erucic acid amide, lauric acid amide, ethylenebisstearic acid amide, ethylenebisoleic acid amide, powdered silica,
Examples include diatomaceous earth, kaolin, talc, zeolite and the like. Among these, oleic acid amide, stearic acid amide, and zeolite are preferable. Other mineral oils (paraffinic, naphthenic, aromatic, etc.), natural oils (castor oil,
At least one compound selected from synthetic oil softeners (low molecular weight liquid polymers such as liquid polybutene or liquid polyisoprene) may be blended.

[0044]

The present invention will be described in more detail with reference to the following examples. It should be noted that the present invention is not limited to these embodiments, and various modifications can be made without departing from the scope of the invention. The measurement conditions and the like are as shown below.

(Loss tangent) For the loss tangent [tan δ], a test piece was cut out from a sample sheet, and a dynamic viscoelasticity measuring device DVA-200 (manufactured by IT measurement control company) was used.
Was used to measure tan δ at 20 ° C. and 10 Hz.

(Number average molecular weight) 510 manufactured by Waters
Type GPC system (using chloroform as solvent,
The flow rate was set to 1 mL / min), and the value in terms of polystyrene was shown.

(Permeability Coefficient) Regarding the water vapor permeability coefficient,
The oxygen permeability coefficient and the carbon dioxide permeability coefficient were measured at 40 ° C. and 90% RH at 23 ° C., respectively.

(Production Example 1) [Production of Isobutylene Block Copolymer] In a 2 L reaction vessel equipped with a stirrer, 1-chlorobutane (dried with molecular sieves) 691 mL, hexane (dried with molecular sieves) 480 mL,
0.596 g of p-dicumyl chloride was added. After cooling the reaction vessel to -70 ° C, dimethylacetamide 1.
12 g and 232 mL of isobutylene were added. Further, 8.7 mL of titanium tetrachloride was added to start polymerization, and the temperature was -70 ° C.
The solution was reacted with stirring for 1.5 hours. Then, 77.9 g of styrene was added to the reaction solution, the reaction was continued for further 60 minutes, and then the reaction solution was poured into a large amount of water to stop the reaction. When the separation state of the organic layer and the aqueous layer was visually confirmed, the separability was good and the separation was easily performed with a separating funnel. After washing twice with water, after confirming that the aqueous layer is neutral, the organic layer is poured into a large amount of methanol to precipitate the polymer, and the obtained polymer is allowed to stand at 60 ° C. for 24 hours. An isobutylene block copolymer (SIBS) was obtained by vacuum drying.

The isobutylene block copolymer (SI
When the GPC analysis of (BS) was performed, the weight average molecular weight was 83,700 and the molecular weight distribution was 1.8. Also 1H
The styrene content determined by NMR was 29% by weight.

Example 1 A monolayer film of the isobutylene block copolymer obtained in Production Example 1 having a thickness of 15 μm was obtained by extrusion and inflation molding. When the dynamic viscoelastic property of the obtained sheet was measured, it was 20 ° C., 10
The tan δ at Hz was 0.5. Water vapor permeability coefficient, 4.3 (g · mm / m 2 · 24hr), the oxygen permeability coefficient × 10 ^{1 0 is, 0.6 (cm 3 · cm /} cm 2 · s · cm
Hg), carbon dioxide permeability coefficient x 10 ¹⁰ is 1.0 (cm
³ · cm / cm ² · s · cmHg). Moreover, it had good adhesiveness and flexibility.

(Example 2) 80 parts by weight of the isobutylene block copolymer obtained in Production Example 1, hydride of alicyclic petroleum resin Alcon P-100 (manufactured by Arakawa Chemical Co., Ltd.)
A film having a thickness of 20 μm and a thickness of 15 μm was obtained by coextrusion and inflation molding.

Example 3 45 parts by weight of the isobutylene block copolymer obtained in Production Example 1, hydride of alicyclic petroleum resin Alcon P-100 (manufactured by Arakawa Chemical Co., Ltd.)
25 parts by weight, propylene-ethylene random copolymer 3
A film having a thickness of 0 .mu.m and a thickness of 15 .mu.m was obtained by coextrusion and inflation molding.

Example 4 80 parts by weight of the isobutylene block copolymer obtained in Production Example 1 and 20 parts by weight of EVA were formed into a film having a thickness of 15 μm by coextrusion and inflation molding.

Example 5 The isobutylene block copolymer obtained in Production Example 1 was used as an intermediate layer, and both surfaces thereof were EV.
As the layer A, a film having a total thickness of 15 μm was obtained by coextrusion and inflation molding.

(Comparative Example 1) As in the example, the thickness is 15 μm.
m EVA single layer film was obtained. When the dynamic viscoelastic property of the obtained sheet was measured, it was 20 ° C., 10 Hz ta
nδ was 0.13. Each film of this example,
It was found that it has suitable packaging suitability including appearance.

(Comparative Example 2) SEBS (made by Shell Chemical Co., K
A 15 μm thick monolayer film of raton G1650) was obtained by extrusion and inflation molding. Water vapor permeability coefficient, 7.8 (g · mm / m 2 · 24hr), the oxygen permeability coefficient × 10 ^{1 0 is, 9.3 (cm 3 · cm /} cm 2 · s
-CmHg), carbon dioxide permeability coefficient x 10 ¹⁰ is 20.
It was 8 (cm ³ · cm / cm ² · s · cmHg). Each film of this example had a suitable loss coefficient (tan δ) and packaging suitability in addition to the appearance. The film was also excellent in water vapor barrier property and gas barrier property.

[0057]

INDUSTRIAL APPLICABILITY The laminated film for stretch packaging of the present invention has excellent appearance, loss factor (tan δ), water vapor barrier property, gas barrier property and suitability for packaging, and has a well-balanced industrial value. It is a laminated film for non-vinyl chloride stretch packaging.

Continued front page    F term (reference) 3E086 AD17 BA04 BA15 BB01 BB02                       BB87 CA01                 4F100 AK03A AK03B AK07A AK07B                       AK07J AK09B AK12A AK12C                       AK12J AK28C AK28J AK62B                       AK68B AL02A AL02C AL05A                       BA01 BA02 BA03 BA07 BA10A                       BA10B BA10C BA15 CA16A                       GB23 JD02 JD04 JK07 JK20                       YY00

Claims (6)

[Claims] 1. A stretch packaging film comprising a laminated film, wherein isobutylene comprises a polymer block containing isobutylene as a monomer main component and a polymer block containing an aromatic vinyl compound as a monomer main component. A film for stretch packaging comprising at least one layer containing a block copolymer as a main component. 2. A mixed layer comprising at least one selected from the group consisting of a tackifier resin, a polyolefin-based polymer and a mixture of a tackifier resin and a polyolefin-based polymer and the isobutylene block copolymer. The stretch packaging film according to claim 1, which has one layer. 3. The stretch packaging film according to claim 1, which is a laminated film having a layer containing a polyolefin-based polymer as a main component. 4. The polyolefin-based polymer is at least one selected from a propylene polymer, a butene-1 polymer, an ethylene-α-olefin copolymer, and an ethylene-vinyl acetate copolymer. Film for stretch packaging according to item 3 5. The stretch packaging film according to claim 1, further comprising a layer containing an aromatic vinyl-conjugated diene block copolymer or a hydrogenated product thereof. 6. The loss tangent (tan δ) measured by dynamic viscoelasticity measurement at a frequency of 10 Hz and a temperature of 20 ° C. is 0.2 to.
It is in the range of 0.8, The film for stretch packaging in any one of Claims 1-4 characterized by the above-mentioned.