JPS5849573B2 - Multilayer laminated structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a multilayer laminate structure comprising a polyethylene composition layer and an ethylene-vinyl alcohol copolymer layer.

Ethylene-vinyl alcohol copolymers with an ethylene content of 15 to 60 moles have excellent transparency and gas permeation resistance, high rigidity, and good heat resistance, making them suitable for packaging films and containers for foods, medicines, etc. It has favorable properties.

However, ethylene-vinyl alcohol copolymers have drawbacks such as high moisture permeability, low sealing strength, and poor heat-sealing properties, so they cannot be put to practical use as laminated structures with polyolefins. many.

In such a laminated structure, the problem is how firmly the layers can be bonded, and this is particularly important when the laminated structure is used after being boiled, such as in packaging materials for boiling-sterilized foods.

Coextrusion is one method of obtaining a laminated structure, but polyolefin and ethylene-vinyl alcohol copolymer have poor affinity and do not adhere to each other using normal coextrusion.)

As a method for adhering a laminated structure consisting of a polyolefin and an ethylene-vinyl alcohol copolymer by coextrusion, for example, an ionomer resin and an ethylene-containing polyolefin and/or an ethylene-vinyl alcohol copolymer are used. ii) A method is known in which an ethylene-vinyl acetate copolymer or a saponified product thereof, chlorinated polyethylene, chlorosulfonated polyethylene, ethylene-ethyl acrylate copolymer, etc. having a molar ratio of 60 or more are mixed.

(JP-A-49-4772, JP-A-49-35482, JP-A-49-37984, etc.) However, as a result of investigation by the present inventors, the interlayer adhesion of the laminated structure obtained by the above method is good. It was only about 5 Q g 7 cm at most, and delamination easily occurred due to decreased adhesion during long-term storage or boiling, so it could hardly be used as a packaging material for boiling-sterilized foods.

The present applicant discovered that polyethylene partially or wholly made of unsaturated carboxylic acid or its derivatives had good adhesion to ethylene-vinyl alcohol copolymer, and previously proposed (Japanese Unexamined Patent Application Publication No. 1973-1972) No. 77485).

Although this method is superior to the method using an ethylene polymer, it still has long-term adhesion,
Adhesion is still insufficient when used under harsh conditions, for example in boiling water.

An object of the present invention is to provide a multilayer laminate structure comprising a polyethylene layer and an ethylene-vinyl alcohol copolymer layer, which has significantly improved interlayer adhesion, particularly interlayer adhesion when immersed in boiling water.

Another object of the present invention is to provide a multilayer laminated structure having excellent water vapor permeation resistance, gas permeation resistance, and good squeezing properties.

That is, the present invention provides (at crystallinity 51 to 64φ
(b) 0.1 to 30 parts by weight of a modified ethylene polymer grafted with at least one monomer selected from unsaturated carboxylic acids or derivatives thereof, and (c) A polyethylene composition layer comprising 3 to 49.9 parts by weight of an ethylene polymer having a crystallinity of 5 to 50 (total 100 parts by weight) and an ethylene-vinyl alcohol copolymer having an ethylene content of 15 to 60 moles. It is a multilayer laminated structure consisting of layers.

The ethylene-vinyl alcohol copolymer used in the present invention has a saponification degree of 9 obtained by saponifying an ethylene-vinyl acetate copolymer having an ethylene content of 15 to 60 mol%.
0 to 100% polymer.

Ethylene-vinyl alcohol copolymers with an ethylene content of less than 15 moles φ are difficult to mold because the moldable temperature approaches the decomposition temperature.

If the ethylene content exceeds 60 molar ratios, the superior properties of the ethylene-vinyl alcohol copolymer, such as gas permeation resistance and mechanical properties, will deteriorate and the effect of forming a laminated structure will be lost.

Ethylene-vinyl alcohol copolymers having a degree of saponification of less than 90% are unfavorable in practical terms because of their poor mechanical properties, oil resistance, and water resistance.

The ethylene-vinyl alcohol copolymer used in the present invention may further include other polymers such as nylon, polyester, polyolefin, polycarbonate, ionomer resin, polyvinyl acetate, polystyrene, ABS resin, to the extent that the object of the present invention is not impaired. , mixtures of acrylic resin, vinyl chloride resin, etc., or epoxy compounds,
It may be modified with an incyanate compound or the like.

Furthermore, the ethylene-vinyl alcohol copolymer contains antioxidants, ultraviolet absorbers, antistatic agents, pigments, dyes, nucleating agents,
Additives such as base fillers, slip agents, lubricants, flame retardants, and plasticizers may be included to the extent that they do not impair the object of the present invention.

In the present invention, the ethylene polymer that is the raw material for the modified ethylene polymer grafted with an unsaturated carboxylic acid or its derivative (f1) is, for example, a homopolymer of ethylene that is polymerized by a high-pressure method or a medium-low pressure method. copolymer of ethylene with other polymerizable monomers of up to 20 mol, preferably 15 mol, such as ethylene and propylene]
-butene, 3-methyl] -butene, 1-hexane, 3
-Methyl-1-pentene, 4-methyl-]-A copolymer of one or more α-olefins such as pentene, a copolymer of ethylene and a vinyl ester such as vinyl acetate or vinyl propionate, or Saponified products thereof, copolymers of ethylene and unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid or derivatives thereof, such as anhydrides, esters, amides, imides, chlorides, metal salts, etc., ethylene and butadiene , dicyclopentadiene,
It refers to a copolymer of ethylidene norporene with a conjugated or non-conjugated diene, or a mixture of the above polymers.

Among these, high-density modified polyethylene is the most preferred because it has excellent adhesiveness to ethylene-vinyl alcohol copolymer, especially adhesive strength after immersion in boiling water.

In the present invention, an unsaturated carboxylic acid or a derivative thereof is used as a monomer (hereinafter referred to as a graft monomer) to be grafted onto the ethylene polymer.

Examples of unsaturated carboxylic acids include acrylic acid, methacrylic acid, maleic acid, fumaric acid, and itaconic acid.

Derivatives of unsaturated carboxylic acids include acid anhydrides, esters, amides, imides, metal salts, etc., such as maleic anhydride, citraconic anhydride, itaconic anhydride, methyl acrylate, methyl methacrylate, ethyl acrylate, Ethyl methacrylate, butyl acrylate, butyl methacrylate, glycidyl acrylate, glycidyl meccrylate,
Maleic acid monoethyl ester, maleic acid diethyl ester, fumaric acid monomethyl ester, fumaric acid dimethyl ester, itaconic acid monomethyl ester, itaconic acid diethyl ester, acrylamide, methacrylamide, maleic acid monoamide, maleic acid diamide, mono-N-maleic acid Ethylamide, maleic acid-N,N
-diethylamide, maleic acid mono-N-monobutylamide, maleic acid mono-N,N-dibutylamide, fumaric acid monoamide, fumaric acid diamide, fumaric acid mono-N-monoethylamide, fumaric acid-N,N-diethylamide, fumaric acid monoamide Examples include N-monobutylamide, fumaric acid-N,N-dibutylamide, maleimide, N-butylmaleimide, N-phenylmaleimide, sodium acrylate, sodium methacrylate, potassium acrylate, potassium methacrylate, etc. .

Among these graft monomers, maleic anhydride is most preferably used.

Various known methods can be used to graft the graft monomer onto the ethylene polymer.

For example, it is carried out by heating an ethylene polymer or a graft monomer at a high temperature in the presence or absence of a solvent, with or without adding a radical initiator.

Other vinyl monomers such as styrene may be present during the reaction.

The amount of the grafting monomer to be grafted onto the ethylene polymer should be in the range of 1σ2 to 10% by weight relative to the ethylene polymer to ensure compatibility with other components and adhesion to the ethylene-vinyl alcohol copolymer. It is preferable from the point of view.

Next, in the present invention, (a) the ethylene polymer with a crystallinity of 51 to 64 is typically high-pressure low-density polyethylene, but may also include ethylene produced by a medium-low pressure method or a high-pressure method; Copolymers with small amounts of other polymerizable monomers, such as ethylenetopropylene, 1-butene, 3-
Methyl-1-butene, 1-hexane, 3-methyl-1-
Copolymers of one or more α-olefins such as pentene and 4-methyl-I-pentene, copolymers of ethylene and vinyl esters such as vinyl acetate and vinyl propionate, or saponified products thereof, ethylene and acrylic acids, unsaturated carboxylic acids such as methacrylic acid and maleic acid or their derivatives, such as anhydrides, esters, amides, imides, chlorides, copolymers with metal salts, etc., ethylene and butadiene, dicyclopentadiene, ethylidene norbornene, etc. A copolymer with a conjugated or non-conjugated diene, etc., or a mixture of the above polymers, which has a crystallinity of 51 to 64 degrees.

In the present invention, (c) an ethylene polymer with a crystallinity of 5 to 50, which is blended as the third component, is a copolymer of ethylene and another polymerizable monomer, such as ethylene and Propylene, 1-butene, 3-methyl-1-butene,
Copolymers with one or more α-olefins such as 1-hexene, 3-methyl-1-pentene, and 4-methyl-1-pentene, and copolymers of ethylene with vinyl esters such as vinyl acetate and vinyl propionate. Copolymers or saponified products thereof, copolymers of ethylene and unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, or derivatives thereof, such as anhydrides, esters, amides, imides, chlorides, metal salts, etc. , a copolymer of ethylene and a conjugated or non-conjugated diene such as butadiene, dicyclopentadiene, enalidennorbornene, etc., or a mixture of the above polymers, with a crystallinity of 5 to 50.

Furthermore, what is the degree of crystallinity as used in the present invention? ASTM-D-6
This is a value obtained by X-ray analysis of a sample prepared under the conditions of 18.

Among the ethylene polymers listed above, ethylene-vinyl acetate copolymer and ethylene-α-olefin copolymer are preferred because they have a good adhesive strength improving effect.

Among these, when an ethylene-1-butene random copolymer with an ethylene content of 85 to 95 mol and a crystallinity of 5 to 30% is used, the transparency, viewing properties, and boiling water resistant adhesion of the polyethylene composition are improved. This is most preferable because it improves both performances.

Ethylene polymers with a crystallinity of 5 to 50% have a melt index (ASTM-D-] 238, 190°C)
A value in the range of 01 to 50 is preferred.

The present invention provides an ethylene polymer grafted with at least one monomer selected from (a) an ethylene polymer having a crystallinity of 51 to 60, and (b) an unsaturated carboxylic acid or a derivative thereof. ) By blending an ethylene polymer with a crystallinity of 5 to 50%. (a),
The advantage is that the adhesiveness to ethylene-vinyl alcohol copolymer, especially the boiling water resistant adhesiveness, was significantly improved compared to the polyenalene composition consisting of (b).

This fact is completely unexpected.

The ratio of component (a), component (b), and component (c) in the present invention is (a) to 96 to 50 parts by weight of (a)
b) component 0] to 30 parts by weight, preferably 1 to 1
5 parts by weight, component (c) 3 to 49.9 parts by weight, preferably 5 to 30 parts by weight (total 100 parts by weight).

If the amount of component (b) is less than 0.1 parts by weight, the adhesion of the polyolefin composition to the ethylene-vinyl alcohol copolymer will be poor, while if it exceeds 30 parts by weight, the adhesion will tend to decrease.

If component (c) is less than 3 parts by weight, the effect of improving adhesion due to component (c) cannot be expected. On the other hand, if it exceeds 49.9 parts by weight, boiling water resistant adhesion will decrease and the object of the present invention will not be achieved. I can not use it.

Additives such as antioxidants, ultraviolet absorbers, pigments, dyes, fillers, nucleating agents, anti-blocking agents, slip agents, antistatic agents, flame retardants, etc. may be added to the polyethylene composition, which may defeat the purpose of the present invention. It may be blended within a range that does not cause

As a method for preparing the polyethylene composition used in the present invention (4), various known methods can be used.

For example, each ingredient may be mixed in a ribbon blender, V-type blender,
After mixing with tumbler Henschel mixer etc., extruder,
A method of melting and kneading with a Banbury mixer, two rolls, a kneader, etc., or a method of dissolving each component in a solvent, stirring and mixing well, and then adding a poor solvent and precipitating with y)pL can be used.

As a method for manufacturing a laminated structure consisting of a polyethylene composition layer and an ethylene-vinyl alcohol copolymer layer of the present invention, (1) a method of manufacturing each film and sheet in advance and bonding them together by thermocompression; , (2) a method of extruding and laminating a polyethylene compound in a solvent on an ethylene-vinyl alcohol copolymer layer, and (3) a method of melting in each separate extruder and coextruding from the same die. can.

In methods (1), (2), and (3) above, the temperature of the polyethylene resin during molding is preferably in the range of 130°C to 300°C, particularly 150°C to 250°C.

The resin temperature of the ethylene-vinyl alcohol copolymer in methods (1) and (3) is 70°C to 250°C.
In particular, a range of 18o<:rx to 230°C is preferred.

The laminated structure comprising a polyethylene composition layer and an ethylene-vinyl alcohol copolymer layer of the present invention includes a two-layer structure in which a polyethylene composition layer and an ethylene-vinyl alcohol copolymer layer are used as an inner layer or an outer layer, Izuγ
A three-layer structure in which one layer is an intermediate layer and another layer is sandwiched, or the above structure is further composed of a polymer having adhesive properties with either a polyethylene composition or an ethylene-vinyl alcohol copolymer, such as polyethylene. For Kumikaimono, polypropylene, polyethylene, ethylene-α
- In the case of an ethylene-vinyl alcohol copolymer such as an olefin copolymer, a laminated structure in which layers of nylon, polyester resin, etc. are laminated, such as polyenalene/polyethylene composition defined in the present invention/ethylene-vinyl alcohol copolymer Polymer, polyethylene composition/ethylene-vinyl alcohol copolymer/nylon three-layer structure, polyethylene/polyethylene composition/ethylene-vinyl alcohol copolymer
polyethylene/polyethylene composition/ethylene-vinyl alcohol copolymer/nylon four-layer structure, polyethylene/polyethylene composition/ethylene-vinyl alcohol copolymer/polyethylene composition/polyethylene In addition to the five-layer structure, various combinations are possible within the range of the laminated structure including the constituent elements of the polyethylene combination Jul/ethylene-vinyl alcohol copolymer.

In these laminated structures, any of the layers may be uniaxially or biaxially oriented.

The laminated structure comprising a polyethylene composite layer and an ethylene-vinyl alcohol copolymer layer of the present invention can be put to practical use as a film, sheet, pipe, hollow bottle, etc.

The laminate structure composed of the polyethylene composition and the ethylene-vinyl alcohol copolymer of the present invention has significantly improved interlayer adhesion, especially the interlayer visibility after boiling water treatment, and the laminate structure has improved significantly during use, which was previously the case. The problem of peeling off has been resolved.

Therefore, by taking advantage of the high rigidity, mechanical strength, boiling water resistance, gas permeation resistance, water vapor permeation resistance, etc. of polyethylene/ethylene-vinyl alcohol copolymer laminates, packaging materials for vegetables, meat, dairy products, etc. It can be suitably used for packaging containers for seasonings, edible oils, pharmaceuticals, etc., food packaging materials such as bag-in pouches, foil-in pouches, etc.

Next, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples as long as the gist thereof is not exceeded.

Examples 1 to 3, Comparative Examples 1 to 2 Modified polyethylene (hereinafter abbreviated as modified PE) obtained by grafting 2.5 weight percent of maleic anhydride onto high-density polyethylene (melt index 12 crystallinity 78%), ethylene]
- Butene random copolymer (Tart index 0.5
, crystallization f! j 15%, ethylene content of over 90 mol, hereinafter abbreviated as EBC), and high-pressure low-density polyethylene (trade name: Mirason M-50, manufactured by Mitsui Polychemicals,
Melt index 1.9, crystallinity 59%, hereinafter LD
The weight parts listed in Table 1 (abbreviated as PE) were mixed in a tumbler blender and then granulated at 210°C in an extruder.

Pellets of this composition are melted in one extruder and fed to a composite inflation molding die at a resin temperature of 210'C.

On the other hand, in another extruder, an ethylene-vinyl alcohol copolymer (ethylene content: 31 moles, degree of saponification: 99 moles) was melted and fed to the die at a resin temperature of 210°C. A blown film having an ethylene-vinyl alcohol copolymer layer on the outside (polyethylene composite layer thickness: 70 μm, ethylene-vinyl alcohol layer thickness: 30 μm) was molded.

A test piece with a width of 15 mm was cut from this film, and after peeling off a portion of the polyethylene composition layer and the ethylene-vinyl alcohol copolymer layer, it was tested using an Instron testing machine to obtain a test piece with a width of f' 50 m7l/min. The strength required for peeling was measured, and the average value was taken as the peel strength.

Moreover, after immersing the above-mentioned test piece in hot water at 98° C. for 1 hour, the peel strength was determined by the same method.

The results are shown in Table 1. Examples 4 to 6, Comparative Example 3 EBC of the polyethylene composition used in Example 1
Instead of ethylene-vinyl acetate copolymer (melt index 1.7, vinyl acetate content 8% by weight, crystallinity 43)
% (hereinafter abbreviated as EVA)) and the blending ratio was set to the parts by weight shown in Table 2.

The results are shown in Table 2.

Comparative Examples 4 to 6 The same procedure as in Example 1 was conducted except that LDPE, EBC, and EVA used in Examples 1 and 4 were used alone.

Claims (1)

[Scope of Claims] 1 (a) 96 to 50 parts by weight of an ethylene polymer having a crystallinity of 51 to 64%; (b) Crafted with at least one monomer selected from unsaturated carboxylic acids or derivatives thereof. A polyethylene composition layer comprising 0 to 30 parts by weight of a modified ethylene polymer and (C) 3 to 49.9 parts by weight (total 100 parts by weight) of an ethylene polymer having a crystallinity of 5 to 50%; Ethylene content 15
A multilayer laminate structure comprising a layer of ethylene-vinyl alcohol copolymer having a mole ratio of 60 to 60. 2. The structure according to claim 1, wherein the ethylene polymer of 2(a) is high-pressure low-density polyethylene. 3. (b) Laminated structure according to claim 1, characterized in that the crippling ethylene polymer is a modified product of an ethylene homopolymer or an ethylene-α-olefin copolymer. 4. Crystallinity The laminated structure according to claim 1, characterized in that 5 to 50% of the ethylene polymer is an ethylene-vinyl acetate copolymer or an ethylene-α-olefin copolymer. Refine or ethylene containing $8
5. The laminated structure according to claim 4, which is a random copolymer of ethylene-1-butene having a content of 5 to 95 moles.