JP2558358B2 - Resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Fields of Industrial Application The present invention has excellent transparency and gas barrier properties, drop impact resistance, bending resistance, air back protection, skin pack packaging suitability, shrink film suitability, etc. The present invention relates to a resin composition having excellent flexibility.

B. Conventional technology Saponified ethylene-vinyl acetate copolymer (hereinafter referred to as EVOH) is a thermoplastic resin that is extremely superior in transparency, gas barrier property, oil resistance, and aroma retention compared to other resins. It is used in various gas barrier films and gas barrier layers of gas barrier containers. However, a multilayer film or a container having EVOH as a gas barrier layer often has a problem due to the high rigidity of EVOH. For example, a multi-layer film filled with contents or a container is easily broken or broken when dropped, a pin hole is generated in the multi-layer film filled with contents due to bending or vibration during transportation, and an air bag of the multi-layer tube is generated. There are problems such as wrinkles occurring during skin pack packaging, stretchability as a film for shrink wrapping, and insufficient shrinkability.
Therefore, there has been proposed a method of blending EVOH with another thermoplastic resin to improve these drawbacks. For example, blending EVOH with ethylene-carboxylic acid vinyl ester copolymer or ethylene-acrylic acid ester copolymer improves the flex resistance (JP-A-61-220839) and EVOH has α,
Blending a β-unsaturated carboxylic acid anhydride-modified ethylene-carboxylic acid vinyl ester copolymer and ethylene-acrylic acid ester copolymer improves the impact resistance of EVOH (JP-A-61-83035). Are known. However, although the bending resistance and impact resistance of EVOH are improved by these methods, the transparency, which is a characteristic of EVOH, is impaired, and it has not been put to practical use in applications requiring transparency.

Examples of the composition having good transparency include a composition composed of EVOH and polyamide, but the deterioration of gas barrier property due to blending is large, the heat stability of moldability is poor, and a problem of gel formation in a short time is encountered. However, this composition has not been put into practical use.

Further, regarding blending EVOH with a partially saponified ethylene-vinyl acetate copolymer, imparting interlayer adhesion with polyolefin, and imparting low-temperature heat-sealing property, JP-B-51-4851 and Kaisho 60-1614
As described in 77, when a molded product such as a film is produced by these conventional techniques, lack of flexibility, poor thermal stability,
There is a problem that the net-quine is violent and the moldability is poor, and there is a defect that patterns such as stripes and satin are generated on the film surface.

C. Problem to be Solved by the Invention The present invention does not have the above-mentioned problems, namely, transparency, gas barrier property is good, drop impact resistance, flex resistance,
It is intended to provide a resin composition having flexibility such as anti-air back property, suitability for skin pack, suitability for shrink film and the like.

D. Means for Solving the Problems The inventors of the present invention have saponified ethylene-vinyl acetate copolymer (A) 60-having an ethylene content of 20 to 60 mol% and a saponification degree of a vinyl acetate component of 95 mol% or more. 95 wt% and at least one olefin selected from ethylene-α-olefin copolymer, ethylene-vinyl acetate copolymer and ethylene-acrylic acid ester copolymer in which epoxy equivalent of 700 to 10,000 is introduced. Type copolymer (B)
The resin composition consisting of 40 to 5% by weight has good transparency and gas barrier properties, and has significantly higher flexibility than EVOH alone.
It has been found that a laminate containing at least one resin composition layer is extremely useful as a laminate excellent in drop impact resistance, air backproofing property, skin pack suitability, shrink film suitability, and completes the present invention. Was reached.

EVOH used in the present invention has an ethylene content of 20 to 60 mol%, preferably 25 to 55 mol%, and a saponification degree of a vinyl acetate component.
The resin is 95 mol% or more, preferably 98 mol% or more. If the ethylene content is less than 20 mol%, not only a beautiful molded product such as a film cannot be obtained because it tends to gel during melt molding, but also the gas barrier property under high humidity deteriorates. On the other hand, when the ethylene content is higher than 60 mol%, the gas barrier property is greatly deteriorated, which is not preferable. When the degree of saponification is less than 95 mol%, like the case where the ethylene content is less than 20 mol%, gelation is likely to occur during melt molding, and stable operation cannot be performed for a long time. Also, the EVOH melt index (temperature 19
Value measured under conditions of 0 ° C and load of 2160g: However, melting point is 19
About 0 ℃ or over 190 ℃, it is measured at multiple temperatures above the melting point under a load of 2160g, and the inverse log of the absolute temperature is plotted on the semi-logarithmic graph with the horizontal axis as the abscissa and the melt index as the vertical axis. Interpolated value; hereinafter referred to as MI),
Although not limited, it is preferably 0.1 to 50 g / 10 minutes, more preferably 0.5 to 15 g / 10 minutes. Furthermore, EVOH referred to in the present invention
May be modified with a copolymerization monomer in the range of 5 mol% or less.
-Butene, 1-hexene, 4-methyl-1-pentene,
Acrylic acid ester, methacrylic acid ester, maleic acid, fumaric acid, itaconic acid, higher fatty acid vinyl ester, alkyl vinyl ether, N-vinylpyrrolidone,
N-normal butoxymethyl acrylamide, vinyltrimethoxysilane, vinylmethyldimethoxysilane, vinyldimethylmethoxysilane, N- (2-dimethylaminoethyl) methacrylamide or quaternary compounds thereof,
Examples thereof include N-vinylimidazole and quaternary products thereof.

The epoxy group-introduced olefin copolymer used in the present invention is an ethylene monomer and at least one monomer selected from α-olefin, vinyl acetate, and acrylate, and an epoxy group-containing ethylenic group. Random copolymerization with unsaturated monomers, or epoxy group-containing ethylene in olefin-based copolymers consisting of ethylene monomer and at least one monomer selected from α-olefin, vinyl acetate and acrylate It is a modified olefin-based copolymer obtained by graft-polymerizing a polymerizable unsaturated monomer with an initiator such as peroxide, heat, light or ionizing radiation. Here, examples of the ethylene-α-olefin copolymer include an ethylene-propylene copolymer and an ethylene-butylene copolymer, and among them, the ethylene-propylene copolymer is preferable. Examples of the epoxy group-containing ethylenically unsaturated monomer include glycidyl methacrylate, glycidyl acrylate, allyl glycidyl ether, vinyl glycidyl ether, hydroxyalkyl acrylate or hydroxyl methacrylate glycidyl ether. The modification amount is 700 to 10000, and more preferably 1000 to 6000 in terms of epoxy equivalent. Here, the epoxy equivalent is represented by the number of grams of a resin containing 1 g equivalent of an epoxy group. When the epoxy equivalent is less than 700, there are drawbacks such as vigorous thickening and gelation, and deterioration of moldability. On the other hand, when it exceeds 10,000, EVO
The transparency and mechanical properties of the composition are unsatisfactory, probably because of poor compatibility with H. Further, MI of the olefin copolymer introduced with an epoxy group in the present invention is not particularly limited, but is preferably 0.1 to 50 g / 10 minutes, more preferably
It is 0.5 to 15g / 10 minutes.

The resin composition of the present invention is a mixture of EVOH (A) and an epoxy group-introduced olefin copolymer (B), and the mixing ratio thereof is A / B = 60 to 95/40 to 5 ( Weight ratio), and more preferably A / B = 70 to 90/30 to 10 (weight ratio). If the amount of the olefin copolymer introduced with an epoxy group is less than 5% by weight based on the composition, the drop impact resistance and flex resistance are poor. On the other hand, when it exceeds 40% by weight, not only the transparency is poor, but also the gas barrier property is poor.

As a method for mixing EVOH and an olefin polymer having an epoxy group introduced, there is a method using a Banbury mixer, a single-screw or twin-screw extruder, a Brabender plast mill, etc., but each resin is directly applied to various molding machines. It may be supplied and subjected to molding while kneading with a molding machine. Further, when kneading these, a plasticizer, a lubricant, an antioxidant, a colorant, various resins and the like may be added within a range that does not impair the effects of the present invention.

The resin composition of the present invention is preferably used in a laminate. At this time, the resin composition of the present invention can be used in any of the intermediate layer, the outermost layer and the innermost layer. The resin to be laminated with the resin composition of the present invention is not particularly limited,
Generally, a resin having good transparency is preferable, and examples thereof include low density polyethylene, linear low density polyethylene, polypropylene, ethylene-propylene copolymer, polyolefin such as polybutene, ethylene-vinyl acetate copolymer, ethylene-acrylic acid. Examples thereof include ester copolymers, olefin-based copolymers such as ionomers, polystyrene, polyamide, polyethylene terephthalate, polycarbonate, polyvinyl chloride, and the like, or a mixture thereof. Of these, particularly preferably used are low-density polyethylene, linear low-density polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, alone or in a mixture thereof.

Further, when the interlayer adhesion between these resins and the resin composition of the present invention is not sufficient, it is preferable to provide an adhesive resin layer. The adhesive resin is not particularly limited as long as it does not cause delamination at a practical stage, and is not particularly limited, and an unsaturated carboxylic acid or an anhydride thereof may be used as an olefin polymer (for example, low-density polyethylene, linear low polymer). Polyolefins such as density polyethylene, polypropylene, polybutylene, etc., and unsaturated monomers that can be copolymerized with olefins (vinyl esters, unsaturated carboxylic acid esters, etc.)
A copolymer with, for example, ethylene-vinyl acetate copolymer,
A modified olefin polymer containing a carboxyl group, which is obtained by chemically bonding (eg, by an addition reaction or a graft reaction) to ethylene-acrylic acid ethyl ester copolymer}. Specifically, one or a mixture of two or more selected from maleic anhydride graft-modified polypropylene, maleic anhydride graft-modified ethylene-ethyl acrylate copolymer, maleic anhydride graft-modified ethylene-vinyl acetate copolymer and the like. Are preferred. EVOH, such as the resin composition of the present invention, may be mixed with these adhesive resins within a range that does not impair the effects of the present invention. The resin composition of the present invention can be formed into a film, a sheet, a tube, a bolt, etc. as a laminate, and the thickness constitution of each layer is not particularly limited, but from the viewpoint of transparency, the resin composition layer of the present invention is formed. Is 300
It is preferable to use with a thickness of μ or less, and more preferably
It is less than 200μ.

The method for laminating the resin composition of the present invention is not particularly limited, and examples thereof include a coextrusion method, an extrusion lamination method, a dry lamination method, and the like. It is suitable because it can exhibit.

The thus obtained laminate has a container excellent in drop impact resistance, a tube excellent in air-back prevention property, a bag inbox excellent in bending resistance, skin pack suitability,
It can be used as a film having excellent suitability for shrink film.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto. "Parts" or "%" in the examples are by weight unless otherwise specified.

E. Example Example 1 ASTM D123 under conditions of ethylene content of 44 mol%, saponification degree of vinyl acetate component of 99.1 mol%, 190 ° C. and 2160 g load.
8 Melt index (MI) measured according to 65T is 1.6
80 parts of EVOH with g / 10 minutes and epoxy equivalent of 5000, MI of 2.0 g / 1
20 minutes of a 0-minute glycidyl methacrylate random copolymer modified ethylene-vinyl acetate copolymer was blended into pellets at a temperature of 220 ° C. by a 30φ twin-direction biaxial extruder.
Then, using this plate, a film forming machine comprising a 40φ extruder and a T-die was used to form a film under the conditions of an extruder temperature of 180 to 220 ° C. and a T-die temperature of 215 ° C. to obtain a film having a thickness of 25 μm. . The film was evaluated for film surface, moldability, haze, loop stiffness, flex resistance, Young's modulus, and oxygen gas transmission rate (OTR).

The evaluation of the film surface was performed by visually scoring streaks, satin and spots in five grades A to E shown in Table 1.

The haze was measured by using a Poitsk integrating sphere type light transmittance meter manufactured by Nippon Seimitsu Optical Co., Ltd.

The loop stayness is a loop stay funnel tester manufactured by Toyo Seiki Co., Ltd., which bends a film with a width of 15 mm into a loop with a length of 60 mm and compresses it until the loop diameter becomes 20 mm. It was measured under the conditions of. Loop stability is important as a measure of air backproofness, and it is considered that a composition having a small loop stability has good air backproofness.

The flex resistance was evaluated by using a Gelbo flex tester manufactured by Rigaku Kogyo Co., Ltd., a 12-inch x 8-inch film was formed into a cylindrical shape having a diameter of 3.5 inches, and both ends were gripped. Gripping interval at maximum bending is 1 inch, twist of 440 degree is added at the first 3.5 inch of stroke, and 2.5 inches after that, the linear reciprocating motion is repeated reciprocating motion at a speed of 40 times / min. The number of pinholes was determined for the film after repeating 300 times and 400 times under the condition of ℃ and 65% RH.

Young's modulus is 65 ° C at 20 ° C according to ASTM D-882-67.
It was measured under% RH conditions. Young's modulus is important in relation to skin pack suitability and shrink film suitability. That is, it can be said that a resin composition having a low Young's modulus that can be stretched with a smaller force is suitable for skin pack packaging and shrink film packaging including a stretching step.

The oxygen gas transmission rate (OTR) was measured by using OX-TRAN 10-50A manufactured by Modern Control under 20 ° C. and 65% RH conditions.

The evaluation results are shown in Table 3. This resin composition has good film surface and permeability, and has excellent loop stability, flex resistance, Young's modulus, and other flexibility and gas barrier properties. There is.

Example 2 Using EVOH and various epoxy group-containing ethylene-propylene copolymers, a film having a thickness of 25 μm was prepared in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 3. Here, various epoxy group-containing olefin polymers used in each example are shown below. That is, in Example 2, 10 parts of allyl glycidyl ether and 0.6 part of dicumyl peroxide were added to 100 parts of an ethylene-propylene copolymer having an ethylene content of 90% by weight, and the mixture was kneaded in a Brabender Plastomill at 170 ° C. for 10 minutes. Obtained, the epoxy equivalent is 1
An allyl glycidyl ether grafted ethylene-propylene copolymer with a MI of 200 and an MI of 3.4 g / 10 min was used. In Example 2, the film surface and the transparency are good, and the loop stiffness, the flexibility represented by Young's modulus and the gas barrier property are excellent.

Comparative Example 1 Table 3 shows the results of various evaluations of a film having a thickness of 25 .mu.m made of EVOH alone having an ethylene content of 32 mol%, a saponification degree of a vinyl acetate component of 99.4 mol% and an MI of 4.0 g / 10 min. Although the film surface, transparency and gas barrier property are good, the Young's modulus is high and the flexibility is poor, so that the flex resistance is poor.

Comparative Examples 2 to 13 Using various EVOH and various epoxy group-containing olefin polymers shown in Table 2, a film having a thickness of 25 μm was prepared in the same manner as in Example 1 and various evaluations were performed. The results are shown in Table 3.

Similar to Comparative Example 1, Comparative Example 2 has a good film surface, transparency and gas barrier property, but has a high Young's modulus and poor flexibility, and therefore has poor flex resistance.

In Comparative Example 3, the flexibility is high, but the gas barrier property is extremely poor.

In Comparative Example 4, the flexibility is high, but probably because the epoxy equivalent is high, the dispersion state of the epoxy group-containing olefin polymer is poor and the transparency is poor.

In Comparative Examples 5 to 7, there are many spots and the film surface is extremely poor.

Comparative Example 8 has good flexibility, but is not practical because of its low gas barrier property.

In Comparative Examples 9 to 11, the film surface, the transparency and the gas barrier property are good, but the bending resistance is not sufficient.

Comparative Examples 12 and 13 have good flexibility, but the film surface, transparency and gas barrier property are extremely poor.

F. Effects of the Invention The resin composition of the present invention has good transparency and gas barrier properties, and has significantly higher flexibility than EVOH alone. Further, a laminate containing at least one layer of the resin composition has a drop impact resistance,
It is extremely useful as a laminate having excellent anti-air backing property, suitability for skin pack, and suitability for shrink film.

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Claims (1)

(57) [Claims] 1. An ethylene-vinyl acetate copolymer saponification product (A) having an ethylene content of 20 to 60 mol% and a saponification degree of a vinyl acetate component of 95 mol% or more, and an epoxy equivalent of 700. Introduce ~ 10000 epoxy groups to ethylene-α
-Olefin copolymer, ethylene-vinyl acetate copolymer and ethylene-acrylic acid ester copolymer at least one olefin copolymer (B) 40-
A resin composition comprising 5% by weight.