JP3222169B2 - Ethylene copolymer composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ethylene copolymer composition having excellent gas barrier properties, pinhole resistance, stretchability, film formability and the like.

[0002]

2. Description of the Related Art An ethylene / vinyl alcohol copolymer having a high vinyl alcohol content is widely used as a packaging material because of its excellent gas barrier properties.
However, this copolymer is easy to absorb water, gas barrier properties are significantly reduced by water absorption, pinhole resistance, poor stretchability, impact resistance in a dry state is not sufficient, heat resistance is poor, It also has major drawbacks, such as the inability to mold at high temperatures. For this reason, the copolymer is rarely used alone, and is often used exclusively as an intermediate layer laminated with another material.

[0003] On the other hand, many proposals have been made to modify such defects by blending them with other resins. Among them, in a system containing an ethylene / vinyl alcohol copolymer as a main component, it has been difficult to remarkably improve the disadvantages of the above copolymer. Conversely, in a system containing other resin in a major amount, the excellent gas barrier property of the ethylene / vinyl alcohol copolymer is generally impaired, and thus cannot be said to be a practical solution. The method of forming a layered structure having a different ethylene / vinyl alcohol content by molding a polyolefin and an ethylene / vinyl alcohol copolymer under specific conditions proposed in Japanese Patent No. 30104 discloses a gas barrier property having a high level. Attention has been paid to improve the drawbacks of ethylene / vinyl alcohol copolymer while maintaining it. However, this proposal has a drawback that the compatibility between the polyolefin and the ethylene / vinyl alcohol copolymer is not good, so that satisfactory properties cannot be obtained for use as a thin film. That is, it is not always easy to produce a thin film,
Further, the gas barrier properties of the produced films were not sufficiently satisfactory.

[0004]

In view of such circumstances, the present inventors have improved the above-mentioned disadvantages of the ethylene / vinyl alcohol copolymer as much as possible and have a sufficient gas barrier property even for a thin film. We studied to get the material. As a result, it was found that a material having desired properties can be obtained by a combination of three types of ethylene copolymers described below.

[0005]

According to the present invention, there is provided an ethylene / unsaturated ester copolymer (A) having an unsaturated ester content of 10 to 35% by weight and an ethylene content of 60 to 90% by weight. % Of amorphous or low crystalline ethylene
Graft-modified α-olefin copolymer with unsaturated carboxylic acid or anhydride thereof (B) 1 to 40% by weight and ethylene / vinyl alcohol copolymer (C) 20 having a vinyl alcohol content of 50 to 80 mol% ~ 50% by weight
An ethylene copolymer composition comprising:

The ethylene / unsaturated ester copolymer (A) used in the present invention has an unsaturated ester content of 10 to 35% by weight, preferably 15 to 28% by weight. When a copolymer having an unsaturated ester content less than the above range is used, it is difficult to obtain a composition having excellent gas barrier properties, and those having a content higher than the above range are film containers and the like. It is not suitable as a packaging material because of its low strength. 190 ° C., 2
Melt flow rate measured under a load of 160 g is 0.5 to
It is preferable to use one having 20 g / 10 min, especially 1 to 15 g / 10 min. The unsaturated ester which is a polymerization component of the copolymer may be any of a carboxylic acid unsaturated ester or an unsaturated carboxylic acid ester, and examples thereof include vinyl acetate, acrylic acid ester, methacrylic acid ester and the like. be able to. As an ester of acrylic acid or methacrylic acid, for example, having 1 to 1 carbon atoms
Preferred are alkyl esters of 8, especially methyl esters or ethyl esters.

The graft-modified product (B) used in the present invention
The ethylene / α-olefin copolymer used as a raw material of the copolymer has an ethylene polymerization ratio of 60 to 90 mol%, preferably
It is a low-crystalline or amorphous material having a crystallinity of not more than 30%, preferably not more than 20% by X-ray diffraction. The α-olefin in the copolymer preferably has about 3 to 8 carbon atoms, particularly preferably propylene or 1-butene. The copolymer preferably has a melt flow rate at 190 ° C. and a load of 2160 g of 0.3 to 50 g / 10 min, particularly 0.5 to 20 g / 10 min.

As the unsaturated carboxylic acid or anhydride thereof used as a graft component of the ethylene / α-olefin copolymer, acrylic acid, methacrylic acid, fumaric acid, maleic acid, nadic acid, maleic anhydride, itaconic anhydride And nadic anhydride.
Of these, maleic anhydride is most preferred. The graft amount of the unsaturated carboxylic acid or its anhydride is 0.03
-7% by weight, preferably 0.05-5% by weight.

The ethylene / vinyl alcohol copolymer (C) used in the present invention has a vinyl alcohol content of 5%.
0 to 80 mol%, preferably 55 to 75 mol%. Such a copolymer is obtained by converting the corresponding ethylene / vinyl acetate copolymer into a saponification degree of 95% or more, preferably 99%.
% Or more.
As the ethylene / vinyl alcohol copolymer, 2
It is preferable to use one having a melt flow rate of 0.5 to 30 g / 10 min, particularly 1 to 20 g / 10 min at 10 ° C. and a load of 2160 g.

In order to easily obtain a molded structure having good gas barrier properties from the ethylene copolymer composition of the present invention, the ethylene / vinyl alcohol copolymer (C) may be used in an amount of 220.
The melt apparent viscosity at 100 ° C. and a shear rate of 100 sec ⁻¹ is 300 to 1000 Pa · S, preferably 400 to 90 Pa, compared to that of the ethylene / unsaturated ester copolymer (A).
It is preferable to use a material smaller by 0 Pa · S.

The ethylene copolymer composition of the present invention contains 30 to 75% by weight, preferably 40 to 65% by weight of the ethylene / unsaturated ester copolymer (A), and 1 to 40% by weight of the graft-modified product (B). % By weight, preferably 5 to 30% by weight,
20-5 ethylene-vinyl alcohol copolymer (C)
0% by weight, preferably 30 to 45% by weight. The ethylene / vinyl alcohol copolymer (C) is an important component contributing to the gas barrier properties of the composition of the present invention. At least 20% by weight is required, but if too much is used, the water absorption of the component (C) It is desirable that the content be 50% by weight or less, since defects in heat resistance, heat resistance, pinhole resistance and the like become apparent, and extrusion kneading property and film formability become unstable.

Excellent gas barrier properties can be obtained by using a small amount of the component (C) even when only the ethylene / unsaturated ester copolymer (A) is blended with the ethylene / vinyl alcohol copolymer (C). However, in such a two-component system, extrusion kneading properties and film forming properties are somewhat insufficient. In the present invention,
By replacing a part of the component (A) to be blended with the component (C) with the graft-modified product (B), the above-mentioned difficulties can be improved without significantly lowering the gas barrier properties. If the substitution amount of the graft-modified product (B) is too large, the gas barrier property is lowered. Therefore, it is desirable to use an appropriate amount that can satisfy the moldability.

When other similar graft-modified products such as a graft-modified ethylene-vinyl acetate copolymer are used in place of the graft-modified product (B), the allowable range of blending is narrow. In some cases, disadvantages such as a significant decrease in gas barrier properties are caused. On the other hand, the present invention has an advantage that the properties and the amount of the graft-modified product (B) can be selected in a wide range.

The composition of the present invention may contain various additives depending on the purpose of use. Examples of such additives include an antioxidant, a heat stabilizer, a desiccant, a nucleating agent, an antistatic agent, and a filler having a barrier property such as mica. Addition of a desiccant can reduce the tendency of the ethylene / vinyl alcohol copolymer component to lower the gas barrier property due to water absorption. The mixing of mica can significantly improve the gas barrier properties.

The composition of the present invention can be formed into films, sheets, hollow containers and the like. Further, the sheet can be subjected to secondary processing such as vacuum forming and pressure forming to form a container having a desired shape. When extruding a film or sheet, an extruder having a usual kneading function may be used, and it is not particularly necessary to employ extrusion conditions that cause a laminar flow.

Such various molded articles may be composed only of the composition of the present invention, or may be used in combination with other materials to form a two- or more-layer structure. Examples of the other materials include high-density polyethylene, hollow polyethylene, low-density polyethylene, linear low-density polyethylene, polypropylene, polyolefins such as poly-4-methyl-1-pentene, polyethylene terephthalate, and polybutylene terephthalate. Examples include thermoplastic resins represented by polyamides such as polyesters, nylon-6, and nylon-6,6; thermosetting resins such as polyurethane; various elastomers; metal materials such as aluminum foil; and paper. be able to. When used in a multilayer structure, the composition of the present invention may have one or more layers, and may be used as a surface layer or as an intermediate layer.

[0017]

Next, the present invention will be described in more detail by way of examples. In addition, the kneading method of the resin in Examples and Comparative Examples,
The molding method, evaluation, and analysis were performed under the following conditions and methods.

1) Method of kneading resin A predetermined ratio of resin was melt-mixed under the following conditions. Kneader: 30 mmφ single screw extruder Screw: Dalmage type single flight screw L / D = 33 Barrel temperature (° C.) C ₁ C ₂ C ₃ C ₄ C ₅ D 80 150 180 200 200 200 180 Screw rotation speed: 40 rpm

2) Extrusion kneading property At the time of kneading the resin of 1), the strand state of the molten resin extruded from the die was visually observed and judged.

3) Film Forming Method and Formability Evaluation An inflation film was formed on an inflation molding machine comprising a 30 mm diameter single screw full flight extruder under the following conditions. Barrel temperature (° C.) C ₁ C ₂ C ₃ C ₄ H D 150 200 200 200 200 200 200 Other than Example 2, Example 2 Screw rotation speed: 45 rpm 60 rpm Take-off speed: 3 m / min 4 m / min Film thickness: 50 μm 50 μm blow Up ratio 2.8 2.8 Film formability was determined by observing the bubble stable state during the formation of this blown film. In Example 2, molding was performed while changing the discharge speed from the extruder. Note that these molding conditions are ordinary blown film molding methods, and do not particularly control the dispersion or flow state of the ethylene / vinyl alcohol resin.

4) MFR (Melt Flow Rate) JIS K-6760 Temperature 190 ° C Load 2160gr

5) Oxygen gas permeation measurement Using a gas permeation tester (differential pressure method) manufactured by Toyo Seiki, measure the oxygen gas permeation amount of the 50 μm thick film obtained in 3) at 23 ° C. × 50% RH atmosphere. did. 6) Apparent melt viscosity Capillary rheometer 3211 manufactured by Instron (USA)
Using a mold, a shear stress at a specified melting temperature and a shear rate was detected, and the apparent melt viscosity was calculated. Details are described below. Capillary rheometer type 3211 Plunger speed: 0.06 to 20 cm / min Load capacity: 500 to 2000 Kg Measurement temperature: 40 to 399 ° C Temperature control: Barrel ± 2 ° C Capillary ± 0.5 ° C Barrel… diameter 0.953 ± 0.0013cm Effective length 25cm (including the capillary part) Capillary… diameter 0.0762cm length 2.54cm Material Tungsten carbide Inflow angle… 90 degrees

The resins used in Examples and Comparative Examples are shown in Tables 1 and 2.

[0024]

[Table 1]

[0025]

[Table 2]

Examples 1 to 12 Ethylene / vinyl acetate copolymer (A) shown in Table 1
The three components of the ethylene / α-olefin copolymer graft modified product (B) and the ethylene / vinyl alcohol copolymer (C) shown in Table 2 were kneaded by the method described in 1) above, and were extruded and kneaded, MFR, and oxygen. The performance such as the amount of permeation was evaluated. Table 3 shows the results.

[0027]

[Table 3]

Comparative Examples 1 to 8 Various ethylene polymers (A) described in Table 1, ethylene copolymer graft modified products (B) and ethylene vinyl alcohol copolymer (C) described in Table 2 The above three components were kneaded by the above-described method, and performances such as extrusion kneading properties, MFR and oxygen permeation amount were evaluated. Table 4 shows the results.

[0029]

[Table 4]

[0030]

According to the present invention, despite having an ethylene / vinyl alcohol copolymer content of 50% by weight or less, it exhibits excellent gas barrier properties, and furthermore has good pinhole resistance, stretchability and moldability. And an ethylene copolymer composition having improved physical properties such as water resistance. In particular, the composition of the present invention has a good gas barrier property even when formed into a thin film, and thus has a wide range of applications, and can be used for various packaging including food packaging.

Claims (2)

(57) [Claims] 1. An ethylene / unsaturated ester copolymer (A) having an unsaturated ester content of 10 to 35% by weight.
Graft-modified product of an amorphous or low-crystalline ethylene / α-olefin copolymer having 5% by weight and an ethylene content of 60 to 90% by mole with an unsaturated carboxylic acid or an anhydride thereof (B) 1 to 40% by weight And an ethylene / vinyl alcohol copolymer (C) having a vinyl alcohol content of 50 to 80 mol%, and 20 to 50% by weight. 2. The melt viscosity of the ethylene / vinyl alcohol copolymer (C) at 220 ° C. under a shear rate of 100 sec ^-1 is 300 to 1000 Pa higher than that of the ethylene / unsaturated ester copolymer (A). The ethylene copolymer composition according to claim 1, wherein S is small.