JPH0525332A - Ethylene copolymer composition - Google Patents

Abstract

PURPOSE:To provide the subject composition excellent in gas barrier resistance, pinhole resistance, etc., useful for packaging materials, comprising each specified amount of a specific ethylene-unsaturated ester copolymer, graft-modified product and ethylene-vinyl alcohol copolymer. CONSTITUTION:The objective composition comprising (A) 10-35wt.% of an ethylene-unsaturated ester copolymer containing 10-35wt.% of an saturated ester, (B) 1-40wt.% of a graft-modified product prepared by grafting a unsaturated carboxylic acid or its anhydride to a noncrystalline or low crystalline ethylene-alpha-olefin copolymer containing 60-90mol% of ethylene, and (C) 20-50wt.% of an ethylene-vinyl alcohol copolymer containing 50-80mol% of vinyl alcohol. In the present composition, the apparent melt viscosity of the component C at 220 deg.C under a shear rate of 100sec -1 is lower than that of the component A by 300-1000Pa.s.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an ethylene copolymer composition having excellent gas barrier properties, pinhole resistance, stretchability, film moldability and the like.

[0002]

2. Description of the Related Art Ethylene / vinyl alcohol copolymers having a high vinyl alcohol content are widely used as packaging materials because of their excellent gas barrier properties.
However, this copolymer easily absorbs water, the gas barrier property is remarkably lowered by water absorption, the pinhole resistance and the stretchability are inferior, the impact resistance in the dry state is not sufficient, the heat resistance is poor, It also has major drawbacks such as inability to mold at high temperatures. For this reason, the copolymer is rarely used alone, and is often used as an intermediate layer by laminating it exclusively with another material.

On the other hand, many proposals have been made to improve such a defect by blending it with another resin. Among them, it is difficult to remarkably improve the drawbacks of the above-mentioned copolymer in a system containing an ethylene / vinyl alcohol copolymer as a main component. On the contrary, in a system containing other resin in a major amount, the excellent gas barrier property of an ethylene / vinyl alcohol copolymer is generally impaired, and thus it cannot be said to be a practical solution, but JP-B-51- A method of forming a layered structure having different ethylene / vinyl alcohol contents by molding a polyolefin and an ethylene / vinyl alcohol copolymer under specific conditions proposed in Japanese Patent No. 30104 has a high gas barrier property. It is attracting attention as an agent for improving the drawbacks of the ethylene-vinyl alcohol copolymer while maintaining it. However, this proposal has a drawback in that the compatibility between the polyolefin and the ethylene / vinyl alcohol copolymer is not good, so that it is not possible to obtain properties that are satisfactory for use as a thin film. That is, it is not always easy to produce a thin film,
Further, the gas barrier property of the produced film cannot be said to be sufficiently satisfactory.

[0004]

In view of the above situation, the present inventors have improved the above-mentioned drawbacks of ethylene / vinyl alcohol copolymer as much as possible, and have sufficient gas barrier property even in a thin film. We examined to obtain the material. As a result, it has been found that a material having desired properties can be obtained by combining the three ethylene copolymers described below.

[0005]

DISCLOSURE OF THE INVENTION According to the present invention, an ethylene / unsaturated ester copolymer (A) having an unsaturated ester content of 10 to 35% by weight, 30 to 75% by weight, and an ethylene content of 60 to 90% by mole. % Amorphous or low crystalline ethylene
1 to 40% by weight of a graft-modified product (B) of an α-olefin copolymer with an unsaturated carboxylic acid or an anhydride thereof and an ethylene / vinyl alcohol copolymer (C) 20 having a vinyl alcohol content of 50 to 80 mol%. ~ 50% by weight
Is an ethylene copolymer composition consisting of

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 a polymer having a content higher than the above range is a film container or the like. Is not suitable as a packaging material because of its low strength. As the copolymer, 190 ° C., 2
The melt flow rate measured with a 160 g load is 0.5 to
It is preferable to use 20 g / 10 minutes, particularly 1 to 15 g / 10 minutes. The unsaturated ester which is a polymerization component of the copolymer may be either a carboxylic acid unsaturated ester or an unsaturated carboxylic acid ester, and vinyl acetate, acrylic acid ester, methacrylic acid ester and the like are exemplified as typical examples. be able to. As the ester of acrylic acid or methacrylic acid, for example, a carbon number of 1 to
Preferred are alkyl esters of 8, especially methyl or ethyl esters.

Graft modified product (B) used in the present invention
The ethylene / α-olefin copolymer used as the raw material has a polymerization ratio of ethylene of 60 to 90 mol%, preferably 70%.
It has a low crystallinity or an amorphous content of ˜85 mol%, and the crystallinity by X-ray diffractometry is usually 30% or less, preferably 20% or less. The α-olefin in the copolymer preferably has about 3 to 8 carbon atoms, and propylene or 1-butene is particularly preferable. As the copolymer, it is preferable to use one having a melt flow rate of 0.3 to 50 g / 10 minutes, particularly 0.5 to 20 g / 10 minutes at 190 ° C. and a load of 2160 g.

The unsaturated carboxylic acid or its anhydride used as the graft component of the ethylene / α-olefin copolymer is acrylic acid, methacrylic acid, fumaric acid, maleic acid, nadic acid, maleic anhydride or itaconic anhydride. , Nadic acid anhydride and the like.
Of these, maleic anhydride is most preferred. Grafting amount of unsaturated carboxylic acid or its anhydride is 0.03
The range of ˜7% by weight, particularly 0.05 to 5% by weight is desirable.

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 has a saponification degree of 95% or more, preferably 99% or more, of the corresponding ethylene / vinyl acetate copolymer.
It is obtained by saponification at a ratio of at least%.
The ethylene / vinyl alcohol copolymer also has 2
It is preferable to use a melt flow rate of 0.5 to 30 g / 10 minutes, especially 1 to 20 g / 10 minutes at 10 ° C. and a load of 2160 g.

In order to easily obtain a molded structure having a good gas barrier property from the ethylene copolymer composition of the present invention, 220 as ethylene-vinyl alcohol copolymer (C) is used.
The apparent melt viscosity at a shear rate of 100 sec ⁻¹ at 300 ° C. is 300 to 1000 Pa · S, preferably 400 to 90 Pa than that of the ethylene / unsaturated ester copolymer (A).
It is preferable to use one having a small 0 Pa · S.

In the ethylene copolymer composition of the present invention, the ethylene / unsaturated ester copolymer (A) is 30 to 75% by weight, preferably 40 to 65% by weight, and the graft modified product (B) is 1 to 40%. % By weight, preferably 5-30% by weight,
20 ~ 5 ethylene / vinyl alcohol copolymer (C)
It is 0% by weight, preferably 30 to 45% by weight. The ethylene / vinyl alcohol copolymer (C) is an important component that contributes to the gas barrier properties of the composition of the present invention, and at least 20% by weight is necessary, but if it is used in a too large amount, it absorbs water of the component (C). It is desirable that the amount be 50% by weight or less because defects such as heat resistance, heat resistance, and pinhole resistance become apparent, and extrusion kneading property and film formability become unstable.

By blending only the ethylene / unsaturated ester copolymer (A) with the ethylene / vinyl alcohol copolymer (C), excellent gas barrier properties can be obtained by using a small amount of the component (C). However, such a two-component system has some drawbacks in extrusion kneading property and film formability. In the present invention,
By substituting the graft-modified product (B) for a part of the component (A) to be blended with the component (C), the above-mentioned difficulties are improved without reducing the gas barrier property so much. If the substitution amount of the graft-modified product (B) becomes too large, the gas barrier property will deteriorate, so it is desirable to use an appropriate amount that is sufficient for moldability.

When other similar graft modified products such as ethylene-vinyl acetate copolymer graft modified products are used instead of the graft modified product (B), the compounding tolerance is narrow. In some cases, there are disadvantages such as a large reduction in gas barrier property, but in the present invention, there is an advantage that the properties and blending amount of the graft modified product (B) can be selected in a wide range.

Various additives can be added to the composition of the present invention depending on the purpose of use. Examples of such additives include antioxidants, heat stabilizers, desiccants, nucleating agents, antistatic agents, and barrier property-imparting fillers such as mica. Addition of the desiccant can alleviate the tendency of the ethylene / vinyl alcohol copolymer component to lower the gas barrier property due to water absorption. Further, the addition of mica can remarkably improve the gas barrier property.

The composition of the present invention can be formed into a film, a sheet, a hollow container or the like. Further, secondary processing such as vacuum forming and pressure forming can be performed on the sheet to form a container having a desired shape. For extrusion molding of a film or sheet, an extruder having a usual kneading function may be used, and it is not necessary to adopt extrusion conditions that produce a laminar flow.

Such various molded articles may be composed of only the composition of the present invention, or may be used as a multi-layer structure of two layers or more in combination with other materials. 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, polybutylene terephthalate and the like. Examples include thermoplastics such as polyesters, polyamides such as nylon-6 and nylon-6,6, thermosetting resins such as polyurethane, various elastomers, metallic materials such as aluminum foil, and paper. be able to. When used in a multi-layer structure, the composition of the present invention may have one or more layers, and may be used as a surface layer or an intermediate layer.

[0017]

EXAMPLES The present invention will be described in more detail with reference to examples. Incidentally, the method of kneading the resin in Examples and Comparative Examples,
The molding processing method, evaluation, and analysis method were performed under the following conditions and methods.

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

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

3) Film molding method and evaluation of moldability An inflation film was molded under the following conditions with an inflation molding machine composed of a 30 mm diameter single screw full flight extruder. Barrel temperature (° C.) C ₁ C ₂ C ₃ C ₄ HD 150 200 200 200 200 200 200 Other than Example 2, Example 2 Screw rotation speed ... 45 rpm 60 rpm Take-up speed ... 3 m / min 4 m / min Film thickness ... 50 μm 50 μm Blow Up ratio ... 2.8 2.8 The film moldability was judged by observing the bubble stable state during the molding of this inflation film. In Example 2, molding was performed by changing the discharge speed from the extruder. Note that these molding conditions are those of a normal blown film molding method, and are not those that control the dispersion or flow state of the ethylene / vinyl alcohol resin.

4) MFR (melt flow rate) JIS K-6760 Temperature 190 ℃ Load 2160gr

5) Measurement of oxygen gas permeation amount Using a gas permeation tester (differential pressure method) manufactured by Toyo Seiki Co., Ltd., the oxygen gas permeation amount of the 50 μm thick film obtained in 3) under an atmosphere of 23 ° C. and 50% RH was measured. did. 6) Melt apparent viscosity Capillary rheometer 3211 manufactured by Instron (USA)
Using a mold, the shear stress under a specified melting temperature and shear rate was detected, and the apparent melting viscosity was calculated. Details are given below. Capillary rheometer 3211 type Plunger speed ・ ・ ・ 0.06〜20 cm / min Load capacity ・ ・ ・ 500〜2000 Kg Measurement temperature ・ ・ ・ 40〜399 ℃ Temperature control ・ ・ ・ Barrel ± 2 ℃ Capillary ± 0.5 ℃ barrel ・ ・ ・ Diameter 0.953 ± 0.0013cm Effective length 25cm (including 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 copolymers (A) listed 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 of 1) above, and extrusion kneadability, MFR and oxygen were mixed. Performances such as transmission amount were evaluated. The results are shown in Table 3.

[0027]

[Table 3]

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

[0029]

[Table 4]

[0030]

EFFECTS OF THE INVENTION 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 further has pinhole resistance, stretchability and moldability. It is possible to provide an ethylene copolymer composition having improved physical properties such as water resistance. In particular, the composition of the present invention has a wide range of applications because it has a good gas barrier property even when formed into a thin film, and can be used for various packaging including food packaging.

Claims (2)

[Claims] 1. An ethylene / unsaturated ester copolymer (A) 30 to 7 having an unsaturated ester content of 10 to 35% by weight.
5% by weight, graft-modified product (B) of an amorphous or low crystalline ethylene / α-olefin copolymer having an ethylene content of 60 to 90 mol% with an unsaturated carboxylic acid or an anhydride thereof (B) 1 to 40% by weight And an ethylene copolymer composition comprising 20 to 50 wt% of an ethylene / vinyl alcohol copolymer (C) having a vinyl alcohol content of 50 to 80 mol%. 2. The apparent melt viscosity of the ethylene / vinyl alcohol copolymer (C) at a shear rate of 220 ° C. and 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.