JP3534141B2 - Thermoplastic resin composition - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoplastic resin composition which provides a packaging material which is flexible and has excellent flex fatigue resistance and gas permeation resistance.

[0002]

2. Description of the Related Art Saponified resin of ethylene / vinyl acetate copolymer (hereinafter abbreviated as EVOH) can be melt-molded with excellent gas permeability, oil resistance, solvent resistance and aroma retention. It is widely known as a thermoplastic resin and is used for films, sheets, containers and the like in various packaging fields. However, EVOH has the drawbacks of being hard, brittle, and lacking in flexibility, so that it is rarely used alone and is widely used mainly as a laminate with other thermoplastic resins. Nevertheless, even if the laminated packaging material having the EVOH layer is subjected to, for example, strong vibration due to transportation, bending fatigue, etc., EV
Cracks and pinholes are generated in the OH layer, and excellent gas permeation resistance cannot be maintained.

[0003]

2. Description of the Related Art Conventionally, by mixing a partially saponified ethylene / vinyl acetate copolymer with a partially saponified ethylene / vinyl acetate copolymer, the interlayer adhesion between the saponified ethylene / vinyl acetate copolymer and the polyolefin can be improved. It has been known that a low temperature sealing property is imparted. (Japanese Patent Publication Sho 5
However, when a film is formed according to these descriptions, lack of flexibility, poor thermal stability, severe neck-in, streaks on the curtain surface, satin finish, etc. The pattern appeared and was not put to practical use.

Further, by blending a saponified product of ethylene / vinyl acetate copolymer, a partial saponified product thereof and an ethylene / vinyl acetate copolymer, excellent adhesion to a polyamide layer or a polyvinyl chloride layer is achieved. It is also known that multi-layer containers can be obtained. (See JP-A-57-32952 and JP-A-57-11050) However, even in this case, streaks and satin are generated on the curtain surface, which is not preferable.

[0005]

Although EVOH has a very excellent gas barrier property, when a EVOH multilayer laminate is molded into a container, a pinhole is added to the EVOH layer,
As a result, cracks, uneven thickness, etc. were generated, and the gas barrier property originally possessed by EVOH was greatly impaired. Therefore, an object of the present invention is to prevent pinholes and crack uneven thickness that occur when thermoforming a multi-layered laminate of this saponified resin into a container or the like without impairing gas barrier properties such as EVOH, and at the same time, to prevent resistance to cracks. An object of the present invention is to provide a resin composition having excellent bending fatigue resistance and adhesive strength.

[0006]

Means for Solving the Problems That is, the present invention provides (a)
Saponified resin of ethylene / vinyl acetate copolymer 98-70
A thermoplastic resin composition comprising 2% to 30% by weight of (b) an acid-modified resin of a partially saponified ethylene / vinyl acetate copolymer , and (b) an ethylene / vinyl acetate copolymer.
The partially saponified acid-modified resin has a vinyl acetate content of 20 to 7
Saponification of 0 mol% ethylene-vinyl acetate copolymer
Acidification by partial saponification to a degree of 30-95 mol%.
It is a functional copolymer and is acid-modified with unsaturated monocarboxylic acid.
Radicals with acids and unsaturated dicarboxylic acids (or with their anhydrides)
Ethylene initiator, and the amount of unsaturated carboxylic acid added is ethylene.
・ 0.1 to 1 for partially saponified vinyl acetate copolymer
0% by weight graft reaction and dicarboxylic acid anhydride
Use water of partially saponified ethylene-vinyl acetate copolymer
Esterification reaction in which 5 to 60 mol% of acid groups are esterified
And a thermoplastic resin composition.

The present invention will be specifically described below. In the resin composition of the present invention, there are various saponified resins of ethylene / vinyl acetate copolymer used as the component (a). For example, saponified ethylene / vinyl acetate copolymer, propylene / acetic acid. There are saponified products of vinyl copolymers or saponified products of butene and vinyl acetate copolymers, and saponified products of ethylene / vinyl acetate copolymers (hereinafter abbreviated as EVOH) are particularly preferred because of easy polymerization. . EV
OH has an ethylene content of 20 to 60 mol% and a saponification degree of 9
Those having a composition of 5 mol% or more are preferably used.
When the ethylene content is less than 20 mol%, the oxygen barrier property at high humidity is deteriorated, while when it is 60 mol% or more, the oxygen barrier property and printability and other physical properties are deteriorated. Further, when the saponification degree of the vinyl acetate component is less than 95%, the oxygen barrier property and the moisture resistance decrease. Particularly, EVOH having an ethylene content of 25 to 55 mol% and a saponification degree of 98% or more is most suitable.

In addition to ethylene and vinyl acetate (or saponified vinyl alcohol), unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid and maleic acid, or their alkyl esters, propylene, butene, α
A small amount of α-olefin such as decene or α-octadecene may be contained as a comonomer.

On the other hand, in the resin composition of the present invention,
To be used as the component (b), an acid-modified product of a partially saponified product of ethylene-vinyl acetate copolymer (hereinafter abbreviated as EVA) (hereinafter abbreviated as HEVA) (hereinafter, HEVA) is used.
Abbreviated as C) is prepared by the following method.

E which is a raw material for producing this resin component
VA is produced by a known production method such as a high pressure method and an emulsification method, and a vinyl acetate content of 20 to 70 mol% is usually used, but preferably 30 to 45 mol%.
Is. When the content of vinyl acetate is low, the crystallinity of polyethylene cannot be suppressed and the transparency cannot be improved. On the other hand, when the content of vinyl acetate is large, it softens to improve the bending fatigue resistance, but when it is too large, the production becomes difficult in the saponification step.

This resin is treated by a known saponification method, for example, a system consisting of a low boiling alcohol such as methanol or ethanol and an alkali such as sodium hydroxide, potassium hydroxide or sodium methylate. The saponification degree is 30 to
HEVA can be obtained by saponification so as to be 95 mol%, preferably 50 to 95 mol%. When the degree of saponification is less than 30 mol%, the compatibility with EV OH is not improved and gel fisheye occurs. On the other hand, the saponification degree is 9
When it is more than 5 mol%, the crystallinity becomes high and the flexibility cannot be obtained.

Next, HEVAC is obtained from this HEVA as a raw material by utilizing a grafting reaction or an esterification reaction. In the case of using the grafting reaction, unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, crotonic acid and itaconic acid, and unsaturated dicarboxylic acids such as maleic acid (or their anhydrides), benzoyl peroxide, lauroyl peroxide,
Using a radical initiator such as α, α′-azobisisobutyronitrile, the amount of unsaturated carboxylic acid added is changed to HEVA.
With respect to 0.1 to 10% by weight, preferably 0.5 to 5
The acid modification is carried out under the condition that the weight ratio becomes.

In the case of utilizing the esterification reaction, the dicarboxylic acid anhydride such as maleic anhydride, succinic anhydride, phthalic anhydride, and hexahydrophthalic anhydride is 5 to 60 mol% of the hydroxyl groups of HEVA, preferably Is 10 to 50
Mol% is added so that it is esterified. This HE
VAC has been modified mainly for the purpose of imparting affinity for EVOH. Therefore, if the amount of the unsaturated carboxylic acid added is less than 0.1% by weight, the compatibility is insufficient and the permeability is not improved. If it exceeds 10% by weight, gelation occurs and the commercial value of the film is lost.

The mixing ratio of EVOH and HEVAC of the present invention is 98 to 70% by weight of EVOH and 2 to HEVAC.
30% by weight, preferably 97-75% by weight of EVOH
HEVAC is 3 to 25% by weight. 2% by weight
If it is less, the bending fatigue resistance is hardly improved. On the other hand, if it exceeds 30% by weight, the transparency may deteriorate,
The oxygen barrier property is reduced.

As a method for obtaining the resin composition of the present invention,
It is manufactured by a known technique. For example, EVOH and HEVA
C and P are uniformly blended in the form of pellets or powder and melt-mixed with a single-screw or twin-screw extruder to form pellets, or pellets or powder of EVOH and HEVAC are uniformly mixed and directly extruded. There is a method of supplying to a molding machine or an injection molding machine and molding while kneading in the molding machine.

In the present invention, if necessary, other additives such as phenol-based antioxidants, phosphorus-based antioxidants, sulfur-based antioxidants, ultraviolet absorbers, hindered amine-based photostabilizers are used. Agent, lubricant, pigment, plasticizer, crystallization accelerator,
You may mix | blend an inorganic filler and the like.

The resin composition of the present invention is molded into a film, sheet, container or the like by melt molding. As the melt molding method, any melt molding method including an extrusion molding method (including a blow molding method and an extrusion coating method) and an injection molding method is adopted.

As a method for producing a film made of the resin composition of the present invention, a known production method can be applied. Specifically, a resin composition is melt-mixed by an extruder, extruded into a flat film by a T-die or a coat hanger die, cast on a casting roll surface to cool the film, a casting method, Alternatively, a tuber method or the like in which a cylindrical die is extruded into a tubular shape and cooled with water is applied.

A flat or tuber-shaped film may be stretched continuously or in a separate step. For example, in the case of the sequential biaxial stretching method,
A flat unstretched film is stretched 2 to 4 times by a roll type longitudinal stretching machine, and then 2 to 4 times by a tenter type transverse stretching machine.
The biaxially stretched film is stretched 5 times, and the obtained biaxially stretched film is heat-treated, if desired, and then the film is gradually cooled and continuously wound up to be produced.

The biaxially stretched film can be produced by the tenter-sequential biaxial stretching method exemplified above, or by other methods such as a tenter-type simultaneous biaxial stretching method and a tuber stretching method.

The film made of the resin composition containing the filler described above can be made into a laminate from other polymer films. The method for forming the laminate is not particularly limited, and for example, a method of adhering a polyamide film and another one or more polymer films with an adhesive can be applied.

The present invention will be described in more detail with reference to the following examples and comparative examples. The methods for measuring or evaluating the physical properties are as follows. (1) Transparency Suga test machine direct reading haze meter
The haze value (haze ratio) of the film was measured according to D-1003. And, the value of 6 or less means that the transparency is improved. (2) Bending fatigue resistance MIL-
After conducting a bending test 100 times at 23 ° C. according to B-131C, the number of pinholes formed on the film was measured using a pinhole detector made by Sanko Denshi.
Then, the value of 10 or less was determined to have the effect of improving the resistance to bending pinholes. (3) Oxygen gas permeation amount OX-TRAN10 manufactured by Modern Control
0, 23 ° C, 0% according to ASTM D-3985
It was measured under the condition of RH.

Example 1 EVOH having an ethylene content of 32 mol% and a saponification degree of 99% or more
99% by weight, vinyl acetate content 32% by weight, saponification degree 90
%, HEVAC with a modification rate of 0.6% modified with acid
After 5 wt% was dry-blended, it was melt-kneaded and pelletized by a 30φ different-direction twin-screw extruder at 220 ° C. Using these pellets, a monolayer film was produced under the following molding machine and spine conditions. Appearance, moldability,
The transparency, bending fatigue resistance, and oxygen gas permeation amount were evaluated. The evaluation results are shown in Tables 1 and 2. Film forming conditions (1) Forming machine: 40 mmφE manufactured by Plastic Engineering Laboratory
x. Using T-die film forming machine (2) Film thickness:
30μ (4) Roll temperature: 30 ° C

Examples 2 to 6 EVOs shown in Tables 1 and 2 were evaluated in the same manner as in Example 1.
The evaluation results obtained by using H and HEVAC are shown in Tables 1 and 2.

Comparative Examples 1 to 6 EVOs shown in Tables 1 and 2 were evaluated in the same manner as in Example 1.
The evaluation results obtained by using H and HEVAC are shown in Tables 1 and 2.

[0026]

[Table 1]

[0027]

[Table 2]

Claims (4)

(57) [Claims] 1. (a) 98 to 70% by weight of a saponified resin of an ethylene / vinyl acetate copolymer, and (b) 2 to 30% by weight of an acid-modified resin of a partially saponified product of an ethylene / vinyl acetate copolymer. (B) an acid of a partially saponified ethylene / vinyl acetate copolymer , which is a thermoplastic resin composition comprising
The modified resin is an ethylene resin having a vinyl acetate content of 20 to 70 mol%.
The ren-vinyl acetate copolymer has a saponification degree of 30 to 95.
Acid saponified copolymer partially saponified to a mol%
And the acid modification is unsaturated monocarboxylic acid or unsaturated dicarboxylic acid.
(Or its anhydride) and a radical initiator
Rubonic acid is added in the ethylene / vinyl acetate copolymer part
Graft repelling amount of 0.1 to 10% by weight with respect to saponification product
However, using dicarboxylic acid anhydride, ethylene / vinyl acetate
5-60 mol% of the hydroxyl groups of the partially saponified copolymer
A thermoplastic resin composition , characterized in that it is an esterification reaction to be stellified . 2. A saponified resin of (a) an ethylene / vinyl acetate copolymer having an ethylene content of 20 to 60 mol% and a saponification degree of 9
The thermoplastic resin composition according to claim 1, which is a saponified resin of 5 mol% or more of an ethylene / vinyl acetate copolymer. 3. The thermoplastic resin composition comprises (a) ethylene.
A vinyl acetate copolymer saponified resin 97-75% by weight,
(B) Acid of partially saponified ethylene / vinyl acetate copolymer
Thermoplastic resin composition comprising 3 to 25% by weight of modified resin
3. The method according to claim 1 or 2, wherein
Thermoplastic resin composition. 4. (a) Saponification of ethylene / vinyl acetate copolymer
Compound resin has an ethylene component content of 20 to 65 mol.
%, Syndiotacticity is 55 in the diamond display.
Ethylene-vinyl alcohol copolymerization of more than mol%
Consists of body (A) and olefin resin (B),
The weight ratio of (A) and (B) is 93: 7 to 60:40.
The content of ethylene component used in the resin composition is 20
~ 65 mol%, syndiotacticity is diat
Ethylene-vinyl alcohol which is 55 mol% or more in the indication
Ethylene-vinyl acetate copolymer excluding copolymer (A)
The saponified resin of the body as claimed in claim 1.
The thermoplastic resin composition according to any one of items.