JPH1180253A - Treatment method of saponified ethylene-vinyl acetate copolymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a treatment method of obtaining a saponified ethylene-vinyl acetate copolymer excellent in extrusion stability and molding stability which enables molding of uniform films and sheets. SOLUTION: In making a saponified ethylene-vinyl acetate copolymer with an ethylene content of Et (molar%) and a saponification value of SV (molar%) contain water, the saponified ethylene-vinyl acetate copolymer is treated to have a moisture content of 10-50 wt.% by contacting the saponified ethylene- vinyl acetate copolymer with water or water vapor under the condition satisfying the formula [wherein T is a treatment temperature ( deg.C) and t is a treatment time (minute)].

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a saponified ethylene-vinyl acetate copolymer (hereinafter abbreviated as EVOH).
And more particularly to a method for treating EVOH having excellent molding stability.

[0002]

2. Description of the Related Art In general, EVOH is excellent in transparency, gas barrier property, fragrance retention, solvent resistance, oil resistance and the like. It is used for materials, agricultural chemical packaging materials, floor heating pipes, building materials such as wallpaper, gasoline tanks, etc., and is used after being formed into films, sheets, tubes, bottles, tanks, pipes and the like. In such molding, usually, melt molding is performed, and by such molding, it is processed into a shape such as a film shape, a sheet shape, a bottle shape, a tank shape, a cup shape, a pipe shape, a tube shape, etc., and put to practical use. ing.

[0003]

However, melt molding conditions at the time of molding often cause inconveniences such as poor appearance of the molded product and insufficient physical properties. Such melt molding conditions are very important problems. Good melt molding conditions such as appearance are desired, and a melt molding method using hydrous EVOH has been proposed for the purpose of improving such melt moldability (high-speed moldability, transparency, mechanical strength, etc.). (JP-B-47-29578), such a water-containing EV
It has been shown that the use of OH is also a useful means for improving the moldability. However, as for the water-containing EVOH as a raw material, its melt viscosity changes depending on the water content, and thus the raw material EVOH is used.
If the water content of the film is not uniform, the film thickness varies and the discharge rate changes, making it difficult to produce a uniform film. Therefore, when melt-extrusion molding water-containing EVOH, it is important to produce a water-containing EVOH whose water content is controlled to be constant. However, in the prior art, no specific study has been made in the production of water-containing pellets, and a water-containing treatment method of EVOH in which the water content is controlled to be constant has been desired.

[0004]

SUMMARY OF THE INVENTION Therefore, the present inventor has proposed an EV
As a result of intensive studies on the water-containing treatment method of OH, as a result of containing EVOH having an ethylene content of Et (mol%) and a saponification degree of SV (mol%), EVOH and water or steam were mixed under the condition satisfying the following formula (1). Contact and moisture content 1
By treating to 0 to 50% by weight, water can be uniformly contained in EVOH, and the obtained water-containing EVOH
Have excellent molding stability, and have completed the present invention.

(Equation 2) (However, T represents the processing temperature (° C.) and t represents the processing time (minute).) That is, in the present invention, the temperature of the water-containing treatment and the temperature of the water-containing treatment are adjusted according to the type of EVOH to be hydrated (ethylene content and saponification degree). By controlling the time to be within the range of the above-mentioned formula (1), a hydrous EVOH having excellent molding stability can be obtained.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The EVOH used in the present invention is not particularly limited, but has an ethylene content of 10 to 60 mol% (more preferably 25 to 60 mol%).
55 mol%), and the degree of saponification is 90 mol% or more (further 99%).
When the ethylene content is less than 10 mol%, the water resistance becomes insufficient. On the other hand, when the ethylene content exceeds 60 mol% or the saponification degree is less than 90 mol%, the gas barrier property becomes poor. It is not preferable because it decreases.

[0006] The EVOH used in the present invention contains a small amount of a modifying component such as unsaturated carboxylic acid, anhydride thereof,
Any modified polymerization component such as salts, esters, α-olefins, vinyl ethers, nitriles, and amides may be contained. In the present invention, as long as the EVOH has an ethylene content and a saponification degree within the above ranges, it may be used alone or two or more EVOHs having different compositions may be used in combination.

The EVOH has a water content of 10 to 50% by weight, preferably 15 to 40% by weight, more preferably 2 to 40% by weight.
If the water content is less than 10% by weight, it is necessary to raise the extrusion molding temperature, and not only the long-run processing (molding) properties decrease, but also the secondary processing becomes difficult, and conversely, 50% by weight. Exceeding the limit causes a partial separation of the resin and the water in the extruder, making the extrusion unstable, which is not preferred.
In the present invention, in order to obtain such an EVOH, the most characteristic feature is that it is brought into contact with water under a condition satisfying the following expression (1). Here, Et is the ethylene content of EVOH (mol%), SV is the saponification degree of EVOH (mol%), t is the processing time (minute), and T is the processing temperature (° C.).

(Equation 3)

When the water-containing treatment is carried out under treatment conditions exceeding the above range, unevenness of the water content may occur, or sufficient water absorption may not be performed.
It is difficult to produce EVOH uniformly containing water,
In addition, when water-containing treatment is performed below this range, EVO
The state of water localized in H becomes very unstable, and even if water is contained, water is rejected from the EVOH with time, and a portion having a non-uniform water content is generated, thereby achieving the object of the present invention. Can not do it. More preferably, the range of the above formula (1) is from 20 to 90.

A method for treating water containing water, which satisfies the above conditions;
That is, the method of bringing EVOH into contact with water is not particularly limited, and examples thereof include a method of immersing EVOH in water, a method of leaving EVOH in water vapor, and a method of spraying water on EVOH with a spray. Specifically, it is preferable to carry out the treatment using an apparatus such as an autoclave.In general, the autoclave is one in which the treatment is carried out with steam by heating in the presence of water in a closed heat-resistant and pressure-resistant container. More specifically, about 0.1 to 5 kg of EVOH in the form of pellets or powder is placed in a stainless steel container having a capacity of 0.5 to 10 l, and the type of EVOH is satisfied in an autoclave so as to satisfy the above formula (1). May be appropriately selected in consideration of the above. At this time, in order to easily absorb water, water may be put into the stainless steel container together with the EVOH, and the treatment may be performed in an autoclave with the EVOH immersed in the water.

The time for such treatment is not particularly limited as long as it is within the range satisfying the formula (1), but is usually preferably about 1 to 200 minutes (more preferably 5 to 120 minutes). If the time is less than 1 minute, EVOH Moisture is not absorbed enough inside,
If the time exceeds 0 minutes, the amount of water absorbed by the EVOH reaches saturation, and even if the treatment is carried out for a long time, the water absorption rate cannot be increased, which is not preferable because it has no effect. The treatment temperature is not particularly limited as long as it falls within the range satisfying the condition (1). Usually, the treatment temperature is preferably from 50 to 160 ° C. (furthermore, from 55 to 155 ° C.). If not carried out, unevenness of the moisture content is produced.
VOH itself melts before absorbing water, which is not preferable. During such treatment, water may be added together with some alcohol such as methanol or isopropyl alcohol, and at this time, a small amount of a plasticizer such as ethylene glycol, propylene glycol or glycerin may be contained.

Thus, EVOH having a controlled water content (10 to 50% by weight) can be obtained by the treatment method of the present invention. The obtained EVOH has excellent molding stability. Usually, a melt extruder is used to form a molded product such as a film. The conditions for such molding are not particularly limited, but usually a non-vented, screw-type extruder is used to obtain a melt temperature of 40 to 15.
Extruded at 0 ° C. A screw having a compression ratio of 2.0 to 4.0 is used to leave water in a uniform distribution in the formed film. The obtained molded product is further processed,
Particularly excellent films and containers can be obtained by stretching treatment and the like. Such stretching can be performed by a usual method, such as a uniaxial stretching method, a biaxial stretching method (simultaneous,
Sequential) and the like are not particularly limited.

The thus obtained EVOH film (including unstretched) is often used not only as a single layer but also as a laminate having at least one such film. In the production of the laminate, the other film is laminated on one or both sides of a layer of a resin molded product such as a film, a sheet, and the like. And a method of laminating a film or sheet of the base material with a known adhesive such as an organic titanium compound, an isocyanate compound, or a polyester compound.

Examples of such other base films include linear low-density polyethylene, low-density polyethylene, medium-density polyethylene, high-density polyethylene, EVA, ionomer, ethylene-propylene copolymer, ethylene-acrylate copolymer. , Polypropylene, propylene-
α-olefin (α-olefin having 4 to 20 carbon atoms) copolymer, homo- or copolymer of olefin such as polybutene, polypentene, or homo- or copolymer of these olefins with unsaturated carboxylic acid or ester thereof Broadly defined polyolefin resin such as graft-modified resin, polystyrene resin, polyester, polyamide, copolymerized polyamide, polyvinyl chloride, polyvinylidene chloride, acrylic resin, vinyl ester resin, polyester elastomer, polyurethane elastomer, chlorinated polyethylene , Chlorinated polypropylene, EVOH and the like,
Further, paper, metal foil, uniaxially or biaxially stretched plastic film or sheet, woven fabric, nonwoven fabric, metal cotton strip, wood surface and the like can also be used. The layer structure of the laminate is EVO
When the layer of the H film is I (I ₁ , I ₂ ,...) And another base material, for example, the thermoplastic resin layer is II (II ₁ , II ₂ ,. if not only a two-layer structure of the I / II, II / I / II, I / II / I, I 1 / I 2 / II, I / II 1
Any combination such as / II ₂ , II ₂ / II ₁ / I / II ₁ / II ₂ is possible.

[0014] The thus obtained EVOH film and its laminate are excellent in their properties, that is, appearance properties, gas barrier properties, etc., and therefore, films, sheets, tubes, bags for packaging foods, pharmaceuticals, agricultural chemicals, and industrial chemicals. It is very useful for applications such as a container.

[0015]

The present invention will be specifically described below with reference to examples. In the examples, “parts” and “%” mean on a weight basis unless otherwise specified. Example 1 1 kg of EVOH (pellet) having an ethylene content of 35 mol% and a saponification degree of 99.8 mol% together with 1 kg of water was added in a volume of 3 l.
And then set in a 50 l autoclave. A water-containing EVOH having a water content of 31% was subjected to a water-containing treatment at a treatment temperature of 120 ° C. and a treatment time of 30 minutes.
I got The value of equation (1) at this time was 50. The stability of the obtained hydrous EVOH was examined in the following manner.

(Stability of water-containing EVOH) After manufacturing water-containing EVOH, water-containing EVOH was put into a mayonnaise bottle, sealed, and left for 1 month at room temperature. The water content in the pellet was measured and evaluated as follows. ○ −−− The decrease in water content is less than 1% △ −−− The decrease in water content is 1 to 3% × −−− The decrease in water content exceeds 3% Also, the obtained water-containing EVOH is equipped with a T-die. And supplied to a single-screw extruder to form an EVOH film having a thickness of 30 μm. The film forming conditions using a single screw extruder were as follows. Screw inner diameter 65mm L / D 28 Screw compression ratio 3.8 T die Coat hanger type Die width 450mm Extrusion temperature C1: 110 ° C, H: 95 ° C C2: 120 ° C, D: 95 ° C C3: 110 ° C, C4: 95 ° C C5: 95 ° C. In forming the above EVOH film, the following evaluation was carried out by performing continuous forming for 96 hours.

(Extrusion stability) The current fluctuation of the extruder during the molding was measured, and the difference between the maximum value and the minimum value of the current (A) was evaluated as follows. ○ −−− (maximum value−minimum value) ≦ 4 × −−− (maximum value−minimum value)> 4 (Evaluation of film uniformity) Film formation between two polarizing plates superimposed in a crossed Nicols state Place the film
The uniformity of the film (whether there is no streak or the like) was visually evaluated and evaluated as follows. ○ −−− Good △ −−− Somewhat good × −−− Non-uniform

Example 2 A water content of 14 was obtained in the same manner as in Example 1 except that the conditions of water treatment were 100 ° C. and the treatment time was 30 minutes.
% EVOH was obtained. The value of equation (1) at this time was 60. Evaluation of the obtained EVOH was performed in the same manner as in Example 1.

Example 3 In Example 1, the processing temperature was 130 ° C. and the processing time was 120
The same procedure was carried out except that the water content was
0% EVOH was obtained. The value of equation (1) at this time is 28
Met. Evaluation of the obtained EVOH was performed in the same manner as in Example 1.

Example 4 An EVOH having a water content of 48% was obtained in the same manner as in Example 1 except that EVOH (pellet form) having an ethylene content of 29 mol% and a saponification degree of 99.8 mol% was used. Was. The value of equation (1) at this time was 44. EVO obtained
The evaluation of H was performed in the same manner as in Example 1.

EXAMPLE 5 3 l of water and 1 kg of EVO were placed in a 5 l stainless steel vat.
H (pellet: ethylene content 35 mol%, saponification degree 99.8 mol%, water content 16 wt%), and heated at 110 ° C. for 300 minutes by direct fire to obtain EVOH having a water content of 30%.
I got At this time, the value of the expression (1) was 32. Evaluation of the obtained EVOH was performed in the same manner as in Example 1.

Example 6 In Example 1, EVOH (pellet) having an ethylene content of 44 mol% and a saponification degree of 99.8 mol% was used.
EVOH having a water content of 28% was obtained in the same manner except that the treatment was performed at a temperature of 120 ° C. for 60 minutes. At this time (1)
The value of the formula was 43. Evaluation of the obtained EVOH was performed in the same manner as in Example 1.

Comparative Example 1 The procedure of Example 1 was repeated, except that the treatment temperature was 80 ° C. and the treatment time was 10 minutes.
VOH (value of equation (1) = 154) was obtained and evaluated in the same manner.

Comparative Example 2 In Example 1, EVOH having an ethylene content of 27 mol% and a saponification degree of 99.8 mol% was used, and a treatment temperature of 140 mol.
EVOH with a water content of 55% (value of the formula (1) = 1)
9) was obtained and evaluated in the same manner as in Example 1. Table 1 shows the evaluation results of the examples and the comparative examples.

[0025]

(Table 1) (Stability of water-containing EVOH) (Extrusion stability) (Film uniformity) Example 1 ○ ○ ○ 〃 2 ○ ○ ○ 〃 3 ○ ○ ○ 〃 4 △ △ ○ 〃 5 ○ ○ ○ 〃 6 ○ ○ ○ Comparative Example 1 ○ × △ 〃 2 × No film formation due to separation of resin and water in the extruder

[0026]

EFFECT OF THE INVENTION EVOH treated with water by the method of the present invention
Has a stable moisture content, and therefore has little fluctuation in viscosity during extrusion processing and is excellent in processing stability. Therefore,
It is excellent in uniformity and can obtain molded products such as films and sheets with less unevenness in thickness, and can be used for foods, pharmaceuticals, agricultural chemicals,
It is very useful for applications such as films, sheets, tubes, bags, containers and the like for packaging industrial chemicals.

Claims (3)

[Claims] An ethylene-vinyl acetate copolymer having an ethylene content of Et (mol%) and a saponification degree of SV (mol%) is made to contain ethylene-vinyl acetate under the conditions satisfying the following formula (1). A method for treating a saponified ethylene-vinyl acetate copolymer, which comprises contacting a saponified copolymer with water or steam to treat the saponified copolymer with a water content of 10 to 50% by weight. (Equation 1) (However, T represents a processing temperature (° C.) and t represents a processing time (minute).) 2. The method for treating a saponified ethylene-vinyl acetate copolymer according to claim 1, wherein the treatment is carried out using an autoclave. 3. The saponified ethylene-vinyl acetate copolymer having an ethylene content (Et) of 10 to 60 mol% and a saponification degree (SV) of 90 mol% or more. 3. The method for treating a saponified ethylene-vinyl acetate copolymer according to 2.