JPH1158500A - Molding method for resin composition - Google Patents

Abstract

(57) [Problem] To provide a method for molding a saponified ethylene-vinyl acetate copolymer excellent in appearance, molding stability and the like. SOLUTION: An extruder melt-molds a saponified ethylene-vinyl acetate copolymer having an ethylene content of 10 to 60 mol% and a saponification degree of 90 mol% or more, adjusted to a water content of 10 to 50 wt%. When the length of the screw of the extruder is L (mm) and the diameter is D (mm), L /
Specific energy (E) at the time of extrusion per D unit is 1 to 20
W · hr / kg.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a saponified ethylene-vinyl acetate copolymer (hereinafter abbreviated as EVOH).
More particularly, the present invention relates to a method for molding a resin composition having excellent moldability.

[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, pesticide packaging materials, floor heating pipes, building materials such as wallpaper, gasoline tanks and the like, and is used after being formed into films, sheets, bottles, tanks, pipes and the like. In such molding, usually, melt molding is performed, and by such molding, it is processed into 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, in such molding, inconveniences such as poor appearance of the molded article and insufficient physical properties often occur depending on molding conditions, and the molding conditions in such molding are very important problems. Therefore, good molding conditions such as appearance are desired.

[0004]

Means for Solving the Problems Accordingly, the present inventors have
As a result of intensive studies on the molding conditions of EVOH, the ethylene content adjusted to a water content of 10 to 50% by weight was 10 to 6%.
EVOH with 0 mol% and saponification degree of 90 mol% or more
When melt extruding with an extruder, when the screw length of the extruder is L (mm) and the diameter is D (mm), the specific energy (E) at the time of extrusion per L / D unit is By setting it to 1 to 20 W · hr / kg, the molding stability of EVOH is excellent, the obtained molded product is excellent in appearance, and after melt molding, the water content is adjusted to 1 to 40% by weight and stretched. As a result, it was found that a stretched EVOH film having excellent appearance was obtained, and the present invention was completed.

[0005] Here, the specific energy means the energy given to the resin (1 kg) per unit discharge amount from the melt extrusion equipment for the effect of melting when the resin is melt-molded. It is defined by installing a meter, a voltmeter, etc., obtaining the power consumption of the motor from this, multiplying this by the power factor of the motor (usually about 0.85), and calculating the power per discharge amount. Is determined from the difference between the energy during resin extrusion and the energy during idle operation.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The EVOH used in the present invention has an ethylene content of 1
0 to 60 mol%, preferably 25 to 55 mol%, and a saponification degree of 90 mol% or more, preferably 99 mol% or more are used.

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 is reduced. Unsuitable.

[0008] The EVOH used in the present invention has a small amount of a modifying component such as an unsaturated carboxylic acid, an 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.

Further, in the present invention, the above-described EV
The water content of OH is 10 to 50% by weight, preferably 15 to 4%.
0% by weight, more preferably 20 to 30% by weight. When the water content is less than 10% by weight, it is necessary to raise the extrusion temperature, and not only does the long-run processability decrease,
Secondary processing is also difficult, and the effects of the present invention cannot be obtained. Conversely, if it exceeds 50% by weight, partial separation of resin and water occurs in the extruder, and extrusion becomes unstable, and the present invention Can not achieve the purpose. The method for adjusting the water content is not particularly limited, and the EVOH pellets and water may be mixed and stirred to cause the pellets to absorb water, or a method of blowing steam may be employed. It is also possible to contain water together with a small amount of alcohol such as methanol or isopropyl alcohol during the production of EVOH. At this time, a small amount of a plasticizer such as ethylene glycol, propylene glycol or glycerin may be contained.

In the present invention, when the above-mentioned hydrated EVOH is melt-molded by an extruder, when the length of the screw of the extruder is L (mm) and the diameter is D (mm), the melt-extrusion is carried out. The specific energy (E) at the time of extrusion per L / D unit is 1 to 20 W · hr / kg, preferably 2 to 1 W · hr / kg.
8 W · hr / kg, more preferably 4 to 15 W · hr /
When the specific energy is less than 1 W · hr / kg, the ejection becomes unstable, and when the specific energy exceeds 20 W · hr / kg, the resin temperature excessively increases due to heat generated by shearing of the resin. Therefore, foaming due to moisture occurs and a good film cannot be obtained, and the object of the present invention cannot be achieved.

The EVOH (molded product such as pellets, films, sheets, and the like) thus formed by the method specific to the present invention can be used in a film, container, or the like, which is further excellent in secondary workability, particularly, by stretching. Can be obtained. Regarding such stretching, it is of course possible to perform the stretching by a usual method without adjusting the water content. However, in the present invention, uniform stretching, improvement of gas barrier properties by providing sufficient stretching orientation, and mechanical properties From the viewpoint of improving the water content, it is preferable to adjust the water content of the EVOH molded product at the time of stretching (immediately before stretching) to 1 to 40% by weight. That is, the water content is 1% by weight.
If it is less than 40% by weight, it tends to cause unevenness in stretching, which may cause breakage. On the other hand, if it exceeds 40% by weight, the effect of improving gas barrier properties and strength by sufficient stretching orientation may not be obtained. Is preferred. The method for adjusting the water content is not particularly limited, and a humidity control operation can be performed immediately after the above-described molding.

At this time, the molded product may contain about 0.2 to 10% by weight of a plasticizer such as ethylene glycol, propylene glycol or glycerin, in addition to water. The stretching includes, for example, a uniaxial stretching method and a biaxial stretching method (simultaneous and sequential), and is not particularly limited. However, the present invention is particularly effective for the primary (MD direction) stretching in the sequential biaxial stretching method. Yes, such a stretching method will be described in detail. The (film-like) EVOH molded article having the adjusted water content is
It is subjected to a first (MD direction) stretching step. For the primary (MD direction) stretching, a known method can be used, and the molded product is stretched 1.5 to 8 times in the machine direction at 30 to 110 ° C. The first (MD
Direction) The water content after the stretching treatment is preferably 0.5 to 30% by weight, more preferably 3 to 25% by weight. If the water content is less than 0.5% by weight, stretching unevenness occurs in the second (TD) stretching, making it difficult to stretch to the same stretching ratio. Conversely, if it exceeds 30% by weight, the primary The effect of stretching orientation cannot be expected, and the effect of improving gas barrier properties and strength is reduced, which is not preferable. As the method of adjusting the water content, the temperature and time of the preheating roll,
The primary (MD direction) stretching can be performed at a temperature and a stretching speed.

The above-mentioned primary (MD direction) stretched EV
The OH film is subsequently subjected to stretching in the transverse direction in a second (TD direction) stretching step. In such a step, a known method can be used, and the above-mentioned EVO is used.
H film at a temperature of 60-170 ° C.
It is stretched up to 8 times. Usually, it is performed by a tenter method in which both ears of a film are clipped. Except for these conditions, breakage occurs at the clip portion, between the clip and the clip, or at an intermediate portion in the film width direction, and it is extremely difficult to obtain a target stretched film. Further, usually, heat setting is further performed.
By heating the film at 0 ° C. for several seconds to several minutes, in order to further impart flexibility and dimensional stability to the heat-set film, the water content is 0.1 to 4% by weight, preferably 0.5% by weight.
The humidity of the film may be adjusted to about 3% by weight.

The EVOH film obtained in the present invention 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, a film obtained by the production method of the present invention, the other substrate is laminated on one or both sides of a layer of a resin molded product such as a sheet, as a lamination method, for example, A method of laminating the resin molded product and a film or sheet of another base material using a known adhesive such as an organic titanium compound, an isocyanate compound, a polyethyleneimine compound, a polyester compound, or a polyurethane compound, etc. .

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.

Thus, the EVO obtained by the method of the present invention
H film and its laminate, its properties, that is, appearance properties,
Because of its excellent gas barrier properties, it can be used for packaging films, sheets, tubes,
Very useful for applications such as bags and containers.

[0017]

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 EVOH [Ethylene content 35 mol%, saponification degree 99.
[8 mol%] 100 parts of 43 parts of water was added to obtain a water-containing EVOH having a water content of 30%. The water-containing EVOH is supplied to a single-screw extruder equipped with a T-die, and is heated and melted at 110 ° C., and the specific energy (E) with respect to the EVOH is L / D.
Under the condition of 16W · hr / kg per unit,
It was formed into a 350 μm thick film.

The conditions for forming a film using a single screw extruder were as follows. Screw inner diameter 65 mm L / D 28 T die Coat hanger type Die width 450 mm Extrusion temperature C1: 110 ° C, H: 100 ° C C2: 120 ° C, D1: 100 ° C C3: 110 ° C, D2: 100 ° C C4: 100 ° C, D3 : 100 ° C. C5: 100 ° C., D4: 100 ° C. D5: 100 ° C. In the above-mentioned EVOH molding, a long run molding was carried out for 96 hours, but a good EVOH film could be obtained without generation of gel or eye repellent. As a result, the long-run formability was good.

Further, the extrusion stability was examined in the following manner. (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 was evaluated as follows. ○ −−− (maximum value−minimum value) ≦ 4 × −−− (maximum value−minimum value)> 4 Then, the EVOH film (water content 27%) obtained by the above molding was continuously used as a raw material. 2 under the following conditions
Axial stretching, heat setting, and humidity control were performed to obtain an EVOH stretched film.

[Primary stretching (longitudinal stretching) conditions] Stretching machine Roll-type primary stretching machine Stretching roll temperature 60 ° C. Longitudinal stretching ratio 4.0 times Film thickness after stretching 75 μm Moisture content after stretching 20% Secondary Stretching (Lateral Stretching) Condition] Stretcher Tenter type biaxial stretching machine Stretching temperature 110 ° C. Stretching ratio in the transverse direction 5.0 times Film thickness after stretching 12 μm Moisture content after stretching 2% [Heat fixing condition] Temperature 160 ° C. Time 20 seconds [Humidity control condition] Leaving at 20 ° C. and 65% RH for 7 days Water content after humidity control 2.7% Transparency, film appearance, gas barrier property of the obtained EVOH (biaxial) stretched film, The film strength was evaluated as follows.

(Transparency) The haze value was measured. (Film appearance) Sampling film (10cm × 1
The number of gels (0.1 cm or more) per 0 cm) was visually measured and evaluated as follows. In addition, the measurement result was made into the average value when the same test was performed about five samples. ○ −−− less than 5 △ −−− 5 to less than 10 × −−− 10 or more

(Gas Barrier Property) Oxygen permeability (cc.20 μm / m ² .day) under conditions of 20 ° C. and 65% RH
Atm) was measured. (Film strength) AS at 20 ° C. and 65% RH
Based on TM-D-882 and 1922, the tensile strength (Ts; kg / mm ² ), elongation (El;%) and tear strength (Tr; kg / μm) were measured.

Example 2 The procedure of Example 1 was repeated except that the specific energy (E) was changed to 5 W · hr / kg per L / D unit.
A VOH film and an EVOH stretched film were obtained and similarly evaluated.

Example 3 An EVOH film and an EVOH stretched film were obtained in the same manner as in Example 1 except that EVOH having an ethylene content of 28 mol% and a saponification degree of 99.4 mol% was used. Evaluation was performed similarly.

Example 4 The procedure of Example 1 was repeated, except that 100 parts of EVOH contained 82 parts of water (water content: 45%).
An H film and an EVOH stretched film were obtained and evaluated similarly. Example 5 In Example 1, the water content of EVOH at the time of stretching was 20%.
EVOH film and EV
An OH stretched film was obtained and evaluated similarly.

Comparative Example 1 An EVOH was prepared in the same manner as in Example 1 except that 100 parts of EVOH contained 7 parts of water (water content: 7%).
An attempt was made to obtain a film and to produce a stretched film, but the production was stopped due to foaming and cutting. Comparative Example 2 An EV was obtained in the same manner as in Example 1, except that 100 parts of EVOH contained 150 parts of water (water content: 60%).
An OH film and an EVOH stretched film were obtained and evaluated in the same manner. However, since water precipitated inside the extruder, no stretched film was produced.

Comparative Example 3 An EVOH film was produced in the same manner as in Example 1 except that the specific energy (E) was changed to 0.5 W · hr / kg per L / D unit. Production of the resin was discontinued due to severe deterioration of the resin. Comparative Example 4 Example 1 was repeated except that the specific energy (E) was changed to 30 W · hr / kg per L / D unit.
An EVOH film and an EVOH stretched film were obtained and evaluated similarly. Table 1 shows the evaluation results of Examples and Comparative Examples.
Shown in

[0028]

[Table 1] Extrusion Transparency Fill Oxygen Permeable Film Strength Stability (Haze ゛ Value) Appearance Permeability Ts El Tr Example 1 ○ 1.0 ○ 0.5 16.5 / 18.0 57/45 0.60 / 0.55 〃 2 ○ 1.0 ○ 0.4 14.3 / 14.4 70/63 0.71 / 0.75 〃 3 ○ 1.3 ○ 0.4 18.3 / 17.4 52/48 0.68 / 0.59 〃 4 ○ 1.1 ○ 0.5 15.2 / 16.7 58/43 0.65 / 0.60 ５ 5 ○ 1.0 ○ 0.6 17.8 / 20.1 41/25 0.40 / 0.73 Comparative Example 1 ○ Discontinued production of stretched film × 2 × No production of stretched film ３ 3 ○ Discontinuation of production of stretched film 4 × 2.3 × 0.7 16.4 / 6.3 55/3 0.05 / 0 / 0.50 Note) Ts is tensile strength (Kg / mm ² ), El represents the elongation (%), Tr represents the tear strength (kg / μm), and the numerical values represent the measured values in the vertical and horizontal directions, respectively. The unit of oxygen permeability is cc · 20 μm / m ² · day · atm.

[0029]

According to the present invention, EVOH is produced at a specific water content.
And because the melt molding is performed at a specific specific energy,
It is excellent in molding stability, and the obtained molded product is also excellent in appearance, furthermore, the molded product is also excellent in secondary workability, especially when stretched at a specific moisture content, appearance, mechanical strength, oxygen Stretched films and sheets with excellent barrier properties can be obtained, and films and sheets for packaging foods, pharmaceuticals, agricultural chemicals, and industrial chemicals.
It is very useful for applications such as tubes, bags, containers and the like, and can be particularly suitably used for secondary processed products involving stretching.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masashi Hasegawa 1000 Higashikiana-cho, Ushiku-shi, Ibaraki Mitsubishi Tsukuba Works

Claims (3)

[Claims] 1. A saponified ethylene-vinyl acetate copolymer having an ethylene content adjusted to a water content of 10 to 50% by weight and an ethylene content of 10 to 60% by mole and a saponification degree of 90% by mole or more is melt-molded by an extruder. In doing so, when the length of the screw of the extruder is L (mm) and the diameter is D (mm), L /
Specific energy (E) at the time of extrusion per D unit is 1 to 20
A method for molding a resin composition, wherein the method is W · hr / kg. 2. The method for molding a resin composition according to claim 1, wherein the temperature of the saponified ethylene-vinyl acetate copolymer at the time of melt molding is 40 to 140 ° C. 3. After melt molding, the water content is 1 to 40% by weight.
3. The stretching according to claim 1, wherein
A method for molding the resin composition according to the above.