JPH10180867A - Manufacture of saponified ethylene/vinyl acetate copolymer stretched film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a saponified ethylene/vinyl acetate copolymer stretched film excellent in transparency, film appearance, gas barrier properties and film strength and also excellent in long-run moldability. SOLUTION: This film is obtained by using a saponified ethylene/vinyl acetate copolymer with ethylene content of 10-60mol%, a saponification value of 90mol% or more and water content of 10-60wt.%, pref., a saponified ethylene/vinyl acetate copolymer satisfying a specific formula. A film obtained by extruding this copolymer in a molten state is stretched in such a state that water content is set to 5-50wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a stretched film of a saponified ethylene-vinyl acetate copolymer (hereinafter abbreviated as EVOH).

[0002]

2. Description of the Related Art Conventionally, stretched EVOH films have been frequently used for various packaging applications by utilizing their gas barrier properties. As a method for producing such an EVOH film, E
In general, VOH (pellet) is formed into a film by a melt extruder or the like, and further uniaxially or biaxially stretched.

[0003]

However, depending on the production method, the obtained EVOH film often has die lines, fish eyes, etc., or is poor in transparency. In some cases, long run molding may be difficult due to the occurrence of eye stains, etc.
In the production of OH films, sufficient consideration is required.

[0004]

The inventors of the present invention have conducted intensive studies in view of such circumstances, and as a result, have found that the ethylene content is 10 to 60 mol%, the saponification degree is 90 mol% or more, and the water content is 10 to 60 mol%. It has been found that the above problems can be solved by stretching a film obtained by melt-extruding the EVOH at a water content of 5 to 50% by weight, preferably 21 to 50% by weight, using EVOH of 5% by weight. The invention has been completed. In the present invention, particularly when the EVOH satisfies the following formula, the effect of the present invention is remarkably exhibited.

[0005] 70 ≦ (0.173 × Sv−20.111) × W + 0.2184 × (Sv−100) ² + 6.5356 × (Sv−100) + 230.67 × exp (−0.0074 × Et) ≦ 130 ··· Et: ethylene content (mol%) Sv: saponification degree (mol%) W: water content (wt%)

That is, according to the production method of the present invention, a homogeneous EVOH having a uniform film thickness and excellent in transparency, gas barrier property, etc.
A film can be obtained, and furthermore, generation of a gel, an eye drop and the like can be suppressed during the production, and a long-run moldability is excellent.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the production method of the present invention will be specifically described. As the EVOH of the present invention, an ethylene content of 10 to 60 mol%, preferably 20 to 60 mol%,
More preferably, 25 to 55 mol%, and the saponification degree of the vinyl acetate component is 90 mol% or more, preferably 95 mol% or more. When the ethylene content is less than 10 mol%, the water resistance becomes insufficient. On the other hand, if it exceeds 60 mol%, the gas barrier property is undesirably lowered. On the other hand, if the saponification degree is less than 90 mol%, the water resistance becomes insufficient, which is not preferable.

The EVOH may be variously modified, if necessary, or may be a mixture of the modified EVOH and the above EVOH. As the modified EVOH, for example, modified EVOH with propylene, isobutene, etc., having 3 carbon atoms
At least one α-olefin having from 30 to 30 carbon atoms or 3 carbon atoms
Saponified terpolymer comprising modified EVOH, modified EVOH obtained by graft polymerization of at least one α-olefin of at least 30 and ethylene and acrylic acid ester, and (meth) acrylate-ethylene-vinyl acetate EVOH, a modified EVOH obtained by modifying the hydroxyl group of EVOH with a cyanoethyl group, a modified EVOH containing a polyester graft obtained by depolymerizing a polyester with vinyl alcohol, a vinyl acetate-ethylene-silicon-containing olefinically unsaturated monomer EVOH obtained by saponifying a monomeric copolymer, modified EVOH obtained by saponifying a terpolymer comprising a pyrrolidone ring-ethylene-vinyl acetate, acrylamide-
Modified EVOH obtained by saponifying a terpolymer of ethylene-vinyl acetate, modified EVOH obtained by saponifying a terpolymer of allyl acetate-ethylene-vinyl acetate, isopropenyl acetate-ethylene-acetic acid Modified EVO obtained by saponifying vinyl terpolymer
H, a modified EVOH in which a polyether component is added to the end of EVOH, a modified EVOH in which a polyether component is added in a graft form as a branch polymer of EVOH, a modified EVOH in which an alkylene oxide is added to EVOH,
And the like.

The EVOH contains comonomer other than the above, such as α-olefin, unsaturated carboxylic acid or salt thereof, partial alkyl ester, complete alkyl ester, nitrile, amide, anhydride, unsaturated sulfonic acid or salt thereof. You can be there.

In the present invention, first, the EVO as described above is used.
The water content of H (pellet) is adjusted to 10 to 60% by weight, preferably 15 to 55% by weight, but such a method is not particularly limited, and the EVOH pellets and water are mixed and stirred to absorb water. Alternatively, a method of blowing steam may be employed. Also, it is possible to make the EVOH contain water with some alcohol such as methanol and 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.

If the water content of such EVOH is less than 10% by weight, it is necessary to raise the extrusion molding temperature, and not only does the long-run processing (molding) property deteriorate, but also it becomes difficult to perform uniform stretching, and conversely, exceeds 60% by weight. And excessive water causes extreme stretching, which causes uneven stretching and eventually breaks, making it difficult to achieve the object of the present invention.

In the present invention, it is preferable that the above formula is particularly satisfied with respect to the above-mentioned EVOH. If the range of the formula is less than 70, water and resin are separated in the extruder to make the extrusion unstable, while the value exceeds 130. This is not preferable because foaming occurs, long-run moldability is reduced, and thickness unevenness of the stretched raw film occurs. In particular, the range of the formula is more preferably from 85 to 125. In order to satisfy such a formula, the ethylene content of EVOH,
This is achieved by appropriately controlling the saponification degree and the water content.

In the present invention, the EVOH whose water content has been adjusted as described above can be blended with various resins or compounds, if necessary. For example, as a blend, for example, mica, talc, sericite, inorganic fillers such as glass flakes, chlorinated paraffin, chlorine-based flame retardants such as tetrachlorophthalic anhydride, phosphate-based phosphorus-based flame retardants, Brominated flame retardants such as 2,4-dibromophenol polycondensate, tribromophenol and octabromodiphenyl oxide; inorganic flame retardants such as antimony trioxide and aluminum hydroxide; aliphatic or aromatic polyamides; Crosslinked polymer, acrylate-vinyl acetate copolymer crosslinked saponified product, starch-acrylate graft copolymer crosslinked product,
Highly water-absorbing resin such as saponified starch-acrylonitrile graft copolymer crosslinked product, maleic anhydride grafted polyvinyl alcohol crosslinked product, polyvinyl alcohol having a degree of polymerization of 50 to 3,000 and a degree of saponification of 20 to 100 mol%, starch, polylactic acid , Biodegradable resins such as polycaprolactone, polyethylene, polypropylene, polystyrene, polyolefins such as chlorinated polyethylene, maleic acid-modified polyethylene, acid-modified polyolefins such as ethylene-vinyl acetate copolymer, aliphatic polyester, polytetraalkylene glycol- Polyesters such as block copolymers of polybutylene terephthalate, ionomers such as metal salts of ethylene-acrylic acid copolymers, polyvinyl chloride, polyvinylidene chloride, ethylene-vinyl acetate-vinyl chloride copolymers, Methyl methacrylate, and the like. Further, EVOH having different ethylene content and saponification degree from EVOH used in the present invention, and ethylene content of 1 or more.
EVO having 0 to 60 mol% and a saponification degree of 20 to 100 mol%
H, ethylene content 61-95 mol%, saponification degree 20-
It is also possible to blend other EVOHs, such as 100 mol% EVOH.

EVO having the water content adjusted as described above
H is then supplied to a melt extruder to be formed into a film. The conditions during the formation are not particularly limited, but usually a non-vented, screw-type extruder is used and the melting temperature is 40 to 150 ° C. Extrusion film formation.
Use a screw with a compression ratio of 2.0 to 3.8, and set the temperature of the barrel feed section to a low temperature of 80 ° C or lower in order to leave water in a uniform distribution in the formed film. Is preferred.

The film-like EVO obtained by the above method
The H molded article is then subjected to stretching. In the present invention, the water content of the EVOH molded article at the time of such stretching (immediately before stretching) is adjusted to 5 to 50% by weight, preferably 21 to 50% by weight. It is also important that the moisture content is 5% by weight.
If it is less than 50%, stretching unevenness is likely to occur, which may cause breakage. Conversely, if it exceeds 50% by weight, the effect of improving gas barrier properties and strength by sufficient stretching orientation cannot be obtained, and it is difficult to achieve the object of the present invention. Becomes The method for adjusting the water content is not particularly limited, and a humidity control operation can be performed immediately after film formation.

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 above-mentioned film-shaped E having the adjusted moisture content
The VOH molded product is subjected to a first (MD direction) stretching step. For the primary (MD direction) stretching, a known method can be used, and the above molded product is stretched 1.5 to 8 times in the machine direction at 40 to 100 ° C. The water content after the first (MD direction) stretching treatment is 0.5 to
If the amount is less than 0.5% by weight, stretching unevenness occurs in the second (TD) stretching, which makes it difficult to stretch to the same stretching ratio. Conversely, if it exceeds 45% by weight, the primary stretching orientation effect cannot be expected, and the effects of improving the gas barrier properties and strength are undesirably reduced. As a method for adjusting the water content, the temperature and time of the preheating roll, the primary (MD direction)
The stretching can be carried out depending on the stretching temperature and the 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 in the transverse direction at 60-140 ° C.
It is stretched up to 8 times. Usually, it is performed by a tenter method in which both ears of the film are clipped. Except for these conditions, any 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, and further imparting flexibility and dimensional stability to the heat-set film, the water content is about 0.3 to 3% by weight, preferably 0.5% by weight. The film may be humidified until it becomes about 2% by weight.

The EVOH film obtained by 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, or a polyester compound may be used.

Such other base films include linear low density polyethylene, low density polyethylene, medium density polyethylene, high density polyethylene, ethylene-vinyl acetate copolymer, ionomer, ethylene-propylene copolymer, ethylene- Acrylic ester copolymer, polypropylene, propylene-α-olefin (C 4-20
Α-olefins) copolymers, polyolefins such as polybutene and polypentene, and polyolefins in a broad sense, such as homo- or copolymers of these olefins, or homo- or copolymers of these olefins graft-modified with unsaturated carboxylic acids or esters thereof Resin, polystyrene resin, polyester,
Polyamide, copolymerized polyamide, polyvinyl chloride, polyvinylidene chloride, acrylic resin, vinyl ester resin, polyester elastomer, polyurethane elastomer, chlorinated polyethylene, chlorinated polypropylene, E
VOH and the like, and further, paper, metal foil, uniaxial or
An axially stretched plastic film or sheet, a woven fabric, a nonwoven fabric, a metal cotton strip, a wooden surface, or the like can also be used.

As the layer structure of the laminate, the layer of the EVOH film is I (I ₁ , I ₂ ,...), And the other base material, for example, the thermoplastic resin layer is II (II ₁ , II ₂ ,...). ·) that time, the film, if the sheet-like, not only the double layer structure of the I / II, II / I / II, I / II / I, I 1 / I 2 / II, I / II 1 / II ₂ ,
Any combination such as II ₂ / II ₁ / I / II ₁ / II ₂ is possible.

Thus, the EVOH film and the laminate thereof of the present invention are excellent in properties, that is, appearance properties, gas barrier properties, etc., and therefore, films, sheets, tubes, bags for packaging foods, pharmaceuticals, agricultural chemicals, and industrial chemicals. , Container, retort container and the like. Further, the present invention relates to a method for producing a stretched film, and the EVOH having the adjusted water content used in the present invention can be used for solution coating, melt coating, etc. It can be used or used as a purging agent for an extruder.

[0023]

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%] was impregnated with water to obtain EVOH having a water content of 35%. Next, the EVOH was supplied to a single-screw extruder equipped with a T die, and an EVOH film having a thickness of 120 μm was formed. (The value of the formula is 77, which satisfies the formula)

The conditions for forming a film using a single screw extruder were as follows. Screw inner diameter 40mm L / D 28 Screw compression ratio 3.2 T die Coat hanger type Die width 450mm Extrusion temperature C1: 70 ° C, H: 110 ° C C2: 80 ° C, D: 110 ° C C3: 100 ° C, C4: 120 ° C

In forming the above EVOH film, long run molding was carried out for 96 hours. However, a good EVOH film could be obtained without generation of gels or tars, and the long run moldability was good. . Next, the EVOH film obtained by the above molding (water content 30%)
Was used as a raw material, and successively biaxially stretched, heat-set, and humidified under the following conditions to obtain an EVOH stretched film.

[Primary stretching (longitudinal stretching) conditions] Stretching machine Roll primary stretching machine Stretching roll temperature 70 ° C Longitudinal stretching ratio 2.0 times Film thickness after stretching 60 μm Moisture content after stretching 30%

[Second Stretching (Lateral Stretching) Conditions] Stretcher Tenter type biaxial stretching machine Stretching temperature 110 ° C. Stretching ratio in the transverse direction 3.0 times Film thickness after stretching 20 μm Moisture content after stretching 2%

[Heat setting conditions] Temperature 160 ° C. Time 3 seconds [Humidity control condition] Leave at 20 ° C. and 65% RH for 7 days Water content after humidity control 2.5%

The transparency, film appearance, gas barrier properties, and film strength of the obtained EVOH (biaxial) stretched film (film after 3 hours of stretching treatment) were evaluated as follows.

(Transparency) The haze value was measured. (Film appearance) Observation was made visually. (Gas Barrier Property) The oxygen permeability (cc · 20 μ / m ² · day · atm) was measured under the conditions of 20 ° C. and 65% RH. (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 In Example 1, EVOH having a water content of 20% was obtained (
(The value of the formula is 120, which satisfies the formula.) An EVOH film and an EVOH stretched film were obtained and evaluated in the same manner. At this time, the moisture content of the EVOH film was 17%, the moisture content after the first stretching was 13%,
The moisture content after the next stretching was 2%, and the moisture content after humidity control was 2.5%. The long run formability of the EVOH film was as good as in Example 1.

Example 3 In Example 1, EVOH having an ethylene content of 45 mol% and a saponification degree of 99.8 mol% was used, and the water content was 25%.
(The value of the equation is 93, which satisfies the equation).
A stretched film was obtained and evaluated similarly. EV at this time
The moisture content of the OH film was 23%, the moisture content after the first stretching was 16%, the moisture content after the second stretching was 2.5%, and the moisture content after humidity control was 2.8%. The long run formability of the EVOH film was as good as in Example 1.

COMPARATIVE EXAMPLE 1 The same procedure as in Example 1 was carried out except that EVOH having a water content of 5% was used. However, in the long run molding of the EVOH film, the die line became severe after about 72 hours.
The long run formability was poor. Also, in the stretching treatment, the film was broken at the time of the first stretching, and stable stretching was impossible, and a stretched film could not be obtained.

Comparative Example 2 The same procedure as in Example 1 was carried out except that EVOH having a water content of 70% was used. However, at the time of long run molding of the EVOH film, water was precipitated at the feed portion of the barrel after about 3 hours. Discharge became unstable, and only a raw film for stretching having a non-uniform film thickness was obtained. However, continuous stretching was performed in the same manner as in Example 1.

Comparative Example 3 In Example 1, EVOH having a water content of 13% was used, and the extrusion temperatures were C ₁ : 110 ° C., C ₂ : 120 ° C., and C ₃ : 140
C, C ₄ : 150 ° C., H: 150 ° C., D: 150 ° C., except that the water content of the EVOH film was 3%, but the long run moldability of the EVOH film was good. In the stretching process, the film was broken at the time of the first stretching, and stable stretching was impossible, and a stretched film could not be obtained.

Comparative Example 4 In Example 1, EVOH having a water content of 60% was used, and the extrusion temperatures were C ₁ : 40 ° C., C ₂ : 60 ° C., C ₃ : 60 ° C., and C ₄ :
The procedure was the same except that the EVOH film was 60 ° C., H: 60 ° C., D: 60 ° C. and the water content of the EVOH film was 55%.
At the time of long run molding of the VOH film, after about 5 hours, water was precipitated at the feed portion of the barrel, the ejection became unstable, and only a raw film for stretching having a non-uniform film thickness was obtained. Was continuously stretched. Table 1 shows the evaluation results of the examples and the comparative examples.

[0037]

[Table 1] Transparency Film appearance Oxygen permeability Film strength (Haze value) Tensile strength Elongation Tear strength Ts El Tr Example 1 0.3 Good 0.4 0.4 17.9 / 19.3 61/47 0.68 / 0.62 Example 20 0.3 good 0.6 0.6 14.3 / 14.4 70/63 0.51 / 0.58 Example 3 0.4 good 0.6 18.3 / 22.1 43/27 0.65 / 0.76 Comparative Example 1 No stretched film was obtained. Bad 0.7 16.4 / 6.3 55/3 0.05 / 0.50 ３3 No stretched film was obtained. 4 1.2 Bad 2.5 12.1 / 12.6 122/130 0.65 / 0.62 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 μ / m ² · day · atm.

[0038]

According to the present invention, in producing a molded product (film) of EVOH and a stretched film from the molded product, the water content of EVOH before molding and the water content of EVOH during stretching are adjusted to specific ranges. It has excellent transparency, film appearance, film thickness stability, gas barrier properties, film strength, etc., and can also suppress the generation of gels and tars during production, and is also excellent in long-run moldability. so,
The multilayer laminate having at least one EVOH stretched film obtained by the production method of the present invention is very useful, and is very useful as a packaging material for foods, pharmaceuticals, agricultural chemicals, industrial chemicals, and the like.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08L 29:04

Claims (3)

[Claims] 1. A saponified ethylene-vinyl acetate copolymer having an ethylene content of 10 to 60 mol%, a saponification degree of 90 mol% or more, and a water content of 10 to 60% by weight.
A method for producing a stretched saponified ethylene-vinyl acetate copolymer film, comprising stretching a film obtained by melt-extruding a saponified vinyl acetate copolymer at a water content of 5 to 50% by weight. 2. A saponified ethylene-vinyl acetate copolymer having an ethylene content of 10 to 60 mol%, a saponification degree of 90 mol% or more, and a water content of 10 to 60% by weight.
A method for producing a stretched saponified ethylene-vinyl acetate copolymer, comprising stretching a film obtained by melt-extruding a saponified vinyl acetate copolymer at a water content of 21 to 50% by weight. 3. An ethylene content (Et) and a saponification degree (S
v) A saponified ethylene-vinyl acetate copolymer film having a water content (W) satisfying the following expression: 3. Production of a stretched saponified ethylene-vinyl acetate copolymer film according to claim 1 or 2. Law. 70 ≦ (0.173 × Sv−20.111) × W + 0.2184 × (Sv−100) ² + 6.5356 × (Sv−100) + 230.67 × exp (−0.0074 × Et) ≦ 130 ·· Et: ethylene content (mol%) Sv: degree of saponification (mol%) W: water content (% by weight)