JPH0641197B2 - Heat-stretched multilayer structure - Google Patents

Description

Detailed Description of the Invention A. INDUSTRIAL APPLICABILITY The present invention has a heating layer having an ethylene-vinyl alcohol copolymer (hereinafter referred to as EVOH) composition layer which is free from pinholes, cracks, local uneven thickness, and has excellent gas barrier properties. The present invention relates to a stretching, particularly a heating high-speed stretching multilayer structure.

B. 2. Description of the Related Art EVOH is today recognized as being effective in fields intended for use in packaging films for foods, etc., especially foods requiring a barrier property against oxygen and other products requiring aroma retention. There is. However, the EVOH single film lacks toughness and has a drawback that it does not exhibit an effective barrier property against water and water vapor.

In order to improve these drawbacks, it is used in the form of a multilayer structure formed by laminating a thermoplastic resin such as polypropylene or polystyrene, and various heat sealant layers represented by ionomers, ethylene-vinyl acetate copolymers and the like. ing.

By the way, the multilayer structure (film,
Sheet, parison, etc.) is secondarily processed into a container, etc., especially when stretch molding is performed below the melting point of EVOH,
Small voids, cracks, local uneven thickness, etc. frequently occur in the EVOH layer, and as a result, the oxygen barrier property of the molding container is greatly deteriorated. Moreover, the appearance was also poor, and the container could not be used as a container for food or the like.

Therefore, conventionally, various plasticizers have been added to EVOH for the purpose of preventing pinholes, cracks and the like in the EVOH layer generated during heating and stretching (JP-A-53-88067 and JP-A-59).
-20345), blends of polyamide resins (JP-A-52-141785, JP-A-58-154755, JP-A-58-36412) and the like have been investigated, but in any case, the following points are sufficient. It turned out to be unsatisfactory. That is, in a plasticizer system represented by a hydroxyl group-containing system, an aromatic sulfonamide system, etc., an addition amount of 10 to 20 parts by weight is necessary with respect to 100 parts by weight of EVOH in order to improve heat stretching characteristics. However, there are many problems such as a significant decrease in the gas barrier property and a decrease in the adhesive strength between the EVOH layer and other resin layers, which is considered to be due to the bleeding of the plasticizer, and it is difficult to use.

On the other hand, a method of imparting flexibility by blending EVOH with a polyamide resin to increase secondary processability is known, and many patents have been filed (Japanese Patent Publication No. 44-24277, Japanese Patent Publication No. 60-24813, and Japanese Patent Publication No. 60-24813). (JP-A-58-129035, JP-B-59-38897, JP-A-58-36412, etc.)
However, although polyamide improves the heating and high-speed stretch formability, E
Probably due to a large chemical reaction with VOH, many gel-like substances are present in the molded product, and coloring is remarkable, so that it cannot be used. On the other hand, EVs and polyamide resins with relatively little gel and coloring
Although a patent on a blending system with OH has been filed, the compatibility with EVOH is not sufficient, so the heat stretch moldability at low speed is apparently due to cracks, pinholes,
It looks good because there is no uneven thickness, but as a result of the measurement of gas barrier properties, the measured values show a large variation and the presence of minute pinholes that cannot be observed with the naked eye can be seen.
To make matters worse, recently, due to the speed up of the heating and stretching machine, when the heating and high speed stretch molding was performed, the variation in the measured value of the gas barrier property increased significantly, and the reliability as a gas barrier container was improved. Results in a decrease.

Therefore, the gas barrier property and the reliability (variation) as a container having a barrier property are good, and at the time of high-speed drawing by heating,
One of the important issues is the development of an EVOH that does not cause minute pinholes, cracks, uneven thickness, etc. in the EVOH layer and that has good molding characteristics.

C. Problems to be Solved by the Invention EVOH has excellent properties as described above, but when a laminate with a thermoplastic resin is secondarily processed into a container or the like, cracks, pinholes or local The gas barrier property is greatly deteriorated due to uneven thickness.

Therefore, the inventors of the present invention did not impair the excellent gas barrier properties of EVOH, and cracks, pinholes, and the like in the EVOH layer that occur when the laminate is subjected to secondary processing into a container or the like.
As a result of intensive studies to develop an EVOH composition for a multi-layer container that has a high gas barrier property while preventing the occurrence of local uneven thickness, the present invention has been completed.

D. MEANS FOR SOLVING THE PROBLEMS The present invention has ethylene content of 25 to 60 mol%, EVOH of 70 to 95% by weight with a saponification degree of 90% or more, and caproamide as main constituent units, and the ratio of the number of methylene groups to the number of amide groups is It is an aliphatic copolymer satisfying the formula 6.6 ≦ CH ₂ / NHCO ≦ 10, and further has a melting point of 110-18.
Heat-stretching having a thermoplastic resin layer on at least one surface of a layer of a composition consisting of 5 to 30% by weight of polyamide at 0 ° C. and having a melt viscosity index of 0.1 to 10 g / 10 min, especially a heat-fast stretching multilayer structure It is the body.

Various sheets having a thermoplastic resin layer are prepared through an adhesive resin on one or both sides of the EVOH layer, and by reheating and stretching operations, when the secondary processing is performed on a cup or a bottle, the appearance of the container and EVO from measurement of gas barrier property
It is possible to judge the superiority or inferiority of the moldability and gas barrier property of the H layer. Therefore, the present inventors blended various plasticizers, polymers and the like with EVOH and measured the moldability and gas barrier properties of the blend. As a result, EVOH having a melting point of 110 to 180 ° C. and a melt-based polyamide resin of 0.1 to 10 g / 10 min was dry-blended and melt-blended into pellets by an extruder, and then adhesive resin was applied to one or both sides. At first glance, a sheet having a thermoplastic resin layer was prepared and reheated and stretched, and it seemed that a good stretched product without appearance, cracks, pinholes, and uneven thickness was obtained. However, when measuring the gas barrier properties of stretched molded products, the gas barrier properties differ greatly depending on the measurement location, and worse, the molding speed, that is, the stretching speed, greatly increases due to recent advances in molding technology. However, when the sheet is subjected to high-speed stretching, the appearance is good, but the gas barrier property (average value) deteriorates and the variation due to the measurement location increases depending on the stretching speed. It was Therefore, as a result of intensive studies on EVOH-polyamide resin blends, the present inventors have been surprised to find that when blending EVOH and polyamide, the polyamide has caproamide as a main constituent unit and has a methylene group number and , The ratio of the number of amide groups is expressed by the formula 6.6 ≦ CH
An aliphatic copolymer satisfying ₂ / NHCO ≦ 10,
Further, the melting point of the polyamide is 110 to 180 ° C., and the melt viscosity index (according to ASTM-D-1238-65T,
Polyamide having a melt index value measured at 190 ° C. and a load of 2160 g of 0.1 to 10 g / 10 min is 5 to 3
In the case where the thermoplastic resin layer was laminated on the ethylene-vinyl alcohol copolymer composition layer blended with 0% by weight, the gas barrier property (average value) did not deteriorate even when the heating and high speed stretching were performed, and the measurement was performed. Not only does it provide a highly reliable gas barrier container with little variation in gas barrier properties depending on the location, but it also shows an unexpected result, which is likely to occur during long-term operation, with almost no gel or lumps. Was found, which led to the present invention. This fact is clear from the examples described later.

In Experiment No. 10 on page 6 of JP-A-54-78749, a single layer film of EVOH blended with an aliphatic copolymer having CH ₂ /NCO=7.20 has a poor stretchability and is not broken by stretching. Although it is described that this occurs, a thermoplastic resin is laminated on this blend layer, and this is heat-stretched, especially high-speed heat-stretched, and by doing so, the excellent effect as described above can be obtained. There is no disclosure about the findings.

By the way, when the EVOH-polyamide composition layer is laminated with a thermoplastic resin layer and subjected to heat-stretching, particularly high-speed heat-stretching, the cause of drastically improving the moldability and the gas barrier property is not significant. EV under high speed drawing conditions
Since the adhesion and strength / elongation property of the interface between OH and polyamide are well harmonized, it is possible to prevent minute cracks occurring at the blending interface and obtain an effective gas barrier and highly reliable barrier container. It seems to be there.

E. More Detailed Description of the Invention Hereinafter, the present invention will be described in more detail.

EVOH used in the present invention has an ethylene content of 25-
It is a saponified product of an ethylene-vinyl acetate copolymer having 60 mol%, preferably 25 to 55 mol%, and a saponification degree of a vinyl acetate component of 90% or more, preferably 95% or more. When the ethylene content is 25 mol% or less, the molding temperature becomes close to the decomposition temperature, and molding becomes difficult.

On the other hand, when the ethylene content is 60 mol% or more, the gas barrier property is lowered, and the gas barrier property of the multilayer container is insufficient, which is not preferable. In addition, EVOH having a vinyl acetate component saponification degree of less than 95%, particularly less than 90%, can be obtained with little or no cracks, pinholes, etc. at the time of container molding, but it is not preferable because of insufficient gas barrier property. . In addition, this EVOH is ASTM-D1238
The melting viscosity index measured by -65T at 190 ° C. under a load of 2160 g is 0.1 to 25 g / 10 minutes, preferably,
It is 0.3 to 20 g / 10 minutes.

The polyamide used in the present invention is mainly composed of caproamide, and the ratio of the number of methylene groups to the number of amide groups is represented by the formula 6.6 ≦ CH ₂ / NHCO ≦ 10, preferably 6.8.
≦ CH ₂ /NHCO≦9.5, more preferably 7.0 ≦
CH ₂ /NHCO≦9.5, optimally 7.3 ≦ CH ₂ /
It is an aliphatic copolymer satisfying NHCO ≦ 9.5.
As the amide component on the other side that is copolymerized with caproamide, laurinlactam (12.nylon), undecane amide (11.nylon), hexamethylene sebacamide (6,10 nylon), hexamethylene adipamide (6,6 nylon) , Ω-aminoheptanoic acid (7 · nylon), ω-aminononanoic acid (9 · nylon), and the like. Especially, laurinlactam (12 · nylon), hexamethyleneadipamide (6,6 nylon),
ω-aminononanoic acid (9 · nylon) is effective. The amide component on the other side may be used alone or in combination of two or more.

By the way, the ratio of the number of methylene groups to the number of amide groups is CH ₂ / N
When HCO <6.6, not only does the appearance of gel and lumps tend to occur during the formation of a multilayer sheet, but the appearance is poor,
The EVOH blend layer is cut at the gel and the spots, and the gas barrier property is greatly deteriorated. On the other hand, CH ₂ / NHC
In the case of O> 10, almost no gel and lumps were generated,
Also, the high-speed stretch-molded container is good in appearance. However, locally poor transparency can be seen, the gas barrier property is not good, and the dispersion becomes large. Perhaps it is because there are many small pinholes.

By the way, even for polyamides satisfying 6.6 ≦ CH ₂ / NHCO ≦ 10, the melting point was {DSC (skining speed 10 ° C./min. Main endothermic peak temperature of 110 to 180 ° C., preferably 120 to 170 ° C., and a melt viscosity index of 0.1.
When the amount is from 10 g / 10 min, and preferably from 0.5 to 9 g / 10 min, a good multi-layered container having a good appearance during heating and high-speed drawing and having little variation in gas barrier properties and gas barrier properties can be obtained. can get.

The amount of polyamide added to EVOH is 5
-30% by weight, preferably 7-25% by weight. If the addition amount is less than 5% by weight, the effect of improving the moldability is not sufficient and cracking and unevenness are likely to occur. On the other hand, if it exceeds 30% by weight, the gas barrier property is significantly deteriorated, and it cannot be used as a gas barrier container.

The blending method of EVOH and polyamide is not particularly limited, but there is a method of dry blending EVOH and polyamide, pelletizing with a Banbury mixer, a single-screw or twin-screw extruder, and drying. . If the blend is non-uniform, or if gels or lumps are mixed during the blending operation, the EVOH blend layer may be broken or uneven during heat stretch molding. It is desirable to use an extruder with a high degree of kneading, N ₂ seal the hopper mouth, and press at a low temperature. Also, the blended pellets are molded into a 50μ sheet by hot pressing at 220 ° C,
When the nylon particle size is measured, it is desirable that the particle size of 0.1 μ or less is 50% or more, and preferably 0.05 μ or less is 50% or more.

On the other hand, when these are mixed, it is free to use other additives (various resins, antioxidants, plasticizers, colorants, etc.) within the range where the effects of the present invention are not impaired. In particular, as a measure against the thermal stability of the resin and the prevention of gel formation, it is preferable to add a hydrotalcite-based compound, a hindered phenol-based or a hindered amino-based thermal stabilizer in an amount of 0.01 to 1% by weight.

The thermoplastic resin used in the present invention may be any resin that can be stretch-molded at the following temperature, such as polypropylene resin, polystyrene resin, polyamide resin, polyvinyl chloride resin, saturated polyester resin (polyether resin). Ethylene terephthalate resin etc.) is suitable. Among these, polypropylene resin and polystyrene resin are most suitable.

When the melting point of EVOH is X ° C. and the heating and stretching temperature of the thermoplastic resin is Y ° C. X-10 ° C. ≧ Y ≧ X-110 ° C. When Y is higher than (X-10) ° C., EVOH during molding
Since it softens and melts, molding is usually possible without adding additives. On the other hand, when Y is (X-110) ° C. or lower, the glass transition temperature (Tg) of the thermoplastic resin is room temperature or lower, so that the shape stability of the molded product at room temperature is poor, and the dimensional change is large, so Can not stand.

As a method for obtaining a multilayer structure, the EVOH composition and a thermoplastic resin are extruded through an adhesive resin, an extrusion laminating method, a dry laminating method, a coextrusion laminating method, a coextrusion sheet forming method (feed block or multi-manifold). Method, etc.), coextrusion pipe making method, co-injection method, various solution coating methods, etc. to obtain a laminate, which is then subjected to a vacuum pressure air drawing machine, a biaxial stretching blow machine, etc. within a range not higher than the melting point of EVOH. A method of reheating and performing a stretching operation, or subjecting the laminate (sheet or film) to a biaxial stretching machine,
Examples thereof include a method of heating and stretching, and a method of co-injection biaxial stretching of an EVOH composition and a thermoplastic resin.

Further, the thickness constitution of the multilayer structure is not particularly limited, but in consideration of moldability and cost, the thickness ratio of the EVOH layer to the total thickness is preferably about 2 to 20%. In addition, as the constitution of the multilayer structure, thermoplastic resin layer / EVOH composition layer / thermoplastic resin layer, E
Typical examples include VOH composition layer / adhesive resin layer / thermoplastic resin layer, thermoplastic resin layer / adhesive resin layer / EVOH composition layer / adhesive resin layer / thermoplastic resin layer. Further, the collected material of the multilayer structure of the present invention can be mixed in each of these layers, or collected waste can be separately provided. When a thermoplastic resin layer is provided on both outer layers, the resins may be different or the same. Here, the adhesive resin is not particularly limited as long as it can be stretch-molded below the melting point of EVOH and can bond the EVOH composition layer and the thermoplastic resin layer, but is preferably ethylenic Polyolefin (eg, polyethylene, polypropylene), ethylene-vinyl acetate copolymer, ethylene-acrylic acid ester (eg, methyl ester) to which unsaturated carboxylic acid or its anhydride (eg, maleic anhydride) is added or grafted.
Ethyl ester) copolymer and the like.

In the present invention, the heat-stretched multilayer structure is, as described above, a container obtained by heat-stretching, a container such as a bottle or a sheet or a film-like material, and heating is required for heat-stretching the multilayer structure. Any method may be used in which the multilayer structure is allowed to stand at a certain temperature for a predetermined time so that the multilayer structure is thermally uniform, and in consideration of operability, a method of heating and homogenizing with various heaters is preferable. .

The heating operation may be performed at the same time as the stretching, or may be performed before the stretching. Stretching means an operation of uniformly forming a multilayer structure that has been heated thermally uniformly into a container, cup, sheet or film by chuck, plug, vacuum pressure, blow, etc., uniaxial stretching, biaxial stretching. Either (simultaneously or sequentially) can be used. The stretching ratio and the stretching speed can be appropriately selected according to the purpose. In the present invention, the high-speed stretching means that the stretching speed is {stretch area ratio (%)} 5 ×
It means a method of uniformly forming into a container or a film at a high speed of 10 ⁵ % / min or more. The molded product thus obtained does not necessarily have to be oriented.

In the present invention, the water content of the EVOH composition layer, which is a constituent of the multilayer structure, is not particularly limited during heating and stretching, but it is 0.01 to 10%.
And more preferably 0.01 to 5%.

The thus-obtained heat-stretched multilayer structure of the present invention does not show pinholes, cracks, or uneven thickness in the EVOH composition layer, and therefore has an extremely good gas barrier property and little variation in gas barrier property. It is effective for very good food packaging containers or containers requiring aroma retention.

The present invention will be further described below with reference to examples, but the present invention is not limited thereto.

F. Examples Example 1 EVOH (EVAL-EP-F101 manufactured by Kuraray Co., Ltd.) containing 49 wt% of an ethylene content of 31 mol%, a saponification degree of 99.4%, and a melt index (MI) of 1.3 / 10 min. 12.6 nylon {melting point (m
p) 155 ° C., MI = 4.0, CH ₂ / NHCO = 7.
4} was blended in an amount of 15% and extruded into pellets at 200 ° C. under N ₂ with a twin screw type, vent type 40φ extruder. The obtained pellet was dried at 80 ° C. for 8 hours. The pellets were applied to a feedblock type 3 type 5 layer coextrusion device to prepare a sheet. The structure of the seat is polypropylene on both outermost layers (Noblene MA- made by Mitsubishi Kasei)
6) has a thickness of 800μ, an adhesive resin layer (Model P-300F maleic anhydride modified polypropylene manufactured by Mitsubishi Petrochemical Co., Ltd.) has a thickness of 50μ, and the innermost layer (center) has the EVOH composition layer of 50μ. The obtained sheet was subjected to a vacuum pressure molding machine (stretching rate: 9 × 10 ⁵ % / min) and thermoformed (SPPF molding) at 155 ° C. The obtained molded product had a good transparency and had no crack or uneven thickness. The gas barrier property of this container at 20 ° C. and 65% RH was measured (Mocon Corporation 10/50 type), 0.5 cc, 20 μ
/ M ² · 24hr · atm, which shows a very good gas barrier property, and the variation of the measured value when 20 samples are measured {R (cc · 20μ / m ² · 24hr · atm) =
Maximum value-minimum value} is 0.1cc · 20μ / m ² · 24hr ·
It was a very small atm and was a good gas barrier container.

Example 2 In Example 1, both outermost layers were made of polypropylene to polystyrene (Styrol ET-61 manufactured by Idemitsu Petrochemical Co., Ltd.).
And the same procedure as in Example 1 except that the adhesive resin layer was changed from Model P-300F to Mersen M-5420 (maleic anhydride-modified ethylene-vinyl acetate polymer manufactured by Toyo Soda Co., Ltd.) at 130 ° C. Vacuum pressure molding (stretching speed 9 × 10 ⁵ % / min) was performed. The obtained molded product had a good appearance and had no crack or uneven thickness. The gas barrier property of this container is 0.6cc ・ 20μ / m ²・ 24hr ・ a
tm (20 ° C.-65% RH), and the variation (R) of the barrier property of 10 samples is 0.2 cc · 20 μ / m ²
-It was a small barrier container of 24 hr-atm and was a good barrier container.

Comparative Example 1 In Example 2, the polyamide blend ratio of 15 wt% was 4
It changed to wt% and it carried out similarly to Example 2. As a result, there are many cracks and uneven thickness, and the gas barrier property is 5
It was cc · 20μ / m ² · 24hr · atm and it was unbearable for use.

Comparative Example 2 Polyamide in Example 2 was used with a caproamide content of 5w.
6/12 nylon containing t% (mp 180 ° C, MI
= 4CH ₂ /NHCO=10.5), and Example 2
Same as above. The obtained container was very good in appearance, and had almost no gel, spots, cracks, or unevenness. However, when the gas barrier property was measured with 20 samples, the average was 1.2 cc, 20 μ / m ² , 24 hr, at
In addition to showing a high value of m, the variation (R) is 5.3.
cc · 20μ / m ² · 24hr · atrm, very large,
As a result, the reliability as a barrier container could not be ensured.

Comparative Example 3 When the molding speed of the vacuum / pneumatic molding machine was greatly reduced in Comparative Example 2 and the stretching speed was 10 ⁵ % / min, the appearance (mold, crack, uneven thickness) of the molded product was 2 tends to be slightly improved, and the gas barrier property (average value) of the container is 0.7cc ・ 20μ / m ²・ 24hr ・
Atm was slightly improved, and the dispersion of the measured values was 0.
It tended to decrease to 9cc, 20μ / m ² , 24hr, atm. From this, it is understood that the moldability and the gas barrier property (variation) largely depend on the molding speed (drawing speed). That is, it is clear from this comparative example how recently the stability and reliability of the quality of the molded product due to the increase of the molding speed are important, and are greatly desired.

Comparative Example 4 In Example 2, the polyamide was mixed with a caproamide content of 61.
6 · polyether nylon elastomer containing wt% (polyoxytetramethylene copolymer mp 190 ° C.,
MI = 2, CH ₂ /NHCO=8.3), and the same as in Example 2 below. As a result, uneven thickness and cracks were found in the obtained deep-drawn molded product. Moreover, when the gas barrier property was measured with 20 samples, the average value was 1.0 cc · 20 μ / m ² · 24 hr · atm, which was a reasonable value, but the variation (R) was 4.5 cc · 20 μm. / M ² ·
It is as large as 24 hr · atm, and there is a problem in reliability as a barrier container, and it cannot be used.

Example 3 EVOH was used in Example 2 with an ethylene content of 44 mol%, a saponification degree of 99.5%, and a melt index (190).
℃) 5.4g / 10 (Kuraray made EVAL EP-E10
5), and the same as in Example 2. The obtained molded product had a good appearance and had no crack or uneven thickness.
The gas barrier property of this container is 1.7cc ・ 20μ /
m ² · 24 hr · atm (20 ° C-65% RH),
And variation of gas barrier property in 20 samples (R)
Is as small as 0.2cc, 20μ / m ² , 24hr, atm,
It was a good barrier container.

Example 4 In Example 1, 12-6 nylon containing 25 wt% of caproamide units as nylon blended in EVOH (melting point 178 ° C., MI = 4.0, CH ₂ / NHCO =
8.8), and the same operation as in Example 1 was performed. The resulting molded article has a good appearance, cracks,
There was no uneven thickness. Measurement of the gas barrier properties at 20 ℃ · 65% PH of the ^{container, 0.7cc · 20μ / m 2 ·} 24
It was very good with hr.atm. In addition, the variation of the measured value when measuring 20 samples {R (cc ・ 20μ / m ²・
24hr ・ atm) = maximum-minimum value} is 0.2cc ・ 20
It was a very small gas barrier container with a very small μ / m ² · 24 hr · atm.

Example 5 In Example 2, 6-9 nylon containing 35 wt% of caproamide units as nylon to be blended with EVOH (melting point 165 ° C., MI = 6.0, CH ₂ / NHCO = 6.
It changed to 7) and it implemented like Example 1 below. As a result, the appearance of the obtained molded product was good. The gas barrier property of this container is 0.5cc ・ 20μ / m ²・ 24hr ・ a
tm (20 ° C, 65% PH), and the variation (R) of the gas barrier property among the 20 samples is 0.1cc / 20μ.
/ M ² · 24 hr · atm, which was a small and good gas barrier container.

Comparative Example 5 In Example 2, 6.9 nylon (melting point 195 ° C., MI = 6.0, CH ₂ /NHCO=5.5) containing 80 wt% of caproamide units was blended with EVOH.
The same procedure as in Example 2 was performed. as a result,
A large number of lumps were observed on the original sheet during film formation.
When this sheet was matured, large cracks were found around the seeds. Not only is this container unfavorable in appearance, but the gas barrier property of the container is 1.2cc ・ 20μ /
m ² · 24 hr · atm is high, and the variation (R) of gas barrier property among 20 samples is 1.8 cc · 20 μ / m ²
・ 24 hr.atm, which is too large to be used.

Example 6 The EVOH and nylon blend pellets used in Example 1 were mixed with polyester ([η] = 0.7 Odl / g) / EV using a Nissei ASB co-injection co-stretch blow molding machine.
OH blend / polyester ([η] = 0.70dl
/ G) Two-kind three-layer or two-kind five-layer containers were molded. As a result, no abnormalities such as vertical thickness unevenness of bottle, uneven thickness, crack, gel, etc. were observed, and gas barrier property was good (0.5 cc · 20 μ / m ² · 24 hr · atm; R =
A container of 0.1 cc · 20 μ / m ² · 24 hr · atm) was obtained.

Comparative Example 6 EVOH in Example 6 before nylon blending
Only in the same manner as in Example 6. As a result, the bottle had many vertical stripe-like thickness unevenness and uneven thickness, and could not be used.

G. EFFECTS OF THE INVENTION The heat-stretched multilayer structure of the present invention has no deterioration in gas barrier properties, has little variation in gas barrier properties depending on measurement points, and has almost no gel or lumps that easily occur during long-term operation.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoshi Kawai 1621 Sakata, Kurashiki City, Okayama Prefecture Kuraray Co., Ltd. (56) References JP-A-53-8807 (JP, A) JP-A-52-141785 ( JP, A) JP 58-129035 (JP, A)

Claims (11)

[Claims] 1. An ethylene-vinyl alcohol copolymer 7 having an ethylene content of 25 to 60 mol% and a saponification degree of 90% or more.
0 to 95% by weight, and having cabroamide as a main constituent unit, and the ratio of the number of methylene groups to the number of amide groups is represented by the formula 6.6 ≦
CH ₂ / NHCO ≦ 10 is satisfied, and the melting point is 110.
C. to 180.degree. C., and melt viscosity index is 0.1 to 10 g /
A heat-stretched multilayer structure having a thermoplastic resin layer on at least one surface of an ethylene-vinyl alcohol copolymer composition layer composed of 5 to 30% by weight of aliphatic copolymerized polyamide for 10 minutes. 2. The thermoplastic resin is selected from polystyrene resin, polypropylene resin, polyvinyl chloride resin, and polyamide resin, and can be stretched within a heat stretching temperature range represented by the following formula. The heat-stretched multilayer structure according to claim 1. X−10 ° C. ≧ Y ≧ X−110 ° C. However, X represents the melting point ° C. of the ethylene vinyl alcohol copolymer, and Y represents the heating stretching temperature ° C. 3. The heat-stretched multilayer structure according to claim 1, wherein the thermoplastic resin is a polystyrene resin. 4. The heat-stretched multilayer structure according to claim 1, wherein the thermoplastic resin is a polypropylene resin. 5. The ratio of the number of methylene groups to the number of amide groups is 6.8 ≦
The heat-stretched multilayer structure according to claim 1, which satisfies CH ₂ /NHCO≦9.5. 6. The ratio of the number of methylene groups to the number of amide groups is 7.0 ≦.
The heat-stretched multilayer structure according to claim 1, which satisfies CH ₂ /NHCO≦9.5. 7. The melting point of the aliphatic copolyamide is 120-.
The heat-stretched multilayer structure according to claim 1, which has a temperature of 170 ° C. 8. The heat-stretched multilayer structure according to claim 1, wherein the melt viscosity index of the aliphatic copolyamide is 0.5 to 9 g / 10 minutes. 9. The heat-stretched multi-layer structure according to claim 1, wherein the heat-stretched multi-layer structure is obtained by vacuum-compressing and deep-drawing the coextrusion laminate. 10. The heat-stretched multilayer structure has a stretching speed of 5 × 1.
0 ^{5% /} min are those obtained by stretching the above patents heating oriented multilayer structure ranging first claim of claim. 11. The heat-stretching according to claim 1, wherein a layer comprising a composition of an aliphatic copolymer polyamide and an ethylene-vinyl alcohol copolymer is an intermediate layer, and thermoplastic resin layers are provided on both layers. Multi-layer structure.