JP3161878B2 - Multi-layer structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer structure including an ethylene-vinyl alcohol copolymer (hereinafter abbreviated as "EVOH") layer. More specifically, the present invention relates to a multilayer structure of an EVOH and a thermoplastic resin, which does not generate pinholes, cracks, local thickness deviation, and the like at the time of heat-stretch molding, and is excellent in transparency and gas barrier properties.

[0002]

2. Description of the Related Art Today, EVOH is used for packaging films for foods and the like, particularly for foods requiring a barrier property against oxygen, odors, flavors, and the like, and other products requiring aroma retention. Has been confirmed to be effective. EVOH is obtained by laminating a thermoplastic resin layer such as polyethylene, polypropylene, polystyrene, polyester, polyamide, and polyvinyl chloride, and various adhesive resin layers represented by ionomer, ethylene-vinyl acetate copolymer, and the like. Used in the form of a multilayer structure. By the way, when a multilayer structure (film, sheet, parison, etc.) manufactured by various methods is subjected to secondary processing into a container or the like, particularly when stretch molding is performed at a melting point of EVOH or less,
Small voids, cracks, local uneven thickness, etc. occur frequently in the EVOH layer, and as a result, the appearance, transparency, and oxygen barrier properties of the molded container are greatly deteriorated.

[0003] Conventionally, EVO generated at the time of heating and stretching is conventionally used.
To prevent pinholes and cracks in the H layer,
Addition of various plasticizers to the VOH layer (JP-A-53-8806)
7, JP-A-59-20345) and blends of polyamide resins (JP-A-52-141785, JP-A-58-36).
412) has been studied, but it has been found that in any case, the following points are not satisfactory. That is, in the addition system of various plasticizers, it is necessary to add 10 to 20 parts by weight of the plasticizer with respect to 100 parts by weight of the EVOH in order to sufficiently improve the heat-stretching property. There are many problems such as lowering and lowering of the interlayer adhesion strength with the EVOH layer, and it is not usable. On the other hand, in the addition system of the polyamide resin, the presence of a large number of gel-like substances in the molded product may be due to the high chemical reactivity with EVOH,
It does not stand use because of remarkable coloring. In addition, in the addition system of polyamide resin with relatively little gel coloring,
Although apparently good containers can be obtained due to insufficient compatibility between the EVOH and the polyamide, in particular, because of the presence of minute pinholes at the time of high-speed stretch molding under heating, there are variations in measured values of gas barrier properties. It was large and unreliable as a gas-barrier container and could not be used. Further, a composition obtained by blending a polyamide with two types of EVOH having different ethylene contents described in JP-B-63-56893 in a weight ratio of EVOH / polyamide of 5/95 to 95/5 has improved thermoformability and the like. However, during long-term operation, gels etc. are likely to occur and appearance defects are likely to occur, because gels etc. cause pinholes during high-speed hot stretching molding, or there are large variations in measured values of gas barrier properties, To make matters worse, abnormalities such as coloring and gel generation tended to occur frequently when scraps and the like were collected and reused. therefore,
Transparency, high gas barrier properties, and reliability as a gas barrier container (development of EVOH with good variation is one of the important issues.

[0004]

DISCLOSURE OF THE INVENTION The present invention provides an EVOH without deteriorating the excellent gas barrier properties of EVOH.
H E generated when secondary processing of a multilayer structure into a container or the like
An object of the present invention is to provide an EVOH resin-containing heat-stretched multilayer structure having transparency, high gas barrier properties, and highly reliable gas barrier properties by preventing the occurrence of cracks, pinholes, local thickness deviation, and the like in a VOH layer. It is.

[0005]

The object of the present invention is to provide an EVOH layer having an ethylene content of 20 to 60 mol% and a saponification degree of 80% or more satisfying the following formulas (1) to (3); The problem is solved by providing a multilayer structure having a thermoplastic resin layer on one side. Tc (A) ≦ 130 ° C. (1) Hc (A) ≦ 20 mJ / mg (2) 1 ≦ 100 × Hc (A) / Hc (T) ≦ 30 (3) Tc (A) indicates the crystallization peak temperature of EVOH when the temperature was decreased at a rate of 10 ° C./min by a differential calorimeter (DSC),
Indicates the lowest temperature among two or more peak temperatures. Hc (A) is the heat of crystallization of EVOH at Tc (A) (mJ / mg), and Hc (T) is the total heat of crystallization of EVOH having two or more peak temperatures (mJ / mg). )
Is shown. In addition, mJ is millijoule and mg is milligram.

[0006] The present inventors conducted biaxial stretching and thermoformability evaluation using a multilayer sheet obtained by laminating a thermoplastic resin, for example, polystyrene (PS) and various EVOHs, and evaluated the stretchability and the resin properties of the EVOH. As a result of evaluating the relationship between the stretching conditions, particularly the stretching temperature, the heating operation method and the stretchability, the process of raising the temperature to the target stretching temperature during the stretching operation, that is, the operation of heating and raising the raw material before stretching. First, after the temperature is raised to a temperature higher by 10 to 30 ° C. than the stretching temperature, heat is radiated to the stretching temperature and stretching is performed.
Was found to be improved. Therefore, as a result of further study, the stretching temperature is set to the EVOH crystallization start temperature Tc (A).
When it was lower, the stretchability was greatly improved. In particular, it was found that the smaller the crystallization heat value Hc (A), the more effective. However, it has been found that the gas barrier properties of these EVOHs are poor and cannot be used in the field where high barrier properties are required. Therefore, as a result of various studies,
By adopting special polymerization conditions as shown below,
As a result of satisfying the above expressions (1) to (3), an EVOH having good stretchability while maintaining high gas barrier properties was found, and the present invention was completed.

In the present invention, EVOH is a saponified product of an ethylene-vinyl ester copolymer and has an ethylene content of 20 to 60 mol%, preferably 25 to 50 mol%.
Further, vinyl acetate having a saponification degree of 80% or more, preferably 85% or more, and more preferably 90% or more using vinyl acetate as a vinyl ester can be used. Ethylene content 2
If it is less than 0 mol%, the melt moldability is poor, while 60 mol%
Above, the gas barrier properties are insufficient. If the degree of saponification is less than 80%, the gas barrier properties and the thermal stability deteriorate.

The EVOH may be used in the form of another comonomer such as propylene, butylene, unsaturated carboxylic acid or its ester (meth), as long as the object of the present invention is not impaired.
Acrylic acid, (meth) acrylic acid ester (methyl, ethyl) and the like, ピ ロ, vinylpyrrolidone (N-methyl-vinylpyrrolidone and the like), and vinylsilane-based compound (vinylmethoxysilane and the like) can also be copolymerized.

The melt viscosity index (MI) of EVOH
(Measured at 190 ° C. under a load of 2160 g: 2160 g if the melting point is around 190 ° C. or exceeds 190 ° C.)
g at a plurality of temperatures equal to or higher than the melting point under a load, and plotting the reciprocal of the absolute temperature on the horizontal axis and the melt index on the vertical axis in a semilogarithmic graph, and extrapolating to 190 ° C.) 50 g / 10 min. Preferably, 0.2 to
25 g / 10 min. It is. The melt viscosity index of the composition is 0.1 g / 10 min. Less than or 50g / 10
min. In the case described above, a molded article having good appearance may not be obtained, possibly due to uneven thickness of the EVOH composition layer during the production of the multilayer structure.

Further, additives (plasticizers, heat stabilizers, ultraviolet absorbers, antioxidants, coloring agents, fillers, other resins, etc.) can be used as long as the object of the present invention is not impaired. In particular, as a measure for preventing gel formation, a hydrotalcite-based compound, a hindered phenol-based, a hindered amine-based heat stabilizer, a metal salt of a higher aliphatic carboxylic acid (for example, calcium stearate, etc.) may be used in an amount of 0.1 or 2%. It is preferable to add from 01 to 1% by weight.

An EVOH satisfying the above formulas (1) to (3)
When ethylene and vinyl ester are copolymerized in the presence of a polymerization catalyst, at least one of polymerization temperature, polymerization pressure, or solvent concentration when a solvent is used, is used. Is changed stepwise or rapidly during the polymerization process to produce an ethylene-vinyl ester copolymer, and then saponifies the vinyl ester portion with an acid or base catalyst to produce EVOH. in this case,
In the polymerization step, (i) raising or lowering the polymerization temperature by 20 to 50 ° C. at about 3/4 of the time for completing the polymerization reaction. (Ii) Raise or lower the polymerization pressure by about 10 to 30 kg / cm ² at about ３ of the polymerization reaction completion time. (iii) Increase or decrease the solvent concentration by 10 to 30% during the polymerization step. And the like, and a method of combining these methods can also be adopted. Further, there is a method of arranging two or more polymerization tanks in series, and operating the polymerization under different polymerization conditions in each polymerization tank. To manufacture EVOH satisfying the above formulas (1) to (3), this method is used. Is more preferable.

An EV satisfying the above equations (1) to (3)
In the production of OH, the conditions of the saponification step of the ethylene-vinyl ester copolymer also have an effect, reducing the amount of acid or alkali catalyst added, increasing the water content, and reducing the distillation rate of by-product methyl acetate. The saponification degree can be achieved by adjusting the degree of saponification such as lowering the degree of saponification to such an extent that the gas barrier property of the obtained EVOH does not deteriorate.
It is important to keep it within 5 mol%, preferably 85 to 99.2 mol%, more preferably 90 to 99.0 mol%. When the degree of saponification is less than 80 mol%, the gas barrier property is not sufficient.
The stretchability of the VOH film becomes insufficient.

When the crystallization peak of the EVOH produced by the above-described production method is measured by a differential calorimeter (DSC), the crystallization peak has two or more crystallization peaks, and the lowest peak temperature Tc (A) and heat of crystallization Hc
(A) greatly affects the stretchability of EVOH, and Tc (A)
= 130 ° C or less, preferably 125 ° C or less, more preferably 120 ° C or less. If Tc (A) exceeds 130 ° C., the effect of improving the stretchability of EVOH is not sufficient. Also,
Regarding Hc (A), it is 20 mJ / mg or less, preferably 1 mJ / mg or less.
5 mJ / mg or less, more preferably 10 mJ / mg or less. When Hc (A) is 20 mJ / mg or more, EV
The stretchability and / or gas barrier properties of the OH film (layer) are not sufficient and are not preferred. On the other hand, of two or more peaks derived from EVOH, a crystallization heat value Hc (A) (mJ) corresponding to the lowest temperature peak temperature Tc (A).
/ Mg) is the total crystallization calorific value Hc derived from EVOH.
(T) It is preferably from 1 to 30% of (mJ / mg), preferably from 2 to 17%, more preferably from 3 to 15%. If it is 1% or less, the stretchability and / or gas barrier properties of the EVOH film (layer) are not sufficient, and 30% or less.
Above this, the gas barrier properties are poor and cannot be used.

Next, the EVOH of the present invention is made to have a multilayer structure,
In particular, a case where the composition is used for a heat-stretched multilayer structure will be described. The thermoplastic resin to be laminated on at least one side of the EVOH layer of the present invention may be a resin that can be stretch-molded at the following temperature, and may be a polyethylene resin, a polypropylene resin, a polystyrene resin, a polyamide resin,
Suitable examples include a polyvinyl chloride resin and a thermoplastic polyester resin. In addition, the adhesive resin used for multilayering the EVOH and the thermoplastic resin is not particularly limited as long as the adhesive resin firmly bonds the EVOH layer and the thermoplastic resin layer. However, unsaturated carboxylic acids or their anhydrides, such as maleic anhydride, can be converted to olefinic polymers or copolymers, such as low density polyethylene (LDPE), linear low density polyethylene (LLDPE), very low density polyethylene (SLDP).
Those grafted to polyethylene such as E), an ethylene-vinyl acetate copolymer, or an ethylene- (meth) acrylate copolymer (methyl ester or ethyl ester) are preferably used.

The EVOH of the present invention can be obtained by a known melt molding method,
Films, sheets, bottles, etc. can be molded into any molded product by the compression molding method.
When the molded article is used as one layer of a multilayer structure, remarkable characteristics are exhibited, and this point will be described below. First, as a method of obtaining a multilayer structure, the EVO
H and thermoplastic resin are often laminated via an adhesive resin by extrusion lamination, dry lamination, coextrusion lamination, coextrusion sheet molding, coextrusion pipe molding, coinjection molding, solution coating, etc. And then subjecting the laminate (film or sheet) to a method of performing a stretching operation by reheating the laminate to a temperature not higher than the melting point of EVOH by vacuum pressure deep drawing, biaxial stretching blow molding, or the like. A method of subjecting the resin to a biaxial stretching machine and performing heat stretching, and a method of co-injection biaxial stretching blow molding of EVOH and a thermoplastic resin, and the like can be given. Furthermore, the thickness configuration of the multilayer structure is not particularly limited, either.
Considering moldability and cost, E
The thickness ratio of the VOH layer is preferably about 2 to 20%. The structure of the multilayer structure is as follows: EVOH layer / adhesive resin layer / thermoplastic resin layer, thermoplastic resin layer / adhesive resin layer / EVOH layer, thermoplastic resin layer / adhesive resin layer / EVO
H layer / adhesive resin layer / thermoplastic resin layer, thermoplastic resin layer / adhesive resin layer / EVOH layer / adhesive resin layer / thermoplastic resin layer / adhesive resin layer / EVOH layer are typical examples. Can be When a thermoplastic resin layer is provided on both outer layers, the resins may be different or may be the same. In many cases, scrap such as trim generated during molding is blended into the thermoplastic resin layer, or a separate recovery layer is provided for reuse.

In producing a molded product by heating and stretching the multilayer structure, the temperature condition is (X−10) ° C. ≧ Y ≧ (X−110) ° C. (where X is the melting point of EVOH, Y indicates the heating temperature ° C.). When Y is higher than (X−10) ° C., the EVOH softens and melts during the heat-stretch molding, so that molding can be performed without adding an additive. On the other hand, when Y is lower than (X−110) ° C., the glass transition temperature of the thermoplastic resin is lower than room temperature, and the shape and dimensional stability of the molded product are poor, and the molded product cannot be used. In the present invention, as described above, the heat-stretched multilayer structure is obtained by heating and stretching the multilayer structure, and is a container or a sheet such as a cup or a bottle, or a film-like material. The body may be left at a temperature required for heating and stretching for a predetermined time, and may be operated so that the multilayer structure is thermally substantially uniform.In consideration of operability, heating is performed with various heaters. A method of homogenization is preferred. The heating operation may be performed simultaneously with the stretching, or may be performed before the stretching. In addition, the stretching operation means an operation of uniformly forming a multilayer structure, which is thermally uniformly heated, into a container, a cup, a bottle, and a film by using a chuck, a plug, a vacuum force, a pneumatic force, or the like. Either stretching or biaxial stretching (simultaneous or successive) can be employed. 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 5 × 10% / mi.
n. This means a method of stretching uniformly at a high speed as described above, and the molded article does not necessarily have to be oriented.

In the present invention, the water content of EVOH is not particularly limited, but may be 0.001 to 0.001.
It is preferred that the content be within 10% by weight. In general,
In the step of forming a composition of EVOH and thermoplastic polyester, or in the step of molding the composition into a multilayer structure, the water content of EVOH is desirably as low as possible, from 0.001 to 1% by weight. On the other hand, in the thermoforming of the multilayer structure, the water content of the EVOH layer is preferably 0.01 to 10% by weight, and it is preferable that the water content is high as long as the EVOH layer does not foam.

[0018]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention. Example 1 Preparation of Ethylene-Vinyl Alcohol Copolymer 90 parts by weight of vinyl acetate and 10 parts by weight of methanol were placed in an autoclave, heated to 60 ° C., and ethylene gas was blown thereinto to increase the pressure to 40 kg / cm ² . Thereafter, methanol of the polymerization catalyst azobisisobutyronitrile (AZN) was continuously injected, and when the polymerization rate reached 40%, the pressure was increased to 65 kg / cm ² with ethylene gas, and further increased to 50%. After the polymerization was carried out until the temperature became lower, the temperature of the polymerization system was returned to room temperature, and a polymerization inhibitor and copper acetate were added. After removing the polymerization solution from the autoclave under normal pressure, unreacted ethylene and vinyl acetate were removed. Then 80
℃, methanol vapor was blown in, and saponification catalyst N
Saponification was performed by removing methyl acetate while adding an aOH methanol solution. At this time, the obtained ethylene-vinyl alcohol copolymer (EVOH) has the formula (1) to (3)
It is important to control the amount of the catalyst to be added and the amount of methanol vapor blown in to satisfy the above. In the case of this test, the concentration of the methanol solution of the saponified polymer was 20% by weight, and Methanol vapor was blown into the solution at a rate of 10 ml / min, and sodium hydroxide was added at a molar ratio of 0.04 to vinyl acetate contained in the polymer.
The following EVOH was obtained when it was added so as to be 3. Ethylene content 35 mol% Saponification degree 99.1% Melt index (MI. 190 ° C, 2160 load) 2.3 g / 10 min. Tc (A) = 120 ° C. Hc (A) = 5 mJ / mg 100 × Hc (A) / Hc (T) = 8% Production of Multilayered Structure Polystyrene was obtained by a three-layer five-layer coextrusion apparatus using the above EVOH. A multilayer sheet composed of a resin layer / adhesive resin layer / EVOH layer / adhesive resin layer / polystyrene resin layer was prepared. The configuration of the sheet is such that the outermost polystyrene resin layers (Stylon 691 manufactured by Asahi Kasei Corporation) are each 425 μm,
In addition, an adhesive resin layer (manufactured by Tosoh Corporation, Mersen-542)
0, maleic acid-modified ethylene-vinyl acetate copolymer) and each EVOH layer has a thickness of 50 μm. Manufacture of Container This multilayer sheet was molded at 130 ° C. by a vacuum pressure air thermoforming machine to manufacture a container. The appearance of the obtained container was free from cracks, unevenness and uneven thickness, and the transparency was good. This container was conditioned under the conditions of 20 ° C. and 65% RH, and the gas barrier property was measured (using a 10/50 type made by Mocon Corp.). As shown in Table 1, 0.8 cc · 20 μm was obtained. / M ²
• day • atm. And very good gas barrier properties. The containers were randomly taken out as 10 samples, and the oxygen permeability of each sample was measured. The variation of the measured value (R = maximum value−minimum value) was 0.3 cc · 20 μm.
/ M ² · 24 hr · atm. And very small and good gas barrier containers. (See the column of gas barrier properties in “Characteristics of thermoformed container (after 3 hours)” in Table 1 (R = max−min)).

Example 2 In Example 1, the initial pressure of ethylene gas was 35 kg.
/ Cm ² , and when the polymerization rate reaches 40%, the ethylene pressure is increased to 50 kg / cm ² . The same operation as in Example 1 was performed except that 20 parts by weight of methanol was further added. As a result, the following EVOH was obtained. Ethylene content 32 mol% Saponification degree 99.0% Tc (A) = 121 ° C Hc (A) = 6 mJ / mg 100 × Hc (A) / Hc (T) = 8% This ethylene-vinyl alcohol copolymer was A multilayer structure having the same structure as in Example 1 was produced except that it was used. Using this multilayer structure, a thermoformed container was manufactured in the same manner as in Example 1, and its appearance and gas barrier properties were measured. Table 1 shows the results.

Example 3 A polystyrene resin layer (manufactured by Philips, K-resin, KR-5) was used instead of the polystyrene resin layer (Stylon 691 manufactured by Asahi Kasei Corporation) used in the multilayer structure of Example 1.
Example 1 was repeated except that the above was used to produce a thermoformed container. The appearance and gas barrier properties of the container were measured, and the results are shown in Table 1.

Example 4 Instead of the polystyrene resin layer used in the multilayer structure of Example 1, a polypropylene resin layer (Noblen EX-6, manufactured by Mitsubishi Yuka Co., Ltd., transparent 425 μm of random polypropylene) was used.
And maleic anhydride-modified polypropylene (manufactured by Mitsui Petrochemical Co., Ltd., Admer QF-50) as the adhesive resin layer.
A thermoformed container was produced by repeating the method of Example 1 except that the thermoformed container was used. The appearance and gas barrier properties of the container were measured, and the results are shown in Table 1.

Comparative Example 1 The procedure of Example 1 was repeated, except that the amount of sodium hydroxide added was changed to a molar ratio of 0.06 to vinyl acetate. Ethylene content of EVOH obtained 3
2 mol%, saponification degree 99.6 mol%, Tc (A) = 16
0 ° C., Hc (A) = 70 mJ / mg, 100 × Hc
(A) / Hc (T) = 0. Using this ethylene-vinyl alcohol copolymer, the method of Example 1 was repeated to produce a thermoformed container. The appearance and gas barrier properties of this container were measured, and the results are shown in Table 1. As is evident from the results in Table 1, cracks were observed from the appearance of the thermoformed container, the gas barrier properties were not good, and the variation between samples was large.

Comparative Example 2 In Example 1, the ethylene pressure was initially 40 kg / c.
m ² , changed to 57 kg / cm ² at the stage of the polymerization rate of 40%,
And it carried out similarly to Example 1 except having changed the molar ratio of sodium hydroxide to 0.005. The ethylene content of the obtained EVOH is 34 mol%, the saponification degree is 99.4 mol%,
Tc (A) = 145 ° C., Hc (A) = 5 mJ / mg, 1
00 × Hc (A) / Hc (T) = 10. Example 1 was prepared using this ethylene-vinyl alcohol copolymer.
Method was repeated. The appearance and gas barrier properties of the obtained thermoformed container were measured, and the results are shown in Table 1.

Comparative Example 3 The procedure of Example 1 was repeated, except that the polymerization pressure was changed when the polymerization rate was 20%. The ethylene content of the obtained EVOH is 35 mol% and the saponification degree is 9
8.5 mol%, Tc (A) = 120 ° C., Hc (A) = 4
5 mJ / mg, 100 × Hc (A) / Hc (T) = 40
Met. Using the ethylene-vinyl alcohol copolymer, the method of Example 1 was repeated. The appearance and gas barrier properties of the obtained thermoformed container were measured, and the results are shown in Table 1.

Comparative Example 4 In a flow system operation using two polymerization tanks with a stirrer, each having a capacity of 50 l (first polymerization tank) and a capacity of 70 l (second polymerization tank), each having a cooling coil therein, were arranged in series. In order to produce an ethylene-vinyl acetate copolymer, continuous polymerization was performed under the following conditions. First polymerization tank Vinyl acetate supply 5850 g / hr Methanol supply 650 g / hr Temperature 60 ° C. Ethylene pressure 40 kg / cm ² G 2,2′-azobisisobu 2.1 g / hr Tyronitrile Average residence time 2.0 hr Second Polymerization tank temperature 60 ° C. Ethylene pressure 57 kg / cm ² G Average residence time 4.9 hr Vinyl acetate and methanol are supplied to the first polymerization tank, and the total amount of the polymerization reaction liquid flowing out of the first polymerization tank is changed to the second polymerization tank. Supply to At this time, the polymerization rates of vinyl acetate measured in the first polymerization tank and the second polymerization tank were 18% and 38%, respectively.
%, And the amount (weight) of the copolymer produced in the first polymerization tank and the second polymerization tank was almost the same. The ethylene content of the obtained copolymer was 37 mol%. Ethylene dissolved in the copolymerization reaction solution is diffused by reducing the pressure to normal pressure, removed, and then supplied to an extrusion column, and unreacted vinyl acetate is converted into a column by introducing methanol vapor from the bottom of the column. After removal from the top, 45 of the copolymer
% Methanol solution was obtained. Next, a methanol solution of the copolymer was introduced into a tower-type saponification tower, and sodium hydroxide was further supplied to the reactor such that a molar ratio to a vinyl acetate component contained in the copolymer was 0.05. Methanol vapor is blown in from the bottom of the tower to perform saponification while removing methyl acetate produced as a by-product from the top of the tower.
A methanol solution of OH was obtained. A mixed vapor having a weight ratio of methanol / water = 7/3 was blown into the methanol solution, and the solvent composition in the solution was changed to a water / methanol mixed system.
The EVOH was discharged into a 10% aqueous solution of methanol at 5 ° C. in the form of a strand, solidified and precipitated, cut, and the EVOH was isolated as a pellet. After sufficiently washing with water, the film was immersed in dilute acetic acid water and dried at 65 to 110 ° C.

[0026]

[Table 1]

(Note) In Table 1, (A) Ethylene-vinyl alcohol copolymer PS1 Asahi Dow Stylon 691 (transparent polystyrene) PS2 Philips K-Resin KR-5 (transparent polystyrene) PP Mitsubishi Yuka Noblen EX-6 ( Ad1 Toyo Soda Mersen M-5420 (maleic anhydride-modified ethylene-vinyl acetate copolymer) Ad2 Mitsui Petrochemical Admer QF-500 (maleic anhydride-modified polypropylene)

[0028]

As described above, the multilayer structure of the present invention can be easily formed into a molded product such as a container by thermoforming without deteriorating the excellent gas barrier property of the ethylene-vinyl alcohol copolymer layer. In addition to being able to be processed, a molded article containing an EVOH layer having transparency and high gas barrier properties can be obtained by preventing the occurrence of cracks, pinholes, local uneven thickness, etc. in the EVOH layer of the molded article.

Claims (5)

(57) [Claims] [Claim 1] the following formulas (1) to (3) an ethylene content of 20 to 60 mol% satisfying a saponification degree of 80% or more ethylene - a layer of vinyl alcohol copolymer, said layer of low Do rather < On one side, other than ethylene-vinyl alcohol copolymer
Multilayer structure having the thermoplastic resin layer. Tc (A) ≦ 130 ° C. (1) Hc (A) ≦ 20 mJ / mg (2) 1 ≦ 100 × Hc (A) / Hc (T) ≦ 30 (3) where Tc (A) indicates a crystallization peak temperature of the ethylene-vinyl alcohol copolymer when the temperature is decreased at 10 ° C./min by a differential calorimeter (DSC). Indicates the lowest temperature among two or more peak temperatures. Hc (A) is Tc (A)
Is the crystallization exotherm (mJ / mg) of the ethylene-vinyl alcohol copolymer, and Hc (T) is the total crystallization exotherm (mJ) of the ethylene-vinyl alcohol copolymer having two or more peak temperatures. / Mg). MJ is millijoule and mg is milligram. 2. An ethylene-vinyl alcohol copolymer
On at least one side of the layer, via an adhesive resin, ethylene
-Laminated thermoplastic resin other than vinyl alcohol copolymer
The multilayer structure according to claim 1, which is formed. 3. The multilayer structure according to claim 1 or 2,
Thermoforming container. 4. An ethylene resin satisfying the following formulas (1) to (3):
With an ethylene content of 20 to 60 mol% and a saponification degree of 80% or more
Len-vinyl alcohol copolymer and ethylene-vinyl
Coextrusion molding with thermoplastic resin other than alcohol copolymer
A method for producing a multilayer structure. Tc (A) ≦ 130 ° C. (1) Hc (A) ≦ 20 mJ / mg (2) 1 ≦ 100 × Hc (A) / Hc (T) ≦ 30 (3) However, Tc (A) is 10 ° C./minute by a differential calorimeter (DSC).
-Vinyl alcohol copolymer when temperature is lowered
Shows the crystallization peak temperature of two or more peak temperatures.
Shows the lowest temperature. Hc (A) is Tc (A)
Of crystallization of ethylene-vinyl alcohol copolymer at high temperature
(MJ / mg), and Hc (T)
Of ethylene-vinyl alcohol copolymer having
The total crystallization calorific value (mJ / mg) is shown. MJ is millimeter
Joules, mg are milligrams. 5. An ethylene-vinyl alcohol copolymer
And thermoplastics other than ethylene-vinyl alcohol copolymer
And a multi-layer structure formed by laminating an adhesive resin via an adhesive resin.
In obtaining the structure, ethylene-vinyl alcohol copolymer
Co-extrusion molding of coalesced, adhesive resin and thermoplastic resin
The multilayer structure according to claim 4, wherein:
Construction method.