JPH0515382B2 - - Google Patents

Description

[Detailed description of the invention]

A. Industrial Application Field The present invention relates to a laminate that is flexible, has excellent bending fatigue resistance, and has gas permeation resistance. B. Conventional technology Ethylene-vinyl alcohol copolymer (hereinafter referred to as
EVOH (abbreviated as EVOH) is widely known as a melt-moldable thermoplastic resin with excellent gas permeability, oil resistance, solvent resistance, and fragrance retention, and is used in various packaging fields for films, sheets, containers, etc. It is widely used, especially as a laminate with other thermoplastic resins. However, EVOH has the drawbacks of being hard, brittle, and lacking in flexibility. For example, strong vibrations caused by transportation, bending fatigue, etc. can cause cracks and pinholes in the EVOH layer, making it difficult to use. It cannot maintain permeability to other gases. In addition, when EVOH is laminated with other thermoplastic resins by coextrusion etc. and then stretch-molded,
The disadvantage is that cracks and uneven stretching occur in the EVOH layer. C Problems to be Solved by the Invention The present invention aims to provide a laminate that is flexible, has excellent bending fatigue resistance, and gas permeation resistance, and is free from cracks and stretching unevenness. D Means for Solving the Problem As a result of intensive studies, the present inventors found that at least two layers, a layer of an EVOH-based polymer in which a polyether component is added to the end of EVOH, and a layer of another thermoplastic resin, The inventors have discovered that the above object can be achieved by using a laminate containing the above-described materials, and have completed the present invention. E Effects of the Invention The laminate according to the present invention has excellent gas permeability, oil resistance, solvent resistance, and fragrance retention, and has better flexibility and bending fatigue resistance than a laminate having a normal EVOH layer. Dramatically improved, and no cracks or uneven stretching occur. Therefore, it is extremely useful in various packaging fields, especially as a flexible laminated packaging material. F. More detailed description of the invention The EVOH used in the invention has an ethylene content of 20
The saponification degree of the vinyl acetate component is 95% or more, preferably 98% or more. If the ethylene content is less than 20 mol%, not only the moldability deteriorates, but also the gas permeability under high humidity conditions deteriorates. When the ethylene content exceeds 60 mol%, the gas permeability resistance deteriorates significantly. Further, if the degree of saponification is less than 95%, although the flexibility increases, the gas permeability resistance deteriorates, which is not preferable. Further, there is no problem in including other copolymerizable unsaturated monomers as long as the characteristics of EVOH are not impaired. Note that the ethylene content of 20 to 60 mol% refers to the ethylene content in EVOH excluding the polyether component. The polyether used in the present invention includes those mainly composed of oxyalkylene units such as oxyethylene units, oxypropylene units, oxyethylene-oxypropylene units, and oxytetrimethylene units. It is preferable that the subject be the main subject. For example, polyether molecules contain polyethylene units,
It may contain an amide group, urethane group, ester group, phenyl group, etc. The properties of the EVOH-based polymer in the present invention vary greatly depending on the weight ratio of the EVOH component to the polyether component. In order to impart flexibility, the polyether component is 2% by weight or more, preferably 5% by weight.
On the other hand, from the viewpoint of gas permeation resistance, the content of the polyether component is 50% by weight or less, preferably 20% by weight or less. To add polyether to the end of EVOH,
Several methods are possible. For example, a method of copolymerizing vinyl acetate and ethylene in the presence of a polyether having a mercapto group at the end, and saponifying this, or a method having a mercapto group at the end.
Examples include a method in which a polyether having a polymerizable double bond at one or both ends is polymerized in the presence of EVOH. Thus, if polyether is represented by P and EVOH is represented by E, then P
A block copolymer represented by -E or E-P-E is obtained. Here, the polyether having a polymerizable double bond at the terminal has the general formula [However, R is hydrogen or a methyl group, R ¹ and R ² are hydrogen or an alkyl group having 1 to 10 carbon atoms, R ³ is hydrogen, an alkyl group having 1 to 10 carbon atoms, an alkyl ester (alkyl having 1 to 10 carbon atoms) ~10) group, alkylamido group (1 to 10 carbon atoms in alkyl) group, etc.
n represents an integer from 1 to 100. ] (meta)
Allyl ether type (e.g. polyoxyethylene (meth)allyl ether, polyoxypropylene (meth)allyl ether, etc.) or general formula [However, R, R ¹ , R ² and R ³ are the same as above] or the (meth)allyl ether type, or the general formula [However, R ⁴ is hydrogen, an alkyl group having 1 to 10 carbon atoms, or

[Formula] X represents an alkylkylene group having 1 to 10 carbon atoms, a substituted alkylene group, a phenylene group, or a substituted phenylene group, and m represents an integer of 0 or 1 or more. R ¹ , R ² , R ³ are the same as above] A (meth)acrylamide type product having a double bond at one end (e.g. polyoxyethylene (meth)acrylamide, polyoxypropylene (meth) (acrylic acid amide, etc.) or general formula [However, R, R ¹ , R ² , R ³ , X, m, and n are the same as above] The (meth)acrylic acid ester type (e.g. polyoxyethylene (meth)acrylate, polyoxypropylene (meth)acrylate, etc.) or general formula [However, R ¹ , R ² , R ³ , X, m, and n are the same as above] (eg, polyoxyethylene vinyl ether, polyoxypropylene vinyl ether, etc.). The melt index (MI) of the EVOH polymer thus obtained is adjusted to 0.1 to 50 g/10 minutes, preferably 0.3 to 25 g/10 minutes.
(Measured at 190℃ using ASTM D-1238-65T) MI can be adjusted by adjusting the degree of polymerization of the EVOH component and polyether component.
This is done by adjusting the weight ratio of the EVOH component and the polyether component. The EVOH polymer thus obtained is
Compared to EVOH, Young's modulus is 2/3 to 1/10, and it is flexible and can be melt-molded like normal EVOH. Thermoplastic resins used for lamination with this EVOH polymer include polypropylene, polyethylene (branched or linear),
Examples include ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, thermoplastic polyester, polyamide, polystyrene, polycarbonate, polyvinyl chloride, etc. Among these, linear polyethylene, polypropylene, ethylene-propylene copolymer, Thermoplastic polyester and polystyrene are particularly suitable. The laminate can have a multilayer structure of two layers, three layers, or more, but when it has three or more layers, an EVOH layer is often used as an intermediate layer. As a molding method for obtaining a laminate, known methods such as co-extrusion, co-injection, extrusion lamination, and coating may be used, and co-extrusion is particularly preferred. When obtaining a laminate, it is preferable to interpose an adhesive resin between each layer, and the adhesive resin is not particularly limited, but polyethylene, ethylene-vinyl acetate copolymer, polypropylene, or ethylene-acrylic acid ester (methyl ester or ethyl ester) copolymers, etc., grafted or addition-modified with an ethylenically unsaturated carboxylic acid (preferably maleic anhydride), or a mixture of these modified and unmodified products are preferably used. Ru. The laminate formed in this way is different from the conventional
Compared to a laminate using EVOH, its EVOH
Due to the improved flexibility of the layers, it is extremely useful as a flexible laminated packaging material, and exhibits extremely excellent performance against strong vibrations that occur during transportation, bending fatigue, impact from dropping, fatigue due to friction, etc. These performances are more effectively exhibited at lower temperatures. Next, the present invention will be explained in more detail with reference to Examples, but these Examples are not intended to limit the present invention in any way. G Examples Example 1 Polyoxypropylene allyl ether with a molecular weight of 1500 having a polymerizable double bond at one end (NOF Corporation)
1,000 g of Unisafe PKA-5014) and 0.065 g of benzoyl peroxide were placed in a reaction tank with a capacity of 2 and equipped with a stirrer, the internal temperature was maintained at 40°C, and thioacetic acid was continuously stirred at a rate of 47 g/hour for 3 hours. added to. Then unreacted thioacetic acid was added to
It was removed from the reaction system under reduced pressure at 40°C. Next, add 200g of methanol and 0.55g of sodium hydroxide.
After stirring for 2 hours at 60°C under a nitrogen stream, acetic acid was added to neutralize excess sodium hydroxide. The mercapto group of the mercaptated polyoxypropylene thus obtained was determined to be 6.45×10 ^-4 e as a result of titration with _I2.
g/g, and the ends with double bonds were almost quantitatively mercaptolated. Next, 27.6 kg of vinyl acetate and 11 g of mercapto polyoxypropylene were charged into a polymerization tank with a capacity of 50 mm and a cooling coil inside, equipped with a stirrer, and after replacing the air in the polymerization tank with nitrogen, the temperature was raised to 60°C. The reactor was heated and ethylene was charged to bring the pressure to 43 Kg/cm ² . Then, the polymerization initiator 2,2'-azobisisobutyronitrile
31 g was dissolved in 400 ml of methanol and added, and then mercaptated polyoxypropylene was added at a rate of 147 g/hour for 5 hours to carry out a polymerization reaction.
The polymerization rate of vinyl acetate was 39%. The copolymer reaction solution was then fed to a purging tower, and unreacted vinyl acetate was removed from the top of the tower by introducing methanol from the bottom of the tower, followed by a saponification reaction using sodium hydroxide as a catalyst by a conventional method. . After thoroughly washing with water, the sample was immersed in a dilute aqueous acetic acid solution, and then dried at 60 to 105°C under a nitrogen stream. The EVOH copolymer thus obtained is a block copolymer in which polyoxypropylene is added to one end of EVOH, and its composition was analyzed by NMR.
Ethylene content 31.0 mol%, polyoxypropylene content 9.4% by weight, saponification degree of vinyl acetate component 99.4
%, and under the conditions of 190℃ and 2060g load,
MI measured using ASTM D-1238-65T method is
It was 6.7g/10 minutes. Next, the copolymer (hereinafter referred to as copolymer A)
The Young's modulus of a single product, and the bending fatigue resistance and oxygen permeation of a laminated film in which the copolymer was disposed as an intermediate layer were measured. The Young's modulus was determined by using a film forming machine with an extruder and a T-die to measure the copolymer at an extruder temperature of 180°C.
The sample was a film produced by extrusion at ~220°C and a T-die temperature of 225°C, and the humidity was adjusted for 7 days at 20°C and 65% RH, according to ASTM D-638.
Measurements were made using an autograph at a tensile rate of 200%/min. The bending resistance and oxygen permeation amount were determined by the following methods:
Adhesive layer/intermediate layer/adhesive layer/outer layer) was measured as a sample. The film forming machine consists of an extruder for the inner and outer layers, an extruder for the intermediate layer, an extruder for the adhesive layer, and a T-die for 5 layers, and the molding temperature is 160 to 220 for the extruder for the inner and outer layers.
The extruder for the intermediate layer was heated at 180-220°C, the extruder for the adhesive layer was heated at 120-220°C, and the T-die was heated at 255°C. The intermediate layer is made of the copolymer A, and the inner and outer layers are made of linear low-temperature polyethylene containing 2.6 mol% of the copolymerized component, with an MI of 2.1 g/10 min. The adhesive layer is made of modified ethylene with a vinyl acetate content of 33% by weight and a degree of maleic anhydride modification of 1.5% by weight.
It is a vinyl acetate copolymer (MI2.0g/10 minutes).
The thickness of the laminated film was 12 μm for the intermediate layer, 30 μm each for the inner and outer layers, and 5 μm each for the adhesive layer. The bending fatigue resistance test was carried out using a Gerbo Flex Tester (manufactured by Rigaku Kogyo Co., Ltd.). A 12in x 8in test piece was shaped into a cylinder with a diameter of 31/2in, gripped at both ends, and the initial gripping interval 7in, grip distance at maximum bending
1in. The first 31/2in of the stroke adds a twist at an angle of 440°, and the subsequent 21/2in is a linear horizontal movement, repeating the reciprocating motion at a speed of 40 times/min.
It was carried out under the conditions of 20°C and 65%RH. The oxygen gas permeation amount was measured using OX-TRAN100 manufactured by Modern Control under the conditions of 20° C., 65% RH and 20° C., 85% RH after 7 days of humidity control. The samples used for this measurement were samples in which the number of repeated reciprocations was varied in the bending fatigue resistance test. The number of pinholes was measured by stacking the sample on blotting paper, applying dye (red) on top of it, rubbing it with a roller, peeling off the sample, and checking the number of colored spots on the blotting paper. The results of these measurements are shown in Tables 1 and 2. Control example 1 In Example 1, the ethylene content was 31.9 mol%, the polyoxypropylene content was 9.4% by weight, the degree of saponification of the vinyl acetate component was 99.4%, and the EVOH had an MI of 6.7 g/10 min.
In place of the copolymer, ethylene content 32.0 mol%,
In the same manner as in the same example, except that the saponification degree of vinyl acetate component was 99.4, and EVOH with MI 6.4 g/10 minutes was used.
The evaluation results are shown in Tables 1 and 2.

【table】

【table】

[Table] Example 2 In Example 1, 1-octene was used as a copolymerization component instead of 4-methyl-1-pentene-modified linear low-density polyethylene, and MI1. A laminated film was obtained in the same manner as in the same example except that 6 g/10 min linear low-density polyethylene was used for the inner and outer layers, and the bending fatigue resistance and oxygen permeation amount were measured. The results are shown in Table 3. Control Example 2 A laminated film was obtained in the same manner as in Example 2, except that EVOH with an ethylene content of 32.0 mol%, a vinyl acetate component with a saponification degree of 99.4%, and an MI of 6.4 g/10 min was used for the intermediate layer. , bending fatigue resistance and oxygen permeation were measured. The results are shown in Table 3.

[Table] Example 3 In the same manner as in Example 1, vinyl acetate and ethylene were copolymerized while continuously adding the mercaptated polyoxypropylene, and then unreacted vinyl acetate was removed, saponified, washed, Drying was performed to obtain a block copolymer in which polyoxypropylene was added to one end of EVOH. The composition was analyzed by NMR and found to have an ethylene content of 37.9 mol%, a polyoxypropylene content of 13.1% by weight, and a saponification degree of vinyl acetate component of 99.6%. Also, the copolymer
MI was 10.1 g/10 minutes. Next, in the same manner as in Example 1, the copolymer (hereinafter referred to as
In addition to measuring the Young's modulus of a single film (referred to as copolymer B), a laminated film having the same structure as in Example 1 except that copolymer B was used as the intermediate layer was formed, and its bending fatigue resistance and The amount of oxygen permeation was measured. The results are shown in Tables 4 and 5. Control example 3 In Example 3, instead of copolymer B, the ethylene content was 38.2 mol%, and the degree of saponification of the vinyl acetate component was
Tables 4 and 5 show the evaluation results in the same manner as in the same example except that EVOH of 99.5% and MI 9.6 g/10 minutes was used.

【table】

[Table] Example 4 Polyoxypropylene allyl ether (NOF) with a molecular weight of 3000 and having polymerizable double bonds at both ends.
1000 g of Unisafe PKA-5018) manufactured by Unisafe Co., Ltd. and 7 mg of benzoyl peroxide were placed in a reaction tank with a capacity of 2 and equipped with a stirrer, the internal temperature was maintained at 30°C, and thioacetic acid was stirred at a rate of 27 g/hour for 3 hours. Added continuously. Then add unreacted thioacetic acid to 35-40%
It was removed from the reaction system under reduced pressure at °C. Next, 200 g of methanol and 0.55 g of sodium hydroxide were added, and the mixture was stirred at 60° C. for 2 hours under a nitrogen stream, and then acetic acid was added to neutralize excess sodium hydroxide. As a result of titration with _I2 , the mercapto group of the mercaptated polyoxypropylene thus obtained was 6.56×10 ^-4 e
g/g, and both ends with double bonds were almost quantitatively mercaptolyzed. Next, vinyl acetate was added to the same polymerization tank as in Example 1.
26.1Kg, above mercaptated polyoxypropylene
After charging 11g of ethylene and replacing the air in the polymerization tank with nitrogen, the temperature was raised to 60℃, ethylene was charged, and the pressure was increased to 44℃.
Kg/ ^cm2 . Next, 50 g of the polymerization initiator 2,2'-azobisisobutyronitrile dissolved in 500 ml of methanol was added, and then mercaptated polyoxypropylene was added at a rate of 230 g/hour for 3.3 hours to carry out a polymerization reaction. Polymerization rate of vinyl acetate is 42%
It was hot. The copolymerization reaction solution was then supplied to a purging tower, and unreacted vinyl acetate was removed from the top of the tower by introducing methanol from the bottom of the tower, followed by a saponification reaction using sodium hydroxide as a catalyst in a conventional manner. After thoroughly washing with water, it was immersed in a dilute acetic acid aqueous solution, and then dried at 60 to 105°C under a nitrogen stream. The EVOH copolymer thus obtained is a block copolymer in which EVOH is added to both terminals of polyoxypropylene, and its composition is determined by NMR.
As a result of analysis, the ethylene content was 31.0 mol%, the polyoxypropylene content was 9.7% by weight, and the degree of saponification of the vinyl acetate component was 99.3%. Also, MI is 1.4g/
It was hot in 10 minutes. Next, the Young's modulus of a single film of the copolymer (hereinafter referred to as copolymer C) was measured in the same manner as in Example 1, and the structure was the same as in Example 2 except that copolymer C was used as the intermediate layer. A laminated film was formed, and its bending fatigue resistance and oxygen permeability were measured. The results are shown in Tables 6 and 7. Control example 4 In Example 4, instead of copolymer C, the ethylene content was 31.3 mol%, and the degree of saponification of the vinyl acetate component was
Tables 6 and 7 show the evaluation results in the same manner as in the same example except that EVOH of 99.5% and MI of 1.6 g/10 minutes was used.

【table】

[Table] Example 5 In the same manner as in Example 4, vinyl acetate and ethylene were copolymerized while continuously adding the mercaptated polyoxypropylene shown in Example 4, and then unreacted vinyl acetate was removed. , saponification, washing, drying, and both terminals of polyoxypropylene.
A block copolymer to which EVOH was added was obtained. As a result of NMR analysis, its composition revealed that the ethylene content was
The polyoxypropylene content was 15.2% by weight, and the degree of saponification of the vinyl acetate component was 99.6%.
Moreover, the MI of the copolymer was 6.1 g/10 minutes. Next, in the same manner as in Example 1, the copolymer (hereinafter referred to as
In addition to measuring the Young's modulus of a single film (referred to as copolymer D), a laminated film having the same structure as in Example 1 except that copolymer D was used as the intermediate layer was formed, and its bending fatigue resistance and oxygen The amount of permeation was measured. The results are shown in Tables 8 and 9. Control example 5 In Example 5, instead of copolymer D, the ethylene content was 44.1 mol%, and the degree of saponification of the vinyl acetate component was used.
Tables 8 and 9 show the evaluation results in the same manner as in the same example except that EVOH of 99.5% and MI 5.8 g/10 minutes was used.

【table】

[Table] Example 6 The polyoxypropylene shown in Example 1
A laminated sheet having an EVOH block copolymer added to one end of EVOH as an intermediate layer was molded in the same manner as in the same example. However, the inner and outer layers are polypropylene (Mitsubishi Noblen MA-6 manufactured by Mitsubishi Yuka),
The adhesive layer is maleic anhydride-modified polypropylene (Admer QF500 manufactured by Mitsui Petrochemicals). Next, the laminated sheet was formed by solid-state air pressure forming under conditions such that the sheet surface temperature was 145°C, and the inner diameter (D) was 100 mm and the depth was 100 mm.
A cylindrical cup with (L) of 200 mm (drawing ratio L/D=2), wall thickness of 0.5 mm, and internal volume of 1.6 was obtained. The thickness ratio of outer layer: adhesive layer: middle layer: adhesive layer: inner layer is 45:
It was 2.5:5:2.5:45. The properties of the cup are
Shown in Table 10. Control Example 6 In Example 6, instead of the EVOH block copolymer in which polyoxypropylene was added to one end of EVOH as the intermediate layer, the interlayer shown in Control Example 1 was used.
A cylindrical cup was molded in the same manner as in Example 6 except that EVOH was used. The properties of the cup are shown in Table 10.

【table】

[Table] 〓
〓× Extremely uneven stretching

Claims (1)

[Scope of Claims] 1. Contains at least two layers: a layer of an ethylene-vinyl alcohol polymer in which a polyether component is added to the end of the ethylene-vinyl alcohol copolymer, and a layer of another thermoplastic resin. A laminate with excellent gas permeability. 2. The laminate according to claim 1, wherein the ethylene content of the ethylene-vinyl alcohol copolymer is 20 to 60 mol%. 3. The laminate according to claim 1, wherein the polyether component is composed of oxypropylene units.