JPH0515383B2 - - Google Patents

Description

[Detailed description of the invention]

A. Industrial Application Field The present invention relates to a laminate that is flexible, has excellent impact resistance, and is resistant to gas permeation. B. Prior art Ethylene-vinyl alcohol copolymer (hereinafter referred to 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, and it is difficult for laminated packaging materials with an EVOH layer to undergo strong vibrations due to transportation, for example.
Due to bending fatigue, etc., cracks and pinholes occur in the EVOH layer, making it impossible to maintain excellent gas permeability. 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 impact resistance, and gas permeation resistance, and is free from cracks and stretching unevenness. D Means for Solving the Problems As a result of intensive studies, the inventors found that a layer of EVOH polymer in which a polyether component is added as a grafted EVOH branch polymer, and a layer of other thermoplastic resin. The inventors have discovered that the above object can be achieved by using a laminate containing at least two layers of the following, 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 significantly higher impact resistance and bending fatigue resistance than a laminate having an EVOH layer. In addition, cracks and uneven stretching do not 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
~60 mol%, preferably 25-55 mol%, and the degree of saponification of the vinyl acetate component is 95%, 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. Also, the saponification degree is 95
If it is less than %, the flexibility will increase, but the gas permeability will deteriorate, 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% means excluding the polyether component.
Shows the ethylene content in EVOH. The polyether used in the present invention includes those mainly composed of oxyalkylene units such as oxyethylene units, oxypropylene units, oxyethylene-oxypropylene units, and oxytetramethylene units, but especially oxypropylene units. It is preferable that the main component is The polyether molecule may contain other units or groups such as polymethylene units, amide groups, urethane groups, ester groups, and phenyl groups. 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 and impact resistance, the polyether component is required to be at least 2% by weight, preferably at least 5% by weight, while in terms of gas permeation resistance, the polyether component is at most 50% by weight, preferably 20% by weight. % or less. Several methods can be considered to add polyether as a branched polymer of EVOH in the form of a graft. For example, it can be obtained by copolymerizing vinyl acetate and ethylene in the presence of a polyether having a polymerizable double bond at the end, and saponifying the copolymer. 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 alkylene 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 and R ³ are the same as above. ] A (meth)acrylamide type having a double bond at one end (e.g. polyoxyethylene (meth)acrylamide, polyoxypropylene (meth)acrylamide, etc.), or a 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, R ¹ , R ² , R ³ , X, m, and n are the same as above] of vinyl ether type (eg, polyoxyethylene vinyl ether, polyoxypropylene vinyl ether, etc.). The melt index (MI) of the EVOH polymer obtained in this way is 0.1 to 50 g/10 min.
Preferably it is adjusted to 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 obtained in this way has a Young's modulus of 2/3 to 2/3 that of normal EVOH.
1/10, impact strength is 2 to 50 times higher, has excellent flexibility and impact resistance, and can be hot-melted and molded like normal EVOH. Thermoplastic resins used for lamination with this EVOH polymer include polypropylene, polyethylene (branched or linear), ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, thermoplastic polyester, polyamide, Examples include polystyrene, polycarbonate, polyvinyl chloride, etc., and among these, linear polyethylene, polypropylene, ethylene-propylene copolymer, thermoplastic polyester, and polystyrene are particularly preferred. 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 esters, ethyl esters, etc.) copolymers, etc., grafted or addition-modified with ethylenically unsaturated carboxylic acids (preferably maleic anhydride), or mixtures 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 and impact resistance 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 In a polymerization tank with a capacity of 50 and equipped with a stirrer and a cooling coil inside, 13.7 kg of vinyl acetate and polyoxypropylene allyl ether (NOF) with a molecular weight of 1500 having a polymerizable double bond at one end were placed Manufactured by Unisafe Co., Ltd.
PKA-5014) 0.70Kg, methanol 1.0Kg and polymerization initiator 2,2'-Azohisisobutyronitrile 11
g, set the ethylene pressure to 40Kg/ ^cm2 , and heated to 60℃.
Copolymerization was carried out for 6 hours. The polymerization rate of vinyl acetate was 40%. Next, the copolymerization reaction liquid is supplied to the expulsion tower, and by introducing methanol from the bottom of the tower,
After removing unreacted vinyl acetate from the top of the column, a saponification reaction was carried out by a conventional method using sodium hydroxide as a catalyst. After thoroughly washing with methanol and water, the sample was immersed in a dilute aqueous acetic acid solution and dried at 60 to 105°C. thus obtained
EVOH copolymer is polyoxypropylene,
It is added in a graft form as a branch polymer of EVOH, and its composition was analyzed by NMR, and the ethylene content was 31.9 mol%, and the polyoxypropylene content was 31.9 mol%.
The saponification degree of the vinyl acetate component was 7.2% by weight and 99.4%. In addition, under the conditions of 190℃ and 2160g load,
MI measured using ASTM D-1238-65T method is
It was 1.3g/10 minutes. Next, the Young's modulus, impact strength, and
The bending fatigue resistance and oxygen permeation of a laminated film in which the copolymer was disposed as an intermediate layer were measured. Young's modulus is determined by extruding the copolymer into a film using a film forming machine having an extruder and a T-die under conditions of an extruder temperature of 180 to 220°C and a T-die temperature of 225°C.
A sample was subjected to humidity control for 7 days under the condition of % RH, and was measured using an autograph at a tensile rate of 200%/min according to ASTM D-638. Impact strength (Izotsu impact strength (notched))
The sample was a molded product (2.5in x 1/2in x 1/8in) obtained by pressure molding the copolymer at 220°C in a standard mold, and the temperature was varied according to ASTM D-256.
Measured under the condition of %RH. The bending resistance and oxygen permeation amount were determined by the following methods:
(intermediate layer/adhesive layer/outer layer) was measured as a sample. Film forming machines include extruders for inner and outer layers, extruders for intermediate layers,
Consists of one extruder for the adhesive layer and a T-die for five layers, and the molding temperature is 160-220℃ for the extruder for the inner and outer layers, 180-220℃ for the middle layer, and 120-220℃ for the extruder for the adhesive layer.
The temperature was 220℃ and the T-die temperature was 225℃. The intermediate layer is made of the polyoxypropylene added in a grafted manner.
EVOH copolymer, inner and outer layers are 4-methyl-1-
Pentene is used as a copolymerization component, and the copolymerization component is 3.2
The adhesive layer is a modified ethylene-vinyl acetate copolymer with a vinyl acetate content of 33% by weight and a degree of maleic anhydride modification of 1.5% by weight (MI2. 0g/10min). The thickness structure of the laminated film is as follows:
The thickness was 12μ, the inner and outer layers each had a thickness of 30μ, and the adhesive layer each had a thickness of 5μ. The bending fatigue resistance test was conducted using a Gelbo Flex Tester (manufactured by Rigaku Kogyo Co., Ltd.). A 12 inch x 8 inch sample piece was shaped into a cylindrical shape with a diameter of 3 1/2 inches, gripped at both ends, and the initial grip was performed. 7in spacing, grip spacing at maximum bending
1 inch, the first 3 1/2 inch of the stroke is a twist at an angle of 440°, and the subsequent 2 1/2 inch is a linear horizontal motion. Repeated reciprocating motion at a speed of 40 times/minute, 20 degrees, It was conducted under the condition of 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. These measurement results are shown in Tables 1 and 2. Control example 1 In Example 1, the ethylene content was 31.9 mol%,
Polyoxypropylene content 7.2% by weight, saponification degree of vinyl acetate component 99.4%, MI 1.3g/10 minutes
In place of EVOH copolymer, ethylene content 32.0 mol%, saponification degree of vinyl acetate component 99.4%, MI 1.3
The evaluation results are shown in Tables 1 and 2 in the same manner as in the same example except that EVOH of g/10 minutes was used.

【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 linear low-density polyethylene of 6 g/10 min was used for the inner and outer layers, and its bending fatigue resistance and oxygen permeation were measured. The results are shown in Table 3. Control example 2 In Example 2, the ethylene content was 32.0 mol%,
Saponification degree of vinyl acetate component: 99.4%, MI1.3g/10
A laminated film was obtained in the same manner as in the same example except that EVOH of 100% was used for the intermediate layer, and its 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, polyoxypropylene allyl ether with a molecular weight of 3000 having polymerizable double bonds at both ends (Unisafe PKA-5018 manufactured by NOF Corporation), and Copolymerize ethylene,
Next, unreacted vinyl acetate is removed, saponified, washed,
After drying, a copolymer in which polyoxypropylene was added as a grafted EVOH branch polymer was obtained. As a result of NMR analysis, the composition of the copolymer was found to have an ethylene content of 38.0 mol%, a polyoxypropylene content of 12.2% by weight, and a degree of saponification of the vinyl acetate component of 99.6%. In addition, the MI of the copolymer is 2.1
g/10 minutes. Next, the Young's modulus and Izod impact strength (notched) of the single copolymer were measured in the same manner as in Example 1, and a laminate having the same structure as in Example 1 except that the interlayer was made of the copolymer. A film was formed, and its bending fatigue resistance and oxygen permeation were measured. The results are shown in Tables 4 and 5. Control example 3 In Example 3, the ethylene content was 38.0 mol%,
Polyoxypropylene content 12.2% by weight, saponification degree of vinyl acetate component 99.6%, MI 2.1g/10 minutes
In place of EVOH copolymer, ethylene content 38.2 mol%, saponification degree of vinyl acetate component 99.5%, MI 1.7
Tables 4 and 5 show the results of evaluation in the same manner as in the same example except that EVOH of g/10 minutes was used.

【table】

【table】

[Table] Example 4 Vinyl acetate, polyoxytetramethylene with a molecular weight of 2300 having a polymerizable double bond at one end, and ethylene were copolymerized in the same manner as in Example 1, and then saponified, washed, and dried. , a copolymer in which polyoxytetramethylene was grafted as a branch polymer of EVOH was obtained. As a result of NMR measurement, the composition of the copolymer was as follows: ethylene content: 44.5 mol%, polyoxytetramethylene content: 9.8% by weight.
The degree of saponification of the vinyl acetate component was 99.3%. Moreover, the MI of the copolymer was 5.1 g/10 minutes. Next, the Young's modulus and Izod impact strength (notched) of the single copolymer were measured in the same manner as in Example 1, and a laminate having the same structure as in Example 1 except that the interlayer was made of the copolymer. A film was formed, and its bending fatigue resistance and oxygen permeation were measured. The results are shown in Tables 6 and 7. Control example 4 In Example 4, the ethylene content was 44.5 mol%,
Polyoxytetramethylene content 9.8% by weight, saponification degree of vinyl acetate component 99.3%, MI 5.1g/10 minutes
In place of EVOH copolymer, ethylene content 44.2 mol%, saponification degree of vinyl acetate component 99.5%, MI5.4
Tables 6 and 7 show the results of evaluation in the same manner as in the same example except that EVOH of g/10 minutes was used.

【table】

[Table] Example 5 The polyoxypropylene shown in Example 1
A laminated sheet having an intermediate layer of an EVOH copolymer grafted as a branch polymer of EVOH was molded in the same manner as in the same example. However, the inner and outer layers are polypropylene (Mitsubishi Noblen MA manufactured by Mitsubishi Yuka)
-6), and the adhesive layer is maleic anhydride-modified polypropylene (Mitsui Petrochemical Admer QF500).
It is. Next, the laminated sheet was subjected to solid-state air forming under conditions such that the sheet surface temperature was 145°C, the inner diameter D was 100 mm, the depth L was 200 mm (drawing ratio L/D = 2),
A cylindrical cup with a wall thickness of 0.5 mm and an internal volume of 1.6 was obtained. The thickness ratio of outer layer: adhesive layer: intermediate layer: adhesive layer: inner layer was 45:2.5:5:2.5:45. The properties of the cup are shown in Table 8. Comparative Example 5 In Example 5, the EVOH shown in Comparative Example 1 was used instead of the EVOH copolymer in which polyoxypropylene was grafted as a branch polymer of EVOH as the intermediate layer.
A cylindrical cup was formed in the same manner as above. The properties of the cup are shown in Table 8.

【table】

[Table] 〓
〓× There is a lot of uneven stretching.

Claims (1)

[Scope of Claims] 1. A layer of an ethylene-vinyl alcohol copolymer to which a polyether component is added in the form of a graft as a branch polymer of an ethylene-vinyl alcohol copolymer, and a layer of another thermoplastic resin. A laminate with excellent gas permeation resistance that includes at least two layers. 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.