JPH0274342A - Laminate structure body - Google Patents

Abstract

PURPOSE:To improve a gas barrier property, steam permeation resistance, pinhole resistance and impact resistance by using a resin composition formed of specified much component copolymer polyamide and EVOH as an imtermediate gas barrier layer and by laminating a non-polar thermoplastic resin layer on the opposite sides thereof. CONSTITUTION:A resin composition being much component copolymer polyamide which is formed of an ethylene-vinyl alcohol copolymer of 90 to 50wt.% having the ethylene content of 25 to 55mol% and polyamide of 10 to 50wt.%, in which said polyamide is formed of a caproamide unit of 20 to 45wt.%, a hexamethylene adipamide unit of 25 to 40wt.%, a polyamide constituent unit derived from hexamethylene diamine and a dicarboxylic acid having carbons in the number of 7 to 12 and at least one kind of polyamide constituent unit of 15 to 55wt.% selected from undecaneamide and dodecaneamide, and which satisfies a melting point of 120 to 180 deg.C, methylene groups in the number of 5.3 to 6.0 for one amide group and a bending modulus of 10,000 to 19,000kg/cm<2>, is made to be an intermediate layer, and non-polar thermoplastic resin is laminated on the opposite sides thereof.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a laminated structure formed by laminating thermoplastic resins, and more specifically to a resin comprising an ethylene/vinyl alcohol copolymer and a specific multicomponent copolymer polyamide. The present invention relates to a laminated structure having excellent gas barrier properties, in which the composition is used as an intermediate layer, and other non-polar thermoplastic resins are laminated on both sides of the intermediate layer.

BACKGROUND OF THE INVENTION Plastic packaging is widely used today, and its usage is steadily increasing. In recent years, high functionality has been required for plastic packaging materials, and in the food packaging field and cosmetics packaging field, there is an increasing demand for plastic packaging materials with high gas barrier properties to improve the storage stability of contents and prevent aroma dissipation. It's coming.

Among plastic packaging materials, ethylene/vinyl alcohol copolymer (hereinafter abbreviated as EVOH) is used.

) has attracted attention in the above-mentioned fields because it has excellent gas barrier properties. However, EVOH is a hard and brittle material when used alone, so when it is formed into films, tubes, etc., it tends to tear or crack, making it difficult to handle, and it also has drawbacks such as hardly any barrier properties against water vapor. . In packaging materials, resins with different functions are usually combined to form a laminate to balance various properties, and EVOH is also used in a laminate structure by combining it with other thermoplastic resins with high water vapor barrier properties. However, this lamination technology cannot prevent the occurrence of pinholes and cracks in films, tubes, etc. due to the hard and brittle nature of EVOH.

It is known that addition of a polyamide resin is effective in improving the pinhole resistance and crack resistance of EVOH and making it flexible. However, the blend of EVOT (and polyamide) has the problem of significant thickening and gelation due to the reaction between polymers during melt molding, making it unsuitable for practical molding. Many attempts have been made to obtain EvOH/polyamide-based materials with well-balanced flexibility.
Method using a mixture of lyamide resins
449, JP-A-62-22840, JP-A-62-106944, etc.), EvOH and Capro,
A method using a mixture of copolyamides containing amide as a main component (Japanese Patent Publication No. 60-24813, Japanese Patent Publication No. 60-24813, Japanese Patent Publication No. 60-24813,
24814, etc.>, a method using a mixture of EVOH and a copolyamide containing caproamide and a copolyamide containing lauramide (JP-A-62-2
25535, etc.).

<Problems to be solved by the research> However, the above-mentioned conventional techniques have not yet produced a packaging material with sufficiently satisfactory characteristics.

In other words, in the method of modifying the terminal groups for the purpose of suppressing the intermolecular reaction between EVOH and polyamide, the terminal modification rate is 100%.
% is very difficult under practical polyamide production conditions, and some unmodified ends still exist, so although thickening and gelation times can be delayed, the long melt molding process It is not possible to completely suppress thickening and gelation. Although the method of mixing EVOH and a copolyamide containing caproamide as a main component has the effect of suppressing thickening to some extent,
Due to the requirement for compatibility between H and the copolyamide, it is necessary to use a copolyamide containing caproamide as the main component and having a relatively high melting point, and the molding temperature is generally set high, which is disadvantageous in suppressing gelation. It is. Furthermore, when using a mixture of two copolyamides each containing caproamide and lauramide as one component, the compatibility between EVOH and the polyamide decreases, making it difficult to form a uniform film sheet.

Therefore, the excellent gas barrier of EVO)I
To create a useful gas barrier packaging material that takes advantage of its properties, overcomes its disadvantages of hardness, brittleness, pinhole resistance, and water vapor permeability, and has good stability during molding and high productivity. has become a problem in our industry.

Means for Solving the Problems> Therefore, the present inventors conducted studies to obtain a gas barrier packaging material with high practical value that satisfies the above-mentioned required properties, and
The intermediate layer is a composition in which VOH is blended with a specific multi-component copolyamide whose properties such as copolymerization components, melting point, crystallization behavior, amide group concentration, elastic modulus, and water absorption are within strictly defined ranges, We have discovered that a laminated structure formed by laminating other non-polar thermoplastic resin layers on both sides of the intermediate layer can provide an extremely excellent gas barrier packaging material that satisfies all of the above-mentioned required properties, and have arrived at the present invention. did.

That is, the present invention uses an ethylene/vinyl alcohol copolymer having an ethylene content of 25 to 55 mol% and an ethylene/vinyl alcohol copolymer of 90 to 50% by weight.
and 10 to 50% by weight of polyamide, and the polyamide is composed of 20 to 45% by weight of caproamide units, 25 to 40% by weight of hexamethylene azide/fE units, and hexamethylenediamine and a dicarboxylic acid having 7 to 12 carbon atoms. A multi-component copolymer comprising 15 to 55% by weight of at least one polyamide structural unit selected from polyamide structural units derived from polyamide structural units, undecaneamide, and dodecanamide, and which satisfies the following properties (a) to (c). The present invention provides a laminated structure characterized in that a resin composition made of polyamide is used as an intermediate layer, and other non-polar thermoplastic resins are laminated on both sides of the layer.

(a) Melting point: 120-180°C (b) Number of methylene groups per amide group = 5.3-6
．． Flexural modulus: 10,000 to 19,000 #/Component (a) and component (9) forming the multi-component copolymer polyamide, which is one raw material for the laminated structure of the present invention, are each ε-aminocaproic acid. or derived from ε-caprolactam and hexamethylenediamine adipate. Examples of dicarboxylic acids that can be combined with hexamethylene diamine in component (c) include speric acid, azelaic acid, sebacic acid, dodecanoic acid, isophthalic acid, terephthalic acid, and 1,4-cyclohexanedicarboxylic acid. , undecaneamide and dodecaneamide are derived from 11-aminoundecanoic acid and 12-aminododecanoic acid or ω-laurolactam, respectively. In the present invention, it is important that the composition ratio, melting point, amide group concentration, and flexural modulus of the multicomponent copolymer polyamide used be within strictly defined ranges.

If the composition ratio of components (a), (g), and (c) is out of the above range, melt stability will decrease, such as decreased compatibility with EVOH and thickening and gelation of the blend of EVOH and polyamide. Undesirable. In particular, if the (al component or mountain) component exceeds the above composition ratio, the EVOH blend will thicken significantly, which is undesirable.On the other hand, if the amount of the (c) component exceeds the above range, the compatibility between EVOH and polyamide will increase. This is undesirable because the blended material becomes cloudy when melted and peeling occurs when molding a film or the like. The multicomponent copolyamide having the composition defined above further has (a) a melting point of 120 to 180°C, a number of methylene groups per amide group of 5.3 to 6.0, and (c) a flexural modulus of 10. ,000 to 19,000 #/d. If the melting point of the multi-component copolymer polyamide exceeds 180°C, it is undesirable because the melt molding stability of the blend with EVOH will be impaired, and on the other hand, if the melting point is less than 120°C, it is undesirable because the heat resistance of the blend will be insufficient. . A more preferable melting point range is 130 to 175°C. If the number of methylene groups per amide group in the multicomponent copolymer polyamide is out of the range of 5.3 to 6.0, the compatibility with EVOH will be impaired, which is not preferable. The elastic modulus of the multicomponent copolymer polyamide is 19,
If the elastic modulus exceeds 10,000 kg/d, the effect of imparting flexibility and impact resistance to EvOH will be insufficient, which is undesirable.On the other hand, if the elastic modulus is less than 10,000 #/d, a decrease in the strength of the blend becomes obvious. Therefore, it is not desirable. In addition, the multi-component copolyamide used in the present invention preferably has appropriate water absorption from the viewpoint of compatibility with EVOH, moldability of blends, and handling properties, particularly at 20°C and relative humidity of 6596. Equilibrium water absorption amount under atmosphere is L5 ~
A range of 4.0% by weight is suitable.

The polymerization method and degree of polymerization of the multi-component copolymer polyamide used in the present invention are not particularly limited, and polyamides having a relative viscosity of 15 to 5.0 obtained by a normal pressure melt polymerization method can be used. In addition, for the purpose of controlling the molecular weight, such polyamides partially contain amino groups, alkyl groups other than carboxylic acid groups, aryl groups, hydroxyalkyl groups,
It may also be substituted with an oxyalkyl group or the like.

E blended with the above multi-component copolymer polyamide in the present invention
VOI (VOI) is an ethylene and vinyl alcohol copolymer with an ethylene content of 25 to 55 mol%, preferably 30 to 50 mol%.EVOH is usually obtained by saponifying the corresponding ethylene/vinyl acetate copolymer. The degree of saponification of EVOH used in the present invention is 90% or more, more preferably 95 or more.If the ethylene content in EVOH is less than 25 mol%, the heat resistance of EVOH itself is low. If the ethylene content exceeds 55 mol%, it is undesirable because coloring and decomposition occur during molding.
It is unfavorable because the gas barrier property of EVOT becomes obvious under the paper. There is no particular restriction on the degree of polymerization of EVOH.
Those having a melt index of 0.3 to 20 F/10 min at 190°C and a load of 2160 F can be used, and those having a melt index of O15 to 15 y/10 min are preferable.

The blend ratio of the blend of EV OH and multi-component copolymer polyamide, which becomes the intermediate layer of the laminated structure of the present invention, is EV
The range is 95 to 50% by weight of OH and 5 to 50% by weight of multi-component copolyamide, and more preferably 90 to 55% by weight of EVOH and 10 to 45% by weight of multi-component polyamide. If the blend amount of the multi-element copolymer polyamide is less than 5% by weight, the flexibility, impact resistance, and pinhole resistance of EV OH will not be sufficiently improved, so it is preferable. If it exceeds 50% by weight, the gas barrier properties will deteriorate significantly, which is not preferable.

The above EVOH and multi-component copolymer polyamide blend is
Because all of its constituent components are hydrophilic,
Its barrier properties against water vapor are low, and its inherent gas barrier properties are also affected by water absorption. The multilayer structure of the present invention has a sandwich structure in which a blend of E V OH and multi-component copolymer polyamide is used as an intermediate layer, and other non-polar thermoplastic resins are laminated on both sides, thereby achieving the above-mentioned water vapor resistance. It is something that has been overcome.

In the present invention, the non-polar thermoplastic resin laminated on both sides of the intermediate gas barrier layer is preferably a hydrophobic resin, examples of which include polyolefins such as polyethylene, polypropylene, and poly-4-methylpentene-1. , polystyrene, polycarbonate, acrylonitrile-butadiene-styrene copolymer, acrylonitrile-butadiene copolymer, acrylonitrile-styrene copolymer, and graft copolymerization of unsaturated carboxylic acid derivatives such as methacrylic acid and methyl methacrylate to these copolymers. In particular, polyethylene, polypropylene, poly-4-methylpentene-1
Polyolefins such as are suitable. In addition, if the adhesion between the intermediate gas barrier layer and the thermoplastic resin of the outer layer is insufficient, it is also possible to interpose an appropriate adhesive between the two layers or a polymer having adhesive properties for both layers as an adhesive layer. be.

Examples of polymers used as adhesive layers include modified polyethylene into which polar groups such as carboxylic acid and carboxylic anhydride groups have been grafted, modified polyolefins such as modified polypropylene, ethylene acrylic acid copolymers, and ethylene acrylic acid copolymers. Polyesters for adhesives, polyamides for adhesives, etc. can be mentioned.

The final shape of the multilayer structure of the present invention may be a film, sheet, or bottle, and the molding method thereof is not particularly limited, and may be molded by any suitable means such as melt molding. For example, multilayer films and sheets can be formed using known forming methods such as extrusion lamination, dry lamination, coextrusion lamination, and coextrusion sheet production. It can also be made into a squeezed container, a bag-like product by heat sealing or adhesion, or a stretched film or sheet using a uniaxial or biaxial stretching machine. Moreover, a multilayer bottle can be molded using a blow molding machine or an injection molding machine that combines a number of extruders and multiple dies according to the types of resin layers to be laminated.

The multilayered films, sheets, bottles, etc. obtained in this way have excellent gas barrier properties, water vapor permeability, pinhole resistance, and flexibility, and are also highly stable during melt molding, making them extremely practical. It is of high value and is suitably used as packaging material for foods, medicines, agricultural chemicals, cosmetics, detergents, etc.

<Example> The present invention will be explained in more detail by giving examples below. In addition, various characteristics in Examples and Reference Examples were measured by the following methods.

(1) Polymer melting point: PerkinElmer DSC
Endothermic peak humidity measured using a type IB thermal differential calorimeter at a heating rate of 20°C/min.

(Relative viscosity of 2-polyamide: according to JIS K6810.

(3) Tensile properties: According to ASTM D63g.

(4) Bending properties: According to ASTM D790.

(5) Water absorption of polymer: thickness 1ff, length 80MM
.

A square plate with a width of 80 ff was left in a constant temperature and humidity atmosphere of 20° C./65% RH, and the weight increase was calculated from the weight increase when the equilibrium weight was reached.

(0 Polymer melt retention stability: The melting point of the polymer (in the case of a blend, the melting point of the polymer with a higher melting point) + 5°C using the L205 type melt indexer manufactured by Takara Kogyo Co., Ltd., with a residence time of 10 minutes and The melt viscosity after 60 minutes was measured, and the rate of change was used as a measure of melt stability.

(7) Gas barrier properties + MOCON 0X-TR
Using ANI OO, the oxygen permeability of the formed film at 20° C. and 0% RH and 100% RH was measured.

(8) Water vapor transmission rate: According to JIS Z-0208.

Reference Example 1 (Polymerization of copolyamide polyamide) 4.0 kg of ε-cabrolactum, 5 kq of hexamethylenediamine-adipate A, 2.5# of hexamethylenediamine-sebacate and 3.0 kg of water were pressurized. The mixture was charged into a polymerization can, and the inside of the can was replaced with N2, followed by heating.

When the water vapor pressure reached 10 phantom/dG, the reaction was carried out with stirring for 2.0 hours while maintaining that pressure, and then the pressure inside the vessel was returned to normal pressure while removing water vapor for 5 hours, and then under a nitrogen stream for 1 hour. I let it react over time. After the polymerization was completed, the gut-like polymer was discharged from the discharge port at the bottom of the polymerization vessel, cooled with water, and pelletized using a pelletizer. As shown in Table 1, the copolyamide A1 obtained here had a melting point of 160°C, a number of methylene groups per amide group of 5.5, and a flexural modulus of 16.
,000#/d.

In addition, polyamide A2 obtained by changing the raw material composition and performing pressure melt polymerization similar to polyamide A1
The characteristic values of ~As were as shown in Table 1.

Table 1 Reference Example 2 (Blend of EVOH and polyamide) Ethylene content 32%, saponification rate 99% or more, melting point 181°C, 1
Melt index at 90℃ is 1.3 y/10
EVOH, which is a minute! -1 Various polyamides shown in Table 1 were prepared using a 30nd single screw extruder at a temperature of 230 shillings.
Melt kneading was carried out at °C. The compatibility between EVOH and nylon was evaluated by the melt gut transparency during extrusion, and the melt retention stability of the blend was evaluated by the method described above.

The results are summarized in Table 2.

Blends of multi-component copolyamide and EVOH having the various properties specified in the present invention all had good compatibility and excellent melt retention stability. On the other hand, a blend of nylon 6 and EVOH was disadvantageous in that severe thickening occurred during melt retention. Furthermore, a blend of polyamide A4 and EVOH is also unsuitable due to its large viscosity during melt retention, and a blend of polyamide A6 and EVOH is unsuitable for forming a uniform film due to insufficient compatibility between the two. I know this.

Ratio of melt viscosity when staying for 60 minutes and melt viscosity when staying for 10 minutes Examples 1 to 4 Using two extruders and a three-layer die, a thickness of 50μ in the middle was obtained.
A three-layer laminated sheet was molded, having a gas barrier layer of 100 µm thick and an outer layer of polyethylene of 100 µm thick on both sides. The gas barrier layer contains the EVOH of the present invention shown in Table 3.
/multi-component copolymer blend was used. All of the three-layer laminated sheets obtained here have excellent pinhole resistance and good appearance, and their gas barrier properties and water vapor barrier properties are also excellent as shown in Table 3, making them extremely useful packaging materials. It turned out to be the material.

<Effects of the Invention> As described above, a resin composition consisting of EVOH and a specific multi-component copolymer polyamide whose composition, amide group concentration, melting point, and flexural modulus are very strictly selected is used as an intermediate gas barrier layer. It has been found that a laminated structure having non-polar thermoplastic resin layers on both sides is an extremely excellent plastic packaging material that has excellent gas barrier properties and water vapor permeability, as well as good pinhole resistance and impact resistance. , it has become possible to obtain plastic packaging materials with high practical value.

Patent applicant Higashi Shikikai Co., Ltd.

Claims (1)

[Claims] Ethylene/vinyl alcohol copolymer with an ethylene content of 25 to 55 mol%, 90 to 50% by weight, and polyamide 1
0 to 50% by weight, and the polyamide contains (a) 20 to 45% by weight of caproamide units, (b) 25 to 40% by weight of hexamethylene adipamide units, and (c) hexamethylene diamine and a carbon number of 7 to 12. Consists of 15 to 55% by weight of at least one polyamide structural unit selected from polyamide structural units derived from dicarboxylic acids, undecaneamide, and dodecanamide, and satisfies the following characteristics (a) to (c). 1. A laminate structure comprising a resin composition made of multi-component copolymer polyamide as an intermediate layer, and other non-polar thermoplastic resins laminated on both sides of the layer. (a) Melting point: 120-180°C (b) Number of methylene groups per amide group: 5.3-6.
0 (c) Flexural modulus: 10,000 to 19,000 kg/
cm^3