JPH0387254A - Gas barrier laminate - Google Patents

Abstract

PURPOSE:To obtain a gas barrier laminate excellent in heat resistance by constituting said laminate from a specific copolyamide layer, a polyolefin layer and/or an ethylene/vinyl alcohol copolymer layer. CONSTITUTION:A laminate is constituted of a copolyamide layer, a polyolefin layer and/or an ethylene/vinyl alcohol copolymer layer. Said copolyamide is composed of a constituent unit derived from meta-xylenediamine being a diamine component and isophthalic acid (a) and 2 - 20C aliphatic dicarboxylic acid (b) being dicarboxylic acid components and constituted so as to satisfy the mol ratio of the dicarboxylic acid components of (a):(b) = 70:30 - 30:70. In this case, as 2 - 20 aliphatic carboxylic acid, adipic acid is most pref. with due regard to the gas barrier properties of obtained polyamide.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention applies retort treatment for the purpose of sterilization,
The present invention relates to a gas barrier laminate that does not deform even when filled with food or beverages at high temperatures, that is, has excellent heat resistance.

[Prior Art] In recent years, multilayer films, sheets, and containers made of various gas barrier resins and polyolefin resins have been widely used for packaging food and beverages that require gas barrier properties.

Such gas barrier resins include ethylene-vinyl alcohol copolymer (hereinafter sometimes abbreviated as EVOH), vinylidene chloride copolymer resin (hereinafter abbreviated as PVDC), and polymethaxylylene adipamide (hereinafter MXD).
・6) etc. are known.

Among these, EVOH has a severe deterioration in gas barrier properties in a high humidity environment or after retort treatment, and PVDC requires a special and expensive molding machine because it contains corrosive halogen.

Furthermore, MXD-6 has various problems such as being susceptible to shrinkage and deformation during retort processing, which limits its use.

[Problems to be Solved by the Invention] As described above, currently no practical laminate has been obtained that can withstand retort treatment for sterilization and has excellent gas barrier properties.

Under these circumstances, it is an object of the present invention to provide a laminate that has excellent heat resistance and maintains excellent gas barrier properties even after retort treatment.

[Means for Solving the Problems] In order to solve these problems, the inventors of the present invention have conducted intensive studies on synthetic resins having gas barrier properties, and have developed a copolyamide resin layer with a specific structure and a polyolefin layer. The present invention was achieved by discovering that a laminate containing an ethylene-vinyl alcohol copolymer layer as an essential component has excellent gas barrier properties and heat resistance.

That is, the gist of the present invention is a laminate comprising a copolyamide layer, a polyolefin layer and/or an ethylene-vinyl alcohol copolymer layer, wherein the copolyamide contains metaxylene diamine as a diamine component,
The dicarboxylic acid component consists of a structural unit derived from (a) isophthalic acid (b) aliphatic dicarboxylic acid having 2 to 20 carbon atoms, and the mo/I ratio of the dicarboxylic acid component (a): (b) - 70: 30-30: 70
A gas barrier laminate characterized by satisfying the following.

The present invention will be explained in detail below.

The meta-xylylene diamine constituting the diamine component unit of the copolyamide used in the present invention may contain a small amount of other diamines.

Other diamines in this case include aliphatic diamines such as tetramethylene diamine, pentamethylene diamine, hexamethylene diamine, and octamethylene diamine;
Examples include aliphatic diamines having a cyclic structure such as 3-bis(aminomethyl)cyclohexane and 1,4-bis(aminomethyl)cyclohexane, and aromatic diamines such as paraxylylenediamine and metaphenylenediamine. I can do it.

Further, the isophthalic acid constituting the dicarboxylic acid component unit of the copolyamide may contain a small amount of terephthalic acid.

Carbon number 2 or more used as a raw material for the polymerized polyamide
As the aliphatic dicarboxylic acid in No. 20, adipic acid is most preferable in consideration of the gas barrier properties of the obtained polyamide, but other dicarboxylic acids include succinic acid, glutaric acid, speric acid, pimelic acid, azelaic acid, and sebacic acid. Examples include acids and dodecanedioic acid.

Of all dicarboxylic acids in the copolyamide, the proportion of aliphatic dicarboxylic acids used is 30 to 70 mol%, preferably 40 to 60 mol%.

That is, if it is less than 30 mol %, the melt viscosity of the obtained polymer increases and the thermal stability during melting decreases, making it difficult to complete the polycondensation reaction and melt molding.

On the other hand, if it exceeds 70 mol %, the resulting polymer will have a low glass transition temperature and poor heat resistance, making the laminate more likely to deform during retort processing. Furthermore, the copolyamide may contain a lactam such as caprolactam or lauryllactam as a component within a range that does not impede the gist of the present invention.

In order to produce a polyamide having the composition described above, melt polymerization may be carried out from a nylon salt or an aqueous solution thereof according to a conventional method. During polymerization, a monobasic acid such as acetic acid or benzoic acid, or a monoacid base such as hexylamine or aniline may be added as a molecular weight regulator. It is also possible to add heat stabilizers such as sodium phosphite, phosphorous acid, sodium hypophosphite, hindered phenol, and other polymerization additives.

The copolyamide thus obtained has a relative viscosity (η"el) of 1.4 to 3.5 di/g, particularly preferably 1.7 to 2.5 dl/g.

Further, it is preferable to incorporate mica into the copolyamide because the gas barrier effect is further improved. The blending amount of mica is 5 to 80, especially 10 to 80, based on the copolyamide.
50% by weight is preferred.

Examples of the polyolefin resin used in the present invention include high density polyethylene, medium density polyethylene, low density polyethylene, or linear low density polyethylene (LLD).
Polyethylene such as PE); Polypropylene such as isotactic polypropylene, syndiotactic polypropylene, atactic polypropylene; Polybutene-1
Or poly-4-methylpentene-1 can be mentioned.

Also, copolymers of ethylene and other olefins such as ethylene-propylene copolymers, ethylene-vinyl acetate copolymers, ethylene-vinyl chloride copolymers1. Copolymers of olefins and other vinyl monomers such as propylene-vinyl chloride copolymers, ethylene-methacrylic acid copolymers, ionomers, etc. can also be used.

Furthermore, modified polyolefins can also be used. Examples of this modified polyolefin include:
Examples include polyolefins modified with unsaturated carboxylic acids such as maleic acid and itaconic acid, or derivatives thereof (including anhydrides and esters).

In the present invention, the ethylene-vinyl alcohol copolymer is
There is no particular restriction as long as it is manufactured by a known method of saponifying an ethylene-vinyl acetate copolymer, and it usually has an ethylene content of 25 to 50 mol%, a degree of saponification of 90% or more, and has high oxygen barrier properties. There is no problem as long as it is a resin, but a resin with a low gel content and excellent thermal stability is particularly preferred.

Although the present invention has the above copolyamide layer, polyolefin layer and/or ethylene-vinyl alcohol copolymer layer as essential components, it is of course possible to further laminate a known packaging resin layer.

Known packaging resins include polyethylene terephthalate (PET), polycarbonate (PC), polyamide, polystyrene (PS), polyvinyl chloride, and the like.

In the laminate of the present invention, any or all of the layers may be oriented along the Kerr axis or biaxially, and the orientation directions may be in the same direction or in different directions. Further, the laminate may be a laminate bottle.

The method for forming the laminate is to coextrude it into a film or sheet using multiple extruders, and furthermore, to stretch the film or sheet extruded in this way in the longitudinal and/or transverse directions. Method and/or method of molding using a deep drawing machine; multiple injection molding machines are used to plasticize multiple resins separately, and the resins are injected almost simultaneously into the same cavity of a mold to form two types and two layers. Or a method of molding a primary molded product having a multilayer structure such as 2 types and 3 layers or 3 types and 3 layers, and blow molding this primary molded product to form a multilayer container (laminated bottle); After forming a pipe-shaped primary formed product such as 2 types 2 layers or 2 types 3 layers using an extruder, one end is welded to form the bottom of the container, the other end is pressed and deformed to form the mouth, and then A method of making a multilayer container by blow molding; a method of manufacturing each film and sheet in advance and bonding them together under heat; a polyamide film,
Examples include a method of extruding and laminating a polyolefin resin and/or ethylene-vinyl alcohol copolymer onto a sheet. Polyamide resin temperature during molding is 200-30
The temperature is 0°C, particularly preferably 220-260°C. The temperature of the polyolefin resin is 130 to 300°C, particularly preferably 150 to 240°C. The temperature of the ethylene-vinyl alcohol copolymer is 185 to 260°C, particularly preferably 200 to 250°C. Various combinations are possible for the layer structure of the laminate of the present invention, but preferably polyamide layers (P, A) and polyolefin layers (PO).
A two-layer structure with PA as the inner or outer layer, a three-layer structure with PA as the middle layer and both outer layers as PO, or a two-layer structure with a modified polyolefin layer (modified PO) as the inner or outer layer.
PA as the middle layer and both outer layers as modified PO, PA/
Three-layer structures such as modified PO/PO, modified PO/P
A: 4-layer structure such as modified PO/PO, 5-layer structure such as PO/modified PO/PA/modified PO/PO, 2-layer structure with PA layer and EVOH layer as inner or outer layer. The layer structure is shown below in order from the inner layer: PA/Modified PO/EVOH/Modified PO/POSPO/Modified PO/P
A/Modified PO/EVOH/Modified PO/POSPO/Modified PO/PA/Modified PO/EVOH/Modified PO/PA/Modified PO/POSPO/Modified PO/PA/Modified PO/PO
/denatured p.

/EVOH/modified P O/P O, polyethylene terephthalate (PET)/modified PO/PA/modified P O/P
O, polycarbonate (PC)/modified PO/PA/modified PO/PO, polystyrene (PS)/modified PO/PA
/modified P O/P O.

PET/Modified PO/PA/Modified PO/EVOH/Modified PO/PO, PC/Modified PO/PA/Modified PO/EV
OH/modified PO/PO, PS/modified PO/PA/modified PO/EVOH/modified p.

/PO etc. Particularly in the case of retort packaging, if a copolyamide layer is provided on the inner layer side, the barrier properties will normally decrease under high humidity conditions due to water absorption during retort processing, but the copolyamide layer of the present invention provides a barrier property under high water absorption conditions. It is preferable because it exhibits its characteristics. The thickness of each layer is preferably 180 mm or more for a polyamide layer, 5 μm or more for a polyolefin layer, and 1 μm or more for an EVOH layer.

[Example code] The present invention will be specifically explained below using examples.

In addition, the following measured values in Examples were measured as follows.

◎ Relative viscosity of polyamide (ηrel): Measured at 25°C using 98% concentrated sulfuric acid at a concentration of 1 g/d+.

◎ Oxygen permeation rate: 0X-TRA manufactured by MODERN C0NTR0LS in the United States
Measured using N10150A.

◎Glass transition point (Tg): It was measured using a differential scanning calorimeter (DSC).

Example 1 A. Production of polyamide Meta-xylene diamine 26.8 kg Isophthalic acid 19.8 kg Adipic acid
11.5kg acetic acid
118g water
A nylon salt aqueous solution consisting of 58 kg was charged into an autoclave equipped with a stirrer, and after purging with nitrogen gas, the temperature was started to rise. When the pressure reached 2.5 kg/cn+', the autoclave valve was opened and the pressure was increased to 2.5 kg/cn+'. Concentration was started by distilling off water to maintain the concentration at cm 2 . The temperature was continued to rise during concentration, and when the internal temperature reached 190°C, the autoclave valve was closed and the temperature was further increased. Next, when the pressure reached 14 kg/cm', the autoclave valve was opened, and water was distilled out again to perform concentration while maintaining the pressure at 14 kg/cm2.

During this concentration, the temperature continued to rise, and when the internal temperature reached 230°C, the pressure was released to atmospheric pressure, and the reaction was continued for 1 hour. After the reaction was completed, the molten polymer was extracted from the bottom of the autoclave.

ηrel of the obtained polyamide = 2, 0ST g
-130°C.

8. 5 layers of 3 types (PP/adhesive layer/polyamide/adhesive layer/
P P) Production of film Using three extruders, the inner and outer layers are made of polypropylene (
PP: Manufactured by Mitsubishi Kasei, product name: Mitsubishi Polypro 4100Y)
A laminated film was prepared in which the intermediate layer was made of the copolyamide produced in A above, and the adhesive layer was made of modified polyolefin (manufactured by Mitsubishi Kasei ■, trade name: Tubatic AP196P). The thickness of each layer of this film was 30 μm for each PP layer, 10 μm for each copolyamide layer, and 10 μm for each adhesive layer.

Measurement of C1 oxygen permeation amount 23° C., 1o for the film produced in B.

When the oxygen permeation amount was measured in %RH, the results were as shown in Table 1.

Further, the film was subjected to retort treatment at 121° C. and 2 kg/cm 2 for 30 minutes, and the amount of oxygen permeation measured again was the same as before the retort treatment.

Example 2.3, Comparative Example 1 A copolyamide was produced by the same procedure as in Example 1, except that the amounts of isophthalic acid and adipic acid were changed to the mol% shown in Table 1, and then ground. followed by 3
A seed 5-layer film was produced and the amount of oxygen permeation was measured. The results are shown in Table 1. In the case of Comparative Example 1, the film was shrunk and deformed due to the retort treatment.

Comparative Example 2 In the production of Example 1.83 types of five-layer film, ethylene-vinyl alcohol copolymer resin CEVOH: manufactured by Nippon Gosei ■, trade name Soarnol E was used instead of copolyamide.
A similar film was produced using T). Table 1 shows the amount of oxygen permeation of the film before and after retorting.

Table Example 4 A copolymerized polyamide was produced in the same manner as in Example 1 except that the amounts of isophthalic acid and adipic acid were 500101%: 50 mo1%.

Subsequently, using three extruders, the inner and outer layers were made of polypropylene (PP: Mitsubishi Chemical, product name: Mitsubishi Polypro 410).
0M), the intermediate layer was the copolyamide produced above, and the adhesive layer was a modified polyolefin (manufactured by Mitsubishi Chemical Corporation,
A laminated sheet consisting of 3 types and 5 layers consisting of the product (trade name: TUBATIK APL96P) was prepared. The thickness of each layer of this sheet is inner layer P
P: 240 μm, outer layer P: 255 μm, intermediate layer copolymerized polyamide: 77 μm, 1 adhesive layer each 15 μm
Met.

The amount of oxygen permeation from the outer layer side to the inner layer side of the produced sheet was measured under conditions of 99% humidity on the inner layer side at 23°C and 60% humidity on the outer layer side at 23°C, and the results are shown in Table 2.

Further, the sheet was subjected to retort treatment with 12 L'Cl2 kg/am2 for 60 minutes, and then measured again, and the oxygen permeation amount was as shown in Table 2.

Comparative Example 3 A similar sheet was produced using an ethylene-vinyl alcohol copolymer resin (EVOH: manufactured by Nippon Gosei, trade name: Soarnol DC) in place of the copolymerized polyamide in the three-type, five-layer laminate sheet of Example 4. did. The thickness of each layer of this sheet was as follows: inner layer PP: 247 um, outer layer PP 22 [i7 μtas, intermediate layer EVOH: 65 μm, 1 adhesive layer, each 13 μm.

Table 2 shows the results of measuring the oxygen permeation amount of the sheet before and after retorting in the same manner as in Example 4.

Example 5 The same copolyamide as produced in Example 4 was coated with mica [trade name Suzolite Mica 200-KlF manufactured by Kuraray Co., Ltd.
After mixing 80% by weight, use a twin-screw extruder (Toshiba Machine TEN
-35) was used for extrusion kneading at 250°C.

Subsequently, in the same laminate sheet of 3 types and 5 layers as in Example 4, 30% by weight of the above mica was added in place of the copolyamide.
A similar sheet was produced using a copolymerized polyamide containing The thickness of each layer of this sheet is inner layer P: 24
2um, outer layer PP: 256μm, middle layer mica 30% by weight copolyamide containing = 77μo, adhesive layer each: 1
It was 5 μm.

The amount of oxygen permeation of the prepared sheet was measured in the same manner as in Example 4, and the results were as shown in Table 2. The gas barrier effect was improved by incorporating mica into the copolyamide.

Example 6 Using three extruders, the inner layer was made of the copolyamide produced in Example 4, the outer layer was made of polypropylene (PP: made by Mitsubishi Kasei, trade name: Mitsubishi Polypro 4100M), and the adhesive layer was made of modified polyolefin (Mitsubishi Kasei). Opening name: Tsubachik AP
A laminated sheet of three types and three layers consisting of L98P) was produced.

The thickness of this sheet is inner layer copolymer polyamidenia'Ht
ms adhesive layer 15 μm s outer layer PP: 510 μm.

After retorting the prepared sheet at 121°C and 2 kg/cm2 for 60 minutes, oxygen permeation from the outer layer side to the inner layer side was performed under conditions of 99% humidity on the inner layer side at 23°C and 60% humidity on the outer layer side at 23°C. The amount was measured for 3 months immediately after retorting, and the results are shown in Table 3.

Example 7 Using four extruders, the inner layer was made of the copolyamide produced in Example 4, and the outer layer and intermediate layer 1 were made of polypropylene (PP:
Mitsubishi Kasei ■ Split product name Mitsubishi Polyflo 4100M), intermediate layer 2 is made of ethylene-vinyl alcohol copolymer resin (EVO
H: manufactured by Nippon Gosei ■, trade name: Soarnol DC), and as an adhesive layer a modified polyolefin (manufactured by Mitsubishi Kasei ■, trade name: Tubatic API96P), a laminate sheet of four types and seven layers was prepared. The thickness of each layer of this sheet is: Inner layer copolymerized polyamide = 75μIIl / Adhesive layer: 15μm / Intermediate layer IPP:
287μIIl/adhesive layer: 15μm/intermediate layer 2 E V
OH: 58μm / Adhesive layer: 15ttm / Outer layer PP:
It was 130 μm.

The prepared sheet was subjected to 121'c retort treatment for 6
After 0 minutes, the inner layer side was heated to 99% humidity at 23°C, and the outer layer side was heated to 6°C.
The amount of oxygen permeation from the outer layer side to the inner layer side was measured for 3 months immediately after retorting under conditions of 0% humidity and 23°C, and the results were as shown in Table 3.

Table 2 [Effects of the invention] As explained above, the copolyamide layer of the present invention,
A laminate composed of a polyolefin layer and/or an ethylene-vinyl alcohol copolymer layer has good gas barrier properties, aroma retention properties, and heat resistance, and is particularly excellent in gas barrier properties after retort processing. It is extremely useful as a packaging material for food and medical products.

Claims (1)

[Claims] A laminate comprising a copolyamide layer, a polyolefin layer and/or an ethylene-vinyl alcohol copolymer layer, the copolyamide containing metaxylene diamine as a diamine component and (
a) Isophthalic acid (b) Consists of a structural unit derived from an aliphatic dicarboxylic acid having 2 to 20 carbon atoms, and the molar ratio of the dicarboxylic acid component is (a):(b) = 70:30 to
A gas barrier laminate characterized by satisfying a ratio of 30:70.