JPH02270550A - Coextruded laminating material excellent in oxygen barrier property and production of laminating material thereof - Google Patents

Abstract

PURPOSE:To obtain the coextruded laminating material which is excellent in oxygen barrier property and capable of long-term preservation of the contents by laminating both a resin layer which has oxygen barrier property and consists of the saponified material (EVOH) of an ethylene-vinyl acetate copolymer and a specified polyester resin layer by coextrusion. CONSTITUTION:The coextrusion laminating material of EVOH is produced by laminating both a resin layer having oxygen barrier property which consists of at least EVOH and a polyester resin layer having 0.75 - 0.90 intrinsic viscosity (I.V.) by coextrusion. EVOH incorporating 20 - 60mol.% ethylene and having >=96% degree of saponification and 0.15 - 1.5 (cc.20mum/m<2>.day.atm) oxygen permeability is preferably utilized. When I.V. of polyester resin is value exceeding 0.9, polyester resin shows high viscosity at the temp. lower than 260 deg.C and thereby the motor of an extruder is overloaded. Therefore polyester resin is necessarily extruded at the temp. higher than 260 deg.C. Accordingly EVOH is allowed to gel. Further when I.V. is value smaller than 0.75, polyester resin shows low viscosity and thereby control of thickness of extruded polyester resin film is made difficult and film formability is deteriorated.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a coextruded laminate material, particularly a coextruded laminate material for packaging materials that has excellent oxygen barrier properties and transparency, and does not adsorb fragrance components, etc. Regarding.

[Prior art] Conventionally, saponified ethylene-vinyl acetate copolymer (hereinafter referred to as
It is written as rEVOHJ. ) is used as a packaging material because it has excellent flexibility, adhesiveness, toughness, transparency, etc., and also has excellent gas barrier properties against oxygen and the like.

However, EVOH has slightly inferior heat sealing properties,
It is also known that moisture deteriorates its oxygen barrier properties, and especially when used in food packaging materials, the oxygen barrier properties are significantly degraded by water vapor from the contents, etc.
Problems also arose from the perspective of food preservation.

Therefore, in order to improve the above-mentioned drawbacks, a method has been used in which a polypropylene heat-sealing resin is laminated by coextrusion as an inner or outer layer, especially an inner layer, of the EVOH layer.

[Problems to be Solved by the Invention] In the method of laminating and using the polypropylene heat-sealable resin described above, the polypropylene inevitably contains additives such as stabilizers and antioxidants; This kind of laminated EV
OHal fat was not particularly suitable as a packaging material for contents containing flavor components, such as food contents.

For this reason, a method has been proposed in which a polyester resin that does not have the above drawbacks is used by laminating it on EVOH instead of polypropylene. However, when laminating polyester resin onto EVOH by coextrusion, EVOH melts at a relatively low temperature, but polyester resin generally does not melt at a relatively low temperature of A, so the extrusion temperature is set to the melting temperature of the polyester resin. Must be carried out at correspondingly high temperatures. For this reason, when extrusion lasts for a relatively long time, EVOH remains in the coextruder flow path, resulting in 7% more EVOH than necessary.
EVOH exposed to m (for example, at a temperature of 240° C. or higher for 30 minutes or longer) undergoes a crosslinking reaction and gels to become an insoluble gel. The resulting molded product as a packaging material had poor appearance, and had problems such as uneven molding during vacuum forming and reduced oxygen barrier properties.

Therefore, the object of the present invention is to provide an EVOH coextruded laminate material that has excellent oxygen barrier properties and that, when used as a packaging material, enables long-term storage of the contents without adsorbing fragrances or flavor components of the contents. An object of the present invention is to provide a method for manufacturing a laminated material.

Another object of the present invention is to provide an EVOH coextrusion laminate material that provides a packaging material with excellent transparency and design, and a method for producing the laminate material.

A further object of the present invention is to provide a method for producing an EVOH coextruded laminate material that can prevent EVOH from gelling and can be easily extruded without making any specific modifications to processing equipment.

[Means for Solving the Problems] In view of the above-mentioned problems, the present inventors have conducted intensive research and found that the above-mentioned object of the present invention is to provide at least an oxygen barrier property made of a saponified ethylene-vinyl acetate copolymer. A coextruded laminated material formed by laminating a resin layer and a polyester resin layer having an intrinsic viscosity of 0.75 to 0.90 by coextrusion, and an oxygen barrier resin consisting of at least a saponified ethylene-vinyl acetate copolymer and an extreme This can be achieved by providing a method for producing a coextruded laminated material, characterized in that a polyester resin having a viscosity of 0.75 to 0.90 is fused and coextruded at a temperature of 260°C or lower. I found it.

The present invention will be explained in more detail below.

Various known EVOHs can be used as the EVOH used in the present invention, but preferably EVOH has an ethylene content of 20
~60 mol%. Further, those having a saponification degree of 96% or more are also preferable, and those having a saponification degree of 99% or more are even more preferable. Oxygen permeability is 0.15 to 1.5 (cc-20μ/f
-day -atm).

The polyester resin used in the present invention is a copolymer of a polybasic acid and a polyhydric alcohol, and such a polybasic acid preferably contains terephthalic acid as a main component.
Moreover, as the polyhydric alcohol, one containing ethylene glycol as a main component is preferable. The above polybasic acids and polyhydric alcohols each contain other polysalts I as comonomer components.
I and other polyhydric alcohols.

Other polybasic acids that can be included as comonomer components in the polybasic acid include aromatic dicarboxylic acids such as isophthalic acid, naphthalene dicarboxylic acid, diphenyl dicarboxylic diphenoxyethane dicarboxylic acid, diphenyl ether dicarboxylic acid, and diphenyl sulfone dicarboxylic acid; hexahydro Alicyclic dicarboxylic acids such as terephthalic acid and hexahydroterephthalic acid; Aliphatic dicarboxylic acids such as adipic acid, cepatic acid and azelaic acid: p-β-hydroxybenzoic acid, p-oxybenzoic acid, ε-oxycaprone Oxyacids such as acids; trimellitic acid, trimesic acid, 3.3
Examples include aromatic polybasic acids such as ',5,5'-tetracarboxydiphenyl; aliphatic polybasic acids such as butanetetracarboxylic acid; and oxypolycarboxylic acids such as tartaric acid and malic acid.

Further, other polyhydric alcohols that can be contained as comonomer components in the polyhydric alcohol include trimethylene glycol, tetramethylene glycol, hexamethylene glycol, decamethylene glycol, neopentylene gellicol, diethylene glycol, 1.1- Cyclohexane dimethylol, 1,4-cyclohexane dimethylol, 2,2-bis(4-β-hydroxyethoxyphenyl)propane, bis-(4-β-hydroxyethoxyphenyl)sulfonecyclohexane, 1゜4-bis(β)
-hydroxyethoxy)benzene, 1,3-bis(β-
Examples include glycols such as hydroxyethoxy)benzene; polyhydric alcohols such as phloroglycine, 1,2°4.5-tetrahydroxybenzene, glycerin, trimethylolethane, trimethylolpropane, and pentaerythritol.

Furthermore, in the present invention, the polyester resin may contain other additives than those mentioned above. Examples of such additives include additives that increase the rate of crystallization, lubricants, antiblocking agents, stabilizers, antifogging agents, pigments, and the like. Examples of additives that increase the crystallization rate include polyolefins such as low-density polyethylene, high-density polyethylene, linear low-density polyethylene, and polypropylene; carbon black;
Inorganic powders such as silica and powdered glass are used.

In the present invention, the intrinsic viscosity (
1, V, ) must be within the range of 0.75 to 0.90. 1. If V exceeds 0.9, 26
At temperatures lower than 0°C, the viscosity is high and there are problems such as excessive load on the extruder motor, so it is necessary to extrude at a high temperature of 260°C or higher.

Therefore, the EVOH gels as described above, and the object of the present invention cannot be achieved. Also, 1. When V is lower than 0.75, the low viscosity makes it difficult to control the extrusion film thickness of the polyester resin, resulting in poor film formation.

In the present invention, the intrinsic viscosity is expressed as a value in a mixed solvent (30°C) of phenol and tetrachloroethane in a weight ratio of 50:50.

As the polyester resin used in the present invention, polyethylene terephthalate (PET) is preferable, and specifically the following ones are used.

Polyester Manufacturer 1. v
.

TEN ITE 9902 Eastman Chemical■
085NEH2050 Unideca 1111
0.78NEH2070 Unideca ■
0.88RT553C Nippon Unibet (II
O, 83J125 Three piece PET resin - ○, 19 The thickness of the above EVOH layer can be arbitrarily adjusted, but is, for example, 20 to 100 μm. Further, since the polyester resin has a role of maintaining the mechanical strength of the entire laminated material, it has a thickness of, for example, 0.1 to 1111ffi.

The laminated material of the present invention is obtained by co-extruding the above-mentioned EVOH and polyester resin, but in the present invention, it is also possible to further provide other resin layers such as an adhesive layer as necessary. Examples of the resin used for such an adhesive layer include unsaturated carboxylic acid-modified polyolefins, and examples of the polyolefins include polyethylene, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, Examples include ethylene-α olefin copolymers. Here, unsaturated carboxylic acid modification means copolymerization or graft polymerization with carboxylic MM1 acid anhydride groups and derivatives thereof. acid, maleic acid, fumaric acid, methacrylic anhydride, maleic anhydride, ethyl methacrylate, glycidyl acrylate, diglycidyl methacrylate, and the like.

The thickness of the adhesive layer is arbitrary, but preferably 20 to 50L.
It is ll.

The layer structure of the laminate of the present invention is EVOH/polyester, polyester/EVOH/polyester, EVOH
/Adhesive layer/Polyester, polyester/Adhesive layer/EV
Although various configurations such as OH/adhesive layer/polyester are possible, the configuration of polyester/adhesive layer/EVOH/adhesive layer/polyester is particularly preferred from the viewpoint of interlayer adhesion and protection of the EVOH layer. .

In the present invention, each of the EVOH and one polyester resin in a molten state is formed into a film along a flow path, and
It is preferable to form a multi-layered laminated material by merging them before or within the die at a temperature of ℃ or below and then coextruding them from the die, but of course it is also possible to merge them after extruding from the die. It is.

In the present invention, the methods shown in FIGS. 1 to 3 are preferably used as the coextrusion method.

Figures 1 to 3 are schematic partial process diagrams showing one example of the method of the present invention. Figure 3 shows the result using the die-outside merging multi-slot method. That is, in FIGS. 1 to 3, EVOH and polyester resin are each melted in an extruder 1, passed through a feed block 2, and extruded from a T-die 3. At this time, in Fig. 1, the above two molten resins are combined at the X part of the feed block section in front of the die, and then extruded from the T-die, and in Fig. 2, the two molten resins are combined at the X part in the T-die. After merging the molten resins, they are extruded. In FIG. 3, the molten resins are merged at the X section immediately after being extruded.

The temperature at the confluence of the above two molten resins should be 260°C or lower, preferably 255 to 260°C, to prevent gelation. If a resin layer other than the above two resins is included, this resin temperature It is also necessary to keep the temperature below 260°C. Furthermore, it is necessary to maintain the temperature below 260°C even after joining.

However, before merging, resins other than EVOH were heated to 260°C.
Higher temperatures are also possible. However, since it is difficult to directly measure the temperature at the confluence, it is sufficient if the temperature at the highest temperature point upstream of the confluence is 260° C. or less.

The laminated material of the present invention formed as described above has, for example, a sheet-like or cylindrical shape, and in the case of a sheet-like shape, it can be molded into a tray shape and used as a packaging material. When used as such a packaging material, the laminated material of the present invention preferably has a polyester layer on the inside in order to protect EVOH and maintain oxygen barrier properties.

Contents suitable for the packaging material using the laminated material of the present invention are mainly contents containing fragrances, and in particular, foods such as jellies, fruit pickled in syrup, curry, and miso can be mentioned.

The method for sealing the above packaging material is metal foil or EVOH.
Contains barrier materials such as barrier plastic films such as paper/aluminum foil/PET (low melting point copolyester), biaxially oriented PET/EVOH/PET.
A method of heat-sealing a lid having a structure such as (ffi melting point conjugated IJ ester), or a double seaming method in which an aluminum or iron lid 4 is rolled together with a container flange as shown in Fig. 4. This method is possible.

[Example] The present invention will be described in more detail below based on Examples. Needless to say, the present invention is not limited to the following examples.

Polyethylene terephthalate (as shown in Table 1) (P
ET) and maleic anhydride-variable ethylene/vinyl acetate copolymer Modic E-300H (Mitsubishi Yuka ■) with a melt index of 2.543/1G (adhesive resin),
Ethylene content 32 mol%, melt index 1.3
13/10 minutes EVOI- (EVAL FIOI (Kuraray ■) and layer structure PET (450μ) / Adhesion II (
25μ)/EVOH (50μ)/JIB layer (25μ)/
Example 1 by coextruding PET (450μ)
-6 and Comparative Examples 1-6 were conducted. PE as an extruder
65eiφ for T, adhesive resin and EVOH
PET extrusion conditions are shown in Table 1.

Further, as shown in FIG. 5, the extrusion was carried out using a die-confluence feedblock method, and the temperature of each resin was measured using a thermometer 7. The temperature of EVOH and adhesive layer is 230°C,
PET was conducted at different temperatures as shown in Table 1. Note that although there is no heater after the measurement point, the temperature at the merging point and after the merging point never becomes higher than the measured PET temperature. In each example and comparative example, EVOH
Gel generation status and film formation suitability were evaluated as follows.

The results are shown in Table-1.

Gum Takumi I EVOI- (The time until the gel flows out after the start of extrusion was measured.

The contact distance with the cooling roll was measured when the molten PET sheet extruded from the T-die sags in front of the cooling roll and partially contacts the cooling roll. Furthermore, the appearance of unevenness and wrinkles due to such contact was visually evaluated.

As shown in Table 1, the temperature of each resin at the merging section can be measured by inserting a resin thermometer 7 into the resin flow path and directly measuring the temperature of the molten resin, as shown in Figure 5 as an example. As described above, according to the method of the present invention, no EVOH gel was generated for more than 200 hours, and the resulting laminated material had a good appearance without unevenness or wrinkles.

[Effects of the Invention] As explained in detail above, the method of the present invention has excellent oxygen barrier properties, and when used in packaging materials, the contents can be preserved for a long time without adsorbing fragrances and flavor components of the contents. An EVOH coextruded laminate material can be provided that allows for.

Further, by the method of the present invention, it is possible to provide an EVOH coextrusion laminate material that provides a packaging material with excellent transparency and excellent design.

Furthermore, the method of the present invention can prevent EVOH from gelling without making any specific modifications to the processing equipment, and can be easily extruded.

[Brief explanation of drawings]

1 to 3 are schematic partial process diagrams showing one example of the manufacturing method of the present invention, FIG. 4 shows a cross-sectional view of double seaming, and FIG. 5 shows various resin temperatures in the example. FIG. 2 is a schematic cross-sectional view showing a measuring method. 1... Extruder 2... Feed block 3.
・・T die 4・・Lid body

Claims (2)

[Claims] (1) At least an oxygen barrier resin layer made of a saponified ethylene-vinyl acetate copolymer, and an intrinsic viscosity of 0.75.
A coextruded laminate material formed by laminating a polyester resin layer of ~0.90 by coextrusion. (2) At least an oxygen barrier resin consisting of a saponified ethylene-vinyl acetate copolymer and an intrinsic viscosity of 0.75 to 0.
．． A method for producing a coextruded laminate material, which comprises coextruding a polyester resin of No. 90 at a temperature of 260° C. or lower.