JPH03169546A - Laminate - Google Patents

Abstract

PURPOSE:To obtain a material for manufacturing a vessel, which can prevent the deterioration of oxygen gas barrier properties by retort bacteria, and can be produced at low cost and has the excellent shelf stability of contents, by using an ethylene-vinyl alcohol copolymer layer as an intermediate layer and forming propylene group polymer mixture layers on both surface layers through adhesive resin layers on both sides of the intermediate layer respectively. CONSTITUTION:An ethylene-vinyl alcohol copolymer layer acquired by saponifying at least 90% of an ethylene-vinyl acetate copolymer, the rate of copolymerization of ethylene of which is 15-65mol%, is employed as an intermediate layer. Layers, the rate of the copolymer of ethylene of which is made smaller than the ethylene-vinyl alcohol copolymer constituting the intermediate layer, are shaped on both sides of the intermediate layer as protective layers through adhesive resin layers, and propylene polymer mixture layers are formed on both surface layers through the adhesive resin layers on both sides of these ethylene-vinyl alcohol copolymer layers respectively, thus manufacturing a laminate.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a material used in containers for retort foods, etc., which has high gas barrier properties even after retort sterilization, and has excellent preservability of contents. The present invention provides a laminate suitable for retort sterilization materials.

[Conventional technology]

Traditionally, packaging materials for foods, pharmaceuticals, etc. have been required to have excellent gas barrier and water vapor barrier properties to prevent deterioration due to oxidation of the packaged food, scattering of aromas, and penetration of penetrating liquids. has been done.

For this reason, a laminated material made of aluminum is generally used as a laminated material for retort sterilization. Laminated materials using aluminum foil are preferable from the viewpoint of food preservation because they have excellent gas barrier properties and water vapor barrier properties.

On the other hand, many laminate materials using ethylene-vinyl alcohol copolymers with excellent gas barrier properties have been proposed as resins. It is known that the gas barrier properties of this ethylene-vinyl alcohol copolymer change depending on the temperature, and that the gas barrier properties are significantly reduced at high humidity. For this purpose, low-humidity hydrophobic polymeric substances such as ethylene polymers and propylene polymers are generally laminated on both sides.

By the way, the reason why ethylene-vinyl alcohol copolymer has excellent gas barrier properties (particularly oxygen barrier properties) is that its intermolecular and intramolecular hydrogen bonds are stronger than those of other polymeric substances. Not, but
One example is that the symmetry and polarity of the molecular chains contribute synergistically.

On the other hand, when the water content of the ethylene-vinyl alcohol copolymer increases, the adsorbed water molecules first bond to hydrophilic hydroxyl groups (OH groups), and as the water content increases, the adsorbed water moves between molecules. It is believed that the hydrogen bonds in the molecule are broken, allowing the molecular movement necessary for oxygen molecule diffusion, resulting in an increase in the oxygen permeability coefficient.

This situation. If the water content increases further from the state, free water will exist in addition to adsorbed water, and as a result, the intermolecular forces will further weaken, and the oxygen permeability coefficient will become larger due to the plasticizing effect on molecular motion. It is being

When such an ethylene-vinyl alcohol copolymer is used as a packaging container for retort sterilization, a tank of polyolefin resin such as ethylene polymer or brobylene polymer is used to provide moisture-proofing and heat-sealing properties. Among them, propylene polymers are most suitable for retort sterilization because of their heat resistance to hot water or steam at about 20°C.

[Problem to be solved by the invention]

When aluminum foil is used as the laminate for retort sterilization, it cannot be shaped and therefore cannot be used as a rigid container.

In addition, in the case of propylene-based polymers, when heated and pressurized during retort sterilization, the water vapor permeability increases by 15 to 20 times compared to at room temperature, so the water content of ethylene-vinyl alcohol copolymers rapidly increases. increases, and the oxygen gas barrier property decreases significantly.

Although the oxygen gas barrier properties of multilayer containers whose oxygen gas barrier properties have been significantly reduced by retort sterilization can be restored by storage after retort sterilization, it takes a long period of time, and the use of multilayer containers is limited to relatively low oxygen tolerance against deterioration. It is limited to large contents and items with a short shelf life.

Three main methods have been proposed to improve these problems. The first method is to impart hot water resistance to the ethylene-vinyl alcohol copolymer itself, and the second method is to increase the release rate of water absorbed by the ethylene-vinyl alcohol copolymer, thereby improving its oxygen gas barrier properties. The third method is to speed up the recovery, and the third method is to provide a protective layer on both sides of the ethylene vinyl alcohol copolymer layer to prevent water from entering, thereby suppressing the deterioration of the oxygen gas barrier property.

In the first method, water resistance and hot water resistance are improved by increasing the ethylene content of the ethylene-vinyl alcohol copolymer. However, as the ethylene content increases, the original oxygen gas barrier properties are significantly reduced, making it impractical.

In addition, in the second method, by making the thickness of the outer brobylene polymer layer thinner than the thickness of the inner propylene polymer layer, ethylene-vinyl alcohol co-ffi during storage after retort sterilization is reduced. This will speed up the release of absorbed water to the outside air and speed up the recovery of oxygen gas barrier properties. However, in this method, since the outer brobylene polymer layer is thin, the ethylene-vinyl alcohol copolymer layer absorbs a large amount of water during retort sterilization.

For these reasons, even if the degree of decrease in oxygen gas barrier properties is large and the rate of recovery is fast, the cumulative amount of permeated oxygen can only be slightly reduced in the long term. Depending on the contents, this may accelerate deterioration due to the high oxygen concentration.

A representative example of the third direction is JP-A-57-17074.
As proposed by No. 8, by protecting both sides of the ethylene-vinyl alcohol copolymer layer with a layer containing a desiccant, water that enters during retort sterilization is captured,
This is a method of reducing the increase in water content of the ethylene-vinyl alcohol copolymer layer and suppressing the deterioration of oxygen gas barrier properties. With this method, deterioration in oxygen gas barrier properties due to retort sterilization can be suppressed. On the other hand, it contains a desiccant (
(10 to 20%), which naturally causes problems in recyclability and increases the cost of the container.

Based on these facts, an object of the present invention is to provide a multilayer container that can be retorted and sterilized using a conventional ethylene-vinyl alcohol copolymer as an oxygen gas barrier layer, and to prevent the deterioration of the oxygen gas barrier property due to retort sterilization. Materials (laminates) for manufacturing containers that can be manufactured at low cost using conventional processing methods and have good shelf life for their contents.
Our goal is to provide the following.

[Means and effects for solving the problems] According to the present invention, these problems can be solved by saponifying at least 90% of an ethylene-vinyl acetate copolymer having an ethylene copolymerization ratio of 15 to 65 mol%. The obtained ethylene-vinyl alcohol copolymer layer having a low copolymerization ratio is used as an intermediate layer, and the ethylene-vinyl alcohol constituting the intermediate layer is provided as a protective layer with an adhesive resin layer on both sides of the intermediate layer. A copolymer layer of ethylene is provided rather than a copolymer, and a brobylene polymer mixture layer is provided on both surface layers with adhesive resin layers on both sides of these ethylene-vinyl alcohol copolymer layers. The mixing ratio of the petroleum resin to i00 parts by weight of the propylene polymer in the propylene polymer mixture layer is 10 to 1.
00 parts by weight. The present invention will be specifically explained below.

(A) Propylene polymer In the present invention, the propylene polymer constituting the brobylene polymer mixture layer, which is both surface layers, is at least 70% by weight of brobylene homopolymer or brobylene.
Random or block copolymers with ethylene or other α-olefins containing ethylene or other α-olefins can be mentioned, and when a container is obtained by thermoforming, such as vacuum forming, a good product can be obtained by mixing an ethylene polymer with a propylene polymer. is obtained. At this time, the mixing ratio of the ethylene polymer to the total amount of the propylene polymer and the ethylene polymer is usually at most 50% by weight (preferably 1 to 50% by weight, preferably 1 to 40% by weight). %). The melt index of these propylene polymers [JIS K-7
According to 210, the conditions in Table 1 are 14 te measurement, hereinafter rM
I (1) J] is 0.005 to 80 g/t
o minutes, preferably 0.01 to Bog/10 minutes, and particularly preferred is a propylene polymer of 0.01 to 40 g/10 minutes. M I (1) is 0.005g/
If a propylene-based polymer is used for less than 10 minutes, the molding processability to obtain a container is poor, a good container cannot be obtained, and
When using a propylene polymer that exceeds g/10 minutes,
The impact resistance of the container is weak and the container is not suitable for practical use.

The rigidity of the laminate can be improved by adding an inorganic filler described later to the propylene polymer mixture in the present invention. In this case, when forming a container and filling the container with food, from the viewpoint of food hygiene, a brobylene polymer containing no inorganic filler is added inside the inner layer of the brobylene polymer containing an inorganic filler. Preferably, a layer of mixture is provided.

The inorganic filler is generally widely used in the fields of synthetic resins and rubbers.

These inorganic fillers are preferably inorganic compounds that do not react with oxygen and water and do not decompose during kneading and molding.

Examples of the inorganic filler include oxides of metals such as aluminum, copper, iron, lead, nickel, magnesium, calcium, barium, zinc, zirconium, molybdenum, silicon, antimony, and titanium, and hydrates (hydroxides) thereof; It is broadly classified into compounds such as sulfates, carbonates, and silicates, their double salts, and mixtures thereof. A representative example of the inorganic prefiller is described in Japanese Patent Application No. 124481/1981.

Among these inorganic fillers, those in powder form have a diameter of 3
01 or less (suitably IOZZII+ or less) is preferable. In addition, fibrous materials have a diameter of 1 to 500 wrl (
The length is preferably 1 to 300) and the length is 0. i~8.0
+n+* (preferably 0.1 to 5 m1) is desirable.

Furthermore, the flat plate-like one is 30 or less (preferably {OII
n or less) is preferred. Among these inorganic fillers, those in the form of flat plates (flake) and those in the form of powder are particularly suitable.

The mixing ratio (content ratio) of the inorganic filler to 100 parts by weight of the total amount of the propylene polymer or the propylene polymer and the ethylene polymer is at most 70 parts by weight,
The amount is preferably 5 to 65 parts by weight, particularly preferably 5 to 60 parts by weight.

If the composition ratio of the inorganic filler to 100 parts by weight of the total amount of brobylene-based polymer or propylene-based polymer and ethylene-based polymer exceeds 70 parts by weight, the impact resistance of the resulting container will significantly decrease, making it impractical for practical use. Only unsuitable laminates are obtained.

(B) Ishiura Resin Furthermore, the petroleum resin used in the present invention is usually a petroleum resin contained in the cracked oil fraction that is produced as a by-product from an ethylene plant that produces ethylene, propylene, etc. by steam cracking petroleum (for example, naphtha). It is obtained by polymerizing olefins and monoolefins without decomposing or separating them. Among the cracked oil fractions, aliphatic petroleum resins whose main raw materials are C5 fractions, aromatic Ishiura resins whose main raw materials are C9 fractions, and C5-C9 copolymer petroleum resins whose raw materials are both of them. These include cyclopentadiene-based petroleum resins produced by polymerizing dicyclobentadiene obtained by dimerizing cyclopentadiene contained in the C5 fraction of naphtha cracked oil, and terpene resins that do not contain polar groups.

These petroleum resins are industrially produced and used in a wide variety of fields, and their production methods and structural formulas are well known.

When producing these petroleum resins, monomers such as styrene, C4-C5 conjugated dienes, vinyl acetate, acrylic esters, and maleic anhydride may be copolymerized in the polymerization step.

In the present invention, these petroleum resins may be used as they are, but hydrogenated ones are preferably used. The hydrogenation rate is preferably 80% or more, particularly 90% or more.

Further, among these petroleum resins, those having a glass transition point of 50°C or higher are preferred, and those having a glass transition point of 60°C or higher are particularly preferred.

In addition, terpene resins that do not contain polar groups are terpene resins that do not have polar groups that are composed of polar groups such as hydroxyl groups, aldehyde groups, ketone groups, carboxyl groups, halogen groups, and sulfone groups, as well as modified groups thereof, i.e. (C5H8). hydrocarbons and modified compounds derived therefrom. Typical compounds include:
Examples include pinene, carene, silman, ocimene, limonene, terbinolene, terbinene, sabinene, trisiphrene, etc. In the case of the present invention, hydrogenation ratios of 80% or more are desirable, and 90% or more are particularly preferred.

(C) Mixing ratio and production of mixture The mixing ratio of petroleum resin to 100 parts by weight of the propylene polymer is 1
The amount is 0 to 100 parts by weight, preferably 10 to 80 parts by weight, and particularly preferably 10 to 60 parts by weight. The mixing ratio of petroleum resin to 100 parts by weight of propylene polymer is 1
If it is less than 0 parts by weight, the barrier properties after retort treatment will deteriorate. On the other hand, if it exceeds i00 parts by weight, the mechanical, thermal and chemical properties of the laminate will be poor.

The propylene polymer mixture of the present invention may be composed of a propylene polymer and a petroleum resin as described above.

Further, other resins may be mixed with these resins. In this case, the proportion thereof is at most 60 parts by weight based on 100 parts by weight of the propylene polymer. As other resins, olefin polymers other than propylene polymers (for example, high-density ethylene polymers) and petroleum resins having polar groups are desirable.

To produce the propylene-based polymer mixture of the present invention, the propylene-based polymer and Ishiura resin or other resins are uniformly mixed at a resin temperature not exceeding 270°C, preferably 180 to 240°C. After that, it can be manufactured by discharging it from a nozzle. In addition,
If the resin is mixed at a temperature exceeding 270° C., a laminate having the excellent properties aimed at by the present invention cannot be obtained.

(D) Ethylene-vinyl alcohol copolymer,
In the present invention, the ethylene-vinyl acetate copolymer which is the starting material for the ethylene-vinyl alcohol copolymer used for the intermediate layer and the protective layer has an ethylene copolymerization ratio of 15 to 65 mol%, 15 to 60 mol% is preferred. In particular, the degree of saponification is 90% or more, 93%
A ratio of 95% or more is desirable, and a ratio of 95% or more is particularly preferred.

Furthermore, melt index [JIS K-721.0
According to the temperature is 210℃ and the load is 2.1Gkg.
(hereinafter referred to as rM I (2) J) is usually 0.1
~50 g/10 minutes, preferably 0.1 to 20 g/10 minutes, particularly preferably 0.5 to 20 g/10 minutes.

If an ethylene-vinyl alcohol copolymer having an M I (2) of less than 0.1 g/10 minutes is used, moldability will not be good when producing a multilayer laminate described later. On the other hand, 20g/10
If an ethylene-vinyl alcohol co-ffl mixture exceeding 10% is used, extrudability will be poor when producing a multilayer laminate, and a good laminate will not be obtained.

Further, in the present invention, an ethylene-vinyl acetate copolymer having an ethylene copolymerization content of 5 to 65 mol% is used at least 9
An ethylene-vinyl alcohol copolymer layer obtained by saponifying 0% is used as an intermediate layer, and an adhesive resin layer is placed on both sides of the intermediate layer as a protective layer to form the ethylene-vinyl alcohol copolymer. Ethylene-vinyl alcohol with a lower ethylene copolymerization ratio than
(A polymer layer is provided. The difference in the copolymerization ratio of ethylene in the ethylene-vinyl alcohol copolymer used for the intermediate layer and the protective layer is preferably 1 to 30 mol%, preferably 3 to 20 mol%, Particularly suitable is 4 to 15 mol%.

If the difference in the copolymerization ratio of ethylene-vinyl alcohol is less than 1 mol% or if the ethylene-vinyl alcohol copolymer of the protective layer has a higher copolymerization ratio of ethylene than that of the intermediate layer, the intermediate The ethylene-vinyl alcohol copolymer layer tends to be insufficiently heated, and problems such as cracks tend to occur in the intermediate layer, which is important for gas barrier properties. On the other hand, if it exceeds 30 mol%, the melting point difference between both ethylene-vinyl alcohol copolymers is 50°C.
For this reason, it is difficult to obtain a good container even if heat-formed.

(E) Adhesive resin and adhesive Further, in the present invention, the adhesive resin used for adhering these layers to each other can be obtained by graft polymerizing an unsaturated carboxylic acid or a derivative thereof to an olefinic polymer. That's what you get. This graft polymerization is generally carried out in the presence of a radical initiator as described below.

The olefin polymer may be an ethylene homopolymer, ethylene and carbon atoms having at most 12 carbon atoms (preferably 3 carbon atoms).
-8) with α-olefin (copolymerization ratio of α-olefin is usually 20% by weight or less, preferably 15% by weight or less, preferably 10% by weight or less) and ethylene as the main component. (generally 65% by weight or more, preferably 70% by weight)
(weight% or more) monomers having polar groups [e.g.
Examples include copolymers with vinyl acetate, (meth)acrylic acid or alkyl esters thereof, and the propylene polymers described above.

The melt index (JI
According to S K-7210, if the conditions in Table 1 are 4,
PJ constant, hereinafter referred to as rM I (3) J] and M I (1) of the brobylene polymer are both generally 0.
．． 0i~100g/10 minutes, 0.02~50g/
10 minutes is preferable, especially 0.05 to 50 g-
/1 minute is suitable. M I (1) or M
I (If a propylene polymer or ethylene polymer with 3 less than the lower limit is used, it is difficult to carry out the graft reaction uniformly.On the other hand, if a polymer with 3 exceeding the upper limit is used for a month, the resulting adhesive resin Poor strength and poor adhesive strength.

Among these olefin polymers, low-density and high-density ethylene homopolymers, propylene homopolymers, copolymers of ethylene and propylene t4, and JJ of ethylene or propylene with other α-olefins: Polymers are preferred.

The unsaturated carboxylic acids used in producing this graft copolymer are broadly classified into monobasic unsaturated carboxylic acids and dibasic unsaturated carboxylic acids. The monobasic unsaturated carboxylic acid usually has at most 20 carbon atoms (preferably 15 or less carbon atoms), and representative examples thereof include acrylic acid and methacrylic acid. Furthermore, the number of carbon atoms in dibasic unsaturated carboxylic acids is generally at most 40.
(preferably 30 or less), typical examples of which include maleic acid, itaconic acid, nadic acid, and fumaric acid. Furthermore, examples of derivatives include esters, acid anhydrides, amides, imides, and metal salts of these monobasic unsaturated carboxylic acids and dibasic unsaturated carboxylic acids. Among these derivatives, for amides and imides, the number of carbon atoms in the amide group and imide group is usually at most 20 (preferably 15 or less). Furthermore, the total number of carbon atoms in an ester is generally at most 40.
30 or less is desirable. Furthermore, the metal of the metal salt generally includes alkali metals and metals of Group 2 of the periodic table. A representative example of these is JP-A-62
It is described in the specification of Publication No. 10107, page 3, bottom right column, line 15 to page 4, top right column, line 12.

Among these unsaturated carboxylic acids and their derivatives, acrylic acid, methacrylic acid, maleic acid and its anhydride, 5-norbornene-2,3-dicarboxylic acid and its anhydride, and glycidyl methacrylate are preferred, and maleic anhydride is particularly preferred. and 5-norbornenic anhydride are preferred.

In addition, the decomposition temperature of the radical initiator used in this graft polymerization with a half-life of 1 minute is usually 100°C or higher, and 100°C.
A temperature of 5°C or higher is preferred, and a temperature of 120°C or higher is particularly preferred. Representative examples of suitable radical initiators include:
dicumyl peroxide, penzoyl peroxide,
Di-tertiary monobutyl peroxide, 2,5-dimethyl-2,5-di(tertiary monobutyl peroxy)hexane, 2,5-dimethyl-2,5-di(tertiary monobutylperoxy) ) Organic peroxides such as hexane-3, lauroyl peroxide, and tertiary monobutyl peroxybenzoate can be mentioned.

The proportions of the unsaturated carboxylic acid and its derivatives and the radical initiator to 100 parts by weight of the olefin polymer are usually as follows.

For unsaturated carboxylic acids and derivatives thereof, the total amount thereof is 0.01 to 5.0 parts by weight, and 0.05 to 3 parts by weight.
,0 parts by weight are preferred, and 0.1 to 2.0 parts by weight are particularly preferred. If the total amount of unsaturated carboxylic acids and their derivatives used is less than 0.01 part by weight, the adhesiveness of the graft copolymer will be insufficient. On the other hand, 5.0
If the amount exceeds 1 part by weight, not only may decomposition or crosslinking reactions occur simultaneously during the production of the graft copolymer, but also
Rather, the adhesion is reduced.

In addition, for radical initiators, the amount is 0.001 to 1.0 parts by weight, preferably 0.01 to 10 parts by weight, and especially 0.01 to 1.0 parts by weight, preferably 0.01 to 10 parts by weight.
．． 01 to 0.5 parts by weight. When the proportion of the radical initiator used is less than 0.001 part by weight, the modification effect is insufficient and it takes a long time to complete the modification.

On the other hand, l. If it exceeds 0 parts by weight, excessive decomposition or crosslinking reaction may occur, which is not preferable.

The graft copolymer of the present invention can be prepared by any known means for producing this type of graft copolymer.

A typical production method is to prepare the olefin polymer, unsaturated carboxylic acid or its derivative, and radicals in a solvent such as an aromatic hydrocarbon compound such as xylene or toluene, or an aliphatic hydrocarbon compound such as hexane or hebutane. A method of manufacturing by heating and mixing an initiator, and a method of mixing these olefinic polymers, unsaturated carboxylic acids or derivatives thereof, and radical initiators in advance under essentially non-crosslinking conditions, and then passing the resulting mixture through a screw extruder, The production method involves melting and mixing using a mixing machine such as a Banbury mixer or a kneader, which is generally used in the field of compounding resins.
The latter method is preferred from the point of view of economy.

In the latter case, the temperature conditions for modification are appropriately selected in consideration of the deterioration of the olefin polymer, the decomposition of the unsaturated carboxylic acid or its derivative, the decomposition temperature of the organic peroxide, etc. ~350℃, 150℃
-350 degreeC is desirable, especially 150-300 degreeC is suitable.

Furthermore, in the present invention, generally commercially available adhesives can also be preferably used. Typical examples of such adhesives include urethane adhesives such as aliphatic and aromatic adhesives.
It is desirable that the adhesive strength is 800 g/15 mm or more even when subjected to retort treatment at 25° C. for 30 minutes.

(P) Laminated product and method for manufacturing the same A partially enlarged cross-sectional view of a typical laminate of the present invention is shown in FIG. In FIG. 1, 1 is an ethylene-vinyl alcohol copolymer layer which is an intermediate layer, and 2 and 2' are adhesive resin layers. Further, 3 and 3' are ethylene-vinyl alcohol copolymer layers which are protective layers, and 4 and 4 are ethylene-vinyl alcohol copolymer layers.
' is an adhesive resin layer, and 5 and 5' are propylene polymer mixture layers.

In the laminate of the present invention, the thickness of each layer varies widely depending on its intended use, but the intermediate layer and protective layer ethylene-
The ratio of each brobylene polymer layer to the total amount of vinyl alcohol copolymer layers is 2 to 100 times (preferably 3 to 80 times). Further, it is important to adjust the thickness of the propylene polymer layer so that the amount of water vapor permeation after retort treatment, measured by the method described later, is 10 g/rrf or less.

Furthermore, for the ethylene-vinyl alcohol copolymer layer that is the intermediate layer, the total thickness of the ethylene-vinyl alcohol copolymer layer and the polyamide resin layer that are the intermediate layer and the protective layer is generally 10 to 90% is desirable, especially 20-80%. Further, it is necessary that the thickness of the ethylene-vinyl alcohol copolymer layer serving as the protective layer is 30 mm or more. If the thickness of the ethylene-vinyl alcohol copolymer layer is less than 3otIfo, deterioration of barrier properties after retort treatment cannot be satisfactorily prevented.

Further, the thickness of the adhesive resin layer is usually 5 to 100 mm,
Particularly preferred is 1O to 50IEa. If the thickness of the adhesive resin layer is less than 5 mm, it is difficult to produce a laminate with a uniform thickness, and uneven adhesion occurs after retort treatment or the like. On the other hand, if it exceeds 10 otm, not only is there an economical problem, but the container may turn yellow. In addition, the thickness of the inner layer and outer layer (brobylene polymer mixture layer) is generally 1000μ or less, and the gas barrier layer is l
It is more than OuIrI.

The laminate of the present invention can be manufactured by methods commonly practiced in this type of field.

When producing multiple layers by coextrusion, the resins of each layer are melt-kneaded using an extruder corresponding to the resin, and then extruded into a predetermined shape through a multilayer die such as a T-die or a circular die. Further, it can be manufactured by laminating methods such as dry lamination, sandwich lamination, and extrusion coating. The molded article may also take the form of a film, sheet, bolt or tube shaped preform, etc. Container shaping from a balisong or preform or extrusion can be easily accomplished by vinching off the extrudate with a pair of split molds and blowing fluid into the interior thereof. Furthermore, after cooling the preform, it is heated to a stretching temperature, stretched in the axial direction, and blow-stretched in the circumferential direction using fluid pressure, thereby obtaining a stretched-blown container or the like.

Further, by subjecting the film or sheet to vacuum forming, pressure forming, plug assist forming, or the like, containers such as cup-shaped and tray-shaped containers can be manufactured.

The thickness of the propylene polymer mixture layer in both surface layers is adjusted so that the amount of water vapor permeation measured by the following method after retort treatment is less than tog,'1.

An important point in the present invention is that the ethylene-vinyl alcohol copolymer constituting the protective layer has a lower copolymerization ratio of ethylene than the ethylene-vinyl alcohol copolymer constituting the intermediate layer. Generally, it is known that an ethylene-vinyl alcohol copolymer with a low ethylene copolymerization ratio has a larger water diffusion coefficient and solubility coefficient at the same water content than one with a high ethylene copolymerization ratio. For example, see Yonezu, Okaya, “Water adsorption strength of ethylene-vinyl alcohol copolymer” (1987, published by Kinki Chemical Society, pp. 571-574). By providing a small amount of ethylene-vinyl alcohol copolymer layer, it is possible to effectively prevent deterioration of gas barrier properties, and even during long-term storage after retort processing, the ethylene-vinyl alcohol copolymer layer from the protective layer to the intermediate layer can be prevented from deteriorating. It becomes possible to reduce the diffusion of water into the vinyl alcohol copolymer layer, and as a result, it becomes possible to reduce the total amount of oxygen permeation during long-term storage.

The amount of water vapor permeation was determined by pressing the propylene polymer mixture to be measured using a press at a temperature of 230°C into two press sheets 6 and 6' with a thickness set as shown in Figure 2.
Create. Next, the adhesive resin is applied to a thickness of 20u.
n adhesive films 7 and 7' at a resin temperature of 220°C.
A saponified product obtained by saponifying an ethylene-vinyl acetate copolymer prepared by the T-die method and having an ethylene copolymerization ratio of 29 mol% [saponification rate 99
. A laminate is prepared from these films and sheets as shown in FIG. 2, and the laminate is heated to a temperature of 1
Retort treatment was performed at 25° C. for 30 minutes, and the amount of water vapor permeation of the resin to be measured after retort treatment was measured from the weight change before and after the retort treatment.

[Examples and comparative examples]

Hereinafter, the present invention will be explained in more detail with reference to Examples.

In addition, in the Examples and Comparative Examples, the oxygen permeability of each sample was measured using an oxygen permeability all J constant device [manufactured by Modern Control (USA), model OX-RTAN10/50] at a temperature of 23°C and a relative humidity in the container. d#j was determined under conditions of 90% and relative humidity outside the container of 60%.

In addition, the adhesive strength was determined from a 111 liter container with a width of 15 m1 that was retorted for 40 minutes at a temperature of 125°C.
A sample was cut out, and the adhesive strength between the polyamide resin layer and the adhesive resin layer was measured using a tensile tester (Toyo Baldwin Co., Ltd.'!A) at a tensile speed of 300 mm/min.
ll+ was determined.

The types, manufacturing methods, physical properties, etc. of the brobylene polymers and their compositions, Ishiura resins, ethylene-vinyl alcohol copolymers, and adhesive resins used in Examples and Comparative Examples are shown below.

[(A) Propylene polymer and its composition] As a propylene polymer and its composition, M I (1)
is 1.0 g/10 min [r P P (A) J. Say: l, Ml(1) is 0.
5glLO content, and the copolymerization ratio of ethylene is L8
601 ffl parts of an ethylene-propylene block copolymer [hereinafter referred to as rPP(B)J] with a concentration of 0.2 g/10 min and a density of 0.965 g/d. Polymer [hereinafter referred to as rP
A composition (referred to as pellets, hereinafter referred to as "composition") was prepared by kneading the 4off parts (referred to as E(1)J) using an extruder with a screw diameter of 65 mm at a resin temperature of 220°C.
P P (B) 60 parts by weight, P
E (1) A composition [pellets, hereinafter referred to as "silk composition"] produced by kneading 10 parts by weight of mica and 30 parts by weight of mica having an average particle size of 5.0 and an aspect ratio of about 60 in the same manner. ``Things (■)''] and P P (B)7
A composition [pellets, hereinafter referred to as "composition (■)"] prepared by melt-kneading 30 parts by weight of talc having an average particle size of 0 parts by weight and an average particle size of 5.0 parts by weight was used.

[(B) Ethylene-vinyl alcohol copolymer] Also,
As an ethylene-vinyl alcohol copolymer, a saponified product obtained by saponifying an ethylene-vinyl acetate copolymer having an ethylene copolymerization ratio of 38 mol% [saponification degree 99%, Ml(2) 4.0 g/ 10 minutes, hereinafter referred to as rEVOH(1)J], a saponified product obtained by saponifying an ethylene-vinyl acetate copolymer with an ethylene copolymerization ratio of 25 mol% [saponification degree]
99%, MI(2) 5.0g/10min, hereinafter "EvOH
(2)], the copolymerization ratio of ethylene is 10 mol%
A saponified product obtained by saponifying an ethylene-vinyl acetate copolymer [degree of saponification 90%, M
I (2) 5.5 g / 10 minutes, hereinafter r E
V O H (3) J] and a saponified product obtained by saponifying ethylene-vinyl acetate octane with an ethylene copolymerization ratio of 89 mol% [saponification degree 91%, M I (2) 8 .0g/10
minutes, hereinafter referred to as r E V O H (4) J] was used.

[(C) Adhesive resin]

Furthermore, M I (L) as adhesive resin is 0.5 g/
100 parts by weight of propylene homopolymer, 0.
3 parts by weight of maleic anhydride and 0.2 parts by weight of benzoyl peroxide were dry blended in advance for 5 minutes using a Henschel mixer. Modified polypropylene CM I (1) 25 g/10 minutes] obtained by melt kneading the resulting mixture at a resin temperature of 220° C. using a single screw extruder (diameter 40 mm) was used.

[(D) Ishiura Resin]

In addition, Ishiura resin has an average molecular weight of 1,600, a softening point of 90°C, an iodine value (Wiss method) of 140, and a specific gravity of 0.97.The main component is 2-methylbutene-1, Hydrogenated product of aliphatic Ishiura resin containing piberylene and isobutylene as main components [hydrogenation rate
90%, hereinafter referred to as "petroleum resin (a)"], indene,
Aromatic petroleum resin containing vinyltoluene and α-methylstyrene as main components, obtained by copolymerizing styrene, etc. (average molecular weight approximately 1,400, bromine 1i
1 [i 20, softening point 140°C, specific gravity 1.07] [hydrogenation rate 92%, hereinafter referred to as "petroleum resin (b)"], the hydrogenation rate is 96%, and the specific gravity is 1. 05, a softening point of 160°C, and an average molecular weight of about 1.2
00 cyclopentadiene-based Ishiike resin hydride [
hereinafter referred to as "petroleum resin (C)"] and has a softening point of 100
℃, a hydrogenation rate of 94%, and an average molecular weight of about i,ooo [hereinafter referred to as "petroleum resin (d)"] was used.

Examples 1 to 11, Comparative Examples 1 to 9 The above p P (
A), P P (B) or 100 parts by weight of each of Compositions (1) to Composition (m) and petroleum resins whose types and mixing ratios are shown in Table 1 were added to a screw with a diameter of 6.
Using a 5-pressure extruder, the resin temperature at the nozzle exit is 220℃.
A pellet (mixture) was prepared while kneading at °C. The abbreviations of the mixtures are shown in Table 1.

As shown in FIG. 1, both surface layers are made of a brobylene polymer mixture or a propylene polymer layer whose type and thickness are shown in Table 2 (hereinafter referred to as "A.A'layer");
The intermediate layer is a gas barrier layer (hereinafter referred to as "B") made of an ethylene-vinyl alcohol copolymer whose thickness is shown in Table 2.
A protective layer (hereinafter referred to as "C layer") whose thickness and type are indicated is provided between layers A, A' and B, and a protective layer whose thickness and type are indicated between each of these layers. As shown in Table 2, the adhesive resin layers (D layer, D' layer, E layer and E
A five-type, nine-layer multilayer sheet manufacturing device (manufactured by Toshiba Machine Co., Ltd., feed block method, screw diameter of 4
Using 5 extruders (0 mm), the temperature of the die was 250°C.
(However, the numerical values for the thickness of each layer in Table 2 indicate the thickness at the multilayer sheet stage.)

Each sheet having such a configuration was molded using a vacuum forming machine (manufactured by Asano Research Institute, model: F L V 44) to a diameter of 81.2 mm, a depth of 40 mm, and a capacity of 160 cm.
A container of c was manufactured. Each container obtained in this way was filled with water so that 5% of the total content was a space, and a propylene-based container with a thickness of 60 mm on both sides was placed between 20 tm thick aluminum foil. A lid made of a polymer was ring-sealed for 3 seconds at a temperature of 200°C and a pressure of 2.5 kg/cj to produce a container filled with water. Each of the obtained containers was placed in a retort pot (manufactured by Daiwa Seikan Co., Ltd., pneumatic type, retort processing device), and retort processing was performed at a temperature of 125° C. for 30 minutes. The oxygen permeability of the retort-treated container and the unretorted container was measured using an oxygen permeation measuring device. The results obtained are shown in Table 3.

It is clear from Table 3 that the barrier properties of the plastic containers manufactured using the laminate of the present invention remain almost unchanged before and after retort treatment.

Table 1 Table 3 (Part 1) 1) cc/Oxygen 1 atm, 24 hours, unit Table 3 (Part 2) 1) cc/Oxygen 1 atm, 24 hours, unit 2) The impact strength of the sheet is weak , could not be heat-shaped.

3) Some cracks appeared in the intermediate layer, and a stable container could not be obtained.

4) Stable due to difference in melting point.

〔Effect of the invention〕

The laminate of the present invention is formed into a plastic container and exhibits the following effects.

In other words, it not only has excellent gas barrier properties, but also
Because the adhesive strength between the ethylene-vinyl alcohol copolymer used in the present invention and the adhesive resin is greatly improved, there is no delamination during retort processing, and even if the contents are stored for a long period of time after retort heat sterilization processing. It is a thermoplastic resin container that will not rot, deteriorate, or denature.

The laminate of the present invention can be formed into a container and used in a wide variety of ways to exhibit the above-mentioned effects. Typical uses are shown below.

(1) Various processed seasoning food containers (2) Various liquid food containers (3) Various food containers (4) Various industrial chemical containers

[Brief explanation of the drawing]

FIG. 1 is a partially enlarged sectional view of the laminates manufactured in Examples and Comparative Examples. Moreover, FIG. 2 is a partially enlarged sectional view of the laminate used to measure the amount of water vapor permeation. 1... Ethylene-vinyl alcohol copolymer (B layer)
2, 2'... Adhesive resin layer (D layer, D' layer) 3.3'
...Protective layer (C layer, C' layer) 44'...Adhesive resin layer (B layer, B' layer) 5,5'...Propylene polymer or its mixture layer (A layer, A' layer) 6.6'... Brobylene polymer or mixture thereof layer 7.7'... Adhesive resin layer

Claims (1)

[Claims] An ethylene-vinyl alcohol copolymer layer obtained by saponifying at least 90% of an ethylene-vinyl acetate copolymer having an ethylene copolymerization ratio of 15 to 65 mol% is used as an intermediate layer, and adhesive is attached on both sides of the intermediate layer. Ethylene, which constitutes the intermediate layer, acts as a protective layer through a plastic resin layer.
An ethylene-vinyl alcohol copolymer layer with a lower proportion of ethylene than the vinyl alcohol copolymer is provided, and adhesive resin layers are provided on both sides of the ethylene-vinyl alcohol copolymer layer. It is a laminate in which a propylene polymer mixture layer is provided as a layer, and the mixing ratio of petroleum resin to 100 parts by weight of propylene polymer in the propylene polymer mixture layer is 10 to 10.
100 parts by weight of a laminate.