JPH04246533A - Laminate - Google Patents

Abstract

PURPOSE:To provide the laminate having excellent gas barrier properties under the condition of high temperature and high humidity in retort-treatment, etc. CONSTITUTION:The aimed laminate is composed of the layer of mixed composition in which polyolefin resin/the saponified material of ethylene-vinyl acetate copolymer/ethylene thermoplastic elastomer and the modified resin of maleic acid of the elastomer are compounded and the innermost and the outer most layers made of polyolefin resin layer through the layer of adhesive, while the layer of saponified material of ethylene-vinylacetate copolymer is used as intermediate layer.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a laminate, and more specifically, an ethylene-vinyl acetate copolymer saponified layer is used as an intermediate layer, and a polyolefin resin layer/ethylene-vinyl acetate copolymer saponified layer is formed as an intermediate layer via an adhesive layer. The object of the present invention is to provide a laminate having excellent barrier properties even in high temperature and high humidity conditions, in which the layer of a compound compound/ethylene copolymer mixture composition and the innermost and outermost layers are composed of a polyolefin resin layer.

0002

BACKGROUND OF THE INVENTION A saponified ethylene-vinyl acetate copolymer is a thermoplastic resin that is mechanically good and has excellent gas barrier properties, aroma retention properties, oil resistance, etc. However, since it is hydrophilic, it has the disadvantage that it loses its properties when exposed to a high humidity atmosphere or when it comes into contact with polar solvents such as water or alcohol. Therefore, a laminate consisting of at least three layers of a saponified ethylene-vinyl acetate copolymer and a hydrophobic polyolefin, especially a saponified ethylene-vinyl acetate copolymer as an intermediate layer, is used as the innermost layer through an adhesive layer. A laminate consisting of five layers of three types protected by polyolefin is commonly used in the current market.

However, in recent years, sterilization and sterilization have become necessary in the fields of food, medicine, etc., and materials with excellent gas barrier properties are required in high-temperature and humid conditions such as retort processing. The loss of the water vapor barrier effect of the polyolefin layer over time leads to a decrease in the barrier properties of the saponified ethylene-vinyl acetate copolymer under high humidity, resulting in the drawback that the saponified ethylene-vinyl acetate copolymer cannot function as a barrier material.

0004

[Problems to be Solved by the Invention] In this way, the saponified ethylene-vinyl acetate copolymer of the prior art is used as an intermediate layer,
A laminate in which polyolefin is used as the innermost layer with an adhesive layer interposed therebetween has a problem in that gas barrier properties are significantly deteriorated under high temperature and high humidity conditions such as retort processing. Based on the above, the present invention does not have these drawbacks (problems), that is, takes advantage of the characteristics of saponified ethylene-vinyl acetate copolymer, such as gas barrier properties and aroma retention properties, and can be used under high temperature and high humidity conditions such as retort processing. The objective is to obtain a laminate whose gas barrier properties do not deteriorate significantly.

[0005]

[Means for Solving the Problems] According to the present invention, these problems are solved when the copolymerization ratio of ethylene is 10 to 65 mol%, and the ethylene-vinyl acetate copolymer is at least 90%.
A saponified ethylene-vinyl acetate copolymer layer obtained by the above saponification is used as an intermediate layer, and a copolymerization of (a) polyolefin resin to 100 parts by weight of (b) ethylene is carried out via an adhesive layer. The proportion is 10-65 mol%
and the ethylene-vinyl acetate copolymer at least 9
10 to 90 parts by weight (c
) A laminate containing a styrene-based thermoplastic elastomer and 5 to 70 parts by weight of its maleic acid-modified resin, the layer of the mixed composition and the outermost layer comprising a polyolefin resin layer can solve the problem. .

The present invention will be explained in detail below. A. Polyolefin Resin Typical examples of the polyolefin resin used for the polyolefin resin layer of the present invention and the polyolefin resin used for the mixture layer include polypropylene, but other examples include random combinations of propylene and ethylene. or block copolymers, random or block copolymers of propylene and/or ethylene with other α-olefins having at most 12 carbon atoms (copolymerization ratio with α-olefins is at most 20% by weight); Examples include homopolymers of ethylene, copolymers of ethylene and α-olefins having 3 to 12 carbon atoms, and homopolymers of α-olefins having 4 to 6 carbon atoms.

Furthermore, the present invention also includes modified polyolefins obtained by graft polymerizing these polyolefin resins with compounds having at least one double bond (for example, unsaturated carboxylic acids, vinyl silane compounds). . These polyolefin resins and modified polyolefins may be used alone or in combination of two or more. In addition, among these polyolefin resins and modified polyolefins,
Two or more types may be used in any ratio as a resin blend.

[0008] Furthermore, an inorganic filler may be further blended with these polyolefin resins, and the inorganic filler is generally one widely used in the fields of synthetic resins and rubber. 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 thereof. It is broadly classified into compounds such as oxides), sulfates, carbonates, silicates, their double salts, and mixtures thereof.

Typical examples of the inorganic filler include the above-mentioned aluminum oxide (alumina), its hydrate, calcium hydroxide, magnesium oxide (magnesia), magnesium hydroxide, zinc oxide (zinc white), red lead, and Lead oxides such as white lead, magnesium carbonate, calcium carbonate, basic magnesium carbonate, white carbon, asbestos, mica, talc, glass fiber, glass powder, glass beads, clay, diatomaceous earth, silica, wollastonite,
Iron oxide, antimony oxide, titanium oxide (titania), lithobon, pumice powder, aluminum sulfate (gypsum, etc.), silica zirconium, zirconium oxide, barium carbonate,
Examples include dolomite, molybdenum disulfide and iron sand.

Among these inorganic fillers, those in powder form have a diameter of 20 μm or less (preferably 10 μm or less).
Preferably. In addition, in the case of fibrous materials, the diameter is 1 to 5.
00 μm (preferably 1 to 300 μm) and a length of 0.1 to 6 mm (preferably 0.1 to 5 mm). Further, it is preferable that the diameter of the flat plate is 30 μm or less (preferably 10 μm or less). Among these inorganic fillers, those in the form of flat plates (flake) and those in the form of powder are particularly suitable.

[0012] The melt index of the polyolefin resin [according to JIS K7210, the conditions are 14
(hereinafter referred to as "MI(1)") is usually 0.0.
05-100g/10 minutes, 0.01-80g/1
0 minutes is preferable, especially 0.02 to 50 g/1
A value of 0 minutes is preferable. MI(1) is 0.005g
If a polyolefin resin is used for less than 10 minutes, extrusion molding cannot be performed due to poor fluidity, making it impossible to form a sheet layer. On the other hand, if a polyolefin resin exceeding 100 g/10 minutes is used, the drawdown will be large when producing these coextruded sheets, making it impossible to obtain a good product.

[0013] When blending an inorganic filler, the proportion of the inorganic filler in the total amount of polyolefin resin and inorganic filler is generally at most 80% by weight, and 70% by weight or less. It is preferably 60% by weight or less. If the proportion of the inorganic filler in the total amount exceeds 80% by weight, extrusion molding into a sheet is difficult and a good sheet cannot be obtained.

B. Saponified ethylene-vinyl acetate copolymer Also saponified ethylene-vinyl acetate copolymer used in the saponified ethylene-vinyl acetate copolymer layer in the present invention, and saponified ethylene-vinyl acetate copolymer used in the mixed composition layer. The saponified polymer contains at least 9 ethylene-vinyl acetate copolymers having an ethylene content of 10 to 65 mol%.
It is saponified at 0 mol% or more.

Furthermore, it is desirable to have a molecular weight that allows it to be formed into a film or sheet, and the melt index [JIS
K7210, measured at a temperature of 210°C and a load of 2.16 kg, hereinafter referred to as "MI(2)"] is usually 0.1 to 50 g/10 minutes, and 0.1 to 20 g/10 minutes.
10 minutes is preferable. MI(2) is 0.1g/10
If a saponified ethylene-vinyl acetate copolymer of less than 50% is used to produce a laminate, the resin will not flow due to the low fluidity of the resin, making it impossible to obtain a good laminate. On the other hand, 20g/
If the saponified ethylene-vinyl acetate copolymer is used for more than 10 minutes, the fluidity of the resin will be too high and a good laminate cannot be obtained when producing a laminate.

C. Styrenic thermoplastic elastomer The styrene thermoplastic elastomer used in the mixed composition in the present invention is a styrene and hydrogenated butadiene copolymer, a styrene and hydrogenated isoprene copolymer, and a styrene and hydrogenated butadiene copolymer. Furthermore, a copolymer of styrene and hydrogenated isoprene with maleic anhydride added thereto is also very good.

The styrene and hydrogenated butadiene copolymer or styrene and hydrogenated isoprene copolymer consists of a styrene polymer block and a hydrogenated butadiene or hydrogenated isoprene block. Examples of styrene polymers include styrene, α
- methylstyrene, p-methylstyrene, vinylxylene, vinylnaphthalene, and mixtures thereof.

In addition, maleic anhydride is added to the styrene and hydrogenated butadiene copolymer or styrene and hydrogenated isoprene copolymer, and the styrene and hydrogenated butadiene copolymer or styrene and hydrogenated isoprene copolymer used in the present invention. The added material has a styrene content of 10 to 40% by weight,
Solution viscosity (25°C, 25% by weight toluene solution) is 10
It has a characteristic of 0 to 50,000 CPS.

If the solution viscosity is less than 100 CPS, the fluidity is high and the compatibility in the mixed composition is poor, resulting in failure to exhibit gas barrier effect and adhesive strength with the polyolefin resin. Furthermore, if the solution viscosity exceeds 50,000 CPS, the fluidity will be poor and the compatibility in the mixed composition will be poor, resulting in failure to exhibit gas barrier effect and adhesive strength with the polyolefin resin.

These products are also commercially available and can be manufactured by methods well known to those skilled in the art.

D. Mixing ratio of the mixed composition and its production The mixing ratio of each resin used in the mixed composition layer of the present invention is 10 to 90 parts by weight of the saponified ethylene-vinyl acetate copolymer to 100 parts by weight of the polyolefin resin. , the styrenic thermoplastic elastomer and its maleic acid-modified resin are 5 to 70 parts by weight, and the proportion of the polyolefin resin in the mixture composition is 20 to 80 parts by weight, preferably 30 to 70 parts by weight. be.

If the proportion of the polyolefin resin in the mixed composition is less than 10% by weight, the adhesion with the outermost polyolefin layer is weak and a laminate that can withstand practical use cannot be obtained, while if it exceeds 80% by weight, the retort Only products with significantly deteriorated gas barrier properties can be obtained under high temperature and high humidity conditions such as during processing.

[0023] Also, the ratio of the saponified ethylene-vinyl acetate copolymer in the mixture is 1 part polyolefin resin
The amount is 10 to 90 parts by weight, preferably 15 to 80 parts by weight. If it is less than 10 parts by weight, only a product with significantly deteriorated gas barrier properties under high temperature and high humidity conditions such as retort processing can be obtained, whereas if it exceeds 90 parts by weight, the adhesion with the outermost polyolefin layer is weak and the laminated layer is not suitable for practical use. I can't get a body.

Furthermore, the proportion of the styrenic thermoplastic elastomer and its maleic acid-modified resin in the mixed composition is 5 to 70 parts by weight per 100 parts by weight of the polyolefin resin.
Parts by weight, preferably 10 to 50 parts by weight. If the proportion of the styrene thermoplastic elastomer and its maleic acid-modified resin is less than 5 parts by weight, the saponified ethylene-vinyl acetate copolymer will be poorly dispersed in the mixed composition.
The impact resistance is extremely low, or the effect of preventing deterioration of gas barrier properties under high temperature and high humidity conditions is not exhibited.

On the other hand, if the amount exceeds 70 parts by weight, only products with significantly deteriorated gas barrier properties, low impact resistance, or poor adhesion with the polyolefin layer under high temperature and high humidity conditions such as retort processing can be obtained. Due to any of these problems, a laminate that can withstand practical use cannot be obtained.

The mixed composition of the present invention can be produced by mixing the resins constituting the mixed composition using a mixer such as a tumbler, Henschel mixer, or super mixer.
It can also be obtained by mixing with a mixing mixer in the raw material supply system before the extruder, and each resin constituting the mixed composition is kneaded using a screw extruder, Banbury mixer, kneader, etc. commonly used in the synthetic resin field. It can also be produced by melt-mixing using a machine.

E. Manufacture of laminate The laminate of the present invention has a saponified ethylene-vinyl acetate copolymer layer as an intermediate layer, the above-described mixed composition layer via an adhesive layer, and a polyolefin resin layer as the outermost layer. It is a laminate. Laminates of these layers are generally obtained by known coextrusion methods, such as coextrusion T-die molding for films and sheets, cocircular die molding for films and sheets, coextrusion blow molding for containers and bottles, and co-injection blow molding for containers and bottles. By molding, various types of containers, etc. can be obtained.

[0028] The extrusion temperature for coextrusion molding to obtain the laminate of the present invention is generally 100 to 350°C, and 150 to 350°C.
A temperature of 30°C is preferred, particularly a temperature of 180 to 300°C.

The thickness of each layer of the laminate of the present invention is 2 to 500 μm, preferably 5 to 300 μm for the saponified ethylene-vinyl acetate copolymer layer forming the intermediate layer. If the thickness of the saponified ethylene-vinyl acetate copolymer layer forming the intermediate layer is less than 2μ, the gas barrier effect will be poor;
If it exceeds 00 μ, it is effective, but the cost increases and the product becomes impractical.

[0030] The thickness of the mixed composition layer is 10 to 300 mm on one side.
It is 0μ, preferably 15 to 2000μ. If the thickness of the mixed composition layer is less than 10μ, the effect of preventing deterioration of gas barrier properties under high temperature and high humidity conditions will not be exhibited;
If it exceeds μ, molding becomes difficult and the product becomes impractical.

Furthermore, the polyolefin resin layer forming the outermost layer has a thickness of 10 to 3000 μm on one side, preferably 15 μm.
~2000μ. If one side of the polyolefin layer constituting the outermost layer is less than 10 μm, there is no effect of preventing deterioration of gas barrier properties under high temperature and high humidity conditions, while if it exceeds 3000 μm, molding is difficult and only a product with poor practicality can be obtained.

In addition, the adhesive between the saponified ethylene-vinyl acetate copolymer and the mixture layer in the present invention is maleic, which is an adhesive between the saponified ethylene-vinyl acetate copolymer and the polyolefin resin, which is already known in the art. A resin made of acid-modified polyolefin or the like may be used as the adhesive layer resin.

[0033]

[Examples] The present invention will be explained in more detail with reference to Examples below. The oxygen permeability of each sample in Examples and Comparative Examples was measured using an oxygen permeation measuring device "Modern Control (USA) Model OX-RTAN10/50" at a measurement temperature of 23°C and a relative humidity of 60%. . Also,
The adhesive strength was determined by sampling a 15 mm wide sample from the obtained laminated sheet and performing a peel test on this sample in a direction of 180 degrees at a take-up speed of 100 mm/min. Furthermore, the impact resistance strength of the sheet was determined by cutting a 150 mm wide x 150 mm sheet from the manufactured laminated sheet to prepare a measurement sample, and conducting a falling weight impact test according to ASTM D 1.
The impact resistance strength at 23° C. was determined in accordance with 709. The types and physical properties of the polyolefin resin, saponified ethylene-vinyl acetate copolymer, styrene thermoplastic elastomer, and maleic acid-modified resin used in Examples and Comparative Examples are shown below.

[(A) Polyolefin resin] As a polyolefin resin, an ethylene-propylene block copolymer having an MI (1) of 0.6 g/10 min and an ethylene copolymerization ratio of 18% by weight [hereinafter “PP(A)
”], propylene homopolymer with MI(1) of 2.0 g/10 min [hereinafter referred to as “PP(B)”], J
MI (3
) is 0.2 g/10 min, and the density is 0.955 g/10 min.
cm3 ethylene homopolymer [hereinafter referred to as "PE(1)"]
], PP (A) is 85% by weight, PE (1)
A mixture containing 15% by weight of PP (hereinafter referred to as "PP(c)") was used.

[(B) Saponified ethylene-vinyl acetate copolymer] As the saponified ethylene-vinyl acetate copolymer, an ethylene-vinyl acetate copolymer having an ethylene copolymerization ratio of 25 mol% is saponified. Saponified product obtained by [saponification degree 99%, MI (2) 5.0 g
/10 minutes, hereinafter referred to as "EVOH (1)"]. Also,
As a saponified ethylene-vinyl acetate copolymer, a saponified product obtained by saponifying an ethylene-vinyl acetate copolymer having an ethylene copolymerization ratio of 38 mol% [saponification degree 99%, MI (2) 3. 0g/10min,
Hereinafter referred to as "EVOH (2)"].

[(C) Styrenic thermoplastic elastomer and its maleic acid-modified resin] As the styrene-based thermoplastic elastomer and its maleic acid-modified resin, FG1901X manufactured by Shell Chemical Co., Ltd. [Styrene content: 28% by weight]
, maleic anhydride addition rate 2% by weight, solution viscosity 6000C
PS, hereinafter referred to as "SEBS-M"]. Also manufactured by Kuraray Co., Ltd. under the trade name Septon 1001 [styrene content 35% by weight, solution viscosity 6100CPS, hereinafter "SEBS"]
].

[(D) Adhesive] The adhesive between the saponified ethylene-vinyl acetate copolymer and the mixture layer is modified polyolefin resin ER321P manufactured by Showa Denko K.K. (hereinafter referred to as " ER321P], if the outermost layer is polyethylene resin, the modified polyolefin resin ER403 manufactured by Showa Denko K.K.
ER403] was used.

Examples 1 to 5, Comparative Examples 1 to 4 The mixed compositions constituting the mixed composition layers were heated in an extruder with L/D=24 and a diameter of 65 mmφ at the mixing ratio of each resin shown in Table 1. use,
Kneading and mixing were performed at an extrusion temperature of 220°C to create pellets for a mixed composition layer.

Next, the obtained mixed composition layer pellets,
and polyolefin resin, adhesive resin, saponified ethylene-vinyl acetate copolymer resin, and 4 types of 7-layer multilayer sheet production equipment (manufactured by Toshiba Machine Co., Ltd., feed block type 65 mmφ extruder, 2 units, 40 mmφ extruder consisting of a polyolefin resin layer/mixed composition layer/adhesive layer/saponified ethylene-vinyl acetate copolymer layer/adhesive layer/mixed composition layer/polyolefin resin layer,
A laminated sheet with a target structure having a saponified ethylene-vinyl acetate copolymer layer as the center layer was produced.

In the production of the laminated sheet, the polyolefin resin layer was formed using an extruder with a diameter of 65 mm and an extrusion temperature of 2.
At 30°C, the mixed composition layer was formed using an extruder with a diameter of 40 mmφ at an extrusion temperature of 230°C, and the adhesive layer was formed using an extruder with a diameter of 40 mmφ at an extrusion temperature of 220°C. A laminated sheet was manufactured using an extruder having a diameter of 40 mmφ and an extrusion temperature of 200° C., with the configuration of each layer shown in Table 2. Table 2 shows the results of measuring the adhesive strength and impact strength of each of the obtained laminated sheets.

Further, each of these laminated sheets was used to produce a container having a diameter of 81.2 mm, a depth of 40 mm, and a capacity of 160 cc using a vacuum forming machine (manufactured by Asano Research Institute, Model FLX02). Then, in each container obtained, 5
% of the space, and a lid made of propylene polymer with a thickness of 60 μm on both sides with an aluminum foil having a thickness of 20 μm interposed therebetween was placed at a temperature of 200° C. and a pressure of 2.0 μm. Ring sealing was performed for 3 seconds under the condition of 5 kg/cm2 to create a container filled with water. This container was placed in a retort pot (Daiwa Can, pneumatic type, retort processing device) and subjected to retort processing at a temperature of 120° C. for 20 minutes. Table 2 shows the results of measuring the oxygen permeability of these retort-treated containers and unretorted containers using an oxygen permeation measuring device.

In addition, as a comparative example, pellets of mixed compositions 6 to 9 shown in Table 1, which have resin compositions outside the scope of the present invention, were prepared.
A laminated sheet having the configuration shown in Table 2 was manufactured. Then, the adhesive strength and impact strength of the obtained laminated sheet were measured, and the results are shown in Table 2. Furthermore, a container was created by vacuum forming the obtained laminated sheet in the same manner as in Example 1, and the oxygen permeability of the retort-treated container and the unretorted container was measured. The obtained results are shown in Table 2.

The results obtained as described above are shown in Table 2 as Examples and Comparative Examples. The laminated sheet of the present invention has strong adhesive strength, excellent impact resistance, and is durable even before and after retort treatment. It is clear that the barrier properties have hardly changed.

[0044]

[Table 1]

[0045]

[Table 2]

[0046]

Effects of the Invention The laminate of the present invention can be made into films, sheets, pipes, and various containers such as balls and trays by coextrusion T-die molding, coextrusion circular die molding, coextrusion blow molding, coextrusion injection molding, etc. It is used in a wide range of fields such as general food packaging, packaging for chemicals and pharmaceuticals, and general industrial applications, especially in high-temperature and high-humidity applications such as retort processing. Demonstrates excellent effects in the field of use.

Claims (1)

[Claims] Claim 1: A saponified ethylene-vinyl acetate copolymer layer having an ethylene copolymerization ratio of 10 to 65 mol% and obtained by saponifying an ethylene-vinyl acetate copolymer of at least 90% or more. layer, and (a) polyolefin resin is 100%
The copolymerization ratio of (b) ethylene to parts by weight is 10 to 6.
5 mol%, obtained by saponifying at least 90% or more of an ethylene-vinyl acetate copolymer,
A layer of a mixed composition containing 10 to 90 parts by weight of a saponified ethylene-vinyl acetate copolymer (c) a styrene thermoplastic elastomer and 5 to 70 parts by weight of its maleic acid-modified resin, and the innermost layer. A laminate comprising a polyolefin resin layer.