TW201708359A - Resin composition and use thereof - Google Patents

Abstract

To provide a resin composition for excellent sealants suitable for use as lid materials for food containers. A resin composition for sealants which comprises 50-99 parts by mass of at least one resin (A) selected from among ethylene/vinyl ester copolymers each comprising 90-95 mol% ethylene units and 5-10 mol% vinyl ester units and ethylene/unsaturated carboxylic acid ester copolymers each comprising 90-95 mol% ethylene units and 5-10 mol% unsaturated carboxylic acid units and satisfying relationship (1): -3.0X+107 > T (1) (in relationship (1), X represents the content (mol%) of the unsaturated carboxylic acid ester(s) and T represents the melting point (DEG C) measured in accordance with JIS K7121-1987), 1-50 parts by mass of at least one resin (B) selected from among ethylene/[alpha]-olefin copolymers and A-B-A block copolymers (wherein A represents a polystyrene block and B represents an alkylene copolymer block), and 0-10 parts by mass of a tackifier resin (C).

Description

Resin composition and use thereof

The present invention relates to a resin composition for a sealant, a cover member comprising the sealant resin composition, and a food container having the cover member.

As various foods or pharmaceutical containers such as jelly, pudding, yogurt, tofu, instant noodles, and noodles, plastic containers having easy-opening lids are widely used. In particular, as a container for instant noodles, noodles, red bean soup, etc., an expanded polystyrene sheet or an impact-resistant polystyrene film, an impact-resistant polystyrene sheet, or the like, have been widely used. A container as a raw material such as polyethylene laminate paper. Further, in order to seal in an easy-opening state as a sealing material used in the lid of the plastic container, conventional containers have been proposed and put into practical use. Among them, a composition mainly composed of a copolymer of ethylene and vinyl acetate or ethylene and acrylate or a polyolefin resin is preferable because the sealing property between the container main body and the lid body is good, and the peeling strength at the time of peeling off the lid body is substantially reasonable. Therefore, it is widely used.

For example, Patent Document 1 discloses that a layered system in which a metal layer, an adhesive layer, and an easily peelable resin layer are sequentially laminated is suitable as an easily peelable cover material for a bead expanded polystyrene container, and the above-mentioned easily peelable resin layer is selected. A resin and an adhesion-imparting agent from an ethylene-vinyl acetate copolymer resin, an ethylene-acrylate copolymer resin, and a polyolefin resin.

Patent Document 2 describes that ethylene-(methyl) is contained in a specific ratio. The sealant composed of the composition of the acrylic copolymer, the polyolefin, the adhesion-imparting resin, and the filler is stronger than the known sealant, and provides a peelable seal.

[Previous Technical Literature] [Patent Literature]

Patent Document 1: Japanese Patent Laid-Open No. Hei 3-79342

Patent Document 2: Japanese Patent Laid-Open Publication No. 2007-522276

On the other hand, it is of course required for the food container to have hygienic properties without impairing the quality of the food of the contents. Therefore, according to the country or the region, the unique hygiene standards for food containers have been established. In Japan, the regulations have been established more than 50 years ago (standards for foods, additives, etc. according to Article 18 of the Food Sanitation Law (Showa 34). Year of the Ministry of Health and Welfare Notice No. 370)). These criteria essentially aim to limit the amount of extraction of the container material to various solvents, such as organic solvents or oils, with the container component not being targeted to the food of the contents. Avoiding the migration of such components is a particularly important goal in containers containing oily foods such as ingredients that are more serious in the migration of plastic containers, fried noodles or dishes conditioned with oil. In the past, materials that meet such hygiene standards have been used in food containers for containers such as containers, lids, and sealing materials. However, food hygiene standards such as solvent extraction rates have become stricter year by year, and some countries have set stricter standards. Benchmark.

However, even though the solvent extraction amount of the sealant material has been successfully reduced so far, it is difficult to satisfy the adhesiveness of the material for the sealant at the same time, and it is not easy to achieve the hygienicity and adhesion of the material for the sealant at the same time. Therefore, as a sealant material which is excellent in the balance between the adhesive strength and the opening property of the container and which is extremely low in the elution of the components of the organic solvent, a sealant composition which can satisfy the recent requirements has not been obtained.

The inventors of the present invention have conducted intensive studies in order to obtain an excellent sealant material which satisfies a stricter sanitary standard in addition to the adhesiveness required for the lid member of a food container. That is, an object of the present invention is to provide a material for a sealant which can obtain a sealability and a good sealability required for a lid member of a food container, and which has a small amount of solvent extraction, and which satisfies a more stringent hygiene standard.

As a result, it has been found that a resin composition containing a specific ethylene copolymer as a main component and an ethylene-α-olefin copolymer and an adhesiveness-imparting resin in a specific amount ratio satisfies the above problems, and can be used as an excellent food container. Sealant material. That is, the present invention is as follows.

(Invention 1)

A resin composition for a sealant comprising: 50 to 99 parts by mass of a resin (A), wherein the resin (A) is selected from the group consisting of 90 mol% or more and 95 mol% or less of ethylene unit, and 5 mol% of a vinyl ester unit. An ethylene-vinyl ester copolymer having a % or more and 10 mol% or less (wherein the total of the ethylene unit and the vinyl ester unit is 100 mol%), and an ethylene unit containing 90 mol% or more and 95 mol% % or less, an unsaturated carboxylic acid ester unit of 5 mol% or more and 10 mol% or less and satisfying the ethylene-unsaturated carboxylic acid ester copolymer of the following general formula (1) (wherein ethylene unit and unsaturated carboxylic acid) At least one of the total of the ester units is set to 100 mol%; -3.0X+107>T...(1)

(In the formula (1), X represents an unsaturated carboxylic acid ester content (% by mole), and T represents a JIS according to JIS The melting point (°C) measured by K7121-1987; the resin (B) is 1 to 50 parts by mass, and the resin (B) is at least one selected from the group consisting of an ethylene-α-olefin copolymer and an ABA type block copolymer ( A represents a polystyrene block, B represents an alkylene copolymer block), and 0 to 10 parts by mass of the adhesion-imparting resin (C) (wherein the total amount of (A), (B), (C) is 100 parts by mass).

(Invention 2)

The resin composition for a sealant according to the first aspect of the invention, which comprises 60 to 95 parts by mass of the resin (A), 5 to 40 parts by mass of the resin (B), and 0 to 10 parts by mass of the resin (C) (wherein (A), The total amount of (B) and (C) is 100 parts by mass).

(Invention 3)

The resin composition for a sealant according to the invention of claim 1 or 2, further comprising ethylene having the following general formula (2) with respect to 100 parts by mass of the total of the resin (A), the resin (B) and the resin (C) The unsaturated carboxylic acid ester copolymer resin (D) is 60 parts by mass or less; T≧-3.0X+107 (2)

(In the formula (2), X represents an unsaturated carboxylic acid ester content (% by mole), and T represents a melting point (°C) measured according to JIS K7121-1987).

(Invention 4)

The resin composition for a sealant according to any one of Inventions 1 to 3 is a sealant for use in a container body and a lid substrate.

(Invention 5)

The resin composition for a sealant according to Invention 4, wherein at least a part of the contact with the cover substrate is a container body composed of impact-resistant polystyrene.

(Invention 6)

The resin composition for a sealant according to any one of Inventions 1 to 5, which is a cover material for a food container.

(Invention 7)

A cover material comprising the layer and the base material layer composed of the resin composition for a sealant according to any one of Inventions 1 to 6.

(Invention 8)

A food container having the cover material of the invention 7.

The resin composition of the present invention is a resin composition for a sealant suitable for heat sealing between a food container main body and a lid member. The resin composition for a sealant of the present invention is prepared by blending a predetermined component, that is, a resin (A), a resin (B), and a resin (C) with a resin (D) which is an optional component in a specific amount. At the same time, the excellent adhesion and high hygienic properties of the subject matter of the present invention are achieved. By heat-sealing the main body of the food container and the lid member through the heat seal layer composed of the resin composition for a sealant of the present invention, it is possible to obtain a food container which has excellent adhesion, easy-opening property and high hygienic property in a balanced manner.

The resin composition of the present invention contains a resin (A), at least one resin (B) selected from the group consisting of an ethylene-α-olefin copolymer and an ABA type block copolymer, and an adhesive imparting resin (C) in a specific amount. The resin (A) is selected from the group consisting of copolymerizing a vinyl ester monomer and ethylene in a specific ratio, and comprises an ethylene unit of 90 mol% or more and 95 mol% or less, and a vinyl ester unit. An ethylene-vinyl ester copolymer having 5 mol% or more and 10 mol% or less (wherein the total of ethylene units and vinyl ester units) Set to 100% by mole. And obtained by copolymerizing an unsaturated carboxylic acid ester monomer and ethylene in a specific ratio, comprising ethylene unit 90 mol% or more and 95 mol% or less, unsaturated carboxylic acid ester unit 5 mol% or more and 10 mol At least one of the ethylene-unsaturated carboxylic acid ester copolymer having a specific relationship between the unsaturated carboxylic acid ester unit and the melting point.

[Resin (A)]

The resin (A) contained in the resin composition for a sealant of the present invention is at least one selected from the group consisting of an ethylene-vinyl ester copolymer and an ethylene-unsaturated carboxylic acid ester copolymer satisfying the following formula (1).

-3.0X+107>T......(1)

(In the formula (1), X represents an unsaturated carboxylic acid ester content (% by mole), and T represents a melting point (°C) measured according to JIS K7121-1987)

The lower limit of the above T is preferably -3.0X+87.

The above vinyl ester is, for example, vinyl acetate or vinyl propionate, preferably vinyl acetate. The ethylene-vinyl ester copolymer used in the present invention is characterized by comprising ethylene unit of 90 mol% or more and 95 mol% or less, preferably 90 mol% or more and 93 mol% or less, and comprising a vinyl ester unit. 5 mol% or more and 10 mol% or less, preferably 7 mol% or more and 10 mol% or less (wherein the total of the ethylene unit and the vinyl ester unit is 100 mol%).

The ethylene-vinyl ester copolymer may be a multicomponent copolymer in which two kinds of the above vinyl esters are copolymerized with ethylene in addition to the ternary copolymer; and further, for example, the vinyl ester copolymer is inherently soft. Other characteristics such as acrylic acid, methacrylic acid, maleic acid, itaconic acid, maleic anhydride, and clothing may be used for the purpose of imparting substantially no change in properties such as elasticity and heat sealability. Acetic anhydride or mono-oxidation A small amount of copolymerization such as carbon.

From the viewpoint of the solvent extraction amount, the ethylene-vinyl ester copolymer of the following formula (1') is more preferably satisfied.

-3.0X’+107>T’...(1’)

(In the formula (1'), X' represents a vinyl ester content (% by mole), and T' represents a melting point (°C) measured according to JIS K7121-1987)

The lower limit of the above T' is preferably -3.0X+87.

The above-mentioned ethylene-vinyl ester copolymer is produced by radical copolymerization of ethylene and vinyl ester under high temperature and high pressure in accordance with a conventional method. It can also be produced by any of the methods of autoclaving or tubular method. The ethylene-vinyl ester copolymer satisfying the above formula (1') can be produced by a high pressure radical polymerization process by autoclaving.

The unsaturated carboxylic acid ester is an alkyl ester of an unsaturated carboxylic acid such as acrylic acid, methacrylic acid, maleic acid, fumaric acid or itaconic acid having a carbon number of about 20. The ethylene-unsaturated carboxylic acid ester copolymer used in the present invention is characterized by comprising an ethylene unit of 90 mol% or more and 95 mol% or less, preferably 90 mol% or more and 93 mol% or less, including The unsaturated carboxylic acid ester unit is 5 mol% or more and 10 mol% or less, preferably 7 mol% or more and 10 mol% or less (wherein the total of the ethylene unit and the unsaturated carboxylic acid ester unit is set to be 100 mol%). The ethylene-unsaturated carboxylic acid ester copolymer satisfying the formula (1) can be obtained by a high pressure radical polymerization process by autoclaving.

The ethylene-unsaturated carboxylic acid ester copolymer which satisfies the above formula (1) may be a multicomponent copolymer in which two or more kinds of the above carboxylic acid esters are copolymerized with ethylene in addition to the ternary copolymer; In the original case of ethylene-unsaturated carboxylic acid ester copolymer If the properties such as flexibility, elasticity, heat sealability and the like are not substantially changed, other polar monomers such as acrylic acid, methacrylic acid, maleic acid, itaconic acid, and cis-butene may be used. A small amount of copolymerized copolymer such as dianhydride, itaconic anhydride or carbon monoxide.

When the content of the vinyl ester unit or the unsaturated carboxylic acid ester unit is within this range, the resin composition for a sealant is excellent in balance between adhesion and hygienic properties. When the content of the vinyl ester unit or the unsaturated carboxylic acid ester unit is less than 5 mol%, the adhesive strength of the resin composition for a sealant is lowered, which may cause problems in the sealing property of the container. When the content of the vinyl ester unit or the unsaturated carboxylic acid ester unit exceeds 10 mol%, the adhesive strength is high, but the adhesion tends to occur, and the workability of the processed product obtained from the resin composition for the sealant is It is not appropriate.

The resin (A) contained in the resin composition for a sealant of the present invention preferably exhibits appropriate fluidity. The melt flow rate (MFR, measured at 190 ° C and 2160 g load) of the ethylene-vinyl ester copolymer and the ethylene-unsaturated carboxylic acid ester copolymer is usually 1 g/10 min or more and 50 g/10 min or less, preferably 10 g/10 minutes or more, more preferably 14 g/10 minutes or more. When the MFR of the resin (A) is extremely low, it is difficult to laminate the resin composition on a substrate to form a sheet-like object such as a lid member, which may be undesirable.

The resin (A) of the present invention may contain at least one selected from the group consisting of the above-mentioned ethylene-vinyl ester copolymer and ethylene-unsaturated carboxylic acid ester copolymer, and two or more kinds of ethylene-vinyl ester may be used. A copolymer or a mixture of two or more ethylene-unsaturated carboxylic acid ester copolymers. When two or more kinds of ethylene-vinyl ester copolymers or a mixture of two or more kinds of ethylene-unsaturated carboxylic acid ester copolymers are used, if the content of the vinyl ester unit or the unsaturated carboxylic acid ester unit in the mixture is the above Within the intended range, it is preferred that the MFR of the mixture is within the above range.

As an ethylene-vinyl ester copolymer, it is also possible to use a combination with a lower MFR. Ethylene-vinyl ester copolymer (A1) and ethylene-vinyl ester copolymer (A2) having a higher MFR; further, as an ethylene-unsaturated carboxylic acid ester copolymer, an ethylene-unsaturated carboxy group having a lower MFR may be used in combination The acid ester copolymer (A1') is an ethylene-unsaturated carboxylic acid ester (A2') having a higher MFR.

The above (A1) and (A2) may, for example, contain 90 mol% or more and 95 mol% or less of the ethylene unit, 5 mol% or more and 10 mol% or less of the vinyl ester unit, and MFR of 1 g/10 min or more. And 50 g/10 minutes or less, preferably 5 g/10 minutes or more and 30 g/10 minutes or less, more preferably 7 g/10 minutes or more and 25 g/10 minutes or less of the ethylene-vinyl ester copolymer (A1), and ethylene is contained. The unit is 90 mol% or more and 95 mol% or less, the vinyl ester unit is 5 mol% or more, 10 mol% or less, and the MFR is 80 g/10 min or more and 300 g/10 min or less, preferably 100 g/10 min or more. And an ethylene-vinyl ester copolymer (A2) of 250 g/10 minutes or less, more preferably 120 g/10 minutes or more and 250 g/10 minutes or less, preferably 1:9 to 9:1 by mass ratio (A1) : (A2)), better 5:5~8:2 ratio is used in combination.

The above (A1') and (A2') may, for example, contain 90 mol% or more and 95 mol% or less of the ethylene unit, 5 mol% or more of the unsaturated carboxylic acid ester unit, and 10 mol% or less and MFR of 1 g/10 min or more and 50 g/10 min or less, preferably 5 g/10 min or more and 30 g/10 min or less, more preferably 7 g/10 min or more and 25 g/10 min or less of the ethylene-unsaturated carboxylic acid ester copolymer (A1'), containing 90 mol% or more and 95 mol% or less of the ethylene unit, 5 mol% or more of the unsaturated carboxylic acid ester unit, 10 mol% or less, and MFR of 80 g/10 min or more and 300 g/10 Preferably, the ethylene-unsaturated carboxylic acid ester copolymer (A2') is preferably 100 g/10 min or more and 250 g/10 min or less, more preferably 120 g/10 min or more and 250 g/10 min or less. 1:9~9:1 (in terms of mass ratio (A1'): (A2')), more preferably 5:5~8:2. tree The lipid (A) may be a combination of (A1) and (A2') other than this, and a combination of (A1') and (A2).

[Resin (B)]

The resin (B) of the resin composition for a sealant of the present invention is selected from the group consisting of ethylene-α-olefin copolymer obtained by copolymerizing ethylene with an α-olefin having 3 to 18 carbon atoms, preferably 4 to 10 carbon atoms, and At least one of the ABA type block copolymers (A represents a polystyrene block, and B represents an alkylene copolymer block). The above ethylene-α-olefin copolymer is, for example, an α-olefin other than ethylene and ethylene, for example, selected from the group consisting of propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, and 1 a copolymer of one or more α-olefins of dodecene and 4-methyl-1-pentene. In consideration of the adhesiveness of the resin composition of the present invention, as the ethylene-α-olefin copolymer used as the resin (B) in the present invention, the density can be preferably 850 kg/m ³ or more and 910 kg/m ³ or less. More preferably, it is an ethylene-α-olefin copolymer of 870 kg/m ³ or more and 900 kg/m ³ or less. The MFR (190 ° C, 2160 g load) of the ethylene-α-olefin copolymer used in the present invention is generally 1 g/10 min or more and 100 g/10 min or less, preferably 1 g/10 min or more and 60 g/10 min or less. More preferably, it is 1 g/10 minutes or more and 20 g/10 minutes or less. The above-mentioned ethylene-α-olefin copolymer is a heterogeneous olefin polymerization catalyst using a highly active Ziegler-Natta catalyst composed of a highly active titanium catalyst component and an organoaluminum compound, a Philips catalyst, or the like, or as A homogeneous metallocene olefin polymerization catalyst such as a metallocene catalyst is produced by copolymerizing ethylene and the above α-olefin by a gas phase method, a solution method, a high pressure method or a slurry method.

In the above A-B-A type block copolymer, A represents a styrene polymer block, and B represents an alkylene copolymer block. Examples of the alkylene copolymer block include, for example, an ethylene-butene copolymer block or an ethylene-propylene copolymer block. Such a block copolymer is obtained by using a styrene-butadiene-styrene block copolymer or a styrene-different The butadiene polymer unit or the isoprene polymer unit of the pentadiene-styrene block copolymer is obtained by hydrogenation, and is generally referred to as SEBS or SEPS. Here, the content of the styrene polymer block is preferably from 1% by mass to 40% by mass, and more preferably from 5% by mass to 30% by mass based on the total mass of the A-B-A type block copolymer. Further, the melt flow rate (MFR) at 230 ° C and 2160 g load of the ABA type block copolymer is preferably from 0.1 g/10 min to 500 g/10 min, more preferably from 1 g/10 min to 100 g/10 min. . The MFR of the A-B-A type block copolymer is a value measured according to the method of JIS K7210-1999 at 230 ° C and a load of 5000 g. Specific examples of the A-B-A type block copolymer include Clayton G1657 manufactured by Clayton Japan, Co. Ltd., and Tuftec H1221 manufactured by Asahi Kasei Corporation.

As the resin (B) of the present invention, one type of the above ethylene-α-olefin copolymer may be used, or a mixture of two or more kinds of ethylene-α-olefin copolymers may be used. In the case where a mixture of two or more kinds of ethylene-α-olefin copolymers is used, it is preferred that the density or MFR of the mixture is within the above-mentioned predetermined range. Further, as the resin (B) of the present invention, one type of the above-mentioned A-B-A type block copolymer may be used, or a mixture of two or more types of A-B-A type block copolymers may be used. Further, as the resin (B) of the present invention, a mixture of one or more of the above ethylene-α-olefin copolymers and one or more of the above A-B-A type block copolymers can be used.

The resin (C) which is contained in the resin composition for a sealant of the present invention in an amount of not less than a certain amount is an adhesiveness-imparting resin. The resin (C) may be selected from resins having a function of imparting adhesion, and is preferably selected from the group consisting of an alicyclic hydrocarbon resin, an aromatic hydrocarbon resin, an aliphatic hydrocarbon resin, a polydecene resin, a rosin, and a styrene resin.

The alicyclic hydrocarbon resin is, for example, a resin obtained by subjecting a Spent C4 or C5 fraction to cyclization dimerization, followed by polymerization, and ring-forming of cyclopentadiene or the like. A resin obtained by polymerizing a monomer or a hydrogenated product thereof, or a resin obtained by intranuclear hydrogenation of an aromatic hydrocarbon resin or an aliphatic-aromatic copolymerized hydrocarbon resin. An alicyclic hydrocarbon resin (partially hydrogenated petroleum resin) which may be partially hydrogenated as part of the unsaturated double bond in the resin, or an alicyclic hydrocarbon resin in which all unsaturated double bonds in the resin are hydrogenated (fully hydrogenated petroleum) Any of the resins).

As the aromatic hydrocarbon resin, an unsaturated aromatic hydrocarbon having 3 to 10 carbon atoms such as at least one of vinyl toluene, isopropenyltoluene, hydrazine, and α-methylstyrene can be used without limitation. A resin obtained by polymerizing a fraction, a resin obtained by copolymerizing such a fraction with an aliphatic hydrocarbon fraction, or the like.

The aliphatic hydrocarbon resin is, for example, a polymer containing, as a main component, an olefin having 4 to 5 carbon atoms and a diene. The polydecene resin is, for example, a polymer such as α-pinene, β-pinene or dipentene, a terpene-phenol resin or a hydrogenated terpene resin. The above rosins are, for example, rosin, polymeric rosin, hydrogenated rosin, rosin ester or a hydride or polymer thereof. The styrene resin is, for example, a polymer such as styrene, vinyltoluene, α-methylstyrene or isopropenyltoluene, or a low molecular weight polymer such as a mutual copolymer. In the case where the color tone, the odor, the food hygiene, and the like which are properties of the resin composition of the present invention are emphasized, the resin (C) is preferably a hydrogenated petroleum resin in the above-mentioned examples.

[Amount ratio of resin (A), (B), (C)]

The resin composition for a sealant of the present invention is a resin composition in which the above resins (A), (B), and (C) are blended in a specific amount. In other words, the resin composition is prepared in a ratio of 50 to 99 parts by mass of the resin (A), 1 to 50 parts by mass of the resin (B), and 0 to 10 parts by mass of the resin (C). Here, the total amount of (A), (B), and (C) is 100 parts by mass. this The resin composition of the invention is preferably 60 to 95 parts by mass of the resin (A), 5 to 40 parts by mass of the resin (B), and 0 to 10 parts by mass of the resin (C), more preferably a resin (A). 70 to 95 parts by mass, 5 to 30 parts by mass of the resin (B), 0.5 to 8 parts by mass of the resin (C), more preferably 70 to 95 parts by mass of the resin (A), and resin (B) A resin composition blended in a ratio of 5 to 20 parts by mass and a resin (C) of 1.0 to 5 parts by mass.

When the amount of the resin (B) is less than 1 part by mass, the adhesive strength of the resin composition for a sealant, particularly the impact strength of the impact-resistant polystyrene, is lowered, which is not preferable. When the amount of the resin (B) is more than 50 parts by mass, the processability of the resin composition for a sealant is lowered, or the amount of solvent extraction is increased, and the hygienic property of the food is deteriorated, which is not preferable. When the amount of the tackifying resin (C) is more than 10 parts by mass, the adhesive strength of the resin composition for a sealant is high, but the solvent extraction amount is increased and the food hygiene is deteriorated, which is not preferable.

[Resin (D)]

The resin composition for a sealant of the present invention may further contain an ethylene-unsaturated carboxylic acid ester copolymer resin satisfying the formula (2) in addition to the above resins (A), (B), and (C). The ethylene-unsaturated carboxylic acid ester copolymer (hereinafter referred to as resin (D)) in the present embodiment is a copolymer of ethylene and an unsaturated carboxylic acid alkyl ester.

The alkyl ester of the unsaturated carboxylic acid may, for example, be an alkyl ester of an unsaturated carboxylic acid such as acrylic acid, methacrylic acid, maleic acid, fumaric acid or itaconic acid having a carbon number of about 20 or so. .

Examples of the alkyl ester of acrylic acid or methacrylic acid include methyl acrylate, ethyl acrylate, isopropyl acrylate, n-propyl acrylate, isopropyl acrylate, isobutyl acrylate, n-butyl acrylate, and acrylic acid 2- Ethylhexyl ester, ethyl methacrylate, A N-propyl acrylate, isopropyl methacrylate, isobutyl methacrylate, n-butyl methacrylate, dimethyl maleate, diethyl maleate, and the like. Among them, an alkyl (meth)acrylate having an alkyl ester having 2 or more and 4 or less carbon atoms is preferred from the viewpoint of availability, performance, and price.

Examples of such a preferred copolymer (D) include an ethylene-ethyl acrylate copolymer, an ethylene-n-propyl acrylate copolymer, an ethylene-isopropyl acrylate copolymer, and an ethylene-n-butyl acrylate copolymer. Ethylene-isobutyl acrylate copolymer, ethylene-ethyl methacrylate copolymer, ethylene-n-propyl methacrylate copolymer, ethylene-isopropyl methacrylate copolymer, ethylene-n-butyl methacrylate copolymerization , ethylene-isobutyl methacrylate copolymer, and the like. Further, the copolymer (D) in the present embodiment is a random binary copolymer, but a copolymer of a plurality of (meth)acrylic acid alkyl esters and ethylene is also included in the category of a random binary copolymer. The copolymer (D) has a melting point T (° C.) (according to JIS K7121-1987) and an unsaturated carboxylic acid ester unit content (X mole%) satisfying the following formula (2).

T≧-3.0X+107......(2)

The upper limit of the above T is preferably -3.0X+125.

The copolymer (D) can be obtained by a high pressure radical polymerization process carried out by a tubular process. For example, the total amount of the ethylene gas and the alkyl (meth) acrylate monomer and the organic peroxide are introduced from the inlet of the tubular reactor, and the average reaction temperature in the reactor is set to be in the range of 150 to 250 ° C. When polymerized, the copolymer (D) satisfying the above formula (2) can be obtained. Since the reactivity of ethylene with the alkyl (meth)acrylate is different, the concentration of the alkyl (meth)acrylate monomer in the ethylene gas changes at the inlet and outlet portions in the tubular reactor. That is, the concentration of the alkyl (meth) acrylate monomer in the ethylene gas becomes higher at the inlet portion, and becomes lower at the outlet portion, and the copolymer having a higher content of the alkyl (meth) acrylate is lower. The copolymer is formed by mixing and forming. Among them, (a Copolymers having a lower alkyl acrylate content impart higher melting points and heat resistance. Therefore, when the average value of the alkyl (meth)acrylate content of the copolymer is the same, the melting point of the copolymer obtained by the tubular method becomes higher than that of the autoclaving method, and thus the above formula can be obtained. Conditional resin (D).

The resin (D) may be a multicomponent copolymer in which two or more kinds of the above unsaturated carboxylic acid esters are copolymerized with ethylene in addition to the ternary copolymer; and the unsaturated carboxylic acid ester copolymer may be used. Other polar monomers such as acrylic acid, methacrylic acid, maleic acid, itaconic acid, and cis-butene may be used as long as the properties such as flexibility, elasticity, and heat-sealability are not substantially changed. A small amount of copolymerized copolymer such as dianhydride, itaconic anhydride or carbon monoxide.

The total of the ethylene unit and the unsaturated carboxylic acid ester unit is set to 100 mol %, and the unit of the unsaturated carboxylic acid ester constituting the resin (D) is usually in the range of 1 to 22 mol %, preferably 5 to 14 Mole% of the range. The MFR (190 ° C, 2160 g load) of the resin (D) used in the present invention is preferably 2 to 50 g/10 from the viewpoint of the adhesive seal strength of the obtained sealant composition and further from the viewpoint of workability and the like. In the range of minutes, it is especially good for 3~20g/10 minutes.

In the case where the resin (D) is, for example, an ethylene-alkyl (meth) acrylate copolymer, the alkyl (meth) acrylate unit content X in the above formula (2) is classified by (meth) The infrared absorbing spectrum (IR) of an alkyl acrylate was measured. For example, in the case of ethyl acrylate (EA), the absorbance at 860 cm ^-1 of the spectrum is determined.

Here, the EA concentration was determined by nuclear magnetic resonance spectroscopy (NMR), and a calibration curve was obtained by correlation with the absorbance of 860 cm ^-1 of IR. The calculation method of X in the formula (1) and X' in the formula (1') is also based on the calculation method of the above X.

The resin composition for a sealant of the present invention is relative to the resin (A), the tree 100 parts by mass of the total of the resin (D) and the resin (D) are preferably contained in an amount of not less than 1 part by mass and not more than 60 parts by mass, more preferably not more than 5 parts by mass and not more than 30 parts by mass, and more preferably It is preferably contained in an amount of 8 parts by mass or more and 30 parts by mass or less. When the amount of the resin (D) is more than 60 parts by mass, the adhesive strength of the resin composition is high, but the solvent extraction amount is increased and the food hygiene is deteriorated, which is not preferable.

As the resin (D) of the present invention, one type of the above-mentioned ethylene-unsaturated carboxylic acid ester copolymer may be used, or a mixture of two or more kinds of ethylene-unsaturated carboxylic acid ester copolymers may be used. When a mixture of two or more kinds of ethylene-unsaturated carboxylic acid ester copolymers is used, the MFR of the preferred mixture is preferably within the above range as long as the content of the mixture is within the above-mentioned predetermined range.

[arbitrary ingredients]

The resin composition for a sealant of the present invention can be removed without damaging the properties of the composition, and may contain other resins. Further, various additives may be further formulated in the resin composition for a sealant of the present invention as needed. Such additives are processing aids such as antioxidants, ultraviolet absorbers, light stabilizers, heat stabilizers, pigments, dyes, antistatic agents, lubricants or roll-off agents.

The sealing resin composition of the present invention is produced by simultaneously or sequentially mixing the above resins (A), (B), (C) and optionally the above resin (D) or the above-mentioned optional components. The mixing method follows a conventional method. It is preferable to melt-mix, for example, using a single-axis extruder, a twin-screw extruder, a Banbury mixer, various kneaders, etc., and the mixing order is not specifically limited. The melt mixing temperature is preferably from 140 ° C to 230 ° C.

When considering the extrusion processability and the adhesive strength, the resin composition for a sealant of the present invention is preferably prepared to have an MFR (190 ° C, 2160 g load) of 0.1 to 100 g/10 minutes. The clock is preferably about 1 to 30 g/10 minutes.

The resin composition for a sealant of the present invention is suitable as a sealant material for a plastic container. When the body of the container and the lid member are sealed using the resin composition of the present invention, the lid member having the layer composed of the resin composition of the present invention is usually heat-sealed to the container body in accordance with a conventional method. It is preferable that the cover material is formed by molding a multilayer laminated body comprising a layer composed of a resin composition for a sealant of the present invention and a lid substrate. The cover substrate is not particularly limited, and paper, aluminum plate (for example, aluminum foil), non-woven fabric, polyester, polyethylene, polypropylene, polystyrene (for example, impact-resistant polystyrene), aluminum-deposited polyester, or the like can be used. Aluminum vapor-deposited polypropylene, ruthenium dioxide vapor-deposited polyester, and the like. The cover substrate may be a single layer or a laminate of two or more layers. The thickness of the lid base layer is not particularly limited, but is usually about 1 to 500 μm, preferably 10 to 200 μm.

When the resin composition for a sealant of the present invention is laminated on a lid substrate, a method in which a film is formed by a casting method or an expansion method in advance by the resin composition and bonded to a lid substrate by dry lamination can be employed. a method of directly extruding and coating the resin composition on a lid substrate, using a polyethylene or the like in the adhesive layer, and laminating the layer through the adhesive layer by a sandwich layer method, and the lid substrate is A method in which the resin composition is coextruded, and the like. In these methods, a single layer or two or more cover base materials and two or more layers of a multilayer material composed of the resin composition for a sealant of the present invention are preferably co-extruded by a T-die method. Methods. The thickness of the layer composed of the resin composition for a sealant of the present invention is not particularly limited, but is usually about 1 to 500 μm, preferably 10 to 200 μm.

The material of the plastic container body may, for example, be a polyolefin such as polyethylene or polypropylene, such as polystyrene or impact-resistant polystyrene-like styrene polymer, such as polyethylene terephthalate. Polyester, polycarbonate, polyvinyl chloride, etc. this The material may be in the form of a foam. Among the materials of the main body, the impact-resistant polystyrene is generally used as a container body of ready-to-eat food, and has good adhesion to the resin composition for a sealant of the present invention. Therefore, the body of the plastic container which is heat-sealed by using the resin composition for a sealant of the present invention is preferably an impact-resistant polystyrene container or a container made of a material containing impact-resistant polystyrene. The container body may be a single layer or a laminate of two or more layers.

One of the characteristics of the resin composition for a sealant of the present invention is that the amount of solvent extraction is still small and the hygienic property is higher when the measurement is carried out under more stringent conditions. As a measurement condition which is more stringent than the conventional conditions, for example, a film-shaped sealant of 300 cm ² is used as a sample, and 600 ml of n-hexane is contacted with one side of the sample for 2 hours at room temperature, and then measured in the above-mentioned n-hexane. A method of the weight (actual elution amount (mg)) of the sample to be eluted. The resin composition for a sealant of the present invention has an actual elution amount measured by the method of preferably 30 mg or less, more preferably 20 mg or less.

In the case of a food container, in order to sufficiently seal the container and the container user can easily unseal the container, it is preferred to adhere the body of the container to the lid material with a certain degree of appropriate strength. One of the characteristics of the resin composition for a sealant of the present invention is that it can be used in such a food container. In the case where the sealant layer composed of the resin composition for a sealant of the present invention and the lid member of the lid base material and the container body are heat-sealed through the seal layer, the peel strength of the lid member and the container body becomes an appropriate strength range. Inside. The peeling strength is, for example, a cover material comprising a sealant layer composed of a resin composition for a sealant of the present invention, a cover material of a lid base material, and a plastic layer constituting the container body, which are heat-sealed via a sealant layer to form a multilayer material. The maximum stress was measured for the test piece having a width of 15 mm cut out from the multilayer material, which was stretched in the horizontally opposite direction and peeled off (180° peeling). The peeling of the resin composition for a sealant of the present invention by such a method The detachment strength is preferably 5 N/15 mm or more and 15 N/15 mm or less, more preferably 7 N/15 mm or more and 14 N/15 mm or less.

Further, the resin composition for a sealant of the present invention can suppress the occurrence of adhesion by optimizing its composition. Therefore, the multilayer film having the resin composition for a sealant of the present invention as a sealant layer does not cause adhesion or is maintained to a slight extent even if it is produced. A multilayer film comprising a sealant layer composed of a resin composition for a sealant of the present invention and a substrate is sequentially laminated in the order of the sealant layer/cover substrate, under a load of 5 kgf/cm ² at 40 When the aging is carried out for 2 days in an environment of ° C, the adhesion strength between the test pieces is preferably less than 100 g / 50 mm, more preferably less than 10 g / 50 mm.

[Examples]

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to the following examples without departing from the spirit thereof. Further, the melt flow rate (MFR) was measured in accordance with JIS K7210-1999 at 190 ° C and a load of 2160 g.

[Examples 1 to 6 and Comparative Examples 1 to 7]

According to the mixing ratio shown in Table 1 and Table 2, mixing was carried out so that the filling amount became 10 kg. Put into the extruder (65mm In the L/D=28, front-end Durmeg-based whole screw, melt-kneading was carried out at a processing temperature of 180 ° C to prepare a resin composition, and the resin composition of the present invention (Example) and comparative use were obtained. Resin composition (comparative example).

‧EVA1: ethylene-vinyl acetate copolymer

The ethylene unit content was 92.9 mol%, the vinyl acetate unit content was 7.1 mol%, the MFR (190 ° C, 2160 g load) was 15 g/10 min, and the melting point was 84 °C. It is produced by high pressure radical polymerization by autoclaving.

EVA2: ethylene-vinyl acetate copolymer

The ethylene unit content is 92.9 mol%, and the vinyl acetate unit content is 7.1 mol. %, MFR (190 ° C, 2160 g load) 150 g/10 min, melting point 79 ° C. It is produced by high pressure radical polymerization by autoclaving.

‧EVA3: ethylene-vinyl acetate copolymer

The ethylene unit content was 96.5 mol%, the vinyl acetate unit content was 3.5 mol%, the MFR (190 ° C, 2160 g load) was 9 g/10 min, and the melting point was 94 °C. It is produced by high pressure radical polymerization by autoclaving.

EVA4: ethylene-vinyl acetate copolymer

The ethylene unit content was 88.8 mol%, the vinyl acetate unit content was 11.2 mol%, the MFR (190 ° C, 2160 g load) was 15 g/10 min, and the melting point was 71 °C. It is produced by high pressure radical polymerization by autoclaving.

PO-1: ethylene-butene random copolymer elastomer manufactured by Mitsui Chemicals, Inc.

MFR (190 ° C, 2160 g load) 3.7 g/10 min, density 885 kg / m ³ .

PO-2: ethylene-hexene random copolymer manufactured by Mitsui Chemicals, Inc.

MFR (190 ° C, 2160 g load) 3.7 g/10 min, density 905 kg / m ³ .

SEBS: styrene-ethylene-butylene-styrene block copolymer

Clayton Japan, Co. Ltd. "Clayton G1657". MFR (230 ° C, 5000 g load) 22 g/10 min, density 900 kg / m ³ .

Adhesive imparting resin: fully hydrogenated aromatic hydrocarbon resin

Arakawa Chemical Industries, Ltd. products. The ring and ball softening point is 115 °C.

EMA: ethylene-methyl acrylate copolymer

The ethylene unit content was 92.5 mol%, the methyl acrylate unit content was 7.5 mol%, the MFR (190 ° C, 2160 g load) was 8 g/10 min, and the melting point was 92 °C. Manufacturing method: Manufactured by high pressure radical polymerization by a tubular method.

EMAA: ethylene-methacrylic acid copolymer

The ethylene unit content was 96.1 mol%, the methacrylic acid unit content was 3.9 mol%, and the MFR (190 ° C, 2160 g load) was 8 g/10 min.

The obtained resin composition was evaluated by the following viewpoint.

[bonding strength to HIPS]

The obtained resin composition was laminated to a polyethylene terephthalate layer (PET), a polyethylene layer (PE), a methyl group by an extrusion lamination method having a processing temperature of 240 ° C and a processing speed of 30 m/min. An ethylene-methacrylic acid copolymer layer (EMAA) having an acrylic acid unit content of 3.9 mol%. A laminate of PET (PET), EMAA, and resin composition in this order, which was laminated with PET (12 μm) / PE (15 μm) / EMAA (20 μm) / resin composition (10 μm) was obtained. The laminate was heat-sealed on a commercially available HIPS sheet having a thickness of 0.4 mm at a pressing force of 0.2 MPa, a heating temperature of 120 ° C, and a heating time of 1.0 second, and allowed to stand at room temperature for 24 hours. . Thereafter, both faces of the 15 mm-wide test piece cut out from the laminate were stretched in the opposite direction (stripping direction at 180 ° C) to obtain the maximum stress. The maximum stress (N/15 mm) was set as the adhesive strength (N/15 mm) of the resin composition to the HIPS at a heat sealing temperature of 120 °C. Except that the heat sealing temperature was changed, the measurement was carried out in the same manner as the above conditions, and the adhesive strength of the resin composition to the HIPS at a heat sealing temperature of 140 ° C and 160 ° C was also determined. The measurement results are shown in Tables 1 and 2.

The adhesion strength to the HIPS was determined according to the following criteria. The judgment results are shown in Tables 1 and 2.

‧A: Very good. 7N/15mm or more and 14N/15mm or less

‧B: Good. 5N/15mm or more and less than 7N/15mm, more than 14N/15mm and 15N/15mm or less

‧C: A little worse. 3N/15mm or more and less than 5N/15mm, exceeding 15N/15mm and 20N/15mm or less

‧D: Unqualified. Less than 3N/15mm or more than 20N/15mm.

[Adhesive strength]

Six samples of a width of 50 mm cut out from the laminate of the above-mentioned PET (12 μm) / PE (15 μm) / EMAA (20 μm) / resin composition (10 μm) were superposed, and under a load of 5 kgf / cm ² and 40 Matured in °C environment for 2 days. Thereafter, the peel strength of the six samples was measured by a measuring machine VG-35 of Vanguard Systems. The obtained strength (g/50 mm) was shown in Table 1 and Table 2 as the blocking strength.

The adhesion resistance was judged according to the following criteria. Here, the sample judged to be excellent is a sample which is less likely to cause adhesion. The results of the determination of the adhesion are shown in Tables 1 and 2.

‧A: Very good. Less than 10g/50mm.

‧B: Good. 10g/50mm or more and less than 100g/50mm.

‧C: Poor. 100g/50mm or more.

[Organic Solvent Extraction Test]

The test was carried out using a single-sided extractor used in the Ministry of Health and Welfare Notice No. 370. In the extraction container, the laminate of the above-mentioned PET (12 μm) / PE (15 μm) / EMAA (20 μm) / resin composition (10 μm) was placed with the resin composition layer facing upward, and 300 cm ² on one side of the laminate. The mixture was allowed to stand at room temperature for 2 hours while being in contact with 600 ml of n-hexane which is a solvent. Thereafter, the solvent was evaporated to measure the amount of residue (mg). The amount of the residue was defined as the solvent extraction amount (mg) from the laminate. The measurement results are shown in Tables 1 and 2.

The obtained solvent extraction amount (mg) was determined according to the following criteria. The judgment results are shown in Tables 1 and 2.

‧A: Very good. 20mg or less.

‧B: Good. More than 20 mg and less than 30 mg.

‧C: Unqualified. More than 30mg.

‧-: Not determined.

In Comparative Examples 1, 2, and 3 in which an ethylene-vinyl acetate copolymer having a too small amount of vinyl acetate unit was used, the adhesive strength to HIPS was low, and sufficient container sealing property could not be expected. In Comparative Example 4 in which the resin (A) was not used, the adhesion tendency was large, and the solvent extraction amount was high, and the desired hygienic property could not be obtained. In Comparative Example 5 in which an ethylene-vinyl acetate copolymer having an excessive amount of vinyl acetate unit was used, the solvent extraction amount and the adhesion tendency were large, and it was predicted that the hygienic property, the handleability of the cover material, and the processability were high. There is a problem. In Comparative Example 6 in which the amount of the resin (A) was too small, the workability was extremely poor. In Comparative Example 7 which did not contain the resin (B), the adhesive strength to the HIPS was lower than that of Comparative Example 1.

As described above, the resin composition for a sealant of the comparative example has problems in any of adhesion, solvent extraction amount, and processability, and is not suitable for practical use.

In contrast, the resin composition for the sealant of the examples is in a wide range. The temperature shows a general bond strength to HIPS and the solvent extraction amount is extremely low. Further, the resin composition for a sealant of the examples has a low adhesion tendency and is excellent in the usability as a heat seal layer of the lid member. As described above, the resin composition for a sealant of the embodiment has a viscosity, a hygienic property, and a processability which can be opened in a well-balanced container.

(industrial availability)

The resin composition for a sealant of the present invention can be used for heat sealing of a container requiring higher hygiene and safety, and can be expected as a next-generation sealant material. The container to which the resin composition for a sealant of the present invention can be applied is a container which is adhered to the lid member by heat sealing, and may be any container. For example, from the viewpoint of easily opening the container, it is preferable to include a container body and a lid member made of impact-resistant polystyrene or a material mainly composed thereof. Further, since the resin composition for heat sealing of the present invention has a low problem of component transfer of foods belonging to the contents, it is suitable for food containers. Examples of the food container using the resin composition for a sealant of the present invention include snacks, cereals, jellies, puddings, yogurt, tofu, side dishes, ready-to-eat foods (for example, instant noodles, instant soup), beverages, and fresh food. Ingredients such as ingredients or processed products. The resin composition for a sealant of the present invention has a high practical value in a country or region where a food container has a stricter sanitary standard.

Claims (8)

A resin composition for a sealant comprising: 50 to 99 parts by mass of a resin (A) selected from the group consisting of 90 mol% or more and 95 mol% or less of ethylene unit, and 5 mol% of a vinyl ester unit. An ethylene-vinyl ester copolymer (wherein the total of the ethylene unit and the vinyl ester unit is 100 mol%) and an ethylene unit of 90 mol% or more and 95 mol% or less, and more than 10 mol% or less, An ethylene-unsaturated carboxylic acid ester copolymer having an unsaturated carboxylic acid ester unit of 5 mol% or more and 10 mol% or less and satisfying the following formula (1) (wherein the total of ethylene units and unsaturated carboxylic acid ester units) At least one of 100 mol %); -3.0X+107>T (1) (in the formula (1), X represents an unsaturated carboxylic acid ester content (% by mole), T The melting point (°C) measured according to JIS K7121-1987; the resin (B) is 1 to 50 parts by mass, and the resin (B) is at least selected from the group consisting of ethylene-α-olefin copolymer and ABA type block copolymer. One (A represents a polystyrene block, B represents an alkylene copolymer block); and the adhesive imparting resin (C) is 0 to 10 parts by mass (wherein the total of (A), (B), (C) The amount is 100 parts by mass). The resin composition for sealant of claim 1, which comprises 60 to 95 parts by mass of the resin (A), 5 to 40 parts by mass of the resin (B), and 0 to 10 parts by mass of the resin (C) (wherein (A) The total amount of (B) and (C) is 100 parts by mass). The resin composition for a sealant according to claim 1 or 2, further comprising ethylene satisfying the following formula (2) with respect to 100 parts by mass of the total of the resin (A), the resin (B), and the resin (C). The unsaturated carboxylic acid ester copolymer resin (D) is 60 parts by mass or less; T≧-3.0X+107 (2) In the formula (2), X represents an unsaturated carboxylic acid ester content (% by mole), and T represents a melting point (°C) measured according to JIS K7121-1987. The resin composition for a sealant according to any one of claims 1 to 3, which is a sealant for use in a container body and a lid substrate. The resin composition for a sealant according to claim 4, wherein at least a part of the contact with the lid substrate is a container body made of impact-resistant polystyrene. The resin composition for a sealant according to any one of claims 1 to 5, which is a cover material for a food container. A cover material comprising a layer and a substrate layer composed of a resin composition for a sealant according to any one of claims 1 to 6. A food container having the cover material of claim 7.