KR102525720B1 - Resin composition and use thereof - Google Patents

Abstract

An excellent resin composition for a sealant suitable for a cover material of a food container is provided.
An ethylene-vinyl ester copolymer containing 90 mol% or more and 95 mol% or less of ethylene units and 5 mol% or more and 10 mol% or less of vinyl ester units, and 90 mol% or more of ethylene units and 95 mol% or less of unsaturated carboxylic acid units 50 to 99 parts by mass of at least one resin (A) selected from ethylene/unsaturated carboxylic acid ester copolymers containing 5 mol% or more and 10 mol% or less and satisfying the formula (1);
-3.0X+107>T ... (1) (In formula (1), X represents the content of unsaturated carboxylic acid esters (mol%), and T represents the melting point (°C) measured in accordance with JIS K7121-1987)
1 to 50 parts by mass of at least one resin (B) selected from ethylene/α-olefin copolymers and ABA block copolymers (A represents a polystyrene block and B represents an alkylene copolymer block) The resin composition for sealants containing 0-10 mass parts of imparting resins (C).

Description

Resin composition and its use {RESIN COMPOSITION AND USE THEREOF}

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

BACKGROUND ART A plastic container having an easy-opening cover is widely used as a container for various foods or medicines such as jelly, pudding, yogurt, tofu, instant noodles, and noodles. In particular, as containers for instant noodles, noodles, red bean porridge, etc. in cups, containers made of expanded polystyrene sheets or those bonded with impact-resistant polystyrene films, impact-resistant polystyrene sheets, polyethylene laminated paper, etc. are widely used. It is becoming. As a sealing material used for the cover of these plastic containers, various materials have been proposed and put into practical use in order to seal the seal in an open-seal shape. Among them, compositions mainly composed of ethylene and vinyl acetate, copolymers of ethylene and acrylic acid esters, or polyolefin resins have relatively good sealability between the container body and the cover body, and generally reasonable peel strength when the cover is peeled off. It is widely used in terms of

For example, in Patent Document 1, a metal layer, an adhesive layer, an ethylene-vinyl acetate copolymer system resin, an ethylene-acrylic acid ester copolymer resin, and a resin selected from polyolefin resins and a tackifier. It is described that a laminate obtained by sequentially laminating resin layers is suitable as an easily removable cover material for a bead expanded polystyrene container.

Patent Literature 2 describes that a sealant comprising a composition containing an ethylene-(meth)acrylic acid copolymer, polyolefin, tackifying resin, and filler in a specific ratio provides a seal that is stronger and can be peeled off than a known sealant. there is.

Patent Document 1: Japanese Unexamined Patent Publication No. 3-79342 Patent Document 2: Japanese Patent Publication No. 2007-522276 On the other hand, food containers are, of course, required to have sanitary properties that do not impair the quality of the food content. For this reason, independent sanitary standards for food containers are established depending on the country or region, and in the case of Japan, standards have already been established more than 50 years ago (standards for food and additives based on Article 18 of the Food Sanitation Law (1959 Ministry of Health and Welfare Notice No. 370)). These standards basically aim at preventing the ingredients of the container from shifting to food as the content, and limit the extraction amount of the container material to various solvents, such as organic solvents and oils. Avoiding such migration of ingredients is a particularly important goal for containers of oily foods, such as fried noodles or oil-cooked side dishes, where migration of ingredients from plastic containers is more of a concern. Conventionally, materials that meet such sanitary standards have been used for food container materials such as container bodies, lids, and sealant materials, but food sanitation standards such as the amount of solvent extraction tend to become stricter every year, and particularly strict standards are established. There are also countries that do. However, even if it has succeeded in lowering the solvent extraction amount of the sealant material so far, it is not always possible to satisfy the adhesiveness of the sealant material at the same time, and it is not easy to achieve both hygiene and adhesiveness of the sealant material. For this reason, a sealant composition that can meet the recent demand as a sealant material for food containers with excellent balance of adhesive strength and openability with containers and very low component elution to organic solvents has not yet been obtained.

The inventors of the present invention conducted intensive studies in pursuit of an excellent sealant material that satisfies stricter sanitary standards in addition to the adhesiveness required for food container cover materials. That is, an object of the present invention is to provide a sealant material that achieves the sealability and good openability required for lid materials for food containers, and also satisfies stricter sanitary standards than before due to a small amount of solvent extraction.

As a result, it was found that a resin composition containing a specific ethylene copolymer as a main component and blending an ethylene/α-olefin copolymer and a tackifying resin in a specific ratio satisfies the above problems and is excellent as a sealant material for food containers. That is, this invention is the following.

(Invention 1)

An ethylene-vinyl ester copolymer containing 90 mol% or more and 95 mol% or less of ethylene units and 5 mol% or more and 10 mol% or less of vinyl ester units (however, the sum of ethylene units and vinyl ester units is 100 mol%) , And an ethylene-unsaturated carboxylic acid ester copolymer containing 90 mol% or more and 95 mol% or less of ethylene units and 5 mol% or more and 10 mol% or less of unsaturated carboxylic acid ester units and satisfying the following general formula (1) (provided that the ethylene unit and 50 to 99 parts by mass of at least one resin (A) selected from

-3.0X+107＞T...(1)

(In Formula (1), X represents the unsaturated carboxylic acid ester content (mol%), and T represents the melting point (°C) measured in accordance with JIS K7121-1987)

1 to 50 parts by mass of at least one resin (B) selected from ethylene/α-olefin copolymers and A-B-A type block copolymers (A represents a polystyrene block and B represents an alkylene copolymer block);

Contains 0 to 10 parts by mass of tackifying resin (C) (however, the total amount of (A), (B) and (C) is 100 parts by mass),

Resin composition for sealant.

(Invention 2)

60 to 95 parts by mass of resin (A), 5 to 40 parts by mass of resin (B), and 0 to 10 parts by mass of resin (C) (however, the total amount of (A), (B), and (C) 100 parts by mass of silver), the resin composition for sealant according to Invention 1.

(Invention 3)

An ethylene-unsaturated carboxylic acid ester copolymer resin (D) satisfying the following general formula (2) is further contained at 60 parts by mass or less based on 100 parts by mass of the total of the resin (A), the resin (B) and the resin (C) The resin composition for sealants of the invention 1 or 2.

T≥-3.0X+107 ... (2)

(In Formula (2), X represents the unsaturated carboxylic acid ester content (mol%), and T represents the melting point (°C) measured in accordance with JIS K7121-1987)

(Invention 4)

The resin composition for a sealant according to any one of Inventions 1 to 3, which is used for a sealant of a container body and a cover base material.

(Invention 5)

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

(Invention 6)

The resin composition for a sealant according to any one of Inventive Aspects 1 to 5, which is for use in covering materials for food containers.

(Invention 7)

A cover material comprising a layer made of the resin composition for sealant according to any one of Inventive Aspects 1 to 6 and a substrate layer.

(Invention 8)

A food container having the cover material of Invention 7.

The resin composition of the present invention is a resin composition for a sealant suitable for heat sealing between a food container body and a cover member. The resin composition for sealants of the present invention is obtained by blending predetermined components, that is, resins (A), resins (B), and resins (C), and resin (D) as an optional component in a specific amount ratio, It made it possible to achieve coexistence of adhesiveness and very high hygiene. By heat-sealing the main body of the food container and the cover material through a heat-sealing layer made of the resin composition for sealant of the present invention, a food container having good adhesiveness, easy-openability and high sanitation in a good balance is obtained.

The resin composition of the present invention is obtained by copolymerizing vinyl ester monomers with ethylene in a specific ratio, and contains 90 mol% or more and 95 mol% or less of ethylene units and 5 mol% or more and 10 mol% or less of vinyl ester units. Ethylene/vinyl ester A copolymer (provided that the total of ethylene units and vinyl ester units is 100 mol%), and 90 mol% or more and 95 mol% or less of ethylene units obtained by copolymerizing an unsaturated carboxylic acid ester monomer and ethylene in a specific ratio, unsaturated At least one resin (A) selected from ethylene/unsaturated carboxylic acid ester copolymers containing 5 mol% or more and 10 mol% or less of carboxylic acid ester units and having a specific relationship between unsaturated carboxylic acid ester units and melting point, and ethylene/α - At least one type of resin (B) selected from olefin copolymers and A-B-A type block copolymers and a tackifier resin (C) are blended in a specific ratio.

[Suzy (A)]

Resin (A) contained in the resin composition for sealants of the present invention is at least one resin selected from ethylene/vinyl ester copolymers and ethylene/unsaturated carboxylic acid ester copolymers satisfying the following general formula (1).

-3.0X+107＞T... (1)

(In Formula (1), X represents the unsaturated carboxylic acid ester content (mol%), and T represents the melting point (°C) measured in accordance with JIS K7121-1987)

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

The vinyl ester is, for example, vinyl acetate or vinyl propionate, preferably vinyl acetate. The ethylene-vinyl ester copolymer used in the present invention contains ethylene units of 90 mol% or more and 95 mol% or less, preferably 90 mol% or more and 93 mol% or less, and vinyl ester units of 5 mol% or more and 10 mol% or less, preferably It is characterized in that it contains 7 mol% or more and 10 mol% or less (provided that the sum of ethylene units and vinyl ester units is 100 mol%).

The ethylene-vinyl ester copolymer may be a multi-component copolymer obtained by copolymerizing two of the above-mentioned vinyl esters with ethylene in addition to a binary copolymer, and the vinyl ester copolymer inherently possesses, for example, flexibility, elasticity, heat seal Other polar monomers such as acrylic acid, methacrylic acid, maleic acid, itaconic acid, maleic acid anhydride, itaconic acid anhydride, carbon monoxide, etc. may be copolymerized in small amounts as long as the properties such as properties are not substantially changed. .

An ethylene/vinyl ester copolymer satisfying the following general formula (1') is more preferable in view of the amount of solvent extraction.

-3.0X'+107>T'...(1')

(In formula (1'), X' represents the vinyl ester content (mol%), and T' represents the melting point (°C) measured in accordance with JIS K7121-1987)

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

The ethylene-vinyl ester copolymer as described above is produced by radical copolymerization of ethylene and vinyl ester under high temperature and high pressure according to a conventional method. It can be manufactured by any method of an autoclave method or a tubular method. An ethylene-vinyl ester copolymer satisfying the above formula (1') can be produced by a high-pressure radical polymerization process according to an autoclave method.

The said unsaturated carboxylic acid ester is an alkyl ester of up to about 20 carbon atoms of unsaturated carboxylic acid, such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, and itaconic acid. The ethylene/unsaturated carboxylic acid ester copolymer used in the present invention contains 90 mol% or more and 95 mol% or less, preferably 90 mol% or more and 93 mol% or less, of ethylene units and 5 mol% or more and 10 mol% or less of unsaturated carboxylic acid ester units. , preferably 7 mol% or more and 10 mol% or less (provided that the sum of ethylene units and unsaturated carboxylic acid ester units is 100 mol%). An ethylene/unsaturated carboxylic acid ester copolymer satisfying Formula (1) can be obtained by a high-pressure radical polymerization process according to an autoclave method.

The ethylene/unsaturated carboxylic acid ester copolymer that satisfies the above formula (1) may be a multi-component copolymer obtained by copolymerizing two or more of the above carboxylic acid esters with ethylene in addition to the binary copolymer, and the ethylene/unsaturated carboxylic acid ester copolymer Other polar monomers, such as acrylic acid, methacrylic acid, maleic acid, itaconic acid, maleic anhydride, itaconic anhydride, as long as the original properties, such as flexibility, elasticity, and heat sealability, are not substantially changed. What copolymerized a small amount of conic acid, carbon monoxide, etc. may be sufficient.

When the content of the vinyl ester unit or the unsaturated carboxylic acid ester unit is within this range, the adhesiveness of the resin composition for sealant and the hygienic balance are excellent. When the content of the vinyl ester unit or the unsaturated carboxylic acid ester unit is lower than 5 mol%, the adhesive strength of the resin composition for sealants is lowered, which may cause a problem in the sealability 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 blocking phenomenon tends to occur, and the handleability of the processed product obtained from the resin composition for sealant is undesirable in some cases.

Resin (A) contained in the resin composition for sealants of the present invention preferably exhibits appropriate fluidity. The melt flow rate (MFR, measured at 190 ° C., under a load of 2160 g) of the ethylene/vinyl ester copolymer and the ethylene/unsaturated carboxylic acid ester copolymer is generally 1 g/10 min or more and 50 g/10 min or less, preferably It is 10 g/10 min or more, More preferably, it is 14 g/10 min or more. When the MFR of the resin (A) is extremely low, it becomes difficult to laminate the resin composition on a base material and process it into a sheet-like material such as a cover material, which is undesirable in some cases.

As the resin (A) of the present invention, it is sufficient to contain at least one selected from the above-mentioned ethylene/vinyl ester copolymers and ethylene/unsaturated carboxylic acid ester copolymers, and two or more types of ethylene/vinyl ester copolymers or two A mixture of more than one kind of ethylene/unsaturated carboxylic acid ester copolymer may be used. When using a mixture of two or more types of ethylene/vinyl ester copolymers or two or more types of ethylene/unsaturated carboxylic acid ester copolymers, the content of vinyl ester units or unsaturated carboxylic acid ester units in the mixture is as long as it is within the above predetermined range, It is preferable that the MFR of the mixture is within the above range.

As the ethylene/vinyl ester copolymer, an ethylene/vinyl ester copolymer (A1) having a relatively low MFR and an ethylene/vinyl ester copolymer (A2) having a relatively high MFR may be used in combination, or an ethylene/unsaturated carboxylic acid ester copolymer As a copolymer, an ethylene/unsaturated carboxylic acid ester copolymer (A1') having a relatively low MFR and an ethylene/unsaturated carboxylic acid ester (A2') having a relatively high MFR may be used together.

As the above (A1) and (A2), for example, the ethylene unit is 90 mol% or more and 95 mol% or less, and the vinyl ester unit is 5 mol% or more and 10 mol% or less, and the MFR is 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, an ethylene-vinyl ester copolymer (A1), and 90 mol% or more of ethylene units 95 mol% or less, including 5 mol% or more and 10 mol% or less of vinyl ester units, MFR of 80 g/10 min or more and 300 g/10 min or less, preferably 100 g/10 min or more and 250 g/10 min or less, more preferably is 120 g/10 min or more and 250 g/10 min or less of the ethylene/vinyl ester copolymer (A2), preferably 1:9 to 9:1 ((A1):(A2) in mass ratio), more preferably 5 It can be used together in a ratio of 5 to 8:2.

As the above (A1') and (A2'), for example, the ethylene unit is 90 mol% or more and 95 mol% or less, the unsaturated carboxylic acid ester unit is 5 mol% or more and 10 mol% or less, and the MFR is 1 g/10 min or more 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 an ethylene/unsaturated carboxylic acid ester copolymer (A1'), and an ethylene unit 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 an MFR of 80 g / 10 min or more and 300 g / 10 min or less, preferably 100 g / 10 min or more 250 g / 10 min or less, more preferably 120 g/10 min or more and 250 g/10 min or less of the ethylene-unsaturated carboxylic acid ester copolymer (A2'), preferably in a ratio of 1:9 to 9:1 ((A1'):( A2')), more preferably in an amount ratio of 5:5 to 8:2. In addition to this, resin (A) may be a combination of (A1) and (A2') or a combination of (A1') and (A2).

[Suzy (B)]

The resin (B) of the resin composition for sealants of the present invention is an 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 an ABA type block copolymer. (A represents a polystyrene block and B represents an alkylene copolymer block). The ethylene/α-olefin copolymer is, for example, ethylene and an α-olefin other than ethylene, such as propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1- It is a copolymer of one or more ?-olefins selected from dodecene and 4-methyl-1-pentene. Considering the adhesiveness of the resin composition of the present invention, the ethylene/α-olefin copolymer used as the resin (B) in the present invention has a density of preferably 850 kg/m ³ or more and 910 kg/m ³ or less, more preferably An ethylene-α-olefin copolymer of 870 kg/m ³ or more and 900 kg/m ³ or less is used. 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, they are 1 g/10 min or more and 20 g/10 min or less. The ethylene/α-olefin copolymer as described above is a heterogeneous olefin polymerization catalyst such as a highly active Ziegler-Natta catalyst or a Phillips catalyst composed of a highly active titanium catalyst component and an organoaluminum compound, or a homogeneous catalyst such as a metallocene catalyst. It is produced by copolymerizing ethylene and the α-olefin in a process such as a gas phase method, a solution method, a high pressure method, or a slurry method using an olefin polymerization catalyst or the like.

In the 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 ethylene/butene copolymer blocks and ethylene/propylene copolymer blocks. Such a block copolymer is obtained by hydrogenating a butadiene polymer unit or an isoprene polymer unit of a styrene-butadiene-styrene block copolymer or a styrene-isoprene-styrene block copolymer, It is generally referred to as SEBS or SEPS. Here, the content of the styrene polymer block is preferably 1% by mass to 40% by mass, more preferably 5% by mass to 30% by mass with respect to the total mass of the A-B-A type block copolymer. Further, the melt flow rate (MFR) of the A-B-A type block copolymer at 230°C and a load of 2160 g is preferably 0.1 g/10 min to 500 g/10 min, more preferably 1 g/10 min to 100 g/10 It is a minute. The MFR of the A-B-A type block copolymer is a value measured at 230°C and a load of 5000 g by a method based on JIS K7210-1999. As a specific example of A-B-A type block copolymer, Kraton G1657 by the Kraton Japan company, Tuftec H1221 by the Asahi Kasei Chemicals company, etc. are mentioned, for example.

As the resin (B) of the present invention, either one of the ethylene/α-olefin copolymers described above may be used, or a mixture of two or more ethylene/α-olefin copolymers may be used. In the case of using a mixture of two or more types of ethylene/α-olefin copolymers, the mixture preferably has a density or MFR within the above-specified range. Moreover, as resin (B) of this invention, 1 type of the above-mentioned A-B-A type block copolymers may be used, or a mixture of 2 or more types of A-B-A type block copolymers may be used. Furthermore, as the resin (B) of the present invention, a mixture comprising at least one of the above ethylene/α-olefin copolymers and at least one of the above A-B-A type block copolymers may be used.

The resin (C) that may be contained in a certain amount or less in the resin composition for sealants of the present invention is a tackifying resin. The resin (C) can be selected from resins having a function of imparting tackiness, and is preferably selected from alicyclic hydrocarbon resins, aromatic hydrocarbon resins, aliphatic hydrocarbon resins, polyterpene resins, rosins, and styrene-based resins. do.

As the alicyclic hydrocarbon resin, for example, a resin obtained by polymerizing spent C4 or C5 fractions after cyclization dimerization, a resin obtained by polymerizing cyclic monomers such as cyclopentadiene, or hydrogenated products thereof, and aromatic carbonization It is a resin obtained by hydrogenating a hydrogen resin or an aliphatic/aromatic copolymerized hydrocarbon resin in the nucleus. An alicyclic hydrocarbon resin in which some of the unsaturated double bonds in the resin are partially hydrogenated (partially hydrogenated petroleum resin) may be used, or an alicyclic hydrocarbon resin in which all of the unsaturated double bonds in the resin are hydrogenated (fully hydrogenated petroleum resin). ) may be any of them.

As the aromatic hydrocarbon resin, a resin obtained by polymerization of oils containing at least one unsaturated aromatic hydrocarbon having 3 to 10 carbon atoms such as vinyltoluene, isopropenyltoluene, indene, and α-methylstyrene, and aliphatic carbonization with these oils A resin obtained by copolymerizing a hydrogen fraction may be used without limitation.

The said aliphatic hydrocarbon resin is a polymer which has a C4-C5 olefin, diene, etc. as a main component, for example. The polyterpene resin is, for example, a polymer such as α-pinene, β-pinene, or dipentene, a terpene-phenol resin, or a hydrogenated terpene resin. The said rosin is, for example, rosin, polymerized rosin, hydrogenated rosin, rosin ester, or its hydrogenated substance or polymer. The styrene-based resin is, for example, a polymer such as styrene, vinyltoluene, α-methylstyrene, and isopropenyltoluene, or a low molecular weight polymer such as a mutual copolymer thereof. As the resin (C), when color tone, odor, food hygiene, and the like are important as performance of the resin composition of the present invention, hydrogenated petroleum resin is preferable among the above examples.

[Ratio of resins (A), (B), and (C)]

In the resin composition for sealants of the present invention, the resins (A), (B) and (C) are blended in a specific ratio. That is, 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) are blended. However, the total amount of (A), (B), and (C) is 100 parts by mass. The resin composition of the present invention preferably contains 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 ( 70 to 95 parts by mass of A), 5 to 30 parts by mass of resin (B), 0.5 to 8 parts by mass of resin (C), more preferably 70 to 95 parts by mass of resin (A), and resin (B) 5 to 20 parts by mass and 1.0 to 5 parts by mass of the resin (C).

When the blending amount of the resin (B) is less than 1 part by mass, the adhesive strength of the resin composition for sealants, particularly the adhesive strength to impact-resistant polystyrene, is lowered, which is not preferable. When the blending amount of the resin (B) exceeds 50 parts by mass, the processability of the resin composition for sealant decreases or the solvent extract content increases to deteriorate food hygiene, so it is not preferable. If the blending amount of the tackifying resin (C) exceeds 10 parts by mass, the adhesive strength of the resin composition for sealant is high, but the solvent extract content increases and food hygiene is poor, so it is not preferable.

[Suzy (D)]

The resin composition for sealant of the present invention may further contain an ethylene/unsaturated carboxylic acid ester copolymer resin satisfying the general 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.

Examples of unsaturated carboxylic acid alkyl esters include alkyl esters of up to about 20 carbon atoms of unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, and itaconic acid.

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, 2-ethylhexyl acrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, n-butyl methacrylate, dimethyl maleate, and diethyl maleate. Among these, (meth)acrylic acid alkyl esters having an alkyl ester having 2 or more and 4 or less carbon atoms are preferable from the balance of availability, performance and price.

Examples of such preferred copolymers (D) include ethylene-ethyl acrylate copolymers, ethylene-n-propyl acrylate copolymers, ethylene-isopropyl acrylate copolymers, ethylene-n-butyl acrylate copolymers, and ethylene-isobutyl acrylate copolymers. , ethylene-ethyl methacrylate copolymer, ethylene-n-propyl methacrylate copolymer, ethylene-isopropyl methacrylate copolymer, ethylene-n-butyl methacrylate copolymer, ethylene-isobutyl methacrylate copolymer, etc. can be heard In addition, although the copolymer (D) in this embodiment is a random dual copolymer, what copolymerized several alkyl (meth)acrylic acid esters with ethylene also falls into the category of a random dual copolymer. The copolymer (D) satisfies the following formula (2) with respect to its melting point T (°C) (based on JIS K7121-1987) and unsaturated carboxylic acid ester unit content (X mol%).

T≥-3.0X+107 ... (2)

As the upper limit of the said T, -3.0X+125 is preferable.

The copolymer (D) can be obtained by a high-pressure radical polymerization process according to a tubular method. For example, when polymerization is performed by introducing ethylene gas, the total amount of an alkyl (meth)acrylate monomer, and an organic peroxide from the inlet of a tubular reactor, and setting the average reaction temperature in the reactor to the range of 150 to 250 ° C, A copolymer (D) satisfying the above formula (2) is obtained. Since the reactivity between ethylene and alkyl (meth)acrylate ester is different, the concentration of the alkyl (meth)acrylate monomer in ethylene gas changes at the inlet and outlet of the tubular reactor. That is, the concentration of the (meth)alkyl ester monomer in the ethylene gas is high at the inlet and low at the outlet, and a copolymer with a high content of (meth)acrylic acid ester and a copolymer with a low content are mixed and produced. Among them, a copolymer having a low content of (meth)acrylic acid alkyl ester has a higher melting point and heat resistance. Therefore, since the melting point of the copolymer obtained by the tubular method is higher than that of the autoclave method when the average value of the content of alkyl (meth)acrylic acid in the copolymer is the same, the resin (D) satisfying the condition of the above formula can be obtained. there is.

The resin (D) may be a multi-component copolymer obtained by copolymerizing two or more of the above-mentioned unsaturated carboxylic acid esters with ethylene in addition to the binary copolymer. Other polar monomers, such as acrylic acid, methacrylic acid, maleic acid, itaconic acid, maleic acid anhydride, itaconic acid anhydride, carbon monoxide, etc. may be copolymerized in small amounts, as long as the properties are not substantially changed.

The unsaturated carboxylic acid ester unit constituting the resin (D) is generally 1 to 22 mol%, preferably 5 to 14 mol%, with the total of the ethylene unit and the unsaturated carboxylic acid ester unit being 100 mol%. . The MFR (190 ° C., 2160 g load) of the resin (D) used in the present invention is preferably in the range of 2 to 50 g / 10 minutes from the viewpoint of the adhesive seal strength of the resulting sealant composition, and furthermore, workability, etc. , particularly preferably 3 to 20 g/10 min.

When the resin (D) is, for example, an ethylene/alkyl (meth)acrylate ester copolymer, the alkyl (meth)acrylate unit content X in the above formula (2) is an infrared absorption spectrum attributed to the alkyl (meth)acrylate ( IR) is measured. For example, in the case of ethyl acrylate (EA), it is determined from the absorbance at 860 cm ^-1 attributed to EA.

However, the calibration curve is obtained by obtaining the EA concentration by nuclear magnetic resonance spectrum (NMR) and by correlation with the IR absorbance at 860 cm ⁻¹ . The calculation method of X in Formula (1) and X' in Formula (1') also conforms to the example of the calculation method of X mentioned above.

In the resin composition for sealants of the present invention, the resin (D) is preferably 1 part by mass or more and 60 parts by mass or less, more than 100 parts by mass in total of the resin (A), the resin (B), and the resin (C). Preferably it is 5 parts by mass or more and 30 parts by mass or less, more preferably 8 parts by mass or more and 30 parts by mass or less. When the blending amount of the resin (D) exceeds 60 parts by mass, the adhesive strength of the resin composition is high, but the solvent extract content increases and the food hygiene is poor, which is undesirable in some cases.

As the resin (D) of the present invention, one of the above ethylene/unsaturated carboxylic acid ester copolymers may be used, or a mixture of two or more ethylene/unsaturated carboxylic acid ester copolymers may be used. In the case of using a mixture of two or more types of ethylene/unsaturated carboxylic acid ester copolymers, the content of the mixture may be within the above-specified range, and the mixture preferably has an MFR within the above range.

[Random ingredient]

The resin composition for sealants of the present invention may contain other resins as long as the characteristics of the composition are not impaired. Moreover, various additives can be further mix|blended with the resin composition for sealants of this invention as needed. Examples of such additives include antioxidants, ultraviolet absorbers, light stabilizers, heat stabilizers, pigments, dyes, antistatic agents, lubricants, and processing aids such as release roll agents.

The sealant resin composition of the present invention is prepared by simultaneously or sequentially mixing the resins (A), (B), and (C) and the resin (D) or the above optional components as necessary. The mixing method is according to the regular law. For example, it is preferable to melt and mix using a single screw extruder, a twin screw extruder, a Banbury mixer, various kneaders and the like, and the mixing order is not particularly limited. The melting and mixing temperature is preferably 140°C to 230°C.

The resin composition for sealant of the present invention is formulated so that the MFR (190°C, 2160 g load) is 0.1 to 100 g/10 min, preferably 1 to 30 g/10 min, considering extrusion processability and adhesive strength. desirable.

The resin composition for sealants of the present invention is suitable as a sealant material for plastic containers. When sealing the container body and lid member using the resin composition of the present invention, usually, the lid member having a layer made of the resin composition of the present invention and the container body are heat-sealed according to a conventional method. The cover material is preferably formed by molding a multilayer laminate comprising a layer made of a resin composition for sealant and a cover base material according to the present invention. The cover substrate is not particularly limited, and paper, aluminum plate (eg aluminum foil), nonwoven fabric, polyester, polyethylene, polypropylene, polystyrene (eg impact resistant polystyrene), aluminum deposited polyester, aluminum deposited poly Propylene, silica deposited polyester and the like are used. 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 generally about 1 to 500 μm, and preferably 10 to 200 μm.

When laminating the resin composition for a sealant of the present invention on a cover base material, a film is made from the resin composition in advance by a casting method or an inflation method, and a dry lamination method is applied to the cover base material, and the resin composition is directly applied to the cover base material A method of extrusion coating on top, a method of using polyethylene or the like as an adhesive layer and laminating through the adhesive layer by sandwich lamination, a method of co-extruding a cover substrate and its resin composition, and the like can be employed. Among these methods, a method in which a single layer or two or more layers of cover base material and a two or three or more layer multilayer material composed of the resin composition for sealant of the present invention is co-extruded by the T-die method is preferable. The thickness of the layer made of the resin composition for sealants of the present invention is not particularly limited, but is generally about 1 to 500 μm, and preferably 10 to 200 μm.

Examples of the material of the plastic container body include polyolefins such as polyethylene and polypropylene, styrene polymers such as polystyrene and impact-resistant polystyrene, polyesters such as polyethylene terephthalate, polycarbonates, and polyvinyl chlorides. Such a material may be in the form of a foam. Among these body materials, impact-resistant polystyrene is common as container bodies for ready-to-eat foods, and has good adhesion to the resin composition for sealants of the present invention. Therefore, as the main body of a plastic container heat-sealed using the resin composition for sealant of the present invention, an impact-resistant polystyrene container or a container made of a material containing impact-resistant polystyrene is preferable. 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 sealants of the present invention is that it has less solvent extraction amount and higher sanitary properties even when measured under more severe conditions than before. As a measurement condition that is more stringent than conventional conditions, for example, a film sealant of 300 cm ² is used as a sample, and 600 ml of n-hexane is brought into contact with one side of the sample for 2 hours at room temperature to elute into the n-hexane. A method of measuring the weight (actual dissolution amount (mg)) of The actual elution amount of the resin composition for sealants of the present invention measured by this method example is preferably 30 mg or less, more preferably 20 mg or less.

In the case of a food container, it is preferable that the main body of the container and the cover material are bonded with a certain degree of appropriate strength in order to ensure that the container is sufficiently sealed and that the user of the container can open the container without difficulty. One of the characteristics of the resin composition for sealants of the present invention is that it is useful for such food containers. When the sealant layer made of the resin composition for sealant of the present invention and the lid member including the lid substrate and the container body are heat-sealed through the sealant layer, the peel strength between the lid member and the container body falls within an appropriate strength range. . This peel strength is obtained by cutting (for example, a sealant layer made of the resin composition for sealant of the present invention) from a multi-layered material obtained by heat-sealing a cover material including a cover base material and a plastic layer constituting the container body through the sealant layer ( It can be measured as the maximum stress when a test piece with a width of 15 mm is pulled out and peeled (180° peeled) by pulling both sides in the opposite direction horizontally. The resin composition for sealant of the present invention has a peel strength measured by the above method, preferably in the range of 5 N/15 mm or more and 15 N/15 mm or less, more preferably in the range of 7 N/15 mm or more and 14 N/15 mm or less.

Moreover, the resin composition for sealants of the present invention is also one in which occurrence of blocking is suppressed by optimizing the composition. For this reason, the multilayer film which has the resin composition for sealants of this invention as a sealant layer does not generate|occur|produce blocking, or even if it occurs, it remains in a slight level. In the case of aging for 2 days in an atmosphere of 40 ° C. under a load of 5 kgf / cm ² by stacking six sheets of a multilayer film including a sealant layer made of the resin composition for sealant of the present invention and a substrate in the order of sealant layer / cover substrate, The blocking strength between test pieces is preferably less than 100 g/50 mm, more preferably less than 10 g/50 mm.

Example

Hereinafter, the present invention will be described more specifically by way of examples, but the present invention is not limited to the following examples unless the gist thereof is exceeded. In addition, the melt flow rate (MFR) was measured at 190°C and a load of 2160 g in accordance with JISK7210-1999.

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

The following resins were mixed at the compounding ratios shown in Tables 1 and 2 so that the amount of introduction was 10 kg. The resin composition was prepared by putting it into an extruder (65 mmφ, L/D = 28, tip dull Meiji flight screw) and melt-kneading at a processing temperature of 180 ° C., and the resin composition of the present invention (Example) and the resin composition for comparison ( Comparative example) was obtained.

EVA 1: ethylene/vinyl acetate copolymer

Ethylene unit content 92.9 mol%, vinyl acetate unit content 7.1 mol%, MFR (190°C, 2160 g load) 15 g/10 min, melting point 84°C. It was prepared by high-pressure radical polymerization according to the autoclave method.

EVA 2: ethylene/vinyl acetate copolymer

Ethylene unit content 92.9 mol%, vinyl acetate unit content 7.1 mol%, MFR (190°C, 2160 g load) 150 g/10 min, melting point 79°C. It was prepared by high-pressure radical polymerization according to the autoclave method.

EVA 3: ethylene/vinyl acetate copolymer

Ethylene unit content 96.5 mol%, vinyl acetate unit content 3.5 mol%, MFR (190°C, 2160g load) 9g/10min, melting point 94°C. It was prepared by high-pressure radical polymerization according to the autoclave method.

EVA 4: ethylene/vinyl acetate copolymer

Ethylene unit content 88.8 mol%, vinyl acetate unit content 11.2 mol%, MFR (190°C, 2160 g load) 15 g/10 min, melting point 71°C. It was prepared by high-pressure radical polymerization according to the autoclave method.

PO-1: Mitsui Chemicals Co., Ltd. ethylene-butene random copolymer elastomer MFR (190 degreeC, 2160g load) 3.7g/10min density 885kg/m ^<3> .

PO-2: ethylene/hexene random copolymer manufactured by Mitsui Chemicals Co., Ltd.

MFR (190℃, 2160g load) 3.7g/10min Density 905kg/m ³ .

SEBS: styrene·ethylene·butylene·styrene block copolymer

"Krayton G1657" manufactured by Kraton Japan. MFR (230℃, 5000g load) 22g/10min, density 900kg/m ³ .

Tackifying Resin: Fully Hydrogenated Aromatic Hydrocarbon Resin

A product made by Arakawa Chemical Co., Ltd. Ring and ball method softening point 115°C.

EMA: ethylene/methyl acrylate copolymer

Ethylene unit content 92.5 mol%, methyl acrylate unit content 7.5 mol%, MFR (190°C, 2160g load) 8g/10min, melting point 92°C. Manufacturing method: It was prepared by high-pressure radical polymerization according to the tubular method.

EMAA: ethylene-methacrylic acid copolymer

Ethylene unit content 96.1 mol%, methacrylic acid unit content 3.9 mol%, MFR (190°C, 2160 g load) 8 g/10 min.

The obtained resin composition was evaluated from the following viewpoints.

[Vs. HIPS Adhesion Strength]

The obtained resin composition was subjected to an extrusion lamination method at a processing temperature of 240° C. and a processing speed of 30 m/min to obtain a polyethylene terephthalate layer (PET), a polyethylene layer (PE), and ethylene/methacrylic acid unit content of 3.9 mol%. It was laminated with an acid copolymer layer (EMAA). PET, PE, EMAA, and the resin composition were laminated in this order to obtain a laminate having a configuration of PET (12 μm)/PE (15 μm)/EMAA (20 μm)/resin composition (10 μm). This laminate was heat-sealed on a commercially available HIPS sheet having a thickness of 0.4 mm under the conditions of a pressure of 0.2 MPa, a heating temperature of 120°C, and a heating time of 1.0 seconds, and left at room temperature for 24 hours. Thereafter, both surfaces of a 15 mm wide test piece cut out from the laminate were pulled in opposite directions (in the peeling direction at 180°C) to determine the maximum stress. This maximum stress (N/15 mm) was taken as the HIPS adhesive strength (N/15 mm) of the resin composition at a heat seal temperature of 120°C. Measurements were made in the same manner as the above conditions except that the heat seal temperature was changed, and the adhesive strength of the resin composition to HIPS at heat seal temperatures of 140°C and 160°C was also determined. The measurement results are shown in Table 1 and Table 2.

The adhesive strength to HIPS was determined according to the following criteria. The determination results are shown in Table 1 and Table 2.

· A: Particularly good. 7N/15mm or more and 14N/15mm or less

· B: It is good. More than 5N/15mm but less than 7N/15mm, more than 14N/15mm and less than 15N/15mm

・C: Slightly bad. 3N/15mm or more and less than 5N/15mm, more than 15N/15mm and less than 20N/15mm

· D: Failed. Less than 3N/15mm or greater than 20N/15mm.

[Blocking strength]

Six samples with a width of 50 mm cut out from the laminate of the above PET (12 μm) / PE (15 μm) / EMAA (20 μm) / resin composition (10 μm) were overlapped, and ² in an atmosphere of 40 ° C. under a load of 5 kgf / cm 2 Aged for days. Thereafter, the mutual peel strength of the six samples was measured using a measuring instrument VG-35 from Vangard. Table 1 and Table 2 show the obtained strength (g/50 mm) as the blocking strength.

Blocking resistance was determined according to the following criteria. Samples judged to be excellent here are those in which the blocking phenomenon is less likely to occur. The judgment results regarding the blocking properties are shown in Table 1 and Table 2.

· A: Particularly good. Less than 10g/50mm.

· B: It is good. More than 10g/50mm, less than 100g/50mm.

・C: Bad. Over 100g/50mm.

[Organic solvent extraction test]

It was tested using a one-sided extractor used in the Ministry of Health and Welfare Notice No. 370 test. In this extraction vessel, the laminate having the above structure of PET (12 μm)/PE (15 μm)/EMAA (20 μm)/resin composition (10 μm) is placed with the resin composition layer facing up, and 300 cm ² of one side of the laminate is placed with the solvent n - It was allowed to stand at room temperature for 2 hours in a state of contact with 600 ml of hexane. After that, the solvent was evaporated and the residual amount (mg) was measured. The amount of this residue was taken as the amount (mg) of solvent extraction from the layered product. The measurement results are shown in Table 1 and Table 2.

The obtained solvent extraction amount (mg) was judged according to the following criteria. The determination results are shown in Table 1 and Table 2.

· A: Particularly good. 20 mg or less.

· B: It is good. More than 20 mg and not more than 30 mg.

· C: Failed. More than 30 mg.

-: Not measured.

[Table 1]

[Table 2]

In Comparative Examples 1, 2, and 3 using an ethylene/vinyl acetate copolymer having an excessively small amount of vinyl acetate units, the adhesive strength to HIPS was low, and sufficient container sealing properties could not be expected. In Comparative Example 4, in which the resin (A) was not used, the blocking tendency was high and the amount of solvent extraction was large, so that the desired sanitary properties were not obtained. In Comparative Example 5 using an ethylene/vinyl acetate copolymer having an excessively large amount of vinyl acetate units, the amount of solvent extraction and the blocking tendency are large, and it is expected that there are problems in hygiene, handleability of the cover material, and workability. Comparative Example 6, in which the blending amount of the resin (A) is too small, has very poor workability. Comparative Example 7 not containing Resin (B) had a lower adhesive strength to HIPS than Comparative Example 1.

Thus, the resin composition for sealant of the comparative example has problems with any one of adhesiveness, solvent extraction amount, and processability, and is not suitable for practical use.

In contrast, the resin compositions for sealants of the Examples exhibit moderate to HIPS adhesive strength in a wide temperature range, and have a very low solvent extraction amount. In addition, the resin compositions for sealants of Examples have a low blocking tendency and are excellent in usability as a heat seal layer of a cover material. In this way, the resin compositions for sealants of the Examples have adhesiveness, sanitation, and processability that allow containers to be opened satisfactorily, with a good balance.

The resin composition for sealants of the present invention can be expected as a next-generation sealant material that can be used for heat sealing of containers requiring higher hygiene and safety. The container to which the resin composition for sealant of the present invention can be applied may be any container to which the container main body and the cover member are bonded by heat sealing. For example, a container composed of a container body made of impact-resistant polystyrene or a material mainly made of this and a cover material is suitable in that the container can be opened without difficulty. Moreover, a food container is suitable at a point with a low possibility of component migration from the resin composition for heat sealing of this invention to the food which is a content. Food containers using the sealant resin composition of the present invention include, for example, snack confectionery, cereal, jelly, pudding, yogurt, tofu, side dishes, ready-to-eat foods (eg, instant noodles, instant soup), beverages, fresh ingredients, or these. processed products of The resin composition for sealants of the present invention has high practical value even in countries and regions where food containers have stricter sanitary standards.

Claims (8)

An ethylene-vinyl ester copolymer containing 90 mol% or more and 95 mol% or less of ethylene units and 5 mol% or more and 10 mol% or less of vinyl ester units (however, the sum of ethylene units and vinyl ester units is 100 mol%) , And an ethylene-unsaturated carboxylic acid ester copolymer containing 90 mol% or more and 95 mol% or less of ethylene units and 5 mol% or more and 10 mol% or less of unsaturated carboxylic acid ester units and satisfying the following general formula (1) (provided that the ethylene unit and at least one resin (A) selected from (the sum of unsaturated carboxylic acid ester units is 100 mol%) 50 to 99 parts by mass of the total of 100 parts by mass of the resin (A), the resin (B), and the resin (C) mass part,
-3.0X+107＞T...(1)
(In Formula (1), X represents the unsaturated carboxylic acid ester content (mol%), and T represents the melting point (°C) measured in accordance with JIS K7121-1987)
At least one resin (B) selected from ethylene/α-olefin copolymers and ABA block copolymers (A represents a polystyrene block and B represents an alkylene copolymer block) B), 1 to 50 parts by mass based on 100 parts by mass of the total of the resin (C),
0 to 10 parts by mass (provided that the total amount of (A), (B) and (C) is 100 mass division),
Ethylene/unsaturated carboxylic acid ester copolymer resin (D) satisfying the following general formula (2) is 1 part by mass or more and 60 parts by mass relative to 100 parts by mass of the total of the resin (A), the resin (B) and the resin (C) The resin composition for sealants, including the following.
T≥-3.0X+107 ... (2)
(In Formula (2), X represents the unsaturated carboxylic acid ester content (mol%), and T represents the melting point (°C) measured in accordance with JIS K7121-1987) The method of claim 1,
60 to 95 parts by mass of resin (A), 5 to 40 parts by mass of resin (B), and 0 to 10 parts by mass of resin (C) (however, the total amount of (A), (B), and (C) is 100 parts by mass) and the resin (D) in an amount of 5 parts by mass or more and 30 parts by mass or less with respect to a total of 100 parts by mass of the resin (A), the resin (B), and the resin (C). The method of claim 1,
A resin composition for a sealant used for a sealant of a container body and a cover base material. The method of claim 3,
A resin composition for a sealant, which is a container body at least a part of which is in contact with a cover base material made of impact-resistant polystyrene. The method of claim 1,
A resin composition for a sealant used as a cover material for food containers. A cover material comprising a layer made of the resin composition for sealant according to any one of claims 1 to 5 and a base material layer. A food container having the cover material according to claim 6. delete