JP2015042738A - Thermoplastic resin composition for sealant material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermoplastic resin composition for sealant material having a peel-easiness due to cohesion detachment in which a seal layer having a sufficiently high heat-seal strength and also having an excellent peel-easiness can be formed with a good formability.SOLUTION: Provided is a thermoplastic resin composition for sealant material having a peel-easiness due to cohesion detachment and is characterized in comprising the following (A) to (C) components. (A) component: low melting point polyester resin; (B) component: resin made by impregnating styrene monomer into polyolefin, and/or poly-styrenic resin; and (C) component: amorphous polyester and/or polyolefin.

Description

The present invention is a thermoplastic resin composition for sealant materials that has an easy-opening property by cohesive peeling, and has a sufficiently high heat-sealing strength and an easy-opening property, with a good moldability. The present invention relates to a thermoplastic resin composition for a sealant material.
The present invention also relates to a lid for an easy-open container and an easy-open container having a seal layer formed from the thermoplastic resin composition for sealant material.

  Conventionally, as a packaging method for foods, beverages, medicines, cosmetics, medical instruments, etc., an article to be packaged is put in a container body molded in a tray shape or a cup shape with a resin such as a polyester resin or a polycarbonate resin, A method in which a lid is brought into contact with the opening and sealed by heat sealing is widely used. In such a package, since it is necessary to peel off the lid when taking out the package, in addition to no leakage of the package from the container, when taking out the package In addition, it is necessary to have a heat seal strength that allows the lid material to be easily peeled off from the container body, that is, to be easily openable.

Generally, there are mainly two types of sealants (seal materials) used for easy-opening lid materials: delamination type and cohesive peeling type.
The delamination-type lid material is composed of a seal layer, a holding layer, and a base material, and the seal layer is formed of the same kind of resin as the adherend (the lid attachment portion of the container), A strong sealing state is maintained by heat sealing, and the holding layer is formed of a resin different from that of the sealing layer and is easily peeled between the sealing layer and the holding layer to provide easy opening.

However, in the case of delamination type sealant, a part of the sealant remains on the container body side at the time of opening or a film residue occurs at the time of opening. Therefore, the cohesive peeling type sealant is advantageous in that there is no such problem. It is.
The cohesive peeling type is the same as the delamination type in that it is formed of a seal layer, a holding layer, and a base material. It is formed from a polymer blend of resins. Thereby, at the time of heat sealing, the sealing layer is partially heat-sealed with the adherend, and at the time of peeling, the sealing layer is peeled off while cohesively destroying the sealing layer itself at the interface of the polymer blended resin. Therefore, the sealing layer has both a sealing function and a peelability function. However, since the thermal fusion between the sealing layer and the adherend is partial, it is impossible to obtain a certain level of sealing strength. There is a point.

Conventionally, for example, the following proposals have been made for cohesive peeling type sealants.
Patent Document 1: A seal layer is made of a thermoplastic resin having a specific tensile strength at break to eliminate the problem of stringing at the time of opening.
Patent Document 2: A seal layer is made of a lacquer of a polyester resin and a urethane resin so that a uniform trace is left on the lid.
Patent Document 3: By making the sealing layer contain foamed particles, selective cohesive peeling is possible and peeling failure is prevented.

JP 2005-335818 A JP 2008-7146 A JP2013-75718A

  However, the actual situation is that sufficient products have not yet been provided for the requirement to achieve both easy opening and heat seal strength while ensuring film formability as a sealing layer. Is desired.

  The present invention is a thermoplastic resin composition for a sealant material that has an easy-opening property by cohesive peeling, and has a sufficiently high heat-sealing strength and also has an easy-opening property with good moldability. There are provided a thermoplastic resin composition for a sealant material, a lid for an easily openable container having a seal layer formed from the thermoplastic resin composition for a sealant material, and an easily openable container having the lid. This is the issue.

  As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be solved by blending a specific fusion component, an aggregating release component, and a moldability auxiliary component. The present invention has been completed.

[1] A thermoplastic resin composition for a sealant material that has an easy-open property by cohesive peeling, and includes the following components (A) to (C).
(A) Component: Low melting point polyester resin (B) Component: Polyolefin resin impregnated with styrene monomer and / or polystyrene resin (C) component: Amorphous polyester and / or polyolefin

[2] In [1], 10 to 90 parts by weight of component (A), 5 to 60 parts by weight of component (B), and 100 parts of component (C) in a total of 100 parts by weight of components (A) to (C). A thermoplastic resin composition for sealant material, comprising 10 to 90 parts by weight.

[3] A thermoplastic resin composition for a sealant material, wherein the low melting point polyester resin as the component (A) is a crystalline polyester resin having a melting point of 130 ° C. or lower in [1] or [2].

[4] The thermoplastic resin composition for sealant material according to any one of [1] to [3], wherein the component (C) includes a polyolefin, and the polyolefin is a low density polyethylene.

[5] The thermoplastic resin composition for sealant material according to [4], wherein the density of the low-density polyolefin is 0.860 to 0.930 g / cm ³ .

[6] An easily openable container lid member having a seal layer formed of the thermoplastic resin composition for sealant materials according to any one of [1] to [5].

[7] An easy-open container having the lid for easy-open containers described in [6].

[8] An easy-open container having the easy-open container cover material according to [6] and a container body made of polyethylene terephthalate resin.

  According to the thermoplastic resin composition for a sealant material of the present invention, a seal layer having sufficiently high heat seal strength and excellent easy-openability can be formed with good moldability.

  Embodiments of the present invention will be described in detail below, but the descriptions described below are examples (representative examples) of embodiments of the present invention, and the present invention is not limited to these contents unless it exceeds the gist. It is not specified.

The thermoplastic resin composition for a sealant material of the present invention is a thermoplastic resin composition for a sealant material that has easy-openability by cohesive peeling, and includes the following components (A) to (C).
(A) Component: Low melting point polyester resin (B) Component: Polyolefin resin impregnated with styrene monomer and / or polystyrene resin (C) component: Amorphous polyester and / or polyolefin

  Of those that are considered to correspond to the “low melting point polyester resin” of the component (A), those that correspond to the “amorphous polyester” of the component (C) are not regarded as the component (A) ( C) It shall be regarded as a component. In addition, among those understood to correspond to “polyolefin” of component (C), those corresponding to “resin obtained by impregnating and polymerizing a styrene monomer in polyolefin” in component (B) are regarded as component (C). First, it shall be regarded as the component (B).

  In the present invention, the component (A) functions as a fusing component responsible for heat sealability, the component (B) is an agglomerated release component responsible for agglomerated releasability (easy openability), and the component (C). Functions as a moldability auxiliary component for improving moldability. The thermoplastic resin composition for a sealant material of the present invention includes these (A) component fusion component, (B) component cohesive release component, and (C) component formability auxiliary component, A seal layer excellent in easy-openability and heat-sealability can be formed with good moldability.

[(A) component]
The polyester resin is produced by polycondensation of a dibasic acid and a polyhydric alcohol. Examples of the dibasic acid include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, and 2,6-naphthalenedicarboxylic acid, and aliphatic dicarboxylic acids such as adipic acid. Examples of the polyhydric alcohol include diols such as ethylene glycol, butanediol, 1,4-cyclohexanedimethanol, pentaethylene glycol, 2,2-dimethyltrimethylene glycol, hexamethylene glycol, and neopentyl glycol. Said dibasic acid and polyhydric alcohol are used by arbitrary combinations. Specifically, terephthalic acid / ethylene glycol copolymer, terephthalic acid / ethylene glycol / 1,4-cyclohexanedimethanol terpolymer, 2,6-naphthalenedicarboxylic acid / ethylene glycol copolymer, terphthalic acid / And isophthalic acid / butanediol terpolymer.

  The low-melting-point polyester resin of the component (A) used in the present invention has a melting point of 130 ° C. or lower, particularly 80 to 130 ° C., and a glass transition temperature of 40 ° C. or lower, particularly −70 to 40 ° C. It is preferable from the viewpoint of lowering the heat seal temperature. Examples of such a crystalline polyester include a resin marketed under the trade name “Byron” (manufactured by Toyobo Co., Ltd.).

The crystalline polyester in the present invention is a resin in which a crystallization peak and / or a melting peak is observed by the following method.
Using a differential scanning calorimeter (DSC220C manufactured by Seiko Denshi Kogyo Co., Ltd.), the melting behavior of the resin is measured under the following conditions. In each step, time is plotted on the horizontal axis, and the heat of fusion is plotted on the vertical axis to obtain a melting curve. The peak observed in the step (ii) is the crystallization peak, and the peak observed in the step (iii) is the melting peak. And
(I) About 5 mg of a sample is heated from room temperature to 200 ° C. at a rate of 30 ° C./minute, and is held for 5 minutes after the temperature increase is completed.
(Ii) Next, the temperature is decreased from 200 ° C. to −100 ° C. at a rate of 10 ° C./min, and held for 5 minutes after the completion of the temperature decrease.
(Iii) Next, the temperature is raised from −100 ° C. to 200 ° C. at a rate of 10 ° C./min.

  (A) The low melting point polyester resin of a component may be used individually by 1 type, and may use 2 or more types together.

[Component (B)]
The component (B) used in the present invention is a resin obtained by impregnating and polymerizing a polyolefin with a styrene monomer (hereinafter sometimes referred to as “modified polyolefin”) and / or general-purpose polystyrene. As the component (B), only one type of modified polyolefin or one type of general-purpose polystyrene may be used, and one or more types of modified polyolefin and one or more types of general-purpose polystyrene are used in combination. Also good.

<Modified polyolefin>
In the modified polyolefin, examples of the styrene monomer impregnated and polymerized in the polyolefin include those represented by the following general formula (1).

(In the formula, R ¹ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and R ^{2 to} R ⁵ each represents a hydrogen atom, a halogen atom, or an alkyl group having 1 to 4 carbon atoms.)

  Examples of the styrene monomer include styrene and a nucleus-substituted styrene such as methyl styrene, isopropyl styrene, chlorostyrene, α-substituted styrene such as α-methyl styrene and α-ethyl styrene. A mixed system of styrene and acrylate is also applied. These may be used alone or in combination of two or more.

  On the other hand, as the polyolefin, a single or copolymer of an olefin having about 2 to 20 carbon atoms such as ethylene, propylene, butene-1, pentene-1, and hexene-1, or a vinyl monomer copolymerizable with these olefins. Examples thereof include copolymers with unsaturated organic acids such as vinyl acetate, acrylic acid, acrylic acid esters, methacrylic acid, methacrylic acid esters, and maleic anhydride, or anhydrides thereof. In the copolymer of olefin and copolymerizable vinyl monomer, the olefin content is 50% by weight or more. Here, the copolymer includes random, block and graft copolymers.

  More specifically, high pressure method, medium pressure method or low pressure method polyethylene, polypropylene, ethylene-propylene random copolymer, ethylene-propylene block copolymer, propylene-butene-1 random copolymer, propylene-ethylene-butene- 1 random copolymer, a copolymer composed of propylene and an α-olefin having 5 to 12 carbon atoms and optionally ethylene or butene-1, ethylene-vinyl acetate copolymer, and the like. Among these, polyethylene Polypropylene, ethylene-vinyl acetate copolymer and the like are preferable. These may be used alone or in combination of two or more.

  The amount of styrene monomer used for the impregnation polymerization is preferably 40 to 95% by weight of polyolefin and 60 to 5% by weight of styrene monomer based on the total weight of polyolefin and styrene monomer. If the amount of styrene monomer used is less than 5% by weight, the effect as an aggregating and peeling component may not be obtained. On the other hand, if it exceeds 60% by weight, the material strength (flexibility) and molding processability of polyolefin are deteriorated. .

Examples of the method for aggregating and removing the styrene monomer from the polyolefin include the following methods.
That is, in an aqueous suspension containing 40 to 95% by weight of polyolefin particles (generally having a particle size of 1 to 7 mm, preferably about 2 to 5 mm), 5 to 60% by weight of a styrene monomer, and a radical polymerization initiator, At least 80% by weight of the styrene monomer is impregnated into the polyolefin particles, and then the styrene monomer is polymerized.
The details of the polymerization initiator and styrene monomer impregnation method and polymerization method used here are as follows.

(Polymerization initiator)
When the polyolefin particles are impregnated in an aqueous medium with substantially no polymerization of the styrene monomer, and then the aqueous dispersion is heated to polymerize the styrene monomer, the polymerization is usually performed with a radical polymerization initiator. Facilitate.
This polymerization initiator needs to be able to be impregnated into the polyolefin particles together with the styrene monomer, and therefore the radical polymerization initiator used is oil-soluble. The polymerization initiator preferably has a decomposition temperature of 50 to 150 ° C. for obtaining a half-life of 10 hours. Here, the “decomposition temperature for obtaining a half-life of 10 hours” means that when 0.1 mol of a polymerization initiator is added to 1 liter of benzene and left at a temperature for 10 hours, the polymerization initiator is decomposed. The temperature at which the rate is 50% is meant. If the impregnation step is carried out at a sufficiently low temperature, a polymerization initiator that can be decomposed at a lower temperature than this can also be used.

  Specific examples of radical polymerization initiators include lauroyl peroxide (62 ° C.), benzoyl peroxide (74 ° C.), t-butyl peroxybenzoate (104 ° C.), dicumyl peroxide (117 ° C.) and the like. Examples include azo compounds such as organic peroxides, azobisisobutyronitrile (65 ° C.) and the like (the temperature in the parenthesis is the decomposition temperature for obtaining the above half-life of 10 hours).

Although there is no restriction | limiting in the usage-amount of a polymerization initiator, Generally it is about 0.01 to 10 weight% of a styrene monomer weight, Preferably it is about 0.1 to 2.0 weight%.
The polymerization initiator is usually used by dissolving in a styrene monomer.

(Impregnation process)
As a typical method of impregnating polyolefin particles with styrene monomer in an aqueous medium, a styrene monomer in which a polymerization initiator (and other additives as required) is preferably dissolved in an aqueous dispersion of polyolefin particles is used. In addition, a method of stirring can be mentioned. As another method, there is a method in which polyolefin particles are added to an aqueous dispersion of a polymerization initiator-dissolved styrene monomer and stirred.

  In the impregnation step, a temperature that is sufficiently low in correlation with the decomposition temperature of the polymerization initiator used, generally a temperature condition of room temperature to 100 ° C., is employed so that substantially no polymerization occurs.

In this step, the styrene monomer is impregnated so that the amount of free styrene monomer is 80% by weight or less of the total amount of styrene monomer used.
Since the polyolefin is relatively compatible with the styrene monomer, even if the styrene monomer is liberated in the range of 80% by weight or less before the polymerization starts, these styrene monomers are impregnated into the polyolefin particles during the polymerization. The polystyrene particles obtained by polymerizing the free styrene monomer are not precipitated separately from the modified polyolefin.

  The impregnation time is generally about 2 to 8 hours.

  Further, the content of the polyolefin particles and the styrene monomer in the aqueous dispersion is generally about 5 to 100 parts by weight with respect to 100 parts by weight of water.

  Such an aqueous dispersion can be stably maintained in a dispersed state by simply performing sufficient stirring. However, if an appropriate suspension stabilizer is used, the dispersion can be prepared more easily and more stably. it can. As the suspension stabilizer in this case, those that can be used as a suspension stabilizer in the aqueous suspension polymerization of styrene monomer can be generally used, and specifically, polyvinyl alcohol, methylcellulose, hydroxycellulose, etc. Water-soluble polymeric substances, anionic surfactants such as alkylbenzene sulfonates, nonionic surfactants such as polyoxyethylene alkyl ethers, water-insoluble inorganic salts such as magnesium oxide and calcium phosphate, alone or It is mixed and used in an amount of about 0.01 to 10% by weight with respect to water.

  When the polyolefin particles are impregnated with the styrene monomer (and the polymerization initiator), auxiliary materials such as a plasticizer, a lubricant and an antioxidant can be impregnated simultaneously. These auxiliary materials may be already added to the polyolefin, or may be added after polymerization.

(Polymerization process)
The aqueous dispersion prepared as described above is heated to a temperature at which the polymerization initiator used is decomposed at an appropriate rate or more, whereby the impregnated styrene monomer is polymerized and the modified polyolefin particles become Generate. This radical polymerization is carried out in an atmosphere substantially free of oxygen, and the aqueous dispersion during the polymerization is preferably stirred appropriately.

  The polymerization temperature is determined in correlation with the decomposition temperature of the polymerization initiator used, but is generally about 50 to 150 ° C. The polymerization temperature need not be constant throughout the polymerization period. The polymerization time is usually about 2 to 10 hours, and the polymerization pressure is usually about normal pressure to about 0.98 MPa.

  In the polymerization step, a chain transfer agent such as n-butyl mercaptan, n-dodecyl mercaptan, or t-dodecyl mercaptan may be present in order to adjust the molecular weight of the modified polyolefin obtained by polymerization of the styrene monomer.

  After the polymerization, modified polyolefin particles that can be used as a raw material of the composition immediately after maintaining the shape of the used polyolefin particles as they are, if the same treatment as that of the usual aqueous suspension polymerization of styrene monomer is performed. Is obtained.

  The modified polyolefin thus obtained is presumed to be a polyolefin containing a polymer from a uniformly dispersed styrene monomer, or a styrene monomer grafted to the polyolefin main chain, or a mixture thereof. The coalesced particles do not exist separately from the polyolefin particles.

<Polystyrene resin>
The polystyrene-based resin is a resin containing at least 25% by weight or more of a structural unit represented by the following general formula (2) in the resin, and among them, one or two of polystyrene, rubber-modified polystyrene, styrene-based elastomer and the like. More than one species can be preferably used.

(In the formula, R represents a hydrogen atom or a methyl group, Z represents a halogen atom or a methyl group, and p is an integer of 0 to 3.)

  As the styrene-based elastomer, a styrene-conjugated diene block copolymer and / or a hydrogenated product thereof can be used.

Suitable conjugated dienes in the styrene-conjugated diene block copolymer and / or its hydrogenation are butadiene, isoprene or mixtures thereof.
Examples of the styrene-conjugated diene block copolymer containing butadiene, isoprene or a mixture thereof as a conjugated diene and / or a hydrogenated product thereof include, for example, a styrene-butadiene-styrene block copolymer (hereinafter simply referred to as “SB— S ”), styrene-ethylene-butylene-styrene, which is a hydrogenated product of S—B—S (hereinafter simply abbreviated as“ hydrogenated S—B—S ”). Copolymer (SEBS), styrene-isoprene-styrene block copolymer (hereinafter sometimes abbreviated as “S-I-S”), hydrogenated product of S-I-S (hereinafter simply “ Styrene-ethylene-propylene-styrene copolymer (SEPS), styrene-butadiene-isoprene-styrene block, which may be abbreviated as “hydrogenated S-I-S”. Copolymer (hereinafter sometimes abbreviated as “S-BI-S”), hydrogenated product of S-BI-S (hereinafter simply abbreviated as “hydrogenated S-BI-S”) .).

  The styrene content of the styrene-conjugated diene block copolymer and / or the hydrogenated product thereof is not particularly limited, but is preferably 5% by weight or more, more preferably 8% by weight or more from the viewpoint of strength and heat resistance. More preferably 10% by weight or more. The styrene content is preferably 50% by weight or less, more preferably 45% by weight or less, and still more preferably 40% by weight or less from the viewpoints of flexibility and impact resistance.

  The conjugated diene of the styrene-conjugated diene block copolymer and / or its hydrogenated product has a 1,2-microstructure analyzed by NMR method of preferably 60 mol% or less, more preferably 45 mol% or less. is there. When the 1,2-microstructure exceeds 60 mol%, the moldability and flexibility tend to decrease. Further, from the viewpoint of weather resistance, the hydrogenated product is preferably a hydrogenated product of a styrene-conjugated diene block copolymer, and the hydrogenation rate is preferably 90 mol% or more, more preferably 95 mol% or more.

  When the conjugated diene in the styrene-conjugated diene block copolymer and / or its hydrogenated product is a mixture of isoprene and butadiene, the weight ratio (isoprene / butadiene) is generally 99/1 to 1/99, preferably 90 / It is 10-30 / 70, Most preferably, it is 80 / 20-40 / 60.

  The weight average molecular weight (Mw) of the styrene-conjugated diene block copolymer and / or its hydrogenated product is preferably 50,000 or more, more preferably 80,000 or more, from the viewpoint of releasability. Preferably it is 100,000 or more. The weight average molecular weight (Mw) is preferably 500,000 or less, more preferably 450,000 or less, still more preferably 400,000 or less, particularly preferably 350,000 or less, from the viewpoint of fluidity. is there.

Here, the weight average molecular weight (Mw) of the styrene-conjugated diene block copolymer and / or the hydrogenated product thereof is measured by a gel permeation chromatography method (GPC method). Can be measured.
Equipment: “HLC-8220 GPC (R)” manufactured by Tosoh Corporation
Column: “TSKgel Super HM-M (6.0 mm ID × 15 cm × 2 + G)” manufactured by Tosoh Corporation
Detector: Differential refractive index detector (RI / built-in)
Solvent: Chloroform Temperature: 40 ° C
Flow rate: 0.25 mL / min Injection volume: 0.1% by weight × 20 μL
Calibration sample: monodisperse polystyrene Calibration method: polystyrene conversion Calibration curve approximation formula: cubic equation (hyperbola): exclusion limit setting time 12 minutes

  As a method for producing these styrene-conjugated diene block copolymers, for example, a styrene-conjugated diene block copolymer in an inert solvent using a lithium catalyst according to the method described in Japanese Patent Publication No. 40-23798. In addition, in the hydrogenated styrene-conjugated diene block copolymer, a styrene-conjugated diene block copolymer is synthesized as described above, and then, for example, Japanese Patent Publication No. 42-8704, According to the methods described in JP-B 43-6636, JP-A 59-133203, and JP-A 60-79005, a method of hydrogenation in the presence of a hydrogenation catalyst in an inert solvent, etc. Can be mentioned. Hydrogenated S-BI-S can be synthesized, for example, by the method described in JP-A-3-188114.

  The styrene-conjugated diene block copolymer and / or the hydrogenated product thereof can be obtained as a commercial product. Examples of the styrene-conjugated diene block copolymer include “Clayton (registered trademark) D” manufactured by Kraton Polymer Japan. Examples of the hydrogenated styrene-conjugated diene block copolymer include “Clayton (registered trademark) G” manufactured by Kraton Polymer Japan, “Septon (registered trademark)” manufactured by Kuraray Co., Ltd., “Tuftec” manufactured by Asahi Kasei Corporation. Registered trademark) ”and the like.

[Component (C)]
(C) component used by this invention is an amorphous polyester and / or polyolefin. As the component (C), only one type of amorphous polyester or one type of polyolefin may be used, and one or more types of amorphous polyester and one or more types of general-purpose polystyrene are used in combination. May be.

<Amorphous polyester>
Amorphous polyester is a polyester resin that exhibits substantially no crystallinity. Specifically, when the resin is left in the temperature range from the glass transition temperature to the melting point, the crystallinity is 5% or less. This means polyester. Further, as the amorphous polyester, preferably, the low melting point polyester resin of the component (A) has a crystal melting heat quantity ΔH of 1 J / g or less in the measurement with the differential scanning calorimeter under the conditions described above. preferable.

  As such an amorphous polyester, for example, an amorphous copolymer polyester obtained by acid-modifying and / or diol-modifying polyethylene terephthalate is preferable. Examples of the acid-modified component used for copolymerization include terephthalic acid, isophthalic acid, adipic acid, azelaic acid, sebacic acid, 2,6-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, and the diol-modified component. Examples thereof include ethylene glycol, 1,4-butanediol, diethylene glycol, triethylene glycol, neopentyl glycol, 1,4-cyclohexanedimethanol, polyethylene glycol and the like. Among such amorphous polyester resins, from the viewpoints of heat resistance, mechanical properties, transparency, etc., the dibasic acid component mainly composed of terephthalic acid and 10-70 mol% of 1,4-cyclohexanedimethanol are included. A polyester resin comprising a diol component is preferred.

<Polyolefin>
Examples of the polyolefin include those exemplified as the polyolefin used for the impregnation polymerization of the styrene monomer of the modified polyolefin of the component (B), preferably a resin represented by a polyethylene resin and a polypropylene resin, More preferred are polyethylene resins such as high-density polyethylene, low-density polyethylene, and linear polyethylene.

A polyethylene resin suitable for the present invention is an ethylene homopolymer having an MFR (melt flow rate) (190 ° C./2.16 kgf) of 0.05 to 50 g / 10 min and a density of 0.850 to 0.950 g / cm ³ It is an ethylene-α-olefin copolymer. The α-olefin constituting the ethylene-α-olefin copolymer is usually an α-olefin not containing a cyclic molecule having 3 to 20 carbon atoms, such as propylene, 1-butene, 1-hexene, 4-methyl-1-pentene. 1-octene, 1-decene, 1-tetradecene, 1-octadecene, etc., each consisting of a single compound or a mixture of two or more. Moreover, vinyl ester (vinyl acetate etc.), unsaturated carboxylic acid or its ester (acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, ethyl acrylate etc.) etc. may be used as a copolymerization component.

Specific examples of polyethylene resins include low density polyethylene (LDPE), high density polyethylene (HDPE), medium density polyethylene (MDPE), linear low density polyethylene (LLDPE), very low density polyethylene (VLDPE), and low crystallinity. And an ethylene- 1-butene random copolymer (EBM), an ethylene-propylene copolymer, an ethylene-vinyl acetate copolymer, an ethylene-acrylic acid copolymer, and an ethylene-acrylic acid ester copolymer.
Of these, low density polyethylene is particularly preferred. In particular, the high-pressure low-density polyethylene is effective for improving the stability of molding processability and the stability of peel strength and improving the peel appearance. The low density polyethylene preferably has a density of 0.860 to 0.930 g / cm ³ .

[Other ingredients]
The thermoplastic resin composition for sealant material of the present invention may contain other components other than the above component (A), component (B) and component (C). Other ingredients include colorants such as dyes and pigments, fillers, stabilizers, plasticizers, antioxidants, UV stabilizers and other light stabilizers, dispersants, thickeners, drying agents, lubricants, antistatic agents. Agents and the like.

[Content ratio of each component]
The thermoplastic resin composition for a sealant material of the present invention contains at least three components (A), (B), and (C), thereby providing effects of heat seal strength, easy-openability, and moldability. Since the content ratio of each of these components is not particularly limited, 10 to 90 parts by weight of the component (A) is contained in 100 parts by weight of the components (A) to (C). 5) to 60 parts by weight of component (C) and 10 to 90 parts by weight of component (C), particularly 10 to 60 parts by weight of component (A), 10 to 50 parts by weight of component (B), (C It is more preferable to contain 20-80 parts by weight of the component, 20-50 parts by weight of the component (A), 10-40 parts by weight of the component (B), and 30-70 parts by weight of the component (C). Is particularly preferred.
When the content ratio of the component (A) which is the fusion component is less than the above lower limit, the heat seal strength tends to be insufficient. When the content ratio is more than the above upper limit, the content ratio of the (B) component and the (C) component is relatively When the amount is reduced, easy-openability and / or moldability tends to decrease. Moreover, when the content rate of the component (B) which is a cohesive peeling component is less than the said minimum, there exists a tendency for easy-opening property to be insufficient, and when more than the said upper limit, it is relatively (A) component and (C) component. When the content ratio decreases, the heat seal strength and / or moldability tends to decrease. Further, if the content ratio of the component (C), which is a moldability auxiliary component, is less than the above lower limit, the moldability tends to be insufficient, and if it is greater than the above upper limit, the components (A) and (B) are relatively When the content ratio decreases, the heat seal strength and / or easy-openability tends to decrease.

  When the thermoplastic resin composition for sealant material of the present invention contains other components other than the components (A) to (C), in order to sufficiently obtain the functions of the components (A) to (C), The total content of other components in the thermoplastic resin composition is preferably 10% by weight or less.

[Film forming]
The thermoplastic resin composition for a sealant material of the present invention can be easily formed as a seal layer or a film for a seal layer by various film forming methods such as extrusion laminate molding, T-die molding, and air-cooled inflation molding.
The thickness of the seal layer or the seal layer film is usually 2 to 100 μm, preferably 5 to 30 μm. If the thickness of the sealing layer is too thin, sufficient heat-sealing strength cannot be obtained and the cohesive peelability will be inferior, but if the thickness is excessively thick, the easy-openability of various easily-openable containers In application to a lid material, the thickness of the lid material is undesirably increased.

[Application to easy-open lids]
Said sealing layer or film for sealing layers is used as an easily openable lid material of various easily openable containers by carrying out lamination | stacking integration with the base material. In this case, a polyolefin resin layer such as polyethylene or polypropylene can be interposed as a holding layer between the seal layer film and the substrate. The thickness of the holding layer is usually 5 to 500 μm, particularly about 10 to 100 μm.

  The base material of the lid material is aluminum foil, paper, polyester resin film represented by polyethylene terephthalate, for example, stretched polyester film, stretched nylon film, polyethylene, olefin resin film such as polypropylene, such as stretched polypropylene film, polystyrene film. Applicable as long as it is generally used as a base material for flexible packaging materials, such as silica-deposited stretched polyester film, aluminum-deposited stretched polyester film, and other barrier films. Can be selected and used.

As a method for laminating and integrating the sealing layer film made of the thermoplastic resin composition for sealant material of the present invention on such a base material, there is a method of adhering with an adhesive such as polyurethane, polyester or polyether. Can be mentioned.
Further, the base film and the sealing layer film may be integrally formed by coextrusion lamination.
Further, in order to produce a cover material in which a holding layer is interposed between the seal layer film and the substrate, the thermoplastic resin composition for sealant material of the present invention is formed by a film forming method such as an inflation method or a T-die method. When manufacturing with the above, it is molded by laminating with a holding layer made of polyolefin resin such as polyethylene and polypropylene, or the holding layer and sealing layer are laminated by coextrusion lamination molding with polyolefin resin such as polyethylene and polypropylene. After that, a method for further bonding the base material, a sealing layer on a base material layer made of various thermoplastic resins such as aluminum foil, paper, polyester resin represented by polyethylene terephthalate, olefin resin such as polyethylene and polypropylene, and the like Manufactured by forming a laminate film by extrusion laminating the holding layer That way, and the like.

  The obtained sealing layer / base material or sealing layer / holding layer / base material laminated film or laminated sheet is placed in the opening of the container body of various containers, and along the flange part of the opening. It can be used for sealing a container by heat-pressing and heat-sealing.

  In this case, the heat sealing conditions are a temperature higher by about 50 ° C. than the melting point of the component (A) to the melting point of the component (A), for example, about 130 to 180 ° C., and a pressure of 0.1 to 0. It is preferable that the pressure is about 3 MPa and the heat sealing time is about 1 to 10 seconds.

  In addition, as a constituent material of the container body of the easy-open container to which the easy-open lid using the thermoplastic resin composition for sealant material of the present invention is applied, polyethylene resin, polypropylene resin, polyethylene terephthalate resin, polystyrene resin, Examples thereof include polycarbonate resins and blended materials thereof. Among these, the container body is preferably made of polyethylene terephthalate resin.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to the following examples unless it exceeds the gist. The values of various production conditions and evaluation results in the following examples have meanings as preferred values of the upper limit or lower limit in the embodiment of the present invention, and preferred ranges are the upper limit or lower limit values described above, and It may be a range defined by a combination of values of the examples or values between the examples.

  The raw materials used in the following examples and comparative examples are as follows.

[Raw materials]
<(A) component>
Crystalline polyester “Byron (registered trademark) GM913” manufactured by Toyobo Co., Ltd. (melting point: 126 ° C., glass transition temperature: −70 ° C.)
<(B) component>
(B-1) Modified polyolefin Modified polyolefin “VMX (registered trademark) AN50F” manufactured by Mitsubishi Chemical Corporation (impregnated and polymerized with low-density polyethylene with styrene. Styrene content: 50% by weight)
(B-2) Polystyrene resin General-purpose polystyrene (GPPS) “679K29” manufactured by PS Japan (styrene content: 100% by weight)
(B-3) Styrene elastomer (SEBS)
Styrene-ethylene-butylene-styrene block copolymer “Clayton (registered trademark) G1652” manufactured by Clayton Polymer Japan Co., Ltd. (styrene content: 30 wt%, hydrogenation rate: 98 mol% or more, weight average molecular weight (Mw) : 68,500, 1,2-microstructure: 30 mol%)
<(C) component>
(C-1) Amorphous polyester "PET-G G6763" manufactured by Eastman Chemical Co. (polyethylene terephthalate resin in which a part of ethylene glycol is changed to cyclohexanedimethanol)
(C-2) Low density polyethylene LDPE “Novatec (registered trademark) LC607” manufactured by Nippon Polyethylene
(Density: 0.919 g / cm ³ , MFR (190 ° C./2.16 kgf): 8 g / 10 min)

  In addition, “Toyobo Polyester Film” (25 μm thickness) manufactured by Toyobo Co., Ltd. is used as the PET film used for producing the evaluation film, and the main component of the two-component curable polyurethane adhesive manufactured by Toyo Morton Co., Ltd. is used as the adhesive. “TM329” and curing agent “CAT-8B” diluted with ethyl acetate were used.

[Examples 1 to 14, Comparative Examples 1 and 2]
<Film formation of sealant film>
The components shown in Tables 1 and 2 were used in the blending ratios shown in Tables 1 and 2 and kneaded with a twin-screw extruder “KZW15TWIN-45MG-NH” (manufactured by Technobel Co., Ltd.). Then, a film was formed to form a sealant film having a thickness of 30 μm. In Comparative Example 2, the film could not be formed because the film was cut.
Molding temperature: 220 ° C
Screw rotation speed: 300rpm
Molding speed: 4-5m / min

<Production of evaluation film>
After applying an adhesive to one side of the PET film using a coater (manufactured by Tester Sangyo) and evaporating the solvent, the sealant film was pasted on each side of the adhesive applied, and in a 40 ° C. oven for one day and night. Each was dried to obtain an evaluation film.

<Evaluation of heat seal strength>
Each evaluation film and the following adherend were cut into a size of 70 mm × 100 mm, and the evaluation film was placed on the adherend. Using a heat sealer (manufactured by Sagawa Seisakusho Co., Ltd.), heat sealing was performed under the following conditions, and the central portion in the length direction of the evaluation film was heat sealed to a width of 10 mm.
Pressure: 0.2MPa
Time: 1.0 seconds Seal bar: 10mm
Temperature: 130 ° C or 160 ° C
Substrate: “Novaclear (registered trademark) SG007” manufactured by Mitsubishi Chemical (A-PET sheet, thickness: 0.3 mm)
Thereafter, the heat seal strength was measured by pulling and peeling the portions of the evaluation film that were not heat-sealed in the direction away from each other, and the results are shown in Tables 1 and 2. The heat seal strength is preferably about 4 to 20 N / 15 mm in terms of both easy opening and seal strength.
In Comparative Example 1, the seal strength was too strong and the material (film) was broken.

From Tables 1 and 2, according to the thermoplastic resin composition for sealant material of the present invention containing the components (A) to (C) as in Examples 1 to 14, the cohesive peeling excellent in easy-openability and seal strength. It can be seen that a conductive sealing layer can be formed.
On the other hand, in the comparative example 1 which has only the (A) component and the (C) component and does not have the (B) component which is a cohesive peeling component, the easy-openability cannot be obtained.
Moreover, film formation is impossible in the comparative example 2 which does not have the (C) component which is a moldability auxiliary | assistance component only with (A) component and (B) component.

Claims (8)

A thermoplastic resin composition for a sealant material having an easy-opening property by cohesive peeling, comprising the following components (A) to (C):
(A) Component: Low melting point polyester resin (B) Component: Polyolefin resin impregnated with styrene monomer and / or polystyrene resin (C) component: Amorphous polyester and / or polyolefin   In Claim 1, in (A)-(C) total 100 weight part of component, (A) component is 10-90 weight part, (B) component is 5-60 weight part, (C) component is 10-90. A thermoplastic resin composition for a sealant material, characterized by containing a part by weight.   The thermoplastic resin composition for sealant material according to claim 1 or 2, wherein the low-melting-point polyester resin as component (A) is a crystalline polyester resin having a melting point of 130 ° C or lower.   The thermoplastic resin composition for sealant material according to any one of claims 1 to 3, wherein the component (C) includes a polyolefin, and the polyolefin is a low density polyethylene. 5. The thermoplastic resin composition for sealant material according to claim 4, wherein the density of the low density polyolefin is 0.860 to 0.930 g / cm ³ .   A lid for an easily openable container having a seal layer formed from the thermoplastic resin composition for sealant material according to any one of claims 1 to 5.   An easy-open container having the lid for an easy-open container according to claim 6.   An easily openable container comprising the easily openable container lid material according to claim 6 and a container body made of polyethylene terephthalate resin.