JPH10121015A - Heat-sensitive, pressure-sensitive adhesive and heat-sensitive, pressure-sensitive adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-sensitive, pressure-sensitive adhesive which can improve adhesion to an area, which is difficult to bond, without lowering the blocking resistance by specifying the amt. of vinyl chloride constituting an ethylene/vinyl acetate/vinyl chloride copolymer (EA) used in a heat-sensitive, pressure-sensitive adhesive. SOLUTION: The amt. of vinyl chloride constituting EA used as a thermoplastic resin is 20 to 60wt.%. Many of EAs have relatively high glass transition temp. and hence is used in combination with other thermoplastic resin having a relatively low glass transition temp. (e.g. ethylene/vinyl acetate copolymer) in order to impart a film-forming property. The glass transition temp. is pref. -5 deg.C or above from the viewpoint of the blocking resistance and is pref. 30 deg.C or below from the viewpoint of the film-forming property. Any conventional tackifier may be used, and, e.g. a tackifier having a softening temp. of 80 deg.C or above, e.g. a terpene resin, may be used. A solid plasticizer, e.g. dicyclohexyl phthalate, may be used, and the regulation of the max. particle diameter thereof to not more than 50μm is pref.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a heat-sensitive adhesive which is non-tacky at normal temperature but develops tackiness by heating, and after tackiness is developed, the tackiness is maintained for a while even if a heating source is removed. The present invention relates to a heat-sensitive adhesive sheet.

[0002]

2. Description of the Related Art A water-dispersed pressure-sensitive adhesive is often used as a conventional heat-sensitive pressure-sensitive adhesive so as to have no tackiness after coating and drying. For example, as described in "Adhesion Handbook" (Twelveth Edition, issued in 1955, issued by the Society of Polymer Publishing), an aqueous dispersion containing a thermoplastic resin, a tackifier and a solid plasticizer as a basic skeleton is used as a composition. A mold adhesive is used. Thermoplastic resin is a source of adhesive strength and adhesive strength. Solid plasticizers are basically solid at room temperature, so they do not impart plasticity to the resin, but are heated to a non-adhesive adhesive at room temperature by melting by heating to swell or soften the resin. It has the function of expressing adhesiveness. At this time, when the pressure-sensitive adhesive imparting agent is present, the tackiness appears more remarkably, and the practical characteristics are improved.

[0003] Heat-sensitive adhesives include paper such as high-quality paper, coated paper, art paper, vapor-deposited paper, synthetic paper, polyethylene, and the like.
It is applied on a plastic substrate such as a polyolefin resin such as polypropylene or a polyester resin represented by polyethylene terephthalate (hereinafter abbreviated as PET) to form a heat-sensitive adhesive sheet, and the heat-sensitive adhesive sheet is formed of metal, glass, or the like. Alternatively, it is used as a label or the like on a surface of plastic or the like. Low surface free energy, such as polyolefin resins such as polyethylene and polypropylene for food packaging and electric appliance exteriors, and polyester resins such as PET for beverage bottles, cooked foods and pharmaceutical bottles, so-called poor adhesion. Plastics are often used. In these fields, ordinary adhesives, pressure-sensitive adhesives, glue pastes or heat-sensitive adhesives are used. However, the conventional heat-sensitive adhesive has a problem that it is difficult to adhere to a polyolefin-based resin or a polyester-based resin, and improvement in adhesiveness has been strongly desired. On the other hand, in the field of packaging materials, there has been a problem that conventional heat-sensitive adhesives are difficult to adhere to a porous surface material such as cardboard which is frequently used.

[0004] To solve this problem, simply,
A method of lowering the glass transition temperature of the thermoplastic resin contained in the heat-sensitive adhesive is conceivable. However, lowering the glass transition temperature causes a new problem that the blocking resistance deteriorates. Therefore, it is necessary to take measures to further improve the blocking resistance. As a method, a heat-sensitive adhesive further containing a wax is disclosed in JP-B-62-21835. However, the demand for blocking resistance has become increasingly severe in recent years, and the compounding of wax has become unable to meet such demand. In order to further improve the blocking resistance, when applying a heat-sensitive adhesive on the sheet, a method of putting the smoothness of the coated surface within a certain numerical range is disclosed in JP-A-63-172784, It is practically difficult to control the smoothness of the coated surface as described.

That is, the conventional heat-sensitive adhesive has the following disadvantages. 1) It is difficult to adhere to a poorly adhered surface such as polyolefin or polyester resin or cardboard. 2) If the improvement of 1) is performed, the blocking resistance deteriorates.
If the blocking resistance is poor, there is a risk that the heat-sensitive adhesive sheet adheres to the surface to be contacted when the heat-sensitive adhesive sheet prepared by applying the heat-sensitive adhesive is wound and stored.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a heat-sensitive adhesive and a heat-sensitive adhesive sheet which have improved adhesion to hardly adhered surfaces without lowering the blocking resistance.

[0007]

That is, the first invention is a heat-sensitive adhesive containing an ethylene-vinyl acetate-vinyl chloride copolymer, a tackifier and a solid plasticizer. A heat-sensitive adhesive characterized in that the vinyl chloride constituting the vinyl-vinyl chloride copolymer is 20 to 60% by weight.

The second invention is directed to an ethylene-vinyl acetate-vinyl chloride copolymer, an ethylene-vinyl acetate copolymer and / or an ethylene-vinyl acetate-acrylic copolymer, a tackifier, and a solid plasticizer. And a heat-sensitive adhesive.

A third invention is the heat-sensitive adhesive according to the second invention, wherein the vinyl chloride constituting the ethylene-vinyl acetate-vinyl chloride copolymer is 20 to 60% by weight.

The fourth invention is characterized in that the ethylene constituting the ethylene-vinyl acetate copolymer and / or the ethylene-vinyl acetate-acryl copolymer is 30 to 50% by weight. 3 is a heat-sensitive adhesive according to the invention.

The fifth invention is characterized in that the glass transition temperature of the ethylene-vinyl acetate copolymer and / or the ethylene-vinyl acetate-acrylic copolymer is -40 to 0 ° C. 4. The heat-sensitive adhesive according to any one of the fourth aspect of the invention.

In a sixth aspect of the present invention, an ethylene-vinyl acetate copolymer and / or an ethylene-vinyl acetate-acrylic copolymer is 5 to 60 parts by weight based on 100 parts by weight of an ethylene-vinyl acetate-vinyl chloride copolymer. The heat-sensitive adhesive according to any one of the second to fifth inventions, wherein the pressure-sensitive adhesive is a part.

A seventh aspect of the present invention relates to a glass transition temperature of -40 to 0.
Acrylic copolymer at ℃ or glass transition temperature -40
The heat-sensitive adhesive according to any one of the first to sixth inventions, comprising a styrene-butadiene copolymer at a temperature of from 0 to 0 ° C.

An eighth invention is directed to an ethylene-vinyl acetate-vinyl chloride copolymer having a glass transition temperature of 0 to 30 ° C., or an ethylene-vinyl acetate-vinyl chloride copolymer and an ethylene-vinyl acetate copolymer. The glass transition temperature of the mixture of the polymer and / or the ethylene-vinyl acetate-acrylic copolymer is -5 to 30 ° C, or the ethylene-vinyl acetate-vinyl chloride copolymer and the acrylic copolymer Or, the glass transition temperature of the mixture with the styrene-butadiene copolymer is -5 to 30C, or the ethylene-vinyl acetate-vinyl chloride copolymer and the ethylene-vinyl acetate copolymer and / or ethylene- The glass transition temperature of a mixture of vinyl acetate-acrylic copolymer and acrylic copolymer or styrene-butadiene copolymer is -5 to 30. A heat-sensitive adhesive of the first invention to the seventh invention according to any one of, wherein the at.

A ninth invention is a heat-sensitive adhesive sheet obtained by applying the heat-sensitive adhesive according to any one of the first to eighth inventions to a substrate.

A tenth invention is the heat-sensitive adhesive sheet according to the ninth invention, wherein the substrate is a polyolefin film.

An eleventh invention is the heat-sensitive adhesive sheet according to the ninth invention or the tenth invention, which is affixed to a poorly adherent adherend.

A twelfth invention is the heat-sensitive adhesive sheet according to the eleventh invention, wherein the hardly adherent adherend is a polyolefin resin, a polyester resin, or cardboard.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Conventionally, thermoplastic resins used for producing heat-sensitive adhesives include acrylic resins, styrene-acrylic resins, styrene-butadiene, styrene-butadiene-acrylic resins, and ethylene-vinyl acetate. , Ethylene-vinyl acetate-acrylic, ethylene-vinyl acetate ─acrylate, vinyl acetate, vinyl acetate-
Polymers such as acrylic, ethylene-acrylic, butadiene, urethane, styrene-isoprene, isoprene, acrylonitrile-butadiene, and isobutylene are mentioned, and they have been used alone or as a mixture. In particular, acrylic, styrene-butadiene, and ethylene-vinyl acetate polymers are often used.However, it is difficult to achieve both the adhesion to a poorly-adhesive surface such as a polyolefin-based or polyethylene terephthalate plastic, or a cardboard box and the blocking resistance. difficult.

The present invention relates to an ethylene-vinyl acetate-vinyl chloride copolymer containing 20 to 60% by weight of vinyl chloride as a thermoplastic resin in a component of the copolymer, or an ethylene-vinyl acetate-vinyl acetate copolymer. By containing a vinyl chloride copolymer and an ethylene-vinyl acetate copolymer and / or an ethylene-vinyl acetate-acrylic copolymer as a thermoplastic resin, the polyolefin or polyethylene can be used without impairing the blocking resistance. Adhesion to hardly adhered surfaces such as terephthalate plastic or cardboard can be improved.

This means that by including ethylene as a component constituting the thermoplastic resin in the heat-sensitive adhesive, the so-called "wetting" on a poorly adhered surface such as a polyolefin or polyethylene terephthalate plastic or a cardboard is prevented. By improving, further, by containing a chlorine group derived from vinyl chloride, the adhesiveness is improved,
It is presumed that the combined action of the two enhances the adhesion to the above-mentioned hardly adhered surface.

Since many ethylene-vinyl acetate-vinyl chloride copolymers have a relatively high glass transition temperature, other thermoplastic resins having a relatively low glass transition temperature are used in combination in order to impart film-forming properties. Is preferred. Examples of the thermoplastic resin used in combination with the ethylene-vinyl acetate-vinyl chloride copolymer include an ethylene-vinyl acetate copolymer, an ethylene-vinyl acetate-acrylic copolymer, an acrylic copolymer, and a styrene-butadiene copolymer. Copolymer, styrene-acrylic copolymer, styrene-butadiene-acrylic copolymer, vinyl acetate polymer, vinyl acetate-acrylic copolymer, ethylene-acrylic copolymer, polybutadiene, polyurethane, styrene-isoprene Copolymers, polyisoprene, acrylonitrile-butadiene-based copolymers, polyisobutylene, and the like, and particularly, ethylene-vinyl acetate copolymer, ethylene-vinyl acetate-
Acrylic copolymer, acrylic copolymer, styrene
It is preferable to use a butadiene copolymer in combination, and it is more preferable to use an ethylene-vinyl acetate copolymer and an ethylene-vinyl acetate-acrylic copolymer in combination.

Examples of the ethylene-vinyl acetate copolymer or ethylene-vinyl acetate-acrylic copolymer include those containing 30 to 50% by weight of ethylene in the constituents of the copolymer and those having a glass transition temperature of -40. ~ 0 ° C is preferred. If the ethylene content in the copolymer component is less than 30% by weight, the adhesion to polyolefin-based or polyester-based resins decreases, while if it exceeds 50% by weight, the blocking properties deteriorate. Further, the glass transition temperature of the copolymer is-
If the temperature is lower than 40 ° C., the blocking property is deteriorated.
When the ratio exceeds the above range, the adhesive strength to a polyolefin or polyester resin tends to decrease.

The acrylic monomers used for the ethylene-vinyl acetate-acrylic copolymer used in combination with the ethylene-vinyl acetate-vinyl chloride copolymer include acrylic acid, vinyl versatate, methacrylic acid, and anhydride. Maleic acid, maleic acid, fumaric acid, alkyl acrylate, glycidyl acrylate, dialkylaminoalkyl acrylate, alkyl methacrylate, glycidyl methacrylate, hydroxyalkyl methacrylate, dialkylaminoalkyl methacrylate, alkyl maleate, alkyl fumarate, Acrylamide, N-methylol acrylamide, acrylol acrylamide, butoxymethyl acrylamide, styrene and the like can be mentioned, among which acrylic acid is preferable.

The ethylene-vinyl acetate copolymer and / or the ethylene-vinyl acetate-acrylic copolymer is used in an amount of 5 to 60 parts by weight based on 100 parts by weight of the ethylene-vinyl acetate-vinyl chloride copolymer. Is preferably 10
It is more preferred to use ５０50 parts by weight.

An acrylic copolymer or a styrene-butadiene copolymer used in combination with an ethylene-vinyl acetate-vinyl chloride copolymer has a glass transition temperature of -40 to 0.
° C is preferred. Examples of such an acrylic copolymer include 2-ethylhexyl (meth) acrylate and butyl (meth) acrylate, in addition to those exemplified as the acrylic monomers used in the above-mentioned ethylene-vinyl acetate-acrylic copolymer. And acrylates such as lauryl (meth) acrylate and methyl (meth) acrylate.

As described above, in the present invention, an ethylene-vinyl acetate-vinyl chloride copolymer is used as an essential thermoplastic resin, and an ethylene-vinyl acetate copolymer, an ethylene-vinyl acetate-acrylic copolymer, an acrylic The copolymer, styrene-butadiene copolymer and other thermoplastic resins can be used in combination, but the entire thermoplastic resin, that is, as a mixture of the thermoplastic resin, the glass transition temperature, from the viewpoint of blocking resistance, -5 ° C. or higher, more preferably 0 ° C. or higher. On the other hand, if the glass transition temperature is too high, the film-forming property is reduced, and the glass transition temperature is preferably 30 ° C. or lower, more preferably 2 ° C. or less.
0 ° C. or less. The glass transition temperature of the mixture of the thermoplastic resins is a value determined based on the glass transition temperature of each single thermoplastic resin and the mixing ratio (weight ratio),
Any one of the values actually obtained by thermal analysis of the mixture.

As the tackifier for improving the adhesive performance of the heat-sensitive adhesive, conventionally known tackifiers can be used. However, those having a low softening temperature have poor blocking resistance, so that the softening temperature is 80 ° C. or higher. Are preferred. Examples of the tackifier include terpene resins, aliphatic petroleum resins, aromatic petroleum resins, cumarone-indene resins, styrene resins, phenolic resins, terpene-phenol resins, rosin derivatives (rosin, polymerized rosin, hydrogenated Rosin and their esters with glycerin, pentaerythritol, etc., resin acid dimers, etc.). The tackifiers can be used alone or as a mixture of two or more. That is, the tackifier of the heat-sensitive adhesive is terpene resin and aliphatic petroleum resin, aromatic petroleum resin and cumarone-indene resin, styrene resin and phenol resin, terpene-phenol resin and rosin derivative, terpene resin and A rosin derivative, an aliphatic petroleum resin and a rosin derivative, an aromatic petroleum resin and a rosin derivative, a cumarone-indene resin and a rosin derivative, a styrene resin and a rosin derivative, a phenol resin and a rosin derivative, or two kinds of rosin derivatives; It is also possible to use a mixture of three or more kinds of aliphatic petroleum resins and aromatic petroleum resins.

On the other hand, examples of the solid plasticizer include diphenyl phthalate, dihexyl phthalate, dicyclohexyl phthalate, dicyclohexyl terephthalate, dihydroabiethyl phthalate, dimethyl isophthalate, sucrose benzoate, ethylene glycol dibenzoate, and tribenzoate. Trimethylol ethane acid, glyceride tribenzoate, pentaerythritol tetrabenzoate, sucrose octaacetate, tricyclohexyl citrate, N-cyclohexyl-p-toluenesulfonamide, and the like, usually, dicyclohexyl phthalate is preferred. used. The particle size of the solid plasticizer has a considerable effect on the smoothness of the surface coated with the heat-sensitive adhesive.If the particle size is too large, the smoothness of the surface coated with the heat-sensitive adhesive becomes poor, and the thermal activation time is long. Therefore, it is preferable to adjust the maximum particle diameter to 50 μm or less.

In addition, fillers and the like can be added to the heat-sensitive adhesive of the present invention as long as the object of the present invention is not hindered. For example, inorganic substances such as titanium oxide, alumina, kaolin and talc, and paraffin Organic substances such as natural waxes, synthetic waxes, and natural fats and oils, and resin powders can be used. Further, if necessary, a dispersant, an antifoaming agent, a thickener and the like can be used. The heat-sensitive adhesive of the present invention,
It can be applied to a substrate as an aqueous emulsion or an organic solvent solution to form a heat-sensitive adhesive sheet.

[0031]

The present invention will be specifically described below with reference to examples. However, the scope of the present invention is not limited at all by the following examples. In the examples, parts are parts by weight,
% Means% by weight, respectively. [Examples 1 to 10 and Comparative Examples 1 to 4] In the formulation shown in Table 1, a solid plasticizer, a maleic acid resin solution and water were first placed in a ball mill, and ground for 24 hours. And an additive were added and mixed and stirred for 5 minutes to prepare a heat-sensitive adhesive. The obtained heat-sensitive adhesive was applied on the back side of one-sided art paper so that the coating amount was 12 g / m ^2, and dried at 40 ° C. for 4 minutes to obtain a heat-sensitive adhesive sheet (1). Further, the obtained heat-sensitive adhesive is applied to an oriented polypropylene (OPP) film under the same conditions.
After drying, a heat-sensitive adhesive sheet (2) was obtained. Both sheets,
There was no tackiness after drying. Table 1 shows the evaluation results of the adhesive strength, the holding power, the blocking resistance, and the adhesion to the substrate (film forming property) for each heat-sensitive adhesive sheet.

[0032]

[Table 1] * 1 Non-volatile content * 2 Glass transition temperature

The evaluation of the adhesive strength, holding power, blocking resistance and adhesion to the substrate of the coated product was carried out by the following methods. Adhesion: Heat the coated material at 150 ° C for 30 seconds to develop adhesiveness, then immediately adhere to a polyethylene plate, PET plate, corrugated cardboard plate, glass plate, etc., and peel 180 ° according to JIS Z-0237 The adhesive strength was measured according to the following criteria. The adhesive strength was measured by leaving it for 1 or 10 days in an environment of 23 ° C. and 65% after pasting. However, the glued portion was 100 mm in length. In the case of the heat-sensitive adhesive sheet (1) (base material is single-sided art paper) ◎ ・ ・ ・ 800g / 25mm or more. ○ ・ ・ ・ ・ ・ ・ 500g / 25mm or more and less than 800g / 25mm. ×: Less than 500g / 25mm. In the case of the heat-sensitive adhesive sheet (2) (the base material is a stretched polypropylene film) ・ ・ ・: 400 g / 25 mm or more. ○ ・ ・ ・ ・ ・ ・ 200g / 25mm or more and less than 400g / 25mm. ×: Less than 200g / 25mm.

Retention: the heat-sensitive adhesive sheet (1)
After heating at 150 ° C. for 30 seconds to develop adhesiveness, immediately adhere to a SUS plate, apply a constant load of 500 g according to JIS Z-0237, perform a creep test, and judge according to the following criteria . However, the glued portion was 25 mm. ◎ ・ ・ ・ ・ ・ ・ 2000 seconds or more ○ ・ ・ ・ ・ ・ ・ 1000 seconds or more and less than 2000 seconds × ・ ・ ・ ・ ・ ・ less than 1000 seconds

Blocking resistance: The heat-sensitive adhesive sheet (1) is overlapped so that the adhesive-coated surface and the non-adhesive-coated surface face each other, and 1000 g / cm ² is applied to the non-adhesive-coated surface of the sheet.
, And peeled after storage at 40 ° C. for 1 hour, and evaluated according to the following criteria. ◎: There is almost no peeling resistance.・ ・ ・: Sound is generated at the time of peeling. ×: The paper fiber is pulled at the time of peeling or the paper is broken by blocking.

Adhesion to substrate (film-forming property): The coated material was peeled off with a cellophane tape, and the degree of peeling of the adhesive was visually observed. ◎ ・ ・ ・ ・ ・ ・ No peeling of the adhesive.・ ・ ・: Part of the adhesive is peeled off. ×: Most of the adhesive is peeled off.

[0037]

According to the present invention, as compared with a conventional heat-sensitive adhesive sheet coated with a heat-sensitive adhesive, poor adhesion such as polyolefin-based or polyester-based resin or cardboard can be achieved without deteriorating the blocking property. It has become possible to obtain a heat-sensitive adhesive sheet capable of satisfying practical characteristics in adhesive strength and holding power to a surface. The industrial significance of being able to pursue economical benefits by saving resources, such as labels, tapes, and packaging seals that do not require release paper, is extremely significant.

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁶ Identification code FI C09J 131/04 C09J 131/04 B 133/06 133/06 (72) Inventor Makoto Kameyama 2-3-1 Kyobashi 2-chome, Chuo-ku, Tokyo No. Toyo Ink Manufacturing Co., Ltd.

Claims (12)

[Claims] 1. A heat-sensitive adhesive comprising an ethylene-vinyl acetate-vinyl chloride copolymer, a tackifier and a solid plasticizer, wherein said ethylene-vinyl acetate-vinyl chloride copolymer comprises vinyl chloride. Is 20 to 60% by weight. 2. An ethylene-vinyl acetate-vinyl chloride copolymer, an ethylene-vinyl acetate copolymer and / or an ethylene-vinyl acetate-acrylic copolymer, a tackifier, and a solid plasticizer. A heat-sensitive adhesive characterized in that: 3. The ethylene-vinyl acetate-vinyl chloride copolymer according to claim 2, wherein the amount of vinyl chloride constituting said ethylene-vinyl acetate-vinyl chloride copolymer is 20 to 60% by weight. Adhesive. 4. The heat-sensitive adhesive according to claim 2, wherein the ethylene constituting the ethylene-vinyl acetate copolymer and / or the ethylene-vinyl acetate-acrylic copolymer is 30 to 50% by weight. Agent. 5. The heat-sensitive material according to claim 2, wherein the glass transition temperature of the ethylene-vinyl acetate copolymer and / or the ethylene-vinyl acetate-acrylic copolymer is -40 to 0 ° C. Adhesive. 6. The ethylene-vinyl acetate-copolymer and / or the ethylene-vinyl acetate-acrylic copolymer is 5 to 60 parts by weight based on 100 parts by weight of the ethylene-vinyl acetate-vinyl chloride copolymer. The heat-sensitive adhesive according to any one of claims 2 to 5, wherein 7. An acrylic copolymer having a glass transition temperature of -40 to 0 ° C. or a styrene-butadiene copolymer having a glass transition temperature of -40 to 0 ° C. Item 7. The heat-sensitive adhesive according to any one of Items 6. 8. The ethylene-vinyl acetate-vinyl chloride copolymer has a glass transition temperature of 0 to 30 ° C., or an ethylene-vinyl acetate-vinyl chloride copolymer and an ethylene-vinyl acetate copolymer and / or Or, the glass transition temperature of the mixture of the ethylene-vinyl acetate-acrylic copolymer is -5 to 30 ° C, or the ethylene-vinyl acetate-vinyl chloride copolymer and the acrylic copolymer or styrene-butadiene The glass transition temperature of the mixture with the copolymer is -5 to 30C, or an ethylene-vinyl acetate-vinyl chloride copolymer, an ethylene-vinyl acetate copolymer and / or an ethylene-vinyl acetate-acrylic The glass transition temperature of a mixture of a copolymer and an acrylic copolymer or a styrene-butadiene copolymer is -5 to -5.
The heat-sensitive adhesive according to any one of claims 1 to 7, wherein the temperature is 30 ° C. 9. A heat-sensitive adhesive sheet obtained by applying the heat-sensitive adhesive according to claim 1 to a substrate. 10. The heat-sensitive adhesive sheet according to claim 9, wherein the base material is a polyolefin-based film. 11. The heat-sensitive adhesive sheet according to claim 9, wherein the heat-sensitive adhesive sheet is attached to a poorly adherent adherend. 12. The heat-sensitive adhesive sheet according to claim 11, wherein the hardly adherent adherend is a polyolefin resin, a polyester resin, or cardboard.