JP2732526B2 - Heat-sensitive adhesive composition and heat-sensitive adhesive sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Industrial application field The present invention is non-adhesive at normal temperature, but is activated by heating to exhibit tackiness (tack), and even after being separated from a heat source, it has a long life. The present invention relates to a heat-sensitive pressure-sensitive adhesive having a long-time tackiness, and a heat-sensitive pressure-sensitive adhesive sheet obtained by applying the heat-sensitive pressure-sensitive adhesive on a base sheet and drying the heat-sensitive pressure-sensitive adhesive.

(B) Conventional technology The heat-sensitive adhesive sheet is also called thermal delayed tack paper, and is described in, for example, "Adhesion Handbook", 12th edition (published by the Society of Polymer Publishing, 1980). ) Polyvinyl acetate, polybutyl methacrylate, vinyl chloride
Vinylidene chloride copolymer, synthetic rubber, vinyl acetate-2-ethylhexyl acrylate copolymer, vinyl acetate-
A polymer resin such as ethylene copolymer, vinylpyrrolidone-styrene copolymer, styrene-butadiene copolymer, vinylpyrrolidone-ethyl acrylate copolymer, and (b) diphenyl phthalate, dihexyl phthalate, dicyclohexyl phthalate, dihydroabiethyl phthalate, Dimethyl isophthalate, sucrose benzoate,
Such as ethylene glycol dibenzoate, trimethylolethane tribenzoate, glyceride tribenzoate, pentaerythritol tetrabenzoate, sucrose octaacetate, tricyclohexyl citrate, N-cyclohexyl-p-toluenesulfonamide, catechol dibenzoate and the like. A plasticizer which is solid at room temperature, and (C) a rosin derivative (rosin, polymerized rosin, hydrogenated rosin and their glycerin, esters such as pentaerythritol, resin acid dimer, etc.) terpene resin, petroleum resin, phenol resin, A sheet having a coating layer made of a heat-sensitive adhesive containing a tackifier such as a xylene resin. Here, the polymer material is a source of tackiness / adhesive strength, and the tackifier is a component for increasing tackiness when activated by heating. A solid plasticizer is a solid at room temperature, does not impart plasticity to the polymer material, melts by heating, and swells the polymer material.
Dissolves to develop stickiness. Since the amorphous state is maintained semi-permanently after being once melted, the pressure-sensitive adhesive sheet after heat activation can have a longer adhesive holding time. Also,
The form of the coating liquid for producing the heat-sensitive adhesive sheet may be a hot melt type (eg, JP-A-55-16055, JP-A-55-16055).
No. 6-106984), organic solvent type (for example, JP-A-51-1)
No. 11246) and aqueous examples ("Polymer Latex Adhesive", published by Soichi Muroi, published by Kobunshi Kankokai).

(C) Problems to be Solved by the Invention When a hot melt type or an organic solvent type (coating liquid) is used as a form of a composition prepared by mixing a polymer resin, a tackifier and a solid plasticizer, Since the solid plasticizer is melted by heat or an organic solvent, the sheet immediately after coating is activated and in a sticky state, and it is necessary to recrystallize the solid plasticizer to detackify the sheet. Therefore, it is necessary to perform a step of leaving the substrate for a very long period of time, or to apply it to a special substrate sheet coated with a release agent.

It is a first object of the present invention to produce a heat-sensitive adhesive sheet which is coated on ordinary paper and wound up immediately after drying for a short period of time without any concern about blocking.

Further, the conventional heat-sensitive adhesive sheet has a low practical value with respect to a particularly low-polarity plastic material among the adherends to be adhered, because it peels off from the adherend early after being adhered. Therefore, a second object of the present invention is to provide a heat-sensitive adhesive sheet that can maintain adhesiveness for a sufficiently long time even with low-polarity plastic materials.

A third object of the present invention is to provide a coating composition that provides such a heat-sensitive adhesive sheet.

(D) Means for Solving the Problems First, as a form of the coating composition, in order to apply a solid plasticizer in a solid state, the coating liquid was entirely converted to an aqueous dispersion. It was decided to. As a result, a heat-sensitive pressure-sensitive adhesive sheet that does not cause blocking by being wound into a roll could be directly produced if drying conditions were selected such that the pressure-sensitive adhesive sheet was not thermally activated.

This is a great advantage due to the preparation and application of each material in the form of an aqueous dispersion. On the other hand, regarding the adhesiveness, when a conventionally known aqueous dispersion of a polymer material as described above is used for the heat-sensitive adhesive sheet, for example, polypropylene, a low-polarity plastic material such as polyethylene, is sufficiently long. Tackiness or adhesion cannot be obtained over a period of time. Therefore, as a result of extensively trying other polymers, a heat-sensitive adhesive sheet that can maintain sufficient adhesiveness or adhesiveness over a long period of time by finally using high-pressure method ethylene copolymer for at least a part of the polymer material has been developed. It was found that it was obtained, and the above object was achieved. A heat-sensitive adhesive sheet produced by aqueous coating using such a high-pressure ethylene copolymer has not yet been known.

That is, the first aspect of the present invention is that (b) 10 to 200 parts by weight of a tackifier and (c) based on 100 parts by weight of a polymer resin containing 10% by weight or more of a high pressure ethylene copolymer.
An object of the present invention is to provide a heat-sensitive adhesive composition comprising a resin aqueous dispersion containing a solid component blended in a proportion of 50 to 300 parts by weight of a solid plasticizer as a basic component.

A second aspect of the present invention is to provide a heat-sensitive adhesive sheet obtained by applying the above-mentioned heat-sensitive adhesive composition on a base sheet by water-based coating and drying.

In the present invention, as the polymer resin of the component (a),
It contains at least 10% by weight, preferably 20 to 50% by weight, of a high pressure ethylene copolymer, and as the other resin, the above-mentioned polyvinyl acetate, polybutyl methacrylate, vinyl chloride-
Vinylidene chloride copolymer, synthetic rubber, vinyl acetate-2-ethylhexyl acrylate copolymer, vinyl acetate-
Examples include ethylene copolymer, vinylpyrrolidone-styrene copolymer, styrene-butadiene copolymer, vinylpyrrolidone-ethyl acrylate copolymer, and metal salts of styrene-maleic anhydride copolymer (Na, Zn, K, etc.). Preferably, resins having a melting point of 130 ° C. or lower are used.

The high-pressure ethylene copolymer used in the present invention is an ethylene copolymer produced by a high-pressure radical copolymerization reaction between ethylene and a functional group-containing comonomer. Acid esters, methacrylic esters, acrylic acid, methacrylic acid, maleic anhydride and the like are used. And the comonomer used in the copolymerization reaction is not limited to one kind,
Two or more types may be used.

For example, terpolymers of ethylene with ethyl acrylate and maleic anhydride are also useful in the present invention.

In the present invention, these high-pressure ethylene copolymers are used in the form of an aqueous emulsion.

As an example of the aqueous emulsion method, a method not using an organic solvent, such as described in JP-A-58-120655 and JP-A-59-4637, is preferred. The high-pressure ethylene copolymer is supplied to the multi-screw screw extruder, which is first heated and kneaded,
Subsequently, a water-soluble polymer aqueous solution, which is a protective colloid, is supplied from a supply port provided in the middle of the extruder and kneaded with the aqueous solution under shear to obtain an aqueous emulsion.

Further, a copolymer of ethylene and acrylic acid or methacrylic acid is emulsified and dispersed in water containing sodium hydroxide or potassium hydroxide to obtain a so-called ionomer resin aqueous dispersion, which is also useful in the present invention. is there.

In order to delicately control the adhesive properties (adhesion, adhesion, cohesion, etc.) to various adherends and the blocking resistance, etc., it is necessary to use a high-pressure method ethylene copolymer in combination with other polymer materials. Is preferred. Examples thereof include those in which the known polymer material is emulsified,
Particularly preferred examples include vinyl acetate copolymer (for example, vinyl acetate-ethylene copolymer), acrylic copolymer (for example, styrene-alkyl acrylate copolymer) and the like. In particular, when the former vinyl acetate-ethylene copolymer 50-90 parts by weight and the high-pressure method ethylene copolymer 50-10 parts by weight are combined, the adhesiveness is remarkably developed by heating, and the adherence to the nonpolar adherend is increased. Excellent heat-sensitive adhesive is obtained.

As the tackifier of the component (b), conventionally known tackifiers can be used, but a preferable example is a softening point (JIS K 59
Rosin or terpene-based resin having a temperature of 70 to 145 ° C is preferred. Rosins such as rosin abietic acid, hydrogenated products thereof and maleic acid adducts thereof, metal salts, glycerin, pentaerythritol, ethylene glycol and diethylene glycol Modified rosin such as an esterified product with an alcohol is exemplified. Further, as the terpene-based resin, homopolymers such as α-pinene, β-pinene, dipentene, or copolymers thereof, terpene / phenol copolymers, and water additives thereof are used. These are available as aqueous emulsions.

Examples of the solid plasticizer (c) include diphenyl phthalate, dihexyl phthalate, dicyclohexyl phthalate, dihydroabiethyl phthalate, dimethyl isophthalate, sucrose benzoate, ethylene glycol dibenzoate, and trimethylol tribenzoate. Plasticizers that are solid at room temperature such as ethane, glyceride tribenzoate, pentaerythritol tetrabenzoate, sucrose octaacetate, tricyclohexyl citrate, N-cyclohexyl-p-toluenesulfonamide, and catechol dibenzoate can be used.

(A) a polymer resin, (b) a tackifier and (c)
As a preferred compounding ratio of the solid plasticizer, the polymer resin 100
10 to 200 parts by weight of the tackifier, 50 to 300 parts by weight of the solid plasticizer, and 10% by weight or more of the high-pressure ethylene copolymer in the polymer resin (a). The object of the present invention can be achieved. When the amount of the tackifier is less than 10 parts by weight, the viscosity / adhesive strength after thermal activation is low, and when the amount is more than 200 parts by weight, the blocking phenomenon when wound up in a roll becomes severe. If the amount of the solid plasticizer is less than 50 parts by weight, adhesiveness due to heat activation hardly occurs.If the amount exceeds 300 parts by weight, the cohesive force of the adhesive part after heat activation is reduced, and the adhesion duration after heat activation. (Open time) is not practical because it is short.

To prepare a heat-sensitive adhesive composition comprising the aqueous resin dispersion of the present invention, a mixture of (a) a polymer resin, (b) a tackifier, and (c) a solid plasticizer is mixed with It may be supplied to a screw extruder, melt-kneaded, supplied with a protective colloid from a supply port provided in the middle of the extruder, and mixed with the protective colloid.

Alternatively, the aqueous emulsions of the components (a), (b) and (c) may be individually prepared and mixed.

The concentration of the solid content of the aqueous resin dispersion is 25 to 60% by weight, and may be diluted with water if necessary.

Further, the solid particles in the resin aqueous dispersion, 0.05 ~ 30μ
m, preferably 0.05 to 10 μm.

The resin-based aqueous dispersion containing the components (a), (b) and (c) is applied on a substrate sheet and dried to obtain a heat-sensitive adhesive sheet.

As the aqueous coating method, a roll coater, an air knife coater, a blade coater, a gravure coater, or the like which is generally used can be used, and the coating amount is preferably 5 to 30 g / m ² in terms of dry solid content.

Substrate sheets include pulp, paper, polyethylene terephthalate film, polypropylene film, polyvinylidene chloride film, art paper, synthetic paper (Japanese Patent Publication No.
No. 40794, JP-A-56-141339) and the like can be used.

This heat-sensitive adhesive sheet is useful as a label material for, for example, carbonated beverage bottles, shampoo bottles, motor oil cans, and tissue paper polyethylene packages.

As described above, a coating prepared by mixing (a) a polymer material containing a high-pressure method ethylene copolymer, (b) a tackifier, and (c) a solid plasticizer into an aqueous dispersion. It has been found that an excellent heat-sensitive adhesive sheet achieving the above-mentioned object can be obtained by performing aqueous coating on a substrate sheet using a liquid, that is, a heat-sensitive adhesive composition, and drying.

(E) Example In this example, all “parts” represent “parts by weight of solid content”.

Example 1 (a) As a polymer material 70 parts of an aqueous emulsion of vinyl acetate-ethylene copolymer (vinyl acetate content 70% by weight) High-pressure ethylene / ethyl acrylate / maleic anhydride terpolymer having a comonomer content of 9% by weight 30 parts of an aqueous emulsion of Bondine HX8210 (trade name, manufactured by Sumitomo Chemical Co., Ltd.) (b) Aqueous emulsion of rosin ester as a tackifier (softening point 100 ° C) 5
0 parts (c) 100 parts of an aqueous dispersion of dicyclohexyl phthalate as a solid plasticizer An aqueous coating solution (solid content: 50%) having the above composition was prepared.
It was applied to one side of art paper having a basis weight of 80 g / m ^{2 so} as to have a dry coating amount of 25 g / m ^2, and dried at 50 ° C. for 2 minutes to obtain a non-adhesive coated paper.

Comparative Example 1 A non-tacky coated paper was obtained in exactly the same manner as in Example 1 except that the polymer resin as the component (a) was a vinyl acetate-ethylene copolymer emulsion (ie, 100 parts were used).

Example 2 (a) Styrene-acrylate copolymer emulsion (manufactured by Chuo Rika Kogyo Co., Ltd., trade name: Ricabond ES-5)
8) 60 parts Aqueous emulsion of terpolymer of ethylene / ethyl acrylate / maleic anhydride with high pressure method having a comonomer content of 9% by weight used in Example 1 40 parts (b) Aqueous emulsion of polymerized rosin pentaerythritol ester (softening) (Part 124 ° C) 30 parts (c) 150 parts of dicyclohexyl phthalate aqueous dispersion An aqueous coating solution (solid content: 50%) having the above composition was prepared.
It was applied to one side of art paper having a basis weight of 80 g / m ^{2 so} as to have a dry coating amount of 23 g / m ² and dried at 50 ° C. for 2 minutes to obtain a non-tacky coating liquid.

Comparative Example 2 A non-adhesive coated paper was obtained in exactly the same manner as in Example 2, except that the polymer resin of the component (a) was a styrene-acrylate copolymer emulsion (ie, 100 parts were used). .

Example 3 The coated paper pieces obtained in Example 1 and Comparative Example 1 were treated at 120 ° C.
Activated under heating conditions of 0 seconds, affixed to a polyethylene film, allowed to stand at room temperature for 3 months, and then peeled off with nails. A practical test was performed. The paper piece of Example 1 was firmly adhered. The base paper was torn when it was forcibly peeled off (substrate breakdown).

In contrast, the paper piece of Comparative Example 1 easily peeled off from the interface with the adherend (interfacial fracture).

Example 4 The coated paper pieces obtained in Example 2 and Comparative Example 2 were used in Example 3
Activated in the same manner as above, pasted on a tableware container made of polypropylene, and three months later, when the same peeling test was performed,
In the case of Example 2, the substrate was broken, whereas in the case of Comparative Example 2, the interface was easily broken from the surface of the adherend and peeled off.

Example 5 (a) Aqueous emulsion of vinyl acetate-ethylene copolymer (vinyl acetate content: 70% by weight) 80 parts Aqueous emulsion of high-pressure ethylene copolymer used in Example 1 20 parts (b) Aqueous emulsion of rosin ester (softening) Point 100
℃) 50 parts (c) Aqueous dispersion of dicyclohexyl phthalate 150 parts
of m ² on one side of the art paper, coated to a dry coating weight 24 g / m ^2, 50
Drying at 2 ° C. for 2 minutes gave a non-adhesive coated paper.

This paper piece was heat-activated by heating at 120 ° C for 20 seconds, and the degree of tack was immediately measured according to the inclined ball tack measurement method (temperature 20 ° C, inclined angle 30 °). Results were obtained. The heat-activated sample paper piece was affixed to a polyethylene bottle for reagent and left at room temperature for 3 months, but it adhered well.

On the other hand, the sample paper piece of Comparative Example 1 using only 100 parts of vinyl acetate-ethylene copolymer as the polymer resin adhered to the same polyethylene bottle after heat activation,
After a lapse of five months, it had peeled off.

Example 6 The same procedure as in Example 1 was carried out except that the polymer resin of the component (a) in Example 1 was 90 parts of a vinyl acetate-ethylene copolymer emulsion and 10 parts of a high-pressure ethylene copolymer emulsion. A sticky coated paper was obtained. Next, in the same manner as in Example 3, when activated under heating conditions of 120 ° C. and 30 seconds, pasted on a polyethylene film, left at room temperature for 3 months, and then subjected to a practical test of peeling with a nail, Although it did not peel off with a weak force, it could be peeled off without forcing the base paper when it was forcibly peeled off.

Comparative Example 3 A polyethylene resin was prepared in the same manner as in Example 6 except that the polymer resin of the component (a) in Example 1 was 95 parts of a vinyl acetate-ethylene copolymer emulsion and 5 parts of a high-pressure ethylene copolymer emulsion. When the film was stuck to a film made from the above and left at room temperature for 3 months, the film was easily peeled when peeled off with a weak force.

Example 7 The procedure of Example 5 was repeated, except that the polymer resin of the component (a) in Example 5 was changed to 50 parts of a vinyl acetate-ethylene copolymer emulsion and 50 parts of a high-pressure ethylene copolymer emulsion. A sticky coated paper was obtained. 120
Activated under heating conditions of 30 ° C. for 30 seconds, attached to a polyethylene bottle for reagent, and allowed to stand at room temperature for 3 months.

Example 8 The same procedure as in Example 5 was repeated except that the polymer resin of the component (a) in Example 5 was changed to 70 parts of a vinyl acetate-ethylene copolymer emulsion and 30 parts of a high-pressure ethylene copolymer emulsion. A sticky coated paper was obtained. 120
The ball was activated under heating conditions of 30 ° C. for 30 seconds, and the ball tack value was measured. As a result, the ball was No. 3. It was activated under the heating condition of 120 ° C. for 30 seconds, stuck to a polyethylene bottle for a reagent, and allowed to stand at room temperature for 3 months.

(F) Effect of the Invention As described above, a polymer resin containing a high-pressure ethylene copolymer is prepared in an aqueous dispersion together with a tackifier and a solid plasticizer, and is subjected to aqueous coating, so that immediately after coating, No blocking phenomenon when stacked or rolled up.
A heat-sensitive adhesive sheet having good adhesiveness was obtained.

Claims (2)

(57) [Claims] 1. An essential copolymerization component comprising (a) ethylene and one or more comonomers selected from the group consisting of acrylic acid, methacrylic acid, acrylates, methacrylates and maleic anhydride. For 100 parts by weight of a polymer resin containing 10% by weight or more of a high-pressure ethylene copolymer, (b) 10 to 200 parts by weight of a tackifier and (c) 50 to 300 parts by weight of a solid plasticizer are blended. A heat-sensitive adhesive composition comprising a resin aqueous dispersion containing the solid component as a basic component. 2. An essential copolymerization component comprising (a) ethylene and one or more comonomers selected from the group consisting of acrylic acid, methacrylic acid, acrylates, methacrylates and maleic anhydride. For 100 parts by weight of a polymer resin containing 10% by weight or more of a high-pressure ethylene copolymer, (b) 10 to 200 parts by weight of a tackifier and (c) 50 to 300 parts by weight of a solid plasticizer are blended. A heat-sensitive adhesive sheet obtained by applying a heat-sensitive adhesive composition comprising an aqueous resin dispersion containing the solid component as a basic component on a base sheet and drying the composition.