JP2001200227A - Heat-sensitive, pressure-sensitive adhesive composition; and heat-sensitive, pressure-sensitive adhesive sheet or label - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-sensitive, delayed tack-type pressure-sensitive adhesive composition which is non-tacky at room temperature, is usable without either a release paper or a release treatment on the back surface of a base material, is excellent in the anti-blocking property at a room temperature, and is excellent in the pressure-sensitive characteristics when heated. SOLUTION: The composition of an aqueous emulsion contains (A) a polymer having an acid value of 30 to 300 mg KOH/g and a glass transition temperature (Tg) of 30 deg.C or higher, (B) a polymer having a Tg of -20 deg.C or lower, and (C) a tackifier having a softening point of 80 to 180 deg.C, with weight ratios between the above components satisfying the following formulae: (A)/(B)=15/85 to 50/50... formula (1) [(A)+(B)]/(C)=100/(2 to 50)... formula (2).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive adhesive composition and a heat-sensitive adhesive sheet or label, and more specifically, does not exhibit adhesiveness at room temperature, but exhibits adhesiveness when heated to a certain temperature or higher. The present invention relates to an emulsion-type pressure-sensitive adhesive composition and a heat-sensitive pressure-sensitive adhesive sheet or label having a pressure-sensitive adhesive layer containing the pressure-sensitive adhesive composition as a main component.

[0002]

2. Description of the Related Art Generally, pressure-sensitive adhesive sheets or labels are coated with release paper (release paper) on the pressure-sensitive adhesive surface, and are stored, distributed, sold, and the like. Further, in a roll-up type product such as an adhesive tape, a base material having a back surface subjected to a release treatment is used so that the product can be rewound during use. The release paper is an unnecessary element after the pressure-sensitive adhesive sheet is attached to the article, and a pressure-sensitive adhesive sheet that does not require a release paper is required from the viewpoint of resource saving and cost reduction. Furthermore, if a base material that has not been subjected to a release treatment on the back surface can be used for the adhesive tape, the manufacturing process of the adhesive tape base material can be simplified, and the cost can be reduced.

As a pressure-sensitive adhesive sheet that does not require release paper, a heat-sensitive pressure-sensitive adhesive sheet coated with a delayed tack-type pressure-sensitive adhesive is known. Conventional heat-sensitive delayed-tack adhesives
"Adhesion Handbook" (12th edition, 1980, published by the Society of Polymer Publishing)
As described in (1), it basically contains a thermoplastic resin and a crystalline plasticizer and a tackifier which are solid at room temperature. Thermoplastic resin is the root of adhesive strength and adhesive strength.Crystalline plasticizer is solid at room temperature and does not give plasticity, but it melts when heated and swells or softens the resin. Sexuality,
The tackifier functions to improve the tackiness. The crystalline plasticizer in the heat-sensitive delayed-tack type adhesive slowly crystallizes after being melted by heating, so that the adhesiveness is maintained for a long time.

As a delayed tack type pressure-sensitive adhesive using a solid plasticizer, Japanese Patent Publication No. Sho 62-21835,
Japanese Unexamined Patent Publication Nos. Hei. 57233 and JP-A-6-100848 are known. This publication discloses, as a delayed tack adhesive, an adhesive obtained by mixing a thermoplastic resin such as an ethylene-vinyl acetate copolymer with a solid plasticizer such as dicyclohexyl phthalate. These prior art documents describe that such an adhesive is non-adhesive at room temperature, and the plasticizer is melted by heating to develop an adhesive force.

However, the conventional delayed tack-type pressure-sensitive adhesive containing a solid plasticizer has various problems as described in the following (1) to (4), and is limited to limited special uses. Currently, it cannot be used.

(1) After the crystallization of the solid plasticizer proceeds, the adhesive strength is lost, so that once the solid plasticizer is peeled off from the adherend, it cannot be adhered to the adherend again. (2) Since the heating temperature for developing the adhesiveness depends on the melting point of the solid plasticizer, the heating temperature cannot be set freely. (3) The pressure-sensitive adhesive becomes hard and loses its flexibility after crystallization proceeds. Therefore, if the pressure-sensitive adhesive is bent or vibrated after the pressure-sensitive adhesive sheet is adhered to the adherend, There is a risk that the layer cannot follow the adherend and peels off. (4) When the base material used for the pressure-sensitive adhesive sheet is high-quality paper or the like, the plasticizer easily oozes out on the sheet surface when the pressure-sensitive adhesive sheet is heated.

On the other hand, in order to solve the above-mentioned problems, JP-A-8-269420 and JP-A-10-3678 disclose a delayed tack type adhesive which does not use a crystalline plasticizer.
No. 8, JP-A-11-5959 and the like, a non-adhesive resin having a glass transition temperature of a certain temperature or more [component (X )], And an adhesive resin emulsion [component (Y)] obtained by copolymerizing a radical polymerizable monomer such as an acrylate ester to cause the adhesive sheet to exhibit adhesiveness by heat treatment. Is disclosed. In the above-mentioned publication, it is described that a non-tacky pressure-sensitive adhesive layer is obtained by drying such a pressure-sensitive adhesive composition at a relatively low temperature, and that the pressure-sensitive adhesive layer is developed by heat treatment.

However, in this case, it is necessary to increase the glass transition temperature of the component (X) and the content of the component (X) in order to suppress the tackiness at room temperature.
If the glass transition temperature (Tg) is increased, it is necessary to reheat at a temperature higher than Tg in order to develop tackiness, which is disadvantageous in terms of thermal energy and uses a substrate which is weak to heat. The problem arises that it is not possible. When the amount of the component (X) is increased, the amount of the component (Y) that relatively exhibits tackiness is reduced, so that there is a problem that a sufficient adhesive strength cannot be obtained.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to remedy the drawbacks of the prior art described above, which is non-adhesive at room temperature and can be used without releasing the release paper or the back surface of the substrate. An object of the present invention is to provide a heat-sensitive delayed-tack type pressure-sensitive adhesive composition and a heat-sensitive pressure-sensitive adhesive sheet or label having excellent blocking resistance at room temperature and excellent pressure-sensitive adhesive properties when heated.

[0010]

That is, the first aspect of the present invention is as follows.
The gist of the polymer (A) having an acid value of 30 to 300 mgKOH / g and a glass transition temperature (Tg) of 30 ° C. or more,
Polymer (B) having a g of -20 ° C or less, and a softening point of 80 to 18
An aqueous emulsion containing a tackifier (C) at 0 ° C., wherein the weight ratio of the above components satisfies the following formulas (1) and (2): Exists.

[0011]

(A) / (B) = 15/85 to 50/50 (1) {(A) + (B)} / (C) = 100/2 to 50 (2) )

In a preferred embodiment of the present invention, the above-mentioned component (A) is 4 to 50% by weight of a radical polymerizable monomer (a1) requiring a carboxyl group or a sulfonic acid group and a hydrophobic radical polymerizable monomer. (A2) a copolymer obtained by subjecting 96 to 50% by weight of emulsion polymerization in the presence of a surfactant and then neutralizing with a base, and the component (B)
Is a polymer obtained by emulsion polymerization of the above component (A) as a polymer emulsifier.

A second gist of the present invention is to provide a heat-sensitive adhesive sheet or label comprising a pressure-sensitive adhesive layer containing the above-mentioned heat-sensitive adhesive composition as a main component on the surface of a substrate. Exists.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
In the following, acryl and / or methacryl are referred to as “(meth) acryl”, and acrylate and / or methacrylate are referred to as “(meth) acrylate”. Also,
In the present specification, the “glass transition temperature” (hereinafter, referred to as “Tg”) of a polymer refers to a value obtained from the following calculation formula. It should be noted that only Tg used in this formula is expressed in absolute temperature (K), and Tg used in other parts of the specification is expressed in degrees Celsius (° C). The meanings of the symbols in the formulas are as shown in Table 1 below.

[0015]

1 / Tg = {W (a) / Tg (a)} + {W (b) / T
g (b)} + {W (c) / Tg (c)} + ...

[0016]

[Table 1] Tg: Tg (K) of polymer W (a): Weight fraction of structural unit composed of monomer (a) in polymer W (b): From monomer (b) in polymer W (c): Weight fraction of structural unit composed of monomer (c) in polymer Tg (a): Glass transition temperature (K) of homopolymer of monomer (a) Tg (b): Glass transition temperature of homopolymer of monomer (b) (K) Tg (c): Glass transition temperature of homopolymer of monomer (c) (K)

(1) Component (A): Component (A) in the present invention is a polymer having an acid value of 30 to 300 mgKOH / g and a glass transition temperature (Tg) of 30 ° C. or higher. Such polymers disperse or dissolve in water and do not aggregate in water.

(1-1) Composition: As the component (A), a radical polymerizable monomer unit (a1) having a carboxyl group or a sulfonic acid group having the above-mentioned acid value and another radical polymerizable monomer And a copolymer composed of the unit (a2).

Examples of the radically polymerizable monomer having a carboxyl group in the component (a1) include acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, and maleic anhydride. One or two or more of α, β-ethylenically unsaturated carboxylic acids such as described above are preferably used. Among these, acrylic acid, methacrylic acid and maleic acid are preferred. On the other hand, examples of the radical polymerizable monomer having a sulfonic acid group include acrylamido-2-methylpropanesulfonic acid and styrenesulfonic acid. The amount of component (a1) used varies depending on the type of unsaturated carboxylic acid used, but is usually 4 to 50% by weight, preferably 4 to 50% by weight, based on the total weight of all the monomers used in the synthesis of component (A). Is 5 to 30% by weight.

As the above component (a2), 100 g of water
A hydrophobic radically polymerizable monomer having a solubility in water of 2 g or less is preferably used. Examples of such a monomer include methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, ( Isobutyl meth) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate,
Alkyl (meth) acrylates such as n-nonyl (meth) acrylate and isononyl (meth) acrylate; styrene,
vinyl aromatic monomers such as α-methylstyrene and vinyltoluene; vinyl esters such as vinyl acetate; and (meth) acrylonitrile. Component (a2) is used in an amount of usually 50 to 96% by weight, preferably 70 to 95% by weight, based on the total weight of all monomers used for the synthesis of component (A).
% By weight.

In the present invention, other hydrophilic radically polymerizable monomers (a3) other than those described above can be used as a copolymerization component when synthesizing the component (A). Examples of such monomers include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, and (meth) acryl. Hydrophilic radically polymerizable monomers such as acid amide, N-methylolacrylamide, and glycidyl methacrylate are preferably used. Component (a3) is used in an amount of usually 30% by weight or less, preferably 20% by weight, based on the total weight of all monomers used in the synthesis of component (A).
The lower limit is usually 1% by weight.

The above component (A) may be a base neutralized product of a graft copolymer. As the graft copolymer, a graft copolymer comprising a hydrophilic main chain and a hydrophobic side chain or a graft copolymer comprising a hydrophobic main chain and a hydrophilic side chain is suitably used. This is because a heat-sensitive adhesive composition having excellent liquid stability can be obtained because of high affinity between the above-mentioned hydrophobic portion and the component (B) described below.

(1-2) Production method: When the above component (A) is a polymer of a radical polymerizable monomer, various polymerization methods are used as a polymerization method for obtaining the component (A). it can. For example, known methods such as a polymerization method by irradiation with radiation and a method using a radical polymerization initiator can be employed. Among these, a polymerization method using a radical polymerization initiator is suitably employed in view of easiness of a polymerization operation, easiness of controlling the molecular weight of the obtained copolymer before neutralization, and the like. Examples of the polymerization type include a solution polymerization method, a bulk polymerization method, a suspension polymerization method, an emulsion polymerization method, and a precipitation polymerization method, and the solution polymerization method or the emulsion polymerization method is suitably employed.

In the above solution polymerization method, it is possible to obtain the component (A) smoothly by dissolving a radical polymerizable monomer in an organic solvent and performing polymerization using an appropriate radical polymerizable initiator. I can do it.

As the organic solvent, one or more organic solvents selected from ketones, acetates, aromatic hydrocarbons, aliphatic hydrocarbons, alcohols and the like can be used. And a water-soluble organic solvent having a boiling point of from 60 to 100 ° C. Examples of such an organic solvent include acetone, methyl ethyl ketone, methanol, ethanol, isopropyl alcohol and the like.

As the radical polymerization initiator, any of those used in general radical polymerization can be used. For example, persulfate polymerization initiators such as potassium persulfate and ammonium persulfate, and azoisomers Examples include azo-based polymerization initiators such as bisbutyronitrile, and redox-based polymerization initiators. The amount of the polymerization initiator used is usually 0.05 to 5% by weight, preferably 0.3 to 5% by weight, based on the total amount of the monomers.
3% by weight.

In the case of the emulsion polymerization method, for example, as disclosed in JP-A-6-271779, a radical polymerizable monomer is mixed and dispersed in water together with an emulsifier to prepare a monomer pre-emulsion. Then, polymerization is carried out by continuously adding the above radical polymerization initiator to the reactor.

The polymerization temperature for obtaining the component (A) is usually from 30 to 120 ° C, preferably from 50 to 100 ° C. The polymerization time is usually 1 to 24 hours, preferably 3 to 1 hour.
0 hours.

The weight average molecular weight of the component (A) is usually from 2,000 to 100,000, preferably from 3,000.
~ 30,000. When the weight average molecular weight is less than 2,000, the water resistance of the pressure-sensitive adhesive layer in the heat-sensitive pressure-sensitive adhesive sheet or label tends to be insufficient, and the blocking property before heating becomes a problem. On the other hand, when the weight average molecular weight is 10
If it exceeds 000, the viscosity becomes high and the component (A)
And the solubility of the component (A) in water becomes insufficient to lower the liquid stability of the composition,
When the emulsion polymerization of the component (B) is performed in the presence of the component (A), the polymerization becomes unstable. In addition, since the fluidity of the component (A) decreases, sufficient adhesiveness may not be obtained by heating the adhesive layer of the heat-sensitive adhesive sheet or tape. In order to adjust the number average molecular weight, a chain transfer agent such as alkyl mercaptan or thioglycolate may be appropriately added to the polymerization system. The amount added is generally 0.5 to 15% by weight, preferably 1 to 10% by weight, based on the total weight of the monomers used for the synthesis of the component (A).

When the component (A) is a neutralized base of a graft copolymer, the base used for neutralization may be ammonia;
Amines such as alkylamine, allylamine, and alkanolamine; alkali metal hydroxides such as sodium hydroxide and potassium hydroxide; alkaline earth metal salts such as magnesium and calcium. Among these,
Bases having a boiling point of 100 ° C. or lower, such as ammonia, trimethylamine and triethylamine, are preferred, and ammonia is particularly preferred. This is because the base is easily removed from the pressure-sensitive adhesive layer in a drying step after the application of the heat-sensitive pressure-sensitive adhesive sheet or tape, so that a pressure-sensitive adhesive layer having excellent water resistance can be obtained.

When the component (A) is a base-neutralized product of the graft copolymer, it is not necessarily required to be a completely neutralized product, but it must be neutralized to such an extent that it becomes water-dispersible or water-soluble. is there. Such a degree of neutralization can be achieved by neutralizing the acidic groups of the component (A) usually at least 40 mol%, preferably at least 60 mol%. When the neutralization amount of the acidic group is less than 40 mol%, the following problem occurs. That is, if the solubility of the component (A) in water is insufficient, the pressure-sensitive adhesive composition tends to be unstable, for example, the liquid is separated with the passage of time, and the component (A) has a low surface activity. When component (B) is emulsion-polymerized in the presence of ()), the polymerization tends to be unstable.

The component (A) preferably has a low crosslinking density or is substantially non-crosslinked. Component (A)
Is excessively crosslinked, there are the following problems. That is, the solubility of the component (A) in water tends to be insufficient. In addition, in the pressure-sensitive adhesive layer before heating of the heat-sensitive pressure-sensitive adhesive sheet or tape, the movement of the molecular chain constituting the component (A) is restricted, so that even in the case of performing the heat treatment, it may be difficult to exhibit the tackiness.

(1-3) Acid value: In the present specification, the “acid value” refers to a theoretical acid value calculated by a conventional method, and when a polymer is neutralized with a base, the acid value is medium. Indicates the acid value before summation. “MgK” used as the unit of acid value
"OH / g" represents the number of milligrams of potassium hydroxide required for neutralization in 1 g of the solid content of the polymer.

The acid value of the above component (A) is 30 to 300 m
gKOH / g. This acid value is 30mg
When it is less than KOH / g, the solubility of the component (A) in water is insufficient, so that the liquid composition of the pressure-sensitive adhesive composition containing the component (A) becomes insufficient or the component (A) When the emulsion polymerization of the component (B) is performed in the presence, the polymerization becomes unstable. Furthermore, since the alkali solubility or swelling property of the component (A) is insufficient, sufficient alkali stripping property cannot be imparted when preparing the alkali stripping adhesive composition. On the other hand, the acid value of component (A) is 300 mgKOH / g
When it exceeds, the water resistance of the pressure-sensitive adhesive layer is insufficient. The acid value of the above component (A) is preferably from 30 to 200 mg KO.
H / g.

(1-4) Glass transition temperature (Tg): The component (A) must have a Tg of 30 ° C. or higher. The Tg of the component (A) is preferably from 40 to 140 ° C.,
20 ° C. is more preferred. When the (Tg) of the component A is lower than 30 ° C., the adhesive strength of the pressure-sensitive adhesive layer before the heat treatment becomes too high, and “peeling treatment for the pressure-sensitive adhesive layer such as release paper or peeling treatment of the back surface of the base material is not performed. To provide a pressure-sensitive adhesive sheet that can be used without performing the process ". On the other hand, when the Tg exceeds 140 ° C., the heating temperature required for developing the tackiness is increased, so that the energy cost is increased and there is a tendency that a heat-sensitive substrate cannot be used.

(2) Component (B): Component (B) in the present invention is a polymer having a Tg of -20 ° C. or lower.

(2-1) Composition: As the component (B), for example, various polymers obtained by emulsion polymerization of a radical polymerizable monomer and having a Tg within the above range can be used. . For example, an emulsion polymer of a radical polymerizable monomer having a (meth) acrylic acid ester as a main component (hereinafter, referred to as an “acrylic monomer”), a radical polymerizable monomer having ethylene and a vinyl ester as a main component. (Hereinafter referred to as “ethylene-vinyl ester monomer”)
, A conjugated diene monomer and a radical polymerizable monomer having a monomer copolymerizable with the conjugated diene monomer (hereinafter, referred to as a “conjugated diene monomer”) as a main component And the like. When the component (B) is an emulsion polymer of an ethylene-vinyl ester monomer or a conjugated diene monomer, the pressure-sensitive adhesive layer of the heat-sensitive adhesive sheet or tape after heating is good for the polyolefin resin. There is an advantage that a pressure-sensitive adhesive composition having a high adhesive strength is easily obtained. On the other hand, when the component (B) is an emulsion polymer of an acrylic monomer, there is an advantage that a pressure-sensitive adhesive layer excellent in weather resistance and transparency can be easily obtained.

Examples of the "vinyl ester monomer" in the above "ethylene-vinyl ester monomer" include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl laurate, vinyl versatate and the like. No. Examples of the “conjugated vinyl monomer” in the “conjugated vinyl monomer” include butadiene, isoprene, chloroprene, and isobutylene.

The above-mentioned “acrylic monomer” includes, as a main component, an alkyl (meth) acrylate and, if necessary, another radical polymerizable monomer (hereinafter referred to as “copolymerizable monomer”). Monomer) is preferably used.

As the "alkyl (meth) acrylate", an alkyl (meth) acrylate having an alkyl group having 1 to 12 carbon atoms is preferably used. Specifically, methyl (meth) acrylate, (meth)
Ethyl acrylate, isopropyl (meth) acrylate,
N-propyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, (meth)
Hexyl acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (meth)
N-octyl acrylate, isooctyl (meth) acrylate, n-nonyl (meth) acrylate and isononyl (meth) acrylate, decyl (meth) acrylate, lauryl (meth) acrylate, and the like. Two or more of these alkyl (meth) acrylates can be used. In particular, in the present invention, as a radical polymerizable monomer used in the production of the component (B), an alkyl (meth) acrylate having an alkyl group having 4 to 12 carbon atoms, particularly n-butyl acrylate, It is preferable to use one or more selected from the group consisting of 2-ethylhexyl acrylate and n-octyl acrylate as a main component.

The above-mentioned "copolymerizable monomer" includes, for example, vinyl aromatic monomers such as styrene, α-methylstyrene and vinyltoluene; (meth) acrylic acid, crotonic acid, Unsaturated carboxylic acids such as acid, itaconic acid, fumaric acid and maleic acid; monoalkyl esters of unsaturated dicarboxylic acids such as monoethyl itaconate, monobutyl fumarate and monobutyl maleate; (meth) acrylic acid Hydroxyl-containing vinyl monomers such as 2-hydroxyethyl, 2-hydroxypropyl (meth) acrylate, polyethylene glycol mono (meth) acrylate, and polypropylene glycol mono (meth) acrylate; (meth) acrylonitrile, vinyl acetate, (meth) Acrylamide, N-methylol acrylamide, methacryl Glycidyl, vinyl acetate, vinyl chloride, vinylidene chloride and the like. Two or more of these copolymerizable monomers can be used.

The use ratio of the above “copolymerizable monomer” is as follows:
The content is preferably 30% by weight or less based on the total weight of the radically polymerizable monomers used for producing the component (B).
When the use ratio exceeds 30% by weight, the adhesive performance of the adhesive layer after heating the heat-sensitive adhesive sheet or tape tends to be insufficient.

(2-2) Production method: As an example of a method for obtaining the above-mentioned component (B), there can be mentioned a usual emulsion polymerization method using a conventionally known surfactant as an emulsifier. Examples of the surfactant used herein include anionic surfactants such as higher alcohol sulfate sodium salt, alkylbenzene sulfone sodium salt, dialkyl succinate sodium sulfonate, and alkyl diphenyl ether disulfone sodium acid; polyoxyethylene alkyl allyl; Nonionic surfactants such as ethers and polyoxyethylene polyoxypropylene block copolymers are exemplified. Further, radically polymerizable anionic surfactants such as sodium allylalkyl sulfonate, alkyl allyl sulfosuccinate, and polyoxyethylene alkyl allyl glycerin ether sulfate may be used.

Another method for obtaining the component (B) is a method in which a radical polymerizable monomer used for producing the component (B) is emulsion-polymerized in the presence of the component (A). In this emulsion polymerization method, since the component (A) functions as a surfactant (polymer emulsifier), the amount of an emulsifier such as a protective colloid or another surfactant used in the emulsion polymerization is set to be smaller than that in a normal emulsion polymerization. Can also be made in small quantities. Further, if desired, no other emulsifier can be used. As a result, component (B) is obtained by ordinary emulsion polymerization.
The water resistance of the pressure-sensitive adhesive layer of the heat-sensitive pressure-sensitive adhesive sheet or tape can be improved as compared with the case where is manufactured.

Further, according to the emulsion polymerization method described above, the non-adhesive component (A) easily forms a protective colloid around the tacky component (B). There is an advantage that the blocking resistance is improved. Further, there is an advantage that the heat-sensitive adhesive composition has excellent storage stability. That is, when the component (A) and the component (B) are blended, the storage stability of the mixed solution may be impaired depending on the blending, and if the mixture is remarkable, the mixed solution may gel and become uncoated. However, such a problem is prevented.

Further, when the radical polymerizable monomer used for producing the component (B) is emulsion-polymerized in the presence of the component (A), an emulsion containing both the component (A) and the component (B) is obtained. can get. Therefore, in this case, there is an advantage that the operation of separately adding the component (A) can be omitted. Of course, the component (A) can be further added to the emulsion thus obtained.

As the polymerization initiator that can be used for the emulsion polymerization for obtaining the component (B), any polymerization initiator generally used for the emulsion polymerization can be used.
Examples of the radical polymerization initiator for obtaining the same include the same organic peroxides, inorganic peroxides, and azo compounds as described above. The amount of the polymerization initiator used is
It is usually 0.05 to 5% by weight, preferably 0.1 to 2% by weight, based on the total amount of the monomers.

(2-3) Acid value: The acid value of the above component (B) is preferably 30 mg KOH / g or less,
More preferably, it is 5 mgKOH / g or less. When the acid value of the component (B) exceeds 30 mgKOH / g, the water resistance of the pressure-sensitive adhesive layer of the heat-sensitive pressure-sensitive adhesive sheet or tape may be insufficient. In addition, the acid value of component (B)
The acid value is preferably 10 mgKOH / g or lower, more preferably 20 mgKOH / g or lower. The difference between the acid value of component (A) and the acid value of component (B) is 10
If it is less than mgKOH / g, the components (A) and (B) may be mixed in the pressure-sensitive adhesive layer before heating, and the blocking resistance at room temperature may be poor.

(2-4) Glass transition temperature (Tg): The Tg of the above-mentioned component (B) must be -20 ° C. or lower, preferably -40 ° C. or lower. When the Tg of the component (B) exceeds -20 ° C, it is not possible to obtain sufficient adhesive performance in the adhesive layer after heating the heat-sensitive adhesive sheet or tape.

(3) Component (C): The component (C) in the present invention is a tackifier having a softening point of 80 to 180 ° C., which not only improves the adhesive strength of the adhesive but also heat-sensitive adhesive. It is an essential component for improving the blocking resistance of a sheet or tape at room temperature.

(3-1) Composition: Component (C) includes terpene resin, aliphatic petroleum resin, aromatic petroleum resin, cumarone-indene resin, styrene resin, phenol resin, terpene-pheno resin. Resin, rosin derivative (rosin, polymerized rosin, hydrogenated rosin and their glycerin,
Ester with pentaerythritol, resin acid dimer
And the like, and a tackifier having a high softening point is preferable for improving the blocking resistance at room temperature.

(3-2) Softening point: The softening point of the component (C) must be 80 to 180 ° C. 180 ° C softening point
If the temperature is higher, the heating temperature for developing the adhesive property at the time of sticking the heat-sensitive adhesive sheet or tape becomes too high, so that problems such as thermal deformation of the base material and coloring occur, and the compatibility with the resin is poor. In some cases, sufficient adhesive strength cannot be obtained. Further, when the softening point is less than 80 ° C., since tackiness is developed at room temperature, a release paper or a release agent is required,
There are also problems such as a low cohesive force after heating and pasting. The softening point of component (C) is preferably from 100C to 160C.

The commercial products of the above tackifiers include “YS
Polyester T-120 "," T-130 "," T-1 "
Terpene phenolic resin such as "45" (all manufactured by Yashara Chemical Co., Ltd.), "S-Crystal A-100", "A
-120 "(manufactured by Nippon Steel Chemical Co., Ltd.) and the like; xylene resins such as" Nicanol HP-100 "(manufactured by Mitsubishi Gas Chemical Co., Ltd.);
J "," Dimalex "(Rika Hercules Co., Ltd.)
"Pencel C", "Pencel D-125", "D
-135 "(manufactured by Arakawa Chemical Industry Co., Ltd.)," Superester A-100 "," A-1 "
15 "," A-125 "(Arakawa Chemical Industry Co., Ltd.)
Rosin esters such as “Tamanol 135” and “145”
(Arakawa Chemical Industries, Ltd.) and the like. These may be neutralized with an alkali or added with an emulsifier to be used as an emulsion. Alternatively, a tackifier that has already been emulsified may be used. As such a tackifier,
“Superester E-720”, “E-730-5”
5 "," E-625 "," E-650 "," Tamanor E
-100 "(Arakawa Chemical Industries, Ltd.)," D-188 "
(Manufactured by Rika Hercules Co., Ltd.), "SK-130D"
(Manufactured by Harima Chemicals, Inc.). These are 2
It is also possible to use a combination of more than one species.

(4) Regarding the heat-sensitive adhesive composition: The heat-sensitive adhesive composition of the present invention comprises the components (A), (B),
An aqueous emulsion containing (C).

(4-1) Weight ratio of component (A) to component (B): The weight ratio of component (A) / component (B) is 15/85.
~ 50/50, 20/80 ~ 40/6
It is preferably 0. When the component (A) is less than 15% by weight, the pressure-sensitive adhesive layer of the heat-sensitive adhesive sheet or tape before heat treatment may unnecessarily exhibit adhesive strength. On the other hand, when the component (A) exceeds 50% by weight, the water resistance of the pressure-sensitive adhesive layer decreases, and the adhesive strength tends to be insufficient. When the weight ratio of the component (A) is too high, the viscosity of the resin emulsion becomes too high at the time of emulsion polymerization of the component (B) using the component (A) as a polymer emulsifier, resulting in excellent coating suitability. In some cases, a heat-sensitive adhesive composition cannot be obtained.

(4-2) Weight ratio of component (C): The weight ratio of component (C) is 2 to 50 parts by weight based on 100 parts by weight of the total amount of component (A) and component (B). And preferably 5 to 30 parts by weight. Component (C)
Is less than 2% by weight, the heat-sensitive adhesive sheet or tape may unnecessarily exhibit adhesive strength in the pressure-sensitive adhesive layer before the heat treatment, and may not provide sufficient adhesive strength even after heating. . On the other hand, when the component (C) is more than 50% by weight, the water resistance of the pressure-sensitive adhesive layer is reduced, and the holding force is apt to be insufficient. Further, the adhesive force is not further improved, which is economically disadvantageous.

(4-3) Other Ingredients: The heat-sensitive adhesive composition of the present invention, depending on its use, is commonly used as a general adhesive in an antifoaming agent, a surfactant, and a fungicide. , Fragrance,
Neutralizer, thickener, leveling regulator, antifreezing agent, foaming agent, antioxidant, ultraviolet absorber, reinforcing agent, filler, pigment, fluorescent brightener, antistatic agent, antiblocking agent, flame retardant , Crosslinking agents, plasticizers, lubricants, organic solvents, colorants, etc.
Species or two or more species may be contained.

(4-4) Aqueous dispersion properties: The solid concentration of the heat-sensitive adhesive composition of the present invention is preferably 30 to 70% by weight, more preferably 40 to 60% by weight. When the solid content is less than 30% by weight, the drying step takes too much time. When it exceeds 70% by weight, the production becomes difficult and the viscosity of the composition becomes too high, resulting in poor coatability.

(5) Heat-sensitive adhesive sheet or label: The heat-sensitive adhesive sheet or label of the present invention is obtained by forming a pressure-sensitive adhesive layer formed from the heat-sensitive adhesive composition of the present invention on the surface of a substrate. Before the heat treatment, the adhesive strength is extremely low. Therefore, in this state, the product can be handled as it is as a product without performing a release treatment on the pressure-sensitive adhesive layer such as a release paper or a release treatment on the back surface of the substrate. Such a heat-sensitive adhesive sheet or label develops an adhesive force only by performing a heat treatment at a certain temperature or higher.

(5-1) Substrate: The type of the substrate is not particularly limited as long as it is a material that can withstand the heat treatment temperature of the heat-sensitive adhesive sheet or label. Good. For example, films, sheets made of cloth, paper, leather, wood, metal, glass, various plastics, etc.
Plates, foamed plastic sheets and the like can be mentioned. The thickness of the substrate is usually 10 μm to 1 mm, preferably 30 μm
１００100 μm. Examples of the plastic include polyester, polyamide, vinyl chloride-based polymer, polyethylene, polypropylene, and polyurethane. Further, the shape of the base material may be any of a long body, a base material cut into a predetermined size (for example, a base material cut in advance into a square, a circle, an ellipse, or another shape) and the like.

(5-2) Adhesive layer: The thickness of the adhesive layer is
It can be adjusted appropriately according to the application, etc.
３００300 μm, preferably 10-100 μm. With such a thickness, it is possible to make the adhesive layer exhibit good adhesiveness after the heat treatment. If the thickness of the pressure-sensitive adhesive layer is too small, good adhesive strength cannot be obtained. If the thickness is too large, it takes time to dry the pressure-sensitive adhesive and is disadvantageous in terms of cost.

(5-3) Production method: The heat-sensitive adhesive sheet or label of the present invention is dried by an appropriate method after applying the heat-sensitive adhesive composition of the present invention to one or both surfaces of a substrate. It can be manufactured by a method. The above-mentioned coating method is not particularly limited, and for example, any method such as roll coater coating, bar coater coating, knife coater coating, spray coating, casting coating, doctor blade coating, brush coating, etc. can be adopted. . The above-mentioned drying must be performed at a temperature lower than a temperature at which the pressure-sensitive adhesive layer of the finally obtained heat-sensitive pressure-sensitive adhesive sheet or label does not exhibit tackiness at room temperature. The specific drying temperature is generally Tg of component (A) + 20 ° C. or lower, preferably Tg of component (A) or lower, more preferably Tg of component (A).
-20 ° C or less.

(5-4) Method of use: The heat-sensitive adhesive sheet or label of the present invention does not exhibit adhesiveness at room temperature or has extremely low adhesive strength at room temperature. Without subjecting the pressure-sensitive adhesive layer to a release treatment, it can be stored, distributed, and sold simply as it is or without packaging, just like a product having no ordinary adhesiveness. At this time, the expression “not subjected to a release treatment” in the present invention means that the pressure-sensitive adhesive layer is not covered with a release paper. Of course, if necessary, for example, in the case where a very small adhesive force becomes a problem, a sheet may be subjected to a peeling treatment depending on its use.

In sticking the heat-sensitive adhesive sheet or label of the present invention to an adherend, the adhesive layer and / or the adherend side is heated. The heating temperature is determined by the Tg of component (A).
Usually, a temperature higher than its Tg, preferably 20 ° C. or more, is suitable. If the heating temperature is too high, there is a possibility that the workability of attaching the pressure-sensitive adhesive sheet or the like and the thermal efficiency may be reduced, or the base material may be altered or deformed.
For this reason, the heating temperature is usually 60 to 180 ° C, preferably 80 to 140 ° C.

The pressure-sensitive adhesive sheet or the like once adhered to the adherend does not come off spontaneously when the temperature returns to the normal temperature, and is favorably adhered to the adherend without losing its adhesiveness. are doing. Then, when it is desired to peel the pressure-sensitive adhesive sheet or the like from the adherend, it can be easily peeled from the adherend by pulling with a hand or the like, similarly to a general-purpose pressure-sensitive adhesive sheet. Can maintain the adhesiveness, so that it can be adhered again to the same adherend or another adherend.

[0066]

The present invention will be described more specifically with reference to the following examples and comparative examples. In the following examples, “parts” and “%” indicate “parts by weight” and “% by weight”, respectively, unless otherwise specified. The abbreviations used below and their contents are shown in Table 2 below. Furthermore, the Tg value of the homopolymer of each monomer used for calculating the Tg of the polymer in this specification is also shown. The molecular weight of the polymer in the examples is a molecular weight in terms of polystyrene measured by GPC.

[0067]

[Table 2]

[1] Preparation of pressure-sensitive adhesive composition: <Production of component A> (a) Production of component A by emulsion polymerization; Production Example A-1 shown below
To A-5 are components (A-) corresponding to component (A) of the present invention.
This is an example in which 1) to (A-5) are synthesized by an emulsion polymerization method.

(Production Example A-1) MMA7 as a monomer
5 parts, 12.5 parts of ST and 12.5 parts of MAA were mixed with 6 parts of butyl thioglycolate as a chain transfer agent to obtain a monomer mixture. To 100 parts of this monomer mixture, 1 part of sodium lauryl sulfate as a polymerization emulsifier and 50 parts of deionized water were added and emulsified by stirring to prepare a monomer emulsion.

A flask equipped with a stirrer, a condenser, a thermometer and a nitrogen inlet tube was charged with 30 parts of deionized water, 1 part of sodium lauryl sulfate, and 1 part of APS. Was dropped over 2 hours. After maintaining the same temperature for 2 hours after the completion of the dropwise addition, the reaction system was cooled to terminate the polymerization, thereby obtaining an aqueous polymer emulsion having a solid content of 50%. This corresponds to the polymer (A) corresponding to the component (A) described above.
This is an emulsion comprising 1). The acid value of the polymer (A1) was 81 mgKOH / g. As for the molecular weight, the weight average molecular weight was 5,800. By gradually adding 25% aqueous ammonia while stirring the emulsion, carboxyl groups in the polymer (A1) were neutralized to obtain an aqueous solution of the polymer (A1). The polymer (solid content) (A1) content of this aqueous solution was 25%.

(Production Examples A-2 to A-5) Except that the monomer composition, the type and amount of the emulsifier for polymerization, and the amount of the chain transfer agent were as shown in Tables 3 and 4, the above-mentioned Production Examples Components (A-2) to (A-5) were synthesized in the same manner as in A-1.

(B) Production of component (A) by solution polymerization:
The following Production Example A-6 is an example in which a component (A-6) corresponding to the component (A) of the present invention was synthesized by a solution polymerization method.

(Production Example A-6) MMA9 as a monomer
0 parts and 10 parts of AA, 3 parts of lauryl mercaptan as a chain transfer agent, 150 parts of methyl ethyl ketone as an organic solvent, and AIB as a polymerization initiator
N was dissolved in 2 parts, charged into a flask equipped with a stirrer, a condenser, a thermometer and a nitrogen inlet tube, and heated at 80 ° C. for 4 hours in a nitrogen atmosphere to carry out polymerization. Thereafter, 0.5 parts of AIBN is further charged and heated to the same temperature for 2 hours.
A methyl ethyl ketone solution of the copolymer having a solid content of 40% was obtained. The acid value of the above copolymer (A6) is 78 mg KO
H / g and weight average molecular weight were 12,000. By gradually adding 28% aqueous ammonia and water to 250 parts of a methyl ethyl ketone solution of the obtained copolymer under stirring, the carboxyl groups of the copolymer are neutralized, and the pH of the reaction solution is adjusted to 7 to 8. did. Thereafter, methyl ethyl ketone was removed under reduced pressure at a temperature of 50 ° C. to obtain an aqueous solution of the component (A6) in which a carboxyl group was neutralized. The solid content of this aqueous solution was 25%.

[0074]

[Table 3]

[0075]

[Table 4]

<Production of Component (B)> (a) Component (B) by emulsion polymerization in the presence of component (A)
Production of the component (A) and the component (B) by subjecting the radical polymerizable monomer used for the production of the component (B) to emulsion polymerization in the presence of the component (A) obtained by the above synthesis example. An aqueous polymer emulsion containing was synthesized.

(Production Example B-1) 90 parts of 2EHA, MMA
Eight parts, 1 part of MAA and 1 part of HEMA were mixed to obtain a monomer mixture. A flask equipped with a stirrer, a condenser, a thermometer and a nitrogen inlet tube was charged with 70 parts of deionized water and 100 parts of an aqueous solution of the component (A1) obtained in Synthesis Example 1 (20 parts as a solid content). After the temperature was raised to 70 ° C., 5 parts of a 10% aqueous solution of t-butyl hydroperoxide, formaldehyde sodium sulfoxylate dihydrate (trade name “Rongalit C” manufactured by Iron and Steel Chemical Co., Ltd .; hereinafter simply referred to as “Rongalit”) 10)
5 parts of the aqueous solution and 80 parts of the above monomer mixture were added dropwise over 3 hours. After maintaining the same temperature for another 2 hours from the end of the dropwise addition, the reaction system was cooled to terminate the polymerization, neutralized with ammonia water to pH 7 to 8, and an aqueous polymer emulsion having a solid content of 50% was obtained. Was.

(Production Examples B-2 to B-7) Production Example B
-1, an aqueous polymer emulsion was prepared in the same manner as in Production Example B-1 except that the component (A) shown in Tables 5 and 6 below was used instead of the component (A-1) used. Obtained.

(B) Production of component (B) by emulsion polymerization:
After the component (B) was obtained by emulsion polymerization as described below, this was blended with the component (A) to prepare an aqueous polymer emulsion containing the component (A) and the component (B).

(Production Example B-8) MMA8 as a monomer
Parts, 2EHA 88 parts, AN 2 parts and AA 2 parts were mixed to obtain a monomer mixture. In 100 parts of this monomer mixture,
One part of sodium lauryl sulfate as a polymerization emulsifier and 50 parts of deionized water were added, and the mixture was emulsified by stirring to prepare a monomer emulsion. 50 parts of deionized water, 1 part of sodium lauryl sulfate, and 0.5 part of APS were charged into a flask equipped with a stirrer, a condenser, a thermometer, and a nitrogen inlet tube. The body emulsion was added dropwise over 3 hours. After maintaining the same temperature for 2 hours after the completion of the dropwise addition, the reaction system was cooled to terminate the polymerization, thereby obtaining an aqueous polymer emulsion having a solid content of 50%. The polymer was neutralized to pH 8 by gradually adding 25% aqueous ammonia while stirring the emulsion.

[0081]

[Table 5]

[0082]

[Table 6]

<Blending of Component (C)> (Examples 1 to 9 and Comparative Examples 1 to 7) The components (C) were added to the components (A) and (B) obtained by the above production examples, as shown in the following table. An aqueous emulsion-type pressure-sensitive adhesive composition was prepared by blending at a solid content ratio of 10 to 13 shown in Table 13. Among them, Examples 8 and 9 are pressure-sensitive adhesive compositions prepared by blending the components (A) and (B).

[2] Evaluation of pressure-sensitive adhesive composition: The pressure-sensitive adhesive layer or pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive compositions obtained in Examples 1 to 9 and Comparative Examples 1 to 7 was subjected to the following (1) The measurement or evaluation of (3) was performed. The results are shown in Tables 10 to 13 below. In these tables, the symbols “E-650” and “E-7” of “type of component (C)”
"30-55" and "E-710" all indicate products (polymerized rosin emulsion) manufactured by Arakawa Chemical Co., Ltd.

(1) Adhesive strength of adhesive sheet before heating: thickness 5
Using a 0 μm polyester film as a base material, a 50 μm applicator is used to coat the pressure-sensitive adhesive composition on the corona-treated surface so that the thickness of the coating film after drying is about 25 μm. It dried and the adhesive sheet was created. A test piece obtained by cutting this adhesive sheet to a width of 25 mm (hereinafter referred to as a “test piece before heat treatment”) is JIS.
The adhesive strength was measured according to the 180 ° peeling method specified in Z0237. That is, a temperature of 23 ° C. and a humidity of 65
%, The test piece was attached to a polished stainless steel plate serving as a test plate, and a 2 kg rubber roller was pressed back and forth once. 30 minutes after crimping, 300mm / mi
At a pulling speed of n, the 180 ° peel adhesion to the test plate was measured. The measurement results were shown in four stages described in Table 7 below.

[0086]

×: 100 g / 25 mm or more △: 10 g / 25 mm or more and less than 100 g / 25 mm ○: More than 3 g / 25 mm and less than 10 g / 25 mm ：: 3 g / 25 mm or less

(2) Adhesive force after heating of pressure-sensitive adhesive sheet: The test piece before heat treatment was heated at 120 ° C. for 2 minutes and 140 minutes.
After heating for 2 minutes at a temperature of 23 ° C and a humidity of 65 ° C
% Of the test piece (hereinafter, referred to as "heat-treated test piece") which was left for 24 hours in an atmosphere of 30%, and peeled 180 ° under the same conditions as above for 30 minutes after the pressure bonding. The measurement results are shown in four stages described in Table 8 below.

[0088]

８: 500 g / 25 mm or more ○: 300 g / 25 mm or more and less than 500 g / 25 mm Δ: More than 100 g / 25 mm and less than 300 g / 25 mm ×: 100 g / 25 mm or less

(3) Holding force: The area of the part to which the test piece heated at 140 ° C. for 2 minutes was applied was 25 mm × 25 mm
Then, the stainless steel plate was fixed vertically in an atmosphere of 60 ° C., a load of 1 kg was applied to the test piece, and the time until the test piece fell was measured. The measurement results are shown in four stages described in Table 9 below.

[0090]

表: 3600 sec or more ○: 1800 sec or more and less than 3600 sec △: More than 300 sec and less than 1800 sec ×: 300 sec or less

[0091]

[Table 10]

[0092]

[Table 11]

[0093]

[Table 12]

[0094]

[Table 13]

[0095]

According to the present invention, by using a tackifier having a specific softening point, non-adhesiveness and excellent blocking resistance at normal temperature and more excellent adhesive strength and holding power after heating can be obtained. Thus, a heat-sensitive adhesive composition having balanced adhesive properties can be obtained. Further, according to the present invention, there is provided a heat-sensitive adhesive sheet or label which is substantially non-adhesive before heating and can exhibit excellent adhesive strength after heating.

 ──────────────────────────────────────────────────の Continuing from the front page (72) Inventor Kiichi Ito 1 Tohocho, Yokkaichi-shi, Mie Mitsubishi Chemical Co., Ltd. Within Industrial Co., Ltd. (72) Inventor Hideo Ota 1-13, Sumika Tsuda, Hirakata-shi, Osaka Central Rika Kogyo Co., Ltd.F-term (reference) 4J004 AA10 CA02 CA04 CA05 CA06 CA08 CB01 CB02 CB04 CC01 CC02 CC08 DB01 FA01 GA01 4J040 CA031 DA051 DB041 DB042 DB081 DB082 DE011 DE021 DE022 DE031 DF041 DF042 DF051 DF052 DF081 DF082 DL121 DL122 GA07 GA25 JA03 JA09 JB09 JB11 KA26 KA38 LA01 LA02 LA06 LA08 LA11 MA11 PA18

Claims (4)

[Claims] 1. A polymer (A) having an acid value of 30 to 300 mg KOH / g and a glass transition temperature (Tg) of 30 ° C. or higher, a polymer (B) having a Tg of −20 ° C. or lower, and a softening point of 80 to An aqueous emulsion containing a tackifier (C) at 180 ° C., wherein the weight ratio of each component satisfies the following formulas (1) and (2): . (A) / (B) = 15/85 to 50/50 (1) {(A) + (B)} / (C) = 100/2 to 50 (2) ) 2. A radically polymerizable monomer (a1) whose component (A) requires a carboxyl group or a sulfonic acid group.
0% by weight and a hydrophobic radical polymerizable monomer (a2) 96
The heat-sensitive adhesive composition according to claim 1, which is a copolymer obtained by subjecting 50 to 50% by weight to emulsion polymerization in the presence of a surfactant and then neutralizing with a base. 3. The heat-sensitive adhesive composition according to claim 1, wherein the component (B) is a polymer obtained by emulsion polymerization of the component (A) as a polymer emulsifier. 4. A heat-sensitive adhesive sheet or label comprising a pressure-sensitive adhesive layer comprising the heat-sensitive adhesive composition according to claim 1 as a main component on a surface of a substrate. .