JPH11217556A - Heat-sensitive tacky agent composition and heat-sensitive tacky sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain both a heat-sensitive tacky agent composition having excellent blocking resistance in a preservation state and coating performances, capable of forming a tacky agent layer for developing sufficient adhesion performances by heat treatment and a heat sensitive tacky sheet using the composition. SOLUTION: This heat-sensitive tacky agent composition comprises a component A which is a water-soluble resin neutralized with a base and has >=1 meq acid value, a component B being an aqueous emulsion which is obtained by emulsion polymerization of a radically polymerizable monomer and contains a polymer having <=-20 deg.C glass transition temperature and a thickening agent (acrylic acid-based thickening agent or the like) and has 200-30,000 cPs (12 rpm) viscosity at 25 deg.C. A tacky layer formed from the composition has <=5 g/25 mm tackiness after preservation for one hour under conditions at 40 deg.C under 10 kg/cm<2> pressure. The tacky agent layer reverses its sea and islands by heat treatment to extremely enlarge tackiness.

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, and more particularly to a heat-sensitive adhesive composition which has excellent blocking resistance in a storage state and is non-adhesive or extremely tacky in an initial state. A heat-sensitive adhesive composition which forms a pressure-sensitive adhesive layer having a low property, while exhibiting an adhesive property by heat treatment and exhibiting excellent coating properties, and a heat-sensitive adhesive having the useful pressure-sensitive adhesive layer on a substrate Regarding the sheet.

[0002]

2. Description of the Related Art Generally, pressure-sensitive adhesive sheets are stored, distributed, sold, and the like, with a pressure-sensitive adhesive surface coated with release paper (release paper). 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 becomes unnecessary 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 the backing of the pressure-sensitive adhesive tape is not subjected to a release treatment, the manufacturing process of the pressure-sensitive adhesive tape substrate can be simplified, and the cost can be reduced.

Japanese Patent Application Laid-Open No. 8-269420 is known as an adhesive sheet which does not require release paper. In the same publication, (A) a resin having a glass transition point of 20 ° C. or more comprising an unsaturated monomer having a carboxyl group and other monomers,
(B) An acrylic water-based emulsion in which a resin having a glass transition point of −30 ° C. or lower is mixed at a specific ratio is disclosed.
However, the problem that blocking occurs when sheets coated with the heat-sensitive adhesive composition are stacked or stored in a rolled state under pressure has not been addressed yet. Further, it has not been known until now what kind of structural change the adhesive layer formed from this heat-sensitive adhesive composition undergoes by heat treatment to exhibit adhesiveness. For this reason, it was also difficult to design the heat-sensitive adhesive composition by predicting the properties of the pressure-sensitive adhesive layer after the heat treatment, for example, adhesive strength, water resistance, alkali releasability, and the like. Further, at the same time, the appearance of a heat-sensitive adhesive composition having excellent coatability is also desired.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide an adhesive which exhibits excellent blocking resistance and coating properties in a storage state, and which exhibits sufficient adhesiveness when the adhesive is developed by heat treatment. An object of the present invention is to provide a heat-sensitive adhesive composition capable of forming an agent layer and a method for producing the same. Another object of the present invention is to provide a heat-sensitive adhesive sheet having a useful pressure-sensitive adhesive layer formed from the above-mentioned pressure-sensitive adhesive composition on a useful pressure-sensitive adhesive layer and usable without further performing a release treatment. .

[0005]

Means for Solving the Problems The present inventors have found that the addition of a thickening agent makes it possible to obtain a composition having excellent coating properties and anti-blocking properties. Has a sea-island structure in which component A is a sea (continuous layer) and component B is an island (discontinuous layer). The heat treatment reverses the sea and the island, so that component A is an island and component B is a sea. The inventors have found that a pressure-sensitive adhesive layer that changes to a sea-island structure is formed, and completed the present invention.

The heat-sensitive adhesive composition of the first invention comprises a glass obtained by emulsion polymerization of a component A which is a water-soluble resin neutralized with a base and having an acid value of 1 meq or more and a radical polymerizable monomer. A heat-sensitive adhesive composition comprising a component B which is an aqueous emulsion containing a polymer having a transition temperature of −20 ° C. or less and a thickener, and having a Brookfield viscosity at 25 ° C. of 200 CPS to 30000 CPS (12 rpm)
m).

The heat-sensitive adhesive composition of the second invention further comprises:
Temperature of the pressure-sensitive adhesive layer formed from the present heat-sensitive adhesive composition,
After storage at 0 ° C. under a pressure of 10 kg / cm 2 for 1 hour, the adhesive strength (representing “blocking resistance”) is 5 g /.
It is assumed to be 25 mm or less. Furthermore, as shown in the third invention, the adhesive strength of the pressure-sensitive adhesive layer at a temperature of 25 ° C. according to JIS Z 0237 at a temperature of 25 ° C. is 10 g / 25 mm or less, and by a heat treatment at 60 ° C. or more, The sea and islands of the pressure-sensitive adhesive layer are reversed to form a sea-island structure in which component A is an island and component B is a sea, so that the pressure-sensitive adhesive layer has an adhesive force of 100 g / 25 m.
m or more.

[0008] The thickener is preferably an acrylic acid-based thickener, as shown in the fourth invention. Further, as shown in the fifth invention, the component A is a polymer emulsifier and is used for the emulsion polymerization of the component B, and the polymer as the component B is prepared in the presence of the component A. It can be obtained by emulsion polymerization of a radical polymerizable monomer.

The heat-sensitive adhesive sheet according to the sixth invention is characterized in that
A pressure-sensitive adhesive layer formed from the heat-sensitive pressure-sensitive adhesive composition according to any one of the fifth to fifth inventions on a substrate, and the pressure-sensitive adhesive after storage for 1 hour at a temperature of 40 ° C. and a pressure of 10 kg / cm 2. The adhesive strength of the agent layer is 5 g / 25 mm or less. The heat-sensitive adhesive sheet of the seventh invention further comprises a JIS
The adhesive strength of the pressure-sensitive adhesive layer at a temperature of 25 ° C. by a 180 ° peeling method specified in Z 0237 is 10 g / 25.
mm or less, and by the heat treatment at 60 ° C. or more, the sea and the island of the pressure-sensitive adhesive layer are reversed, and the component A is an island and the component B
Has a sea-island structure in which is a sea, whereby the adhesive strength of the adhesive layer is changed to 100 g / 25 mm or more.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below 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”. (I) About the heat-sensitive adhesive composition of the present invention First, the heat-sensitive adhesive composition of the present invention will be described. In the present specification, the "glass transition temperature" of a polymer (hereinafter referred to as "T
g ". ) Means a value obtained from the following 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.).

[0011]

1 / Tg = ｛W (a) / Tg (a)｝ + ｛W (b) / Tg (b)｝ + ｛W (c) / Tg (c)｝ + ... In the above formula: Tg = Tg (K) of polymer W (a) = weight fraction of structural unit consisting of monomer (a) in polymer W (b) = monomer (b) in polymer W (c) = weight fraction of structural unit consisting of monomer (c) in polymer Tg (a) = glass transition temperature of homopolymer of monomer (a) K) Tg (b) = glass transition temperature of homopolymer of monomer (b) (K) Tg (c) = glass transition temperature of homopolymer of monomer (c) (K) The “sea-island structure” described is a well-known concept. For example, the “sea-island structure” on page 31 of the “New Edition Polymer Dictionary (edited by the Society of Polymer Science, Editing Committee of Polymer Dictionary, published by Asakura Shoten)” It is described in detail. In this specification, “having a sea-island structure” is not limited to a structure in which the sea (continuous layer) is completely continuous and all of the islands (discontinuous layers) are independently dispersed in the sea. The meaning includes a state in which the island is partially interrupted and a state in which a part of the island is fused with each other.

(1) Component A Component A in the present invention is a water-soluble resin and has an acid value of 1
A resin in which meq / g or more is neutralized with a base. (1-1) Acid Value First, in this specification, the “acid value” refers to an acid value per solid content of a resin or a polymer, and refers to a theoretical acid value calculated by an ordinary method. When the polymer or resin is neutralized with a base, it indicates the acid value before neutralization. “Meq / g” used as a unit of the acid value represents a milligram equivalent number of an acid in 1 g of a solid content of a resin or a polymer.

The acid value of the component A must be 1 meq / g or more, preferably 1 to 5 meq / g, more preferably 1.2 to 4 meq / g. No. When the acid value is less than 1 meq / g, the solubility of the component A in water is insufficient, so that the liquid stability of the pressure-sensitive adhesive composition containing the component A becomes insufficient or the presence of the component A When the emulsion polymerization of the component B is performed below, the polymerization becomes unstable. When the component A is used for an alkali-peelable pressure-sensitive adhesive composition, if the acid value is less than 1 meq / g, the alkali solubility or swellability of the component A is insufficient, so that the component A is formed from the composition. A sufficient alkali release property cannot be imparted to the pressure-sensitive adhesive layer. On the other hand, when the acid value of component A exceeds 5 meq / g, the water resistance of the pressure-sensitive adhesive layer may be insufficient.

(1-2) Composition The component A having the acid value includes a radical polymerizable monomer unit having a carboxyl group or a sulfonic acid group having the acid value and another radical polymerizable monomer unit. And rosin derivatives. As the rosin derivative, a resin obtained by modifying rosin or hydrogenated rosin with an organic acid, specifically, a dibasic anhydride such as maleic anhydride or phthalic anhydride (hereinafter referred to as “organic acid-modified rosin”). And a neutralized product with a base can be used. Specific examples of the organic acid-modified rosin include “Harimac T-80” (trade name, manufactured by Harima Kasei Co., Ltd.) and “Pentaline 255” (trade name, manufactured by Rika Hercules Co., Ltd.) and “26.
1 "; trade name" Marquid NO3 "manufactured by Arakawa Chemical Co., Ltd.
1 "," NO32 "," NO33 "and" KE-6 "
04 "; and the like.

In the present invention, α,
A copolymer having a β-ethylenically unsaturated carboxylic acid unit and a hydrophobic radically polymerizable monomer unit as main constituent units is preferably used, and among the above copolymers, those having a glass transition temperature of 20 ° C or higher are preferred. More preferably used. The above α,
Examples of the β-ethylenically unsaturated carboxylic acid include acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, maleic anhydride and the like. Alternatively, two or more kinds can be used. The amount of the α, β-ethylenically unsaturated carboxylic acid that gives the acid value varies depending on the kind of the unsaturated carboxylic acid used, but is usually based on the total weight of all the monomers used for the synthesis of the component A. 3-40% by weight
It is preferred that it is about.

The radical polymerizable monomer used together with the above α, β-ethylenically unsaturated carboxylic acid includes water 100
Hydrophobic radically polymerizable monomers having a solubility in g of 2 g or less are preferable, for example, methyl methacrylate,
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,
Alkyl (meth) acrylates such as n-octyl (meth) acrylate, isooctyl (meth) acrylate, n-nonyl (meth) acrylate and isononyl (meth) acrylate; styrene, α-methylstyrene, vinyltoluene, etc. And the like. The amount of these monomers to be used is preferably 30 to 80% by weight based on the total amount of all the monomers used for the synthesis of the component A.

In order to synthesize the component A, the above α,
A hydrophilic radically polymerizable monomer other than β-ethylenically unsaturated carboxylic acid may be used if necessary. Examples of such a hydrophilic radical polymerizable monomer include methyl acrylate, vinyl acetate, acrylonitrile, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and polyethylene glycol mono (meth) acrylate. ) Acrylate, polypropylene glycol mono (meth) acrylate, (meth) acrylamide, N-methylolacrylamide, glycidyl methacrylate, styrenesulfonic acid and its sodium salt, and 2-acrylamide-2-methylpropanesulfonic acid and its sodium salt Is mentioned.

The component A may be a base neutralized product of a graft copolymer. As the graft copolymer, a graft copolymer having a hydrophilic main chain and a hydrophobic side chain, or a graft copolymer having a hydrophobic main chain and a hydrophilic side chain is preferably used. In this case, since the affinity between the hydrophobic part of the component A and the component B is high, the liquid stability of the composition is excellent, and the hydrophilic part of the component A in the pressure-sensitive adhesive layer has a hydrophobic portion inside the island after heating. Since the adhesive portion is oriented to the outside of the island, the water resistance of the pressure-sensitive adhesive layer is improved. Component A
Has a high affinity between the hydrophobic portion of component (A) and the component B, so that the liquid stability of the pressure-sensitive adhesive composition is improved.

Furthermore, the T of the hydrophilic portion of the graft copolymer
g is preferably higher than the hydrophobic portion of the graft copolymer. In this case, in the pressure-sensitive adhesive layer before heating, a hydrophobic portion having a low Tg is oriented inside the island composed of the component B, and a hydrophilic portion having a high Tg is oriented outside the island. Even if it is low, the pressure-sensitive adhesive layer before heating can be made non-tacky. Thereby, it is possible to prevent the development of adhesiveness before heating and to develop the adhesiveness by a heat treatment at a lower temperature than before in use.

Component A is obtained by neutralizing some or all of the acidic groups, such as carboxyl groups and sulfonic acid groups, of component A synthesized as described above with a base. Examples of the base used for neutralization include 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; Can be used. Among them, it is preferable to use a base having a boiling point of 110 ° C. or lower, such as ammonia, methylamine, ethylamine, propylamine, and isopropylamine, and it is particularly preferable to use ammonia. In this case, since the base is easily removed from the pressure-sensitive adhesive layer in the drying step after coating, a pressure-sensitive adhesive layer having excellent water resistance can be obtained.

The component A in the present invention may not necessarily be completely neutralized, but must be neutralized to the extent that the component A becomes water-soluble. Specifically, it is preferable that 30 mol% or more of the acidic group of the component A is neutralized, and it is more preferable that 50 mol% or more is neutralized. When the neutralization amount of the acidic group is less than 50 mol%, if the solubility of the component A in water is insufficient, the pressure-sensitive adhesive composition tends to be unstable, such as separation of the liquid over time. In addition, since the surface activity of component A is low, this component A
When component B is emulsion-polymerized in the presence of, the polymerization tends to be unstable.

The component A is preferably a resin having a low crosslinking density or a substantially non-crosslinked resin. If the component A is excessively crosslinked, the solubility of the component A in water tends to be insufficient. Further, if the crosslink density of the component A forming the sea-island structure sea in the pressure-sensitive adhesive layer before heating is too high,
In some cases, the movement of the molecular chain constituting the component A is limited, and the sea-island is difficult to reverse even when the heat treatment is performed.

(1-3) Glass Transition Temperature Component A has a glass transition temperature of 20 ° C. or higher (usually 13 ° C.).
0 ° C. or lower, preferably 120 ° C. or lower), more preferably 30 to 130 ° C., and 40 ° C. or lower.
It is more preferable that the temperature be from about 120 ° C to 120 ° C. However, this is not the case when component A is a graft copolymer as described above, and the glass transition temperature of the entire graft copolymer is −30 to 100 ° C. (more preferably −20 to 60 ° C.,
More preferably, it is 0 ° C. or more and less than 20 ° C.). Further, the glass transition temperature of the hydrophilic portion of the graft copolymer is 20 ° C. or more (more preferably 30 to 130).
° C, more preferably 40 to 120 ° C), and the glass transition temperature of the hydrophobic part is -20 ° C or less (more preferably-
30 ° C. or lower, more preferably −40 ° C. or lower).

If the glass transition temperature of the component A or the glass transition temperature of the hydrophilic portion or the hydrophobic portion thereof is less than the above range, the adhesive strength of the pressure-sensitive adhesive layer before the heat treatment becomes too high, so that "release paper" To provide a pressure-sensitive adhesive sheet that can be used without performing a peeling treatment on the pressure-sensitive adhesive layer such as a peeling treatment of the base material or the back surface of the base material ”in some cases. On the other hand, if the glass transition temperature exceeds the above range, the heating temperature required to develop the adhesiveness becomes high, and the energy cost increases, which is not preferable.

The number average molecular weight of the component A is 1,000
Preferably it is ~ 50,000. When the number average molecular weight is less than 1,000, the water resistance of the pressure-sensitive adhesive layer tends to be insufficient. On the other hand, when the number average molecular weight exceeds 50,000, the viscosity becomes high and the production of the component A becomes difficult, and the solubility of the component A in water becomes insufficient and the liquid stability of the composition is lowered. When the emulsion polymerization of the component B is performed in the presence of the component A, the polymerization becomes unstable. Further, it may be difficult to reverse the sea and the island by heating the pressure-sensitive adhesive layer, or it may be difficult to form a sea-island structure before and / or after heating the pressure-sensitive adhesive layer. In order to adjust the number average molecular weight, a chain transfer agent may be appropriately added to the polymerization system.

(1-4) When the component A is a polymer of a radical polymerizable monomer, various polymerization methods can be employed as a polymerization method for obtaining the component A, for example, a polymerization method by irradiation with radiation. A known method such as a method using a radical polymerization initiator can be used. Among them, a polymerization method using a radical polymerization initiator is preferable from the viewpoint of easiness of polymerization operation, easiness of controlling the molecular weight of the obtained copolymer before neutralization, and the like. Examples of the polymerization method include a solution polymerization method, a bulk polymerization method, a suspension polymerization method, an emulsion polymerization method, and a precipitation polymerization method, and it is preferable to use the solution polymerization method or the emulsion polymerization method.

In particular, in order to obtain a homogenous and stable copolymer (a) (a copolymer before neutralization), the monomer ratio should be kept as constant as possible in the reaction system. It is desirable to control the dropping speed or the dropping method. In particular,
Of the monomers used for component A, monomers having poor copolymerizability and having low reactivity in copolymerization are initially charged in a part or the whole amount into a reactive group, and a monomer having a high reaction rate during copolymerization is prepared. The monomer is dropped into the reaction group, or substantially all of the monomer having a slow reaction rate and a part of the monomer having a fast reaction rate are charged into the reaction group, and By dropping a monomer having a high reaction rate into the reaction group in accordance with the consumption rate, it is possible to produce the component A having a substantially uniform composition and molecular weight.

In the solution polymerization method, Component A can be obtained smoothly by dissolving the radically polymerizable monomer in an organic solvent and conducting polymerization using an appropriate radically polymerizable initiator. 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 among them, methyl ethyl ketone And / or isopropyl alcohol is preferably used. As the radical polymerization initiator used in the solution polymerization, any of those used in general radical polymerization can be used. For example, a persulfate-based polymerization initiator, an azo-based polymerization initiator, a redox-based polymerization initiator can be used. Initiators and the like can be mentioned. The preferred amount of the polymerization initiator to be used is 0.1 to 5% by weight based on the total amount of the monomers.

When the component A is produced by an emulsion polymerization method, the radical polymerizable monomer is mixed and dispersed in water together with an emulsifier as disclosed in, for example, JP-A-6-271779. The above component A can be smoothly obtained by preparing a monomer emulsion by means of a continuous polymerization method using a suitable radically polymerizable initiator and continuously adding it to a reactor. The polymerization temperature for obtaining component A is 1
It is preferably about 0 to 150 ° C, and 60 to 100 ° C.
Is more preferable. The polymerization time is 1 to 100.
The time is appropriate, more preferably 3 to 10 hours.

(2) Component B Component B in the present invention is a polymer having a Tg of -20 ° C. or lower, obtained by emulsion polymerization of a radical polymerizable monomer.

(2-1) Glass transition temperature The Tg of the above component B is -20 ° C or less (usually -100 ° C).
Or more, preferably -90 ° C or higher),
It is preferably 50 ° C. or lower. Tg of component B is -2
If the temperature exceeds 0 ° C., sufficient adhesive performance cannot be obtained in the adhesive layer after heating.

(2-2) Composition As the component B, various polymers obtained by emulsion polymerization of a radical polymerizable monomer and having a Tg satisfying 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. Polymer (hereinafter, referred to as “ethylene-vinyl ester monomer”), a conjugated diene monomer, and a monomer copolymerizable with the conjugated diene monomer (hereinafter, referred to as “conjugated diene monomer”). An emulsion polymer of a radical polymerizable monomer having a main component of “monomer”) can be used. When the component B is an emulsion polymer of an ethylene-vinyl ester monomer or a conjugated diene monomer, the pressure-sensitive adhesive layer after heating shows a good pressure-sensitive adhesive strength to a polyolefin-based resin. There is an advantage that a composition 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 is 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 and vinyl versatate. . Examples of the “conjugated vinyl monomer” in the “conjugated vinyl monomer” include butadiene, isoprene, chloroprene, and isobutylene.

The “acrylic monomer” includes, as a main component, an alkyl (meth) acrylate and, if necessary, another radical polymerizable monomer copolymerizable therewith (hereinafter referred to as “acrylic monomer”). Is sometimes referred to as a "copolymerizable monomer.") Is preferably used in a small amount, preferably 40% by weight or less. As the “alkyl (meth) acrylate”, the alkyl group has 1 carbon atom.
And (12) alkyl (meth) acrylate are preferably used. Specifically, 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, n-nonyl (meth) acrylate and ( Examples thereof include isononyl (meth) acrylate, decyl (meth) acrylate, and lauryl (meth) acrylate, and one or more of these alkyl (meth) acrylates can be used. In particular, in the present invention, as the radical polymerizable monomer used for the production of the component B, one or more alkyl (meth) acrylates having 4 to 9 carbon atoms in the alkyl group are used as the main component. Is preferred.

As described above, in the production of the component B, together with the alkyl (meth) acrylate,
Other copolymerizable monomers may be used as the minor component. Examples of such “other copolymerizable monomers” include, for example, vinyl aromatic monomers such as styrene, α-methylstyrene, and vinyl toluene; (meth) acrylic acid, crotonic acid,
Unsaturated carboxylic acids such as cinnamic acid, itaconic acid, fumaric acid and maleic acid; monoalkyl esters of unsaturated dicarboxylic acids such as monoethyl itaconate, monobutyl fumarate and monobutyl maleate; (meth) Hydroxyl-containing vinyl monomers such as 2-hydroxyethyl acrylate, 2-hydroxypropyl (meth) acrylate, polyethylene glycol mono (meth) acrylate, and polypropylene glycol mono (meth) acrylate; (meth) acrylonitrile, vinyl acetate, ( Meta)
Examples thereof include acrylamide, N-methylolacrylamide, glycidyl methacrylate, vinyl acetate, vinyl chloride, and vinylidene chloride. One or more of these copolymerizable monomers can be used.

When the above-mentioned "other copolymerizable monomer" is used, its use ratio is 40% by weight or less as described above, based on the total weight of the radical polymerizable monomer used for producing the component B. It is preferred that 40% by weight
This is because, if it exceeds, the adhesive performance of the adhesive layer after heating tends to be insufficient. (2-3) Acid Value The acid value of the component B is preferably 0.6 meq / g or less, more preferably 0.2 meq / g or less. When the acid value of component B exceeds 0.6 meq / g,
The water resistance of the pressure-sensitive adhesive layer may be insufficient. As the component B of the present invention, a polymer having an acid value of 0 meq / g is particularly preferably used. The value of the acid value of component B is
Is preferably lower than 0.5 meq / g or more, more preferably lower than 1 meq / g with respect to the acid value.

(2-4) Method for Producing Component B As an example of a method for obtaining the component B, a conventional emulsion polymerization method using a conventionally known surfactant as an emulsifier can be mentioned. Examples of the surfactant used herein include anionic surfactants such as higher alcohol sulfate sodium salt, alkylbenzene sulfonate sodium salt, dialkyl succinate sodium sulfonate, and alkyl diphenyl ether disulfone sodium acid; and polyoxyethylene alkylallyl. Nonionic surfactants such as ether and polyoxyethylene polyoxypropylene block copolymers can be mentioned. Further, a reactive anionic surfactant such as sodium allyl alkyl 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 the radical polymerizable monomer used for the production of 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 (emulsifier), the amount of an emulsifier such as a protective colloid or another surfactant used during the emulsion polymerization can be made smaller than in the case of ordinary emulsion polymerization. . Further, if desired, no other emulsifier can be used. As a result, the water resistance of the pressure-sensitive adhesive layer can be improved as compared with the case where the component B is produced by ordinary emulsion polymerization. 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. Therefore, in this case, the pressure-sensitive adhesive composition or pressure-sensitive adhesive layer of the present invention can be formed from this emulsion without separately adding the component A, and the production method is most preferable from the viewpoint of water resistance.
Alternatively, component A may 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 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 preferred amount of the polymerization initiator to be used is 0.1 to 5% by weight based on the total amount of the monomers. The component B preferably does not have an acidic group, but may have an acidic group within a range of the acid value or less. In order to prevent the inside of the system from becoming unstable when component A is added, component B is neutralized with a base or the like used for neutralizing component A to bring its pH closer to the pH of component A. It is preferable to keep it.

(3) Thickener As this thickener, hyderanite, hectorite,
Inorganic pigments such as magnesium carbonate, montmorillonite, bentonite, sabonite, silicon oxide, mica, alumina,
Fibrous derivatives such as carboxymethylcellulose, methylcellulose and hydroxycellulose, proteins such as casein and caseinate, polyacrylic polymers (meaning "acrylic thickener"), polyurethane polymers, alginic acid, Polyvinyl polymers such as polyvinyl alcohol, polyvinyl pyrrolidone, polyvinyl ether maleic acid, and polyvinyl benzyl ether; polyether polymers such as pluronic polyether, polyether polycarboxylic acid, polyether dialkyl ester, polyether dialkyl ether, and urethane-modified polyether. Etc. are used.

Among these, polyacrylic acid polymers, polyurethane polymers, polyvinyl alcohol polymers, and polyether polymers are preferred because of their high viscosity increasing effect and little decrease in the adhesive performance upon development. Among them, in particular, as can be seen from the test results in Table 2,
This acrylic acid-based thickener is more preferable in that the anti-blocking property is improved and the anti-blocking property surely shows excellent anti-blocking property even when the viscosity fluctuates. This acrylic acid-based thickener has high blocking resistance and is surely superior to other polyurethane-based and polyvinyl alcohol-based thickeners. The acrylic acid-based thickener usually contains at least (meth) acrylic acid of (meth) acrylic acid and (meth) acrylic acid ester, and these (meth) acrylic acid and / or (meth) acrylic acid It is composed of a copolymer containing an acid ester as a main component.

Examples of the (meth) acrylic acid include acrylic acid and methacrylic acid. Examples of the (meth) acrylate include methyl methacrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, and (meth) acrylate. Isobutyl acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate,
Examples include polyethylene glycol mono (meth) acrylate and polypropylene glycol mono (meth) acrylate. In addition, other monomers, for example, crotonic acid,
Maleic acid, fumaric acid, itaconic acid, citraconic acid, maleic anhydride, allylonitrile, (meth) acrylamide, N-methylolacrylamide, glycidyl methacrylate and the like may be copolymerized.

Specific examples of the acrylic acid-based thickener include “Alon B-300” and “Alon KM-3” manufactured by Toagosei Co., Ltd.
6, "Aron EM-25", "Primal ASE-60", "Primal ASE" manufactured by Rohm and Haas
-1000 "," Primal RM-5 "," SN Thickener A-850 "manufactured by Sannobuco, and the like. Examples of the polyether-based polymer include “Sannobuco SN Thickener A-812” and “SN Thickener A-813”.
Thickener A-813 "and the like. As the polyurethane-based polymer, "ADEKANOL UH-420" and "UH-140S" manufactured by Asahi Denka Kogyo KK, "Kolaclar PU-85" manufactured by BASF, "QR-708" manufactured by Rohm and Haas, "RM-8", "RHEOLATE278" manufactured by RHEOX, and the like. Among polyvinyl-based polymers, as polyvinyl alcohol-based polymers, "PVA-420" and "PVA-2" manufactured by Kuraray Co., Ltd.
24 ”,“ Gohsenol GH-
17 "and the like. As the polyvinyl hydridone type, “Colaclar VL” manufactured by BASF is exemplified. The number average molecular weight of this polyacrylic polymer is 5
It is preferably at least 000, more preferably at least 100,000, particularly preferably at least 300,000 in order to obtain an excellent thickening effect.

(4) Pressure-sensitive adhesive composition The pressure-sensitive adhesive composition of the present invention may be a composition obtained by blending the above-mentioned component A, the above-mentioned component B, and the above-mentioned thickener.
A component obtained by emulsion polymerization of the radical polymerizable monomer used in the production of the component B in the presence of the component A and a thickener added thereto may be used. In the above case, there is an advantage that the production of the pressure-sensitive adhesive composition is simple and a composition having a high solid content is easily obtained. On the other hand, in the above case, since the component A is used as an emulsifier in the emulsion polymerization of the component B, the water resistance of the pressure-sensitive adhesive layer can be improved as described above, and the storage stability of the composition can be improved. There is an advantage that it is excellent. That is, when the component A and the component B are blended, a part or all of the surfactant adsorbed on the polymer particle surface of the emulsion composed of the component B is desorbed and replaced by the component A. In some cases, the storage stability is impaired. In a remarkable case, the mixture may be gelled to make application impossible. In the above case, such a problem is prevented. Furthermore, the pressure-sensitive adhesive composition of the present invention further blended the above component A with a polymer obtained by emulsion polymerization of the radical polymerizable monomer used for the production of the above component B in the presence of the above component A. It may be something.

(4-1) Weight Ratio of Component A to Component B In the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of the present invention and the pressure-sensitive adhesive composition of the present invention, the weight ratio of component A to component B is /
Component B is preferably 10/90 to 50/50, and more preferably component A / component B is 15/85 to 40/60. If the weight ratio of component A to the total weight of component A and component B is less than 10%, it is difficult for the pressure-sensitive adhesive layer before the heat treatment to have a sea-island structure in which component A is the sea and component B is the island. As a result, the pressure-sensitive adhesive layer before the heat treatment may unnecessarily exhibit an adhesive force. On the other hand, component A
If the weight ratio exceeds 50%, the water resistance of the pressure-sensitive adhesive layer is reduced, and the adhesive strength is apt to be insufficient. If the weight ratio of the component A is too high, it is difficult to form a sea-island structure in which the component A is an island and the component B is a sea in the pressure-sensitive adhesive layer after the heat treatment.

(4-2) Liquid Properties The pressure-sensitive adhesive composition of the present invention has a solid concentration of 30 to 70.
%, More preferably 35 to 65% by weight. If the solid content is less than 30% by weight, the drying property of the composition is insufficient, while if it exceeds 70% by weight, the production becomes difficult and the viscosity of the composition tends to be excessively high. The composition of the present invention usually comprises particles in which component A, which is a water-soluble resin, is located on the outside and component B is located on the inside. Therefore, the dispersion state of the component B in water is stabilized by the presence of the component A, so that the amount of other emulsifiers added to supplement the liquid stability of the composition can be reduced, whereby the adhesiveness can be reduced. The water resistance of the agent layer is further improved. In addition, since the component A of the present invention is water-soluble, unlike the case where the component A is insoluble in water, the liquid stability of the composition is good because no sedimentation or aggregation of the component A occurs in the composition. is there.

(4-3) Viscosity The viscosity of the present composition is 200 to 30,000 cps (12 r
pm). When the heat-sensitive adhesive is applied to the base material, if the viscosity is lower than 200 CPS, if the viscosity is low in a paper base or the like, the permeation of water and resin into the base material is fast, and the strength of the base material tends to decrease. In the case of a film substrate that does not penetrate, there is a problem that a uniform coated surface cannot be obtained due to repelling or shrinkage of the coated surface due to surface tension. 30,000
When the CPS is applied, there is a problem that the liquid cannot be sent from the storage tank to the coating device due to poor fluidity in the pipe. still,
This viscosity is preferably between 500 CPS and 20,000.
CPS, more preferably 2,000 to 15,000C
PS. The amount of the thickener to be added is 0.4 to 4.0 parts by weight, preferably 0.4 to 2.0 parts by weight, per 100 parts by weight of the solid content of the components A and B.

(4-4) Other Components The pressure-sensitive adhesive composition of the pressure-sensitive adhesive sheet of the present invention and the pressure-sensitive adhesive layer of the present invention can be used as antifoaming agents commonly used in general pressure-sensitive adhesives, depending on the application. , Surfactants, fungicides, fragrances, neutralizers,
Tackifier, leveling regulator, antifreeze, foaming agent,
Antioxidants, ultraviolet absorbers, reinforcing agents, fillers, pigments,
Optical brighteners, antistatic agents, anti-blocking agents, flame retardants,
One or more of a crosslinking agent, a plasticizer, a lubricant, an organic solvent, a colorant, and the like may be contained.

(II) Pressure-sensitive adhesive sheet The heat-sensitive pressure-sensitive adhesive sheet of the present invention has a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the first to fifth inventions on a substrate. The adhesive strength of the pressure-sensitive adhesive layer after storage for 1 hour at a temperature of 40 ° C. and a pressure of 10 kg / cm 2 is 5 g / 25 mm or less. Therefore, the anti-blocking performance is excellent. The adhesive strength of this adhesive layer is, as shown in the seventh invention,
Before the heat treatment, it is as low as 10 g / 25 mm or less. Therefore, in this state, the product can be handled as it is without performing a release treatment on the adhesive layer such as a release paper or a release treatment on the back surface of the substrate. By performing a heat treatment at 60 ° C. or higher, the pressure-sensitive adhesive sheet has a sea-island structure in which the sea and islands of the pressure-sensitive adhesive layer are reversed and the component A is an island and the component B is a sea. / 2
It exhibits an adhesive strength of 5 mm or more.

(1) Substrate The type of the substrate in the pressure-sensitive adhesive sheet of the present invention is not particularly limited as long as it can withstand the heat treatment temperature of the pressure-sensitive adhesive sheet. It is sufficient to use, for example, a film or sheet made of cloth, paper, leather, wood, metal, glass, various plastics,
Plates, foamed plastic sheets and the like can be mentioned. Examples of the substrate made of the plastic include substrates made of polyester, polyamide, vinyl chloride polymer, polyethylene, polypropylene, polyurethane, and the like. Further, the shape of the base material is a long body, one cut into a predetermined size (for example, square, circular, elliptical,
(Pre-cut into other shapes).

(2) Pressure-sensitive adhesive layer In the heat-sensitive pressure-sensitive adhesive sheet of the present invention, the thickness of the pressure-sensitive adhesive layer can be appropriately adjusted depending on the use and the like, but is generally about 1 μm to 1 mm. Is preferred. Thereby, it is possible to make the adhesive layer exhibit good adhesiveness after the heat treatment. This pressure-sensitive adhesive layer has a sea-island structure in which the component A is a sea and the component B is an island before the heat treatment, and the heat-treatment at 60 ° C. or more reverses the sea-island and the component A is an island. The component B changes to a structure in which it is a sea. This situation is shown in FIGS. 1A and 1B.
Is shown schematically in FIG.

FIG. 1A shows the state of the pressure-sensitive adhesive layer before heating, in which a sea-island structure is formed in which component A is the sea and component B is the island. Therefore, if a substantially non-tacky material at room temperature is used as the component A, the pressure-sensitive adhesive layer before the heat treatment can be made non-tacky. Thereby, the pressure-sensitive adhesive sheet before heating can be used without using a release paper or performing a release treatment such as a release treatment on the back surface of the base material.

FIG. 1 (B) shows the pressure-sensitive adhesive layer after the above-mentioned pressure-sensitive adhesive layer before heating is subjected to a heat treatment at 60 ° C. or higher. By this heat treatment, the sea and the island are reversed, and a sea-island structure is formed in which component A becomes an island and component B becomes a sea. As described above, since the pressure-sensitive adhesive layer after heating of the present invention has a structure in which the low-viscosity or non-tacky component A is dispersed in the component B, when the component A and the component B are uniformly mixed, In comparison, the adhesive strength of the adhesive layer after heating is better. Further, if a hydrophobic material is used as the component B, the continuous layer in the adhesive layer after heating becomes hydrophobic. Therefore, even if the component A which is a discontinuous layer is hydrophilic, the adhesive layer after heating can be made water-resistant. It is possible to make it excellent. Furthermore, if the component A has high alkali solubility or alkali swellability,
It is possible to achieve both good water resistance and excellent alkali peelability in the pressure-sensitive adhesive layer after heating.

The non-adhesive resin [component (A)] and the adhesive acrylic resin emulsion [component (B)] as described in the above-mentioned JP-A-8-269420.
The pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition comprising, after the heat treatment, the component A and the component B are not uniformly mixed, but the “sea-island structure in which the component A becomes an island and the component B becomes the sea” Is found for the first time by the present inventors.

(3) Production method of heat-sensitive adhesive sheet The heat-sensitive adhesive sheet of the present invention is prepared by applying the pressure-sensitive adhesive composition of the present invention to one or both surfaces of the above-mentioned substrate and drying it by an appropriate method. And the like. At this time, the method of applying the pressure-sensitive adhesive composition to the substrate is not particularly limited, and may be performed using any method such as roll coater coating, spray coating, casting coating, doctor blade coating, brush coating, and the like. it can. In drying the pressure-sensitive adhesive composition applied on the base material, the temperature of the pressure-sensitive adhesive layer in the finally obtained pressure-sensitive adhesive sheet is such that the pressure-sensitive adhesive layer does not exhibit tackiness at room temperature, or the pressure-sensitive adhesive layer is such that the component A becomes sea. It is necessary to heat at a temperature at which the pressure-sensitive adhesive layer having a sea-island structure in which the component B is an island can be formed.

(4) Method of Use The heat-sensitive adhesive sheet of the present invention has an adhesive strength at a temperature of 25 ° C. of 10 g / 25 mm or less according to JIS Z 0237 at a temperature of 25 ° C., and exhibits adhesiveness at room temperature. Unlike conventional adhesive sheets, since they have no or very low adhesive strength at room temperature, they are simply packaged as they are for products that do not have normal adhesiveness, without subjecting the adhesive layer to release treatment. Or can be stored, distributed, and sold without packaging. At this time, the term "not subjected to release treatment" in the present invention means that the pressure-sensitive adhesive sheet of the heat-sensitive adhesive sheet is not covered with a release paper. Means not to apply. Needless to say, if necessary, for example, when the adhesive strength at 25 ° C. is 3 to 10 g / 25 mm, the adhesive sheet may be subjected to a release treatment depending on its use.

When the heat-sensitive adhesive sheet of the present invention is adhered to an adherend, the adhesive layer of the heat-sensitive adhesive sheet is heated, the adherend side is heated, or the heat-sensitive adhesive sheet is adhered to the adhesive layer. The heat-sensitive adhesive sheet can be adhered to the adherend by heating both of the adherends. The heating temperature for causing the pressure-sensitive adhesive layer to exhibit tackiness depends on the Tg of the entire component A contained in the pressure-sensitive adhesive composition, and is usually at least 10 ° C, preferably at least 30 ° C higher than the Tg. ing. Here, if the heating temperature is too high, there is a possibility that the workability of attaching the pressure-sensitive adhesive sheet and the thermal efficiency may be reduced, or the base material may be deteriorated or deformed. For this reason, the heating temperature is preferably set to 60 to 180 ° C.,
More preferably, the temperature is set to 0 ° C.

The pressure-sensitive adhesive sheet of the present invention once adhered to the adherend does not peel off spontaneously when the temperature returns to normal temperature, and is favorably adhered to the adherend without losing its adhesiveness. I'm wearing Then, when it is desired to peel the heat-sensitive adhesive sheet of the present invention from the adherend, it can be easily peeled off from the adherend by pulling with a hand or the like, similarly to a general-purpose pressure-sensitive adhesive sheet, and the peeled material is an adhesive. Since the layer remains tacky, it can be re-applied to the same or another adherend.

The material and type of the adherend to which the heat-sensitive adhesive sheet of the present invention can be adhered are not particularly limited. For example, cloth, paper, leather, wood, metal, glass, concrete, ceramic,
It can be satisfactorily adhered to any of polyester, polyethylene, polypropylene, polyvinyl chloride, polyurethane, polycarbonate, polyamide, polyimide, styrene-based polymer, rubbers and the like.

The heat-sensitive adhesive sheet of the present invention, for example, in the case where the acid value of component B is 0.6 meq / g or less, is an alkaline peeling agent for a label to be attached to a bottle for filling beverages such as a beer bottle. It can be suitably used as a pressure-sensitive adhesive sheet.
Such an alkali-peelable pressure-sensitive adhesive sheet has a high adhesive strength to a bottle as an adherend, and has good water resistance at the time of immersion in cold water. Peeling property (alkali peeling property)
Is required. In the pressure-sensitive adhesive sheet of the present invention, the pressure-sensitive adhesive layer after heat treatment has a hydrophilic portion with a high acid value in a continuous layer (sea) composed of Component B having a low acid value and good water resistance, and has an alkali-soluble property. Alternatively, since it has a sea-island structure in which a discontinuous layer (island) composed of the component A having a high alkali swelling property is dispersed, it is possible to achieve both good water resistance and adhesiveness, and excellent alkali releasability.

[0061]

The present invention will be described more specifically with reference to the following examples and comparative examples. In the following examples, “parts” and “%” are “parts by weight” unless otherwise specified.
And "% by weight". The abbreviations used below and their contents are shown in Table 1 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.

[0062]

[Table 1] 略 Abbreviation: Contents Tg (° C) ──── Ｍ MMA: methyl methacrylate 105 HEMA: 2-hydroxyethyl methacrylate 55 AA: acrylic acid 105 AEH : 2-ethylhexyl acrylate -85 BA: butyl acrylate -54 AIBN: 2,2'-azobisisobutyronitrile ───────────

[I] Investigation of the relationship between the type of thickener and blocking resistance, and the relationship between viscosity by adding the thickener and coating properties or blocking resistance (1) Synthesis of component A Component A, which is a conductive resin, was synthesized. Synthesis Example 1 A flask equipped with a stirrer, a condenser, a thermometer and a nitrogen inlet tube was charged with 20 parts of methyl ethyl ketone as a solvent, and then 20 parts of a monomer mixture of 90 parts of MMA and 10 parts of AA as a monomer. 1.5 parts of a chain transfer agent dodecyl mercaptan was added and charged, and the polymerization initiator AI was added.
Polymerization was started by adding 0.5 parts of BN. When the polymerization started, 80 parts of methyl ethyl ketone and 1.0 part of AIBN as a polymerization initiator were added to 80 parts of the remaining monomer mixture, mixed and dissolved, and the mixture was dropped continuously over 4 hours to polymerize. Thereafter, 0.5 parts of AIBN was further charged, and the mixture was heated to the same temperature for 5 hours to obtain a solution of a copolymer (acid value: 1.4 meq / g) containing 50% solids in methyl ethyl ketone.
This polymer corresponds to the component A described above. To 200 parts of the methyl ethyl ketone solution of the copolymer obtained above, ammonia water was gradually added with stirring to neutralize the carboxyl groups in the copolymer, and the pH of the reaction solution was reduced to about 7 to 8. did. Thereafter, the methyl ethyl ketone was removed under reduced pressure at a temperature of 50 ° C., and the aqueous solution A1 of the component A1 in which the carboxyl group was neutralized.
aq was obtained. The solid content of this aqueous solution A1aq is 50
% And its pH was 7.7.

Synthesis Example 2 45 parts of “AB-6”, 45 parts of MMA, and AA
Component A was prepared in the same manner as in Synthesis Example 1 except that the amount of the transfer agent was 1.0 part and the amount of the initiator was 2.0 parts.
2 (acid value of the graft polymer trunk: 1.4 meq / g)
Was synthesized. This "AB-6" is a methacryloylated polybutyl acrylate macromonomer at one end (manufactured by Toagosei Co., Ltd., trade name "Macromonomer AB-6", number average molecular weight 6,000). In addition, the obtained component A2
Is a graft copolymer having a hydrophilic main chain composed of an MMA-AA copolymer and a hydrophobic side chain composed of polybutyl acrylate.

(2) Preparation of heat-sensitive adhesive composition and preparation of heat-sensitive adhesive sheet Emulsion polymerization of a radical polymerizable monomer used for production of component B in the presence of component A obtained by the above synthesis example. Thus, aqueous polymer emulsions were synthesized, and predetermined amounts of various thickeners were added thereto to synthesize the respective pressure-sensitive adhesive compositions as shown below. Table 2 shows the type and amount of the thickener and the viscosity of the composition in each composition. Furthermore, each heat-sensitive adhesive sheet was produced using this adhesive composition.

Example 1 A monomer mixture was prepared by mixing 99 parts of BA and 1 part of HEMA. A flask equipped with a stirrer, a condenser, a thermometer and a nitrogen inlet tube was charged with 70 parts of deionized water and 40 parts of an aqueous solution A1aq of the component A1 obtained in Synthesis Example 1 (20 parts of an active ingredient), and heated at 60 ° C. in a nitrogen atmosphere. , And 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"). 5 parts of a 10% 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 dropping, the reaction system was cooled to terminate the polymerization, neutralized with aqueous ammonia, and adjusted to pH.
Was set to 7 to 8, and an aqueous emulsion having a solid content of about 50% was obtained.

To 100 parts of this aqueous emulsion, 1 part of an acrylic acid-based thickener “KM-36” (manufactured by Toagosei Co., Ltd. (solid content: 30%)) Is 0.6 parts. And neutralized to pH 7.5 with aqueous ammonia to obtain a heat-sensitive adhesive. The Brookfield viscosity at 12 rpm of this heat-sensitive adhesive at 25 ° C. was 2,000 CPS. The heat-sensitive adhesive obtained above has a coating thickness of 15 after drying.
is applied on a 50μ polyester film as a base material with an applicator, and heated to 40 ° C and 5 ° C with a hot air drier.
After drying for a minute, a heat-sensitive adhesive sheet was obtained.

Example 2 1 of the acrylic thickener “KM-36” in Example 1
3 parts of the thickener [the solid content of the thickener is 1.8 parts based on 100 parts of the solid content of the aqueous emulsion. ], And a heat-sensitive adhesive composition and a heat-sensitive adhesive sheet were obtained in the same manner as in Example 1. The Brookfield viscosity at 12 rpm of this pressure-sensitive adhesive composition at 25 ° C. was 20,000 CPS.

Example 3 Instead of the composition of the aqueous emulsion in Example 1,
A heat-sensitive adhesive composition and a heat-sensitive adhesive sheet were obtained in the same manner as in Example 1 except that an aqueous emulsion composition of AEH 90 parts and MMA 10 parts was used. The Brookfield viscosity at 12 rpm of this pressure-sensitive adhesive composition at 25 ° C. was 15,000 CPS. Incidentally, the thickener solid content is 0.6 part with respect to 100 parts of the aqueous emulsion solid content.

Example 4 An acrylic thickener "RM-5" manufactured by Rohm and Haas Co. (solid content: 30%) was used instead of 1 part of the acrylic thickener "KM-36" in Example 1. 1 part [100 parts of aqueous emulsion solids and 0.6 parts of thickener solids. A heat-sensitive adhesive composition and a heat-sensitive adhesive sheet were obtained in the same manner as in Example 1 except that they were blended.
The Brookfield viscosity at 12 rpm of this pressure-sensitive adhesive composition at 25 ° C. was 10,000 CPS.

Example 5 Instead of 1 part of the acrylic thickener "KM-36" in Example 1, the urethane thickener "Adecanol U" was used.
H-420 "manufactured by Asahi Denka Chemical Co., Ltd. (solid content 30%)
1 part [100 parts of aqueous emulsion solids and 0.6 parts of thickener solids. A heat-sensitive adhesive composition and a heat-sensitive adhesive sheet were obtained in the same manner as in Example 1 except that they were blended. 12 rpm of this pressure-sensitive adhesive composition at 25 ° C.
The Brookfield viscosity at m was 4,000 CPS.

Example 6 A heat-sensitive adhesive composition and a heat-sensitive adhesive sheet were prepared in the same manner as in Example 1, except that the water-soluble resin A2 synthesized in Synthesis Example 1 was used instead of the water-soluble resin A2. I got The Brookfield viscosity at 12 rpm of this pressure-sensitive adhesive composition at 25 ° C. was 14,000 CPS. Incidentally, the thickener solid content is 0.6 part with respect to 100 parts of the aqueous emulsion solid content.

Example 7 In Example 1, the acrylic thickener "KM-36" 1
Parts instead of the polyvinyl chloride thickener “PVA-4”
20 "Kuraray Co., Ltd. dissolved in water and 5 parts of a 10% solids solution [100 parts of aqueous emulsion solids and 1.0 part of thickener solids. A heat-sensitive adhesive composition and a heat-sensitive adhesive sheet were obtained in the same manner as in Example 1 except that they were blended. 12 rpm of this pressure-sensitive adhesive composition at 25 ° C.
Brookfield viscosity in m is 12,000 CPS
Met.

Comparative Example 1 A heat-sensitive adhesive composition and a heat-sensitive adhesive sheet were obtained in the same manner as in Example 1 except that no thickener was used. The Brookfield viscosity at 12 rpm of this pressure-sensitive adhesive composition at 25 ° C. was 40 PS.

Comparative Example 2 Instead of 1 part of the acrylic thickener "KM-36" in Example 1, 10 parts of the thickener was added to 100 parts of the aqueous emulsion solids. Is 6.0 parts. A heat-sensitive adhesive composition and a heat-sensitive adhesive sheet were obtained in the same manner as in Example 1 except that they were blended. The Brookfield viscosity at 12 rpm of this heat-sensitive adhesive composition at 25 ° C. was 45,000 CPS.

(3) Evaluation of Pressure-Sensitive Adhesive Composition For each of the above-mentioned heat-sensitive pressure-sensitive adhesive sheets, the following was evaluated (the presence or absence of a sea-island structure in the pressure-sensitive adhesive layer, the adhesive strength before and after heating, blocking resistance, coating properties and storage stability). The measurement was performed, and the results are shown in Table 2. Sea-island structure of the pressure-sensitive adhesive layer The low-temperature-dried pressure-sensitive adhesive layer prepared in Examples 1 and 2 is subjected to vapor dyeing in the presence of an aqueous ruthenic acid solution, and is further embedded with an epoxy resin. Observation was performed using a microscope (TEM). These TEMs
The photographs are shown in FIGS. 2A and 3A, respectively. On the other hand, the adhesive composition of Example 1 was applied in the same manner as described above, and 1
An adhesive layer obtained by drying at 40 ° C. for 2 minutes (hereinafter referred to as “adhesive layer”).
It is called "high-temperature drying adhesive layer". ) Was treated in the same manner and observed with a transmission electron microscope. These TEM photographs are shown in FIG. 2 (B) and FIG. 3 (B), respectively. According to the above method of dyeing with ruthenic acid vapor, it is known that polystyrene and the like are strongly dyed, while polymethyl methacrylate and the like are not dyed much (Macromo
lecules, Vol. 16, No. 4, 1983, P. 589-598).

Measurement of Adhesive Strength of Adhesive Sheet Before and After Heating A heat-sensitive adhesive composition was applied to a coated paper for label as a substrate so that the thickness of the dried coating film became 20 to 30 μm, For 5 minutes to form an adhesive sheet.
A test piece obtained by cutting this adhesive sheet to a width of 25 mm and a length of about 250 mm (hereinafter referred to as a “test piece before heat treatment”), and a heat treatment at 140 ° C. for 2 minutes are performed on the test piece before heat treatment. Of the test piece (hereinafter referred to as “heat-treated test piece”) left for 24 hours in an atmosphere at a temperature of 23 ° C. and a humidity of 65%, and then measured the adhesive strength according to the 180 ° peeling method specified in JISZ0237. did. That is, under the conditions of a temperature of 23 ° C. and a humidity of 65%, the above test piece was attached to a polished stainless steel plate as a test plate, and 2K
g rubber roller was reciprocated once. 30 from crimping
After one minute, the 180-degree peeling adhesion to the test plate was measured at a tensile speed of 300 mm / min. The measurement results were shown in the following four stages. The results are shown in Table 2. still,
Significant increase in adhesion after heating compared to before heating is a strong proof that the sea and islands of the sea-island structure have reversed. A: 500 g / 25 mm or more B: 100 g / 25 mm or more, less than 500 g / 25 mm C: More than 10 g / 25 mm and less than 100 g / 25 mm D: 10 g / 25 mm or less

Evaluation of anti-blocking performance A test piece of the pressure-sensitive adhesive sheet prepared as described above was treated at a temperature of 40.
The adhesive strength after storage for 1 hour at a temperature of 10 ° C. and a pressure of 10 kg / cm 2 was measured according to the 180-degree peeling method specified in JIS Z 0237. The measurement results were shown in the following four stages. The results are shown in Table 2. ◎: 5 g / 25 mm or less ○: More than 5 g / 25 mm and less than 10 g / 25 mm △: 10 g / 25 mm or more, less than 50 g / 25 mm

Coating Properties Using a coated paper for labels as a base material and a coating machine “Multicoater M-200” manufactured by Hirano Tecseed Co., Ltd., a coating method: a converse method, a coating roll / Back roll ratio: 10/9, line speed: 2 m /
The coating suitability was evaluated at a drying temperature of 50 ° C. and a drying air velocity of at most every minute. The supply of the heat-sensitive adhesive which is a coating liquid is performed by a diaphragm type pump “EX-A20SH-” manufactured by Iwaki Co., Ltd.
100S "was used. Table 2 shows the evaluation results. still,
The evaluation is as follows. ；: A uniform coated surface is obtained. That is, there was no abnormality such as cissing and fish eyes on the coated surface after coating and drying, and the difference in coating film thickness in the width and length directions of the coated surface was within ± 10%. X: A uniform coated surface cannot be obtained. That is, the coating surface after coating and drying has abnormalities such as cissing and fish eyes, or the difference in coating thickness in the width and length directions of the coating surface is ± 10.
% Or more. Further, the moisture of the coating liquid soaked into the coated base paper for labels, and the paper was broken due to a decrease in the strength of the paper.

Storage stability A 9 cm heat-sensitive adhesive solution was placed in a glass tube having a diameter of 2 cm and a length of 1 m.
The mixture was sealed for about a minute, left in an atmosphere of 30 ° C. for 30 days, and the change in the liquid state was observed. Before and after the standing, the viscosity was measured with a Brookfield viscometer. The results are shown in Table 2. In addition, this evaluation is as follows. ；: No separation or the like, and the change in viscosity is within 10%. X: Separation is observed or viscosity change is 10% or more.

[0081]

[Table 2]

Effects of Examples 1 to 7 and Comparative Examples 1 and 2 (1) FIG. 2 showing the result of TEM observation in Example 1.
(A) is a result of observing the low-temperature-dried pressure-sensitive adhesive layer at a magnification of 40,000, and shows a portion that is easily dyed by ruthenic acid (component A; St that is easily dyed is copolymerized).
It can be seen that a sea-island structure (a non-adhesive pressure-sensitive adhesive layer) is formed in which is a sea and a portion (component B) that is not easily dyed is an island. FIG. 2 (B) shows the high-temperature dried pressure-sensitive adhesive layer observed at a magnification of 40,000. In contrast to FIG. 2, a portion which is hardly stained with ruthenic acid (component B) becomes a sea and a portion which is easily dyed ( A sea-island structure in which the component A) is an island (excellent pressure-sensitive adhesive layer) is formed. That is, it can be seen that the sea-island of the component A and the component B was reversed by heating to form the pressure-sensitive adhesive layer of the present invention. FIGS. 3A and 3B in Example 2 are TEM photographs of the low-temperature dried pressure-sensitive adhesive layer and the high-temperature dried pressure-sensitive adhesive layer, respectively, observed at a magnification of 100,000. Also in these figures, the same sea-island structure as in Example 1 was observed. In Examples 3 to 7, TEM photographs of the sea-island structure were not observed. However, the polymer compositions of Examples 3 to 7 were the same as in Example 1, and the polymer composition after heating was higher than that before heating. Judging from the large increase in the adhesive strength, it can be said that it also shows the same sea-island structure. Furthermore, as shown in Table 2, it was confirmed that the heat-treated test pieces of Examples 1 to 7 all had higher adhesive strength than the pre-heat-treated test pieces, and as a result, the sea-island structure was reversed. As well as excellent heat resistance after heat treatment.

(2) As can be seen from Table 2, Examples 1 to 7
Is excellent in blocking resistance as compared with Comparative Example 1. In particular, the acrylic acid-based thickener is clearly superior to other urethane-based thickeners and PVA-based thickeners in the relationship between the type of thickener and the blocking resistance. In particular, even if the viscosity fluctuates greatly from 2,000 to 20,000 cps, all show excellent blocking resistance.

(3) When the viscosity of the composition is 40 cps (Comparative Example 1), the viscosity is too low, resulting in poor coatability and poor storage stability. On the other hand, when the viscosity is 45,000 cps (Comparative Example 2), the viscosity is too large to be pumped, and the workability is poor. In Examples 1 to 7, the viscosity was 2,0.
Since the balance is 00 to 20,000 cps, the coatability and storage stability are good.

[0085]

The heat-sensitive adhesive composition and heat-sensitive adhesive sheet of the present invention are substantially non-tacky before heating by reversing the sea-island of component A and component B before and after heat treatment. On the other hand, after heating, excellent adhesive strength can be exhibited. At this time, since the pressure-sensitive adhesive layer after heating has a sea-island structure in which component A is an island and component B is a sea, the adhesive strength after heat treatment is lower than a structure in which component A and component B are uniformly mixed. Is good. Further, in this case, since the component B has a sea-island structure in which the component B is sea after heating, the performance of the component B can be strongly reflected on the pressure-sensitive adhesive layer after heating. Therefore, the pressure-sensitive adhesive composition of the present invention can predict the performance of the pressure-sensitive adhesive layer to some extent from the performance of the pressure-sensitive adhesive layer formed from the component B alone, so that the pressure-sensitive adhesive composition can be efficiently designed. It is possible to do. Further, the pressure-sensitive adhesive composition of the present invention is further excellent in blocking resistance, excellent in coating properties and storage stability, and is extremely useful for applications of pressure-sensitive adhesives.

In particular, when the acrylic acid-based thickener of the fourth invention is used, it has excellent blocking resistance as compared with other thickeners (eg, polyurethane-based and polyvinyl alcohol-based thickeners). Even if the viscosity fluctuates, excellent blocking resistance can be secured. Therefore,
This composition is extremely useful as a heat-sensitive adhesive. Furthermore, in the pressure-sensitive adhesive composition of the present invention, component A
Are discontinuously dispersed, so that if a material having a high alkali solubility or alkali swelling property is used as the component A and a hydrophobic material is used as the component B, the pressure-sensitive adhesive composition or pressure-sensitive adhesive sheet of the present invention can be used. The post-adhesive layer can be used as an alkali-peelable heat-sensitive adhesive sheet having good water resistance and excellent alkali-peelability.

[Brief description of the drawings]

FIG. 1A is a schematic diagram showing a state of a pressure-sensitive adhesive layer of the present invention before heat treatment, and FIG. 1B is a schematic diagram showing a state after heat treatment.

FIG. 2A is a TEM photograph showing the structure of a pressure-sensitive adhesive layer obtained by drying the pressure-sensitive adhesive composition of Example 1 at 40 ° C.
(B) is a TEM photograph showing the structure of the pressure-sensitive adhesive layer obtained by drying the pressure-sensitive adhesive composition of Example 2 at 140 ° C.

FIG. 3A is a TEM photograph showing the structure of a pressure-sensitive adhesive layer obtained by drying the pressure-sensitive adhesive composition of Example 2 at 40 ° C.
(B) is a TEM photograph showing the structure of the pressure-sensitive adhesive layer obtained by drying the pressure-sensitive adhesive composition of Example 3 at 140 ° C.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Jin Kato 1 at Funamicho, Minato-ku, Nagoya-shi, Aichi, Japan

Claims (7)

[Claims] An acid value neutralized with a base of 1 meq /
g or more of the water-soluble resin component A, and a glass transition temperature of -2 obtained by emulsion polymerization of a radical polymerizable monomer.
Component B which is an aqueous emulsion containing a polymer at 0 ° C. or lower
A heat-sensitive adhesive composition comprising:
Brookfield viscosity of 200 CPS to 3
A heat-sensitive adhesive composition having a molecular weight of 000 CPS (12 rpm). 2. The pressure-sensitive adhesive layer formed from the present heat-sensitive pressure-sensitive adhesive composition has an adhesive force of 5 g / 25 mm or less after being stored at 40 ° C. under a pressure of 10 kg / cm 2 for 1 hour. The heat-sensitive adhesive composition as described in the above. 3. 180 defined in JIS Z 0237
The adhesive strength of the pressure-sensitive adhesive layer at a temperature of 25 ° C. by the peeling-off method is 10 g / 25 mm or less, and the heat treatment at 60 ° C. or more reverses the sea and islands of the pressure-sensitive adhesive layer so that the component A becomes an island. 3. The heat-sensitive adhesive composition according to claim 2, wherein the adhesive component of the pressure-sensitive adhesive layer changes to 100 g / 25 mm or more by having a sea-island structure in which the component B is a sea. 4. The heat-sensitive adhesive composition according to claim 1, wherein the thickener is an acrylic acid-based thickener. 5. The component A is a polymer emulsifier used in the emulsion polymerization of the component B, and the polymer as the component B is a radical polymerizable monomer in the presence of the component A. The heat-sensitive adhesive composition according to any one of claims 1 to 4, which is obtained by subjecting a body to emulsion polymerization. 6. A pressure-sensitive adhesive layer formed from the heat-sensitive pressure-sensitive adhesive composition according to any one of claims 1 to 5, which is provided on a substrate, at a temperature of 40 ° C. and a pressure of 10 kg / cm 2.
The adhesive strength of the adhesive layer after storage for 5 hours is 5 g / 25 mm
A heat-sensitive adhesive sheet characterized by the following. 7. 180 defined in JIS Z 0237
The adhesive strength of the pressure-sensitive adhesive layer at a temperature of 25 ° C. according to the peeling method is 10 g / 25 mm or less, and the heat treatment at 60 ° C. or more reverses the sea and islands of the pressure-sensitive adhesive layer, and the component A becomes an island. 7. The heat-sensitive adhesive sheet according to claim 6, wherein the adhesive component of the pressure-sensitive adhesive layer changes to 100 g / 25 mm or more by having a sea-island structure in which the presence component B is a sea.