JP3431768B2 - Composition for heat-sensitive adhesive and heat-sensitive adhesive sheet - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a pressure-sensitive adhesive sheet and its use.
The present invention relates to a pressure-sensitive adhesive composition and a method for producing the pressure-sensitive adhesive composition . More specifically, the present invention is unique in that it is non-adhesive at room temperature or exhibits extremely low adhesiveness and does not exhibit adhesiveness, while it exhibits adhesiveness when heated, and also exhibits adhesiveness when pressed. The heat-sensitive adhesive sheet having the properties of, and having extremely excellent water resistance and moisture resistance ,
Composition for heat-sensitive adhesive used for producing heat-sensitive adhesive sheet and
And a manufacturing method thereof.

[0002]

2. Description of the Related Art Usually, a pressure-sensitive adhesive sheet is stored, distributed, or sold by coating a pressure-sensitive adhesive surface with release paper (release paper). Further, in a roll-up type product such as an adhesive tape, a base material having a back surface subjected to a peeling treatment is used so that it can be rewound when used. The release paper becomes unnecessary after the pressure-sensitive adhesive sheet is attached to the article, and there is a demand for a release-paper-free pressure-sensitive adhesive sheet for reasons such as resource saving and cost reduction. Further, if the adhesive tape can also be used as the base material, the back surface of which is not subjected to the peeling treatment, 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 a release paper, a heat-sensitive pressure-sensitive adhesive sheet coated with a delayed tack type pressure-sensitive adhesive (Japanese Patent Publication No. 62-21835 and Japanese Patent Laid-Open No. 6-10084) is known. Discloses, as a delayed tack type pressure-sensitive adhesive, a pressure-sensitive adhesive obtained by mixing a solid plasticizer such as dicyclohexyl phthalate or its surface coated with a colloid into a thermoplastic resin such as ethylene-vinyl acetate copolymer. There is. And these prior art documents describe that the pressure-sensitive adhesive is non-tacky at room temperature, and the plasticizer is melted by heating to develop the pressure-sensitive adhesive force.

However, the above-mentioned conventional delayed tack type pressure-sensitive adhesive containing a solid plasticizer has various problems as listed in the following (a) to (d), and is limited to a limited special use. Currently, it cannot be used. (A) After the solid plasticizer has been crystallized, the adhesive force is lost, so once it is peeled off from the adherend, it cannot be adhered to the adherend again; (b) Heating to develop the adhesiveness The heating temperature cannot be freely set because the temperature depends on the melting point of the solid plasticizer; (c) The adhesive sheet becomes sticky and loses its flexibility after crystallization, so the adhesive sheet is attached to the adherend. If the adherend is bent or vibration is applied to the adherend after that, there is a risk that the adhesive layer cannot follow the adherend and is peeled off; and (d) The base material used for the adhesive sheet is high-quality paper. In such cases, the plasticizer is likely to exude to the surface of the sheet when the pressure-sensitive adhesive sheet is heated.

[0005]

Therefore, an object of the present invention is that it is non-adhesive or has very low adhesiveness at room temperature, and therefore, it is necessary to use a release paper or to release the surface of the substrate.
It can be handled as it is as a product without any treatment for facilitating it, and when it is heated or pressed, it develops adhesiveness and can be effectively used as an adhesive sheet or tape. Adhesive sheet , it
The present invention is to provide a composition for heat-sensitive adhesive used in, and a method for producing the same. The object of the present invention is to solve the above-mentioned problems (a) in the conventional delayed tack type adhesive.
It is an object of the present invention to provide a heat-sensitive adhesive sheet which is free from (d) and has excellent quality. Furthermore, the objective of this invention is to provide the heat-sensitive adhesive sheet which has more outstanding water resistance and moisture-heat resistance.

[0006]

Means for Solving the Problems The inventors of the present invention have made extensive studies to solve the above problems. As a result, in the presence of a specific water-soluble or water-dispersible copolymer having a carboxyl group neutralized with a specific base, a specific radical-polymerizable monomer containing (meth) acrylic acid alkyl ester as a main component When an aqueous polymer emulsion obtained by emulsion polymerization of the body is applied onto a substrate to form a pressure-sensitive adhesive layer, the pressure-sensitive adhesive sheet obtained thereby shows no tackiness or almost no tackiness at room temperature. It has been found that, when not shown, and when heated or pressurized, it exhibits adhesiveness and can be effectively used as an adhesive sheet.

Further, the present inventors have found that the pressure-sensitive adhesive sheet obtained as described above has a degree of freedom in setting the heating temperature for expressing the tackiness, and that time has passed after being adhered to an adherend. Even if the adhesiveness once expressed is not lost, a good adhesive state is maintained, the adhesive layer does not become hard over time, and the components in the adhesive layer bleed onto the substrate even when heated. I found that I didn't.

Further, the present inventors obtain it by mixing an aqueous emulsion composed of an alkyl (meth) acrylate polymer having a glass transition temperature of −10 ° C. or lower with an aqueous polymer having a Tg of 20 ° C. or higher. A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer formed from the composition has already been applied for a patent, finding that it has the above-described heat-sensitive adhesive property of exhibiting adhesiveness by heating, but this time, its improved invention, namely carboxyl Having a certain proportion of groups and
In the presence of a specific water-soluble or water-dispersible copolymer hexyl group is neutralized with a particular base, emulsion polymerization of a radical polymerizable monomer as a main component (meth) acrylic acid alkyl ester It was found that the heat-sensitive adhesive sheet having an adhesive layer formed from the aqueous polymer emulsion obtained as described above is further excellent in water resistance. In addition, the present inventors
The above-mentioned specific aqueous solution in which the ruboxyl group is neutralized with a specific base.
In water-soluble or water-dispersible copolymers
If the amount of neutralization of the carboxylic acid group exceeds a specified ratio, the polymer
Good surface activity and sufficient water solubility
And completed the present invention based on these various findings.
did.

That is, the present invention provides (1) the following copolymer (a); ○ copolymer (a): α, β-ethylenically unsaturated carboxylic acid unit and hydrophobic radically polymerizable monomer With the unit as the main constitutional unit, the acid value before neutralization with a base is from 30 to 1 per 1 g of the copolymer before neutralization.
A water-soluble or water-dispersible copolymer having a glass transition temperature of 20 ° C. or higher in which a part or all of the carboxyl groups in the copolymer having 260 mg KOH / g are neutralized with a base having a boiling point of 110 ° C. or lower; In the presence, the glass transition temperature of which the main component is (meth) acrylic acid alkyl ester is −
An aqueous polymer emulsion obtained by emulsion-polymerizing a radical-polymerizable monomer that gives a polymer at 10 ° C. or lower ,
And [copolymer (a) part]: [(meth) acrylic acid
Glass transition temperature of -10 containing rutile ester as the main component
Weight ratio of the polymer portion below ℃, the weight ratio of the solid content
And 10:90 to 60:40, which is a composition for heat-sensitive adhesives, and has an adhesive strength of 10 g / 25 at a temperature of 25 ° C. according to a 180 degree pull-off method specified in JIS Z 0237.
The composition for heat-sensitive adhesives is characterized by having a size of not more than mm. And this invention is (2) 30 of the carboxyl groups in the copolymer (a).
The heat-sensitive adhesive composition according to the above (1), wherein mol% or more is neutralized with a base having a boiling point of 110 ° C. or less. Furthermore, this invention is (3) JIS Z which has the adhesive layer formed from the composition for heat-sensitive adhesives of said (1) or (2) on a base material.
The heat-sensitive adhesive sheet is characterized in that the adhesive strength at a temperature of 25 ° C. according to the 180 degree peeling method specified in 0237 is 10 g / 25 mm or less. And this invention is (4) the following copolymer (a);-Copolymer (a): Mainly consisting of an α, β-ethylenically unsaturated carboxylic acid unit and a hydrophobic radically polymerizable monomer unit. As a constitutional unit, the acid value before neutralization with a base is 30 to 30 g per 1 g of the copolymer before neutralization.
A water-soluble or water-dispersible copolymer having a glass transition temperature of 20 ° C. or higher in which a part or all of the carboxyl groups in the copolymer having 260 mg KOH / g are neutralized with a base having a boiling point of 110 ° C. or lower; In the presence, the glass transition temperature of which the main component is (meth) acrylic acid alkyl ester is −
A radically polymerizable monomer that gives a polymer at 10 ° C. or lower ,
[Copolymer (a) part]: [Is the radical polymerizable monomer?
A polymer part having a glass transition temperature of −10 ° C. or lower formed from
Min] used in an amount of 10:90 to 60:40 by weight.
By emulsion polymerization Te, a method for producing a heat-sensitive adhesive composition according to claim 1 consisting of an aqueous polymer Emarujiyon; and, of the carboxyl group in (5) copolymer (a) 30
The method according to (4) above, wherein the mol% or more is neutralized with a base having a boiling point of 110 ° C. or less.

The above-mentioned heat-sensitive adhesive sheet of the present invention can be used without applying a release treatment to the adhesive layer (that is, without using release paper or releasing the back surface of the substrate). It can also be used in a state where a peeling treatment is applied if desired. The glass transition temperature (hereinafter sometimes abbreviated as “Tg”) of the polymer in the present invention is
The value obtained from the following formula.

[0011]

1 / Tg = {W (a) / Tg (a)} + {W (b) / Tg (b)} + {W (c) / Tg (c)} + ... in the above formula Tg = Tg of polymer W (a) = weight fraction of structural unit of monomer (a) in polymer W (b) = weight of structural unit of monomer (b) in polymer Rate W (c) = weight fraction Tg (a) of structural unit consisting of monomer (c) in polymer = glass transition temperature Tg (b) = monomer of homopolymer of monomer (a) = monomer Glass transition temperature of homopolymer (b) Tg (c) = glass transition temperature of homopolymer of monomer (c)

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is described in detail below. First, in the present invention, "presence of the copolymer (a)
The main component is (meth) acrylic acid alkyl ester
To give a polymer having a glass transition temperature of −10 ° C. or lower
Aqueous polymerization obtained by emulsion polymerization of radically polymerizable monomers
"Body emulsion" means the above-mentioned composition for heat-sensitive adhesive.
The fruit of the copolymer (a) constituting the aqueous polymer emulsion
Qualitatively, the total amount is mainly composed of (meth) acrylic acid alkyl ester
It exists in the emulsion polymerization system of the radically polymerizable monomer as a component.
Emulsion polymerization of the radically polymerizable monomer in the presence state
Aqueous polymer emulsion obtained directly by
To taste. Further, the "heat-sensitive adhesive sheet" in the present invention means
Made of the water-soluble or water-dispersible copolymer in the presence of (a) (meth) aqueous polymer emulsion obtained by emulsion polymerization of radical-polymerizable monomer composed mainly of acrylic acid alkyl esters Composition for heat-sensitive adhesive (hereinafter
The heat-adhesive composition is simply referred to as "aqueous polymer emulsion".
U) is used to have a pressure-sensitive adhesive layer formed on a base material, and the shape, size, form, material, etc. of the base material in the heat-sensitive adhesive sheet are not particularly limited and may be any. Therefore, the “heat-sensitive adhesive sheet” of the present invention means a heat-sensitive adhesive sheet in which the base material is a sheet, a heat-sensitive adhesive tape in which the base material is in a tape shape, a base material in a plate shape, and a base material other than those described above. Means the general term for the shapes and forms. Further, the heat-sensitive adhesive sheet of the present invention may have a pressure-sensitive adhesive layer only on one side of the substrate, or may have a pressure-sensitive adhesive layer on both sides of the substrate, or When the base material has a certain thickness, the base material may have an adhesive layer on the surface other than the front surface and / or the back surface.

In the pressure-sensitive adhesive layer of the heat-sensitive pressure-sensitive adhesive sheet of the present invention, the Tg of the copolymer (a) used for producing the above-mentioned aqueous polymer emulsion is 20 ° C. or higher. When the Tg of the copolymer (a) is less than 20 ° C., it is obtained by emulsion-polymerizing a radically polymerizable monomer containing a (meth) acrylic acid alkyl ester as a main component in the presence of the copolymer (a). The pressure-sensitive adhesive layer formed from the aqueous polymer emulsion obtained does not become non-tacky or low-tackiness at room temperature, that is, the tackiness at a temperature of 25 ° C. by the 180 ° peeling method specified in JIS Z 0237 is 10 g / It does not become less than 25 mm, and it becomes tacky even at room temperature, and the object of the present invention cannot be achieved. Further, when the Tg of the copolymer (a) is extremely high, the heating temperature for expressing the adhesiveness becomes high, and the workability and thermal efficiency at the time of sticking the adhesive sheet are lowered, and further, the heating temperature at the time of heating is high. The base material of the heat-sensitive adhesive sheet is likely to deteriorate due to the high temperature. Therefore, from those points, the Tg of the copolymer (a) is preferably 30 to 200 ° C, more preferably 70 ° C to 150 ° C.

Examples of the α, β-ethylenically unsaturated carboxylic acid used for producing the copolymer (a) (copolymer before neutralization) include acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, Itaconic acid, citraconic acid, maleic anhydride, etc. can be mentioned, and 1 type (s) or 2 or more types of these monomers can be used. The amount of the α, β-ethylenically unsaturated carboxylic acid used is obtained by copolymerizing such an unsaturated carboxylic acid and another copolymerizable monomer,
The acid value of the copolymer before neutralization with a base (pre-neutralization copolymer) is 30 to 260 mgKOH per 1 g of the pre-neutralization copolymer.
/ G. If the acid value of the pre-neutralization copolymer is less than 30 mg KOH / g per 1 g of the pre-neutralization copolymer, a copolymer that can be well dissolved or dispersed in water even if it is neutralized with a base is obtained. Difficult to obtain, while 260mgK
If it exceeds OH / g, the water resistance will be poor. The amount of the α, β-ethylenically unsaturated carboxylic acid that gives the above acid value varies depending on the type of the unsaturated carboxylic acid used, but is based on the total weight of all the monomers used for producing the copolymer before neutralization. Based on the above, it is usually preferable to be about 3 to 40% by weight.

As the hydrophobic radically polymerizable monomer used together with the above α, β-ethylenically unsaturated carboxylic acid for producing the copolymer (a) (copolymer before neutralization), 100 g of water is used. Having a solubility to 2 g or less is preferable, for example, methyl methacrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, (meth)
N-propyl acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (meth) acrylic acid n-octyl, isooctyl (meth) acrylate,
Examples thereof include alkyl (meth) acrylates such as n-nonyl (meth) acrylate and isononyl (meth) acrylate; vinyl aromatic monomers such as styrene, α-methylstyrene and vinyltoluene. The amount of the above hydrophobic monomer used is preferably 30 to 80% by weight, based on the total amount of all the monomers provided for synthesizing the copolymer (a).

In order to synthesize the copolymer (a),
A hydrophilic radical-polymerizable monomer other than the above α, β-ethylenically unsaturated carboxylic acid can also be used as necessary, and as such a hydrophilic radical-polymerizable monomer,
For example, methyl acrylate, vinyl acetate, acrylonitrile, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, (meth) Examples thereof include acrylic acid amide, N-methylol acrylamide, glycidyl methacrylate, styrene sulfonic acid and its sodium salt, and 2-acrylamido-2-methylpropane sulfonic acid and its sodium salt.

The type and the proportion of the α, β-ethylenically unsaturated carboxylic acid, the hydrophobic radical-polymerizable monomer and the hydrophilic radical-polymerizable monomer that are optionally used are obtained as described above. The Tg of the polymer is selected to be 20 ° C. or higher based on the above calculation formula.

As the polymerization method for obtaining the above-mentioned pre-neutralized copolymer, various polymerization methods can be adopted, and for example, known methods such as a radiation irradiation polymerization method and a method using a radical polymerization initiator can be used. . Among them, the polymerization method using a radical polymerization initiator is preferable from the viewpoints of easiness of polymerization operation and easiness of controlling the molecular weight of the obtained pre-neutralized copolymer. 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. However, the solution polymerization method is preferable, and α, β-ethylenically unsaturated carboxylic acid and A copolymer before neutralization can be smoothly obtained by dissolving another copolymerizable monomer in an organic solvent and polymerizing with a suitable radical polymerization initiator.

In order to obtain a homogeneous and stable copolymer (a) (copolymer before neutralization), the dropping rate of the monomer is kept so that the monomer ratio in the reaction system is kept as constant as possible. It is desirable to control Specifically, a method in which a monomer having a low copolymerizability and a low reactivity is charged in a reactor in a part or the whole amount at the initial stage of the polymerization, and a monomer having a fast reaction rate is dropped during the reaction. , A part of the monomer with slow reaction rate and a part of the monomer with fast reaction rate are charged in the reactor and the monomer with slow reaction rate is adjusted according to the consumption rate of the monomer with fast reaction rate. A homogeneous copolymer (a) (copolymer before neutralization) can be obtained by adopting a method in which is added dropwise to the reactor.

Examples of the organic solvent preferably used in carrying out the solution polymerization described above include ketone solvents such as acetone, methyl ethyl ketone and methyl isobutyl ketone; acetic acid ester solvents such as ethyl acetate and butyl acetate;
Aromatic hydrocarbon solvents such as benzene, toluene, xylene; Aliphatic hydrocarbon solvents such as cyclohexane, hexane, heptane; Methanol, ethanol, isopropanol, methyl cellosolve, ethyl cellosolve, normal butyl cellosolve, ethylene glycol, propylene glycol, tri Examples thereof include alcohol solvents such as methylolpropane and glycerin; tetrahydrofuran, dioxane, dimethylformamide, dimethylsulfoxide, hexamethylphosphoamide, and the like. These organic solvents may be used alone or in combination of two or more. May be.
Among these, methyl ethyl ketone and / or isopropyl alcohol are more preferably used as the organic solvent.

As the radical polymerization initiator used in the above solution polymerization, any of those used in general radical polymerization can be used. For example, persulfate polymerization such as potassium persulfate and ammonium persulfate. Initiator: 2,2'-azobisisobutyronitrile, 2,2 '
-Azo polymerization initiators such as azobis (2-methylbutyronitrile); organic peroxides such as benzoyl peroxide, lauroyl peroxide; cumene hydroperoxide, te
rt-Butyl hydroperoxide, an oxidizing agent consisting of organic hydroperoxides such as diisopropylbenzene hydroperoxide, and a redox polymerization initiator in combination with a reducing agent such as Rongalit, sodium bisulfite, and ascorbic acid. You can The preferred amount of the polymerization initiator used is 0.1 to 5% by weight based on the total amount of the monomers.

In the above solution polymerization, a chain transfer agent may be appropriately added to the polymerization system in order to adjust the molecular weight of the obtained pre-neutralized copolymer. , Mercaptoacetic acid, mercaptopropionic acid, 2-propanethiol, 1-butanethiol, 2-
Methyl-2-propanethiol, 2-mercaptoethanol, ethylmercaptoacetate, thiophenol,
2-naphthalene thiol, dodecyl mercaptan, thioglycerol, etc. can be mentioned.

The polymerization temperature for obtaining the copolymer before neutralization is
It is preferably about 10 to 150 ° C, and 60 to 100
More preferably, it is ° C. The polymerization time is 1 to 10
0 hours is suitable, and more preferably 3 to 10 hours.

The pre-neutralized copolymer preferably has a number average molecular weight of 1,000 to 500,000.
If the number average molecular weight of the pre-neutralization copolymer is less than 1,000, the water resistance and moisture resistance of the pressure-sensitive adhesive layer in the heat-sensitive pressure-sensitive adhesive sheet tend to be poor, while if it exceeds 500,000, the viscosity becomes high. Therefore, it becomes difficult to produce the pre-neutralized copolymer itself.

Next, some or all of the carboxyl groups in the pre-neutralized copolymer obtained by the above-mentioned polymerization are neutralized with a base having a boiling point of 110 ° C. or lower to obtain the copolymer (a) used in the present invention. ). When the boiling point of the base used for neutralization exceeds 110 ° C., the base remains in the pressure-sensitive adhesive layer after coating and drying, resulting in poor water resistance and moisture resistance of the pressure-sensitive adhesive layer. Specific examples of the base having a boiling point of 110 ° C. or lower used for neutralizing the carboxyl group of the pre-neutralization copolymer include ammonia, methylamine, ethylamine, propylamine, isopropylamine, butylamine, amylamine, dimethylamine, diethylamine, and diamine. Propylamine, diisopropylamine, trimethylamine, triethylamine, allylamine and the like can be mentioned,
Of these, ammonia is preferably used.

The neutralization amount of the carboxyl group of the copolymer before neutralization is preferably 30 mol% or more, and 50 mol%
The above is more preferable. When the amount of neutralization of carboxyl groups in the pre-neutralization copolymer is less than 50 mol%, the surfactant (A) and water solubility of the copolymer (a) are likely to decrease.

In neutralizing the carboxyl group in the pre-neutralized copolymer with a base, the pre-neutralized copolymer obtained by the solution polymerization as described above is directly recovered in the reaction medium without being recovered from the reaction medium. From the viewpoint of easy operation, it is preferable to make it exist (particularly dissolved in an organic solvent) and then add a neutralizing base thereto. At that time, it is more preferable to add a neutralizing base as an aqueous solution because the carboxyl groups are smoothly neutralized.

By the above, a copolymer (a) in which some or all of the carboxyl groups are neutralized can be obtained.
The copolymer (a) may be taken out from the neutralized reaction system and used for emulsion polymerization of a radical-polymerizable monomer mainly composed of (meth) acrylic acid alkyl ester. However, the pre-neutralization copolymer is produced by solution polymerization, and an aqueous solution of a base for neutralization is added to neutralize the carboxyl groups in the pre-neutralization copolymer to give the copolymer ( After forming a), the organic solvent present in the system is removed by a suitable method (for example, under reduced pressure) to obtain the copolymer (a).
It is preferred that the solution is made into an aqueous solution or aqueous dispersion having a concentration of about 10 to 60% by weight, and a part or the whole thereof is taken out and used in the next step of producing an aqueous emulsion.

The aqueous polymer emulsion used in the present invention has a glass transition temperature of -10.degree. C. or less containing a (meth) acrylic acid alkyl ester as a main component in the presence of the above-mentioned copolymer (a). It is formed by emulsion-polymerizing a radical-polymerizable monomer that gives a coalescence. The radical-polymerizable monomer containing (meth) acrylic acid alkyl ester as a main component for forming an aqueous polymer emulsion has (meth) acrylic acid alkyl ester as a main component, and is copolymerized with this as necessary. It is preferable to use a small amount (preferably 40% by weight or less) of a combination of other possible radically polymerizable monomers (hereinafter, this may be referred to as “copolymerizable monomer”).

The above-mentioned (meth) acrylic acid alkyl ester used for producing the aqueous polymer emulsion has an alkyl group having 1 to 12 carbon atoms (meth).
Alkyl acrylates are preferably used, for example, 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, (meth)
2-ethylhexyl acrylate, (meth) acrylic acid n
-Octyl, isooctyl (meth) acrylate, n-nonyl (meth) acrylate and isononyl (meth) acrylate, decyl (meth) acrylate, lauryl (meth) acrylate, etc. may be mentioned. )
One kind or two or more kinds of alkyl acrylate can be used. Particularly, in the present invention, in the production of the aqueous polymer emulsion, as the (meth) acrylic acid alkyl ester, one or more of (meth) acrylic acid alkyl ester having an alkyl group having 4 to 9 carbon atoms is mainly used. It is preferably used as a component.

Further, as described above, in the production of the aqueous polymer emulsion, other copolymerizable monomers may be used as a minor component together with the (meth) acrylic acid alkyl ester, but such copolymerizable monomer may be used. Examples of the monomer include vinyl aromatic monomers such as styrene, α-methylstyrene, and vinyltoluene; and (meth) acrylic acid, crotonic acid, cinnamic acid, itaconic acid, fumaric acid, maleic acid, and the like. Saturated carboxylic acid; itaconic acid monoethyl ester,
Monoalkyl esters of unsaturated dicarboxylic acids such as fumaric acid monobutyl ester and maleic acid monobutyl ester; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, polyethylene glycol mono (meth) acrylate, Hydroxyl group-containing vinyl monomers such as polypropylene glycol mono (meth) acrylate; (meth) acrylonitrile, vinyl acetate,
(Meth) acrylamide, N-methylol acrylamide, glycidyl methacrylate, vinyl acetate, vinyl chloride, vinylidene chloride and the like can be mentioned, and one or more of these copolymerizable monomers can be used.

When the above-mentioned other copolymerizable monomer is used, the use of the other copolymerizable monomer is based on the total weight of the radical-polymerizable monomers used for producing the aqueous polymer emulsion. The proportion is preferably 40% by weight or less as described above. If the proportion of the other copolymerizable monomer used exceeds 40% by weight, the pressure-sensitive adhesive layer formed from the aqueous polymer emulsion tends to have insufficient tackiness, and the tackiness of the heat-sensitive pressure-sensitive adhesive sheet may be increased. It becomes difficult to express.

The method for producing the aqueous polymer emulsion is not particularly limited and can be carried out in the same manner as the conventionally known emulsion polymerization. That is, in the presence of the copolymer (a), the radical-polymerizable monomer containing (meth) acrylic acid alkyl ester as a main component is uniformly dispersed in an aqueous medium, and emulsion polymerization is performed using a polymerization initiator. By doing so, an aqueous polymer emulsion can be obtained. In such emulsion polymerization, since the copolymer (a) functions as a surfactant (emulsifier), the amount of the emulsifier such as a protective colloid or other surfactant used during emulsion polymerization is more than that in the case of normal emulsion polymerization. It is possible to make it small and, if desired, to use no other emulsifier at all. As a result, the heat-sensitive adhesive sheet of the present invention is superior in water resistance to an adhesive sheet having an adhesive layer formed by using an aqueous emulsion obtained by ordinary emulsion polymerization.

As the polymerization initiator that can be used in emulsion polymerization, any of the polymerization initiators generally used in emulsion polymerization can be used. For example, to obtain the above-mentioned copolymer (a) As the radical polymerization initiator, the same organic peroxides, inorganic peroxides, azo compounds and the like as exemplified above can be used. The preferred amount of the polymerization initiator used is 0.1 to 0.1, based on the total amount of the monomers.
It is 5% by weight.

In the above-mentioned emulsion polymerization for producing the aqueous polymer emulsion, a chain transfer agent may be used for controlling the molecular weight of the obtained polymer, and such a chain transfer agent may be a copolymer ( Chain transfer agents having a mercapto group similar to those described above for the production of a) are preferably used.

The polymerization temperature in the production of the aqueous polymer emulsion is preferably about 0 to 150 ° C, more preferably 20 to 90 ° C. Further, the polymerization time at that time is preferably about 1 to 24 hours,
More preferably, it is about 3 to 8 hours.

In the aqueous polymer emulsion, a polymer portion produced from the copolymer (a) and a radical-polymerizable monomer containing an alkyl (meth) acrylate as a main component [hereinafter referred to as "(meta ) May be referred to as "acrylic acid alkyl ester-based polymer portion"] means a core / shell structure, that is, a structure in which the (meth) acrylic acid alkyl ester-based polymer serves as the core and the copolymer (a) serves as the shell. It is presumed that it is composed.

In the aqueous polymer emulsion, the weight ratio of the copolymer (a) portion and the (meth) acrylic acid alkyl ester-based polymer portion is such that the copolymer (a) has a weight ratio of solid content. moiety: (meth) acrylic acid alkyl ester-based polymer portion = 5: 95 to 80: is preferably 20, 10: 90-60: and more preferably 40. When the content of the copolymer (a) is less than 5% by weight based on the solid content (total amount of the polymer) in the aqueous polymer emulsion, in the resulting pressure-sensitive adhesive sheet, the pressure-sensitive adhesive layer has a room temperature (25 ° C.). In this case, the adhesive strength in 10) exceeds 10 g / 25 mm, and such an adhesive sheet is not included in the scope of the present invention, which is an adhesive sheet that does not require release treatment (treatment with release paper or release agent). On the other hand, when the proportion of the copolymer (a) part in the aqueous polymer emulsion exceeds 80% by weight based on the solid content of the aqueous polymer emulsion, the Tg of the pressure-sensitive adhesive layer formed from the aqueous polymer emulsion is If the temperature becomes too high, the adhesive performance developed by heating or pressing tends to be inferior. Numerical range mentioned above
Of these, particularly in the present invention, the copolymer (a) moiety:
Weight of alkyl (meth) acrylate polymer
The amount ratio is from 10:90, which is the more preferable range described above.
60:40, the aqueous polymer emulsion
Prepare yon .

The above-mentioned aqueous polymer emulsion used in the pressure-sensitive adhesive layer of the heat-sensitive pressure-sensitive adhesive sheet of the present invention is an antifoaming agent, a surfactant or a fungicide which is usually used for general pressure-sensitive adhesives depending on its use. , Fragrance, neutralizer, tackifier, thickener, leveling adjuster, antifreeze, foaming agent, antioxidant, UV absorber, reinforcing agent, filler, pigment, optical brightener, antistatic agent , Anti-blocking agent, flame retardant, crosslinking agent, plasticizer, lubricant, organic solvent or colorant, etc.

In the heat-sensitive adhesive sheet of the present invention, the kind of the substrate is not particularly limited, and any suitable one can be used depending on the application of the heat-sensitive adhesive sheet.
Examples thereof include films and sheets made of paper, leather, wood, metal, glass and various plastics, plates, foamed plastic sheets and the like. In this case, examples of the above-mentioned base material made of plastic include base materials made of polyester, polyamide, vinyl chloride polymer, polyethylene, polypropylene, polyurethane and the like. Further, the shape of the base material may be any of a long body, a body cut into a predetermined size (for example, a shape cut beforehand into a rectangular shape, a circular shape, an elliptical shape, or the like).

The heat-sensitive adhesive sheet of the present invention can be produced by applying the above-mentioned aqueous polymer emulsion onto one or both surfaces of the above-mentioned substrate and drying it by a suitable method. At that time, the method for applying the pressure-sensitive adhesive composition to the substrate is not particularly limited, and for example, it may be performed using any method such as roll coater coating, spray coating, cast coating, doctor plate coating, and brush coating. You can In drying the pressure-sensitive adhesive composition applied on the substrate, it is necessary to heat the pressure-sensitive adhesive sheet in the finally obtained pressure-sensitive adhesive layer at a temperature at which the pressure-sensitive adhesive layer does not exhibit tackiness at room temperature. The copolymer (a) contained in the product is dried at a temperature not higher than Tg. A more preferable drying temperature is 10 to 20 ° C. lower than the Tg of the copolymer (a).

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 application, etc., but generally it is preferable to set the thickness to about 1 μm to 1 mm, whereby the heat-sensitive adhesive layer When the sheet is heated and / or pressed to be adhered to the adherend, the pressure-sensitive adhesive layer can exhibit good tackiness.

The heat-sensitive adhesive sheet of the present invention is manufactured according to JIS Z
180 degree temperature specified by 0237 2
Since the adhesive strength at 5 ° C is 10g / 25mm or less and does not show the adhesiveness at room temperature or the adhesive strength at room temperature is very small, the release treatment for the adhesive layer is different from the conventional general-purpose adhesive sheet. The product can be stored, distributed, or sold without being subjected to the above, simply packaged as it is as in a normal non-sticky product, or without packaging.
At that time, the term “without peeling treatment” in the present invention means
This means that the pressure-sensitive adhesive layer of the heat-sensitive pressure-sensitive adhesive sheet is not covered with release paper, and that the roll-up type pressure-sensitive adhesive tape is not subjected to a special release treatment on the back surface of the substrate. Of course, if necessary, for example, the adhesive strength at 25 ° C is 3 to 10 g / 25 mm.
In the case, depending on the application of the pressure-sensitive adhesive sheet, it may be subjected to a peeling treatment before use.

In attaching the heat-sensitive adhesive sheet of the present invention to an adherend, the pressure-sensitive adhesive layer of the heat-sensitive adhesive sheet is heated, the side of the adherend is heated, or the pressure-sensitive adhesive layer of the heat-sensitive adhesive sheet and The heat-sensitive adhesive sheet can be attached to the adherend by heating both of the adherends. The heating temperature for expressing the tackiness of the pressure-sensitive adhesive layer depends on the Tg of the copolymer (a) contained in the pressure-sensitive adhesive composition, and is usually 10 ° C or higher, preferably 30 ° C or higher higher than the Tg. Is suitable. In the case where the pressure-sensitive adhesive layer of the heat-sensitive pressure-sensitive adhesive sheet of the present invention is made to exhibit tackiness by pressurization, the pressure-sensitive adhesive sheet is applied with a pressing force which is about the writing pressure when writing with a ballpoint pen. Can be attached to an adherend.

The pressure-sensitive adhesive sheet of the present invention once adhered to an adherend, even if the temperature returns to room temperature or the pressing force is released,
It adheres well to the adherend without losing its adhesiveness,
It will not come off naturally. When the heat-sensitive adhesive sheet of the present invention is desired to be peeled off from the adherend, it can be easily peeled off from the adherend by pulling it with a hand or the like, like a general-purpose pressure-sensitive adhesive sheet. Since the layers are sticky,
It can be reattached to the same adherend or another adherend.

The material and type of the adherend to which the heat-sensitive adhesive sheet of the present invention can be stuck are not particularly limited, and examples thereof include 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 polymer, and rubbers.

[0047]

EXAMPLES The present invention will be specifically described below with reference to Synthesis Examples, Examples and Comparative Examples, but the present invention is not limited thereto. In the following examples, "parts" and "%" represent "parts by weight" and "% by weight", respectively, unless otherwise specified. The adhesive strength, holding power, probe tack and water resistance of the adhesive sheet were measured or evaluated by the following methods.

(1) Adhesive Strength of Adhesive Sheet: A polyester film having a thickness of 50 μm was coated with the adhesive composition so that the thickness of the coating film after drying was 20 μm to 30 μm, and dried at 70 ° C. for 5 minutes. Make an adhesive sheet.
The adhesive sheet was cut into a specimen having a width of 25 mm and a length of about 250 mm. The test piece was (i) as it was without heating (25 ° C.), (ii) after heating to 100 ° C. for 2 minutes, or (iii) after heating to 140 ° C. for 2 minutes, and then a polished stainless steel test plate. Stick it on a plate and press it back and forth once with a 2 kg rubber roller, and after 30 minutes 300 mm /
The 180- degree peeling adhesion to the test plate was determined at a pulling speed of min. It was measured according to the adhesive strength of JIS Z 0237.

(2) Holding power of adhesive sheet: JIS Z
It was measured according to the holding power of 0237. That is, the same pressure-sensitive adhesive sheet as in the case of the pressure-sensitive adhesive test was prepared, and the pressure-sensitive adhesive sheet was cut into a width of 25 mm and a length of about 150 mm to obtain a test piece. (I) The test piece was left as it was without heat treatment (25
C.), (ii) after heating at 100 ° C. for 2 minutes, or (iii) after heating at 140 ° C. for 2 minutes, the test plate is attached to a stainless steel plate so that the area of 25 mm × 25 mm of the test piece is in contact, A 2 Kg rubber roller was reciprocated once for pressure bonding, and after 30 minutes, a time of applying 1 kg load at 40 ° C. and peeling off was measured. When it was held for 3 hours, the displaced distance was measured. In addition, when a load was applied and the film peeled off immediately, it was set to "0 minutes".

(3) Adhesive sheet probe tack: JI
It was measured according to the probe tack test of S Z 0237. That is, the same pressure-sensitive adhesive sheet as in the case of the pressure-sensitive adhesive strength test was prepared, and the pressure-sensitive adhesive sheet was cut into a width of about 20 mm and a length of about 20 mm to obtain a test piece. Using a test piece, after performing the same operations as (i) to (iii) in the above item (2), a cylindrical probe having a diameter of 5 mm, a contact speed and a peeling speed of 0.2 per second.
cm, contact load 0.98 ± 0.01 N / cm.

(4) Water resistance of pressure-sensitive adhesive sheet: The same pressure-sensitive adhesive sheet as in the case of the pressure-sensitive adhesive strength test was prepared, and it was immersed in water at 20 ° C for 1
The whitening state after immersion in time was observed with the naked eye, and the case where no whitening occurred was evaluated as ◯, and the case where whitening occurred was evaluated as x.

<< Synthesis Example 1 >> [Preparation of Copolymer (a ₁ ) Aqueous Solution] (1) 20 parts of butyl methacrylate, 10 parts of methyl methacrylate, 35 parts of acrylonitrile, 2-methacrylic acid
0.5 part of 2,2′-azobisisobutyronitrile was dissolved in a mixed solution of 10 parts of hydroxyethyl, 25 parts of methacrylic acid and 100 parts of methyl ethyl ketone, and a stirrer, a condenser, a thermometer, and a nitrogen introduction tube were provided. After charging into a flask and heating at 80 ° C. for 4 hours under a nitrogen atmosphere, 0.5 part of 2,2′-azobisisobutyronitrile was further charged, and the mixture was heated at the same temperature for 5 hours to obtain a solid content of 50. % Of a pre-neutralized copolymer (acid value 162.5 mg KOH / g copolymer) in methyl ethyl ketone was obtained. (2) To 201 parts of the methylethylketone solution of the pre-neutralized copolymer obtained in (1) above, with stirring, 3.9%
100 parts of ammonia water was gradually added to neutralize the carboxyl groups in the pre-neutralization copolymer to adjust the pH of the reaction solution to 7
After adjusting to about -8, methyl ethyl ketone was removed under reduced pressure at a temperature of 50 ° C to obtain an aqueous solution (pH 7.7) of the carboxyl group-neutralized copolymer (a) (solid content 54%). Hereinafter, this is referred to as "copolymer (a ₁ ) aqueous solution".

<Synthesis Examples 2 to 7> Solution polymerization was carried out in the same manner as in Synthesis Example 1 using the monomers shown in Table 2 below to obtain a methyl ethyl ketone solution of the copolymer before neutralization. Ammonia water or triethanolamine aqueous solution was added in the same manner as in Synthesis Example 1 to neutralize the carboxyl groups in the pre-neutralization copolymer to adjust the pH of the reaction solution to about 7 to 8, and then methyl ethyl ketone was added under reduced pressure. removal of the neutralized copolymer of a carboxyl group (a ₂₎ ~ copolymer (a ₃₎ solution and the copolymer (b ₁₎ ~ copolymer (b ₄₎ aqueous solution was prepared respectively.

Contents of aqueous solution of copolymer (a ₁ ) -copolymer (a ₃ ) and copolymer (b ₁ ) -copolymer (b ₄ ) obtained in Synthesis Examples 1 to 7 above Table 2 below shows the monomer composition of the copolymer (copolymer before neutralization) contained in the aqueous solution, the Tg, and the type of the neutralizing base. Monomers are shown by abbreviations in Tables 2 and 3 below, and the abbreviations and their contents are as shown in Table 1 below.

[0055]

[Table 1] Symbol: Kind of monomer BMA: Butyl methacrylate MMA: Methyl methacrylate AN: Acrylonitrile HEMA: 2-Hydroxyethyl methacrylate MAA: Methacrylic acid ST: Styrene AA: Acrylic acid AEH: 2-Ethylhexyl acrylate BA: Butyl acrylate EA: Ethyl acrylate INA : Isononyl acrylate NMAM: N-methylol acrylamide

[0056]

[Table 2]

Example 1 (1) A monomer mixture was prepared by mixing 95 parts of 2-ethylhexyl acrylate and 5 parts of 2-hydroxyethyl methacrylate. (2) 100 parts of deionized water and Synthesis Example 1 were placed in a flask equipped with a stirrer, a thermometer, a condenser, and a nitrogen introducing tube.
30 parts of the aqueous solution of the copolymer (a ₁ ) prepared in _1. was added and heated to 60 ° C. under a nitrogen atmosphere, and then 5 parts of an aqueous solution of t-butyl hydroperoxide, Rongalit (trade name; formaldehyde sodium sulfo) 5 parts of a 10% aqueous solution of xylate dihydrate) and 100 parts of the monomer mixture prepared in (1) above were added dropwise over 3 hours as separate supplies. After the dropping, the reaction was continued for another 2 hours at the same temperature to complete the polymerization to obtain an aqueous polymer emulsion having a solid content concentration of about 49%. The content of the obtained aqueous polymer emulsion was as shown in Table 3 below. (3) The aqueous polymer emulsion obtained in (2) above is applied to a polyester film having a thickness of 50 μm by a bar coater so that the pressure-sensitive adhesive layer has a thickness of 20 to 30 μm and dried at 70 ° C. An adhesive sheet was prepared by drying at a drying temperature for 5 minutes. (4) When the adhesive strength, holding power, probe tack and water resistance of the pressure-sensitive adhesive sheet obtained in (3) above were measured or evaluated by the above methods, the results were as shown in Table 4 below.

Example 2 (1) 25 parts of butyl acrylate, 70 parts of 2-ethylhexyl acrylate, 4.9 parts of acrylonitrile and N
A monomer mixture was prepared by mixing 0.1 part of methylol acrylamide. (2) Copolymer (a ₂ ) aqueous solution 3 prepared in Synthesis Example 2
0 part and 40 parts of deionized water were mixed with the monomer mixture prepared in the above (1) and emulsified by a three-one motor to prepare an aqueous emulsion dispersion. The content of the obtained aqueous polymer emulsion was as shown in Table 3 below. (3) In a flask similar to that used in (2) of Example 1, 60 parts of deionized water and sodium carbonate (neutralizing agent).
0.2 part was added, the inner temperature of the flask was maintained at 70 ° C. while blowing nitrogen, and the aqueous solution of ammonium persulfate (ammonium persulfate / deionized water = 0.3 part /
9.7 parts) and 200 parts of the aqueous emulsion dispersion prepared in (2) above were added dropwise over 3 hours, and then the reaction was continued for another 2 hours to complete the polymerization, and the solid content concentration was about 49
% Aqueous polymer emulsion was prepared. The content of the obtained aqueous polymer emulsion was as shown in Table 3 below. (4) Using the aqueous polymer emulsion obtained in (3) above, a pressure-sensitive adhesive sheet was prepared in the same manner as in (3) of Example 1, and its adhesive strength, holding power, probe tack and water resistance were described above. When measured or evaluated by the method, the results were as shown in Table 4 below.

Example 3 (1) 35 parts of ethyl acrylate, 6 butyl acrylate
A monomer mixture was prepared by mixing 0 parts, 4.7 parts of methyl methacrylate and 0.3 parts of N-methylol acrylamide. (2) Synthesis Example 3 at the time of producing the aqueous polymer emulsion
20 parts of the aqueous copolymer (a ₃ ) solution prepared in
When an aqueous polymer emulsion was prepared by emulsion polymerization in the same manner as in (2) of Example 1 except that 100 parts of the monomer mixture prepared in Example 1 was used, the aqueous polymer emulsion as shown in Table 3 below was obtained. was gotten. (3) Using the aqueous polymer emulsion obtained in (3) above, a pressure-sensitive adhesive sheet was prepared in the same manner as in (3) of Example 1, and its adhesive strength, holding power, probe tack and water resistance were described above. When measured or evaluated by the method, the results were as shown in Table 4 below.

Example 4 (1) 95 parts of butyl acrylate, 4 acrylonitrile
Parts and 1 part of acrylic acid were mixed to prepare a monomer mixture. (2) Synthesis Example 1 during the production of the aqueous polymer emulsion
30 parts of the aqueous solution of the copolymer (a ₁ ) prepared in (1) above
Using 100 parts of the monomer mixture prepared in Example 1, emulsion polymerization was carried out in the same manner as in (2) of Example 1 to prepare an aqueous polymer emulsion. As a result, an aqueous polymer emulsion as shown in Table 3 below was obtained. Was given. (3) Using the aqueous polymer emulsion obtained in (3) above, a pressure-sensitive adhesive sheet was prepared in the same manner as in (3) of Example 1, and its adhesive strength, holding power, probe tack and water resistance were described above. When measured or evaluated by the method, the results were as shown in Table 4 below.

Comparative Examples 1 to 4 As a radical-polymerizable monomer mixture containing a (meth) acrylic acid alkyl ester polymer as a main component, a monomer mixture 10 shown in Table 3 below.
Emulsion polymerization was carried out in the same manner as in Example 1 except that 0 part by weight and 30 parts by weight of the aqueous copolymer solution shown in Table 3 below were used to prepare aqueous polymer emulsions. A pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1 by using the combined emulsion, and its adhesive strength, holding power, probe tack and water resistance were measured or evaluated by the above-mentioned methods, and the results shown in Table 4 below were obtained. there were.

Comparative Example 5 The copolymer (a
₁ ) An aqueous polymer emulsion was prepared in the same manner as in Example 1 except that 20 parts of 25% sodium dodecylbenzenesulfonate aqueous solution was used in place of 30 parts of the aqueous solution, and the aqueous polymer emulsion was used. When a pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1 and its adhesive force, holding force, probe tack and water resistance were measured or evaluated by the above-mentioned methods, the results were as shown in Table 4 below.

[0063]

[Table 3]

[0064]

[Table 4]

From the results shown in Table 4 above, it is a copolymer obtained by copolymerizing a monomer mixture mainly composed of α, β-ethylenically unsaturated carboxylic acid and a hydrophobic radically polymerizable monomer. Copolymer (a ₁ ) having a glass transition temperature of 20 ° C. or higher in which some or all of carboxyl groups in the copolymer are neutralized with a base having a boiling point of 110 ° C. or less
Example 1 having a pressure-sensitive adhesive layer formed from an aqueous polymer emulsion obtained by emulsion-polymerizing a radical-polymerizable monomer containing a (meth) acrylic acid alkyl ester as a main component in the presence of (a ₃ ). -4 adhesive sheets are JIS Z
The adhesive strength at a temperature of 25 ° C. according to the 180 degree peeling method specified in 0237 is 10 g / 25 mm or less and does not exhibit adhesiveness at room temperature, while it exhibits good adhesiveness when heated, and as a heat-sensitive adhesive sheet It turns out that it can be used effectively.

On the other hand, Comparative Example 1 and Comparative Examples 3 to
No. 4, which is a copolymer obtained by copolymerizing a monomer mixture mainly composed of α, β-ethylenically unsaturated carboxylic acid and a hydrophobic radically polymerizable monomer, and having one carboxyl group. Radical polymerizable monomer containing (meth) acrylic acid alkyl ester as a main component in the presence of a copolymer whose part or the whole amount is neutralized by a base but whose Tg is lower than 20 ° C. In the case of a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer formed from an aqueous polymer emulsion obtained by emulsion-polymerizing, it already has high adhesiveness even at room temperature and has no heat-sensitive property.

Further, from the results of Comparative Examples 2 and 4, it is obtained by copolymerizing a monomer mixture mainly composed of α, β-ethylenically unsaturated carboxylic acid and a hydrophobic radically polymerizable monomer. It can be seen that the water resistance of the pressure-sensitive adhesive sheet becomes poor when a copolymer having a carboxyl group neutralized with a base having a boiling point higher than 110 ° C. is used. In addition, from the results of Comparative Example 5, a usual surfactant was used without using the above-mentioned copolymer (a) (meta).
In a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer formed from an aqueous polymer emulsion obtained by emulsion-polymerizing a radical-polymerizable monomer having an alkyl acrylate as a main component,
The pressure-sensitive adhesive layer already exhibits tackiness even at room temperature, and the tackiness is basically the same before and after the heat treatment.

[0068]

EFFECTS OF THE INVENTION The heat-sensitive adhesive sheet of the present invention exhibits no or almost no adhesiveness at room temperature, and therefore, an adhesive such as the use of release paper or the application of a release agent to the back surface of a substrate. There is no need to perform a peeling treatment on the layers, and it can be stored, distributed and / or sold as it is without packaging, and in terms of resource saving, simplification of the process at the time of manufacturing an adhesive sheet and cost. Very good. Then, the heat-sensitive adhesive sheet of the present invention can express various adhesive properties from high adhesiveness to moderate adhesiveness, and in some cases to slightly low adhesiveness by heating and / or pressurizing. By utilizing such characteristics, it can be effectively used in, for example, labels, tapes, seals for packages, wallpaper, marking, and a wide range of other applications. Especially when used for wallpaper etc.,
It is also possible to use the method of positioning by utilizing low adhesiveness and then fixing the wallpaper by applying heat by applying heat.

Moreover, the heat-sensitive adhesive sheet of the present invention exhibits adhesiveness by heating and / or pressurizing and is adhered to an adherend, and even after the temperature returns to room temperature, the adhesive force once exhibited is exhibited. Since it is maintained, the adhered pressure-sensitive adhesive sheet does not peel off from the adherend. Then, if you want to peel off the heat-sensitive adhesive sheet of the present invention stuck to the adherend, it can be easily peeled off by just pulling with a hand,
The peeled one can be re-attached to the same adherend or another adherend if necessary. Furthermore, in the heat-sensitive adhesive sheet of the present invention, there is a degree of freedom in setting the heating temperature for expressing the adhesiveness, and since the adhesive layer does not become hard over time, even if the adhesive sheet is folded, There is no fear of peeling from the adherend, and there is no trouble that the components in the pressure-sensitive adhesive layer ooze out onto the substrate. Then, in the present invention, the aqueous polymer emulsion used to form the pressure-sensitive adhesive layer does not contain a low molecular weight surfactant, or even when it contains a water-based emulsion obtained by ordinary emulsion polymerization. Since it can be less than the amount contained in the polymer emulsion, a heat-sensitive adhesive sheet having an adhesive layer with excellent water resistance can be obtained.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-57-12084 (JP, A) JP-A-8-269420 (JP, A) US Pat. No. 5385967 (US, A) (58) Fields investigated (Int .Cl. ⁷ , DB name) C09J 7/02 C08F 2/22 C08F 2/44 C08F 265/06 C09J 133/06

Claims (5)

(57) [Claims] 1. A copolymer (a) below: ○ Copolymer (a): An α, β-ethylenically unsaturated carboxylic acid unit and a hydrophobic radically polymerizable monomer unit as main constituent units, The acid value before neutralization with a base is 30 to 1 g of the copolymer before neutralization.
A water-soluble or water-dispersible copolymer having a glass transition temperature of 20 ° C. or higher in which a part or all of the carboxyl groups in the copolymer having 260 mg KOH / g are neutralized with a base having a boiling point of 110 ° C. or lower; In the presence of an aqueous polymer emulsion obtained by emulsion-polymerizing a radically polymerizable monomer containing a (meth) acrylic acid alkyl ester as a main component and having a glass transition temperature of −10 ° C. or less , and [Copolymer (a) part
Min]: [(meth) acrylic acid alkyl ester as the main component
Of the polymer portion having a glass transition temperature of −10 ° C. or less]
The weight ratio is 10:90 to 60: 4 as the weight ratio of the solid content.
A composition for a heat-sensitive adhesive, which is 0, and has an adhesive strength of 10 g / 25 mm or less by a 180 degree pull-off method specified in JIS Z 0237 at a temperature of 25 ° C. . 2. The composition for heat-sensitive adhesives according to claim 1, wherein 30 mol% or more of the carboxyl groups in the copolymer (a) are neutralized with a base having a boiling point of 110 ° C. or less. 3. A JI having a pressure-sensitive adhesive layer formed from the composition for heat-sensitive pressure-sensitive adhesive according to claim 1 or 2 on a substrate.
A heat-sensitive adhesive sheet characterized by having an adhesive strength of 10 g / 25 mm or less at a temperature of 25 ° C. according to a 180 degree peeling method specified in S Z 0237. 4. The following copolymer (a); ○ copolymer (a): An α, β-ethylenically unsaturated carboxylic acid unit and a hydrophobic radically polymerizable monomer unit as main constituent units, The acid value before neutralization with a base is 30 to 1 g of the copolymer before neutralization.
A water-soluble or water-dispersible copolymer having a glass transition temperature of 20 ° C. or higher in which a part or all of the carboxyl groups in the copolymer having 260 mg KOH / g are neutralized with a base having a boiling point of 110 ° C. or lower; In the presence of a radical-polymerizable monomer having a glass transition temperature of −10 ° C. or less containing a (meth) acrylic acid alkyl ester as a main component , a [polymer (a) part]
Min]: [glass formed from the radically polymerizable monomer
Polymer portion having a transition temperature of -10 ° C or less] is 1 by weight.
Emulsion polymerization is performed using an amount of 0:90 to 60:40 ,
The method for producing the composition for a heat-sensitive adhesive according to claim 1, which comprises an aqueous polymer emulsion. 5. The method according to claim 4, wherein 30 mol% or more of the carboxyl groups in the copolymer (a) are neutralized with a base having a boiling point of 110 ° C. or less.