JP2000191984A - Watwer dispersion type pressure sensitive adhesive composition, production thereof and its adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a pressure sensitive adhesive composition excellent in adhe sive characteristics, being a water dispersion type showing less problems in environmental hygiene and safety and health, and also excellent in water proof property by using a urethane-modified acrylic material. SOLUTION: This water dispersion type pressure sensitive adhesive is produced by processes comprising (a) a process for obtaining a urethane pre- polymer containing carboxyl group and (meth)acryloyl group, (b) a process for mixing 2-10 wt.% urethane pre-polymer with 98-90 wt.% acrylic monomer and neutralizing with a base, (c) a process for dispersing the neutralized material into water and (d) a process for chain extending the urethane pre-polymer by adding a polyamine and polymerizing the acrylic monomer by adding a radical polymerization initiator.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-dispersed pressure-sensitive adhesive composition comprising a urethane-modified acrylic polymer dispersed in water, a method for producing the same, and a sheet-shaped pressure-sensitive adhesive composition. Adhesive tape in the form of tape or tape
About

[0002]

2. Description of the Related Art In recent years, in view of environmental hygiene and safety and hygiene, a method of producing an adhesive sheet using a pressure-sensitive adhesive has been switched to a method using no organic solvent. These include hot melt type and emulsion type. The former has a problem of lack of heat resistance, and the latter has a problem of lack of water resistance.

[0003] It is known that the lack of water resistance of emulsion type is mainly caused by the residual emulsifier used for stably dispersing in water. In order to improve the water resistance, for example, Japanese Patent Application Laid-Open No. 5-98222 discloses an attempt to incorporate an emulsifier into a polymer molecule using a reactive emulsifier. However, since the reactive emulsifier is polymerized in the aqueous phase or remains unreacted, it cannot be completely incorporated into polymer molecules, and as a result, water resistance has not been significantly improved.

In the field of paints and inks, as shown in US Pat. No. 5,173,526, in order to obtain good physical properties, an emulsion-type urethane-acryl composite material is used. It has been proposed. However, it is not easy to apply the technology applied to paints and inks of this kind to the field of pressure-sensitive adhesives in terms of adhesive properties, and such examples are rarely seen.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, using urethane-modified acrylic materials,
A water-dispersible adhesive composition that has excellent adhesive properties, has no problems with environmental hygiene and safety and hygiene, and does not cause water resistance problems caused by emulsifiers. -The purpose is to obtain a class.

[0006]

Means for Solving the Problems The present inventors have conducted intensive studies in order to achieve the above object, and as a result, a urethane prepolymer containing a carboxyl group and a (meth) acryloyl group as raw material components and an acrylic monomer. -And, in particular, the latter acrylic monomer is used in a larger amount than the former urethane prepolymer, and these are reacted in an aqueous medium by a specific method to produce a urethane-modified acrylic polymer. By doing so, while good adhesive properties are obtained, as a water-dispersed type, because no solvent is used,
It was found that there was no problem in environmental hygiene and safety and hygiene, and that no emulsifier was required, so that excellent water resistance could be obtained, and the present invention was completed.

That is, according to the present invention, there is provided an urethane prepolymer containing 2-10% by weight of a carboxyl group and a (meth) acryloyl group in water and an acrylic monomer 98
And a water-dispersed pressure-sensitive adhesive composition (Claim 1), characterized in that a urethane-modified acrylic polymer whose mixture is about 90% by weight as a raw material component is dispersed. An adhesive sheet having an adhesive layer comprising a water-dispersed pressure-sensitive adhesive composition (claim 5).

Further, the present invention provides a) a step of obtaining a urethane prepolymer containing a carboxyl group and a (meth) acryloyl group, and b) a step of obtaining the urethane prepolymers 2 to 4 described above.
A step of mixing 10% by weight of the acrylic monomer with 98 to 90% by weight and neutralizing with a base; c) a step of dispersing the neutralized product in water; and d) adding a polyamine to the aqueous dispersion. A method for producing a water-dispersed pressure-sensitive adhesive composition comprising a step of chain-extending the urethane prepolymer and adding a radical polymerization initiator to polymerize the acrylic monomer (claim 2) ).

Further, the present invention relates to a method for producing the above-mentioned water-dispersed pressure-sensitive adhesive composition, particularly, in step a), a polyisocyanate and a carboxyl group-containing polyol.
To obtain a urethane prepolymer containing a carboxyl group and a (meth) acryloyl group by reacting a hydroxyl group-containing acrylic monomer with an alicyclic polyisocyanate as the polyisocyanate.
Each of the methods (claim 4) that use the object can be provided.

[0010]

DETAILED DESCRIPTION OF THE INVENTION In the present invention, a mixture of 2 to 10% by weight of a urethane prepolymer containing a carboxyl group and a (meth) acryloyl group and 98 to 90% by weight of an acrylic monomer in water is used as a raw material. An aqueous dispersion in which a urethane-modified acrylic polymer as a component is dispersed is obtained, and this is used as a water-dispersible pressure-sensitive adhesive composition. Here, the above-mentioned aqueous dispersion has the following a ~ D process.

In step a, the polyisocyanate, the carboxyl group-containing polyol and the hydroxyl group-containing acrylic monomer are reacted to obtain a urethane prepolymer containing a carboxyl group and a (meth) acryloyl group. At this time, in order to suppress the reaction between the polyisocyanate and water, it is preferable to replace the material with dry air or nitrogen or to dehydrate and dry each material. Further, as a reaction catalyst between the isocyanate group and the hydroxyl group, for example, dibutyltin dilaurate, tin octoate, 1,4-diazabicyclo-2,2,2-octane and the like may be used.

As the polyisocyanate, any of aromatic, aliphatic and alicyclic polyisocyanates can be used. Of these, isophorone diisocyanate, cyclohexane-1,4-diisocyanate, and cyclohexane-1,4-diisocyanate are preferred from the viewpoint of prompt reaction with polyol and suppression of reaction with water.
Alicyclic polyisocyanates such as 4,4'-dicyclohexylmethane diisocyanate are particularly preferably used. As the polyisocyanate, diisocyanate is usually used, but in some cases, tri- or more polyisocyanates can be used.

The carboxyl group-containing polyol is obtained by introducing a carboxyl group into the molecule of a urethane prepolymer,
This is for imparting water dispersibility by the neutralization.
Specific examples include 2,2-dimethylolacetic acid, 2,2-dimethylolpropionic acid, and 2,2-dimethylolbutyric acid, and 2,2-dimethylolpropionic acid is particularly preferable. In addition, when adding these, it is desirable to add them by dissolving them in a solvent such as N-methylpyrrolidone so that the reaction proceeds promptly.

The hydroxyl group-containing acrylic monomer is obtained by introducing a (meth) acryloyl group into the molecule of the urethane prepolymer to impart copolymerizability with the acrylic monomer and to form a phase between the urethane component and the acrylic component. This is for increasing the solubility and contributing to the improvement of the adhesive properties. In particular,
Hydroxylethyl (meth) acrylate, hydroxylpropyl (meth) acrylate, hydroxylbutyl (meth) acrylate, hydroxylhexyl (meth)
Acrylate is used.

In the production of the urethane prepolymer, the amount of the polyisocyanate used is 1.1 to 1.1% based on the total amount of the hydroxyl group containing the carboxyl group-containing polyol and the hydroxyl group-containing acrylic monomer. The ratio is preferably 2.0 equivalents. If the amount of the polyisocyanate is too large or too small, the chain elongation after dispersion in water is not sufficient, and it is difficult to obtain good results in the adhesive properties. In addition, carboxyl group-containing polyol and hydroxyl group-containing acrylic monomer
It is desirable that the proportion of the hydroxyl group is 50 to 80 equivalent% of the carboxyl-containing polyol and 50 to 20 equivalent% of the hydroxyl group-containing acrylic monomer. If either of the two components is too large or too small, it is difficult to obtain a stable aqueous dispersion.

In step b, an acrylic monomer is mixed with the urethane prepolymer containing a carboxyl group and a (meth) acryloyl group thus obtained,
In addition, a carboxyl group in the prepolymer molecule is neutralized with a base. Any base can be used as long as it does not react with the isocyanate group and can neutralize the carboxyl group. Examples of the base include inorganic alkalis such as sodium hydroxide and potassium hydroxide, and tertiary amines such as triethylamine. Used.

The acrylic monomers include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, pentyl (meth) acrylate, Alkyl (meth) acrylates such as hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate Esters are mainly used. In addition, (meth) acrylic acid, (meth) acrylamide, N-methylol (meth) acrylamide, N, N-dimethyl (meth) acrylamide and the like are also used.

The composition of these acrylic monomers is selected so that good adhesive properties are finally obtained. These acrylic monomers are used in an amount of 2 to 10% by weight (preferably 8% by weight or less, more preferably 5% by weight or less) of the urethane prepolymer containing a carboxyl group and a (meth) acryloyl group. 98-90% by weight (preferably at least 92% by weight,
It is important to use it at a ratio of more preferably 95% by weight or more. If the amount of the acrylic monomer is less than 90% by weight, the adhesive strength is reduced. If the amount is more than 98% by weight, there is a problem that a stable aqueous dispersion is hardly obtained.

In step c, an acrylic monomer is mixed with a urethane prepolymer containing a carboxyl group and a (meth) acryloyl group as described above, and the mixture is neutralized with a base. Disperse in water. This dispersion may be carried out by either adding the neutralized substance to water or adding water to the neutralized substance. In this case, the dispersion is preferably performed while stirring. The stirring may be performed using a usual stirrer, or may be performed using a homomixer or a homogenizer as needed. Thereby, an aqueous dispersion in which the neutralized product is stably dispersed in water is obtained.

In step d, a polyamine is added to such an aqueous dispersion to extend the chain of the urethane prepolymer, and a radical polymerization initiator is added to polymerize the acrylic monomer. The chain extension reaction may be performed at room temperature or by heating. Diamines such as ethylenediamine, propylenediamine, and hexamethylenediamine are preferably used as the polyamine for chain extension. The amount used may be equivalent to the amount of isocyanate remaining in the urethane prepolymer.

The polymerization of the acrylic monomer is desirably performed by heating to a predetermined temperature. Examples of the radical polymerization initiator for polymerization include azo compounds such as azobisisobutyronitrile, azobisisobutylvaleronitrile, and 2,2'-azobis [2- (2-imidazolin-2-yl) propane]; An organic peroxide such as benzoyl peroxide is used. The radical polymerization initiator may be oil-soluble or water-soluble. In the case of a powder, it is used by dissolving it in water or a small amount of an organic solvent. Amount used is acrylic monomer-1
The amount is usually 0.005 to 5 parts by weight, preferably 0.01 to 2 parts by weight based on 00 parts by weight. In the polymerization of such an acrylic monomer, the (meth) acryloyl group contained in the urethane prepolymer also simultaneously participates in the polymerization reaction after chain extension, and gives good results such as improvement in adhesive properties.

By such chain extension and polymerization, a high molecular weight urethane-modified acrylic polymer is formed, and an aqueous dispersion in which the urethane-modified acrylic polymer is stably dispersed in water is obtained. In the present invention, this aqueous dispersion may be used as it is as an aqueous dispersion type pressure-sensitive adhesive composition, or may be added with polyvinyl alcohol or other dispersibility improvers or thickeners as necessary. May be used.

The water-dispersible pressure-sensitive adhesive composition of the present invention may further contain, if necessary, various kinds of general pressure-sensitive adhesive compositions such as tackifier resins, softeners, pigments and crosslinking agents. Additives can also be added. When a cross-linking agent is added, the cross-linking agent may be water-soluble or oil-soluble. If oil-soluble, the cross-linking agent may be dissolved in a small amount of an organic solvent or emulsified in water. The same applies to other additives.

The adhesive sheet of the present invention is obtained by applying the water-dispersed pressure-sensitive adhesive composition having the above constitution on a support, heating and drying the composition to remove water. By forming a layer, a shape such as a sheet shape or a tape shape is obtained. As the support, a non-peelable support such as a plastic film, a nonwoven fabric, a paper, a metal foil, a foamed sheet, or the like, or a releasable support such as a release paper is used. In some cases, a sheet or tape may be used without using a support at all.

The adhesive sheets of the present invention thus produced are excellent in adhesive performance, exhibit a large adhesive strength, and are excellent in water resistance. It can be fully used for applications where is required.

[0026]

The present invention will now be described more specifically with reference to examples. However, the present invention is not limited only to the following examples. In the following, “parts” means “parts by weight”.

Example 1 In a flask equipped with a reflux cooling pipe, a gas inlet pipe (cum-degassing pipe), a stirrer, and a thermometer, dimethylol was added together with 10 parts of 4,4'-dicyclohexylmethane diisocyanate. Dissolve and add 2.13 parts of propylpropionic acid to 5.33 parts of dried N-methylpyrrolidone, and add 3.69 parts of hydroxylethyl acrylate (hydroxyl acrylate and hydroxylethyl acrylate of dimethylolpropionic acid). Of the hydroxyl acrylate in the total of 50% by weight of the total of the hydroxyl groups of
07 parts were added and reacted at 65 ° C. for 4 hours.

The obtained urethane prepolymer containing a carboxyl group and an acryloyl group had a residual isocyanate group content of 16.7% of the charged amount as theoretically. The urethane prepolymer was cooled to 30 ° C., and 331.2 parts of dried butyl acrylate (corresponding to 95% by weight in the total amount of the urethane prepolymer) was added thereto, followed by sufficient stirring. 1.61 parts of triethylamine was added, and the mixture was thoroughly stirred and neutralized. Distilled water 52 into another flask
2.95 parts were added, and the above neutralized product was dropped by a dropping funnel. After dropping is completed, ethylenediamine 0.38
The mixture was diluted with 3.42 parts of distilled water, and the mixture was stirred for 1 hour. After purging with nitrogen for 1 hour, 2,2'-azobis [2-
(2-imidazolin-2-yl) propane] 0.13 part was dissolved in 4 parts of methanol, diluted with 4 parts of distilled water, added, and heated to 60 ° C. to react for 4 hours.

By performing the chain extension and the polymerization reaction in this way, an aqueous dispersion in which the urethane-modified acrylic polymer is stably dispersed in water was obtained, and this was directly used as a water-dispersible pressure-sensitive adhesive composition. Next, the water-dispersed pressure-sensitive adhesive composition was applied on a polyethylene terephthalate film having a thickness of 38 μm as a support by an applicator, and then dried at 130 ° C. for 5 minutes in a drier. To form an adhesive layer having a thickness of 50 μm,
An adhesive sheet was used.

Example 2 The urethane prepolymer containing a carboxyl group and an acryloyl group obtained in Example 1 was cooled to 30 ° C., and 427.08 parts of butyl acrylate and 2-ethylhexyl acrylate 427 were dried. 0.08 parts (corresponding to 98% by weight in the total amount of the urethane prepolymer) and stirred well. Triethylamine 1.6
One part was added and stirred well to neutralize. In a separate flask, 1,307.37 parts of distilled water were added, and the neutralized product was dropped into the flask by a dropping funnel. After completion of the dropwise addition, 0.38 part of ethylenediamine was diluted with 3.42 parts of distilled water and added.
Stir for 1 hour. After purging with nitrogen for 1 hour, 2,2'-azobis [2- (2-imidazolin-2-yl) propane]
0.34 part was dissolved in 4 parts of methanol, diluted with 4 parts of distilled water, added, heated to 60 ° C., and reacted for 4 hours.

By conducting the chain extension and the polymerization reaction in this way, an aqueous dispersion in which the urethane-modified acrylic polymer is stably dispersed in water was obtained, and this was used as it was as a water-dispersible pressure-sensitive adhesive composition. Next, the water-dispersed pressure-sensitive adhesive composition was applied on a polyethylene terephthalate film having a thickness of 38 μm as a support by an applicator, and then dried at 130 ° C. for 5 minutes in a drier. To form an adhesive layer having a thickness of 50 μm,
An adhesive sheet was used.

Example 3 In a flask equipped with a reflux condenser, a gas inlet tube (also used as a degassing tube), a stirrer, and a thermometer, dimethylol was added together with 10 parts of 4,4'-dicyclohexylmethane diisocyanate. Dissolve 2.77 parts of propionic acid in 6.93 parts of dried N-methylpyrrolidone and add 2.58 parts of hydroxyl ethyl acrylate (hydroxyl acrylate and hydroxyl ethyl acrylate of dimethylolpropionic acid). Of the hydroxyl acrylate in the total amount of the hydroxyl group of the above, and 35 equivalent% of the hydroxyl acrylate).
07 parts were added and reacted at 65 ° C. for 4 hours.

The resulting urethane prepolymer containing a carboxyl group and an acryloyl group had a residual isocyanate group content of 16.7% of the theoretically charged amount. The urethane prepolymer was cooled to 30 ° C., and 854.88 parts of dry butyl acrylate (corresponding to 98% by weight in the total amount with the urethane prepolymer) was added thereto, followed by thorough stirring. Then, triethylamine 2.09
And stirred well to neutralize. 1,308.48 parts of distilled water was put into another flask, and the neutralized product was dropped into the flask with a dropping funnel. After completion of the dropwise addition, 0.38 part of ethylenediamine was diluted with 3.42 parts of distilled water and added.
Stirred for hours. After purging with nitrogen for 1 hour, 2,2'-azobis [2- (2-imidazolin-2-yl) propane]
0.34 part was dissolved in 4 parts of methanol, diluted with 4 parts of distilled water, added, heated to 60 ° C., and reacted for 4 hours.

By conducting the chain extension and the polymerization reaction in this way, an aqueous dispersion in which the urethane-modified acrylic polymer is stably dispersed in water was obtained, and this was directly used as an aqueous dispersion type pressure-sensitive adhesive composition. Next, the water-dispersed pressure-sensitive adhesive composition was applied on a polyethylene terephthalate film having a thickness of 38 μm as a support by an applicator, and then dried at 130 ° C. for 5 minutes in a drier. To form an adhesive layer having a thickness of 50 μm,
An adhesive sheet was used.

Comparative Example 1 10 parts of 4,4'-dicyclohexylmethane diisocyanate was added to a flask equipped with a reflux cooling pipe, a gas introduction pipe (cum-degassing pipe), a stirrer, and a thermometer. Then, 4.26 parts of dimethylolpropionic acid were dissolved in 10.65 parts of dried N-methylpyrrolidone, and 0.007 part of dibutyltin dilaurate was further added. The mixture was reacted at 65 ° C. for 4 hours.

After obtaining the urethane prepolymer containing a carboxyl group in this manner, the urethane prepolymer was cooled to 30 ° C., and 332.14 parts of dried butyl acrylate (the urethane prepolymer and (Corresponding to 95% by weight in the total amount of the above) and stirred well. 3.22 parts of triethylamine was added, and the mixture was stirred well and neutralized. 524.43 parts of distilled water was put into another flask, and the neutralized product was dropped into the flask by a dropping funnel. After the completion of the dropwise addition, 0.38 part of ethylenediamine was diluted with 3.42 parts of distilled water and added. When the mixture was stirred, it was aggregated on the way, and a stable aqueous dispersion was not obtained. For this reason, the polymerization reaction by the addition of the radical polymerization initiator could not be performed, and a urethane-modified acrylic polymer could not be produced.

Comparative Example 2 The urethane prepolymer containing a carboxyl group and an acryloyl group obtained in Example 1 was cooled to 30 ° C., and dried with 172.35 parts of butyl acrylate (with the urethane prepolymer). (Corresponding to 99% by weight of the total amount) and stirred well. Triethylamine 1.61
And stirred well to neutralize. In a separate flask, 2,614.16 parts of distilled water were added, and the neutralized product was dropped into the flask by a dropping funnel. After completion of the dropwise addition, 0.38 part of ethylenediamine was diluted with 3.42 parts of distilled water and added.
Stirred for hours. After purging with nitrogen for 1 hour, 2,2'-azobis [2- (2-imidazolin-2-yl) propane]
When 0.69 part was dissolved in 4 parts of methanol, diluted with 4 parts of distilled water, and added, the mixture was heated to 60 ° C. and reacted. As a result, agglomeration occurred during the polymerization, and the urethane-modified acrylic polymer was dissolved in water. It has not been possible to obtain a stable aqueous dispersion.

Comparative Example 3 The urethane prepolymer containing a carboxyl group and an acryloyl group obtained in Example 1 was cooled to 30 ° C., and 69.71 parts of dried butyl acrylate (with the urethane prepolymer) (Corresponds to 80% by weight in the total amount)
Was added and stirred well. 1.61 parts of triethylamine was added, and the mixture was stirred well and neutralized. 130.71 parts of distilled water was put into another flask, and the above neutralized product was dropped thereinto.
And dropped. After completion of the dropwise addition, ethylenediamine 0.
38 parts were diluted with 3.42 parts of distilled water, and the mixture was stirred for 1 hour. After purging with nitrogen for 1 hour, 2,2'-azobis [2-
(2-Imidazolin-2-yl) propane] was dissolved in 4 parts of methanol, diluted with 4 parts of distilled water, added, and reacted by heating to 60 ° C.

By performing the chain extension and the polymerization reaction in this way, an aqueous dispersion in which the urethane-modified acrylic polymer is stably dispersed in water was obtained, and this was directly used as a water-dispersible pressure-sensitive adhesive composition. Next, the water-dispersed pressure-sensitive adhesive composition was applied on a polyethylene terephthalate film having a thickness of 38 μm as a support by an applicator, and then dried at 130 ° C. for 5 minutes in a drier. To form an adhesive layer having a thickness of 50 μm,
An adhesive sheet was used.

Comparative Example 4 95 parts of butyl acrylate and 5 parts of acrylic acid were placed in a flask equipped with a reflux condenser, a gas, an inlet tube, a stirrer, and a thermometer.
, 3 parts of sodium dodecylbenzenesulfonate as an emulsifier and 150 parts of distilled water were previously emulsified and mixed by a homomixer, and further N was added thereto.
-0.15 parts of azobisisobutylvaleronitrile dissolved in 2 parts of methylpyrrolidone were added,
After stirring for an hour, the mixture was heated to 60 ° C. and reacted for 4 hours.

Thus, an acrylic polymer emulsion was obtained, which was used as it was as a water-dispersed pressure-sensitive adhesive composition. Next, this water-dispersed pressure-sensitive adhesive composition,
By coating on a polyethylene terephthalate film having a thickness of 38 μm as a support with an applicator, and then drying in a dryer at 130 ° C. for 5 minutes,
An adhesive layer having a thickness of 50 μm was formed to form an adhesive sheet.

The adhesive sheets obtained in Examples 1 to 3 and Comparative Examples 3 and 4 were subjected to an adhesive strength test and a water resistance test by the following methods. The results of these tests were as shown in Table 1.

<Adhesion Test> A 180 ° peel adhesion to a stainless steel plate was measured according to JIS Z 0237.

<Water Resistance Test> The adhesive sheet was immersed in distilled water, and the degree of whitening after 24 hours was measured with a Haze meter. Compared to the Haze value before immersion in distilled water,
When the ze value increases by 100% or more, x, 100
% Or less was evaluated as Δ.

[0045]

As is evident from the results in Table 1 above, by using the water-dispersed pressure-sensitive adhesive compositions of Examples 1 to 3 of the present invention, an adhesive sheet having excellent adhesiveness can be produced. Further, it can be seen that this adhesive sheet is excellent in water resistance.

On the other hand, in the synthesis of the urethane prepolymer, Comparative Example 1 which did not use hydroxyl ethyl acrylate, which is a hydroxyl group-containing acrylic monomer,
In Comparative Example 2 in which the amount of the acrylic monomer, butyl acrylate, was too large, an aqueous dispersion in which the urethane-modified acrylic polymer was stably dispersed in water could not be obtained. In addition, in the adhesive sheet using the water-dispersed pressure-sensitive adhesive composition of Comparative Example 3 in which the amount of the acrylic monomer, butyl acrylate, was too small, the adhesive force was significantly reduced. The adhesive sheet of Comparative Example 4 using the conventional acrylic polymer emulsion was remarkably inferior in water resistance.

In synthesizing the urethane prepolymer, the amount of the hydroxyl group-containing acrylic monomer used is excessively large. For example, in Example 1, the amount of the hydroxyl ethyl acrylate used is determined by the amount of the hydroxyl group being dimethyloyl. When it is changed to 75 equivalent% in the total amount of the number of hydroxyl groups of lupropionic acid, a mixture of the obtained urethane prepolymer and butyl acrylate, which is an acrylic monomer, is neutralized with triethylamine. In the step of dispersing in water, there was a tendency that it was difficult to stably disperse the neutralized product. Therefore, the hydroxyl group-containing acrylic monomer has a hydroxyl group number of a carboxyl group-containing polyol.
It has also been found that it is desirable to set within the range of 20 to 50 equivalent% in the total amount with the number of hydroxyl groups of the compound.

[0049]

As described above, in the present invention, a urethane polymer containing a carboxyl group and a (meth) acryloyl group and an acrylic monomer are used at a specific ratio, and these are specified in an aqueous medium by a specific method. By forming a urethane-modified acrylic polymer by reacting with water, it is excellent in adhesive properties and water resistance, as a water-dispersed type without problems in environmental hygiene and safety and health.
It is possible to provide a highly practical pressure-sensitive adhesive composition, a method for producing the same, and adhesive sheets thereof.

 ──────────────────────────────────────────────────続 き Continued on front page (72) Inventor Yuko Yamamoto 1-1-2 Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation (72) Inventor Yoshinori Yoshida 1-1-2 Shimohozumi, Ibaraki-shi, Osaka F-term in Nitto Denko Corporation (reference) 4J004 AA01 AA02 AA10 AA14 AB01 BA02 CA02 CA06 CA08 CB01 CB02 CB04 4J040 EF062 EF082 EF292 EF352 FA141 FA292 HB41 HC18 JA03 JA09 JB09 KA12 LA07 QA01

Claims (5)

[Claims] 1. A method according to claim 1, wherein a carboxyl group and (meth)
Urethane prepolymers containing acryloyl groups 2-1
Urethane-modified acrylic polymer made from a mixture of 0% by weight of an acrylic monomer and 98 to 90% by weight as a raw material component
Are dispersed in a water-dispersed pressure-sensitive adhesive composition. 2. A) a step of obtaining a urethane prepolymer containing a carboxyl group and a (meth) acryloyl group; b) 2 to 10% by weight of the urethane prepolymer and 98 to 90% by weight of an acrylic monomer. And neutralizing with a base; c) dispersing the neutralized product in water; d) adding a polyamine to the aqueous dispersion to extend the chain of the urethane prepolymer and radical polymerization. A method for producing a water-dispersed pressure-sensitive adhesive composition, comprising a step of adding an initiator to polymerize the acrylic monomer. 3. In step a, a polyisocyanate, a carboxyl group-containing polyol and a hydroxyl group-containing acrylic monomer are reacted to obtain a urethane prepolymer containing a carboxyl group and a (meth) acryloyl group. A method for producing the water-dispersed pressure-sensitive adhesive composition according to claim 2. 4. The method for producing a pressure-sensitive adhesive composition according to claim 3, wherein the polyisocyanate is an alicyclic polyisocyanate. 5. An adhesive sheet having an adhesive layer comprising the water-dispersed pressure-sensitive adhesive composition according to claim 1 on a support.