CA1171997A

CA1171997A - Water-soluble pressure-sensitive adhesive composition

Info

Publication number: CA1171997A
Application number: CA000354807A
Authority: CA
Inventors: Makoto Sunakawa; Yutaka Moroishi; Isao Mune; Takanori Tomomoto; Kikuo Takeyama
Original assignee: Nitto Electric Industrial Co Ltd
Current assignee: Nitto Denko Corp
Priority date: 1979-07-04
Filing date: 1980-06-25
Publication date: 1984-07-31
Also published as: DE3067615D1; FI70037B; US4442258A; JPS5610575A; FI70037C; EP0022339B1; EP0022339A2; EP0022339A3; JPS5844711B2; FI802088A

Abstract

ABSTRACT OF THE DISCLOSURE
A water-soluble pressure-sensitive adhesive composition is described containing. a polymerization product obtained by the solution polymerization of a water-soluble ethylenically unsat-urated monomer in the presence of an alcoholic plasticizer having a molecular weight of less than about 3,000 and which is a liquid at room temperature, selected from the group consisting of poly-ether polyols and polyhydric alcohols, wherein the polymerization product contains as a polymer component at least an addition co-polymex of the water-soluble ethylenically unsaturated monomer and the alcoholic plasticizer.

Description

~:~7~7 Field of the Invention . = . ~
This invention relates to a novel pressure-sensitive adhesive composition, and more particularly to a pressure-sensi-tive adhesive co~position which is water solu~le and which shows adhesive properties upon the application of pressure under any conditions, Description of the Prior Art ~ater-soluble adhesives are kno~n in the art; for ex-ample, a so-called "gum tape", comprising a paper su~strate with glue, dextrin, or polyvinyl alcohol coated thereon, is well known.
Under dry conditions, however, this type of tape lacks ru~ber - elasticity and viscosity, showing no pressure-sensitive adhesive properties. Rather such a tape shows pressure-sensitive adhesive properties only when water is applied thereon. Thus conventional water-solu~le adhesives have disadvantages in that they need a complicated wetting apparatus when used for industrial appli-cations, and when they are used on stamps and envelope6, diffi-culties are also encountered in wetting and applying.them~
More recently, various kinds of water-soluble or water-dispersible adhesives avoiding the a~ove described disadvantages and sho~ing pressure-sensitive adhesive properties under various conditions have ~een developed, For example, U.S~ Patent No.

2,838,421, Japanese Patent Pu~lication Nos. 34578/1975, 22768/
lQ77 and 23813/1974 disclose suc~ pressure-sensitive adhesive comprisin~ a polymer component, such as a polymer containing specific car~oxyl groups or a water-solu~le polymer salt thereof, e,g " an alkali metal salt, an amine salt or an alkanolamine salt, and a water-solu~le or water-dispersi~le plasticizer, such as polyether polyol, a polyhydric alcohol or an alkanolamine salt

3~.

~'7~
1 of acidic rosin.
U.S. Patent No, 3,096,202 discloses a pressure-sensi-tive adhesive wherein a polyvinyl-pyrrolidone elastomer is used as the polymer component, and to this polymer component, a water-solu~le plasticizer, such as polyether polyol, i5 added in com-bination with a polyfunctional polymerizable cross-linking agent, such as ethyleneglycol dimethacrylate, or an activation catalyst.
These water-solu~le or water-dispersible pressure-sensivtive adhesives have advantages in that they will easily adhere ~y the application of nothing more than manual pressure, and in that they provide strong adhesive strength lmmediately after application.
In this type of conventional pressure-sensitive adhe-sive, as described above, the component employed as the polymer has a very high polarity, and a glass transition temperature higher than room temperature, such as a car~oxyl group-contain-ing polymer or polyvinyl-pyrrolidone, in order to provide the function of water solubility, and in order to plasticize such a polymer to provide it with pressure-sensitive adhesive properties, a large amount of a water-soluble or water-dispersi~le liquid plasticizer having a relatively low molecular weight i5 incorp-orated. A particular problem encountered with these pressure-sensitive adhesives is poor compatibility of the polymer com-ponent with the water-soluble or water-dispersible plasticizer, and when they are stored for a long period of time, the plastic-izer ~egins to migrate Calso referred to as bleedingL. When a paper material is employed as a substrate on which the adhesive is applied, the bleeding is accelerated by the affinity between the paper material and the water-soluble or water-dispersible plasticizer, ~:~7.~39~7 1 Therefore, when this type of adhesive is used, for example, in bonding original papers together or adhering pieces of paper in the paper industry, the plasticizer in the adhesives easily migrates into the paper, deteriorating the quality of the print ~eing applied on the paper Water-solu~le or water-dispersi~le pressure-sensitive adhesive have ~een developed as an adhesive suitable for use in the above-descri~ed applications in the paper industry. The reason for this is that the pressure-sensitive adhesive character-istics improve the adhesive, while at the same time, the water-soluble or water-dispersible characteristics render the paper easîly solu~le or dispersi~le in water upon repulping of the -paper.
~owever, the bad print resulting from bleeding of the plasticizer which has been encountered with the conventional adhesives is a serious hindrance to the use of the adhesives in the a~ove-descri~ed applications, greatly reducing the value of such adhesives in water-solu~le or water-dispersi~le pressure-sensitive adhesives.
Recently it has been reported in, for example~ U.S
Patent 3,891,58~ that graft copolymers produced by addition-poly-merization of an unsaturated monomer, such as vinyl acetate, vinyl propionate or vinyl ~utyrate, with a high molecular weight water-soluble polymer, such as polyethylene glycol having a molecular weight of about 3,00Q to a~out 20, oao, can be used in providing an adhesive with suita~le water-dispersion character-istics.
In producing these graft copolymers from a water-solu~le polymer and an unsaturated monomer, a bulk polymerization method 3 i5 employed in copolymerizing the unsaturated monomer, in order ~`3~

~.~'7.~
1 to minimize the formation of homopolymers, and the graft copoly-mers so formed are high molecular weight polymers in the gel form Therefore, although t~ese graft copolymers can ~e com-pounded with rosin or its deriYative, or a viscous resin such as a cumarone-indene resin to obtain hot melt adhesives, they cannot ~e employed at all for the production of the pressure-sensitive adhesive of this invention, In addition, the water-dispersion characteristics obtained ~y the~choice o$ the unsat-urated monomer are unsatisfactory.

SUMMARY OF T~IE INVENTION
An object of this invention is to provide a novel ~ater-soluble pressure-sensitive adhesive which is free from the above described defects of the prior art adhesives.
This object is attained hy employing a polymerization product ohtained by the solution polymerization o~ a water-sol-uble ethylenically unsat1lrated monomer, alone or in com~ination with a water-insoluhle ethylenically unsaturated monomer copoly-meriza~le with the water-soluhle ethylenically unsaturated mon-omer, in the presence of a plasticizer selected from the group consisting of polyetherpolyols and polyhydric alcohols having a molecular weight of less than a~out 3,000 and which i5 liquid at room temperature.
It has been found that ~y employing such a low molecular weight alcoholic platicizer which is liquid at room temperature, and w~ich is well known in the field of pressure-sensitive ad-hesives, in place of the previously described water-soluble poly-mer, and h~ polymerizing an unsaturated monomer including at least a water-soluhle ethylenically unsaturated monomer in the presence of the alcoholic plasticizer and a solvent, such as water and an or~anic solvent, a polymer component comprising an addition 1 copolymer of the unsaturated monomer and the alcoholic plastic-izer is ohtained, as well as a homopolymer of the unsaturated monomer, The addition copolymer and homopolymer are provided with appropriate molecular weights and are formed in an appro-priate ratio, such that the polymer component comprising the addition copolymer and the hornopolymer possesses pressure-sen-sitive adhesive characteristics and improved solu~ility in water.
In addition, it has been found that since the polymer component contains the addition copolymer of the alcoholic plasticizer and the unsaturated monomer, when an additional water~
solu~le plasticizer is added to the polymer component, the com-pati~ility of the additional water-soluble plasticizer with the polymer component is very good, and the bleeding of the plastic-izer encountered with conventional water-soluble or water-disper-si~le pressure-sensitive adhesives is greatly reduced.
Therefore this invention provides a water-soluble pressure-sensitive adhesive composition comprising a composition o~tained ~y the solution polymerization of a water-solu~le ethylenically unsaturated monomer, alone or in com~ination with a water-insoluble ethylenically unsaturated monomer copolymer iza~le with the water-solu~le ethylenically unsaturated monomer, in the presence of a plasticizer selected from the group con-sisting of polyetherpolyols and polyhydric alcohols Calso referred to herein as the alcoholic plasticizers) having a molecular weight of less than a~out 3,000 and which is liquid at room temperature, wherein said composition contains as a polymer com-ponent at least an addition copolymer of the unsaturated monomer and the alcoholic plasticizer, and, if desired, another water-soluhle plasticizer and a polyfunctional compound.

~'7~ 7 In this invention, alcoholic plasticizers having average molecular weights of less than a~out 3, oao and which are liquid at room temperature are employed. Preferably the alcoholic plasticizers have a molecular weight of less than a~out 2,000, and especially prefera~ly they have a molecular weight of less than a~out 1,000.
Alcoholic plasticizers having average molecular weights of more than 3,000 do not provide satisfactory pressure-sensitive adhesive properties. For obtaining satisfactory pressure-sen-sitive adhesive properties, it is required to increase markedly the amount of the alcoholic plasticizer added or the amount of the ~ater-solu~le plasticizex added after the solution polymer-ization, This is likely to cause the ~leeding of the plasticizer.
Furthermore, in the method of this invention employing a solution polymerization technique in which the chain transfer occurs with ease, the use of such high average molecular weight platicizers decreases the amount of the alcoholic plasticizer-unsaturated monomer addition copolymer formed to an extent more than is de-sira~le, The term "chain transfer" used in this invention isexplained as follows.
In general, the chain transfer of radical occurs to monomer, solvent, polymer, plasticizer, polymerization initiator and the like, In this invention, radical is formed due to the chain transfer of plasticizer, resulting in the polymerization or the coupling of the polymer into the radical, and as a result, the addition polymer is o~tained, Where high average molecular weight plasticizers having small number of molecules are used as descri~ed a~ove~ the pro~a~ility of occurring the chain transfer 3L~7.1l~7 1 at the terminal carbon of the plasticizer is small and the amount of addition polymer produced decrease~. Further, due to-the use of solvent in the solution polymerization it is necessary to con-sider the chain transfer to solvent, and from this point the use of high average molecular ~eight plasticizers is disadvantageous, On the other hand, the use of alcoholic plasticizers having average molecular weights of less than about 3,000 elim-inates the a~ove-descri~ed defects, and improves the soluhility of the alcoholic plasticizer itself or the adhesive formed in water. For providing the pressure-sensitive adhesive properties, it is required that the alcoholic plasticizer be a liquid at room temperature.
The alcoholic plasticizer is selected from the group consisting of polyetherpolyols and polyhydric alcohols. In partic-ular, those alcoholic plasticizers are chosen which are less vaporizable in the air and are able to provide pressure-sensitive adhesive properties under a broad range of conditions.
It has been ~ound that polyetherpolyols containing an ether bond or bonds in the molecule and primary or secondary hydroxy groups at the terminal thereof, produced by polymerizing propylene oxide or ethylene oxide, are suitable as the alcoholic plasticizer of this invention, and that in particular, polyether-polyols produced by polymerizing (adding~ propylene oxide or ethylene oxide with hydroxyl groups of polyhydric alcohols ~that is, containing at least 3 hydroxyl groups) exhibit the most suit-able characteristics, The representative example of this poly-merization (additionl aspect is shown below.
CIH20H H2fO (CH2CH20~n H
CHOH + C ~ - CH2- ~ H fo - (CH2CH20)n H
CH2H O H2CO - ~CH2CH20 ~ H

:~7~ 7 1 Examples of these polyhydric alcohols include glycerin, trihydroxyisobutane, erythrite, pentaerhthrite, xythrite, adonite, allodulcit, and sor~ite.
Examples of polyeth~rpol~ols of this type available A commercially include ~ i~ TP-400, GP-600, GP-10~0, GP-3000, GEP-2800, and SP-750, all produced by Sanyo Chemical Industries Co., Ltd. The numbers indicate the average molecular weights of the polyetherpolyols.

Ordinary polyetherpolyols such as polyethyleneglycol, polypropyleneglycol or a copolymer of ethylene oxide and propylene oxide can also be used. The above descri~ed polyhydric alcohols can also fie used alone.
The amount of the alcohlic plasticizer ~eing added greatly influences the amount of the addition copolymer formed, the adhesive characteristics, and so forth. Though the most suitahle amount varies depending upon the kind of the unsaturated monomer heing used, the kind of the solvent, etc., it is generally used in an amount from about 20 to 400 parts ~y weight per 100 parts ~y weight of the unsaturated monomer, and preferably is from 50 to 3QQ parts by weight.
When the amount of the alcoholic plasticizer being added is extremely small, the amount of the addition copolymer formed is reduced and the compati~ility of the formed addition copolymer with t~e alcoholic plasticizer cannot ~e improved. On the other hand, when the alcoholic plasticizer is used in an ex-tremely large amount, the molecular weight of the addition co-polymer formed is decreased, although it is formed in a larger amount. This leads to a decrease in the pressure-sensitive ad-hesive characteristics, particularly cohesive strength, If an organic solvent is used as the solvent of this æ~D~ ~ c ~t~ 7 1 invention, the chain transfer to the organic solvent takes place with ease during the solution polymerization. In this case, therefore, it is desired that the alcoholic plasticizer be added in a larger amount, within the a~ove range, than when water is used as the solvent.
The Unsaturated monomer to be used in this invention should include at least one water-soluble ethylenically unsat-urated monomer in order to increase the solubility of the adhesive obtained in water. Representative examples of suitable water-soluble ethylenically unsaturated monomers are those ethylenicallyunsaturated monomers containing a carboxyl group or groups in the molecule, such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, monoalkylmaleic acid, monoalkyl fumaric acid, monoalkylitaconic acid and the like.
Other useful water-soluble ethylenically unsaturated monomers include vinylpyrrolidone, acrylamide, and unsaturated monomers represented by the formulae (1~ and C2~:

Rl H2C=C-C-O-~R21-0-R3 (1 IRl ~ 4 H2C=C-C-o-~R22- C2) where Rl is hydrogen or a methyl group, R2 is a lower alkylene group, and R3, R4 and R5 are each hydrogen or a lower alkyl group.
These water-solu~le ethylenically unsaturated monomers can be used alone. However, it is preferred that they be used in combination with the a~ove-described carboxyl group-containing unsaturated monomers.

7.~37 1 The water-solu~le ethylenically unsaturated monomer may be used in com~ination with water-insoluble ethylenically un~
saturated monomers wl~ich are copolymeriza~le with the water-sol-u~le ethylenically unsaturated monomer. These water insoluble ethylenically unsaturated monomers are used to improve the ad-hesive characteristics, for example, to increase the cohesive strength, of the adhesive.
Preferred examples of water-insoluble ethylenically unsaturated monomers are alkyl acr~late or alkyl methacrylate con-taining 14 or less carbon atoms, vinyl acetate, dialkyl esters or dibasic unsaturated acids, such as maleic acid, fumaric acid or itaconic acid, containîng 8 or less carbon atoms, and the like.
In addition, vinyl propionate, acrylonitrile, styrene, etc , can be used.
The water-insoluble ethylenically unsaturated monomer is chosen depending upon the kinds of water~soluble ethylenically unsaturated monomer, alcoholic plasticizer, and solvent keing used. For example, where acrylic acid or methacrylic acid is polymerized in water in the presence of a polyetherpolyol having secondary hydroxyl groups at the terminals thereof, it is pre-ferred that lower alkyl esters, such as ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, butyl methacrylate, vinyl ace-tate, and the like are used.
The amount of the water-insolu~le ethylenically unsat-urated monomer varies greatly depending upon the kind of solvent used~ and it also varies slig~tly depending upon the application of the adhesive, the kind of the water-soluble ethylenically unsaturated monomer and/or alcoholic plasticizer being used, and so forth. It is not desira~le for the amount of the water-in-soluble ethylenically unsaturated monomer to exceed 85% ~y weight, 1 ~ased upon the total weight of the water-solu~le ethylenically unsaturated monomer and the water insoluble ethylenically unsat-urated monomer. If the water-insoluble ethylenicall~ unsaturated monomer is used in an amount greater than 85% ~y weight, the solu~ility of the adhesive obtained in water is greatly reduced, and the compatibility of the polymer component and the plasticizer is also reduced~ This is li~;ely to cause the ~leeding of the plasticizer, and is undesira~le. In general, when water is used as the solvent, it is usually used in an amount of less than 25% by weight, whereas when a solvent containing an organic sol-vent is employed, water-soluble ethylenically unsaturated monomer is preferably used in an amount of less than 75% by weight.
In the polymerization of this invention, the use of the solvent is essential. When the polymerization is carxied out without using any solvent, the addition polymerizatlon proceeds excessivel~, increasing the molecular weight of the addition co-polymer to be obtained. ~inally, the addition copolymer gels with ease, making it difficult to obtain polymers having desir-a~le pressure sensitive adhesive characteristics That is to say~ the solvent acts effectively as a chain transfer agent and produces addition copolymer and homopolymer having appropriate molecular weights in an appropriate ratio.
Solvents which can ~e used in this invention include water and aqueous mediums consisting of water and a water-soluble organic solvent, such as methanol, ethanol, isopropanol, acetone, and methylethyl ketone. In place of these solvents, water less-soluble or insoluble organic solvents, such as benzene, toluene and ethyl acetate, and the a~ove water~soluble organic solvents ma~ he used alone or in admixture with each other The solvent is chosen depending upon whether a water-~:~7~97 1 insolu~le unsaturated monomer is used as a part of the unsatur-ated monomer, and on the amount of the water-insoluble unsatur-ated monomer ~eing added. The use of the organic solvent offers the advantage that the molecular weight of the polymer o~tained can be easily controlled. On the other hand, when the aqueous medium, particularly water, is used alone, it is advantageous that pollution encountered in producing the adhesive or using it can be more easily controlled.

The amount of solvent added has a great influence on the adhesive characteristics, compatibility of the polymer and the plasticizer, and the polymerization workability. When the amount of solvent is reduced excess~vely, gelation takes place, reducing the adhesive characteristics and workability. On the other hand, the use of a large amount of solvent reduces markedly the amount of the addition polymer to ~e formed and deteriorates the adhesive characteristics and the compatibility of the polymer with the plasticizer.
In general, the amount of the solvent used is from a~out 5 to 1000 parts by weight per 10a parts by weight of the unsatur-ated monomer, with a range of from 2Q to 600 parts by weight being preferred. The suitable amount varies greatly depending upon the kind of the solvent. For example, when water is used alone as the solvent, the amount of the water used is usually from about 5Q to lQaQ parts by weight, and preferably is from lQ0 to 6no parts by weight. When an organic solvent is used alone or in a mixture with water, it is usually from about 5 to 50Q parts by weight, and prefexably is from 20 to 3Q0 parts by weight, which is much lesser than with the use of water, In determining the amount of the solvent, it is desirable to take into consideration the particular kinds of the alcoholic plasticizer, unsaturated :~'7~ 7 1 monomer, and polymerization initiator ~einq used, and the amounts thereof.
In polymerizing the ethylenically unsaturated monomer in the presence of the alcoholic plasticizer by use of the sol-vent as descri~ed a~ove, an appropriate radical polymerization initiator i5 used in an amount of from about 0 05 to 2 parts by weight per 100 parts by weight of the unsaturated monomer. The polymerization is usually carried out for a period of from about 6 to 12 hours at a temperature of 6Q to 80C.
~en the solution polymerization is carried out in an aqueous medium, polymerization initiators comprising persulfates, such as ammonium persulfate and potassium persulfate, hydrogen peroxide, and redox catalysts comprising persulfate or hydrogen peroxide and sodium hydrogensulfite~ sodium ascor~ate, a metal salt, or the like have been found to be most suitable for pro-ducing the desired addition copolymer; and organic peroxides, such as dibenzoyl peroxide, have ~een found to be most suitably usa~le in thé organic solvent. As necessary~ the persulfates and hydrogen peroxide may ~e used in the polymerization using the organic solvent, and in the polymerization using the a~ueous medium, the organic peroxide may be used.
On the other hand, azo compounds which are commonly used as a polymerization initiators in polymerization reactions, are not suitable in ~oth the aqueous medium and the organic sol~
vent, and the desired adhesive characteristics and compatibility cannot ~e obtained.
The thus~obtained polymerization product contains as the polymer component the addition copolymer resulting from the addition polymerization of the unsaturated monomer and the alco-holic ~lasticizer, and the homopolymer of the unsaturated monomer.

1 The pol-~merization product itself exhihits pressure-sensitive adhesive properties and good soluhility in water~ and therefore it can ~e used as a water-solu~le pressure~sensitive adhQsive as 15 .
However~ when a large amount of the water insolu~le ethylenically unsaturated monomer is employed as the unsaturated monomer, the solubility of the polymerization product in water is sometimes somewhat reduced. In this case, an appropriate pro-cedure, as descri~ed ~elow, can ~e applied to increase the sol-19 ubility.

Where a carboxyl group~containing unsaturated monomeris used as a part or all of the water-solu~le ethylenically un-saturated monomer, the most common procedure to increase the sol-ubility Oc the polymerization product is to ionically crosslink with a metal ion or amine through some~of the car~oxyl groups.
This ionical crosslinking can be achieved hy adding a solution containing a predetermined metal ion or amine to the reaction solution after the polymerization has been carried out. In necessary, the solution may ~e added to the reaction solution prior to the polymerization. The term "ionical crosslinking" used in this invention means neutralization or salt formation~ There-fore, in the case of containing a large amount of a water insol-u~le ethylenically unsaturated monomer, there is the advantage that the water solubility increases ~y the ionical crosslinking ~neutraliæation~, This ionical crosslinking not only improves the sol-ubility of the polymerization product in water, but also improves its adhesive characteristics/ particularly shear adhesive and cohesive properties. Therefore~ even when the adhesive obtai-ned possesses a sufficient solubility in water, the ionical cross-9~

1 linking procedure can be employed to improve the adhesive char-acteristics.
Metal ions and amines which can be used in the ionical crosslinking include univalent metal ions and amines, such as a potassium ion, a sodium ion, hexylamine and monoet~anol amine For improving the adhesive characteristics, divalent or trival-ent metal ions and diamines, such as a calcium ion, a magnesium ion, a zinc ion, a copper ion, an aluminum ion, and hexamethylene-diamine, are especially useful. In addition~ polyvalent amines such as tetramethylenehexamine and triethylenepentamine can be used, if necessary.
The amount of the univalent metal ion or monoamine being used can usually ~e varied from about Q.Ql to Q.8 equivalent, based upon the equivalents of carboxyl group contained in the polymer component, with the range of 0.02 to 0.6 equivalent being preferred. It is not desired to increase the amount because it may deteriorate the compati~ility of the polymer with the plast icizer In the case of the di- or trivalent metal ions or di-amines, it can usually ~e 0.002 to O.Q5 equivalent per car~oxyl `group contained in the polymer component, with the range of 0.003 to Q.Q3 equivalent being preferred. It is not preferred to in-crease the amount because it may deteriorate the solu~ilit~ in water ~ 7hen the polymerization product has somewhat poor pres~
sure sensitive adhesive characteristics, an additional plasticizer can ~e added after the polymerization reaction. As this addition-al plasticizer, it is desirable to use polyetherpolyols and poly-hydric alcohols, having the same structure as those for use in the polymerization reaction ~7~7 1 The incorporation of such an additional plasticizer causes no ~leeding, ~ecasue of good compatibility of the plast-icizer with the polymer~ EIowever~ it is not suita~le to add the additional plasticizer in an amount in excess of 7Q0 parts by weight per 100 parts by weight of the unsaturated monomer used in the polymerization reaction, since then hleeding may take place irrespective of good compatibility.
To the polymerization product can ~e added a polyfunc-tional compound to crosslink the polymers through the functional groups contained therein so that the moisture resistance and the adhesive characteristics, particularly cohesive strength ~e im-proved~
When the ~ater-soluhle or water-dispersible pressure-sensitive adhesive is used in bonding or sticking papers in the paper industry~ it is usually applied at very high temperatures and humidities. Under these conditions, the adhesive absorbs water and softens, resulting in a marked reduction in the creep strength of the adhesive, and in the cohesive failure of the adhesive even ~y application of only low strength~ This causes various pro~lems in the paper industry. Therefore, the ~ater-- solufile pressure-sensitive adhesive is also required to have a certain extent of water resistance and moisture resistance~
This invention can provide adhesives capa~le of comply-ing ~ith the requirements as descrihed since incorporation of the polyfunctional compound into the adhesive of this invention enahles to increase its moisture resistance and cohesive strength, Polyfunctional compounds which can he used for this purpose include an epoxy resin, a melamine compound, a reactive phenol resin, a chelate compound of a polyvalent metal, and the like. The appropriate one is chosen depending upon the kind of i.~7~
1 the unsaturated monomer to be used.
A suitable epoxy resin is triglycidyl isocyanurate; in additon, an aliphatic glycidyl ester type, an aliphatic glycidyl ether type, a ~isphenol type and an aliphatic type of low mole-cular weight epoxy compounds containing terminal 1.2-epoxy groups can also be used. Representative examples of the epoxy resins A on the market are Epikote #828, ~1031, produced ~y Ciba ~eigy Co , Epon #834 produced by Shell Co., ECN ~1235 produced by Ciba Geigy Co., TEPIC produced ~y Nissan Chemical Co~ Ltd~, and the like, Suitable examples of the melamine compounds are mel-amine or its derivatives, such as polymeth~lolmelamine, e g., mono-, di-, tri-, tetra-, penta- or hexamethylolmelamine, and alkoxy methylmelamine, e,g., trimethoxy methylmelamine or tri-butoxy methylmelamine.
A represen~at/ve example of the reactive phenol resins on the market is Ta]cirulc #2Ql produced by Sumitomo Chemical Co., Ltd.
Suitable examples of the polyvalent metal chelate com-pounds are titanium acetylacetonate, ammonium titanium lactateand the like.
The amount of the polyfunctional compound compounded is usually from about 0.01 to a~out 2~Q parts by weight per 100 parts ~y weight of the unsaturated monomer used~ The use of an excess of the polyfunctional compound may reduce the solubility of the ad~esive in ~ater.
The water-soluble pressure-sensitive adhesive composit-ion of this invention can contain, as necessary, well known add-itives such as a colouring agent r a filler r and an antiaging agent.
0 In addition, if desired, natural or synthetic polymers such as æ~D6 ~

polyvinyl alcohol, car~oxymethyl cellulose, polyacrylic acid and glue canbe added as water-soluble adhesion providing agents.
The addition of the water-soluble adhesion providing agent mainly increases the shear adhesive properties However, if it is added in a large amount, the compati~ility of the poly-mer with the plasticizer may be reduced. Thus the amount of the water-soluble adhesion-providing agent is usually S to 30 parts by weight per 100 parts by weight of the unsaturated mon-omer used in the polymerization reaction, with the range of 1 to 20 parts ~y weight being preferred.
The water-soluble pressure-sensitive adhesive of this invention, as apparent from the above description, exhibits pressure-sensitive adhesive properties under any conditions and is solu~le in water~ The use of the water-soluble pressure-sen-sitive adhesive of this invention reduces greatly the bleeding of the plasticizer encountered with the prior art adhesives ~ecause it has excellent compatibility of the water-solu~le plast-icizer with the polymer component. In addition, it has advant-ages in that its pressure-sensitive adhesive characteristics deriving from the good compatibility and its stability as an ad-hesive are improved and in that its adhesive characteristics atlow temperatures are increased.
By coating the adhesive composition of this invention on one or both surfaces of a water-soluble or water-dispersi~le tape-like su~strate of Japanese paper, rayon or unwoven fabric, there can ~e o~tained a pressure-sensitive adhesive tape which is very suita~le for use in the paper industry. This tape creates no problems such as bad print. In addition, the adhesive com-position of this invention can suitably be used in producing a label, a tape for fixing napkàn, or the like products. Further-more, it can be used in usual applications as a pressure-sensitive '3~7 1 adhesive; for example, an adhesive tape or sheet prepared by coating the adhesive composition of this invention on one or both surfaces of a tape or sheet of polyvinyl, chloride, poly-ethylene, polypropylene or polyethylene laminated paper has the advantage that in removing the tape or sheet after the adhesion thereof on a su~strate, it can easily be removed with water although leaving the adhesive on the surface of the substrate.
The following examples are given to explain this in-vention in greater detail, although this invention is not in-tended to be limited thereby. Various variations and modifi-cations can ~e made within the scope not departing from the tech-nical concept of this invention. All parts are by weight unless otherwise indicated~
EXAMPLE
A mixture of 50 parts of polyetherpolyol CSanix SP-750 produced by Sanyo Chemical Industries Co.~ and 1 part of pot-assium persulfate was dissolved in 30a parts of water, and 100 parts of acrylic acid was added thereto. The resulting mixture was charged to a 1 liter flask e~uipped with a stirrer, a ther-mometer, a reflux condenser and nozzle for introduction of nit-rogen gas, and it was then polymerized with stirring for 8 hours while keeping the temperature at 60C in a nitrogen stream.
The thus-o~tained reaction solution was a clear solu-tion having a high viscosity of lQ,OQQ poises when measured with a B-type rotary viscometer ~produced by Tokyo Keiki Co.) at 2 r,p,m, A part of the solution was dried, and free polyetherpolyol was extracted therefrom with benzene. Examination of the addition ratio of polyetherpolyol and acrylic acid from the above extracted amount indicated that q0~ of the polyetherpolyol charged reacted with acrylic acid.

~P7~7 l Then, 55 parts of Sanix SP~750 was added to 100 parts of the above solution to give a water-solu~le pressure-sensitive adhesive composition of this invention.
EXAMPLE
To 100 parts of the polymer solution obtained ~y the method of Example 1 were added an aqueous solution prepared by dissolving 2.1 parts of potassium hydroxide ~0.125 equivalent per car~oxyl group) in 20 parts of water and S5 parts of Sanix SP-75Q to give a water-soluble pressure-sensitive adhesive composit-ion of this invention.
COMPARATIVE EXAMPLE
A mixture of 100 parts of acrylic acid and 2 parts of potassium persulfate was dissolved in ~00 parts of water, and the resulting solution was charged to a l liter flask equipped with a stirrer, a thermometer, a reflux condensor and a nozzle for intro-duction of nitrogen gas. It was then polymerized with stirring ., . i for 8 hours while keeping the temperature at 60C in a nitrogen stream.

To the thus-obtained pol~mer solution were added an aqueous solution prepared ~y dissolving ~.7 parts of potassium hydroxide (0.125 equivalent per carboxy groupl in 50 parts of water S;A~ `X ~
and 30Q parts of-~Y~ SP-750 to give a water-soluhle pressure-sensitive adhesive composition.
The adhesive compositions obtained in Examples 1 and 2, and the comparative adhesive compositon obtained in Comparative Example were subjected to the following tests. The results are shown in Table l.
Sticking Test An adhesive composition was coated on one surface of a stainless steel plate. On the thus coated surface was placed a ~:~7~7 1 cylindrical stainless steel ~eight of a diameter of 5 mm and a weight of 1.5 g at a speed of 3Q0 mm/min. After 5 seconds the cylindrical stainless steel weight was elevated vertically at a speed of 300 mm/min., and the adhesion strength (g2 was measured by use of Tensilo~ UTM III (produced by Toyo Boldwin Co.), Peel ~Strength Test On one surface of a 25 ~ thick polyester film was coated an adhesive composition to give an adhesive tape of a wid-th of 25 mm. This adhesive tape was bonded to a thick glossy paper by use of 2 Kg loaded rollers. After being allowed to stand for 20 minutes, t~e ~onded member was subjected to a 180C tensile test a~: a tensile speed of 3Q0 mm/min. on a Shopper*type tension tester (~r-duced ~y Tsuchijima Manufacturing Co~
Solu~ility Test .
On both surfaces of a Japanese paper was coated an ad-hesive composition to give a 2~ mm x 200 mm adhesive tape piece.
'!'his tape piece was placed in 300 cc. of water of pH 2 or pH 12 maintained at 20+2C and the ~ater was stirred with a mixer for one minute. Thereafter the water was made to flow over a filter paper. When there remained no piece on the filter paper and the filtrate was clear, the solu~ility of the adhesive composition was indicated by ~O~, and when there remained a small piece or the filtrate was milky, it was indicated by ~X)~
Compatibility Test The same 20 mm x 200 mm adhesive tape piece as used in Solu~ility Test was prepared and interposed between two sheets of high quality paper (weight: 45 g~m2; thickness: 3Q Yl to give a sandwiched structure. This member was allowed to stand under a load of 600 g/cm in a desiccator adjusted to a temperature of 3Q+
2C and a humidity of 90 3% R.H. for 7 days, Then the member was *Trade Mark -21-~ j 9'7 1 taken out of the desiccator, and the migration of the plasticizercontained in the adhesive into the high quality paper (bleeding) was examined. As indicated in the following Table l, where no migrat:ion was.observed the compatibility of the adhesive composit-ion is indicated by ~O~, where a slight migration was o~served it is indicated ~y (~l, and the symbol (X~ indicates substantial migration of the plasticizer into the surface of the paper.
TABLE

Comparative ~xample l Exam~le 2 Example Sticking Cgl 80 95 25 Peel Strength Cg~25 mml 72a 1050 650 Solu~ility p~ 2 O O O
pH 12 O O O
Compatibility O O X
EX~MPLE 3 The procedure of Example .l was repeated wherein 90 parts of acrylic acid and lO parts of n-butyl acrylate were used in place of lO0 parts of acrylic acid and 2 parts of ammonium per-sulfate was used in place of l part of potassium persulfate.
To the thus obtained polymer solution was added 300 parts of Sanix SP-750 and the ion crosslinking agents as shown below to give three kinds of water-soluble pressure-sensitive ad~esive compositions, Ion Crosslinking Agents No. l An aqueous solution of 7 parts Co.l equivalent per car~oxyl group~ of potass~um hydroxide and 50 parts of water No. 2 An a~ueous solution of 0,28 part (0.005 equival-ent per carboxyl groupl of aluminum chloride and 30 parts of water 1~7~ '7 1 No. 3 An aqueous solution of 13.14 parts ~0.1 equiv-alent per car~oxyl group~ of diethanolamino and 30 parts of water EXAMPLE~ 4 To 100 parts of the adhes~ve composition prepared by adding No. l in Example 3 was added 0O2 parts of a 10% aqueous solution of a water-soluble trifunctional polyepoxide: trigly-cidyl isocyanurate ~epoxy equivalent 9-9l to form a water-solu~le pressure-sensitive adhesive composition of this invention.
The adhesive compositions of Example 3 and 4 were sub-jected to the same tests as in the foregoing examples and to co-hesive strength, shear adhesive strength and moisture resistance tests. The results are shown in Table 2, The cohesive strength, shear adhesive strength and moisture resistance tests were conducted as follows: -Cohesive Strength Test An adhesive composition was coated on one surface of a 25 ~ thick polyester film to provide a 10 mm x 2~ mm adhesive tape piece. This tape piece was sticked onto a Bakelite plate, and 500 g of load was applied on the tape piece in the vertical direction. After one hour, the distance that the tape piece txavelled downwards was measured, Sh~ar Adhesive Strength-Test On both surfaces of an unwoven cloth was coated an ad-hesive composition to provide a 20 mm x 20 mm adhesive tape piece, This adhesive tape piece was interposed between 2 sheets of thick gloss~ paper and bonded together in the sandwiched structure, and its shear adhesive strength was measured at a tensile speed of 3QQ mm/min~ in a ~ox heated at the predetermined temperature.

1 Moisture Resistance Test On both surfaces o~ an un~oven cloth ~as coated, an adhesive composition to provide a 20 mm x 2~ mm adhesive tape piece. This adhesive tape piece was interposed hetween two sheets of high quality paper ~weight: 60 g~m2; thickness: 50 ~) and ~onded together in t~e sandwiched structure. This member was placed under a load of 5Q g in a ~ox into which steam was always hlown, and the time at which the high quality paper dropp-ed was measured.

Example 3 ~ Example 4 No. 1 No. 2 No. 3 , Sticking Cgl ~2 81 23 ~8 Peel Strength 960 880 980 1000 ~g/25 mm~ -Cohesive Strength 0~04 0.04 0.08 0.05 , ~1 Shear Adhesive C*) Strength (Kg/2ax20 mm~

20C28.2 28.2 28.8 27.~

10QC26.4 26.0 26.Q 26.2 15QC25.0 24.8 24.5 25.2 Solubility pH 2 O O O O

pH 12 O O O O

Compati~ility O O O O

Mositure 5Q 46 50 more Resistance than ~min.L

~*~ In each example, the ~reakage of the substrate took place at the test, 1:3L7~L'997 A mixture of 200 parts of polyethyleneglycol (average molecular weight 4001, 2 parts of potassium persulfate, and 5.8 part~; of sodium hydroxide ~0.125 equivalent per carboxyl group) was dissolved in 3Q0 parts of water, and laOparts of methacrrylic acid was added thereto. The resulting mixture was polymerized in the same manner as in Example 1.
The polymer solution so obtained was used as it is as a water-soluble pressure-sensitive adhesive composition of this invention. This composition was su~jected to the same tests as used in the foregoing examples.
The results are as follows:
Sticking 85 g Peel Strength 85Q g/25 mm Cohesive Strength 0.10 mm Shear Adhesive Strength 20 C 22.1 Kg~20x20 mm ~su~strate ~roken~
100C 25.~ "

150C 14.5 "

Solu~ility pH 2 O
pH 12 O
Compati~ility O
Mositure Resistance42 min.

EXAMPLES 6 to 9 The procedure of Example 1 was repeated wherein the kinds and amounts of the unsaturated monomer, the alcohol-based plasticizer and the polymerization initiator ~as changed as in-dicated in Table 3.

~25 ~7~9~7 1 TA~LE 3 Unsaturated Alcoholic Polymerization ~*) Monomer Plasticizer Initiator Ex. (Parts~ ~Parts~ ~Parts) 6 Acrylic Acid Polyethyleneglycol KPS ll]
~100) having a molecular weight of 8ao U50) 7 Acrylic Acid Sanix TP-400 C50~APS (~
(951 2-Ethylhexyl Acrylate ~5~
8 Acrylic Acid Polypropyleneglycol KPS C21 C75~ having a molecu~ar Vinyl Acetate weig~t of 300 (50 C25~
Acrylic Acid Sanix TP-4QQ KPS ~22 ~50) (50) Maleic Acid (50~
~*~, KPS = potassium persulfate APS = ammonium persulfate To the thus-obtained polymer solutions the water-sol-uble plasticizers and ionical-crosslinking agents were added, as indicated in Table 4, to provide four kinds of water-solu~le pressure-sensitive adhesive compositions of this invention. The ionical-crosslinking agents were added after being dissolved in 3Q parts of water in Exam~les6 to 8, and in 20 part of water in Example ~.

Water Soluble Plasticizer Ionical-Crosslinking Agent Example(parts) ~partsl 6 - Potassium Hydroxide (3.q; 0.05 equivalent per carboxylic group~
7Sanix TP-400 (150~ Sodium Hydroxide (5.3; 0.1 equivalent per car~oxyl groupl 8Sanix GEP-2800 (150i Sodium Hydroxide (2.8; 0.067 equivalent per carboxyl group) .7:~l9~
1 TABLE ~4 cont Water Solu~le Plasticizer Ionical-Crosslinking Agent Example(parts~ (parts~
Sanix TP-4QQ U5Q1 Sodium Hydroxide (5,6; 0,125 equivalent per car~oxyl groupl T~e thus-o~tained adhesive compositions were subjected to the samè tests as used in the foregoing examples.
The results are shown in Table 5.

' 10 ExampleExample Example Example , . . .
Sticking ~g2 85 ~.0 83 40 m ~ Peel Strength ~00 950 ~00 88Q
(g/25 mml Cohesive Strength ~mml 0.10 0.05 0.07 a . li Shear Adhesive Strength ~*2 ~Kg/ZOx20 mm 2Q~(27~8~ (29Ø~ ~28.81 ~2~.Q~
laOC2Q.0 ~26~2~ ~25.6~ 24.6 150C11.~ (24.51 (25.02 14.6 Solu~ility pH 2 O O O O
pH 12 O O O
Compati~ility O O o O
Mositure Resistance 4Q 45 . 55 43 ~min. L
.
~*) The ~racket means that the ~reakage of the substrate occurred.
EXAMPLES 10 to 20 In the same manner as in Example 1, the compositions 3L~'7~ 7 1 as indicated in Table 6 were pol~merized in water.
The symbols used in Table 6 indicate the follo~ing compound~.
AA Acrylic Acid n-BA n-Butyl Acr~late MAA Methacrylic Acid iso-BA Isobutyl Acrylate VP Vinylpyrrolidone MM Monometh~l Malate MeEMA 2-Methoxyeth~l Methacrylate VAC Vin~l Acetate APSj KPS Same as in Ta~le 3 BPO Di~enzylperoxide Polymeri-Unsaturated Alcoholic zation Monomer Plasticizer Water Initiator Example ~partsl (parts) (parts2 ~parts) lQ AA (852 Sanix SP-750 500 APS Cl) n-BA C151 (200) 11 MAA ~75~ Sanix GP-400lOa H20 ~0.1) iso-BA ~252 (100~ Sod~um Ascor~ate (0.05~
12 AA ~802 Sanix SP-750600 APS (0.5) VP (102 ~2002 MM (102 Pentaerthlite (50) 13 AA ~65) Sanix SP-75050 APS C0.052 MeEMA ~301 ~202 VAC (52 14 AA ~1~02 Sanix GP-250 200 KPS ~0.5) ~200~
AA Cl~01 Sanix GP-40Q 200 KPS ~0.5) ~lQ0~
16 AA C1~02 Sanix GP-60Q 200 KPS CQ.5) ~100 1 17 AA (1002 Sanix GP-1000 200 KPS (0.5 (1002 1 TABLE 6 cont Polymeri- `
Unsaturated Alcoholic zation MonomerPlasticizer Water Initiator E mple (parts) (parts) (parts) (parts) 18 AA Clo01 Sanix GP-300 200 KPS (0.5 Clo O ) 12 AA ~5~ Sanix SP-750 100 APS C2.0) iso-BA C5~ Cloo~

AA C60) Sanix GP-600 200 BPO ~0.1) MM ~30~ (1501 n-BA (10) To the thus-o~tained polymer solutions were added t~e polyfunctional compounds, the water-solu~le plasticizers and the ionical-crosslinking agents as indicated in Table 7 to pro-vide 11 kinds of water-soluble pressure-sensitive adhesive com-positions of this invention. The ionical-crosslinking agents ~ere added in the state of aqueous solution, and the figures in Table 7 indicate the num~er of equivalents per car~oxyl group contained in the pol~mer component.

Polyfunctional Water-Solu~le Ionical-Crosslinking Compound Plasticizer Agent 20Example _Cparts) ~parts2 ~equivalent~

Trimethoxy Sanix SP-750 KOH C0.251 Methylmelamine ~200 ~0.5) 11 - Sanix GP-400 ~50 12 TEPIC - NaOH (0. a2 ~

13 - Sanix SP-750 Ethanolamine C0.3) (5001 14 Trimethoxy Sanix GP-25~ KOH (0,12) Methylmelamine csa~
C0.03 " Sanix GP-400 , (100~
16 . " Sanix GP-60a "
(200) -29- .

~7~
1 ~ABLE~ 7 cont ~ . .
Polyfunctional Water-Soluble Ionical-Crosslinking Compound Plasticizer Agent Example (~arts) (~arts) (eauivalent) 17 Trimethoxy Sanix GP-60Q KOH (0.12 Methylmelamine (3QQ~
(Q.03) 18 " Sanix GP-1000 "
CSOO.~
19 - Sanix SP-750 Hexameth~lene-~100~ diamine C0.03) 2Q Trimethoxy Sanix GP-600 KOH (0.1 - Methylmelamine ~5Q) ~Q.12 All of the thus-obtained water-soluble pressure-sen-sitive adhesive compositions exhibited good pressure-sensitive adhesive characteristics like the compositions of Examples 1 to q, and their solubilities in water and compatibility of polymer with plasticizer were satisfactory. In this explanation, only the test results of compatibility, which are considered to be the most important effect of this invention, are disclosed, and other test results about adhesive characteristics are omitted.
In measuring the compatibility, specimens were allowed to stand in an atmosphere of 35C and 80% RH, and the migration of the plasticizer was examined with a laspe of time. The other tests were conducted in the same manner as in the foregoing examples.
The results are shown in Table 8.
For comparison, adhesive compositions were prepared in the same manner as in Comparative Example from the compositions corresponding to those in Examples 10 to 20. The results obtain-ed are shown in brackets in Tahle 8.

9~

Example and Time for which Corresponding specimens were allowed to stand Comparatlve Example ( ~ 1 day 3 days 7 days14 days30 days 0 (o) O (x) O (XlO (X) O tX) ~1 0 (O~ O (X) o (X)/~ (X) ~ (X) 12 0 (O) O (O) O (X)O (X~ ~ (X) 13 0 (02 o (X~ o ~X)o ~X~ o (.X) 14 0 (X) O (X~ O ~X~A (X~ ~ (X) o ~X) (X~ O ~X~~ (X) ~ (~) 16 o (X) o CX~ o ~X~~ (X~ ~ (X~
17 0 ~X) O (X~ O (X~~ (X~ ~ (X~
18 o (X~ (X~ O ~X~~ (X2 A (X~
1~ 0 ~o) o () o ~2 (X~ o (X) 2~ 0 (O). o ~O). O (X~o (X) o (X) . EXAMPLES 21 TO 27 In the same manner as in Example 1, the compositions indicated in Ta~le Q were polymerized in an aqueous medium con-taining organic solvents.
The symbols used in Ta~le 9 indicate the following compounds, and the other symbols are the same as in Ta~le 6.
EA Ethyl Acrylate MeEA 2-Methoxyethyl Acrylate M Maleic Acid ~5MA Methyl Methacrylate OA Octyl Acrylate .
Polymeri-Vnsaturated Alcoholic zation Monomer Plasticizer Solvent Initiator Example ~parts) ~parts~ ~parts~. ~parts) 21 AA (801 Sanix SP-750 Water ~:50~ APS-(0.~) EA C20L (100~ Meth~l Ethyl Ketone ~50l.

22 MA~ ~60) " Water (80) APS (.1.0).
MeEMA (301 Isopropanol OA C10~ ~20) 23 AA C801 " Water ~20~ APS (Ø1) EA (202 Acetone C801 24 AA (.301 " Water ~.50~ APS ~0.3 EA (.701 Methanol ~50~

M ~30) Sanix GP-600 Water ~20~ BPO (n.l) VP C52 ~lOOl Methanol MeEA ~651 (80) 26 AA (90~ Sanix GP-600 Water (30) BPO (0.1 MMA (10). ~25~). Ethanol (.70) 27 VP (.100) Sanix SP-750 Water C80) KPS (Ø5).
~1001 Isopropanol (~20) To the thus-obtained polymer solutions the polyfunction-al compounds, the water-soluhle plasticizers, and the ionical-crosslinking agents were added, as indicated in Tahle 10, to provide 7 kinds of water-solu~le pressure-sensitive adhesive com-positions of this invention~ The ionical-crosslinking agents were added in the state o aqueous solution, and the figures in Ta~le lQ indicate the num~er of equivalent per carhox~l group contained in the pol~mer component.

3~

1 TABLE lQ
. ~ ~
Polyfunctional ~ater-Solu~le Ionical-Crosslink-CompoundPlasticizer ing Agent Example ~parts~. ~partsl Cequivalent~.

2:l TEPIC ~0.11Sanix SP-750 KO~ C0.25) Cl~o ) 22 Trimethyoxy " "
Methylmelamine Co ,1~
23 TEPIC (0.1~ " "
24 TEPIC (0.1~ " KOH (0.8~

Trimethoxy - FeC12 (0.02) Methylmelamine ~0.1~

2~ Trimethoxy - KOH ~0,2) Methylmelamine (0.12 27 -Sanix SP 750 "
(50j These water-solu~le pressure-sensitive ad~esive com-positions were all produced ~y use as a solvent of an aqueous medium containing organic solvents, They exhi~ited good pres-sure-sensitive adhesive properties similar to those of the com-~O positions of Examples 1 to 20 which were produced ~ used as asolvent of water only, and their solubilities in water and com-pati~ilities of the polymer in the composition with the plastic-izer were satisfactory. In this example, only the test results of compatibility were indicated, and the other results are omitt-ed, The method of measuring the compati~ility is the same as in Examples 10 to 20.
. The results are shown in Ta~le 11.

~7J~997 Example and Time for which Corre~sponding specimens were allowed to stand Comparative Example C ) 1 day 3 days 7 days14 days 30 days 21 O (O) O (O) O (X) O (X~ O (X) 22 O ~. O (X) O (X~ o (X~ ~ (X) 23 O (O~ O (O~ O (~1 o (X~ o ~X) 24 0 (O~ O ~O~ O (~ O (~ O (X) O (O~ O ~X~ O (X~ o (X~ ~ (X~
26 0 (Ol O ~O) O (~ o ~X~ (X) 27 O ~) O (~) O ~X~ O (X~~ (X) The compositions as shown in Tables 12 and 13 were polymerized in the same manner as in Example 1 in organic sol-vents.
The meanings of the sym~ols used in these tables are the same as in Tables 6 and 9, and the new symbols indicate the following compounds.

2EHA 2-Ethylhexyl Acrylate EEMA 2-Ethoxyethyl MethacryIate IA Itaconic Acid HEA 2-Hydroxyethyl Acrylate EM Monoethyl Maleate iso-OA Isooctyl Acrylate -DMM Dimethyl Maleate -34~

1~L7~997 1 TABLE l?
Polymeri-Unsaturated Alcoholic zation Monomer Plasticizer Solvent Initiator Example (parts? (parts) ~parts) (parts) 28 AA ~80~ Sanix SP-750 Methanol APS C0.2) EA (20~ (lO0). (lO0~ -29 " " Ethanol "
(100) AA (50~. " Ethyl BPO (O.l) EA ~301 Acetate BA ~2Q) (lO0~
3l AA ~40~ " Toluene "
2EHA ~60~ (50) 32 " " Benzene "
~200) 33 AA ~lO~ Sanix SP-750 Methanol BPO C0.5) Me~MA Cq~ (lO0) (80) Glycerin Toluene ~b ) ~20 ~
34 AA ~20~ Sanix SP-750 Toluene BPO ~Q.2) BA ~30~ ~30) (60) MeEMA ~50) X~lite Methyl ~0.) Ethyl Ketone ~,~0.~
. AA (501 Sanix SP-750 Ethyl BPO ~O,l) EMA ~30L (50~ Acetate 2EifA (20~ Sorbit* ~0) (lO01 . TABLE 13 -i . Polyme~ri-Unsaturated Alcoholic zation Monomer Plasticizer Solvent Initiator Example (parts) (parts) (parts) (parts) 36 AA (20) Sanix TP-400 Acetone BPO (O,l~
MeEA ~70) (50) (lO0) VAC ~lO~
37 AA ~lO0) Sanix SP-750 Ethanol BPO ~0.05) (100~ ~100) 38 MAA (51 ~' Ethanol BPO ~0.4~.
BA ~5~ ~50) : MeEA ~.0). Toluene (50) ~ 303Q IA (50) Sanix ~P~60Q Met~anol BPO (Q,l~.
HEA (20) Cl50). (lQo~
EEMA (3aL

*Trade Mark -35-' 1:~7~997 TABLE 13 cont ' ''' Polymeri-Unsaturated Alcoholic zation Monomer Plasticizer Solvent Initiator Example (partsl ~ (partsl ~ (part~l ` Cparts) AA (4Q~ San~x SP~75~ ~ethanol BPO (0.1 EM ~30) tl501 csol iso-OA (3Q~ Toluene ~Q~
41 AA ~80) Sanix GP~60Q Ethanol "
D~M (20~ (150~ C60~
Xylene ~4Ql To t~e thus-o~tained polymer solutions the polyfunction-al compounds, the water-soluble plasticizers, and the ionical-crosslinking agents were added, as shown in Ta~le 14, to provide 14 kinds of water-soluble pressure-sensitive adhesive compositions of this invention. The ionical-crosslinking agents were added in the form of aqueous solutions, and the figures in Table 14 indicate the number of equivalents per car~oxyl group contained in the polymer component.

Polyfunctional Water-Soluble Ionical-Crosslinking Compound Plasticizer Agent Example (parts~ tparts) ~ (equivalent) 28 TEPIC ~0.1) Sanix SP-750 KOH (0.25) lloo~
29 ~ 1 "

Alkylphenol Sanix SP-750 "
(0,2l ~200) 31 " Sanix SP-750 "
(50) 32 "
33 - - NaOH (0.8~
34 TEPIC C0.05~ - Hexylamine (0.7) - Sanix SP-750 KOH (0.5) ~0 117~ 7 1 ~ABLE 14 cont Polyfunctional Water-Solu~le Ionical-Crosslinking Compound Plasticizer Agent Example ~arts~ ~partsl ~equivalent~
. ~ . .
36 - - ~OH ~Q.6) 37 Tri~utoxy Sanix SP-750 Calcium Acetate Methylmelamine ClQol (P.005l Co.ol~, 38 Triethoxy - Zinc Chloride Methylmelamine ~0.01 ~O .1~

3~ Trimethoxy - Tin Chloride Methylmelamine (0.01l ~O .1 4Q Alkylphenol Sanix SP-750 KOH ~0,5 Resin C0.05~

41 " Sanix GP-600 NaOH (Q.l) . ~50~

Although these water-soluble pressure-sensitive adhesive compositions wer~ prepared by use as a solvent of organic solvents, they exhibited good pressure-sensitive characteristics substant-ially similar to those of the water-soluble pressure-sensitive . adhesive compositions of Examples 1 to 27, which were prepared ~ use as a solvent of water alone or mixtures of ~ater and or-ganic solvents, and in addition, their solubilities in water and compati~ilities of polymer with plasticizer were sufficiently satisfactory.
In this example, only the results of the compatibility test are listed, and other test results are omitted. The com-patibility test was the same as that used in Examples 1~ to 27, and the results are shown in Table 15.
' ~37-~'7~'3~7 1 ~ABLE 15 Example and Corresponding Time for which Comparative s~ecimens were allowed to stand Example (. 2 1 day 3 days~7 days14 days 30 days 28 0 (01 (~ o (X)o ~X) ~ (X) 2~ 0 ~~ ~~ o (X)o (X) ~ (X) 0 (0~ 0 ~1 0 C~)o ~X) o (X) 31 0 ~0). 0 (02 0 ~ o (X) o (X) 32 0 (0~. 0 (0).0 (~) 0 (X). 0 (X~
10 33 0 ~0~ 0 ~0~0 ~) 0 ~) 0 (X
34 0 ~ 0 C020 (~)o (X) ~X) 0 (01 0 (0~0 (~)o (X] o ~X~
36 0 (02 0 ~.~20 (X).O (.X~ A (X) 37 0 (0~ 0 (~ 0 CX20 (X) ~ (X~
38 0 ~02 0 (~).0 (X)0 (X~ 0 (X~
3Q 0 (0~. 0 ~X20 (X) (Xl ~ (X~ , 4Q O ~2 0 (X20 (X)~ (X) ~ (X) 41 0 )~ 0 CXlO (X2~ CXI ~ (X~

While the invention has fieen descri~ed in detail and with reference to specific emfiodiment thereof, it will ~e apparent to one skilled in the art that various changes and modificiations can fie made therein without departing from the spirit and scope thereof.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A water-soluble pressure-sensitive adhesive composition comprising a composition obtained by the solution polymerization of an unsaturated monomer comprising a water-soluble ethylenically unsaturated monomer alone or a mixed system of the water-soluble ethylenically unsaturated monomer and a water-insoluble ethylenically unsaturated monomer copolymerizable therewith in the presence of water and an alcoholic plasticizer selected from the group consisting of polyether polyols and polyhydric alcohols, said alcoholic plasticizer having an average molecular weight of less than about 3,000 and which is liquid at room temperature, wherein water is present in an amount of from 50 to 1,000 parts by weight per 100 parts by weight of the unsaturated monomer, wherein the alcoholic plasticizer is present in an amount of from 20 to 400 parts by weight per 100 parts by weight of the unsaturated monomer, wherein the water-insoluble ethylenically unsaturated monomer comprises not more than 25% by weight of the total unsaturated monomer, wherein said composition contains as a polymer compo-nent a homopolymer of the unsaturated monomer and an addition copolymer of the unsaturated monomer and the alcoholic plasticizer, wherein a part or all of the water-soluble ethylenically unsaturated monomer is a carboxyl group-containing unsaturated monomer, and wherein the polymer component is crosslinked with a metal ion or amine through a part of the carboxyl groups con-tained therein.

2. A water-soluble pressure-sensitive adhesive composition of Claim 1, wherein a polymerization initiator for use in the solution polymerization is selected from the group consisting of a persulfate, hydrogen peroxide and a redox catalyst,

3. A water-soluble pressure-sensitive adhesive composition of Claim 1, wherein the metal ion or amine is a univalent metal ion or monoamine, and the amount of the metal ion or amine used is from about 0.01 to 0.8 equivalents per carboxyl group contained in the polymer component,

4. A water-soluble pressure-sensitive adhesive composition of Claim 1, wherein the metal ion or amine is a di- or trivalent metal ion or diamine, and the amount of the metal ion or amine used is from 0.002 to 0.05 equivalents per carboxyl group con-taining in the polymer component.

5. A water-soluble pressure-sensitive adhesive composition of Claim 1, wherein the water-insoluble ethylenically unsaturated monomer is selected from the group consisting of alkylacrylate or alkylmethacrylate containing up to 14 carbon atoms, vinyl acetate and dialkyl esters of dibasic unsaturated acids.

6. A water-soluble pressure-sensitive adhesive composition of Claim 1 including a polyfunctional compound.

7. A water-soluble pressure-sensitive adhesive composition of Claim 6, wherein the polyfunctional compound is compounded in an amount of 0.01 to 2.0 parts by weight per 100 parts by weight of the unsaturated monomer.

8. A water-soluble pressure-sensitive adhesive composition of Claim 6, wherein the polyfunctional compound is selected from the group consisting of an epoxy compound, a melamine com-pound, a chelate compound of a polyvalent metal, and a reactive phenol resin.

9. A water-soluble pressure-sensitive adhesive composition comprising a composition obtained by the solution polymerization of an unsaturated monomer comprising a water-soluble ethylenically unsaturated monomer or a mixed system of the water-soluble ethylenically unsaturated monomer and a water-insoluble ethylenically unsaturated monomer copolymerizable therewith in the presence of at least one solvent selected from the group consisting of a water-soluble organic solvent, a mixture of water and a water-soluble organic solvent, a water-insoluble organic solvent and a mixture of a water-soluble organic solvent and a water-insoluble organic solvent and an alcoholic plasticizer selected from the group consisting of polyether polyols and polyhydric alcohols, said alcoholic plasticizer having an average molecular weight of less than about 3,000 and which is liquid at room temperature, wherein the solvent is present in an amount of from 50 to 500 parts by weight per 100 parts by weight of the un-saturated monomer, wherein the alcoholic plasticizer is present in an amount of 20 to 400 parts by weight per 100 parts by weight of the unsaturated monomer, wherein the water-insoluble ethylenically unsaturated monomer comprises not more than 75% by weight of the total unsaturated monomer, and wherein said composition contains as a polymer com-ponent a homopolymer of the unsaturated monomer and an addition copolymer of the unsaturated monomer and the alcoholic plasticizer.

10. A water-soluble pressure-sensitive adhesive composition of Claim 9, wherein a part or all of the water soluble ethyl-enically unsaturated monomer is a carboxyl group-containing unsaturated monomer.

11. A water-soluble pressure-sensitive adhesive composition of Claim 10, wherein the polymer component is cross-linked with a metal ion or amine through carboxyl groups contained therein.

12. A water-soluble pressure-sensitive adhesive composition of Claim 11, wherein the metal ion or amine is a univalent metal ion or monoamine, and the amount of the metal ion or amine used is from about 0.01 to 0.8 equivalents per carboxyl group contained in the polymer component.

13. A water-soluble pressure-sensitive adhesive composition of Claim 11, wherein the metal ion or amine is a di- or trivalent metal ion or diamine, and the amount of the metal ion or amine used is from 0.002 to 0.05 equivalents per carboxyl group containing in the polymer component.

14. A water-soluble pressure-sensitive adhesive composition of Claim 9, wherein the water-insoluble ethylenically unsaturated monomer is selected from the group consisting of alkylacrylate or alkylmethacrylate containing up to 14 carbon atoms, vinyl acetate and dialkyl esters of dibasic unsaturated acids.

15. A water-soluble pressure-sensitive adhesive composition of Claim 9 including a polyfunctional compound.

16. A water-soluble pressure-sensitive adhesive composition of Claim 15, wherein the polyfunctional compound is com-pounded in an amount of 0.01 to 2.0 parts by weight per 100 parts by weight of the unsaturated monomer.

17. A water-soluble pressure sensitive adhesive composition of Claim 15, wherein the polyfunctional compound is selected from the group consisting of an epoxy compound, a melamine com-pound, a chelate compound of a polyvalent metal, and a reactive phenol resin.

18. A water-soluble pressure-sensitive adhesive composition of Claim 9, wherein the water-soluble organic solvent is selected from the group consisting of methanol, ethanol, isopropanol, acetone, and methylethyl ketone.

19. A water-soluble pressure-sensitive adhesive composition of Claim 9, wherein the water-insoluble organic solvent is selected from the group consisting of benzene, toluene, and ethyl acetate.

20. A water-soluble pressure-sensitive adhesive composition of Claim 9, wherein the water-insoluble ethylenically unsaturated monomer is selected from the group consisting of alkylacrylate or alkylmethacrylate containing 14 or less carbon atoms, vinyl acetate, and dialkyl esters of dibasic unsaturated acids con-taining 8 or less carbon atoms.