JPH08134423A - Self-adhesive acrylic emulsion composition - Google Patents

Abstract

PURPOSE: To obtain a self-adhesive acrylic emulsion compsn. which gives a dried coating film improved in water resistance and self-adhesive power by adding a small amt. of a polyfunctional compd. to a product obtd. by the emulsion polymn. of a vinyl monomer mixture mainly comprising an alkyl (meth) acrylate. CONSTITUTION: 0.1-2 pts.wt. polyfunctional compd. having at least two carboxyl- reactive groups in the molecule is added to 100 pts.wt. (solid base) product which is obtd. by the emulsion polymn. of an emulsified mixture comprising 100 pts.wt. monomer mixture contg. 60-99wt.% alkyl (meth)acrylate having a 4-12C alkyl group and 1-40wt.% vinyl monomer having at least one polar group selected from among carboxyl, amide, and hydroxyl groups and 0.5-8 pts.wt. polyoxyethylene alkyl ether carboxylate represented by the formula (wherein R is alkyl; n is 1-40; and M is an alkali metal or an ammonium ion).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acrylic emulsion type pressure-sensitive adhesive composition having a dry film with good water resistance.

[0002]

2. Description of the Related Art Conventionally, a pressure-sensitive adhesive tape using an acrylic emulsion-type pressure-sensitive adhesive composition has a hydrophilic group of an emulsifier itself which causes moisture in the pressure-sensitive adhesive layer of the above-mentioned pressure-sensitive adhesive tape due to moisture or moisture in the air. There were problems such as a decrease in cohesive force and white turbidity due to the attraction.

In order to solve the above-mentioned problems, for example, (1) a method of stably dispersing polymer particles in water by introducing a carboxyl group into the polymer without using an emulsifier (JP-A-52-33982). ), (2) a method using a reactive emulsifier that is incorporated into the polymer finally obtained because the emulsifier has an unsaturated double bond in the molecule (JP-A-4-53802) and the like. There is.

[0004]

However, although the water resistance of the pressure-sensitive adhesive obtained by the methods described in the above (1) and (2) publications has been considerably improved, the pressure-sensitive adhesive still contains an emulsifier. Since there is an ionic functional group such as a carboxyl group derived from the above, it is not yet sufficient in terms of water resistance that can withstand practical use.

An object of the present invention is to provide an acrylic emulsion type pressure-sensitive adhesive composition having a dry film having good water resistance and having a sufficient pressure-sensitive adhesive force.

[0006]

The vinyl-based mixed monomer used in the present invention contains (A) an alkyl (meth) acrylate as a main component and a specific amount of (B) a vinyl monomer having a polar group. Is.

The above alkyl (meth) acrylate (A)
Is an alkyl group having 4 to 12 carbon atoms,
For example, n-butyl (meth) acrylate, sec-butyl (meth) acrylate, t-butyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl ( (Meth) acrylate, n-
Nonyl (meth) acrylate, isononyl (meth) acrylate, lauryl (meth) acrylate and the like can be mentioned, and n-butyl acrylate, 2 is particularly preferable in that the obtained adhesive has a low glass transition temperature and good room temperature adhesiveness is obtained. -Ethylhexyl acrylate and the like are preferably used. These may be used alone or in combination of two or more.

The above alkyl (meth) acrylate (A)
The content of the cohesive force of the obtained dried pressure-sensitive adhesive becomes high, the sticking property at low temperature is lowered, and when the content is high, the cohesive force of the pressure-sensitive adhesive becomes low, and it becomes difficult to obtain shear strength. , In the total amount of vinyl-based mixed monomers,
It is preferably 60 to 99% by weight, more preferably 7
It is 0 to 98% by weight.

Vinyl monomer (B) having the above polar group
Are those having at least one or more polar groups selected from the group consisting of a carboxyl group, an amide group and a hydroxyl group, and examples thereof include (meth) acrylic acid, itaconic acid, (anhydrous) maleic acid and (anhydrous) fumaric acid. Vinyl monomers having a carboxyl group such as carboxyalkyl (meth) acrylates such as carboxyethyl acrylate and carboxypropyl acrylate, N-vinylpyrrolidone,
N-vinylcaprolactam, N-vinyllaurylolactam, (meth) acryloylmorpholine, (meth) acrylamide, dimethyl (meth) acrylamide, N-methylol (meth) acrylamide, N-butoxymethyl (meth) acrylamide, dimethylaminopropyl ( Vinyl monomers having an amide group such as (meth) acrylamide, N, N′-dimethyl (meth) acrylamide, isopropyl (meth) acrylamide, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxy. Butyl (meth) acrylate, caprolactone modified (meth) acrylate,
Examples thereof include vinyl monomers having a hydroxyl group such as polyethylene glycol (meth) acrylate and polypropylene glycol (meth) acrylate, and these can be used alone or in combination of two or more kinds.

Vinyl monomer (B) having the above polar group
The content of the cohesive force of the obtained pressure-sensitive adhesive after drying becomes low, it becomes difficult to obtain shear strength, and when the content is high, the cohesive force of the pressure-sensitive adhesive becomes high and the sticking property at low temperature decreases. , 1 to 10% by weight, preferably 2 to 7% by weight, based on the total amount of vinyl-based mixed monomers.

The vinyl-based mixed monomer may be copolymerized with the above-mentioned essential component alkyl (meth) acrylate (A) and another vinyl monomer copolymerizable with the vinyl monomer (B) having a polar group. Examples thereof include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, vinyl acetate, vinyl pivalate, vinyl propionate, and styrene.

When the content of the vinyl monomer increases, the cohesive force of the pressure-sensitive adhesive after drying becomes high and the sticking property at low temperature deteriorates.
Preferably 35% by weight or less, more preferably 25% by weight
It is the following.

The emulsion polymer used in the present invention can be obtained by emulsion polymerization of an emulsion mixture comprising the vinyl mixed monomer and the polyoxyethylene alkyl ether carboxylate (C).

The above polyoxyethylene alkyl ether carboxylic acid salt (C) is added as an emulsifier during emulsion polymerization, and is represented by the general formula

[0015]

Embedded image

(Wherein R is an alkyl group, n = 1 to 40,
M represents an alkali metal or ammonium ion, respectively, and is, for example, "MX-RLM4" manufactured by Kao Corporation.
5 "(R is a mixture of 12 and 14 carbon atoms, n is an average value of 4.
5) and "MX-RLM100" (R is carbon number 12 and 14
And n is an average value of 10) such as sodium salt and ammonium salt obtained by neutralizing commercially available polyoxyethylene alkyl ether carboxylic acid. These may be used alone or in combination of two or more kinds. May be done.

If the amount of the polyoxyethylene alkyl ether carboxylic acid salt (c) added is reduced, it becomes difficult to obtain polymerization stability, and if it is increased, it becomes difficult to obtain sufficient water resistance of the adhesive after drying. The amount is 0.5 to 8 parts by weight, and preferably 0.5 to 4 parts by weight, based on 100 parts by weight of the total amount of the vinyl-based mixed monomer.

In addition to the above polyoxyethylene alkyl ether carboxylate (c), other anionic emulsifiers may be used in combination, such as sodium polyoxyethylene lauryl sulfate, dialkyl sodium sulfosuccinate, and sodium dodecyl sulfonate. Non-reactive emulsifiers such as salt (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., trade name "Monogen Y-100"), ammonium polyoxyethylene nonylphenyl ether sulfate (made by Dai-ichi Kogyo Seiyaku Co., Ltd., trade name "Aqualon HS-10") , Methacrylic group, allyl group,
Examples thereof include reactive emulsifiers having an unsaturated double bond such as a propenyl group, but reactive emulsifiers are preferable because they are finally incorporated into the polymer chain.

When the amount of the above-mentioned non-reactive anionic emulsifier is increased, it becomes easy to liberate at the interface of the pressure-sensitive adhesive after drying due to moisture in the air, etc., and the adhesive force is easily changed with time, and when the amount of the above-mentioned reactive anionic emulsifier is increased. In addition, since the absolute amount of the emulsifying agent incorporated into the polymer chain during the polymerization gradually decreases during the polymerization, it becomes difficult to obtain sufficient polymerization stability until the completion of the polymerization.
It is preferably 0.5 parts by weight or less, more preferably 0.3 parts by weight or less, based on parts by weight.

In addition to the above anionic emulsifiers, for example, non-reactive nonionic emulsifiers such as polyoxyethylene nonylphenyl ether, or methacryl groups thereof,
A reactive nonionic emulsifier having an unsaturated double bond such as an allyl group or propenyl group added thereto can be used in combination, but the reactive emulsifier is preferably used for the same reason as above.

In the above emulsion polymerization, a water-soluble thermal polymerization initiator is generally used. For example, a peroxide such as ammonium persulfate or potassium persulfate, a water-soluble such as azobiscyanovalerianic acid or azobis-2-amidinopropane is used. Azo compounds or redox initiators.

The above emulsion polymerization is roughly classified into a batch polymerization method, a monomer dropping method and an emulsion monomer dropping method according to the difference in the monomer addition method, but it is not particularly limited. The batch polymerization method is, for example, pure water, an emulsifier,
In this method, a thermal polymerization initiator and a vinyl-based mixed monomer are added all at once, and the mixture is sufficiently emulsified by stirring under conditions where oxygen is removed by a nitrogen stream, and then the inside of the vessel is heated to perform polymerization. Further, the monomer dropping method is, for example, under the condition that pure water, an emulsifier, and a thermal polymerization initiator are put in a polymerization reactor and oxygen is removed by a nitrogen stream, after heating the inside of the reactor, a vinyl-based mixed monomer is added. This is a method of gradually polymerizing by dropwise addition of a fixed amount. Further, the emulsified monomer dropping method, for example, vinyl-based mixed monomer, emulsifier, to prepare the emulsified monomer in advance by sufficiently emulsifying pure water by stirring, then put pure water, the polymerization initiator in the polymerization reactor, This is a method in which the interior of the vessel is first heated under the condition where oxygen is removed by a nitrogen stream, and then the above-mentioned emulsified monomer is added dropwise in a constant amount to perform polymerization. Among the above-mentioned polymerization methods, the emulsion monomer dropping method is preferable because the polymerization stability is high even when the polymerization is performed at a high solid content.

When an emulsion polymer is obtained by the above emulsion polymerization, a chain transfer agent such as n-dodecyl mercaptan or the like is used for the purpose of adjusting the molecular weight, and an amine such as an amine is used for the purpose of obtaining dispersion stability during the polymerization. A pH adjusting agent such as caustic soda may be appropriately added.

The acrylic emulsion type pressure-sensitive adhesive composition of the present invention is obtained by adding a polyfunctional compound to the emulsion polymer obtained above.

The above-mentioned polyfunctional compound is added for the purpose of improving the water resistance by reacting with the carboxyl group in the polyoxyethylene alkyl ether carboxylate to make it nonionic, and the polyfunctional aziridine compound and polyfunctional compound are added. Functional carbodiimide compounds may be mentioned.

Furthermore, the above-mentioned polyfunctional aziridine compound and polyfunctional carbodiimide compound may be used as a cross-linking agent for the emulsion polymer, and particularly when the polymer in the emulsion polymer contains a carboxyl group, Since the polyoxyethylene alkyl ether carboxylic acid salt itself is incorporated into the polymer, there is no problem of a decrease in adhesive strength due to the deposition of the polyoxyethylene alkyl ether carboxylic acid salt on the adhesive layer interface, which is preferable.

The above-mentioned polyfunctional aziridine compound is
For example, 4,4-bis (ethyleneiminocarbonylamino) diphenylmethane, N, N-hexamethylene-1,
Examples thereof include compounds having an aziridine ring such as 6-bis (1-aziridinecarboxamide).

The above polyfunctional carbodiimide compound is
Examples of commercially available products that are compounds having a carbodiimide group include "Yucarlink XL-29SE" (trade name, manufactured by Union Carbide Co.).

When the amount of the polyfunctional compound added is small, it becomes difficult to sufficiently suppress the ionization of the carboxyl group in the emulsifier, and when the amount is large, the crosslinking density of the finally obtained pressure-sensitive adhesive becomes high, Since it becomes difficult to obtain sufficient adhesive properties, the solid content of the emulsion polymer is 100%.
It is 0.1 to 2 parts by weight, preferably 0.1 to 1 part by weight, based on parts by weight.

Further, a cross-linking agent other than the polyfunctional compound may be added for the purpose of cross-linking the emulsion polymer, and in this case, the polarities in the copolymer as used in general solvent-type pressure-sensitive adhesives are added. All that can react with a group can be used, and if the polymer in the emulsion polymer contains a hydroxyl group, for example, tolylene diisocyanate (TDI), naphthylene-1,5-diisocyanate, diphenylmethane. Isocyanate type crosslinking agents such as -4,4'-diisocyanate (MDI), hexamethylene diisocyanate (HMDI), isophorone diisocyanate (IPDI), xylene diisocyanate (XDI), trimethylolpropane modified TDI, MDI-ε caprotactam block, TDI-ε caprotactam block, MDI
Preferred examples thereof include blocked isocyanate crosslinking agents such as methyl ethyl ketoxime block and TDI-methyl ethyl ketoxime block, and ethylene glycol diglycidyl ether and propylene if the polymer in the emulsion polymer contains a carboxyl group. Glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, N, N,
Preferable examples include epoxy crosslinking agents such as N ′, N′-tetraglycidyl-m-xylenediamine.

When the amount of the above-mentioned crosslinking agent added is small, the crosslinking density of the obtained pressure-sensitive adhesive after drying becomes low, and it is difficult to obtain sufficient cohesive force. When the addition amount is large, the crosslinking density becomes high and flexibility is impaired. Since it becomes difficult to obtain sufficient pressure-sensitive adhesiveness, it is preferably 0.01 to 5 parts by weight, more preferably 0.05 to 3 parts by weight, based on 100 parts by weight of the solid content of the emulsion polymer. is there.

A tackifying resin may be appropriately added to the acrylic emulsion type pressure-sensitive adhesive composition of the present invention within a range not impairing the physical properties. For example, a terpene resin such as terpene phenol, a disproportionated rosin, a polymerization Examples thereof include rosin resins such as rosin and C5 or C9 petroleum resins.

As a method of adding the tackifying resin, the tackifying resin may be dissolved in the emulsified mixture in advance so as to be added together with the polymerization or after completion of the polymerization. However, when they are added together at the time of polymerization, a hydrogenated product, a disproportionate, a polymerized product such as dimerization, or the like, which hardly causes polymerization inhibition, is preferably used. Further, the addition amount of the tackifying resin is difficult to obtain a sufficient adhesive force when it becomes small, and it becomes difficult to obtain the cohesive force of the adhesive when it becomes large,
It is preferably 5 based on 100 parts by weight of the solid content of the emulsion polymer.
-30 parts by weight, more preferably 10-25 parts by weight.

Further, a defoaming agent, an antiseptic agent and the like may be appropriately added in addition to the viscosity adjusting agent such as polyacrylic acid salt and water-soluble urethane resin.

A pressure-sensitive adhesive tape is obtained by laminating the acrylic emulsion-type pressure-sensitive adhesive composition of the present invention on at least one surface of a substrate.

Examples of the base material include acetate,
Non-woven fabric made of rayon, polyester, Japanese paper, synthetic resin foam sheet, polyolefin, nylon,
A plastic sheet of polyester, acetate, polyvinyl chloride, or the like, a sheet of (meth) acrylate copolymer, or the like is used.

[0037]

In the present invention, since the polyoxyethylene alkyl ether carboxylate which is a non-reactive emulsifier is used during the polymerization, there is almost no change in the amount of the emulsifier during the polymerization, and the acrylic emulsion is suitable as a pressure-sensitive adhesive or a pressure-sensitive adhesive tape. A pressure-sensitive adhesive composition is obtained. Further, by adding the polyfunctional compound to the emulsion polymer, the carboxyl group in the emulsifier is deionized, the hydrophilicity of the carboxyl group is impaired, there is no whitening due to water absorption, and long-term cohesive force It is considered that the pressure-sensitive adhesive holding the above was obtained. Furthermore, when the polymer in the emulsion polymer contains a carboxyl group, the polyfunctional compound causes the polyoxyethylene alkyl ether carboxylate to be incorporated into the polymer in the emulsion polymer. It is possible to obtain a pressure-sensitive adhesive which does not cause precipitation or the like and has little change in pressure-sensitive adhesive properties over time.

[0038]

EXAMPLES Examples of the present invention will be described below. still,
Hereinafter, "part" means "part by weight". [Preparation of Emulsion Polymer] [Emulsion Polymer A] 20 parts of 2-ethylhexyl acrylate, 77 parts of n-butyl acrylate, 3 parts of acrylic acid, 0.05 part of n-dodecyl mercaptan, polyoxyethylene alkyl ether carboxylate in advance. (Kao Corporation, trade name "MX-REL100", hereinafter "MX-RE
L100 ") ammonium salt and 1 part of ion-exchanged water were mixed and stirred to obtain an emulsified mixture. Next, in a separable flask equipped with a reflux condenser, a thermometer, a stirrer, and a nitrogen gas inlet tube, 50 parts of an aqueous solution prepared by dissolving 0.1 part of ammonium persulfate in ion-exchanged water was placed and heated under a nitrogen gas atmosphere. Then, the temperature was maintained at 70 ° C., and the emulsion mixture was added dropwise using a dropping funnel over 3 hours to carry out emulsion polymerization. After completion of the dropping, the inside of the dropping funnel was washed with 2 parts of ion-exchanged water, and the reaction was performed at 70 ° C. for 1 hour and then at 90 ° C. for 2 hours to obtain an emulsion polymer having a monomer conversion rate of 99% by weight or more. Then, the emulsion polymer was cooled to 30 ° C., and then neutralized with 25 wt% -ammonia water to obtain an emulsion polymer A.

[Emulsion Polymer B] An emulsion polymer B was obtained in the same manner as the emulsion polymer A except that 3 parts of the ammonium salt of MX-REL100 was used.

[Emulsion Polymer C] As an emulsifier, MX-R
Other than the combined use of 1 part of the ammonium salt of EL100 and 0.5 part of a reactive nonionic emulsifier obtained by adding a propenyl group to polyoxyethylene nonylphenyl ether (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., trade name "Aqualon RN-20"). An emulsion polymer C was obtained by the same procedure as the emulsion polymer A.

[Emulsion Polymer D] As an emulsifier, polyoxyethylene nonyl phenyl ether ammonium sulfate salt (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., trade name "Aqualon HS-1"
0 ") except that 2 parts were used to obtain an emulsion polymer D by the same procedure as the emulsion polymer A.

[Emulsion Polymer E] The same procedure as for emulsion polymer A except that 1 part of dodecylsulfonic acid sodium salt (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., trade name “Monogen Y-100”) was used as an emulsifier. Emulsion polymer E was obtained.

(Examples 1 to 6 and Comparative Examples 1 to 6) According to the composition of Table 1, a polyfunctional aziridine compound (25% by weight aqueous dispersion, based on 100 parts of solid content of the emulsion polymers A to E, Product name “Chemite DZ-22” manufactured by Nippon Shokubai Co., Ltd.
E ", hereinafter referred to as" aziridine ") or a polyfunctional carbodiimide compound (50 wt% aqueous dispersion, manufactured by Union Carbide Co., trade name" Yukerlink XL-29SE ",
(Hereinafter referred to as “carbodiimide”) is mixed and stirred to uniformly disperse the acrylic emulsion-type adhesive composition, and then applied to a polyethylene terephthalate film having a thickness of 38 μm and dried in an oven to obtain a paste thickness. A 25 μm adhesive tape was obtained.

The evaluation items and evaluation methods are shown below. (Measurement of Peel Adhesive Strength) The adhesive tapes obtained in Examples and Comparative Examples were cut into strips having a width of 20 mm, and JIS Z
Table 1 shows the results of measuring the peel adhesive strength at 180 ° C. with respect to the SUS plate in accordance with 0237. However, the unit is gf
/ 20 mm. (Measurement of Haze Value) The adhesive tapes obtained in Examples and Comparative Examples were attached to the same polyethylene terephthalate film, and cut into a size of 100 mm × 25 mm to obtain a sample, which was obtained by a haze meter (manufactured by Tokyo Denshoku Co., Ltd., Table 1 shows the results of measuring the haze value at the initial stage and after immersing in water at 23 ° C. for 4 days as a substitute property of water resistance using a trade name “MODEL TC-HIIIDP”). However, the unit is%.

[0045]

[Table 1]

[0046]

The acrylic emulsion type pressure-sensitive adhesive composition of the present invention is used as a pressure-sensitive adhesive after drying because the carboxyl group in the emulsifier becomes nonionic by adding the carboxylic acid-reactive compound. In this case, the emulsifier does not take in water due to water or humidity in the air, and the cohesive force does not decrease or whitening occurs, and the emulsifier is suitably used for adhesive tapes and the like. For this reason, it is possible to carry out solvent-free applications in fields requiring water resistance and moisture resistance, which until now could not be replaced by acrylic emulsion type pressure-sensitive adhesives.

Claims (1)

[Claims] 1. A vinyl monomer containing (A) an alkyl (meth) acrylate having an alkyl group having 4 to 12 carbon atoms as a main component and (B) having a polar group in an amount of 1 to 10% by weight.
100 parts by weight of the vinyl-based mixed monomer contained, and
(C) The following general formula: (Wherein R is an alkyl group, n = 1 to 40, M is an alkali metal or ammonium ion, respectively), and an emulsion mixture of 0.5 to 8 parts by weight of a polyoxyethylene alkyl ether carboxylate is emulsion-polymerized. An acrylic emulsion type in which 0.1 to 2 parts by weight of a polyfunctional compound having two or more groups that react with a carboxyl group in the molecule is added to 100 parts by weight of the solid content of the emulsion polymer thus obtained. Adhesive composition.