JP2000096020A - Production of aqueous dispersion-type pressure-sensitive adhesive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for industrially advantageously producing the subject adhesive of high water resistance. SOLUTION: This method for producing an aqueous dispersion-type pressure- sensitive adhesive comprises the following process: a monomer with the glass transition point of the polymer therefrom at <=-20 deg.C is emulsion-polymerized using an anionic emulsifier at <=1 pt.wt. based on 100 pts.wt. of the monomer; after the emulsion polymerization, a nonionic emulsifier at 0.5-5 pts.wt. and/or a rosin- or terpene-based tackifying resin >=50 deg.C in softening point at 3-40 pts.wt., based on 100 pts.wt. of the monomer, is added to the system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for producing a water-dispersible pressure-sensitive adhesive having excellent water resistance, which is used for producing pressure-sensitive adhesive sheets such as sheets and tapes. About.

[0002]

2. Description of the Related Art Conventionally, in the production of pressure-sensitive adhesive sheets,
Primarily, solvent-based acrylic pressure-sensitive adhesives have been used, but since this kind of adhesive is synthesized in an organic solvent, there is an environmental problem with the volatilization of the solvent during coating, Conversion to water-dispersed acrylic pressure-sensitive adhesives is being pursued. However, the water-dispersed acrylic pressure-sensitive adhesive generally has a problem that the adhesive itself tends to absorb water, or to be whitened or clouded under high humidity or in a place where water drops are present. Therefore, water-dispersible acrylic pressure-sensitive adhesives have not been used for applications requiring water resistance.

In order to improve these characteristics, for example,
JP-A-6-49431 discloses a method for removing a water-soluble ion contained in a water-dispersed pressure-sensitive adhesive by contacting it with an ion-exchange resin, thereby obtaining a water-dispersed pressure-sensitive adhesive which hardly causes whitening. Is disclosed. However, this method has a problem that the production cost is high and the production process is complicated due to the use of the ion exchange resin.

Further, JP-A-6-65551 and JP-A-7-278521 disclose a method for improving the water resistance of a water-dispersible pressure-sensitive adhesive or the like by using a reactive emulsifier as an emulsifier. Is disclosed. However, this method has a problem that the type of the reactive emulsifier is limited, so that the composition of the monomer is changed, and the method cannot cope with the required characteristics required for the pressure-sensitive adhesive. .

[0005]

As described above, in the prior art, no general-purpose method for producing a water-dispersible pressure-sensitive adhesive excellent in water resistance at low cost and simply has not been found.
Accordingly, it is an object of the present invention to overcome such problems and to provide an industrially useful method for producing a water-dispersible pressure-sensitive adhesive having excellent water resistance.

[0006]

Means for Solving the Problems In order to overcome the above-mentioned problems, the present inventors have conducted intensive studies on water-dispersed pressure-sensitive adhesives. As a result, they have used a small amount of an anionic emulsifier as an emulsifier during emulsion polymerization. When a specific amount of a nonionic emulsifier or a rosin-based or terpene-based tackifier resin having a softening point of 50 ° C. or more is added after the emulsion polymerization, the detailed reason is not clear, but the above component added after the emulsion polymerization is water. Helps the fusion of polymer particles that make up the dispersion during film formation,
Because the gap where water enters by this is closed,
It was found that when an adhesive sheet was produced from the water-dispersed pressure-sensitive adhesive, the water resistance of the pressure-sensitive adhesive layer was greatly improved, and the present invention was completed.

According to the present invention, the polymer has a glass transition point of -2.
A monomer having a temperature of 0 ° C. or less is emulsion-polymerized using an anionic emulsifier in a proportion of 1 part by weight or less per 100 parts by weight of the monomer.
A nonionic emulsifier in a ratio of 0.5 to 5 parts by weight and / or a rosin or terpene-based tackifying resin having a softening point of 50 ° C. or more in a ratio of 3 to 40 parts by weight per part by weight is characterized by being added. And a method for producing a water-dispersed pressure-sensitive adhesive.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The monomers in the present invention have a glass transition point of a polymer (homopolymer or copolymer) of -20 ° C. or lower, preferably -25 °, so as to obtain satisfactory pressure-sensitive adhesiveness. The type and composition are not limited as long as the temperature is lower than or equal to ° C. Generally, one or two or more selected from alkyl acrylates and alkyl methacrylates are used as main monomers, and
A monomer mixture obtained by adding one or more kinds of modifying monomers in a proportion of 50% by weight or less and having a glass transition point of the copolymer equal to or lower than the above temperature is preferably used.

The above-mentioned alkyl acrylates include methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, isobutyl acrylate, sec-butyl acrylate, t-butyl acrylate, acrylic acid Pentyl, neopentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate, decyl acrylate, isodecyl acrylate, lauryl acrylate, bornyl acrylate, isobornyl acrylate, acrylic acid Myristyl, pentadecyl acrylate, stearyl acrylate and the like can be mentioned.

Examples of the alkyl methacrylate include methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, butyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, t-butyl methacrylate, methacrylic acid. Pentyl, neopentyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, isooctyl methacrylate, 2-ethylhexyl methacrylate, decyl methacrylate, isodecyl methacrylate, lauryl methacrylate, lauryl methacrylate,
Isobornyl methacrylate, myristyl methacrylate,
Examples include pentadecyl methacrylate and stearyl methacrylate.

The above-mentioned modifying monomers include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, styrene, substituted styrene, butadiene, acrylonitrile, ethylene, vinyl acetate, vinyl chloride and sodium vinyl sulfonate. , Acrylamide, methacrylamide, hydroxyl-containing monomers such as hydroxyalkyl (meth) acrylate, N-vinylpyrrolidone, (meth) acryloylmorpholine, cyclohexylmaleimide, isopropylmaleimide, N, N-dimethyl (meth) acrylamide, (meth) ) Glycidyl acrylate and the like.

In the present invention, emulsion polymerization is carried out using such a monomer by a conventional method. In this case, in order to secure polymerization stability, 1 part by weight per 100 parts by weight of the monomer is used as an emulsifier. Parts or less (usually up to 0.001 part by weight) of an anionic emulsifier is used. Examples of the anionic emulsifier include sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzenesulfonate, sodium polyoxyethylene alkyl ether sulfate, and sodium polyoxyethylene alkyl phenyl ether sulfate. Further, a radical polymerizable emulsifier having a propenyl group or the like may be used. If the amount of the anionic emulsifier exceeds 1 part by weight, it is difficult to obtain a good result in improving the water resistance of the pressure-sensitive adhesive.

In the emulsion polymerization, an appropriate polymerization initiator such as an azo type, a persulfate type, a peroxide type, or a redox type obtained by combining a persulfate or a peroxide with a reducing agent is used. Specifically, 2,2'-azobis (2-methylpropionamidine) disulfate, 2,2'-azobis (2-
Amidinopropane) dihydrochloride, potassium persulfate, ammonium persulfate, benzoyl peroxide,
T-butyl hydroperoxide, hydrogen peroxide and the like are used. As the redox initiator, a combination of a persulfate and sodium bisulfite, a combination of a peroxide and sodium ascorbate, or the like is used.

In the present invention, after the above emulsion polymerization,
By adding a predetermined amount of a nonionic emulsifier or a predetermined amount of a rosin-based or terpene-based tackifying resin having a softening point of 50 ° C. or higher, preferably 70 ° C. or higher, alone or together, a pressure-sensitive adhesive is obtained. Is to greatly improve the water resistance. On the other hand, when the above components are added at the time of emulsion polymerization, the above-mentioned improvement in water resistance is not achieved. The reason for this is that only when the above components are added after emulsion polymerization, these components work well on the polymer particles in the aqueous dispersion, assist in the fusion of these particles during film formation, and create a gap into which water enters. It is presumed that it may be to close effectively.

The above-mentioned nonionic emulsifier includes polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene fatty acid ester, polyoxyethylene polyoxypropylene block polymer and the like. The amount added is 0.5 to 5 parts by weight, preferably 1 to 4 parts by weight, per 100 parts by weight of the monomer. If the addition amount is less than 0.5 parts by weight, the water resistance of the pressure-sensitive adhesive is not so improved, and if it exceeds 5 parts by weight,
The water resistance deteriorates.

The rosin-based or terpene-based tackifying resins include rosin ester resins, disproportionated rosin ester resins, polymerized rosin ester resins, hydrogenated rosin ester resins, terpene phenol resins, and the like. These need to have a softening point of 50 ° C. or higher. If the softening point is lower than 50 ° C., the water resistance of the pressure-sensitive adhesive hardly improves. These tackifier resins may be emulsified and added to the aqueous dispersion after emulsion polymerization. The amount to be added is 3 to 40 parts by weight, preferably 5 to 40 parts by weight per 100 parts by weight of the monomer.
20 parts by weight. When the addition amount is less than 3 parts by weight, the water resistance of the pressure-sensitive adhesive is not so improved, and when it exceeds 40 parts by weight, the elastic modulus of the pressure-sensitive adhesive becomes too high,
Good pressure-sensitive adhesiveness cannot be obtained.

The water-dispersed pressure-sensitive adhesive thus produced can be applied to any support such as plastic film, paper, metal foil, etc., according to a conventionally known method for producing pressure-sensitive adhesive sheets. Sheets and tapes with improved water resistance by directly coating and drying, or by coating on a separator and drying and then transferring to the above support Pressure-sensitive adhesive sheets.

[0018]

Next, an embodiment of the present invention will be described in more detail. However, the present invention is not limited only to the following examples. In the following, all parts are parts by weight.

Example 1 84 parts of ion-exchanged water was placed in a reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube and a reflux condenser, and stirred for 1 hour.
The atmosphere was replaced with nitrogen for hours. Ammonium peroxosulfate 0.3
After adding 100 parts, the temperature was brought to 70 ° C., 100 parts of butyl acrylate, 5 parts of acrylic acid, and 0.005 part of sodium lauryl sulfate emulsified with 50 parts of water were added dropwise over 3 hours, followed by emulsion polymerization treatment. . It was neutralized with 10% by weight of aqueous ammonia to obtain an emulsified aqueous dispersion. To this aqueous dispersion, 4 parts of polyoxyethylene nonylphenol (HLB15.5) per 100 parts of solids was added and mixed well to prepare an aqueous dispersion type pressure-sensitive adhesive. This is 3
The composition was applied on an 8 μm polyester film and dried at 130 ° C. for 3 minutes to prepare a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer having a thickness of 40 μm.

Example 2 50 parts of ion-exchanged water was placed in a reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube and a reflux condenser, and the mixture was stirred for 1 hour.
The atmosphere was replaced with nitrogen for hours. After adding 0.25 parts of 2,2'-azobis (2-methylpropionamidine) dihydrochloride and adjusting the temperature to 50 ° C, 250 parts of butyl acrylate, 12.5 parts of acrylic acid, and polyoxyethylene nonylphenyl A solution obtained by emulsifying 0.5 part of ammonium ether sulfate with 212.5 parts of water was added dropwise over 3 hours to carry out emulsion polymerization.
It was neutralized with 10% by weight of aqueous ammonia to obtain an emulsified aqueous dispersion. To this aqueous dispersion was added polyoxyethylene nonylphenol (HLB10.8) per 100 parts of solids.
Two parts were added and mixed well to prepare a water-dispersed pressure-sensitive adhesive. Using this, a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer having a thickness of 40 μm was produced in the same manner as in Example 1.

Example 3 To the emulsified aqueous dispersion obtained in Example 1, 20 parts (solid content: 10 parts) of rosin phenol resin emulsion having a softening point of 125 ° C. were added per 100 parts of solid content. By mixing well, a water-dispersed pressure-sensitive adhesive was prepared. Using this, Example 1
In the same manner as in the above, a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer having a thickness of 40 μm was prepared.

Example 4 To the emulsified aqueous dispersion obtained in Example 2, 20 parts (solid content: 10 parts) of an emulsion of a polymerized rosin ester resin having a softening point of 125 ° C. per 100 parts of solid content was added. By mixing well, a water-dispersed pressure-sensitive adhesive was prepared. Using this, a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer having a thickness of 40 μm was produced in the same manner as in Example 1.

Example 5 The emulsified aqueous dispersion obtained in Example 1 was mixed with polyoxyethylene nonylphenol (HLB) per 100 parts of solids.
15.5) 2 parts, 30 parts of a rosin phenol resin emulsion having a softening point of 125 ° C. (solid content: 15 parts) were added and mixed well to prepare a water-dispersed pressure-sensitive adhesive. Using this,
A pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer having a thickness of 40 μm was produced in the same manner as in Example 1.

Example 6 To the emulsified aqueous dispersion obtained in Example 2 was added 30 parts (solid content: 15 parts) of a terpene phenol resin emulsion having a softening point of 130 ° C. per 100 parts of solid content. By mixing well, a water-dispersed pressure-sensitive adhesive was prepared. Using this, a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer having a thickness of 40 μm was produced in the same manner as in Example 1.

Comparative Example 1 The emulsified aqueous dispersion obtained in Example 1 was directly used as a water-dispersible pressure-sensitive adhesive, and the pressure-sensitive adhesive having a thickness of 40 μm was used in the same manner as in Example 1 A pressure-sensitive adhesive tape having an adhesive layer was prepared.

Comparative Example 2 To the emulsified aqueous dispersion obtained in Example 2 was added 2 parts of sodium lauryl sulfate per 100 parts of solid content and mixed well to prepare an aqueous dispersion type pressure-sensitive adhesive. Using this, a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer having a thickness of 40 μm was produced in the same manner as in Example 1.

Comparative Example 3 The emulsified aqueous dispersion obtained in Example 1 was mixed with polyoxyethylene nonylphenol (HLB) per 100 parts of solids.
15.5) 7 parts were added and mixed well to prepare a water-dispersed pressure-sensitive adhesive. Using this, a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer having a thickness of 40 μm was produced in the same manner as in Example 1.

Comparative Example 4 At the time of emulsion polymerization, 4 parts of polyoxyethylene nonylphenol (HLB15.5) was additionally used as an emulsifier.
A water dispersion in an emulsified state was obtained in the same manner as in Example 1 except that the emulsion polymerization treatment was carried out, and this water dispersion was used as it is as a water dispersion type pressure-sensitive adhesive. Thus, a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer having a thickness of 40 μm was produced.

Each of the pressure-sensitive adhesive tapes of Examples 1 to 6 and Comparative Examples 1 to 4 was subjected to a water resistance test. In the water resistance test, each pressure-sensitive adhesive tape was immersed in ion-exchanged water at room temperature, and the haze value before and 24 hours after immersion and the water absorption after 24 hours of immersion were measured. These results were as shown in Table 1.

[0030]

As is clear from the results shown in Table 1, each of the pressure-sensitive adhesive tapes of Examples 1 to 6 of the present invention was obtained in Comparative Example 1.
It can be seen that the increase rate of the haze value after immersion for 24 hours is small and the water absorption rate is low as compared with the pressure-sensitive adhesive tapes of Nos. 1 to 4 above.

[0032]

As described above, according to the present invention, a small amount of an anionic emulsifier is used as an emulsifier during emulsion polymerization, and a nonionic emulsifier or a rosin or terpene-based tackifying resin having a softening point of 50 ° C. or higher is used after emulsion polymerization. With a configuration in which a specific amount is added, it is possible to provide a method for industrially advantageously producing a water-dispersible pressure-sensitive adhesive having excellent water resistance.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Akiko Miyano 1-1-2 Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation F-term (reference) 4J004 AA04 AA10 AB01 CA01 CA02 CA06 CA08 CB02 CC02 GA01 4J011 KA02 KA04 KA12 KA15 KA29 KB09 KB29 PA57 PA69 PB39 PC06 4J040 BA20 DF041 DF051 JA04 JA09 JB09 KA26 KA38 LA02 LA07

Claims (1)

[Claims] 1. An emulsion polymerization of a monomer having a glass transition point of -20 ° C. or lower of a polymer using an anionic emulsifier in a ratio of 1 part by weight or less per 100 parts by weight of the monomer. After this emulsion polymerization, a nonionic emulsifier having a ratio of 0.5 to 5 parts by weight and / or a softening point of 50 having a ratio of 3 to 40 parts by weight per 100 parts by weight of the monomer.
A method for producing a water-dispersed pressure-sensitive adhesive, characterized by adding a rosin-based or terpene-based tackifying resin at a temperature of at least ° C.