JP2748033B2 - Aqueous adhesive composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

The present invention relates to a novel water-based pressure-sensitive adhesive composition having excellent mechanical stability.

2. Description of the Related Art

The pressure-sensitive adhesive is usually applied to paper, a plastic film, or the like, and applied to tapes, sheets, labels, and the like. Conventionally, a solvent-type pressure-sensitive adhesive has been widely used in the pressure-sensitive adhesive industry. However, in recent years, aqueous emulsion pressure-sensitive adhesives have various advantages such as being free from air pollution, being superior in safety and health, and being suitable for resource saving as compared with solvent-type pressure-sensitive adhesives. From water to an aqueous emulsion type pressure-sensitive adhesive. Along with this, a tackifier resin, which is a component of the pressure-sensitive adhesive, is also made into an aqueous emulsion, and added to a base resin such as an acrylic polymer emulsion to be used as a water-based emulsion-type pressure-sensitive adhesive. Thus, as the application of the aqueous emulsion-type pressure-sensitive adhesive expands, the required performance also becomes higher, and one of such required performances is renewed emphasis on the stability of the emulsion, especially the stability against the mechanical share. It became so. Here, the stability against mechanical share is
In addition to the stability against shear added in gear pumps and roll coating machines that have been known,
It refers to the stability against the shear added during spray coating, which has been increasing in the coating system in recent years, and when the stability against the mechanical shear is inferior, it has been a cause of generation of aggregates in the emulsion. In order to improve the stability against such mechanical share,
The type or amount of the dispersing agent used in the base resin such as acrylic polymer emulsion or the tackifier resin emulsion is adjusted and studied, but the improvement has not been made sufficiently, and the mechanical share is still high. Aqueous emulsion-type pressure-sensitive adhesives having good stability to water have not been obtained.

[Means for Solving the Problems]

The present inventors have conducted intensive studies in order to solve the above-mentioned problems of the prior art, and as a result, have found that the aqueous acrylic emulsion and the tackifier resin emulsion comprising a rosin ester and / or a rosin phenol are used. The present inventors have found that an aqueous pressure-sensitive adhesive composition, in which a water-soluble polymer having a specific composition is further blended with the agent composition, is stable against mechanical shear, and have completed the present invention. That is, the present invention relates to an acrylic polymer emulsion containing an acrylic ester and / or a methacrylic ester as a main component.
Parts by weight (in terms of solids), 5 to 30 parts by weight (in terms of solids) of a tackifier resin emulsion comprising rosin esters and / or rosin phenols, and at least one selected from acrylic acid, methacrylic acid, acrylamide or methacrylamide One kind of water-soluble polymer or water-soluble polymer alkali salt 0.01
The present invention relates to an aqueous pressure-sensitive adhesive composition comprising from 5 to 5 parts by weight (in terms of solid content). As the acrylic polymer emulsion used in the present invention, emulsions generally used for various acrylic pressure-sensitive adhesives can be used. The acrylic polymer emulsion is prepared by a batch charge polymerization method, a sequential addition polymerization method of an emulsion monomer, a sequential addition polymerization method of an emulsion monomer, a seed polymerization method, etc. which are usually performed as a method of emulsion polymerization of an acrylic ester and / or a methacrylic ester. It can be easily manufactured. Here, the acrylic acid ester and methacrylic acid ester (hereinafter, referred to as (meth) acrylic acid ester) monomers used are (meth) acrylic acid methyl ester, (meth) acrylic acid ethyl ester, and (meth) acrylic acid butyl ester. Examples thereof include esters, 2-ethylhexyl (meth) acrylate, glycidyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, and these may be used alone or as a mixture of two or more. It is preferable to use a small amount of (meth) acrylic acid instead of the (meth) acrylic ester in order to impart stability to the obtained resin emulsion. If desired, a copolymerizable monomer such as vinyl acetate or styrene can be used in combination to the extent that the adhesive properties of the (meth) acrylate polymer are not impaired. The glass transition temperature of these acrylic acid and methacrylic acid ester-based polymers is -70 to 0 ° C,
Preferably it is −60 to −10 ° C. If the temperature exceeds 0 ° C., the tack is remarkably reduced, which is not preferable. As the emulsifier used for the acrylic emulsion, an anionic emulsifier, partially saponified polyvinyl alcohol, or the like can be used, and the amount of the emulsifier used is about 0.1 to 5 parts by weight, preferably 0.5 to 3 parts by weight based on 100 parts by weight of the polymer. . On the other hand, as the tackifier resin emulsion used in the present invention, a resin emulsion of rosin esters and / or rosin phenols is used. Here, rosin esters are gum rosin, wood rosin or tall oil rosin, a raw material rosin or a material obtained by subjecting a stabilized rosin obtained by disproportionation or hydrogenation treatment of the raw material rosin and a polyhydric alcohol to an esterification reaction, Polyhydric alcohol ester of polymerized rosin, partially fumarized or maleated starting rosin, then polyhydric alcohol ester of partially maleated rosin obtained by esterification, polyalcohol ester of partially fumarated rosin, rosin starting material Is partially fumarated or maleated, then disproportionated and then esterified to obtain a polyhydric alcohol ester of a partially maleated disproportionated rosin, a polyhydric alcohol ester of a partially fumarated disproportionated rosin, or the like. Say. Rosin phenols refer to those obtained by adding phenols to raw rosin or stabilized rosin and thermally polymerizing them, or then esterifying them. Further, the polyhydric alcohol used for the esterification is not particularly limited, diethylene glycol, glycerin, trimethylolpropane, trimethylolethane, 1,2,6-hexanetriol, 1,2,4-butanetriol, Various known substances such as pentaerythritol can be exemplified. The softening point of the rosin ester thus obtained and the tackifier resin composed of rosin phenols are not particularly limited, and may be any of those having a high softening point of 200 ° C. or less to liquid ones. It may be appropriately selected for use. The tackifier resin is emulsified using an emulsifier, and the emulsifier used herein includes α-olefin sulfonate, alkyl sulfate, alkyl phenyl sulfate, polyoxyethylene alkyl phenyl ether sulfate, and polyoxyethylene aralkyl phenyl ether. Sulfosuccinic acid half ester salt,
Examples include anionic emulsifiers such as rosin soap and nonionic emulsifiers such as polyoxyethylene alkylphenyl ether. The amount of the emulsifier used is not particularly limited, but is usually about 1 to 10 parts by weight, preferably 1 to 5 parts by weight, in terms of solid content, based on 100 parts by weight of the resin. When the amount exceeds 10 parts by weight, the water resistance of the obtained pressure-sensitive adhesive decreases. If the amount is less than 1 part by weight, the stability of the resin emulsion at the time of emulsification becomes poor. The method for producing the tackifier resin emulsion is not particularly limited, and examples thereof include the following methods. For example, a method of dissolving the tackifier resin in a solvent such as benzene and toluene, adding the emulsifier and soft water, emulsifying using a high-pressure emulsifier, and then removing the solvent under reduced pressure. , A solvent such as toluene is mixed, and then an emulsifier is kneaded, and further hot water is gradually added, followed by phase inversion emulsification to obtain an emulsion, and then the solvent is removed under reduced pressure or used as it is, in an autoclave. , The temperature of the resin is raised to a level higher than the softening temperature of the resin, the emulsifier is kneaded, hot water is gradually added, and the emulsion is emulsified by phase inversion emulsification. In the present invention, it is essential to use a water-soluble polymer or a water-soluble polymer alkali salt composed of at least one selected from acrylic acid, methacrylic acid, acrylamide or methacrylamide. That is, the present invention has improved the mechanical stability of the aqueous pressure-sensitive adhesive composition, which has been a problem of the prior art, by using the water-soluble polymer or the alkali salt of the water-soluble polymer. The water-soluble polymer, acrylic acid, methacrylic acid,
It is a homopolymer of acrylamide or methacrylamide, or a copolymer of two or more thereof, and is usually a high molecular weight polymer having an average molecular weight of 10,000 or more. Examples of the alkali of the water-soluble polymer alkali salt include ammonia, sodium hydroxide, potassium hydroxide, alkanolamine, alkylamine, and morpholine. The polymerization method may be any known method, and may be any one of an aqueous solution polymerization method, a solution polymerization method, an emulsion polymerization method, a suspension polymerization method, and any other polymerization method. The aqueous pressure-sensitive adhesive composition of the present invention has a tackifier resin emulsion having a solid content conversion of 5 to 30 parts by weight, preferably 7 to 100 parts by weight of a solid content of the acrylic emulsion.
~ 20 parts by weight, and the solid content equivalent of the water-soluble polymer is 0.01
To 5 parts by weight, preferably 0.05 to 2 parts by weight. If the amount of the tackifier resin emulsion is less than 5 parts by weight, sufficient adhesion cannot be imparted. If the amount exceeds 30 parts by weight, not only the adhesion decreases but also the adhesive becomes hard. It is not preferable because tack is also reduced. When the amount of the water-soluble polymer is less than 0.01 part by weight, the contribution to the improvement in stability against mechanical shear is small, and when it exceeds 5 parts by weight, the aqueous pressure-sensitive adhesive composition is significantly thickened. Or gelled. The aqueous pressure-sensitive adhesive composition of the present invention may contain a small amount of a disintegrating agent, a thickener, a filler, an antioxidant, a water-proofing agent, a film-forming auxiliary, etc., if necessary. Hereinafter, the present invention will be described in detail with reference to Production Examples, Examples, and Comparative Examples, but the present invention is not limited to these Examples. In each example, all parts and percentages are by weight unless otherwise specified. Production example Water 43.40 parts Anionic emulsifier (“HITENOL S”, solid content 50%, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) 0.92 parts Butyl acrylate 45.10 parts Acrylic acid 1.40 parts Catalyst (potassium persulfate) 0.24 parts pH adjuster (Heavy Sodium) 0.11 part Water 8.83 part In a four-necked flask equipped with a stirrer, cooling tube, dropping funnel and nitrogen inlet tube, the above was dissolved under a nitrogen gas stream at 70 ° C., and then stirred. Add 1/10 amount
Preliminary reaction was carried out at 70 ° C. for 30 minutes under a nitrogen gas stream, and then 9/10 amount of the mixture was added dropwise over 2 hours to carry out dropwise polymerization. After completion of the dropwise addition, the reaction was completed at 70 ° C. for 1 hour, cooled to room temperature, and then taken out while performing 100 mesh wire mesh filtration to obtain an acrylic emulsion having a solid content of 45.7%. Example 1 After dissolving 100 parts of a rosin-modified phenol resin having a softening point of 150 ° C. in 60 parts of toluene at 100 ° C. for about 1 hour, the mixture was cooled to 80 ° C. and an anionic emulsifier (sulfosuccinic acid half ester of polyoxyethylene alkyl ether) was dissolved. 3 parts in terms of solid content and 160 parts of water were added thereto, and the mixture was vigorously stirred at 75 ° C. for 1 hour to perform preliminary emulsification. The obtained preliminary emulsified product was emulsified at a pressure of 300 kg / cm ² by a high-pressure emulsifier (manton gauulin) to obtain an emulsified product. Next, 200 parts of the above-mentioned emulsion was charged into a vacuum distillation apparatus and subjected to vacuum distillation at 50 ° C. and 100 mmHg for 8 hours to obtain a rosin-modified phenol resin emulsion having a solid content of 55%. On the other hand, 23 parts of an 80% aqueous solution of acrylic acid was added to 100 parts of water, and after raising the temperature to 60 ° C., 0.2 part of an aqueous solution of 25% ammonium persulfate was further added, followed by polymerization for 2 hours to obtain a water-soluble polymer of polyacrylic acid. Obtained. 20 parts of the rosin-modified phenol resin emulsion thus obtained (in terms of solid content), 0.3 parts of the water-soluble polymer of polyacrylic acid (in terms of solid content) and 80 parts of the acrylic emulsion obtained in the above production example (in terms of solid content) ) Were mixed to obtain an aqueous pressure-sensitive adhesive composition adjusted to pH = 8 and a nonvolatile content of 30% with 28% aqueous ammonia. Example 2 An emulsion was obtained in the same manner as in Example 1 except that the rosin-modified phenolic resin was replaced by a partially fumarated disproportionated rosin pentaerythritol ester (softening point: 125 ° C.). Was. Further, an aqueous pressure-sensitive adhesive composition was obtained by the same blending. Example 3 In Example 1, glycerin ester of disproportionated rosin (softening point 100 ° C.) was used instead of the rosin-modified phenol resin.
The same operation as in Example 1 was carried out except for using, to obtain an emulsion. Further, an aqueous pressure-sensitive adhesive composition was obtained by the same blending. Example 4 An emulsion was obtained in the same manner as in Example 1, except that diethylene glycol ester of disproportionated rosin (liquid) was used instead of the rosin-modified phenol resin. Further, an aqueous pressure-sensitive adhesive composition was obtained by the same blending. Example 5 The same operation as in Example 2 was carried out except that in place of polyacrylic acid, a copolymer of acrylamide / methacrylic acid (90/10 weight ratio) was used as the water-soluble polymer. An emulsion was obtained. Further, an aqueous pressure-sensitive adhesive composition was obtained by the same blending. Example 6 An emulsion was obtained in the same manner as in Example 2, except that sodium polyacrylate was used instead of polyacrylic acid as the water-soluble polymer. Further, an aqueous pressure-sensitive adhesive composition was obtained by the same blending. Comparative Example 1 An emulsion was obtained in exactly the same manner as in Example 2, except that the amount of the water-soluble polymer added was changed to 0.005 part. Further, an aqueous pressure-sensitive adhesive composition was obtained by the same blending. Comparative Example 2 The procedure of Example 2 was repeated except that the amount of the water-soluble polymer was changed to 10 parts to obtain an emulsion. Further, an aqueous pressure-sensitive adhesive composition was obtained by the same blending. Comparative Example 3 An emulsion was prepared in the same manner as in Example 2 except that 1 part of polyvinyl alcohol ("PVA205", manufactured by Kuraray Co., Ltd.) was used instead of polyacrylic acid as the water-soluble polymer. I got Further, an aqueous pressure-sensitive adhesive composition was obtained by the same blending. Comparative Example 4 An emulsion was obtained in the same manner as in Example 2 except that the water-soluble polymer was not added. Further, an aqueous pressure-sensitive adhesive composition was obtained by the same blending. Comparative Example 5 Comparative Example 4 was the same as Example 4 except that a polymer emulsifier (styrene / n-butyl methacrylate / methacrylic acid = 39/13/48 weight ratio) was used in place of the anionic emulsifier of the resin emulsion. The same operation was performed to obtain an emulsion. Further, an aqueous pressure-sensitive adhesive composition was obtained by the same blending. Table 1 shows the results of a test of stability of the aqueous pressure-sensitive adhesive composition prepared in each of Examples and Comparative Examples against mechanical shear. Various tests are performed according to the following methods. 300 g of the water-based pressure-sensitive adhesive composition was placed in a glass container, and a small gear pump (“B9463” manufactured by Tuthill pump Co.) was used.
The mixture was circulated at 00 (g / min) for 30 minutes to form an emulsion, filtered through a 200-mesh stainless steel net, and dried at 105 ° C. for 2 hours, and the weight of the residue was measured. The method of calculating the amount of residue was calculated value below x 100 (%).

【The invention's effect】

The aqueous pressure-sensitive adhesive composition of the present invention can be very suitably used for various applications in which a conventional acrylic pressure-sensitive adhesive has been used, and has stability against high mechanical shear such as during pumping, roll coating, and spray coating. , The workability during coating can be greatly improved.

Claims (1)

(57) [Claims] 1. A tackifier resin emulsion 5 comprising rosin esters and / or rosin phenols in an amount of 100 parts by weight (in terms of solid content) of an acrylic polymer emulsion containing acrylate and / or methacrylate as a main component. To 30 parts by weight (in terms of solid content), and a water-soluble polymer or a water-soluble polymer alkali salt of at least one selected from acrylic acid, methacrylic acid, acrylamide or methacrylamide.
An aqueous pressure-sensitive adhesive composition comprising 5 parts by weight (in terms of solid content).