JP4763379B2 - Pressure-sensitive adhesive resin composition - Google Patents

Description

  The present invention relates to a pressure-sensitive adhesive resin composition.

  Conventionally, when joining a building member, an adhesive tape is sometimes used for temporary fixing or semi-permanent adhesion. As an adhesive constituting the adhesive layer of this pressure-sensitive adhesive tape, a solvent-based adhesive has been used.

  By the way, in consideration of the environment such as a recent sick house, it is desired to use a water-based adhesive instead of a solvent-based adhesive in order to reduce residual VOC (volatile organic compound). Examples of this water-based adhesive include the adhesive described in Patent Document 1.

JP 2001-40313 A

  However, water-based adhesives tend to be inferior in tackiness and water resistance compared to solvent-based adhesives.

  Then, this invention makes it a subject to obtain the water-based adhesive which is inferior in adhesiveness and water resistance compared with a general solvent-based adhesive.

  The present invention relates to a resin composition obtained by emulsion polymerization of a monomer mixture containing a predetermined (meth) acrylic acid alkyl ester (A) and a polymerizable monomer (B) copolymerizable with the component (A). The above-mentioned problems have been solved by using a resin composition having a gel content of 20 to 50% by weight which is insoluble in tetrahydrofuran.

  Since a resin composition comprising a specific component is used and has a predetermined gel content, a water-based adhesive that is inferior in tackiness and water resistance can be obtained as compared with a general solvent-based adhesive.

  The pressure-sensitive adhesive resin composition according to the present invention comprises a predetermined (meth) acrylic acid alkyl ester (hereinafter referred to as “component (A)”) as a main component, the component (A), and the component (A). The composition containing an aqueous emulsion of a (meth) acrylic polymer obtained by emulsion polymerization of a monomer mixture containing a polymerizable monomer copolymerizable with the component (hereinafter referred to as “component (B)”). It is a thing.

  The (meth) acrylic acid alkyl ester constituting the component (A) is a (meth) acrylic acid alkyl ester having an alkyl group having 1 to 12 carbon atoms. When this is used, the performance that the balance of the softness | flexibility and cohesion force at the time of using a polymer as an adhesive agent is excellent is acquired. When the number of carbon atoms is 13 or more, the polymer becomes excessively flexible and the cohesive force tends to be insufficient.

  Examples of such (meth) acrylic acid alkyl esters include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) ) Acrylate, octyl (meth) acrylate, undecyl (meth) acrylate and the like. In the present specification, “(meth) acryl” means “acryl or methacryl”.

  Next, as the polymerizable monomer copolymerizable with the component (A) as the component (B), (meth) acrylic acid, itaconic acid, fumaric acid, maleic acid, maleic anhydride, fumaric acid or maleic Carboxylic acids such as acid half ester compounds, nitriles such as (meth) acrylonitrile, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxycyclohexyl (meth) acrylate, ( Examples thereof include hydroxyl group-containing monomers such as (meth) acrylic acid dodecyl, aromatic vinyl compounds such as styrene and α-methylstyrene, vinyl esters such as vinyl acetate and vinyl propionate, and polymerizable nitrile compounds such as acrylonitrile.

  The monomer mixture contains the component (A) as a main component and contains the components (A) and (B). Here, “the component (A) is the main component” means that the content of the component (A) is the largest among the monomers contained in the monomer mixture.

  The content of the component (A) is preferably 80 to 99.9 parts by weight and more preferably 90 to 98 parts by weight in 100 parts by weight of the monomer mixture. When the amount is more than 99.9 parts by weight, the adhesive force (holding force) tends to be insufficient. On the other hand, when the amount is less than 80 parts by weight, the polymer becomes hard and the adhesive strength tends to be insufficient.

  The content of the component (B) preferably includes 0.1 to 20 parts by weight, more preferably 1 to 10 parts by weight, in 100 parts by weight of the monomer mixture. When the amount is more than 20 parts by weight, the adhesive strength tends to be insufficient. On the other hand, when the amount is less than 0.1 parts by weight, the adhesive force (holding force) tends to be insufficient.

  An aqueous emulsion of a (meth) acrylic polymer can be produced by subjecting the monomer mixture to emulsion polymerization by an ordinary method using an emulsifier. For example, the above monomer mixture, polymerization initiator, chain transfer agent, etc. are charged in a batch, divided or continuously into a reaction vessel in which water or an aqueous medium mainly containing water is charged in advance, and the emulsion is kept in an emulsified state while stirring. It can be produced by polymerization under predetermined reaction conditions.

  When the concentration of the monomer mixture at the time of the polymerization is 15 to 60% by weight, preferably 30 to 50% by weight, the resulting dispersion has a low viscosity, which is preferable from the viewpoint of handleability.

  The emulsifier is not particularly limited, and anionic, cationic, and nonionic emulsifiers can be used. Examples of anionic emulsifiers include fatty acid soaps, alkyl sulfonates, alkyl benzene sulfonates, alkyl sulfosuccinates, higher alcohol sulfates, polyoxyethylene alkyl sulfates, polyoxyethylene alkyl aryl sulfates, p-styrene sulfone. And acid salts.

  Furthermore, examples of the cationic emulsifier include laurylamine hydrochloride, alkylbenzyldimethylammonium chloride, lauryltrimethylammonium chloride, alkylammonium hydroxide, polyoxyethylene alkylamine and the like.

  Examples of nonionic emulsifiers include polyoxyethylene alkyl aryl ethers, polyoxyethylene sorbitan fatty acid esters, and oxyethylene oxypropylene block copolymers.

  The amount of the emulsifier used is preferably 0.05 to 20% by weight, more preferably 1 to 5% by weight, based on the monomer mixture. If it is less than 0.05% by weight, the dispersion stability during polymerization tends to deteriorate. On the other hand, when it is more than 20% by weight, the water resistance tends to decrease.

  As the polymerization initiator used in the emulsion polymerization, generally used radical polymerization initiators can be used, and typical examples thereof include persulfates such as ammonium persulfate and potassium persulfate, 2,2- Examples thereof include azo compounds such as azobisisobutyronitrile and 2,2-azobis (2,4-dimethyl) valeronitrile, peroxides such as t-butylhydroxyl peroxide, benzoyl peroxide, and lauroyl peroxide. These may be used alone or in combination of two or more. These compounds may be used in combination with reducing compounds such as sodium sulfite, ascorbic acid, Rongalite (sodium formaldehyde sulfoxylate) and used as a redox initiator. The amount of the polymerization initiator used is preferably 0.01 to 3 parts by weight with respect to 100 parts by weight of the monomer mixture.

  The reaction temperature of the emulsion polymerization reaction is preferably 20 to 95 ° C., and the reaction time is preferably 2 to 8 hours.

  An aqueous emulsion of a (meth) acrylic polymer is obtained by the above emulsion polymerization. The glass transition temperature (Tg) of the (meth) acrylic polymer is preferably −80 ° C. or higher, and −70 ° C. or higher. preferable. When it is lower than -80 ° C, the polymer tends to be excessively flexible and the holding force tends to be insufficient. On the other hand, the upper limit of Tg is preferably −20 ° C., and preferably −40 ° C. When it is higher than −20 ° C., the copolymer tends to be hard and the adhesive strength tends to be insufficient.

The Tg can be calculated according to the following formula (1).
1 / Tg = Wa / Tga + Wb / Tgb + (1)
In the above formula (1), Tg is the glass transition temperature (K) of the copolymer, Tga and Tgb are the glass transition temperature of the homopolymer of monomer a and the glass transition of the homopolymer of monomer b, respectively. Temperature, Wa, and Wb represent the weight fraction of monomer a and the weight fraction of monomer b, respectively.

  The amount of the insoluble gel in the aqueous emulsion of the (meth) acrylic polymer with respect to tetrahydrofuran (THF) needs to be 20% by weight or more, and preferably 25% by weight or more. If it is less than 20% by weight, the adhesive force (holding force) tends to decrease. On the other hand, the upper limit of the gel content needs to be 50% by weight, preferably 45% by weight. When it is more than 50% by weight, the adhesive strength tends to be insufficient.

  As a method for controlling the THF-insoluble content to 20 to 50% by weight, a method for setting the polymerization reaction temperature to 40 to 80 ° C., a polymerization regulator, and a polyfunctional monomer having two or more polymerizable vinyl groups are used. For example, a method of copolymerization, a method of adding the above-mentioned curing agent at the time of blending, and the like, and these may be adjusted experimentally by combining one or more methods.

  Further, the weight average molecular weight (Mw) of the soluble part excluding the gel content of the (meth) acrylic polymer is preferably 30,000 or more, and more preferably 50,000 or more. If it is smaller than 30,000, the polymer tends to be soft and the holding power tends to be insufficient. On the other hand, the upper limit of the weight average molecular weight (Mw) is preferably 700,000, more preferably 500,000. When it is larger than 700,000, the polymer may become excessively hard, and the tackiness tends to decrease.

  In addition, the said weight average molecular weight made the measured value by GPC (gel permeation chromatograph) into the value converted into the polystyrene standard sample about the solution obtained by melt | dissolving resin in tetrahydrofuran and filtering a gel part.

  The obtained water-based emulsion can be used as it is as a resin composition, and if necessary, a tackifier and a curing agent may be added within a range not inhibiting the effects of the present invention.

  By adding the tackifier, it is possible to exhibit the feature of improving the initial adhesive force due to tackiness. The amount of the tackifier added is preferably 1 part by weight or more and more preferably 3 parts by weight or more per 100 parts by weight of the (meth) acrylic polymer. If it is less than 1 part by weight, the initial adhesive force tends to decrease. On the other hand, the upper limit of the amount added is preferably 30 parts by weight, and more preferably 20 parts by weight. When the amount is more than 30 parts by weight, the holding force tends to decrease.

  Specific examples of the tackifier include polymerized rosin-based, terpene-based, and petroleum resin-based tackifiers.

  Moreover, water-resistant adhesive force and holding | maintenance force can be improved by adding the said hardening | curing agent. Examples of the curing agent include polyfunctional epoxy compounds, polyvalent isocyanate compounds, or metal crosslinking agents such as zinc oxide. The amount of the curing agent added is preferably 0.01 parts by weight or more, more preferably 0.1 parts by weight or more per 100 parts by weight of the (meth) acrylic polymer. If it is less than 0.01 part by weight, the effect of addition tends to be insufficient. On the other hand, the upper limit of the addition amount is preferably 10 parts by weight, and more preferably 5 parts by weight. When the amount is more than 10 parts by weight, the progress of crosslinking is too fast and the adhesive force tends to be lowered.

  Specific examples of the epoxy compound include glycerin monoglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, sorbitol polyglycidyl ether, pentaerythritol monoglycidyl ether, pentaerythritol diglycidyl ether, pentaerythritol triglycidyl ether, pentaerythritol tetra Examples thereof include glycidyl ether and trimethylolpropane polyglycidyl ether.

  Examples of the polyvalent isocyanate-based compounds include those in which an oligomer of an isocyanate partially modified by an addition reaction of polyethylene oxide at one terminal hydroxyl group can be dispersed in water. Specific examples include “Aquanate 100” and “Aquanate 200” manufactured by Nippon Polyurethane Co., Ltd., “SBU Isocyanate 0722” manufactured by Sumitomo Bayer Urethane Co., Ltd., and the like.

  Furthermore, the above-mentioned water-based emulsion may contain the above-described tackifier and curing agent additives, for example, a colorant such as a pigment, a wax, an antifoaming agent, a plasticizer, and a film-forming aid. You may add in the range which does not inhibit.

  The adhesive strength of the obtained resin composition, that is, the adhesive strength between the obtained pressure-sensitive adhesive and the adherend is preferably at least 5.0 N / 25 mm. If it is less than 5.0 N / 25 mm, peeling occurs after bonding, and the double-sided tape can no longer support the member, and problems are likely to occur.

  The water-resistant adhesive strength of the obtained resin composition is an index indicating whether the obtained pressure-sensitive adhesive and the adherend can be adhered and sufficiently retained after exposure to moisture, and is at least 5.0 N / 25 mm. It is preferable that If it is less than 5.0 N / 25 mm, it will peel off when it is exposed to moisture after being bonded, and the double-sided tape will not be able to support the member, and problems will easily occur.

  The pressure-sensitive adhesive resin composition obtained in this invention can be used as a pressure-sensitive adhesive for pressure-sensitive adhesive tapes, pressure-sensitive adhesive labels, and pressure-sensitive adhesive sheets. Moreover, a double-sided tape can be obtained by coating on both surfaces of a tape base material and forming an adhesive layer. This double-sided tape can be used as a tape for temporarily fixing or semi-permanently bonding a building member or the like.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail using an Example, this invention is not limited by a following example, unless the summary is exceeded. First, tests and evaluation methods performed in Examples and Comparative Examples and raw materials used will be described.

[raw materials]
<Monomer>
2-ethylhexyl acrylate: manufactured by Mitsubishi Chemical Corporation, hereinafter abbreviated as “2EHA”.
-Butyl acrylate: manufactured by Mitsubishi Chemical Corporation, hereinafter abbreviated as "BA".
・ Hydroxyethyl acrylate: manufactured by Nippon Shokubai Co., Ltd., hereinafter abbreviated as “HEA”.
-Methacrylic acid: Mitsubishi Rayon Co., Ltd., hereinafter abbreviated as "MAA".

<Polymerization regulator>
-Thiocalcol 20: manufactured by Kao Corporation, hereinafter abbreviated as "C20".
<Emulsifier>
NHS-20: Sanyo Chemical Industries, Ltd., hereinafter abbreviated as “NHS20”.
<Polymerization initiator>
Azobis-2-amidinopropane hydrochloride: manufactured by Wako Pure Chemical Industries, Ltd .; V-50, hereinafter abbreviated as “V50”.

<Other additives>
Superester E-720: Arakawa Chemical Co., Ltd .: Rosin resin, hereinafter abbreviated as “E720”.
Aquanate 100: manufactured by Nippon Polyurethane Co., Ltd .: Isocyanate compound, hereinafter abbreviated as “A100”.

[Test and evaluation method]
<Gel content>
As for the gel content, 3 g of a film prepared by drying the aqueous pressure-sensitive adhesive composition obtained by the above method in an atmosphere at 50 ° C. for 3 days was collected, soaked in THF for 24 hours, and then the film was insoluble in THF. It can be calculated by taking out the minute by filtration or the like, drying in an atmosphere of 100 ° C. for 3 hours, measuring the weight, and applying it to the following formula.
Gel fraction (% by weight) = (THF insoluble matter (after drying) Weight (g) / 3 (g)) × 100

<Initial adhesive strength>
Under the conditions of 23 ° C. and 65% RH, the test piece cut to a width of 25 mm was pressure-bonded to an adherend (stainless steel plate) by reciprocating a roller with a load of 2 kg.
Subsequently, in accordance with JIS A 0237, 180 degree peeling adhesive strength was measured.

<Retention force>
The adherend was a stainless steel plate, and the measurement composition was pasted according to the above method so that the pasting area was 25 mm ² . Next, it was left for 5 hours under a 40 ° atmosphere with a load of 300 g. Thereafter, the amount of deviation generated was measured.

<Water resistant adhesive strength>
The adherend was a stainless steel plate, and the composition to be measured was pasted according to the above method. And it was immersed in water for 24 hours. Thereafter, excess moisture was wiped off, and the 180 ° peel adhesive strength was measured according to the method described in JIS Z 0237.

(Examples 1-3 , Comparative Examples 1-2 , Reference Examples 1-4 )
[Preparation of aqueous emulsion of acrylic resin]
A stirrer, a reflux condenser, a thermometer, and a reaction vessel equipped with a dropping funnel, containing water 40 parts by weight, the mixture was heated to 70 ° C. under a nitrogen atmosphere, azo Bisuiso butyronitrile 0.3 weight into the reaction vessel Parts were added.
On the other hand, the monomers listed in Table 1 and the emulsifier NHS20 were mixed by 1.0 part by weight, and then 50 parts by weight of water were mixed to prepare a mixed solution. This mixed solution was mechanically emulsified with a homomixer to prepare a pre-emulsion.
Next, the pre-emulsion was dropped into the reaction vessel over 4 hours. During this time, the reaction temperature was maintained at 70 ° C. After dropwise addition of the pre-emulsion, 0.3 part by weight of t-butyl hydroperoxide was added, and the mixture was further reacted at 80 ° C. (however, 90 ° C. in Comparative Examples 1 and 2) and then cooled. A milky white aqueous emulsion was obtained.

( Reference Comparative Example 1 )
In a reaction vessel equipped with a thermometer, a reflux condenser, a stirrer, and a dropping funnel, each component shown in Table 1 was added and mixed, and the temperature was raised to 80 ° C. Next, 0.3 part by weight of V50 was added to 1000 parts by weight of 80 ° C. ethyl acetate (manufactured by Wako Pure Chemical Industries, Ltd .: reagent grade), and then dropped into the reaction vessel over 2 hours. During the dropping, the temperature of the reaction vessel was maintained at 80 ° C. Thereafter, the mixture was aged at 80 ° C. for 2 hours to obtain a solvent-based composition. Said evaluation was performed using the obtained solvent type composition. The results are shown in Table 1.

Claims (4)

A main component having an alkyl group having 1 to 12 carbon atoms (meth) acrylic acid alkyl ester (A), the component (A) of this component (A) capable of copolymerizing the polymerizable monomer (B), and resulting et is a monomer mixture containing a polymerization modifier emulsion polymerization to,
The component (B) is a component containing a hydroxyl group-containing monomer, and 2 to 20 parts by weight of the hydroxyl group-containing monomer is contained in 100 parts by weight of the monomer mixture.
A pressure-sensitive adhesive resin composition comprising a (meth) acrylic polymer aqueous emulsion having a gel content insoluble in tetrahydrofuran of 20 to 50% by weight.   The pressure-sensitive adhesive resin composition according to claim 1, wherein the glass transition temperature of the (meth) acrylic polymer is -80 to -20 ° C. The pressure-sensitive adhesive resin composition according to claim 1 or 2 , comprising 1 to 30 parts by weight of a tackifier per 100 parts by weight of the (meth) acrylic polymer. A double-sided tape having an adhesive layer obtained from the pressure-sensitive adhesive resin composition according to any one of claims 1 to 3 .