TWI426113B - Water-dispersible acrylic pressure-sensitive adhesive composition and pressure-sensitive adhesive tape - Google Patents

Description

Water-dispersed acrylic adhesive composition and tape

The present invention relates to a water-dispersible acrylic pressure-sensitive adhesive composition in which an acrylic copolymer latex particle is dispersed in an aqueous medium, and an adhesive tape having the adhesive composition as an adhesive layer.

Adhesive tape is used as a bonding means for excellent workability and high adhesion reliability, and is used for labeling of parts for fixed-use or product information in various industrial fields such as office automation equipment (OA equipment), home electric appliances, and automobiles. Wait. On the other hand, from the viewpoint of global environmental protection, there are more and more cases where assembled products such as office automation machines are disassembled and reused and reused after use. In this case, in the case where the component is bonded by the adhesive tape or the label is attached, the adhesive tape or the label needs to be peeled off, and the adhesive is not required to be left, and the peeling property is not damaged by the support substrate (ie, Peelability). In addition, in recent years, volatile organic compounds (also known as VOCs) have been strongly restricted by emissions. Among adhesive tapes, solvent-free adhesives have attracted attention, and it is currently expected to use a water-dispersible adhesive instead of a solvent-based adhesive.

Heretofore, a double-sided adhesive tape having high adhesion reliability and further removability has been disclosed, which is composed of (a) an alkyl (meth)acrylate having an alkyl group having 1 to 12 carbon atoms. And (b) a nitrogen-containing vinyl monomer, (c) an acrylic copolymer composed of a hydroxyl group-containing monomer or a carboxyl group-containing monomer, which is a main component, and (d) an isocyanate crosslinking agent. In the acrylic pressure-sensitive adhesive composition, the acrylic pressure-sensitive adhesive composition is further composed of a non-woven fabric core material having a specific strength (see Patent Document 1). However, when the double-sided adhesive tape of the present technology is constituted by the emulsion polymerization method, it is difficult to exhibit excellent removability.

Further, an adhesive sheet using a latex type adhesive and having both adhesive reliability and re-peelability has been disclosed. (refer to Patent Document 2) As a means for having both adhesive reliability and re-peelability, a technique has been disclosed in which the composition of the acrylic adhesive is used in combination with acrylic acid and methacrylic acid, and 1.5 to 2.5% by mass is used as a total amount. The ratio of methacrylic acid to acrylic acid is 0.5 to 2.0 in terms of mass ratio. However, when a double-sided adhesive tape having a higher adhesive strength is prepared, it is difficult to ensure sufficient removability.

Further, as a latex type adhesive in which acrylic acid and methacrylic acid are used in combination, a technique has been disclosed regarding the composition of the acrylic pressure-sensitive adhesive, and acrylic acid is contained in a ratio by weight of 1/1 to 1/5. With methacrylic acid, and containing acrylic acid and methacrylic acid a total of 2 to 10% by weight. (Refer to Patent Document 3) However, the influence of the combination of acrylic acid and methacrylic acid on the removability is not described. Further, in the case where the acrylic pressure-sensitive adhesive disclosed in the present patent document is used as a constituent component, the adhesive strength which increases with time after the adhesion is increased, and it is difficult to maintain the re-peelability. In particular, there is a problem that the adhesion to a metal surface such as stainless steel is greatly increased.

In addition, when an adhesive tape containing a latex-type adhesive is used for the purpose of fixing a urethane foam or a high-air permeable member such as a nonwoven fabric, the double-sided adhesive tape may be high in a high-humidity environment. The problem of peeling of the air permeable member.

[Patent Document 1] Japanese Patent Laid-Open No. 8-209086

[Patent Document 2] Japanese Patent Laid-Open No. 2006-265537

[Patent Document 3] Japanese Patent Laid-Open 2005-248059

The problem to be solved by the present invention is to provide a water-dispersible latex type adhesive which can form an adhesive tape, which has good adhesion and retention to an adherent, and does not adhere to a long-term adhesion. Excessive adhesion is caused, and special treatment such as heating is not required at the time of peeling, that is, the adhesive is not left and the support substrate is not damaged.

Further, a water-dispersible latex type adhesive which can form an adhesive tape for fixing a foam such as a urethane or a high-air permeable member such as a non-woven fabric, even at a high humidity, is also provided. In the environment, it also has excellent water resistance without peeling.

In the present invention, the first finding is that a water-dispersed adhesive composition is formed not only on the surface of the latex particles but also on the inside of the particles; specifically, the purpose is to prepare an acrylic system. The copolymer latex particles have a carboxyl group equivalent to or higher than the surface of the particles, and a carboxy group-containing monomer such as methacrylic acid, acrylic acid or a nitrogen-containing vinyl monomer. The acrylic copolymer latex particles obtained by the adhesive composition of the specific composition can maintain the cohesive force between the latex particles due to the acid groups present on the surface of the particles, and can be enhanced by the acid groups present in the particles. The cohesive force inside the latex particles can form an adhesive layer which is less likely to cause peeling of the adhesive layer or residual adhesive when the film is peeled off. In general, when there is a portion having a low cohesive force in the adhesive layer, the fluidity of the portion having a low cohesive force is high, so that the adhesion to the adherend of the adherend tends to increase with time, resulting in long-term sticking. At the time of adhesion, the adhesion will rise excessively, making it difficult to peel off again. By the adhesive composition containing the acrylic copolymer latex of the above configuration, the portion having a low cohesive force in the adhesive layer can be reduced, and the deterioration of the removability which increases with time can be preferably suppressed.

Further, the acrylic copolymer latex particles act by the cohesive force between the latex particles due to the acid groups present on the surface of the particles and the cohesive force inside the latex particles caused by the acid groups existing inside the particles. The immersion of water into the adhesive layer can be easily suppressed. In addition, the latex of the present invention in which the hydrophilic acid group which is easily aligned to the surface of the particle is placed inside the particle can inhibit the hydrophilicity of the surface of the adhesive layer, and the hydrophobicity will rise, making the water less likely to aggregate. The interface between the high-ventilating member and the adhesive tape improves the water resistance.

In addition, it has been found that by using methacrylic acid and acrylic acid in combination, it is possible to maintain stable and strong adhesion from a highly polar metal-based adherend to a low-polarity olefin-based adherend.

Further, in the present invention, the second finding is that 2-ethylhexyl acrylate is used as a main monomer constituting the acrylic copolymer latex. By using the monomer, the impregnation of the adhesive to the nonwoven fabric can be improved, and the removability can be greatly improved.

Further, in the present invention, the third finding is that a (meth) acrylate having an alkyl group having 4 to 8 carbon atoms and 2-ethylhexyl acrylate are used in combination. By using the monomer in combination, the re-peelability can be maintained while the strong adhesion is greatly improved.

According to the water-dispersible acrylic pressure-sensitive adhesive composition of the present invention, the emission of a volatile organic compound (ie, VOC) or the odor of an organic solvent can be greatly reduced, and a stable adhesion to an adherend such as a metal can be obtained, even in the long-term. When it is attached, it does not cause an excessive increase in adhesion, and it is not necessary to perform special treatment such as heating at the time of peeling, that is, the adhesive tape is not left and the adhesive tape of the support substrate is not damaged.

Further, the adhesive tape comprising the water-dispersible acrylic pressure-sensitive adhesive composition of the present invention is used for fixing a urethane foam or a high-air permeable member such as a nonwoven fabric, even in a high-humidity environment. Excellent water resistance without peeling can also be obtained when used.

<Water-dispersed acrylic adhesive composition> (acrylic copolymer)

In the water-dispersible acrylic pressure-sensitive adhesive composition of the present invention, as the acrylic copolymer forming the acrylic copolymer latex particles, an alkyl group having a carbon number of 4 to 8 and containing 2-ethylhexyl acrylate is used. An acrylic copolymer having (meth) acrylate, acrylic acid, methacrylic acid, and a nitrogen-containing vinyl monomer as a monomer component.

In the present invention, by using 2-ethylhexyl acrylate as a monomer component, the adhesive is easily impregnated into the nonwoven fabric, and the nonwoven fabric is less likely to be broken when it is peeled off. The content of 2-ethylhexyl acrylate is preferably 10 to 90% by mass, more preferably 20 to 80% by mass. By setting the content of 2-ethylhexyl acrylate in the range, adhesion between the adhesive and the adherend which is increased with time can be easily suppressed, so that the adhesive force is not easily excessively increased, so that even if it increases with time, Maintain proper re-peelability.

Further, by using 2-ethylhexyl acrylate in combination and using a (meth) acrylate having an alkyl group having 4 to 8 carbon atoms, the re-peelability can be maintained while the strong adhesion is greatly improved. As the (meth) acrylate having an alkyl group having 4 to 8 carbon atoms, n-butyl (meth)acrylate, isobutyl (meth)acrylate, and tert-butyl (meth)acrylate can be used. (meth) acrylate such as isooctyl methacrylate or n-octyl (meth) acrylate, wherein an acrylate monomer having an alkyl group having 4 to 8 carbon atoms is preferably used, and acrylic acid is used. Butyl ester is especially good. Further, n-butyl acrylate and t-butyl methacrylate are preferably used in combination. The amount of the (meth) acrylate having an alkyl group having 4 to 8 carbon atoms is preferably from 10 to 80% by mass, more preferably from 20 to 70% by mass.

In the present invention, in order to more suitably exhibit the effect of the above-mentioned 2-ethylhexyl lactone and the (meth) acrylate having an alkyl group having 4 to 8 carbon atoms, it is preferred to form an acrylic copolymer. The total content of 2-ethylhexyl acrylate and (meth) acrylate having an alkyl group having 4 to 8 carbon atoms in the monomer component is 50 to 98% by mass, particularly preferably 80 to 98. quality%. Further, the content ratio of 2-ethylhexyl acrylate to the (meth) acrylate having an alkyl group having 4 to 8 carbon atoms in the monomer component of the acrylic copolymer is preferably (acrylic acid 2- Ethylhexyl ester / (meth) acrylate having an alkyl group having 4 to 8 carbon atoms represents a mass ratio of 9/1 to 2/8, particularly preferably 75/25 to 25/75.

In the present invention, as the (meth) acrylate monomer forming the acrylic copolymer, a (meth) acrylate monomer other than the above may be used in combination. The (meth) acrylate monomer other than the above may, for example, be a (meth) acrylate monomer such as methyl (meth) acrylate or ethyl (meth) acrylate, or one of these may be used in combination. Or two or more. Further, a (meth) acrylate having an alkyl group having 2 or less carbon atoms such as methyl (meth) acrylate or ethyl (meth) acrylate is preferably used in combination, and the amount thereof is preferably from 1 to 10% by mass. .

In the present invention, in order to introduce an acid group into the surface and inside of the acrylic copolymer latex, acrylic acid and methacrylic acid are used together as a monomer having an acid group. The carboxyl group of acrylic acid and methacrylic acid has the following advantages: the carboxyl group can easily maintain the cohesive force by the interaction between the carboxyl groups, and there are many crosslinkers which can react, and there are many means for improving the cohesive force, which can be described later. Interaction between nitrogen-containing vinyl monomers and the like. Further, in the present invention, by using a combination of acrylic acid having a relatively high hydrophilicity and methacrylic acid having a higher hydrophobicity than acrylic acid, the tendency of the internal olefinic acid to be aligned to the vicinity of the surface of the particle and the orientation of the methacrylic acid to the inside of the particle can be exhibited. On the other hand, the acid groups can be disposed in a well-balanced manner on the surface and inside of the acrylic copolymer latex particles. By the presence of an acid group in the vicinity of the particle surface, the cohesive force between the latex particles can be maintained, and the cohesive force inside the latex particle can be enhanced by the presence of an acid group existing inside the particle. As described above, the obtained adhesive layer can reduce the portion having a low cohesive force, and can preferably suppress the deterioration of the re-peelability with an increase in time, so that the peeling of the adhesive layer or the adhesive residue is less likely to occur at the time of re-peeling. . In addition, by using methacrylic acid and acrylic acid in combination, it has an effect of greatly improving the required load performance for strong adhesion.

The content of acrylic acid and methacrylic acid is preferably 0.5 to 10% by mass based on the total content of methacrylic acid and acrylic acid in the monomer component forming the acrylic copolymer. More preferably, it is 0.5 to 5% by mass, and most preferably 1.5 to 3.5% by mass. When the sum of the contents of methacrylic acid and acrylic acid is within this range, the crosslinking reaction with the crosslinking agent can be easily carried out satisfactorily. Further, when the adhesive layer is formed, an appropriate cohesive force can be maintained in the adhesive layer, and the re-peelability and the strong adhesiveness can be easily coexisted. Further, the cohesive force necessary for maintaining water resistance and the hydrophobicity of the surface of the adhesive layer can be ensured.

The merging ratio of methacrylic acid and acrylic acid is preferably 0.2 or more, more preferably 3 or more, particularly preferably 4 or more, and most preferably 6 or more. By setting the mixing ratio within this range, the amount of surface acid groups and the amount of internal acid groups in the acrylic copolymer latex particles can be appropriately controlled.

Further, in the range which does not inhibit the distribution of the acid groups in the acrylic copolymer latex particles described above, other carboxyl group-containing monomers may be used in combination as the monomer having an acid group. As the other carboxyl group-containing monomer, for example, one or more selected from the group consisting of carboxyl group-containing vinyl monomers such as isaconic acid, maleic acid, maleic anhydride, phthalic acid, phthalic anhydride, and crotonic acid can be used. . When the carboxyl group-containing monomer is used in combination, the total amount of the carboxyl group-containing monomer containing acrylic acid and methacrylic acid is preferably used in the range of 0.5 to 10% by mass.

In the present invention, as the monomer component of the acrylic copolymer, a nitrogen-containing vinyl monomer is further used. The nitrogen-containing vinyl monomer is presumed to have an effect of interposing a carboxyl group which is easily aligned on the surface of the particle into the particle by interacting with an acid group, particularly a carboxyl group, in the acrylic copolymer latex particle. In order to produce the effect, it is preferred that the content of the nitrogen-containing vinyl monomer be at least the above lower limit. On the other hand, when the content is increased, the reactivity with a crosslinking agent to be described later tends to be lowered. However, when the content of the nitrogen-containing vinyl monomer is not more than the above upper limit, the necessary reactivity can be maintained. . When the content of the nitrogen-containing vinyl monomer is within the content range, the distribution of the acid groups in the acrylic copolymer latex particles can be easily dropped within an appropriate distribution range.

As the nitrogen-containing vinyl monomer, for example, N-vinylpyrrolidone, N-vinyl caprolactam, and propylene fluorene can be used. One or more of phenyl, acrylonitrile, acrylamide, N,N-dimethyl acrylamide, and dimethylamine ethyl (meth) acrylate.

Among them, as the nitrogen-containing monomer, a monomer having a guanamine group is preferably used. When an amine-based nitrogen-containing monomer is used, the interaction with the acid group becomes too strong, so the amount of the acid group on the surface of the particle tends to be small, and the interaction between the latex particles becomes weak, which is difficult to obtain. As a cohesive force of the adhesive.

The content of the nitrogen-containing vinyl monomer in the monomer component forming the acrylic copolymer is 0.1 to 4.5 mass, preferably 0.5 to 4 mass%, more preferably 0.5 to 3.5 mass%, by adjusting to the above range. The effects of the present invention are preferably exhibited.

The ratio of the nitrogen-containing vinyl monomer in the acrylic copolymer to the vinyl monomer having a carboxyl group is not particularly limited, and the mole of the nitrogen-containing vinyl monomer constituting the monomer component of the acrylic copolymer is not particularly limited. When the number of moles of the vinyl monomer having a carboxyl group is X and the number of moles of the vinyl monomer having a carboxyl group is Y, the molar ratio X/Y is preferably from 1/1 to 1/20, more preferably from 1/1 to 1/5, most Good is 1/1~1/3. When the molar ratio X/Y is within this range, the reaction between the vinyl monomer having a carboxyl group and a crosslinking agent described later can be easily carried out. Further, the distribution of the carboxyl group in the acrylic copolymer latex can be simply made to fall within the range described later.

In the acrylic copolymer used in the present invention, a monomer other than the above may be used as necessary. As an example of the monomer, 2-hydroxyethyl (meth)acrylate may be suitably used as the monomer having a hydroxyl group. An alcoholic hydroxyl group-containing monomer such as 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate or 4-hydroxybutyl (meth)acrylate. Examples of the monomer having a ketone group or an aldehyde group include diacetone acrylamide, diacetone methacrylamide, acrolein, styrene methyl ketone, vinyl methyl ketone, vinyl ethyl ketone, and ethylene equivalent. Butyl ketone, diacetone acrylate, diacetone methacrylate, acetonitrile acrylate, 2-hydroxypropyl acrylate acetonitrile acetate, butane diol acrylate acetate, and the like. Examples of the decane-based monomer include 3-methylpropenyloxypropylmethyldimethoxydecane [for example, KBM-502 manufactured by Shin-Etsu Chemical Co., Ltd.], 3-methylpropenyloxypropane Trimethoxy decane [for example, KBM-503 manufactured by Shin-Etsu Chemical Co., Ltd.], 3-methacryloxypropylmethyldiethoxy decane [for example, KBE-502 manufactured by Shin-Etsu Chemical Co., Ltd.], 3-methacryloxypropyltriethoxydecane [for example, KBE-503 manufactured by Shin-Etsu Chemical Co., Ltd.], 3-acryloxypropyltrimethoxydecane [for example, Shin-Etsu Chemical Co., Ltd. KBM-5103] and so on. Further, examples of the monomer having a methylol group include N-methylol acrylamide and the like. Further, the monomer having a phosphate group may, for example, be Sipomer PAM-100, PAM-200, PAM-300, etc., manufactured by RHODIA NICCA CO., LTD., and the above monomers may be formed into an acrylic copolymer. The ratio of 20% by mass or less of the monomer components may be used, and one type or two or more types may be used.

The acrylic copolymer used in the present invention preferably has a weight average molecular weight of from 500 to 1.2 million, more preferably from 60 to 1,000,000. When the weight average molecular weight of the acrylic copolymer is within this range, the cohesive force necessary for the flexibility and re-peelability when the adhesive is impregnated with the nonwoven fabric can be balanced in a balanced manner. The above weight average molecular weight is obtained by converting a standard polystyrene into a gel chromatograph (GPC). For the measurement conditions, TSKgel GMHXL [manufactured by Tosoh Corporation] was used for the column, the column temperature was 40 ° C, the eluent was tetrahydrofuran, the flow rate was 1.0 mL/min, and the standard polystyrene was TSK standard polystyrene.

In order to adjust the molecular weight, a chain transfer agent can also be used in the polymerization. As the chain transfer agent, a known chain transfer agent such as dodecyl mercaptan, propylene propyl thiol, hydrazine acetic acid, 2-hydrazine ethanol, hydrazine acetic acid, 2-ethylhexyl phthalate acetate, 2, 3- can be used. Dithiol-1-propanol and the like.

(Type of adhesive imparting resin)

In the water-dispersible acrylic pressure-sensitive adhesive composition of the present invention, in order to adjust the strong adhesiveness of the obtained pressure-sensitive adhesive layer, it is preferred to use an adhesion-imparting resin. As the adhesion-imparting resin to be used in the present invention, a latex-type adhesion-imparting resin can be preferably used from the viewpoint of the water-dispersible pressure-sensitive adhesive composition. Examples of the latex-type adhesion-imparting resin include rosin-based, polymerized rosin-based, polymerized rosin-ester-based, rosin-phenol-based, stabilized rosin-ester-based, heterogeneous rosin-ester-based, fluorene-based, indophenol-based, and petroleum-based resin. .

Among them, a polymerized rosin ester-based adhesion-imparting resin and a rosin-phenol-based adhesion-imparting resin are preferable, and it is particularly preferable to use them in combination. Specific examples of the polymerized rosin ester-based adhesion-imparting resin include SUPER ESTER E-650 [Arakawa Chemical Industry Co., Ltd.], SUPER ESTER E-788 [Arakawa Chemical Industry Co., Ltd.], and SUPER ESTER E-786-60. [Arakawa Chemical Industry Co., Ltd.], SUPER ESTER E-865 [Arakawa Chemical Industry Co., Ltd.], SUPER ESTER E-865NT [Arakawa Chemical Industry Co., Ltd.], HARIESSTER SK-508 [Harima Chemicals, Inc. HARIESTER SK-508H [manufactured by Harima Chemicals, Inc.], HARIESTER SK-816E [manufactured by Harima Chemicals, Inc.], HARIESTER SK-822E [manufactured by Harima Chemicals, Inc.], HARIESTER SK-323NS [Harima Chemicals, Inc.制 等 ; ; ; ; ; ; TA TA TA TA TA TA TA TA TA TA TA TA TA TA TA TA TA TA TA TA TA TA TA TA TA TA TA TA TA TA TA TA TA TA TA TA TA TA TA TA TA TA TA TA TA TA TA TA TA TA TA TA TA TA Stock system] and so on.

When these are used, the ratio of the above-mentioned polymerized rosin ester-based adhesion-imparting resin (A) rosin-based adhesive-imparting resin (B) is preferably 5/1 to 1/5 as (A)/(B). It is more from 3/1 to 1/3, and the best is 1/1 to 1/3. If it is within this range, the re-peelability and the strong adhesion can be improved in a well-balanced manner.

In the softening point of the adhesive imparting resin, the softening point is preferably from 120 to 180 ° C, more preferably from 140 to 180 ° C. By bonding the resin with a high softening point, the adhesion can be improved.

In the blend ratio of the acrylic copolymer/adhesive-imparting resin, the acrylic copolymer/adhesive resin is preferably 100/10 to 100/40, more preferably the acrylic copolymer/adhesive resin = 100/15 to 100. /35. If it is within this range, the re-peelability and the strong adhesion can be improved in a well-balanced manner.

(crosslinking agent)

In the water-dispersible acrylic pressure-sensitive adhesive composition of the present invention, in order to achieve agglomeration of the pressure-sensitive adhesive layer obtained, it is preferred to use a crosslinking agent. As the crosslinking agent, a known isocyanate crosslinking agent, an epoxy crosslinking agent, an aziridine crosslinking agent, a polyvalent metal salt crosslinking agent, a metal chelating agent crosslinking agent, and a ketone can be used. A crosslinking agent, an oxazoline crosslinking agent, a carbodiimide crosslinking agent, a decane crosslinking agent, a glycidyl (alkoxy) epoxy decane crosslinking agent, etc. Among them, it is preferred to add a crosslinking agent which is added after the completion of the polymerization to make a crosslinking reaction type. For example, an isocyanate type crosslinking agent, an epoxy type crosslinking agent, an oxazoline type crosslinking agent, a carbodiimide type crosslinking agent, and a glycidyl (alkoxy) epoxy decane type cross-linking are mentioned. Agents, etc. Specifically, the isocyanate-based crosslinking agent is BURNOCK DNW-5000 [manufactured by DIC Co., Ltd.], BURNOCK DNW-5010 [manufactured by DIC Co., Ltd.], and BURNOCK DNW-5100 [manufactured by DIC Co., Ltd.] , BURNOCK DNW-5500 [DIC system], AQUANATE 100 [made by Japan Polyurethane Industry Co., Ltd.], AQUANATE 105 [made by Japan Polyurethane Industry Co., Ltd.], AQUANATE 110 [ Japan Polyurethane Industry Co., Ltd., AQUANATE 120 [made by Japan Polyurethane Industry Co., Ltd.], AQUANATE 130 [made by Japanese Polyurethane Industry Co., Ltd.], AQUANATE 200 [Nippon Polyurethane Industry Co., Ltd.], AQUANATE 210 [made by Japan Polyurethane Industry Co., Ltd.], LS2319 [Shenhua Bayer Aminoate (Stock)], LS2336 [ Manufactured by Bayer urethane (manufactured by Bayer), Bayhydur 3100 [manufactured by Bayer urethane (manufactured by the company), etc.; for the epoxy-based crosslinking agent, DENACOL EX-832 [long 濑] Chemical Industry Co., Ltd., DENACOL EX-841 [Changchun Chemical Industry Co., Ltd.], TETRAD C [Mitsubishi Gas Chemical Co., Ltd.], TETRAD X [Mitsubishi Gas Chemical Co., Ltd.], etc. As the oxazoline crosslinking agent, EPOCROS WS-500 [Japanese catalyst ( Stock system], EPOCROS WS-700 [Japan catalyst (share) system], EPOCROS K-2010E [Japan catalyst (share) system], EPOCROS K-2020E [Japan catalyst (share) system], EPOCROS K- 2030E [Nippon Catalyst Co., Ltd.]; for the carbonic acid diamide crosslinking agent, CARBODILITE SV-02 [Nissin Textiles Co., Ltd.], CARBODILITE V-02 [Nisshin Textile Co., Ltd.], CARBODILITE V-02-L2 [Nissin Textiles Co., Ltd.], CARBODILITE V-04 [Nissin Textiles Co., Ltd.], CARBODILITE E-01 [Nissin Textiles Co., Ltd.], CARBODILITE E-02 [Nissin Textiles Co., Ltd.], CARBODILITE E-03A [Nissin Textiles Co., Ltd.], CARBODILITE E-04 [Nissin Textiles Co., Ltd.]; and epoxy propyl (alkoxy) epoxy decane crosslinking agents, 2-(3) , 4-epoxycyclohexylethyltrimethoxydecane [KBM-303; Shin-Etsu Chemical Co., Ltd.], γ-glycidoxypropyltrimethoxydecane [KBM-403; Shin-Etsu Kang (share) system], γ-glycidoxypropylmethyldiethoxy decane [KBE-402; Shin-Etsu Chemical Co., Ltd.], γ-glycidoxypropyl three Ethoxy decane [KBE-403; Shin-Etsu Chemical Co., Ltd.] and the like. As an index of the degree of crosslinking, the degree of crosslinking was adjusted by measuring the gel fraction of the insoluble component after the adhesive layer was immersed in toluene for 24 hours. The gel fraction is preferably from 20 to 45% by mass. More preferably, it is 25 to 45% by mass, and most preferably 28 to 38% by mass. If it is in the above range, the re-peelability and the strong adhesion can be maintained in a well-balanced manner.

Among them, it is preferred to use a crosslinking agent which reacts with the above-mentioned vinyl group-containing monomer, and the above isocyanate crosslinking agent, epoxy compound, oxazoline compound, carbodiimide crosslinking agent, A glycidyl (alkoxy) epoxy decane compound or the like is preferred. The technical feature of the present invention is to ensure the cohesive force of the entire acrylic copolymer by aligning the surface of the latex particles with the inside of the particles with an appropriate amount of acid groups, and by using a crosslinking agent reactive with the above acid groups. The elevation of the cohesive force can be appropriately exhibited.

(additive)

In the water-dispersible acrylic pressure-sensitive adhesive composition of the present invention, as an additive, an alkali (ammonia water or the like) or an acid for adjusting the pH may be optionally added to the adhesive composition as long as the effect required by the present invention is not impaired. , plasticizers, softeners, antioxidants, fibers made of glass or plastics ‧ balloons, beads, metal powders, fillers, pigments, dyes, etc., color regulators, film forming aids, leveling agents , known as tackifiers, water repellents, defoamers, etc.

(Production method)

The water-dispersible acrylic pressure-sensitive adhesive composition of the present invention can be produced by an emulsion polymerization method in which a latex type adhesive is obtained. In the emulsion polymerization, an anionic or nonionic emulsifier or other dispersion stabilizer may be used in an appropriate amount in order to secure the polymerization stability. The emulsifier is not particularly limited, and a known emulsifier can be used. Examples of the anionic emulsifier include sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzenesulfonate, sodium polyoxyethylene alkyl ether sulfate, and sodium polyoxyethylene alkylphenyl ether sulfate. The nonionic emulsifier may, for example, be a polyoxyethylene alkyl ether or a polyoxyethylene alkylphenyl ether.

Further, it is preferred to use a known "reactive emulsifier" (an emulsifier having a polymerizable unsaturated group in the molecule). Specific examples include LATEMUL S-180 [made by Kao Co., Ltd.], LATEMUL PD-104 [made by Kao Co., Ltd.], AQUALON HS-10 [manufactured by Daiichi Kogyo Co., Ltd.], and AQUALON HS-20 [ First Industrial Pharmaceutical Co., Ltd., AQUALON KH-10 [First Industrial Pharmaceutical Co., Ltd.], AQUALON KH-1025 [First Industrial Pharmaceutical Co., Ltd.], AQUALON KH-05 [First Industrial Pharmaceutical ( Stock system], AQUALON RN-10 [First Industrial Pharmaceutical Co., Ltd.], AQUALON RN-20 [First Industrial Pharmaceutical Co., Ltd.], AQUALON ER-10 [First Industrial Pharmaceutical Co., Ltd.], AQUALON ER-20 [First Industrial Pharmaceutical Co., Ltd.], NEWFRONTIER A-229E [First Industrial Pharmaceutical Co., Ltd.], ADEKA REASOAP SE-10 [Asahi Chemical Co., Ltd.], ADEKA REASOAP SE-20 [Asahi Chemical Industry Co., Ltd.], ADEKA REASOAP SR-10N [Asahi Chemical Industry Co., Ltd.], ADEKA REASOAP SR-20N [Asahi Chemical Industry Co., Ltd.]. By using a reactive emulsifier, it is preferable to improve the water resistance of the film in addition to the polymerization stability.

Among the emulsion polymerization methods, a dropping polymerization method is preferably used. Further, in order to easily introduce the acid group into the inside of the particles, a dropping polymerization method may be selected, and the composition of the emulsion which is added dropwise in the first half of the dropping and the second half in the dropwise addition may be changed and controlled by this method. Specifically, the ratio of the acid monomers in the first half of the dropwise addition can be increased, and the ratio of the acid monomers in the latter half of the dropwise addition can be lowered, whereby the acid monomer can be introduced into the inside of the particles.

The polymerization used in the emulsion polymerization is not limited, and a known polymerization initiator can be used. Specific examples thereof include 2,2′,-azobis(2-methylpropionamidine) dihydrochloride and 2,2′-azobis(2-methylpropionamidine) disulfate. 2,2'-azobis(2-methylpropanepropane) dihydrochloride, 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine hydrate, 2,2'-azobis(N,N'-dimethyleneisobutylphosphonium) dihydrochloride, 2,2'-azobis[2-(2-imidazolin-2-yl)propane An azo-based initiator such as dihydrochloride, a persulfate-based initiator such as potassium persulfate, ammonium persulfate or sodium persulfate; benzammonium peroxide; and a third butyl hydroperoxide; A redox system such as a peroxide initiator such as hydrogen peroxide or a carbonyl initiator such as an aromatic carbonyl compound; a combination of a persulfate and sodium hydrogen sulfite; and a combination of a peroxide and sodium ascorbate; Starter and so on.

In addition, the solid content concentration of the water-dispersible acrylic pressure-sensitive adhesive composition of the present invention is not particularly limited, and is solid from the viewpoint of cost at the time of production or transportation cost, and excellent dryness when used for drying. The concentration of the component is preferably from 40 to 70% by weight.

The aqueous medium used in the water-dispersible acrylic pressure-sensitive adhesive composition of the present invention may be either water alone or a mixed solvent of water and a water-soluble solvent. The above-mentioned "mixed solvent of water and a water-soluble solvent" as used in the present invention means a solvent mixture substantially in combination with a water-soluble solvent mainly composed of water, and the content ratio of the water-soluble solvent is relatively larger than the total amount of the mixed solvent. It is preferably 10% by weight or less, more preferably 5% by weight or less. The water-soluble solvent may be used in combination with an alcohol such as methanol, ethanol, isopropanol, ethyl carbitol, ethyl celecoxib or butyl sarbuta, or a polar solvent such as N-methylpyrrolidone. These may be used alone or in combination of two or more.

In addition, the average particle diameter of the acrylic copolymer latex particles of the present invention is not particularly limited. However, when the thickness is 150 nm or less, it may be difficult to introduce an acid group into the latex particles. Therefore, it is preferably a particle diameter of more than 150 nm. It is preferably 200~1000nm, especially 200~800nm, especially 200~600nm, and the best is 250~400nm.

The average particle diameter of the particles herein means a 50% median diameter based on the volume of the latex particles, and the values are values determined by dynamic light scattering. If the average particle size is too small, the surface area of the particles increases, and the ratio of the surface of the particles to water contacts increases. As a result, for example, when a carboxyl group is used as the acid group, the carboxyl group is easily ionized into a carboxylate anion, and the tendency of the carboxyl group to locally exist on the surface of the particle becomes strong.

As described above, the ratio (AN _IN )/(AN _SUR ) between the amount of the acid group on the surface of the obtained acrylic copolymer latex and the amount of the internal acid group may not easily fall within the above-mentioned desired range. Therefore, the average particle diameter is preferably more than 150 nm. On the other hand, if the average particle diameter is too large, the average particle diameter is not excessively large in order to promote the fusion of the latex particles after the formation of the pressure-sensitive adhesive layer, and it is preferably controlled to be 1000 nm or less.

<Amount of acid group on the surface of the acrylic copolymer latex particles and inside the particles> (distribution of acid groups)

The acrylic copolymer latex particles in the water-dispersible acrylic pressure-sensitive adhesive composition of the present invention have an acid group amount (AN _SUR ) on the surface of the acrylic copolymer latex particles and an acid base amount in the acrylic copolymer latex particles. The ratio between (AN _IN ), that is, (AN _IN )/(AN _SUR ), is preferably one or more acrylic copolymer latex particles. In the present invention, the amount of the internal acid group can be achieved by using an acrylic copolymer having the same amount or more as the surface acid group to reduce the adhesive residue or to suppress an excessive increase in the adhesive force with an increase in time. A preferred re-peelable adhesive tape. As described above, by using the water-dispersed acrylic adhesive composition having the acrylic copolymer latex particles, it is excellent in re-peelability as an adhesive tape having an adhesive layer having a strong adhesive force. Therefore, an adhesive tape having excellent two characteristics of strong adhesion and re-peeling can be realized. Further, by aligning the acid group to the particles and the particles to maintain the cohesive force and suppressing the amount of the acid group on the surface of the particles, the hydrophilicity of the surface of the adhesive layer is lowered (hydrophobicity is improved), and water resistance is excellent. Adhesive tape. The ratio of the amount of the acid groups, that is, (AN _IN )/(AN _SUR ), is preferably 1.3 or more, more preferably 1.5 or more, and most preferably 2.0 or more. On the other hand, as the upper limit, if there is a surface acid group amount (A _SUR ) capable of maintaining the cohesive force between the acrylic copolymer latex particles, (AN _IN )/(AN _SUR ) is not particularly limited, and the above comparison is preferably 10 Hereinafter, it is more preferably 5 or less. When it is within the above upper limit range, the interaction between the particles can be easily performed, the aggregation force between the particles is easily increased, and the re-peelability and water resistance are increased.

(Method for measuring acid group distribution)

The distribution of the acid groups in the acrylic copolymer latex particles of the present invention is measured by the following method. In the method for measuring the distribution of acid groups in the acrylic copolymer latex particles in the present invention, it is preferred to use potentiometric titration because the measurement error is small and the operation is simple. The measurement of the acid group of the potentiometric titration can be carried out in accordance with the disclosure of Japanese Patent Laid-Open No. 2007-003454, and the measurement is carried out in the following manner.

(Method for measuring acid group distribution by potentiometric titration)

In the present invention, a method of measuring the distribution of acid groups in the acrylic copolymer latex particles by potentiometric titration is as follows.

The adjustment of the acidic sample dispersion used for the potentiometric titration is such that the acrylic copolymer latex particles (solid content) and ion-exchanged water are adjusted so that the mass ratio expressed by (acrylic copolymer latex/ion exchange water) becomes 3/100. . The extraction of the acrylic copolymer latex particles composed of the water-dispersible acrylic pressure-sensitive adhesive composition may be carried out in a state of being dispersed in an aqueous medium or being separated from an aqueous medium. The adjusted acidic sample dispersion liquid is preferably an acidic sample dispersion liquid having a pH of 4 or less, and is obtained by dispersing in an aqueous medium in a water-dispersed acrylic pressure-sensitive adhesive composition neutralized with ammonia water or the like. In the case of the acrylic copolymer latex, it is preferred to adjust the pH to 4 or less by adding a weak acid such as formic acid or butyric acid to the sample dispersion as needed.

For the titration, a potentiometric auto-titration device can be used as the potentiometric automatic titration device, and examples thereof include AT-610, AT-420N-WIN manufactured by Kyoto Electronics Co., Ltd., and the like.

The calculation of the acid group amount (AN _SUR ) and the internal acid group amount (AN _IN ) on the surface of the acrylic copolymer latex particles was calculated based on the titration curve obtained by titration with the potential difference. The X-axis is set to the amount of alkali to be dropped, and the Y-axis is set to pH to perform potentiometric titration. It is possible to obtain a minimum point P from the titration starting point P ₀ to the titration end point P ₃ after the start of the alkali titration. ₁ and a titration curve (Fig. 1) of the inflected point P ₂ indicated by the minimum point P ₁ . The minimum point P ₁ and the inflection point P _{2 are} converted into a differential curve (Fig. 2) in which the X axis is the alkali dropping amount (mL) and the Y axis is set to the ΔE/mL titration curve (Fig. 2). Read P ₁ and P ₂ simply and explicitly.

The region of P ₀ ~ P ₁ in the titration curve is the region where the free acid of the sample dispersion in the aqueous phase is neutralized, and the pH value of the neutral acid in the aqueous phase is reduced, during complete neutralization. The pH value indicates a minimum value P _{1 which} is extremely small. Therefore, the amount of alkali added in this area is the amount of titration required to neutralize the acid in the aqueous phase. The amount of acid groups (AN _AQUA ) [meq/g] in the aqueous phase in the sample dispersion was calculated from the alkali titer and the alkali concentration of the inorganic salt-based solution used for titration.

In the water-dispersible acrylic pressure-sensitive adhesive composition, the acid used in the polymerization of the acrylic copolymer is usually left. Therefore, when the acrylic copolymer latex particles are dispersed in an aqueous medium, the sample dispersion is used. Free acid will be present in the aqueous phase. On the other hand, when only the acrylic copolymer latex particles are separated and dispersed in ion-exchanged water, the acid is theoretically not present in the aqueous phase, so P ₀ = P ₁ may be present.

If the acid in the aqueous phase is neutralized, the acid group on the surface of the next acrylic copolymer latex particle which is easily neutralized will be neutralized. Since it is located in the region of P ₁ to P ₂ of the titration curve, the amount of alkali added in the region is used to neutralize the amount of the acid group required for the acid group on the surface of the acrylic copolymer latex particle. The amount of acid groups (AN _SUR ) [meq/g] on the surface of the acrylic copolymer latex particles was calculated from the alkali titer and the alkali concentration of the inorganic alkali solution used for titration.

When the acid group on the surface of the acrylic copolymer latex particle is neutralized, the acid group inside the acrylic copolymer latex particle which is hard to be neutralized starts to be neutralized, and it appears in the inflection point P ₂ in the titration curve. When the amount of the acid group (AN _IN ) in the acrylic copolymer latex particles is such that the latex particles are stably formed, it is difficult or troublesome to measure the total amount of the acid groups present in the latex particles. From the above calculation results and the total acid base amount (AN _TOTAL ) in the sample dispersion, it is calculated by the following formula.

AN _IN =AN _TOTAL -(AN _SUR +AN _AQUA )

As the inorganic alkali solution used for the above titration, potassium hydroxide or sodium hydroxide can be preferably used as the inorganic base for titration, and potassium hydroxide is preferably used. The concentration of the inorganic base used for titration is preferably adjusted to a range of 0.1 to 2 mol/L.

As another titration condition, it is preferable to perform titration by intermittent constant-speed titration, the intermittent time is 10 seconds, the maximum dropping amount is 20 mL, and the first injection amount at the time of intermittent injection is preferably 0.16 mL/time. The speed was 5 sec/mL, the potential of the data was 4 mL, and the method of measuring the pH titer was 0.16 mL each time.

The specific measurement method is as follows: a water-dispersed acrylic pressure-sensitive adhesive composition containing 3 g of acrylic copolymer latex particles (solid content) is weighed in a 300 mL polyethylene beaker using a dropper, and then ion-exchanged water is injected. The polyethylene beaker was stirred and allowed until the total amount of the test sample became 100 g. Then, immerse the electrode and the temperature assurance electrode. The tip of the titration nozzle is higher than the liquid level and is kept 2 cm with the electrode so that the titration reagent does not touch the electrode. Under the above conditions, the potential difference was automatically titrated while stirring. After the end of the measurement, meq/g was calculated from the titer of the equivalent point automatically printed on the obtained titration curve.

(Method of measuring the total amount of acid groups)

The total acid group amount (AN _TOTAL ) in the above-mentioned acidic sample dispersion liquid can be calculated from the theoretical amount of the acid group calculated from the filling amount, or can be obtained by measuring the potentiometric titration using a mineral acid solution as shown below. value. The method for measuring the total acid group amount (AN _TOTAL ) in the sample dispersion by potentiometric titration is as follows.

The sample dispersion was adjusted by adding potassium hydroxide to a sample dispersion similar to the above-mentioned acidic sample dispersion, until all the acid groups in the inside of the particles were neutralized. When the acrylic copolymer latex particle dispersion is an alkaline sample dispersion having a pH of 13, the internal acid groups are all extracted to the surface of the latex particles due to the interaction of static electricity. Therefore, by subjecting the alkaline sample dispersion liquid to reverse titration using a mineral acid solution, the acid group on the surface of the acrylic copolymer latex particle can be titrated in the same manner as the internal acid group, and the total acid group in the sample dispersion can be calculated. the amount.

The acid used for the titration is preferably sulfuric acid, and its concentration is preferably 0.1 mol/L. As the potential difference titration device, the same device as described above can be preferably used.

When the X-axis is set to the acid drop amount and the Y-axis is set to pH to perform the potential difference titration, it is possible to obtain a change point from the titration starting point Q ₀ to the titration end point Q ₄ in the order of decreasing the acid titer. Titration curves for Q ₁ , Q ₂ , and Q ₃ (Fig. 3). These inflection points can be read more easily and clearly by converting the X-axis to the acid drop amount (mL) and the Y-axis to the differential curve of the titration curve of ΔE/mL (Fig. 4). Change points. The X-coordinates of the inflection points Q ₁ , Q ₂ , and Q ₃ are acid drops at different points, and the acid drops of Q ₀ to Q ₁ are used to neutralize the hydrogen used to adjust the pH to 13. The titration required for the residue of potassium oxide. The acid drop amount of Q ₁ ~Q ₂ is used to neutralize the titration required for all the acid groups present in the acrylic copolymer latex particles, and the acid drop amount of Q ₂ ~ Q ₃ is used for And the required titer of the acid group in the aqueous phase. Therefore, the total acid groups in the above-mentioned acidic sample dispersion are calculated by converting the acid drop amount of Q ₁ to Q ₃ added in the acid drop amount to the concentration of the acid used for titration into meq/g. Quantity (AN _TOTAL ).

The specific measurement method is as follows: a water-dispersed acrylic pressure-sensitive adhesive composition containing 3 g of acrylic copolymer latex particles (solid content) is weighed in a 300 mL polyethylene beaker using a dropper, and then ion-exchanged water is injected. The polyethylene beaker was stirred and allowed until the total amount of the test sample became 100 g. Next, 1N potassium hydroxide was added and stirred until the pH of the test sample became 13. Then, immerse the electrode and the temperature assurance electrode. The potentiometric auto-titration was started with the same titration conditions as described above. After the end of the measurement, meq/g was calculated from the titer of the equivalent point automatically printed on the obtained titration curve.

The introduction of the acid group into the inside of the acrylic copolymer latex particles can be controlled by appropriately selecting a monomer composition or a polymerization method. In terms of the monomer composition, the acid group can be introduced into the interior of the particle by increasing the hydrophobicity of the acid monomer. Further, the acid group can be introduced into the interior of the particle by copolymerizing a nitrogen-containing monomer that interacts with the acid group. On the other hand, in the polymerization method, it is also possible to control by changing the composition of the emulsion which is added dropwise in the first half of the dropwise addition and the second half of the dropwise addition by the selective dropping polymerization method. Specifically, by increasing the ratio of the acid monomer in the first half of the dropwise addition, the ratio of the monomer having an acid group is lowered in the latter half of the dropwise addition, and the acid monomer can be introduced into the inside of the particle.

<adhesive tape> (constitution)

The adhesive tape of the present invention is an adhesive tape having an adhesive layer composed of the above-described water-dispersible acrylic adhesive composition. The adhesive layer may be a single layer of adhesive layer, or may be a plurality of layers of a plurality of adhesive layers and sheets such as double-sided adhesive tape. In the case of using two or more members for fixing, it is preferred to use a double-sided adhesive tape.

(adhesive layer)

The adhesive layer of the adhesive tape of the present invention is a layer obtained by removing a solvent from the water-dispersible acrylic adhesive composition. The thickness of the adhesive layer on both sides of the double-sided adhesive tape is preferably from 30 to 300 μm, more preferably from 50 to 200 μm.

In the adhesive layer of the present invention, the peak temperature of the embossing loss on the dynamic viscoelastic spectrum is preferably -60 ° C to -5 ° C, more preferably -30 ° C to -10 ° C. When it is in this range, it is possible to balance the re-peelability and the strong adhesion in a well-balanced manner.

The dynamic viscoelastic property described above was measured by using a viscoelasticity tester (manufactured by Rheometric Co., Ltd., trade name: ARES 2KSTD) for measuring the dynamic viscoelasticity, and the test piece was sandwiched between parallel disks of the measuring portion of the test machine. Storage elastic modulus (G') and loss elastic modulus (G") at a frequency of 1 Hz -50 ° C to 150 ° C. The test piece can also be sandwiched between parallel disks by an adhesive having a thickness of 0.5 to 2.5 mm. It is also possible to overlap several layers of the substrate and the adhesive layer between the parallel disks. In addition, in the latter case, the thickness of the adhesive alone is adjusted within the above range. If the thickness of the adhesive is adjusted In the above range, even if the substrate is interposed, the dynamic viscoelastic spectrum of the adhesive is not affected, which has been confirmed by the inventors.

(not woven)

When a double-sided adhesive tape is formed, it is preferable to use a nonwoven fabric as a center core, and it is preferable to use a tensile strength, a crack strength, and an interlayer strength in a specific range as the nonwoven fabric in order to achieve good balance between removability and adhesion. Not woven.

The tensile strength of the non-woven fabric is preferably 10 to 50 N/20 mm in the MD direction (longitudinal direction, flow direction), and TD direction (lateral direction, width direction), more preferably 15 to 40 N/20 mm, and most preferably 25 to 25 40N/20mm. In the double-sided adhesive tape of the present invention, when the tensile strength of the nonwoven fabric substrate is set to the strength in the range, the tape is less likely to be broken at the time of peeling, and it is not easily peeled off even when it is adhered to a curved surface or the like. In addition, the above-mentioned tensile strength is determined by using a TENSILON tensile tester using a TENSILON tensile tester under the conditions of a tensile speed of 300 mm/min in an environment of 23 ° C and ‧50% RH. The maximum strength.

The crack resistance of the nonwoven fabric is preferably 1 N or more as defined by JIS-P-8116. When the crack resistance is 1 N or more, the starting point of the break due to the pulling at the moment of the peeling step is gradually increased, so that the breakage of the generated nonwoven fabric can be remarkably suppressed, and the base material is less likely to be broken. As a result, the removability of the double-sided adhesive tape adhering to the adherend for a long period of time can be greatly improved. The upper limit of the cracking strength is not particularly limited, and the upper limit of the crack strength is generally considered to be about 3 N in order to use a nonwoven fabric as a substrate. It is preferably 1.2 to 2.5 N, more preferably 1.5 to 2.5 N.

The interlayer strength of the nonwoven fabric is preferably 1 N/15 mm or more. For the method of measuring the interlayer strength, first, a 24 mm-wide adhesive film (cellulose tape: CT405AP-24 manufactured by Nichiban Co., Ltd.) was attached to both sides of a 25 × 150 mm non-woven fabric. The length of the adhesive film is set to be longer than the non-woven fabric. The both ends of the sample were cut out, and the cellulose tape was peeled off at one end of the sample adjusted to 15 × 150 mm, and the nonwoven fabric layer of about 30 mm was peeled off. The sample was prepared in three sheets in the longitudinal direction and the lateral direction. Measurement temperature and humidity: 23 ° C 50% RH; measuring machine: TENSILON RTA-100 manufactured by ORIENTIC Co., Ltd.; test piece clamping interval: the above samples were placed at a jig at intervals of 20 mm; speed: 100 mm/min; measuring distance: 50 mm Then, the average load of the integral obtained by the above conditions was calculated, and the average value of the longitudinal direction, the lateral direction, and each of the three sheets was defined as the interlayer strength (N/15 mm). The upper limit of the interlayer strength is not particularly limited, and in general, when the nonwoven fabric is used as the substrate, the upper limit of the interlayer strength is considered to be about 4N.

As the material of the non-woven fabric, a conventionally known non-woven fabric used as a non-woven fabric of an adhesive tape can be used. Typical examples thereof include Manila hemp; pulp; chemical fibers such as rayon, acetate fiber, polyester fiber, polyvinyl alcohol fiber, and polyamide fiber; and the like. In addition, the mucus fiber impregnated material or the thermoplastic resin may be impregnated as an adhesive as needed.

Among them, it is better to use a single hemp, or a mixture of hemp and vinylon, rayon, polyester, pulp, and the like. As hemp, Manila hemp is preferred from the viewpoint of strength. Further, the content of Manila hemp is preferably 50% by mass or more, and more preferably 70% by mass or more.

Further, in order to achieve the purpose of improving the strength of the nonwoven fabric, it is preferred to add a conventionally known reinforcing agent in the nonwoven fabric manufacturing step. The reinforcing agent may be added with a reinforcing agent or an external reinforcing agent alone or in combination. As the internal reinforcing agent, a polypropylene amide type resin, a urea-formaldehyde type resin, a melamine-formaldehyde type resin, an epoxy-polyamide type resin, or the like can be used. In particular, the polyamine-amine ‧ epichlorohydrin resin of the epoxy-polyamine resin can remarkably improve the interlayer strength of the nonwoven fabric. The amount of the internal reinforcing agent added is preferably from 0.2 to 1%, more preferably from 0.3 to 0.5%, based on the nonwoven fabric. On the other hand, as the external reinforcing agent, a thermoplastic resin such as starch; mucin fiber, carboxymethyl cellulose, polyvinyl alcohol or polypropylene decylamine can be used. Among them, in order to enhance the interlayer strength of the nonwoven fabric substrate, it is preferred to use the above-mentioned internal reinforcing agent.

The basis weight of the above non-woven fabric is preferably from 10 to 30 g/m ² , more preferably from 13 to 25 g/m ² , most preferably from 14 to 20 g/m ² . Further, the density is preferably from 0.15 to 0.35 g/m ² , more preferably from 0.2 to 0.3 g/m ² . If it is in this range, the difficulty of breaking the non-woven fabric and the impregnation of the adhesive to the non-woven fabric can be balanced and the re-peelability can be further improved.

The papermaking method as the non-woven fabric is not particularly limited, and can be obtained by a known wet method, and various paper making methods such as a cylinder paper machine, a short-web paper machine, a Fourdrinier paper machine, and a tilted short-web paper machine can be used. Among them, in order to make the nonwoven fabric less likely to be broken, it is preferable to increase the strength in the MD direction and the TD direction or the isotropic property of stretching, and it is preferable to use the inclined short-web paper machine which can easily improve the isotropic property.

When the double-sided adhesive tape is formed, it is preferred to fix an acrylic copolymer having a glass transition temperature (Tg) of -10 ° C or less on the nonwoven fabric. Compared with the general non-woven fabric to which the acrylic copolymer is not fixed, when the acrylic copolymer is fixed to the nonwoven fabric, since the surface of the nonwoven fabric is coated with acrylic acid, the non-woven fabric and the acrylic adhesive composition are interposed. The chemical affinity is improved, and the bond between the non-woven substrate and the adhesive becomes stronger. As a result, during the re-peeling process of the adhesive tape attached to the adherend during the long peeling period, the adhesive becomes difficult to fall off from the non-woven substrate. Further, in general, when the nonwoven fabric is treated with an acrylic fiber processing agent, the tensile strength of the nonwoven fabric tends to increase, but the crack resistance is greatly reduced and the tear is easily broken. However, when an acrylic copolymer having a low glass transition temperature is used, as long as the temperature is close to -10 ° C, the crack resistance is enhanced, which greatly contributes to the improvement of the removability.

Further, the glass transition temperature of the acrylic copolymer fixed to the nonwoven fabric is preferably -10 ° C or lower, more preferably -15 ° C or lower, and most preferably -20 ° C or lower. When the acrylic copolymer having a glass transition temperature higher than -10 ° C is fixed to the nonwoven fabric substrate, the brittleness of the nonwoven fabric substrate is enhanced, and the crack resistance of the nonwoven fabric substrate is lowered. As a result, it is apparent that the non-woven substrate becomes easily torn at the time of re-peeling. On the other hand, when the acrylic copolymer having a low glass transition temperature of -10 ° C or less is fixed to the nonwoven fabric substrate, the effect of relaxing the stress applied to the nonwoven fabric substrate during the re-peeling process is obtained, and the nonwoven fabric is not woven. The substrate will become less susceptible to tearing.

(manufacturing steps of adhesive tape)

The method of laminating the adhesive layer on the non-woven fabric may be carried out by directly applying the adhesive solution to the non-woven fabric substrate by a roll coater or a die coater, and then performing a drying step and then adhering to the spacer ( Hereinafter, it is referred to as a direct coating method, or a method in which an adhesive solution is applied to a spacer, and after being dried, and then transferred onto a nonwoven fabric (hereinafter referred to as a transfer method). In the manufacturing process of the double-sided tape, the impregnation property tends to be deteriorated by the direct coating method in which the adhesive is impregnated with the nonwoven fabric in a solution state, and the adhesive layer after drying is impregnated with the nonwoven fabric by the transfer method. However, since the acrylic copolymer composed of the present invention has excellent impregnation properties to the nonwoven fabric, excellent impregnation properties can be maintained even by the transfer method.

The gel fraction of the insoluble component measured after immersing the adhesive layer in toluene for 24 hours at the end of the drying step is preferably 15% or less, more preferably 10% or less, and most preferably 5% or less. When the gel fraction at the end of the drying step is 15% or less, the adhesive becomes easily impregnated with the non-woven fabric, and the re-peelability can be improved. The gel fraction can be adjusted by appropriately selecting the reaction temperature, the reaction time, the type and amount of the initiator, the type and amount of the chain transfer agent in the synthesis of the acrylic copolymer latex.

(characteristics of adhesive tape)

The tensile strength of the adhesive tape of the present invention is preferably 20 N/20 mm or more and less than 50 N/20 mm in the MD direction (longitudinal direction; flow direction) and TD direction (lateral direction; width direction). More preferably, it is 20 N/20 mm or more and less than 40 N/20 mm, and most preferably 30 N/20 mm or more and less than 40 N/20 mm. When the thickness is 20 N/20 mm or more, the adhesive tape is remarkably hard to be peeled off when the adhesive tape is peeled off for a long period of time. On the other hand, if the tensile strength is too high, the toughness of the adhesive tape itself becomes strong, so that the repulsive force cannot be withstood and peeling easily occurs, so it is preferably less than 50 N/20 mm. In particular, when the adhesive tape is used for applications requiring a repulsive force such as a curved surface, it is preferably less than 40 N/20 mm.

Further, the tensile strength as described above means that the wire length is 100 mm and the width is 20 mm when the tensile strength is 300 mm/min under an environment of 23 ° C ‧50% RH using a TENSILON tensile tester. The maximum strength measured at the time of the sample.

The 180-degree adhesion of the adhesive tape is measured by JIS-Z-0237. The stainless steel plate is used as an adherend, and is pressurized by a 2 kg roll at a temperature of 23 ° C in ‧50%. Adhesive preparation, [A] sample (retained for 1 hour at ‧50% environment at 23 ° C) and [B] sample (after standing at 60 ° C for ‧0 to 5% for 10 days, then at 23 ° C ‧50% of the environment was allowed to stand for 1 hour), and the adhesive tape samples of [A] and [B] were measured for adhesion at a rate of 1000 m/min in the direction of 180 degrees ([A] and [B] When the adhesive strength of [A] is preferably 12 to 19 N/20 mm, the difference of adhesion between [B] and [A] is preferably 10 N/20 mm. If the adhesion is within the range, the re-peelability and the strong adhesion can be balanced in good balance. In addition, the adhesive tape was cut into a width of 20 mm × a length of 100 mm to adjust the adhesive tape sample; in the case of a double-sided adhesive tape, the double-sided adhesive tape was reinforced with a PET film having a thickness of 25 μm, and cut into a width of 20 mm. × Length 100mm to adjust the double-sided adhesive tape sample.

<Use>

The adhesive tape of the present invention has excellent peeling resistance against the repulsive force of the adherend, durability against being applied to the load in the fracture direction, and adhesion reliability under extreme environmental conditions such as a high-humidity environment, and for a small area. The fixing between the parts, etc., also has excellent adhesion to stabilize the fixing members. In addition to this, excellent re-peelability can be exhibited when the work process is poorly bonded or when the components are separated during re-recycling. In addition, unlike the conventional adhesive which uses a solution polymerization type acrylic resin as a main component, it is preferable to use a water-dispersible acrylic pressure-sensitive adhesive composition, and it is also expected to reduce the effect of the volatile organic compound. Adhesive tape that is fixed between parts in various products for industrial use such as automobiles, building materials, office automation, and home appliance industries.

Example

Next, the present invention will be described in detail by way of examples and comparative examples.

[Modulation Method of Water-Dispersed Acrylic Adhesive Composition] (Example 1) <Preparation of emulsion>

The container was filled with 75.00 g of ion-exchanged water, a surfactant AQUALON KH-1025 [manufactured by First Industrial Pharmaceutical Co., Ltd.; 25% active ingredient] 20.00 g, and a surfactant LATEMUL PD-104 [King Co., Ltd.]; The active ingredient was 20%] 37.50 g to dissolve it evenly. 227.5 g of n-butyl acrylate, 227.5 g of 2-ethylhexyl acrylate, 25.00 g of methyl methacrylate, 7.50 g of N-vinylpyrrolidone, acrylic acid [80% of active ingredient], 12.50 g of methacrylic acid were added thereto. 80% of the active ingredient] 3.13 g and 0.20 g of dodecanol were emulsified to obtain 635.83 g of an emulsion.

<Manufacture of Acrylic Copolymer Latex>

In a reaction vessel having a stirrer, a reflux cooling tube, a nitrogen gas introduction tube, a thermometer, and a dropping funnel, 290 g of ion-exchanged water was charged, and the temperature was raised to 60 ° C while introducing nitrogen gas. Under stirring, a portion of the emulsion [3.18 g], an aqueous solution of ammonium persulfate 5.00 g [3% of active ingredient], and 5 g of an aqueous solution of sodium hydrogen sulfite [3% active ingredient] were added, and the mixture was polymerized while maintaining at 60 ° C. hour. Next, 632.65 g of the remaining emulsion and 40 g of an aqueous solution of ammonium persulfate [1.25% of active ingredient] were used, and a reaction vessel was used while maintaining the reaction vessel at 60 ° C for 8 hours while dropwise addition polymerization. After completion of the dropwise addition, the reaction vessel was stirred while maintaining the temperature at 60 ° C for 2 hours, and then the content was cooled to obtain an acrylic copolymer latex (A). Next, the pH was adjusted to 7.0 by adjusting with ammonia water (active ingredient: 10%). This was filtered through a 200 mesh metal mesh to obtain an acrylic copolymer latex (B). Here, the obtained water-dispersed acrylic polymer had a solid content concentration of 52.6% and an average particle diameter of 323 nm.

<Manufacture of Water-Dispersed Acrylic Adhesive Composition>

SURFYNOL PSA-336 [manufactured by Air‧Products‧Japan; active ingredient 100%] 2.5 g as a leveling agent, SURFYNOL DF was added to 950.57 g [dry; 500 g] of the above acrylic copolymer latex (B). -110D[Air‧Products‧Japan Co., Ltd.; active ingredient 100%] 2.5g as defoamer, epoxy compound TETRAD C [Mitsubishi Gas Chemical Co., Ltd.] 0.15g as crosslinking agent, latex type polymerized rosin Ester-based adhesive-providing resin SUPER ESTERE-865NT [manufactured by Arakawa Chemical Co., Ltd.; softening point 160 ° C] 50 g of solid component as adhesion-imparting resin, latex type rosin-based adhesive-imparting resin TAMANOL E-200NT [Arakawa Chemical Industry Co., Ltd. A softening point of 150 ° C] 50 g of a solid component was filtered through a 100 mesh metal mesh to obtain a water-dispersed acrylic adhesive composition of the present invention.

(Example 2) <Preparation of emulsion>

An emulsion was prepared in the same manner as in Example 1 except that 12.50 g of acrylic acid [80% of active ingredient] was changed to 9.38 g, and 3.13 g of methacrylic acid [80% of active ingredient] was changed to 6.25 g.

<Manufacture of Acrylic Copolymer Latex>

An acrylic copolymer latex was produced in the same manner as in Example 1 except that the emulsifier prepared above was used. The acrylic copolymer latex prepared herein had a solid content concentration of 52.6% and an average particle diameter of 302 nm.

<Manufacture of Water-Dispersed Acrylic Adhesive Composition>

A water-dispersed acrylic pressure-sensitive adhesive composition was produced in the same manner as in Example 1 except that the acrylic copolymer latex obtained above was used.

(Example 3) <Preparation of emulsion>

An emulsion was prepared in the same manner as in Example 1 except that 12.50 g of acrylic acid [80% of active ingredient] was changed to 6.25 g, and 3.13 g of methacrylic acid [80% of active ingredient] was changed to 9.38 g.

<Manufacture of Acrylic Copolymer Latex>

An acrylic copolymer latex was produced in the same manner as in Example 1 except that the emulsifier prepared above was used. The acrylic copolymer latex prepared herein had a solid content concentration of 52.6% and an average particle diameter of 300 nm.

<Manufacture of Water-Dispersed Acrylic Adhesive Composition>

A water-dispersed acrylic pressure-sensitive adhesive composition was produced in the same manner as in Example 1 except that the acrylic copolymer latex obtained above was used.

(Example 4) <Preparation of emulsion>

The emulsion was prepared in the same manner as in Example 1 except that 12.50 g of acrylic acid [80% of active ingredient] was changed to 3.13 g, and 3.13 g of methacrylic acid [80% of active ingredient] was changed to 12.50 g.

<Manufacture of Acrylic Copolymer Latex>

An acrylic copolymer latex was produced in the same manner as in Example 1 except that the emulsifier prepared above was used. The acrylic copolymer latex prepared herein had a solid content concentration of 52.6% and an average particle diameter of 315 nm.

<Manufacture of Water-Dispersed Acrylic Adhesive Composition>

A water-dispersed acrylic pressure-sensitive adhesive composition was produced in the same manner as in Example 1 except that the acrylic copolymer latex obtained above was used.

(Example 5) <Preparation of emulsion>

An emulsion was prepared in the same manner as in Example 1 except that 12.50 g of acrylic acid [80% of active ingredient] was changed to 1.88 g, and 3.13 g of methacrylic acid [80% of active ingredient] was changed to 13.75 g.

<Manufacture of Acrylic Copolymer Latex>

An acrylic copolymer latex was produced in the same manner as in Example 1 except that the emulsifier prepared above was used. The acrylic copolymer latex obtained herein had a solid content concentration of 52.6% and an average particle diameter of 341 nm.

<Manufacture of Water-Dispersed Acrylic Adhesive Composition>

A water-dispersed acrylic pressure-sensitive adhesive composition was produced in the same manner as in Example 1 except that the acrylic copolymer latex obtained above was used.

(Example 6) <Preparation of emulsion>

An emulsion was prepared in the same manner as in Example 1 except that 12.50 g of acrylic acid [80% of active ingredient] was changed to 0 g, and 3.13 g of methacrylic acid [80% of active ingredient] was changed to 15.63 g.

<Manufacture of Acrylic Copolymer Latex>

An acrylic copolymer latex was produced in the same manner as in Example 1 except that the emulsifier prepared above was used. The acrylic copolymer latex prepared herein had a solid content concentration of 52.6% and an average particle diameter of 367 nm.

<Manufacture of Water-Dispersed Acrylic Adhesive Composition>

A water-dispersed acrylic pressure-sensitive adhesive composition was produced in the same manner as in Example 1 except that the acrylic copolymer latex obtained above was used.

(Example 7) <Preparation of emulsion>

The container was filled with 75.00 g of ion-exchanged water, a surfactant AQUALON KH-1025 [manufactured by First Industrial Pharmaceutical Co., Ltd.; 25% active ingredient] 20.00 g, and a surfactant LATEMUL PD-104 [King Co., Ltd.]; The active ingredient was 20%] 37.50 g to dissolve it evenly. 230.5 g of n-butyl acrylate, 230.5 g of 2-ethylhexyl acrylate, 25.00 g of methyl methacrylate, 1.50 g of N-vinylpyrrolidone, acrylic acid [80% of active ingredient], 3.13 g of methacrylic acid were added thereto. The active ingredient 80%] 12.50 g and 0.20 g of dodecanol were emulsified to obtain 635.83 g of an emulsion.

<Manufacture of Acrylic Copolymer Latex>

An acrylic copolymer latex was produced in the same manner as in Example 1 except that the emulsifier prepared above was used. The acrylic copolymer latex obtained herein had a solid content concentration of 52.6% and an average particle diameter of 339 nm.

<Manufacture of Water-Dispersed Acrylic Adhesive Composition>

A water-dispersed acrylic pressure-sensitive adhesive composition was produced in the same manner as in Example 1 except that the acrylic copolymer latex obtained above was used.

(Example 8) <Preparation of emulsion>

The container was filled with 75.00 g of ion-exchanged water, a surfactant AQUALON KH-1025 [manufactured by First Industrial Pharmaceutical Co., Ltd.; 25% active ingredient] 20.00 g, and a surfactant LATEMUL PD-104 [King Co., Ltd.]; The active ingredient was 20%] 37.50 g to dissolve it evenly. 231.25 g of n-butyl acrylate, 231.25 g of 2-ethylhexyl acrylate, 25.00 g of methyl methacrylate, 3.13 g of acrylic acid [80% active ingredient], and 12.50 g of methacrylic acid [80% of active ingredient] were added thereto. 0.20 g of dodecanol was emulsified to obtain 635.83 g of an emulsion.

<Manufacture of Acrylic Copolymer Latex>

An acrylic copolymer latex was produced in the same manner as in Example 1 except that the emulsifier prepared above was used. The acrylic copolymer latex prepared herein had a solid content concentration of 52.6% and an average particle diameter of 336 nm.

<Manufacture of Water-Dispersed Acrylic Adhesive Composition>

A water-dispersed acrylic pressure-sensitive adhesive composition was produced in the same manner as in Example 1 except that the acrylic copolymer latex obtained above was used.

(Comparative Example 1) <Preparation of emulsion>

The container was filled with 75.00 g of ion-exchanged water, a surfactant AQUALON KH-1025 [manufactured by First Industrial Pharmaceutical Co., Ltd.; 25% active ingredient] 20.00 g, and a surfactant LATEMUL PD-104 [King Co., Ltd.]; The active ingredient was 20%] 37.50 g to dissolve it evenly. 227.5 g of n-butyl acrylate, 227.5 g of 2-ethylhexyl acrylate, 25.00 g of methyl methacrylate, 7.50 g of N-vinylpyrrolidone, acrylic acid [80% active ingredient] 15.63 g, and dodecyl mercaptan were added thereto. 0.20 g was emulsified to obtain 635.83 g of an emulsion.

<Manufacture of Acrylic Copolymer Latex>

An acrylic copolymer latex was produced in the same manner as in Example 1 except that the emulsifier prepared above was used. The acrylic copolymer latex obtained herein had a solid content concentration of 52.6% and an average particle diameter of 338 nm.

<Manufacture of Water-Dispersed Acrylic Adhesive Composition>

A water-dispersed acrylic pressure-sensitive adhesive composition was produced in the same manner as in Example 1 except that the acrylic copolymer latex obtained above was used.

(Comparative Example 2) <Preparation of emulsion>

The container was filled with 75.00 g of ion-exchanged water, a surfactant AQUALON KH-1025 [manufactured by First Industrial Pharmaceutical Co., Ltd.; 25% active ingredient] 20.00 g, and a surfactant LATEMUL PD-104 [King Co., Ltd.]; The active ingredient was 20%] 37.50 g to dissolve it evenly. Emulsification was carried out by adding 231.25 g of n-butyl acrylate, 231.25 g of 2-ethylhexyl acrylate, 25.00 g of methyl methacrylate, 15.63 g of acrylic acid [80% active ingredient], and 0.20 g of dodecanol. Liquid 635.83g.

<Manufacture of Acrylic Copolymer Latex>

An acrylic copolymer latex was produced in the same manner as in Example 1 except that the emulsifier prepared above was used. The acrylic copolymer latex prepared herein had a solid content concentration of 52.6% and an average particle diameter of 358 nm.

<Manufacture of Water-Dispersed Acrylic Adhesive Composition>

A water-dispersed acrylic pressure-sensitive adhesive composition was produced in the same manner as in Example 1 except that the acrylic copolymer latex obtained above was used.

(Comparative Example 3) <Preparation of emulsion>

The container was filled with 75.00 g of ion-exchanged water, a surfactant AQUALON KH-1025 [manufactured by First Industrial Pharmaceutical Co., Ltd.; 25% active ingredient] 20.00 g, and a surfactant LATEMUL PD-104 [King Co., Ltd.]; The active ingredient was 20%] 37.50 g to dissolve it evenly. 227.5 g of n-butyl acrylate, 227.5 g of 2-ethylhexyl acrylate, 25.00 g of methyl methacrylate, 7.50 g of N-vinylpyrrolidone, acrylic acid [80% active ingredient] 3.13 g, methacrylic acid were added thereto. The active ingredient 80%] 12.50 g and 0.20 g of dodecanol were emulsified to obtain 635.83 g of an emulsion.

<Manufacture of Acrylic Copolymer Latex>

580 g of ion-exchanged water and a surfactant AQUALON KH-1025 (manufactured by Daiichi Kogyo Co., Ltd.; 25% active ingredient) were placed in a reaction vessel equipped with a stirrer, a reflux cooling tube, a nitrogen inlet tube, a thermometer, and a dropping funnel. 30.00 g, the temperature was raised to 60 ° C while introducing nitrogen gas. Under stirring, a portion of the emulsion [19.07 g], an aqueous solution of ammonium persulfate 5.00 g [3% of the active ingredient], and 5 g of an aqueous solution of sodium hydrogen sulfite [3% of the active ingredient] were added, and the mixture was polymerized while maintaining the temperature at 60 ° C. hour. Next, 616.75 g of the remaining emulsion and 40 g of an aqueous solution of ammonium persulfate [1.25% of active ingredient] were used, and the reaction vessel was maintained at 60 ° C while dropwise addition polymerization was carried out for 8 hours. After completion of the dropwise addition, the reaction vessel was stirred while maintaining the temperature at 60 ° C for 2 hours, and then the content was cooled to obtain an acrylic copolymer latex (C). Next, the pH was adjusted to 7.0 by adjusting with ammonia water (active ingredient: 10%). This was filtered through a 200 mesh metal mesh to obtain an acrylic copolymer latex (D). Here, the obtained water-dispersed acrylic polymer had a solid content concentration of 40.2% and an average particle diameter of 112 nm.

<Manufacture of Water-Dispersed Acrylic Adhesive Composition>

To the above-mentioned acrylic copolymer latex (D) 1243.78 g [dry; 500 g], SURFYNOL PSA-336 [manufactured by Air‧Products‧Japan; active ingredient 100%] 2.5 g as a leveling agent, SURFYNOL DF was added. -110D[Air‧Products‧Japan Co., Ltd.; active ingredient 100%] 2.5g as defoamer, epoxy compound TETRAD C [Mitsubishi Gas Chemical Co., Ltd.] 0.15g as crosslinking agent, latex type polymerized rosin Ester-based adhesive-providing resin SUPER ESTERE-865NT [manufactured by Arakawa Chemical Co., Ltd.; softening point 160 ° C] 50 g of solid component as adhesion-imparting resin, latex type rosin-based adhesive-imparting resin TAMANOL E-200NT [Arakawa Chemical Industry Co., Ltd. A softening point of 150 ° C] 50 g of a solid component was filtered through a 100 mesh metal mesh to obtain a water-dispersed acrylic adhesive composition of the present invention.

[Modulation method of non-woven substrate]

A solution containing 90% of Manila hemp, 10% of polyester, and 0.5% of polyamidoamine-epichlorohydrin resin was used in a tilted short-web paper machine to have a basis weight of 17 g/m ² and a density of 0.28 g/cm ³ . Papermaking was carried out to obtain a nonwoven fabric substrate having a tensile strength of 25.3 N/20 mm in the MD direction and 23.5 N/20 mm in the TD direction.

[Modulation method of double-sided adhesive tape]

The polyester film having a thickness of 75 μm after the release treatment of the water-dispersible acrylic pressure-sensitive adhesive composition was applied to a polyester film having a thickness of 65 μm after drying, and dried at 100 ° C for 5 minutes to obtain an adhesive sheet. The adhesive sheet was transferred onto both sides of the above-mentioned nonwoven fabric substrate, and laminated by a hot roll of 90 ° C at a pressure of 4 kgf/cm to obtain a double-sided adhesive tape. Further, the double-sided adhesive tape was used for the test after being aged at 40 ° C for 2 days. The gel fraction of the obtained double-sided adhesive tape after curing at 40 ° C for 2 days was 35%.

[Evaluation method (water-dispersed acrylic adhesive composition)] (Method for measuring carboxyl group distribution in acrylic copolymer latex)

5.7 g (solid content: 3 g) of the acrylic copolymer latex (A) obtained in Example 1 [solid content concentration: 52.6%] was weighed into a 300 mL polyethylene beaker by a pipette, and then 94.3 g of ion-exchanged water was injected into the beaker. The mixture was stirred in a polyethylene beaker (the total amount of the test sample was taken as 100 g). Next, immerse the electrode and the temperature assurance electrode. The tip of the titration nozzle is higher than the liquid level and is set to 2 cm with the electrode so that the titration reagent does not touch the electrode. The setting of the method conditions is specified as follows: the titration mode is set to intermittent constant-speed titration, the intermittent time is 10 seconds, the maximum dropping amount is 20 mL, the one-time injection amount during intermittent injection is 0.16 mL/time, and the injection speed is 5 seconds. /mL, take the data potential is 4mL, the titration taken is 0.16mL. The potential difference is automatically titrated while stirring. The amount of acid groups present on the surface of the acrylic copolymer latex particles calculated from the obtained titration curve was 0.143 meqv./g, and the amount of acid groups present in the particles was 0.149 meqv./g.

The acrylic copolymer latexes of Examples 2 to 8 and Comparative Examples 1 to 4 were also measured in the same manner, and the amount of acid groups present on the surface of the acrylic copolymer latex particles calculated from the titration curve was calculated and found in the particles. The amount of acid base inside. The results obtained are shown in Table 1.

(Average particle size of acrylic copolymer latex)

The measured average particle diameter (50% median diameter on a volume basis) was determined by a Microtrac UPA type particle size distribution measuring apparatus manufactured by Nikkiso Co., Ltd.

[Evaluation method (double-sided adhesive tape)] (evaluation of re-peelability)

The double-sided adhesive tape was reinforced with a PET film having a thickness of 25 μm, and cut into a width of 20 mm × a length of 100 mm to adjust the double-sided adhesive tape sample. Next, the stainless steel plate was used as an adherend, and it was pressure-bonded by using a 2 kg roll once in a ‧50% environment at 23 ° C, and allowed to stand in an environment of 60 ° C for 10 days. Thereafter, the mixture was allowed to stand in an environment of 23° C. and 50% RH for 1 hour, and then the re-peelability at the time of peeling of the double-sided adhesive tape sample at a speed of 25 m/min in the direction of 135 degrees was evaluated. Further, the evaluation of the removability was measured by the following criteria.

◎: The residual area of the adhesive on the adherend and the residual area of the adhesive tape due to the breakage of the non-woven fabric are less than 3% of the adhesive area.

◎~○: The residual area of the adhesive on the adherend and the residual area of the adhesive tape due to the breakage of the non-woven fabric are 3% or more of the adhesive area and less than 10%.

○: The residual area of the adhesive on the adherend and the residual area of the adhesive tape due to the breakage of the non-woven fabric are 10% or more of the adhesive area and less than 30%.

△: The residual area of the adhesive on the adherend and the residual area of the adhesive tape due to the breakage of the non-woven fabric are 30% or more of the adhesive area and less than 80%.

×: The residual area of the adhesive on the adherend and the residual area of the adhesive tape due to the breakage of the non-woven fabric are 80% or more of the adhesive area.

(Evaluation of adhesion and adhesion increase with time after adhesion by adhesive)

The double-sided adhesive tape was reinforced with a PET film having a thickness of 25 μm, and cut into a width of 20 mm × a length of 100 mm to adjust the double-sided adhesive tape sample. Next, a stainless steel plate was used as an adherend, and a pressure was applied by using a 2 kg roll at a temperature of 23 ° C in an environment of ‧50% to prepare a sample [A] (disposed in an environment of ‧50% at 23 ° C) 1 hour) and [B] sample (after standing for 10 days in an environment of ‧0 to 5% at 60 ° C, and then standing at ‧50% in 23 ° C for 1 hour)

Thereafter, the double-sided adhesive tape samples of [A] and [B] were measured to have a peeling force ([A] and [B]) at a speed of 1000 m/min in a 180-degree direction. Next, the adhesion of the lift ([B]-[A]) is calculated. Further, the measurement of the adhesion was carried out in accordance with JIS-Z-0237.

(Evaluation of water resistance)

The double-sided adhesive tape was pressure-bonded to the ECS urethane foam (5 mm thick by INOAC Co., Ltd.) in a 2 kg roll at 23 ° C for ‧ 50%, and then allowed to stand for 24 hours. Next, the sample was cut into a 10 mm-wide sample, and the adhesive length was set to 10 mm, and the stainless steel plate having a thickness of 2 mm was held in a state of being adhered, and the urethane foam surface was applied by a 2 kg roll. Press and hold, then let stand for 1 hour. Subsequently, it was allowed to stand for 3 days in an environment of ‧90% RH at 60 ° C, and the distance from the double-sided adhesive tape adhered to the stainless steel plate to the peeling of the urethane foam was measured (Fig. 5). Further, the evaluation of water resistance was measured by the following criteria.

◎: The urethane foam and the double-sided adhesive tape were in a state of close contact with each other, and the peeling distance was less than 2 mm.

○: The urethane foam and the double-sided adhesive tape were confirmed to have a little floating and peeling, but the degree of peeling was less than 3 mm.

△: The urethane foam and the double-sided adhesive tape were confirmed to have significant floating peeling, and the peeling distance was 3 mm or more.

X: The urethane foam and the double-sided adhesive tape were completely peeled off after being allowed to stand in an environment of 60 ° C and ‧90% RH for 3 days.

××: The urethane foam and the double-sided adhesive tape were completely peeled off after being allowed to stand in an environment of 60° C. and ‧90% RH for one day.

(Evaluation of fixed load peelability)

A 10 mm wide double-sided adhesive tape sample reinforced with a polyester film having a thickness of 25 μm was adhered to a stainless steel plate, a HIPS plate, and a polypropylene plate (manufactured by Nippon Testpanel Co., Ltd.) so as to have a length of 50 mm. The 2 kg roll was pressed and bonded one time on the double-sided adhesive sheet. After standing for 1 hour in an atmosphere of 23° C. and 50% RH, a load of 300 g was applied in a direction of 90° with respect to the peeling direction, and the time until the tape sample having a length of 50 mm was dropped was measured and evaluated according to the following criteria. In addition, the evaluation of the constant load peelability is a substitute evaluation method in which a deformation stress is applied to the double-sided adhesive tape from the outside for a long period of time, and the longer the time required for the fall, the more excellent the peeling resistance is, that is, it is excellent. Strong adhesion.

○: The drop time is 3 hours or longer.

△: It falls within 3 hours.

×: It falls within 1 hour.

As is clear from the above Table 1, the adhesive tape using the water-dispersed acrylic adhesive composition of the present invention of Examples 1 to 8 has good adhesion and holding force to the adherend (fixed load peeling property). And has excellent re-peelability. On the other hand, the adhesive tapes of Comparative Examples 1 to 2 lacked re-peelability, and the adhesive tape of Comparative Example 3 had poor load-disbonding properties for a plurality of adherends. Further, the adhesive tapes of the water-dispersible acrylic pressure-sensitive adhesive compositions of the present invention which are used in Examples 1 to 8 have excellent adhesion even in a high-humidity environment.

1. . . Stainless steel plate

2. . . Urethane foam

3. . . Peeling distance

Fig. 1 is a conceptual diagram of a titration curve obtained by potentiometric titration of an acrylic copolymer latex using an alkaline solution.

Fig. 2 is a conceptual diagram of a differential curve converted from a titration curve obtained by potentiometric titration of an acrylic copolymer latex using an alkaline solution.

Fig. 3 is a conceptual diagram of a titration curve obtained by potentiometric titration of an acrylic copolymer latex using an acidic solution.

Fig. 4 is a conceptual diagram of a differential curve converted from a titration curve obtained by potentiometric titration of an acrylic copolymer latex using an acidic solution.

Fig. 5 is a schematic view showing a water resistance evaluation method in the examples of the present invention.

Claims (11)

A water-dispersible acrylic adhesive composition in which an acrylic copolymer latex particle is dispersed in an aqueous medium, characterized in that an acrylic copolymer forming the acrylic copolymer latex particle contains 2-acrylic acid Ethylhexyl ester, (meth) acrylate having an alkyl group having 4 to 8 carbon atoms, (meth) acrylate having an alkyl group having 2 or less carbon atoms, acrylic acid, methacrylic acid, and decylamino group a nitrogen-containing vinyl monomer as a monomer component, and 2-ethylhexyl acrylate and a (meth) acrylate having an alkyl group having 4 to 8 carbon atoms in the monomer component of the acrylic copolymer are formed. The content of the (meth) acrylate having an alkyl group having a carbon number of 2 or less is 1 to 10% by mass, and the total content of methacrylic acid and acrylic acid is 0.5 to 10% by mass, The content of the nitrogen-containing vinyl monomer having a guanamine group is 0.1 to 4.5% by mass. The water-dispersed acrylic pressure-sensitive adhesive composition according to claim 1, wherein a content ratio of acrylic acid to methacrylic acid in the monomer component of the acrylic copolymer is represented by (methacrylic acid/acrylic acid). The molar equivalent ratio is 1.3 or more. The water-dispersed acrylic pressure-sensitive adhesive composition according to claim 1, wherein a content ratio of acrylic acid to methacrylic acid in the monomer component of the acrylic copolymer is represented by (methacrylic acid/acrylic acid). The molar equivalent ratio is 2 or more. The water-dispersible acrylic pressure-sensitive adhesive composition according to claim 1, wherein the (meth) acrylate having an alkyl group having 4 to 8 carbon atoms is selected from n-butyl (meth)acrylate, Isobutyl methacrylate, (meth) propyl At least one of octa butterenoic acid, isooctyl (meth)acrylate, and n-octyl (meth)acrylate. The water-dispersible acrylic pressure-sensitive adhesive composition according to claim 1, wherein the crosslinking agent is further contained. The water-dispersible acrylic pressure-sensitive adhesive composition according to claim 1, wherein the acrylic copolymer latex particles have a particle diameter of 200 to 1000 nm. The water-dispersible acrylic pressure-sensitive adhesive composition according to claim 1, wherein 2-ethylhexyl acrylate and an alkyl group having 4 to 8 carbon atoms are formed in a monomer component of the acrylic copolymer. The content ratio of (meth) acrylate is represented by (2-ethylhexyl acrylate / (meth) acrylate having a carbon number of 4 to 8), and the mass ratio is 9/1 to 2/8. . The water-dispersible acrylic pressure-sensitive adhesive composition according to claim 1, wherein the acrylic copolymer latex particles have an acid group amount (AN _SUR ) on the surface of the acrylic copolymer latex particles as determined by potentiometric titration. The ratio (AN _IN )/(AN _SUR ) of the acid group amount (AN _IN ) inside the acrylic copolymer latex particles is 1 or more. The water-dispersible acrylic pressure-sensitive adhesive composition according to any one of claims 1 to 8, wherein the nitrogen-containing ethylene is a single system N-vinylpyrrolidone. An adhesive tape comprising an adhesive layer comprising the water-dispersible acrylic adhesive composition according to any one of claims 1 to 9. For example, in the adhesive tape of claim 10, in the environment of 23 ° C and relative humidity of 50% RH, a 2 kg roll is used for the stainless steel plate, and the pressure is crimped once and back, and left to stand for 1 hour. The 180° peel adhesion (F _A1 ) of the peeling speed of 1000 mm/min is 12 to 19 N/20 mm.