JP2002363521A - Water-dispersed pressure-sensitive adhesive composition and pressure-sensitive adhesive tape - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water-dispersible pressure-sensitive adhesive composition having a proper initial adhesiveness and a proper peeling force after bonding an adherend, and a pressure-sensitive adhesive tape using the water-dispersible pressure-sensitive adhesive composition. To provide. SOLUTION: This is a water-dispersed pressure-sensitive adhesive composition containing a crosslinked acrylic polymer (A) obtained by emulsion polymerization and a crosslinking agent (B), wherein the crosslinked acrylic polymer (A) is used. 50% by weight or more of an alkyl acrylate (a) having 4 to 12 carbon atoms in an alkyl group, 30 to 45% by weight of an alkyl methacrylate (b) having 1 to 4 carbon atoms in an alkyl group, and a crosslinking agent (B A) a functional monomer which does not participate in crosslinking with (c). Water-dispersible type obtained by emulsion polymerization of a monomer compound containing 5 to 2.5% by weight and a functional monomer (d) involved in crosslinking with a crosslinking agent (B). Adhesive composition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a water-dispersed PSA composition and a PSA tape. The water-dispersed pressure-sensitive adhesive composition of the present invention is suitable as a removable pressure-sensitive adhesive or the like, and is widely used, for example, for a surface protection film, a coating masking tape, and the like.

[0002]

2. Description of the Related Art Conventionally, in order to prevent scratches, contamination and corrosion during transportation, storage and processing of metal products and plastic products, the surface is temporarily protected, and after the above-mentioned object is achieved, the surface is easily protected. In addition, a surface protective film that can be peeled off integrally is used. Therefore, the surface protective film is required to have an initial adhesive force that does not peel off at the time of sticking, while requiring an appropriate peeling force (adhesive force) that can be easily peeled at the time of peeling. The peeling speed in a normal peeling operation is about 10 to 50 m / min, and it is preferable that the peeling force be good in this speed range.

Acrylic pressure-sensitive adhesives are widely used in place of conventional rubber-based pressure-sensitive adhesives because of their excellent adhesive properties and weather resistance. In addition, from the viewpoints of environmental measures, resource saving, safety, and the like, the development of water-dispersed acrylic pressure-sensitive adhesives that do not use an organic solvent has been progressing, and their use has been increasing. In some cases, this water-dispersed acrylic pressure-sensitive adhesive is applied to a surface protective film. However, conventionally, water-dispersed acrylic pressure-sensitive adhesives for surface protective films tend to cause an increase in adhesive strength due to changes over time after being adhered to an adherend, which requires time for peeling work, and also causes adhesive residue. May occur. Also,
The water-dispersed acrylic pressure-sensitive adhesive used for the surface protective film has a smooth surface, for example, Ra = 0. The peeling force at the time of high-speed peeling for an adherend of 1 μm or less is high, and improvement thereof has been desired. As a method of improving these, for example, there is a method of adding a peeling rib to the adhesive, but this peeling aid sometimes causes adherend contamination after the surface protective film is peeled off.

[0004]

SUMMARY OF THE INVENTION In the present invention, a water-dispersible PSA composition having a proper initial adhesiveness and a proper peeling force after laminating an adherend is used. The purpose of the present invention is to provide an adhesive tape.

[0005]

Means for Solving the Problems The present inventors have conducted intensive studies in order to solve the above-mentioned problems, and as a result, have found that the above-mentioned object can be achieved by the following water-dispersed pressure-sensitive adhesive composition, and completed the present invention. I came to.

That is, the present invention relates to a water-dispersed PSA composition comprising a crosslinked acrylic polymer (A) and a crosslinking agent (B) obtained by emulsion polymerization, wherein the crosslinked acrylic polymer is provided. (A) is an acrylic acid alkyl ester having 4 to 12 carbon atoms in the alkyl group (a) 50% by weight
As described above, 30 to 45% by weight of an alkyl methacrylate (b) having 1 to 4 carbon atoms in the alkyl group, and a crosslinking agent (B)
Functional monomer (c) which does not participate in crosslinking with Five ~
A water-dispersible pressure-sensitive adhesive obtained by emulsion polymerization of a monomer compound containing 2.5% by weight and a functional monomer (d) involved in crosslinking with a crosslinking agent (B). A composition.

The water-dispersed pressure-sensitive adhesive composition of the present invention provides a suitable initial adhesive property by using a monomer compound containing a specific monomer in a specific ratio as a monomer compound constituting the crosslinked acrylic polymer. And an appropriate peeling force after bonding the adherend.

The alkyl acrylate (a) having an alkyl group having 4 to 12 carbon atoms is a main component of the monomer mixture, and is used in an amount of 50% by weight or more in the monomer mixture. The alkyl acrylate (a)
If the ratio is too small, it is not possible to obtain good initial adhesive strength and peeling strength required when the adhesive tape is used. The acrylic acid alkyl ester (a) is contained in the monomer mixture at 53%.
Preferably it is ~ 65% by weight.

The alkyl methacrylate (b) having an alkyl group having 1 to 4 carbon atoms is used to control the increase in the daily peeling force after the adherend is adhered, and is used in the monomer compound in an amount of 30 to 45. Used in weight percent. If the proportion of the methacrylic acid alkyl ester (b) is small, the daily peeling force after bonding the adherend increases, so that the proportion of the methacrylic acid alkyl ester (b) is 30% by weight or more, further 35% by weight. % Is preferable. On the other hand, when the ratio of the methacrylic acid alkyl ester (b) is large, the adhesive strength at the initial stage of bonding is insufficient, and the pressure-sensitive adhesive tape floats from the adherend over the bonding days. The proportion is not more than 45% by weight,
It is preferably at most 3% by weight.

The functional monomer (c) which does not participate in the crosslinking with the crosslinking agent (B) is used to secure the adhesiveness at the initial stage of bonding, and is used at 0.5 to 2.5% by weight in the monomer compound. Can be If the ratio of the functional monomer (c) is small, the adhesiveness at the initial stage of bonding is insufficient, so that the ratio of the functional monomer (c) is 0.5% by weight or more, and more preferably 1%.
It is preferred that the content be not less than% by weight. On the other hand, if the ratio of the functional monomer (c) is large, the daily peeling force after bonding the adherend increases, so that the ratio of the functional monomer (c) is 2.5% by weight or less, Preferably it is less than or equal to% by weight.

The functional monomer (d) involved in the crosslinking with the crosslinking agent (B) is obtained by crosslinking the crosslinked acrylic polymer (A) with the crosslinking agent (B), and It controls the rise of the peeling force. The ratio of the functional monomer (d) is not particularly limited as long as the water-dispersed pressure-sensitive adhesive composition is in a range that does not increase the daily peeling strength and is a sufficiently crosslinked product. The proportion of (d) is preferably 0.5% by weight or more, more preferably 1% by weight or more. On the other hand, when the proportion of the functional monomer (d) is large, the number of residual functional groups increases when the reaction with the crosslinking agent (B) is insufficient, and the daily peeling force increases. If the ratio of the crosslinking between the crosslinking agent (B) and the functional group in the crosslinking fraction increases as compared with the crosslinking at the polymerization stage, the reason is not clear, but the initial adhesion deficiency or the adhesion due to the difference in the crosslinking form between the two. In some cases, the tape may float on the combined date, so the ratio of the functional monomer (d) is 2.5%.
It is preferably at most 2% by weight, more preferably at most 2% by weight.

[0012] In the water-dispersed PSA composition, it is preferable that the monomer composition is adjusted so that the glass transition temperature of the obtained acrylic polymer crosslinked product (A) is -20 to -35 ° C.

Glass of crosslinked acrylic polymer (A)
Monomer blending so that the transition temperature (Tg) falls within the above range
Those prepared are preferred because they have good tackiness. Said
The glass transition temperature is more preferably from -23 to -32 ° C.
New The glass transition temperature (Tg) is generally
The following equation used: 1 / Tg = (W₁ / Tg₁ ) + (W_Two / Tg_Two ) + ----
(W_n / Tg_n ) ｛Tg: Tg of copolymer (° K), W_n : W₁ , W_Two -
--W_n Weight fraction, Tg _n : Weight polymerized from each monomer
Calculated from the monomer formulation by the Tg of the coalescence (° K)｝
And the monomer mixture is the monomer (a) to
When any monomer other than (d) is included,
Glass transition temperature calculated from monomer blends containing nomers
Is done. Optional monomers can be copolymerized as needed.
Of each monomer in a range of less than 10% by weight of the total monomers.
The amount used can be appropriately selected according to the type of the monomer.

In the water-dispersed pressure-sensitive adhesive composition, the crosslinked fraction of the crosslinked acrylic polymer (A) is 85% by weight or more, and the crosslinked acrylic polymer (A) is crosslinked with the crosslinker (B). After that, it is preferable that the crosslinking fraction be 95% by weight or more.

When the crosslinked fraction of the crosslinked acrylic polymer (A) is low, the uncrosslinked portion is large, and the crosslinked fraction is not sufficiently increased even after the addition of the crosslinking agent (B).
Undesirably, the peeling force increases with time. The crosslinked fraction of the crosslinked acrylic polymer (A) is 85% by weight or more,
More preferably, it is 87% by weight. If the cross-linking fraction of the crosslinked acrylic polymer (A) is too high, the final cross-linking fraction after the addition of the cross-linking agent (B) is too high, resulting in insufficient initial adhesiveness or the pasting time. In some cases, the tape may float, and in order to prevent such a phenomenon, the crosslinked fraction of the crosslinked acrylic polymer (A) is preferably 95% by weight or less. After the crosslinked acrylic polymer (A) is crosslinked with the crosslinking agent (B), the crosslinkage fraction is preferably 95% by weight or more, more preferably 97% by weight or more. If the cross-linking fraction is 95% by weight or more, the increase in the peeling force can be suppressed over time after the lamination to the adherend.

The above-mentioned cross-linking fraction means the ratio of the cross-linking pressure-sensitive adhesive in the pressure-sensitive adhesive solids. For example, the dried adhesive solid content is wrapped with a Teflon (registered trademark) membrane having a diameter of 0.2 μm, a dissolved component is extracted in ethyl acetate at room temperature for one week, and the crosslinked adhesive remaining in the Teflon membrane is taken out. It can be calculated by an equation. Crosslinking fraction (% by weight) = (crosslinked adhesive (g) / total adhesive (g)) × 100.

Furthermore, the present invention relates to a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer formed on a substrate by a crosslinked product of the water-dispersed pressure-sensitive adhesive composition.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a water-dispersed pressure-sensitive adhesive composition and a pressure-sensitive adhesive tape containing a crosslinked acrylic polymer (A) and a crosslinker (B) of the present invention will be described in detail.

The alkyl group, which is the main monomer used in the preparation of the crosslinked acrylic polymer (A), has 4 to 1 carbon atoms.
Specific examples of the alkyl acrylate (a) 2 include butyl acrylate, isobutyl acrylate, pentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, and isooctyl acrylate. , Isononyl acrylate, decyl acrylate, lauryl acrylate, and the like. One or more of these alkyl acrylates (a) are appropriately selected and used.

Specific examples of the alkyl methacrylate (b) having an alkyl group having 1 to 4 carbon atoms include:
For example, methyl methacrylate, ethyl methacrylate,
Examples thereof include propyl methacrylate, isopropyl methacrylate, butyl methacrylate, and isobutyl methacrylate. These methacrylic acid alkyl esters (b)
One or two or more of them are appropriately selected and used.

The functional monomer (c) which does not participate in the crosslinking with the crosslinking agent (B) and the functional monomer (d) which participates in the crosslinking with the crosslinking agent (B) are added to the functional group of the crosslinking agent (B). It is appropriately selected according to the situation. Examples of the functional group of the functional monomer include a carboxyl group, an acid anhydride group, a hydroxyl group, an amino group, an epoxy group, an isocyanate group, and an aziridine group. Specific examples of the functional monomer (c) or (d) include carboxyl group-containing monomers such as (meth) acrylic acid, itaconic acid, crotonic acid, maleic acid, and fumaric acid; and acid anhydrides such as maleic anhydride. Hydroxyl-containing monomers such as hydroxyalkyl (meth) acrylate and glycerin di (meth) acrylate; epoxy-containing monomers such as glycidyl (meth) acrylate and methyl glycidyl methacrylate; aminoethyl (meth) acrylate And an isocyanate group-containing monomer such as 2 methacryloyloxyethyl isocyanate. The (meth) acrylic acid is acrylic acid and / or methacrylic acid, and (meth) has the same meaning in the present invention.

From these, it is possible to appropriately select and use them in consideration of the reactivity with the functional group of the crosslinking agent (B). For example,
Examples of combinations of functional groups having reactivity include a carboxyl group and an epoxy group, a carboxyl group and an aziridine group, a hydroxyl group and an isocyanate group, and a carboxyl group and an oxazoline group.

The crosslinked acrylic polymer of the present invention (A)
In the monomer mixture used for the preparation of the above, other copolymerizable monomers may be used in addition to the above monomers, if necessary. The other copolymerizable monomer is one of all monomers.
It is used in a range of less than 0% by weight. Other copolymerizable monomers include, for example, alkyl acrylates having 1 to 3 carbon atoms in the alkyl group such as methyl acrylate, ethyl acrylate and isopropyl acrylate; alkyls such as tridecyl acrylate and stearyl acrylate Alkyl acrylates having 13 to 18 carbon atoms; alkyl methacrylates having 5 to 18 carbon atoms in alkyl groups such as isooctyl methacrylate, ethylhexyl methacrylate, tridecyl methacrylate, and stearyl methacrylate; vinyl acetate, styrene , (Meta)
Acrylonitrile, n-vinylpyrrolidone, (meth) acryloylmorpholine, cyclohexylmaleimide, inpropylmaleimide, (meth) acrylamide and the like can be mentioned. Other examples include polyfunctional monomers such as triethylene glycol diacrylate, ethylene glycol dimethacrylate, and trimethylolpropane tri (meth) acrylate.

The preparation of the crosslinked acrylic polymer (A) is carried out by emulsion polymerization of the monomer mixture in the presence of an emulsifier. The polymerization method is generally a batch charging method,
A monomer dropping method, a monomer emulsion dropping method and the like can be mentioned. Among these methods, a high molecular weight acrylic polymer crosslinked product (A) suitable for re-peeling can be prepared.
For example, it is preferable to use a batch charging method or the like.

In general, as a method for preparing an acrylic pressure-sensitive adhesive, there is a method of polymerizing with a solvent system to obtain an acrylic polymer having a low cross-linking fraction, and then increasing the cross-linking fraction with a cross-linking agent. Is difficult to balance the amount of the functional monomer in the acrylic polymer and the cross-linking fraction, it is difficult to achieve both the initial adhesiveness and the proper peeling force after lamination storage, and the adhesion after peeling due to the generation of low molecular weight It is not preferable because it easily pollutes the body. There is also a method of preparing a high-molecular-weight acrylic polymer by a UV polymerization method or the like to obtain an adhesive,
This method is not preferable because the production cost increases. Emulsion polymerization is suitable as a method for synthesizing a crosslinked acrylic polymer as a removable pressure-sensitive adhesive because a high-molecular-weight pressure-sensitive adhesive can be easily obtained at a relatively low cost.

As the emulsifier, an anionic emulsifier or a nonionic emulsifier used in emulsion polymerization can be used without any particular limitation. For example, anionic emulsifiers such as sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzenesulfonate, sodium polyoxyethylene alkyl ether sulfate, sodium polyoxyethylene alkyl phenyl ether sulfate, polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether And nonionic emulsifiers. In addition, in any case of anionic emulsifier and nonionic emulsifier, to reduce adherend contamination,
It is preferable to use a radical polymerizable reactive emulsifier in which a reactive functional group such as a propenyl group, an allyl group, or a (meth) acryloyl group is introduced into the emulsifier. Radical polymerizable reactive emulsifiers are described, for example, in JP-A-4-53802.

As the polymerization initiator, for example, 2,
Azo-based compounds such as 2'-azobis (2-amidinopropane) dihydrochloride and 2,2'-azobis (N, N'-dimethyleneisobutylamidine), and persulfates such as potassium persulfate and ammonium persulfate are used. .

The water-dispersed PSA composition of the present invention is obtained by blending the crosslinked acrylic polymer (A) and the crosslinking agent (B).

Examples of the crosslinking agent (B) include, as water-soluble crosslinking agents, epoxy crosslinking agents such as polyethylene glycol diglycidyl ether, water-dispersed isocyanate crosslinking agents, oxazoline crosslinking agents, aziridine crosslinking agents, and hydrophilic compounds. Carbodiimide-based crosslinking agents, active methylol crosslinking agents, active alkoxymethyl crosslinking agents, metal chelates and the like. Further, as the oil-soluble crosslinking agent, N,
Epoxy crosslinking agents such as N, N, N-tetraglycidyl m-xylene diamine, isocyanate crosslinking agents such as hexamethylene diisocyanate, and oil-soluble carbodiimide crosslinking agents.

The selection of the crosslinking agent (B) is such that the functional group of the crosslinking agent (B) is reactive with the functional group of the functional monomer (d) used in the preparation of the crosslinked product (A) by the acrylic polymer. Then, those having no reactivity with the functional group of the functional monomer (c) are selected and used. For example, when a hydroxyl group-containing monomer such as 2-hydroxyethyl acrylate is used as the functional monomer (c) for securing initial adhesiveness, and a carboxyl group-containing monomer such as acrylic acid is used as the functional monomer (d) The epoxy-based crosslinking agent is suitably used as the crosslinking agent (B).

The amount of the cross-linking agent (B) is not particularly limited, but after the cross-linked acrylic polymer (A) is cross-linked with the cross-linking agent (B), the cross-linking ratio is 95% by weight or more. Is preferred. Usually, the number of functional groups (equivalents) of the crosslinking agent (B) is 1 to 1 to the number of functional groups (equivalents) of the functional monomer (d) blended in the crosslinked acrylic polymer (A) as a crosslinking component. It is preferable to mix them so as to be about 5 times. If the number of functional groups (equivalents) of the crosslinking agent (B) is smaller than one, the crosslinking reaction tends to be insufficient, and the peeling force tends to increase. If it is more than 5 times, it causes contamination by the remaining unreacted cross-linking agent, and both are not preferable.

The water-dispersed pressure-sensitive adhesive composition of the present invention may further contain various additives such as a tackifier, if necessary.
Plasticizers, softeners, fillers, pigments, dyes, antioxidants and the like can be added.

The pressure-sensitive adhesive tape of the present invention is obtained by forming a pressure-sensitive adhesive layer on one surface of a substrate by using a crosslinked product of the water-dispersed pressure-sensitive adhesive composition. The substrate is not particularly limited, for example, a polyester film, a plastic film such as polypropylene, paper, a nonwoven fabric, a foam, a simple substance such as a metal foil or a composite substrate thereof can be used, and the substrate is subjected to a surface treatment. Anything can be used. The substrate is usually about 9 to 120 μm.

The pressure-sensitive adhesive layer can be formed by directly applying the water-dispersed pressure-sensitive adhesive composition on a substrate and drying the same. It may be transferred on top. The adhesive tape of the present invention,
One or more pressure-sensitive adhesive layers may be provided on one or both sides of the base material to obtain a sheet or tape form. The pressure-sensitive adhesive layer usually has a thickness of about 1 to 50 μm.

[0035]

According to the water-dispersed pressure-sensitive adhesive composition of the present invention, it is possible to provide a pressure-sensitive adhesive tape having an excellent initial adhesiveness and excellent stability over time. It can be easily peeled off even after long-term storage. Further, the water-dispersed pressure-sensitive adhesive composition of the present invention does not particularly require a release aid, and is excellent in non-staining property to an adherend at the time of re-peeling.

[0036]

EXAMPLES Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples. In each example, “parts” means “parts by weight”.

Example 1 (Preparation of crosslinked acrylic polymer) Thermometer, stirrer,
In a reactor equipped with a nitrogen inlet tube and a reflux condenser, 60 parts of 2-ethylhexyl acrylate and 38 parts of methyl methacrylate were added.
Parts, 1 part of acrylic acid, 2 hydroxyethyl acrylate 1
Parts and an anionic reactive emulsifier (Aqualon BC-2
020, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) and emulsified with 144 parts of water, and the mixture was purged with nitrogen for 2 hours. Then
After the temperature was raised to 55 ° C., 0.03 parts of 2,2′-azobis (2-amidinopropane) hydrochloride was added and polymerization was carried out for 8 hours. Thereafter, the mixture was cooled to room temperature and neutralized with 10% aqueous ammonia to prepare a crosslinked acrylic polymer. The crosslinked product of this acrylic polymer had a Tg of -25 ° C and a crosslinked fraction of 899%.

(Preparation of water-dispersed pressure-sensitive adhesive composition and preparation of pressure-sensitive adhesive tape) Crosslinked acrylic polymer (solid content) 1
In 00 parts, a water-soluble epoxy crosslinking agent (Denacol EX-
614B, manufactured by Nagase Kasei Kogyo Co., Ltd.) in an amount of 2.4 parts so that the equivalent of the epoxy group is equivalent to the carboxyl group of acrylic acid in the crosslinked acrylic polymer, to give a water-dispersed PSA composition. Prepared. This water-dispersed pressure-sensitive adhesive composition was applied to a 12-μm polyethylene terephthalate substrate so as to have a thickness of 5 μm after drying, and dried to prepare a pressure-sensitive adhesive tape. The crosslinking fraction after the addition of the crosslinking agent was 96%.

Example 2 A crosslinked acrylic polymer was prepared in the same manner as in Example 1 except that the amount of 2-ethylhexyl acrylate was changed to 55 parts, and 38 parts of methyl methacrylate was changed to 43 parts of isobutyl methacrylate. Was prepared. The Tg of the crosslinked acrylic polymer was −30 ° C., and the crosslink fraction was 86%. Next, in the same manner as in Example 1, preparation of a water-dispersed PSA composition and preparation of a PSA tape were performed. The crosslinking fraction after the addition of the crosslinking agent was 97%.

Comparative Example 1 A crosslinked acrylic polymer was prepared in the same manner as in Example 1 except that the amount of 2-ethylhexyl acrylate was changed to 40 parts, and 38 parts of methyl methacrylate was changed to 58 parts of methyl acrylate. Was prepared. The Tg of the crosslinked acrylic polymer was -29 ° C, and the crosslinking fraction was 93%.
Next, in the same manner as in Example 1, preparation of a water-dispersed PSA composition and preparation of a PSA tape were performed. The crosslinking fraction after the addition of the crosslinking agent was 96%.

Comparative Example 2 A crosslinked acrylic polymer was prepared in the same manner as in Example 1 except that the amount of 2-ethylhexyl acrylate was changed to 70 parts and the amount of methyl methacrylate was changed to 28 parts. did. The Tg of the crosslinked acrylic polymer was −38 ° C., and the crosslink fraction was 87%. Next, in the same manner as in Example 1, preparation of a water-dispersed PSA composition and preparation of a PSA tape were performed. Crosslinking fraction after addition of crosslinking agent is 95%
Met.

Comparative Example 3 The procedure of Example 1 was repeated except that the amount of 2-ethylhexyl acrylate was 53 parts, the amount of methyl methacrylate was 43 parts, and the amount of 2-hydroxyethyl acrylate was 3 parts. In the same manner as in Example 1, a crosslinked acrylic polymer was prepared. Tg of the crosslinked acrylic polymer is -16
° C, the cross-linking fraction was 93%. Next, in the same manner as in Example 1, preparation of a water-dispersed PSA composition and preparation of a PSA tape were performed. The crosslinking fraction after the addition of the crosslinking agent was 96%.

Comparative Example 4 The procedure of Example 1 was repeated except that the amount of 2-ethylhexyl acrylate was changed to 60 parts, the amount of methyl methacrylate was changed to 36 parts, and the amount of 2-hydroxyethyl acrylate was changed to 3 parts. In the same manner as in Example 1, a crosslinked acrylic polymer was prepared. The Tg of the crosslinked acrylic polymer is -26.
° C, the cross-linking fraction was 92%. Next, in the same manner as in Example 1, preparation of a water-dispersed PSA composition and preparation of a PSA tape were performed. The crosslinking fraction after the addition of the crosslinking agent was 95%.

The following evaluations were made on the pressure-sensitive adhesive tapes obtained in Examples and Comparative Examples. Table 1 shows the results.

(Initial Adhesive Force) A pressure-sensitive adhesive tape of 20 mm × 100 mm was pressure-bonded to the adherend by a method of reciprocating once with a 2 kg roller, the force required for the peeling was measured, and the initial adhesiveness was evaluated (180 ° peeling, Tensile speed 30m / min,
23 ° C, 65% RH). Substrate: Stainless steel plate (SU
S430BA). Standing condition: 23 ° C. × 20 minutes.

(Peel Force Over Time) A sample pressed to an adherend by the same method as above was heated at 60 ° C. for 7 days, and then allowed to cool to room temperature. It was evaluated.

[0047]

[Table 1] As is clear from the results in Table 1, Examples 1 and 2 of the present invention
It can be seen that each of the pressure-sensitive adhesive tapes has an initial adhesiveness and an appropriate peeling force over time as compared with the pressure-sensitive adhesive tapes of Comparative Examples 1 to 4. In Table 1, 2EHA: 2-ethylhexyl acrylate, MMA: methyl methacrylate, iB
MA: isobutyl methacrylate, MA: methyl acrylate, AA: 1 part of acrylic acid, HEA: 2 hydroxyethyl acrylate.

Continuation of the front page F term (reference) 4J004 AA10 AA17 AB01 CA02 CA06 CA08 CB01 CB02 CB04 CC02 EA05 FA08 4J040 DF041 JA03 KA16 LA02 LA06 MA02 MA10 PA23 QA01 QA02

Claims (4)

[Claims] 1. A water-dispersed pressure-sensitive adhesive composition comprising a crosslinked acrylic polymer (A) obtained by emulsion polymerization and a crosslinking agent (B), wherein the crosslinked acrylic polymer (A) Is 50% by weight or more of an alkyl acrylate (a) having 4 to 12 carbon atoms in an alkyl group, 30 to 45% by weight of an alkyl methacrylate (b) having 1 to 4 carbon atoms in an alkyl group, and a crosslinking agent ( Functional monomer (c) which does not participate in crosslinking with B) Water-dispersible type obtained by emulsion polymerization of a monomer compound containing 5 to 2.5% by weight and a functional monomer (d) involved in crosslinking with a crosslinking agent (B). Adhesive composition. 2. The aqueous dispersion according to claim 1, wherein the monomer mixture is adjusted so that the glass transition temperature of the obtained crosslinked acrylic polymer (A) is −20 to −35 ° C. Type pressure-sensitive adhesive composition. 3. The crosslinked fraction of the crosslinked acrylic polymer (A) is at least 85% by weight, and after the crosslinked acrylic polymer (A) is crosslinked with the crosslinker (B), the crosslinked fraction is 95%. The water-dispersed pressure-sensitive adhesive composition according to claim 1 or 2, wherein the amount of the water-dispersed pressure-sensitive adhesive composition is equal to or more than 10% by weight. 4. A pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer formed on a substrate by a crosslinked product of the water-dispersed pressure-sensitive adhesive composition according to claim 1.