JP6537171B2 - Polymer emulsion, aqueous pressure-sensitive adhesive composition and pressure-sensitive adhesive sheet - Google Patents

Description

  The present invention relates to a heterogeneous polymer emulsion suitable as an aqueous pressure-sensitive adhesive, an aqueous pressure-sensitive adhesive composition using the same, and a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer formed by the aqueous pressure-sensitive adhesive composition.

  Conventionally, pressure-sensitive adhesives which are excellent in adhesion to adherends and adhesiveness are developed, among which, it is possible to perform initial reattachment, and in the end, it is possible to obtain strong adhesiveness. There is a growing demand for better adhesives. For example, a pressure-sensitive adhesive sheet (see Patent Document 1) obtained by applying a solvent-based acrylic resin pressure-sensitive adhesive having a long chain alkyl group to an acrylic substrate obtained by special UV curing is a special substrate It is essential to use and not suitable for processing of general adhesive sheet. Moreover, this pressure-sensitive adhesive is solvent-based and has a high environmental impact.

  For example, Patent Document 2 discloses that a layer of an acrylic resin emulsion-type pressure-sensitive adhesive is formed on one side of a polypropylene-based synthetic paper. A pressure-sensitive adhesive sheet having a tackiness of 0.5 to 8 N / 25 mm after holding for 10 minutes and a tack strength of 6 N / 25 mm or more after leaving for 7 days after sticking is described. Since this adhesive sheet does not use a solvent, the load on the environment is reduced, and because the adhesive strength immediately after the application is suppressed, it is described that the adhesion operation can be performed again. There is. However, the pressure-sensitive adhesive sheet shown in the example of Patent Document 2 has an initial adhesive strength of 6.2 N / mm to 7.8 N / mm after 10 minutes from affixing, and after 24 hours has elapsed from affixing The adhesive strength (7.5 N / mm to 9.8 N / mm) is about the same level, and there is a problem that the adhesive strength is too large for re-sticking (see Examples 1 and 2).

  There is also known a pressure-sensitive adhesive sheet in which the initial adhesive strength is suppressed by printing a heat-sensitive adhesive in a water bead pattern on a substrate and coating an acrylic pressure-sensitive adhesive from above (see Patent Document 3) In addition to the complicated manufacturing method, there is a problem that it is necessary to perform heat pressing in order to obtain the target adhesive strength.

  On the other hand, various types of aqueous emulsion pressure-sensitive adhesives are conventionally known. For example, Patent Document 4 discloses that the glass transition temperature of the solvent-soluble component is -20 ° C or less, and the weight average molecular weight is 100,000 or more. A first step of obtaining a seed emulsion containing an acrylic polymer (A), and a composition having a glass transition temperature (Tg) of 40.degree. Water-based pressure-sensitive adhesive including a second step of obtaining an acrylic polymer (B) having a weight-average molecular weight of 300 to 50,000 of a solvent-soluble component by adding and polymerizing the monomer mixture of and the polymerization initiator Methods of making the agent composition are described. In this method, the initial adhesion is somewhat suppressed because the Tg of the polymer obtained in the second step is high, but there is a problem that the adhesion is too large for re-sticking.

  Patent Document 5 also describes (meth) acrylic copolymers (A) having a glass transition temperature (Tg) of −55 ° C. to 0 ° C., (meth) acrylic copolymers having a Tg of 0 ° C. to 180 ° C. (B) and a water-soluble resin (C), at least one of the (meth) acrylic copolymers (A) and (B) contains a carboxyl group-containing monomer as a monomer unit, Water dispersion type wherein the difference between Tg of (A) and (B) is 50 ° C. or more, and the mixing ratio is in the range of (A) / (B) = 50 to 95/5 to 50 (solids weight ratio) Adhesive compositions have been described. In Patent Document 5, this pressure-sensitive adhesive composition is excellent in initial adhesive strength and is useful as a pressure-sensitive adhesive for optical members, and the above (meth) acrylic copolymer (A) and (meth) The acrylic copolymer (B) may be an emulsion particle having a core-shell structure in which either one exists as a core layer and the other as a shell layer, and in particular, the (meth) acrylic copolymer (B) has a core layer It is described that the emulsion particle which is is preferable (refer Claim 4 and 5). However, this adhesive is developed for the purpose of enhancing the initial adhesion, so once it is attached, it is disliked because the adhesion is too large for peeling off and reattaching. There is a problem that the adhesive remains on the adherend, which causes non-uniformity of the adhesive layer after reattachment, resulting in a decrease in adhesive performance.

  Furthermore, as polymer particles, it is composed of a segment of a soft polymer having a low Tg and a segment of a hard polymer having a Tg higher than that of the soft polymer, and the hard polymer is produced by a power feed method. Emulsion particles of heterogeneous polymers are also known. For example, Patent Document 6 discloses an ethylenic unsaturated compound (A) in which the Tg of the polymer is -30 ° C or lower, and an ethylenic unsaturated compound (B) in which the Tg of the polymer is 30 ° C or higher. A process is described for power-feed polymerizing in-situ to produce a heterogeneous polymer with a Tg of -35 ° C to -15 ° C. Specifically, the total amount of the ethylenically unsaturated compound (A) is divided into the (A1) component and the (A2) component, and after the (A1) component is polymerized, the (A2) component and the ethylenically unsaturated compound (B) (B) / (A2) (mass ratio) is a method in which polymerization is carried out while continuously introduced so that the mass ratio of each of the polymerizable components is (A1) + (A2) +. When (B) = 100, control is performed such that 20 ≦ (A1) ≦ 60, 10 ≦ (A2) ≦ 40, and 10 ≦ (B) ≦ 40. In this heterogeneous polymer, the proportion of the ethylenically unsaturated compound (B) contained in the polymerizable component supplied in the subsequent polymerization step increases with the passage of time, so the Tg of the hard polymer is the inner side of the particles. It is thought that it is getting higher gradually from the outside. Therefore, when the emulsion containing the heterogeneous polymer particles is used as a binder for a coating material or a water-based paint, it has an advantage that the surface tack of the formed film can be suppressed. However, this patent document 6 does not describe anything about using the obtained aqueous emulsion as an adhesive.

  As described above, the adhesion to the substrate and the adhesion are excellent, and by intentionally reducing the initial tackiness, the re-sticking operation can be performed without the need for a complicated adhesion processing method. Aqueous adhesives have not been known so far.

JP 07-316515 A JP, 2006-104269, A JP 2000-234081 A JP 2003-105298 A JP 2012-126789 A JP 2000-319301 A

  The present invention has been completed under such background art, and the object thereof is an aqueous pressure-sensitive adhesive composition which is excellent in adhesiveness and which is suitable for producing a re-stickable adhesive sheet, and the aqueous pressure-sensitive adhesive composition. It is providing the adhesive sheet provided with the adhesive layer formed with objects. Another object of the present invention is to provide an aqueous emulsion suitable as a binder component of the aqueous pressure-sensitive adhesive composition and a method for efficiently producing the emulsion.

  The present inventors modify only the particle surface of the low Tg polymer which can obtain sufficient adhesive strength and its vicinity as a means of suppressing the initial adhesive strength to a composition of high Tg where the adhesive strength is small. The pressure-sensitive adhesive composition is prepared using, as a binder component, an emulsion of a heterogeneous polymer composed of a segment of a soft polymer and a segment of a hard polymer described in Patent Document 6, which is considered to be effective. The performance was evaluated. However, the pressure-sensitive adhesive sheet obtained by using this pressure-sensitive adhesive composition has problems that not only the initial tackiness is small but also that sufficient tackiness can not be obtained even if time passes, and it is not always satisfactory. It has been found. Therefore, as a result of further investigations based on this finding, the present inventors further reduced the ratio of the hard polymer segment and, by making the soft polymer segment Tg lower than -35 ° C, the adhesion. It has been found that the present invention makes it possible to produce a pressure-sensitive adhesive sheet having an initial adhesive strength which is sufficient to temporarily fix in the initial stage of sticking and which can be easily attached again. It came to complete.

The present invention provides the following [1] to [16].
[1] The step (I) of emulsion polymerization of the first polymerizable component to produce a soft polymer and the second polymerizable component continuously or intermittently supplied to the polymerization system of the step (I) An aqueous emulsion of a heterogeneous polymer comprising a segment of a soft polymer and a segment of a hard polymer obtained by the production method including the step (II) of performing polymerization and satisfying the following conditions.
(1) The first polymerizable component is composed of a monomer component (A1) giving a Tg lower than -35 ° C., and the amount thereof is 65 to 90% by mass of the total monomer amount.
(2) The second polymerizable component is composed of a monomer component (A2) giving a Tg lower than -35 ° C and a monomer component (B) giving a Tg higher than -20 ° C, and Each of the monomer component (A2) and the monomer component (B) should be 5 to 20% by mass of the total amount of monomers.
(3) The monomer component (B) / monomer component (A2) (mass ratio) in the second polymerizable component is gradually added from the supply start time point of the second polymerizable component to the supply stop time point Make it bigger.
[2] The aqueous emulsion according to the above [1], wherein the Tg of the heterogeneous polymer is −80 ° C. to −40 ° C.
[3] The aqueous emulsion according to the above [1] or [2], wherein the monomer components (A1) and (A2) give Tg of −40 ° C. or less when they are polymerized.
[4] The monomer component (A1) and the monomer component (A2) are mainly composed of an alkyl acrylate having an alkyl group having 2 to 10 carbon atoms, and the monomer component (B) is The aqueous emulsion as described in any one of said [1]-[3] which is a thing containing the methacrylate which has a C1-C8 alkyl group.
[5] Any one of the above [1] to [4], wherein the monomer component (A1), the monomer component (A2) and the monomer component (B) all contain an unsaturated carboxylic acid The aqueous emulsion as described in.
[6] The aqueous emulsion according to any one of the above [1] to [5], wherein the monomer component (A1) contains butyl acrylate and / or 2-ethylhexyl acrylate as a main component.
[7] In any one of the above [1] to [6], wherein the polymerization of the first polymerizable component in step (I) is carried out while continuously or intermittently supplying the polymerizable component. Aqueous emulsion as described.
[8] The aqueous emulsion according to any one of the above [1] to [7], which has a gel fraction of 90% or more.
[9] The aqueous emulsion according to any one of the above [1] to [8], wherein the first polymerizable component and / or the second polymerizable component comprises a chain transfer agent and / or a silane coupling agent. .
[10] The aqueous emulsion according to any one of the above [1] to [9], wherein the first polymerizable component and / or the second polymerizable component comprises a chain transfer agent and a silane coupling agent.

[11] The step (I) of emulsion polymerization of the first polymerizable component to produce a soft polymer and the second polymerizable component continuously or intermittently supplied to the polymerization system of the step (I) A method for producing an aqueous emulsion of a heterogeneous polymer comprising a segment of a soft polymer and a segment of a hard polymer, which comprises the step (II) of performing polymerization and satisfies the following conditions.
(1) The first polymerizable component is composed of a monomer component (A1) giving a Tg lower than -35 ° C., and the amount thereof is 65 to 90% by mass of the total monomer amount.
(2) The second polymerizable component is composed of a monomer component (A2) giving a Tg lower than -35 ° C and a monomer component (B) giving a Tg higher than -20 ° C, and Each of the monomer component (A2) and the monomer component (B) should be 5 to 20% by mass of the total amount of monomers.
(3) The monomer component (B) / monomer component (A2) (mass ratio) in the second polymerizable component is gradually added from the supply start time point of the second polymerizable component to the supply stop time point Make it bigger.
[12] An aqueous pressure-sensitive adhesive composition comprising the aqueous emulsion according to any one of the above [1] to [10].
[13] The aqueous pressure-sensitive adhesive composition according to the above [12], which is used as a pressure-sensitive adhesive for housing materials.
[14] A pressure-sensitive adhesive sheet provided with a pressure-sensitive adhesive layer formed using the aqueous pressure-sensitive adhesive composition according to the above [12] or [13] on a substrate.
[15] The adhesive layer has a 180 degree peel strength against a SUS # 304 plate measured at a temperature of 23 ° C, 50% RH, and a peel rate of 300 mm / min, and after 1 minute of attachment is 1 to 5 N / 25 mm. The adhesive sheet as described in said [14] which is 6 N / 25 mm or more after 24 hours.
[16] The adhesive sheet according to the above [15], wherein B / A is 2 or more, where 180 ° peel force after 1 minute of attachment is A and 180 ° peel force after 24 hours of attachment is B.

  According to the present invention, in the construction of wallpaper, floor material, etc., it has an initial adhesive strength that enables re-sticking to improve the quality of the construction, and has sufficient adhesive power after one hour. An aqueous pressure-sensitive adhesive composition is obtained. Further, by using the aqueous pressure-sensitive adhesive composition, it is possible to obtain a pressure-sensitive adhesive sheet which can be attached again and which can obtain sufficient adhesion only by standing at room temperature. Furthermore, according to the present invention, a heterogeneous polymer emulsion suitable for the preparation of the aqueous pressure-sensitive adhesive composition and a method for efficiently producing the heterogeneous polymer emulsion are provided.

In the present invention, the description of “A to B” representing a numerical range is a numerical range including an upper limit and a lower limit, and A or more and B or less (for A <B), or A or more and B or more (A> B) Case). Moreover, the description of "(meth) acrylate" is a general term for methacrylate and acrylate, and the same applies to (meth) acrylic and the like.
Heterogeneous polymer
In the present invention, the term "heterogeneous polymer" refers to the segment of the soft polymer (i.e., a polymer having a low Tg (glass transition temperature)) obtained in the step (I), and the segment obtained by the step (II) It means that it is composed of segments of a hard polymer (that is, a polymer having a higher Tg than a soft polymer), and the segments of the hard polymer have a composition distribution which constitutes the polymer of the polymerization time. It changes so that it becomes high Tg gradually with progress.

In the present invention, as a polymerizable component used for producing a heterogeneous polymer, an ethylenically unsaturated monomer is preferable, and as the ethylenically unsaturated monomer, for example, methyl (meth) acrylate, ethyl (meth ) Acrylate, n-butyl (meth) acrylate, iso-butyl (meth) acrylate, tert-butyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) ) (Meth) acrylates such as acrylates, isoboronyl (meth) acrylates;
Aromatic vinyl compounds such as styrene, α-methylstyrene, p-methylstyrene and ethylvinylbenzene;
Heterocyclic vinyl compounds such as vinyl pyrrolidone;
Hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate;
Polyalkylene glycol (meth) acrylates such as ethylene glycol (meth) acrylate, propylene glycol (meth) acrylate, butylene glycol (meth) acrylate;
Alkylamino (meth) acrylates such as N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate;

Vinyl ester compounds such as vinyl formate, vinyl acetate, vinyl propionate, vinyl versatate;
Monoolefin compounds such as ethylene, propylene, butylene and isobutylene;
Conjugated diolefin compounds such as butadiene, isoprene and chloroprene;
Amineimide group-containing vinyl compounds such as 1,1,1-trimethylamine methacrylamide;
Vinyl cyanide compounds such as acrylonitrile and methacrylonitrile;
An amide group or a substituted amido group-containing α, β-ethylenically unsaturated compound such as (meth) acrylamide, N-methylacrylamide, N, N-dimethyl (meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylamide;
Α, β-unsaturated mono- or di-carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, citraconic acid, itaconic acid, maleic acid, maleic anhydride, fumaric acid, 2-carboxyethyl acrylate oligomer, 2-acryloyloxyethyl succinic acid, etc. acid;

Carboxyl group-containing vinyl compounds such as monohydroxyethyl phthalate (meth) acrylate and monohydroxypropyl oxalate (meth) acrylate;
Sulfonic acid group-containing α, β-ethylenically unsaturated compounds such as allyl sulfonate, sodium p-styrene sulfonate;
Ethylenically unsaturated group-containing UV absorbers such as 2- (2'-hydroxy-5'-methacryloyloxyethylphenyl) -2H-benzotriazole; and 1,2,2,6,6-pentamethyl-4-piperidyl methacrylate And known polymerizable vinyl compounds such as ethylenically unsaturated group-containing light stabilizers.

In addition, if necessary, as a crosslinkable monomer, glycidyl (meth) acrylate, 3,4-epoxycyclohexylmethyl (meth) acrylate, glycidyl vinyl ether, glycidyl (meth) allyl ether, 3,4-epoxycyclohexyl (meth) acrylate Epoxy group-containing α, β-ethylenically unsaturated compounds such as
Hydrolyzable alkoxysilyl group-containing α, β-ethylenically unsaturated compounds such as vinyltriethoxysilane, vinyltris (β-methoxyethoxy) silane, γ-methacryloxypropyltrimethoxysilane;
Multifunctional vinyl compounds such as ethylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, allyl (meth) acrylate, divinylbenzene, diallyl phthalate;
It is also possible to copolymerize a carbonyl group-containing α, β-ethylenically unsaturated compound or the like such as diacetone acrylamide.

  The manner of crosslinking depends on the type of crosslinking monomer to be used, and in the case of forming a crosslinking structure only by copolymerizing the crosslinking monomer, the functional group of the crosslinking monomer and the active hydrogen group contained in the polymer or in the crosslinking agent May form a crosslinked structure by bonding with oxalic acid, and when a carbonyl group-containing α, β-ethylenically unsaturated compound is used, oxalic acid dihydrazide, succinic acid dihydrazide, adipic acid dihydrazide, polyacrylic acid hydrazide, etc. A crosslinked structure can be formed by using a polyhydrazine compound having two or more hydrazide groups as a crosslinker.

  In the present invention, it is necessary to lower the Tg of the soft polymer prepared in step (I) to less than -35 ° C, and -120 ° C to -40 ° C, particularly -80 ° C to -40 ° C. Is preferred. If the Tg of the soft polymer is -35 ° C. or more, the tackiness is reduced, and the aqueous pressure-sensitive adhesive composition excellent in tackiness can not be obtained. If the Tg is excessively low, the cohesion when used as an adhesive will be low, and the peel strength will be insufficient. Moreover, the ratio which a soft polymer occupies to the whole heterogeneous polymer is 65-90 mass%, Preferably it is 70-85 mass%. When this proportion is less than 65% by mass, the final adhesion strength is not sufficient, and conversely, when it exceeds 90% by mass, the suppression of the initial adhesion is not sufficient.

  The polymerizable component (hereinafter sometimes referred to as the first polymerizable component, or the ethylenically unsaturated monomer (A1)) for producing a soft polymer has a weight of Tg lower than -35 ° C. It may be a single monomer or a mixture of two or more monomers, as long as they can be combined. For example, even when using a monomer having a Tg of polymer lower than -35 ° C alone or in combination, using a monomer having a Tg of polymer lower than -35 ° C in combination with other monomers You can also

  The first polymerizable component may be appropriately selected from the above-mentioned ethylenically unsaturated monomers, and preferred examples thereof include ethyl acrylate and n-butyl acrylate in terms of excellent stability during polymerization. Alkyl acrylates having an alkyl group having 2 to 10 carbon atoms such as n-amyl acrylate, isoamyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, i-octyl acrylate, and the like, methoxyethyl acrylate, 2 -A substituted alkyl acrylate having an alkyl group having 1 to 10 carbon atoms, which is substituted with an alkoxy group or a hydroxy group such as hydroxyethyl acrylate, and the like can be mentioned.

  In addition, in order to enhance adhesion, the first polymerizable component preferably contains an unsaturated carboxylic acid having 3 to 5 carbon atoms such as acrylic acid, methacrylic acid, fumaric acid, maleic acid, itaconic acid, etc. .

Preferred specific examples of the soft polymer include alkyl acrylate polymers, in particular, alkyl acrylates having an alkyl group having 2 to 10 carbon atoms as a main component, and 0.1 to 10% by mass, particularly 0, as a copolymerization component. Copolymers containing 5 to 5% by mass of a C 3 to C 5 unsaturated carboxylic acid can be mentioned. Here, the main component means that the component is the component with the highest content among the components, and is preferably 50% by mass or more of the whole. The same applies to the following description.
Among them, a copolymer having butyl acrylate and / or 2-ethylhexyl acrylate as a main component and copolymerized with acrylic acid, methacrylic acid or itaconic acid is preferably used from the viewpoint of final adhesive strength. Specifically, it is preferable that butyl acrylate and / or ethylhexyl acrylate be contained in a total amount of 50 to 99.9% by mass of the first polymerizable component, and it is more preferable that 80 to 99.8% by mass be contained. Preferably, the content is further preferably 95 to 99.5% by mass. It is preferable to contain acrylic acid, methacrylic acid or itaconic acid in an amount of 0.1 to 20% by mass of the first polymerizable component, and more preferably 0.5 to 10% by mass.

  The heterogeneous polymer of the present invention is constituted by the segment of the soft polymer and the segment of the hard polymer having a higher Tg as described above. The composition of the monomer constituting the hard polymer changes so as to give a high Tg with the passage of polymerization time, so the layer of the hard polymer adjacent to the surface of the soft polymer particle is almost equivalent to the soft polymer. Although having a Tg, the composition of the hard polymer forming the surface layer is preferably selected to give a Tg as high as 30 to 230 ° C., more preferably 80 to 200 ° C., than that of the soft polymer. Further, the Tg of the entire hard polymer may be higher than the Tg of the soft polymer, but in particular, the Tg is preferably 10 ° C. or more, more preferably 40 ° C. or more.

  The ratio of the hard polymer to the entire heterogeneous polymer is preferably 10 to 35% by mass, and more preferably 15 to 30% by mass. When the proportion is 10% by mass or more, the effect of suppressing the initial tackiness is excellent, and when the proportion is 35% by mass or less, the final adhesive strength is excellent.

  The polymerizable component (hereinafter sometimes referred to as the second polymerizable component) for producing a rigid polymer is higher than -20 ° C and the monomer component (A2) giving a Tg lower than -35 ° C. It is comprised with the monomer component (B) which gives Tg. The monomer component (A2) may be any as long as it can be used as the first polymerizable component, but preferably, the Tg of the polymer is -120 ° C to -40 ° C, particularly -80 ° C to- 40 ° C. When the monomer component (A2) having the same composition as the first polymerizable component is used, the interface between the soft polymer segment and the hard polymer segment has almost the same composition, and therefore distortion generally tends to occur at the heterophase interface Can be suppressed. In addition, the first polymerizable component and the monomer component (A2) can be prepared only by dividing the same monomer component into two, which is convenient in production.

  The monomer component (B), which is another component of the second polymerizable component, has a polymer Tg of higher than −20 ° C., preferably Tg of 0 ° C. to 105 ° C., more preferably 30 ° C. to 105 ° C. When the Tg is −20 ° C. or less, the effect of suppressing the initial adhesive strength is reduced, and the workability of re-sticking is reduced. The monomer component (B) may be a single monomer or a mixture of two or more as long as it satisfies the above Tg requirements.

Specific examples of the monomer used as the monomer component (B) include methyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, butyl acrylate and the like, with methyl methacrylate, butyl methacrylate and butyl acrylate being preferred. Further, the monomer component (B) preferably contains an unsaturated carboxylic acid having 3 to 5 carbon atoms such as acrylic acid, methacrylic acid, fumaric acid, maleic acid, itaconic acid, etc., in order to enhance adhesion. . As said C3-C5 unsaturated carboxylic acid, acrylic acid, methacrylic acid, and itaconic acid are preferable, acrylic acid and methacrylic acid are more preferable, and acrylic acid is further more preferable.
More specifically, the monomer component (B) is mainly composed of methyl methacrylate and / or butyl acrylate and preferably contains acrylic acid, methacrylic acid or itaconic acid, and is a total of methyl methacrylate and / or butyl acrylate The content is preferably 50 to 99.9% by mass of the monomer component (B), more preferably 80 to 99.8% by mass, and preferably 95 to 99.5% by mass. More preferable. Further, it is preferable to contain acrylic acid, methacrylic acid or itaconic acid in an amount of 0.1 to 50% by mass of the monomer component (B), more preferably 0.2 to 20% by mass. It is more preferable to contain -10 mass%.

  Preferred specific examples of the hard polymer include alkyl acrylate polymers which may have a substituent, and in particular, alkyl methacrylates having an alkyl group having 1 to 8 carbon atoms and alkyl groups having 3 to 10 carbon atoms. Copolymers containing an alkyl acrylate as a main component and an unsaturated carboxylic acid having 3 to 5 carbon atoms of 0.1 to 10% by mass, particularly 0.5 to 5% by mass as a copolymerization component can be mentioned. In particular, a copolymer having methyl methacrylate and / or 2-ethylhexyl acrylate as a main component and copolymerized with acrylic acid, methacrylic acid or itaconic acid is preferably used in order to suppress the initial tack.

  The proportion of the monomer component (A2) in the entire heterogeneous polymer is 5 to 20% by mass, preferably 5 to 10% by mass. When this proportion is less than 5% by mass, the final adhesion is reduced, and conversely, when it exceeds 20% by mass, the initial tackiness suppressing effect is not sufficient. The proportion of the monomer component (B) in the entire heterogeneous polymer is 5 to 20% by mass, preferably 5 to 10% by mass. When this proportion is less than 5% by mass, the initial tackiness suppressing effect is not sufficient, and conversely, when it exceeds 20% by mass, the final tackiness is reduced. Furthermore, the use ratio of the monomer component (A2) and the monomer component (B) is 20 to 80 mass% of the monomer component (A2) and 80 to 80 parts by weight of the monomer component (B2) based on the total amount of the two. The content is preferably 20% by mass, and particularly preferably 40 to 60% by mass of the monomer component (A2) and 60 to 40% by mass of the monomer component (B).

  In addition, Tg of each polymer shown above is a theoretical value obtained by calculating according to the formula of FOX shown below from the monomer unit which comprises a polymer, and its ratio.

Tg = T-273
However, 1 / T = (W1 / T1 + W2 / T2 + W3 / T3 +... + Wn / Tn)
(Wherein, Tg is the glass transition temperature (Celsius temperature) of the copolymer, T is the glass transition temperature (absolute temperature) of the copolymer, and Wn is each monomer component (preferably, ethylenic acid) Tn is the mass fraction of the saturated compound component), and Tn is the glass transition temperature (absolute temperature) of the homopolymer of each monomer component (preferably, the ethylenically unsaturated compound component).

  In the present invention, the calculation of Tg of the soft polymer (polymer obtained from the first polymerizable component) and the hard polymer (polymer obtained from the second polymerizable component) is based on the monofunctional monomer. Shall be calculated. That is, even when a polyfunctional monomer is contained in the polymerizable component, the amount of the polyfunctional monomer used is small, and the influence on the Tg of the produced polymer is small, so it is not included in the calculation of Tg I assume. Further, the theoretical glass transition temperature determined by the equation of FOX is in good agreement with the measured glass transition temperature determined by differential scanning calorimetry (DSC) or dynamic viscoelasticity.

<Method of Producing Aqueous Emulsion of Heterogeneous Polymer>
In the heterogeneous polymer emulsion of the present invention, the first polymerizable component is emulsion-polymerized to produce a soft polymer, and the second polymerizable component is continuously added to the polymerization system of the step (I). Alternatively, it is produced through the step (II) of forming a rigid polymer by conducting polymerization while intermittently supplying. At that time, gradually increasing the content ratio of the monomer component (B) in the second polymerizable component in the step (II), that is, the monomer component (B) / single in the second polymerizable component It is necessary to gradually increase the mass component (A2) (mass ratio) from the feed start time point of the second polymerizable component to the feed stop point. Such polymerization method is referred to as power feed polymerization, for example, as described in L. et al. H. Kenneth, J. et al. of Coating Technol. 51, 651, 27-41 (1979), JP-B-51-46555, JP-A-11-512774, and the patent document 5 described above.

  In step (I), an emulsion of a soft polymer is prepared by emulsion polymerization of the first polymerizable component in the presence of water and an emulsifier using a polymerization initiator. The total amount of the polymerizable components may be previously charged in the reactor, but in order to obtain uniform particles, it is preferable to adopt a method of polymerization while continuously or intermittently supplying. The polymerization is usually carried out at a temperature of about 5 to 100 ° C, preferably about 50 to 90 ° C.

  As an emulsifier which can be used in process (I), surfactant is mentioned, This surfactant is not specifically limited. Specifically, anionic surfactants such as sodium dodecyl benzene sulfonate and sodium dodecyl sulfate, nonionic surfactants such as polyoxyethylene alkyl ether and polyoxyethylene nonyl phenyl ether, sedyl trimethyl ammonium bromide, lauryl pyridinium chloride and the like Cationic surfactants, amphoteric surfactants such as laurylbedine, and other reactive surfactants. These surfactants may be used alone or in combination.

  Examples of polymerization initiators used in emulsion polymerization include persulfate initiators such as potassium persulfate and ammonium persulfate, and water-soluble azo initiation such as 2,2'-azobis (2-methylpropionamidine) dihydrochloride and the like. Agents, organic peroxides such as t-butyl hydroperoxide and cumene hydroperoxide, hydrogen peroxide and the like. These polymerization initiators may be used alone or in combination.

  In addition, a reducing agent can be used together with these polymerization initiators, if necessary. As such a reducing agent, reducing organic compounds such as ascorbic acid, tartaric acid, citric acid, glucose, formaldehyde sulfoxylate metal salt, etc., reducing materials such as sodium thiosulfate, sodium sulfite, sodium bisulfite, sodium metabisulfite and the like Inorganic compounds and the like can be mentioned.

  In the emulsion polymerization, a chain transfer agent can be used as needed. As such a chain transfer agent, n-dodecyl mercaptan, tert-dodecyl mercaptan, n-butyl mercaptan, 2-ethylhexyl thioglycolate, 2-mercaptoethanol, β-mercaptopropionic acid, methyl alcohol, n-propyl alcohol, Isopropyl alcohol, t-butyl alcohol, benzyl alcohol and the like can be mentioned.

  After preparing the emulsion of the soft polymer in the above step (I), the second polymerizable component is continuously supplied to the reaction system to continue the polymerization, thereby comprising the soft polymer and the hard polymer. Heterogeneous polymers are produced. The conditions for polymerization are the same as in step (I) except that the method of supplying the polymerizable component is as follows. In the step (II), first, a second polymerizable component containing the monomer component (A2) alone or the monomer component (A2) and a low concentration of the monomer component (B) is supplied, and then, The second polymerizable component is supplied continuously or intermittently while gradually increasing the concentration of the monomer component (B). Then, when the supply of the second polymerizable component is stopped, the concentration of the monomer component (B) is controlled to be the largest. The composition at the start of supply of the second polymerizable component, ie, monomer component (B) / monomer component (A2) (mass ratio) is 0/10 to 10/90, and further 0/100 to It is preferable that the ratio is 1/99, and that the monomer component (B) / monomer component (A2) (mass ratio) is 100/0 to 95/5, and more preferably 100/0 to 5 at the supply stop point. It is preferable that it is 99/1.

  As a method of continuously changing the composition of the second polymerizable component, it is preferable to adopt a power feed polymerization method, and a specific method thereof is a container (tank 1) of the monomer component (A2) And the vessel (tank 2) of the monomer component (B) are connected, and at the same time as the monomer component (A2) is supplied from the tank 1 to the polymerization reactor, the monomer component (B) is A method in which the supply from tank 2 to tank 1 is terminated (serial feed method), tank 1 and tank 2 being continuously supplied to tank 1 and in time with the end of supply from tank 1 to the polymerization reactor. Are connected to the respective polymerization reactors, and the composition of the second polymerizable component is controlled by controlling the respective feed rates appropriately (parallel feed method). Among them, the in-line feed method is preferably used from the viewpoint of operability and productivity.

  After the completion of the supply of the second polymerizable component, the soft polymer and the hard weight are normally maintained by continuing the polymerization at a temperature of about 5 to 100 ° C., preferably about 50 to 90 ° C., for 0.5 to 5 hours. A heterogeneous polymer composed of coalescing is obtained. The heterogeneous polymer preferably has a Tg lower than -35 ° C, more preferably a Tg of -80 ° C to -40 ° C, and the particle size is usually 10 nm to 5 μm, preferably It is 50 nm-0.5 micrometer.

  In step (II), the surface charge of the aqueous emulsion is raised to impart stability by adjusting the pH to 4 to 10 by adding one or more acids or bases to the obtained aqueous emulsion. be able to. Typical acids to be used include acetic acid, lactic acid, hydrochloric acid, phosphoric acid, sulfuric acid and the like. Moreover, as a general base to be used, amine compounds such as triethylamine, ammonia, diethanolamine, diethylaminoethanol and the like; alkali metal hydroxides such as potassium hydroxide, sodium hydroxide, lithium hydroxide and the like can be mentioned.

  In the present invention, an aqueous emulsion having a solid content concentration of usually 30 to 70% by mass, preferably 40 to 65% by mass, can be obtained. Such aqueous emulsions of the present invention may be blended with rosin-based, terpene-based, petroleum-based, and other tackifiers, if necessary. These tackifiers may be used alone or in combination. In addition, if necessary, a crosslinking agent (polyfunctional epoxy, polyfunctional isocyanate, silane coupling agent, etc.), a viscosity improver, a thickener, an antifoaming agent, a pigment (body pigment, color pigment, hollow balloon, etc.), Dispersants, wetting agents, light stabilizers, UV absorbers, preservatives, antibacterial agents and the like can be blended.

<Gel fraction of aqueous emulsion>
About 1.0 g of a sample obtained by drying the aqueous emulsion at 105 ° C. is weighed and immersed in about 30 ml of toluene at room temperature for 1 day, then the toluene insoluble portion is taken out, dried at 110 ° C. for about 1 hour and weighed By doing this, (gel fraction) = [(toluene insoluble content weight) / sample weight] × 100 can be calculated. The larger the gel fraction, the better the removability and the less the adhesive residue on the adherend. The gel fraction is preferably 80% or more, more preferably 85% or more, and most preferably 90% or more.

  The gel fraction can be adjusted by a chain transfer agent or a silane coupling agent, and such chain transfer agents include the above-mentioned chain transfer agents. As a silane coupling agent, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2- (3,4-epoxycyclohexyl) ethyl tritrile Epoxy group-containing silane coupling agents such as methoxysilane, 3-aminopropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, 3-triethoxysilyl-N- (1,3- Amino group-containing silane coupling agents such as dimethylbutylidene) propylamine and N-phenyl-γ-aminopropyltrimethoxysilane (meth) such as 3-acryloxypropyltrimethoxysilane and 3-methacryloxypropyltriethoxysilane Acrylic group containing silane Coupling agent, isocyanate group-containing silane coupling agents such as 3-isocyanate propyl triethoxysilane and the like. Among them, thiol group-containing chain transfer agents and (meth) acrylic group-containing silane coupling agents are preferable because they are relatively inexpensive and easy to handle industrially.

  The chain transfer agent and the silane coupling agent may be used alone or in combination of two or more. The more the chain transfer agent, the lower the gel fraction and the higher the adhesion. On the other hand, the gel fraction increases as the amount of the silane coupling agent increases, and the removability increases, so that both the chain transfer agent and the silane coupling agent are required to achieve both strong tackiness and removability. It is desirable to add. The total content of the chain transfer agent is preferably 0.01 to 2 parts by mass, more preferably 0 based on 100 parts by mass of the total of the ethylenically unsaturated monomers (A) and (B). It is preferable that the amount of the silane coupling agent is 0.01 to 2 parts by mass, and more preferably 0.02 to 0 parts by mass. .8 parts by weight, most preferably 0.05 to 0.3 parts by weight.

<Aqueous adhesive composition>
In the present invention, the emulsion of the heterogeneous polymer obtained in the step (II) can be used as an aqueous pressure-sensitive adhesive composition as it is or by adjusting the solid content concentration as appropriate. If necessary, the above-mentioned compounding agents can be appropriately added to make an aqueous pressure-sensitive adhesive composition.

  The adherend in the case of using the aqueous pressure-sensitive adhesive composition of the present invention as a pressure-sensitive adhesive is not particularly limited, but paper, plastic film, metal, glass, woven fabric, non-woven fabric, foam of plastic or rubber, etc. may be mentioned. Be

<Adhesive sheet>
A pressure-sensitive adhesive sheet can be produced by applying the aqueous pressure-sensitive adhesive composition of the present invention to one side or both sides of a substrate and then drying to form a pressure-sensitive adhesive layer. Various methods are used in the application step of the aqueous pressure-sensitive adhesive composition. Specifically, for example, roll coat, kiss roll coat, gravure coat, reverse coat, roll brush, spray coat, dip roll coat, bar coat, knife coat, air knife coat, curtain coat, lip coat, die coater etc. Methods such as extrusion coating may be mentioned.

  In the application step, the amount of application is controlled so that the pressure-sensitive adhesive layer to be formed has a predetermined thickness (thickness after drying). The thickness (thickness after drying) of the pressure-sensitive adhesive layer is usually set in the range of 5 to 200 μm, preferably 10 to 100 μm. Then, the applied aqueous pressure-sensitive adhesive composition is dried according to a conventional method to form a pressure-sensitive adhesive layer.

  The material of the substrate is not particularly limited, and may be paper, plastic film, foam of plastic or rubber, metal, glass, woven fabric, non-woven fabric, inorganic plate and the like. An anchor layer can be formed on the surface of the substrate to improve adhesion with the pressure-sensitive adhesive layer, and various easy adhesion treatments such as corona treatment and plasma treatment can be performed. Further, the surface of the pressure-sensitive adhesive layer may be subjected to an easy adhesion treatment.

  The pressure-sensitive adhesive sheet of the present invention has a 180 ° peel strength to a SUS # 304 plate measured at a temperature of 23 ° C., 50% RH and a peel rate of 300 mm / min, and is 1 to 5 N / 25 mm after 1 minute of paste It is preferable to have a pressure-sensitive adhesive layer which is 6N / 25 mm or more after 24 hours, and in particular, it is 2 to 4.5 N / 25 mm after 1 minute pasting and 9N / 25 mm or more after 24 hours pasting It is preferable to have a layer in terms of excellent reworkability and final adhesion. In addition, assuming that the 180 degree peeling force after 1 minute of bonding is A, and the 180 degree peeling force after 24 hours is B, B / A is preferably 2 or more, particularly 3 or more.

  The pressure-sensitive adhesive sheet of the present invention can be provided with a releasable protective film layer on the pressure-sensitive adhesive layer. Examples of the constituent material of the protective film include plastic films, paper, cloth, porous materials such as non-woven fabrics, nets, foamed sheets, metal foils, and appropriate thin sheets such as laminates thereof.

  The plastic film is not particularly limited as long as it can protect the adhesive layer. For example, polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer A united film, a polyethylene terephthalate film, a polybutylene terephthalate film, a polyurethane film, an ethylene-vinyl acetate copolymer film and the like can be mentioned. The thickness of the release film is generally 5 to 200 μm, preferably about 5 to 100 μm.

  The use of the aqueous pressure-sensitive adhesive composition and the pressure-sensitive adhesive sheet of the present invention is not particularly limited, but, for example, daily products such as pressure-sensitive adhesive tapes, double-sided tapes, pressure-sensitive labels, wallpaper, floor tiles, floor sheets (cushion floor), It is suitably used in the field of housing materials such as carpets, ceiling materials, pressure-sensitive adhesive sheets for windows (for example, heat shield sheets, reflective sheets, crime prevention sheets), etc., and also manufactures automotive products, home appliances, electronic parts, etc. Can also be used.

  EXAMPLES Hereinafter, the present invention will be described in detail by way of examples, but the present invention is not limited by these examples. Unless otherwise indicated, "part" and "%" in an Example, a comparative example, and a reference example show a mass part and mass%. The measurement of the properties of the emulsion and the tack of the aqueous pressure-sensitive adhesive composition was carried out according to the following method.

(Properties of the emulsion)
(A) Nonvolatile content: Calculated from the residue after drying at 105 ° C. for 1 hour.
(Ii) Viscosity: Measured at 23 ° C. and 10 rpm using a BH type viscometer.
(C) pH: measured by pH meter.

(Measurement of adhesion)
Bonding the test piece of 25 mm x 250 mm to the adherend (SUS # 304 plate) by reciprocating one 2 kg roller under an atmosphere of 23 ° C x 50% RH so that the bonding area is 25 mm x 125 mm. After that, it was left under the same atmosphere. After left to stand for 1 minute, 20 minutes and 24 hours, 180 ° peel force was measured under the condition of peel rate 300 mm / min to obtain adhesion.

(Measurement of gel fraction)
Weigh about 1.0 g of the emulsion sample dried at 105 ° C. and immerse it in about 30 ml of toluene at room temperature for 1 day, then remove the insoluble matter in toluene, dry at 110 ° C. for about 1 hour, and weigh it Then, it was calculated as (gel fraction) = [(toluene insoluble content weight) / sample weight] × 100.

(Removable)
After the measurement of the adhesive strength, it was visually judged whether the adhesive residue occurred on the adherend.

Example 1
Process (I):
In a polymerization apparatus equipped with a stirrer, thermometer, and reflux condenser, 224 parts of ion-exchanged water and 1 part of an emulsifier (Aqualon KH-10, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) are charged in advance, and nitrogen substitution is sufficiently performed. After the operation, the temperature rose. The internal temperature was maintained at 80 ° C. while stirring at about 120 rpm, and a 5% aqueous potassium persulfate solution was added as a polymerization initiator. Separately, each component shown in the item of (A) emulsion of Table 1 is emulsified using a homomixer at a ratio described in Table 1 to prepare (A) an emulsion, which is used for a soft polymer (A1) was used as an emulsion.
(A1) The emulsion and a 2.5% aqueous potassium persulfate solution (dropping catalyst) were added dropwise to the polymerization system, and polymerization was carried out to obtain a soft polymer. The dropping rate of the emulsion (A1) was about 239 parts / hour, and the dropping rate of the aqueous initiator solution was about 13.3 parts / hour.

Process (II):
On the other hand, the (A) emulsion having the same composition as the (A) emulsion and the (B) emulsion having the composition shown in Table 1 were respectively provided in the container 1 and the container 2 with a stirrer. Next, using (A2) emulsion and (B) emulsion, a hard polymer is produced by performing power feed polymerization as follows, and having a segment of a soft polymer and a segment of a hard polymer A heterogeneous polymer was produced.

  First, at the same time as the dripping of the (A1) emulsion was completed, it was started to drip the (A2) emulsion from the container 1 into the polymerization apparatus. At the same time, the dropping of the (B) emulsion from the container 2 into the (A2) container 1 containing the emulsion was started. The two containers were made to be uniform by constantly stirring. The dropping speed of the (B) emulsion from the container 2 is the speed at which the dropping of the (B) emulsion ends simultaneously with the completion of the dropping of the mixture of the (A2) emulsion and the (B) emulsion from the container 1, It was about 119.5 parts / hour. The amount of the (A2) emulsion used at the end of the dropwise addition was 10 parts based on 80 parts of the (A1) emulsion.

  After completion of the dropwise addition, reaction was carried out at 80 ° C. for 2 hours, and then cooled to room temperature (25 ° C.). Finally, ammonia water as a neutralizing agent was added while adjusting the pH to about 8.5, to obtain an aqueous emulsion of a heterogeneous polymer having a segment of a soft polymer and a segment of a hard polymer. The amount (parts by mass) of each component used for (A) emulsion shown in Table 1 is the total amount of each component used as (A1) emulsion and (A2) emulsion. The properties of the obtained aqueous emulsion are shown in Table 1.

  Next, the obtained aqueous emulsion is used as it is as an aqueous pressure-sensitive adhesive composition, the aqueous pressure-sensitive adhesive composition is applied to the corona-treated surface of a 50 μm thick polyester film, and the film thickness of the pressure-sensitive adhesive layer after drying becomes 25 μm. It applied as it did, and it dried at 105 degreeC for 2 minutes, and created the adhesive sheet. The 180 ° peel force of the obtained adhesive sheet was measured. The results are shown in Table 1.

Examples 2 to 8
An aqueous emulsion and an aqueous pressure-sensitive adhesive composition were prepared in the same manner as in Example 1 except that the compositions of (A1) emulsion, (A2) emulsion and (B) emulsion were changed as shown in Table 1. Each of the properties was evaluated. The results are shown in Table 1. In the following table, "-" means that the component is not contained.

The abbreviations and trade names in Tables 1 and 2 are as follows.
MMA: methyl methacrylate BuA: n-butyl acrylate 2EHA: 2-ethylhexyl acrylate Aa: acrylic acid Silicon KBM-503: 3-methacryloxypropyltrimethoxysilane (silane coupling agent, Shin-Etsu Chemical Co., Ltd.) Made)
In addition, c attached at the end of the numerical value of the 180 ° peel strength indicates that the adhesive layer has cohesive failure.
Furthermore, the amount of each component shown in the item of (A) emulsion is the total of the amounts used in (A1) emulsion and (A2) emulsion.
"Peeling force after 20 minutes" was evaluated as ○ if the peeling force (N / 25 mm) after leaving for 20 minutes was 1.5 or more and x if it was less than 1.5.
The "re-peelability" was evaluated as ○ if there was no adhesive residue on the adherend after measurement of peel strength, and x if there was adhesive residue.

Comparative Example 1
Aqueous emulsion and aqueous pressure-sensitive adhesive composition in the same manner as in Example 1 except that the compositions of (A1) emulsion and (A2) emulsion are changed as shown in Table 2 and (B) the emulsion is not used. Were prepared and their properties were evaluated. The results are shown in Table 2.

Comparative examples 2 to 4
An aqueous emulsion and an aqueous pressure-sensitive adhesive composition were prepared in the same manner as in Example 1 except that the compositions of (A1) emulsion, (A2) emulsion and (B) emulsion were changed as shown in Table 2. Each of the properties was evaluated. The results are shown in Table 2.

Comparative example 5
According to Example 2, except that in the step (II), instead of power feed polymerizing the (A2) emulsion and the (B) emulsion, polymerization is carried out while continuously dropping only the (B) emulsion. An aqueous emulsion was prepared. The amounts of (A) emulsion and (B) emulsion used are as described in Table 2. The properties of the obtained aqueous emulsion were evaluated as an aqueous pressure-sensitive adhesive composition. The results are shown in Table 2.

  From the results of Table 1, the aqueous pressure-sensitive adhesive composition using the aqueous emulsion of the present invention is at a level at which temporary stopping can be achieved and at the initial stage of bonding (one and 20 minutes after bonding). It can be seen that the adhesive strength is suppressed to the extent that it can be done, and that it has sufficient adhesive strength after standing for one day (Examples 1 to 8). In particular, in the aqueous pressure-sensitive adhesive composition of Example 2, the ratio of adhesion after 1 minute to 24 hours after adhesion (the adhesion after 24 hours / the adhesion after 1 minute) is 4 or more. In addition to excellent reworkability, the final adhesion is also excellent.

  On the other hand, as shown in Table 2, when the (B) emulsion is not used, the initial tack becomes high, and it becomes difficult to re-stick (see Comparative Example 1). In addition, when the proportion of the (A1) emulsion is 40% by mass, both the initial tackiness and the tackiness with time are very small even when the (A2) emulsion and the (B) emulsion are subjected to power feed polymerization, and the pressure-sensitive adhesive Not have sufficient performance (see Comparative Examples 2 and 3). Furthermore, when Tg of a heterogeneous polymer was -19 degreeC, it was inferior to adhesiveness and was less than the measurement limit of peeling strength (refer comparative example 4). In addition, when a hard polymer segment is formed by dropping only the emulsion (B) after producing a soft polymer (Comparative Example 5), the initial tack becomes high, and it is difficult to reattach. Become.

  From the results in Tables 1 and 2, it is preferable that the peel strength after 20 minutes of bonding is 1.5 N / 25 mm or more, and that the gel fraction is higher than 90% to exhibit good removability. (Examples 3 and 7). When the gel fraction is lower than 90%, cohesive failure occurs after 24 hours even if the peeling force after 20 minutes of bonding is 1.5 N / 25 mm or more (Examples 1, 2, 4 and 6) , 5, 6, and 8). Even if the gel fraction is low, the removability after 24 hours of bonding may be good, but the peel strength after 20 minutes of bonding is smaller than 1.5 N / 25 mm (Comparative Examples 2 and 3) .

  According to the present invention, in the construction of wallpaper, floor material, etc., it has an initial adhesive strength that enables re-sticking to improve the quality of the construction, and has sufficient adhesive power after one hour. An aqueous pressure-sensitive adhesive composition is obtained. In addition, by using this aqueous pressure-sensitive adhesive composition, it is possible to re-stick, and it is possible to obtain an adhesive sheet by leaving it at room temperature and obtaining a pressure-sensitive adhesive sheet. Furthermore, according to the present invention, a heterogeneous polymer emulsion suitable for preparation of the aqueous pressure-sensitive adhesive composition can be efficiently produced.

Claims (16)

The polymerization is carried out while continuously or intermittently supplying the second polymerizable component to the polymerization system of the step (I) and the step (I) of producing a soft polymer by emulsion polymerization of the first polymerizable component. An aqueous emulsion of a heterogeneous polymer comprising a segment of a soft polymer and a segment of a hard polymer obtained by the production method comprising the step (II) and satisfying the following conditions.
(1) The first polymerizable component is composed of a monomer component (A1) giving a Tg lower than -35 ° C., and the amount thereof is 65 to 90% by mass of the total monomer amount.
(2) The second polymerizable component is composed of a monomer component (A2) giving a Tg lower than -35 ° C and a monomer component (B) giving a Tg higher than -20 ° C, and Each of the monomer component (A2) and the monomer component (B) should be 5 to 20% by mass of the total amount of monomers.
(3) The monomer component (B) / monomer component (A2) (mass ratio) in the second polymerizable component is gradually added from the supply start time point of the second polymerizable component to the supply stop time point Make it bigger.   The aqueous emulsion according to claim 1, wherein the heterogeneous polymer has a Tg of -80 ° C to -40 ° C.   The aqueous emulsion according to claim 1 or 2, wherein the monomer components (A1) and (A2) give Tg of -40 ° C or less when they are polymerized.   A monomer component (A1) and a monomer component (A2) have as a main component the alkyl acrylate which has a C2-C10 alkyl group, A monomer component (B) has 1 carbon number The aqueous emulsion according to any one of claims 1 to 3, which comprises a methacrylate having an alkyl group of 8 to 8.   The aqueous emulsion according to any one of claims 1 to 4, wherein the monomer component (A1), the monomer component (A2) and the monomer component (B) all contain an unsaturated carboxylic acid.   The aqueous emulsion according to any one of claims 1 to 5, wherein the monomer component (A1) comprises butyl acrylate and / or 2-ethylhexyl acrylate as a main component.   The aqueous emulsion according to any one of claims 1 to 6, wherein the polymerization of the first polymerizable component in step (I) is carried out while continuously or intermittently supplying the polymerizable component.   The aqueous emulsion according to any one of claims 1 to 7, which has a gel fraction of 90% or more.   The aqueous emulsion according to any one of claims 1 to 8, wherein the first polymerizable component and / or the second polymerizable component comprises a chain transfer agent and / or a silane coupling agent.   The aqueous emulsion according to any one of claims 1 to 9, wherein the first polymerizable component and / or the second polymerizable component comprises a chain transfer agent and a silane coupling agent. The polymerization is carried out while continuously or intermittently supplying the second polymerizable component to the polymerization system of the step (I) and the step (I) of producing a soft polymer by emulsion polymerization of the first polymerizable component. A method for producing an aqueous emulsion of a heterogeneous polymer comprising a segment of a soft polymer and a segment of a hard polymer, which comprises the step (II) and satisfies the following conditions.
(1) The first polymerizable component is composed of a monomer component (A1) giving a Tg lower than -35 ° C., and the amount thereof is 65 to 90% by mass of the total monomer amount.
(2) The second polymerizable component is composed of a monomer component (A2) giving a Tg lower than -35 ° C and a monomer component (B) giving a Tg higher than -20 ° C, and Each of the monomer component (A2) and the monomer component (B) should be 5 to 20% by mass of the total amount of monomers.
(3) The monomer component (B) / monomer component (A2) (mass ratio) in the second polymerizable component is gradually added from the supply start time point of the second polymerizable component to the supply stop time point Make it bigger.   The aqueous adhesive composition containing the aqueous emulsion as described in any one of Claims 1-10.   The aqueous pressure-sensitive adhesive composition according to claim 12, which is used as a pressure-sensitive adhesive for housing materials.   A pressure-sensitive adhesive sheet comprising a substrate and a pressure-sensitive adhesive layer formed using the aqueous pressure-sensitive adhesive composition according to claim 12 or 13.   The adhesive layer has a 180 degree peel strength to the SUS # 304 plate measured at a temperature of 23 ° C, 50% RH and a peel rate of 300 mm / min, 1 to 5 N / 25 mm after 1 minute of application, and after 24 hours of application The pressure-sensitive adhesive sheet according to claim 14, which is 6N / 25 mm or more.   The pressure-sensitive adhesive sheet according to claim 15, wherein B / A is 2 or more, where A represents a 180 ° peel force after 1 minute of application and B represents a 180 ° peel force after 24 hours of application.