JP2003292922A - Emulsion type adhesive and pressure-sensitive adhesive sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aqueous emulsion type adhesive having characteristics of excellent water resistance and maintenance of the excellent adhesive power even after the adhesive layer formed on a substrate is soaked in water or left in high humidity for a long time. <P>SOLUTION: The aqueous emulsion type adhesive is obtained by emulsifying and dispersing resin particles in an aqueous medium. The resin particles have core-shell structures and ≤0.3 μm average particle diameter. The resin (A) constituting the core has ≥15°C Tg and the resin (B) constituting the shell has ≤-30°C Tg. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous emulsion type adhesive having adhesive resin particles dispersed in an aqueous medium, and more specifically, an adhesive having excellent water resistance and formed on a substrate. The present invention relates to an aqueous emulsion-type pressure-sensitive adhesive having a property of maintaining excellent adhesive strength even after the layer is immersed in water or left under high humidity for a long time.

[0002]

2. Description of the Related Art Organic solvent-based pressure-sensitive adhesives using an organic solvent as a medium have recently been used as an aqueous emulsion-type pressure-sensitive adhesive using an aqueous medium in some fields of application from the viewpoint of preventing pollution of the global environment. Has been replaced. However, water-based pressure-sensitive adhesives generally have poorer water resistance than solvent-based pressure-sensitive adhesives. That is, among the water-based pressure-sensitive adhesives, the pressure-sensitive adhesive in which fine particles of the pressure-sensitive adhesive resin are emulsified in an aqueous medium in the presence of an emulsion stabilizer (hereinafter simply referred to as an emulsifier), that is, an aqueous emulsion-type pressure-sensitive adhesive is most preferable. As is well known, the reason is that the emulsifier contained therein is hydrophilic and that the hydrophilic functional group must be introduced into the adhesive resin itself for dispersion stability in an aqueous medium. It was extremely difficult to provide the water-based emulsion type adhesive with high water resistance.

There are many proposals for improving the water resistance of an aqueous emulsion type pressure-sensitive adhesive. The main means for waterproofing adopted in them are: (1) use of a polymerizable emulsifier as emulsifier (sometimes referred to as reactive emulsifier), (2)
Introducing a specific monomer unit having excellent water resistance into the resin, (3) miniaturizing the resin particles, and (4) making the resin particles have a two-layer structure of a core and a shell. These means are used alone or in combination. In the invention described in JP-A-7-330813, as a monomer for obtaining a resin, 75-99% by weight of a long-chain alkyl (meth) acrylic acid ester having an alkyl group having 9 to 13 carbon atoms, an aromatic group is used. In the presence of an emulsifier, 2 to 0.1 μm of monomer fine particles obtained by emulsifying and dispersing a monomer mixture consisting of 0.5 to 20% by weight of a vinyl monomer and 5% by weight or less of a crosslinkable monomer are used. The emulsion-type pressure-sensitive adhesive is produced by polymerizing the above.

JP-A-9-143444 and JP-A-9-143444
No. 278837 proposes a reactive emulsifier. By using the reactive emulsifier, the water resistance is considerably increased in that the free emulsifier is not contained in the adhesive resin film. Further, in the invention described in JP-A-9-278837, in addition to the use of a specific reactive emulsifier, the resin particles are made into a core-shell structure by adopting a two-step emulsion polymerization and the resin particle size is It is also adopted that the thickness is 0.1 to 0.3 μm. Japanese Patent Laid-Open No. 2000-10978
No. 4 discloses that the resin particles have a particle size of 0.3 μm or less and the particle size distribution (ratio of the weight average particle size to the arithmetic average particle size) is 1.0 to
The resin emulsion of 1.5 is described as having excellent water resistance. Further, in the publication, as a means for waterproofing, a monomer having a cyclic structure such as styrene is used together with an alkyl (meth) acrylate as a monomer for obtaining a resin, and a core / shell structure is formed by two-step polymerization. Is introduced. According to each of the above proposals, although an aqueous emulsion type pressure-sensitive adhesive having improved water resistance to some extent can be obtained, there is a large limitation in application such as a significant decrease in adhesive strength when the pressure-sensitive adhesive film is immersed in water. It was That is, an adhesive film having a pressure-sensitive adhesive layer formed on one side of a polyethylene terephthalate film using a conventional aqueous emulsion type adhesive is attached to a stainless steel plate, and after being immersed in water for 1 day, the adhesive strength is 10 It is generally lower than%.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide an aqueous emulsion type pressure-sensitive adhesive that retains a practically sufficient degree of tackiness even after immersion in water.

[0006]

Means for Solving the Problems As a result of intensive studies for solving the above-mentioned problems, the present inventors have found that the resin constituting the core has a glass transition temperature (Tg) of 15 ° C. or higher.
The present inventors have found that an aqueous emulsion-type pressure-sensitive adhesive composed of resin particles having a shell structure is extremely excellent in water resistance, and completed the present invention. That is, the present invention is a resin particle having a core-shell structure and an average particle diameter of 0.3 μm or less, wherein the resin (A) constituting the core has a Tg of 15 ° C. or higher, and the resin constituting the shell ( An aqueous emulsion-type pressure-sensitive adhesive obtained by emulsifying and dispersing resin particles having a Tg of B) of −30 ° C. or lower in an aqueous medium. Hereinafter, the present invention will be described in more detail.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The main component constituting the emulsion-type pressure-sensitive adhesive of the present invention is pressure-sensitive adhesive resin particles having a two-layer structure of a core and a shell. Furthermore, the average particle diameter of the resin particles is 0.3 μm or less, the Tg of the resin (A) constituting the core is 15 ° C. or higher, and the Tg of the resin (B) constituting the shell is −30 ° C. It is the following. Such adhesive resin particles are synthesized by two-step polymerization. That is, first, by synthesizing the resin particles to be the core by the first-stage polymerization, and then performing the second-stage polymerization in the presence of the resin particles to provide a resin layer to be the shell on the surface of the core, -Form a two-layer structure of the shell. Each of the first-stage and second-stage polymerizations is preferably performed by a polymerization method in which a polymer is obtained as fine particles in an aqueous medium, that is, an aqueous polymerization method which belongs to emulsion polymerization in a broad sense.

Preferred monomers for forming the core in the present invention include the following monomers. In the present invention, the monomer is selected so that the Tg of the resin component serving as the core is 15 ° C. or higher. More preferred core resin T
g is 20 to 60 ° C., more preferably 30 to 55
℃. If the Tg of the core is less than 15 ° C, a coarse grid is likely to be formed during the second-stage polymerization, and the adhesive strength when the adhesive tape using the obtained adhesive is immersed in water. Grows larger. On the other hand, when the Tg of the core exceeds 60 ° C., it becomes difficult to obtain the desired adhesive performance. In selecting the monomer, it is preferable to refer to the Tg of the homopolymer of each monomer. In the following examples of monomers, the Tg values of the homopolymers of some representative monomers are shown in parentheses after each monomer.

Alkyl (meth) acrylate: methyl acrylate (5 ° C.), methyl methacrylate (103
C), ethyl acrylate (-27 C), ethyl methacrylate (12 C), isopropyl acrylate (-1
1 ° C.), isopropyl methacrylate (27 ° C.), n
-Butyl acrylate (-57 ° C), n-butyl methacrylate (-24 ° C), i-butylmethacrylate (8 ° C), n-hexylmethacrylate (-5 ° C),
n-octyl acrylate (-65 ° C), n-octyl methacrylate (-25 ° C), 2-ethylhexyl acrylate (-70 ° C), 2-ethylhexyl methacrylate (-5 ° C), n-nonyl (meth) acrylate,
i-nonyl (meth) acrylate, n-decyl (meth)
Acrylate and n-lauryl acrylate (-65
℃) etc.

Α, β-ethylenically unsaturated carboxylic acid:
Acrylic acid (166 ° C), methacrylic acid (185 ° C),
Crotonic acid, maleic acid (130 ° C), fumaric acid, itaconic acid, citraconic acid and cinnamic acid. ○ Vinyl monomer having an aromatic ring or a saturated hydrocarbon ring:
Styrene (90 ° C), vinyltoluene, divinyltoluene, α-methylstyrene (168 ° C), paramethylstyrene (97 ° C), parachlorostyrene (131 ° C), vinyldibenzyl chloride, benzyl (meth) acrylate, cyclohexyl acrylate (15 ° C.) and cyclohexyl methacrylate (66 ° C.) and the like.

Hydroxyl group-containing (meth) acrylate: 2-
Hydroxyethyl acrylate (-15 ° C), 2-hydroxyethyl methacrylate (55 ° C), 2-hydroxypropyl methacrylate (-7 ° C), 2-hydroxy-3-phenoxypropyl (meth) acrylate, glycerol mono (meth) acrylate , Polyethylene glycol mono (meth) acrylate and polypropylene glycol mono (meth) acrylate. ○ Acrylamides: Acrylamide (109 ℃), N
-Methylol acrylamide, N-methoxymethyl acrylamide, N-methoxybutyl acrylamide and the like. ○ Other vinyl monomers: vinyl acetate (32 ° C), glycidyl acrylate (46 ° C), acrylonitrile (1
10 ° C.) and allyl alcohol, etc.

As a polymerization method for forming the core, generally known emulsion polymerization is preferable, and the above-mentioned monomers are present in an aqueous medium in the presence of an emulsifier in the presence or absence of a chain transfer agent. The resin particles to be the core can be synthesized by radically polymerizing. As the emulsifier, alkyl sulfate ester salt, polyoxyethylene alkyl ether sulfate ester salt, alkylbenzene sulfonate,
Anionic surface-active compounds such as alkyl ether disulphonate, fatty acid salt, and naphthalene sulfonic acid formalin condensate, or polyoxyethylene alkyl ethers, polyoxyethylene alkylphenol ethers, sorbitan higher fatty acid esters, polyoxyethylene sorbitan higher Nonionic surface active compounds such as fatty acid esters, polyoxyethylene higher fatty acid esters and glycerin higher fatty acid esters can be preferably used. The amount of the emulsifier used is preferably 0.02 to 0.4 parts by mass per 100 parts by mass of the monomer. When the amount of the emulsifier used is small, a grid is likely to be generated during production, while when the amount of the emulsifier is too large, the emulsifier absorbs water during the formation of the pressure-sensitive adhesive layer, which causes deterioration of water resistance and decrease of adhesive strength.

As the polymerization initiator, known radical initiators are used. Examples thereof include hydroperoxides, dialkyl peroxides, diacyl peroxides, peroxides, ketone peroxides, azo compounds and persulfates. The preferred amount of the polymerization initiator used is 100
It is 0.1 to 10 parts by mass per part by mass. Examples of the chain transfer agent include n-dodecyl mercaptan, t-dodecyl mercaptan, n-butyl mercaptan, 2-ethylhexyl thioglycolate, 2-mercaptoethanol, trichlorobromomethane and mercaptopropionic acid. The preferred amount used is monomer 1
It is 0.01 to 1.0 part by mass per 00 parts by mass.

In the above polymerization, the average particle size is 0.1 μm.
It is preferable to obtain an emulsion in which resin particles of m or less are dispersed. According to the resin particles having such an average particle diameter, it becomes easy to control the final resin particle diameter to 0.3 μm or less by the second-stage polymerization. In order to obtain an emulsion in which resin particles having an average particle diameter of 0.1 μm or less are dispersed by the first-stage polymerization, it is preferable to use the emulsifier in excess of the critical micelle concentration, and it depends on the kind of the monomer to be polymerized. Usually, an excessive emulsifier concentration of about 20 to 30% of the critical micelle concentration is adopted. Incidentally, the critical micelle concentration, at the concentration of the emulsifier below that most of the monomers do not become micelles and exist as oil droplets, but above that, all the monomers exist as micelles, the critical concentration That is.

By carrying out the second stage polymerization in the presence of the aqueous resin dispersion obtained by the above polymerization, a resin layer called a shell is formed around the core. The monomers that can be used for molding the shell overlap with the monomers exemplified as the monomer for forming the core. However, the monomer needs to be selected so that the Tg of the shell resin is −30 ° C. or lower. Tg of the resin on the shell side is preferably -40 to -6.
It is 0 ° C. The Tg on the shell side has a great influence on the adhesive properties before immersion in water, and at Tg of -60 ° C or lower, cohesive failure tends to occur on the adherend, and at Tg of -30 ° C or higher, the tack becomes too low. Becomes difficult to maintain.

The monomer preferable for forming the shell resin is at least (a) a linear or branched alkyl group having at least 4 carbon atoms in view of the adhesive property and water resistance of the finally obtained adhesive. Alkyl (meth) acrylate having, (b) α, β-ethylenically unsaturated carboxylic acid,
(C) A monomer mixture containing a vinyl monomer having an aromatic ring or a saturated hydrocarbon ring, and more preferably (d) a crosslinkable monomer together with (a), (b) and (c) above. It is a monomer mixture containing. As the monomer (a), the monomer (b) and the monomer (c), various monomers exemplified as the monomer for the core resin can be used. Also,
Examples of the (d) crosslinkable monomer include 2-hydroxyethyl (meth) acrylate, glycidyl (meth) acrylate, (meth) acrylamide and N-methylolacrylamide.

The monomer (a) in the monomer mixture,
The preferred use ratios of (b) and (c) are, based on the total amount thereof, (a) 50 to 85 mass% and (b) 0.1.
˜5% by mass and (c) 2 to 20% by mass. Also,
When the crosslinkable monomer (d) is used in combination, the preferable amount thereof is 0.1 to 2.0% by mass based on the total amount of all the monomers. If the usage ratio of the monomer (a) is less than 50% by mass, it may be difficult to balance the adhesive force, cohesive force and tack of the obtained pressure-sensitive adhesive, and if it exceeds 85% by mass. The cohesive strength of the adhesive may be insufficient. If the usage ratio of the monomer (b) is less than 0.1% by mass, the cohesive force, adhesive force and whitening resistance of the resulting pressure-sensitive adhesive may be insufficient, and if it exceeds 5% by mass, tack and adhesive force The whitening resistance may be reduced. If the usage ratio of the monomer (c) is less than 2% by mass, the whitening resistance of the obtained pressure-sensitive adhesive may be insufficient, and if it exceeds 20% by mass, tack and adhesive strength may be reduced. In the polymerization for forming the shell resin, it is preferable to use a chain transfer agent, and as the chain transfer agent, those exemplified in the section regarding the polymerization of the core resin can be used.
0.01 to 10.0 parts by mass per 100 parts by mass is suitable.

As the polymerization method for forming the shell layer, a new monomer is added to the reactor in which the aqueous resin dispersion obtained by the first stage polymerization is present, below the critical micelle concentration or at the micelle concentration. The method of polymerizing while dropping the pre-emulsion dispersed in the aqueous medium with the above amount of emulsifier is preferable. In addition, in the present invention, an aqueous emulsion dispersion of monomers is referred to as a pre-emulsion. In the present invention, it is more preferable that the emulsifier concentration in the pre-emulsion is less than the critical micelle concentration. If the emulsifier concentration in the pre-emulsion is a critical micelle concentration or more, in addition to the polymerization reaction to form a shell layer on the surface of the first-stage resin particles in the reactor containing the resin particles by the first-stage polymerization, As a result of the progress of the polymerization using new micelles as the place of polymerization, the particle size distribution of the finally obtained resin particles is widened and the water resistance thereof is likely to decrease.

As described above, in the present invention, it is preferable to use an emulsifier having a concentration lower than the critical micelle concentration when carrying out the second stage polymerization. The aqueous resin emulsion thus obtained forms a film having a narrow particle size distribution of resin particles and excellent water resistance. In order to improve the emulsification stability of the obtained aqueous resin emulsion, particularly to improve the mechanical stability, it is preferable to add 0.2 to 0.5 parts by mass of a nonionic emulsifier per 100 parts by mass of the polymer. In this case, if an anionic emulsifier is used, the water resistance of the emulsion is likely to decrease. Examples of nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene alkylphenol ethers, sorbitan higher fatty acid esters, polyoxyethylene sorbitan higher fatty acid esters, polyoxyethylene higher fatty acid esters and glycerin higher fatty acid esters. Etc.

In the present invention, the average particle size of the resin particles in the aqueous resin emulsion obtained after the second-stage polymerization is 0.3 μm or less, more preferably 0.2 μm.
It is the following. If the average particle size of the resin particles exceeds 0.3 μm, a pressure-sensitive adhesive having excellent water resistance cannot be obtained. The second-stage polymerization basically occurs so as to form a shell layer on the outside of the first-stage resin particles, so that the particle size of the final resin particles is the same as that used in the second-stage polymerization. It can be controlled by the quantity of the quantity. The amount of the monomer used for the second-stage polymerization (hereinafter referred to as the second-stage monomer) is not particularly limited, but in terms of the tackiness of the resulting aqueous emulsion-type adhesive, The amount of the first-stage monomer is 5 to 95% by mass, based on the total amount of both compared to the amount of the monomer used for the first-stage polymerization (hereinafter referred to as the first-stage monomer). Amount of second-stage monomer 95
It is preferably in the range of 5 mass%. By appropriately selecting the ratio of the core resin having a high Tg and the shell resin having a low Tg, the adhesive force of the adhesive can be adjusted.
The particle size distribution of the resin particles in the aqueous resin emulsion according to the present invention is preferably as narrow as possible, and when the particle size distribution is represented by the ratio of the weight average particle size and the number average particle size, the ratio is 1.0 to It is preferably 1.15. If this ratio exceeds 1.15, it is difficult to obtain an aqueous emulsion type pressure-sensitive adhesive having excellent water resistance. The average particle size and particle size distribution of the fine resin particles according to the present invention is HOR.
IBA Laser Diffraction / Scattering Particle Size Analyzer LA-
910 or the like.

The aqueous emulsion type pressure-sensitive adhesive of the present invention is extremely excellent in water resistance as an aqueous emulsion type,
For example, in the conventional case, when the film with a pressure-sensitive adhesive prepared after being applied to a PET (polyethylene terephthalate) film and dried is immersed in water as it is, the pressure-sensitive adhesive layer whitens in about 5 to 30 minutes. According to the pressure-sensitive adhesive of the present invention, almost no whitening is observed after 30 minutes. The degree of whitening can be measured with a haze meter (represented by a haze value). The haze value of the pressure-sensitive adhesive layer formed of the aqueous emulsion-type pressure-sensitive adhesive of the present invention after immersion in room temperature for 1 day is usually 10% or less. In addition, the adhesive film (P
Speaking of the adhesive strength after immersing the test piece in which the ET film base material) is adhered to the stainless steel plate in water for 1 day, when the conventional aqueous emulsion type adhesive is used, it is 10% or less before the immersion. While the adhesive strength is reduced, the adhesive of the present invention can maintain 40% or more before immersion. Incidentally, the aqueous emulsion-type pressure-sensitive adhesive of the present invention, if desired, a dispersant, a defoaming agent, a thickener, a lubricant, a film-forming auxiliary, a fiber auxiliary, a cleaning agent, an antistatic agent, a leveling agent, a wetting agent. Agents and leveling improvers may be added.

As described above, the aqueous emulsion-type pressure-sensitive adhesive of the present invention can be suitably used for pressure-sensitive adhesive applications in which organic solvent-type pressure-sensitive adhesives have been conventionally used, but since it is extremely excellent in water resistance, for example, when whitening occurs. It is particularly suitable for an undesired transparent sheet, an aluminum vapor-deposited sheet in which the hiding power is lowered due to the aluminum contacting the pressure-sensitive adhesive layer being changed to aluminum hydroxide due to water absorption, and the like.

An aqueous emulsion type pressure-sensitive adhesive is prepared by a conventional method.
The pressure-sensitive adhesive sheet or pressure-sensitive adhesive film of the present invention can be easily obtained by applying it on a substrate film so that the thickness of the pressure-sensitive adhesive layer after drying is 5 to 100 μm, and then drying by a method such as hot air drying. You can As the base sheet or film, PET, polypropylene, polyethylene, polyvinyl chloride, polyurethane, cellulose,
Cellophane, paper and the like can be mentioned. Hereinafter, the present invention will be described more specifically by giving examples and comparative examples. In each example, "part" means "part by mass", "%" means "mass &", and the following abbreviations mean the following.

HA: 2-ethylhexyl acrylate BA: Butyl acrylate St: Styrene MMA: methyl methacrylate HEA: 2-humanroxyethyl acrylate N-MAM: N-methylol acrylamide MAA: methacrylic acid DBS: sodium dodecylbenzene sulfonate DM: Dodecyl mercaptan

[0025]

EXAMPLES (1) Production Example 1; Synthesis of core resin particles (hereinafter referred to as seed particles) A A water reactor was equipped with water 78 in a reactor equipped with a stirrer, thermometer, cooler, nitrogen introducing tube and two dropping funnels. .3 parts and 1.0 part of sodium dodecylbenzene sulfonate were charged and the temperature was raised to 85 ° C. In a separate container, BA 52.0 parts, MMA 46.7 parts,
Sodium dodecylbenzene sulfonate 1 part in MAA 1.3 parts
6.4 parts and 26.3 parts of water were added and emulsified. 2.8 parts of 15% ammonium persulfate aqueous solution and 2.2% of the above emulsion were charged into the above reactor, and 5 minutes later, the remaining emulsion was added dropwise over 3 hours to carry out emulsion polymerization. . Thirty minutes after the completion of dropping, the system was cooled to terminate the polymerization, and an aqueous resin emulsion having a solid content concentration of 47.0% was obtained. The obtained resin particles were used as seed A. The Tg (calculated value) of this seed was -1.2 ° C and the average particle size was 0.08 µm. (2) Production Examples 2 to 5; Synthesis of Seed Particles B to E Seed particles B to E were synthesized by polymerizing the monomers shown in Table 1. The Tg and average particle size of the obtained seed particles are as shown in Table 1.

[0026]

[Table 1] The units of the monomer and emulsifier DBS in Table 1 are "parts", and the amount of DBS is the amount of pure water-free components.

[0027]

Example 1 41.1 parts of water and 12.43 parts of seed B were placed in a reactor equipped with a stirrer, a thermometer, a cooler, a nitrogen introducing tube and two dropping funnels, and the temperature was raised to 85 ° C. . HA81.4 parts, ST12.6 parts, MAA2.3 in another container
Part, HEA 3.7 part, N-MAM 0.5 part, DM0.0
1 part, 30.6 parts of water and 0.028 part of DBS were added and emulsified. 0.4 part of a 10 wt% ammonium persulfate aqueous solution was placed in the reactor, and 3 minutes later, 3 parts of the emulsion was placed in a separate container.
It dripped over time. Keep the temperature for 30 minutes,
The polymerization was terminated by cooling. The amount of DBS used in this polymerization is the critical micelle concentration (per 100 parts of monomer).
The amount is less than 0.04). The particle diameter of resin constituting the obtained emulsion-type pressure-sensitive adhesive was 0.21 μm, and the dispersity (volume average diameter / number average diameter) was 1.1. After the obtained resin was neutralized, it was coated on a PET film so that the thickness of the dried pressure-sensitive adhesive layer was 20 μm, and dried with hot air (100 ° C. for 120 seconds) to obtain a test pressure-sensitive adhesive sheet. It was The pressure-sensitive adhesive sheet was immersed in room temperature water with the adhesive side (resin-coated side) facing downward, and the whitening status after 24 hours was ○, and the haze value (measured by Sigma Color measuring device manufactured by Nippon Denshoku Co., Ltd.) Was 7.9.

[0028]

[Examples 2 to 5] Polymerization was carried out in the same manner as in Example 1 using the seed particles and monomers shown in Table 2 to synthesize emulsion-type pressure-sensitive adhesives. Table 2 also shows the evaluation results of the shape of the resin particles constituting the obtained pressure-sensitive adhesive and the water resistance of the pressure-sensitive adhesive.

[0029]

[Table 2]

The adhesive strength, the water resistant adhesive strength, the holding power and the ball tack in Table 2 are measured by the following methods. ○ Adhesive force: Using a test piece obtained by adhering the above-mentioned adhesive sheet for testing to a stainless steel plate, 180 ° peel strength was measured according to JIS Z 0237, and was taken as the adhesive force. ○ Water-resistant adhesive strength; After immersing a test piece in which a test adhesive sheet is adhered to a stainless steel plate in room temperature water for 24 hours, JI
A 180 ° tensile test is performed according to S Z 0237. ○ Holding power: Adhesive sheet for testing was attached to a stainless steel plate so that the adhesion area would be 25 mm × 25 mm, and 1 at 40 ° C
Measure the time until peeling off by applying a load of kg,
The holding time was defined as the holding power. When a deviation from the initial attachment position occurred after 180 minutes, the deviation width at that time was adopted as a measure of the holding force. ○ Ball tack: Using a test adhesive sheet, JIS
It was measured under the conditions of 23 ° C. and 65% RH according to the ball rolling method of Z 0237.

[0031]

Comparative Examples 1 to 4 Polymerization was carried out in the same manner as in Example 1 using the seed particles and monomers shown in Table 3 to synthesize emulsion type pressure-sensitive adhesives. Table 3 also shows the evaluation results of the shape of resin particles constituting the obtained pressure-sensitive adhesive and the water resistance of the pressure-sensitive adhesive. As can be seen from Table 3, the Tg of the seed particles used in Comparative Examples 1, 2 and 4 were all lower than 15 ° C., the water-whitening resistance of each of the obtained pressure-sensitive adhesives was Δ, and the water-resistant pressure-sensitive adhesiveness was It cannot be said that the power is also high. In Comparative Example 3, seed particles are not used, and the water-resistant adhesive strength of the obtained pressure-sensitive adhesive is considerably low.

[0032]

[Table 3]

[0033]

The emulsion-type pressure-sensitive adhesive of the present invention has extremely high water resistance despite being an aqueous type.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4J004 AA01 AA10 AB01 CA02 CA04                       CA05 CA06 CB02 CC02                 4J026 AA17 AA28 AA38 AA42 AA45                       AA48 AA49 AA50 BA14 BA15                       BA20 BA26 BA30 BA31 BA32                       BB01 DA04 DA13 DB04 FA02                       GA10                 4J040 DL111 DL121 JA03 JA09                       JB09 LA02 LA07

Claims (5)

[Claims] 1. The average particle size having a core-shell structure is 0.
Resin particles having a particle size of 3 μm or less, in which the resin (A) forming the core has a Tg of 15 ° C. or higher and the resin (B) forming the shell has a Tg of −30 ° C. or lower in an aqueous medium. An aqueous emulsion-type pressure-sensitive adhesive obtained by emulsifying and dispersing in. 2. Both of the resin (A) constituting the core and the resin (B) constituting the shell are at least (a).
(Meth) acrylic acid ester having a linear or branched alkyl having 4 or more carbon atoms, (b) α, β-ethylenically unsaturated carboxylic acid, and (c) vinyl unit having an aromatic ring or a saturated hydrocarbon ring. The aqueous emulsion type pressure-sensitive adhesive according to claim 1, which is a polymer obtained from a monomer mixture containing a monomer. 3. The mass ratio of the resin (A) forming the core and the resin (B) forming the shell is 5 to 95% by mass of the resin (A) to 95 to 5% by mass of the resin (B). 1. The water-based emulsion type pressure-sensitive adhesive as described in 1 or 2. 4. The resin (A) constituting the core has a Tg of 20.
The aqueous emulsion-type pressure-sensitive adhesive according to claim 1, which has a temperature of not less than ° C. 5. A pressure-sensitive adhesive sheet provided with a pressure-sensitive adhesive film comprising the emulsion-type pressure-sensitive adhesive according to claim 1.