JP2006008831A - Aqueous adhesive composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aqueous adhesive composition having excellent polymerization stability and stability of the polymer and good water resistance. <P>SOLUTION: The aqueous adhesive composition contains (A) an aqueous dispersion of a resin composition for adhesive obtained by polymerizing a radically polymerizable ethylenic unsaturated monomer in an aqueous medium containing an emulsifier, a polymerization initiator and water as essential components and (B) a block copolymer of (b-1) a polyalkylene oxide having n carbon atoms (n is an integer of ≥1) in the repeating unit and (b2) a polyalkylene oxide having n+1 carbon atoms in the repeating unit, as essential components. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an aqueous pressure-sensitive adhesive composition. Specifically, it is excellent in polymerization stability and polymer stability, and is also excellent in water whitening resistance, and is particularly preferred for transparent film substrates such as labeling and overlaminating applications that require a high degree of design. It is related with the water-based adhesive composition which can do. More specifically, the aqueous resin composition for pressure-sensitive adhesives exhibits an effect as described above by mixing a block copolymer composed of two types of polyalkylene oxide blocks having one different carbon atom number in the repeating unit. The present invention relates to an adhesive composition.

  In recent years, solvent removal has progressed in consideration of safety and health and environmental problems, and the shift from solvent type to aqueous type is also progressing in adhesives. However, in aqueous adhesives, the effects of emulsifiers used at the time of emulsion polymerization, or leveling agents added for the purpose of preventing smoothness of the coating film and ensuring smoothness during the coating of adhesives, are due to the effects of aqueous adhesives. The water resistance of the dried coating film was inferior to that of the solvent-type pressure-sensitive adhesive.

In order to remedy this drawback, water resistance can be improved by reducing the total amount of emulsifiers used during emulsion polymerization, or by using nonionic emulsifiers that have a lower affinity for water than ionic ones. There are attempts to improve it. However, there are drawbacks such as a large amount of agglomerates during polymerization and poor stability of the polymer, making it difficult to put it to practical use.
In addition, a polymerizable group such as a vinyl group or an allyl group is introduced into the structure of the emulsifier, and copolymerized with an ethylenically unsaturated monomer, which is the main constituent of the resin composition for pressure-sensitive adhesives, during polymerization. Attempts have been made to improve water resistance by reducing the amount of emulsifier to be used, but it has not yet been put to practical use.
On the other hand, from the viewpoint of selecting an ethylenically unsaturated monomer to be used, the amount of the monomer containing a carboxyl group such as acrylic acid or methacrylic acid, which is used in combination to impart affinity for water, should be reduced. Although attempts have been made to improve the water resistance, there have been drawbacks such as the occurrence of a large amount of aggregates during polymerization and poor stability of the polymer, making it difficult to put it to practical use.

  An object of the present invention is to provide an aqueous pressure-sensitive adhesive composition which is excellent in polymerization stability and polymer stability and has good water resistance.

1st invention is the resin composition aqueous | water-based dispersion for adhesives obtained by superposing | polymerizing the radically polymerizable ethylenically unsaturated monomer in the aqueous medium which has an emulsifier, a polymerization initiator, and water as an essential component ( A) and a polyalkylene oxide (b-1) in which the number of carbon atoms in the repeating unit is n (n represents an integer of 1 or more) and a polyalkylene oxide in which the number of carbon atoms in the repeating unit is (n + 1) Regarding the aqueous pressure-sensitive adhesive composition containing the block copolymer (B) with (b-2) as an essential component,
The second invention relates to the aqueous pressure-sensitive adhesive composition according to the invention, wherein n of the block copolymer (B) is n = 2,
The third invention is a structure in which the block copolymer (B) has a linear structure, the (b-1) part is bonded to both ends of the (b-2) part, and both ends are hydroxyl groups. The aqueous pressure-sensitive adhesive composition according to any one of the above inventions, characterized by having
4th invention is related with the aqueous adhesive composition as described in any one of the said invention characterized by the average molecular weights of block copolymer (B) being 1000-6000,
5th invention WHEREIN: The average molecular weight of the (b-2) part in a block copolymer (B) is 900-3000, and the ratio for which the (b-1) part accounts with respect to the whole (B) is 5- The aqueous pressure-sensitive adhesive composition according to any one of the above inventions, wherein the aqueous pressure-sensitive adhesive composition is 50% by weight,
Sixth invention is any one of the above, characterized in that 0.01 to 20 parts by weight of the block copolymer (B) is mixed with 100 parts by weight of the aqueous resin composition dispersion for pressure-sensitive adhesive (A). The present invention relates to the aqueous pressure-sensitive adhesive composition described in the invention.

  The aqueous pressure-sensitive adhesive composition obtained in the present invention is imparted with good water resistance without impairing the stability during polymerization or the stability of the polymer. Therefore, it can be preferably used even when applied to a transparent film substrate such as a label application or an overlaminate application that require a particularly high design property.

  As the radically polymerizable ethylenically unsaturated monomer for use in the present invention to obtain the composition aqueous dispersion (A) for pressure-sensitive adhesives, (a-1) the alkyl group has 1 to 14 carbon atoms. Examples include alkyl acrylates and alkyl methacrylates. (A-1) Acrylic acid alkyl ester and methacrylic acid alkyl ester having 1 to 14 carbon atoms in the alkyl group include methyl (meth) acrylate and [methyl (meth) acrylate together with methyl acrylate and methyl methacrylate. To do. The same applies below. ], Ethyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, lauryl (meth) acrylate, 2-ethylhexyl (meth) acrylate, dodecyl (meth) acrylate or the like Examples include acrylic esters of branched aliphatic alcohols and corresponding methacrylic esters. Among them, (meth) acrylic acid alkyl esters having 4 to 12 carbon atoms in the alkyl group are preferably used. These are contained in 70 to 99.5% by weight in 100% by weight of the ethylenically unsaturated monomer, and can be used alone or in combination of two or more.

The monomer (a-1) is preferably copolymerized with (a-2) an ethylenically unsaturated monomer having a carboxyl group.
(A-2) Examples of the ethylenically unsaturated monomer having a carboxyl group include (meth) acrylic acid, maleic acid, fumaric acid, and itaconic acid. These are contained in an amount of 0.5 to 5% by weight based on 100% by weight of all ethylenically unsaturated monomers, and can be used alone or in combination of two or more.

As monomers other than (a-1) and (a-2), (a-3) a copolymerizable (meth) having an alcoholic hydroxyl group, depending on the type of crosslinking agent to be blended as required An acrylic monomer or a copolymerizable (meth) acrylic monomer having a (a-4) carbonyl group is used.
(A-3) Examples of copolymerizable acrylic monomers having an alcoholic hydroxyl group include 2-hydroxylethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxylbutyl (meth) acrylate, and the like. it can. These are contained in an amount of 0.5 to 5% by weight based on 100% by weight of all ethylenically unsaturated monomers, and can be used alone or in combination of two or more.
(A-3) When a copolymerizable acrylic monomer having an alcoholic hydroxyl group is used, as a crosslinking agent that can be blended when obtaining a pressure-sensitive adhesive composition, an isocyanate compound, a metal such as titanium or zirconium is used. An alkoxide compound etc. are mentioned.

(A-4) As a copolymerizable acrylic monomer having a carbonyl group, acrolein, diacetone (meth) acrylamide, formylstyrene, preferably a vinyl alkyl ketone having 4 to 7 carbon atoms (for example, vinyl methyl ketone) , Vinyl ethyl ketone, vinyl isobutyl ketone, etc.), diacetone (meth) acrylate, acetonyl (meth) acrylate, acetoacetoxyethyl (meth) acrylate, diacetone (meth) acrylate, 2-hydroxypropyl (meth) acrylate-acetyl acetate, butane Examples thereof include diol-1,4- (meth) acrylate-acetyl acetate.
These are contained in an amount of 0.5 to 5% by weight based on 100% by weight of all ethylenically unsaturated monomers, and can be used alone or in combination of two or more.
(A-4) When using the copolymerizable acrylic monomer which has a carbonyl group, amines, a hydrazide compound, etc. are mentioned as a crosslinking agent which can be mix | blended when obtaining an adhesive composition.

  Other monomers include polyethylene glycol (meth) acrylate, glycidyl (meth) acrylate, mono- (2-hydroxylethyl-α-chloro (meth) acrylate) acid phosphate, vinyl blocked isocyanate, N-methylol (meta ) Acrylamide, N-methylaminoethyl (meth) acrylate, N-tributylaminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, (meth) acrylamide , Vinyl pyrrolidone, vinyl ester, vinyl pyridine, vinyl acetate, vinyl propionate, styrene, (meth) acrylonitrile, butadiene, chloroprene and the like. These can be contained at 30% by weight or less, if necessary, and can be used alone or in combination of two or more.

Furthermore, the dispersed particles in the aqueous resin composition dispersion for pressure-sensitive adhesives (A) of the present invention may have an intraparticle crosslinked structure.
As the intraparticle crosslinking agent, various polyfunctional monomers such as diallyl ester of phthalic acid and polyfunctional acrylic monomers can be used.
Examples of phthalic acid diallyl esters include orthophthalic acid, isophthalic acid, and terephthalic acid diallyl esters.
The polyfunctional acrylic monomers include methylene bis (meth) acrylamide, 1,6-hexanediol di (meth) acrylate, ethylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, dipenta An example is erythritol hexa (meth) acrylate. These are contained in an amount of 0.1 to 3% by weight based on 100% by weight of the ethylenically unsaturated monomer, and can be used alone or in combination of two or more.

As the emulsifier for obtaining the aqueous resin composition dispersion (A) for use in the present invention, a reactive emulsifier, a non-reactive emulsifier, etc. can be used alone or in combination of two or more. .
Examples of the reactive emulsifier include the following compounds. Examples of anionic emulsifiers include nonylphenyl skeleton "Adekaria Soap SE-10N" manufactured by Asahi Denka Kogyo Co., Ltd. and "Aqualon HS-10, HS-20" manufactured by Daiichi Kogyo Seiyaku Co., Ltd. Examples include “AQUALON KH-05, KH-10” manufactured by Kogyo Seiyaku Co., Ltd., “ADEKA rear soap SR-10N” manufactured by Asahi Denka Kogyo Co., Ltd., and “KAYARAD” manufactured by Nippon Kayaku Co., Ltd. having a phosphate ester skeleton.
Nonionic emulsifiers include polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, sorbitan higher fatty acid esters, glycerin higher fatty acid esters and the like having an unsaturated double bond at the molecular terminal or in the middle. Asahi Denka Kogyo Co., Ltd. “Adekaria Soap NE-10”, Daiichi Kogyo Seiyaku Co., Ltd. “Aqualon RN-10, RN-20, RN-50”, Japan Emulsifier Stock Examples include “Antox NA-16” manufactured by the company.

  Moreover, the following compounds can be illustrated as a non-reactive emulsifier. Anionic emulsifiers include higher fatty acid salts such as sodium stearate, alkylaryl sulfonates such as sodium dodecylbenzene sulfonate, alkyl sulfate salts such as sodium lauryl sulfate, and polyoxyethylene alkyl such as sodium polyoxyethylene lauryl ether sulfate. Examples thereof include ether sulfate esters and polyoxyethylene alkylaryl ether sulfate salts such as sodium polyoxyethylene nonylphenyl ether sulfate.

  Nonionic emulsifiers include polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether, polyoxyethylene alkyl phenyl ethers such as polyoxyethylene nonylphenyl ether, sorbitan higher fatty acid esters such as sorbitan monostearate, oleic acid Examples include glycerin higher fatty acid esters such as monoglyceride.

  As the polymerization initiator for obtaining the resin composition aqueous dispersion (A) for use in the present invention, a persulfate such as potassium persulfate and ammonium persulfate, an azobis cation salt, a hydroxyl group addition substance, etc. A water-soluble thermal decomposition polymerization catalyst or a redox polymerization catalyst can be used. The redox polymerization catalyst includes a combination of an organic peroxide such as t-butyl hydroperoxide, benzoyl peroxide, cumene hydroperoxide and a reducing agent such as Rongalite, sodium metabisulfite, or potassium persulfate or ammonium persulfate. And combinations of Rongalite and sodium thiosulfate, and combinations of hydrogen peroxide and ascorbic acid.

  The aqueous resin composition for pressure-sensitive adhesive of the present invention (A) is a mercaptan-based or thioglycol-based chain transfer agent for controlling the molecular weight or molecular weight distribution when an ethylenically unsaturated monomer is polymerized. Thiol compounds such as β-mercaptopropionic acid, rosin compounds having allylic hydrogen, terpene compounds, and the like can be used. The addition amount is preferably 0.01 to 10.0 parts by weight, and more preferably 0.1 to 5 parts by weight with respect to 100 parts by weight of the total amount of ethylenically unsaturated monomers.

The polyalkylene oxide (b-1) in which the number of carbon atoms in the repeating unit is n (n represents an integer of 1 or more) and the number of carbon atoms in the repeating unit (n + 1) are used in the present invention. Examples of the block copolymer (B) with the alkylene oxide (b-2) include a block copolymer of polyethylene oxide and polypropylene oxide, and a block copolymer of polypropylene oxide and polybutylene oxide. In view of the solubility of the composition in water as a solvent, a block copolymer of polyethylene oxide and polypropylene oxide is preferable.
These may have a straight chain structure or a branched structure in the molecule, but preferably a straight chain in which a polyethylene oxide portion is bonded to both ends of a polypropylene oxide portion and both ends of the molecule are hydroxyl groups. A compound having a structure (generally referred to as “pluronic nonionic surfactant”) is used. Furthermore, it is preferable that the average molecular weight of this block copolymer (B) is 1000-6000, and it is more preferable that it is 1200-4000. If the molecular weight is small, the effect of improving water whitening resistance cannot be obtained sufficiently, and if the molecular weight is large, it is difficult to dissolve in water. Further, in the block copolymer (B), the average molecular weight of the (b-2) part is 900 to 3000, and the ratio of the (b-1) part to the whole (B) is 5 to 50% by weight. It is more preferable from the viewpoint of improving the water whitening resistance and solubility in water. Furthermore, it is preferable to mix 0.01 to 20 parts by weight of the block copolymer (B) with respect to 100 parts by weight of the aqueous resin composition dispersion for pressure-sensitive adhesive (A), and 0.1 to 10 parts by weight of the mixture is mixed. It is more preferable to do. When the amount of the block copolymer (B) used is small, the effect of improving water whitening resistance cannot be obtained sufficiently, and even if the amount used is increased, not only the further improvement effect can be obtained, but it is also uneconomical.

Next, the pressure-sensitive adhesive composition of the present invention will be described.
The pressure-sensitive adhesive composition of the present invention contains an aqueous resin composition dispersion (A) for pressure-sensitive adhesives and the block copolymer (B) as essential components, and is suitable for adjusting the pressure-sensitive adhesive force as necessary. An appropriate amount of a tackifier such as rosin resin, phenol resin, polyterpene, acetylene resin, petroleum hydrocarbon resin, ethylene vinyl acetate copolymer, synthetic rubber, natural rubber, etc. can be added. Further, a crosslinking agent, a viscosity modifier, an antifoaming agent, a leveling agent, a plasticizer, a filler, a neutralizing agent, a coloring agent, a silane coupling agent, an antiseptic, and the like may be added.

The pressure-sensitive adhesive composition of the present invention is applied onto a paper or film substrate or a peelable sheet by various coating apparatuses such as a comma coater, a reverse coater, a slot die coater, a lip coater, a gravure chamber coater, and a curtain coater. By drying, various adhesive coated products such as an adhesive sheet and an adhesive label can be obtained. It is preferable to dry at 80 ° C. to 120 ° C. after applying the pressure-sensitive adhesive composition to paper or the like. When the drying temperature is 80 ° C. or lower, it is difficult to dry, and it takes a long time to dry. On the other hand, drying at a temperature higher than 120 ° C. is not preferable because it causes thermal deterioration of the substrate or the peelable sheet.
When the pressure-sensitive adhesive composition is applied on a paper or film substrate, it is bonded to the peelable sheet after drying. When the pressure-sensitive adhesive composition is applied to the peelable sheet, the paper or film base is dried. By adhering to the material, various adhesive coated products can be obtained by either method.
The peelable sheet is also referred to as a separator, and is formed by peeling at least one surface of paper or a plastic film. A conventionally known release treatment agent can be used.

The present invention will be described below with reference to examples, but is not limited thereto. In the examples, “part” means “part by weight” and “%” means “% by weight”.
(Example-1)
93.7 parts of 2-ethylhexyl acrylate, 5 parts of methyl methacrylate, 1 part of acrylic acid, 0.3 part of diacetone acrylamide, reactive ammonia neutralization type anionic emulsifier for 100 parts of all ethylenically unsaturated monomers As a solution, 2 parts of “AQUALON KH-10” manufactured by Daiichi Kogyo Seiyaku Co., Ltd. dissolved in 30.2 parts of deionized water were added and stirred to obtain an emulsion, which was placed in a dropping funnel.
A four-necked flask equipped with a stirrer, a condenser, a thermometer and the above dropping funnel was charged with 43.9 parts of deionized water and 0.1 part of Aqualon KH-10, and the inside of the flask was replaced with nitrogen gas. While stirring, the internal temperature was raised to 80 ° C., and 0.15 part of 3% potassium persulfate aqueous solution was added as a solid content. After 5 minutes, dropping of the emulsion was started from the dropping funnel, and in parallel with this, 0.45 part of 3% potassium persulfate aqueous solution was added dropwise from another dropping port over 3 hours.
While maintaining the internal temperature at 80 ° C., 30 minutes after the completion of dropwise addition of the above emulsion and 3% aqueous potassium persulfate solution, 0.06 parts were divided into two portions each containing 30% aqueous 3% potassium persulfate solution every 30 minutes. Added.
The mixture was further aged at 80 ° C. for 2 hours with stirring, then cooled and neutralized with aqueous ammonia to obtain an aqueous resin composition dispersion for pressure-sensitive adhesive having a solid content of 51%.
This aqueous resin composition for pressure-sensitive adhesives was taken out of the reaction vessel, and 100 parts thereof were charged into a mixing apparatus equipped with a stirrer and stirred as a pluronic type nonionic surfactant manufactured by Asahi Denka Kogyo Co., Ltd. 1 part of "Adekapluronic L-61" (average molecular weight = 2000, average molecular weight of polypropylene oxide part = 1750, ratio of ethylene oxide part to the whole molecule = 12% by weight), antifoaming agent, leveling agent, preservative In addition, the pH is adjusted to 7.5 to 8 with aqueous ammonia, and 10 parts as solid content of “Superester E-720” (solid content 50%) manufactured by Arakawa Chemical Co., Ltd. as a rosin-based tackifying resin, In addition, 0.1 part of a 6% adipic acid dihydrazide aqueous solution as a cross-linking agent was added as a solid content, and a viscosity modifier of 3000 mPa · s ( L-type viscometer, # 4 rotor used to adjust the measurement) at 60 rpm, to obtain an aqueous PSA composition.
This was coated on a release paper with a comma coater so that the dry coating amount was 20 g / m ² , dried in a drying oven at 100 ° C. for 40 seconds, laminated with a PET film having a thickness of 50 μm, wound up, and adhered. An agent coating was obtained.

(Example-2)
“Adeka Pluronic L-64” (average molecular weight = 2900, average of polypropylene oxide part) manufactured by Asahi Denka Kogyo Co., Ltd. as a pluronic type nonionic surfactant instead of “Adeka Pluronic L-61” used in Example-1 An aqueous pressure-sensitive adhesive composition and a pressure-sensitive adhesive coated product were obtained in the same manner as in Example 1 except that 2 parts of molecular weight = 1750 and the ratio of ethylene oxide part to the whole molecule = 40% by weight were used.

(Example-3)
93.7 parts of butyl acrylate, 5 parts of methyl methacrylate, 1 part of acrylic acid, 0.3 part of diacetone acrylamide, 2 parts of “Aqualon KH-10” are deionized to 100 parts of all ethylenically unsaturated monomers What was dissolved in 30.2 parts of water was added and stirred to obtain an emulsion, which was placed in a dropping funnel.
A four-necked flask equipped with a stirrer, a condenser, a thermometer and the above dropping funnel was charged with 43.9 parts of deionized water and 0.1 part of Aqualon KH-10, and the inside of the flask was replaced with nitrogen gas. While stirring, the internal temperature was raised to 80 ° C., and 0.15 part of 3% potassium persulfate aqueous solution was added as a solid content. After 5 minutes, dropping of the emulsion was started from the dropping funnel, and in parallel with this, 0.45 part of 3% potassium persulfate aqueous solution was added dropwise from another dropping port over 3 hours.
While maintaining the internal temperature at 80 ° C., 30 minutes after the completion of dropwise addition of the above emulsion and 3% aqueous potassium persulfate solution, 0.06 parts were divided into two portions each containing 30% aqueous 3% potassium persulfate solution every 30 minutes. Added.
The mixture was further aged at 80 ° C. for 2 hours with stirring, then cooled and neutralized with aqueous ammonia to obtain an aqueous resin composition dispersion for pressure-sensitive adhesive having a solid content of 51%.
This resin composition aqueous dispersion for pressure-sensitive adhesive was taken out of the reaction vessel, 100 parts thereof were charged into a mixing apparatus equipped with a stirrer, and 2 parts of “Adeka Pluronic L-61” were added while stirring. Thereafter, an aqueous pressure-sensitive adhesive composition and a pressure-sensitive adhesive coated material were obtained in the same manner as Example 1.

(Comparative Example-1)
An aqueous pressure-sensitive adhesive composition and a pressure-sensitive adhesive coated product were obtained in the same manner as in Example 1 except that “Adeka Pluronic L-61” was not added in Example-1.

(Comparative Example-2)
9A part of 2-ethylhexyl acrylate, 5 parts of methyl methacrylate, 1 part of acrylic acid, 0.3 part of diacetone acrylamide, "AQUALON KH-10" 0.6 against 100 parts of these all ethylenically unsaturated monomers A part dissolved in 30.2 parts of deionized water was added and stirred to obtain an emulsion. Thereafter, an aqueous pressure-sensitive adhesive composition and a pressure-sensitive adhesive coated material were obtained in the same manner as in Comparative Example-1.

(Comparative Example-3)
"Aqualon KH-10" 2 for 94.3 parts of 2-ethylhexyl acrylate, 5 parts of methyl methacrylate, 0.4 part of acrylic acid, 0.3 part of diacetone acrylamide and 100 parts of these all ethylenically unsaturated monomers A part dissolved in 30.2 parts of deionized water was added and stirred to obtain an emulsion. Thereafter, an aqueous pressure-sensitive adhesive composition and a pressure-sensitive adhesive coated material were obtained in the same manner as in Comparative Example-1.

[Test method]
1) Polymerization stability Visual evaluation of the amount of agglomerates adhering to the inner wall of the container and the stirring blade when the resin composition aqueous dispersion for pressure-sensitive adhesive obtained in each Example and Comparative Example was taken out from the reaction container. Judged by.
○: There is almost no aggregate.
Δ: Some agglomerates are seen on the inner wall of the reaction vessel, and adhesion is also seen on the stirring blades.
X: A large amount of agglomerates adhere to almost the entire inner wall of the reaction vessel and the stirring blades.

2) Mechanical stability test 5 g of water was added to 50 g of the aqueous pressure-sensitive adhesive composition obtained in each of the examples and comparative examples and diluted, and 50 g of that was used as a test sample. Using a Marlon mechanical stability tester, a sample was mechanically loaded under a load of 15 kg for 10 minutes, filtered through a 300-mesh wire mesh, and the coagulum remaining on the wire mesh after drying was removed. The weight was measured, and the coagulation rate (%) was calculated by the following formula.
Coagulation rate (%) = weight of coagulum / weight of test sample × 100
A higher coagulation rate means inferior mechanical stability of the pressure-sensitive adhesive composition.

3) Measurement of water whitening resistance The release paper of the pressure-sensitive adhesive coated product was peeled off, laminated with a PET film on which both sides were vapor-deposited with aluminum, immersed in water, and left in a 60 ° C. atmosphere for 72 hours. After the elapse of a predetermined time, the whiteness of the film was evaluated by wiping off water and using a spectrocolorimeter and measuring the L value of the surface on the side where the pressure-sensitive adhesive layer exists by a reflection method.
The higher the numerical value, the more the whitening is progressing, which means that the appearance is poor.
Table 1 shows the evaluation results of measurement of polymerization stability, mechanical stability, and water whitening resistance.

As shown in Comparative Example-1, when the block copolymer (B) is not used, the water whitening resistance of the pressure-sensitive adhesive coated product is extremely inferior to the examples. Further, as shown in Comparative Examples-2 and 3, respectively, when the amount of the emulsifier used in the polymerization is reduced to one third with respect to Comparative Example-1, or a component for imparting water affinity to the polymer. When the amount of acrylic acid used is reduced to less than half, water whitening resistance tends to be slightly improved, but it still does not reach the measured value in the examples of the present invention, and further, polymerization stability and mechanical stability In addition to being extremely uneconomical, causing industrial decline in yield and filterability, it is uneconomical, and agglomerates are likely to occur due to the mechanical shearing force applied from the coating equipment during the application of the adhesive. The risk of causing problems such as rough surfaces and clogged piping is increased.
On the other hand, as shown in the Examples, water whitening resistance is achieved by adding the block copolymer (B) as an essential component to the aqueous resin composition dispersion (A) for the pressure-sensitive adhesive to produce a pressure-sensitive adhesive composition. It can be used for labeling and overlaminating applications that require particularly good design, and when the substrate on which the adhesive is applied is transparent and the adhesive layer is visible from the outside, its surface is Even if it is immersed in water or exposed to high humidity, the pressure-sensitive adhesive layer is not easily whitened, so that the design can be maintained without impairing the appearance.

Claims (6)

Resin composition aqueous dispersion (A) obtained by polymerizing an ethylenically unsaturated monomer capable of radical polymerization in an aqueous medium containing an emulsifier, a polymerization initiator, and water as essential components, and a repeating unit A polyalkylene oxide (b-1) in which the number of carbon atoms in the n is n (n represents an integer of 1 or more), and a polyalkylene oxide (b-2) in which the number of carbon atoms in the repeating unit is (n + 1); An aqueous pressure-sensitive adhesive composition comprising the block copolymer (B) as an essential component. 2. The aqueous pressure-sensitive adhesive composition according to claim 1, wherein n of the block copolymer (B) is n = 2. The block copolymer (B) has a linear structure and has a structure in which the (b-1) part is bonded to both ends of the (b-2) part and both ends are hydroxyl groups. The aqueous pressure-sensitive adhesive composition according to claim 1 or 2. The aqueous pressure-sensitive adhesive composition according to any one of claims 1 to 3, wherein the block copolymer (B) has an average molecular weight of 1000 to 6000. The average molecular weight of the (b-2) part in the block copolymer (B) is 900 to 3000, and the ratio of the (b-1) part to the whole (B) is 5 to 50% by weight. The aqueous pressure-sensitive adhesive composition according to claim 1, wherein: 6. The aqueous composition according to claim 1, wherein 0.01 to 20 parts by weight of the block copolymer (B) is mixed with 100 parts by weight of the aqueous resin composition dispersion for pressure-sensitive adhesive (A). Adhesive composition.