JP2005281548A - Repeelable aqueous pressure-sensitive adhesive composition and pressure-sensitive adhesive product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a repeelable aqueous pressure-sensitive adhesive composition having an excellent pressure-sensitive adhesiveness, easily peelable from a surface of an adherend even when being left to stand for a long period after sticking it to the adherend, and also excellently exhibiting resistance to whitening by water even when being used in the field of necessitating resistance to whitening by water. <P>SOLUTION: The repeelable aqueous pressure-sensitive adhesive composition is obtained by emulsion polymerization by charging a monomer component composed mainly of a (meth)acrylate at one time into a hermetically sealed pressure vessel reactor including an aqueous medium therein, and is composed of polymer particles [X] having ≤300 nm average particle diameter and constituted of a polymer having carbonyl and carboxy groups, and 3-30 acid value, and a hydrazine derivative [Y] having at least two hydrazino groups in the molecule. A film formed from the adhesive composition is characterized by the followings: a glass transition temperature is ≤-25°C; a gel fraction is ≥80 wt.%; and an amount of a water extract is ≤2 wt.%. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a re-peelable aqueous pressure-sensitive adhesive composition having excellent pressure-sensitive adhesive properties and re-peelability, and a pressure-sensitive adhesive product obtained by applying the same to a substrate.

  Adhesive labels are used in various fields, and some of them are used to be peeled off from an adherend after a predetermined time has elapsed since being attached to the adherend. At this time, a part of the pressure-sensitive adhesive often remains on the adherend. In addition, when the base material is paper, the strength of the paper is weak, so it is often difficult to tear the paper and remove it from the adherend. There has been proposed a re-peelable pressure-sensitive adhesive that can be easily peeled off from an adherend without such a situation.

  In recent years, the shift from solvent-based resins to water-based resins has progressed in view of environmental problems. In the field of pressure-sensitive adhesives, it is desired to replace solvent-based pressure-sensitive adhesives with water-based pressure-sensitive adhesives. A typical example of this aqueous adhesive is an emulsion-type aqueous adhesive obtained by polymerizing various ethylenically unsaturated monomers. However, emulsion-type water-based pressure-sensitive adhesives are easily whitened when they come into contact with water, that is, they have a low water whitening resistance, and are therefore a big problem in replacing solvent-type pressure-sensitive adhesives. In particular, when replacing the solvent-type pressure-sensitive adhesive conventionally used for transparent film label applications with an emulsion-type water-based pressure-sensitive adhesive, improvement of water whitening resistance is a problem.

  Therefore, reduce the low molecular weight component in the water-dispersed acrylic polymer as much as possible, improve the adhesion failure to the adherend due to the low molecular weight component at the time of adhesion for a long time, and when peeling again after adhering to the adherend As a measure for improving the contamination on the adherend, the relationship of log M> 3 log S-2, where S is the soluble fraction (%) in tetrahydrofuran and M is the weight average molecular weight (10,000) of the soluble fraction. An aqueous pressure-sensitive adhesive composition characterized by satisfying the above requirements is disclosed (for example, see Patent Document 1). However, the pressure-sensitive adhesive having such characteristics not only does not provide sufficient performance due to removability, but is also notable for water whitening resistance, which is the biggest problem of emulsion-type aqueous pressure-sensitive adhesives. is there.

JP-A-7-228612

  The object of the present invention is excellent in adhesiveness, can be easily peeled off from the adherend surface even after being left for a long time after being attached to the adherend, and is further used in fields where water whitening resistance is required. In such a case, the present invention also provides a re-peelable water-based pressure-sensitive adhesive composition and a pressure-sensitive adhesive product that exhibit excellent water whitening resistance.

As a result of earnest examination to solve the problem, the following knowledge was obtained.
(1) The aqueous extract amount of the film formed from the aqueous pressure-sensitive adhesive composition is 2% by weight or less, and consists of a polymer having a carbonyl group and a carboxyl group dispersed in an aqueous medium and having an acid value of 3 to 30. Water-whitening resistance is improved when the average particle diameter is polymer particles [X] of 300 nm or less.
(2) The polymer particles obtained by subjecting the aqueous pressure-sensitive adhesive composition to emulsion polymerization by collectively charging a monomer component mainly composed of (meth) acrylate into a closed pressure reaction vessel in which an aqueous medium is present. When the gel fraction of the film formed of [X] and the compound [Y] having at least two hydrazino groups and formed from the aqueous pressure-sensitive adhesive composition is 80% by weight or more, removability is obtained. improves.
(3) When the glass transition temperature of the film is −25 ° C. or lower, the balance between the removability of the pressure-sensitive adhesive film and the adhesive force is good.

  The present invention is based on such knowledge. That is, the present invention relates to an acid value containing a carbonyl group and a carboxyl group by collectively charging a monomer component mainly composed of (meth) acrylate into a closed pressure reaction vessel in which an aqueous medium is present and emulsion polymerization. A re-peelable water-based pressure-sensitive adhesive composition comprising polymer particles [X] having an average particle size of 300 nm or less and a hydrazine derivative [Y] having at least two hydrazino groups in the molecule The film formed from the re-peelable water-based pressure-sensitive adhesive composition has a glass transition temperature of −25 ° C. or lower, a gel fraction of 80% by weight or higher, and an amount of water extract of 2 Provided is a re-peelable water-based pressure-sensitive adhesive composition characterized in that the content is not more than wt%.

  Moreover, this invention also provides the adhesive product comprised from a base material and the layer of said re-peelable water-based adhesive composition.

  According to the present invention, a re-peelable water-based pressure-sensitive adhesive composition having excellent water whitening resistance, adhesive strength, and re-peelability can be provided. The pressure-sensitive adhesive product of the present invention is excellent in water whitening resistance, adhesive strength, and removability, and is suitable as a pressure-sensitive adhesive label, pressure-sensitive adhesive tape, special pressure-sensitive adhesive sheet, and the like.

  The content of the carboxyl group in the polymer particle [X] needs to be an amount in the range of 3 to 30 as the acid value. If the acid value is in the range, the polymer particle [X] It is possible to impart dispersion stability in an aqueous medium, re-peelability of the pressure-sensitive adhesive film and adhesive force in a well-balanced manner, and improve water whitening resistance. When the acid value is less than 3, the adhesive strength decreases, and when the acid value exceeds 30, the adhesive force increases with time, and the removability decreases.

  Further, the average particle size of the polymer particles [X] used in the present invention is required to be 300 nm or less in order to obtain a re-peelable water-based pressure-sensitive adhesive exhibiting good water whitening resistance. When the average particle diameter exceeds 300 nm, the water whitening resistance is lowered, which is not preferable. Among these, 10 to 300 nm is particularly preferable. Here, the average particle diameter of the particles refers to the 50% median diameter of the emulsion particles on the volume basis, and the numerical values are based on values obtained by measurement by the dynamic light scattering method described in Examples below.

  Moreover, the gel fraction of the film formed from the re-peelable water-based pressure-sensitive adhesive composition of the present invention is required to be 80% by weight or more from the balance between the adhesive strength of the pressure-sensitive adhesive and the re-peelability. When the gel fraction is less than 80% by weight, the removability is lowered, which is not preferable. Among these, it is usually preferable to control at 85 to 98%. The said gel fraction means the ratio of the insoluble content with respect to the toluene of the film | membrane of an aqueous adhesive composition. A gel fraction is based on the numerical value calculated | required by the measuring method and formula described in the postscript Example.

  Moreover, the amount of the water extract formed from the re-peelable aqueous pressure-sensitive adhesive composition of the present invention needs to be 2% by weight or less. The smaller the amount of water extract, the better, and it is usually preferable to control the amount to 0.1 to 1.8% by weight. When the amount of the water extract exceeds 2% by weight, the water whitening resistance of the re-peelable water-based pressure-sensitive adhesive film is lowered, which is not preferable.

  Therefore, in order to have good water whitening resistance, the average particle diameter of the polymer particles [X] is 300 nm or less, and the amount of water extract formed from the re-peelable aqueous pressure-sensitive adhesive composition is 2 wt% or less. It is necessary to be.

  Next, the film formed from the re-peelable aqueous pressure-sensitive adhesive composition of the present invention needs to have a glass transition temperature (hereinafter referred to as Tg) of −25 ° C. or lower. When the Tg is within this range, the physical properties of the pressure-sensitive adhesive, that is, the balance of physical properties such as adhesive strength and holding power are excellent. When Tg exceeds −25 ° C., the adhesive force necessary for the re-peelable aqueous pressure-sensitive adhesive cannot be obtained, which is not preferable. Furthermore, it is especially preferable that it is -25--60 degreeC. Here, Tg in this invention is based on the numerical value obtained by the measuring method described in the postscript Example.

  Next, the re-peelable aqueous pressure-sensitive adhesive composition of the present invention can be obtained, for example, by emulsion copolymerization of monomer components described later. Specifically, the polymer of the polymer particles [X] is (a) at least one carbonyl group-containing ethylenically unsaturated monomer in the molecule, 0.1 to 2 wt. %, (B) carboxyl group-containing ethylenically unsaturated monomer, 0.5 to 4% by weight, and (c) alkyl (meth) acrylate having an alkyl group having 4 to 12 carbon atoms, 45 to 99. Examples thereof include a copolymer obtained by copolymerizing a polymerizable monomer mixture containing 4% by weight as an essential component. Under the present circumstances, you may use together unsaturated monomer (d) other than said (a)-(c) as needed in 0.001-55 weight%.

  The carbonyl group-containing ethylenically unsaturated monomer (a) is not particularly limited, and has a functional group having reactivity with the hydrazino group of the hydrazine derivative [Y] described above. For example, acrolein, diacetone Examples include acrylamide, formylstyrene, vinyl ethyl ketone, acetoacetoxyethyl (meth) acrylate, diacetone (meth) acrylate, acetonyl acrylate, 2-hydroxypropyl acrylate-acetyl acetate, butanediol-1,4-acrylate-acetyl acetate, and the like. It is done. In particular, it is preferable to use diacetone acrylamide because the adhesive strength and removability of the pressure-sensitive adhesive can be imparted with a good balance. The amount of the carbonyl group-containing ethylenically unsaturated monomer used is preferably in the range of 0.1 to 2% by weight, particularly preferably 0.2 to 2% by weight. When in this range, good removability can be imparted.

  Next, as an ethylenically unsaturated monomer (b) which has a carboxyl group, if it has a carboxyl group and an ethylenically unsaturated group in a molecule | numerator, it will not be specifically limited, It can use. Examples of the ethylenically unsaturated monomer include acrylic acid, methacrylic acid, β-carboxyethyl (meth) acrylate, 2- (meth) acryloylpropionic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, and itacone. Acid half ester, maleic acid half ester, maleic anhydride, itaconic anhydride, ω-carboxy-polycaprolactone (meth) acrylate, β- (meth) acryloyloxyethyl hydrogen succinate, β- (meth) hydroxyethyl hydrogen phthalate, And salts thereof and the like, and one or a mixture of two or more thereof can be used. Among these, methacrylic acid is preferably used in terms of excellent stability during polymerization of the monomer component and excellent water whitening resistance. The amount of the ethylenically unsaturated monomer having a carboxyl group used is preferably 0.5 to 4% by weight, particularly preferably 0.5 to 3% by weight. When it exists in this range, adhesive force and removability can be provided with good balance.

  Examples of the alkyl (meth) acrylate (c) having an alkyl group having 4 to 12 carbon atoms include n-butyl (meth) acrylate, i-butyl (meth) acrylate, n-hexyl (meth) acrylate, n-octyl (meth) acrylate, i-octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-nonyl (meth) acrylate, i-nonyl (meth) acrylate, n-decyl (meth) acrylate, n- A lauryl (meth) acrylate etc. can be mentioned, The 1 type (s) or 2 or more types of mixture can be used. Among these, an alkyl (meth) acrylate having an alkyl group having 4 to 9 carbon atoms is preferable because of good polymerizability. The amount of the alkyl (meth) acrylate having an alkyl group having 4 to 12 carbon atoms used is preferably 45 to 99.4% by weight, particularly preferably 64 to 95% by weight. . When it exists in this range, since Tg of the adhesive film mentioned above can be adjusted to a desired range and an adhesive physical property can be provided with sufficient balance, it is preferable.

  Examples of the unsaturated monomer (d) other than (a) to (c) include methyl (meth) acrylate, ethyl (meth) acrylate, t-butyl (meth) acrylate, and stearyl (meth) acrylate. , (Meth) acrylic esters such as phenyl (meth) acrylate and benzyl (meth) acrylate; 2,2,2-trifluoroethyl (meth) acrylate, 2,2,3,3-pentafluoropropyl (meth) Fluorine-containing ethylenically unsaturated monomers such as acrylate, perfluorocyclohexyl (meth) acrylate, 2,2,3,3-tetrafluoropropyl (meth) acrylate, β- (perfluorooctyl) ethyl (meth) acrylate Vinyl acetate, vinyl propionate, vinyl butyrate, vinyl versatate, etc. Nyl esters; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, amyl vinyl ether, hexyl vinyl ether; nitrile group-containing ethylenically unsaturated monomers such as (meth) acrylonitrile; styrene, α-methylstyrene, vinyl Vinyl compounds having an aromatic ring such as toluene, vinylanisole, α-halostyrene, vinylnaphthalene, divinylstyrene; isoprene, chloroprene, butadiene, ethylene, tetrafluoroethylene, vinylidene fluoride, N-vinylpyrrolidone and the like. The amount of these substances used is preferably 0.1 to 55% by weight, particularly preferably 5 to 55% by weight.

  Among these, it is preferable to use (meth) acrylic acid esters in terms of excellent stability during polymerization of the monomer component.

  Moreover, as unsaturated monomers (d) other than the above (a) to (c), for the purpose of improving the gel fraction of the releasable aqueous pressure-sensitive adhesive to a desired range, other than carbonyl group and carboxyl group It is also possible to use an ethylenically unsaturated monomer containing a crosslinkable reactive group. Examples of these include glycidyl group-containing polymerizable monomers such as glycidyl (meth) acrylate and allyl glycidyl ether; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, polyethylene glycol mono (meth) Hydroxyl group-containing polymerizable monomers such as acrylate and glycerol mono (meth) acrylate; amino such as aminoethyl (meth) acrylate, N-monoalkylaminoalkyl (meth) acrylate, and N, N-dialkylaminoalkyl (meth) acrylate Group-containing polymerizable monomer: methylol amide such as N-methylol (meth) acrylamide, N-isopropoxymethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, N-isobutoxymethyl (meth) acrylamide Group or an alkoxylate-containing polymerizable monomer; vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (β-methoxyethoxy) silane, γ- (meth) acryloxypropyltrimethoxysilane, γ- ( (Meth) acryloxypropyltriethoxysilane, γ- (meth) acryloxypropylmethyldimethoxysilane, γ- (meth) acryloxypropylmethyldiethoxysilane, γ- (meth) acryloxypropyltriisopropoxysilane, N-β Silyl group-containing polymerizable monomers such as-(N-vinylbenzylaminoethyl) -γ-aminopropyltrimethoxysilane and its hydrochloride; aziridinyl group-containing polymerizable monomers such as 2-aziridinylethyl (meth) acrylate Mer; (meth) acryloyl isocyana Isocyanate- and / or blocked isocyanate group-containing polymerizable monomers such as phenol or methyl ethyl ketoxime adduct of (meth) acryloyl isocyanate ethyl; 2-isopropenyl-2-oxazoline, 2-vinyl-2 -Oxazoline group-containing polymerizable monomers such as oxazoline; Amide group-containing polymerizable monomers such as (meth) acrylamide, N-monoalkyl (meth) acrylamide, N, N-dialkyl (meth) acrylamide; Dicyclopentenyl Examples include cyclopentenyl group-containing polymerizable monomers such as (meth) acrylate; allyl group-containing polymerizable monomers such as allyl (meth) acrylate. The amount of these substances used is preferably 0.001 to 20% by weight, particularly preferably 0.01 to 10% by weight.

  Further, the crosslinkable reactive group of the polymer composed of these monomer components is used to crosslink between the polymers, so that the gel fraction of the film formed from the re-peelable aqueous pressure-sensitive adhesive composition described later can be 80 wt. % Or more can be adjusted.

  Moreover, as unsaturated monomer (d) other than said (a)-(c), in order to improve the gel fraction of a releasable water-based adhesive to a desired range, two in a molecule | numerator Polyfunctional ethylenically unsaturated monomers containing the above ethylenically unsaturated groups can also be used. For example, ethylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol Examples include di (meth) acrylate, diallyl phthalate, divinylbenzene, allyl (meth) acrylate, and the like. The amount of these substances to be used is preferably 0.001 to 10% by weight, particularly preferably 0.001 to 5% by weight.

  When these polyfunctional ethylenically unsaturated monomers are used, the cohesive force of the pressure-sensitive adhesive is improved and the holding power is good, but in order to make the balance between the adhesive force and the holding power good, As described above, the polyfunctional ethylenically unsaturated monomer is preferably used in such an amount that the gel fraction of the pressure-sensitive adhesive film is 80% by weight or more. The amount of these substances used is preferably 0.001 to 10% by weight, particularly preferably 0.5 to 5% by weight.

  Further, as the unsaturated monomer (d) other than the above (a) to (c), the releasable aqueous pressure-sensitive adhesive obtained for the purpose of improving the stability during emulsion polymerization and the storage stability of the emulsion. Ethylenic unsaturation containing sulfonic acid groups and / or sulfate groups (and / or salts thereof), phosphoric acid groups and / or phosphate ester groups (and / or salts thereof) within a range not deteriorating the water whitening resistance of A monomer can be used in combination. Examples of the unsaturated monomer (d) include vinyl sulfonic acids such as vinyl sulfonic acid and styrene sulfonic acid or salts thereof, allyl group-containing sulfonic acids such as allyl sulfonic acid and 2-methylallyl sulfonic acid, or the like. Its salts, (meth) acrylate group-containing sulfonic acids such as 2-sulfoethyl (meth) acrylate, 2-sulfopropyl (meth) acrylate or salts thereof, (meth) such as (meth) acrylamide-t-butylsulfonic acid Examples thereof include acrylamide group-containing sulfonic acids or salts thereof, “Adekaria Soap PP-70, PPE-710” (manufactured by Asahi Denka Kogyo Co., Ltd.) having a phosphate group, and one or a mixture of two or more of these. Can be used. The amount of these substances used is preferably 0.1 to 2% by weight, particularly preferably 0.1 to 1% by weight.

  Next, the manufacturing method for obtaining the aqueous pressure-sensitive adhesive composition of the present invention will be described. The re-peelable aqueous pressure-sensitive adhesive composition of the present invention includes, for example, the aforementioned carbonyl group-containing ethylenically unsaturated monomer (a), an ethylenically unsaturated monomer (b) containing a carboxyl group, and a carbon atom. It is obtained by emulsion copolymerization of an alkyl (meth) acrylate (c) having an alkyl group having 4 to 12 numbers and other ethylenically unsaturated monomer (d).

  In general, the production method for obtaining a water-dispersed acrylic polymer by emulsion polymerization is as follows: (1) Polymerization by mixing water, an ethylenically unsaturated monomer, a polymerization initiator, and if necessary, an emulsifier and a dispersion stabilizer. And (2) a so-called pre-emulsion method in which water, an ethylenically unsaturated monomer, and an emulsifier previously mixed are dropped, and (3) a monomer dropping method. The production method of the present invention is classified into (1) a method in which water, an ethylenically unsaturated monomer, a polymerization initiator, and if necessary, an emulsifier and a dispersion stabilizer are mixed and polymerized.

  As a method for polymerizing by mixing water, an ethylenically unsaturated monomer, a polymerization initiator and, if necessary, an emulsifier and a dispersion stabilizer as described above, for example, as a water-soluble radical polymerization initiator, 2, 2- Using a low decomposition temperature such as azobis [2- (2-imidazolin-2-yl) propane], which is used at 0.001 to 0.05% by weight with respect to 100% by weight of the monomer component, In addition, there is a method for producing an aqueous pressure-sensitive adhesive composition, wherein emulsion polymerization is carried out by setting the polymerization temperature to substantially 20 to 60 ° C. This method requires a long reaction time to control the polymerization exotherm.

However, the production method of the present invention is a production method in which a monomer component mainly composed of (meth) acrylate is collectively charged into a closed pressure reaction vessel in which an aqueous medium is present and emulsion polymerization is performed. The time required for the polymerization conversion to reach 95% is substantially within 180 minutes. The manufacturing method of this aqueous pressure-sensitive adhesive composition, that is, the manufacturing method of the present invention is remarkably superior in terms of production efficiency as compared with the above-described method for controlling the polymerization heat generation.

Specifically, the re-peelable water-based pressure-sensitive adhesive composition of the present invention includes, for example, the aforementioned carbonyl group-containing ethylenically unsaturated monomer (a) and an ethylenically unsaturated monomer containing a carboxyl group ( b), an alkyl (meth) acrylate (c) having an alkyl group having 4 to 12 carbon atoms, and another ethylenically unsaturated monomer (d) are placed in a closed pressure reaction vessel in which an aqueous medium is present. Obtained by batch charging and emulsion polymerization. Furthermore, this production method is characterized in that the time required for the polymerization conversion rate of the monomer component to reach 95% is substantially within 180 minutes.

The polymerization conversion rate of the monomer component in the present invention is the total charge of the monomer component (that is, the weight when all the monomers are converted into a polymer) and the solid content weight in the water-dispersed acrylic polymer. It is the value calculated | required by calculation from, and is calculated | required by the following formula.

Polymerization conversion rate (%)
= 100 x (solid content concentration of water-dispersed acrylic polymer: measured value (%)-solid content concentration of raw material other than monomer component: calculated value (%)) / concentration of monomer component with respect to all charged raw materials :Calculated values(%)

The time required for the polymerization conversion rate of the monomer component to reach 95% refers to the contents in the reaction vessel in order starting from the time when the polymerization exotherm is observed after adding the polymerization initiator to the reaction vessel. The polymerization conversion rate is obtained from the above-mentioned formula by sampling the product, and indicates the time required for the polymerization conversion rate to reach 95%.
The purpose of the present invention is to efficiently produce a water-dispersed acrylic polymer, and therefore the time required for the polymerization conversion rate of the monomer component to reach 95% is preferably within 180 minutes. .

Here, the aqueous pressure-sensitive adhesive composition of the present invention has isoprene, chloroprene, butadiene, ethylene, tetrafluoroethylene, fluorine as ethylenically unsaturated monomers (d) other than (a), (b), and (c). As described above, vinylidene chloride, N-vinylpyrrolidone and the like can be used. However, in the case of using the production method of the present invention, it is necessary to consider that when a monomer other than these (meth) acrylates is used in combination, the polymerization rate during emulsion polymerization is not significantly reduced. That is, in the production method for obtaining the aqueous pressure-sensitive adhesive of the present invention, when the monomer component mainly composed of (meth) acrylate is emulsion-polymerized, the polymerization conversion rate of the monomer component reaches 95%. The time required for this is substantially within 180 minutes, and in order to increase productivity, it is preferable to use a combination of highly reactive monomer components.

  Next, the sealed pressure reaction vessel of the present invention refers to a pressure-resistant sealed reaction vessel such as an autoclave, and is preferably provided with a stirrer, a pressure increasing / decreasing device, and an inert gas inlet. Furthermore, when the material of the inner surface of the closed pressure reaction vessel is made of glass lining, the amount of aggregates generated during the emulsion polymerization of the monomer component is reduced, or the aggregates are difficult to adhere in the container. Or, even when aggregates adhere to the container, it is easy to remove the aggregates, the maintenance in the container is easy, and the productivity when water-dispersed acrylic polymer is continuously produced in the same sealed pressure reaction container (Time required for maintenance can be shortened) is preferable.

  In the present invention, the aqueous medium for emulsion polymerization of the monomer component is not particularly limited, but only water may be used, or a mixed solution of water and a water-soluble solvent may be used. May be. Examples of the water-soluble solvent used here include alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol, ethyl carbitol, ethyl cellosolve, and butyl cellosolve, and polar solvents such as N-methylpyrrolidone. A mixture of two or more can be used.

  The amount of the water-soluble solvent used in the case of using a mixture of water and the water-soluble solvent can be arbitrarily selected from the viewpoint of stability during polymerization, but there is a risk of ignition of the resulting polymer aqueous dispersion. From the viewpoints of safety and health and safety, it is preferable to reduce the amount of water-soluble solvent used as much as possible. For these reasons, it is particularly preferable to use water alone.

  Further, in the production method of the present invention, when an aqueous medium in which the polymer particles [A] having an average particle diameter of 10 to 300 nm are dispersed is used as the aqueous medium, the amount of aggregates generated during emulsion polymerization is greatly reduced. This is preferable because it can be suppressed to a small extent and the particle diameter of the obtained water-dispersed acrylic polymer can be easily controlled within a practical range (50 to 1000 nm). Water-dispersed acrylic polymers generally increase in viscosity when the particle size decreases, so to obtain water-dispersed acrylic polymers with a high solid content, the particle size should be controlled to a certain size. is required.

  Here, the solid content concentration of the water-dispersed acrylic polymer of the present invention is not particularly limited, but the operability during production and transportation costs and the aqueous pressure-sensitive adhesive composition are used after being dried. From the viewpoint of excellent dryness, the solid content is preferably 40 to 70% by weight.

  The type of the polymer particles [A] is not particularly limited. For example, a polymer obtained by radical polymerization of an ethylenically unsaturated monomer such as an acrylic polymer or a butadiene polymer (hereinafter referred to as a polymer) , An ethylenic polymer), a polyurethane resin and a polyester resin containing a polymer having a urea bond and a urethane bond. In addition, a mixture of these various polymers, for example, an acrylic polymer / polyurethane resin mixture, a grafted (blocked) product of various polymers, for example, an unsaturated polyester polymer or an alkyd resin, Examples include grafted products. In particular, the polymer particle [A] is preferably an ethylenic polymer from the viewpoint that the adjustment of the particle diameter and the polymer design are easy and the polymer particle [A] can be easily produced by the method described later. In particular, when the polymer particle [A] is an acrylic polymer obtained by emulsion polymerization of a monomer component mainly composed of (meth) acrylate in an aqueous medium, emulsification is performed in the presence thereof. Water-dispersed acrylic system that is compatible with the monomer component that contains (meth) acrylate as the main component and that is compatible with the polymer that is produced by the polymerization of the monomer component, and has good dispersion stability This is preferable because a polymer is easily obtained.

  The production method of polymer particles [A], which is an acrylic polymer, is as follows: (1) Raw materials such as water, monomer components, polymerization initiator, and (if necessary, emulsifier and dispersion stabilizer) are charged together. It can be produced by a polymerization method, (2) a so-called pre-emulsion method in which water, a monomer component and an emulsifier are mixed in advance, or (3) a monomer dropping method. Among these, the method of batch charging and polymerizing the raw materials of (1) is particularly preferable because the polymer particles [A] can be efficiently produced in a short time.

Moreover, what was illustrated as the above-mentioned monomer component can be used as (meth) acrylate and other monomers used in the case of superposition | polymerization.

  Furthermore, when producing the polymer particles [A] composed of an acrylic polymer, an emulsifier or other dispersion stabilizer may be used, or a polymerization initiator or a chain transfer agent may be used. it can. As these specific examples, those similar to those used at the time of emulsion polymerization of the monomer components described later can be used.

The ratio of the polymer particle [A] and the monomer component mainly composed of (meth) acrylate is not particularly limited, but the polymer particle [A] (weight of solid content) is based on weight. / Monomer component = in the range of 5/95 to 40/60, maintains high productivity at the time of emulsion polymerization of the monomer component, and suppresses the amount of agglomerates to stably disperse in water An acrylic polymer is preferable because it can be produced.

  Next, when the monomer component is emulsion-polymerized in an aqueous medium, it may be polymerized using an emulsifier or other dispersion stabilizer, if necessary, within a range not reducing the water resistance of the pressure-sensitive adhesive film. Can do. Further, as described above, when the monomer component is emulsion polymerized in the presence of the polymer particles [A], it is possible to stably emulsion polymerize without using an emulsifier and other dispersion stabilizers. In addition, when the obtained water-dispersed acrylic polymer is formed into a film, it is preferable because various physical properties such as water resistance of the film are improved.

  Here, as an emulsifier that can be used in the present invention, known anionic emulsifiers, nonionic emulsifiers, and cationic emulsifiers can be used. Examples of the anionic emulsifier used in the present invention include sulfates of higher alcohols and salts thereof, alkylbenzene sulfonates, polyoxyethylene alkylphenyl sulfonates, polyoxyethylene alkyl diphenyl ether sulfonates, alkyl diphenyl ether disulfonic acids. And nonionic emulsifiers include polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene diphenyl ether, polyoxyethylene-polyoxypropylene block copolymer Etc., and one or a mixture of two or more of these can be used.

  Furthermore, an emulsifier having a polymerizable unsaturated group in the molecule generally called “reactive emulsifier” can also be used. As reactive emulsifiers that can be used in the present invention, for example, “Latemul S-180” (manufactured by Kao Corporation) having a sulfonic acid group and a salt thereof, “Eleminol JS-2, RS-30” (Sanyo Chemical Industries ( "Aqualon HS-10, HS-20, KH-05, KH-10" (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), "Adekaria soap SE-10, SE-20, SR-10N, SR-20N "(Asahi Denka Kogyo Co., Ltd.), etc .;" New Frontier A-229E "having a phosphate group (Daiichi Kogyo Seiyaku Co., Ltd.), etc .; nonionic “AQUALON RN-10, RN-20, RN-30, RN-50, ER-10, ER-20, ER-30, ER-40” (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) etc. having a hydrophilic group One or a mixture of two or more of these can be used.

  Other dispersion stabilizers other than the emulsifier that can be used in the present invention include, for example, polyvinyl alcohol, fiber ether, starch, maleated polybutadiene, maleated alkyd resin, polyacrylic acid (salt), polyacrylamide. Synthetic or natural water-soluble polymer substances such as water-based acrylic resins, water-based polyester resins, water-based polyamide resins, and water-based polyurethane resins can be used, and one or a mixture of two or more of these can be used.

  The amount of the emulsifier and the dispersion stabilizer is preferably as small as possible from the viewpoint of the water resistance and adhesive strength of the resulting pressure-sensitive adhesive film, and the amount used is 2 with respect to the solid content of the polymer. It is preferable to set the weight% or less.

In the present invention, the monomer component is emulsion-polymerized using a sealed pressure reaction vessel. At that time, the emulsion polymerization is performed under the condition that the dissolved oxygen concentration in the liquid in the sealed pressure reaction vessel is 3 ppm or less. Inhibition of radical polymerization by oxygen can be avoided, and emulsion polymerization can proceed smoothly to produce a water-dispersed acrylic polymer efficiently. As a method for reducing the dissolved oxygen concentration in the liquid in the sealed reaction vessel, the aqueous medium, the monomer component, and the polymerization initiator are each reduced in a separate vessel, and then these are mixed together. , An aqueous medium, a monomer component, and a polymerization initiator are charged into a sealed pressure reaction vessel, and then a method of reducing dissolved oxygen is mentioned. A method can be appropriately selected according to the apparatus to be used. Also in this method, it is preferable that the dissolved oxygen concentration in the liquid in the closed pressure reaction vessel at the start of emulsion polymerization is 3 ppm or less. Specifically, the dissolved oxygen concentration in the liquid (a mixture of an aqueous medium or, in some cases, an aqueous medium containing polymer particles [A] or an emulsifier, a monomer component, and a polymerization initiator) is reduced. Specifically, (1) while stirring in the container, an inert gas is continuously blown or bubbled from one mouth of the container, and an inert gas and oxygen are blown out from the other mouth. (2) A method of lowering the dissolved oxygen concentration by boiling the liquid in the vessel once and then cooling it under an inert gas atmosphere. Examples of the method include reducing the dissolved oxygen concentration by lowering the partial pressure of oxygen in the container by lowering the pressure in the container after the inside of the container is stirred and pressurized with an inert gas. Among these, in order to reduce the dissolved oxygen in the liquid in the container, (3) the method of repeating the operation of lowering the pressure in the container after pressurizing and filling with an inert gas is efficient. Since dissolved oxygen can be reduced, it is preferable. The step of lowering the pressure in the container after pressurizing and filling with the inert gas is preferably repeated 2 to 10 times. The greater the number of repetitions of this step, the lower the dissolved oxygen concentration. Since the oxygen concentration is difficult to decrease, the efficiency is deteriorated.

  When the inert gas is pressure-filled into the sealed pressure reaction vessel, for example, the pressure is filled at 0.1 to 2.0 MPa, preferably 0.2 to 1.5 MPa. When the pressure is lower than this range, the number of repetitions may be increased to make the dissolved oxygen concentration 3 ppm or less, or it may not be possible to make it 3 ppm or less. Moreover, when lowering the pressure in the reaction vessel, for example, the pressure is reduced to -0.04 to -0.09 MPa. If the degree of vacuum is lower than this range, the number of repetitions may be increased to make the dissolved oxygen concentration 3 ppm or less, or the existing oxygen concentration may not be made 3 ppm or less. Furthermore, the pressure in the reaction vessel at the time of emulsion polymerization of the monomer component can be carried out by normal pressure or pressurization with an inert gas depending on the reaction temperature at the time of emulsion polymerization described later. . The pressure here does not mean an absolute pressure but a differential pressure obtained by setting the normal pressure to 0 MPa. Moreover, as inert gas, noble gases, such as nitrogen gas, helium, and argon, can be mentioned, You may use these 1 type or in mixture of 2 or more types. As the type of inert gas, nitrogen gas is particularly preferable from the viewpoints of economy and versatility. The purity of the inert gas is usually 95% or more, preferably 98% or more.

  In the present invention, since the monomer component is subjected to emulsion polymerization in a closed pressure reaction vessel, the temperature in the vessel at the time of emulsion polymerization is not particularly limited. For example, it is safe even under conditions that exceed the boiling point of water as a medium. It is possible to emulsion polymerize. In the case of a reaction vessel attached to a condenser, which is used when producing an ordinary acrylic polymer by emulsion polymerization, if the reaction vessel boils, the content may blow out from the reaction vessel, or the reaction vessel will boil. However, since a closed pressure reaction vessel is used in the present invention, these problems can be avoided. In particular, when emulsion polymerization is performed at a high temperature (a temperature higher than the boiling point of the mixture of the aqueous medium and the monomer component), if the reaction vessel is pressurized with an inert gas, boiling in the reaction vessel can be suppressed. From the viewpoint that the generation of aggregates can be prevented. The pressure when pressurizing with an inert gas to suppress boiling in the reaction vessel is the liquid in the reaction vessel at the highest temperature reached within the reaction vessel during emulsion polymerization (mixture of aqueous medium and monomer components). It is preferable to set the pressure to be equal to or higher than the vapor pressure, and if the pressure equal to or higher than the vapor pressure is maintained, boiling in the reaction vessel can be completely suppressed.

  In the present invention, as described above, the polymerization temperature at the time of emulsion polymerization is not limited, but it is preferable to start the emulsion polymerization from a low temperature, particularly when it is desired to increase the molecular weight of the resulting water-dispersed acrylic polymer. . Specifically, when emulsion polymerization is started from a temperature within the range of 10 to 50 ° C., a high molecular weight polymer is easily obtained. When the polymerization start temperature is lower than this range, it is difficult for the polymerization to proceed smoothly. On the other hand, when the polymerization start temperature is higher than this range, it may be difficult to obtain a high molecular weight polymer.

  As the polymerization initiator used in the emulsion polymerization in the present invention, a radical polymerization initiator is used. Examples of the radical polymerization initiator include persulfates, organic peroxides, hydrogen peroxide, and the like.

  In the emulsion polymerization of the monomer component, it can be obtained by radical polymerization using only these peroxides, or by a redox polymerization initiator in which a reducing agent is used in combination with the above peroxides.

  Furthermore, azo initiators such as 4,4'-azobis (4-cyanovaleric acid) and 2,2'-azobis (2-amidinopropane) dihydrochloride can also be used as the polymerization initiator. Among the polymerization initiators, in particular, a redox polymerization initiator using a combination of persulfates and / or organic peroxides and a reducing agent can smoothly promote emulsion polymerization even at a low temperature. Thus, when it is desired to obtain a high molecular weight water-dispersed acrylic polymer, it is preferable because emulsion polymerization can be started from a temperature within the range of 10 to 50 ° C. Furthermore, it is more preferable to use an organic peroxide polymerization initiator because the water whitening resistance of the pressure-sensitive adhesive film is remarkably improved.

  Specific examples of persulfates include potassium persulfate, sodium persulfate, and ammonium persulfate. Specific examples of organic peroxides include benzoyl peroxide, lauroyl peroxide, and decanoyl peroxide. Diacyl peroxides such as oxide, dialkyl peroxides such as t-butylcumyl peroxide and dicumyl peroxide, peroxyesters such as t-butylperoxylaurate and t-butylperoxybenzoate, cumene hydroper Examples thereof include hydroperoxides such as oxide, paramentane hydroperoxide, and t-butyl hydroperoxide.

  Examples of the reducing agent used in the above redox polymerization initiator system include ascorbic acid and its salt, erythorbic acid and its salt, tartaric acid and its salt, citric acid and its salt, metal salt of formaldehyde sulfoxylate, Examples include sodium thiosulfate, sodium bisulfite, and ferric chloride.

  These polymerization initiators may be used in amounts that allow the polymerization to proceed smoothly. However, if water resistance is required for the obtained water-dispersed acrylic polymer film or the like, the amount used is minimized. The amount used is preferably 0.3% by weight or less based on the weight of the monomer component (in the case of a redox polymerization initiator in combination with a reducing agent, the total amount of an oxidizing agent and a reducing agent) and It is preferable to do.

In the present invention, when it is necessary to adjust the molecular weight of the water-dispersed acrylic polymer, a compound having a chain transfer ability as a molecular weight adjusting agent in emulsion polymerization of the monomer component, for example, lauryl mercaptan, octyl mercaptan, Mercaptans such as dodecyl mercaptan, 2-mercaptoethanol, octyl thioglycolate, 3-mercaptopropionic acid, thioglycerin, or α-methylstyrene dimer may be added.

  The aqueous pressure-sensitive adhesive composition of the present invention thus obtained can be used by adding a water-soluble or water-dispersible crosslinking agent as necessary. In this case, examples of the crosslinking agent include a polyfunctional melamine compound, a polyfunctional polyamine compound, a polyfunctional polyethyleneimine compound, a polyfunctional (block) isocyanate compound, a metal salt compound, and the like. In addition to being able to be used as a mixture of two or more kinds, a water-soluble or water-dispersible thermosetting resin, for example, a phenol resin, a urea resin, a melamine resin, a urethane resin, etc. can be mixed and used. .

  Further, the re-peelable water-based pressure-sensitive adhesive composition of the present invention includes a filler, a pigment, a pH adjuster, a film forming aid, and a leveling agent described later, as long as the desired effect of the present invention is not impaired as necessary. Well-known ones such as thickeners, water repellents, tackifiers and antifoaming agents can be appropriately added and used.

  That is, in the production method for obtaining the aqueous pressure-sensitive adhesive composition of the present invention, as one of preferred methods, a monomer component mainly composed of (meth) acrylate is an acrylic having an average particle size of 10 to 300 nm. In a manufacturing method in which an aqueous medium in which an aqueous medium in which polymer particles [A] of a polymer are dispersed is present is charged all at once and emulsion polymerization is carried out, the dissolved oxygen concentration of the aqueous medium is 3 ppm or less, and as a polymerization initiator Using a redox peroxide polymerization initiator, starting the emulsion polymerization with the temperature at the start of polymerization within the range of 10 to 50 ° C., and the polymerization conversion rate of the monomer component reaches 95% And a method characterized in that the time required for the treatment is substantially 180 minutes or less.

  The re-peelable water-based pressure-sensitive adhesive composition of the present invention can be applied to various pressure-sensitive adhesive products, particularly products requiring water whitening resistance and re-peelability.

  When manufacturing an adhesive product (adhesive tape, adhesive label, etc.), a method of directly applying to a base material used for a tape or a label and then bonding to a release paper, and a base material after applying to a release paper and drying In particular, in the latter method, the releasable water-based adhesive is applied to the release paper, and the surface energy of the release paper is low. However, the re-peelable water-based pressure-sensitive adhesive has a problem that repelling and squeaking are likely to occur during coating. In order to suppress these phenomena, it is necessary to improve the wettability of the re-peelable water-based pressure-sensitive adhesive with respect to the release paper to obtain a smooth coated surface. Conventionally, the interface has been used as a wettability improver (hereinafter referred to as leveling agent). An activator is added to solve the problem. However, when a leveling agent is added, there is a drawback that the water whitening resistance of the pressure-sensitive adhesive film is deteriorated.

  Commonly used leveling agents include anionic surfactants, nonionic surfactants, cationic surfactants, and zwitterionic surfactants. More specifically, examples of the anionic surfactant include sulfates of higher alcohols and salts thereof, alkylbenzene sulfonates, polyoxyethylene alkylphenyl sulfonates, polyoxyethylene alkyl diphenyl ether sulfonates, alkyls. Examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene diphenyl ether, polyoxyethylene- Examples thereof include polyoxypropylene block copolymers and acetylenic diol surfactants. Examples of cationic surfactants include alkyl (amido) betaines and alkyldimethyls. Min'okishido, and the like.

  In addition to the above surfactants, fluorine-based surfactants and silicone-based surfactants can also be used as special surfactants.

  Among these, the re-peelable water-based pressure-sensitive adhesive composition of the present invention includes an anionic surfactant, a succinic acid dialkyl ester sulfonate surfactant, and a nonionic surfactant. Examples of acetylenediol surfactants and fluorosurfactants include megafac F-142D, megafac F-1405 (manufactured by Dainippon Ink and Chemicals), and ZONYL FSN (manufactured by DuPont). Examples of the fluoroalkylethylene oxide adduct and silicone surfactant include polyether-modified dimethylsiloxanes such as SILWET FZ-2166 (manufactured by Nihon Unicar Co., Ltd.), BYK 348 (manufactured by Big Chemie Japan Co., Ltd.), It is preferable to use one or a mixture of two or more of these from the viewpoint of excellent coating properties. Arbitrariness.

  Furthermore, it is more preferable to use an acetylenic diol surfactant [Z] from the viewpoint that the good water whitening resistance of the pressure-sensitive adhesive film is not impaired. Specific examples of the acetylenic diol surfactant [Z] include Surfinol 104PA, Surfinol 420, Surfinol 440, Surfinol 465, Surfinol 485, Surfinol 504, Surfinol 504, Surfinol PSA204, Surfinol PSA216. , Surfinol PSA 336, Dinol 604 (manufactured by Air Products Japan Co., Ltd.) can be used, and one or a mixture of two or more of these can be used. The addition amount of the acetylenic diol surfactant [Z] is not particularly limited, but is 0.1% per 100 parts by weight of the polymer particles [X] from the viewpoint of not impairing the good water whitening resistance of the pressure-sensitive adhesive film. -3.0 weight part is preferable.

  The amount of the leveling agent used is not particularly limited as long as repelling and squeezing at the time of coating are sufficiently suppressed and a smooth coating surface can be obtained, but it is 0.1% relative to the solid content of the re-peelable water-based pressure-sensitive adhesive. Use in the range of ˜2 parts by weight is preferable because it does not adversely affect the adhesive physical properties such as adhesive strength of the adhesive.

  The leveling agent may be used in addition to the method of adding the polymer particles [X] to the aqueous dispersion in which the polymer particles [X] are dispersed. The method of using as a surfactant for emulsion polymerization at the time of manufacture is also mentioned.

  In general, in order to impart polymerization stability during emulsion polymerization, as described above, surfactants such as an anionic emulsifier, a cationic emulsifier, a nonionic emulsifier, and a reactive emulsifier, and other A dispersion stabilizer is used. However, the polymerization stability improves as the amount of use increases, but the water whitening resistance of the resulting re-peelable aqueous pressure-sensitive adhesive film decreases.

  On the other hand, when the acetylenic diol surfactant [Z] is used during emulsion polymerization among the leveling agents, polymerization stability can be imparted in addition to the effect as the leveling agent. Furthermore, since the water-whitening resistance of the obtained re-peelable water-based pressure-sensitive adhesive film is not impaired, it is particularly preferable.

  Next, the hydrazine derivative [Y] having at least two hydrazino groups in the molecule used in the present invention is not particularly limited. For example, carbodihydrazide, oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, glutaric acid Dihydrazide, adipic acid dihydrazide, sebacic acid dihydrazide, maleic acid dihydrazide, fumaric acid dihydrazide, itaconic acid dihydrazide, ethylene-1,2-dihydrazine, propylene-1,3-dihydrazine, butylene-1,4-dihydrazine, etc. Among them, carbodihydrazide and adipic acid dihydrazide are particularly preferable because they can give good removability.

  Since the blending ratio of the hydrazine derivative [Y] having at least two hydrazino groups in the molecule is good in adhesive strength and removability, hydrazino groups per equivalent of carbonyl groups in the polymer particles (X). However, it is preferable that it is 0.05-5 equivalent, and 0.2-3 equivalent is especially preferable.

  Next, the pressure-sensitive adhesive product of the present invention will be described.

  The pressure-sensitive adhesive product of the present invention is composed of a substrate and a layer of the above-described re-peelable water-based pressure-sensitive adhesive composition. Examples of the substrate include paper, plastic film, and nonwoven fabric.

  In particular, since the re-peelable water-based pressure-sensitive adhesive composition of the present invention is excellent in water whitening resistance, it can be suitably used for the production of pressure-sensitive adhesive products using a transparent substrate. Specific examples of the transparent substrate include plastic films such as cellophane, polyethylene, polypropylene, polyester, polyethylene terephthalate, polystyrene, polyvinyl chloride, polyacetate, polycarbonate, and acrylic resin.

  As a method of forming a layer of the pressure-sensitive adhesive composition using the re-peelable water-based pressure-sensitive adhesive composition of the present invention, the re-peelable water-based pressure-sensitive adhesive composition is directly applied on the substrate and dried. The water-based pressure-sensitive adhesive composition is coated on a release material such as a silicone film or a release material such as a plastic film or dried to form a pressure-sensitive adhesive layer. There is a transfer method in which a base material is stacked on the adhesive layer and pressed to transfer the pressure-sensitive adhesive layer onto the base material.

  Examples of the coating method include a method using a roll coater, a comma coater, a lip coater, a fountain die coater, a gravure coater or the like as a coating machine.

  The re-peelable aqueous pressure-sensitive adhesive composition of the present invention generally has a solid content concentration of 50 to 70% by weight, a viscosity of 10 to 10,000 mPa · s (BM type viscometer, 60 rotations, 25 ° C.), and a pH of 6 to. Nine. In the case of coating by the above direct method, although it depends on the type of coating method, in general, a low viscosity is often required for coating at a higher speed. Moreover, when applying by a transfer method, the thing whose viscosity is 300-10,000 mPa * s (BM type | mold viscosity meter, 60 rotations, 25 degreeC) is preferable.

  Since the pressure-sensitive adhesive product of the present invention is excellent in adhesive strength and water whitening resistance, it is suitable for pressure-sensitive adhesive labels, pressure-sensitive adhesive tapes, special pressure-sensitive adhesive sheets and the like.

The aqueous pressure-sensitive adhesive composition of the present invention can be used for various pressure-sensitive adhesive products.
The pressure-sensitive adhesive product is composed of a base material and a layer of the aqueous pressure-sensitive adhesive composition. Examples of such a substrate include paper, plastic film, and nonwoven fabric.

As a method for forming a layer of the pressure-sensitive adhesive composition using the aqueous pressure-sensitive adhesive composition of the present invention, a direct method in which the water-based pressure-sensitive adhesive composition is directly coated on the substrate and dried, silicone or the like The aqueous pressure-sensitive adhesive composition is applied onto a release material such as paper or plastic film that has been subjected to release treatment in step 1 and dried to form a pressure-sensitive adhesive layer. There is a transfer method in which the materials are stacked and pressed to transfer the pressure-sensitive adhesive layer onto the substrate.
Examples of the coating method include a method using a roll coater, a comma coater, a lip coater, a fountain die coater, a gravure coater or the like as a coating machine.

  The aqueous pressure-sensitive adhesive composition generally has a solid content concentration of 50 to 70% by weight, a viscosity of 10 to 10,000 mPa · s (BM type viscometer, 60 rotations, 25 ° C.), and a pH of about 6 to 9. In the case of coating by the above direct method, although it depends on the type of coating method, in general, a low viscosity is often required for coating at a higher speed. Moreover, when applying by a transfer method, a thing with a viscosity of 300-10,000 mPa * s (same as the above) is preferable.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, the scope of the present invention is not limited to these Examples. In the following, unless otherwise specified, “%” represents “% by weight”, and “part” represents “part by weight”.

The evaluation method used in the present invention will be described below.
[Method for measuring polymerization conversion rate]
10 g of the content liquid is sampled from a closed pressure reaction vessel during emulsion polymerization, 0.2 g of a 10% aqueous solution of hydroxylamine sulfate is added as a polymerization inhibitor, and stirred to obtain a sample for measuring the polymerization rate. Next, the solid content concentration of this sample was measured from the weight of the residue after drying at 110 ° C. for 1 hour, and the polymerization conversion rate was determined according to the following formula.
Polymerization conversion rate (%)
= 100 x (Solid content concentration of sample: actual measurement value (%)-solid content concentration of raw material other than monomer component: calculated value (%)) / Concentration of monomer component with respect to all charged raw materials: calculated value (% ))

[Measurement method of acid value]
A re-peelable water-based pressure-sensitive adhesive composition is coated on a glass plate with a 3 mil applicator, and dried at room temperature for 1 hour to create a semi-dry pressure-sensitive adhesive film (sample). Then, 1 g of this pressure-sensitive adhesive film was precisely weighed and dissolved in 100 g of tetrahydrofuran (THF) as a measurement sample. The measuring method was a neutralization titration method using an aqueous potassium hydroxide solution. In addition, about the sample which did not melt | dissolve in tetrahydrofuran, since the measurement by this method is impossible, the calculated value calculated | required from the preparation amount of the carboxyl group-containing monomer used at the time of re-peeling type water-based adhesive composition manufacture Was determined as the acid value.
[Measurement method of average particle size]
The value of the average particle diameter (50% median diameter based on volume) measured with a Nikkiso Co., Ltd. Microtrac UPA type particle size distribution analyzer was determined.
[Method for measuring Tg]
The re-peelable aqueous pressure-sensitive adhesive composition was coated on a glass plate so that the film thickness after drying was 0.3 mm, dried at 25 ° C. for 24 hours, then peeled off from the glass plate, and further at 100 ° C. for 5 minutes. Using the dried sample as a sample, about 10 mg of a sample was weighed in an aluminum cylindrical cell having a diameter of 5 mm and a depth of 2 mm, and a DSC-2920 modulated differential scanning calorimeter manufactured by TA Instruments was used. It was determined by measuring an endothermic curve when the temperature was increased from −150 ° C. to 100 ° C. at a temperature increase rate of 20 ° C./min in an atmosphere.
[Measurement method of gel fraction]
The re-peelable water-based pressure-sensitive adhesive composition was applied on a glass plate so that the film thickness after drying was 0.3 mm, dried at 25 ° C. for 24 hours, then peeled off from the glass plate, and further at 100 ° C. 5 The dried material was cut into 50 mm squares and used as samples. Next, the weight (G1) of the sample before being immersed in toluene is measured in advance, and the toluene insoluble portion of the sample after being immersed in a toluene solution at room temperature for 24 hours is separated by filtering through a 300 mesh wire mesh. The weight (G2) of the residue after drying at 110 ° C. for 1 hour was measured, and the gel fraction was determined according to the following formula.

Gel fraction (% by weight) = (G2 / G1) × 100
[Method for measuring the amount of water extract]
The re-peelable aqueous pressure-sensitive adhesive composition was applied to a glass plate so that the film thickness after drying was 0.3 mm, dried at 25 ° C. for 24 hours, then peeled off from the glass plate, and further at 120 ° C. for 5 minutes. The remaining water was evaporated by heat treatment. The film was cut into 20 mm squares, and the weight (W1) was measured to obtain a test film. After immersing the test film in 25 ° C. water for 7 days, pulling up and wiping off the moisture on the film surface, the film was dried at 110 ° C. for 1 hour, allowed to cool, and then the weight (W2) was measured. The water extract amount of the film was determined according to

Water extract amount (% by weight) = {(W1-W2) / W1} × 100
[Measurement method of water whitening resistance test]
A re-peelable water-based pressure-sensitive adhesive composition was applied to the surface of a polyethylene terephthalate film having a thickness of 25 μm so that the film thickness after drying was 25 μm, and dried at 100 ° C. for 2 minutes to prepare a pressure-sensitive adhesive sheet as a sample. . Soak the sample in water at 30 ° C for 24 hours so that the adhesive coated surface is exposed, measure the turbidity of the sample before and after water immersion with a turbidimeter, and measure the degree of change in turbidity by W The water whitening resistance was evaluated as a value.

Turbidity meter: Nippon Denka Kogyo Co., Ltd. turbidity meter NDH-300A
Measurement light source: Halogen lamp Light receiving element: Silicon photocell according to JIS K7105 Turbidity and the degree of change in turbidity before and after immersion in water were determined according to the following equations.

Turbidity H = (DF / TL) × 100
TL: Total transmittance (%)
DF: Diffuse transmittance (%)
The degree of change in turbidity: W value = H1 / H0 (H0: turbidity before water immersion, H1: turbidity after water immersion), and then the result was determined according to the following criteria.

○: The degree of turbidity change W value is less than 5 Δ: The degree of turbidity change W value is 5 or more and less than 30 ×: The degree of turbidity change W value is 30 or more [Measurement method of adhesive strength]
The re-peelable water-based pressure-sensitive adhesive composition was applied to the surface of a 25 μm-thick polyethylene terephthalate film so that the film thickness after drying was 25 μm, and dried at 100 ° C. for 2 minutes to prepare a pressure-sensitive adhesive sheet. A 180-degree peel strength was measured under an atmosphere of 23 ° C. and 50% RH in accordance with JIS Z-0237 using a mirror-finished stainless steel plate as the pressure-sensitive adhesive sheet and the adherend to determine the adhesive strength.
[Measurement of holding power]
Create a pressure-sensitive adhesive sheet in the same way as when measuring the adhesive strength, affix the pressure-sensitive adhesive sheet to the stainless steel plate so that the bonding area is 25 mm x 25 mm, and measure the time until it slips off under a load of 1 kg at 40 ° C. The holding time was defined as holding power. Moreover, when it was hold | maintained after 720 minutes, the holding time was made into 720 minutes or more, the gap | deviation width from an initial sticking position was measured, and it described together.
[Removability]
An adhesive sheet is prepared in the same manner as when measuring the adhesive force, and the adhesive sheet is pasted on a stainless steel plate so that the adhesive area is 25 mm × 25 mm. After being left in an atmosphere of 23 ° C. and 65% RH for 30 days, it is placed in a tensile tester. Then, peeling was performed at a pulling speed of 300 mm / min, and the state of the adherend surface after peeling was visually determined.

  ○: It can be peeled cleanly without glue residue or paper tearing.

  Δ: Residue remaining or paper tears partially.

×: There are adhesive residue and paper tears on the entire surface.
[tack]
A pressure-sensitive adhesive sheet was prepared in the same manner as when measuring the adhesive force, and measured under an atmosphere of 23 ° C. and 50% RH according to the ball rolling method of JIS Z-0237.

Reference Example 1 (Production of polymer particles [A] (aqueous dispersion))
A sealed pressure reaction vessel having a volume of 2 L equipped with a stirrer, a nitrogen inlet pipe capable of pressurization, a pressure reduction pipe (pressure reduction pump), a raw material charging port, and a thermometer (material in the container: made of glass lining), 25 560 parts of deionized water at 0 ° C. was charged, nitrogen gas was introduced into the reaction vessel from a nitrogen introduction tube with stirring, and the pressure in the reaction vessel was increased to 0.3 MPa over 1 minute. Thereafter, the pressure in the reaction vessel was reduced to −0.08 MPa over 5 minutes using a vacuum pump from the vacuum tube. After repeating this operation three times, the dissolved oxygen concentration in the deionized water in the reaction vessel was measured and found to be 0.5 ppm. Under stirring in the reaction vessel, 2 parts of Aqualon KH-10 [Daiichi Kogyo Seiyaku Co., Ltd .: active ingredient 100%], 80 parts of 2-ethylhexyl acrylate, 72 parts of butyl acrylate and 8 parts of methacrylic acid were charged. Subsequently, 16.4 parts of a 2.4% aqueous solution of sodium bisulfite was charged, nitrogen gas was introduced into the reaction vessel from a nitrogen introduction tube, and the pressure inside the reaction vessel was increased to 0.3 MPa over 1 minute. Thereafter, the pressure in the reaction vessel is reduced from the pressure reducing tube to −0.08 MPa over 5 minutes, and this operation is repeated three times, and then the reaction vessel pressure is increased to 0.05 MPa. Pressed. During this time, the temperature in the reaction vessel was adjusted to 30 ° C.
Next, 16.8 parts of a 4.8% aqueous solution of ammonium persulfate was charged into another sealed pressure vessel having an internal volume of 0.2 L, and pressurized so that the internal pressure of the vessel became 0.3 MPa over 10 seconds. did. Then, using a vacuum pump from the vacuum tube, the pressure in the container is reduced to -0.08 MPa over 20 seconds, this operation is repeated three times, and then the pressure in the container is increased to 0.15 MPa. did.
After confirming that the internal temperature of the sealed pressure reaction vessel was 30 ° C., a pressure vessel containing ammonium persulfate was placed in the raw material charging port, and an aqueous ammonium persulfate solution was pressed into the closed pressure reaction vessel. Immediately after the injection of the ammonium persulfate aqueous solution, the temperature inside the reaction vessel started to rise, and it was confirmed that emulsion polymerization was started. After 45 minutes from the start of the emulsion polymerization, the temperature rise in the reaction vessel stopped at 45 ° C. During this time, the temperature adjustment operation of the reaction vessel was not performed. Thereafter, the temperature in the reaction vessel was adjusted to 55 ° C. and held for 60 minutes. Thereafter, the contents were cooled, the pressure inside the reaction vessel was returned to normal pressure, and then filtered through a 200 mesh wire mesh to obtain the polymer particles [A] of the present invention. The polymer particles [A] obtained here had a solid content concentration of 21.6%, a viscosity of 5 mPa · s, an average particle diameter of 160 nm, and a polymerization conversion rate of 100%.

Example 1
Detach into a 2 L sealed pressure reaction vessel (material in the container: made of glass lining) equipped with a stirrer, pressurizable nitrogen inlet tube, decompression tube (decompression pump), raw material inlet, and thermometer. 224 parts of ionic water, 400 parts of the polymer particles [A] (aqueous dispersion) of 25 ° C. of Reference Example 1 and 0.8 part of Aqualon KH-10 are charged, and nitrogen gas is introduced into the reaction vessel from the nitrogen introduction tube with stirring. The pressure in the reaction vessel was increased to 0.3 MPa over 1 minute. Thereafter, the pressure in the reaction vessel was reduced to −0.08 MPa over 5 minutes using a vacuum pump from the vacuum tube. After repeating this operation three times, the dissolved oxygen concentration of the polymer particles [A] (aqueous dispersion) in the reaction vessel was measured and found to be 0.5 ppm. While stirring the reaction vessel, 640 parts of 2-ethylhexyl acrylate, 72 parts of methyl methacrylate, 8 parts of methacrylic acid, 8 parts of diacetone acrylamide and 0.8 part of lauryl mercaptan were charged. Subsequently, 32.8 parts of a 2.4% aqueous solution of ascorbic acid was charged, nitrogen gas was introduced into the reaction vessel from a nitrogen introduction tube, and the pressure in the reaction vessel was increased to 0.3 MPa over 1 minute. Thereafter, the pressure in the reaction vessel is reduced to -0.08 MPa over 5 minutes using a pressure reduction pump, and this operation is repeated three times. Thereafter, the pressure in the reaction vessel is reduced to 0.30 MPa. Pressurized. During this time, the temperature in the reaction vessel was adjusted to 40 ° C.
Next, 33.6 parts of a 4.8% aqueous solution of potassium persulfate was charged into another sealed pressure vessel with an internal volume of 0.2 L so that the internal pressure of the vessel became 0.3 MPa over 10 seconds. Pressed. After that, the pressure inside the container is reduced to -0.08 MPa over 20 seconds using a pressure reducing pump, and this operation is repeated three times, and then the pressure inside the container is increased to 0.40 MPa. did.
After confirming that the internal temperature of the sealed pressure reaction vessel was 40 ° C., a pressure vessel containing ammonium persulfate was placed in the raw material charging port, and an aqueous ammonium persulfate solution was pressed into the sealed pressure reaction vessel. Five minutes after immediately after the injection of the ammonium persulfate aqueous solution, the temperature inside the reaction vessel started to increase, and it was confirmed that the emulsion polymerization was started. After 40 minutes from the start of the emulsion polymerization, the increase in the reaction vessel temperature stopped at 105 ° C. During this time, the temperature adjustment operation of the reaction vessel was not performed. Thereafter, the temperature in the reaction vessel was adjusted to 90 ° C. and held for 90 minutes. Meanwhile, after confirming the start of emulsion polymerization, sampling was performed at intervals of 10 minutes, the polymerization conversion rate was measured, and the time until the polymerization conversion rate reached 95% was determined. The time required for the polymerization conversion to reach 95% was 55 minutes after confirming the start of emulsion polymerization. Thereafter, the contents were cooled and adjusted with aqueous ammonia (active ingredient 10%) so that the pH was 8.0. It was confirmed that the polymerization conversion rate reached 100% before cooling. After pH adjustment, the mixture was filtered through a 200 mesh wire mesh to obtain the water-dispersed acrylic polymer of the present invention. The water-dispersed acrylic polymer obtained here has a solid content concentration of 55.2%, a viscosity of 410 mPa · s, an average particle size of 220 nm, and an acid value determined from the charged amount of the carboxyl group-containing monomer of 9. It was 8.

  As a leveling agent, Surfinol 420 [manufactured by Air Products Japan Co., Ltd .: active ingredient 100%] 1.6 parts and adipic acid dihydrazide 4.0 parts are added to the above aqueous dispersion of polymer particles [X]. Then, the mixture was filtered through a 100 mesh wire net to obtain a re-peelable water-based pressure-sensitive adhesive composition of the present invention.

  Glass transition temperature (actually measured Tg), gel fraction (toluene insoluble fraction), water extract amount, water whitening resistance of adhesive sheet, adhesion of film obtained using re-peelable water-based pressure-sensitive adhesive composition of the present invention Table 1 shows the evaluation results of force, holding force, removability, and tack.

Examples 2-5
A re-peelable water-based pressure-sensitive adhesive composition of the present invention was obtained in the same manner as in Example 1 except that the monomer mixture shown in Table 1 was used. The acid value, average particle diameter (50% median diameter), solid content concentration, and viscosity of the polymer particles contained in this re-peelable aqueous pressure-sensitive adhesive composition were as described in Table 1. Further, the glass transition temperature (actually measured Tg), gel fraction (toluene insoluble fraction), water extract amount, water whitening resistance and adhesive strength of the pressure-sensitive adhesive sheet obtained from this re-peelable water-based pressure-sensitive adhesive composition , Holding power, removability, and tack evaluation results are as described in Table 1.

Comparative Example 1
In a reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, a thermometer, and a dropping funnel, 0.4 part of Latemul E-118B [manufactured by Kao Corporation: active ingredient 25%] and 500 parts of deionized water The temperature was raised to 75 ° C. while blowing nitrogen. Under stirring, 0.24 parts of tartaric acid and 0.4 parts of t-butyl hydroperoxide were added, followed by 688 parts of 2-ethylhexyl acrylate, 80 parts of methyl methacrylate, 16 parts of methacrylic acid, 16 parts of diacetone acrylamide. A monomer pre-emulsion in which 4.0 parts of Latemul E-118B and 144 parts of deionized water are added to a monomer mixture composed of 8 parts of lauryl mercaptan and emulsified, and the monomer is mixed with the monomer mixture, emulsifier and water. A part (3 parts) of an emulsified state) was added, and polymerization was carried out for 60 minutes while maintaining the temperature in the reaction vessel at 75 ° C. Subsequently, while maintaining the temperature in the reaction vessel at 75 ° C., the remaining monomer pre-emulsion (927.3 parts), 33.6 parts of 2.4% aqueous solution of t-butyl hydroperoxide, and 1.2% aqueous solution of tartaric acid Using a separate dropping funnel, 32.8 parts were dropped and polymerized over 240 minutes while maintaining the temperature in the reaction vessel at 75 ° C. After completion of the dropwise addition, the mixture was stirred at the same temperature for 120 minutes, the contents were cooled, and adjusted with ammonia water (active ingredient 10%) so that the pH was 8.0. The solid content concentration was 52.3%, the viscosity was 120 mPa · s, the average particle size was 500 nm, and the acid value determined from the charged amount of the carboxyl group-containing monomer was 13.

  As a leveling agent, Surfinol 420 [manufactured by Air Products Japan Co., Ltd .: active ingredient 100%] 1.6 parts and 9.6 parts of adipic acid dihydrazide are added to the above aqueous dispersion of polymer particles [X]. Then, the mixture was filtered through a 100 mesh wire net to obtain a re-peelable water-based pressure-sensitive adhesive composition of the present invention.

  Glass transition temperature (actually measured Tg), gel fraction (toluene insoluble fraction), water extract amount, water whitening resistance of adhesive sheet, adhesion of film obtained using re-peelable water-based pressure-sensitive adhesive composition of the present invention Table 2 shows the evaluation results of force, holding power, removability, and tack.

Comparative Examples 2 and 3
A re-peelable aqueous pressure-sensitive adhesive composition of the present invention was obtained in the same manner as in Comparative Example 1 except that the monomer mixture shown in Table 2 was used. The acid value, average particle diameter (50% median diameter), solid content concentration, and viscosity of the polymer particles contained in this re-peelable aqueous pressure-sensitive adhesive composition were as described in Table 2. Further, the glass transition temperature (actually measured Tg), gel fraction (toluene insoluble fraction), water extract amount, water whitening resistance and adhesive strength of the pressure-sensitive adhesive sheet obtained from this re-peelable water-based pressure-sensitive adhesive composition Table 2 shows the evaluation results of holding power, removability, and tack.
Met.

Comparative Example 4
Into a reaction vessel equipped with a stirrer, reflux condenser, nitrogen inlet tube, thermometer, and dropping funnel, 0.4 parts of Rebenol WZ [manufactured by Kao Corporation: 25% active ingredient] and 28 parts of deionized water are added, and nitrogen is added. The temperature was raised to 75 ° C. while blowing. Under stirring, 0.02 part of potassium persulfate was added, and then, to a monomer mixture consisting of 48.5 parts of 2-ethylhexyl acrylate, 1 part of acrylic acid and 0.5 part of diacetone acrylamide, 1. 6 parts and 20 parts of deionized water were added to emulsify the monomer pre-emulsion (referred to the monomer mixture, emulsifier and water in which the monomer was emulsified), and a reaction (3 parts) was added. Polymerization was performed for 60 minutes while maintaining the temperature in the container at 75 ° C. Subsequently, while maintaining the temperature in the reaction vessel at 75 ° C., the remaining monomer pre-emulsion (75.9 parts) and 10 parts of an aqueous solution of potassium persulfate (active ingredient 1%) were each added using a separate dropping funnel. The polymerization was carried out dropwise over 120 minutes while maintaining the temperature in the reaction vessel at 75 ° C.

  After completion of the dropwise addition, while keeping the temperature in the reaction vessel at 75 ° C., 1.6 parts of rebenol WZ and 1.6 parts of deionized monomer mixture consisting of 47 parts 2-ethylhexyl acrylate, 1 part acrylic acid and 2 parts diacetone acrylamide A monomer mixture consisting of a monomer pre-emulsion emulsified with the addition of 20 parts of water and 10 parts of an aqueous solution of potassium persulfate (active ingredient 1%) were immediately put in the reaction vessel temperature using separate dropping funnels. Was polymerized dropwise over 120 minutes while maintaining at 75 ° C. After completion of the dropwise addition, the mixture was stirred at the same temperature for 120 minutes, the contents were cooled, and adjusted with ammonia water (active ingredient 10%) so that the pH was 8.0. The aqueous dispersion obtained here had a solid content concentration of 51.8%, a viscosity of 300 mPa · s, an average particle size of 290 nm, and an acid value determined from the charged amount of the carboxyl group-containing monomer was 15.6. It was.

After adding 0.3 part of adipic acid dihydrazide to said aqueous dispersion, it filtered with a 100 mesh metal-mesh, and obtained the releasable water-based adhesive composition.
Glass transition temperature (measured Tg), gel fraction (toluene insoluble fraction), water extract amount of coating film obtained using this re-peelable water-based pressure-sensitive adhesive composition, water whitening resistance, adhesive strength of pressure-sensitive adhesive sheet, Table 2 shows the evaluation results of holding power, removability, and tack.

<Comparative example corresponding to Example 2 of JP-A-7-228612>
Comparative Example 5
A reaction vessel equipped with a stirrer, a nitrogen introduction tube, a condenser (cooling tube), a raw material charging port, and a thermometer was charged with 280 parts of deionized water at 25 ° C., and 50 mL / Nitrogen gas was introduced at a flow rate of min. After 120 minutes, the dissolved oxygen concentration in the reaction vessel was measured and found to be 2.3 ppm. While introducing nitrogen gas under stirring in the reaction vessel, 7.5 parts of polyoxyethylene alkylphenyl ether sulfate ammonium salt, 237.5 parts of butyl acrylate, 10 parts of acrylonitrile, 2.5 parts of acrylic acid were charged. Emulsified uniformly. Thereafter, the temperature in the reaction vessel was adjusted to 40 ° C. Next, after confirming that the temperature in the reaction vessel was 40 ° C., 0.25 part of a 5 wt% methanol solution of 2,2-azobis [2- (2-imidazolin-2-yl) propane] was added, and 40 The emulsion polymerization was carried out by maintaining at 12 ° C. for 12 hours. The polymerization conversion rate was 95.1%. Thereafter, 0.1 part of the above 5 wt% methanol solution was further added and maintained at 40 ° C. for 24 hours. Thereafter, the contents were cooled, adjusted with aqueous ammonia (active ingredient 10%) so that the pH was 8.0, and then filtered through a 200 mesh wire net to obtain the water-dispersed acrylic polymer of the present invention. The water-dispersed acrylic polymer obtained here has a solid content concentration of 46.6%, a viscosity of 180 mPa · s, an average particle size of 220 nm, and an acid value of 7 determined from the charged amount of the carboxyl group-containing monomer. .8. The polymerization conversion rate was 100%.

After adding 0.5 part of Surfinol 420 [manufactured by Air Products Japan Co., Ltd .: active ingredient 100%] as a leveling agent to the above water-dispersed acrylic polymer, the mixture is filtered through a 100-mesh wire mesh, and acrylic An aqueous pressure-sensitive adhesive composition was obtained.
Glass transition temperature (measured Tg), gel fraction (toluene insoluble fraction), water extract amount of coating film obtained using this re-peelable water-based pressure-sensitive adhesive composition, water whitening resistance, adhesive strength of pressure-sensitive adhesive sheet, Table 2 shows the evaluation results of holding power, removability, and tack.

The official names of the abbreviations in Tables 1 and 2 are shown below.
2-EHA; 2-ethylhexyl acrylate BA; n-butyl acrylate AN; acrylonitrile MMA; methyl methacrylate MAA; methacrylic acid AA; acrylic acid DAAM; diacetone acrylamide L-SH; lauryl mercaptan TBHP; Potassium persulfate AIIP; 2,2-azobis [2- (2-imidazolin-2-yl) propane]
POEA; polyoxyethylene alkylphenyl ether sulfate ammonium salt ADH; adipic acid dihydrazide CDH; carbodihydrazide WS-500; Nippon Shokubai Epocross WS-500
OT-75; AEROSIL OT-75 manufactured by Mitsui Cytec Co., Ltd.
The amounts of monomers, surfactants, polymerization initiators, crosslinking agents, and leveling agents used in Tables 1 and 2 are expressed in parts by weight of solid content.

Furthermore, the contents of the words shown in the polymerization conditions in Tables 1 and 2 are as follows.
Polymerization start temperature; temperature in the reaction system when a polymerization initiator is added to the monomer and polymerization exotherm starts.
Exothermic stop temperature; temperature in the reaction system when the polymerization exotherm stops.
Exothermic time: Time required for the polymerization exotherm to start and stop.
Reaction time: Total reaction time required to obtain a polymer for aqueous adhesives.

Claims (7)

It is necessary for the monomer component mainly composed of (meth) acrylate to be collectively charged into a closed pressure reaction vessel in which an aqueous medium is present and subjected to emulsion polymerization, and the weight conversion rate of the monomer component reaches 95%. Polymer particles [X] having a time substantially within 180 minutes, containing a carbonyl group and a carboxyl group and having an acid value of 3 to 30, and a hydrazine having at least two hydrazino groups in the molecule An aqueous pressure-sensitive adhesive composition comprising the derivative [Y], wherein the film formed from the aqueous pressure-sensitive adhesive composition has a glass transition temperature of −25 ° C. or lower and a gel fraction of 80% by weight or higher. A re-peelable water-based pressure-sensitive adhesive composition. An average particle diameter of the polymer particles [X] is 300 nm or less, and is an aqueous pressure-sensitive adhesive composition comprising the polymer particles and the hydrazine derivative [Y], which is formed from the aqueous pressure-sensitive adhesive composition. The re-peelable water-based pressure-sensitive adhesive composition according to claim 1, wherein the amount of water extract of the film is 2% by weight or less. The polymer particle [X] is (a) at least one carbonyl group-containing ethylenically unsaturated monomer in the molecule, 0.1 to 2% by weight, (b) a carboxyl group per all monomers. Containing ethylenically unsaturated monomer, 0.5 to 4% by weight, and (c) an alkyl (meth) acrylate having an alkyl group having 4 to 12 carbon atoms and 45 to 99.4% by weight as essential components The re-peelable water-based pressure-sensitive adhesive composition according to claim 1, which is a copolymer obtained by copolymerizing the obtained polymerizable monomer mixture. The re-peelable aqueous pressure-sensitive adhesive composition according to claim 1, wherein the polymer particles [X] are emulsion-polymerized using an organic peroxide polymerization initiator. Furthermore, the re-peelable water-based pressure-sensitive adhesive composition according to any one of claims 1 to 4, further comprising an acetylenic diol surfactant [Z]. The re-peelable aqueous pressure-sensitive adhesive composition according to claim 5, wherein the polymer particles [X] are obtained by emulsion polymerization in the presence of an acetylenic diol surfactant [Z]. A pressure-sensitive adhesive product comprising a substrate and a layer of the re-peelable water-based pressure-sensitive adhesive composition according to any one of claims 1 to 5.