JP6645799B2 - Emulsion pressure-sensitive adhesive, pressure-sensitive adhesive sheet, method for producing emulsion pressure-sensitive adhesive, and method for producing pressure-sensitive adhesive sheet - Google Patents

Description

  The present invention relates to an emulsion pressure-sensitive adhesive, a pressure-sensitive adhesive sheet, a method for producing an emulsion pressure-sensitive adhesive, and a method for producing a pressure-sensitive adhesive sheet.

  Conventionally, as an adhesive, an adhesive obtained by dissolving an adhesive polymer in an organic solvent has been widely used. However, from the viewpoint of consideration for air pollution and the environment, conversion to an adhesive that does not use an organic solvent has been promoted.

  Emulsion polymerization (emulsion polymerization) in which a monomer and a surfactant are mixed in a medium such as water, and a polymerization initiator soluble in the medium is added and polymerization is performed in micelles as an adhesive without using an organic solvent. ), A pressure-sensitive adhesive containing a polymer having tackiness is known (Patent Document 1).

JP-A-2005-052060

However, the pressure-sensitive adhesive obtained by the conventional emulsion polymerization method described in Patent Document 1, etc., is applied to a substrate or the like, dried and broken into micelles. Separate. Then, a thin layer containing a surfactant is formed between the pressure-sensitive adhesive and the substrate or the like, and the adhesive strength with the substrate or the like may be reduced.
In addition, when the pressure-sensitive adhesive obtained by the conventional emulsion polymerization method is dried and then comes into contact with water, the surfactant may be eluted, and the properties of the pressure-sensitive adhesive are easily changed by water, resulting in poor water resistance. was there.

  Accordingly, an object of the present invention is to provide an emulsion pressure-sensitive adhesive having excellent adhesion to a substrate or the like and excellent water resistance. Another object of the present invention is to provide a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer having excellent adhesion between a substrate and a pressure-sensitive adhesive layer and also having excellent water resistance. Another object of the present invention is to provide a method for producing an emulsion pressure-sensitive adhesive which can provide an emulsion pressure-sensitive adhesive having excellent adhesion to a substrate or the like and excellent water resistance. Another object of the present invention is to provide a method for producing a pressure-sensitive adhesive sheet, which is capable of obtaining a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer having excellent adhesiveness between a substrate and a pressure-sensitive adhesive layer and also having excellent water resistance. .

That is, the functional groups emulsion adhesive of the present invention, the terminal with a surfactant having a functional group capable of generating a radical by the energy ray irradiation has been modified, to look containing an adhesive polymer, to generate radicals by the energy ray irradiation Is at least one selected from the group consisting of an N, N-dialkyldithiocarbamylmethyl group, a benzophenone group, a camphorquinone group, and a phenylazide group .
ADVANTAGE OF THE INVENTION According to the emulsion adhesive of this invention, it is excellent in adhesiveness with a base material etc., and is also excellent in water resistance.

The pressure-sensitive adhesive sheet of the present invention has a pressure-sensitive adhesive layer comprising the above-mentioned emulsion pressure-sensitive adhesive on at least one surface of a substrate.
ADVANTAGE OF THE INVENTION According to the pressure sensitive adhesive sheet of this invention, the adhesiveness of a base material and a pressure sensitive adhesive layer is excellent, and it is excellent also in water resistance.

The method for producing an emulsion pressure-sensitive adhesive according to the present invention includes irradiating a polymerizable composition containing a surfactant having a functional group that generates radicals by irradiation with energy rays and a monomer that imparts tackiness after polymerization with energy rays. to the surfactant saw including a step of terminal obtaining a modified adhesive polymer agent, the functional groups generating radicals by the energy ray irradiation, N, N-dialkyl dithiocarbamyl methyl group, benzophenone group, It is characterized by being at least one selected from the group consisting of a camphorquinone group and a phenylazide group .
According to the method for producing an emulsion pressure-sensitive adhesive of the present invention, it is possible to obtain an emulsion pressure-sensitive adhesive excellent in adhesion to a substrate or the like and excellent in water resistance.

The method for producing a pressure-sensitive adhesive sheet of the present invention is characterized in that it includes a step of applying the emulsion pressure-sensitive adhesive on at least one surface of a substrate, drying and irradiating with an energy ray to form a pressure-sensitive adhesive layer. I do.
According to the method for producing a pressure-sensitive adhesive sheet of the present invention, it is possible to obtain a pressure-sensitive adhesive sheet having excellent adhesion between a substrate and a pressure-sensitive adhesive layer and excellent water resistance.

  ADVANTAGE OF THE INVENTION According to this invention, the emulsion adhesive which is excellent in adhesiveness with a base material etc. and is also excellent in water resistance can be provided. Further, the present invention can provide a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer having excellent adhesiveness between a substrate and a pressure-sensitive adhesive layer and excellent water resistance. Further, the present invention can provide a method for producing an emulsion pressure-sensitive adhesive capable of obtaining an emulsion pressure-sensitive adhesive having excellent adhesion to a substrate or the like and excellent water resistance. Further, the present invention can provide a method for producing a pressure-sensitive adhesive sheet, which can provide a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer having excellent adhesion between a substrate and a pressure-sensitive adhesive layer and excellent water resistance.

  EMBODIMENT OF THE INVENTION Hereinafter, one Embodiment is described in detail about the emulsion adhesive, the adhesive sheet, the manufacturing method of an emulsion adhesive, and the manufacturing method of an adhesive sheet of this invention.

[Emulsion adhesive]
The emulsion pressure-sensitive adhesive of the present invention contains at least a pressure-sensitive adhesive polymer whose terminal has been modified with a surfactant having a functional group that generates a radical upon irradiation with energy rays.
In addition to the above-mentioned adhesive polymer, the emulsion adhesive of the present embodiment may be a solvent such as water or a lower alcohol (eg, ethanol); a pigment, a dispersant, a plasticizer, a stabilizer, an antioxidant, a polymerization inhibitor and the like. May be included.

Since the surfactant having a functional group that generates a radical by irradiation with energy rays has properties as a surfactant, micelles can be formed in an aqueous solvent. Furthermore, the above-mentioned surfactant generates a radical by irradiation with energy rays and functions as a polymerization initiator during emulsion polymerization. Therefore, it is possible to obtain a sticky polymer in which the surfactant is integrated with the sticky polymer and the surfactant molecule is bonded to the α-terminal.
The emulsion pressure-sensitive adhesive of the present embodiment contains a pressure-sensitive adhesive polymer in which a surfactant molecule having a functional group that generates a radical upon irradiation with an energy ray is bonded to the α-terminal. Even if the surfactant is destroyed, the surfactant and the adhesive polymer are separated from each other, so that the surfactant is not eluted, and a thin layer containing the surfactant is not easily formed on the surface of the substrate or the like. Therefore, it is difficult to peel off from the substrate or the like. Further, since the surfactant is not eluted by water, the water resistance is excellent.

(Surfactant)
The surfactant has a functional group that generates a radical upon irradiation with energy rays, and has properties as a surfactant.
The functional group contained in the surfactant and capable of generating a radical upon irradiation with energy rays is selected from the group consisting of an N, N-dialkyldithiocarbamylmethyl group, a benzophenone group, a camphorquinone group, and a phenylazide group. At least one selected is preferred. Among them, N, N-dialkyldithiocarbamylmethyl group and benzophenone group are preferable from the viewpoint that radicals are easily generated by irradiation with energy rays in the near ultraviolet to visible region having high substance permeability, and from the viewpoint that the radical life is particularly long. And a N, N-dialkyldithiocarbamylmethyl group is particularly preferred.
The functional group may be contained alone or plurally in the surfactant.

The surfactant has properties as a surfactant, and has at least a hydrophobic group and a hydrophilic group in a molecule. The functional groups that generate radicals upon irradiation with energy rays are all hydrophobic, but in order to stably exhibit hydrophobic properties, for example, a linear alkyl group having 8 or more carbon atoms, carbon A number of eight or more branched alkyl groups may be bonded. Above all, it is preferable to bond a dodecyl group, a decyl group, a diethylhexyl group, or the like, from the viewpoint of easily forming micelles.
Examples of the hydrophilic group include an oxyethylene group, a oxypropylene group, a hydroxyl group, a carboxyl group, a sulfonic acid group, and alkali metal salts thereof. Among them, an oxyethylene group and a oxypropylene group are preferable from the viewpoint of being chemically stable and having little effect on the polymerization reaction.
The above-mentioned hydrophobic group and the above-mentioned hydrophilic group may be contained singly or plurally in the surfactant.

Examples of the surfactant include polyethylene glycolated benzophenone, 1- (N, N-diethyldithiocarbamylmethyl) -4- (polyethylene glycol monomethyl ether) -benzene, and the like. Among them, 1- (N, N-diethyldithiocarbamylmethyl) -4- (polyethylene glycol monomethyl ether) -benzene is preferable from the viewpoint of easily forming micelles containing an adhesive monomer.
The surfactants may be used alone or in combination of two or more.

The adhesive polymer contained in the emulsion adhesive of the present embodiment has at least one terminal modified with a surfactant. That is, the adhesive polymer has a structural unit derived from a surfactant at at least one end.
For example, when 1- (N, N-diethyldithiocarbamylmethyl) -4- (polyethylene glycol monomethyl ether) -benzene is used as a surfactant, the α-terminal of the adhesive polymer is changed to polyethylene glycol-benzyl ether. Ω-terminal is preferably derived from an N, N-diethyldithiocarbamylmethyl group. When polyethylene glycolated benzophenone is used as the surfactant, the α-terminal of the adhesive polymer is preferably derived from polyethylene glycolated benzophenone.

(Adhesive monomer)
The adhesive polymer contains a monomer unit derived from an adhesive monomer that imparts adhesiveness after polymerization.
Examples of the adhesive monomer include acrylic monomers such as alkyl (meth) acrylate having an alkyl group having 4 to 20 carbon atoms; diene monomers such as butadiene and isoprene; and silicones having an organopolysiloxane as a main chain. And the like. Above all, from the viewpoint of excellent adhesiveness, an alkyl acrylate having an alkyl group having 4 to 8 carbon atoms is preferable, and butyl acrylate and ethylhexyl acrylate are more preferable.
The above-mentioned adhesive monomers may be used alone or in combination of two or more.
In this specification, “(meth) acryl” refers to “acryl” and / or “methacryl”.

The content of the monomer unit derived from the adhesive monomer in the adhesive polymer (100% by mass) contained in the emulsion adhesive of the present embodiment is preferably from 50 to 99% by mass, more preferably from 70 to 95% by mass. % By mass. When the content is 70% by mass or more, the adhesion of the emulsion adhesive to the adherend is further improved. Further, when the content is 99% by mass or less, the high molecular weight of the adhesive polymer can be obtained by stable emulsion polymerization.
The content of the monomer unit derived from each monomer in the polymer can be determined by measuring the molecular weight by GPC or the like.

  The number of monomer units derived from the adhesive monomer contained in the adhesive polymer is preferably from 50 to 300, and more preferably from 100 to 170. When the number of monomer units derived from the adhesive monomer is 50 or more, the adhesive strength of the emulsion adhesive to the adherend is further improved. Moreover, when it is 300 or less, it can be stably suspended in water.

(Other monomers)
The adhesive polymer may include a monomer unit derived from another monomer other than the monomer unit derived from the adhesive monomer.
Examples of the other monomer include a monomer having a functional group that generates a radical by irradiation with energy rays, a monomer having a functional group that generates a radical by heat, vinyl acetate, acrylonitrile, acrylamide, styrene, a polyfunctional monomer, and ( (Meth) acrylic acid and the like.
By using a monomer having a functional group that generates a radical by irradiation with energy rays or a monomer having a functional group that generates a radical by heat, the adhesiveness between the substrate and the pressure-sensitive adhesive layer may be further improved. . Examples of the monomer having a functional group that generates a radical upon irradiation with energy rays include, for example, o- (N, N-dimethyldithiocarbamylmethyl) styrene and m- (N, N-dimethyldithiocarbamylmethyl) styrene, p- (N, N-dimethyldithiocarbamylmethyl) styrene, o- (N, N-diethyldithiocarbamylmethyl) styrene, m- (N, N-diethyldithiocarbamate) A monomer having an N, N-dialkyldithiocarbamylmethyl group and a vinyl group such as milmethyl) styrene and p- (N, N-diethyldithiocarbamylmethyl) styrene; benzophenone such as 3-vinylbenzophenone and 4-vinylbenzophenone Monomer having a vinyl group and a vinyl group; a camphorquinone group and a vinyl group Monomers; and the like; 1-vinyl-3-azido benzene, a monomer having a phenyl azide group and vinyl group such as 1-vinyl-4-azido benzene. Among them, N, N-diethyldithiocarbamylmethylstyrene and 1-vinyl-3-azidobenzene are preferred from the viewpoint of easily generating radicals by light irradiation. Examples of the monomer having a functional group that generates a radical by heat include 2,2′-azobis [N- (2-propenyl) -2-methylpropionamide].
Further, as the other monomer, from the viewpoint of improving the cohesive force of the adhesive polymer, vinyl acetate, acrylonitrile, acrylamide, and styrene are preferable, and from the viewpoint of introducing a crosslinking point into the adhesive polymer, a polyfunctional monomer, (Meth) acrylic acid is preferred.
These other monomers may be used alone or in combination of two or more.

  In the adhesive polymer (100% by mass) contained in the emulsion adhesive of the present embodiment, the content of the monomer unit derived from the other monomer is preferably more than 0% by mass and 10% by mass or less, more preferably 0.001 to 1% by mass.

  In the adhesive polymer contained in the emulsion adhesive of the present embodiment, the molar ratio of the monomer unit derived from the adhesive monomer to the monomer unit derived from the other monomer (adhesive monomer unit / other monomer unit) is: 4-20 are preferable, and 5-10 are more preferable. When the molar ratio is 4 or more, the adhesive strength of the emulsion adhesive to the adherend is further improved. Further, when it is 20 or less, the function by other monomers is easily exhibited.

(Method of producing emulsion adhesive)
The method for producing an emulsion pressure-sensitive adhesive according to the present embodiment includes the steps of applying an energy ray to a polymerizable composition containing a surfactant having a functional group that generates a radical by irradiation with energy rays and a monomer that imparts tackiness after polymerization. Irradiating to obtain a sticky polymer terminal-modified with the surfactant. The method for producing an emulsion pressure-sensitive adhesive of the present embodiment can be suitably used to obtain the above-mentioned emulsion pressure-sensitive adhesive.

  The adhesive polymer contained in the emulsion adhesive of the present embodiment can be obtained by irradiating an energy ray to the polymerizable composition containing the surfactant and the adhesive monomer to perform emulsion polymerization. it can. The polymerizable composition may further contain the other monomer and the additive.

The emulsion polymerization of the adhesive polymer can be performed in a solvent containing water. The water-containing solvent may be water or a mixed solvent of water and a water-miscible organic solvent. Above all, water is preferable from the viewpoint that there is no influence on air pollution and environmental destruction.
When using a mixed solvent of water and a water-miscible organic solvent, the content of water relative to the total amount of the mixed solvent (100% by mass) is preferably 50% by mass or more, more preferably 70% by mass or more, and preferably 90% by mass or more. More preferred.
Examples of the water-miscible organic solvent include alcohols such as methanol and ethanol, ethers such as tetrahydrofuran, ketones, and amides.

  The content of the surfactant in the polymerizable composition (100% by mass) is preferably, for example, 5 to 20% by mass. When the content of the surfactant is 5% by mass or more, the hydrophobic sticky monomer can be surely emulsified, and a sufficient amount of radicals are generated, so that the sticky polymer can be efficiently produced in a short time. Easy to obtain. Further, when the content is 20% by mass or less, the remaining amount of the surfactant which is not originally required for the pressure-sensitive adhesive material is reduced, and the adhesiveness to the base material is further improved.

  The content of the adhesive monomer in the polymerizable composition (100% by mass) is preferably, for example, 20 to 60% by mass. When the content of the tacky monomer is 20% by mass or more, the tackiness is improved. When the content is 60% by mass or less, the amount of volatile substances remaining as a monomer without being polymerized can be reduced.

  It is preferable that the components of the polymerizable composition be uniformly mixed with each other in a light-shielded manner, from the viewpoint of suppressing the reaction of the functional group that generates the radical of the surfactant by the energy ray. Further, the obtained polymerizable composition is preferably stored in a light-shielded state until immediately before use.

  The emulsion polymerization of the polymerizable composition is preferably performed while irradiating energy rays. The method of irradiating the energy ray is not particularly limited, and it can be performed according to a conventional method.

  Examples of the energy ray include far ultraviolet rays, ultraviolet rays, near ultraviolet rays, visible light rays, near infrared rays, infrared rays, far infrared rays, microwaves, electron beams, β rays, γ rays, and the like. Above all, from the viewpoint that it has moderate energy and is easy to handle, light such as far ultraviolet rays, ultraviolet rays, near ultraviolet rays, visible light rays, near infrared rays, infrared rays, far infrared rays, and the like are preferable, and the viewpoint of high permeability in an aqueous solvent To near ultraviolet rays are particularly preferred.

  The wavelength of the light is, for example, preferably from 350 to 380 nm, and more preferably from 360 to 375 nm. When the wavelength of the light is 350 nm or more, the light can sufficiently reach the inside of the micelle, and the radical can be sufficiently generated from the surfactant. When the wavelength is 380 nm or less, light having a high energy density reaches the micelles, and radicals can be efficiently generated.

  The irradiation time of the energy beam is, for example, preferably 1 hour to 48 hours, and more preferably 12 hours to 24 hours. When the irradiation time is 1 hour or more, the polymerization reaction can proceed, and when the irradiation time is 48 hours or less, mass productivity can be ensured.

  The temperature at the time of energy beam irradiation is preferably, for example, 20 to 40 ° C. When the temperature is 20 ° C. or higher, emulsion polymerization can proceed at an appropriate speed. When the temperature is 40 ° C. or lower, the adhesive polymer produced by the polymerization can be stably sealed in the micelle.

  If the functional group that generates radicals by light or heat remains in the adhesive polymer used in the emulsion adhesive of the present embodiment, the emulsion adhesive is coated on a substrate, dried, and then exposed to light. By applying heat, the surface of the substrate and the functional group that generates radicals can be covalently bonded, and the adhesiveness between the substrate and the pressure-sensitive adhesive layer is further improved. Therefore, it is preferable that a functional group that generates a radical remains in the adhesive polymer after emulsion polymerization.

As a method of leaving a functional group that generates a radical in the adhesive polymer after emulsion polymerization, for example, a monomer having a functional group that generates a radical by light irradiation in a polymerizable composition, and / or a radical is generated by heat A method of increasing the content of a monomer having a functional group to be generated is exemplified.
Specifically, the content of the monomer having a functional group that generates a radical by light irradiation and / or the monomer having a functional group that generates a radical by heat in the polymerizable composition (100% by mass) is 5% by mass. % Or more.

  The adhesive polymer after emulsion polymerization may be used as an emulsion adhesive as it is, or may be used as an emulsion adhesive after adding additives, purifying and the like.

[Adhesive sheet]
The pressure-sensitive adhesive sheet of this embodiment has a pressure-sensitive adhesive layer made of the emulsion pressure-sensitive adhesive of this embodiment on at least one surface of a substrate. The pressure-sensitive adhesive sheet of the present embodiment may be a single-sided pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer on one side of a substrate, or a double-sided pressure-sensitive adhesive sheet having pressure-sensitive adhesive layers on both sides of the substrate.

  Examples of the base material used for the pressure-sensitive adhesive sheet of the present embodiment include paper base materials such as Japanese paper, high-quality paper, and resin-coated paper; fiber base materials including fiber materials such as natural fibers and chemical fibers; and aluminum. Base materials containing metal materials such as copper and copper; urethane resins, polyolefin resins, polyester resins, polyvinyl chloride resins, polyamide resins, polyimide resins, fluorine resins, polystyrene resins, polycarbonates, etc. A rubber-based substrate; a substrate containing a material obtained by mixing the above materials; a foam substrate having voids inside the substrate; a laminate of the above-mentioned substrates; Is mentioned. Examples of the plastic-based substrate include polyurethane, polystyrene, polyethylene, polypropylene, and polyethylene terephthalate (PET). Examples of the rubber base material include (i) natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), and chloroprene rubber (CR). ) Etc .; (ii) ethylene-propylene rubber (EPM), ethylene-propylene-diene rubber (EPDM), urethane rubber (U), silicone rubber, chlorosulfonated polyethylene, chlorinated polyethylene, acrylic rubber And non-diene rubber bases such as epichlorohydrin rubber, fluoro rubber, butyl rubber (IIR), and halogenated butyl rubber.

[Production method of adhesive sheet]
The method for producing a pressure-sensitive adhesive sheet of the present embodiment includes a step of applying the above-mentioned emulsion pressure-sensitive adhesive on at least one surface of a substrate, drying and irradiating with energy rays to form a pressure-sensitive adhesive layer. The method for producing a pressure-sensitive adhesive sheet of the present embodiment can be suitably used to obtain the above-described pressure-sensitive adhesive sheet.

  The method for applying the emulsion pressure-sensitive adhesive of the present embodiment is not particularly limited. For example, gravure coat, roll coat, spin coat, reverse coat, bar coat, screen coat, blade coat, air knife coat, dipping, dispensing And the like.

  The method of drying the applied emulsion pressure-sensitive adhesive is not particularly limited, and can be performed according to a conventional method.

  In the pressure-sensitive adhesive polymer, in the monomer unit derived from the other monomer, if a functional group that generates a radical remains, the pressure-sensitive adhesive sheet of the present embodiment, when drying the applied emulsion pressure-sensitive adhesive or After drying, the adhesive polymer in the emulsion adhesive may be chemically bonded to the substrate via a functional group that generates radicals by light irradiation or heating. The conditions for light irradiation include the above-described conditions for energy beam irradiation. The heating conditions include, for example, a heating temperature of 25 to 150 ° C. and a heating time of 1 to 48 hours.

  The thickness of the pressure-sensitive adhesive layer in the pressure-sensitive adhesive sheet of the present embodiment is preferably, for example, 10 to 1000 μm. When the thickness of the pressure-sensitive adhesive layer is 10 μm or more, the adhesiveness with the adherend is improved. Further, when the thickness of the pressure-sensitive adhesive layer is 1000 μm or less, it is advantageous in terms of cost.

  The emulsion pressure-sensitive adhesive and pressure-sensitive adhesive sheet of the present embodiment are used, for example, for applications such as automobiles, medical care, sanitary materials, architecture, and electronic devices.

  Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples.

(Example 1)
<Surfactant>
The surfactant was synthesized as follows.
0.1 mol of polyethylene glycol (monomethyl) [4- (chloromethyl) benzyl] ether (synthesized by the Williamson method) is dispersed in methanol, and 0.12 mol of N, N-diethyl is dispersed therein. The mixture was mixed with sodium dithiocarbamate and stirred at room temperature for 48 hours under light shielding.
After the solvent is distilled off, the solid is dissolved in chloroform, washed with a small amount of water five times, then the chloroform layer is dried over magnesium sulfate, the chloroform is distilled off, and a surfactant that generates radicals upon irradiation with energy rays is removed. I got

<Adhesive monomer>
N-butyl acrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) was used as the adhesive monomer.

<Preparation of emulsion adhesive>
In a nitrogen-substituted environment, 15 g of polyethylene glycol (monomethyl) [4- (N, N-diethyldithiocarbamylmethyl) benzyl] ether as a surfactant and 600 g of water as a solvent, Was mixed with 400 g of n-butyl acrylate to prepare a polymerizable composition. Then, near-ultraviolet rays of 365 nm were irradiated for 48 hours to perform an emulsion polymerization reaction, thereby synthesizing an adhesive polymer to obtain an emulsion adhesive.
A part of the solid was measured with an absorptiometer, and the specific absorption at 278 nm derived from dithiocarbamate was analyzed. As a result, the obtained adhesive polymer had a structural unit derived from a surfactant at at least one end. Was.

<Production of adhesive sheet>
The emulsion pressure-sensitive adhesive obtained as described above was applied to the surface of a polyurethane foam (trade name “Everlight”, manufactured by Bridgestone Corporation) as a substrate by a bar coating method. Next, the adhesive sheet was obtained by drying at 80 ° C. for 10 hours using a dryer (trade name “MOV212F”, manufactured by Panasonic Corporation).

(Example 2)
Under a nitrogen-substituted light-shielding environment, 15 g of the surfactant synthesized in Example 1 and 2,2′-azobis [N- (2-propenyl) -2-methylpropion as another monomer were added to 600 g of water as a solvent. Amide] (Wako Pure Chemical Industries, Ltd.) and 350 g of n-butyl acrylate as an adhesive monomer were mixed to prepare a polymerizable composition, and an emulsion polymerization reaction was carried out in the same manner as in Example 1 to obtain emulsion adhesion. Agent was obtained.
As a result of analyzing by UV absorption at 278 nm absorption derived from dithiocarbamate, the obtained adhesive polymer had a structural unit derived from a surfactant at at least one end.
The obtained emulsion pressure-sensitive adhesive was applied to a polyurethane foam in the same manner as in Example 1, and dried at 80 ° C. for 10 hours using a drier (trade name “MOV212F”, manufactured by Panasonic Corporation) to obtain a pressure-sensitive adhesive sheet. .
In addition, before and after washing the pressure-sensitive adhesive sheet with water, the infrared absorption was analyzed by a change in absorption at 1780 cm ⁻¹ derived from the pressure-sensitive adhesive polymer, and it was confirmed that the residual amount of the pressure-sensitive adhesive polymer was larger than that in Example 1. Was. This is because the diazo bond present in the unit of 2,2′-azobis [N- (2-propenyl) -2-methylpropionamide] in the adhesive polymer molecule of the present example is a drying step in the production of the adhesive sheet. Radicals were generated by the applied heat, and the radicals were bonded to the polyurethane foam as the base material, suggesting that the urethane foam and the adhesive polymer formed a covalent bond.

(Comparative Example 1)
In a nitrogen-substituted environment, 600 g of water as a solvent, 10 g of disodium dodecyl diphenyl ether disulfonate as a surfactant (trade name "Sanded BL", manufactured by Sanyo Chemical Industries, Ltd.) and an oxyethyleneoxypropylene copolymer 5 g of a product (“Pluronic F-68”, manufactured by ADEKA Corporation), 1 g of ammonium persulfate as a polymerization initiator (manufactured by Tokyo Chemical Industry Co., Ltd.), and 400 g of butyl acrylate as an adhesive monomer were mixed. An adhesive sheet was obtained in the same manner as in Example 1 except that the polymerizable composition was prepared by stirring at 70 ° C. for 48 hours.

[Evaluation]
The following evaluation was performed about the adhesive sheet obtained by the Example and the comparative example.

(water resistant)
The pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples were evaluated in accordance with JIS G 4305. The pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples were cut into a width of 25 mm and a length of 150 mm to obtain test pieces.
The test piece was affixed to a SUS 304 plate, and the urethane foam was pulled in a 90 ° direction with respect to the SUS plate to measure the adhesive strength with the test piece. As the numerical value, the maximum value of the stress in the range of 80 mm to 100 mm peeled from the start of peeling was adopted. The tensile tester used was Autograph AG-1 manufactured by Shimadzu Corporation.
The test piece was immersed in water at a temperature of 25 ° C. for 72 hours. Thereafter, the test piece taken out of the water was dried at a temperature of 60 ° C. for 48 hours, affixed to a SUS304 plate, and the urethane foam was pulled in a 90 ° direction with respect to the SUS plate to measure the adhesive strength with the test piece.

(Adhesion with substrate)
From the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples, 15 test pieces were produced in the same manner as in the evaluation of water resistance. Then, after immersing in water at a temperature of 40 ° C. for 72 hours, the test piece taken out of the water was dried at a temperature of 40 ° C. for 48 hours, and then the test piece was visually observed. The number at which the pressure-sensitive adhesive layer was peeled off at the interface was measured.

Claims (4)

Terminally modified with a surfactant having a functional group capable of generating a radical by energy ray irradiation, looking containing an adhesive polymer,
The functional group that generates a radical by irradiation with energy rays is at least one selected from the group consisting of an N, N-dialkyldithiocarbamylmethyl group, a benzophenone group, a camphorquinone group, and a phenylazide group. Emulsion adhesive. A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer comprising the emulsion pressure-sensitive adhesive according to claim 1 on at least one surface of a substrate. A surfactant having a functional group that generates a radical by energy ray irradiation, and a polymerizable composition containing a monomer that imparts tackiness after polymerization, are irradiated with energy rays, and the terminal is modified with the surfactant. the step of obtaining the adhesive polymer viewed including,
The functional group that generates a radical by irradiation with energy rays is at least one selected from the group consisting of an N, N-dialkyldithiocarbamylmethyl group, a benzophenone group, a camphorquinone group, and a phenylazide group. A method for producing an emulsion adhesive. A method for producing a pressure-sensitive adhesive sheet, comprising a step of applying the emulsion pressure-sensitive adhesive according to claim 1 on at least one surface of a substrate, drying and irradiating with energy rays to form a pressure-sensitive adhesive layer. Method.