JP2017082021A - Emulsion adhesive, adhesive sheet, method for producing emulsion adhesive, and method for producing adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an emulsion adhesive excellent in adhesion to a substrate or the like and also excellent in water resistance.SOLUTION: The emulsion adhesive of the present invention contains an adhesive polymer whose terminal is modified with a surfactant having a functional group which generates radicals by energy ray irradiation. The functional group which generates radicals by energy ray irradiation is preferably at least one selected from the group consisting of an N,N-dialkyldithiocarbamylmethyl group, a benzophenone group, a camphorquinone group, and a phenylazide group.SELECTED DRAWING: None

Description

  The present invention relates to an emulsion adhesive, an adhesive sheet, a method for producing an emulsion adhesive, and a method for producing an 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 air pollution and environmental considerations, the switch to adhesives that do not use organic solvents is being promoted.

  As an adhesive that does not use an organic solvent, emulsion polymerization (emulsion polymerization) is performed in which a monomer and a surfactant are mixed in a medium such as water, and a polymerization initiator that is soluble in the medium is added to perform polymerization in a micelle. The pressure-sensitive adhesive containing an adhesive polymer obtained by (1) is known (Patent Document 1).

Japanese Unexamined Patent Publication No. 2015-052060

However, the pressure-sensitive adhesive obtained by the conventional emulsion polymerization method described in Patent Document 1 and the like is applied to a base material and the like, and after drying and destroying the micelle, Is separated. And the thin layer containing surfactant was formed between the adhesive and the base material etc., and the base material etc. and adhesive force might fall.
In addition, when the adhesive obtained by the conventional emulsion polymerization method is dried and then touched with water, the surfactant may be eluted, and the properties of the adhesive are likely to change with water, resulting in poor water resistance. was there.

  Accordingly, an object of the present invention is to provide an emulsion pressure-sensitive adhesive that is excellent in adhesiveness to a substrate and the like and excellent in water resistance. Another object of the present invention is to provide a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer that is excellent in adhesiveness between the substrate and the pressure-sensitive adhesive layer and is excellent in water resistance. Another object of the present invention is to provide a method for producing an emulsion pressure-sensitive adhesive, which is capable of obtaining an emulsion pressure-sensitive adhesive that is excellent in adhesion to a substrate and the like and is excellent in water resistance. Moreover, this invention aims at providing the manufacturing method of an adhesive sheet which can obtain the adhesive sheet which has the adhesive layer which is excellent in the adhesiveness of a base material and an adhesive layer, and is excellent also in water resistance. .

That is, the emulsion pressure-sensitive adhesive of the present invention is characterized by containing a pressure-sensitive adhesive polymer whose terminal is modified with a surfactant having a functional group that generates radicals upon irradiation with energy rays.
According to the emulsion pressure-sensitive adhesive of the present invention, the adhesiveness with a substrate and the like is excellent, and the water resistance is also excellent.

In the emulsion adhesive of the present invention, the functional group that generates radicals upon irradiation with energy rays is selected from the group consisting of N, N-dialkyldithiocarbamylmethyl group, benzophenone group, camphorquinone group, and phenylazide group. It is preferable that there is at least one.
According to this structure, it is further excellent in adhesiveness with a base material etc., and is further excellent in water resistance.

The pressure-sensitive adhesive sheet of the present invention is characterized by having a pressure-sensitive adhesive layer made of the emulsion pressure-sensitive adhesive on at least one surface of a substrate.
According to the pressure-sensitive adhesive sheet of the present invention, the adhesion between the substrate and the pressure-sensitive adhesive layer is excellent, and the water resistance is also excellent.

The method for producing an emulsion pressure-sensitive adhesive of the present invention irradiates a polymerizable composition containing a surfactant having a functional group that generates radicals upon irradiation with energy rays and a monomer that imparts tackiness after polymerization with energy rays. And a step of obtaining an adhesive polymer having a terminal modified with the surfactant.
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 having excellent adhesion to a substrate and the like and excellent water resistance.

The method for producing a pressure-sensitive adhesive sheet of the present invention comprises a step of forming a pressure-sensitive adhesive layer by applying the emulsion pressure-sensitive adhesive, drying and irradiating energy rays on at least one surface of a substrate. To do.
According to the method for producing a pressure-sensitive adhesive sheet of the present invention, a pressure-sensitive adhesive sheet having excellent adhesion between the substrate and the pressure-sensitive adhesive layer and excellent in water resistance can be obtained.

  ADVANTAGE OF THE INVENTION According to this invention, the emulsion adhesive which is excellent in adhesiveness with a base material etc. and excellent in water resistance can be provided. Moreover, this invention can provide the adhesive sheet which has the adhesive layer which is excellent in the adhesiveness of a base material and an adhesive layer, and is excellent also in water resistance. Moreover, this invention can provide the manufacturing method of an emulsion adhesive which can obtain the emulsion adhesive which is excellent in adhesiveness with a base material etc. and is excellent also in water resistance. Moreover, this invention can provide the manufacturing method of an adhesive sheet which can obtain the adhesive sheet which is excellent in the adhesiveness of a base material and an adhesive layer, and has an adhesive layer excellent also in water resistance.

  Below, one embodiment is described in detail about an emulsion adhesive of the present invention, an adhesive sheet, a manufacturing method of an emulsion adhesive, and a manufacturing method of an adhesive sheet.

[Emulsion adhesive]
The emulsion pressure-sensitive adhesive of the present invention contains at least a pressure-sensitive adhesive polymer whose terminal is modified with a surfactant having a functional group that generates radicals upon irradiation with energy rays.
In addition to the above-mentioned adhesive polymer, the emulsion adhesive of this embodiment includes solvents such as water and lower alcohols (eg, ethanol); pigments, dispersants, plasticizers, stabilizers, antioxidants, polymerization inhibitors, etc. And so on.

Since the surfactant having a functional group that generates radicals upon irradiation with energy rays has a property as a surfactant, micelles can be formed in an aqueous solvent. Furthermore, the surfactant generates radicals upon irradiation with energy rays and acts as a polymerization initiator during emulsion polymerization. Therefore, it is possible to obtain an adhesive polymer in which a surfactant molecule is combined with an adhesive polymer and a surfactant molecule is bonded to the α-terminal.
The emulsion pressure-sensitive adhesive of the present embodiment contains a pressure-sensitive polymer in which a surfactant molecule having a functional group that generates radicals upon irradiation with energy rays is bonded to the α-terminal. Even if the surfactant is broken, the surfactant and the adhesive polymer are separated and the surfactant is not eluted, and a thin layer containing the surfactant is hardly formed on the surface of the substrate or the like. Therefore, it is difficult to peel from the base material. In addition, since the surfactant is not eluted by water, the water resistance is excellent.

(Surfactant)
The surfactant has a functional group that generates radicals upon irradiation with energy rays and has properties as a surfactant.
The functional group contained in the surfactant molecule that generates radicals upon irradiation with energy rays is selected from the group consisting of N, N-dialkyldithiocarbamylmethyl group, benzophenone group, camphorquinone group, and 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 a high material permeability, and from the viewpoint that the radical lifetime is particularly long. N, N-dialkyldithiocarbamylmethyl group is particularly preferred.
One type of the functional group may be contained in the surfactant, or a plurality of types may be contained.

The surfactant has properties as a surfactant and has at least a hydrophobic group and a hydrophilic group in the 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 branched alkyl group of several 8 or more may be bonded. Among these, it is preferable to bond a dodecyl group, a decyl group, a diethylhexyl group, or the like from the viewpoint of facilitating the formation of micelles.
Examples of the hydrophilic group include oxyethylene group, poxypropylene group, hydroxyl group, carboxyl group, sulfonic acid group, and alkali metal salts thereof. Among these, from the viewpoint of being chemically stable and having little influence on the polymerization reaction, an oxyethylene group and a poxypropylene group are preferable.
One or more of the hydrophobic group and the hydrophilic group may be contained 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 these, 1- (N, N-diethyldithiocarbamylmethyl) -4- (polyethylene glycol monomethyl ether) -benzene is preferable from the viewpoint of easy formation of micelles containing an adhesive monomer.
The said surfactant may be used individually by 1 type, and may use 2 or more types together.

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

(Adhesive monomer)
The adhesive polymer includes a monomer unit derived from an adhesive monomer that imparts adhesiveness after polymerization.
Examples of the adhesive monomer include acrylic monomers such as (meth) acrylic acid alkyl ester having an alkyl group having 4 to 20 carbon atoms; diene monomers such as butadiene and isoprene; silicone having organopolysiloxane as a main chain. System monomers and the like. Among these, from the viewpoint of excellent tackiness, an alkyl acrylate ester having an alkyl group having 4 to 8 carbon atoms is preferable, and butyl acrylate and ethylhexyl acrylate are more preferable.
The said adhesive monomer may be used individually by 1 type, and may use 2 or more types together.
In the present specification, “(meth) acryl” means “acryl” and / or “methacryl”.

As for content of the monomer unit derived from the said adhesive monomer in the said adhesive polymer (100 mass%) contained in the emulsion adhesive of this embodiment, 50-99 mass% is preferable, More preferably, it is 70-95. % By mass. When the content is 70% by mass or more, the adhesive force of the emulsion adhesive to the adherend is further improved. Moreover, when the content is 99% by mass or less, the adhesive polymer can have a high molecular weight by stable emulsion polymerization.
In addition, content of the monomer unit derived from each monomer in a polymer can be calculated | required by the molecular weight measurement by GPC etc.

  The number of monomer units derived from the adhesive monomer contained in the adhesive polymer is preferably 50 to 300, more preferably 100 to 170. When the number of monomer units derived from the adhesive monomer is 50 or more, the adhesive force 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 contain a monomer unit derived from another monomer other than the monomer unit derived from the adhesive monomer.
Examples of the other monomers include monomers having a functional group that generates radicals upon irradiation with energy rays, monomers having a functional group that generates radicals by heat, vinyl acetate, acrylonitrile, acrylamide, styrene, polyfunctional monomers, ( And (meth) acrylic acid.
Adhesion between the substrate and the pressure-sensitive adhesive layer may be further improved by using a monomer having a functional group that generates radicals upon irradiation with energy rays or a monomer having a functional group that generates radicals by heat. . Examples of the monomer having a functional group that generates radicals upon irradiation with energy rays include, for example, o- (N, N-dimethyldithiocarbamylmethyl) styrene, m- (N, N-dimethyldithiocarbamylmethyl) styrene, p- (N, N-dimethyldithiocarbamylmethyl) styrene, o- (N, N-diethyldithiocarbamylmethyl) styrene, m- (N, N-diethyldithiocarba) A monomer having an N, N-dialkyldithiocarbamylmethyl group and a vinyl group such as (milmethyl) styrene and p- (N, N-diethyldithiocarbamylmethyl) styrene; a benzophenone such as 3-vinylbenzophenone and 4-vinylbenzophenone Monomer having vinyl group and vinyl group; camphorquinone group and 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 these, N, N-diethyldithiocarbamylmethylstyrene and 1-vinyl-3-azidobenzene are preferable 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].
In addition, as the other monomer, vinyl acetate, acrylonitrile, acrylamide, and styrene are preferable from the viewpoint of improving the cohesive force of the adhesive polymer. From the viewpoint of introducing a crosslinking point into the adhesive polymer, a polyfunctional monomer, (Meth) acrylic acid is preferred.
The said other monomer may be used individually by 1 type, and may use 2 or more types together.

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

  In the adhesive polymer contained in the emulsion adhesive of this 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, More preferably, it is 5-10. When the molar ratio is 4 or more, the adhesive force of the emulsion adhesive to the adherend is further improved. Moreover, the function by another monomer is easy to be exhibited because it is 20 or less.

(Method for producing emulsion adhesive)
In the method for producing an emulsion adhesive according to this embodiment, an energy ray is applied to a polymerizable composition containing a surfactant having a functional group that generates radicals upon irradiation with energy rays and a monomer that imparts adhesiveness after polymerization. Irradiating to obtain a sticky polymer whose ends are modified with the surfactant. The manufacturing method of the emulsion adhesive of this embodiment can be used conveniently in order to obtain the emulsion adhesive mentioned above.

  The pressure-sensitive adhesive polymer contained in the emulsion pressure-sensitive adhesive of the present embodiment can be obtained by irradiating the polymerizable composition containing the surfactant and the pressure-sensitive monomer with energy rays and performing emulsion polymerization. it can. The polymerizable composition may further contain the other monomer and the additive.

The emulsion polymerization of the above-mentioned adhesive polymer can be performed in a solvent containing water. The solvent containing water may be water or a mixed solvent of water and a water-miscible organic solvent. Among these, water is preferable from the viewpoint of no influence on air pollution and environmental destruction.
When a mixed solvent of water and a water-miscible organic solvent is used, the content of water with respect 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 more preferably 90% by mass or more. Further preferred.
Examples of the water-miscible organic solvent include alcohols such as methanol and ethanol, ethers such as tetrahydrofuran, ketones and amides.

  As for content of the said surfactant in the said polymeric composition (100 mass%), 5-20 mass% is preferable, for example. When the content of the surfactant is 5% by mass or more, the hydrophobic adhesive monomer can be reliably emulsified, and a sufficient amount of radicals are generated to efficiently produce the adhesive polymer in a short time. Easy to obtain. Further, when the content is 20% by mass or less, the residual amount of the surfactant that is not originally required for the pressure-sensitive adhesive material is reduced, and the adhesion to the substrate is further improved.

  As for content of the said adhesive monomer in the said polymeric composition (100 mass%), 20-60 mass% is preferable, for example. Adhesive force improves because content of an adhesive monomer is 20 mass% or more. Moreover, when content is 60 mass% or less, the quantity of the volatile substance which remains as a monomer without superposing | polymerizing can be reduced.

  From the viewpoint of suppressing the reaction of the functional groups that generate radicals of the surfactant with energy rays, the polymerizable composition is preferably shielded from light and uniformly mixed. Moreover, it is preferable to store the obtained polymerizable composition protected from light until just before use.

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

  Examples of the energy rays include far ultraviolet rays, ultraviolet rays, near ultraviolet rays, visible rays, near infrared rays, infrared rays, far infrared rays, microwaves, electron beams, β rays, and γ rays. Among them, from the viewpoint of having moderate energy and being easy to handle, light such as far ultraviolet rays, ultraviolet rays, near ultraviolet rays, visible rays, near infrared rays, infrared rays, far infrared rays is preferable, and a view point of high permeability in an aqueous solvent. To near ultraviolet rays are particularly preferred.

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

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

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

  If functional groups that generate radicals by light or heat remain in the adhesive polymer used in the emulsion adhesive of this embodiment, the emulsion adhesive is applied on the 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 adhesion between the substrate and the pressure-sensitive adhesive layer is further improved. Therefore, it is preferable that a functional group that generates radicals remains in the adhesive polymer after emulsion polymerization.

Examples of a method for leaving a functional group that generates radicals in an adhesive polymer after emulsion polymerization include, for example, a monomer having a functional group that generates radicals upon irradiation with light in a polymerizable composition, and / or radicals by heat. A method of increasing the content of the monomer having a generated functional group is exemplified.
Specifically, in the polymerizable composition (100% by mass), the content of the monomer having a functional group that generates radicals by light irradiation and / or the monomer having a functional group that generates radicals by heat 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 addition and purification of additives.

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

  Examples of the substrate used in the pressure-sensitive adhesive sheet of the present embodiment include paper-based substrates such as Japanese paper, fine paper, and resin-coated paper; fiber-based substrates including fiber materials such as natural fibers and chemical fibers; aluminum Metal base materials including metal materials such as copper; urethane resin, polyolefin resin, polyester resin, polyvinyl chloride resin, polyamide resin, polyimide resin, fluorine resin, polystyrene resin, polycarbonate, etc. A plastic base material including a plastic base material; a rubber base material; a base material including a material in which the above materials are mixed; a foam base material having a void inside the base material; a laminate of the base material; Is mentioned. Examples of the plastic substrate include polyurethane, polystyrene, polyethylene, polypropylene, polyethylene terephthalate (PET) and the like. The rubber-based substrate includes (i) natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR (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 base materials such as epichlorohydrin rubber, fluorine rubber, butyl rubber (IIR), halogenated butyl rubber, and the like.

[Method for producing adhesive sheet]
The method for producing a pressure-sensitive adhesive sheet according to this embodiment includes a step of forming a pressure-sensitive adhesive layer by applying the emulsion pressure-sensitive adhesive on the surface of at least one surface of the substrate, drying it, and irradiating it with energy rays. The manufacturing method of the adhesive sheet of this embodiment can be used conveniently in order to obtain the adhesive sheet mentioned above.

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

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

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

  As for the thickness of the said adhesive layer in the adhesive sheet of this embodiment, 10-1000 micrometers is preferable, for example. When the thickness of the pressure-sensitive adhesive layer is 10 μm or more, the adhesion with the adherend is improved. Moreover, it is advantageous in terms of cost when the thickness of the pressure-sensitive adhesive layer is 1000 μm or less.

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

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to the following Example at all.

Example 1
<Surfactant>
The surfactant was synthesized as follows.
Polyethylene glycol (monomethyl) [4- (chloromethyl) benzyl] ether (synthetic method, synthesized by the Williamson method) was dispersed in 0.1 mol of methanol, and 0.12 mol of N, N-diethyl was added thereto. Sodium dithiocarbamate was mixed and stirred at room temperature for 48 hours in the dark.
After distilling off the solvent, the solid is dissolved in chloroform, washed 5 times with a small amount of water, and then the chloroform layer is dried over magnesium sulfate, and the chloroform is distilled off to generate radicals upon irradiation with energy rays. Got.

<Adhesive monomer>
As an adhesive monomer, n-butyl acrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) was used.

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

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

(Example 2)
In a light-shielding environment substituted with nitrogen, 600 g of water as a solvent, 15 g of the surfactant synthesized in Example 1, and 2,2′-azobis [N- (2-propenyl) -2-methylpropion as another monomer Amide] (Wako Pure Chemical Industries, Ltd.) 50 g and n-butyl acrylate 350 g 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 an emulsion adhesive. An agent was obtained.
When analyzed by UV absorption and absorption at 278 nm derived from dithiocarbamate, the obtained adhesive polymer had a structural unit derived from a surfactant at at least one end.
The obtained emulsion adhesive was applied to polyurethane foam in the same manner as in Example 1 and dried at 80 ° C. for 10 hours using a dryer (trade name “MOV212F”, manufactured by Panasonic Corporation) to obtain an adhesive sheet. .
Moreover, when the adhesive sheet was analyzed by the change in absorption at 1780 cm ⁻¹ derived from the adhesive polymer by infrared absorption before and after washing with water, it was confirmed that the residual amount of the adhesive polymer was larger than that in Example 1. It was. This is a drying process in which the diazo bond present in the unit of 2,2′-azobis [N- (2-propenyl) -2-methylpropionamide] in the adhesive polymer molecule of this example is produced during the production of the adhesive sheet. As a result of generating radicals with the applied heat and bonding the radicals to the polyurethane foam as the base material, it was suggested that the urethane foam and the adhesive polymer formed covalent bonds.

(Comparative Example 1)
Under a nitrogen-substituted environment, 600 g of water as a solvent, 10 g of disodium dodecyl diphenyl ether disulfonate as a surfactant, (trade name “Sun Dead BL”, manufactured by Sanyo Chemical Industries, Ltd.) and an oxyethylene oxypropylene copolymer (Product name “Pluronic F-68”, manufactured by ADEKA Co., Ltd.) 5 g, ammonium persulfate 1 g (manufactured by Tokyo Chemical Industry Co., Ltd.) as a polymerization initiator, and 400 g of butyl acrylate as an adhesive monomer are mixed to prepare a solution. A pressure-sensitive 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)
About the adhesive sheet obtained by the Example and the comparative example, it evaluated based on JISG4305. The pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples were cut to 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 adhesive strength with the test piece was measured by pulling the urethane foam in a 90 ° direction with respect to the SUS plate. As the numerical value, the maximum value of the stress in the range of 80 mm to 100 mm peeling from the start of peeling was adopted. As the tensile tester, Autograph AG-1 manufactured by Shimadzu Corporation was used.
The test piece was immersed in water at a temperature of 25 ° C. for 72 hours. Then, the test piece taken out from water was dried at 60 degreeC for 48 hours, affixed on the SUS304 board, and the adhesive force with a test piece was measured by pulling a urethane foam to a 90 degree direction with respect to a SUS board.

(Adhesiveness with substrate)
From the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples, 15 test pieces were prepared 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 from the water was dried at a temperature of 40 ° C. for 48 hours, and then visually observed, the substrate and the adhesive layer The number of sheets from which the adhesive layer was peeled off at the interface was measured.

Claims (5)

  An emulsion pressure-sensitive adhesive comprising an adhesive polymer having a terminal modified with a surfactant having a functional group that generates radicals upon irradiation with energy rays.   The functional group that generates radicals upon 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. The emulsion adhesive according to 1.   A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer made of the emulsion pressure-sensitive adhesive according to claim 1 or 2 on at least one surface of a substrate.   A polymerizable composition containing a surfactant having a functional group that generates radicals upon irradiation with energy rays and a monomer that imparts tackiness after polymerization is irradiated with energy rays, and the ends thereof are modified with the surfactant. A method for producing an emulsion pressure-sensitive adhesive comprising the step of obtaining an adhesive polymer.   A pressure-sensitive adhesive sheet comprising a step of coating the emulsion pressure-sensitive adhesive according to claim 1 or 2 on at least one surface of a substrate, drying, and irradiating energy rays to form a pressure-sensitive adhesive layer. Manufacturing method.