JP2022096726A - Coating agent for forming water-containing gel sheet and water-containing gel sheet - Google Patents

Abstract

To provide coating agents that can form a water-containing gel sheet having sufficient pot life at the time of painting, excellent wettability to a peeling film, and sufficient adhesion to a bonded substrate.SOLUTION: Provided is a coating agent for forming a water-containing gel sheet, which is obtained by mixing an unneutralized water-soluble carboxyl group-containing polymer (A), a crosslinking agent (B) ionically bonding with the polymer (A), and an acrylic emulsion (C) with pH 1.0 to 10.5, in which a completely or partially neutralized water-soluble carboxyl group-containing polymer is not mixed, and a desiccant may be contained. The coating agent for forming a water-containing gel sheet has a pH of 1.0 or more and less than 3.0. Also provided is a water-containing gel sheet containing 10 to 95 mass% of a drying conditioner in the total amount excluding water.SELECTED DRAWING: None

Description

The present invention relates to a coating agent for forming a hydrogel sheet and a hydrogel sheet.

The water-containing gel sheet having moderate adhesive strength and low skin irritation is a water-containing gel sheet laminate laminated on a base material, such as a medical paping agent, a medical electrode fixing material, a sheet-like skin cooling material, a wound dressing, and a sheet. It is used as a cosmetic pack.

The water-containing gel sheet is obtained by swelling a crosslinked or insolubilized hydrophilic polymer with water, and there are various types depending on the type of the hydrophilic polymer, the method of crosslinking or insolubilization, and the like. As the polymer used for the water-containing gel sheet, a carboxyl group-containing polymer such as non-crosslinked polyacrylic acid or a salt thereof, crosslinked polyacrylic acid or a salt thereof, or carboxymethyl cellulose or a salt thereof is known. As a method for cross-linking a carboxyl group-containing polymer, a method for forming an ionic bond complex with a polyvalent metal cation such as aluminum hydroxide or aluminum sulfate is known, and this method is widely used industrially. ing.

However, when the above-mentioned polyvalent metal cation, which is generally used in the past, is mixed with an aqueous solution of a carboxyl group-containing polymer, the cross-linking reaction proceeds rapidly at room temperature to form a gel, so that the polyvalent metal cation and the carboxyl group are formed. The period during which the mixture for forming a hydrogel sheet containing the contained polymer (hereinafter referred to as a coating agent) can be stored in a fluid state (hereinafter referred to as pot life) is shortened. Therefore, even if an attempt is made to apply this coating agent on a support in the form of a sheet using a roll coater or the like, there is a problem that the coating cannot be performed because the cross-linking reaction has already proceeded and the fluidity has been lost. ..

In order to solve this problem, a chelating agent typified by ethylenediaminetetraacetic acid (EDTA) or a sodium salt thereof is added to the coating agent as a gelation rate adjusting agent. The coating agent to which the gelation rate adjusting agent is added can be applied onto the support using a roll coater or the like because the gelation reaction is delayed and the coating agent has sufficient fluidity at the time of coating. become. However, since the effect of delaying the gelation reaction remains even after coating, there is a problem that it is necessary to keep the coated material for a long time without deforming it (hereinafter referred to as seasoning).
Therefore, when applying a coating agent to a single-wafer support, there is a problem that a production facility is required to wait for the completion of the cross-linking reaction without deforming the monolithic water-containing gel sheet laminate after coating. there were.
When the coating agent is applied on a web-shaped long support instead of a single leaf, the cross-linking reaction occurs without deforming the long water-containing gel sheet laminate after coating without winding it. There was the problem of requiring a larger special production facility to wait for the end. When an attempt is made to wind a long water-containing gel sheet laminate after coating into a roll in a state where cross-linking is not perfect, there is also a problem that the water-containing gel sheet protrudes from the end of the roll-shaped laminate due to the pressure at the time of winding. ..
If it becomes possible to wind up a long web-shaped water-containing gel sheet laminate in a roll shape without seasoning, the manufacturing process can be simplified because it can be transported in a roll shape to the next processing process such as slitting and punching. In addition, the product can be supplied in roll form, and the productivity is significantly improved compared to the single-leaf hydrogel sheet laminate.

In Patent Document 1, it is excellent in productivity because it has a sufficient pot life at the time of coating, and it does not transfer to an adherend because gelation progresses sufficiently, and it has a followability to an adherend. As a good water-containing gel sheet, it contains a carboxyl group-containing polymer and a cross-linking agent ionically bonded to the carboxyl group-containing polymer, has a pH of 1 or more and less than 3, and has a water content of 1 to 30% by mass. The hydrogel sheet is disclosed.

Japanese Patent No. 6593566

By the way, there are the following two methods for obtaining a water-containing gel sheet laminate by applying a coating agent on a support and heating it to volatilize and remove a part of water.
(1) Direct coating: A peeling sheet whose surface has been peeled off for the purpose of applying a coating agent on a support such as a resin film and, if necessary, protecting the formed hydrogel sheet after the drying step. How to paste together.
(2) Transfer coating: A coating agent is applied on a release sheet that is a support during coating, and after a drying step, a base material such as a resin film is attached to the surface thereof to form a water-containing gel sheet. A method of integrating with a base material.

In the transfer coating of the above (2), heat is not applied to the base material, and strong tension derived from the structure of the coating machine is not applied to the base material. It is widely used in the manufacture of products that use highly elastic substrates.

The coating agent described in Patent Document 1 is repelled when the coating agent is applied on a release sheet such as a PET (polyethylene terephthalate) film whose surface has been peeled off in transfer coating, and a uniform gel sheet can be obtained. There was a problem that it wasn't there. Further, when a base material such as a resin film is bonded after coating and the water-containing gel sheet and the base material are integrated, there is a problem that sufficient adhesion to the base material cannot be obtained.

The problem to be solved by the present invention is a water-containing gel sheet having a sufficient pot life at the time of coating, excellent wettability to a release sheet, good gelation degree, and sufficient adhesion to a substrate. It is to provide a coating agent which can form a laminated body.

As a result of diligent studies to solve the above-mentioned problems, the present inventor has found that the above-mentioned problems can be solved, and has completed the present invention.

That is, the present invention comprises an unneutralized water-soluble carboxyl group-containing polymer (A), a cross-linking agent (B) ionically bonded to the polymer (A), and an acrylic emulsion (C) having a pH of 1.0 to 10.5. A water-soluble carboxyl group-containing polymer that has been mixed and completely neutralized or partially neutralized is not mixed and may contain a drying conditioner, having a pH of 1.0 or more and less than 3.0, a coating agent for forming a hydrogel sheet. Regarding.

Further, the present invention is for forming the water-containing gel sheet, wherein the viscosity increase rate after 24 hours at 25 ° C. after mixing the polymer (A), the cross-linking agent (B) and the acrylic emulsion (C) is 20% or less. Regarding coating agents.

Further, the present invention relates to a water-containing gel sheet formed from the above-mentioned coating agent for forming a water-containing gel sheet, which has a pH of 1.0 or more and less than 3.0 and a water content of 1 to 30% by mass.

Furthermore, the present invention relates to the above-mentioned water-containing gel sheet containing a drying conditioner in an amount of 10 to 95% by mass in the total amount excluding water.

INDUSTRIAL APPLICABILITY According to the present invention, a coat capable of forming a water-containing gel sheet laminate having sufficient pot life at the time of coating, excellent wettability to a release sheet, good gelation degree, and sufficient adhesion to a substrate. It became possible to provide the agent.

Hereinafter, embodiments of the present invention will be described in detail.

The coating agent for forming a water-containing gel sheet of the present invention (hereinafter, also referred to as a coating agent) includes an unneutralized water-soluble carboxyl group-containing polymer (A), a cross-linking agent (B) ionically bonded to the polymer (A), and a cross-linking agent (B). A completely neutralized or partially neutralized water-soluble carboxyl group-containing polymer obtained by mixing an acrylic emulsion (C) having a pH of 1.0 to 10.5 is not mixed and may contain a drying conditioner, pH 1. A coating agent for forming a hydrogel sheet, which is 0 or more and less than 3.0.

The unneutralized water-soluble carboxyl group-containing polymer (A) used in the present invention is a polymer having a carboxyl group and is a water-soluble, that is, an unneutralized polymer that is soluble in water.
The water-soluble polymer is an expression for a polymer that swells or disperses in water, and means a polymer having a concentration of 10% by mass and a liquid at 23 ° C. that is transparent. A polymer that swells or disperses in water means a polymer having a concentration of 10% by mass and a liquid at 23 ° C. that becomes cloudy. The concentration of 10% by mass refers to the case where 10 parts by mass of the polymer is added to 90 parts by mass of water. White turbidity means that the haze measured by a cell having an optical path length of 10 mm is 50% or more.

Examples of the unneutralized water-soluble carboxyl group-containing polymer (A) used in the present invention include synthetic polymers such as homopolymers and copolymers of (meth) acrylic acid, hyaluronic acid, xanthan gum, gellan gum, pectin, and caraginan. Examples include proteins such as sugars and glycinin (soy protein). As the carboxyl group-containing polymer, one kind or two or more kinds of components can be used. Of these, polyacrylic acid is preferably used.

The mass average molecular weight of the water-soluble carboxyl group-containing polymer is preferably 20,000 or more, more preferably 150,000 or more. The upper limit of the mass average molecular weight is not particularly limited, but is generally 5 million or less. By using an unneutralized product of a water-soluble carboxyl group-containing polymer having a mass average molecular weight of 20,000 or more, the gel strength required for sheet formation can be obtained.

As the cross-linking agent (B) that ionically bonds with the unneutralized water-soluble carboxyl group-containing polymer (A), polyvalent metal cations such as aluminum chloride, zirconium chloride, magnesium chloride, calcium chloride, and titanium chloride are generated. Examples thereof include inorganic compounds and organic compounds that generate polyvalent cations such as 1,3-diaminoethane, 4,4'-diaminodiphenylmethane, and melamine. As the cross-linking agent (B), one kind or two or more kinds of components can be used. Of these, alum, which is an aluminum salt, is preferably used.

The cross-linking agent (B) can be used in any amount, but is preferably 0.1 to 50 parts by mass with respect to 100 parts by mass of the unneutralized water-soluble carboxyl group-containing polymer (A). More preferably, it is 5 to 50 parts by mass. When the amount of the cross-linking agent (B) added is 0.1 parts by mass or more, gelation proceeds rapidly as the water content of the coating agent decreases, and when it is 50 parts by mass or less, the appearance is excellent with high transparency. A gel sheet can be produced.

As the acrylic emulsion (C) used in the present invention, any acrylic emulsion having a pH of 1.0 to 10.5 can be used, but from the viewpoint of safety, an acrylic emulsion that has been used for human skin is preferable.
For example, in a dispersion medium containing water as a main component, an alkyl (meth) acrylate such as n-butyl (meth) acrylate or 2-ethylhexyl (meth) acrylate is used as a main monomer and copolymerizable with the main monomer (for example). Meta) Acrylic acid ["Acrylic acid" and "methacrylic acid" are collectively referred to as "(meth) acrylic acid". The same applies below. ], Etc., a carboxyl group-containing monomer such as 2-hydroxyethyl (meth) acrylate, a hydroxyl group-containing monomer such as 2-hydroxyethyl (meth) acrylate, an amide group-containing monomer such as dimethylacrylamide, etc. Alternatively, it can be obtained by emulsifying and polymerizing a main monomer and a submonomer.
The pH of the acrylic emulsion (C) and the pH of the coating agent for forming a hydrogel sheet can be measured using a pH meter having a sensor having an arbitrary shape such as a probe, a dome, or a flat surface. A commercially available device can be used, and for example, LAQUAtwin <pH-22B> (manufactured by HORIBA, Ltd.) can be used.

As the acrylic emulsion (C), more specifically, the methyl acrylate / -2-ethylhexyl acrylate copolymer resin emulsion listed in the pharmaceutical additive standard, and the acrylic listed in the non-pharmaceutical raw material standard. Alkyl Acid Copolymer Emulsion (2), Alkyl Acrylate Copolymer Ammonium Registered in INCI (International Naming for Cosmetic Ingredients), (Acrylate / Diacetoneacrylamide) Copolymer, (Dimethylacrylamide / Hydroxyethyl Acrylate / methoxy Acrylate) Ethyl) copolymers and the like are mentioned, and among them, methyl acrylate / -2-ethylhexyl acrylate copolymer resin emulsion and alkyl acrylate copolymer emulsion (2) are particularly preferable.

The acrylic emulsion (C) can be used in any amount, but is preferably 10 to 2000 parts by mass in terms of solid content with respect to 100 parts by mass of the unneutralized water-soluble carboxyl group-containing polymer (A). , 50 to 2000 parts by mass, more preferably. When the amount is 10 parts by mass or more, the wettability to the release sheet at the time of transfer coating and sufficient adhesion to the substrate can be ensured, and when the amount is 2000 parts by mass or less, the water-containing gel sheet having a sufficient gel feeling can be obtained. Can be formed.

The coating agent may further contain a hydrophilic polymer other than the components (A) to (C) and other additives, if necessary.

Examples of the hydrophilic polymer include polyvinyl alcohol, polyvinylpyrrolidone, polyallylamine or a salt thereof, polyethyleneimine or a salt thereof, polyacrylamide or a salt thereof, synthetic polymers such as polydialyldimethylammonium and polyvinylpyridine, starch, locust bean gum, and guar gum. Examples include polysaccharides such as tamarind seed gum, chitosan, carboxymethyl cellulose, alginic acid and karaya gum. These hydrophilic polymers can adjust the rheology of the coating agent and the physical properties such as the gel strength and adhesive strength of the obtained hydrogel sheet according to the type and amount of the polymer to be added.

Other additives include drying adjusters, pH adjusters, antioxidants, preservatives, UV absorbers, lubricants, colorants (dye or pigment), chemicals, fillers (particle or fibrous), and conductivity-imparting agents. And so on.

As the drying adjusting agent, a hydrophilic compound having a small influence on the viscosity of the coating agent and having a mass average molecular weight of 10,000 or less can be used. Examples thereof include room temperature liquid compounds such as glycerin and polyethylene glycol, and sugars. By using the drying adjusting agent, it is possible to suppress the deterioration of the usability of the water-containing gel sheet due to excessive evaporation of water in the drying step, and further to suppress the change in the water content after the water-containing gel sheet is produced.

The amount of the drying adjuster added is preferably 10 to 95% by mass, more preferably 15 to 92% by mass, based on the total amount of the water-containing gel sheet formed excluding water. When it is 10% by mass or more, overdrying can be suppressed, and when it is 95% by mass or less, a water-containing gel sheet having sufficient strength is obtained. In other words, the drying conditioner can contain 10 to 95% by mass in a total of 100% by mass of the components other than water contained in the coating agent.

As the pH adjuster, in addition to a strong acid such as sulfuric acid, a coating agent or a weak acid such as phosphoric acid having pKa capable of lowering the pH of the formed hydrogel sheet to less than 3.0 can be used. The pH adjuster can be added in any amount.

The pH of the coating agent for forming a hydrogel sheet of the present invention is 1.0 or more and less than 3.0. When the pH is less than 3.0, the generation of ionic carboxyl groups contributing to the crosslinking reaction is suppressed, and the pot life of the coating agent can be guaranteed. Specifically, after mixing the polymer (A), the cross-linking agent (B) and the acrylic emulsion (C), the viscosity increase rate after 24 hours at 25 ° C. is 20% or less, and the coating is applied when producing a hydrogel sheet. Workability can be maintained. The viscosity increase rate is ([viscosity after 24 hours]-[initial viscosity]) ÷ [initial viscosity] × 100 (%). For example, when the initial viscosity is 10 Pa · s and the viscosity after 24 hours is 12 Pa · s, the viscosity increase rate is 20%.
Further, when the pH is 1.0 or higher, the ionic carboxyl group required for gelation can be secured, and the addition of excessive acid becomes unnecessary.

The coating agent for forming a hydrogel sheet of the present invention can be diluted with water, but has a non-volatile content (concentration) of 20 to 80% by mass, and is a mixture of the polymer (A), the cross-linking agent (B) and the acrylic emulsion (C). The viscosity at 23 ° C. at the time of the above is preferably 0.1 Pa · s or more and 30 Pa · s or less, and more preferably 0.2 Pa · s or more and 20 Pa · s or less.
If the viscosity is too low, repelling may occur when the release sheet is coated, and if the viscosity is too high, stirring becomes difficult, and problems such as deterioration of liquid transportability and rough coating surface occur during coating. ..
In the present invention, the viscosities of the coating agent for forming a hydrogel sheet, the polymer (A), the acrylic emulsion (C) and the like can be measured using a B-type viscometer. A commercially available device can be used, for example, a TVB10 type viscometer (manufactured by Toki Sangyo Co., Ltd.) can be used. The measurement conditions are 25 ° C., and the rotation speed and rotor suitable for the viscosity of the measurement target are set. For example, when measuring a coating agent having a viscosity of 10 Pa · s, an M3 rotor having a rotation speed of 12 rpm can be used.

By using the coating agent of the present invention, the coating agent is applied onto a support (base material or release sheet) by the above-mentioned direct coating or transfer coating, and dried to volatilize and remove a part of water. A water-containing gel sheet laminate in which a water-containing gel sheet is provided on the material can be obtained.

The pH of the hydrogel sheet is 1.0 or more and less than 3.0. The pH of the hydrogel sheet reflects the pH of the coating agent that forms it. The pH of the hydrogel sheet can be measured using a pH meter having a planar sensor. A commercially available device can be used, and for example, LAQUAtwin <pH-22B> (manufactured by HORIBA, Ltd.) can be used.

The water content of the water-containing gel sheet formed by the coating agent is 1 to 30% by mass, more preferably 2 to 25% by mass. The flexibility of the water-containing gel sheet can be ensured when the water content of the water-containing gel sheet is 1% by mass or more. Further, when the water content is 30% by mass or less, gelation proceeds rapidly. The water content of the water-containing gel sheet can be measured using a Karl Fisher Moisture Meter. A commercially available device can be used, and for example, a coulometric method curl fisher moisture meter CA-200 type (manufactured by Mitsubishi Chemical Analytec Co., Ltd.) can be used.

The hydrogel sheet of the present invention can be obtained by direct coating or transfer coating using a coating agent.
As the base material, a resin film, a natural fiber, a semi-synthetic fiber, a synthetic fiber, or a cloth or knitted fabric made of a composite fiber thereof, a non-woven fabric, paper, a synthetic paper, or the like can be used. These base materials may be subjected to surface treatment such as primer treatment or water repellent / hydrophilic treatment, or may be composited with the same type or different types of base materials. Among them, polyurethane, non-woven fabric and their composite base materials are preferably used because they have good adhesion to the water-containing gel sheet formed by the coating agent. However, as described above, when these materials are used as the base material. Is preferably by transfer coating.
The type of the release sheet is not particularly limited, and a sheet whose surface has been peeled off with a silicone resin or the like can be used. The thickness of the base material and the release sheet is not particularly limited, but is preferably 5 to 3000 μm.

The method of applying the coating agent to the base material or the release sheet is not particularly limited as long as it can be applied to a material having fluidity, and for example, a roll coater, a knife coater, a gravure coater, a bar coater, a die coater, or the like can be used. The method to be used can be mentioned. The amount of the coating agent to be applied is not particularly limited, but is preferably 10 to 2000 g / m ² .
The atmospheric temperature in the heating step is not particularly limited, but is preferably 50 ° C to 200 ° C, more preferably 80 ° C to 120 ° C. When the atmospheric temperature in the heating process is 50 ° C or higher, the coating agent can be dried efficiently in terms of time, and when it is 200 ° C or lower, sudden changes in the moisture content are suppressed, and the appearance is poor due to the generation of bubbles, and the gel is not good. Uniformization can be prevented.

In the case of direct coating, a release sheet is attached to the coating film that has been coated and some of the water has been removed by heating and drying, and in the case of transfer coating, a base material is attached to the water-containing gel sheet. Laminates are obtained, which can be rolled up as needed. A normal winder can be used for winding.

Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples.
<Raw materials>
The raw materials of the coating agents used in the examples and comparative examples shown in Tables 1 and 2 are as follows.
<< Water-soluble polymer with carboxyl group >>
-Julimer AC-10SH: non-bridged polyacrylic acid, mass average molecular weight 1 million, aqueous solution having a non-volatile content concentration of 10% by mass, manufactured by Toa Synthetic Co., Ltd.-Julimer AC-10L: non-bridged polyacrylic acid, mass average molecular weight 2 .50,000, aqueous solution with non-volatile content concentration of 40% by mass, Julima AC-10H manufactured by Toa Synthetic Co., Ltd .: (non-bridged polyacrylic acid, mass average molecular weight 150,000, aqueous solution with non-volatile content concentration of 20% by mass, Toa Synthetic Co., Ltd. Aquaric AS58: Non-bridged polyacrylic acid, mass average molecular weight 800,000, manufactured by Nippon Catalyst Co., Ltd. Aquarick HL-415: Non-bridged polyacrylic acid, mass average molecular weight 10,000, manufactured by Nippon Catalyst Co., Ltd. Alonbis SX: non-bridged sodium polyacrylate, mass average molecular weight 4.5 million, manufactured by Toa Synthetic Co., Ltd.

<< Acrylic Emulsion >>
・ Nicazole TS-620 (methyl acrylate / acrylic acid-2-ethylhexyl copolymer resin emulsion, non-volatile content concentration 60% by mass, pH 2.5), manufactured by Nippon Carbide Industries ・ BPW HW-2 (methyl acrylate / acrylic acid- 2-Ethylhexyl copolymer resin emulsion, non-volatile content concentration 60% by mass, pH 2.4), manufactured by Toyochem Co., Ltd.-TOCRYL FSK-6649T (alkyl acrylate copolymer emulsion, non-volatile content concentration 58% by mass, pH 7.1), Made by Toyochem Co., Ltd.

<< Drying conditioner >>
Macrogol 400: Polyethylene glycol, mass average molecular weight 400, Sanyo Chemical Industries, Ltd.
<< Hydrophilic polymer >>
-Gosenol EG-40: polyvinyl alcohol, viscosity 43 mPa · s, non-volatile component concentration 4% by mass, 20 ° C, manufactured by Nippon Synthetic Chemical Co., Ltd.-PAA-HCL-10L: polyallylamine hydrochloride, mass average molecular weight 150,000, non-volatile content PH 2.5 as a 50% by mass, 5% by mass aqueous solution, manufactured by Nittobo Medical Co., Ltd.

[Example 1]
Julimer AC-10SH: 50 parts (including 5 parts of non-volatile content), Julimer AC-10L: 12.5 parts (including 5 parts of non-volatile content), potassium aluminum sulfate 12hydrate: 1 part, Nicazole TS-620: 17 parts (including 10 parts of non-volatile content), 60 parts of glycerin, and water were mixed to obtain a coating agent having a viscosity of 10 Pa · s, and the pot life was evaluated according to the method described later.
The obtained coating agent is coated on a silicone peeling-treated polyethylene terephthalate (PET) film, which is a peeling sheet, with a knife coater so that the coating film amount is about 200 g / m ² , and then heated and dried to have a water content of 10%. A gel sheet was obtained. The coatability was evaluated according to the method described later.
This was bonded to each of the following two types of substrates to obtain two types of water-containing gel sheet laminates, which were wound into a roll. The adhesion of the hydrogel sheet to the substrate was evaluated according to the method described later.
Base material 1: DN-11U: Polyurethane film, average thickness 11 μm, manufactured by Nippon Materials Co., Ltd. Base material 2: Sontara: non-woven fabric, average thickness 180 μm, manufactured by Teijin DuPont Co., Ltd.

[Examples 2 to 3]
As shown in Table 1, the viscosities were the same as in Example 1 except that BPW HW-2 and TOCRYL FSK-6649T were used as non-volatile components instead of Nicazole TS-620 as acrylic emulsions. A coating agent of 10 Pa · s was obtained, and the heating and drying conditions were appropriately changed to obtain a gel sheet laminate having a water content of 10%, which was evaluated in the same manner.

[Comparative Example 1]
As shown in Table 1, a coating agent having a viscosity of 10 Pa · s and a water-containing gel sheet laminate having a water content of 10% were obtained in the same manner as in Example 1 except that Nikazole TS-620 was not mixed, and evaluated in the same manner. ..

[Comparative Example 2]
As shown in Table 1, a coat having a viscosity of 10 Pa · s was obtained in the same manner as in Example 3 except that 10 parts of Aronbis SX, which is a sodium neutralized product, was mixed instead of the unneutralized water-soluble carboxyl group-containing polymer. An agent and a water-containing gel sheet laminate having a water content of 10% were obtained and evaluated in the same manner. If a uniform coating agent could not be obtained due to gelation, it was judged that coating was not possible because a hydrogel sheet laminate could not be produced.
[Comparative Examples 3 to 5]
As shown in Table 1, a coating agent having a viscosity of 10 Pa · s and a water content are in the same manner as in Example 3 except that an unneutralized water-soluble carboxyl group-containing polymer and a sodium neutralized product are mixed with an acrylic emulsion or the like. A water-containing gel sheet laminate having a rate of 10% was obtained and evaluated in the same manner. If a uniform coating agent could not be obtained due to gelation, it was judged that coating was not possible because a hydrogel sheet laminate could not be produced.

[Comparative Examples 6 and 7]
As shown in Table 1, instead of the water blended in Example 3, a coating agent having a viscosity of 10 Pa · s and a coating agent having a viscosity of 10 Pa · s were prepared in the same manner as in Example 3 except that an aqueous solution in which sodium hydroxide was dissolved in water was blended. A water-containing gel sheet laminate having a water content of 10% was obtained and evaluated in the same manner. If a uniform coating agent could not be obtained due to gelation, it was judged that coating was not possible because a hydrogel sheet laminate could not be produced.

[Examples 4 to 10]
As shown in Table 1, based on the composition of Example 3, a coating agent having a viscosity of 10 Pa · s and a water-containing gel sheet having a water content of 10% were obtained in the same manner as in Example 3 except that the mixing amount of the acrylic emulsion was changed. A laminate was obtained and evaluated in the same manner.

[Examples 11 to 18]
As shown in Table 2, as an unneutralized water-soluble carboxyl group-containing polymer, Aquaric AS58: Aquaric HL-415 was mixed with a non-volatile content of 8: 2, and different amounts and types of cross-linking agents and acrylics were used. The emulsion was mixed to obtain a coating agent having a viscosity of 10 Pa · s and a water-containing gel sheet laminate having a water content of 10%, which were evaluated in the same manner.

[Examples 19 to 26]
As shown in Table 2, based on the composition of Example 14, a coating agent having a viscosity of 10 Pa · s and a water content of 10% were obtained in the same manner as in Example 14 except that the amount and type of the drying adjusting agent were changed. A water-containing gel sheet laminate was obtained and evaluated in the same manner.

[Examples 27 to 31]
As shown in Table 2, the type of the unneutralized water-soluble carboxyl group-containing polymer was changed, or the hydrophilic polymer was further mixed to obtain a coating agent having a viscosity of 10 Pa · s and a water-containing gel sheet laminate having a water content of 10%. Obtained and evaluated in the same manner.

[Comparative Example 8]
A coating agent having a viscosity of 10 Pa · s and a water-containing gel sheet laminate having a water content of 10% were obtained in the same manner as in Example 13 except that the acrylic emulsion was not mixed based on the composition of Example 13, and evaluated in the same manner. ..
[Comparative Example 9]
A coating agent having a viscosity of 10 Pa · s and a water-containing gel sheet laminate having a water content of 10% were obtained in the same manner as in Example 27 except that the acrylic emulsion was not mixed based on the composition of Example 27, and evaluated in the same manner. ..

(Pot life of coating agent)
The viscosity increase rate of the coating agent left at 25 ° C. for 24 hours after preparation was evaluated. The evaluation was performed according to the following criteria.
⊚: Increase rate is 10% or less. (Very good)
◯: The rate of increase is greater than 10% and 20% or less. (Good)
×: The rate of increase is greater than 20%, or gelling occurs and coating is not possible. (Defective)

(Coatability for peeling PET film of coating agent)
The coatability when the coating agent was applied to the peeled PET film was visually observed. The evaluation was performed according to the following criteria.
⊚: No cissing or ear height was observed at the center and edges, and the thickness of the membrane was uniform throughout. (Very good)
◯: Ear height is slightly seen at the edges, but the thickness of the other parts of the coated surface is uniform. (Good)
Δ: The ear height is clear at the end, but most of the film is within the permissible range while maintaining the assumed film thickness. (Practical lower limit)
X: Repellent spreads over the entire coating film and the film thickness becomes non-uniform, or circular repellent is randomly formed. (Defective)

(Adhesion to the base material in the water-containing gel sheet laminate)
The adhesion between the formed hydrogel sheet and the polyurethane film or non-woven fabric as the base material was evaluated.
The evaluation was performed according to the following criteria after the release sheet was peeled off.
⊚: The water-containing gel sheet surface does not come off from the base material even if it is rubbed with a finger. (Very good)
◯: When the surface of the water-containing gel sheet is rubbed with a finger, the base material and the gel sheet peel off at the interface, but even if the sheet is attached to the skin and peeled off, no gel remains on the skin. (Good)
X: When the water-containing gel sheet surface is attached to the skin and then peeled off, the gel remains on the skin. Alternatively, when the release sheet is peeled off, part or all of the water-containing gel sheet is peeled off from the substrate and adhered to the release sheet. (Defective)

In the table, the number of parts of the carboxyl group-containing polymer and acrylic emulsion blended is expressed as the number of parts (mass part) of the resin.
Further, in Table 1, "%" means "mass%".

In each of Examples 1 to 30, the pot life of the coating agent was sufficiently long, there was no coating defect on the release sheet in the coating process, and a water-containing gel sheet that sufficiently adhered to the substrate could be produced. On the other hand, in Comparative Examples 1 to 9, defects were found in any of the pot life of the coating agent, the coatability on the release sheet, and the adhesion to the substrate.

Claims (4)

An unneutralized water-soluble carboxyl group-containing polymer (A), a cross-linking agent (B) ionically bonded to the polymer (A), and an acrylic emulsion (C) having a pH of 1.0 to 10.5 are mixed to complete the process. A coating agent for forming a hydrogel sheet having a pH of 1.0 or more and less than 3.0, which is not mixed with a neutralized or partially neutralized water-soluble carboxyl group-containing polymer and may contain a drying conditioner. The coating agent for forming a water-containing gel sheet according to claim 1, wherein the viscosity increase rate after 24 hours at 25 ° C. after mixing the polymer (A), the cross-linking agent (B) and the acrylic emulsion (C) is 20% or less. .. A hydrogel sheet formed from the coating agent for forming a hydrogel sheet according to claim 1 or 2, wherein the pH is 1.0 or more and less than 3.0, and the water content is 1 to 30% by mass. The water-containing gel sheet according to claim 3, wherein the drying adjusting agent is contained in an amount of 10 to 95% by mass in the total amount excluding water.