JP7039386B2 - Hydrogel - Google Patents

Description

The present invention relates to hydrogels.

Hydrogel is basically a polymer that has a high affinity for water and swells in an aqueous solvent. Hydrogels have various properties such as water absorption, swelling, adhesiveness, and conductivity, and by utilizing these properties, they are used in a wide range of fields such as civil engineering, agriculture, food, medical care, cosmetics, and electricity. It's being used.

For example, in the medical field, a hydrogel having adhesiveness is used as an electrode pad of a measuring device such as an electrocardiogram. In addition, a hydrogel having adhesiveness is also used for the electrode pad of EMS (Electrical Muscle Stimulation) for the purpose of slimming and strength training. EMS is an exercise device in which an electrode pad made of hydrogel is attached to the skin and muscles are contracted by electrical stimulation. The hydrogel used for such an electrode pad is required to have high adhesive strength.

As such an adhesive hydrogel, a hydrogel containing a crosslinked polymer composed of an acrylic monofunctional monomer and a crosslinkable monomer, water, and a polyhydric alcohol is known (see Patent Documents 1 and 2). However, with conventional hydrogels, when the adhesive strength is reduced early or the initial adhesive strength is improved by repeating sticking and peeling to an adherend such as skin several times, it is used repeatedly. There is a problem that the adhesive strength is significantly reduced.

Patent Document 3 describes a reinforced composite hydrogel using a polymer blend containing a UV-sensitive molecule as a base material and containing a network of fibers, and describes using cellulose nanofibers as the fiber. However, this document is not related to applications that require adhesiveness, and it is also suggested that the combination of cellulose nanofibers and polyoxyalkylene polyol poly (meth) acrylate improves the adhesiveness during repeated use. do not have.

Patent Document 4 describes a patch gel containing cellulose nanofibers, glycerin or a derivative thereof, and a functionalizing agent. However, it is a technique for gelling using cellulose nanofibers instead of a gelling agent made of a general-purpose synthetic polymer, and the composite of a crosslinked polymer using a crosslinkable monomer and cellulose nanofibers is described. do not have. Further, it relates to a one-time use patch such as a poultice, and does not improve the adhesive strength during repeated use.

Patent Document 5 describes a hydrogel composed of water, a gel strength improver, and a polymer matrix containing them, and the polymer matrix is monofunctional having one ethylenically unsaturated group. It is described that a polyvinyl alcohol-based polymer and / or a cellulose nanofiber is used as a gel strength improving agent, which comprises a copolymer of a monomer and a polyfunctional monomer having 2 to 6 ethylenically unsaturated groups. However, it has not been known that the adhesiveness during repeated use can be improved by combining a polyoxyalkylene polyol poly (meth) acrylate as a polyfunctional monomer with cellulose nanofibers.

Japanese Unexamined Patent Publication No. 2013-185119 Japanese Unexamined Patent Publication No. 3-258239 Japanese Patent Publication No. 2013-535232 Japanese Unexamined Patent Publication No. 2013-82650 JP-A-2017-179328

It is an object of the present invention to provide a hydrogel having excellent initial adhesiveness and adhesiveness after repeated use.

The hydrogel according to the embodiment of the present invention is a crosslinked polymer composed of a monofunctional monomer having one ethylenically unsaturated group and a polyoxyalkylene polyol poly (meth) acrylate, cellulose nanofibers, water, and many. It contains valence alcohol.

According to the embodiment of the present invention, it is possible to provide a hydrogel having excellent initial adhesiveness and adhesiveness after repeated use.

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

The hydrogel according to the present embodiment includes (A) a crosslinked polymer composed of a monofunctional monomer having one ethylenically unsaturated group and a polyoxyalkylene polyol poly (meth) acrylate, and (B) cellulose nanofibers. , (C) water and (D) polyhydric alcohol.

[(A) Crosslinked polymer]
The crosslinked polymer is composed of a copolymer of (A1) a monofunctional monomer and (A2) a polyoxyalkylene polyol poly (meth) acrylate, and is also referred to as a reticulated polymer. Specifically, the crosslinked polymer has a three-dimensional network structure in which the polymer chains made of monofunctional monomers are crosslinked with polyoxyalkylene polyol poly (meth) acrylate, and water and polyhydric alcohol are contained in the hydrogel. It is a polymer matrix for holding.

The monofunctional monomer is a compound having one ethylenically unsaturated group (polymerizable carbon-carbon double bond). As the monofunctional monomer, a hydrophilic monomer having a hydrophilic group such as a carboxyl group, a salt thereof, a hydroxyl group, an amino group, a sulfonic acid group, a salt thereof, and an ammonium group is preferable, and one or more of these hydrophilic groups are present. You may.

Specific examples of the monofunctional monomer include (meth) acrylate, (meth) acrylate (eg, sodium (meth) acrylate, potassium (meth) acrylate, zinc (meth) acrylate, etc.), (meth) acrylamide. , (Meta) acrylamide derivatives (eg N, N-dialkyl (meth) acrylamides such as N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (Meta) acrylamide, N-alkyl (meth) acrylamide such as N-propyl (meth) acrylamide), vinyl sulfonic acid, vinyl sulfonic acid salt (for example, sodium vinyl sulfonate), p-styrene sulfonic acid, p-styrene Sulfonic acid (eg, sodium p-styrene sulfonate), allyl sulfonic acid, allyl sulfonate (eg, sodium allyl sulfonate), 2- (meth) acrylamide-2-methylpropane sulfonic acid, 3-((meth) ) Acryloyloxy) -1-propanesulfonic acid, 3-((meth) acryloyloxy) -2-methyl-1-propanesulfonic acid, N-vinylacetamide, N-vinylformamide, allylamine and the like can be mentioned. These monofunctional monomers may be used alone or in combination of two or more. Among these, it is preferable to use at least one selected from the group consisting of (meth) acrylic acid, (meth) acrylate, (meth) acrylamide, and (meth) acrylamide derivative.

Here, "(meth) acrylic acid" means at least one of acrylic acid and methacrylic acid. "(Meta) acrylamide" means at least one of acrylamide and methacrylamide. "(Meta) acryloyloxy" means at least one of acryloyloxy and methacryloyloxy.

Polyoxyalkylene polyol Poly (meth) acrylate has a structure in which (meth) acrylic acid is ester-bonded to the hydroxyl group of a polyoxyalkylene polyol (a structure in which a plurality of alkylene oxides are added to a polyhydric alcohol having a valence of 2 or more). It is a compound having and is used as a crosslinkable monomer (polyfunctional monomer). Here, "(meth) acrylate" means at least one of acrylate and methacrylate. "Poly (meth) acrylate" means a (meth) acrylate having 2 to 8 (meth) acryloyl groups, and examples thereof include di (meth) acrylate, tri (meth) acrylate, and tetra (meth) acrylate. Be done. "(Meta) acryloyl group" means at least one of an acryloyl group and a methacryloyl group.

Specific examples of the polyoxyalkylene polyol poly (meth) acrylate include polyethylene glycol di (meth) acrylates such as diethylene glycol di (meth) acrylate, trimethylolpropane di (meth) acrylate, and tetraethylene glycol di (meth) acrylate; Polypropylene glycol di (meth) acrylates such as propylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, tetrapropylene glycol di (meth) acrylate; dibutylene glycol di (meth) acrylate, tributylene glycol di (meth) acrylate. ) Polybutylene glycol di (meth) acrylates such as acrylates and tetrabutylene glycol di (meth) acrylates; polyoxyethylene trimethylolpropane tri (meth) acrylates, polyoxypropylene trimethylolpropane tri (meth) acrylates, polyoxybutylenetri Polyoxyalkylene trimethylolpropane tri (meth) acrylates such as methylolpropane tri (meth) acrylates; and the like. These may be used alone or in combination of two or more.

The polyoxyalkylene polyol poly (meth) acrylate is preferably bifunctional from the viewpoint of adhesiveness, that is, polyalkylene glycol di (meth) acrylate is preferable. Further, as the oxyalkylene group, an oxypropylene group and an oxybutylene group are preferable, and a oxypropylene group is more preferable, from the viewpoint of imparting appropriate hydrophobicity. The number of alkylene glycol units (that is, oxyalkylene groups) is preferably 2 to 8, more preferably 2 to 5, and even more preferably 3 from the viewpoint of enhancing the affinity with the cellulose nanofibers. ~ 4 pieces. The polyoxyalkylene polyol poly (meth) acrylate according to a preferred embodiment is polypropylene glycol di (meth) acrylate, and more preferably tripropylene glycol di (meth) acrylate.

In the crosslinked polymer, the content of the structural unit derived from the (A1) monofunctional monomer is not particularly limited, but is preferably 90 to 99.95 parts by mass, more preferably 90 parts by mass, out of 100 parts by mass of the crosslinked polymer. It is 95 to 99.9 parts by mass, more preferably 97 to 99.8 parts by mass.

The content of the structural unit derived from the (A2) polyoxyalkylene polyol poly (meth) acrylate in the crosslinked polymer is not particularly limited, but is 0.05 to 5.0 parts by mass in 100 parts by mass of the crosslinked polymer. It is preferably 0.1 to 2.0 parts by mass, more preferably 0.2 to 1.0 parts by mass. Within such a range, the crosslink density can be increased, the shape stability of the hydrogel can be enhanced, and the uniformity of the crosslinked structure can be enhanced.

In the crosslinked polymer, basically only (A2) polyoxyalkylene polyol poly (meth) acrylate is used as the crosslinkable monomer, but other crosslinkable monomers as long as the effects of the present embodiment are not impaired. May be used together. The amount of the other crosslinkable monomer used is preferably 10% by mass or less based on the total amount of the crosslinkable monomer used.

The content of the crosslinked polymer is not particularly limited, but is preferably 1 to 40 parts by mass, more preferably 5 to 35 parts by mass, and further preferably 10 to 25 parts by mass in 100 parts by mass of the hydrogel. It is a department. Within such a range, the strength of the hydrogel can be increased.

[(B) Cellulose nanofibers]
Cellulose nanofibers are fine cellulose fibers having a fiber diameter on the nanometer level. Since the cellulose nanofibers are fine, they are considered to be intertwined in the three-dimensional network structure of the crosslinked polymer, thereby improving the adhesiveness to the adherend such as skin. In particular, due to the high affinity between the polyoxyalkylene polyol poly (meth) acrylate in the crosslinked polymer and the cellulose nanofibers, the hydrogel becomes tenacious at the time of peeling, and the hydrogel has excellent initial adhesiveness and adhesiveness during repeated use. It is considered that sex is given.

The number average fiber diameter of the cellulose nanofibers is not particularly limited, but is preferably 2 to 800 nm, more preferably 2 to 200 nm, still more preferably 2 to 100 nm, from the viewpoint of enhancing the adhesiveness and its durability. It is more preferably 2 to 50 nm.

The number average fiber diameter of the cellulose nanofibers can be measured as follows. That is, a cellulose nanofiber aqueous dispersion having a solid content of 0.05 to 0.1% by mass is prepared, and the aqueous dispersion is cast on a carbon film-coated grid that has been hydrophilized to generate transmission electrons. Use as a sample for observation with a microscope (TEM). The observation sample may be negatively stained with, for example, a 2 mass% uranyl nitrate aqueous solution. Then, observation is performed using an electron microscope image at a magnification of 5000 times, 10000 times, or 50,000 times depending on the size of the constituent fibers. At that time, an axis having an arbitrary vertical and horizontal image width is assumed in the obtained image, and the sample and observation conditions (magnification, etc.) are adjusted so that 20 or more fibers intersect the axis. Then, after obtaining an observation image satisfying this condition, two random axes are drawn vertically and horizontally for each image, and the fiber diameters of the fibers intersecting the axes are visually read. In this way, images of at least three non-overlapping surface portions are taken with an electron microscope and the value of the fiber diameter of the fibers intersecting each of the two axes is read (hence, at least 20 fibers × 2 × 3 = 120). Information on the fiber diameter of the book can be obtained). The arithmetic mean of the fiber diameters thus obtained is defined as the number average fiber diameter.

As the cellulose nanofibers, those having a cellulose type I crystal structure are preferably used. The fact that the cellulose constituting the cellulose nanofibers has an I-type crystal structure means that, for example, in the diffraction profile obtained by wide-angle X-ray diffraction image measurement, 2θ = 14 ° to 17 ° and 2θ = 22 ° to 23 °. It can be identified by having typical peaks at the two positions of.

As the cellulose nanofibers, anion-modified cellulose nanofibers in which an anionic group is introduced into a glucose unit in a cellulose molecule are preferably used. Examples of the anionic group include at least one selected from the group consisting of a carboxyl group, a phosphoric acid group, a sulfonic acid group, and a sulfate group. In the present specification, the carboxyl group is a concept including not only an acid type (-COOH) but also a salt type, that is, a carboxylic acid base (-COOX, where X is a cation forming a salt with a carboxylic acid). Acid type and salt type may be mixed. Similarly, the phosphoric acid group, the sulfonic acid group, and the sulfate group are concepts that include not only the acid type but also the salt type, and the acid type and the salt type may be mixed.

The anion group salt is not particularly limited, but is an alkali metal salt such as sodium salt, potassium salt and lithium salt, alkaline earth metal salt such as magnesium salt, calcium salt and barium salt, and onium such as ammonium salt and phosphonium salt. Examples thereof include salts, primary amines, secondary amines, and amine salts such as tertiary amines.

The content of anionic groups (for example, carboxyl groups) in the cellulose nanofibers is not particularly limited, and may be 0.2 mmol / g or more, 0.5 mmol / g or more, or 1.0 mmol per dry mass of the cellulose nanofibers. It may be / g or more. Further, it may be 2.5 mmol / g or less, or 2.0 mmol / g or less. The content of anionic groups can be determined by measuring the electrical conductivity. For example, a cellulose nanofiber-containing slurry prepared to a concentration of about 0.05 to 1% by mass is neutralized with an aqueous solution of sodium hydroxide, and a neutralization step is performed. It can be obtained by the following formula using the amount V (mL) of the aqueous sodium hydroxide solution consumed in 1 and the molar concentration c (mol / L) of the aqueous sodium hydroxide solution.
Anion group amount (mmol / g) = V × [c / cellulose sample mass (g)]

In one embodiment, the carboxyl group is preferred as the anion group. Examples of the cellulose nanofibers containing a carboxyl group include oxidized cellulose nanofibers obtained by oxidizing the hydroxyl group of a glucose unit in a cellulose molecule.

Specifically, it is preferable to use oxidized cellulose nanofibers in which the hydroxyl group at the C6 position of the glucose unit in the cellulose molecule is selectively oxidized and modified to a carboxyl group. Here, it can be confirmed by, for example, the ¹³ C-NMR chart that the hydroxyl group at the 6-position was selectively oxidized. The cellulose oxide nanofibers may have an aldehyde group or a ketone group together with a carboxyl group, that is, the C6 position of the glucose unit may become a carboxyl group by oxidative modification, but an aldehyde group or a ketone group. It may become a hydroxyl group, or it may be contained as a hydroxyl group without being modified.

The above-mentioned oxidized cellulose nanofibers are obtained, for example, by oxidizing natural cellulose such as wood pulp with an oxidizer in the presence of an N-oxyl compound and subjecting it to defibration (miniaturization). As the N-oxyl compound, a compound having a nitroxy radical generally used as an oxidation catalyst is used, for example, a piperidine nitroxy oxy radical, and particularly 2,2,6,6-tetramethylpiperidinooxy radical (TEMPO). ) Or 4-acetamide-TEMPO is preferred.

Cellulose nanofibers may be obtained by performing a defibration treatment. The defibration treatment may be carried out after the anion group is introduced, or may be carried out before the introduction. As the defibration treatment, for example, a homomixer under high-speed rotation, a high-pressure homogenizer, an ultrasonic dispersion processing machine, a beater, a disc type refiner, a conical type refiner, a double disc type refiner, a grinder and the like can be used.

The content of the cellulose nanofibers is not particularly limited, but is preferably 0.2 to 20 parts by mass with respect to 100 parts by mass of the (A) crosslinked polymer, from the viewpoint of enhancing the adhesiveness and its durability. , More preferably 0.4 to 10 parts by mass, still more preferably 0.5 to 5.0 parts by mass, and even 1.0 to 3.0 parts by mass.

Further, the mass ratio of (A2) polyoxyalkylene polyol poly (meth) acrylate and (B) cellulose nanofibers, that is, the mass ratio of the content of polyoxyalkylene polyol poly (meth) acrylate to the content of cellulose nanofibers ( A2) / (B) is preferably in the range of 1/10 to 1/1. When this mass ratio is 1/10 or more and 1/1 or less, the effect of the present embodiment that the initial adhesiveness and the adhesiveness during repeated use are excellent can be further enhanced. The mass ratio (A2) / (B) is more preferably 1/8 to 1/2, still more preferably 1/4 to 1/8, and particularly preferably 1/6 to 1/8. ..

[(C) Water]
The hydrogel according to this embodiment contains water. The content of water is not particularly limited, but is preferably 10 to 50 parts by mass, more preferably 12 to 40 parts by mass, and may be 15 to 30 parts by mass in 100 parts by mass of hydrogel.

[(D) Multivalent alcohol]
The hydrogel according to this embodiment contains a polyhydric alcohol. By containing the polyhydric alcohol, the viscosity of the solution at the time of producing the hydrogel can be increased, and the moisturizing property of the hydrogel can be enhanced.

Examples of the polyhydric alcohol include ethylene glycol, propylene glycol, butanediol, glycerin, pentaerythritol, sorbitol, polyethylene glycol, polypropylene glycol, polyglycerin, polyoxyethylene polyglyceryl ether and the like. These may be used alone or in combination of two or more. Among these, at least one selected from the group consisting of ethylene glycol, propylene glycol, glycerin, and pentaerythritol is preferable, and glycerin is more preferable.

The content of the polyhydric alcohol is not particularly limited, but is preferably 10 to 80 parts by mass, more preferably 20 to 70 parts by mass, and further preferably 30 to 65 parts by mass in 100 parts by mass of the hydrogel. It may be 40 to 60 parts by mass.

[Other ingredients]
The hydrogel according to the present embodiment may contain other polymer components (polymers) in addition to the above-mentioned (A) crosslinked polymer. The other polymer component is contained in a form that does not polymerize with the (A) crosslinked polymer. The content of the other polymer component is not particularly limited, but is preferably less than 20 parts by mass with respect to 100 parts by mass of the (A) crosslinked polymer.

The hydrogel according to this embodiment may further contain an electrolyte. Since the hydrogel contains an electrolyte, a conductive hydrogel suitable for an electrode pad of a measuring device such as an electrocardiogram, an electrode pad of EMS, or the like can be obtained. The electrolyte is not particularly limited, and examples thereof include alkali metal halides such as sodium chloride, alkaline earth metals halides, metal salts or ammonium salts of inorganic acids, various complex salts, metal salts or ammonium salts of organic acids, and the like. Will be. The content of the electrolyte is not particularly limited, and may be, for example, 0.05 to 10 parts by mass or 0.1 to 2.0 parts by mass in 100 parts by mass of the hydrogel.

The hydrogel according to this embodiment may further contain a surfactant. The surfactant is added, for example, to increase the viscosity of the hydrogel, improve the wettability of the surface of the hydrogel to an adherend such as skin, and improve the adhesive strength. The surfactant is not particularly limited, and examples thereof include a polyalkylene polyamine alkylene oxide adduct, polyoxyethylene octylphenyl ether, and polyoxyethylene nonylphenyl ether. The content of the surfactant is not particularly limited, and may be, for example, 0.01 to 15 parts by mass or 1.0 to 10 parts by mass in 100 parts by mass of the hydrogel.

Additives such as pH adjusters, preservatives, bactericides, rust inhibitors, antioxidants, stabilizers, fragrances, colorants, and anti-inflammatory agents are added to the hydrogel according to the present embodiment, if necessary. May be included.

[Hydrogel manufacturing method]
The hydrogel according to the present embodiment is, for example, (A1) a monofunctional monomer, (A2) a polyoxyalkylene polyol poly (meth) acrylate, (B) cellulose nanofibers, (C) water, and (D). By a method of copolymerizing (A1) a monofunctional monomer and (A2) a polyoxyalkylene polyol poly (meth) acrylate to form a (A) crosslinked polymer using a composition for a hydrogel containing a polyhydric alcohol. Can be manufactured. In this way, by copolymerizing (A1) a monofunctional monomer and (A2) a polyoxyalkylene polyol poly (meth) acrylate in the presence of (B) cellulose nanofibers, (A) a three-dimensional crosslinked polymer. (B) Cellulose nanofibers can be intertwined in the network structure.

When the hydrogel is produced by this method, the content of the structural unit derived from each monomer in the crosslinked polymer is substantially equal to the content of each monomer in the composition for hydrogel. The mass ratio of the content of cellulose nanofibers to the total amount of monofunctional monomer and polyoxyalkylene polyol poly (meth) acrylate in the composition for hydrogel is the ratio of cellulose nano to the content of crosslinked polymer in hydrogel. It is substantially equal to the mass ratio of the fiber content. The content of water and polyhydric alcohol in the hydrogel may be adjusted by drying after forming the crosslinked polymer or by adding water and / or polyhydric alcohol.

The hydrogel composition preferably contains a polymerization initiator. The polymerization initiator is not particularly limited, and examples thereof include a photoradical polymerization initiator and a thermal radical polymerization initiator. By including the polymerization initiator in the composition for hydrogel, the hydrogel may contain the polymerization initiator.

Examples of the photoradical polymerization initiator include α-hydroxyketone, α-aminoketone, benzylmethyl ketal, bisacylphosphine oxide, metallocene and the like. Specifically, 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-propane-1-one, 2-hydroxy-2-methyl-1-phenyl-1-propane- 1-one, 1-hydroxy-cyclohexyl-phenyl-ketone, 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropane-1-one, 2-benzyl-2-dimethylamino-1- (4) -Morphorinophenyl) -butane-1-one and the like. Any one of these may be used, or two or more thereof may be used in combination.

Examples of the thermal radical polymerization initiator include organic peroxides such as benzoyl peroxide, azo polymerization initiators such as azobisisobutyronitrile, and persulfates such as potassium persulfate, 2,2-azobisamidino. Examples thereof include azo compounds such as propane dihydrochloride.

The content of the polymerization initiator in the composition for hydrogel is not particularly limited, and may be, for example, 0.01 to 1.0% by mass or 0.05 to 0.5% by mass.

The method for copolymerizing the (A1) monofunctional monomer and the (A2) polyoxyalkylene polyol poly (meth) acrylate is not particularly limited, and the hydrogel composition is molded into a predetermined shape and then heated or irradiated with ultraviolet rays. There is a way to do this. For example, in the case of producing a sheet-shaped hydrogel, a hydrogel composition is applied onto a sheet-shaped support to form a sheet-shaped hydrogel precursor, which is then heated or irradiated with ultraviolet rays. It may be polymerized (gelled).

The hydrogel according to the present embodiment has excellent initial adhesiveness to an adherend such as skin due to the combination of the crosslinked polymer having the above-mentioned unique crosslinked structure and the cellulose nanofibers, and is used repeatedly. It is also excellent in adhesiveness, and it is possible to suppress a sudden decrease in adhesive strength due to repeated use. Also, the irritation to the skin is small. Therefore, the hydrogel according to the present embodiment is preferably used as an adhesive hydrogel for skin application, and is repeatedly applied to the skin, for example, an electrode pad of a measuring device such as an electrocardiogram or an EMS electrode pad. It is suitably used as an adhesive hydrogel for use.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto. In the following, "%" means a mass standard unless otherwise specified.

Details of each component used in Examples and Comparative Examples are as follows.

[Crosslinkable monomer]
-Tripropylene glycol diacrylate: "NK ester (APG-200)" manufactured by Shin Nakamura Chemical Industry Co., Ltd.
-Tributylene glycol diacrylate: manufactured by Aldrich
-Triethylene glycol diacrylate: "NK ester (3G)" manufactured by Shin Nakamura Chemical Industry Co., Ltd.
-Dipropylene glycol diacrylate: "NK ester (APG-100)" manufactured by Shin Nakamura Chemical Industry Co., Ltd.
-Tetrapropylene glycol diacrylate: Aldrich Co., Ltd.-Polyoxypropylene trimethylolpropane triacrylate: "New Frontier (TMP-3P)" manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.
・ N, N'-methylenebisacrylamide: MCC Unitech Co., Ltd. ・ Divinylbenzene: Nippon Steel & Sumikin Chemical Co., Ltd. ・ Sodium divinylbenzene sulfonate: Toso Finechem Co., Ltd.

[Monofunctional monomer]
・ Acrylic acid: NIPPON SHOKUBAI Co., Ltd. [cellulose nanofiber]
Cellulose aqueous dispersion b1: 2% by mass aqueous dispersion of unmodified cellulose nanofibers (average fiber diameter 10 to 50 nm, I-type crystal structure "Yes") manufactured by Sugino Machine Co., Ltd.)
-Cellulose aqueous dispersion b2: 2 mass% aqueous dispersion of TEMPO oxidized cellulose nanofibers obtained by the following Production Example 1-Cellulose aqueous dispersion b3: 2 mass of TEMPO oxidized cellulose nanofibers obtained by the following Production Example 2. % Aqueous dispersion

-Discol N-518 (trade name): Polyalkylene polyamine alkylene oxide adduct manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.-PVP: Polyvinylpyrrolidone, "Pitzcol K-30L" manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.
-Photoradical polymerization initiator: 1-hydroxy-cyclohexyl-phenyl-ketone, BASF's "Irgacure 184"

[Manufacturing Example 1]
To 2 g of coniferous pulp, 150 ml of water, 0.25 g of sodium bromide, and 0.025 g of TEMPO were added, and after sufficiently stirring and dispersing, a 13 mass% sodium hypochlorite aqueous solution (cooxidant) was added. Sodium hypochlorite was added to 1.0 g of pulp so that the amount was 12.0 mmol / g, and the reaction was started. Since the pH decreases as the reaction progresses, a 0.5 N aqueous sodium hydroxide solution was added dropwise to maintain the pH at 10 to 11, and the reaction was carried out until no change in pH was observed (reaction time: 120 minutes). ). After completion of the reaction, 0.1N hydrochloric acid was added for neutralization, and then filtration and washing with water were repeated for purification to obtain cellulose fibers having an oxidized fiber surface. Subsequently, after solid-liquid separation with a centrifuge, purified water was added to adjust the solid content concentration to 4% by mass. Then, the pH of the slurry was adjusted to 10 with a 24% NaOH aqueous solution. The slurry was reduced at a temperature of 30 ° C. by adding 0.3 g (0.2 mmol / g) of NaBH ₄ and reacting for 2 hours. After the reaction, 1M HCl was added to neutralize the mixture, and the mixture was purified by repeating filtration and washing with water to obtain cellulose fibers. Next, 0.15 g of pure water and sodium hydroxide were added to the cellulose fibers to dilute them to 2% by mass, and the cellulose fibers were treated once with a high-pressure homogenizer (H11, manufactured by Sanwa Engineering Co., Ltd.) at a pressure of 100 MPa to obtain cellulose water. Dispersion b1 was obtained.

As a result of measurement by the method described later, the content of the carboxyl group of the anion-modified cellulose nanofiber contained in the obtained aqueous cellulose dispersion b1 was 1.98 mmol / g, and the content of the carbonyl group was 0.10 mmol / g. Yes, on the other hand, no detection of aldehyde groups was observed. The number average fiber diameter of the anion-modified cellulose nanofibers contained in the water-cellulose dispersion b1 was 4 nm. When the crystal structure of the cellulose contained in the cellulose nanofibers was confirmed by wide-angle X-ray diffraction image measurement, the type I crystal structure was "yes". In addition, the peak of 62 ppm corresponding to the C6 position of the primary hydroxyl group of glucose unit, which can be confirmed on the ¹³ C-NMR chart of cellulose before oxidation, disappears after the oxidation reaction, and instead, the peak derived from the carboxyl group is 178 ppm. Was appearing. Therefore, it was confirmed that only the C6-position hydroxyl group of the glucose unit was oxidized to the carboxyl group or the like.

[Manufacturing Example 2]
In the step of dispersing the cellulose fibers after the oxidation and reduction treatment, an aqueous cellulose dispersion b2 was obtained in the same manner as in Production Example 1 except that 0.56 g of triethanolamine was used instead of sodium hydroxide. The content of the carboxyl group of the anion-modified cellulose nanofiber contained in the obtained aqueous cellulose dispersion b2 was 1.97 mmol / g, the content of the carbonyl group was 0.10 mmol / g, and the detection of the aldehyde group was confirmed. I couldn't. The number average fiber diameter of the anion-modified cellulose nanofibers contained in the cellulose aqueous dispersion b2 was 6 nm. When the crystal structure of the cellulose contained in the cellulose nanofibers was confirmed by wide-angle X-ray diffraction image measurement, the type I crystal structure was "yes". In addition, the peak of 62 ppm corresponding to the C6 position of the primary hydroxyl group of glucose unit, which can be confirmed on the ¹³ C-NMR chart of cellulose before oxidation, disappears after the oxidation reaction, and instead, a peak derived from the carboxyl group is found at 178 ppm. It was appearing. Therefore, it was confirmed that only the C6-position hydroxyl group of the glucose unit was oxidized to the carboxyl group or the like.

Using the above-mentioned aqueous cellulose dispersion as a sample, each characteristic was measured as follows.
[Measurement of carboxyl group amount]
60 ml of an aqueous dispersion in which 0.25 g of a sample is dispersed in water is prepared, the pH is adjusted to about 2.5 with a 0.1 M aqueous hydrochloric acid solution, and then a 0.05 M aqueous sodium hydroxide solution is added dropwise to conduct electrical conduction. The degree was measured. The measurement was continued until the pH reached about 11. From the amount of sodium hydroxide (V) consumed in the neutralization step of the weak acid with a gradual change in electrical conductivity, the amount of carboxyl group was determined according to the following formula.
Carboxyl group amount (mmol / g) = V (mL) x [0.05 / cellulose sample mass (g)]

[Measurement of carbonyl group amount (semicarbazide method)]
Approximately 0.2 g (dry mass) of the sample was precisely weighed, and exactly 50 ml of a 3 g / l aqueous solution of semicarbazide hydrochloride adjusted to pH = 5 with a phosphate buffer solution was added, the mixture was sealed, and the mixture was shaken for 2 days. Then, 10 ml of this solution was accurately collected in a 100 ml beaker, 25 ml of 5N sulfuric acid and 5 ml of a 0.05 N potassium iodate aqueous solution were added, and the mixture was stirred for 10 minutes. Then, 10 ml of a 5% potassium iodide aqueous solution is added, and the sample is immediately titrated with a 0.1 N sodium thiosulfate solution using an automatic titrator. The total content of the aldehyde group and the ketone group) was determined.
Carbonyl group amount (mmol / g) = (DB) × f × [0.125 / w]
D: Sample titration (ml)
B: Titration of blank test (ml)
f: Factor of 0.1N sodium thiosulfate solution (-)
w: Sample amount (g)

[Detection of aldehyde group]
After weighing 0.4 g of the sample and adding a failing reagent (a mixed solution of 5 ml of a mixed solution of sodium potassium tartrate and sodium hydroxide and 5 ml of an aqueous solution of copper sulfate pentahydrate) prepared according to the Japanese Pharmacopoeia, 80 It was heated at ° C. for 1 hour. When the supernatant was blue and the sample portion (solid content) was dark blue, it was judged that no aldehyde group was detected, and the sample was evaluated as "none". In addition, when the supernatant was yellow and the sample part was red, it was judged that an aldehyde group was detected, and it was evaluated as "yes".

[Number average fiber diameter]
The number average fiber diameter of the cellulose nanofibers was observed using a transmission electron microscope (TEM) (JEM-1400, manufactured by JEOL Ltd.). That is, from the TEM image (magnification: 10,000 times) negatively stained with a 2% by mass uranyl acetate aqueous solution after the sample was cast on a carbon film-coated grid that had been hydrophilized, the number average fiber diameter was according to the method described above. Was calculated.

[Crystal structure]
The diffraction profile of the sample is measured using an X-ray diffractometer (RINT-Ultima3, manufactured by Rigaku), which is typical of two positions, 2θ = 14 ° to 17 ° and 2θ = 22 ° to 23 °. When no peak was observed, the crystal structure (type I crystal structure) was evaluated as "present", and when no peak was observed, it was evaluated as "absent".

[Examples 1 to 11 and Comparative Examples 1 to 6]
According to the formulation (parts by mass) shown in Table 1 below, each component is charged into a homomixer (“TK Robomix” manufactured by Primix Corporation), treated at 4000 rpm for 10 minutes, and uniformly dispersed and mixed to form a dispersion liquid. (Composition for hydrogel) was prepared. In Table 1, the numerical values in parentheses for the aqueous cellulose dispersion mean the blending amount as the cellulose nanofibers. The obtained dispersion was applied onto a PET film to a thickness of 0.7 mm to prepare a sheet-shaped hydrogel precursor. The obtained hydrogel precursor was put into a UV curing device together with the PET film, and a step of irradiating with ultraviolet rays having an energy of 200 mJ / cm ² was performed three times to prepare a hydrogel.

Using the obtained hydrogel, the initial adhesiveness and the adhesiveness after repeated use were evaluated. The evaluation method is as follows.

[Initial adhesiveness]
The hydrogel was cut out as a test piece of 2.5 cm × 10.0 cm together with the PET film. The surface of the hydrogel of the test piece was attached to the skin as an adhesive surface. The adhered test piece was subjected to a 180-degree peeling test according to JIS Z0237, and the peeling adhesive strength was measured and evaluated according to the following criteria.
5: Adhesive strength is 0.5N / 10mm or more 4: Adhesive strength is 0.4N / 10mm or more and less than 0.5N / 10mm 3: Adhesive strength is 0.3N / 10mm or more and less than 0.4N / 10mm 2: Adhesive strength is Less than 0.2N / 10mm Less than 0.3N / 10mm 1: Adhesive strength is less than 0.2N / 10mm

[Adhesiveness during repeated use]
After the initial adhesiveness test, the peeled test pieces were pasted together in the same manner as above, and the operation of peeling them was repeated. The peeling adhesive strength at the 10th peeling from the first peeling was measured, and the value (N10 / N1) obtained by dividing the 10th adhesive strength (N10) by the measured 1st adhesive strength (N1) was obtained. It was determined as the adhesive strength retention rate and evaluated according to the following criteria.
5: Adhesive strength retention rate is 0.95 or more 4: Adhesive strength retention rate is 0.90 or more and less than 0.95 3: Adhesive strength retention rate is 0.85 or more and less than 0.90 2: Adhesive strength retention rate is 0. 80 or more and less than 0.85 1: Adhesive retention rate is less than 0.80

The results are shown in Table 1. In Comparative Example 1, since the cellulose nanofibers were not blended, the initial adhesiveness and the adhesiveness after repeated use were inferior. In Comparative Example 2, the initial adhesiveness was improved by blending the polyalkylene polyamine alkylene oxide adduct, but the adhesiveness during repeated use was inferior. In Comparative Example 3, PVP was blended, but the initial adhesiveness and the adhesiveness after repeated use were inferior. On the other hand, in Comparative Examples 4 to 6, although cellulose nanofibers were blended, a crosslinkable monomer other than the polyoxyalkylene polyol poly (meth) acrylate was used, so that the effect of improving the initial adhesiveness and the adhesiveness after repeated use was obtained. I couldn't.

On the other hand, in Examples 1 to 11 in which the polyoxyalkylene polyol poly (meth) acrylate was used as the crosslinkable monomer and the cellulose nanofibers were blended, the initial adhesiveness was excellent and the adhesiveness during repeated use was also improved. It was excellent. From the comparison between Examples 4 and 10, it can be seen that as the polyoxyalkylene polyol poly (meth) acrylate, the bifunctional di (meth) acrylate is superior in both initial adhesiveness and adhesiveness after repeated use. Further, from the comparison between Examples 4, 6 and 7, as the oxyalkylene group, the oxypropylene group (Example 4) is superior to the oxyethylene group (Example 7) and the oxybutylene group (Example 6). I understand. Further, from the comparison between Examples 4, 8 and 9, the number of oxyalkylene groups of 3 (Example 4) is superior to that of 2 (Example 8) or 4 (Example 9). I understand.

Although some embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments, omissions, replacements, changes, etc. thereof are included in the scope and gist of the invention, as well as in the scope of the invention described in the claims and the equivalent scope thereof.

Claims (4)

A crosslinked polymer composed of a monofunctional monomer having one ethylenically unsaturated group and a polyoxyalkylene polyol poly (meth) acrylate.
Cellulose nanofibers,
Water and
Multivalent alcohol,
Hydrogel containing. The hydrogel according to claim 1, wherein the mass ratio of the polyoxyalkylene polyol poly (meth) acrylate to the cellulose nanofibers is 1/10 to 1/1. The hydrogel according to claim 1 or 2, wherein the cellulose nanofiber is an oxidized cellulose nanofiber in which the hydroxyl group at the C6 position of the glucose unit in the cellulose molecule is selectively oxidized and modified to a carboxyl group. The hydrogel according to any one of claims 1 to 3 , which is used for skin application.