JP2853416B2 - Hygroscopic material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hygroscopic material, and more particularly to a material having excellent hygroscopic and hygroscopic properties, and capable of obtaining hygroscopic properties by irradiation with active energy rays such as ultraviolet rays and electron beams. The present invention relates to a water-based moisture-absorbing / desorbing material useful for an anti-fogging material, a condensation preventing material, a desiccant, a humidity sensor, a humidity regulator, and the like.

[0002]

2. Description of the Related Art Conventionally, as a material having a hygroscopic property, a material in which a water-absorbing resin such as a polyacrylate, a polyvinyl alcohol, and a polyacrylamide is blended has been widely used. Materials containing these water-absorbing resins are excellent in the amount of moisture absorption and the rate of moisture absorption, and absorb moisture, water droplets and the like in the air in a short period of time. However, although these materials have excellent moisture absorption properties, they do not have a function of self-releasing moisture once absorbed, and thus cannot be used in fields requiring moisture absorption / release properties, such as humidity regulators. In addition, when a water-based paint is used, the water-absorbent resin is blended, so that the water-based paint often thickens or gels, and it has been difficult to use the paint as a paint.

[0003]

SUMMARY OF THE INVENTION Accordingly, the present inventors
After extensive research to solve the above problems, when a material containing a photosensitive polymer fine particle having a carboxyl group and a polymerizable double bond on the surface of the polymer fine particle is used, ultraviolet rays, active energy rays such as an electron beam are used. The present inventors have found that good moisture absorption / desorption characteristics are exhibited after crosslinking by irradiation, and have reached the present invention.

[0004]

That is, the present invention relates to a method for producing a polymer having a polymerizable double bond, which is obtained by emulsion polymerization of a monomer having a polymerizable double bond. , A carboxyl group-containing polymerizable monomer is subjected to seed polymerization, and then a compound (B) having an epoxy group and at least one polymerizable double bond in one molecule is reacted with a carboxyl group on the surface of the polymer fine particles (A). Apply an aqueous dispersion containing photosensitive polymer fine particles having a carboxyl group and a polymerizable double bond introduced to a substrate,
Alternatively, there is provided a moisture absorbing / releasing material characterized by being formed into a sheet and then three-dimensionally crosslinked by irradiation with active energy rays. Among the monomers having a polymerizable double bond used in the present invention, monofunctional monomers include (a) (meth) acrylates: methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate , Isopropyl (meth) acrylate, (meth)
C1-C18 alkyl esters of (meth) acrylic acid such as butyl acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, lauryl (meth) acrylate: glycidyl (meth) acrylate: allyl (meth)
C2-C20 alkenyl esters of (meth) acrylic acid such as acrylates: C2-C20 hydroxylalkyl esters of (meth) acrylic acid such as hydroxylethyl (meth) acrylate and hydroxylpropyl (meth) acrylate: allyloxylethyl (meth) acrylate (B) vinyl aromatic compounds: for example, styrene, α-methylstyrene, vinyltoluene, p-chlorostyrene, etc. (C3 to C19 alkenyloxyl alkyl esters of (meth) acrylic acid: (meth) acrylic acid) c) Others: acrylonitrile, methacrylonitrile, methyl isopropenyl ketone: vinyl acetate, vinyl propionate and the like.

Next, (a) (meth) acrylate-based crosslinkable monomers having two or more polymerizable double bonds include:
Trimethylolpropane tri (meth) acrylate, glycol di (meth) acrylate, polyol di (meth) acrylate, polyurethane di (meth) acrylate, polyester di (meth) acryl (B) polyolefin compounds such as acid esters: butadiene, isoprene, chloroprene, divinylbenzene and the like. These monomers are appropriately selected depending on desired physical properties, and may be used alone or in combination of two or more. However, when a monofunctional monomer is used, the polymer particles (A) alone do not undergo three-dimensional cross-linking and lose physical properties such as strength when used as a moisture absorbing / releasing material. By using in combination with the crosslinking monomer having the above, polymer fine particles (A)
It is desirable to improve physical properties by three-dimensionally cross-linking the inside. The ratio of the monofunctional monomer to the crosslinkable monomer is usually 100: 0.1 to 50, preferably 100: 100 in molar ratio.
0.1 to 30.

[0006] When the above-mentioned monomer having a polymerizable double bond is emulsion-polymerized, a usual nonionic surfactant or anionic surfactant can be used as an emulsifier for the purpose of assisting emulsification. As nonionic surfactants, polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene alkyl ether such as polyoxyethylene cetyl ether, polyoxyethylene octyl phenyl ether,
Examples include polyoxyethylene alkyl allyl ethers such as polyoxyethylene nonylphenyl ether, polyoxyethylene derivatives, oxyethylene / oxypropylene block copolymers, glycerin fatty acid esters, and polyoxyethylene fatty acid esters. Examples of the anionic surfactant include sodium dodecylbenzenesulfonate, sodium dodecylsulfate, sodium dialkylsulfosuccinate, formalin condensate of naphthalenesulfonic acid, and ammonium polyoxyethylene alkylphenyl ether sulfate ammonium salt. These emulsifiers may be used alone or in combination of two or more. The amount of the emulsifier used is preferably from 0.1 to 50% by weight, more preferably from 0.1 to 20% by weight, based on the total weight of the monomer having a polymerizable double bond used in the polymer fine particles (A). %. The total solid content of the monomer having a polymerizable double bond and the emulsifier during the emulsion polymerization is 10 to 60% by weight, preferably 15 to 45% by weight.
The polymerization initiator is not particularly limited as long as it is one used in ordinary emulsion polymerization.

The polymer fine particles (A) thus obtained are used as seed polymer particles in the presence of which the carboxyl group-containing polymerizable monomer is subjected to seed polymerization. When the polymerization rate of the polymer particles (A) is 100%, the polymer particles (A) and the carboxyl group-containing polymerizable monomer do not polymerize, so that the desired material of the present invention cannot be obtained. The polymerization rate of the polymer fine particles (A) during the seed polymerization is preferably from 5 to 90%, more preferably from 10 to 80%. As the carboxyl group-containing polymerizable monomer used in the present invention, acrylic acid,
Examples thereof include polymerizable monomers having a carboxyl group such as methacrylic acid, maleic acid, and itaconic acid, and those in which some or all of them are converted to alkali metal salts or ammonium salts are used. The ratio of the polymer fine particles (A) to the carboxyl group-containing polymerizable monomer is 5 to 300 parts by weight, preferably 10 to 200 parts by weight, based on 100 parts by weight (solid content) of the polymer fine particles (A). If the amount of the carboxyl group-containing polymerizable monomer is less than 5 parts by weight, the desired property cannot be obtained because the amount of absorbed moisture is reduced.
If the amount is more than 00 parts by weight, the amount of moisture absorption increases, but the moisture release characteristics deteriorate, which is not preferable.

A method for adding a carboxyl group-containing polymerizable monomer to an aqueous dispersion of polymer fine particles (A) includes:
Either batch addition, continuous addition by a drip method, or a combination of these may be used. In the step of polymerizing the carboxyl group-containing polymerizable monomer, an emulsifier may not be added at all. However, in order to maintain the polymerization stability at a high level, a nonionic or anionic surfactant exemplified in the step of emulsion-polymerizing the polymer fine particles (A) may be added as necessary. As for the polymerization initiator, the same one as that used in emulsion polymerization of the polymer fine particles (A) may be appropriately used. Thus, fine particles having a carboxyl group on the surface of the polymer fine particles (A) are obtained, and the particle diameter of the obtained fine particles is 10 to 500 nm as measured by a light scattering method.

The carboxyl group present on the surface of the polymer fine particles (A) thus produced is reacted with a compound (B) having an epoxy group and at least one polymerizable double bond in one molecule, A polymerizable double bond is introduced on the surface. Examples of the compound (B) include epoxy compounds having a polymerizable double bond such as glycidyl (meth) acrylate, N-glycidyl (meth) acrylamide, glycidyl allyl ether, 1,2-epoxy-5-hexene, and glycidyl cinnamate. Is mentioned. These compounds (B) are appropriately selected according to the desired physical properties, and may be used alone or in combination of two or more. 100 mole ratio of epoxy compound to carboxyl group on the surface of polymer fine particles.
%, But the reaction ratio is appropriately selected according to various physical properties such as moisture absorption / release properties, strength, and hardness. This reaction is based on a polymer having carboxyl groups on the surface.
An epoxy compound is mixed with the aqueous dispersion of fine particles,
The stirring is completed only by stirring at 0 ° C., preferably 60 ° C. to 80 ° C. for 2 hours or more. Thus, photosensitive polymer fine particles having a carboxyl group and a polymerizable double bond introduced on the surface of the fine particles can be obtained. However, the present invention has an advantage that the reaction can be performed even in an aqueous dispersion.

[0010] The aqueous dispersion containing the photosensitive polymer fine particles may, if necessary, have a monomer, oligomer, polymer compound or polymer compound having a polymerizable double bond for various functions. A high molecular compound having no acidic double bond may be added in a range that does not impair the original purpose. Polymer fine particles having no carboxyl group on the surface and non-photosensitive polymer fine particles having no polymerizable double bond on the surface, which are obtained during the process of producing the moisture-absorbing and desorbing material of the present invention, also include these. Examples can be given. Also,
Additives such as an antifoaming agent, an antioxidant, and a preservative may be added as long as the intended purpose is not impaired.

By irradiating an active energy ray such as an ultraviolet ray or an electron beam to the hygroscopic material containing the photosensitive polymer fine particles produced as described above, good hygroscopic properties are provided. In order to promote a crosslinking reaction by irradiation with active energy rays, a photoinitiator can be added as needed. As the photopolymerization initiator, benzophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1- (4-isopropylphenyl) 2-hydroxy-2-methylpropan-1-one, 2-methyl -1- [4- (methylthio) phenyl] 2-morpholinopropanone and the like. The addition amount of these photopolymerization initiators is 100
It is used in the range of 0.1 to 10 parts by weight with respect to parts by weight. When irradiating with an active energy ray, it is preferable to apply the aqueous dispersion onto a plastic substrate, a metal substrate, a paper substrate, or the like, or form a sheet by a casting method, and then irradiate the active energy beam. desirable. The coating method is not particularly limited, and a commonly used coater or the like can be appropriately used depending on the viscosity of the aqueous dispersion and the coating film thickness. As described above, the reason for having good moisture absorption / desorption properties for the first time after irradiation with active energy rays is that the carboxyl group-containing polymerizable monomer does not have a three-dimensional cross-linked structure before irradiation, so that sufficient moisture absorption cannot be exhibited. is there. Therefore, before taking a three-dimensional crosslinked structure, that is, in a state in which the photosensitive polymer fine particles are dispersed in water, the thickening and gelation phenomena caused by the hygroscopic force are less likely to occur, and the photosensitive polymer-based paint can be used. It becomes possible.

[0012]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. In the examples, “parts” and “%” refer to
The "parts by weight" and "% by weight" are respectively shown. (Example 1) 95 parts of 2-ethylhexyl acrylate, 5 parts of ethylene glycol dimethacrylate, Emulgen 9
20 (nonionic surfactant manufactured by Kao Corporation) 10 parts,
While stirring 300 parts of deionized water in a 1 liter reaction vessel,
Heated to 80 ° C. in a nitrogen atmosphere. 1% aqueous solution of 5% azobisamidinopropane dihydrochloride (hereinafter referred to as AAPD)
6 parts were added and maintained for 30 minutes to obtain an aqueous dispersion containing polymer fine particles. The polymerization rate of the polymer particles was 50%. Subsequently, 20 parts of acrylic acid (70 mol% neutralized with a 10% aqueous solution of sodium hydroxide) and 4 parts of a 5% aqueous solution of AAPD were added to the aqueous dispersion of polymer particles, and after the addition was completed, the reaction mixture was cooled to 80 ° C. The polymerization was completed by holding for a time to obtain an aqueous dispersion of polymer fine particles having a carboxyl group on the surface. After leaving the obtained aqueous dispersion overnight, 11.8 parts of glycidyl methacrylate was added, the mixture was heated to 80 ° C. in an air atmosphere, and stirred for 4 hours to polymerize the surface of the polymer fine particles. An aqueous dispersion of photosensitive polymer fine particles having a double bond was obtained. The particle size of the photosensitive polymer fine particles in this aqueous dispersion was about 1 as measured by a light scattering method.
00 nm. The solid content of this photosensitive polymer-fine particle aqueous dispersion was adjusted to 30%, and Darocur 2959 as a photoinitiator was added to 50 parts (solid content 30%) of the aqueous dispersion.
(Manufactured by Merck & Co.) was added to obtain a sheet having a dry film thickness of 500 μm by a casting method. The obtained sheet was irradiated with 1000 mJ of ultraviolet light to crosslink, thereby obtaining a moisture absorbing / releasing material.

Example 2 In Example 1, R-45ACR-LC (modified polybutadiene dimethacrylate manufactured by Idemitsu Petrochemical Co., Ltd.) was used in place of 95 parts of 2-ethylhexyl acrylate and 5 parts of ethylene glycol dimethacrylate.
100 parts Emulgen 8 instead of Emulgen 920
A moisture-absorbing / desorbing material was obtained in the same manner as in Example 1 except that No. 10 (a nonionic surfactant manufactured by Kao Corporation) was used. The polymerization rate of the polymer fine particles before seed polymerization of acrylic acid was 45%. The particle size of the photosensitive polymer fine particles in the aqueous dispersion was about 250 nm.

(Examples 3 and 4) In Example 2, the addition amount of acrylic acid was changed to 40 parts (70% neutralized with a 10% aqueous sodium hydroxide solution) and 60 parts (70% neutralized with a 10% aqueous sodium hydroxide solution). Sums) were used in Examples 3 and 4, respectively.
In the same manner as in Example 1, a hygroscopic material was obtained. In addition,
The particle size of the photosensitive polymer fine particles in the aqueous dispersion was determined in Example 3.
Was about 130 nm, and Example 4 was 150 nm. (Comparative Example 1) The aqueous dispersion of polymer-fine particles having no carboxyl group on the surface obtained in Example 2 was made into a sheet having a dry film thickness of 500 µm by a casting method, and is referred to as Comparative Example 1. (Comparative Example 2) In Example 2, acrylic acid (70% neutralized with sodium hydroxide) was subjected to R-45ACR-LC and Emulgen 81.
0, and charged at the same time as deionized water. Thereafter, a sheet having a dry film thickness of 500 μm was prepared in the same manner as in Example 2, and the sheet was subjected to cross-linking as Comparative Example 2.

(Evaluation of moisture absorption / release properties) The moisture absorption / release properties of the obtained sheets were evaluated as follows. Hygroscopicity, 50 sheets
The sample was cut into a size of mm × 100 mm, left in an atmosphere at a temperature of 30 ° C. and a relative humidity of 90% for 24 hours, and the moisture absorption of each sample was determined by the following equation.

[0016]

(Equation 1)

Regarding the moisture release property, each sample whose moisture absorption was measured was left in an atmosphere at a temperature of 25 ° C. and a relative humidity of 65%, and the time-dependent change in the weight of each sample was measured. The amount was determined, and the relationship between the standing time and the remaining amount was determined.

[0018]

(Equation 2)

The results are shown in Table 1.

[0020]

[Table 1]

[0021]

As described above, the moisture-absorbing and desorbing material of the present invention is characterized in that moisture-absorbing properties are obtained in accordance with the amount of carboxyl groups on the surface of the photosensitive polymer, and that moisture is quickly released under low humidity. In addition, by changing the type of the monomer having a polymerizable double bond constituting the seed polymer fine particles or the functional group density on the surface of the photosensitive polymer fine particles, various physical properties such as the strength, hardness, and weather resistance of the moisture absorbing and releasing material can be improved. Because it can be controlled, it can be widely used for antifogging materials, desiccants, humidity sensors, humidity regulators, and the like.

Claims (2)

(57) [Claims] 1. A method for seed polymerization of a carboxyl group-containing polymerizable monomer in the presence of polymer fine particles (A) obtained by emulsion polymerization of a monomer having a polymerizable double bond and having a polymerizable double bond remaining. Then, the compound (B) having an epoxy group and at least one polymerizable double bond in one molecule is reacted with a carboxyl group on the surface of the polymer fine particles (A) to form a carboxyl group and a polymerizable double bond on the surface. Based on the aqueous dispersion containing the introduced photosensitive polymer fine particles
Apply to the material or make it into a sheet.
A moisture-absorbing and desorbing material characterized by being three-dimensionally cross-linked by irradiation with negative rays . 2. The method according to claim 1 , wherein the monomer having a polymerizable double bond is polymerized.
2. The moisture-absorbing and desorbing material according to claim 1 , comprising a crosslinkable monomer having two or more reactive double bonds .