JPH0597914A - Moisture-absorbing and releasing material - Google Patents

Abstract

PURPOSE:To obtain the subject material containing fine particles of a photo- sensitive polymer having carboxyl group and polymerizable double bond introduced to the particle surface by carrying out the seed-polymerization of a polymerizable monomer in the presence of fine particles of a specific polymer and reacting the obtained polymer with a specific compound. CONSTITUTION:The objective material can be produced by carrying out the seed-polymerization of (A) a polymerizable monomer having carboxyl group (e.g. acrylic acid or maleic acid) in the presence of (B) fine particles of a polymer having residual double bond and obtained by the emulsion polymerization of a monomer having polymerizable double bond [e.g. methyl (meth)acrylate], adding (C) a compound having one or more epoxy groups and polymerizable double bonds in one molecule [e.g. glycidyl (meth)acrylate] to the system, stirring for >=2hr at preferably 60-80 deg.C to effect the reaction with the surface carboxyl group of the component B and finally irradiating the product with actinic energy ray.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a moisture absorptive and desorptive material, and more specifically, it has excellent moisture absorptive and moisture absorptive properties, and can obtain a moisture absorptive and desorptive property by irradiation with active energy rays such as ultraviolet rays and electron beams. The present invention relates to a water-based moisture absorbing / releasing material useful as an antifogging material, a condensation preventing material, a desiccant, a humidity sensor, a humidity adjusting agent and the like.

[0002]

2. Description of the Related Art Conventionally, as a material having hygroscopicity, a material containing a water-absorbing resin such as a polyacrylic acid type, a polyvinyl alcohol type or a polyacrylamide type has been widely used. Materials containing these water-absorbent resins are excellent in moisture absorption amount and speed, and absorb moisture in the air, water droplets, etc. in a short time, and therefore are very effective materials for applications such as dew condensation preventing materials. However, although these materials have excellent hygroscopicity, they do not have the function of self-releasing the water once absorbed, and therefore cannot be used in the fields requiring hygroscopicity, for example, humidity control agents. Further, when the water-based paint is used, since the water-absorbent resin is blended, it often thickens or gels, and it is difficult to use it as a paint.

[0003]

Therefore, the present inventors have found that
When intensively researched 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 electron beams It was found that good moisture absorption and desorption properties are exhibited after crosslinking by irradiation, and the present invention has been completed.

[0004]

Means for Solving the Problems That is, the present invention is obtained by emulsion-polymerizing a monomer having a polymerizable double bond,
In the presence of the polymer fine particles (A) in which the polymerizable double bond remains, the carboxyl group-containing polymerizable monomer is seed-polymerized, and then has an epoxy group and at least one polymerizable double bond in one molecule. Provided is a moisture absorptive and desorptive material, characterized in that the compound (B) is reacted with a carboxyl group on the surface of the polymer fine particles (A) to contain photosensitive polymer fine particles having a carboxyl group and a polymerizable double bond introduced on the surface. To do. Among the monomers having a polymerizable double bond used in the present invention, as the monofunctional monomer, (a) (meth) acrylate-based: methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate , Isopropyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate,
C1 to C18 alkyl ester of (meth) acrylic acid such as octyl (meth) acrylate and lauryl (meth) acrylate: Glycidyl (meth) acrylate: C2 to C20 of (meth) acrylic acid such as allyl (meth) acrylate
Alkenyl ester: hydroxylethyl (meth) acrylate, hydroxylethyl (meth) acrylate,
C2-C20 hydroxyl alkyl ester of (meth) acrylic acid such as hydroxypropyl (meth) acrylate, hydroxypropyl (meth) acrylate: C3-C19 alkenyloxyl alkyl ester of (meth) acrylic acid such as allyloxylethyl (meth) acrylate : (Meth) acrylic acid and the like, (b) vinyl aromatic compound: for example, styrene, α-methylstyrene, vinyltoluene, p-chlorostyrene and the like, (c) other: acrylonitrile, methacrylonitrile, methyl isopropenyl ketone: Vinyl acetate, vinyl propionate, etc.
Can be mentioned.

Next, as the cross-linking monomer having two or more polymerizable double bonds, (a) (meth) acrylate-based:
Trimethylolpropane tri (meth) acrylic acid ester, di (meth) acrylic acid ester of glycols, di (meth) acrylic acid ester of polyols, di (meth) acrylic acid ester of polyurethanes, di (meth) acrylic acid of polyesters (B) Polyolefin compounds such as acid esters: butadiene, isoprene, chloroprene, divinylbenzene and the like. These monomers are appropriately selected depending on the desired physical properties and may be used alone or in combination of two or more. However, when a monofunctional monomer is used, the inside of the polymer fine particles (A) does not three-dimensionally crosslink by itself, and the physical properties such as strength when used as a moisture absorptive and desorptive material are impaired. Polymer fine particles (A) when used in combination with the above-mentioned crosslinkable monomer
It is desirable to three-dimensionally crosslink the inside to improve the physical properties. The molar ratio of the monofunctional monomer to the crosslinkable monomer is usually 100: 0.1 to 50, preferably 100: 100.
It is 0.1 to 30.

When emulsion-polymerizing the above-mentioned monomer having a polymerizable double bond, a conventional nonionic surfactant or anionic surfactant can be used as an emulsifier for the purpose of assisting the emulsification. Nonionic surfactants include polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene alkyl ethers such as polyoxyethylene cetyl ether, polyoxyethylene octyl phenyl ether,
Examples thereof 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 dodecylbenzene sulfonate, sodium dodecyl sulfate, sodium dialkyl sulfosuccinate, formalin condensate of naphthalene sulfonic acid, and 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 0.1 to 50% by weight, more preferably 0.1 to 20% by weight, based on the total weight of the polymerizable double bond-containing monomer used in the polymer fine particles (A). %. The solid content ratio of the monomer having a polymerizable double bond and the emulsifier at the time of emulsion polymerization is 10 to 60% by weight, preferably 15 to 45% by weight.
Further, the polymerization initiator is not particularly limited as long as it is used in ordinary emulsion polymerization.

The polymer fine particles (A) thus obtained are used as seed polymer particles to seed-polymerize the carboxyl group-containing polymerizable monomer in the presence of the polymer particles (A). When the polymerization rate of the polymer fine particles (A) is 100%, the polymer fine particles (A) and the carboxyl group-containing polymerizable monomer do not polymerize, and the desired material of the present invention cannot be obtained. The polymerization rate of the polymer fine particles (A) during seed polymerization is preferably 5 to 90%, more preferably 10 to 80%. 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 these are 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 amount of moisture cannot be obtained because the moisture absorption decreases.
If the amount is more than 00 parts by weight, the moisture absorption amount increases, but the moisture releasing property deteriorates, which is not preferable.

As a method for adding the carboxyl group-containing polymerizable monomer to the polymer fine particle (A) aqueous dispersion,
Either batch addition, continuous addition by a drip method, or a combination thereof may be used. In the step of polymerizing the carboxyl group-containing polymerizable monomer, no emulsifier may be added. 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, if necessary. Also, as the polymerization initiator, the same ones as those used in the 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 the light scattering method.

The carboxyl group present on the surface of the polymer fine particles (A) thus produced is reacted with the compound (B) having an epoxy group and at least one polymerizable double bond in one molecule, Introduce a polymerizable double bond on the surface. Examples of the compound (B) include glycidyl (meth) acrylate, N-glycidyl (meth) acrylamide, glycidyl allyl ether, epoxy compounds having a polymerizable double bond such as 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. The molar ratio of the epoxy compound to the carboxyl group on the surface of the polymer particles is 100.
The reaction can be performed within the range of%, but the reaction ratio is appropriately selected according to various physical properties such as moisture absorption / desorption characteristics, strength, and hardness. This reaction is a polymer having a carboxyl group on the surface.
Epoxy compound is mixed with the fine particle aqueous dispersion and the mixture is heated to 30 ° C to 9
It only needs to be stirred at a temperature of 0 ° C., preferably 60 ° C. to 80 ° C. for 2 hours or more to finish. In this way, photosensitive polymer fine particles having a carboxyl group and a polymerizable double bond introduced on the surface of the fine particles can be obtained, but in the present invention, there is an advantage that they can be reacted even in an aqueous dispersion.

In addition, the aqueous dispersion containing photosensitive polymer fine particles may optionally contain a monomer, an oligomer, and a polymer compound having a polymerizable double bond, or a polymer, for the purpose of providing various functions. A polymer compound or the like which does not have a sex double bond may be added to the extent that the original purpose is not impaired. Polymer fine particles not having a carboxyl group on the surface thereof, which are obtained during the process of producing the moisture absorptive and desorptive material of the present invention, and non-photosensitive polymer fine particles having no polymerizable double bond on the surface, etc. are also included in these 1 As an example: Also,
Additives such as defoaming agents, antioxidants and preservatives may also be added within a range that does not impair the original purpose.

The hygroscopic material containing the photosensitive polymer fine particles produced as described above is irradiated with an active energy ray such as an ultraviolet ray or an electron beam so as to have a good moisture absorbing / releasing characteristic. A photo-initiated polymerization agent may be added, if necessary, for the purpose of accelerating the crosslinking reaction by irradiation with active energy rays. 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 active energy rays, 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 or the like, and then irradiate with active energy rays. 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. Thus, the reason why it has a good moisture absorption / desorption property only after irradiation with active energy rays is that sufficient moisture absorption cannot be expressed because the carboxyl group-containing polymerizable monomer does not have a three-dimensional crosslinked structure before irradiation. is there. Therefore, before taking the three-dimensional crosslinked structure, that is, in the state where the photosensitive polymer fine particles are dispersed in water, thickening and gelation phenomenon due to the hygroscopic force hardly occur, and thus it can be used as a photosensitive water-based paint. It will be possible.

[0012]

EXAMPLES The present invention will be described in more detail with reference to examples. In the examples, "part" and "%" mean
"Parts by weight" and "% by weight" are shown, respectively. (Example 1) 95 parts of 2-ethylhexyl acrylate, 5 parts of ethylene glycol dimethacrylate, 9 of Emulgen
20 (non-ionic surfactant manufactured by Kao Corporation) 10 parts,
Stirring 300 parts of deionized water in a 1 liter reaction vessel,
It was heated to 80 ° C. in a nitrogen atmosphere. 1% of a 5% azobisamidinopropane dihydrochloride (hereinafter referred to as AAPD) aqueous solution
6 parts was added and the mixture was held for 30 minutes to obtain an aqueous dispersion containing polymer particles. The polymerization rate of the polymer fine particles was 50%. To this aqueous polymer fine particle dispersion, 20 parts of acrylic acid (neutralized with 10% aqueous sodium hydroxide solution at 70 mol%) and 4 parts of 5% AAPD aqueous solution were added, and the reaction mixture was heated to 80 ° C. Polymerization was completed by holding for a period of time to obtain a polymer fine particle aqueous dispersion having a carboxyl group on the surface. After allowing the obtained aqueous dispersion to stand overnight, 11.8 parts of glycidyl methacrylate was added, and the mixture was heated to 80 ° C. in an air atmosphere and stirred for 4 hours to polymerize the surface of the polymer particles. An aqueous dispersion of photosensitive polymer fine particles having a double bond was obtained. The particle size of the photosensitive polymer particles in this aqueous dispersion is about 1 as measured by the light scattering method.
It was 00 nm. This photosensitive polymer-fine particle aqueous dispersion was adjusted to a solid content of 30%, and 50 parts of the aqueous dispersion (solid content 30%) was added to Darocur 2959 as a photoinitiator.
0.3 part (manufactured by Merck) was added, and then a sheet having a dry film thickness of 500 μm was formed by a casting method. The obtained sheet was irradiated with 1000 mJ of ultraviolet rays to be crosslinked to obtain a moisture absorbing / releasing material.

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

(Examples 3 and 4) In Example 2, the amount of acrylic acid added was 40 parts (70% neutralized with 10% sodium hydroxide aqueous solution), 60 parts (70% neutralized with 10% sodium hydroxide aqueous solution). (Japanese) are shown 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 microparticles in the aqueous dispersion was determined according to Example 3
Was about 130 nm, and in Example 4 it was 150 nm. (Comparative Example 1) Comparative Example 1 is a sheet having a dry film thickness of 500 [mu] m obtained by casting the polymer fine particle aqueous dispersion liquid having no carboxyl group on the surface obtained in Example 2. (Comparative Example 2) In Example 2, acrylic acid (70% neutralized with sodium hydroxide) was added to R-45ACR-LC and Emulgen 81.
Comparative Example 2 was prepared by charging 0 and deionized water at the same time, and then producing a sheet having a dry film thickness of 500 μm in the same manner as in Example 2 and crosslinking the same.

(Evaluation of Moisture Absorption / Desorption) The moisture absorption / desorption of the obtained sheet was evaluated as follows. Hygroscopic, 50 sheets
The sample was cut into a size of 100 mm × 100 mm, left in an atmosphere of a temperature of 30 ° C. and a relative humidity of 90% for 24 hours, and the moisture absorption amount of each sample was determined by the following formula.

[0016]

[Equation 1]

Regarding the moisture releasing property, each sample whose moisture absorption amount was measured was left in an atmosphere having a temperature of 25 ° C. and a relative humidity of 65%, and the time-dependent change of 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 absorptive and desorptive material of the present invention is characterized in that it has hygroscopicity depending on the amount of carboxyl groups on the surface of the photosensitive polymer, and that it rapidly dissipates moisture under low humidity. In addition, various physical properties such as strength, hardness, and weather resistance of the moisture absorptive and desorptive material can be controlled by changing the type of monomer having a polymerizable double bond constituting the seed polymer particles or the functional group density on the surface of the photosensitive polymer particles. Since it can be controlled, it can be widely used for anti-fog materials, desiccants, humidity sensors, humidity regulators, and the like.

Claims (2)

[Claims] 1. 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 the carboxyl group on the surface of the polymer fine particles (A) to form a carboxyl group and a polymerizable double bond on the surface. A moisture absorptive and desorptive material comprising a photosensitive polymer fine particle having introduced thereinto. 2. The moisture absorptive and desorptive material according to claim 1, which is three-dimensionally crosslinked by an active energy ray. [0001]