JP2850632B2 - Hygroscopic material and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a moisture-absorbing and desorbing material, and more particularly, to an anti-fogging material capable of obtaining excellent moisture-absorbing and desorbing properties by irradiation with active energy rays such as ultraviolet rays and electron beams. Anti-condensation material, desiccant, humidity sensor,
The present invention relates to a water-based hygroscopic material useful as 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 using a material containing photosensitive microgel fine particles having a carboxyl group and a polymerizable double bond on the surface, ultraviolet rays, after crosslinking by irradiation with active energy rays such as electron beams The present inventors have found that good moisture absorption / release properties are exhibited, and have reached the present invention.

[0004]

That is, the present invention relates to a method for preparing a carboxyl group of a microgel fine particle (A) obtained by synthesizing a monomer having a polymerizable double bond by emulsion polymerization using a carboxyl group-containing compound as an emulsifier. Aqueous system comprising photosensitive microgel fine particles having a carboxyl group and a polymerizable double bond on the surface by reacting an epoxy group and an epoxy group of compound (B) having at least one polymerizable double bond in the molecule. Provided is a moisture-absorbing / desorbing material characterized in that the dispersion is dried and then crosslinked by irradiation with active energy rays.

Among monomers having a polymerizable double bond,
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 ester of (meth) acrylic acid such as acrylate: (meth) acrylic acid such as hydroxylethyl (meth) acrylate, hydroxylethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxypropyl (meth) acrylate C
2-C20 hydroxylalkyl ester: C3-C19 alkenyloxylalkyl ester of (meth) acrylic acid such as allyloxylethyl (meth) acrylate:
(B) vinyl aromatic compounds: for example, styrene, α-methylstyrene, vinyltoluene, p-chlorostyrene, etc. (c) others: acrylonitrile, methacrylonitrile, methylisopropenyl ketone: acetic acid Vinyl, vinyl propionate and the like.

The crosslinkable monomer having two or more polymerizable double bonds for three-dimensionally cross-linking the inside of the microgel fine particles is as follows: (a) (meth) acrylate: trimethylolpropanetri (meth) Acrylic ester, di (meth) acrylate of glycols, di (meth) of polyol
(B) polyolefin-based compounds: butadiene, isoprene, chloroprene, divinylbenzene, and the like; and acrylic acid esters, di (meth) acrylic acid esters of polyurethanes, and di (meth) acrylic acid esters of polyesters.

[0007] These monomers are appropriately selected depending on the desired physical properties, and may be used alone or in combination.
Species or more can be used in combination.
However, when a monofunctional monomer is used, since the inside of the microgel fine particles is not three-dimensionally crosslinked by itself, it is used in combination with a crosslinkable monomer having two or more polymerizable double bonds, or has a polymerizable double bond as an emulsifier. It is necessary to use a reactive emulsifier capable of reacting with the monomer. By three-dimensionally cross-linking the inside of the microgel fine particles, it is possible to improve physical properties such as strength when the material is made to absorb and release moisture. The ratio between the monofunctional monomer and the crosslinkable monomer is usually 10 moles.
0: 0.1 to 50, preferably 100: 0.1 to 30.

The carboxyl group-containing compound has an effect as an emulsifier. Usually, a carboxyl group obtained by neutralizing the carboxyl group in the carboxyl group-containing compound with an alkali metal or ammonium or the like is used. Among such emulsifiers, low molecular weight emulsifiers include saturated fatty acids such as caprylic acid, lauric acid and stearic acid, or polymerizable monomers such as acrylic acid, methacrylic acid, maleic acid and itaconic acid, and alkali metals and ammonium. And reactants.

The polymer emulsifier includes a homopolymer of a reaction product of a polymerizable monomer having a carboxyl group such as acrylic acid, methacrylic acid, maleic acid, and itaconic acid with an alkali metal or ammonium, or the above-mentioned carboxyl group. Reaction product of a polymerizable monomer having an alkali metal or ammonium with another polymerizable monomer such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate C1 to C18 alkyl esters of (meth) acrylic acid such as hexyl (meth) acrylate: glycidyl (meth) acrylate: C2 to C8 alkenyl esters of (meth) acrylic acid such as allyl (meth) acrylate: hydroxyethyl (meth) ) C2 -C of (meth) acrylic acid such as acrylate 8Hydroxyalkyl ester: A compound obtained by copolymerizing at least one vinyl monomer selected from C3 to C19 alkenyloxyl alkyl esters of (meth) acrylic acid such as allyloxylethyl acrylate can be selected. . When the polymer emulsifier is used, the reaction between the polymerizable monomer having a carboxyl group and an alkali metal or ammonia may be performed before homopolymerization or copolymerization with another vinyl monomer, as described above, The polymerization may be performed after homopolymerization or copolymerization with another vinyl monomer.

These polymer emulsifiers may be used as such or as a reactive emulsifier having a polymerizable double bond introduced by reacting an epoxy group such as glycidyl (meth) acrylate with a part of a carboxyl group. Can be. Since a polymer emulsifier can control the degree of water solubility, it is a preferable emulsifier in applications requiring water resistance. Further, for the purpose of assisting emulsification, an anionic or nonionic low molecular surfactant may be used in combination with a high molecular emulsifier as long as physical properties such as water resistance are not impaired. Emulsion polymerization of a monomer having a polymerizable double bond is carried out in an aqueous system at 50 to 95%.
C., preferably at a temperature of 65 to 80.degree. C., and 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 can be used without any particular limitation as long as it is used in ordinary emulsion polymerization.

The ratio of the monomer having a polymerizable double bond to the carboxyl group-containing compound used as an emulsifier is preferably 2 to 300 parts by weight, based on 100 parts by weight (solid content) of the monomer having a polymerizable double bond. Is 5-20
0 parts by weight. If the amount of the carboxyl group-containing compound is less than 2 parts by weight, the desired characteristics cannot be obtained because the amount of moisture absorption is reduced. If the amount of the compound is more than 300 parts by weight, the amount of moisture absorption is increased, but the moisture release characteristics are unfavorably deteriorated. The particle size of the microgel fine particles (A) thus obtained is 10 to 500 nm as measured by a light scattering method.

Further, by reacting a carboxyl group present on the surface of the microgel fine particles (A) with an epoxy group of the compound (B) having an epoxy group and at least one polymerizable double bond in one molecule. Then, a polymerizable double bond is introduced into the surface of the microgel fine particles. As the compound (B), glycidyl (meth) acrylate,
Examples thereof include epoxy compounds having a polymerizable double bond such as N-glycidyl (meth) acrylamide, glycidyl allyl ether, and 1,2-epoxy-5-hexene, and glycidyl cinnamate. These compounds (B) are appropriately selected according to desired physical properties, and may be used alone or in combination of two or more.

[0013] The epoxy group is a microgel fine particle (A)
The reaction can be carried out in a molar ratio of 100% with respect to the carboxyl groups on the surface. The reaction ratio is appropriately selected according to various physical properties such as moisture absorption / desorption characteristics, strength and hardness. This reaction is performed by mixing an epoxy compound with an aqueous dispersion of microgel fine particles having a carboxyl group on the surface,
The stirring is completed only by stirring at a temperature of 90 ° C, preferably 60 ° C to 80 ° C for 2 hours or more. It is to be noted that not only this reaction but also all the reactions in the present invention can be carried out in an aqueous dispersion.

The aqueous dispersion containing the photosensitive microgel fine particles may, if necessary, have monomers, oligomers, polymer compounds, or polymer compounds having polymerizable double bonds 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. The microgel fine particles (A) having no polymerizable double bond on the surface obtained during the production process of the moisture-absorbing and desorbing material of the present invention can also be mentioned as one example of these. Further, additives such as an antifoaming agent, an antioxidant, and a preservative may be added as long as the intended purpose is not impaired.

After drying the aqueous dispersion containing the photosensitive microgel fine particles produced as described above, it is irradiated with an active energy ray such as an ultraviolet ray or an electron beam so as to have good moisture absorption / desorption properties. Material can be obtained. In order to promote a crosslinking reaction by irradiation with active energy rays, a photoinitiator can be added as needed. Examples of the photopolymerization initiator include 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. It is desirable to use the photopolymerization initiator in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the solid content of the photosensitive microgel fine particles.

When irradiating with active energy rays, an aqueous dispersion containing photosensitive microgel fine particles is applied onto a plastic substrate, metal substrate, paper substrate, or the like, or formed into a sheet by a casting method or the like. Thereafter, it is desirable to irradiate with active energy rays. The coating method is not particularly limited, and a commonly used coater or the like can be appropriately used according to the viscosity of the aqueous dispersion and the coating film thickness. As described above, the reason for having good moisture absorption / desorption properties only after irradiation with active energy rays is that before the irradiation, the carboxyl group-containing compound does not have a three-dimensional crosslinked structure, so that sufficient moisture absorption cannot be exhibited. It is. Therefore, before taking the three-dimensional crosslinked structure, that is, in the state where the photosensitive microgel fine particles are dispersed in water, the viscosity increase due to the hygroscopic force and the gelation phenomenon are less likely to occur, and the photosensitive microgel particles can be used as a photosensitive aqueous paint. It becomes possible.

[0017]

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) (a) Synthesis of polymer emulsifier 70 parts of acrylic acid, 2-ethylhexyl acrylate 7
0 parts and 140 parts of 2-propanol were heated to 80 ° C. in a nitrogen atmosphere with stirring in a 1 liter reaction vessel. Azobisisobutyronitrile (hereinafter AIB) as a polymerization initiator
N) was added and maintained at 80 ° C. for 2 hours, then 0.3 parts of AIBN was added, and then the reaction mixture was maintained at 80 ° C. for 4 hours to complete the polymerization. Then 10%
A mixture of 272.2 parts of an aqueous sodium hydroxide solution and 200 parts of water was added, and the mixture was heated to remove 2-propanol and water by azeotropic distillation to obtain a polymer emulsifier. After standing overnight, 13.8 parts of glycidyl methacrylate was added, and the mixture was heated to 80 ° C. in an air atmosphere and maintained for 4 hours to obtain a reactive polymer emulsifier. Thereafter, the solid content of the reactive polymer emulsifier was adjusted to 25%.

(B) Synthesis of photosensitive microgel 100 parts of R-45ACR-LC (dimethacrylate modified polybutadiene manufactured by Idemitsu Petrochemical Co., Ltd.), (a)
80 parts of a polymer emulsifier aqueous solution synthesized in (20 parts solids)
And 200 parts of deionized water was heated to 80 ° C. in a nitrogen atmosphere with stirring in a 1 liter reaction vessel. 16 parts of a 5% aqueous solution of azobisamidinopropane dihydrochloride (hereinafter referred to as AAPD) was added, and the mixture was kept at 80 ° C. for 2 hours. Then 5% A
4 parts of APD aqueous solution was added, and after the addition was completed, the reaction mixture was added to 80 parts.
The polymerization was completed by holding at 4 ° C. for 4 hours to obtain an aqueous dispersion of microgel fine particles. After leaving the obtained microgel fine particle aqueous dispersion liquid overnight, glycidyl methacrylate4.
Five parts were added, and the mixture was heated to 80 ° C. in an air atmosphere and kept for 4 hours to obtain an aqueous dispersion of fine photosensitive microgel particles having a carboxyl group and a polymerizable double bond on the surface.
The measurement result of the particle diameter of the photosensitive microgel fine particles by the light scattering method was about 220 nm.

(C) Production of moisture-absorbing and desorbing material The solid content of the photosensitive microgel fine particle aqueous dispersion obtained in (b) was adjusted to 30%, and the aqueous dispersion was added to 50 parts (solid content: 15 parts). 0.3 parts of Darocure 2959 (manufactured by Merck) was added as a photoinitiator, 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 light to crosslink, thereby obtaining a moisture absorbing / releasing material.

(Example 2) R-45 ACR-LC100
95 parts of 2-ethylhexyl acrylate instead of parts
A hygroscopic material was obtained in the same manner as in Example 1 except that 5 parts of ethylene glycol dimethacrylate was used. The particle diameter of the photosensitive microgel fine particles was about 70 nm.

(Examples 3 and 4) The same procedure as in Example 1 was repeated except that the amount of the aqueous polymer emulsifier was changed to 100 parts and 120 parts, respectively. The material was obtained. The particle size of the photosensitive microgel fine particles was about 210 nm in Example 3 and 19 in Example 4.
It was 0 nm.

Comparative Example 1 A dried product of the reactive polymer emulsifier obtained in Example 1 (a) and R-45ACR-
LC was kneaded with two rolls at the same ratio as in Example 1 to prepare a 500 μm sheet, and the obtained sheet was irradiated with 1000 mJ of ultraviolet light to crosslink.

(Evaluation of moisture absorption / release properties) The moisture absorption / release properties of the obtained sheets were evaluated as follows. Table 1 shows the results. The hygroscopicity was measured by cutting a sheet into a size of 50 mm × 100 mm, leaving it in an atmosphere of a temperature of 30 ° C. and a relative humidity of 90% for 24 hours, and calculating the moisture absorption of each sample by the following formula.

[0024]

(Equation 1)

With respect to the moisture release, each sample whose moisture absorption was measured was allowed to stand in an atmosphere at a temperature of 25 ° C. and a relative humidity of 65%, and the change over time in the weight of each sample was measured. I asked.

[0026]

(Equation 2)

[0027]

[Table 1]

[0028]

The hygroscopic material of the present invention has a hygroscopic property corresponding to the amount of the carboxyl group on the surface of the photosensitive microgel, and has a characteristic of rapidly releasing moisture under low humidity. Also, by changing the type of the monomer having a polymerizable double bond constituting the core, or the functional group density on the surface of the photosensitive microgel fine particles, the strength of the moisture absorbing and releasing material,
Since various physical properties such as hardness and weather resistance can be controlled, it can be widely used for antifogging materials, desiccants, humidity sensors, humidity regulators and the like.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) C09K 3/00-3/32 C08F 299/00-299/08 C08F 8/00-8/50 C08F 2 / 00-2/60

Claims (2)

(57) [Claims] 1. A carboxyl group of microgel fine particles (A) prepared by emulsion polymerization of a monomer having a polymerizable double bond using a carboxyl group-containing compound as an emulsifier, and an epoxy group and at least one polymer in one molecule. compounds having sex double bond (B) Ri Na by reacting the epoxy group, have a polymerizable double bond with a carboxyl group on the surface
Of aqueous dispersion containing photosensitive microgel particles
A moisture-absorbing and desorbing material characterized by being crosslinked by irradiation with active energy rays . 2. The method for producing a hygroscopic material according to claim 1, wherein the aqueous dispersion containing the photosensitive microgel fine particles is dried and then irradiated with active energy rays.