JPH01156304A - Manufacture of water-absorptive fine particle - Google Patents

Abstract

PURPOSE:To easily obtain the title fine particles which have proper water absorptivity and moisture retentivity and are useful as material for, e.g., cosmetics, by saponifying a particulate polymer prepared from a specified vinyl monomer and a polyfunctional monomer. CONSTITUTION:A particulate polymer having a particle diameter of 1-20mum is prepared by the suspension polymerization of 50-95wt.% vinyl monomer (A) (e.g., methyl methacrylate) containing at least 30mol.% saponifiable monomer having radical-polymerizable groups (e.g., methyl acrylate) and 5-50wt.% polyfunctional monomer (B) preferably having two or more radical-polymerizable groups (e.g., ethylene glycol dimethacrylate) at 50-100 deg.C in water in the presence of an oil-soluble radical polymerization initiator (e.g., azobisisobutyronitrile), a suspending agent (e.g., calcium phosphate) and, if required, a suspension aid (e.g., an alpha-olefinsulfonate). This polymer is saponified at 50-150 deg.C in a solvent (e.g., methanol) in the presence of an alkali (e.g., NaOH).

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for producing water-absorbing microparticles, and more particularly to a method for producing water-absorbing microparticles suitable as materials for cosmetics and the like.

<Prior Art> In recent years, water-absorbing resins that absorb water to a high degree have been used for various purposes such as sanitary products, disposable diapers, water retention agents for agriculture and arts, and sludge coagulants.

The above-mentioned water-absorbing resins include acrylic acid salts, saponified vinyl acetate-acrylic acid ester copolymers, polyvinyl alcohol crosslinked products, polyvinyl alcohol-maleic anhydride polymers, and inbutylene-maleic acid copolymer crosslinked products. , saponified products of polyacrylonitrile, saponified products of starch-acrylonitrile graft copolymer, crosslinked carboxymethyl cellulose, crosslinked polyethylene oxide, etc.
Various types of water-absorbing resins are known, and these water-absorbing resins usually have a water-absorbing capacity of 30 to 1000 times that of pure water, and thus have a high water-absorbing rate. The water-absorbing resin has a high water absorption rate, so it is useful in fields where high water absorption is required as described above. However, for applications that do not require the above-mentioned high water absorption performance, such as cosmetics that require a moderate amount of water absorption, the water absorption performance is too high and exhibits excessive moisturizing properties, resulting in a sticky feeling. I don't like it.

Further, the water-absorbing resin is usually used in a powder form in order to increase the contact area with water and improve water absorption efficiency. The powdery water-absorbing resin is obtained by drying and solidifying a highly viscous aqueous solution or water-absorbing gel and then pulverizing it with a pulverizer or the like, so the shape of the powdery water-absorbing resin is usually amorphous. On the other hand, as for the shape of the water-absorbing resin, a spherical one has been proposed, but if the particle size of the water-absorbing resin is made small, the powdery water-absorbing resin tends to aggregate when water is absorbed, resulting in a lumpy state, which results in warping and poor water absorption performance. The particle size of the water-absorbing resin cannot be made too small because the particle size of the water-absorbing resin decreases. In view of the above points, powdered water absorbent resins having a diameter of 30 μm or more are usually used. However, when a powdered water-absorbing resin having the above-mentioned particle size is used as a cosmetic, etc., the particle size is large, so not only does it not have sufficient slipperiness during application, but it also gives a rough feeling during application.

As mentioned above, conventionally widely used powdered water absorbent resins have a high water absorption rate, and even if the particle shape is spherical, the particle size is large, so they have moderate water absorption and have low slip properties. There is a problem in that it is difficult to produce water-absorbing microparticles that are excellent and do not give a rough feeling when applied.

<Objective of the Invention> The present invention has been made in view of the above-mentioned problems, and provides a method for producing water-absorbing microparticles that has appropriate water absorption and moisture retention properties and can easily produce microparticles. The purpose is to

<Means and effects for solving the problems> In order to achieve the above object, the method for producing water-absorbing microparticles of the present invention includes the following steps:
A particulate polymer is obtained by suspension polymerizing 50 to 95% by weight of a vinyl monomer containing at least 30 mol% of a saponifiable monomer having a radically polymerizable group and 5 to 50% by weight of a polyfunctional monomer; It is characterized by saponifying the particulate polymer.

According to the method for producing water-absorbing microparticles having the above structure, 50 to 95% by weight of a vinyl monomer containing at least 30 mol% of a saponifiable monomer having a radically polymerizable group and 5 to 50% by weight of a polyfunctional monomer are used. Since the particles are subjected to suspension polymerization, the particulate polymer does not have an amorphous shape but becomes a spherical fine particle.

Therefore, when used as a cosmetic, it has excellent slipperiness and spreadability, and does not give a rough feeling. In addition, since the granular polymer is saponified after obtaining the granular polymer, hydrophilic groups are generated as a result of saponification, and the ratio of the saponifiable monomer to the polyfunctional monomer is adjusted. By doing so, water absorption and the like can be controlled, and water-absorbing microparticles having appropriate water-absorbing and moisturizing properties can be obtained.

The present invention will be explained in detail below.

The method for producing water-absorbing microparticles of the present invention includes the steps of suspension polymerizing a vinyl monomer containing a saponifiable monomer having a radically polymerizable group and a polyfunctional monomer to obtain a particulate polymer; It consists of a step of saponifying the particulate polymer.

Examples of saponifiable septamers having the above radically polymerizable group include vinyl acetate, acrylonitrile, methyl crotonate, ethyl crotonate, propyl crotonate, isopropyl crotonate, butyl crotonate, dimethyl maleate, diethyl maleate. , dipropyl maleate,
Dibutyl maleate, dimethyl fumarate, diethyl fumarate, dibutyl fumarate, dimethyl itaconate, diethyl itaconate, dibutyl itaconate, etc. may be used, but acrylic esters are preferred. Examples of acrylic esters include methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, isobutyl acrylate, pentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, and -2 acrylate. -Ethylhexyl, dodecyl acrylate, stearyl acrylate, cyclohexyl acrylate, phenyl acrylate, etc., but acrylic esters having an alkyl group having 1 to 4 carbon atoms that can be easily saponified are preferred. The above-mentioned saponifiable monomers may be used alone or in combination of two or more.

In addition, vinyl monomers containing saponifiable monomers include methyl methacrylate, ethyl methacrylate,
Propyl methacrylate, isopropyl methacrylate, butyl methacrylate, isobutyl methacrylate, pentyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, stearyl methacrylate, cyclohexyl methacrylate , methacrylic acid esters such as phenyl methacrylate; styrene, α-
Examples include styrenic monomers such as methylstyrene. The above vinyl monomers may be used alone or in combination.

In addition, the above vinyl monomers include acrylic acid, methacrylic acid, acrylamide, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, glycidyl acrylate, diethylaminoethyl acrylate, glycidyl methacrylate, and 2-hydroxy methacrylate. Ethyl, 2-hydroxypropyl methacrylate, diethylaminoethyl methacrylate, etc. may be contained within a range that does not impair suspension polymerization.

The vinyl monomer contains at least 30 mol%, preferably at least 50 mol%, more preferably at least 75 mol% of saponifiable monomer. If the content of the saponifiable monomer is less than 30 mol %, the saponification rate of the particulate polymer will be insufficient and it will be difficult to produce a water absorbent resin having an appropriate water absorption rate.

Further, in order to adjust water absorption and water retention, a polyfunctional monomer is used together with the above vinyl monomer. This polyfunctional monomer may be any monomer as long as it can introduce a crosslinked structure into the particulate polymer during or after suspension polymerization. For example, it may be N-methylol acrylamide, etc. a polyfunctional monomer having two or more,
For example, ethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, diethylene glycol dimethacrylate, propylene glycol diacrylate, propylene glycol dimethacrylate, dipropylene glycol diacrylate, dipropylene glycol dimethacrylate, glycerin diacrylate, glycerin dimethacrylate, Preferred are glycerin triacrylate, glycerin trimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol tetraacrylate, pentaerythritol tetramethacrylate, divinylbenzene, and the like. The above polyfunctional monomers may be used alone or in combination of two or more.

In order to avoid impairing suspension polymerizability, it is preferable to use a polyfunctional monomer that is insoluble or sparingly soluble in water.

Furthermore, the vinyl monomer containing the saponifiable monomer having a radically polymerizable group and the polyfunctional monomer are used in a ratio of 50 to 95% by weight of the vinyl monomer and 5 to 50% by weight of the polyfunctional monomer. . If the amount of polyfunctional monomer is less than 5% by weight, water absorption becomes too large;
If it exceeds 50% by weight, it exhibits almost no water absorption.

In addition, the polymerizable monomer containing the vinyl monomer and the polyfunctional monomer is precipitated with a precipitant such as hexane, pentane, isooctane, etc. in order to make the particulate polymer obtained by suspension polymerization porous. You can.

The polymerizable monomers containing the above-mentioned vinyl monomer and polyfunctional monomer are subjected to suspension polymerization.

The suspension polymerization is carried out by polymerizing the polymerizable upper polymer in water using an oil-soluble radical polymerization initiator in the presence of a suspending agent.

As the suspending agent, various dispersants such as polyvinyl alcohol can be used, but inorganic salts such as calcium phosphate and magnesium pyrophosphate, and suspension aids such as α-olefin sulfonate and sodium dodecylbenzenesulfonate can also be used. surfactants are preferably used. The suspending agent is used in an appropriate amount depending on the desired particle size of the particulate polymer.

Examples of the oil-soluble radical polymerization initiator include peroxides such as benzoyl peroxide and lauroyl peroxide, and azo compounds such as azobisisobutyronitrile.

The suspension polymerization is usually carried out under reaction conditions of 50 to 100°C.
This is carried out for a predetermined period of time while stirring, preferably at high speed. Suspension polymerization conditions can be variously set depending on the particle size of the desired particulate polymer, etc., and the concentration of the polymerizable monomer,
By adjusting the amount of suspending agent, stirring conditions, etc., the particle size of the particulate polymer that is the suspension polymer can be controlled. The particle size of the particulate polymer can be variously set depending on the intended use of the final product, but it is preferably 1 to 20 μm, preferably 5 to 15 μm. If the particle size is less than 1 micron, not only is the granular polymer likely to aggregate during saponification, but also it is difficult to control the granular polymer to the above particle size by suspension polymerization. Moreover, if the thickness exceeds 20 μm, when used as a cosmetic, not only the slipperiness and spreadability will be insufficient, but also it will give a rough feeling, which is undesirable. In addition, since the particulate polymer is obtained by a suspension polymerization method, it exhibits a spherical shape and is excellent in slipperiness and elongation, as well as providing an excellent feel in use without giving a rough feeling.

Next, the particulate polymer obtained as described above is saponified to impart water absorbency to the particulate polymer. The above-mentioned saponification may be carried out in a predetermined solvent as necessary after suspension polymerization, in a state in which the particulate polymer is dispersed, or after filtering the produced particulate polymer. In addition, saponification of particulate polymers is
Various conventional methods may be used, for example, in the presence of an acid such as hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, perchloric acid, etc., but sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium hydrogen carbonate, , in the presence of an alkali such as potassium hydrogen carbonate, usually at 50 to 150°C, especially at 75°C.
It is preferable to carry out the reaction at a temperature of about 100°C. The above-mentioned alkali etc. can be used in the amount necessary to saponify the saponifiable monomer residue introduced into the particulate polymer, but in order to increase the saponification efficiency, it is necessary to It is used in an amount of 0.8 to 1.2 moles, preferably equimolar.

Further, the saponification step can be carried out in the presence of various solvents such as water that does not dissolve the particulate polymer;
It is preferable to carry out the reaction in the presence of an alcohol such as methanol or ethanol. Further, saponification of the particulate polymer is preferably carried out under high-speed stirring as in the suspension polymerization.

Through the above-mentioned saponification step, a hydrophilic group is introduced into the particulate polymer, and a water-absorbing resin in the form of microparticles exhibiting water-absorbing properties is obtained. The degree of saponification of the particulate polymer can be set in various ways depending on the application, but in order to provide appropriate water absorption and moisture retention, the water absorption is 1.5 to 20 times, preferably 2 to 1.
It is preferable to saponify it so that it becomes 0 times. Water absorption rate is 1
．． If it is less than 5 times, water absorption and moisturizing properties are insufficient, and 20
If the amount exceeds twice that, when used as a cosmetic amount, the water absorption rate will be too high, giving a sticky feeling, which is undesirable. The water absorption rate can be controlled by adjusting the amounts of the saponifiable monomer and polyfunctional monomer used, the degree of saponification, and the like.

The water-absorbing fine particles of the present invention can be obtained by washing and drying the granular polymer saponified as described above.

As an example, an electron micrograph showing the particle structure of polymer microparticles obtained by the production method of the present invention (magnification:
500) is shown as a reference photograph. In this reference photo, the polymerizable microparticles are spherical and have a diameter of 1 to 811 m.
have.

According to the method for producing water-absorbing microparticles having the above structure, suspension polymerization is carried out using a vinyl monomer containing a specific amount of a saponifiable monomer having a radically polymerizable group and a polyfunctional monomer in a specific ratio. At the same time, since the particulate polymer obtained by suspension polymerization is saponified, it is possible to easily produce a water-absorbing resin that is spherical and has fine particles and has appropriate water absorption and moisture retention properties. Therefore, it is particularly useful for applications that require properties such as excellent moisturizing properties, slipperiness and spreadability, and no rough feeling, such as cosmetics such as basic cosmetics and makeup cosmetics.

<Examples> The present invention will be described in more detail below based on Examples.

Example 1 In a 5-note autoclape, 2850 g of water, 150 g of poorly soluble tertiary calcium phosphate, 0.3 g of α-olefin sulfonate, 2.4 g of common salt, 0.9 g of azobisisobutyronitrile, and methyl acrylate. 360 g and 240 g of ethylene glycol dimethacrylate were charged, and suspension polymerization was carried out for 6 hours at a temperature of 70° C. while stirring at high speed. The polymer was then filtered, placed in a 5J autoclave with 2 g of methanol and 168 g of sodium hydroxide, and saponified at a temperature of 70°C for 1 hour and at a temperature of 90°C for 3 hours. In addition, after filtering the saponified product, it was put into an autoclave with 2 parts of methanol again and stirred at a temperature of 90°C for 4 hours, and after cooling, filtration, washing, and drying were performed to obtain fine polymer particles. Ta.

The obtained polymer microparticles are spherical and have an average particle size of 7.
, 2 μm 1 showed a water absorption rate of 2 times.

Example 2 Polymer microparticles were produced by changing the amounts of methyl acrylate and ethylene glycol dimethacrylate used in Example 1. That is, using 540 g of methyl acrylate and 60 g of ethylene glycol dimethacrylate, Example 1
Polymer microparticles were obtained in the same manner as above.

The obtained polymer microparticles were spherical and had an average particle size of 6.
8μm1 showed a water absorption rate of 6 times.

16 Example 3 In place of the polymerizable monomer of Example 1, 222 g of methyl acrylate, 258 g of methyl methacrylate, and 120 g of trimethylolpropane trimethacrylate-t-t were used, and the same operation as in Example 1 was carried out to obtain a polymer. Coalesced microparticles were produced.

The obtained polymer microparticles were spherical and had an average particle size of 7.
It showed a water absorption rate of 3.5 times.

Example 4 In place of the polymerizable monomer of Example 1, 270 g of butyl acrylate, 210 g of methyl methacrylate, and 120 g of ethylene glycol dimethacrylate were used.
Polymer microparticles were produced in the same manner as described above.

The obtained polymer microparticles were spherical and had an average particle size of 7.
2 μm, and showed a water absorption rate of 5.0 times.

Comparative Example 1 In place of the polymerizable monomer of Example 1, 200 g of methyl acrylate and 400 g of ethylene glycol dimethacrylate were used.
Polymer microparticles were produced using the same procedure as in Example 1.

The obtained polymer microparticles were spherical and had an average particle size of 7.
Although it was 0 μm, it showed almost no water absorption.

Comparative Example 2 Polymer microparticles were produced in the same manner as in Example 1 except that 594 g of methyl acrylate and 6 g of ethylene glycol dimethacrylate were used in place of the polymerizable monomer of Example 1.

The obtained polymer microparticles had an average particle size of 6.8 μm, but had a water absorption capacity as high as 50 times.

<Effects of the Invention> As described above, according to the method for producing water-absorbing microparticles of the present invention, a vinyl monomer containing a specific amount of a saponifiable monomer having a radically polymerizable group and a polyfunctional monomer are combined. By using it in a specific ratio, carrying out suspension polymerization, and saponifying the obtained granular polymer, it is possible to easily produce a water-absorbing resin that is spherical and fine particles, and has appropriate water absorption and moisture retention properties. It has the unique effect of being able to

Patent applicant: Sekisui Plastics Co., Ltd. = 19-

Claims (1)

[Claims] 1. Vinyl monomer 50-9 containing at least 30 mol% of a saponifiable monomer having a radically polymerizable group
5% by weight of a polyfunctional monomer and 5 to 50% by weight of a polyfunctional monomer to obtain a granular polymer, and the granular polymer is saponified. 2. The method for producing water-absorbing microparticles according to claim 1, which comprises saponifying a particulate polymer to produce microparticles with a water absorption rate of 1.5 to 20 times. 3. The method for producing water-absorbing microparticles according to claim 1, wherein the saponifiable monomer having a radically polymerizable group is an acrylic ester. 4. The method for producing water-absorbing microparticles according to claim 3, wherein the acrylic ester has an alkyl group having 1 to 4 carbon atoms. 5. The method for producing water-absorbing microparticles according to claim 1, wherein the particle size of the granular polymer is 1 to 20 μm.