JPS6169854A - Water-absorbing resin composition - Google Patents

Abstract

PURPOSE:To provide the titled compsn, which has excellent dispersibility in water. excellent water absorption rate and powder fluidity at a high temp., by mixing a cationic surfactant-treated water-absorbing resin contg. carboxylic groups and an inorg. material and/or a high-melting org. compd. CONSTITUTION:0.1-20wt% cationic surfactant contg. at least one 12-24C alkyl or alkenyl group (e.g. lauryltrimethylammonium chloride) molten by heating is mixed with a carboxyl group-contg. water-absorbing resin having an average particle size of 5-1,000mum (e.g. saponified starch/acrylonitrile copoly mer) to coat the surface of the resin with the surfactant. 0.01-10wt% inorg. material (e.g. SiO2) having an average particle size of 100mum or below and/or high-melting org. compd. (e.g. calcium stearate) having a m.p. of 80 deg.C or above and a particle size of 100mum or below are/is mixed with said coated resin.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention has a wide range of applications such as body fluid absorbent for sanitary napkins and disposable diapers, soil water retention agent, seed coating agent, water stop agent, dew condensation prevention agent, etc. The present invention relates to a water-absorbing resin having improved water-absorbing properties and fluidity.

[Conventional technology]

Until now, water-absorbing resins such as carboxymethylcellulose crosslinked products, partially crosslinked polyethylene oxide products, starch-acryloni (IJ) graft copolymers, and crosslinked polyacrylates have been used to reduce the amount of mako that occurs when they come into contact with liquids. Various studies have been made to prevent this and improve the water absorption rate. For example, aliphatic hydrocarbons with a melting point of 35°C or less, nonionic derivatives, and carbon atoms with a carbon number of 12
~18 alkyl groups) A method of surface treatment with IJ methylammonium chloride (Japanese Patent Application Laid-Open No. 1983-1983)
-, No. 50355), method of coating water-absorbent resin with water-soluble surfactants such as nonionic surfactants and water-soluble polymers such as polyvinyl alcohol (JP-A No. 57-1
68921), anionic surfactants) (L87 or higher 7-ionic surfactants with water absorbency (method for treating M fats)
JP-A No. 58-32641). However, in these methods, although the wettability of the water-absorbing resin is improved and it is possible to considerably prevent clumping, the water absorption rate is still insufficient. In addition, in these methods, the fluidity of the water-absorbing resin powder decreases. In particular, when the temperature reaches about 40° C., the fluidity decreases significantly and workability etc. are impaired.

On the other hand, studies are also being conducted to prevent a decrease in fluidity caused by moisture absorption peculiar to water-absorbing resin powders. For example, a method of mixing water-absorbing resin powder with hydrophobic ultrafine particle solica (Japanese Unexamined Patent Publication No. 56-133028"), hydrous silicon dioxide,
There are methods such as mixing with hydrated aluminum oxide, hydrated titanium oxide, etc. (Japanese Unexamined Patent Publication No. 59-80459), but these methods simply prevent a decrease in fluidity due to moisture absorption, and do not improve mako etc. There wasn't.

[Problem that the invention seeks to solve]

The present invention provides a water-absorbing resin composition that has good dispersibility (wettability) in water, can prevent lumpiness, has a high water absorption rate, and has excellent powder fluidity at high temperatures.

[Means for solving problems]

In order to solve the above problems, we investigated various treatment agents and selected a specific cationic surfactant that can form an ionic bond with the carboxyl group in the water-absorbing resin. After that, it was discovered that a water-absorbing resin with uniquely excellent performance can be achieved by combining it with an inorganic powder or a specific organic powder treatment, leading to the present invention.

That is, in the present invention, after treating a water-absorbing resin having a carboxyl group with a cationic surfactant having at least one alkyl group (or alkenyl group) having 12 to 24 carbon atoms in the molecule, an inorganic substance and/or The present invention provides a water absorbent resin composition characterized in that it contains a high melting point organic compound.

The water-absorbing resin used in the present invention may be any type of polymer and any polymerization method as long as it has a carboxyl group in its constituent unit. The commonly used monomers are
Examples include vinyl monomers having carboxyl groups such as acrylic acid, methacrylic acid, maleic acid, itaconic acid, and salts thereof. These materials can be homopolymerized or copolymerized in combination of two or more, and further copolymerized with other components such as acrylamide, vinyl acetate, starch, etc. Examples of the water-absorbing resins obtained by polymerization include saponified starch-acrylonitrinole graft copolymers, starch-acrylic acid graft copolymers and their salts, and saponified starch-acrylamide copolymers. , cross-linked carboxymethyl cellulose, polyvinyl alcohol-acrylic acid copolymer and its salt, saponified vinyl ester-unsaturated carboxylic acid copolymer, polymer of acrylic acid or its salt, saponified acrylonitrile polymer, etc. can give. These also include those crosslinked using a crosslinking agent and self-crosslinking types. These water absorbent resins are synthesized by known polymerization methods such as solution polymerization and (reverse phase) suspension polymerization. this house,
In the case of reverse-phase suspension polymerization, the particle size of the produced water-absorbing resin is adjusted to a desired value, and then the resin is used as it is or after solvent removal or dehydration treatment and drying. In addition, sheets or blocks obtained by solution polymerization or the like are dried and then mechanically pulverized to a desired particle size. The particle size of the water-absorbing resin powder is determined depending on various uses, but the average particle size is usually 5 to 1000 μm, preferably 30 to 1000 μm.
It is assumed to be 300 μm. The shape of the particles may be spherical, flaky, amorphous, or the like.

In the present invention, the water-absorbing resin described above is first treated with a cationic surfactant. The cationic surfactants used here are quaternary ammonium salts, imidazolinium salts, and amine salts having at least one alkyl group (or alkenyl group) having 12 to 24 carbon atoms in the molecule. Among these, lauryltrimethylammonium chloride, stearyltrimethylammonium methyl sulfate,
dilauryl diethylammonium ethyl sulfate,
Preferred are quaternary ammonium salts having one or two alkyl groups having 12 to 18 carbon atoms in the molecule, such as simyristyldimethylammonium chloride, distearyldimethylammonium methyl sulfate, dicured tallow alkyldimethylammonium chloride, and particularly, A di-long-chain alkyl di-short-chain alkyl quaternary ammonium salt having two alkyl groups having 12 to 18 carbon atoms in the molecule is preferred. Various methods can be adopted to treat the water absorbent resin with such a cationic surfactant, but by mixing the cationic surfactant melted by heating and the water absorbent resin powder, It is preferable to use a method in which the surface of the powder is coated and then cooled. In addition, a method may be used in which the cationic surfactant is dissolved in a solvent, coated on a dry water-absorbent resin powder or a hydrous polymer in the process of producing the water-absorbent resin, and then the solvent and/or water are removed.

The amount of the cationic surfactant to be used is preferably in the range of 0.1 to 20% by weight (hereinafter abbreviated as %), preferably 1 to 10%, based on the water absorbent resin composition.

Next, an inorganic substance and/or a high melting point organic compound are mixed with the above-mentioned treated object, and these are attached to the surface of the above-mentioned treated object. The inorganic substance used here usually has an average particle size of 100 μm.
Examples include inorganic fine particles and clay minerals containing silicon oxide, aluminum oxide, titanium oxide, calcium silicate, magnesium silicate, calcium phosphate, zinc oxide, magnesium carbonate as a main component and having a diameter of 30 μm or less, preferably 30 μm or less. . Further, the high melting point organic compound usually has a melting point of 80°C or higher, preferably 100°C or higher.
℃ or higher and a particle size of 100 μm or less, preferably 30 μm or less, powder of metal salts of fatty acids such as calcium stearate and magnesium stearate, polyethylene, polystyrene, polyacrylic (methacrylic) acid ester,
Examples include synthetic resin powders such as nylon and polyvinyl chloride. The amount used is 0.01 to 10% of the water absorbent resin.
%, preferably in the range of 0.1 to 1%. If the amount is too small, the powder fluidity will not be improved, and if the amount is too large, the fluidity will not be improved compared to when used within the above range, which is disadvantageous in terms of water absorption and economic efficiency.

These powders are mixed and stirred with water-absorbent resin powder whose surface is coated with a cationic surfactant.

In some cases, the dispersion medium may be removed after mixing using a dispersion medium (for example, aliphatic carbohydrates or alcohols) that does not affect the powder of the inorganic substance or the high melting point organic compound. However, when using a high melting point organic compound and heating it to remove the dispersion medium or re-drying the water absorbent resin after mixing, do not heat below the melting point of the compound. .

〔Effect of the invention〕

The water-absorbing resin composition of the present invention prevents dispersibility (meltability) in water and improves water absorption rate by combining a specific cationic surfactant with an inorganic substance and/or a high melting point organic compound. can be achieved extremely effectively. In addition, when filling water-absorbent resin between two sheets such as tissue paper, the temperature rises to about 40°C due to the abrasive heat and ambient temperature during the process.
Even at such high temperatures, it has excellent fluidity and is extremely easy to work with.

Therefore, since it has the above-mentioned water absorption characteristics,
It is effective to apply the product in the form of a sheet-like product that is sandwiched between two sheets of tissue paper or the like and embossed.Such sheet products can be used to absorb water such as sanitary napkins, disposable diapers, and bed sheets for patients. Sexuality.

- It is advantageously used as a tool. It can also be used in a wide variety of applications, including water retention agents for soil, water stop agents for civil engineering and construction, anti-condensation agents, sip agents, poultice agents, and fragrance base materials.

Next, the present invention will be explained with reference to Examples, but the present invention is not limited thereto.

〔Example〕

In the examples, water absorption rate, powder fluidity, and mako formation were measured as follows.

0 Water absorption degree: 0.3 g of water absorbent resin is sealed in a non-woven fabric bag, and the bag is held vertically and the sample is packed at the bottom. This is immersed vertically into physiological saline in a beaker at 300 mA for 30 seconds. after that,
Pull it out, drain it on a wire mesh for 1 minute, and measure its weight.

Separately, the weight obtained by testing a nonwoven bag containing no water-absorbing resin is used as a blank.

The value obtained by subtracting the blank from the above measurement value and converting it into the weight per 1 g of water absorbent resin was defined as the water absorption rate. The larger the number, the faster the water absorption rate.

20 g of the powder flowable water absorbent resin composition was placed in a 70 m, g glass sample bottle, and the fluidity was observed at 40°C.

The evaluation was as follows.

3...It's smooth and flows just by tilting the bottle a little.

2... It flows, but it clumps up a little.

1...Does not flow.

Production of 0 macomo 2 parts of the water absorbent resin were placed in a 100 mt' beaker, 50 parts of ion-exchanged water was added thereto, and the mixture was stirred gently with a glass rod, and the water absorption state of the water absorbent resin was visually determined.

Synthesis of water absorbent resin (No. 1) 500 equipped with a stirrer, reflux condenser, and nitrogen gas inlet pipe
rr+j! 150 g of n-hexane in a four-necked flask
and sorbitan monostearate 1. 5 g was added and dissolved, and the mixture was replaced with nitrogen while stirring.

Separately, 30 g of acrylic acid was neutralized with 12.9 g of sodium hydroxide dissolved in 39 g of water, and 0.05 g of potassium persulfate A was added.
g and N, N'-methylenebisacrylamide 0.002
g was added, dissolved, and then replaced with nitrogen.

This solution was added to the above-mentioned four-bottle flask, dispersed with stirring, and polymerized at 60° C. for 3 hours under a nitrogen atmosphere. After polymerization, n-hexane was removed and dried at 80°C under reduced pressure.
A dry water absorbent resin in powder form was obtained.

500 with a stirrer, reflux condenser and nitrogen gas inlet tube
180 g of cyclohexane was placed in a four-meter mf flask, and 1.8 g of sorbitan laurate was added thereto and dissolved. While stirring, the temperature was raised to 75° C. under a nitrogen atmosphere.

Separately, 30 g of acrylic acid was neutralized with 52 g of 24% sodium hydroxide aqueous solution, and then 0.1 g of ammonium persulfate and 0.01 g of ethylene glycol diglylicidyl ether were added.
g was added and dissolved, and the mixture was replaced with nitrogen while stirring.

This solution was added dropwise to the above-mentioned four-hole flask under a nitrogen atmosphere over 1 hour to polymerize, and then aged at 75° C. for 1 hour to complete the polymerization. After polymerization, cyclohexane was removed and the mixture was dried at 80° C. under reduced pressure to remove the powdery water absorbent resin.

0 Production of water-absorbing resin (Nα3) 30 g of acrylic acid was put into a 200 rr+1 beaker, and then neutralized by adding an aqueous solution of 12.9 g of sodium hydroxide dissolved in 39 g of water.

After cooling to room temperature, add 0.05 g of potassium persulfate and N.

0.005 g of N-methylenebisacrylamide was added and dissolved. The diameter of the aqueous solution log thus obtained is 1
Place in a 5cm glass petri dish, then add 1jL15
It was left in a constant temperature bath at 0° C. for 20 minutes to perform polymerization and drying at the same time. The obtained film-like product was pulverized to obtain a powdery dry water-absorbing resin.

Example 1 1 g of distearyldimethylammonium chloride was heated and melted, and 19 g of water absorbent resin (No. 1) was added to it.
was added, stirred at 80° C. for 10 minutes, and then cooled to obtain a coating powder (Comparative Example 4).

Add 0.1 g of hydrated silicic acid powder (Tokusil GLI-N manufactured by Toyama Soda Co., Ltd.) to 20 g of this coating powder and let it stand at room temperature.
The water absorbent resin composition was stirred for 0 minutes.

Example 2 20 g of methanol was added to 1 g of dilauryldimethylammonium chloride, heated to 60°C, and dissolved. 19 g of water absorbent resin (V(11)) was added thereto, stirred for 10 minutes, and then heated at 80°C for 2 hours. The coating powder (Comparative Example 5) was dried for hours under reduced pressure.

0.1 g of titanium oxide powder (Teikoku Kako JR-801 containing aluminum silicate) was added to 20 g of this coating powder, and the mixture was stirred at room temperature for 10 minutes to obtain a water absorbent resin composition of 1 grade.

Example 3 Distearyldimethylammonium chloride 0.4g
is heated and melted, and water absorbent resin (Nα2) 19.
Add 6g and stir at 80°C for 10 minutes.

Thereafter, it was cooled to obtain a coating powder (Comparative Example 6).

Add 20g of this coating powder to hydrated silicic acid powder (DEG).
USSA Aerosil 130) 0.04
g and stirred at room temperature for 10 minutes to evaporate the water absorbent resin composition.

Example 4 0.4 g of dilauryl dimethyl ammonium chloride was heated and melted, and 19.6 g of water absorbent resin (Nα2) was added to it.
After stirring at 80° C. for 10 minutes, the mixture was cooled to remove the coating powder (Comparative Example 7).

0.08 g of precipitated calcium carbonate powder was added to 20 g of this coating powder, and the mixture was stirred at room temperature for 10 minutes to obtain a water absorbent resin composition.

Example 5 2 g of distearyldimethylammonium chloride was heated and melted, 18 g of water-absorbing resin (Nα3) was added thereto, stirred at 80°C for 10 minutes, cooled, and coated powder (Comparative Example 8) was prepared. I was humiliated. 0.1 g of calcium phosphate dihydrate powder (manufactured by Toyo Stoffer) was added to 20 g of this coating powder, and the mixture was stirred at room temperature for 10 minutes to obtain a water-absorbing resin composition.

Example 6 2 g of dilauryl dimethyl ammonium chloride was heated and melted, 18 g of water absorbent resin (Nα3) was added thereto, stirred at 80° C. for 10 minutes, and then cooled to obtain a coating powder (Comparative Example 9). .

Add 20g of this coating powder to a clay compound whose main component is aluminum silicate (Nipia F manufactured by Kunimine Industries).
0.2 g was added and stirred at room temperature for 10 minutes to form a water absorbent resin composition.

Example 7 The same procedure as in Example 1 was carried out except that polystyrene powder (laboratory prepared product, average particle size 20 μm) was used instead of the hydrated silicic acid powder.

Example 8 The same procedure as in Example 1 was carried out except that polyvinyl chloride (Sumikabeads BC-30 manufactured by Sumitomo Chemical) was used instead of the hydrated silicic acid powder.

Comparative Example Water absorbent resin (Nlll) (N(12) and (Na3) were respectively used as Comparative Example 1.2.3. Also, the above Comparative Example 4
In addition to Examples 1 to 9, Comparative Examples 10.11 below were conducted.

Comparative Example 10 0.5 g of sorbitan monolaurate was added to 19.5 g of water absorbent resin (No. 1), and the mixture was stirred at room temperature for 10 minutes to obtain a coated powder.

Comparative Example 11 0.5 g of polyethylene glycol was added to 19.5 g of water absorbent resin (No. 1) and stirred at room temperature for 10 minutes to remove the coating powder.

The performances of the water absorbent resin compositions obtained in Examples and Comparative Examples are summarized in Table 1.

Table 1 Table 1 clearly shows that the product of the present invention has excellent water absorption properties and powder fluidity.

In addition, the above water absorbent resin composition is sandwiched between two sheets of thin paper,
After embossing, the amount of water absorbed under pressure was measured, and the products of the present invention all showed superior water absorption compared to the comparative example.

Claims (1)

[Claims] The water-absorbing resin having a carboxyl group has 12 to 2 carbon atoms.
A water-absorbing resin composition characterized in that it is treated with a cationic surfactant having at least one alkyl group (or alkenyl group) in its molecule, and then mixed with an inorganic substance and/or a high melting point organic compound.