JPH05178924A - Water-absorbent resin and its production - Google Patents

Abstract

PURPOSE:To provide the title production whereby a fine spherical water- absorbent resin of a mean particle diameter of 1-50mum is obtained by reacting a copolymer of an alpha-olefin or a vinyl compound with maleic anhydride with an alkali metal compound and a cross-linking agent in the presence of a 3C or higher alcohol as a reaction solvent while the production on an industrial scale is possible because the polymer suspension is filterable, no grinding step is necessary and therefore the productivity and economic profitability can be attained. CONSTITUTION:A water-absorbent resin having a mean particle diameter of 1-50mum and directly obtained by reacting a copolymer of an alpha-olefin or a vinyl compound with maleic anhydride with an alkali metal compound and a cross- linking agent. A process for producing a water-absorbent resin comprising reacting a copolymer of an alpha-olefin or a vinyl compound with maleic anhydride with an alkali metal compound and a cross-linking agent in the presence of a 3C or higher alcohol as a reaction solvent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a water absorbent resin which is useful as a water retention agent, a water absorption agent, a dehydration agent, a drying agent, a wetting agent, a water blocking material and the like.

[0002]

2. Description of the Related Art In recent years, hydrophilic polymer materials have been widely used in various fields. Especially insoluble in water,
Moreover, the water-absorbent resin that can absorb a large amount of water is
From the fields of disposable sanitary products such as sanitary products, diapers, and kitchen appliances and household products, to the industrial field of water-stopping and dehydrating materials that utilize water swellability, and the field of civil engineering and construction such as soil conditioners and dew condensation prevention materials. It is used for purposes. Recently, among these applications, there is an increasing demand for water absorbent resins having particularly fine particle shapes. For example, in water-stopping material and sealing material applications in which various rubbers and water-absorbent resin are used in combination, fine water-absorbent resin is used because dispersibility of the water-absorbent resin is important. Further, for concrete curing / modifying agents, there is known a method of producing high-strength concrete by microdispersing excess water of cement hardening with fine powder of a water-absorbent resin to absorb and retain water. A copolymer of an α-olefin or vinyl compound and maleic anhydride and an acrylic acid polymer are known as water-absorbent resins, but the production method thereof is described in Examples of JP-B-60-56724. As described above, water is used as a reaction solvent, an alkali metal compound and a crosslinking agent are reacted in an aqueous solution, and then the water solvent is removed and dried, and the obtained reaction product is pulverized into fine particles to absorb water. It is a resin.

[0003]

However, with these conventional methods, it is not possible to directly obtain a fine water-absorbing resin, and the reaction product must be crushed. Also,
It takes a lot of labor and time to make a fine powder of 100 μm or less by the pulverizing process, which is economically disadvantageous. further,
The use of water as the reaction solvent has the drawback of limiting the molecular weight of the copolymer. That is, when the molecular weight of the copolymer is greater than 8 (dl / g) in the intrinsic viscosity [η] measured at 30 ° C. in a dimethylformamide solution, the solution viscosity in an aqueous solution is large, and therefore workability and production are improved. There is a problem and it cannot be polymerized.

[0004]

Therefore, the present inventors have
As a result of extensive study, by selecting a reaction solvent, a copolymer of an α-olefin or a vinyl compound and maleic anhydride, an alkali metal compound and a crosslinking agent are reacted in the presence of a specific reaction solvent, and a pulverizing step It was found that a fine water-absorbent resin having an average particle diameter of 1 to 50 μm can be directly obtained without going through the above, and the present invention has been completed.

That is, according to the present invention, (1) water absorption having an average particle size of 1 to 50 μm directly obtained by reacting a copolymer of an α-olefin or a vinyl compound with maleic anhydride, an alkali metal compound and a crosslinking agent. And (2) a copolymer of an α-olefin or a vinyl compound and maleic anhydride in the presence of an alcohol having 3 or more carbon atoms as a reaction solvent, an alkali metal compound and a crosslinking agent. Is a method for producing a water absorbent resin. The present invention will be described in more detail below.

In the present invention, the water-absorbent resin means one having a water absorption capacity for water (distilled water) of at least 20 times its own weight, preferably 50 times or more. A water-absorbing substance having a water absorption ratio of less than 20 times absorbs water, but not only its speed is slow, but also sanitary products, diapers, disposable kitchen wipes It cannot be used for applications such as water materials or soil conditioners. Further, if the water-absorbent resin is dissolved in water, it cannot be used in the above-mentioned applications, and therefore it is cross-linked so as to swell without being dissolved in water. The maximum water absorption capacity is usually about 800 times, usually 50-
It is often used that is about 500 times.

The α-olefin used in the present invention is a linear or branched unsaturated hydrocarbon having 2 to 12 carbon atoms, preferably 2 to 8 carbon atoms, examples of which include ethylene and Propylene, butene-1, butene-2,
Isobutylene, n-pentene, isoprene, 2-methyl-1-butene, n-hexene, 2-methyl-1-pentene, 3-methyl-1-pentene, 2-ethyl-1-butene, diisobutylbutylene, 1,3 -Butadiene, 1,
3-pentadiene, 1,3-hexadiene, 1,3-octadiene, 2-methyl-4-dimethyl-2-pentene, 2-methyl-4-dimethyl-1-pentene, 2-methyl-4-dimethyl-2- Penten etc. are mentioned.

The vinyl compound means an unsaturated compound which can be copolymerized with maleic anhydride, and includes aromatic vinyl such as styrene and α-methylstyrene, acrylic ester such as methyl acrylate and ethyl acrylate, methyl vinyl ether, Alkyl vinyl ethers such as ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, 2-ethylhexyl vinyl ether, dodecyl vinyl ether and octadecyl vinyl ether,
Alternatively, vinyl alcohol obtained by saponifying vinyl acetate, as well as vinyl chloride, vinyl propionate, acrylonitrile, vinylpyrrolidone and the like can be mentioned.

These α-olefin or vinyl compound monomers may be used alone or in combination of two or more kinds. Of these monomers, α-olefins such as ethylene and isobutylene, vinyl compounds such as styrene and alkyl vinyl ethers are preferably used, and methyl vinyl ether is particularly preferably used.

The composition ratio of the α-olefin or vinyl compound and maleic anhydride in the maleic anhydride-based copolymer (including a maleic anhydride copolymer such as maleic acid and maleic acid ester) is as follows. Any amount can be used as long as the reaction product (alkali metal neutralized product) obtained by reacting the copolymer with alkali metal hydroxide can be dissolved in water. In the case of a copolymer of ethylene, isobutylene, styrene or methyl vinyl ether and maleic anhydride preferably used in the present invention, ethylene, isobutylene, styrene or methyl vinyl ether 1 to 1 mol of maleic acid is used.
It is 3 mol, preferably about 1 mol. Such maleic anhydride-based copolymers can be used alone or in combination of two or more. The molecular weight of these copolymers is preferably 10,000 or more in terms of weight average molecular weight measured by GPC (Gel Permeation Chromatography). When the weight average molecular weight is less than 10,000, the crosslinking rate becomes very slow, and it is difficult to obtain a resin having a large water absorption capacity.

The above copolymer is sodium, potassium,
An alkali metal salt can be obtained by reacting with a hydroxide (alkali metal compound) of an alkali metal such as lithium. The proportion of the alkali metal compound used is 40 to 100%, preferably 50 to 80% of the carboxyl groups in the copolymer, from the viewpoint of maintaining excellent durability.
Is to make salt. The most preferred combination of the copolymer and the alkali metal compound used in the present invention is a sodium or potassium salt of a methyl vinyl ether-maleic anhydride copolymer.

Examples of the cross-linking agent include polyhydric amines, polyhydric alcohols, amino alcohols, polyhydric epoxy compounds, and isocyanates. Examples of the polyvalent epoxy compound include glycerin diglycidyl ether, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin tridiglycidyl ether, propylene diglycol diglycidyl ether, and trimethylolpropane triglycidyl ether. Examples of polyvalent amines include ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexane, and linear or branched polyethyleneimine. The amount of the cross-linking agent used varies depending on the type of the hydrophilic copolymer used, the cross-linking conditions, the water absorption capacity of the resulting water-absorbent resin, and the use of the water-absorbent resin, but with respect to 100 parts by weight of the hydrophilic copolymer. 10,
It is to be in the range of not more than 1 part by weight, preferably 0.
It is in the range of 005 to 2 parts by weight.

In the present invention, when the copolymer of α-olefin or vinyl compound and maleic anhydride is reacted with an alkali metal and a crosslinking agent, an alcohol having 3 or more carbon atoms is specifically used as a reaction solvent. Although water is used as a reaction solvent in the conventional manufacturing method, when water is used, the copolymer becomes water-soluble by reacting with an alkali metal. The reaction product obtained by removing the water content of the aqueous solution and drying it becomes a lump or a film, and therefore needs a pulverization step.
Further, in the case of an alcohol having 2 or less carbon atoms as the reaction solvent,
The maleic anhydride group in the copolymer reacts with the alcohol to form a maleic acid ester, which is a product different from the intended product. However, it has 3 carbon atoms as a reaction solvent.
When the above alcohols are used, the esterification does not proceed easily, and the copolymer of α-olefin or vinyl compound and maleic anhydride is not dissolved in the reaction solvent and can be handled as a slurry. Furthermore, by adding an alkali metal compound to this slurry solution, an alkali metal salt can be easily obtained.

By filtering the slurry of the copolymer alkali metal salt, a fine powder of the copolymer alkali salt can be obtained, which can be used as a water-soluble resin. When used as a water absorbent resin, the required amount of the above-mentioned crosslinking agent is added to crosslink the copolymer. The cross-linked product of the alkali metal salt of this copolymer is also dispersed in the form of slurry and can be easily filtered. The obtained crosslinked product retains the fine particle shape before reacting the alkali metal compound and the crosslinking agent, and the water absorbent resin can be obtained without pulverizing. The alcohol to be used has no particular problem as long as it has 3 or more carbon atoms, but isopropanol, n-propanol, n-butanol, isobutanol, secondary butanol and tertiary butanol having 3 to 4 carbon atoms are preferably used. ..
Alcohols having 5 or more carbon atoms have low solubility in sodium hydroxide and require a long reaction time with the copolymer. Further, water or another alcohol can be mixed and used within a range that does not change the shape of the water-absorbent resin produced.

When the alkali metal compound of the copolymer of α-olefin or vinyl compound and maleic anhydride and the crosslinking agent are reacted in an alcohol having 3 or more carbon atoms,
The reaction temperature is preferably 100 ° C or lower, and 40 ° C to 8 ° C.
The range of 0 ° C. is particularly preferable. Below 40 ° C, the reaction speed of the cross-linking agent becomes slow, and above 100 ° C,
The reaction between the maleic anhydride group and the alcohol gradually occurs and esterification occurs. The reaction pressure is not particularly limited. In addition, in the crosslinking reaction, after removing the reaction solvent, a certain heat treatment is further performed to complete the crosslinking reaction.

The particle size and the average particle size were measured by Coulter submicron (manufactured by Coulter Electronics Co.) which is a laser diffraction type particle size distribution measuring method. The shape of the particles was observed with a scanning electron microscope (Hitachi Ltd.).
Further, the water absorption ratio was measured by the tea-back method after immersing in water for a predetermined time and then measuring the weight increase.

The water-absorbent resin obtained by the present invention includes
A filler, a pigment, a dye, an ultraviolet absorber, an antioxidant, an insecticide, a bactericide, a herbicide, a fertilizer, a fragrance, a deodorant and the like may be contained and used.

The water-absorbent resin obtained by the present invention is excellent in durability, and furthermore, by utilizing the fine particle shape, industrial applications such as sealing material, packing material, water blocking material, cement water reducing agent, mortar admixture and It is preferably used for applications such as cosmetics and adhesives.

[0019]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto.

Example 1 A 5-liter 4-neck separable flask equipped with a stirrer was used as a reaction vessel. The reaction vessel was heated on a water bath. 77 g of sodium hydroxide and 2.7 kg of isopropanol were charged into a reaction vessel, and heated and stirred at 50 ° C. to prepare a uniform solution. Next, a methyl vinyl ether-maleic anhydride copolymer (weight average molecular weight: 66
10,000, molar ratio of methyl vinyl ether in copolymer-maleic anhydride = 1: 1, average particle size: 5 μm, particle size distribution 1-3
0 μm, GANTRE made by GAF Chemical Corporation
Z AN-169) 300 g, hexamethylene diamine 1 g, and isopropanol 50 g
5.3 g was added and reacted for about 15 hours to obtain a slurry solution having a pH of about 7. The slurry solution was separated by filtration using a 400-mesh wire net and dried at 50 ° C. using a vacuum dryer. 367 g of white powder (water-absorbent resin) was obtained.
When the water absorbent resin was analyzed, the particle size was 1 to 30 μm,
The particles were spherical particles having an average particle size of 5 μm and maintained the particle shape before the reaction. This water absorbent resin was insoluble in water, swollen rapidly in water, and had a water absorption capacity of 400 times against distilled water. The results are shown in Table 1.

[0021]

[Table 1]

Example 2 Using the same apparatus as in Example 1, the same operation was performed using n-butanol instead of isopropanol as a reaction solvent. The reaction proceeds as a slurry in the same manner as in Example 1,
After the reaction, it was separated by filtration and dried at 50 ° C. using a vacuum dryer. 363 g of white powder (water-absorbent resin) was obtained.
When the water absorbent resin was analyzed, the particle size was 1 to 30 μm,
The particles were spherical particles having an average particle size of 5 μm and maintained the particle shape before the reaction. This water absorbent resin was insoluble in water, swollen rapidly in water, and had a water absorption capacity of 350 times against distilled water. The results are shown in Table 1.

Example 3 A styrene-maleic anhydride copolymer (weight average molecular weight: 160,000, was used in place of the methyl vinyl ether-maleic anhydride copolymer as the copolymer used, using the same apparatus as in Example 1. Molar ratio of styrene-maleic anhydride in the copolymer = 1: 1, average particle size: 5 μm, particle size distribution 1-30 μm
m, particle shape: spherical), 15.3 g of a cross-linking agent solution consisting of 1 g of hexamethylenediamine and 50 g of isopropanol was added and reacted for about 15 hours to obtain a slurry solution of PH about 7. The slurry solution was separated by filtration using a 400-mesh wire net and dried at 50 ° C. using a vacuum dryer. 366 g of white powder (water-absorbent resin) was obtained. The reaction proceeded as a slurry in the same manner as in Example 1. After the reaction, it was separated by filtration and dried at 50 ° C. using a vacuum dryer. 363 g of white powder (water-absorbent resin) was obtained. When this water absorbent resin was analyzed, it was found to be spherical particles having a particle size of 1 to 30 μm and an average particle size of 5 μm, and the particle shape before the reaction was retained. This water absorbent resin was insoluble in water, swollen rapidly in water, and had a water absorption capacity of 230 times with respect to distilled water. The results are shown in Table 1.

Example 4 Using the same apparatus as in Example 1, an isobutylene-maleic anhydride copolymer (weight average molecular weight: 160,000, was used as the copolymer to be used instead of the methyl vinyl ether-maleic anhydride copolymer). The molar ratio of isobutylene-maleic anhydride in the copolymer = 1: 1, average particle size: 20 μm, particle size distribution 10-50 μm, particle shape: spherical) 300 g of hexamethylenediamine 1 g and isopropanol 50 g Add 0.3 g and react for about 15 hours,
A slurry solution having a pH of about 7 was prepared. Add this slurry solution to 4
It was separated by filtration using a 00 mesh wire mesh and dried at 50 ° C. using a vacuum dryer. 36 white powder (water-absorbent resin)
6 g was obtained. The reaction proceeds in the form of slurry in the same manner as in Example 1, and after the reaction, it is separated by filtration and a vacuum dryer is used.
It was dried at ° C. 360 g of white powder (water-absorbent resin) was obtained. Analysis of this water-absorbent resin revealed a particle size of 10
The spherical particles had a particle size of 50 μm and an average particle size of 20 μm, and retained the particle shape before the reaction. This water-absorbent resin was insoluble in water, swollen quickly in water, and had a water absorption capacity of 320 times with respect to distilled water. The results are shown in Table 1.

Comparative Example 1 Using the same apparatus as in Example 1, water was used as the reaction solvent. The same operation as in Example 1 was performed. Methyl vinyl ether-maleic anhydride copolymer, 1 g of hexamethylenediamine and 50 g of water were added to an aqueous solution in which sodium hydroxide was dissolved.
The reaction was carried out by adding 15.3 g of a cross-linking agent solution consisting of g.
At the beginning of the reaction, it was in the form of a slurry solution, but the reaction was about 1
After a lapse of time, the copolymer dissolved and became a transparent viscous solution. Evaporation of this viscous solution yielded 365 g of agglomerates. Then, heat treatment was performed for 8 hours in a 120 ° C. hot air dryer. This lump was crushed to obtain a resin powder of 400 mesh pass. When this resin powder was analyzed, it was a square resin powder having a particle size of 20 to 50 μm and an average particle size of 40 μm. The water absorption capacity of this pulverized resin was 320 times. The results are shown in Table 1.

Comparative Example 2 Using the same apparatus as in Example 1, methanol was used as a reaction solvent. The same operation as in Example 1 was performed. To the aqueous solution in which sodium hydroxide was dissolved, 15.3 g of a cross-linking agent solution composed of a methyl vinyl ether-maleic anhydride copolymer, 1 g of hexamethylenediamine and 50 g of methanol was added and reacted. At the beginning of the reaction, it was in the form of a slurry solution, but after about 1 hour of the reaction, the copolymer dissolved and became a transparent viscous solution. When the infrared absorption spectrum of this viscous solution was measured, it was confirmed that the absorption of the maleic anhydride group had disappeared and the product was converted into an ester, so the subsequent operation was stopped. The results are shown in Table 1.

[0027]

As described above, in the presence of an alcohol having 3 or more carbon atoms as a reaction solvent, a copolymer of an α-olefin or a vinyl compound and maleic anhydride is reacted with an alkali metal compound and a crosslinking agent. As a result, a fine spherical water absorbent resin having an average particle diameter of 1 to 50 μm can be directly obtained. Further, the polymerization suspension can be filtered and further the pulverization step is omitted, so that the productivity and the economic efficiency are improved, and the polymer suspension can be manufactured on an industrial scale.

Claims (2)

[Claims] 1. A water-absorbent resin having an average particle size of 1 to 50 μm, which is obtained directly by reacting a copolymer of an α-olefin or a vinyl compound with maleic anhydride, an alkali metal compound and a crosslinking agent. 2. Water absorption characterized by reacting a copolymer of an α-olefin or vinyl compound and maleic anhydride with an alkali metal compound and a crosslinking agent in the presence of an alcohol having 3 or more carbon atoms as a reaction solvent. Of producing a flexible resin.