JPH0258507A - Production of highly water absorbing resin - Google Patents

Abstract

PURPOSE:To obtain the subject resin having high water absorptivity and excellent water holding properties by reaction at relatively low temperatures by reacting a maleic anhydride-based copolymer with a polyhydric alcohol in the presence of an alkaline substance. CONSTITUTION:A maleic anhydride-based copolymer is reacted with a polyhydric alcohol (preferably ethylene glycol, propylene glycol, polyethylene glycol, polyethylene glycol, PVA, etc.) in the presence of an alkaline substance (e.g., ammonia, sodium hydroxide, calcium hydroxide, methylamine or trimethylamine) and preferably further a solvent to afford the objective resin.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing a superabsorbent resin. More specifically, the present invention relates to a method for producing a super absorbent resin having high water absorption and water retention capacity from a maleic anhydride copolymer and a polyhydric alcohol under relatively mild conditions.

[Conventional technology]

In recent years, the development of water-absorbent resins has been remarkable, and their functional properties have been utilized to create disposable diapers, sanitary products, water-retaining agents, water-stopping agents, etc.
A variety of uses have been developed, including as a dew prevention agent and as a soil improvement material for agriculture, forestry, and horticulture.

These water-absorbing resins include starch-Ac IJ lonitrile graft polymer hydrolyzate, carboxymethylcellulose crosslinked product, polyacrylate crosslinked product, polyethylene oxide partially crosslinked product, vinyl alcohol-acrylate copolymer. etc. are known.

Among them, acrylic acid-based water-absorbing resins have high water-absorbing power (Japanese Patent Laid-Open No. 1084071/1983). However, the acrylic acid-based water-absorbing resin has the disadvantage that a high temperature of around 150° C. is required for the crosslinking reaction in order to increase the water-absorbing power. Furthermore, maleic anhydride-based water-absorbing resins are also known (Japanese Patent Application Laid-open No. 36504/1983). However, in order to make this resin water-absorbing, it is necessary to treat it with alkali to open the ring and then crosslink it at a high temperature.

[Problems that the invention attempts to solve]

Therefore, an object of the present invention is to provide a water-absorbing resin that can be cross-linked at a relatively low temperature and has high water-absorbing properties.

[Means to solve the problem]

The present invention relates to a method for producing a superabsorbent resin, which comprises reacting a maleic anhydride copolymer and a polyhydric alcohol in the presence of an alkaline substance.

Furthermore, the present invention relates to a method for producing a superabsorbent resin, which includes partially reacting a maleic anhydride copolymer and a polyhydric alcohol, and then further reacting both in the presence of an alkaline substance.

The present invention will be explained below.

In the present invention, the term "maleic anhydride copolymer" refers to a copolymer consisting of maleic anhydride and at least one monomer selected from the group consisting of olefins and vinyl compounds. Here, olefin means a linear or branched unsaturated hydrocarbon having 2 to 12 carbon atoms, preferably 2 to 8 carbon atoms, and examples thereof include ethylene, propylene, -2, isobutylene, pentene-1, isoprene, 2-methyl-butene-1, hexene-1,2-methyl-pentene-1,3-methyl-pentene-1,4-methyl-pentene-1,2-ethyl-
Butene-2, diisobutylene, 1,3-butadiene, 1
．． 3-pentadiene, 1,3-hexadiene, 1,3-
Octadiene, 2-methyl4,4-dimethylpentene-
Examples include 1,2 methyl 4,4-dimethyl-pentene-2. Here, return BB containing isobutylene can also be used as is. Also,
Vinyl compounds refer to unsaturated compounds that can be copolymerized with maleic anhydride, such as those obtained by saponifying styrene, vinyl chloride, vinyl propionate, vinyl acetate, acrylonitrile, methyl vinyl ether, acrylic esters, or vinyl acetate. Vinyl alcohol, etc.

These monomers may be used alone for copolymerization with maleic anhydride, or two or more types may be used in combination for copolymerization with maleic anhydride.

The composition ratio of the olefin or vinyl compound to maleic anhydride in the copolymer is preferably 1 to 1 maleic anhydride.
The amount is about 0.8 to 5.0 moles. but,
There are no particular limitations as long as the copolymer is soluble in the below-mentioned solvent and an acid anhydride group is present in the copolymer. In addition, the molecular weight of the copolymer is 1,000 to i,o in terms of polystyrene.
oo, ooo1 preferably 1.000 to 500.00
It is appropriate that it be 0. Here, polystyrene conversion refers to a method of converting a measured value based on a value calibrated using commercially available standard polystyrene. If the molecular weight of the copolymer is small, the water absorption performance tends to decrease, while if the molecular weight is extremely large, the viscosity of the reaction solvent may become high, making it difficult to manufacture the superabsorbent resin.

As a polymerization method for obtaining a maleic anhydride copolymer, for example, J, ^, C, S,, 67. 2044 (194
The method described in 5) can be used.

For example, 1 part by weight of styrene purified in advance, 1 part by weight of maleic anhydride, Benzene 215, and benzoyl peroxide are polymerized under reflux and stirring under a nitrogen atmosphere. A white gel-like substance is obtained, which is cooled and separated. The obtained white substance is washed three times under refluxing benzene and then dried under vacuum to obtain the desired white powder of maleic anhydride-styrene copolymer.

The "polyhydric alcohol" used in the production method of the present invention is selected from the group consisting of monomeric polyhydric alcohols such as ethylene glycol and propylene glycol, and polymeric polyhydric alcohols such as polyethylene glycol, polypropylene glycol, and polyvinyl alcohol. and at least one polyhydric alcohol.

The polyhydric alcohol is suitably used in an amount of 0.001 to 5.0 mol, preferably 0.01 to 5.0 mol, per equivalent of acid anhydride in the maleic anhydride copolymer. be. Here, the molecular weight of the high-molecular polyhydric alcohol is preferably 50 to 100,000, preferably 300 to 10,000, considering solubility in a solvent.

In the present invention, the maleic anhydride copolymer and the polyhydric alcohol are reacted in the presence of an alkaline substance. The alkaline substance refers to a substance that can react with the acid anhydride in the maleic anhydride copolymer to generate a carboxyl group (-Cooθ). Examples of alkaline substances include ammonia, alkali metal hydroxides such as hydroxide, alkaline earth metal hydroxides such as potassium hydroxide, calcium hydroxide, magnesium hydroxide, amines such as methylamine, ethylamine, diethylamine,
Triethylamine and the like (primary and secondary amines are particularly preferred). It is preferable that ammonia be present in the reaction system as a gas or an aqueous solution, and the alkali metal hydroxide etc. be present as an aqueous solution.

In the production method of the present invention, it is appropriate to carry out the reaction between the maleic anhydride copolymer and the polyhydric alcohol in the presence of a solvent. As the solvent, polar solvents are particularly preferred, such as tetrahydrofuran, acetone, dimethylformamide, 4-dioxane, methyl ethyl ketone,
Examples include diethyl ether. The amount of solvent used is 5 parts by weight of the maleic anhydride copolymer.
A suitable amount is 500 parts by weight.

The method for producing a super absorbent resin of the present invention will be explained in more detail. The maleic anhydride copolymer and polyhydric alcohol are dissolved in a solvent and mixed and stirred.

At this time, if necessary, it may be heated to about the boiling point of the solvent (reflux conditions). After sufficient stirring at 10 to 80° C. (for example, for 1 to 10 hours), an alkaline substance is added to the reaction system to form a gel. Gel formation is completed within 1 hour at 0-80°C. Alternatively, immediately after mixing a solution of a maleic anhydride copolymer dissolved in a solvent and a solution of a polyhydric alcohol dissolved in a solvent, add 0 to 8% of an alkaline substance into the system.
A gel can also be produced by adding at 0° C. over 1 minute to 10 hours. When ammonia gas is used, a gel is generated simply by bubbling the ammonia gas into the mixed solution. At this time, the flow rate of ammonia was 100%. 50 to 500.7/min is preferable. or,
When using an aqueous solution, the concentration of the alkaline substance is 0.
05 to 2.0 mol/liter is preferred.

The obtained gel is washed with a solvent as necessary.

As the cleaning method, Soxhlet method, dialysis membrane method, decantation, etc. are used. The gel is finally dried using a vacuum dryer or the like to become a white to pale yellow super absorbent resin.

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited by these in any way.

In Examples or Reference Examples, the names of substances, etc. are defined as follows.

sty-lock: styrene-maleic anhydride copolymer PEG: polyethylene glycol THF: tetrahydrofuran MEK: methyl ethyl ketone Water absorption capacity was measured by the following method.

(Water absorption amount) 150 g of pure water was prepared in a 300 d beaker, 0.1 g of water absorbent resin was added, and after being left for 2 hours, it was filtered through a 200 mesh wire mesh, and the weight of the water that flowed into the receiving tray for 2 hours was measured. . The amount of water absorbed was calculated according to the following formula.

(Water retention capacity) 200 g of pure water was absorbed per 1 g of water-absorbing resin, left for 2 hours, then transferred to the cell shown in Figure 1, and centrifuged at 11,000 rpm, 200 Orpm, and 3,000 rpm in sequence.
Then, centrifugal force was applied to each sample for 20 minutes, and the amount of water absorbed at that time was measured.

Reference example 1 26 g of pre-purified styrene, 2 i-water maleic acid
5 g and 240 d of benzene were introduced into a Mitsuro flask and stirred on an oil bath at 60° C. under a nitrogen atmosphere for 30 minutes. A solution of 0.06 g of benzoyl peroxide dissolved in benzene lO- was added dropwise using a dropping funnel over about 10 minutes. After about 10 minutes, cloudiness occurred, and after 1 hour, a white gel-like substance was obtained.

After cooling, filtration, washing, and purification were performed to obtain 20 g of white powder of Sty-MAn. The average molecular weight measured by GPC was 260.000 in terms of polystyrene.

Reference Example 2 10 g of 7-leic acid anhydride and 0.2 g of benzoyl peroxide were dissolved in 200 g of benzene and stirred on an oil bath at 80° C. under a nitrogen atmosphere for 30 minutes. Isobutylene (99% purity)
or more) for 100. Bubbling was carried out at a flow rate of // minutes. Approximately 1
White turbidity occurred in 0 minutes, and a white gel-like substance was obtained in 1 hour. After cooling, filtration, washing, and purification are performed to obtain iC4-MAn.
12 g of white powder was obtained. The average molecular weight measured by GPC was 100.000 in terms of polystyrene.

Example 1 Sty-MANlg and PEG (molecules li 100
0) Dissolve 0.5g in THFloo-, stir, and then flow ammonia gas to 1300. Bubble at Z/min, approx. 1
A white gel-like substance was obtained in 0 minutes. The gel was transferred to a nylon mesh (#200) bag, and after washing unreacted polyethylene glycol with THF, it was dried in a vacuum smoker to obtain 1.2 g of a water absorbent resin (SAP-4). .

For Sty-MANlg, PEG (molecular weight 1000
) respectively I O, Og, 5.0 g, 2.5 g, 0
, 25 g, 0. I Og Tori, T) (Floo, Z
After dissolving in S
AP-1 to 5AP-3, 5AP-5, 5AP-6).

Table 1 shows the water absorption amount of each.

Table 1 Table 2 Example 2 Sty-MAnlg and molecular weight are each 106.1
000, 3000.7500 PEG respectively
．． 053g, 0.5g, 1.5g.

A water absorbent resin was obtained in the same manner as in Example 1 using 3.75 g (SAP-7 to SAP-to).

Table 2 shows the water absorption amount of each.

Example 3 Sty-MANlg and PEG (molecule ffi +0
00) 0.5g was dissolved in THF 100, Z, and ammonia gas was bubbled therein immediately and 4 hours later to obtain a water absorbent resin in the same manner as in Example 1 (S
AP-11, 12). Table 3 shows the water absorption amount.

Table 3 Example 4 Sty-MAn Ig, PEG (molecule ff1l 00
0) 0.5g each in THF25. ,/,50m,1
00- and the same method as in Example 1 to prepare a water-absorbing resin (
SAP-13 to 5AP-15) were obtained. Table 4 shows the water absorption amount of each.

Table 5 Example 5 S with different molecular weights synthesized by the same method as Reference Example 1
1 each of ty-MAnb and commercially available Sty-MAn.
After dissolving in THFloo, etc., along with 5.0 g of PEG (molecular weight 1000), water absorbent resins (SAP-16 to 5AP-18) were obtained according to Example 1.The water absorption amounts of each are shown in Table 5. show.

Molecular weight was measured by GPC (polystyrene equivalent value) Example 6 0.5 g of S ty-MAn 1 g'J3 and PEG (molecular weight 1000) were added to THF, acetone,
Water absorbent resins were obtained by dissolving in MEK50 and Z in the same manner as in Example 1 (SAP-19 to 5AP-21). Table 6 shows the respective water absorption amounts.

Table 6 Example 7 +C4MAnlg and PEG (molecular weight 1000) 0
．． 5 g and 0.25 g were dissolved in THFloo-, and a water absorbent resin was obtained in the same manner as in Example 1 (SA
P-22 to 5AP-23). Table 7 shows the water absorption amount of each.

Example 8 Sty MAnlg and PEG (11000 molecules
) 2.5g in THF 100. =/Dissolved in, after stirring, 0
．． 3 mol/l hydroxide) IJium 16.3.7 to 1
The solution was added dropwise for 0 minutes to precipitate a white gel. After washing and drying the gel, 1.2 g of water absorbent resin was obtained (SAP
-24).

Sty-MAnlg and PEG (molecule 11000)
After dissolving 0.5g in THF 100-Z and stirring, 0.5g was dissolved in THF 100-Z.
3 mol/I) K sodium oxide 16.3.7 to 1
The solution was added dropwise for 0 minutes to precipitate a white gel. After washing and drying the gel, 1.2 g of water absorbent resin was obtained (SAP
-25).

Sty-MAn 1 gJ6 and PEG (molecular weight 1000) 0.1g are dissolved in THF 100gI, stirred, and then 0.3mol/l hydroxylated) IJumI 6.3
．． 7 was added dropwise over 10 minutes to precipitate a white gel. After washing and drying the gel, 1.2 g of water absorbent resin was obtained.
, :, (SAP-26>.

Table 8 shows the water absorption amount of each.

Example 9 Sty-MANl, g and PEG (molecule ffi 2
000) 2.5g was dissolved in THF 100-, after stirring,
0.3 mol/1 ammonium hydroxide 16.3-10
Add dropwise over a period of minutes to precipitate a white gel, and ladle. After washing and drying the gel, 1.3 g of water absorbent resin was obtained (SAP27
). The water absorption amount is shown in Table 8.

Example 10 5AP-4 synthesized in Example 1 in physiological saline (0
, 85%-NaCl aqueous solution) was measured. Water retention capacity was also measured. The results are shown in Table 9 in comparison with market products.

〔Effect of the invention〕

According to the production method of the present invention, a superabsorbent resin having high water absorption and excellent water retention can be obtained by reaction at a relatively low temperature.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a cell for measuring water retention capacity.

Claims (2)

[Claims] (1) A method for producing a super absorbent resin, which comprises reacting a maleic anhydride copolymer and a polyhydric alcohol in the presence of an alkaline substance. (2) A method for producing a superabsorbent resin, which includes partially reacting a maleic anhydride copolymer and a polyhydric alcohol, and then further reacting both in the presence of an alkaline substance.