JPH06306118A - Production of highly water-absorptive polymer - Google Patents

Abstract

PURPOSE:To obtain a highly water-absorptive polymer free from a decrease in water absorbency and excellent in dispersibility in water, rate of water absorption, and long-term stability in a state of gel containing absorbed water, by treating a water-soluble and/or water-absorptive polymer with an alkoxytitanium in the presence of water. CONSTITUTION:A water-soluble and/or water-absorptive polymer is treated with an alkoxytitanium in the presence of water. The amount of the alkoxytitanium used is usually about 0.001-10wt.% based on the polymer. The amount of water present is usually about 0.5-300wt.% based on the polymer. The treatment of the polymer is performed by, for example, the wet treatment wherein a slurry made by dispersing the water-absorptive polymer containing water in an inert solvent is mixed with an alkoxytitanium, or the dry treatment wherein an alkoxytitanium is sprayed onto the water-absorptive polymer containing water with agitation.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a super absorbent polymer. The superabsorbent polymer obtained by the production method of the present invention does not have a decrease in water absorption capacity due to treatment, and has improved water dispersibility, water absorption rate, and temporal stability in a water-absorbed gel state. Therefore, it can be suitably used for various water absorbing materials such as sanitary materials, industrial materials, agriculture and horticulture.

[0002]

2. Description of the Related Art Conventionally, as a super absorbent polymer, a hydrolyzate of a starch-acrylonitrile graft copolymer, a carboxymethylcellulose derivative, a polyacrylic acid (salt) crosslinked product, an acrylic acid (salt) -vinyl Alcohol copolymers, polyethylene oxide cross-linked products, etc. are known, but all of the polymers have substantially good water absorption ability,
It is not sufficient in terms of dispersibility in water, water absorption speed, and the like.

On the other hand, as a method for improving the dispersibility in water and the water absorption rate, a method of coating the surface with a lipophilic surfactant or the like, a polyglycidyl compound (Japanese Patent Publication No. 61-48).
521, JP-B-60-18690), silane coupling agents (JP-A-61-211305,
JP-A-61-252212), a method of surface-crosslinking with a polyhydric alcohol (Japanese Patent Publication No. 1-17411), a method of dispersing inorganic powder such as silicon dioxide on a polymer surface as a lubricant, and the like are known. There is. However, none of the methods had durability in a water-absorbed gel state.

On the other hand, as a method for improving the durability in the gel state of absorbing water, a method of incorporating carbon black or activated carbon into a super absorbent polymer (Japanese Patent Laid-Open No. 59-382).
No. 71), a method of adding an oxygen-containing reducing inorganic salt (JP-A-63-118375), a method of adding an antioxidant (JP-A-63-127754), and a metal chelating agent. Method (JP-A-63-1469)
No. 64), a method of adding a radical chain inhibitor (JP-A-63-152667), a method of adding an oxidizing agent (JP-A-63-153060), and a method of adding a sulfur-containing reducing agent ( JP-A-63-272349
Japanese Laid-Open Patent Publication No. 6), and a method of incorporating a polyvalent metal oxide (Japanese Patent Laid-Open No. 6-242242)
4-29257), a method of incorporating a specific amine compound (JP-A-1-275661), and the like. However, all of these methods are methods of adding an additive to a superabsorbent polymer, and from the viewpoint of the safety of the additive, a method that is always preferable when considering the handling of the additive, the use of the polymer as a sanitary material, etc. Was not.

[0005]

DISCLOSURE OF THE INVENTION The present invention has improved the above-mentioned problems and has no deterioration in water absorption capacity due to treatment, dispersibility in water, water absorption speed, and stability over time in a gel state absorbed by water. It is an object of the present invention to provide a method for producing an excellent superabsorbent polymer.

[0006]

Means for Solving the Problems As a result of intensive studies made by the present inventors for the purpose of improving the above-mentioned problems, as a result of treating a hydrophilic polymer with a titanium coupling agent, the water-absorbing ability does not decrease. It was discovered that the dispersibility in water, the water absorption rate, and the stability with time in a water-absorbed gel state were improved, and the present invention was achieved. That is, the present invention is
"A method for producing a superabsorbent polymer, which comprises treating a water-soluble and / or water-absorbent polymer with alkoxytitanium in the presence of water."

[0007]

[Action]

<Water-soluble and / or water-absorbent polymer> The water-soluble and / or water-absorbent polymer used in the present invention is not particularly limited as long as it can absorb water.

Examples of such polymers include starch-acrylonitrile copolymer hydrolyzate, starch-
(Meth) acrylic acid (salt) copolymer, hydrolyzate of starch- (meth) acrylic acid ester copolymer, carboxymethylcellulose derivative, poly (meth) acrylic acid (salt), polyvinyl alcohol, (meth) Examples thereof include a hydrolyzate of an acrylic acid ester-vinyl acetate copolymer, polyethylene oxide, and the like, and one kind or two or more kinds of them can be used.

<Alkoxy Titanium> The alkoxy titanium used in the present invention may be any organic titanium compound having a reactive alkoxy group in the molecule. Examples of such alkoxy titanium, tetramethoxy titanium, tetraethoxy titanium, tetraisopropoxy titanium, tetrabutoxy titanium, tetrakis (2-ethylhexyloxy) titanium, tetrastearyloxy titanium, tetraisopropoxy titanium polymer, tetrabutoxy titanium polymer, Examples include diisopropoxybis (acetylacetonato) titanium, dibutoxybis (triethanolaminato) titanium, tributoxytitanium stearate, dihydroxybis (lactato) titanium, diisopropoxytitanium distearate, and one of them or Two or more kinds can be used.

The amount of alkoxytitanium used in the present invention varies depending on the type of polymer used and cannot be specified unconditionally, but is usually 0.0
01 to 10% by weight. If the amount used is too small, the improvement effect will not be obtained, and if it is too large, it will be economically disadvantageous and the water absorption capacity may sometimes decrease.

<Water> It is essential that the treatment of the polymer of the present invention with alkoxytitanium is carried out in the presence of water. As a form of existence of this water, the polymer may contain a predetermined amount of water in advance, or water may be additionally added. The amount of water present in the present invention varies depending on the type of polymer and the type of alkoxytitanium used and cannot be specified unconditionally, but is usually 0.5 to 300% by weight relative to the polymer. If the amount of water present is too small, the reaction with the alkoxytitanium will not proceed effectively. On the other hand, if the amount is too large, the effect of improving the water absorption rate is reduced and a large amount of alkoxytitanium is required, which is economically disadvantageous.

<Treatment Method> The treatment of the polymer of the present invention with alkoxytitanium can be carried out in various modes. As an example of the processing mode, for example,
Examples thereof include a wet method in which alkoxy titanium is added in a slurry state in which a water-containing polymer is dispersed in a solvent, and a dry method in which alkoxy titanium is sprayed with dry air or nitrogen gas while forcibly stirring the water-containing polymer. Here, the solvent may be an inert solvent, for example, alcohols,
Examples thereof include ethers and hydrocarbons. The treatment temperature with the alkoxytitanium in the present invention varies depending on a series of conditions and cannot be specified unconditionally, but is usually 10 to 1
80 ° C. The polymer treated with alkoxytitanium becomes the target superabsorbent polymer as it is or after removing water.

[0013]

EXAMPLES In order to explain the present invention more specifically, production examples,
It shows an example, a test method and a test result.

Production Example 1 Cyclohexane (318 g) was placed in a 5-liter separable round-bottomed flask having a capacity of 1 liter equipped with a stirrer, a reflux condenser, a thermometer, a nitrogen gas introducing tube and a dropping funnel, and sorbitan monostearate was used as a dispersant. (HLB 4.7)
2.39 g was added and dissolved, and nitrogen gas was blown in to expel dissolved oxygen. Separately, take 116.5 g of acrylic acid and 55.8 g of ion-exchanged water in a conical beaker, and gradually add 181.2 g of 25% sodium hydroxide aqueous solution while cooling with ice from the outside to make 70% of carboxyl groups.
Neutralized. To this, 0.082 g of N, N'-methylenebisacrylamide, sodium hypophosphite monohydrate 0.
111 g and 0.121 g of potassium persulfate were dissolved, and nitrogen gas was blown thereinto to expel dissolved oxygen. Next, this aqueous monomer solution was added to the separable flask to disperse the solution, the bath temperature was raised to 73 ° C. to start the polymerization reaction, and the temperature was kept at the same temperature for 2 hours to complete the polymerization. Subsequently, the bath temperature was raised to 100 ° C. and azeotropic dehydration was performed for 4 hours. When the stirring was stopped, the wet polymer particles settled to the bottom of the round bottom flask, so they could be easily separated from the cyclohexane phase by decantation. 1 for the obtained wet polymer
It was dried under reduced pressure at 00 ° C to obtain a water-absorbent polymer A.

Example 1 9 g of water with stirring was added to a slurry solution consisting of 100 g of the water-absorbent polymer A obtained in Production Example 1 and 100 g of cyclohexane.
Was added, and 1 g of di-n-butoxybis (triethanolaminato) titanium was added at 50 ° C. and mixed for 30 minutes. Then, it was dried at a bath temperature of 105 ° C. under reduced pressure for 30 minutes to obtain a super absorbent polymer.

Example 2 To a slurry solution consisting of 100 g of water-absorbent polymer A and 100 g of cyclohexane was added 10 g of water with stirring, and 1
At 0 ° C, 2 g of di-i-propoxybis (acetylacetonato) titanium was added and mixed for 30 minutes. Then, it was dried at a bath temperature of 105 ° C. under reduced pressure for 30 minutes to obtain a super absorbent polymer.

Example 3 To a slurry solution consisting of 100 g of the water-absorbent polymer A and 100 g of cyclohexane, 6 g of water was added with stirring and 10
Add 0.5 g of tetraisopropoxy titanium at ℃ 3
Mix for 0 minutes. Then, under reduced pressure at a bath temperature of 105 ° C, 30
After being dried for a minute, a super absorbent polymer was obtained.

Example 4 To a slurry solution consisting of 100 g of water-absorbent polymer A and 100 g of cyclohexane was added 25 g of water with stirring, and 5
At 0 ° C., 1 g of a polymer of tetra-n-butoxytitanium (B-4, manufactured by Nippon Soda Co., Ltd.) was added and mixed for 30 minutes. Then, it was dried at a bath temperature of 105 ° C. under reduced pressure for 30 minutes to obtain a super absorbent polymer.

Example 5 20 g of water with stirring was added to a slurry solution consisting of 100 g of the water-absorbent polymer A and 100 g of cyclohexane, and 5
Add 3 g of tetrastearyloxytitanium at 0 ° C and add 3
Mix for 0 minutes. Then, under reduced pressure at a bath temperature of 105 ° C, 30
After being dried for a minute, a super absorbent polymer was obtained.

Production Example 2 While cooling 39.1 g of acrylic acid in a conical flask from the outside, a 22.6 wt% sodium hydroxide aqueous solution 7 was added.
6.5 g was added dropwise to neutralize 80%. Then, 0.13 g of potassium persulfate was added as a polymerization initiator and dissolved at room temperature. Cyclohexane of 213 g in a five-neck separable round bottom flask with a capacity of 500 ml equipped with a stirrer, a reflux condenser, a thermometer, a nitrogen gas introducing pipe and a dropping funnel.
Then, 1.9 g of sorbitan monolaurate was added and dissolved, and then nitrogen gas was blown thereinto to expel dissolved oxygen. After the contents of the conical flask were added dropwise to the five-necked flask and suspended, and the system was sufficiently replaced with nitrogen again,
The temperature was raised and the bath temperature was maintained at 55 to 60 ° C. to carry out a polymerization reaction for 3 hours. The water-absorbent polymer B was obtained by evaporating the obtained polymerization liquid to dryness under reduced pressure.

Example 6 9 g of water with stirring was added to a slurry solution consisting of 100 g of the water-absorbent polymer B obtained in Production Example 2 and 100 g of cyclohexane.
Was added, and 1 g of di-n-butoxybis (triethanolaminato) was added at 50 ° C. and mixed for 30 minutes. Then, it was dried at a bath temperature of 105 ° C. under reduced pressure for 30 minutes to obtain a super absorbent polymer.

Production Example 3 74.95 mol% of acrylic acid, 25 mol% of acrylic acid,
And trimethylolpropane triacrylate 0.0
100 parts by weight of an aqueous solution of 43% by weight of an acrylic acid salt monomer consisting of 5 mol% was added with 0.015% of ammonium persulfate.
The polymer was allowed to stand still at 55 to 80 ° C. in a nitrogen atmosphere using parts by weight and 0.005 parts by weight of sodium hydrogen sulfite to obtain a gel-like hydropolymer. This polymer was dried with a hot air drier at 180 ° C., then pulverized with a hammer type pulverizer, and sieved with a 28 mesh wire net to obtain a 28 mesh passed product (polymer C).

Example 7 To a slurry solution consisting of 100 g of polymer C and 100 g of n-butanol, 10 g of water was added with stirring, and 1 g of di-n-butoxybis (triethanolaminato) titanium was added at 70 ° C. and mixed for 30 minutes. did. Then, bath temperature 12
It was dried at 0 ° C. under reduced pressure for 60 minutes to obtain a super absorbent polymer.

(Test method) <Water absorption capacity> About 1 g of a super absorbent polymer is precisely weighed, put in a 250 mesh nylon bag (10 cm x 10 cm), and immersed in 500 cc of artificial urine for 30 minutes. Then, the nylon bag was pulled up and drained for 15 minutes, then weighed and subjected to blank correction, and the weight of the artificial urine absorbed by 1 g of the superabsorbent polymer was defined as the water absorption capacity. The composition of artificial urine is as shown below. Urea 1.94% by weight Sodium chloride 0.80% by weight Calcium chloride 0.06% by weight Magnesium sulfate 0.11% by weight Pure water 97.09% by weight

<Water Absorption Rate> The water absorption rate was measured using the apparatus shown in FIG. The super absorbent polymer 1g1 is placed on the non-woven fabric 3 provided on the support plate 2 having small holes. Artificial urine from below 4
Was contacted, and the weight of the artificial urine absorbed by the polymer in 10 minutes was defined as the water absorption rate. Reference numeral 5 in FIG. 1 is a burette containing artificial urine, and 9 is an air inlet. The space in the burette enclosed by the stopper 6 is prevented from being decompressed. Reference numerals 8 and 7 are valves for adjusting the amount of air and the amount of urine, respectively.

<Dispersibility in Water> Water was placed in a beaker, and a state of dispersion when a small amount of superabsorbent polymer was dropped was observed, and the presence or absence of mamako formation was visually judged. ○: Mamako does not occur ×: Mamako is possible

<Gel strength> 40 g of artificial urine previously held at 40 ° C. was absorbed into 1.6 g of a superabsorbent polymer, and the mixture was kept at the same temperature for a certain period of time and then a rheometer (Fudo Kogyo NRM-2
(002J type), the force at the time when the cell entered the gel was measured as the gel strength.

<Gel state> After measuring the gel strength after 24 hours, the state of the swollen gel was measured by touch, and the following three-stage evaluation was performed. ◯: The swollen gel is crispy and has a dry feeling. Δ: Swelling gel is partly sticky. X: The swollen gel is sticky and the hands are greasy. Table 1 shows the evaluation results of the water absorption performance of the superabsorbent polymers obtained in the above Examples and Experimental Examples.

[0029]

[Table 1]

[0030]

EFFECTS OF THE INVENTION According to the present invention, it is possible to produce a highly water-absorbent polymer which is free from deterioration in water absorption capacity due to treatment and is excellent in dispersibility in water, water absorption speed, and stability over time in a water-absorbed gel state. I can.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an outline of an apparatus used for measuring a water absorption rate of a superabsorbent polymer.

[Explanation of symbols] 1 Super absorbent polymer 2 Support plate with small holes 3 Nonwoven fabric 4 Artificial urine 5 Viewlet 6 Rubber stopper 7 Valve 8 Valve 9 Air inlet

Claims (5)

[Claims] 1. A method for producing a superabsorbent polymer, which comprises treating a water-soluble and / or water-absorbent polymer with alkoxytitanium in the presence of water. 2. Water in an amount of 0.5 to 30 relative to the water-absorbing polymer.
The method for producing a superabsorbent polymer according to claim 1, wherein 0% by weight is present. 3. The alkoxy titanium is used in an amount of 0.001 to 10% by weight based on the water-absorbing polymer.
The method for producing a superabsorbent polymer described in 1. 4. The method according to claim 1, wherein the treatment with the alkoxytitanium is a wet treatment in which the alkoxytitanium is added to and mixed with a slurry in which a water-containing water-absorbing polymer is dispersed in an inert solvent. For producing super absorbent polymer. 5. The method for producing a superabsorbent polymer according to claim 1, wherein the treatment with the alkoxytitanium is a dry treatment in which the alkoxysilane is sprayed while stirring the hydrous water-absorbent polymer. .