JPH0696619B2 - Super absorbent polymer composition, method for producing the same, and super absorbent article comprising the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a polymer composition made of cross-linked polyacrylic acid and capable of forming an aqueous gel, and a method for producing the same.

In particular, the present invention relates to a super absorbent polymer composition having excellent absorbency of water or other aqueous liquids and a method for producing the same.

Prior Art Water-insoluble hydrogel-forming polymers that have the ability to absorb large amounts of water and aqueous liquids are well known structures. Such polymers are known as superabsorbent polymer compositions and are polymers with partially cross-linked acid functional groups that swell in water or aqueous liquids but are insoluble in these fluids. Superabsorbent polymers have been found to be particularly useful in diapers, feminine hygiene products and surgical dressings.

A description of superabsorbent polymer compositions and their uses is found in US Pat. Nos. 3,669,103 and 3,670,731.

US Pat. No. 4,654,039 shows an aqueous gel-forming polymer structure, which is described as a substantially water-insoluble, slightly cross-linked, partially neutralized polymer, which contains acid group-containing polymerizations. It is produced from a polyunsaturated monomer and a crosslinking agent. Such a polymer is produced by polymerizing an acid monomer and a crosslinking monomer in water using a redox reaction catalyst, and then the acid group is partially neutralized with sodium hydroxide and the polymer is dried. It can be obtained by powdering.

British Patent 2119384 discloses the polymerization of acrylic acid in water with sodium acrylate and a crosslinking monomer using a persulfate catalyst, then drying the resulting polymer and reacting with the carboxyl groups in the polymer. Get at least 2
Disclosed are superabsorbent polymer compositions obtained by heating with a cross-linking agent having three functional groups.

U.S. Pat. No. 4,497,930 discloses that superabsorbent polymer compositions are obtained by polymerizing acrylic acid in a reverse emulsion and then crosslinking with a diepoxide compound.

In U.S. Pat. No. 4,295,987, superabsorbent polymers are prepared by polymerizing acrylic acid and a polyfunctional acrylate monomer in water with a persulfate catalyst, followed by neutralization of the acid groups with caustic, and additionally. Made by mixing in a divalent cation salt such as zinc acetate to crosslink.

Others, for example, U.S. Patents 4076663, 4552938, 450743
Many other patents, such as 8 and 4535098, also disclose superabsorbent polymers and their uses.

Many improvements have been made over the years in the performance and properties of superabsorbent polymers, such as gel strength and resorbability. However, such superabsorbent polymers do not have balanced properties. Polymers that typically have high gel strength have poor resorption capacity, resulting in reduced dryness, for example, on the diaper surface. A polymer having a large resorbability has a low absorbency under pressure, has a low elastic modulus, and also reduces the dryness of the diaper surface.

The superabsorbent polymer composition should have balanced performance such that, for example, if the polymer is used in a diaper, the result is improved diaper surface dryness.

[Problems to be Solved by the Invention] The present invention has improved the above-mentioned drawbacks of the prior art and is excellent in a superabsorbent polymer composition having a good balance of absorbability under pressure, reabsorbability, elastic modulus, dryness and the like. The present invention also provides a method for producing the same, and an applied article including the method.

It is an object of the present invention to provide superabsorbent polymer compositions, ie hydrogel-forming polymer compositions.
Further, it is an object of the present invention to provide improved superabsorbent polymer compositions. Still another object of the present invention is to provide a method for producing a super absorbent polymer composition.

In another aspect, the invention relates to articles made with the superabsorbent polymer composition.

[Means for Solving the Problems] In order to solve the above problems, the present invention has the following configuration.

(1) (a) An aqueous solution comprising acrylic acid, a water-soluble polysaccharide and a polyfunctional monomer having at least two polymerizable ethylenically unsaturated double bonds per molecule, wherein the acrylic acid and the polysaccharide are The acrylic acid is used in an amount of about 90 to 100% by weight and the polysaccharide is used in an amount of about 0 to 10% by weight based on the total weight, and the polyfunctional monomer is used in a ratio of about 0.075 to 1% by mole based on the number of moles of acrylic acid. The acrylic acid and the polysaccharide are in an aqueous solution of about 5 to 30% by weight based on the weight of acrylic acid, the polysaccharide and water, and (b) consist of a redox catalyst and a thermal decomposition type free radical initiator, The reducing agent portion of the redox catalyst is about 6 × 10 ^{−5 to} 2.5 × 10 ⁻³ mol% with respect to the number of moles of acrylic acid, and the oxidizing agent portion is about 3.4 × with respect to the number of moles of acrylic acid. 1
0 ^{-3 to} 0.42 mol%, and a thermal decomposition type free radical initiator containing a thermal decomposition type free radical initiator in an amount of about 0.1 to 0.4% by weight based on the weight of acrylic acid. A catalyst composed of an agent is added to the aqueous solution at a temperature of about 5 to 20 ° C, and (c) the reaction is exothermic, and the reaction system is 90 ° C under adiabatic conditions.
The temperature of the reaction system is kept within 10 ° C of the maximum temperature for a sufficient period of time so that the temperature rises to a maximum temperature that does not exceed 100 ° C, thereby forming a polymer gel, and (d) the residual monomer content is reduced to 1000 ppm or less. (E) about 50 of the carboxylic acid groups in the polymer in an aqueous base solution
(F) a post-crosslinking agent composed of a polyfunctional compound having at least two groups capable of forming an ionic bond or a covalent bond with a carboxylic acid group is neutralized to about 100% of the acrylic acid. 0.05-15 mol%, (g) heat-dry the polymer at a temperature of about 20 ° C-200 ° C until the water content is about 10% by weight or less, (h) and add about 20-400% of the polymer. A method for producing a superabsorbent polymer, which comprises a step of pulverizing to a particle size of mesh.

(2) The method for producing a superabsorbent polymer composition according to the above item 1, wherein the polysaccharide is natural starch.

(3) The amount of the polyfunctional monomer is about 0.1 to 0.3 mol%, and the reducing agent portion of the redox catalyst is about 6 × 10 ^{−4 to} 2.5.
X 10 ^-3 mol% and the oxidant portion is about 0.15-0.25.
Mol%, and the thermal decomposition type free radical initiator is about
It is included in an amount of 0.25 to 0.35% by weight, and the postcrosslinker is about 0.
The method for producing the superabsorbent polymer composition according to the above 1, wherein the amount is from 05 to 0.15 mol%.

(4) The method for producing a superabsorbent polymer composition according to the above item 1, wherein the maximum temperature of the reaction system is about 60 ° C. to 75 ° C. and the reaction system is kept within the maximum temperature of 5 ° C.

(5) The method for producing a superabsorbent polymer composition according to the above item 1, wherein the polymer gel after addition of the post-crosslinking agent is post-crosslinked and heated at about 100 ° C. to 200 ° C. to dry the polymer. .

(6) The method for producing a superabsorbent polymer composition according to the above item 1, wherein the polyfunctional monomer is tetraallyloxyethane and the post-crosslinking agent is diglycidyl ether of ethylene glycol.

(7) The reducing agent is ascorbic acid, the oxidizing agent is hydrogen peroxide, and the thermal decomposition type free radical initiator is 2,2 '.
-The method for producing a superabsorbent polymer composition according to the above item 1, which is azobis (amidinopropane) dihydrate chloride.

(8) The polyfunctional monomer is contained in an amount of about 0.075 to 1 mol% based on the number of moles of acrylic acid, and the polysaccharide is contained in an amount of about 0 to 10 wt% based on the weight of acrylic acid and the polysaccharide. Is a graft copolymer composed of acrylic acid, a polyfunctional monomer and a polysaccharide, in which about 50 to 100% of the carboxylic acid groups are neutralized with a base, and the number of moles of acrylic acid is It is post-crosslinked with a post-crosslinking agent consisting of a polyfunctional compound in an amount of about 0.05 to 15 mol%, with a water content of 10% by weight or less, a particle size of about 20 to 400 mesh, and a minimum A superabsorbent polymer composition having an absorbency under pressure of 28 g / g, a resorption capacity of at least 35 g / g, and an elastic modulus of at least 8.0 × 10 ⁴ dyn / cm ² .

(9) The superabsorbent polymer composition according to the above item 8, wherein the polysaccharide is natural starch.

(10) The superabsorbent polymer composition according to the above item 8, wherein the polyfunctional monomer is contained in an amount of about 0.1 to 0.3 mol% and the post-crosslinking agent is contained in an amount of about 0.05 to 0.15 mol%.

(11) The superabsorbent polymer composition according to the above item 8, wherein the polyfunctional monomer is tetraallyloxyethane and the post-crosslinking agent is diglycidyl ether of ethylene glycol.

(12) A superabsorbent article containing the superabsorbent polymer composition according to the above item 8, which has a dryness of at least 40.

(13) The superabsorbent article according to the above item 12, which is a diaper.

The first monomer used to make the superabsorbent polymer composition in the present invention is acrylic acid. The crosslinking monomer copolymerized with acrylic acid is a multi-ethylenically unsaturated polymerizable monomer having at least two polymerizable functional groups per molecule, which is soluble in water or in aqueous acrylic acid.

Examples of such a polymerizable functional group include an acrylic group, a methacrylic group, an allyl group and a vinyl group.

As the above-mentioned crosslinking monomer, polyacrylic acid ester of polyol, polymethacrylic acid ester of polyol,
Included are polyallylamine, polyallyl ether, polyacrylamide compounds, polymethacrylamide compounds and divinyl compounds.

Specific examples of the crosslinking monomer include tetraallyloxyethane, N, N'-methylenebisacrylamide, N, N'-methylenebismethacrylamide, triallylamine, trimethylolpropane triacrylate, glycerol propoxytriacrylate, divinylbenzene and these. Similar to.

Optional ingredients optionally used to make the superabsorbent polymer compositions of the present invention are water-soluble polysaccharides, such as starch, water-soluble cellulose and polygalactomannan.

Suitable starches include natural starches such as sweet potato starch, potato starch, wheat starch, corn starch, rice starch, tapioca starch and the like.

As the modified or modified starch, dialdehyde starch, alkyl etherified starch, allyl etherified starch, oxyalkylated starch, aminoethyl-etherified starch, cyanoethyl-etherified starch and the like are also mentioned as preferable ones.

The water-soluble cellulose useful in the present invention includes those obtained from raw materials such as wood, stems, palm leather fibers, and fluff seeds, and also from the above cellulose raw materials for forming hydroxyalkyl cellulose, carboxymethyl cellulose, methyl cellulose and the like. Examples include those induced.

Suitable polygalactomannans include guar gum, locust bean gum as well as its hydroxyalkyl, carboxyalkyl and aminoalkyl derivatives.

Suitable polysaccharides used in the present invention are, for example, natural starches such as wheat starch, corn starch and pregelatinized starch.

During the production of the superabsorbent polymer composition of the present invention,
Acrylic acid and water-soluble polysaccharide are reacted in amounts of about 90-100% by weight acrylic acid and 0-about 10% by weight water-soluble polysaccharide. The weight% in that case is based on the weight of acrylic acid and a polysaccharide. The amount of polyethylenically unsaturated crosslinking monomer is about 0.075 to 1 mol% based on the number of moles of acrylic acid.
More preferably in the range of about 0.1 to 0.3 mol%.

The polymerization catalyst used in the present invention is both a redox catalyst and a thermal decomposition type. The redox catalyst is used to initiate the polymerization reaction and substantially achieve the polymerization reaction. Pyrolysis catalysts are used to reduce the residual free monomer content in the product to less than 1000 ppm by weight.

Regarding redox catalysts, commonly known water-soluble reducing agents and oxidizing agents can be used in the present invention. Examples of the reducing agent, ascorbic acid, alkali metal sulfite, alkali metal bisulfite, ammonium sulfite, ammonium bisulfite, alkali metal bisulfite, ammonium bisulfite, for example iron metal salts such as iron sulfate, These include sugars, aldehydes, primary or secondary alcohols and the like.

Oxidizing agents include compounds such as hydrogen peroxide, alkali metal persulfates, ammonium persulfates, alkyl hydroperoxides, peresters, diacrylic peroxides, silver salts, and the like.

A particularly preferred combination of redox catalysts is ascorbic acid and hydrogen peroxide.

In order to obtain a superabsorbent polymer composition having excellent properties in the present invention, the reducing agent is used in an amount of about 6 × 10 ⁻⁵ to 2.5 × 10 ⁻³ mol%, preferably 6% based on the molar amount of acrylic acid.
It is used in an amount of × 10 ^{-4 to} 2.5 × 10 ^-3 mol%. The amount of the oxidant is about 3.4 × 10 ⁻³ based on the molar amount of acrylic acid.
It is used in the range of 0.42 mol%, preferably about 0.15 to 0.25 mol%.

A thermal decomposition type catalyst is also used in this polymerization reaction to ensure complete polymerization of the acrylic acid monomer and the crosslinking monomer. A useful thermal decomposition type free radical initiator is an azo type reaction initiator, which is a compound having a so-called -N = N-atom structure. Any azo compound can be used that has some solubility in water or aqueous acrylic acid mixtures and also has a half-life of 10 hours at temperatures of 30 ° C. or higher.

Examples of useful azo initiators include 2,2'-azobis (amidinopropane) dihydrochloride, 4,
4'-azobis (cyanovaleric acid), 4,4'-butylazo-cyanovaleric acid, 2,2'-azobis (isobutyronitrile) and the like can be mentioned. Azo-based reaction initiator preferably used is 2,2'azobis (amidinopropane)
It is dihydrochloride. The pyrolytic free radical initiator is used in an amount of about 0.1-0.4% by weight, preferably 0.25-0.35% by weight, based on the weight of acrylic acid.

The polymerization to produce the polymer composition of the present invention is carried out in water at a concentration of acrylic acid and polysaccharide in a total of about 5 to 30% by weight. The weight% of the above concentrations is the concentration based on the total weight of water, acrylic acid and polysaccharides.

The process used to make the polymer composition of the present invention is an adiabatic reaction, first initiated at a temperature of about 5-20 ° C and ramped to a temperature not exceeding a maximum temperature of about 90 ° C. Generally the maximum temperature will be about 60-75 ° C.

The time required to reach the maximum temperature can vary depending on the concentration of monomer, the amount of catalyst, and the size of the reaction batch, the type of catalyst used and whether the reaction system is adiabatic.

Generally this time will be about 1-2 hours. After the maximum temperature is reached, the temperature is maintained within about 10 ° C of the maximum temperature, preferably for about 1-12 hours within about 5 ° C of the maximum temperature to achieve complete polymerization and the remaining monomer. Keep it below 1000ppm.

An amount of about 50 to 100 mol%, preferably about 65 to 75 mol%, of the carboxylic acid groups of the polymer composition of the present invention is neutralized with a base.
The preferred base is an alkali metal hydroxide and the most preferred base is sodium hydroxide.

As other bases, for example, alkaline earth metal hydroxides, ammonium hydroxides, alkali metals, alkaline earth metals, ammonium carbonates, bicarbonates, alcoholates, amines and the like can be used. .

The post-crosslinking agent, which is added to the reactant after the neutralization step, is slightly water-soluble and has at least two groups capable of reacting with a carboxylic acid group or a carboxylate group or forming a bond. It is a compound having a reactive moiety.
Organic compounds containing epoxy groups, hydroxyl groups, amino groups, phenol groups, halohydrin groups, etc. are suitable for use.

In addition to the more useful compounds, there are polyvalent metals, such as zinc, titanium, aluminum and zirconium, which form ionic bonds with carboxyl groups.

Examples of useful post-crosslinking agents include ethylene glycol diglycidyl ether, epichlorohydrin, glycerol,
Examples include ethylenediamine, bisphenol A, aluminum hydroxide, zinc nitrate, titanium lactate, zirconium lactate and the like.

The post-crosslinking agent is 0.05 based on the mole% of acrylic acid in the polymer.
~ 15 mol%, preferably about 0.05-0.15 mol% when the post-crosslinking agent is diglycidyl ether.

As described above, the polymerization reaction is an adiabatic reaction that is performed without supplying heat from the outside. The monomers, ie acrylic acid, cross-linking monomers and optionally polysaccharides, are dissolved in water in the reaction vessel. Dissolved oxygen is removed from the solution by bubbling with an inert gas such as nitrogen. Then lower the temperature to about 5 ° to 20 ° C. The polymerization catalyst, that is, the thermal decomposition type free radical initiator, the reducing agent and the oxidizing agent are sufficiently mixed and added to the reaction vessel. When the polymerization catalyst is added, the temperature rises and the polymerization reaction starts after a short induction period. The maximum temperature is reached in about 1 to 3 hours. The maximum temperature is controlled so that it does not exceed approximately 90 ° C if necessary. Generally, the maximum temperature is usually about 60 ° -75 ° C. When the maximum temperature is reached, the polymer is placed in an adiabatic reaction vessel, the residual monomer content is reduced to 1000 ppm or less, and the polymer is kept for a sufficient time to complete the polymerization. Generally this time is about 2
~ 12 hours.

After the polymerization reaction is completed, the polymer gel is taken out and cut into small particles.

Then an aqueous base solution is added to neutralize some or all of the acid groups.

The polymer gel is shredded again to facilitate uniform mixing of the base and polymer.

Then, the aqueous solution of the post-crosslinking agent is added, and the polymer gel is shredded again so that the mixing is performed uniformly. The gel is then heated to a temperature of about 20 ° to 200 ° C in order to effect the reaction of the postcrosslinker with the carboxyl groups.

This heating time is about 0.1 to 3 hours. After the reaction is completed, the polymer gel is heated to about 100 ° C to 200 ° C and dried until the water content is about 110% by weight or less. The dried polymer is then ground and ground on a US standard sieve to a particle size of approximately 20-400 mesh.

Model diapers are used to evaluate the polymer properties of superabsorbent polymer compositions. The model diaper has a pulp layer with a basis weight of 200 g / m ² (1
4 x 37 cm).

Then 5 g of the superabsorbent polymer composition is spread over the pulp layer as evenly as possible. Then 100 g / m of polymer composition
Cover with a pulp layer (14 x 37 cm) having a basis weight of ² and a non-woven topsheet. The test of the model diaper is performed as follows.

50 ml of 0.9% by weight saline in the center of the diaper
Pour until a total of 150 ml of solution is dispensed at minute intervals.

The dryness of the diaper surface is evaluated by 10 monitors touching the diaper 5 minutes and 2 hours after the final physiological saline is supplied to the diaper. Each person is rated on the following scale from 1 to 5 every hour.

The types of grades (entry items and explanations) are as follows.

5: Completely dry condition 4: Slightly moist condition 3: Wet condition 2: Slightly wet condition 1: Completely wet condition The grades from each monitor are summed every hour.

The total of 10 grades in the above test is a minimum of 10 and a maximum of 50. The dryness rating of diapers using the superabsorbent polymer composition of the present invention is at least 40 by this criterion.

The superabsorbent polymer composition of the present invention is further evaluated by the following tests.

Absorbency under pressure This test is intended to measure the absorbency of a superabsorbent polymer composition under a pressure of 20 g / cm ² (for example, with a child sitting).

Resorption capacity This test shows that the superabsorbent polymer composition contains some water (10 g /
g saline) and then under a pressure of 22 g / cm ² (e.g. when a child with a slightly damp diaper is in the sleeping or sitting pressure state) for a total of 50
The absorption capacity of the superabsorbent polymer composition after being subjected to lap shear is measured.

Modulus of elasticity This test measures the ability of a superabsorbent polymer composition to maintain its original state against pressure in a saturated absorption state just before the gel structure is destroyed or the liquid in the gel flows out. To do.

The absorption capacity under pressure is an automatic liquid absorption tester, model KM350 (made by Kyowa Seiko Co., Ltd.), with an inner diameter of 28 mm and a length of 50 mm at the bottom.
It is measured using a plastic tube equipped with a 100-mesh metal mesh. Samples with a size of 32 to 100 mesh are used for the test. Place 0.100 ± 0.01g of test sample in a plastic tube and spread evenly over the wire mesh. Place a 120 g weight on top of the sample. This plastic tube is placed in the center of the porous plate of the above tester, whose lower part is a container containing physiological saline (0.9 wt / vol.% Saline).

After absorption for 1 hour, the volume of physiological saline absorbed (a
ml) is measured. The blank is done in a similar manner without the superabsorbent polymer composition (this is b ml). The absorbency under pressure is represented by (ab) × 10.

The resorption capacity is measured as follows. Test sample 1.00
g is placed in a car containing 10.0 g of physiological saline (0.9 wt / vol.% saline) and left for 1 hour to obtain a uniform gel.

Then, this gel is put into a polyethylene bag, air inside the bag is expelled, and then sealed. The bag containing the gel is set on a pressure roller and sheared under the following conditions.

Roller weight 1 kg Roller shear rate 1 min / rev Rotation frequency 50 times Shear load (load) 22 g / cm ^{2 The} gel's resorption capacity is in a plastic tube using the same method described for absorbency under pressure. Gel after shearing
Add 1.10g and measure.

The elastic modulus is measured as follows. 0.50 of test sample
g artificial urine (NaCl 0.8% by weight, urea 2.0% by weight, MgSO ₄
An aqueous solution of 0.08% by weight 7H ₂ O, 0.03% by weight CaCl ₂ , 0.02% by weight is based on the weight of the solution) and placed in a beaker with 25.0 g and left for 1-3 hours to obtain a uniform gel.

Next, a part of gel, 0.2 ± 0.01 g, creep meter, model
Place on a RE3305 type (manufactured by Yamaden Co., Ltd.) and measure the resistance to deformation under a constant load of 15 g / cm ² . dyn / cm ²
The elastic modulus per hit is calculated from the ratio of unit stress to unit deformation.

Next, the present invention will be described in detail with reference to examples, but the present invention is not limited thereto. In addition, parts and% which are not particularly specified are parts and% by weight.

Example 1 800 parts of acrylic acid, 4 parts of tetraallyloxyethane, 1818.2 parts of a 2.2% aqueous solution of oxidized starch and 1347.8 parts of water were added to a suitable reaction vessel. Nitrogen was bubbled through the solution for bubbling and the temperature was reduced to 10 ° C. Dissolved oxygen is 1ppm
The following catalysts were added in the following order when:

2.4 parts 2,10-azobisamidinopropane dihydrochloride in 10 parts water; 0.2 parts ascorbic acid in 10 parts water; 2.29 parts 35% hydrogen peroxide in 10 parts water; short induction period Polymerization started after 2 hours and reached a maximum temperature of 65 ° to 70 ° C. in 2 hours. Generate gel in a heat-insulating container 3
The remaining monomer was reduced to 1000 ppm or less over a period of time.

The polymer gel was cut with a grinder and then 640 parts of a 50% aqueous solution of sodium hydroxide was added. The temperature of the gel was about 66 ° C before the addition of the aqueous sodium hydroxide solution, and the temperature of the aqueous sodium hydroxide solution was 38 ° C. The gel was shredded again for mixing in an aqueous base solution to achieve uniform neutralization.

The gel, which exothermed to 88 ° -93 ° C, was added to the gel followed by a solution of 2.4 parts ethylene glycol diglycidyl ether to 50 parts water at 24 ° C. The gel was shredded again in order to evenly disperse the postcrosslinker. The polymer was then dried using a rotary drum dryer at 105 ° C. to a water content of 10%. The resulting flake polymer composition was then ground and sieved to a particle size of 20-400 mesh (US standard sieve).

The polymer composition exhibited the following characteristics.

Absorbency under pressure (Ab.under P) 29g / g Reabsorption capacity (Reab Cap) 39g / g Modulus of elasticity (Elast.Mod) 8.8 × 10 ⁴ dyn / cm ² Dryness of model diapers 5 minutes-43 2 hours -43 Example 2 except that the first monomer solution consisted of 800 parts acrylic acid, 4 parts tetraallyloxyethane and 3166 parts water.
A polymer composition was synthesized using the same methods and components described in Example 1.

The resulting polymer composition exhibited the following properties.

Absorbency under pressure 34 g / g Resorption capacity 41 g / g Modulus 11.2 × 10 ⁴ dyn / cm ² Dryness of model diaper 5 min-45 2 h-46 Example 3 mol of ascorbic acid to mol of acrylic acid Several polymer compositions were synthesized using the same method as described in Example 2 except the percentages were varied. The properties of the polymer composition are as follows.

This example shows the critical amount of reducing agent used in the redox polymerization reaction.

Example 3d contained a high amount of ascorbic acid and produced a polymer composition with inferior properties.

Example 4 2,2'-Azobisamidino-based on the weight of acrylic acid
Several polymer compositions were obtained using the same method described in Example 2 except that the amount of propanedihydrochloride (ABAPD) added (wt%) was varied. The properties of the polymer composition were as follows:

This example shows the critical amount of pyrolytic free radical initiator.

The properties of Example 4d with a high ABAPD content were inferior to those of the other examples.

Example 5 Several polymer compositions were synthesized in the same manner as described in Example 2 except that the mol% of the cross-linking monomer, tetraallyloxyethane (TAE), based on the number of moles of acrylic acid, was varied. The properties of the polymer composition were as follows:

This example shows the critical amount of crosslinking monomer. Example 5a
Contains less than the critical amount of TAE and has inferior properties.

Example 6 Several polymer compositions were synthesized by a method similar to that described in Example 2 except that the amount of post crosslinker, ethylene glycol cyglycidyl ether (EGDE), was varied. The properties of the polymer composition were as follows:

This example shows the critical amount of postcrosslinker.

Only Examples 6c and 6d meet all conditions.

Example 7 Glycidyl ethers, such as the diglycidyl ether of ethylene glycol, are partially hydrolyzed when heated in the presence of water under basic conditions, thereby reducing their effectiveness as crosslinkers. Therefore, the polymer was polymerized by using the components described in Example 2 based on the method described in Example 1. However, neutralization and post-crosslinking were carried out according to the following conditions.

The temperature of the solution in the polymer gel shredded with a meat grinder is 16
1600 parts of a 20% aqueous solution of sodium hydroxide at 0 ° C was added.

The temperature of the gel before the addition of the aqueous sodium hydroxide solution was about 66 ° C. The gel was chopped again to mix with the base solution so that uniform neutralization was achieved. For gels with temperatures around 66 ° C 1.
25 parts of diglycidyl ether of ethylene glycol (0.05 mol% based on the number of moles of acrylic acid) were added. The temperature of diglycidyl ether was 4 ° C. The polymer was then heated, dried and milled as described in Example 1.

The resulting polymer composition exhibited the following properties.

Absorbency under pressure 31g / g Resorption capacity 38g / g Modulus of elasticity 10.5 × 10 ⁴ dyn / cm ² Model diaper dryness 5 minutes-40 2 hours-45 About 65 ° between addition of diglycidyl ether and initiation of reaction ~
By maintaining the maximum temperature of 70 ° C, the effect of the cross-linking agent becomes greater. Therefore, using diglycidyl ether in an amount as low as 0.05 mol% based on the number of moles of acrylic acid,
A satisfactory product can be obtained.

Comparative Example A A commercially available polymer composition used in diapers was removed, tested and compared with the polymer composition of the present invention.
(However, "Sunwet IM-1000" and "IM-1500" were compared with each other before they were used in the diaper.) The results were as follows.

The concept, preferred embodiments and manufacturing method of the present invention have already been explained in the present specification. However, the protection scope of the present invention is not limited to the particular forms disclosed. Various changes may be made without departing from the spirit of the present invention.

EFFECTS OF THE INVENTION The present invention provides a highly water-absorbent polymer composition having excellent balance of performances such as absorbency under pressure, re-absorption capacity, elastic modulus, and dryness, a method for producing the same, and the polymer composition. It is possible to provide a highly absorbent application article using a product.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location C08F 265/02 MQM 7308-4J 291/00 MRB 7308-4J (72) Inventor Douglas Ronald Chambers United States of America New Mill Drive 1243 (72) Chesapeake, Virginia 1241 (72) Inventor Hubert Henri Fowler, Zunia United States Virginia 23321 Chesapeake, Duke of Groschester Drive 4121

Claims (13)

[Claims] 1. (a) Acrylic acid, a water-soluble polysaccharide and 1.
An aqueous solution comprising a polyfunctional monomer having at least two polymerizable ethylenically unsaturated double bonds per molecule, wherein the acrylic acid and the polysaccharide are about 90 to 100% by weight of acrylic acid, based on the total weight thereof. The saccharide is used in a range of about 0 to 10% by weight, the polyfunctional monomer is used in a proportion of about 0.075 to 1 mol% based on the number of moles of acrylic acid, and the acrylic acid and the polysaccharide are acrylic acid, polysaccharide and In an aqueous solution of about 5 to 30% by weight based on the weight of water, (b) consists of a redox catalyst and a thermal decomposition type free radical initiator, and the reducing agent part of the redox catalyst is the number of moles of acrylic acid. To about 6 × 10 ^{−5 to} 2.5 × 10 ⁻³ mol%, and the oxidant portion is about 3.4 × 1 with respect to the number of moles of acrylic acid.
0 ^{-3 to} 0.42 mol%, and a thermal decomposition type free radical initiator containing a thermal decomposition type free radical initiator in an amount of about 0.1 to 0.4% by weight based on the weight of acrylic acid. A catalyst composed of an agent is added to the aqueous solution at a temperature of about 5 to 20 ° C, and (c) the reaction is exothermic, and the reaction system is 90 ° C under adiabatic conditions.
The temperature of the reaction system is kept within 10 ° C of the maximum temperature for a sufficient period of time so that the temperature rises to a maximum temperature that does not exceed 100 ° C, thereby forming a polymer gel, and (d) the residual monomer content is reduced to 1000 ppm or less. (E) about 50 of the carboxylic acid groups in the polymer in an aqueous base solution
(F) a post-crosslinking agent composed of a polyfunctional compound having at least two groups capable of forming an ionic bond or a covalent bond with a carboxylic acid group is neutralized to about 100% of the acrylic acid. 0.05-15 mol%, (g) heat-dry the polymer at a temperature of about 20 ° C-200 ° C until the water content is about 10% by weight or less, (h) and add about 20-400% of the polymer. A method for producing a superabsorbent polymer, which comprises a step of pulverizing to a particle size of mesh. 2. The method for producing a superabsorbent polymer composition according to claim 1, wherein the polysaccharide is natural starch. 3. The polyfunctional monomer is in an amount of about 0.1 to 0.3 mol%, and the reducing agent portion of the redox catalyst is about 6 × 10 ⁻⁴ to 2.
5 is the amount of × 10 ^-3 mol%, part of the oxidizing agent is about 0.15 to 0.2
In an amount of 5 mol%, the pyrolytic free radical initiator is included in an amount of about 0.25 to 0.35% by weight, and the postcrosslinker is about
The method for producing a superabsorbent polymer composition according to claim 1, wherein the amount is 0.05 to 0.15 mol%. 4. The maximum temperature of the reaction system is about 60 ° C. to 75 ° C.,
The method for producing a superabsorbent polymer composition according to claim 1, wherein the reaction system is kept at a maximum temperature of 5 ° C. 5. About 100 ° C. to 200 ° C. for post-crosslinking the polymer gel after addition of the post-crosslinking agent and drying the polymer.
The method for producing a superabsorbent polymer composition according to claim 1, wherein the superabsorbent polymer composition is heated by heating. 6. The method for producing a superabsorbent polymer composition according to claim 1, wherein the polyfunctional monomer is tetraallyloxyethane and the post-crosslinking agent is diglycidyl ether of ethylene glycol. 7. The reducing agent is ascorbic acid, the oxidizing agent is hydrogen peroxide, and the thermal decomposition type free radical initiator is 2,
The method for producing a superabsorbent polymer composition according to claim 1, which is 2'-azobis (amidinopropane) dihydrate chloride. 8. The polyfunctional monomer is contained in an amount of about 0.075 to 1 mol% based on the number of moles of acrylic acid, and the polysaccharide is included in an amount of about 0 to 10 wt% based on the weight of acrylic acid and the polysaccharide. Is a graft copolymer composed of acrylic acid, a polyfunctional monomer and a polysaccharide contained in, wherein the graft copolymer has about 50 to 100% of the carboxylic acid groups neutralized with a base,
And is post-crosslinked with a post-crosslinking agent composed of a polyfunctional compound in an amount of about 0.05 to 15 mol% with respect to the number of moles of acrylic acid,
Water content less than 10% by weight, with particle size of about 20-400 mesh, absorbency under pressure of 28g / g minimum, 35g minimum
Superabsorbent polymer composition having a resorption capacity of / g and an elastic modulus of at least 8.0 × 10 ⁴ dyn / cm ² . 9. The superabsorbent polymer composition according to claim 8, wherein the polysaccharide is natural starch. 10. The superabsorbent polymer composition according to claim 8, wherein the polyfunctional monomer is contained in an amount of about 0.1 to 0.3 mol%, and the post-crosslinking agent is contained in an amount of about 0.05 to 0.15 mol%. 11. The superabsorbent polymer composition according to claim 8, wherein the polyfunctional monomer is tetraallyloxyethane and the post-crosslinking agent is diglycidyl ether of ethylene glycol. 12. A superabsorbent article comprising the superabsorbent polymer composition according to claim 8, which has a dryness of at least 40. 13. The super absorbent article according to claim 12, wherein the article is a diaper.