JPS5927764B2 - Manufacturing method of urethane foam with excellent water absorption and water retention properties - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing urethane foam with excellent water absorption and water retention properties.

Conventionally, polyurethane foam has been obtained as a relatively highly foamed product by reacting polyisocyanate and polyol, and has been used for various purposes that take advantage of its light weight, heat insulation properties, etc. In particular, urethane foam, which has a rich open-cell structure, is used not only for its cushioning properties but also for its excellent water absorption properties, and is used as a plant culture medium, sanitary products, water-stopping agents, and cleaning products for tableware and other items. However, although the urethane foam with a high cell content has excellent water absorption properties, it releases most of the water it retains when subjected to a slight external pressure. Such properties are extremely suitable for applications in which the reversibility of water absorption and water discharge is utilized by external force. On the other hand, they cannot be satisfactorily used in applications that require a high degree of water absorption and retention, such as diapers, sanitary products, or plant culture media. The present inventors have made extensive studies to improve the drawbacks of polyurethane foam as described above,
We have discovered a method for obtaining polyurethane foam that has excellent water retention even under external pressure, and have completed the present invention. That is, in the present invention, when producing polyurethane foam by reacting polyol and polyisocyanate,
Ethylene flash, vinyl ester (to) and ethylenically unsaturated carboxylic acid or its derivative (4 as the main component,
The component is X:(Y-1 layer Z)=0:100 to 15:85
Water absorption and water retention characterized by adding and mixing a water-insoluble super absorbent hydrogel mainly composed of a saponified product of a copolymer having a molar ratio of Y:Z = 20:80 to 80:20. The present invention provides a method for producing polyurethane foam with excellent properties.

The hydrogel used in the present invention is relatively stable physically and chemically, and has less influence on microorganisms than starch-based or cellulose-based hydrogels, and has excellent stability even in long-term hydrated conditions. Not only that, but it is also almost non-toxic to the human body.

Therefore, the polyurethane foam obtained by the present invention is extremely useful not only in sanitary products and diapers, but also in applications that are used over a long period of time, such as plant culture media and water-stopping materials. be. The hydrogel used in the present invention usually has a weight of 10 times or more to 1500 times its own weight.
Although it has about twice the water absorption rate, for example, patent application No. 50-9085
No. 0 (Unexamined Japanese Patent Publication No. 5227455), 50-141931
It can be produced by various methods, such as those shown in Japanese Patent Application Laid-Open No. 52-65597.

That is, examples of its production include the following.

Example 1 A copolymer having the above composition is saponified using an alkaline substance in a suitable solvent, preferably alcohol, water, or a mixture of alcohol and water, and then the saponified product is converted into an aqueous solution or an appropriate water-containing state to reduce the water content. A method of drying to 100% by weight, preferably 50% by weight or less.

Example 2 After saponifying the copolymer in the same manner as in Example 1, the saponified product is treated with a polyfunctional compound that can react with a hydroxyl group or a carboxyl group, such as a dialdehyde compound, an epihalohydrin compound, a di(tri)epoxy A method of slightly cross-linking using a chemical compound, etc.

Example 3 A method of saponifying the copolymer in a suitable solvent, preferably alcohol and a mixture of alcohol and water, under conditions in which the copolymer is not dissolved in the solvent.

Example 4 During or after the polymerization of the copolymer, if necessary, a crosslinking agent having two or more polymerizable unsaturated bonds, such as a polyallyl compound such as diallyl phthalate or diallyl maleate, divinylbenzene, ethylene glycol diacrylate, etc. The crosslinked copolymer obtained by moderate crosslinking using a polyvinyl compound, etc.
Preferably, the method is saponification in alcohol, water, or a water-alcohol mixture.

In each of these methods, the saponification reaction preferably uses an alkali substance such as an alkali metal hydroxide such as sodium hydroxide, potassium hydroxide, sodium methylate, potassium methylate, or an alcoholade.

Further, the copolymer hydrogel applied to the present invention must contain at least a hydroxyl group and a carboxylate group in its molecule.

Therefore, in any of the above production method examples, the saponification degree may be within a range that satisfies the above conditions, but in order to obtain a hydrogel with a high water absorption ability, for example, vinyl ester and ethylenically unsaturated carbon In the case of starting from a copolymer with an acid ester, the vinyl ester component is 50 mol% or more, preferably 90 mol% or more, and the ethylenically unsaturated carboxylic acid component is 30 mol% or more, preferably 70 mol%. It is desirable that the above is saponified. The alkaline substance used in the saponification reaction is the salt-forming substance for the carpoxylate group in the saponified copolymer, but the salt form can be arbitrarily changed by a well-known method.

For example, by converting a hydrogel in the form of an alkali metal salt into an organic amine salt by a known method, or by carrying out a saponification reaction in the presence of two or more types of alkali substances,
It can also be made into a salt form that is more than a seed. Common salt-forming substances include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide; ammonium hydroxide; mono-, di-, tri-methylamine; mono-, di-, tri-ethylamine; Isopropylamine; mono-, di-triethanolamine; mono-, di-, tri-
Isopropanolamine; N-N-dimethylethanolamine; N-N-dimethylisopropanolamine: N
-N-diethylethanolamine: N・N-diethylisopropanolamine; N-methylethanolamine,
N-methylisopropanolamine, N-ethylethanolamine, cyclohexylamine, benzylamine,
Examples include aniline, pyridine, and other organic amines. Furthermore, when the hydrogel of the present invention is in the form of an alkaline earth metal salt such as magnesium or calcium, its water absorption capacity is significantly reduced, making it unsuitable for the purpose of producing a highly water-absorbent gel. In the case of forming a mixed salt, a polyvalent metal salt-forming substance can also be used. In the above-mentioned hydrogel production method examples, vinyl esters used to produce the starting copolymer include vinyl acetate, vinyl propionate, vinyl stearate, etc., but vinyl acetate is usually used. It is preferable.

Examples of ethylenically unsaturated carboxylic acids or derivatives thereof include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, maleic anhydride, itaconic anhydride and esters thereof, acrylamide, methacryl Among these, preferred compounds include acrylic acid, methacrylic acid, and their methyl-ethyl-n-propyl-,
These are IsO-propyl-, n-butyl-, t-butyl-esters, acrylamide, and methacrylamide. The hydrogel used in the method of the present invention has the most favorable absorption property for water, but depending on its salt form, it can absorb not only water but also other organic solvents.
For example, sodium salts or ammonium salts have almost no absorption capacity for organic solvents, but have a certain degree of absorption capacity for mixtures of organic solvents and water that form arbitrary homogeneous solutions with water. Has absorption capacity. Furthermore, in the case of a hydrogel in the form of an organic amine salt, it has excellent absorption ability not only for water but also for polar organic solvents such as methanol dimethylformamide and ethanolamine. The polyol used in the present invention refers to polyesters, polyethers, etc. for polyurethane foams that are generally used.

Specifically, polyesters such as adipic acid polyester and dimer acid polyester, diols such as polyethylene glycol and polypropylene glycol, triols such as propylene oxide trimethylolpropane and propylene oxide glycerin, and sorbitol polyethers are exemplified. As the polyisocyanate, tolylene diisocyanate, metaphenylene diisocyanate, and various other general-purpose polyisocyanates are used. The polyurethane foam of the present invention can be produced in accordance with commonly known polyurethane foam production methods. For example, a method of producing a foam by sufficiently mixing two components consisting of polyisocyanate, polyol, catalyst, blowing agent, surfactant, etc., or a method of producing a foam by thoroughly mixing two components consisting of polyisocyanate, polyol, catalyst, blowing agent, surfactant, etc., or a method of producing a foam by sufficiently mixing a pre-reacted product of polyol and polyisocyanate with the remaining polyol and blowing agent, In the method of manufacturing a foam by sufficiently mixing two components consisting of a catalyst, a surfactant, etc., a hydrogel may be mixed in advance with either component, or the hydrogel may be used as a third component. They may be added and mixed individually. That is, it is important that the hydrogel is sufficiently and uniformly dispersed, and as long as this is satisfied, there are no particular restrictions on the method or order of adding the hydrogel. The shape of the hydrogel is not particularly limited, but it is usually desirable to have a granular shape or a short grain shape. In particular, when producing using a nozzle injection type mixer, it is desirable to use a spherical or amorphous hydrogel having a particle size of 60 mesh or less. The amount of the hydrogel added is appropriately determined depending on the required water absorption amount, water retention amount, foaming ratio, water absorption rate of the hydrogel, etc., and can be used arbitrarily as long as it can form a foam, but usually it is 100% by weight of the polyurethane raw material component. 0.5 to 100 parts by weight per part. If the amount added is less than 0.5 part by weight, no practically effective improvement in water retention capacity can be expected.

Further, if the amount exceeds 100 parts by weight, the expansion ratio of the foam tends to decrease. Catalysts that may be used as necessary when producing the polyurethane foam of the present invention include tertiary amines such as triethylenediamine and trialkylamine, dibutyltin dilaurate, stannous 2-ethylcaproate, and stannous oleate. Organic tin compounds such as and various other general-purpose catalysts are used.

As blowing agents, water, hydrous compounds such as borax, carboxyl polyesters, volatile solvents such as trichloromonofluoromethane, formaldehyde generators such as bis(hydroxymethyl)thiourea, nitrogen gas such as azobisisobutyronitrile, etc. Generating agents etc. are used. When producing the polyurethane foam of the present invention, additives such as organic or inorganic fibers, inorganic powder, pigments or dyes, fragrances, etc. can be added as necessary.

The polyurethane foam of the present invention obtained by the method described above has extremely excellent water absorption and water retention properties, and its performance does not deteriorate even after long-term use. It can be used for a variety of purposes, including materials, agricultural materials such as plant culture media, water-stopping materials, dehydrating agents, and moisturizing agents.

Furthermore, by using hydrogels with different salt shapes, they can be suitably used for the purpose of absorbing and retaining not only water but also polar organic solvents, water-organic solvent mixtures, and the like. EXAMPLES The present invention will be explained below using Examples, but the present invention is not limited thereto.

Note that all parts in the examples are expressed in parts by weight. Example 1 An acetone solution of a terpolymer having a composition of 50 mol% methyl acrylate, 43 mol% vinyl acetate, and 7 mol% ethylene was spun and then cut into short pieces with a diameter of 10 μm and a length of 5 mm. Obtained fiber.

Next, the short fibers 10f7 were soaked in methanol 2007 at 20°C.
After immersing it in water and dispersing it, water 407 and NaOH7
7 was added and saponified at 25° C. for 1 hour, and then the saponified solution was heated to 65° C. and the saponification reaction was further carried out for 4 hours. The fiber shape remained intact during the saponification reaction. After the saponification reaction was completed, 8 tons of fibrous saponified material was obtained by thoroughly washing with methanol and drying under reduced pressure.

The degree of saponification of the saponified product was 94 mol%. The fibrous hydrogel thus obtained is insoluble in water;
It absorbed water extremely rapidly and swelled, having a water absorption rate of 700 V/V.

Next, 50 parts of the dried hydrogel was added to 150 parts of toluene diisocyanate and sufficiently dispersed to prepare a solution A.

On the other hand, a mixture of 300 parts of propylene oxide glycerin, 12 parts of water, 0.45 parts of triethylene diamine, and 4.5 parts of silicone surfactant was used as liquid B, and then, in the stirring liquid B, tinnous oleate was added. After adding 1.2 parts, immediately add the above-mentioned Part A and continue stirring at high speed for 8 seconds. It was poured into a wooden box and allowed to foam freely. Then take out the foam,
Heat in an oven at 100°C for 20 minutes until the density is 0.0.
35 forms were obtained. The water absorption rate of the foam is 30t/
The water retention rate after pressurization of t and 200'fl/Cd was 267/7. Example 2 0.7 mol of vinyl acetate, 0.5 mol of methyl methacrylate and 0 ethylene glycol diacrylate as a crosslinking agent
．． 0.02 mole of benzoyl peroxide as a polymerization initiator were mixed, and this was dispersed in 300 d of water containing partially saponified polyvinyl alcohol as a dispersion stabilizer and 3 t of NaClIO7, and suspension polymerization was carried out at 65° C. for 6 hours. .

The resulting copolymer had a methyl methacrylate content of about 47 mol% and an insoluble content in acetone solvent of 63% by weight. Next, the copolymer 107 was dispersed in 200 ml of methanol, 40 ml of a 40% NaOH aqueous solution was added, and the mixture was saponified at 60° C. for 5 hours.

The degree of saponification was about 91 mol%. The obtained hydrogel has a spherical shape with a diameter of 20 to 200μ, is insoluble in ζ water, and has a diameter of 55
It had a water absorption rate of 0 times. The dried hydrogel 1
00 parts of propylene oxide glycerin (triol)
300 parts of water, 12 parts of water, 0.45 parts of triethylenediamine, and 4.5 parts of silicone surfactant and thoroughly mixed. Next, 1.0 parts of stannous oleate was added to the stirred mixed solution. 2 parts, toluene diisocyanate 15
After sequentially adding 0 parts, stir for 8 seconds and cover with graft paper in a 25x25x30? It was poured into a wooden box and allowed to foam freely. The foam was then taken out and heated in an oven at 100°C for 20 minutes. The density of the obtained urethane foam was 0.038y/Cd. Comparative example 1 Japanese Patent Application Laid-Open No. 1983-
According to the method described in Example 1 of Japanese Patent Publication No. 75796, a starch-based hydrogel was produced by the following method.

After stirring 40 t of cornstarch and 500 ml of water at 90°C for 1 hour, it was cooled to 25°C, and 527 ml of acrylonitrile was added.
and 1.327 ml of cerium () ammonium nitrate dissolved in 324 ml of 0.1N HNO were added, and graft polymerization was carried out at 30° C. for 2 hours.

The obtained graft polymer was saponified in a 15% aqueous solution of KOH46V at 90'C for 3 hours, and then treated with 5N-HC.
The pH was adjusted to 4 with l. The precipitated copolymer was washed with water, neutralized with a 10% NaOH aqueous solution, and then dried. The obtained starch-based hydrogel was water-insoluble and 39
It had a water absorption rate of 0 times. Using this starch-based hydrogel, the formulation and formulation were carried out in exactly the same manner as in Example 2.
A urethane foam with a density of 0.039t/Cri was obtained. Comparative Example 2 A urethane foam having a density of 0.030 t/Cd was obtained by carrying out the same blending and prescription as in Example 2 except that no hydrogel was included.

Comparative Test 1 From each urethane foam obtained in Example 2, Comparative Example 1, and Comparative Example 2, 5? , length 5? , thickness 2? A sample was cut out, and the saturated water absorption rate under no load and the water retention rate when a pressure of 200 t/Cd was applied to the foam in a saturated water absorption state were measured.

The results are shown in Table 1. As is clear from Table 1,
The urethane foam obtained in Example 2 has extremely superior water retention compared to the urethane foams obtained in Comparative Examples 1 and 2. Comparative Test 2 From each urethane foam obtained in Example 2 and Comparative Example 1, a vertical 5 cm
1 length 5 to length 2? A specimen was cut out and immersed in water for 3 months in a saturated water absorption state, and then the saturated water absorption rate under no load and the water retention rate when a pressure of 200 t/leakage was applied to the saturated water absorption foam were measured. .

Claims (1)

[Claims] 1. When producing polyurethane foam by reacting polyol and polyisocyanate, ethylene (X
), vinyl ester (Y) and ethylenically unsaturated carboxylic acid or its derivative (Z) as main components, and the components are X:(Y+Z)=0:100-15:85Y:Z=2
It has excellent water absorption and water retention properties, and is characterized by the addition and mixing of a water-insoluble, highly water-absorbent hydrogel mainly composed of a saponified copolymer with a molar ratio in the range of 0:80 to 80:20. Method of manufacturing polyurethane foam.