JPS5857974B2 - Water absorption/water retention agent and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a water-insoluble water-absorbing and water-retaining agent based on fibroin.

Conventionally, paper, non-woven fabric, pulp, urethane sponge sponge, etc. have been used as water-absorbing materials in sanitary products, diapers, kitchen utensils, etc. However, these materials do not have a very high water-absorbing capacity, and the absorbed water will come out under slight pressure. It had poor water retention.

In recent years, materials with higher water absorption and water retention properties have been required in the food industry, medical field, and horticultural field. Polymer electrolytes such as decomposition products and starch-polyacrylic acid crosslinked graft products have been proposed.

However, these materials also have drawbacks such as insufficient water absorption performance, decay, and unstable quality, or complicated and expensive manufacturing processes.

On the other hand, as for graft polymerization to fibroin, it is known that a vinyl monomer such as styrene is grafted to silk thread as a method for increasing the volume of silk thread, but this method involves graft polymerization to crystallized fibroin. Therefore, the grafting rate is small and it is difficult to make an excellent water absorbing and retaining agent.

The present inventors have conducted extensive research to improve the drawbacks of conventional water-absorbing materials. By graft polymerizing fibroin in an aqueous solution state with appropriate monomers, the present inventors have succeeded in making it soluble in water without any cross-linking or water-insolubilization treatment. The present invention was completed based on the discovery that it is possible to obtain a material that is insoluble and has excellent water absorption and water retention properties.

An object of the present invention is to provide a water-absorbing and water-retaining polymeric material that has high water-absorbing and water-retaining properties and is resistant to decay.

The above-mentioned objectives are 3-40% by weight of fibroin, 50-9
This is achieved by using a water absorbing and water retaining agent whose main component is a polymer consisting of 5% by weight of an acrylic acid monomer and 0 to 20% by weight of an olefinically unsaturated monomer.

The water absorption and water retention agent of the present invention contains 3 to 40% by weight of fibroin.
, preferably 5 to 30% by weight, and 50 to 9% of acrylic acids.
5% by weight, preferably 60-90% by weight, and 0-20% by weight, preferably 0-1 olefinically unsaturated monomer.
It is a graft copolymer containing 0% by weight.

If the fibroin content is less than 3% by weight or the (meth)acrylic acid (salt) content exceeds 95% by weight, the water-absorbing gel tends to become very weak, and if the above range is significantly exceeded, it tends to dissolve into water. As a result, it becomes difficult to fully demonstrate its performance as a water retention agent.

On the other hand, if the fibroin content exceeds 40% by weight, the acrylic acid content exceeds 50% by weight, or the olefinically unsaturated monomer component exceeds 20% by weight, the water absorption amount or water absorption rate tends to decrease.

The form of the water-absorbing and water-retaining agent of the present invention is not limited to %, but can be powdery,
The shape can be suitably selected depending on the application, such as film, fiber, or block, but if water absorption performance is particularly required, a powder form with a large surface area is preferable.

When using acrylic acid salts, acrylic acid salts may be used as monomers before graft polymerization, but in order to maintain a high graft polymerization rate, acrylic acids such as acrylic acid and methacrylic acid or hydrolyzed It is preferable to carry out graft polymerization with monomers that form acrylic acids (together referred to as acrylic acid monomers) and then neutralize to form a salt.

Examples of salts of acrylic acids include alkali metal salts, alkaline earth metal salts, aluminum salts, ammonium salts, etc., but sodium, potassium, calcium, magnesium, or ammonium salts are preferred from the viewpoint of water absorption performance and ease of production or production cost. .

For neutralization, hydroxides or carbonates of iron metal or ammonia may generally be used.

Furthermore, when using a monomer that becomes an acrylic acid by hydrolysis, if the hydrolysis is carried out using an alkaline aqueous solution of the metal or ammonia, the salt of the acrylic acid can be obtained at the same time as the hydrolysis is completed.

The aqueous fibroin solution applied to the method of the present invention is usually obtained by scouring and removing sericin from silk raw materials such as raw silk, cocoon, raw silk waste, kiki, bis, and boulet in accordance with a conventional method, and then preparing a copper-ethylenediamine aqueous solution, copper hydroxide-alkali Dissolved in solvents such as glycerin aqueous solution, copper hydroxide-ammonia aqueous solution, sodium halide aqueous solution, calcium, magnesium or zinc hydrochloride or nitrate or thiocyanate aqueous solution, alkali metal thiocyanate aqueous solution, or further Examples include those obtained by dialysis and desalting, but those obtained by dialysis are particularly preferred.

As the solvent, hydrochloride or nitrate of caracalcium or magnesium is preferred due to cost and ease of use.

Furthermore, lower alcohols such as methyl alcohol, ethyl alcohol, and flobyl alcohol may be added to the solvent in order to further improve the solubility of the silk raw material.

Acrylic acids or monomers that become acrylic acids by hydrolysis and, if necessary, olefinically unsaturated monomers are mixed into these fibroin aqueous solutions.

In this case, the combined concentration of fibroin and monomer is usually 1
The content is adjusted to 30% by weight, preferably 5 to 20% by weight.

Monomers that become acrylic acids by hydrolysis, ie, acrylic acid monomers, include (meth)acrylonitrile, (meth)acrylamide, or methyl (meth)acrylate;
Examples include (meth)acrylic acid esters such as ethyl (meth)acrylate and 2-ethylhexyl (meth)acrylate.

In addition, as olefinically unsaturated monomers that are effective in improving the degree of gelation upon water absorption, in addition to the (meth)acrylic acid derivatives that remain without forming acrylic acids regardless of the presence or absence of hydrolysis, K. Any material may be used as long as it copolymerizes with (meth)acrylic acids, such as ethylene derivatives, styrene derivatives, and vinyl esters.

Next, preferably, oxygen is removed from the reaction system and graft polymerization is carried out by irradiation with radiation, electron beams, ultraviolet rays, or by adding a radical polymerization catalyst.

Examples of the radical polymerization catalyst include hydrogen peroxide, benzoyl peroxide, azobisbutyronitrile, ceric salt, potassium persulfate, and ammonium persulfate.

Further, redox polymerization can also be carried out by simultaneously using sulfites and polyamines.

From the viewpoint of equipment and operation, it is preferable to use a radical polymerization catalyst for graft polymerization.

Further, as a solvent, a water-soluble solvent such as methyl alcohol, ethyl alcohol or acetone may be added, or if necessary, an emulsion system may be used.

The polymerization temperature is usually 10 to 110°C, preferably 20°C.
~90°C, and the polymerization time is usually 20 to 200 minutes, preferably 30 to 150 minutes.

Hydrolysis of the polymerized product obtained above may be carried out by a conventionally known method, if necessary, and may be carried out in water or a mixed solvent of water and a lower alcohol, usually using a caustic alkali.

Next, the reaction product can be used as it is or after being subjected to treatments such as neutralization, or can be used as various forms of water-absorbing and water-retaining agents by drying, molding, or pulverizing.

Drying is usually carried out in a water-containing state at 40 to 120 °C, preferably 60 to 100 °C, under normal pressure or reduced pressure, or at a certain °C is washed with a water-soluble solvent such as a lower alcohol or acetone and replaced with water. You can also dry it afterwards.

Because it is based on fibroin, a protein that crystallizes very easily, it has the advantage that a water-insoluble water-absorbing and water-retaining agent can be stably obtained without the need for further insolubilization treatment.

The water-absorbing and water-retaining agent of the present invention has a wide variety of uses, including in the sanitary field such as sanitary products and disposable diapers, as a water-retaining agent for soil, and as a slow-release effect by impregnating pesticides, fertilizers, fragrances, etc.

The water absorption and water retention agent of the present invention has a water absorption capacity of 50 to 250 times that of water, and also has a high absorption capacity for various types of aqueous solutions such as urine and blood, and is easy to manufacture and inexpensive. be.

In addition, although the protein called fibroin is extremely thick, it has much higher rot resistance and biodegradability than those made with other proteins or starches, and it contains almost no sulfur, making it easy to dispose of. It has the advantage of being easy to process.

The present invention will be specifically explained below with reference to Examples.

Example 1 1 part raw silk waste and 9 parts were mixed into 1% by weight Marcel soap aqueous solution 3 (l
The sample was immersed in the liquid and treated at 98°C for 3 hours to substantially remove sericin and oil.

0.5 kg of the raw silk waste after the scouring was added to 2 kg of a 65% by weight aqueous calcium nitrate solution and 0.5 ky of ethyl alcohol.
was added and stirred and dissolved at 70 to 75°C for 1 hour.

Next, 2 kg of 70°C hot water was mixed and diluted, and after cooling, desalination was performed using a hollow fiber type dialysis device.

Fibroin and acrylic acid are in the proportions shown in Table 1-1 below in terms of solid content, and the total amount of both solid content is
A reaction solution was prepared so that the concentration was 10% by weight.

Each reaction solution 101' was charged into a reaction vessel equipped with a stirring bar, a nitrogen blowing tube, and a thermometer, 20 m9 of ammonium persulfate was added under a nitrogen stream, and the temperature was raised from 25°C to 80°C for 1 hour, and then heated to 80°C. The reaction was continued for 1 hour.

The resulting viscous reaction solution was heated as it was or after neutralization with an aqueous sodium hydroxide solution, an aqueous potassium hydroxide solution, an aqueous calcium hydroxide solution, or aqueous ammonia, at 60°C.
Dry under reduced pressure for 8 hours, then pulverize to a
A powder with a particle size of 0μ was obtained.

The acrylic acid content in Table 1-2 was calculated from the quantitative determination of carboxyl groups by neutralization titration.

The water absorption rate was calculated from the weight of the insoluble gel obtained by dispersing the graft polymer powder in water, filtering free water through a 300-mesh wire mesh.

It can be seen from Table 1-2 that all the graft polymers obtained by the method of the present invention have high water absorption capacity.

Example 2 Fifuroin aqueous solution obtained by dialysis in Example 1 and No. 2-1
Graft polymerization was carried out using the monomers shown in the table.

The equipment and concentration used were the same as in Example 1, and the polymerization catalyst was 20 m of potassium persulfate and 101 m of sodium sulfite.
11g was used together.

* In experiments &2-2 to 2-7, after the polymerization reaction, hydrolysis was carried out for 2 hours under methanol reflux conditions in a mixed solution of 50% by weight of methanol and 50% by weight of 3N aqueous sodium hydroxide solution or potassium hydroxide aqueous solution.

In Experiments &2-5 and 2-6, some acrylamide remained without being hydrolyzed under the above conditions.

It can be seen from the above table that all the graft polymers obtained by the method of the present invention have high water absorption capacity and moderately strong gel strength.

Example 3 1 kg of boulet was immersed in 0.5% by weight Marcel soap aqueous solution 25 and treated at 80° C. for 1 hour to substantially remove sericin and oil.

0.5 kg of the refined boulet is mixed with 4 ky of a 60% by weight calcium chloride aqueous solution and 1 kg of ethyl alcohol.
The mixture was placed in a kneader containing 100% chloride, and stirred and dissolved at 70 to 80°C for 1 hour.

After removing insoluble impurities, the tube was placed in a cellulose tube with an inner diameter of 2 cm and desalted by dialysis in running water for 24 hours.

Graft polymerization was carried out in the same manner as in Example 1 using the obtained aqueous fibroin solution, acrylic acid, and an olefinically unsaturated monomer.

Next, experimental form 3-7 was left as is, and the others were neutralized with an aqueous sodium hydroxide solution and thoroughly washed with methyl alcohol.
It was dried at 0° C. for 5 hours to obtain a graft polymer having a particle size of 100 to 700 μm.

As shown in Table 3-2, all of them had a high water absorption capacity and water retention capacity for water, and also had a practically acceptable water absorption capacity for an electrolyte aqueous solution.

Claims (1)

[Scope of Claims] A water absorbent whose main component is a polymer consisting of 13 to 40% by weight of fibroin, 50 to 95% by weight of an acrylic acid monomer, and 0 to 20% by weight of an olefinically unsaturated monomer.・Water retention agent. 2 Fibroin is 5-30% by weight, acrylic acids are 6%
0 to 90% by weight, 0 to 10 olefinically unsaturated monomers
The water absorbing/water retaining agent according to claim 1, which is % by weight. 3. The water absorbing/water retaining agent according to claim 1, wherein the acrylic acid monomer is acrylic acid, methacrylic acid, or a salt thereof. 4. The water absorbing/water retaining agent according to claim 3, wherein the salt of acrylic acid or methacrylic acid is a sodium, potassium, calcium, magnesium or ammonium salt. 5. The water absorbing/water retaining agent according to claim 1, wherein the polymer is in powder form.