JPH0122388B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to absorbent cotton with improved absorbency for water, blood, saliva, and the like. Absorbent materials made by sprinkling superabsorbent resin powder on paper, pulp cotton, or absorbent cotton are used as various sanitary materials. BACKGROUND ART Superabsorbent resins containing an alkali metal acrylic acid salt as a main component are well known, and there are many documents regarding their production methods. The following method is disclosed for incorporating a super absorbent resin into a fiber material. (1) A method of dispersing resin powder onto the fiber material, (2) A method of making the fiber surface hydrophilic through a chemical reaction and introducing cross-linking bonds as necessary (Japanese Patent Application Laid-Open No. 144476/1973), (3) High water absorption A method in which fibers are coated with an uncrosslinked resin solution, which is a synthetic resin precursor, and then insolubilized by reacting with a crosslinking agent
204680), (4) A method for producing a super absorbent resin by polymerizing a resin stock solution, by mixing pulp, cotton, etc. into the stock solution to obtain a water absorbent containing these fillers (Japanese Patent Publication No. 53-46199, 46200). Problems to be Solved by the Invention In order to obtain absorbent cotton containing a superabsorbent resin and having improved absorbency, the above-mentioned known methods were tried, but each method was found to have drawbacks. In the method (1) of dispersing resin powder, the hydrated gel is released from the fibers when water is absorbed and adheres to the skin, causing discomfort, and also poses safety problems. (2)
carboxymethylated on the cellulose fiber surface of
Furthermore, the method of introducing crosslinking to impart water absorption properties is as follows.
It is expensive and impractical for the purpose of the present invention. In the method (3) of applying and impregnating fibers with an aqueous solution of sodium polyacrylate, the viscosity of the aqueous solution is high, making impregnation difficult, and the crosslinked product has poor feel. The product obtained by impregnating absorbent cotton with the resin stock solution (4) and polymerizing it is hard, and the water-absorbed product has the unpleasant feel of a hydrated gel. Means for Solving the Problems The inventor of the present invention conducted extensive research to solve the above-mentioned problems and completed the present invention. Polyacrylic acid-based superabsorbent resin absorbs several hundred times its own weight in water, and also has high absorbency against blood, saliva, and the like. Since the water absorption rate of absorbent cotton is about 10 times, it is possible to increase the water absorption rate by 2 to 3 times by incorporating several percent of resin into the absorbent cotton. The product obtained by impregnating absorbent cotton with an aqueous stock solution containing an alkali metal acrylic acid salt as a main component and producing a superabsorbent resin through a radical polymerization reaction, and polymerizing the impregnated product has the above-mentioned drawbacks. By drying and opening the material and uniformly mixing it with absorbent cotton, these drawbacks are not only eliminated, but also
An unexpected effect was found: absorption performance was significantly improved. When opening the dried polymerization reaction product, if the resin content exceeds 35% by weight, the fibers will break and become powder, which is unsuitable. Also, the resin content is 5
% or less, the resin content of the mixture with absorbent cotton decreases, and sufficient improvement in absorbency is not observed. Therefore, the amount of the aqueous stock solution impregnated into the absorbent cotton is such that the amount of resin in the dried polymerization reaction product is 5 to 35% by weight.
should be adjusted within the range of Function The modified absorbent cotton of the present invention has remarkable characteristics compared to resin-impregnated absorbent cotton obtained by impregnating absorbent cotton with an aqueous stock solution and polymerizing it. For example, when making absorbent cotton containing 5% super absorbent resin, compared to the product obtained by impregnating and polymerizing the undiluted solution, open the resin-impregnated absorbent cotton with a resin content of 20%, and use three times the amount of unfiltered cotton. The product obtained by homogeneously mixing with treated absorbent cotton has a significantly lower manufacturing cost, as is clear from the fact that (1) four times the amount of product can be obtained by mixing products obtained through the same process; 2) It has a soft feel similar to that of untreated absorbent cotton, the unpleasant feeling of the hydrated gel is significantly weakened even when water is absorbed, and the hydrated gel does not come loose; (3) the water absorption rate and water absorption capacity are Absorption performance expressed by is significantly improved. Among these characteristics, the improvement in absorption performance shown in (3) is due to the following reasons. When the undiluted solution-impregnated polymer absorbs water, the resin fixed to the entangled fibers absorbs water and swells, binding each other, and the resin's original absorption performance is not exhibited. The phenomenon in which resin is spatially constrained and its swelling is inhibited is also seen, for example, in the case of absorbent materials in which resin powder is sandwiched between sheets of paper. On the other hand, in the modified absorbent cotton of the present invention, which is made by opening the undiluted solution-impregnated polymer and uniformly mixing it with absorbent cotton, the resin-impregnated fibers are spatially diluted by mixing with absorbent cotton, and the resin's original swelling water absorption properties and exhibits high absorption performance. Embodiment An aqueous stock solution containing an alkali metal acrylic acid salt as a main component and producing a superabsorbent resin through a radical polymerization reaction is already known, and these known knowledge are applied to the present invention. The aqueous stock solution is mainly composed of a partial alkali metal salt of acrylic acid, and is adjusted by selectively adding a crosslinkable monomer, another type of water-soluble monomer, and a water-soluble polymer to adjust the crosslink density. Multifunctional monomers such as methylene bisacrylamide and (poly)ethylene glycol bisacrylate are used as crosslinkable monomers. Other components include water-soluble comonomers such as acrylamide, maleic anhydride, and methacrylic acid, and water-soluble polymers such as starch and poval. Concentration is usually 20-50%
The pH is adjusted to a neutral range. Persulfates are commonly used as polymerization initiators. As a method of introducing crosslinks into polymers, a crosslinking agent such as a polyhydric alcohol compound or a polyfunctional epoxy compound that is reactive with the carboxyl groups of the polymer is added to an aqueous stock solution, and a crosslinking reaction occurs during heat drying after polymerization. Methods are also known. Spray the aqueous stock solution onto cotton wool or compress it further to ensure uniform impregnation. The amount of impregnation is adjusted so that the resin content in the dried polymerization product is 5 to 35% by weight. The polymerization reaction is carried out under heating in an atmosphere of an inert gas such as nitrogen, and usually takes less than 30 minutes. The polymerization reaction product is dried and adjusted to an appropriate moisture content, opened by a fiber opening machine, and further mixed uniformly with absorbent cotton. It is also possible to perform opening and mixing at the same time. The modified absorbent cotton of the present invention is further processed into a sheet by secondary processing, and is commercialized in the form of rolled cotton, cut cotton, cotton swabs, etc., and is put into practical use. The secondary processing method is the same as for regular absorbent cotton. Example 1-3 72 parts of acrylic acid, caustic soda (93% purity) 34
0.15 parts methylene bisacrylamide to 250 parts water
1 part, and 0.3 parts of potassium persulfate was added thereto to prepare a stock solution with a concentration of 25%. The stock solution has a pH of 5.8 and is an aqueous solution in which about 80% of acrylic acid is neutralized as a sodium salt. Each sample was uniformly impregnated by spraying 70 parts, 50 parts, and 30 parts of the above stock solution onto 50 parts of absorbent cotton, and was heated to 100°C in a nitrogen atmosphere, while releasing the generated water vapor to the outside of the system. Polymerization was carried out for 30 minutes. The product was dried in a dryer at 120° C. for 1 hour to produce three types of resin-impregnated absorbent cotton with resin contents of 26%, 20%, and 13%, respectively. Next, the above resin-impregnated absorbent cotton was opened and uniformly mixed with twice the amount of absorbent cotton to produce modified absorbent cotton. 1 g of each of the above materials was added to pure water and physiological saline (0.9% saline), and after 1 hour, it was filtered onto a wire mesh, and the water absorption capacity was determined from the weight of the water absorbed. The water absorption ratio represents the weight ratio of water absorbed per 1 g of sample. The results are shown in Table 1.

【table】

[Table] 1 2 3 Comparative example

Claims (1)

[Claims] 1. Absorbent cotton is impregnated with an aqueous stock solution containing an alkali metal acrylic acid salt as the main component and which produces a superabsorbent resin through a radical polymerization reaction at a resin content of 5 to 35% by weight, and the impregnated material is heated and polymerized. death,
A modified absorbent cotton with improved absorbency that does not contain fine resin powder and is obtained by drying and opening a product uniformly impregnated with resin and uniformly mixing it with absorbent cotton.