JPH022982B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing an absorbent material, and more particularly, to a method for producing an absorbent material having excellent absorbency for aqueous liquids. [Prior art] Thermoplastic resin fibers are mixed with a vegetable fiber material made by finely pulverizing wood pulp, etc., and moderately pressurized while applying heat to form a three-dimensional fibrous absorbent material, which is used for purposes such as disposable diapers. is Japanese Patent Publication No. 53-17455
It is disclosed in the publication No. In addition, JP-A No. 55-16611 discloses that wood pulp, thermoplastic resin fibers, and powders of water-retentive polymers such as polyglucose or sutucarose grafted with acrylic acid are used in combination to obtain paper by dry papermaking. It is disclosed that the water-absorbent sheet is used for purposes such as disposable diapers. In these technologies, it is desirable that the thermoplastic resin fiber material is mixed more uniformly into the wood pulp, and the thermoplastic resin fibers are melted by heat treatment and the wood pulp is moored at various locations. . It is known that such absorbent materials have strengthened intertwining of fibers, resulting in products with excellent shape stability such as elasticity and restorability. [Problems to be Solved by the Invention] However, when a large amount of thermoplastic resin fiber is blended, although the mechanical strength of the absorbent material is improved, a decrease in water absorbency cannot be avoided. Therefore, the proportion of thermoplastic resin fibers used is determined depending on the application, taking into consideration mechanical strength and water absorption performance. On the other hand, to improve the hydrophilicity of thermoplastic resin,
The surface was treated with various surfactants such as polyvinyl alcohol and polyacrylic acid.
It is known from Publication No. 47049. However, the absorption performance of absorbent materials made by using these fibers in combination differs markedly depending on the type of surfactant, and some require repeated compression and restoration to absorb water forcibly. For some products, simply dropping water on the surface will not absorb the water. Furthermore, JP-A-54-59466 discloses a pulp-like material prepared by blending a polypropylene resin with 10% by weight of a surfactant, which is then used as a vegetable fiber material. . However, since most of the surfactant in such absorbent materials is present inside the pulp-like material, its contribution to hydrophilicity is low despite the large amount of surfactant contained within the pulp, and on the contrary, it is difficult to maintain low temperatures during heat fusion processing. There is a risk that the fiber form will be easily lost, making it undesirable as an absorbent material. The present invention
This was developed in view of these circumstances, and relates to a method for producing an absorbent material that uses thermoplastic resin fibers as described above. The purpose is to provide a method for producing absorbent materials. [Means for solving the problem] In order to achieve the above object, in the method for producing an absorbent material according to the present invention, the surface or surface layer is coated with a nonionic surfactant having an HLB value in the range of 3 to 20. The retained amount of the nonionic surfactant was treated with
5 to 50% by weight of thermoplastic resin pulp which is 0.5% to 4% by weight and vegetable fiber material 95
It is characterized in that it is mixed with 50% by weight and subjected to heat fusion treatment via a fluid heat medium. [Preferred Embodiments of the Invention] Preferred embodiments of the method for producing an absorbent material according to the present invention will be described below. (1) Thermoplastic resin pulp used (hereinafter referred to as
It is sometimes abbreviated as "synthetic pulp." ) is one or two α-olefins such as polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-1-butene copolymer, and ethylene-4-methyl-1-pentene copolymer.
A fine fibrous material of a polyolefin resin consisting of at least one type of polyolefin resin is suitable, and one obtained, for example, by the flash spinning method disclosed in Japanese Patent Publication No. 52-47049 is preferred. (2) The nonionic surfactants used are:
Examples include polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene fatty acid ester, and the like. Among them, 1,5-sorbitan, 3,4-
Sorbitan, sorbitan monofatty acid ester such as 1,4-sorbitan, or a compound obtained by reacting sorbitan monofatty acid with polyalkylene oxide such as polyethylene oxide,
Partial esters of polyhydric alcohols such as glycerine difatty acid ethylene are preferred. These nonionic surfactants are used to pre-treat the surface and surface layer of thermoplastic resin pulp (in the case of flash spinning described below), and then mix it with vegetable fiber material and heat it. By fusion treatment, only the surface of the thermoplastic resin pulp is melted, and while maintaining the form of the thermoplastic resin pulp, it is combined with the vegetable fiber material and becomes an absorbent material. be.
At this time, the nonionic surfactant is added to the surface and surface layer of the thermoplastic resin pulp in an amount of 0.5% by weight or more and 4% by weight or less, preferably 0.7 to 3% by weight.
retained at a rate of If the amount of nonionic surfactant is large or contained in a large amount inside the thermoplastic resin pulp, the mechanical strength will decrease.
The commercial value as an absorbent material will be inferior. Absorbent materials obtained using these nonionic surfactants have particularly excellent permeability to aqueous liquids, and also excellent retention of permeated aqueous liquids. The nonionic surfactants used in the present invention are generally not water-soluble and can have various HLB values. Among them, those with a large HLB value improve the aqueous liquid permeability even in a relatively small amount, and even after the aqueous liquid has penetrated into the absorbent material, the absorbent material can continue to effectively retain the aqueous liquid. In addition, if the HLB value is too large, the lipophilicity will decrease and the compatibility with the thermoplastic resin will deteriorate, and the nonionic surfactant will have poor adsorption to the thermoplastic resin during processing and Retention to resin deteriorates. Therefore, in order to meet these requirements,
The HLB value of the nonionic surfactant is in the range of 3 to 20, more preferably in the range of 4 to 17. The following various methods are employed to treat synthetic pulp with a nonionic surfactant. A wet method in which synthetic pulp is immersed in a water chiller containing a nonionic surfactant. In addition, when forming a thermoplastic resin into a synthetic pulp-like material by a flash spinning method or the like, a high-temperature solution or melt of the thermoplastic resin is spouted into a solution containing a nonionic surfactant. It is preferable to impregnate the surface layer of the synthetic pulp with a nonionic surfactant at the same time as forming the synthetic pulp of the thermoplastic resin. A dry method in which the surface of synthetic pulp is coated with a nonionic surfactant by spraying or other methods. Among these, in the present invention, a nonionic surfactant with an HLB value of 3 to 20 is preferable because almost the entire amount can be efficiently adsorbed to the synthetic pulp by simply adding and stirring it to the water slurry of the synthetic pulp. Recommended treatment method. (3) Vegetable fiber materials (hereinafter sometimes abbreviated as "wood pulp") include various wood pulps,
Rayon short fibers are exemplified. (4) The absorption material is a mixture of 5 to 50% by weight of synthetic pulp previously treated with a nonionic surfactant and 95 to 50% by weight of wood pulp, formed into a web, and then heated with a fluid heat medium. It is manufactured by heat-sealing the material through a heat-sealing method. To obtain a mixture of synthetic pulp and wood pulp, either a wet papermaking method or a dry papermaking method can be employed. When the proportion of synthetic pulp is less than 5% by weight,
There is almost no improvement in mechanical strength due to fusing treatment, and if the content exceeds 50% by weight, a decline in absorption performance is unavoidable. Further, in order to fuse the synthetic pulp, indirect heating using an air oven, an infrared heater, etc. is performed. Indirect heating means heating by a fluid heat medium such as gas or liquid. This type of indirect heating can uniformly heat-fuse the surface and interior of the absorbent material at the same time in a pressureless state. Therefore, it is possible to create bulky absorbent materials while maintaining the form of synthetic pulp. can be obtained. Although the heating temperature depends on the type of thermoplastic resin that is the raw material for the synthetic pulp, it is preferably in the range of at least the melting point of the thermoplastic resin used to about 50° C. higher than the melting point. The absorbent material of the present invention is usually in the form of a web, and its bulk density can be adjusted to a certain extent by adjusting the heating temperature and pressurizing conditions, and if necessary, press treatment is performed simultaneously with fusing treatment. Products can be made of various bulk densities. The absorbent material of the present invention may contain other water-retaining substances in order to further improve its absorbent performance. Examples of such water-retentive substances include fine particles of various polymer electrolytes as disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 16611/1983. Among these, suitable concomitant materials are wood pulp, cotton, polyglycose or succalose such as starch, and hydrophilic groups or hydrolysates such as acrylic acid and acrylonitrile. [Effects of the invention] The absorbent material obtained by the production method of the present invention is
It has excellent absorbency and retention of water-based liquids, has excellent mechanical strength, and can be easily manufactured.It is used for sanitary napkins, medical sponges, wound dressing pads, towels, etc., and has water retention properties depending on the purpose. Lamination of a small exterior material or water-impermeable backing material is carried out. [Example] Examples are shown below. Example 1 20 g of high-density polyethylene synthetic pulp (average fiber length: 0.9 mm) was put into 1 water, 150 mg of glycerin monostearate was added, stirred, and then separated and collected. This synthetic pulp contained 0.75% by weight of glycerin monostearate. 12 g of this synthetic pulp and 48 g of paper cotton were uniformly mixed and formed into a web-like product with a basis weight of 375 g/m ² by dry papermaking. This web-like material was placed in an air oven at 150° C. for 10 minutes to perform a synthetic pulp fusing treatment. In order to check the absorption performance of the obtained absorbent material, 1 c.c. of tap water was dropped with a dropper onto the surface of the absorbent material placed horizontally, and the water droplets penetrated into the interior of the absorbent material from the surface. As a result of measuring the time required to complete the process, it was 0.7 seconds. Examples 2 and 3 The same procedure as in Example 1 was carried out except that the amount of glycerin monostearate used for the synthetic pulp was changed. The results are shown in Table 1. 【table】

Claims (1)

[Claims] 1 The surface or surface layer is treated with a nonionic surfactant with an HLB value in the range of 3 to 20, and the retained amount of the nonionic surfactant is 0.5% by weight or more 4
Thermoplastic resin pulp-like material that is not more than 5% by weight
1. A method for producing an absorbent material, which comprises mixing 50% by weight of a vegetable fiber material and 95 to 50% by weight of a vegetable fiber material, and subjecting the mixture to heat fusion treatment via a fluid heat medium.