JPS6357539B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field] The present invention relates to a method for producing absorbent nonwoven fabrics. More specifically, carboxymethylcellulose sodium chloride can be used as a moisture retaining material for plant growth, and can also be used in sanitary materials such as hospital underpads, diapers, and absorbent belts for sanitary napkins. The present invention relates to a method for producing an absorbent nonwoven fabric made of continuous filaments of cellulose fibers. [Prior Art] It has been known that carboxymethyl cellulose sodium salt (hereinafter abbreviated as CMC-Na) has a high absorption capacity for normal water, physiological saline, and the like. Further, an absorbent body made of CMC-Na with a crosslinked fiber structure is also known from Japanese Patent Publication No. 17965/1983. However, these conventional absorbers are in the form of powders, granules and short fibers. Therefore, in order to use it for the above-mentioned purpose, it is sprayed onto other nonwoven fabrics and bonded thereto to produce a product. However, if it is in powder or granular form, there is a problem that it may spill and it is difficult to disperse it uniformly because it moves easily. There are also paper-like products made using short fibers, but the tensile strength, flexibility,
There are problems with texture, ease of handling, etc. The present inventors conducted intensive research to develop a fabric-like absorbent body that solves the problems of these conventional absorbent bodies, and gradually arrived at the present invention. [Object of the Invention] The object of the present invention is to form a structure by intertwining the constituent fibers themselves without using an adhesive, to have a structure that is firm enough to be handled as a single piece of cloth, and to be able to be wound into a roll. It is highly flexible, has high tensile strength, has a good texture, is easy to handle, and can be used as a sanitary material such as a moisture retention material for growing plants or an absorbent material for sanitary napkins. The present invention provides a method for producing an absorbent nonwoven fabric made of continuous filaments of CMC-Na-contained cellulose fibers. [Structure of the Invention] The gist of the present invention is to roll a nonwoven fabric made of continuous filaments of cellulose fibers, in which the constituent fibers themselves are entangled without an adhesive, onto a cylinder in which injection holes are distributed. After the roll-shaped material is stored in the processing bath, an aqueous alkaline solvent is injected from the cylindrical injection hole so as to penetrate the roll-shaped material, and then the solvent is circulated from the processing bath into the cylinder for processing. A method for producing an absorbent nonwoven fabric containing sodium carboxymethyl cellulose, comprising a continuous filament of cellulose fibers,
A nonwoven fabric made by intertwining the constituent fibers themselves without an adhesive is layered with a spacer and wound into a roll, the roll is placed in a processing bath, and an aqueous alkaline solvent is pumped from the longitudinal direction of the roll. The present invention provides a method for producing an absorbent nonwoven fabric containing carboxymethylcellulose sodium chloride, which is characterized in that the treatment is carried out by circulating the solvent. Conventionally, the starting material fibers for producing CMC-Na are wood pulp, linter, etc. In contrast, in the present invention, a nonwoven fabric is used. According to a conventionally known manufacturing method for CMC-Na, cellulose fibers are converted into alkali cellulose, and then monochloroacetic acid is applied to the cellulose fibers in the presence of isopropanol to convert CMC-Na to salt. Although conventionally known conditions such as composition and concentration can be used for treatment using these conventionally known CMC-Na conversion treatment agents, the present invention will explain them in more detail. A method for producing an absorbent nonwoven fabric is, for example, a method in which cellulose and a carboxymethylated etherifying agent are reacted in an aqueous alkaline medium, and the aqueous alkaline medium is
It is an isopropanol-based aqueous alkaline mixed solvent, preferably a mixed solvent consisting of isopropanol, water, methanol and caustic soda.
As the etherification agent, monochloroacetic acid or a salt thereof is used, and this etherification agent is used in addition to the above solvent. The effective composition of the reaction solvent consisting of the above mixed solvent is basically 45 to 80% by volume of isopropanol, 10 to 30% by volume of methanol, and 10 to 25% by volume of water. Etherification, as is generally known, involves dissolving caustic soda in a solvent, reacting it with cellulose to form alkali cellulose, and then adding an appropriate amount of an etherification agent, i.e., monochloroacetic acid or its salt, to the solvent. Then, it is reacted with alkali cellulose to form CMC-Na. Next, since the starting material is a nonwoven fabric, the following process is used. This is a process in which a spray treatment cylinder with solvent spray holes distributed around its circumference is prepared, a nonwoven fabric as a starting material is wound into a roll, and the cylinder is placed in a treatment bath and a solvent is sprayed internally. . According to such a process, the nonwoven fabric can be treated uniformly. To explain this in more detail, a nonwoven fabric made of continuous filaments of cellulose fibers as a starting material is wound into a roll around an injection treatment cylinder in which solvent injection holes are distributed, and this roll is the treatment bath. Stored in a closed container. A solvent containing caustic soda and monochloroacetic acid as an etherification agent is forced into the cylinder by a pump. The injected solvent is injected from the injection hole and penetrates the nonwoven fabric layer. Meanwhile, the reactant in the solvent (caustic soda or monochloroacetic acid)
will come into contact with cellulose and cause a reaction.
After the treatment, the solvent is discharged from the treatment bath to the outside, and is again forced into the cylinder by the pump, and the treatment is carried out by circulating the solvent. that time,
Since the solvent is adjusted outside the processing bath, the processing is always carried out under constant conditions. Furthermore, since the solvent is forced to pass through the fibers, all treatments are performed uniformly on any part of the nonwoven fabric, resulting in a product of uniform quality. It is desirable that the nonwoven fabric used in this process be porous to the extent that the solvent can penetrate through it due to the injection pressure, or that there are gaps between the fibers. If there are few openings and the fiber gaps are narrow and densely formed, it is difficult for the solvent to penetrate. A separate device is used to process nonwoven fabrics with dense fiber gaps. For example, a nonwoven fabric is layered with a plastic net or corrugated material as a spacer, and this is wound into a coil to form a single roll. This is placed in a processing bath consisting of a cylindrical case, and the roll is rolled. This is a process in which the solvent is pumped in a direction parallel to the axis of rotation. This process allows uniform treatment of densely formed nonwoven fabrics. Needless to say, porous non-woven fabrics can also be treated with this process. The process using the internal injection type device described above is more advantageous because it can shorten the processing time. In addition, to produce absorbent nonwoven fabrics with crosslinked structure on fiber structure, CMC
It is produced by either adding a crosslinking agent to the nonwoven fabric that has been converted into -Na, or converting the nonwoven fabric that has been treated with a crosslinking agent to form a crosslinked structure into CMC-Na. As the crosslinking agent, a processing agent conventionally used as a resin processing agent for cellulose fibers can be used. For example, urea-formaldehyde,
Melamine-formaldehyde, methylated methylol melamine, melamine, dimethylol ethylene urea, dimethylol uron, tetramethylol acetylene diurea, dimethylol triazone, dichloropropanol, divinyl sulfone, epochlorohydrin, acrylic glycidyl ether, butadiene diepoxide etc. The starting material fibers used in the present invention are nonwoven fabrics consisting of continuous filaments of recycled fibers, the recycled fibers being cuprammonium rayon and viscose rayon. The constituent fibers of the nonwoven fabric have a single filament denier of 10 deniers or less, preferably 7 deniers or less.
If it is less than 10 denier, the nonwoven fabric will have poor flexibility and texture. Furthermore, the apparent specific gravity of the nonwoven fabric used in the present invention is 0.03.
Preferably, the range is 0.5 to 0.5 g/cm ³ , and the most preferred range is 0.05 to 0.3 g/cm ³ . 0.03g/
If it is less than 0.5 g/cm ³ , it will be too thin and easily damaged, and if it is more than 0.5 g/cm ³ , it will be too thick and the penetration of the treatment liquid during manufacturing will be poor, making the absorbent treatment less effective. For the apparent specific gravity, a measured value calculated from the basis weight (g/m ² ) and thickness (mm) of the nonwoven fabric is used. Apparent specific gravity (g/cm ³ ) = Area weight (g/m ² )/1000×
Thickness (mm) Fabric weight: Under standard conditions according to JIS-Z-8703, 5 samples of 250 x 150 mm are taken after moisture equilibrium state, their weights are measured, and the average value is calculated per unit area (g/m ² ). Thickness: Take 10 samples under standard conditions, measure the thickness using a microgauge, and express the thickness as the average value (mm). The nonwoven fabric as a starting material used in the present invention is made of a large number of continuous filaments, and the filaments are intertwined with each other to maintain the structure.
No adhesives are used. According to experiments conducted by the present inventors, it has been found that when an adhesive is used, the part is not converted to CMC-Na during treatment, and only a product with a low absorption rate can be obtained. As is conventionally known, cellulose treated with CMC-Na has an excellent ability to absorb water, body fluids, and saline. In the present invention, the above nonwoven fabric is
CMC-Sodium distilled water absorption capacity 20-30 times, 1%
An absorbent nonwoven fabric having an absorption capacity of 20 to 30 times that of saline solution is obtained. CMC-Na having a cross-linked structure also generally has excellent absorption ability for water, body fluids, and saline. In the present invention, the nonwoven fabric is CMC-Na with a crosslinked structure, and the absorption capacity of distilled water is 50 to 100 times, and the absorption capacity of 1% to saline is 20 times.
An absorbent nonwoven fabric exhibiting ~40 times is obtained. The nonwoven fabric used as a starting material in the present invention is, for example, the one disclosed in Japanese Patent Publication No. 1983-6381 filed by the applicant of the present invention. This nonwoven fabric is a porous nonwoven fabric formed from continuous filaments of copper ammonia rayon, and can be selected from a single yarn having a denier of 10 or less and an apparent specific gravity in the range of 0.03 to 0.50 g/cm ³ . The structure is tightly formed by intertwining a large number of continuous filaments, and has high tensile strength, high flexibility, and a good texture. Products processed to form CMC-Na and products made into a cross-linked structure exhibit good flexibility and texture, with only a 20 to 30% decrease in tensile strength. Furthermore, in the present invention, since the starting material itself becomes the absorber, the absorption rate is very fast and the liquid retention after absorption is perfect. [Effects of the Invention] According to the present invention, a structure is formed by intertwining the structural fibers themselves without an adhesive, and the structure is firm enough to be handled as a single piece of cloth, and strong enough to be rolled. It is highly flexible, has high tensile strength, has a good texture, is easy to handle, and can be used as a sanitary material such as a moisture retaining material for growing plants or an absorbent material for sanitary napkins. A method of manufacturing an absorbent nonwoven fabric is provided. [Example] Hereinafter, the present invention will be explained in detail with reference to Examples. Example 1 An example of CMC-Na conversion and an example using an internal injection device A nonwoven fabric made of a continuous filament of copper ammonia rayon disclosed in Japanese Patent Publication No. 52-6381 filed by the applicant of the present invention was used as a starting material. there was. This is a porous material made by intertwining a large number of single 2-denier continuous filaments.
Gives a cotton gauze-like texture. We selected materials with different apparent specific gravity and converted them into CMC-Na. Diameter 1 on the outer peripheral wall of a cylinder with a diameter of 60 mmφ and a length of 300 mm.
An internal injection cylinder with 276 mmφ injection holes evenly distributed was prepared. A nonwoven fabric was wound around this cylinder to form a roll. The width of the non-woven fabric is 40cm, and the length is 30cm~
It was 50m. This was immersed in a treatment bath, heated to 65°C, and a solvent was sprayed and circulated to perform CMC-Na conversion. The solvent was a mixed solvent of 10.3% isopropanol, 2.0% methanol, and 1.7% water per 250g of cellulose, and a concentration of caustic soda of 6.0% by weight.
The solvent was adjusted to have a monochloroacetic acid concentration of 0.6% by weight. The liquid feeding pressure of the circulation pump was 3 to 4 kg/cm ² and the treatment time was 3 to 4 hours. After treatment, the nonwoven fabric is removed from the cylinder and the water content is reduced to 100 using a centor dehydrator.
Dehydrate to ~200%, then methanol
It was washed and dehydrated by immersing it in a solvent of 80:water and 20% (volume ratio). After repeated washing with methanol to completely replace the methanol, the product was dried to obtain a product. Table 1 lists the apparent specific gravity of the starting material nonwoven fabric and the characteristic values of the product.

[Table] Weight of Sample As shown in Table 1, the tensile strength of the product obtained in this example is slightly lower than that of the blank (CMC-Na non-woven fabric for comparison). However, this value is such that the structure does not easily collapse even if it is stretched manually when handled as a single piece of cloth. The flexibility was measured separately for cotton gauze and showed a value of 25 to 30 mm, which was almost the same as that of cotton gauze. In addition, the texture remains almost unchanged before and after treatment, showing a texture similar to cotton gauze. The absorption capacity of distilled water and 1% saline are both 20~
The value is 30 times higher, indicating approximately twice the absorption capacity of the blank. Example 2 Example of cross-linked absorbent nonwoven fabric and example using internal injection device The same nonwoven fabric as used in Example 1 was used as the starting material. and cross-linked structuring and CMC-Na
We carried out transformation. SMITEXNF-113 Special (Sumitomo Chemical KK) as a crosslinking agent, Smitex Accelerator as an auxiliary agent
Using MX (Sumitomo Chemical KK), set the crosslinking agent concentration to 1% (wt%) and the auxiliary agent concentration to 0.5%, prepare a solvent with an amount 15 times the weight of cellulose, fill the treatment bath with this, and let it stand at room temperature. The nonwoven fabric was immersed in this. 15～
After soaking for 20 minutes, take it out and dehydrate it with a centor dehydrator to a moisture content of 100-200%, then hang it on a pin tenter and heat it to the temperature.
It was heat treated at 140°C and dried at the same time. Subsequently, CMC-Na conversion was performed. The internal injection treatment device used was the one used in Example 1, but other chemical concentrations were used,
The processing time and the like were also in accordance with Example 1. Table 2 shows the characteristic values of the product.

[Table] As shown in Table 2, the product obtained in this example shows almost the same tensile strength and flexibility as the product obtained in Example 1. This product usually has excellent water absorption capacity, with an absorption capacity of 60 to 100 times.
The absorption capacity of 1% saline is 20 to 40 times, and Example 1
This value is slightly higher than that of the product obtained in . Example 3 Example of CMC-Na conversion, example using a coil-type device A nonwoven fabric manufactured by the nonwoven fabric manufacturing method disclosed in Japanese Patent Publication No. 1988-988 filed by the applicant of the present invention was used as the starting material nonwoven fabric. This nonwoven fabric is formed from continuous filaments of copper ammonia rayon and has a paper-like appearance and feel. The structure is densely formed, and the processing liquid cannot pass through it using the injection method. A plastic net having the same width and length as the non-woven fabric with a width of 40 cm and a length of 30 to 50 m is layered and wound into a coil shape, and this is stored in a stainless steel cylinder, and the solvent is poured into the cylinder from the long axis direction. The concentration and temperature of the solvent injected and circulated (cylindrical dimensions: diameter 30 cm, length 50 cm) are as in Example 1. The liquid feeding pressure of the circulation pump is 2 to 3 Kg/ ^cm2 , and the processing time is 4 to 5
It was time. The treatment after the completion of the reaction was in accordance with Example 1. Table 3 shows the characteristic values of the product.

[Table] As shown in Table 3, the tensile strength is higher than that of Example 1. This is due to the high cost of the starting materials themselves, but is the more preferred direction. The flexibility is also slightly high, but there are no problems when handling it. The absorption capacity is 15 to 30 times higher for both distilled water and 1% saline. However, as the basis weight increases, the permeation of the treatment liquid becomes poor, and as a result, the absorption capacity decreases. Example 4 Example of crosslinked structured absorbent nonwoven fabric, example using coil type device The same starting material nonwoven fabric as used in Example 3 was used. First, in order to carry out the crosslinking treatment, the same crosslinking agent used in Example 2 was used, the concentration was adjusted in the same manner as in Example 2, the treatment bath was filled with a solvent, the nonwoven fabric was immersed in it, and the crosslinking reaction took place at room temperature. was made to do so. After soaking for 20 to 30 minutes, it was pulled out, dehydrated to a water content of 100 to 200% using a centor dehydrator, placed in a pin tenter, heat-treated at a temperature of 140°C, and dried at the same time. Subsequently, CMC-Na conversion was performed. Plastic nets having the same width and length as the nonwoven fabric were layered and wound into a coil, which was then stored in a stainless steel cylinder, and a solvent was injected into the cylinder and circulated. The concentration and temperature of the solvent are as in Example 1. The liquid feeding pressure of the circulation pump was 2 to 3 kg/cm ² and the treatment time was 4 to 5 hours. The treatment after the completion of the reaction was in accordance with Example 1. Table 4 shows the characteristic values of the product.

[Table] As shown in Table 4, the tensile strength and flexibility values are almost the same as those of the product obtained in Example 3. This product has an excellent ability to absorb normal water, with an absorption capacity of 50 to 70 times. The absorption capacity of 1% saline is
This value is 15 to 30 times higher than that of the product obtained in Example 3. In general, coil systems have poorer solvent penetration and lower absorption capacity than jet systems. Even so, the value is several times higher than that of the blank.

Claims (1)

[Claims] 1. A nonwoven fabric made of a continuous filament of cellulose fibers, in which the constituent fibers themselves are intertwined without an adhesive, is wound into a roll on a cylinder in which injection holes are distributed, and the roll is rolled. After storing it in a processing bath, an aqueous alkaline solvent is injected from the cylindrical injection hole so as to penetrate the roll-shaped object, and the solvent is subsequently circulated from the processing bath into the cylinder to perform processing. A method for producing an absorbent nonwoven fabric characterized by carboxymethyl cellulose sodium chloride. 2. A nonwoven fabric made of continuous filaments of cellulose fibers, in which the constituent fibers themselves are intertwined without an adhesive, is layered with a spacer and wound into a roll, and the roll is placed in a processing bath. 1. A method for producing an absorbent nonwoven fabric containing carboxymethyl cellulose sodium chloride, characterized in that the treatment is carried out by pumping an aqueous alkaline solvent from the long axis direction of the fabric and subsequently circulating the solvent.