JPS6367577B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a hot-press molded product made of water-absorbing acrylonitrile (hereinafter referred to as AN) fibers, and more specifically, it uses two types of AN-based polymers with different AN contents, and moreover, The large polymer component exhibits a microporous structure with a void diameter of 0.2μ or less, and the polymer component with a small AN content exhibits a dense structure, providing excellent water absorption and good mechanical strength. The present invention relates to an AN-based fiber molded product having excellent shape stability, which is obtained by thermo-pressing a fiber aggregate containing AN-based fibers having the following properties. Conventionally, the mainstream method for manufacturing nonwoven fabrics or sheets has been to use organic solvent solutions or emulsion type binders, but this method requires steps such as solvent recovery and binder wastewater treatment, and also depends on the type of binder. There are problems in that the quality and feel of the starting fiber material are significantly affected by the On the other hand, in order to improve these drawbacks, attempts are being made to form non-woven fabrics etc. by heat-pressing self-fusing fibers, but this method involves melting some or all of the constituent fibers. The texture of the resulting nonwoven fabrics, etc. has the disadvantage of being rigid or brittle, and it is necessary to use heat-melting fiber materials such as polypropylene that have no water absorption or hygroscopicity. There are inherent difficulties in manufacturing. Therefore, in order to improve the lack of water absorbency of such nonwoven fabrics, attempts have been made to incorporate highly water-swellable organic polymers between the nonwoven fibers; Therefore, deformation during water absorption cannot be avoided, and this method cannot be applied in fields of use where shape stability is required. The present inventors have conducted intensive studies to obtain a fiber molded product that has a flexible texture and excellent water absorption without the above-mentioned drawbacks. It is possible to easily form a fiber molded product with excellent shape stability by easily causing interfiber adhesion while maintaining good texture, good water absorbency, and good mechanical properties, and the hot-press molded product is free from capillary action. The present invention was achieved based on the discovery that the diffusion rate of water increases significantly and the wettability increases. That is, the object of the present invention is to create a fiber molded product that has practical properties such as the soft texture, dye fastness, and strong elongation inherent to AN fibers, and also exhibits stable water absorption without losing its shape. It is about providing. Another object of the present invention is to provide an industrially advantageous water-absorbing AN fiber molded product that does not cause problems such as changes in the quality or texture of the starting fibers or wastewater treatment due to the use of a binder, and has low energy consumption. The purpose is to propose a means of production. Still other objects of the present invention will become clear from the description below. Thus, a water-absorbing AN that achieves the above object of the present invention
The fiber contains more than 90% by weight of AN.
consisting of an AN-based polymer () and an AN-based polymer () containing 88% by weight or less of AN in combination, and the polymer () component has a microporous structure with a void diameter of 0.2 μ or less, A fiber aggregate containing AN fibers in which the polymer () component has a dense structure is formed by hot-press molding. The AN fiber according to the present invention has an AN of 90
The void diameter is 0.2μ in the polymer component containing more than % by weight.
Because it has the following large number of micropores and has a dense structure in the polymer component of 88% by weight or less, it simultaneously has water absorbency and mechanical properties on the same level as conventional AN fibers. It will satisfy you. What is even more surprising is that there is no skin layer in the porous part, and the micropores maintain an appropriate particle size and exhibit capillary behavior, which has the ability to instantly absorb water. becomes. In addition, the moisture that is instantly absorbed is released to the outside through the voids inside the fibers, and this release rate is faster than that of cotton, so that it does not give a sticky feeling.
The water absorption, water diffusivity, and mechanical properties of the AN-based fibers of the present invention greatly affect the water absorption, water diffusivity, tensile strength, and morphological stability of molded products obtained by hot-press molding. It's what it does. In water-absorbing AN-based fibers having the above-mentioned unique structure, an AN-based polymer () containing 90% by weight or more of AN and 88% by weight or less of AN
It is important to use the AN-based polymer () as both components, and to form the polymer () component into a microporous structure and the polymer () component into a dense structure. When the AN content of the polymer () is less than 90% by weight and when the AN content of the polymer () is 88
If the amount exceeds the weight percentage, AN-based fibers that achieve the desired purpose cannot be obtained. Both polymer components can be arbitrarily selected from composite types (for example, side-by-side type, sheath core type, random type) in which at least a part of the polymer () has a cross-sectional shape exposed on the fiber surface, but side-by-side type is preferable. Alternatively, the object of the present invention can be advantageously achieved by adopting a sheath core type. Moreover, the above-mentioned polymers () and () can be produced by well-known polymerization methods (suspension polymerization method, emulsion polymerization method, solution polymerization method, etc.). Each of these polymers is produced by copolymerizing a predetermined amount of AN and an unsaturated vinyl compound that is copolymerizable with AN. Such unsaturated vinyl compounds include:
Acrylic acid, methacrylic acid or esters such as methyl esters and ethyl esters; acrylamide, methacrylamide or N-alkyl substituted products thereof; vinyl esters such as vinyl acetate and vinyl propionate; vinyl chloride, vinyl bromide, Vinyl halides or vinylidenes such as vinylidene chloride; Unsaturated sulfonic acids such as vinyl sulfonic acid and p-styrene sulfonic acid, or their salts; Dimethylaminoethyl ester of acrylic acid and methacrylic acid; Styrene, etc. alone or in combination Can be used. The polymer () or polymer () produced in this manner is dissolved in a common fiber solvent to form a spinning dope, which is then spun through a known nozzle. Composite spinning is used as the spinning means in this case, but
Among these, side-by-side composite spinning is recommended.
The composite ratio (abundance ratio) of polymer ()/polymer () in such composite spinning can be selected from the range of 80/20 to 10/90. Outside this range, problems such as insufficient water absorption performance and no improvement in mechanical strength may occur. Although spinning is performed in this manner, formation of a heterogeneous structure between both polymer components is difficult under normal wet spinning conditions, and can be achieved by selecting the following means. That is, when an inorganic salt such as sodium rhodanate is used as a solvent, the fibers spun as described above are heated at 3°C to
It is produced by solidifying at 15°C, washing with water, hot stretching, further moist heat treatment, and drying at 80°C to 130°C. If the coagulation bath temperature is less than 3℃
If the temperature exceeds 15°C, the spinnability deteriorates, which is not preferable. On the other hand, if the drying temperature is less than 80°C, productivity will decrease, and if it exceeds 130°C, micropores may disappear, which is not desirable. Note that the moist heat treatment includes steam treatment, boiling water treatment, and the like. In addition, when using organic solvents,
It is desirable to maintain the coagulation bath temperature at 40°C or higher, preferably at 50°C or higher. The AN-based fiber obtained in this way has excellent water absorption performance because it has a part with many micropores with a void diameter of 0.2μ or less and a dense part that are integrated into the fiber structure. Moreover, it has good processability such as spinning and is rich in commercial value. Further, as described above, the AN-based fiber according to the present invention also has the ability to instantly absorb water, so it greatly increases consumption performance. The above-mentioned fiber aggregate containing AN fibers according to the present invention refers to the AN fibers alone or the fibers and various synthetic fibers such as polyester, polyamide, polyacrylonitrile, modacrylic, polyolefin, etc. Refers to products that are mixed with other fibers such as synthetic fibers and natural fibers. Also the above AN
The fiber content may be set as appropriate depending on the use of the final product, but from the viewpoint of water absorption, strength and elongation of the final product, it is desirable to set the content to 10% by weight or more. Next, a method of thermoforming such a fiber aggregate will be described. As such molding conditions, a temperature of approximately 100 to 220°C, preferably 125 to 200°C, and a pressure of approximately 2 kg/cm ² or more, preferably approximately 3 to 50 kg/cm ² are employed. Note that it is preferable to carry out such hot-press molding in a moist heat atmosphere because the molding can be performed effectively at relatively low temperature and low pressure conditions. The shape of the fiber aggregate subjected to such thermoforming is as follows:
A web-like material is preferable, and in such an embodiment, a nonwoven fabric or sheet can be provided industrially advantageously without using a binder or the like, but it is not formed into a specific shape for final use. Also, if desired,
It may be a fiber aggregate subjected to secondary processing such as needle felt, roving, yarn, knitted fabric, etc., and further,
As long as it can be molded under heat and pressure, it may be coated with or contain a fiber oil, a stabilizer, or the like, or it may be dyed. Furthermore, it goes without saying that products in the process of fiber production, such as undried products, can be used if desired. In this way, it is possible to provide a fiber molded product having a water retention rate of 15% or more, more preferably 20% or more. In this way, although conventional AN-based fibers had insufficient hot-press moldability, by adopting the specific water-absorbing AN-based fibers of the present invention, the water-absorbing properties
Maintaining the properties inherent in AN-based fibers,
A notable advantage of the present invention is that it can provide a hot-press molded product that has industrially advantageous form stability, water absorption, etc. while maintaining the practical properties such as strength and elongation and dyeability inherent to AN fibers. It is. Although it is not clear why the water-absorbing AN-based fibers according to the present invention have thermoforming ability, it is possible that the fine structure of the fibers is partially modified by voids created by introducing a specific AN content in the fibers or on the fiber surface. It is thought that interfiber adhesion occurs due to appropriate turbulence. However, it makes the water absorbent
The water absorption capacity, water diffusion capacity, and mechanical properties of AN-based fibers are not impaired. Another advantage of the present invention is that it can be provided with a soft texture to a texture with an appropriate hardness depending on the hot-press molding conditions (temperature, pressure, etc.), the amount of adhesion between fibers, etc. It is. As mentioned above, the water-absorbing AN-based fiber molded product according to the present invention, which has many advantages in terms of practical performance, takes advantage of its characteristics such as strong elongation, dyeability, texture, shape retention, and water absorption, and can be used as a nonwoven fabric, It can be used in various fields such as sanitary products such as napkins and tampons, diapers, absorbent paper, and filters in sheet or desired shapes. The effects of the present invention will be explained in more detail with reference to Examples below. In the examples, parts and percentages are expressed on a weight basis unless otherwise specified. In addition, the water retention rate and water diffusion area shown in the following examples were measured or calculated by the following method, and the tensile strength was a value measured according to JISP8113. (1) Water retention rate (%) Approximately 1 g of sample fibers cut to a length of approximately 5 cm and well opened were immersed in pure water, and after 2 hours at 25°C, the sample fibers were soaked in a centrifugal dehydrator (Konkusan Enshinki). KK)
The water between the fibers was removed using a 12cm diameter spinner with a rotation speed of 2000 rpm for 5 minutes. The weight (w ₁ ) of the sample thus prepared is measured. Next, the sample is dried in a vacuum dryer at 80° C. until it reaches a constant weight, and the weight (w ₂ ) is measured. Based on the above measurement results, it is calculated using the following formula. Water retention rate = w ₁ −w ₂ /w ₂ ×100 (2) Water diffusion area (cm ² ) One drop of water was dropped with a dropper from a distance of 2 cm, and the area that was diffused and wet after 1 minute had passed is shown. Example 1 AN copolymer () consisting of 91% AN, 8.7% methyl acrylate (MA) and 0.3% sodium methallylsulfonate (MAS) and 87% AN, 12.7% MA and
AN copolymer (2) consisting of 0.3% MAS was dissolved in an aqueous solution of sodium rhodanate to prepare two types of spinning stock solutions. Using these spinning stock solutions, (i) each individual spinning (ii) polymer (); polymer () = 1:1
Composite spinning (spinning equipment was manufactured by the Special Publication Corporation in 1977)
11122)) and three types of AN
A fiber based on this method was produced. Coagulation was performed in a 12% sodium rhodanate aqueous solution at 10°C, followed by water washing and hot stretching, and the resulting fibers were stretched in a relaxed state without drying.
Steam treatment at 115°C, then 15°C at 100°C.
It was prepared by drying for minutes. When the cross section of the obtained No. 3 fiber was observed with a scanning electron microscope at a magnification of 10,000 times, it was found that there were many micropores with a void diameter of 0.2μ or less on the polymer () component side. On the other hand, the polymer () component side exhibited a complete dense structure. The fiber performance of each AN-based fiber is listed in Table 1.

[Table] From the results in Table 1, it can be seen that the AN-based fiber (No. 3) according to the present invention is a product with excellent water absorption capacity, strength and elongation, and has high commercial value. In addition, good water retention capacity requires a water retention rate of 15% or more, and a knot strength of 1.5 g/d.
If the dry elongation is not above 30% or more, problems will occur during processing such as spinning. Furthermore, when the underwear made from No. 3 AN-based fiber came into contact with water, it instantly absorbed the water, and after a while it regained a smooth feel. The above fibers (Nos. 1 to 3) were made into a web with a weight of 60 g/m ² using a card machine. Fibers No. 2 and 3 showed good card passing properties, but fiber No. 1 was found to have static electricity and fly. Further, webs No. 1 and 3 had excellent entanglement properties and excellent moldability, whereas web No. 2 had poor entanglement properties and thus had poor moldability. Table 2 shows the results of measuring the tensile strength and water retention of three types of sheets obtained by thermoforming this web under conditions of 180° C. x 10 kg/cm ² in a dry heat atmosphere.

[Table] As is clear from the above results, the fiber molded article according to the present invention (used No. 3) was excellent in strength, water retention, and water diffusivity, and did not lose its shape at all even when water was absorbed. On the other hand, with normal AN fibers, almost no thermoformability was observed. Example 2 Water absorption according to Example 1 containing 20% moisture
Web made of AN fiber (No. 3) (weighing 100
g/m ² ) is placed in a cup-shaped female mold, a male mold is placed on top of this, and a pressure of 15 kg/cm ² is placed in a heated oven. When processed at 130°C, a flexible product molded along the female mold is formed. A thick web was obtained. The water retention rate of the obtained web was 38%, and no swelling or deformation of the web was observed when it absorbed water.

Claims (1)

[Claims] 1. Acrylonitrile polymer () containing 90% by weight or more of acrylonitrile combined with 88% by weight
It consists of an acrylonitrile polymer () containing the following acrylonitrile in combination, and the polymer () component has a microporous structure with a poid diameter of 0.2 μ or less, and the polymer () component has a dense structure. A water-absorbing acrylonitrile fiber molded product obtained by thermo-pressing a fiber aggregate containing acrylonitrile fibers. 2. The molded product according to claim 1, which uses acrylonitrile fibers in which the polymer () and the polymer () form a composite form. 3. The molded article according to claim 2, which uses acrylonitrile fibers in which the polymer () and the polymer () form a side-by-side composite structure. 4 Water-absorbing acrylonitrile fiber at least
The molded article according to claim 1, which uses a fiber aggregate containing 10% by weight. 5 Claim 1 where the water retention rate is 15% or more
Molded products described in Section 1.