JPH0377318B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Fields> The present invention is capable of exhibiting the excellent properties of the fluororesin itself, such as heat resistance, chemical resistance, weather resistance, nonflammability, electrical insulation, and non-adhesive properties, as it is as a paper-like product. This invention relates to a method for producing fluorine fiber paper. <Prior Art> In recent years, with the remarkable development of synthetic resins, various synthetic fiber papers containing these synthetic resins as main ingredients have been developed and are widely used in industrial fields. Among them, fluorocarbon resins have excellent heat resistance and chemical resistance, so their production into sheets has been studied, and sheet-like processed products such as films, felts, and cloths have been proposed. However, these sheet-like processed products have drawbacks such as film lacking in air permeability and liquid permeability, felt not being easily made into thin sheets, and cloth having too large pore diameter, so there are major limitations in terms of use. It was hot. In order to solve these problems, paper-like materials made of fluorocarbon fibers are desired, but paper-like materials made from fluorocarbon fibers have the characteristics unique to fluorocarbon resins, that is, they have low surface energy and are non-adhesive. Therefore, the bonding strength between fibers is insufficient, and the actual situation is that it has not yet been obtained. <Problems to be Solved by the Invention> The present invention has been made in view of the above-mentioned circumstances, and provides a sheet made of fluororesin as a paper-like product by a wet papermaking method. <Means for Solving the Problems> The present invention involves mixing fluorine fibers and natural pulp or PVA fibers using a wet papermaking method and drying to produce a fluorine fiber mixed paper that can be handled. After impregnating or applying a resin-based dispersion liquid and drying it to fix the fibers between the fluorocarbon fibers with fluorocarbon resin particles, the natural pulp or PVA fiber used in wet papermaking is Fluorine fibers obtained by dissolving natural pulp or PVA fibers by immersing them in a dissolving solvent, removing the natural pulp or PVA fibers by washing with a solvent, and then re-drying. A paper manufacturing method is provided. The fluorine fiber used in the present invention is a tetrafluoroethylene-ethylene copolymer. The tetrafluoroethylene-ethylene copolymer provides a fluorine fiber having a low softening temperature, excellent processability, and improved water dispersibility. The fluorine fibers used in the present invention need to be short fibers with a fiber length of 1 to 20 mm, and preferably have a fiber diameter of 2 to 30 μmφ in order to be made into a paper-like product by a wet papermaking method. Here, for example, if the fiber length is short, the strength will be weak; conversely, if the fiber length is long, the formation will be poor; if the fiber diameter is thin, the fibers will easily twist; and if the fiber diameter is thick, the sheet will be rough. I become confused. This results in disadvantages such as: The natural pulp used in wet papermaking with fluorine fibers includes wood commonly used for papermaking,
Examples include vegetable fibers such as cotton, linen, and straw. Also,
Paper strength enhancers made of natural polymers or synthetic polymers can be used. In addition, because mixed paper made of fluorocarbon fibers and natural pulp or PVA fibers is impregnated or coated with a dispersion liquid containing fluorocarbon resin as its main component during the process, it is necessary to add it to give it moisture-resistant strength. As the additive for imparting wet strength, for example, known additives such as polyamide epichlorohydrin, fixing hardening agent, etc. can be used as appropriate. In this case, the additive is contained in the mixed paper in a state of being adsorbed to the hydroxyl groups of the natural pulp and PVA fibers, but the content thereof is extremely small. Examples of dispersion liquids whose main component is fluororesin include PTFE, TFE, PFE, ETFE,
A dispersion of fine particles whose main component is a fluororesin such as PVDF or PVF is used. In this case, the type of fluororesin, the size of the dispersed fine particles, the concentration of the dispersion liquid, etc. affect the physical and chemical properties of the fluorocarbon fiber paper, and therefore need to be selected appropriately. In the method for producing fluorine fiber paper according to the present invention, a fluorine fiber mixed paper is first produced by a wet papermaking method. In this case, first, fluorine fibers and natural pulp or PVA fibers are disintegrated and dispersed in water at a predetermined blending ratio. The dispersion is then directly applied to a wet paper machine. Unlike ordinary cellulose fiber paper, it is not necessary in the beating process immediately before papermaking. At this time, any known wet papermaking method can be used without being limited to the type of paper machine. The wet papermaking method uses water as a medium to process fluorine fibers and natural pulp or
PVA fibers are the easiest to disperse and mix;
It can be controlled by additives such as surfactants and adhesives, and is most effective in obtaining paper-like materials with uniform texture. Next, in order to fix the fluorine fibers in the fluorine fiber-mixed paper and obtain interfiber bonding, the fluorine fiber-mixed paper is impregnated or coated with a dispersion liquid containing a fluororesin as a main component. and dry. As a result, the fluorine fine particles adhere to the intertwined points of the fibers and contribute to the bonding between the fibers. As a means for impregnating or coating the fluorine fiber mixed paper with the dispersion liquid, conventionally known impregnation methods, coating methods, and drying methods can be appropriately selected and used. Next, natural pulp or
In order to remove PVA fibers, a method of dissolving them using a solvent is used, but in this case, since fluorine fibers are resistant to a wide range of chemicals, the solvent used is inorganic in the case of natural pulp. Acids and, in the case of PVA fibers, warm water are used. Further, conditions for dissolving and removing the solvent, such as stirring, heating, and circulation, are appropriately set in consideration of productivity and the like.
After removing the natural pulp or PVA fibers in this way, fluorine fiber paper can be obtained by washing with water or the like if necessary and re-drying by any method. Furthermore, in order to obtain fluorocarbon fiber paper with desired physical properties, the type of fluorocarbon fiber, fiber diameter, fiber length and blending ratio, paper-making conditions, the type and amount of fluorocarbon resin to be impregnated or coated, This can be achieved by appropriately controlling the drying conditions and the like. <Examples> The present invention will be further explained by examples. All compounding ratios are expressed in weight ratios. Example 1 90 parts of thermoplastic fluorine fiber made of a copolymer of tetrafluoroethylene and ethylene (Aflon COP manufactured by Asahi Glass Co., Ltd., 10 μmφ x 11 mm product was used) and 10 parts of PVA fiber (VPB105-1 manufactured by Kuraray Co., Ltd.) were mixed. Then, a betaine-type amphoteric surfactant (manufactured by Daiwa Chemical Industry Co., Ltd., using Desglan B) was added to the raw materials (fluorine fiber + PVA).
Indicates fiber. Same as below) Add 0.5%, raw material concentration
It was disintegrated with a stirrer at 0.5%. After that, 2% of the raw material was added with an acrylamide-based dispersant (using Acrypas PMP manufactured by Diafloc Co., Ltd.), formed into a sheet using a TAPPI standard sheet machine, and dried using a Yankee dryer to obtain a fluorine fiber mixed paper with a basis weight of 118 g/ ^m2 . . Next, the paper was immersed in a 15% dispersion solution of DAIFLON D-1 (manufactured by Daikin Industries, Ltd.), which mainly consists of tetrafluoroethylene, to impregnate and adhere a fluororesin, and the paper was deliquified and dried. Thereafter, the paper was placed in hot water of 90° C. or higher to dissolve the PVA fibers, washed with water, and then dried again to obtain the fluorine fiber paper of the present invention. Example 2 80 parts of thermoplastic fluorocarbon fiber made of a copolymer of tetrafluoroethylene and ethylene (Afron COP manufactured by Asahi Glass Co., Ltd., 10 μmφ x 6 mm product) and freeness
Mix 20 parts of NBKP beaten to 40°SR, add 0.5% of betaine type amphoteric surfactant (using Desgulan B manufactured by Daiwa Chemical Industry Co., Ltd.) to the raw material, and make a raw material concentration of 0.5%.
The mixture was disintegrated using a stirrer. After that, polyamide epichlorohydrin (Polyfix 301 manufactured by Showa Kobunshi Co., Ltd.)
(Used) was added in an amount of 0.5% based on the pulp, and a fixing curing agent (Polyfix 33HA manufactured by Showa Kobunshi Co., Ltd. was used) was added in an amount of 0.2% based on the pulp. Further, 1% of an acrylamide dispersant (using Acrypas PMP manufactured by Diafloc Co., Ltd.) was added to the raw material, and the sheet was formed into a sheet using a TAPPI standard sheet machine and dried to obtain a fluorine fiber mixed paper having a weight of 131 g/m ² . Next, the paper was immersed in a 15% dispersion liquid of Daifun D-1 (manufactured by Daikin Industries, Ltd.) whose main component is tetrafluoroethylene, and after impregnating and adhering the fluororesin, the paper was drained and dried. . Thereafter, the paper was immersed in 98% H ₂ SO ₄ liquid at room temperature to dissolve the pulp, washed with water, dried, and treated to obtain fluorine fiber paper as referred to in the present invention. As described above, the fluorine fiber paper obtained in Examples 1 and 2 is a handleable sheet with sufficient physical properties to the extent that it can be handled as a normal paper-like material without any problem, as shown in Table 1. As shown in the enlarged view in Figure 1, its structure is that of fluorine fiber 1.
It was confirmed that the sheet was oriented in an irregular direction, and fine particles of fluororesin were mixed and fixed at the intersection point 2 of the fibers to form interfiber bonds, and the sheet had a porous paper layer structure. . Furthermore, microscopic observation and color reaction tests confirmed that the pulp or PVA fibers used during wet papermaking were completely removed.

[Table] <Effects of the invention> Conventionally, it was not possible to obtain porous thin sheets from fluorocarbon fibers due to their essential characteristics.
The present invention has made it possible to produce paper-like products made of fluorine fibers. Therefore, the fluorocarbon fiber paper obtained in the present invention has the heat resistance, chemical resistance, and
Excellent functions such as nonflammability, electrical insulation, and non-adhesive properties can be used in many applications as a paper-like material, such as insulating materials, filtration materials, spacers, insulating materials, non-adhesive materials, etc. Can be used in the field.

[Brief explanation of drawings]

FIG. 1 is an enlarged view of the surface of the fluorine fiber paper referred to in the present invention. 1...Fluorine fiber, 2...Intersection of fibers, 3...
Fine particles of fluororesin.

Claims (1)

[Claims] 1. Fluorine fiber mixed paper obtained by mixing and drying fluorine fibers made of tetrafluoroethylene-ethylene copolymer and PVA fibers by a wet papermaking method,
A method for producing fluorine fiber paper, which comprises impregnating or applying a dispersion liquid containing fluorine fat as a main component and drying the paper, followed by dissolving and removing the PVA fibers with warm water and drying again. 2 Fluorocarbon fibers made of tetrafluoroethylene-ethylene copolymer and natural pulp are mixed by a wet papermaking method and dried to obtain a fluorocarbon fiber mixed paper,
A method for producing fluorine fiber paper, which comprises impregnating or applying a dispersion liquid containing fluorine fat as a main component and drying, followed by dissolving and removing natural pulp with an inorganic acid and drying again.