JPH0450432B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Field of Application> The present invention allows the excellent properties of the fluororesin itself, such as heat resistance, chemical resistance, weather resistance, nonflammability, electrical insulation, and non-adhesiveness, to be exhibited as they are in the form of a paper-like product. This paper relates to fluorine fiber paper and its manufacturing method. <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 unique characteristics of fluorocarbon resins, namely, low surface energy and non-adhesion. Therefore, the bonding strength between fibers is insufficient, and the actual situation is that it has not yet been achieved. <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 inventors have carried out extensive studies in order to obtain a paper-like material made of fluorocarbon fibers, and as a result, they have found that fluorocarbon fibers are produced by mixing fluorocarbon fibers with natural pulp or PVA fibers. We have discovered that fluorocarbon paper can be obtained by producing a mixed paper, heat-sealing the fluorocarbon fibers, and then removing the natural pulp or PVA fibers. That is, the present invention uses fluorine fiber and natural pulp or
By mixing PVA fiber with wet papermaking method and drying it, we create a fluorine fiber mixed paper that can be handled.
Next, the paper is thermocompressed at a temperature higher than the softening point of the fluorine fibers to heat-fuse the fibers of the fluorine fibers to make moisture-resistant strong paper, and then the natural pulp or PVA used for wet papermaking is Natural pulp or PVA fibers are dissolved by immersing them in a solvent that dissolves fibers, and further washed with a solvent if necessary to produce natural pulp or PVA fibers.
The present invention provides a fluorine fiber paper obtained by removing PVA fibers and then re-drying the paper, and a method for producing the same. For the fluorine fiber of the present invention, a tetrafluoroethylene-ethylene copolymer is used. The tetrafluoroethylene-ethylene copolymer has a low softening temperature, excellent processability, and provides fluorine fibers with 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. This results in disadvantages such as: The natural pulps used in wet papermaking include wood, cotton, hemp, and
Examples include plant fibers such as straw. Further, a paper strength enhancer made of a natural polymer or a synthetic polymer can be used. In the method for producing fluorine fiber paper of the present invention,
First, fluorine fiber mixed paper is 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, the beating process immediately before papermaking is not necessary. 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, thermocompression bonding is performed in order to fix the fluorine fibers in the obtained fluorine fiber mixed paper together and obtain fiber-to-fiber bonding, and known methods such as hot press and heat roll can be used for this purpose. Applicable. In this case, the treatment temperature needs to be set above the softening point of the fluorine fiber, and is usually about 180 to 300°C.
Conditions such as nip pressure and pressurizing time may be appropriately set depending on the type of fluorine fiber, that is, softening point, fiber hardness, fiber diameter, etc. By thermocompression bonding treatment using such temperature settings, bonding occurs between the fluorocarbon fibers by heat fusion. Next, a method of dissolving and removing natural pulp or PVA fibers using a solvent is used to remove the natural pulp or PVA fibers from the thermocompressed fluorine fiber mixed paper, but in this case, fluorine fibers are resistant to a wide range of chemicals. Therefore, the solvent used is natural pulp or
It may be selected appropriately considering the type of PVA fiber.
For example, in the case of natural pulp, inorganic acids and PVA
In the case of fibers, warm water is used as a solvent. 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, this can be achieved by appropriately controlling the type of fluorocarbon fiber, fiber diameter, fiber length, blending ratio, papermaking conditions, thermocompression bonding conditions, etc. can do. <Examples> The present invention will be further explained by examples. All compounding ratios are expressed on a weight basis. Example 1 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 11 mm product) and beating degree
Disperse and mix 20 parts of NBKP beaten to 40°SR in water, and add a betaine type amphoteric surfactant (manufactured by Daiwa Chemical Co., Ltd., using Desgrand B) to the raw materials (for fluorocarbon fibers and pulp. The same applies below) ) 0.5% and melted with a stirrer at a raw material concentration of 0.5%. After that, 1% of the raw material was added with an acrylamide-based dispersant (using Acrypas PMP manufactured by Diafloc Co., Ltd.), and TAPPI
It was formed into a sheet using a standard sheet machine and dried to obtain a fluorine fiber mixed paper having a basis weight of 115 g/m ² . After that, this fluorine fiber mixed paper was heated and pressurized at 220°C at 10 kg/cm ² for 20 minutes, and then immersed in 98% H ₂ SO ₄ solution at room temperature to dissolve the pulp in the fluorine fiber mixed paper.
This was washed with water and dried again to obtain the fluorine fiber paper of the present invention. Example 2 90 parts of thermoplastic fluorocarbon fiber made of a copolymer of tetrafluoroethylene and ethylene (Aflon COP, 10 μm x 6 mm manufactured by Asahi Glass Co., Ltd.) and 10 parts of PVA fiber (VPB105-1 manufactured by Kuraray Co., Ltd.) were used. Disperse and mix in water, add 0.5% of betaine type amphoteric surfactant (using Desblan B manufactured by Daiwa Chemical Industry Co., Ltd.) based on the raw material,
Disintegration was performed using a stirrer at a raw material concentration of 0.5%. Then add 2% acrylamide dispersant to the raw material.
It was 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 111 g/m ² . Then the paper was heated to 222℃10
Kg/cm ² The paper was heated and pressurized for 20 minutes, then immersed in hot water of 90° C. or higher to dissolve the PVA fibers, washed with water, and then dried to obtain the fluorine fiber paper of the present invention. Example 3 95 parts of thermoplastic fluorocarbon fiber made of a copolymer of tetrafluoroethylene and ethylene (Aflon COP manufactured by Asahi Glass Co., Ltd., 10 μmφ x 5 mm) and 5 parts of microfibrous cellulose (MFC manufactured by Daicel Chemical Industries, Ltd.)
Disperse and mix in water, add 0.5% betaine-type amphoteric surfactant (using Desglan B manufactured by Daiwa Chemical Industry Co., Ltd.) to the raw material, mix with a stirrer at a raw material concentration of 0.5%, and add the acrylamide-based dispersant to the raw material. 2% was added, formed into a sheet using a TAPPI standard sheet machine, and dried to obtain fluorine fiber mixed paper with a basis weight of 140 g/m ² . Next, the paper was heated and pressurized at 220°C for 20 minutes at 10 kg/cm ² and then immersed in 98% H ₂ SO ₄ solution at room temperature to dissolve the fine cellulose fibers in the fluorine fiber-mixed paper, which was then washed with water. It was dried again to obtain the fluorine fiber paper of the present invention. Example 4 After obtaining fluorine fiber mixed paper in the same manner as in Example 1, the paper was heated and pressurized using a hard roll at 220°C, 200 kg/cm, and 3 m/min, and further heated to 98% at room temperature. The bulb portion in the fluorine fiber mixed paper was dissolved by dipping it in H ₂ SO ₄ liquid, and this was washed with water and dried again to obtain the fluorine fiber paper of the present invention. As shown in Table 1, the fluorine fiber papers obtained in Examples 1 to 4 have sufficient physical properties and are easy to handle without causing any problems when handled as ordinary paper-like materials. It is a sheet, and its structure is as shown in the enlarged view in Figure 1.
It was confirmed that the sheet had a porous paper layer structure in which the fibers were oriented in irregular directions and were thermally fused at the intersection points 2 of the fibers. Furthermore, it was confirmed through a microscope and a color reaction test that the pulp or PVA fibers used during wet papermaking were completely removed.

【table】

[Table] <Effects of the invention> Conventionally, it was not possible to obtain porous thin sheets from fluorine 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 the drawing]

FIG. 1 is an enlarged view of the surface of the fluorine fiber paper of the present invention. 1...Fluorine fiber, 2...Adhesion part.

Claims (1)

[Scope of Claims] 1. Consisting of fluorine fibers made of short fibers of tetrafluoroethylene-ethylene copolymer oriented in irregular directions, and the fibers of the fibers are bonded by heat fusion. Fluorine fiber paper featuring 2 Fluorine fiber mixed paper obtained by mixing fluorine fibers made of tetrafluoroethylene-ethylene copolymer and natural pulp using a wet papermaking method and drying the paper.
Production of fluorocarbon fiber paper, which is characterized in that the fibers of the fluorocarbon fibers are thermally bonded at a temperature higher than the softening point of the fluorocarbon fibers, and then the natural pulp is dissolved and removed using an inorganic acid, and then re-dried. Method. 3 Fluorine fiber mixed paper obtained by mixing fluorine fibers made of tetrafluoroethylene-ethylene copolymer and PVA fibers using a wet papermaking method and drying the paper.
A method for producing fluorine fibers, which comprises heat-sealing the fibers of the fluorine fibers by thermocompression bonding at a temperature equal to or higher than the softening point of the fluorine fibers, then dissolving and removing the PVA fibers with hot water, and drying again.