JPH0243785B2 - - Google Patents

Description

[Detailed description of the invention]

(a) Industrial Application Field The present invention relates to a composite gasket used for high-pressure gaskets, high-temperature gaskets, and the like. (b) Conventional technology Generally, glass cloth and carbon cloth
PTFE (abbreviation for polytetrafluoroethylene; the same applies below)
Pre-preg is made by impregnating dispersion or FEP (abbreviation for tetrafluoroethylene-16-fluoropropylene copolymer) dispersion alone, and then stacking these and pressing them with a hot plate press. Gaskets formed into laminated plates by heating above their melting temperature have been known for a long time. (c) Problems to be solved by the invention However, products made of PTFE dispersion alone have poor sealing properties and are unsuitable as gas sealing materials, while products using FEP dispersion have poor sealing properties. Good but the materials are very expensive
Another disadvantage was that the high temperature strength was lower than that of PTFE. In addition, in order to improve sealing performance, the base fabric was made extremely thin to ensure even impregnated prepreg, which required a large number of base fabrics, resulting in high costs. It was low and unsuitable for high-pressure piping flanges. Therefore, this invention alternately overlaps prepregs made of a thick heat-resistant base fabric with a low batting density and a thin heat-resistant base fabric with a high batting density (number of warp threads/inch). The objective is to provide a composite gasket that not only has excellent sealing properties but also has high compressive strength and tensile strength by laminating and integrating the gaskets. (d) Means for solving the problems This invention provides polytetrafluoroethylene dispersion with a solid content of 5 to 50 wt%.
An impregnating agent containing ultrafine powder of propylene hexafluoride copolymer or ethylene tetrafluoride-perfluoroalkyvinyl ether copolymer dispersed or mixed with a dispersion thereof is applied at a ratio of 1.5 to 2.5. A prepreg is formed by impregnating heat-resistant base fabrics made of two types of coarse and dense glass cloth, carbon cloth, etc. It is characterized by being a composite gasket formed by lamination molding at the gelation temperature of polytetrafluoroethylene using a hot plate press. (E) Embodiment of the Invention An embodiment of the invention will be described in detail below based on the drawings. The drawings show a composite gasket of the present invention, and the first
In the composite gasket 1 shown in FIGS.
is an impregnating agent and is added to the PTFE dispersion in an economical proportion, i.e., 5 to 50 wt% solids content.
It is a product in which ultrafine powder of FEP or PFA (abbreviation for tetrafluoroethylene-perfluoroalkyvinylether copolymer, hereinafter the same applies) is dispersed, or a dispersion thereof is mixed. Reference numerals 3 and 4 denote base fabrics, which are made of heat-resistant fabrics made of glass cloth, carbon cloth, or a mixture thereof, and one base fabric 3 has a batting density (warp number/ inch) 1.5
The ratio is changed to ~2.5, and each prepreg is impregnated with the composite agent and formed into a prepreg, and a plurality of prepregs are made of thin base fabric 3 with high implant density and thick base fabric 4 with low implant density. They are stacked alternately so that the prepreg of thin base fabric 3 with high implant density is located on the outermost side. Then, the prepregs of the laminated base fabrics 3 and 4 are laminated and molded using a hot plate press at a temperature of 340 to 390°C (PTFE gelling temperature) and a molding pressure of 5 to 20 kg/cm ² . Note that when the thick base fabric 4 has high tensile strength or compressive strength, the thin base fabric 3 is preferably combined with a soft material such as carbonized fiber (low-temperature treated product). The composite gasket 1 constructed as described above has a thin base fabric 3 with a high implant density superimposed on both sides of a thick base fabric 4 with a low implant density, and the thin base fabric 3 overlaps the thick base fabric 4 with a low implant density. The impregnating agent 2 is completely impregnated in various places between the fibers of the cloth 4, and the unevenness of the weave of the thick base cloth 4 is covered by the thin base cloth 3, making it smooth. This results in a gasket that is uniformly impregnated in all parts. Therefore, when this composite gasket 1 is tightened with a flange or the like, uniform surface pressure can be obtained at each location, there is no seepage leakage or contact surface leakage, and a complete seal can be achieved with a low tightening surface pressure. The excellent sealing properties are also supported by the experimental results shown in FIG. The composition of the composite gasket used in this experiment is shown in the table below.

[Table] Show
(F) Effects of the Invention The composite gasket of the present invention consists of alternating layers of prepregs made by impregnating a thin base fabric with an impregnating agent, forming a prepreg made from the outermost thin base fabric, and then lowering the prepreg to a gelling temperature. Because it is pressure-molded, the impregnating agent melts at the gelling temperature and can impregnate even the minute voids between the fibers of the base fabric, and even the unevenness of the texture of a thick base fabric can be reduced compared to a thin base fabric. It disappears due to
It can be impregnated uniformly over the entire surface, creating a smooth shape, and achieving uniform tightening surface pressure.
Excellent sealing properties can be obtained by adding PFA. Furthermore, the composite gasket of the present invention uses a thick base fabric, has high compressive strength and tensile strength, and also uses a heat-resistant base fabric, so it can be used as a gasket for high temperature and high pressure applications. In addition, since a thick base fabric is used between thin base fabrics, the number of base fabrics used can be significantly reduced compared to when the entire base fabric is composed of thin base fabrics, resulting in material costs. can be reduced.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention; FIG. 1 is a longitudinal sectional view of a composite gasket, FIG. 2 is a partially enlarged sectional view of FIG. 1, and FIG. 3 is a diagram showing the sealing characteristics of the composite gasket. . 1...Composite gasket, 2...Impregnating agent, 3,4
...Base fabric.

Claims (1)

[Scope of Claims] 1. Polytetrafluoroethylene dispersion with a solid content of 5 to 50 wt% of tetrafluoroethylene-propylene hexafluoride copolymer or tetrafluoroethylene-perfluoroalkyvinyl ether copolymer A prepreg is produced by impregnating a heat-resistant base fabric made of two types of coarse and dense glass cloth or carbon cloth with different impregnating densities in the ratio of 1.5 to 2.5 with an impregnating agent containing ultra-fine powder dispersed or mixed with the dispersion. At the same time, base fabrics with high implant density are placed on both sides of base fabrics with low implant density, and laminated and molded using hot plate press at the gelling temperature of polytetrafluoroethylene. Gasket.