Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K3/00—Materials not provided for elsewhere
  • C09K3/10—Materials in mouldable or extrudable form for sealing or packing joints or covers
  • C09K3/1025—Materials in mouldable or extrudable form for sealing or packing joints or covers characterised by non-chemical features of one or more of its constituents
  • C09K3/1028—Fibres
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16J—PISTONS; CYLINDERS; SEALINGS
  • F16J15/00—Sealings
  • F16J15/02—Sealings between relatively-stationary surfaces
  • F16J15/06—Sealings between relatively-stationary surfaces with solid packing compressed between sealing surfaces
  • F16J15/10—Sealings between relatively-stationary surfaces with solid packing compressed between sealing surfaces with non-metallic packing
  • F16J15/102—Sealings between relatively-stationary surfaces with solid packing compressed between sealing surfaces with non-metallic packing characterised by material
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K2200/00—Chemical nature of materials in mouldable or extrudable form for sealing or packing joints or covers
  • C09K2200/02—Inorganic compounds
  • C09K2200/0243—Silica-rich compounds, e.g. silicates, cement, glass
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K2200/00—Chemical nature of materials in mouldable or extrudable form for sealing or packing joints or covers
  • C09K2200/02—Inorganic compounds
  • C09K2200/0243—Silica-rich compounds, e.g. silicates, cement, glass
  • C09K2200/0252—Clays
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K2200/00—Chemical nature of materials in mouldable or extrudable form for sealing or packing joints or covers
  • C09K2200/02—Inorganic compounds
  • C09K2200/0243—Silica-rich compounds, e.g. silicates, cement, glass
  • C09K2200/0252—Clays
  • C09K2200/026—Kaolin
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K2200/00—Chemical nature of materials in mouldable or extrudable form for sealing or packing joints or covers
  • C09K2200/06—Macromolecular organic compounds, e.g. prepolymers
  • C09K2200/0607—Rubber or rubber derivatives
  • C09K2200/0612—Butadiene-acrylonitrile rubber
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K2200/00—Chemical nature of materials in mouldable or extrudable form for sealing or packing joints or covers
  • C09K2200/06—Macromolecular organic compounds, e.g. prepolymers
  • C09K2200/0615—Macromolecular organic compounds, e.g. prepolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • C09K2200/0635—Halogen-containing polymers, e.g. PVC
  • C09K2200/0637—Fluoro-containing polymers, e.g. PTFE
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K2200/00—Chemical nature of materials in mouldable or extrudable form for sealing or packing joints or covers
  • C09K2200/06—Macromolecular organic compounds, e.g. prepolymers
  • C09K2200/0692—Fibres
  • C09K2200/0695—Polyamide fibres

Definitions

• This invention relates to industrial gaskets for steam applications and more particularly to such gaskets which are asbestos-free and manufactured by the calendering process using organic synthetic fibers, fillers and polymeric binders.
• para-aramid pulp such as poly (g.-phenylene terephthalamide) pulp available commercially, has been steadily increasing as a replacement for asbestos.
• Para-aramid pulp is a good material as a replacement because of its high temperature stability, strength and wear resistance.
• Para-aramid pulp can be manufactured according to the process described in U.S. Patent 3,767,756. In this process, para-aramid filaments are mechanically converted into pulp by first cutting them into short fibers and then abrading them into pulp. This pulp is then used to make such products as brake linings, gaskets, laminates and composites.
• an industrial gasket for steam applications consisting of a flexible sheet manufactured by the calendering process with organic synthetic fibers, fillers and polymeric binders characterized in that the organic fibers in the flexible sheet are a blend of (1) p_-polyaramid pulp and (2) at least one of (a) m -polyaramid staple or fibrids, and (b) polytetrafluoroethylene powder.
• the drawing is an expanded scale graph showing water loss in percent versus days of testing.
• Gaskets according to the present invention are flexible sheets manufactured according to the conventional calendering process for making compressed gaskets using calenders well-known to those skilled in the art.
• the organic fibers which are used in these flexible sheets comprise a blend of (1) j . -polyaramid pulp (fibrillated fibers of variable length, usually averaging less than 12 mm in length) and (2) at least one of (a) m_-polyaramid short fibers (usually called staple or fibrids), and (b) polytetrafluoroethylene powders.
• the blend of (1) to (2) has a weight ratio in the range of 99:1 and 50:50, preferably a weight ratio in the range of 99:1 and 80:20. It has been found surprisingly that when such blends are used to make gaskets by the calendering process that water lost through the gasket is very low when compared to conventional gaskets made by this process from asbestos and ji-polyaramid pulp alone.
• Para-polyaramid pulp and m.-polyaramid fibers are well known and are sold commercially under the trademarks KEVLAR® and NOMEX® respectively by E.I. du Pont de Nemours & Co.
• Para-polyaramid pulp can be prepared as described in EP-392 559-A2. It is preferred that a short fiber pulp of the blend useful in this invention be prepared by turbulent air grinding as described in U.S. Patent Application Ser.No. 07/506968, filed February 27, 1990, in the names of Haines and Schuler (KB-3040).
• a blend of p.-polyaramid and m_-polyaramid can also be prepared as described in EP-392 559-A2 prior to the shredding procedure.
• the fibrillated fibers in the pulp generally have a length of about 0.2 to 8 millimeters, preferably about 1 to 3 mm.
• Polytetrafluoroethylene (PTFE) powder is a white free-flowing powder of submicron size particles. It is also available commercially under the trademark TEFLON® of E.I. du Pont de Nemours & Co. A useful PTFE powder has a bulk density from 300-600 g/1, preferably
• SUBSTITUTE SHEET from 500-550 g/1, has an average particle size distribution on a volume basis of from 3-100 microns, and has a melt flow rate of 0.5- 50 g/10 minutes.
• the PTFE powder is generally blended with the p_- polyaramid pulp prior to shredding.
• An organic fiber blend as described above is made into a flexible sheet useful as a gasket for steam applications by mixing it with other materials known to be useful for gaskets and then forming the sheet by the well-known calendering process. This process can be carried out by using any of the calendering machines available commercially for this purpose.
• fillers both organic and inorganic materials
• polymeric binders include optional ingredients such as antioxidants, colorants, curing agents, and the like.
• additional fibers can be included, e.g., inorganic silicate fibers.
• inorganic filler materials are talc, barium sulfate, calcium carbonate, and wollastonite.
• polymeric binders are preferred binders of rubber, e.g., nitrile butadiene rubber (NBR), styrene butadiene rubber (SBR), natural rubber and ethylene propylene diene monomer rubbers (EPDM).
• NBR nitrile butadiene rubber
• SBR styrene butadiene rubber
• EPDM ethylene propylene diene monomer rubbers
• Compressed gaskets were prepared (about 2mm thick) using a blend of (1) 80% by weight rj-polyaramid pulp (KEVLAR® IF 356) having fiber lengths of 1-3 mm and 20% by weight m_-polyaramid staple short fibers (3-6 mm) and (2) 80% by weight p_-polyaramid pulp as above and 20% by weight of PTFE powder (TEFLON® MP1000).
• gaskets were then compared in a steam test with a commercially available gasket of asbestos and one of p_-poly-aramid pulp alone (KEVLAR® IF356). All four gaskets were formulated with the same binder, fillers, and other ingredients such that the approximate gasket formulation was as follows: 15% weight % of blend (1), blend (2), asbestos, or p- polyaramid pulp;
• NBR rubber 15% weight % of NBR rubber as a binder
• inorganic fillers i.e. a mixture of talc, kaolin and silicate powder.
• Each formulation contained about 1 weight % of a cross-linking agent and an antioxidant.
• gasket A is blend (1) and gasket B is blend (2); gasket C is KEVLAR® pulp alone.
• a stainless steel steam cell having a stainless steel cover with 6 calibrated bolts, and having a capacity of 0.08 liters is filled with about 70 grams of water.
• the gasket under study is bolted between the flanges of the cell and cover to a bolt torque of l lkgm.
• the completed system is placed in an air oven maintained at 240°C and is heated over a period of 3 hours so as to produce a predetermined internal water pressure of 32 bar.
• the system is removed from the oven and allowed to cool at room temperature for three hours. This cycle is repeated for up to 40 days.
• the cell is weighed and the water loss is measured with the total weight loss at the end of the test period being the water loss through the gasket.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• General Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Mechanical Engineering (AREA)
• Sealing Material Composition (AREA)
• Gasket Seals (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (1)

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ID=6430134

Family Applications (1)

Country Status (4)

Cited By (9)

Families Citing this family (3)

Citations (4)

Family Cites Families (2)

• 1991
  • 1991-04-23 DE DE19914113153 patent/DE4113153A1/de active Granted
• 1992
  • 1992-04-03 EP EP19920913319 patent/EP0581893A1/en not_active Withdrawn
  • 1992-04-03 WO PCT/US1992/002445 patent/WO1992018578A1/en not_active Application Discontinuation
  • 1992-04-03 JP JP4511714A patent/JPH06507196A/ja active Pending

Patent Citations (4)

Non-Patent Citations (3)

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