Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H13/00—Pulp or paper, comprising synthetic cellulose or non-cellulose fibres or web-forming material
  • D21H13/10—Organic non-cellulose fibres
  • D21H13/20—Organic non-cellulose fibres from macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
  • D21H13/26—Polyamides; Polyimides
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
  • D21H17/63—Inorganic compounds
  • D21H17/67—Water-insoluble compounds, e.g. fillers, pigments
  • D21H17/68—Water-insoluble compounds, e.g. fillers, pigments siliceous, e.g. clays

Definitions

• This invention relates to papers particularly, but not exclusively, suitable for use in fluid sealing applications such as cylinder head gaskets. It is known to make gasket papers from non-asbestos formulations based on other fibres such as glass fibres and/or mineral fibres and including a minor proportion of cellulose as a web-forming agent.
• GB-A-2138854 and 2138855 disclose cellulose-containing compositions using ball clay as a filler.
• GB-A-2250302 discloses a gasket material which is cellulose-free and which includes a carefully selected mixture of calcined china clay and ball clay as filler.
• GB-A-2254346 discloses a high temperature gasket material including glass or carbon fibre staples and temperature tolerants. fillers.
• GB-A-2093474 and EP-A2-0522441 disclose compositions including aramid fibre staple materials.
• a method of manufacture of a paper stock for dewatering to paper comprising, by weight, 4-15% aramid fibre pulp, 60-90% silicate mineral, 4-10% polymeric binder, and 2-15% inorganic binder, comprises the steps set out in the precharaterising part of claim 1 further characterised by producing a first mixture containing said aramid fibres and silicate mineral prior to adding the inorganic binder thereto and, prior to adding said inorganic binder, adding to said first mixture a 10% solution of papermakers alum such that the dry content is 1% of the total composition and agitating the mixture to prepare the surface of the silicate mineral by said alum to receive the inorganic binder, and, after addition of said inorganic binder, adding said polymeric binder having a solid content of 50% by weight and dispersing said polymeric binder in the mixture without precipitation thereof.
• At least some of the silicate mineral is constituted by attapulgite.
• the inorganic binder is preferably colloidal silica.
• the polymeric material is preferably nitrile rubber.
• a particularly preferred paper according to the inventive method comprises by weight, 4-8% aramid fibre pulp, 5-8% polymeric binder, 75-87% silicate mineral and 4-10% colloidal silica. It will be appreciated that in the present context "aramid” is a reference to polyaromatic amide material.
• the formulations of the present invention may be used in at least two different ways.
• the use of calcined china clay in combination with colloidal silica lends itself to the product of a paper which can be impregnated with a silicone or other resin such as polybutadiene in order to enhance resistance to and sealabilty against fluids such as water-antifreeze mixtures and oil.
• a paper which can be impregnated with a silicone or other resin such as polybutadiene in order to enhance resistance to and sealabilty against fluids such as water-antifreeze mixtures and oil.
• attapulgite it is possible to produce a paper which swells when exposed to water.
• Such papers can be used without a resin impregnation treatment.
• the process of the invention leads to a paper stock which is capable of producing gaskets both with and without a post-treatment with a resin impregnant.
• testing was carried out by bonding the test paper to both sides of a plain steel core, blanking out annular samples of inside diameter 14.7mm and outside diameter 34.5mm. These were then tested, again based on ASTM F1276, by applying an initial stress of 58.6 MPa. After 22 hours at 300°C the residual stress was measured, the stress relaxation calculated and then normalised to a paper thickness of 1.0mm, in the usual way. This procedure was used throughout the following Examples, including tests on paper made according to prior art.
• a paper was made having the following composition: % by dry weight Fibrillated Aramid Fibre Pulp 8 Calcined China Clay 76 Nitrile Rubber 6 Colloidal Silica 10
• the aramid fibres were dispersed in water to give a slurry of around 2% solids content by weight. This pulp had a freeness of 50°SR. The pulp was transferred to a mixing vessel and further diluted with water at 40°C. The calcined china clay was added and the mixture agitated. Further water was added to give a slurry having a solids content of approximately 4% by weight. A 10% solution of papermakers alum was added such that the dry content was approximately 1% of the total composition. The mixture was agitated for 2 minutes before adding the colloidal silica as a 30% solids content suspension. The mixture was agitated for a further 5 minutes and nitrile rubber added in latex form, having a solids content of around 50%.
• the nitrile rubber latex was diluted 5:1 with water before adding to the mix. When fully dispersed the latex was then caused to precipitate onto the fibres and fillers by the addition of a further quantity of papermakers alum solution until the supernatant liquid became clear.
• a paper was produced from the above stock by the conventional technique of dewatering on a wire mesh, pressing and drying, a polyacrylamide flocculant was used to aid processing.
• the paper was subsequently calendered to the required density using a conventional 2-bowl calender.
• the resulting paper had the following properties: Thickness 0.83mm Substance 920gm -2 Density 1100kgm -3 Tensile Strength 4.2 MPa Compression at 34.5 MPa 14.3% Stress Relaxation 24.8%
• a conventional paper made according to GB 2250302 showed a stress relaxation of 42% by the same test method.
• a paper was prepared largely as described above from the following formulation. % by dry weight Fibrillated Aramid Fibre Pulp 4 Calcined China Clay 30 Attapulgite 50 Colloidal Silica 10 Nitrile Rubber 6
• the paper had the following properties: Thickness 0.65mm Substance 860gm -2 Density 1330kgm -3 Tensile Strength 7.0 MPa Compression at 34.5 MPa 15.3% Stress Relaxation 29.8%
• a sealing test was carried out as described above and the paper was found to seal an internal pressure of 10 bar without detectable leakage at a sealing stress of 10.3 MPa.
• the paper also sealed 10 bar fluid pressure at a reduced sealing stress of 3.4 MPa.

Landscapes

• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Dispersion Chemistry (AREA)
• Inorganic Chemistry (AREA)
• Sealing Material Composition (AREA)
• Paper (AREA)
• Materials For Medical Uses (AREA)

Applications Claiming Priority (3)

Publications (2)

Family

ID=10795958

Family Applications (1)

Country Status (9)

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Family Cites Families (10)

• 1996
  • 1996-06-27 GB GB9613456A patent/GB2314569B/en not_active Expired - Fee Related
• 1997
  • 1997-06-12 DE DE69704947T patent/DE69704947T2/de not_active Expired - Fee Related
  • 1997-06-12 EP EP97926103A patent/EP0916001B1/en not_active Expired - Lifetime
  • 1997-06-12 JP JP10502481A patent/JP2000513053A/ja active Pending
  • 1997-06-12 WO PCT/GB1997/001587 patent/WO1997049864A1/en not_active Application Discontinuation
  • 1997-06-12 KR KR1019980709356A patent/KR20000015807A/ko not_active Application Discontinuation
  • 1997-06-12 BR BR9709944A patent/BR9709944A/pt unknown
  • 1997-06-12 AU AU30990/97A patent/AU713243B2/en not_active Ceased
  • 1997-06-25 ZA ZA9705620A patent/ZA975620B/xx unknown

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