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US 4,483,889 AGranted
Method for the production of fibre composite materials impregnated with resin
AssigneeKemaNord AB
InventorBengt Andersson
Life of this patent
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Abstract
A method for the production of a composite material in the form of a web, the material comprising fibres, a curable resin and expanded microspheres. A web of fibres and microspheres is formed, and the curable resin is added subsequently.
Claims7
A method for the manufacture of a composite material in the form of a web and comprising fibres, a formaldehyde-based resin and expanded thermoplastic microspheres comprising the steps of
- (a) forming a liquid suspension of fibres and unexpanded thermoplastic microspheres containing a blowing agent,
- (b) depositing a web containing fibres and the unexpanded microspheres from said liquid suspension, the amount of fibres deposited being between 20 and 500 g/m.sup.2 and the thickness of the web being between 0.01 and 1.5 mm,
- (c) heating the deposited web to a temperature sufficient to expand the thermoplastic microspheres but insufficient for melting the thermoplastic material of the microspheres,
- (d) drying the web containing the expanded thermoplastic microspheres,
- (e) impregnating the dried web with a precondensate of the formaldehyde-based resin to give a ratio of microspheres to the sum of microspheres and resin between 2 and 80 percent by weight, and
- (f) drying the web containing the precondensate of the formaldehyde based resin while maintaining the resin in a nonsticky B-stage,
- whereby the volume content of microspheres in the dried web containing resin and expanded microspheres is between 70 and 90 percent.
4 more elements
A method for the manufacture of a composite material in the form of a web and comprising fibres, a formaldehyde-based resin and expanded thermoplastic microspheres comprising the steps of
- (a) forming a suspension in liquid of fibres and unexpanded thermoplastic microspheres containing a blowing agent,
- (b) depositing a web containing the fibres and unexpanded microspheres from the suspension,
- (c) drying the web containing fibres and the unexpanded thermoplastic microspheres at a temperature below the vaporizing temperature for the blowing agent of the thermoplastic microspheres,
- (d) impregnating the dried web containing unexpanded thermoplastic microspheres with a precondensate of a formaldehyde-based resin to give a ratio of microspheres to the sum of microspheres and resin between 2 and 80 percent by weight, and
- (e) heating the web impregnated with the precondensate of formaldehyde-based resin to a temperature sufficent to expand the thermoplastic microspheres while maintaining the resin in a non-sticky B-stage,
- whereby a dry web having a volume content of microspheres between 70 and 95 percent is obtained.
3 more elements
Dependencies are inferred from the claim text.