US Patent: 5,516,819, 14th May 1996
D R Blackburn, S F Bush, J M Methven
Abstract
A method of producing a thickened organic polymeric composition useful for molding and capable of resisting post-molding shrinkage after being crosslinked comprising a cross-linkable base resin dissolved in an unsaturated monomer, and an additive resin selected from saturated polyesters and saturated amide waxes, the additive resin being crystalline at ambient temperatures and having a melting point (Tm) below a temperature (Tc) at which the base resin cross-linking reaction proceeds at a significant rate. The base resin and additive resin have only a partial degree of compatibility. When cooled from a temperature between Tm and Tc to temperature between Tm and ambient the composition thickens, whereas, when it is heated to a temperature below Tc, it reverts to a flowable composition.
To see the patent in full, go to US Patent Office. On the first page click on USPTO Patent Full-Text and Image Database (PatFT), then under the heading “Searching Full Text Patents (since 1976)”, click on Patent Number Search and enter the patent number (with or without commas) into the “Query” box, then click on “Search”. To search for another US patent, click on Pat Num in the red display at the top of the page.
US Patent: 5,496,873, 5th March 1996
D R Blackburn, S F Bush, J M Methven
Abstract
A thickened organic polymeric composition useful for molding and capable of resisting post-molding shrinkage after being cross-linked comprises a cross-linkable base resin dissolved in an unsaturated monomer, and an additive resin selected from saturated polyesters and saturated amide waxes, the additive resin being crystalline at ambient temperatures and having a melting point (Tm) below a temperature (Tc) at which the base resin cross-linking reaction proceeds at a significant rate. The base resin and additive resin have only a partial degree of compatibility. When cooled from a temperature between Tm and Tc to a temperature between T.sub.m and ambient the composition thickens, whereas, when it is heated to a temperature below Tc, it reverts to a flowable composition.
To see the patent in full, go to US Patent Office. On the first page click on USPTO Patent Full-Text and Image Database (PatFT), then under the heading “Searching Full Text Patents (since 1976)”, click on Patent Number Search and enter the patent number (with or without commas) into the “Query” box, then click on “Search”. To search for another US patent, click on Pat Num in the red display at the top of the page.
Also
European Patent: EP 0396 625 B1, 14th November 1990
Abstract
Polymer compositions useful for moulding comprise a cross-linkable base resin, an unsaturated monomer in which the base resin is dissolved and a saturated additive resin which by itself is crystalline at ambient temperatures with a melting point (Tm) below that temperature (Tc) at which the base resin cross-linking reaction is designed to proceed at a significant rate. The composition is such that on cooling from a temperature between Tm and Tc, to a temperature between Tm and ambient the additive resin forms distributed microcrystalline domains connected severally by chains of the additive resin threading through the base resin chains. This produces a thickening network which may be reversibly broken down to the original additive resin molecules by heating to a temperature below Tc. The additive resin molecules swell the permanent base resin network created by the said cross-linking reaction which occurs during moulding, and thereby providing resistance to post-moulding shrinkage.
