Cross-linked polyvinyl butyral
AssigneeMonsanto Company
InventorsGeorge E. Cartier, Peter H. Farmer
Life of this patent
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Abstract
Polyvinyl butyral (PVB) resin lightly cross-linked through stable intermolecular linkages developed, for example, through use of a dialdehyde or trialdehyde, to selectively increase PVB molecular weight and the modulus of a plasticized sheet formed therefrom intended for use in laminated safety glass assemblies.
Claims13
A process for increasing the viscosity of polyvinyl butyral which comprises having a cross-linking agent present before or during acetalization of polyvinyl alcohol with butyraldehyde to lightly cross-link the acetalized product through adjacent polyvinyl alcohol chains, the extent of cross-linking being adequate to increase the viscosity of the polyvinyl butyral by about 2% to about 85% over its viscosity in the absence of said cross-linking agent, said polyvinyl butyral containing 65 to 95 weight % vinyl butyral units.
A method of forming polyvinyl butyral sheet which comprises:
- a. acetalizing polyvinyl alcohol with butyraldehyde in the presence of a cross-linking agent to produce polyvinyl butyral resin containing 65 to 95 weight % vinyl butyral units which is lightly cross-linked through stable intermolecular linkages, the extent of cross-linking being adequate to increase the viscosity of the polyvinyl butyral resin by about 2% to about 85% over its viscosity in the absence of said cross-linking agent;
- b. mixing said resin with plasticizer and other optional additives to form an extrusion formulation;
- and
- c. extruding said formulation in melt form through an extrusion opening without rupturing said cross-links to form said sheet.
Dependencies are inferred from the claim text.