# US 5,710,434 A · Isocyanate impregnating compositions

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- Number: US 5,710,434 A
- Document ID: US5710434A
- Status: Granted
- Kind: A
- Application number: 08/715,977
- Filed: 1996-09-19
- Granted: 1998-01-20
- Earliest claimed: 1995-06-06
- Assignees: Weyerhaeuser Company
- Inventors: David W. Park; Frank R. Hunter
- Web page: https://patentgrep.com/patent/US5710434A

## CPC

- C08G 18/6484: {Polysaccharides and derivatives thereof}
- B65D 65/42: Applications of coated or impregnated materials
- C08G 18/168: {Organic compounds}
- C08G 18/302: {Water}
- C08K 5/10: Esters; Ether-esters
- Y10T 428/2965: Cellulosic
- Y10T 428/31975: Of cellulosic next to another carbohydrate
- Y10T 428/31982: Wood or paper
- Y10T 428/31993: Of paper
- C08G: MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- B65D: CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
- C08K: Use of inorganic or non-macromolecular organic substances as compounding ingredients (paints, inks, varnishes, dyes, polishes, adhesives C09)
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

The invention is directed to a composition of matter useful as a paper impregnant, to the method of its use, and to the products produced by the method. Poly (diphenylmethane diisocyanate) or PMDI has been used in the past as a paper impregnant with or without propylene carbonate as a diluent. These products have generally required pressing under high pressures and at elevated temperatures. It has now been found that triacetin and/or triethyl citrate in usages up to about 20% of PMDI give superior performance in impregnated products. The modified PMDI will cure at essentially ambient conditions in times as short as 1-2 days to insoluble polyureas with low residual amounts of isocyanates and reaction byproducts such as 4,4'-diaminodiphenylmethane. The treated papers can be used in applications of which skins for sandwich panels and high strength corrugated board would be exemplary.

## Claims

### Claim 1

An impregnating composition for cellulosic materials consisting essentially of a polyisocyanate at least difunctional in --NCO and from 1-20% by weight of the composition of triethyl citrate.

### Claim 2 (depends on 1)

The composition of claim 1 wherein the polyisocyanate is poly(diphenylmethane diisocyanate).