# US 8,784,518 B2 · Method of making polyurethane foam

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- Number: US 8,784,518 B2
- Document ID: US8784518B2
- Status: Granted
- Kind: B2
- Application number: 13/347,994
- Filed: 2012-01-11
- Published: 2012-07-19
- Granted: 2014-07-22
- Earliest claimed: 2011-01-17
- Assignees: 3M Innovative Properties Company
- Applicants: Elizabeth Anna Benson-Sargent; David R. Dow; Grady A. Dunham; Douglas E. Earl; Jeffrey P. Lenzendorf
- Inventors: Elizabeth Anna Benson-Sargent; David R. Dow; Grady A. Dunham; Douglas E. Earl; Jeffrey P. Lenzendorf
- Web page: https://patentgrep.com/patent/US8784518B2

## CPC

- C08G 18/06: with compounds having active hydrogen
- B24D 3/32: for porous or cellular structure
- B24D 11/02: Backings, e.g. foils, webs, mesh fabrics
- B29B 7/7404: {Mixing devices specially adapted for foamable substances (B29B7/76 takes precedence)}
- B29B 7/7433: {Plants}
- B29B 7/7471: {Mixers in which the mixing takes place at the inlet of a mould, e.g. mixing chambers situated in the mould opening}
- B29B 7/7615: {characterised by arrangements for controlling, measuring or regulating, e.g. for feeding or proportioning the components}
- B29B 7/84: Venting or degassing {; Removing liquids, e.g. by evaporating components}
- B29C 44/3442: {Mixing, kneading or conveying the foamable material (mixing plastics B29B7/00; mixing in general B01F)}
- B29C 67/246: {Moulding high reactive monomers or prepolymers, e.g. by reaction injection moulding [RIM], liquid injection moulding [LIM] (casting monomers B29C39/006, mixing construction B29B7/74)}
- C08G 18/6607: {with compounds of group C08G18/3203}
- C08G 18/7664: {containing alkylene polyphenyl groups}
- B29K 2075/00: Use of {PU, i.e.} polyureas or polyurethanes {or derivatives thereof}, as moulding material
- C08G 2110/0058: ≥50 and <150kg/m3
- C08G 2110/0083: prepared using water as the sole blowing agent
- C08G: MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- B24D: TOOLS FOR GRINDING, BUFFING OR SHARPENING (abrading-bodies specially designed for tumbling apparatus, e.g. abrading-balls B24B31/14; honing tools B24B33/08; lapping tools B24B37/11)
- B29B: PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
- B29C: SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING (making preforms B29B11/00; making laminated products by combining previously unconnected layers which become one product whose layers will remain together B32B37/00 - B32B41/00)
- B29K: INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR {MOULDS, } REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS

## Abstract

Herein are disclosed an apparatus and method for reaction injection molding of polyurethane foam. In the method, a recirculation loop containing polyols along with an effective amount of water, and a recirculation loop containing isocyanates, are each partially evacuated.

## Claims

### Claim 1

A method of reaction injection molding a polyurethane foam, comprising:
recirculating a polyol mixture in a first partially evacuated recirculation loop,
wherein the polyol mixture comprises from about 0.5% to about 4% by weight of water;
recirculating an isocyanate mixture in a second partially evacuated recirculation loop;
impingement mixing a portion of the polyol mixture with a portion of the isocyanate mixture to form a reaction mixture;
injecting the reaction mixture into a mold;
and,
allowing the reaction mixture to react to form a polyurethane foam.

### Claim 2 (depends on 1)

The method of claim 1 wherein the first partially evacuated recirculation loop comprises at least a first storage tank and a first metering pump and a first vacuum pump, and is fluidly connected to an impingement mixing head.

### Claim 3 (depends on 2)

The method of claim 2 wherein the second partially evacuated recirculation loop comprises at least a second storage tank and a second metering pump and a second vacuum pump, and is fluidly connected to the impingement mixing head.

### Claim 4 (depends on 3)

The method of claim 3 wherein the first and second metering pumps serve to recirculate the polyol mixture and the isocyanate mixture, respectively, or wherein the first and second recirculation loops each comprise a recirculation pump that is separate from the metering pump of the loop.

### Claim 5 (depends on 3)

The method of claim 3 wherein the first and second vacuum pumps are operated so that the pressure in the first and second storage tanks is reduced by an increment of from about 150 Torr to about 300 Torr.

### Claim 6 (depends on 5)

The method of claim 5 wherein the first and second vacuum pumps are respectively fluidly connected to the headspace of the first and second storage tanks.

### Claim 7 (depends on 6)

The method of claim 6 wherein the first and second vacuum pumps are separate vacuum pumps or wherein they comprise a single vacuum pump that is fluidly connected to both the first and second storage tanks.

### Claim 8 (depends on 1)

The method of claim 1 with the proviso that no physical blowing agent or gaseous nucleation agent is added to the polyol mixture or to the isocyanate mixture or is injected into either of the first or second recirculation loops.

### Claim 9 (depends on 1)

The method of claim 1 with the proviso that both the polyol mixture and the isocyanate mixture are substantially free of polymeric microspheres.

### Claim 10 (depends on 1)

The method of claim 1 wherein the polyurethane foam comprises an open-celled polyurethane foam with an average cell size of less than about 0.02 mm.

### Claim 11 (depends on 1)

The method of claim 1 wherein the polyurethane foam comprises less than about one void of length greater than 1.0 mm, per cubic centimeter of the polyurethane foam.

### Claim 12 (depends on 1)

The method of claim 1 wherein the polyurethane foam comprises a density of between about 0.03 grams/cc and about 0.10 grams/cc.

### Claim 13 (depends on 1)

The method of claim 1 wherein the reaction mixture is injected into the mold so as to fill about 10 volume % or less of the interior of the mold.

### Claim 14 (depends on 1)

The method of claim 1 wherein the polyurethane foam comprises a molded bun in the shape of the mold, and wherein the method further comprises cutting the molded bun into smaller articles each article comprising first and second oppositely-facing major surfaces.

### Claim 15 (depends on 14)

The method of claim 14 further comprising disposing an abrasive layer on the first and second major surfaces of each article to form an abrasive sponge.

### Claim 16 (depends on 1)

The method of claim 1 wherein the polyol mixture comprises from about 1.2 wt. % to about 1.6 wt. % of water.

### Claim 17 (depends on 1)

The method of claim 1 wherein the isocyanate mixture is substantially free of toluene diisocyanate and oligomers and prepolymers thereof.

### Claim 18 (depends on 1)

The method of claim 1 wherein the polyurethane foam comprises a TABER abrasion of less than about 300 milligrams weight loss.