# US 12,428,535 B2 · High throughput manufacture of polyurethane foam layers

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- Number: US 12,428,535 B2
- Document ID: US12428535B2
- Status: Granted
- Kind: B2
- Application number: 17/621,312
- Filed: 2020-06-22
- Published: 2022-11-10
- Granted: 2025-09-30
- Earliest claimed: 2019-06-24
- Assignees: Mölnlycke Health Care AB
- Applicants: Mölnlycke Health Care AB
- Inventors: Antti Tapani Holopainen
- Web page: https://patentgrep.com/patent/US12428535B2

## CPC

- B29C 44/3415: {Heating or cooling}
- C08J 9/02: using blowing gases generated by the reacting monomers or modifying agents during the preparation or modification of macromolecules
- A61L 15/26: Macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds; Derivatives thereof {(A61L15/225 takes precedence)}
- A61L 15/425: {Porous materials, e.g. foams or sponges}
- B29C 44/321: {the preformed part being a lining, e.g. a film or a support lining}
- C08G 18/10: Prepolymer processes involving reaction of isocyanates or isothiocyanates with compounds having active hydrogen in a first reaction step
- C08G 18/48: Polyethers
- C08G 18/755: {and at least one isocyanate or isothiocyanate group linked to a secondary carbon atom of the cycloaliphatic ring, e.g. isophorone diisocyanate}
- C08G 18/7621: {being toluene diisocyanate including isomer mixtures}
- C08G 18/7671: {containing only one alkylene bisphenyl group}
- C08G 18/792: {formed by oligomerisation of aliphatic and/or cycloaliphatic isocyanates or isothiocyanates}
- A61F 2013/530481: {having superabsorbent materials, i.e. highly absorbent polymer gel materials}
- A61F 2013/530649: {in sponge or foam}
- B29C 2035/0822: {using IR radiation}
- B29K 2075/00: Use of {PU, i.e.} polyureas or polyurethanes {or derivatives thereof}, as moulding material
- C08G 2110/0008: flexible
- C08G 2110/0083: prepared using water as the sole blowing agent
- C08J 2207/10: Medical applications, e.g. biocompatible scaffolds
- C08J 2375/04: Polyurethanes
- C08J 2375/06: from polyesters
- 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)
- C08J: WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H (working, e.g. shaping, of plastics B29)
- A61L: METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES (preservation of bodies or disinfecting characterised by the agents employed A01N; preserving, e.g. sterilising, food or foodstuffs A23; preparations for medical, dental or toiletry purposes A61K)
- C08G: MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- A61F: FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS (dental prosthetics A61C)
- 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

Described is an at least partly continuous process for making polyurethane foam layers that are suitable for medical applications, in particular in wound dressings, at a high throughput rate. The described process includes a step of accelerated curing of the polyurethane foam performed at a stage of the overall curing process at which the risk of a run-away reaction is minimized.

## Claims

### Claim 1

Process for making polyurethane foam layer, said process comprising at least the following steps:
(i) at least one mixing step in which one or more polyurethane prepolymer(s) comprising an isocyanate-capped polyol or an isocyanate-capped polyurethane is/are mixed or brought in contact, with each other, and with water, in a mixing or contact zone, wherein said polyurethane prepolymer derive(s) from a reaction between a polyol, and a diisocyanate compound selected from the group consisting of hexamethylene diisocyanate (HDI), toluene diisocyanate (TDI), methylene diphenyl diisocyanate (MDI), and isophorone diisocyanate (IPDI), or any mixture thereof;
(ii) at least one layer forming step in which the mixture from step (i) is applied onto a moving substrate to form a layer and to begin the curing process on the substrate;
(iii) at least one transporting step during which the foam layer on the substrate from step (ii) is a least partly moved along a production line, during which step the polyurethane prepolymer or precursor thereof in the foam layer at least partly cures, and the thickness of the layer increases due to foaming;
(iv) at least one step of accelerated curing, which occurs at a predetermined point in time after conclusion of step (ii) and, correspondingly, at a predetermined location along the production line, wherein curing is accelerated by subjecting the foam as moving on the substrate to radiation heating,
wherein said “predetermined point” in time in step (iv) is reached 2 to 10 minutes after the beginning of step (iii), or
wherein said “predetermined point” in time in step (iv) is reached once a given volume segment of the foam layer has reached a degree of curing of from 50% to 90%.

### Claim 2 (depends on 1)

Process according to claim 1, wherein said process comprises at least further step (v), which is implemented after step (iv):
(v) separately from and after conclusion of step (iv): at least one drying step during which the essentially cured wet foam from step (iv) is dried to reach a predetermined lower water content.

### Claim 3 (depends on 1)

The process according to claim 1, wherein said polyol is selected from the group consisting of a polyester polyol, a polyacrylate polyol, a polyurethane polyol, a polycarbonate polyol, a polyether polyol, a polyesterpolyacrylate polyol, a polyurethane polyacrylate polyol, a polyurethane polyester polyol, a polyurethane polyether polyol, a polyurethane polycarbonate polyol, and a polyester polycarbonate polyol, or a mixture thereof.

### Claim 4 (depends on 1)

The process according to claim 1, wherein the initial thickness of the foam layer as applied on the substrate, i.e. at the beginning of step (ii) is from 100 μm to 8 mm.

### Claim 5 (depends on 1)

The process according to claim 1, wherein said “predetermined point” in time in step (iv) is reached (A) when the thickness of the foam has increased by at least 60% vis-à-vis the thickness of the layer as initially applied in step (ii), or
(B) when the peak temperature of foam curing has been reached, or
(C) when the temperature of the foam layer is in the range from 25° C. to 35° C., after the temperature had been in the range of from 18° C. to 24° C. at the beginning of step (iii).

### Claim 6 (depends on 1)

The process according to claim 1, wherein said “predetermined location” along the production line in step (iv) is 5 m or more from the point in the production line at which the mixture from step (i) is applied onto the substrate.

### Claim 7 (depends on 1)

The process according to claim 1, wherein the maximum temperature reached by way of the accelerated curing of step (iv) is controlled to be in the range of from 30° C. to 95° C.

### Claim 8 (depends on 2)

The process according to claim 2, wherein the maximum temperature or average temperature, is lower in the drying step (v) than in the accelerated curing step (iv).

### Claim 9 (depends on 1)

The process according to claim 1, wherein the foam resulting after step (iv) or after step (v) is an open cell foam.

### Claim 10 (depends on 1)

The process according to claim 1, wherein the accelerated curing of step (iv) is achieved by infrared heating with 2 or more infrared lamps.

### Claim 11 (depends on 1)

A medical dressing comprising a foam produced from the process according to claim 1.

### Claim 12 (depends on 11)

The medical dressing according to claim 11, wherein said medical dressing further comprises at least one further layer.

### Claim 13 (depends on 1)

The process according to claim 1, wherein said “predetermined point” in time in step (iv) is reached 2 to 10 minutes after the beginning of step (iii).

### Claim 14 (depends on 1)

The process according to claim 1, wherein said “predetermined point” in time in step (iv) is reached once a given volume segment of the foam layer has reached a degree of curing of from 50% to 90%.