Coating processes – Foraminous product produced – Filter – sponge – or foam
Reexamination Certificate
1999-02-12
2001-04-03
Cameron, Erma (Department: 1762)
Coating processes
Foraminous product produced
Filter, sponge, or foam
C427S273000, C427S274000, C427S280000, C427S341000, C427S358000, C427S407100
Reexamination Certificate
active
06210753
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a process for producing decorative three-dimensionally structured coatings from polyurethane foam on a substrate.
2. Description of Prior Art
Polyurethane foams are based on three components:
A: polyisocyanates;
B: polyols; and
C: auxiliaries, optionally including blowing agents.
The polyurethane is obtained by polyaddition of dihydric and/or polyhydric alcohols (B) and isocyanates and/or prepolymers with terminal isocyanate groups (A). Auxiliaries (C) are known catalysts, stabilizers, pigments, blowing agents, surfactants, emulsifiers, foam stabilizers, flame retardants, fillers, antioxidants, antistatic agents and biocides.
Polyurethane foam is produced either by a chemical blowing process, based on the reaction between isocyanate and water which yields CO
2
as blowing gas, or by the physical blowing process with low boiling point blowing agent components, such as halogenated hydrocarbons and/or readily volatile nonhalogenated hydrocarbons, such as pentane, cyclopentane, propane, isobutane, and dimethylether.
The raw materials are commercially available as a one-component or two-component mixture for processing into polyurethane foam.
Diphenylmethane-4,4′-diisocyanate (MDI) or 2,4- or 2,6-toluene diisocyanate is preferably used as isocyanate for producing polyurethane foam.
Polyurethane foams which are more flexible are obtained by chemical foaming with polyalkylene glycol ethers as diols and isocyanates as well as water.
Polyurethane foams which are more rigid are obtained with mixtures based on polyols and isocyanates which are foamed using physical blowing agents.
Normally polyurethane foam is processed into finished products by foam molding in closed molds or is used as bonding foam for filling cavities and fastening components in the construction industry, because polyurethane foam is tacky in the nascent state at the beginning of crosslinking and adheres well to many materials, such as wood, metal, concrete, masonry.
German Patent Reference DE-OS 21 12 397 describes a plastics material based on polyurethane foam which can be used as a decorative domestic rendering for internal and external walls in the form of foam wall panels.
Japanese Patent Reference JP 54083524 A discloses foamable paints containing a foamable resin, such as foamable polystyrene, foamable polyethylene or foamable polyurethane and a colorant and a binder, in particular a plastics material such as PVC, polyacrylonitrile or polymethacrylate to which organic or inorganic blowing agents, such as azodicarbonamide or sodium bicarbonate, are added, for painting pictures which, after drying at room temperature, are heated to a temperature of 90 to 200° C. depending on the plastics material, for foaming purposes.
Foamable paints of this type are not suitable for producing domestic renderings used over large areas, as they cannot be heat treated to 200° C. in order to obtain a foam.
European Patent Reference EP-A-0160 716 discloses a process for the production of thin flat insulating layers, whereby a low-boiling solvent comprising a one-component-PUR-mixture is applied to a surface like a lacquer by rolling, spreading, spraying or dipping thereafter, these layers being foamed up to a uniform insulation layer.
SUMMARY OF THE INVENTION
This invention achieves one object with a process for producing three-dimensionally structured, in particular flat coatings or layers of polyurethane foam on a substrate.
Such object of this invention is to find further advantageous fields of application for polyurethane foam, in particular for foamable polyurethane mixtures packaged as one-component or two-component systems, optionally with physical blowing agents, in pressurized containers such as aerosol cans for producing polyurethane foam in rigid or semi-rigid formulations.
The property of known commercially available foamable polyurethane mixtures to foam and crosslink very rapidly and uncontrollably inhibits many types of shaping and application so these foamable polyurethane mixtures have formerly been introduced only into existing, substantially closed molds or cavities for foaming purposes or, during free-rise foaming, subsequent mechanical treatment and shaping by cutting or the like has been carried out only after curing of the foam.
This invention relates to a process for producing coatings from polyurethane foam (PUR foam) on a substrate, in which a foamable mixture for producing polyurethane foam based on a one-component or two-component system, containing isocyanate and/or prepolymers with terminal isocyanate groups and dihydric and/or polyhydric alcohols as well as auxiliaries is applied to the substrate to be coated as a layer.
This invention achieves the object with improvement of the process because the mechanical structuring and influencing of the surface of the foamable mixture being flat applied onto the substrate for producing a decorative three dimensionally structured coating immediately thereafter and during foaming and incipient crosslinking of the mixture on the substrate superficially under the influence of force by mechanical regularly or irregularly distribution of the mixture is processed and consequently a regionally varied volume of the developing foam of the structured layer such formed is obtained.
In particular, foamable mixtures which cure with moisture from the environment while crosslinking are used.
This invention can be accomplished using polyurethane foams produced from a one-component system or two-component system based on isocyanates, polyols and auxiliaries by the chemical blowing process and/or physical blowing process with a physical blowing agent.
Coatings are preferably produced from rigid and semi-rigid polyurethane foams for this invention.
With the two-component system, a base component comprises the polyols, catalysts, stabilizers, optionally blowing agents, pigments and other auxiliaries while the second component, as crosslinking component, contains the isocyanate. It is possible to react the isocyanate with a proportion of the total quantity of polyol required to form a prepolymer leaving only the remainder of polyol in the base component for producing the polyurethane foam.
According to this invention, it is possible to produce flat and structured polyurethane foam coatings by free foaming a foamable mixture applied to a substrate chemically or using physical blowing agents or as a combination of the two processes, optionally with additional wefting or spraying the surface of the applied mixture with water, which forms an excellent external rendering or internal rendering on walls of buildings.
Advantageous developments of the process according to this invention can be inferred from the features of the claims.
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Cameron Erma
Pauley Petersen Kinne & Fejer
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