IMPROVED DIELECTRIC EMBOSSING OF FOAM

Abstract: A process for dielectrically embossing flexible foam, e.g. polyurethane foam assemblies, in which the foam is thermally reticulated prior to being dielectrically embossed. Inconsistencies in the dielectric embossing process are essentially eliminated by the thermal reticulation pretreatment of the foam. There is also disclosed a dielectrically embossed laminate including a thermally reticulated dielectrically active flexible foam.

Description: DESCRI PTI ON IMPROVED DIELECTRIC EMBOSSING OF FOAM" The present invention relates to processes for dielectri cally embossing foam and thermal reticulation processes for flexible foam to remove the windows in said foam. Processes for dielectrically embossing foam laminates are known and disclosed in patents such as U.S. patent 3,244,571, inventor M. Weisman and Canadian patent 601,681, inventor A. Cox et al. The laminate is a composite product made by dielectrically embossing foam and a cover fabric or film material such as nylon fabric or vinyl plastic sheet. Well known products such as seat cushions and automotive door panels are examples of #uch products. The advantage of dielectrically embossing foam and a cover fabric or film is that the process simultaneously shapes and embosses the product and adheres the cover material to the foam particu marly in the areas of greatest embossment. Any inconsistency in response of the foam to the dielectric energy field is manifested by inadequately embossed or adhered sections or overly heat treated sections of the product. This is believed to be due to irregularities in the effect of the dielectric field upon the foam from one part of the piece of foam to another. U.S. Patent 3,844,876, inventor Shuffman et al. discloses a particularly suitable process of simultaneously embossing and adhering a flexible film or fabric material to a flexible polyure thane foam by placing the foam and the material to be laminated to the foam in an embossing press, pressing the pieces together while subjecting them to a dielectric field to heat set the foam and adhere it to the flexible material. Such a process is im proved by the present invention. Foam materials that are not inherently active in a dielectric field, have been impregnated with chemicals such as polyvinyl chloride that are active in a dielectric field so that the result ing impregnated foam can be used in dielectric processes. Some times these foams, prior to being impregnated with the dielec trically active material, have been treated to open or reticulate the foam in order to facilitate impregnating the foam with a dielectrically active material. U. S. Patent 3,061,460, inventor E. Schickedanz discloses such technology. However, such foams are not inherently dielectrically active but require the posttreat ment of impregnating to become sufficiently dielectrically active anti accordingly are not suitable for use in the present invention. The present invention provides an improved dielectric embossing process for simultaneously adhering a dielectric ally active flexible foam to a flexible cover material and embossing the composite by the combined actions of pressure and a dielectric energy field. The process improved by the present invention comprises contacting a dielectrically active flexible foam with a flexible cover material, com pressing the foam and cover material as between two platens, to impress a predetermined pattern into the cover material and the foam (embossing) and subjecting the embossed composite to a dielectric energy field of at least 12 mH for a sufficient time to dielectrically heat the foam and set the impressed pattern into the foam and cover material and adhere the cover material to the foam. Such a process is improved by the present invention by thermally reticulating the foam prior to contacting the foam with the tover material which improves the uniformity of the embossed product particularly the consistency of the embossing and the adhesive bond between the foam and the cover material that is dielectrically heat set into the product during the process. The process, known in the art as dielectrically heat sealing or embossing, has been used to manufacture articles such as seat cushions, door panels for automobiles and similar laminated articles in which the foam component usually functions as a cushion, the cover material functions as a decorative and durable surface and the embossed pattern gives a decorative look and functional shape to the laminate. U. S. Patent 3,844,876, inventor Shuffman et al. and 3,244,571, inventor M. Weisman are incorporated herein by reference for their disclosures of dielectrical embossing processes employing a dielectrically active foam covered with a film such as vinyl or a fabric material such as woven nylon. Thermal reticulation of the foam prior to dielectrically embossing the foam is performed in accordance with the disclosure in U. S. Patent 3,175,025, inventor H. Geen which disclosure is incorporated herein by reference with respect to its teaching of thermally reticulating foam. In essence, a pressure vessel is filled with the foam, the gases in the vessel are evacuated, the vessel is then filled with an explosive mixture such as hydrogen and oxygen, the vessel is then sealed and the explosive mixture ignited. Because the pressure vessel is filled with foam, the explosive front or flame front precedes through the foam and the explosive force is absorbed by the foam. The flame front preceding through the foam burns or consumes the thin window membranes connecting the cells strands and forming cell walls. Thermally reticulated foam is described in U. S. Patent 3,390,106, inventor H. Geen which patent is incorporated herein by reference with respect to the description of thermally reticulated foam. it is believed that the thin cell membranes #connecting the strands of the cell walls have an ability to quickly assimilate energy because of their large surface area in comparison to the strands. Commercially produced foams tend to vary in their number and location of cell membranes which is manifested by a lalsge variance in the porosity of the foam. Thermal reticulation of the foam removes the cell membranes and essentially eliminates the porosity variance. The reticulated foam gives consistent performance in the dielectric embossing process. A comparison of two samples of foam, one thermally reticulated and one not thermally reticulated but otherwise identical, shows the difference between reticulated foam vs. the non-reticu lated foam in a dielectric energy field. A non-reticulated foam, when covered with a film or fabric material and put in a typical dielectric heat press gives irregular or inconsistent results in that for a particular energy setting in the press, one portion of the foam may be dielectrically heat set and the film material adhesively attached to the foam while another portion of the same piece of foam may not be adequately heat set although exposed to the same level of dielectric energy. If the dielectric energy to which the foam is exposed is increased to insure dielectrically heat setting all the foam, some portions or pieces of foam may be overly heat treated and arcing through the foam will occur. It has been found that pieces of foam from the same foam bun, though apparently uniform in chemistry and physical pore size, does vary significantly in porosity. This porosity variance is due to the difference in the number of cell windows and is believed to cause the difference in performance of the foam in dielectric embossing processes. By reticulating the foam, the porosity variance can be essentially eliminated and the variation in performance in dielectric heat sealing or embossing processes is thereby dramatically reduced. Preferred foams for use in the present invention are flexible polyurethane foams that are inherently active in a dielectric energy field. Inherently active means that the foam, as made, is sufficiently heated in a dielectric field of about 12 megahertz (mHz) to be heat set while compressed without requiring any separate treatments to acquire such dielectric activity. The preferred polyurethane foam is made from a polyol resin and isocyanate mixture with the polyol- selected for its activity in a dielectric field or the mixture is modified to be active in a dielectric field by adding dielectrically active ingredierrts such as polyvinyl chloride, vinyl acetate, metal powders, or salts to the mixture so that the resulting foam can be heated dielectrically. Foams that cannot be heated dielectrically but are posttreated, e.g., coated or impregnated after foaming, to be dielectrically active, are not suitable for use in the present Invention because such foams are not inherently dielectrically active, that is without the posttreatment, the foam is not signiti- cantly heated in a dielectric field of about 12 mH The preferred, inherently dielectrically active, flexible polyurethane foam is made by a conventional one-shot, polyurethane foam manufacturing process from the following recipe: : Ingredient Parts by weight NIAX polyol E-396 100 Water 2.3 Diethanolamine 0.8-1.0 NIAX A-l 0.10 DABCO 33LV 0.30 Dibutyltindilurate, T12 0.30 Silicone surfactant Y-6922 1.5-1.8 Fyrol FR-2 5.0 Blowing Agent 8.0 NIAX Isocyanate TDI 32.7-33.2 Some of the ingredients listed in the above recipe for the preferred polyurethane foam are listed according to their commer tidal trade name and are defined chemically as follows: NIAX polyol E-396 is a polymer polyol, based on a polyether polyol, with a molecular weight in the range of about 4,500 to 5,500, having a high ethylene oxide cap to provide a high percentage of primary hydroxyl end groups, and grafted with acrylonitrile and styrene. The dielectric activity of the resulting foam is mainly imparted by this polymer polyol primarily. due to the grafting with acrylonitrile and styrene and the molecular weight of the polyether based polymer polyol with its highly active primary hydroxyl terminal groups. NIAX polyol E-396 is available from Union Carbide Corporation. NIAX catalyst A-l is a mixture of 70% dis (2dimethylaminoethyl) ether and 30% dipropylene glycol. This catalyst is available from Union Carbide Corporation. DABCO 33LV is a mixture of one part triethylenediamine and two parts dipropylene glycol and available from Houdry Process and Chemical Company of Philadelphia, Pennsylvania. Silicone surfactant Y-6922 is available from Union Carbide Corporation and it is a copolymer of dimethyl polysiloxane and polyoxyalkylene ether. Fyrol FR-2 is available from Stauffer Chemical Company and is Tris (dichloropropyl) phosphate. The Blowing Agent is preferably methylene chloride or NIAX blowing agent 11 which is a fluorocarbon (trichloromonofluoro methane) . NIAX isocyanate is toluene diisocyanate, ¯ the 80/20 isomer blend. The above recipe has an index. of 105. Polyurethane foam can be either thermally or chemically reticulated. However, for practicing the present invention, it is necessary that the foam be thermally reticulated. After reticulation of the foam, a cover material is placed thereon and the composite is compressed with a predetermined embossing pattern by placing the composite into a press that impresses a pattern simultaneously into the cover material and the foam. The pattern is set by subjecting the composite to dielectric energy which heats the - foam and thermally bonds the foam in the shape of the impressed pattern and adheres the foam to the cover material (referred to as dielectrically heat set). Suitable cover materials are flexible, thermoplastic films such as vinyl plastic with or without a fabric backing and woven and nonwoven cloth preferably containing thermoplastic fibers. Dyes if used to color the cloth or the vinyl film should be a nonmetallic dye so as to avoid arcing during dielectric heating which would cause scorching and discolorations of the cover material. The patents cited in the background of the art which disclosed dielectric embossing processes (Weisman, Shuffman and Schickedanz) disclose suitable cover materials and dielectric embossing processes and those patents are incorporated herein by reference with respect to such disclosures. The dielectric embossing processes for simultaneously embossing a foam and adhering a cover material to the foam as disclosed .in those patents are improved in accordance with the present invention. The best mode presently contemplated for practicing the present invention is by thermally reticulating with hydrogen and oxygen in a pressure vessel, the# polyurethane foam made according to the preferred recipe given above, placing a cover material of woven nylon fabr-ic over a piece of the reticulated foam, placing the reticulated foam with the cover material between two platens, at least one of which has a predetermined embossing pattern, compressing the foam and fabric between the platens with the fabric covered surface being compressed by a platen- having a predetermined embossing pattern, subjecting the compressed reticulated foam and cover material fo a dielectric field of at least 12 mH and preferably between 12 and 60 mH for sufficient time to- dielectrically heat set the embossed pattern into the foam and fabric material and adhesively bond the fabric material to the foam followed by partially cooling the embossed foam and cover material while still compressed between the platens. When a stronger adhesive bond is desired, an adhesive can be placed between the cover material and the foam to supplement the dielec Ily induced adhesive bond between the foam and the cover material. The product produced by the above process has significantly improved consistency in the adhesive bond when subjected to a uniform dielectric field compared to product produced by an otherwise identical dielectric embossing process but using nonreticulated foam.

Claims: CLAIMS 1. A dielectric embossing process for simultaneously adhering a flexible cover material to a dielectrically active flexible foam and embossing the composite of the foam and the cover material, which process comprises contacting the foam with the cover material, compressing the foam and cover material to impress a predetermined pattern into the cover material and the foam, subjecting the compressed composite to a dielectric energy field of at least 12 mHz for a sufficient time to dielectrically heat the foam and set the impressed pattern into the foam and the cover material and adhere the cover material to said foam, characterised by thermally reticulating the foam prior to contacting the foam with the cover material. 2. A-method as claimed in claim 1, characterised in that said foam is a polyurethane foam made from a polyether based polymer polyol. 3. A method as claimed in claim 1 or 2, characterised in that said cover material is a thermoplastic film or nylon fabric and dyed with a non-metallic dye. 4. A product characterised by being produced by a process as claimed in any one of claims to 3. 5. A dielectrically embossed laminate characterised by comprising a thermally reticulated inherently dielectrically active, flexible foam, a flexible cover material adhesively attached to the reticulated foam, a dielectrically heat set adhesive bond between said cover material and said foam and a dielectrically heat set embossing. pattern in said cover material and polyurethane foam. 6. An embossed laminate as claimed in claim $ characterised in that said foam is free of posttreatments to impregnate the foam with a dielectrically active material. 7. An embossed laminate as claimed in claim 5 or 6, characterised in that said cover material is a woven or non-woven fabric containing thermoplastic fibers, or a thermoplastic film. 8. An embossed laminate as claimed in any one of claims 5 to 7, characterised in that said cover material is dyed with a non-metallic dye. 9. An embossed laminate as claimed in any one of claims 5 to 8, characterised in that said foam is a polyurethane foam.

Inventors: VOLZ, ROBERT ANDREW
Applicants: SCOTT PAPER COMPANY
Application year: 1980
Main classification: B29D27
IPC codes: B29C67, B29C59, B29C65, B29C44, B29C43