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United States Patent  [ii] Patent Number: 5,424,016
Kolosowski  Date of Patent: Jim. 13,1995
Related U.S. Application Data
 Continuation of Ser. No. 960,049, Oct. 13, 1992, abandoned, which is a division of Ser. No. 693,835, Apr. 30, 1991, abandoned.
 Int. CI.* B29C 44/00; B26F 1/24
 U.S. CI 264/156; 264/51;
264/52; 264/DIG. 5; 264/DIG. 13; 425/4 C;
425/290; 425/817 C
 Field of Search 264/51-54,
264/153, 154, 155, 156, 41, DIG. 5, DIG. 13, DIG. 16; 425/4 R, 4 C, 290, 817 C
 References Cited
U.S. PATENT DOCUMENTS
3,396,616 8/1968 Wright 83/16
3,573,152 3/1971 Wiley et al 264/54
3,682,739 8/1972 Tesch et al 264/156
3,867,498 2/1975 Krouskop 264/156
3,966,526 6/1976 Doerfling 428/131
3,967,991 7/1976 Shimano et al 264/230
4,183,984 1/1980 Brewers et al 428/131
4,340,129 7/1982 Salyers 428/131
4,368,276 1/1983 Park 264/53
4,395,510 7/1983 Park 524/230
4,440,703 4/1984 Akiyama et al 264/53
4,485,193 11/1984 Rubens et al 264/53
4,663,361 5/1987 Park 264/DIG. 5
4,824,720 4/1989 Malone 428/294
4,931,484 6/1990 Hovis et al 521/143
5,059,376 10/1991 Pontiff et al 264/234
5,059,631 10/1991 Hovis et al 264/52
5,066,531 11/1991 Legg et al 264/154
5,124,097 6/1992 Malone 264/51
5,225,451 7/1993 Rogers et al 521/94
FOREIGN PATENT DOCUMENTS
46-25639 7/1971 Japan 264/156
54-6593 3/1979 Japan 264/154
56-8237 6/1979 Japan 264/156
61-06801310 7/1986 Japan .
2102808A 2/1993 United Kingdom .
Primary Examiner—Jay H. Woo
Assistant Examiner—Duane S. Smith
Attorney, Agent, or Firm—J. Robert Dean, Jr.
Disclosed is a method for providing accelerated release of a flammable blowing agent from a plastic foam. The method comprises (a) providing the plastic foam having the blowing agent and a permeability modifier therein and (b) perforating the foam at its surface to form a multiplicity of channels extending from the surface into the foam. The channels are in gaseous communication with the environment outside the foam structures and provide accelerated released of blowing agent.
20 Claims, 2 Drawing Sheets
METHOD FOR PROVIDING ACCELERATED
RELEASE OF A BLOWING AGENT FROM A
CROSS-REFERENCE TO RELATED
This application is a continuation of application U.S. Ser. No. 07/960,049, filed Oct. 13, 1992, now abandoned which is a divisional of application U.S. Ser. 10 No. 07/693,835, filed Apr. 30, 1991, now abandoned.
BACKGROUND OF INVENTION
Concern over ozone depletion in the atmosphere has prompted calls for the replacement of chlorofluorocar- 15 bon foam blowing agents with blowing agents offering substantially reduced ozone depletion potential such as hydrocarbons.
Hydrocarbons and some other alternative blowing agents present their own unique problems. Chief among 20 these is greater fire hazard in closed-cell foams due to entrapped blowing agent. Other problems however, may include toxicity or environmental incompatibility. The flame retardancy or environmental incompatibility of closed-cell foams may be slow to recover due to the 25 relatively slow permeation of some blowing agents, including hydrocarbons, from the foams.
To address the problem of flame retardancy, it would be desirable to have a closed-cell foam structure which more quickly releases blowing agents, particularly flam- 30 mable blowing agents. Also desirable would be a process for making such a foam structure.
SUMMARY OF THE INVENTION
According to the present invention, there is a closed- 35 cell plastic foam structure comprising a plastic foam defining a multiplicity of channels extending from the surface of the foam into and preferably through the foam. The channels are free of direction with respect to the longitudinal extension of the foam. The channels are 40 in gaseous communication with the environment outside of the foam structure, and provide enhanced release of blowing agent from the foam structure.
Further according to the present invention, there is a process for making a plastic foam structure comprising 45 (a) providing the plastic foam and (b) perforating the foam at its surface to form a multiplicity of channels extending from the surface into and preferably through the foam to form the foam structure. The channels are free of direction with respect to the longitudinal exten- 50 sion of the foam and in gaseous communication with the environment outside of the foam structure.
BRIEF DESCRIPTION OF THE DRAWING
The novel features of the present invention and the 55 context within which they are set will be better understood upon reviewing the following specification together with the drawings.
FIG. 1 shows a foam structure according to the present invention. 60
FIG. 2 shows a cross-sectional view along line 2—2 of the foam structure of FIG. 1.
FIG. 3 shows a typical structure for perforating the plastic foam according to the present invention.
DETAILED DESCRIPTION 65
A closed-cell plastic foam structure of the present invention providing enhanced release of blowing agent
is seen in FIGS. 1 and 2, and is referenced generally by the reference numeral 10. Foam structure 10 comprises plastic foam 20 and a multiplicity of channels 30 extending into foam 20 from one or both of opposing surfaces 40. Structure 10 also defines opposing surfaces 50, which are generally perpendicular to surfaces 40!
Plastic materials suitable for the foams of the present foam structure include any known foamable thermoplastic or thermoset material. Suitable plastic materials may include blends of two or more thermoplastic materials, two or more thermoset materials, or thermoset and thermoplastic materials. Suitable plastic materials include polystyrene, polyolefins such as polyethylene and polypropylene, polyurethanes, and polyisocyanurates. Suitable thermoplastic materials may be homopolymers or copolymers of monoethylenically unsaturated comonomers. Useful polystyrene or known derivatives thereof include alphamethylstyrene, butylstyrene, and divinyl benzene. The present invention is particularly useful with polyethylene. Useful polyethylenes include those of high, medium, low, and ultra-low density types. Useful polyethylenes include copolymers thereof such as ethylene-acrylic acid, ethylene-vinyl acetate, and the like.
The foam of the foam structure may further contain elastomeric components such as polyisobutylene, polybutadiene, ethylene/propylene copolymers, and ethylene/propylene diene interpolymers if desired. Other possible additional components include crosslinking agents if desired. Other additional components may include nucleating agents, extrusion aids, antioxidants, colorants, pigments, etc. if desired.
The foam of the foam structure may contain one or more permeability modifiers in a quantity sufficient to prevent substantial shrinkage of the structure upon its formation from premature excessive loss of blowing agent yet allow evolution of the blowing agent from it. Suitable permeability modifiers include fatty acid amides and esters such as stearyl stearamide and glycerol monostearate.
The present foam structure is extruded with one or more of any blowing agents known in the art. Suitable volatile blowing agents include halocarbons such as fluorocarbons and chlorofluorocarbons; hydrohalocarbons such as hydrofluorocarbons and hydrochlorofluorocarbons; alkylhalides, such as methyl chloride and ethyl chloride; hydrocarbons such as alkanes or alkenes; and the like. Other suitable blowing agents include pristine blowing agents such as air, carbon dioxide, nitrogen, argon, water, and the like. The blowing agent may comprise a mixture of two or more of any of the above blowing agents. Other suitable blowing agents also include chemical blowing agents such as ammonium and azo type compounds. Such compounds include ammonium carbonate, ammonium bicarbonate, potassium bicarbonate, diazoaminobenzene, diazoaminotoluene, azodicarbonamide, diazoisobutyronitrile, and the like.
Preferred blowing agents are hydrocarbons, which include alkanes having from 2 to 9 carbon atoms. Preferred alkanes include butane, isobutane, pentane, isopentane, hexane, isohexane, heptane, and the like. A most preferred blowing agent is isobutane.
Though the blowing agent may be flammable or nonflammable, the present foam structure is particularly useful with flammable blowing agents because of the accelerated release of blowing agents that it provides.