Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • 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
  • B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
  • B29C44/34—Auxiliary operations
  • B29C44/36—Feeding the material to be shaped
  • B29C44/46—Feeding the material to be shaped into an open space or onto moving surfaces, i.e. to make articles of indefinite length
  • B29C44/468—Feeding the material to be shaped into an open space or onto moving surfaces, i.e. to make articles of indefinite length in a plurality of parallel streams which unite during the foaming
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2323/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers

Definitions

• the invention relates to a closed-cell, non- crosslinked polyolefin foam structure of relatively small cell size and relatively low cross-section minor to major dimension ratio.
• the extruded structure is substantially free of distortion, convolution, or corrugation from its intended shape or geometry.
• Solid closed-cell polyolefin foam structures of relatively low cross-section minor to major dimension ratio, height to width in the case of those of rectangular cross-section, have found numerous commercial applications such as cushioning, packaging, insulation, sheeting, and the like. To enhance insulative performance, softness, sound absorption, and nonabrasiveness of such structures, it would be desirable to reduce the cell size of the polyolefin foam comprising the structure.
• a problem with making solid closed-cell, non- crosslinked polyolefin foam structures of relatively small cell sizes (e.g. 0.02 to 0.5 millimeters (mm)) and relatively low cross-section dimension ratios (e.g. 1/8 or less) is that the structure actually formed may be in a geometry or shape other than that intended.
• the foamable composition from which the structure is made exits the die, it is not able to expand directionally outward with respect to the major dimension of the die orifice at a rate sufficient to prevent the structure from becoming distorted, convoluted, or corrugated along its major dimension.
• the structure cannot expand rapidly enough because relatively small cell size foams
• a 5 closed-cell, non-crosslinked foam structure of a ratio of minor dimension to major dimension of about 1/8 or less in cross-section comprised of coalesced strands or profiles of a foamed polyolefin composition having an average cell size of from 0.02 to 0.5 millimeters.
• the 0 foam structure substantially corresponds in cross- sectional geometry to the geometry of the overall arrangement of the orifices of the die from which it was extruded.
• the extrusion of the foam structure in the form of coalesced strands or profiles allows structures of such relative cross-sectional dimension ratios (e.g.
• a process for making a closed-cell, non-crosslinked foam structure of a ratio of minor dimension to major dimension in cross-section of 1/8 or less and comprised of a foamed polyolefin composition having an average cell size of from 0.02 to 0.5 millimeters comprises extruding a foamable polyolefin composition through a die defining a plurality of orifices therein to form a plurality of coalesced extruded strands or profiles of the foamed polyolefin composition forming the above foam structure substantially corresponding to the geometry of the overall arrangement of the orifices of the die.
• the present foam structure is formed of coalesced closed-cell, non-crosslinked polyolefin foam strands or profiles having an average cell size of from 0.02 to 0.5 millimeters and minor to major dimension ratios of less than 1/8 or less to be made substantially corresponding to the shape or geometry of the overall arrangement of the orifices of the die from which the structure was extruded.
• the present foam structure circumvents the problems associated with prior art foam structures of that cell size range and relative dimension by its ability to accommodate the high rate of foaming without being distorted, convoluted, or corrugated.
• the present foam structure is formed by extrusion of a molten foamable, non-crosslinked polyolefin composition through a multiorifice die.
• the foamable composition is formed by melt plastifying the polyolefin and blending therein a blowing agent and other additives such as a nucleating agent.
• the streams of molten extrudate exiting the die take the form of strands or profiles, which desirably foam, coalesce, and adhere to one another to form a unitary structure.
• the coalesced individual strands or profiles 0 of polyolefin foam should remain adhered into unitary structure to prevent strand delamination under stresses encountered in preparing, shaping, and using the foam. Apparatuses and methods for producing foam structures of strand form are seen in U.S. Patents 3,573 * 152 and 5 4,82-4, 720.
• the strands or profiles will vary in cross- sectional shape or geometry according to the shape or geometry of the orifices in the die.
• the strands or 0 profiles may be the same or different shape or geometry than the foam structure which they coalesce to form.
• the orifices may take on a circular shape or a noncircular shape though circular is preferred. Suitable noncircular shapes include X-shaped, cross- or star-shaped, or polygonal-shaped.
• the various orifices in the die may be specially arranged in a desired configuration or array such as a sine wave, honeycomb, square saw tooth, or a triangular saw tooth wave pattern.
• the individual strands have a major dimension in cross-section, diameter in the case of circular strands, of between 0.5 and 10 millimeters and most preferably between 1.0 and 5.0 millimeters.
• the orifices in the die will be of shape or
• the streams of molten extrudate may foam to either partly or completely fill the open channel volume 0 between the strands or profiles.
• the geometry or shape of the resulting foam structure will substantially correspond to the overall arrangement or geometry of the die orifices or, in other 5 words, to the intended or desired shape or geometry. For instance, a plurality or multiplicity of circular orifices arranged in a rectangular pattern will yield a rectangular foam structure. A plurality or multiplicity of circular orifices arranged in a circular pattern will 0 yield a cylindrical or circular foam structure.
• the geometry or shape of the present foam structure will correspond to the overall arrangement or geometry of the orifices in the die from which it is extruded without substantial distortion, convolution, or corrugation therefrom.
• the foam structure typically will have cross- sectional dimensions larger than the dimensions defined by the overall arrangement or geometry the die orifices of the die from which it was extruded due to foaming of the molten extrudate, but the relative cross-sectional dimensions of the foam structure will substantially correspond to the relative dimensions of the overall
• the resulting foam structure will have rectangular cross-sectional dimensions exceeding _.,- that of the overall arrangement or geometry of the die orifices, but will have substantially the same relative cross-sectional dimensions.
• a mixer, extruder, or other suitable blending device is employed to obtain a homogeneous melt.
• the extruder or other 5 suitable blending device is also employed to incorporate a blowing agent. Nucleating agents, extrusion aids, antioxidants, colorants, pigments, etc. may also be incorporated as desired.
• Suitable foamable polyolefin compositions include polyethylene or polypropylene. Preferred are copolymers of ethylene and a monoethylenically unsaturated polar monomer copolymerizable therewith, especially carboxyl-containing comonomers.
• Examples include copolymers of ethylene and acrylic acid or methacrylic acid and C ⁇ _4 alkyl ester or ionomeric derivatives thereof; ethylene vinyl-acetate copolymers; ethylene/carbon monoxide copolymers; anhydride containing olefin copolymers of a diene and a polymerizable; copolymers of ethylene and an ⁇ -olefin having ultra low molecular weight (i.e., densities less than 0.92 grams/cubic centimeter); blends of all of the foregoing resins; blends thereof with polyethylene (high, intermediate or low density); etc.
• ultra low molecular weight i.e., densities less than 0.92 grams/cubic centimeter
• compositions are copolymers of ethylene and acrylic acid, (EAA copolymers) having up to about 30 percent by weight of copolymerized acrylic acid; ionomeric derivatives of the foregoing, copolymers of ethylene and vinyl acetate; ultra low density polyethylene; and blends of the foregoing with one another and with low density polyethylene.
• EAA copolymers having up to about 30 percent by weight of copolymerized acrylic acid
• ionomeric derivatives of the foregoing, copolymers of ethylene and vinyl acetate ultra low density polyethylene
• blends of the foregoing with one another and with low density polyethylene are particularly preferred compositions.
• the polymers of ethylene and a polar comonomer may be prepared by known addition polymerization techniques, or by a grafting reaction of the reactive comonomer with a preformed polymer of ethylene. Additional elastomeric components such as polyiso- butylene, polybutadiene, ethylene/propylene copolymers, and ethylene/propylene diene interpolymers may be included in the blend if desired.
• a most preferred resin composition comprises a copolymer of ethylene and acrylic acid or ethylene and vinyl acetate containing from 85 percent to 98 percent ethylene by weight.
• a most preferred polyolefin composition comprises a homogeneous, random copolymer of ethylene and acrylic acid. Copolymers of ethylene and acrylic acid or of ethylene and vinyl acetate may be obtained from The Dow Chemical Company. Ethylene vinyl acetate copolymer may also be obtained under tradename Elvax from E. I. duPont deNemours & Company. Anhydride modified copolymers or ethylene are available under the tradename Plexar from Norchem, Inc. Ionomeric copolymers are available under the tradename Surlyn from E. I. duPont deNemours & Company.
• the polyolefin composition comprises greater than 50 percent, preferably greater than 80 percent, and more preferably greater than 95 percent polyolefin by weight of the foam structure.
• blowing agents include halocarbons such as fluorocarbons and chlorofluorocarbons; hydrohalocarbons 5 such as hydrofluorocarbons and hydrochlorofluorocarbons; alkylhalides such as methyl chloride and ethyl chloride; hydrocarbons such as the alkanes or alkenes of 2 to 9 carbon atoms; common gases such as air, carbon dioxide, Q nitrogen, argon; water; or mixtures of any of the above.
• halocarbons such as fluorocarbons and chlorofluorocarbons
• hydrohalocarbons 5 such as hydrofluorocarbons and hydrochlorofluorocarbons
• alkylhalides such as methyl chloride and ethyl chloride
• hydrocarbons such as the alkanes or alkenes of 2 to 9 carbon atoms
• common gases such as air, carbon dioxide, Q nitrogen, argon; water; or mixtures of any of the above.
• blowing agents are alkanes such as butane, isobutane, pentane, isopentane, hexane, isohexane, heptane, and the like.
• a most preferred C blowing agent is isobutane.
• hydrocarbons such as alkanes are preferred due to their relatively low ozone depletion potential.
• 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.
• non-crosslinked foam structure means that the foam composition comprising the strands from which the foam structure is formed is substantially free of crosslinking.
• non-crosslinked is inclusive however, of the slight degree of crosslinking which may occur naturally without the use of crosslinking agents.
• Suitable foam structures have gross densities (that is bulk densities or densities of the closed-cell foam including interstitial channels or voids between strands or profiles), preferably varying from 3.2 to 48 kilograms per cubic meter (kg/m3). Most preferred foam
• a preferable alternate embodiment comprises portions having densities less than 32 kg/m3.
• the individual * - strands of foam comprising the foam structure preferably possess a local or strand density from 8.0 to 96 kg/m3, and most preferably from 16 to 48 kg/m3.
• the present foam structure is comprised of foam 0 strands having an average cell size of between 0.02 to 0.5 millimeters.
• a particularly preferred foam structure is comprised of foam strands having an average cell size of between 0.1 and 0.3 millimeters.
• closed-cell foam structure preferably at least 70 percent closed-cell according to ASTM D-2856 not including interstitial channels or voids between the foam strands comprising the foam structure.
• a polyolefin foam structure of the present invention was formed by extruding a composition of polyethylene/ Surlyn ® 8660 ionomer in a 90/10 weight ratio, 26 parts per hundred CFC-114/CFC-12 in a 80/20 weight ratio, and 0.8 parts per hundred at a rate of 136 kilograms per hour through a multiorifice die containing 1500 circular orifices arranged in a rectangular configuration.
• the resulting structure had a cross- sectional dimension of 3.8 centimeters by 62.2 centimeters and an average cell size of 0.3 millimeters.
• the structure was substantially free of distortion

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
• Extrusion Moulding Of Plastics Or The Like (AREA)

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Publications (2)

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Family Applications (1)

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Citations (3)

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• 1992
  • 1992-02-21 JP JP4508185A patent/JPH06505935A/ja active Pending
  • 1992-02-21 EP EP92908512A patent/EP0587581A1/en not_active Withdrawn
  • 1992-02-21 WO PCT/US1992/001394 patent/WO1992016363A1/en not_active Application Discontinuation
  • 1992-02-21 KR KR1019930702859A patent/KR100195552B1/ko not_active IP Right Cessation
  • 1992-02-21 HU HU9302683A patent/HU213639B/hu not_active IP Right Cessation
  • 1992-02-21 AU AU15812/92A patent/AU1581292A/en not_active Abandoned
  • 1992-02-21 CA CA002104961A patent/CA2104961C/en not_active Expired - Fee Related
  • 1992-03-24 MX MX9201305A patent/MX9201305A/es unknown
  • 1992-03-24 TW TW81102220A patent/TW257774B/zh active
• 1993
  • 1993-09-24 NO NO933415A patent/NO933415D0/no unknown
  • 1993-09-24 FI FI934187A patent/FI934187A/fi not_active Application Discontinuation

Patent Citations (3)

Non-Patent Citations (1)

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