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
  • C08J9/04—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent
  • C08J9/12—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent by a physical blowing agent
  • C08J9/122—Hydrogen, oxygen, CO2, nitrogen or noble gases
• • 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
  • C08J9/0061—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof characterized by the use of several polymeric components
• • 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
  • C08J9/04—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent
  • C08J9/12—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent by a physical blowing agent
  • C08J9/125—Water, e.g. hydrated salts
• • 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
  • C08J2201/00—Foams characterised by the foaming process
  • C08J2201/02—Foams characterised by the foaming process characterised by mechanical pre- or post-treatments
  • C08J2201/03—Extrusion of the foamable blend
• • 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
  • C08J2203/00—Foams characterized by the expanding agent
  • C08J2203/10—Water or water-releasing compounds
• • 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
  • C08J2203/00—Foams characterized by the expanding agent
  • C08J2203/12—Organic compounds only containing carbon, hydrogen and oxygen atoms, e.g. ketone or alcohol
• • 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
  • C08J2205/00—Foams characterised by their properties
  • C08J2205/04—Foams characterised by their properties characterised by the foam pores
  • C08J2205/052—Closed cells, i.e. more than 50% of the pores are closed
• • 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
  • C08J2325/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an aromatic carbocyclic ring; Derivatives of such polymers
  • C08J2325/02—Homopolymers or copolymers of hydrocarbons
  • C08J2325/04—Homopolymers or copolymers of styrene
  • C08J2325/06—Polystyrene
• • 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
  • C08J2425/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an aromatic carbocyclic ring; Derivatives of such polymers

Definitions

• the present invention generally relates to foam structures, and more particularly, to foam structures made from a melt polymer material comprised of a styrenic polymer, a random styrene butadiene copolymer resin, and an inorganic blowing agent, and to a process for forming the same.
• Extruded synthetic resinous foams such as extruded polystyrene foams
• Rigid foams for insulation and food packaging are made by the extrusion of molten polystyrene to which a blowing agent has been added.
• Typical blowing agents include hydrocarbons, halofluorocarbons, and mixtures of these blowing agents with carbon dioxide.
• Foam structures can also be made using alternative methods, such as injection molding.
• Thermal insulation is a particularly important application for styrene polymer foams.
• Polystyrene is combined in molten form under pressure with a 100% carbon dioxide blowing agent and the mixture is extruded through a die into an atmosphere of reduced pressure to form the foam structure.
• the foam structure has a basis weight of less than 20 gms/100 sq. inch and a density of about 6 lbs/cubic feet or less.
• the resins may be styrene homopolymers or copolymers containing a predominant portion of styrene, i.e. greater than about 50% wt styrene.
• the comonomer may be any other ethylenically unsaturated material such as the conjugated 1 ,3-dienes, e.g., butadiene, isoprene, etc.
• the foam structure has a density of 10 to 150 kilograms per cubic meter (kg/m 3 ) according to ASTM D-166; an average cell size of 0.05 to 5.0 millimeters according to ASTM D3576-77; and preferably is greater than 90 percent closed-cell according to ASTM D2856-A.
• the aforesaid U.S. Patent No. 6,268,046 B1 issued to Larry M. Miller, et al on July 31 , 2001 and assigned to Owens Corning Fiberglas Technology Inc. discloses foamable mixtures containing two different styrenic polymers and carbon dioxide as a blowing agent.
• the foamable mixture comprises a minor amount of styrenic polymer having a high melt index of 10 to 35, a major amount of styrenic polymer having a low melt index; and a blowing agent having a major amount of carbon dioxide.
• elastomeric rubbers may be added to the foamable mixture to facilitate processing of the foamable mixture in the extruder and to enhance relaxation of the resultant foam bodies.
• the elastomers may be copolymers of styrene and a diene, such as butadiene or isoprene.
• the copolymers typically are block copolymers such as diblock, triblock or radial block copolymers.
• a first control agent consists of ethanol that dissolves and cools the melt
• the second control agent consists of H 2 0 2 that cools the melt.
• the amount of ethanol is sufficient to achieve the highest possible dissolution of C0 2 in the melt and the injected amount of H 2 0 2 is such that the foaming produced by ethanol is minimized.
• the styrenic polymer foam emerging from a foam extrusion line attains a stable physical form as quickly as possible.
• a stable physical form is achieved when the dimensional and/or mechanical properties of the extruded structure do not change appreciably with time. Factors that influence the rate of achieving such stability include: 1 ) the rate at which the blowing agent gas diffuses from the nascent foam at the extruder die head, and 2) the solubility of the blowing agent in the polymer.
• a further disadvantage of using an inorganic blowing agent in extruded styrenic polymer foam structures is that the foam structures require a long storage time in order for the foam structures to reach mechanical stability, which adds to the overall production costs.
• the present invention relates to styrenic polymer foams, which may be referred to as "extruded foams" if made by extrusion.
• the invention involves the addition of a low molecular weight random styrene butadiene copolymer resin (SBC) to a styrenic polymer, e.g. polystyrene of the type conventionally used in making polystyrene foam, e.g. extruded polystyrene foam, particularly insulation board, where in the invention the time for the foam board to achieve at least the required mechanical stability is substantially reduced.
• SBC low molecular weight random styrene butadiene copolymer resin
• a melt polymer material for a foam structure comprises from about 80% to about 98% by weight of a styrenic polymer; from about 1 % to about 10% by weight of a low molecular weight random styrene butadiene copolymer resin; and from about 1% to about 10% by weight of an inorganic blowing agent.
• the inorganic blowing agent is carbon dioxide.
• the foam structure is preferably an extruded foam structure, but may be, for example, an injection molded structure.
• the present invention relates to a process for making a styrenic polymer foam structure, comprising: a) heating a styrenic polymer to form a melt polymer material; b) incorporating into the melt polymer material, a low molecular weight random styrene butadiene copolymer resin in an amount ranging from about 1 % to about 10% by weight based on the total weight of the melt polymer material, and an inorganic blowing agent in an amount ranging from about 1% to about 10% by weight based on the total weight of the melt polymer material material; and c) subjecting the resultant mixture of b) to a molding process to form a foam structure.
• step c) the resultant mixture of b) is extruded through a die to form the foam structure. If the foam structure is an injection molded structure, then in step c) the resultant mixture of b) is injection molded to form the foam structure,
• the random styrene butadiene copolymer resin has a low weight average molecular weight ranging from about 100,000 to about 140,000; a molecular weight distribution (MWD) ranging from about 2.0 to about 8.0; and a ratio of styrene monomer to butadiene monomer ranging between about 80:20 and about 95:5 by weight.
• the weight percent of styrene is 86% and that of butadiene is 14% based on the weight of the copolymer resin.
• the random styrene butadiene copolymer resin and the blowing agent generally are mixed or blended into the styrenic polymer in a heat plastifying and mixing apparatus, such as an extruder.
• an object of the present invention to provide a melt polymer material for a styrenic foam structure, e.g. an extruded styrenic foam structure, that uses an inorganic blowing agent whereby at least mechanical stability can be achieved faster than that of conventional extruded foam structures, thereby reducing storage time and production costs while still maintaining the required mechanical properties and/or thermal properties for a foam structure.
• a melt polymer material is extruded and foamed into foam products, such as foam board, foam sheet and other foam structures, or can be subject to other processes, such as injection molding, to produce foam structures.
• the melt polymer material is comprised of a styrenic polymer, a low molecular weight random styrene butadiene copolymer resin, and an inorganic blowing agent.
• a suitable styrenic polymer includes styrene homopolymers or copolymers containing a predominant portion of styrene, i.e. greater than about 50% by weight styrene.
• the comonomer can be any other ethylenically unsaturated material such as the conjugated 1 ,3-dienes, e.g. butadiene, isoprene, etc.
• the styrenic polymer as used in the invention may also include polymers of alkyl and halogen substituted styrene such as alpha-methylstyrene, para-isobutylstyrene, para-chlorostyrene, and the like as well as copolymers of styrene and vinyl substituted monomers such as maleic anhydride, etc.
• a preferred styrenic polymer has styrenic monomer units greater than 50% by weight, and preferably, about 90% to about 100% by weight.
• Preferred styrenic polymers are polystyrene, styrene-acrylonitrile, styrene methylmethacrylate, and styrene-maleic anhydride.
• the styrenic polymer is polystyrene, preferably, it is crystal polystyrene with a melt flow index of about 5 g/10 minutes.
• the styrenic polymer has a weight average molecular weight ranging from about 200,000 to about 500,000.
• Suitable styrenic polymers are available commercially from a variety of sources and are available with different properties such as melt flow index, molecular weight, and so on. Such polystyrenes are available from NOVA Chemicals Inc. (U.S., Canada, and Europe).
• the melt polymer material of the invention may include flame-retardant chemicals, stabilizers, pigments, extrusion aids, antioxidants, fillers, antistatic agents, UV absorbers, etc.
• these additives may be included in any amount to obtain the desired characteristics in the melt polymer material or in the resultant foamed bodies, and may be added to the styrenic polymer before, during, or after polymerization of the styrenic polymer, or may be added to the styrenic polymer in an extrusion, or other, process.
• the random styrene butadiene copolymer resin has a low molecular weight ranging from about 100,000 to about 140,000 weight average molecular weight; a molecular weight distribution (MWD) ranging from about 2.0 to about 8.0; and a ratio of styrene monomer and butadiene monomer ranging between about 80:20 and about 95:5 by weight.
• MWD molecular weight distribution
• the weight percent of styrene in the random styrene butadiene copolymer resin is about 86% and the weight percent of butadiene is about 14% based on the weight of the copolymer.
• the weight average molecular weight of the random styrene butadiene copolymer is about 120,000, and the molecular weight distribution (MWD) is about 4, and more preferably, about 3.
• the MWD is obtained by dividing the weight average molecular weight by the number average molecular weight. Thus if the weight average molecular weight is 120,000 and the MWD is 4, the number average molecular weight is 30,000.
• a suitable random styrene butadiene copolymer resin is one that is made through a suspension polymerization process via a free radical polymerization initiator.
• Such random styrene butadiene copolymer resin is that produced by the process taught in the aforesaid U.S. Patent No. 4,558,108, which is incorporated herein by reference in its entirety.
• This random styrene butadiene copolymer resin may be obtained from NOVA Chemicals (International) S.A., Fribourg, Switzerland under the trade name XP-808.
• a "random styrene butadiene copolymer resin” is defined as a low molecular weight copolymer of styrene and butadiene monomers in which the monomers are incorporated randomly into the copolymer chains.
• the amount of random styrene butadiene copolymer resin (SBC) ranges from about 1% by weight to about 10% by weight, and preferably from about 2% to about 9% by weight, based on the weight of the melt polymer material.
• the amount of styrenic polymer ranges from about 80% to about 98% by weight, and preferably from about 82% by weight to about 96% by weight based on the weight of the melt polymer material.
• the amount of inorganic blowing agent ranges from about 1% to about 10% by weight, and preferably from about 2% to about 9% by weight based on the weight of the melt polymer material.
• the inorganic blowing agent is selected from the group consisting of carbon dioxide, nitrogen, air, water, helium, and argon, and/or blends thereof.
• a preferred inorganic blowing agent is carbon dioxide. If a blend of inorganic blowing agents is used, then preferably, the amount of carbon dioxide will be greater than about 50% by weight, and preferably 90% by weight, based on the total weight of the blowing agent.
• the blowing agent may be a mixture of carbon dioxide and at least one lower alcohol.
• a lower alcohol is an alkyl alcohol containing from 1 to about 4 carbon atoms. Lower alcohols include methanol, ethanol, propanol, isopropanol and butanol.
• the carbon dioxide and blowing agent mixtures may also be used with additional, optional and supplemental blowing agents, such as air, nitrogen, helium, argon, and water.
• the amount of alkyl alcohol will range from about 0.1% to about 0.5% by weight based on the weight of the melt polymer material.
• the alkyl alcohol and the blowing agent may be combined as a mixture or may be added separately to the melt polymer material.
• these additives are added in an extrusion, or other, process for forming the foam structure.
• the random styrene butadiene copolymer resin preferably is added to the styrenic polymer during the extrusion, or other, process.
• a general procedure for forming a foam structure in an extrusion process involves the following steps: The resin is heat plastified and the blowing agent is incorporated and thoroughly mixed into the plastified resin under conditions that permit thorough mixing of the blowing agent into the plastified resin and that prevent foaming of the mixture. The mixture of resin, blowing agent, and optional additives is cooled, and the pressure on the mixture is reduced resulting in foaming of the mixture and formation of the desired foam body. That is, foam bodies are obtained by extruding the cooled plastified mixture of resin, blowing agent and optional additives into a region of lower pressure. In the invention, a similar procedure is followed in a tandem extruder foam line.
• the foam line consists of a first extruder in which the low molecular weight random styrene butadiene copolymer resin is blended with the styrenic polymer. This polymer mixture is then melted at a temperature ranging between about 200°C and about 220°C, preferably 210°C, and held at this temperature to form the melt polymer material.
• the inorganic blowing agent, and optionally the alkyl alcohol, is injected into the barrel of the extruder and is dissolved in the molten polymer.
• the gassed molten polymer is passed continuously to a second extruder where the polymer material is cooled at a temperature ranging from about 110°C to about 130°C, preferably 120°C, and then is passed to a slit die from which the polymer emerges to form a foam structure.
• the die width is about 0.8 meters and the die gap is about 6 millimeters.
• the resultant foam generally will have a density ranging from about 20 grams per litter (g/l) to about 45 grams per liter (g/l) and a thickness up to about 100 millimeters (mm), and preferably around 80 millimeters. This resultant foam generally is suitable for insulation purposes.
• the type of tandem extruder may be any of the several extruders known to those skilled in the art and commercially available.
• the low molecular weight random styrene butadiene copolymer resin added to a styrenic polymer, especially polystyrene and when an inorganic blowing agent, for example carbon dioxide, is used, the solubility of the inorganic blowing agent in the molten polymer is enhanced and the behavior of the nascent foam board at the extruder die head is stabilized.
• an inorganic blowing agent for example carbon dioxide
• the resultant foam structure generally is closed-cell; has an average cell size of about 300 microns (0.3 millimeters); and as stated herein above, has a density ranging from about 20 g/l to about 45 g/l; is about 1 meter wide, and has a thickness of up to about 100 millimeters thick, preferably around 80 millimeters thick.
• Crystal polystyrene obtained from NOVA Chemicals, Breda, The Netherlands, under the designation "171 N" with a melt flow index of 1.5 g/10 minutes was fed to a tandem extruder foam line similar to that discussed herein above.
• the polystyrene was melted and held at a temperature of 210°C.
• Carbon dioxide at 4% by weight and ethanol at 0.4% by weight based on the weight of the polystyrene were injected into the barrel of the extruder and were dissolved in the molten polystyrene.
• This melt polymer material was passed continuously to the second extruder where it was cooled to 120°C.
• the cooled polymer material was then passed to the slit die where it was formed into a foam board.
• the resultant foam board was 80 millimeters thick and had a density of 45 g/l.
• the low molecular weight random styrene butadiene copolymer (SBC) resin was the XP 808 product obtained from NOVA Chemicals (International) S.A., Fribourg, Switzerland, having a weight average molecular weight of about 120,000 and a MWD of about 4.
• the composition of the random styrene butadiene copolymer resin was 86% by weight styrene and 14% by weight butadiene. Using a load of 2.16 kilograms, the melt index of the melt polymer material was 28 g/10 minutes when measured at 120°C.
• the extrusion conditions and the addition of the carbon dioxide and ethanol were the same as for the Control. Also, the resultant foam board had the same density and dimensions as that of the Control. Periodic measurements of the compressive and flexural strengths of the foam board indicated that the mechanical stability was achieved in 40 days. The thermal conductivity of the foam board after 90 days was 34 mW/m/°C.
• This Example illustrates that the random styrene butadiene copolymer resin in the styrenic polymer reduces the storage time necessary for the foam board to achieve mechanical stability without affecting the insulating properties of the foam board.

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• 2004
  • 2004-04-01 GB GB0407463A patent/GB0407463D0/en not_active Ceased
• 2005
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