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
  • C08J11/00—Recovery or working-up of waste materials
  • C08J11/04—Recovery or working-up of waste materials of polymers
  • C08J11/06—Recovery or working-up of waste materials of polymers without chemical reactions
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
  • B29B17/00—Recovery of plastics or other constituents of waste material containing plastics
  • B29B17/0026—Recovery of plastics or other constituents of waste material containing plastics by agglomeration or compacting
  • B29B17/0036—Recovery of plastics or other constituents of waste material containing plastics by agglomeration or compacting of large particles, e.g. beads, granules, pellets, flakes, slices
• • 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
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/25—Component parts, details or accessories; Auxiliary operations
  • B29C48/36—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die
  • B29C48/395—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die using screws surrounded by a cooperating barrel, e.g. single screw extruders
  • B29C48/397—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die using screws surrounded by a cooperating barrel, e.g. single screw extruders using a single screw
• • 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
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/25—Component parts, details or accessories; Auxiliary operations
  • B29C48/36—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die
  • B29C48/395—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die using screws surrounded by a cooperating barrel, e.g. single screw extruders
  • B29C48/40—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die using screws surrounded by a cooperating barrel, e.g. single screw extruders using two or more parallel screws or at least two parallel non-intermeshing screws, e.g. twin screw extruders
• • 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
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/25—Component parts, details or accessories; Auxiliary operations
  • B29C48/36—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die
  • B29C48/395—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die using screws surrounded by a cooperating barrel, e.g. single screw extruders
  • B29C48/40—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die using screws surrounded by a cooperating barrel, e.g. single screw extruders using two or more parallel screws or at least two parallel non-intermeshing screws, e.g. twin screw extruders
  • B29C48/405—Intermeshing co-rotating screws
• • 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
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/25—Component parts, details or accessories; Auxiliary operations
  • B29C48/36—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die
  • B29C48/50—Details of extruders
  • B29C48/68—Barrels or cylinders
  • B29C48/682—Barrels or cylinders for twin screws
• • 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
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/25—Component parts, details or accessories; Auxiliary operations
  • B29C48/36—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die
  • B29C48/50—Details of extruders
  • B29C48/76—Venting, drying means; Degassing means
  • B29C48/765—Venting, drying means; Degassing means in the extruder apparatus
  • B29C48/766—Venting, drying means; Degassing means in the extruder apparatus in screw extruders
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2033/00—Use of polymers of unsaturated acids or derivatives thereof as moulding material
• • 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
  • C08J2333/00—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 only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Derivatives of such polymers
  • C08J2333/04—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 only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Derivatives of such polymers esters
  • C08J2333/06—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 only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Derivatives of such polymers esters of esters containing only carbon, hydrogen, and oxygen, the oxygen atom being present only as part of the carboxyl radical
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
  • Y02W30/00—Technologies for solid waste management
  • Y02W30/50—Reuse, recycling or recovery technologies
  • Y02W30/62—Plastics recycling; Rubber recycling

Definitions

• the present invention relates to a method of extruding a polymer having crosslinked properties, and the products that are produced therefrom.
• the invention relates to a method of reclaiming scrap crosslinked polymer.
• This process results in an extrudable composition wherein the crosslinked particles are comminuted and dispersed to levels never before achieved.
• the exdrudate may be in any form used in the art, but it is preferably pelletized.
• This invention also encompasses the reduction of residual monomer levels, and capturing the volatile emissions associated with these type of processes.
• thermoformable thermoplastic sheet having a smooth matte finish.
• acrylic powder is an effective blasting medium in paint removal processes. If acrylic powder is ground to a size less than 250 micron, it can be incorporated as a thermoplastic sheet filler. This process can enhance the impact resistance, thermoformability, and surface appearance of a thermoplastic sheet.
• grind consistency One problem inherent to this process is grind consistency. Commercial processors cannot maintain an economically reliable consistency, nor can they achieve reliable stability within the grind.
• Laminates of combined crosslinked and thermoplastic substrates have been put to wide industrial use.
• the term crosslinked refers to a polymer wherein a substantial portion of the molecular chains are linked to each other.
• the same commercial need for scrap reclamation exists. It is impossible to fully segregate the scrap of these products into their component parts. This makes treatment of the individual components impossible. Additionally, the discards of these laminates cannot be comminuted to a size less than 250 micron for incorporation into a thermoplastic sheet.
• screw-type extrusion devices Some of these devices are known for their ability to produce high temperatures and impart a large amount of shear onto polymeric compounds.
• McCullough et al. in U.S. Patent 4,663,103 discloses an apparatus to perform a method of extrusion. The apparatus is designed to accept various disparate materials and ultimately process these materials into highly filled thermoplastic material.
• a further object of this invention is to employ the techniques of underwater pelletization and vacuum venting. These techniques reduce residual monomer formation and capture the volatile emissions associated with the high temperature and high shear environments of applicants' invention.
• Predominantly (or completely) crosslinked polymer sheet material is reduced to a size of 0.5 inch or less by any means. These coarsely-ground products are then fed separately or in combination to a twin-screw extruder.
• the source of the predominantly (or completely) crosslinked polymer sheet material is not important. Scrap crosslinked polymer is common, and can be derived from sources that use crosslinked polymers, such as acrylic and methacrylate sheets, in commercial processes.
• Screw configuration is not found to be important. However, it is found to be beneficial to have the predominantly (or completely) crosslinked polymer processed at a temperature above the glass transition temperature for that polymer.
• State-of-the-art twin-screw extruders are capable of sustaining large torque loads thereby producing high shear zones.
• high shear applicants mean a system wherein a shear stress is sufficient to comminute the particular crosslinked particles to sizes of 10 microns or less. Applicants have found a shear stress level of 10 Pascals or more imparted onto the particles to be sufficient. However, with varying conditions within the extruder, high shear may be obtained at different shear rate levels.
• Typical twin-screw extruders have between 7 and 11 barrel elements.
• the temperature range along the barrel element train may vary. Temperatures typically range between 25° to 285°C from feed barrel to die head.
• the use of kneader blocks within the extruder is found to be beneficial. These blocks may be strung together in multiple groups separated by conveying elements to successively shear and mix the polymer. Applicants' method teaches the use of at least one kneader block group.
• crosslinked polymer Within the extruder the crosslinked polymer is reduced in size as it passes through the high shear zone(s). The polymer size reduction is most effective when high levels of crosslinked feed are used. If a combination crosslinked/uncrosslinked polymer feed is used, it may be augmented with the addition of a crosslinked polymer in order to obtain higher weight percentages of the crosslinked polymer.
• the range of weight percentage is one of preference. Applicants' method will produce the disclosed results with a crosslinked polymer weight percentage between 35 and 100 wt% of the feed stream. However, best results are obtained when said crosslinked content is about 80% of the feed stream.
• the crosslinked pellets can be blended with a thermoplastic material and extruded into a thermoformable sheet product.
• This thermoplastic material can be added in an amount to be about 80 wt% or less of the combined extrusion product and thermoplastic material.
• This second extrusion can take place by any appropriate extrusion means known in the art.
• Crosslinked polymer scrap products suitable for processing by this invention include, but are not limited to products made by the following processes: continuous casting, cell casting, and extrusion where the product has been subsequently treated to impart molecular crosslinking.
• the crosslinked polymer is poly (methyl methacrylate) copolymer. That is, poly (methyl methacrylate) is mixed with insignificant amounts of one or more comonomers such as butyl acrylate, ethylene glycol dimethylacrylate, 2-ethyl hexyl acrylate, and others. These comonomers may be present in amounts up to and about 6 wt% of the poly (methyl methacrylate) copolymer.
• the poly (methyl methacrylate) copolymer should be about 80 to 100 wt% crosslinked. That is, at least about 80 wt% of the molecular chains are linked. A copolymer having less than 80 wt% of its molecular chains crosslinked will work. However, applicants' invention accomplishes more difficult extrusions associated with copolymer having 80 wt% or greater crosslinkage.
• the thermoplastic component may be any suitable uncrosslinked thermoplastic. This group includes, but is not limited to acrylonitrile butadiene styrene (ABS), uncrosslinked acrylic polymers, and uncrosslinked methacrylate polymers.
• ABS acrylonitrile butadiene styrene
• the poly (methyl methacrylate) copolymer is prepared for processing by comminution by any means to the maximum size that can be accommodated by weigh-belt or volumetric feeders and accepted in the throat of a twin-screw extruder.
• crosslinked poly (methyl methacrylate) copolymer scrap fed by a weigh-belt feeder, and a minor stream of ground acrylic/ABS laminate scrap fed by volumetric feeder are used.
• the laminate scrap contains about 40 wt% acrylic and is fed to the compounder in about a 1:5 ratio to poly (methyl methacrylate) copolymer scrap.
• the preferred screw element configuration of the twin-screw extruder has co-rotating intermeshing screws, a short heating/conveying zone, and from about one to four kneader block sections, with the first kneader section fairly close to the feed throat. Sufficient capacity for vacuum venting is provided and is placed just prior to the die adapter section.
• temperature zone settings are typically set for a 7 to 11 barrel element extruder, and range from about 127-207°C.
• a typical extrudate temperature measured at the die head is 302°C.
• thermoformable sheet having a smooth matte finish.
• Example 1 The following are examples of the application and use of the invention. They are for illustration purposes, and in no way are to be construed as limiting the invention in any manner.
• Example 1
• a Werner Pfleider ZSK-58 co-rotating compounder was configured in a 7 barrel element with four kneader block screw sections, and a temperature range of 240-285°C for each zone.
• the feed was a blend of 90 wt% scrap Aristech AltairTM 1-300 acrylic (80 wt% crosslinked and granulated to -3mm) and 10 wt% ABS regrind.
• a stranding die, water trough, and chopper were used to process the output.
• the output was 225 lbs/hr at a screw speed of 279
• Typical crosslinked particles were from 1 to
• the bulk density of the pellet product was 37.4 lbs/cu ft.
• the product was compounded again with additional ABS in a single-screw extruder to a let-down of 40 wt% acrylic. This product was thermoformable and displayed a smooth matte finish.
• the sheet impact by the Gardner impact method was 210 in-lbs/in thickness.
• a Werner Pfleiderer 2SK-70 co-rotating compounder was configured in a 9 barrel element with two kneader blocks along the screw section, and a temperature range of 149-207°C for each zone.
• the feed was a blend of 83 wt% 1-300 acrylic scrap (granulated to -3mm) and 17% Aristech Altair TM Plus scrap (granulated to -3.35mm).
• An underwater pelletizer die with 50 holes of 0.110 inch diameter was used for product takeoff.
• the bulk density of the product was 38 lbs/cu ft. Its residual monomer level was 0.25 wt%.
• Typical crosslinked particle sizes ranged from 1 to 10 microns.
• the output was

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• 1995
  • 1995-05-05 EP EP95919032A patent/EP0712423A4/de not_active Withdrawn
  • 1995-05-05 WO PCT/US1995/005672 patent/WO1995033002A1/en not_active Application Discontinuation
  • 1995-05-05 JP JP50087596A patent/JPH09501118A/ja active Pending
  • 1995-05-05 CA CA 2167733 patent/CA2167733A1/en not_active Abandoned

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