Double belt plastic sheet forming and take-off method

Claim 1

THE METHOD OF PRODUCING PLASTIC SHEETS HAVING DESIRABLE SURFACE CHARACTERISTICS, SUPERIOR DIMENSIONAL STABILITY, AND WHICH APPROACH ISOTROPIC PROPERTIES, COMPRISING THE STEPS OF: AL. EXTRUDING THROUGH AN ADAPSTOR A VISCOUS, UNPLASTICIZED THERMOPLASTIC POLYMER AT LOW PRESSURE IN A TEMPERATURE RANGE ABOVE THE GLASS TRANSISTION TEMPERATURE BUT BELOW THE DEGRADATION TEMPERATURE OF SAID POLYMER WHEREIN A ROPE-LIKE STRAND IS CONTINUOUSLY FORMED AT A VOLUMERIC FLOW RATE WHEREIN SAID THERMOPLASTIC POLYMER IS SELECTED FROM THE GROUP CONSISTING OF: POLY(METHYL METHACRYLATE), COPOLYMERS OF METHYL METHACRYLATE WITH UP TO 50 PERCENT TO LOWER ALKYL ACRYLATES, LOWER ALKYL METHACRYLATES, ISOBORNYL METHACRYLATE, STYRENE, AND ACRYLONITRILE; BLENDS OF SAID POLYMETHACRYLATE HOMO AND COPOLYMERS WITH MULTI-STAGED ACRYLIC RUBBER IMPACT MODIFIERS; POLYVINYL CHLORIDE; COPOLYMERS OF VINYL CHLORIDE WITH UP TO 10 PERCENT OF SUCH MONOMERS AS VINYL PIVALATE, VINYL ACETATE, ETHYLENE AND PROPYLENE; BLENDS OF VINYL CHLORIDE HOMO AND COPOLYMERS WITH MULTISTAGED ACRYLIC AND BUTADIENE RUBBERS, AND WITH POLYMETHACRYLATE HOMO AND COPOLYMERS; ACRYLONITRILE/BUTADIENE/STYRENE AND AMETHYLSTYRENE PLASTICS, ACRYLONITRILE/STYRENE/ACRYLATE PLASTICS; METHYL METHACRYLATE/ACRYLONTRILE/BUTADIENE/STYRENE PLASTICS; METAHYL METHACRYLATE/ BUTADIENE/STYRENE PLASTICS; IMPACT POLYSTYRENE BLENDS; POLYPHENYLENE OXIDE; BLEND OF POLY(PHENYLENE OXIDE) AND POLYRENE, IMPACT POLYSTYRENE AND MULTISTAGED BUTADINE RUBBER IMPACT MODIFIERS; POLYCARBONATES; POLYSULFONES; AND POLY (2,2-BIS(4-HYDROXYPHENYL) PSROPANE ISOPHTHALATE); A. PROMPTYL DELIVERING AT SAID TEMPERATURE RANGE SAID STRAND TO TAKE-UP MEANS COMPRISING JUXTAPOSED ENDLESS CONVEYOR BELTS WHICH ARE ADAPTED TO TAKE UP THE SAME AND ADHERING THERETO; B. COMPRESSING, SPREADING AND FLATTENING THE CONTINOUS STRAND BETWEEN SAID TAKE-UP MEANS BY ADJUSTMENT OF THE LIANER TAKE-OFF RTAKE-UP SPEED OF SAID TAKE-UP MEANS IN RELATION TO SAID VOLUMETRIC FLOW RATE; C. DRIVING SAID BELTS SYNCHRONOUSLY; D. ADJUSTABLY HEATING SAID BELTS IN THE ZONE OF THEIR INTAKE NIP WITHIN A TEMPERATURE GRADIENT RANGING FROM ABOUT THE GLASS TEMPERATURE OF THE THERMOPLASTIC MATERIAL BEING POCESSED BUT BELOW STHE DETERIORATION TEMPERATURE THEREOF; E. MAINTAINING THE BELT TENSION TO COMPENSATE FOR VARIATIONS IN THE BELT LENGTH ATTRIBUTABLE TO VARIABLE HEATING THEREOF, WHEREBY THE BELTS RUN TRUE; F. COOLING BOTH OF SAID BELTS TO A TEMPERATURE BELOW THE GLASS TEMPERATURE OF SAID SHEET TO FURTHER ALLOWING PARTING OF SAID FORMED SHEETS WITHOUT ADHERENCE TO EITHER BELT; AND G. TAKING OFF THE RESULTING COOLED POLISHED POLYMER SHEETS FROM THE DISCHARGE END OF THE SAID BELTS.

Claim 2

THE METHOD OF PRODUCING PLASTIC SHEETS HAVING DESIRABLE SURFACE CHARACTERISTICS, SUPERIOR DIMENSIONAL STABILITY, AND WHICH APPROACH ISOTROPIC PROPERTIES, COMPRISING THE STEPS OF: AL. EXTRUDING THROUGH AN ADAPSTOR A VISCOUS, UNPLASTICIZED THERMOPLASTIC POLYMER AT LOW PRESSURE IN A TEMPERATURE RANGE ABOVE THE GLASS TRANSISTION TEMPERATURE BUT BELOW THE DEGRADATION TEMPERATURE OF SAID POLYMER WHEREIN A ROPE-LIKE STRAND IS CONTINUOUSLY FORMED AT A VOLUMERIC FLOW RATE WHEREIN SAID THERMOPLASTIC POLYMER IS SELECTED FROM THE GROUP CONSISTING OF: POLY(METHYL METHACRYLATE), COPOLYMERS OF METHYL METHACRYLATE WITH UP TO 50 PERCENT TO LOWER ALKYL ACRYLATES, LOWER ALKYL METHACRYLATES, ISOBORNYL METHACRYLATE, STYRENE, AND ACRYLONITRILE; BLENDS OF SAID POLYMETHACRYLATE HOMO AND COPOLYMERS WITH MULTI-STAGED ACRYLIC RUBBER IMPACT MODIFIERS; POLYVINYL CHLORIDE; COPOLYMERS OF VINYL CHLORIDE WITH UP TO 10 PERCENT OF SUCH MONOMERS AS VINYL PIVALATE, VINYL ACETATE, ETHYLENE AND PROPYLENE; BLENDS OF VINYL CHLORIDE HOMO AND COPOLYMERS WITH MULTISTAGED ACRYLIC AND BUTADIENE RUBBERS, AND WITH POLYMETHACRYLATE HOMO AND COPOLYMERS; ACRYLONITRILE/BUTADIENE/STYRENE AND AMETHYLSTYRENE PLASTICS, ACRYLONITRILE/STYRENE/ACRYLATE PLASTICS; METHYL METHACRYLATE/ACRYLONTRILE/BUTADIENE/STYRENE PLASTICS; METAHYL METHACRYLATE/ BUTADIENE/STYRENE PLASTICS; IMPACT POLYSTYRENE BLENDS; POLYPHENYLENE OXIDE; BLEND OF POLY(PHENYLENE OXIDE) AND POLYRENE, IMPACT POLYSTYRENE AND MULTISTAGED BUTADINE RUBBER IMPACT MODIFIERS; POLYCARBONATES; POLYSULFONES; AND POLY (2,2-BIS(4-HYDROXYPHENYL) PSROPANE ISOPHTHALATE); A. PROMPTYL DELIVERING AT SAID TEMPERATURE RANGE SAID STRAND TO TAKE-UP MEANS COMPRISING JUXTAPOSED ENDLESS CONVEYOR BELTS WHICH ARE ADAPTED TO TAKE UP THE SAME AND ADHERING THERETO; B. COMPRESSING, SPREADING AND FLATTENING THE CONTINOUS STRAND BETWEEN SAID TAKE-UP MEANS BY ADJUSTMENT OF THE LIANER TAKE-OFF RTAKE-UP SPEED OF SAID TAKE-UP MEANS IN RELATION TO SAID VOLUMETRIC FLOW RATE; C. DRIVING SAID BELTS SYNCHRONOUSLY; D. ADJUSTABLY HEATING SAID BELTS IN THE ZONE OF THEIR INTAKE NIP WITHIN A TEMPERATURE GRADIENT RANGING FROM ABOUT THE GLASS TEMPERATURE OF THE THERMOPLASTIC MATERIAL BEING POCESSED BUT BELOW STHE DETERIORATION TEMPERATURE THEREOF; E. MAINTAINING THE BELT TENSION TO COMPENSATE FOR VARIATIONS IN THE BELT LENGTH ATTRIBUTABLE TO VARIABLE HEATING THEREOF, WHEREBY THE BELTS RUN TRUE; F. COOLING BOTH OF SAID BELTS TO A TEMPERATURE BELOW THE GLASS TEMPERATURE OF SAID SHEET TO FURTHER ALLOWING PARTING OF SAID FORMED SHEETS WITHOUT ADHERENCE TO EITHER BELT; AND G. TAKING OFF THE RESULTING COOLED POLISHED POLYMER SHEETS FROM THE DISCHARGE END OF THE SAID BELTS.

Claim 5

The method of continuously producing plastic sheets of desirable surface characteristics, superior dimensional stability, and which approach isotropic properties comprising: a1. producing a continuous rope-like strand of a viscous thermoplastic polymer, at low pressure, in a temperature range above the transition temperature but below the degradation temperature wherein said strand is formed, said polymer selected from the group consisting of: poly(methyl methacrylate), copolymers of methyl methacrylate with up to 50 percent of lower alkyl acrylates, lower alkyl methacrylates, isobornyl methacrylate, styrene, and acrylonitrile; blends of said polymethacrylate homo and copolymers with multi-staged acrylic rubber impact modifiers; polyvinyl chloride; copolymers of vinyl chloride with up to 10 percent of such monomers as vinyl pivalate, vinyl acetate, ethylene and propylene; blends of vinyl chloride homo and copolymers with multistaged acrylic and butadiene rubbers, and with polymethacrylate homo and copolymers; acrylonitrile/butadiene/styrene and Alpha -methylstyrene plastics; acrylonitrile/styrene/acrylate plastics; methyl methacrylate/acrylonitrile/butadiene/styrene plastics; methyl methacrylate/butadiene/styrene plastics; impact polystyrene blends; polyphenylene oxide; blends of poly(phenylene oxide) and polystyrene, impact polystyrene and multistaged butadiene rubber impact modifiers; polycarbonates; polysulfones; and poly (2,2-bis (4-hydroxyphenyl) propane isophthalate); a2. promptly delivering at said temperature range said strand to a take-up means Comprising juxtaposed endless conveyor belts which are adapted to take-up the same and adhering thereto; b. compressing, spreading and flattening the continuous strand between said take-up means by adjustment of the linear speed of said take-up means; c. driving said belts synchronously; d. adjustably heating said belts in the zone of their intake nip within said temperature range; e. maintaining the belt tension to compensate for variations in the belt length attributable to variable heating thereof, whereby the belts run true; f. cooling both of said belts to a temperature below the glass temperature of said sheet to further allow parting of said formed sheets without adherence to either belt; and g. taking off the resulting cooled polished polymer sheets from the discharge end of said belts.

Claim 6

The method of continuously producing plastic sheets of desirable surface characteristics, superior dimensional stability, and which approach isotropic properties comprising: a1. producing a continuous rope-like strand of a viscous thermoplastic polymer, at low pressure, in a temperature range above the transition temperature but below the degradation temperature wherein said strand is formed, said polymer selected from the group consisting of: poly(methyl methacrylate), copolymers of methyl methacrylate with up to 50 percent of lower alkyl acrylates, lower alkyl methacrylates, isobornyl methacrylate, styrene, and acrylonitrile; blends of said polymethacrylate homo and copolymers with multi-staged acrylic rubber impact modifiers; polyvinyl chloride; copolymers of vinyl chloride with up to 10 percent of such monomers as vinyl pivalate, vinyl acetate, ethylene and propylene; blends of vinyl chloride homo and copolymers with multistaged acrylic and butadiene rubbers, and with polymethacrylate homo and copolymers; acrylonitrile/butadiene/styrene and Alpha -methylstyrene plastics; acrylonitrile/styrene/acrylate plastics; methyl methacrylate/acrylonitrile/butadiene/styrene plastics; methyl methacrylate/butadiene/styrene plastics; impact polystyrene blends; polyphenylene oxide; blends of poly(phenylene oxide) and polystyrene, impact polystyrene and multistaged butadiene rubber impact modifiers; polycarbonates; polysulfones; and poly (2,2-bis (4-hydroxyphenyl) propane isophthalate); a2. promptly delivering at said temperature range said strand to a take-up means Comprising juxtaposed endless conveyor belts which are adapted to take-up the same and adhering thereto; b. compressing, spreading and flattening the continuous strand between said take-up means by adjustment of the linear speed of said take-up means; c. driving said belts synchronously; d. adjustably heating said belts in the zone of their intake nip within said temperature range; e. maintaining the belt tension to compensate for variations in the belt length attributable to variable heating thereof, whereby the belts run true; f. cooling both of said belts to a temperature below the glass temperature of said sheet to further allow parting of said formed sheets without adherence to either belt; and g. taking off the resulting cooled polished polymer sheets from the discharge end of said belts.

Claim 9

The method of continuously producing thermoplastic sheets of desirable surface characteristics, superior dimensional stability, and which approach isotropic properties comprising: a1. producing at low pressure through an adapter a continuous strand of a thermoplastic polymer, in a temperature range above the glass transition temperature but below the degradation temperature wherein said strand is formed, said polymer selected from the group consisting of: poly(methyl methacrylate), copolymers of methyl methacrylate with up to 50 percent of lower alkyl acrylate, lower alkyl methacrylates, isobornyl methacrylate, styrene, and acrylonitrile; blends of said polymethacrylate homo and copolymers with multistaged acrylic rubber impact modifiers; polyvinyl chloride; copolymers of vinyl chloride with up to 10 percent of such monomers as vinyl pivalate, vinyl acetate, ethylene and propylene; blends of vinyl chloride homo and copolymers with multistaged acrylic and butadiene rubbers, and with polymethacrylate homo and copolymers; acrylonitrile/butadiene/styrene and Alpha -methylstyrene plastics; acrylonitrile/styrene/acrylate plastics; methyl methacrylate/acrylonitrile/butadiene/styrene plastics; methyl methacrylate/butadiene/styrene plastics; impact polystyrene blends; polyphenylene oxide; blends of poly(phenylene oxide) and polystyrene, impact polystyrene and multistaged butadiene rubber impact modifiers; polycarbonates; polysulfones; and poly(2,2-bis (4-hydroxyphenyl) propane isophthalate); a2. promptly delivering at said temperature range said strand to a take-up means; b. introducing said strand between juxtaposed and horizontally disposed, first and second flat endless polished conveyor belts, adapted to take-up same in a manner whereby said strand intimately contacts the nip of said belts and is compressed, spread and flattened there between by adjustment of the linear take-up speed of said belts; c. providing a tapering down section, commencing at a point where said plastic strand enters the intake end of said belts; d. providing an adjustable aperture subsequent to said section, whereby further compression and polishing of the flattened sheet is achieved as it travels through said aperture; e. adjustably heating the tapering down section within a temperature gradient ranging from above the glass temperature of the thermoplastic material being processed but below the deterioration temperature thereof; f. providing means to independently heat said adjustable aperture; g. providing adjustable supporting means associated with at least one end of said belts to vary the sheet forming aperture defined between said moving belts in said tapering down section; h. maintaining the belt tension to compensate for varIations in belt length attributable to variable operating temperatures thereof; and i. taking off the resulting cooled polished polymer sheets from the discharge terminal of said belts.

Claim 10

The method of continuously producing thermoplastic sheets of desirable surface characteristics, superior dimensional stability, and which approach isotropic properties comprising: a1. producing at low pressure through an adapter a continuous strand of a thermoplastic polymer, in a temperature range above the glass transition temperature but below the degradation temperature wherein said strand is formed, said polymer selected from the group consisting of: poly(methyl methacrylate), copolymers of methyl methacrylate with up to 50 percent of lower alkyl acrylate, lower alkyl methacrylates, isobornyl methacrylate, styrene, and acrylonitrile; blends of said polymethacrylate homo and copolymers with multistaged acrylic rubber impact modifiers; polyvinyl chloride; copolymers of vinyl chloride with up to 10 percent of such monomers as vinyl pivalate, vinyl acetate, ethylene and propylene; blends of vinyl chloride homo and copolymers with multistaged acrylic and butadiene rubbers, and with polymethacrylate homo and copolymers; acrylonitrile/butadiene/styrene and Alpha -methylstyrene plastics; acrylonitrile/styrene/acrylate plastics; methyl methacrylate/acrylonitrile/butadiene/styrene plastics; methyl methacrylate/butadiene/styrene plastics; impact polystyrene blends; polyphenylene oxide; blends of poly(phenylene oxide) and polystyrene, impact polystyrene and multistaged butadiene rubber impact modifiers; polycarbonates; polysulfones; and poly(2,2-bis (4-hydroxyphenyl) propane isophthalate); a2. promptly delivering at said temperature range said strand to a take-up means; b. introducing said strand between juxtaposed and horizontally disposed, first and second flat endless polished conveyor belts, adapted to take-up same in a manner whereby said strand intimately contacts the nip of said belts and is compressed, spread and flattened there between by adjustment of the linear take-up speed of said belts; c. providing a tapering down section, commencing at a point where said plastic strand enters the intake end of said belts; d. providing an adjustable aperture subsequent to said section, whereby further compression and polishing of the flattened sheet is achieved as it travels through said aperture; e. adjustably heating the tapering down section within a temperature gradient ranging from above the glass temperature of the thermoplastic material being processed but below the deterioration temperature thereof; f. providing means to independently heat said adjustable aperture; g. providing adjustable supporting means associated with at least one end of said belts to vary the sheet forming aperture defined between said moving belts in said tapering down section; h. maintaining the belt tension to compensate for varIations in belt length attributable to variable operating temperatures thereof; and i. taking off the resulting cooled polished polymer sheets from the discharge terminal of said belts.

Claim 12

The method of continuously producing thermoplastic sheets of desirable surface characteristics; superior dimensional stability, and which approach isotropic properties, comprising: a. producing at low pressure through an adapter a continuous rope-like strand of a thermoplastic polymer in a temperature range above the glass transition temperature but below the degradation temperature of said polymer wherein said strand is formed, said polymer selected from the group consisting of: poly(methyl methacrylate), copolymers of methyl methacrylate with up to 50 percent of lower alkyl acrylates, lower alkyl methacrylates, isobornyl methacrylate, styrene, and acrylonitrile; blends of said polymethacrylate homo and copolymers with multistaged acrylic rubber impact modifiers; polyvinyl chloride; copolymers of vinyl chloride with up to 10 percent of such monomers as vinyl pivalate, vinyl acetate, ethylene and propylene, blends of vinyl chloride homo and copolymers with multistaged acrylic and butadiene rubbers, and with polymethacrylate homo and copolymers; acrylonitrile/butadiene/styrene and Alpha -methylstyrene plastics; acrylonitrile/styrene/acrylate plastics; methyl methacrylate/acrylonitrile/butadiene/styrene plastics; methyl methacrylate/butadiene/styrene plastics; impact polystyrene blends; polyphenylene oxide; blends of poly(phenylene oxide) and polystyrene, impact polystyrene and multistaged butadiene rubber impact modifiers; polycarbonates; polysulfones; and poly (2,2-bis (4-hydroxyphenyl) propane isophthalate); b. introducing at said temperature range said strand between substantially parallel and horizontally disposed, first and second flat endless polished conveyor belts and adapted to take-up same in a manner whereby said strand emerges and firmly contacts said belts and is compressed, spread and flattened there between by adjustment of the linear take-off speed; c. adjustably heating the pressing section within a temperature gradient ranging from above the glass temperature of the thermoplastic material being processed, but below the deterioration temperature thereof; d. providing adjustable supporting means associated with at least one of said belts to vary the sheet forming aperture defined between said moving belts; e. maintaining the belt tension to compensate for variations in belt length attributable to variable operating temperature; f. cooling both of said belts to a temperature below the glass temperature of said sheet and to allow parting of said sheets without adherence to either belt; and g. taking off the resulting cooling polished polymer sheets from the discharge terminal of said belts.

Claim 13

The method of continuously producing thermoplastic sheets of desirable surface characteristics; superior dimensional stability, and which approach isotropic properties, comprising: a. producing at low pressure through an adapter a continuous rope-like strand of a thermoplastic polymer in a temperature range above the glass transition temperature but below the degradation temperature of said polymer wherein said strand is formed, said polymer selected from the group consisting of: poly(methyl methacrylate), copolymers of methyl methacrylate with up to 50 percent of lower alkyl acrylates, lower alkyl methacrylates, isobornyl methacrylate, styrene, and acrylonitrile; blends of said polymethacrylate homo and copolymers with multistaged acrylic rubber impact modifiers; polyvinyl chloride; copolymers of vinyl chloride with up to 10 percent of such monomers as vinyl pivalate, vinyl acetate, ethylene and propylene, blends of vinyl chloride homo and copolymers with multistaged acrylic and butadiene rubbers, and with polymethacrylate homo and copolymers; acrylonitrile/butadiene/styrene and Alpha -methylstyrene plastics; acrylonitrile/styrene/acrylate plastics; methyl methacrylate/acrylonitrile/butadiene/styrene plastics; methyl methacrylate/butadiene/styrene plastics; impact polystyrene blends; polyphenylene oxide; blends of poly(phenylene oxide) and polystyrene, impact polystyrene and multistaged butadiene rubber impact modifiers; polycarbonates; polysulfones; and poly (2,2-bis (4-hydroxyphenyl) propane isophthalate); b. introducing at said temperature range said strand between substantially parallel and horizontally disposed, first and second flat endless polished conveyor belts and adapted to take-up same in a manner whereby said strand emerges and firmly contacts said belts and is compressed, spread and flattened there between by adjustment of the linear take-off speed; c. adjustably heating the pressing section within a temperature gradient ranging from above the glass temperature of the thermoplastic material being processed, but below the deterioration temperature thereof; d. providing adjustable supporting means associated with at least one of said belts to vary the sheet forming aperture defined between said moving belts; e. maintaining the belt tension to compensate for variations in belt length attributable to variable operating temperature; f. cooling both of said belts to a temperature below the glass temperature of said sheet and to allow parting of said sheets without adherence to either belt; and g. taking off the resulting cooling polished polymer sheets from the discharge terminal of said belts.