# US 5,695,709 A · Method and apparatus for producing highly oriented polyester sheet > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,695,709 A - Document ID: US5695709A - Status: Granted - Kind: A - Application number: 08/485,538 - Filed: 1995-06-07 - Granted: 1997-12-09 - Earliest claimed: 1992-10-09 - Assignees: Signode Corporation - Inventors: Donald L. Van Erden; Manuel C. Enriquez - Web page: https://patentgrep.com/patent/US5695709A ## CPC - B29C 43/24: Calendering - B29C 55/06: parallel with the direction of feed - B29C 55/065: {in several stretching steps} - B29C 55/18: by squeezing between surfaces, e.g. rollers - B29K 2067/00: Use of polyesters {or derivatives thereof}, as moulding material - B29L 2007/007: {Narrow strips, e.g. ribbons, tapes, bands (belts B29L2029/00; tapes as carrier of sound or information B29L2017/008)} - 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 (making preforms B29B11/00; making laminated products by combining previously unconnected layers which become one product whose layers will remain together B32B37/00 - B32B41/00) - 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 - B29L: INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES ## Abstract A method and apparatus for producing highly-oriented polyester sheet comprises a two-stage drawing process. The first drawing stage is performed within a zero-gap milling and stretching roller assembly comprising a pair of opposed rollers defining a nip therebetween and wherein the rollers are rotated in opposite directions at different lineal surface velocities such that a predetermined draw ratio is defined therebetween. Amorphous polyester sheet is conducted through the nip of the opposed rollers, and as a result of the simultaneous milling and stretching of the polyester sheet, the amorphous polyester is transformed into crystalline polyester as a result of orientation-induced crystallization. The crystalline polyester sheet is heated above the glass transition temperature (T.sub.g) immediately downstream of the nip defined between the pair of opposed rollers, and an exit bridle assembly is disposed downstream of the pair of opposed rollers. The rollers of the bridle assembly are rotated at lineal surface velocities which are greater than the lineal surface velocity of the downstream one of the pair of opposed rollers such that a second draw ratio is defined with respect to such downstream one of the pair of opposed rollers. The heating of the crystalline polyester sheet facilitates the additional stretching thereof within the second drawing stage of the apparatus, the overall drawing ratio being approximately 6:1. Highly oriented polyester, having tensile strength values of approximately 100,000 psi, and modulus values of approximately 3,000,000-5,000,000, is achieved. ## Claims ### Claim 1 Apparatus for producing highly-oriented polyester sheeting, comprising: a pair of opposed rollers defining a nip therebetween through which a solid sheet workpiece of polyester is passed so as to be simultaneously milled and stretched as said sheet workpiece passes through said nip in a single pass and in a predetermined direction of travel; means for driving said pair of opposed rollers in opposite directions and at sufficiently different lineal surface velocities for simultaneously milling and stretching said sheet workpiece within said nip defined between said pair of opposed rollers in accordance with a predetermined first draw ratio defined between said pair of opposed rollers by said different lineal surface velocities of said pair of opposed rollers; at least one additional roller disposed downstream from a downstream one of said pair of opposed rollers as viewed along said predetermined direction of travel for withdrawing said milled and stretched sheet workpiece away from said pair of opposed rollers; and means for driving said at least one additional roller at a sufficiently different lineal surface velocity with respect to said lineal surface velocity of said downstream one of said pair of opposed rollers so as to additionally stretch said milled and stretched sheet workpiece in accordance with a predetermined second draw ratio. ### Claim 2 (depends on 1) The apparatus as set forth in claim 1, wherein: said polyester sheet workpieces comprises polyethylene terephthalate. ### Claim 3 (depends on 1) The apparatus as set forth in claim 1, wherein: said at least one additional roller comprises a set of rollers forming an exit bridle assembly for said milled and stretched workpiece with respect to said pair of opposed rollers. ### Claim 4 (depends on 1) The apparatus as set forth in claim 1, wherein: said means for driving said pair of opposed rollers drive said pair of opposed rollers such that said predetermined first draw ratio defined between said pair of opposed rollers is within the range of 4-5:1; and said means for driving said at least one additional roller drives said at least one additional roller such that said predetermined second draw ratio defined between said at least one additional roller and said downstream one of said pair of opposed rollers is within the range of 1.1-1.5:1, whereby the overall draw ratio impressed upon said polyester sheet workpiece is approximately 6:1, and said highly-oriented polyester sheeting exhibits tensile strength values of approximately 100,000 psi and modulus values within the range of approximately 3,000,000-5,000,000 psi. ### Claim 5 (depends on 1) The apparatus as set forth in claim 1, further comprising: said polyester sheet workpiece comprises amorphous polyester prior to passage of said sheet workpiece through said nip defined between said pair of opposed rollers, whereupon passage of said sheet workpiece through said nip defined between said pair of opposed rollers said sheet workpiece undergoes orientation-induced crystallization so as to comprise crystalline polyester; means for heating an upstream one of said pair of rollers so as to in turn preheat said sheet workpiece to a temperature level which is below the glass transition temperature (T.sub.g) of said sheet workpiece so as to prevent sticking of said amorphous polyester sheet workpiece to said upstream one of said pair of rollers; and means for heating said downstream one of said pair of rollers to a temperature level which is substantially above said glass transition temperature (T.sub.g) of said sheet workpiece so as to facilitate said additional stretching of said crystalline polyester sheet workpiece. ### Claim 6 (depends on 5) The apparatus as set forth in claim 5, further comprising: means for heating said sheet workpiece, at a location immediately upstream of said nip defined between said pair of opposed rollers, to a temperature level which is greater than said glass transition temperature (T.sub.g) of said polyester sheet so as to predetermine control of said orientation of said polyester sheet by said milling and stretching of said polyester sheet within said nip defined between said pair of opposed rollers; and means for supplying a lubricant to a surface of said polyester sheet at a position upstream of said nip defined between said pair of opposed rollers so as to prevent any sticking of said polyester sheet to said upstream one of said pair of opposed rollers when said polyester sheet workpiece is heated to said temperature level greater than said glass transition temperature (T.sub.g). ### Claim 7 (depends on 1) The apparatus as set forth in claim 1, wherein: said pair of opposed rollers each has a configuration comprising a concave central portion and cylindrical end portions so as to provide said sheet workpiece with thinner edge portions than said central portion when said sheet workpiece is conducted through said nip defined between said pair of opposed rollers such that an increased degree of flatness of said simultaneously milled and stretched sheet workpiece, across the width of said simultaneously milled and stretched sheet workpiece after said simultaneously milled and stretched sheet workpiece has passed through said nip defined between said pair of opposed rollers, is achieved. ### Claim 8 (depends on 7) The apparatus as set forth in claim 7, wherein: said central portions of said pair of opposed rollers are arcuate in configuration. ### Claim 9 (depends on 7) The apparatus as set forth in claim 7, wherein: said central portions of said pair of opposed rollers have a trapezoidal configuration. ### Claim 10 (depends on 1) The apparatus as set forth in claim 1, further comprising: die means for extruding said sheet workpiece wherein said die means has a predetermined cross-sectional configuration such that said extruded sheet workpiece has thinner edge portions than central portions such that an increased degree of flatness of said simultaneously milled and stretched sheet workpiece, across the width of said simultaneously milled and stretched sheet workpiece after said simultaneously milled and stretched sheet workpiece has passed through said nip defined between said pair of opposed rollers, is achieved. ### Claim 11 (depends on 10) The apparatus as set forth in claim 10, wherein: said predetermined cross-sectional configuration of said die means comprises a trapezoid. ### Claim 12 (depends on 11) The apparatus as set forth in claim 11, further comprising: a plurality of casting rolls disposed within a vertical array and defining spaces therebetween which have a trapezoidal configuration for accommodating trapezoidal-configured sheet workpieces produced by said die means. ### Claim 13 A method for producing highly-oriented polyester sheeting, comprising the steps of: providing a pair of opposed rollers defining a nip therebetween through which a solid sheet workpiece of polyester is passed so as to be simultaneously milled and stretched as said sheet workpiece passes through said nip in a single pass and in a predetermined direction of travel; driving said pair of opposed rollers in opposite directions and at sufficiently different lineal surface velocities for simultaneously milling and stretching said sheet workpiece within said nip defined between said pair of opposed rollers in accordance with a predetermined first draw ratio defined between said pair of opposed rollers by said different lineal surface velocities of said pair of opposed rollers; providing at least one additional roller downstream from a downstream one of said pair of opposed rollers, as viewed along said predetermined direction of travel, for withdrawing said milled and stretched sheet workpiece away from said pair of opposed rollers; and driving said at least one additional roller at a sufficiently different lineal surface velocity with respect to said lineal surface velocity of said downstream one of said pair of opposed rollers so as to additionally stretch said milled and stretched sheet workpiece in accordance with a predetermined second draw ratio. ### Claim 14 (depends on 13) The method as set forth in claim 13, wherein: said polyester sheet workpiece is fabricated from polyethylene terephthalate. ### Claim 15 (depends on 13) The method as set forth in claim 13, wherein: said at least one additional roller comprises a set of rollers defining an exit bridle assembly for said milled and stretched workpiece with respect to said pair of opposed rollers; and all of said rollers of said set of rollers defining said exit bridle assembly are driven at a rotational speed so as to define with said downstream one of said pair of opposed rollers said second draw ratio. ### Claim 16 (depends on 13) The method as set forth in claim 13, wherein: said first draw ratio is within the range of 4-5:1; and said second draw ratio is within the range of 1.1-1.5:1, whereby the overall draw ratio impressed upon said polyester sheet workpiece is approximately 6:1, and said highly-oriented polyester sheeting exhibits tensile strength values of approximately 100,000 psi and modulus values within the range of approximately 3,000,000-5,000,000 psi. ### Claim 17 (depends on 13) The method as set forth in claim 13, further comprising the steps of: said polyester sheet workpiece comprises amorphous polyester prior to passage of said sheet workpiece through said nip defined between said pair of opposed rollers, whereupon passage of said sheet workpiece through said nip defined between said pair of opposed rollers, said sheet workpiece undergoes orientation-induced crystallization so as to comprise crystalline polyester; heating an upstream one of said pair of rollers so as to in turn preheat said sheet workpiece to a temperature level which is below the glass transition temperature (T.sub.g) of said sheet workpiece so as to prevent sticking of said amorphous polyester sheet workpiece to said upstream one of said pair of rollers; and heating said downstream one of said pair of rollers to a temperature level which is substantially above said glass transition temperature (T.sub.g) of said sheet workpiece so as to facilitate said additional stretching of said crystalline polyester sheet workpiece. ### Claim 18 (depends on 17) The method as set forth in claim 17, further comprising the steps of: heating said sheet workpiece, at a location immediately upstream of said nip defined between said pair of opposed rollers, to a temperature level which is greater than said glass transition temperature (T.sub.g) of said polyester sheet so as to predetermine control of said orientation of said polyester sheet by said milling and stretching of said polyester sheet within said nip defined between said pair of opposed rollers; and supplying a lubricant to a surface of said polyester sheet which will be disposed in contact with said upstream one of said pair of opposed rollers and at a position upstream of said nip defined between said pair of opposed rollers so as to prevent any sticking of said polyester sheet to said upstream one of said pair of opposed rollers when said polyester sheet workpiece is heated to said temperature level which is greater than said glass transition temperature (T.sub.g). ### Claim 19 (depends on 13) The method as set forth in claim 13, further comprising the step of: providing said pair of opposed rollers with a configuration which comprises a concave central portion and cylindrical end portions so as to provide said sheet workpiece with thinner edge portions than said central portion when said sheet workpiece is conducted through said nip defined between said pair of opposed rollers such that an increased degree of flatness of said simultaneously milled and stretched sheet workpiece, across the width of said simultaneously milled and stretched sheet workpiece after said simultaneously milled and stretched workpiece has passed through said nip defined between said pair of opposed rollers, is achieved. ### Claim 20 (depends on 13) The method as set forth in claim 13, further comprising the step of: providing die means for extruding said sheet workpiece wherein said die means has a predetermined cross-sectional configuration such that said extruded sheet workpiece has thinner edge portions than central portions such that an increased degree of flatness of said simultaneously milled and stretched sheet workpiece, across the width of said simultaneously milled and stretched sheet workpiece after said simultaneously milled and stretched sheet workpiece has passed through said nip defined between said pair of opposed rollers, is achieved. ### Claim 21 (depends on 20) The method as set forth in claim 20, wherein: said predetermined cross-sectional configuration of said die means comprises a trapezoid. ### Claim 22 (depends on 21) The method as set forth in claim 21, further comprising the step of: providing a plurality of casting rolls disposed within a vertical array and defining spaces therebetween which have a trapezoidal configuration for accommodating trapezoidal-configured sheet workpieces produced by said die means.