Classifications

• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
  • D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
  • D01F6/58—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolycondensation products
  • D01F6/62—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolycondensation products from polyesters

Definitions

• This- invention relates to polyethylene naphthalate (PEN) multifilament yarn and other yarns made from similarly rigid monomer " combinations with extremely high modulus, good tenacity, and low shrinkage particularly useful for the textile reinforcement of tires.
• the PEN yarn of this invention provides enhanced modulus and dimensional stability when compared to conventionally processed PEN yarns.
• a process for production of the multi-filament PEN yarn is an aspect of this invention.
• PET polyethylene terephthalate
• U.S. Patent 3,616,832 to Shima et al. provides rubber articles reinforced with PEN of good dimensional stability and tenacity
• U.S. Patent 3,929,180 to Kawase et al. provides a tire with PEN used as a carcass reinforcement.
• the yarns of this invention are prepared by spinning PEN or other semi-crystalline polyester polymers made from similarly rigid monomer combinations to a state of optimum amorphous orientation and crystallinity.
• the invention is accomplished by selection of process parameters to form an undrawn polyester yarn of birefringence at least 0.030.
• the spun yarn is then hot drawn to a total draw ratio of between 1.5/1 and 6.0/1 with the resulting drawn semi-crystalline polyester yarn having Tg greater than 100'C and a melting point elevation at least 8°C.
• the preferred yarn has a tenacity at least 6.5 g/d, dimensional stability (EASL + Shrinkage) of less than 5%, and shrinkage 4% or less.
• the resulting yarn exhibits surprisingly high modulus and tenacity together with low shrinkage when compared to prior art yarns.
• Fig. 1 represents a comparison of modulus at a tenacity of 6.2 g/d for the PEN yarns of Examples 1 and 2.
• the polyester multifilament yarn of the present invention provides high modulus, high dimensional stability and good tenacity, characteristics which are extremely desirable when this material is incorporated as fibrous reinforcement into rubber composites such as tires.
• PEN multifilament yarns or other yarns of polyester polymers made from similarly rigid monomer combinations can be used advantageously to reinforce two parts of a radial passenger tire, the carcass and the belt.
• passenger tire carcasses are reinforced primarily by polyethylene terephthalate.
• the high modulus and dimensional stability of the PEN or other polyester yarns of this invention relative to PET and prior art PEN yarns means that tires with carcasses reinforced with the yarns of this invention will exhibit lower sidewall indentation and better handling behavior.
• the yarns of this invention are also a desirable reinforcement material because of their high glass transition temperature (Tg) greater than 100 ° C , i.e. 120°C for PEN, compared to a Tg of 80°C for PET.
• Tg glass transition temperature
• the high Tg will result in lower cord heat generation over a wider temperature range relative to PET tires, resulting in longer tire lifetimes and overall cooler tire operating temperatures.
• PEN multifilament yarns and other polyester yarns of this invention can also be used to reinforce the belts of radial passenger tires and the carcasses of radial truck tires.
• Currently steel is used for these applications since PET possesses insufficient strength and modulus for a given cord diameter.
• the high modulus of PEN relative to PET, and the additional modulus advantages of the PEN of this invention will make PEN an ideal material to be used as a steel substitute.
• the polyethylene naphthalate yarn of the invention contains at least 90 mol percent polyethylene naphthalate.
• the polyester is substantially all polyethylene naphthalate.
• the polyester may incorporate as copolymer units minor amounts of units derived from one or more ester-forming ingredients other than ethylene glycol and 2,6 naphthylene dicarboxylic acid or their derivatives.
• ester forming ingredients which may be copolymerized with the polyethylene naphthalate units include glycols such as 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, etc., and dicarboxylic acids such as terephthalic acid, isophthalic acid, hexahydroterephthalic acid, stilbene dicarboxylic acid, bibenzoic acid, adipic acid, ⁇ ebacic acid, azelaic acid, etc.
• polyester yarns of the invention can be prepared to contain polyester polymer made from suitable combinations of rigid and flexible monomers providing the resulting polymer is melt-spinnable, is semi-crystalline, and has a Tg greater than 100°C.
• rigid monomers include dicarboxylic acids such as 2,6-naphthalene dicarboxylic acid, 2,7-naphthalene dicarboxylic acid, diphenyl dicarboxylic acid, stilbene dicarboxylic acid and terephthalic acid; dihydroxy compounds such as hydroquinone, biphenol, p-xylene glycol, 1,4 cyclohexanedimethanol, neopentylene glycol; and hydroxycarboxylie acid such as P-hydroxybenzoic acid and 7-hydroxy- ⁇ -naphthoic acid.
• Examples of flexible monomers include dicarboxylic acids such as oxalic acid, succinic acid, adipic acid, sebacic acid, and dihydroxy compounds such as ethylene glycol, 1,3 propanediol, 1,4 butanediol, 1,6 hexanediol. It is important that the thermal stability of the polymer above its melting point be sufficient to allow melt processing without excessive degradation.
• the multi-filament yarn of the present invention commonly possesses a denier per filament of about 1 to 20 (e.g. about 3 to 10) , and commonly consists of about 6 to 600 continuous filaments (e.g. about 20 to 400 continuous filaments) .
• the denier per filament and the number of continuous filaments present in the yarn may be varied widely as will be apparent to those skilled in the art.
• the multi-filament yarn is particularly suited for use in industrial applications wherein high strength polyester fibers have been utilized in the prior art.
• the fibers are particularly suited for use in environments where elevated temperatures (e.g. 100°C) are encountered. Not only does the filamentary material provide enhanced modulus but it undergoes a very.low degree of shrinkage for a high modulus fibrous thermoplastic.
• the unexpected dimensional stability advantage seems to originate from the formation of a unique morphology during spinning which arises from the crystallization of highly oriented amorphous regions characterized by an undrawn birefringence of at least 0.03, preferably 0.03 to 0.30. This crystallization occurs in either the drawing stage or the spinning stage depending on the level of stress imposed during spinning. If too much stress is applied during spinning, the undrawn yarns tend to lack drawability and characteristically exhibit melting points greater than 290°C for PEN.
• the characterization parameters referred to herein may conveniently be determined by testing the multifila ent yarn which consists of substantially parallel filaments.
• BIREFRINGENCE - Birefringence was determined using a polarizing light microscope equipped with a Berek compensator. If the black primary extinction band is not visible the purple colored band should be used for this measurement.
• DENSITY - Densities were determined in a n-heptane/carbon tetrachloride density gradient column at 23°C. The gradient column was prepared and calibrated according to ASTM D1505-68.
• MELTING POINT - Melting points were determined with a Perkin-Elmer Differential Scanning Calorimeter (DSC) from the maxima of the endotherm resulting from scanning a 10 mg sample at 20°C per minute. Tg is to be taken under the same experimental conditions as the inflection point in the change heat capacity associated with the glass transition temperature. Melting point evaluation for drawn yarns ( ⁇ Tm) is defined as:
• Tm 1 the melting point of the drawn yarn of interest
• Tm 11 the melting point of a yarn which is pre-melted and rapidly cooled in the DSC before analysis.
• IV Intrinsic viscosity of the polymer and yarn is a convenient measure of the degree of polymerization and molecular weight. IV is determined by measurement of relative solution viscosity ( T ) i n a mixture of phenol and tetrachloroethane (60/40 by weight) solvents. (_r ⁇ s the rat i° of the flow time of a PEN/solvent solution to the flow time of pure solvent through a standard capillary. IV is calculated by extrapolation of relative solution viscosity data to a concentration of zero.
• PHYSICAL PROPERTIES The tensile properties referred to herein were determined through the utilization of an Instron tensile tester using a 10 inch gauge length and a strain rate of 120 percent per minute. All tensile measurements were made at room temperature. Dimensional stability refers to the level of stress achieved at a given shrinkage. In the tire industry, dimensional stability is defined as the sun of elongation at a specified load plus shrinkage. For the present case, the elongation at a specified load (EASL) is derived from the initial modulus data using the following equation:
• EASL 454/Modulus (g/d) It is well known that tenacity and modulus increase with increasing draw-ratio. While higher tenacity per se is almost always highly desirable, the high extension ratios are often not acheivable due to yarn quality problems or to excessive shrinkage. Materials of this invention possess high levels of modulus for a given level of tenacity. This is quantified as the L. parameter, by ratioing L-5 to tenacity as follows:
• L j , ((L-5) 4 /T 5*16 ) 1000 L-5 or LASE-5 is a measure of modulus defined as load in g/d at 5% elongation.
• the materials of this invention have Lr p at least 25. If L-5 is not measurable because of yarn elongations less than 5% the yarns will be pre-relaxed at elevated temperatures before testing to increase elongation beyond 5%.
• Shrinkage values were determined in accordance with ASTM D885 after one minute at 177°C employing a constraining force of 0.05 g/denier.
• the melt-spinnable polyester is supplied to an extrusion spinnerette at a temperature above its melting point and below the temperature at which the polymer degrades substantially.
• the residence time at this stage is kept to a minimum and the temperature should not rise above 350°C, preferably 320°C.
• the extruded filaments then traverse a conventional yarn solidification zone where quench air impinges on the spun yarn thereby freezing in desirable internal structural features and preventing the filaments from fusing to one another.
• the solidification zone preferably comprises (a) a retarded cooling zone comprising a gaseous atmosphere heated at a temperature to at least 150°C, preferably 150 to 500°C, and (b) a cooling zone adjacent to said retarded cooling zone wherein said yarn is rapidly cooled and solidified in a blown air atmosphere.
• the key to the current process is to adjust processing conditions to achieve a highly oriented undrawn yarn of birefringence at least 0.03 and an elevated melting point of 1-25°C, preferably 3-23 C C.
• PEN a melting point of 265 to 290°C, preferably 268 to 288°C must be achieved.
• the spun yarn is then drawn by conventional means in either a continuous or non-continuous process .to yield a drawn yarn with Tg greater than 100°C and a melting point elevation at least 8°C, preferably 8 to 15"C. It is preferred to have the following drawn yarn properties: tenacity at least 6.5 g/d, preferably at least 7.5 g/d; dimensional stability (EASL + shrinkage) of less than 5%; and shrinkage of 4% or less.
• a PEN undrawn yarn was produced by extruding 32 filaments through a spinnerette with orifices of length 0.042 inches and of width 0.021 inches at a thruput of 23.2 cc/min.
• the filaments were solidified in an air quenching column and taken up at winder speeds cf 305 m/min.
• PEN yarns were produced by extruding seven filaments through a spinnerette with orifices of length 0.036 inches and width of 0.016 inches at a thruput of 9.6 cc/min. The filaments were solidified in an air quenching column and taken up at winder speeds ranging from 770-5000 m/min. These yarns were drawn in two stages using a heating plate in draw zone two. The undrawn yarn properties, drawn yarn properties, and drawing conditions are summarized in Table II.
• EXAMPLE III The undrawn yarns of Example II spun at 770 /min and 4000 m/min were drawn to their ultimate lir.it. The 770 m/min sample was drawn in one stage using an oven in the draw zone and the 4000 m/min sample was drawn in two stages using a heated plate in the second draw zone. The drawn yarn properties and drawing conditions are summarized in Table III. This example shows that the yarns of this invention possess extremely high modulus, high tenacity, and low shrinkage making them desirable for in-rubber applications.
• PEN yarns were produced by extruding seven filaments through a spinnerette with orifices of length 0.069 inches and width 0.030 inches at a thruput of 9.6 cc/ in. The filaments were solidified in an air quenching column and taken up at winder speeds ranging from 410 m/min to 2500 m/min. The properties of these yarns are summarized in Table IV.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Textile Engineering (AREA)
• Artificial Filaments (AREA)
• Tires In General (AREA)
• Yarns And Mechanical Finishing Of Yarns Or Ropes (AREA)

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• 1992
  • 1992-12-22 EP EP93901119A patent/EP0623179B2/en not_active Expired - Lifetime
  • 1992-12-22 AU AU33312/93A patent/AU3331293A/en not_active Abandoned
  • 1992-12-22 WO PCT/US1992/011063 patent/WO1993014252A1/en active IP Right Grant
  • 1992-12-22 ES ES93901119T patent/ES2091589T5/es not_active Expired - Lifetime
  • 1992-12-22 JP JP5512461A patent/JP2629075B2/ja not_active Expired - Fee Related
  • 1992-12-22 CA CA002126328A patent/CA2126328C/en not_active Expired - Fee Related
  • 1992-12-22 BR BR9207038A patent/BR9207038A/pt not_active IP Right Cessation
  • 1992-12-22 DE DE69213474T patent/DE69213474T3/de not_active Expired - Fee Related
• 1993
  • 1993-01-13 MX MX9300142A patent/MX9300142A/es not_active IP Right Cessation
  • 1993-01-19 TW TW082100327A patent/TW224960B/zh active
  • 1993-01-20 TR TR00065/93A patent/TR28032A/tr unknown
  • 1993-01-21 CN CN93101268A patent/CN1051586C/zh not_active Expired - Fee Related

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