Patent EA-004442-B1 (EA)
Title: Polyester-staple fibers and method for the production thereof
Inventor: CORDES INGO
IPC: D01F6/92
Filed: 2000-07-25
Abstract: 1. Polyester staple fibres, consisting of alpha) a polyester comprising at least 85 mol % of poly(C2-C4-alkylene) terephthalate, beta) from 0.1 to 2.0% by weight of an incompatible, thermoplastic, amorphous, polymeric additive having a glass transition temperature in the range from 90 to 170 degree C and gamma) from 0 to 5.0% by weight of further additives, where the sum of alpha), beta) and gamma) is equal to 100%, the ratio of the melt viscosity of the polymeric additive beta) to the melt viscosity of the polyester component alpha) is from 1:1 to 10:1, and the polymeric additive beta) is present in the staple fibres in the form of fibrils having a mean diameter of <= 80 nm which are distributed in the polyester component alpha). 2. Polyester staple fibres according to claim 1, wherein the ratio of the melt viscosities is from 1.5:1 to 7:1. 3. Polyester staple fibres according to claim 1 wherein the polyester additive beta) is a copolymer which comprises the following monomer units: A=acrylic acid, methacrylic acid or CH2=CR-COOR', where R is an H atom or a CH3, and R' is a C1-15-alkyl radical or a C1-12-cycloalkyl radical or a C6-14-alkyl radical, B=styrene or C1-3-alkyl-substituted styrenes, where the copolymer consists of from 60 to 98% by weight of A and from 2 to 40% by weight of B. 4. Polyester staple fibres according to claim 3, wherein the copolymer consists of from 83 to 98% by weight of A and from 2 to 17% by weight of B. 5. Polyester staple fibers according to claim 3 or 4, wherein the copolymer consists of form 90 to 98% by weight of A and from 2 to 10% by weight of B. 6. Polyester staple fibres according to claim 1 or 2, wherein the polymeric additive beta) is a copolymer which comprises the following monomer units: C=styrene or C1-3-alkyl-substituted styrenes, D=one of more monomers of the formula I, II or III where R1, R2 and R3 are each an H atom or a C1-15-alkyl radical or a C5-12-cycloalkyl radical or a C6-14-aryl radical, and where the copolymer consists of from 15 to 95% by weight of C and from 5 to 85% by weight of D, where the sum of C and D together gives 100%. 7. Polyester staple fibres according to claim 6, wherein the copolymer consists of from 50 to 90% by weight of C and from 10 to 50% by weight of D, where the sum of C and D together gives 100%. 8. Polyester staple fibres according to claim 6 or 7, wherein the copolymer consists of from 70 to 85% by weight of C and from 15 to 30% by weight of D, where the sum of C and D together gives 100%. 9. Polyester staple fibres according to claim 1 or 2, wherein the copolymer additive beta) is a copolymer which comprises the following monomer units: E=acrylic acid, methacrylic acid or CH2=CR-COOR', where R is an H atom or a CH3 group, and R' is a C1-15-alkyl radical or a C5-12-cycloalkyl radical or a C6-14-aryl radical. F=styrene or C1-3-alkly-substituted styrenes, G=one of more monomers of the formula I, II or III where R1, R2 and R3 are each an H atom or a C1-15-alkyl radical or a C5-12-cycloalkyl radical or a C6-14-aryl radical, H=one or more ethylenically unsaturated monomers which can be copolymerized with E and/or with F and/or G, from the group consisting of alpha-methylstyrene, vinyl acetate, acrylates and methacrylates which are different from E, vinyl chloride, vinylidene chloride, halogen-substituted styrenes, vinyl esters, isopropenyl ethers and dienes, where the copolymer consists of from 30 to 99% by weight of E, from 0 to 50% by weight of F, from >0 to 50% by weight of G and from 0 to 50% by weight of H, where the sum of E, F, G and H together gives 100%. 10. Polyester staple fibres according to claim 9, wherein the copolymer consists of from 45 to 97% by weight of E, from 0 to 30% by weight of F, from 3 to 40% by weight of G and from 0 to 30% by weight of H, where the sum of E, F, G and H together gives 100%. 11. Polyester staple fibres according to claim 9 or 10, wherein the copolymer consists of from 60 to 94% by weight of E, from 0 to 20% by weight of F, from 6 to 30% by weight of G and form 0 to 20% by weight of H, where the sum of E, F, G and H together gives 100%. 12. Process for the production of the polyester staple fibers of any one of the preceding claims, wherein, a) a polyester alpha) which comprises at least 84% mol % of poly-(C2-4-alklylene) therephthalate and from 0.1 to 2.0% by weight of an incompatible, thermoplastic, amorphous, polymeric additive beta) which has a glass transition temperature in the range from 90 to 170 degree C, where the ratio of the melt viscosity of the polymeric additive beta) to the melt viscosity of the polyester component alpha) is from 1:1 to 10:1, and from 0 to 5.0% by weight of further additives gamma), are mixed in the molten state in a static mixer with shearing, where the shear rate is from 12 to 128 sec<-1>, and the product of the shear rate and the residence time in the mixer in seconds to the power 0.8 is at least 250; b) the melt mixture from step a) is spun to give spun filaments, where the spinning take-off speed is from less than 2500 n/min; c) the spun filaments from step b) are combined to form tows and stretched in a separate fibre stretching stage, heat-set, crimped, dried and comminuted to give staple fibres, where the stretching is carried out in at least one step at a temperature between 20 and 120 degree C and an overall stretching ratio DR of at least 2.5, the heat-setting is optionally carried out at a residence time of at least 3 seconds in a temperature range between 80 and 225 degree C with subsequent cooling, the crimping is carried out in a compression crimping chamber, where the tows can be exposed to a steam atmosphere either just before or during crimping, the drying is carried out at a temperature in the range between 40 and 190 degree C, and the chopping to give staple fibres having a mean length of between 6 and 220 mm, or the deposition of the tow in cans followed by comminution to give staple fibres, is carried out at a production speed in the fibre stretching stage of between 100 and 500 m/min. 13. Process for the production of polyester staple fibres according to claim 12, wherein the throughput per time unit in step b) during spinning with the take-off speed V1 is set higher by the factor relative to spinning of polyester component alpha) without a polymeric additive beta at the take-off speed V0, where: HD0/1 is the holy density (n/cm<2>) of the spinneret plate, C is the concentration of the polymeric additive in % by weight, DR0/1 is the overall stretching ratio without an additive at the respective spinning take-off speed V0 or V1 respectively, V0/1 is the spinning take-off speed in m/min, and z is between 39 and 153. 14. Process for the production of polyester staple fibres according to claim 12 or 13, wherein the concentration C of the polymeric additive is in the range from 0.1 to 2.0% by weight in accordance with where DR and DR0 are the stretching ratios with and without addition of an additive respectively, and DR>=DR0+0.153. 15. Process for the production of polyester staple fibres according to claim 13 or 14, wherein z is between 66 and 146, and (DR-DR0) is >= 0.45. 16. Process for the production of polyester staple fibres according to one of claims 12-15, wherein the staple fibres have a titre of from 0.5 to 4.0 dtex, the spinning take-off speed is in the range from 900 to 2200 m/min, and the concentration C of the polymeric additive is in the range from 0.1 to 2.0% by weight in accordance with where b is between 80 and 160, Rd is the desired elongation at break of the spun filament in %, Rd0 is the elongation at break in % of the spun filament without addition of an additive, and Rd>= 370% if Rdo<= 354%. 17. Process for the production of polyester staple fibres according to claim 16, wherein b is between 115 and 152.