Patent ID: 6420025
Filing Date: 2002-07-16
Classification: D01F,Y10T

Abstract:
A process of producing a synthetic ultrafine endless yarn on the basis of polyester or polyamide in the range from 0.25 to 0.9 denier per POY filament by melt spinning at draw-off speeds between 2000 and 6000 m/min, characterized in that(i) as filtration medium in the spinning package there is used a sequence of different fabric layers with microfine mesh sizes of 5 to 15 &mgr;m in combination with or without fine steel sand with a grain size of 88 to 250 &mgr;m, and for shearing the melt there is used in the spinning package either steel sand or corresponding components with microfine pore holes of 50 to 1000 &mgr;m such that a total package pressure of at least 105 bar is achieved with filter surface loads of 0.25 to 0.80 g/min/cm2, (ii) the hole density of the nozzle plates used lies between 1.5 and 6.0 hole/cm2, (iii) the diameter d of the capillary bores in the nozzle plate is chosen with reference to the relationship dcap=533&CenterDot;m.fil.Ï melt&CenterDot;Ï€&CenterDot;Î³.3,â€ƒ&it;with:&it;â€ƒ&it;m.fil.=v&CenterDot;dpfPOY,â€ƒsuch that the apparent wall shear rate of the melt inside the capillaries lies between 5,000 and 25,000 sâˆ’1, (iv) the length L of the capillaries is chosen with reference to the relationship L=1930&CenterDot;Ï melt&CenterDot;dcap4m.fil.&CenterDot;(Î·1-Î·2&CenterDot;log&it;â€ƒ&it;â€ƒ&it;Î³.)&it;â€ƒ&CenterDot;Î”&it;â€ƒ&it;pcap&it;â€ƒ[mm],â€ƒ&it;whereÎ³.=533&it;â€ƒ&it;m.fil.Ï melt&CenterDot;Ï€&CenterDot;dcap3&it;â€ƒ&it;Î·1=3510&it;â€ƒ&it;Î·2=690â€ƒsuch that the melt pressure before the nozzle plate lies between 50 and 100 bar and preferably between 60 and 100 bar, (v) in the cross-section of the filament bundle before reaching the draft zone a balanced temperature profile is formed, where the distance h from the nozzle plate, on which this temperature profile is reached, is smaller than the distance of the solidification point h0.98% from the nozzle plate, and the solidification point is chosen such that it is located directly subsequent to the protected snap-back and h0.98% from the nozzle plate is defined by the following relationship: h0.98&it;%=38&CenterDot;9000&CenterDot;m.filvdraw&it;-&it;off&CenterDot;VV&CenterDot;(9000&CenterDot;m.filvdraw&it;-&it;off&CenterDot;VV+6,0)&it;â€ƒ[mm],â€ƒwhere h0.98% is adjusted by means of the temperature of the polymer at the entrance of the spinning package in dependence on the filter surface load according to the following relationship: Tmelt=308âˆ’25 ffilter [Â° C.], ffilter in g/min/cm2, (vi) to reach the balanced temperature profile in the filament bundle, an excessive temperature (Tedgeâˆ’Tedge) is adjusted, which as measured as surface temperature difference between the middle and the edge of the nozzle plate must be adjusted in the claimed range of titers by means of the temperature difference from spinning bar heating and polymer (Tmeltâˆ’Theating), in dependence on the filament throughput mfil, the draw-off speed Vdraw-off, and the filter area Afilter, as follows: Theating-Tmelt=f&CenterDot;(Tedge-Tcenter)&it;(-2,2&CenterDot;m.fil0,141&it;â€ƒ&it;g&it;/&it;min&CenterDot;2600&it;â€ƒ&it;m&it;/&it;minvdraw&it;-&it;off&CenterDot;61&it;â€ƒ&it;cm2Afilter)with&it;â€ƒ&it;f=14,3&CenterDot;e&it;â€ƒ&it;and&it;â€ƒ&it;4&it;K&leq;(Tedge-Tcenter)&leq;13&it;K,(vii) a precisely defined amount of heat, which is defined by the ratio l/t, is transferred to the partial polymer stream running on the outside in the spinning package, where l describes the length of the inner wall of the package along which the partial polymer stream running on the outside in the package is heated to an excessive temperature, and t describes the contact time available for the heat transfer with the inner wall of the package, approximately defined by the following relationship t=l&CenterDot;AQ&CenterDot;Ï melt&CenterDot;&varepsilon;n&CenterDot;m.fil,where &egr; represents the part taken by the melt in a certain cross-section of the spinning package and may be constant in certain sections or may be a function of the height, and the ratio l/t is chosen within the following range:0.6 cm/min&lE;l/t&lE;3.8 cm/min, (viii) the still melt-liquid thread is not directly exposed to the blow air, but is first of all cooled in a so-called snap-back, the snap-back being smaller than the draft point, (ix) there is adjusted a speed profile of quenching which is symmetrical transverse to the longitudinal axis of the bar, where on the side facing away from quenching a controlled self-suction is effected by corresponding flow resistances, (x) the individual thread bundles are separated by partitions, (xi) all members getting in contact with the yarn, such as oilers, guide members and treatment members of ceramics, are equipped with friction-optimized surfaces, so that upon passage through the members there occurs a maximum build-up of tension in the yarn of 60 to 110%, (xii) selectively, the thread bundles are subjected to an entangling, and (xiii) the freshly spun yarn is spooled with a spooling tension, Ïƒdraw&it;-&it;off=(0.5&it;â€ƒ&it;â€¦&it;â€ƒ&it;1.4)&it;â€ƒ&it;cNtex.