Method for spinning and winding pet filaments

Abstract

The present invention relates to a process for producing and winding POY filaments not less than 90% by weight PET, based on the total weight of the POY, at spinning takeoff speeds above 3 800 m/min, which comprises

Description

[0001] The present invention relates to processes for spinning and winding POY filaments not less than 90% by weight, based on the total weight of the POY, polyethylene terephthalate (PET).

[0002] PET POY filaments are customarily produced at takeoff speeds from 2 500 to 3 500 m/min, depending on the linear density to be produced. Such filaments have breaking extension values of 90-165%, which have proved advantageous for further processing in a drawing or draw-texturing operation. The speed range mentioned is too low to induce crystallization in the PET filaments, as is discernible for example from fig. 2 on page 27 of Chemiefasern/Textilindustrie January 1980.

[0003] However, on increasing the takeoff speed, akin to the production of spin-oriented, crystalline FOY or HOY PET filaments, the lower thermal and mechanical stability of the POY yarns results in higher breakage rates, less uniform test data and/or defects in further processing, especially in draw-texturing.

[0004] The first approaches to solving these problems are described in WO 99/51799, WO 99/07927 and WO 93/19229. WO 99/51799 discloses a process for spinning continuous filaments by cooling the freshly spun filaments in a tube using an accelerated cooling gas. This makes it possible to raise the spinning takeoff speed to 4 530 m/min without reducing the breaking extension of the filaments. As to breakage rates, no information is provided.

[0005] WO 99/07927 relates to a process for producing POY filaments from polyester-based polymer blends. PET filaments having high breaking extension values are obtained in the presence of a certain amount of an additive copolymer even at high spinning takeoff speeds of up to 6 000 m/min. As to breakage rates, no information is provided in this reference either.

[0006] In contrast, WO 93/19229 describes a process for spinning and cooling continuous filaments using a spinning apparatus comprising spin heads (containing die plates) and quench chimneys having an air-pervious wall through which an airstream is sucked into the interior of the quench chimneys. Uniform PET filaments were obtained with a low number of spin breakages. However, high speeds from 4 200 to 5 700 m/min provide distinctly lower breaking extension from 85 to 54%. Such values are typical of spin-oriented, crystalline filaments.

[0007] Although the cited processes make it possible to spin and wind POY filaments at high spinning takeoff speeds, there is still a need of improvement in many respects with regard to the production of POY. Disadvantages include the following issues:

[0008] faulty filaments are obtained as a consequence of mechanical and/or thermal fiber damage;

[0009] process efficiency is substantially reduced by loop formation and broken ends;

[0010] package ridging and dropped ends.

[0011] It is an object of the present invention to provide a process for spinning and winding POY filaments not less than 90% by weight, based on the total weight of filament, PET at high spinning takeoff speeds to a low defect rate. More particularly, the POY PET filaments shall have breaking extension values in the range of 90%-165% and high uniformity with regard to filament parameters and spin finish application.

[0012] It is a further object of the present invention to provide an economical industrial process for spinning and winding POY PET filaments. The process of the invention shall permit very high spinning takeoff speeds, preferably above 3 800 m/min, especially in the range from 4 200 to 8 000 m/min, combined with a very low spinning defect rate. It shall further provide for good package build to provide high yarn weights on the package of more than 4 kg and good package unwinding performance in further processing.

[0013] It is yet a further object of the present invention that the POYs obtainable by the process of the invention be drawable or draw-texturable and possess a very good dyeing and processing performance coupled with a very low material defect rate.

[0014] These and other objects not explicitly mentioned but readily derivable or apparent from the related matters discussed herein at the beginning are achieved by a process for spinning and winding that comprises all the features of claim 1. Advantageous modifications of the process according to the invention are protected in subclaims appendant to claim 1.

[0015] The present invention accordingly provides a process for producing and winding POY PET filaments, at spinning takeoff speeds above 3 800 m/min, which comprises

[0016] a) setting the spinline extension ratio in the range from 50 to 250,

[0017] b) passing the filaments directly upon exit from the spinneret through a quench delay zone 20 mm to 300 mm in length,

[0018] c) quenching the filaments to below the solidification temperature,

[0019] d) converging the filaments at a distance between 500 mm and 2 500 mm from the underface of the spinneret,

[0020] e) using at least one oiler pin per yarn to add spin finish to a standard deviation of less than 90 digits for the finish application variation,

[0021] f) using oiler pins and yarn converging and yarn guiding elements that have low-friction surfaces,

[0022] g) setting the yarn tension above the takeoff godets between 0.07 cN/dtex and 0.5 cN/dtex,

[0023] h) entangling the yarn at a yarn tension between 0.05 cN/dtex and 0.20 cN/dtex and air pressure between 1.0 bar and 5.5 bar to a node count of at least 10 n/m with a coefficient of variation of less than 100%,

[0024] i) winding the yarn up at a yarn tension between 0.03 cN/dtex and 0.20 cN/dtex by the contact roll of the winder at an at least 0.3% higher frequency than the winding chuck and varying the winding angle between a minimum of 3.5° and a maximum of 7.5° over the winding time.

[0025] This unforeseeable process produces and winds POY PET filaments at a high spinning takeoff speed to a low breakage rate. The POY PET filaments have breaking extension values in the range from 90%-165% and a high uniformity with regard to filament parameters and spin finish application.

[0026] The process of the invention has a number of further advantages. They include:

[0027] The process of the invention is simple and economical to practice on a large industrial scale. More particularly, the process permits spinning and winding at high takeoff speeds of above 3 800 m/min, especially between 4 200 and 8 000 m/min, and the production of packages with high yarn weights of more than 4 kg.

[0028] The POY PET filament packages obtainable by the process can thus be further processed in a simple manner in a drawing or draw-texturing process with minimal unwinding defects.

[0029] The high uniformity of the POY filaments obtainable by the process ensures uniform and substantially defect-free dyeing and further processing of the POY polyester filament.

[0030] The present invention provides a process for producing and for winding POY filaments not less than 90% by weight, based on the total weight of the filament, polyethylene terephthalate PET which is obtainable for example from terephthalic acid and ethylene glycol in a convention manner by polycondensation.

[0031] The polyethylene terephthalate may be a homopolymer but also a copolymer. Useful copolymers include especially copolymers which, as well as the abovementioned repeat units, contain up to 15 mol %, based on all the repeat units of the PET, of repeat units of customary comonomers, for example 1,3-propanediol, 1,4-butanediol, diethylene glycol, triethylene glycol, 1,4-cyclohexanedimethanol, polyethylene glycol, isophthalic acid and/or adipic acid. For the purposes of the. present invention, however, PET homopolymers are preferred.

[0032] The PET may further comprise a small fraction, preferably up to 0.5% by weight, based on the total weight of the filament, of brancher components. Preferred brancher components according to the invention include polyfunctional acids, such as trimellitic acid or pyromellitic acid, or tri- to hexavalent alcohols, such as trimethylolpropane, penthaerythritol, dipentaerythritol, glycerol or corresponding hydroxyacids. In the context of the present invention, it may further be advantageous to admix the PET with up to 2.5% by weight, based on the total weight of the filament, of additive polymers as extensibility enhancers. Particularly useful additive polymers for the purposes of the invention include the hereinbelow mentioned polymers and/or copolymers:

[0033] 1. A copolymer containing the following monomer units:

[0034] A=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,

[0035] B=styrene or C1-3-alkyl-substituted styrenes,

[0036] the copolymer consisting of 60 to 98% of A and 2 to 40% by weight of B, preferably of 83 to 98% by weight of A and 2 to 17% by weight of B, and more preferably of 90 to 98% by weight of A and 2 to 10% by weight of B (sum total=100% by weight).

[0037] 2. A copolymer containing the following monomer units:

[0038] C=styrene or C1-3-alkyl-substituted styrenes,

[0039] D=one or more monomers of the formula I, II or III 1

[0040] where R1, R2 and R3 are each an H atom or a C1-15-alkyl radical or a C6-14-aryl radical or a C5-12-cycloalkyl radical, the copolymer, consisting of 15 to 95% by weight of C and 2 to 80% by weight of D, preferably of 50 to 90% by weight of C and 10 to 50% by weight of D and more preferably of 70 to 85% of C and 15 to 30% by weight of D, the sum total of C and D being 100% by weight.

[0041] 3. A copolymer containing the following monomer units:

[0042] 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,

[0043] F=styrene or C1-3-alkyl-substituted styrenes,

[0044] D=one or more monomers of the formula I, II or III 2

[0045] 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,

[0046] H=one or more ethylenically unsaturated monomers which are copolymerizable with E and/or with F and/or G and are selected from the group consisting of &agr;-methylstyrene, vinyl acetate, acrylic esters, methacrylic esters other than E, vinyl chloride, vinylidene chloride, halogen-substituted styrenes, vinyl ethers, isopropenyl ethers and dienes,

[0047] the copolymer consisting of 30 to 99% by weight of E, 0 to 50% by weight of F, >0 to 50% by weight of G and 0 to 50% by weight of H, preferably of 45 to 97% by weight of E, 0 to 30% by weight of F, 3 to 40% by weight of G and 0 to 30% by weight of H and more preferably of 60 to 94% by weight of E, 0 to 20% by weight of F, 6 to 30% by weight of G and 0 to 20% by weight of H, the sum total of E, F, G and H being 100% by weight.

[0048] 4. A polymer of the following monomer unit: 3

[0049] where R1 and R2 are substituents consisting of the optional atoms C, H, O, S, P and halogen atoms and the sum total of the molecular weights of R1 and R2 is at least 40. Exemplary monomer units include acrylic acid, methacrylic acid and 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, and also styrene and C1-3-alkyl-substituted styrenes.

[0050] Details of the production of these substances and of the blending of the additive polymers with the PET are described in WO 99/07 927. For the metered addition and dispersing of the additive in the PET reference is further made to DE 100 22 889.5.

[0051] Preference for the purposes of the present invention is given to additive polymers and/or copolymers which are amorphous and insoluble in the polyester matrix. They preferably possess a glass transition temperature of 90 to 200° C., the glass transition temperature being determined in a known manner, preferably by differential scanning calorimetry. Further details are discernible from the prior art, for example from WO 99/07927, the disclosure of which is hereby expressly incorporated herein by reference.

[0052] According to the invention, the additive polymer and/or copolymer is selected so that the ratio of the melt viscosities of the additive polymer and/or copolymer and of the matrix polymer is in the range from 0.8:1 to 10:1, preferably in the range from 1.5:1 to 8:1. The melt viscosity is measured in a known manner using an oscillation rheometer at an oscillation frequency of 2.4 Hz and at a temperature equal to the melting temperature of the matrix polymer plus 34° C. For polyethylene terephthalate, the temperature at which the melt viscosity measured is 290° C. Further details may again be found in WO 99/07927. The melt viscosity of the additive polymer and/or copolymer is preferably higher than that of the matrix polymer, and it has been determined that the choice of a specific viscosity range for the additive polymer and/or copolymer and the choice of the viscosity ratio contributes to optimizing the properties of the yarn product. Given an optimized viscosity ratio, it is possible to minimize the amount of additive polymer and/or copolymer added and so, inter alia, improve the economics of the process. The polymer blend to be spun preferably contains 0.05 to 2.5% by weight of additive polymer and/or copolymer.

[0053] The choice of the favorable viscosity ratio provides a narrow distribution of the particle sizes of the additive polymer and/or copolymer in the polymer matrix combined with the desired fibril structure for the additive polymer and/or copolymer in the fiber. The high glass transition temperature of the additive polymer and/or copolymer compared with the matrix polymer ensures rapid consolidation of this fibril structure in the spun fiber. The maximum particle sizes of the additive polymer and/or copolymer amounts to about 1 000 nm immediately following emergence from the spinneret, while the average particle size is 400 nm or less. The favorable fibril structure is obtained after the fiber has been drawn down, the filaments containing at least 60% by weight of the additive polymer and/or copolymer in the form of fibrils having lengths in the range from 0.5 to 20 &mgr;m and diameters in the range from 0.01 to 0.5 &mgr;m.

[0054] The polyethylene terephthalate of the invention may contain customary amounts, preferably 0 to 5% by weight, preferably 0 to 1% by weight, each percentage being based on the total weight of the filament, of further additives as admixtures, such as catalysts, stabilizers, antistats, antioxidants, flame retardants, dyes, dye uptake modifiers, light stabilizers, organic phosphites, optical brighteners and delusterants.

[0055] According to the invention, the PET is spun into POY filaments at a takeoff speed above 3 800 m/min, advantageously at least 4 200 m/min, preferably above 4 600 m/min, especially at least 6 000 m/min, more preferably above 6 000 m/min and finally wound up. A most preferably preferred range for the purposes of the invention is between 4 200 and 8 000 m/min, especially between 4 600 and 6 000 m/min.

[0056] For the purposes of the present invention, POY filaments are filaments having a breaking extension between 90 and 165%.

[0057] It may be advantageous for the process of the invention to use a spinning-cooling means which reduces stress-induced crystallization at high spinning takeoff speeds. A particularly preferred embodiment of the present invention utilizes a spinning-cooling means as described in WO 99/51799. The disclosure of this reference is explicitly incorporated herein in this context by reference.

[0058] Useful PET for the purposes of the invention preferably has an intrinsic viscosity (limiting viscosity number) in the range from 0.55 dl/g to 0.75 dl/g.

[0059] In the process of the invention, a PET melt is pumped by spinning pumps at constant speed, the speed being calculated by a known formula so that the desired fiber linear density is obtained, into spinneret packs to be extruded through the holes in the die plate of the pack to form molten filaments.

[0060] The melt may be prepared for example from polymer chips in an extruder, in which case the chips must first be dried to a water content ≦100 ppm, especially to a water content ≦50 ppm. Direct feeding of the PET melt from the final reactor of a polycondensation plant into the spinning plant is preferred.

[0061] The temperature of the melt, which is commonly referred to as the spinning temperature and which is measured before entering the spinning pump, depends on the melting point of the PET. It is preferably situated in the range given by formula 1:

[0062] Formula 1:

Tm+19° C.≦TSp≦Tm+49° C.

[0063] where

[0064] Tm is PET melting point, about 260° C. and

[0065] TSp is spinning temperature [° C.].

[0066] Melt homogeneity has a direct influence on the properties of the spun filament materials. It is therefore preferable to use a static mixer having at least two elements and installed before entering and/or after leaving the spinning pump to homogenize the melt. For example, a Promix spinning pump from Barmag/Germany with integrated mixer can be used.

[0067] Die plate temperature, which depends on the spinning temperature, is controlled by the die plate's secondary heating system. Useful secondary heating systems include for example a spinning beam heated with Diphyl or additional convective, inductive or radiative heaters. The temperature of the die plates is customarily equal to the spinning temperature.

[0068] A temperature increase at the die plate can be obtained through the pressure gradient in the spinneret pack. Known derivations, for example K. Riggert “Fortschritte in der Herstellung von Polyester-Reifenkordgarn” Chemiefasern 21, page 379 (1971), describe a temperature increase of about 4° C. per 100 bar of pressure drop.

[0069] It is further possible to control pack pressure through the use of loose filter media, especially through the use of steel sand having an average particle size between 0.10 mm and 1.2 mm, preferably between 0.12 mm and 0.75 mm and/or filter disks, which can be formed from woven or nonwoven metal fabrics having a fineness ≦40 &mgr;m, preferably 5 to 20 &mgr;m.

[0070] In addition, the pressure drop in the die hole contributes to the overall pressure. The pack pressure is preferably set between 80 bar and 450 bar, especially between 100 bar and 250 bar, the latter corresponding to a 4-10° C. increase in the melt temperature directly before extrusion.

[0071] The spinline extension ratio iSp, i.e. the ratio of the takeoff speed to the extrusion speed, is calculated in accordance with U.S. Pat. No. 5,250,245 via formula 2 from the density of the PET, the spinneret hole diameter and the filament linear density:

[0072] Formula 2:

iSp=2.25·105(&dgr;·&pgr;)·D2(cm)/dpf(den)

[0073] where

[0074] &dgr; is density of melt [g/cm3]; for PET=1.22 g/cm3

[0075] D=spinneret hole diameter [cm]

[0076] dpf=denier per filament [den].

[0077] For the purposes of the present invention, the spinline extension ratio is between 50 and 250, preferably between 70 and 170.

[0078] The length/diameter ratio of the spinneret hole is preferably selected to be between 1.5 and 6, especially between 1.5 and 4.

[0079] The extruded filaments pass through a quench delay zone. The quench delay zone is configured directly below the spin pack as a recess zone in which the filament emerging from the spinneret holes are protected from the direct action of the cooling gas and are delayed in spinline extension or cooling. An active part of the zone is constructed as an recess of the spin pack into the spinning beam, so that the filaments are surrounded by heated walls. A passive part is formed by insulating layers and unheated frames. The lengths of the active recess are between 0 to 300 mm and those of the passive part between 20 to 150 mm, subject to an overall length of 20-300 mm.

[0080] As an alternative to the active recess, an annealer can be disposed below the spinning beam. In contrast to the active recess, this zone of cylindrical or rectangular cross section then comprises at least one heating system independent of the spinning beam.

[0081] In the case of radial porous quenching systems which surround the spinline concentrically, the quench delay can be attained using cylindrical shrouds.

[0082] The filaments are subsequently cooled to temperatures below the solidification temperature. For the purposes of the invention, the solidification temperature is the temperature at which the melt passes into the solid state.

[0083] Means for quenching or cooling filaments are known from the prior art. It is particularly useful according to the invention to use cooling gases, especially cooled air. The temperature of the cooling air is preferably in the range from 12° C. to 35° C., and especially in the range from 16° C. to 26° C. The velocity of the cooling air is advantageously in the range from 0.20 m/sec to 0.55 m/sec.

[0084] The filaments may be cooled using for example single end systems comprising single cooling tubes having a perforated wall. Cooling of each individual filament is obtained through active cooling air supply or by utilizing the self-suction effect of the filaments and/or through aspiration of the cooling air. As an alternative to the individual tubes, it is also possible to use the familiar crossflow quench systems.

[0085] In a particular embodiment of the cooling and spinline extension region, the filaments emerging from the delay zone are exposed to cooling air in a zone 10 to 175 cm and preferably 10-80 cm in length. A zone 10-40 cm in length is particularly suitable for filaments having a linear density at windup ≦1.5 dtex per filament and a zone length of 20-80 cm is particularly suitable for filaments having a linear density between 1.5 and 9.0 dtex per filament.

[0086] The filaments and the accompanying air are subsequently conjointly passed through a channel having a reduced cross section at a ratio of the air to the spinline speed at takeoff in the range from 0.2 to 20:1, preferably in the range from 0.4 to 5:1, by controlling the cross-sectional constriction and the dimensioning in the spinline transportation direction.

[0087] After the filaments have been cooled down to temperatures below the solidification point, they are converged to form a yarn bundle. A suitable distance according to the invention for the point of convergence from the underface of the spinneret can be determined using conventional methods for-online measurement of the yarn speed and/or yarn temperature, for example using a laser doppler anemometer from TSI/Germany or an infrared camera from Goratec/Germany type IRRIS 160. It is in the range from 500 to 2 500 mm. Filaments having an as-spun linear density ≦4.5 dtex are preferably converged into a multifilament bundle at a smaller distance ≦1 500 mm, while thicker filaments are preferably converged at a greater distance.

[0088] It is advantageous for the purposes of the present invention that preferably all surfaces which come into contact with the spun filament are fabricated of particularly low-friction materials. This substantially avoids broken filaments and provides higher quality filament yarns. Particularly suitable for this purpose are low-friction surfaces of the “TriboFil” specification from Ceramtec/Germany.

[0089] The filaments are converged in an oiler pin which supplies the yarn with the desired amount of spin finish at a uniform rate. A particularly suitable oiler pin is characterized by an inlet part, the yarn duct with oil inlet orifice and an outlet part. The inlet part is funnellike, so that contact by the still dry filaments is avoided. The contact point of the filaments occurs within the yarn duct after the supply of spin finish. Yarn duct and oil inlet orifice are conformed in width to the yarn linear density and the number of filaments. Orifices and widths in the range from 1.0 mm to 4.0 mm are particularly suitable. The outlet part of the oiler pin is configured as a uniformizing zone, which preferably comprises oil reservoirs. Suitable oiler pins are available for example from Ceramtec/Germany, TriboFil, from Goulston/USA, LuroJet, from Kyocera/Japan, SF, and from Rauschert/Germany, PN.

[0090] The uniformity of oil application is of immense importance for the invention. The uniformity can be determined for example using a Rossa meter as per the method described in Chemiefasern/Textilindustrie, 42/94 November 1992 at page 896. The magnitude of the amount of oil applied and its spread is reported in relative units, so-called digits. For the purposes of the present invention, such a procedure provides standard deviation values for the oil application which are less than 90 digits and especially less than 60 digits. Particular preference for the purposes of the invention is given to oil application standard deviation values of less than 45 digits and especially less than 30 digits. A standard deviation value of 45 digits corresponds approximately to 3.1% of the coefficient of variation.

[0091] It is particularly advantageous for the purposes of the present invention to design spin finish lines and pumps to be self-degassing to avoid gas bubbles, since gas bubbles can lead to an appreciable variation in oil application. A very particularly preferred embodiment of the present invention utilizes a Profin spin finish pump from Barmag/Germany.

[0092] According to the invention, the filaments are entangled before being wound up. Conventional entangling systems have been found to be less suitable, since they give rise to appreciable numbers of loops and broken filaments as a consequence of the high speed and the increased air pressure. They also require high winding tensions, which have an adverse effect on package build and lead to ridging and trapped and dropped ends on the package.

[0093] In the context of the present invention, these disadvantages are advantageously avoided by using jets having closed yarn ducts, since such systems prevent snubbing of the yarn in the feed slot even at low yarn tension and high air pressure. The entangling jets are preferably disposed between godets, and the yarn exit tension is controlled via the different speeds of the inlet and outlet godets. The yarn exit tension should not exceed 0.20 cN/dtex, and the yarn inlet tension should primarily have values between 0.05 cN/dtex and 0.18 cN/dtex. The entangling air pressure is between 1.0 and 5.5 bar.

[0094] The yarns are entangled to node counts of at least 10 n/m. Maximum nodeless gaps of less than 100 cm and node count coefficient of variation values below 100% are of particular interest. Advantageously, the employment of air pressures ≧3.0 bar provides node counts ≧15 n/m, which are characterized by high uniformity in that the coefficient of variation is not more than 70% and the maximum nodeless gap is 50 cm.

[0095] In actual service, systems of the LD type from Temco/Germany, the double system from Slack & Parr/USA or Polyjet from Heberlein have been found to be particularly useful.

[0096] Particularly positive effects with regard to reducing the number of broken filaments are obtained on employing a migration jet prior to the actual entangling. Operating at air pressures of less than 1 bar, a migration jet provides a further uniformization of the applied spin finish and a thorough mixing of the individual filaments. These jets are employed above the first takeoff godet, preferably directly below the oiler pin.

[0097] The circumferential speed of the first godet unit is referred to as takeoff speed. Further godet systems can be employed before the yarn is wound up in the winder assembly to form packages (bobbins) on tubes.

[0098] Stable, defect-free packages are a basic prerequisite for defect-free unwinding of the yarn and for an ideally defect-free further processing. In the context of the present invention, the winding tension employed is in the range of 0.03 cN/dtex-0.20 cN/dtex, preferably in the range from 0.05 cN/dtex-0.15 cN/dtex.

[0099] It is preferable to provide the winder with a traversing system including rotary blades for traversing the yarn and with a driven contact roll for controlling the speed of the driven chuck onto which the bobbin tubes have been fixed. To avoid dropped ends, it is advantageous to control the drive of the contact roll at an at least 0.3% higher frequency than the winding chuck control.

[0100] It is further exceedingly advantageous to employ a ribbon-breaking mechanism to vary the winding angle in steps of at least 1° in order that trapped yarn coils may be avoided in the ribbon positions specifically. A variation of the winding angle during the winding time of the bobbin between 3.5° and 7.5° is particularly preferred according to the invention to stabilize the package build. Here the winding angle is the angle, viewed perpendicularly to the package tube, between the yarn transportation direction on the package body and the perpendicular to the package tube.

[0101] The entangling and winder conditions according to the invention provide stable packages.

[0102] An important parameter of the process according to the invention is the yarn tension setting above the takeoff godets. As will be known, this tension is made up essentially of Hamana's actual orientation tension, the frictional tension on the yarn guides and the oiler pin and the yarn-air frictional tension. For the purposes of the present invention, the yarn tension above the takeoff godets is in the range from 0.07 cN/dtex to 0.50 cN/dtex, preferably between 0.07 cN/dtex and 0.20 cN/dtex.

[0103] An excessively low tension below 0.07 cN/dtex no longer provides the desired degree of pre-orientation. When the tension exceeds 0.50 cN/dtex, yarn damage occurs due to frictional heat and leads to a deterioration in yarn parameters.

[0104] The tension is controlled according to the invention by the spinning takeoff speed, the distance of the oiler pin from the spinneret, the frictional surfaces and the length of the gap between oiler pin and takeoff godet. This length is advantageously not more than 6.0 m, preferably less than 2.5 m, while the spinning system and the takeoff machine being disposed in such a way by parallel construction as to ensure a straight yarn path.

[0105] To set the winding tension according to the invention, the winding speed of the POY is advantageously 0-2% below the takeoff speed. It is preferable to select a winding speed to be 0-1% below the spinning takeoff speed.

[0106] Advantageously, the process according to the invention is carried out by adjusting the environment of the winding machine to be at a temperature ≦35° C., especially between 12 and 28° C., and a relative humidity between 40-90%. It is further advantageous to condition the POY packages at 12 to 28° C. and a relative humidity between 40-90% prior to further processing for 4 hours at least.

[0107] Processes for determining the material parameters reported are well known to one skilled in the art. They are discernible from the technical literature, for example WO 99/07927, the disclosure of which is hereby expressly incorporated herein by reference.

[0108] The entangling parameters are determined using a node counter of the ITEMAT type from Enka-Tecnica/Germany at a speed of 100 m/min and a setting of level No. 1.

[0109] The online detection of broken ends in spinning is done using a Fraytec instrument from ENKA-Technica/Germany. The broken filaments sensor must trigger a directly following video camera, the picture of which is stored to make possible defects analyzable and classifiable. Mismeasurements, for example due to oil droplets or vibrations, can be avoided with such an approach. The evaluation provides information about texturing-relevant defects in particular. The defects, which look like filament tufts and are caused by broken filaments being bunched up were reduced by the process according to the invention to 0 per hour at a spinning takeoff speed of 5 000 m/min.

[0110] An illustrative embodiment of the invention will now be more particularly described without the invention being restricted to this example.

[0111] A polyethylene terephthalate melt was discharged from a reactor at an intrinsic viscosity of 0.64 dl/g, corresponding to a melt viscosity of 250 Pas at 290° C., and a temperature of 282° C. and pumped by a pressure raising pump through the melt line at a pressure of 205 bar and a rate of 302.4 kg/h. The melt flows through a 20 &mgr;m filter and a heat exchanger which lowered the melt temperature of 292° C. to the spinning temperature of 290° C.

[0112] This filtered part stream 1, having a rate of 302.4 kg/h, was divided into the second part stream, rate 13.98 kg/h, corresponding to 4.62% by weight of the first stream, and the third part stream, rate 288.42 kg/h, and branched off.

[0113] The second part stream and additives stream were metered and transported using a lefthandedly operated 6-fold planetary wheel pump from Mahr GmbH, Göttingen/DE. This is a 6-fold spinning pump which, through reversal of the center of rotation and hence the direction of flow, combines the equal volume flows of 6 input channels into one output channel.

[0114] The second part stream was fed in equal parts to 5 of 6 inlets of a lefthandedly operated 6-fold planetary wheel pump from Mahr GmbH, Göttingen/DE.

[0115] A copolymeric additive of the 3rd group of substances, containing 9% by weight of styrene, 89% by weight of methyl methacrylate and 2% by weight of N-cyclohexylmaleimide, was chosen with a viscosity ratio of 5.8.

[0116] The additive dried to a residual moisture content of <0.1% by weight was melted in an extruder and fed at a melt temperature of 265° C. and at a rate of 2.33 kg/h, corresponding to 0.77% by weight of the first part stream, to the remaining inlet channel of the 6-fold planetary wheel pump.

[0117] This additive stream was combined in the exit channel of the planetary wheel pump with the polyester stream from one of the 5 polyester-fed inlet channels and premixed using a static premixer of the SMXS DN 12 type from Sulzer AG, Zurich/CH, having an internal diameter of 12.9 mm and 3 times the length of the internal diameter before the polyester streams of the 4 remaining inlet channels were added to this premix in the outlet of the planetary wheel pump.

[0118] The residence time of the additive melt until brought together with the other polymers was about 70 sec.

[0119] The subsequent preparation of the first polymer blend having an additive content of 16.7% by weight took place in a first static main mixer of the SMXS DN 17 type from Sulzer AG, Zurich/CH, having an internal diameter of 17.8 mm and 9 times the length of the internal diameter.

[0120] This first blend was introduced into the third part stream and, after a flow length L amounting to 4 times the internal diameter of the first main mixer, fed to a second main mixer of the SMX type from Sulzer AG, having an internal diameter of 52.5 mm and a length 10 times the diameter, was homogenized and dispersed.

[0121] The residence time of the additive melt to the point of contact with the 3rd part stream was about 100 sec.

[0122] The polymer blend was distributed by product lines to 12 spinning positions, each position containing 6 spinneret packs. Each spinneret pack contained a round spinneret having 34 holes 0.25 mm in diameter and 2-diameters in length. In addition, the spinneret pack contained above the spinneret plate a spin filter pack consisting of a steel sand packing 30 mm in height and 0.35 to 0.50 mm in particle size and also a finest woven filter of 40 &mgr;m and a steel nonwoven filter 20 &mgr;m in pore diameter. The cross-sectional area of the spin filter pack was 45 cm2. As the molten blend passed through, a pack pressure of 150 bar ensued. The residence time of the melt in the filter pack was about 1.5 min. The surface of the spinneret was situated 30 mm above the lower edge of the heating box (active recess). The total recess was 110 mm. The spin pack heating was set to 290° C. using HTM heat transfer oil.

[0123] The molten filaments extruded from the spinneret holes were quenched with air flowing horizontally against the spinline over a length of 1500 mm at a velocity of 0.5 m/sec and having a temperature of 19° C. and converged at a distance of 1400 mm from the spinneret plate in an oiler pin of the TriboFil type from CeramTec to form a yarn, the diameter of the oil channel being 1 mm, and the yarn was coated with a spin finish from Goulston to an add-on of 0.35%. Oil add-on standard deviation was 38 digits.

[0124] An S-wrapped pair of godets has taken off the yarn at a speed of 5 000 m/min with the spinline extension ratio having been set to 141 and the yarn tension above the first godet to 28 cN. Situated between the godets was an LD type entangling jet from Temco, which is closed in the event of normal yarn transportation and which utilized an air pressure of 4.0 bar to confer on the yarn an entangling node count of 22 n/m coupled with a CV value of 53.9%. The yarn tension was set to 16 cN at the inlet to the entangling jet and to 18 cN at the outlet. The yarn guides were of the “Low Friction” surface type from Barmag/Germany.

[0125] The six ends of one spinning position were wound up in a winder to form packages, the speed of 4985 m/min having been chosen so that the yarn tension before windup was 12 cN. The overfeed of the contact roll was raised by 0.6% compared with the chuck. The winding angle was varied between 4.3° and 6.5. The fault detector found no filament tufts in the course of the production of a 19 kg package.

[0126] The POY obtained was characterized by a linear density of 141 dtex, a breaking strength of 25 cN/tex and a breaking extension of 117%. The POY packages were draw textured in a Barmag texturing machine of the FK6 type at a speed of 900 m/min. The draw ratio chosen was 1.70. The first heater had a temperature of 210° C. and the second heater had a temperature of 170° C.

[0127] The textured yarn had a linear density of 88 dtex, a breaking strength of 42 cN/tex and a breaking extension of 22% and was characterized by good dye uniformity. The process of the invention was here notable in particular also for the low number of broken ends in spinning and texturing.

[0128] The spinning stage produced 98% for 19 kg packages and the draw-texturing stage 92% for 5 kg packages.

Claims

1. A process for producing and winding POY filaments not less than 90% by weight PET, based on the total weight of the POY, at spinning takeoff speeds above 3 800 m/min, which comprises

a) setting the spinline extension ratio in the range from 50 to 250,

b) passing the filaments directly upon exit from the spinneret through a quench delay zone 20 mm to 300 mm in length,

c) quenching the filaments to below the solidification temperature,

d) converging the filaments at a distance between 500 mm and 2 500 mm from the underface of the spinneret,

e) using at least one oiler pin per yarn to add spin finish to a standard deviation of less than 90 digits for the finish application variation,

f) using oiler pins and yarn converging and yarn guiding elements that have low-friction surfaces,

g) setting the yam tension above the takeoff godets between 0.07 cN/dtex and 0.5 cN/dtex,

h) entangling the yarn at a yarn tension between 0.05 cN/dtex and 0.20 cN/dtex and air pressure between 1.0 bar and 5.5 bar to a node count of at least 10 n/m with a coefficient of variation of less than 100%,

i) winding the yarn up at a yarn tension between 0.03 cN/dtex and 0.20 cN/dtex by driving the contact roll of the winder at an at least 0.3% higher frequency than the winding chuck and varying the angle of wind between a minimum of 3.5° and a maximum of 7.5° over the winding time.

2. A process as claimed in claim 1, wherein the spinning takeoff speed is in the range from 4 200 to 8 000 m/min, especially in the range from 4 600 to 6 000 m/min.

3. A process as claimed in claim 1 and/or 2, wherein the PET used contains up to 2.5% by weight, based on the total weight of the filament, of additive polymer extensibility enhancer in admixture.

4. A process as claimed in at least one of the preceding claims, wherein the filaments are cooled using a cooling means reducing stress-induced crystallization at high spinning speeds.

5. A process as claimed in any of the preceding claims, wherein the PET used contains up to 2.5% by weight, based on the total weight of the filament, of additive polymer stretch enhancer in admixture and the filaments are cooled using a cooling means reducing stress-induced crystallization at high spinning speeds.