FORM • 2 THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
PROVISIONAL
Specification
(See section 10 and rule 13)
POLYESTER STAPLE FIBER (PSF)/FILAMENT YARN (POY and PFY) FOR TEXTILE APPLICATION
FUTURA POLYESTERS LIMITED
an Indian Company of
Paragon Condominium, 3rd floor, Pandurang Budhkar Marg, Mumbai 400 013,
Maharashtra, India,
THE FOLLOWING SPECIFICATION DESCRIBES THE INVENTION.

Field of the Invention
The invention relates to polyester staple fiber (PSF) /filament yarn (POY and PFY) for textile applications.
Background of the Invention
PTT, Polytrimethylene Terephthalate also known as 3GT, has achieved growing commercial interest as a fiber due to its desirable properties like its easy disperse dyeability at atmospheric pressure, low bending modulus, good elastic recovery and resiliency. PTT fiber, like PET fiber, is melt extrusion spun followed by the conventional two stage drawing of the undrawn spun fiber. However there are process parameter differences while processing due to the inherent difference in the characteristics of the polymers PET and PTT. PTT has a lower melt temperature by ~ 30°C and necessitates a shorter time until the spun yarn in the melt spinning is cooled down resulting in differences in quench air adjustment and the length of the cooling path in comparison with PET spinning. Another important difference is PTT's lower glass transition temperature (Tg) when compared to PET which causes much faster cold crystallization in PTT leading to a difference in fiber morphology during solidification and cooling down. The unique molecular structure of PTT gives the fiber intrinsic elasticity.
Processes for the production of PTT staple fibers and continuous filament are well known and are described in US 2006/0020103, 6835339, 6752945, 6495254, 2003/0111171, 6645621, 6423407, 6287688, WO 0222925, 99/11845, 9/27168, EP 0547553. 0754790, JP 52/08124, 52/08123, 52/05320, 2005256242, and other documents.
PTT staple fiber is manufactured by the conventional two stage process but with different process parameters when compared to processing PET. Typical production process equipment include an extruder, spin beam, melt metering pump, spin pack, cross flow or radial quenching systems, spin finish application units, take-up systems, undrawn fiber storage and conditioning, creel formation, draw frames with or without
heat setting, crimper, dryer and fiber cutter.
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However PTT as spun undrawn fiber produced by the conventional two stage process have extremely low degrees of orientation and crystallization with a Tg as low as 35°C. Due to this, as explained earlier, the undrawn fiber properties change quickly with time resulting in the generation of fluffs, neps and yarn breakage during the drawing process. This is also reflected in the shrinkage of the undrawn PTT fiber in comparison with PET undrawn fiber. PET undrawn fiber is quite stable and shows a very low % shrinkage for a prolonged storage time of even up to one week. On the contrary PTT undrawn fiber is highly susceptible for shrinkage under ambient conditions of temperature and relative humidity (RH) and shows increased shrinkage with storage time. To get a stable low shrinkage similar to PET, the PTT undrawn has to be stored at low temperatures of < 20°C. PTT fiber processors recommend that the PTT undrawn fiber creel to be stored in an air-conditioned atmosphere to avoid shrinkage. Different attempts have been reported in prior art to overcome these disadvantages.
WO 99/27168 and WO 96/00808 suggest a method of continuously performing spinning and drawing in one stage without taking up the undrawn yarn.
US 6495254 proposes a method of increasing the spinning rate to develop higher degrees of orientation and crystallization but still the variation in shrinkage with time was inevitable.
US 6383632 describes a process for preparing fine denier PTT feed yarns and drawn yarns
WO 99/39041 discloses a method of improving specific surface properties of PTT fibers by coating the fibers with a surface finishing agent having a specific composition but not dealt with the shrinkage differences.
EP 1016741 describes using a phosphorous additive in PTT spinning to get spinning stability.
US 6423407 deals with a process of producing PTT filament yarn comprising not less than 95 mole % PTT repeating unit and not more than 5 mole % of other ester repeating unit and spinning at not less than 2000m/min followed by coating the extrudate with a
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finishing agent. At less spinning speeds shrinkage of fibers in the undrawn yarn is caused by formation of crystallite and relaxation of oriented molecules.
US 6740270 describe a spin draw process of making POY from PTT. Spin draw process comprising two or three pairs of heated godets are generally used to make fully oriented yarn (FOY). But this process, though more expensive than the conventional process used to make PET POY, is used with PTT mainly to stabilize the PTT POY against shrinkage and to improve the package stability and shelf life.
US 7005093 deals with PTT POY spinning and provides an analytical method to predict the aging process of the bobbins.
JP 2002061038 relates to PTT POY spinning using a special spinning method of extruding the PTT polymer at a surface temperature of a spinneret within a specified range to reduce the rapid cooling of the molten yarn.
US 6218008 have disclosed an easy dyeable polyester filament yarn consisting of 60-95 mol% of PET and 5-40 mol% of PTT.
US 4167541 describes continuous carrierless dyeable polyester filament yarn preparation by using a melt blend system comprising not less than 78 wt.% PET coploymerized with major amounts (2-12 wt.%) of a dicarboxylic acid other than terephthalic acid (PTA) like adipic acid, sebacic acid etc. and a homopolymer selected from PTT, Polybutylene terephthalate (PBT) and Polyhexamethylene terephthalte (PHT) at levels of 1-10 wt.%.
The above mentioned last two US patents emphasize the fibers affinity to disperse dyestuffs but do not provide information on the spinning and drawing processes.
Non circular cross sectional fibers (e.g. tetralobal, hexalobal, octalobal etc.) are generally used for moisture wicking or transport properties in the yarn and subsequently in the fabric. Moisture wicking is desirable in fabrics used for sportswear as they help in
keeping the moisture away from the wearer and gives comfort.
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US 4634625 describes continuous filament PET yarns of tetralobal (tetra channel) cross section with the resulting fabric having a combination of soft hand and natural luster without glitter.
US 5736243 deals with continuous PET filaments with a 4-groove cross section (tetra channel) resulting in better processing in worsted system.
US 2001/0033929 describes a process for making fully oriented yarn of octalobal cross section comprising PTT present to the extent of at least 85 mole%.
US 6835339 and 6458455 are about a process of making PTT tetrachannel cross-section staple fibers, yarns, fiberfill, fabrics etc.
US 6620505 provides a method of making PTT trilobal yarn wherein the PTT component is at least 95% and containing 5% or less of other ester repeating units.
US 6287688 deals with a process for making PTT POY with cross-sections of oval, octalobal, trilobal, tetralobal etc.
US 6656586 describes bicomponent fibers (POY, Fully Drawn Yarn and Staple fibers) with high moisture wicking rates comprising PET and its copolyesters and PTT of ratios of at least about 30:70 but not more than about 70:30. The tetralobal, hexalobal, and octalobal bicomponent fibers consisted of the two types viz. side-by-side and eccentric sheath-core.
Disclosure of the Invention
PTT staple fiber spinning results in satisfactory drawing performance and yield acceptable fiber properties only if the undrawn spun fiber is stored under controlled low temperature conditions. Similarly unless the more expensive spin draw process is used, as detailed earlier, it is difficult to get stable POY package with longer shelf life. Storage of PTT as spun fiber under ambient atmosphere results in reduction of shrinkage and the residual shrinkage varies with time and temperature. This variation in shrinkage affects the Natural Draw Ratio (NDR) of the fiber resulting in processacibility difficulties in drawing. Due to the limitation in drawing the finished staple fiber /
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filament yarn gives low strength and very high elongation which gets reflected in poor performance in the mills particularly while carding and roving to yarns or in knitting.
To overcome these problems in PTT staple fiber spinning and POY production incorporation of polymer composition comprising PTT and a CoPET is suggested in this invention. The invention envisages the use of PTT - CoPET as a resin composition for making staple fiber and POY deals with the regular round or circular cross section and also multilobal cross sections particularly the tetralobal or tetrachannel cross sections.
The CoPET is a copolyester of PET with dicarboxylicacids selected from aliphatic compounds like oxalic acid, malonic acid, succinic acid, adipic acid etc, and aromatic acids like isophthalic acid, sulfoisophthalic acid etc. The as spun fiber resulting from this copolyester composition when stored under normal ambient conditions does not show a varying shrinkage with time but gives a constant residual shrinkage which shows good performance in the drawing process and also yield finished fiber with proper elongation and tenacity. Staple fiber /POY obtained through this process performs well in the mills. Avoiding the low temperature storage conditions minimizes the energy cost by way of the refrigeration load resulting in considerable saving in the cost of production. Additionally improvement in mechanical properties is seen which results in easy processability of the fiber.
Considerable trials were taken with varying PTT : CoPET ratios from 5:95 to 95:5 and arrived at an optimum blended composition of PTT:CoPET in the range of 90:10 and 70:30 resulting in the following features in the case of staple fiber spinning of circular and tetralobal cross sections.
• The residual shrinkage of the spun fiber was higher than observed with 100% PTT ( Refer Table 1 & 3)
• No variation in residual shrinkage when the spun fiber was stored under ambient conditions (Refer Table 3)
• No significant variation in residual shrinkage up to 50 - 60 hours of storage
• Consistent drawing process performance (Refer Table 3)
• Fiber properties like strength, elongation and elastic recovery are slightly better when compared to 100 % PTT fiber. (Refer Table 2 & 4)
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• Fiber strength expressed as tenacity (g/d) is greater by 10 - 15 % (Refer Table 2&4)
• In tetrachannel fiber produced from the PTT-CoPET alloy/blend resin there is an appreciable increase in moisture wicking property when compared to that produced from 100% PTT fiber
• Improved and good performance while converting to yarn in the mills
• As an additional advantage fiber show a 10 % increase in dyeing strength when dyed at boil
In the case of POY spinning using an alloy blend of PTT with CoPET instead of 100% PTT the following additional advantages are seen
• Winding tension can be brought to a minimum for good runnability even with godetless spinning.
• POY spinning with 100% PTT often needs thick walled bobbins as winding an elastic filament at high speed results in tightening of the package. This is not the case with PTT-CoPET spinning and the normal bobbins as used in PET spinning is adequate.
• In contrast to 100% PTT, lower spinning speeds and godetless spinning are possible with PTT-CoPET resin.
Example:
PTT:CoPET alloy / blended chips, of I.V. 0.90 + 0.05:0.60 ± 0.05, comprising of a composition between the range of 90:10 and 70:30, is thoroughly dried at 120 -130°C and extruded to a molten polymer melt through an extruder with zone temperatures maintained from 240 to 280°C and then spun through a spinneret provided in the spinning head at a take-up speed ranging from 700-1500 meters/minute. The group of spun filaments is solidified in a quench chamber with cooling air followed by application of chilled finish. The resulting as spun or undrawn yarn is collected in cans while simultaneously spraying chilled demineralized water in the can during the fiber collection. The cans containing the undrawn yarn are stored both at ambient storage conditions and also at controlled temperature conditions and samples of undrawn fiber are collected at different hours
and tested for residual boiling water shrinkage. The undrawn fiber from the cans are
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processed through a two stage drawing system followed by heat setting , crimping, relaxing and cutting the drawn fiber to specific staple lengths of finished fibers.
Similar experiments were conducted with 100% PTT and the results of the undrawn fiber of both PTT and PTT-CoPET stored under different conditions and the drawn fiber properties are given in the following Tables 1 to 4.
As described in the prior art PTT-CoPET composition has been used (US 6656586) for making tetrachannel bicomponent staple fiber with moisture wicking property. In our invention PTT-CoPET composition is used to make the tetra channel staple fiber with a homogenously blended composition rather than the bicomponent type. Bicomponent fiber making involves expensive and complex spin pack components. Also in the bicomponent fiber due to a clear boundary between the two components there is a possibility of delamination and lack of synergy in the final properties of the fiber due to the non-mixing and discreet presence of the two components. There are advantages in blending PTT and CoPET resins either during the resin manufacture or prior to extrusion of filaments. The blended fiber process is economical as the normal spin pack components are sufficient to produce the fiber. Also the fiber properties like tenacity, elongation and moisture wicking will be better in the blended fiber when compared to the bicomponent . This is because in blending there is perfect homogenization of the two components viz.PTT and CoPET which improves the processability and also helps in obtaining fibers for specific needs by tailoring one or more properties with minimum sacrifice in other properties. Due to the homogeneity of the blend the composition behaves as a single polymer. The interphase interactions and adhesion between the crystalline phase of the components , resulting from their miscibility in the amorphous phase, improves mechanical properties such as tenacity and modulus of elasticity of the PTT-CoPET blend. Table-5 gives the properties of the undrawn and drawn tetrachannel staple fiber using the blended composition of PTT-CoPET
Preliminary studies carried out with PTT- CoPET alloy/blend for producing PFY through POY (Partially Oriented Yarn) showed trends similar to that observed with staple fiber. Properties of POY obtained from these studies are summarized in Table-6.
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TABLE -1
PTT Undrawn Fiber - Shrinkage and Storage Conditions

Trial No. Final Fiber Denier UndrawnStorageCondition UndrawnStorageHours Initial, Zero Hour, % Boiling Water Shrinkage (BWS) Residual % BWS at different Hours of Storage
1. 3.0 Room Temp.~32°C 48 29-32 10-13
2. 3.0 —do— 5 31 17
3. 2.5 —-do- 18 39 3
4. 2.5 Controlled Temp.~24°C 18 39 33
5. 1.4 Room Temp.~32°C 24 50 17
6. 1.4 —do— 36 44 16
7. 1.4 Controlled Temp.~24°C 24 51 48
8. 1.4 do-— 36 44 43
9. 1.4 —do 78 44 43
10. 1.4 -—do- 96 44 45
TABLE-2
PTT Drawn Fiber Properties from Undrawn of Table - 1.

Serial No. Final Finished Fiber Denier Tenacity, g/d % Elongation % Shrinkage, 180°C, 20 minutes
1. 3.1 -3.2 1.6-2.0 109-143 3.4-3.7
2. 2.4-2.6 2.3-2.8 106-120 6.5-6.8
3. 1.3-1.4 3.2-3.4 82-85 8.1-8.9
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TABLE-3
PTT - CoPET Undrawn Fiber - Shrinkage and Storage Conditions

Trial No. Final Fiber Denier UndrawnStorageCondition UndrawnStorageHours Initial, Zero Hour, % Boiling Water Shrinkage(BWS) Residual % BWS at different Hours of Storage
1. 3.0 Room Temp.~32°C 58 56 55
2. 3.0 —do- 58 55 54
3. 2.5 —do— 98 62 57
4. 2.5 —do— 98 61 53
5. 2.5 —do— 36 55 53
6. 2.5 —do- 58 55 54
7. 1.2 Controlled Temp.~24°C 36 56 53
8. 1.2 —do— 58 56 55
TABLE - 4
PTT - CoPET Drawn Fiber Properties

Serial No. Final Finished Fiber Denier Tenacity, g/d % Elongation %Shrinkage, 180°C, 20 minutes
1. 1.4 3.8 70.0 9.0
2. 2.5 3.0 80.0 10.0
3. 3.0 2.9 84.0 11.0
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Table - 5 PTT-CoPET TetraChannel Cross Section Fiber Properties

Serial No. UNDRAWN FIBER DRAWN FIBER
1. Denier 4.31 3.33 Denier 1.85 2.75
2. Breaking Load, g 9.09 6.58 Tenacity, g/d 3.4 3.0
3. % Elongation 226 223 T12,g/d 0.8 0.8
4. Natural Draw Ratio 2.71 2.74 % Elongation 73 84
5. Hot Air Shrinkage,180°C, 20 minutes 11.3 10.7
Table- 6
PTT - CoPET POY Properties

Serial No. Parameters 100 % PTT PTT - CoPET
1. Denier/No.of Filaments 110/72 110/36 110/72 110/36
2. Winder Speed, m/min. 3200 3600 3200 -3600 3200 - 3600 3200 -3600
3. % Elongation 63-65 62-64 66-68 64-67
4. Tenacity, g/d 2.8-3.1 2.6-2.9 3.0-3.3 3.4-3.8
5. Shrinkage at 60°C, in air, 15 minutes 7-10 8-10 7-9 6-9
Thus this invention discloses a polyester resin composition comprising an alloy / blend of PTT and CoPET as a better alternate to 100 % PTT in making staple fiber or POY with circular or tetrachannel cross-sections. This alloy/blend composition of PTT and CoPET helps in avoiding the storage of the undrawn fiber/filament yarn under controlled temperature conditions. The undrawn fiber/filament yarn produced with this composition of the resin performs better in the two stage drawing system for staple fiber
or in the process of making partially oriented yarn (POY) or fully drawn yarn (FDY) giving better properties in the finished staple fiber and filament yarn.
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While emphasis has been laid on the composition of the fiber it will be obvious to one skilled in the art that various modifications can be envisaged within the ambit and scope of the invention.

MOHAN DEWAN
OF R.K.DEWAN & COMPANY
APPLICANTS' PATENT ATTORNEY