Copolyester tape

Abstract

Provided is a tape including a composition having a copolyester including polymeric units derived from ethylene glycol and terephthalic acid or a diester thereof and >0.50 and <5.00 wt % of polymeric units with regard to the total weight of the polyester derived from an oligomeric dihydroxy compound having a number average molecular weight of >500 g/mol and <5000 g/mol. Such tape has an improved tensile-impact strength and a reduced proneness to splitting during weaving.

Claims

1. A tape comprising a composition comprising: a copolyester comprising polymeric units derived from ethylene glycol and terephthalic acid or a diester thereof and >0.50 and <5.00 wt % of polymeric units with regard to the total weight of the polyester derived from an oligomeric dihydroxy compound having a number average molecular weight of >500 g/mol and <5000 g/mol.

2. The tape according to claim 1, wherein the oligomeric dihydroxy compound is selected from a polyester polyol, a polyethylene glycol, a polypropylene glycol, a polytetrahydrofuran, or a polydimethyl siloxane.

3. The tape according to claim 1, wherein the oligomeric dihydroxy compound is a polyethylene glycol.

4. The tape according to claim 1, wherein the polyester has an intrinsic viscosity as determined in accordance with ASTM D2857-95 (2007) of >0.50 and <2.50 dl/g.

5. The tape according to claim 1, wherein the tape has a width of ≥1.0 and ≤50.0 mm and a thickness of ≥10 μm and ≤250 μm.

6. The tape according to claim 1, wherein the tape is unidirectionally oriented along the longitudinal axis.

7. The tape according to claim 1, wherein the tape is stretched to a drawing rate of >4 and <10, wherein the drawing rate is the ratio of the length of the tape subsequent to stretching and the length of the tape prior to stretching.

8. A process for the production of a tape according to claim 1, wherein the process comprises the following steps in this order: melt extrusion to form a molten film; film casting to form a solidified unoriented film; cutting the film in the longitudinal direction to form a plurality of unoriented tapes; subjecting the unoriented tapes to a stretching step in the longitudinal direction to form unidirectionally oriented tapes; and heat-setting the oriented tapes.

9. The process according to claim 8, wherein the stretching step is performed at a temperature of >70° C. and <90° C.

10. The process according to claim 8, wherein the tape is produced at a stretching speed of >100 m/min.

11. The process according to claim 8, wherein the unidirectionally oriented tapes are subjected to a heat-setting step at a temperature in the range of 140-250° C.

12. A woven article comprising the tape according to claim 1.

13. The woven article according to claim 12 wherein the woven article is a bag having a volume of ≥500 l.

14. The process according to claim 8, wherein the stretching step is performed at a temperature of >70° C. and <90° C.; wherein the tape is produced at a stretching speed of >100 m/min; and wherein the unidirectionally oriented tapes are subjected to a heat-setting step at a temperature in the range of 140-250° C.

15. The tape according to claim 1, wherein the oligomeric dihydroxy compound is selected from a polyester polyol, a polyethylene glycol, a polypropylene glycol, a polytetrahydrofuran, or a polydimethyl siloxane; wherein the polyester has an intrinsic viscosity as determined in accordance with ASTM D2857-95 (2007) of >0.50 and <2.50 dl/g; wherein the tape is unidirectionally oriented along the longitudinal axis; and wherein the tape is stretched to a drawing rate of >4 and <10, wherein the drawing rate is the ratio of the length of the tape subsequent to stretching and the length of the tape prior to stretching.

16. The tape according to claim 15, wherein the tape has a width of ≥1.0 and ≤50.0 mm and a thickness of ≥10 μm and ≤250 μm.

17. The tape according to claim 15, wherein the oligomeric dihydroxy compound is a polyethylene glycol.

18. A tape comprising a composition comprising: a copolyester comprising polymeric units derived from ethylene glycol and terephthalic acid or a diester thereof; and >0.50 and <5.00 wt % of polymeric units with regard to the total weight of the polyester derived from an oligomeric dihydroxy compound having a number average molecular weight of >500 g/mol and <5000 g/mol; wherein the polyester has an intrinsic viscosity as determined in accordance with ASTM D2857-95 (2007) of >0.50 and <2.50 dl/g; wherein the tape has a width of ≥1.0 and ≤50.0 mm and a thickness of ≥10 μm and ≤250 μm; wherein the tape is unidirectionally oriented along the longitudinal axis; and wherein the tape is stretched to a drawing rate of >4 and <10, wherein the drawing rate is the ratio of the length of the tape subsequent to stretching and the length of the tape prior to stretching.

19. The tape according to claim 1, wherein the oligomeric dihydroxy compound has a number average molecular weight of 1,000 g/mol to 2,000 g/mol.

Description

EXAMPLE 1

PET Homopolymer

(1) A quantity of a PET homopolymer was prepared in a bench-scale setup involving an esterification step, a polycondensation step and a solid state polymerisation step.

(2) The esterification was performed in a 25 l. bench-scale reactor with agitation. To the reactor vessel, 6917 g terephthalic acid, 3358 g ethylene glycol, 5.66 g antimony triacetate, and 0.5 g cobalt acetate were supplied under agitation at 100 rpm to form a feed paste. The temperature of the paste was increased to 250° C. under a pressure of 5 bar triggering the esterification reaction. Water was continuously removed during the esterification via a separation column of the reactor. Esterification occurred under continued agitation at 100 rpm. Upon completion of the esterification reaction, which was after 184 min, the pressure was reduced to atmospheric pressure. Subsequently, 0.6 g phosphoric acid was added to the reactor and allowed to mix with the esterification product for 3 min during which the temperature was increased to 260° C.

(3) The polycondensation was subsequently performed in the same reactor vessel. During polycondensation the reactor was stirred at 60 rpm. The temperature was increased to 275° C. and the pressure reduced to 2 mbar over a period of 25 min. Polycondensation occurred with formation of ethylene glycol and water which were continuously removed. The reaction was allowed to continue until the stirrer torque reached 19 Nm, which was after 181 min, upon which stirring was stopped and the reactor pressurized to atmospheric with nitrogen. The formed polymer, which has an intrinsic viscosity of 0.64 dl/g, was evacuated from the reactor via an outlet nozzle to form strands which were cooled in a water bath and cut to form amorphous granules.

(4) The granules were subsequently crystallised and then subjected to solid state polymerisation (SSP) in a 50 kg tumble drier. The granules were introduced to a rotating drier and temperature increased to 110° C. to dry the granules, and further increased to 170° C. and kept for 2 hours to induce crystallisation, under a flush of 2 m.sup.3/h of nitrogen to drive out moisture. Then the temperature was further increased to 210° C. and a vacuum of 1 mbar was applied. Solid state polymerisation was allowed to take place for 16 hours under nitrogen flush of 0.5 m.sup.3 /h to drive out moisture and reaction gases. After 16 hours, the PET homopolymer having an intrinsic viscosity of 0.84 dl/g was collected which is further referred to as sample 1.

EXAMPLE 2-5

PET Copolymers

(5) Using the same setup as in the preparation of sample 1, PET copolymers were prepared in examples 2-5 that differed from example 1 in that: In example 2, 160 g of PEG-1000 was added together with the other ingredients before esterification; the esterification time was 190 min; polycondensation time was 183 min, resulting in a PET copolymer comprising 2 wt % of units derived from PEG-1000 (sample 2); In example 3, 240 g of PEG-1000 was added together with the other ingredients before esterification; the esterification time was 188 min; polycondensation time was 130 min, resulting in a PET copolymer comprising 3 wt % of units derived from PEG-1000 (sample 3); In example 4, 160 g of Priplast 1838 was added after polycondensation to and intrinsic viscosity (I.V.) of about 0.4 dl/g by breaking the vacuum, addition of the Priplast 1838 and re-applying of the vacuum to continue the polycondensation; the esterification time was 118 min; polycondensation time was 95 min, resulting in a PET copolymer comprising 2 wt % of units derived from BPA (sample 4); and In example 5, 160 g of BPA was added together with the other ingredients before esterification, resulting in a PET copolymer comprising 2 wt % of units derived from BPA (sample 5).

(6) In examples 2, 3, 4 and 5 above, the I.V. after melt polycondensation was about 0.64 dl/g, and after SSP the pellets reached an I.V. of 0.84 dl/g.

(7) Materials: PEG-1000 is a poly(ethylene glycol) having a number average molecular weight of 1000 g/mol; Priplast 1838 is a polyester polyol having a number average molecular weight of 2000 g/mol, CAS reg. nr. 856170-63-3, obtainable from Croda; BPA is bisphenol-A-bis(2-hydroxyethyl)ether, number average molecular weight 316 g/mol, CAS reg nr. 901-44-0.

(8) Of each of the samples, sufficient material was produced to prepare sample tapes. The sample tapes were produced by preparation of a cast film by melt extrusion of each of the samples through a slit die at 280° C. followed by a quench cooling on chilled cast rollers at 15° C., to obtain a film having a thickness of 100 μm and a width of about 15 cm. All films were transparent except the film of the copolymer of example 4, which was translucent.

(9) The cast films were cut into rectangular pieces from the centre-line portion of the film. The sample pieces were subjected to unidirectional drawing in the longitudinal direction to achieve a drawing rate of 5.2, i.e. an increase in sample length of 5.2 times, in a Zwick tensile machine equipped with a hot cabinet. The drawing speed was 50 mm/min for all samples. The final thickness of the tape after unidirectional drawing was 20-30μm. The final width was 2-5 mm. All samples were heat set under tension at the temperatures shown in table II for 1 min.

(10) Material properties of the tapes of each of the sample polymers were determined as presented in table II below.

(11) TABLE-US-00001 TABLE II Split Sample T.sub.m TI TMod fractures T.sub.g T.sub.draw T.sub.heat set 1 253 1977 4.20 4/10 81 100 240 2 250 2915 4.63 0/10 63 85 220 3 250 2350 4.06 4/10 61 85 220 4 249 2800 0/10 74 95 240 5 248 2000 5/10 75 95 240

(12) Wherein: IV is the intrinsic viscosity of the polyester as determined in accordance with ASTM D2857-95 (2007), expressed in dl/g; T.sub.m is the melt temperature of the polyester as determined via differential scanning calorimetry (DSC) as the peak melt temperature in the second heating run in accordance with ISO 11357-3 (2011), expressed in ° C.; TI is the tensile-impact strength as determined in accordance with ASTM D1822-06 heat set as 240° C., expressed in kJ/m.sup.2; TMod is the tensile modulus as determined in accordance with ASTM D882-12, expressed in GPa; Split fractures is the number of tape samples out of a set of 10 samples used in the tensile-impact strength test that demonstrated split fractures; T.sub.g is the glass transition temperature in ° C. as determined via differential scanning calorimetry in accordance; T.sub.draw is the temperature in the hot cabinet during the drawing step, in ° C.; T.sub.heat set is the temperature applied during the heat-setting step, in ° C.

(13) The above results demonstrate that the tapes according to the present invention demonstrate an increased tensile-impact strength, coupled with and improved splitting resistance and retention of modulus. This can be observed from comparison of the inventive sample 2, a copolymer polyester comprising 2 wt % of comonomer where the comonomer has a number average molecular weight of 1000 g/mol, with sample 1, the PET homopolymer. The presence of 2 wt % of such comonomer in the PET can be observed to result in an improved tensile-impact strength and reduced proneness to splitting.