Method for producing thermoplastic polyurethanes

Abstract

The present invention relates to a method for producing a thermoplastic polyurethane that comprises reacting an isocyanate composition at least comprising 4,4′-diisocyanatodicyclohexylmethane (H12MDI) with a polyol composition (PZ) in the presence of a catalyst composition at least comprising a bismuth-containing compound selected from bismuth (tricarboxylate) catalysts, where the carboxyl radicals independently of one another have 6 to 12 carbon atoms, to give a melt and producing pellets from the resulting melt. The present invention further relates to a thermoplastic polyurethane obtained or obtainable by the method of the invention, and also to the use for producing films, profiles, cable sheathing, and sheathing of LED strips.

Claims

1. A method for producing a thermoplastic polyurethane, the method comprising: (i) reacting an isocyanate composition comprising 4,4′-diisocyanatodicyclohexyl-methane (H12MDI) with a polyol composition (PZ) in a presence of a catalyst composition comprising a bismuth-containing compound selected from at least one bismuth (tricarboxylate) catalyst, where carboxyl radicals independently of one another have 6 to 12 carbon atoms, to give a melt; wherein no isocyanate is used other than H12MDI; (ii) producing pellets from the melt obtained in (i); and (iii) storing the pellets obtained in (ii), wherein a catalytically accelerated reaction continues during the storing (iii) and wherein the pellets are produced in (ii) by underwater pelletizing or strand pelletizing.

2. The method according to claim 1, wherein the polyol composition (PZ) comprises at least one polyol selected from the group consisting of a polycarbonate diol, a polyether and a polyester.

3. The method according to claim 1, wherein the polyol composition (PZ) comprises at least one chain extender selected from the group consisting of diols having 2 to 6 carbon atoms.

4. The method according to claim 1, wherein the reacting (i) includes 50 to 600 ppm of the catalyst composition, based on a total amount of components present in the reacting (i).

5. The method according to claim 1, wherein the catalyst composition comprises bismuth neodecanoate.

6. The method according to claim 1, wherein the reacting (i) takes place in an extruder.

7. The method according to claim 6, wherein a residence time in the extruder is such that a conversion of at least 98% is achieved.

8. A thermoplastic polyurethane pellet based on an isocyanate composition comprising 4,4′-diisocyanatodicyclohexylmethane (H12MDI) and on a polyol composition (PZ) comprising a polyol and a chain extender selected from the group consisting of diols having 2 to 6 carbon atoms, the TPU pellet has a bismuth content of 1 to 200 ppm and is capable of undergoing a catalytically accelerated reaction during storage, wherein the isocyanate composition comprises no isocyanate other than the 4,4′-diisocyanatodicyclohexylmethane (H12MDI) and produced with underwater pelletizing or strand pelletizing.

9. A thermoplastic polyurethane pellet obtained by the method according to claim 1.

10. The thermoplastic polyurethane pellet according to claim 8, wherein the thermoplastic polyurethane is comprised in a film.

11. The method according to claim 1, wherein the pellets are produced in (ii) by underwater pelletizing.

12. The method according to claim 1, wherein the pellets have a yellowness indices of <5, wherein the yellowness index is determined according to ASTM E313.

13. The method according to claim 1, wherein the molecular weight buildup is 88,000 after 20 hours at 80° C.

14. The method according to claim 1, wherein the catalyst is selected from the group consisting of bismuth tri(2-ethylhexanoate), bismuth octoate, bismuth neodecanoate, or a combination thereof.

15. The thermoplastic polyurethane pellet according to claim 8, wherein said thermoplastic polyurethane is prepared with a catalyst that is at least one bismuth (tricarboxylate).

16. The thermoplastic polyurethane pellet according to claim 15, wherein said catalyst is selected from the group consisting of bismuth tri(2-ethylhexanoate), bismuth octoate, bismuth neodecanoate, or a combination thereof.

Description

EXAMPLES

1. Starting Materials

(1) SDO: metal catalyst 93690, tin bis(2-ethylhexanoate), CAS number: 301-10-0, BASF Polyurethanes GmbH, 49440 Lemfoerde, GERMANY. DBTL: dibutyltin dilaurate, CAS 77-58-7, Sigma-Aldrich Chemie GmbH, Riedstrasse 2, D-89555 Steinheim. DBTA: dibutyltin acetate for synthesis, CAS 1067-33-0, Sigma-Aldrich Chemie GmbH, Riedstrasse 2, D-89555 Steinheim. Bicat 4130M: zirconium neodecanoate, CAS 51601-43-5, Shepherd Mirecourt S.A.R.L., Rue de Lorraine, BP 47—Juvaincourt, FR-88502 Mirecourt Cedex, France. Bicat ZM: zinc neodecanoate, CAS 27253-28-8, Shepherd Mirecourt S.A.R.L., Rue de Lorraine, BP 47—Juvaincourt, FR-88502 Mirecourt Cedex, France. Bicat 8124: bismuth neodecanoate, CAS 34364-26-6, Shepherd Mirecourt S.A.R.L., Rue de Lorraine, BP 47—Juvaincourt, FR-88502 Mirecourt Cedex, France. Poly PTHF® 1000: polytetrahydrofuran 1000, CAS number: 25190-06-1, BASF SE, 67056 Ludwigshafen, GERMANY, Intermediates Division. 1,4-Butanediol: butane-1,4-diol, CAS number: 110-63-4, BASF SE, 67056 Ludwigshafen, GERMANY, Intermediates Division. 1,3-Propanediol: SUSTERRA® PROPANEDIOL, propane-1,3-diol, CAS number: 504-63-2, DuPont Tate & Lyle Bio Products Company, 198 Blair Bend Drive, Loudon TN 37774, USA. Vestanat® H.sub.12MDI: 4,4′-diisocyanatodicyclohexylmethane, CAS 5124-30-1, Evonik Degussa GmbH, Coatings & Adhesives, D-45765 Marl. Irganox® 245 FF: ethylenebis(oxyethylene)bis[3-(5-tert-butyl-4-hydroxy-m-tolyl)propionate], CAS number: 36443-68-2, BASF SE, 67056 Ludwigshafen, GERMANY, Antioxidants/Process Stabilizers.

2. Formulations

(2) TABLE-US-00001 TABLE 1 Formulations TPU A TPU B TPU C PolyTHF ® 1000 [g] 1365.6 1264.1 1365.6 Vestanat ® H.sub.12MDI [g] 931.7 1001.4 940.9 1,4-Butanediol [g] 191.2 134.0 191.2 1,3-Propanediol [g] 75.5 Irganox ® 245 FF [g] 10 5.0 10

3. Method Description, Reactive Extruder

(3) The aforementioned starting components were mixed, and the reactive species were reacted, in the case of the reactive extrusion, in self-cleaning twin-screw extruders, by the method described in EP1846465B1 or EP1213307B1. The apparatus selected here for reacting the reaction mixture was a twin-screw extruder having a ratio of screw length to screw diameter of 56. After a residence time in the reactive extruder of at least 40 seconds, preferably greater than 60 seconds, the polyaddition of the isocyanate-containing compounds with the isocyanate-reactive compounds produces a polymer melt whose viscosity is high enough to allow it to be processed to pellets by means of underwater or strand pelletization.

4. Determination of Weight-Average Molecular Weights

(4) The weight-average molecular weights Mw of the thermoplastic polyurethanes are determined for the purposes of the present invention by means of GPC. The molecular weight is determined according to Example 1 (two GPC columns connected in series: PSS Gel; 100 A; 5μ; 300*8 mm, Jordi-Gel DVB; mixed bed; 5μ; 250*10 mm; column temperature 60° C.; flow rate 1 mL/min; RI detector). Calibration here takes place using polymethyl methacrylate (EasyCal; from PSS, Mainz), and the mobile phase used is dimethylformamide.

5. Examples

(5) 5.1 Mixture TPU A was prepared in a reactive extruder process using the catalysts DBTL, DBTA, and SDO. All three experiments were produced in the same reactive extruder at the same temperatures, screw speeds, and throughputs. The results are compiled in Table 2. With the organotin catalysts DBTL, DBTA, and SDO, a good buildup of molecular weight can be achieved during the short residence time in the reactive extruder. Following the underwater pelletizing, the buildup of molecular weight is faster with the organotin compounds DBTL and DBTA. These highly efficient organotin catalysts DBTL and DBTA, however, are undesirable in the TPU on account of their toxicity.

(6) TABLE-US-00002 TABLE 2 Catalysis Mw Mw ppm fresh 2 weeks/45° C. DBTL 100 ppm 46 000 102 000 dibutyltin dilaurate DBTA 100 ppm 47 000  77 000 dibutyltin diacetate SDO 300 ppm 40 000  48 000 Sn dioctoate 5.2 Mixture TPU B was prepared by a reactive extruder process using the catalysts SDO, Bicat 4130M, Bicat ZM, and Bicat 8124. All four experiments were produced in the same reactive extruder at the same temperatures, screw speeds, and throughputs. With the catalysts Bicat ZM, Bicat 8124, and SDO, it is possible to achieve a good buildup in molecular weight during the short residence time in the reactive extruder. This is not the case when using Bicat 4130M. It was found that the pellets obtained when using the Bicat ZM catalyst have very high yellowness indices. The use of SDO and Bicat 8124 leads to pellets having acceptable yellowness indices of <5. The yellowness index is determined according to ASTM E 313. Following underwater pelletizing, the buildup of molecular weight is quicker when using Bicat 8124. The results are compiled in Table 3.

(7) TABLE-US-00003 TABLE 3 Yellowness Mw Catalysis Mw Index 4 weeks/ [ppm] fresh [YI] 23° C. SDO Sn 250   43 000 <5 58 000 dioctoate Bicat 4130M 500 <10 000 n.d. n.d. Zr neodecanoate Bicat ZM 100   48 000 110 n.d. Zn neodecanoate Bicat 8124 Bi(III) 100   51 000 <5 89 000 neodecanoate 5.3 Mixture TPU C was prepared by a reactive extruder process using the catalysts SDO, TBOT and Bicat 8124. All three experiments were produced in the same reactive extruder at the same temperatures, screw speeds, and throughputs. With the catalysts SDO, TBOT, and Bicat 8124, it is possible to achieve a good buildup in molecular weight during the short residence time in the reactive extruder. Following underwater pelletizing, the buildup of molecular weight is quicker when using Bicat 8124. The results are compiled in Table 4.

(8) TABLE-US-00004 TABLE 4 Yellowness Mw Catalyse Mw Index 20 hours/ [ppm] fresh [YI] 80° C. SDO 300 42 000 <5 53 000 Sn dioctoate TBOT 200 40 000 10 50 000 tetrabutylorthotitanate Bicat 8124 bi(III) 400 49 000 <5 88 000 neodecanoate