Production and use of new thermoplastic polyurethane elastomers based on polyether carbonate polyols

Abstract

The invention relates to a method for producing a thermoplastic polyurethane elastomer, comprising the reaction of at least A) one organic diisocyanate containing two isocyanate groups with B) a polyol having a number-average molecular weight Mn>=500 and <=5000 g/mol, which has at least two isocyanate-reactive groups, and C) one or more chain extenders having a molecular weight >=60 and <=490 g/mol, which have two isocyanate-reactive groups, and optionally D) a monofunctional chain stopper, which has one isocyanate-reactive group, and/or E) a catalyst, wherein the molar ratio of the isocyanate groups from A) to the sum of the groups reactive to isocyanate in B), C), and, if applicable, D) is >=0.9:1 and <=1.2:1, and component B) contains at least one polyether carbonate polyol, which can be obtained by adding carbon dioxide and alkylene oxides to H-functional starter substances. The invention further relates to a thermoplastic polyurethane elastomer produced in accordance with the method according to the invention, the use of said thermoplastic polyurethane elastomer to produce extruded or injection molded items, and the items produced by extrusion or injection molding.

Claims

1. A process for the production of an injection-molded or extruded item comprising preparing a thermoplastic polyurethane elastomer by reacting, in a one-shot process in a reactive extruder or by a mixing-head-belt process, at least A) one organic diisocyanate comprising two isocyanate groups, with B) one polyol with number-average molar mass M.sub.n 500 and 5000 g/mol, which has at least two isocyanate-reactive groups, and C) one or more diols with molar mass 60 and 490 g/mol, selected from the group consisting of ethanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, 1,12-dodecanediol, diethylene glycol, dipropylene glycol, neopentyl glycol, bis(ethylene glycol) terephthalate, bis(1,4-butanediol) terephthalate, 1,4-di(hydroxyethyl)hydroquinone, and ethoxylated bisphenols, and also reaction products of any of these with -caprolactone, and optionally D) a monofunctional chain terminator which has an isocyanate-reactive group and/or in the presence of E) a catalyst where the molar ratio of the entirety of the isocyanate groups from A) to the entirety of the groups in B), C), and optionally D) reactive toward isocyanate is 0.9:1 and 1.2:1, and component B) comprises at least one polyether carbonate polyol obtainable via an addition reaction of carbon dioxide and a mixture of 75 to 100% by weight of propylene oxide and 0 to 25% by weight of ethylene oxide onto H-functional starter substances, and granulating the thermoplastic polyurethane elastomer to form a granulated thermoplastic polyurethane elastomer.

2. The process as claimed in claim 1, wherein the polyether carbonate polyol is obtainable via an addition reaction of carbon dioxide and a mixture of 75 to 100% by weight of propylene oxide and 0 to 25% by weight of ethylene oxide onto H-functional starter substances with the use of multimetal cyanide catalysts.

3. The process as claimed in claim 1, wherein the content of carbonate groups, calculated as CO.sub.2 in the polyether carbonate polyol is 3 and 35% by weight.

4. The process as claimed in claim 1, wherein the number-average molar mass Mr, of the polyether carbonate polyol is 500 and 10000 g/mol.

5. The process as claimed in claim 1, wherein the average OH functionality of the polyether carbonate polyol is 1.85 and 2.5.

6. The process as claimed in claim 1, wherein the organic diisocyanate A) comprises at least one aliphatic and/or one cycloaliphatic diisocyanate.

7. The process as claimed in claim 1, wherein component B) comprises at least one polyether carbonate polyol and at least one polyether polyol.

8. The process as claimed in claim 1, wherein component B) comprises at least one polyether carbonate polyol and at least one polyester polyol.

9. The process as claimed in claim 1, wherein component B) comprises at least one polyether carbonate polyol and at least one polycarbonate polyol.

10. The process as claimed in claim 1, wherein component B) comprises two polyether carbonate polyols that differ from one another.

11. An injection-molded or extruded item obtained by a process as claimed in claim 1.

12. The process as claimed in claim 1, wherein the organic diisocyanate A) comprises at least one aliphatic and/or one cycloaliphatic diisocyanate, wherein the content of carbonate groups, calculated as CO.sub.2 in the polyether carbonate polyol is 3 and 35% by weight, and wherein component C) comprises a diol.

13. The process as claimed in claim 1, wherein the average OH functionality of the polyether carbonate polyol is 1.96 and 2.05.

14. The process as claimed in claim 1, wherein the proportion of polyether carbonate polyols, based on the total mass of component B), is 20 and 100% by weight.

15. The process as claimed in claim 1, wherein the organic diisocyanate A) is hexamethylene 1,6-diisocyanate, wherein the content of carbonate groups, calculated as CO.sub.2 in the polyether carbonate polyol is 10 and 28% by weight, and wherein component C) comprises a diol.

Description

EXAMPLES

(1) The following methods were used to characterize the polymeric polyols used:

(2) The CO.sub.2 content incorporated within the polyether carbonate polyols was determined by means of .sup.1H NMR (Bruker, DPX 400, 400 MHz: pulse program zg30, delay d1: 5 s, 100 scans). In each case the sample was dissolved in deuterated chloroform. Internal standard added to the deuterated solvent comprised dimethyl terephthalate (2 mg for every 2 g of CDCl.sub.3). The relevant resonances in the .sup.1H NMR (based on MCI; =7.24 ppm) are as follows:

(3) Carbonates, resulting from carbon dioxide incorporated within the polyether carbonate polyol (resonances at from 5.2 to 4.8 ppm) PO not consumed in the reaction with resonance at 2.4 ppm, polyether polyol (i.e. without incorporated carbon dioxide) with resonances at from 1.2 to 1.0 ppm.

(4) The molar content of the carbonate incorporated within the polymer, of the polyether polyol fractions, and also of the PO not consumed in the reaction are determined via, integration of the corresponding signals.

(5) All of the number-average molar masses M.sub.n stated in the description and in the examples for the polymeric polyols were determined as follows: the OH number was first determined experimentally via esterification followed by back-titration of the excess esterification reagent with standard alcoholic potassium hydroxide solution in accordance with DIN 53240-2. The OH number is stated in mg KOH per gram of polyol. The number-average molar mass can be calculated from the OH number by way of the following formula: number-average molar mass M.sub.n=561000OH functionality/OH number. The OH functionality F was assumed to be approximately 2.

(6) In the case of low-molecular-weight polyols with defined structure, the molar mass is calculated from the molecular formula.

(7) Production of TPUs 1 and 2

(8) The appropriate polyol, 1,6-hexanediol and 1% Irganox 1010 (product available commercially from BASF SE, Ludwigshafen) were used as initial charge in a reaction vessel as in table 1 and heated to 120 C., with stirring. 30 ppm of dibutyltin dilaurate were then added as catalyst. The hexamethylene diisocyanate (HDI), heated to 110 C., was then added in one portion, with stirring. The reaction temperature reached a temperature maximum of about 190 C., and was stirred for about 90 to 105 sec until the maximum possible torque of the stirrer was reached. The reaction mixture was then poured onto a coated metal sheet and subjected to postconditioning at 80 C. for 30 minutes. After cooling, this gave a cast TPU sheet.

(9) Table 1 describes the components used, and proportions thereof, for the production of the TPUs.

(10) TABLE-US-00001 TABLE 1 Molar proportions of the starting components for the synthesis of the TPUs Polyol HDI 1,6-Hexanediol Example Polyol No. [mol] [mol] [mol] 1 2 1 3.1 2.1 2* 1 1 3.1 2.1 Polyol 1: Acclaim 2200 (polypropylene oxide glycol with OH number 56.7 mg KOH/g (M.sub.n = 1979 g/mol, from Bayer MaterialScience AG). Polyol 2: Polyether carbonate diol based on propylene oxide and CO.sub.2 with OH number 58.2 mg KOH/g (M.sub.n = 1928 g/mol) and with 15.1% by weight CO.sub.2 content. *comparative example not of the invention
Studies on TPUs 1 and 2:

(11) The resultant cast TPU sheets were chopped and granulated. The granulated material was processed in an Arburg Allrounder 470S injection-molding machine in a temperature range from 180 to 230 C. and in a pressure range from 650 to 750 bar with an injection flow rate of from 10 to 35 cm.sup.3/s to give bars (mold temperature: 40 C.; bar size: 80104 mm) and sheets (mold temperature: 40 C.; size: 125502 mm).

(12) The following test methods were used:

(13) Hardness was measured in accordance with DIN 53505, the tensile test was carried out in accordance with ISO 37 and abrasion was measured in accordance with DIN ISO 4649-A.

(14) Dynamic mechanical analysis (DMA: storage-tensile modulus of elasticity):

(15) Rectangles (30 mm10 mm2 mm) were punched out from the injection-molded sheets. These test sheets, under constant preloadwhere appropriate dependent on the storage moduluswere subjected to periodic excitation with very small deformations, and the force acting on the clamp system was measured as a function of the temperature and excitation frequency.

(16) The preload additionally applied serves to retain adequate clamping of the sample when deformation amplitude is negative.

(17) The DMA measurements were taken using a Seiko DMS 210 at 1 Hz in the temperature range from 150 C. to 200 C. with a heating rate of 2 C./min.

(18) The behavior of the invention under warm conditions was characterized by measuring and stating the storage-tensile modulus of elasticity at +20 C. and at +60 C., for comparison.

(19) Heat resistance is characterized by stating the temperature at which the value is less than 2 MPa, i.e. the injection-molded part no longer retains a stable shape. The higher the temperature value, the more stable the TPU.

(20) Table 2 describes the properties determined for the TPUs 1 and 2.

(21) TABLE-US-00002 TABLE 2 Results Example 1 2* Immediate hardness [Shore A] 83 83 Abrasion [mm.sup.3] 58 84 100% modulus [MPa] 6.13 4.3 300% modulus [MPa] 8.65 6.45 Tensile strength [MPa] 16.5 10.2 Tensile strain value [%] 728 751 DMA measurement: Modulus of elasticity (20 C.) [MPa] 23 19 Modulus of elasticity (60 C.) [MPa] 15 0 T (2 MPa) [ C.] 119.7 103.6 *comparative example not of the invention

(22) The TPU of the invention and the TPU not of the invention have equally high hardness. The TPU of the invention has a markedly better level of mechanical properties than the comparative product, this being particularly apparent from the 100% modulus, 300% modulus and tensile strength. The modulus of elasticity values from DMA at 20 C. and at +60 C. are markedly higher for example 1 than for the corresponding comparative example 2, as also is the temperature at which a minimum stress of 2 MPa is retained. At high temperatures, the TPU of the invention is therefore markedly more heat-resistant than the comparative TPU. The abrasion value is also markedly lower for the TPU of the invention than for the comparative TPU.