Sulphur-containing polyester polyols, their production and use

Abstract

The present invention relates to sulfur-containing polyester polyols and to the preparation and use thereof.

Claims

1. A polyester polyol, comprising an esterification product of: at least one dicarboxylic acid component A), wherein the at least one dicarboxylic acid component A) comprises at least one disulfide-containing dicarboxylic acid a-1); and a polyol component K) comprising at least one diol D), wherein the at least one diol D) comprises at least one diol b-1) selected from the group consisting of cyclohexanedimethanol and hexane-1,6-diol, wherein the at least one dicarboxylic acid component A) additionally comprises a non-sulfur-containing dicarboxylic acid a-2).

2. The polyester polyol of claim 1, wherein the at least one dicarboxylic acid component A) additionally comprises terephthalic acid.

3. The polyester polyol of claim 1, wherein the at least one diol D) additionally comprises a further diol b-2).

4. The polyester polyol of claim 1, wherein the polyol component K) additionally comprises at least one polyhydric alcohol C) having a functionality greater than 2.

5. The polyester polyol of claim 1, wherein at least one of the at least one disulfide-containing dicarboxylic acid a-1) is an aliphatic disulfide-containing dicarboxylic acid.

6. The polyester polyol of claim 5, wherein the at least one disulfide-containing dicarboxylic acid a-1) is 3-(2-carboxyethyldisulfanyl)propanoic acid.

7. The polyester polyol of claim 4, wherein the at least one polyhydric alcohol C) is selected from the group consisting of glycerol, trimethylolpropane (TMP), pentaerythritol, reaction products thereof with an alkylene oxide, and mixtures thereof.

8. A process for preparing the polyester polyol of claim 1, the processing comprising: reacting the at least one dicarboxylic acid component A) with the polyol component K).

9. The process of claim 8, wherein no additional catalyst is used during the reaction.

10. A process for preparing the polyester polyol of claim 1, the process comprising: reacting the at least one dicarboxylic acid component A) with the polyol component K), to obtain the esterification product, wherein the reacting is first conducted at standard pressure up to an acid number of 80 to 20 mg KOH/g, determined according to DIN EN 1241, and then continued at a pressure of less than 500 mbar up to an acid number of less than 10 mg KOH/g.

11. A process for producing a rigid polyurethane foam, the process comprising reacting a reaction mixture comprising an organic and/or modified organic di- and/or polyisocyanate with at least one polyester polyol of claim 1, one or more blowing agents and a catalyst.

12. The process of claim 11, wherein the reaction mixture additionally comprises a further polyester polyol and/or a polyether polyol.

Description

EXAMPLES

(1) The examples below are intended to illustrate some aspects of the present invention. The examples are in no way intended to restrict the scope of the invention.

(2) Methods

(3) Viscosity determination:

(4) Unless stated otherwise, the viscosity of the polyols was determined at 25° C. to DIN EN ISO 3219 (October 1994) with a Rheotec RC 20 rotary viscometer using the CC 25 DIN spindle (spindle diameter: 12.5 mm; internal measuring cylinder diameter: 13.56 mm) at a shear rate of 50 1/s.

(5) Measurement of hydroxyl number:

(6) Hydroxyl numbers were determined by the phthalic anhydride method DIN 53240 (December 1971) and reported in mg KOH/g.

(7) Measurement of acid number:

(8) Acid number was determined to DIN EN 1241 (May 1998) and is reported in mg KOH/g.

(9) Permeability measurement on polyurethane films

(10) The permeability of polyurethane films was determined against 4 gases in each case. Transmissions against nitrogen, methane and carbon dioxide were measured with a Brugger gas permeability tester according to ASTM D 1434 82 (1982 original, 2015 rev.). The measurement area is 78 cm.sup.2. Oxygen permeability was determined in a Mocon Oxtran 2/21 according to ASTM D 3985 (2005 orig., 2010 rev.). The measurement area here is 50 cm.sup.2.

(11) Water permeability was determined according to ASTM F-1249 (2013 original).

Inventive Example 1

(12) A 2 l round-neck flask equipped with thermometer, nitrogen inlet, heating mantle, distillation column and stirrer was charged with 565.3 g of 3-(2-carboxyethyldisulfanyl)propanoic acid and 531.6 g of cyclohexanedimethanol and heated to 120° C. In the course of further heating to 140° C., water forms on attainment of a temperature of 135° C. and is removed by distillation. Once 80% of the water of condensation calculated has been removed, the pressure in the apparatus is reduced to 60 mbar and the mixture is heated further until an acid number of less than 2 mg KOH/g is attained. A polyester polyol is obtained with a hydroxyl number of 111 mg KOH/g, an acid number of 1.17 mg KOH/g and a viscosity of 1719 mPas at 75° C.

Inventive Example 2

(13) A 4 l round-neck flask equipped with thermometer, nitrogen inlet, heating mantle, distillation column and stirrer was charged with 1557 g of 3-(2-carboxyethyldisulfanyl)propanoic acid, 1127 g of cyclohexanedimethanol and 82.8 g of trimethylolpropane and heated to 120° C. In the course of further heating up to 210° C., the water of condensation formed is distilled off continuously until an acid number of less than 2 mg KOH/g has been attained. The reaction affords a polyester polyol with a hydroxyl number of 61.5 mg KOH/g, an acid number of 0.6 mg KOH/g and a viscosity of 13,090 mPas at 75° C.

Inventive Example 3

(14) A 4 l round-neck flask equipped with thermometer, nitrogen inlet, heating mantle, distillation column and stirrer was charged with 1563 g of 3-(2-carboxyethyldisulfanyl)propanoic acid, 1127 g of cyclohexanedimethanol and 77.4 g of trimethylolpropane and heated to 120° C. In the course of further heating up to 210° C., the water of condensation formed is distilled off continuously until an acid number of less than 2 mg KOH/g has been attained. The reaction affords a polyester polyol with a hydroxyl number of 55.5 mg KOH/g, an acid number of 0.526 mg KOH/g and a viscosity of 16,540 mPas at 75° C.

(15) cl Inventive Example 4

(16) A 4 l round-neck flask equipped with thermometer, nitrogen inlet, heating mantle, distillation column and stirrer was charged with 1317 g of 3-(2-carboxyethyldisulfanyl)propanoic acid, 1211.7 g of cyclohexanedimethanol and 197 g of glycerol and heated to 120° C. In the course of further heating up to 210° C., the water of condensation formed is distilled off continuously until an acid number of less than 2 mg KOH/g has been attained. The reaction affords a polyester polyol with a hydroxyl number of 234.5 mg KOH/g, an acid number of 0.028 mg KOH/g and a viscosity of 807 mPas at 75° C.

Comparative Example 1

(17) A 4 l round-neck flask equipped with thermometer, nitrogen inlet, heating mantle, distillation column and stirrer was charged with 1230 g of adipic acid and 1605 g of cyclohexanedimethanol and heated to 120° C. After addition of 1 ppm of titanium tetrabutoxide as catalyst, the mixture is stirred and heated to 240° C., with continuous removal of water released by distillation. Once 80% of the calculated water of reaction has been removed, a vacuum of 60 mbar is applied and the reaction is continued until an acid number of less than 2 mg KOH/g is measured. The polyester polyol obtained had a hydroxyl number of 114.8 mg

(18) KOH/g, an acid number of <0.1 mg KOH/g and a viscosity of 420 mPas at 100° C.

Comparative Example 2

(19) A 4 l round-neck flask equipped with thermometer, nitrogen inlet, heating mantle, distillation column and stirrer was charged with 1660 g of adipic acid and 1249 g of butanediol and heated to 120° C. After addition of 1 ppm of titanium tetrabutoxide as catalyst, the mixture is stirred and heated to 240° C., with continuous removal of water released by distillation. Once 80% of the calculated water of reaction has been removed, a vacuum of 60 mbar is applied and the reaction is continued until an acid number of less than 2 mg KOH/g is measured. The polyester polyol obtained had a hydroxyl number of 56 mg KOH/g, an acid number of 0.6 mg KOH/g and a viscosity of 670 mPas at 75° C.

(20) Use example 1—production of TPU films

(21) Polyester polyols produced in inventive example 1 and comparative example 2 were used to produce TPUs and processed to give flat films. The TPUs were produced by methods known to the person skilled in the art. The flat films were produced on a 30 mm Arenz with a three-zone screw with a mixing section (screw ratio 1:3) and a 250 mm slot die.

(22) The films obtained were examined for their permeability properties as described under “Permeability measurement”. (In the tables below, “E” means to the power of ten.)

(23) TABLE-US-00001 TABLE 1 Use of the PESOL of the invention Film Transmission rate Permeability thickness cm.sup.3/m.sup.2/d at cm.sup.3 .Math. 1 μm/m.sup.2/d/bar Material in μm Gas 23° C., dry at 23° C., dry TPU film 220.3 +/− 7.8 nitrogen 3.19E+01 7.75E+03 (inv. example 1) TPU film 220.3 +/− 7.8 carbon dioxide 3.31E+02 8.06E+04 (inv. example 1) TPU film 220.3 +/− 7.8 methane 5.82E+01 1.41E+04 (inv. example 1) TPU film 220.3 +/− 7.8 oxygen  1.2E+02 2.91E+04 (inv. example 1) TPU film 220.3 +/− 7.8 water 1.99E+01 4.69E+03 (inv. example 1)

(24) TABLE-US-00002 TABLE 2 Use of a comparative PESOL Film Transmission rate Permeability thickness cm.sup.3/m.sup.2/d cm.sup.3 .Math. 1 μm/m.sup.2/d/bar Material in μm Gas at 23° C., dry at 23° C., dry TPU film 40 nitrogen 3.83E+02 1.53E+04 (comparative example 2) TPU film 40 carbon dioxide 9.24E+03 3.70E+05 (comparative example 2) TPU film 40 methane 9.07E+02 3.63E+04 (comparative example 2) TPU film 40 oxygen 1.38E+03 5.53E+04 (comparative example 2) TPU film 40 water 2.13E+02 8.58E+03 (comparative example 2)

(25) It can be seen from the permeability measurements presented above that flat TPU films based on polyesterols without dithiodipropionic acid have distinctly higher permeability with respect to the gases tested.

(26) This is associated with elevated thermal conductivity of those polyurethane systems that are not based on the sulfur-containing PESOLs of the invention.

(27) Further use examples: production of rigid polyurethane foams for thermal insulation

(28) For production of the rigid polyurethane foams of the invention on the laboratory scale, the components of comparative examples X and Y and of inventive examples A and B that are listed in tables 3 and 4 are mixed in the ratios specified at 20′C. The reaction mixture either remains in the mixing vessel (beaker) or is transferred into an open cubic mold of dimensions 22×22×22 cm in which the foam rises freely. Test specimens for determination of thermal conductivity (TC), compressive strength and closed-cell content were taken from the cubic foam block. Cell size and cell gas content were determined from beaker foams.

(29) TABLE-US-00003 TABLE 3 Comparative Inventive example X example A Polyol 1 78 58.5 Polyol 2 19.5 Polyol 3 Polyol 4 8 8 Additives 18.6 18.6 Formic acid 1.2 1.2 Pentane 13.5 13.5 Polyol component, pts. by wt. 119.3 119.3 Isocyanate component, pts. by wt. 298.3 257.9 Mechanical properties/analysis Fiber time [s] 52 49 Free-foamed envelope density [g/L] 50.5 44.9 TC [mW/mK] after 24 h to DIN EN 21.7 20.9 12667 TC [mW/mK] after 21 d, 70° C. to DIN 26.7 25.3 EN 12667 Compressive strength at 40 g/L 0.170 0.164 [N/mm2] to DIN EN ISO 844 Cell sizes [μm] — — Closed-cell content [%] to DIN EN 91 93 ISO 4590 Cell gases [% by vol.] Air/CO/CO.sub.2/pentane  1 d 10/8/35/47  3/8/37/52 28 d 43/6/16/35 25/8/26/40

(30) TABLE-US-00004 TABLE 4 Comparative Inventive example Y example B Polyol 1 77 27 Polyol 2 Polyol 3 50 Polyol 4 7.8 7.8 Additives 18.8 19.2 Formic acid 1.4 1.55 Pentane 14 14 Polyol component, pts. by wt. 119.0 120.8 Isocyanate component, pts. by wt. 225.5 226.6 Mechanical properties/analysis Fiber time [s] 50 52 Free-foamed envelope density [g/L] 39.8 40.5 TC [mW/mK] after 24 h to DIN EN 21.8 20.7 12667 TC [mW/mK] after 21 d, 70° C. to DIN 26.3 25.1 EN 12667 Compressive strength at 40 g/L 0.172 0.184 [N/mm2] to DIN EN ISO 844 Cell sizes [μm] 198 204 Closed-cell content [%] to DIN EN 92 91 ISO 4590 Polyol 1: Polyester polyol based on terephthalic acid, diethylene glycol, C.sub.18 fatty acid and alkoxylated glycerol, OH number 240 mg KOH/g. Polyol 2: Polyester polyol based on 3,3′-dithiodipropionic acid, cyclohexanedimethanol and trimethylolpropane, OH number 55 mg KOH/g. Polyol 3: Polyester polyol based on 3,3′-dithiodipropionic acid, cyclohexanedimethanol and glycerol, OH number 235 mg KOH/g. Polyol 4: Polyether polyol based on diethylene glycol and ethylene oxide, OH number 190 mg KOH/g. Additives: Mixture of tris(1-chloro-2-propyl) phosphate flame retardant, a silicone-based copolymer from Evonik Goldschmidt as foam stabilizer and a catalyst mixture consisting of a formate salt and a tertiary amine. Isocyanate: Polymeric MDI with an NCO content of 31.5% by weight.

(31) Thermal conductivity is determined with an EP500e λ-meter from Lambda Messtechnik GmbH Dresden at an average temperature of 10° C. on PU specimens of dimensions 200×200×50 mm that were taken from the above-described cubic foam block 24 hours after its production. To determine the cell size, a specimen of about 10×10×10 cm in size is taken from the interior of a beaker foam. For the measurement, a clean cut surface perpendicular to the direction of rising of the foam is produced and contrasted with soot spray. This is then followed by the imaging of the cut surface with a light microscope and evaluation with the PORE!SCAN software from Goldlücke. This generates a size class distribution of the cells and the arithmetic average over the area.

(32) The cell gases are determined by the method of M. Svanström and O. Ramnäs described in the Journal of Cellular Plastics, vol. 31, 1995, pages 375-388, in which a gas sample from the foam interior is taken with a brass syringe from the intact beaker foams under an inert gas atmosphere.

(33) Tables 3 and 4 show examples in which the inventive polyols 2 and 3 replace the polyol 1 in different proportions in the A component of a representative PIR formulation. Both examples show that the use of the polyols of the invention lowers the thermal conductivity of the foam after 24 hours and after aging at 70° C. for 21 days. In addition, the compressive strength in the case of replacement of 50 parts by weight of polyol 1 by polyol 3 improves by 7%. The improvement in thermal conductivities can be explained by the slower exchange mainly of CO.sub.2 for air in the foam cells. These results confirm the results of the permeability measurements on TPU films from tables 1 and 2.

(34) It is apparent from these further use examples that, in the case of use of the polyester polyols of the invention, it is possible to reduce thermal conductivity in the resulting polyurethanes before and after aging.

(35) Formulae

(36) ##STR00001##