LOW-DAMPING POLYURETHANE ELASTOMER

Abstract

The present invention relates to a method of preparing a polyurethane elastomer. The method includes a step of reacting at least one isocyanate composition and one polyol composition containing a poly--caprolactone polyol obtained by reacting caprolactone and a diol having a number average molecular weight of from 80 to 1500 g/mol to obtain an isocyanate-functional prepolymer; and a step of reacting the prepolymer with at least one chain extender. The polyol composition contains -hydro--hydroxypoly(oxytetramethylene) polyols in an amount ranging from 0 to 1 wt % based on the entire polyol composition. The present invention further relates to a polyurethane elastomer prepared by such a method and also to the use of the polyurethane elastomer in the manufacture of a shaped article, especially a damping element, a shock absorber, a stop buffer, or a part of a shoe, such as a shoe sole, in particular, an insert sole or a midsole.

Claims

1. A method of preparing a polyurethane elastomer, said method comprising: (i) reacting at least one isocyanate composition (ZI) and one polyol composition (ZP) comprising a poly--caprolactone polyol obtained by reacting caprolactone and a diol having a number average molecular weight ranging from 80 to 1500 g/mol to obtain an isocyanate-functional prepolymer, (ii) reacting the prepolymer with at least one chain extender (KV) in the presence of a blowing agent, wherein the polyol composition (ZP) comprises -hydro--hydroxypoly(oxytetramethylene) polyols in an amount ranging from 0 to 1 wt % based on the entire polyol composition (ZP).

2. The method according to claim 1, wherein said reacting (i) employs the components in such amounts that the prepolymer obtained has an isocyanate (NCO) content ranging from 2% to 8%.

3. The method according to claim 1, wherein said reacting (i) is effected at a temperature ranging from 110 C. to 180 C.

4. The method according to claim 1, wherein said reacting (i) employs the components in such amounts that the prepolymer obtained has an isocyanate (NCO) content ranging from 8% to 22%.

5. The method according to claim 1, wherein said reacting is effected at a temperature ranging from 40 C. to 110 C.

6. The method according to claim 1, wherein the poly--caprolactone polyol is obtained by reacting caprolactone and a diol selected from the group consisting of a -hydro--hydroxypoly(oxytetramethylene) diol, a polyethylene glycol, and a polypropylene glycol.

7. The method according to claim 1, wherein the polyol composition (ZP) comprises the -hydro--hydroxypoly(oxytetramethylene) polyol in an amount of 0.1 to 1 wt %, based on the polyol composition.

8. The method according to claim 1, wherein said reacting (ii) employs at least one further component selected from the group consisting of a polyol, water, a chain-extending agent and/or crosslinking agent, a catalyst, other auxiliary, and an added substance.

9. The method according to claim 1, wherein the polyisocyanate composition (ZI) comprises an isocyanate selected from the group consisting of 1,5-naphthylene diisocyanate (NDI), 4,4-diphenylmethane diisocyanate (MDI), p-phenyl diisocyanate (PPDI), o-tolidine diisocyanate (TODI), and a mixture thereof.

10. The method according to claim 1, wherein the polyisocyanate composition comprises 1,5-naphthylene diisocyanate (NDI) in an amount ranging from 90 to 100 wt % based on the entire polyisocyanate composition (ZI).

11. The method according to claim 1, wherein the chain extender (KV) is selected from the group consisting of water, a diol having a molecular weight ranging from 50 to 500 g/mol, a triol having a molecular weight ranging from 50 to 500 g/mol, and a diamine having a molecular weight ranging from 50 to 500 g/mol.

12. The method according to claim 1, wherein the poly--caprolactone polyol has a number average molecular weight ranging from 1500 to 2500 g/mol.

13. A polyurethane elastomer, obtained by a method comprising: reacting at least one isocyanate composition (ZI) and one polyol composition (ZP) comprising a poly--caprolactone polyol obtained by reacting caprolactone and a diol having a number average molecular weight ranging from 80 to 1500 g/mol to obtain an isocyanate-functional prepolymer, (ii) reacting the prepolymer with at least one chain extender (KV) in the presence of a blowing agent, wherein the polyol composition (ZP) comprises -hydro--hydroxypoly(oxytetramethylene) polyols in an amount ranging from 0 to 1 wt % based on the entire polyol composition.

14. The polyurethane elastomer according to claim 13, wherein the polyurethane elastomer is microcellular.

15. The polyurethane elastomer according to claim 13, having a density ranging from 0.12 to 0.8 kg/m3 according to DIN EN ISO 845.

16. The method of making a shaped article, the method comprising: preparing the shaped article from the polyurethane elastomer according to claim 13.

17. The method according to claim 16, wherein the shaped article is a damping element, a shock absorber, a stop buffer, or a part of a shoe.

Description

SHORT DESCRIPTION OF FIGURES

[0122] FIG. 1: shows the schematic test setup for determining the stiffening factor. The test specimen (1) is inserted between a test adapter at the top (2) and a test adapter at the bottom (3).

[0123] FIG. 2: shows the result of the measurement on compressing the material. To analyze the measurement, the force is plotted against the distance (FIG. 2a) and the derivative as stiffness against distance (FIG. 2b).

[0124] FIG. 2a: shows the static curve where the x-axis represents the distance (in mm) and the y-axis represents the force (in kN). Only the ascending branch is considered.

[0125] FIG. 2b: shows the first derivative of the trajectory of the static curve. The stiffness (y-axis, in kN/mm) is plotted against the distance (x-axis, in mm).

[0126] FIG. 3: shows the dynamic modulus (y-axis, in kN/mm) against the frequency (x-axis, in Hz).

[0127] Further embodiments of the present invention are derivable from the claims and the examples. It will be understood that the aforementioned and hereinbelow elucidated features of the article/method/uses according to the present invention can be used not just in the particular combination recited, but also in other combinations, without departing from the realm of the invention. For instance, the combination of a preferred feature with a particularly preferred feature or of a not further characterized feature with a particularly preferred feature, etc., is also implicitly comprehended even when this combination is not expressly mentioned.

[0128] Exemplary embodiments of the present invention, which do not limit the present invention, are recited hereinbelow. More particularly, the present invention also comprehends those embodiments which result from the hereinbelow recited dependency references and hence combinations. More particularly, in the recitation hereinbelow of a range of embodiments, for example the expression The method according to any one of embodiments 1 to 4 is to be understood as meaning that every combination of the embodiments in this range is explicitly disclosed to a person skilled in the art, i.e., the expression is to be understood as interchangeable with The method according to any one of embodiments 1, 2, 3 and 4. [0129] 1. A method of preparing a polyurethane elastomer, said method comprising at least the steps (i) and (ii): [0130] (i) reacting at least one isocyanate composition (ZI) and one polyol composition (ZP) comprising a poly--caprolactone polyol obtained or obtainable by reacting -caprolactone and a starter molecule selected from the group consisting of diols having a number average molecular weight in the range from 80 to 1500 g/mol to obtain an isocyanate-functional prepolymer, [0131] (ii) reacting the prepolymer obtained as per step (i) with at least one chain extender (KV), [0132] wherein the polyol composition (ZP) comprises -hydro--hydroxypoly(oxytetramethylene) polyols in an amount ranging from 0 to 1 wt % based on the entire polyol composition (ZP). [0133] 2. The method according to embodiment 1 wherein the reacting step as per step (i) employs the components in such amounts that the prepolymer obtained as per step (i) has an isocyanate (NCO) content in the range from 2% to 8%. [0134] 3. The method according to either of embodiments 1 and 2 wherein the reacting step as per step (i) is effected at a temperature in the range from 110 C. to 180 C. [0135] 4. The method according to embodiment 1 wherein the reacting step as per step (i) employs the components in such amounts that the prepolymer obtained as per step (i) has an isocyanate (NCO) content in the range from 8% to 22%. [0136] 5. The method according to either of embodiments 1 and 4 wherein the reacting step as per step (i) is effected at a temperature in the range from 40 C. to 110 C. [0137] 6. The method according to any one of embodiments 1 to 5 wherein the poly--caprolactone polyol is obtained or obtainable by reacting -caprolactone and a starter molecule selected from the group consisting of -hydro--hydroxypoly(oxytetramethylene) diols, polyethylene glycols and polypropylene glycols. [0138] 7. The method according to any one of embodiments 1 to 6 wherein the polyol composition (ZP) comprises the -hydro--hydroxypoly(oxytetramethylene) polyol in an amount of 0.1 to 1 wt %, based on the polyol composition. [0139] 8. The method according to any one of embodiments 1 to 7 wherein the reacting step as per step (ii) employs further components selected from the group consisting of polyols, blowing agents, comprising water, chain-extending agents and/or crosslinking agents, catalysts and other auxiliaries and/or added substances. [0140] 9. The method according to any one of embodiments 1 to 8 wherein the polyisocyanate composition (ZI) comprises an isocyanate selected from the group consisting of 1,5-naphthylene diisocyanate (NDI), 4,4-diphenylmethane diisocyanate (MDI), p-phenyl diisocyanate (PPDI) and o-Tolidine Diisocyanate (TODI), or mixtures thereof. [0141] 10. The method according to any one of embodiments 1 to 9 wherein the polyisocyanate composition comprises 1,5-naphthylene diisocyanate (NDI) in an amount ranging from 90 to 100 wt % based on the entire polyisocyanate composition (ZI). [0142] 11. The method according to any one of embodiments 1 to 10 wherein the chain extender (KV) is selected from the group consisting of water, diols having a molecular weight in the range from 50 to 500 g/mol, triols having a molecular weight in the range from 50 to 500 g/mol and diamines having a molecular weight in the range from 50 to 500 g/mol. [0143] 12. The method according to any one of embodiments 1 to 11 wherein the poly--caprolactone polyol has a number average molecular weight in the range from 1500 to 2500 g/mol. [0144] 13. A polyurethane elastomer obtained or obtainable by a method of preparing a polyurethane elastomer that comprises at least the steps (i) and (ii): [0145] (i) reacting at least one isocyanate composition (ZI) and one polyol composition (ZP) comprising a poly--caprolactone polyol obtained or obtainable by reacting -caprolactone and a starter molecule selected from the group consisting of diols having a number average molecular weight in the range from 80 to 1500 g/mol to obtain an isocyanate-functional prepolymer, [0146] (ii) reacting the prepolymer obtained as per step (i) with at least one chain extender (KV), [0147] wherein the polyol composition (ZP) comprises -hydro--hydroxypoly(oxytetramethylene) polyols in an amount ranging from 0 to 1 wt % based on the entire polyol composition. [0148] 14. The polyurethane elastomer according to embodiment 13 wherein the polyurethane elastomer is microcellular. [0149] 15. The polyurethane elastomer according to embodiment 13 or 14 having a density in the range from 0.12 to 0.8 kg/m.sup.3 according to DIN EN ISO 845. [0150] 16. The method of using a polyurethane elastomer obtained or obtainable according to a method according to any one of embodiments 1 to 12 or of a polyurethane elastomer according to any one of embodiments 13 to 15 in the manufacture of a shaped article. [0151] 17. The method according to embodiment 16 wherein the shaped article is a damping element, a shock absorber or a stop buffer or part of a shoe or of a shoe sole, for example part of an insert sole or of a midsole.

[0152] The invention will now be more particularly described with reference to examples without limiting the subject matter of the invention.

EXAMPLES

1. Determination of NCO Content:

1.1 Solutions Used:

[0153] Di-n-hexylamine solution:

[0154] 166.8 g of di-n-hexylamine are made up with xylene to 1.0 L (in a 1 L volumetric flask) and the mixture is homogenized.

[0155] 1% bromophenol blue solution:

[0156] 0.5 g of bromophenol blue is dissolved in 49.5 g of ethanol and the solution is transferred to a pipette bottle.

1.2 Procedure:

[0157] 10 ml of the amine solution are introduced into an Erlenmeyer flask. 20 ml of chlorobenzene are then added. For an expected isocyanate content of 4%, 2 g-2.5 g of prepolymer are weighed into the flask with an accuracy of 0.1 mg (for other isocyanate concentrations, the weights have to be appropriately conformed). After dissolution is complete (visual check), 50 ml of methanol are added. After 3 drops of bromophenol blue solution have been added, the unconsumed amine is then backtitrated with HCl (c=1.0 mol/L) until the color changes from blue to yellow.

[0158] Blank samples, i.e., samples without prepolymer, are treated in the same wayexcept for the absence of the sample weight.

[0159] The following formula is used for the computation:

[00001]$\mathrm{NCO}.Math..Math.\mathrm{free}=\frac{\left(\mathrm{VBW}-\mathrm{VProbe}\right)*M*c*t}{m}*100.Math.\%$

[0160] VBW: consumption of HCl (1.0 mol/L) for blank value in L

[0161] V Probe: consumption of HCl (1.0 mol/L) for sample in L

[0162] M: molar mass of NCO 42.02 g/mol

[0163] c: amount-of-substance concentration of HCl 1.0 mol/L

[0164] t: titer of HCl (1.0 mol/L)

[0165] m: sample weight of prepolymer in g

2. ExampleForming a Shaped Article

2.1 Compounds Used

[0166]

TABLE-US-00001 polyol 1 polycaprolactone polyol, started with pTHF1000 having an OH number of about 56 (MW: ca 2000), obtained from Perstorp polyol 2 polytetrahydrofuran (pTHF; polytetramethylene ether glycol, PTMEG) having an OH number of about 56 (MW: ca. 2000), obtained from BASF polyol 3 polyester diol with OH number about 56 constructed from adipic acid and 1,4-butanediol (MW: ca. 2000), obtained from BASF polyol 4 polycaprolactone polyol, started with neopentyl glycol having an OH number of about 56 (MW: ca 2000), obtained from BASF polyol 5 polytetrahydrofuran (pTHF; polytetramethylene ether glycol, PTMEG) having an OH number of about 112 (MW: ca. 1000), obtained from BASF polyol 6 polycaprolactone polyol, started with neopentyl glycol having an OH number of about 56 (MW: ca 2000), obtained from Perstorp NDI 1,5-naphthylene diisocyanate

2.2 Forming an Isocyanate-Functional Prepolymer

[0167] One or more polymer polyols were heated to 140 C. and admixed at that temperature with a diisocyanate under intensive agitation. The exact amounts of the compounds used are reported in tables 1a to 1d.

[0168] An NCO-terminated prepolymer was obtained. Viscosity data and NCO content and also further properties of the materials obtained are reported in tables 2a to 2d.

2.3 Forming Shaped Cellular Articles

[0169] Crosslinker component:

[0170] 32.7 parts by weight of a 50% aqueous solution of a fatty acid sulfonate,

[0171] 16.4 parts by weight of water,

[0172] 28 parts by weight of a carbodiimide based on 1,3-bis(1-isocyanato-1-methylethyl)benzene (TMXDI)

[0173] 18.1 parts by weight of a fatty acid polyglycol ester,

[0174] 4.2 parts by weight of a mixture of fatty acid polyglycol esters and amine salts of alkylbenzenesulfonates,

[0175] 0.6 part by weight of a mixture of:

[0176] 30 wt % of pentamethyldiethylenetriamine and

[0177] 70 wt % of N-methyl-N-(dimethylaminoethyl)piperazine.

[0178] 100 parts by weight of the hot isocyanate-functional prepolymer (a) at 90 C. were intensively stirred with the hot crosslinker component at 50 C. for about 10 seconds. The reaction mixture was then introduced into a hot sealable metallic mold at 90 C., the mold was sealed and the reaction mixture was allowed to cure. After 30 minutes the molded microcellular shaped article was demolded and thermally postcured by conditioning at 110 C. for 16 hours.

[0179] Good processability is ensured at 90 C. prepolymer viscosities of up to 4000 mPas. The examples show that the polyurethane elastomers of the present invention display a good combination of properties. There are many applications where polyurethane elastomers have to have a 100 Hz stiffening factor of above 1.8 coupled with a tan d at RT of above 0.015 and a tan d at 30 C. of above 0.15.

TABLE-US-00002 TABLE 1a Component Example 1 Example 2 Example 3 Example 4 polyol 1 1000 1000 1000 1000 (parts by weight) NDI 210 200 240 240 (parts by weight)

TABLE-US-00003 TABLE 1b Component Example 5 Example 6 Example 7 Example 8 polyol 2 1000 250 (parts by weight) polyol 3 1000 1000 (parts by weight) polyol 5 750 (parts by weight) NDI 210 240 230 240 (parts by weight)

TABLE-US-00004 TABLE 1c Component Example 9 Example 10 Example 11 Example 12 polyol 2 500 1000 (parts by weight) polyol 4 1000 (parts by weight) polyol 5 500 (parts by weight) polyol 6 1000 (parts by weight) NDI 180 240 180 240 (parts by weight)

TABLE-US-00005 TABLE 1d Component Example 13 Example 14 Example 15 polyol 2 1000 1000 1000 (parts by weight) polyol 4 (parts by weight) polyol 5 (parts by weight) polyol 6 (parts by weight) NDI 270 300 330 (parts by weight)

TABLE-US-00006 TABLE 2a Property Example 1 Example 2 Example 3 Example 4 prepolymer viscosity 2510 3600 1980 1760 at 90 C. [mPas] density g/l 478 476 449 396 tensile strength 4.8 4.2 4.3 3.6 elongation at break 367 337 293 302 tear strength 15.2 14.5 14.7 12.8 rebound resilience 89 89 87 87 stiffening factor at 1.72 1.74 1.73 1.78 100 Hz tan d at RT 0.012911 0.012986393 0.014541989 0.01338032 tan d at 30 C. 0.11415268 0.10491831 0.08638857 0.100884267

TABLE-US-00007 TABLE 2b Property Example 5 Example 6 Example 7 Example 8 prepolymer viscosity 3560 2070 2560 2632 at 90 C. [mPas] density g/l 481 482 460 480 tensile strength 6.1 4.8 4.8 5.8 elongation at break 476 306 230 449 tear strength 24.2 14.8 14.7 23.6 rebound resilience 77 82 79 74 stiffening factor at 2.18 1.82 2.24 2.3 100 Hz tan d at RT 0.027860767 0.0135561 0.03256369 0.02944064 tan d at 30 C. 0.711160488 0.1646066 0.5451386 0.73662872

TABLE-US-00008 TABLE 2c Property Example 9 Example 10 Example 11 Example 12 prepolymer viscosity 9510 2160 9680 1600 at 90 C. [mPas] density g/l 470 484 514 476 tensile strength 2.8 4.8 3.1 4.9 elongation at break 177 346 191 380 tear strength 8.4 19.6 10.4 19.5 rebound resilience 83 79 83 81 stiffening factor at 1.84 1.83 1.64 1.85 100 Hz tan d at RT 0.02181259 0.018134668 0.010632635 0.016207199 tan d at 30 C. 0.141530387 0.287501171 0.177349143 0.295595373

TABLE-US-00009 TABLE 2d Property Example 13 Example 14 Example 15 prepolymer viscosity 1365 989 681 at 90 C. [mPas] density g/l 305 292 291 tensile strength 1.6 1.7 1.6 elongation at break 162 199 164 tear strength 7.6 6.9 6.7 rebound resilience 84 81 79

3. Methods of Measurement:

[0180]

TABLE-US-00010 prepolymer viscosity measured with Rheomat RM 180 at 90 C. [mPas] viscometer (shear rate 60 s.sup.1) density g/l DIN 53420 tensile strength DIN 53504 elongation at break DIN 53504 tear strength DIN ISO 34-1, B rebound resilience DIN 53512 tan d at RT DIN EN ISO 6721-2 tan d at 30 C. DIN EN ISO 6721-2

4. Properties of Polyurethane Elastomers

[0181] A cylindrical sample piece having the dimensions (in mm) 3527 is prepared as the final specimen. This cylindrical sample piece is cut out, by waterjet cutting, from a previously foamed Cellasto slab having the dimensions (in mm) 21011030. This cylindrical sample piece is placed between two likewise cylindrical alloy adapter plates and precompressed twice using a force of 4329.5 N and a speed of 30 mm/min (FIG. 1). The setting cycles are intended to simulate a material-based setting under accelerated conditions.

[0182] In the measuring cycle, the sample piece is precompressed by 30% of the sample height at a speed of 10 mm/min. The material displays a progressive characteristic in compression and an approximately linear region develops at 30% compression (FIG. 2). This region is often also sought in the design of component parts. The last cycle, called the measuring cycle, is recorded and analyzed by depicting the force against the distance (left-hand diagram) and the derivative as stiffness against distance (right-hand diagram). There is an ascending branch and a descending branch in the recording, but for the purpose of analysis a mean value against the distance is formed from the two branches.

[0183] Immediately following the static measurement, the sample piece is measured dynamically. The plates are moved to produce a pre-load previously read off in every measurement at a static distance of 8.1 mm (which corresponds to 30% of the sample height).

[0184] A frequency sweep up to 400 Hz is run at amplitude of 0.1 mm and the dynamic modulus against the frequency is evaluated (FIG. 3).

[0185] The project definition stipulates that the stiffening value be determined at 100 Hz. This stiffening factor is the ratio of dynamic stiffness to static stiffness. The resulting value is always >1.

[0186] The loss angle and the damping may also be considered in addition to the stiffening factor.

Cited Prior Art

EP 62 835 A1

EP 36 994 A1

EP 250 969 A1

DE 195 48 770 A1

DE 195 48 771 A1

EP 1 379 568 A1