POLYAMIDE CORD FOR USE AS A CARCASS REINFORCEMENT, PNEUMATIC VEHICLE TIRE COMPRISING ONE OR MORE POLYAMIDE CORDS AND METHOD FOR PRODUCING ONE OR POLYAMIDE CORDS, METHOD FOR PRODUCING A RUBBERIZED REINFORCING PLY AND METHOD FOR PRODUCING A MOTOR VEHICLE TIRE

Abstract

The invention relates to a polyamide cord for use as carcass strength member in a pneumatic vehicle tire, wherein the polyamide cord has a residual shrinkage in the range from 0% to 2% and a shrinkage at 180 C. in the range from 0% to 4.5%, where the residual shrinkage of the polyamide cord and the shrinkage at 180 C. of the polyamide cord are determined to ASTM D 855. The invention also relates to a pneumatic vehicle tire comprising one or more polyamide cords and to a process for producing one or more polyamide cords, to a process for producing a rubberized reinforcement ply and to a process for producing a pneumatic vehicle tire.

Claims

1.-11. (canceled)

12. A polyamide cord for use as carcass strength member in a pneumatic vehicle tire, wherein the polyamide cord has a residual shrinkage in the range from 0% to 2% and a shrinkage at 180 C. in the range from 0% to 4.5%, and wherein the residual shrinkage of the polyamide cord and the shrinkage at 180 C. of the polyamide cord are determined to ASTM D 855.

13. The polyamide cord as claimed in claim 12, wherein the polyamide cord has a total linear density in the range from 940 dtex to 6000 dtex, and consists of two, three, four or more than four twisted multifilament yarns, where each of the multifilament yarns has a linear yarn density in the range from 1000 dtex to 3000 dtex.

14. The polyamide cord as claimed in claim 12, wherein the polyamide cord has a twist factor in the range from 170 to 250.

15. The polyamide cord as claimed in claim 12, wherein the polyamide cord has a total linear density of 2800 dtex, wherein the polyamide cord consists of two twisted multifilament yarns, each of the multifilament yarns having a linear yarn density of 1400, wherein the polyamide cord has a twist factor in the range from 190 to 210, wherein the polyamide cord has a residual shrinkage of 1.1%, wherein the polyamide cord has a shrinkage at 180 C. of 3.9%, and wherein the polyamide cord consists of PA6.6.

16. The polyamide cord as claimed in claim 12, wherein the polyamide cord has a total linear density of 3760 dtex, wherein the polyamide cord consists of two twisted multifilament yarns, each of the multifilament yarns having a linear yarn density of 1880, wherein the polyamide cord has a twist factor of 190 to 210, wherein the polyamide cord has a residual shrinkage of 0.9%, wherein the polyamide cord has a shrinkage at 180 C. of 3.8%, and wherein the polyamide cord consists of PA6.6.

17. The polyamide cord as claimed in claim 12, wherein the polyamide cord has a residual shrinkage in a range from 0.5% to 2%.

18. The polyamide cord as claimed in claim 17, wherein the polyamide cord has a residual shrinkage in a range from 0.8% to 2%.

19. The polyamide cord as claimed in claim 18, wherein the polyamide cord has a residual shrinkage in a range from 0.9% to 1.1%.

20. The polyamide cord as claimed in claim 12, wherein the polyamide cord has a shrinkage at 180 C. in a range from 0.5% to 4.5%.

21. The polyamide cord as claimed in claim 12, wherein the polyamide cord has a shrinkage at 180 C. in a range from 1% to 4.5%.

22. The polyamide cord as claimed in claim 12, wherein the polyamide cord has a shrinkage at 180 C. in a range from 3% to 4%.

23. The polyamide cord as claimed in claim 14, wherein the polyamide cord has a twist factor in the range from 170 to 230.

24. The polyamide cord as claimed in claim 23, wherein the polyamide cord has a twist factor in the range from 190 to 210.

25. The polyamide cord as claimed in claim 24, wherein the polyamide cord has a twist factor in the range from 200 to 210.

26. A pneumatic vehicle tire comprising one or more polyamide cords as claim in claim 12.

27. The pneumatic vehicle tire as claimed in claim 26, wherein the pneumatic vehicle tire is a pneumatic agricultural tire.

28. The pneumatic vehicle tire as claimed in claim 26, wherein the pneumatic vehicle tire comprises a radial carcass having 1 to 6 carcass plies.

29. A process for producing one or more polyamide cords, wherein the process comprises at least the following process steps in the following sequence: a. dipping one or more textile strength members into at least one dip bath containing at least one latex; b. then heat treating the one or more dipped strength members within a temperature range from 120 to 260 C. and simultaneously stretching the one or more strength members such that, over the entire process, the one or more strength members have been subjected to a total extension in the range from 0% to 6%; c. further processing the one or more heat-treated strength members so as to give one or more polyamide cords.

30. The process for producing one or more polyamide cords as claimed in claim 29, further comprising: d. rubberizing the one or more polyamide cords with a rubberization mixture and further processing so as to form a rubberized reinforcement ply.

31. The process for producing one or more polyamide cords as claimed in claim 30, further comprising: e. incorporating the rubberized reinforcement ply into a tire blank and further processing the tire blank to give a pneumatic vehicle tire.

Description

EXAMPLE 1 (COMPARATIVE EXPERIMENT V1): NONINVENTIVE POLYAMIDE CORD FOR USE AS CARCASS STRENGTH MEMBER WITH A TOTAL LINEAR DENSITY OF 2880 DTEX

[0135] Cords produced from two PA6.6 yarns in each case having a total linear density of 2880 dtex (14402) with a yarn twist of 290 were dipped by means of a pre-dip containing 46.49 parts by weight of water, 45.67 parts by weight of vinyl-pyridine latex and 2.25 parts by weight of ammonia, 3.14 parts by weight of Penacolite resin (commercially available aqueous solution with 75% by weight of Penacolite resin as resorcinol-formalin reaction product), 0.17 part by weight of a commercially available aqueous NaOH solution (50% by weight of NaOH) and 2.28 parts by weight of formaldehyde (commercially available 37% by weight solution). Subsequently, the PA6.6 cords were dried between 140 C. and 160 C. for 30 to 120 seconds and then heat-treated in a heat-stretching zone between 210 C. and 260 C. In the normalization zone, the heat-stretched PA6.6 cords were cooled down to room temperature. The total extension in the pretreatment was 7%.

EXAMPLE 2 (EXPERIMENTS E1 TO E4): INVENTIVE POLYAMIDE CORD FOR USE AS CARCASS STRENGTH MEMBER WITH A TOTAL LINEAR DENSITY OF 2880 DTEX

[0136] Cords produced from two PA6.6 yarns in each case having a total linear density of 2880 dtex (14402) with various yarn twists (see table 1) were dipped by means of a pre-dip containing 46.49 parts by weight of water, 45.67 parts by weight of vinyl-pyridine latex and 2.25 parts by weight of ammonia, 3.14 parts by weight of Penacolite resin (commercially available aqueous solution with 75% by weight of Penacolite resin as resorcinol-formalin reaction product), 0.17 part by weight of a commercially available aqueous NaOH solution (50% by weight of NaOH) and 2.28 parts by weight of formaldehyde (commercially available 37% by weight solution). Subsequently, the PA6.6 cords were dried between 140 C. and 160 C. for 30 to 120 seconds and then heat-treated in a heat-stretching zone between 210 C. and 260 C. In the normalization zone, the heat-stretched PA6.6 cords were cooled down to room temperature. The total extension in the pretreatment was 1.2%.

EXAMPLE 3 (EXPERIMENT E5): INVENTIVE POLYAMIDE CORD FOR USE AS CARCASS STRENGTH MEMBER WITH A TOTAL LINEAR DENSITY OF 3760 DTEX

[0137] Cords produced from two PA6.6 yarns in each case having a total linear density of 3760 dtex (18802) with a yarn twist of 335 tpm were dipped by means of a pre-dip containing 46.49 parts by weight of water, 45.67 parts by weight of vinyl-pyridine latex and 2.25 parts by weight of ammonia, 3.14 parts by weight of Penacolite resin (commercially available aqueous solution with 75% by weight of Penacolite resin as resorcinol-formalin reaction product), 0.17 part by weight of a commercially available aqueous NaOH solution (50% by weight of NaOH) and 2.28 parts by weight of formaldehyde (commercially available 37% by weight solution). Subsequently, the PA6.6 cords were dried between 140 C. and 160 C. for 30 to 120 seconds and then heat-treated in a heat-stretching zone between 210 C. and 260 C. In the normalization zone, the heat-stretched PA6.6 cords were cooled down to room temperature. The total extension in the pretreatment was 1.2%.

[0138] For all PA6.6 cords, the process steps of the drying in the drying zone and of the heat treatment were executed as known to the skilled person. The temperature in the drying zone or in the normalization zone was not varied in all the above experiments. The temperature exerted on the PA6.6 polyamide cords in the heat-stretching zone, by contrast, was adjusted such that the properties, for example tensile strength, elongation at break and shrinkage at 180 C. of the cord, were not adversely affected.

[0139] The total extension in the pretreatment is the sum of the individual stretches in the drying zone, heat-stretching zone or normalization zone.

[0140] Production of the Test Specimens for the Disk Fatigue Test

[0141] The respective PA6.6 cords cooled down to room temperature, after being produced as described above, were rubberized with an unvulcanized standard rubberization mixture. The rubberization is effected by placing the cords onto or between calendered thin rubber sheets of the rubberization mixture and then compressing the entire test specimen in a hot press.

[0142] Production of the Pneumatic Vehicle Tires

[0143] The heat-treated PA6.6 polyamide cords were rubberized with an unvulcanized standard rubberization mixture and then processed further in a manner known to those skilled in the art with the tire components that were still required to give a pneumatic vehicle tire. The resulting pneumatic vehicle tires were then tested for their tire uniformity as described above in the corresponding test method.

[0144] Results:

[0145] The test results of the study of inventive and noninventive polyamide cords having different total extensions and having the same linear yarn densities in the pretreatment are shown in table 1 below:

TABLE-US-00001 TABLE 1 Experimental data of the polyamide cords produced in accordance with the invention and not in accordance with the invention and test results of the industrial rubber particles produced with the polyamide cords (test specimens and pneumatic vehicle tires). Comp. exp. V1 Exp. E1 Exp. E2 Exp. E3 Exp. E4 Property Unit Non-inv. Inv. Inv. Inv. Inv. Production of the polyamide cord Total extension in % 7 1.2 1.2 1.2 1.2 the pretreatment Comp. Property Unit exp. V1 Exp. E1 Exp. E2 Exp. E3 Exp. E4 Polyamide cord Production material PA6.6 PA6.6 PA6.6 PA6.6 PA6.6 Linear yarn density dtex 1400 1400 1400 1400 1400 Number of yarns 2 2 2 2 2 Total linear density dtex 2800 2800 2800 2800 2800 Yarn twist tpm 290 300 350 370 390 Twist factor 153 159 185 196 206 Elongation at break % 21 24 25 24 26 Tensile strength N 227 228 224 223 221 Shrinkage at 180 C. % 4.8 3.4 3.6 3.9 3.7 Residual shrinkage % 2.3 0.9 0.9 1.1 0.9 Test specimen Disk fatigue test % 100 113 111 109 111 (relative values*) Max. el.: 9.9% Min el.: 5.1% Pneumatic vehicle tire Number of radial 2 carcasses Tire uniformity (1st mm not not not 0.18 not harmonic)** tested tested tested tested *The value measured for comp. exp. V1 in table 1 was normalized to 100% and the improvement in the values for the polyamide cords of the invention was reported by comparison with the normalized value for comp. exp. V1. **What was measured was the deviation between the ascertained geometric center of the circumferential shape of the pneumatic vehicle tire produced and the axis of rotation of the wheel on which the pneumatic vehicle tire was mounted in the measurement (see test method Tire uniformity).

[0146] It can be inferred from table 1 that a decrease in total extension in the pretreatment from 7% to 1.2% can achieve a significant decrease in residual shrinkage and shrinkage at 180 C. As a result, it is possible to achieve not only better results in the disk fatigue test but also pneumatic vehicle tires having elevated uniformity (see the last three lines in table 1). More particularly, the results for the pneumatic vehicle tire with a polyamide cord of the invention having a twist factor of 196 show that the above-described production method can produce pneumatic vehicle tires having exceptional tire uniformity (cf. 0.18 mm, last line in table 1).

[0147] Moreover, the proportion of pneumatic vehicle tires produced that has an above-described deviation of less than 1.25 mm was well above 90% (measurement results not indicated in table 1).

[0148] The test results from the study of polyamide cords of the invention with equal total extension in the pretreatment and different linear yarn densities are shown in table 2 below:

TABLE-US-00002 TABLE 2 Experimental data of the polyamide cords of the invention with different twist factors and test results of the industrial rubber articles produced with the polyamide cords of the invention (test specimens and pneumatic vehicle tires). Exp. E1 Exp. E2 Exp. E3 Exp. E4 Exp. E5 Property Unit Inv. Inv. Inv. Inv. Inv. Production of the polyamide cord Total extension in % 1.2 1.2 1.2 1.2 1.2 the pretreatment Polyamide cord Production material PA6.6 PA6.6 PA6.6 PA6.6 PA6.6 Linear yarn density dtex 1400 1400 1400 1400 1880 Number of yarns 2 2 2 2 2 Total linear density dtex 2800 2800 2800 2800 3760 Yarn twist tpm 300 350 370 390 335 Twist factor 159 185 196 206 205 Elongation at break % 24 25 24 26 26 Tensile strength N 228 224 223 221 285 Unit Exp. E1 Exp. E2 Exp. E3 Exp. E4 Exp. E5 Shrinkage at 180 C. % 3.4 3.6 3.9 3.7 3.8 Residual shrinkage % 0.9 0.9 1.1 0.9 0.9 Test specimen Disk fatigue test % not 100 136 146 141 (relative values*) measured Max. el.: 13.5% Min el.: 1.4% Pneumatic vehicle tire Number of radial 2 carcasses Tire uniformity mm not tested not 0.18 not not (1st harmonic)** tested tested tested *The value measured for exp. E2 in table 2 was normalized to 100% and the improvement in the values for the remaining polyamide cords of the invention in table 2 was reported by comparison with the normalized value for exp. E2. **What was measured was the deviation between the ascertained geometric center of the circumferential shape of the pneumatic vehicle tire produced and the axis of rotation of the wheel on which the pneumatic vehicle tire was mounted in the measurement (see test method Tire uniformity).

[0149] It can be inferred from table 2 that an increase in the twist factor with establishment of the new production parameters of a production method of the invention can achieve a significant improvement in the results in the disk fatigue test and in tire uniformity (see last three lines in table 2). The test conditions in the disk fatigue test with which the results were ascertained in table 2, as already elucidated above, differ in that the conditions were more aggressive (maximum elongation was 13.5% and minimum elongation was 1.4%) than the test conditions in the disk fatigue test with which the results in table 1 were ascertained. The test conditions as used for the determination of the measurements in table 2 simulate the real demands on a polyamide cord when used in a pneumatic agricultural tire better than the test conditions in the disk fatigue test with which the results in table 1 were ascertained. It can therefore be concluded from the measurement results from the disk fatigue test in table 2 that polyamide cords of the invention having a twist factor in the range from 190 to 210 are more advantageous for pneumatic tires that are used in vehicles with heavy loads, especially in pneumatic agricultural tires. The comparison is made here with polyamide cords having a twist factor below 190.

[0150] The total extension in the pretreatment in all examples in table 2 was 1.2% In the pneumatic vehicle tire produced, a deviation of the ascertained geometric center of the tread contour of the motor vehicle tire produced of less than 1.25 mm from the center of the bead circle of the radial first harmonic was measured.

[0151] Moreover, the proportion of pneumatic vehicle tires produced that has an above-described deviation of less than 1.25 mm was well above 90% (measurement results not indicated in table 2).