MELT-DRAWN POLYAMIDE FILAMENTS

Abstract

Stretched filaments based on linear, branched or cyclic, aliphatic or semiaromatic polyamides, wherein the filaments have been stretched at a temperature between glass transition temperature and melting point and wherein the filaments are cooled down to room temperature under full tensile load.

Claims

1. A stretched filament containing at least 80% by weight of linear, branched or cyclic, aliphatic or semiaromatic polyamides, wherein the dry filaments have been stretched at a temperature between glass transition temperature and melting point and wherein the filaments are cooled down in the dry state to below 100° C. under full tensile load, without using water for cooling.

2. The stretched filament according to claim 1, wherein the minimum stretching temperature T.sub.str,min is determined with the aid of equation (1):
T.sub.str,min=((T.sub.m−T.sub.g)*X.sub.c)+T.sub.g   (G1) where T.sub.m=melting point, T.sub.g=glass transition temperature and X.sub.c is the crystallinity, and wherein the crystallinity is determined by equation (2) $\begin{array}{cc}{X}_C=\frac{\Delta H_m}{\Delta H_m^0}& \left(\mathrm{G2}\right)\end{array}$ where the parameters T.sub.m, T.sub.g and ΔH.sub.m are determined by DSC to EN ISO 11357-1:2016D and ΔH.sub.m.sup.0 is taken from standard tabular works.

3. The stretched filament according to claim 1, which have only low shrinkage/relaxation in the direction of tension when heated to a temperature above the glass transition temperature and below the melting point, preferably below the stretching temperature, a maximum of 6% in relation to the stretched length.

4. The stretched filament according to claim 1, wherein the monomers of the polyamides, aminocarboxylic acid or the lactam or a mixture of different monomers of this kind, have an arithmetic average of at least 7.0 carbon atoms, and in the case of a combination of diamine and dicarboxylic acid the arithmetic average of the carbon atoms of diamine and dicarboxylic acid is at least 7.0.

5. A method for production of the stretched filaments according to claim 1, wherein the filaments have been stretched at least by a factor of 2.5.

6. A composite comprising the stretched filaments according to claim 1.

7. A winding layer comprising the stretched filaments according to claim 1.

8. The stretched filament according to claim 2, which have only low shrinkage/relaxation in the direction of tension when heated to a temperature above the glass transition temperature and below the melting point, preferably below the stretching temperature, a maximum of 6% in relation to the stretched length.

9. The stretched filament according to claim 2, wherein the monomers of the polyamides, aminocarboxylic acid or the lactam or a mixture of different monomers of this kind, have an arithmetic average of at least 7.0 carbon atoms, and in the case of a combination of diamine and dicarboxylic acid the arithmetic average of the carbon atoms of diamine and dicarboxylic acid is at least 7.0.

10. The stretched filament according to claim 3, wherein the monomers of the polyamides, aminocarboxylic acid or the lactam or a mixture of different monomers of this kind, have an arithmetic average of at least 7.0 carbon atoms, and in the case of a combination of diamine and dicarboxylic acid the arithmetic average of the carbon atoms of diamine and dicarboxylic acid is at least 7.0.

11. A method for production of the stretched filaments according to claim 2, wherein the filaments have been stretched at least by a factor of 2.5.

12. A method for production of the stretched filaments according to claim 3, wherein the filaments have been stretched at least by a factor of 2.5.

13. A method for production of the stretched filaments according to claim 4, wherein the filaments have been stretched at least by a factor of 2.5.

14. A composite comprising the stretched filaments according to claim 2.

15. A composite comprising the stretched filaments according to claim 3.

16. A composite comprising the stretched filaments according to claim 4.

17. A composite comprising the stretched filaments according to claim 5.

18. A winding layer comprising the stretched filaments according to claim 2.

19. A winding layer comprising the stretched filaments according to claim 3.

20. A winding layer comprising the stretched filaments according to claim 4.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0056] FIG. 1 shows graphs of the results according to table 1; and

[0057] FIG. 2 shows a plot of maximum strength, δm [MPa] against temperature at which δm was determined for the samples.

[0058] FIG. 1: graph of the results according to table 1; [0059] left-hand group stretching factor 1.1 (P 1.1); right-hand group SF=2.5 (P 1.2); [0060] bold shading: relaxation temperature 80° C., fine shading: relaxation temperature 120° C.; [0061] Vertical shading represents shrinkage in stretching direction and horizontal shading represents extension at right angles to stretching direction.

[0062] FIG. 2: Plot of max. strength, σ.sub.m [MPa] against temperature at which σ.sub.m was determined; [0063] determinations for samples with different stretching factor SF.

EXAMPLES

[0064] Materials

[0065] PA 6.10: VESTAMID Terra HS 16 (Evonik)

[0066] PA 10.10: VESTAMID Terra DS 18 (Evonik)

[0067] PA 12: VESTAMID L2101 nf (Evonik)

[0068] Trogamid: CX7323 (Evonik)

[0069] PA 11

[0070] Methods

[0071] DSC:

[0072] Perkin Elmer, Diamond type, automatic peak recognition and integration, in accordance with DIN EN ISO 11357-1:2010, heating rate 20 K/min.

Example 1, Production of the Specimens

[0073] The abovementioned polyamides were extruded by means of an extruder (Collin E45M) at a temperature of 5 to 10° C. above the melting point (for example at 250-260° C. for PA 12) to give a ribbon having a thickness of 150, 350 and 650 μm, and cooled to 30-40° C.

[0074] The ribbons were calendered at a speed of 1.4 m/min; the width was 35 mm.

[0075] P 1.* are samples of PA 12;

[0076] P 2.* are samples of Trogamid;

[0077] P 3.* are samples of PA 6.10;

[0078] P 4.* are samples of PA 10.10;

[0079] P5.* are samples of PA 11.

Example 2, Stretching of the Specimens

[0080] Method 1:

[0081] In a tensile tester (Zwick, Z101-K), specimens according to Example 1 were stretched at a speed of 50 mm/min at 140° C. Before the tensile stress was released, the specimens were cooled down to room temperature. The cooling was conducted slowly within 2 min or quickly within 10 sec. Further samples according to the following table:

TABLE-US-00002 P 1.0 P 1.3 P 2.0 P 2.1 P 3.0 P 3.1 P5.0 P5.1 Stretching factor 1 5 1 4.5 1 4.6 1 4.6 Stretching speed 50 50 25 25 [mm/min] Stretching 140 60 80 60 temperature [° C.] Cooling [min] 2 2 2 2

[0082] Method 2:

[0083] An endless specimen according to Example 1 was provided on a coil, and stretched on a continuous machine (Retech Drawing) at a material feed rate of 1 to 2.5 rpm and a tension rate of up to 32 rpm to a stretching factor (SF) of 3.5 to 8. The stretching took place at a temperature of 60 to 140° C.

[0084] Example 0: Continuous stretching process—samples P 1,* (PA12), thickness 650 μm, width 10 mm.

TABLE-US-00003 P 1.5 P 1.6 P 1.7 P 1.8 Stretching 3.5 5 6.6 8 factor Stretching 130 80 60 140 temperature [° C.] Speed of 2.5 2.5 2.5 1 the first roll Speed of 8.75 12.50 16.5 8 the last roll

Example 3, Relaxations

[0085] Specimens from Example 2 were cut to a length of 10 cm. The specimens according to Example 2, Method 1, were cut at both ends. The specimens were stored in a thermal oven without tensile load, individually lying horizontally in a freely mobile manner, at temperatures of 80° C. and 120° C. for 5 h.

[0086] After cooling, the two areal dimensions of the samples were measured. The results are shown in Table 1 and FIG. 1.

[0087] Table 1, relative change in the dimensions of the specimens according to Example 3, length=in direction of tension, width=90° to the direction of tension

TABLE-US-00004 Length Width Length Width Sample 80° C. 120° C. P 1.1; RF = 1.1 −4.03 +1.23 −11.96 +2.38 P 1.2; RF = 2.5 −2.67 +0.61 −4.17 +1.39

[0088] Polyamide samples have low relaxation and surprisingly show increasingly lower relaxation with rising stretching factor.

Example 4, Mechanical Tests

[0089] Tensile Tests

[0090] Dumbbell specimens according to DIN 527-5:1997 (A specimen) were punched out of the stretched ribbons; the thickness was the result of the stretching experiment and was not altered. The tensile strength was measured on 3 specimens in each case by means of a Zwick tensile tester at different temperatures. Testing speed=5 mm/min, clamped length=120 mm and measurement length of the incremental gauge=75 mm.

[0091] Temperature 23° C., relative humidity 50%.

[0092] The results are reported in Tables 2 and 3, and FIG. 2.

[0093] The results are the arithmetic average from 3 specimens.

TABLE-US-00005 TABLE 2 T = 23° C., results from the tensile test according to Example 4. P 1.0 P 1.3 P 2.0 P 2.1 P 3.0 P 3.1 P.5.0 P5.1 Stretching factor 1 5 1 4.5 1 4.6 1 4.6 Elastic 982 3277 1572 3049 686 2189 873 1984 modulus [MPa] max strength, 76 332 56 207 49.2 182.9 56.3 174.1 σ.sub.m [MPa] max strain, 189 9.1 88 11.8 233.5 23.6 267.7 46.0 ε.sub.m [%] strength 73 332 55 207 49.2 182.4 56.3 174.1 at break, σ.sub.b [MPa] strain at 181 9.12 102 12 234.2 23.9 267.7 46.0 break, ε.sub.b [%]

TABLE-US-00006 TABLE 3 T = 23° C., results of the tensile tests according to Example 0 P 1.5 P 1.6 P 1.7 P 1.8 Stretching 3.5 5 6 8 factor Modulus of 3060 2030 1860 2856 elasticity [MPa] Max strength, 266 314.6 313.7 351.9 σ.sub.m [MPa] Max strain, ε.sub.m 12.4 23.33 23.15 18.075 [%] Strength at 266 308.5 308.2 351.9 break, σ.sub.b [MPa] Strain at 12.4 23.35 23.16 18.075 break, ε.sub.b [%]

TABLE-US-00007 TABLE 4 max strength, σ.sub.m [MPa] for different testing temperatures, results of the tests according to Example 4, for samples with different stretching factors P 1.0 P 1.1 P 1.2 P 1.4 Stretching factor 1 1.1 2.5 4.7 σ.sub.m σ.sub.m σ.sub.m σ.sub.m Testing temperature [° C.] [MPa] [MPa] [MPa] [MPa] 23 76 135 223 294 40 77.6 118 209 288 60 70 113 195 270 80 67.7 102 147 222