HIGH STRENGTH POLYAMIDE YARN

Abstract

The invention relates to a yarn comprising a copolyamide in an amount of at least 90 wt % with respect to the total weight of the yarn, which copolyamide comprises a) at least 95 wt % by weight with respect to the total weight of copolyamide, monomeric units derived from hexamethylene diamine and adipic acid and b1) cyclic monomeric units derived from a diamine X, and cyclic monomeric units derived from a diacid Y, and/or b2) cyclic monomeric units derived from an amino acid Z, in which the summed amount of monomeric units derived from X, Y and Z is between 0.1 to 4.5 wt % by weight with respect to the total weight of the copolyamide and wherein the yarn has a tensile strength of at least 80 cN/tex as measured according to ASTM D885-04. The invention also relates to a process for preparing the yarn.

Claims

1. Yarn comprising a copolyamide in an amount of at least 90 wt % with respect to the total weight of the yarn, which copolyamide comprises a) at least 95 wt % by weight with respect to the total weight of copolyamide, monomeric units derived from hexamethylene diamine and adipic acid and b1) cyclic monomeric units derived from a diamine X, and cyclic monomeric units derived from a diacid Y, and/or b2) cyclic monomeric units derived from an amino acid Z, in which the summed amount of monomeric units derived from X, Y and Z is between 0.1 to 4.5 wt % by weight with respect to the total weight of the copolyamide and in which the yarn has a tensile strength of at least 80 cN/tex as measured according to ASTM D885-04.

2. Yarn according to claim 1, comprising at least 95 wt % of the copolyamide with respect to the total weight of the yarn.

3. Yarn according to claim 1, in which X and Y are present in essentially equal molar amounts.

4. Yarn, according to claim 1, in which the yarn has a tensile strength of at least 85 cN/tex as measured according to ASTM D885-04.

5. Yarn according to claim 1, in which the summed amount of monomeric units derived from X, Y and Z is between 0.5 to 4.0 wt % with respect to the total weight of the copolyamide.

6. Yarn according to claim 1, in which the diamine X is isophorone diamine and the diacid Y is chosen from the group of isophthalic acid and terephthalic acid.

7. Yarn according to claim 1, in which the yarn has a hot air shrinkage of between 1.0 to 7.0% as measured according to ASTM D4974-04 at 177 C. for 2 minutes.

8. Yarn according to claim 1, in which the yarn has a titer of between 200 to 700 dtex.

9. Yarn according to claim 1, in which the yarn as a titer of between 300 dtex and 500 dtex and a tenacity of at least 85 cN/tex.

10. Yarn according to claim 1, in which the yarn has a HAS of at most 5.0% and a tenacity of at least 85 cN/tex, and a titer of between 300 dtex and 500 dtex.

11. Process for preparing a yarn according to claim 1, in which the process comprises the following steps: Providing a composition comprising a copolyamide to an extruder and melting it, optionally mixing with additives, such as stabilizer or pigment, to obtain a molten composition; The molten composition is extruded through a spinneret to form filaments, which are subsequently stretched, cooled and combined to form at least one yarn; The at least one yarn is subsequently subjected to a drawing process at a temperature between 25 C. and 265 C. to a draw ratio between 4 and 6; After drawing, the yarn is relaxed by from 4% to 10% in at least three stages while being kept in a temperature range of 250 C. to 260 C.; The at least one yarn is wound up.

12. Process according to claim 11 in which the drawing process is carried out at a temperature between 50 C. and 215 C.

13. Air bag fabric, comprising a yarn according to claim 1.

Description

EXAMPLE 1 (Ex 1)

[0078] A 350 dtex yarn consisting of 72 filaments is prepared from a copolyamide PA66/IPDT according to process A. The copolyamide is synthesized from a mixture of hexamethylene diamine, adipic acid, isophorondiamine (IPD), and terephthalic acid (T). The monomeric unit derived from IPD was 0.5 wt % with respect to the copolyamide and the monomeric unit derived from T was 0.5 wt % with respect to the copolyamide. The remainder of the copolyamide are monomeric units derived from hexamethylene diamine and adipic acid, thus 99 wt %.

[0079] The process is applied using an apparatus as illustrated in FIG. 1. After take up, the yarn is drawn in a two-step process to a draw ratio of 5.0. After hot drawing, relaxation of in total 6% is applied between the 3.sup.rd and the 4.sup.th rolls pair and between the 4.sup.th rolls pair and the reeling device.

[0080] The yarn has an expected tenacity of about 93 cN/tex, elongation at break of 20%, and an expected hot air shrinkage, at 177 C. 2 min, of about 7%.

EXAMPLE 2 (Ex 2)

[0081] The same copolyamide is used as in the Example 1. The yarn is prepared according to process B using an apparatus as illustrated in FIG. 2. After take up, the yarn was drawn in a two-step process to a draw ratio of 4.9. After hot drawing, three-step relaxation process of in total 10% has been applied between the 3.sup.rd and the 4.sup.th rolls pair, between the 4.sup.rd and the 5.sup.th rolls pair and between the 5.sup.th rolls pair and the reeling device.

[0082] The yarn has an expected tenacity of 90 cN/tex, elongation at break of 22%, titer of 350 dtex, and an expected hot air shrinkage, at 177 C. 2 min, of 4%.

COMPARATIVE EXAMPLE A (Comp A)

[0083] A 350 dtex yarn consisting of 72 filaments is prepared from a homopolyamide PA66 according to process A. The homopolymer is synthesized from hexamethylene diamine and adipic acid contributing 100 wt % of the monomers.

[0084] The process is performed using an apparatus as illustrated in FIG. 1. After take up, the yarn is drawn in a two-step draw process to a draw ratio of 4.5. Higher draw ratios are not achievable as they lead to spinline breakages.

[0085] After hot drawing, relaxation of in total 6% is applied between the 3.sup.rd and the 4.sup.th rolls pair and between the 4.sup.th rolls pair and the reeling device.

[0086] The yarn has an expected tenacity of 85 cN/tex, elongation at break of 18%, and an expected hot air shrinkage, at 177 C. 2 min, of 6%.

COMPARATIVE EXAMPLE B (Comp B)

[0087] The same homopolyamide PA66 is used as in the Comparative Example A and the yarn is prepared according to process B using an apparatus as illustrated in FIG. 2. After take up, the yarn is drawn in a two-step process to a draw ratio of 4.3.

[0088] After hot drawing, three-step relaxation process of in total 10% is applied between the 3.sup.rd and the 4.sup.th rolls pair, between the 4.sup.rd and the 5.sup.th rolls pair and between the 5.sup.th rolls pair and the reeling device.

[0089] The yarn has an expected tenacity of 81 cN/tex, elongation at break of 25%, titer of 350 dtex, and expected hot air shrinkage, at 177 C. 2 min, of 4%.

[0090] The examples show the advantages of the yarn according to the invention as compared to a yarn prepared from a homopolyamide.

[0091] As Example 1 shows, the yarn according to the invention can be drawn to a draw ratio of 5.0 and reaches a tenacity of about 93 cN/tex.

[0092] As Comparative example A shows, a homopolyamide being spun at very similar conditions can be drawn only 4.5 times resulting in a yarn with tenacity of about 85 cN/tex, which is approximately 10% lower than the yarn made with the copolyamide from the Example 1.

[0093] Example 2 illustrates that if a process B is employed yarns with a tenacity of about 90 cN/tex and low hot air shrinkage can be obtained by employing the copolyamide.

[0094] If a homopolyamide is used in a process B as shown in the Comparative example B, then the yarn tenacity reaches only about 81 cN/tex, which is approximately 10% lower than the yarn obtainable from the copolyamide in Example 2.