LU100697A1 - High modulus single twisted nylon 6.6 wire - Google Patents

Abstract

ABRIDGED: High modulus, single twist, nylon 6.6 wire having tensile stress values at 4% elongation between 2.0 and 2.8 cN / dtex are used as reinforcement in shaped rubber composites. The minimum heat shrinkage of said cords is 4% and the maximum heat shrinkage is 7%.

Description

The present invention relates to high modulus nylon 6.6 twisted yarns as reinforcement in tires and industrial rubbers.

BACKGROUND OF THE INVENTION

It is well known that nylon 6.6 yarns have bielastic tensile properties, which means a low initial modulus and a high final modulus. The low initial module makes the softening / expansion process of the tire possible without any distortion in a green tire, and the high final module (module after the transition point from the low to high module) improves the durability at high speed of the tire as ply peak in radial tires (PCR and LT).

In document US 3,343,363, strands / threads of nylon 6.6 with single twist and cords having an initial modulus between 25 and 60 g / d and a toughness greater than 7.0 g / d at room temperature were exposed as tire reinforcements. Initial modulus values are determined in accordance with

ASTMA1380-61 T.

In document US Pat. No. 3,849,976, high modulus nylon 6.6 cords twist one strand, two strands and three strands having an L5 module greater than 60 g / d obtained by applying a high stretch at a high temperature during a process of hot stretch were exposed as a tire reinforcement.

In document US 4,284,117, nylon, polyester, rayon and aramid yarns with a single twist are exposed as reinforcements of crown ply in radial tires.

In order to obtain the high modulus single twist yarns, existing ordinary nylon 6.6 yarns having an ordinary modulus (tensile stress level less than 1.25 cN / dtex at 4% elongation, or a modulus level tensile at 4% elongation less than 31.25 cN / dtex or 35.4 g / d) were used. These single twist yarns prepared from ordinary modulus yarns had very high stiffness and lower bending fatigue resistance due to excessive stretching at high temperatures.

SUMMARY OF THE INVENTION

The object of the present invention is to produce single twist strands having a high modulus as reinforcement in industrial tires and rubbers.

As can be seen in the patent literature, the values of initial modulus or LASE (Load At Specified Elongation) of nylon yarn and cord can be increased by applying high stretches at high temperatures. In order to obtain stable (non-reversible) properties, which are largely maintained even after going into the resting state (conditioned with free cut ends under laboratory conditions), it was necessary to expose the nylon 6.6 wires or cords at a temperature above 250 ° C. Under these conditions (high stretching at high temperature), the wires and cables become more rigid and they partially lose their resistance to fatigue in bending and compression.

According to the invention, nylon 6.6 threads are drawn at more than 5% and less than 12% in a temperature range of 230-250 ° C and wound on reels or drums with a winding tension between 150 g and 500 g per thread (strand). The same conditions are also valid for single-twist yarn fabrics such as a roll.

DETAILED DESCRIPTION OF THE INVENTION

According to the invention, in order to produce high modulus single twist yarns, high modulus raw nylon 6.6 yarns are used instead of ordinary modulus raw nylon 6.6 yarns which resulted in improved fatigue resistance.

The tensile stress value at 4% of said raw nylon 6.6 yarns is greater than 1.30 cN / dtex, preferably between 1.35 and 1.60 cN / dtex (determined with a dynamometer in accordance with ASTM D885-16).

Long stretch yarns with a high modulus retain their properties in coils, because they are not allowed to relax, and they are used in a tire without encountering significant relaxation (fall in modulus).

High modulus strands in stretch fabrics also retain their drum properties, because they are not allowed to relax, and they are used in a tire without encountering significant relaxation (fall in modulus).

The tensile properties of twisted nylon 6.6 high modulus yarns are determined after 24 hours conditioning on a reel (without unwinding) under a winding tension at 24 ° C and with a relative humidity of 55% (ASTM D885-16 ). After conditioning, the twisted wires are tested within one minute after unwinding the coil.

In the case of fabrics, the test fabric weaves are packaged as fabric weave (without separation or cutting of the threads of the fabric weave as fabric) under the same conditions as mentioned above. After conditioning, the threads cut in the plain weave are tested within one minute.

Such single twist yarns have a 4% elongation stress from 2.0 cN / dtex (modulus of 51 g / dtex and 56.7 g / d) to 2.8 cN / dtex (modulus of 71.4 g / dtex and 79.3 g / d) and heat shrinkage at 177 ° C from 4.0% to 7.0%.

The stress at 4% elongation is determined according to the following formula: Constraint at 4% elongation (cN / dtex) = Tension at 4% elongation (cN) / linear density (dtex).

The nominal dtex of the wire is taken as the linear density (for example 1400 for a construction of 1400x1).

The modulus values are calculated by multiplying the stress values at an elongation of 4% by 25 in order to find the stress value necessary for an elongation of 100%.

The heat shrinkage of wires and cables is determined with a Testrite heat shrinkage tester under pretension of 0.045 g / dtex at 177 ° C with an exposure time of 2 minutes.

According to the invention, the heat shrinkage of cables is within the limits of 4% and 7%, preferably 5.0% and 6.5%.

According to the invention, the total nominal dtex of cables can vary between 300 and 20,000 dtex.

According to the invention, in order to have an optimum retention force and resistance to fatigue in bending, the twisting factors of the wires are adjusted between 30 and 50, preferably 35 and 45, in accordance with the following formula:

Twist factor = (t / m x SORT (tex / 1000).

The high modulus twisted nylon 6.6 strands can be used as reinforcement in industrial tires and rubbers.

Definitions:

Dtex: the weight in grams of wire having a length of 10,000 meters.

Denier: the weight in grams of thread having a length of 9,000 meters.

g / d: gram / denier g / dtex: gram / dtex

Linear density: weight per unit length in g / dtex or g / d (denier)

Module at 4% elongation: (constraint at 4% elongation) x25 in g / d or g / dtex

Module L5: module at 5% elongation (constraint at 5% elongation) x20 in g / d or g / dtex

Tenacity: breaking force / total linear density (g / dtex)

Twisting: twist per meter (t / m or rpm)

Claims (4)

1. Single twist polyamide 6.6 wire coated and thermofixed (twisted strand) which is prepared from a raw polyamide 6.6 yarn having the value of 5 tensile stress greater than 1.30 cN / dtex, preferably between 1.35 and 1.60 cN / dtex at 4% elongation (determined with a dynamometer in accordance with ASTM D885-16) characterized in that - its tensile stress at an elongation of 4% (determined with a dynamometer in accordance with ASTM D885-16) is greater than 2.0 cN / dtex 10 and less than 2.8 cN / dtex, - and its heat shrinkage is greater than 4.0% and less than 7.0% determined at 177 ° C under a pretension of 0.045 g / dtex with an exposure time of 2 minutes. 2. The stress value at a 4% elongation of the raw wire according to claim 1 is preferably greater than 1.35 cN / dtex and less than 1.50 cN / dtex. 3. The said simple twisted wire according to claim 1 preferably has a 20 heat shrinkage of 5.0 to 6.5%. 4. The dtex of said single twisted wire according to claim 1 is at least 300 dtex and at most 4,000 dtex. 5. The twist factor of the single twist yarn according to claim 1 is at least 30 and at most 50, preferably between 35 and 45 calculated according to the following formula: Twist factor = (t / m x SORT (tex / 1000).