LU100697B1 - 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

NYLON 6.6 THREAD YARNS WITH HIGH MODULE DOMAIN OF THE INVENTION

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

BACKGROUND OF THE INVENTION

It is well known that nylon 6.6 threads have bi-elastic tensile properties, which means a low initial modulus and a high end modulus. The initial low module makes the tire softening / expanding process possible without any distortion in a green tire, and the high end module (modulus after the low to high modulus transition point) improves the high speed durability of the tire as a web top in radial tires (PCR and LT).

In US 3,343,363, single twisted nylon 6.6 strands / yarns and cords having an initial modulus of 25 to 60 g / d and a toughness greater than 7.0 g / d at room temperature have been disclosed as tire reinforcements. Initial modulus values are determined in accordance with ASTM A1380-61T.

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

In US 4,284,117, single twisted nylon, polyester, rayon and aramid yarns are exposed as crown ply reinforcements in radial tires.

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

SUMMARY OF THE INVENTION

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

As is apparent in the patent literature, the initial modulus or LASE (Load At Specified Elongation) values of nylon yarns and cords can be increased by applying high stretching at elevated temperatures. In order to obtain stable (non-reversible) properties, which are maintained to a large extent even after going to rest (packaged with free-cutting ends under laboratory conditions), it was necessary to expose the wire or cords of nylon 6.6 at a temperature above 250 ° C. Under these conditions (high stretch under high temperature), the wires and cords become stiffer and they partially lose their resistance to flexural and compressive fatigue.

According to the invention, nylon threads 6.6 are stretched to 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 wire (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 the high modulus single twist yarns, the high modulus raw nylon 6.6 yarns are used instead of ordinary modulus raw nylon 6.6 yarns that result in improved fatigue strength.

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).

High-modulus high-modulus yarns retain their roll properties because they are not allowed to relax, and they are used in a tire without experiencing significant relaxation (modulus drop).

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

The tensile properties of the high modulus nylon 6.6 twisted yarns are determined after a 24 hour reel (non unwind) package under winding tension at 24 ° C and 55% relative humidity (ASTM D885-16 ). After conditioning, the twisted wires are tested within one minute after unwinding the coil.

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

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

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

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

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

Heat shrinkage of the wires and cords was determined with a Testrite heat shrink tester at a pretension of 0.045 g / dtex at 177 ° C with an exposure time of 2 minutes.

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

According to the invention, the total nominal dtex of the cords can change between 300 and 4000 dtex.

According to the invention, in order to have optimum retention force and flexural fatigue strength, the twisting factors of the yarns are adjusted between 30 and 50, preferably 35 and 45, according to the following formula:

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

High modulus twisted nylon 6.6 strands can be used as reinforcement in tires and industrial rubbers. Definitions:

Dtex: the weight in grams of thread 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: (stress at 4% elongation) x25 in g / d or g / dtex

L5 module: modulus at 5% elongation (stress at 5% elongation) x20 in g / d or g / dtex Toughness: breaking force / total linear density (g / dtex)

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

Claims (5)

1. A single-stranded, heat-set (twisted strand) polyamide 6.6 twisted yarn which is prepared from a raw polyamide 6.6 yarn having a tensile stress value greater than 1.30 cN / dtex, preferably between 1.35 and 1.60 cN / dtex at an elongation of 4% (determined with a dynamometer according to ASTM D885-16) characterized in that - its tensile stress at 4% elongation (determined with a dynamometer according to ASTM D885- 16) is greater than 2.0 cN / dtex 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 pretension. 0.045 g / dtex with an exposure time of 2 minutes. 2. The stress value at a 4% elongation of the raw yarn according to claim 1 is preferably greater than 1.35 cN / dtex and less than 1.50 cN / dtex. 3. The single twisted wire of claim 1 preferably has a 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 4000 dtex. 5. The twisting factor of the single twist wire 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 / mx SORT (tex / 1000) .