KR930010801B1 - Polyester fiber for rubber reinforcement - Google Patents

Abstract

The polyester filament yarn for rubber reinforcement is characterised in that the yarn has a max. thermal stress of at most 0.5 g/d in the temp. range of 60-250 deg.C and exhibits a decrease of thermal stress beyond 210 deg.C. The yarn satisfies the following characteristics; a long period value of at most 15.5 μm; fa x (1-Xc) > 0.330 (where fa = amorphous orientation, and Xc = percent crystallinity, 0.30-0.45); a crystallite face size ((105) plane) of at most 6.5 μm; and a crystal volume of 0.5 x 105 ∦3 - 1.54 x 105 ∦3.

Description

Polyester fiber for rubber reinforcement

1 is a shrinkage stress graph according to the temperature change.

The present invention relates to a polyester fiber for reinforcing rubber excellent in thermal dimensional stability and chemical resistance.

Industrial polyester fiber represented by polyester tire cord has benzene ring in its structure, and its molecular chain is rigid, so it has better elastic modulus than nylon tire cord and extremely fatigue resistance compared to rayon yarn.

In addition, due to the high glass transition temperature, flat spots are low, and creep resistance and durability are excellent, which are widely used as rubber reinforcements for passenger tires and light trucks, and the demand is increasing.

In addition, polyester yarns are required to improve thermal dimensional stability and chemical stability, in particular, adhesion to reinforcing materials such as rubber.

However, since polyester yarn has a large work loss and generates a large amount of heat, the physical properties of the yarn are severely degraded. This deterioration is caused by moisture and amines present in the tire, and the greater the concentration of the terminal carboxyl group in the molecular chain, the more severe the degradation of strength and fatigue resistance.

In other words, many studies have been conducted to manufacture polyester tire cords having high elasticity and excellent shape stability, which are advantages of polyester, while minimizing heat generation due to hysteresis loss, which is the biggest problem of polyester tire cords. It is done.

That is, Japanese Patent Application Laid-Open No. 61-97493 proposes a method of improving the strength utilization by having a terminal modulus, which is the modulus of elasticity at the cutting point on the stress load curve, of a yarn having a negative value. In 58032, a method of improving fatigue resistance by increasing molecular chain fluidity of non-government using high-speed spinning has been proposed.

In addition, Japanese special publications 63-528, 41-7892 and the like have a fine structure of yarn, i.e., a yarn having a crystallinity of 45% or more, a crystal orientation function of 0.97 or more, and a non-orthogonal orientation function of 0.6 or less, thereby producing work loss of polyester. Improved manufacturing techniques have been proposed.

However, lowering the terminal modulus appears to have a significant effect on improving strength utilization, but there is no mention of specific methods of making yarns with such characteristics. In Japan Special Publication No. 41-7892, high-temperature steam was used, and in Japanese Patent Application No. 57-15441, the method of reducing the draw ratio through high-speed spinning and reducing was used. At high terminal modulus unfolded in a favorable direction. In addition, the method by the steam method is effective, but it is not preferable because the cutting factor in terms of the operation when manufacturing the yarn increases.

In addition, the method of lowering the terminal modulus by strengthening the heat treatment or relaxation rate has the effect of lowering the value, but rather, the strength deterioration tends to be more severe during the twisting and dipping treatment. In addition, the terminal modulus was lowered but the trend was not consistent with the strong utilization rate.

In addition, the method of improving the work loss of polyester by producing yarns having high crystallinity and low non-orientation function can be regarded as a valid method from the viewpoint of preventing the binding of molecular chains in the amorphous region.

However, even if it satisfies the same structure as described above, since the orientation of the amorphous chain is maintained at a low level, it is not sufficient because the stress history due to heat varies depending on stretching, heat treatment, or relaxation conditions during yarn manufacturing.

Particularly, in the case of yarn having high crystallinity, the shrinkage stress caused by the heat of the yarn is also great as the heat history of the yarn manufacturing process is so large, and this is accompanied by recrystallization process during high heat treatment such as dipping process. Folded crystals are mainly formed around free molecular chains with misaligned orientations in the region, leading to a decrease in strength, elasticity and retention, and high crystallinity in terms of dimensional stability in terms of heat stability in the yarn structure. It is excellent in fatigue resistance, but it already forms a distinct two phase in the yarn state, so the increase in crystal size and long cycle size can be caused by high temperature post-heat treatment, so that the work loss of the yarn itself can be improved. It is difficult to expect the effect of improving fatigue resistance by twisting and post heat treatment.

The present inventors have improved the conventional method as described above, and the overall physical properties, such as excellent strength and high heat treatment as well as excellent fatigue resistance even when used in conjunction with rubber to produce a yarn with excellent strength and hydrophilic stability For this reason, the yarn is not clearly distinguished from the crystal and the amorphous region, that is, a three-phase structure in which a semi-crystalline structure with indefinite long-cycle formation coexists is formed so that the recrystallization is formed in the tension heat treatment during the dipping process and the rex zone. The loss of the ties molecular chain, that is, the defect has a crystal structure with low defects to minimize the physical properties such as strength and modulus due to the post-process.

In addition, quasi-crystals that are already present in the yarn undergo crystallization while undergoing heat treatment during dipping, and are composed of crystals having a crystal size of 10% or more smaller than the conventional method. By developing the network structure, the shape stability is excellent. Especially, the folded crystal formation is minimized during the recrystallization, and the content of the tensioned tie molecular chain that connects the crystal is increased, so that a yarn having high elastic modulus can be manufactured. .

And JOURNAL OF POLYMER SCIENCE, 1989, Vol. 37 ＂explains that the dry heat shrinkage of polyester fiber is proportional to the product of the content of amorphous region and the orientation of molecular chains of amorphous region.

In addition to these facts, the present inventors found that the following facts are more important factors in rubber reinforcing fibers such as tire materials.

In other words, it is important to improve toughness due to extreme strength and elastic modulus, and fiber stiffeners under repeated fatigue, compression, and bending fatigue at high temperatures, such as tires, require high dimensional stability. The crystal regions should be evenly distributed.

In other words, the shrinkage phenomenon, an important indicator of dimensional stability, is a phenomenon in which the molecular orientation of the amorphous region is distorted when heat is applied to the molecular chain. If these crystals have a dense net structure, that is, even if they have the same crystallinity, small crystals are distributed, and if the long period value, which is an index representing the size of crystals and amorphous phases, forms small, dense, regular macrostructures, Deformation by heat, especially at higher temperatures, prevents morphological changes such as shrinkage, that is, plays a role such as crosslinking with sulfur in rubber.

In other words, there is a limit to the improvement of physical properties of rubber reinforcing yarns without improving the size and distribution long period of crystal in improving shape stability.

The present invention aims to produce a polyester yarn excellent in fatigue resistance and dimensional stability even under conditions subjected to repeated fatigue movement at a high temperature of 100 ° C. or higher by arranging in rubber, and having physical properties of the following characteristics.

That is, in the yarn, the crystallinity value measured under the condition of temperature 20 ℃ in the density gradient tube made of carbon tetrachloride and normal heptane is 45% or less, the crystal size of (100) plane representing the crystal a axis is 40Å or less, and the (010) of the b axis The size of the surface is 55 kPa or less, the size of the (T05) crystal plane close to the fiber axis is 60 kPa or less, and the long period is characterized by having a compact structure of 155 kPa or less.

Hereinafter, the characteristics of the formed crystal will be defined as the crystallization formula below.

Crystal volume ³ = (a-axis crystal size) x (b-axis crystal size) x (long period) x (crystallization degree)

The size of the crystal was calculated by obtaining the half width from the equatorial and meridian X-ray interference peaks and substituting it into the Scherrer equation (X = 0.9).

The long period value was calculated from Bragg's equation by obtaining an meridian interference diffraction line using an incineration X-ray scattering apparatus using CuKα rays with a wavelength of 1.54 Å.

Another feature of the present invention is the heat shrinkage stress behavior according to the temperature change in the yarn. Since the yarn used for rubber reinforcement requires excellent mechanical properties, stresses due to strong elongation, high heat treatment, etc. accumulate, and in order to alleviate this as much as possible, a method of applying a rex process during yarn manufacturing is effective. The study found that there was a limit to relieving stress in the Relex process. This is mainly because the cumulative stress is mostly a stress caused by heat from drawing and heat treatment.

Therefore, the conventional manufacturing method that induces high crystallization like the conventional fiber, there is no limit to stress relaxation.

In addition, one of the limitations of other stress relaxation methods, including the Relex process, is to reduce the orientation of the amorphous region to 0.6 or less, as in Japanese special publications 63-528 and 41-7392 to reduce shrinkage in yarn. Even in the case of flotation, the folded molecular chain and many defects on the crystal surface of the crystal surface during the high crystallization and the recrystallization process by the post-process cannot completely free the restraint of the non-molecular chain, and also reduce the Thai molecular chain fraction. It is not easy to obtain the properties of high elasticity due. Therefore, the inventors have found that the crystallinity degree (Xcv) by the density gradient pipe method is 30% or more and 45% or less required to maintain the polyester fiber after the stretching process to maintain at least 6.0 g / d, which is the minimum physical property of the yarn for rubber reinforcement. Has a long period of 155 Å or less, and has a unique microstructure having a crystal volume of 0.5 × 10 ⁵ Å ³ or more and 1.54 × 10 ⁵ Å ³ or less, and has a maximum heat shrinkage stress of 0.5 g / d or less. All post-treatment temperatures applied for the use of polyester fibers for rubber are above 220 ° C. Above this temperature, thermal shrinkage stress was not very high at temperatures before 200 ° C in the case of conventional rubber, especially tire yarns. The heat shrinkage stress tends to be considerably higher at high temperatures above ℃, whereas the yarns invented by the present inventors exhibit heat shrinkage at high temperatures above 210 ℃. The force has a sharp drop.

Therefore, the yarn of the present invention has a crystal orientation function value of less than 0.94 and the non-orientation function also has a value of 0.6 or more, and the yarn itself has a dry heat shrinkage ratio of 8% or more measured in a hot air oven at 150 ° C. for 30 minutes under tension. Dimensional stability and fatigue resistance due to factors such as compact macrostructure and network of crystals due to recrystallization during dipping process due to the microstructural characteristics and different heat shrinkage stress behaviors, and a significant decrease in heat shrinkage stress at high temperature. This is an excellent polyester fiber for rubber reinforcement.

And the characteristics of the present invention will be described in detail with the heat shrink stress curve of FIG.

1 is a characteristic of the heat shrink stress curve tested on the basis of 1,000 denier, a curve is a general polyester cord polyester yarn, b curve is a polyester yarn with a slightly improved conventional dimensional stability, c is a The heat shrink stress curve of the yarn was shown, and the test conditions were measured for the heat shrink stress from room temperature to 300 ° C. at a heating rate of 4 ° C. at an initial load of 50 g.

In addition, the orientation function (f _c ) of the crystal among the important fiber microstructural factors of the present invention is obtained from the half width (X _hkl ) in the azimuth diffraction patterns of the (010) plane and the (100) plane as shown in Equation 1 below. the average value of the orientation function, amorphous orientation function (f _a) was obtained from (2) below, by the birefringent value (Δn), a crystallinity (Xcv) and crystal orientation function (f _c) by a polarization microscope expression.

f _c = … … … … … … … … … … … … … … … … … … … (One)

only,

Δn = … … … … … … … (2)

only, Is 0.27, Has a value of 0.20.

[Examples 1-3 and Comparative Examples 1-4]

Polyethylene terephthalate having an intrinsic viscosity of 0.80 prepared by the polycondensation reaction was made into a chip (CHIP) form and then subjected to solid phase polymerization to obtain high polymerization degree.

Melt spinning was using a spin-drawing apparatus, and the melt spinning machine is an extruder. The melt polymer temperature and the feed pipe temperature were controlled between 295 ° C and 305 ° C. The intrinsic viscosity of the polyester fiber thus obtained has a value in the range of 0.90 to 1.0.

The spinneret was extruded to a diameter of 0.50 mm, and a thermos cylinder having a length of 200 mm and a temperature of 330 ° C. was installed in the lower portion of the cap, and cooled and solidified under a cooling air of 25 ° C. under the thermo cylinder.

It was then radially drawn under the conditions of Table 1. The single yarn fineness of the final yarn was adjusted to 4.00 denier, and the yarn physical properties at this time are shown in Table 2.

Compared with the comparative example according to the prior art (Japanese Patent Application No. 63-528), the present invention has a completely different heat shrinkage stress behavior ((b) and (c) in FIG. 1) and a fiber fine structure. After heat treatment for 1 minute at 160 ℃ temperature for 2 minutes under tension condition of 3% at 245 ℃ temperature, loose heat treated fiber at 1.5 ℃ for 1.5 minutes at 240 ℃ temperature for 30 minutes at 150 ℃ A yarn with excellent dimensional stability with a dry heat shrinkage value of 3% or less measured under tension could be prepared.

TABLE 1

TABLE 2

Claims (1)

At least 90 mol% is made of polyethylene terephthalate, and polyester fiber for reinforcing rubber, characterized in that to satisfy all of the following characteristics at the same time. Below i) Polyester fiber with the characteristic that the maximum heat shrinkage stress is 0.5g / d or less between 60 ℃ and 250 ℃, and the heat shrinkage stress is reduced above 210 ℃ ii) Long period value is less than 155Å iii) f _a × (1-Xcv)> 0.330 iv) The crystal size of the plane (T05) perpendicular to the molecular chain is 65 Å or less, and the size of the crystal volume is 0.5 × 10 ⁵ Å ³ or more and 1.54 × 10 ⁵ Å ³ or less F _a : non-orientation function, X _CV ; Crystallinity