KR19980068466A - Polyester fiber for rubber reinforcement and manufacturing method thereof - Google Patents

Abstract

According to the present invention, a fiber that is melt spun at a pulling rate of 2500 m / min or more and is directly stretched, and has a tensile strength of at least 7.0 g / d, an elongation at least 10%, an at least birefringence of at least 0.06, and a density value of 1.36 g / cm 3 to 1.38 g There is provided a polyester fiber for rubber reinforcement, which satisfies / cm 3. This polyester yarn prevents the strong deterioration and the decrease of the elastic modulus even when treated under high temperature with a rubber solution for the production of tire cords, and minimizes the strong deterioration of the cord even when used as a rubber reinforcing material. When used in the process, it has excellent dimensional stability to maintain the high elasticity of the fiber material even in the post processing step such as high temperature vulcanization process.

Description

Polyester fiber for rubber reinforcement and manufacturing method thereof

The present invention relates to a polyester fiber for rubber reinforcement represented by a tire cord or V belt fiber and a method of manufacturing the same.

In general, polyester fibers are widely used for clothing and industrial materials, and as the demand for high performance of tire cords and V-belt fibers increases, the demand for fibers having excellent dimensional stability against heat is expanding.

However, polyester yarns have a significant decrease in modulus, especially when subjected to high temperature history in the processing stages, such as the molding process of tires. This decrease in elastic modulus is accompanied by a loss of mechanical properties of the final product. Leads to degradation of product quality. In addition, if the product is subjected to repeated fatigue such as tension, compression, and bending depending on the conditions of use of the product, the heat generation is large, and thus the work loss is large.

Therefore, even in the case of automobile tires, the use of polyester fiber materials is limited for applications that require high loads or high-speed driving, and the use thereof is limited to those for low-load tires such as light trucks and passenger cars, or for speed-limited applications. This is the reason. The reason for this is that the uniaxially oriented polymer materials such as fibers can be thought of as relaxation of molecular chains caused by shrinkage in the fiber axial direction when subjected to high temperature heat. And an amine component, and it is known that the greater the concentration of the terminal carboxyl group in the polyester molecular chain, the more severe it becomes.

Therefore, studies have been actively conducted to improve the dimensional stability of heat through chemical shrinkage of polyester fibers or to reduce the shrinkage of fibers in the direction of active improvement, but have not yet achieved high elastic modulus even at a sufficiently high temperature.

In addition, as a method of reducing shrinkage, a method of lengthening the heat treatment time or increasing the heat treatment temperature during yarn manufacturing has been proposed, but this also has disadvantages due to the high manufacturing cost.

Further, as a method for imparting thermal dimensional stability, for example, the microstructure of yarns, such as Japan Special Office 63-528, 41-7892, that is, the crystallinity is 45% or more, the crystal orientation function is 0.97 or more, and the non-orthogonal orientation function is 0.6 or less. Manufacturing technology to improve the dimensional stability of polyester by manufacturing yarn, and high-oriented unoriented yarn drawn by high-speed spinning in US Patent Nos. 4,101,525 and 4,195,052 by steam or the like, the work loss is 0.004 to 0.02 lb.in at 150 ℃ Manufacturing techniques have been proposed, such as manufacturing a multi-stretched yarn and immersing it in a rubber solution to produce a cord, and using the same for a tire.

The polyester yarn thus prepared has the effect of significantly lowering the shrinkage of the yarn compared to the prior art by forming a unique microstructure having high crystallinity and low non-orientation function, thereby improving the fatigue resistance and dimensional stability of the polyester. Is a valid method from the viewpoint of preventing the restraint of non-molecular chains, and is the root of the technology currently used by many yarn makers to manufacture tire cord fibers and the like.

However, even if the above structure is satisfied, 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 the stretching, heat treatment or relaxation conditions during yarn manufacturing. In particular, in the case of a yarn having high crystallinity, the heat shrinkage stress due to the heat of the yarn is so large that the heat history in the yarn manufacturing process is large. There exists a tendency for the strength and elasticity retention of a cord to fall by the nonuniformity of a Rex effect, high tension, etc. The high crystallinity is excellent in fatigue resistance such as dimensional stability in terms of stability due to heat on the yarn itself, but it has already formed a distinctive two-phase structure (TWO PHASE) in the yarn state. The increase in the temperature may occur rapidly, and the effect in the post-processing process involving twisting and heat as much as the improvement effect of the yarn itself is insufficient.

In other words, the conventional manufacturing method of the polyester fiber for rubber reinforcement while maintaining high crystallinity through the manufacturing process with a high temperature heat treatment in order to improve the mechanical properties and thermal shrinkage in the yarn state, while minimizing the orientation of non-government After forming the yarn of the above structure to immerse in the rubber solution to achieve the required characteristics as the final tire cord as described above, in the case of such a manufacturing process is accompanied by a high temperature process in the yarn to achieve the required cord characteristics To increase the residual thermal stress of the yarn, to limit the yarn production at high speed by high temperature treatment, and to increase the energy used, the yarn production cost increases and the thermal stress accumulated during yarn making in the dipping process is relaxed. There is a limit in dipping speed, because higher thermal energy must be involved than in. In addition, there is a limit on the amount of microstructure change during the dipping process, which is evaluated as a disadvantageous method for acquiring the mechanical properties and the dimensional stability of the cord.

An object of the present invention is to provide a polyester fiber excellent in dimensional stability against heat and suitable as an fiber for industrial materials, and a method for producing the same.

In order to achieve the above object, the present inventors form a three-phase structure in which the semi-crystal structure coexists in the yarn, which is not clearly distinguished from the crystal and the amorphous region, unlike the conventional method, and post-processing, that is, adhesion with rubber In order to improve the dimensional stability of the heat by using a structural reforming technology that allows the recrystallization to be formed in the heat treatment process, such as latex treatment process to maintain the high strength and high elasticity even at high temperatures during rubber reinforcement.

That is, according to the present invention, the fibers are melt spun at a pulling rate of 2500 m / min or more and are directly drawn, and the tensile strength is 7.0 g / d or more, the elongation at least 10%, the specific birefringence of 0.06 or more, and the density value of 1.36 g / cm 3 to Provided is a polyester reinforcing polyester fiber characterized by satisfying 1.38 g / cm 3.

Further, according to the present invention, melt spinning at a pulling rate of 2500 m / min or more to obtain a polyester non-drawn yarn having a density value of 1.355 g / cm 3 or more, which is stretched at a temperature below the secondary transition temperature of the polyester, and below the polyester crystallization temperature. The heat-fixing and re-treatment at is provided with a method for producing a polyester fiber for rubber reinforcement, characterized in that the tensile strength is at least 7.0 g / d, the elongation at least 10%.

Hereinafter, the present invention will be described in more detail.

The dry heat shrinkage rate of polyester-treated cord is related to the content of amorphous region and the orientation of molecular chains in amorphous region, and it is used for rubbers which are repeatedly subjected to fatigue, compression, bending, etc. under high temperature during use such as tires and belts. Fiber reinforcement materials require high dimensional stability due to extreme strength and low elastic modulus. To do this, the morphology of single filament filaments, especially the individual single filament filaments and the fiber microstructure of the filament during the formation of molten fibers, There is a strong relationship between maintaining strength and dimensional stability.

According to the present invention, in order to facilitate the microstructural change during the dipping process and to increase the amount of change, the density value representative of the crystallization level is limited within a certain range and the non-governmental birefringence is maximized from the time of yarn manufacturing. A three-phase crystal structure having a specific microstructure is formed on the yarn.

Preferably, the polyester yarn of the present invention satisfies the properties of at least 7.0 g / d of tensile strength, at least 10% of cut elongation, at least 0.06 of non-refractive birefringence, and a density value of 1.36 g / cm 3 to 1.38 g / cm 3.

Thus, the polyester yarn of the three-phase structure is changed into a stable two-phase structure in the process of manufacturing the tire cord. That is, after the fiber microstructure is rearranged through the recrystallization process using the thermal energy in the dipping process of the yarn into the rubber solution, a tire cord having a stable two-phase structure of crystal and amorphous is obtained.

According to the present invention, in order to exhibit the properties of the rubber reinforcing fibers as described above, in the spinning and stretching process, a non-stretched yarn having a molecular chain having a degree of crystallinity of 10% or more determined by the density method is produced. After stretching to low draw ratio at low temperature below the secondary transition temperature, the tension of the molecular chains in the amorphous region by stretching is minimized, and heat crystallization and reflex treatment at the temperature below the crystallization temperature are used to increase the strength of the yarn. Polyester filament yarns are produced under conditions that minimize to within the range maintained only at 7.0 g / d or more.

In this production method, it is preferable that the undrawn yarn is spun at a speed of 2500 m / min or more to have a density value of 1.355 g / cm3 or more. The reason for producing a non-drawn yarn having a density value of 1.355 g / ㎣ or more is to promote crystallization even at low temperatures during the multistage drawing process by forming molecular crystals and crystal nuclei by well-developing molecular chain orientation in the take-off stage after spinning. to be. Such unstretched yarn is drawn at a low draw ratio at a low temperature below 80 ° C., which is below the secondary transition temperature where crystallization is not abruptly involved. At this time, the draw is preferably at least two stages of multistage stretching, in particular two stages of stretching. It is preferable that 50% or more of the magnification is stretched in the first stage, and the elongation of the fibers is 10% or more in the second stage or more. After stretching, the fiber strength can be maintained in the heat treatment zone, the density value does not exceed 1.380 g / cm 3, and is maintained at a temperature of 130 ° C. or lower, which is below the polyester crystallization temperature, in order to suppress high crystallization. do.

The polyester yarn prepared as described above prevents the strong decrease and the decrease in the elastic modulus even when treated at high temperature with a rubber solution for the production of tire cords, and minimizes the strong drop in the cord even when used as a rubber reinforcement material. The treatment cord thus obtained has excellent dimensional stability to maintain high elasticity of the fiber material even in post-processing steps such as high temperature vulcanization processes when used for rubber reinforcement such as tire materials.

The physical properties shown in the above descriptions and the examples and comparative examples presented below are measured and evaluated by the following method.

◇ Density: Make density gradient tube with normal heptane and carbon tetrachloride solution and measure the density of yarn at 25 ℃.

◇ Non-governmental birefringence rate (△ n _a ): obtained by the following equation.

Where Δn is the average birefringence, Is the crystallinity degree, Is the crystal orientation coefficient.

The average birefringence (Δn) is obtained by measuring the retardation obtained from the interference chromaticity of the sample using a Berek compensator attached to a polarizing microscope and calculating the result by the following equation.

Δn = R / d

Where d is the thickness of the sample (nm) and R is the retardation (nm).

The crystallinity Vc can be calculated by the following formula using a density value (ρ: g / cm 3).

here, (g / cm 3) = 1.455, (g / cm 3) = 1.335

◇ dry heat shrinkage ratio of treated cords: in the one left the sample at 25 ℃, 65% RH atmosphere, 24 hours a weighed during early summer corresponding to 0.1 g / d of the sample measurement length L _o, left standing sample 150 ℃ hot air oven After the heat treatment under tension for 30 minutes, it was taken out of the oven, left for 4 hours, and then weighed with a superload corresponding to 0.1 g / d of the sample.

ΔS (%) = [(L -L _o ) / L _o ] × 100

Features and other advantages of the present invention as described above will become more apparent from the embodiments described below. However, the present invention is not limited to the following examples.

Examples 1-3 and Comparative Examples 1-3

Polyethylene terephthalate with an intrinsic viscosity of 1.0 was extruded through a spinneret having 250 orifices with a diameter of 0.6 mm at a spinning temperature of 300 ° C., and a thermos box with a length of 150 mm and a temperature of 300 ° C. was installed in the lower part of the cap. Thus, the yarn was uniformly cooled and solidified, and was not wound separately, but was stretched through heated gothrol, and heat-set and rexed. The single yarn fineness of the final yarn was adjusted to 4 to 6 deniers. Other sacrificial conditions for each example are shown in Table 1 below.

The yarn prepared by the method of Example and Comparative Example was twisted with 47.5 times / 10 cm lower edge in Z direction and 47.5 times / 10 cm in S direction using a twisting machine and immersed in a conventional RFL solution. After drying at 1 ° C. for 1 minute, heat treatment was performed at 245 ° C. for 2 minutes under 3% tension, and 1.5% of relaxation was performed for 1 minute at 245 ° C. to prepare a treatment cord. The physical properties of the yarn and the treatment cord for each example are shown in Table 2 below.

division unit Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Room speed m / min 3000 3000 3200 1300 1150 2600 Undrawn Density g / cm 3 1.358 1.357 1.360 1.345 1.343 1.355 1 stage draw ratio ship 1.63 1.60 1.57 1.75 1.10 1.70 1st draw temperature ℃ 75 75 75 100 100 100 2-stage draw ratio ship 1.20 1.23 1.12 1.35 1.95 1.30 2 stage drawing temperature ℃ 80 80 80 180 180 180 Heat setting temperature ℃ 130 130 130 230 230 240 Relex temperature ℃ cold 120 120 120

division unit Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Yarn Properties burglar g / d 7.5 7.8 7.9 8.4 8.4 8.2 Elongation % 12.5 12.0 14.0 12.6 12.7 10.1 Mill degree value g / cm 3 1.369 1.373 1.380 1.398 1.396 1.401 Non-governmental birefringence 0.100 0.092 0.072 0.047 0.051 0.043 Treatment Code Properties strong Kg 15.0 15.2 14.9 14.0 14.1 14.2 Dry heat shrinkage % 2.6 2.4 2.4 4.3 4.2 3.9

The polyester yarn obtained by the method of the present invention prevents the strong drop and the decrease in the modulus of elasticity even when treated at high temperature with a rubber solution for the production of tire cords, and minimizes the strong drop in the cord even when used as a rubber reinforcing material. When used for reinforcing rubber as the material, it has excellent dimensional stability to maintain high elasticity of the fiber material even in the post-processing step such as high temperature vulcanization process.

Claims (3)

Fibers melt-spun at a pulling rate of 2500 m / min or more and directly drawn to satisfy tensile strength of at least 7.0 g / d, elongation at least 10%, specific birefringence of 0.06 or more, and density values of 1.36 g / cm 3 to 1.38 g / cm 3 Polyester fiber for reinforcing rubber, characterized in that. Melt spinning at a pulling speed of 2500 m / min or more to obtain polyester unstretched yarn having a density value of 1.355 g / cm3 or more, which is stretched at a temperature below the secondary transition temperature of the polyester, and heat-set and rexed at a temperature below the polyester crystallization temperature. Process for producing a polyester fiber for rubber reinforcement characterized in that the tensile strength of 7.0 g / d or more, the elongation at least 10%. The method according to claim 2, wherein the secondary transition temperature is 80 ° C or less and the crystallization temperature is 130 ° C or less.