KR100235758B1 - High modulous polyester yarn for tire cord and composites and the manufacture method - Google Patents

Abstract

The yarns of the present invention are made by spinning PEN or other semi-crystalline polyester polymers produced by combining similar hard monomers in a suitable amorphous state with orientation and crystallinity. This is accomplished by selecting process parameters such that undrawn polyester yarns having a birefringence of at least 0.030 are formed. Thereafter, the spin yarn is hot drawn to have a total draw ratio of 1.5 / 1-6.0 / 1, and the resulting Tg of the semi-crystalline polyester yarn is at least 100 캜 and the melting point is raised at least 8 캜. Yarns with a stiffness of at least 6.5 g / d, dimensional stability (EASL + shrinkage) of less than 5% and shrinkage of 4% or less are preferred.

The resulting yarns exhibit lower shrinkage and surprisingly high modulus and stiffness than conventional yarns.

Description

[Name of invention]

High Modulus Polyester Yarn for Tire Cords and Composites and Manufacturing Method Thereof

[Brief Description of Drawings]

1 is a graph comparing the modulus for the PEN yarns of Examples 1 and 2 at a stiffness of 6.2 g / d (54.7 mN / dtex).

Detailed description of the invention

[Technical Field]

The present invention is particularly advantageous as a fiber reinforcement of tires and relates to yarns made of polyethylene naphthalate (PEN) multifilament yarns and similar rigid monomer combinations having very high modulus, good stiffness and low shrinkage. PEN yarn according to the present invention has improved modulus and dimensional stability compared to PEN yarn prepared by conventional processes. According to one aspect of the invention there is provided a multifilament PEN manufacturing process.

[Background]

Generally, polyethylene terephthalate (PET) filaments are widely used in industrial applications such as radial tire bodies, conveyor belts, seat belts, V belts and hoses. However, for more demanding applications such as the body of monoply high performance tires, higher modulus and dimensional stability are desirable and are required for radial passenger car tire belts.

Dimensional stability is determined by the sum of elongation and shrinkage at 4.5 g / d (39.7 mN / dtex). US Pat. No. 3,616,832 to Shima et al. Presents a rubbery article reinforced with PEN with good dimensional stability and stiffness. US Pat. No. 3,929,180 to Kawase et al. Presents a tire using PEN as a carcass reinforcement. However, these patents relate to low undrawn birefringence PENs prepared by conventional methods and are unable to fully achieve the potential properties of this material as for the purposes of the present invention. This is also the case in Hamana et al. 1,445,464, which teaches about optimal drawing of spun PEN, which is typically radiated.

US Pat. No. 4,000,239 to Hamana et al. Provides an unstretched PEN manufacturing process for electrically melting fabrics with high melting points. Because these materials are manufactured under high stress conditions that are effective in high crystallinity or at least highly nucleated structures, they have reduced drawability and do not achieve high modulus for the intended applications of the present invention. will be.

Products for such applications are provided in US Pat. No. 4,001,479, et al., Which relates to some oriented yarns having high elongation and low stiffness.

The yarns of the present invention are made by spinning other semicrystalline polyester polymers prepared from the combination of PEN or similar hard monomers in an optimal state of amorphous orientation and crystallinity. The present invention is accomplished by selecting process parameters such that undrawn polyester yarns having a birefringence of at least 0.030 are formed. Thereafter, the drawn yarn is thermally drawn to have a total draw ratio of 1.5 / 1-6.0 / 1, and the resultant Tg of the stretched semicrystalline polyester yarn is 100 ° C or more and the melting point is raised by at least 8 ° C. Preferred is a yarn having a stiffness of at least 6.5 g / d (57.4 mN / dtex), dimension stability (EASL + shrinkage) of less than 5%, and shrinkage of 4% or less.

The resulting yarns show surprisingly high modulus, stiffness and low shrinkage compared to conventional yarns.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

The polyester mulfilament yarns of the present invention exhibit high modulus, high dimensional stability and excellent stiffness properties which are very desirable when incorporated into fibrous reinforcements in rubber composites such as tires. Other polyester polymer yarns made from a combination of PEN multifilament yarns or similar rigid monomers can be advantageously used to reinforce the two parts of car radial tires, carcass and belts. In general, car tire carcasses are mainly reinforced with polyethylene terephthalate.

Two characteristics of the tire, controlled by the dimensional stability of the carcass cord (modulus at a given shrinkage), are side grain and tire handling. The higher modulus and dimensional stability of the PEN or other polyester yarns of the present invention compared to PET and conventional PENs indicate that the tires reinforced with carcass of the present invention exhibit lower side etch and better handling. it means. In addition, the present invention is because the glass transition temperature (Tg) of the present invention is more than 100 ℃, that is higher than the Tg 120 ℃ of PEN, Tg 80 ℃ of PET is a preferred reinforcing material.

Higher Tg results in less heat generation of the cord over a wider temperature range than PET tires, resulting in longer tire life and lower overall tire operating temperatures. Moreover, since the modulus drops sharply at temperatures above Tg, the modulus of the yarns according to the invention can be maintained over a wider range of temperature than PET. High performance tires require low cord heat generation and high modulus in these applications, especially when the operating temperature rises at high speeds, so all of the above advantages are very important when the present invention is used to reinforce high performance tires.

PEN multifilament yarns and other polyester yarns of the present invention may also be used for carcass reinforcement of radial passenger car tire belts and radial truck tires. Currently for these applications, PET is mainly used because of the insufficient strength and modulus for a given cord diameter. The modulus of PEN is higher than that of PET, and the PEN of the present invention has an additional modulus, which makes PEN an ideal material that can be used as a substitute for steel.

The polyethylene naphthalate yarn of the present invention contains at least 90 mole percent polyethylene naphthalate. In one preferred embodiment, the polyester is substantially all polyethylene naphthalate.

Optionally, the polyester may incorporate small units derived from one or more ester-forming components other than ethylene glycol and 2,6-naphthalene dicarboxylic acid or derivatives thereof as copolymer units. Examples of other ester forming components copolymerizable with polyethylene naphthalate units include glycols such as 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, and the like, terephthalic acid, isophthalic acid, hexahydroterephthalic acid, stilbene Dicarboxylic acids such as dicarboxylic acid, bibenzoic acid, adipic acid, sebacic acid, azelaic acid.

Other polyester yarns of the present invention may be prepared to contain polyester polymers prepared by combining appropriately rigid and flexible monomers, provided that the resulting polymer is melt-spinable, semicrystalline, and has a Tg of 100 ° C. or higher. have.

Examples of rigid monomers include dicarboxylic acids such as 2,6-naphthalene dicarboxylic acid, 2,7-naphthalene dicarboxylic acid, diphenyl dicarboxylic acid, stilbene dicarboxylic acid and terephthalic acid; Dihydroxy compounds such as hydroquinone, biphenol, p-xylene glycol, 1,4-cyclohexanedimethanol, neopentylene glycol; And hydroxycarboxylic acids such as p-hydroxybenzoic acid and 7-hydroxy-β-naphthoic acid. Examples of soft monomers include dicarboxylic acids such as oxalic acid, succinic acid, adipic acid, sebacic acid, and dihydroxy compounds such as ethylene glycol, 1,3-propanediol, 1,4-butanediol, and 1,6-hexanediol. Include. It is important that the thermal stability of the polymer above its melting point should be sufficient to avoid excessive decomposition during melt processing.

The multifilament yarns of the present invention are about 1-20 (eg about 3-10) denier per filament and consist of about 6-600 continuous filaments (eg about 20-400 continuous filaments). The number of continuous filaments present in denier and yarn per filament can vary widely, which will be readily apparent to those skilled in the art.

The multifilament yarn is particularly suitable for industrial applications where high strength polyester fibers have conventionally been used. The fibers are particularly suitable when used in high temperature (eg 100 ° C.) conditions. This filament material not only improves modulus but also has very low shrinkage for high modulus fibrous thermoplastics.

The unexpected dimensional stability is likely due to the formation of a unique tissue morphology during spinning, which is due to the crystallization of highly oriented amorphous sites characterized by an unstretched birefringence of at least 0.03, preferably 0.03-0.30. . This crystallization takes place in the stretching or spinning phase, depending on the level of stress applied during spinning. If too much stress is applied during spinning, the unstretched yarn tends to be lowered in stretchability, and has a melting point of more than 290 ° C for PEN.

Characterization parameters herein can be readily determined by testing multifilament yarns consisting of substantially parallel filaments.

1. Birefringence-The birefringence was measured using a polarizing microscope equipped with a Berek compensator. If black matt bands are not visible to the naked eye, purple bands should be used for the measurement.

2. Density-Density was measured on an n-heptane / carbon tetrachloride density gradient column at 23 ° C. The gradient column was prepared and calibrated according to ASTM D1505-68.

3. Melting point-Melting point was determined from the maximum absorption result by injecting 10 mg of sample at 20 ° C. per minute using a Perkin-Elmer Differential Scanning Calorimeter (DSC). Under the same test conditions, Tg is obtained by taking the inflection point when the heat capacity changes with respect to the glass transition temperature. Melting | fusing point rise ((DELTA) Tm) with respect to a stretched yarn is calculated by (DELTA) Tm = Tm'-Tm ". Where Tm 'is the melting point of the target stretched yarn, and Tm ″ is the melting point of the yarn quenched in DSC prior to premelting and analysis.

4. Intrinsic Viscosity-The intrinsic viscosity (IV) of polymer and yarn is convenient for measuring polymerization and molecular weight. IV is determined by measuring the relative solution viscosity (ηγ) in a mixed solvent of phenol and tetrachloroethane (60/40 weight). ηγ is the ratio of the flow time of the PEM / solvent solution to the flow time of the pure solvent through the standard capillary. IV is calculated by extrapolating relative solution viscosity data at concentration 0.

5. Physical Properties-Tensile properties were measured using an Instron tensile tester with a gauge length of 10 inches (25.4 cm) and a strain rate of 120% per minute. All tensile measurements were made at room temperature. Dimensional stability refers to the stress level obtained at a given shrinkage. In the tire industry, dimensional stability is defined as the sum of elongation and shrinkage at a particular load. In this case, elongation at a specified load (EASL) is derived from the initial modulus test results using the following equation.

It is well known that stiffness and modulus increase as the draw ratio increases. Higher stiffness by itself is always very desirable, but high extension ratios are often not achieved due to yarn quality or severe shrinkage problems.

The materials of the present invention have a high level of modulus for a given level of stiffness. It is quantified by the parameter L _T by the ratio of L-5 to stiffness as follows:

L-5 or LASE-5 is the magnitude of the modulus determined by the load at 5% elongation (g / d). The L _T of the inventive material is at least 25. If the elongation of the yarn is less than 5% and the L-5 measurement is not possible, the yarn may be pre-loosed at elevated temperature prior to the test to increase the elongation above 5%.

Shrinkage was measured in accordance with ASTM D885 after holding for 1 minute at 177 ℃ pressed by a force of 0.05gr / denier (0.44mN / dtex).

The following describes the process found to be able to produce the improved yarn of the present invention. However, the process parameters described herein are not intended to limit the scope of the present invention.

Melt-spun polyester is fed to an extrusion spinnerette at temperatures above its melting point and substantially below the temperature at which the polymer degrades. The retention time at this stage should be minimized and the temperature should not be above 350 ° C, preferably above 320 ° C.

The extruded filaments are then passed through a conventional yarn solidification zone where they are cooled to the desired internal structure form to prevent filaments from fusing together.

The solidification zone is preferably (a) a zone for delaying cooling consisting of a gaseous atmosphere heated to at least 150 ° C., preferably 150-500 ° C. (hereinafter referred to as a retarded cooling zone) and ( b) adjoining the delayed cooling zone, it is preferred that the yarn consists of a cooling zone that is quenched and solidified in the blown air. It is important in the process of the present invention to adjust the process conditions such that a highly oriented undrawn yarn with a birefringence of at least 0.03 and a melting point raised by 1-25 ° C., preferably 3-23 ° C. is produced. For PEN the melting point should be 265-290 ° C, preferably 268-288 ° C. Those skilled in the art adjust conditions such as the length and temperature of the delayed cooling zone adjacent to the spinneret, the diameter of the spinneret hole, the quenching and blowing method, the quenching air velocity and the drawdown in the solidification zone. To achieve the above. The rate of yarn recovery from the solidification zone is an important parameter affecting the stress of the spun fiber and should be adjusted to achieve the required properties. The spun yarn is then stretched by conventional means in a continuous or discontinuous process to yield a stretched yarn having a Tg of 100 ° C. or higher and a melting point of at least 8 ° C., preferably 8-15 ° C ..

It is preferable that the properties of the drawn yarns are as follows: a stiffness of at least 6.5 g / d (57.4 mN / dtex), preferably at least 7.5 g / d (66.2 mN / dtex); Dimensional stability of less than 5% (EASL + shrinkage); And shrinkage of 4% or less.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated.

Example 1

[Comparative Example]

PEN undrawn yarn was prepared by extruding 32 filaments by passing an amount of processed raw material of 23.2 cc / min through a spinning nozzle having an orifice of 0.042 inches (0.107 cm) and a width of 0.021 inches (0.053 cm). The filaments were solidified in an air quench column and wound up at a winder speed of 305 m / min.

This yarn was extended | stretched in two steps using the normal heating roll. The properties of the undrawn yarn, the properties of the drawn yarn and the stretching conditions are shown in Table 1 below.

The yarn of this example, which is usually manufactured from undrawn yarn with Δn = 0.004, has a low modulus compared to the yarn of the present invention with an L _T of less than 24. Also, the dimensional stability (EASL + shrinkage) was 8.3, which was higher than that of the present invention, indicating that the dimensional stability was poor (see Example 3).

TABLE 1

Example 2

7 filaments were extruded by passing a processed raw material of 9.6 cm 3 / min through a spinneret having an orifice of 0.036 inch (0.091 cm) and a width of 0.016 inch (0.041 cm) to manufacture PEN. The filaments were solidified in an air quench column and wound at 770-5000 m / min in the winder. These yarns were drawn in two stages using heating plates in both stretching zones. The properties of the undrawn yarn, the properties of the drawn yarn and the stretching conditions are shown in Table 2 below.

Visual inspection of the data in this example shows that modulus increases with increasing spin rate and stretch and unstretched melting points for yarns drawn to a given stiffness. This reflects the increase in the L _T parameter as the spinning speed increases. Unstretched birefringence alone is not sufficient to specify the yarn of the present invention. Since this parameter is not sensitive to morphological changes occurring at high radial stresses, both melting point and birefringence should be used to define the scope of the present invention. In order to compare the test results of this example with Comparative Example 1, the modulus values of Table 2 were extrapolated to the stiffness of 6.2 g / d (54.7 mN / dtex) and presented as a graph of the spinning speed.

According to this, the advantage of the yarn of this invention is clearly seen compared with the yarn of the prior art.

TABLE 2

Example 3

The undrawn yarn of Example 2 spun at 770 m / min and 4000 m / min was drawn to their final limit.

The 770 m / min sample was drawn in one step using an oven in the drawing zone and the 4000 m / min sample was drawn in two steps using a heating plate in the second drawing zone.

The properties and stretching conditions of the drawn yarn are shown in Table 3 below. This example shows that the yarns of the present invention have very high modulus, high stiffness and low shrinkage when used inside rubber applications.

TABLE 3

Example 4

This example shows that undrawn yarn with high birefringence, modulus and melting point can be produced at a slower spinning rate than in Example 2, thus providing a more commercially easy process.

PEN was manufactured by extruding seven filaments by passing a processed raw material of 9.6 cc / min through a spinning nozzle having an orifice of 0.069 inch and a width of 0.030 inch. The filament was solidified in an air quench column and wound up at a winder speed of 410 m / min-2500 m / min. The properties of these yarns are shown in Table 4 below.

TABLE 4

Claims (9)

(a) extruding a molten crystallizable polyester polymer having a Tg of 100 ° C. or higher and an intrinsic viscosity of 0.6 or more through a molded extrusion orifice having a plurality of openings to form a molten spun yarn (spun yarn). Forming step; (b) solidifying the spun yarn through a solidification zone; (c) recovering the solidified yarn at a sufficient undrawn winding rate to form partially oriented yarn having a birefringence of at least 0.030; And (d) hot stretching the yarn so that the total draw ratio is at least 1.5 / 1 to form a stretched yarn. 2. The spun yarn of claim 1, wherein the spun yarn is adjacent to (a) a retarded cooling zone comprising a gaseous atmosphere heated to a temperature of at least 150 [deg.] C., and (b) the delayed cooling zone. Cooling zones quenched and solidified in the interior; And solidified by passing through a solidification zone. The method according to claim 1 or 2, wherein the unstretched winding speed is 400-4500 m / min, and the unstretched birefringence is 0.030-0.30. The molten polyester polymer of claim 1 or 2, wherein the molten polyester polymer extruded in step (a) is polyethylene naphthalate, and the melting point rise of the non-drawn yarn partially oriented in step (c) is 1-25 ° C. How to. 5. The method of claim 4, wherein the unstretched winding speed is 400-4500 m / min, the unstretched birefringence is 0.030-0.30 and the melting point rise of the partially oriented yarn is 3-23 ° C. Semi-crystalline polyester multifilament stretched yarn having a Tg of 100 ° C. or more and a melting point of at least 9 ° C .. The stretched yarn according to claim 6, wherein the stiffness is at least 6.5 g / d (57.4 mN / dtex), the dimensional stability (EASL + shrinkage) is less than 5%, and the shrinkage is 4% or less. The drawn yarn according to claim 7, which is polyethylene naphthalate. 9. The drawn yarn according to claim 8, wherein the melting point rises 9-15 ° C, the modulus is at least 280 g / d (2470 mN / dtex), and the stiffness is at least 7.5 g / d (66.2 mN / dtex).