KR20200111512A - Polyester tire cord and manufacturing method of the same - Google Patents

Abstract

A manufacturing method of a polyester tire cord comprises: a step of manufacturing a raw cord by twisting polyester fibers; a step of immersing the raw cord in a first treating liquid including polyfunctional isocyanate; a step of drying and heat-treating the raw cord immersed in the first treating liquid; a step of immersing the raw cord in a second treating liquid including resorcinol formalin latex (RFL); and a step of manufacturing a dip cord by drying and heat-treating the raw cord immersed in the second treating liquid. The present invention can improve durability of a tire.

Description

Polyester tire cord and manufacturing method thereof {POLYESTER TIRE CORD AND MANUFACTURING METHOD OF THE SAME}

The present invention relates to a polyester tire cord and a method of manufacturing the same.

Tire reinforcing materials, generally represented by polyethylene terephthalate (hereinafter, polyester), have excellent mechanical strength, elastic modulus, dimensional stability, and heat resistance, which are important properties that rubber reinforcements must have, so rubber composites such as tires, It is widely used as a reinforcing material for belts or hoses. However, the need for more high-performance reinforcing materials has emerged due to the high performance of automobiles, development of roads, and harsher conditions for using rubber composites. Since the polyester fiber has a relatively inert surface, there is a problem of insufficient adhesion to rubber. Thus, the surface of the polyester fiber is treated with a primary treatment solution consisting of epoxy and blocked diisocyanate or para-chlorophenol resin, and then a general resorcinol-formalin latex (hereinafter referred to as'RFL'). Methods of secondary treatment are known.

On the other hand, in order to increase the heat-resistant adhesion of the polyester tire cord, a method such as increasing the epoxy and blocked isocyanate content of the primary treatment solution and adding a heat-resistant additive has been used. However, in this case, the epoxy penetrates deep into the fiber, and the stiffness of the polyester fiber increases due to the epoxy crosslinking reaction, thereby reducing the fatigue resistance, and may cause a problem of tip rising during the tire manufacturing process. .

An object of the present invention is to provide a polyester tire cord having low rigidity and improved fatigue resistance, and a method of manufacturing the same.

A method of manufacturing a polyester tire cord according to an embodiment of the present invention includes the steps of producing a raw cord by twisting polyester fibers; Immersing the raw cord in a primary treatment solution containing a polyfunctional isocyanate; Drying and heat treating the raw cord immersed in the primary treatment solution; Immersing the raw cord in a secondary treatment solution containing resorcinol formalin latex (RFL); And drying and heat treating the raw cord immersed in the secondary treatment liquid to prepare a dip cord.

Here, the polyfunctional isocyanate may be 3 to 7% by weight based on the total weight of the first treatment liquid.

In addition, the first treatment liquid further includes polyvinyl chloride latex, and the total content of the polyfunctional isocyanate and the polyvinyl chloride latex may be 3 to 7% by weight based on the total weight of the first treatment liquid. .

In this case, the weight ratio of the polyfunctional isocyanate and the polyvinyl chloride latex may be 3:1 to 1:1.

In addition, the polyester tire cord according to an embodiment of the present invention is manufactured by the above manufacturing method, has an initial adhesive force of 18 kgf or more with rubber measured by the H-test, a heat resistance of 12 kgf or more, and a stiffness of 5.0 g/ end or less, and fatigue resistance may be 88% or more.

According to an embodiment of the present invention, as the polyester tire cord is treated using a primary treatment liquid containing a polyfunctional isocyanate, the composition is simpler than that of the conventional primary treatment liquid, thus reducing the time and production cost for preparing the treatment liquid. It can be, and there is an advantage in that it is easy to manage subsidiary materials.

In addition, the polyester tire cord as described above has low rigidity, can solve the tip rising problem that occurs during the tire manufacturing process, and improves fatigue resistance, thereby improving the durability and driving stability of the tire, Due to the high reactivity of the polyfunctional isocyanate, it is possible to obtain the same level of adhesion as the existing epoxy treatment solution.

In the present invention, various modifications may be made and various forms may be applied, and specific embodiments will be illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to a specific form disclosed, it should be understood to include all changes, equivalents, and substitutes included in the spirit and scope of the present invention.

In the present application, terms such as "comprise" or "have" are intended to designate the presence of features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, but one or more other features. It is to be understood that the presence or addition of elements or numbers, steps, actions, components, parts, or combinations thereof, does not preclude in advance the possibility of being added. Further, when a part such as a layer, film, region, plate, etc. is said to be "on" another part, this includes not only the case where the other part is "directly above", but also the case where there is another part in the middle. Conversely, when a part such as a layer, film, region, plate, etc. is said to be "under" another part, this includes not only the case where the other part is "directly below", but also the case where there is another part in the middle. In addition, in the present application, the term "above" may include a case where it is disposed not only above but also below.

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

A method of manufacturing a polyester tire cord according to an embodiment includes the steps of manufacturing a raw cord by twisting polyester fibers, immersing the raw cord in a primary treatment solution; Drying and heat treating the raw cord immersed in the primary treatment solution; Immersing the raw cord in a secondary treatment solution; And drying and heat treating the raw cord immersed in the secondary treatment liquid to prepare a dip cord.

The step of preparing the raw cord may be a step of preparing the raw cord by twisting polyester fibers in order to manufacture the polyester tire cord.

The polyester fiber may be manufactured by melting polyethylene terephthalate (PET) chips having an intrinsic viscosity of 1.0 or more and extruding them while passing through a nozzle. Hereinafter, a method of manufacturing a polyester fiber will be described in detail.

The polyethylene terephthalate polymer may contain at least 85 mol% or more of ethylene terephthalate units, but may optionally contain only ethylene terephthalate units. In this case, polyethylene terephthalate is described as an example of polyester, but is not limited thereto.

In addition, the polyethylene terephthalate may optionally include a small amount of units derived from ethylene glycol and terephthalene dicarboxylic acid or derivatives thereof, and one or more ester-forming components as a copolymer unit. Examples of other ester-forming components that can be copolymerized with polyethylene terephthalate units include glycols such as 1,3-propanediol, 1,4-butanediol, 1,6-hexadiol, terephthalic acid, isophthalic acid, hexahydroterephthalic acid, and stilbendica Dicarboxylic acids such as carboxylic acid, bibenzoic acid, adipic acid, sebacic acid, and azelaic acid may be included, but the present invention is not limited thereto.

Terephthalic acid (TPA) and ethylene glycol raw materials are melt-mixed in a ratio of 2.0 to 2.3 in polyethylene terephthalate chips prepared using the polyethylene terephthalate polymer as described above, and the melt mixture becomes transesterification and condensation polymerization. It can be formed as a raw chip.

Thereafter, the low chip may be solid-phase polymerization to have an intrinsic viscosity of 1.0 to 1.15 under a temperature of 240 to 260°C and vacuum. Here, when the intrinsic viscosity of the raw chip is less than 1.0, the intrinsic viscosity of the final drawn yarn is lowered, so that high strength cannot be exhibited as a treated cord after heat treatment. On the other hand, when the intrinsic viscosity of the low chip exceeds 1.15, the spinning tension is excessively increased, and the cross section of the radiating yarn becomes uneven, resulting in a problem that many filaments are cut during stretching, resulting in poor stretching workability.

In addition, in the condensation polymerization reaction, an antimony compound, which is a polymerization catalyst, may be optionally used, and antimony trioxide may be preferably used. For this reason, it can be added so that the residual amount of antimony metal in the final polymer is 180 to 300 ppm. At this time, when the residual amount of antimony metal is less than 180 ppm, the polymerization reaction rate may be slowed, resulting in a decrease in polymerization efficiency, and when the residual amount exceeds 300 ppm, more than necessary antimony metal acts as a foreign material, resulting in deterioration of spinning and stretching workability.

The polyethylene terephthalate chip as described above may be melted and extruded while passing through a nozzle to prepare a discharge yarn. Thereafter, the discharged sand is rapidly cooled and solidified by passing through the cooling zone. At this time, if necessary, a heating device of a certain length may be installed in the distance from the nozzle to the starting point of the cooling zone, that is, in the length section of the hood.

The section in which the heating device is installed is called a delayed cooling zone or a heating zone, and the zone preferably has a length of 50 to 250 mm and a temperature of 250 to 400°C (air contact surface temperature), but is not limited thereto.

Meanwhile, in the cooling zone, depending on the method of blowing cooling air, open quenching, circular closed quenching, radial outflow quenching, radial inflow quenching, etc. May be applied, but is not limited thereto.

In this case, the temperature of the cooling air injected for rapid cooling in the cooling zone may be adjusted to 20 to 50°C. Rapid cooling using such a sharp temperature difference between the hood and the cooling zone can increase the solidification point and spinning tension of the spun polymer, thereby increasing the orientation of the undrawn yarn and the formation of a linking chain between the crystal and the crystal.

Thereafter, the discharged yarn solidified while passing through the cooling zone can be oiled at 0.5 to 1.2% by weight of the discharged yarn by an oil agent applying an oil agent having excellent stretchability and thermal efficiency while reducing the coefficient of friction between the single yarns.

Undrawn yarn can be formed by spinning the oiled yarn. At this time, the spinning draft is 1500 to 1800, the spinning speed is preferably 3,000 to 3,200 m/min, and when spinning at the spinning draft and spinning speed in the above range, excellent strength of the yarn can be secured even at a low draw ratio.

If the spinning draft is less than 1500 or the spinning speed is less than 3,000 m/min, the cross-sectional uniformity of the yarn deteriorates and the drawing workability decreases, and the degree of orientation of the undrawn yarn decreases to decrease the degree of crystallinity and the crystal part does not develop. In this case, the thermal stability is lowered, so that the strength of the tire cord decreases, and when high elongation is performed to improve strength and modulus, the shape stability may decrease. In addition, when the spinning speed exceeds 3,200 m/min, the stretchability of the undrawn yarn is reduced, so that the strength and the stretching workability of the yarn may be reduced.

Thereafter, the undrawn yarn may be stretched in multiple stages by passing it through a stretching roller to manufacture a yarn.

Yarn can be formed by stretching the yarn that has passed through the first stretching roller while passing through a series of stretching rollers using a spin draw method.

In the stretching process, the undrawn yarn may be multi-stage stretched, and each stretching roller temperature is higher than the glass transition temperature of the undrawn yarn and lower than 95°C, but the temperature of the last stretching roller is preferably 200 to 250°C.

If the temperature of the last drawing roller is less than 200°C, the crystallinity and the size of the crystal cannot be increased in the drawing process, and thus the strength and thermal stability of the yarn cannot be expressed, resulting in a decrease in shape stability at high temperatures, and the temperature of the last drawing roller exceeds 250°C. If it is too close to the melting point, the microstructure of the yarn becomes uneven, such as crystal decomposition, and thus the strength of the yarn may decrease.

In addition, it is preferable that the total draw ratio of the formed yarn is 2.14 to 2.22. If the draw ratio is less than 2.14, productivity decreases and the strength of the yarn and cord decreases, and if the draw ratio exceeds 2.22, the crystallization of the oriented non-hardened portion increases, resulting in a decrease in drawing workability and threading. The molecular chain of the amorphous portion is broken, resulting in a decrease in the uniformity of the molecular chain, which is not preferable because the strong utilization rate may be reduced.

Thereafter, two manufactured yarns may be twisted using a direct twisting machine in which false twisting and plying are simultaneously performed to produce a raw cord.

At this time, the twisted yarn may be manufactured by applying a ply twist to the yarn and then applying a cable twist to the yarns, and the upper and lower edges may have the same number of threads or a different number of threads as necessary.

The number of years of the raw code may be from 370/370 TPM (twist per meter) to 430/430 TPM with the same upper/lower edge. When the upper and lower edges are twisted with the same value, the manufactured cord does not exhibit rotation or twist, and it is easy to maintain a straight line, thereby maximizing the expression of physical properties. On the other hand, when the number of years of the upper/lower edge is less than 370/370 TPM, the length of the cord decreases and fatigue resistance tends to decrease, and when it exceeds 430/430 TPM, the strength decreases, making it unsuitable for tire cords.

Thereafter, the prepared raw cord may be immersed in the first treatment solution, followed by drying and heat treatment.

The primary treatment liquid may contain a polyfunctional isocyanate for adhesion between the polyester cord and the rubber. Since the polyfunctional isocyanate does not dissolve in water and exists in a dispersed state of fine particles, the amount of penetration into the fiber is reduced compared to the conventional epoxy. Accordingly, the rigidity of the tire cord can be lowered and fatigue resistance can be improved. In addition, despite the low permeability inside the fiber, since it has a high reactivity due to the polyfunctional group, there is an advantage that it is possible to develop an adhesive force equal to or higher than that of a treatment solution containing an epoxy.

These polyfunctional isocyanates may be included in 1.0 to 10.0% by weight, and preferably 3.0 to 7.0% by weight, based on the total weight of the first treatment solution. When the content of the polyfunctional isocyanate is less than 3.0% by weight, the problem of lowering the adhesive strength with the rubber occurs, and when it exceeds 7.0% by weight, the stiffness of the polyester fiber increases, and thus the fatigue resistance decreases. There may be a problem of cost increase.

Meanwhile, the first treatment liquid may further include polyvinyl chloride latex. As described above, in order to compensate for the decrease in adhesion to rubber that may occur when the content of the polyfunctional isocyanate is less than 3% by weight, a latex having high compatibility with polyester may be included.

At this time, the total content of the polyfunctional isocyanate and the polyvinyl chloride latex is preferably 3 to 7% by weight, and more preferably 3 to 5% by weight based on the total weight of the first treatment liquid. In addition, the weight ratio of the polyfunctional isocyanate and the polyvinyl chloride latex may be 3:1 to 1:1, more preferably 2:1 to 1:1.

On the other hand, the drying should avoid rapid treatment at high temperatures, and is preferably carried out at 90 to 180°C for 180 to 220 seconds. If the drying temperature is less than 90°C, drying may not be sufficiently performed, and when heat treatment after drying, gel may be generated by the treatment liquid, and if it exceeds 180°C, gel due to the treatment liquid may occur due to rapid drying and And non-uniform adhesion between the treatment liquid may occur.

The heat treatment is performed so that the cord impregnated with the treatment liquid has an appropriate adhesive strength with the tire rubber, and the heat treatment temperature is preferably performed at 220 to 250°C for 50 to 90 seconds. If the heat treatment is performed for less than 50 seconds, the reaction time of the adhesive solution is insufficient and the adhesive strength is lowered. If the heat treatment is performed for more than 90 seconds, the hardness of the treatment solution may be lowered and thus the fatigue resistance of the cord may be reduced.

Then, after immersing in a secondary treatment solution containing resorcinol formalin latex (RFL), drying and heat treatment may be performed to prepare a dip cord. The process of drying and heat treatment of the raw cord impregnated with the secondary treatment liquid may be the same as described above.

The polyester tire cord prepared as described above has an initial adhesive strength of 18 kgf or more with rubber measured by H-test, a heat resistance of 12 kgf or more, a stiffness of 5.0 g/end or less, and a fatigue resistance of 88% or more. , The stiffness decreases, and thus fatigue resistance may be improved, and an effect of improving initial adhesion and heat resistance may be exhibited. This can improve the durability and running stability of the tire.

Hereinafter, the present invention will be described in detail through examples. However, the following examples are only illustrative of the present invention, and the present invention is not limited by the following examples.

[Example 1]

A raw cord was prepared by combining two polyester fibers for tire cord 1500 denier with 370 TPM of upper softening water and 370TPM of lower softening water. The prepared raw cord was immersed in the first treatment solution while applying a tension of 0.1 g/d and passed, dried at 160°C for 2 minutes, and heat treated at 245°C. At this time, the first treatment liquid was prepared by adjusting as shown in Table 1 below. Thereafter, the raw cord was impregnated with the secondary treatment solution, dried at 160° C. for 2 minutes, and heat treated at 245° C. to prepare a polyester tire cord. At this time, the secondary treatment liquid was prepared by mixing 76.5% by weight of water, 0.1% by weight of caustic soda, 2.4% by weight of resorcinol, 0.8% by weight of formalin, 20.0% by weight of vinylpyridine latex, and 0.2% by weight of ammonia.

[Examples 2 to 4]

Polyester tire cords were each prepared through the same process as in Example 1, except that the content of the first treatment liquid composition was adjusted as shown in Table 1 below.

[Comparative Examples 1 to 4]

Polyester tire cords were each prepared through the same process as in Example 1, except that the content of the first treatment liquid composition was adjusted as shown in Table 1 below.

1st treatment liquid Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Example 1 Example 2 Example 3 Example 4 Water (wt%) 97.0 98.0 97.0 97.0 97.0 97.0 97.0 97.0 Epoxy (wt%) 0.7 - - - - - - - Blocked diisocyanate (wt%) 1.5 - - - - - - - Polyfunctional isocyanate (wt%) - 2.0 1.0 8.0 3.0 2.0 1.5 7.0 Polyvinyl chloride latex (wt%) 0.4 - 2.0 - - 1.0 1.5 - Heat resistant additive (wt%) 0.4 - - - - - - - Total concentration (wt%) 3.0 2.0 3.0 8.0 3.0 3.0 3.0 7.0

[Experimental Example]

The physical properties of the polyester tire cords prepared in Examples 1 to 4 and Comparative Examples 1 to 4, respectively, were evaluated using the following method, and the results are shown in Table 2 below.

1) Adhesion: H-test

This is a method of indicating the adhesion between the heat-treated cord and the rubber. After putting the cord in a rubber block and vulcanizing it at 160°C, 20 minutes (initial) or 170°C, 60 minutes (heat resistance) at 50kgf/cm ² , Instron's The adhesion was measured at a tensile speed of 300 m/min using a low-speed elongation type tensile tester. The same test was performed 10 times to obtain an average value, and other methods were performed according to ASTM D4776-98.

2) fatigue

As a measure representing the resistance value of the heat-treated cord to external stress, it was carried out by simulating tire running conditions. In the present invention, a shoe-shine type test was performed, and a rubber topping was applied to a cord of 30 EPI (Ends Per Inch) intervals, and then two layers of rubber were applied and cured at 160°C for 20 minutes to prepare a specimen. And, after applying a load of 80kg in a flexural fatigue tester and applying a repeated load of 37,500 times, take the cord and measure the strength at a tensile speed of 300m/min using an Instron's low-speed elongation type tensile tester. The strong residual rate was measured for the original strength before fatigue. The strength of the cord was measured by collecting 10 strands of cord before and after fatigue, and the fatigue test result was obtained by performing three fatigue tests and obtaining an average value. The code strength measurement method was carried out according to ASTM D885.

Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Example 1 Example 2 Example 3 Example 4 DPU (%) 2.4 2.3 2.4 2.5 2.5 2.5 2.4 2.5 Initial adhesion (Pull-out, kgf) 18.0 17.6 17.2 18.4 18.3 18.2 18.1 18.2 Heat-resistant adhesion (Pull-out, kgf) 12.6 11.8 11.5 12.8 12.7 12.0 12.6 13.0 Stiffness (g/end) 5.4 3.6 3.3 6.3 4.5 4.8 4.4 6.2 Fatigue resistance (%) 88.6 92.1 90.4 87.5 91.7 90.6 89.0 88.1

Referring to Table 2, it can be seen that the polyester tire cord manufactured according to the Example maintains the adhesive strength, decreases the stiffness, and improves the fatigue resistance, although the composition of the primary treatment solution is simplified compared to Comparative Example 1. have. On the other hand, it can be seen that when the content ratio of the polyfunctional isocyanate and the polyvinyl chloride latex is 2: 1 (Example 2), compared to the case of 1:1 (Example 3), the adhesion was improved and the rigidity was further reduced. On the other hand, in the case where the content ratio of the polyfunctional isocyanate and the polyvinyl chloride latex is 1:2 (Comparative Example 3), it can be seen that the initial adhesive strength and the heat-resistant adhesive strength are lowered.

On the other hand, it can be seen that the polyester tire cord (Comparative Example 2) treated with the primary treatment solution containing less than 3% by weight of polyfunctional isocyanate had lower initial adhesive strength and heat-resistant adhesive strength compared to the Examples. In addition, with respect to the primary treatment liquid (Comparative Example 4) containing more than 7% by weight of polyfunctional isocyanate, the effect of improving adhesion is insignificant, and there is a possibility of causing an increase in rigidity and cost.

Accordingly, the polyester tire cord manufactured according to the present invention has reduced stiffness and thus fatigue resistance may be improved, and an effect of improving initial adhesion and heat resistance adhesion may be expressed. This can improve the durability and running stability of the tire.

Although the above has been described with reference to the preferred embodiments of the present invention, those skilled in the art or those of ordinary skill in the art will not depart from the spirit and scope of the present invention described in the claims to be described later. It will be understood that various modifications and changes can be made to the present invention within the scope of the invention.

Therefore, the technical scope of the present invention should not be limited to the content described in the detailed description of the specification, but should be determined by the claims.

Claims (5)

Preparing a raw cord by twisting polyester fibers;
Immersing the raw cord in a primary treatment solution containing a polyfunctional isocyanate;
Drying and heat treating the raw cord immersed in the primary treatment solution;
Immersing the raw cord in a secondary treatment solution containing resorcinol formalin latex (RFL); And
A method of manufacturing a polyester tire cord comprising the step of manufacturing a dip cord by drying and heat treating the raw cord immersed in the secondary treatment liquid. The method of claim 1,
The polyfunctional isocyanate is 3 to 7% by weight, based on the total weight of the primary treatment solution, a method for producing a polyester tire cord. The method of claim 1,
The first treatment liquid further comprises polyvinyl chloride latex,
The total content of the polyfunctional isocyanate and the polyvinyl chloride latex is 3 to 7% by weight based on the total weight of the primary treatment solution. The method of claim 3,
The weight ratio of the polyfunctional isocyanate and the polyvinyl chloride latex is 3:1 to 1:1, a method for producing a polyester tire cord. It is manufactured by the manufacturing method according to any one of claims 1 to 4,
Polyester tire cord with an initial adhesive strength of 18 kgf or more with rubber, a heat resistance of 12 kgf or more, a stiffness of 5.0 g/end or less, and a fatigue resistance of 88% or more as measured by the H-test