KR20090114507A - Aramid tire cord - Google Patents

Abstract

PURPOSE: Aramid tire cord is provided to improve shape stability of a tire and shape stability at high temperature conditions, and to offer good durability and driving safety. CONSTITUTION: Aramid tire cord includes aramid filament. The work loss rate represented by a calculus 1 is 30% or less in 120°C. The work loss rate(%) = work loss / loading energy × 100. The work loss rate is represented by a calculus 2. The weighting energy is an energy value of the repeated experiments with the load of 10% based on the shear strength of the aramid tire cord. The unloading energy is the energy value after removing the load of the aramid tire cord.

Description

Aramid tire cord

The present invention relates to an aramid tire cord for rubber reinforcement.

The tire is a composite of fiber / steel / rubber and generally has a structure as shown in FIG. 1. In other words, steel and fiber cords serve to reinforce rubber and form a basic skeletal structure in the tire. In other words, compared to the human body is a bone-like role.

The performance required for the cord as a tire reinforcement is fatigue resistance, shear strength, durability, resilience and adhesion to rubber. Therefore, a cord of appropriate material is used according to the performance required for the tire.

Commonly used materials for the cord are rayon, nylon, polyester, steel, and aramid, and rayon and polyester are used for body plies (also called carcasses) (6 in FIG. 1), and nylon is mainly a cap. In the ply (4 in FIG. 1), and steel and aramid are mainly used in the tire belt portion (5 in FIG. 1).

The following briefly illustrates the tire structure and its characteristics shown in FIG. 1.

Tread (1): It is a part in contact with the road surface, which provides the necessary frictional force for braking and driving, has good abrasion resistance, can withstand external shocks and has low heat generation.

Body Ply (or Carcass) (6): A layer of cord inside the tire, which must support loads, withstand impacts, and be resistant to flexing movements while driving.

Belt (5): Located between the body plies, most of them are made of steel wires to mitigate external shocks and maintain a wide tread grounding surface for excellent driving stability.

Side Wall (3): refers to the rubber layer between the bottom of the solder (2) from the bead (9) and serves to protect the internal body ply (6).

Bead (9): A square or hexagonal wire bundle with rubber coating on the wire that rests and secures the tire to the rim.

Inner Liner (7): Located on the inside of the tire instead of the tube, this prevents air leakage and enables pneumatic tires.

CAP PLY (4): A special cord paper placed on the belt of some passenger radial tires that minimizes belt movement when driving.

APEX (8): This is a triangular rubber filler used to minimize the dispersion of beads, to mitigate external impacts, to protect the beads, and to prevent the inflow of air during molding.

Generally used tire cord material is nylon, polyester, rayon and the like. These materials are limited in size and use, etc. of the tires used due to their advantages and disadvantages.

Nylon fiber has high tensile elongation and high strength, and is mainly used for tires used on curved roads such as heavy trucks and unpaved roads.

However, the nylon fiber is not suitable for a tire for a passenger car in which concentrated heat accumulation occurs inside the tire, and a low modulus is used to travel at high speed or require a ride comfort.

Polyester fiber has better shape stability and price competitiveness than nylon, and strength and adhesion are improved due to continuous research, and its usage is increasing in the tire cord field. However, it is not suitable for high-speed running tires because of limitations in heat resistance and adhesive strength.

Rayon fiber, a regenerated cellulose fiber, has excellent strength retention and shape stability at high temperature. Therefore, rayon fiber is known as an optimal tire cord material. However, due to the strong deterioration due to moisture, thorough water management is required in tire manufacturing, and due to non-uniformity in yarn manufacturing, the rate of defective products is high. Above all, its price / performance ratio is very low compared to other materials, and it is mainly applied only to high speed or expensive tires.

However, general cellulosic fibers such as rayon have a rigid structure and high work loss rate, which leads to low durability and poor form stability at high temperatures.

The present invention is to provide an aramid tire cord excellent in high-speed driving stability and shape stability of the tire.

The present invention provides an aramid tire cord, comprising an aramid multifilament and having a work loss rate of 30% or less at 120 ° C defined by the following formula (1).

[Calculation 1]

Daily loss rate (%) = daily loss / weighting energy × 100

(In the above formula, the work loss is defined by Equation 2 below, where the weighted energy is an energy value after 10 times of tensile repetition experiments with a load corresponding to a cutting strength of 10% on the aramid tire cord, and the weighted energy is a load removed from the aramid tire cord. The energy value after

[Calculation 2]

Work loss = loading energy-unloading energy

Hereinafter, the present invention will be described in detail.

In the present invention, a filament bundle including a plurality of filament fibers is referred to as 'multifilament', and a raw cord manufactured by upper and lower edges (or lower and upper edges) of the multifilament is referred to as 'ply twisted yarn', The deep cord treated with the adhesive for tire cord in the twisted yarn is referred to as 'tire cord'.

According to the present invention, as a result of experiments on deformation that may occur due to a specific load under the internal temperature (120 ° C.) generated when driving a tire, the aramid tire cord of the present invention exhibits a change in work loss rate and elongation strain when the temperature rises to 120 ° C. above room temperature. Insignificant, it was confirmed that it can have a high modulus of elasticity and high fatigue resistance when heated.

The aramid tire cord of the present invention is characterized in that 20% or less at a work loss rate of 120 ℃ defined by the following formula (1).

[Calculation 1]

Daily loss rate (%) = daily loss / weighting energy × 100

(In the above formula, the work loss is defined by Equation 2 below, where the weighted energy is an energy value after 10 times of tensile repetition experiments with a load corresponding to a cutting strength of 10% on the aramid tire cord, and the weighted energy is a load removed from the aramid tire cord. The energy value after

[Calculation 2]

Work loss = loading energy-unloading energy

In addition, in the present invention, the aramid tire cord may have a work loss ratio of 40% or less at 150 ° C and 25% or less at 30 ° C.

In addition, in the present invention, the aramid tire cord has an elongation strain of 2% or less at 120 ° C as defined by the following formula (3).

[Calculation 3]

(L ₀ is the length value of the aramid tire cord before applying the load, L ₁₀ is the length value of the aramid tire cord measured after 10 tensile repeat tests with a load corresponding to 10% of the cutting strength)

In addition, in the present invention, the cellulose-based tire cord may have an elongation strain of 3% or less at 150 ° C and 1% or less at 30 ° C.

In the present invention, each physical property value of the aramid tire cord is measured based on the KSK 0412 standard using an Instron low speed extension type tensile tester (Instron's universal testing machine).

In addition, the work loss will be described in more detail as follows.

In other words, if the fiber is subjected to load-extension cycling, the strain increases gradually as the load increases in the first few cycles, but after a certain cycle the stress-strain curve is one loop. To form. This means that the energy is dissipated by the internal friction, and the heat generated at this time changes the properties of the fiber. In general, in the case of polymer fibers, deformation occurs upon loading, and after unloading, the deformation shows incomplete elasticity, which does not completely recover.

In this case, the weighted curve and the weighted curve do not coincide with each other during the cycle test and show a hysteresis, and the widths of these two curves represent work loss defined by Equation 2. In addition, the lower the work loss, the better, since the modulus fluctuation is low, improving durability and running stability.

Thus, the aramid tire cord of the present invention can improve the tire durability and high-speed running performance is low work loss rate and elongation strain as described above.

In addition, the aramid tire cord of the present invention, the less the change in the modulus of the initial modulus section at high temperature conditions, the less the change in stress of the fiber according to the external stress, and thus form stability is excellent, the tire capable of high-speed running It can have the properties of a code. In the present invention, "initial modulus interval" means an average slope of 0% to 5% strain in the strain curve of the fiber.

In addition, the tire cord of the present invention can be prepared by jointly twisting aramid filament fibers, and then treating the adhesive solution for tire cords according to a conventional dipping method, and drying and heat-treating them.

Looking at an example of a method for producing an aramid tire cord according to the present invention, first, using the aramid multifilament for the tire cord Alma twister and the like as shown in Fig. Next, the twisted two strands are twisted while giving a twist of the lower edge (S edge) in which the twist direction is clockwise as shown in FIG. 2 to manufacture a twisted yarn.

2 to 3 are diagrams showing the definition of the upper edge (Z edge) and the lower edge (S edge), respectively.

At this time, the twist number of each of the upper (Z) and the lower (S) is preferably 20 to 60 times / 10 cm.

If the number of twist is less than 20 times / 10 ㎝ low twist number is high, but the cutting elongation is very low, the fatigue characteristics of the cord is bad, and the adhesion may be poor as the surface area is lowered.

If the number of twist exceeds 60 times / 10 cm may cause a problem that the strength of the tire cord is reduced due to excessive twist.

The aramid multifilament is a wholly aromatic polyamide filament composed of poly (para-phenylene terephthalamide), as shown in Figure 4 containing an aromatic diamine and an aromatic dieside chloride N-methyl-2-pyrrolidone Polymerizing in a polymerization solvent to produce an aramid (fully aromatic polyamide) polymer; Dissolving the polymer in a concentrated sulfuric acid solvent to prepare a spinning stock solution; Spinning the undiluted solution from a spinneret to pass the spun spine through a non-coagulant fluid layer into a coagulation bath to form a multifilament; And it may be produced by a manufacturing method comprising a step of producing aramid multifilament fibers through the process of washing, drying and heat treatment the multifilament.

4 is a process schematic diagram of producing the aramid multifilament fibers.

In this case, the aromatic diamine is P-phenylenediamine and the like, and the aromatic dieside chloride is terephthaloyl chloride and the like.

The polymerization solvent is N-methyl-2-pyrrolidone or the like in which calcium chloride is dissolved.

The intrinsic viscosity of the aramid (fully aromatic polyamide) polymer is 5.0 or more is good for improving the strength and elastic modulus of the filament.

The aramid polymer may be prepared using known polymerization conditions disclosed in US Pat. No. 3,869,429, etc., but the present invention does not specifically limit the polymerization conditions of the aramid polymer.

One example of preparing the polymer is a solution of 1 mole of para-phenylenediamine dissolved in N-methyl-2-pyrrolidone containing about 1 mole of calcium chloride and 1 mole of terephthaloyl chloride in a polymerization reactor. After the addition, it is stirred to prepare a gel polymer, which is ground, washed with water and dried to prepare a fine powder aramid polymer. At this time, the terephthaloyl chloride may be added to the reactor for polymerization divided into two stages.

The concentration of concentrated sulfuric acid used in the production of the spinning stock solution is preferably 97% to 100%, and chlorosulfuric acid, fluorosulfuric acid, and the like may also be used.

At this time, when the concentration of sulfuric acid is less than 97%, the solubility of the polymer is reduced and the liquid crystalline expression of the anisotropic solution becomes difficult. Therefore, it is difficult to manufacture a spinning solution having a constant viscosity, which makes it difficult to control the process during spinning and to provide mechanical properties of the final fiber. Can be degraded.

On the other hand, if the concentration of the concentrated sulfuric acid exceeds 100%, gwari (過離) because in oleum containing SO _3, as well as undesirable phase handled becomes an SO ₃ over takes place is partly dissolved in the polymer spinning solution to the inadequate and In addition, even if the fiber is obtained by spinning, there may be a problem that the internal structure of the fiber is not dense, the appearance is not gloss, and the speed of sulfuric acid diffused into the coagulation solution is lowered, thereby lowering the mechanical properties of the fiber.

On the other hand, the concentration of the polymer in the spinning stock solution is preferably 10 to 25% by weight for the fiber properties.

However, the present invention does not specifically limit the concentration of concentrated sulfuric acid and the concentration of the polymer in the spinning stock solution.

The non-coagulating fluid layer may mainly be an air layer or an inert gas layer.

The length of the non-coagulating fluid layer, that is, the distance between the bottom surface of the spinneret 40 and the surface of the coagulating liquid contained in the coagulating liquid bath 50 is preferably 0.1 to 15 cm to improve the properties of the radioactive or filament.

The coagulant in the coagulant bath 50 may overflow. As the coagulating solution, water, brine or an aqueous sulfuric acid solution having a concentration of 70% or less is used.

Next, the formed filaments are washed with water, dried and heat treated to produce wholly aromatic polyamides.

At this time, the spinning winding speed is set to 300 to 1500 m / min.

The strength of the aramid multifilament used in the present invention is 10 ~ 25g / d, when less than 10g / d, the strength is low, it is difficult to support the car load when applied as a tire cord, the problem of the performance of the tire is impossible, 25g In the case of exceeding / d, a problem arises that the tire performance is not efficient due to sufficient physical properties.

In addition, the cut elongation of the aramid multifilament is 2 ~ 6%, if less than 2% due to the low cutting elongation occurs a problem that the fatigue characteristics are insufficient to be applied to the tire cord, when the stability exceeds 6% form stability This lacking problem occurs.

In addition, as the modulus of the aramid multifilament 400 ~ 750g / d, less than 400g / d, due to the low modulus, a problem that the lack of support capacity for high-speed driving occurs during tire manufacturing, if the exceeding 750g / d The high modulus creates a problem that makes tire molding difficult.

It is preferable that the total fineness of the aramid tire cord is 800 to 10,000 denier, and the aramid multifilament preferably has a total fineness of 400 to 5,000 denier and is composed of 500 to 1,200 aramid monofilaments. Moreover, it is preferable that the single yarn fineness of the said aramid monofilament is 1-2 denier.

Various physical properties of the aramid multifilament is measured by the following method.

Strength (g / d) and elongation at break (%)

According to ASTM D-885 test method, the strength (g) at the time of fracture of the sample yarn was measured using a sample yarn having a length of 25 cm in an Instron Engineering Corp. (Canton, Mass), and then the sample yarn was denier. The strength was calculated by dividing. Elongation at break was calculated as the ratio of the length of the sample yarn to the length of the sample yarn until the sample yarn was broken. The strength and the elongation at break were taken as the average value after five tests. At this time, the tensile speed was 300 mm / min, the ultra-load was fineness × 1 / 30g.

Modulus (g / d)

The stress-strain curve of the sample yarn is obtained under the above-described strength measurement conditions, and then calculated from the slope on the stress-strain curve.

Next, the aramid-ply-twisted yarn spliced as described above is immersed in a conventional resorcinol-formaldehyde-latex (RFL) solution so that the pickup ratio is 3 to 12% by weight based on the aramid-ply-twisted yarn. Bath dipping can be used.

Examples of RFL adhesive solution used in the present invention include 2.0% by weight of resorcinol, 3.2% by weight of formalin (37%), 1.1% by weight of sodium hydroxide (10%), styrene / butadiene / vinylpyridine (15/70/15) An RFL adhesive solution comprising 43.9% by weight of rubber (41%), and water is used.

In the present invention, as an example of the adhesive liquid for the adhesive strength of the aramid cord and the rubber can be prepared and used as described above, the above examples are only intended to more clearly understand the present invention, it is intended to limit the scope of the present invention no.

· Dry heat shrinkage (%)

After treatment under a load of 0.01 g / d for 2 minutes at 180 ° C with a length (L1) measured under a constant load of 0.01 g / d using a shrinkage behavior tester (manufactured by TestRite) according to ASTM D 4974-04 Dry heat shrinkage was measured using the ratio of length (L2).

Medium elongation (%)

According to the ASTM D-885 test method, it is expressed as the change in elongation length at the point of 6.75 kg load in the elongation load graph measured by an Instron Engineering Corp. (Instron Engineering Corp, Canton, Mass).

In the present invention, matters other than those described above can be added or subtracted as necessary, and therefore the present invention is not particularly limited.

The aramid tire cord according to the present invention has a low work loss rate and a low modulus variation, which is excellent in durability and driving stability, and excellent in form stability in high temperature conditions, thereby greatly improving the high-speed driving performance of the tire.

Hereinafter, preferred embodiments of the present invention are described. However, the following examples are only preferred embodiments of the present invention, and the present invention is not limited to the following examples.

Example  One

An aromatic diamine solution was prepared by maintaining 1,000 kg of N-methyl-2-pyrrolidone at 80 ° C. and dissolving 80 kg of calcium chloride and 48.67 kg of para-phenylenediamine.

The aromatic diamine solution was introduced into the polymerization reactor 20, and at the same time, a molten terephthaloyl chloride of an equimolar amount of para-phenylenediamine was simultaneously introduced into the polymerization reactor 20, followed by stirring them to have an intrinsic viscosity of 6.8. Poly (para-phenyleneterephthalamide) polymer (aramid polymer) was prepared.

Next, the prepared aramid polymer was dissolved in 99% concentrated sulfuric acid to prepare an optically anisotropic radiation stock solution having a polymer content of 18% by weight.

Next, after spinning the spinning stock solution prepared as described above at a spinning winding speed of 1,000 m / min through the spinneret 40 as shown in Figure 3, the radiated spinning material 7 mm air layer (non-coagulation) Fluid layer), and then passed through a coagulation bath 50 containing a sulfuric acid aqueous solution (coagulant) having a sulfuric acid concentration of 13% to prepare aramid multifilament.

Next, the multifilament formed as described above was washed with water and dried, followed by repeated five times of heat treatment at 550 ° C. for 0.3 seconds to prepare aramid multifilament.

The number of filaments of the aramid multifilament yarn produced by the above method is 1000, the average fineness is 1.5 d, the strength is 22.3 g / d, the modulus is 714 g / d, the elongation at break is 3.2%.

The prepared aramid multifilament was staged using a cable & Cord 3 type twister (CC Twister, Allma Co.) 30 times / 10 cm twisted (Z length), and the stranded two strands again 30 times / 10 times The twisted yarns of cm were rolled (S rolled), and these were spliced together to prepare a cord dough.

As described above, the raw material of the cord is 2.0% by weight of resorcinol, 3.2% by weight of formalin (37%), 1.1% by weight of sodium hydroxide (10%), and styrene / butadiene / vinylpyridine (15/70/15) rubber (41%). The RFL adhesive solution containing 43.9% by weight, and water was immersed so that the pick-up rate was 5% by weight based on the aramid twisted yarn, dried at 150 ° C. for 60 seconds, and then heat-treated at 250 ° C. for 120 seconds.

Various physical properties of the aramid tire cord thus prepared were as shown in Table 1.

Example  2

Aramid tire cord was prepared in the same manner as in Example 1, except that the number of twists of the upper and lower edges was changed to 40 times / 10 cm.

Various physical properties of the aramid tire cord thus prepared were as shown in Table 1.

Example  3

An aramid tire cord was prepared in the same manner as in Example 1 except that the number of twists of each of the upper and lower edges was changed to 50 times / 10 cm.

Various physical properties of the aramid tire cord thus prepared were as shown in Table 1.

Example  4

Aramid tire cord was prepared in the same manner as in Example 1 except that the heat treatment conditions were changed to 90 seconds at 260 ° C., and the RFL pickup rate was changed to 6 wt%.

Various physical properties of the aramid tire cord thus prepared were as shown in Table 1.

Aramid tire physical property evaluation result division Weighted energy (mJ) Work loss (mJ) Elongation at Strain Daily loss rate (%)  Example 1 30 ℃ 207.4 16.6 0.5 8 120 ℃ 255.8 38.4 0.6 15 150 ℃ 282.4 107.3 0.7 38  Example 2 30 ℃ 221.1 15.5 0.5 7 120 ℃ 256.1 35.9 0.6 14 150 ℃ 290.2 95.8 0.8 33  Example 3 30 ℃ 202.4 10.1 0.4 5 120 ℃ 261.5 44.5 0.7 17 150 ℃ 274.6 101.6 0.7 37  Example 4 120 ℃ 198.6 15.9 0.4 8 120 ℃ 249.9 27.5 0.6 11 150 ℃ 282.4 110.1 0.7 39

Referring to Table 1 and the results of FIGS. 3 and 4, it can be seen that the aramid tire cord of the present invention has low work loss rate and elongation strain rate, thereby improving stability at high speed of tire travel.

1 is a partial cutaway perspective view showing a typical tire.

2 to 3 show the definition of the upper and lower edges.

4 is a process schematic diagram of making aramid filament fibers.

Claims (14)

Aramid tire cords comprising aramid multifilament, characterized in that the work loss rate defined by the following formula 1 is 30% or less at 120 ℃: [Calculation 1] Daily loss rate (%) = daily loss / weighting energy × 100 (In the above formula, the work loss is defined by Equation 2 below, where the weighted energy is an energy value after 10 times of tensile repetition experiments with a load corresponding to a cutting strength of 10% on the aramid tire cord, and the weighted energy is a load removed from the aramid tire cord. The energy value after [Calculation 2] Work loss = loading energy-unloading energy The aramid tire cord according to claim 1, wherein the aramid tire cord has a work loss ratio of 40% or less at 150 ° C. The aramid tire cord according to claim 1, wherein the aramid tire cord has a work loss ratio of 25% or less at 30 ° C. The aramid tire cord according to claim 1, wherein the aramid tire cord has a strain rate of 2% or less at 120 ° C, which is defined by Equation 3 below. [Calculation 3]

(L ₀ is the length value of the aramid tire cord before applying the load, L ₁₀ is the length value of the aramid tire cord measured after 10 times tensile repetition test with a load corresponding to 10% of the cutting strength) The aramid tire cord according to claim 3, wherein the aramid tire cord has an elongation at break of 3% or less at 150 ° C. The aramid tire cord according to claim 3, wherein the aramid tire cord has an extension strain of 1% or less at 30 ° C. The aramid tire cord according to claim 1, wherein the total fineness of the aramid tire cord is 800 to 10,000 denier. The aramid tire cord according to claim 1, wherein the aramid is poly (para-phenylene terephthalamide). The aramid tire cord according to claim 1, wherein the aramid multifilament has a strength of 10 to 25 g / d, an elongation at break of 2 to 6%, and a modulus of 400 to 750 g / d. The aramid tire cord according to claim 1, wherein the total fineness of the aramid multifilament is 400 to 5,000 denier. The aramid tire cord according to claim 1, wherein the aramid multifilament is composed of 500 to 1,200 aramid monofilaments. The aramid tire cord according to claim 6, wherein the single yarn fineness of the aramid monofilament is 1 to 2 denier. The aramid tire cord according to claim 1, wherein the median elongation of the aramid tire cord measured under a load of 6.75 kg is 0.3 to 1.5%. The aramid tire cord according to claim 1, wherein the dry heat shrinkage rate of the aramid tire cord is 0.3 to -1.0%.

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