JPS627295B2 - - Google Patents

Description

[Detailed description of the invention]

(a) Technical Field The present invention relates to a dip cord for tire reinforcement. (b) Prior Art In general, tire reinforcing materials are used in the form of woven fabric. Dip cord is a material that constitutes the warp of such a woven fabric, and is usually made by first twisting and final twisting a complementary number of yarns, and then applying an adhesive, such as a polyhydric phenol and formalin condensate, to rubber latex. Added aqueous dispersion (hereinafter referred to as
It's called RF/L. ) and is heat-cured. Among tire reinforcing materials, nylon fiber has excellent strength, durability, and heat resistance.
It is applied to large tires in fields with heavy loads and severe usage conditions, such as trucks and buses, construction vehicles, and aircraft. However, compared to passenger car tires, these tires
The amount of reinforcing material used per tire is extremely large, requiring a large amount of energy and fuel consumption. On the other hand, reflecting the recent rise in raw material and fuel prices, there is a growing trend toward energy conservation and fuel efficiency, and efforts are being made to reduce the weight of tires by reducing the number of layers of reinforcing material and reducing the number of reinforcing materials inserted. It is strongly requested. In addition, along with such weight reduction, it is highly expected that fatigue resistance will be improved by reducing the amount of heat generated while the tire is running, and productivity will be improved in the tire molding process. To this end, it is necessary to develop nine fibers that are even stronger than the currently used nylon fibers. Generally, it is known that in order to obtain a high-strength nylon fiber material, a polymer with a high degree of polymerization is spun and then stretched at a high magnification. However, when fibers drawn at a high magnification are used as a tire reinforcing material, the strength decreases in the dipping process and the vulcanization process in which they are combined with rubber. Furthermore, toughness (load ~
The area of the elongation curve is (breaking strength) x
(Elongation at break)/2. ) becomes significantly smaller. The present inventors have made various attempts to increase the strength of the nylon fiber itself. However, even if a tire reinforcing dip cord is made of high-strength nylon fibers, the strength level will not be increased enough to reduce the weight of the tire if the dip cord is fabricated using a normal dip method. (c) Object of the invention An object of the invention is to provide a tire reinforcing dip cord that can reduce the weight of a tire without reducing tire performance. (d) Structure of the invention The tire reinforcing cord according to the present invention is made of nylon 66
It is characterized by satisfying the following characteristics (a), (b), (c) and (d). (a) Breaking strength: 8.2 g/d or more, (b) Elongation at a load of 8 g/d: 18% or more, (c) Slope of the load-elongation curve just before breakage (TE coefficient): 0.75 or less, (d) Load 450 against cord diameter (D ₀ ) with no load
Cord diameter change rate (VG value) expressed by the ratio of cord diameter (D) under g (D/D ₀ ): 0.65 or less. (e) Specific explanation of the structure The dip cord of the present invention has a breaking strength of 8.2 g/
d or more, preferably 8.4 to 9.0 g/d. If the breaking strength is less than 8.2 g/d, it is not possible to reduce the number of layers of reinforcing material and reduce the weight of the tire.
Here, d is solid content such as RF/L, number of twists, moisture content
Indicates the denier of the dip cord itself, including 4.5%, etc. Further, the dip cord of the present invention has a load of 8 g/d.
It is necessary that the elongation at is 18% or more, preferably 18 to 30%. If it is less than 18%, the breaking energy obtained from the area of the cord load-elongation curve is small, reducing tire performance.
It cannot function as a tire reinforcing material. Furthermore, the slope of the load-elongation curve of the dip cord of the present invention immediately before breakage is gentle, that is,
It is important that the TE coefficient is small, and the TE coefficient is 0.75.
It must be less than or equal to, preferably 0.70 to 0.30. If the TE coefficient exceeds 0.75, not only will the strength in subsequent processing steps, such as the vulcanization step, be greatly reduced, but also the performance of the tire, particularly impact resistance and durability, will be reduced. Furthermore, the dip cord of the present invention exhibits flexibility not found in conventional high-strength cords. In other words, when measuring the cord diameter, when the diameters under no load and under a load of 450g are D ₀ and D, respectively, the ratio of both cords D/
_Dip cord diameter change rate (VG
value) must be less than or equal to 0.65, preferably
It is between 0.60 and 0.40. If the VG value exceeds 0.65,
That is, if the dip cord is rigid, it not only has low toughness but also impedes workability in the tire manufacturing process. Note that the breaking strength and elongation at a load of 8 g/d are measured when the cord is heated at 24°C and 55% R after dipping.
This is the average value of n=10 obtained by measurement based on JISL-1017 after being left in an H atmosphere for 72 hours.
The slope of the load-elongation curve just before breakage is determined by measuring under the above conditions, copying the curve recorded on the chart onto graph paper, and comparing the breakage point of the curve with (breakage elongation - 0.5)%.
It is found by connecting the points. Figure 1 is a schematic diagram of the load-elongation curve, where A is the breaking point and B is the point at (break elongation - 0.5%). By connecting A and B, we can calculate the slope just before breaking, That is, the TE coefficient is determined. The VG value is determined from the ratio of the cord diameters measured with a dial gauge on a sample left in the same atmosphere as in the case of measuring strength and elongation. The dial gauge
It is listed in JISL-1017 and has a measuring stand diameter of approximately 40 mm and a measuring leg diameter of approximately 10 mm.
Measured by falling from a height of 6.5mm. 2 samples
The legs are set so that they are perpendicular to each other under no tension, and their intersections are located at the center of the measuring legs. First, measure the cord diameter with no load on the measuring leg and set it as D ₀ . Next, a load of 450 g is applied to the measuring leg, the measuring leg is lowered onto the sample, and the cord diameter is measured after 1 minute has passed and is designated as D. The VG value is expressed as the ratio between the two (D/D ₀ ), and the smaller the VG value, the softer the cord. The tire reinforcing dip cord of the present invention has the above-mentioned essential characteristics, but
Other properties have the same values as normal tire reinforcing dip cords. That is, the intermediate elongation is 7 to 11%, preferably 8 to 10%, and the dry burn shrinkage rate is: Free shrinkage rate at 160℃ x 30 minutes is 2 to 9
%, preferably 3 to 8%, the number of twists is T, where the number of twists per 10 cm is D, and the total denier of the yarns that make up the cord is D, the twist coefficient calculated by K = T × √ is 1700
≦K≦2200, preferably 1800≦K≦2100, and the amount of adhesive deposited is usually 3 to 7% by weight, preferably 4 to 6% by weight. The method for manufacturing the dip cord of the present invention will be explained based on FIG. FIG. 2 shows a dip cord manufacturing device. 1
is a twisted yarn feeding device, 2 and 3 are adhesive dipping devices, 4, 5, and 6 are tension control devices, and 7
Reference numeral 8 indicates a softening device, and 8 indicates a dip cord winding device. 9 and 9' are the first zone, 10 is the second zone, and 11 is the third zone, the tension in the first zone is between 2 and 4, the tension in the second zone is between 4 and 5, and the tension in the third zone is between 2 and 4. The tension of is applied between 5 and 6. Generally, yarns obtained by first twisting and final twisting raw yarn having a breaking strength of 9.8 g/D or more, preferably 10.0 g/D or more, and a breaking strength of 19.0% or more, preferably 20.0% or more are used. Deep processing is performed as follows. ) The cord tension when immersed in RF/L is usually 1.0.
Depth above Kg/cord. (Immerse the RF/L at 3 in Figure 2 and apply tension between 2 and 4):) In the final step of dip (position 7 in Figure 2), soften it by squeezing it with a metal blade, for example. do. ) Before the dip process,
Tension heat treatment at 160℃ or higher. The nylon that is the object of the present invention consists of nylon 66. Nylon 66 may be used alone, and
A copolymer in which the nylon 66 component accounts for 80% by weight or more, such as a nylon 6/66 copolymer, and other compounds capable of forming an amide in addition to the nylon 66 forming component, such as aliphatic dicarboxylic acids, aromatic dicarboxylic acids, and fatty acids. Copolyamides derived from monomer compositions containing small amounts of group diamines, aromatic diamines, etc. may also be polymer mixtures in which nylon 66 accounts for 80% or more by weight, such as nylon 6/nylon 66 mixtures. . Furthermore, the dip cord of the present invention contains additives contained in ordinary nylon tire cord yarn, such as heat stabilizers, antioxidants, light stabilizers,
It may also contain lubricants, plasticizers, thickeners, etc. (f) Effects of the Invention As described above, the nylon dip cord of the present invention has an adhesion level equivalent to that of conventional products, and has significantly improved strength and toughness, making the tire lighter and more durable. It is also possible to improve properties such as durability and impact resistance. (G) Examples Hereinafter, the present invention will be specifically explained with reference to Examples. In the examples, formic acid relative viscosity refers to a solution of 90% formic acid with a polymer concentration of 8.4% by weight, and sulfuric acid relative viscosity refers to
of a 1.0 wt% polymer concentration solution in 95.5% sulfuric acid, each
This is the relative viscosity of the solution at 25°C. Fatigue resistance is the fracture time of a tube (n=4) in a tube fatigue test conducted in accordance with JISL-1017. The bending angle of the tube is 90°, and the number of cords in the tube is 65 in the case of 1260D/2.
In the case of 1680D/2, it is 50 lines, and in the case of 1890D/2, it is 45 lines. The tube internal pressure is 3.5Kg/cm ² and the rotation speed is
It is 850rpm. Vulcanization deterioration is a characteristic that indicates the degree of decrease in the strength of the dip cord during the vulcanization process, and is expressed as the retention rate of the cord strength before and after the vulcanization process. In the test, the dip cord was sandwiched between 5 mm thick carcass rubber sheets and vulcanized in a mold. Vulcanization conditions are 180℃
×30 minutes, gauge pressure 35Kg/cm ² . The rubber sheet obtained after vulcanization was disassembled, the cord was peeled off from the rubber, and its strength was measured. The measurement conditions were as described in the text. Example 1 A high polymerization degree polymer with a formic acid relative viscosity of 88.0 obtained by polymerizing nylon 66 chips having a formic acid relative viscosity of 32.0 at 210°C in a nitrogen atmosphere was 0.25 at 300°C.
The material was spun through a spinneret of 210 mmφ x 210 mm, passed through a heating cylinder at 350°C, cooled, and applied with a spinning oil. Subsequently, stretching heat setting was performed in three stages using first to fourth Nelson rollers having temperatures of 80°C, 210°C, 220°C, and 245°C, respectively, and the film was wound at a speed of 1600 m/min. The draw ratio was 6.05. The obtained yarn is
1260D/210f, formic acid relative viscosity 80.5, strength
It was 10.5g/D and elongation was 21.5%. Ply twist (Z direction) 39 to these two yarns separately.
Add twists/cm, align the two strands, and further twist (S direction)
was added 39 times/cm to create a yarn of 1260D/2.
Next, it was dipped using the dipped cord manufacturing apparatus shown in FIG. RF/L is under tension in the first zone;
It was immersed in step 3 in Figure 2. 1st zone temperature 150℃,
Tension 1.2Kg/cord, time 120 seconds, 2nd zone temperature
The test was carried out under the following conditions: 225°C, tension: 2.8 kg/cord, time: 40 seconds, third zone temperature: 225°C, tension: 1.9 kg/cord, time: 40 seconds. Table 1 shows the characteristics of the dip cord obtained. Example 2 A raw yarn of nylon 66, 1890D/312f having a formic acid relative viscosity of 81.7, a strength of 10.4 g/D, and an elongation of 20.9% was obtained by substantially the same method as in Example 1. The raw yarn is twisted 32 times/10cm each for the first twist and the second twist.
The yarn was made into a yarn of 1890D/2, and then dipped using the dip cord manufacturing apparatus shown in FIG. RF/L was immersed at 3 in Figure 2 under tension in the first zone. The conditions are: 1st zone temperature 160℃, tension 4.0Kg/cord,
Time 120 seconds, second zone temperature 232℃, tension 4.8Kg/
Code, time 40 seconds, 3rd zone temperature 232℃, tension
It weighed 3.6Kg/cord and took 40 seconds. The dipcord obtained was very flexible. The characteristics of this code are shown in Table 1. Comparative Example 1 A nylon 66 polymer having a formic acid relative viscosity of 65.0 was spun according to Example 1 to obtain a yarn of 1260D/210f. The draw ratio was 6.25. The obtained yarn had a strength of 9.9 g/D and an elongation of 14.8%. Twisting and dipping were carried out under the same conditions as in Example 1.
Table 1 shows the characteristics of the obtained dip cord. Although the tire has high strength, if the elongation at break is small and the TE coefficient is large, the fatigue resistance of the tire will be significantly reduced. Comparative Example 2 In Comparative Example 1, a raw yarn of 1260D/210f was obtained at a drawing ratio of 5.4. The physical properties of the yarn are strength 9.4g/D and elongation.
It was 23.5%. Twisting and dipping were carried out in the same manner as in Example 1. Table 1 shows the characteristics of the obtained dip cord. Although the dip cord has an excellent TE coefficient, its breaking strength is insufficient, and it is not possible to reduce the weight of the tire. Comparative Example 3 The cord obtained in Example 2 was dipped using the dipped cord manufacturing apparatus shown in FIG. Immerse it in RF/L at 2 in Figure 2 under the tension of 0.1Kg/cord,
1st zone temperature 160℃, tension 3.0Kg/cord, time
100 seconds, 2nd zone temperature 234℃, tension 4.5Kg/cord, time 30 seconds, 3rd zone temperature 234℃, tension 3.2
Kg/cord, time 30 seconds. Table 1 shows the characteristics of the obtained code. Even if the tire has high strength and high elongation, if the load-elongation curve at break is not gentle, the strength will decrease in the heat treatment process after dipping, which will have a negative impact on the tire's durability and impact resistance. Example 3 In the dip of Example 2, the first zone temperature
160℃, tension 3.0Kg/cord, time 120 seconds, second zone temperature 232℃, tension 4.5Kg/cord, time 40 seconds,
3rd zone temperature 232℃, tension 2.3Kg/cord, time
Deep processing was carried out for 40 seconds. RF/L
is immersed under tension in the first zone, and between the third zone and the winding process, a pair of metal blades is pressed against the cord at position 7 in Figure 2 with a tension of 0.5 kg/cord to soften the cord. Processed. The dip cord obtained was extremely flexible. The characteristics of this dip cord are shown in Table 1. Example 4 The relative viscosity of formic acid was determined by the same method as in Example 1.
90 parts by weight of 88.0 nylon 66 high polymerization degree polymer;
A mixture of 10 parts by weight of nylon 6 polymer having a relative viscosity of 3.4 was spun to obtain a raw yarn of 1260D/210f.
The physical properties of the yarn were a strength of 10.2 g/D and an elongation of 22.1%. This raw yarn was twisted and dipped according to Example 1. Table 1 shows the characteristics of the obtained dip cord.

【table】

[Table] As shown in Table 1, the dip cord according to the present invention satisfies both the objective of reducing tire weight and maintaining tire characteristics.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a load/elongation curve of a dip cord according to the present invention, and FIG. 2 is a diagram showing a manufacturing apparatus for a dip cord according to the present invention.

Claims (1)

[Scope of Claims] 1. A dip cord for reinforcing tires, which is composed of fibers made of nylon 66 and satisfies the following characteristics (a), (b), (c), and (d). (a) Breaking strength: 8.2 g/d or more, (b) Elongation at a load of 8 g/d: 18% or more, (c) Slope of the load-elongation curve just before breaking (TE coefficient): 0.75 or less, (d) Load 450 against cord diameter (D ₀ ) with no load
Cord diameter change rate (VG value) expressed by the ratio of cord diameter (D) under g (D/D ₀ ): 0.65 or less.