JPS61160446A - Tire cord - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] <Industrial application field> The tire needle is constructed using a plurality of yarns.

The present invention relates to a tire cord that effectively utilizes the strength of the yarn. More specifically, the present invention relates to a tire cord that improves the reduction in tenacity utilization rate, which is a problem associated with increasing the tenacity of the tire cord yarn or increasing the spinning speed during the production of the tire cord yarn.

<Prior Art> Polyamide tire cord still occupies the mainstream of tire cords due to its high strength, durability, and good adhesive properties with rubber. In recent years, new grades of polyamide tire cord have been developed in two directions. One direction is toward higher strength, and tire cord fibers with a strength exceeding 10 g/d have already begun to be produced. Another direction is to use high-speed spinning, which originated from polyester, and is intended to improve dimensional stability and durability.

Increasing strength is a combination of various techniques, but typical techniques include increasing the degree of polymerization, lowering the spinning speed, providing a higher drawing ratio, and using a suitable spinning oil. can give. On the other hand, with regard to high-speed spinning, there is a remarkable phenomenon in which it becomes difficult to obtain strength when the spinning speed is increased, especially for polyamides. This is because during spinning, the difference in cooling between the inner and outer layers of the single filament increases.
To improve this problem, efforts have been made to provide a heating zone directly below the spinneret and to reduce the single yarn denier.

<Problems to be solved by the invention> If a method of simply increasing the drawing ratio is adopted to increase the strength, even though the strength of the raw yarn becomes high, the tires treated with adhesive and heat At the cord stage, there is a problem in that the strength of the tire cord is not improved as much as the strength of the raw yarn is improved.

As mentioned above, the most effective means for improving the decrease in yarn strength when the spinning speed is increased is to reduce the technical denier. However, if the yarn sizing denier is set to a small value that allows high yarn strength to be obtained, the yarn strength will improve, but the strength will decrease significantly at the twisting and weaving stages, adhesive treatment, and heat treatment stages, and the yarn strength will increase. The problem is that the high strength of the tire cord is not effectively utilized for tire cords.

Improvements in this strength utilization rate are currently being addressed by improving spinning oils, adhesives, and devising heat treatment methods.
It's still not enough.

An object of the present invention is to provide a tire cord with improved strength utilization in the stages of twisting and weaving, adhesive treatment, and heat treatment of the tire cord from the raw yarn side.

Here, the strength utilization rate indicates tire cord strength/(raw yarn strength x number of yarns twisted during twisting).

<Means for Solving the Problems> The purpose of the present invention is to use a yarn containing 2 to 20 filament groups having 0 twists of 2 to 100 times per meter as a raw yarn, and to This is achieved by a tire cord formed with the desired non-combustibility, doubling and ply twisting.

When raw yarn for tire cord is twisted to a normal number of twists to form a raw cord and subjected to adhesive treatment and heat treatment, the strength utilization rate generally decreases. In other words, it is less than 100%. This phenomenon is caused both by the twist angle and by other factors.

The decrease in the strength utilization rate due to the twist angle is determined by the yarn fineness, density, number of twisted yarns, and number of twists. If these conditions are the same, there is no difference in the effect of the twist angle. If the elongation at break is significantly different, the diameter of the tire cord and the number of twists at break will be different, so there may be a difference in the strength utilization rate, but this difference is small.

The reason why the strength utilization rate differs depending on the raw yarn in the processes of twisting, weaving, adhesive treatment, and heat treatment is due to causes other than the twist angle.

As a result of intensive study, we clarified the cause of this problem and arrived at an improvement in the power usage rate. That is, this cause is manifested by twisting the yarn. In tire cord, the number of twists is 1
Considering a short cord length of about 100 mm, the length of the filament is not uniform, but has a distribution of long and short lengths.

Therefore, when the tire cord is stretched, even at the time when the short filaments break, the long filaments have not been stretched to the point where they break and do not exert sufficient strength.

As a result, the tire cord strength has a low value. At the time when a short filament breaks, the ratio of each filament's own breaking strength to its own shows the difference in the tire cord strength utilization rate.

Specification of Japanese Patent Publication No. 41-7892 and Japanese Patent Publication No. 57-15
4410, the strength of the tire cord can be increased by decreasing the rate of change in stress strain near the break point in the stress-strain curve of the tire cord (the slope of the stress-strain curve if the horizontal axis is the strain). The utilization rate can be improved for the above reason.

However, in order to increase the yarn strength, it is necessary to increase the drawing ratio, making it difficult to reduce the above rate of change.

In the case of polyamide tire cords, a decrease in the strength utilization rate during adhesive treatment and heat treatment is often more of a problem than the strength utilization rate during the twisting stage. The reason for this is that in the raw code,
If we consider a short cord length of about t281, the filament length will be non-uniform, but if we consider a long cord length, the filament length will be uniform, so due to the action of tension during stretching,
The length of the filament changes between twists, and at the point of breakage, the strength of the filament changes to a length suitable for the strength of the filament, so the strength of the filament is effectively utilized. When this green cord is treated with an adhesive and heat treated, the adhesive is applied and the filament length becomes difficult to move, resulting in a decrease in the strength utilization rate.

Whether this movement occurs sufficiently or not is one of the deciding factors in whether the power utilization rate is good or bad.

The degree of filament movement of fuel is determined by the balance between friction between filaments and how much tension the filament can withstand.

The greater the strength of the filament, the more likely it is to overcome frictional resistance and move.

Decreasing the filament denier reduces the tension that can be withstood and reduces filament movement in the tire cord, resulting in lower strength utilization. Therefore, reducing the filament denier in order to increase the spinning speed poses a problem.

These problems regarding strength utilization are more likely to occur with polyhexamethylene adipamide than with polycapramide due to differences in the stress-strain curves of the raw yarns, while with polyester tire cords, problems are already present at the raw cord stage. Movement of filament length is difficult to occur (strong utilization rate decreases).

Based on the above analysis, we determined that when the tire cord is stretched,
As a result of studies to make it easier for the filament length to shift in fuel amount, the present invention having the above-mentioned configuration was arrived at.

With ordinary yarns, there is a limit to the tension that the filaments can withstand even when attempting to move each filament of the yarns that make up the tire cord, and the expected effect is small.

However, by treating multiple filaments as a group of an appropriate number, tension was obtained to overcome friction, resulting in a good strength utilization rate.

That is, a large number of filaments of the raw yarn forming the tire cord are divided into a plurality of groups, and each group is slightly twisted.

This does not reduce the friction between the filaments within the group, but it prevents the filaments from moving in and out between the groups, making it easier for slippage between the groups to occur.For this reason, when the tire cord is stretched, on average, the individual filaments This will enable you to effectively express the power that you possess.

If the number of this group is too large, the effect will be small. As the groups bind each other, friction increases and effectiveness decreases. 2 to 20 pieces is good. Also, if the number of twists added to each group is too large, the strength utilization rate will be reduced. The reason for this is that the power of the group itself decreases. The appropriate number of twists to be added to one group is about 2 to 100 twists per meter.

Care must be taken not to vary the twist angle between groups. If this is not done correctly, the power usage rate may decrease.

If (denier of group) x (number of twists) 2 is made the same, the twist angle will be approximately constant. Preferably, the groups have the same denier and number of twists.

In the present invention, for example, when the polymer constituting the filament is polyhexamethylene adipamide, a significantly good effect is exhibited when the fineness of the filament is 4 deniers or less.

<Examples> Next, the present invention will be specifically illustrated by Examples, but the present invention is not limited to these Examples.

A polyhexamethylene adipamide polymer with a formic acid relative viscosity of 80 containing copper iodide and potassium iodide as heat stabilizers is discharged from a spinneret having 104 nozzles, and after cooling, it contains water. An oil agent was applied and the film was wound up at a speed of 300 m/min. Subsequently, drawn yarns were obtained using two different methods.

For one, two undrawn yarns were combined and drawn without unwinding to obtain a raw yarn of 260 denier (Table 1a).

The other one was drawn from one undrawn yarn to obtain a drawn yarn of 630 denier. The stretching conditions are as follows. One unheated supply roll to provide tension and three pairs of heated Nelson rolls provide horizontal stretching while the second one is heated at 210°C.
Supplied to Nelson roll, further stretched 1.55 times and 2
fed to a third Nelson roll at 35 °C, then 0.91 °C
It was wound up onto a paper tube at twice the speed of 1200 m/min. Both of the drawn yarns obtained here had a strength of 10.6 g/denier.

2 twists shown in Table 1 b-g were applied to the drawn yarn of 630 denier.
In addition, the two yarns were then combined to obtain a raw yarn of about 1260 denier.

Using these yarns, a two-strand raw cord with a non-combustible (Z direction) and ply twisted (S direction) twist count of 39 twists per 10 cm was created. Subsequently, adhesive treatment and heat treatment were performed using conventional methods to obtain tire cords.

The strength and strength utilization rate of these tire cords are as shown in Table 1.

It can be seen that a tire cord constructed by dividing the raw yarn into two groups and twisting each group from 2 to 100 times per meter has an excellent strength utilization rate.

Margin below Table 1 Note 1) Number of twists per meter of 630 denier drawn yarn.

Note 2) Naa is obtained by combining two undrawn yarns and drawing them.

b-g are undrawn yarns drawn and then gold threaded.

Example 2 Using the polymer of Example 1, a water-containing oil agent was applied by discharging from a spinneret having 210 nozzles at a speed of 3500 m/min.
I wound it up. This was stretched in two ways. The first is
Three undrawn yarns were combined and drawn without unwinding to obtain a raw yarn of 1890 denier (Table 2 h). Second
One undrawn yarn was directly drawn to obtain a drawn yarn of 630 denier. Both of these drawn yarns had a strength of 8.5 g/denier and an elongation of 16%. Add the twist shown in Table 21-m to the drawn yarn of 630 denier, combine the three yarns,
The raw yarn was approximately 1890 denier. The stretching method used all non-heated stretching rolls, and after passing the first stage over a hot plate at 248°C and stretching it to 2.2 times, the second stage was passed over a hot plate at 255°C and stretched to 1.1 times. The film was stretched in stages and then passed through a hot plate at 252°C to undergo a relaxation heat treatment to a factor of 0.92, and then wound up at a speed of 80 m/min in a non-twisted state.

Tire cords were obtained from these yarns in the same manner as in Example 1, and their strength and strength utilization rate are shown in Table 2. However, the number of twists of the raw cord is 3 per 10 am for both non-combustible and ply twisted cords.
It is 2.

It can be seen that the strength utilization rate can be improved by dividing the raw yarn into three groups and adding an appropriate twist to each group (see examples in Table 2 j to l).

Table 2 Note 1) Number of twists per meter added to 630 denier drawn yarn.

Note 2) Thickness is obtained by doubling and drawing three undrawn yarns.

Example 3 Using the polymer of Example 1, it was discharged from a spindle having 24 nozzles and wound up at 3500 m/min.
A drawn yarn of 50 denier was obtained by the second method.

The drawn yarn had a strength of 8.6 g/denier and an elongation of 15.5%.

Take care not to untwist the drawn yarn by 1, 2, or 4 yarns.
A total of 40, 20, 10, 4, 2 drawn yarns, each of which is twisted 20 times per meter, are One yarn was combined to make six types of raw yarn of about 2000 denier.

Using these yarns, tire cords were obtained in the same manner as in Example 1, and their strength and strength utilization rate are shown in Table 3. However, the number of twists in the raw cord is non-flammable.

The final twists were 32 times and 31 times per lQcm, respectively.

It can be seen that the tire cord formed satisfying the conditions of the present invention has an excellent strength utilization rate (see examples o''-r in Table 3).

Table 3 Note 1) The actual number of twisted drawn yarns is 1u11. Using the polymer of Example 1, each yarn is 104.140°21.
It was discharged from a spindle with 0.312 nozzles.

After passing through a steam moisture applicator, a water-containing oil agent was applied and the product was wound up at 998 m/min. Only the stretching ratio is 4th.
Using the apparatus of Example 1, one undrawn yarn was drawn using the values shown in the table so that no untwisting occurred. The drawn yarn physical properties are the fourth
Shown in the table.

For each of the drawn yarns shown in Table 4, the original yarn is one in which three yarns are twisted together to prevent untwisting, and the original yarn is in which three yarns are twisted after twisting the drawn yarn 20 times per meter. Making thread, Example 2
Tire cords were obtained by the method shown in Table 5, and their strength and strength utilization rate are shown in Table 5.

It can be seen from Table 5 that the effect of the present invention becomes remarkable when the filament denier is 4 denier or less.

Margin below Table 4 Table 5 <Effect of the invention>

Claims (1)

[Claims] 1. A yarn containing 2 to 20 filament groups with twists of 2 to 100 times per meter is used as the raw yarn,
A tire cord formed by imparting desired non-combustibility, doubling and ply twisting to the raw yarn.