JPS599652B2 - Manufacturing method of weft yarn for tire reinforcement fabric - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a weft yarn for a tire reinforcing fabric, and more particularly to a method for producing a weft yarn for a tire reinforcing fabric, which is suitable as a weft yarn for a reinforcing fabric in the carcass portion of a radial tire.

Conventional tire reinforcing fabrics have generally been fabrics called sudare-ori, in which tire cords are closely arranged as warp threads, and weft threads are arranged at coarse intervals. It was common for tires to be made by heat-molding them together with rubber so that they would stick together.

As radial tires have become more popular in recent years, there has been an increasing demand for uniform distribution of tire cords within the tire.The elongation of cotton yarn, which has been mainly used as weft yarn up until now, is as low as approximately 8%, so it has become difficult to make tire cords evenly distributed during tire molding. Unable to follow the large deformation of the weft, the weft is broken during tire molding due to the weak point depending on unevenness in the longitudinal direction of the weft, resulting in an asymmetrical distribution of the warp, which is the tire cord. It has come to be recognized that it is unsuitable for tires that require high performance, such as radial tires.

From this point of view, there has recently been an example in which an undrawn synthetic fiber yarn with high extensibility is used as a core yarn, coated with a stable fiber such as cotton to form a core yarn, and this is used as a weft yarn (U
SP 3,828,544), an example using a core yarn in which cotton is wrapped around undrawn polyester yarn spun at high speed (US Pat. No. 4,024,895), or heat treatment of undrawn polyester yarn to increase the residual shrinkage rate (dry heat at 150°C).
) is ±2% or less (Unexamined Japanese Patent Publication No. 52-7
0167), the degree of orientation Δn is 13×10-3 to 80
An example using a highly oriented polyester filament of x10-3 (Japanese Patent Application Laid-Open No. 5124973/1983) has been proposed.

However, in the first two cases, the coated fibers tightly cover and constrain the core yarn, so even though the core yarn itself has high extensibility, when it undergoes elongation deformation, the load is first applied to the coated fibers. When this breaks, local tension stress concentrates on the core thread at the break point, and the core thread also breaks from that point, making it difficult to obtain sufficient elongation. , and was expensive.

On the other hand, if the ratio of coated fibers is lowered so as not to hinder the elongation of the core yarn, incomplete coverage tends to occur, and the high temperature baking process is required after applying the RFL resin liquid to improve adhesion to the rubber. During processing, the undrawn yarn serving as the interlining suffered thermal deterioration and the desired elongation could not be obtained.

In addition, even if multifilaments with special physical properties such as the latter two are used, the filaments are easy to disperse in the fabric because they are not twisted, so a large amount of RF'L resin liquid tends to adhere, and the elongation after baking is low. There was a tendency for it to decline dramatically.

In addition, when cotton yarn is wrapped around a multifilament with a small residual shrinkage rate, the tensile stress behavior of the cotton yarn becomes dominant, and not only is it difficult to stretch, but also excessive stress is applied to the high elongation filament yarn when the cotton yarn is cut. Because of this, there was a drawback that they would be cut at the same time.

Preferred weft yarns for tire (particularly radial tire) reinforcing fabrics include: (1) Even after being impregnated with R F L resin liquid and subjected to baking treatment at a high temperature of about 230 to 250°C for several minutes, the weft yarn still has a 60% weft yarn. % or more, and (2) the ability to uniformly maintain a large number of warp threads intersecting with the weft threads at a predetermined density.

The present invention provides a method for producing a weft yarn for tire reinforcing fabrics that satisfies such required performance, and the gist thereof is to prepare a polyester manolet filament yarn having a breaking elongation of 80 to 200% as defined by the following formula (1). Lower twist coefficient K1 is 10~
50, and then the first twisted multifilament yarn and the first twisted multifilament yarn have a 7 to 7
0% by weight of non-melting short fiber bundles are merged and the same direction as the first twisting is performed.The product of the first twisting coefficient K1 and the first twisting coefficient K2 defined by the following equation (2) is calculated by the following equation (3). This is a method for producing a weft for a tire reinforcing fabric, characterized in that ply-twisting is performed under conditions that satisfy the following: The ply-twisted multifilament yarn is made into a core yarn covered with the non-meltable short fibers.

(However, in the above formulas (1), (2), and (3), K1 is the lower twist coefficient, K2 is the upper twist coefficient, and T0 is the lower twist number (T/c
IrL), T2 is the number of ply twists (T/in), D is the total denier (d) of the polyester multifilament yarn, N
e indicates the English cotton count of the core yarn.

) The weft yarn of the present invention is a core yarn used as the core yarn of a polyester multifilament yarn, particularly an ethylene terephthalate polyester multifilament yarn, as described above, and the core yarn has a cutting elongation of 80% or more and 200% or less and a fiber A polyester multifilament yarn whose main repeating unit is ethylene terephthalate unit and has an intrinsic viscosity of vf (measured at 30°C in a mixed solvent of phenol/tetrachloroethane-6/4) of 0.60 or more, especially 0.68 or more. be.

Such a polyester multifilament yarn is produced by melting a polyester mainly composed of ethyne terephthalate units and having an intrinsic viscosity vP of about 0.61 or more, particularly 0.70 or more, and spinning it through a spinneret having a plurality of spinning holes. After being taken out, it is once cooled with a cooling air stream, and then an appropriate oil agent is applied, and the spinning speed is approximately 1800 to 4000 m.
The birefringence Δn is approximately 17 to 1 by high speed spinning of lmin.
It can be obtained by highly oriented melt spinning so that the fiber diameter is 0-3 to 80 x 10-3.

In this case, the diameter of the spinning hole, the number of holes, the discharge amount of the polymer, and the spinning speed are appropriately selected depending on the single fiber denier and the number of single fibers.

The number of single threads of multifilament yarn is 10 or more, especially 1
It is best to use 9 to 50 strands, and the total denier of the multifilament yarn is 50 to 300 d, especially 100 to 50 d.
The range is preferably 250d.

Low-oriented undrawn yarn produced at low spinning speeds has the drawbacks of significant aging (deterioration of mechanical properties) due to standing, poor heat resistance, and excessive residual shrinkage.
The spinning speed is such that the elongation at break of the resulting polyester multifilament yarn is 200% or less (approximately 18
0 0 m/mirr or more).

However, if the spinning speed becomes too high, the orientation during spinning will advance to a high degree, and the breaking elongation may decrease to 80% or less.
4000 m/mi such that it is about ×10-3
It is around n.

As the ethylene terephthalate-based polyester multifilament yarn, from the viewpoint of heat resistance, a multifilament yarn made of polyethylene terephthalate is most preferable, but a small amount (approximately 5 mol% or less, especially 3 mol% or less) of a third component is copolymerized. It may also be a multifilament yarn made of a copolymerized polyester mainly composed of ethylene terephthalate units.

As mentioned above, it is desirable that the weft for reinforcing fabrics for radial tires has a residual elongation of 60% or more after high-temperature baking following RFL resin treatment, so the weft should have a cutting elongation of at least 80% before baking. It is necessary to have a degree.

If the cutting elongation is less than 80%, it is difficult to increase the residual elongation after baking to 60% or more, and
If the polyester resin exceeds this value, the polyester cannot be used because the degree of molecular orientation is small as described above, so that the degree of molecular orientation is so low that the degree of change over time due to standing is significant, and there is also a problem with the heat resistance of the polyester itself.

The second property required of the weft yarns for tire reinforcement fabrics is that the warp yarns must be stably arranged, but in order to reduce the smoothness of the weft yarns, short fibers are wound around the polyester core yarn to form the core yarn. It is known that a core yarn is preferable, and in the case of the present invention, a polyester multifilament yarn and a non-melting short fiber bundle (sliver) are merged to form a core yarn.

When making a core yarn by drafting using a spinning machine using a high elongation polyester multifilament yarn as described above as a core yarn, it is important that the components of the covering fiber do not hinder the elongation of the polyester core yarn. Non-melting short fibers that are not altered by baking heat treatment are preferred, and low-strength fibers that are easily cut are preferred.

As a fiber that satisfies these properties, short cotton fibers are most suitable, and rayon staples and polynojinx table can also be used.

Of course, as the coated short fibers in the present invention, any kind of non-melting short fibers other than those exemplified above can be used.

Here, the short fibers used to cover the multifilament yarn protect the core yarn from harsh heat treatment, and with their moderate frictional properties, they play an important role in preventing warp yarns from slipping in blind fabrics. Meltability and 7 to 7 for core yarn
A proportion of 0% by weight is required.

If the multifilament yarn serving as the core yarn is not twisted and the filaments constituting the multifilament yarn are loose, some of the ends of the short fibers will be held in the gaps between the filaments. As the ratio of short fibers increases, the intertwining of the short fibers increases, and during elongation deformation, the elongation stress of the short fibers appears more dominant than that of the filament yarn, which has a higher elongation.

Moreover, unlike filament yarn, core yarn has uneven thickness in the longitudinal direction of the yarn, so when it is stretched, it breaks first at weak points where short fibers are intertwined, and a large stress is locally applied to the core yarn. The core yarn is also broken by the impact and cannot exhibit large elongation.

This tendency is further accentuated because the adhesion between the fibers is strengthened after the resin liquid is deposited and baked.

Therefore, it is necessary to prevent this, and for that purpose, the first twist applied to the multifilament yarn is important.

That is, the multifilament yarn is twisted when the twist coefficient K1 is 10 to
When a core yarn is formed by applying a weak first twist so that the core yarn is 50%, and then applying a second twist in the additional twisting direction to form a core yarn, the filament yarn that has been first twisted has improved convergence and the gap between the filaments is reduced. As a result, the ends of the coated short fibers are less likely to be gripped, and the bond between the multifilament yarn, which is the core yarn, and the coated fibers is weakened, so the core yarn is much less likely to be restrained by the short fibers during stretching. , the core yarn also shares the stress evenly in the longitudinal direction, and even after the weft yarn stretches during tire molding and the covering of short fibers breaks down,
The core yarn can maintain sufficient elongation.

Therefore, the first twist added to the core yarn and the final twist (spun twist) added during core yarn production must be twisted in the same direction.

The greater the number of twists added to the core yarn, the greater the effect; however, if it is too large, the core yarn becomes highly twisted and damaged due to the additional twist added to cover the short fibers, and the desired result cannot be achieved. If the elongation cannot be ensured, and if the number of twists is too loose, the binding of short fibers will decrease and they will fall off, so it is necessary to maintain the number of twists within an appropriate range, Coefficient K
It has been found that it is necessary to set conditions such that 1 is 10 or more and 50 or less, and %K is 15 or more and 45 or less.

The preferred range of the number of ply twists changes in relation to the number of ply twists, and when the ply twist coefficient is defined by the formula (2) above, the product of the ply twist coefficient K1 and the ply twist coefficient K2 is (3)
It has been found that it is necessary to set the value to satisfy the condition of 30 or more and 150 or less as shown in the formula.

If the product of K1 and K2 is less than 30, the intertwining of the short fibers for covering and the core yarn is insufficient, and the short fibers may fall off during the process of inserting them into the fabric as weft yarns, or during the dipping and baking processes of resin liquid. On the other hand, if it exceeds 150, although the entanglement of short fibers with the core yarn is improved, it may hinder the elongation of the core yarn or cause damage to the core yarn. This is because the elongation of the weft yarn is reduced due to the strong twist of the core yarn in relation to the pre-twist applied in advance, so that the weft yarn does not stretch smoothly with respect to the elongation during tire molding.

The weight ratio of the coated short fibers to the core yarn is related to the number of twists during the production of the core yarn, but the strength must be lower than the descending point strength of the polyester multifilament yarn serving as the core yarn.

In other words, in order to arrange the warp cords evenly during tire molding, the weft yarns must be stretched evenly, but if the weight ratio of short fibers is high, weak points with a low proportion of short fiber components will be intensively stretched during weft stretching. As a result, the arrangement of the warp cords becomes extremely disordered, so the upper limit of the short fiber weight ratio must be set to a ratio that does not cause such disorder. The upper limit is 70% by weight.
Hereinafter, it has been found that it is particularly preferable to set the content to 50% by weight or less.

On the other hand, if the weight ratio of the coated staple fibers is too small, the entire core yarn may not be coated uniformly, or even if uniform coverage is achieved, the core yarn will not have sufficient thermal protection during baking heat treatment, resulting in The yarn undergoes thermal deterioration, and as a result, it becomes impossible to secure a residual elongation of 60% or more.

Therefore, the lower limit of the weight ratio of the coated staple fibers needs to be determined from the two viewpoints of lowering the smoothness of the weft yarns to a satisfactory level and preventing thermal deterioration of the core yarns. According to the research conducted by the present inventors, It has been found that the lower limit of the weight ratio is 7% by weight or more, particularly 20% by weight or more.

As described above, the present invention involves applying a specific first twist to a polyester multifilament yarn having a specific elongation, and then adding a specific amount of non-melting short fiber bundles (sliver) to the yarn and drafting it with a spinning machine to create a specific twist. Desirable properties as a weft for a tire reinforcing fabric made by applying ply twist in the number of ply twists and in the ply twist direction and coating the ply twisted multifilament yarn with non-melting short fibers, namely (1) after impregnating with RFL resin liquid. Approximately 230~
It still retains a residual elongation of 60% or more even after being subjected to baking treatment at a high temperature of 250°C for several minutes, and (2) has the effect of uniformly maintaining a large number of warp yarns interlaced with weft yarns at a predetermined density. A novel method for producing weft yarns is provided.

Next, the present invention will be further clarified by examples.

Examples: Manufactured by a conventional method, with an intrinsic viscosity of 0.63 (phenol/L).
Polyethylene terephthalate (measured at 30°C in a mixed solvent of 6/4 chloroethane) was melt-spun using a conventional method, and the cutting elongation (hereinafter abbreviated as DE) was obtained by variously changing the spinning take-up speed. A polyethylene terephthalate multifilament yarn (setting tenier 155d/36f) having physical properties as shown in Table 1 was prepared.

Next, this multifilament yarn is pre-twisted to have various pre-twist twist coefficients K1 as shown in Table 1, and the thus obtained pre-twisted multifilament yarn is used as a core yarn, and cotton or polynostable is used as the core yarn. A spinning machine was used to draft a bundle (sliver) of the short fibers as the coated short fibers, and the two were merged together, and then a final twist was applied in the same direction as the first twist direction to produce a core yarn.

In addition, the weight ratio of the coated short fibers to the first twisted multifilament yarn (hereinafter abbreviated as sheath ratio) and the first twist coefficient K
2 was changed in various ways as shown in Table 1.

Next, these core yarns were subjected to a moist heat setting treatment at 65° C. for 20 minutes while still in the spinning spun spun to prevent vibration.

Next, a polyethylene terephthalate tire cord (1000 d×
A tire reinforcing fabric was woven by weaving a tire reinforcing fabric by closely arranging the two strands of yarn as the wefts of a blind weave with the warp as the warp.

The fabric thus obtained was then treated with an RFL resin solution in a conventional manner, dried at 140°C for 3 minutes, and then heated at 240°C.
Baking treatment was performed for 3 minutes by blowing hot air.

Next, only the weft yarns were taken out from the fabric after the baking treatment so as not to be damaged, and the residual elongation was measured using a Tensilon type tensile tester.

The results are summarized in Table 1.

As shown in Table 1, in the present invention, the cutting elongation of the polyester multifilament yarn as the core yarn, the first twist coefficient, the sheath ratio of the non-melting coated short fibers, and the product of the first twist coefficient and the first twist coefficient are Items that satisfy the specified requirements (editions 2-6, 10,
It can be seen that Samples Nos. 13 to 15, 17, 18, and 20) all have residual elongation of 60% or more after baking treatment, and have desirable physical properties as weft yarns for tire reinforcing fabrics.

On the other hand, those lacking at least one of the requirements specified in the present invention (Eds. 1, 7 to 9, 11,
Nos. 12, 16, and 19) all had residual elongation of less than 60% after baking treatment, and it is clear that they do not have satisfactory physical properties as weft yarns for tire reinforcing fabrics.

Claims (1)

[Claims] 1. A polyester multifilament yarn having a breaking elongation of 80 to 200% is first twisted so that the twist coefficient K1 of the first twist specified by the following formula (1) is 10 to 50, and then The twisted multifilament yarn and the non-fusible short fiber bundle of 7 to 70% by weight of the first twisted multifilament yarn are merged and the first twist coefficient K1 and the first twist coefficient K1 defined by the following equation (2) are combined in the same direction as the first twist multifilament yarn. A tire reinforcement characterized in that the first-twisted multifilament yarn is made into a core yarn covered with the non-melting short fibers by performing pre-twisting under conditions such that the product with the twist coefficient K2 satisfies the following formula (3). A method for producing weft yarns for textiles. (However, in the above formulas (1), (2), and (3), K1 is the lower twist coefficient, K2 is the upper twist coefficient, and T1 is the number of lower twists (T/
cm), T2 is the number of ply twists (T/in), and D is the total denier of the polyester multifilament yarn (d
), Ne indicates the English cotton count of the core yarn. )