JP2000096370A - Polyester fiber cord - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester fiber cord suitable as a tire carcass material because of enabling tires' durability, shape and dimensional stability to be significantly raised, and producible through conventional high-speed spinning technique and requiring no special treatment process such as low-temperature dipping treatment. SOLUTION: This polyester fiber cord is such one as to consist of a polyethylene terephthalate copolymerized with A mol% of isophthalic acid as an acid component and B mol% of butylene glycol and/or propylene glycol as alcohol component(s) and meet the following relationships: 0<=A<=10, 0<=B<=10, 1<=A+B<=10, S1>=2.5, and S2<=S1-2.0 (S1 is a shrinkage (%) at an ambient temperature of 177 deg.C under a load of 0.03 g/d; S2 is a shrinkage (%) at an ambient temperature of 177 deg.C under a load of 0.10 g/d).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester fiber cord capable of providing excellent productivity and running performance as a carcass material for reinforcing rubber, particularly as a pneumatic radial tire.

[0002]

2. Description of the Related Art Conventionally, organic fiber cords whose surfaces are treated with an adhesive for reinforcing rubber have been widely used. The selection of the organic fiber cord type is extremely important because it has a great effect on not only the mechanical properties of the rubber / fiber composite but also its productivity, heat resistance, durability and the like.

[0003] In recent years, it has become mainstream to use a cord made of polyester fiber as a carcass material for radial tires for passenger cars. This is mainly because polyester fibers have a better balance of properties such as strength, modulus, and dimensional stability than conventionally used nylon fibers, rayon fibers, and the like. Especially recently, high speed
A so-called HMLS (high modulus low shrinkage) polyester fiber having higher dimensional stability and modulus than that obtained by high-stress spinning has been developed. Steering stability and uniformity have been improved.

[0004] At the time of tire production (vulcanization), the carcass material is 17
Exposed to a high temperature of 0 to 180 ° C., and the heat shrinkage of the carcass material at this time affects the uniformity of the tire and the design reproducibility of the tire (whether or not the shape is as designed), and the heat shrinkage of the carcass material The smaller the is, the better the shape of the tire becomes. Therefore, the demand for the conventional polyester cord for carcass material such as the above-mentioned HMLS polyester fiber is that the shrinkage rate is low at 170 to 180 ° C. No. 71033,
JP-A-6-179304, JP-A-3-16700
No. 2, JP-A-5-16606, JP-A-6-2
No. 4208).

However, recently, higher requirements have been made on the heat shrinkage characteristics of the cord for carcass material. This is because when a cord having a small heat shrinkage, which has been considered to have good dimensional stability, is used, the arrangement of the beads at the bead portion tends to be disordered at the time of molding the tire. This is due to the problem of having a serious adverse effect on fatigue resistance. As a solution to this problem, Japanese Unexamined Patent Publication No. Hei 9-118108 discloses that the thermal shrinkage is large at a low load corresponding to the molding conditions in the bead portion and small at a high load corresponding to the molding conditions at the sidewall portion. That is, the use of a cord having a large slope in a load-shrinkage curve has been proposed.

However, using a polyethylene terephthalate fiber usually used for a carcass material cord,
It is not easy to efficiently obtain the shrinkage characteristics described in -118108. For example, in the spinning of HMLS polyethylene terephthalate fiber usually used for a carcass cord, when the heat shrinkage ratio is changed by changing the drawing conditions without largely changing the spinning speed, the shrinkage characteristics under a low load and the shrinkage characteristics under a high load are almost the same. As a result, the difference in the shrinkage ratio between the low load and the high load cannot be made large.

[0007] Reducing the spinning speed is advantageous for increasing the difference in shrinkage between a low load and a high load, but reduces the productivity.

As a method for solving such a problem, Japanese Patent Application Laid-Open No. Hei 9-118108 proposes to lower the temperature of a final zone of a dip treatment step using a conventional HMLS yarn. By reducing the temperature of the dipping step in this way, the difference in shrinkage between a low load and a high load increases, but since the activity of the adhesive is reduced by lowering the temperature, the dipping time is required to maintain the adhesive activity. This requires a long time, which increases the cost of the dip processing.

[0009]

As described above, although a guide has been obtained for a carcass cord for further improving the durability and dimensional stability of a tire, it is actually used efficiently and with special At present, it cannot be obtained without performing a dip process.

[0010] An object of the present invention is to use as a carcass material, and to greatly improve the durability and stability of the shape and dimensions of a tire. An object of the present invention is to provide a polyester fiber cord that does not require a special treatment method.

[0011]

The present invention mainly has the following constitution in order to solve the above-mentioned problems. That is, a polyester fiber cord composed of polyethylene terephthalate obtained by copolymerizing an isophthalic acid component A (mol%) as an acid component and a butylene glycol and / or propylene glycol component (B mol%) as an alcohol component, wherein A, B, and atmosphere 0.03 at a temperature of 177 ° C
The shrinkage rate S ₁ (%) under a load of g / d and the shrinkage rate S ₂ (%) under a load of 0.10 g / d under an ambient temperature of 177 ° C. satisfy the following relationship. Polyester fiber cord.

0 ≦ A ≦ 100 0 ≦ B ≦ 101 1 ≦ A + B ≦ 10 S ₁ ≧ 2.5 S ₂ ≦ S ₁ −2.0

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The polyester fiber cord of the present invention will be specifically described below.

The polyester fiber cord of the present invention is a copolymer polyester obtained by copolymerizing polyethylene terephthalate with 0 to 10 mol% of an isophthalic acid component as an acid component and 0 to 10 mol% of a butylene glycol and / or propylene glycol component as an alcohol component. Consists of In the present invention, the isophthalic acid fraction A (mol%) in the acid component and the butylene glycol and / or propylene glycol fraction B (mo) in the alcohol component are used.
1%) is 1 mol% or more and 10 mol% or less, and the sum A + B is preferably 2 to 8 mol%, more preferably 3 to 7 mol%. A + B is 1mol
%, The difference in physical properties from the polyester fiber cord comprising only ethylene terephthalate becomes small, and it is necessary to lower the spinning speed and lower the dipping temperature in order to obtain desired shrinkage characteristics. Conversely, A + B is 10 mol
%, And the ratio of the ethylene terephthalate component is 90%.
If the amount is less than mol%, the melting point of the cord decreases, and the permeability of the cord in the dipping process and the heat resistance of the cord decrease.

The copolymerization component copolymerized with the ethylene terephthalate component may be an acid component alone or an alcohol component alone, or may be both an acid component and an alcohol component. When an isophthalic acid component is used as an acid component as a main copolymer component and a component other than butylene glycol and / or propylene glycol is used as an alcohol component, desired shrinkage characteristics cannot be obtained or strength is significantly reduced. . That is, among the various copolymer compositions, only when isophthalic acid component is used as the acid component and butylene glycol and / or propylene glycol is used as the alcohol component, without causing a decrease in physical properties that specifically poses a problem. The shrinkage characteristics can be changed in a desired direction.

The addition of the copolymer composition may be carried out during the polymerization, or may be adjusted by mixing chips containing a higher concentration of the copolymer component with chips having a higher ethylene terephthalate component before spinning. Oxidation resistance degradation in the polymer,
A small amount of an organic or inorganic additive may be included for the purpose of preparing a terminal group or the like. If the amount is small, isophthalic acid component,
A copolymerization component other than the butylene glycol and / or propylene glycol component may be contained, but the copolymerization ratio is preferably smaller than the total of the isophthalic acid component and the butylene glycol and / or propylene glycol component. And less than half the total of the butylene glycol and / or propylene glycol components.

The degree of polymerization of the polyester fiber cord is not particularly limited, but the IV value is preferably 0.8 or more, more preferably 0.9 or more. With such an IV value, sufficient strength characteristics required for reinforcing tires and the like can be obtained.

Production of high modulus, low shrinkage (HMLS) polyester fibers by the usual high-speed, high-stress spinning method described in, for example, Japanese Patent Publication No. 1-27164, by using the above-mentioned copolymer as the polyester. The shrinkage rate under low load is larger than that of polyethylene terephthalate (PET), which is usually used as polyester for tire cords by the usual dip treatment. A dip processing code having a large difference can be obtained.

The shrinkage S ₁ (%) of the polyester fiber cord of the present invention under an atmosphere temperature of 177 ° C. and a load of 0.03 g / d is 2.5% or more, preferably 3% or more. . S ₁ corresponds to the temperature and stress applied to the carcass material at the bead turn-back portion, and S ₁ is 2.5%
By doing so, the looseness of the cord end caused at the time of molding the green tire is eliminated, and the durability of the tire can be maintained at a high level. If S ₁ is less than 2.5%, the carcass turn height at the bead portion will vary, causing a decrease in tire durability.

0.10 g / d at an atmosphere temperature of 177 ° C.
The shrinkage ratio S ₂ (%) under a load corresponds to the heat and stress applied to the cord in the carcass between the pair of beads during vulcanization of the tire. If S ₂ is large, the shape of the carcass line may deviate from the design, so it is better to be small, and the preferred value of S ₂ is 2.5% or less, more preferably 2% or less.

What is important in the present invention is that S ₁
To increase the difference between S ₂ and S ₂ , where S ₂ ≦ S ₁ −2.0
It is necessary to be. If the relationship is not satisfied, it is impossible to achieve both tire durability and dimensional stability during molding.

It is well known that cords having such shrinkage characteristics are preferable. However, by using a specific copolymer as the polyester used in the present invention, it is possible to reduce the spinning speed and dip. Such shrinkage characteristics can be obtained for the first time without lowering the processing temperature.

The polyester fiber cord of the present invention may be subjected to a dipping treatment at a particularly low temperature,
It is not necessary to employ special conditions such as lowering the temperature of the normalizing zone by 40 to 80 ° C. with respect to the temperature of the heat setting zone as described in JP-A-9-118108. Both the normalizing zone and the normal polyester fiber cord can be treated in the range of 230 ° C to 250 ° C.

The heat shrinkage characteristics to be satisfied by the polyester fiber cord of the present invention have been described above. The heat shrinkage characteristics of the dip-treated cord are generally called an intermediate elongation expressed by an elongation under a load of 2.25 g / d. There is a close relationship with the value E (%). If the tension during the dipping process is increased, the inside of the fiber constituting the cord has a tight structure, so that the heat shrinkage increases and the intermediate elongation decreases. Conversely, if the tension at the time of dipping is reduced, the structure becomes relaxed, so that the heat shrinkage decreases and the intermediate elongation increases. Therefore, it is preferable that the heat shrinkage property to be satisfied by the polyester fiber cord of the present invention is more specifically defined in relation to the intermediate elongation E (%).

[0025] Under 25 ° C., and more preferably heat-shrinkable properties of the polyester fiber cord of the present invention, S _1/2 + E ≧ relative to the elongation (intermediate elongation) E (%) at an applied load of 2.25 g / d 5.3, and more preferably, S _1/2 + E ≧ 5.5.
Satisfying the following relationship. By satisfying this relationship, it is possible to sufficiently increase the heat shrinkage at the time of low load with respect to the intermediate elongation, and to obtain a sufficiently large heat shrinkage at the time of low load when the preferable intermediate elongation is adopted. Obtainable.

[0026] S ₁ is the thermal shrinkage ratio at low load application has thermal shrinkage rate S ₀ both correlation at no load, to represent the preferred relationship between the intermediate elongation E in relation to the S _0, S ₀ /2≧6.5-
E, and more preferably S ₀ /2≧6.7-E. By satisfying such a relationship, it is possible to sufficiently increase the heat shrinkage ratio at the time of low load with respect to the intermediate elongation,
When a preferable intermediate elongation is adopted, a sufficiently large heat shrinkage can be obtained under a low load.

Further, the polyester fiber cord of the present invention has a shrinkage ratio S under a load of 0.06 g / d.
It is preferable that the shrinkage ratio S ₄ (%) under a load of ₃ (%) and 0.15 g / d satisfies the relationship of S ₃ −S ₄ ≦ 0.5 (7.5-E). , S ₃ −S ₄ ≦ 0.
It is preferable to satisfy the relationship 5 (7.3-E).

S ₃ -S ₄ is important for stability of the tire shape.
₂ shows a change in the heat shrinkage rate with respect to a change in the applied load in the vicinity of ₂ . The smaller the value of S ₃ -S ₄ , the more stable the thermal shrinkage of the cord against a change in the applied load near S ₂ , that is, the more excellent the dimensional stability of the tire obtained with respect to the change in the molding conditions. It indicates that Although S ₃ -S ₄ also varies depending on the intermediate elongation, the preferred polyester fiber cord of the present invention has a relationship between S ₃ -S ₄ and the intermediate elongation E of S ₃ -S ₄ ≦ 0.5 (7.5). -E) is satisfied.

In the present invention, the preferred value of the intermediate elongation E is 6% or less, more preferably 5% or less. By setting the intermediate elongation E in this range, it is possible to prevent the steering stability from deteriorating due to the decrease in the elastic modulus of the cord.

[0030]

The present invention will be described below in more detail with reference to Examples and Comparative Examples.

The measuring method of various characteristics in the present invention is as follows.

1) Dry heat shrinkage (S ₀ ) 0.05 g / sample in a room adjusted to 20 ° C. and 65 RH
The code length L ₀ measured with a load corresponding to d, and 0.05 g of the sample in a room adjusted to 20 ° C. and 65 RH again after putting the sample in an oven at 177 ° C. for 30 minutes under no tension.
/ Was determined by the following equation from the code length L ₁ was measured by applying a load corresponding to d.

S ₀ = {(L ₀ −L ₁ ) / L ₁ } × 100 (%) 2) The heat shrinkage of the cord under load (S ₁ , S ₂ ,
S ₃ , S ₄ ) In an oven kept at 177 ° C. in advance, 0.03 g / d for heat shrinkage S ₁ and 0.10 g / d for S _2.
d, in the case when the S ₃ of 0.06 g / d, S ₄ 0.15
After putting the cord with a load of g / d for 30 minutes,
Shrunk. Heat shrinkage ratio was calculated by the following equation from the code length L ₁ after Hochijimi and previous code length L ₀ that put in the oven. Although the formula is the case for S _1, it was determined by the equation in the case of S ₂ to S _4.

S ₁ = {(L ₀ −L ₁ ) / L ₁ } × 100 (%) 3) Strength and Elongation A “Tensilon” tensile tester manufactured by Orientec Co., Ltd. was used. The measurement was performed at a speed of 30 cm / min.

4) Intermediate elongation A stress-elongation curve was obtained under the conditions described in the section on strength and elongation.
It was determined by reading the elongation at a load of 2.25 g / d.

5) Intrinsic viscosity: IV The relative viscosity η of a solution in which 8 g of a sample was dissolved in 100 ml of orthochlorophenol was measured using an Ostwald viscometer, and determined by the following approximate formula.

IV = 0.242η + 0.2634 [Examples 1 to 3] Copolymerized polyester obtained using 95 mol% of terephthalic acid and 5 mol% of isophthalic acid as acid components and ethylene glycol as alcohol component Was subjected to solid-phase polymerization to obtain a chip having an IV of 1.26. The obtained chips are melted by an extruder and then extruded from a die plate.
After passing through a heating cylinder having a length of 15 ° C. and cooling with a chimney, lubricating the oil, circling around a take-up roller at a peripheral speed of 2,300 m / min, stretching the heating roller 2.3 times between the heat rollers without once winding up the oil, and then feeding the oil. A stretched yarn was obtained by performing a relaxation treatment 96 times. Table 1 shows the physical properties of the obtained drawn yarn.

A cord obtained by twisting two drawn yarns shown in Table 1 and then twisting them with a twist / prime twist of 40/40 (twice / 10 cm) was subjected to a dip treatment under the conditions shown in Table 2. Got dip processing code.

Table 3 shows the characteristics of the obtained dip processing code.
Summarized in

As is clear from Table 3, the use of the isophthalic acid copolymerized yarn made it possible to obtain a dip-treated cord having desired heat shrinkage properties from the original yarn obtained by the high-speed spinning method.

[0041]

[Table 1]

[Table 2]

[Table 3] [Examples 4 to 6] Copolymerized polyester obtained using terephthalic acid as an acid component and 94 mol% of ethylene glycol and 6 mol% of butylene glycol as an alcohol component was subjected to solid-state polymerization, and IV = 1. 2
0 chips were obtained. Spinning / combining / twisting was performed under the same conditions as in Example 1 except that the obtained copolymer chips were used. Table 1 also shows the physical properties of the drawn yarn. Dip processing was performed on the obtained code under the conditions shown in Table 2 to obtain a dipped processing code. Table 3 summarizes the characteristics of the obtained dip processing codes.

As is clear from Table 3, the use of the butylene glycol copolymer yarn enabled a dipping treatment cord having desired heat shrinkage characteristics to be obtained from the original yarn obtained by the high-speed spinning method.

Comparative Examples 1-4 Spinning, plying and twisting under the same conditions as in Example 1 except that a polyethylene terephthalate chip having an IV of 1.28 substantially having no copolymer component was used as a raw material. Was done. The physical properties of the drawn yarn are also shown in Table 1.

A dip process was performed on the obtained code under the conditions shown in Table 2 to obtain a dip-processed code.

Table 4 shows the characteristics of the obtained dip processing code.
Summarized in

As can be seen from Table 4, a cord consisting essentially of polyethylene terephthalate cannot obtain desired heat shrinkage characteristics under general dipping conditions, and has a desired heat only under low-temperature long-time dip conditions with poor production efficiency. Shrinkage characteristics could be obtained.

[0047]

[Table 4]

[0048]

According to the present invention, the durability and shape of a tire can be improved by using a conventional high-speed spinning method without performing a special dipping process leading to high cost, as a tire carcass material. It is possible to obtain a polyester fiber cord capable of improving dimensional stability.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) D02G 3/48 D02G 3/48 F-term (Reference) 4L035 BB52 BB77 BB88 BB91 EE01 FF01 HH10 4L036 MA05 MA33 PA21 PA26 PA26 UA06 UA08 UA30

Claims (5)

[Claims] An isophthalic acid component A (mo) as an acid component.
1%) and a butylene glycol and / or propylene glycol component (Bmol%) as an alcohol component.
A polyester fiber cord comprising polyethylene terephthalate obtained by copolymerizing A, B and an ambient temperature of 17
Shrinkage ratio S ₁ (%) under a load of 0.03 g / d at 7 ° C. and 0.10 g under an ambient temperature of 177 ° C.
A polyester fiber cord, wherein a shrinkage ratio S ₂ (%) under a load of / d satisfies the following relationship. 0 ≦ A ≦ 100 0 ≦ B ≦ 10 1 ≦ A + B ≦ 10 S ₁ ≧ 2.5 S ₂ ≦ S ₁ −2.0 2. The polyester fiber cord according to claim 1, wherein the elongation E (%) under a load of 2.25 g / d at 25 ° C. satisfies the following relationship. S _1/2 + E ≧ 5.3 3. The polyester fiber cord according to claim 1, having an elongation E (%) at 25 ° C. under a load of 2.25 g / d of not more than 6.0%. 4. 0.06 g / d at an atmosphere temperature of 177 ° C.
Shrinkage ratio S ₃ (%) at the time of load application, ambient temperature 1
The polyester fiber cord according to claim 1, wherein the shrinkage ratio S ₄ (%) under a load of 0.15 g / d at 77 ° C satisfies the following relationship. S ₃ −S ₄ ≦ 0.5 (7.5-E) 5. The polyester fiber cord according to claim 1, wherein the shrinkage S ₀ (%) under no load at an ambient temperature of 177 ° C. satisfies the following relationship. E + S ₀ /2≧6.5%