JPH09256220A - Polyester fiber for rubber reinforcement - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the subject fibers having desired high dimensional stability, excellent in heat resistance, and capable of replacing rayon by containing respectively a specific amount of a nickel compound and an antimony compound. SOLUTION: A polyester containing a nickel compound (e.g. nickel acetate) in an amount of 2-120ppm reduced to a nickel metal and an antimony compound (e.g. antimony trioxide) in an amount of 150-450ppm reduced to an antimony metal is fiberized and a total amount of intermediate elongation (elongation corresponding to 4.5g/d stress in a stress-strain curve; defined in this invention) and dry heat shrinkage (at 150 deg.C) is made to <8% to obtain the objective polyester fiber.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polyester fiber for rubber reinforcement. More specifically, the present invention relates to a polyester fiber for rubber reinforcement, which has excellent dimensional stability and heat resistance in rubber as compared with conventional products and can substitute rayon.

[0002]

2. Description of the Related Art Polyester fiber has excellent mechanical properties, dimensional stability, and durability, and is therefore used not only for clothing but also for tires.
It is widely used in industrial applications as a reinforcing material for rubber products such as belts and hoses. In particular, it is widely used in rubber reinforcing applications such as tire cords by taking advantage of its excellent performance. Conventionally, a high-strength raw yarn obtained by stretching a low-oriented undrawn yarn at a high ratio has been used for tire cord applications.
Such a high-strength yarn has a high dry heat shrinkage ratio, and when a tire cord is embedded in rubber to form a tire, there is a problem that the uniformity of the tire is deteriorated due to the shrinkage of the cord. In order to solve such a problem, it has been proposed to improve the dimensional stability as a tire cord by drawing a relatively highly oriented undrawn yarn (so-called POY) to obtain a high strength yarn. It has become the mainstream of code technology. Although shrinkage can be reduced by such highly oriented spinning and drawing techniques, since the level is still higher than that of rayon cord, further reduction of shrinkage rate is desired.

In order to further improve the performance of tires, various proposals have heretofore been made as techniques for achieving low shrinkage. For example, as described in JP-A-63-165547, when the spinning speed is 5000 m / min or more, the Δn of the undrawn yarn is 80 × 10 ⁻³ or more and the density is 1.375 g / cm 3.
^A method of promoting oriented crystallization to ³ or more is disclosed. In addition, JP-A-61-232616 and JP-A-6-132616
A low shrinkage tire cord based on a similar idea is also proposed in JP-A 1-252332 and JP-A-62-69819. However, although the above-mentioned method according to the conventional technique can provide a tire cord with good dimensional stability (intermediate elongation + low dry heat shrinkage), it does not reach a practical level in strength, Since the heat resistance of the tire is remarkably reduced, the life of the tire is short even if it is used as a tire cord, and there is a problem in durability. Further, since there is a problem in heat resistance in rubber, by adding a low COOH agent such as a bisoxazoline compound, an epoxy compound, or a carbodiimide compound to reduce the amount of terminal carboxyl groups contained in the polyester, However, the use of such a low COOH agent deteriorates the spinnability,
There have been many problems in use due to operational problems such as increased fluff, reduced strength, reduced fatigue resistance, and increased costs.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a rubber-reinforcing polyester fiber which is excellent in dimensional stability and heat resistance in rubber and which can be substituted for rayon. .

[0005]

The object of the present invention is achieved by the following constitutions. 2-120 as nickel metal
1 ppm as nickel compound and antimony metal
A polyester fiber for rubber reinforcement, comprising polyester containing 50 to 450 ppm of an antimony compound and having a dimensional stability (intermediate elongation + dry heat shrinkage) of less than 8%.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The amount of the antimony compound contained in the polyester fiber of the present invention needs to be 150 to 450 ppm as the amount of antimony metal. Antimony compounds are used as polymerization catalysts for polyester, but the amount of antimony is 150 pp
If it is less than m, the polymerization reactivity is insufficient, so that it is not possible to obtain a polymer having a practical intrinsic viscosity with good productivity, but also it is caused by an antimony compound that influences the oriented crystallization behavior during spinning. Since the number of particles decreases, the dimensional stability and heat resistance in rubber decrease. If the amount of antimony is more than 450 ppm, coarse particles are generated by the antimony compound and the strength of the fiber is reduced.
Further, since the number of foreign matter defects increases, the heat resistance in rubber becomes poor, which is not preferable. From this viewpoint, the antimony metal content of the antimony compound is preferably 180 to 400 ppm,
More preferably, it should be 200 to 350 ppm.

The amount of the nickel compound contained in the polyester fiber of the present invention is 2 to 12 as the amount of nickel metal.
It should be 0 ppm. If the amount of nickel is less than 2 ppm, the effect of refining the particles caused by the catalyst due to the combined use of the antimony compound and the nickel compound becomes insufficient, resulting in a decrease in dimensional stability and a poor heat resistance in rubber. Further, when the amount of nickel exceeds 120 ppm, coarse particles are generated due to the nickel compound, and the strength of the fiber and the heat resistance in rubber are reduced. From this point of view, the amount of the nickel compound is preferably 3 to 100 ppm, more preferably 5 to 80 ppm as the amount of nickel metal.

As the antimony compound used for the polyester fiber of the present invention, antimony trioxide, antimony pentoxide, antimony acetate and the like are used, and among these, antimony trioxide is particularly preferable. As the nickel compound, nickel formate, nickel acetate, nickel benzoate, nickel chloride, nickel bromate and the like are used, and among these, nickel acetate is particularly preferable.

The dimensional stability (intermediate elongation + dry heat shrinkage) of the polyester fiber of the present invention must be less than 8%. If the dimensional stability exceeds 8%, the dimensional stability of the cord during tire molding becomes poor and the uniformity of the tire deteriorates, so rayon substitution is not possible. From this viewpoint, the dimensional stability is preferably 7.5% or less.

The polyester fiber of the present invention has a carboxyl group terminal amount (hereinafter referred to as COOH) of 25 eq / t.
On or less is preferable from the viewpoint of heat resistance in rubber, and it is preferable that the amount of diethylene glycol (hereinafter referred to as DEG) is 1.3 wt% or less from the viewpoint of heat resistance in rubber and dimensional stability. It is not limited.

The polyester in the present invention is preferably one mainly composed of polyethylene terephthalate (hereinafter abbreviated as PET) and polybutylene terephthalate, and P
ET is more preferable, but a part of the dicarboxylic acid component is isophthalic acid, 5-sodium sulfoisophthalic acid, 2,6-naphthalenedicarboxylic acid, diphenoxyethanedicarboxylic acid, adipic acid, sebacic acid, azelaic acid, It may be substituted with one or more of dodecanedicarboxylic acid and the like. In addition, part of the glycol component is propylene glycol, neopentyl glycol,
Hexamethylene glycol, pentamethylene glycol, 1,4-cyclohexanedimethanol, glycerin, pentaerythritol, polyethylene glycol,
It may be replaced with polytetramethylene glycol or the like.
Further, in addition to pigments such as titanium oxide, silicon oxide, calcium carbonate, silicon nitride, clay, talc, kaolin, carbon black, etc., conventionally known coloring inhibitors, stabilizers, antioxidants and other additives are contained. Does not matter. In addition, the above-mentioned modified polyester resin is added to the polyester of the present invention.
More than one kind may be blended, and further, a small amount of resins such as polyamide, polyesteramide, epoxy resin, silicone resin, polyolefin resin, various rubbers, polycarbonate, polyurethane and polyacrylate may be blended.

The polyester fiber for rubber reinforcement of the present invention is
For example, it can be obtained by the following method. An antimony compound is used as a polymerization catalyst, a nickel compound is used in combination, and a phosphorus compound is used to perform a polycondensation reaction. In the polycondensation, the charged amount, the polymerization temperature, and the polymerization time are appropriately selected, the intrinsic viscosity is 0.65 or more, and COOH ≦ 25 eq / t.
On, a PET chip with DEG ≦ 1.3 wt% is obtained.

The chips thus obtained are subjected to solid phase polymerization according to a conventional method to obtain an intrinsic viscosity of 0.95 or more, melt spinning, and the yarn discharged from the spinneret is gradually cooled in a heating zone and then cooled by chimney air. Solidify, take-off speed 3500 m / min or more,
It is preferably collected at 4000 m / min or more. At this time, the residence time during spinning and the spinning temperature are controlled to obtain a yarn having a COOH of 25 eq / ton or less. Also, low COOH
It is preferable not to use additives such as agents because they deteriorate the spinnability and reduce the strength. Sequentially or after being once wound, a polyester stretched yarn is obtained by stretching and heat treatment according to a conventional method. The drawn yarn thus obtained is twisted 30 times to 60 times (up-twisting) per 10 cm according to a conventional method, then a plurality of plied yarns are combined, and 30 to 10 cm per 10 cm in the opposite direction.
Twist 60 times (bottom twist) to make a cord. Then, this cord is treated with an adhesive according to a conventional method to obtain a treated cord.

It is not clear why the polyester fiber of the present invention has improved dimensional stability and heat resistance in rubber.
Particles due to the antimony compound in the polymer are made finer by containing a specific amount of nickel metal, and it is possible to control the orientation crystallization behavior during spinning, and thus it is possible to suppress a decrease in dimensional stability, and further to reduce the dimensional stability. It is considered that this is because the disorder of the fine structure is reduced and the promotion of deterioration due to hydrolysis is prevented or suppressed. Generally, when polyester is spun at high speed to improve dimensional stability, the fine structure of the fiber (particularly the amorphous structure) is disturbed.
The polyester fibers of the present invention are particularly suitable for high speed spinning yarns.

As described above, the polyester fiber of the present invention is suitable for rubber reinforcement, particularly for tire cords, and can be used as a substitute for rayon, which is more excellent in dimensional stability and heat resistance in rubber than conventional products. It is a polyester fiber.

[0016]

The present invention will be described in detail below with reference to examples. Physical properties in the examples were measured as follows.

(1) Strength and Intermediate Elongation Using a Tensilon tensile tester manufactured by Toyo Baldwin,
An elongation curve was calculated by obtaining an SS curve at a test length of 25 cm and a take-up speed of 30 cm / min. In addition, the strength is 4.5 from the SS curve.
The elongation corresponding to g / d was read to determine the intermediate elongation.

(2) Dry Heat Shrinkage Samples are taken in a skein shape and placed in a temperature control room at 20 ° C. and 65% RH.
After standing for 4 hours or more, a sample with a length L ₀ measured by applying a load equivalent to 0.1 g / d of the sample was left in an oven at 150 ° C for 30 minutes in a tensionless state, and then removed from the oven. Then, the temperature was left for 4 hours in the temperature control room, and the above load was applied again to calculate from the length L ₁ measured by the following equation. Dry heat shrinkage = [(L ₀ −L ₁ ) / L ₀ ] × 100 (%)

(3) Amount of metal in polymer and fiber It was determined by the fluorescent X-ray method.

(4) 0.5 g of COOH sample was dissolved in 10 ml of o-cresol, completely dissolved and cooled, and then 3 ml of chloroform was added to the solution, and NaO was added.
It was determined by performing potentiometric titration with a methanol solution of H.

(5) The DEG sample was alkali-decomposed and then quantified by gas chromatography.

(6) Intrinsic viscosity (IV) Orthochlorophenol (hereinafter OC)
Dissolve 0.8 g of the sample in 10 m of P), calculate the relative viscosity (ηr) using the Ostwald viscometer by the following formula, and calculate IV. ηr = η / η ₀ = (t × d) / (t ₀ × d ₀ ) IV = 0.0242 ηr + 0.2634 η: Viscosity of polymer solution η ₀ : Viscosity of OCP t: Drop time of solution (seconds) d: Solution density (g / cm ³ ) t ₀ : OCP fall time (sec) d ₀ : OCP density (g / cm ³ )

(7) Heat resistance in rubber The cord was embedded in rubber and evaluated by the strength retention after vulcanization at 150 ° C. for 6 hours. Strength retention of 60% or more is ◎, 5
0% or more and less than 60% was evaluated as O, and less than 50% was evaluated as X.

(8) Tire Uniformity Post cure inflation (P
When the tire surface temperature becomes 45 ° C. or less, tire diameters are measured at eight locations (at intervals of 45 degrees) in the tire circumferential direction, and the minimum measured value is obtained. A value obtained by dividing by the maximum value of the measured values and multiplying by 100 was 90 or more, ⊚, 80 or more and less than 90% was ◯, and less than 80 was x.

Examples 1 to 4 and Comparative Example 1 100 parts of dimethyl terephthalate and 5 parts of ethylene glycol
0.036 parts of manganese acetate tetrahydrate was added to 0 parts, and transesterification was carried out by a conventional method. After adding 0.014 parts of phosphoric acid to the obtained product, antimony trioxide (0.14 parts) was added.
033 parts and nickel acetate 0.012 parts were added, and polycondensation reaction was performed at a polymerization temperature of 285 ° C. The polymer obtained has an intrinsic viscosity of 0.70, a COOH content of 16.8 eq / ton, D
EG is 0.83% and the amount of nickel in the polymer is 28 p
The amount of pm and antimony were 275 ppm. This polymer was pre-dried at 160 ° C. for 5 hours and then solid-phase polymerized at 225 ° C. to obtain a PET solid-state polymerized chip having an intrinsic viscosity of 1.15.
The PET chips after the solid-state polymerization were spun by an extruder type spinning machine. The spinning was discharged from a spinneret having a discharge hole having a diameter of 0.6 mm. Spinned yarn length 300 mm, temperature 350
After gradually cooling with a heating cylinder of ℃, it was cooled and solidified by applying a cold air of 18 ℃, and the take-up speed was changed to take it up. The undrawn yarn thus obtained is drawn at a drawing temperature of 85 ° C. and a heat treatment temperature of 240.
The draw ratio and the relaxation rate were changed at 0 ° C. to obtain drawn yarns of 1000d-240f as shown in Table 1. The twisted yarn has a lower twist of 49 T / 10 cm in the S direction and an upper twist of 4 T in the Z direction.
9T / 10cm cord was used. Next, this code is treated with an adhesive using a Liller computer,
Created the processing code.

Table 1 shows the physical properties of the raw yarn and the treated cord. As is clear from Table 1, Examples 1 to 4 satisfying the range of the present invention have excellent dimensional stability and heat resistance in rubber. However, in Comparative Example 1, the uniformity of the tire was unsatisfactory because the dimensional stability was 8% or more, and the object of the present invention was not achieved.

Example 5 In the same manner as in Example 1, the chips after solid state polymerization were subjected to spinning temperature,
Spinning was performed while changing the residence time to obtain yarns having different COOH contents. Table 1 shows the physical properties of the raw yarn and the treated cord. Example 5 satisfying the range of the present invention has good heat resistance in rubber.

Example 6 Spinning was carried out in the same manner as in Example 1 using chips in which DEG was added when producing a polymer and the DEG content was changed,
Stretched. Example 6 satisfying the range of the present invention has good heat resistance in rubber.

[0029]

[Table 1] Examples 7 to 11 and Comparative Examples 2 to 5 Spinning was performed in the same manner as in Example 1 except that the amounts of antimony trioxide and nickel acetate used as the polymerization catalyst were changed.
The obtained undrawn yarn was drawn in the same manner as in Example 1 to prepare a treated cord. As is clear from Table 2, Examples 7 to 11 satisfying the range of the present invention have excellent dimensional stability and heat resistance in rubber. However, the amount of nickel is 2ppm
Comparative Example 2 below is poor in dimensional stability and heat resistance in rubber. In Comparative Example 3 in which the amount of nickel exceeds 120 ppm, the strength was low and the heat resistance in rubber was poor. Further, in Comparative Example 5 in which the amount of antimony exceeded 450 ppm, the strength was low as in Comparative Example 2, and the heat resistance in rubber was also poor. In Comparative Example 4 in which the amount of antimony is less than 150 ppm, the polymerization reactivity is inferior, and therefore the polymerization time is 8 to achieve the intrinsic viscosity of 0.65 or more.
Not only did it take more time, but the dimensional stability and heat resistance in rubber were poor.

[0030]

[Table 2]

[0031]

EFFECT OF THE INVENTION The polyester fiber of the present invention has excellent dimensional stability and heat resistance in rubber which have not been heretofore available, and therefore is suitable as a rubber-reinforcing polyester fiber that can be used as a rayon substitute.

Claims (5)

[Claims] 1. A nickel compound of 2-120 ppm as nickel metal and 150-4 as antimony metal.
Made of polyester containing 50ppm antimony compound, 8% dimensional stability (intermediate elongation + dry heat shrinkage)
Polyester fiber for rubber reinforcement which is less than. 2. The rubber-reinforcing polyester fiber according to claim 1, which has a carboxyl end group content of 25 eq / ton or less. 3. The diethylene glycol content is 1.3 w
The polyester fiber for rubber reinforcement according to claim 1 or 2, which has a content of t% or less. 4. The polyester fiber for rubber reinforcement according to claim 1, wherein the antimony compound is antimony trioxide. 5. The polyester fiber for rubber reinforcement according to claim 1, wherein the nickel compound is nickel acetate.