JPH04342602A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To improve durability and fatigue resistance by using a specific kind of polyester cord for at least one between a belt and a carcass which are arranged inside the tread of a peumatic tire. CONSTITUTION:At least one between a belt and a carcass which are arranged inside the tread of a pneumatic tire is constituted of the polyester cords which substantially consisting of polyethylene terephthalate fibers. The characteristics of the above-described polyethylene terephthalate fiber are as follows: the carboxyl terminal group is 25ep/ton or less, the content of diethylene glycol is 1.3wt.% or less, the intrinsic viscosity is 0.85 or more, the sum S of intermediate elongation and dry thermal contraction rate is less than 10%, the strong elongation product is (2S+11) or more, and the terminal modulus is less than 40g/d. Further, the above-described polyethylene terephthalate is synthesized by using the Sb compound in Sb reduction of 30-150ppm and the Ge compound in Ge reduction of 5-120ppm.

Description

Detailed Description of the Invention [0001] [Industrial Application Field] The present invention relates to a pneumatic tire, and more specifically, the present invention relates to a pneumatic tire. The present invention relates to high-performance pneumatic tires using highly improved polyethylene terephthalate fibers that are highly tough and durable. [0002] Polyester fibers have excellent mechanical properties, dimensional stability, and durability, and are widely used not only for clothing but also for industrial purposes. For industrial use, it is widely used for reinforcing rubber materials, and in particular, it is used in large quantities as tire cord for reinforcing rubber in pneumatic tires, taking advantage of its characteristics. [0003] Conventionally, in tire cord applications, high-strength yarn obtained by drawing low-oriented undrawn yarn at a high ratio has been used.
In recent years, relatively highly oriented undrawn yarn (so-called POY) has been used.
The raw yarn obtained by drawing began to be used. This technology was born from the need to improve the dimensional stability of the cord and improve the performance of pneumatic tires, even at the cost of some strength. [0004] Rayon, polyamide, and polyester are well known organic fibers as reinforcing materials for pneumatic tires, and typical inorganic fibers are steel and glass fiber. [0005] Among organic fibers, demand for polyester fiber has increased significantly in recent years due to its price and characteristics, and recently there has been a trend to use polyester fiber in areas where rayon is used in passenger car tire cords. Due to the rapid movement of polyester fibers, unprecedented dimensional stability is required of polyester fibers. [0006] In response to this request, Japanese Patent Laid-Open No. 1655/1983
As proposed in Japanese Patent No. 47 and Japanese Unexamined Patent Publication No. 1981-1981, a technique has been disclosed to increase the spinning speed of undrawn yarn (POY) and improve its dimensional stability, and the resulting fibers can be used for rubber reinforcement. It is proposed to be used as a code. For example, Japanese Unexamined Patent Publication No. 12804/1984 is known as a method in which the above-mentioned rubber reinforcing cord is used in a high-performance pneumatic tire. [0007] However, by extension of the conventional technology, it is simply possible to
Although increasing the spinning speed of Y does improve some dimensional stability, it is still insufficient compared to rayon in terms of ensuring uniformity in the tire manufacturing process, and increasing the spinning speed of POY As a result, the toughness of the yarn is significantly reduced, and the durability of the tire, especially its fatigue resistance, is significantly reduced, and in reality, it is not used for reinforcing rubber in pneumatic tires. was. SUMMARY OF THE INVENTION An object of the present invention is to provide a pneumatic tire that solves the problems of the prior art described above and has excellent durability, particularly fatigue resistance. [Means for Solving the Problems] The structure of the present invention is as follows: (1)
In a pneumatic tire, a polyester cord is used for at least one of a belt and a carcass ply disposed inside the tread of the pneumatic tire, the polyester cord is substantially made of polyethylene terephthalate fibers, and the polyester cord is made of polyethylene terephthalate fibers. A pneumatic tire characterized by simultaneously satisfying the following characteristics. b) The amount of carboxyl terminal group ([COOH]) is 25 eq
/ton or less b) Diethylene glycol content (DEG) is 1.3w
t% or less c) Intrinsic viscosity (IV) ≧0.85 d) Sum of intermediate elongation and dry heat shrinkage rate (S) < 10% e) Strong elongation product (T x E1/2 ) ≧ 2S + 11 f) Terminal modulus (TM) ≦40 g/d, and (2) a polyester cord made of a polyester obtained using an antimony compound containing 30 to 150 ppm as antimony and a germanium compound containing 5 to 120 ppm as germanium as a polymerization catalyst. The pneumatic tire according to (1) above, characterized in that the reinforcing material is: It is in. [Embodiment] The pneumatic tire according to the present invention has good dimensional stability, toughness, and durability that could not be achieved with conventional polyester cords made of polyethylene terephthalate fibers, and can be used as a substitute for rayon. As a result of intensive research on pneumatic tires reinforced with
By controlling the particles generated in the polymer that forms the polyethylene terephthalate fibers and controlling the orientation characteristics during spinning from the viewpoint of polymer properties, it is possible to control the physical properties of polyester fibers within a strict range. It has been discovered that a high-performance pneumatic tire reinforced with polyester cord that achieves the above objectives can be obtained. [0011] The fiber for reinforcing the rubber of the pneumatic tire according to the present invention is made of polyester having ethylene terephthalate as its main repeating unit. In order to improve dimensional stability and strength, the polyester may be made by adding a third component other than by-product diethylene glycol, by copolymerization, or by using polyethylene terephthalate that does not substantially contain inorganic particles. preferable. The sum (S) of intermediate elongation and dry heat shrinkage, which indicates the dimensional stability of the rubber reinforcing polyester fiber used in the pneumatic tire according to the present invention, that is, the dimensional stability is 10%.
Must be less than If the dimensional stability is 10% or more, a polyester cord with low shrinkage and high modulus cannot be obtained.
It is insufficient to ensure uniformity in the tire manufacturing process, and unsatisfactory handling stability is obtained when the tire is running, making it impossible to maintain sufficient performance to completely replace rayon. Toughness (T×E1/2) of polyester fiber for rubber reinforcement used in the pneumatic tire according to the present invention
must be a high toughness fiber that satisfies T×E1/2≧2S+11. In general, when highly oriented spinning is performed to reduce dimensional stability, toughness (T x E1/2
) also decreases significantly. However, the tire code
Regarding fatigue resistance as a bond, the smaller the dimensional stability, the better the toughness. The toughness limit that satisfies the durability of a pneumatic tire becomes lower as the dimensional stability decreases. In other words, it has been found that where the dimensional stability is low, the durability reaches a satisfactory level even with a relatively low toughness. As a result of further consideration of the lower limit of toughness, we found that by setting T×E1/2 ≧2S+11, sufficient durability (fatigue resistance) can be achieved if the dimensional stability is small enough to be a substitute for rayon. We have discovered that this can be achieved. From this point of view, T
By using fibers satisfying ×E1/2≧2S+14, the pneumatic tire targeted by the present invention can be obtained. Amount of carboxyl terminal groups [COOH] of polyester fiber for reinforcing rubber of pneumatic tires according to the present invention
must be 25 eq/ton or less. [COO
If H] exceeds 25 eq/ton, the heat resistance in the rubber deteriorates, resulting in insufficient durability as a tire cord. Amount of diethylene glycol in polyester fiber for rubber reinforcement (D
EG) needs to be 1.3 wt% or less. When DEG exceeds 1.3 wt%, dimensional stability deteriorates and durability becomes poor. From this point of view, DEG is 1.1wt%
The content is preferably 0.9 wt% or less, and more preferably 0.9 wt% or less. The intrinsic viscosity (IV) of the polyester fiber for reinforcing the rubber of the pneumatic tire according to the present invention must be 0.85 or more. If IV is less than 0.85, durability is insufficient no matter what conditions are adopted. The terminal modulus of the polyester fiber for reinforcing the rubber of the pneumatic tire according to the present invention is 40 g/d.
Must be below. Terminal modulus is 40g
If /d is exceeded, no matter how high the toughness of the yarn is obtained, the strength will decrease during twisting, and the toughness as a tire cord will decrease, resulting in poor durability. From this perspective, tar
The terminal modulus is preferably 30 g/d or less. The polyester fiber for reinforcing the rubber of the pneumatic tire according to the present invention contains 30 to 150 p of antimony.
5 to 5 as antimony compounds and germanium in pm
Polyethylene terephthalate fibers made of polyester using 120 ppm of germanium compound as a polymerization catalyst are used. As for measures to improve toughness in a region where the dimensional stability (sum of intermediate elongation and dry heat shrinkage rate (S)) of the polyethylene terephthalate fiber is small as in the present invention, oriented crystallization such as high-speed spinning is recommended. It is important to strictly control the oriented crystallization behavior in the field. Conventionally, such structural control of POY has been carried out mainly by controlling the cooling conditions, but by strictly controlling the catalyst composition during polymer production, the number of particles in the polymer can be significantly reduced. Furthermore, it is effective to modify the polymer from the viewpoint of controlling the orientation and crystallinity of POY by selecting a catalyst. As the above catalyst composition, a combination system of an antimony compound and a germanium compound, which have not been used in conventional rubber reinforcing material applications, is effective.As the antimony compound, antimony trioxide and antimony pentoxide are preferable, and as the germanium compound, antimony trioxide and antimony pentoxide are preferable. Germanium dioxide is preferred. If the amount of the antimony compound is less than 30 ppm, it is necessary to use a large amount of germanium compound in combination in order to maintain polymerization reactivity, which not only increases cost but also increases the amount of diethylene glycol and reduces the size. Stability decreases. The amount of antimony compound is 150pp
If it exceeds m, even if the amount of germanium compound used in combination is increased, the amount of metallic antimony produced by reduction of the antimony compound cannot be reduced, and not only the strength and toughness of the yarn cannot be improved, but also the heat resistance in the rubber decreases. do. On the other hand, when the amount of the germanium compound is 5p
If it is less than 150 ppm, the amount of antimony compound used to maintain polycondensation reactivity cannot be reduced to 150 ppm or less,
If the amount of the germanium compound exceeds 120 ppm, the cost will increase significantly and not only will it not be industrially usable, but the amount of diethylene glycol will also increase and the dimensional stability will deteriorate. [0022] The amount of the antimony compound is preferably 40 to 120 ppm as antimony, and 80 to 120 ppm.
m is more preferred. Further, the amount of the germanium compound is preferably 6 to 30 ppm as germanium. As mentioned above, controlling the catalyst composition of the polymer contributes to improving toughness and durability, and it becomes possible to reduce the amount of antimony metal precipitated by reducing the antimony compound, and by reducing the amount of antimony metal, the properties of the polyester cord can be improved. Improved durability, particularly fatigue resistance and dimensional stability of pneumatic tires reinforced by the polyester cord. The amount of antimony metal in the polyethylene terephthalate fiber is 5 ppm or less, more preferably 3 ppm or less.
A more preferable pneumatic tire can be obtained by controlling the content to ppm or less. The polyester fiber for reinforcing the rubber of the pneumatic tire according to the present invention contains 30 to 150 antimony.
5 as ppm antimony compounds and germanium
A polyester obtained using ~120 ppm of a germanium compound as a polymerization catalyst is highly oriented and spun to have an intrinsic viscosity of 0.
9 or higher and an orientation degree (Δn) of 60×10 −3 or higher, the fibers are then stretched at a stretching ratio of 0.93 times or lower than the limit stretching ratio, and heat set at a temperature of 210° C. or higher. When the degree of orientation (Δn) is 60×10-3 or less, the sum of the intermediate elongation and the dry heat shrinkage rate (S
) exceeds 10% and when used as a rubber reinforcing fiber for pneumatic tires, it cannot be used as a substitute for rayon because a post-cure inflation device is required to maintain uniformity after tire vulcanization. If the stretching ratio exceeds the limit stretching ratio of 0.93, thread breakage will occur frequently and there is a concern that operability will be lowered. When the drawing temperature is lower than 210° C., the heat setting property of the yarn decreases, the intermediate elongation + dry heat shrinkage (S) of the polyester fiber exceeds 10%, and the drawability decreases. [0026] The polyester cord used in the pneumatic tire according to the present invention is manufactured by the method shown below. 30 to 150 ppm antimony compound as antimony and 5 to 120 ppm as germanium
A polycondensation reaction is carried out using a pm germanium compound as a polymerization catalyst. In this case, it is preferable to use phosphoric acid as the phosphorus compound and to add phosphoric acid at the initial stage of polycondensation and before addition of the antimony compound and germanium compound. Select the conditions of charging amount, polymerization temperature, and polymerization time appropriately, and make sure that IV0.65 or more, COOH≦25eq/ton
, DEG≦1.3wt% polyethylene terephthalate
Get tips. [0028] The polyethylene terephthalate chips were subjected to solid phase polymerization, if desired, according to a conventional method to obtain polyethylene terephthalate having an IV of 1.0 or higher. The thus obtained chips are melt-spun according to a conventional method, slowly cooled in a heating cylinder, and then taken off while being cooled and solidified in a chimney wind. At this time, it is preferable to chromium plate the piping and pack parts in the spinning machine to suppress precipitation (reduction) of antimony metal. The chimney air is blown out through a filter for filtration, and it is preferable that the filter uses a metal wire (SUS) nonwoven fabric with an absolute filtration diameter of 30 μm or less. Furthermore, it is more preferable to reduce the amount of dust in the nitrogen used for solid phase polymerization and the nitrogen in the spinning machine as much as possible, and to filter the air used in the chimney wind to reduce the amount of dust. The number of foreign substances in the obtained polyester fiber was 800 pieces/mg.
It is possible to maintain the level below, preferably 500 pieces/mg or less, which greatly contributes to improving toughness and durability. After the cooled polyester fibers were applied with an oil agent, the speed was regulated so that the degree of orientation (Δn) was 60×10 −3 or more, preferably (Δn) was 80×10 −3 or more. taken over by the roll. The taken-up polyester fiber is continuously or once wound up.
Stage or multistage hot roller stretching is performed and heat set at a temperature of 210°C or higher. [0031] After the polyester fiber obtained in the above step is twisted and twisted to form an untreated cord, an adhesive for rubber is applied to the untreated cord and dried. The pneumatic tire of the present invention is manufactured using the polyester cord made of the polyester fiber thus obtained. That is, it is a pneumatic tire reinforced with a belt and/or carcass ply placed inside the tread portion. [0033] The structure and effects of the pneumatic tire of the present invention will be explained in more detail with reference to Examples below. The physical properties in the Examples were measured as follows. A. Amounts of metals (antimony, germanium, etc.) in polymers and fibers Determined by fluorescent X-ray method. B. Carboxyl terminal group amount ([COOH]
) Dissolve 0.5 g of the sample in 10 ml of o-cresol, cool it after complete dissolution, add 3 ml of chloroform, and add NaO
It was determined by potentiometric titration using a methanol solution of H. C. After alkali decomposition of the sample, DEG amount was determined using gas chromatography. D. Strong elongation, intermediate elongation (medium elongation), terminal modulus using a Tensilon tensile tester manufactured by Toyo Baldwin Co., Ltd.
An SS curve was obtained with a sample length of 25 cm and a take-up speed of 30 cm/min to calculate the strength and elongation. Also, from the same S-S curve, the strength is 4.5 g/d for raw yarn, and 2.25 g/d for cord.
The corresponding elongation was read and the intermediate elongation was determined. The terminal modulus was determined by dividing the difference between the stress at the point where 2.4% was subtracted from the cutting elongation and the breaking stress by 2.4 x 10-2. E. Dry heat shrinkage rate (dry yield) (ΔSd) A sample was taken in the form of a skein, left in a temperature-controlled room at 20°C and 65% RH for 24 hours or more, and then measured by applying a load equivalent to 0.1 g/d of the sample. A sample of length L0 is heated for 15 minutes without tension.
After being left in an oven at 0° C. for 15 minutes, it was taken out from the oven and left in the temperature-controlled room for 4 hours, and then the load was applied again and the measured length L1 was calculated using the following formula. ΔSd=(L0 - L1)/L0×100 (%)
. F. Number of foreign objects in the thread The sample was divided into individual threads, and the thread was stretched on a slide glass so that it did not slacken.
Using an Olympus optical microscope (phase contrast method), magnification 20
Scan at 0x magnification and count the number of foreign objects in the thread. Measurement is carried out using 5 N samples to obtain an average value X (ke/6 cm), and this value is converted to the number of foreign substances per mg. G. Intrinsic viscosity (IV) Orthochlorophenol (OC
Dissolve 0.8 g of the sample in 10 ml (referred to as P), determine the relative viscosity (ηr) using the following formula using an Ostwald viscometer, and further calculate the IV. ηr=η/η0 =t×d/t0×d0 IV=0.
0242ηr+0.2634η: Viscosity of polymer solution η0: Viscosity of solvent t: Falling time of solution (sec) d: Density of solution (g/cm3) t0: Falling time of OCP (sec) d0: Density of OCP (g/cm3) )0041H
．． 40g of antimony metal polymer and 50g of orthochlorophenol (OCP)
After dissolving in 0 ml and centrifuging (12,000 rpm x 2 hours), washing and drying. The spectrum of the obtained centrifuged grains is measured using an X-ray diffraction device, and metal antimony is determined from the spectrum. I. In tire uniformity tire manufacturing, the post cure inflation (PCI) process is omitted and the tire surface temperature is 45℃.
When the tire diameter is below, measure the tire diameter at 8 locations (45 degree intervals) in the tire circumferential direction, divide the minimum measured value by the maximum measured value, and multiply by 100 to obtain a value of 90 to 100. ○,
80 to 89 was rated Δ, and 79 or less was rated ×. [0043]J. How to collect tire cord: The cord was taken out from the tire before and after driving, and the attached rubber was removed with scissors before measurement. [0044]K. Maneuvering Performance Focusing on the cornering characteristics during slalom running, the handling performance of Tire Comparative Example 5 was set at 100, and those that were better than this were judged as 100 or more, and those that were poor were judged as 100 or less. [Example] Examples 1 to 2 and Comparative Examples 1 to 5 0.035 parts of manganese acetate tetrahydrate was added to 100 parts of dimethyl terephthalate and 50.2 parts of ethylene glycol, and an ester was prepared by a conventional method. An exchange reaction was performed. Next, 0.0091 part of phosphoric acid (29 ppm as phosphorus) was added to the obtained product, and then a polycondensation reaction was carried out for 3 hours and 10 minutes while changing the amounts of germanium dioxide and antimony trioxide. (Polymerization temperature: 285°C) The above polymer was pre-dried at 160°C for 5 hours and then subjected to solid phase polymerization at 225°C to obtain solid phase polymerized chips with IV=1.35. This chip was spun using an extruder type spinning machine at a spinning temperature of 295°C. At this time, a metal nonwoven fabric with an absolute filtration diameter of 15 μm was used as the filter, and the mouthpiece was 0.5 μm.
A round hole with a diameter of 6 mm was used. In addition, chromium plating was applied to the parts of the polymer piping and pack parts that came into contact with the polymer, and the nitrogen in the hopper and nitrogen for the chimney were all filtered through a 1μ filter. The yarn discharged from the nozzle was slowly cooled in a heating cylinder with a length of 25 cm, an inner diameter of 25 cmφ, and a temperature of 300° C., then cooled and solidified by applying chimney cooling air, and after oiling, the yarn was taken off at the take-up speed shown in Table 1. The resulting undrawn yarn was drawn at a drawing temperature of 90° C. and at a heat treatment temperature of 240° C. while changing the magnification and relaxation rate to obtain a drawn yarn. Note that the stretching ratio is the same as that of Example 1.
, 2, Comparative Examples 1 to 4 were set to 0.88 to 0.92 times the limit magnification, and Comparative Example 5 was set to 0.95 times the limit magnification. The manufacturing conditions are shown in Table 1, and the properties of the obtained polyester fibers are shown in Tables 2 and 3. [Table 1] [0047] [Table 2] [0049] NO. Strength Elongation T x Medium elongation
Dry yield Nakashin 2S+11 Terminal
E1/2
+Dry yield
Modulus g/d
% % %
% % g/d Example 1
8.2 13.5 29.9 6.3
1.1 7.4 25.8 24.
0 Example 2 7.7 13.8 28.4
6.3 0.8 7.1 25.
2 15.0 Comparative Example 1 7.1 12.
4 25.0 6.2 1.1 7
．． 3 25.6 24.5 Comparative example 2
8.0 12.9 28.7 6.3
1.4 7.7 26.4 24.1
Comparative example 3 7.6 12.6 26.9
6.4 1.0 7.4 25.8
23.8 Comparative example 4 7.6 12.0
26.3 6.2 1.7 7.
9 26.8 25.2 Comparative example 5 8
．． 7 10.5 28.2 5.7
1.9 7.6 26.2 48.4 [0050] [Table 3] 0051] NO. COOH DEM
IV Sb Metal
eq/ton%
% Example 1
17.1 0.7 0.98
0.3 Example 2 16.8
0.6 0.98 0.
3 Comparative Example 1 17.7 0.7
0.97 0.8 Comparative example 2
28.5 1.2 0.98
0 Comparative Example 3 29.6
0.7 0.97 4
．． 5 Comparative Example 4 20.2 1.5
0.99 0 Comparative example 5
17.1 0.7 0.9
8 0.3 The number of foreign substances in the polyester fiber produced in this way is 150 pieces/mg to 450 pieces/mg.
and the IV was 0.96 to 0.99. Next, this drawn yarn was first twisted at 40T/10cm in the S direction, and the first twisted yarn was twisted in the Z direction.
It was made into a raw cord with 40T/10cm applied in the direction. Next, run this code using a Riller computer processor.
After being immersed in an adhesive solution containing FL as the main component, it was dried in a dry heat oven at 150°C, stretched by 10% in a dry heat oven at 240°C, and then heat treated with 4% relaxation in a dry heat oven at the same temperature. , created the processing code. Using the cord obtained by the above method as a carcass material, a radial tire (tire size 165-SR13) was manufactured in the same manner as in a normal tire manufacturing process except that the post-cure inflation process was omitted. Two steel belts were placed inside the tread for reinforcement. These Examples 1 and 2 and Comparative Example 1
-5 tires were mounted on a passenger car and after driving for 50,000 km, the cords in the carcass of the tires were taken out and the residual strength of the cords was measured, and the results are shown in Table 4 along with the uniformity results. [Table 4] [0053] Before driving
Unifor after running
Pilot No. Strong Medium Growth Dry Yield Medium Growth
Powerful Powerful Mitty Performance

+Dry yield retention rate
Kg % % %
Kg % Example 1 22.4
3.8 2.7 6.5 20.4
91.0 ○ 110 Example 2 21.1 3.3 2.3 5.
6 19.7 93.5 ○
115 Comparative Example 1 19.0 3.7
2.7 6.4 16.0 84
．． 1 ○ 108 Comparative example 2
21.9 3.8 3.9 7.7
17.3 79.2 ×
95 Comparative Example 3 20.5 3.9
2.8 6.7 16.1 78.7
○ 105 Comparative example 4 20
．． 6 3.7 4.0 7.7 1
6.7 81.0 ×
95 Comparative Example 5 22.3 3.0 4.2
7.2 18.4 82.5
△ 100 As is clear from Table 4, although the uniformity and handling performance of the tire using the fiber of Comparative Example 1 with low T/×E1/2 is good, the strength before and after running is low, and the durability is insufficient. be. In addition, the sum (S) of intermediate elongation (medium elongation) and dry heat shrinkage rate (dry yield) is high, and D
The tires in Comparative Examples 2 and 4, which have a large amount of EG, not only have poor uniformity and poor handling performance, but also have low strength after running. Further, the tire used in Comparative Example 3, which contains a large amount of Sb metal, has good uniformity and maneuverability, but has low strength after running and poor durability. Furthermore, the tire of Comparative Example 5, which had a high terminal modulus, was somewhat insufficient in terms of strength, uniformity, and handling performance after running. On the other hand, the tires of Examples 1 and 2 were good in all characteristics such as strength, uniformity, and handling performance after running. Examples 3, 4 and Comparative Examples 6 to 8 Example 1
, 2. Five types of polyester cords (
Example 3 is the polyester fiber obtained in Example 1, Example 4 is the polyester fiber obtained in Example 2, and Comparative Example 6.
The polyester fiber obtained in Comparative Example 1, the polyester fiber obtained in Comparative Example 2 in Comparative Example 7, and the polyester fiber obtained in Comparative Example 5 in Comparative Example 8 were used as belt reinforcing materials. A radial tire (tire size 165-SR13) consisting of a belt layer and a carcass layer made of two conventional polyester cords was manufactured using the same process as the normal tire manufacturing process except that the post-cure inflation process was omitted. Manufactured. After running 70,000 km, the polyester cord used for reinforcing the belt was removed from the tire, and the residual strength of the polyester cord was measured. The measurement results are shown in Table 5. The above tire is composed of four belt layers and two carcass layers, and the residual strength was determined by measuring the belt strength of the outermost layer. [Table 5] 0056] Run
Row Before Run After No.
．． Strong Medium elongation Dry yield Medium elongation + Dry yield
Strong Strong retention rate Kg
% % %
Kg % Example 3 22.1 3.8 2.8 6
．． 6 19.6 88.8 Example 4 21.0 3.5 2.2
5.7 18.9 90.0
Comparative example 6 18.8 3.8 2.7
6.5 14.6 77
．． 7 Comparative Example 7 22.0 3.7 3.8
7.5 15.7
71.2 Comparative example 8 22.4 3.4 3
．． 7 7.1 16.9
75.6 As shown in Table 5, similar to Example 1,
The tires of Examples 3 and 4 using polyester fibers with high toughness, good dimensional stability, low terminal modulus, appropriate amounts of carboxyl terminal groups and DEG, and low antimony metal amount It has high strength and durability. [0057] The pneumatic tire according to the present invention has excellent durability and fatigue resistance because it uses polyester fiber, which has extremely good dimensional stability and high toughness, as a rubber reinforcing agent. In addition, since the pneumatic tire according to the present invention has extremely good dimensional stability of the rubber reinforcing polyester fiber,
It can be used as a substitute for rayon, and since it is stronger than rayon cord, the amount of cord used in the tire can be reduced and the weight of the tire can be reduced. Furthermore, it is possible to simplify the post cure inflation (PCI) process performed in the tire manufacturing process, improve tire manufacturing efficiency, and reduce manufacturing costs.

Claims (2)

[Claims] Claims: 1. A pneumatic tire, wherein a polyester cord is used for at least one of a belt and a carcass ply disposed inside a tread of the pneumatic tire, the polyester cord substantially consisting of polyethylene terephthalate fibers, A pneumatic tire characterized in that the polyethylene terephthalate fiber satisfies the following properties at the same time. b) The amount of carboxyl terminal group ([COOH]) is 25 eq
/ton or less b) Diethylene glycol content (DEG) is 1.3w
t% or less c) Intrinsic viscosity (IV) ≧0.85 d) Sum of intermediate elongation and dry heat shrinkage rate (S) < 10% e) Strong elongation product (T x E1/2 ) ≧ 2S + 11 f) Terminal modulus (TM)≦40g/d 2. Claim 1, characterized in that the reinforcing material is a polyester cord made of polyester obtained by using as a polymerization catalyst an antimony compound containing 30 to 150 ppm of antimony and a germanium compound containing 5 to 120 ppm of germanium as a polymerization catalyst. Pneumatic tires listed in.