JPS6171205A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To improve high speed and resistance to fatigue without deteriorating steering stability and resistance to wear by comprising a reinforcing material cord for a carcass ply with such linear polyester fiber as the strength maintenance factor after the cord is strength- and heat-deteriorated at new product is specified, respectively. CONSTITUTION:The codes consisted of linear polyester fiber in which the strength of a carcass cord extracted from a new tire that is not used after the tire is vulcanized exceeds 6.0g/D and the strength maintenance rate of a cord extracted from a tire after the static heat deterioration of 140 deg.CX240hr has been performed exceeds 70% of that at its new product is used as the reinforcing material of a carcass ply. As a result of this structure, high speed property and resistance to fatigue can be improved while keeping steering stability, resistance to wear and the like.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire comprising a polyester cord with improved resistance to strong deterioration due to heat and arranged in a carcass ply. It is related to tires.

(Prior Art) A tire constructed by arranging a conventional polyester cord in a carcass ply has a p! I4 has excellent longitudinal stability and abrasion resistance, but the carcass cord has poor heat resistance and strong deterioration resistance, and the carcass cord has the disadvantage of rapid thermal deterioration due to heat generation during high-speed running, eventually leading to breakage and breakage. .

The reason for this is that the polyester cord generates more heat due to repeated vibrations and stress (strain) input than the nylon cord, and that its strength deteriorates rapidly at high temperatures.For this reason, the polyester cord could not be used with large bias tires that generate a lot of heat.In recent years, there has been a growing demand for improvements in noise, flat spots, etc. for large size tires for light trucks, and changes from nylon cord to polyester cord as carcass cord materials have been considered. However, materials with sufficient heat resistance and strong deterioration resistance have not been obtained.

(Problems to be Solved by the Invention) Therefore, the present invention improves the heat resistance and strength deterioration of the conventional polyester cord as described above, maintains high strength when unused after tire vulcanization, and maintains strength even at high temperatures when used. The purpose is to provide a pneumatic tire with excellent high speed and fatigue resistance while maintaining handling stability, wear resistance, etc. by arranging cords made of improved polyester fibers that maintain retention in the carcass ply. shall be.

(Means for Solving the Problems) The pneumatic tire of the present invention that satisfies the above object has a tread portion, a pair of side portions connected to the tread portion on both shoulders of the tread portion, and an inner periphery of the side portion. A carcass layer is provided with a pair of bead wires formed on each peady portion, and is reinforced by at least one carcass layer that is secured to a pair of bead wires provided on the peady portions, and a belt layer provided on a crown portion between the carcass and the tread. In a pneumatic tire that has been vulcanized, the strength of the carcass cord when not in use (when new) is 6.097D or more, and the strength is 140'C.
Static thermal deterioration for x240 hours (i.e. 10 days) (conditions set to estimate the conditions equivalent to the P1 history from the deterioration rate of the cord until the tire is completely worn out in normal driving and becomes scrapped by guide evaluation) The reinforcing material for the carcass is a cord made of linear polyester fibers that has a strength retention rate of 70% or more, preferably 80% or more of the strength before deterioration, that is, when it was new, when taken out from the tire after undergoing Features.

The polyester treated cord used as the carcass cord in the pneumatic tire of the present invention, which has been dip-treated with adhesive, has higher elastic modulus characteristics and thermal dimensions of the polyester fiber before treatment than conventional polyester treated cords. It maintains stability and strength, and has improved resistance to strong deterioration due to heat.

The polyester cord improved in this way will be explained below. Methods to improve the strength deterioration of conventional polyester cords due to heat include reducing the content of terminal carboxyl groups in the polyester polymer, and reducing the heat generation of the cord itself by increasing its toughness.
-7882), a method of increasing compatibility with external forces by increasing heat shrinkage during dipping treatment and lowering the elastic modulus is known. However, the method of reducing the number of terminal carboxyl groups in the polyester polymer reduces the number of reactive groups with the adhesive, resulting in a decrease in adhesive properties and does not lead to improved durability. In the case of increasing the toughness as disclosed in Japanese Patent Publication No. 56-7882, the strength of the cord after dip treatment is only about 4.5 to 5.597D, which is extremely low. The problem remains that many cords must be used to obtain carcass strength. Furthermore, in the method of lowering the elastic modulus, since the cord has high relaxation properties against external forces, it becomes difficult to maintain the excellent properties inherent to polyester, such as handling stability and riding comfort. For this reason, the inventors
As a result of intensive research on combinations of polyester polymer materials, adhesive types, heat treatment conditions, etc., we have confirmed the following.

(b) Regarding polymer materials, in general, increasing the polymerization degree of the polymer improves its strength, so in order to maintain the strength above a certain level, it is necessary to increase the polymerization degree.

Furthermore, heat resistance is improved by reducing the amount of polymer terminal carboxyl groups. This is because when a large number of terminal carboxyl groups are bonded to rubber and vulcanized, they react with amine compounds in vulcanization accelerators, anti-aging agents, etc. that migrate from the rubber, and active water is generated. It is thought that this causes the ester bonds in the polyester main chain to be hydrolyzed and deteriorated.

However, to reduce this terminal carboxyl group, two-bath adhesives are commonly used, that is, welding agents that use an epoxy compound or blocked isocyanate in the first bath and RFL, H as a treatment agent in the second bath. Since the terminal carboxyl group in the polymer is used as an adhesion reaction group, the adhesion properties are significantly reduced. Furthermore, in polymers using a monofunctional epoxy capping agent as a method of reducing the number of terminal carboxyl groups, the bonding is weak and no improvement in heat resistance can be expected. Then, by polymerization, E.

By using a polymer with fewer carboxyl terminal groups and using an adhesive system that does not utilize carboxyl terminal groups as described below, it is possible to simultaneously satisfy both adhesion and heat resistance.

(b) Regarding I'&ffi#'l, there are broadly two types of polyester adhesive systems. The most common adhesive is a two-bath type, in which the first bath is treated with an epoxy thread compound or blocked isocyanate compound that reacts with the terminal carboxyl group of the polymer, and the second bath is treated with R.
This method uses FL adhesive. Another method is a one-bath adhesive, which uses polyester polymer VULNAX VUI, CABOND-E 1 without using terminal carboxyl groups.
Tahaiou modified fi resorcin RF. This is a method of mixing it with L and adhering it.

The latter adhesive system is presumed to achieve adhesion through physical mutual diffusion with the polyester polymer (hereinafter referred to as a diffusion type adhesive), and is a thread that can provide high adhesive strength even with a small number of terminal carboxyl groups. Of course - one way to use a bath RFL adhesive is to use a diffusion adhesive in the first bath and an RF adhesive in the second bath.
A similar effect can be obtained by using L.

(c) Regarding heat treatment conditions, polyester cords are generally heat treated at low tension, but when a diffusion type adhesive is used, there are some bases whose strength decreases by 3 to 5% due to heat treatment. If this happens, the method is to adjust the elastic system by increasing the tension in the beat set zone < L and decreasing the tension in the norm zone to contract the cord (
Apply the Stretch-Relax 2 Step Tension) to prevent intoxication. By applying this method, 3
It is possible to prevent a ~5% decrease in strength and maintain strength.

Therefore, the polyester processing cord used in the present invention does not use a carboxyl terminal group blocking agent (including those that do not use a difunctional northern blocking agent to block the terminal carboxyl groups and simultaneously bond mainly into the polyester and become terminal free). A high degree of polymerization polyester polymer with fewer terminal carboxyl groups is used as an adhesive.
? J R F L (Resorcin formalin latex) N n 昂1, e.g., t i;! 'VULNAX
2% per month RFL with VULOABOND-E
Alternatively, a sulfur-modified resorcinol adhesive is used, and the heat treatment conditions are 240 to 255°C, and the tension is stretched in the heat set zone, and the tension is lowered in the norm zone to contract, which are the two steps of stretch-relaxation. This is a cord made of linear fibers and ester fibers obtained by combining the use of tension materials, and the strength of the carcass cord taken out from the tire when the tire is new is 6.09/D or more, and the tire is 140℃×240
It has the characteristic that the strength retention rate of the cord taken out from the tire after being subjected to static thermal deterioration for a period of time is 70% or more of that of new. It has three characteristics that were used as follows.

The above cord used as a reinforcing material for the carcass ply in the present invention has a strength of 6.097D or more when taken out from the tire when the tire is new. If the strength of the tire carcass layer is low, the carcass strength will be insufficient unless the cord density is increased or the number of plies is increased. When the degree is increased, the cord spacing between the carcass cords becomes smaller and the peeling resistance decreases. On the other hand, if the number of plies is increased, the thickness of the carcass will increase and the heat generation property when the tire is running will be λ6, causing the problem of hastening the deterioration of the polyester. ;'/D or higher strength is required. In addition, the strength retention rate of the cord taken out from the tire after statically thermally deteriorating for 140' CX 240 hours is 70% or more of that of new, but if it is lower than 70%, the thermal deterioration is large and the There is a danger that the elasticity of the carcass layer will be insufficient and the tire will eventually burst.

The strength retention rate of the above cord (well, it can be calculated by the static thermal strength deterioration test method shown below. First, unused (new) tires after Japanese sulfurization are tested several times (later, the cord is taken out and the strength N1j is determined). Cut it into pieces (possible size), take out the cord from the IK, and test it with a tensile tester to JIS L-
1017 to determine the strength. ...The strength is determined by the average value of fil0 pieces of 1j constant cord, and this value is divided by the denier to calculate the strength when new. If the denier value is known when the code is not processed, use that value. If unknown, take out the cord and determine the cord denier by determining the rM diameter of the filament, the total number of filaments, and the number of pins using an optical microscope and a scanning electron microscope. Next, cut the other tire pieces at 140°C ± 3.
Place in a hot air circulation dryer adjusted to 'C' and leave for 240 hours. Thereafter, the tire was taken out, and after cooling to room temperature, the cord was taken out from the tire piece and its strength was measured in the same manner as described above. The thermal deterioration strength retention rate was calculated according to the formula below.

In addition, in the present invention, the linear polyester fiber forming the h1+ carcass cord is phenol/tetrachloroethane=
507. It is preferable that the intrinsic viscosity determined from the mixed solvent is 0.80 or more, and the terminal carboxyl group content of the polyester polymer is 18 eq/lo 9 or less. This is because if the intrinsic viscosity is less than 0.80, it becomes difficult to increase the strength of the coating to 69/D or more, and if the terminal carboxyl method is 18 or more, thermal deterioration is poor and the strength retention rate is reduced by the above test method. This is because it becomes difficult to keep the value above 70%.

(Example) The board name is explained in the next 'L(I!I) example.

The pneumatic tires of the present invention are not limited to those shown in the examples, but include all tires that use cords made of polyester fibers defined by the present invention as reinforcing materials for the carcass ply, such as radial tires and bias tires. including. As a twisted column of polyester cord used as carcass material! ':t 1000 D/2
, 1000 D/s, 1100 D/2°1100
D/'3, l5 (10D/2, 1500 D/
a, 1600D/2 + 16oo D/3, etc., and belt materials for pneumatic radial tires combining belt materials using this carcass material include steel, polyester, rayon, nylon, aramid, glass fiber, Includes tires made from charcoal fiber. In the case of multi-layer ply, it is specified by the strength and strength retention rate of the outer layer carcass cord.

The terminal carboxyl group of the polyester polymer in Examples and Comparative Examples was measured using the method described in Kogyo Kagaku Zasshi Vol. 63, No. 8, p. 110 (1962).

Example 1 Intrinsic viscosity determined from 7 E/L/ethane tetrachloride = 50150 mixed medium 0.90, polyester polymer powder %i
Contains carboxyl group! 18 eq/106g no 150
0D/190 (where 190 is the number of filaments) multifilament polyester yarn was twisted to make a two-strand cord (40SX40Z). The cords were heat treated under the treatment conditions shown in Table 1. For adhesive cutting, one-bath treatment was performed using RF'L-based assisted cutting containing sulfur-modified resorcire.

Bias tires 7.00-15 8 PR tires 3 for light trucks were created using the above heat treatment code, and drum durability and field tests were conducted.
The tire was mounted on the same shoulder as the tire of Comparative Example 1 shown later under normal road running conditions under a load of 00 to 120%, and evaluated by a zeta test when running on a slope.

Example 2 I+lff limiting viscosity number 0.92 determined from a mixed solvent of phenol/ethane tetrachloride = 50150, polyester bolima powder, carboxyl agent content] 5 eq/10
6g of 15UOD/25(l filament twisted into 2
This was a real twist coat' (403X◆02). This code was processed under the QIL pp conditions shown in Table 1. For bonding and cutting, I used RFL type adhesive t1l with VLJLcA-BONLI-E.

A bias tire for racks (7.00-158 PR) was prepared using the obtained heat-treated cord, and a drum durability test and a field test were conducted. The practical test was carried out on the same vehicle as in Comparative Example 2, and a 1ri 1 hour test was carried out.

Example 3 Phenol/ethane tetrachloride = 50/s o 1% combined fE tlX 0.80 because the limit v3 degree was determined from 15 eq
A heat-treated cord similar to Example 1 was prepared using 1500D/250 filament polyester yarn with a diameter of 10', and a bias tire for light trucks of 7.00-15 was prepared.
8 PR tires were created and tested by 161 people. However, in the field test, the tire was installed on the same vehicle as the Hisen Example 3 tire and evaluated by simultaneous testing.

The above test results are also listed in Table 1.

Comparative Example 1 Intrinsic viscosity determined from a mixed solvent of phenol/tetrachloroethane ""/so, intrinsic viscosity number 0.00, polyester polymer terminal carboxyl group content 29 eq/lo 9, 1500
A multifilament polyester yarn of D/190 was twisted and subjected to the same heat treatment and f! R agent treatment was performed. Bias tire 7 for light truck using this code
．． 00-158 PR was prepared and used for comparison.

Comparative Example 2 The same raw yarn as in Example 1 was twisted to create a two-strand cord (
40SX40Z). This cord was heat treated under the heat treatment conditions shown in Table 1 using an epoxy thread adhesive in the first bath and RFL (D-5A manufactured by Dupont) as a sliding agent in the second bath. A light truck bias tire 7.00-158 PR was made using the obtained treated code and used for comparison.

Ratio 62 Example 3 Kashi limiting viscosity number 0.67 determined from a mixed solvent of phenol/tetrachloroethane = 50/50, polyester polymer 15
A heat treated cord similar to Actual ifQ Example 1 was prepared using 00D/190 filament polyester yarn.

A light truck bias tire 7, 00-158 PR tire was prepared using this QL (! code) and used as a comparative example.

Phenol/Ethane tetrachloride / 6o mixed fB
Intrinsic viscosity determined from & (1,90, polyester polymer terminal carboxyl group 18 eq/10 of 69
A two-strand cord (+9SX49Z) was prepared by twisting 0OD/190 filament polyester yarn. The cords were heat treated under the treatment conditions shown in Table 2. The same adhesive as in Example 1 was used. This heat treated foot.

was used for the carcass layer, and I X 5 X was used for the belt layer.
Belt layer 2 using steel twisted cord of O, 25mm diameter
Radial tires for passenger use P235 /
A 75R15 (2-ply carcass) tire was created.

The performance of this tire was rated n, and the results are also listed in Table 2.

Comparative Example 4 Intrinsic viscosity determined from phenol/ethane tetrachloride/6o mixed solvent io, 92. Polyester polymer terminal carboxyl group 29 eq/lO'gI 100+ID
/250 filament polyester yarn was twisted into a two-strand cord (49SX49Z). The cords were treated under the heat treatment conditions shown in Table 2. The same adhesive as shown in Example 1 was used. Using this heat treatment code, a tire similar to that of Actual Face Example 4 was made, and its performance was evaluated. The obtained results are also listed in Table 2.

Table 2 “I Based on JIS L-1o1 F*2 First/J
rWf509/piece 177° (:X30 minute dry heat shrinkage rate★
δ Test tire internal pressure 6 to 9 / load 1680 ~.

Traveling degree: 60 Km/Hr (Effects of the invention) As explained above, the pneumatic tire of the present invention has
Cords made of specific linear polyester fibers are used as reinforcing materials for carcass plies, resulting in excellent handling stability and abrasion resistance.The carcass cords also have significantly improved heat resistance and strength deterioration, resulting in excellent high-speed performance and durability. It has the effect of having fatigue resistance, and is applicable to all radial tires and bias tires, and is particularly useful for light trucks and trucks/buses.

Claims (1)

[Scope of Claims] 1. A tread portion, a pair of side portions connected to the tread portion at both shoulders of the tread portion, and a pair of bead portions formed respectively on the inner periphery of the side portions; In a pneumatic tire reinforced by at least one carcass layer secured to a pair of provided bead wires and a belt layer provided at the crown portion between the carcass and the tread, the carcass removed from the tire when the tire is new. Linear polyester fiber with a cord strength of 6.0 g/D or more, and a strength retention rate of the cord taken out from the tire after statically thermally aging the tire at 140°C for 240 hours is 70% or more of that of new. A pneumatic tire characterized by using a cord made of as a reinforcing material for the carcass ply. 2. In the carcass cord, the linear polyester fiber has an intrinsic viscosity of 0.80 or more determined from a mixed solvent of phenol/tetrachloroethane = 50/50, and the terminal carboxyl group content of the polyester polymer is 18eq/10^6g or less. 2. The pneumatic tire according to claim 1, wherein the pneumatic tire is a cord that has been heat-treated using a one-bath type RFL adhesive as an adhesive.