CN1061390C - Light weight tire - Google Patents

Abstract

A tire is described which includes polybenzazole (PBZ) fibers. The PBZ fibers can be used as part of either the carcass of the tire or as the reinforcing belts of the tire or as both. Tires made with PBZ fibers weigh less than do tires made with steel or other organic fibers, therefore the fuel efficiency of vehicles with tires that contain PBZ fibers is greater than that of vehicles that have tires that do not contain PBZ fibers.

Description

lightweight tires

The present invention relates to lightweight tires.

A tire is defined as "a continuous solid or air-filled rubber cushion surrounding a wheel", see Webster's Ninth New Collegiate Dictionary, p. 1237, 1989 by Mer-riam-Webster Inc. . Tires are made of rubber, fabric, chemicals and metal (steel), see Tires, pp. 834-861, Vol. 16 of the Encyclopedia of Poly-mer Science and Engineering, 1989 by John Wiley & Sons, Inc. . Pneumatic tires are toroidal and comprise a composite of high-performance polymers with an outer rubber and a fiber sheath. In these tires, there are reinforcing cords for stability and impact resistance, fatigue resistance and heat resistance.

In bias ply tires, the reinforcing ply traverses the tire diagonally from bead to bead. In order to balance the strength of the tire, each reinforcing ply passes symmetrically through the centerline of the tread at a top angle of 30°-70°.

A radial tire is a pneumatic tire in which the filament fibers in the ply or carcass of the reinforcing cord are radially (from bead to bead) arrangement. Steel belts are used in radial tires to tighten the carcass plies at 90 degrees, the rigidity of which is necessary for the function of the tire. Without the steel belts, the radial carcass would be unstable. In addition to steel belts, polyester cord and/or steel cord are used in the basic structure or "casing" (the carcass is that part of the tire between the tread and the lining) of the tire to reinforce the tire as pressure The characteristics of the container.

When steel reinforcements are used in the tire structure, the ride performance of the tire is improved; however, the weight of the tire is increased due to the weight of the steel. The extra weight of steel-reinforced tires means vehicles with steel-reinforced tires have increased rolling resistance, which leads to higher fuel consumption. For efficiency, cost and environmental reasons, reducing fuel consumption in all vehicles is a goal.

Trials have been done to replace steel in tires with high performance organic fibers. but. These known organic fibers, such as para-aramid fibers, have not been widely used due to their performance problems. These performance issues include that the fibers do not have enough tensile strength to give equivalent performance in tires that use organic fibers instead of steel, requiring much more tires to weigh the same as steel-reinforced tires of organic fibers. At the same time it has been found that tires made of known organic fibers do not have the desired level of wear resistance and fatigue resistance.

It would be desirable to produce tires that perform as well as steel tires, but weigh significantly less than steel tires.

A first aspect of the invention is a tire characterized by polybenzazole-containing fibers.

A second aspect of the invention is a tire containing polybenzazole fibers, characterized in that the polybenzazole fibers have:

a) The tensile strength is at least 4.0GPa;

b) The tensile modulus is at least 140GPa;

c) The average pore diameter is 25 mm or less.

A third aspect of the invention is a polybenzazole fiber-containing tire characterized by the addition of polybenzazole fibers to the reinforcing tape.

A fourth aspect of the present invention is a polybenzazole fiber-containing tire characterized in that the polybenzazole fiber is added to the carcass of the tire.

Preparation of Polybenzazole Polymers

As used herein, the term polybenzazole ("PBZ") includes polybenzoxazole ("PBO") homopolymers, polybenzothiazole ("PBT") homopolymers, and derivatives of PBO and/or PBT. Regular, sequential and block copolymers. Polybenzoxazole, polybenzothiazole, and random, sequential, block copolymers of polybenzoxazole and polybenzothiazole have been described in the literature, such as Wolfe et al. , Liquid Crystalline Polymer Compositions, Pro-cess and Prokucts, U. S． Patent 4,703,103 (October 27, 1987); wolfe et al. , Liquid Crystalline Polymer Compositions, Pro-cess and Products, U. S． Patent 4,533,692 (August 6, 1985)-; Wolfe et al. , Liquid Crystalline Poly (2,6-Benzothiazole) Compositions, Process and Products, U. S． Patent 4,533,724 (August 6, 1985); Wolfe, Liquid Crystalline Polymer Compositions, Process and Products, U. S． Patent 4,533,693 (August6, 1985); Evers, thermooxidatively Stable Articulated p-Benzo-bisoxazole and p-Benzobisthiazole Polymers, U. S． Patent 4,359,567 (November 16, 1982); and Tsai et al. , Method for Making Heterocyclic Block Copolymer, U. S． Patent 4,578,432 (March 25, 1986). Preferred structural units in polybenzazole polymers are those which enable the polymer to form lyotropic liquid crystals. Preferred monomer units are listed in formulas (a)-(h). More preferred polymers consist essentially of monomer units selected from those listed in (a)-(h), while most preferred polymers consist essentially of several of the same monomer units selected from those listed in (a)-(c). composed of units. Poly[benzo(1,2-d:5,4-d')bisoxazole-2.6-diyl-1.4-phenylene] Poly[benzo(1,2-d:5,4-d')bisoxazole-2.6-diyl-1.4-phenylene]

Solvents suitable for forming polybenzazole polymer slurries include cresols and non-oxidizing acids capable of dissolving the polymer. Examples of suitable acidic solvents include polyphosphoric acid, methanesulfonic acid, concentrated sulfuric acid, and mixtures of these acids. A very preferred solvent is polyphosphoric acid or methanesulfonic acid, the most preferred solvent is polyphosphoric acid. The concentration of polymer in the solvent is preferably at least about 7% by weight, more preferably at least about 10% by weight, and most preferably at least about 14% by weight. The maximum concentration is mainly limited by practical factors such as the solubility of the polymer, the viscosity of the slurry as already mentioned. Due to these constraints, the polymer concentration is rarely greater than 30% by weight, and usually not greater than about 20% by weight.

Suitable polymers or copolymers and slurries can be synthesized by known methods, such as in Wolfe et al. , U． S． Patent 4533693 (August 6, 1985), Sybert et al. , U． S． Patent 4772678 (September 20, 1988) and Harris, U. S． Described in Patent 4847 350 (July 11, 1989). According to Gregory et al. , U． S． Patent No. 5089591 polybenzazole polymer can rapidly develop into high molecular weight under the action of high temperature and high shear force in anhydrous solvent acid.

fiber preparation

The spun slurry is spun into fibers by known dry-jet wet spinning techniques in which the spun slurry is passed through a spinneret and bundled into one or more slurry filaments of a slurry fiber. Fiber spinning technology for PBZ polymers has been developed in the jointly owned and licensed U. S． Described in Patent Application Number 07/985079 (Method for Spining a Polybenzazole Fiber) and 07/985078 (Method for Rapid Spinning of a Polybenzazole Fiber).

After passing through the air gap, the slurry fibers are contacted with a fluid (which is a non-solvent for the polymer) to dilute the solvent therein. Contact with the fluid causes the polymer to separate from the solvent, a process known as coagulation. After coagulation, most of the residual solvent in each fiber has been washed or leached off and the fibers are wet. See jointly owned, co-pending U. S． Description of coagulation method in Patent Ap-plication Number 08/110149 (Improved Process for Coagulation and Washing of Polybenzole Fibers).

The wet fibers are then dried. Fiber drying methods are in commonly owned, co-pending U. S． It is described in Patent Application 08/142526 entitled "Method for Rapid Drying of a Polybenzole Fiber".

After the fibers are dried, they can be heat treated if necessary to improve the physical properties of the fibers. The heat treatment of PBZ fibers has been carried out in the jointly owned and licensed U. S． Described in Patent Ap-plication Serial Number 07/985068 (Rapid Heat Treatment Method for polybenzazde Polymer) and 07/985067 (Steam Heat Treatment Method for Polybernzazole Fiber).

Application of PBZ fiber in tire

The carcass and reinforcing belt are the two main reinforcing components of the tire. PBZ reinforcing fibers can be used as part of the tire carcass. The tire carcass is the part of the tire between the tread and the liner, the carcass is also called the basic structure of the tire, which includes reinforced plies. PBZ fiber can also be used as a material for the tire circumferential restraint belt.

In order to be used in tires, PBZ fibers must be twisted to form cords, see Addis Finney entitled "That Left-hand Turn and its Effect on Tires" (in the May 1979, issue of Rubber world) on plying Description and illustrations of cords and cables. The PBZ fiber is twisted to form a ply cord, and "T/10cm" is the twist per 10cm of the cord. Once the PBZ plied cord is formed then two or more plied cords are twisted together into a cable cord. The twist of these cable cords is represented by cable twist (turn/10 cm) x ply twist (turn/10 cm). In this application the PBZ cord and cable twist can vary from 20x20 to 100x100. The twist factor of PBZ cord can be calculated as follows: Twist factor = (number of twists/10cm) × (total fineness of fibers/density of fibers) ^1/2 . The twist factor of the PBZ cords used in this application ranges from 800 to 3000. At this stage, the PBZ plied cord is called the natural color cord, and the natural color cord indicates that it is the cord before the dipping state. These PBZ natural color cords have a thickness of 0.30 mm to 0.60 mm.

In order to convert natural color cords to be usable in the manufacture of layered reinforcements or layered tapes, the natural color cords must be dipped in an adhesive to form "soaked" cords and/or cables, which can then be Bonds to other tire components. These adhesives can be standard epoxy adhesives such as glycerol polyglycidyl ether or compounds such as Pexul ^™ , which is a 2,6-bis(2',4'-dihydroxyphenylmethyl)-4-chlorophenol compound (the The compound is also sold under the name Vulcanbond-E ^™ by the company Rhone-Poulenc) or RFL (resorcinol-formaldehyde latex). These adhesives may also be replaced by other suitable adhesives.

The actual dipping process is a two-step method. First, the cord/cable is dipped in the first dipping solution that may contain epoxy or Pexul ^TM (as the main adhesive component), and then the cord/cable is placed at 235°C- A temperature of 250°C for about 60 seconds; the cord/cable is then contacted with a second dipping liquid, possibly RFL (resorcinol-formaldehyde latex), and placed at a temperature of 230°C-240°C for about 60 seconds.

Once the PBZ cords/cables are formed, they are assembled into tires using standard tire manufacturing techniques, and the tires are then subjected to various performance tests.

Because polybenzazole fiber has higher (about 2 times) tensile strength and tensile modulus, the carcass material of the present invention that is used for car tire can be two layers of 500 deniers (or less) PBZ fiber cord equivalent Two layers of 1000 denier paraaramid fiber cord (denier is the weight in grams of 9000 meters of fiber). For this reason, after using PBZ tire cord in the carcass, the thickness of the cord can be reduced to 0.39mm or less, which is equivalent to two layers of 0.67mm thick polyester cord of 1500 denier.

Therefore, it is possible to reduce the weight of the tire by replacing organic fibers and steel strands in the carcass and belts with PBZ. An example of weight reduction: standard 195/65 R 15 tires ("195/65 R15" tires are designed according to JIS D4202-1982, as follows: tire width 195mm, tire flat rate 65%, "R" stands for radial tires, The rim is 15 inches) using PBZ cord, the tire weight may be reduced by 1.5kg. The weight reduction is calculated as follows:

The use of PBZ cord in the carcass can reduce the weight by 500 grams;

The use of PBZ cord instead of steel in the belt can reduce the weight by 600 grams;

The weight of the carcass can be reduced by an additional 400 grams due to the reduced thickness of the rubber in the carcass; this is due to the use of PBZ cords in the carcass, which requires less rubber.

It has been found that if the PBZ fiber used to make the cord has a tensile strength of preferably at least 2.8 GPa, more preferably about 4.0 GPa, more preferably at least about 5.7 GPa and most preferably about 6.9 GPa, the tensile strength With an elongation modulus of preferably at least about 140 GPa, more preferably at least about 276 GPa, and most preferably at least about 380 GPa, the performance characteristics of the cord in the tire can be improved.

It has also been found that the fatigue resistance of PBZ fibers for tire cords is better if the average diameter of the voids in the fibers is 25mm or less. The average diameter of pores in PBZ fibers can be determined by the "small angle X-ray scattering" technique, which can measure the diameter of pores in fibers smaller than 100mm. It has been found that a tire made with a carcass of PBZ cord having an average pore size of 25 Å or less is twice as durable as the same tire made with a PBZ cord having an average pore size of 30 Å or greater.

A feature of the present invention is that it is possible to make passenger car tires with only PBZ cord belts and PBZ carcass (these tires will be the lightest tires), and also to make passenger car tires with steel belts and PBZ carcass (these tires should be heavier than tires made with only PBZ cord) and passenger car tires can be made with PBZ cord belts and polyester carcass (these tires will cost less than other tires).

A feature of the present invention is that it is possible to make truck/bus tires with only PBZ cord belts and carcass (these tires should be the lightest tires) and to also manufacture truck/bus tires with steel belts and PBZ carcass ( These tires should be heavier than tires made with only PBZ cord) and truck/bus tires made with PBZ cord belts and steel carcass (these tires should be heavier than tires made with only PBZ cord).

The following examples are for illustration only and should not be considered as limiting the scope of the specification or claims. All parts and percentages are by weight unless otherwise indicated.

The following are the testing techniques employed in the examples.

Pore diameter

Small angle X-angle scatter intensity measurements can be made with appropriate X-ray equipment, such as a Kratkey camera. A fiber sample about 6 meters long is wound on the measuring support. X-rays are generated under the conditions of 45KV and 150mA, and the Cuka line is filtered out by nickel color filter for measurement.

The collimating slit of the Kratkey camera is 42mm (length)×0.14mm (width), and the receiving slit is 10mm (length)×0.14mm (width).

Measure the equatorial (scattering angle 0.1-3 degrees) scattering of the fiber sample with a step width of 0.25 degrees, and the accumulation time is 30 seconds or longer. The background scattering is obtained from the scattering measurement results of the sample and air by the following formula compensate.

In the formula, I is the actual scattering intensity, Isample is the measured intensity of the sample, and Iair is the measured intensity without the sample. In order to determine the absorption coefficient of the sample, after the sample is measured, the intensity at a scattering angle of 0 degrees is measured. The pore size can be determined using the Guinier curve.

The square of the scattering vector (k) is plotted against the logarithm of the scattering intensity, and a straight line is fitted in the range of K2 from ⁰ to ^0.01_2 . The average diameter of the pores can be calculated from the slope of the straight line by the following formula. $\mathrm{D.}=2\sqrt{2K}$

Fatigue test of dipped cord

The disc fatigue test results are expressed as the percentage of strength retention, and the tubular fatigue test results are expressed in minutes. The test method is based on JIS-L1017-1983.

tire test

See ASTM F538-91b and ASTMF551-89 for basic terms and conditions of test tires

The determination of high-speed durability and load durability adopts indoor drum test, and the test method is drawn up according to JIS-D4230-1986.

The damage life of the tires is expressed as an index relative to 100 for passenger car tires (Table III) and as an index relative to 100 for truck and bus tires (Table V).

The cracking of the carcass after running for a predetermined period of time was studied, the durability of which is expressed as an index relative to 100 for passenger car tires (Table III) and for truck or bus tires (Table V) .

Rolling resistance was measured on an indoor drum testing machine and expressed as an index relative to 100 for passenger car tires (Table III) and for truck and bus tires (Table V). The index is the average value of the test at a speed of 20-150km/h.

The ride feeling test is subjectively evaluated by the special panel members during the actual driving of the vehicle during the test. Ride feel is expressed as an index relative to 100 for passenger car tires (Table III) and as an index relative to 100 for trucks and buses (Table V).

Fuel consumption, expressed as an index relative to 100 for wheeled vehicles (Table III), for trucks

and buses are expressed as indices relative to 100 (Table V). The results show that the fuel consumption of vehicles with tires made of PBO fibers is lower than that of vehicles without tires made of PBO fibers.

The high-speed durability test is carried out using an indoor drum testing machine, and the specified load is applied to the tire. The test speed is increased in steps as follows:

80km/h 120min

120km/h 30min

130km/h 30min

140km/h 30min

150km/h for 30min until damage is observed.

load durability

A constant rotational speed is applied to the tire using an indoor drum testing machine, and the load on the tire is increased in sections as follows:

car tire

Speed = 80km/h

load

100% max load 4hrs

110% max load 6hrs

150% of maximum load for 6hrs until failure is observed.

Truck/Bus Tires

Speed = 65km/h

load

70% of maximum load for 7 hours

90% of the maximum load for 16 hours

105% of maximum load for 24 hours

steering force

The lateral slip force of the tire was measured on a drum testing machine at 10 km/h and a slip angle of 2 degrees. Steering power is steering force divided by slip angle. It is expressed as an index relative to 100 for passenger car tires (Table III) and for truck and bus tires (Table V). The number of carcass weft yarns refers to the number of weft yarns per 10 cm carcass cord. Strength of carcass cord This refers to the breaking strength of one carcass cord, which is measured with an Instron tensile testing machine.

Embodiment 1 Car tire

Polyester, para-oriented aramid and polybenzazole fibers are twisted and made into two layers of natural cord.

Each natural color cord is processed into a dipped cord/cable using a two-step dipping process. The dipping treatment solution and the treatment temperature used for the dipping process are listed in Table I, and the properties of the cord after dipping are listed in Table II. In Table II there are 5 cords made of PBO such as Examples A, B, C, D and E (Table II), and one cord made of para-aramid for comparison (Table II). For comparison, there is also a cord made of polyester in Table II.

The disc fatigue and tubular fatigue test results listed in Table II show that the fatigue strength of the PBO fiber increases if the void diameter in the PBO fiber is 25 mm or less, such as samples A, B and C.

The strength factor is the tensile strength divided by the square of the cord thickness. Higher values indicate higher strength per unit thickness of the ply. Therefore, the modulus of strength is an important measure of fiber performance for reducing tire weight.

These impregnated cord carcasses and reinforcing belts were used to manufacture passenger car tires and to perform performance tests on the tires. The composition and test results for each tire are listed in Table III.

Table I PBO p-aramid polyester first dipping solution Epoxy Epoxy Pexul First furnace temperature 250 250 240 second dipping solution RFL RFL RFL Second furnace temperature 235 235 235

"EPOXY" is glycerol polyglycidyl ether (sold under the trade name Denakol ^TM by Nagase)

"RFL" is resorcinol-formaldehyde-latex

"Pexul ^™ " is a product of 2,6-bis(2',4'-dihydroxyphenylmethyl)-4-chlorophenol (also known as Vulcabond E ^™ , marketed by Rhone-Poulenc), with a dipping solution Dipping for 1 second and drying for 60 seconds. Table II sample A B C D. E. f G fiber type PBO PBO PBO PBO PBO p-aramid polyester Pore diameter_ 20 20 25 30 34 --- --- Denier (denier) 500 500 500 500 500 1000 1500 Tensile strength GPa 5.5 5.5 5.5 5.5 5.3 3.0 1.2 Elongation at break % 2.0 3.8 3.9 3.8 3.7 4.3 13.8 Tensile modulus GPa 344.2 179.0 169.4 172.1 151.5 480.0 125.0 natural color cord Twist T/10cm 72×72 72×72 72×72 72×72 72×72 49×49 39.5×39.5 twist factor 1823 1823 1823 1823 1823 1832 1835 Cord Thickness mm 0.36 0.38 0.37 0.37 0.37 0.50 0.65 Strength kg 30.3 31.8 31.5 32.0 30.7 35.3 25.3 Elongation at break % 4.9 5.4 5.3 5.3 5.2 6.6 18.2 dipped cord Twist T/10cm 72×72 72×72 72×72 72×72 72×72 49×49 39.5×39.5 twist factor 1823 1823 1823 1823 1823 1832 1835 Cord Thickness mm 0.38 0.39 0.39 0.39 0.39 0.54 0.67 Strength kg 27.2 25.8 26.0 25.7 24.3 28.5 23.8 Strength factor kg/mm ² 188.4 169.3 170.9 169.0 159.8 97.7 53.0 Load kg at 3% elongation 20.6 18.1 17.8 18.0 17.9 17.0 16.9 Elongation at break % 3.7 4.3 4.2 4.2 4.3 4.4 Hot air shrinkage % 0.0 0.0 0.0 0.0 0.0 0.0 Disc fatigue % 53 61 59 40 twenty three 56 63 Tubular Fatigue Minutes 23.7 265 226 148 119 145 150 Table III sample tire 1 tire 2 tire 3 tire 4 tire 5 Control 1 Control 2 belt material A B C D. E. f Steel Carcass material A B C D. E. f G Carcass cord weft head /10 cm 108 108 108 108 108 108 108 Tire weight kg 9.0 9.0 9.0 9.0 9.0 9.8 10.5 Carcass cord strength kg 26.5 25.8 26.0 25.3 23.9 25.3 22.5 High Speed Durability Index 110 108 105 96 92 98 100 Load Durability Index 102 102 102 97 89 97 100 rolling resistance index 83 85 85 85 85 90 100 Ride Feel Index 115 115 115 115 115 110 100 steering power index 100 98 98 98 98 97 100 fuel consumption index 93 95 95 95 95 98 100

Example 2 Truck and Bus Tires

The oriented para-aramid fiber and PBO fiber are twisted to make two layers of natural color cord.

Each natural color cord was dipped in the same manner as described in Table I of Example 1 to make a dipped cord.

The properties of the resulting dipped cords are listed in Table IV. Truck or bus radial tires were manufactured using these impregnated PBO cords and/or steel cords, and the performance of these tires was tested.

The composition of the cords in each tire and the test results for the tires are listed in Table V. Table IV sample h I J K L m fiber type PBO PBO p-aramid steel steel Pore diameter, _ 20 20 - - - - Denier (denier) 1500 1500 3000 3000 Intensity GPa 5.5 5.5 3.0 3.0 2.3 2.3 Elongation at break % 2.0 3.8 4.5 4.5 1.7 1.7 Modulus GPa 344.2 179.0 68.8 68.8 194 194 natural color cord Twist T/10cm 30×30 44×44 22×22 32×32 3×0.20+6×0.38 3+9+15×0.175+0.15 twist factor 1316 1930 1364 1985 Cord Thickness mm 0.56 0.58 1.01 1.04 1.16 1.05 Strength kg 111.2 98.1 112.8 99.6 192.3 149.7 Elongation at break % 4.1 5.4 5.3 5.3 1.7 1.7 dipped cord Twist T/10cm 72×72 72×72 72×72 72×72 twist factor 1316 1930 1364 1985 Cord Thickness mm 0.58 0.60 1.03 1.05 Strength kg 105.5 92.3 98.1 86.5 Strength factor kg/mm ² 313.6 256.4 92.5 78.5 Elongation at break % 3.7 4.3 4.2 4.2 Hot air shrinkage % 0.0 0.0 0.0 0.0 Table V tire 1 tire 2 Control 1 Control 2 Control 3 belt material h L J L L Carcass material I I K K m Tire weight kg 41.6 45.3 47.0 50.2 53.8 Carcass cord strength kg 107.0 92.6 99.4 85.7 149.2 High Speed Durability Index 105 106 99 102 100 Load Durability Index 101 105 95 97 100 rolling resistance index 81 83 90 88 100 Ride Feel Index 115 110 115 109 100 steering power index 100 103 95 96 100 fuel consumption index 85 89 93 95 100

Claims (10)

1. a tire is characterized in that indole-containing poly fiber, and a) its tensile strength is at least 4.0GPa; With

B) stretch modulus is at least 140Gpa.

2. the tire of claim 1, wherein said polybenzazole fiber is characterized in that they are polybenzoxazole fibers.

3. the tire of claim 2, wherein said polybenzoxazole fibers is characterised in that they have average pore diameter 25_ or lower.

4. the tire of claim 2, wherein said polybenzoxazole fibers is characterized in that they are combined in the enhancing band of tire.

5. the tire of claim 2, wherein said polybenzoxazole fibers is characterized in that fiber combinations is in the carcass of tire.

6. the tire of claim 2, wherein said polybenzoxazole fibers is characterized in that they are combined in the enhancing band and carcass of tire.

7. the tire of claim 1, wherein said polybenzazole fiber is characterized in that they are polybenzothiozole fibers.

8. the tire of claim 7, wherein said polybenzothiozole fiber is characterized in that they have average pore diameter 25_ or lower.

9. the tire of claim 7, wherein said polybenzothiozole fiber is characterized in that they are combined in the enhancing band of tire.

10. the tire of claim 7, wherein said polybenzothiozole fiber is characterized in that they are combined in the carcass of tire.