AU613512B2 - Tires for construction vehicles - Google Patents

Description

i:'i i k is AUSTRALIA u PATENTS ACT 1952 COMPLETE SPECIFICATION Form Form

(ORIGINAL)

FOR OFFICE USE Short Title: Int. Cl: Application Number: Lodged: Complete Specification-Lodged: Accepted: Lapsed: Published: Priority: Related Art: TO BE COMPLETED BY APPLICANT Name of Applicant: Address of Applicant: BRIDGESTONE CORPORATION 10-1 KYOBASHI 1-CHOME

CHUO-KU

TOKYO

JAPAN

Actual Inventor: Address for Service: GRIFFITH HACK CO., 601 St. Kilda Road, Melbourne, Victoria 3004, Australia.

Complete Specification for the invention entitled: TIRES FOR CONSTRUCTION VEHICLES.

The following statement is a full description of this invention including the best method of performing it known to me:-

L

~rramnr~n~l I 63-213,541 TIRES FOR CONSTRUCTION VEHICLES This invention relates to a tire for use in construction vehicles having considerably improved cut resistance and appearance.

Since the tire for construction vehicle is run on severely rough road surfaces, there is caused a phenomenon that the tread portion is subjected to cut 0 5, failure through sharp rock and stone or rubber is 0 o 0 "o teared, resulting in the remarkable degradation of tire 1 life.

3 10 For this end, it has hitherto been attempted to make the tread rubber hard by using styrene-butadiene copolymer or adding a great amount of a reinforcing filler for the prevention of cut failure.

o oo 00 It is known that the hardness of the tread rubber is advantageous to be made high for enhancing the 0 n0 cut resistance as mentioned above. For this purpose, the change of polymer or filler has been adopted as a o°o° countermeasure. In this case, however, there are the Q as t< 'following drawbacks.

When styrene-butadiene copolymer SBR #1500) is used as a polymer, the cut resistance is improved, but troubles are caused in the tire casing portion due to the heat accumulation during the high speed running or -2- L i 2 0 o0 "0 0 0 0000 oOn 0 00 00°0 0 0 0 0 0 0o 0 ;i 0 00 0 00 i ca i °a at a high working ratio, which considerably lowers the tire life.

When carbon black is added at a high grade or at a large amount as a filler, the cut resistance is improved, but the heat build-up is lowered or the appearance is considerably degraded.

Moreover, it is known to make the tread rubber soft for enhancing the appearance. For this purpose, an oil, a resin or the like is usually added to the tread 10 rubber. In this case, however, the cut resistance is considerably degraded.

In any case, it is very difficult to improve both the cut resistance and the appearance by these conventional techniques, so that the tread rubber is always prepared at a compromise level between the cut resistance and the appearance.

The inventors have made various studies in order to solve the aforementioned problems in the tires for construction vehicles and found that when the tread 20 portion is made from a rubber composition comprising particular rubber ingredient(s), particular carbon black and addition product of dicyclopentadiene series resin with ethylidenenorbornene, the cut resistance and appearance of the tire for construction vehicle can considerably be improved, and as a result the invention has been accomplished.

-3- I- According to the invention, there is the provision of a tire for construction vehicle comprising a tread portion constituted with a rubber composition containing 40 to 76parts by weight of carbon black having a specific surface area of nitrogen adsorption

(N

2 SA) of 110-170 m2/g and a dibutylphthalate absorption (DBP) of 85-150 me/100 g and 0.5 to 20 parts by weight of ethylidenenorbornene added dicyclopentadiene series resin represented by the following general formula: ot. (wherein n is an integer of 3-100) based on 100 parts by weight of rubber ingredient being styrene-butadiene copolymer rubber alone or a rubber blend of at least by weight of said styrene-butadiene copolymer rubber and the remainder of other diene series rubber; and not less than 10% by weight of said styrene-butadiene copolymer rubber being a styrene-butadiene copolymer rubber having a bound styrene content of 25-35% by weight and a content of vinyl bond in butadiene portion of iot more than According to the invention, the rubber composition constituting the tread portion of the tire comprises styrene-butadiene copolymer rubber (SBR) -4- 4-,

I:

Co0 0 having a high bound styrene content alone or a blend of not less than 50% by weight of such SBR and the other diene series rubber as a rubber ingredient. The reason why the amount of this SBR is at least 50% by weight as 05 a rubber ingredient is due to the fact that when the amount is less than 50% by weight, the effect of improving the cut resistance and rubber chipping resistance in the tire can not be achieved. The diene series rubber to be blended with the above high-styrene 10 SBR includes natural rubber, synthetic polyisoprene rubber and polybutadiene rubber. Furthermore, not less than 10% by weight of the above SBR is necessary to have a bound styrene content of 25-35% by weight and a content of vinyl bond in butadiene portion of not more than 30%. When the bound styrene content is less than 25% by weight, the cut resistance and rubber chipping resistance of the tire are not improved but are rather degraded, while when the bound styrene content exceeds 35% by weight and the vinyl bond content exceeds the resistance to heat build-up lowers to raise the tire temperature, which is unfavorable as a construction vehicle tire.

According to the invention, the SBR is used in an amount of 50-100% by weight as a rubber ingredient, so that the amount of the filler added may be reduced.

That is, hard carbon black having N 2 SA of 110-170 m 2 /g, o 0 o 0, o 000f preferably 130-170 m 2 /g and DBP of 85-150 me/100 g, preferably 100-150 me/100 g is added in an amount of 40-75 parts by weight, preferably 50-65 parts by weight based on 100 parts by weight of the rubber ingredient.

When N 2 SA and DBP of carbon black are less than 110 m/g and less than 85 me/100 g, respectively, the cut resistance and rubber chipping resistance of the tire are degraded, while when N 2 SA and DBP exceed 170 m 2 /g and 150 me/100 g, the resistance to heat build-up undesirably lowers. Further, when the amount of carbon black is less than 40 parts by weight, the cut resistance and rubber chipping resistance of the tire are degraded, while when it exceeds 75 parts by weight, the resistance to heat build-up lowers to undesirably raise the tire temperature.

According to the invention, both the cut resistance and the appearance are established by adding 0.5-20 parts by weight, preferably 5-15 parts by weight of ethylidenenorbornene added dicyclopentadiene series resin represented by the general formula: (wherein n is an integer of 3-100) to the above rubber composition. When the amount of such a resin is less -6i

I.

than 0.5 part by weight, the cut resistance and the appearance are not satisfied, while when it exceeds parts by weight, the effect of improving the cut resistance and the rubber chipping resistance is saturated and the cost becomes inadvantageous.

Further, when n in the above general formula is less than 3, the modulus of elasticity, particularly dynamic modulus of the rubber composition lowers and the wear resistance of the tire is degraded. While, when it exceeds 100, the elongation at break of the rubber composition lowers and the cut resistance of the tire is unfavorably degraded. Especially, when n is within a range of 8-50, both the wear resistance and the cut resistance of the tire are favorably established.

The ethylidenenorbornene added dicyclopentadiene series resins used in the invention are industrially manufactured by forming a resin through thermal polymerization process at a high temperature above 2000C in the absence of a catalyst, which is a general method of dicyclopentadiene resin, and then subjecting to an addition reaction with ethylidenenorbornene.

Moreover, there is known a method of producing a ring-opened polymer or a ring-opened copolymer as a method for the production of dicyclopentadiene series 26 resin Japanese Patent laid open No. 53-115763).

However, the resin produced by this method is low in the -7-

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0 00 00 0 090 0 00 0 0 0 0 S0000 00 reactivity, so that it can not be applied to the invention.

The following examples are given in illustration of the invention and are not intended as limitations 06 thereof.

Examples 1-3, Comparative Examples 1-7 Ten rubber compositions were prepared by compounding various ingredients as shown in the following Table 1 at a compounding amount shown in Table 1.

10 0000 0 A 0 00 0 o 00 00 0 O o O 00 0 00 0 0 t t -8o a a a a a Table 1 Rubber composition 1 2 3 4 5 6 7 8 9 SBR 11500 *1 100 70 70 70 70 70 70 HR 30 HR 30NR3 SBR #1500 70 SBR #1500 40 SBR *1500 High-styrene, low-vin~yl SBR *2 30 30 30 130 30 30 30 Kind of carbon black *3 ISAF ISAF ISAF ISAFI SAF SAF SAF ISAF ISAF ISAF Amount of carbon black 60 60 60 60 60 60 60 60 60 Kind of resin aroma *4 aroma A *5 B *6 rroma A B aroma aroma B Amountof resin 10 10 10 10 10 10 10 J.0 10 Stearic acid 2 2 2 2 12 2 2 2 2 2 Paraffiwax 1 1 1 1 1 1 1 1 1 1 Antioxidant *7 1 1 1 1 1 1 1 1 1 1 zinc white 4 4 4 4 4 14 4 4 4 4 Vulcanization accelerator DPG *8 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 Vulcanization accelerator NOBS *9 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 Sulfur 1.5 1.5 1. 5 11. 5 11.5 1. 5 1.51 1.5 1.5 Note) emulsion-polymerized SBR, made by solution-polymeriz~d SBR: styrene ISAF: 125 m 2 /g (N2SA), 114 mf/laO SAF 163 m 2 /g (N2SA), 120 me/10O Japan Synthetic Rubber content: 30 wt%, vinyl g (DBP) g (DBP) Co. Ltd.

aromatic oil dicyclopentadiene resin ethylidenenorbornene added dicyclopentadiene resin (average molecular weight Mw=1,700) Santoflex 13, N-(1,3-dimethyl)-H'-phenyl-p-phenylenediamine diphenylguanidine 2-(4-morpholino-dithio) benzothiazole 2I i Ten test tires having a tire size of 10.00 as shown in the following Tables 2 to 4 were manufactured by using the rubber compositions No. 1 No. shown in Table i, respectively. After each of these test tires was run on a stone pit and a dam site over a distance of 4,000-6,000 km, the depth of the remaining groove for the evaluation of wear resistance of tread portion, number of cuts and rubber chipping number were measured. The results are also shown in Tables 2 to 4.

Table 2 Compar- Compar- Compar- Tire ative ative ative Example 1 Example 1 Example 2 Example 3 Rubber 1 2 3 4 composition No.

Wear resistance 483 532 573 596 Number of cuts 108 59 50 37 Rubber chipping 43 32 28 19 number Table 3 Compar- Compar- Tire ative ative Example 2 Example 4 Example Rubber composition No. 5 6 7 Wear resistance 638 680 692 Number of cuts 52 41 28 Rubber chipping number 29 25 11 Table 4 Compar- Compar- Tire ative atlve Example 3 Example 6 Example 7 Rubber composition No. 8 9 Wear resistance 352 408 466 Number of cuts 187 92 47 Rubber chipping number 68 41 28 Wear resistance: running distance until tread rubber is worn by 1 mm Number of cuts :cut number in tread length of cm Rubber chipping number: rubber chipping number in tread length of 50 cm As mentioned above, the tread portion of the tire for construction vehicle according to the invention is made from a rubber composition containing 40-75 parts by weight of carbon black having N 2 SA of 110-170 m 2 /g i and DBP of 85-150 m/100 g and 0.5-20 parts by weight of ethylidenenorbornene added dicyclopentadiene series resin based on 100 parts by weight of rubber ingredient being a high-styrene, low-vinyl SBR alone or a blend with other diene series rubber, whereby the cut resistance and rubber chipping resistance are considerably improved and also the appearance is excellent.

11 -u A 'WMy...

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Claims (4)

1. A tire for construction vehicle comprising a tread portion constituted with a rubber composition containing 40 to 75 parts by weight of carbon black having a specific surface area of nitrogen adsorption (N 2 SA) of 110-170 m 2 /g and a dibutylphthalate absorption (DBP) of 85-150 me/100 g and 0.5 to 20 parts by weight of ethylidenenorbornene added dicyclopentadiene series resin represented by the following general formula: (wherein n is an integer of 3-100) based on 100 parts by weight of rubber ingredient being styrene-butadiene copolymer rubber alone or a rubber blend of at least i by weight of said styrene-butadiene copolymer rubber and the remainder of other diene series rubber; and not less than 10% by weight of said styrene-butadiene copolymer I rubber being a styrene-butadiene copolymer rubber having a bound styrene content of 25-35% by weight and a K content of vinyl bond in butadiene portion of not more than

2. The tire according to claim 1, wherein n in said general formula is within a range of 8-50. -12- y i. ~rl~U

3. The tire according to claim 1 or 2, wherein said carbon black has N 2 SA of 130-170 m 2 /g and DBP of 100-150 mt/100 g.

4. A tire for construction vehicle substantially as hereinbefore described with reference to any one of the foregoing examples except for the comparative examples. Dated this 16th day of May, 1991 BRIDGESTONE CORPORATION By its Patent Attorneys: GRIFFITH HACK CO. Fellows Institute of Patent Attorneys of Australia. o 4 C o t o to o 4 o 0o .0 4 4 C c c t 4 13