JPS5996143A - Tire rubber composition - Google Patents

Abstract

PURPOSE:To provide a tire rubber compsn., which gives tire tread having excellent wet grip performance and low rolling performance and has excellent wear resistance, by using a styrene/isoprene copolymer obtd. by solution polymn. as a blending elastomer. CONSTITUTION:A tire rubber compsn. is obtd. by using an elastomer consisting of 30-100pts.wt. styrene/isoprene copolymer (A) obtd. by solution polymn. and 0-70pts.wt. at least one member (B) selected from among natural rubber, isoprene rubber and a synthetic diene rubber as a blending elastomer. The use of the styrene/isoprene copolymer obtd. by solution polymn. can afford the compsn. which gives a tire tread having excellent wet grip performance and low rolling performance and has wear resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tire rubber composition that has excellent wet grip performance and low rolling performance of a tire tread, and has wear resistance.

It is effective to reduce the rolling resistance of tires in response to the social demand for reducing fuel consumption of automobiles, and it is known that the contribution of the tread to the rolling resistance of tires is approximately 50 cm. ing.

It is also believed that the rolling resistance of automobile tires is caused by energy loss in the tire material due to repeated deformation that the tire undergoes during running.

On the other hand, from the viewpoint of automobile safety, it is necessary that braking performance on wet road surfaces (hereinafter abbreviated as wet braking performance) be high.

This wet braking performance is determined by the energy loss caused by the frictional resistance caused by the deformation of the trend rubber material that follows minute irregularities on the road surface when the tire is braked and slides on the road surface. has been done.

As mentioned above, both transfer resistance and wet braking performance are largely due to the energy loss of trend rubber materials.To reduce transfer resistance, it is necessary to reduce energy loss, and to improve wet braking performance, it is necessary There is a trade-off between them: you have to intensify your losses.

Regarding rolling resistance, it is known that the higher the rebound resilience at high temperatures, the lower the rolling resistance.
LUPKE type rebound resilience at C (JISK6301-19
7'5 measurement method)), it can be judged that the higher the value, the better the fuel efficiency.

RUBBERCI (
EMISTRY AND TECHNOLOGY.

(R, C, T) 38.840 (1965), using a porta-pull wet skid tester manufactured by Stanley, UK, the higher the test value, the lower the performance of the rubber in actual driving. The tires with the trend used are said to have good wet grip properties, so we decided to compare them using this test value.

In terms of the balance between wet skid (WET 5KID) and rolling resistance, rolling resistance is 10
2H2, weight skid is on the order of 106 Hz, and is said to be a phenomenon in different dimensional regions. If we consider this frequency in terms of temperature, it is approximately 1
Since a temperature of the order of 0 Hz is considered to be about 10° C., the difference between 106 Hz and 102 Hz is considered to be a temperature difference of 40° C. Considering this as the temperature dependence of rebound resilience, assuming that the transfer resistance is approximately 60°C, the wet skid will be 40°C lower at 20°C.
It is thought that this value corresponds to the value of rebound resilience around °C.

Therefore, a good balance between these two means that
It is considered that a material having a low impact resilience at around 20°C and a high impact resilience at 60°C is good. In other words, the greater the temperature dependence within this range, the better.

As mentioned above, various polymers have been proposed as new rubber materials for cap treads in order to obtain a compound with a large temperature-dependent impact resilience value (difference between 60°C impact resilience value and 23°C impact resilience value). . Among them, British patent number 1.
166,832 and 1.261.371 [hereinafter referred to as vinyl butadiene rubber (vinyl butadiene rubber)]
It is abbreviated as V-BR). ] and natural rubber, polyisoprene rubber, styrene-butadiene copolymer rubber, and 1.
2-Tires whose camping treads are made of a rubber composition made of one type of polybutadiene rubber (abbreviated as BR) with a low content of bonding units or a blend thereof have excellent wet braking performance, and in particular, 55-1043
As shown in the specification of No. 43, 1.2-bonding units are 65 to 90 mol% (7) V -B R is 25 to 75
Weight cracking and natural rubber and/or polyisoprene rubber7
It is known that when a rubber composition comprising 5 to 25 equivalents is used for a tread, low rolling resistance and wet braking performance are no longer in a trade-off relationship and are balanced at a high level.

However, when a rubber composition made of the above-mentioned raw material rubber is used for a tread cap, it has a drawback in that it is inferior in wear resistance compared to a general-purpose cap tread.

Regarding wear resistance, R, C,, T, 34.1 (196
As disclosed in the document 1), it is said that there is a high correlation between the PICOIC experience and the tire actual running wear test, so it can be said that if the pico wear is good, the actual running wear is also good. I did a test.

The patent application was filed as a search for a tire composition that improves the above abrasion resistance and achieves a balance of wet grip (wet braking), low rolling resistance (low fuel consumption), and abrasion resistance. There is a tire rubber composition using a styrene-isoprene copolymer (hereinafter abbreviated as SiR) as a raw material polymer, as disclosed in No. 86861/1983.

However, among 5iRO, styrene-isoprene/copolymer (hereinafter S
-8iR) was found to be excellent in the balance of the above three properties, wet braking performance, low rolling resistance, and wear resistance.

Rubber elastic bodies were prepared from various nidistomer formulations based on the following standard formulations, and the physical properties of each were compared, and the results are shown in Table 1 below.

Standard formulation example: 100 parts of elastomer, 3 parts of ZnO, 2 parts of stearic acid
1 part, anti-aging agent [N-phenyl-N'-(1,3-dimethylbutyl)-1)-phinidinediamine] 2 parts, carbon (N-339) 45 parts, highly aromatic oil 5 parts , Accelerator D (diphenylguanidine) 0.2 parts, Accelerator MSA
(1.5 parts of N-oxindinitylene-2-benzothiazolesulfenamide, 2.0 parts of sulfur.

Note) v-BR... Vinyl butadiene rubber (1
, 2m addition 83 t butadiene rubber) E -S B R, Emulsion polymerization Stin-in-prene rubber (5BR-1502) E -S i R, Emulsion polymerization Stin-in prene rubber S -S j R,,,,,Solution polymerization styrene-inglen rubber TDR,,,,,Temperature-dependent impact resilience (difference between 60°C impact resilience (2*) and 23°C impact resilience (1*)) The above physical properties are , was measured by the method below.

1) Pyrogenicity c).

The heat generation property was measured using a Gutdrich Flexmeter, with a stroke of 4.4 and a load of 10.886 kg (24 bond).
, the temperature of the rubber surface was measured after vibration for 25 minutes at a temperature of 40''C-?l'.

2) Resilience (related).

The impact resilience was determined by the impact resilience test method of JIS K6301-1975.

3) Compensatory damage.

Tests were conducted using a Pico abrasion tester in accordance with ASTM-D2228 method, and compared using index values. A material with a large pico wear index is good.

4) Wet grip properties.

This measurement was carried out using a porta-pull wet skid tester made by British Stanley Co., Ltd. A 1 mm water film was spread on the asphalt density test surface, and the value was measured by sliding a rubber piece over the surface. The higher the porta-pull wet skid value, the better the wet grip property.

5) Glass transition point ('l''g,).

This measurement was performed using a Toyo Rika measuring machine at a heating rate of 20°C.
Measured at /min.

Observing the physical properties in Table 1 above, the heat generation property is related to the rolling resistance of the tire tread rubber, and the lower the heat generation property, the lower the rolling resistance. Furthermore, in terms of the transfer resistance and wet skid resistance, as explained above9, it is better to have a strong temperature dependence. Therefore, in Table 1, the difference between the resilience at 60°C and the resilience at 23°C (60'C resilience - 2
3°C rebound resilience) or temperature-dependent rebound resilience (abbreviation T
DR) values are displayed.

The results showed that elastomer E-8BR (SBR-150
Sample A using elastomer V-BR (83% addition of 1,2 type) and sample C using elastomer 5iRk were compared to sample A using elastomer V-BR (83% addition of 1,2 type) and sample C using elastomer 5iRk.
ds ex fl gs h is TDR=25 or more, and the balance is considered to be sufficient, but,
The value of rebound resilience at 60°C indicates the actual degree of transfer resistance.
(5BR-1502)) When the impact resilience index is expressed as klOO, sample b (elastomer V, -BR) is 96, sample d (elastomer S-8iR, styrene 16% by weight,
'Isoprene 84 weight ratio (hereinafter abbreviated as 16784) was 96, indicating that both samples b and d had reduced and improved transfer resistance. On the other hand, sample c, (,:11
The elastomer, E-8iRX 16/84) had a rating of 98 and was inferior to S-8iR in rolling resistance. In addition, sample e with a large amount of styrene (elastomer, S-8iR, 25/
75) becomes 104, making it worse than I)E-8BR.

Similarly, as in sample g+h, 3.
S-8iR, which has a small proportion of type 4 additions, has better transfer resistance than E-8BR, but when the proportion of type 3 and 4 additions in Imprene exceeds 45%, as in sample f, the transfer resistance decreases. Inferior in smell.

From the above, it can be seen that Nidistomer SiR produced by solution polymerization has better rolling resistance than SiR produced by emulsion polymerization.
In addition, the amount of styrene is 20% by weight or less, 3,
The amount of type 4 added is preferably 45% by weight or less, and T
DR is preferably 20 or more, particularly preferably 25 or more.

In addition, the amount of styrene is 20% by weight or less, 3,
Those with a type 4 addition amount of 45% by weight or less have a glass transition point (
Tg) is -50°C or less.

Regarding surface wear resistance, it can be said that the larger the Pico wear index, the better the actual running wear. Therefore, sample b (elastomer V-B R) in Table 1 has a Pico wear index of 66. However, the compound rubber of elastomer SiR shows almost the same value as the commonly used elastomer E-8BR (SBR-1502), so it is not bad in terms of wear. It is determined that In particular, SiR with a styrene content of 20% by weight or less is good.

Further, as an index of wet braking performance, it is considered that it is better that the value of rebound resilience (023°C) near 20°C is low, that is, that the energy loss in this temperature range is large.

Samples d, e, fXgXh elastomer S-8i
For R, the rebound resilience values at 23°C are 29.5 and 25.
It has a low value of 28.28.30, indicating superior wet braking performance compared to the E-8iR.

Another indicator of wet braking performance is the porta-pull wet skid value. Regarding this as well, the S-8iR of sample dX el f) gz h is 54
．． It shows a high value of 56.56.55.54 and is superior to ES]R.

From the test results in Table 1 above, it is clear that S-
It has been found that good results can be obtained when the styrene content of 8iR is 20% by weight or less, and the 3,4-type addition in imprene is 45% or less, so next, the styrene content is 20% or less and the 3,4-type addition in isoprene is 45% or less. Table 2 shows the results of all changes in physical properties of blends of S-8iR with a type addition of 45% or less and other nidistomers using standard formulations in the same manner as in Table 1.

Table 2 (Note) S-3iR, 18% by weight of styrene, 82% by weight of imprene, 32% addition of 3.4 type in imprene, NR, natural rubber IR,... Results from Table 2 of imprene rubber. For consideration, sample J has S-8iR.
and NR (or IR) blended distomer (IR
is the same effect as NR), and its impact resilience (060°C) value is also that of sample a, general-purpose 5BR-15.
02 is also higher, TDR [60°C rebound resilience (2*) -
The value of rebound resilience (1*) at 23°C was also 20 or more, and it can be judged that there is a sufficient balance between transfer resistance and wet skid. Furthermore, the pico wear index regarding wear is considered to be on the same level as SB'R-11502.

However, when blended with NR, sample i with 25 parts by weight of S-8iR had a TDR (2*-1*)=14, and the general-purpose S
BR-1,502 sample a and approximate values are shown.
Since the value is less than 0, it is difficult to think that it is effective in terms of the balance between transfer resistance and wet skid. Therefore, S
It is considered that the blending ratio of iR is required to be 30 parts by weight or more.

Also, in the ternary Friend system of NR/5BR-150'2/S iR, 'rDR (21-1 end) = 23, 60°C rebound resilience is 60, pico wear index is 93,
The porta pull wet skid value is 56 and the TDR
The value is 20 or more, and the portaple wet skid value of wet grip property is 50 or more, which indicates a good balance between transfer resistance and wet skid, and a good wet grip property. The SBR of

Above, S-8iR alone in Table 1 and S'-8i in Table 2
As shown in the blend composition of R and other diene rubbers, the styrene content is 2 as a compound rubber compound.
S-8i R alone or 30 parts by weight or more of this S-S i R and natural rubber or diene thread synthetic rubber with a weight ratio of 0% or less and 3,4 type addition in isoprene of 45% or less By using an elastomer blended with the above, it has become possible to obtain an excellent tire composition that has excellent wet grip performance and low rollover performance of the tire tread, and has wear resistance.

Next, Table 3 shows the results of research on coupling agents used in producing S-8iRk.

Note) Samples m, n, and o of the S-8iR used were all styrene and 20% isoprene by weight.
Type 3 and 4 addition in 80 weight split isogrene
It was 30% by weight.

As camping agents, metal salts such as silicon tetrachloride (SiCA!+), tin tetrachloride (
Samples m and n using SnC14) have higher exothermic properties, lower rolling resistance, and lower rolling resistance than sample 0 using an ester coupling agent.
Excellent in both wear resistance and wet braking performance.

In particular, it shows extremely superiority in the rebound resilience value at 60''c, which is an index of transfer resistance.

Next, Table 4 shows the results of testing the S-8iRO coupling efficiency.

Table 4 Note: The microstructure of the elastomer S-8iR used is p
+ q + r are all styrene 20 weight ratio isoprene
Type 3 and 4 addition in 80 weight steamed isoprene
It was 25% by weight.

As shown in Table 4, sample p with S-8IR coupling efficiency of 30% has a rebound resilience value of 55 at 60°C, which is inferior to sample a of general-purpose 5BR-1502. Therefore, there is no advantage in terms of transfer resistance. It also has poor abrasion resistance.

Sample q+r with a coupling efficiency of 40% or more has excellent heat generation properties, low transfer properties, wear resistance, and wet braking characteristics.

From the test results listed in Tables 3 and 4, it was found that solution polymerized styrene-isoprene copolymer (S-8
In iR), it is desirable to use a metal salt as a camping agent and to increase the camping efficiency to 40% or more.

Claims (7)

[Claims] (1) As a compounding elastomer, 30 to 100 of a styrene-isoprene copolymer obtained by a solution polymerization method
1. A tire rubber composition comprising an elastomer having a composition of 0 to 70 parts by weight of one or more of natural rubber, impregnated rubber, and diene synthetic rubber. (2) Styrene isoplast obtained by solution polymerization method
2. The tire rubber composition according to claim 1, wherein the microstructure of the copolymer is such that styrene is 20% by weight or less and the proportion of 3,4-type adducts in isoprene is 45% by weight or less. (3) Styrene Imp V obtained by solution polymerization method
The tire rubber composition according to claim 1, wherein the glass transition point of the copolymer is 150°C or less. (4) Temperature-dependent rebound resilience value of tire rubber (60″
2. The tire rubber composition according to claim 1, wherein the tire rubber composition has a difference between C-repulsion resilience value and 23°C impact-resilience value of 20 or more. (5) The tire rubber composition according to claim 1, wherein the tire rubber has a wet grip value of 50 or more. (6) The tire rubber composition according to claim 1, which contains a metal salt-based coupling agent. (7) The tire rubber composition according to claim 6, which has a compacting efficiency of 40% or more.