JP3210700B2 - Tire with tread - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention is made from a mixture of at least three rubbers containing 3,4-polyisoprene rubber, cis-1,4-polyisoprene rubber and at least one additional diene rubber. Pneumatic tire having a tread embossed.

[0002]

2. Description of the Prior Art Pneumatic tires for passenger cars and trucks are made up of several components, including treads, usually made of rubber compositions. It is often desirable to formulate the tread rubber to provide a tire that exhibits relatively low rolling resistance with good wear and shrinkage.

[0003] While it is desirable that the composition of the tire tread be formulated to reduce the rolling resistance of the tire without causing a substantial reduction in the shrinkage characteristics of the tire, the shrinkage of the tire is determined by wet slip resistance and dryness. It is expected that some sacrifice will be made as indicated by reduced slip resistance.

Various rubber compositions have been prepared for various purposes, including tire treads. Tire treads are often composed of synthetic rubber or a mixture of synthetic and natural rubbers to achieve the desired properties of the tire tread, for example, reduced wear, shrinkage and rolling resistance. In the manufacture of tires having such treads, styrene / butadiene copolymers (copolymers made by emulsion or solution polymerization), often designated as SBR, high cis-1,4-polybutadiene rubber and Various synthetic rubbers have been used, including high- and medium-vinyl- (1,2) -polybutadiene rubbers.
Synthesized cis-1,4-polyisoprene is sometimes at least a portion can be replaced with natural rubber in the composition of the tire tread.

[0005] Until now, vinyl isoprene rubber (3,4-polyisoprene rubber) can be used as a compound with other rubbers, for example, in a tread of a tire. It is useful for use in industrial products.

Representative examples of various patents and patent application publications include Japanese Patent Publication Nos. 58-196245 and 59-96143.
Nos. 59-210958, 62-104847 and Heisei 1-1
58056, Japanese Patent Publication Showa 63-4578, German Patents 3,707,434, 3,720,461 and 3,835,79
2, and U.S. Patent Nos. 4,383,085 and 4,756,353
And No. 4,946,887.

For tire tread applications, the viscoelastic properties of the rubber or rubber compound are important. For example, the so-called tan
The δ characteristic is the ratio of the viscous contribution to the elastic contribution for a viscoelastic rubber subject to dynamic deformation. Such properties are typically represented in the form of a curve plotting tan δ value versus temperature.

[0008] For tires with low rolling resistance, about 50
Tread rubber with optimized tan δ value for temperatures in the range of -60 ° C to 60 ° C is desirable, and for tires exhibiting good wet slip resistance, tan δ value is optimized for the temperature range from about -20 ° C to about + 10 ° C It is desirable to do.
It is difficult to adjust the rubber compound to achieve an optimization of the tanδ value simultaneously for both of these temperature ranges, and thus substantially simultaneously for rolling resistance and wet slip resistance, and often the middle must be employed. Must.

Here, the optimization of the tan δ value means that the tire tread exhibits a high wet slip resistance of about -20 ° C to + 10 ° C.
The value of the tan δ of the rubber or rubber compound has a maximum value in the range of ° C. and means that this tan δ value has a minimum value in the region of about 60 ° C. so that the tire tread exhibits low rolling resistance.

[0010]

While various rubber compositions are known to provide various advantages, for example, for tire treads, high rolling resistance and / or tread wear with good shrinkage are provided. There is still a desire to provide rubber tires having a rubber tread with good properties.

[0011]

According to the present invention, a rubber 1 is provided.
Per 100 parts by weight (phr), (A) 10 to 25 parts by weight of 3,4
-Polyisoprene rubber and (B) 40 to 55 parts by weight
Cis-1,4-polyisoprene rubber and (C) 20 or
50 parts by weight of styrene / butadiene prepared by solution polymerization
Ethylene copolymer rubber or rubber made by solution polymerization
Tylene / butadiene copolymer rubber and cis-1,4-polybutene
It is composed of Tadiene rubber.
Polyisoprene rubber is -15 ° C
Glass transition temperature Tg in the range of -20 ° C, 70 to 90
Mooney (ML1 + 4) values in the range of 40 to 70 mole % 3,4-isoprene, 30 to 50 mole % 1,4-ci
s and trans ipsolene and 2 to 10 mole % of 1,
Having a polymer structure containing 2-isoprene,
The polyisoprene rubber is substantially incompatible with the remaining rubber components of the compound, which indicates that the compound has a tan δ versus temperature curve showing a peak of tan δ in the temperature range of -60 ° C to -30 ° C, The second tanδ in the range of -20 ° C to + 10 ° C
Shows a peak and this tan δ vs. temperature curve is -20 ° C
Also has a maximum value in the range of + 10 ° C. from have a minimum value between 60 ° C. from + 50 ° C., the 3,4-polyisoprene rubber,
The presence of butyllithium catalyst in a continuous reaction system for isoprene
Hexane (organic solvent) and tetramethylethylene
Polymerize in diamine (polar modifier)
Isopropanolamine, rosin acid or methanol
Stop at -15 ° C with one or more terminators.
It is designed to obtain a glass transition temperature Tg in the range of -20 ° C.
A tire having a tread constituted by a vulcanized rubber composition characterized by being manufactured .

[0012]

In the present text, Tg is the glass transition temperature of the target rubber, which is appropriately determined by a differential scanning calorimeter at a heating rate of 1 ° C. for 1 minute.

Thus, the rubber of the tread is at least 3
It is required to be a rubber compound of a kind.

The cis-1,4-polyisoprene rubber (B) is preferably a natural rubber.

[0016]

In a prudent embodiment, the tread is 1
For parts by weight of rubber, i) as defined above
(A) 3,4-polyisoprene rubber, (B) cis-1,4-polyisoprene rubber, and (C) styrene / butadiene copolymer rubber (a copolymer produced by a solution polymerization method. (Hereinafter sometimes referred to as S-SBR)) or ii) (A) 3,4-polyisoprene rubber, (B) cis-1,4-polyisoprene rubber and (C ) soluble
Styrene / butadiene copolymer prepared by liquid polymerization method
And cis-1,4-polybutadiene rubber .

Certain properties, especially Tg and Mooney
(ML1 + 4) The use of a specific 3,4-polyisoprene rubber having a limit on viscosity, and the use of certain other selected 3,4-polyisoprene as a minor component in the tire tread composition. It is an important feature of the present invention that it is used with rubber and that the 3,4-polyisoprene rubber described above is relatively incompatible with the other rubber components in the tread composition.

The Mooney (ML4 + 1) of the above 3,4-polyisoprene in combination with the required Tg range
It is considered important that the value be in the range of about 70 to 90, preferably about 75 to 85.

It is generally desirable for the processability of 3,4-polyisoprene rubber to have a low Mooney (ML1 + 4) value, which is a measure of the viscosity of the rubber and a relative measure of its molecular weight.

However, the rubber compound exhibits low hysteresis and the rolling resistance of a tire having a tread of such a rubber compound is low, and the abrasion resistance of the rubber compound in the compounded and vulcanized state is low. 60% of the rubber compound to determine good
In order to achieve the desired low values of tan δ in the region of ° C, a high molecular weight 3,4-polyisoprene polymer is required and is therefore used in the present invention.
Those having relatively high Mooney (ML1 + 4) values as specified for 3,4-polyisoprene rubber are required.

Thus, for the purposes of the present invention, a relatively narrow range of Tg values as well as Mooney (ML1 + 4)
It is specified by the combination of 4-, 1,2- and 1,4-rubber contents, in which the total of 3,4-units and 1,2 units is specified relatively narrowly as 56 to 63%. That is also included.

The ML (1 + 4) value is a measure or value well known to those skilled in the art, and is a value typically determined by a Mooney disk viscometer.

The 3,4-polyisoprene rubber for the present invention has the above-mentioned properties in order to form a tire tread which enables the tire to have good wear resistance and low rolling resistance. It is to be understood that It is therefore required that this rubber has a relatively high molecular weight or Mooney (ML1 + 4) value while maintaining good processability. Good processability of the rubber is a desirable property as long as the good rolling resistance of the tire and the wear resistance of the tread described above are not significantly impaired.

Preferably, the 3,4-polyisoprene is relatively incompatible in the rubber formulation of the tread due to having the Tg properties defined above. Incompatible herein means that the 3,4-polyisoprene is blended with the rubber components (B) and (C) as shown by the viscoelastic response of the cured compound to dynamic deformation. In addition to the peak tan δ values for these diene rubbers (B) and (C) as they appear, the 3,4-polyisoprene rubber is uniquely secondary.
Or an additional tan δ value of a ridge or an upward curve thereof.

In order that the invention may be better understood, reference will now be made to the accompanying drawings.

FIG. 1 shows the Tg at -11 ° C., -18 ° C. and -25 ° C.
Shows the viscoelastic properties of a 3,4-polyisoprene rubber having a microstructure as indicated by and is compounded with cis-polyisoprene rubber (natural rubber). This is -80 ° C to + 20 ° C for the above three vulcanized rubber compounds.
The relationship between tan δ and temperature at a temperature in the range of is shown in comparison with a control product, a vulcanized natural rubber / styrene-butadiene rubber composition (NR / SBR CONTROL).

FIG. 2 is a table of tan δ values measured at 60 ° C. for each of the vulcanized rubber compounds shown in FIG.

FIG. 3 shows the relationship between the vulcanizate of rubber blended with 3,4-polyisoprene having a Tg of -18 ° C., natural rubber and S-SBR [indicated by X (3,4 PI)]. 60 ° C to +
5 shows a curve of tan δ over a temperature range of 60 ° C.
[indicated by Y (Control)] in comparison with tan δ.

The curves in FIG. 1 are for three vulcanized rubber blends of 3,4-polyisoprene rubber and natural rubber,
-Polyisoprene Tg of -18 ℃, -11 ℃ and -25 ℃
In the table below, the 3,4-isoprene rubber containing the vulcanized compound is abbreviated as 3,4-PI, and the experimental compound (A), the experimental compound (B) and the experimental compound (C), respectively. ). Each formulation was a vulcanized rubber formulation consisting of 25 parts by weight of 3,4-polyisoprene and 75 parts by weight of natural rubber.

Rubber Compounds Compound Tg of 3,4-polyisoprene 1 Experimental compound (A) -18 ° C 2 Experimental compound (B) -11 ° C 3 Experimental compound (C) -25 ° C

Taken together with the data listed in the accompanying FIG. 2 table, the curves in FIG. 1 show the curves for the binary rubber compound.
Tan indicating a maximum in the range of -20 ° C to + 10 ° C combined with a minimum in the region of 60 ° C (shown in Figure 2)
The δ curve is shown to be achieved with 3,4-polyisoprene having a Tg of -18 ° C, and thus has a Tg of about -18 ° C.
4- shows that polyisoprene is the preferred rubber for the purposes of the tertiary and quaternary rubber compounds of the present invention.

That is, only Formulation (A) is optimized for both the region of 60 ° C. and the region of -20 ° C. to + 10 ° C.
3,4- with an T curve of about -18 ° C.
It has been shown that it is desirable to use polyisoprene.

Each of -11 ° C., -18 ° C. and -25 ° C.
Each 3,4-polyisoprene rubber with Tg and cis-1,4-
Three rubber pneumatic tires having treads comprising a blend of vulcanized corners in a 25/75 ratio with polyisoprene rubber (natural rubber) were prepared and tested for wet shrinkage or slip resistance (20%).
mph) and rolling resistance. The results are shown in the table below in comparison with a control tire having a tread consisting of a vulcanized rubber blend of 50/50 natural rubber and S-SBR.

[0035]

[Table 1] Notes: 1) An increase in the standardized value indicates a decrease in rolling resistance, which is considered to be an improvement. 2) For treads containing 3,4-polyisoprene having a Tg of -11 ° C and -25 ° C, no tread abrasion data were obtained.

The values indicating the various properties for the control tire were standardized as standard values of 100, and each property of the experimental tire was compared to that of the control tire.

Binary rubber formulations using 3,4-polyisoprene having a Tg of -18 ° C. have shown increased properties as shown in the table above, however, there are several ways to use them as tire treads. Inadequate tread wear was also observed in tire tests with treads comprising such binary rubber compounds.

Thus, a ternary rubber compound was prepared and vulcanized. The result is shown in FIG. 3, and as can be seen,
Similar and desirable tan δ curves with reasonable maximum and minimum values were obtained with 3,4-polyisoprene having a Tg of -18 ° C. In a subsequent tire test performed using such a ternary compounded rubber for the tread,
The resulting tire exhibited adequate tread wear resistance.

Referring to FIG. 3 in more detail,
3,4-polyisoprene rubber with Tg of -18 ℃ and cis-
The tan δ versus temperature curve is shown for a vulcanized ternary compound, an experimental compound X and a vulcanized control, rubber compound Y, consisting of 1,4-polyisoprene natural rubber and S-SBR rubber. I have. Formulation X is a cis-1,4-polyisoprene natural rubber and a styrene / butadiene rubber made by a solution polymerization process and a -18 ° C T
v. vulcanized compound with a polyisoprene rubber having a g. Control, Formulation Y, was a vulcanized rubber compound of cis-1,4-polyisoprene natural rubber and a styrene / butadiene copolymer rubber made by solution polymerization.

FIG. 3 shows that the vulcanized rubber composition of the above ternary compound has a maximum value and a maximum value in the range of -20 ° C. to + 10 ° C.
T has a minimum value in the range of 50 ° C to about 60 ° C
It shows that it shows an anδ curve. Also this curve is about-
It also shows a peak tan δ value in the range of 60 ° C. to about -30 ° C. and a second ridge of tan δ in the range of about -20 ° C. to + 10 ° C., which indicates that the 3,4-polyisoprene has It is substantially incompatible with the rest of the material. The change of this curve from a smooth curve to a curve containing an upward curve in the range of -20 ° C. to + 10 ° C. indicates that it is relatively incompatible as described above.

For some applications, the tire tread has a quaternary rubber compound to more fully optimize the tread's wear resistance, including rolling resistance, shrinkage and winter tire performance. It has been found practical to use a pneumatic tire.

Although the contribution of the various components or elements in the composition is not always fully understood, one of the key components of the formulation is that certain components having a Tg of about -18 ° C. 4-polyisoprene which, when compounded with the remaining rubber components (B) and (C), is particularly useful as a ternary vulcanized rubber compound and a quaternary vulcanized rubber compound for tire treads In this case, it is considered to have a Mooney viscosity limit characteristic that clearly gives unique viscoelastic characteristics.

Each sample of the vulcanized rubber compound for FIG.
Rheometrics Viscometer obtained from trics Company
Tested with System IV dynamic viscoelasticity tester,
The relationship between the value of tan δ and the temperature over a temperature range from -80 ° C to + 25 ° C was determined. During this test, each sample is kept in tension (0.5% strain) and is subjected to a cyclic deformation at a frequency of 1 Hz. The viscoelastic tester described above measures the response of the sample to applied deformation and from this calculates the value of tan δ at each desired temperature.

Each sample of the various vulcanized rubber compounds for FIG. 2 was also tested on a Rheovibron dynamic viscoelasticity tester provided by Imass, Inc. to determine their tan δ at 60 ° C. The value was determined.

Each sample of the cured rubber compound for FIG.
The test was performed with an Autovibron automatic dynamic viscoelasticity tester provided by Imass, Inc.
g for a given rubber compound containing 3,4-polyisoprene rubber having a temperature of from -60 ° C to + 60 ° C
The relationship between the values of anδ was examined. 0.1% tension (strain) and 11 H
The cycle of z was adopted.

The purpose of these tests is to determine the viscoelastic response of a vulcanized rubber sample to an applied deformation under tension at a particular stress, period and temperature or temperature range. This viscoelastic response is stored during cyclic deformation and is used by the device to determine the stored modulus E ', a measure of energy recovered, and the loss modulus E ", a measure of energy dissipated as heat. E" / E 'is the tan for a certain temperature
δ.

Thus, in practice, the value of tan δ is a measure of the viscoelastic properties of a formulation and is a value measured to correlate with the performance of the tire's tread. Rubber
The tan δ vs. temperature characteristic is well known to those skilled in the art.

As already pointed out, in practice for pneumatic rubber tires a high tan in the range of -20 ° C to + 10 ° C is necessary to give the tire good wet shrinkability.
A value of δ is desirable for the tread of the tire, while 50 ° C or less is required to give the tire good rolling resistance.
It has been found that low values of tan δ in the range of 60 ° C. are desirable for tire treads.

When taken together with the data given in the table of FIG. 2, the curve of the experimental tread rubber (A) of FIG. 1 shows a high value of tan δ in the range from -20 ° C. to + 10 ° C., and is therefore good for tires. And a low value of tan δ in the region of 60 ° C is suitable for giving the tire good rolling resistance for this rubber compound. Has been prophesied.

The significance of this phenomenon is that the rubber compound of the present invention allows the relative optimization of the tan δ characteristics at a given temperature,
On the other hand, it also means to maintain or even optimize the rolling and wet slip resistance properties of the tire.

Conversely, when taken together with FIG. 2, the Tg at -11 ° C.
The curve for rubber (B) in FIG. 1 which shows properties for 3,4-polyisoprene having a higher value of tan δ in the range of -20 ° C. to + 10 ° C., is therefore better than (A). A tread with good shrinkage at 60 ° C
The value of tan δ higher than that of the curve (A) in the region (1) makes it possible to estimate a higher tire rolling resistance for this rubber compound as compared to the curve (A).

Similarly, when taken together with FIG.
The curve (C) in FIG. 1 for a 3,4-polyisoprene having a Tg of 10 ° C. shows low tan δ values in the region of 60 ° C., but low tan δ values in the range of -20 ° C. to + 10 ° C. The object is to estimate low wet tread shrinkage as well as low tire rolling resistance.

The advantages of both such optimizations are many times greater, especially including rolling and slip resistance.

In the description of the present invention, the cis-1,4-polyisoprene rubber includes both natural rubber and synthetic rubber, but as mentioned above, natural rubber is preferred. The cis-1,4-polyisoprene rubber, whether natural or synthetic, typically contains about 96 to 99% by weight of cis-1,4-polyisoprene.
4- Has content.

The polybutadiene rubber, when made with a Ziegler-type catalyst, has about 95% or more of cis-1,4
-Can be of structural and at least about 90% when made using an alkyl lithium catalyst
It can be composed of the above cis- and trans-1,4-structures. Such various polybutadiene rubbers are well known.

The terms butadiene and polybutadiene as used herein are 1,3-butadiene and 1,3 butadiene, respectively.
-Means a polymer derived from butadiene.

The copolymer rubber of styrene and butadiene (S-SBR) produced by the solution polymerization method is produced by copolymerizing styrene and butadiene in an organic solvent in the presence of a suitable catalyst. be able to. The copolymer typically has a substantially narrower average molecular weight distribution than the styrene and butadiene copolymer rubber (E-SBR) made by emulsion polymerization, and more typically the tire molecular weight distribution. When used as a rubber component of a tread, it improves or improves the wear resistance and rolling resistance of the tread of the tire.

Styrene / butadiene copolymer rubber made by emulsion polymerization is made by an emulsion polymerization process and is often referred to herein as E-SBR.

Both S-SBR and E-SBR are well-known rubbers, and their differences in molecular weight distribution are also well-known.

As one of the embodiments of the invention, such embodiments need not of course be limited to these applications only, but in particular tires used under normal loads and speeds, such as, for example, passenger tires. An example of a tire used in such a case is a pneumatic tire with such a tread, where the tread is (A) about 10 to 100 parts by weight of rubber.
25 phr of the above 3,4-polyisoprene and (B) about 40
To 55 phr of the above natural rubber, and (C) about 20 to 50 phr of a styrene / butadiene copolymer rubber prepared by a solution polymerization method, or prepared by a solution polymerization method.
A vulcanized rubber composition comprising a styrene / butadiene copolymer rubber and a cis-1,4-polybutadiene rubber.

Another exemplary embodiment can be a tire having a tread consisting of each of the rubber compound embodiments illustrated above.

[0062] Such pneumatic tires typically have an outer peripheral tread suitable for grounding, spaced beads, and radially extending from the bead, with the tread along with the sidewall connecting the bead. It consists of a generally toroidal carcass with a circumferential tread.

Required for the rubber composition of the present invention
3,4-polyisoprene rubber is continuous reaction scheme isoprene
Polar modifier is polymerized in the, triisopropanolamine polymerization as in example butyl organic solvent and, for example, tetramethylethylenediamine as the original, for example, hexane the presence of an organic lithium catalyst, such as lithium (TMEDA) Termination with rosin acid, methanol or other suitable terminating agent to make the desired Tg .

The amount of organolithium catalyst will vary greatly depending on the desired molecular weight of the resulting polymer.

As already described with reference to the accompanying drawings, several kinds of 3,4-polyisoprene rubber polymers having various polymer arrangements (Tg and the like) have been synthesized, and various kinds of polymers have been prepared in order to realize the present invention. Compounded with other rubbers. Therefore, the 3,4-polyisoprene rubber must have a Tg in the range of -15 ° C to -20 ° C to impart microstructure to the tire tread due to wet shrinkage, ternary compound rubber or quaternary rubber of the tread. Mooney (ML1 + 4) values in the range of 70 to 90, preferably 75 to 85, to contribute to low heat generation and therefore to low rolling resistance for compounded rubber, in the compound 3,4-isoprene content in the range of 50 to 60% to give microstructure due to polymer incompatibility with other rubbers and thus improve the wet shrinkability of the tire tread A 1,2-isoprene content of 2 to 10% to help provide a microstructure to obtain wet shrinkage of the tire tread; Rubber (B) and ( ) 56 not to help give an incompatibility factor to 63% of 3,4 and 1,2 iso
It was thought to have a total content of prenes .

The specified 3,4-polyisoprene rubber is used in small amounts (up to 25 phr) in rubber compositions for treads. The first contribution is to increase the shrinkage of the tread, especially wet shrinkage. In order to increase the rolling resistance of the tire tread and reduce the tear resistance, it is considered that a larger amount of rubber is desirable,
Or found.

The other rubbers are used as main parts of the tread rubber. This is because natural rubber contributes to reducing rolling resistance and tread wear, and the third and fourth rubber components of ternary and quaternary formulations generally have wet shrinkage and tread properties. This is because it contributes to wear resistance.

The rubber components used here, in particular the rubbers of the high viscosity range of Mooney (ML1 + 4), may optionally be separated individually to facilitate processing before or during mixing with various rubber compounding materials. Although it is possible to carry out the oil addition, it is preferable not to use the oil addition in carrying out the method of the present invention. When adding oil to promote processing,
The rubber processing oil of aromatic or aromatic / naphthenic oil or paraffin / naphthenic oil is usually about 10 to
Used in an amount of 50 phr.

As will be readily appreciated by those skilled in the art, the rubber or other material in that portion of the tread of a pneumatic tire, as well as its base carcass, which typically includes reinforcing agents in the tread area, is a rubber compounding technique. For example, various vulcanizable component rubbers may be compounded in various ways, for example, curing aids such as sulfur, activators, retarders and accelerators, for example, various oils, Resins including adhesive resins, processing additives such as silica, plasticizers, fillers, pigments, stearic acid, zinc oxide, waxes, antioxidants and antiozonants, deflocculants and carbon blacks. It can be compounded by mixing with a commonly used additive such as a reinforcing material.
Vulcanizable and vulcanized substances (rubber components)
Depending on the intended use of the compound, the various additives mentioned above are selected and generally used in conventional amounts, as is well known to those skilled in the art.

Typical amounts of carbon black added are about 20 to 100 parts by weight of diene rubber (phr), preferably
0 to 60 phr. Typical amounts when using tackifiers are about 0.5 to 10 phr. Typical amounts of processing aids are 1 to 5 phr. Typical amounts when using silica are from about 5 to 25 phr, and amounts when using silica couplers are from about 0.05 to 0.5 per silica.
Parts by weight. A typical silica is, for example, a hydrated amorphous silica. Representative coupling agents include, for example, DeGussa
Such as silica grafted with bis- (3-triethoxy-silylpropyl) tetrasulfide, bis- (3-trimethoxy-silylpropyl) tetrasulfide and bis- (3-trimethoxy-silylpropyl) tetrasulfide from AG. It can be a bifunctional sulfur-containing organosilane compound. Typical amounts of antioxidants are about 1 to 5 phr. Representative antioxidants include, for example, "Vander
BiltRubber Handbook "(1978), pages 344-346, and the like. Suitable antiozonants and waxes, especially microcrystalline waxes, are described in" Vanderbilt Rubbe ".
r Handbook "(1978), pages 346-347. Typical amounts of antiozonants are about 1 to 5 phr. Typical amounts of stearic acid are about 1 to 3 phr. The typical amount of zinc oxide is 2 to 5 phr, the typical amount of waxes is 1 to 5 phr, the typical amount of deflocculant is 0.1 to 1 phr. The amount is not one of the features of the invention, the essence of the invention being the use of a specific rubber compound in the tire tread as a vulcanizable composition.

The vulcanization is performed in the presence of a sulfur vulcanizing agent. Suitable sulfur vulcanizing agents include elemental sulfur (free sulfur)
Or a sulfur releasing vulcanizing agent such as, for example, an amine disulfide, a polymerizable polysulfide or an olefin adduct of sulfur. Elemental sulfur is preferably used as the sulfur vulcanizing agent. As is well known to those skilled in the art, the sulfur vulcanizing agent is in an amount of about 0.5 to 8 phr, preferably
Used in amounts ranging from 1.5 to 2.25.

Accelerators are used to control the time and / or temperature required for vulcanization and to improve the properties of the vulcanized rubber. In one embodiment, a single accelerator system, the primary accelerator, can be used. Usually about 0.5
The primary accelerator is used in amounts ranging from to 2.0 phr. In another embodiment, a combination of two or more accelerators generally used in higher amounts (0.5 to 1.0 phr), and generally lower amounts (0.05 to 0.50 phr).
Activated with the co-accelerator used at phr) and improve the properties of the vulcanized rubber. Combinations of such accelerators are known to have a synergistic effect on the final properties of the vulcanized rubber, and often the properties obtained by using only one of the accelerators alone. Slightly better than In addition, delayed action accelerators can be used which, while having little effect at normal processing temperatures, provide satisfactory cure at normal vulcanization temperatures. Representative examples of accelerators are amines, disulfides, guanidines,
Thioureas, thiazoles, thiurams, sulfenamides, dithiocarbamates, and xanthates. Preferably, the primary accelerator is sulfenamide. If a co-promoter is used, it is preferably a guanidine, dithiocarbamate or thiuram compound.

A tire can be made by assembling, molding, molding, and curing by various methods, which will be obvious to those skilled in the art.

In the practice of the present invention, the tread of the polymer blend can be integrated and adhered to various tire carcass base rubber compositions. Typically such rubber compositions are styrene / butadiene copolymer rubbers , ci
It consists of s-1,4-polyisoprene rubber (natural or synthetic rubber) and 3,4-isoprene rubber. In some cases, for certain portions of the tread, especially where the tread is in the region of the tire sidewall, such a compound may be a butyl rubber, for example a halobutyl rubber such as chlorobutyl rubber or bromobutyl rubber and ethylene /
It may include one or more of propylene / conjugated diene terpolymer rubber, polyisoprene and polybutadiene rubber.

In another implementation of the present invention, the tread is typically assembled such that the green, uncured tread is assembled on a carcass during assembly of the green tire, and subsequently the green tire is molded and cured. Can be applied.

Alternatively, a new tread can be applied on a cured tire carcass with the old tread removed and the tread cured as a re-tread.

As already mentioned, one of the important contributions of a particular 3,4-isoprene rubber to the tread component of a tire can be attributed to the increased wet slip resistance of the ternary or quaternary rubber for the tread. These formulations show a minimal increase in rolling resistance based on the relatively high molecular weight as indicated by the relatively high Mooney (ML1 + 4) values. The contribution of natural rubber to the tread component of the tire is attributable to low rolling resistance and tread wear values and improved tear resistance. The contribution of the additional diene rubber can be attributed in part to shrinkage, tread wear resistance and / or tire rolling resistance.

[0078]

EXAMPLES The present invention will be further described below with reference to some examples, which are for illustrative purposes only and do not limit the scope of the present invention. Unless otherwise stated, all parts and percentages are by weight.

Example 1 Conventional construction (grooved treads, sidewalls, spaced beads and supporting fiber reinforced carcass)
Was assembled, molded, and cured in a conventional tire mold. The tread was assembled on a pre-extruded uncured carcass. Those tires are P
195 / 75R14, which indicates that they are belt-wound and radially stacked passenger car tires.

Here, one tire is referred to as a control product X and the other tire is referred to as an experimental Y. Control tire X
50 phr of butadiene / styrene rubber (A) and 50 phr
Of natural rubber (B), and is intended to represent a tread of a normal passenger car tire.

The experimental tire Y is a 3,4-polyisoprene rubber as defined in the present invention, which has a Tg of about -18 ° C. and a 3,4- isoprene content of about 55% (A)
And natural rubber (B) and styrene / butadiene copolymer
And a tread composed of the material rubber (C).

Thus, the 3,4-polyisoprene rubber used essentially replaces at least a portion of the butadiene / styrene in the tread rubber compound.

The tires X and Y were mounted on wheel rims and inflated for testing. The tire with the experimental tread was tested with each test value for the control standardized as 100 for comparison and the test results were compared to the standardized value of 100 compared to the control tire value. They are listed as relative values.

The tires using the experimental tread rubber composition Y exhibited low rolling resistance and high sliding resistance, which provided similar tread wear resistance as compared to the control tire X. These results, in the absence of the above experiments reported here, are significantly different from the commonly thought results.

The tread compositions for each of tires X and Y consisted of the materials listed in Table 1 below:

[0086]

[Table 2] Note: 1) Volume values are rounded up and down. 2) the polymer is composed of about 55% 3,4-units, about 5% 1,2-units, and about 40% 1,4-units;
The polyisoprene is described in this specification, in particular of the type shown in the experimental rubber A of Table 2 therein. It had a Tg of -18 ° C and a Mooney viscosity (ML1 + 4) of about 80 at 100 ° C.

The rubber compound is used in the usual amount of an antioxidant,
It contained antiozonants, stearic acid, deflocculants, waxes, silica and coupling agents, sulfur, accelerators and zinc oxide, but these were not considered to be a feature of the present invention, This is because the present invention is essentially directed to the rubber compound itself.

Table 2 below shows various characteristic values of the rubber compounds of the control tire X and the experimental tire Y.

[0089]

[Table 3]

Table 3 shows the rolling resistance, wet slip resistance and tread wear resistance of the experimental tire Y in which the value of the control tire X was set to 100 and compared with that.

[0091]

[Table 4] Note: 1) A decrease in rolling resistance is represented by an increase in relative value, and is considered to be an improvement. 2) An increase in the wear resistance of the tread is considered to be an improvement.

The rolling resistance is such that the tire is inflated by mounting it on a metal wheel rim and its rated load is approximately 80%.
6% at a speed equivalent to a vehicle speed of 50 mph
It was rotated with a 7 inch diameter dynamometer and its drag was measured. This test method is considered a fairly good standard method.

Slip resistance was a standard test in which the tires were mounted on a towed, towed trailer, the trailer was moved at various speeds, and the brakes were applied to measure the slip force (peak and slide values).

The amount of wear of the tread is approximately 200
It was evaluated as a measure of tread thickness reduction after the 00 km test.

The tread wear value was determined by actually mounting both the control tire and the experimental tire on the vehicle and operating it under controlled conditions (inflation pressure 38 psig), with each tire attached to the vehicle The position was maintained while being rotated by the vehicle for comparison.

In this example, the 3,4-polyisoprene was synthesized as described above using hexane as the solvent.

Although some typical embodiments and detailed descriptions have been given to explain the present invention, those skilled in the art can make various changes and modifications without departing from the technical scope of the present invention. Obviously you can.

[Brief description of the drawings]

FIG. 1 is a graph of tan δ versus temperature when three types of polyisoprene rubber are blended with natural rubber. The control is natural rubber / styrene butadiene rubber.

FIG. 2 is a table of values of tan δ at 60 ° C. for various vulcanized compounded rubbers.

FIG. 3 shows a tan δ versus temperature curve for a sulfur vulcanized rubber composition of the present invention in comparison to that of a conventional sulfur vulcanized binary rubber composition.

──────────────────────────────────────────────────続 き Continuation of front page (73) Patent holder 590002976 1144 East Market Street, Akron, Ohio 44316-0001, U.S.A. S. A. (72) Inventor Gregory Martin Holtzupple United States 44240 Ohio Kent Sandy Lake Road 800 (72) Inventor Raymond Robert Dirossy United States 44313 Ohio Akron Kingsley Avenue 1630 (72) Inventor Paul Harry Sandstrom United States 44278 Ohio Tallmidge Milton Drive 96 (72) J. Inventor. Dale Massy. Second United States 44236 Hudson-Nicholson, Ohio 5781 (56) References JP-A-4-227943 (JP, A) JP-A-61-18504 (JP, A) (58) Fields studied (Int. Cl. ⁷ , DB) Name) C08L 9/00 C08L 21/00 B60C 1/00

Claims (1)

(57) [Claims] (1) Per 100 parts by weight of rubber (phr), (A) 10
Or 25 parts by weight of 3,4-polyisoprene rubber,
(B) 40 to 55 parts by weight of cis-1,4-polyisoprene
And (C) 20 to 50 parts by weight of solution polymerization method
The prepared styrene / butadiene copolymer rubber,
Is a styrene / butadiene copolymer prepared by solution polymerization
Compound rubber and cis-1,4-polybutadiene rubber , wherein the 3,4-polyisoprene rubber has a glass transition temperature Tg in the range of -15 ° C to -20 ° C in an uncured state.
And a Mooney (ML1 + 4) value in the range 70-90,
40 to 70 mol % of 3,4-isoprene, 30 to
Having a polymer structure comprising 50 mole % of 1,4-cis and trans ipsolene and 2 to 10 mole % of 1,2-isoprene, wherein said 3,4-polyisoprene rubber is composed of Substantially incompatible, which means that the t
anδ vs. temperature curve is tan in the temperature range from -60 ℃ to -30 ℃
δ peak, a second tan δ peak in the range of −20 ° C. to + 10 ° C., and this tan δ vs. temperature curve also has a maximum value in the range of −20 ° C. to + 10 ° C., and + 50 ° C.
Have a minimum value between the 60 ° C., the 3,4-polyisoprene rubber, continuous anti-isoprene
Hexane in the presence of a butyllithium catalyst
(Organic solvent) and tetramethylethylenediamine (polarity modification)
Agent) and polymerize in triisopropanol
One or more of amine, rosin acid or methanol
In the range of -15 ℃ to -20 ℃
A tire having a tread composed of a vulcanized rubber composition, which is produced so as to obtain a glass transition temperature Tg .