Resilient tires and wheels – Tires – resilient – Pneumatic tire or inner tube
Reexamination Certificate
2001-07-10
2003-07-29
Mullis, Jeffrey C. (Department: 1711)
Resilient tires and wheels
Tires, resilient
Pneumatic tire or inner tube
C152S525000, C152S541000, C525S088000, C525S09200D, C525S093000, C525S094000, C525S095000, C525S098000, C525S099000
Reexamination Certificate
active
06598637
ABSTRACT:
BACKGROUND OF THE INVENTION
U.S. Pat. No. 6,031,053 discloses a thermoplastic elastomer that is a block styrene butadiene copolymer. The block copolymer has at least one block A having polymerized units of a styrene and forming a rigid phase and at least one elastomeric block B/A having polymerized units of both styrene and butadiene and forming a flexible phase. In U.S. Pat. No. 5,880,156, these thermoplastic elastomers are disclosed as being dispersed as particles in a continuous phase of polystyrene or a styrene copolymer containing up to 50 percent of comonomers to form an expandable styrene polymer for elastic polystyrene forms. These expandable styrene polymers are prepared by polymerization of styrene in the presence of the block copolymers and impregnation with a blowing agent.
SUMMARY OF THE INVENTION
The present invention relates to a pneumatic tire having a rubber component containing a block styrene butadiene copolymer.
DETAILED DESCRIPTION OF THE INVENTION
There is disclosed a pneumatic tire having a rubber component comprising a sulfur cured rubber composition composed of, based on 100 parts by weight of rubber (phr):
(a) 99 to 50 parts by weight of a first rubber containing olefinic unsaturation; and
(b) 1 to 50 parts by weight of a second rubber which is different from said first rubber and which is an elastomeric block copolymer of
(1) from 15 to 65 percent by weight, based on the total block copolymer, of butadiene, and
(2) from 35 to 85 percent by weight, based on the total block copolymer, of styrene, which block copolymer has:
(a) at least two blocks A which have polymerized units of styrene, a glass transition temperature Tg above 25° C. and forms a rigid phase, and
(b) at least one elastomeric block which is composed of about 25 to 70 percent by weight of butadiene and 75 to 30 percent by weight of styrene, and which has polymerized B/A units of styrene and butadiene in a random structure; a glass transition temperature Tg from −50° C. to 25° C., and is located between two blocks A and forms a flexible phase, and the amount of the rigid phase accounts for 5 to 40 percent by volume.
The present invention relates to a pneumatic tire containing an elastomeric block copolymer comprising at least one block A which has polymerized units of a styrene and forms a rigid phase and at least one elastomeric block B/A which has polymerized units of styrene and of butadiene and forms a flexible phase, the glass transition temperature Tg of the block A being above 25° C. and the phase volume ratio of black A to block B/A being chosen so that the amount of the rigid phase in the total block copolymer is from 5 to 40 percent by volume and the amount of the diene in the total block copolymer is less than 50 percent by weight. These elastomeric block copolymers and their preparation are disclosed in U.S. Pat. No. 6,031,053 which is incorporated herein in its entirety.
The block copolymer may be of, for example, one of the general formula 1 to 11:
(A − B/A)n;
(1)
(A − B/A)n − A;
(2)
B/A(A − B/A)n;
(3)
X − [(A − B/A)n]m + 1;
(4)
X − [(B/A − A)n]m + 1;
(5)
X − [(A − B/A)n − A]m + 1;
(6)
X − [(B/A − A)n − B/A]m + 1;
(7)
Y − [(A − B/A)n]m + 1
(8)
Y − [(B/A − A)n]m + 1
(9)
Y − [(A − B/A)n − A]m + 1
(10)
Y − [(B/A − A)n − B/A]m + 1
(11)
where A is the styrene block and B/A is the flexible phase, i.e. the block composed of random butadiene and styrene units, X is a radical of an n-functional initiator, Y is the radical of a m-functional coupling agent and m and n are natural numbers from 1 to 10.
A preferred block copolymer is one of the general formula A-B/A—A, X-[-B/A—A]2 or Y-[-B/A—A]2 (the meanings of the abbreviations are as above) and a particularly preferred block copolymer is one whose flexible phase is divided into blocks
(B/A)
1
− (B/A)
2
(12)
(B/A)
1
− (B/A)
2
− (B/A)
1
(13)
(B/A)
1
− (B/A)
2
− (B/A)
3
(14)
whose styrene/butadiene ratio differs in the individual blocks B/A or changes continuously within a block within the limits (B/A)
1
→(B/A)
2
, the glass transition temperature Tg of each sub-block being below 25° C.
A block copolymer which has a plurality of blocks B/A and/or A having different molecular weights per molecule is likewise preferred.
The B/A block is composed of about 75 to 30 percent by weight of styrene and 25 to 70 percent by weight of butadiene. A flexible block particularly preferably has a butadiene content of from 35 to 70 percent and a styrene content of from 65 to 30 percent.
In the case of the monomer combination styrene/butadiene, the amount of the diene in the total block copolymer is 15 to 65 percent by weight and that of the vinylaromatic component is correspondingly 85 to 35 percent by weight. Butadiene/styrene block copolymer having a monomer composition comprising 25 to 60 percent by weight of diene and 75 to 40 percent by weight of vinylaromatic compound are particularly preferred.
The block copolymer may be prepared by anionic polymerization in a nonpolar solvent with the addition of a polar cosolvent. The cosolvent acts as a Lewis base toward the metal cation. Preferably used solvents are aliphatic hydrocarbons, such as cyclohexane or methylcyclohexane. Polar aprotic compounds, such as ethers and tertiary amines, are preferred as Lewis bases. Examples of particularly effective ethers and tetrahydrofuran and aliphatic polyethers, such as diethylene glycol dimethyl ether. Examples of tertiary amines are tributylamine and pyridine. The polar cosolvent is added to the nonpolar solvent in a small amount, for examples 0.5 to 5 percent by volume. Tetrahydrofuran in an amount of 0.1 to 0.3 percent by volume is particularly preferred. Experience has shown that an amount of about 0.2 percent by volume is sufficient in most cases.
The copolymerization parameters and the amount of 1,2- and 1,4-bonds of the diene units are determined by the metering and structure of the Lewis base. The novel polymers contain, for example, 15 to 50 percent of 1,2-bonds and 85 to 60 percent of 1,4-bonds, based on all diene units.
The anionic polymerization is initiated by means of organometallic compounds. Compounds of the alkali metals, particularly lithium, are preferred. Examples of initiators are methyllithium, ethyllithium, propyllithium, n-butyllithium, sec-butyllithium and tert-butyllithium. The organometallic compound is added as a solution in a chemically inert hydrocarbon. The amount metered depends on the desired molecular weight of the polymer but is as a rule from 0.002 to 5 mol percent, based on the monomers.
The polymerization temperature may be from 0 to 130° C., preferably from 30 to 100° C.
The amount of volume of the flexible phase in the solid is of decisive importance for the mechanical properties. According to the invention, the amount by volume of the flexible phase composed of butadiene and styrene sequences is 60 to 95, preferably 70 to 90, particularly preferably 80 to 90 percent by volume.
It should be pointed out that there is no strict correlation between the above mentioned ratios of styrene and butadiene, the above mentioned limits of the phase volumes and the composition which arises from the novel ranges of the glass transition temperature, since the relevant numbers in each case are numerical values rounded up to the nearest tens unit. Any correlation is likely to be merely accidental.
The volume fraction of the two phases can be measured by means of high-contrast electron microscopy or solid-state NMR spectroscopy. The amount of styrene blocks can be determined by precipitation and weight following osmium degradation of the polybutadiene content. The future phase ratio of a polymer can also be calculated from the amounts of monomers used if polymerization is taken to completion every time.
In addition, it
Jozef Klinkenberg Maurice Peter Catharina
Lechtenböhmer Annette
DeLong John D.
Hendricks Bruce J.
Mullis Jeffrey C.
The Goodyear Tire & Rubber Company
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