Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1999-11-05
2002-04-02
Michl, Paul R. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
active
06365668
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to rubber compounds which contain fillers and which contain solution rubbers which contain carboxyl groups, to the production of the above-mentioned rubber compounds; and to the use thereof for the production of vulcanized rubber materials which are particularly suitable for the production of highly reinforced rubber moldings, most preferably for the production of tires which exhibit particularly high wet slip resistance and abrasion-resistance.
SUMMARY OF THE INVENTION
Anionically polymerized solution rubbers which contain double bonds, such as solution polybutadiene and solution styrene/butadiene rubbers, have advantages compared with corresponding emulsion rubbers for the production of tire treads which exhibit low rolling resistance. These advantages comprise, amongst others, the feasibility of controlling the vinyl content and the glass transition temperature which is associated therewith, and of controlling the extent of molecular branching. This results in particular advantages in practical use which are related to the wet grip and rolling resistance of the tire. Thus, U.S. Pat. No. 5,227,425 describes the production of tire treads from a solution of SBR rubber and hydrated silica. Numerous methods of modifying the terminal groups have been developed in order to achieve a further improvement in properties. Examples of methods such as these include those described in EP-A 334 042, which employs modification with dimethylaminopropylacrylamide, or that described in EP-A 447,066, which employs modification with silyl ethers. However, the proportion by weight of terminal groups is small due to the high molecular weight of rubbers, and is, therefore, only capable of exerting a slight influence on the interaction between the filler and the rubber molecule. One object of the present invention, amongst others, was to produce solution rubbers comprising a significantly higher content of groups which are effective for interaction with the filler.
A process for the production of solution polybutadiene rubbers which contain carboxyl groups (3.9 to 8.9% by weight) is described, amongst other features, in DE-OS 2,653,144. However, due to their strength, which is too low, and due to their acceptable stress values, which are likewise too low, these rubbers are not suitable as the major component in tire treads.
SUMMARY OF THE INVENTION
The object of the present invention was, therefore, to provide rubber compounds comprising solution rubbers containing carboxyl groups, from which tires can be produced which exhibit improved wet grip and a lower rolling resistance, as well as a high mechanical strength and improved abrasion properties.
DETAILED DESCRIPTION OF THE INVENTION
The present invention, therefore, relates to rubber compounds which consist of at least one rubber and of 10 to 500 parts by weight, preferably 20 to 200 parts by weight, of a filler with respect to 100 parts by weight rubber, wherein the rubber has been produced by the polymerization of aromatic vinyl monomers with diolefins in solution and by the introduction of carboxyl groups, said rubber has a content of 0.1 to 3% by weight of bound carboxyl groups or salts thereof, a content of aromatic vinyl monomers incorporated by polymerization of 5 to 40% by weight, and a content of diolefins of 60 to 95% by weight, wherein the content of 1,2-bonded diolefins (vinyl content) is 5 to 60% by weight, with respect to the solution rubber used in each case.
Rubber compounds according to the present invention, which are preferred, are those in which the rubber constituent has a content of bound carboxyl groups or salts thereof of 0.2 to 2.5% by weight, a content of aromatic vinyl monomers incorporated by polymerization of 5 to 30% by weight, and a content of diolefins of 70 to 95% by weight, wherein the content of 1,2-bonded diolefins (vinyl content) falls within the range from 5 to 55% by weight.
Examples of aromatic vinyl monomers which can be used for polymerization include styrene, o-, m- and p-methylstyrene, p-tert.-butylstyrene, &agr;-methylstyrene, vinylnaphthalene, divinylbenzene, trivinylbenzene and/or divinylnaphthalene. Styrene is most preferably used.
Examples of diolefins which can be used according to the invention for polymerization include 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethylbutadiene, 1-phenyl-1,3-butadiene and/or 1,3-hexadiene. 1,3-butadiene and isoprene are most preferably used.
The rubbers which can be used according to the invention in the rubber compounds and which. are based on aromatic vinyl monomers and diolefins with a content of 0.1 to 3% by weight of bound carboxyl groups, have average molecular weights (number average) of 50,000 to 2,000,000, preferably 100,000 to 1,000,000, and glass transition temperatures of −50° C. to +20° C., preferably −40° C. to 0C., and have Mooney viscosities ML 1+4 (100° C.) of 10 to 200, preferably 30 to 150.
In addition to carboxyl groups the rubbers of the invention may contain other functional groups like hydroxyl-, carboxylic ester-, carboxamide- or sulfonic acid groups.
Production of the rubbers which are used according to the invention is effected by anionic solution polymerization, i.e., by means of a catalyst based on an alkali metal, e.g., n-butyllithium, in an inert hydrocarbon as the solvent. The known randomizing agents and control agents for the microstructure of the polymer can be used in addition. Anionic solution polymerization methods of this type are known and are described, for example, by I. Franta in Elastomers and Rubber Compounding Materials; Elsevier 1989, pages 73-74, 92-94, and in Houben-Weyl, Methoden der Organische Chemie, Thieme Verlag, Stuttgart, 1987, Volume E 20, pages 114-134.
The carboxyl groups can be introduced into the rubber either by adding chemical compounds which supply carboxyl groups, for example, CO
2
, to the metal-containing solution, or by treating the finished rubber in a subsequent reaction with chemical compounds which contain carboxyl groups, for example with mercaptans which contain carboxyl groups.
The carboxyl group content can be determined by known methods, e.g. titration of the free carboxylic acid, spectroscopy or elemental analysis and others.
The carboxyl groups are preferably introduced into the rubber after the completion of the solution polymerization of the monomers used, by the reaction of the polymers obtained, optionally in the presence of radical initiators, with carboxylmercaptans of formula
HS-R′-COOX,
wherein
R′represents a linear, branched or cyclic C
1
-C
36
alkylene group which may optionally be substituted with up to 3 further carboxyl groups or which can be interrupted by nitrogen, oxygen or sulfur atoms, and
X represents hydrogen or represents a metal or an, optionally substituted with Cl-C36-alkyl-, cycloalkyl- or arylgroups, ammonium ion.
The preferred carboxylmercaptans are thioglycolic acid, 2-mercaptopropionic acid (thiolactic acid), 3-mercaptopropionic acid, 4-mercaptobutyric acid, mercaptoundecanoic acid, mercaptooctadecanoic acid, 2-mercaptosuccinic acid and alkali, alkaline earth or ammonium salts thereof. 2-and 3-mercaptopropionic acid, mercaptobutyric acid and 2-mercaptosuccinic acid, or the lithium, sodium, potassium, magnesium, calcium or ammonium salts thereof, are more preferably used. 3-mercaptopropionic acid or the lithium, sodium, potassium, magnesium, calcium or ammonium, ethylammonium, diethylammonium-, triethylammonium-, octadecylammonium-, and cyclohexylammonium-salts thereof are most preferably used.
In general, the reaction of the carboxylmercaptans with the solution rubbers is conducted in a solvent, for example, in hydrocarbons such as pentane, hexane, cyclohexane, benzene and/or toluene, at temperatures from 40 to 150° C., in the presence of radical initiators, e.g., peroxides, especially acylperoxides, such as dilauroyl peroxide and dibenzoylperoxide and ketalperoxides as di-tert.-butyltrimethylcyclohexaneperoxide, azo initiators such as azo-bis-isobutyronitrile, or be
Scholl Thomas
Trimbach Jürgen
Cheung Noland J.
Gil Joseph C.
Michl Paul R.
LandOfFree
Rubber compounds containing solution rubbers which contain... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Rubber compounds containing solution rubbers which contain..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Rubber compounds containing solution rubbers which contain... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2913345