Organic compounds -- part of the class 532-570 series – Organic compounds – Heavy metal containing
Reexamination Certificate
2000-10-20
2002-04-30
Shaver, Paul F. (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heavy metal containing
C556S012000, C524S502000, C524S515000, C526S335000, C526S338000, C526S339000, C526S340000
Reexamination Certificate
active
06380411
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application is based on German Application DE 199 50 608.6, filed Oct. 21, 1999, which disclosure is incorporated herein by reference.
FIELD OF THE INVENTION
The present invention provides an organosilicon compound, a process for its preparation and its use.
BACKGROUND OF THE INVENTION
It is known that sulfur-containing organosilicon compounds such as 3-mercaptopropyltrimethoxysilane, 3-mercapto-propyltriethoxysilane, 3-thiocyanatopropyltriethoxysilane or bis-(3-[triethoxysilyl]-propyl)tetrasulfane are used as silane bonding agents or reinforcing additives in oxidically filled rubber mixtures. The rubber mixtures are used, inter alia, for industrial rubber items and for parts of rubber tires, in particular for treads (DE 2 141 159, DE 2 212 239, U.S. Pat. Nos. 3,978,103, 4,048,206).
It is also known that the alkoxysilyl function, generally a trimethoxysilyl or triethoxysilyl group, reacts with silanol groups on the fillers, generally silica, during mixing-preparation and thus the silane becomes fixed onto the surface of the filler. Production of the filler/rubber bond then takes place during the vulcanization process, via the sulfur groupings on the fixed silane. Accordingly, the resulting properties of this type of vulcanizate, for a given constant amount of silane, depends critically on how high the coupling yield of the silane is and what network structure is produced. Furthermore, it is known that silanes with polysulfane functions such as, for example, bis-(3-[triethoxysilyl]-propyl)tetrasulfane, tend to participate in disadvantageous premature cross-linking during the mixing process, at appropriately high temperatures. Therefore, it is important that a maximum batch temperature of about 155° C. is not exceeded when using these silanes.
SUMMARY OF THE INVENTION
The object of the present invention is to provide organosilicon compounds which have higher coupling yields, improved rubber properties and higher process reliability than the silanes known hitherto, when used as a bonding agent or reinforcing additive in rubber mixtures.
The invention provides an organosilicon compound of the general formula I
R
1
R
2
R
3
Si—R
4
—S—Zn—S—R
4
—SiR
1
R
2
R
3
(I)
wherein
R
1
, R
2
, R
3
, independently, represent H, a halogen, a straight-chain or branched alkyl group or a straight-chain or branched alkoxy group and
R
4
represents a straight-chain or branched alkylidene group.
The straight-chain alkyl groups may be methyl, ethyl, n-propyl, n-butyl-, n-pentyl- or n-hexyl groups. The branched alkyl groups may be iso-propyl, iso-butyl or tert-butyl groups. The halogen may be fluorine, chlorine, bromine or iodine. The alkoxy groups may be methoxy, ethoxy, propoxy, butoxy, isopropoxy, isobutoxy or pentoxy groups.
In the organosilicon compound in accordance with formula I, R
1
, R
2
, R
3
preferably represent ethoxy and R
4
preferably represents CH
2
CH
2
CH
2
or isobutylidene.
The invention also provides a process for preparing the organosilicon compound of the general formula (I), characterised in that a mercaptan compound of the general formula (II)
R
1
R
2
R
3
Si—R
4
—S—H (II)
wherein
R
1
, R
2
, R
3
, independently, represent H, a halogen, a straight-chain or branched alkyl group or a straight-chain or branched alkoxy group and
R
4
represents a straight-chain or branched alkylidene group,
is reacted with a zinc alcoholate. The reaction may be performed in alcoholic solution. The reaction may be performed at a temperature range of 20° to 200° C., preferably 50° to 80° C.
Zinc ethanolate may be used as the zinc alcoholate. Ethanol may be used to prepare the alcoholic solution. The zinc alcoholate may be prepared by reacting zinc chloride with sodium ethanolate in alcoholic solution. The zinc alcoholate may be reacted with double the molar amount of the mercaptan compound of formula (II) in alcoholic solution.
3-Mercaptopropyltriethoxysilane may be used as a mercaptan compound. In one embodiment, a compound of formula (II) with R
1
, R
2
, R
3
=ethoxy and R
4
=CH
2
CH
2
CH
2
, may be reacted with zinc ethanolate in ethanolic solution.
The organosilicon compound according to the invention is highly reactive and may be used in rubber mixtures.
Rubber mixtures which contain the organosilicon compound according to the invention as a bonding agent or as a reinforcing additive and the molded items which are produced after a vulcanization step, in particular pneumatic tires or tire treads, have a low rolling resistance with, simultaneously, good wet adhesion and high resistance to abrasion.
The invention also provides rubber mixtures, characterised in that they contain rubber, fillers, preferably precipitated silica, at least one organosilicon compound of formula (I) and optionally other rubber auxiliary substances.
The organosilicon compound of the formula (I) may be used in amounts of 0.1 to 15 wt. %, preferably 5-10 wt. %, with respect to the amount of filler used.
Natural rubber and/or synthetic rubber may be used as the rubber. Preferred synthetic rubbers are described, for example, in W. Hofmann, Kautschuktechnologie, Genter Verlag, Stuttgart 1980. The rubbers may be used individually or in combination. Anionic polymerized S-SBR rubbers with a glass transition temperature above −50° C. and its mixtures with high-cis diene rubbers are used in particular for preparing motor vehicle tires.
The following may be used as fillers:
carbon blacks, which are prepared by the lamp black, furnace black or channel black process and have a BET surface area of 20 to 200 m
2
/g,
highly disperse silicas prepared, for example, by precipitation from silicate solutions or by flame hydrolysis from silicon halides, with specific surface areas of 5 to 1000 m
2
/g, preferably 20 to 400 m
2
/g (BET surface area) and with primary particle sizes of 10 to 400 nm, optionally also as mixed oxides with metal oxides such as Al, Mg, Ca, Ba, Zn and titanium oxides,
synthetic silicates such as aluminum silicate, alkaline earth silicates such as, for example, magnesium silicate or calcium silicate, with BET surface areas of 20 to 400 m
2
/g and primary particle diameters of 10 to 400 nm,
natural silicates such as kaolin and other naturally occurring silicas,
glass fibers and glass fiber products (mats, ropes) or glass microbeads.
The rubber mixtures may contain synthetic rubber and silica as a filler. Highly disperse silicas, prepared by precipitation from silicate solutions, with BET surface areas of 20 to 400 m
2
/g are preferably used, in amounts of 10 to 150 parts by weight, with respect to 100 parts by weight of rubber.
The fillers mentioned may be used individually or as a mixture.
In a particularly preferred embodiment of the rubber mixture, 10 to 150 parts by weight of a pale filler, optionally together with 0 to 100 parts by weight of carbon black, with respect to 100 parts by weight of rubber, and 0.1 to 15 parts by weight, preferably 5 to 10 parts by weight of a compound of formula (I), with respect to 100 parts by weight of the filler used, may be used to prepare the mixtures.
The organosilicon compounds according to the invention may be used either in the pure form or attached to an inert organic or inorganic support. Preferred support materials may be silica, natural or synthetic silicates, aluminum oxide or carbon black. The organosilicon compound according to the invention may be used on its own or combined with other organosilicon compounds, in particular monofunctional alkylalkoxysilanes.
Rubber auxiliary products which may be used are reaction accelerators, reaction delayers, antioxidants, stabilizers, processing aids, plasticizers, waxes, metal oxides and activators such as triethanolamine, polyethylene glycol or hexanetriol which are well-known in the rubber industry.
The rubber auxiliary substances may be used in conventional amounts which are governed, inter alia, by the ultimate application. Conventional amounts may be 0.1 to 50 wt. %, with respect to rubber. The organosilicon compounds may b
Batz-Sohn Christoph
Luginsland Hans-Detlef
Münzenberg Jörg
Zezulka Gerd Rainhard
Degussa-Huls AG
Pillsbury & Winthrop LLP
Shaver Paul F.
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