Compositions: coating or plastic – Materials or ingredients – Pigment – filler – or aggregate compositions – e.g. – stone,...
Reexamination Certificate
1999-02-16
2001-09-11
Green, Anthony (Department: 1755)
Compositions: coating or plastic
Materials or ingredients
Pigment, filler, or aggregate compositions, e.g., stone,...
C106S490000, C524S155000
Reexamination Certificate
active
06287376
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to hydrophobic, oxidic or siliceous fillers and the use of these fillers to produce rubber mixtures and vulcanisates. The rubber mixtures and vulcanisates which contain the hydrophobic, oxidic or siliceous fillers are particularly suitable for producing highly reinforced, abrasion-resistant moulded items, in particular for producing tyres which have a low rolling resistance and high resistance to abrasion.
BACKGROUND OF THE INVENTION
The treatment of surfaces of fillers to improve filler/matrix bonding in thermoplastic and thermoset composites and in filled rubber systems is known. Thus in U.S. Pat. Nos. 4,514,231 and 4,704,414 the treatment of siliceous fillers with polysulfidic silylethers, in particular bis-(triethoxysilyl-propyl) tetrasulfide, is described. According to DE 2 141 159 and 2 255 577, the surface modification of untreated fillers can be performed in situ by adding polysulfidic silylether to a mixture of the corresponding rubbers and untreated filler. The disadvantage of using polysulfidic silylethers to improve the filler/matrix bonding is the costly method of preparation of the polysulfidic silylethers and the associated high cost of raw materials. U.S. Pat. Nos. 2,736,669 and 2,801,185 describe processes for rendering silica hydrophobic in which silicas are treated with alcohols. The silicas treated in this way, however, do not exhibit an improved reinforcing effect in a rubber matrix.
EP 0 631 982 describes a special method for preparing silica aggregates and their use for reinforcing elastomers. As is also specified in EP 0 631 982, the silica aggregates which are obtained may be provided with additional functional groups in a subsequent reaction. A number of chemical compounds with functional groups is used for treating the silica aggregates obtained in order to introduce a variety of functional groups. The silicon-free compounds for treating silica aggregates, listed in particular in column 8 of the European patent application mentioned above, do not produce sufficient improvement in the reinforcing fillers with regard to the physical properties of the rubber mixtures prepared therefrom, in particular when they are intended for the preparation of highly reinforced, abrasion-resistant moulded items.
SUMMARY OF THE INVENTION
The object of the present invention is to provide activated, hydrophobic, oxidic or siliceous fillers from readily accessible raw materials which produce a substantial improvement in filled rubber mixtures in particular with regard to the low abrasion and low rolling resistance, high wet skid resistance and low mixing viscosity which are important when producing tyres.
DETAILED DESCRIPTION OF THE INVENTION
The present invention therefore provides new oxidic and/or siliceous fillers, obtainable by treating an oxidic and/or siliceous filler with 0.1 to 50 parts by weight, per 100 parts by weight of filler, of an adduct of sulfur and unsaturated primary and/or secondary alcohols with 3 to 60 carbon atoms at temperatures of 20 to 250° C., wherein the adduct has been obtained by reacting 1 to 10 moles of sulfur and/or the corresponding amount of sulfur-providing compound per mole of double bonds in the alcohols.
The oxidic or siliceous fillers according to the invention are preferably subjected to a treatment with the adducts of sulfur and unsaturated primary and/or secondary alcohols mentioned above have preferably a concentration of physically-bonded water of ≦4 wt. %, preferably ≦3 wt. %, in particular ≦1 wt %, with respect to the total amount of filler.
The adducts of sulfur and unsaturated alcohols used to prepare the oxidic or siliceous fillers according to the invention have a concentration of bonded sulfur of 10 to 65 wt. %, in particular 15 to 40 wt %.
The hydrophobic oxidic or siliceous fillers in the present invention have a methanol wettability of 1 to 55, preferably 5 to 40. The methanol wettability is determined as follows according to the invention: 200 mg of silica and 50 ml of water are placed in a 250 ml round-bottomed flask with a magnetic stirrer. The hydrophobic silica remains on the surface of the water. Then the tip of a graduated pipetted filled with methanol is immersed into the liquid phase (in order to avoid direct contact with the silica) and the methanol is allowed to flow out slowly. The mixture is stirred with the magnetic stirrer so that a vortex is produced in the liquid. Methanol is added until the solid substance becomes wetted. This is the case when the silica is no longer distributed over the surface of the liquid phase (now containing methanol) and the clear film-free liquid is visible. The result for methanol wettability, expressed as wt. % of methanol in the methanol/water mixture, is calculated from the formula:
Methanol wettability (in wt. %)=(0.79×number of ml MeOH/0.79×number of ml MeOH+50)×100
As mentioned above, the oxidic or siliceous fillers to be rendered hydrophobic possess a certain water content. This water content can be adjusted by drying the oxidic and/or siliceous filler at elevated temperature, generally 80 to 250° C., optionally under vacuum, until the desired water content is achieved, prior to making it hydrophobic. Obviously it is also possible to treat the oxidic or siliceous filler with the sulfur adduct at the temperatures mentioned above, wherein the physically bonded water is also removed from the oxidic or siliceous filler. The oxidic and/or siliceous filler to be rendered hydrophobic is preferably dried until the desired water content is achieved prior to treatment with the sulfur adduct.
The content of physically bonded water in this connection is understood to be the loss on drying the oxidic or siliceous filler used at 105° C. for 2 hours in accordance with DIN ISO 787/2 (previously DIN 53 198).
The hydrophobic, oxidic or siliceous fillers are preferably obtained by treating with 5 to 25 parts by weight, per 100 parts by weight of filler, of a sulfur adduct mentioned above. Treatment of the fillers used according to the invention with the sulfur adducts may be performed at temperatures from above room temperature to below the decomposition temperature of the particular sulfur adduct used. Treatment of the oxidic or siliceous filler, optionally adjusted to a specific water content, with the sulfur adducts may be regarded as complete when the theoretical amount of sulfur adduct can no longer be extracted using a suitable solvent and the wettability with water of the treated filler has become substantially poorer. Treatment may also be terminated, however, before complete reaction as soon as the water-repellence of the filler is within the desired range.
As mentioned above, the hydrophobic, oxidic or siliceous fillers according to the invention have a specific methanol wettability, wherein the methanol wettability gives the wt. % of methanol in a methanol/water mixture which is capable of just wetting the treated filler. Determination of the methanol wettability has been described above.
Treatment of the oxidic or siliceous filler used with the sulfur adduct can be performed in the presence of a suitable solvent and/or diluent and in the presence of suitable catalysts. The most appropriate amount of solvent and/or diluent and the most appropriate amount of catalyst to be used in a particular case can be determined in appropriate preliminary trials.
The following may be used as solvent and/or diluent: aliphatic or aromatic hydrocarbons, e.g. cyclohexane, xylene, mineral oil.
The sulfur adducts used for treatment may be obtained in a known manner by reacting sulfur and/or sulfur-providing compounds, such as dialkyl polysulfides, such as e.g. dioctyl polysulfides, diamino polysulfides or dichloro polysulfides, with unsaturated primary or secondary alcohols with 3 to 60 carbon atoms, preferably 6 to 36 carbon atoms.
One to 6 moles of sulfur or sulfur-providing compounds per mole of double bond in the alcohol are preferably used during preparation of the sulfur adducts. When using sulfur
Konigshofen Heinrich
Scholl Thomas
Weidenhaupt Hermann-Josef
Wendling Peter
Bayer Aktiengesellschaft
Cheung Noland J.
Gil Joseph C.
Green Anthony
LandOfFree
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