Method for preparation of a dual phase filler for elastomers

Abstract

A method for preparation of a dual phase filler for elastomers for manufacturing technical rubber items, including such for microwave protection. The method involves the following stages: first stage—1/10 of the silicasol impregnating solution obtained by its dilution in distilled water at a 1:10 ratio is pulverized over the carbon black at constant stirring; second stage—the carbon black pulverized with the silicasol impregnating solution is let stay in air at room temperature for 24 hours; third stage: a two-step thermal activation in a drying cabinet is carried out—at first at 80° C. for 2 hours, and then at 250° C. for 2 hours; fourth stage—9/10 of the impregnating solution that remained from the first stage is pulverized successively over the already impregnated carbon black at constant stirring. It again is let stay for 24 in air at room temperature; fifth stage: a three-step thermal activation in a drying cabinet is carried out—at first at 80° C. for 2 hours, then at 150° C. for 4 hours and finally at 250° C. for 4 hours. The dual phase filler includes SiO.sub.2 in amounts 1 to 10% and carbon black 90 to 99%. It has the following parameters: specific surface area /BET/−20-50 m.sup.2/g, Iodine adsorption number—15-30 mg/g, Oil absorption number—50-90 ml/100 g, mesopore volume—0.05-0.20 cm.sup.3(STP)/g, mesopore diameter—10-20 nm. According to the invention the advantages ensured by the method are in the implementation of a multistage thermal activation at not very high temperature; in yielding improved texture of the dual phase filler obtained and in better insulation of the carbon black aggregates by the silica phase.

Claims

1. A method for preparing an elastomer reinforcing dual phase filler based on carbon black with introduced silica, wherein the carbon black is pulverized with an impregnating silicasol solution according to a thin layer chromatography technique, said method comprising: (1) pulverizing the silicasol over carbon black with constant stirring, wherein said impregnating solution is obtained by spraying carbon black with silicasol in a thin layer chromatography method with constant stirring, wherein the obtained impregnated carbon black is then diluted in distilled water at a 1:10 ratio; (2) resting the carbon black pulverized with the silicasol impregnating solution obtained in (1) in air at room temperature for 24 hours; (3) performing a two-step thermal activation in a drying cabinet, with a first step being performed at 80° C. for 2 hours, and then a second step being performed at 250° C. for 2 hours; (4) successively pulverizing impregnating solution over the already impregnated carbon black with constant stirring; (5) resting the carbon black pulverized with the silicasol impregnating solution obtained in (4) for 24 hours in air at room temperature; and (6) performing a three-step thermal activation in a drying cabinet, with a first step being performed at 80° C. for 2 hours, a second step being performed at 150° C. for 4 hours and a third step being performed at 250° C. for 4 hours.

2. The method for preparation of a dual phase filler according to claim 1, wherein an amount of silicasol needed for the carbon black impregnation is 1.0-20.0 ml/100 g carbon black.

3. The method for preparation of a dual phase filler according to claim 1, wherein said silicasol comprises SiO.sub.2 in an amount of 40% based upon the total amount of silicasol, wherein said silicasol has a pH of 9 and a density of 1.3 g/cm.sup.3.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The patent or application file contains at least one color drawing. Copies of this patent or patent application publication with color drawings will be provided by the USPTO upon request and payment of the necessary fee.

(2) FIGS. 1(a)-1(d). High-angle annular dark field images of the dual phase filler: (a) a dual phase filler obtained according to Example 1 of the invention; maps of elements distribution in it: (b) carbon; (c) silica and (d) oxygen.

(3) FIGS. 2(a)-2(d). TEM images of the dual phase filler obtained according to Example 1. of the invention at different magnifications: a/x 10 000; b, c/x 25000; d/x 250 000

(4) FIGS. 3(a)-3(c). Energy dispersive x-ray spectra of a dual phase filler prepared according to Example 1. of the invention: a) scanned areas; b) spectrum 3; c) spectrum 4.

(5) FIGS. 1(a)-1(d) present the high-angle annular dark field images of the dual phase filler. The images taken by scanning transmission electron microscopy are in FIGS. 2(a)-2(d). FIGS. 3(a)-3(c) present the x-ray spectra and the scanned areas.

(6) The results presented in FIGS. 1(a)-1(d), 2(a)-2(d), and 3(a)-3(c) prove that the silica particles are mostly distributed over the surface of carbon black aggregates isolating them from each other. In some cases silica particles have also penetrated the aggregates.

(7) The dual phase-filler obtained according to the method has the following characteristic: specific surface area (BET)—20-50 m.sup.2/g, iodine number—15-30 mg/g, oil number—50-90 ml/100 g, mesopore volume—0.05-0.20 cm.sup.3(STP)/g, mesopore diameter—10-20 nm.

(8) The dual phase filler obtained according to the invention finds application in manufacturing compositions based on natural and synthetic elastomers used in rubber processing industry for production of technical rubber items, of such for microwave protection, inclusive.

(9) As a result of the method subject to the invention the synthesized dual phase filler is of significantly improved texture characteristics whose clusters are better isolated from each other. That makes the filler applicable in manufacturing of rubber items for microwave protection.

(10) The rubber compounds comprising the dual filler subject of the utility model were prepared on a open two-roll mill (rolls Length/Diameter 320×160 mm, friction 1.27). Slow roll speed was 25 min.sup.−1.

(11) The rubber had been plasticized on the rolls for 6 min prior to introducing the ingredients.

(12) According to the invention, after the plasticization zinc oxide, stearin and one third of the dual filler were added at the 6.sup.th minute. Then the second third of the dual filler was added at the 15.sup.th and the third one—at the 20.sup.th minute. Sulfur and the accelerator were added at the end. When the rubber matrix absorbed the ingredients, the compound was cut diagonally and the strip was crossed at the opposite end of the roll. The compound was coiled and passed through a narrow nip. The ready compound was taken off the rolls in the form of a sheet at the 25.sup.th minute and let stay for 24 hours prior to its vulcanization.

(13) The vulcanization was carried out on an electrically heated hydraulic press using a special homemade mold at temperature 150° C. and under pressure of 10 Mpa at the vulcanization optimums determined for each compound on an oscillating disc vulcameter.

(14) The microwave characteristics of the elastomer based composites comprising the dual filler prepared according to Example 1. of the invention, as well as those of the substrate carbon black (given as references) are presented in Table 1.

(15) TABLE-US-00001 TABLE 1 Comparative table of the microwave characteristics of furnace carbon black and dual phase filler prepared according to Example 1 of the invention at 10 GHz Furnace Dual phase filler carbon prepared according Characteristic black to the invention 1. Absorption, dB/cm 13 15 2. Reflection coefficient 0.65 0.57 3. Shielding effectiveness, dB 7 9

(16) As seen from Table 1, the composite comprising the filler prepared according to the invention has higher microwave absorption values and lower reflection coefficient values than the substrate carbon black. The microwave shielding effectiveness of the filler is also slightly higher than that of the substrate carbon black.