United States Patent (19) (11) 4,161,455 Wason 45) Jul
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United States Patent (19) (11) 4,161,455 Wason 45) Jul. 17, 1979 (54) NOVEL PRECIPITATED SILICEOUS 57 ABSTRACT PRODUCTS AND METHODS FORTHER A method for producing a precipitated silicon dioxide USE AND PRODUCTION having a new combination of physical and chemical Satish K. Wason, Havre de Grace, properties is disclosed. The pigments are produced by 75 Inventor: acidulating a solution of an alkali metal silicate with an Md. acid under controlled precipitation conditions. The 73) Assignee: J. M. Huber Corporation, Locust, aqueous reaction medium comprising the precipitated N.J. silica is then post-conditioned by introducing a second silicate solution into the reaction vessel and thereafter 21) Appl. No.: 911,003 adding additional acid to react with the said second 22 Filed: May 30, 1978 silicate solution. By varying the amount of the silicate employed in the post-conditioning step, a product is Related U.S. Application Data obtained which has a unique combination of physical and chemical properties including reduced wet cake 60) Continuation of Ser. No. 796,913, is a division of Ser. moisture content, high surface areas and oil absorptions, No. 557,707, Mar. 12, 1975, abandoned. improved surface activity, friability, wetting character (51) Int. Cl’............................................... C11D 3/08 istics, and the like. The product has particular utility for (52) U.S. C. ............................... 252/174.25; 252/135; use as a rubber reinforcing agent because of its in 252/140; 106/288 B; 423/339 creased surface activity and oil absorption, etc. The (58) Field of Search ......................... 252/89, 135, 140; product, however, may be used in paints, paper, deter 423/339; 106/288B gents, dentifrice compositions, molecular sieves, and polymeric compositions. An unexpected discovery of 56) References Cited the invention involves the production of a rubber rein U.S. PATENT DOCUMENTS forcing silica which has a decreased wet cake moisture content. In one particularly advantageous embodiment, 3,868,336 2/1975 Mazzola et al. ................. 252/.40X an adduct material, such as aluminum, is added to con Primary Examiner-Mayer Weinblatt trol the refractive index and surface area of the product. Attorney, Agent, or Firm-Ernest A. Schaal; Robert L. Price; Harold H. Flanders 1 Claim, 16 Drawing Figures U.S. Patent Jul. 17, 1979 Sheet 1 of 16 4,161,455 N | | | | | | | | | | | | | |N| | | | | | | | |P|| | | ||NF||| | | Yi ||III || |||| | | | | | | | | N | | | | | | | | | | | | | | | N | | | | | | | | | | NT || N || || || || || ||N| 390 2O 3. 8O % SILICATE POST-TREATMENT FIGURE U.S. Patent Jul. 17, 1979 Sheet 3 of 16 4,161,455 3 5O 3OO 2.95 C. StLICATE POST-TREATMENT FIGURE 3 U.S. Patent Jul. 17, 1979 Sheet 4 of 16 4,161,455 | | | | | | | | V||V | | | ||| | ||| | ||| | ||| | ||| f | V / PINITIATIN | | | | | | V | / SILICATE POST-TREATMENT FIGURE 4 U.S. Patent Jul 17, 1979 Sheet 5 of 16 4,161,455 I | | | | | / | | | | | | | 4-H O o O 2O 3O 4O 5O 6O 7O 8O % SILICATE POST-TREATMENT FIGURE 5 U.S. Patent Jul. 17, 1979 Sheet 8 of 16 4,161,455 O?|3...2-2| |OT(t)=1--| |LLLLLLLL(FFELTTTTTTTILLFIT-TFITTI |&|LITTLINJ) ILLITTLE(FR), ||TTTTTTTNTTTTTTTTTT)||Ns?|| 2 nº O © O % SILICATE POST-TREATMENT EEEEEEEEN-EEHHHHHHHHHH–He FIGURE 8 U.S. Patent Jul 17, 1979 Sheet 9 of 16 4,161,455 12||\,|||Œ|| …O |_|_|-|[LLLLLLLLLLAZILLLLLL OOOO ||| % SLICATE POST-TREATMENT EEEHHHHHHHEZHHHHHHHHHH– FIGURE 9 U.S. Patent Jul. 17, 1979 Sheet 10 of 16 4,161,455 % SILICATE POST-TREATMENT FIGURE O U.S. Patent Jul. 17, 1979 Sheet 11 of 16 4,161,455 | | | | | | | | | | | | | | | | | | |N| | | | | ||| | ||| | |7 ||N| |N| ||| | 82O825 ---------4------------------------ O O 2O 3O 4O 5O 6O 7O 8O % SILICATE POST-TREATMENT FIGURE 11 U.S. Patent Jul 17, 1979 Sheet 12 of 16 4,161,455 i. U.S. Patent Jul 17, 1979 Sheet 13 of 16 4,161,455 ::::::::::::: 3:33 U.S. Patent Jul. 17, 1979 Sheet 14 of 16 4,161,455 U.S. Patent Jul. 17, 1979 Sheet 15 of 16 4,161,455 U.S. Patent Jul. 17, 1979 Sheet 16 of 16 4,161,455 FIG.6 4,161,455 1 2 patent discloses a process wherein an aqueous alkali NOVEL PRECIPITATED SILICEOUS PRODUCTs metal silicate solution and acid are simultaneously AND METHODS FORTHEIR USE AND added to a reaction vessel. In the Nauroth et al patent, : :"PRODUCTION it is pointed out that this simultaneous addition is contin ued until the viscosity of the pool rises through a maxi This is a continuation of application Ser. No. 796,913, mum and then falls to a substantially lower value. The filed May 16, 1977, now abandoned; which is a division amount of the acidification agent and the alkali metal of application Ser. No. 557,707, filed Mar. 12, 1975, now silicate are proportioned so as to maintain the pH of the abandoned; which is related to application Ser. No. resulting slurry substantially constant throughout the 286,655, filed Sept. 6, 1972, which issued as U.S. Pat. 10 major portion of the reaction and in the range of about No. 3,893,840. 10 to 12. The process is generally conducted at a tem perature of 80 to 90° C. and the end product, after BACKGROUND OF THE INVENTION drying, results in a silica which may have a surface area 1. Field of the Invention of 260 square meters per gram. The patentees point out The present invention relates to novel synthetic pre 15 that the product is satisfactory as a reinforcing agent for cipitated silicas and to a process for producing a syn rubber. thetic precipitated silicon dioxide having a new and In U.S. Pat. No. 3,445,189 issued May 20, 1969 to improved combination of properties and characteristics. Maat et al, there is described a process for producing More particularly, the invention relates to the produc finely divided silicic acid by simultaneously adding tion of precipitated high structure silicas produced by 20 solutions of an alkalisilicate and a strong mineral acid to reacting aqueous alkali metal silicate solutions with an water at a temperature between 70° C. and 90' C. while acidification agent. The novel products are high struc maintaining the reaction pH between 7 and 9. The pat ture finely divided silicas having certain unique proper entees point out that the product obtained by the afore ties particularly with respect to structure index, oil mentioned process is a finely divided non-gelatinous absorption, void volume, surface activity, friability, 25 silicic acid which is useful as a filler for natural and wetting characteristics, and further properties. The synthetic rubber and other elastomers. It is also dis novel products are especially suitable for use as rein closed in this patent that for a silica to be useful as a forcing agents in rubber, in paints, paper, detergents, filler for natural and synthetic rubber and other elasto molecular sieves, and in polymeric compositions. mers, its surface area and oil absorption are of vital 2. Description of the Prior Art 30 importance. This patent further discloses that extensive As known in the art, finely divided silica or silicon investigations have further indicated that if a finely dioxide particulates can be prepared by the acidulation divided silicic acid is to have good reinforcing proper of an aqueous silicate solution with an acid, such as ties for rubber, it must have a surface area of 100 to 250 sulfuric acid. Such products are commercially available m/g and an oil absorption of more than 2 cc/g or 200 and are characterized by, and have, the following prop 35 cc/100g. See column 2, lines 18 through 22. erties: high structure, high wet cake moisture content, In U.S. Pat. No. 3,730,749, which issued May 1, 1973 high oil absorption, low valley abrasion, high surface to James E. Morgan, there is disclosed a process for area, and low pack density. Because of properties such preparing silica for use in reinforcing compositions. It is as high oil absorption, the pigments have been success pointed out in Morgan that the viscosity increase which fully used as reinforcing pigments in rubber. However, occurs during the acidification or neutralization of the high wet cake moisture content is disadvantageous aqueous alkali metal silicate is substantially minimized in that the drying and filtration rates are decreased. by adding a controlled amount of an alkali metal sili Further, the aforementioned properties of said known cate. In Examples I, II, and III of this patent, it is also and commercially available silicas render them unsuit noted that the silica filter cakes had solid contents of able for many uses. 45 18.5; 24.9; and 25.1 percent, respectively. This means In this regard and generally speaking for the moment, that the percent wet cake moisture of the silicas dis known processes including those described in the litera closed in Examples I, II, and III is one hundred minus ture as well as those techniques employed in the indus the percent solid content in the filter cake. In other try produce products suitable for use as reinforcing words, the percent wet cake moisture (% WCM) of fillers. Thus, in U.S. Pat. No. 2,940,830 which issued 50 silicas mentioned in Examples I, II, and III is 81.5; 75.1; June 14, 1960 to F. S. Thornhill, there is described a and 74.9, respectively. The surface area, the average process for preparing finely divided silicas which are ultimate particle sizes, and rubber data of silicas pro suitable as reinforcing agents in rubber compositions. duced by the teachings of Examples II and III are listed Thornhill more specifically describes a process of pre in Table 3 which also sets forth that rubber composi paring a silica material which is characterized by having 55 tions incorporating the silicas of Examples II and III an average ultimate particle size of 0.015 to 0.04 micron have desirable rubber properties.