DE2150346A1 - Process for the production of silica granules - Google Patents

Description

DR. BERG DIPL.-ING. STAPF

PATENT LAWYERS 21503A6

a MUNICH 8O. MAUERKIRCHERSTR. 45

Dr. Berg Dipl.-Ing. Stapf, 8 Munich 80, MauerkircherstraBe 45

Your reference Your letter Our reference Date Oi 0 Kti Mf \

Attorney Dossierβ 21 594
Be / deer

AKZO N.V., Arnliem / Netherlands

"Process for the production of silicon dioxide granules"

This invention relates to a method for producing granular silica using a silica powder converted into a granulate in a granulating device in the presence of water as a binder, and that

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■. "." Water is obtained from the granulate obtained by means of Irliitzen βι: .τ- f-icnt .

The term "silica" means amorphous
Silicon dioxide with a SiO ^ content of more than 9C Ge ... whereby the fiest consists practically exclusively of free u: i'l / c: i ~ bound water. The term "free asj ^ r ¹ " denotes water that can be removed by heating for two hours at 105 C. The term "bound
Water "means water that is close to the free water
is expelled by heating to 1000 C.

E-3 is known to feed powdery materials, for example in a rotating, inclined drum or pan
granulate (see for example French patent specification 1 065 519) · The wet granulation of powdery materials in a granulating device, using a liquid, for example from Y.'asser, as a binder, and the removal of the liquid from the
granules obtained by heating is also general
known.

Dutch patent specification 83 880 describes a
Process for the granulation of finely divided silicon dioxide, which was obtained pyrogenically in the gaseous phase from volatile compounds, for which purpose the powdery silicon dioxide is dispersed in a liquid and
the dispersion obtained drop by drop onto finely divided -

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allowed to act dry silica, this latter is kept in continuous motion and the resulting granules, wet then dried at temperatures below 400 ⁰ C. Good results are obtained under these conditions when the dispersion used has a pH of 7 and above. This process produces a non-dusting granulate of high mechanical strength and excellent adsorption capacity.

Dutch patent specification 129 928 describes a process for the granulation of silica powder obtained by precipitation and having a specific density of 50 to 10 ($ / l and an average particle size of 1 to 70 u, for which the powdered silica is obtained in the presence of water, which is removable by heating to 105 ⁰ C, passes through an inclined Drehmiecher and heated, the obtained spherical granules in a rotary kiln at 900 ⁰ C for stabilization. the granule obtained has good mechanical strength and is used as insulating material.

Silica is also used as a reinforcing filler in rubber. A silica with good rubber reinforcing properties Properties has a BET area of 100 to 300 m / g and an oil absorption of more than 2 cmvg A silica of this kind can be obtained by adding an acid and an aqueous silicate

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Ic solution implements. The appropriate selection of conditions for reaction like the temperature, the PiI-V / ert it, the concentrations, the loading time and the loading speed provides a precipitate from such a aqueous solution, the precipitate being filtered, Wash and dry a finely divided silica with the physical properties mentioned above and a particle size mean of less than 100 η (see for example the disclosed Dutch Patent application 67 15563, in particular page 1, line to page 2, line 16 and page 4, line 18 to page 5 »line 20).

The disadvantage of such finely divided silica during handling and during addition to rubber in the rubber mill is that dust is caused. It is also difficult to remove fine powder if it is spilled. For these reasons, it would be advantageous to granulate the fine powder after it has been produced, to handle it in the granulated form and to supply rubber. However, if Siliciumdioxidpuiver under humid conditions, for example in the Dutch Patentscnrift 129,920 described manner, or "is else as iet described in Netherlands Patent C? S80, granulated in a similar ', it was found that d * .v degree of dispersion of the granular Silicon dioxide 22; learn rubber we-

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senclicii after its interfering in comparison with the The degree of dialerion of the non-granulated material is reduced is. It was also found that the reinforcing effect of the granulated silica filler is less than that of the silica powder, and this can be seen from the reduction in tensile strength and abrasion resistance of the vulcanized rubber-silica mixture .

The degree of dispersion of silicon dioxide in rubber is determined by:

Sections of 5 m thickness with a microtome was added to the vulcanizate of IEM the silica truncated. Kontaktdx-ucke r / earth made from these cuts in a contact microradiograph. The X-rays read through are absorbed to a greater extent when silica agglomerations are present in the section than when the silica particles are dispersed in the rubber. A greater adsorption of X-rays is made possible by a less intensive washing of the film. By measuring the -; j3ar: iten areas of lighter spots of the film and dividing this area by the total area of the film and multiplying de; -; obtained fraction with 100, one obtains the!) d3i er -pergrad ' ^IGS 3iljoiumdioxids in the rubber as r ca · /. -.:Λ. -, aIζ.

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powdered silicon dioxide given to your KautoCiiuk .vird, the degree of diapering is in the range from 90 to 98? O, where the percentage depends on the manufacturing method of the Silicon dioxide3 is dependent. In the case of traditional milk wet granulated silica is the degree of dispersion in Rubber $ 80 to $ 85.

It has now been found that if the Ψ LTAI granulation of silicon dioxide with a "stir-pH" 7 of silicon;? S as between he mixtures of less than 6.3, and preferably with a "stir-PH" 2 and 5.5, the silica granules obtained have the same degree of dispersion and the same processing effect in rubber as the pulverized finishing material. In this way, therefore, the advantages of the granular form of silica are obtained without the disadvantage that the degree of dispersion and the reinforcing effect of silica in rubber are reduced.

The term "stirring pH value" of silicon dioxide refers to the pH value which is measured in a dispersion of 5 g of silicon dioxide in 50 g of water, stirred at a constant pH value. This is "iiühr-PH" in the case of conventional silica fillers 6 to 7 · The "Hühr-PI value" of conventional wassergranuliertem silica is also within the range of 6 FCIA 7. ¹ -ie already erv /. ". Hnt, a granulated silicon dioxide of this type has a di-

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BADORiGfNAL

/ 3ZCoJj ^ a iii K ^ utochuk veil 50 oij o5 ^ _? v / JiirezsL the o_. ori; ic ^ 3 jra-Λ ^ i; 3 iiiaht-jr ^ riuli j ^ 'cor * M ^ ttrials S'G ei "v ~;

^, _-. ^ *. J _ \ ^ -. ^ VV - ^ ^. ^, - JU.— j- wo. ΙΧί- ^ ζ ^ uc; X j; -!. «. Wl ::. -.ι. ux * - ¹ ^ - 1λ— -. c; _ ü VU-.

nijv.r ils 5.5 durchgexüart: vird, hit dü.a received liciuri-ioxid- or ^ nul ^ t a Dii ^ ersionsgrcd. in Z ^ u ^ oonu .... r de ::. I.C3 non-granulated mitorials equal or iu

3 _: "" 1.- .εΐ ^ 3 by adding 3ch: 7i; rock ^ ure to the granulation ^ j "72.33or reduced v / earth.

Lie granulation Ir.ünn in every suitable granulation configuration, bc; i3j "ii.l3" .7oi3e of a granulating device curongo-dl: ri; v / ground, which has a 3ich rotating, inclined pan of the "Eirich" type. The dry powder can be fed to the granulator and sprayed with acidified Y / ater. In silicon dioxide plants, in which silicon dioxide is produced by precipitation from an aqueous silicate solution and the precipitate is washed out, there is an aq. Silicon dioxide sludge is available, which must be dried on plates or by means of spray drying u.vd υ ia'U d- ^ ner in the process of the invention Ycr; cil-

naon Λη:;. ^; uerun_j .ils Gr ^ .nulierung.3.7 ^ .33er "at the Gr ^ nuliö-; -u-..-ο 7 .: Ii oiun :: Licxid" .ulv3r3 ver'enlät .ird. In i: lon ^ "

ζ - “Is iron

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ρ _

mixed with such a length of the v / ilssrigeri silicon dioxide solanuae that a wet mixture with a moisture content of about 75% is obtained. A wet Geni.ch of your kind can easily be j-ranulated / grounded. The granules can be 7 ^! . ei \ -, e -./orden dried // obei 3I a obis 24st: .inuige drying on plates at einsr Teiir ^ temperature zvischen 105 ⁰ C and 175 ° C has been proven. iiin Trocknuii ^ sb ^ nd can eberibo 'i' for the l'x'ocknun ^ szv / corner vsrv.endet v / ground.

The invention in .vird w Eiteren Individual it en broom consumed by the examples, without dai: the irfindurigsberejcn in e /, e s ^EHRC: nkt .vird.

example 1

An oleic silica powder obtained by the process of German patent specification 1 OA9 834 was produced and

2
had a BET surface area of 159 m / g, an oil absorption of 2.8 ciiiVg and a stirring pH of 6.3, was dispersed in rubber in a conventional manner. The degree of dispersion was $ 92. Then the powder was first wet granulated in the usual way (stirring pH value 6.3) and the granules, after drying, were introduced into the rubber in the usual way, the degree of dispersion being 84%. When the powder has been wet-granulated after the invention at a stirring pH of 3-3 by adding dilute sulphuric acid to the granulating water,

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ORIGINAL BATHROOM.

the granules obtained had a weight of 92% after drying Dispersion in rubber, i.e. the same degree of dispersion as powdery material.

Example 2

An oleic silica powder obtained by the process of published Dutch patent application 65.02791 and a BET surface area of 145 m / g » had an oil absorption of 2.5 cm / g and a stirring pH of 6.4 was used in rubber in the conventional Way dispersed. The degree of dispersion was $ 97 · Wenn the powder was first wet-granulated in the conventional manner (stirring pH value 6.4) and the dried granules then incorporated into the rubber in the conventional manner, the degree of dispersion was $ 85. if the powder according to the invention at a stirring pH of 5.5 with the addition of dilute sulfuric acid to the Granulating water was wet-granulated, the granulate had after drying a 97% dispersion in rubber, i.e. the same as the oleilica powder.

Example 5

A spray-dried silica powder that is after Method of the laid-open Dutch patent application 65.02791 and a BET surface

P ^ i

of 151 m / g, an oil absorption of 5.0 cm / g and one Stirring pH of 6.3 was matched with such

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Amount of an aqueous silica suspension mixed so that the moisture content of the mixture was approximately 75% by weight. The aqueous silica suspension was a suspension obtained in the manufacture of silica after the washing step and immediately before spray drying. The-wetted powder was granulated ¹ -Pfannengranuliervorrichtung in a "üJirich. The wet granules were then dried 16 hours blatten overall ™ at 160 ⁰ C. The stirring-PH-value of the dried granules was 6.3.

The obtained silica granules were mixed into a rubber mixture introduced, as it is often used for shoe soles. The mixture had the following composition (in parts by weight):

SBR, type 1502 100 zinc oxide 2 Stearic acid 2 Triethanolamine 0.5 Diet Hygiene Glycol 3.0 Diphenylguanidine 1.2 Mercaptobenzothiazyl disulfide 0.8 sulfur 2.5 Silicon dioxide 50

Mixing was done in the conventional manner accordingly the Guinraiv elaboration using a "Banbury"

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Mixer with a capacity of 1.6 1 carried out. The rubber composition obtained was vulcanized 30 minutes at 15O ⁰ C. The tensile strength, tear strength and abrasion of the vulcanizate were determined. The degree of dispersion of the silica in the rubber was then determined. The results are shown in column a of table A.

The mixed with an aqueous silica suspension Spray-dried silicon dioxide powder was added to the Eirieh granulator granulated in the same manner as described above except that the wet powder is included dilute sulfuric acid was acidified prior to granulation. The Kühr pH value of the dried granules was 4.5 · The granules were also placed in a rubber mix the composition given above is introduced and the rubber mixture is vulcanized. The physical properties of the vulcanizate are given in column b of table A.

For comparison purposes, the results for a vulcanizate in which the spray-dried powdery material in this form in the rubber compound was introduced.

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i'abelle A

- ρ
Tensile strength in kg / cm
(ASTM D 4-12-66) a b C. ο
Tensile strength in kg / cm
(NM 5603) 180 210 205 Abrasion DVM in mm (DIN 53516) 40 46 47 Degree of dispersion % 180 160 160 85 97 97

"A comparison of columns a, b and c shows that after According to the invention, granulated material (column b) does not have the same reinforcing effect on rubber as it does not granulated starting material, while the conventionally granulated material is clearly inferior to this is. The use of "acid" granulation therefore provides the advantages of the granulated material in terms of Handling and processing without the vulcanizates being damaged by the introduction of the filler into the rubber.

fe be deteriorated.

Example 4

Powdery silicon dioxide, which was obtained by means of wet precipitation from an aqueous silicate solution with acid and by washing and spray-drying the precipitate, a BET surface area of 161 m / g, an oil absorption of 3 »1 μmVg and a 98% dispersion in rubber was found in a Stirring pH of 4.5 wet granulated. The i \ iaßgranulat was 16 hours at a temperature of 160 ⁰ O

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a b 215 215 45 48

and dried at 1 atmosphere pressure. The granules also showed a 98% dispersion in rubber.

Both the powdery starting material and the Granules were tested in the same way as in Example 3 in an SBR-15O2 mixture. The rubber values of the Vulcanizates are given in Table B (column a values for the powder and column b for the Specify granules).

Table B.

Tensile strength in kg / cm

ρ
Tensile strength in kg / cm

Abrasion DVM in mm 180 I70

Example 5

Powdered silicon dioxide with a BET surface area of 146 m / g, an oil absorption of 2.8 cm / g and a 97 # dispersion in rubber was granulated at different KUhr pH values in the range from 1.5 to 8.5 . The dispersion of the silica in rubber was determined at each -Kühr pH. The values are shown in the graph in which the agitation pH value of the granules is plotted on the x-axis and the degree of dispersion in% on the y-axis. The graph shows that if the stirring pH is less than 6.3, the granules

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has approximately the same degree of dispersion in rubber as the silicon dioxide powder and that at a Kühr pH value above 6.3 the degree of dispersion rapidly drops to a value of about 80.

-Patent claims-

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Claims (9)

Pat entails ρ r ü ο h e 1. Process for the production of a silicon dioxide granulate, iem a silica powder to a granulate in one pan granulator in the presence of water as Processed binder, and the water from the obtained Granulate is removed by heating, thereby marked i ο Ii η e t that the granulation occurs a silica meter pH of less than 6.5 carried out v / ird. 2 «The method according to claim 1, characterized in that g e k e η η, that the granulation is carried out with a stirring pH in the range of 2 to 5.5. 3. The method according to any one of the preceding claims characterized in that the stirring pH of the silicon dioxide to the desired value by means of Sulfuric acid added to the granulation water, is set. 4. The method according to one of the preceding claims characterized by the fact that the granulation is carried out with a silicon dioxide powder that has a BET-Ob; rf 1.ehe z.visohen 100 and 300 m / g and a J! Has absorption greater than 2 cm / g. -16- 209816 / U25
BATH ORIGINAL 5. The method according to any one of the preceding claims, characterized in that the granulation is carried out with a silica powder obtained by wet precipitation from an aqueous silicate solution and obtained by filtering, washing and drying, preferably spray drying, the precipitate, 6. The method according to any one of the preceding claims marked by the fact that the granulation a.vasser fed to the silicon dioxide powder in the form of an aqueous slurry of finely divided silicon dioxide is, this being done by wet precipitation an aqueous silicate solution and washing the precipitate had received. 7. The method according to one of the preceding claims marked by the fact that the granules at a temperature between 1O5 ° C and 175 C, 8 to ^ To be dried for 24 hours. 6. Silica granules, provided it is after a process according to one of claims 1 to 7 is produced. 9. A process for the production of rubber vulcanizates containing silicon dioxide as a reinforcing filler, characterized in that a silicon dioxide granulate according to claim 8 is used as a reinforcing filler. 209816 / U26