DE1224481B - Process for the production of homogeneous rubber-silica mixtures - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

C08c

C08d
German class: 39 b-5/07

Number: 1224481

File number: C 26517 IV d / 39 b

Filing date: March 17, 1962

Opening day: September 8, 1966

A number of processes are already known, homogeneous mixtures of rubber and silica by joint precipitation of rubber dispersions and alkali silicate solutions. In all cases, mixtures containing anionic or cationic emulsifiers are selected Rubber dispersions and alkali silicate assumed and homogeneous precipitation by adding acids achieved in the presence or absence of electrolytes.

It is also known by mixing alkaline Silica dispersions with synthetic rubber dispersions containing vinyl pyridine or its derivatives, and subsequent acidification to produce rubber-silica mixtures.

Finally, it has already been proposed that mixtures of polymers of conjugated diolefins or their Copolymers with monovinyl compounds and silica, by joint precipitation of the mixture an aqueous rubber dispersion, which is not more than 5 percent by weight, based on the polymer, anion-active emulsifiers from the group of alkali salts of long-chain fatty acids or resin acids contains and an electrolyte-free, aqueous dispersion of silica, to be prepared in that precipitation with an aqueous solution of a salt of a polyamine with primary, secondary and / or tertiary nitrogen which has at least 5 nitrogen atoms, or a quaternary ammonium salt which has at least 2 nitrogen atoms, made and the coagulum worked up in a manner known per se will.

It has now been found that homogeneous rubber-silica mixtures can be obtained from aqueous Silicic acid dispersions and rubber dispersions by mixing and precipitation are particularly advantageous can produce if one works in the presence of quaternary ammonium salts with a nitrogen atom.

The process has the advantage that any rubber and silica dispersions can be used. The preparation of the silica dispersions can contain salts or they can be washed free of salts prior to mixing with the rubber dispersion. The SiO ₂ concentration in the dispersion is arbitrary, however, in order to avoid excessive dilution, it is expediently kept between 3 and 20%. The dispersions should be neutral or slightly alkaline (pH 7 to 9).

The rubber dispersions can, for example, contain anionic emulsifiers such as fatty acid or resinous acid Salts or alkyl, aryl or alkylarylsulfonates and optionally cationic or nonionic emulsifiers contain.

Method of making more homogeneous
Rubber-silica mixtures

Applicant:

Chemical works Hüls Aktiengesellschaft, Mari

Named as inventor:
Dr. Günther Maaß, Mari

For the joint precipitation of silica and rubber to succeed, one of these two must be used Components contain a cationic emulsifier. These include, in particular, quaternaries understood nitrogen-containing organic compounds, for example tetraalkylammonium halides, alkylarylammonium halides, Alkylpyridinium halides and their sulfates or carbonates. The cationic emulsifier can be both the silica dispersion as can also be added to the rubber dispersion. In the latter case it can occasionally happen that As a result of the pH shift, coagulation already occurs. However, you can prevent this if you the rubber dispersion an amount of a base equivalent to the amount of cationic emulsifier adds, for example sodium hydroxide solution, potassium hydroxide solution or ammonium hydroxide, or more simply by adding in In this case, the cationic emulsifier is added to the silica dispersion. You can either do the Submit the silica dispersion and then add the rubber dispersion with stirring or in the put in the rubber dispersion introduced into the silica dispersion. Both methods are possible in principle, however, the latter is preferred, as the addition of the rubber dispersion to the submitted Silicic acid dispersion must proceed relatively slowly in order to coagulate coagulated rubber with coarse flakes avoid. This is particularly the case when the silica dispersion still contains salts. After this Mixing of the components can be filtered off directly, but this is particularly the case with salt-free Mixing is often very time consuming. The precipitation is expediently coarsened by the Mixture adds acid and / or salts. The setting of a pH value <7 is recommended if the rubber dispersion contains a fatty acid or resin acid salt as an emulsifier, which after • conversion in which the free fatty or resin acid should remain in the rubber. If necessary, before the

609 659/441

Acidification and / or addition of salt, the precipitation can be heated for a certain period of time. This process gives mixtures with any high SiO ₂ contents. The process can also be carried out continuously.

Further details on the mode of operation can be found in the following examples.

example 1

In a stirred vessel, 5 percent by weight, based on the silica, of cetyltrimethylammonium bromide are added to 2354 g of a 3.2% strength, neutral, salt-free silica dispersion (surface area of the isolated silica 175 m ^{2 / g).} 685 g of a butadiene-styrene dispersion with a solids content of 21.9% (emulsifier: 3.75% potassium oleate + 3.75% resinous potassium) are added with stirring. The addition is made in such a time that each time the mixture becomes thick, it is interrupted until the dispersion is again thin. A total of 15 minutes are required for this. The dispersion is heated to 9O ⁰ C, left for 10 minutes at this temperature and. then adjusted to pH 3 with 1.5 N HCl. The product is filtered, washed and dried. SiO ₂ content 32.0%.

Example 2

In a stirred vessel, 1368 g of the rubber dispersion described in Example 1 with 150 g of solid, while stirring, with 2418 g of a 3.1% aqueous silica dispersion, the silica of which has a surface area of 160 m ² / g after drying and which is 3 percent by weight, is obtained contains on SiO ₂ , cetyltrimethylammonium bromide and 30 g of sodium chloride, added. The mixture is heated to 90 ⁰ C, held for 10 minutes at 9O ⁰ C and adjusted with acid to a pH value of 3. The finely divided product is filtered, washed and dried. It contains 32.0% SiO.

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Example 3

1368 g of a dispersion of a synthetic butadiene-styrene copolymer (solids content: 150 g), which contains 8 percent by weight, based on solids, of resinous potassium as an emulsifier, were initially charged and 1476 g of an aqueous silica dispersion (pH 7.7 ; SiO ₂ content 75 g; content of cation-active emulsifier 5 percent by weight, based on SiO ₂ ). The mixture is worked up as in Example 2. SiO ₂ content 31.5%.

Example 4

1365 g of a dispersion of a butadiene-styrene copolymer (solids content 150 g), which as Emulsifier 3.3 percent by weight, based on solids, of diisobutylnaphthalene sulfonate, are like in Example 3 precipitated with a silica dispersion. Final pH 6.

Example 5

^{75 g of silica with a surface area of 48 m 2} / g are precipitated from water glass using hydrochloric acid in the presence of common salt. The silica is washed free of salt and has a pH of 7.5. It is dispersed in water using a high-speed, intensive stirrer, and 3.75 g of tetradecylpyridinium bromide are added. The dispersion is introduced into 1368 g of the dispersion described in Example 1 (solids content 150 g). The mixture is worked up as described in Example 4. A homogeneous precipitation of about 1 mm particles, which _{contain 32.0% SiO 2} , is produced.

Examples

83 g of a commercially available highly active silica (loss on ignition 10.2%) are dispersed in 1450 g of water with the addition of 3.75 g of trimethylbenzylammonium chloride. The dispersion is stirred into 1368 g of the dispersion mentioned in Example 1 (solids content 11%). The mixture is ^{heated to 90 °} C. and adjusted to pH 3 with 35 ml of 1.5 N HCl hydrochloric acid. The product is filtered, washed and dried. SiO ₂ content 30.8%.

Example 7

687 ml of the dispersion described in Example 1 (solids content 75 g) are added in 2 minutes with stirring with 1476 g of a neutral, salt-free silica _{dispersion (SiO 2} content 75 g, content of cetyltrimethylammonium bromide = 5 percent by weight, based on SiO ₂ ). The product is worked up as described in Example 1. SiO ₂ content of the dried homogeneous mixture 47.6%

Claims (1)

Claim: Process for the production of homogeneous rubber-silica mixtures from aqueous silica dispersions and rubber dispersions by mixing and precipitating, characterized in that in the presence of quaternary Ammonium salts are worked with a nitrogen atom. Legacy Patents Considered:
German Patent No. 1195 941. 609 659/441 8.66 © Bundesdruckerei Berlin