DE1148067B - Process for the production of homogeneous rubber-silica mixtures - Google Patents

Description

It is already known that mixtures of rubber and silica can be mixed together Produce cases of aqueous rubber dispersions and water glass solutions or silica sols by mixing the rubber dispersion with water glass and adding ammonium sulfate, possibly with the addition of common salt or alcohol, or the rubber dispersion with a silica sol mixes and falls with the addition of acids. These methods have the disadvantage that you can only Mixtures with a low silica content of less than 10 Vo are obtained which are subsequently obtained still other fillers, e.g. colloid kaolin or active carbon black, must be added, and that the silica is not precipitated in a highly active form.

It has been found that homogeneous rubber-silica mixtures can advantageously be produced by joint precipitation of synthetic rubber latices and alkali metal silicate solutions in the presence of neutral electrolytes with acids and subsequent filtering, washing and drying if a creamable rubber dispersion which is only alkaline Contains area stable emulsifier, mixed with the desired amount of alkali silicate solution and such an amount of aqueous neutral electrolyte solution that the electrolyte concentration between 30 and 80 g / l, preferably between 40 and 60 g / l, in the cream obtained, then this cream at temperatures between 15 and 30 ° C with vigorous stirring within 10 to 180 minutes evenly _{mixed with acid up to a p jr} value between 9 and 7, the electrolyte concentration must be at the upper limit of the above range for shorter acid addition times, then the reaction mixture if necessary s heated for 10 to 120 minutes at 80 to 100 ° C and optionally by further addition of acid to a _pH value of 3 is adjusted to the second

Under these conditions, rubber-silica mixtures with any content can be used highly active silica can be produced. The ratio of 100 parts of rubber to 100 parts of silica z. B. can easily be achieved. It can be proved by soaking in water that even with this ratio the rubber is completely evenly interspersed with silica.

For example, dispersions of copolymers of diolefins, such as butadiene, and monoolefins such as styrene, acrylonitrile, acrylic acid esters and methacrylic acid esters or vinyl pyridine.

Method of manufacture
homogeneous rubber-silica mixtures

Applicant:

Chemical works Hüls Aktiengesellschaft,
Marl (district of Recklinghausen)

Dr. Günter Maaß, Dr. Frederico Engel,

Marl (district of Recklinghausen),
Dr. Paul Bernemann, Haltern (Westphalia),

and Dr. Harald Blümel,

Hamm near Marl (Kr. Recklinghausen),

have been named as inventors

The first requirement for this process is the use of a rubber dispersion that contains Electrolytes are able to form a stable cream. The cream in this case is the state of Rubber dispersion in which the primary particles agglomerate to form large aggregates, but are still imperceptibly fine. Accordingly, it represents an intermediate state in terms of particle size between the rubber dispersion and a coagulate and is still due to the lack Marked tendency to further coagulation. The total mixture is under the cream understood from rubber dispersion and electrolyte without separation of a serum.

The duration of the stability of a cream depends on the amount of salt added. A usable rubber dispersion must remain stable with the addition of the amount of salt required for the precipitation of the silica and the amount of salt that is formed by the neutralization of the alkali content of the waterglass during the precipitation as long as the precipitation of the silica takes during the preparation of the rubber-silica mixture . This corresponds to the period from the preparation of the cream until reaching the approximate neutral point (p _H 7 to 9).

To test a rubber dispersion for its ability to form a stable frame the conditions that are adhered to during the production of the rubber-silica mixture

309 578/287

3 4

the should, based on. It should be able to vary, for example, from a fatty acid salt between 25 and 99 parts of the rubber dispersion with a solids content of the total amount of emulsifier.
19% and a water glass solution with a silica. For the success of a precipitation, the acid content of 26.1% and an alkali content of concentrations in the starting suspension and 8.25% must be prepared a mixture that takes about 5 the duration of the precipitation (acid addition time) until it is reached Contains 33% silica; the precipitation should be around the approximate neutral point and the precipitation rate of 50 g sodium chloride per liter cream in temperature. Concentrations Fällzeiten 10 minutes at room temperature to p _H 8 with and temperatures, take place outside the specified 1.5 η-hydrochloric acid. The test conditions are not uniform and can be calculated as follows from these data: io rubber-silica mixtures. According to the invention

-, - ^ η r. tr- , "ij r, n rv π , ι ^sc & the falling temperature are between 15 and 30 ° C,

1. For 15 g of rubber, 78.9 g of rubber _{- the felling time} ^^ _{10 and 180} minutes. the

dispersion required. Electrolyte concentration and the duration of the felling are at

2. For 7.5 g of silica (corresponding to 33% silica-constant rubber and silica concentrate acid in the mixture), 21.3 ml of _aqueous properties are required, depending on one another in the sense that glass is required. low electrolyte concentrations, prolonged precipitation

3. During the neutralization, the times must be adhered to. However, it is er alkaline of the water glass 4.4 g sodium is required, with longer acid addition times also chloride. Choose low electrolyte levels, though

Chloride 4. In order to set the cream to 50 g sodium ^{20 this in mind, it obi} g per liter depending done to 28.0 ml of 20% Na · ^{In DEQ can} be observed according to the invention Fälltriumchloridlösung = 6.4 g sodium chloride loading ^times between 10 and 180 minutes the drained, speaking electrolyte concentrations are between 30

c tv ο- ™ "" v. * ·· * ^ cn ^ i ι c "e" i "and 80 g / l, preferably between 40 and 60 g / l, ie

5. The amount of acid is about 50 ml 1.5 n-aalz- _n,. A ·.,. ^b . - .. ,,. ^ _N τ-τ ι * ι -τ · *
_acid &s' as z. B. with a 10 minute fall time 60 g electrolyte per liter,

at 180 minutes 40 g of electrolyte per liter, if one

The liquid amounts of 2, 4 and 5 make a mixture with a rubber-silica ratio combined 99.3 ml, the total salt content as a sum of 100:50 with a rubber concentration of 3 and 4 is 10.8 g of sodium chloride. In a 100 to 150 g / l and a 250 ml silica cone beaker 78.9 g of rubber at a concentration between 50 and 75 g / l are now to be precipitated, dispersion submitted, within one minute with As already mentioned, but can also be z. B. 10.8 g of sodium chloride, dissolved in 99.3 ml of water, the precipitation time is 60 minutes with an electrolyte concentration below added vigorous stirring and 10 minutes tration of 60 g / l. (Under »Rubber Stirring calmly. After this time, the cream must be concentrated here and in the following still be stable, d. This means that there must be no noticeable solids content of the rubber dispersion, converted parts of the suspension must be present or it must be the same as in the cream before the addition of acid the entire suspension understood a sieve with a mesh dilution; those in the form of water glass pass a width of 0.5 mm (Din 12) smoothly. present silica component is called »silica

The rubber dispersion must also have an acid concentration «calculated.)

Contain emulsifier which is only available in alkaline 40 The rubber and silica concentrations in the

Pn area is stable and the neutrali cream is separated from the following three components

sation, ie, by adding acid, up to p _H 7 inactive pending:

and loses its ability to emulsify. To this 1. the desired rubber-silica composition

Emulsifier group includes above all the ratio in the mixture,

Alkali salts of fatty acids, in particular salts of the 45 ₂ the solids content of the chewing to be used

Carboxylic acids with 15 to 18 carbon atoms, e.g. B. Tschukdispersion and

Palmitates, stearates and oleates and mixtures of the ",". , ..,. .., ". ,

the same as, for example, in the case of paraffin oxidation at ³ "of ^the silica concentration in the water glass.

fall, especially the potassium salts. Although likewise Since these three variables huge farce accident may be subject gen to the group of p in the alkaline range _H 50, no allbeständigen emulsifiers belonging salts can of dis- common accepted rules up. In the case of the generally proportioned resin acids, because of their usual electrolyte solids content of the rubber dispersion, trolyte sensitivity is practically unsuitable. Between 20 and 30% and the commercially available ones, the silica content of the water glass between 25 and 35 can only be formed in the case of extremely low salt concentrations and that is why rubber concentrations between mixtures with high silica contents are not in 50 and 200 g / l, depending on that in the mix question. Very particularly suitable, however, is the desired rubber / silica ratio, without a mixture of fatty acid salts and a suitable silica concentration, e.g. B. resin acid salts as emulsifiers, the proportion at a rubber-silica ratio

from 100: 30 = 150 g rubber and 45 g silica per liter

or 120 g rubber and 36 g silica per liter,
of 100: 40 = 150 g rubber and 60 g silica per liter

or 120 g rubber and 48 g silica per liter.

The closer the ratio of rubber to silica approaches, the higher it becomes if you have a considerable one acid in the desired mixture to the value 1 additional dilution of the cream with water

5 6

A mixture which, according to the above conditions, requires the use of electrolyte per unit of mixture, which is produced and in which the silica is in an optimal silica concentration. It has now been found, painter distribution is contained, can already be made that the electrolyte concentration may also be varied with the silica of the nature of the precipitation suspension after Einsäurekonzentration in the frame, 5 represent the p _H -value 2 to 3 in the form and that , at high silica concentrations can recognize the size of the particles. The particles are at electrolyte concentration without lengthening the precipitation - almost spherical structures. The acid content of the mixture decreases with increasing silica duration without the homogeneity. B. 0.1 to 3 mm for a silicic acid, ίο content of 10% to 1 to 3 μ at a content of

To make these relationships clear, let 30% silica be used. Due to the small particle size

The following examples are given: must the product expediently be placed on a suction

It should be mixed with a rubber filter, a rotary filter, a centrifuge or similar

Silica ratio of 100: 100 can be made Filtration of the finest substances using suitable equipment.

the. The concentrations can now be trated within 15. The ablution can either by

can be set as follows: repeated suspension in cold or tempered

a) 90 g rubber ie liter water ^system or directly on the filter. The 90 g of silica per liter of product is dried at temperatures between 60 and 50 g of sodium chloride per liter at 120.degree.

Felling time up to p _H 8 · 15 minutes; ² ° ^The production of the mixtures can also be carried out continuously

b) when the solid content of the rubber dispersion nuierHch be carried out by passing the suspension _ "" _r i _al, Kt. ^a series of vessels in which the em-

Co Oi.ld.UUL · 1 », η 1 τη ..« 1 ·, · 1

mn tr <. ι. 1 · τ · <. individual mares of the fall one after the other.

120 g of rubber per liter are needed.

^{8 J} '25 The raw materials for the silica are alkali

Felling time up to pH 8: 15 minutes;

c) any higher electrolyte concentration as long as the value in the water glass is generally 1: 3.3, however

The framing resistance of the rubber _{dispersion has no effect} other than the other possible conditions.

it is allowed, is possible: _{3 <J Under} neutral electrolytes, the salts are rigid

90 g of rubber per liter, to understand ker acids and strong alkalis, z. B.

90 g of silica per liter, sodium chloride, sodium sulfate, potassium chloride and

60 g sodium chloride per liter, potassium sulfate. Any strong acids can be used as acids

Precipitation time to p _H 8: 15 minutes. Acids are used, e.g. B. the mineral acids,

In summary it can be said that masticatory 35 sulfuric acid and hydrochloric acid, lower carboxylic acids,

chuk, silica and electrolyte concentration as well as formic acid and acetic acid, or surfo-

like the duration of the precipitation (acid addition time) acidify from one another.

are dependent, however, the dependency between the As can be seen from the examples, the

Silica concentration and the electrolyte concentration according to the invention compared to tration or the silica concentration and the mixtures of masticatory acid addition time produced in other ways are not as great as the dependency on chuk and light filler in the electrolyte concentration and acid added vulcanizates produced from them, the advantages of higher elasticity with time. There is a lower limit for each concentration or for the room temperature and higher temperature, higher strength acid addition time, which must not be exceeded with the same elongation at break and higher moduli if a homogeneous mixture 45 and thus better wear resistance, whereby from Rubber and silica should be achieved. the mixing plasticities are very similar. Furthermore, the upper limit is determined by the concentrations of the starting materials, the solubility of the electrolyte and produced, e.g. B. determined by mixing filler and the invoice stability of the rubber dispersion rubber on a rolling mill or in an indoor. It is essential that the acid is added to the cream in a uniform flow in the form of vulcanization agents, and that requires or is given the possibility of avoiding the same properties at the point of entry in order to reduce costs will. The best way to do this is to use a working oil or an extender oil. The acid can be injected or sprayed, 55 Rubber articles produced from the mixtures, if the reaction mixture is stirred intensively and uniformly like seals and profiles, sole material at the same time. The stirrer can be known footwear, cellular articles and toys, show ter type, z. B. Hoesch, anchor or propeller stirrer through the aforementioned property improvements. better performance characteristics and longer preservation-60 ness compared to set the reaction mixture with the acid to a p _H by using the usual 9-7, it should be appropriate an overall manner premixes prepared or mixtures certain time to be heated. In doing so, either directly manufactured articles. In particular, in articles such as tires and parts and the mixture, buffers and suspension elements of all kinds, which are exposed to temperatures between 80 and 100 ° C for a long time by blowing in water vapor or indirectly to continuous periodic alternating stresses, the mixture is left at this temperature for 10 minutes to 2 hours . Then - on single and conveyor belts, V-belts, air suspension, sometimes or gradually - further acid up to pg possible, the better elastic properties and from 3 to 2 can be added. thus lower hysteresis values as well as the

Part of the increased wear resistance caused by this to be used technically. Especially in the manufacture of motor vehicle tires This makes it possible to completely color tires and their visible parts, such as the sidewall and tread or partly light-colored mixtures contain, with considerably better performance than this was previously possible using mixtures of conventional production methods.

example 1

774 g of a synthetic rubber dispersion with a solids content of 19.4%, the solid, consisting of 76 parts of butadiene and 24 parts of styrene, which contains 8.2% potassium stearate, based on the solids as an emulsifier, are mixed with 281 g of soda waterglass, Density = 1.348, SiO ₂ content = 26.1%, mixed and then mixed with 321 g of a 2Q% saline solution within one minute while stirring. Then 350 ml of 1.5 η-sulfuric acid are injected up to Ph 8 in 10 minutes at 20 to 22 ° C. The batch is heated to 90 ° C. in 15 minutes and held at 90 ° C. for 10 minutes. It is then adjusted to pn 3 with 190 ml of 1.5 η-sulfuric acid. The product is washed by decantation and dried at 80 ⁰ C. Silica content: 30.8%, H ₂ O content: 2%.

Example 2 is described, with a solids content of 16.9%, in a 300 l V2A stirred vessel equipped with a high-speed propeller stirrer and a steam jacket, with 26.9 kg of water glass and then within 5 minutes with 41.5 kg of 20% saline solution framed. The concentrations in this cream are then: 100 g rubber, 49.75 g SiO ₂ and 60 g sodium chloride per liter.

ίο At 20 ⁰ C, 321 1.5 η-sulfuric acid are injected evenly through three mud nozzles while stirring vigorously. The _pH value of the suspension is then about 8. The suspension is heated to 90 ° C and held for 30 minutes at 90 ° C. Subsequently, the batch with 21 1 1.5 η-sulfuric acid is adjusted to p _H 2, the finely divided product is filtered off on a rotary filter and released by three times suspending in hot water and filtering on the rotary filter of the salts. The filter sludge is

ao air cabinet at 80 ° C except for a residual moisture of 2%, determined by drying at 140 ° C, dried. The silica content of the mixture is 32.4%.

On a laboratory roller mill 400/250 mm, friction 1: 1.15, cooling water temperature 50 ° C, the Mixtures A, B and C (Table 1) according to the following Recipes made:

Example 2 Table 1

661 g of a synthetic rubber dispersion of 76 parts of butadiene and 24 parts of styrene with a solids content of 22.7% and with 8% emulsifier, based on solids, the emulsifier being made from a mixture of 50 parts of disproportionated resin acid and 50 parts of a mixture of the potassium salts consists of fatty acids with 15 to 18 carbon atoms, are diluted with 186 ml of water _{, stirred with 285 g of soda waterglass, density = 1.35, SiO 2} content = 26.3%, and then mixed with 256.8 g in one minute 20% saline solution added. The concentrations in this cream are:

116.8 g rubber per liter,
58.4 g silica per liter,
40 g sodium chloride per liter.

The cream is set in 33 minutes by 350 ml I, 5n-Schwefelsäurebeil8 to 22 ⁰ C with vigorous stirring to p _H 8, heated the suspension in 15 minutes to 90 ° C and held for 10 minutes at this temperature. _{The pH is then adjusted to H} 3 with 170 ml of 1.5 η-sulfuric acid, filtered, washed and dried at 80.degree. Silica content of the mixture: 31.9%; Water content: about 2%.

Example 3
82 kg of a synthetic rubber dispersion, as in

Rubber-silica mixture according to Example 3

Styrene butadiene cold

rubber

Silica filler,
highly active

Stearic acid

Zinc oxide

Amine mixture

Ethylene glycol

sulfur

N-cyclohexyl-

2-benzothiazylsulfenamide

A. B. 150 - - 100 50 2 2 5 5 2.5 2.5 2.5 2.5 2 2 1.5 3

100

50
2

The quantitative data are to be understood here in parts by weight. The mixing time saving of mixture A compared to B and C can be between 50 and 25%, depending on the type of mixing sequence. From the seasoned Ready-mix test flaps are vulcanized at 150 ° C, from which ring-shaped test specimens are punched will. The test gives the following values:

Tabel

VuI canalization

Time
(Minutes)

strength
(kg / cm ² )

strain
(Vo)

module
100 Vo / 300 »Ό

(kg / citf)

hardness

22 ° C / 75 ° C

(Shore)

elasticity

22 ° C / 75 ° C

(Vo)

Permanent
strain

C / o)

Mooney plasticity

(M 1-4)

15th 155 410 33/123 73/69 40/58 22nd 30th 159 435 37/121 73/70 40/58 23 60 148 435 36/113 73/69 38/57 21 120 150 475 32/104 72/68 38/57 17th

90

Table II (continued)

VuI canalization

Time
(Minutes)

strength
(kg / cm ² )

strain

module
100 «/ ο / 300» / ο

(kg'cms) hardness

22 ° C / 75 ° C

(Shore)

elasticity

22 ° C / 75 ° C

Permanent stretch

Mooney plasticity

(M 1-4)

15th 111 455 19/44 66/65 33/53 14th 30th 108 440 22/45 69/65 33/53 11 60 111 450 22/44 69/65 33/53 10 120 108 475 19/39 67/63 33/51 9 15th 206 685 11/25 C.
65/60 33/47 20th 30th 159 630 12/26 63/60 33/50 16 60 165 650 9/25 61/60 33/50 14th 120 164 660 9/23 60/60 33/49 11

71

74

From the data in Table 2 it can be seen that with the one in recipe B for vulcanization commercial highly active reinforcing filler-containing mixture applied sulfur accelerator amount an increase in modulus and elasticity not to the extent that it took place in A, can be reached. Since a further increase in the amount of sulfur accelerator is clearly noticeable If the tear strength in B deteriorates further, it is very likely that this is due to vulcanization variants a data combination similar to A cannot be achieved. The same amount of sulfur accelerator used in C as in A brings about a significant one, which can in principle also be achieved for mixture A with a corresponding reduction Improvement of the strength-elongation properties, but the moduli are already in an uninteresting position Area, and the elasticities have decreased even further compared to A.

Recipes D and E (Table 3) are compared under the same mixing conditions, with which in principle apply the same statements as above. The comparative values are summarized in Table 4 summed up.

Table 3

Silica mixture according to Example 3 150 -

Styrene-butadiene cold rubber - 100 silica filler, highly active,

commercially available - 50

Stearic acid 1 1

Zinc oxide 3 3

Sulfur 2 2

Zinc salt of the 2-mercaptobenzo

thiazoles 1.75 1.75

Diphenylguanidine 1.75 1.75

Hexamethylenetetramine 1 1

The test specimens are vulcanized at 150 ° C.

Tabel

VuI canalization

Time
(Minutes)

strength
(kg / cm ² )

strain
(Vo)

module
100 ° / o / 3OO ° / o

(kg / cm ² ) hardness

22 ° C / 75 ° C

(Shore)

elasticity
22 ° C / 75 ° C

Permanent stretch

Mooney plasticity

the mix

15th

30th

60

120

197
182
177
160

510
445
450
400

39/129
40/134
40/132
40/133

71/68
73/68
73/70
73/70

43/55
43/57
43/57
43/57

21 18 17 11

93

15th 154 740 30th 168 670 60 178 665 120 156 640

9/24
9/34
9/37
15/35 65/64
67/65
70/67
70/58

38/48
38/48
38/49
39/48

18 17 17 14

103

Example 4

436 g of a synthetic rubber dispersion with a solids content of 22.7% and an emulsifier, as described in Example 2, are placed in a 4-1 beaker and, one after the other, with 165.5 ml of water, 380.5 g of one Water glass with 26% SiO ₂ content and 247.5 g of 20% sodium chloride solution are added. With a metering pump at 20 to 25 ° C in 16 minutes 510 ml of 1.5 η-sulfuric acid are injected through a mud nozzle. The then reached _pH value is 7. The suspension is heated to 9O ⁰ C and held for 30 minutes at this temperature. Then in 6 minutes

309 578/287

utes with 160 ml of 1,5-η sulfuric acid to p _H adjusted. 3 The fine powdery precipitate is filtered off with suction on a suction filter, washed by decanting and dried at 80 ° C. for hours. The mixture contains 50% silica.

Claims (1)

PATENT CLAIM: Process for the production of homogeneous rubber-silica mixtures by co-precipitation of synthetic rubber dispersions and alkali silicate solutions in the presence of neutral electrolytes with acids and subsequent filtering, washing and drying, characterized in that a creamable rubber dispersion which is only resistant in the alkaline range is obtained Contains emulsifier, with the desired amount of alkali silicate solution and such an amount of aqueous neutral electrolyte solution added that the electrolyte concentration between 30 and 80 g / l, preferably between 40 and 60 g / l, in the cream obtained, then this cream at temperatures between 15 and 30 ° C under intensive stirring was added over 10 to 180 minutes evenly with acid to a _pH value 9-7, wherein the electrolyte concentration must be at shorter acid addition times at the upper limit of the above range, then the reaction mixture optionally 10 to 120 minutes at 80 heated to 100 ° C and optionally by further addition of acid to a _pH value of 3 is adjusted to the second 1 309 578/287 4.63