DE1209287B - Process for the production of aqueous, light colored reinforcing fillers containing rubber dispersions - Google Patents

Description

B UN D ES REF UE LI IL GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. α .:

C08c

German KL: 39b -1

Number: f 209 287

File number: R31632IVd / 39b

Filing date: December 7, 1961

Opened on: January 20, 1966

The good technical rubber properties of vulcanizates made from natural rubber mixtures, the bright ones Containing active fillers are evaluated in many fields of technology. So far the manufacture has been and shaping these natural rubber vulcanizates reinforced by light active fillers essentially carried out so that the practically anhydrous components of the mixture in the internal kneader or on the mixing roller after masticating the rubber portion mixed with one another, the resulting plastic Mixture brought into the desired external shape and vulcanized.

It is also known to make natural rubber using natural substances, such as casein, or clay or other finely divided minerals as dispersants into an aqueous dispersion, wherein the natural rubber can optionally also contain inorganic pigments based on the Rubber does not have a reinforcing effect. However, those from these aqueous mixtures show by molding, The vulcanizates produced by dewatering and vulcanizing do not have good technical properties. Films, which were produced from such dispersions, for example, had very low tear strength and showed a high sensitivity to water.

It is also known to use rubber mixtures which contain inactive fillers after prior swelling in a rubber solvent to disperse in water. This procedure is supported by the Use of organic solvents, however, is economical and also requires additional Precautions and protective measures to prevent nuisance and damage to the health of the operating personnel to exclude. In addition, the obtained films or moldings or their vulcanizates have only low technical rubber values, which are used for production exclude high-quality articles.

In the Austrian patent specification 120 863 is also a process for the production of aqueous Dispersions of rubber, regrind, factice or the like. Has been described. Bright reinforcing fillers and polyacrylic acid derivatives are not used here. The amounts of used there Protective colloids are large, but the dispersions produced are not very durable.

A dispersing process has also become known from British patent specification 538 505, in which fillers are only mentioned as part of a general list. Polyacrylic acid derivatives as protective colloids have not been used.

In the German patent specification 854 573 there is also a process for the production of aqueous, light-colored
Rubber dispersions containing reinforcing fillers

Applicant:

Rhein-Chemie G. mb H.,
Mannheim, Mülheimer Str. 24-26

Named as inventor:

Dr. Rudolf Kern, Neustadt an der Weinstrasse;
Dr. Gregor Groppenbächer, Schwetzingen;
Dr. Hans Scheurer, Heidelberg-Schlierbach

Processes for preparing aqueous dispersions of isobutylene have been described. Fillers are after that not used. Water-soluble polyacrylic acid compounds are used in the context of a general List of protective colloids mentioned among other things, but they are given a special position not awarded. In addition, the dispersions prepared by this process still have to be different from those in Large amounts of emulsifiers and protective colloids used are freed by complex measures will. So they are not yet ready for use at first.

The previously known processes for the production of rubber dispersions by the action of shear forces on a compact natural rubber mixture with the use of wetting agents with an alkaline effect Substances and protective colloids and with the gradual addition of water failed, however, when the solid natural rubber mixture to be dispersed contained light-colored reinforcing fillers. When incorporating Water was not a finely divided stable aqueous dispersion, but a kind of rubber sponge, the no longer absorbs any more water.

Attempts have also been made to add light-colored active fillers to natural rubber latex fill in this way with the in the latex

509 779/444

3 4

processing of the usual methods into high-quality, a rubber mixture produced in a known manner

to get reinforced rubber vulcanizates. It represents, in which the usual rubber auxiliaries,

is, however, as E. W. M a d g e in Naunton, »The like anti-aging agents, light stabilizers, soft-

Applied Science of Rubber ", published by Edward macher, etc., can be incorporated. Among other Arnold (Publishers) Ltd., 1961, on p. 32 writes, 5 The action of strong shear forces in this

not yet possible, the rubber of the latex by rubber mixture wetting agents, alkaline acting

bright active fillers in the same way to reinforce substances as well as those to be used according to the claim

how this can be done with dry rubber. Protective colloids and possibly also volcanic

With the help of the shaving agent according to the claimed method evenly distributed and the mixture so It is now possible to work through the dispersions produced for a long time until the whole thing is complete

to avoid the disadvantages outlined above has become homogeneous. This homogeneous mixture

and to produce reinforced vulcanizates, which are each made under further action of shear forces,

Nigen from light active fillers containing dry - preferably in an internal mixer, water in

Rubber mixtures are not gradually added in their values - small proportions. The water

stand. 15 is taken up by the mixture, with

The invention relates to a process for initially producing a water-in-oil dispersion

Forms production of aqueous rubber dispersions.

by dispersing a solid rubber mixture, with further gradual addition of water in

the fillers, wetting agents, small amounts of alkaline substances eventually phase reversal occurs,

and protective colloids and optionally vulcanizing 20 and a dispersion of the oil in type is formed

agent and other rubber auxiliaries, in water. From that moment on, the mix becomes

Water with the application of shear forces, but quickly becoming softer and finally liquid. From here

Without the use of organic solvents, the water can be applied more quickly and in larger proportions

which is characterized in that solid mixtures are added. The resulting dispersion is

are used, the natural rubber and given 25 extremely finely divided and contains 90% particles with a

at least up to 50 percent by weight synthetic rubber diameter up to 1.5 μ, while only 10% of the par-

and / or thermoplastic polymers, based on particles having a diameter of 1.5 to 3 μ . the

the mixture of polymers and, as fillers, particles of this dispersion contain the light-colored active

bright reinforcing fillers as well as protective colloids ven fillers and the other ingredients in completely

water-soluble or water-swellable salts of the poly-homogeneous mixture with the rubber. These

acrylic acid or water-soluble or water-swellable dispersions are resistant to temperature fluctuations

Contain polyacrylic acid amide. and stable against mechanical influences and can

The aqueous di- prepared according to the invention can be diluted as desired by adding water,

dispersions are ready to use, stable, do not tend without coagulation occurring,

to settle the incorporated fillers and allow 35 In the preparation of the dispersions according to the

For the production of high-quality vulcanizates according to the claimed processes, it has proven to be expedient

the usual processing methods when using latex, with the exception of all vulcanizing agents

methods. These "dispersion vulcanizates" surpass the sulfur in the practically anhydrous premix

in addition, those rubber products that incorporate. Is separate and independent of it

obtained from latex according to previously known methods 40 the sulfur is converted into an aqueous suspension,

are, in their physical dimensions and use- This aqueous sulfur suspension, for example so-

properties. so-called colloidal sulfur, is the finished aqueous

The polyacrylic rubber dispersion to be used according to the invention, all other constituents Acid derivatives make it possible, even when they are used, advantageously only shortly before their proportions small amounts, natural rubber 45 twist added. This measure will Mixtures that contain light-colored reinforcing fillers prevent the sulfur from getting on the rubber into finely divided stable ready-to-use dispersions aqueous dispersion prematurely vulcanizing. can ken. This will increase the shelf life

The use of large amounts of protective colloids has made the rubber dispersion, especially in the case of increased

namely, the disadvantage that the temperature produced therefrom improves.

Objects are not waterproof. In some cases, it is advantageous to remove the bulk of the protective colloid from sewage chemicals, including sulfur, by means of complex measures, and to suspend these together in water before they are technically usable. However, larger protective aqueous suspensions of the finished aqueous amounts of rubber colloid not only have an unfavorable dispersion to be mixed in. The production of this aqueous influence on the water resistance of the objects produced from the suspension of the vulcanization chemicals is persion, but does not result in the subject matter of the invention,
also a deterioration in the rubber engineering values of the finished article. the aqueous dispersions according to the claimed

The dispersions are produced as follows: Out of 60 processes is natural rubber. This natural rubber

Natural rubber or mixtures of natural rubber can optionally be admixed with synthetic rubber

and synthetic rubber or mixtures of natural rubber, but the proportion of synthetic rubber should be

rubber and thermoplastic polymers or not more than 50% of that made from natural rubber and

Mixtures of natural rubber, synthetic rubber, synthetic rubber consisting of an elastomer mixture

and thermoplastic polymers and bright active 05.

ven fillers are used on one in the rubber As synthetic rubber can be of all common types

Industry-standard mixing mill or used in a, d. H. Polymers made from conjugated

Internal mixers due to the action of strong shear forces, as well as copolymers of these conjugated

Serve with one another or with other unsaturated compounds that can be copolymerized with them.

It is also possible to use such rubber mixtures by the process according to the invention to disperse, which contain a proportion of thermoplastic polymers. Such mixtures of rubber and thermoplastic polymers are used in technology because of their special properties increasingly used. Here, too, it has been shown that the consumer goods, which consist of the said mixtures of rubber and thermoplastic polymers by dispersing in water, Molding, draining and vulcanizing were made to have the same rubber engineering properties like those consumer goods that are made from the same mixture components, however by immediately vulcanizing the dry mixture, i.e. without dispersing it in water became.

Particularly suitable thermoplastic polymers are low-pressure and high-pressure polyethylene, polyamides, Polystyrene, polyacrylic acid esters, polymethacrylic acid esters, polyvinyl acetate, polyvinyl chloride or copolymers of vinyl chloride and other polymerizable monomers.

The term »light active fillers« includes pyrogenic and precipitated silicas, precipitated calcium silicates, understood precipitated aluminum silicates and alumina gel. The reinforcement effect is evident the vulcanizates, especially the high values for tear strength. These bright active fillers can either be used individually or mixed with one another. Ever according to the desired degree of reinforcement, d. H. depending on the requirements that are placed on the product are, if necessary, other fillers such as kaolin, chalk, chalk, surface-treated Chalk, zinc oxide and magnesium oxide can also be used.

The proportion of light active fillers can be 10 to 150 percent by weight, based on rubber, the optimum of the reinforcement effect with a content of light active fillers of 20 to 50 percent by weight.

The finished dispersions prepared according to the invention can also contain thickeners and sensitizing agents active substances and buffer substances are added to the dispersions to the respective To adapt the intended use.

Anion-active and non-ionic capillary-active substances are suitable as wetting agents. As particularly beneficial has the use of potassium oleate, water-soluble resin soaps, polyalkylene oxide derivatives as well Fatty alcohol sulfates, alkylbenzenesulfonates containing 12 to 24 carbon atoms, and also the dialkyl esters of sulfosuccinic acid, preferably 2-ethylhexanol, proved.

Of the wetting agents, 0.5 to 10%, preferably 1 to 5%, are used, based on the disperse Phase, d. H. based on the rubber mixture to be dispersed.

Protective colloids which are particularly suitable in the claimed process have proven to be water-soluble or at least water-swellable derivatives of polyacrylic acid have proven successful, such as. B. polyacrylamide or salts of polyacrylic acid. Even in small amounts, these substances provide excellent stabilization of the aqueous dispersions. The amount of these protective colloids is 0.5 to 10%, preferably 1 up to 3%, based on the rubber mixture to be dispersed.

A 10% strength aqueous solution of the polyacrylic acid amides which can be used according to the invention shows in 25 ° C, measured according to Höppi, a viscosity from 10,000 to 250,000 cP. Those polyacrylic acid amides are preferably used, their 10% solution under the same conditions a viscosity of

ίο has 50,000 to 100,000 cP. As water-soluble salts of polyacrylic acid such are used, their 10% strength aqueous solution at 25 ⁰ C, measured according to Höpler, a viscosity 200-270 00OcP comprising, preferably 200-50 00OcP. Lithium, sodium, potassium, ammonium and substituted ammonium salts are preferably used.

Alkali hydroxides, ammonia or amines are mainly used as alkaline substances. The amount depends on the type of filler and the amount of filler, but it is usually 1 to 10%, preferably 2 to 6%, based on the disperse phase.

The effectiveness of these auxiliaries or additives is if they are added according to the invention to the practically anhydrous rubber mixture and together with this dispersed in water, better than having the same substances in the same amount in natural ones Rubber latex can be incorporated. This improvement is due to the fact that it is in processing according to the claimed process inside the rubber particles of the aqueous dispersion and can develop their full effectiveness there. When adding the auxiliary and Additives to natural rubber latex, on the other hand, are distributed in the aqueous phase of the latex and cannot develop their full effectiveness in the rubber particles of the latex.

The dispersions prepared by the claimed process have a pH value that is preferably is between 8 and 10.

The viscosity of the dispersions depends on the starting materials and the amount of water added. Thick, paste-like dispersions can be prepared which can be diluted with water without coagulation occurring. The dispersions produced by the claimed process are also resistant to mechanical influences, shear effects and temperature influences.
It has been shown that the dispersions prepared according to the invention can be mixed with electrically neutral and synthetic rubber latexes containing negatively charged particles and artificially produced dispersions of other types.
The dispersions prepared according to the invention can be used to advantage in many fields of technology. They are preferably used where the use of dispersions has application advantages over the use of solid rubber mixtures, but the same properties are required of the finished products as in the processing of practically anhydrous rubber mixtures.

The dispersions can be vulcanized before or after shaping.

The parts of the rubber mixtures given in the examples below are parts by weight, based on 100 parts by weight of rubber. The amount of wetting agent, protective colloid and alkali is related

to 100 parts of the disperse phase, d. H. to 100 parts of the rubber mixture to be dispersed.

example 1

On a mixing roller, the following approach was homogeneously blended at a roll temperature of 60 to 8O ⁰ C:

100 parts natural rubber,
20 to 80 parts of precipitated silica,

2 parts of stearic acid,

3 parts triethanolamine,
1.0 part zinc oxide active,

1.0 part zinc diethyl dithiocarbamate,
0.2 parts of zinc mercaptobenzothiazole.

The series were incorporated by in an internal mixer at 6O ⁰ C homogeneously into this mixture:

2 parts octadecenylpentaethylene glycol ether,

2 parts of potassium hydroxide, as 40% aqueous

Solution,
1.0 part polyacrylic acid amide, in the form of a 10% strength

aqueous swelling.

Then, with further mechanical processing, water was slowly added in small portions up to added for phase inversion and the dispersion adjusted to a solids content of 50%.

The dispersion obtained had the following key figures:

pH 9 to 9.5

Particle size 90% to 1.5 μ

10% 1.5 to 3 μ

Viscosity measured with a rotation viscometer at 20 ^° C. and a shear gradient of 22 (see- ¹ ): 2500 to 3000 cP.

Before the test films were produced, 1.5 parts of sulfur were added to the dispersions as a 50% sulfur suspension intensely stirred.

The dispersions prepared in this way were diluted with 10% water, defoamed, deaerated and 25 cm ³ of each were evenly distributed on a horizontal 200 × 200 mm glass plate provided with a circumferential edge and dried in air for 24 hours. The films had a uniform thickness averaging 0.3 mm. They were then vulcanized in hot air ^{at 100 ° C. for 20 minutes.}

In order to compare these vulcanizates produced from the aqueous dispersion with such vulcanizates, which were made from the same rubber mixture, but without dispersion in water from the corresponding practically anhydrous, containing 20 or 40% precipitated silica Rubber compounds samples are made and heated in a vulcanizing press. The tensile strength and the elongation at break of these samples were according to DIN 53504, the tear strength according to DIN 53507 certainly. The technical rubber values obtained are summarized in Table 1.

Table 1

Fallen Tear Tear Tear on Remark
kunsen Silica strain strength strength Parts by weight 7o kg / cm ² kg / cm D, F 20th 800 160 31 M, P 20th 840 165 22nd D, F 40 730 225 34 M, P 40 750 218 34

In the "Comments" columns:
D = made from the dispersion,
F = freely heated,

M = made from the dry rubber mixture,
P = heated in the press.

The physical values of the vulcanized films from dispersions, which after the claimed Processes have been produced, depending on the filler content, is shown in Table 2.

Table 2

Fallen Tear Tear Tear on Silica strain strength strength Parts by weight Vd kg / cm ² kg / cm 20th 800 160 31 30th 750 210 38 40 730 225 34 50 670 200 30th 60 670 187 33 70 650 170 31 80 600 150 34

Example 2

Dispersions whose composition was that given in Example 1 were prepared Dispersion with 40% precipitated silica corresponded, but also additionally varying amounts Contained chalk in the disperse phase. The rubber technology obtained under the same test conditions Values and a comparative value for a silica precipitated from the dry 40 parts and The vulcanizate produced by 60 parts of the rubber mixture containing chalk is shown in Table 3 below summarized.

chalk Table 3 Tensile strength Tear strength Remarks Teüe Elongation at break kg / cm ² kg / cm (see table 1) filler
precipitated silica 20th Vo 182 37 D ₅ F Parts 40 617 156 34 D, F 40 60 653 130 34 D ₅ F 40 60 620 148 26th M ₅ P 40 640 40

Example 3

The following rubber mixture was applied to a mixing roller at a roller temperature of 60 to 80.degree manufactured:

100 parts natural rubber,
40 parts of fumed silica,

2 parts of stearic acid,

3 parts triethanolamine,

2 parts light protection agent based on paraffin.

IO

In this mixture were at 60 ° C in one Internal mixer 3 parts of potassium oleate, 2 parts of potassium hydroxide as a 40% aqueous solution and 2 and 5 parts of polyammonium acrylate, as a 20% strength aqueous source ling, incorporated homogeneously. Then was under further action of shear forces, water is slowly added in small portions until the phase is reversed and the dispersion is adjusted to a solids content of 50% with water.

Before the test films were produced, the following vulcanizing agents were added to the dispersions in the form added to a 50% aqueous paste:

1.0 part zinc oxide,

1.0 part zinc diethyl dithiocarbamate, ^a5

0.2 parts of zinc mercaptobenzothiazole,

1.5 parts sulfur.

The test films produced as in Example 1 were vulcanized for 20 minutes at 100 ° C. The rubber-technical Table 4 shows the values.

Tabel 4th Tear on
strength
kg / cm Polyanimonium
acrylate
Parts by weight Tear
strain
Ό Tear
strength
kg / cm ² 49
30th 2
5 600
450 232
127

Table 4 shows that the increase in the amount of protective colloid from 2 to 5 parts, based on the disperse phase, leads to a considerable deterioration in the rubber properties. It is therefore It is important to keep the protective colloid content as low as possible.

The grinding of the vulcanizing agents was carried out by grinding the substances in the specified for 48 hours Ratio together with the same parts by weight of water containing 2% of a wetting agent in one Ball mill received. Polyalkylene oxide derivatives or alkylnaphthalene sulfonates are preferably used as wetting agents.

Example 4

As described in Example 1, a dispersion of the following composition was prepared:

66.7 parts natural rubber,

33.3 parts of butadiene-styrene rubber (styrene

content: 30%),

25.0 parts of precipitated silica,
30.0 parts of precipitated aluminum silicate,
1.0 part potassium salt of rosin,
1.0 part of Ä- (Na-sulfonyl) -bis- (ethylhexyl) -bern-

stinic acid,
6.0 parts of morpholine,

1.0 part polyacrylamide, as 10% aqueous

Swelling,

1.0 part zinc oxide active,
1.0 part zinc diethyl dithiocarbamate,
0.2 parts of zinc mercaptobenzothiazole,
1.5 parts sulfur.

It was adjusted to a dry content of 50% with water.

The 20 minutes at 100 ⁰ C in hot air vulcanized Prüffilme showed the following mechanical rubber values:

Elongation at break,% 520

Tensile strength, kg / cm ² 144

Tear strength, kg / cm 20

Example 5

90 parts of natural rubber and 10 parts of high-pressure polyethylene were ^{mixed homogeneously at 120 °} C. on the roller. C were homogeneously incorporated into this mixture at a roll temperature of 60 to 8O ^0:

35 parts of precipitated silica,
3 parts triethanolamine,
2 parts of stearic acid,
1.0 part zinc oxide active,
1.0 part zinc diethyl dithiocarbamate,
0.2 parts of zinc mercaptobenzothiazole.

Then the following were added to a screw mixer with the further action of shear forces:

2 parts of nonylphenyldecaethylene glycol ether,

2 parts of potassium hydroxide, as a 40% aqueous solution,
1.0 part polyacrylamide, as 10% aqueous

Swelling.

Then water was incorporated in small portions and the resulting dispersion in one Set solids content of 50%.

Before the test films were produced, the

Dispersion 1.5 parts of sulfur in the form of a 50% aqueous paste was added and the Prüffilme as prepared in Example 1 vulcanized 30 minutes at 100 ⁰ C. They had the following technical rubber values:

Elongation at Break,% 570

Tensile strength, kg / cm ² 180

Tear strength, kg / cm 48

Example 6

In a homogeneous mixture of 50 parts

Natural rubber and 50 parts of butadiene-styrene copolymer (Styrene content: 70%) were the following substances at a roller temperature of 60 to 80 ° C homogeneously distributed:

30 parts of precipitated silica,
1.0 part of stearic acid,

2 parts triethanolamine,
1 part octadecenyl sulfuric acid ester,
1 part sodium tetrapropylene benzene sulfonate,
5 parts of morpholine,

5 parts of polyammonium acrylate, as a 20% aqueous swelling.

Then, with continued exposure to shear, an internal paddle mixer slowed

509 779/444

Water was added in small portions until the phase reversed and the dispersion with water to one Solids content of 50 ° / "set.

Before the preparation of the dispersion Prüffilme the following vulcanizing agent in the form of a 50 ° / ₀ aqueous paste was added:

1 part zinc diethyl dithiocarbamate,

1 part sulfur,

1 part zinc oxide active.

IO

The test films vulcanized in hot air at 100 ° C for 20 minutes showed the following rubber properties:

Elongation at break,% 330

Tensile Strength, kg / cm ² 78.5

Example 7

As described in Example 6, a dispersion of the following composition was prepared:

70 parts natural rubber,
30 parts of polyvinyl acetate,
40 parts of precipitated silica,

1.0 part stearic acid,

2 parts triethanolamine,

2 parts of the salt of a naphthalenesulfonic acid condensation product,

5 parts of morpholine,

5 parts polyammonium than 20 ° / ₀ sodium
aqueous swelling.

The dry content was adjusted to 50% with water.

Before the preparation of the dispersion Prüffilme the following vulcanizing agent in the form of a 50 ° / ₀ aqueous paste was added:

1.4 parts of zinc diethyl dithiocarbamate,
1.4 parts sulfur,
1.4 parts of zinc oxide.

The 20 minutes at 100 ⁰ C in hot air vulcanized test movies showed the following mechanical rubber values:

Elongation at break, ° / ₀ 350

Tensile Strength, kg / cm ² 60

Claims (1)

Claim: Process for the preparation of aqueous rubber dispersions by dispersing a solid Rubber mixture, the fillers, wetting agents, alkaline substances and protective colloids as well as optionally vulcanizing agents and other rubber auxiliaries, in water below Application of shear forces, but without the use of organic solvents, thereby characterized that solid mixtures are used, the natural rubber and optionally up to 50 percent by weight synthetic rubber and / or thermoplastic Polymers, based on the mixture of polymers, and light-colored reinforcing fillers as fillers and also, as protective colloids, water-soluble or water-swellable salts of polyacrylic acid or contain water-soluble or water-swellable polyacrylic acid amide. 35 Publications considered:
German Patent No. 854 573;
Austrian Patent No. 120 863;
British Patent No. 538 505. 509 779/444 1.66 Q Bundesdruckerei Berlin