DE1806194B2 - Process for the pressureless curing of ethylene polymers - Google Patents

Description

bare mass before the hardening process a vacuum hardening is possible, even without use is subjected to kuum treatment. a desiccant at atmospheric pressure or 7. Application of the method according to claim 1 45 including practically pore-free shaped bodies or cables 6 to produce an insulated electrical coating. The cable covers show the

Cable, characterized in that the hardenable mass is applied around an electrical conductor and is cured.

The present invention relates to a process for pressureless curing of ethylene polymers for the production of pore-free moldings and cable covers.

The freedom from pores of the hardened insulating coating of extreme importance for the required dielectric strength.

To produce such pore-free moldings, it has hitherto been customary ^{to harden at relatively high pressures (about 14 to 17.5 kg / cm a} or more) using steam. The magazine "Modem Plastics", February 1967, pp. 91 to 93 and 169 to 172, does not say anything else in this regard. Such hardening at relatively high pressure, however, is necessary because of the dielectric strength required for this, also for high voltage loads. Based on the state of the art, it was not to be expected that with such a

So multiple process pressureless pore-free moldings and Cable covers can be made.

The invention is explained in more detail below with reference to the drawing, with advantageous Embodiments of the method according to the invention result. The terms used "Wire" and "cable" have been used synonymously for insulated electrical conductors. In detail shows F i g. 1 shows a schematic view of an apparatus for carrying out the method according to the invention in elevation and

F i g. 2 to 10 photomicrographs (with 7x magnification) of typical cross-sections of those according to the invention cured masses which have been prepared according to the following examples.

The insulation compound is mixed together in a Banbury mixer labeled 10 and arrives then into a mill 11, where it is rolled out for further processing. The mass will then

fed from a container from an extruder, and For this purpose, the rolled mass is usually granulated or pelletized at 12 and in this Mold used as extruder feedstock. As will be explained in detail below, can the mineral filler can be pretreated with the organosilane by adding the silane to the filler intimately mixed in and then the pretreated filler is added to the Banbury mixing operation, or else the The filler and the organosilane are added separately to the Banbury mixer for treatment of the filler takes place. The mass is then fed to a conventional wire wrapping machine 14. A metallic conductor 16 passes from a wire roll 18 through the extruder where the polymer compound is extruded and an insulation coating "juf the head forms.

When exiting the extruder, the insulated wire 19 passes through an elongated tube 20, which is a heat-transferring medium 22, for example an organic liquid and which continues with suitable valves or drainage devices 23 is provided. The heat transfer medium is on maintained at an elevated temperature sufficient to substantially cure the polymer in place to effect. The temperature required depends primarily on such factors as that The type of polymer compound, the heat transfer medium and the curing agent used. The length of the tube 20 and the speed of passage through this tube should be sufficient Allow residence time of the product 19 in the heat-transferring medium to a large extent To effect curing of the polymer, and they can be easily determined by those skilled in the art. The tube 20 is for example by an electrical heating coil (not shown) or by other suitable means heated. Of course, other devices, for example a tub, can also be used as the hardening bath or a tank, may be used in place of the tube 20. However, it has been found that a tubular Device a convenient and practical means for use in the manufacture of wire and Cable represents, which requires little equipment and little heat transfer medium requires.

The tube 20 ends in a housing 24, which is preferably provided with an exhaustor 28 Flue pipe 26 communicates with the atmosphere. In the housing 24 is also located a reel 30, and the cable passes from the tube 20 via the reel into an elongated cooling tube 32, which is kept at a sufficiently low temperature to cool the insulated wire. In general, it is sufficient to keep the cooling tube at room temperature and to use the exhaustor 28 in the Countercurrent to the cable to suck air through the tube. If desired, you can of course other means of cooling the cable can also be used. For example, the tube can be equipped with a cooling jacket be provided and a coolant can be passed through this cooling jacket, or the cooling tubes may contain a liquid which is kept at the desired low temperature. Of course A tub or a tank can also be used in place of the cooling tubes 32. One in the tube 32 attached collecting container 34 is used to any. Liquids coming from the cable and have been transported out of the tube for 20 mh. The product obtained is then on the Reel 36, which is provided with a guide mechanism 38, to ensure that the cable is rolled up evenly to ensure wound up.

As has already been stated above, the cable emerging from the extruder is through a heat transfer medium, which is kept at a sufficiently high temperature to a

ίο to bring about extensive hardening of the polymer, passed through. It should be noted that the heat transfer medium compared to the polymer im must be essentially inert. For example, any number of heat transferring Materials used are organic liquids, gases, molten salts and salt solutions and molten metal alloys will. According to a preferred embodiment of the invention, a polyalkylene glycol is

ao applies, which is either water-soluble or water-insoluble and has a viscosity of 50 to 90,000 Saybolt Universal seconds at 38 ° C amounts to. Other suitable organic liquids are glycerine and its esters and propylene glycol and its ester. Suitable gaseous heat transfer materials are air, carbon dioxide and Nitrogen, which at the curing temperature is essentially free of water vapor and opposed to the polymer are practically inert. The gaseous heat transfer medium, which can be preheated, is preferably passed through the curing tube or chamber in countercurrent to the insulated conductor, and curing is carried out practically at atmospheric pressure.

According to the invention, the hardenable composition contains an ethylene-containing polymer, a hardening agent and a mineral filler that has been treated with an organosilane compound. Farther Will usually also add certain additives to the polymer mix mixed together. These blend additives can contain antioxidants, such as polymerized Trimethyldihydroquinoline, a lubricant such as calcium stearate, to prevent sticking together during processing, a non-flammable one Agents such as antimony oxide and a halogenated compound to increase flame resistance Coagenz, such as polybutadiene, to facilitate crosslinking and a small amount of pigment or Contain dye. The mix additives can

vary so considerably, and so may others than those already mentioned, depending on the properties desired in the end product.

If desired, polyethylene can be used alone or in conjunction with one or more other poly

mers can be used. However, this largely depends on the requirements placed on the end product away. The ethylene-containing component can be polyethylene, which with other polymers and Copolymers of ethylene and other polymerizing

material is blended. Suitable copolymers of ethylene are ethylene-propylene copolymers, ethylene-propylene-diene terpolymers and Ethylene vinyl acetate. The amount of ethylene used in the copolymer changes the properties

shafts of the end product and can therefore be varied to achieve the desired results. A typical copolymer of ethylene and propylene contains about 50 mole percent of each ingredient,

5 6

and a copolymer of ethylene vinyl acetate contains depending on the desired properties of the

about 72 to 95 weight percent ethylene, and the remainder of the end product can be varied. The filler content

is vinyl acetate. is 25 to 60 percent by weight of the mass and

The polyethylene or the copolymer of the poly- preferably 30 to 50 percent by weight,

Ethylene can be mixed with a chlorine-containing polymer such as 5 The mineral filler is mixed with an organic

chlorinated polyethylene, chlorosulfonated polyethylene, preferably the alkylalkoxysilanes, in which the

len and polyvinyl chloride be blended around the alkyl group has at least 2 carbon atoms

Increase the flame resistance of the mass. It is treated on and the vinylalkdxysilanes. It was

known that the flame retardant properties surprisingly found that a mass that

the polyethylene masses by using a chlorine-io a mineral treated with an organosilane

containing polymers can be enlarged. The filler contained and according to the invention

Masses can contain up to about 15 percent by weight of chlorine, the process had been hardened, a significantly larger

based on the total weight of all present ßere density (less porous) than the same

Polymers. A higher chlorine content can result in a mass that contained a filler that was not compatible with a

adversely affecting the mass by treating a porous organosilane compound. White

Froduct is formed. The chlorine-containing polymer was subsequently found that the invention with regard to

rthiiv seen more expensive than the polyethylene, and therefore borrowed the mineral filler is selective and that

it is advisable to use a low chlorine content, carbon black fillers that are pretreated in the same way and

which are just mixed in with a sufficient flame resistance result in a hardened product,

speed guaranteed, so that the hardened mass which is relatively porous and as an insulating material is not

the end product is suitable for the requirements set. It should be noted, however, that small amounts

Flicker resistance met. The tensile strength of the final carbon black can be added to the mass as a color pigment

Product is generally increased by a can and that in such a case the soot in

Proportion of the unchlorinated polymer or copolymer in an amount of 2 to 7 parts per 100 parts of the poly

elevated. However, at least a chlorine content of 25 mers is added. The filler is 0.15 to

2 percent by weight, based on all polymer components, 4 percent by weight of an organosilane and preferably

nents, used to achieve the desired flame retardancy, 0.5 to 3 percent by weight. An over-

to give the product its ability to perform. The shot of the organosilane obviously acts as a soft

The proportions of the individual ingredients can thus be internal to the tensile strength and electrical strength

half of the set limits can be varied to reduce the properties of the hardened mass and

the mechanical required for an insulation compound continues to result in a porous product and from this

To meet properties and performance characteristics. Basically should be avoided. Suitable silanes

A suitable mineral filler, ethyl-triäthoxysilan, N-hexyl-triäthoxysilan, is added to the insulation mass, which provides the mass with the necessary dodecyl-trimethoxysilane, "-Methacryloxypropyltridigen strength, which is necessary for the processing of the 35 methoxysilane and amyl-triäthoxysilan the Vi cable is necessary so that it retains its structure during the vinylsilanes, for example vinyl-tri- (2-methoxyethoxy) processing. With those in the silane, vinyl-trimethoxysilane and vinyl-triäthoxysilan. The mixing process is carried out in a temperature range around those generally used for polymer compounds, which is high enough to keep the mixture of fillers such as aluminum silicate, aluminum oxide, 40 sufficiently plastic for processing, calcium silicate, silicon dioxide, magnesium silicate, However, the titre is below the reaction temperature or the tandioxide and mixtures thereof. If the filler decomposes temperature of the hardening agent, certain inert impurities, for example that the hardening agent is contained during normal metal oxides, which up to 5 percent by weight of the mixing process do not yet decompose and can thus make up part of the filler. Such Füllmate- 45 or initially a hardening of the polyethylene rialien are well known and brought about on the market. The hardening agent used is easily available for the purpose. The type of filler used, an organic peroxide, such as a tertiary peroxide, depends largely on the desired properties of the oxide, which is formed by at least one structural unit
of the end product and can easily be ς q
to be determined. The titanium dioxide filler has 50 ι ι

A particle size of 0.2 to P i, ~ _ '

0.4 microns (the diameter is used) and a · r

specifi xh: s C e blows from 3.9 to 4.1. The other filling ''

materials are typically calcined to * - C

the moisture content is marked to less than 0.5 weight ₅₅ and that is at a temperatui

percent, and generally have decomposed above 135 ° C. The use of suchei

they have a particle size on the order of peroxide curing agent to effect a ver

2 microns in diameter and a specific gravity wetting of polymers such as polyethylene compounds

from 2.5 to 2.8. However, it is also applicable in U.S. Patents 3,079,370 and 2,888,424

a magnesium silicate filler having a flake 60 3,086,966 and 3,214,422 is described. The master

like structure, a particle size of no longer preferred and commonly used peroxydher

than 6 microns and expediently a specific medium is the di - «- comyl peroxide.

Surface zone from 18 to 20 m »/ g. the after the bare curing agents include the tert. Diperoxides

BET gas adsorption method has been determined, such as 2,5-dimethyl-2,5- (t.-butylperoxydVhexan 2,5-di-

and a specific gravity of 2.7 to 2.8. S ₅ methyl-2,5- (t-butylperoxy) -hexyne-3 rad like Di

The function of these fillers in polymeric isoloperoxy compounds.

tion masses is well known, and the amount of Peroxyhärtungsinmittel!

The fillers incorporated in the mass can depend largely on the desired mechanical properties

des, old or-

the is -de die en th raw ier eihtaß nd; n, ht en en in

h-: n id m ne n, rii-> n. ch ig a,; r ο η 1- IS C-Γ-

Properties, such as tensile strength, in the cured product. A range from 0.5 to 10 parts by weight of peroxide per 100 parts of polymer meets most requirements, and the usual one The proportion is in the order of 2 to 4 parts peroxide. In a typical procedure where a tertiary peroxide is used as a curing agent, mixing together at a temperature of about 93 to 135 ° C. If the Consistent Procedure avoids an aqueous environment and curing is carried out in the absence of elevated pressure, such an isolated one Sodium cables are manufactured.

According to a further embodiment of the present invention, the hardenable composition can before Hardening process are subjected to a vacuum treatment, for. B. the extruder can be equipped with a venting device be provided and vacuum to the

mix at a much higher temperature io cylinder liner of the extruder, if occurs, the peroxide decomposes and thereby causes the mass to become liquid or plasticized and of

the cylinder worm is pressed through the cylinder liner. If necessary, the mixture can also be fed to the extruder from a storage container kept under vacuum. Carrying out this operation under vacuum has proven particularly advantageous in order to obtain a relatively tight product.
The following examples serve to further

curing at least a portion of the polymer prematurely. As a result, the mass is difficult to process, and the final product has an irregular or rough surface.

Apart from the fact that economic advantages are achieved by avoiding high pressure during curing, there is another one
Significant advantage that the present invention makes it possible to conduct cables with a sodium conductor, which is made by a chemically crosslinked polyolefin.

is isolated. A cable of this type and the example 1 bis η

Manufacturing processes are in the own FR-PS In Examples 1 to 15, the masses were after

1 561 864 described and claimed. It is without conventional mixing methods according to the in dei It is further evident that such a cable was not manufactured in the recipes listed in Table I. The in dei can be cured under steam pressure, since the quantities listed in the table represent each component

nent parts by weight. The masses were then formed into sheets of 29 cm ² with a thickness of about 0.1905 cm. The plates were then cured by 2 minuter immersion in polyalkylene glycol having Einei temperature of 200 ⁰ C. The polyalkylene glycol had a viscosity in Saybolt-Universal seconds of 300. The hardened products were

Working with sodium in an aqueous or steam-containing one Atmosphere is extremely dangerous. In addition, sodium is at the temperatures which are used for the manufacture and hardening of the cable, liquid, and as the insulation layer when it exits the extruder and enters the curing oven, it is in the plastic state the high amount used in the hardening furnace would reduce the degree of hardening due to toluene extraction

Pressure to pinch the walls of the cable together and test it out. A 2 g sample was used in accordance with de: the sodium out of its insulating jacket - test specification ASTM D-297 durcl for 16 hours to squeeze. However, because the toluene boiling point of the invention is extracted.

Table I.
Recipes and toluene extracts

Polyethylene

Ethylene vinyl acetate copolymer

(6 percent by weight vinyl acetate) ........

Poh merized trimethyldihydroquinoline

(Antioxidant)

Γ ΐ-.Λ-cumyl peroxide (90% active)

2 5-Dimethyl-2,5-di- (t-butyl-peroxy) -hexane

(50 / "active)

2,5-dimethyl-2,5-di- (t-butylperoxy) -hexyne-3

(90% active)

Aluminum silicate (calcined)

Magnesium silicate

Hydrated aluminum silicate

Precipitated hydrated silica aluminum silicate, pretreated with

Vinyl suan

Titanium dioxide (pyrolytic process)

Vinyl-trisH (2-methoxy-ethoxy-silane)

Vinyltriethoxysilane

Ethyltriethoxysilane

N-hexyl-trimethoxysilane

Dodecyltrimethoxysilane

"-Methacryloxypropyhrimethoxysilane

Amyltriathoxysilane

Toluene extract (% by mass)

2 3 example 5 δ 1 100 4th 100 100 100 100 100 1
3.5 1
3.5 1
3.5 1.75
3.55 1
3.5 50 50 1
3.5 50 50 1.5 1.5 50 1.5 115
3.45 1.5 6.8 11.9 1.5 14th 11.5 10.8 11.4

100

Table I Recipes and Toluene Extracts (continued)

10

S. 9 10 Ex
11th el
12th 13th 14 I. 100 100 100 100 100 100 100 1 1 1
3.5 1
3.5 1
3.5 1
3.5 1
3.5 6.77 3.34 50 50 50 50 50 50 50 1.5 1.5 1.5 1.5 1.5 1.5 1.5 13.0 15.4 10.5 12.9 14.1 12.4 13th

Polyethylene

Ethylene vinyl acetate copolymer

(6 percent by weight vinyl acetate)

Polymerized trimethyldihydroquinoline

(Antioxidant)

Di-A-cumyl peroxide (90% active)

2,5-dimethyl-2,5-di- (t-butyl-peroxy) -hexane

(50% active)

2,5-dimethyl-2,5-di- (t-butylperoxy) -hexyne-3

(90% active)

Aluminum silicate (calcined)

Magnesium silicate

Hydrated aluminum silicate

Precipitated hydrated silica. Aluminum silicate, pretreated with

Vinyl silane

Titanium dioxide (pyrolytic ^ process) ....

Vinyl-tris- (2-methoxy-ethoxy-silane)

Vinylträthoysilan

Ethyl triethylsilane

N-hexyl-t m thoxysilane

Dodeyltrimethoxysilane

a-Mc h r 'loxypropyltrimethoxysilane ....

Amytriä h) xysilane

Toluene extract (% by mass)

100

50

11.2

In Example 7, the mineral filler was pretreated with a vinylsilane compound and the pretreated one Banbury mix operation filler has been added. Likewise, in Example 7, the sample was initially subjected to a vacuum treatment of about 711 mm Hg for one hour and then as above hardened as described. In all of the other examples above, the filler and the Organosilane compound added separately to the mixing operation.

The toluene extracts show that the polymer compared to conventional steam curing processes was cured to a relatively high degree. These conventional steam curing processes gave toluene extracts in the range of about 6 to 15 degrees.

All samples were visually checked for porosity, and they were found to have little or no porosity and therefore as insulation were useful for wires and cables. This property is clear from FIGS. 2 and 3 can be seen, the Present microphotographs of Examples 1 and 2. To better explain the problem of porosity and also better express the fact that the invention is selective for the mineral fillers treated and is not for carbon black fillers, three compositions were mixed together according to the following recipes :

Table II

Polyethylene

Polymerized
Trimethyldihydro

quinoline

Soot ]

Aluminum silicate ....
Di - \ - cumyl peroxide ..
Vinyltri- <2-methoxy-

ethoxy) silane

Toiuolextrakt (° ₀ der
Link)

Example 17

100

3.5

11.6

100

1 40

2.2

24.6

100

40

23.1

6 <? The sample plates of these masses were in the same Hardened in the same manner as in the preceding examples in the polyalkylene glycol mentioned. Example 16 is a control sample for mineral fillers that are not with Organosilane were treated. Example 17 is a

6s control sample for carbon black filler that does not match the Organosilane was treated and Example 18 contained a pre-treated carbon black filler. The microphotographs of FIG. 4, 5 and 6, each corresponding to the

play 16, 17 and 18, show that these samples are relatively porous and therefore used as insulation for wires and cables were not suitable.

Example 19

An ethylene propylene copolymer with about 40 to weight percent ethylene (about 50 mol percent ethylene) and a 40 Mooney ML value at 100 ^° C. was mixed together in a Banbury mixer according to the following recipe:

Ethylene propylene copolymer 100

Polymerized trimethyldihydro-

quinoline 2

Zinc oxide 3

PbO ₂ 2

Buton 150 (Coagenz) 5

Aluminum silicate 100

Flexon 865 (processing aid) .. 5

Vinyl tri- (2-methoxy-ethoxysilane) 1.5

Di-a-cumyl peroxide (90% active) 3

Toluene extract (% of compound) 10.6

A plate made from this mass was cured as in the previous examples, and the cured Product turned out to be relatively tight and therefore suitable for use as an insulation material. This works out also clearly from FIG. 7 emerges.

Example 20

An isolation wedge was made according to the following Recipe made using traditional mixing methods in a Banbury mixer:

Ethylene vinyl acetate copolymer 91.6

Chlorinated polyethylene

(43V ₂ + 2% CI ₂ ) 8.4

Calcium stearate 0.9

Magnesium silicate 72.5

Vinyltri- (2-methoxy-ethoxy) -silane .... 0.9

Dibasic lead phthalate 2.8

Thermax black (color pigment) 3.7

Polymerized trimethyldihydro-

quinoline 1.5

Di-nt-cumyl peroxide (90% active) 4.5

Toluene extract (% of compound) ... 11.2

The mixed mass was pressed with a wall thickness of 0.397 mm onto a twisted conductor with a diameter of about 1 mm and cured in the polyalkylene glycol liquid described above at about 190 ^° C. for 1.5 minutes. The cured insulation compound proved to be relatively dense (non-porous) and therefore as i llation suitable.

Example 21

Using a conventional mixing technique, an insulation compound was made in a Banbury mixer according to the following recipe. The quantities given are percentages by weight:

Polyethylene 61.80

Aluminum silicate 30.90

Vinyl tri- (2-methoxy-ethoxy) -silane .... 0.93

Di-a-cumyl peroxide (90% active) 2.20

Carbon black (pigment) 3.09

Polymerized trimethyldihydro-

quinoline 1.08

The mass was at about 132 ° C at a rate of about 0.9 to 1.5 meters per minute extruded while at the same time the extruded tube was filled with liquid sodium. The extruded The cable had an outside diameter of about 1.97 cm and a wall thickness of the insulation of about 0.44 cm.

After exiting the extruder, the cable was passed through a 9 m long tube and by means of an electrical heating coil to a temperature between about 163 and 204 ° C. The tube was with filled with a polyalkylene glycol, which had a viscosity of 300 or 280 Sebolt Universal seconds.

The cable was then passed through an air-cooled tube approximately 9 m in length to feed the cable cool and solidify the sodium.

Examples 22 to 24

Masses were produced according to the recipe described in Example 1. Plate samples were distributed in a tube heated by an electric coil and provided with an opening in the bottom. Gas was introduced into this ^{tube, which was kept at 200 °} C., and the samples were kept in the tube for 4 minutes. The cured samples were found to be tight, and the gases used as the heat exchange medium and the degree of cure were as follows:

example gas Toluene extract
CV _{0 of} the mass) 22nd
23
24 air
Carbon dioxide
nitrogen 22.5
16.9
11.8

The cured products were relatively dense, which is clear from Figs. 8, 9 and 10 of Examples 22, 23 and 24, respectively.

From the above description and examples it can be seen that according to the present invention Invention, while avoiding a high-pressure hardening system, a relatively dense product is obtained which is particularly useful as an insulation material for wires and cables.

For this purpose 2 sheets of drawings

Claims (6)

Patent claims: 1. Process for the pressureless curing of ethylene polymers for the production of pore-free Moldings and cable covers, thereby characterized in that from a) customary ethylene homopolymers or copolymers or mixtures of these polymers with other polymers of the mass equipment and monitoring expensive and has especially with regard to the application van Steam has the further disadvantage that, for. B. cables with sodium conductors because of its responsiveness not damii can be hardened. The invention was therefore based on the object of providing a process for the pressureless curing of ethylene polymers to create that leads to pore-free moldings and cable covers. The one with one optionally impart flame resistance, io difficulties associated with the process b) 0.5 to 10 parts by weight, based on 100 Ge Avoid the in the to be vulcanized parts by weight polymer, usual peroxides and mixture contained air and moisture conditioned c) 25 to 60 percent by weight, based on the porosity, result from the publication Mass, one with 0.15 to 4 percent by weight from Bayer-Werke »Vulkanisation und Vulkanisationseines Organosilans treated mineral 15 auxiliaries «in which this issue in particular The filler mentioned on pages 78 and 79 is mentioned. The solution mentioned in this publication is to use a Desiccant. However, such desiccants are not always desirable in insulating cable covers. The invention was therefore based on the further task e, a method for pressureless hardening for Production of pore-free moldings without the use of a drying agent. According to the present invention, the a hemogenic mass is produced and this Mass at at most atmospheric pressure by an essentially inert, non-aqueous, heat-transferring Medium is passed through, which is sufficient on one for the hardening of the mass high temperature is maintained. 2. The method according to claim 1, characterized in that the ethylene-containing polymer is a Polyethylene, an ethylene-propylene copolymer 25 named tasks achieved by the fact that in a ver or an ethylene vinyl acetate copolymer. drive out of the type mentioned at the beginning a) customary ethylene homopolymers or copolymers or mixtures of these polymers with 3. The method according to claim 1 or 2, characterized in that the mineral filler Aluminum silicate, calcium silicate, magnesium silicate, silicon dioxide, aluminum oxide or titanium dioxide is. 4. The method according to any one of claims 1 to 3, characterized in that the organosilane compound is an alkylalkoxysilane in which the alkyl group has at least 2 carbon atoms, or a vinylalkoxysilane. 5. The method according to any one of the preceding claims, characterized in that the heat transfer medium is a polyalkylene glycol. 6. The method according to any one of the preceding claims, characterized in that the hard other Polymers, if necessary, of the mass Impart flame resistance, b) 0.5 to 10 parts by weight, based on 100 parts by weight of polymer, conventional peroxides and c) 25 to 60 percent by weight, based on the mass, of one with 0.15 to 4 percent by weight of an organosilane treated mineral filler a homogeneous mass is produced and this mass is passed at atmospheric pressure at most through an essentially inert, non-aqueous, heat-transferring medium which is kept at a temperature sufficiently high for the hardening of the mass.
With this inventive method for