CA1185054A - Resorcinol-filler preparation, process for producing same and its use - Google Patents

Abstract

ABSTRACT OF THE DISCLSOURE
The preparation according to the invention comprises resorcinol and at least one carbon black in homogeneous dis-tribution. The preparation is preferably in the form of beads or granulates. The preferred granular form is attained when the resorcinol has an average particle size of 0.10 to 0.40 mm or is reduced to this average particle size during the pro-duction process. Furnace blacks having a specific particle surface area of approximately 40 to 120 square metres per gram, an average primary particle size of 20 to 45 nm and a dibutyl phthalate absorption of 45 to 130 millilitres per 100 grams are preferred as carbon blacks. The preparation according to the invention preferably has a weight ratio of carbon black to resorcin between 70 to 30 and 30 to 70. The upper limit of this weight ratio is 95 to 5. The process for producing the resorcin-filler preparation in which carbon black is put into a mixer capable of high-speed performance and provided with a heating device, and when required with a cooling device, as well as with a propeller-type or rough mixing tool, resorcinol is liquefied by heating, the liquid resorcinol is fed into the fast running, heated mixer in batches or continuously, the step for forming the preparation is thus initiated, continued and completed until beads are formed and the beads are cooled or allowed to cool in the running mixer until they are free from tackiness.

Description

f(354 The ~esent lnvention relate~ to a reso~cinol in filler pXepa~ations useful in rubbe~ adhesion ~ixtures for the better adhesion o~ ~ubber yulcani~ates to metal textile or glass ~ibxe structures.
In particular the ~resent invention relates to a process for the production of such a preparation.
This application is a divisional application of copending application No. 369,997, filed February 3, 1981.
It is known that to improve the stability of vulcani-zed moulded rubber articles, as ~or example, tires, conveyorbelts, V belts and hoses against mechanical deformation, they are reinforced with inserts. These composite articles have inserts of textile fibres or textile fibre structures such as fabrics or fleeces, or metal wires or metal wire structures, as for example, steel cord, which can also have coatings of brass, zinc or the like. Glass fibres or glass fibre struc-tures have also been used as insert materials.
The rigid anchoring or adhesion of the insert material to the rubber vulcanizates is important so that a long service life of the dynamically stressed moulded articles is attained. Thus, it is known that in order to attain a high degree of adhesion, the filler carbon black in the rubber mixtures partially replaced by a silica filler (see German Patent No. 1,620,786). As is known, the adhesion can be further improved substantially by adding components capable of forming synthetic resin, such as phenol and/or amines and al-dehydes or compounds splitting off aldehydes, to the rubber nuxtures. Resorcinol and hexamethylene, tetramine (see British Patent No. 801,928 and French Patent No. 1,021,959), when~ required in combination with a silica filler (see German Auslegeschrift No. 1,078,320) are in wide-spread use as resin-forming co~ponents in rubber adhesion muxtures.
Because of its poox dispe~sibility resorcinol is ~ ~S~5~
difficult to process in rubber adhesion mixtures Therefore, more readil~ dispe~sible mixtures of resorcinol with a silica filler (see German Patent No. 1,031,478~, as for example the product supplied under the trademark Cofill II by DEG~SA, which is a 1:1 mixture of resorcinol and a specific silica filler, are used in most cases. In fact, the resorcinol, which usually is in the form of lumps or platelets, is homo-geneously distributed in this product. However, this product also has disadvantages. Thus, for example, when using it an undesirable dust formation can result.
The mixture also reduces the tendency of the re-sorcinol to sublime out of the rubber mixture at the usual processing temperatures only slightly or not at all so that dust extraction plants are required to keep the ambient air clean. Moreover, easy dosability and fluidity of the powdered product leave a lot to be desired.
The present invention provides as disclosed and claimed in copending application No. 369,997 a resorcinol-containing preparation which is homogeneously distributed, readily fluid and dosable, and which preferably does not form dust on being weighed; and mixed in and is well dispersible in rubber mixtures and whose resorcinol component shows reduced sublimation, without impairing the quality of rubber articles produced with these preparations, i.e., particularly that neither their rubber-technological properties nor their good adhesion properties between insert or coating and vulcanizate are reduced.
According to the present invention as disclosed and claimed in copending application No. 369,997 there is provided a resorcin-filler preparation which comprises resorcinol and at least one carbon black in homogeneous distribution.
In one embodiment of the present invention the 5~
carbon black is a furnace black having a specific particle surface area of approximately 120 square metres per yram, as measured by nitrogen adsorption (DIN 66132), and electron-microScopically determined average ~rimary particle size of 20 to 45 nm and a dibutyl phthalate absorption (DIN 53601) of 45 to 130 ml, which is present in an amount of 30 to 70 parts by weight per 70 to 30 parts by weight of resorcinol made up to 100 in each case.
~n another embodiment of the present invention the carbon black is a furnace black which has a specific particle surface area of approximate~y 7~ to 85 square metres per gram, an electron-microscopically determined average primary par-ticle size of 24 to 30 nm and a dibutyl phthalate absorption (DIN 53601) of 110 millilitres per 100 grams, which is present in an amount of 50 parts by weight per 50 parts by weight of resorcinol.
The present invention also provides a rubber adhesion mixture for improved adhesion of rubber vulcanizates to metal, textile and glass fibre structures containing the aforesaid resorcinol in filler preparations.
The present invention further provides as disclosed and claimed in copending application No. 369,997 a process for producing the resorcinol filler preparation in which a resorcinol in the form of platelets or in a similar form and carbon black in the form of a powder are mixed in a high-speed mixer for several seconds, b) the product formed is processed in a low-speed mixer to a preparation assuming sub-stantially a bead-like structure and in order to attain the bead-like or granular structure of the preparation in the process step a) the resorcinol is reduced to an average par-ticle size of 0.10 to Q.4Q ~m or when the resorcinol is pre-sent and used as a powcle~ havin~ sa~d avera~e particle sizes 3~

only a short-term treatment in the high-speed mixer is per~
formed or only the process step b) is carried out. Suitably, step Ib~ is carried out in ~ closed cylindrical vessel having an inside diameter of approximately 2 metres and at a speed be-tween 10 and 20 r.p.m. and a residence time of 1 to 5 hours. ~lternatively, step b) is carried out in the re-volviny drum of a drying beading device.
According to the present invention of this applica-tion there is provided a process for producing a resorcin-filler preparation in which carbon black is put into a mixercapable of high-speed performance and provided with a heating device, and when required with a - 3a -3s~

coolinq device, as well as with a propeller-type or rough mixing tool, resorcinol is liquefied by heating, the liquid resorcinol is fed into the fast running, heatecl mixer in batches or continuously, the step for forming the preparation is thus initiated, continued and completed until beads are formed and the beads are cooled or allowed to cool in -the running mixer until they are free from tackiness.
Rubber adhesion mixtures and mixtures based on synthetic and/or natural rubber which contain - in addition to the usual mixture ingredients such as sulphur, accelerators, fillers, plasticizer(oil), antiagers, antioxidants, metallic oxides, stearic acid and similar known mixture ingredients, particularly the aldehydic compounds or compounds splitting off aldehydes, such as hexamethylene tetramine or paraform-aldehyde, which Eorm resins with resorcinol. It is a known fact that the adhesion mixtures are used for improved adhesion of the vulcanization products produced therefrom to metal, -textile or glass fibre structures and inserts or coatings.
While carbon black is used in powdered form for practical and economic reasons, the resorcinol can be used in various forms as described hereinbefore. It has been found that if it is desired to obtain the preparations according to the invention in the form of beads or granulates, the resorcinol must have an average particle size between approximatel~ 0~10 and 0.~0 mm or it must be reduced to these par icle sizes during the first process step referred to as a). Particle sizes smaller than approximately 0.10 mm impede or prevent the formation of beads or granulates. When the average particle sizes are larger than approximately 0.40 mm, then no homogeneous beads (in size and shape) or no corresponding granulates are ob-tained.
The particle sizes are determined by sieve analysis and the evaluation of the sieve analysis permits the average par-ticle sizes -to be computed (see ASTM D 1511-74), As mentioned hereinbefore, in a favourable embodiment the resorcinol can also be used in a liquid form, i.e., in the molten state.
The ratio by weight of carbon black to resorcinol in -the preparation according to the invention may vary within wide limlts. Thus, the upper limit of this ratio can be 95 to 5O
For practical reasons the ratio by weight of carbon black to resorcinol is preferably between 70 to 30 and 30 to 70. When required the lower limit may be fallen short of.
The ~resent lnventlon will be further illustrated by way of the following production Examples.
Example 1 The starting products characterized hereafter were used:

carbon carbon carbon silica black black black filler no. 1 no. 2 no. 3 average particle 1) diameter in nm 27 29 25 18 specific 2 surface area ) in sq.m/g 80 95 180 175 DBP number ) in ml/g 100 120 110 170 volatile 4) components 1.0 6.0 14.5 filler type furnace gas gas precipi-black black black tated silica ) average value determined electron - microscopically and with the aid of the partlcle-size analyzer TGZ3 of the firm of Zeiss.
) determined with the nitrogen adsorption method according -to DIN 66132.
3) dibutyl-phthalate adsorption according to DIN 53601.
) determined according to DIN 53552.

s~

3000 g of the carbon black no. 1 and 3000 g o~
resorcinol were mixed in a high-speed mixer at 1400 r.p.m. for five seconds. In this short-term mixing step the resorcinol which had consisted of approximately 5 x 10 mm platelets and of lumps of a similar size, was converted along with the carbon black into a homogeneous form while the resorcinol was comminuted. The average particle size thus decreased to 0.21 mm.
This mixture was then put into a so-called drying bead drum o~ cylindrical shape which had a diameter of 2 m and a length of 50 cm, and rotated therein at a speed of 12 r.p.m. for appro~imately 90 minutes. After this time a bead~like preparation (preparation I) was removed from the drum.
Further bead-like preparations were produced in the same manner always in a 1:1 mixture with resorcinol, i.e., the preparation no. II with carbon black no. 2 and the preparation no. III with carbon black no. 3. The most important properties of the preparations I to III thus produced and, for comparison, the 1:1 mixture according to the prior art (Cofill 11( ) of Degussa) have been listed herafter:

Preparation No. I II III mixture according to the prior art powder density ) in g/litre 448 440 400 260 tamping density ) in g/litre 506 484 452 338 )measured according to DIN 53600 6)determined according to DIN 53194 Sieve Analysis in Percent Preparation No. I II III
_ _ larger than 1 mm lOt4 13.2 17.8 0.7 to 1.0 mm 14.6 15.2 14.4 5'~

0.5 to 0.7 mm 14.4 16.0 16.6 0.25 to 0.5 mm 26.4 24.8 27.0 0.125 to 0~25 mm 20.0 16.8 14.0 smaller than 0.125 mm 14.2 14.0 10.2 average par-ticle size (in mm) 0.51 0.56 0.62 residue after washing out the resorcin with hot water, in percent by weight 51.4 50.7 49.3 The three preparations according to the invention have the following favourable properties. The preparations are readily fluid, dust-free granulates and have a distinctly higher powder density and tamping density. Particularly the tamping densities of the preparations according to the invention (i.e., the tamping densities corresponding to -those in practice) in the range from 450 to 500 g per litre are noticeably more favourable than those of the product according to the prior art, i.e., 338 g per litre.
The following tests were carried out to prove a further important advantage of the preparations according to the invention, namely, the decreased sublimation tendency of the resorcinol in the preparation.
~ x mple 2 10 g of each the resorcinol-filler preparations according -to the invention and of the product according to the prior art (for comparison) were weighed into a flat porcelain dish and these samples were heated for 24 hours at 8 different defined temperatures. After cooling the samples they were reweighed and the loss in weight was computed in percent. The following results for the loss in weight were thus obtained.

Loss :in Weight in ~ for sublimation preparation preparation prepartion product temperature ~ II III accord-in C i.ny to the pri-or art _ _ 0,23 0,48 0,79 1,2 0,38 0,94 1,3 1,8 0,47 1,0 1,5 1,9 0,93 1,6 2,2 2,8 1,3 2,1 2,6 3,8 100 2,5 3,6 4,5 5,3 110 3,3 4,2 5,0 7,2 150 16,8 20,2 16,8 29,4 The products according to the invention show distinctly more favourable values than the product according to the prior art. The preparation I has the lowest losses in weiyht at all the temperatures, i.e., it has the most favourable values.
Example 3 In order to exclude the effect of entrained water in the test for sublimation tendency, three preparations were once more produced from the same three kinds of carbon black in the manner described in Example 1, Elowever, these carbon blacks had been prev.iously dried at 125C. Furthermore, for comparison, a product according to the prior art was produced from the silica filler (which had also been previously dried in the same manner~ and resorcin (1:1 mi.xture). The test for sublimation was carried out at 70C. The test results again show a distinct super.iority of the preparations according to the invention:

5 ~ 5 L~

Decrease ln Sublimation in ~ercent by Weight at 70~C

preparation preparation prior art No. IV No. V 1:1 mixture 1:1 mixt~lre 1:1 mixture o-~ dried of dried of dried silica filler carbon black carbon black and No. 1 and No. 3 and resorcin resorcin resorcin _ after 24 hours 0.32 0.46 1.04 after 48 hours 0.49 0.53 1.13 after 72 hours 0.63 0.67 1.38 after 96 hours 0.99 0.96 2.02 after 168 hours 1.46 1.67 2.37 E mple 4 A further variant in the production of -the preparation according to the invention lies in that the solid resorcinol lies in the form of platelets or lumps is not used as the starting product but that the resorcinol is first liquefied by heating and according to experience the resorcinol assumes temperature of approximately 120C, whereupon 480 g of the carbon black no. 1 described in Example 1 are put into a high-speed mixer having a propeller-type mixing tool, the speed being 500 r.p.m. The heating jacket of the mixer is charged with hot water or steam of approximately lOO~C. 520 g of the liquid resorcinol are then added while the mixer is running. As the result of the intensive mixing process beads are forming while their temperatures decrease until they are no longer sticky.
After further cooling, the final product is obtained. The following properties of this product are determined by sieve analysis and by defining the powder density and the tamping density.
;o 5~

Sieve Analysis in Percent larger than 2 mm 10.8 1.0 to 2.0 mm 50.8 0.7 to 1.0 mm 20.8 0.5 to 0.71 mm 12.6 0.25 to 0.5 mm 4.6 0.125 to 0.25 mm 0.2 smaller than 0.125 mm 0.2 average particle size (in mm) 1.30 powder density (DIN 53600) 680 g/litre tamping density (DIN 53194) 780 g/litre Preparations having particularly high powder densities are obtalned in this manner. It is assumed that these high powder densities are attained because the liquid resorcin can penetrate the interstices formed by the carbon black and is fixed therein.
The production variant of this Example can also be carried out continuously. For example, carbon-black beading machines li~e t~ose described in the German Patent No. 2,147,503 can be used with advantage for this purpose.
Example 5 If the premix is ground in a drying bead drum instead of the second step of the trea~ent described in Example 1, an optimal distribu-tion of the resorcinol on the carbon black surface is obtained but the grinding causes the product to loosen up substantially and the product then has a very low and thus an unfavourable powder density.
In order to avoid this disadvan~age, the following production variant was used.
The resorcinol which was in the form of 5 x 10 mm platelets and lumps was ground in a pinned disc mill to an average particle size of 0.17 mm. The proportion of resorcinol having a --1.0--particle size smaller than 0~125 mm was 33~.
3000 g of -this finely ground resorcinol were mixed with 3000 g of carbon black no. 1 from Example 1 in a high-speed mixer. The mixing time was 7 seconds (and should generally be between 5 and 10 seconds) and the speed of the mixing tool was 1400 r.p.m. After removing this preparation from the mixer it had the following test values:
powder density 301 g/litre tamping density 375 g/litre These values of the powdered preparation according to the invention still surpass the values of the mixture according to the prior art in Example 1.
The preparations are used with technological advantages in so-called rubber adhesion mixtures, i.e., rubber mixtures which, in the vulcanized state, strongly adhere to inserts or coatings of 1) textile structures of fibres, threads, wires, yarns, fabrics, webs and the like from -textile fibres of natural or synthetic origin, 2) of metal structures and particularly of steel struc-tures or 3) of glass, particularly of silicate glass. Said fibres ) threads, wires, etc., include particularly synthetic products of polyesters, as for example, polyethylene glycol terephthalate, of polyamides, as for example, polyamide-6, polyamide-6,6, polyamide-6,10, polyamide ll and polyamide-12, also of polyamides such as polv-p-and/or m-phenylene terephthalamide or isophthalamide and of regenerated cellulose (viscose). The metal structures preferably include metal wires and particularly uncoated, brass-plated or zinc-coated steel cord.
The following Examples show the extent to which good adhesion values can be attained from rubber mixtures which had been 0 produced with the use of the preparations according to the invention.

Examples of Application A) The followin~ four rubber mixtures were produced from the mix-ture ingredients listed hereafter and were tested for adhesion. The amounts are in parts by weight. The mix-ture noO 4 is -the comparison mixture.
Ingredients Mixture No.

_ _ . _ . _ . . .. . _ _ .
natural rubberl) 30 30 30 30 polyisoprene rubber ) 70 70 70 70 stearic acid poly-2,2,4-trimethyl -1,2-dihydro-quinoline plasticizer oil, highly aromatic, cold setting point + 0C 4 4 4 4 HAF-Black N 330 ) 45 45 45 45 granulated, activated, precipitated silica filler 3) +) 15 15 15 12.5 zinc oxide 6 6 6 6 lead oxide 2 2 2 2 preparation no. I of Example 1 5 - _ _ preparation no. II of Example 1 - 5 preparation no. III of Example 1 _ - 5 mixture according to the pri+o)r art (see Example _ . - 5 benzothiazyl-2-di-cyclohexylsulphen-amide 0.7 0.7 0.7 0.7 hexamethylene tetramine containing 3P6 of SiO2 1.5 1.5 1.5 1.5 sulphur, insoluble 4 4 4 4 ) Producer: Degussa, Postfach 2644, D 6000 Frankfurt/Main 1.

3s~

) ribbed smoked sheets No. l 60 Mooney L 4 (lOO~C) con-tent of zinc-pentachloro thiophena-te 0.2 ) with a cis-1,4 content of 98-99~
3) average primary particle size 18 ~m;
specific surface area (DIN 66132) 175 sq m/g (Ultrasil ~ VN3 of Degussa) In accordance with the ASTM Standard D2229-73 the four rubber mixtures were then vulcanized and tested together with or on brass-plated steel cord. The following test conditions were chosen:
Construction of the brass-plated steel cord:
7 x 3 x 0.15 mm.
Length of embedding the steel cord in rubber: 1 cm Vulcanization temperature: 145C.
Vulcanization time: 100 minutes.
The tests were carried out with a tensile testing machine according to DIN 51221, page 3.
Rate of pulling out the steel cord (pull out test):
100 mm/minute.
The force required to pull the steel cord out of the test sample was measured and the average value of 10 measurements was determined.
The ten test readings and the average value in N/cm have been listed in the Table hereafter.
Table 1 Vulcanizate containing:
preparation preparation preparation for comparison:
I II III mixture according to the prior art _ . _ . . ._ . . ._ 390 360 340 3~0 ~ 5~S~

400 390 3~0 30n _ ~_ aver- 365 341 328 352 age value Slnce the results of this adhesion test (which is close to actual conditions) show a fairly substantialy extent of variation, it appears tha-t the vulcanizates from the rubber mixtures containing the preparations according to the invention have at leas-t equally good adhesive strengths as those according to the prior art. Insofar as a trend is concerned -the adhesion test with the preparation I shows the best values.
B) The following two rubber mixtures were produced from the 20 mixture ingredients listed hereafter and used for testing the adhesion on textile fabrics. The amounts are in parts by weight.
The mixture no. 6 is the comparison mixture.
Ingredients Mixture No.
__ natural rubber ) 50 50 na-tural rubber 2) 50 50 stearic acid 3 3 poly-2,2,4-trimethyl-1,2-dihydro quinoline 1 30 plasticizer oil, highly aromatic, cold setting point ~ 0C. 7 7 GPF Black N 660 ) 27 30 granulated activated, precipitated silica filler 3) +) 1 15 12 s~-~
zinc oxide 6 6 preparation no. I oE Example 1 6 mixture accoxding to ~he prior art (see ~xample 1) + _ 6 benzothiazyl-2-cyclohexyl sulphenamide 1 hexamethylene tetramine containing 3% of SiO2 +) 1.5 1.5 sulphur, insoluble 2.5 2.5 ) Producer: Degussa, Postfach 2644 D 6000 Frankfurt/Main 1 GPF = General Purpose Furnace (Black) ) ribbed smoked sheets no. l;
60 Mooney L 4 (100C), content of zinc pentachloro thiophenate 0.2%

brown crepe; 60 Mooney L 4 (100C);
content of zinc pentachloro thiophenate 0.2%

3) average primary particle size 18 ~Im;
specific surface area (DIN 66132) 175 sq.
m/g (Ultrasil ~ VN3 of Degussa) The two rubber mixtures were then vulcanized, in each case together with or on a fabric of polyethylene glycol teraphthalate (Trevira ~ EP) having a square metre weight of 550 g and consisting of threads having a strength (measured in dtex) of lOG x 3 in the warp and 940 x 3 in the wef~ and a thread number of 116 per 10 cm in the warp and 45 per 10 cm in the weft, in a press at a pressure of 1.4 kN per sq cm and the bond was tested for adhesion (textile adhesion test according -to DIN 53530). The fabric used was nei-ther impregnated nor treated.
In each case the separating force required to pull the fabric layer from the rubber test strip of 2.5 cm width was measured. The pull-test machine defined in DIN 51221, page 3 was used. Minimum and maxirnum values of the force readings in the individual phases of t}le separation of the fabric from the rubber were measured in N and the following values were obtained:
Table 2 Vulcanizate containing:

preparation I for comparison:
(from mixture 5) mixture according to the prior art (from mixture 6) 1. 200 3 270 180 ~ 240

2. 220 J 300 180 ~ - ~ 260 It is evident from the test results that the adhesive strengths of the fabrics on rubber show favourable values and that they are superior to those according to the prior artO
Altogether, it is evident from the examples that the preparations according to the invention result in a distinct advance in the art as compared with the prior art. This is borne out by the improved fluidity and dosability of the products according to the invention and by the fact that they do not form dust. The reduced sublimation tendency is a further important advantage. In the adhesive effect and in the rubber~technological properties at least rends towards better test values can be detected. In this respect the preferred embodiment of the preser.t invention (preparation I according to Example 1) must also be regarded as an advance in the art as compared with the prior art.
The preparations according to the invnetion are used in rubber mixtures for producing all kinds of vehicle tires, particularly pneumatictires, for retreading tires, for producing conveyor belts, technical hoses, as for example, fire hoses and compressed-air hoses, as well as rubberized fabrics, containers, shoes, camping articles, boats, V-belts and other moulded articles, all of which are composite articles of rubber and the inser-ts or coatings mentioned hereinbefore.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for producing a resorcin-filler pre-paration in which carbon black is put into a mixer capable of high-speed performance and provided with a heating device, and when required with a cooling device, as well as with a propeller-type or rough mixing tool, resorcinol is liquefied by heating, the liquid resorcinol is fed into the fast running, heated mixer in patches or continuously, the step for forming the preparation is thus initiated, continued and completed until beads are formed and the beads are cooled or allowed to cool in the running mixer until they are free from tackiness.