DE1130159B - Process for improving the adhesion of metal to rubber - Google Patents

Description

Process for improving the adhesion of metal to rubber There are known methods for improving the adhesive strength of metal to rubber, in which a vulcanizable rubber compound adheres firmly to a metal in The presence of a heavy metal salt of an organic acid is vulcanized.

These previously used fatty acid heavy metal salts or soaps but do not produce the adhesive strength of rubber on metal that many do Purposes is desired, so especially when the rubber is attached to metal wire should be to produce fabric layers in tires. In such cases it is extremely important is the bond between the rubber layer and the wire mesh is as elastic and as firm as possible to prevent premature destruction of the Tire body and breakage of the tire during use can be avoided.

It has now been found that the process mentioned is very essential can improve if the salt is partially calcined and oxidized used and when you think of it with regard to the rubber compound just a lot sufficient to secure the rubber compound to the metal. One can convert the small amount of partially calcined and oxidized salt into the vulcanizable one Introduce the rubber mixture and vulcanize it in contact with the metal surface, or you can apply the salt as a thin layer on the metal or rubber surface apply and then vulcanize the whole thing. Another method of attachment Rubber to metal consists in being a rubber adhesive or binder containing the partially calcined and oxidized salt, the Metal or rubber surface coated with the adhesive, this optionally is dried, metal and rubber with the adhesive layer in between. are brought into contact and the whole is vulcanized.

The metal atom in the organic salt can be any metal. Preferred but the polyvalent heavy metals such as cobalt, copper, iron, lead, mercury and nickel. The heavy metal salts of aliphatic fatty acids are particularly suitable and especially those with few carbon atoms. Mixtures of salts can also be used to be used. Examples of such heavy metal salts are: cobalt acetate, cobalt benzoate, Cobalt butyrate, cobalt citrate, cobalt formate, cobalt oleate, cobalt tartrate, copper acetate, Copper benzoate, copper butyrate, copper stearate, ferric acetate, ferric benzoate, ferric formate, Lead acetate, lead citrate, lead platinum, mercury (II) acetate, mercury (II) benzoate, Mercury (II) propionate, nickel acetate, nickel oxalate, nickel propionate, nickel stearate, Silver acetate and silver stearate.

The organic heavy metal salts are in the air, in oxygen or another oxidizing gas calcined at such a temperature for so long until the compound is partially calcined and oxidized.

Depending on the desired degree of calcination, the calcination can be at different temperatures and different lengths of time, as long as the Compound is not completely converted into its oxide. The best results will be by heating under oxidizing conditions below the flash point of the compound achieved. Such a process for partial calcination which is not protected here consists z. B. in cobalt acetate (2.3 kg) in a pan in the air for about 24 to Heat to a temperature between about 150 and 1700 C for 72 hours. Time and temperature depend of course on the amount, thickness and chemical composition the sample that is to be partially calcined and oxidized.

Based on the weight of the rubber, the result is very little Amounts of partially calcined and oxidized heavy metal organic salt improvements the adhesive strength of the rubber detn metal ground. About 0.1 Weight percent of the partially calcined and oxidized salt improves this Adhesion between rubber and metal is noticeable. Amounts up to about 10 percent by weight of the salt gives significant improvements.

But it is not practical; apply more than 10 percent by weight, since the properties (e.g. tensile strength) of the rubber compound are impaired can be. The best. Results are obtained when, based on the weight of the Rubber based, 1 to 4 percent by weight of the partially calcined and oxidized Salt can be applied.

The "rubber compound" that is attached to the metal base Should be any natural or synthetic rubber or a vulcanizable Be mixture of the same. The rubbers vulcanizable with sulfur are preferred applied.

The partially calcined and oxidized organic heavy metal salt can simply be added or mixed with the rubber mixture in a rubber mixer be mixed. It can also be distributed in aqueous dispersions of rubber and be coagulated with the rubber, or it can be dispersed in rubber, which is dissolved in a rubber solvent when coatings, adhesives or Binders are to be produced.

If necessary, other co-workers can also be added to the rubber compound Components are added as they are known in rubber technology, e.g. B. Accelerators, antioxidants, bactericidal substances, pigments, extenders, Reinforcing pigments, plasticizers and vulcanizing agents.

The metal base on which the rubber compound is applied which contains the partially calcined and oxidized organic heavy metal salt, should have a clean surface, i.e. from dust, oxides, rust, hammer blows, Oil and grease must be free, but it needs to be done before the rubber mixture is applied -not to be specially treated. Particularly suitable metal surfaces exist made of copper, iron, lead, tin, zinc or their alloys. The rubber compound with the partially calcined and oxidized salt and optionally also to be processed Components can be applied directly to the clean metal surface and through Heat and pressure are vulcanized on. The mixture can also be applied directly to wire mesh layers be calendered using the rubber compound and method of the present In the invention, many useful products can be made, e.g. B. difficult to tiresome tires with firm and elastic layers, tubeless tires and Hoses. Can be on an electrical conductor made of copper or another metal a sheath made from a rubber mixture of the above type to improve the adhesive strength the sheath can be applied to the conductor. The invention can also be applied to others Metal rubber items are applied, such as motor frames, seamless bearings, Torsionally elastic springs, drive belts, pressure rollers, reinforced with metal wire Hoses, shoe heels, in short whenever rubber is attached to metal and an elastic and firm bond between them should be created.

The following examples serve to further illustrate the invention.

Example 1 2.3 kg hydrated cobalt (lI) acetate - (CO (CHCOO) 24H2O) had been heated in an electric oven to about 1600 C for 24 hours to achieve the Salt easy to calcine and oxidize. 2 parts by weight of the treated salt were then in a rubber mixer with 100 parts by weight masticated natural rubber, 4.5 parts by weight of sulfur and other commonly included ingredients (Soot, zinc oxide, antioxidants, accelerators and plasticizers) in the usual Mixed quantities. Similar mixtures were then made in which the partial calcined cobalt acetate by hydrated cobalt acetate or anhydrous cobalt acetate was replaced. Further, a control sample was made without any cobalt compound. The mixtures were then used to test their adhesion to wire.

The wire used was uncoated, shiny, twisted steel wire used, which was rust and hammer-free and by wiping with ethylene dichloride was cleaned of grease or oil.

Six wires were placed 2.5 cm apart in a '152.5 cm wide Block embedded from any of the above rubber compounds. The blocks were under Pressure in a platen press for 60 minutes at 1380 C and vulcanized for 24 hours Left at room temperature. After storage, samples were cut from each block, which were tested in a Scott disrupter; the maximum load (in kilograms), which is used to detach the wire from the respective vulcanized mixture was required was referred to as the adhesive strength and is in the following table A.

Table A. average Adhesive strength contained in the mixture Cobalt compound area in adhesive strength Kilograms to kilograms Slightly calcined Cobalt Acetate ... 31 to 41 36 Anhydrous cobalt acetate. . . .. 25 to 33.5 31 Hydrated cobalt acetate ..... 24 to 28 26 Control sample .. .. 7.2 to 10 9 As can be seen, a slight calcination of the cobalt acetate results in a significant improvement in bond strength; the wire from each sample had rubber particles adhered to it, while the other wires were clean.

Example 2 The procedure was as in Example 1, except that a special part of the cobalt acetate had been heated to about 1600 ° C. for 72 hours in order to strongly calcine it, so that the product obtained was even more oxidized. Another part of the cobalt acetate was completely oxidized. 2 parts by weight of the heavily calcined cobalt acetate were then mixed with 100 parts by weight of masticated natural rubber, 2.5 parts by weight of sulfur and other conventional ingredients to be processed in the usual amounts and vulcanized with a twisted steel wire which was heavily electroplated with zinc. Similar blends were made using oxidized, anhydrous, hydrated, and lightly calcined cobalt acetate and vulcanized with the galvanized wire. After the study, the following results were obtained: Table B Adhesive strength contained in the mixture special ones Cobalt compound area in adhesive strength Kilograms to kilograms Heavily calcined Cobalt acetate. . 39 to 52.5 45 Slightly calcined Cobalt acetate. ... 39.5 to 48.5 43.5 Anhydrous cobalt acetate ..... 37.1 to 44.5 40.3 Hydrated cobalt acetate. .. 36.7 to 41 39 Cobalt oxide. . 20.4 to 22.7 21.8 Control sample. ... 9.1 to 10.9 10 As can be seen, by further calcining the cobalt compound, a remarkable increase in the bond strength of rubber to metal is achieved; however, it is not favorable to completely calcine the cobalt salt, since in this case the adhesive strength is almost completely lost or there is no noticeable improvement over the control sample. All wires were pulled cleanly from the samples, except where the rubber contained lightly or highly calcined cobalt acetate. This again shows that the bond obtained by using the partially calcined cobalt acetate is stronger than the rubber compound itself.

If partially calcined cobalt butyrate, benzoate, citrate, formate, -oleate or -tartrate is used similar improvements in bond strength obtained from rubber on metal. Partially calcined works in the same way Copper acetate or benzoate, iron (III) benzoate, lead acetate, mercury (II) benzoate, Nickel oxalate and silver stearate.

When rubber compounds, the partially calcined cobalt acetate included, calendered onto twisted steel wire strands for the purpose of producing wire layers, Investigations have shown that truck tires were incorporated and vulcanized on the road using such wire band tires improved Durability and usability, d. that is, there was little or no separation or Destruction of the layers after several months of heavy use.

Claims (4)

PATENT CLAIMS: 1. Method for improving bond strength of metal to rubber, in which a vulcanizable rubber compound is attached to a Metal adheres firmly in the presence of a heavy metal salt of an organic acid is vulcanized, characterized in that the salt is partially calcined and oxidized state and with respect to the rubber compound in only is present in a small amount sufficient to adhere the rubber compound to the metal attach. 2. The method according to claim 1, characterized in that a cobalt, Copper, iron, lead, mercury or nickel salt is used. ~~~~~~~ In Documents considered: German Patent No. 898 809; Römpp, chemistry lexicon, 3rd edition, 1953, Vol. II, p. 1156, left column, 4th paragraph.