HRP930594A2 - Process for the preparation of combinations rubber/metal by means of mally stable binder - Google Patents

Description

The technical field to which the invention belongs

The invention belongs to the field of chemistry, more precisely to the field of making binders for joining rubber and metal. The symbols of the International Patent Classification are C08C 4/00.

Technical problem

The technical problem is how to obtain a thermally stable rubber/metal connection.

State of the art

For the production of rubber/metal joined bodies, in the industry that processes rubber, for economic reasons, increasingly higher vulcanization temperatures with a shortened heating time are chosen. In order to achieve the desired required values in rubber technology, under such changed vulcanization conditions, especially natural rubber compounds, sulfur-poor crosslinking systems must be used. But such systems have a significant impact on bonding behavior, and as a rule, in a negative sense. Then, especially, when metal parts coated with binder are additionally exposed to an extended preheating time, joints that have an error are often obtained.

Description of the solution to the technical problem with implementation examples

This invention relates to a process for obtaining rubber/metal compounds using a thermostable binder for making connecting bodies by vulcanizing rubber mixtures on metal and other substrates stable under the conditions of vulcanization.

The task of this invention was therefore the development of rubber/metal compounds, which under dangerous vulcanization conditions have good stability during preheating and especially with natural rubber compounds, but also with synthetic rubber compounds as such, from styrene butadiene rubber, nitrile rubber, but also butyl rubber , and enables good bonding between the rubber and the substrate.

This task could be solved by using thermostable binders as an aid in vulcanizing natural or synthetic rubber mixtures from a metal or other rigid base, consisting of a mixture based on chlorinated rubber, subsequently brominated dichlorobutadiene and quinonedioxime. One of the characteristics of the procedure is that the applied binder does not contain oxidizing agents for quinonedioxime.

According to a particular embodiment of the process according to the invention, they contain 1 to 30, especially 5 to 25 wt. -%, sulfur, calculated on the sum of chlorinated rubber and subsequently brominated dichlorobutadiene. In addition, it is advantageous when up to 15 wt. -%, calculated on both previously mentioned components of soot.

The resulting compound between rubber/metal according to the invention is essentially based on chlorinated rubber, which has long been used as a raw material for the production of such compositions. A further essential ingredient is post-brominated polydichlorobutadiene, which has also been used for this purpose for decades. Carbon black is also needed, with both of the above-mentioned components and numerous materials, common in rubber technology. At the same time, the expert knows which type of carbon black is suitable or he is able to find a suitable type of soot through simple experiments. It has also long been state of the art to combine these ingredients with p-dinitrosobenzene.

Previously, attempts were made to replace this substance and instead p-quinonedioxime was used together with an oxidizing agent, so that at high temperatures of vulcanization or by preheating formed p-dinitrosobenzene. Until now, it was considered that quinonedioxime is not effective as such, but can only be used together with an oxidizing agent. This invention overcomes this obstacle and it is shown that quinonedioxime can very well lead to good rubber/metal bonds, if used together with the commonly used ingredients chlorinated rubber, subsequently brominated polydichlorobutadiene and primarily carbon black. It also proved to be particularly advantageous to add about 1 to 25 wt. -% ground sulfur.

To create a rubber/metal joint, the individual components are purposefully first melted, from. suspended in a solvent. Solvents that are assumed are ketones or esters such as methylethyl ketone, methylisobutyl ketone, diethyl ketone, acrylic acetate, ethylene glycol diacetate and butyl acetate. In addition, chlorinated hydrocarbons such as trichloroethane, trichloroethylene, perchlorethylene, but also aromatic solvents such as toluene xylene come into consideration. The amount of solvent used can vary widely, but generally so much is applied that the adhesion promoter of. the binder has a solids content of 5 to about 400 wt. -% dry matter.

According to the suitable form of reconnaissance, suspension or solution in the above-mentioned solvents, which are characterized by the content of os 3 to 90 wt. - parts of chlorinated rubber, 5 - 40 wt. - parts of subsequently brominated polydichlorobutadiene, 5 to 20 wt. - parts of soot, 5 to 30 wt. - parts of cononodioxime and 1 to 25 wt. – parts of ground sulfur. In many cases, it has proven expedient that the metal parts to be joined according to the state of the art are coated with a primer before applying the binder.

Such primers for rubber/metal binders have long been state of the art and can consist of a solution or suspensions of chlorinated rubber and phenolic resins that have reactive groups as well as pigments such as titanium dioxide, zinc oxide, carbon black or the like. They are applied in relatively thin layers after the usual pretreatment of the surface by sandblasting, degreasing, using solvents, etc.

After applying the primer and applying the layer with the binder, leave the solvent to wash off thoroughly. When the binder films are dry, the metal parts are placed in the press. After preheating to a suitable temperature, the rubber mixture is applied and the first vulcanization is performed at temperatures between 120 and 190°C under pressure for 3 to 15 minutes. The vulcanization conditions are governed by the applied rubber compounds and should be adapted to the vulcanization behavior of the same as well as to the substrates to be joined.

The rubber/metal connection according to the invention is suitable for bonding natural and synthetic rubber to metals and other solid substrates such as plastics, wood and fabric during vulcanization.

It is quite understandable that a suitable pre-treatment of the surface is required and different types of rubber can also be connected to each other using the rubber/metal connection according to the invention.

It is of particular advantage with this invention that the compound obtained without an oxidizing agent, which has many advantages compared to binders containing dinitrosobenzene or which contain quinonedioxime plus an oxidizing agent. Worthy of attention is the particularly good resistance to preheating, which improves even more markedly in the presence of sulfur and thus leads to improved joining.

Examples

In the following examples, testing was performed on steel according to ASTM-D429 Procedure B and C. Pretreatment was performed by degreasing with trichlorethane, steam and a jet of hard cast iron. Vulcanization was carried out in a commercial press. The tear test was performed after 24 hours of storage of the joined parts at room temperature.

The compound was created using suspension or dissolution

146 g of chlorinated rubber

62 g of brominated dichloro (2,4) - polybutadiene

11 g of lead phosphite

21 g of soot

in the mixture

640 g of calliol and xylene

120 g of perchlorethylene.

In the basic recipe, it is then distributed by mixing

1) 20 g of quinonedioxime

2) 40 g of p-quinonedioxime

3) 40 g of p-quinonedioxime i

10 g of ground sulfur

4) 40 g of p-quinonedioxime i

20 g of ground sulfur.

To test the bond strength on steel surfaces, they previously treated it using a well-known commercially available primer for rubber/metal joints, which essentially consists of solutions/suspensions of 8 wt. -parts of chlorinated rubber and phenolic resin that still contains reactive groups, 5 wt. -parts of titanium dioxide as well as 1.5 wt. - parts of zinc oxide, and 1.5 wt. -parts of soot in 80 wt. - parts of methyl ethyl ketone.

The applied rubber mixtures had the composition listed in Table 1. The numbers indicate parts of the mass.

Table 1

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For testing the strength of adhesion on steel bodies, the procedure C was used according to ASTM-D429. In the following table 2, depending on the used rubber mixture I to IV as well as the binder according to Example I up to 4 days, the tear strength is in kN.

Table 2

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To determine the durability according to preheating with the application of rubber compounds And before contact with the rubber compound, the steel body is heated for 3 or 5 or 7 or 8 minutes at a temperature of 160 °C. Vulcanization of the rubber mixture was also done at 160°C for 10 minutes.

During testing according to ASTM-D429, procedure B in the following Table 3, the specified peeling values in daN/2.5 cm as well as pictures of peeling in % breaks in the rubber layer according to the definition according to ASTM (-%R) were obtained.

Table 3

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Comparative trial

A binder that does not contain either quinonedioxime or sulfur is used. In this case, binding is not achieved in any case. The steel and rubber separated when they were removed from the vulcanizing press.

Claims (3)

1. The process of obtaining rubber/metal compounds using a thermostable binder based on chlorinated rubber, subsequently brominated polydichlorobutadiene, as well as quinonedioxime without an agent for its oxidation, characterized by the fact that the components of the thermostable binder: chlorinated rubber, subsequently brominated polydichlorobutadiene, quinonedioxime, then sulfur 1 to 30 wt. % where the percentages are calculated on the sum of the quantities of the first two components, previously dissolved in an organic solvent so that the solution contains 5-40 wt.% of dry matter, and then a layer of binder solution or suspension is applied to the cleaned metal surface and the solvent is allowed to evaporate afterwards where the metal part is placed in a press and a natural or synthetic rubber mixture is applied and vulcanized at a temperature of 140 to 180°C under a pressure of 10 to 40 bar for 3 to 25 minutes. 2. The method according to claim 1, characterized by the fact that ketones such as methyl ethyl ketone or diethyl ketone, esters such as ethyl acetate or ethylene glycol diacetate, chlorinated hydrocarbons such as trichloroethane or trichloroethylene, as well as aromatic hydrocarbons such as toluene or xylene can be suitable solvents for the binder components. 3. The method according to claims 1 and 2, characterized in that the solution of binder components contains 30 to 90 parts by mass of chlorinated rubber, 10 to 40 parts by mass of subsequently brominated polydichlorobutadiene, 5 to 20 parts by mass of carbon black, 5 to 30 parts by mass of quinonedioxime, and 1 to 25 parts by mass of ground sulfur.