CS220798B2 - Method of rubber regeneration - Google Patents

Description

The present invention relates to a process for the recovery of rubber, wherein the ground or crushed rubber waste in the form of particles of at most 1 mm, preferably at most 0.8 mm, which has been virtually stripped of its textile or metal constituents, is degraded by chemical regenerants including a reducing agent, an oxidizable metal chloride, an iron group and a plasticizer, wherein the regeneration is carried out in a solid phase in an oxygen-containing gas or consisting of free oxygen at a temperature of at most 100 ° C by stirring in a powder mixer reacts with double bonds in rubber.

In the rubber industry, large amounts of reclaimed rubber are used, which is obtained by reducing rubber waste, such as old tires. The degradation of rubber waste is normally carried out by heat, mechanical treatment and chemicals, in which the textile and metal materials contained in the rubber are removed mechanically or chemically. Like raw rubber, recovered rubber is a plastic material that can be processed and cured in the same way as raw rubber.

There are six different conventional procedures for the recovery of rubber waste. The oldest method is a boiler or autoclave process in which rubber waste is heated by steam. The autoclave process uses high pressure steam at a temperature of about 200 degrees Celsius. Another conventional method is the acidic process in which all of the textile material contained in the rubber waste is dissolved by boiling in acids, whereupon the residue is plasticized by steam and rolled on a calender. The third method is an alkaline method in which sodium hydroxide solution is used instead of acid to dissolve the textile material. This method also results in the removal of free sulfur.

This method is not suitable in conjunction with chemical regenerating agents and has therefore lost its importance now with the increasing incidence of synthetic rubber in rubber waste. The fourth method is a neutral process in which metal chloride is used instead of alkali to dissolve the textile material. This neutral process is generally carried out in large boilers with steam-heated water (at a temperature of about 200 ° C), whereby the textile material is usually dissolved by the action of calcium chloride. The fifth method is a thermomeclian or · thermochemical process, in which, after mechanical removal of the textile material, kau220798, the rubble waste is treated at high temperature in a closed mixer, generally in a propeller mixer or extruder ·

In Chemical Abstracts, Vol. 84 (1976), col. No. 45783h describes a sixth method for the recovery of rubber waste. This method can be described as direct solid phase regeneration; it comprises two stages, in which, in the first step, the mixture of natural rubber waste powder, regeneration oil, phenylhydrazine, ferrous chloride and methanol is stirred for 4 hours, and in the second step the mixture is heated at 100 ° C for 60 minutes. Thus, the sixth known regeneration method requires a relatively long processing time, i.e. 5 hours.

All these known methods of rubber regeneration can be said to be first crushed (rubber waste) and finely ground. In the autoclave process, the thermochemical process and the neutral process, the material after heat treatment must also be subjected to intensive mechanical processing in a calender and extruder, which is called 'refining'. This treatment consumes a lot of energy and labor, since the material is intensely heated during processing in the refining plant and in the extruder. Therefore, a large amount of thermal energy must be dissipated by water cooling. The refining plant must also be supervised, which requires a lot of experience in adjusting the plant for best results.

In a further development of the known neutral process, the rubber material, after autoclaving and hot air drying, is then treated at low temperatures, for example in a vibrating or rotating paddle tray, in which the material is subjected to temperatures below -60 ° C. the temperatures of which are achieved by supplying a coolant, in particular liquid nitrogen or solid carbon dioxide. It is true that processing at low temperatures results in considerable energy savings, but even this known variant of the neutral process involves high energy consumption.

The disadvantages of the five known regeneration processes are therefore mainly the high production costs in the form of energy consumption wages. Another disadvantage inherent in these processes is that the rubber waste after its own regeneration, i.e. after the double bonds in the rubber material have been removed, must be subjected to a special refining treatment in order to be used as raw material for new vulcanized rubber products.

It is true that direct regeneration according to the aforementioned sixth method described in Chemical Abstracts, Vol. 84, is an improvement over other known regeneration processes, but still requires a relatively long processing time and a number of unnecessary work operations.

The invention is based on the discovery that expensive and energy-intensive refining can be avoided and, moreover, the regeneration process can be substantially simplified and cheaper if the vulcanized waste rubber is directly regenerated using special plasticizers and a special redox system with a special catalyst. in this case, the regeneration can be carried out rapidly in a normal mixer at low temperature, often at room temperature. The invention thus differs from the above sixth method described in Chemical Abstracts, Vol. 84.

The method of the present invention for the recovery of rubber, wherein the ground or crushed rubber waste in the form of particles of at most 1 mm, preferably at most 0.8 mm, which has been practically stripped of its textile or metal constituents, is degraded by chemical regenerating agents including a reducing agent, an oxidizable metal chloride, an iron group, and a plasticizer, wherein the regeneration is carried out in a solid phase in an oxygen-containing gas or consisting of free oxygen at a temperature of at most 100 ° C, preferably at most 80 ° C When the reducing agent has reacted virtually completely with the double bonds in the rubber, it is characterized in that either the phenylhydrazine in the amount of 0.2 to 1% by weight or the diphenylguanidine in the amount of 0.2 to 0.8 ° are added as reducing agent. % of the iron group metal chloride is added in an amount of 0.1 to 0.4% by weight, such as z at least one substance selected from the group consisting of tall oil resin and dipentene, optionally in admixture with another plasticizer, is added, and the stirring to achieve regeneration is allowed to take place for a maximum of 30 minutes, with a total plasticizer mass amount of at most 17.5 ' why, the amount of dipentene by weight is at most 5%, the weight by weight of tall oil resins is at most 17.5% by weight, the weight by weight of dipentene when used as the sole plasticizer or when mixed with another plasticizer is 0.5 up to 5% by weight of tall oil resins, when used as the sole plasticizer or in admixture with a plasticizer other than dipentene, amounts to 7 to 17.5%, by weight of plasticizer other than tall oil resin and dipentene is at most 10, and the weight amount of tall oil resins in e.g. when used together with dipentene, it varies in proportion to the amount of dipentene by weight, and is 8 to 16% for dipentene by weight of 5 to 0.5%, all of the above percentages being based on the total weight of the rubber blend. fall, reducing agent, iron chloride metal chloride and plasticizer.

. Preferably, the stirring is carried out at a temperature of at most 80 ° C, in particular at most 60 ° C. The particle size of the rubber waste is preferably at most 0.8 mm, in particular at most 0.4 mm. Stirring is generally carried out for 3 to 15 minutes. Iron chloride is preferably added as the iron group oxidizable metal chloride. Diphenylguanidine is preferably added as a reducing agent in an amount of 0.3 to 0.5% by weight.

A great advantage of the process according to the invention is that the regeneration can be carried out in a powder mixer of the usual type. It is possible to use powder mixers with at least one stirrer, which here is preferably driven at a peripheral speed of the order of 2000 m / min. In industrial scale production, very good results have also been achieved, with trough mixers with agitators made of tape. More important, however, is careful and accurate mixing rather than rapid and intensive mixing during the mixing phase.

The ground or crushed powdered rubber, which has been virtually free of textile and metal components, is then fed directly into the powder mixer container together with chemicals and plasticizers, after which the batch is mixed and mixed for a relatively short time. Generally, 3 to 10 minutes are required, and often the total mixing time may last as little as 4 to 7 minutes. However, stirring must be continued until virtually all of the phenylhydrazine or diphenylguanidine has reacted with the double bonds in the rubber.

The rubber waste thus recovered can be used directly without any subsequent refining. This results in a substantial reduction in recovery costs; it is also possible to reduce the number of operators to a considerable extent, by up to about 50 ° / o, while at the same time the energy consumption of the regeneration process can be reduced by up to 40 to 50 ° / o. Also, with this new regeneration process, the investment costs are substantially lower compared to most previously known regeneration processes that require refining in expensive refining plants.

The new rubber regeneration method yields a better end product, as can be seen from the accompanying examples. However, a relatively small disadvantage of the process according to the invention is that the rubber waste used as a raw material for regeneration must be ground to particles of a smaller size than required by the five known regeneration processes prior to regeneration. However, the extra costs of this fine grinding have to be regarded as small compared to the advantages which, on the other hand, are achieved in this new way.

In the rubber recovery process according to the invention, phenylhydrazine or diphenylguanidine and oxidizable metal chloride are used as the chemical degradation system, which acts in conjunction with air oxygen. Phenylhydrazine or diphenylguanidine acts as a peptizing agent. Phenylhydrazine can be added as such or as a precursor, for example hydrazine hydrochloride, which is converted to phenylhydrazine during the regeneration process.

The regeneration according to the invention is carried out at unusually low temperatures, below 100 ° C, while most of the known methods used for the regeneration of chemicals generally operate at temperatures above 150 ° C and normally at temperatures up to 200 ° C. Thus, other peptizing agents, known for example for the degradation of crude rubber, initially act at temperatures above 100 ° C, in which case the peptizing agents dissolve in the rubber material. Experiments have shown that the recovery of vulcanized rubber waste by the method according to the invention cannot be achieved by the known peptizing agent RENASID 4 (manufactured by Bayer AG), which consists of the zinc salt of pentachlorthiophenol. Thus, this known peptizing agent does not act at temperatures below 100 ° C. In any case, such a known peptizing agent does not provide an industrially usable recovered product.

Another known peptizing agent that is useful in known methods of rubber recovery is hydrazine sulfonic acid. However, it has also been found that this peptizing agent is not useful in the method of the invention.

Phenylhydrazine is a very aggressive agent towards organic substances with double bonds. However, phenylhydrazine has the great advantage that the phenylhydrazine degradation products in the reaction with the double bonds of the rubber waste will comprise only a few tenths of a percent of benzene and nitrogen gas, which is highly advantageous in terms of environmental purity, although the process of the invention in a closed mixing system.

As mentioned above, diphenylguanidine may be used instead of phenylhydrazine. Experiments have shown that regeneration results are the same when approximately the same amount of diphenylguanidine is used.

Compared to the costly, unpleasant and skin-attacking phenylhydrazine, the use of diphenylguanidine is considerably simpler and more pleasant, inter alia because diphenylguanidine is powdered. Diphenylguanidine can be used in an amount of 0.2 to 0.8% by weight, but is preferably used in an amount of 0.3 to 0.5% by weight, since diphenylguanidine is also a vulcanization accelerator and can therefore be used in larger quantities , influence the vulcanization process in rubber mixtures prepared from regenerate.

It is known that the rubber contains a very high proportion of double bonds, of which only about 2 to 3 have reacted with sulfur during vulcanization, but the remaining double bonds are still available for disruption by the regeneration process. When regenerated by the process according to the invention, the phenylhydrazine and optionally diphenylguanidine are destroyed by a few percent of the double bonds in the rubber waste and virtually no phenylhydrazine or diphenylguanidine remains in the material after the regeneration process. That is, each rubber particle is regenerated to a certain depth during regeneration, which is given by the ratio of the amount of phenylhydrazine and optionally diphenylguanidine to the amount of rubber material in the feed introduced into the powder mixer.

as mentioned above, rubber waste in the form of particles with a size of at most 1 mm is added. Preferably, however, rubber waste having a particle size of, for example, at most 0.8 mm is used. However, it has been found that generally better results are obtained if the rubber particles have an even smaller size, the most preferred particle size being up to 0.4 mm. There is no doubt that the coarser rubber particles will also be satisfactorily regenerated, but because of the later use of the regenerated material, it is preferable that the particle size is smaller.

The smaller particle size, at most 0.4 mm, is therefore very advantageous in terms of use and also in terms of quality of the resulting vulcanized rubber product, which is produced using regenerated powdered rubber.

The regeneration is allowed to proceed for a sufficiently long time so that the added phenylhydrazine or optionally diphenylguanidine can react virtually completely with the rubber waste. This usually means that the regeneration must take place for a maximum of 15 minutes, usually for 3 to 10 minutes or 4 to 7 minutes.

As mentioned above, the plasticizer is to be added together with the rubber powder, the reducing agent and the iron group oxidizable metal chloride.

The plasticizer may consist only of dipentene or only tall oil resins, but it is also possible (and in many cases preferred) to use dipentene and tall oil resins in combination with each other or in combination with some other plasticizer, for example, regenerating oil.

It has been found that dipentene, which could appear to serve in part as a plasticizer and in part as a surfactant and thereby keep the other components of the mixture dispersed, induces a very rapid plasticization of the rubber particle surfaces and thereby permits the penetration of the reducing agent into the rubber. in it could react with double bonds.

As already mentioned, dipentene can only be used as a plasticizer in regeneration, and can be used in an amount of from 1 to 5% by weight based on the weight of the mixture of reducing agent, iron chloride metal chloride, rubber waste dust and plasticizer. Although higher than 5% w / w is technically feasible, the maximum content should be limited to 5% w / w for environmental safety reasons.

If more softening is desired or if it is desired to set the dipentene, it can be used in combination with some other conventional plasticizer. A useful plasticizer is an aromatic mineral oil of the spindle oil type. An additional plasticizer, such as spindle oil, may be added in such an amount that the plasticizer will also act when using the regenerated product in the manufacture of new rubber products.

If dipentene is used in combination with another plasticizer, the dipentene content can in many cases be reduced to 0.5% by weight.

In addition to or instead of dipentene, tall oil resins may be used as the emollients during regeneration. Tall oil resins are known per se as plasticizer based on reclaimed rubber, but experts have thought against using tall oil resins in high concentrations above 10% by weight, since for processing on a processing plant this has resulted in poor processability, sticky consistency, sticking to the rollers, and the resulting product too soft. It should therefore be considered surprising that the high content of tall oil resins provides very good results in the recovery of rubber by direct solid phase recovery. Tall oil resins up to 17.5% by weight have been tested with positive results, but below 7% by weight, additional plasticizer needs to be added.

The emollient may be dipentene or, for example, a regenerating oil. However, the amount of plasticizer other than tall oil resins or dipentene should not exceed 10% by weight in order to avoid migration problems in products made of reclaimed rubber.

However, when used together with dipentene, it must also be ensured that the tall oil resin content is in an indirect ratio to the dipentene content in the range of 8 to 16% by weight with the dipentene content in the range of 5 to 0.5% by weight, otherwise a completely inadequate and soft consistency of the rubber compositions which are prepared from reclaimed rubber would be achieved.

A great advantage of the regeneration process according to the invention is that the regeneration can be carried out at low temperatures below 100 ° C. Most often it is possible to work at a room temperature of 210798. During the regeneration process, the temperature of the rubber material increases partly as a result of the reaction of the reducing agent with the rubber and partly as a result of the introduction of mechanical energy during the mixing phase; using slow mixing methods, such as a trough mixer with a stirrer formed from a tape at a speed of 20 rpm, the temperature increase due to the drawing will not be as large as the temperature increase using high speed mixers can be 20-25 ° C at high speed stirrer. The temperature rise due to the reaction of the phenylhydrazine with the rubber itself may be several degrees Celsius, for example from 15 to 20 ° C at a phenylhydrazine content of 0.7% by weight.

In the regeneration process of the invention, only a small amount of phenylhydrazine is required; its preferred content ranges from 0.2% to 1% by weight. Frequently, the most preferred content may be in the range of 0.2 to 0.8% by weight.

The iron group metal used must have an oxidizable metal, i.e. the iron group metal should be in a lower oxidation state than the maximum metal level. Although it is possible to use all three metals of the iron group, ie iron, nickel and cobalt, ferrous chloride is preferred. The metal chloride of the iron group may be present in a small amount, preferably from 0.1 to 0.4% by weight. During regeneration, the metal chloride of the iron group is contained in a redox system where, for example, ferrous ions are oxidized to ferric ions.

In the regeneration process of the invention, the individual components are to be added to the mixer in a specific order for best results. First powdered rubber was added, followed by dipentene followed by phenylhydrazine and finally iron chloride metal chloride. By following this order of addition, a better dispersion of the phenylhydrazine is achieved before the addition of the metal chloride of the iron group, which chloride initiates its own regeneration reaction, for which oxygen is required from the air to the mixer.

To facilitate the addition and distribution or dispersion of the iron chloride metal chloride, it may be dissolved in a small amount of methanol before addition. However, the total methyl alcohol content should be low due to environmental safety. Most of the methanol evaporates while stirring. A suitable amount of methyl alcohol is in the range of 0.5 to 1.5% by weight, based on the total weight of the mixture of the powdered rubber, plasticizer, reducing agent and iron group metal chloride.

When using diphenylguanidine instead of phenylhydrazine, it is preferable to add the individual components in a different order. After introducing the powdered rubber waste, diphenylguanidine powder is added, followed by the addition of a plasticizer, for example tall oil resins, and finally an iron chloride metal chloride, which can be dissolved in methanol, is added. However, the metal chloride of the iron group can first be dissolved in the plasticizer, in which case it is added together with the plasticizer.

It may be advantageous to add an anti-sticking agent to the end of the mixing and mixing phase, for example ordinary kaolin, talc, and the like. As a result of the anti-sticking agent being added, the individual regenerate particles will not adhere to each other.

The reclaimed rubber material produced by the process according to the invention can be vulcanized after admixture with zinc oxide, stearic acid, sulfur and accelerator and, in the vulcanized state, typically has the following properties:

hardness, ° Shore 60 to 66 tensile strength, MPa 7.0 to 9.0 elongation at break,% 190 to 230 density, g / cm ³ 1.18 to 1.22 aging at the same level as the newly manufactured conventional blend on treads

It has been found that reclaimed rubber material produced by the process of the present invention can be directly used to produce simple products with fully satisfactory physical properties (e.g., footwear mats, bus floors, rubber pedals, dust covers etc.). In this context, natural rubber or butadiene styrene rubber may be used as the raw rubber.

The invention is illustrated by the following examples. In these examples, commercially available rubber waste obtained from used tires of conventional composition is used. The rubber waste is produced in a conventional manner by crushing and separating virtually all metal and textile components from the rubber. The regulations for the regeneration mixtures of Examples 1 to 4 are given in Table I.

Example 1

In this example, a rubber waste powder with a particle size of at most 0.8 mm is used. The mixing is carried out in a powder mixer provided with a circulating stirrer at the bottom of the cylindrical vessel. The stirrer is rotated at a peripheral speed of approximately 2000 m / min. First, a powdered rubber waste batch is charged to the mixer with a stirrer, to which dipentene and tall oil resin are then added, followed by phenylhydrazine after stirring for some time. Iron (II) chloride is added in admixture with methanol.

2207S8

Stirring is continued for 7 minutes after the addition of ferrous chloride. Thus, the mixing takes place in the solid phase with intensive mixing of the material in the air present in the mixing vessel. It has been shown that during the mixing with phenylhydrazine together with air oxygen, the degradation of the rubber particles is achieved to such an extent that the rubber powder can then be used directly to produce vulcanized masterbatches. The temperature at the start of mixing was room temperature, although temperatures up to 100 ° C could be used.

It has been found that the added phenylhydrazine reacts almost completely with the rubber powder, producing a few tenths of the percentage of benzene and nitrogen gas present in the atmosphere in the powder mixer.

After approximately 1 day, the rubber regenerate thus produced is subjected to tests and compared with known commercially available reclaimed rubber materials. For these tests, the rubber recipe shown in Table II is used.

The comparative material used is commercially available reclaimed rubber material from Poland and commercially available reclaimed rubber material from the Federal Republic of Germany. After processing the three rubber mixtures, they are rolled on a calender into 2 mm sheets which are cured for 10 minutes at 160 ° C. After vulcanization, the hardness, tensile strength, elongation at break, tear strength and density of the three materials were tested. The results of these tests are shown in Table III.

Example 2

This example is performed on a laboratory scale. The mixer used is a conventional household mixer with two opposite whip rotating whisks and a rotating bowl (Phylips "5 Electronics"). The beater rotates at its maximum speed. In this case, the particle size of the rubber powder is at most 0.4 mm. The order of addition of the components is as follows: powdered rubber, dipentene, phenylhydrazine, ferrous chloride, and then an anti-tack agent. This is added up to 12 minutes after the addition of ferrous chloride. The total mixing time, calculated from the addition of ferrous chloride, is 15 minutes. Stirring is performed at room temperature and during the reaction the temperature of the mixture is raised. Even after stirring, the temperature rises slightly for about 1 hour.

After approximately one day of storage, the regenerate is mixed with the vulcanizing agent according to the formula in Table II and cured in sheets of 2 mm thickness for 10 minutes at 160 degrees Celsius. Vulcanized sheets have a 62 ° Shore hardness, a tensile strength of 6.8 MPa and an elongation at break of 230 ° / o.

This example demonstrates that dipentene can be used as the sole plasticizer.

EXAMPLE 3 This example is also carried out on a laboratory scale according to the procedure described in Example 2. In this case, however, two plasticizers are used, namely dipentene and a regenerating oil, i.e. a spindle-type aromatic mineral oil (ESL 385). The recovered regenerate is vulcanized and tested in the same way as the regenerate of Example 2. The vulcanized sheets have a hardness of 65 ° shore, a tensile strength of 6.3 MPa and an elongation at break of 190 ° / o.

Example 4

This example is carried out on a large scale in a trough mixer with a stirrer made of tape; stirring time is 15 minutes. The rubber powder has a particle size of at most 6.6 mm. The order of addition of the individual components is the same as in Example 1. The regenerate thus obtained is tested in a mixture according to the following regulation:

parts by weight powdered regenerate 100 zinc oxide 2 stearic acid 0.80 sulfur 1 accelerator 0.60 regeneration oil 2

In this case, the accelerator is SULFENAX CB (cyclohexylbenzothiazylsulfenamide) and the regeneration oil is the above-mentioned aromatic mineral oil ESL 385.

After processing on a 2 mm sheet calender and after curing for 10 minutes at 160 ° C, the following mechanical properties are measured: 60 ° Shore hardness, 7.0 MPa tensile strength, 260% elongation at break, and density 1 , 18 g / cm ³ .

Examples 5 to 7

In these examples, a laboratory apparatus is used as in Example 2; the examples are performed to illustrate the effect of dipentene in comparison with mineral oil (regeneration oil) as a plasticizer.

• For this purpose, rubber waste, obtained only from used tires, containing approximately 50% of the carbon black and which has been comminuted to a particle size below about 0.59 mm (30 mesh US mesh) is used. The individual components are added to the mixer in the order shown in Table IV, wherein the ferrous chloride is added as a solution in methanol. The addition time was 5 minutes, after which the mixer was allowed to run for an additional 30 minutes. At the end of mixing, each of the recovered powdered regenerates was allowed to stand overnight, after which the regenerate was used according to the recipe in Table IV.

It is apparent from the results also shown in Table IV that only when mineral oil is used in an amount of about 4.7% by weight (based on the total amount of material introduced into the mixer), or 5 parts by weight per 100 parts by weight of rubber, very poor workability in the mixer. Such a powdered regenerate is not usable in commercial production, since the workability in the mixer is of critical importance in order to achieve a rational and high quality processing of the rubber composition. The Mooney viscosity is greater than 200.

Although the amount of mineral oil is greatly increased to about 12.1% by weight in Example 6 (14 parts by weight per 100 parts by weight of rubber), the workability in the mixer is still very poor and a brittle unvulcanised sheet is difficult to handle without falling apart. However, increasing the amount of plasticizer will reduce the Mooney viscosity, but in total, this powdered regenerate must also be considered commercially unusable.

If a small amount of dipentene (approximately 2.75% or 3 parts by weight per 100 parts by weight of rubber) is added as a plasticizer in addition to the mineral oil (regeneration oil) as in Example 5, a significant improvement in the workability in the mixer is achieved. as can be seen from Example 7, which thereby demonstrates the apparent effect of dipentene as a plasticizer in the direct recovery of solid rubber rubber waste.

Examples 8 to 10

In these examples, the same laboratory equipment, rubber scrap, prescription, addition time, additional mixer run time, and aging of the regenerates were used as in Examples 5-7.

Examples 8 to 10 illustrate the effect of tall oil resins as plasticizer and the possibility of using diphenylguanidine instead of phenylhydrazine as peptizing agent. In Examples 8 and 9, phenylhydrazine is dissolved in methanol and iron (II) chloride dispersed in tall oil resins; the individual components are introduced into the mixer in the following order: rubber waste, phenylhydrazine (dissolved in methanol), ferrous chloride (dispersed in tall oil resins) and finally (in Example 8) regeneration oil. In Example 10, ferrous chloride is dissolved in methanol and then blended with tall oil resins. The individual components are then introduced into the mixer in the following order: rubber waste, diphenylguanidine (powder) and a mixture of ferric chloride and tall oil resins. In all these cases, the tall oil resins are pre-heated to a temperature in the range of 30 to 40 ° C for easier handling.

By comparison with the results shown in Tables IV and V, tall oil resins, either alone or in admixture with regenerating oil, provide useful regenerates and thus can be dispensed with without dipentene. Furthermore, it is apparent from the results that phenylhydrazine could be replaced by diiphenylguanidine. This is advantageous in several respects, since phenylhydrazine is expensive, unpleasant to handle and invades the skin. Powdered diphenylguanidine is much easier and more convenient to work with.

Examples 11 to 16

In these examples, the same laboratory equipment, rubber waste and regeneration maturation times were used as in Examples 5-7. The regeneration was carried out at room temperature. The batch size is 300 g of rubber waste. The addition time is approximately 3 minutes and the mixer is then allowed to run for an additional 12 minutes so that the total residence time in the mixer is approximately 15 minutes. The powdered regenerate is allowed to stand overnight and then used as prescribed in Table VI; according to this recipe, it contains natural rubber to reduce Mooney viscosity and improve the conditions of use of the rubber regenerates down to approximately normal.

Mixing is carried out in a laboratory mixer and the resulting unvulcanized rubber mixture is used to produce test plates which are cured for 10 minutes at 160 ° C. The results of the tests with individual rubber mixtures are shown in Table VII.

Examples 11-16 illustrate the effect of a plasticizer. The use of tall oil resins as such results in good recovery (rubber waste. As shown in Table VII, good results are obtained with as high a content as 20 parts by weight of tall oil resins per 100 parts by weight of rubber waste powder. low content of tall oil resins, especially when tall oil resins are below 8 parts by weight per 100 parts by weight of rubber waste powder, it is necessary to support the effect of the tall oil resins by adding dipentene (example 1j). Examples 15, 16 and also 3 and 7 show that the use of dipentene yields a good regenerate even when used together with other plasticizers in the form of mineral oil. The use of a single mineral oil softener does not give satisfactory results, as shown in Examples 5, 6 and 16. Workability, i.e. workability in a mixer, is poor in this case and the Mooney viscosity is too high if unvulcanised natural rubber is not added to the rubber mixture. When mineral oil is used in an amount of 8 parts by weight per 100 parts by weight of rubber, even as little as 1 part by weight of dipentene per 100 parts by weight of rubber (Example 15) results in improved workability in the mixer. Good results are obtained by adding 3 parts by weight of dipentene per 100 parts by weight of rubber, as shown in Example 16.

Examples 17 and 18

In these examples, phenylhydrazine is compared with diphenylguanidine as a component in the redox system used. In these examples, the same laboratory equipment, rubber waste, aging time of the regenerate, batch size, duration of addition and total residence time in the mixing were used as in Examples 11 to 16. The regeneration was carried out at room temperature. The prescription, mixing equipment, vulcanization conditions and test results are given in Table VIII.

From the results in this table, it can be concluded that phenylhydrazine can advantageously be replaced with approximately the same amount of diphenylguanidine, giving equivalent results. However, the diphenylguanidine content should preferably be lower than the phenylhydrazine content since diphenylguanidine also acts as a vulcanization accelerator and could exert this effect in the vulcanization of the finished product under consideration.

Example 19

This example describes the recovery of powdered rubber waste on an industrial scale. For this purpose, a trough mixer with a Toaster made of 1 m ³ tape was used. The batch size is 350 kilograms of pulverized rubber waste, which has been pulverized to a particle size of less than 0.59 mm (30 mesh US mesh). When the feed is introduced into the trough mixer, the rubber powder has a temperature of approximately 10 ° C. Powdered diphenylguanidine is then added and the mixer is allowed to run for approximately 2 minutes. This is followed by the addition of tall oil resins which have been preheated to a temperature of about 40 ° C, resulting in an increase in the batch temperature of about 6 ° C. Finally, ferrous chloride dissolved in methanol is added. The addition of tall oil resins and ferrous chloride will take about 5 minutes. Once the addition of ferrous chloride is complete, the mixer is allowed to run for a further about 15 minutes. The regenerate is allowed to stand overnight before testing.

For the testing of the regenerate thus obtained, the prescription given in Table VI shall apply. Mixing is carried out in a Banbury mixer and the resulting rubber mixture is used to produce test plates which are cured for 10 minutes at 160 ° C. The test results are shown in Table IX; From these results, it is evident that a good regenerate is obtained on an industrial scale.

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Table II

Test Regulation parts by weight powdered regenerate 100 zinc oxide 2 stearic acid 0.80 sulfur 1 accelerator SANTOCURE (cyclohexylbenzothlazylsulphenamide) 0.60

Table III

Properties powder regenerate according to the invention (Example 1) reclaimed rubber powder from Poland powdered regenerated rubber from Germany hardness, ° Shore 66 54 56 tensile strength, MPa 7.6 6.9 5.4 elongation at break,% 190 340 230 tear strength, N 55 42 38 density, g / cm ³ 1,22 1.16 1.20 Table IV Example 5 Example 6 Example 7

Safety parts Safety parts Safety parts Safety parts Safety parts Safety%

Regulation:

rubber waste 300.0 93.90 300.0 86.58 300.0 91.32 regenerating oil 15.0 4.69 42.0 12.12 15.0 4.57 dipenten - - - - 9.0 . 2.74 phenylhydrazine 3.0 0.94 3.0 0.87 3.0 0.91 FeCl ₂ .4H ₂ O 1.5 0.47 1.5 0.43 1.5 0.46 319.5 100.00 346.5 100.00 328.5 100.00 methanol 15.0 15.0 15.0 initial temperature, ° C 25.5 26.0 25.5 final temperature, ° C 25.0 26.0 28.0 test results (note 1): Mooney viscosity, 100 ° C, ML 1 + 4 > 200 100 ALIGN! 144 durability, ° Shore 62 52 64 tensile strength, MPa 7.0 6.0 10.3 elongation at break,% 210 230 240 specific gravity, g / cm ³ 1.17 1.16 1.17 Note: C. 2 2, 3

Note: 1:

Code for testing parts by weight

Powdered regenerate zinc oxide stearic acid sulfur accelerator SANTOCURE (cyclohexylbenzothiazylsulfenamide)

Mixing is carried out in a mixer for minutes

2,0

0,9 Test plates are vulcanized

1.1 for 10 minutes at 160 ° C

0.8 note 2:

Workability in the mixer is very poor. A brittle, unvulcanized dewater is obtained, which is almost impossible to handle. 3:

(Workability in the mixer is satisfactory,

Table V

Example 8 Example 9 wt

Example 10 weight parts by weight

Regulation

powdered rubber waste 300.0 87.34 300.0 91.57 300.0 91.74 regenerating oil 15.0 4.37 - - - - tall oil resin 24.0 6.99 24.0 7.33 24.0 7.34 phenylhydrazine 3.0 0.87 2.1 0.64 - - diphenylguanidine - - - - 1.5 0.46 FeCl ₂ .4H ₂ O 1.5 0.43 1.5 0.46 1.5 0.46 methanol 343.5 15.0 100.00 327.6 15.0 100.00 327.0 15.0 100.00

initial temperature, ° C final temperature, ° C

25.5 25.5 25.5

30 28.5

Test results (note 1):

Mooney viscosity,

100 ° C, ML 1 + 4 100 hardness, ° Shore 62 tensile strength, MPa 8.4 elongation at break,% 250 specific weight g / cm ³ 1.15 note. No 2

132

137

11.3

260

1.17

11.8

260

1.17

Note 1: see Table IV

Note 2: workability satisfactory Note. 3: workability in mixer good

Table VI

Regulation for weight%

powdered regenerate 89.7 natural rubber 6.0 zinc oxide 1.9 stearic acid 0.8 sulfur 1.0 SANTOCURE accelerator (cyclohexylbene- zothiazylsulfenamid) 0.6

100.0

Table VII

Example 11 Example 12 Example 13 weight-weight-weight-weight parts parts parts parts parts

Regulation: powdered tall oil resin waste 100 87.34 13.7 11.96 100 84.89 17.0 14.43 100 82.78 20.0 16.56 mineral oil - - - - - - dipenten - - - _ ferrous chloride 0.5 0.44 0.5 0.42 0.5 0.41 dlphenylguanidine 0.3 0.26 0.3 0.26 0.3 0.25 114.5 100.00 117.8 100.00 120,8 100.00 methanol 1.0 1.0 1.0 temperature increase, ° C +4 +3 +2 Test results Mooney viscosity 100 ° C ML 1 + 4 45 37 32 hardness, ⁰ Shore 64 60 61 tensile strength, MPa 8.2 9.1 9.0 elongation at break,% 280 320 320 specific gravity, g / cm ³ 1,2 1.16 1.15 Note: C. 4 4 3 Table VII - continued Example 14 Example 15 Example 16 hm- hm- hm- hm- hm- hm-

parts parts% s parts parts% s parts parts% s

regulation: powdered rubber waste 100 ALIGN! 91.91 100 ALIGN! 91.07 100 ALIGN! 89.44 tall oil resin - - - - - - mineral oil 8.0 7.35 '8.0 7.29 8.0 7.16 dipenten - - 1.0 0.91 3.0 2.68 ferrous chloride 0.5 0.46 0.5 0.46 0.5 0.45 diphenylguanidine 0.3 0.28 0.3 0.27 0.3 0.27 108.8 100.00 109.8 100.00 111.8 100.00 methanol 1.0 1.0 1.0 temperature increase, ° C ± o +1,5 +0,5 Test results Mooney viscosity 100 ° C, ML 1 + 4 68 60 49 hardness, ° Shore 61 60 57 tensile strength, MPa 9.2 8.4 8.5 elongation at break,% 220 230 250 specific gravity, g / cm ³ '1.16 1.16 1.16 Note: C. 1 2 3

Note 1:

Workability in the mixer is very poor; a brittle, unvulcanised sheet is obtained which is almost impossible to handle despite the addition of unvulcanised natural rubber to the test code,

Note 2:

Workability in the mixer is satisfactory.

Note 3:

Workability in mixing equipment good.

Note 4:

Workability in mixing equipment excellent.

Table VIII

Example 17 Example 18% by weight% by weight% by weight

parts parts Regulation: powdered rubber waste 100 ALIGN! 90.29 100 ALIGN! 90.46 tall oil resin 10 9.03 10 9.05 FeCl ₂ .4H ₂ O 0.25 0.23 0.25 0.22 phenylhydrazine 0.50 0.45 - - diphenylguanidine - - 0.30 0.27 110.75 100.00 110.55 100.00 methanol 1.00 1.00 temperature increase, ° C +3,5 +2,9 Test results (note 1): Mooney viscosity, 100 ° C, 100 ALIGN! ML 1 + 4 72 36 hardness, ⁰ Shore 70 71 tensile strength, MPa 8.4 8.3 elongation at break,% 230 230 specific gravity, g / cm ³ 1.20 1,21 Note 1: Regulation for testing wt. % powdered regenerate 95.2 Mixing is performed in the laboratory. zinc oxide 2,0 mixing equipment stearic acid 0.8 sulfur 1.0 The test plates are vulcanized accelerator SANTOCURE Mohr 15 minutes at 143 ° C (cyclohexylbenzothiazylsulfen- 1.0 amid)

Table IX weight parts Example 19 weight% Regulation: talc oil resin rubber powder FeCl ₂ .4 H ₂ O diphenylguanidine, 100 ALIGN! 13.9 0.5 0.3 87.18 12.12 0.44 0.26 methanol 114.7 1.0 100.00 Test results: Mooney viscosity, 100 ° C, hardness, ⁰ Shore tensile strength, MPa elongation at break,% specific weight, g / cm ³ ML 1 + 4 ~ 50 64 10.7 310 1.19

Claims (10)

Subject A method for the regeneration of rubber, wherein the ground or crushed rubber waste in the form of particles of at most 1 mm, preferably at most 0.8 mm, which has been practically stripped of its textile or metal constituents, is degraded by chemical regenerants which include reducing agents. agent chloride oxidizable metal of the iron group and the plasticizer ·, and wherein the regeneration is carried out in the solid phase in a gas containing oxygen or consisting of free oxygen at a temperature of at most 100 ° C, preferably at most 80 ^Q C, mixing in a mixer of powders so long until the reducing agent has reacted virtually completely with the double bonds in the rubber, characterized in that either the phenylhydrazine in a quantity of 0.2 to 1 why or diphenylguanidine in a quantity of 0.2 to 0.8 is added as the reducing agent % of the metal chloride of the jelly group is added in an amount of 0.1 to 0.4 by weight as plasticizer o at least one substance selected from the group consisting of tulle oil resin and dipentene, optionally in admixture with another plasticizer, is allowed to stir for at most 30 minutes, the total amount of plasticizer being at most 17.5% , the mass of dipentene is at most 5%, the mass of tulle oil resins is at most 17.5%, the mass of dipentene when used as the sole plasticizer or in admixture with another plasticizer is 0.5 to 5%, the amount of tall oil resins, when used as the sole plasticizer or in admixture with a plasticizer other than dipentene, is 7 to 17.5 why, the amount of plasticizer other than tall oil resin and dipentene is at most 10% and weight INVENTION the amount of tall oil resins when used together with dipentene varies in proportion to the weight of dipentene and is 8 to 16% at a weight of dipentene of 5 to 0.5%, all of the above. data refer to the total weight of the mixture of rubber waste, reducing agent, iron chloride metal chloride and plasticizer. 2. A process according to claim 1, wherein the stirring is carried out at a temperature of at most 80 ° C. • 3. The process according to claim 2, wherein the stirring is carried out at a temperature of at most 60 [deg.] C. 4. Process according to claim 1, characterized in that the rubber waste is treated in the form of particles having a size of at most 0.8 mm. 5. Method according to claim 1, characterized in that the rubber waste is treated in the form of particles having a size of at most 0.4 mm. 6. A process according to claims 1 to 5, characterized in that the stirring is carried out for 3 to 15 minutes. 7. A process as claimed in any one of Claims 1 to 6, wherein iron chloride is added as the chloride of the oxidizable metal of the iron group. 8. A process according to claim 1, wherein diphenylguanidine in an amount of 0.3 to 0.5% by weight is added as reducing agent. ¹ 9. The method according to claims 1 to 8, characterized in that the direct regeneration is carried out with stirring in an impeller equipped with an impeller type, which rotates at a peripheral speed of the order of 2000 m / min. Method according to Claims 1 to 8, characterized in that the direct regeneration is carried out with stirring in a trough mixer equipped with a stirrer made of tape.