DE10251032A1 - Process for the production of rubber compounds - Google Patents

Abstract

The invention relates to a process for the production of rubber mixtures in a stamp kneader (1) or an aggregate combination of a stamp kneader (1) and a stampless kneader (4) preferably arranged underneath it. DOLLAR A The mixture mixed in the stamp kneader (1) is mixed with the stampless kneader (4) during the mixing process while simultaneously increasing its working volume and / or during the emptying process and / or if a stampless kneader (4) (aggregate combination) is also present. transferred mixture applied superficially in the course of the further mixing process, the boiling point of which is below the desired final temperature of the mixture and which is evaporated without residue in the course of further processing. Alternatively, the inner metal surfaces of the stampless kneader (4) can be cooled before or during the transfer of the mixed material from the stamp kneader (1) into the stampless kneader (4) by applying liquid and / or blowing, preferably with dried air, the liquid flowing the further processing is evaporated residue-free.

Description

The invention relates to a method for the production of rubber compounds in a stamp mixer or an aggregate combination of a stamp kneader and one preferably below the same stampless kneader attached.

In the production of rubber compounds one strives for one if possible low mixing temperature on: during basic mixing because of the better filler; when finished mixing because of the lower risk of premature vulcanization; for heat sensitive Polymers, for example natural rubber, to damage the Avoid polymer chains by exposure to high temperatures.

The reduction of the mixing temperature has therefore been the subject of machine and process development for decades, such as B. through the development of kneaders with interlocking Rotors, from HESC rotors (High Efficiency, Super Cooling rotors), due to the different position of the cooling channels in the kneading troughs the use of low speeds and many other measures more.

These are the procedures but indirect cooling, the one surrounding the kneader Trough or the rotor is cooled by the water circulating in the cooling channels and so the heat generated during mixing is dissipated. The one circulating in the cooling channels Water has no contact with the mixture. Kick cracks on the kneader on, the Kneaders are shut down and repaired.

A fundamental disadvantage of the process of indirect cooling by running water in the trough or in the rotors is that one on thermal conductivity and the capacities the metal layers in the trough or in the rotors are dependent, it is known that in particular highly wear-resistant metal alloys poor thermal conductivity exhibit.

As a result, the The temperatures of the mixture and the metal masses are countercyclical, d. H. in the required cooling process during the Mixing process first the metal masses of the kneader are cooled down before any significant cooling of the mixed material. The production of rubber compounds in a mixed stage ("one-stage process") is therefore despite many other advantages, such as B. small space requirement in the Usually on small kneaders and / or plastic, slowly vulcanizing Mix limited and is for adequate (online) cooling while of the mixing process often combined with long total mixing times.

To help in the production of rubber compounds to ensure a sufficiently low mixing temperature, 80 to 90% of all mixtures produced worldwide are therefore currently especially those in large kneaders manufactured tire mixtures, manufactured in two or multi-stage processes, the mixtures being required after each mixing stage eject from the kneader on a rolling mill or a discharge extruder to form into a fur, to cool and subsequently one or more mixing processes). This approach is associated with high costs and time and is therefore uneconomical.

From the EP 0 472 931 A1 and the DE 37 02 833 A1 It is known to produce a rubber mixture in an aggregate combination of a stamp kneader and a stampless kneader arranged underneath, it being possible, in particular when using stampless kneaders with intermeshing rotors, to cool the mixture before adding further substances and thus to complete it in a system cycle Mix. Since the stampless kneader is usually operated at a lower speed, it is possible to reduce the counter-cyclical temperature profile between the kneader and the mixture, as a result of which the desired cooling of the mixture starts earlier and the cooling of the mixture is accelerated.

But also with this method, in particular in the production of very hot running Mixtures or for mixtures that only require a very short mixing time a support or Improve cooling desirable.

A direct addition of water for rubber compound for cooling purposes stands in the way that rubber mixtures are made almost exclusively from hydrophobic Mixture components (rubber, paraffinic plasticizers, carbon black, paraffinic waxes etc.) exist, but water is hydrophilic.

In the EP 0 837 095 A1 describes a method for producing a rubber mixture containing silica, in which an improved distribution of the filler silica and good vulcanizate properties can be achieved by kneading the mixtures according to very specific temperature profiles. The coupling of the silica to the silane coupling agent should take place at temperatures of 130 to 140 ° C. The temperature can be controlled by the speed of rotation of the rotors or by the introduction of water directly into the mixture. In the latter case, the water is incorporated into the mixture. But even this system, although a partially hydrophobic element is introduced via the silica, adheres to the basic deficiencies of water-containing mixtures, such as. B that trapped water residues remain in the mixture, which during later processing, e.g. B. during vulcanization, to irregularities on Lead product.

The invention is therefore the object the basis for a mixing process of the type mentioned at the beginning cooling down to improve.

The task is solved according to the invention by that the mixture mixed in the stamp mixer during the Mixing process with simultaneous increase in his work volume and / or while the emptying process and / or if there is an additional one stampless kneader (aggregate combination) on the in the stampless Kneader transferred mixture a liquid appears superficially in the course of the further mixing process is applied, the boiling point below the desired end temperature the mixture lies in the course of further processing residue is evaporated.

The angry, especially cold liquid is about its heat of vaporization for direct cooling of the mix. The liquid evaporates on the hot Obertläche the rubber compound and leaves no residue on the compound. The moisture content the mixture is unchanged before and after the cooling process. there it is important that the liquid superficially applied and is not worked into the mixture, because only at the superficial Can apply the liquid residue evaporate and it can be cooled effectively. There are none left trapped liquid residues in the mixture that is used in the later Processing, e.g. B. in vulcanization, to irregularities lead on the product would.

Since the one used to cool the mix liquid superficial An essential point is that the usable volume is applied of the stamp kneader is not reduced.

The method according to the invention is particularly effective in the case of aggregate combinations of a stamp kneader and one preferably stampless kneader arranged underneath it and there again particularly preferably during the emptying process of the stamp kneader and / or in the stampless kneader, since in the stampless kneader in the Usually mixed at lower temperatures and therefore it turns on particularly effective cooling arrives.

The working volume of the stamp kneader can be increased by venting the stamp and / or increasing the center distance of the rotors during mixing and / or by opening the emptying flap. Devices that allow an increase in the center distance of the rotors are such. B. from the EP 0 230 333 A2 known.

According to the secondary claim 3 the task is also solved by a method for producing a rubber mixture in an aggregate combination from a stamp kneader and preferably below it attached stampless kneader, in which the inner metal surfaces of the stampless kneader before or during the transfer of the Mixed material from the stamp kneader into the stampless kneader by application of liquid and / or blowing with preferably dried air, being the liquid is evaporated without residue in the course of further processing.

Since it is the stampless kneader is an open system advantageously, the gases generated during evaporation are unhindered escape. The inner metal surfaces the kneader, d. H. the kneader walls and the rotors, are directly from the inside with a liquid and / or air cooled and the cool ones inner metal surfaces then cause cooling the mixture transferred to the stampless kneader. This process is for the aggregate combination of stamp kneader and stampless kneader can be carried out in a particularly economical manner since while the cooling of the stampless kneader mixed in the stamp kneader at the same time can be. The liquid applied evaporates some of the hot ones Metal walls. The unevaporated part can be drained through the drain opening become. However, it is preferred that liquid residues after application on the metal surfaces remain in the stampless kneader. These leftovers, at the latest in the course of further mixing work by the enthalpy of the mixture kneaded into the stampless kneader evaporates and thus contribute to further effective cooling of the Mix at.

The liquid can be injected and / or spray on be applied to one as possible uniform and fine distribution of the liquid on the surface to achieve the rubber mixture or the inner metal surfaces. To this Purpose into the kneader wall introduced and / or over attached to the stampless kneader spray nozzles become.

It has proven to be beneficial when the evaporation of the applied to the mix or the inner metal surfaces liquid by an air flow, in particular by means of a blower or fan, is accelerated.

Depending on the liquid used and the desired final temperature of the mixture, the cooling process can be accelerated or made possible by lowering the boiling point of the liquid applied by evacuation. The cooling can, for. B. can be strengthened in an advantageous manner by - such. B. in the registration DE 40 27 261 C1 described - the evacuation takes place by partitioning the space between the emptying opening of the stamp kneader and the filling opening of the stampless kneader and applying a vacuum.

In order to ensure sufficient cooling of the material to be mixed, it has proven to be advantageous if per 100 parts by weight of mixture in the kneader 5 up to 20 parts by weight of liquid can be applied to the mix or the inner metal surfaces.

The liquid can be in one or several portions applied to the mix and / or the inner metal surfaces become.

The application of liquid according to the invention in the mixing process also offers the possibility, other rubber aggregates, especially reactive aggregates, with the help of the liquid in the form of an emulsion or suspension in the mix. A more even distribution the aggregates, such as B. fillers or Crosslinking chemicals in the rubber mixture is achieved. Temperature peaks within the mixture and a prior reaction are due to the cooling effect the liquid avoided.

To optimize processing, for networking and improving the adhesive properties of Rubber mixtures become the rubber and / or the rubber mixtures reactive additives added. These reactive aggregates affect the plasticity the rubber mixtures, the crosslinking speed of the mixtures, the degree of crosslinking, the properties of the vulcanizates and the Adhesion to various materials (e.g. textile reinforcements, steel, other metals, plastics etc.) and the connection of the rubber molecules to fillers z. B. on silica.

The reactive aggregates go thereby chemical reactions, the reaction speed of which Laws of chemical reaction kinetics follow; that is the reaction rate at a temperature increase of 10 K approximately doubled. For this reason, play when processing mixtures with reactive aggregates both the level of the temperature as well an even temperature distribution play an important role within the mix. In the preparation of of mixtures on rolling mills, as was customary in the past, show the mixtures a low temperature and a relatively even temperature distribution on while almost exclusively today used kneaders (internal mixers) mixed hotter and inhomogeneous becomes.

The maximum is found in the kneaders Energy input between the effective edges of the rotors and the kneader wall instead, this makes the rubber or the rubber mixture inhomogeneous heated. A The consequence of this is that the additives are preferably mixed in there where the rubber or rubber mixture is already the softest and most receptive has become. The higher the temperature, the more inhomogeneous the temperature distribution and the more uneven the local concentration of reactive additives, the greater the risk that the reactive additives, e.g. B. networking, Degradation and / or adhesive, react early (scorch), before even distribution at all can only begin.

Because the aggregates in stamp kneaders only while of ventilation of the stamp can be added takes the risk of local over-concentrations with this type of mixer too. The danger increases when the reactive Aggregates - like common nowadays - for improvement handling and / or to reduce dust pollution in Polyethylene films are added packaged. In this case The polyethylene must first be melted before the substances are distributed become.

In the case of a stampless kneader, the additives, if this z. B. as usual in a tandem arrangement a stamp kneader is attached, added via a downpipe become. In this case there is a risk of constipation in the downpipe.

All of the disadvantages mentioned the introduction of, in particular, reactive additives can be counteracted in that in the method according to the invention the additives, in particular the reactive additives, emulsify or suspended in the (cooling) liquid the mixture can be introduced. The emulsions or suspensions can by injecting or spraying into the kneader and applied to the mixture, whereby it is particularly preferred if the reactive additives as Emulsion or suspension introduced into the stampless plasticine as the temperatures of the mixture in the stampless kneader are generally not that high.

The liquid acts when it is introduced on or into the rubber mixture at the same time as a coolant and, since it prefers the hottest parts of the kneader evaporates as a thermostat. The mixture also disintegrates in the mixer when it is introduced of liquid (Emulsion, suspension) in smaller lumps of mixture on the surface of the reactive aggregates are then widely distributed and after the evaporation of the liquid and continue evenly can be mixed in.

The aggregates are preferred in a volume of liquid emulsified or suspended between 0.1 to 10% of the volume the mixture is.

As for cooling and optionally emulsifying or suspending liquid used can be various liquids be used. However, water and Ethanol used. These substances are available in large quantities a low boiling point and are in terms of environmental impact and the easy regeneration option to be viewed as critical.

In a preferred embodiment of the invention, at least one wetting agent is added to the water used for cooling. The wetting agent reduces the surface tension and is in the Able to wet the surface completely and extensively, which further improves the cooling effect.

Suitable wetting agents are anionic, cationic or non-ionic wetting agents. That or the wetting agents become the cooling water used in concentrations of 0.01 to 5 wt .-%, preferably from 0.2 to 1% by weight. It is also an advantage if such wetting agents are used that prevent limescale deposits or delay.

The invention is now based on the Drawing showing an embodiment represents closer described. The only drawing figure shows a vertical one Section through that variant of the invention a device for the production of rubber compounds, the one Stamp kneader and a stampless kneader.

In the following only the essential components of this device are described, with further details on the EP 0 472 931 A1 referenced, which relates to this kneader arrangement and describes in more detail.

The upper stamp in the drawing figure and an up and down movable stamp 10 stamp kneaders 1 has a loading opening 2 via which the mixture components of the mixing chamber forming the basic mixture 13 are fed. In the mixing chamber 13 there are two the actual mixing process after lowering the stamp 10 performing rotors 14 ,

After completing the basic mix, the mixing chamber 13 by opening an emptying flap 17 opened in the form of a saddle and the mix passes freely through a channel-shaped space 22 in the second kneader without stamp 4 , When the mixers are transferred from the kneader 1 in the kneader 4 is one between the kneaders 1 . 4 provided flap 23 has been pivoted into its open position shown in dashed lines. In the stampless kneader 4 can the mixed material further, in particular reactive additives, such as. B. the vulcanization chemicals are added.

According to the invention, the mix is in the kneader without a stamp 4 for cooling with a liquid, e.g. B. water, which may contain emulsified or suspended reactive additives in it, sprayed or the inner metal surfaces of the stampless kneader 4 are sprayed with a liquid which may contain reactive additives emulsified or suspended in it. This can be done by spraying liquid with or without the use of nozzles. The nozzles or the devices via which the liquid is sprayed on are positioned at the relevant point (s) or are positioned and used there if necessary.

But it is also possible to have the liquid in the stamp mixer 1 , preferably shortly before or during the emptying process. In this case, the liquid is injected with pressure into the kneader via injection nozzles.

The injection takes place in the stamp mixer 1 immediately before the emptying flap 17 opened and the mix in the second stampless kneader 4 is transferred.

A wetting agent can be added to the water used for cooling or to the emulsion or suspension in order to distribute the largest possible area on the surface of the mixture or on the inner metal surfaces of the stampless kneader 4 to achieve. Known anionic, cationic or non-ionic agents can be used as wetting agents. The proportion of wetting agent in the water is in particular between 0.01 and 5%, preferably between 0.2 and 1%. It is also advantageous if wetting agents are used that prevent or delay any limescale deposits. It is of course also advantageous if the sprayed-on water, in particular wetting agent-containing water, is sprayed onto as large a part as possible of the surface of the mixture or the inner metal surfaces. In order to accelerate the cooling process, it is also advantageous if the evaporation is accelerated immediately after the water is sprayed on by blowing in or supplying air, and thus the cooling is improved.

Another option is the gap between the discharge opening of the stamp mixer and the loading opening of the stampless mixer seal off and the evaporation process of the water by applying of a vacuum further accelerate and the mix of residues of water, low molecular weight proportions of chemicals and / or oligomers Rid of polymerization chemicals.

Claims (18)

Process for the production of rubber compounds in a stamp kneader ( 1 ) or an aggregate combination from a stamp mixer ( 1 ) and a stampless kneader preferably placed underneath it ( 4 ), characterized in that on the in the stamp mixer ( 1 ) mixed mixture during the mixing process with simultaneous increase in its working volume and / or during the emptying process and / or with the additional presence of a stampless kneader ( 4 ) (Aggregate combination) on the in the stampless kneader ( 4 ) transferred mixture is superficially applied in the course of the further mixing process, the boiling point of which is below the desired final temperature of the mixture and which is evaporated without residue in the course of further processing. A method according to claim 1, characterized records that the working volume of the stamp mixer ( 1 ) by lifting the stamp ( 10 ) and / or increasing the center distance of the rotors ( 14 ) and / or by opening the emptying flap ( 17 ) he follows. Process for the production of rubber mixtures in an aggregate combination from a stamp kneader ( 1 ) and a stampless kneader preferably placed underneath it ( 4 ), characterized in that the inner metal surfaces of the stampless kneader ( 4 ) before or during the transfer of the mix from the stamp mixer ( 1 ) in the stampless kneader ( 4 ) are cooled by applying liquid and / or blowing with preferably dried air, the liquid being evaporated without residue in the course of further processing. Method according to at least one of claims 1 to 3, characterized in that that the liquid by injecting and / or spraying is applied. Method according to at least one of claims 1 to 4, characterized in that that the evaporation of the liquid applied by an air stream, especially by means of a blower or fan, is accelerated. Method according to at least one of claims 1 to 5, characterized in that that the boiling point of the liquid applied by evacuation is lowered below the target final temperature of the mixture. A method according to claim 6, characterized in that the evacuation by partitioning the space ( 22 ) between the discharge opening of the stamp mixer ( 1 ) and the filling opening of the stampless kneader ( 4 ) and applying a vacuum. Method according to at least one of claims 1 to 7, characterized in that that per 100 parts by weight of mixture in the kneader 5 to 20 parts by weight of liquid be applied. Method according to at least one of claims 1 to 8, characterized in that that the liquid is applied in one or more portions. Method according to at least one of claims 1 to 7 and 9, characterized characterized that the liquid emulsified or suspended rubber additives, in particular contains reactive additives which are introduced into the mixture. A method according to claim 10, characterized in that the Emulsion or suspension introduced into the stampless kneader becomes. A method according to claim 10 or 11, characterized in that the aggregates emulsify in a volume of liquid or suspended between 0.1 to 10% of the volume of the mixture is. Method according to at least one of claims 1 to 12, characterized in that that as a liquid Water is used. A method according to claim 13, characterized in that the At least one wetting agent is added to water. A method according to claim 14, characterized in that the Water is an anionic, a cationic or a non-ionic Wetting agent is added Method according to one of claims 14 or 15, characterized in that that the wetting agent or agents in a concentration of 0.01 to 5% by weight, preferably 0.2 to 1% by weight, is added. Method according to at least one of claims 14 to 16, characterized in that that wetting agents are added to the water, the lime deposits prevent. Method according to at least one of claims 1 to 12, characterized in that that as a liquid Ethanol is used.