DE102013104592A1 - Process for the preparation of a rubber mixture - Google Patents

Abstract

The invention relates to a process for producing a rubber mixture which contains at least one diene rubber and which is characterized by the following process steps: Homogeneous mixing of at least one polymer with a glass transition temperature Tg of greater than + 50 ° C (high Tg polymer) with at least one oil in a first mixing stage; - Adding the homogeneous mixture of high-Tg polymer and oil to one or more diene rubbers and one or more fillers and one or more anti-aging agents and one or more ozone protection waxes and one or more plasticizers and one or more inorganic activators and one or more vulcanization accelerators and a vulcanization system and further processing aids in at least one further mixing stage in a mixer; - Subsequent vulcanization of the rubber compound. The rubber mixture produced according to the invention can be used for the production of tires and other technical rubber articles such as belts, hoses and belts.

Description

The invention relates to a method for producing a rubber mixture, in particular for pneumatic vehicle tires, straps, belts and hoses.

The physical properties of a rubber compound are determined essentially by the nature and also by the amount of the ingredients contained therein, such as, for example, various polymers, fillers, plasticizers, etc. It is essential here that the other polymers present in the rubber mixture in addition to the other ingredients are well distributed, ie as evenly as possible, in the polymer matrix. Such a uniform distribution is called good dispersion. Only with a good dispersion, the rubber compound shows correspondingly good physical properties, since only then optimal interaction or binding of the individual ingredients is guaranteed to the polymer matrix. In order to optimize the physical properties, it has been attempted, inter alia, to introduce thermoplastic polymers directly into the rubber mixture, such as, for example, in US Pat DE 603 02 265 T2 or DE 60 2004 001 008 T2 described. In particular with rubber mixtures which contain at least one diene rubber as the main polymer component, thermoplastic polymers (TP), in particular polyethers, can not be incorporated homogeneously, but in some cases will even be visible as macroscopic particles with the naked eye. Even if the particle size is chosen to be very small, the TP particles tend to agglomerate, ie larger domains of TP are formed in the polymer matrix. This poor dispersion or poor solubility is, for example, in DE 696 19 900 T2 or in JP 2004 238 547 A described.

The invention is based on the object to provide a process for the preparation of a rubber mixture, which is characterized by an improved dispersion of polymers having a glass transition temperature T _g of greater than + 50 ° C in rubber mixtures containing at least one diene rubber. The glass transition temperature T _{g of} the polymer having a T _g of greater than + 50 ° C. should remain after vulcanization of the rubber mixture which contains a diene rubber.

This object is achieved by a process for the preparation of a rubber mixture, which is characterized by the following process steps: In at least one first mixing step is a homogeneous mixing of at least one polymer having a glass transition temperature T _g of greater + 50 ° C (high-T _g polymer ) with at least one oil instead. Subsequently, this now homogeneous mixture of high-T _g polymer and oil to one or more diene rubbers and one or more fillers and one or more anti-aging agents and one or more ozone protective waxes and one or more plasticizers and one or more inorganic activators and one or more Vulkanisationsbeschleunigern and a vulcanization system and other process auxiliaries added in at least one other mixing stage in a mixer. Subsequently, the resulting rubber precursor mixture is vulcanized.

It has surprisingly been found that the dispersion of high-T _g polymer in a polymer matrix which contains at least one diene rubber as the main rubber component is significantly improved if the high-T _g polymer is homogeneously mixed with at least one oil in at least one first mixing stage and then added to the other ingredients of the rubber composition. Main rubber component means that the polymer matrix contains at least 50 phr of at least one diene rubber. The mixing of the high-T _g polymer with oil initially lowers the Tg. It is surprising that the T _{g of} the high-T _g polymer has returned to its original value after vulcanization, since it was originally assumed that the Tg Mixture of high-T _g polymer and oil is relatively stable. After heating, however, it can be seen that the oil used is found in the rubber matrix of the diene rubber. This preserves the advantageous properties of the high-T _g polymer in the rubber mixture. This was not to be expected.

The other ingredients are essentially one or more diene rubbers and one or more fillers and one or more anti-aging agents and one or more antiozonant waxes and one or more plasticizers and one or more inorganic activators and one or more vulcanization accelerators and a curing system and others processing aids.

All values given for the glass transition temperatures were determined by means of DSC measurements.

The first mixing step, the homogeneous mixing of high-T _g polymer with at least one oil, preferably takes place in an extruder. It is particularly advantageous if the homogeneous mixing of the high-T _g polymer with polystyrene and with at least one oil takes place at a temperature above the melting point of the high-T _g polymer, ie preferably in a temperature range between 140 ° C and 250 ° C. It is particularly preferred if the high-T _g polymer is a thermoplastic, preferably a polyether. Preferably, the polyether is selected from the group consisting of polyphenylene ether (PPE) and polyoxyphenylenes (PPO), also referred to as polyphenylene oxide. The use of other, other thermoplastics, such as polyethylene, polypropylene, polybutene, polyvinyl chloride, polyacrylonitrile, polyamide, polycarbonate, polyester or polysulfone, alone or in combination is also conceivable. The oil is preferably a mineral oil. When using mineral oil, this is preferably selected from the group consisting of DAE (distilled aromatic extracts) and / or RAE (residual aromatic extract) and / or TDAE (treated distilled aromatic extracts) and / or MES (mild extracted solvents), with TDAE being particularly preferred.

In at least one further mixing stage in a mixer, preferably an internal mixer, the now homogeneous mixture of high-T _g polymer and oil to one or more diene rubbers and one or more fillers and one or more anti-aging agents and one or more ozone protective waxes and one or a plurality of plasticizers and one or more inorganic activators and one or more vulcanization accelerators and a vulcanization system and other process auxiliaries.

For example, polyether preferably has a glass transition temperature (Tg) of over 140 ° C and thus difficult to blend into a rubber composition containing diene rubbers. The homogeneous mixing of the high Tg polyether with an oil, which generally has a Tg of less than 0 ° C, leads to a total Tg of this homogeneous mixture between 0 and 160 ° C. Due to the lowering of the total Tg of the homogeneous mixture, the polyether is better dispersed in the rubber mixture containing diene rubbers. During the further mixing stage, the oil leaves the polyether domains during mixing and the polyether remains with extremely small domain size and therefore well dispersed in the rubber composition. Likewise, the polyether after vulcanization again has the original T _g .

Diene rubbers are rubbers which are formed by polymerization or copolymerization of dienes and cycloalkenes and thus have C = C double bonds either in the main chain or in the side groups. Diene rubbers have a T _g of less than 0 ° C. The diene rubber is in a preferred embodiment selected from the group consisting of natural polyisoprene (NR) and / or synthetic polyisoprene (IR) and / or butadiene rubber (BR) and / or styrene-butadiene rubber (SBR) and / or solution-polymerized styrene-butadiene rubber (SSBR ) and / or emulsion-polymerized styrene-butadiene rubber (ESBR) and / or nitrile rubber and / or chloroprene rubber and / or butyl rubber and / or bromobutyl rubber and / or ethylene-propylene-diene rubber and / or styrene-butadiene copolymer and / or styrene-isoprene-butadiene rubber. Copolymer zbd / or isoprene-butadiene copolymer and / or acrylonitrile-butadiene copolymer. In particular, nitrile rubber, chloroprene rubber, acrylonitrile-butadiene copolymer, butyl rubber, halobutyl rubber or ethylene-propylene-diene rubber are used in the production of technical rubber articles such as belts, belts and hoses. But it is quite possible that at least one other rubber is used, which is not a diene rubber.

It is preferred if the diene rubber is natural and / or synthetic polyisoprene and / or butadiene rubber and / or styrene-butadiene rubber, which may be solution-polymerized or emulsion-polymerized, with natural polyisoprene being very particularly preferred. Furthermore, the styrene-butadiene rubber may be modified with hydroxyl groups and / or epoxy groups and / or siloxane groups and / or amino groups and / or aminosiloxane and / or carboxyl groups and / or phthalocyanine groups. But there are also other known to the expert person, modifications, also referred to as functionalizations in question.

The diene rubber or diene rubbers, if more than one diene rubber is used, is used in amounts of from 50 to 100 phr, preferably in amounts of from 80 to 100 phr, more preferably in amounts of 100 phr. In particular, when the above amount of diene rubber contains 10 to 50 phr of synthetic rubber such as styrene-butadiene rubber, the best dispersion results are exhibited.

When using natural polyisoprene, this is used in amounts of from 50 to 100 phr, preferably in amounts of from 80 to 100 phr, more preferably in amounts of 100 phr. In this case it is advantageous or necessary if the high-T _g polymer is first mixed with polystyrene in the first mixing stage and only then the oil is added.

The term phr (parts per hundred parts of rubber by weight) used in this document is the quantity used in the rubber industry for mixture formulations. The dosage of the parts by weight of the individual substances is always based on 100 parts by weight of the total mass of all the rubbers present in the mixture.

The filler used is a light and / or dark filler, so that the total amount of filler thus can only consist of light or dark filler or a combination of light and dark fillers.

In a particularly preferred embodiment, the light filler used is silica, preferably precipitated silica. The use of silica usually has a positive influence on the rolling resistance behavior. Advantageously, the silica is used in amounts of 1 to 300 phr, preferably 1 to 250 phr, particularly preferably 1 to 200 phr, again particularly preferably 1 to 150 phr, again very particularly preferably 1 to 100 phr. The silicas used in the tire industry are generally precipitated silicas, which are characterized in particular according to their surface. To characterize the nitrogen surface (BET) according to DIN 66131 and DIN 66132 as a measure of the inner and outer filler surface in m ² / g and the CTAB surface according to ASTM D 3765 as a measure of the outer surface, which is often considered the rubber-effective surface, in m ² / g. Silicas are preferred with a nitrogen surface area greater than or equal to 100 m ² / g, more preferably between 110 and 300 m ² / g, most preferably between 140 and 250 m ² / g, and a CTAB surface between 100 and 250 m ² / g, particularly preferably between 110 and 230 m ² / g and very particularly preferably between 140 and 200 m ² / g used.

If a coupling agent, in the form of silane or an organosilicon compound, is used to attach the silica to the polymer matrix, the amount of coupling agent is 0 to 20 phr, preferably 0.1 to 15 phr, more preferably 0.5 to 10 phr , As coupling agents, all of the skilled person can be used for the use in rubber compounds known coupling agents. Particularly noteworthy here are mercaptosilanes and here in particular those which are characterized by a reduction of volatile organic compounds, and / or in which the mercapto group may be blocked or protected. It is preferred if the rubber mixture according to the invention contains at least one dark filler.

The dark filler is preferably carbon black, preferably in amounts of from 1 to 100 phr, more preferably in amounts of from 5 to 80 phr and most preferably in amounts of from 10 to 60 phr. In a particularly preferred embodiment, the carbon black has an iodine value, according to ASTM D 1510, also referred to as iodine absorption number, of from 75 to 140 g / kg, preferably from 90 to 130 g / kg, and a DBP number between 70 and 150 cm ³ / 100g, preferably between 90 and 140 cm ³ / 100g. The DBP number according to ASTM D 2414 determines the specific absorption volume of a carbon black or a light filler by means of dibutyl phthalate. The use of such a type of rubber in a rubber compound, in particular for pneumatic vehicle tires, ensures the best possible compromise between abrasion resistance and heat build-up, which in turn influences the ecologically relevant rolling resistance. It is preferred in this case if only one type of carbon black is used in the respective rubber mixture, but it is also possible for different types of carbon to be mixed into the rubber mixture.

In addition to silica and carbon black, other fillers such as aluminum hydroxide, phyllosilicates, lime, chalk, starch, magnesium oxide, titanium dioxide, rubber gels, short fibers, etc. can also be mixed in any desired combinations.

The other ingredients, such as anti-aging agents, antiozonants, plasticizers, inorganic activators, vulcanization accelerators, vulcanization system and other process auxiliaries are used in the process according to the invention in the usual amounts in the rubber industry. For example, plasticizers may be used in a total amount of 1 to 100 phr, preferably 1 to 80 phr, most preferably 1 to 60 phr. The plasticizer preferably selected from the group consisting of mineral oils and / or naphthenic oils and / or synthetic plasticizers and / or fatty acids and / or fatty acid derivatives and / or resins and / or ingredients and / or glycerides and / or terpenes and / or vegetable oils and / or biomass-to-liquid oils and / or liquid polymers.

The vulcanization system is often referred to as a crosslinking system and contains essentially crosslinkers, sulfur donors and / or elemental sulfur, accelerators and retarders.

The amount of vulcanization accelerator is 0.1 to 10 phr, preferably 0.5 to 5 phr, wherein at least one vulcanization accelerator is selected from the group consisting of thiazole accelerator, mercapto accelerator, sulfenamide accelerator, sulfenimide accelerator, guanidine Accelerators, thiuram accelerators, dithiocarbamate accelerators, amine accelerators, thioureas, dithiophosphate accelerators and / or other accelerators.

The vulcanization of the rubber mixture is preferably carried out in the presence of elemental sulfur or sulfur donors, with some sulfur donors can act simultaneously as a vulcanization accelerator.

Adding the homogeneous mixture of high T _g polymer and oil to one or more diene rubbers and one or more fillers and one or more anti-age agents and one or more ozone protectants and one or more plasticizers and one or more inorganic activators and one or more vulcanization accelerators and a vulcanization system and other processing aids take place in at least one further mixing stage in a mixer. It is advantageous if the vulcanization system and the vulcanization accelerators are added in a last, preferably in a third and final, mixing stage. By adding the vulcanization system, the so-called ready mix is produced. The finished mixture is further processed eg by an extrusion process or a calendering process and brought into the appropriate form. The rubber composition prepared according to the invention can be used for the production of tires and other technical rubber articles such as belts, hoses and straps.

The invention will now be explained in more detail with reference to comparative and exemplary embodiments, without, however, being restricted to these examples. Table 1 shows the first mixing stage, in which polyphenylene ether is homogeneously mixed as a polyether with polystyrene and with at least one oil in an extruder. The data in Table 1 relate to percent by weight. Table 1 also shows the dispersion of the PPE in the rubber mixture on the basis of a vulcanized test specimen. The dispersion was treated with the disperGRADER + ^™ from Dynisco according to ISO 11345 (at 30% magnification). The dispersion is given in percent [%], with higher values representing an improvement. Table 2 shows the formulations of blends prepared by the process of the present invention (E1 and E2) and thus containing at least one high T _g polymer. Blends E1 and E2 contain NT33, ie, 0.7 weight percent PPE was pre-mixed with 0.3 weight percent TDAE oil. The corresponding dispersion values of the rubber mixture are likewise to be taken from Table 2, the determination being carried out as described above. Table 1 NT33 NT45 NT46 NT47 PPE Wt .-% 0.7 0.56 0.49 0.56 Oil (TDAE) Wt .-% 0.3 0.20 0.30 0.30 Polystyrene (PS) Wt .-% - 0.24 0.21 0.14 T _g (PPE + oil + PS) DSC measurement ° C 99 101 92 84 Disperson % 31.6 98.86 98.83 97.19 Original T _g ° C 220 180 180 195

If 100 phr of natural rubber and 43.85 phr of carbon black (N234) and the other constituents of the mixture are added to the indicated amounts of NT45, NT46 and NT47 in a further mixing stage, the dispersion values shown result. For the NT33, a "toblerone-like" coarse structure is already recognizable macroscopically after the first mixing stage, which is also reflected in the poor dispersion values. Table 2 Ref. E1 E2 NO phr 20 20 20 BR phr 44 44 44 SBR phr 36 36 36 silica phr 95 85 85 silane phr 6.65 5.95 5.95 oil phr 45 42.5 40 Additives ^a phr 11 11 11 NT33 phr - 7.6 15 SBS block copolymer ^b phr - 3.8 7.6 Vulcanization system ^c phr 5.6 5.6 5.6 dispersion % 92 94 92 ^a ozone protection, aging protection, ZnO, stearic acid
^b Vector 4461, Dexco Polymers
^c DPG, CBS, sulfur

It can be seen from Table 2 that PPE can be dispersed just as well in a diene rubber-containing rubber mixture as silica. The block copolymers listed in Table 2 are hereby added as processing aids.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 60302265 T2 [0002]
• DE 602004001008 T2 [0002]
• DE 69619900 T2 [0002]
• JP 2004238547 A [0002]

Cited non-patent literature

• DIN 66131 [0017]
• DIN 66132 [0017]
• ISO 11345 [0026]

Claims (9)

Process for the preparation of a rubber mixture containing at least one diene rubber, characterized by the following process steps: Homogeneous mixing of at least one polymer having a glass transition temperature T _g of greater than 50 ° C (high T _g polymer) with at least one oil in a first mixing stage ; - Adding the homogeneous mixture of high-T _g polymer and oil to one or more diene rubbers and one or more fillers and one or more anti-aging agents and one or more ozone protective waxes and one or more plasticizers and one or more inorganic activators and one or more vulcanization accelerators and a vulcanization system and other processing aids in at least one further mixing stage in a mixer; - subsequent vulcanization of the rubber final mixture. A method according to claim 1, characterized in that the high-T _g polymer is homogeneously mixed with oil in an extruder. A method according to claim 1 or 2, characterized in that the homogeneous mixing of the high-T _g polymer with at least one oil at a temperature above the melting point of the high-T _g polymer takes place. Method according to one of claims 1 to 3, characterized in that the oil is a mineral oil. Method according to one of claims 1 to 4, characterized in that in the first mixing stage additionally at least one polystyrene with at least one high-T _g polymer and with at least one oil is homogeneously mixed. Method according to one of claims 1 to 4, characterized in that the high-T _g polymer is a polyether. A method according to claim 6, characterized in that the polyether is selected from the group consisting of polyphenylene ether (PPE) and polyoxyphenylenes (PPO). A method according to any one of claims 1 to 7, characterized in that the diene rubber is selected from the group consisting of natural or synthetic polyisoprene or butadiene rubber or styrene-butadiene rubber or solution-polymerized styrene-butadiene rubber or emulsion-polymerized styrene-butadiene rubber. Method according to one of claims 1 to 8, characterized in that the filler is silica.