MXPA02000243A - High-concentration cross-linking masterbatches. - Google Patents

Abstract

The invention relates to a cross-linking masterbatch comprises more than 40 % by weight of organic peroxide, a synthetic rubber, and a specific silica. More specifically, a highly concentrated cross-linking masterbatch is provided comprising from 40 to 70 % organic peroxide, a synthetic rubber such as EPM and/or EPDM, preferably having a propylene content of 45 % or more and a Mooney viscosity at 100 °C of 30 or more, and a wet-treated and/or dry-treated silica having a specific surface area of 150 m2/g or more or a porous silica having a pore volume of 1.4 ml/g or more.

Description

LOTS MASTERS OF HIGH CONCENTRATION CRACKING The present invention relates to master lots of entanglement, more particularly to master lots used for the interlacing of thermoplastics (elastomers) and rubbers. Thermoplastics, elastomeric thermoplastics and rubbers, elastomers for short, include preferred products such as polyethylene, ethylene vinyl acetate copolymer, ethylene-propylene copolymer (EPM), ethylene-octene copolymer (POE), ethylene propylene diene rubber (EPDM), and butadiene-acrylonitrile co-polymer, all of which have a low price, are widely available, and have excellent physical properties that allow a wide range of uses. The elastomers may be entangled in a conventional manner by heating in the presence of a suitable organic peroxide, for example, to increase their resistance to heat. When elastomers are interlaced, it is preferred, from an economical point of view, to mix the pure organic peroxide with the elastomer. However, such a procedure is not feasible in view of the security considerations. Also, it is known that the use of such pure organic peroxide leads to a less homogeneous distribution in the elastomer to be interlaced, resulting in an irregularly interlaced product with inferior properties, especially compared to a process wherein the elastomers are mixed with organic peroxides formulated with inactive fillers such as calcium carbonate, silica, clay, and talc, or with a polymer or elastomer (called master batches), in the form of sheets or granules. Therefore, in the industry, powder formulations and master batches are generally used in the form of sheets or granules. Powdered formulations wherein the organic peroxide is diluted with inactive fillers have the following advantages when used as an entanglement agent: 1.- They are safe to store and handle, 2. Because they are powders they can be measured within the elastomer of a simple way, regardless of the organic peroxide (solid or liquid) used, and 3. They are not expensive. However, these powder formulations suffer from the following disadvantages: 1. It usually takes a long time to obtain a homogeneous dispersion of the peroxide in the elastomers to be entangled. 2. The formulations tend to be dusty leading to operator exposure to dusts during the measurement of the formulation and while being molded with the elastomers to be entangled. Master batches in the form of sheets or granules, wherein the peroxide is dispersed in a polymer, preferably an elastomer, have the same benefits as powder formulations. Additionally, they require less time to prepare homogeneous dispersions of the peroxide in the elastomer to be interlaced and can be handled without dusting. Therefore, such master batches (sheet or granular type) are often the product of choice for processes where a peroxide and an elastomer are to be intimately mixed. However, master batches of the sheet or granular type typically suffer from the fact that highly concentrated products can not be formed. Where commercial formulations are known to contain 50% by weight of peroxide, commercial master batches of the sheet or granular type are limited to formulations containing 40% by weight of peroxide. Conventional master batch batches containing up to 40% by weight of organic peroxide, EPM or EPDM, and silica with wet treatment or dry treatment as essential ingredients are known to be produced in a conventional manner, for example, in a roller mixer open, kneading said ingredients, optionally with inactive fillers such as the added calcium carbonate, the physical state of the organic peroxide, the properties of the EPM or EPDM (such as Mooney viscosity), ethylene or propylene content), and the properties of the silica treated by wet or dry process (such as specific surface area and oil absorption capacity) are not important in this case. Silicas treated by wet or dry methods used for this purpose have a specific surface area of 40-140 m2 / g and a pore volume of 0.1- 0.6 ml / g. However, if a masterbatch containing more than 40% by weight of a liquid organic peroxide is to be produced by kneading said peroxide with EPM or EPDM and such conventional silica treated either wet or dry in a roller mill, the masterbatch it tends to stick to the roller, making mixing more difficult, it is difficult to remove it from the (thin) sheet roller, and it produces lower force sheets. In addition, it was discovered that the resulting sheets or granules are not stable when stored, they suffer from exudation of the peroxide from the master batch. Similarly, if the masterbatch contains more than 40% by weight of solid organic peroxide, the mass in the rolls breaks easily on the roll when kneading, making it difficult to efficiently knead the product.

It was found that the resulting master batch suffered from peroxide blooming from the master batch. To overcome these problems, W098 / 54249 discloses the production process of a high concentration master batch that essentially contains liquid polymers such as EPM / EPDM having Brookfield viscosity at 60 ° C of 10,000 mPas and lower. However, these liquid polymers are expensive, which is considered to be the main reason why they have not gained acceptance in the market. Accordingly, there is still a need for master batch of peroxide, especially batches based on EPM and / or EPDM, containing more than 40% by weight of peroxide, whether liquid or solid that do not produce dust, are easy to handle and store , which do not contain expensive low molecular weight polymers, and which lead to a homogeneous distribution in the elastomer to be entangled. It was discovered that the high concentration entanglement masterbatches of the present invention solve these problems. These are characterized in that they contain a solid synthetic rubber, such as EPM and / or EPDM, such as the base polymer, from 40 to 70% by weight of an organic peroxide, and a specific silica. More preferably, the master batches of the invention contain from 40 to 70% by weight of organic peroxide and rubber EPM and / or EPDM of which the propylene content is 35% by weight or more, preferably 40% by weight or more , more preferably at least 45% by weight, and a Mooney viscosity, determined from ML 1 + 4 at 100 ° C, as is conventional in the area, of 30 or more. The specific silica to be used can be characterized by (a) its specific surface area 150 m2 / g if the organic peroxide is solid at room temperature or (b) its pore volume of at least 1.4 ml / g, Preference 1.5 ml / g or more, if the organic peroxide is a liquid at room temperature. Accordingly, the present invention relates to: (1) An entanglement masterbatch containing at least one organic peroxide in an amount of 40 to 70% by weight, based on the weight of the total masterbatch, at least one rubber Synthetic, and a silica having a specific area area of 150 m2 / g or more or a pore volume of 1.4 ml / g or more. (2) A high concentration entanglement masterbatch according to (1), wherein said masterbatch contains the silica treated by dry or wet process with (a) a specific surface area of 150 m2 / g or more if said peroxide organic is solid at room temperature, or (b) a pore volume of 1.4 ml / g or more if said organic peroxide is liquid at room temperature. (3) A high concentration entanglement masterbatch according to (1) or (2) above, wherein said synthetic rubber is an ethylene-propylene rubber or an ethylene-propylene-diene rubber of which the content of Propylene is 45% or more and the Mooney viscosity at 100 ° C is 30 or more. (4) A master lot of high concentration entanglement according to (1) or (3) above, wherein said hydrogen peroxide is present in an amount of 40 to 65% by weight, said synthetic rubber being present in a amount of 10 to 30% by weight, and said silica is present in an amount of 5 to 30% by weight, each based on the weight of the total masterbatch. The organic peroxides for use in the present invention have a half-life of 10 hours at a temperature of 60 ° C or more and are liquid or solid at room temperature. Ambient temperature here means about 15 ° C-30 ° C, depending on the region, the station and the work environment. The term "half-life temperature of 10 hours" is used in the conventional manner, meaning the temperature at which 50% of the peroxide decomposes in a time of 10 hours when measured by thermal decomposition of a 0.2 mol / l solution. of peroxide in monochlorobenzene. Preferred organic peroxides that are solid at room temperature include dialkyl peroxides, such as dicumyl peroxide, 1,3-bis (tert-butylperoxyisopropyl) benzene, and 1,4-bis (tert-butylperoxyisopropyl) benzene, and diacyl peroxides such as dibenzoyl peroxide. Preferred organic peroxides that are liquid at room temperature include the dialkyl peroxides, such as 2,5-dimethyl-2,5-di (tert-butylperoxy) hexane, 2,5-dimethyl-2,5-di (tert- butylperoxy) hexyne-3, tert-butyl cumyl peroxide, di-tert-butyl peroxide, and di-tert-amyl peroxide; peroxycetals such as 1,1-di-tert-butylperoxy-3,3,5-trimethyl cyclohexane, 4,4-n-butyl ester of di-tert-butylperoxy valeric acid, and 1,1-di-tert-butylperoxy cyclohexane . Of these organic peroxides, the most preferred for use in master batches according to the invention include dicumyl peroxide, 1,3-bis (tert-butylperoxyisopropyl) benzene, and 1,4-bis (tert-butylperoxyisopropyl) benzene, 2,5-dimethyl-2,5-di (tert-butylperoxy) hexane, 1,1-di-tert-butylperoxy-3,3-5-trimethyl cyclohexane, and n-butyl ester of 4,4-di- tert-butylperoxy valeric.

The organic peroxides can be used individually or as a mixture of one or more peroxides. A mixture can be handled either as a liquid or as a solid, depending on its physical form at room temperature. The entanglement masterbatch of the present invention may contain any of these organic peroxides in a total peroxide concentration of 40 to 70% by weight, preferably 42.5 to 65% by weight, even more preferably 45 to 62.5% by weight, and more preferably from 47.5 to 60% by weight. Preferred synthetic rubbers for use in the present invention are EPM and EPDM. These are the ethylene-propylene co-polymer and the ethylene-propylene-diene ter-polymer, respectively, of which the Mooney viscosity (ML1 +4 100 ° C) is 30 or more and the propylene content is 35% or more, preferably 40% or more, more preferably 45% or more. Although neither the Mooney viscosity nor the propylene content has its respective upper limits, the available EPM and EPDM generally have a Mooney viscosity (ML 1 +4 100 ° C) of about 20-150 and a propylene content of about 20. -fifty%. However, in the master batches of the present invention EP (D) M has a higher Mooney viscosity and / or a higher content of propylene can also be used. Other preferred elastomers to be used according to the present invention are the co-polymer of ethylene-vinyl acetate, and ethylene octene co-polymers (POE's), such as Engage® ex Duppont Dow elastomers. Preferably the POE has a high content of octene.

Any silica that meets the specific surface area and / or the pore volume criteria can be used in the master batches of the present invention. Silica-treated silica being silica that is precipitated from an aqueous phase, which includes essentially all conventional precipitated silicas as well as silicates, and silica treated by the dry route, being silica of pyrogenic nature. Examples of wet-treated silica are NipsiINS-P ™, NipslVN-3 ™, NipsiINS-K ™ (made by Nihon Silica), MizukasilP-802 ™, MizukasilP-554A ™ (made by Mizusawa Chem. Ind.), FinesilEdO ™, FinesilT32 ™, FindsilX37 ™, FinesilXdO ™, FinesilK41 ™ (made by Tokuyama), Sipemat 22 ™, Sipemat 50S ™, Sipemat 50 ™, FK500LS ™, FK700 ™ (made by Degussa), Ketjensil SM660 ™, Ketjensil SM614 ™, Ketjensil SM611 ™ (made by Akzo-PQ), Hi-Sil132 ™, and HIS-SH135 ™ (made by PPG). Examples of dry-treated silica are Aerosil200 ™, Aerosil300 ™, Aerosil380 ™ (made by Nihon Aerosil). The most preferred silica for use in the invention has a specific surface area of 200 m2 / g or more. Preferred porous silicas (silica gel) have a pore volume of 1.5 ml / g or more, such as Mizukasil P-707 ™, Mizukasil P-740 ™, Mizukasil P-78F ™, Mizukasil P-78D ™, Mizukasolb Cl ™ , Mizukasolb C-6 ™ (made by Mizusawa Chem. Ind.), Silicia 250 ™, Silicia 250N ™, Silicia 256 ™, Silicia 256N ™, Silicia 310 ™, Silicia 320 ™, Silicia 350 ™, Silicia 358 ™ (made by Fuji Silicia). The silica (porous) is generally used in a powdered state, the preferred average particle size is approximately 1-15 μm.

Silica which has been treated to make it more hydrophobic can also be used, for example, by means of a treatment with methylchlorosilane, as long as it has a specific surface area and / or pore volume. A specific type or type of silica can be used. However, mixtures of various silicas are also suitable, as long as the final mixture of silicas has the specific surface area required and / or the pore volume. The specific surface area and the pore volume of the silica are determined in a conventional manner by measuring the isothermal absorption line of N2 according to the BET method (as in DIN 66131). Silica-treated silica has small holes due to the aggregation of particles. In the determination of the pore volume, these holes are analyzed between the particles and the pores of the silica. It was found that, regardless of the true pore volume, any wet treated silica is suitable as long as the BET analysis shows a pore volume of at least 1.4 ml / g, more preferably at least 1.5 ml / g. Although the present invention does not impose an upper limit on the specific surface area and pore volume of the silica, a practical limit can be found in the commonly available silicas. At present, a practical upper limit for the specific surface area and the pore volume appears to be about 700 m2 / g and about 1.8 ml / g, respectively. However, if available, also silicas having a greater specific surface area, for example, up to 1,000 m2 / g, and a larger pore volume, for example, up to 2.0 ml / g, can be used. In order to make master batches with the highest possible concentration of organic peroxide, the specific surface area and the pore volume should be as high as possible. Therefore, it is preferred to use silicas with a specific surface area of at least 200 m2 / g and / or a pore volume of at least 1.5 ml / g, preferably at least 1.6 ml / g. The high concentration entanglement masterbatch of the present invention containing organic peroxide, synthetic rubber, and silica may additionally contain one or more conventional inorganic fillers (as is commonly used in the elastomer processing process), as long as these fillers do not adversely affect the performance and storage stability of the master batch. Preferred inorganic fillers are precipitated calcium carbonate, heavy calcium carbonate, talc, clay, and black carbon. Their surfaces can be treated with fatty acids, silane coupling agent, and other compounds. The master batches of the present invention may additionally contain one or more adjuvants selected from the group of antioxidants, UV stabilizers, flame retardants, pigments, dyes, process oils, lubricants and other additives that are commonly used in elastomers. These products will be used in conventional quantities, as long as they do not adversely affect the performance and storage stability of the master batch. Typically, these constitute 5% by weight or less of the total masterbatch. The entanglement masterbatch of the present invention can be produced by mixing the above ingredients in any suitable manner. Typically, use is made of an open roll mill, a Banbury mixer, and a kneader, an extruder, or a transfer mixer, the equipment of which is commonly used for the processing of elastomers. The preferred mixer is an open roller mill. To produce sheets or granules of the masterbatch of the present invention, a pelletizer, cutter and similar equipment can be added to the mixer. The masterbatch of the present invention is suitable for use in interlacing a crosslinkable elastomer. Examples of preferred elastomers for interlacing are EPM, EPDM, ethylene-vinyl acetate co-polymer, natural rubber, polybutadiene, polyisoprene, polybutylene, polyisobutylene, polyacrylic acid ester, styrene-butadiene copolymer, acrylonitrile co-polymer -butadiene, hydrogenated acrylonitrile-butadiene co-polymer, acrylonitrile-butadiene-styrene ter-polymer, fluorinated rubber, silicone rubber, urethane rubber, ethylene-α-olefin co-polymer, and chlorinated polyethylene. The high concentration entanglement masterbatch of the present invention is typically used in amounts of 0.2-20% by weight, preferably 1-10% by weight, relative to the weight of the elastomer to be entangled.

The entanglement of the elastomer can be carried out using any conventional process. In such processes the elastomer to be interlaced is typically first mixed homogeneously with an inactive filler such as talc and calcium carbonate, a pigment known as black carbon, a processing oil for better processing, etc., and then kneaded with the required amount of high concentration entanglement masterbatch of the present invention. In the subsequent entanglement step the mixture is typically heated to 140-200 ° C for 5-30 minutes in a mold. Depending on the type of elastomer and the types of ingredients used, the entanglement conditions may vary. EXAMPLES Example 1 Kayacumil D (dichumil peroxide by Kayaku Akzo, p.Fus. (Melting point) 38 ° C, purity 99%) was mixed homogeneously with Nipsil NS-P (specific surface area 170 m2 / g), and then homogeneously kneaded with Esprene (EPDM made by Sumitomo Kagaku, Mooney viscosity (ML 1 +4 120 ° C) 80, 45% propylene content in an open roll mill using the amounts shown in Table 1. Accordingly, the mixed product was cooled and pelletized in a conventional manner, to obtain a master batch of high concentration interleaving according to the present invention.

Example 2 Perkadox 14 (m, p-bis (tert-buty-peroxyisopropyl) benzene made by Kayaku Akzo, p.Fus. (Melting point) 43 ° C, purity 99%) was mixed homogeneously with Sipernat 50S (specific surface area 450 m2 / g) and conventional light calcium carbonate, and then kneaded homogeneously with Keltan 312 (EPDM manufactured by Idemitsu DSM, Mooney viscosity (ML 1 +4 100 ° C) 52, 50% propylene content) using a mill of open roll and the proportions of the composition are shown in Table 1. The product was cooled to room temperature and cut into square sheets of 50X50 cm (master batch) according to the present invention.

Example 3 Kayacumil D was homogenously mixed with Aerosil 200 (specific surface area 200 m2 / g), calcium carbonate with treated surface (Hakuenka CCR made by Shiroishi Kogyo), and regular polybutene as a processing oil, and then homogeneously kneaded with Mitsui EPT0045 (EPM made by Mitsui Kagaku, Mooney viscosity (ML 1 +4 100 ° C) 38, 49% propylene content) in an open roll mill using the composition proportions shown in table 1. The product was cooled at room temperature and cut into square sheets of 50X50 cm (master batch) according to the present invention.

Example 4 Perkadox 14 was mixed homogeneously with Finesil X80 (specific surface area 250 m2 / g) and regular talcum and then kneaded homogeneously with JSR-EP11 (EPM made by Nihon Gosei Gum, Mooney viscosity (ML 1 +4 100 ° C 40, 49% propylene content) using an open roller mill and the composition proportions shown in Table 1. The product was cooled and pelletized to obtain a high granular concentration interlacing masterbatch of the present invention. The storage stability of the entangle master lots of the present invention obtained in Examples 1-4 was analyzed. Its proportions of composition and results are shown in Table 1 and Table 2. In the tables, the hardness is a measured value in the conventional manner using a Type C Rubber Analyzer, the composition ratio is shown as% by weight , and the abbreviations have the following meaning: PO: Organic peroxide KYKD: Kayacumil D PKD: Perkadox 14 Mitsu¡O045: Mitsui EPT0045 EP11: JSR-EP11 ES532: Esprene 532 KT312: Keltan 312 NipNSP: Nipsil NS-P SipedOS: Sipemate 50S FÍ50S: Finesil 50S Aero200: Aerosil 200 LCC: Calcium carbonate light CCR: Hakuenka CCR PO Conc (%): (% concentration of PO as analyzed in the product Table 1 Proportions of composition Table 2 Storage stability tests (40 ° C / after 4 weeks) Example 5 Trigonox 29 (made by Kayaku Akzo, 1, 1-di-tert-butylperoxy-3,3,5-trimethyl cyclohexane, liquid at room temperature, 95% purity) was mixed homogeneously with Silicia 250N (pore volume 1.80 ml / g), Hakuenka CCR, and conventional polybutene, and then homogeneously kneaded with Esprene 532 using an open roll mill and the composition ratios shown in Table 3. The product was cooled to room temperature and cut into square sheets of 50X50 cm, to give a master batch of high concentration interleaving of the present invention.

Example 6 Trigonox 29 was mixed homogeneously with Mizukasolb C-1 (pore volume 1.70 ml / g) and then kneaded homogeneously with Keltan 312 in an open roller mill, using the composition proportions shown in Table 3. The product was cooled to room temperature and cut into 50X50 cm square sheets, to give a high concentration entanglement masterbatch of the present invention.

Example 7 Kayahexa AD (made by Kayaku Akzo, 2,5-dimethyl-2,5-di (tert-butylperoxy) hexane, liquid at room temperature, purity 90%) was mixed homogeneously with Mitzukasil P-7 (pore volume 1.57 ml / g) and regular talc, and then homogeneously kneaded with Mitsui EPT 0045 using an open roll mill and the composition ratios shown in Table 3. The product was cooled to room temperature and pelleted, to give a batch high concentration interlacing granular master of the present invention.

Example 8 Trigonox 17 (made by Kayaku Akzo, n-butyl ester of 4,4-di-tert-butylperoxivaleric acid, liquid at room temperature, purity 90%) was mixed homogeneously with Silicia 350 (pore volume 1.60 ml / g) and then homogenously kneaded with JSR-EP11 using an open roll mill and the composition ratios shown in Table 3. The product was cooled to room temperature and pelletized, to give a granular master batch of high concentration interlacing of the present invention. The master entanglement batches of the present invention obtained in Examples 5-8 were analyzed for storage stability, see Tables 3 and 4. In the tables, the composition composition is shown as weight percent. , and the abbreviations have the following meaning: TRN29: Trigonox 29 KYHAD: Kayahexa AD Si: Silicon Miso: Mizukasolb Misi: Mizukasil Si porosa: Porous silica The other abbreviations have the same meaning as in the Table 1. Table 3 Proportion of compounds Table 4 Storage stability tests (40 ° C / after 4 weeks) Table 2 and Table 4 reveal that the high concentration entanglement masterbatch of the present invention loses little organic peroxide and shows almost no change in appearance and hardness during storage, so it has excellent storage stability.

Examples 9-12 The master batches produced in Examples 1-4 were evaluated with respect to their respective entanglement performances. The prescribed ingredients were mixed in the proportions shown in Table 5. A Banbury mixer was used to obtain the EPDM compound within which each master batch of Examples 1-4 was dispersed at a given rate using a two-roll mill. The amount of master batch dispersed within the EPDM compound was chosen such that 0.185 g of active oxygen (of the organic peroxide) was added to 100 g of EPDM. Table 5 shows the time required to disperse each of the corresponding master lots within the EPDM compound. Each of the elastomer compositions was entangled at 180 ° C for 15 minutes. The entanglement property of each treated elastomer composition was measured by an elastometer (type JSR3). Uncle and T90 represent the tempo to reach 10% and 90% of the maximum torque, respectively. The interlaced elastomer was subjected to a tensile strength test based on JISK-6301. Tb and Eb mean tension and elongation when broken, respectively. Hs and TR signify hardness and strength of resistance against tearing of an interlaced elastomer, respectively.

Table 5 shows the proportions of composition of the ingredients and the results of the tests. In the Table, JSR-EP86 is the trademark for EPDM made by Nihon Gosei Gum KK. Asahi coal # 70 and Sunpar 2280 made by Nihon Sun Sekiyu KK were used as HAF black carbon and naphthenic oil processing, respectively. A phenolic protector against aging was used. The abbreviations have the following meaning: TMPT: Trimethylpropane trimethacrylate JSREP86: JSR-EP86 HAF-C: Carbon black HAF Oil NP: naphthenic processing oil A: The master batch produced in Example 1 B: The master batch produced in the Example 2 C: The master batch produced in Example 3 D: The master batch produced in Example 4"A 7.2" in the master batch line of the table means that 7.2 parts of the master batch produced in Example 1 were used. The others abbreviations of the master batch have corresponding meanings. Table 5 Compositions of elastomer (parts by weight) and results Examples 13-16 The crosslinking properties of the master batches produced in Examples 13-16 were evaluated in the same manner as in Examples 5-8, except that the interlacing conditions were 150 ° C for 15 minutes in the Examples 13 and 14, 180 ° C for 15 minutes in Example 15, and 160 ° C for 15 minutes in Example 16. The results are compiled in Table 6. The following abbreviations were used: E: The master batch produced in Example 5 F: The master batch produced in Example 6 G: The master batch produced in Example 7 H: The master batch produced in Example 8 Table 6. Elastomer compositions (parts by weight and results Table 5 and Table 6 show that the master batch batches of the present invention can easily be dispersed in an elastomer and that their use results in interlaced products having excellent properties such as mechanical strength, i.e. tensile strength. and resistance against tearing. Clearly, the present invention provides organic, effective, highly concentrated masterbeds that have excellent storage stability.

Claims (7)

NOVELTY OF THE INVENTION CLAIMS

1. A master batch of concentrated entanglement containing one or more organic peroxides, one or more synthetic rubbers, and silica, wherein said organic peroxide constitutes 40 to 70% by weight, based on the total weight of the master batch, and said silica has a specific surface area of 200 m2 / g or more or a pore volume of 1.4 ml / g or more, with the proviso that the master batch does not contain a trans-polyoctenamer.

2. A master batch according to claim 1, further characterized in that the silica is characterized by (a) a specific surface area of 200 m2 / g or more if the organic peroxide is solid at room temperature, or (b) a volume of pore of at least 1.4 ml / g, or more, if the organic peroxide is a liquid at room temperature.

3. A masterbatch according to claim 1 or 2 further characterized in that said synthetic rubber is an ethylene propylene rubber or an ethylene propylene diene rubber that preferably contains at least 45% by weight of propylene and has a Mooney viscosity at 100 ° C of 30 or more.

4. A masterbatch according to any of claims 1-3 further characterized in that said organic peroxide is present in an amount of 42.5 to 65% by weight, said synthetic rubber is present in an amount of 10-30% by weight, and said silica is present in an amount of 5-30% by weight, relative to the total weight of the master batch. A masterbatch according to any of the preceding claims further characterized in that it additionally contains one or more inorganic fillers, preferably chosen from the group of calcium carbonate, heavy calcium carbonate, talc, clay, and black carbon. 6. A masterbatch according to any of the preceding claims further characterized in that it additionally contains one or more adjuvants chosen from the group of antioxidants, UV stabilizers, flame retardants, pigments, dyes and processing oils. 7. The use of a master batch as claimed in any of claims 1-6 in the vulcanization process of an elastomer.