Rubber composition containing a polyorganosiloxane as a plasticizer

Abstract

The present invention relates to rubber compositions provided with polyorganosiloxanes as plasticizer. The rubber compositions can be vulcanized by crosslinking resins and they are particularly suitable for use as curing capsules in tire production. The invention also relates to the use of polyorganosiloxanes as corresponding plasticizer.

Description

TECHNICAL FIELD

[0001] The present invention relates to a rubber composition containing a polyorganosiloxane as plasticizer.

[0002] In particular, the present invention relates to the use of a polyorganosiloxane modified with a (meth)acrylate as plasticizer in a rubber composition which is used for a bladder employed in tire production.

[0003] The present invention also relates in particular to a bladder and its manufacture as well as its use in tire production. BACKGROUND

[0004] Rubber compositions which are vulcanized by resin crosslinking are known and have a wide range of applications in various branches of industry. On this basis, rubber articles are used for example in the manufacture of bladders employed in various tire productions.

[0005] In tire production itself, uncrosslinked green tires are vulcanized. The vulcanization process describes the crosslinking of rubber compositions under pressure and elevated temperature. In this process, covalent bonds are formed between the polymers and an elastomer network is built.

[0006] The vulcanization of rubber mixtures can take place via different mechanisms. The most commonly used type of vulcanization is sulfur vulcanization. In addition, rubber mixtures can also be crosslinked or vulcanized using peroxides, amines or resins.

[0007] For the production of vehicle tires, green tires are placed in a tire press for shaping and vulcanization. The bladder has the function of pressing the green tire against the inner wall of the tire press during the vulcanization process under pressure and high temperature, in order to give the tire a tread pattern. For this purpose, the bladder is filled with a pressurized medium, for example hot water or steam.

[0008] The required bladder can be made of a rubber composition. Typically, the rubber composition used for the bladder consists of a polymer system, a filler, zinc oxide, a plasticizing oil and a crosslinking resin. In addition, conventional deep processing additives are also constituents of the rubber composition.

[0009] The polymer is typically butyl rubber, optionally chlorobutyl rubber if the crosslinking resin is not halogenated. Carbon black is typically used as a filler. Zinc oxide is used as a catalyst for the crosslinking of the resin and for increasing the thermal conductivity. In the known bladders, castor oil is used as a plasticizing oil, as described in more detail below. Halogenated alkyl phenolic resins, optionally with hydroxymethyl groups, are typically used as crosslinking resins. In addition, further additives, for example homogenizing agents, can be added to the respective composition. Bladders comprising butyl rubber as well as rubber having units derived from alpha-methylstyrene as the polymer system are also described.

[0010] In the tire vulcanization process, the bladder undergoes a cycle comprising a filling process, expansion with a pressurized medium, and then decompression, releasing the pressurized medium. The bladder is thereby subjected to mechanical loads. However, in addition to this mechanical load, the respective physical conditions also change significantly during the entire cycle. Significant pressure and temperature changes are of particular importance here.

[0011] The materials used in the bladder must take into account this particular form of loading, especially in the context of being able to produce as many tires as possible with one bladder. Depending on various factors, such as tire size or vulcanization conditions, the bladder will undergo a different number of cycles. However, despite this, after a certain degree of loading, signs of fatigue occur in each bladder, and eventually failure occurs due to, for example, the formation of cracks, with the result that the bladder has to be replaced.

[0012] This leads to an unwanted interruption of the continuous tire production process. In addition, additional costs arise due to the replacement. It has therefore always been desirable to be able to provide a bladder with the longest possible service life. This is because extending the service life not only significantly improves the efficiency and costs of the associated tire producer, but also makes a significant contribution to more environmentally friendly tire production.

[0013] In order to counteract the considerable loads during use, a plasticizer component is essential in rubber-based bladders. In this regard, since the 1950s, in particular castor oil has been used as a plasticizer component in rubber-based bladders, as described, for example, in DE 1283521.

[0014] Castor oil is considered a particularly suitable plasticizer and has proven successful over the past few decades, as it has a relatively low volatility even at high temperatures and is generally suitable for reducing the tendency to increasing modulus exhibited by the crosslinking mixture of the resins. In this regard, the low modulus and good steam aging resistance of rubber compositions containing castor oil are described in WO 2013 / 052206 A1, in which, in addition to the castor oil, further increasing the resistance of the produced bladder is attempted by adding a hydrocarbon resin (hydrocarbon polymer modifier, HPM).

[0015] Despite the advantages of using castor oil in the rubber compositions in question, the bladders produced from the respective compositions fail after a certain number of vulcanization cycles. So far, the long service life required of the bladders has not been successfully achieved by the addition of castor oil.

[0016] EP 2354154 A1 and EP 2151479 A1 relate to a rubber composition which is peroxidically vulcanized and contains polyorganosiloxanes for increasing the viscosity of the rubber during processing without reducing the relevant mechanical properties of the resulting vulcanized rubber (e.g. modulus reduction). These polyorganosiloxanes have at least one organic group R which has at least one carbon-carbon multiple bond and optionally further hydrocarbon groups R2 having a chain length of 5 to 50 carbon atoms. It should be noted that no conclusions are drawn from the effect of the additives (e.g. reduction of viscosity) during rubber processing on the finished vulcanizate, e.g. on specific target physical properties such as deformability, elasticity or reduced hardness due to plasticizers.

[0017] US 2011 / 0262573 A1 describes a manufacturing method for a bladder for tire production, wherein the surface of the bladder is modified by applying a layer which serves as a release agent but is firmly fixed to the surface of the bladder facing the interior of the tire. Castor oil is used as a plasticizer in the rubber composition of the bladder known from US 2011 / 0262573 A1.

[0018] The polyorganosiloxane used for the surface coating of the release agent substitute in US 2011 / 0262573 A1 has a high molecular weight (average molecular weight, number average) of up to 12,000.

[0019] US 4,710,541 describes a method for molding and vulcanizing rubber products such as tires, wherein a modified bladder is used. The bladder described in US 4,710,541 is modified in order to improve its release properties from the tire material, e.g. by appropriate surface modification. Thus, the invention described in US 4,710,541 is a search for a substitute for conventional release agents. The polyorganosiloxane described in US 4,710,541 has a high molecular weight of > 1000, e.g. 7000 dimethylsiloxy units. It is used in large proportions, e.g. 30 parts by weight to 70 parts by weight of rubber.

[0020] Despite the different improvements in rubber compositions, there is still a great need for new modified rubber compositions which, taking into account the significant load on the material that occurs during the vulcanization cycle of tire production, are not only suitable as such for vulcanization to form a bladder which can be used in tire production, but also for providing a bladder with a longer service life.

[0021] According to a first aspect, the present invention relates to the use of one or more modified polyorganosiloxanes as plasticizer in a rubber composition, wherein the rubber is vulcanized by one or more crosslinking resins, wherein the polyorganosiloxane comprises 3 or more siloxane units and one or more organic groups R 1having one or more carbon-carbon multiple bonds and at least 4 carbon atoms.

[0022] According to another aspect, the present application relates to a method for producing a bladder for tire production, wherein a rubber composition comprising one or more modified polyorganosiloxanes, one or more crosslinking resins for crosslinking and optionally other conventional additives is vulcanized via the crosslinking resins, wherein the modified polyorganosiloxanes and the rubber composition are as defined herein.

[0023] Finally, the present application relates to a bladder for tire production comprising a rubber composition which is vulcanizable using a crosslinking resin, said rubber composition comprising a modified polyorganosiloxane and having been vulcanized by the crosslinking resin, wherein the modified polyorganosiloxanes and the rubber composition are as defined herein.

[0024] The term "modified" means that organic groups R 1 .

[0025] If features of the present application can be present in one or more different embodiments, then the varying features of the following detailed description can relate to all (different) embodiments, even if not explicitly addressed in the plural.

[0026] The preferred embodiments of the present application can consist of the features disclosed in the following without the presence of other components.

[0027] Figure 1 The results of the flex endurance test according to De Mattia on the vulcanized rubber compositions 1 to 4 are shown.

[0028] Figure 2 The results of the flex endurance test according to De Mattia on the vulcanized rubber compositions 1 to 4 after steam aging (48 hours at 190°C) are shown. DETAILED DESCRIPTION

[0029] The inventors have surprisingly found that the use of a specific polyorganosiloxane with functional groups ("modified polyorganosiloxane") as plasticizer in a rubber composition which can be used as a bladder for tire production solves the problems addressed by the present application. In particular, if the castor oil which is usually used in the base rubber composition is partially or completely replaced by the polyorganosiloxane described in the present application, it is possible to produce a bladder for tire production which has a longer service life compared to previously known bladders.

[0030] The plasticizer described in the present application thus acts in the volume of the rubber composition in which it is contained. According to the present application, only the material present at the surface of the rubber composition, for example a layer which is temporarily or permanently bonded thereto, is not suitable as a plasticizer.

[0031] Polyorganosiloxanes )

[0032] Polyorganosiloxanes are known substances per se. They are (large) molecules which are built up according to the formula (R2SiO) x where R is usually a hydrocarbon radical (most often methyl, less often ethyl, propyl, phenyl, etc.), see for example Chemistry Lexicon 9th Edition 1992 Volume 5, p. 4168).

[0033] The polyorganosiloxanes used according to the application are characterized in that they have 3 or more siloxane units and have one or more organic radicals R 1 , in particular two or more organic radicals R 1 , and preferably one or more hydrocarbon radicals R 2 .

[0034] The radicals R 1 and R 2 present in the polyorganosiloxanes according to the application can in each case be identical or different.

[0035] The organic radicals R 1

[0036] The polyorganosiloxanes used according to the application have one or more organic radicals R 1 where R 1 contains one or more carbon-carbon multiple bonds and has at least 4 carbon atoms.

[0037] The carbon-carbon multiple bond in R 1 is preferably a carbon-carbon double bond, for example in a carbon chain or a ring of carbon atoms. In a preferred embodiment, the organic radical R 1 is a monovalent radical.

[0038] In all embodiments of the application, it is particularly preferred that R 1 in the polyorganosiloxanes has at least five, for example at least six, in particular at least seven carbon atoms.

[0039] Preferably, the polyorganosiloxanes according to the application have at least two carbon-carbon multiple bonds. This means that if the radical R 1 has only one carbon-carbon multiple bond, there must be at least two radicals R 1 . This embodiment is preferred. Alternatively, the radical R 1It can have at least two carbon-carbon multi-bonds. However, this embodiment is not preferred because the preparation of the corresponding polyorganosiloxane is more complex. For example, cycloalkenyl, alkenyl, vinyl-containing groups, allyl-containing groups, norbornyl, (bis)cyclopentenyl, or groups derived from unsaturated acyloxy groups (such as methacrylates or acrylates) are considered as R. 1 Preferred monovalent group R 1 The R group is derived from cyclohexene and (meth)acrylates, especially from (meth)acrylates. 1 It is attached to the main chain of polyorganosiloxane via a hydrocarbon chain, which may be replaced by one or more heteroatoms such as oxygen or sulfur and / or interrupted by one or more heteroatoms such as oxygen and sulfur.

[0040] According to a preferred embodiment, R 1 It is a monovalent unsaturated acyloxy group (i.e., a group of type RCOO-) having up to 15 carbon atoms (the total number of carbon atoms includes all substituents), wherein the acyloxy group has a substituted or unsubstituted double bond at the end (i.e., in unit R) and is bonded to the silicon atom of the polyorganosiloxane backbone through a hydrocarbon chain, wherein the hydrocarbon chain preferably contains at least one oxygen atom and preferably has at least one hydroxyl substitution. The substituent on the C atom of the terminal double bond is preferably methyl, particularly a single methyl group (e.g., in the case of a group derived from methacrylate CH2=C(CH3)COO-).

[0041] R 1 A particularly preferred embodiment is the following groups

[0042]

[0043] In each case, the carbon atoms bonded to silicon atoms are indicated by an arrow.

[0044] These functionalizations can be obtained by reacting the SiH unit with compounds having double bonds that can be used for hydrosilylation, for example:

[0045] (A) Allyl (meth)acrylate,

[0046] (B) 4-Vinylcyclohexene, or

[0047] (C) Allyl glycidyl ether, which subsequently opens the epoxide ring by reacting with (meth)acrylic acid.

[0048] Reaction (C) is particularly preferred to form the structure described above (C). This general type of polyorganosiloxane is known, for example, from EP 0 269 114 A2 and DE 30 44 237 A1.

[0049] With the group R 1The number of carbon atoms between the silicon atom and the carbon atoms of the carbon-carbon multiple bond is preferably 1 to 10, more preferably 2 to 7, for example 4. In the case of cyclic groups or groups containing a ring, the shortest path to the double bond is counted.

[0050] In a preferred embodiment, R 1 occur in the polyorganosiloxanes of the present application as part of structural unit I:

[0051] [R 1 x R a SiO [4-(x+a)] / 2 ] (I),

[0052] wherein x is equal to 1, 2 or 3, preferably 1, a is equal to 0, 1 or 2, preferably 1 or 2, especially 2, and R is a linear or branched alkyl group, a cycloalkyl group or an aryl group, with up to 9 C atoms, in particular up to 6 C atoms. R is preferably selected from the group consisting of methyl, ethyl, propyl, butyl, pentyl or phenyl, wherein R is particularly preferably methyl.

[0053] Preferred structural unit I, wherein x = 1, is the bifunctional structural unit I D wherein a = 1 :

[0054] [R 1 RSiO 2 / 2 ] (I D ),

[0055] and the monofunctional structural unit I M wherein x = 1 and a = 2:

[0056] [R 1 R2SiO 1 / 2 ] (I M ).

[0057] The polyorganosiloxane according to the present application preferably has 15 to 70, preferably 20 to 40 or 50, especially 20 to 30, structural units of the type I D which is a measure of the chain length of the polyorganosiloxane.

[0058] The hydrocarbon group R 2

[0059] The polyorganosiloxane according to the present application optionally has one or more longer alkyl groups R 2 wherein R 2 have a chain length of 5 to 50 carbon atoms.

[0060] According to one embodiment, R 2 is selected from branched or unbranched alkyl groups having 5 to 30 C atoms, in particular unbranched alkyl groups having 5 to 30 C atoms, for example n-C8to C30alkyl groups.30 Alkyl, preferably nC 10 To C 26 Alkyl, more preferably nC 12 To C 18 Alkyl groups, such as nC 18 alkyl.

[0061] Alkyl R 2 Preferably, it is included in the polyorganosiloxane as part of Unit II:

[0062] [R 2 y R' b SiO [4-(y+b)] / 2 (II),

[0063] Where y equals 1, 2, or 3, preferably 1; b equals 0, 1, or 2, preferably 1 or 2, especially 1; and R' is a monovalent organic group as defined for R in the above structural unit (I), but independent of the choice of R. Preferably, R' is selected from methyl, ethyl, propyl, butyl, pentyl, or phenyl, wherein R' is particularly preferably methyl.

[0064] Preferred structural unit II, where y = 1, is a bifunctional structural unit II. D Where b = 1:

[0065] [R 2 R'SiO 2 / 2 (II) D ),

[0066] and monofunctional structural unit II M Where y = 1 and b = 2:

[0067] [R 2 R'2SiO 1 / 2 (II) M ).

[0068] Structure of polyorganosiloxanes

[0069] In addition to the preferred structural units I and II mentioned above, the polyorganosiloxane according to the present invention preferably also has a bifunctional structural unit III. D :

[0070] [R″2SiO 2 / 2 (III) D ),

[0071] wherein the radicals R" are identical or different (preferably identical) and are selected from linear alkyl, branched alkyl, cycloalkyl or aryl groups which can be bound via an oxygen atom to the polyorganosiloxane, and the radicals R" are preferably methyl, ethyl, propyl and phenyl, in particular methyl. In one embodiment, one (or two) monofunctional structural units III M are also present in the polyorganosiloxane according to the application:

[0072] [R'"3SiO 1 / 2 ] (III M ),

[0073] wherein the radicals R'" are identical or different and are selected from hydroxyl and linear alkyl, branched alkyl, cycloalkyl or aryl groups which can be bound via an oxygen atom, and the radicals R'" are preferably hydroxyl, methyl, ethyl, propyl and phenyl, in particular hydroxyl and methyl. In a particularly preferred embodiment, the radicals R'" are identical and are methyl.

[0074] One preferred structure of the polyorganosiloxane according to the application is as follows:

[0075] [I D ] m [I M ] n [II D ] o [II M ] p [III D ] q [III M ] (2-n-p) ,

[0076] wherein

[0077] (i) m and o are independently of one another in the range from 0 to 40 and n and p can independently of one another be 0, 1 or 2,

[0078] - with the proviso that the sum (m+n) is at least 1 and preferably the sum (o+p) is at least 1,

[0079] - with the further proviso that the sum (n+p) is at most 2,

[0080] - wherein the sum (m+n+o+p) is preferably in the range up to 20, and

[0081] (ii) q is in the range from 0 to 100.

[0082] Bifunctional structural units I D , II D and III DGenerally and preferably, the arrangement is not blockwise, but statistical along the polysiloxane chain. It will be clear to the person skilled in the art that the parameters m, n, o, p and q are average values, since the polyorganosiloxane according to the application will not generally occur as a defined compound during production.

[0083] In a preferred embodiment, n is equal to 1 or 2, preferably 2, i.e. the R 1 functionalization in the polyorganosiloxane is contained exclusively in the monofunctional (terminal) building blocks I M .

[0084] In a further preferred embodiment, n is equal to 2 and m is equal to zero (0), i.e. the R1functionalization in the polyorganosiloxane is contained exclusively in the monofunctional (terminal) building blocks I M .

[0085] In a further preferred embodiment, n is equal to 1 or 2, preferably 2, and m is not equal to zero (0), i.e. the R 1 functionalization in the polyorganosiloxane is contained in the monofunctional (terminal) building blocks I M and in the bifunctional (bridging) building blocks I D , as is the case for m = 1 or 2.

[0086] In all embodiments of the application, preferably, the groups R 1 are bound to different silicon atoms as groups R 2 .

[0087] In a preferred embodiment, the total number of siloxane units (m + o + q + 2) of the polyorganosiloxane according to the application is from 10 to 100, more preferably from 15 to 70, in particular from 20 to 50, for example from 20 to 30 or 40.

[0088] In a further preferred embodiment, the total sum of functional siloxane units (m + n + o + p) in the polyorganosiloxane according to the application is from 2 to 15, more preferably from 2 to 6 or 10.

[0089] The preferred ratio of the functionalization of R 1 and R 2 in the bifunctional siloxane units I D and II D is from 10 / 90 to 99 / 1, more preferably from 30 / 70 to 98 / 2, in particular from 50 / 50 to 97 / 3, for example from 70 / 30 to 96 / 4 or from 75 / 25 to 95 / 5.

[0090] The unsubstituted bifunctional siloxane units III DThe number of (q) is preferably from 5 to 60, more preferably from 10 to 50, especially from 15 to 40, for example from 20 to 30.

[0091] The polyorganosiloxane according to the application can exist as a compound which is liquid at room temperature (25°C) with a high viscosity. Depending on, inter alia, the length of the siloxane chain (i.e. the sum of SiO units, sum (m+o+q+2), from approximately 30), the length of the possible hydrocarbon group R 2 and the number of possible hydrocarbon groups R 2 , the polyorganosiloxane according to the application can be solid at room temperature.

[0092] The polyorganosiloxane according to the application can be used as a masterbatch which contains

[0093] a) one or more rubbers, and

[0094] b) one or more polyorganosiloxanes according to the application.

[0095] The masterbatch preferably contains from 0.5 to 30 parts by weight, more preferably from 0.5 to 20 parts by weight, especially from 0.5 to 10 parts by weight, of the polyorganosiloxane according to the application, relative to 100 parts by weight of rubber (phr, parts per hundred rubber). Rubbers which can be crosslinked by crosslinking resins, such as butyl rubber and chlorobutyl rubber, are generally used as rubbers in the masterbatch.

[0096] The use of a masterbatch makes it easier to incorporate the polyorganosiloxane according to the application into the rubber.

[0097] In addition, the polyorganosiloxane according to the application can be used in the form of a mixture which contains:

[0098] a) one or more solid carrier materials (preferably selected from inorganic fillers (such as silica) or waxy materials (such as polyethylene wax)), and

[0099] b) one or more polyorganosiloxanes according to the application.

[0100] In the mixture, the polyorganosiloxane according to the application is present in a weight ratio of from 10 / 90 to 90 / 10, more preferably from 20 / 80 to 80 / 20, especially preferably about 60 / 40. Preferred materials for the mixture are silica or other inorganic fillers, such as chalk powder, or waxy materials such as polyethylene wax.

[0101] In particular, the use of a mixture makes the polyorganosiloxane according to the application easier to handle if it is liquid at room temperature.

[0102] Process for the preparation of polyorganosiloxanes according to the invention

[0103] In a preferred process for preparing the polyorganosiloxane according to the application,

[0104] a) a polyorganosiloxane having two or more SiH groups is reacted with a compound having at least one group R 1 to obtain a polyorganosiloxane having at least one group R 1 and optionally one or more remaining SiH groups, and

[0105] b) optionally, the polyorganosiloxane having at least one or more remaining SiH groups obtained in step a) is reacted with an a-olefin to obtain the polyorganosiloxane according to the application.

[0106] In a particularly preferred process for preparing the polyorganosiloxane according to the application,

[0107] a) a polyorganosiloxane having two or more SiH groups is reacted with a compound having at least one hydrosilylation group and a different other functional group R 3 which is inert under standard hydrosilylation conditions, such as an epoxide, in particular a glycidyl ether, to obtain a polyorganosiloxane having at least one group R 3 and

[0108] b) the polyorganosiloxane obtained in step a) is reacted with a compound having at least one group R 1 and a different other functional group R 3 suitable for selectively bonding to the group R 4 to obtain a polyorganosiloxane having at least one group R1and optionally one or more remaining unreacted groups R 3 and

[0109] c) optionally, the polyorganosiloxane obtained in step b) is reacted with a compound having at least one group R 2 and a different other functional group R 3 suitable for selectively bonding to the group R 4 to obtain the polyorganosiloxane according to the application.

[0110] In another process for preparing the polyorganosiloxane according to the application,

[0111] a) a silane having one or more hydrolysable groups is functionalized with a group R 1

[0112] b) optionally, a silane having one or more hydrolysable groups is functionalized with a group R 2

[0113] ​​c) the compound obtained in step a) is reacted under alkaline conditions in water with the optional compound obtained in step b) and with a compound providing a siloxane backbone, such as octamethylcyclotetrasiloxane.

[0114] Use and vulcanization process

[0115] The polyorganosiloxane is used as a plasticizer in the rubber composition according to the present application. In other words, the polyorganosiloxane according to the present application acts in the volume of the rubber composition into which it is incorporated, unlike a pure modification of the surface of the rubber composition (when it is the case of a shaped part having a defined surface). According to one embodiment of the present application, the rubber composition is not modified on the surface with a coating.

[0116] The rubber composition preferably contains 0.5 to 30 parts by weight, more preferably 0.5 to 20 parts by weight, particularly preferably 1 to 15 parts by weight, more particularly preferably 1 to 15 parts by weight, in particular 2 to 8 parts by weight, of the polyorganosiloxane according to the present application, relative to 100 parts by weight of rubber (phr, parts per hundred rubber). The rubber composition preferably contains 1 to 10 phr of the polyorganosiloxane according to the present application. The rubber composition preferably contains 2 to 7 phr of the polyorganosiloxane according to the present application. The rubber composition preferably contains 2.5 to 6.5 phr of the polyorganosiloxane according to the present application. The rubber composition preferably contains 6 phr of the polyorganosiloxane according to the present application.

[0117] In a preferred embodiment, the rubber is a rubber that can be crosslinked by a crosslinking resin. In particular, such rubbers that can be crosslinked by a crosslinking resin cannot be vulcanized using peroxide crosslinking agents, since these rubbers would deteriorate under the corresponding reaction conditions. According to the present application, a rubber is used that is particularly suitable for the production of bladders used in tire production.

[0118] A preferred rubber that can be used in the context of the use according to the present application is, for example, a butyl rubber, a brominated copolymer of isobutylene and p-methylstyrene, and mixtures thereof.

[0119] A crosslinking resin suitable for use in the context of the use according to the present application is, in particular, a crosslinking resin used in the vulcanization of rubber compositions for the production of bladders used in tire production. Preferably, a crosslinking resin is used that can form a three-dimensional network structure. In particular, phenol-formaldehyde resins are suitable for this purpose. The ability of the groups of this compound to crosslink is based on the reactivity of the phenolic methylol groups in the phenol-formaldehyde resin, which, upon thermal exposure and elimination of water, form α,β-unsaturated carbonyl compounds containing exomethylene, which in turn react with isoprene-based rubber units to form chromene ring systems. The phenol-formaldehyde resins used contain at least two phenolic methylol groups for crosslinking. According to the present application, alkylphenol-formaldehyde resins can be used in particular for crosslinking, in which the alkyl group is preferably C4 to C12.10 Alkyl, for example, in particular octyl. The crosslinking resin can optionally be halogenated, for example brominated, such as the brominated octylphenyl-formaldehyde resin SP-1055, available from Akrochem. If a non-halogenated crosslinking resin is used, for example the octylphenyl-formaldehyde resin SP-1045, available from Akrochem, a suitable halogen-containing component, for example chlorobutyl rubber, is added. It is also possible to use acidic substances (Lewis acids, for example SnCl2or FeCl3).

[0120] The rubber composition preferably contains 0.5 to 30 parts by weight, more preferably 1 to 20 parts by weight, most preferably 2 to 15 parts by weight, in particular 2 to 12 parts by weight, of crosslinking resin, relative to 100 parts by weight of rubber (phr, parts per hundred rubber).

[0121] The rubber composition preferably contains the usual amounts of additives such as fillers (for example carbon black, silicic earth, zinc oxide, calcium carbonate, barium sulfate, magnesium oxide, aluminum oxide, iron oxide, silicates) and substances required for crosslinking (zinc oxide, accelerators, magnesium oxide, sulfur), catalysts / activators for the resin crosslinking (for example chlorobutyl rubber, zinc oxide, stearic acid or salts formed therefrom), anti-aging agents, homogenizing agents.

[0122] Furthermore, the present application relates to a process for producing a capsule for tire production, wherein a rubber composition containing one or more modified polyorganosiloxanes according to the present application, one or more crosslinking resins for crosslinking and optionally other conventional additives is vulcanized via the crosslinking resin. As disclosed in detail in the examples below, the components are mixed thoroughly using suitable devices and conditions. Mixing processes and devices suitable for this purpose are known per se to the expert.

[0123] The present application also relates to a capsule for tire production, comprising a rubber composition, which can be vulcanized using a crosslinking resin, wherein the rubber composition comprises a modified polyorganosiloxane according to the present application and is vulcanized by the crosslinking resin.

[0124] The present inventors surprisingly found that the polyorganosiloxane according to the present application used as plasticizer in a rubber composition significantly prolongs the service life of a tire producing capsule produced from this rubber composition compared to a capsule produced with castor oil as plasticizer (with the same concentration) while the other ingredients and the processing of the vulcanization mixture are identical.

[0125] In the context of the present application, the service life of the capsule is determined after steam aging (48 hours at 190°C) by means of the test pieces in the bending endurance test according to De Mattia. The crack growth of the test pieces of the different compounds is compared to each other. The lower the value of the crack propagation by a given number of pressure cycles, the longer the service life of the capsule.

[0126] According to the precise composition of the rubber composition, if any reduction in crosslinking density is observed, it can be compensated by increasing the concentration of crosslinking resin in the rubber composition without any problem. The improved resistance of the rubber composition according to the application is not significantly impaired in the context of the use of the capsule.

[0127] Further aspects of the application are described in the following paragraphs A to P.

[0128] A. Use of one or more modified polyorganosiloxanes as plasticizer in a rubber composition, wherein the polyorganosiloxane comprises 3 or more siloxane units and one or more organic groups R 1 having one or more carbon-carbon multiple bonds and at least 4 carbon atoms.

[0129] B. Use according to paragraph A, characterized in that R 1 has up to 15 C atoms, wherein R 1 is a monovalent unsaturated acyloxy group (i.e. a group of the type RCOO-) having up to 15 C atoms, wherein the acyl group has a substitued or unsubstituted double bond at the end and is bound to a silicon atom of the polyorganosiloxane backbone via a hydrocarbon chain, which preferably comprises at least one oxygen atom in the chain and preferably has at least one hydroxyl substituent.

[0130] C. Use according to paragraph A or B, characterized in that the modified polyorganosiloxane has two or more organic groups R 1 and / or one or more further longer alkyl groups R 2 wherein R 2 has a chain length of 5 to 50 carbon atoms.

[0131] D. Use according to paragraph A or B, characterized in that the rubber is vulcanized via one or more crosslinking resins, wherein the rubber in particular comprises a brominated copolymer of butyl rubber, isobutylene and p-methylstyrene or mixtures thereof, and chlorobutyl rubber can be used as a crosslinking co-agent.

[0132] E. Use according to any of the preceding paragraphs A to D, characterized in that the rubber composition comprising the polyorganosiloxane comprises one or more further plasticizers other than polyorganosiloxane in an amount of less than 5 parts by weight per 100 parts by weight of rubber (mixture).

[0133] F. Use according to paragraph E, wherein the further plasticizer other than polyorganosiloxane comprises castor oil and / or hydrocarbon resin, preferably comprises castor oil, in particular castor oil and / or hydrocarbon resin, in particular castor oil.

[0134] G. Use according to one of the preceding paragraphs A to C, characterized in that the rubber composition does not contain other plasticizers in addition to the modified polyorganosiloxane.

[0135] H. Use according to any of the preceding paragraphs A to G, characterized in that the rubber composition contains other additives and ingredients suitable for the production of a bladder for tire production.

[0136] I. Use according to any of the preceding paragraphs A to H, characterized in that the rubber composition, after vulcanization, is suitable for use as a bladder in tire production.

[0137] J. Use according to paragraph G or H, characterized in that the rubber composition contains, as further components, fillers, catalysts for the crosslinking of the resin and, optionally, further additives, in particular homogenizing agents.

[0138] K. Use according to any of the preceding paragraphs D to J, characterized in that the crosslinking resin is an optionally halogenated alkylphenol-formaldehyde resin, in which the alkyl group is in particular Ci to C 10 alkyl.

[0139] L. Use according to any of the preceding paragraphs A to K, characterized in that the amount of polyorganosiloxane in the rubber composition is 3 to 8 parts by weight per 100 parts by weight of rubber (blend), in particular in that the rubber composition comprises a crosslinking resin in a concentration of from 2 parts by weight to 12 parts by weight per 100 parts by weight of rubber (blend).

[0140] M. Use according to any of the preceding paragraphs A to L, characterized in that the service life of a bladder for tire production produced from the rubber composition is extended by a factor of 1.2 or more, determined according to the crack propagation method of De Mattia, compared to a bladder for tire production produced with castor oil as plasticizer (with the same concentration) and with the same processing of the vulcanization mixture and other ingredients.

[0141] N. Use according to any of the preceding paragraphs A to M, without adversely altering one or more of the following physical properties: torque increment, modulus, compression set, compared to a rubber composition containing the corresponding amount of castor oil as plasticizer.

[0142] O. A method for producing a bladder for tire production, in which a rubber composition, which comprises one or more modified polyorganosiloxanes, one or more crosslinking resins for crosslinking and, optionally, further conventional additives, is vulcanized by means of the crosslinking resin, wherein the modified polyorganosiloxane and the rubber composition are as defined in one of the preceding paragraphs A to N.

[0143] P. A capsule for tire production comprising a rubber composition vulcanizable using a crosslinking resin, said rubber composition comprising a modified polyorganosiloxane and having been vulcanized with a crosslinking resin, wherein the modified polyorganosiloxane and the rubber composition are as defined in one of the paragraphs A to O above.

[0144] The advantages of the present application can be embodied in particular from the following examples. All quantities relate to weight, unless otherwise stated.

[0145] Examples

[0146] Preparation of polyorganosiloxanes according to the invention

[0147] The synthesis of the polyorganosiloxane according to the present application is described below based on the selected sample ("POS"):

[0148] In the first reaction step, 14.63 g (0.057 mol) tetramethyldisiloxane, 14.8 g (0.006 mol) polymethylhydrosiloxane and 76.3 g (0.26 mol) octamethylcyclotetrasiloxane are reacted in a three-necked pan in the presence of a calcium chloride catalyst (3%) at 80°C, resulting in a hydrogen dimethylpolysiloxane (M H 2D H 4D 18 [that is, all (average) silicon atoms of the 24 siloxane units in the compound, (average) two terminal groups (M H ) and 4 pendant groups (D H ) are in each case replaced by a hydrogen atom, so that they are available for subsequent functionalization].

[0149] In the second reaction step, 64.63 g (0.038 mol) hydrogen dimethylpolysiloxane are introduced and heated to 80°C. Then, a catalyst (10 ppm Speier catalyst) is added and 8.38 g (0.033 mol) of an alpha-olefin (chain length C 14 to C 22 ) is slowly added. The reaction is carried out at 90°C.

[0150] In the third reaction step, 26.89 g (0.236 mol) allyl glycidyl ether is slowly added at 80°C. The degree of conversion is monitored by infrared spectroscopy HSi measurement. If no more HSi is detected, the reaction is complete and the excess components are distilled off.

[0151] In the fourth reaction step, the product formed in step 3, 83.91 g (0.034 mol) was heated to 80 °C with catalyst (triethylamine or 1,4-diazabicyclo[2.2.2]octane value 0.5 %) and inhibitor (butylated hydroxytoluene 0.2 %) and 15.09 g (0.175 mol) of methacrylic acid was slowly added dropwise. The subsequent reaction was carried out at 95 °C and monitored by acid number. POS is a short, two terminal and multi-pendant, functionalized polyorganosiloxane.

[0152] Chemicals

[0153] The following chemicals were used (Table 1).

[0154] Table 1. Chemicals

[0155]

[0156] Furthermore, the following polyorganosiloxanes according to the application were used:

[0157] Modified polydimethylsiloxane POS as prepared above.

[0158] Test methods

[0159] The following test methods were employed.

[0160] Mooney viscosity: ISO 289-1 Rubber, unvulcanized - Determination of the viscosity using a shear disc viscometer - Part 1 : determination of the Mooney viscosity.

[0161] Shore A hardness: DIN ISO 7619-1 :2012-02 Rubber, vulcanized or thermoplastic - Determination of indentation hardness - Part 1 : durometer method (Shore hardness).

[0162] Tensile strength / stress value / elongation at break: DIN 53504 Rubber testing - Determination of the tensile strength at break, tensile stress at yield, elongation at break and stress value in tensile test.

[0163] Tear resistance: DIN ISO 34-1 Rubber, vulcanized or thermoplastic - Determination of the tear resistance - Part 1 : trouser, angle and moon test pieces.

[0164] Crack propagation: DIN ISO 132 Rubber, vulcanized or thermoplastic - Determination of the flex cracking and crack propagation (De Mattia).

[0165] Crosslinking: DIN 53529 Part 2 - Testing of rubbers and elastomers; vulcameter; determination of vulcanization characteristics and evaluation of the reaction kinetics of crosslinking isotherms.

[0166] Rubber compositions

[0167] The following rubber compositions 1 to 4 were prepared, comprising the following ingredients, wherein all amounts are in parts by weight (Table 2).

[0168] Table 2. Amounts of ingredients of rubber compositions

[0169] 1 2 3 4 Butyl RB 301 (IIR) 100 100 100 100 Neoprene WRT 5 5 5 5 Luvomaxx BC N-330 50 50 50 50 ZnO Harzsiegel 5 5 5 5 Struktol 40MS Flakes 5 5 5 5 Castor oil 6 3 - - POS - 3 6 6 SP 1045H 8 8 8 10 Total 179 179 179 181

[0170] The rubber compositions 1 to 4 were prepared as follows.

[0171] Rubber composition 1

[0172] A mixture of 50 parts by weight of carbon black (Luvomaxx BC N-330), 5 parts by weight of zinc oxide (Harzsiegel GR), 5 parts by weight of Struktol 40MS Flakes, 6 parts by weight of castor oil and 100 parts by weight of butyl rubber (Butyl RB 301) and 5 parts by weight of chloroprene rubber (Neoprene WRT) was placed in a laboratory internal mixer with reverse mixing, starting at 80 °C and at a speed of 70 revolutions per minute.

[0173] After 30 seconds, the plunger was raised and brushed, and the mixture was discharged after 180 seconds.

[0174] After 24 hours, 8 parts by weight of octylphenol crosslinking resin (SP 1045) were added to the resulting composition on a mill at 100 °C. Mixing was carried out for a total of 10 minutes.

[0175] Rubber composition 2

[0176] A mixture of 50 parts by weight of carbon black (Luvomaxx BC N-330), 5 parts by weight of zinc oxide (Harzsiegel GR), 5 parts by weight of Struktol 40MS Flakes, 3 parts by weight of castor oil and 3 parts by weight of POS and 100 parts by weight of butyl rubber (Butyl RB 301) and 5 parts by weight of chloroprene rubber (Neoprene WRT) was placed in a laboratory internal mixer with reverse mixing, starting at 80 °C and at a speed of 70 revolutions per minute.

[0177] After 30 seconds, the plunger was raised and brushed, and the mixture was discharged after 180 seconds.

[0178] After 24 hours, 8 parts by weight of octylphenol crosslinking resin (SP 1045) were added to the resulting composition on a mill at 100 °C. Mixing was carried out for a total of 10 minutes.

[0179] Rubber composition 3

[0180] A mixture of 50 parts by weight of carbon black (Luvomaxx BC N-330), 5 parts by weight of zinc oxide (Harzsiegel GR), 5 parts by weight of Struktol 40MS Flakes, 6 parts by weight of POS and 100 parts by weight of butyl rubber (Butyl RB301) and 5 parts by weight of chloroprene rubber (Neoprene WRT) was placed in a laboratory internal mixer with the inverse mixing method, with an initial temperature of 80 °C and a rotation speed of 70 revolutions / minute.

[0181] After 30 seconds, the plunger was raised and brushed, and the mixture was discharged after 180 seconds.

[0182] After 24 hours, 8 parts by weight of octylphenol crosslinking resin (SP 1045) were added to the resulting composition on a mill at 100 °C. The mixing was carried out for a total of 10 minutes.

[0183] Rubber composition 4

[0184] A mixture of 50 parts by weight of carbon black (Luvomaxx BC N-330), 5 parts by weight of zinc oxide (Harzsiegel GR), 5 parts by weight of Struktol 40MS Flakes, 6 parts by weight of POS and 100 parts by weight of butyl rubber (Butyl RB301) and 5 parts by weight of chloroprene rubber (Neoprene WRT) was placed in a laboratory internal mixer with the inverse mixing method, with an initial temperature of 80 °C and a rotation speed of 70 revolutions / minute.

[0185] After 30 seconds, the plunger was raised and brushed, and the mixture was discharged after 180 seconds.

[0186] After 24 hours, 10 parts by weight of octylphenol crosslinking resin (SP 1045) were added to the resulting composition on a mill at 100 °C. The mixing was carried out for a total of 10 minutes.

[0187] Crosslinking degree of rubber compositions 1 to 4

[0188] The torque of the rubber compositions 1 to 4 was determined as a measure of crosslinking in isothermal measurements at 210 °C using a RPA 2000 device (Table 3).

[0189] Table 3. Crosslinking RPA 2000 at 210 °C

[0190] 1 2 3 4 Torque ML [dNm] 1.87 1.91 2.03 1.93 Torque MH [dNm] 8.05 6.49 5.70 6.74 Torque increment (MH-ML) [dNm] 6.18 4.58 3.67 4.81 tc 10% [min] 0.84 0.68 0.57 0.61 tc 90% [min] 13.05 9.62 6.53 7.78

[0191] Vulcanization of rubber compositions 1 to 4

[0192] In each case 2 mm test plaques and 6 mm test pieces were prepared from the rubber compositions 1 to 4. For vulcanization the 2 mm test pieces were vulcanized at 210 °C for 13 minutes and the 6 mm test pieces for 14 minutes, the conditions being identical. The following properties of the vulcanized rubber compositions 1 to 4 were determined (Table 4).

[0193] Table 4. Properties of the vulcanized rubber compositions 1 to 4

[0194] 1 2 3 4 Vulcanization-time 2mm @ 210°C [min] 13 13 13 13 Vulcanization-time 6mm @ 210°C [min] 14 14 14 14 Hardness SH A [SH E] 56 52 53 58 Elasticity [%] 8 7 9 9 Tensile strength [MPa] 12.3 12.0 9.8 11.5 Standard deviation (sigma n-1) 1.08 0.38 0.42 1.12 Elongation at break [%] 640 741 697 670 Standard deviation (sigma n-1) 45.39 15.63 31.91 65.66 Modulus 100% [MPa] 1.5 1.1 1.1 1.4 Modulus 300% [MPa] 4.2 3.1 2.8 3.7 Modulus 500% [MPa] 8.4 6.6 5.9 7.6 Pants tear strength [kN / m] 16.6 16.5 15.5 16.6 DVR 24h / 100°C 25% [%] 28.4 33.6 41.0 28.2 Density [g / cm 3 ]]]> 1.110 1.112 1.107 1.115

[0195] The vulcanized rubber compositions 1 to 4 were also investigated in the flex fatigue test according to De Mattia (Table 5 and Figure 1 ) after steam aging.

[0196] Table 5. Flex fatigue test according to De Mattia [%] of the vulcanized rubber compositions 1 to 4

[0197] Thousand cycles 1 2 3 4 20 13.0 22.8 8.0 22.3 40 21.9 28.9 19.0 26.9 60 30.2 32.4 29.1 41.5 80 55.2 42.7 41.0 52.3 100 64.5 59.2 48.4 70.6 120 69.9 63.3 51.4 76.1 140 101.8 72.9 55.6 93.8 160 107.0 82.9 56.1 110.3 180 128.3 85.2 58.5 119.2 200 151.2 91.6 67.8 141.4 250 171.9 105.4 76.0 174.2 300 200.3 110.8 81.4 212.7

[0198] Steam aging of vulcanized rubber compositions 1 to 4

[0199] The vulcanized rubber compositions 1 to 4 were subjected to steam aging at 190 °C for 48 hours. The following properties of the vulcanized rubber compositions 1 to 4 were determined after steam aging. In addition, the corresponding property changes due to steam aging are also listed in the following table (Table 6).

[0200] Table 6. Properties of the vulcanized rubber compositions 1 to 4 after steam aging (48 hours at 190 °C) and corresponding property changes due to steam aging

[0201]

[0202] The vulcanized rubber compositions 1 to 4 were also investigated in the flex fatigue test according to De Mattia (Table 7 and Figure 2 ) after steam aging (48 hours at 190 °C).

[0203] Table 7. Vulcanized rubber compositions 1 to 4 in the flex fatigue test according to De Mattia after steam aging (48 hours at 190 °C) [%]

[0204] Thousand cycles 1 2 3 4 20 45.8 9.1 1.3 10.9 40 127.5 23.2 1.9 42.5 60 183.8 44.4 4.9 73.9 80 249.0 68.7 5.1 111.9 100 308.5 83.4 15.8 134.8 120 356.1 109.9 15.8 142.5 140 401.0 126.0 16.4 174.9 160 457.8 153.3 16.6 197.4 180 513.3 184.5 40.5 228.5 200 570.7 189.9 42.1 243.9 250 709.2 234.5 44.5 298.2 300 823.2 277.8 44.5 342.9

[0205] Evaluation of the measurement data

[0206] Rubber composition 1 shows the current state of the art and serves as a comparison (control). By using 3 phr of POS in combination with 3 phr of castor oil in rubber composition 2 or 6 phr of POS in rubber composition 3, the curemeter curve is reduced depending on the amount of POS used. By using 6 phr of POS and using a high 2 phr of crosslinking resin SP 1045, the curemeter curve of rubber composition 4 reaches a level comparable to rubber composition 1.

[0207] Similar trends are to be expected considering the results after steam aging in an autoclave (48 hours at 190°C). It should be noted here that the test pieces of vulcanized rubber composition 3 swelled significantly and the physical values could not be determined. This can be due to insufficient crosslinking of the vulcanized rubber composition 3.

[0208] Vulcanized rubber composition 4 has a very balanced profile of properties. In particular, it is remarkable that vulcanized rubber composition 4, in terms of crack propagation according to De Mattia, is now clearly different from the control (rubber composition 1) and has significantly improved crack resistance.

[0209] The flexibility of the vulcanized rubber of rubber composition 1 is also poor. This can be illustrated by the large increase in Shore hardness, tensile strength and modulus.

[0210] The combination of using only 3 phr of POS with 3 phr of castor oil (rubber composition 2) also leads to good results in the flex endurance test (De Mattia test).

Claims

1. Use of one or more modified polyorganosiloxanes as plasticizer in a rubber composition, wherein the rubber is a rubber which can be crosslinked by a crosslinking resin and is vulcanized by one or more crosslinking resins, wherein the polyorganosiloxane comprises 3 or more siloxane units and one or more organic groups R 1 wherein R 1 is a monovalent unsaturated acyloxy group having at least 4 up to 15 carbon atoms, wherein the acyl group has a terminal double bond which is substituted or unsubstituted and is bound to a silicon atom of the polyorganosiloxane backbone via a hydrocarbon chain.

2. Use according to claim 1, wherein the hydrocarbon chain contains at least one oxygen atom in the chain.

3. Use according to claim 1, wherein the hydrocarbon chain has at least one hydroxyl group substitution.

4. The use according to claim 1, characterized in that the modified polyorganosiloxane has two or more organic groups R 1 and / or one or more further longer alkyl groups R 2 wherein R 2 has a chain length of 5 to 50 carbon atoms.

5. Use according to claim 1, characterized in that the rubber comprises butyl rubber and / or chlorobutyl rubber.

6. Use according to claim 1, characterized in that the rubber comprises a brominated copolymer of butyl rubber, isobutylene and p-methylstyrene or mixtures thereof, and chlorobutyl rubber is used as a crosslinking co-agent.

7. Use according to any one of claims 1 to 6, characterized in that the rubber composition comprising polyorganosiloxane comprises one or more other plasticizers than polyorganosiloxane in an amount of less than 5 parts by weight per 100 parts by weight of the rubber mixture.

8. Use according to claim 7, wherein the other plasticizer than polyorganosiloxane comprises castor oil and / or hydrocarbon resin.

9. Use according to claim 8, wherein the other plasticizer than polyorganosiloxane comprises castor oil.

10. Use according to claim 8, wherein the other plasticizer than polyorganosiloxane is castor oil and / or hydrocarbon resin.

11. Use according to claim 10, wherein the other plasticizer than polyorganosiloxane is castor oil.

12. Use according to any one of claims 1 to 6, characterized in that the rubber composition does not contain other plasticizers than the modified polyorganosiloxane.

13. Use according to any one of claims 1 to 6, characterized in that the rubber composition contains other additives and ingredients suitable for the manufacture of a bladder for tire production.

14. Use according to any one of claims 1 to 6, characterized in that the rubber composition, after vulcanization, is suitable for use as a bladder in tire production.

15. Use according to claim 13, characterized in that the rubber composition contains as other components a filler, a catalyst for crosslinking of the resin and optionally other additives.

16. Use according to claim 15, wherein the other additives are homogenizing agents.

17. Use according to any one of claims 1 to 6, characterized in that the crosslinking resin is an optional halogenated alkylphenol-formaldehyde resin.

18. The use according to claim 17, wherein the alkyl groups in the halogenated alkyl phenol- formaldehyde resin are Ci to C 10 alkyl groups.

19. Use according to any one of claims 1 to 6, characterized in that the amount of polyorganosiloxane in the rubber composition is 3 to 8 parts by weight per 100 parts by weight of the rubber mixture, in particular in that the rubber composition comprises a crosslinking resin in a concentration of from 2 parts by weight to 12 parts by weight per 100 parts by weight of the rubber mixture.

20. Use according to any one of claims 1 to 6, characterized in that the total number of siloxane units of the polyorganosiloxane is 10 to 100.

21. Use according to claim 20, wherein the total number of siloxane units of the polyorganosiloxane is 15 to 70.

22. Use according to claim 21, wherein the total number of siloxane units of the polyorganosiloxane is 20 to 50.

23. Use according to any one of claims 1 to 6, characterized in that the service life of a bladder for tire production prepared from the rubber composition is extended by a factor of 1.2 or more, as determined according to the crack propagation method of De Mattia, compared to a bladder for tire production prepared with the same concentration of castor oil as plasticizer, while the other ingredients and the processing of the vulcanization mixture are identical.

24. Use according to any one of claims 1 to 6, wherein one or more of the following physical properties are not adversely changed: torque increment, modulus, compression set, compared to a rubber composition containing the corresponding amount of castor oil as plasticizer.

25. A method of preparing a capsule for tire production, wherein a rubber composition, comprising one or more modified polyorganosiloxanes, one or more crosslinking resins for crosslinking, and optionally other conventional additives, is vulcanized by the crosslinking resins, wherein, The modified polyorganosiloxane and the rubber composition are the materials used in the use according to any one of claims 1 to 24.

26. A bladder for tire production comprising a rubber composition that is vulcanizable using a crosslinking resin, the rubber composition comprising a modified polyorganosiloxane and having been vulcanized using a crosslinking resin, wherein the modified polyorganosiloxane and the rubber composition are the materials used in the use according to any one of claims 1 to 24.

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