EP4363428A1

EP4363428A1 - Organosilyl polysulfides, and rubber mixtures containing same

Info

Publication number: EP4363428A1
Application number: EP22738423.7A
Authority: EP
Inventors: Hermann-Josef Weidenhaupt; Irene MOLL; Michaela Meiers
Original assignee: Lanxess Deutschland GmbH
Current assignee: Lanxess Deutschland GmbH
Priority date: 2021-06-30
Filing date: 2022-06-27
Publication date: 2024-05-08
Also published as: EP4112624A1; KR20240027105A; CN117715919A; WO2023274909A1

Abstract

The new organosilyl polysulfides of formula (I), in which substituents R¹ to R⁸ and index x have the meanings indicated in the description, are extremely well suited for the manufacturing of rubber mixtures, vulcanized products and rubber products which are characterized by greater hardness, strength and elongation at break as well as low rolling resistance of the tires made therefrom.

Description

Organosilyl polysulfides and rubber compositions containing them

The present invention relates to new organosilyl polysulfides and their use as reinforcing additives for rubber, rubber mixtures containing these organosilyl polysulfides and the use of these organosilyl polysulfides for the production of these rubber mixtures, vulcanizates obtainable from these rubber mixtures and moldings, in particular tires.

Sulfur-containing organosilicon compounds which can be used as reinforcing additives in rubber mixtures are known. Thus, DE-A 2141159, DE-A 2141160 and DE-A 2255577 describe sulfur-containing organosilanes as reinforcing additives, in particular for rubber vulcanizates containing silica for tire applications. The sulfur-containing organosilanes disclosed there are derived from bis(trialkoxysilylalkyl)polysulfides; bis(triethoxysilylpropyl)tetrasulfide (TESPT), for example, is explicitly described.

DE-A 2035778 also discloses organosilane-based reinforcing additives which are derived from trialkoxysilylpropyl compounds. A disadvantage of these connections known from the prior art is that the hysteresis losses are reduced not only at high temperatures (approx. 60° C., correlating with the rolling resistance) but also at low temperatures (0° C.). In principle, a reduction in the hysteresis losses is desirable because it leads to a reduction in the rolling resistance of motor vehicle tires and thus to lower fuel consumption by the vehicles. However, it is known that a low hysteresis at low temperatures (0 to 20°C) is associated with poor wet skid resistance of vehicle tires. It is therefore difficult to reconcile the two requirements of low rolling resistance and good wet skid resistance at the same time.

EP-A 447066 also describes the use of sulphur-containing organosilanes as adhesion promoters in rubber mixtures for the production of tire treads which are filled to a large extent with silica. The combination of a special, silane-modified rubber, a silicic acid filler and adhesion promoters based on special trialkoxyalkyl polysulfides made it possible to reduce the rolling resistance of the tire. However, these tire compounds also show that the adhesion promoters mentioned not only reduce the rolling resistance, but also the reduce wet grip.

EP-A 0680997 also discloses the use of certain bis-alkoxy/alkyl-substituted silylmethylene polysulfides as reinforcing additives for rubber mixtures with good rolling resistance and good wet grip. The disadvantage here is on the one hand that the The raw materials used in the production of the reinforcing additives have to be produced in a complex manner via photochlorination and, on the other hand, the rubbers have a significant deterioration in performance properties such as strength, elongation at break and hardness. EP-A 3622015 describes the use of bis(dimethylethoxysilylisobutylene)polysulfide as a reinforcing additive for rubber mixtures with good rolling resistance and good wet grip properties. However, when these compounds are used in tire production, 2 moles of ethanol are released per mole, which can be disadvantageous in practice. The object of the present invention was therefore to provide new reinforcing additives for rubbers based on sulfur-containing organosilicon compounds, and new rubber mixtures, which overcome the abovementioned disadvantages of the prior art.

Surprisingly, it has been found that certain organosilyl polysulfides, each of which has a propylene group or a propylene group branched in the 2-position as a spacer between the silicon and sulfur atoms, are very suitable as reinforcing additives in rubber compounds without it being the case during the vulcanization of the rubber compound to the emission of volatile organic components (VOC).

The new organosilyl polysulfides bring about a rapid full vulcanization time (T95) in the rubber mixtures and lead to advantageous temperature-dependent hysteresis properties in the vulcanizates obtainable from them and to positive performance properties, such as high strength and high elongation at break. In particular, tires made from these vulcanizates are distinguished by low rolling resistance and good wet grip. The present invention therefore relates to new organosilyl polysulfides of the formula (I) wherein

R ¹ , R ³ , R ⁶ and R ⁸ are identical or different and are Ci-C4-alkyl, R ⁴ and R ⁵ are identical or different and represent hydrogen or CrC ₄ -alkyl,

R ² and R ⁷ represent a radical of the formula

CH ₃ CH 2 C(CH ₂ OH) 2 CH 2 -, and x is an integer from 2 to 8.

Preference is given to organosilyl polysulfides of the formula (I) in which R1, R3, R6 and R8 are identical or different and are methyl or ethyl, ^R4 and ^R5 ^are identical or different and are hydrogen, methyl or ^ethyl , ^R2 and R ⁷ is a group of the formula CH ₃ CH 2 C(CH ₂ OH) 2 CH 2 -, and x is an integer from 2 to 8.

Particular preference is given to organosilyl polysulfides of the formula (I) in which R ¹ , R ³ , R ⁶ and R ⁸ are methyl, R ⁴ and R ⁵ are identical or different and are hydrogen or methyl,

R ² and R ⁷ represent a radical of the formula

CH ₃ CH ₂ C(CH ₂ OH) 2 CH 2 -, and x is an integer from 2 to 8. Very particular preference is given to organosilyl polysulfides of the formula (I) in which R ¹ , R ³ , R ⁶ and R ⁸ are methyl,

R ⁴ and R ⁵ are the same and represent hydrogen or methyl,

R ² and R ⁷ represent a radical of the formula

CH ₃ CH ₂ C(CH ₂ OH) 2 CH 2 -, and x is an integer from 2 to 8.

Particular preference is given to organosilyl polysulfides of the formula (Ia) and (Ib) where x is an integer from 2 to 8. with the chemical name bis[di(hydroxymethyl)butoxydimethylsilylpropyl]polysulfide, and where x is an integer from 2 to 8, chemically named bis[di(hydroxymethyl)butoxydimethylsilylisobutyl]polysulfide.

It is known to those skilled in the art that organosilyl polysulfides can disproportionate under the influence of temperature and/or solvents. The organosilyl polysulfides according to the invention are therefore usually present as mixtures, the number of sulfur atoms in the organosilyl polysulfides being around a number average value which is generally from 3.6 to 4.4, preferably from 3.8 to 4.2 and in particular 4.0.

The present invention also relates to mixtures containing at least two organosilyl polysulfides of the formula (I), in which the substituents R ¹ to R ⁸ and x have the general and preferred meanings given above and which differ at least in the value of x, where the number average value x of the number x of sulfur atoms is 3.6 to 4.4, preferably 3.8 to 4.2 and in particular 4.0.

Particularly preferred are mixtures containing at least two organosilyl polysulfides of the formula (Ia) and/or the formula (Ib) which differ in the value x, where the number average value x of the number x of the sulfur atoms is 3.6 to 4.4, preferably 3, is 8 to 4.2 and in particular 4.0.

The organosilyl polysulfides of the formula (I) according to the invention can be prepared by reacting at least two haloalkylsilyl ethers of the formula (II) wherein

R ⁹ is a radical R ⁴ or R ⁵ ,

R ¹⁰ is a radical R ³ or R ⁶ ,

R ¹¹ is an R ² or R ⁷ radical and R ¹² is an R ¹ or R ⁸ radical, where the R ¹ to R ⁸ radicals have the general and preferred meanings given for formula (I) and

Hal is halogen, preferably chlorine, with at least one metal polysulfide of the formula (III) SXM ₂ (III) in which x has the general and preferred meaning given for formula (I), and M is a metal ion selected from lithium, sodium and potassium, preferably sodium, in the presence of at least one alcoholic solvent.

Processes for preparing organosilyl polysulfides are known in principle. The organosilyl polysulfides of the formula (I) according to the invention can be prepared analogously to the known processes (as described, for example, in DE-A 2 141 159).

In general, 0.5 mol of metal polysulfide of the formula (III), particularly preferably sodium polysulfide, is used to prepare the organosilyl polysulfides according to the invention, based on one mole of the total amount of haloalkylsilyl ether of the formula (II).

The process for preparing the organosilyl polysulfides according to the invention can be carried out over a wide temperature range. It is preferably carried out at a temperature in the range from -20 to +90°C.

The process for preparing the organosilyl polysulfides according to the invention is preferably carried out in the presence of at least one alcohol from the group consisting of methanol, ethanol, n-propanol, i-propanol, i-butanol, amyl alcohol, hexyl alcohol, n-octanol, i-octanol, ethylene glycol, 1,2 - and 1,3-propylene glycol, 1,4-butanediol and/or 1,6-hexanediol.

The process for the preparation of the organosilyl polysulfides according to the invention can be carried out over a wide pressure range. In general, it is carried out at a pressure of 0.9 to 1.1 bar, preferably at atmospheric pressure.

In general, the organosilyl polysulfides (I) according to the invention are prepared by initially placing the metal polysulfide of the formula (III) in an anhydrous alcohol, preferably in anhydrous methanol, and heating to boiling under inert conditions and then adding at least two haloalkylsilyl ethers of the formula (II). After the reaction has taken place, the alkali metal salt which has separated out is filtered off as a by-product and the compounds of the formula (I) are separated from the solvent by distillation and isolated in pure form as the remaining bottom product in a yield of >85%.

The haloalkylsilyl ethers of the formula (II) are new and also a subject of the present invention.

Processes for preparing haloalkylsilyl ethers are known in principle.

The haloalkylsilyl ethers of the formula (II) according to the invention can be prepared in a known manner, for example analogously to the process described in EP-A 0669338, by reacting at least one haloallyl compound of the formula (IV) in which R ⁹ has the general and preferred meaning given for formula (II) and Hal represents halogen, preferably chlorine, with at least one silane of the formula (V) in which R ¹⁰ , R ¹¹ and R ¹² have the general and preferred meanings given for formula (II), in the presence of at least one ruthenium catalyst.

The haloalkylsilyl ethers of the formula (II) according to the invention are preferably prepared without the addition of a solvent.

In general, 1.15 to 2 mol, preferably 1.6 to 2.0 mol, of silane of the formula (V) are used per mole of halogen allyl compound of the formula (IV). The compounds listed in EP-A 0669338 are preferably suitable as ruthenium catalysts. The ruthenium catalyst Ru3(CO)i2 is particularly suitable for preparing the haloalkylsilyl ethers of the formula (II) according to the invention _. .

In general, 10 to 200 ppm, preferably 15 to 100 ppm, of at least one ruthenium catalyst are used per mole of halogenated allyl compound of the formula (IV). The reaction of the haloallyl compounds of the formula (IV) with the silanes of the formula (V) generally takes place at a temperature in the range from 20.degree. C. to 150.degree. C., preferably from 70 to 90.degree. The reaction generally takes place over a period of 1 to 100 hours, preferably over a period of 1.5 to 5 hours.

The course of the reaction can be followed by means of TLC (thin layer chromatography). After the reaction is complete, the haloalkylsilyl ether of the formula (II) can be purified by distillation. Yields of up to 97% can be achieved in this way.

The halogen allyl compound of the formula (IV) are known and can be purchased, for example, as commercial products from Aldrich (CAS: 107-05-1 or CAS: 563-47-3).

The silanes of the formula (V) can be prepared in a manner known per se (cf. eg US2011/0105780) by reacting halosilanes of the formula (VI) wherein

R ¹ and R ³ have the general and preferred meanings given for formula (I) and

Hal is halogen, preferably chlorine, with an alcohol of the formula R ¹¹ OH, in which R ¹¹ has the general and preferred meanings given for formula (I).

Silanes of the formula (VI) are known and can be purchased as commercial products, e.g. from Sigma-Aldrich.

The present invention also relates to rubber mixtures containing at least one rubber and at least one compound of the formula (I) in which the substituents R ¹ to R ⁸ and the index x have the general and preferred meanings given above.

In general, the total content of compounds of the formula (I) in the rubber mixtures according to the invention is 0.1 to 15 parts by weight, preferably 1 to 12 parts by weight, particularly preferably 2 to 10 parts by weight and very particularly preferably 3 to 8 parts by weight, each based on 100 parts by weight of the total amount of rubber.

The compounds of the formula (I) can be added to the rubber mixtures either in pure form or applied to an inert organic or inorganic carrier. Silicic acids, natural or synthetic silicates, aluminum oxide and carbon blacks are particularly suitable as support materials.

The rubber mixtures according to the invention contain at least one rubber.

The rubber mixtures according to the invention preferably contain at least one natural rubber (NR) and/or synthetic rubber.

As synthetic rubbers come for example

BR - polybutadiene

ABR - butadiene/acrylic acid-Ci-C4-alkyl ester copolymer

CR - polychloroprene

IR - polyisoprene

SBR - styrene/butadiene copolymers with a styrene content of 1-60, preferably 20-50% by weight

IIR - isobutylene/isoprene copolymers

NBR - butadiene/acrylonitrile copolymers with acrylonitrile contents of 5 to 60% by weight, preferably 10-50% by weight

HNBR - partially hydrogenated or fully hydrogenated NBR rubber

EPDM - ethylene / propylene / diene copolymers and mixtures of two or more of these rubbers in question.

The rubber mixtures according to the invention preferably contain at least one SBR rubber, preferably a functionalized SBR rubber and optionally one or more BR rubbers.

According to the invention, functionalized SBR rubber is to be understood as meaning an SBR rubber which is attached to the main chain and/or to the end groups by one or more functional groups, in particular carboxyl groups and/or mercaptan-containing groups is substituted.

The rubber mixtures according to the invention very particularly preferably contain mixtures of SBR and BR rubbers in an SBR:BR weight ratio of from 100:0 to 60:40.

In a further advantageous embodiment, the rubber mixtures according to the invention contain at least one natural rubber.

The rubber mixtures according to the invention preferably contain one or more fillers. In principle, all fillers known from the prior art for this purpose are suitable.

Oxidic compounds containing hydroxyl groups, such as special silicic acids and also carbon blacks, are particularly suitable as active fillers.

The rubber mixtures according to the invention generally contain 10 to 190 parts by weight, preferably 30 to 150 parts by weight and particularly preferably 50 to 130 parts by weight of at least one filler, based in each case on 100 parts by weight of the total amount of rubber.

The rubber mixtures according to the invention preferably contain at least one hydroxyl-containing oxidic filler.

In general, the content of hydroxyl-containing oxidic fillers in the rubber mixtures according to the invention is at least 10 parts by weight, preferably 20 to 150 parts by weight, particularly preferably 50 to 140 parts by weight and very particularly preferably 80 to 130 parts by weight. in each case based on 100 parts by weight of the total filler content.

Suitable hydroxyl-containing oxidic fillers are preferably those from the series

- Silicic acids with a specific surface area (BET) of 5 to 1000, preferably 20 to 400 m ² / g and with primary particle sizes of 100 to 400 nm, the silicic acids optionally also being present as mixed oxides with other metal oxides such as Al, Mg, Ca, Ba, Zn, Zr, Ti oxides are present, and

- Synthetic silicates such as aluminum silicate, alkaline earth silicates such as magnesium silicate or calcium silicate, with specific surface areas (BET) of 20 to 400 m ² / g and primary particle diameters of 10 to 400 nm. The hydroxyl-containing oxidic fillers from the silicic acid series present in the rubber mixtures according to the invention are preferably those which can be prepared, for example, by precipitation of solutions of silicates or flame hydrolysis of silicon halides.

The rubber mixtures according to the invention preferably contain at least one hydroxyl-containing oxidic filler from the series of silicic acids with a specific surface area (BET) in the range from 20 to 400 m2/g in an amount of 5 to 150 parts by weight, preferably 50 to 140 parts by weight. parts and more preferably from 80 to 130 parts by weight, each based on 100 parts by weight of the total amount of rubber.

The rubber mixtures according to the invention can also contain at least one carbon black as a filler.

According to the invention, preference is given to carbon blacks which can be obtained by the lamp black, furnace or gas black process and which have a specific surface area (BET) in the range from 20 to 200 m ² /g, such as SAF, ISAF, IISAF, HAF, FEF or GPF carbon blacks.

In general, the rubber mixtures according to the invention contain at least one carbon black with a specific surface area (BET) in the range from 20 to 200 m ² /g in an amount of 0 to 40 parts by weight, preferably 0 to 30 parts by weight and particularly preferably from 0 to 20 parts by weight, each based on 100 parts by weight of the total amount of rubber.

All information on the BET relates to the specific surface area measured in accordance with DIN 66131. The information on the primary particle size relates to values determined using a scanning electron microscope.

In a preferred alternative embodiment, the rubber mixtures according to the invention contain at least one of the abovementioned carbon blacks and at least one of the abovementioned silicas as fillers.

In a particularly preferred alternative embodiment, the rubber mixtures according to the invention contain at least one hydroxyl-containing oxidic filler from the series of silicic acids with a specific surface area (BET) in the range from 20 to 400 m2/g in an amount of 20 to 120 parts by weight, preferably 30 to 100 parts by weight and more preferably from 40 to 90 parts by weight, and at least one carbon black having a specific surface area (BET) in the range of 20 to 200 m ² /g in an amount of 20 to 90 parts by weight , preferably from 30 to 80 parts by weight and particularly preferably from 40 to 70 parts by weight, in each case based on 100 parts by weight of the total amount of rubber. The rubber mixtures according to the invention can contain one or more crosslinkers.

Crosslinkers preferred according to the invention are, in particular, sulfur and sulfur donors and metal oxides such as magnesium oxide and/or zinc oxide.

Sulfur can be used in elemental soluble or insoluble form or in the form of sulfur donors. Possible sulfur donors are, for example, dithiodimorpholine (DTDM), 2-morpholinodithiobenzothiazole (MBSS), caprolactam disulfide, dipentamethylenethiuram tetrasulfide (DPTT) and tetramethylthiuram disulfide (TMTD).

The rubber mixtures according to the invention particularly preferably contain at least one sulfur donor and/or sulfur, in particular sulfur.

The rubber mixtures according to the invention generally contain from 0.1 to 10 parts by weight, preferably from 0.2 to 5 parts by weight, of at least one of the crosslinkers mentioned, based in each case on 100 parts by weight of the total amount of rubber.

The rubber mixtures according to the invention can contain one or more vulcanization accelerators.

According to the invention, preferred vulcanization accelerators are mercaptobenzothiazoles, mercaptosulfenamides, thiocarbamates, thiocarbonates and dithiophosphates, and sulfur donors such as dithiodicaprolactams, dithiodimorpholines and xanthogenates.

The rubber mixtures according to the invention generally contain from 0.1 to 10 parts by weight, preferably from 0.2 to 5 parts by weight, of at least one of the vulcanization accelerators mentioned, based in each case on 100 parts by weight of the total amount of rubber.

In addition to the compounds of the formula (I), the rubber mixtures according to the invention may also contain one or more other reinforcing additives which are known from the prior art and are customary for this purpose.

In addition to the additives mentioned above, the rubber mixtures according to the invention can also contain other rubber auxiliaries familiar to the person skilled in the art, such as reaction accelerators, aging inhibitors, heat stabilizers, light stabilizers, ozone protection agents, processing auxiliaries, plasticizers, tackifiers, blowing agents, dyes, pigments, waxes, extenders, organic acids, reaction retarders, Metal oxides, activators such as triethanolamine, polyethylene glycol, hexanetriol and fillers from the group of natural silicates such as kaolin and other naturally occurring silicic acids and also glass fibers and glass fiber products, for example in the form of mats, strands or microspheres. The rubber mixtures according to the invention contain the rubber auxiliaries mentioned in the amounts customary for these auxiliaries, typically in an amount of from 0.1 to 30 parts by weight, based in each case on 100 parts by weight of the total amount of rubber.

The rubber mixtures according to the invention can contain one or more secondary accelerators.

In rubber mixtures based on silica, such as those used in tire production, typically diphenylguanidine (DPG) or structurally similar aromatic guanidines are used as a secondary accelerator in order to be able to specifically adjust the crosslinking speed and the mixture viscosity within the mixing process. However, a very crucial, negative feature of using DPG is that it releases aniline during vulcanization, which is suspected of being carcinogenic. Surprisingly, it has now been found that, in the rubber mixtures according to the invention, DPG can advantageously be substituted by 1,6-bis(N,N-dibenzylthiocarbamoyldithio)hexane (trade name Vulcuren®). It is also possible to replace DPG with secondary accelerators such as TBzTD (tetrabenzylthiuram disulfide) or dithiophosphates.

The present invention therefore also encompasses essentially DPG-free rubber mixtures.

The silica-based rubber mixtures according to the invention preferably contain at least one secondary accelerator from the series 1,6-bis(N,N-dibenzylthiocarbamoyldithio)hexane (trade name Vulcuren®), tetrabenzylthiuram disulfide (TBzTD) and dithiophosphates.

The rubber mixtures according to the invention generally contain from 0.1 to 1.0 part by weight, preferably from 0.2 to 0.5 part by weight, of at least one of the secondary accelerators mentioned, based in each case on 100 parts by weight of the total amount of rubber.

The present invention therefore also provides rubber mixtures according to the invention which are essentially free of diphenylguanidine and/or substituted diphenylguanidines, in particular those which have a content of diphenylguanidine and/or substituted diphenylguanidines of at most 0.4 parts by weight, preferably 0.1 to 0.2 parts by weight, more preferably from 0.05 to 0.1 part by weight and most preferably from 0.001 to 0.04 part by weight, based in each case on 100 parts by weight of the total amount of rubber.

Preference is given to rubber mixtures according to the invention containing at least one rubber, 5 to 150 parts by weight, preferably 50 to 140 parts by weight and particularly preferably 80 to 130 parts by weight of at least one silica, 0 to 40 parts by weight, preferably 0 to 30 Parts by weight and particularly preferably 0 to 20 parts by weight of carbon black and 0.1 to 15, preferably 1 to 12, particularly preferably 2 to 10 parts by weight and in particular 3 to 8 parts by weight of at least one compound of the formula (I), each based on 100 parts by weight of the total amount of rubber.

Preference is also given to rubber mixtures according to the invention containing at least one rubber, 5 to 150 parts by weight, preferably 50 to 140 parts by weight and particularly preferably 80 to 130 parts by weight of at least one silica, 0 to 40 parts by weight, preferably 0 to 30 parts by weight and particularly preferably 0 to 20 parts by weight of carbon black and 0.1 to 15, preferably 1 to 12, particularly preferably 2 to 10 parts by weight and in particular 3 to 8 parts by weight of at least one compound of the formula (I) and 0.1 to 1.0 part by weight of 1,6-bis(N,N-dibenzylthiocarbamoyldithio)hexane (Vulcuren®), in each case based on 100 parts by weight of the total amount of rubber.

Very particular preference is given to rubber mixtures according to the invention containing at least one rubber, in particular at least one SBR rubber, preferably a functionalized SBR rubber and optionally one or more BR rubbers, 5 to 150 parts by weight, preferably 50 to 140 parts by weight and particularly preferably 80 to 130 parts by weight of at least one silica, in particular with a specific surface area (BET) of 5 to 1000, preferably 20 to 400 m2/g and with primary particle sizes of 100 to 400 nm, 0 to 40 parts by weight, preferably 0 to 30 parts by weight and particularly preferably 0 to 20 parts by weight of carbon black, in particular with a specific surface area (BET) in the range from 20 to 200 m2/g, and 0.1 to 15, preferably 1 to 12, particularly preferably 2 to 10 parts by weight and in particular 3 to 8 parts by weight of at least one compound of the formula (I), in particular the formula (Ia) (bis[di(hydroxymethyl)butoxydimethylsilylpropyl]polysulfide) and/or the formula (Ib) (bis[di(hyroxymethyl l) butoxydimethylsilylisobutyl] polysulfide), in each case based on 100 parts by weight of the total amount of rubber.

Furthermore, very particular preference is given to rubber mixtures according to the invention containing at least one rubber, in particular at least one SBR rubber, preferably a functionalized SBR rubber and optionally one or more BR rubbers, 5 to 150 parts by weight, preferably 50 to 140 parts by weight. Parts and particularly preferably 80 to 130 parts by weight of at least one silica, in particular with a specific surface area (BET) of 5 to 1000, preferably 20 to 400 m2/g and with primary particle sizes of 100 to 400 nm, 0 to 40 parts by weight Parts, preferably 0 to 30 parts by weight and particularly preferably 0 to 20 parts by weight, of carbon black, in particular having a specific surface area (BET) in the range from 20 to 200 m2/g, and 0.1 to 15, preferably 1 to 12, particularly preferably 2 to 10 parts by weight and in particular 3 to 8 parts by weight of at least one compound of the formula (I), in particular of the formula (Ia) (bis[di(hydroxymethyl)butoxydimethylsilylpropyl]polysulfide) and/or of formula (Ib) (Bis[di(hydroxymethyl)butoxydimethylsilylisobutyl]polysulfide) and 0.1 to 0.5 parts by weight of 1,6-bis(N,N-dibenzylthiocarbamoyldithio)hexane (Vulcuren®) and containing diphenylguanidine and/or substituted ones Diphenylguanidines of not more than 0.4 part by weight, preferably from 0.1 to 0.2 part by weight, particularly preferably from 0.05 to 0.1 part by weight and very particularly preferably from 0.001 to 0.04 part by weight Parts, each based on 100 parts by weight of the total amount of rubber.

Also very particularly preferred are rubber mixtures according to the invention containing at least one natural rubber, 5 to 150 parts by weight, preferably 50 to 140 parts by weight and particularly preferably 80 to 130 parts by weight of at least one silica, in particular with a specific surface area (BET) from 5 to 1000, preferably 20 to 400 m2/g and with primary particle sizes from 100 to 400 nm, 0 to 40 parts by weight, preferably 0 to 30 parts by weight and particularly preferably 0 to 20 parts by weight carbon black, in particular having a specific surface area (BET) in the range of 20 to 200 m2/g, and 0.1 to 15, preferably 1 to 12, more preferably 2 to 10 parts by weight and especially 3 to 8 parts by weight of at least one Compound of the formula (I), in particular of the formula (la) (bis[di(hyroxymethyl)butoxydimethylsilylpropyl]polysulfide) and/or of the formula (Ib) (bis[di(hyroxymethyl)butoxydimethylsilylisobutyl]polysulfide), in each case based on 100 wt. -Parts of the total amount of rubber.

Also very particularly preferred are rubber mixtures according to the invention containing at least one natural rubber, 5 to 150 parts by weight, preferably 50 to 140 parts by weight and particularly preferably 80 to 130 parts by weight of at least one silica, in particular with a specific surface area (BET) from 5 to 1000, preferably 20 to 400 m2/g and with primary particle sizes from 100 to 400 nm, 0 to 40 parts by weight, preferably 0 to 30 parts by weight and particularly preferably 0 to 20 parts by weight carbon black, in particular having a specific surface area (BET) in the range of 20 to 200 m2/g, and 0.1 to 15, preferably 1 to 12, more preferably 2 to 10 parts by weight and especially 3 to 8 parts by weight of at least one Compound of the formula (I), in particular of the formula (Ia) (bis[di(hyroxymethyl)butoxydimethylsilylpropyl]polysulfide) and/or of the formula (Ib) (bis[di(hyroxymethyl)butoxydimethylsilylisobutyl]polysulfide) and 0.1 to 0, 5 parts by weight of 1,6-bis(N,N-dibenzylthiocarbamoyldithio)hexane (Vul curen®) and a content of diphenylguanidine and/or substituted diphenylguanidines of at most 0.4 parts by weight, preferably from 0.1 to 0.2 parts by weight, particularly preferably from 0.05 to 0.1 parts by weight and very particularly preferably from 0.001 to 0.04 parts by weight, in each case based on 100 parts by weight of the total amount of rubber. Another subject of the present invention is a process for producing the rubber mixtures according to the invention, by mixing at least one of the rubbers mentioned generally and preferably above with at least one of the fillers mentioned above generally and preferably and at least one compound of the formula (I) and optionally with at least one of the general and preferred reinforcement additives mentioned above, optionally one or more of the general and preferred vulcanization accelerators mentioned above and optionally one or more of the secondary accelerators mentioned generally and preferably and optionally one or more of the rubber auxiliaries mentioned above in the general and preferred ones mentioned for these additives Amounts and heating of the mixture so produced to a temperature in the range from 60 to 200°C, particularly preferably from 90 to 180°C.

Typically, to produce the rubber mixtures according to the invention, 10 to 190 parts by weight, preferably 30 to 150 parts by weight and particularly preferably 50 to 130 parts by weight of at least one filler and 0 1 to 15 parts by weight, preferably 1 to 12 parts by weight, particularly preferably 2 to 10 parts by weight and very particularly preferably 3 to 8 parts by weight of at least one compound of the formula (I) and optionally a or more of the additives specified above are used in the amounts specified for these additives.

Alternatively, the rubber mixtures according to the invention can be prepared by mixing at least one compound of the formula (I) with x=2 at a temperature of 100 to 200° C., preferably 130 to 180° C., with sulfur and at least one rubber and at least one filler. In this alternative process, further sulfur atoms are incorporated in situ into the compound of formula (I) with x=2, as a result of which the compounds of formula (I) according to the invention with x=2 to 8 and a number average value of x=4 are formed.

The rubber mixtures according to the invention are produced in the customary manner in known mixing units, such as rolls, internal mixers and mixing extruders, at melt temperatures of 60 to 200° C., preferably 100 to 200° C., and at shear rates of 1 to 1000 sec ¹ .

The compounds of the formula (I) and the fillers are preferably added in the first part of the mixing process at melt temperatures of 60 to 200° C., preferably 100 to 200° C., and at the shear rates mentioned. However, it can also be carried out later in the mixing process at lower temperatures (40 to 130° C., preferably 40 to 100° C.), for example together with sulfur and vulcanization accelerators. A further subject matter of the present invention is a process for the vulcanization of the rubber mixtures according to the invention, which is preferably carried out at melt temperatures of 100 to 200.degree. C., particularly preferably at 130 to 180.degree. In a preferred embodiment, the vulcanization takes place at a pressure of 10 to 200 bar.

The present invention also includes rubber vulcanizates obtainable by vulcanization of the rubber mixtures according to the invention. Particularly when used in tires, these vulcanizates have the advantages of an excellent property profile and an unexpectedly low rolling resistance.

The rubber vulcanizates according to the invention are suitable for the production of moldings with improved properties, e.g. for the production of cable sheaths, hoses, drive belts, conveyor belts, roller coverings, tires, shoe soles, sealing rings and damping elements, particularly preferably for the production of tires.

Another subject of the present invention is the use of the compounds of the formula (I) for the production of rubber mixtures and their vulcanizates.

examples

The invention is to be explained using the following examples, without, however, restricting them thereto.

Determining the properties of rubber mixtures or vulcanizates:

Rheometer (vulcameter) full vulcanization time 170°C/t95:

The course of vulcanization on the MDR (moving die rheometer) and its analytical data are measured on a Monsanto rheometer MDR 2000 according to ASTM D5289-95. The cure time is determined as the time at which 95% of the rubber is crosslinked. The temperature chosen was 170°C.

Hardness determination:

To determine the hardness of the rubber mixture according to the invention, 6 mm thick rolled skins were produced from the rubber mixture according to the formulations in Table 1. Test specimens with a diameter of 35 mm were cut from the rolled skins and their Shore hardness A was determined using a digital Shore hardness tester (Zwick GmbH & Co. KG, Ulm). The hardness of a rubber vulcanizate gives an initial indication of its rigidity. tensile test:

The tensile test is used directly to determine the load limits of an elastomer and is carried out in accordance with DIN 53504. The linear expansion at break is related to the initial length and corresponds to the elongation at break. Furthermore, the force when certain elongation levels are reached, usually 50, 100, 200 and 300%, is determined and expressed as a stress value (tensile strength at the specified elongation of 300% or module 300).

Dynamic damping:

Dynamic test methods are used to characterize the deformation behavior of elastomers under periodically changing loads. Externally applied stress changes the conformation of the polymer chain. The loss factor tan d is determined indirectly via the ratio between loss modulus G” and storage modulus G'. The loss factor tan d at 60 °C goes hand in hand with the rolling resistance and should be as low as possible. The loss factor tan d at 0 °C is associated with wet grip and should be as high as possible. List of ingredients. Abbreviations and manufacturers

Production of organosilyl polysulfides

Example 1a: Preparation of bis[2,2-di(hydroxymethyl)butoxydimethylsilylpropyl]polysulfide

28.54 g (0.5 mol) of sodium polysulfide in anhydrous methanol were initially taken and heated to boiling under inert conditions. Then 268.86 g (1.0 mol) Di(hydroxymethyl)butoxydimethylsilylpropyl chloride was added and the reaction mixture heated at reflux for 1.5 hours.

After the reaction was complete, the sodium chloride which separated out was filtered off and the methanol solvent was distilled off in vacuo. The distillation residue contained the bis[2,2-di(hydroxymethyl)butoxydimethylsilylpropyl]polysulfide.

Yield: 86% of theory. Theory.

Example 1b: Preparation of bis[2,2-di(hydroxymethyl)butoxydimethylsilylisobutyl]polysulfide

Bis[2,2-di(hydroxymethyl)butoxydimethylsilylisobutyl]polysulfide was prepared analogously to Example 1a, but using 1.0 mol (282.88 g) of di(hydroxymethyl)butoxy- dimethylsilylisobutyl chloride was used.

Yield: 88% of theory. Theory.

Making the output connections

Example 1c: Preparation of di(hydroxymethyl)butoxydimethylsilylpropyl chloride

0.025 g of the ruthenium catalyst Ru3(CO)i2 (100 ppm Ru) and 113.46 g (0.59 mol) of di(hydroxymethyl)butoxydimethylsilane were placed in a reaction vessel. The reaction mixture was refluxed at 76° C. and 28.16 g (0.37 mol) of allyl chloride from Aldrich (CAS: 107-05-1) were added dropwise over a period of 30 minutes. After the reaction mixture had been heated at 80° C. for a further 90 minutes, complete conversion of the allyl chloride could be determined by means of gas chromatographic analysis. After purification by distillation under high vacuum, the target compound was obtained with a yield of 97% of theory. obtain. Example 1d: Preparation of di(hydroxymethyl)butoxydimethylsilylisobutyl chloride

0.025 g of the ruthenium catalyst Ru ₃ (CO)i2 (100 ppm Ru) and 113.48 g (0.59 mol) of di(hydroxymethyl)butoxydimethylsilane were placed in a reaction vessel. The reaction mixture was refluxed at 76° C. and 33.32 g (0.37 mol) of isobutene chloride from Aldrich (CAS: 563-47-3) were added dropwise over a period of 30 minutes. After the reaction mixture had been heated at 80° C. for a further 90 minutes, complete conversion of the allyl chloride could be determined by means of gas chromatographic analysis. After purification by distillation under high vacuum, the target compound was obtained with a yield of 94% d. Th. received.

Example 1e: Preparation of di(hydroxymethyl)butoxydimethylsilane

94.62 g (1.0 mol) of chlorodimethylsilane (CAS No.: 1066-35-9) (from Sigma-Aldrich) were placed in a reaction vessel and heated to 70° C. under reflux. Then 147.59 g (1.1 mol) of anhydrous trimethylolpropane (CAS No.: 77-99-6) (from Lanxess Germany

GmbH) over a period of 4.5 hours. The resulting HCl gas was passed through the cooler into an HCl trap (water+NaOH). The reaction mixture was then stirred at 80° C. under a nitrogen atmosphere for a further hour.

The di (hydroxymethyl) butoxydimethylsilane was so in a yield of 98% d. Th. received. Production of rubber mixtures

example 1

In each case, the rubber mixtures A and B according to the invention and the non-inventive rubber mixture Comparison 1 were produced according to the recipes as given in Table 1. The compound bis(triethoxysilylpropyl)tetrasulfide (TESPT) and the compounds of the formulas (Ia) and (Ib) were each used in equimolar amounts. In order to achieve a comparable crosslinking density, which is required for the module 300, the elongation at break and the strength is essential, however, a somewhat higher amount of sulfur was metered in for the compounds of the formulas (Ia) and (Ib). The mixtures were produced in a kneader at an internal temperature of 150.degree. Sulfur and accelerator were mixed on the roller at 50°C. For vulcanization, the mixtures were heated to 170° C. for 30 minutes in heatable presses.

The properties of the rubber mixtures and vulcanizates of mixtures A, B and comparison 1 were tested using the methods given above.

The test data shows that the rubber mixtures of Examples A and B according to the invention have a significantly lower mixture viscosity and thus lead to a much more advantageous production of the vulcanizates than with the rubber mixture of Comparison 1, which is not according to the invention.

In addition to the improved manufacturability of the vulcanizates, the rubber mixtures according to the invention also show an improvement in dynamic damping at 60° C. (measured as loss factor tan d), which correlates with the rolling resistance of a tire, lower values being advantageous. In addition, it is surprising that one of the major disadvantages of rubber mixtures with the additive TESPT, namely the so-called Marching modulus of the crosslinking curve, does not occur in the rubber mixtures A and B according to the invention. This means a simplification when determining the full vulcanization time without constantly changing the mechanical-dynamic vulcanizate properties. Further advantages in the production (vulcanization) of moldings can result from the shortened full vulcanization time (t95) of the rubber mixtures according to the invention.

Table 1 example 2

In each case, the rubber mixtures C and D according to the invention and the rubber mixture not according to the invention, comparison 1, were produced according to the recipes as given in Table 2. The compound bis(triethoxysilylpropyl)tetrasulfide (TESPT) and the compounds of the formulas (Ia) and (Ib) were each used in equimolar amounts. However, in order to achieve a comparable crosslinking density, which is essential for the modulus 300, the elongation at break and the strength, a somewhat higher amount of sulfur was metered in for the compounds of the formulas (Ia) and (Ib).

Furthermore, in rubber mixtures C and D according to the invention, the secondary accelerator DPG was replaced in each case by VULCUREN®.

The mixtures were produced in a kneader at an internal temperature of 150.degree. Sulfur and accelerator were mixed on the roller at 50°C. For vulcanization, the mixtures were heated to 170° C. for 30 minutes in heatable presses.

The properties of the rubber mixtures and vulcanizates of mixtures C, D and comparison 1 were tested using the methods given above.

The test data shows that when VULCUREN® is used as a DPG substitute in the rubber mixtures C and D according to the invention, after the first mixing stage (5-stage mixing process) a lower mixture viscosity with improved scorch safety (longer scorch time) compared to the rubber mixture not according to the invention of comparison 1 is reached. The full vulcanization time T95 compared to comparison 1 was significantly reduced.

The profile of mechanical properties of the compounds according to the invention with regard to hardness, modulus 300, elongation at break and tensile strength remained largely unaffected when DPG was substituted by VULCUREN®. The rebound resilience at 60°C is significantly increased along with a smaller loss factor tan delta at 60°C. This improvement is an indicator of lower rolling resistance.

Table 2

Conclusion:

Rubber mixtures according to the invention can be produced with the organosilyl polysulfides of the formula (I) according to the invention, which are distinguished by improved mixing properties coupled with higher strength and significantly increased elasticity (at 60° C.) of the vulcanizates produced therefrom. Furthermore, the tires produced from the vulcanizates are distinguished by a low rolling resistance.

Claims

patent claims

1. Compounds of formula (I) in which R ¹ , R ³ , R ⁶ and R ⁸ are identical or different and are CrC ₄ -alkyl,

R ⁴ and R ⁵ are identical or different and represent hydrogen or CrC ₄ -alkyl,

R ² and R ⁷ represent a radical of the formula

CH ₃ CH 2 C(CH ₂ OH) 2 CH 2 -, and x is an integer from 2 to 8.

2. Compounds according to claim 1, characterized in that in formula (I)

R ¹ , R ³ , R ⁶ and R ⁸ are the same or different and are methyl or ethyl, R ⁴ and R ⁵ are the same or different and are hydrogen, methyl or ethyl, R ² and R ⁷ are a radical of the formula

CH ₃ CH 2 C(CH ₂ OH) 2 CH 2 -, and x is an integer from 2 to 8.

3. Compounds according to claim 1 or 2, characterized in that they have the formula or the formula where x is an integer from 2 to 8.

4. Mixtures containing at least two organosilyl polysulfides of the formula (I) according to claim 1, wherein the substituents R ¹ to R ⁸ and x have the meanings given in claim 1 and which differ from one another at least in the value of x, the number average x being the Number x of sulfur atoms is 3.6 to 4.4, preferably 3.8 to 4.2 and in particular 4.0.

5. A process for the preparation of compounds according to any one of claims 1 to 3 or mixtures according to claim 4, characterized in that at least two haloalkylsilyl ethers of the formula (II) wherein

R ⁹ is a radical R ⁴ or R ⁵ ,

R ¹⁰ is a radical R ³ or R ⁶ ,

R ¹¹ is an R ² or R ⁷ radical and R ¹² is an R ¹ or R ⁸ radical, where the R ¹ to R ⁸ radicals are as defined in claim 1 and

shark stands for halogen, with at least one metal polysulfide of formula (III)

S _X M ₂ (IN) where x is as defined in claim 1, and

M is a metal ion selected from lithium, sodium and potassium, in the presence of at least one alcoholic solvent.

6. Haloalkylsilyl ethers of formula (II) wherein

R ⁹ is a radical R ⁴ or R ⁵ ,

R ¹⁰ is a radical R ³ or R ⁶ ,

Hai stands for halogen.

7. A rubber mixture containing at least one rubber, at least one filler and at least one compound of the formula (I) as claimed in any of claims 1 to 3.

8. The rubber mixture according to claim 7, characterized in that it contains a total of 0.1 to 15 parts by weight, preferably 1 to 12 parts by weight, particularly preferably 2 to 10 parts by weight and very particularly preferably 3 to 8 parts by weight. parts of compounds of formula (I) and 10 to 190 parts by weight, preferably 30 to 150 parts by weight and especially preferably 50 to 130 parts by weight of at least one filler, based in each case on 100 parts by weight of the total amount of rubber.

9. The rubber mixture as claimed in claim 7 or 8, characterized in that it contains at least one SBR rubber in the form of styrene/butadiene copolymers with a styrene content of 1 to 60% by weight, preferably 20 to 50% by weight, preferably a functionalized SBR rubber, optionally contains one or more BR rubbers and/or at least one natural rubber (NR).

10. The rubber mixture as claimed in any of claims 7 to 9, characterized in that it contains at least one hydroxyl-containing oxidic filler from the silicic acid series with a specific surface area (BET measured according to DIN 66131) of 5 to 1000, preferably 20 to 400 m ² / g and with primary particle sizes of 100 to 400 nm, the silicas optionally also being present as mixed oxides with other metal oxides, such as Al, Mg, Ca, Ba, Zn, Zr, Ti oxides, and the synthetic silicates, such as aluminum silicate, alkaline earth metal silicates such as magnesium silicate or calcium silicate, with specific surface areas (BET measured according to DIN 66131) from 20 to 400 m ² /g and primary particle diameters from 10 to 400 nm; contains.

11. The rubber mixture as claimed in any of claims 7 to 10, characterized in that it contains at least one carbon black with a specific surface area (BET measured according to DIN 66131) in the range from 20 to 200 m ² /g.

12. The rubber mixture as claimed in any of claims 7 to 11, characterized in that it contains at least one crosslinking agent from the group consisting of sulfur and sulfur donors and metal oxides.

13. Rubber mixture according to one of claims 7 to 12, characterized in that it contains at least one vulcanization accelerator from the series of mercaptobenzothiazoles, mercaptosulfenamides, thiocarbamates, thiocarbonates and dithiophosphates and sulfur donors such as dithiodicaprolactams, dithiodimorpholines and xanthogenates.

14. The rubber mixture as claimed in any of claims 7 to 13, characterized in that it contains at least one secondary accelerator from the group consisting of 1,6-bis(N,N-dibenzylthiocarbamoyldithio)hexane, TBzTD (tetrabenzylthiuram disulfide) and dithiophosphate.

15. The rubber mixture as claimed in any of claims 7 to 14, characterized in that it has a content of diphenylguanidine and/or substituted diphenylguanidines of at most 0.4 parts by weight, preferably from 0.1 to 0.2 parts by weight, in particular preferably from 0.05 to 0.1 part by weight and very particularly preferably from 0.001 to 0.04 part by weight, in each case based on 100 parts by weight of the total amount of rubber.

16. A process for producing a rubber mixture according to any one of claims 7 to 15, characterized in that at least one rubber is mixed with at least one filler and at least one compound of the formula (I) according to any one of claims 1 to 3 and the mixture is heated to a temperature in the range from 60 to 200°C, preferably from 90 to 180°C.

17. A process for producing a rubber mixture according to any one of claims 7 to 15, characterized in that at least one rubber, at least one filler and at least one compound of the formula (I) according to claim 1, in which x is 2, together with sulfur at a temperature in the range from 100 to 200°C, preferably from 130° to 180°C.

18. Process for the production of rubber vulcanizates by vulcanizing a rubber mixture according to one of Claims 7 to 15, preferably at a temperature in the range from 100 to 250°C, particularly preferably from 130 to 180°C.

19. Use of a rubber mixture according to any one of claims 7 to 15 for the production of vulcanizates.

20. Vulcanizates obtainable by vulcanizing a rubber mixture according to any one of claims 7 to 15.

21. Shaped bodies, in particular tires, containing one or more vulcanizates according to claim 20.

22. Use of compounds of the formula (I) as claimed in any of claims 1 to 3 for the production of rubber mixtures as claimed in any of claims 7 to 15, vulcanizates as claimed in claim 20 or moldings as claimed in claim 21.