CA2000631A1 - Process for the production of rubber vulcanizates having reduced hysteresis losses and moldings of these vulcanizates - Google Patents
Process for the production of rubber vulcanizates having reduced hysteresis losses and moldings of these vulcanizatesInfo
- Publication number
- CA2000631A1 CA2000631A1 CA 2000631 CA2000631A CA2000631A1 CA 2000631 A1 CA2000631 A1 CA 2000631A1 CA 2000631 CA2000631 CA 2000631 CA 2000631 A CA2000631 A CA 2000631A CA 2000631 A1 CA2000631 A1 CA 2000631A1
- Authority
- CA
- Canada
- Prior art keywords
- rubber
- weight
- vulcanizates
- carbon black
- iii
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K5/00—Use of organic ingredients
- C08K5/36—Sulfur-, selenium-, or tellurium-containing compounds
- C08K5/37—Thiols
- C08K5/372—Sulfides, e.g. R-(S)x-R'
- C08K5/3725—Sulfides, e.g. R-(S)x-R' containing nitrogen
Abstract
A PROCESS FOR THE PRODUCTION OF RUBBER VULCANIZATES
HAVING REDUCED HYSTERESIS LOSSES AND MOLDINGS OF THESE
VULCANIZATES
A B S T R A C T
Carbon-black-filled rubber vulcanizates having reduced hysteresis losses may be obtained by mixing unvulcanized rubber with carbon black in the presence of certain sul-fides at elevated temperature and vulcanizing the resulting mixture.
Le A 26 398
HAVING REDUCED HYSTERESIS LOSSES AND MOLDINGS OF THESE
VULCANIZATES
A B S T R A C T
Carbon-black-filled rubber vulcanizates having reduced hysteresis losses may be obtained by mixing unvulcanized rubber with carbon black in the presence of certain sul-fides at elevated temperature and vulcanizing the resulting mixture.
Le A 26 398
Description
z!~naPf~
A PR~Ci~ L~HE PRODUCTION OF RUBBER W LCANIZATES
HAVING REDyCED HYSTERESIS LOSSES AND MOLDINGS OF HESE
W LCANIZATES
m is invention relates to a process for the production of carbon-black-filled rubber vulcanizates having reduced hysteresis losses by shearing of carbon-black-filled rubber in the presence of certain disulfides. The invention also relates to moldings of vulcanizates produced by this pro-cess, including for example vehicle tires, conveyor belts, drive belts and compressed-air bellows.
In rubber technology, a hysteresis loss is understood to be the energy loss which is irreversibly converted into heat in the event of dynamic stressing of the elastomer.
The measured quantity for hysteresis losses is the tan ~
which is defined as the ratio of loss modulus to storage modulus, cf. for example DIN 53 513 and DIN 53 535. Any reduction in the tan ~ in the applicationally important temperature/frequency or amplitude range leads, for ex-ample, to reduced heat buildup in elastomers. Tires of rubber having a reduced hysteresis 108s are distinguished by reduced rolling resistance and, hence, by lower fuel consumptlon of the vehicles fitted with them.
US-PS 4,690,965 describes, for example, carbon-black-filled rubber vulcanizates which show reduced heat buildup and, hence, a reduced hysteresis loss by virtuç of their content of nitrosoanilines. However, on account of the danger of carcinogenic nitrosamines being formed trans-nitrosation, there i8 a need for rubber auxiliaries which are ~ree ~rom nitro~o groups.
It has now surprisingly been found that carbon-black-filled rubber vulcanizates having reduced hysteresis losses can be obtained by mixing unvulcanized rubber with carbon black in the presence of di(acylaminoaryl) disulfide free ~rom nitroso groups at elevated temperature and vulcanizing Le A 26 398 the resulting mixture in known manner. The principal advantage of the process according to the invention is that the disulfides used to improve hysteresis do not affect the mechanical properties of the vulcanizates, such as for example their strength, elongation and modulus, to the extent where the vulcanizates no longer satisfy the demands made of the end products (for example tires or drive belts).
The use of di(o-acylaminoaryl) disulfides as masti-cating agents for natural and synthetic rubber is known (US-PS 2,470,948). It is known that rubbers are masticated to reduce viscosity. Accordingly, the auxiliaries accord-ing to US-PS 2,470,948, as normal for masticating agents, are mixed with the rubber before addition of the usual fillers and auxiliaries, particularly before the addition of carbon black (for example on mixing rolls or in an in-ternal mixer at 120C), and the resulting mixture is then sheared until the desired viscosity is reached. The re-duced viscosity established in this way enables fillers and auxiliaries to be incorporated without difficulty; a homo-geneous mixture could otherwise only be obtained with dif-ficulty. The shearing of carbon black/rubber mixtures in the presence of di(o-acylaminoaryl) disulfides is neither disclosed nor suggested in US-PS 2,470,948.
The present invention relates to a process for the production of carbon-black-filled rubber vulcanizates by mixing of unvulcanized rubber, carbon black and, option-ally, other auxiliaries and subsequent vulcanization, com-prising adding (i) to the unvulcanized rubber, (ii~ 10 to 120~ by weight and preferably 30 to 80% by weight, based on rubber (i), carbon black and (iii) 0.1 to 10% by weight and preferably 0 1 to 3~ by weight, based on rubber (i), diphenyl sulfide corresponding to the following formula Le A 26 398 2 z~ p~
1 ~ s ~ R7 (I) 5 R~-CO-NH NH-co-Rlo in which Rl to R8 independently of one another represent hydrogen, fluorine, chlorine, bromine, C~-8 and preferably C~ alkyl, more especially methyl, C~
~ and preferably C~ alkoxy, more especially methoxy, nitro and R~ and Rl independently of one another represent hydrogen, C~, preferably C~2and more preferably Cl_3 alkyl, C2~8, preferably Cz-~2 and more preferably C2~ alkenyl, C5-~2 cycloalkyl and alkenyl, C~-~2 aryl, the above-hydrocarbon radicals for R9 and Rl optionally being ~ubstituted by halogen (~luorine, chlorlne), carboxyl, hydroxy, nltro, amino, di-C~a-alkylamino, mercapto, C~aalkoxy and nltro, at melt temperatures o~ at least 140-C and preferably of at lea~t 150-C and at ~hear rates of 1 to 1000 sec~~ in such a way that at least 10% by weight carbon black ~ , based on rubber (i), are added be~ore there ls any ~ignificant reduction in the molecular weight o~ the rubber.
Rubber~ (i) suitable for the process according to the lnvention include not only natural rubber, but al~o ~yn-theti¢ rubber~ cont~lnlng at lea~t 5~ by weight copoly-merized unit~ emanating ~rom a C~2 dlene. Pre~erred syn-thetic rubbers are de~cribed, ~or example, in W. Ho~fmann, Kaut whuk-Technologie, Genter Verlag, Stuttgart 1980. They include i~çr ~
e A ~6 398 3 Z!~ Pfi:~1 BR - polybutadiene ABR - butadiene/Cl4 alkylacrylate copolymers with acrylate contents of 5 to 60% by weight and pref-erably 15 to 50% by weight, CR - polychloroprene IR - polyisoprene SBR - styrene/butadiene copolymers with stirene con-tents of 1 to 60% by weight and preferably 20 to 50% by weight, NBR - butadiene/acrylonitrile copolymers with acrylo-nitrile contents of 5 to 60% by weight and pref-erably 10 to 50% by weight and mixtures of these rubbers. The rubbers to be used for the process according to the invention have glass tran-sition temperatures below 20C and preferably below OoC, as determined in the torsion pendulum test according to DIN 53 445.
Particularly preferred rubbers (i) are polybutadiene and styrene/butadiene copolymers. SBR solution and emul-sion polymers are preferred for vehicle tires, particularly for treads. SBR solution polymers are particularly prefer-red. The content of 1,2-bonds may vary within wide limits and is generally between 5 and 80%, based on the number of copolymerized butadiene groups.
If desired, other rubbers (i) may be added to and mixed with individual rubbers (i) before vulcanization and before or after the addition of carbon black (ii) and di-sulfide (iii).
Any reinforcing carbon blacks may be used for the process according to the invention. Preferred surfaces are in the range from 35 to 200 m2/g ~CTAB determination). SAF, HAF, FEF, ISAF and SRF carbon blacks are mentioned in par-ticular. Mixtures of two or more different carbon blacks or mixtures of carbon blacks with silicas (with and without filler activators) may readily be used. The degree of Le A 26 398 4 - Zf~ fi:~1 filling may be varied within wide limits, 30 to 80 parts by weight carbon black (ii), including silica if any, to 100 parts rubber (i) being preferred.
Preferred disulfides (iii) include, for example, those in which all the substituents Rl to R~ are hydrogen and in which the acylamino qroups are in the 2,2', 3,3' or 4,4'-position, the substituents R~ and R10 independently of one another, but preferably together, assuming the following meanings:
-H
-CH
-CH2CH3 `13 ~ Cl ~,N02 CH2C 1 ~
-CHC12 ~ H
-CC
Le A 26 398 5 ?~
-CF3 -CH=CH ~
c~3 -CH2CH2C1 ~
~0 -CH2COOH ~ ~OH
- CH2CH2CH ~N~CH3 -(CH2)3-COOH ~ NH2 -(CH2)4-~
-CH~CH2 -C~ CH2 ~0 -CH-CH-C
~OH
Le A 26 398 6 2S~
Preferred sulfides (iii) also include, for example, compounds in which the substituents R~ and Rl are hydrogen and in which the phenylene radicals each bear a chlorine, nitro, methyl, butyl or ethoxy group.
The following are preferred examples of such compounds:
Cl Cl OHC-HN ~ S-S ~ NH-CHO
OHC-HN ~ S -S ~ NH-CHO
OHC-HN NH-CHO
H3C ~ S-S ~ H3 OHC-H ~ 8~ 8 ~ NH-CHO
OC2H5 ~5Cæ
OHC-H ~ 8------6 ~ ~H-CHO
The disulfidss (iii) are known from the literature or may be produced by methods known ~er ~e, cf. for example US-PS 2,470,948; Farm., Ed. Sci. 29 ~1974) 2, 120-128.
A particularly ~uitable method is the acylation of diamlnodiphenyl disul~ides which in turn may largely be produced by three different methods, namely:
a) by hydrolysis of benzthiazoles and oxidation to the disulfide, ç~. Beil~tein, Vol. 13 E III, 907;
b) by nucleophilic substitution of aromatic nitro com-Le A 26 398 7 pounds by sodium hydrogen sulfide with simultaneous reduction of the nitro group to the amino group, followed by oxidation of the mercaptan to the disul-fide; cf. Methoden der Organischen Chemie (Houben-Weyl), Vol. 11/1, Georg-Thieme-Verlag, Stuttgart 1957, page 416 and c) by reduction of nitroaryl sulfochlorides to amino-thiophenols, followed by oxidation to the disulfide, cf. Methoden der Organischen Chemie (Houben-Weyl), Vol. 11/1, Georq-Thieme-Verlag, Stuttgart 1957, page 431.
The disulfides (iii) used will generally be those of which the half life period in the rubber mixture used at the processing temperature (melt temperature) is less than half the processing time, i.e. disulfides (iii) which have a half life period of less than 3 minutes. Particularly preferred disulfides (iii) are those of which the half life period is between one tenth and one third of the processing time.
For the process according to the invention, standard fillers and auxiliaries such as, for example, plasticizers, resin~, factlces and stabilizers may be added to the rubber mixtures to obtain certain crude mixture or vulaanization properties.
The melt temperature of the mixture required for the process according to the invention of preferably 140 to 250C and more preferably 150 to 200C may be obtained by external application of heat or by corresponding friction during the mixing process. The desired melt temperature is generally below the decomposition temperature of the rubber (i) used. In special cases, i.e. where the mixture has an extremely short residence time in the high temperature zone, the decomposition temperature of the rubher (i) may even be exceeded providing no significant decomposition occurs (on account of the short residence time). In most Le A 26 398 8 fi;~
cases, it may be advisable to base the choice of the melt temperature on the half life period of the disulfide (iii) used at that temperature.
Preferred mixing units are the mixing rolls, internal mixers and mixing extruders typically used in the rubber industry which generally operate with shear rates of 1 to 1000 sec.~l and preferably 1 to 200 sec.~1.
The mixing times are governed by the desired degree of dispersion of the carbon black (ii) and the remaining mix-ture constituents in the mixture. They are often between 30 and 1000 seconds and are preferably between 30 and 360 seconds. Where internal mixers are used, excellent results are obtained with mixing times of this order.
In the context of the invention, a "significant reduc-tion" in the molecular weight of the rubber would be a re-duction of more than 10% and preferably more than 5~ in the weight average molecular weight Mw.
The carbon black (ii) is preferably added before a melt temperature of 140C and preferably 150~C is reached.
The disul~ides (iii) may be added to the rubber (i) to-gether with the total quantity of carbon black (ii) or with parts thereof, in which case the remaining quantity of car-bon black is sub~equently added in accordance with the ~ormulation.
The crosslinklng systems known from rubber technology, ~uch ~s sulfur, peroxides, polyisocyanates, metal oxides, phenolic resins and combinations thereof, may be used for vulcanization. The crosslinking system used for vulcaniz-ation will preferably be adapted to the type of rubbers (i) used. Sulfur crosslinking systems are particularly prefer-red.
The crosslinking systems are pre~erably added at temperatures below 130C and preferably at temperatures below lOO'C. Vulcanization may take place at temperatures in the range from 100 to 200~C and preferably at temper-Le A 26 398 9 2n(~fi~1 atures in the range from 130 to 180C, optionally under a pressure of lO to 200 bar.
Articles subjected to severe dynamic stressing, such as vehicle tires, conveyor belts, drive belts, such as V
belts and gear belts, compressed-air bellows, etc., may be produced by the process according to the invention.
Accordingly, the present invention relates to moldings of vulcanizates obtainable by the process according to the invention.
In the following Examples, parts are parts by weight.
EXAMPLES
The following compositions were prepared in accordance with the following mixing sequence in a laboratory com-pounder (of the type manufactured by Haake Mess-Technik GmbH ~ Co., Karlsruhe 41) at various shell temperatures of the mixing compartment and at rotational speeds of the CAM
blades of 30 to 100 r.p.m.:
A~ter [mins.]
I addition of rubber 0.5 addition of half the carbon black to-gether with the disulfide 1.5 addition of the other half of the car-bon black and the remaining aomponents 4-6 ejection The final batch temperature is shown in the Tables.
The vulcanization system was subsequently incorporated in the mixture on laboratory mixing rolls at 40 to 60C.
30Formulation:
137.5 parts Buna SL 750 (a product of Bunawerke Huls GmbH, Marl) containing 100 parts solution SBR and 37.5 parts oil 70 part~ carbon black N 220 (a product of Degussa, Wesseling) Le A 26 398 10 2n~p~
l part stearic acid 3 parts zinc oxide 1 part Vulkanox 4010 NA (a product of BAYER AG, Leverkusen = IPPD = N-isopropyl-N'-phenyl-p-phenylenediamine 1 part disulfide of formula I
1.8 parts sulfur 1.2 parts Vulkacit NZ (a product of BAYER AG, Leverkusen) = TBBS = benzthiazyl-2-tert -butyl sulfenamide Vulcanization took place for 20 minutes at 150~C
EXAMPLES 1-3 and COMPARISON EXAMPLE 1 These Examples demonstrate the effect of the final batch temperature with reference by way of example to 2,2'-diformamidodiphenyl disulfide (Rl-R10 = H). Comparison Example C-l contains no hysteresis promoter ~ tan ~
represents the percentage change in the tan ~ in relation to the di~ulflde-~ree standard.
Le A 26 398 ll 2(~
o c~ v o o OD ~ ~ ~ ~
o ~ ~ o 7 ~ o o o a.
o o ~ u~
o ~ ~ ~ .q ` o o o o ~ ~ ~ u~
o o o ~ ~ ~ ~
/ ~ O O O
:~
u o 0 o o ~ u~ ~ l` ~ `
O 1~ ~D ~` ~ ~ -o ~ ~ . ~ o --~ ~1 ~ ~ N ~1 O O I O I
C~ C.) oD
O O m u7 ~ ~
O 0 ~ O ~1 ~ ~ ~ ~ O
1~ ) O ~ o\
~1 ~1 ~ U~ O O I O I o O
C) U
o U~ O ~ O ~1` ~ 0 0 O N ~ 1 0 r/
~ ~ O
~1 ~1~1~JIr1 N ~1 OO I O 1 ~1 ~ _l ~ a) ~l~
~ - ~ 0 C ~ ~ O L
~ o o C) ~,) o ~ ~
Q~~ ~ O Ot~ C.) o O ~ 0 ~ O O ~
_1 ~ ~ ~ ~ ~ 0 u~ a~ ~ -I ' ~
X ~ ~ ~
~ ~ ~ U~ ~ ~ X ~ ~ ~ ~ C
Le A 26 398 2~ r~l'fi~31 In these Comparison Examples, the effect of the mixing sequence is demonstrated by comparison with Example 3.
Once again, the addition was 2,2'-diformamidodiphenyl di-sulfide.
In Comparison C-2, the disulfide was subsequently added to the mixture together with the vulcanization system. Tensile strength deteriorated considerably as a result.
Buna SL 750 was first mixed with the disulfide to be used in accordance with the invention (as in conventional mastication) for 5 minutes at a shell temperature of 120C
(melt temperature 150C) in comparison C-3 and for 5 minutes at a shell temperature of 170~C (final melt temper-ature 190C) in comparison C-4, the basic mixture was pre-pared in a second mixing step and the vulcanization system subsequently added on mixing rolls. There was no clear reduction in the hysteresis losses.
Le A 26 398 13 ~!~ f ~
C~O
o o oo o ~r oo o NU') 1~11~ O t~
OC~
O O
O ~ OD_I -~U~ O ~ O ~1 C~ ~ I +
~) V
o o U~
U V
o oD ~
O 00 ~ ~D~ ~1 CO
t~O~ O
Ul U _-O
~ ~p, ~ o~ ~ o~
~ OOOOO
Il) ~ O R ~ ~ 0oo ~
~ ~ X ~ ~ o ~ ~ ~ ~ ~ ~O
X ,q-r~ O O
1~ U7 ~ X <I G <I
Le A 26 398 2(~
EXA~E~ =9 These Examples demonstrate the influence of the position of the acylamino group and of the substituents R~
and R10 on the effect of the process according to the inven-tion.
R9-oC-NN:~S S~NH-CO-R10 Le A 26 398 15 Pfi;~
~ C~
,a o o ~ ~ ~ _, o ,, ,, ,i ,1 CO , l l l l l l o o _, ~ ~ a~ ~ o~ ~ I` I~
o X ,~ o ,,_, o , X--~
,a o ~ 1 0 P~
X o ,1 o,~, U~
o O ~ ~ N N NNd' d' ~ ~ t~ ~ ~ d' ~ O=t~
O
Le A 26 398
A PR~Ci~ L~HE PRODUCTION OF RUBBER W LCANIZATES
HAVING REDyCED HYSTERESIS LOSSES AND MOLDINGS OF HESE
W LCANIZATES
m is invention relates to a process for the production of carbon-black-filled rubber vulcanizates having reduced hysteresis losses by shearing of carbon-black-filled rubber in the presence of certain disulfides. The invention also relates to moldings of vulcanizates produced by this pro-cess, including for example vehicle tires, conveyor belts, drive belts and compressed-air bellows.
In rubber technology, a hysteresis loss is understood to be the energy loss which is irreversibly converted into heat in the event of dynamic stressing of the elastomer.
The measured quantity for hysteresis losses is the tan ~
which is defined as the ratio of loss modulus to storage modulus, cf. for example DIN 53 513 and DIN 53 535. Any reduction in the tan ~ in the applicationally important temperature/frequency or amplitude range leads, for ex-ample, to reduced heat buildup in elastomers. Tires of rubber having a reduced hysteresis 108s are distinguished by reduced rolling resistance and, hence, by lower fuel consumptlon of the vehicles fitted with them.
US-PS 4,690,965 describes, for example, carbon-black-filled rubber vulcanizates which show reduced heat buildup and, hence, a reduced hysteresis loss by virtuç of their content of nitrosoanilines. However, on account of the danger of carcinogenic nitrosamines being formed trans-nitrosation, there i8 a need for rubber auxiliaries which are ~ree ~rom nitro~o groups.
It has now surprisingly been found that carbon-black-filled rubber vulcanizates having reduced hysteresis losses can be obtained by mixing unvulcanized rubber with carbon black in the presence of di(acylaminoaryl) disulfide free ~rom nitroso groups at elevated temperature and vulcanizing Le A 26 398 the resulting mixture in known manner. The principal advantage of the process according to the invention is that the disulfides used to improve hysteresis do not affect the mechanical properties of the vulcanizates, such as for example their strength, elongation and modulus, to the extent where the vulcanizates no longer satisfy the demands made of the end products (for example tires or drive belts).
The use of di(o-acylaminoaryl) disulfides as masti-cating agents for natural and synthetic rubber is known (US-PS 2,470,948). It is known that rubbers are masticated to reduce viscosity. Accordingly, the auxiliaries accord-ing to US-PS 2,470,948, as normal for masticating agents, are mixed with the rubber before addition of the usual fillers and auxiliaries, particularly before the addition of carbon black (for example on mixing rolls or in an in-ternal mixer at 120C), and the resulting mixture is then sheared until the desired viscosity is reached. The re-duced viscosity established in this way enables fillers and auxiliaries to be incorporated without difficulty; a homo-geneous mixture could otherwise only be obtained with dif-ficulty. The shearing of carbon black/rubber mixtures in the presence of di(o-acylaminoaryl) disulfides is neither disclosed nor suggested in US-PS 2,470,948.
The present invention relates to a process for the production of carbon-black-filled rubber vulcanizates by mixing of unvulcanized rubber, carbon black and, option-ally, other auxiliaries and subsequent vulcanization, com-prising adding (i) to the unvulcanized rubber, (ii~ 10 to 120~ by weight and preferably 30 to 80% by weight, based on rubber (i), carbon black and (iii) 0.1 to 10% by weight and preferably 0 1 to 3~ by weight, based on rubber (i), diphenyl sulfide corresponding to the following formula Le A 26 398 2 z~ p~
1 ~ s ~ R7 (I) 5 R~-CO-NH NH-co-Rlo in which Rl to R8 independently of one another represent hydrogen, fluorine, chlorine, bromine, C~-8 and preferably C~ alkyl, more especially methyl, C~
~ and preferably C~ alkoxy, more especially methoxy, nitro and R~ and Rl independently of one another represent hydrogen, C~, preferably C~2and more preferably Cl_3 alkyl, C2~8, preferably Cz-~2 and more preferably C2~ alkenyl, C5-~2 cycloalkyl and alkenyl, C~-~2 aryl, the above-hydrocarbon radicals for R9 and Rl optionally being ~ubstituted by halogen (~luorine, chlorlne), carboxyl, hydroxy, nltro, amino, di-C~a-alkylamino, mercapto, C~aalkoxy and nltro, at melt temperatures o~ at least 140-C and preferably of at lea~t 150-C and at ~hear rates of 1 to 1000 sec~~ in such a way that at least 10% by weight carbon black ~ , based on rubber (i), are added be~ore there ls any ~ignificant reduction in the molecular weight o~ the rubber.
Rubber~ (i) suitable for the process according to the lnvention include not only natural rubber, but al~o ~yn-theti¢ rubber~ cont~lnlng at lea~t 5~ by weight copoly-merized unit~ emanating ~rom a C~2 dlene. Pre~erred syn-thetic rubbers are de~cribed, ~or example, in W. Ho~fmann, Kaut whuk-Technologie, Genter Verlag, Stuttgart 1980. They include i~çr ~
e A ~6 398 3 Z!~ Pfi:~1 BR - polybutadiene ABR - butadiene/Cl4 alkylacrylate copolymers with acrylate contents of 5 to 60% by weight and pref-erably 15 to 50% by weight, CR - polychloroprene IR - polyisoprene SBR - styrene/butadiene copolymers with stirene con-tents of 1 to 60% by weight and preferably 20 to 50% by weight, NBR - butadiene/acrylonitrile copolymers with acrylo-nitrile contents of 5 to 60% by weight and pref-erably 10 to 50% by weight and mixtures of these rubbers. The rubbers to be used for the process according to the invention have glass tran-sition temperatures below 20C and preferably below OoC, as determined in the torsion pendulum test according to DIN 53 445.
Particularly preferred rubbers (i) are polybutadiene and styrene/butadiene copolymers. SBR solution and emul-sion polymers are preferred for vehicle tires, particularly for treads. SBR solution polymers are particularly prefer-red. The content of 1,2-bonds may vary within wide limits and is generally between 5 and 80%, based on the number of copolymerized butadiene groups.
If desired, other rubbers (i) may be added to and mixed with individual rubbers (i) before vulcanization and before or after the addition of carbon black (ii) and di-sulfide (iii).
Any reinforcing carbon blacks may be used for the process according to the invention. Preferred surfaces are in the range from 35 to 200 m2/g ~CTAB determination). SAF, HAF, FEF, ISAF and SRF carbon blacks are mentioned in par-ticular. Mixtures of two or more different carbon blacks or mixtures of carbon blacks with silicas (with and without filler activators) may readily be used. The degree of Le A 26 398 4 - Zf~ fi:~1 filling may be varied within wide limits, 30 to 80 parts by weight carbon black (ii), including silica if any, to 100 parts rubber (i) being preferred.
Preferred disulfides (iii) include, for example, those in which all the substituents Rl to R~ are hydrogen and in which the acylamino qroups are in the 2,2', 3,3' or 4,4'-position, the substituents R~ and R10 independently of one another, but preferably together, assuming the following meanings:
-H
-CH
-CH2CH3 `13 ~ Cl ~,N02 CH2C 1 ~
-CHC12 ~ H
-CC
Le A 26 398 5 ?~
-CF3 -CH=CH ~
c~3 -CH2CH2C1 ~
~0 -CH2COOH ~ ~OH
- CH2CH2CH ~N~CH3 -(CH2)3-COOH ~ NH2 -(CH2)4-~
-CH~CH2 -C~ CH2 ~0 -CH-CH-C
~OH
Le A 26 398 6 2S~
Preferred sulfides (iii) also include, for example, compounds in which the substituents R~ and Rl are hydrogen and in which the phenylene radicals each bear a chlorine, nitro, methyl, butyl or ethoxy group.
The following are preferred examples of such compounds:
Cl Cl OHC-HN ~ S-S ~ NH-CHO
OHC-HN ~ S -S ~ NH-CHO
OHC-HN NH-CHO
H3C ~ S-S ~ H3 OHC-H ~ 8~ 8 ~ NH-CHO
OC2H5 ~5Cæ
OHC-H ~ 8------6 ~ ~H-CHO
The disulfidss (iii) are known from the literature or may be produced by methods known ~er ~e, cf. for example US-PS 2,470,948; Farm., Ed. Sci. 29 ~1974) 2, 120-128.
A particularly ~uitable method is the acylation of diamlnodiphenyl disul~ides which in turn may largely be produced by three different methods, namely:
a) by hydrolysis of benzthiazoles and oxidation to the disulfide, ç~. Beil~tein, Vol. 13 E III, 907;
b) by nucleophilic substitution of aromatic nitro com-Le A 26 398 7 pounds by sodium hydrogen sulfide with simultaneous reduction of the nitro group to the amino group, followed by oxidation of the mercaptan to the disul-fide; cf. Methoden der Organischen Chemie (Houben-Weyl), Vol. 11/1, Georg-Thieme-Verlag, Stuttgart 1957, page 416 and c) by reduction of nitroaryl sulfochlorides to amino-thiophenols, followed by oxidation to the disulfide, cf. Methoden der Organischen Chemie (Houben-Weyl), Vol. 11/1, Georq-Thieme-Verlag, Stuttgart 1957, page 431.
The disulfides (iii) used will generally be those of which the half life period in the rubber mixture used at the processing temperature (melt temperature) is less than half the processing time, i.e. disulfides (iii) which have a half life period of less than 3 minutes. Particularly preferred disulfides (iii) are those of which the half life period is between one tenth and one third of the processing time.
For the process according to the invention, standard fillers and auxiliaries such as, for example, plasticizers, resin~, factlces and stabilizers may be added to the rubber mixtures to obtain certain crude mixture or vulaanization properties.
The melt temperature of the mixture required for the process according to the invention of preferably 140 to 250C and more preferably 150 to 200C may be obtained by external application of heat or by corresponding friction during the mixing process. The desired melt temperature is generally below the decomposition temperature of the rubber (i) used. In special cases, i.e. where the mixture has an extremely short residence time in the high temperature zone, the decomposition temperature of the rubher (i) may even be exceeded providing no significant decomposition occurs (on account of the short residence time). In most Le A 26 398 8 fi;~
cases, it may be advisable to base the choice of the melt temperature on the half life period of the disulfide (iii) used at that temperature.
Preferred mixing units are the mixing rolls, internal mixers and mixing extruders typically used in the rubber industry which generally operate with shear rates of 1 to 1000 sec.~l and preferably 1 to 200 sec.~1.
The mixing times are governed by the desired degree of dispersion of the carbon black (ii) and the remaining mix-ture constituents in the mixture. They are often between 30 and 1000 seconds and are preferably between 30 and 360 seconds. Where internal mixers are used, excellent results are obtained with mixing times of this order.
In the context of the invention, a "significant reduc-tion" in the molecular weight of the rubber would be a re-duction of more than 10% and preferably more than 5~ in the weight average molecular weight Mw.
The carbon black (ii) is preferably added before a melt temperature of 140C and preferably 150~C is reached.
The disul~ides (iii) may be added to the rubber (i) to-gether with the total quantity of carbon black (ii) or with parts thereof, in which case the remaining quantity of car-bon black is sub~equently added in accordance with the ~ormulation.
The crosslinklng systems known from rubber technology, ~uch ~s sulfur, peroxides, polyisocyanates, metal oxides, phenolic resins and combinations thereof, may be used for vulcanization. The crosslinking system used for vulcaniz-ation will preferably be adapted to the type of rubbers (i) used. Sulfur crosslinking systems are particularly prefer-red.
The crosslinking systems are pre~erably added at temperatures below 130C and preferably at temperatures below lOO'C. Vulcanization may take place at temperatures in the range from 100 to 200~C and preferably at temper-Le A 26 398 9 2n(~fi~1 atures in the range from 130 to 180C, optionally under a pressure of lO to 200 bar.
Articles subjected to severe dynamic stressing, such as vehicle tires, conveyor belts, drive belts, such as V
belts and gear belts, compressed-air bellows, etc., may be produced by the process according to the invention.
Accordingly, the present invention relates to moldings of vulcanizates obtainable by the process according to the invention.
In the following Examples, parts are parts by weight.
EXAMPLES
The following compositions were prepared in accordance with the following mixing sequence in a laboratory com-pounder (of the type manufactured by Haake Mess-Technik GmbH ~ Co., Karlsruhe 41) at various shell temperatures of the mixing compartment and at rotational speeds of the CAM
blades of 30 to 100 r.p.m.:
A~ter [mins.]
I addition of rubber 0.5 addition of half the carbon black to-gether with the disulfide 1.5 addition of the other half of the car-bon black and the remaining aomponents 4-6 ejection The final batch temperature is shown in the Tables.
The vulcanization system was subsequently incorporated in the mixture on laboratory mixing rolls at 40 to 60C.
30Formulation:
137.5 parts Buna SL 750 (a product of Bunawerke Huls GmbH, Marl) containing 100 parts solution SBR and 37.5 parts oil 70 part~ carbon black N 220 (a product of Degussa, Wesseling) Le A 26 398 10 2n~p~
l part stearic acid 3 parts zinc oxide 1 part Vulkanox 4010 NA (a product of BAYER AG, Leverkusen = IPPD = N-isopropyl-N'-phenyl-p-phenylenediamine 1 part disulfide of formula I
1.8 parts sulfur 1.2 parts Vulkacit NZ (a product of BAYER AG, Leverkusen) = TBBS = benzthiazyl-2-tert -butyl sulfenamide Vulcanization took place for 20 minutes at 150~C
EXAMPLES 1-3 and COMPARISON EXAMPLE 1 These Examples demonstrate the effect of the final batch temperature with reference by way of example to 2,2'-diformamidodiphenyl disulfide (Rl-R10 = H). Comparison Example C-l contains no hysteresis promoter ~ tan ~
represents the percentage change in the tan ~ in relation to the di~ulflde-~ree standard.
Le A 26 398 ll 2(~
o c~ v o o OD ~ ~ ~ ~
o ~ ~ o 7 ~ o o o a.
o o ~ u~
o ~ ~ ~ .q ` o o o o ~ ~ ~ u~
o o o ~ ~ ~ ~
/ ~ O O O
:~
u o 0 o o ~ u~ ~ l` ~ `
O 1~ ~D ~` ~ ~ -o ~ ~ . ~ o --~ ~1 ~ ~ N ~1 O O I O I
C~ C.) oD
O O m u7 ~ ~
O 0 ~ O ~1 ~ ~ ~ ~ O
1~ ) O ~ o\
~1 ~1 ~ U~ O O I O I o O
C) U
o U~ O ~ O ~1` ~ 0 0 O N ~ 1 0 r/
~ ~ O
~1 ~1~1~JIr1 N ~1 OO I O 1 ~1 ~ _l ~ a) ~l~
~ - ~ 0 C ~ ~ O L
~ o o C) ~,) o ~ ~
Q~~ ~ O Ot~ C.) o O ~ 0 ~ O O ~
_1 ~ ~ ~ ~ ~ 0 u~ a~ ~ -I ' ~
X ~ ~ ~
~ ~ ~ U~ ~ ~ X ~ ~ ~ ~ C
Le A 26 398 2~ r~l'fi~31 In these Comparison Examples, the effect of the mixing sequence is demonstrated by comparison with Example 3.
Once again, the addition was 2,2'-diformamidodiphenyl di-sulfide.
In Comparison C-2, the disulfide was subsequently added to the mixture together with the vulcanization system. Tensile strength deteriorated considerably as a result.
Buna SL 750 was first mixed with the disulfide to be used in accordance with the invention (as in conventional mastication) for 5 minutes at a shell temperature of 120C
(melt temperature 150C) in comparison C-3 and for 5 minutes at a shell temperature of 170~C (final melt temper-ature 190C) in comparison C-4, the basic mixture was pre-pared in a second mixing step and the vulcanization system subsequently added on mixing rolls. There was no clear reduction in the hysteresis losses.
Le A 26 398 13 ~!~ f ~
C~O
o o oo o ~r oo o NU') 1~11~ O t~
OC~
O O
O ~ OD_I -~U~ O ~ O ~1 C~ ~ I +
~) V
o o U~
U V
o oD ~
O 00 ~ ~D~ ~1 CO
t~O~ O
Ul U _-O
~ ~p, ~ o~ ~ o~
~ OOOOO
Il) ~ O R ~ ~ 0oo ~
~ ~ X ~ ~ o ~ ~ ~ ~ ~ ~O
X ,q-r~ O O
1~ U7 ~ X <I G <I
Le A 26 398 2(~
EXA~E~ =9 These Examples demonstrate the influence of the position of the acylamino group and of the substituents R~
and R10 on the effect of the process according to the inven-tion.
R9-oC-NN:~S S~NH-CO-R10 Le A 26 398 15 Pfi;~
~ C~
,a o o ~ ~ ~ _, o ,, ,, ,i ,1 CO , l l l l l l o o _, ~ ~ a~ ~ o~ ~ I` I~
o X ,~ o ,,_, o , X--~
,a o ~ 1 0 P~
X o ,1 o,~, U~
o O ~ ~ N N NNd' d' ~ ~ t~ ~ ~ d' ~ O=t~
O
Le A 26 398
Claims (9)
1. A process for the production of carbon-black-filled rubber vulcanizates by mixing of unvulcanized rubber, carbon black and, optionally, other auxiliaries and subsequent vulcanization, comprising adding (i) to the unvulcanized rubber, (ii) 10 to 120% by weight, based on rubber (i), carbon black and (iii) 0.1 to 10% by weight, based on rubber (i), diphenyl sulfide corresponding to the following formula (I) in which R1 to R6 independently of one another represent hydrogen, fluorine, chlorine, bromine, C1-8 alkyl, C1-8 alkoxy, nitro and R9 and R10 independently of one another represent hydro-gen, C1-18 alkyl, C2-18 alkenyl, C5-12 cycloalkyl and alkenyl, C5-12 aryl, at melt temperatures of at least 140°C and at shear rates of 1 to 1000 sec-1 in such a way that at least 10% by weight carbon black (ii), based on rubber (i), are added before there is any significant reduction in the molecular weight of the rubber.
2. A process as claimed in claim 1, in which 30 to 80% by weight carbon black, based on rubber (i), is used.
3. A process as claimed in claims l and 2, in which 0.1 to 3% by weight diphenyl sulfide (iii), based on rubber (i) is used.
4. A process as claimed in claims 1 to 3, in which the Le A 26 398 17 substituents R1 to R8 are selected from the group consist-ing of hydrogen, chlorine and nitro in such a way that at least six of these substitutents are hydrogen and the sub-stitution at both phenylene rings is symmetrical.
5. A process as claimed in claims 1 to 4, in which the substituents R9 and R10 are hydrogen, methyl or ethyl.
6. A process as claimed in claims 1 to 5, in which the acylamino groups of the disulfide (iii) are in the o-position to the sulfur.
7. A process as claimed in claims 1 to 6, in which the melt temperature during mixing is 150 to 200°C.
8. A process as claimed in claims 1 to 7, in which vul-canization is carried out at temperatures of 100 to 200°C.
9. Moldings of vulcanizates obtainable by the process claimed in claims 1 to 8.
Le A 26 398 18
Le A 26 398 18
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19883835198 DE3835198A1 (en) | 1988-10-15 | 1988-10-15 | METHOD FOR PRODUCING RUBBER VULCANISES WITH REDUCED HYSTERESIS LOSSES AND FORM BODIES FROM SUCH VULCANISTS |
| DEP3835198.6 | 1988-10-15 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2000631A1 true CA2000631A1 (en) | 1990-04-15 |
Family
ID=6365216
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2000631 Abandoned CA2000631A1 (en) | 1988-10-15 | 1989-10-13 | Process for the production of rubber vulcanizates having reduced hysteresis losses and moldings of these vulcanizates |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0366952A1 (en) |
| JP (1) | JPH02155937A (en) |
| CA (1) | CA2000631A1 (en) |
| DE (1) | DE3835198A1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6426365B1 (en) | 1997-02-12 | 2002-07-30 | Japan Tobacco Inc. | CETP activity inhibitors |
| US7276536B2 (en) | 2003-03-17 | 2007-10-02 | Japan Tobacco Inc. | Method for increasing the bioavailability of the active form of S-[2-([[1-(2-ethylbutyl)cyclohexyl]carbonyl]amino) phenyl] 2-methylpropanethioate |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2470948A (en) * | 1945-01-26 | 1949-05-24 | Us Rubber Co | Di (orthoacylaminoaryl) disulfide softeners for rubbers |
| GB1508134A (en) * | 1975-07-28 | 1978-04-19 | Rubber & Plastic Res Ass | Peptised natural or synthetic rubber |
-
1988
- 1988-10-15 DE DE19883835198 patent/DE3835198A1/en not_active Withdrawn
-
1989
- 1989-10-03 EP EP89118298A patent/EP0366952A1/en not_active Withdrawn
- 1989-10-12 JP JP26410789A patent/JPH02155937A/en active Pending
- 1989-10-13 CA CA 2000631 patent/CA2000631A1/en not_active Abandoned
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6426365B1 (en) | 1997-02-12 | 2002-07-30 | Japan Tobacco Inc. | CETP activity inhibitors |
| US6753346B2 (en) | 1997-02-12 | 2004-06-22 | Japan Tobacco Inc. | CETP activity inhibitor |
| US7271196B2 (en) | 1997-02-12 | 2007-09-18 | Japan Tabacco Inc. | CETP activity inhibitors |
| US7579379B2 (en) | 1997-02-12 | 2009-08-25 | Japan Tobacco Inc. | CETP activity inhibitors |
| US9000045B2 (en) | 1997-02-12 | 2015-04-07 | Japan Tobacco Inc. | CETP activity inhibitors |
| US7276536B2 (en) | 2003-03-17 | 2007-10-02 | Japan Tobacco Inc. | Method for increasing the bioavailability of the active form of S-[2-([[1-(2-ethylbutyl)cyclohexyl]carbonyl]amino) phenyl] 2-methylpropanethioate |
Also Published As
| Publication number | Publication date |
|---|---|
| EP0366952A1 (en) | 1990-05-09 |
| DE3835198A1 (en) | 1990-04-19 |
| JPH02155937A (en) | 1990-06-15 |
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