DE1053775B - Process for vulcanizing rubber - Google Patents

Description

When processing mixtures of natural and / or synthetic rubber, which already Vulcanizing agents, accelerators and carbon blacks or other fillers are included before the actual Vulcanization always has a more or less strong tendency to vulcanize.

With the recent increase in the use of high-quality reinforcing fillers, in particular modern furnace blacks, acetylene blacks or highly dispersed fillers based on silica, silicates or oxides or carbonates of magnesium, aluminum or calcium, which show an increased heat development during processing of the rubber compounds and at the same time, due to their partially basic character, they can pose a risk of easier scorching, the problem of finding new types of accelerator with superior delay in use has become urgent. In addition, operational Konfektionierungen carried in part at temperatures of about 13O ⁰ C. These temperatures are a little below the actual vulcanization temperatures.

Even when using semi-active fillers, there is interest in accelerator types with extreme delay in use, which can be used in higher doses without an obstructive tendency to scorch, for optimal elastic properties, lower damping and heat generation or higher fatigue strength in the vulcanizates or to achieve better static aging.

Improvements in the aging properties (fatigue protection and ozone protection) continue to be used of high-quality anti-aging agents, e.g. from the range of p-phenylenediamine derivatives. These cause such a strong activation of the vulcanization that neither with the usual retarders by using the previously known accelerators with delayed use (e.g. from the benzothiazole sulfenamide group) a smooth production, e.g. in tire compounds, can be carried out.

So far, accelerators have been out of line, especially in the production of high-quality running surfaces of the mercaptobenzothiazole derivatives are preferred because vulcanizates produced with them have good aging properties distinguish. These accelerators include, in particular, the sulfenamides of 2-mercaptobenzothiazole and above all sulfenamides of secondary amines or primary amines, especially of cyclohexylamine. These are among the 'most widely used accelerators in tire manufacturing. Because this accelerator but for many purposes their delay was no longer sufficient in recent times benzothiazole-2-sulfen-morpholide and benzothiazyl-2-tert.-butylsulfenamide as accelerators with improved processing reliability used. Compared to the process for vulcanizing rubber

Applicant:

Paint factories Bayer Aktiengesellschaft, Leverkusen-Bayerwerk

Dr. Helmut Freytag, Cologne-Stammheim,

Dr. Friedrich Lober and Dr. Hans Pohle, Leverkusen,

have been named as inventors

The above-mentioned sulfenamides show this already considerable Advantages in terms of vulcanization.

It was now in the benzothiazole-2-dicycloalkyl-sulfenamides with 5 to 7 carbon atoms in the cycloalkyl rings, a number of new sulfenamide accelerators not previously described found which compared to previously known compounds of this series surprising application technology Have merits. These compounds correspond to the following general formula:

c - s - n:

in which R ₁ and R _{2 can be} identical or different cycloalkyl radicals with 5 to 7 carbon atoms. Examples include the cyclopentyl, cyclohexyl and cycloheptyl radical or their substitution products with alkyl or cycloalkyl radicals having 1 to 6 carbon atoms or with alkoxy radicals whose alkyl groups have 1 to 4 carbon atoms, furthermore hydrogenated fused ring systems, such as a- or / 3-tetrahydronaphthyl or a- or / S-decalyl radicals. These new sulfenamides stand out from the known derivatives of this series both in mixtures with semi-active fillers and in mixtures with reinforcing fillers and optionally additionally with strongly activating anti-fatigue and anti-ozone agents

809 787/577

from the series of p-phenylenediamine by one with regard to the time span and the working temperature significantly superior processing reliability, such as for example is required when spraying tread compounds. Even preferred over today Benzothiazyl-2-morpholyl-sulfenamide used is this superiority is still considerable. The benzothiazole - 2 - dicycloalkyl - sulfenamides according to the invention permit furthermore a greater dosage latitude without the processing safety being impaired.

The processing of the still plastic mixtures and the vulcanization are within easy reach a relatively narrow temperature interval is possible, d. That is, the processing can be done with certainty at high Temperature can only be carried out a few degrees below the vulcanization temperature. The course of the Vulcanization then differs in no way from the previously known sulfenamide, so that at least the same, in some cases even superior properties of the vulcanizates can be achieved. The next stand out new vulcanization accelerator is characterized by a particularly pronounced plateau. You can either alone or can be used in combination with one another and finally also combined with known vulcanization accelerators to form combinations will.

The aging and fatigue properties and in certain cases the abrasion are noticeably improved. the Vulcanization accelerators according to the invention can be used as the sole accelerator in that for the known sulfenamides customary dosage are used, d. H. e.g. with vulcanized treads made of natural rubber with 0.3 to 1.5% in tread vulcanizates based on

ίο synthetic rubbers with 0.6 to 4 ° / ₀ . In the latter dosage range, soft rubber made from natural rubber can also be vulcanized. These dosages can also be exceeded in order to improve the dynamic or static aging properties of the vulcanizates in a known manner.

The sulfenamides according to the invention can be prepared in a known manner from mercaptobenzothiazole and the corresponding Dicycloalkylamines are obtained. They make partly crystallized, partly viscous liquid products with a faint characteristic odor. They are mainly found in gasoline, aromatic hydrocarbons, chlorinated hydrocarbons are readily soluble and therefore show good and rapid distribution in rubber.

Benzothiazyl-2-di-cycloalkyl-sulfenamide: / ^/ \ / - _:

c — s — n:

N / A R,

- N '

Calculated
N ° / o

Found N ° / "

Dicyclopentylamine

Dicyclohexylamine

Dicycloheptylamine

Cyclopentyl-cyclohexylamine ...

2-methyl-dicyclohexylamine

S-methyl-dicyclohexylamine

4-methyl-dicyclohexylamine

2,2'-dimethyl-dicyclohexylamine.
S.S'-dimethyl-dicyclohexylamine.
2,3'-dimethyl-dicyclohexylamine.
2,6-diethyl-dicyclohexylamine ..
4-tert-butyl-dicyciohexylamine.
4-ethoxy-dicyclohexylamine
4-cyclohexyl-dicyclohexylamine.
Cyclohexyl-jS-decalylamine

up to 77 ° C

up to 105 ⁰ C

fluid

fluid

fluid

fluid

fluid

fluid

fluid

fluid

fluid

fluid

fluid

up to 148 ° C

fluid

8.80
8.09
7.48
8.43
7.77
7.77
7.77
7.48
7.48
7.48
6.96
6.96
7.17
6.54
7.00

8.42 7.83 6.98 8.25 7.15 7.40 7.62 6.90 7.25 6.96 6.52 6.86 6.73 6.35 7.34

The following examples illustrate the application properties of these new sulfenamide accelerators partly also shown against known accelerators from this series and the individual Connections are designated as follows:

example 1

A Benzothiazyl-2-cyclohexyl-sulfenamide (for comparison)

B Benzothiazyl-2-morpholyl-sulfenamide (for comparison)

C benzothiazyl-2-dicyclohexyl-sulfenamide D Benzothiazyl-2-cyclohexyl-cyclopentyl-sulienamide E Benzothiazyl-2-dicyclopentyl-sulfenamide F Benzothiazyl-2- (4-cyclohexyl-cyclohexyl) -cyclohexyl-sulfenamide

60 Benzothiazyl-2- (3-methylcyclohexyl) -cyclohexylsulfenamide

Benzothiazyl-2- (4-methylcyclohexyl) -cyclohexylsulfenamide

Benzothiazyl-2- (4-tert-butylcyclohexyl) -cyclo-

hexyl sulfenamide
A base mixture containing, per 100 parts of smoked sheets, 24 parts of furnace black with average abrasion resistance, 10 parts of zinc oxide, 3 parts of sulfur and 0.5 part of stearic acid, is mixed in 10 parts with the above accelerators (based on 100 parts of rubber content). With a vulcanization of 25 and 40 minutes at 110 ° C and with a vulcanization of 30 and 45 minutes or 45 and 60 minutes at 135 ° C, the module values and breaking strengths (kg / cm ² ) listed in the table below were measured:

Additive % 5 > n at 120 ^° C
Module 300% strength t 6th C.
strength 0.6 Scorchite 6th
43 30th
240 30 '
45 ' 265
255 A. 0.6 25 '
40 ' 5
26th 25th
195 30 '
45 ' Vulcanization at 135 ° ^C
j module 300% I 260
245 B. 0.75 25 '
40 ' 5
32 25th
215 30 '
45 ' 260
255 B. 0.75 25 '
40 ' 6th
6th co to
cn Cn 45 '
60 ' 250
250 C. 0.75 25 '
40 ' 6th
13th 25th
95 45 '
65 ' 250
245 D. 0.75 25 '
40 ' 6th
12th Oo to
cn Cn 45 '
65 ' 250
250 E. 0.75 25 '
40 ' 6th
6th CO CO
Cn O 45 '
65 ' 240
235 F. 0.75 25 '
40 ' 6th
13th 30th
95 45 '
65 ' 255
250 G 0.75 25 '
40 ' 5
6th 20th
35 45 '
65 ' 235
225 H 0.75 25 '
40 ' OO Cn 20th
50 45 '
65 ' 245
235 I. 25 '
40 ' 59
58 50
51 59
57 49
50 46
48 60
59 46
47 49
49 46
46 39
41

While the known sulfenamides, for example, after exposure ^{to the press for 40 minutes at 120 °} C., already provide strength ^{values of 200 kg / cm 2} , and are therefore practically vulcanized, the sulfenamides of the dicycloalkylamine type are still almost unchanged, ie strength values as they are are to be expected with a non-vulcanized, highly filled carbon black mixture under the same treatment. This is particularly evident in the case of the compounds C, F, H and I, while another group, especially the compounds D, E, G, on the basis of the modulus and strength values, corresponds to the values of benzothiazyl-2-morpholine previously known to be optimal. sulfenamids are still about 50% superior.

Example 2

A basic mixture, soft on 100.0 parts smoked sheets 42.0 parts furnace black for maximum abrasion resistance, 3.0 parts zinc oxide, 2.0 parts softening) !, 2.0 parts pine tar, 2.5 parts stearic acid, 2.5 parts sulfur, 1.0 part of a mixture of N-cyclohexyl-N'-phenyl-pphenylenediamine and phenyl- / 9-naphthylamine and 0.8 parts of ozokerite is used in 5 parts with those in the example 1 mentioned accelerators A, B and C (based on 100 parts rubber content) mixed.

When processed uniformly, the raw mixtures provide the following plasticity values (defo hardness) on the defo device (Baader, Kautschuk, volume 14 [1938], p. 233 ff.), Depending on 30 minutes at HO ⁰ C or 10 minutes at 133 ° C.

time to
temperature

A 0.4 /,

B 0.4% B
0.5 · / ,,

0.5%

C.
0.6%

30 ': 110 ^° C
10 ': 133 ° C

1900 2 900

1800 2 300 Defo hardening:
1900
2,600

1800
1700

1800
1700

The known sulfenamides A and B show after tempering at 133 ° C a clearly increasing viscosity increase due to vulcanization, while the Product C has a constant, previously unknown stability (i.e. no signs of scorching) can be recognized even with increased dosage of the accelerator. The comparative measurements also show in the Mooney device (cf. M. Melvin Mooney, Industrial and Engineering Chemistry Analyt. Ed. 6 [1934], p. 147ff.) the strongly delayed increase in viscosity of the benzothiazole-2-dicycloalkyl-sulfenamides used according to the invention compared to the well-known sulfenamides.

The results are shown by the figure, in which the ordinate shows the Mooney values and in which the The abscissa is the time (in minutes). The measuring temperature is 121 ° C. The individual curves represent the values obtained using the following accelerators. The addition is in Percentage by weight, based on the rubber content of the base mixture.

Curve 1 = 0.40% of accelerator A.
Curve 2 = 0.40% of the accelerator B
Curve 3 = 0.60% of the accelerator C.
Curve 4 - 0.50% ■ of the accelerator C

In the vulcanization at 135 ° C at least the same module and strength values as achieved with the known sulfenamides:

temperature 7th A. 1 053 775 96 to 285 8th C.
0.6 ° / 300 C. 100 to 285 C.
0.5% 290 time to 135 ° C to 285 B.
0.4% B.
0.5% 98 to 275 kg / cm ² ) 104 to 280 135 ° C 89 up to 280 Module 300% - strength 91 to 295 107 to 45 ' 135 ° C 94 to 270 86 to 275 104 to 295 105 to 65 ' 91 92 to 280 101 to 280 100 ' 90 to 265

In the oxygen aging by Bierer-Davis at 6O ⁰ C clearly superior compared to the known Sulfenatniden is detected.

Time to temperature A.
0.4% B.
0.4% 155 B.
0.5% C.
0.5% 165 C.
0.6 »/" 130 155 after 12 days of oxygen aging: 150 130 65 ': 135 ° C 160 Strengths (kg / cm ² 155 180 100 ': 135 ° C 155 145 145 170 145 Days of oxygen aging: 65 ': 135 ⁰ C 135 100 ': 135 ° C (in mm ³ ) after 12 130 Abrasion loss according to DIN 53516 - 145 - 140

The test bottles were produced by vulcanizing the rubber mixture specified at the beginning for 65 minutes at 135 ° C. The profiled test bottles were then subjected to 3 million bends. The cracking that took place is shown in the table below. The crack formation is thereby through rated the following numbers:

0 = no cracking

1 = beginning of cracking

2 = increased cracking

3 = cracks longer than 4 mm

concentration
Cracking

Accelerator B [

0.4% 2.5

0.4% 1.5

0.6% 0.5

Example 3

A basic mixture without the addition of reinforcing fillers or anti-aging agents, which is based on 100 parts Smoked sheets containing 5 parts of zinc oxide, 2.65 parts of sulfur and 0.5 part of stearic acid are divided into 4 parts and each part with one of the following accelerator additives (based on 100 parts rubber content):

A 0.5 BenzotMazyl-2-cyclohexyl-sulfenamide (for comparison)

B 0.5 benzothiazyl-2-morpholyl-sulfenamide (for comparison)

C 0.5 benzothiazyl ^ -dicyclohexyl-sulfenamide

D 0.6 benzothiazyl-2-dicyclohexyl-sulfenamide

The comparison vulcanizates, which were vulcanized as usual in the press according to the table below, provide the following modulus values and breaking strengths (kg / cm ² ) in the Schopper ring test on the Schopper tear tester

temperature A. 25th vulcanization B. C I υ 6th not vulcanized 9 to 90 time to 170 Module 500% - breaking strength (kg / cm ² ) 7th not vulcanized 10 to 115 133 ⁰ C 4 to 6th 3 to 10 16 not vulcanized 19 to 175 20 ' 133 ° C 24 to 170 13 to 100 18th up to 60 21 to 190 30 ' 143 ⁰ C 3 to 200 19th to 95 22 to 195 10 ' 143 ° C 33 to 195 27 to 160 up to 150 20 ' 143 ° C 34 to 185 27 to 205 to 185 30 ' 143 ° C 29 to 180 26 to 185 until 195 45 ' 143 ° C 26 to 24 to 180 70 ' 143 ° C 24 to 22 to 175 90 '

Claims (1)

Claim: Process for the vulcanization of mixtures of natural and / or synthetic rubber, which active fillers and / or fatigue or Contain ozone protection agents from the range of activating aromatic bases of the p-phenylenediamine series can, characterized in that the vulcanization accelerator benzothiazyl-2-dicycloalkyl-sulfenamides the general formula 9 10 jij · "various cycloalkyl radicals with 5 to 7 ring carbon atoms \ ^; / ¹ men or their substitution products with alkyl | jc SN _x or cycloalkyl radicals or with alkoxy radicals or \ / ^ / \ hydrogenated fused ring systems, such as a- or ^{x /} S Ra 5/5 tetrahydronaphthyl or a- or ^ -decalyl radicals can be used in which R ₁ and R _{2 are the} same or. 1 sheet of drawings © 809 787/577 3.59