DE1769268B2 - HEAT VULCANIZABLE MASS - Google Patents

Description

ίο \ '- C ^- J-

where .ν denotes a whole Z; ih) from I to 4, and

b) 0.1 to 5 parts by weight of a thiuram sulphide or a metal dithiocarbonate.

Di: The invention relates to a heat-vulcanizable mass, consisting of (A)

a) an ethylene-propylene-diene terpolymer or

b) butyl rubber,

or mixtures of a) and b) with other sulfur-ulcanizable rubbers. (B) sulfur, zinc oxide (and the usual other additives, which are characterized by the fact that the mass is used to accelerate vulcanization
a) 0.1 to 5 parts by weight, based on 100 parts by weight of A, of a bis (morpholinothiocarbonyl) sulfide of the general formula

S!

N-C

wherein χ denotes an integer from 1 to 4, and b) 0.1 to 5 parts by weight of a thiuram sulfide or

of a metal dithiocarbamate.
Some of the newer hydrocarbon elastomers, especially ethylene propylene rubber and butyl rubber, have been modified to contain small amounts of unsaturation so that they can be vulcanized using a sulfur vulcanization system. In the case of ethylene propylene rubber, this modification is generally carried out by Coreaction of a non-conjugated diene, e.g., dicyclopentadiene, 1,5-cyclo-octadiene, norbornadiene, etc. In this respect, diene-modified ethylene propylene rubber (EPDM) is of particular importance None of these elastomers were suitable for conventional vulcanization systems because of the low level of unsaturation they contain compared to other, more unsaturated, all-purpose elastomers, e.g. styrene-butadiene copolymers (SBR) or natural rubber .

The sulfur vulcanization of (EPDM) and butyl rubber was usually achieved with the help of zinc oxide and organic accelerators. the more effective primary accelerators are either thiurarn mono-, di- or tetrasulfides or metal dithiocarbamates. A thiazole. z. B. mercaptobenzothiazole,

ίο is usually used as a secondary accelerator to achieveuna satisfactory curing speeds are required.

The development of satisfactory vulcanization systems for EPDM has mainly been through

the tendency of the elastomer to vulcanize prematurely (i.e. for so-called scorching) and the tendency of the constituents or their reaction products to migrate to the surface of the pre-vulcanizate and the vulcanizate. One usually system used for EPDM, tetramethylthiuram disulfide, mercaptobenzothiazole and sulfur contains, leads to sufficient safety during processing (scorch resistance). with form-hardened However, vulcanizates show strong efflorescence. Attempts to remedy this disadvantage have to reduced security during processing. If you z. B. one half of the tetramethylthiuram disulfide replaced by dipentamethylene thiuram tetrasulfide and the concentration of mercaptobenzothiazole increased, the blooming is decreased and the modulus increased, the scorch resistance on the other hand, is greatly reduced. Other systems have been developed that have a tendency to bloom is reduced, but the resistance to cracking of the preparation is low. Similar Difficulties, including a slow cure rate, arise with butyl rubber. It exists hence a need for a sulfur vulcanization system for EPDM and butyl rubber that is safe Processing, a good hardening speed and a good state of hardening are guaranteed and not blooms. The invention aims to provide such an improved vulcanization system.

Surprisingly, it has been found that vulcanizable rubber having a low degree of unsaturation can be sulfur vulcanized safely and with good cure rate to form satisfactory, non-blooming vulcanizates when the vulcanization is carried out in the presence of an organic accelerator composition of a combination of a bismorpholinothiocarbonyl sulfide and a thiuram sulfide or a metal dithide .
Thiuram sulfides and metal dialkyldithiocarbamates have been known for many years and have been used extensively in vulcanization systems for many types of rubbers. Bismorpholinothiocarbonyl sulfides as described above are not effective accelerators for EPDM or butyl rubber when used alone because they are very slow to act and give a low degree of cure. It is therefore very surprising that with the accelerator system according to the invention, which is obtained by combining a thiuram sulfide or a metal dialkyldithiocarbamate with a bismorpholinothiocarbonyl sulfide, it is possible to achieve a high degree of hardening without adversely affecting safe processing. That

17th

System is unique in that there is no other Bisthiocarbonyl sulfides have been found which lead to the lead to the same or a similar result. For example is bis (2,6-dimethylmorpholinothiocarbonyu disulfide. an analog connection, relatively ineffective.

The diene content of the ethylene-propylene-diene terpolymers used according to the invention originates, for example, from a copolymerization with dicyclopentadiene or 1.5 cyclooctadiene. _{| 0}

According to the invention suitable thiuram mono-. -di and -tetrasulfiden and Metalldialkyldithiocarbamaten include, for example, lower alkyl, monocyclic aryl lower alkyl, aryl and cyclic alkylene thiuram sulfides and dithiocarbamates such as:, <

Tetramethylthiuram sulfide.

Tetramethylthiuram monosulfide,

Tetraethylthiuram disulfide.

Tetrabutyithiuram monosulfide.

Dipentamethylene thiuram tetrasulfide.

Cyclohexamethylene thiuram disulfide,

Diisopropylthiuram disulfide,

Phenylethylthiuram disulfide,

Zinc dibutyl dithiocarbamate.

Zinc pentamethylene dithiocarbamate, bismuth dimethyldithiocarbamate,

Nickel dibutyl dithiocarbamate,

Copper dimethyl dithiocarbamate,

Selenium diethyl dithiocarbamate,

Lead dimethyl dithiocarbamate, selenium dimethyl dithiocarbamate.

Tell dimethyl dithiocarbamate,

Partial diethyl dithiocarbamate.

Cadmium diethyl dithiocarbamate,

Zinc dibenzyl dithiocarbamate, zinc diethyl dithiocarbamate.

The sulfur vulcanization system always contains sulfur and zinc oxide and often a secondary accelerator, z. B. a thiazole. The amount of sulfur used depends on the particular desired Vulcanization properties. In general, by increasing the sulfur concentration, the Scorch resistance reduced and the degree of hardening increased. The useful range for sulfur is generally about 0.5 to 3.0 parts / 100 parts rubber, but may be so for some purposes have high value like 5 or more pieces.

Zinc oxide (or zinc soaps, e.g. zinc stearate) is always used in the sulfur vulcanization system, which contains the accelerator according to the invention. The concentration of zinc oxide is not critical, provided that at least 1.0 part / 100 parts rubber be used. In general, the use of about 3 to 5 parts of zinc oxide proves to be well effective.

Mercaptobenzothiazole (MBT) is commonly used as a secondary accelerator in the vulcanization of EPDM and butyl rubber used. Increasing the concentration of merc ^ ptobenzthiazole leads to &> a reduction in scorch resistance. In general, effective amounts of MBT will be in the range from about 0.5 to 2.0 parts / 100 parts rubber. Benzthiazyl disulfide (MBTS) is another common one Secondary accelerator, which is in the same concentration 6 "; can be applied.

The vulcanizable compositions of this invention can be prepared by known methods, e.g. B. with water-268 £ ■?

steam in open operation, by pressure hardening with liquid hardening media (»LC'M«) and the like, under the common conditions used for these elastomers are vulcanized. The concentration des bis (morpholinothiocarbonyl) -s, ulfide3 varies depending on the desired Range of properties of the vulcanizate or of the one used in connection with it Thiuram sulfide or metal alkyldithiocarbamal. When using tetramethylthiuram disulfide and bisiMorpholinothiocarbonyltdisulfide as an accelerator combination lead more than about 0.75 parts of tetramethylthiuram disulfide with 1.5 parts of bis (morpholinothiocarbonyl) disulfide to increased blooming. If 2.0 parts of bis (morpholinothiocarbonyl) disulfide or more with 0.75 parts of tetramethylthiuram disulfide are used, the cure rate becomes retarded, and a less favorable degree of cure is achieved. Less than 1.5 parts will usually result in increased efflorescence. It can thus be seen that the concentration of each component of the accelerator system according to the invention depending on the factors mentioned above and also on the respective field of application, for which the vulcanizate is to be used, e.g. B. for tires. Wire and cable sheaths. Hoses, belts, other mechanical goods. Cell structure products and the like fluctuates. A general effective concentration range for each component is about 0.1 to 5.0 parts. 100 parts of rubber.

Other commonly used compounding ingredients, z. B. carbon black, mineral fillers, clays, processing oils. Soaps, waxes and the like, can Mass can be added as required to achieve certain properties. The crowds can get on mixed, molded, extruded or in conventional rubber or plastics processing equipment can be processed in any of the many ways known to those skilled in the art of rubber.

The following examples illustrate the invention without restricting it. Parts refer to that Weight.

example 1

Four EPDM rubber compounds were produced as follows:

Basic mass

Hydrocarbon rubber
100 parts by weight EPDM and

50 parts by weight of naphthenic oil 150

SAF carbon black 60

ISAF-H carbon black 20

Zinc oxide 5

Stearic acid 1

Sulfur 2

Mercaptobenzothiazole 1.5

link

A B C D

accelerator
Bis (morpholinothiocarbonyl) disulfide

1.5 1.5

continuation link B. C. IJ A. 0.75 0.7 accelerator 0.75 Tetramethyl - __. thiuram disulfide 0.75 Dipentamethylene thiuram disulfide Vulcanization 17.3 61 29 duration at 121 C 13.7 Rise on 5 points in Minutes, T ₅ 300% modulus. kg cm ² , at 160 ° C 38.3 15.5 44.6 hardened 48.5 42.2 20.0 50.6 after 15 minutes 52.7 63.3 48.5 75.2 after 20 minutes 79.8 middle very very after 60 minutes middle Well Well resistance Well against blooming

The values show that EPDM is very strong when cured with conventional accelerators (A and B)

Scorch shows. Connection B provides greater processing security, but has result in a lower degree of hardening and greater efflorescence. 8is (morpholinothiocarbonyl) sulfide cures too slowly to be of any practical use (Compound C) and performs to a very low degree of hardening. The combination of bis (morpholinothiocarbonyl) disulfide and Tctramethylthiuram disulfide (compound D) doubled the processing reliability of a conventional hardening system (A) and leads to a good degree of hardening and low efflorescence.

Example 2

EPDM rubber compounds were produced as follows. The ingredients are given in parts by weight.

Basic dimension c

Composed of 100 parts by weight of EPDM

and 50 parts by weight of naphthene oil 150

SAF carbon black 60

iSAF-H carbon black 20

Zinc oxide 5

Stearic acid 1

Sulfur 2

Mercaplobenzthiazole 1.5

Tetramethylthiuram disulfide 0.75

link B. C. D. A. accelerator - Dipentamethvlenthiuramtetra- 0.75 sulfide 1.5 Diisopropylthiuram disulfide 1.5 Phenylthiuram sulfide 1.5 Bis (2,6-dimethylmorpholino- 1.5 thiocarbonyl sulfide Scorch duration at 121 C 14.2 15th 15.9 5 points increase 11.7 in minutes. T ₅ 300% modulus, kg / cm ² hardened at 160 C. 47.1 52.7 after 15 minutes 45.7 66.1 73.8 73.8 after 20 minutes 62.6 73.8 82.6 80.9 after 60 minutes 84.4 very bad medium good bad medium Resistance to blooming medium good

The values show that none of the different Thiuram sulfides in combination with tetramethylthiuram disulfide results in a good curing system for EPDM because all of them have too much scorching and the connections bloom excessively.

Example 3

The basic mass for this mass was in equals; Made as in Example I. The basic measure c accelerator systems were added as indicated, which bis (morpholinothioearbonyl) disulfide in In combination with other common thiuram sulfides. The accelerators used in the experiments are designated as follows:

A - tetramethylthiuram monosulfide,

B-tetramethylthiuram disulfide,
C — tetraethylthiuram disulfide,

D-tetrabutylthiuram disulfide,

Π - Dipentamethylene thiuram tetrasulfide,

F - zinc dimethyldithiocarbamate,

G zinc dibutyl dithiocarbamate,
H -zinc dibenzyldithiocarbamate,

1 - diphenyldimethylthiuram disulfide,

J - iron dibenzyldithiocarbamate,

K - bisdnorpholinothiocarbonyl disulfide.

^ 8

accelerator 0.75 0.75 0.75 - 0.75 - - - -. A. _ - - _ .. _. - B. -. 0.75 - _. - C. - - 0.75 - - D. - 0.75 - - E. - - F. - - - 0.75 - - G - - 0.75 - H - ■ 1.5 1.5 0.75 - I. 1.5 1.5 1.5 - - _._ 0.75 J 1.5 1.5 1.5 1.5 1.5 1.5 K 32.0 14.5 *) Vulcanization 29.0 32.0 23.5 *) duration at 121 C 28.5 63.0 *) 38.0 *) 32.0 *) 53.5 *) 33.5 *) Increase by 5 points in Minutes. T ₅ 39.0 34.5 300% modulus at 44.6 48.9 32.7 38.0 36.6 Hardened at 160 C. 42.5 50.6 70.3 47.1 40.4 17.2 65.0 25.3 28.1 26.4 26.4 after 1 1/2 minutes 57.3 75.2 very 70.3 66.8 22.5 very 32.7 35.9 33.0 32.7 after 20 minutes 74.5 very Well very out 56.2 Well 57.3 64.7 61.9 63.3 after 60 minutes very Well Well drawing very out out out out Resistance to Well net Well drawing drawing drawing drawing Blooming net net net net

* l These masses were rolled again: Modulus and Seorch values are therefore worse: see connection B and E as the basis for Comparisons.

Example 3 illustrates the effective combination scorch time of 14.5 minutes, although shorter than that

of bis (morpholinothiocarbonyl) disulfide with different times in the series, but considerable different thiurams and dithiocarbamic acid salt- 40 longer than the scorch time of the same compound

zen of various metals. The good vulcanizate if the bis (morpholinothiocarbonyl) disulfide through

properties, processing reliability and excellent- a different thiuram, z. B. Tetramethylthiuramdisul ·

A good resistance to blooming is evident. is replaced,
borrowed. In the case of zinc dimethyldithiocarbamate, the

Example 4
The following base material was produced:

Butyl rubber 100

FEF carbon black 60

Naphthenic oil 40

Zinc oxide 5

Stearic acid 1

Sulfur 1.5

Mercaptobenzothiazole 0.5

Mixture of 33% N-methyl-N.

4-dinitrosoaniline and 67%

inert material 0.5

Using this matrix, the following compositions were tested:

ABCD E F G

component

Tetramethylthiuram disulfide 1.0 1.0 1.0 1.0 1.0 - -

Dipentamethylene thiuram- 1-0 2.0 - 2.0 -

tetrasulfide

continuation

ι / t> y

10

C D

component

Bis (morpholinothiocarbonyl) disulfide

Scorch time at 132 ° C

2.0

2.0

Increase by 5 points in
Minutes. T ₅ 17.9 16.7 23.6 17.6 33.6 13.9 64.0 300% modulus kg, cm ² at 160 ° C
hardened after 12.5 minutes 27.1 31.3 32.3 34.1 27.1 24.3 after 25 minutes 35.2 38.7 41.5 43.6 39.7 36.2 after 50 minutes 38.3 43.2 47.5 48.9 39.7 39.4 23.2 after 75 minutes 38.3 42.9 43.9 46.4 40.4 40.8 26.7 Resistance to blooming middle
Well middle Well out
draws very good
out
draws out
draws out
draws
(nothing)

This example shows what effect is achieved if either one or the other component of the accelerator according to the invention is separated used. It also shows the effect of using a two-component accelerator, the bis (morpholinothiocarbonyl) disulfide does not contain as one of its components.

Claims (1)

Palent claim: Heat-vulcanizable compound. Consisting of (Al a) an ethylene-propylene-diene terpolymer or b) butyl rubber, or mixtures of a) and b) with other sulfur-vulcanizable rubbers, (B) sulfur, zinc oxide and customary further additives, characterized in that the mass is used to accelerate vulcanization
a) 0.1 to 5 parts by weight, based on 100 parts by weight of A, of a bisfMorphoIinothiocarbonyDsulfids of the general formula