DE1221439B - Anti-degradation agents for natural or synthetic rubber - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

C08c

C08d

German class: 39b-8

Number: 1 221439

File number: M 40516IV d / 39 b

Filing date: February 16, 1959

Opened on: July 21, 1966

It is well known that rubber tends to deteriorate when exposed to heat, Light and gases containing oxygen, e.g. B. air, is exposed. To counter this effect, has the rubber is mixed with a wide variety of anti-aging agents, but many of them have them the disadvantage that they darken over time and the types of rubber into which they have been incorporated, especially if they are light-colored varieties, discolour strongly.

Further deterioration in rubber is caused by ozone, which is present in small amounts in the atmosphere is present. This makes the rubber more susceptible to cracking Noticeable on the surface, especially when the rubber has a twist or is subjected to stretching. Now it is not said that an ordinary rubber antioxidant must also provide protection against the effects of ozone. Protective means, however, which both Combining properties with one another are known as anti-degradation agents.

A new class of anti-degradation agents has been found in rubber that has both represent good anti-aging agents as well as anti-ozone agents. They discolour light colored rubbers barely.

The invention relates to the use of compounds of the formula

-NHR,

in which R ₁ denotes an alkyl radical or a benzyl radical and R ₂ denotes an alkyl radical with more than 6 carbon atoms or a cyclohexyl radical and in which the benzene nucleus can optionally be substituted by lower alkyl groups, as a degradation-preventing agent for natural or synthetic rubber. These additives are added to the rubber in amounts of 0.1 to 5 parts by weight per 100 parts by weight of rubber.

4-methoxy- and 4-ethoxy-N-n-octylaniline, 4-methoxy- and 4-ethoxy-N-n-decylaniline are preferred as well as 4-methoxy- and 4-ethoxy-N-cyclohexylaniline are used. They are excellent antioxidants, which also offer very good protection against ozone.

Other substituted anilines with good properties are 4-methoxy-N- (l ', 5'-djmethyl-n-hexyl) aniline, 4-methoxy-N-benzylaniline, 4-ethoxy-N-benzyl degradation inhibitors Means for natural or synthetic rubber

Applicant:

Monsanto Chemicals Limited, London

Representative:

Dr. M. Eule, patent attorney,

Munich 2, Hilblestr. 20th

Named as inventor:

Bertrand Ernest Wilde,

Marion Ilse Hedwig Wilde,

Pentre, Wrexham, Denbighshire (UK)

Claimed priority:
Great Britain dated February 17, 1958 (5025), dated! January 1959

aniline, 4-n-hexyloxy-N-benzylaniline, 4-n-butoxy-N-n-hexylaniline, 2-methyl-4-methoxy-N-n-hexylaniline and 2-methyl-4-ethoxy-N- (l ', 3'-dimethyl-n-butyl) aniline.

The amount of substituted aniline to be incorporated into the rubber can vary within wide limits, however, 0.2 to 3 parts by weight per 100 parts by weight of rubber are preferably used.

These substituted anilines are effective anti-aging agents for both natural rubber as well as for synthetic rubbers.

The invention is illustrated in more detail by the following examples.

example 1

A white rubber premix of the following composition was kneaded on a laboratory roller mill:

Parts by weight

Light crepe rubber 100

Blanc fixe 50

Titanium dioxide 5

Zinc oxide 5

Stearic acid 1

Sulfur 2.5

Diphenylguanidine 0.5

609 590/414

One part by weight of one of the following substituted anilines was then added to each mixture. It a control experiment was carried out in each case, which did not contain any of these compounds.

Each premix was rolled into a sheet 4 mm thick and added over the course of one hour 141.5 ° C vulcanized. There were then ring-shaped test pieces with a diameter of 50 mm and cut out a radial width of 1 mm.

The effect of the substituted anilines as antioxidants was determined by measuring the so-called "Tension - relaxation - half life" at 110 ° C using the method and device as it is

by Robinson and Vo ddeη in »Industrial and Engineering Chemistry ”, 47, 1477 (1955). The "half life" is the time it takes to reduce the tension to half of its value in the 100% stretched sample allow. The effect of an antioxidant is to reduce the rate of chain splitting to delay with rubber and thus to increase the stress-relaxation half-life. The relative Effectiveness of the antioxidant tested is then represented by the ratio the half-life values for the treated and control mixtures.

The values of the anti-aging effectiveness of these substituted anilines result from the table below:

Anti-degradation agent

Tension relaxation treated Ratio of treated Half life mixture for control mix able to 2.66 roll test 2.79 3.02 0.88 3.18 3.17 0.88 2.96 3.58 0.89 2.89 3.65 0.81 2.88 3.23 0.89 2.90 3.27 0.88 3.07 3.29 0.88 2.64 3.49 0.88 2.71 3.26 0.81 2.84 3.08 0.88 2.60 3.19 0.89 2.93 2.92 0.89 3.83 3.19 0.92 4.17 0.92

4-methoxy-N- (n-hexyl) aniline

4-methoxy-N-cyclohexyl-aniline

4-methoxy-N- (n-octyl) aniline

4-methoxy-N- (n-decyl) aniline

4-methoxy-N- (n-hexadecyl) aniline

4-ethoxy-N- (n-hexyl) aniline

4-ethoxy-N- (cyclohexyl) aniline

4-ethoxy-N- (n-octyl) aniline

4-ethoxy-N- (n-decyl) aniline

4-ethoxy-N- (n-hexadecyl) aniline

4- (n-Decyloxy) -N- (1 ', 3'-dimethyl-n-butyl) aniline

4- (n-decyloxy) -N-cyclohexylaniline

4-Benzyloxy-N- (1 ', 3'-dimethyl-n-butyl) -aniline .. 4-Benzyloxy-N-cyclohexylaniline

The above results show high levels of aging for all of the compounds in question inhibitory effectiveness. 4-Methoxy-N- (n-octyl) -aniline in particular have excellent properties, 4-methoxy-N- (n-decyl) -aniline and 4-benzyloxy-N-cyclohexyl-aniline. They are considerably better than the homologous compounds, in which instead of one bonded to the nitrogen atom, proportionally large aliphatic group is a straight-chain group with a small number of carbon atoms is available. So when testing 4-methoxy-N- (n-butyl) -aniline for the control mixture a half-life of 0.77 hours, for the treated mixture a half-life of 1.71 established; this gives a ratio of the treated to the control mixture of only 2.22 compared to 3.58 and 3.65 for the n-octyl and n-decyl homologues, respectively.

Example 2

A rubber premix of the following composition was made on a laboratory mixer roll mill kneaded:

Parts by weight

Smoked Sheets 100

Carbon black 50

Plasticizing aid based on

Mineral oil 3

Zinc oxide 5

Stearic acid 3

Sulfur 2.5

N-Cyclohexyl-2-benzthiazylsulfenamide 0.4

This mixture was divided into several parts.
1 part by weight of the following anti-aging agent was then added to each mixture. Control mixtures without these agents were also tested.

Each mixture was rolled into a sheet 4 mm thick and over the course of 30 minutes vulcanized by heating to 141.5 ° C. The vulcanized pelts were then made as described in Example 1 is cut into test pieces and tested.

Anti-degradation agent

Tension relaxation

Half life

in hours

Control attempt

treated
mixture

Ratio of the treated to the control mixture

4-methoxy-N- (n-hexyl) aniline

4-ethoxy-N- (l ', 3'-dimethyl-n-butyl) aniline

4-ethoxy-N- (n-octyl) -aniÜn

4-ethoxy-N-benzylaniline

4- (n-Hexyloxy) -N- (1 ', 3'-dimethyl-n-butyl) aniline

4- (n-hexyloxy) -N-cyclohexylaniline

4-benzy] oxy-N- (l ', 3'-dimethyl-n-butyl) aniline

2-methyl-4-methoxy-N-cyclohexylaniline

Example 3

This example describes the use of various substituted anilines in a natural rubber premix and shows their protection against the effects of ozone.

A rubber masterbatch of the following composition was made on a laboratory mill

kneaded: _,. . ^ ₄ ..

° weight position

Smoked Sheets 100

Carbon black 50

Plasticizing aid based on

Mineral oil 3

Zinc oxide 5

Stearic acid 3

Sulfur 2.5

N-Cyclohexyl-2-benzthiazylsulfenamide 0.4

A portion of the mixture was used as a control mixture without any addition. Other Parts of the mixture were processed with 3 parts by weight each of the compounds to be tested. These Mixtures were formed into a tape and vulcanized by heating at 141.5 ° C for half an hour. The band-shaped test pieces obtained were approximately rectangular with rounded corners and internal dimensions of 76.2 x 15.9 mm. They were 4 mm wide and 1 mm thick.

The effectiveness against ozone was measured according to the test method described below.

The basis of this test method is the fact that the presence of surface cracks due to exposure to ozone causes an elongated sample of rubber to rapidly decrease in the resistance to elongation inherent in the sample. The effect of an antiozonant can therefore be estimated by measuring the time for the stress release on a rubber sample that is 0.27
0.27
0.27
0.27
0.27
0.27
0.27
0.27

0.98
1.08
1.03
0.56
1.17
1.28
0.98
0.59

3.62
4.00
3.80
2.07
4.33
4.74
3.63
2.19

has been treated with this remedy. The times for the relaxation of the stretch resistance are for measured a number of different linear strains.

These measurements take place both under static load, whereby the sample is subjected to a constant linear expansion, and under dynamic load, whereby the sample is continuously alternately stretched first up to a constant linear expansion and then relaxed again, namely at 60 expansions per Minute. For the static load tests, the equipment used was essentially the same as that used to measure antioxidant activity. However, the measurements were ^{carried out at room temperature instead of at 110 °} C., and in an atmosphere which, in addition to air, also contained traces of ozone (about 7 parts per million).

When the test was carried out, one of the tape-shaped test pieces increased by a constant amount elongated, measuring the stress necessary to maintain this elongation. It was found that this stress decreased in a logarithmic relationship with time. The measurements were taken at various degrees of elongation. They happened for both static and dynamic loads.

For each of the blends treated, the peak ratio was calculated; H. so the ratio the peak values for the amount of internal tension release of the control mixture to the treated mixture. The greater this ratio than one, the higher the protective effect of the to strike tested compound against ozone.

The peak ratios for each of the substituted anilines tested are in the following Table specified:

Anti-degradation agent

Peak ratio dynamic static Stress Stress 3.9 4.2 6.4 4.2 6.2 3.0 4.8 2.9 3.9 3.4 5.8 5.6 5.2 4.1 5.5 7.7

4-methoxy-N- (n-decyl-aniline

4-ethoxy-N- (n-hexyl) aniline

4-ethoxy-N- (l ', 3'-dimethyl-n-butyl) aniline

4-ethoxy-N- (n-octyl) aniHn

4-ethoxy-N- (n-decyl) aniline

4-n-decyloxy-N- (r, 3'-dimethyl-n-butyl) -aniline 4-benzyloxy-N- (l ', 3'-dimethyl-n-butyl) -aniline. 4-n-decyloxy-N-cyclohexylaniline

A comparison with the well-known o-ethoxy ^ l ^ -trimethyl-l ^ -dihydroquinoline, which, however, the rubber discolored gave a peak ratio of only 2.0 to 2.5.

7 8

Example 4 First, a mixture with the addition of

3 parts by weight of 6 - ethoxy - 2.2.4 - trimethyl -1.2 - di-

In this example the anti-ozone effect of the hydroquinone is established. Then two mixed

according to the claim to be used substituted ani with the addition of 3 parts by weight of the following

line made on butadiene-styrene rubber with those 5 standing compounds. Ribbon-shaped

of 6-ethoxy-2,2,4-trimethyl-l, 2-dihydrocbinohn ver test pieces were, as described in Example 3,

resembled. manufactured and tested. Here, too, were the top

A rubber mixture with the following values at approx. 10 ° / ₀ linear elongation,

Settlement was carried out on a laboratory rolling mill. When the peak value ratio was calculated

Well kneaded: OK, however, the peak value of the decrease in the inner

Parts by weight of tension in the mixture containing 6-ethoxy-2,2,4-tri-

Butadiene-styrene rubber (78:22) .. 100 methyl-l ^ -dihydroquinoline contained, with the tip carbon black 50 values of the two mixtures compared, which the

Zinc oxide contained 4 substituted anilines. The peak stearic acid 2 15 ratios were greater than one in both cases,

Plasticizing aids on the basis of which the extent to which is recognizable

Mineral oil 8 the tested substituted anilines the known

Sulfur 2 were superior to ozone protection agents, which

N-Cyclohexyl-2-benzthiazylsuh ° enamid 1,2 can be found in the table below:

substance

Peak ratio

static
Stress

dynamic stress

4-Ethoxy-N- (l ', 3'-dimethyl-n-butyl) -aniline 4-ethoxy-N- (n-hexyl) -aniline

2.6
2.6

1.9 1.5

Claims (1)

Claim: Use of compounds of the formula -NHR ₉ in which R _{1 is} an alkyl radical or a benzyl radical and R _{2 is} an alkyl radical having more than 6 carbon atoms or a cyclohexyl radical, and in which the benzene nucleus can optionally be substituted by lower alkyl groups, as degradation-preventing Agent for natural or synthetic rubber in amounts of 0.1 to 5 parts by weight per 100 parts by weight of rubber. References considered: U.S. Patent Nos. 1,965,948, 2,063,2 220,065, 2,779,789;
French patent specification No. 848 867. 609 590/414 7.66 © Bundesdruckerei Berlin