DE1543843B1 - 4,4'-bis- (alpha, alpha-dimethylbenzyl) -diphenylamine, its production and use as an anti-aging agent - Google Patents

Description

The present invention relates to 4,4'-bis (a, <z-dimethylbenzyl) diphenylamine as a new compound, a process for its preparation, which is characterized in that a-methylstyrene with Diphenylamine in the presence of a sulfuric acid of 66 ° Be in one under the working conditions Reacts inert solvent, as well as the use of 4,4'-bis- (a, a-dimethylbenzyl) -diphenylamine as an anti-aging agent for natural or synthetic rubbers.

With the method according to the invention achieved excellent yields. The best yields are obtained with a molar ratio of α-methylstyrene to diphenylamine between 2 and 4 obtained. Below 2, the proportion of monosubstituted Product too considerable, and above 4 there is formation of large amounts of dimers of a-methylstyrene instead.

The reaction temperature is between 50 and 150 ° C. However, reflux is usually used.

The solvent can be, for example, hydrocarbons or mixtures of hydrocarbons, for example those obtained by petroleum distillation, or saturated carboxylic acids such as acetic acid, use. The amount of solvent is preferably between 1 and 5 liters per kilogram Diphenylamine.

The sulfuric acid is preferably used in an amount of 0.5 to 3 moles per mole of diphenylamine used.

When the condensation reaction has ended, the sulfuric acid is neutralized and released of the amine is alkaline, which can be removed from the reaction medium by suitable extraction and purification treatments (generally by fractional crystallization) separates. You get one like that pure crystalline white product with a melting point of 97 ° C of the formula

general properties of rubbers (especially tensile strength, elongation at break, modulus). In particular, it protects against oxygen, cracks caused by repeated bending and deterioration Effect of heat. It is therefore used in the preparation of rubber mixtures, intended for the manufacture of vulcanized products. Its low volatility gives it great durability.

This product is also not very sensitive to the effects of light and can therefore be used in little colored mixtures can be used. It also shows little "spotting"; H. that the rubber products that contain it without Damage can be brought into contact with paints and varnishes.

When using 4,4'-bis (a, a-dimethylbenzyl) -diphenylamine as an anti-aging agent, the rubber is predominantly 0.2 to 4 percent by weight added to the product. The optimal amount depends on the rubber treated and is generally between 0.5 and 2%.

The rubbers stabilized with the product (I) are, for example, the polybutadienes, which are natural or synthetic polyisoprenes, the butadiene / acrylonitrile copolymers, the butadiene / styrene copolymers and the polychloroprenes. The following examples illustrate the invention.

Example!

CH ₃

CH,

CH ₃

CH,

(D

This product is an effective protective agent against the various forms of aging Rubber (natural or synthetic rubber). It ensures the maintenance of the 8.45 kg (50 mol) of diphenylamine (technical product) are placed in an enamelled reaction vessel and 37.5 1 of a mixture of hydrocarbons (distillation range: 110 to 160 ° C).

Keep moving and heat to 50 ° C to dissolve the diphenylamine. Then allowed while maintaining a temperature of 50 ° C 7.5 kg of sulfuric acid of 66 ⁰ Be (97gewichtsprozentige sulfuric acid) accrue.

When the addition of the acid has ended (30 minutes), the mixture is refluxed and then brought within 17.7 kg (150 moles) of α-methylstyrene in 1 hour.

It is then refluxed for a further 2 hours. The temperature of the mass is about 115 ° C. After this period of time, the heating is discontinued and cools down to 75 to 80 ° C. 25 liters of 5N sodium hydroxide solution are then left in the course of 15 minutes and then 37.5 l of the mixture of hydrocarbons (distillation range: 110 to 160 ° C) flow.

5.5 Keep the temperature at 75 to 80 ° C and then check the alkalinity of the medium (the pH value should be at least 12).

It is decanted in the heat and the separated organic layer is placed in a crystallization container. The remaining aqueous layer is extracted again with 25 l of the mixture of hydrocarbons (boiling range: 110 to 160 ° C), and the two organic extracts obtained are combined and cooled to 15 ° C. The crystallized 4,4 ^/ -Bis- (a, a-dimethylbenzyl) -diphenylamine is separated off by filtration. After drying, 14.5 kg of 4,4'-bis (a, a-dimethylbenzyl) diphenylamine are obtained.

The product is a well-crystallized white solid substance with a temperature of 97 ° C. It corresponds to the formula

NH

CH,

CH,

X /

(I)

as can be seen from the ultraviolet and infrared test. The product is tested by thin layer chromatography pure.

Example 2 volatility test

The protective agent to be tested is applied from a toluene solution to a filter paper strip. By weighing the losses due to volatile

^I5

after the action of a stream of warm air on the strips. (This test is often used to determine the volatility of products used in the rubber industry. The ^{results obtained after 180 minutes at 120 °} C. are expressed as a percentage loss:

product Loss in% IO
Diphenylamine
Product (I) 100
2

This experiment shows the superiority of the

^{ducts (I)} g ^e S ^{en on} diphenylamine. Although diphenyl _{amine has a good protective effect} , its effect ceases fairly quickly due to its relatively rapid disappearance from mixtures containing it.

Example 3

To check the qualities of the product (I) D 1206 -52 T 24 hours and 48 hours at 100 ^° C., the following mixtures were prepared: 25 subjected.

The following results were obtained:

Components Black
mixture White
mixture Smoked sheets
Pale CrSpe
Soot HAF
Titanium oxide
Pine Tar
Zinc oxide
Stearic acid
sulfur
Tetramethylthiurammono-
sulfide 100
50
3
5
2
2.25
0.5
1 100
10
5
1
2.5
0.5
1 N-Cyclohexylbenzothiazyl-
sulfenamide
Tested protective agent ....

30 means of protection
of the white mixture

None

Product (I) ...
Diphenylamine

“Creep”% at 100 ^° C
after 24 hours after 48 hours

35.5

8.2

32.3

over 100
18.5
over 100

35

40

45 means of protection

The mixes were under the press at 143 ° C for 30 minutes for the black mix and vulcanized at 138 ° C for 15 minutes for the white mixture. The white and black Comparative samples, d. H. those without a protective agent were vulcanized in the same way.

1. "Creep" test

Test pieces cut out of the white vulcanizates were not subjected to the "creep" test according to ASTM product (I)

2. Heat aging test

_{Dumbbell test specimens H 2} , AFNOR T 46 002, cut out of plates from the vulcanized mixtures, were placed in cell ovens at 80 ° C. for varying periods of time. The changes in tensile strength over time (expressed as a percentage of the initial value) were followed.

Black mixture

Initial tensile strength

(kg / cm ² )

272
270

Later tear strength in%
of the initial
Worth after

3 days

66
91

5 days

50
82

White mixture

Protective agent

Later tear strength in%
of the initial value

3 days 5 days

7 days

10 days

None

Product (I) ..
Diphenylamine

315 310 305

46 76 60 24
72
51

61
46

6th
59
21

3. Test of photosensitivity

In the case of the white mixtures, the photosensitivity was determined by exposure to an intense light source and the time required for a color change to occur and the color were evaluated detected after a certain exposure time.

White mixture of 4,4'-bis- (a, a -dimethylbenzyl) -diphenylamine according to the invention of the formula

NH

Protective agent For one
Color change
necessary
Period of time Coloring after
60 hours None ........
Product® .....
Diphenylamine .. 60 hours
5 hours
5 hours Pale yellow
Cream colors
Dark yellow

Protective agent

Number of cycles

to achieve the

Appearance of cracks

(in thousands)

Number of cycles

to achieve

a middle one

Cracking state

(in thousands)

None 120 ± 20 420 ± 20

Product (I) ... 390 1100 ± 100

Example 4

Comparison of the protective effect of the Dutch patent application 6 507 710 known as anti-aging agents

4,4'-bis (α-methylbenzyl) diphenylamine

the formula

CH,

CH ₃ -C - // \

CH ₃ CH ₃

(hereinafter referred to as compound B).

1. Examination of the volatility according to the method given in example 2, p. 6 of the registration documents

The following percentage losses were determined:

4. Resistance to repeated bending

The strength against repeated flexing of the black mixture was determined according to ASTM D 430-59 B. certainly. It has been used to cause cracks to appear as well as to achieve one through numerous fine Crack-marked conditions required number of cycles determined. The results are the following:

Black mixture

product loss
in percent by weight Connection A
Connection B 7th
2

2. "Creep" test with the black or white mixture, produced according to Example 3,

P. 7 of the registration documents

The black mixture was vulcanized 25 minutes at 143 ⁰ C, the white mixture for 10 minutes at 143 ° C. The test specimens were subjected to the "Creep" - test according to ASTM D 1206-52 T subjected to 24 hours at 100 ⁰ C.

The following results were obtained:

Protective agent
in the white mixture % "Creep" at 100 ^° C
after 24 hours 0
Connection A
Connection B 42
14.3
11.1

The black mixture was subjected to a heat aging test. Dumbbell test specimens H 2 according to the AFN OR T 46 002 standard were used. The test specimens were exposed in the shown in the table periods in Zellöfen a temperature of 8O ⁰ C. The changes in tensile strength were determined as a function of time (expressed in% of the initial value).

Protective agent

(hereinafter referred to as compound A) with the

Connection A
Connection B ....

Initial tensile strength

(kg / cm ² )

300
284
284

Subsequent tensile strength in% of the initial value

after 3 days

75 83 86

after 5 days

60

74 82

Claims (3)

Patent claims: 1. 4,4'-bis (a, a-dimethylbenzyl) diphenylamine. 2. A process for the preparation of 4,4'-bis- (a, a-dimethylbenzyl) -diphenylamine, characterized in that a-methylstyrene is reacted with diphenylamine in the presence of a sulfuric acid of 66 ⁰ Be in a solvent which is inert under the working conditions. 3. Use of 4,4'-bis (a, a-dimethylbenzyl) diphenylamine as an anti-aging agent for natural or synthetic rubbers.