DE1225854B - Anti-ozone agent for vulcanizates made from natural or synthetic rubber - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY GERMAN 4MWWI PATENT OFFICE Int. Cl .:

C08c

EDITORIAL

C08d
German class: 39 b - 8

Number: 1 225 854

File number: U 4978IV d / 39 b

Filing date: December 9, 1957

Opening day: September 29, 1966

Vulcanized rubber can cause three types of deterioration their physical properties suffer: an oxidation of the mass, an oxidation the surface and cracking caused by ozone. , The oxidation of the mass is characterized by a slow decrease in the tensile strength of the vulcanizate and a change in the ultimate elongation and the elastic modulus without any visible surface change. The surface oxidation is the very fast, light-catalyzed oxidation of the vulcanizate and results in a hard, inelastic, but flexible surface "with shallow furrows. The properties (tensile strength, modulus, etc.) are not adversely affected.

The oxidation of a rubber vulcanizate, in particular its surface, can be carried out by known Anti-aging agents such as phenols or. Amines, especially p-phenylenediamine derivatives, effectively prevented will.

The third type of deterioration; ozone cracking is also a surface phenomenon caused by ozonolysis will. Although there are very few parts of ozone per 100,000,000 parts of air, this is sufficient small amount already, in order to, the formation of deep cracks in rubber vulcanizates, which are under tension standing and exposed to the atmosphere. Unfortunately, most of the offer on the market available anti-aging agents little or no protection against cracking caused by ozone, even not the important protection under dynamic conditions that is necessary for car tires. Also with those in "Rubber World", Vol. 130, pp. 636ff. and "Rubber Age", Vol. 77, pp. 705ff. specified ozone protection agents this protection is not achieved, because in these articles only N, N'-dialkyl- or Ν, Ν'-diphenyl derivatives are used.

The invention therefore relates to the use of N-alkyl-N'-phenyl-p-phenylenediamines in which the alkyl groups have 2 to 9 carbon atoms, in amounts of 0.5 to 5 parts by weight and petroleum wax, at least 60% microcrystalline Wax exists in amounts of 0.5 to 10 parts by weight as an anti-cracking agent from ozone for vulcanizates made from natural or highly unsaturated synthetic rubber, with the quantities are based in each case on 100 parts by weight of rubber.

Due to the mixture of N-alkyl-N'-phenyl-p-phenylenediamine and Wax will provide protection that is effective for a very long time, especially under dynamic conditions.

Ozone protection agents for vulcanizates
natural or synthetic rubber

Applicant:

United States Rubber Company, New York,

N. Y. (V. St. A.)

Representative:

Dipl.-Ing. Dr.-Ing. R. Poschenrieder,

Patent attorney, Munich 8, Lucile-Grahn-Str. 38

Named as inventor:

Paul Louis Merz,

Robert Reel Barnhart, Naugatuek, Conn.

(V. St. A.)

Claimed priority:
V. St. v. America December 17, 1956
(628 517)

hold, d. that is, excellent protection is obtained even if the vulcanized article has a Is subjected to continuous bending stress, as it is, for. B. is the case with sidewalls of pneumatic tires. the excellent protection against cracking caused by ozone under dynamic conditions, the achieved by the mixture used according to the invention was not foreseeable because it was of Petroleum waxes are known to have resilience rubber vulcanizates against cracking caused by ozone under dynamic conditions clearly harmful and continue to act, because the N-alkyl-N'-phenyl-p-phenylenediamine alone is only one Has a moderate protective effect.

The N-alkyl-N'-phenyl-p-phenylenediamines to be used can carry straight or branched chain alkyl groups.

The microcrystalline waxes used according to the invention have a melting point in the range from 150 to 195 ^° C. A mixture of microcrystalline wax and paraffin wax is preferably used. These contain petroleum wax mixtures

609 668/472

always at least 60% microcrystalline wax, preferably 60 to 95% microcrystalline wax. The paraffin waxes used according to the invention melt in the range from approximately 130 to 145 ^° C.

The rubber mixture to be protected contains the usual vulcanizing agents, accelerators, plasticizers, Fillers and anti-aging agents. Such rubber mixtures, the inventive Contain ozone protective combination can be in any desired way according to the conventional methods are molded and vulcanized.

The following examples, in which all parts are parts by weight, are intended to detail the invention explain.

example 1

A rubber compound for tire treads is prepared by putting in an internal mixer 100 parts smoked sheets, 5 parts zinc oxide, 1 part anti-aging agent (a reaction product of diphenylamine and acetone), 1 part anti-aging agent (mixture of 65% diphenylamine acetone reaction product and 35% N, N'-diphenyl-p-phenylenediamine), 3.5 parts of zinc laurate, 45 parts of a medium processable Carbon black 3.5 parts of pine tar, 1 part of mercaptobenzothiazole and 3 parts of sulfur are mixed. Three different experimental wax blends were used. Wax A is a mixture of equal parts paraffin (melting point 130 ° C) and microcrystalline wax (Melting point 165 ° C). Wax B consists of 80% paraffin (melting point 130 ° C) and 20% microcrystalline Wax (melting point 165 ° C). Wax C consists of 20% paraffin (melting point 145 ° C) and 80% microcrystalline wax (melting point 165 ° C). Wax C represents that to be used according to the invention Wax mixture. 1 part wax alone or in

ίο Combination with 2 parts one in the following Ozone generators listed in the table are incorporated into the tread compound. After vulcanizing entangled test pieces are subjected to static cracking in the open air, as shown in FIG the ASTM determination method D 518-44, method B is described.

To determine the resistance of the same masses to dynamic cracking in the open air, were not pierced specimens as shown in

ao of the ASTM determination method D 813-52T are specified. These specimens were placed outdoors in a machine which subjected them to a 78 degree bend 150 times per minute.
The extent of deterioration of the specimens containing the various protectants after one year of static exposure and after more than 12,000,000 cycles of outdoor flexing is shown in Table I.

Table I.

Anti-ozone agents wax Condition after 356 days
static storage
outdoors Condition after 12 megacycles
Bend outdoors None none three tenths of the sample four tenths of the sample were badly cracked were badly cracked None A. two tenths of the sample seven tenths of the sample were badly cracked were badly cracked None B. two tenths of the sample four tenths of the sample were badly cracked were badly cracked None C. one tenth of the sample seven tenths of the sample was badly cracked were badly cracked N-isopropyl-N'-phenyl-p-phenylenediamine none three tenths of the sample one tenth of the sample were badly cracked was badly cracked N-isopropyl-N'-phenyl-p-phenylenediamine A. almost no cracks; six tenths of the sample good condition were very cracked N-isopropyl-N'-phenyl-p-phenylenediamine B. perfect four tenths of the sample were badly cracked N-isopropyl-N'-phenyl-p-phenylenediamine C. perfect perfect 6-ethoxy-2,2,4-tri-methyldmydroquinoline none three tenths of the sample eight tenths of the sample were badly cracked were very cracked 6-ethoxy-2,2,4-tri-methy] dihydroquinone Hn A. very few cracks; five tenths of the sample good condition were badly cracked o-ethoxy ^^^ - tri-methyldihydroquinoline B. very few cracks; six tenths of the sample good condition were very cracked 6-ethoxy-2,2,4-tri-methyldihydroquinoline C. perfect six tenths of the sample were very cracked

It can be seen from the table that only the vulcanizate containing the combination of N-isopropyl-N'-phenyl-p-phenylenediamine together with the wax mixture C (with a large proportion of microcrystalline wax), both after long static as well as after long dynamic

Try was outdoors in perfect condition. All other vulcanizates were at one or the other or both attempts were very cracked. The significantly better results obtained if the wax mixture C was combined with the N-iso-propyl-N'-phenyl-p-phenylenediamine, are completely unexpected, as the wax C does not show any superiority over the other two waxes A and B when used alone.

Example 2

A tread compound is made from the following components:

150 parts of butadiene-styrene copolymer with
50 parts furnace black with high abrasion resistance,

2.5 parts zinc oxide,

2 parts zinc laurate,

3 parts of petroleum oil containing naphthenic acids, 7 parts of a plasticizer based on saturated, polymerized hydrocarbons obtained from petroleum,

2 parts sulfur,

1.5 parts of mercaptobenzothiazole and

0.2 parts diphenylguanidine.

1 part each of the wax mixtures A, B and C described in Example 1 are used alone or in combination incorporated into the tread compound with 2 parts of the ozone protection agent given in Table II. The vulcanizates are subjected to the same static and dynamic loads as they are in Example 1 described are subjected.

Table II

wax Condition after 356 days State after 29.4 mega- Anti-ozone agents static storage cyclen bend none outdoors outdoors None completely cracked more than half of the A. 114 days The sample was very cracked None three tenths of the sample more than half of the B. were badly cracked The sample was very cracked None two tenths of the sample more than half of the C. were badly cracked The sample was very cracked None two tenths of the sample more than half of the none were badly cracked The sample was very cracked N-isopropyl-N'-phenyl-p-phenylenediamine perfect two tenths of the sample A. were badly cracked N-isopropyl-N'-phenyl-p-phenylenediamine perfect a tenth of the sample was B. severely cracked N-isopropyl-N'-phenyl-p-phenylenediamine perfect two tenths of the sample C. were badly cracked N-isopropyl-N'-phenyl-p-phenylenediamine none perfect perfect 6-ethoxy-2,2,4-tri-methyldihydroquinoline four tenths of the sample more than half of the A. were very cracked The sample was very cracked 6-ethoxy-2,2,4-tri-methyldihydroquinoline almost no cracks; two tenths of the sample B. good condition were badly cracked 6-ethoxy-2,2,4-tri-methyldihydroquinoline almost no cracks; three tenths of the sample C. good condition were badly cracked 6-ethoxy-2,2,4-tri-methyldihydroquinoline perfect three tenths of the sample were badly cracked

The results obtained are summarized in Table II:

The results show that again only the combination of N-alkyl-N'-phenyl-p-phenylenediamine with the wax mixture C, which has a high content of microcrystalline wax, is able to produce a Mixture containing butadiene-styrene rubber during long periods of static or dynamic stress protect outdoors.

Example 3

There were comparative tests with the ozone protection agent mixture used according to the invention and known anti-aging agents used in Example 1 carried out as follows:

The following rubber mixture was used for the tests:

Natural rubber 100

Very highly abrasion-resistant furnace black 45

Zinc oxide 5

Zinc laurate 3.5

Pine tar 3.5

Antioxidants like

specified

Sulfur 2.25

N-isopropyl-bis- (2-benzothiazyl-

sulfen) amide 0.5

Mixtures of this composition are vulcanized for 45 minutes at 14 ° C.

Table III Appearance after 88 days of static outdoor storage

None

1,5 N-isopropyl-N'-phenylp-phenylenediamine

1,5 N-isopropyl-N'-phenylp-phenylenediamine. + I ₅ O diphenylamine-acetone reaction product + 0.2 N, N'-diphenyl-p-phenylenediamine

1.0 diphenylamine-acetone reaction product + 0.2 N, N'-diphenyl-p-phenylenediamine

No wax

wet cracked

cracked

cracked

1.5 wax

cracked

immaculate condition

immaculate condition

cracked

Table IV Appearance after 12.2 megacycle flexion outdoors

None

1,5 N-isopropyl-N'-phenylp-phenylenediamine

1,5 N-isopropyl-N'-phenylp-phenylenediamine + 1.0 diphenylamine acetone reaction product

+ 0.2 N, N'-diphenylp-phenylenediamine

1.0 diphenylamine-acetone reaction product + 0.2 N, N'-diphenylp-phenylenediamine

no wax

heavily cracked flawless

perfect

cracked

1.5 wax

heavily cracked flawless

perfect

severely cracked

Similar results as with the N-isopropyl-N'-phenyl-p-phenylenediamine shown are obtained with others N-alkyl-N'-phenyl-p-phenylenediamines, which have 2 to 9 carbon atoms on the alkyl radical, obtained, for. B. with N-ethyl-N'-phenyl-p-phenylenediamine or N- (n-hexyl) -N'-phenyl-p-phenylenediamine.

Claims (1)

* Claim: Use of N-alkyl-N'-phenyl-p-phenylenediamines, in which the alkyl groups have 2 to 9 carbon atoms, in amounts from 0.5 to 5 parts by weight and petroleum wax, at least 60% of which consists of microcrystalline wax in amounts of 0.5 to 10 parts by weight as an anti-ozone cracking agent for Vulcanized products made from natural or highly unsaturated synthetic rubber, the Quantities are based in each case on 100 parts by weight of rubber. References considered: Rubber World, Vol. 130, pp. 636-642; Rubber Age, Vol. IT, pp. 705-715. 609 668/472 9.66 © Bundesdruckerei Berlin