CA1083606A - Process of preparing para styrenated diphenylamine. - Google Patents

Abstract

INVENTOR: Vipin M, Kothari INVENTION: PROCESS OF PREPARING PARA STYRENATED
DIPHENYLAMINE

Abstract of the Disclosure Styrenated diphenylamine with high or increased para substitution is prepared by reacting styrene with diphenylamine 1n the presence of an acidic clay catalyst at high temperatures, i.e., from about 185° C. to 275° C.

Description

This invention relates -to the prepara-tion of para styrenated diphenylamine. More par-ticularly it relates to the use of acidic clays in the prepara-tion o~
para styrenated diphenylamine.
The prior art reveals the preparation of ~-methyl styrenated diphenylamines, e.g., U.S. Patent 3,505,225, and the use of said compounds as antioxidants. Diphenylamine when substituted with styrene or ~-me-thyl styrene in either one or both of -the para positions will provide age resist-ance to materials susceptible to oxidative degradation which is superior to that offered by the ortho substituted diphenylamines. Although para subs-titution can be obtained when alkylating diphenylamine with a-methyl styrene at low temperatures, e.g, from about 120C. to 150C., using acidic clays, very low amounts of para substitution result when one atte~pts to react styrene, rather than a-methyl styrene, with diphenylamine at these low temperatures. A
process which would provlde increased amounts of para sty-renated diphenylamine is desirable.
The present invention provides a process for producing s-tyrenated diphenylamine containing a substant- ;
ial amount of p-substituted diphenylamine comprising reacting a combination comprising (a) diphenylamine and (b) styrene in the presence of a catalytic amount of an 25 acid activated clay catalyst containing a major amount of ;
~ aluminum hydrosilicate, at a reaction tempera-ture of from ;, 170C. to 300C. wherein the level of styrene is from 1 to ~ 2.5 moles per mole of diphenylamine.

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The present invention also provides a process for producing a styrenated diphenylamine wherein the ~-methylbenzyl substi-tuent i5 selected from either or both of the para posi-tions.
Further, according to the present invention the preferred process incorporates a reaction temperature of from 185C. to 275C., a more preferred temperature is from 200C. to 250C.

-lA-~L0836~6 Preferably 1.5 to 2 moles of styrene are charged per 1 mole of diphenylamine.
The acidic clay used in the practice of the present invention is extremely well known in the art as Montmorillonite clay catalyst and is prepared from mineral, Montmorillonite. A major amount of the acid clay is com-- posed of aluminum hydrosilicate. The ~eneral composition is of the type M[~102)X(SiO2)y]-ZH20 where M is metal cation selected from K*, Na+, Ca+2, Fe+2~Fe+3~ etc. and Z is the number of moles of water of hydrotion. The activity of the clay catalyst is dependent upon several factors such as the particle size~ moisture content, sur~ace area, acidity, etc.
A typical clay composition would be as follows.
ComponentWei~ht Percent SiO2 70 - 75 Fe203 CaO - 15 Examples of these catalysts are the activated Montmorillonite catalyst of the K series produced by Chemetron Corporation, and activated clay adsorbents of Filtrol Corporation.
The reaction products of the present invention are a mixture of p-monostyrodiphenylamine and p,p'-distyryl-diphenylamine. Alpha-methyl styrene can be substituted for a portion of the styrene but the styrene should always com-prise at least 50 percent of the molar amount of the ole-finic portion o~ the reaction system.
The reaction may be accomplished batchwise or on ~LCi8360~
a continuous basis at various pressures, including atmos-pheric pressure. The product is an effecti~e antioxidant which can be used in the stabilization of materials subject to oxidation degradation, particularly diene rubbers such as butadiene/nitrile rubbers, at elevated temperatures.
The clay catalysts are used and preconditioned in a conventional manner, e.~., water is removed preferably from the clay catalyst prior to use, for example, by azeo-tropic distillation of benzene. Alternatively water can also be removed by predrying the product at 100 C. to 200 C. in an o~en. In such a situation, no solvent is necessary.
In a typical operation styrene is added slowly to a hot mixture of diphenyla~ine and the catalyst at the desired reaction temperature~
The amount of catalyst is not critical to the ; practice of the invention. ~aturally9 as with any process, the catalyst level can be reduced to such a low level that the reaction rate will either be extremely low or nil. As a guideline7 but not a limitation, at least 8 parts by weight of catalyst should be used per 100 parts by weight of diphenylamine. More preferably at least 10 parts by ; - weight should be used. There is no upper limit on catalyst level. For example, 100 parts of catalyst or more can be used. However, merely as a practical matter, the amount of catalyst should not exceed 20 or 25 parts.
It should be noted that some-times the addition of an acid will increase -the effectiveness of some catalysts.
The following example illustrates but does not limit the practice of the present invention.

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- 10836i06 All of the catalysts were of the generic structure described earlier herein.
Exam~le 1 -A mixture of 50 grams of diphenylamirle~ 8 grams of montmorillo~ite clay catalyst (Girdler designation KS ~
and 180 milliliters of benzene was heated to reflux temper-ature with stirring. Water (0.3-0.5 milliliters) was re- ;~
moved from the catalyst by azeotroping it out with benzene.
Enough benzene was then removed to allow the pot to reach the desired temperature. About 95-98 percent (175 milll-liters) needed to be removed to add styrene at 220-225O C.
Fifty-rour grams o~ styrene was added during 30 minutes5 the mixture was stirred for an additio~al one to two hours at 2Z0 C. Although not necessary to the success o~ the process~ the reaction mixture containing styryldiphenyl-- amines was left over the catalyst overnight at room temper-ature. The mixture was heated the ne~t day~ cooled to 90-lOOo C. and filtered hot on a steam heated ~unnel to remove solid catalyst. The flltrate is a dark or light amber viscous product. The identity of the components of the viscous product was done by gas chromatography and the components identified primarily as mono- and distyryldi-phenylamlne. m is product can be used as is as an anti-oxidant. Howev~r~ it is desirable to strip of~ lights (unreacted dlphenylamine, styrene, dimer of styrene~ etc.) by heating the viscous li~uid at 200-2500 C. under 1-10 mlllimeters vacuum for two hours to obtain improvement in act~vity.
Example 1 was repea-ted using various molar xatios of styrene to diphenylamine, reaction temperatures, 1 [)8361~6 catalysts and amounts of catalys-ts and at different rates of styrene addition. Different solvents, i.e.~ dichloro-benzene and toluene were also evaluated. ~hese variables along with -the results obtained~ i.e.~ amount of total alkylation and amount of selective para subs-titution, are shown in the following tables.

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( ~836~6 ~ S ~, KSF/ ~, K-l ~ and K-30 ~are produced by the Catalysts Di~ision of Chemetron Corporation and are based on the mineral Mon-tmorillonite. All but K-306 are powdered.
K-30~ is in spherical form.
- ~ Runs 7, 8, 15 and 16 in Table II are illustra-tions of attempts to prepare styrenated diphenylamines using reaction conditions outside the scope of the present invention. As indicated by the percent para substituted diphenylamine and in some cases even the total percent conversion, i.e., percent alkylation, the conditions of the process of the present invention are quite important in obtaining high values, particularly of para subs-titution.
Runs 7~ 8 and 9 indicate the importance of reaction temperature. Run 15 indicates the importance of ~ .
~ the catalyst being in a form which provides adequate - catalyst surface area, e.g.~ powdered form.
While certain representative embodiments and details have been shown ~or the purpose of illustrating the invention, it will be apparent to those skilled in 2a this art that various changes and modifications may be made therein without departin~ from the spirit or scope of the inVention.

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Claims (3)

The embodiments of the invention in which an exclusive.
property or privilege is claimed are defined as follows:

1. A process of preparing styrenated diphenyl-amine containing a substantial amount of p-substituted diphenylamine comprising reacting a combination comprising (a) diphenylamine and (b) styrene in the presence of a catalytic amount of an acid activated clay catalyst containing a major amount of aluminum hydrosilicate, at a reaction temperature of from 170° C. to 300° C. wherein the level of styrene is from 1 to 2.5 moles per mole of diphenylamine.

2. The process of claim 1 wherein the reaction temperature is from 185° C. to 275° C. and the level of styrene is from 1.5 to 2 moles per mole of diphenylamine.

3. The process of claim 2 wherein the reaction temperature is from 200° C. to 250° C.