CA1109894A - Method for preparing sterically hindered bis- or polyphenols - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A method for preparing sterically hindered bis- or poly-phenols of the formula:
R" - CH - R"' R' wherein R' is hydrogen, a C1-C4 alkyl, R" and R"' the same or different and are each:

or wherein R is a tertiary C4-C8 alkyl, R1 and R2 are the same or different and represent a C1-C8 alkyl or a C6-C8 cycloalkyl, or a C7-C9 aralkyl, which comprises reacting the starting sterically hindered 2,4,6-trialkylphenols of the formula:

wherein A is a C1-C8 alkyl or a C6-C8 cycloalkyl or a C7-C9 aralkyl or a 3,5-dialkyl-2-hydroxybenzyl of the formula:

B is a C1-C8 alkyl, or a C6-C8 cycloalkyl, or a C7-C9 aralkyl, or a 3,5-dialkyl-4-hydroxybenzyl of the formula:

Description

11~3989~

Field of the Invention -The present invention relates to methods for preparing sterically hindered bis- or polyphenols which are useful as effective non-colorating, non-toxic and low-volatile stabilizing agents for rubbers, vulcanizates, plastics and other organic products.
Said stabilizing agents can be exemplified by such a well known compound as 2,2'-methylene-bis-(4-methyl-6-tert.
butylphenol) produced under the trade marks "~ntioxidant 2246~, KAO -5, and the like.
Backqround of the Invention Known in the art are various methods for preparing sterically hindered bisphenols of polyphenols. For example, currently used is a method for preparing 2,2'-methylene-bis-(4-methyl-6-tert.butylphenol), wherein the desired product is prepared by alkylation of 4-methylphenol with isobutylene in the presence of a catalyst, followed hy separation and condensation of the resulting 2-tert.butyl-4-methylphenol with formaldehyde.
Condensa~ion is conducted in the presence of acidic ca-talysts such as sulphuric acid. The process is carried outin an aqueous emulsion containing a surfactant and an organic solvent at a temperature within the range of from 75 to 90C.
This prior art method has a disadvantage residing in a complicated technology of the process.

q~

11(~9894 Tha process is performed in two stages, a great amount o~ waste w3ters i8 formed (about 30 m3 per to~ o~ the product) which are contami~ated wit~ ~ur~aota~t~ and orga~iC solve~ts.
Besides~ a8 the starting product i~ the process use is made of p-cresol which is di~ficult to obtain.
Due to p-cresol bei~g a critical product, anothex met~od ~or the preparation o~ 2,2'-methyle~e-bis-(4-methyl-6--tert.butylphenol) from 2~6-ditert.but~1-4-m~thylphenol ha~
been developed, based on t~e production o~ the latter ra-ther readily ~rom cheap and easily available phe~ol. The process is based on dealkylatio~ of 2,6-di~ert.butyl-4-methylphenol, ~ollowed by separatio~ a~d co~deusation o~ the re~ulti~g

2-tert butyl-4-met~ylphenol with formaldehyde.
One of principal disad~antageE of tbis method also re-eides in the formatiou of a great amount of acidic waste waters co~taining surfactants a~d or~anic solve~ts. Puri~i-cation of suc~ waste waters on a commercial scale is rather complicated and eco~omically ine~ficient.
Also know~ in t~e art is a method for prepari~g 2,2'-methylene-bis(4-methyl-6-tert.butylphenol) which has certain advautages over t~e methods me~tio~ed hereinabo~e, since it makes possibls to elimi~ate the formation o~ waste waters.
Acoordi~g to this method, t~e desired product is obtained ~rom 2,6-ditert~butyl 'I-methylphenol ~ two sta~es, namely:
dealkylation o~ 2,6-ditert.butyl-4-methylphenol, ~ollowed by I

1~09~94 separation and condensation of the result ng 2--tert.b-utyl-4-methylphenol with an acetal in the pres~nce of a~ acidic catalyst a~ a temperature within the ran$e of from 30 to 14() C .
~ his prior art process as well as those described here-i~before are two-sta~ed and require separation, in pure form, of 2-tert.butyl-4-methylphe~ol havin~ a stro~g un-pleasant odour, high toxicity a~d volatility. Further~iore, a complicated process technology is required to perform all the above-discussed prior art methods.
Moreover, the prior art methods described hereinbefore make it possible to prepare snly bisphenols. A8 regards poly-phenols, know~ in the art are complicated multi-staged meth-ods of preparing same. For example, polyphenols are prepared by reacting paraalkylphenols with free ortho-pssitionq with chloromethyl derivatives of 2,6-dialk~lphe~ols according to th~ followi~g scheme:
t _ ~(C~ C~ , C~
~ J.s OJ3Ae ~ ~
Ou rC~ ~ C~c~sJ~
Sn C~4 C'(CIJ3)~ ~zC~ C r~3)~' ~(cU . ) OH

C~c/4~)3 ~ 8 9'~

Brie~ Summary of the I~vent on It is a main object of the pres~nt invention to simplify the process technology.
It is another object of the prese~t invention to incre-ase the desired product ~ield and quality as well as improve sanitar~ and hygienic co~ditio~s o~ work for th~ perso~nel-~ he main a~d other objects of the present inventio~ areaccomplished by that in the ~erein-proposed method for prepa-ri~g sterically hingered bis- or polyphenols of the formula:
R" - ~X - R"' Rl wherei~ R' i5 hydrogen or a C1-C4 alkyl~ R" and R"' bei~g either th~ same or different a~d each representing:
Q o~ Q C~ ~ q ~, o~ ~, C~ 40 ~C~ ~

~2 ~herein R is a tertiary C4-C8 alkyl, R1 and ~ ar~ the same or di~ferent and represe~t a C1-C8 al~yl or a C6-C8 cycloal- :
kyl, or a C7-C9 aralkyl, i~ wbich met~od according to the prese~t i~vention the starti~g sterically hindered 2,4,6-trial-kylphenols o~ the ~ormula:

B

" : :

9 8 9 ~

~herein A is a C1-C~ alkyl or a C6-C~ cycloalkyl, or a C7-Cg aralkyl or a 3,5-dialkyl-2-hydroxybenzyl of th~ ~ormula:
0~
~ ~ C~-B is a C1-C8 alkyl~ olr a C6-C8 cycloalkyl, or a C7-C9 ~ral-B kyl, or a 3,5 ~ ~4-hydroxybe~zyl o~ the ~ormula: Q~
~,~ ' C'f2 -wherei~ R is a tertiary C4-C8 alkyl, R1 is a C1-C~ al~yl, or a C6-C8 cycloaLkyl, or a C7-C9 aralkyl, are reacted with acetals, aldehyde~ or donors of C1-&5 aldehydes in a~ acidic medium at a temperature within the ra~Oe of ~rom 60 to 200C i~ the prese~ce of an acidi¢ ca-talyst, followed by isolatiou of the desired product.
As the acidic catalysts it is pre~erable to use 3rnstedt acids such as qulphuric acid, ortho-phosphoric acid, polyphos-phoric acid, perchloric acid, toluenesulphonic acid, ~aptha-leuesulphonic acid, catio~ite~ in H+ form a~d the like, or Iewis acids suc~ as i~c chloride, alumlDium chloride, ~erric chloride, boro~ tri~luoride and the like. ~hese catalysts axe readily separated ~rom the desired produ~t an~ e~ure a hioh yield thereo~, i.e. at least 78.7~ of t~e reacted starti~g 2~4,6-trialkylphe~ols, predomi~antl~ at least 95%
of the theoretical yield.

. -7-11~98~d~

As the acetals use is preferably made of commonly avail-able and simple in handling compounds of the formula:
R3-0(-CH-O~)n - R3, wherein R3 is Cl to C5 alkyl and R4 is hydrogen or Cl to C4 alkyl, n = 1 to 4.
Certain acetals comprise waste products from other syntheses, in particular, methylal is a waste product from the synthesis of isoprene rubber. Most preferable among acetals are methylal, ethylal, dipentylformal, however, use may be made of other acetals such as dimethylacetal, diethylacetal, diisopropyl-acetal and the like.
As aldehydes it is preferred to use acetaldehyde, pro-pionic aldehyde, butyric aldehyde, isobutyric aldehyde, valeric aldehyde, isovaleric aldehyde, because these comprise readily available and easy-to-handle reagents. It is also possible to use formaldehyde and other aldehydes.
As donors of Cl-C5 aldehydes in an acidic medium use can be made of cyclic polymers of aldehydes such as trioxane, paral-dehyde, 2,4,6-tri-isobutyl-1,3,5-trioxane, since these products are more stable upon storage and easier to handle as compared to monomeric aldehydes.
Among cyclic polymers trioxane is most preferred, since most valuable antioxidants are those sterically hindered bis-or polyphenols which have methylene bridges between aromatic rings.
As donors of C1-C5 aldehydes in an acidic medium use l39~

ca~ be also made of lin~ar polymers of aldehydes~ since the latter polymers just as cyclic polymers o~ aldehydes, are more stable upo~ s-torage. Paxaform is the most preferred linear polymeric ~ldehyde, since it, like trioxane, ensures incorporatior~ o~ methylene bridges in between aromatic ri~s thus providing ~or the formation of most valuable methylene-bisphenols or methylene-polyphenol~.
Detailed Disclosure of the Inventio~
The method according to the presant invention is per ~ormed in the following manner.
Into a four-neck reactor provided with a stirrer, ther-mometer, cooler, and a heating bath there are charged a steri-cally hindered 2,4,6-trialkylphe~ol such as 2,6-ditert. butyl--4-methylphenol, a~ acidic catalyst such as sulphuric acid or a cationite i~ H+ -form, or zinc chloride and the mi~ture is heated to a predatermined temperature under stirring. While maintai~in3 thifi temperature, into tke reactor, still under stirri~g for 0.5 - 2 hours, there is ~ed an acetal such as methylal, or a~ aldehyde such as acetaldehyde, or a donor of a C1-C5 aldehyde in an acidic medium, such as paraform.
The process temperature is maintained within tha ranve of from 60 to 200C. On completio~ o-~ the process~ the ca-ta-lyst is separated a~d the desired product is isolated by con-ventio~al techniques such as, for example, crys~allizatio~.

_9_ llQ9894 The yield of the desired products is as high as 78.7 to 99.1% of the theoretical, as calculated for the reacted ste-rically hindered 2,4,6-trialkylphenol, predorninantly above 95%;
for the most effective stabilizing agent, i.e. 2,2'-methylene-bis-(4-methyl-6-tert.butylphenol) the yield is as high as 97.8-99.1%. The method according to the present invention ensures the production of high-quality compounds. Thus, melting point of 2l2'-methylene-bis(4-methyl-6-tert.butylphenol) prepared by the method of the present invention is 131-131.5C (according to the literature data, m.p. of the product is 131-132C)~
The method according to the present invention features certain advantages over the prior art methods. The selected re-actants and conditions of interaction thereof ensure the pro-duction of the desired bisphenols or polyphenols from sterically hindered 2,4,6-trialkylphenols in a single stage, wherefore the process technology is substantially simplified and the sanitary and hygienic conditions of labour are improved, since no pure 4-methyl-2-tert.butylphenol possessing high toxicity, strong unpleasant odour and high volatility is evolved in the process.
High-quality products are obtained in the process requiring no additional crystallization. Bis-phenols or polyphenols can be obtained from monophenols following the method according to the present invention, by appropriately selecting the reaction condi-tions. The unreacted starting products are recycled back into the process. ~le -1.0--~110989~

tertiary olefines resulting from t~e reaction are u ed in the preparation o~ the starti~g sterically hindered 2,4,6-trialkylphenols. ~he method according to the prese~t invention completely eliminates the formation of waste ~aters and atmosp-here pollutants.
For a better understanding of the present inve~tion, some spcci~ic examples illustrating the method for preparin~
sterically hindered bis- and polyphenols are ~iven hereinbelow.
Example 1 Into a reactor provided with a stirrer, thermometer and a heating bath there are charged 220 g (1g.-mol) of 2,6-di-tert.butyl 'I-methylphenol~ 2.2. g of concentrated sulphuric acid and the mixture is heated to the temperature o~ 12~C.
i~hile maintaini~g the temperature at 120C, 94 g (1.24 g-mol) of methylal are ~ed into the reactor for 1.5 hour. On comp-letion of t~e reaction, the catalyst is separated, volatile products are distilled under vacuum to give 143.0 g o~ 2,2'-methylene-bi~4-methyl-6-tert.butylphenol) which corresponds to 97~% of theory calculated ~or the reacted 2,6-ditert.butyl -4-methylphe~ol (co~version degree o~ the latter is 86.0~).
A~ter a single recrystallizatio~ the resulting product has ~t~ melti~ point of 131-131.5C ~rom the literature data m.p. is 131-132C).
~ he unreacted 2,6-ditert.buty~-4-methylphenQl and methyl-al are recycled back into the proce~s.

~ample 2 Into a relctor similar to that d~scribed in F~ample 1 hereinabove there are charged 22~ g (1 ~-mol) of 2,6-ditert.-~utyl-4-methylphenQl, 2~2 g o~ co~centrated sulphuric acid and at the temperature of 1~C 76 g (1.0 g-mol) of ~thylal are fed i~to the reactor for 1 hour. The reaction mass is trea-ted following the procedure described in the ~oregoing Exa~ple 1 to give 112.9 g of 2,2'-methylene-bis-(4-methyl-6 tert.butyl-phenol) which co~stitute~ 99.1% o~ theory, as calcula~ed for the reacted 2,6-dltert.butyl-4-methylphenol (conversion o~ th~
latter is 67.0O . ~he u~reacted methylal and 2~6-ditert.butyl--4-methylphe~ol are recyclad back into the process.
Example 3 Into the reactor described in the foregoi~g Example 1 t~ere are charged 220 g (1.0 g-mol) of 2,6-ditert.butyl-4-methylpheuol, 2.2 g o~ sulphuric acid and 44 g (1 g-mol) of acetaldehyde are fed i~to the reactor ~or one hour at the temperature of 125C. 0~ completio~ o~ t~e reaction, the reaction mass is treated ~ollowi~g the procedure described in tha ~oregoing Example 1 to give 124.6 g of 1,1,-(5-methyl-

3-tert.butyl-2-hydroxypheuyl)etha~e which constitutes 95.4%
of theory, as calculated for the reacted 2,6-ditert.butyl-4--methylphenol (couversion o~ the latter iP 73%).
A~ter a single recrystallization the resultinæ product has its melting poi~t of 1U4-104.5C (~ro~ the literature data m.p. o~ the product i~ 104.5C).

11~398~4 The unroac-ted 2,6-ài~ert.bu~yl-4-met~ylphenol a~d acct-aldehyde are recycled back i~to the process.
~ xample 4 Into the reactor de~cribed i~ Ex~mple 1 hereinbefore there are char~ed 212 g (0~5 g-mol) of 4,4'-m~thylene-bis-(2,6-ditert.butylphenol), 8.4 g of zinc chloride and 10 g (O.111 g-mol) of trioxane are added to the mixturé o~er 3 minutes at the temp~ra~ure o~ 200C. On completion of the reaction, the catalyst is separated, volatile products are distilled u~der vacuum to give 193.7 g o~ 2,2'-methylene-bis- ~4-(3,5-ditert.butyl-4-hydrox~benzyl)-6-tert.butylpheno~
i~ the form o~ a resi~ having molecular wei~ht of 736 (the theoretical molecular wei~ht o~ the condensation product is 748)-Example 5 Into the reactor described in the foregoing Example~there are charged 170 g (0.5 g-mol) of 2,2'-methylene-bis-(4-meth~1-6-tert.butylphenol), 34 g of a cation-exchange resi~ in H+-form (sulp~onated copolymer o~ styrene with diYinylbenzene) a~d at tha temperature of 16~C 8.2 g (~.26 g-mol) of para~orm (calculated for the 95% product) are added to the reaction ~ass over one hour. On completion of ~he reactio~, the catalyst is separated, volatile products are distilled u~der vacuum to ~i~e 141.9 g o~ a resi~ con-taining 46.1% by weight o~ the condensat~on product, i.e.
2,2' methylene-bis- r4-methyl-6~(3-tert.butyl-5-methyl-2-1~U~ 8~

hydroxybenzyl~phcnol~ a~d 53 9% by wcight of t~e starti~g product. ~he thus-obtain~d resin can be used a8 a~ antioxi-da~t.
Exal~ple 6 Into the reactor d~scribed in Example 1 herein~efore there are charged 282 g (1 g-mol) o~ 2,4,6-tritert.butylp~enol, 9 g o~ a concentrated sulphuric acid and 110 g (1.17 g-mol) of dipentylformal are i~troduced into the reactor over 2 hours at the temperature of 60C. On completio~ of the reac-tion, the catalyst is separated, volatile products are distil-led under vacuum to give 120.7 g of the desired prcduct, i.e.
2,2'-methylene-bis-(4,6-ditert.butyl_phenol) ~hich constitu-tes 98.2% of t~eory, as calculated ~or the reacted 2,4,6-tritert.but7lphenol (conversion of the latter is 53%).
After a single recrystallizatio~ the re~ulting product has its melting poi~t o~ 141-142C.
~ he u~reacted 2,4,6-tritert.butylphenol and dipe~tyl-~ormal are recycled back into tho process.
Example 7 I~to t~e reactor described i~ Example 1 hereinbefore the-re are charged 155 g (0.5 g-mol) of 2,6-ditert.butyl-4- ~ -methylbenzene,phenol, 3.2 g o~ para-toluenesulpho~ic acid and 21.9 g (0.255 ~-mol) of isovaleric aldehyde are added thereto at the temperature o~ 150C over 1.5 hour. 0~ completio~ of the reaction, the catalyst is separated, volatile products are distilled under vacuum to give 12Q.9 ~ of 1,1-(6-tert.
butyl-4- ~-methylbe~zylphe ol)i~opentane which corresponds to .

1~9894 95.8% of theory, as calculated ~or the reacted 2,6-ditert.
butyl-4~ ethylbenzylphenol (conversio~ of the latter is ~0) ~ample 8 In~o the reactor described i~ ~ampla 1 hereinbefore there are charged ~30 g (1. 5 g-~ol) ol 2,~-d~ ~r~.butyl-4-methylphenol, 6. 5 g o~ concentrated sulphuric acid and 152 g (2 g-mol~ o~ ~ethylal are added thereto over 2 hours at the temp0rature of 150C. On completion o~ the react~on, the cata-lyst is separated, volatile products are distilled under ~a-cuu~ to give 200.3 ~ of the desired product, i.e. 2,6-di-~5--methy1-3-tert.butyl-2 hydro~ybenzyl)-para-cresol which co~s-titutes 87.1~ of tbe theory as calculated ~or the reacted 2,6-ditert.butyl-4-met~ylp~enol (co~versio~ of tbe latter is 1 00%) ~
After recrystallizatlo~ the thus-prepared product has its melti~g point of 163-163.5C.
Example 9 Into the reactor described in Example 1 there are char-~d 22~ g (1Ø g-mol) of 2,6-ditert.buty~-4-methylphenol, 11 g o~ ortho-phops~oric acid and 66 g (1.5 g-mol) o~ acetal-dehyde are added there-to at the temperature o~ 150C over one hour. On co~pletion Q~ the reactiou, the catalyst is se-parated, volatile products are distilled under ~acuu~ to gi~e 210 ~ o~ a ~ixture of 1,1-(5-met~y1-3-tert.butyl-2-h~d-roxyphenyl)ethane and 2~6-di-(5-m~t~yl-3-tert.butyl-2-~ydro-Yymet~lbenzy:~para-cresol. ~e resultir~ mixture can be used .

1~39894 without any separatio~ as an antioYidant. Co~version of 236-ditert . butyl~-methy~phenol i8 99%.

Example 10 Into th~ reactor described in Example 1 hereinbefore there are charged 12~ g (0.5 g mol) o~ 2-tert.butyl-6~c~clo-~exyl 'I-~ethylphenol, 42.2 g o~ a concentrated sulphuric acid and the mixture is heated at the tempera~ure o~ 120C
Then at this temperature 47 g (1.12 g-mol~ of m~thylal are added into the reactor over 1.5 hour. On completio~ of the reaction, the catalyst is separ~ted, volatile products are distilled under vacuum to give 163.1 g o~ 2,2'methylene-bis-(4-methyl-6-cyclohexylphenol) which constitute~ 99.1%
of theory, as calculated ~or the reacted 2-tert.butyl-6-cyclo-hexyl 'I-methylphenol (conversion o~ the latter is 84%).
After recrystallization the resulti~g produot has its melting point of 117-117.5C.
~ he unreacted 2-tert.butyl-6-cyclo~exyl-4-methylphenol and methylal are recycled bac~ into the process.
Exa~ple 11 Into the raactor described in Example 1 hereinbe~ore there are charged 159 g (0.5 g-mol) of 2,6-ditert.butyl-4-tert.octylphenol, 2 g o~ concentrated sulphuric acid and 36 g (0.5 g-mol) o~ bu~yric aldehyde are added into the reac-tor at the temperature o~ 125C over one hour. 0~ completion o~ the reaction, the catalyst is separated, volatile products are distilled under vacuum to give 1~.3 g of the desired pro-389~

dllct, i.e. 1,1-(3-tert.butyl-5-tert.octyl-2-hydroxyphenyl)butane which corresponds to 95.3% of theory, as calculated for the reacted 2,6-ditert.bl1tyl-4-tert.octylphenol (conversion of the latter is 75.0%).
Ihe unreacted 2,6-d;tert.butyl-4-tert.octylphenol and hutyric alclehyde are recycled back into the process.
Example 12 Into the reactor described in Example 1 hereinbefore there are charged 234 g (1 g-mol) of 2-tert.octyl-4,6-xylenol, ~,4 g of a concentrated sulphuric acid and 76 g (1 g-mol) of methylal are added thereto at the temperature of 100C over one hour. I~e reaction mass is treated following the procedure of the foregoing Example 11 to give 63.5 g of the desired product, i.e. 2,2'-methylene-bis-(4,6-dimethylphenol) which constitutes 81.1% of the theoretical yield as calculated for the reacted 2-tert.-octyl-4,6-xylenol (conversion of the latter is 61.2%).
The unreacted 2-tert.octyl-4,6-xylenol and methylal are recycled back into the process.
Example 13 Into the reactor described in Example 1 hereinbefore there are charged 58.5 g (0.25 g-mol) of 2,6-ditert.butyl-

4-ethylphenol, 1 g of a concentrated sulphuric acid and 19 g (0.25 g-mol) of methylal are added into the reactor at the temperature of 130C over 30 minlltes. The reaction mass is treated and 26.2 g of 2,2'-methylene-bis-(4-ethyl-6-tert.butyl-phenol) are thus obtained which corresponds to 98.9% of the theoretical yield calculated for the reacted 2,6-ditert.butyl--4-ethylphenol (CQnversion of the latter is 57.5).

.~, ~ -17-98g~

After a single recrystallization a product is obtained which melts at 124.5-125.0C.
The unreacted 2,6-ditert.butyl-4-ethylphenol and methyl-al are recycled back into the process.
Example 14 Into the reactor described in the foregoing Example 1 there are charged 141.0 g (0.5 g-mol~ of 2-tert.butyl-4-methyl-6-cumylphenol, 1.5 g of a concentrated sulphuric acid and 52 g (0.5 g-mol) of eth~lal are added to the mixture at the temper-ature of 130C for one hour. On completion of the reaction, the catalyst is separated, the unreacted 2-tert.butyl-4-methyl-6-cumylphenol and ethylal are distilled under vacuum to give 62.5 g of the desired product, i.e. 2,2'-methylene-bis-(4-methyl-6-cumylphenol) which constitutes 78.7% of the theoretical yield calculated for the reacted 2-tert.butyl-4-methyl-6-cumylphenol (conversion of the latter is 68.5%). The unreacted products are recycled back to the process.
Example 15 Into the reactor described in the foregoing Example 1 there are charged 70.5 g (0.25 g-mol) of 2-tert.hexyl-4-methyl--6-benzylphenol, 20 g of a cation-exchange resin in H -form (sulphonated copolymer of styrene with divinylbenzene) and 17.4 g ( b . 3 g-mol) of propionic aldehyde are added into the reactor at the temperature of 145C over 30 minutes. On completion of the reaction, the catalyst is separated, volatile products are distilled under vacuum to give 31.4 g of 1,1-(5-methyl-3-benzyl-2-hydroxyphenyl)propane which constitutes 91.1% of the theoretical yield calculated for the reacted 2-tert.hexyl-4-methyl-benzylphenol (conversion of the latter is 63.2%).
The unreacted 2-tert.hexyl-4-methyl-6-benzylphenol and propionic aldehyde are recycled back to the process.

Claims (9)

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

1. A method for preparing sterically hindered bis- or poly-phenols of the formula:
R" - CH - R"' R' wherein R' is hydrogen, a C1-C4 alkyl, R" and R"' the same or different and are each:

or or wherein R is a tertiary C4- C8 alkyl, R1 and R2 are the same or different and represent a C1-C8 alkyl or a C6-C8 cycloalkyl, or a C7-C9 aralkyl, which comprises reacting the starting sterically hindered 2,4,6-trialkylphenols of the formula:

wherein A is a C1-C8 alkyl or a C6-C8 cycloalkyl or a C7-C9 aralkyl or a 3,5-dialkyl-2-hydroxybenzyl of the formula:

B is a C1-C8 alkyl, or a C6-C8 cycloalkyl, or a C7-C9 aralkyl, or a 3,5-dialkyl-4-hydroxybenzyl of the formula:

and R1 and R are as identified above, is reacted with acetals, aldehydes or donors of aldehydes C1-C5 in an acidic medium at a temperature of from 60 to 200°C in the presence of an acidic catalyst, followed by isolation of the desired product.

2. A method according to Claim 1, wherein as the acidic catalyst Lewis acids or Bronstedt acids are used.

3. A method according to Claim 1, wherein as the acetals use is made of a compound of the formula R3-O (-??-O)n - R3, wherein R3 is C1 to C5 alkyl and R4 is hydrogen or C1 to C4 alkyl, n = 1 to 4.

4. A method according to Claim 3, wherein as the acetals use is made of the acetals selected from the group consisting of ethylal, methylal or dipentylformal.

5. A method according to Claim 1, wherein as the aldehydes use is made of acetaldehyde, propionic aldehyde, butyric aldehyde or isovaleric aldehyde.

6. A method according to Claim 1, wherein as the donors of C1 - C5 aldehydes in an acidic medium use is made of cyclic poly-mers of aldehydes.

7. A method according to Claim 6, wherein as the cyclic polymer of an aldehyde use is made of trioxane.

8. A method according to Claim 1, wherein as the donors of C1-C5 aldehydes in an acidic medium use is made of linear polymers of aldehydes.

9. A method according to Claim 8, wherein as a linear poly-mer of an aldehyde use is made of paraform.