IE45388B1 - Preparation of sterically hindered polyphenols - Google Patents

Abstract

Sterically hindered bisphenols or polyphenols of the general formula wherein the substituents are defined in Claim 1, are obtained by reacting sterically hindered 2,4,6-trialkylphenols with acetals or with aldehydes or with cyclic or linear polymers of these aldehydes at a temperature of 60 to 200 DEG C in the presence of an acid catatlyst. The sterically hindered bisphenols or polyphenols may be used, for example, as effective, non-staining, non-toxic and low-volatility stabilisers for natural and synthetic rubbers, plastics and other organic products.

Description

The present invention relates to a process for the preparation of sterically hindered bis- and higher poly- phenols, which are useful as stabilizers for robbers, vulcanizates, plasties and many other organic products.

Tktse sterically hindered polyphenols are generally non-toxic and have low volatility. They are, therefore, of considerable value in preventing the discolouration of various organic products caused byexposure to light and specifically to ultraviolet light.

An example of such a compound is 2, 2'-methylenebis(4-methyl-6-t-butylphenol), which may be obtained undersuch trade names as ’’Antioxidant 224G” and KAO-5.

Various methods are known for preparing these sterically hindered polyphenols, for example, a method which is currently used for producing 2, 2'-methylenebis(4-methyl-6-t-butylphenol) comprises alkylating 4-methylphenol with isobutylene in the presence of a catalyst and then separating the resulting 4-methyl-2-1-butylphenol and condensing it with formaldehyde. The condensation is effected in the presence of an acidic catalyst (such as sulphuric acid) and the process is 2, H 43368 carried out in an aqueous emulsion containing a surfactant and an organic solvent at a temperature in the range of from 7-5 to 90°C. This process has a number of disadvantages arising from the complex technology involved. Thus, the process is performed in two stages (which, as is well-known, should be avoided in commercial processes) and produces a large quantity of waste water (generally about 30 cubic metres per ton of product) contaminated with surfactants and organic ' solvents,. Moreover, the starting material for the process, 4-methylphenol (g-cresol) is difficult to obtain.

Since p-cresol is a critical material for the process described above, another method for preparing IS 2, 2’-methylenebis{4-methyl-6-t-butylphenol) has been developed, this time starting from 4-methyl-2, 6-di-tbutylphenol, which can readily be obtained from the cheap and easily available phenol. This process involves dealkylating the 4-methyl-2, 6-di-t-butylphenol and then separating the resulting 4-methyl-2-t-butylphenol and condensing it with formaldehyde. One of the principal disadvantages of this method, like the previous method, is the large amount of acidic waste 3. 'ΐ S 3 ϋ S water containing surfactants and organic solvents which is produced. Purification of euch waste water on a commercial scale is rather complicated and economically is inefficient.

Another method having certain advantages over the previous iwo methods described above is also known.

In this method, the desired 2, 2'-methyienebis(4-methyl-Gt-butylphenol) is obtained from 4-methyl-2, G-di-t-butylphenol in two stages, namely; dealkylation of 4-methyl10 2,6-di-t-butylphenol; and then separation of the resulting 4-methyl-2-t-butylphencl and condensation of it with an acetal in the presence of an acidic catalyst at a temperature of from 30 to 3s0°C. Although this process does not have the disadvantage of producing large quantities IS of waste iraler, it shares with the previous tv/o processes discussed the disadvantage that it is a two-stage process involving the intermediate separation of 4-methyl-2-t-butylphenol, which has a strong and most unpleasant odour, high toxicity and high volatility. Furthermore., complicated process technology is required to carry out all of these methods.

A further disadvantage of all of these known methods 4, --, 45383 is that they are only useful for the preparation of bisphenols. Higher polyphenols must be prepared by complicated multistage methods, for example by the reaction of p-alkylphenols having a free ortho - position with a chloromethyl derivative of a 2,-6-dialkylphenol according to the following reaction scheme: Steph Step 2; HC1, CH2O , Step 8: This, however, is a complicated and expensive process.

We have now surprisingly found that, by proper 5 selection of reagents and conditions, sterically hindered polyphenols can be produced in high yield in a simple one-stage process. 6. f 45383 Thus, the present invention consists in a process for preparing a sterically hindered polyphenol of formula (I): F~CH~RW(I) k' [in which R1 represents a hydrogen atom or an 5 alkyl group having from 1 to 4 carbon atoms; and R*1 and R111 are the same or different and each represents a group of formula ; OH or 7, ‘1535 8 HO—(Q Ο/-°H (in which; R represents a tertiary alkyl group having' 2 from 4 to 8 carbon atoms; and R and R are the same or different and each represents an alkyl group having from 1 to 8 carbon atoms, a cycloalkyl group having from 6 to 8 carbon atoms or an aralkyl group having from 7 to 9 carbon atoms)^, which comprises reacting, in an acidic medium at a temperature of from 60 to 200°C in the presence of an acidic catalyst, a sterically hindered phenol of formula (II): OH 8.

On which; A represents an alkyl group having from 1 to 8 carbon atoms,'.a cycloalkyl group having from to 8· carbon atoms, an aralkyl group having from to 9 carbon atoms or a 2-hydroxybenzyl group of formula; qjj represents an alkyl group having from 1 to 8 carbon atoms, a cycloalkyl group having from 6 to 8 carbon atoms, an aralkyl group having from 7 to 9 carbon atoms or a 4-hydroxybenzyl group of formula: (in which R and R are as defined aboveQ with an acetal, aldehyde or C^-Cg aldehyde precursor.

As the acid catalyst, we prefer to use a 9. 3 ίϊ 3 .

. Bronsted acid (such as sulphuric acid, orthophosphoric acid, polyphosphoric acid, perchloric acid, toluenesulphonic acid or napthalenesulphonic acid), a cation exchanger in H form, or a Lewis acid (such as zinc chloride, aluminium chloride, ferric chloride or boron trifluoriae).

These catalysts are readily separable from the desired product and ensure that the desired product is obtained in a high yield, generally at least 78 % of the theoretical yield and often at least 95 % of the theoretical yield, calculated on the basis of the reacted alkylphenol of formula (II).

The acetal used is preferably chosen to be commonly available and simple to handle, for example a compound of formula (HI): (Ill) represents an alkyl group having from 1 to 3 carbon atoms and n is a number from 1 to 4), Certain acetals are commonly available as waste products from , other syntheses and these are particularly preferred; in particular, methylal is a waste product from the synthesis of isoprene rubber. Of the acetals the most preferred are methylal, ethylal and dipentylformal; however, other . acetals, such as dimethylacetal, diethylacetal and diisopropylaeetal, may also be used.

Preferred aldehydes are acetaldehyde, propionaldehyde, butyraldehyde, isobutyraldehyde, valeraldehyde and isovale'raldehyde. Since these are readily available and easy to handle reagents. It is, however, also possible to use formaldehyde and other aldehydes.

The aldehyde precursors employed in the present invention are compounds which, under the conditions of the reaction, act as, or react to form, - Cg aldehydes,' Since the· process of the invention is carried out in an acidic medium, it is possible to use cyclic polymers of aldehydes, such as trioxan, paraldehyde and 2,4,6-triisobutyl-1,3,5-trioxan. These compounds are particularly preferred, since they are more stable on storage and are easier to handle than the monomeric aldehydes. Of the cyclic polymers, trioxan is the most preferred, since the most valuable polyphenol 11. 453:':· antioxidants are those sterically hindered polyphenols having methylene bridges between the aromatic rings.

It is also possible to use linear polymers of aldehydes as the aldehyde precursors since these, litre the cyclic polymers, are storage stable. Paraformaldehyde is the most preferred linear polymeric aldehyde since it, like tricxan, ensures the incorporation of methylene bridges between aromatic rings, thus providing the most valuable methylene-polyphenols, The process o the invention can be carried out as follows: A sterically hindered alkylphenol of formula (II) (such as 4 -methyl-2,6-di-t-butylphenol) and an acidic catalyst (such as sulphuric acid, a cation exchanger in H+ form or zinc chloride) are charged into a four-necked reactor provided vzith a stirrer, a thermometer, a cooler and a heating bath. The mixture is then heated to a predetermined temperature, with stirring.

Whilst maintaining this temperature, there is fed into the reactor an acetal (such as methyl»), an aldehyde (such as acetaldehyde) or aCj - Cg aldehyde precursor (such 12, 45383 . as paraform) and stirring is continued for a further 0.5-2 hours. The process temperature is maintained within the range of from 60 to 200°C.

On completion of the reaction, the catalyst is separated and the desired product is isolated by conventional techniques, e.g, crystallization.

The process of the invention enables the desired polyphenols of formula (I) to be obtained in relatively high yields; thus, in various experiments, we have achieved yields ranging from 78.7 to 99.1 % of theory, calculated on the reacted compound of formula (II).

Most commonly, the yields have been above 95 % and, for the most effective stabilizing agent, i. e. 2,2'-methylenebis(4-methjyl-6-t-butylphenol), the yield has ranged from 97.8 to 99,1 %. The process of the invention also has the advantage of giving very pure compounds. Thus, the melting point of 2, 2'-methylenebis(4-methyl-6-t-butylphenol) prepared by the process of the invention is 131 - 131, 5°C (the melting point according to the literature is 131-132°C), The process of the invention also has certain other advantages over known methods. Thus, the 13. •i ΰ 3 S β selected reagents and reaction conditions ensure the production of the desired polyphenols from sterically hindered alkylphenols of formula (II) in a single stage; this greatly simplifies process technology and improves safety and sanitary and hygiene conditions, since no 4-methyl-2-t-butylphenol (which is highly toxic and has a strong and unpleasant odour and high volatility) is evolved in the process. Highly pure products are obtained from the process without additional recrystallization. Bisphenols or higher polyphenols can be obtained from monophenols by the process oi -the invention by appropriate selection of reaction conditions. Unreacted starting materials can be recycled back to the start of the process. Tertiary olefins (which are byproducts in the r eaction) ear, be used In the preparation of the steriesliy hindered alkylphenols of formula (II) used as starting materials. The process of the invention also completely eliminates waste water and atmospheric pollution.

The invention is further illustrated by the following Examples, 14.

EXAMPLE 1 Into a reactor provided with a stirrer, a thermometer and a heating Bath were charged 220 g (1 mole) of 4-methyl 2, 6-di-t-butylphenol and 2. 2 g of concentrated sulphuric acid; the mixture was heated to a temperature of 120°C, Whilst maintaining this temperature, 94 g (1. 24 mole) of methylal were fed into the reactor over a period of 1.5 hours. On completion of the reaction, the catalyst was separated off and volatile products were distilled off under vacuum to give 143, 0 g of 2, 2'-niethylenebis(4-methyl-6-t-buiylphenol), corresponding to 97.8 % oi theory, calculated on the basis of the 4-methyl-2,6-di-t-butylphenol reacted; the degree of conversion of this compound was 86.0 %, After a single recrystallization, the'melting point of the product was found to be 131 - 131. 5°C (literature data gives the melting point as 131- 132°C).

The unreacted 4-methyl-2,6-di-t-butylphenol and methylal were recycled.

. EXAMPLE 2 Into a reactor similar to that described in Example 1 were charged 220 g (i mole) of 4-methyl-2, S-di-t-fcutylphenol and 2. 2 g of concentrated sulphuric acid; the mixture was heated to a temperature of 120°C.

Maintaining this temperature, 76 g (1. C mole) of meihylal were fed ir to the reactor over a period of 1 hour.

The reaction mass was then treated as described in Example 1 to give 112. 9 g of the desired 2, 2'-methylenebis(4-methyl-6~t-butyjphenol), constituting 33.1 % of theory, calculated cn the basis of reacted 4-methyl-2, 6-dit-butylphenol (conversion of the latter was 67. 0 %), The unreacted iriethv’al and 4-methyl-2, 6-di-i-butylphenol were recycled, EXAMPLE 3 Into a reactor similar to that described in Example 1, were charged 220 g (1 mole; of 4-methyl-2,6di-t-butylphenol and 2, 2 g of sulphuric acid and ths mixture was heated to 125 C. Maintaining this temperature, 44 g (1 mole) of acetaldehyde were fed into the reactor over a period of 1 hour.

IS.

On completion of the reaction, the reaction mass was treated as described in Example 1 to give 124, 6 g of 1,1-(2-hydroxy-5-methyl3-t-butylphenol)ethane, representing a yield of 96.4 % ι ι of theory, calculated on the basis of the reacted 4-methyl5 2,6-di-t-butylphenol (conversion of the latter was 73 %). ί 1 After a single recrystallization, the resulting i product was found to have a melting point of 104 - 104. 5°C (the melting point given in the literature is 104. 5°C), J Unreacted 4-methyl-2,6-di-t-butylphenol and j 10 acetaldehyde were recycled, EXAMPLE 4 Into a reactor similar to that described in Example 1 were charged; 212 g (0. 5 mole) of 4,4'-methylenebis(2, 6-di-t-butylphenol) and 8,4 g of zinc chloride; the mixture was heated to 200°C. Maintaining this temperature, 10 g (0. Ill mole) of trioxan were added to the mixture over a period of 30 minutes. On completion of the reaction, the catalyst was separated off, and volatile products were distilled off under vacuum 17. i53 to give 193, 7 g of 2, 2'-methylenebis £4-(4-hydroxy-3,. di-t-butylbenzyl)~6-t-butylphenolj in tho form of a resin having a molecular weight of 73G, The theoretical molecular weight of this condensation product is 748, EXAMPLE 5 Into a reactor similar to that described in Example 1 were charges 170 g (0.5 mole) of 2, 2'-methylenebis(4-methy!-6-t-bv.tylphenol) and 34 g of a cation J10 exchange resin m H form (a sulphonated copolymer of styrene with divinyibenzene); the mixture was heated to a temperatm, i ·..’ 1GO°C. Over a period of hour, there were then added to the mixture 8. 2 g (0. 26 mole, calculated for the 95 % product) of paraformalde15 hyde. On completion of the reaction, the catalyst was separated off and volatile products were distilled off under vacuum, to give 141. 9 g of a resin containing 46,1 % by weight of the condensation product, i,e. 2, 2'methylenebief 6 · (2-hydroxy-5-methyl- 3-t-butylbenzyl)-420 mcthylpiienolj and 53, 9 % by weight of the starting material. This resin can be used as an antioxidant. 18. iS388 EXAMPLE 6 , Into a reactor similar to that described in Example 1 were charged 282 g (1 mole) of 2,4,6-tri-tbutylphenol and 9 g of concentrated sulphuric acid; the mixture was heated to 60°C. Maintaining this temperature, 110 g (1.17 mole) of dipentylformal were introduced into the reactor over a period of 2 hours. On completion of the reaction, the catalyst was separated off and volatile products were distilled off under vacuum to give 120,7 g of the deeired product, i.e. 2,2*-methylenebis(4,6-di-t-butylphenol), representing a yield of 98.2 % of theory, calculated on the basis of the amount of 2,4,6-tri-t-butylphenol reactant (conversion of the latter was 53 %). After a single recrystallization, the resulting product was found to have a melting point of 141 - 142°C.

Unreacted 2,4, G-tri-t-butyiphenol and dipentylformal were recycled. 19. ϊ 3 3 8 8 EXAMPLE 7 Into a reactor similar to that described in Example 1 were charged 155 g (0, 5 mole) of 4-(u-methylbenzyl)-2,6-di-t-butylphenol and 3. 2 g of p-toluenesulphonic acid; the mixture was heated to a temperature of150°C. MMutaining this tamperatui’e, 21.9 g (0. 255 mole) of isovalaraldenyde were aoded to the mixture over a period cf 1.5 hours. On completion of'he reaction, the catalyst was separated off and volatile products were di^EHe-d oi: under vaeuum to give 120, 9 g oi 1, l-bis-{2-hydroxy-5-a-metdiylbeazyl-3t-butylphenyl)isopcn'i.ane, representing a yield of 85. 8 % of theory as calculated for the amount of 4-(ar-methylbenzyl)-2, 6 -di-i-butylphenol reacted {conversion of the latter was 38 %), EXAMPLE 8 Into a reactor similar to that described in Example 1 were charged 330 g (1,5 mole) of 4-methyl-2,6di-t-butylphenol and C. 3 g of concentrated sulphuric acid; the mixture was heated to a temperature of 150°C. . ¢5333 ; Maintaining this temperature, 152 g (2 mole) of methylal } ι were added to the mixture over a period of 2 hours, ι : ' On completion of the reaction, the catalyst was separated ί off and volatile products were distilled under vacuum i J 5 to give 200, 3 g of 2,6-di(2-hydroxy-5-methyl-3-t-butyl benzyl)-jp-cresol, This represented the yield of 87,1 % of theory, calculated on the basis of the amount of 4-methyl-2, 6-di-t-butylphenol reacted (conversion of the latter was 100%), After recrystallization, the product was found to have a melting point of 163 - 163.5°C.

EXAMPLE 9 { % Into a reactor similar to that described in Example 1 were charged 220 g (1,0 mole) of 4-methyl1S 2,6-di-t-butylphenol and 11 g of orthophosphorie acid; : · the mixture was heated to 150°C, Maintaining this temperature, 66 g (1. 5 mole) of acetaldehyde were added to the mixture over a period of 1 hour. On completion of the reaction, the catalyst was separated off and volatile products were distilled off under vacuum 21? -i 3 3 L' 8 to give 210 g of a mixture of 1,1-bis--fZ-hydroxy-S-mcthyl-3t-butylphenyl)ethane and 2, G-di-ftLiiydraxymeihyl-S-nneihyl3-t-butylbenzyl)-p-eresol, The resulting mixture can be used without any .separation as an anti5 oxidant. Conversion of 4-methyl-2, G- di--t-butylphenol was SO %, EXAMPLE 10 Into a reactor similai· to that described in Example 1 were charged 123 g (0.5 mole) of θ-cycloid hexyl-4-methyl-2-t-buiylphenol and 2, 2 g of concentrated sulphuric acid; he mixture was heated to a temperature of 120°C. Maintaining this temperature, 47 g (1,12 mole', <>f methyls,1 were added to the mixture over a period of 1.5 hours. On completion of the reaction, the catalyst was separated off and volatile products were distilled off under vacuum to give 163.1 g of 2, 2'-methylenetis(6-cyclohexyl-4-methylphenol), representing a yield of 99.1 % oi theory calculated on the basis of the amount of 5-cyclohexyl-4-metbyl-2-t-butylphenol reacted (conversion of the latter 84 %). 22. ,j 5 3 8 8 After recrystallization, the resulting product had a melting point of 117 - 117. 5°C. Unreacted 6-cyclohexyl-4-methyl-2-t-butylphenol and methylal were recycled to the process.

EXAMPLE 11 Into a reactor similar to that described in Example 1 were charged 159 g (0, 5 mole) of 2, 6-di-tbutyl-4-t-octylphenol and 2 g of concentrated sulphuric acid; while maintaining the temperature of the mixture at 125°C, 36 g (0,5 mole) of butyraldehyde were added to the mixture over a period of 1 hour. On completion of the reaction, the catalyst was separated off and volatile products were distilled off under vacuum to give 103, 3 g of 1,1-(2-hydroxy-3-t-butyl-5-t-octyl15 phenyl)butane. This represented a yield of 95.3 % of theory, calculated on the basis of the amount of 2, S-dit-butyl-4-t-octylphenol reacted (conversion of the latter was 75,0%),. ' Unreacted 2, 6-di-t-butyl-4-t-octyl· phenol and butyraldehyde were recycled. 23. i 3 5 ί EXAMPLE 3 2 Into a reactor similar to that described in Example 1 were charged 234 g (3 mole) of 2-t-octyl-4, 6xylcuol and 2,4 g of concentrated sulphuric acid; maintaining the temperature at 100°C, 76' g (1 mole) of methyl·.’ were added over a period of 1 hour.

The react, in mass was then treated as described in Example 11 to give G3. 5 g of 2, 2'-methylenebis(4, G-dimethylphenol). This represented a yield of 31.1 % of theory, calculated on Gts basis of the amount of 2-toctyl-4,6-xylznol reacted (conversion of the latter was 61.2 %).

Ur reacted 2-t-octyl-4, C-xylcnol and methylal were recycled, EXAMPLE 13 Into a reactor similar to tiiat described in Example 1 were charged 58. 5 g {0. 25 mole) of 4-ethyl2,6-di-t-butylphenol and 1 g of concentrated sulphuric :4. 45383 acid. Maintaining the temperature at 130°C, g (0. 25 mole) of methylal were added over 30 minutes. The reaction mass was treated as described in Example 11 to give 26, 2 g of 2, 2'-methylenebis(4-ethyl-6-t-butylphenol), a yield of 98, 9 % of theory calculated on the basis of the amount of 4-ethyl-2,6-di-t-butylphenol reacted {conversion of the latter was 57, 5 %).

After a single recrystallization, the melting point of the product was 124,5 - 125°C. Unreacted 4-ethyl-2, 6di-t-butylphenol and methylal were recycled.

EXAMPLE 14 Into a reactor similar to that described in Example 1 were charged 141.0 g (0.5 mole) of 6-cumyl4-methyl-2-t-butylphenol and 1.5 g of concentrated sulphuric acid; maintaining the temperature at 130°C, g (0.5 mole) of ethylal were added to the mixture over a period of 1 hour. On completion of the reaction, the catalyst was separated off and unreacted 6-cumyl-4-methyl-2-t-butylphenol and ethylal were distilled off under vacuum to give 62. 5 g of 2, 2'-methylenebis(6-cumyl-4-methylphenol).

This . ί03.: 8 represented a yield of 78,7 % of U.eory calculated on the basis of die amount of G-cumyl-4-nictnyj-2-t-buiy]p!icnol reacted (conversion of the latter was «8, 5 %).

Unreacted products were recycled.

EXAMPLE 15 Into a reactor similar to that described in Example 1 were charged 70.5 g (0.25 mole) of G-benzyl4-jnethyl-2-t-liexyIphenol and 20 g of a cation exchange resin in the II1 form 'a sulphonated copolymer of styrene 1θ with divinvlbenaene,·; maintaining the temperature at 145°C, 17.4 g (0. 3 mole) of propionaldehyde were added over a period 39 minutes. On completion of the reaction, the catalyst was separated off and volatile materials were distilled off under vacuum to give 31.4 g 1” of 1,1 - bis-(2-hydroxy-5-methyl-3-b«=nzylphenyl)propane.

This represented a yield of 91.1 % of theory, calculated on the basis of the amount of G-benzyl-4-methyl-2-t-hexylphenol reacted (conversion of the latter was 03. 2 %).

Unreacted 6-benzyl-4-methyl-2-t-hexylphenol θ and propionaldehyde were recycled.

Claims (5)

1. A process for preparing a sterically hindered polyphenol of formula (I): K-CH-R W (i • I, 5 Kn which: R* represents a hydrogen atom or an alkyl group having from 1 to 4 carbon atoms and R H and R' are the same or different and each represents a group of formula: (in which: R represents a tertiary alky] group having from 4 to 8 carbon atoms; and R* and R are the same or different and each represents an alkyl group having from 1 to 8 carbon atoms, a cyeloalkyl group having from G to 8 carbon atoms or an aralkyl grotip having from 7 to 9 carbon atoms) [J, which comprises reacting, in an acidic medium at a temperature of from 60 to 200°C in the presence of an acidic catalyst, a stericallv hindered phenol of formula (Π): lo OH [[in which: A represents an alkyl group having from 1 to 8 carbon atoms, a cyeloalkyl group having from 6 to 8 carbon atoms, an aralkyl group having from 7 to 9 carbon atoms or a 3-hydroxybenzyl group of formula: R. 28, i538 s (in which R and R are as defined above); and B represents an alkyl group having from 1 to 8 carbon atoms, a cycloalkyl group having from 6 to 8 carbon atoms, an aralkyl group having from 7 to 9 carbon atoms or a 4-hydroxybenzyl group of formula; acetal, aldehyde or - Cg aldehyde precursor.

2. , A process according to Claim'1, in which said acid is a Lewis acid.

3. , A process according to Claim 1, in which said acid is a Bhonsted acid.

4. A process according to any one of the preceding Claims, in which said acetal is a compound of formula (ΠΙ): (in) 29. in v.hich n° and A art tin· tame or difiereri a. ’ u.ih represents, jm alkyl groi.p bav’ng from 1 to a c.-, bon-atoms and .·; in a number from 3 to 4. 5. A process according to Claim 4, in which .- h aec-1al i c:hyl;h, r.dyliii or diptmylforn-ial, 6. A process according to any one of Claim.-s 1 io S, in which said aldehyde is acetaldehyde, propionaldch;. ic, butyraldehyde or isvvaleraldehyce. 7. A process according to any one of Claims 1 io 3, in which said cd i; :, yde precursor is a cyclic polymer of ar. aldehyde, (s, A process according to Claim 7, in which a:-id cyclic polymer is trioxan. <5, A process according to any one of Claims 1 to 3, in which said aldehyde perem-sor is a linear polymer of an aldehyde. 1C, A process according to Claim 9, in which said Jincar polymer is paraformaldehyde. ¢5388 11. A process according to Claim 1, substantially as hereinbefore described with reference to any one of the foregoing Examples. 12. A sterically hindered polyphenol when prepared

5. By a process according to any one of the preceding Claims.