GB2126214A

GB2126214A - Amine or polyamine salts of p- nitroso-phenols

Info

Publication number: GB2126214A
Application number: GB08320554A
Authority: GB
Inventors: Isom Everett Wagoner; Ruth Shaw Hudson
Original assignee: Sandoz AG
Current assignee: Sandoz AG
Priority date: 1982-08-04
Filing date: 1983-07-29
Publication date: 1984-03-21
Also published as: IT1168951B; ES8502414A1; ES524715A0; IT8322396A0; IT8322396A1; GB8320554D0; FR2531425A1; DE3326723A1; JPS5962552A

Abstract

There are provided amine or polyamine salts of p-nitroso-phenols comprising, per molecule, from 1 to 4 p-nitrosophenolate units each associated with a single primary, secondary or tertiary nitrogen atom on the amine, which compounds are useful as polymerisation inhibitors.

Description

SPECIFICATION Improvements in or relating to organic compounds The present invention relates to amine salts of p-nitrosophenols which are useful as polymerisation inhibitors.

Polymerisation of monomers at undesired times and places is still a persistent problem in monomer manufacture, particularly when polymerisation occurs during preparation, purification or storage of the monomers. Inhibitors are widely used to prevent or delay undesired polymerisation.

However, their inhibitory action very often lasts for only a short time or is less effective at a higher temperature and this results in frequent and costly shutdowns and cleaning of equipment.

It has now been found that amine salts of p-nitrosophenols can be used as polymerisation inhibitors and that they inhibit the polymerisation of monomers for a substantially longer time than do conventional polymerisation inhibitors e.g. sodium p-nitroso-phenolate.

Accordingly, the present invention provides amine or polyamine salts of p-nitroso-phenols comprising, per molecule, from 1 to 4 p-nitrosophenolate units each associated with a single primary, secondary or tertiary nitrogen atom on the amine.

Preferably the amine or polyamine salts of the invention comprise an amine moiety selected from mono-, di-, tri- and tetramines. More preferably, the compounds of the invention are derived from mono-, di-, tri- or tetramines in which a single p-nitrosophenolate unit is associated with each primary, secondary and tertiary nitrogen atom.

More preferably, the invention provides compounds of formula I

wherein each R1, R2 or R3, independently, is H; Alkyl or C24alkanol; R is H; C1~20alkyl; C24alkanol; C37cycloalkyl; C36cycloalkyl-C14alkyl; aryl or aryl-C1~4alkyl; each B, independently, is C,~aalkylene or

wherein each D or E, independently, is a direct bond or C,~4alkylene; m is 0, 1, 2 or 3; and n is an integer from 1 to 4, inclusive, with the proviso that n6m+1 the benzene ring A being, independently, unsubstituted or substituted by up to two substituents selected from chlorine, methyl, methoxy and ethyl, and a single p-nitroso-phenolate anion being associated with each protonized nitrogen atom on the amine moiety.

Any alkyl as R or R1 to R3 may be branched or straight chain. Any alkanol as R or R1 to R3 preferably bears the hydroxy group in -, y- or S-position to the nitrogen to which it is linked. Preferably alkanol is C23alkanol, more preferably p-hydroxyethyl.

Any alkylene represented or contained by B may be straight or branched chain, preferably straight.

When R1, R2 or R3 is C1~4alkyl, it is preferably methyl, ethyl, isopropyl or butyl. When R is alkyl, it is preferably C118alkyl, more preferably methyl, ethyl, isopropyl, butyl, hexyl, n-octyl, tert.-octyl, decyl, dodecyl or hexadecyl.

When R is cycloalkyl, it is preferably cyclohexyl. Preferably cycloalkyl-alkyl as R is cyclohexylmethyl.

Any aryl represented or contained by R is preferably phenyl. Preferably aralkyl as R is phenyl C1~4alkyl, more preferably benzyl or phenethyl.

Preferably

as B is unsubstituted 1 ,4-phenylene.

Preferably n is equal to m+1,i.e. each nitrogen atom present in the amine moiety is protonized with a single p-nitrosophenolate group.

Preferably R is R', where R' is H, C1~,8alkyl, C23alkanol, cyclohexyl, phenyl or benzyl.

Preferably R1 is Rí where R1, is H, C14alkyl or C2alkanol. Preferably R3 is R3, where R3 has, independently, one of the significances given for R1.

Preferably each R2 is hydrogen.

Preferably each B is B', where each B' independently, is straight C1alkylene or 1 ,4-phenylene.

Preferably the benzene ring A is unsubstituted.

As a preferred class of compounds of formula I may be given the compounds of formula 1a

wherein n, R', R'1, R3, and B' are as defined above, a single p-nitroso-phenolate anion being associated with each protonized nitrogen atom of the amine moiety.

Further preferred compounds of formula 1a are those where the amine moiety

is selected from the following amines; dimethylamine, diethylamine, triethylamine, isopropylamine, nbutylamine, n-octylamine, tert.-octylamine, hexadecylamine, cyclohexylamine, benzylamine, triethanolamine, ethylenediamine, 1,6-hexanediamine, p-phenylenediamine and hexamethylenetetramine.

Most preferred compounds of formula 1a are those wherein n=1, especially those wherein R3, is hydrogen, R; is hydrogen or C14alkyl and R' is C116alkyl, cyclohexyl or benzyl, preferably C1~16alkyl.

The compounds of the invention may be prepared by reacting an amine or polyamine comprising at least one primary, secondary or tertiary nitrogen atom, preferably a mono-, di-, tri- or tetramine, or a mixture thereof, with an optionally substituted p-nitroso-phenol or a mixture of such, in a mol ratio of 1:1 -4 with the proviso that the number of mols of p-nitrosophenols is equal to or lower than the total sum of protonizable primary, secondary and tertiary nitrogen atoms present in the amine or polyamine.

More particularly, the compounds of formula I may be prepared by reacting an amine of formula II

wherein m, R, R1, R2, R3 and B are as defined above; or a mixture thereof, with a compound of formula III

wherein the benzene ring A is unsubstituted or substituted as defined above, or a mixture thereof, in a mol ratio of 1 :m+1.

The reaction is conducted in a liquid medium such as water or an inert organic solvent such as dimethylformamide or toluene. When the amine is liquid, the reaction may be carried out without the addition of a further liquid.

The compounds are stirred at a temperature from 0 to 400 C, preferably at room temperature, until the reaction is complete. Reaction time varies from 10 minutes to 1 5 hours.

According to a preferred embodiment of the invention, to produce the compounds of the invention where each primary, secondary or tertiary nitrogen atom of the amine is protonized with a single p-nitroso-phenolate group, the number of mols (selected from 1 to 4) of p-nitroso-phenol brought into reaction is equal to the total sum of protonizable nitrogen atoms on the amine.

The compounds of the invention may be isolated and purified according to known methods.

The compounds of the invention are useful as polymerisation inhibitors. In particular they inhibit the polymerisation of monomers capable of being polymerised by free radical mechanism. The compounds of the invention are particularly effective to inhibit the polymerisation of vinyl monomers such as acrolein, acrylonitrile, styrene, chlorostyrene, vinyl acetate, acrylic acid esters, e.g. methyl, ethyl, butyl or 2-ethylhexyl acrylate, methacrylic acid esters, e.g. methyl, ethyl methacrylate, and acrylic acid, more preferably butyl acrylate.

According to the invention, to inhibit polymerisation, the monomer is contacted with an inhibitory amount of a compound of the invention. The inhibitor of the invention may be added, e.g. by admixture with or dissolution in the monomer, to prevent premature polymerisation during the preparation, purification, particularly the distillation step of the impure monomeric material, storage or transportation of the monomer under aerobic or substantially anaerobic conditions.

A suitable amount of inhibitor of the invention is from 0.00001% to 1% by weight based on the weight of the monomer.

If desired, the compounds of the invention may be used in pure form or in form of the reaction mixture partially purified, e.g. after dissolution in water and filtration. The reaction mixture may contain a low amount of unreacted p-nitroso-phenol and/or a low amount of sodium p-nitroso-phenolate, e.g.

each up to 1 5% by weight of the reaction product. The compounds of the invention may also be used in admixture with other polymerisation inhibitors.

The compounds of the invention are particularly interesting polymerisation inhibitors. They stabilise monomers, particularly acrylic acid esters, especially butyl acrylate, against premature polymerisation for a considerable long time, even at a temperature above room temperature.

Furthermore, they have a good solubility in the monomers, particularly in butyl acrylate. In addition, the compounds of the invention do not have the disadvantages shown by sodium p-nitroso-phenolate.

They have an improved self-life and are substantially less inflammable than sodium p-nitrophenolate.

Isopropylamine, dimethylamine, diethylamine and tert.-octylamine salts of p-nitroso-phenol are particularly preferred as polymerisation inhibitors, especially for acrylic acid esters, preferably butyl acrylate, acrylonitrile and acrolein.

The following Examples further serve to illustrate the invention. In the Examples all parts are by weight and all temperatures are in degrees Centigrade.

Example 1 The p-nitrosophenoi salt of hexadecylamine may be prepared by adding slowly, at room temperature, 21 parts hexadecylamine to a stirring mixture of 10.7 parts p-nitrosophenol suspended in 400 parts water, stirring for 3.5 hours, collecting the salt by filtration, washing with 80 parts water, and air drying at 200--300. 31.7 Parts of greenish powder having a melting range of 60.5--620 results.

Example 2 An aqueous solution of the p-nitrosophenol salt of benzylamine may be prepared by adding 4.3 parts benzylamine dropwise, at room temperature, to a stirring mixture of 4.92 parts p-nitrosophenol suspended in 100 parts water, and stirring for 2 hours. The reaction mixture is filtered, the filter cake discarded, and the filtrate is an aqueous solution containing approximately 8.3 parts of the pnitrosophenol salt of benzylamine.

Example 3 An aqueous solution of the p-nitrosophenol salt of cyclohexylamine may be prepared in the same manner as the product of Example 2, by substituting 3.96 parts cyclohexylamine for the benzylamine used in Example 2. The resulting filtrate is an aqueous solution containing about 8.65 parts of the pnitrosophenol salt of cyclohexylamine.

Example 4 An aqueous solution of the bis-p-nitrosophenol salt of 1 ,6-hexanediamine may be prepared in the same manner as the product of Example 2, by substituting 2.35 parts 1 ,6-hexanediamine for the benzylamine used in Example 2. The resulting aqueous filtrate contains about 7 parts of the bis-pnitrosophenol salt of 1 ,6-hexanediamine.

Example 5 An aqueous solution of the p-nitrosophenol salt of n-butylamine may be prepared in the same manner as the product of Example 2, by substituting 2.92 parts of n-butylamine for the benzylamine used in Example 2. The resulting aqueous filtrate contains about 7.4 parts of the p-nitrosophenol salt of n-butylamine.

Example 6 An aqueous solution of the p-nitrosophenol salt of diethylamine may be prepared in the same manner as the product of Example 2, except that 3 parts of diethylamine are substituted for the benzylamine used in Example 2. The resulting aqueous filtrate contains about 7.2 parts of the pnitrosophenol salt of diethylamine.

Example 7 The p-nitrosophenol salt of n-octylamine may be prepared by adding, with stirring, at 150--200.

1 3 parts p-nitrosophenol to 13.65 parts n-octylamine and stirring 2 hours. The resulting pnitrosophenol salt of n-octylamine was collected as 25.4 parts of a black oil.

Example 8 The p-nitrosophenol salt of tert-octylamine may be prepared by adding 6.85 parts pnitrosophenol at 150--200 to 7.2 parts tert-octylamine dissolved in 26 parts toluene, stirring 4 hours, and filtering to dryness on a suction filter. The resulting product consisted of 14 parts of dull violet powder melting at 530--580.

Example 9 The bis-p-nitrosophenol salt of ethylenediamine may be prepared by adding 4.4 parts pnitrosophenol, at 200--250 to a stirring solution of 1.3 parts ethylenediamine in 50 parts toluene, stirring 5 hours at room temperature, and filtering to dryness on a suction filter. The resulting product consisted of 5.5 parts of olive-colored powder melting at 73.50--7 50.

Example 10 A solution of the bis-p-nitrosophenol salt of ethylenediamine may be prepared by dissolving 1.84 parts ethylenediamine in 1 2 parts dimethyl formamide, adding thereto 9 parts wet presscake of pnitrosophenol containing 7.38 parts p-nitrosophenol and 1.62 parts water, and stirring 2.5 hours at room temperature. The resulting product consisted of 22.8 parts of black liquid.

Example 11 A solution of the p-nitrosophenol salt of triethanolamine may be prepared by adding 12 parts of wet presscake of p-nitrosophenol containing 9.8 parts p-nitrosophenol and 2.2 parts water to 100 parts cold water, adding 11.8 parts triethanolamine at 50--7 0, stirring 1 hour at 3 300, and filtering.

120.2 parts of dark filtrate containing the dissolved product results. The filter cake of 0.45 parts is discarded.

Example 12 A solution of the p-nitrosophenol salt of triethylamine may be prepared by adding 12 parts wet presscake of p-nitrosophenol containing 9.8 parts p-nitrosophenol and 2.2 parts water to 100 parts cold water and mixing, adding 8 parts triethylamine at 120--150, stirring one hour at 130--170.

warming to 250, stirring at 250 for 30 minutes, and filtering at 250. The resulting dark filtrate was 11 6.6 parts and contained the dissolved product. No filter cake resulted.

Example 13 A solution of p-nitrosophenol salt of isopropylamine may be prepared by dissolving 5.3 parts isopropylamine into 1 8 parts dimethyl formamide at 15"--20", sprinkling in at about 100 11 parts of p-nitrosophenol as a wet presscake containing 8285% solids, and stirring 3 hours at 5"--100. The resulting dark solution contained the product.

Example 14 The p-nitrosophenol salt of isopropylamine may be prepared by adding, dropwise, 13 parts isopropylamine to a stirring mixture of 24.6 parts p-nitrosophenol suspended in 100 parts water maintained at room temperature, stirring 2 hours at room temperature, adding 25 parts NaCI to the stirring mixture, stirring 3 more hours, filtering, collecting and air drying the solids, which yields 32.2 parts crystalline product.

Three parts of the product were treated with 50 parts water, and dissolved quickly, leaving 0.26 part (dry weight) of undissolved material on filtration.

Accordingly, the 32.2 parts contained 63.92% p-nitrosophenol salt of isopropylamine, 17.61% NaCI, 9.72% unreacted p-nitrosophenol or extraneous material, and 8.75% sodium p-nitrosophenolate.

Example 15 An aqueous solution of p-nitrosophenol salt of isopropylamine may be prepared by adding 2.46 parts isopropylamine, dropwise, at 150 to a stirring mixture of 4.92 parts p-nitrosophenol suspended in 69 parts water, and stirring for 2 hours. No solids were collected on filtration.

The filtrate contained 7.2 parts p-nitrosophenol salt of isopropylamine.

Example 16 A dimethyl formarnide slurry of the tetrakis-p-nitrosophenol salt of hexamethylene tetramine may be prepared by adding 3.2 parts hexamethylene tetramine to 18 parts dimethyl formamide at 150- 200, sprinkling in 10.8 parts (100% basis) p-nitrosophenol, in the form of 8285% solids wet presscake, at about 100, and stirring for 2 hours at 5 10 . The resulting dark slurry contains the product.

Example 17 The p-nitrosophenol salt of diethylamine may be prepared by adding 1 5.7 parts diethylamine, dropwise, to a stirring mixture of 24.6 parts p-nitrosophenol suspended in 100 parts water maintained at room temperature, stirring 2 hours at room temperature, adding 25 parts NaCI to the stirring mixture, stirring 1 5 hours, filtering, and air drying the collected solids, which yields 31.4 parts dry crystals.

Sulfated ash analysis of 26.98% indicates 2.74 parts sodium, in the form of salts, in the product.

The ash analysis of 17.45% indicates the presence of 5.48 parts sodium chloride in the product.

Three parts of the crystals dissolve quickly when treated with 50 parts water, leaving 0.41 part (dry weight) undissolved material on filtration.

The 31.4 parts consist of 55.34% p-nitrosophenol salt of diethylamine, 1 7.45% NaCI, 1 5.36% unreacted p-nitrosophenol or extraneous materials, and 11.85% sodium p-nitrosophenolate.

Example 18 The bis-p-nitrosophenol salt of p-phenylenediamine may be prepared by adding 4.4 parts pnitrosophenol to 2 parts p-phenylenediamine suspended in 100 parts water. The mixture is stirred 5 hours at ambient temperature, filtered, washed with water, and the filtercake air dried to yield 6.35 parts of the product.

The following examples relate to testing compounds of the present invention as inhibitors for butyl acrylate monomer.

Example 19 20 ml purified butyl acrylate containing 10 ppm by weight of the inhibitor of the invention calculated on 100% basis inhibitor and based on weight of the butyl acrylate, is placed in a reaction vessel, flushed with nitrogen, and maintained under nitrogen throughout the experiment. The reaction vessel is heated at 900 with a thermocouple device for measuring and recording the solution temperature. When the butyl acrylate polymerizes, it gives off heat (exotherm), which is measured by the thermocouple device. The elapsed time from the start of the experiment until the maximum temperature of the exotherm occurs is noted. The experiment is repeated.

Compounds of Examples 12, 14 and 1 7 exhibit an inhibitory action during a substantially long time at 900.

Example 20 The procedure of Example 19 is repeated except that 5 ppm of the inhibitor (100% basis) of Examples 6, 13, 1 5 and 16 are substituted for the 10 ppm of inhibitor (100% basis) used in Example 19.

Compounds of Examples 6, 13, 1 5 and 1 6 prevent premature polymerisation of butyl acrylate for a durable time at 900C.

Claims

1. Amine or polyamine salts of p-nitrosophenols comprising, per molecule, from 1 to 4 p-nitrosophenolate units each associated with a single primary, secondary or tertiary nitrogen atom on the amine.

2. Amine or polyamine salts of p-nitroso-phenols according to Claim 1, in which the amine moiety is selected from mono-, di-, tri- and tetramines.

3. Amine or polyamine salts of p-nitroso-phenols according to Claim 2, in which a single pnitroso-phenolate unit is associated with each primary, secondary and tertiary nitrogen atom of the amine moiety.

4. Amine or polyamine salts of p-nitroso-phenols according to Claim 1, of formula I

wherein each R1, R2 or R3, independently, is H; C14alkyl or C24alkanol; R is H; C1~20alkyl; C2~4alkanol; C37cycloalkyl; C3~6cycloalkyl-C1~4alkyl; aryl or aryl-C1~4alkyl; each B, independently, is C1~8alkylene or

wherein each D or E, independently, is a direct bond or C,~4alkylene; m is 0, 1, 2 or 3; and n is an integer from 1 to 4, inclusive, with the proviso that nim+ 1 the benzene ring A being, independently, unsubstituted or substituted by up to two substituents selected from chlorine, methyl, methoxy and ethyl, and a single p-nitroso-phenolate anion being associated with each protonized nitrogen atom on the amine moiety.

5. Amine or polyamine salts of p-nitroso-phenols according to Claim 4, in which any alkyl as R, R1,R2 or R3 is branched or straight chain.

6. Amine or polyamine salts of p-nitroso-phenols according to Claim 4 or 5, in which n is equal to m+1.

7. Amine or polyamine salts of p-nitroso-phenols according to any one of Claims 4 to 6, in which R is R', where R' is H, C 118aI kyl, C23alkanol, cyclohexyl, phenyl or benzyl.

8. Amine or polyamine salts of p-nitroso-phenols according to any one of Claims 4 to 7, in which R1 is R1, where R1 is H, Alkyl or C23alkanol.

9. Amine or polyamine salts of p-nitroso-phenols according to any one of Claims 4 to 8, in which R3 is R3, where R3 is H, Alkyl or C2~3alkanol.

10. Amine or polyamine salts of p-nitroso-phenols according to any one of Claims 4 to 9, in which R2 is hydrogen.

11. Amine or polyamine salts of p-nitroso-phenols according to any one of Claims 4 to 10, in which B is straight C1alkylene or 1,4-phenylene.

12. Amine or polyamine salts of p-nitroso-phenols according to any one of Claims 4 to 11, in which the benzene ring A is unsubstituted.

13. Amine or polyamine salts of p-nitroso-phenols according to any one of Claims 4 to 12, of formula 1a

wherein n, R', R1, R3 and B' are as defined above, a single p-nitroso-phenolate anion being associated with each protonized nitrogen atom of the amine moiety.

14. Amine or polyamine salts of p-nitroso-phenois of formula la according to Claim 1 3, in which the amine moiety is selected from triethylamine, n-butylamine, n-octylamine, hexadecylamine, cyclohexylamine, benzylamine, triethanolamine, ethylenediamine, 1 ,6-hexanediamine, p phenylenediamine and hexamethylene-tetramine.

1 5. Compounds of formula la according to Claim 13 in which n=1.

1 6. Compounds of formula la according to Claim 13 or Claim 1 5 in which R1 is hydrogen or C1~4alkyl, R3 is hydrogen and R' is C116alkyl, cyclohexyl or benzyl.

17. p-Nitroso-phenol salt of dimethylamine.

18. p-Nitroso-phenol salt of diethylamine.

19. p-Nitroso-phenol salt of isopropylamine.

20. p-Nitroso-phenol salt of tert.-octylamine.

21. Amine or polyamine salts of p-nitroso-phenols substantially as hereinbefore described with reference to any one of Examples 1 to 18.

22. A process for producing amine or polyamine salts of p-nitroso-phenols comprising, per molecule, from 1 to 4-p-nitroso-phenolate units each associated with a single primary, secondary or tertiary nitrogen atom on the amine, which process comprises reacting an amine or polyamine comprising at least one primary, secondary or tertiary nitrogen atom or a mixture thereof, with an optionally substituted p-nitroso-phenol or a mixture of such, in a mol ratio of 1:1-4 with the proviso that the number of mols of p-nitrosophenols is equal to or lower than the total sum of protonizable primary, secondary and tertiary nitrogen atoms present in the amine or polyamine.

23. A process for producing compounds of formula I as indicated in Claim 4 comprising reacting an amine of formula II

wherein m, R, RI, R2, R3 and B are as defined above; or a mixture thereof, with a compound of formula Ill

24. A process for inhibiting polymerisation of monomers, comprising contacting the monomer with an inhibitory amount of an amine or polyamine salt of p-nitroso-phenols as defined in any one of Claims 1 to 21.

25. A process according to Claim 24, in which the monomer is a monomer capable of being polymerised by free radical mechanism.

26. A process according to Claim 25, in which the monomer is a vinyl monomer.

27. A process according to Claim 26, in which the monomer is selected from acrolein, acrylonitrile, styrene, chlorostyrene, vinyl acetate, acrylic acid esters, methacrylic acid esters and acrylic acid.

28. A process according to any one of Claims 24 to 27, in which an amount from 0.00001% to 1% by weight of an amine or polyamine salt of p-nitroso-phenols based on the weight of the monomer is contacted with the monomer.

29. A process for inhibiting polymerisation of monomers substantially as hereinbefore described with reference to an" one of Examples 19 and 20.

30. Monomers capable of being polymerised by free radical mechanism, containing an amine or polyamine salt of p-nitroso-phenols as defined in any one of Claims 1 to 21.