EP1140772A1

EP1140772A1 - Composition and method for inhibiting radical polymerisation of ethylenically unsaturated aliphatic monomers

Info

Publication number: EP1140772A1
Application number: EP99959507A
Authority: EP
Inventors: Françoise LARTIGUE-PEYROU
Original assignee: Rhodia Chimie SAS
Current assignee: Rhodia Chimie SAS
Priority date: 1998-12-22
Filing date: 1999-12-21
Publication date: 2001-10-10
Also published as: WO2000037412A1; AU1665600A; FR2787444A1; FR2787444B1; CN1331669A; BR9916403A; JP2002533309A; KR20010103717A

Abstract

The invention concerns a composition for inhibiting radical polymerisation of ethylenically unsaturated aliphatic monomers characterised in that it comprises at least a diphenylamine derivative of general formula (I) wherein: A and B represent the radical of a cycle forming all or part of a carbocyclic, aromatic, monocyclic or polycyclic system; R1 and R2, identical or different, represent a hydrogen atom or one or several substituents; and n + m not less than 1: n and m representing the number of substituents on the cycle.

Description

COMPOSITION AND METHOD FOR INHIBITING RADICAL POLYMERIZATION MONOMERS AL1PHA TICKS UNSATURATED ETHYLENE ^Λ _WHA-

The subject of the present invention is a composition which can be used as an inhibitor of the radical polymerization of ethylenically unsaturated aliphatic monomers and a process intended to prevent the radical polymerization of such unsaturated monomers during their industrial preparation. It relates more particularly to vinyl aliphatic monomers.

It is described in US Pat. No. 3,959,358 that it was possible to inhibit the polymerization of acrylic acid esters by using p-hydroxydiphenylamine. It is also proposed according to US Pat. No. 4,692,544 to inhibit the polymerization of an unsaturated ethylenic monomer using p-phenylenediamine derivatives and the best results are obtained using 4,4'-diaminodiphenylamine.

Inhibitors have now been found exhibiting improved properties compared to those conventionally used such as in particular, hydroquinone.

More specifically, the invention relates to a composition intended to prevent the radical polymerization of ethylenically unsaturated aliphatic monomers, characterized in that it comprises at least one diphenylamine derivative corresponding to the general formula (I):

in said formula (I):

- A and B symbolize the rest of a cycle forming all or part of a carbocyclic, aromatic, monocyclic or polycyclic system,

- R ₁ and R2, identical or different, represent a hydrogen atom or one or more substituents,

- and n + m greater than or equal to 1: n and m representing the number of substituents on the cycle. It has been found according to the invention that the inhibitory action of the diphenylamine derivative as defined, is reinforced when said derivative which carries at least one hydroxyl group on one of the rings, comprises at least one other substituent on the one of the rings which can be a substituent such as R- | and / or R2 and in particular another hydroxyl group.

Thus, a first class of inhibitors according to the invention are of the hydroxydiphenylamine type comprising at least one substituent other than a hydroxyl group.

Another class of inhibitors according to the invention are of the dihydroxydiphenylamine type optionally comprising other substituents on the rings.

A variant of the invention consists in combining the diphenylamine derivative of the invention with another polymerization inhibitor.

More specifically, the diphenylamine derivative according to the invention corresponds to the general formula (I) in which A and B represent one of the following cycles:

In the preferred compounds, A and B are identical and represent a benzene ring. One of the rings A and B carry at least one substituent other than the hydroxyl group. It should be noted that if n is equal to 0, m is at least greater than or equal to 1 or if m is equal to 0, n is at least greater than or equal to 1. The number of substituents on rings A and B can vary. Thus, n is less than or equal to 3, preferably equal to 0 or 1. For m, m is less than or equal to 4, preferably equal to 1 or

2.

The remainder A and B may optionally carry one or more substituents which are represented in formula (I), by the symbol Ri and R2 and whose preferred meanings are defined below:. a hydrogen atom,

. an alkyl radical, linear or branched, having from 1 to 12 carbon atoms, preferably from 1 to 4 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl,. a linear or branched alkenyl radical having from 2 to 6 carbon atoms, preferably from 2 to 4 carbon atoms, such as vinyl, allyl, . a linear or branched aikoxy or thioether radical having from 1 to 6 carbon atoms, preferably from 1 to 4 carbon atoms such as the methoxy, ethoxy, propoxy, isopropoxy, butoxy radicals, an alkenyloxy radical, preferably an allyloxy radical or a phenoxy radical,. a radical of formula:

-R3-OH -R3-SH -R3-COOR4 -R3-CO-R4 -R3-N (R4) ₂

-R ₃ -CO-N (R4) ₂ -R3-NH-CO-R4 -R3-NH-COO-R4 in said formulas, R3 represents a valence bond or a divalent, linear or branched, saturated or unsaturated hydrocarbon radical, having from 1 to 6 carbon atoms such as, for example, methylene, ethylene, propylene, isopropylene, isopropylidene; the identical or different R4 radicals represent a hydrogen atom or a linear or branched alkyl radical having from 1 to 6 carbon atoms.

Among the diphenylamine derivatives of formula (I), some are particularly preferred and in particular those corresponding to formula (la):

in said formula (la): - R- |, R2, n and m have the meaning given above.

Among the compounds of formula (la), preference is given to those which correspond to formula (I) in which R ^ represents a hydrogen atom, an alkyl or aikoxy group having from 1 to 4 carbon atoms and R ₂ represents a hydrogen atom, an alkyl or aikoxy group having from 1 to 4 carbon atoms.

The preferred compounds correspond to formula (la) in which n is equal to 0 and m is equal to 1.

The examples given below illustrate the diphenylamine derivatives preferably used. They are more particularly chosen from: - 2-hydroxy-5-methyldiphenylamine, - 2-hydroxy-4-methyldiphenylamine, - 2-hydroxy-4 ', 5-dimethyldiphenylamine,

- 2,2'-dihydroxydiphenylamine, - 3-hydroxy-4'-methoxydiphenylamine, - 3,3'-dihydroxy-2,2'-dimethyldiphenylamine, - 3,3'-dihydroxy-2,2'-dimethoxydiphenylamine,

- 4-hydroxy-4'-methyldiphenylamine, - 4-hydroxy-4 '- (methoxycarbonylamino) -diphenylamine,

- N- (4-hydroxyphenyl) -2-naphthylamine,

- 4,4'-dihydroxydiphenylamine, - 4,4'-dihydroxy-2,2'-dimethyldiphenylamine, - 4,4'-dihydroxy-2,2'-dimethoxydiphenylamine, - 2-hydroxy-4'-hydroxydiphenylamine.

It is also possible to use a mixture of diphenylamine derivatives. The preferred derivatives according to the invention are of the dihydroxydiphenylamine type and mention may more particularly be made of 4,4'-dihydroxydiphenyiamine, 2,2'-dihydroxydiphenylamine, 2-hydroxy-4'-hydroxydiphenylamine

Thus, the compositions of the invention comprising at least one diphenylamine derivative of formula (la) constitute a particularly preferred embodiment of the invention.

The compositions of the invention are suitable for the stabilization of aliphatic monomers having at least one ethylenic unsaturation.

The ethylenically unsaturated monomers more specifically comprise olefinic monomers comprising one or two unsaturations such as isoprene and butadiene; halogenated unsaturated monomers of the type of vinyl chloride, chloroprene, vinylidene chloride, vinylidene fluoride and vinyl fluoride; unsaturated acids such as acrylic acid, methacrylic acid and crotonic acid; unsaturated esters in particular the unsaturated esters of acrylic acid of the methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, hydroxypropyl acrylate; unsaturated esters of methacrylic acid such as methyl methacrylate, butyl methacrylate, lauryl methacrylate, dimethylaminoethyl methacrylate, stearyl methacrylate; vinyl acetate; unsaturated resins such as, for example, acrylated epoxy resins and polyethylene glycol diacrylate; unsaturated amides such as acrylamide, N, N-dimethylacrylamide, methylenebisacrylamide and N-vinylpyrrolidone; unsaturated nitriles of the Pacrylonitrile type; unsaturated ethers such as vinyl ether; the diethyl vinylphosphonate. It should be understood that this list is by no means exhaustive, the invention generally relating to the stabilization of any type of ethylenically unsaturated aliphatic monomer.

Nevertheless, the compositions of the invention are particularly effective in the case of the stabilization of ethylenically unsaturated aliphatic monomers such as the esters of acrylic acid and of methacrylic acid.

The compositions of the invention form either true solutions, that is to say that they consist of perfectly miscible ingredients, or emulsions, or else suspensions. According to a preferred embodiment, however, the compositions are in the form of true solutions in the monomer itself.

According to a variant of the invention, the compositions of the invention may contain other polymerization inhibitors such as hydroquinone; p-methoxyphenol; phenothiazines; nitroxide compounds such as tetramethylpiperidine-N-oxyl (TEMPO), 4-hydroxytetramethylpiperidine-N-oxyl, 4-oxotetramethylpiperidine-N-oxyl; imidalines / imidazolines-N-oxyl as described in FR 97/04230, preferably 2,2,3,4,5,5-hexamethylimidazolidine-1-oxyl or any other inhibitor known in the art provided that these these are compatible with the other ingredients of the composition under the operating conditions to which the monomer to be stabilized is subjected.

Certain diphenylamine derivatives of formula (I) are commercial. The others are easily prepared by a person skilled in the art from commercial products.

The invention further relates to a method for preventing the radical polymerization of an ethylenically unsaturated aliphatic monomer, preferably a vinyl aliphatic monomer. This method comprises, for example, adding to said monomer, an effective amount of a composition of the invention as defined above.

The amount of diphenylamine derivative to be added to achieve effective inhibition of polymerization varies widely. It is a function of the monomer to be stabilized and of the operating conditions to which this monomer is subjected. It is clear that at high temperatures, the amount of inhibitor will be greater. The process of the invention is in fact applicable for the stabilization of the monomer, during manufacture and purification. However, it is not uncommon for the purification to be carried out by distillation of the monomer, the temperature at the reboiler being able to exceed 120 ° C.

Thus, the ideal amount of inhibitor should be assessed on a case-by-case basis. Anyway, by way of indication, a total quantity of diphenylamine derivative of between 1 and 2000 ppm, preferably between 5 and 1000 ppm is generally sufficient, this quantity being expressed relative to the total weight of the monomer to be stabilized. As indicated above, it is possible to add to the monomer one or more known polymerization inhibitors.

The proportion of the polymerization inhibitor (s) is preferably such that the ratio of the total mass of components of the diphenylamine type of formula (I) to the total mass of all the components is between 90/10 and 10/90, better still between 80/20 and 20/80.

The diphenylamine derivative according to the invention optionally combined with other conventional polymerization inhibitors can be added to the monomer in a completely conventional manner. The point of introduction, in the case of a distillation, is very variable: one can consider adding each of these compounds at the level of heat exchangers, pipes, pumps, reboilers, compressors or more generally distillation columns. It should be understood that the addition can be carried out continuously or else repeated over time at one or different particular sites.

According to the invention, it is possible to envisage the simultaneous or separate addition of the inhibitor of the invention and of another inhibitor.

The invention also includes the use of the diphenylamine derivatives according to the invention for the stabilization of the monomer during storage by adding an amount equivalent to that previously mentioned. The invention also contemplates mixing with other inhibitors. The process of the invention is particularly advantageous in terms of effectiveness in inhibiting the radical polymerization of vinyl aliphatic monomers, in particular the esters of acrylic acid and methacrylic acid.

The composition of the invention is advantageously used as an emergency inhibitor during the synthesis of polymers from aliphatic monomers containing ethylenic unsaturation.

The following examples are given by way of illustration and relate to preferred embodiments of the invention.

Examples

In order to evaluate the inhibition properties of the products of the invention, with respect to the radical polymerization of the unsaturated aliphatic monomers, tests inhibition with methyl methacrylate were undertaken with the following operating protocol.

The effectiveness of an inhibitor according to the invention (or of a mixture of inhibitors comprising at least one inhibitor according to the invention) for methyl methacrylate is determined by measuring the induction time which represents the time to end of which the monomer begins to polymerize when it is heated in a temperature-controlled bath and in the presence of an initiator. This time is determined by a slight exothermicity of the sample studied.

The measurements are carried out in a laboratory calorimeter, the time and temperature parameters are recorded and converted on a microcomputer.

The tests were carried out with methyl methacrylate (MMA) previously destabilized by passage over an activated alumina column in order to completely eliminate the p-methoxyphenol (initial stabilizer) from the medium.

20 ml of MMA restored with 20 ppm of inhibitor to be tested are then introduced into a test tube and then 100 ppm of azobisisobutyronitrile initiator (AIBN). The tube is immersed in a bath thermostatically controlled at 80 ° C. and the temperature difference between this sample and a reference tube containing silicone oil is recorded continuously. The induction time Ti corresponds to the visible exotherm which indicates the start of the polymerization of MMA. The curve T as a function of time is recorded continuously. The longer the induction time, the more effective the inhibitor tested at constant weight concentration.

The following table (I) indicates the induction time values of some "classic" inhibitors of the (meth) acrylates industry

Table (I)

Examples 1 to 9

For each polymerization inhibitor, the operating procedure given above is repeated.

Table (II) summarizes the results obtained on the induction time for various inhibitors of the invention

The induction time values are better or equivalent to hydroquinone which is currently one of the best industrial inhibitors for the (meth) acrylates industry.

Comparative tests 10 and 11

The operating protocol described above is repeated, but using unsubstituted hydroxydiphenylamine type compounds.

The results are recorded in table (III):

^TableauBoard

The comparison of Examples 1 to 3 and Comparative Example 10 shows that the presence of methyl or hydroxyl substituents makes it possible to increase the induction time. The same is true when comparing Comparative Example 11 and Examples 4 to 7.

The same remark applies when comparing Example 8 with the two comparative examples 10 and 11.

Examples 12 to 15

In these examples, the association of the diphenylamine of the invention of Examples 5, 4, 6 and 2 with another inhibitor, namely hydroquinone, is described.

In the test, the following are used: 20 ml of MMA + 100 ppm of AIBN + mixture of inhibitors (10 ppm of hydroquinone (HQ) + 10 ppm of inhibitor of the invention)

Table (IV) summarizes the results obtained on the induction time for the mixture of inhibitors of the invention

Table (IV)

The result is better than the 2 products alone at 20 ppm.

Example 16

In this example, the association of the diphenylamine of the invention of Example 2 with another inhibitor, namely TEMPO, is described.

In the test, the following are used: 20 ml of MMA + 100 ppm of AIBN + mixture of inhibitors (10 ppm of TEMPO + 10 ppm of inhibitor of the invention). Table (V) summarizes the results obtained on the induction time for the mixture of inhibitors of the invention Table (V)

Claims

1. Composition intended to prevent the radical polymerization of ethylenically unsaturated aliphatic monomers characterized in that it comprises at least one derivative of diphenylamine corresponding to the general formula (I):

in said formula (I): - A and B symbolize the remainder of a cycle forming all or part of a carbocyclic, aromatic, monocyclic or polycyciic system,

- Ri and R2, identical or different, represent a hydrogen atom or one or more substituents,

- and n + m greater than or equal to 1: n and m representing the number of substituents on the cycle.

2. Composition according to Claim 1, characterized in that the diphenylamine derivative corresponds to formula (I) in which A and B represent a benzene cycle or a naphthalene cycle and preferably, A and B are identical and represent a benzene cycle .

3. Composition according to Claim 1, characterized in that the diphenylamine derivative corresponds to formula (I) in which n is less than or equal to 3, preferably equal to 0 or 1 and m is less than or equal to 4, preferably equal to 1 or 2.

4. Composition according to one of claims 1 to 3 characterized in that the diphenylamine derivative corresponds to formula (I) in which R ₁ and R ₂ represent:. a hydrogen atom,

. an alkyl radical, linear or branched, having from 1 to 12 carbon atoms, preferably from 1 to 4 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl,. a linear or branched alkenyl radical having from 2 to 6 carbon atoms, preferably from 2 to 4 carbon atoms, such as vinyl, allyl,

. a linear or branched aikoxy or thioether radical having from 1 to 6 carbon atoms, preferably from 1 to 4 carbon atoms such as the methoxy, ethoxy, propoxy, isopropoxy, butoxy radicals, an alkenyloxy radical, preferably an allyloxy radical or a phenoxy radical,. a radical of formula:

-R3-OH -R3-SH -R3-COOR4 -R3-CO-R4 -R ₃ -N (R4) 2

-R ₃ -CO-N (R4) ₂ -R3-NH-CO-R4 -R3-NH-COO-R4 in said formulas, R3 represents a valence bond or a divalent, linear or branched, saturated or unsaturated hydrocarbon radical, having from 1 to 6 carbon atoms such as, for example, methylene, ethylene, propylene, isopropylene, isopropylidone; the identical or different R4 radicals represent a hydrogen atom or a linear or branched alkyl radical having from 1 to 6 carbon atoms.

5. Composition according to one of claims 1 to 4 characterized in that the diphenylamine derivative corresponds to formula (la):

in said formula (la): - Ri, R2, n and m have the meaning given previously in one of claims 1 to 4.

6. Composition according to claim 5 characterized in that the diphenylamine derivative corresponds to formula (la) in which R- | represents a hydrogen atom, an alkyl or aikoxy group having from 1 to 4 carbon atoms and R2 represents a hydrogen atom, an alkyl or aikoxy group having from 1 to 4 carbon atoms.

7. Composition according to one of claims 1 to 6 characterized in that it comprises a derivative of diphenylamine chosen from: - 2-hydroxy-5-methyidiphenylamine, - 2-hydroxy-4-methyldiphenylamine, - 2-hydroxy-4 ', 5-dimethyldiphenylamine,

- 2,2'-dihydroxydiphenylamine, - 3-hydroxy-4'-methoxydiphenylamine,

- 3,3'-dihydroxy-2,2'-dimethyldiphenylamine, - 3,3'-dihydroxy-2,2'-dimethoxydiphenylamine, - 4-hydroxy-4'-methyldiphenylamine, - 4-hydroxy-4 '- (methoxycarbonylamino ) -diphenylamine, - N- (4-hydroxyphenyl) -2-naphthylamine,

8. Composition according to one of claims 1 to 7 characterized in that it further comprises another polymerization inhibitor.

9. Composition according to claim 8 characterized in that the polymerization inhibitor is hydroquinone; p-methoxyphenol; phenothiazines; nitroxide compounds such as tetramethylpiperidine-N-oxyl, 4-hydroxytetramethylpiperidine-N-oxyl, 4-oxotetramethylpiperidine-N-oxyl; imidalines / imidazolines-N-oxyl, preferably 2,2,3,4,5,5-hexamethylimidazolidine-1-oxyl or any other known inhibitor.

10. Composition according to claim 8 characterized in that the polymerization inhibitor is hydroquinone or phenothiazine.

11. Composition according to one of claims 9 and 10 characterized in that the amount of polymerization inhibitor is such that the ratio of the total mass of components of the diphenylamine type of formula (I) to the total mass of the components is included between 90/10 and 10/90, preferably between 80/20 and 20/80.

12. A process intended to prevent the radical polymerization of an ethylenically unsaturated aliphatic monomer, comprising the addition to said monomer of an effective amount of at least one diphenylamine derivative corresponding to the general formula (I): in said formula (I):

13. Method according to claim 12 characterized in that the diphenylamine derivative corresponds to formula (I) in which A and B represent a benzene ring or a naphthalene ring and preferably, A and B are identical and represent a benzene ring .

14. The method as claimed in claim 12, characterized in that the diphenylamine derivative corresponds to formula (I) in which n is less than or equal to 3, preferably equal to 0 or 1 and m is less than or equal to 4, preferably equal to 1 or 2.

15. Method according to one of claims 12 to 14 characterized in that the diphenylamine derivative corresponds to formula (I) in which R ^ and R2 represent:

. a hydrogen atom,. an alkyl radical, linear or branched, having from 1 to 12 carbon atoms, preferably from 1 to 4 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl,

. a linear or branched alkenyl radical having from 2 to 6 carbon atoms, preferably from 2 to 4 carbon atoms, such as vinyl, allyl,. a linear or branched aikoxy or thioether radical having from 1 to 6 carbon atoms, preferably from 1 to 4 carbon atoms such as the methoxy, ethoxy, propoxy, isopropoxy, butoxy radicals, an alkenyloxy radical, preferably an allyloxy radical or a phenoxy radical,. a radical of formula: -R3-OH

-R3-SH -R3-COOR4 -R3-CO-R4

-R ₃ -N (R4) ₂

-R ₃ -CO-N (R4) ₂ -R3-NH-CO-R4

-R3-NH-COO-R4 in said formulas, R3 represents a valential bond or a divalent hydrocarbon radical, linear or branched, saturated or unsaturated, having from 1 to 6 carbon atoms such as, for example, methylene, ethylene, propylene , isopropylene, isopropylidene; the identical or different R4 radicals represent a hydrogen atom or a linear or branched alkyl radical having from 1 to 6 carbon atoms.

16. Method according to one of claims 12 to 15 characterized in that the diphenylamine derivative corresponds to formula (la):

in said formula (la):

- R _{1 f} R2, n and m have the meaning given previously in one of claims 12 to 15.

17. The method of claim 16 characterized in that the diphenylamine derivative corresponds to formula (la) in which R- | represents a hydrogen atom, an alkyl or aikoxy group having from 1 to 4 carbon atoms and R2 represents a hydrogen atom, an alkyl or aikoxy group having from 1 to 4 carbon atoms.

18. Method according to one of claims 12 to 17 characterized in that the diphenylamine derivative chosen from:

- 2-hydroxy-5-methyldiphenylamine, - 2-hydroxy-4-methyldiphόnylamine,

- 2-hydroxy-4 ', 5-dimethyldipheny lamin,

- 2,2'-dihydroxydiphenylamine, - 3-hydroxy-4'-methoxydiphenylamine, - 3,3'-dihydroxy-2,2'-dimethyldiphenylamine, - 3,3'-dihydroxy-2,2'-dimethoxydiphenylamine, - 4 -hydroxy-4'-methyldiphenylamine, - 4-hydroxy-4 '- (methoxycarbonylamino) -diphenylamine, - N- (4-hydroxyphenyl) -2-naphthylamine, - 4,4'-dihydroxydiphenylamine _f - 4,4'-dihydroxy-2,2'-dimethyldiphenylamine, - 4,4'-dihydroxy-2,2'-dimethoxydiphenylamine, - 2-hydroxy-4'-hydroxydiphenylamine. - 4,4'-dihydroxy-2,2'-dimethyl-diphenylamine.

19. Method according to one of claims 12 to 18 characterized in that the total amount of diphenylamine derivative of formula (I) added, is between 1 and 2000 ppm, preferably between 5 and 1000 ppm relative to the weight total of said monomer.

20. Method according to one of claims 12 to 19 characterized in that the amount of polymerization inhibitor is such that the ratio of the total mass of components of the diphenylamine type of formula (I) to the total mass of the components is between 90/10 and 10/90, preferably between 80/20 and 20/80.

21. Method according to one of claims 12 to 20 characterized in that the said ethylenically unsaturated aliphatic monomer is chosen from olefinic monomers comprising one or two unsaturations; halogenated unsaturated monomers; unsaturated acids; unsaturated esters; unsaturated resins; unsaturated amides; unsaturated nitriles; unsaturated ethers.

22. The method of claim 21 characterized in that said aliphatic ethylenically unsaturated monomer is chosen from isoprene and butadiene; vinyl chloride, chloroprene, vinylidene chloride, vinylidene fluoride and vinyl fluoride; acrylic acid, methacrylic acid and crotonic acid; unsaturated esters of acrylic acid of the methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, hydroxypropyl acrylate; unsaturated esters of methacrylic acid such as methyl methacrylate, butyl methacrylate, lauryl methacrylate, dimethylaminoethyl methacrylate, stearyl methacrylate; vinyl acetate; acrylated epoxy resins and polyethylene glycol diacrylate; acrylamide, N, N-dimethylacrylamide, methylenebisacrylamide and N-vinylpyrrolidone; acrylonitrile; vinyl ether; diethyl vinylphosphonate.

23. The method of claim 22 characterized in that said aliphatic monomers are the esters of acrylic acid and methacrylic acid.

24. Use of the composition described in one of claims 1 to 11 as an emergency inhibitor during the synthesis of polymers from aliphatic monomers containing ethylenic unsaturation.