GB1568445A - Free radical polymerisation of ethylenically unsaturated mnomers - Google Patents

Description

(54) FREE RADICAL POLYMERISATION OF ETHYLENICALLY UNSATURATED MONOMERS (71) We, ICI UNITED STATES INC., a corporation organised under the laws of the State of Delaware, United States of America, of New Murphy Road and Concord Pike, Wilmington, State of Delaware, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention concerns the polymerization of ethylenically unsaturated polymerizable monomers susceptible to free radical polymerization. Specifically the invention concerns novel methods for initiating polymerization of such monomers and monomer systems containing inactive initiators which initiators may be activated to polymerize the system.

Polymerization of ethylenically unsaturated monomers may be initiated by several methods well known to the art. Some of these include the use of high energy electromagnetic radiation such as gamma radiation and x-rays, ultraviolet light radiation, chemical initiators, and thermal means. Many polymerization reactions depend upon the formation of free radicals to cause the initiation of the polymerization. The use of free radical producing agents containing an acetic acid group has been disclosed in Chambers' U.S. Patent No. 3,479,185. The Chambers patent discloses for example the use of a system of N-phenyl glycine or N,N,N',N'ethylenediamino tetraacetic acid in combinationwith a 2,4,5-tri-phenylimidazolyl dimer as a photopolymerization catalyst.

It has now been discovered however that certain N-substituted aromatic imino acetic compounds produce free radicals and provide for excellent and versatile initiators without the additional presence of a dimer.

An additional advantage of the initiators of the present invention is their versatility in that they can cause polymerization in presence or absence of air, oxygen, heat, visible or ultraviolet light. While such sources of radiation energies are therefore not required, the presence of them as promoters will tend to increase the activity of the initiator and consequently the rate of polymerization.

According to the invention there is therefore provided a method of polymerizing a monomer system containing one or more ethylenically unsaturated compounds susceptible to free radical polymerization wherein the polymerization is initiated by means of a compound of the formula:

where R1 is a substituted or unsubstituted aryl radical as hereinafter defined and is hydrogen, alkyl, alkoxy or CH,COOH group, the said compound being the sole initiating species and being dissolved in the system and providedthat the ethylenically unsaturated compounds do not contain any group with which the acid group of the initiator will preferentially react chemically (as hereinafter defined). According to the invention there is also provided a monomer system susceptible to free radical polymerization which comprises one or more ethylenically unsaturated monomers and dissolved therein as sole initiating species of a compound of the formula

wherein R, is a substituted or unsubstituted aryl radical as hereinafter defined and R2 is hydrogen, alkyl, alkoxy or CH2COOH group, or a salt or ester of said compound which salt or ester upon treatment with acid will yield said compound, provided that the ethylenically unsaturated monomers do not contain any group with which the acid group of the compound will preferentially react chemically. By aryl is meant a monovalent radical containing an aromatic ring wherein the free valence is on a carbon atom of the aromatic ring.

An important aspect of the invention requires that the initiator must be soluble in at least one phase of the polymerizable system. This polymerizable system may be an emulsion suspension or solution polymerizable system. Often the initiator is soluble in the polymerizable monomer or monomers and no additional solvent is required. Alternatively in a polymerizable system where the initiator is not directly soluble in the monomer, the system must comprise a solvent such as for example, water or methanol for the initiator. The term "dissolved initiator" is therefore meant to include initiators dissolved in the polymerizable monomer and initiators dissolved in a solvent.

Initiators which are useful in the practice of the invention include:

N-(Carboxymethyl)-N-ethylaniline (N-ethylanilineacetic acid)

N-(carboxymethyl)-4-hydroxyaniline

N-(carboxymethyl)-4-chloroaniline

N(carboxymethyl)-4-methoxyaniline

N-(e arboxym ethyl)-4-t- butyl- aniline

N-(carboxymethyl)aniline (N-phenylglycine)

(1 -naphthylimino)acetic acid

[( 1,1 '-biphenyl)-4-ylimino] acetic acid Preferred initiators are those wherein R, has the formula

wherein R is hydrogen or an alkyl, alkoxy, phenyl, aralkyl, alkaryl or bis-(Ncarboxymethyl)amino group.

p-methylenedianiline tetraacetic acid

m-phenylenediamine tetraacetic acid

anilinediacetic acid

p-toluidinediacetic acid

p-(n-butyl)anilinediacetic acid

2,4-dimethylanilinediacetic acid

2,4-diethylanilinediacetic acid

[(2,4-dimethoxyphenyl)imino]diacetic acid

[(4-hydroxyphenyl)imino]diacetic acid

[(4-chlorophenyl)imino]diacetic acid

[(1,1 '-biphenyl).4-ylimino]di acetic acid

(2-naphthylimino)diacetic acid

(I-naphthylimino)diacetic acid

[(4-phenylmethylphenyl)imino]diacetic acid Preferred initiators showing high activity are those containing alkyl or alkoxy substituted aromatic ring group. Other preferred initiators also having high activity are those containing two aromatic rings.

The initiators useful in the process of the invention may be prepared by reacting in an aqueous solution the corresponding amine component with a slight excess of sodium chloroacetate at elelated temperatures. During the reaction, which is usually complete in 2 hours at reflux, the pH of the reaction mixture is carefully controlled at about 7 by the addition of sodium hydroxide. After the reaction is completed the product may usually be obtained as the inactive sodium salt by stripping or alternatively as an active precipitate by acidification such as with hydrochloric acid. In instances where precipitation will not occur after acidification, extraction procedures may be employed to obtain the product.

The unsaturated materials which may be polymerized by the practice of this invention are eth lenically unsaturated compounds susceptible to free radical polymerization. These compounds include esters, nitriles and organic halogen compounds which are olefinically unsaturated compounds of both aromatic and aliphatic types. By way of illustation, vinyl esters such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, and other vinyl esters containing as many as 18 or more carbon atoms in the acid moiety, may be polymerized in accordance herewith.

Other vinyl derivatives such as vinyl chloride, vinyl fluoride, chlorotrifluoroethylene, tetrafluoroethylene, butadiene, nitroethylene, methyl vinyl ketone, methyl isopropenyl ketone, butyl vinyl sulfone, vinyl triethoxysilane, ethyl vinyl sulfoxide, stryrene nuclear substituted styrenes including o-methyl, m-methyl, p-methyl styrene, divinylbenzene, and other related compounds may also be polymerized in accordance herewith. Vinylidine derivatives, viz., vinylidene chloride, and vinylidene carbonate respond to this polymerization also.

The acrylates respond particularly well to the techniques disclosed herein and the invention extends to include acrylates and methacrylates containing up to 18 or more carbon atoms such as ethyl acrylate, propyl acrylate, butyl acrylate, cc lbhexyl acrylate, cyclohexyl methacrylate, isobutyl acrylate, decyl acrylate, dodecyl methacrylate, methyl methacrylate, benzyl acrylate, tetrahydrofurfuryl acrylate, 2-methoxyethyl acrylate, methyl chloacrylate, pentaerythritol triacrylate, neopentyl-glycol diacrylate, ethyleneglycol acrylate phthalate, 2-hydroxy-propyl methacrylate, 2-hydroxyethyl acrylate and other related compounds such as acrylamide, acrylic acid, methacrylic acid respond to treatment set forth herein.

Other materials susceptible to the practice hereof include: acrylonitrile, methacrylonitrile, 2-chloroacrylonitrile, and allyl esters, such as the bisallyl biscarbonate ester of diethylene glycol.

Copolymers of the aforementioned unsaturated materials may be obtained.

Among the copolymers which may be prepared in accordance herewith are: copolymers of butadiene, acrylonitrile, vinyl acetate, vinylidene chloride, methyl acrylate, and divinyl-benzene with stryrene, and one another. Copolymers of butadiene with styrene, butadiene with acrylonitrile, acrylic acid with acrylamide, vinyl acetate with vinylindene chloride, styrene with methyl acrylate, and stryrene with divinylbenzene, are examples of specific copolymers which may be prepared pursuant to this invention. Terpolymers prepared in accordance herewith are often of special utility, such as those derived from butadiene, acrylonitrile, styrene mixtures and other mixtures wherein vinyl acetate or methyl methacrylate may be components of the terpolymers.

Preferred monomer systems of the present invention are those containing water soluble monomers such as acrylamide, diacetone acrylamide, acrylic acid, methacrylic acid; monomers such as diethylaminoethyl methacrylate, dimethylaminoethyl methacrlyate or dimetnylaminoethyl acrylate and their derivatives; vinyl monomer systems containing unsaturated maleate and fumarate polyesters; monomers containing acrylate or methacrylate unsaturation either separately or in combination with comonomers such as stryrene, methyl methacrylate, acrylonitrile, vinyl acetate or vinylidene chloride, and latex forming systems containing butadiene either alone or in combination with copolymerizable vinyl monomers such as stryene, acrylonitrile, vinyl acetate or vinylidene chloride.

The initiators of the invention have different effectiveness in different polymerization media, which may be aqueous or organic in nature. Most of the initiators are soluble in organic media. However, in aqueous media the selection of the best initiator is best determined experimentally, In general the least substituted aromatic monoacetic acid initiator is water soluble. As groups are substituted on the molecules, initiators may lose water solubility. N-carboxymethyl-4-t-butyl aniline was not found soluble in aqueous media.

The ethylenically unsturated monomers which are polymerizable according to the method of the invention should not contain any group with which the acid group of the initiator will preferentially react chemically. For example, monomer substituents such.as for examDle. amines isocvanate or vinyl epoxy groups are highly reactive with the acid groups of the initiator. Such substituents, if present, will derivatize the acid groups to amides or esters. While amine substituents may cause derivation reactions which may be reversible by acidification, substituents such as isocyanate or vinyl epoxy groups will cause irreversible reactions which will permanently diminish or terminate the ability of the initiators to generate free radicals. By the phrase "groups with which all the acid groups of the initiator will preferentially react chemically" is therefore meant those highly reactive groups which will non-reversibly derivatize all the acid groups of the initiator.

As is well known to those skilled in the art, free radical polymerization refers to those polymerization reactions which take place through intermediates having an odd number of electrons and, consequently, an unpaired electron. It is these intermediates which are geneally referred to as free radicals. The free radicals are normally generated in one or more of a variety of ways such as by the decomposition of a chemical initiator added to the polymerizable mixture or by the application of heat or ionizing radiation to the composition. If the free radical is generated in the presence of an ethylenically unsaturated monomer described above, the radical will add to the double bond with the regeneration of another radical. This radical will, in-turn, react with another monomer and in the course of the reaction generate another free radical resulting in growth of the polymer chain through the addition of one chain to another. Free radical polymerization is described in detail in, for example, the Encylopedia of Polymer Science and Technology, Vol. 7, pages 361431, Interscience Publishers, 1967, and in the Textbook of Polymer Science. Billmeyer, Interscience Publishers, 1962, pages 262-290.

In addition to growth of the polymer chain, several side reactions can also take place during the cource of the polymerization reaction. One of these, identified as chain transfer refers to the transfer of an atom from a molecule to a free radical in the reaction mixture. Depending upon the nature of the other material, this can result in the formation of additional polymer molecules, the formation of branch chain polymers or in termination of the polymertization reaction on a growing radical chain.

Chain transfer agents do not terminate the polymerization reaction entirely but merely terminate a growing chain and allow the polymerization to start elsewhere. If premature termination of the growing polymer chain occurs, a reduced molecular weight results and other polymer properties are achieved. It is, for this reason, desirable to include in a free radical polymerisation system a chain transfer agent which would function in this manner allowing molecular weight control.

The concentration of the various components utilized in the production of polymers in accordance with the invention may be varied over extremely wide ranges and appears to be not narrowly critical. The concentration of the initiator is dependent on the activity of the initiator used; the type and concentration of other components such as solvent and monomer; and promoters such as heat and light.

Although a concentration range of from .01 to 2% is economically preferred for optimum monomer conversion, under favorable conditions shown hereafter in the examples, any amounts which are effective may be used e.g., initiator concentation of as low as 0.01% by weight of monomer system and as high as 9% or more by weight of monomer system may be used successfully. For example, in non-aqueous systems the activity of p-toluidine acetic acid is greater than an initiator having an unsubstituted aromatic ring such as aniline acetic acid. Hence the concentration a greatly active initiator may be less than those of less active initiators. In general in the presence of air, oxygen or other polymerization inhibitors, larger amounts of initiator may be required.

The temperatures used in the practice hereof may vary widely and are only limited by the freezing and boiling point of the polymerizable system. In aqueous systems the polymerization may be conducted between 0 and 100 C. Non-aqueous media such as stryene or isopropyl methacrylate may allow for polymerization temperatures as high as 125"C. Other non-aqueous media may allow for polymerization temperatures of 200"C. or higher.

The polymerization process according to the invention may occur over a wide range of pH. The optimum pH of the polymerizable system will be affected by the stability of the monomer and the solubility and stability of the initiator.

It has also been discovered that the initiators are considerably less active when not substantially in the acid form. The activity of the initiator and thus the rate of polymerization may therefore be regulated by adustment ofpH. Advantageously a latent polymerizable system may be provided by having the initiators present not in the acid form but as the inactive salt, for example, the inactive sodium salt or amine salt, or a readily acid-hydrolyzable ester, for example the methylester. Such a latent system may then be activated by the simple adjustment of pH to a point below the neutralization point of the system. For example, in a system in which the monomer is selected from acrylamide, acrylic acid and mixtures thereof and a salt or ester of the initiating compound is present, the pH may be adjusted to a range of 3-5 in order to bring about polymerisation. The neutralization point is hereby defined as the H point of the polymerizable system at which the initiator becomes active due to the presence of acid group. Generally the lower the pH of the polymerizable system, the more active the initiator and conversely the higher the pH, the slower the rate of polymerization will be. It should be noted that the neutralization point of the polymerizable system will vary depending of the specific initiator employed.

A particular advantage of a latent polymerizable system is the ability to polymerize a liquid polymerizable system at any time in situ merely by the addition of acid to lower the pH of the system. For example, in oil recovery operations, water soluble monomer mixture of sodium acrylate and acrylamide and an inactive salt of an initiator may be introduced into an oil bearing formation as a low viscosity liquid and subsequently polymerized by the addition of acid to activate the initiator to produce a highly viscous polymer solution in situ.

The invention is further illustrated by the following examples in which all parts and percentages are by weight unless otherwise specified. In the case of the water soluble polymers, the symbol "Ni" represents intrinsic viscosity (i.v.) as measured in dVg in a 2N sodium chloride solution at 25.5"C.

EXAMPLE 1 To a solution of 2 g of acrylamide in 8 ml. of distilled water were added 20 mg of N-ethyl anilineacetic acid. The solution polymerized in 14 hours at room temperature while being exposed to laboratory day light.

EXAMPLE 2 To a solution of 2 g of acrylamide in 8 g of methanol were added 100 mg Nphenylglycine. The solution polymerized in 9 hours at room temperature while being exposed to laboratory day light. A sample not containing N-phenylglycine, acting as control, did not polymerize.

EXAMPLE 3 To a solution of 2 g acrylamide in 8 g of methanol were added 50 mg Nphenylglycine. The solution polymerized in 17 hours at room temperature while being exposed to laboratory day light. A sample not containing N-phenylglycine, acting as control, did not polymerize.

EXAMPLE 4 To a solution of 1 g acrylamide in 4 g of methanol were added 200 mg Nphenylglycine. The solution was kept at room temperature in the dark. A precipitate indicating polymerization formed within three days. A sample not containing N-phenylglycine, acting as control, did not polymerize.

EXAMPLE 5 To a solution of 1 g acrylamide in 4 g of water were added 100 mg Nphenylglycine. The solution was kept at room temperature in the dark. The solution polymerized within three days. A sample not containing N-phenylglycine, acting as control, did not polymerize.

EXAMPLE 6 To a solution of I g acrylamide in 4 g of water were added 100 mg Nphenylglycine. The pH was adjusted with dilute hydrochloric acid to 1. The solution was kept at room temperature in the dark. The solution polymerized within 60 hours. A sample not containing N-phenylglycine, acting as control, did not polymerize.

EXAMPLE 7 To a solution in a glass container of 2 g acrylamide in 8 g of methanol were added 50 mg N-phenylglycine. The pH was adjusted with dilute hydrochloric acid to 2. After exposure of the solution to laboratory day light for 14 hours at room temperature polymerization was observed. A sample not containing Nphenylglycine, acting as control, did not polymerize.

EXAMPLE 8 To a solution containing 3 grams of acrylamide and 1.5 grams of sodium chloride in 5.5 g water, were added 200 mg N-phenylglycine. The solution was kept at room temperature in the dark. The solution polymerized within three days. A sample not containing N-phenylglycine, acting as control, did not polymerize. The molecular weight of the polyacrylamide proudced in the presence of sodium chloride was found to be higher than that produced without the presence of the salt.

EXAMPLE 9 A solution of 25 grams of glacial acrylic acid, 75 grams of acrylamide and 100 grams distilled water was prepared. To this monomer solution was added a solution of catalyst consisting of 0.2 gram p-toluidine diacetic acid and 2.5 grams NaOH, and 87.5 grams distilled water. This mixture resulted in a very light tan colored clear solution. The pH was 4.4, the monomer concentration was 20.0% and the catalyst concentration was 0.20% The monomer solution was then poured into a polyethylene bag, flushed with nitrgen for 1 minute then sealed with tape. The sample was placed in a dark cabinet for 17 hours at room temperatuire. A rubber gel had resulted. Isolation of copolymer with a methanol-sodium hydroxide solution showed the conversion of monomers to copolymer to be essentially 100% complete. The intrinsic viscosity of the copolymer was 16.6 dl/gm when measured in 2N NaCI at 24"C.

To illustrate the wide range of concentrations in which the initiators are useful in free radical polymerizations, p-toluidine diacetic acid was used to initiate a 20 , aqueous acrylamide solution in the presence of air and sunlight at room temperature. The following Table I shows the results: TABLE I Initiator Ni % Monomer Example Concentration % i.v. Conversion 10 4 1.6 dl/g 99 11 2 2.8 dl/g 100 12 1 3.8 dl/g 100 13 0.5 5.8 dl/g 100 14 0.16 9.0 dl/g 100 15 0.04 - little reaction The results of Examples 10 to 15 also indicate that the intrinsic viscosity of the polymer is inversely proportional to the concentration of the catalyst.

Different initiators were evaluated for their activity by polymerizing 2 g of acrylamide dissolved in 8 ml of distilled water. The following Table II indicates the results. Where the indicated light source is sunlight, the samples were exposed to direct sunlight in an open jar at 280 C. Where the indicated source is laboratory daylight the samples were stored in a closed jar near a window under ambient conditions.

TABLE II Light Exposure Example Initiator Concentration Source Light 16 aniline- 2% sunlight 9 minutes diacetic acid 17 toluidine- 2% sunlight 45 seconds acetic acid 18 p-phenylene di- 0.5% sunlight 20 minutes aminetetra acetic acid 19 2,Sdimethyl- 1.0% lab. 14 hours anilinedi acetic daylight acid 20 2,Sdimethoxy- 1.0% lab. 1 hour anilinediacetic daylight acid All of the Examples 16-20 produced polymer in the indicated time period.

EXAMPLE 21 To a solution of 2 g acrylamide and 40 mg p-toluidine diacetic acid in 8 g water were added 2 drops of a 33% sodium hydroxide solution. The resulting pH was 9.

The solution was exposed to sunlight for 80 minutes but failed to gel. Thereupon, pH was adjusted to 4.5 by addition of concentrated hydrochloric acid and exposure continued. Gelation was complete within 6 minutes. Conversion: 97.5%. The intrinsic viscosity of the polyacrylamide was Ni = 4.6 dl/g in 2N NaCl at 25.50C.

EXAMPLE 22 To a solution of 2 g acrylamide and 8 g water were added 20 mg of the sodium salt of p-toluidine diacetic acid. Upon illumination with a 300 watt visible light source at 12" for 1--3i4 hours, no gelation occurred. Thereupon, 20 mg of ptoluene sulfonic acid were added. The resulting pH was 3. A clear, colorless gel formed after 9 minutes of additional exposure indicating the acrylamide had polymerized.

EXAMPLE 23 To a solution of 2 g acrylamide and 8 g water were added 20 mg of the sodium salt of p-toluidine diacetic acid. Upon heating at 60"C. in the dark for over 4 hours, no polymerization occurred. Thereupon, 20 mg of p-toluene sulfonic acid were added. The resulting pH was 3. Heating at 600C. in the dark was continued. A clear, colorless gel formed in 15 minutes.

EXAMPLE 24 To a solution of 2 g acrylamide in 4 g water and 4 g methanol were added 40 mg of the sodium salt of p-n-butylaniline diacetic acid. The sample was illuminated for 1--1/2 hours with a 300 watt visible light source at a distance of 12". No polymerization occurred. Thereupon, 40 mg p-toluene sulfonic acid were added.

The resulting pH was 3. Further illumination for 4 minutes resulted in a cloudy, white gel containing polyacrylamide.

EXAMPLE 25 To 2 g of a polyoxypropylene bisphenol A fumarate resin (commercially available from ICI-US Inc. as ATLAC--3822-05 unsaturated polyester resin) was added 0.3 ml of a solution of dimethylaminoethylmethacrylate containing 10 mg of p-n-butyl-aniline diacetic acid. The acid is presumably present as the amine salt.

The sample was illuminated for 1--1/4 hours with a 300 watt visible light source at a distance of 12". A very slight amount of polymerization occurred. After addition of 300 mg p-toluene sulfonic acid and further illumination, a hard cure occurred within 4 minutes.

EXAMPLE 26 To 2 g of polyoxypropylene bisphenol A fumarate resin was added 0.3 ml of a solution of dimethylaminoethylacrylate containing 10 mg of p-n-butyaniline diacetic acid. The sample was heated at 600 overnight in the dark. No cure occurred. After addition of 200 mg p-toluene sulfonic acid, the sample cured overnight to a hard solid.

EXAMPLE 27 To 1 g polyoxypropylene bisphenol A fumarate resin was added 50 mg of dimethyl p-toluidine diacetate. The sample was illuminated for one hour using a 300 watt visible light source at a distance of 12". No cure occurred. Thereupon, 50 mg p-toluene sulfonic acid were added, illumination continued, and complete cure occurred within 6 minutes.

PREPARATION A Preparation of ntphenylenediamine tetraacetic acid Into a three-neck, round bottom (r.b.) flask, equipped with glass stirrer, reflux condenser, thermometer, and addition funnel were placed 32.4 g (0.3M) mphenylenediamine dissolved in 300 ml. water and 203.1 g sodium chloroacetate in 300 ml water, and 10 drops of a mixed acid/base indicator. The solution was heated to reflux and a solution of 48 g sodium hydroxide in 150 ml water added dropwise so as to maintain the pH between 5 and 8. Reaction was completed within 65 minutes. The reaction mixture was cooled and acidified to pH 1 with 120 ml conc.

hydrochloric acid. The formed precipitate was filtered, washed with water at pH = 1, and vacuum dried below 40"C. Recovered 49.4 g gray solids (mp = 188 C., oN = 7.6).

PREPARATION B Preparation of p- (n-butyl/aniline diacetic acid Into a three-neck r.b. flask, equipped with glass stirrer, reflux condenser, thermometer, and addition funnel were placed 29.9 g (0.2M) p-n-butylaniline; 46.6 g (0.4M) sodium chloroacetate dissolved in a solution of 200 ml water and 45 ml dioxane and 10 drops of a mixed acid/base indicator. The solution was heated to reflux and a solution of 16 g sodium hydroxide in 64 ml water was added dropwise so as to maintain the pH between 5 and 8 as shown by the indicator. Reaction was completed within 4 hours. The reaction mixture upon dilution with 500 ml water and cooling was acidified with 43 ml conc. hydrochloric acid. The formed precipitate was filtered and washed twice with 200 ml of water at pH 1.3 and dried under vacuum at 40"C. Yield: 41.2 g beige solids (%N = 4.9).

PREPARATION C Preparation of dimethyl p-toluidinediacetate Into a three-neck r.b. flask, fitted with stirring assembly, thermometer, reflux condenser, and a dropping funnel were placed 10.7 g (0.1M) p-toluidine, 21.7 g (0.2m) methylchloroacetate, 50 ml water, and 80 ml dioxane. The solution was heated to reflux and 32 g of an aqueous solution containing 8 g (0.2M) sodium hydroxide was added dropwise so as to maintain the charge at a neutral pH.

Addition was completed within 1--1/2 hours. The flask was cooled to 5"C., and the product was Poured ito a 4 1. beaker. Upon addition of 3 1. of water, a ppt. formed which was discarded. Extraction of the aqueous phase with chloroform and stripping the extract gave 24.6 g of light-yellow solid.

PREPARATIO

Claims (15)

**WARNING** start of CLMS field may overlap end of DESC **. dioxane and 10 drops of a mixed acid/base indicator. The solution was heated to reflux and a solution of 16 g sodium hydroxide in 64 ml water was added dropwise so as to maintain the pH between 5 and 8 as shown by the indicator. Reaction was completed within 4 hours. The reaction mixture upon dilution with 500 ml water and cooling was acidified with 43 ml conc. hydrochloric acid. The formed precipitate was filtered and washed twice with 200 ml of water at pH 1.3 and dried under vacuum at 40"C. Yield: 41.2 g beige solids (%N = 4.9). PREPARATION C Preparation of dimethyl p-toluidinediacetate Into a three-neck r.b. flask, fitted with stirring assembly, thermometer, reflux condenser, and a dropping funnel were placed 10.7 g (0.1M) p-toluidine, 21.7 g (0.2m) methylchloroacetate, 50 ml water, and 80 ml dioxane. The solution was heated to reflux and 32 g of an aqueous solution containing 8 g (0.2M) sodium hydroxide was added dropwise so as to maintain the charge at a neutral pH. Addition was completed within 1--1/2 hours. The flask was cooled to 5"C., and the product was Poured ito a 4 1. beaker. Upon addition of 3 1. of water, a ppt. formed which was discarded. Extraction of the aqueous phase with chloroform and stripping the extract gave 24.6 g of light-yellow solid. PREPARATION D Preparation of p-toluidine diacetic acid Into a three-neck, r.b. flask, equipped with glass stirrer, reflux condenser, thermometer, and addition funnel were placed 53.5 g p-toluidine (0.5M), and 116.5 g sodium chloroacetate dissolved in a solution of 200 ml water and 10 drops of a mixed acid/base indicator. The solution was heated to reflux and a solution of 40 g sodium hydroxide in 120 ml water added dropwise so at to maintain the pH between 5 and 8. Reaction was complete within 80 minutes. The reaction mixture upon cooling was acidified with 15 ml of conc. hydrochloric acid solution. The formed precipitate was filtered, washed with water at pH 2, and vacuum dried below 40"C. Yield: 86 g beige solids (%N = 6.0.) PREPARATION E Preparation of the sodium salt of pn-butyl)anlline diacetic acid Into a three-neck r.b. flask, equipped with glass stirrer, reflux condenser, thermometer and addition funnel were placed 29.9 g (0.2M) p-n-butylaniline; 46.6 g (0.4M) sodium chloroacetate dissolved in a solution of 200 ml water and 45 ml dioxane and 10 drops of a mixed acid/base indicator. The solution was heated to reflux and a solution of 16 g sodium hydroxide in 64 ml water was added dropwise so as to maintain the pH between 5 and 8 as shown by the indicator. Reaction was completed within 4 hours. The reaction mixture was stripped to dryness to give 50 g of the sodium salt of p-(n-butyl)aniline diacetic acid. Some sodium chloride impurity may be present in the product. EXAMPLE 28 To a solution containing 2 grams of acrylamide, 2.0 grams of sodium chloride, 40 mg p-toluidine diacetic acid were added 2 drops of a 33% sodium hydroxide solution. The resulting pH was 9. The solution was exposed to sunlight for 80 minutes but failed to gel. Thereupon, pH was adjusted to 4.5 by addition of concentrated hydrochloric acid and exposure continued. Gelation was complete within 6 minutes. Conversion was 97.5%. The molecular weight was higher than that of a control sample, with no salt added, as evidenced by its solution viscosity. EXAMPLE 29 To a solution of 2 g acrylamide in 7.95 g of water were added 0.05 cc of a solution containing 250 mg of p-toluidine diacetic acid in 100 ml of water. The catalyst concentration based on monomer weight was 0.006%. the sample was degassed in a vial and kept under vacuum. After illumination with a 300 watt visible light source at 12" for 25 minutes gelation was observed. A control sample similarly exposed did not gel. Conversion 60%. The intrinsic viscosity of the polyacrylamide was Ni = 19.4 dl/g in 2N NaCl at 25.5 "C. WHAT WE CLAIM IS:

1. A monomer system susceptible to free radical polymerisation which comprises one or more ethylenically unsaturated monomers and dissolved therein

as sole initiating species a compound of the formula:

wherein R, is a substituted or unsubstituted aryl radical as hereinbefore defined, and R2 is hydrogen, alkyl, alkoxy or -CH2COOH, or a salt or ester of said compound which will yield the compound upon treatment with acid and which has been so treated, provided that the ethylenically unsaturated monomers do not contain any group with which the acid group of the initiator compound will Dreferentially react chemically (as hereinbefore defined).

2. A monomer system according to Claim 1, where R1 has the formula

wherein R is hydrogen or an alkyl, -alkoxy, phenyl, aralkyl, alkaryl or bis-(N carboxymethyl) amino group.

3. A monomer system according to Claim 2, wherein the initiator compound is N-phenylglycine, anilinediacetic acid, N-ethylanilineacetic acid, p-toluidinediacetic acid, p-n-butylanilinediacetic acid, 2:4-dimethylanilinediacetic acid, 2:4 dimethoxyanllinediacetic acid or m- or p- phenylenediaminetriacetic acid.

4. A monomer system according to Claim l, wherein the salt of the initiator compound is an alkali metal salt or an amine salt.

5. A monomer system according to Claim 1, wherein the ester of the initiator compound is the methyl ester.

6. A monomer system according to any one of Claims 1 to 5, wherein the monomers are selected from acrylamide, acrylic acid, methacrylic acid, diethylaminoethyl methacrylate, dimethylaminoethyl methacrylate, dimethylaminoethyl acrylate, maleate or fumarate polyester, butadiene, stryene, methyl methacrylate, acrylonitrile, vinyl acetate and vinylidene chloride.

7. A monomer system according to Claim 1 substantially as hereinbefore described with reference to the foregoing Examples.

8. A method of polymerising a monomer system containing one or more ethylenically unsaturated monomers susceptible to free radical polymerisation wherein the polymerisation is initiated by means of a compound of the formula

where R, is substituted or unsubstituted aryl radical as hereinbefore defined, R2 is hydrogen, alkyl, alkoxy or CH2COOH, the said compound being the sole initiating species and being dissolved in.the system and provided that the ethylenically unsaturated compounds do not contain any group with which the acid group of the initiator will preferentially react chemically.

9. A method according to Claim 8, wherein there is introduced into the system a salt or ester of the initiating compound which salt or ester upon treatment with acid will yield said compound and wherein the system is subsequently acidified so as to yield in the said compound in the dissolved state.

10. A method according to Claim 9, wherein the acidification is effected by pH adjustment of the system to within a range of 1--4.5.

11. A method according to Claim 9 or Claim 10, wherein the salt is an alkali metal salt or an amine salt.

12. A method according to Claim 9 or Claim 10, wherein the ester is the methyl ester

13. A method according to Claim 8, wherein the monomers are selected from acrylamide, acrylic acid, methacrylic acid, diethylaminoethyl methacrylate, dimethylaminoethyl methacrylate, dimethylaminoethyl acrylate, maleate or fumarate polyester, butadiene styrene, methyl methacrylate, acrylonitrile, vinyl acetate and vinylidene chloride.

14. A method according to Claim 9, wherein the ethylenically unsaturated monomers are selected from acrylamide and acrylic acid and mixtures thereof and wherein the pH is adjusted to a range of 3-5.

15. A method according to Claim 8 substantially as herein before descrbed with reference to the foregoing Examples.