WO1998013392A1

WO1998013392A1 - No-compounds for pseudo-living radical polymerization

Info

Publication number: WO1998013392A1
Application number: PCT/EP1997/005009
Authority: WO
Inventors: Luc Louis Theophile Vertommen; Hendrik Jan Willem Van Den Haak; Peter Hope; Christine Pascale Mireille Lacroix; John Meijer; Auke Gerardus Talma
Original assignee: Akzo Nobel N.V.
Priority date: 1996-09-25
Filing date: 1997-09-11
Publication date: 1998-04-02
Also published as: ATE210156T1; JP2001500914A; DE69708896D1; AU4773997A; DE69708896T2; EP0928296B1; EP0928296A1

Abstract

The invention pertains to a process for pseudo-living radical polymerization's in which use is made of specific NO-compounds, called initers, according to formula (I) or (II) wherein: R represents a group which has at least one carbon atom and is such that the free radical R. is capable of initiating the free radical polymerization of unsaturated monomers; at most five of the groups represented by X1-X6 are the same or different straight-chain or branched substituted or unsubstituted alkyl groups, wherein two or more of the groups may be linked to form cyclic structures, or wherein -CX1X2X3 and/or -CX4X5X6 are phenyl, the complementary groups X1-X6 are functional groups, and, X7 and X8 are independently selected from alkyl, aryl, alkaryl, and aralkyl, while X7 is optionally linked with X8 to form bridged structures. The invention further relates to certain NO compounds, (block) (co)polymers, and to a recycling process for such polymers.

Description

NO-COMPOUNDS FOR PSEUDO-LIVING RADICAL POLYMERIZATION

Background of the invention

The present invention relates to the use of NO-compounds as initers in pseudo-living radical polymerization processes, as well as to the polymers formed in such processes and to certain novel NO-compounds.

Currently, numerous institutes are investigating so-called "pseudo-living polymerization" processes. Such polymerization processes allow the production of polymers with a very narrow molecular weight distribution as well as of specific block-copolymers. Living polymerization processes have long been known from ionic processes such as the anionic polymerization of styrene. There is a great interest in (pseudo) living polymerizations using free radicals, because such polymerizations would not suffer from many of the problems associated with living ionic polymerizations, for instance the need to use reactants of very high purity to avoid poisoning the reactive centre.

The current state of the art for (pseudo-) living polymerization processes involving radicals typically requires the use of a "stable free radical agent' in combination with an initiator, as described, for instance, in the recently issued patents US 5,498,679, US 5,449,724, US 5,412,047, and US 5,312,871 , as well as in patent applications WO 95/26987 and WO 94/11412. The stable free radicals of choice are usually compounds possessing stable nitroxide radicals. However, the synthesis of such stable free radical agents, as described, for instance, in Macromolecules 1996, 29, 3323-3325, is cumbersome, and the nitroxide radicals thus obtained are quite expensive. The initiator in such prior art processes is typically used in such a quantity that the ratio of free radical agent to the amount of radicals generated by the initiator is not unity, see for example WO 94/11412, and many side reactions take place, leading to both undesired side products and a reduced initiator efficiency. The reduced initiator efficiency is often counterbalanced by using an excess of this product, with all associated disadvantages.

As an improvement on these known pseudo living radical polymerization processes, US 4,581 ,429 describes how nitroxide stable free radical compounds can be reacted with azo-initiators or with unsaturated compounds in combination with an initiator. The resulting alkoxyamines can be used in what are called "controlled-growth free radical polymerization" reactions of a "living" nature. This concept was further elaborated on in Macromolecuies, 1995, 28, 8722-8728, and Macromolecuies 1996, 29, 5246-5254, where it is demonstrated "how the alkoxyamine structure determines the C-O bond strength and what is required for these species to be successful initiators of living radical polymerization." In the former article it is disclosed that electron donating or withdrawing groups - i.e., electron donating or withdrawing as compared with alkyl groups - on the nitroxide are undesired since they are "unlikely to be useful in living polymerization." Evaluation of the disclosed alkoxyamine compounds showed that they do not perform to full satisfaction in the polymerization. More particularly, both the polymer yield and control of the molecular weight of this polymer needed improvement. Also, not all desired monomers could be polymerized in a controlled way.

The present invention relates to processes and NO-compounds which serve to avoid or minimize the disadvantages as reported for current polymerization processes and existing NO-compounds.

Accordingly, it is the primary object of this invention to provide a pseudo-living polymerization process in which specific NO-compounds are combined with one or more of various monomers with subsequent polymerization at a variety of temperatures. It is another object of the invention to provide an economical polymerization process in which no additional initiators are used and no chain transfer agent or other means is required to produce polymers with a controlled molecular weight in high yields

A third object of the invention is to provide an economical process to produce block copolymers using NO-compounds in pseudo-living polymerization processes These copolymers can be, for instance, block, star, and/or comb copolymers

A further object of the invention is to provide certain NO-compounds that can be used as miters in pseudo-living polymerization processes in which a variety of monomers can be polymerized in high yields, with accurate control of the molecular weight of the formed polymer, at various temperatures, which NO- compounds are easy to synthesize

Still another object of the invention is to provide a polymer that can easily be recycled to its monomenc compound(s) because of the NO end group of the polymer This will make it possible for the polymers to be recycled at fairly low temperatures without the addition of high-temperature initiators, thus allowing a more economical and environment-fnendlyrecycling process

These and other aspects of the invention are outlined in more detail below

Description of the invention

As used herein, the term "pseudo-living polymerization process" stands for the radical polymerization process in which one or more ethylenically unsaturated monomers are polymerized by means of at least one miter According to a non-limiting theory, the polymerization kinetics in these novel processes depend, amongst others, on the thermal decomposition rate of the miter that is used It is noted that the polymerization will not be of a perfect "living" nature Also, it was observed that these polymerization kinetics are not necessarily the same as conventional "pseudo-living" processes

The term "miter" as used herein defines NO-compounds of a specific structure, as defined below Such NO-compounds are referred to here as miters, for it is believed that the carbon-centred radical formed upon decomposition initiates the polymerization, whereas the nitroxide radical will terminate the growing chain Without the invention being limited to such a theory, it is further believed that the termination reaction is reversible at the polymerization temperature, so that monomers can be inserted between the last monomeπc unit and the nitroxide moiety of the miter

The first embodiment of the invention relates to a polymerization process in which at least one NO-compound with at least one moiety according to formula (I) or (II),

wherein • R represents a group which has at least one carbon atom and is such that the free radical R- is capable of initiating the free radical polymerization of unsaturated monomers,

• at most five of the groups represented by X--X₆ are the same or different straight-chain or branched, substituted or unsubstituted (cyclo) alkyl groups, while two or more of the groups XrX₆ may be linked to form cyclic structures,

• the complementary groups X* through X₆ are functional groups selected from substituted or unsubstituted phenyl cyano, ether, hydroxy nitro, dialkoxyphosphonyl, and carbonyl containing groups, or, alternatively,

-CK^X_{2 2} and/or -CX₄X-jX₆ represent a phenyl group,

• X₇ and X₈ are independently selected from alkyl, aryl, alkaryl, and aralkyl, while X₇ is optionally linked with X₈ to form bridged structures, and is combined with a monomer composition to be polymerized

Preferred examples of carbonyl containing functional groups are ester, carboxyalkyl, aldehyde, anhydride, and ketoalkyl groups

Although X -X₆ may be linked to form cyclic structures, they preferably are not so linked Also it is preferred that each of XrX₈ contains fewer than 30 carbon atoms More preferably, each of X*-X₈ contains fewer than 10 carbon atoms in order to produce miters with a low molecular weight Most preferably, at most five of X_rX₆ are independently selected from methyl, ethyl, propyl, isopropyl, butyl, sec butyl, tert butyl, and cyclohexyl X₇ and X₈ are preferably linked More preferably, X₇ and X₈ are part of one substituted or unsubstituted phenyl or naftyl group Most preferably, X₇ and X₈ ar part of one phenyl group

Furthermore, it is preferred that the process involves miters with a moiety of formulae I or II, with the functional group being selected from phenyl, cyano, dialkoxyphosphonyl, carboxyalkyl, and ester More preferred is a process where the miter possesses a cyano, phenyl, ester or dialkoxyphosphonyl group Even more preferred, is a process where the miter possesses a cyano or phenyl group Most preferred is a process with at least one miter with a cyano moiety Preferably, these iters can be produced without toxic byproducts being formed In this respect, it is noted that miters derived from 2,2'- azobιs(ιsobutyronιtπl) are less favoured because the toxin tetramethylsucciπonitnl is a known decomposition product of this material

Non-limiting examples of functional groups of the miter further include methylether, ethylether, propylether, butylether, poly(alkylether), methylketone, ethylketone, propylketone, isopropylketone, butylketone, isobutylketone, tert butylketone, diethoxyphosphonyl, ethoxypropoxyphosphonyl, dipropoxy- phosphonyl, dιbutoxyphosphonyl,dιιsobutoxyphosphonyl,-C(O)OCH₃, -C(0)OC₂H₅, and C--C₂₀ carboxylicacid esters

The R group may bear one or more of the ONC(X₁.₃)C(X₄.₆) functions as long as each of the radicals R* formed upon scission of one or more of the R-0 bonds is capable of initiating the free radical polymerization of an unsaturated monomer Furthermore, in the first instance it is preferred that R is not of a polymeric nature, meaning that R preferably does not comprise more than approximately 4 recurring units incorporated by radically polymerizing one or more unsaturated monomers Preferably, R does not contain more than two of such recurring units Most preferred are compounds wherein R equals C(X₁.₃) or C(X₄.₆) However, the polymer that results from the polymerization process can be reused as an miter according to the invention Therefore, R is not limited to a non-polymeric group

The NO-compounds can be used at various temperatures, with the choice of the NO-compound depending on the desired polymerization temperature In this respect it is noted that radical polymerization reactions of (meth)acrylιc monomers are typically conducted at lower temperatures than (co)polymeπzatιons involving styrene monomer For other, regularly used, monomers suitable polymerization temperatures are also well-known The NO- compound of choice has an acceptable decomposition rate at the desired polymerization temperature, which is generally between 50 and 180°C From, for instance, Macromolecuies, 1995, 28, 8722-8728, it is known that the use of electron withdrawing functional groups will stabilize the R-0 bond, whereas electron donating functional groups will labihze it Given this information and the teaching of this document, the man skilled in the art will have no problem selecting suitable types and numbers of functional groups to obtain usable NO-compounds Before conducting actual polymerization experiments, the half-life of the NO-compound may be determined in one or more well-known ways

The invention is not limited to the use of NO-compounds alone Also encompassed is the combination of such an NO-compound with additives catalyzing its decomposition

Preferably, the process according to the invention results in polymers with a number average molecular weight (Mn) close to the theoretical value (Mth), calculated from

More particularly, it is preferred that the Mn does not exceed the Mth by 15 times Most preferred is a process wherein Mn is less than five times Mth

The ethylenically unsaturated monomers that can be polymerized and/or copolymeπzed by means of the NO-compounds include styrene, divmyl- benzene, α-methylstyrene, chloromethylstyrene, acrylic acid, esters of acrylic acid, methacrylic acid, esters of methacry c acid, maleic acid, maleic anhydride, esters of maleic acid, fumaπc acid, esters of fumaπc acid, acrylonitπle, vinylpyndine, isoprene, butadiene, tπenes, styrene phosphonic acid, vinyl phosphonic acid, styrene phosphonic esters, vinyl phosphonic acid esters, maleimides, citraconimides, itaconimides, and vinylacetate Also derivatives of these monomers obtained, for instance, by substituting a functional group for a proton, can be used Examples of suitable functional groups are halogen, hydroxy, ammo, methoxy, nitro, carboxy, and cyano, but the invention is not limited to these

In a second embodiment, the invention relates to a process in which an iter according to formula (I) or (II) is combined with a monomer composition to produce (co)polymerswιth a controlled molecular weight in good yield, without that additional radical generating species or chain transfer agents which are known from classic radical polymerization processes, are introduced in the process Examples of radical generating species include, organic peroxides, azo-initiators and UV-initiators The use of one or more miters with at least one moiety according to formula (I) or (II) in polymerization processes obviates such radical generating species or chain transfer agents because they allow a very high polymerization rate while the degree of polymerization (the number of polymerized monomer units in the final polymer) remains close to the calculated value of the molar ratio of monomer to miter The dispersity of the molecular weight distribution of the polymer will typically not be close to unity as in living polymerizations, but may vary from, for instance, 1 4 to 2 7 This range is indicative only, especially when block copolymers are made by sequentially adding monomers, higher dispersity values have been observed

Should the molecular weight of the polymer and/or its dispersity become too high, for instance, when excessive thermal polymerization of one or more of the monomers takes place, then the miter may be combined with a stable free radical agent In such a case, the stable free radical agent preferably will have the same structure as the nitroxide radical that results from thermal decomposition of the NO compound according to the invention

In a third embodiment, the invention relates to polymers which are obtainable by the polymerization processes according to the invention and will have one alkoxyamine end group, said end group being of the structure -ON(CX₁X₂X₃)CX₄X₅X₆ or -ON(C(0)X₇)C(O)Xg, wherein X_rX_β are defined as above Consequently, these polymers are themselves iters according to the invention Hence, they can be used in further pseudo-living polymerization reactions in order to make, for instance, block copolymers Before being used in such a fashion, the polymers may first be collected, purified, and dried Preferably, however, the fresh monomer or monomer mixture can be added directly to the reaction mixture when it contains the desired polymer, for example, when a desired conversion, for example 90 percent by weight (%w/w), of the first monomer or monomer mixture is attained Depending upon the reaction kinetics of the monomers involved, the presence of two or more monomers at the same time may result in a monomer distribution within the growing polymer segment of a random or more regular (for instance, alternating) nature In this way, it is possible to produce (block) copolymers of varying nature in an economical fashion Since the (block) copolymer obtained in turn is an iter according to the invention, subsequent polymerization steps are possible Preferably, however, the miters according to the invention are low-molecular weight materials More preferably, such miters have fewer than four recurring monomer units, since such products are easier to handle With the miters and the process according to the invention one can produce block copolymers with specifically designed block compositions and sequences, resulting in materials with specific properties They may be used as, for example, compatibi zers, coupling agents dispersing agents for filled thermoplastics and SιO₂ filled rubber, telechelic slip agents, impact modifiers, anti-static agents, sizing agents, emulsifiers/surfactants, pigment dispersants, lubricants, processing aids, thickeners, adhesives, oil additives, and/or additives for the preservation and hardening of wood

In a further embodiment, the invention relates to specific NO-compounds containing at least one moiety of the formula (I) which are pre-eminently suited to be used in the polymerization process according to the invention, wherein • R represents a group which has at least one carbon atom and is such that the free radical R* is capable of initiating the free radical polymerization of unsaturated monomers,

• at most five of the groups represented by X- through X₆ are the same or different straight-chain or branched substituted or unsubstituted (cyclo) alkyl groups, while two or more of the groups may be linked to form cyclic structures,

• the complementary groups X- through X₆ are functional groups selected from substituted or unsubstituted phenyl, cyano, ether, dialkoxyphosphonyl and carbonyl containing groups, such as ester anhydride, and keto groups, and

• R is not polymeric when -N(CX₁X₂X₃) CX₄X₅X₆ is 2 5-dιmethyl-2,5- dιphenylpyrrolιdιn-1 -, with the proviso that the NO-compound is not tπs-(2-cyano-2-propyl)- hydroxylamine, trιs-(2-carboxyethyl-2-propyl) hydroxylamine, and/or trιs-(2- carboxymethyl-2-propyl)hydroxylamιne

Incidentally, it is noted that certain specific alkoxyammes are known which are not mentioned in US 4,581 ,429 Gingras and Waters describe the preparation of tπs-(2-cyano-2-propyl) hydroxylamine in J Chem Soc , 1954, 1920-1924 Trιs-(2-carboxymethyl-2-propyl)hydroxylamιne is synthesized as described by Boyd in J Chem Soc , 1958, 2056, and tπs-(2-carboxyethyl-2-propyl) hydroxylamine is synthesized by Masui in Tetrahedron, 1965, 21 , 2831 Also, the polymers mentioned in Macromolecuies 1996, 29, 3323-3325 and J M S - Rev Macromol Chem Phys. 1994, 34(2), 288-289 are accidental anticipations of some miters according to the invention

Upon thermal decomposition, with the R-0 bond being broken, the NO- compounds according to formula (I) will generate two radicals The carbon centred R^» radical can initiate a polymerization reaction However, during such a polymerization the nitroxide radical will terminate the growing chain, forming a new miter which in turn is thermally labile and may be involved in subsequent polymerization reactions In this way a pseudo-living radical polymerization will take place in which monomeπc units are inserted at the nitroxide terminated end of the polymer Because of the nature of such a process, the polymer that is formed will have a polydispersity (D) typically greater than unity (1 0), the dispersity observed in regular living polymerization reactions

The compounds according to the invention can be produced in various conventional ways It was surprisingly found that the reaction of carbon- centred radicals and nitric oxide (NO), which has been known since 1954 (see, for instance, J Chem Soc , 1954, 1920-1924), results in a very economical route to effective miters Reactants and reaction conditions are chosen such that during the synthesis at least one of the two carbon-centred radicals attached to the nitrogen atom will bear a functional group This is most easily achieved by selecting the proper concentration of one or more of the functional group bearing carbon-centred radical precursors Preferably, the functional group bearing carbon-free radical is obtained by the decomposition of one or more appropriate azo, C-C or other initiators such as diacyl peroxides with a high decarboxylation rate Depending on the use of the miter, it may be preferable to react only one type of carbon-centred radical (containing a functional group) with the NO gas

Alternatively, compounds according to the invention can be produced by the well-known reaction of a nitroso compound under influence of heat or with carbon-centred radicals Depending on the structure of the nitroso compound, the man skilled in the art will have no problem selecting a suitable carbon- centred radical generating species in order to arrive at compounds according to the invention An example of such a process is the preparation of N-tert - butoxy phthalimide (BuPI), according to formula (II), and of the structure

as described by T Kolasa, A. Chimiak and A. Kitowski in J Prakt. Chem , 1975,317, 252-256

The (block) (co)polymers that are made in the process of the present invention can fairly easily be recycled into low-molecularweight fragments In contrast to current recycling processes as, for instance, known from European patent application EP-A-0273274 and non-prepublished European patent application 96202111.9, filed on July 25, 1996, large amounts of compounds capable of generating free radicals and very high temperatures are not needed The low- molecular weight fragments that are formed can be used as a fuel Hence, the (block) (co)polymers according to the invention can be recycled using less energy and without the use of specific additives Preferably, the temperature in this recycling process is kept below 300°C

The invention will be further illustrated by the following examples

Experimental

The chemicals used in the following examples were all reagent grade unless specified otherwise. Styrene and 1 ,2-dιchlorobenzene (ODCB) were supplied by Baker (Baker PA grade) Styrene was freed of inhibitor by a treatment with an alkaline Al₂0₃ column. Methyl methacrylate (MMA), 2,2,6,6-tetramethy - pyrrolidinyloxy (TEMPO®), and (+)camphorsulfonιc acid (CSA), an agent which is presumed to reduce thermal polymerization in pseudo-living radical polymerizations, were supplied by Aldπch. Perkadox® AIBN (2,2'- azobιs[ιsobutyronιtπle]), Perkadox® AMBN (2,2'-azobιs[2-methylbutyronιtπle]), and all other initiators were supplied by Akzo Nobel or synthesized as laid down in the available documentation NO gas was supplied by Indugas Tinuvm® 123 is a product of Ciba Geigy

Cumyl-TEMPO as used in the comparative examples was synthesized following the general procedure of EP 0 309 402, Example 63 More specifically, 0 454 mol of tert butylhydroperoxidewas dosed in five hours to a refluxing solution (atmospheric pressure) of 0 14 mol tetramethylpipeπdine, 1 582 mol cumene, and 4 mmol Mo0₃, and the mixture was reacted further at this temperature for 12 hours The reaction product was reacted with 0 17 mol of di-tert butylperoxide an autoclave at 140°C for four hours Cumene was removed using a rotary evaporator, and cumyl-TEMPO was obtained by crystallization

For polymerizations conducted in sealed tubes, the reaction mixture was degassed by means of well-known freeze-thaw techniques, after which the ampoule was sealed under vacuum For polymerizations conducted in an open flask, a three-necked flask was fitted with a (gas) inlet, a stirrer, and a condenser The contents of the flask were flushed with Argon before and during the polymerization

The conversion of monomer into polymer was determined in conventional ways by gas chromatographic (GC) analysis for monomer, using monochlorobenzene as the internal standard Samples were taken by either breaking an ampoule or through one of the necks of the flask, using a syringe The reactants were quenched by rapid cooling and dissolved in dιchloromethane(for GC analysis) or THF (for molecular weight analysis)

The number average molecular weight (Mn), weight average molecular weight (Mw), and dispersity (D) of the polymers were analyzed in conventional ways by means of size exclusion chromatography, using the THF solution as the eluent. Polystyrene samples were used as calibration standards Polymers were isolated from the solution by precipitation in n-pentane and subsequent drying in a vacuum oven at 50°C to constant weight (20-100 hours).

Polymers were characterized by means of 300 or 400MHz ¹H and 100 MHz ¹³C NMR.

No attempt was made to optimize yields.

Example 1

Preparation of NO-compounds using NO gas

a) N,N,0-Trιs-(1-cvano-1-methylethyl)hvdroxylamιne ((IBN)_?NO)

A solution of Perkadox AIBN (152.7 gr, 0.93 mol) in 1500 ml of toluene was stirred, flushed with nitrogen gas, and heated to 76°C. A stream of nitrogen monoxide (5 l/hr) was passed through the solution, and a deep greenish/blue colour appeared. Heating was continued for 2 hours at 76°C, 1 hour at 82°C, 30 minutes at 88°C, 15 minutes at 94°C, and finally 15 minutes at 119°C to achieve complete decomposition of the AIBN Residual nitrogen monoxide was removed by flushing the reaction mixture with nitrogen gas, at which point the colouration changed to yellow. The solvent was removed at the rotary evaporator, and the resulting solution was steam-distilled to remove the by- product tetramethyl succinonitrile. Next, the water/product mixture was left to cool down to room temperature, and the product precipitated. This solid was removed by filtration, dissolved in dichloromethane, and then dried with magnesium sulfate. Evaporation of the solvent gave 84.3 g (58%) of a yellow solid, the (IBN)₃NO.

b) N,N,0-Tris-(1-cvano-1-methylpropyl)-hvdroxylamine((MBN)₃NO)

A solution of Perkadox AMBN (178.8 gr, 0.93 mol) in 1500 ml of toluene was stirred, flushed with nitrogen gas, and heated to 76°C. A stream of nitrogen monoxide was passed through the solution, and a deep greenish/blue colour appeared. Heating was continued for 2 hours at 76°C, 1 hour at 82°C, 30 minutes at 88°C, 15 minutes at 94°C, and finally 15 minutes at 1 19°C to achieve complete decomposition of the AMBN. Residual nitrogen monoxide was removed by flushing the reaction mixture with nitrogen gas, at which point the colouration changed to yellow. The solvent was removed using a rotary evaporator, and the resulting solution was steam-distilled in order to remove the by-product hexane-3,4-dinitrile. Next, the water/product mixture was left to cool down to room temperature. The solution was extracted with ether, and the organic layer was dried with magnesium sulfate. Evaporation of the solvent gave 85.8 g (50%) of a yellow liquid, the (MBN)₃NO. c) N,N,0-Trιs-(1 -cvano-1-cvclohexyl)hvdroxylamιne ((CCH)₃NO)

A solution of 30 g (0.123 mol) 1 ,1 '-azobιs(1 -cyanocyclohexane)ιn 130 ml of toluene was stirred, flushed with nitrogen gas, and heated to 76°C A stream of nitrogen monoxide (5 l/hr) was passed through the solution until a constant blue colour appeared Heating was continued for 2 hours at 100°C, 1 hour at 107°C, 30 minutes at 1 12°C, 15 minutes at 118°C, and finally 15 minutes at 125°C Residual nitrogen monoxide was removed by flushing the reaction mixture with nitrogen gas The solvent was removed at the rotary evaporator, and the resulting solution was steam-distilled to remove the by-product dι(cyclohexylnιtrile). Next, the water/product mixture was left to cool down to room temperature, and the product precipitated. This solid was removed by filtration, dissolved in dichloromethane. and then dried with magnesium sulfate Evaporation of the solvent gave 15 3 g (53%) of an off-white powder, the (CCH)₃NO

Example 2

Preparation of NO-compounds involving nitroso compounds

Bts-(2-cvano-2-propyD-N-phenylhvdroxylamιne ((IBN)₂ArNO)

A suspension of Perkadox AIBN (65 6 gr, 0 4 mol) in 100 ml of toluene was added to a refluxing solution, at atmospheric pressure, of nitrosobenzene (21 , 4 g, 0 2 mol) in toluene (400 ml), with the aid of a Watson Mariow pump The solution turned greenish/blue AIBN was dosed during a period of 80 minutes. Heating was continued for 1 hour to complete decomposition of the AIBN The solution became yellow After steam-distillation, the residue was twice recrystallized in ether. 16 g (35%) of a yellow powder were obtained

Example 3

Styrene, in a concentration of 4 1 mol/l in ODCB, was polymerized in a stirred open flask under an argon atmosphere, at a temperature of 140°C for 6 hours (IBN)₃NO was used in a concentration of 0 087 mol/l, and CSA was present in a concentration of 0 027 mol/l Samples were taken every 30 minutes. Analyses of the samples gave following results

Time Conversion Mn

(mm) (% w/w) (dalton)

0 0

30 301 1430

60 45.9 2120

90 56.9 2550

120 65.7 2950

150 71.8 3100

180 767 3310

210 80.3 3400

240 83.1 3520

270 854 3530

300 86.7 3680

330 88.1 3670

360 89.3 3670

Extrapolation of the Mn to 100 % conversion results in values close to the theoretical value for pseudo-living polymerizations, viz 4200 vs [M]/[l]*M_styrene =4900. The deviation is be eved to have been caused by some polymerization of styrene monomer at the very beginning of the polymerization process The polymer was retrieved and characterization showed it to contain the expected bιs(2-cyano-2-propyl)-hydroxylamιne groups. Comparative Example A

Styrene (bulk = 8 7 mol/l) was polymerized in a stirred open flask at 130°C under argon, using dibenzoyl peroxide (BPO) in a concentration of 0 072 mol/l and 2,2,6,6-tetramethylpιperιdιnoxyfree radical (TEMPO), with the following results

Time Conversion Mn D

(mm) (%w/w) (Dalton)

0 0

60 39 6090 133

120 44 7350 135

180 47 8430 137

240 65 12180 143

300 68 12810 143

360 82 15840 142

Also in this polymerization employing both a stable free radical agent and an initiator, pseudo-living polymerization kinetics were observed Also this polymer was analyzed after precipitation The Tempo endgroups were clearly detectable together with the benzoyl end groups

Examples 4-8 and Comparative Examples B-E

Pyrex tubes containing styrene, an NO-compound, and optionally CSA and/or ODCB were degassed using a freeze-thaw method and sealed under vacuum The reaction mixture was polymerized at 140°C The concentration of the NO- compound was selected such as to give the indicated theoretical number average molecular weight (Mth) at 100 % monomer conversion In Examples 4 and 7 the styrene was mixed with ODCB in a 50/50 ratio (by weight) The conversion and the molecular weight (distribution) of the polymer were determined after 6 hours of reaction time, with the following results

Exp Initer CSA Mth Mn Conversion D

(mol/l) (Dalton) (Dalton) (%w/w)

4 BuPI 0 027 4000 50300 30 1 n d

5 (IBN)₂ArNO 0 027 5000 30000 97 5 2 2

6 (IBN)₃NO 0 027 5000 4800 98 2 3 3

7 (MBN)₃NO 0 027 4000 3600 100 0 1 7

8 (CCH)₃NO 0 053 4300 3875 98 6 2 3

B None 0 - 143400 90 9 2 4

C None 0 027 - 173000 37 1 3 1

D Cumyl- 0 053 5000 119000 71 7 2 6 TEMPO

E Tinuvin 123 0 053 1000 17000 n d n d n d = not determined

Clearly, the iter of choice has a pronounced effect on the molecular weight of the polymer Examples 9-1 1 and Comparative Examples F-H

Example 4 was repeated using methyl methacrylate (MMA) (bulk = 9.3 mol/l) instead of styrene. Initers were selected and used in such a concentration as to give a polymer with Mth=5000, except in Example 11 , where Mth=4000. CSA was used in a concentration of 0.027 mol/l in Examples G and 9-1 1. CSA was absent from Example F. In Example 11 , the MMA was mixed with ODCB in a ratio of 50/50 (by weight). The following was observed after 6 hours of polymerization time.

Experiment Initer Mn Conversion D (Dalton) (%w/w)

9 (IBN)₂ArNO 13670 76.6 1.9

10 (IBN)₃NO 1892 79.4 2.6

11 (MBN)₃NO 3400 93.0 1.7

F None 1106000 8.8 2.4

G None 951250 6.6 2.1

H Cumyl- 205000 78.1 2.4 TEMPO

Again, the influence of the initers according to the invention on both the conversion rate and the molecular weight of the polymer is pronounced. Also, it was observed that using other TEMPO based initers did not allow control of the molecularweight. Example 12

In sealed tubes, a solution of 4 4 mol/l of MMA in ODCB was polymerized at 140°C for 6 hours. (IBN)₃NO was used as initer at a concentration of 0 1 mol/l CSA was present in a concentration of 0.027 mol/l The resulting polymer was isolated and characterized with ¹H-NMR.

Time Conversion Mn D

(mm) (%w/w) (Dalton)

0 15 -

45 84.3 2560 17

90 84.5 2545 1.7

135 84.4 2520 1.7

180 841 2550 1.7

225 84.6 2580 17

270 84.6 2565 1.7

315 84.3 2640 1.7

360 84.3 2615 1.7

The polymerization rates were exceptionally high. As in Examples 10 and 11 , a lower molecular weight than the theoretical value was observed. One of the reasons for this may have been the fact that polystyrene standards were used for calibration of the size exclusion chromatograph NMR showed the expected structure. Example 13

In an open flask, a solution of 4.7 mol/l of MMA in ODCB was polymerized at 120°C for 6 hours (IBN)₃NO in a concentration of 0 12 mol/l and CSA in a concentration of 0 028mol/l were used The final polymer was isolated and analyzed The following results were obtained'

Time Conversion Mn D

(mm) (%w/w) (Dalton)

0 10 -

15 55.7 3300 14

30 750 3335 1.4

45 81.1 3330 14

60 84.3 3260 1.4

75 86.2 3250 1.5

90 874 3190 1.5

105 88.0 3200 1.5

120 884 3240 1.5

240 899 3040 1.5

300 91.3 3030 1.5

360 913 3050 1.5

The results are comparable with the results from the previous example

Examples 14-18 and Comparative Examples I and J

Example 4 was repeated using butyl acrylate (BA) instead of styrene and a polymerization temperature of 120°C CSA was used in a concentration of 0 05 mol/l in all examples, except for Examples 14 and 16 The following was observed after 6 hours of polymerization time

Initer Mth Mn Conversion D

(Dalton) (Dalton) (%w/w)

14 (IBN)₃NO 6432 6470 99 7 2 4 15 (IBN)₃NO 6184 6100 99 7 2 4 16 (MBN)₃NO 6066 5474 99 7 8 1 17 (MBN)₃NO 5926 5426 99 7 8 6 18 (IBN)₂ArNO 6531 53000 43 5 4 7 I None - 200000 44 6 2 8

Cumyl- 5766 68900 16 6 2 2

TEMPO

These experiments show that butyl acrylate also can be polymerized efficiently

Examples 19 and 20

In Examples 19 and 20, isoprene in ODCB (4.87 mol/l) was polymerized using 0.123 mol/l of (IBN)₃NO and (MBN)₃NO, respectively (Mth=2700) in accordance with the procedure of Example 4, except that the polymerization temperature was 130°C. At some intervals, the content of a tube was analyzed, with the following results.

Example 19

Time Conversion Mn D

(min) (%w/w) (Dalton)

60 26.3 4850 1.5

120 30.1 4850 1.6

180 36.3 4880 1.7

240 46.4 4930 1.7

300 52.1 4800 1.7

360 55.8 4860 1.7

Example 20

Time Conversion Mn D

(min) (%w/w) (Dalton)

60 27.5 31200 1.5

120 38.1 3180 1.6

180 49.4 3330 1.7

240 59.2 3320 1.7

300 64.2 3470 1.7

360 68.6 3460 1.7

These experiments show that isoprene also can be polymerized efficiently. Examples 21-28

Using pyrex tubes, styrene (4.12 mol/l) in ODCB was polymerized for six hours using 0.12 mol/l of (IBN)₃NO, (Mth = 3550) as described in Example 4, at a temperature as specified in the following table. In Examples 21 -24 no CSA was used, while in Examples 25-28 the concentration of CSA was 0.027 mol/l.

Example Temperature Conversion Mn ro (%) (Dalton)

21 80 <1 950 22 100 4.5 1050 23 120 41.2 3000 24 150 99.0 3390 25 80 <1 1000 26 100 4.6 970 27 120 36.3 2780 28 150 98.0 2280

Repeating these experiments with (MBN)₃NO gave comparable results, except that faster polymerization rates were observed.

Examples 29-31 and Comparative Example K

In these examples the performance of initers- in a polymerization to make high solid acrylic resins was evaluated. To this end, using a stirred glass reactor equipped with a condensor, a mixture consisting of 40 g butyl acrylate, 28 g hydroxyethyl methacrylate, 20 g styrene, 10 g methyl methacrylate, 2 g maleic anhydride, and 21.4 meq. initer or 30.0 meq. tert.butylperoxy2-ethylhexanoate (Tπgonox® 21 ) (see table) was metered to 40 g solvent (see table), in a nitrogen atmosphere at atmospheric pressure, in four hours. During the addition the temperature of the reaction mixture was maintained at 126 or 140°C (see table) After the addition, the reaction mixture was further reacted for one hour at the specified temperature The following results were obtained after analysis of the product.

Example Radical reaction solvent solids Mn Disf source temp. (°C) (%) (Dalton)

29 (IBN)₃NO 126 nBuAc 66.0 4100 1.9

30 (IBN)₃NO 140 S-100 70.0 3000 2.1

31 (MBN)₃NO 140 S-100 70.9 2700 2.1

K Trigonox 21 140 S-100 70.8 3200 2.1

nBuAc = n -butylacetate

S-100 = Sol vesso® 100

The miters according to the invention allow the production of a high solids resin at various temperatures in good yields with a molecular weight that is lower than observed in conventional processes. Example 32

In an open flask, 3.3 mol/l styrene (18 g) in ODCB was polymerized at 140°C for 6 hours, using 9 g of the product obtained in Example 3 as the initer and 0.027 mol/l CSA. The following results were obtained'

Time Conversion Mn D

(mm) (%w/w) (Dalton)

0 0 -

45 14.8 8620 2.0

90 30.2 10100 2.2

135 41.7 11050 2.2

180 51.3 12070 2.3

225 58.9 12830 2.2

270 65.4 13170 2.3

315 70.7 13530 2.3

360 74.6 13730 2.3

Characterization of the polymer showed the expected product to be formed.

Example 33

The previous example was repeated, except that the initer of Example 3 was replaced by the initer obtained in Example 13, with the following results.

Time Conversion Mn D

(min) (%w/w) (Dalton)

0 1.2 3170 1.8

45 6.7 3590 2.1

90 12.7 4200 2.4

135 16.7 4650 2.5

180 21.3 5060 2.5

225 25.0 5320 2.6

270 27.4 5650 2.5

315 28.9 5930 2.5

360 31.2 6070 2.5

Again it was shown with 1 H-NMR that the expected copolymer was formed.

Claims

1 A pseudo-living polymerization process in which at least one NO- compound with at least one moiety according to formula (I) or (II),

wherein

• R represents a group which has at least one carbon atom and is such that the free radical R^» is capable of initiating the free radical polymerization of unsaturated monomers,

• at most five of the groups represented by X--X₆ are the same or different straight-chain or branched, substituted or unsubstituted (cyclo) alkyl groups, while two or more of the groups X X₆ may be linked to form cyclic structures, • the complementary groups X-, through X₆ are functional groups selected from substituted or unsubstituted phenyl, cyano, ether, hydroxy, nitro, dialkoxyphosphonyl, and carbonyl containing groups, or, alternatively, -CX-X^ and/or -CX₄X₅X₆ represent a phenyl group, • X₇ and X₈ are independently selected from alkyl, aryl, alkaryl, and aralkyl, while X₇ is optionally linked with X₈ to form bridged structures, and is combined with a monomer composition to be polymerized

2 A process according to ciaiml wherein the complementary functional groups X--X₆ are phenyl or cyano A process according to claim 1 or 2 wherein two or more ethylenically unsaturated monomers are polymerized, either sequentially or simultaneously

A process according to any one of the preceding claims, characterized in that the ethylenically unsaturated monomers are selected from styrene, divinylbeπzene, α-methylstyrene, chloromethylstyrene, acrylic acid, esters of acrylic acid, methacryl.c acid, esters of methacrylic acid, maleic acid, maleic anhydride, esters of maleic acid, fumaπc acid, esters of fumaπc acid, acrylonitπle, vinylpyπdine, isoprene, butadiene, tπenes, styrene phosphonic acid, vinyl phosphonic acid, styrene phosphonic esters, vinyl phosphonic acid esters, maleimides, citraconimides, itaconimides, vmylacetate, their derivatives, and substituted analogues

A process according to any any one of claims 1-4, characterized in that the reactants do not comprise free radical generating species other than one or more NO-compounds of formula I or II

A process according to any one of claims 1-5, characterized in that the molecular weight (distribution) of the resulting polymer is controlled by the concentration of monomer and NO-compound

A process according to any one of claims 1-6 wherein an additional stable free radical is used

A process according to claim 7 wherein the stable free radical is similar to the nitroxide radical that is formed when one or more of the applied NO-compounds is thermally decomposed A (block) (co)polymer obtainable by any one of the processes of claims 1-8

10. An NO-compound containing at least one moiety of the formula (I),

wherein:

• R represents a group which has at least one carbon atom and is such that the free radical R- is capable of initiating the free radical polymerization of unsaturated monomers;

• at most five of the groups represented by X- through X₆ are the same or different straight-chain or branched substituted or unsubstituted (cyclo) alkyl groups, while two or more of the groups may be linked to form cyclic structures, • the complementary groups X. through X₆ are functional groups selected from substituted or unsubstituted phenyl, cyano, ether, hydroxy, nitro, dialkoxyphosphonyl, and carbonyl containing groups, such as ester, carboxyalkyl, aldehyde, anhydride, and ketoalk(ar)yl groups, and • R is not polymeric when -N(CX-X₂X₃) CX₄X₅X₆ is 2,5-dιmethyl-2,5- diphenylpyrrolidin-1-, with the proviso that the NO-compound is not tπs-(2-cyano-2-propyl)- hydroxylamme, tris-(2-carboxyethyl-2-propyl)hydroxylamιne, and/or tπs- (2-carboxymethyl-2-propyl)hydroxylamιne.

11. An NO-compound according to claim 10, characterized in that the complementary groups X are selected from substituted or unsubstituted phenyl, cyano ether, and carbonyl containing groups, such as ester anhydride, and ketoalk(ar)yl groups

A recycling process in which a polymer is converted into low-molecular weight fragments, characterized in that the polymer is obtained from a pseudo-living polymerization process according to any one of claims 1 - 8

A recycling process according to claim 12, characterized in that the processing temperature is below 300°C