EP1259551A1

EP1259551A1 - Polymerization compositions and methods

Info

Publication number: EP1259551A1
Application number: EP00968537A
Authority: EP
Inventors: John Ta-Yuan Lai; Deborah S. Filla
Original assignee: Noveon IP Holdings Corp
Current assignee: Noveon IP Holdings Corp
Priority date: 1999-09-30
Filing date: 2000-09-29
Publication date: 2002-11-27

Abstract

Improved polymerization agents and processes are disclosed. In particular, the nitrogen-containing free radicals and free radical precursors are used to effect efficient, controlled polymerization of polymeric materials, including monomers, to form polymers, including homopolymers, copolymers, and block polymers. In particular, nitroxide compounds, methods of making nitroxide compounds, methods of using the nitroxide compounds to polymerize monomer compositions, and polymer compositions made using the nitroxide compounds are disclosed.

Description

POLYMERIZATION COMPOSITIONS AND METHODS

FIELD OF THE INVENTION

The present disclosure relates to nitrogen containing compounds useful in polymerization, including the polymerization of monomer compositions. In particular, the disclosure includes nitroxide compounds, methods of making nitroxide compounds, methods of using the nitroxide compounds to polymerize monomer compositions, and polymer compositions made using the nitroxide compounds.

BACKGROUND OF THE INVENTION

Various methods exist for performing polymerization reactions. A typical method involves polymerization of monomers with free radicals. The free radicals serve to propagate the addition of a monomer unit onto a growing polymer chain. Polymerization of methacrylic monomers is one such reaction propagated by free radicals.

Numerous free radical compounds are known and used as free radical for polymerization reactions. For example, certain common free radical compounds can be generated from thermal decomposition of peroxides, as represented below:

ROOR <-> 2 RO»

Wherein RO» is a free radical containing a hydrocarbon substituent and an oxygen atom having a free electron. This free electron can assist in the formation and extension of a polymeric chain. Although free radical polymerization can be used to produce a wide variety of polymers, a significant obstacle to free radical polymerization is that the polymerization reaction can be difficult to control. One particular control problem with free radical polymerization is that growing polymers often undergo undesired chain terminations at unpredictable lengths, thereby producing polymer molecules having a widely varying distribution of molecular weights. These varying molecular weights are often expressed as the parameter polydispersity (PDI), which is the weight average molecular weight (M_vv) divided by the number average molecular weight (M_n). For many applications it is preferable that the polydispersity be relatively low.

One reason for such preference is that a polymer having a low polydispersity often has more predictable properties, making the polymer more suitable for incorporation into commercial products. In recent years, additional free radical compounds have been proposed that have been asserted to result in predictable and controlled polymerization. These free radical compounds are sometimes referred to as "stable free radical polymerization" compounds, or "SFRP's". One of the objectives of SFRP's is controlled free radical polymerization with minimization of chain termination reactions. In addition, it is the objective of SFRP's to improve the molecular weight and polymer architecture of the resulting polymer.

One SFRP that has been proposed is 2,2,6,6-tetramethyl-l- piperidinyloxy free radical (referred to as TEMPO) and variations thereof described in United States Patent No. 5,412,047 ("the '047" patent) which issued May 2, 1995 to Georges, et al. The '047 patent proposes using TEMPO in the preparation of polymers of methacrylic monomers. The polymerization process comprises heating a mixture of free-radical initiator and TEMPO along with a polymerizable monomer and optionally a solvent. However, some TEMPO variations are unsuccessful at synthesizing polymers in a controlled fashion with high yields. In addition, some TEMPO variations are difficult to synthetically produce, degrade at higher reaction temperatures, or do not have a satisfactory shelf life. Similarly, free radical nitroxides (referred to as "nitroxyls") are disclosed in United States Patent No. 4,665,185 ("the ' 185 patent") that issued May 12, 1987 to Winter, et al. The ' 185 patent describes a number of nitroxides, however these nitroxides are unstable in certain desirable reaction conditions. Thus, there remains a need for improved controlled free radical polymerization processes and free radical compounds for conducting such polymerization. The improved free radical compounds should preferably provide for stabilized free radical polymerization and should preferably be easily synthesized and suitable for storage over extended periods of time. The improved free radical polymerization processes should also preferably provide for simple and economical synthesis of polymers at high yields.

SUMMARY OF THE INVENTION This disclosure is directed to improved polymerization agents and processes. In particular, the disclosure is concerned with using nitrogen- containing free radicals and free radical precursors to effect efficient, controlled polymerization of polymeric materials, including monomers, to form polymers, including homopolymers, copolymers, and block polymers. Suitable polymerization agents include compounds containing free radicals and compounds containing free radical precursors (also referred to as "adducts"), including nitroxide free radicals and precursors, and in particular hindered nitroxide free radicals and precursors. The free radicals described herein, including nitroxide compounds (containing nitroxyl groups, which have one unpaired electron), can be used to efficiently yield polymers with narrow polydispersities.

According to a first aspect of the invention, a free radical precursor including the functionality:

O-R₅

I -(R₁)(R₂)C-N-C(R₃)(R4)—

is disclosed, wherein R,, R₂, R₃, and R₄ are independently selected from the group consisting of aryls having 6 to 24 carbon atoms, alkyls having from 1 to 24 carbon atoms, cycloalkyls having from 5 to 7 carbon atoms, aralkyls having from 7 to about 20 carbon atoms, cyanoalkyls having from 2 to about 12 carbon atoms, ethers having from 4 to about 18 carbon atoms, and hydroxyalkyls having from 1 to 18 carbon atoms; R₅ represents an aryl containing radical of the formula:

wherein R₉ and R_]0 independently represent hydrogen, alkyls having from 1 to 24 carbon atoms, cycloalkyls having from 5 to 7 carbon atoms, aryls having 6 to 24 carbon atoms, aralkyls having from 7 to 20 carbon atoms, cyanoalkyls having from 2 to about 12 carbon atoms, ethers having from 4 to about 18 carbons atoms, and hydroxyalkyls having from 1 to 18 carbon atoms. The group -(R,)(R₂)C- comprises (R₆)(R,)(R₂)C, wherein R^ is selected from the group consisting of R₇OH, and R₇ contains at least one carbon atom. In one aspect of the invention R₇ is a linear or branched alkylene group containing 1 to 10 carbon atoms. The group -C(R₃)(R₄)- comprises -C(R₃)(R₄)(R₈) and R_g is -COOM, wherein M is a metal cation.

In one aspect of the invention M is selected from the groups IA and IIA of the Periodic Table of the Elements. In another aspect M is selected from Li, Na, K, and Ca. The invention is also directed to methods of making the free radical precursor, methods of using the free radical precursor to make polymers, and polymers made using the free radical precursor.

The disclosure is also directed to a free radical polymerization process for the preparation of a polymer. The process typically comprises heating from about 60°C to about 150°C a mixture of a free radical initiator, at least one polymerizable compound, and a stable free radical agent to form a thermoplastic polymer having a polydispersity that is preferably from about 1.0 to about 3.0. A free radical suitable for conducting the reaction has the following formula:

O

I

- (R₁)(R₂)C-N-C(R₃)(R₄)—

wherein R,, R₂, R₃, and R₄ are independently selected from the group consisting of aryls, alkyls having from 1 to about 24 carbon atoms, cycloalkyls having from 5 to 7 carbon atoms, aralkyls having from 7 to about 20 carbon atoms, cyanoalkyls having from 2 to about 12 carbon atoms, ethers having from 4 to about 18 carbon atoms, and hydroxyalkyls having from 1 to about 18 carbon atoms. According to another aspect of the present invention, a free radical polymerization process for the preparation of a thermoplastic resin or resins is disclosed. This process comprises reacting a polymerizable monomer compound with a free radical. In a preferred implementation, the resin or resins is prepared by heating a mixture of at least one polymerizable monomer compound and a nitroxide precursor to form the thermoplastic resin or resins. The heating temperature is typically from about 80°C to about 160°C. The preformed nitroxide precursor may be a nitroxide precursor having the following formula:

O— R. la

R₆-(R,)(R₂)C-N-C(R₃)(R₄)— R₈

wherein R„ R₂, R₃, and R₄, are independently selected from the group consisting of aryls and alkyls having from 1 to about 24 carbon atoms; cycloalkyls having from about 5 to about 7 carbon atoms; including ethyl benzene; aralkyls having from 7 to about 20 carbon atoms, cyanoalkyls having from 2 to about 12 carbon atoms; ethers having from 4 to about 1 carbon atoms; and hydroxyalkyls having from 1 to about is carbon atoms; and R, and R₂ together, or R₃ and R₄ together, or each pair may be cyclized to form a ring having from about 5 to about 14 carbon atoms; R₅, R^, and R₈ are as previously defined.

One advantage of the present invention is that nitroxides useful in the controlled free radical polymerization of a thermoplastic resin or resins can be easily synthesized, particularly with regard to tailoring the nitroxide structure to improve reaction rates, introduce functionality, tailoring solubility, etc. Another advantage of the present invention is that nitroxides useful in the controlled free radical polymerization of a thermoplastic resin or resins can have a desirable shelf-life. Some such nitroxides are highly crystalline and can be stored for extended periods at room temperature (i.e. about 25°C). Additional benefits and advantages of the invention will become apparent to those skilled in the art upon reading and understanding of the following detailed specification.

DETAILED DESCRIPTION This disclosure is directed to free radicals and free radical precursors useful in the polymerization of monomers, as well as methods of forming free radicals and precursors, methods of using free radicals to promote polymerization of monomers, and polymers formed using free radicals. Free radicals disclosed herein comprise nitrogen-containing compounds, including nitroxide free radicals, and in particular hindered nitroxide free radicals suitable for conducting stable free radical polymerization. Specific free radicals, methods of forming and using the free radicals, and polymers formed by free radical polymerization are described below. Although this description provides references to specific alternate embodiments, it is intended to include all such modifications and alternatives insofar as they come within the scope of the appended claims or the equivalents thereof. In addition to the following description, United States Patent Nos. 5,412,047; 4,914,232; 4,466,915; 5,401,804; 4,581,429; and pending PCT application Publication Number WO98/44008 published 10/8/98, and entitled "Controlled Free Radical Polymerization Process", are incorporated herein by reference.

I. Nitrogen-containing free radicals and free radical precursors

The present disclosure is directed in part to nitrogen-containing compounds, including nitrogen-containing free radicals and free radical precursors (also referred to as free radical adducts). These free radicals and free radical precursors include compounds having a nitrogen atom bonded to two carbon atoms and an oxygen atom. Each of the two carbon atoms bonded to the nitrogen atom is also preferably substituted with two hydrocarbon substituents. Specific suitable hydrocarbon substituents include alkyls, aryls and arylalkyl groups. The oxygen atom includes a free electron when in the free radical state.

Suitable nitrogen-containing free radicals described herein include free radical nitroxides that may be represented by the following general formula:

O lb

R,— (R,)(R₂)C— N— C(R₃)(R₄)— R₈

wherein R,, R₂, R₃, and R₄ are independently selected from the group consisting of aryls, alkyls, and aralkyls, including aryls and alkyls having from 1 to 24 carbon atoms. Suitable alkyls include branched and unbranched alkyls, including methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, pentyl, hexyl, and heptyl.

The alkyls may also be cycloalkyls, including cycloalkyls having from 5 to 7 carbon atoms. Cycloalkyls include alkyls that are formed of a ring comprising both R, and R₂ or both R₃ and R₄. Thus, R, and R₂ and/or

R₃ and R₄ taken together with the carbon atom to which they are attached form a cycloalkyl moiety. ^ and R₈ are as previously defined. Examples of suitable compounds include 3,3-tetramethylene-5,5-dimethyl-l- isopropyl-2-piperazinone-oxide; 3,3-pentamethylene-5,5,-dimethyl-l- isopropyl-2-piperazinone-oxide; 3,3-hexamethylene-5,5-dimethyl-l - isopropyl-2-piperazinione-oxide, and 3,3-pentamethyl-5,5-dimethyl-2- morpholone oxide.

Suitable aralkyl groups can have from 7 to about 20 carbon atoms. Suitable aryl groups include phenyl or naphthyl and substituted derivatives thereof including linear and/or branched alkyl groups containing 1 to 14 carbon atoms such as, for example, toluyl, xylyl, and ethyl benzyl groups. The alkyls may further include cyanoalkyls having from 2 to about 12 carbon atoms, ethers having from 4 to about 18 carbon atoms, and hydroxyalkyls having from 1 to about 18 carbon atoms. In addition to the R„ R₂, R₃, and R₄ substituents, the two carbon atoms bonded to the nitrogen atom may also be joined to an additional substituent. In certain embodiments, these two carbon atoms are bonded to the same substituent in order to form a cyclic compound that incorporates the two carbon atoms and the nitrogen atom of the general formulae provided above.

In the general formula provided herein, a free electron is shown positioned on the oxygen atom. However, it will be appreciated that this electron is not necessarily stationary. Thus, the representation of the free electron isolated on the oxygen is provided for illustrative purposes, and the electron may in fact be localized around the oxygen without being specifically identifiable on the oxygen atom. In addition, the compound shown above in the general formula will often exist in equilibrium with a precursor having a hydrocarbon group attached to the oxygen atom. The disclosure is also directed to various precursors of the free radicals, as represented below: O

R,— (R,)(R₂)C— N— C(R₃)(R₄)— R₈

With the exception of the substitution of R₅ on the oxygen atom, the precursor may have the same formula and configuration as a corresponding nitroxide free radical. Thus R,, R₂, R₃, and R₄ can be independently selected from the group consisting of aryls, alkyls, and aralkyls, including aryls and alkyls having from 1 to about 24 carbon atoms. The alkyls may be cycloalkyls, including cycloalkyls having from 5 to 7 carbon atoms. Suitable aralkyls can have from 7 to about 20 carbon atoms. The alkyls can further include cyanoalkyls having from 2 to about 12 carbon atoms, ethers having from 4 to about 18 carbon atoms, and hydroxyalkyls having from 1 to about 18 carbon atoms. In addition to the R,, R₂, R₃, and R₄ substituents, the two carbon atoms bonded to the nitrogen atom may be further joined to an additional substituent. In certain embodiments, these two carbon atoms are bonded to the same substituent in order to form a cyclic compound. The radicals R₅, R^, and R₈ are as previously defined.

In another aspect of the invention, an advantageous nitroxide composition is shown below:

wherein X and Y are optionally bonded to one another; and X is -CH₂- joined to Y, or CH,OH; Y is -O- joined to X, NH or NR joined to X, or OM, with M being a metal cation. The other substituents follow the identification provided above. Particularly useful nitroxide compositions are based on morpholone and piperazinone structures, as disclosed in PCT application Publication Number WO98/44008 published 10/8/98. Other nitroxides obtained and used in the practice of the present invention, including their abbreviations, are identified in Table I of application WO98/44008, and incorporated herein by reference. Another useful nitroxide composition is:

O-R₅ O

(CH₂OH)(R₁)(R₂)C-N ¹ -C(R₃)(R₄)— C 11-OM

wherein R,, R₂, R₃, and R₄ are independently selected from the group consisting of aryls, alkyls having from 1 to 24 carbon atoms, cycloalkyls having from 5 to 7 carbon atoms, aralkyls having from 7 to about 20 carbon atoms, cyanoalkyls having from 2 to about 12 carbon atoms, ethers having from 4 to about 18 carbon atoms, and hydroxyalkyls having from 1 to 18 carbon atoms; R₅ is as previously defined; and M is a metal cation selected from Groups IA and IIA of the Periodic Table. It will be appreciated that in certain implementations the cation may be divalent, such as calcium (Ca⁺⁺), in which event the compound still contains the moiety provided above, but the metal cation may further associated with an anion or with a second nitroxide free radical. The invention is also directed to methods of making the free radical precursor, methods of using the free radical precursor to make polymers, and polymers made using the free radical precursor. II. Synthesis and formation of free radicals and free radical adducts

The nitrogen containing compositions of the present invention may be synthesized using conventional synthetic methods, including methods described in United States Patent Nos. 5,412,047, 4,914,232, 4,466,915, 5,401,804, 4,581,429, and pending PCT application Publication Number WO98/44008 published 10/8/98, which are incorporated herein by reference to the present disclosure. The methods may include providing a nitroxide free radical, a peroxide, and a catalyst. Preferred peroxides include hydroperoxide and alkane peroxides. Preferred catalysts include metal catalysts.

Free radicals suitable for use with the presently described method include those having a moiety of the general formula:

O

— (R₁XR2)C-N-C(R3)(R₄)—

wherein R,, R₂, R₃, and R₄ are independently selected from the group consisting of aryls, alkyls, and aralkyls, including aryls and alkyls having from 1 to about 24 carbon atoms. The alkyls may be cycloalkyls, including cycloalkyls having from 5 to 7 carbon atoms. Suitable aralkyls may have from 7 to about 20 carbon atoms. The alkyls may further include cyanoalkyls having from 2 to about 12 carbon atoms, ethers having from 4 to about 18 carbon atoms, and hydroxyalkyls having from 1 to about 18 carbon atoms. In addition to the R,, R₂, R₃, and R₄ substituents, the two carbon atoms bonded to the nitrogen atom may be further joined to an additional substituent. Specific starting compounds suitable for reaction include morpholones and piperazinones. shown above.

The free radical adducts of the nitrogen containing compounds of the invention can be prepared by reacting a compound containing the functionality:

H

(R,)(R₂)C— N— C(R₃)(R,

with an aryl containing compound of the formula:

in the presence of a peroxide and/or a hydroperoxide in optional combination with a transition metal oxide catalyst. The radicals R,, R₂, R₃, R₄, Rg, and R,₀ are as previously defined, and n represents the number of times the associated radical is taken about the aryl ring. Accordingly, n is O, 1, 2, 3, 4, or 5. Peroxides and or hydroperoxides suitable for use with the invention should provide favorable formation of the nitroxide, and thus the peroxides and hydroperoxides preferably allow for controlled formation of the nitroxide and nitroxide adduct. Suitable hydroperoxides include t-butyl peroxide, cumyl hydroperoxide, and t-amyl hydroperoxide. Hydrogen peroxide is used in certain implementations. Typical peroxides useful in the present invention are hindered peroxides, including di-t-butyl hydroperoxide, di-amyl peroxide, di-cumyl peroxide, methylethyl ketone peroxide, dibenzoyl peroxide and t-butyl cumyl peroxide. Also, di-t-butyl diperoxilate may be used.

The transition metal oxide catalysts include, for example, molybdenum oxide and iron oxide. The hydroperoxides and peroxides are combined with the reaction materials in a manner to facilitate the reaction. In certain implementations, the peroxides and hydroperoxides are added directly to the reaction vessel without being first diluted in solvent. In other implementations, the peroxides and hydroperoxides are dissolved in an organic solvent. The hydroperoxides may be dissolved in an organic solvent or water. When dissolved in water, the hydroperoxides are typically dissolved in greater than 50 percent water, and more typically from 70 to 90 percent water. Similarly, the hydroperoxides and peroxides may be mixed together, optionally with alcohols or water, prior to or after being combined with other reaction ingredients. In a specific implementation, from 70 to 80 percent t-butyl peroxide is dissolved in a combination of di-t-butyl peroxide, t-butanol, and water.

In addition, the free radical may be formed by combining a morpholone with a metal hydroxide in an organic solvent, such as methanol, to produce the free radical functionality represented below:

O-R₅ O

(CH₂OH)(Rι)(R₂)C-N ¹ -C(R₃)(R₄)— C I-OM

When employing a monosubstituted aryl containing compound wherein n is 0, e.g., a compound of the formula:

The adduct formed will contain only one nitrogen containing moiety as shown in formulae I and II, for example. When employing a disubstituted aryl containing compound (e.g., n is 1) such as p-xylene exemplified in Example 1 , the resulting adduct will contain a nitrogen containing moiety connected to each substituent on the aryl ring.

HI. Polymerization of monomers using free radicals

Nitrogen containing free radicals identified above are useful to form polymers from polymerizable compositions, including monomers and oligomers. As used herein, the term "polymers" includes homopolymers, copolymers, block polymers, and other hydrocarbons formed by the joining of a plurality of smaller elements, particularly hydrocarbon elements, including monomers and oligomers. In preferred implementations, a free radical initiator, a monomer composition, and a free radical agent are combined under reaction conditions to polymerize the monomer. These reaction conditions typically include initiating the polymerization reaction with the addition of heat, radiation, or an initiator compound. Exemplary monomer compositions and free radical agents are described below. In addition, free agent initiators are described, as are additional typical reaction components and conditions, such as the presence of solvents, preferred reaction temperatures, reaction times, and reaction containers. A. Monomer Compositions

Numerous different monomer compositions are suitable for polymerization in accordance with the teachings of this disclosure. These monomer compositions include carboxylic acid monomers, acrylic monomers, and styrene monomers.

One class of carboxylic acid monomers suitable for use in the present invention are C₃-C₆ monoethylenically unsaturated monocarboxylic acids, and the alkaline metal and ammonium salts thereof. The C₃-C₆ monoethylenically unsaturated monocarboxylic acids include acrylic acid, methacrylic acid, crotonic acid, vinyl acetic acid, and acryloxypropionic acid. Acrylic acid and methacrylic acid are preferred monoethylenically unsaturated monocarboxylic acid monomers useful in accordance with the methods taught herein.

Another class of carboxylic acid monomers suitable for use are C₄-C₆ monoethylenically unsaturated dicarboxylic acids and the alkaline metal and ammonium salts thereof, and the anhydrides of the dicarboxylic acids. Suitable examples include maleic acid, maleic anhydride, itaconic acid, mesaconic acid, fumaric acid, and citraconic acid. Maleic anhydride and itaconic acid are preferred monoethylenically unsaturated dicarboxylic acid monomers.

Acid monomers useful in this invention may be in their acid form or in the form of the alkaline metal or ammonium salts of the acid. Suitable bases useful for neutralizing the monomer acids includes sodium hydroxide, ammonium hydroxide, potassium hydroxide, and the like. The acid monomers may be neutralized to a level of from 0 to 50% and preferably from 0 to about 20%. More preferably, the carboxylic acid monomers are used in the completely neutralized form.

In addition, up to 100% by weight of the total polymerizable monomers may be monoethylenically unsaturated carboxylic acid-free monomers. Typical monoethylenically unsaturated carboxylic acid-free monomers suitable for use in the invention include alkyl esters of acrylic or methacrylic acids such as methyl acrylate, ethyl acrylate, butyl acrylate; hydroxyalkyl esters of acrylic or methacrylic acid such as hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, and hydroxypropyl methacrylate; acrylamide, methacrylamide. N-tertiary butylacrylamide, bi-methylacrylamide, N, N-dimethyl acrylamide; acrylonitrile, methacrylonitrile, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, phosphoethyl methacrylate, N vinyl pyrrolidone. bi-vinylformamide, N-vinylimidazole, vinyl acetate, styrene, hydroxylated styrene, styrenesulfonic acid and salts thereof, vinylsulfonic acid and salts thereof, and 2-acrylamido-2 methylpropanesulfonic acid and salts thereof. Other suitable comonomers include acrylamides, alkyl and aryl amide derivatives thereof, and quaternized alkyl and aryl acrylamide derivatives.

B. Free Radicals

The nitrogen containing free radical agents identified above are suitable for polymerization of monomer compositions. As noted above, the free radicals include compounds having a nitrogen atom bonded to two carbon atoms and an oxygen atom. Each of the two carbon atoms bonded to the nitrogen atom is preferably substituted with two hydrocarbon substituents. Specific suitable hydrocarbon substituents include alkyls, aryls and aralkyl groups.

C. Initiators

Suitable free radical initiators include conventional free radical initiators known in the art. These initiators can include oxygen, hydroperoxides, peresters, percarbonates, peroxides, persulfonates and azo initiators. Specific examples of suitable initiators include hydrogen peroxide, t-butyl hydroperoxide, ditertiary butyl peroxide, tertiaryamyl hydroperoxide, dibenzoyl peroxide (AIBN), potassium persulfate, and methylethyl ketone peroxide. The initiators are normally used in amounts of from about 0.01 % to about 4% based on the weight of total polymerizable monomer. A preferred range is from about 0.05% to about 2% by weight of the total polymerizable monomer. The molar ratio of free radical agent to free radical initiator is preferably from about 1 : 1 to 10:1. The molar ratio of free radical agent to free radical initiator is preferably from about 1.3 : 1 to 1.7:1.

Redox initiators may also be used and include sodium bisulfite, sodium sulfite, isoascorbic acid, sodium formaldehydesulfoxylate, and the like, used with suitable oxidizing agents, such as the thermal initiators noted above. If used, the redox initiators may be used in amounts of 0.001% to 5%, based on the weight of total monomer. A preferred range is from about 0.01% to about 3% by weight of total polymerizable monomer.

D. Solvents and additives In the polymerization of the present invention, reactants can be supplemented with a solvent or co-solvent to help insure that the reaction mixture remains a homogeneous single phase throughout the monomer conversion. However, in a preferred embodiment, the polymerization reactions are carried out in the absence of a solvent. Exemplary solvent or co-solvents useful in the present invention include compatible aliphatic alcohols, glycols, ethers, glycol ethers, pyrrolidones, N-alkyl pyrrolidones, N-alkyl pyrrolidones, polyethylene glycols, polypropylene glycols, amides, carboxylic acids and salts thereof, esters, organosulfides, sulfoxides, sulfones, alcohol derivatives, hydroxyether derivatives such as CARBITOL^® or CELLOSOLVE^® available from Union Carbide Corp. of New York, New York, amino alcohols, ketones, and the like, derivatives thereof, and mixtures thereof. Specific examples include ethylene glycol, propylene glycol, diethylene glycol, glycerine, dipropylene glycol, tetrahydrofuran, and the like, and mixtures thereof.

When mixtures of water and water soluble or miscible organic liquids are selected as the reaction media, the water to co-solvent weight ratio typically ranges from about 100:0 to about 10:90, and preferably from about 97:3 to about 25:75.

Additives such as camphorsulphonic acid (CSA), or 2-fluoro- 1 -methyl pyridinium p-toluene sulfonate (FMPTS) can be added to the polymerization mixture to increase the rate of polymerization. These additives and their usefulness in a stable free radical polymerization process are discussed in detail in EP 735,052, which is incorporated herein by reference. Batch or metered addition of CSA can further enhance monomer conversion. The polymers obtained from these acid accelerated polymerizations can be chain extended with styrene to form block copolymers.

E. Reaction temperature, time, and vessels

Temperature of the polymerization reaction may range from about 80°C to about 160°C, preferably from about 1 10°C to about 130°C. Applicants have observed that at temperatures above about 180°C, conversion of the monomer into polymer decreases and uncertain and undesirable by-products are formed. Frequently, these by-products discolor the polymer mixture and may necessitate a purification step to remove them or they may be intractable. The reaction temperature for polymerization of the monomer components should be great enough to effectuate polymerization but low enough that the monomer components or resulting polymer is degraded. Thus, the reaction temperature is typically dependent upon the monomer components used. For example, the reaction temperature for acrylates is typically less than styrene using the nitroxide free radicals disclosed herein. In a preferred implementation, the reaction temperature is held at approximately 100°C, and more preferably greater than 100°C. For acrylate monomer, the reaction temperature is preferably equal to or greater than 80°C, and for styrene monomer the reaction temperature is preferably greater than 90°C. These temperatures allow for satisfactory reaction rates and stability of the nitroxide free radical in typical implementations.

As stated above, the reaction temperature is typically held below the point at which reactants are degraded. Thus, the reaction temperature is preferably kept below the temperature at which the monomers, polymers, and free radicals are destroyed or degraded. The temperature is preferably kept below 150°C, and more preferably kept below 130°C. In regard to specific implementations, when acrylate monomers are reacted, the temperature is preferably held below 120°C, while the temperature is preferably held below 130°C for styrene monomers. Thus, for most monomers and resulting polymers the reaction range is from about 80°C to about 160°C, and preferably from about 110°C to 130°C.

In certain embodiments, the elevated temperatures of the polymerization require that the polymerization reactor be equipped to operate at elevated pressure. In general it is preferred to conduct the polymerization at from about 10 to about 2000 lbs. per square inch (psi), and more preferably at from about 50 to about 1000 (psi). The processes can be run as batch, semi-continuous or continuous processes. IV. Polymers formed by free radical polymerization of monomers

The present invention provides polymerization processes for preparing polymers with well-defined molecular weight properties and narrow polydispersities, including methacrylate and acrylate polymeric resins. As used in the present specification, the terminology "acrylate containing" means that about 5 to 100 wt.% of the total monomer polymerized is an acrylate type monomer and that the acrylate monomer is polymerized in the presence of the stable free radical compound or nitroxide containing prepolymers.

The influence of the ratio of initiator to stable free radical is significant in the polymerization of n-butyl acrylate when AIBN is used as the initiator. First-order plots of polymerization conducted in the presence of AIBN and 3,3-hexamethylene-5,5-dimethyl-l-isopropyl-2- piperazinone-oxide nitroxide at 130°C show that at a 1 : 1.6 ratio, the first- order plot becomes more linear. Below this ratio, an exotherm is often observed, the molecular weight does not increase with conversion, and the polydispersity is broad. Above this ratio molecular weight increases with increasing conversion. The stoichiometry can be extremely important, and a ratio 1 : 1.60 may give an exotherm, whereas 1 : 1.70 gives a slow but controlled polymerization. Even small experimental error or the presence of small amounts of impurities can give widely varying results.

Applications of (meth)acrylate block copolymers or styrene block copolymers or styrene or (meth)acrylate homopolymers can include toner compositions, adhesives, cellulosic fiber binders, compatibilizers for thermoplastic blends, emulsifiers, thickeners, processing aids for thermoplastic resins, pigment dispersants, coatings, asphalt modifiers, molded articles, sheet molding compounds, and impact modifiers. The processes of the present invention provide, in embodiments, a conversion rate or degree of polymerization as high as 95% by weight. The processes of the present invention results in weight average molecular weights ranging from about 500 to about 200,000 and more preferably from about 2000 to about 100,000 while maintaining narrow polydispersity. Monomers, polymers and copolymers of the present invention can in certain embodiments be separated from one another, or from the polymerization reaction mixture. One method of separating these constituents is by changing the pH of the reaction media. Other known conventional separation techniques be also be employed.

EXAMPLES

The present invention will now be described in greater detail in the following examples. In addition, the examples in pending PCT application Publication Number WO98/44008 published 10/8/98, and entitled "Controlled Free Radical Polymerization Process", are incorporated herein by reference.

EXAMPLE 1 This experiment was conducted to demonstrate formation of a tetramethyl morpholone adduct with a/?-xylene. The resulting product contained a morphonone connected to each methyl group of the /. -xylene.

In conducting the experiment, tetramethyl morpholone (8.64 g, 0.055 mol), -xylene (2.66 g, 0.025 mol), and molybdenum oxide (0.2 g) were mixed in a reaction flask with 2 condensers, a thermometer, addition funnel, and mechanical stirrer. The ingredients were refluxed at approximately 97°C, followed by dropwise addition of 70 percent aqueous t-butyl hydroperoxide (16 g, 0.125 mol) over approximately 1 hour. The reflux temperature dropped to approximately 90°C and the solution turned reddish during the addition of the t-butyl hydroperoxide. These ingredients were refluxed for approximately 20 minutes, after which additional t-butyl hydroperoxide (20 g, .156 mol) was added while refluxing over approximately 1 hour. The ingredients were refluxed for 15 more hours, after which the contents were dried over sodium sulfate and concentrated to a dark oil, which solidified on standing. The solid was recrystallized from hexanes to obtain 155 g of beige-colored crystals.

EXAMPLE 2 This experiment was conducted to demonstrate formation of a tetramethyl morpholone nitroxide using a mixture of peroxide and hydroperoxide.

In conducting the experiment, tetramethyl morpholone (15.7 g, 0.1 mol) and molybdenum oxide (0.5 g) were mixed in a reaction flask with toluene (50 ml). The ingredients were brought to approximately

115°C, at which point 12.4 g of a solution of 80 percent t-butyl hydroperoxide and 20 percent t-butyl peroxide were added, followed by reflux and addition of an additional 6 g of the solution of 80 percent t-butyl hydroperoxide and 20 percent t-butyl peroxide, after which the contents were dried over sodium sulfate and concentrated to a orange oil, which was recrystallized from hexanes.

EXAMPLE 3

This experiment was conducted to demonstrate formation of a tetramethyl morpholone nitroxide using t-butyl hydroperoxide and t-butyl peroxide.

Tetramethyl morpholone (15.7 g, 0.1 mol), and molybdenum oxide (0.25 g) in chlorobenzene (50 ml) were mixed in a 250 ml round bottom reaction flask with a thermometer, magnetic stirrer, and long-stem distillation head and heated to approximately 130°C. After mixing, 80 percent t-butyl hydroperoxide (16.9 g, 0.15 mol) in 20 percent t-butyl peroxide was added dropwise. The distillation head was kept at approximately 80°C to allow for the release of t-butyl alcohol that formed, while retaining the hydroperoxide. The ingredients were refluxed for

4 hours, after which they were allowed to cool, filtered, rinsed with chlorobenzene and concentrated to get a dark oil that was distilled at 121 to 123°C at 8 mm mercury to obtain 15.2 grams of an orange oil. Gas chromatographic analysis indicated 95.94 percent product and 1.97 percent starting material.

EXAMPLE 4

This experiment was conducted to demonstrate formation of a tetramethyl morpholone nitroxide precursor with ethyl benzene using t-butyl hydroperoxide and t-butyl peroxide.

Tetramethyl morpholone (78.5 g, 0.5 mol), 400 ml of ethyl benzene, and molybdenum oxide (1.0 g) in ethyl benzene (400 ml) were mixed in a reaction flask and heated to approximately 100°C. After mixing, 70 percent aqueous hydroperoxide (115.7 g, 0.9 mol) was added dropwise. The distillation head was kept at approximately 80°C to allow for the release of t-butyl alcohol that formed, while retaining the hydroperoxide. The reaction was followed by gas chromatography, and after it was at least 90 percent complete the temperature was raised to 120°C and t-butyl peroxide (39.5 g, 0.27 mol) was added. The reaction products were allowed to cool, filtered, rinsed with hexane and concentrated to get a dark oil that was distilled to obtain 74 grams of an oil. Gas chromatographic analysis indicated 98.5 percent product. EXAMPLE 5

This experiment was conducted to demonstrate formation of a tetramethyl morpholone nitroxide precursor ethyl benzene using excess t-butyl hydroperoxide without t-butyl peroxide. Tetramethyl morpholone (78.5 g, 0.5 mol), 80 ml of ethyl benzene, and molybdenum oxide (0.5 g) were mixed and heated to approximately 90°C. After mixing, 90 percent aqueous hydroperoxide (80 g, 0.89 mol) was added dropwise. The reaction products were allowed to cool, filtered, rinsed with hexane and concentrated to get an orange oil.

EXAMPLE 6

This experiment was conducted to demonstrate formation of a tetramethyl morpholone nitroxide adduct of ethyl benzene using excess t-butyl hydroperoxide without t-butyl peroxide.

Tetramethyl morpholone (78.5 g, 0.5 mol), 80 ml of ethyl benzene, and molybdenum oxide (1.5 g) in ethylbenzene (280 ml) were mixed in a reaction flask and heated to approximately 100°C. After mixing, 90 percent aqueous hydroperoxide (197.2 g, 1.96 mol) was added dropwise. The distillation head was kept at approximately 80°C to allow for the release of t-butyl alcohol that formed, while retaining the hydroperoxide. The reaction products were allowed to cool, filtered, rinsed with hexane and concentrated to get an orange oil.

Claims

Claims:

1. A free radical precursor including the functionality:

O-R₅

— (R,)(R₂)C-N-C(R₃XR4)—

wherein R,, R₂, R₃, and R₄ are independently selected from the group consisting of aryls having 6 to 24 carbon atoms, alkyls having from 1 to 24 carbon atoms, cycloalkyls having from 5 to 7 carbon atoms, aralkyls having from 7 to about 20 carbon atoms, cyanoalkyls having from 2 to about 12 carbon atoms, ethers having from 4 to about 18 carbon atoms, and hydroxyalkyls having from 1 to 18 carbon atoms; R₅ represents a radical of the formula:

wherein R, and R|₀ independently represent hydrogen, alkyls having from 1 to 24 carbon atoms, cycloalkyls having from 5 to 7 carbon atoms, aryls having 6 to 24 carbon atoms, aralkyls having from 7 to 20 carbon atoms, cyanoalkyls having from 2 to about 12 carbon atoms, ethers having from

4 to about 18 carbons atoms, and hydroxyalkyls having from 1 to

18 carbon atoms; wherein -(R,)(R₂)C- comprises (R₆)(R,)(R₂)C, wherein R^ is

R₇OH, wherein R₇ contains at least one carbon atom; and wherein -C(R₃)(R₄)- comprises -C(R₃)(R₄)(R₈), and R_g is -COOM, wherein M is a metal cation.

2. The free radical precursor according to claim 1 , wherein R₇ is a linear or branched alkylene radical containing 1 to 10 carbon atoms.

3. The free radical precursor according to claim 1, wherein M is selected from the group consisting of lithium, sodium, potassium, and calcium cations.

4. The free radical precursor according to claim 2 wherein R₇ is methylene (-CH₂-).

5. A method comprising the steps of: providing a substituted nitrogen compound of the formula:

wherein R,, R₂, R₃, and R₄, are independently selected from the group consisting of aryls, alkyls having from 1 to 24 carbon atoms, cycloalkyls having from 5 to 7 carbon atoms, aralkyls having from 7 to 20 carbon atoms, cyanoalkyls having from 2 to about 12 carbon atoms, ethers having from 4 to about 18 carbon atoms, and hydroxyalkyls having from 1 to about 18 carbon atoms; R₅ represents a radical of the formula:

wherein R, and R,₀ independently represent hydrogen, alkyls having from

1 to 24 carbon atoms, cycloalkyls having from 5 to 7 carbon atoms, aryls having 6 to 24 carbon atoms, aralkyls having from 7 to 20 carbon atoms, cyanoalkyls having from 2 to about 12 carbon atoms, ethers having from

4 to about 18 carbons atoms, and hydroxyalkyls having from 1 to

18 carbon atoms; providing a metal hydroxide of the formula MOH wherein M is a metal cation; reacting the substituted nitrogen compound and metal hydroxide to create a compound including the moiety:

6. The method of forming a free radical precursor according to claim 5, wherein said step of providing a metal hydroxide comprises providing a metal hydroxide selected from the group consisting of lithium hydroxide, sodium hydroxide, potassium hydroxide, and calcium hydroxide.

7. The method of forming a free radical precursor according to claim 5, wherein said step of providing a substituted nitrogen compound comprises providing a substituted nitrogen compound wherein R,, R₂, R₃, and R₄ are CH₃ and R₅ is ethyl benzene; and wherein said step of providing a metal hydroxide comprises providing lithium hydroxide.

8. A polymerization method, the method including the step of: conducting a free radical polymerization of a polymerizable composition with a free radical precursor, the free radical precursor having the formula:

O-R₅

I (R₁)(R₂)C-N-C(R₃)(R₄)—

wherein R,, R₂, R₃, and R₄ are independently selected from the group consisting of aryls, alkyls having from 1 to 24 carbon atoms, cycloalkyls having from 5 to 7 carbon atoms, aralkyls having from 7 to about 20 carbon atoms, cyanoalkyls having from 2 to about 12 carbon atoms, ethers having from 4 to about 18 carbon atoms, and hydroxyalkyls having from 1 to 18 carbon atoms; R₅ represents a radical of the formula:

wherein Rg and R,₀ independently represent hydrogen, alkyls having from 1 to 24 carbon atoms, cycloalkyls having from 5 to 7 carbon atoms, aralkyls having from 7 to 20 carbon atoms, cyanoalkyls having from 2 to about 12 carbon atoms, ethers having from 4 to about 18 carbons atoms, and hydroxyalkyls having from 1 to 18 carbon atoms; wherein -(R,)(R₂)C- comprises (R₆)(R,)(R₂)C, wherein R₆ is R₇OH, wherein R₇ contains at least one carbon atom; and wherein -C(R₃)(R₄)- comprises -C(R₃)(R₄)(R₈), and R₈ consists of -COOM, wherein M is a metal cation.

9. The method according to claim 8 wherein R₇ is a linear or branched alkylene radical containing 1 to 10 carbon atoms.

10. The method according to claim 9 wherein R₇ is methylene (-CH₂-).

11. The method according to claim 8, wherein said step of conducting comprises conducting free radical polymerization with a polymerizable composition comprising a hydrocarbon selected from the group consisting of carboxylic acid monomers, acrylic monomers, monoethylenically unsaturated carboxylic acid-free monomers, styrene, and mixtures thereof.

12. The method according to claim 8, wherein said step of conducting comprises conducting polymerization with a polymerizable composition comprising butyl acrylate at a temperature below 100°C.

13. The method according to claim 8, further comprising the step of providing a free radical initiator selected from the group consisting of hydrogen peroxide, t-butyl hydroperoxide, di-t-butyl peroxide, t-amyl hydroperoxide, dibenzoyl peroxide, methylethyl ketone peroxide, and mixtures thereof.

14. The method according to claim 8, wherein said step of conducting comprises conducting free radical polymerization to form a polymer having a polydispersity of no greater than 3.0.

15. The method according to claim 8, wherein said step of conducting comprises conducting free radical polymerization at a temperature of less than 100°C.

16. The method according to claim 8, wherein the metal cation is selected from the group consisting of lithium, sodium, potassium, calcium, and combinations thereof.

17. A polymer prepared according to the process of claim 8.

18. A method of forming a stable free-radical agent, the method comprising: a) providing a substituted nitrogen compound containing a moiety having the formula:

H

I -(R₁XR2)C-N-C(R₃)(R4)—

wherein R„ R₂, R₃, and R₄ are independently selected from the group consisting of aryls, alkyls having from 1 to about 24 carbon atoms, cycloalkyls having from 5 to 7 carbon atoms, aralkyls having from 7 to about 20 carbon atoms, cyanoalkyls having from 2 to about 12 carbon atoms, ethers having from 4 to about 18 carbon atoms, and hydroxyalkyls having from 1 to 18 about carbon atoms; b) reacting the substituted nitrogen compound with hydroperoxide and a metal catalyst to get an intermediate compound; c) providing an aryl containing compound of the formula:

d) reacting the intermediate compound and the aryl containing compound with peroxide to form a free radical of the formula:

O-R₅

I -(R₁)(R₂)C-N-C(R₃)(R₄)—

R₅ represents a radical of the formula:

wherein Rg and R₁₀ independently represent hydrogen, alkyls having from 1 to 24 carbon atoms, cycloalkyls having from 5 to 7 carbon atoms, aryls having 6 to 24 carbon atoms, aralkyls having from 7 to 20 carbon atoms, cyanoalkyls having from 2 to about 12 carbon atoms, ethers having from 4 to about 18 carbon atoms, and hydroxyalkyls having from 1 to 18 carbon atoms.

19. The method according to claim 18, wherein the step of reacting the substituted nitrogen compound with hydroperoxide comprises providing hydroperoxide selected from the group consisting of t-butyl peroxide, cumyl hydroperoxide, and t-amyl hydroperoxide and mixtures thereof.

20. The method according to claim 18, wherein the step of reacting the intermediate compound with peroxide comprises providing peroxide selected from the group consisting of including di-t-butyl hydroperoxide, di-amyl peroxide, di-cumyl peroxide, methylethyl ketone peroxide, dibenzoyl peroxide, t-butyl cumyl peroxide and mixtures thereof.

21. The method according to claim 18, wherein the hydroperoxide and peroxide are simultaneously combined with the substituted nitrogen compound.

22. The method according to claim 18, wherein the step of reacting with peroxide comprises reacting with peroxide having a molar concentration of between 1.5 and 2.5 times the molar concentration of the substituted nitrogen compound.

23. A method of forming a stable free-radical precursor, the method comprising: a) providing a substituted nitrogen compound having the following formula: H

wherein X is CH₂ or C=O; Y is O or N-R; R, R„ R₂, R₃, and R₄ are independently selected from the group consisting of aryls having 6 to 24 carbon atoms , alkyls having from 1 to 24 carbon atoms, cycloalkyls having from 5 to 7 carbon atoms, aralkyls having from 7 to 20 carbon atoms, cyanoalkyls having from 2 to about 12 carbon atoms, ethers having from 4 to about 18 carbon atoms, and hydroxyalkyls having from 1 to 18 carbon atoms; b) providing an aryl containing compound of the formula:

wherein Rg and R,₀ are as previously defined; c) reacting the compound and arylalkane in the presence of t-butyl hydroperoxide, and t-butyl peroxide to form a free radical precursor having the formula:

R₅ d

wherein R₅ is derived from the aryl containing compound.

24. The method according to claim 23, wherein the t-butyl hydroperoxide is provided at a molar concentration of between 1.5 and 2.5 times the molar concentration of the substituted nitrogen compound.

25. The method according to claim 23, wherein step of providing an aryl containing compound providing ethyl benzene.

26. A polymer formed from reacting with the free radical precursor of claim 23.