MXPA98001976A - Procedure for preparing anhydrid polymers - Google Patents

Abstract

The present invention relates to: A process for preparing anhydride polymers in aromatic hydrocarbon solvents, using a dialkyl peroxide initiator / amine compound system is disclosed. This amine compound allows the most efficient use of free radical initiators, while achieving polymerizations with high monomer conversions, compared to conventional initiator systems, particularly in the preparation of polymers of maleic anhydride.

Description

PROCEDURE FOR PREPARING ANHYDRID POLYMERS This invention relates to an improved process for preparing polymers of anhydrides, notably that of poly (maleic anhydride). In particular, this invention relates to the use of amines, during polymerization, which allow the most efficient use of free radical initiators in achieving high conversion of monomers of maleic anhydride. Polymers of low molecular weight hydrolyzed maleic anhydride and their salts are well known as dispersants, scale inhibitors, detergent additives and segregates, generally, molecular weights below about 2,000 are typical for these applications. precursors for preparing poly (maleic anhydride) with the use of aromatic hydrocarbon solvents, such as toluene and xylene, employ large amounts of free radical initiators, but the final polymers contain substantial amounts of unpolymerized maleic anhydride. Attempts to improve the polymerization efficiency include the use of the tertiary di-butyl peroxide initiator in xylene, and an isolation-dependent temperature of the poly (maleic anhydride) as a non-miscible phase (US Patent, No. 3,919,258) , the use of peroxyester initiators (U.S. Patent No. 4,818,795) and the polymerization of solution diluted in xylene with limited concentrations of the initiator (patent of U. U. A., No. 5,077,364). However, these approaches do not yet combine the efficient use of readily available primers with high monomer conversion. The present invention is directed to overcoming the problems associated with the processes of the prior art, used to prepare poly (maleic anhydride) by providing an efficient polymerization process with the use of garlic levels of initiator, while providing a high conversion of monomers.

EXPOSITION OF THE INVENTION According to a first aspect of the present invention, a polymerization process for preparing anhydride polymers is provided, which comprises polymerizing a monomer selected from one or more of: maleic anhydride, citracholine anhydride, anhydride itaconic, 1, 2, 3, 6-tetrahydrophthalic anhydride, 5-norbornene-2, 3-dicarboxylic anhydride, bicyclo [2.2.2] -5-octen-2, 3-dicarboxylic anhydride, 3-methyl-1, 2 anhydride , 6-tetrahydrophthalic and 2-methyl-1,3,6-tetrahydrophthalic anhydride, in the presence of (a) an aromatic hydrocarbon, (b) from 3 to 30 weight percent, based on the weight of the monomer , of a dialkyl peroxide and (c) 0.01 to 3 weight percent, based on the weight of the monomer, of an amine compound; up to more than 90 weight percent of the anhydride monomer has been converted to the polymer. In another aspect, the present invention provides a process, as described above, wherein the amine compound is selected from one or more of: dibutylamine, ethylhexylamine, methyldibutylamine, ethylenediamine, diethylenetriamine, n-octylamine, 1, 1, 3 , 3-tetramethylbutylamine and dimethylaniline.

DETAILED DESCRIPTION In the process of the present invention, the anhydrides are polymerized in an aromatic hydrocarbon or in a mixture of hydrocarbons. Suitable aromatic hydrocarbons include, for example, benzene and toluene; aromatic hydrocarbons (Cg), such as ethylbenzene and xylenes (ortho, meta and para isomers); aromatic hydrocarbons (Cg), such as propylbenzene, isopropylbenzene (also known as eumeno), ethyltoluenes (ortho, meta and para isomers), trimethylbenzenes (1, 2, 4-trimethylbenzene or pseudocumene, 1, 3, 5-trimethylbenzene or mesitylene ) and indano; aromatic hydrocarbons (C? _o) such as diethylbenzenes (ortho, meta and para isomers), isopropyltoluenes (ortho, meta and para isomers, also known as eumeno), butyl-benzenes (n-butyl, secondary butyl, isobuyl and tertiary butyl), tetralin, ethyldimethylbenzenes, naphthalene, isodurene and durene; aromatic hydrocarbons (11-C14) such as methylnaphthalenes, dimethylnaphthalenes, ethyl-naphthalenes, dimethylindane, biphenyl and diisopropylbenzene (ortho, meta and para isomers). Preferred aromatic hydrocarbons are toluene, ethylbenzene, ortho-xylene, meta-xylene, para-xylene and mixtures thereof. Optionally, other solvents can be used in combination with aromatic hydrocarbon solvents, for example halogenated aromatic hydrocarbons, such as chlorobenzene; non-aromatic hydrocarbons (branched and linear); comminuted glycol-ethers, such as (C 1 -C 4) alkyl diethers of diethylene glycol; l-methyl-2-pyrrolidinone. The amount of the optional solvent used is preferably less than 50%, more preferably less than 20% and especially preferred less than 10%, based on the weight of the total solvent used. Optional solvents may be used as long as they do not significantly affect the polymerization of the anhydride or the solubility of the anhydride monomer in the polymerization medium. Anhydrides that can be polymerized in the process of the present invention include, for example: maleic anhydride, citraconic anhydride, itaconic anhydride, 1,2,3,6-tetrahydrophthalic anhydride, 5-norbornene-2,3-dicarboxylic anhydride, anhydride bicyclo [2.2.2] -5-octen-2, 3-dicarboxylic, 3-methyl-l, 2,6-tetrahydrophthalic anhydride and 2-methyl-1,3,6-tetrahydrophthalic anhydride, anhydride 3,6 -epoxy-l, 2, 3, 6-tetrahydrophthalic, 2-methyl-1,3,5-tetrahydrophthalic anhydride, and mixtures thereof. Preferably, the anhydride monomer is comprised of at least 50 percent (%), more preferably at least 75% and more preferably at least 90% maleic anhydride by weight, based on the total weight of the monomer. Optionally, other monomers can be polymerized in combination with the monomers of anhydrides, for example acrylic acid, methacrylic acid, vinyl acetate, styrene, esters of alkyl (meth) acrylate (Ci-C4), (meth) acrylamides substituted with alkyl, and vinyl ethers. The amount of the optional monomer used is preferably less than 20%, more preferably less than 10% and especially preferred less than 5%, based on the total weight of the monomer. The optional monomers may be used so long as they do not significantly affect the polymerization of the anhydride or the solubility of the anhydride monomer in the polymerization medium. Suitable free radial initiators of dialkyl peroxide, useful in the process of the present invention, include, for example, tertiary dibutyl peroxide, tertiary diamyl peroxide, 4,4-di (tere.-butylperoxy) pivalate of n- butyl, tertiary dibutyl peroxide and cumyl and dicumyl peroxide. The preferred free radical initiator is tertiary dibutyl peroxide. The amount of the free radical initiator used in the process of the present invention is from 3 to 30%, preferably from 5 to 25% and more preferably from 10 to 20% by weight, based on the weight of the anhydride monomer. As used herein, the term "dialkyl peroxide" refers to an initiator containing the dialkyl peroxide bond, Rj_-O-0-R2, where R] _ and R2 may be the same or different and represent alkylene groups or substituted alkyl; the groups R] _ and R2 may contain aromatic and other functionalities (such as ester linkages) as long as they do not adversely affect the performance of the dialkyl peroxide as a free radical initiator. In the process of the present invention, we have found that the amine compounds used in conjunction with the free radical initiator, increase the polymerization efficiency of the anhydride by allowing lower temperatures and lower levels of the free radical initiator used compared to the temperatures and conventional initiator levels used to supply high conversions of the anhydride monomer, i.e., greater than 90%, preferably greater than 95% and more preferably greater than 99% of the monomer conversion. The use of amine compounds to improve the free radical polymerization efficiency of the anhydride is surprising, given the teachings in the prior art regarding the detrimental effect of the amine compounds on free radical polymerizations in general. For example, polymerization of methyl methacrylate with benzoyl peroxide was shown to be accelerated by dimethylaniline and other tertiary aromatic amines, but polymerization was not accelerated by primary, secondary and tertiary aliphatic amines, or primary and secondary aromatic amines (J. Lal and R. Green in J. Polymer Science, Vol. XVII, pages 403-409 (1955); Similar effects with respect to the polymerization of styrene with benzoyl peroxide are also disclosed. In contrast to these teachings, we have found that the aliphatic, primary, secondary and tertiary amines increase the polymerization rate of the anhydride monomers, using the dialkyl peroxides; we have further observed that this effect is absent when the diacyl peroxide initiator is used in the polymerization of the anhydride monomers (see Examples 27 and 28). Suitable amine compounds include, for example, ammonia, aliphatic amines (C 1 -C 22) and aromatic amines (C 5 -C 20) • Suitable aliphatic amines include, for example, primary, secondary and tertiary alkylamines (branched or linear) such as methylamine, dimethylamine, trimethylamine, butylamine, dibutylamine, ethylhexylamine, methyldibutylamine, n-octylamine, 1,1,3,3-tetramethylbutylamine (also known as tert-octylamine), amine mixture (Cj_2-C; ) tere. -alkyl-primary, mixture of amines (16-C22) tere. -alkyl-primary, and poly-amines, such as ethylenediamine, diethylenetriamine, triethylenetetramine and 1,8-diamino-p-menthane. Suitable aromatic amines include, for example, aniline and dimethylaniline. Preferred amine compounds are ammonia, dibutylamine, ethylhexylamine, methyldibutylamine, ethylenediamine, diethylenetriamine, n-octylamine, 1,1,3,3-tetramethylbutylamine and dimethylaniline; more preferably, the amine compound is n-octylamine. The amount of the amine compound used in the process of the present invention is from 0.01 to 3%, preferably from 0.05 to 2% and more preferably from 0.1 to 1% by weight, based on the weight of the anhydride monomer. In addition, preferred weight ratios of the amine to the free radical initiator range from 0.001 / 1 to 0.5 / 1, more preferably from 0.005 / 1 to 0.2 / 1 and especially preferred from 0.01 / 1 to 0.1 / 1. The poly (anhydrides) are prepared by dissolving the anhydride monomer in the aromatic hydrocarbon and then polymerizing by the addition of one or more free radical initiators and amine compounds. The concentration of the anhydride in the aromatic hydrocarbon solution is typically 25 to 70%, preferably 30 to 60% and more preferably 35 to 55% by weight, based on the total weight of the reaction mixture. The polymerization can be carried out using a range of process variations. For example, all reagents (anhydride, initiator, amine compounds) can be combined in the aromatic hydrocarbon solvent and heated to the desired polymerization temperatures and maintaining the polymerization conditions until a high conversion of the monomers has been achieved; however, this type of polymerization will rre the extensive heat removal capacity to accommodate the exothermic reaction of the polymerization. Preferably, the anhydride monomer is dissolved in the aromatic hydrocarbon by heating and the initiator and amine compound (typically in an aromatic hydrocarbon or in an inert solvent) are then added at a polymerization temperature over a period of time (in continuous or intermittent form); preferably, the amine compound is added to the anhydride solution before the addition of the free radical initiator. Alternatively, some or all of the anhydride monomer (in the aromatic hydrocarbon) may be added to the polymerization reactor at the same time that the initiator is added to this polymerization reactor. In another embodiment of the invention, the additional initiator, after a larger portion of the anhydride monomer has been polymerized (first stage), for example greater than 75% and preferably greater than 85% anhydride conversion, can be added to the polymerization reactor to complete this polymerization (second stage or post-polymerization stage), ie, greater than 95% and more preferably greater than 99% conversion of the anhydride; the additional initiator can be used only in the second stage or an additional amine compound can be added in conjunction with the additional initiator. Preferably from 50 to 100%, more preferably from 50 to 70% and especially preferred from 50 to 60% of the total initiator is used in the first stage, with the remainder being used in the second stage. Preferably, from 75 to 100% and more preferably from 90 to 100%, of the total amine, is used in the first stage, with any remainder being used in the second stage. The polymerization is typically conducted using an inert gas atmosphere, for example nitrogen. This polymerization is preferably carried out near or at the boiling point of the aromatic solvents used, that is, the reflux conditions. Generally, the polymerization temperature can be up to the boiling point of the aromatic solvents used, for example from 80 to 180 ° C, preferably from 110 to 165 ° C, more preferably from 120 to 150 ° C and especially preferred from 130 to 150 ° C. 145 ° C, although the polymerization can be carried out under pressure when higher temperatures are used. The polymerization (which includes the charges of the monomer and initiator and the retention times) is generally carried out in about 2 to 10 hours, preferably 3 to 6 hours, or until the desired conversion of the monomers has been reached, by example, until at least 90%, preferably at least 95%, more preferably at least 97% and especially preferred at least 99% of the anhydride monomer has been converted to the polymer. As recognized by those skilled in the art, the time and temperature of the reaction are dependent on the selection of the initiator and the target molecular weight and can be conveniently varied. The poly (anhydride) product can be isolated as the poly (anhydride) or can be hydrolyzed to the corresponding acid or salt form. When the poly (carboxylic acid) is formed in the desired product, the water can be added to the solution of the poly (anhydride) in the aromatic hydrocarbon or a larger portion of the aromatic hydrocarbon can be removed from the poly (anhydride) by first distillation, followed by the addition of water. The remaining aromatic hydrocarbon may then be removed by steam distillation or azeotropic distillation upon completion of the hydrolysis step. The resulting aqueous solution of the hydrolyzed poly (anhydride) can then be neutralized with alkali, ammonia or amines to provide the corresponding salt form of the polycarboxylic acid. Alternatively, the neutralization agent can be added before the removal of the aromatic hydrocarbon solvent, followed by separation of the distillation or aromatic hydrocarbon during the hydrolysis and neutralization. Useful neutralization agents include, for example, sodium hydroxide, potassium hydroxide, ammonium hydroxide, triethanolamine, diethylaminoethanol, ethanolane and trimethylhydroxyethylammonium hydroxide. Preferred neutralizing agents are sodium hydroxide and potassium hydroxide. The molecular weight control of the resulting poly (carboxylic acid) product is achieved by the level of the initiator used and the chain transfer action characteristic of the aromatic hydrocarbon solvents. The process of the present invention is useful in providing low molecular weight water soluble polymers containing carboxylic acid moieties. The low molecular weight refers to the weight average molecular weight (Mw) of less than 5,000, preferably less than 2,000. The mentioned molecular weights are those measured by aqueous gel permeation chromatography (GPC) in relation to the poly (acrylic acid) standard, which has an Mw of 2,000.

The abbreviations used in the Examples and in the Tables are listed below, with the corresponding descriptions. DNP = tertiary dibutyl peroxide LPC = lauroyl peroxide DAP = tertiary diamyl peroxide BDBV = n-butyl-4,4-di (tert-butylperoxy) valerate NOA = n-octylamine EDA = ethylenediamine DETA = diethylenetriamine TMBA = 1, 1, 3, 3-tetramethylbutylamine EHAm = ethylhexylamine DBAm = dibutylamine MBAm = methyldibutylamine DMAn = dimethylaniline Some embodiments of the invention are described in detail in the following examples. All ratios, parts and percentages (%) are expressly by weight, unless otherwise specified, and all reagents are of good commercial quality, unless specified otherwise. A summary of the reaction parameters and the types and concentrations of the amine used in the polymerization of maleic anhydride with di-tert. Peroxide. -butyl are presented in Table 1.

Example 1 (comparative) To a 1-liter, 4-necked flask, equipped with mechanical stirrer, reflux condenser topped with nitrogen inlet, and a thermal pair, 200.00 grams (g) of maleic anhydride and 200.00 g of xylenes were added. of technical grade. After making the reactor inert with nitrogen, the stirred solution was heated to reflux (140-145 ° C), then 40.00 g of tertiary dibutyl peroxide (DBP) were added gradually over 2 hours. The solution was then refluxed for 2 hours. The reactor was then modified for vacuum distillation and the xylene was removed by distillation (227.7 g). The remaining reaction solution was cooled below 100 ° C and 100 g of deionized water was added. The reaction solution was then heated to reflux (103-107 ° C) and any remaining xylene was removed by azeotropic distillation. The remaining reaction solution was then cooled again below 100 ° C and further diluted with 212.9 g of deionized water. The final aqueous solution contained 8.5% residual maleic acid, corresponding to 79% conversion, based on maleic anhydride.

Example 2 (comparative) To a Parr pressure reactor, 2.5 liters (pressure of 3.5 x 106 Passes (Pa) or 35 kg / cm2, at 400 ° C), equipped with mechanical agitator, nitrogen inlet, thermal pair and charge inputs, were added 200.40 g of maleic anhydride and 200.20 g of xylenes of reactive grade .. The stirred solution was made inert with nitrogen, placed under a moderate vacuum (3.4 x 10 ^ Pa or vacuum of 0.7 kg / cm2) and heated to 139-141 ° C, then gradually added, over 60 minutes, 20.10 g of DBP in 24.40 g of xylenes. The solution was then kept at that temperature for 2.5 hours (reactor pressure of 1.3 x 10 ^ Pa or 028 kg / cm2) and then diluted with 180.55 g of xylenes in 36 minutes. After dilution, 14.00 g of DBP in 27.60 g of xylenes were added over 30 minutes at 139-141 ° C and the solution was maintained at that temperature for an additional 110 minutes (reactor pressure of 1.3 x 10 ^ Pa or 0.35 kg). / cm2 of vacuum) before cooling to 95 ° C. To the stirred solution, 200.0 g of distilled water were slowly added. The solution was stirred for a further 20 minutes, allowed to cool to 75 ° C and the aqueous and organic phases were separated. The xylene phase was washed twice with 50.Og of distilled water and the combined aqueous phases were distilled under a nitrogen sweep, to concentrate to a weight of 470.5 g of an aqueous reaction solution. The final aqueous solution contained 16% residual maleic acid, which corresponds to 68% conversion, based on maleic anhydride.

Example 3 To a 1-liter, 4-necked flask, equipped with a mechanical stirrer, reflux condenser topped with nitrogen inlet, and a thermal pair, was added 200.00 grams (g) of maleic anhydride and 200.00 g of technical grade xylenes. . After making the reactor inert with nitrogen, the contents of the reactor were heated to 60 ° C to dissolve the anhydride maleic and then 1.00 g of n-octylamine (NOA) were added. The stirred contents of the reactor were then heated to reflux (140-145 ° C) and 20.00 of DBP were added gradually in 167.00 g of xylenes over 1 hour. The solution was then refluxed for 2 hours. The reactor was then modified for vacuum distillation and the xylene was distilled off (278.9 g). The remaining reaction solution was cooled below 100 ° C and 100 g of deionized water was added. The reaction solution was then heated to reflux (103-107 ° C) and 45 g of xylenes were removed by azeotropic distillation. The remaining reaction solution was then cooled again below 100 ° C and further diluted with 264.7 g deionized water. The final aqueous solution did not contain detectable maleic acid (limit of detection of 0.1% by weight), which corresponds to 99.8% conversion, based on maleic anhydride.

Example 4 To a Parr pressure reactor, 2.5 liters (pressure 3.5 x 106 Passes (Pa) or 35 kg / cm2, at 400 ° C), equipped with mechanical stirrer, nitrogen inlet, thermal pair and charge inputs, 400.10 g of maleic anhydride and 327.30 g of reactive grade xylenes and 1.10 g of NOA were added. The stirred solution was made inert with nitrogen, placed under a moderate vacuum (3.4 x 10 ^ Pa or vacuum of 0.7 kg / cm2) and heated to 140 ° C, then 40.30 g of DBP were added gradually over 60 minutes. in 48.00 g of xylenes. The solution was then kept at that temperature for 60 minutes. The solution was then maintained at 140-142 ° C for 62 minutes (reactor pressure of 1.2 x 10 ^ Pa or 014 kg / cm2) and then diluted over 35 minutes with 363.00 g of xylenes. After dilution, 28.20 g of DBP in 45.00 g of xylenes were added over 30 minutes at 140-142 ° C and the solution was maintained at that temperature (reactor pressure of 1.6 x 10 ^ Pa or 0.56 kg / cm2 of vacuum ) for an additional 60 minutes, before cooling to 95 ° C. 396.00 g of distilled water were slowly added to the stirred solution. The solution was stirred for a further 15 minutes, allowed to cool to 75 ° C and the aqueous and organic phases were separated. The xylene phase was washed twice with 100.0 g of distilled water and the combined aqueous phases were distilled under a nitrogen sweep, to concentrate to a weight of 979.0 g of an aqueous reaction solution. The final aqueous solution did not contain detectable residual maleic acid (limit of detection of 0.1% by weight), which corresponds to at least 99.8% conversion, based on maleic anhydride.

Examples 5-28 In a manner similar to that described in the Examples above, different levels and types of initiator and different levels and types of or amine compounds were used to prepare the polymaleic acid. Examples 1 and 2 are representative of the one-step and two-stage polymerization processes of the prior art, respectively. Examples 3 and 4 represent one-step and two-stage polymerization processes, respectively, of the present invention. Examples 5-11 depict one-step polymerization methods of the present invention, which were performed in a manner similar to that described in Example 3. Examples 12-23 depict two-step polymerization processes, according to the present invention , which were carried out in a manner similar to that of Example 4 (except that Examples 13, 17, 18 and 20-23 were carried out in multiple neck reactors of 1 or 2 liters, equipped with reflux condenser). Examples 2A-2C show the effect of temperature in the two-step polymerization process of the prior art, ie, that only the increase in temperature in the absence of the amine compound was not effective in producing high conversion of monomers. Examples 5-11 show the beneficial effect of the low levels of different amine compounds in the conversion of monomers for the polymerization of a stage; for example, Example 11 demonstrates that the free radical initiator can be reduced by a factor of four n the presence of 0.25% n-octylamine and still provide an improvement in monomer conversion over 90% (compared to Example 1 of 79% conversion). Examples 12-23 show the beneficial effect of the low levels of different amine compounds in the conversion of monomers to the two-step polymerization; for example, Examples 21-23 demonstrate that monomer conversions in excess of 95% can be achieved in the presence of 0.06 to 0.25% of the n-octylamine at lower temperatures, when compared to Example 2 of 68% conversion.

Table 1 Example # Conc. of the Starter Conc. of the Amine Temp. ° C Amineb Initiator Conversion c 1 20 DBP 0 - reflow 79 2 17a DBP 0 - 145d 68 2A 17a DBP 0 - 140 58 2B 17a DBP 0 - 155 82 2C 17a DBP 0 - 165d 93 3 10 DBP 0.5 NOA reflow 99.8 * 4 17a DBP 0.25 NOA 140d 99.8+ 20 DBP 0.5 DBAm reflow 99.8+ 6 20 DBP 0.5 MBAm reflow 99.8+ 7 20 DBP 0.5 DMAn reflow 99.8+ 8 20 DBP 0.5 NOA reflow 99.8+ 9 20 DBP 0.25 NOA reflow 99.8+ 10 DBP 0.25 NOA reflow 98.7 11 5 DBP 0.25 NOA reflow 91 12 17a DBP 1 NH3 155d 99.8+ 13 17a DBP 1 TMBA 140 99.4 14 17a DBP 1 TMBA 145d 99.8+ 17a DBP 1 TMBA 155d 99.8+ 16 17a DBP 0.5 EHAm 140d 99.6 17 15a DBP 0.25 EDA 140 99.8+ 18 15th DBP 0.27 DETA 140 99.8+ 19 17a DBP 0.5 NOA 140d 99.6 20 15a DBP 0.25 NOA 140 99.8+ 21 15a DBP 0.25 NOA 130 96.8 22 17th DBP 0.125 NOA 140 99.8+ 23 17a DBP 0.06 NOA 140 96 to. percent by weight of the initiator used, based on the monomer, 10% in the first stage of polymerization and the remaining 5 or 7% in the second stage of polymerization b. percent by weight of the amine used, based on the monomer c. monomer conversion, weight percent of monomer used; 99.8+ indicates that residual maleic acid was below detectable analytical limits, less than 0.1% in solution. d. pressurized or topped polymerization reactor. and. Operation under reflux conditions, at 140-145 ° C Table 2 presents a summary of maleic anhydride polymerizations involving free radical initiators in addition to tertiary dibutyl peroxide. Examples 24 to 26 depict polymerization procedures using dialkyl peroxides and were performed in a manner similar to that described in Example 3. Examples 24 and 26 show the effect of dialkyl peroxide on maleic anhydride conversion in the absence of the amine compound and Example 25 demonstrates that the concentration of the dialkyl peroxide can be reduced by 50% in the presence of 0.25% of the amine compound, while maintaining a high conversion of the monomer. Example 27 represents a polymerization process of the prior art, which uses the diacyl peroxide initiator (lauroyl peroxide) and Example 28 demonstrates that the presence of the amine compound does not have a beneficial effect on the polymerization using the peroxide of diacyl, in contrast to the beneficial effect of the amine compound in the polymerizations of the dialkyl peroxide of anhydrides (as shown in Examples 1-25).

Table 2 Example # Conc. Of the Starter Conc. Of the Amine Temp. ° C Conversion Initiator amine * 3 c 24 24 DAP 0 reflow0 99.8+ 252 12 DAP 0.25 NOA reflow0 99.8+ 26 20 BDBV 0 reflow0 77 27 20 LPO 0 reflow0 96 28 20 LPO 0.25 NOA reflow0 94.5 to. percent by weight of the amine used, based on monomer b. monomer conversion, weight percent of monomer used; 99.8+ indicates that residual maleic acid was below detectable analytical limits, less than 0.1% in solution. c. Operation under reflux conditions, at 140-145 ° C

Claims (1)

1. CLAIMS 1. A polymerization process, for preparing anhydride polymers, this process comprises the polymerization of a monomer selected from one or more of: maleic anhydride, citraconic anhydride, itaconic anhydride, 1, 2, 3,6-tetrahydrophthalic anhydride, 5-norbornene-2, 3-dicarboxylic anhydride, bicyclo- [2.2.2] -5-octen-2, 3-dicarboxylic anhydride, 3-methyl-l, 2,6-tetrahydrophthalic anhydride and 2-methyl-1-anhydride, 3,6-tetrahydrophthalic acid, in the presence of: (a) an aromatic hydrocarbon, (b) from 3 to 30 weight percent, based on the weight of the monomer, of a dialkyl peroxide and (c) of the 0.01 to 3 weight percent, based on the weight of the monomer, of an amine compound; up to more than 90 weight percent of the anhydride monomer has been converted to the polymer 2. The process, according to claim 1, wherein the polymerization is conducted at a temperature of 80 to 180 ° C. 3. The method according to claim 1, wherein the monomer comprises at least 90 percent of the maleic anhydride by weight, based on the total weight of the monomer. 4. The process according to claim 1, wherein the aromatic hydrocarbon is selected from one or more of: toluene, aromatic hydrocarbons (C3), aromatic hydrocarbons (C9) and aromatic hydrocarbons (C] _Q). 5. The process according to claim 4, wherein the aromatic hydrocarbon (Cg) is selected from one or more of the ethylbenzene, ortho-xylene, meta-xylene and para-xylene. 7. The process, according to claim 1, wherein the amine compound is selected from one or more of the ammonia, aliphatic amines (C1-C22) and aromatic amines (C6-C20) • 7. The process, according to the Claim 1, wherein the amine compound is selected from one or more of: dibutylamine, ethylhexyl ina, methyldibutylamine, ethylenediamine, diethylene triamine, n-octylamine, 1,1,3,3-tetramethyl-butylamine and dimethylaniline. 8. The process, according to claim 1, wherein the dialkyl peroxide is used in an amount of 10 to 20 weight percent, based on the weight of the monomer. The method, according to claim 1, wherein the amine compound is used in an amount of 0.1 to 1 weight percent, based on the weight of the monomer. The process, according to claim 1, wherein the anhydride polymer has a weight average molecular weight of less than 2,000.