WO2007044169A1

WO2007044169A1 - Processes for the production of hydroxyalkylmaleimides

Info

Publication number: WO2007044169A1
Application number: PCT/US2006/035386
Authority: WO
Inventors: Chi Hung Cheng; Mahmood Sabahi; Gerry M. Sulzer; Venkataraman Ramachandran
Original assignee: Albemarle Corporation
Priority date: 2005-10-06
Filing date: 2006-09-13
Publication date: 2007-04-19
Also published as: TW200724527A

Abstract

A process is provided for producing high purity hydroxyalkylmaleimides in high yields. Hydroxyalkylmaleimides can be represented by: Formula (I) wherein R is an aliphatic, substituted aliphatic, cycloaliphatic or substituted cycloaliphatic linkage having 1 to 12 carbon atoms.

Description

PROCESSES FOR THE PRODUCTION OF HYDROXYALKYLMALEIMIDES

FIELD OF THE INVENTION

[0001] The present invention relates to improved processes for producing hydroxyalkylmaleimides, and in particular 2-hydroxyethylmaleimide (HEMI). The present invention also relates to a dry, easy flowing HEMI product and methods for its manufacture. Novel intermediate compositions are also featured.

BACKGROUND OF THE INVENTION

[0002] Maleimides are a class of photopolymerizable heterocyclic compounds having a polymerizable double bond and are particularly useful in manufacturing oligomers capable of self-initiated photopolymerization. However, wide-spread use of aliphatic maleimides is limited by their relatively high cost due to the difficulty of obtaining high purity product in high yields.

[0003] For example, in International Application No. WO 01/68601, which is incorporated herein by reference in its entirety, 2-hydroxyethyhnaleimide was produced by a) mixing a molar surplus of furan with maleic anhydride dissolved in an organic solvent and allowing the furan to react with the maleic anhydride for 2-20 hours at a temperature of 10- 5O⁰C and atmospheric pressure to form a furan-adduct (Furan-A), b) adding a molar surplus of ethanolamine at a temperature of 10-85⁰C and atmospheric pressure forming a reaction mixture which is refluxed to produce 2-hydroxyethyhnaleimide-adduct (HEMI-A), and c) dissolving the HEMI-A in an organic solvent at a temperature above 130-170⁰C wherein 2- hydroxyethylmaleimide is obtained after cooling, filtration and washing. Three examples utilizing this process are disclosed in WO 01/68601 and the yields of HEMI, based on maleic anhydride, are 43%, 21%, and 43%, respectively. These low overall yields are primarily due to the low yield of HEMI-A produced in step b).

[0004] Similarly, in US Patent No. 6,369,124, which is also incorporated herein by reference in its entirety, HEMI was obtained by a process similar to that of WO 01/68601 and its yield was 54.95% based upon maleic anhydride.

[0005] hi addition to cost concerns, there is a concern in handling conventionally shaped hydroxyalkylmalemiide crystals due to their toxicity. The conventional crystals are needle shaped and have a tendency to collect in clothing, work equipment, and, in their smallest form, present an aspiration danger to those handling hydroxyalkylmaleimide. SUMMARY OF THE INVENTION

[0006] The present invention relates to significant improvements over the conventional process disclosed in the prior art. The improved process of this invention produces high purity hydroxyalkyhnaleimides and in high yields. Hydroxyalkylmaleimides can be represented by:

Formula

wherein R is an aliphatic, substituted aliphatic, cycloaliphatic or substituted cycloaliphatic linkage having 1 to 12 carbon atoms. A highly useful hydroxyalkylmaleimide is the before mentioned HEMI

[0007] According to WO 01/68601, HEMI can be produced by a three-step process. The first step, Reaction A, is the cycloaddition of furan and maleic anhydride to form the furan-adduct, Furan-A. An ethyl acetate solvent is used. Reaction temperatures are from 1O⁰C to 50C° and the reaction is run at atmospheric pressure.

Furan Maleic Anhydride Furan-A

[0008] This step does not present an ideal situation as it has been observed that Furan- A in solution or as a solid undergoes a slow reverse or retro Diels Alder Reaction producing the original starting materials, furan and maleic anhydride, that result in a loss in reaction yield. [0009] In the second step, Reaction B, the separated Furan-A is slurried with ethanol. Excess ethanolamine is added to the slurry to form 2-hydroxyethyknaleimide-adduct, HEMI- A. The reaction temperature is 10 to 85°C and the reaction pressure is atmospheric.

ethanolamine

Furan-A HEMI-A

[0010] In addition to the Furan-A retro Di els Alder reaction affecting product quality and yield, there is also a reaction competing with the ethanolamine/Furan-A reaction, the reaction of Furan-A with the alcohol solvent, which is facilitated in the presence of a base. This competing reaction results in the formation of an acid-ester. This acid ester does not ' readily yield the desired product.

[0011] Finally, in the third step, Reaction C, HEMI-A is heated in an. aromatic solvent to remove furan. HEMI precipitates from solution upon cooling.

HEMI-A HEMI

[0012] As stated above, the prior art describes HEMI yields from 21% to 55% based on the maleic anhydride starting material.

[0013] In comparison, the process of the present invention (described below) is a vast improvement over the conventional process as it obtains yields of from about 55% to about 75% based on the nialeic anhydride starting material. Also, the HEMI product purity is greater than about 98%.

[0014] The processes of this invention feature, amongst other things: 1) allowing Reaction A to proceed underpressure from about 10 psig to about 50 psig and at a temperature from about 5O⁰C to about 7O⁰C utilizing only excess furan as the reaction solvent to form a furan and Furan-A containing slurry; 2) without purification, filtration or crystallization treatment of the slurry formed in Reaction A, utilizing at least a portion of the slurry as a reactant for Reaction B; 3) allowing the Furan-A produced in Reaction A to react with ethanolamine at low temperatures, from about -3O⁰C to about 2⁰C, to form an intermediate composition comprising from about 70 wt% to about 100 wt% amic-acid and from about 0 wt% to about 30 wt% acid-ester; 4) adding a tertiary amine to the intermediate composition and heating it to an elevated temperature (between about 50⁰C to about 100⁰C) to form HEMI-A; 5) precipitating HEMI-A with greater than 98% purity from the reaction mixture thus eliminating the need for further purification; and 6) thermolyzing HEMI-A to HEMI in a high boiling point organic solvent, such as xylene.

[0015] Not only does the process of this invention provide for high yields and highly pure product, the improved process also results in a safer and more manageable final product. The isolated HEMI is dried in a tumble dryer rather than by other conventional drying methods resulting in substantially round particles rather than needle-like crystals. This is a significant improvement since the needle-like crystals are problematic from a safe handling standpoint.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a photograph of HEMI flakes.

[0017] Figure 2 is a photograph of substantially round particles of HEMI.

DETAILED DESCRIPTION OF THE INVENTION

[0018] As stated above, the first step (Reaction A) for producing HEMI is the cycloaddition of furan and maleic anhydride. In the conventional process, the reactants are dissolved in an organic solvent, such as ethyl acetate. Furan-A is not stable at room temperature in organic solvents, such as ethyl acetate and alcohols, and will undergo a reverse or retro Diels Alder reaction producing the starting reactants, furan and maleic anhydride. Even if isolated from the organic solvents, solid Furan-A will also slowly decomposes to furan and maleic anhydride upon standing at room temperature. [0019] It has been discovered that this reverse or retro Diels Alder reaction can be attenuated by running the reaction under pressure from about 10 psig to about 50 psig and at an elevated temperature, say from about 50⁰C to about 7O⁰C, and by utilizing excess furan as the reaction solvent. By excess furan, it is meant a molar excess, i.e. greater than a 1:1 molar ratio of furan to maleic anhydride. Preferably the ratio of furan to maleic anhydride is between about 2:1 to about 10:1, more preferably between about 4:1 to about 8:1, and most preferably from about 5:1 to about 7:1. It is to be understood that it is preferred to use furan as the sole reaction solvent. However, it is not outside of the scope of this invention to use co-solvents provided that they do not contribute to any significant retro Diels Alder reactions.

[0020] In Reaction A, the reaction mass is formed from the furan and maleic anhydride and by adding either one to the other or both at the same time into a stirred reaction vessel. The reaction mass is maintained for a reaction period that is within the range of from about 1 to about 4 hours. Good results can be obtained with reaction times of 2 to 3 hours. The higher the reaction temperature, generally the shorter the reaction time needed. In all cases, the preferred reaction times are those that obtain reaction of all or nearly all (say 90+%) of the maleic anhydride. The Reaction A product is a slurry comprising furan and a Furan-A precipitate. The resulting slurry is initially hot, e.g. 50 to 70°C, but is then cooled or allowed to cool. Since the next step, Reaction B, is to use a low temperature, say -30 to 5°C, it is efficient to cool the slurry to the Reaction B temperature chosen.

[0021] The cooled slurry is suitable for use in Reaction B as is, there being no need for any liquid-solid separation step or purification step, etc. The cooled slurry is mixed with an C₁ - C₅ alcohol solvent, preferably methanol or ethanol. The alcohol, before mixing, may be cooled to a temperature similar to that of the cooled slurry. The slurry and alcohol can be mixed together by any order of addition of one to the other or both together into a reaction vessel. Quantitatively, the amount of alcohol solvent used is that amount sufficient to dissolve all of the Furan-A and yield an easy flowing liquid mass.

[0022] As discussed previously, Furan-A in alcohol undergoes a slow and temperature dependent reverse or retro Diels Alder reaction that negatively affects product yield and purity.

[0023] In addition, the Furan-A reacts with alcohols in the presence of a base, such as a hydroxyalkylamine, to form a Furan-A acid-ester. This is an undesirable reaction since it is in competition with the desired reaction of Furan-A with ethanolamine to yield the Furan-A amic acid. The competing reactions are shown below. Furan-A Acid-ester

[0024] Surprisingly, it has been discovered that this competition can be biased heavily in favor of the formation of the desired Furan-A amic acid by carrying out Reaction B at a temperature in the range of about -30⁰C to about 2°C and in the presence of a tertiary amine. By using the low temperature and tertiary amine in Reaction B, a unique composition comprising about 70 wt% to about 100 wt% Furan-A amic-acid and about 0 wt% to about 30 wt% Furan-A acid-ester is obtained. Preferably the composition comprises between about 80 wt% to about 100 wt% Furan-A amic acid and about 0 wt% to about 20 wt% Furan-A acid- ester. Such compositions are useful as precursors for high purity HEMI.

[0025] hi order to convert the Furan-A amic acid to HEMI-A with high yields at relatively low temperature, a tertiary amine, preferably triethylamine, is added to the reaction mass, after which the temperature is allowed to increase to between about 50°C to about 70⁰C. The increase in temperature also results in the evaporation and removal of much of the excess furan and alcohol solvent. The higher concentration of amic acid relative to the acid- ester in the reaction mass ultimately goes to the obtainment of the higher yields and purity of the HEMI-A intermediate.

[0026] The reaction mass in Reaction B is formed from the alcohol/Furan-A/furan solution, ethanolamine and tertiary amine. A stochiometric amount of ethanolamine is added to form the reaction mass solution; however, a molar excess may be utilized.

[0027] The tertiary amine can be depicted as R₁R₂R₃N wherein R₁, R₂ and R₃ are not necessarily the same and are alkyls, cycloalkyls or aromatics. A highly preferred tertiary amine is triethylamine. The tertiary amine is believed to promote a high conversion of the Furan-A amic acid to HEMI-A despite the low reaction temperature used.

[0028] The molar ratio of tertiary amine to furan-adduct used in to the reaction mass during Reaction B may range from about 0.5:1 to about 2:1, preferably between about 0.5:1 to about 1.5:1, more preferably about 0.75:1 to about 1.25:1, and most preferably about 0.8:1 to about 1.1:1

[0029] The reactor is preferably a stirred reactor that is supportable of an inert pad above the reaction mass solution. The inert pad can be provided by nitrogen, argon or any other well-known inert gas.

[0030] The HEMI-A laden reaction mass is concentrated by subjecting it to a reduced pressure thereby evolving volatiles such as alcohol and furan. The concentrated reaction mass is then cooled to about room temperature and the HEMI-A crystallizes out of solution. The HEMI-A can be filtered, by any conventional and suitable means, to yield a filter cake which is then washed with an alcohol, e.g. isopropyl alcohol, and dried under a reduced pressure. There is no need to re-crystallize the HEMI-A. More HEMI-A can be recovered from the filtrate.

[0031] The filtrate (mother liquor) is further concentrated by heating to evolve volatiles. The concentrate is then cooled to room temperature. After, say 12 hours, the cooled concentrate is filtered. The filtered HEMI-A is washed with alcohol, e.g. isopropyl alcohol and dried.

[0032] In Reaction C, the HEMI-A formed in Reaction B is thermally treated to effect a thermal retro Di els Alder reaction of the HEMI-A to yield HEMI. This thermal treatment also preferably removes the furan produced by any retro reaction leaving a high concentration of very pure HEMI. The thermal treatment comprises dissolving the HEMI-A in a high boiling point solvent and bringing the resultant solution to a temperature in excess of the boiling point of furan, preferably refluxing the solution. The solvent must not exhibit high solubility for HEMI and preferably has a boiling point above 12O⁰C. Preferred solvents are aromatics, such as toluene and xylene. Xylene is highly preferred since the thermal retro reaction has been observed to go to completion within a relatively short time. An antioxidant, such as methyl hydroquinone may also be added during this step to improve yields. If employed, the amount of antioxidant added can range from 10 to 200 ppm, preferably between 10 and 100 ppm. [0033] The HEMI product is recovered by any suitable solid/liquid recovery technique. The filtered HEMI can then be washed with an inert wash, such as xylene. The washed HEMI is then dried.

[0034] The HEMI formed by the processes of this invention can have a purity, as confirmed by quantitative H-NMR, in the range of from about 98% to about 99+%, preferably greater than about 99.5%.

[0035] Further, the solid HEMI product of this invention can be comprised of particles having a rounded smooth shape by the simple expedient of tumble drying the wet HEMI product from the thermal retro reaction. It has been found that washing of the normally needle like HEMI flakes with a inert liquid medium, say xylene, and then tumble drying the wet flakes in a tumble dryer yields a semi-spherical HEMI particle having rounded smooth surfaces, such form being safer to handle and much less likely to suffer attrition during handling. This new form of HEMI is exemplified in Fig. 1 while the needle-like prior art form of HEMI is exemplified in Fig. 2.

EXAMPLES

[0036] The above description is directed to several preferred means for carrying out the present invention. Those skilled in the art will recognize that other means, which are equally effective, could be devised for carrying out the spirit of this invention. The following examples will illustrate the effectiveness of the present process, but are not meant to limit the present invention in any manner.

EXAMPLE 1 (COMPARATIVE)

[0037] A one-liter stainless steel Parr reactor equipped with a mechanical agitator, an electrical furnace, cooling coil, temperature probe and controller, pressure gauge, and a sampling line was used to perform this experiment. The reactor was charged with 0.70mol (68.6g) of maleic anhydride (Lancaster, 98%) and the reactor was fully evacuated. 4.7 mol (32Og) of furan (Aldrich) was sucked into the reactor via a 1/8" Teflon tubing. The mixture was heated to 55⁰C under agitation, and the pressure was allowed to increase to 17 psig (218.55kPa). The mixture was held at 55⁰C, under agitation, for two hours, and the agitator was then turned off to allow the furan-adduct solids to settle. A supernatant liquid sample was withdrawn from the reactor and analyzed by H-NMR to confirm complete conversion of the maleic anhydride to furan-adduct. [0038] The reactor was cooled for 2 hours 16 minutes until the furan-adduct mixture was cooled from 55⁰C to O⁰C. After cooling, 8.55 mol (273.8g) of methanol at O⁰C was incrementally added to the reactor over a four minute time period while maintaining the reactor at a temperature of about 0-2⁰C After all of the methanol was added, 0.8 mol (48.7g) of ethanolamine was incrementally fed to the reactor over a 1 hour 25 minutes using a peristaltic metering pump while maintaining the reactor temperature at about O⁰C. The reactor temperature was incrementally increased to 78⁰C over 27 minutes and held at this temperature for five hours. The reactor pressure was then vented through a condenser to allow the pressure of the reactor to reach atmospheric pressure, while maintaining the reactor at a temperature of 73-76⁰C. The condensate from the condenser was collected and analyzed via H-NMR, and the condensate was determined to contain 71.8 weight percent furan and 28.2 weight percent methanol, both based on the collected condensate.

[0039] The reactor was allowed to reach ambient temperature overnight, and the precipitated yellow solid was collected, filtered using a fritted glass funnel, and then dried under full vacuum. The dried solid was weighed and determined to weigh 60.6g, and the dried solid was analyzed by H-NMR and determined to contain 98.7 weight percent 2- hydroxyethylmaleimide-adduct ("HEMI-A"), residual methanol, ethanolamine, and methyl ester of the HEMI-A. Thus, 59.8g of HEMI-A was formed, which equated to a yield of 42%, based on the maleic anhydride.

[0040] The mother liquor was collected and determined to weigh 240. Ig. The mother liquor was analyzed via H-NMR and determined to contain 8.2 weight percent (19.7g) HEMI-A, 65.8 weight percent methanol, 2.62 weight percent ethanolamine, 7.47 weight percent HEMI-A methyl ester, 7.7 weight percent fumaric acid, 1.8 weight percent furan, and 0.14 weight percent maleic acid, all weight percent based on the mother liquor. The conversion of the starting material, i.e. maleic anhydride, to HEMI-A was calculated to be 88%. Thus, assuming 100% conversion of the starting material, the isolated yield of HEMI- A would be about 48%.

EXAMPLE 2 (ACCORDING TO THE PRESENT INVENTION)

[0041] 0.7 mol (68.6g) of maleic anhydride and 4.74 mol (322.3g) of furan were added to a one liter Pyrex flask, used as the reactor and referred to herein as such, fitted with a stirrer, thermometer, reflux condenser, and cooling bath. The contents of the reactor were stirred for 16 hours at ambient temperature, and the mixture turned into a white slurry containing furan-adduct in furan. [0042] The furan-adduct/furan mixture was cooled via the cooling bath to a temperature of O⁰C, and 8.75 mol (28Og) of methanol was added to the reactor. 0.73 mol (44.7g) of ethanolamine and OJmol (70.8g) of triethylamine were added dropwise to the reactor over a period of 30 minutes while maintaining the reactor temperature at 0-2⁰C under a nitrogen atmosphere. The cooling bath was then removed, and the temperature of the reactor was steadily increased to 67⁰C. Most of the furan and methanol were removed and condensed in the overhead during this heating period. The reactor was maintained at 67⁰C for 12 hours 30 minutes, and after this time, an additional 0.07 mol (4.4g) of ethanolamine was added and the temperature increased to 7O⁰C over a 2 hour time period. The reaction mass was collected and analyzed by NMR and it was determined that the reaction mass contained 0.58 mol HEMI-A, which equates to an 83% yield, based on the maleic anhydride, and the conversion of the starting material and intermediates, i.e. amic acid and methyl ester acid, was greater than 97%.

[0043] The reaction mass was then concentrated by drawing a 460 mmHg vacuum on the reactor at 6O⁰C, followed by filtration of the concentrated reaction mass, washing the recovered concentrated reaction mass with 63g of isopropyl alcohol, and drying the washed reaction mass under vacuum conditions. The dried reaction mass was then analyzed via NMR and found to be 100.5 g HEMI-A₅ a yield of 69%, based on the maleic anhydride.

[0044] Concentrated the mother liquor (78% by volume) at 53⁰C in 275 mmHg vacuum, cooling the concentrated mother liquor to room temperature over night, filtering the concentrated mother liquor, washing the filtered solids with isopropyl alchol, and drying the washed solids resulted in an additional 4.5g of HEMI-A. These HEMI-A solids were then added to the other HEMI-A solids that were originally recovered, and via quantitative H- NMR, the purity of the HEMI-A solids thus obtained was determined to be 99.8%. The actual yield of the combined HEMI-A, i.e. the original HEMI-A recovered from the reaction mass and the HEMI-A recovered from the mother liquor, was calculated to be 73%.

[0045] A 0.19 mol (4Og) sample of the HEMI-A from above was mixed with 227g of xylene and 0.005g methyl hydroquinone (MEHQ), an antioxidant. After heating under reflux and nitrogen sparging for 3 hours 15 minutes at 130⁰C, the conversion of HEMI-A to HEMI reached 98.7% and the reaction yield was determined to be approximately 98.7%. The reactor was cooled to room temperature, and the cooled reaction product was filtered at room temperature, and the filtered solids were washed with 15g of xylenes. The washed solids were dried under vacuum, and 25. Ig of HEMI, a 93% yield based on the HEMI-A, was obtained. The purity of the HEMI was determined to be greater than 99% by H-NMR. It was also determined that the mother liquor and wash liquid was combined and determined to weigh 230.2g and contain 1.17g of HEMI, which could be recovered as described above, or recycled.

Claims

WHAT is CLAIMED:

1 ) A process for producing a hydroxyalkylmaleimide of formula I

Formula

wherein R is an aliphatic, substituted aliphatic, cycloaliphatic or substituted cycloaliphatic linkage having 1 to 12 carbon atoms, the process comprising the steps of a) reacting furan with maleic anhydride in the presence of a stochiometric excess of furan, such excess furan acting as the sole reaction solvent, b) combining the furan-adduct with an alcohol and a primary hydroxyalkylamine and allowing the primary hydroxyalkylamine to react with the furan-adduct to form a maleimide-adduct, and c) combining the maleimide-adduct with an organic solvent and heat, thereby allowing the formation of the maleimide compound from the maleimide-adduct.

2) The process of claim 1 , wherein the alcohol is methanol.

3) The process of claim 2, wherein the organic solvent is xylene.

4) The process of claim 3, wherein the primary hydroxyalkylamine is ethanolamine and the hydroxyalkylmaleimide is 2-hydroxyethymalelimide (HEMI).

5) The process of claim 4, wherein the molar ratio of furan to maleic anhydride is in the range of about 2:1 to about 10:1.

6) The process of claim 5, wherein the molar ratio of furan to maleic anhydride is in the range of about 4: 1 to about 8:1.

7) The process of claim 6, wherein the molar ratio of furan to maleic anhydride is in the range of about 5:1 to about 7:1.

8) A process for producing furan-adduct comprising the step of reacting furan with maleic anhydride in the presence of a stochiometric excess of furan, such excess furan acting as the sole reaction solvent. 9) A process for producing a hydroxyalkylmaleimide of formula I

Formula I

wherein R is an aliphatic, substituted aliphatic, cycloaliphatic or substituted cycloaliphatic linkage having 1 to 12 carbon atoms, the process comprising the steps of a) mixing a stochiometric surplus of furan with maleic anhydride and allowing the furan to react with the maleic anhydride to form a furan-adduct, b) combining the furan-adduct with an alcohol to create a reaction mass, c) adding a primary hydroxyalkylamine and a tertiary amine to the reaction mass and allowing the formation of a maleimide-adduct, and d) combining the maleimide-adduct with an organic solvent and heat, thereby allowing the formation of the hydroxyalkylmaleimide from the maleimide-adduct.

10) The process of claim 9, wherein prior to step b) the furan-adduct is cooled to a temperature between about -30⁰C to about 2⁰C.

11) The process of claim 10, wherein prior to step b) the furan-adduct is cooled to a temperature between about -1O⁰C to about 0⁰C.

12) The process of claim 11, wherein the addition of the primary hydroxyalkylamine and the tertiary amine in step c) is initially carried out at a temperature between about -1O⁰C to about O⁰C after which the temperature of the reaction mass is allowed to increase to between about 50⁰C to about 7O⁰C.

13) The process of claim 12, wherein the alcohol is methanol.

14) The process of claim 13, wherein the organic solvent is xylene.

15) The process of claim 14, wherein the tertiary amine is triethylamine.

16) The process of claim 15, wherein the primary hydroxyalkylamine is ethanolamine and the hydroxyalkylmaleimide is 2-hydroxyethylrnaleimide (HEMI).

17) A process for producing a hydroxyalkylmaleimide comprising a) reacting furan with maleic anhydride in the presence of a stochiometric excess of furan, such excess furan acting as the sole reaction solvent, thereby forming a furan-adduct/excess furan slurry, b) combining the furan-adduct/excess furan slurry with an alcohol and a primary hydroxyalkylamine and allowing the primary hydroxyalkylamine to react with the furan- adduct to form a maleimide-adduct, and c) combining the maleimide-adduct with an organic solvent and heat, thereby allowing the formation of the hydroxyalkylmaleimide from the maleimide-adduct.

18) The process of claim 17, wherein the alcohol is methanol.

19) The process of claim 18, wherein the organic solvent is xylene.

20) The process of claim 19, wherein the primary hydroxyalkylamine is ethanolamine and the hydroxyalkylmaleimide is 2-hydroxyethylmaleimide (HEMI).

21) A hydroxyalkylmaleimide having a substantially round particle shape formed by drying the maleimide compound in a tumble dryer.

22) The hydroxyalkylmaleimide compound of claim 21 , wherein the hydroxyalkylmaleimide compound is 2-hydroxyethylmaleimide (HEMI).

23) A process for forming a substantially round particle shape of a hydroxyalkylmaleimide compound by drying the hydroxyalkylmaleimide compound in a tumble dryer.

24) The process of claim 23, wherein the hydroxyalkylmaleimide compound is 2- hydroxyethyhnaleimide (HEMI).

25) A process for forming a maleimide-adduct from a furan-adduct comprising the steps of a) cooling the furan-adduct to a temperature between about -30⁰C to about 2°C, b) creating a reaction mass by adding an organic solvent and a primary hydroxyalkylamine to the furan-adduct, c) adding a tertiary amine to the reaction mass, and d) allowing the temperature of the reaction mass to increase to between about 50⁰C to about 70⁰C.

26) The process of claim 25, wherein the organic solvent is an alcohol.

27) The process of claim 26, wherein the organic solvent is methanol.

28) The process of claim 25, wherein the tertiary amine is triethylamine.

29) The process of claim 25, wherein the primary hydroxyalkylamine is ethanolamine and the hydroxyalkylmaleimide is 2-hydroxyethymalelimide (HEMI).

30) The process of claim 25, wherein the molar ratio of tertiary amine to furan- adduct is in the range of about 0.5: 1 to about 2:1.

31) The process of claim 30, wherein the molar ratio of tertiary amine to furan- adduct is in the range of about 0.5:1 to about 1.5:1.

32) The process of claim 31 , wherein the molar ratio of tertiary amine to furan- adduct is in the range of about 0.75 : 1 to about 1.25:1. 33) The process of claim 22, wherein the molar ratio of tertiary amine to furan- adduct is in the range of about 0.8 : 1 to about 1.1:1.

34) An intermediate composition for forming a hydroxyalkylmaleimide-adduct from a furan-adduct in which about 0 to about 30 weight percent of the reacting furan-adduct forms an acid-ester and about 70 to about 100 weight percent of the reacting furan-adduct forms an amic acid.

35) An intermediate composition for forming a hydroxyalkylmaleimide-adduct from a furan-adduct obtained by cooling the furan-adduct to a temperature between about - 3O⁰C to about 2⁰C and creating a reaction mass comprising the cooled furan-adduct, an organic solvent and a primary hydroxyalkylamine, such that about 0 to about 30 weight percent of the reacting furan-adduct forms an acid-ester and about 70 to about 100 weight percent of the reacting furan-adduct forms an amic acid.

36) The composition of claim 35, wherein the hydroxyalkylmaleimide-adduct is 2- hydroxyethylmaleimide-adduct (HEMI-A).

37) The composition of claim 36, wherein the organic solvent is methanol.

38) The composition of claim 37, wherein the tertiary amine is triethylamine.

39) A process for producing 2-hydroxyethylmaleimide comprising a) reacting furan with maleic anhydride in the presence of a stochiometric excess of furan, such excess furan acting as the sole reaction solvent, thereby creating a furan-adduct/excess furan slurry, b) cooling the furan-adduct/excess furan slurry to a temperature between about -30⁰C to about 2⁰C, c) creating a reaction mass by adding methanol and triethylamine to the furan- adduct/excess furan slurry, d) adding ethanolamine to the reaction mass, f) allowing the temperature of the reaction mass to increase to between about 5O⁰C to about 7O⁰C, thereby allowing the formation of 2-hydroxyethylmaleimide-adduct, g) removing the 2- hydroxyethylmaleimide-adduct from the reaction mass, h) dissolving the 2- hydroxyethylrnaleirnide-adduct in xylene, i) heating the hydroxyethylmaleimide-adduct and xylene to allow the formation of 2-hydroxyethylmaleimide, j) removing the 2- hydroxyethylmaleimide from solution, and k) recovering any excess triethylamine, methanol or xylene.