METHOD FOR THE PREPARATION OF COPOLYMERS OF ALKYL METHACRYLATES AND MALEIC ANHYDRIDE

Abstract

A method for the preparation of a copolymer containing at least one alkyl methacrylate and maleic anhydride having a number average molecular weight of 4000 to 18000 g/mol proceeds by solution polymerization in the presence of a radical initiator.

Claims

1: A method for the preparation of a sulfur-free copolymer comprising alkyl methacrylate monomer units and maleic anhydride monomer units by solution polymerization of one or more alkyl methacrylates and maleic anhydride in a solvent in the presence of a radical initiator, said method comprising: a) providing an initial reaction solution comprising maleic anhydride, a portion of the radical initiator and solvent, and b) adding a feed solution comprising one or more alkyl methacrylates and a portion of the radical initiator to the initial reaction solution.

2: The method according to claim 1, wherein the feed solution is added over the course of 30 minutes to 12 hours.

3: The method according to claim 1, wherein the initial reaction solution comprises 50 to 100 wt-% maleic anhydride based on the total amount of maleic anhydride.

4: The method according to claim 1, wherein the molar ratio of the one or more alkyl methacrylates to the maleic anhydride is in the range of 10:1 to 1:1.

5: The method according to claim 1, wherein the initial reaction solution does not comprise any alkyl methacrylate.

6: The method according to claim 1, wherein the portion of the one or more alkyl methacrylates in the feed solution is 50 to 100 wt-% based on the total amount of the one or more alkyl methacrylates.

7: The method according to claim 1, wherein the total amount of the one or more alkyl methacrylates and the maleic anhydride is in the range of 10 to 80 wt.-% relative to the total weight of the sum of the initial reaction solution and the feed solution.

8: The method according to claim 1, wherein at least 80 mol-% of the one or more alkyl methacrylates are selected from the group of C.sub.6 to C.sub.22 alkyl methacrylates, or a mixture thereof.

9: The method according to claim 1, wherein a portion or all of the solvent is selected from the group consisting of methyl ethyl ketone, isobutyl methyl ketone, anisole, n-butanol, dimethylformamide, dimethyl sulfoxide, benzene (petroleum ether), acetone, 1-hexene, ethanol, ortho-xylene, and mixtures thereof.

10: A sulfur-free copolymer obtained by the method as defined in claim 1, wherein the number average molecular weight of the copolymer is in the range of 4000 to 18000 g/mol and the polydispersity index of the copolymer is in the range of 1 to 5, wherein the number average molecular weight and the polydispersity index are determined by gel permeation chromatography against poly(methyl methacrylate) standards, and the molar ratio of the one or more alkyl methacrylates to the maleic anhydride in the resulting copolymer is in the range of from 10:1 to 1:1, based on the total molar amounts of the one or more alkyl methacrylates and maleic anhydride used for the preparation of the sulfur-free copolymer.

11: The sulfur-free copolymer according to claim 10, wherein the sulfur-free copolymer comprises equimolar amounts of the one or more alkyl methacrylates and maleic anhydride.

Description

EXAMPLES

[0047] The following examples illustrate the present invention. In these examples, the following abbreviations are used:

TABLE-US-00001 MIBK methyl isobutyl ketone LMA lauryl methacrylate, comprising a mixture of linear C12, C14 and C16 methacrylates SMA stearyl methacrylate, comprising a mixture of linear C14, C16, and C18 methacrylates SA stearyl acrylate, comprising a mixture of linear C14, C16, and C18 acrylates BeMA behenyl methacrylate, comprising a mixture of C18, C20 and C22 methacrylates BeA behenyl acrylate, comprising a mixture of C18, C20 and C22 acrylates HODMA Hexyl octyl decyl methacrylate, comprising a mixture of C6, C8, and C10 methacrylate IDMA isodecyl methacrylate DPMA dodecyl pentadecyl methacrylate, comprising a mixture of branched and linear C12 to C15 methacrylates DPA dodecyl pentadecyl acrylate, comprising a mixture of branched and linear C12, C13, C14 and C15 acrylates MSA maleic anhydride

Example 1

[0048] Several copolymers of alkyl methacrylate and maleic anhydride were prepared using the method of the present invention and using different alkyl methacrylates and different comonomer molar ratios according to the following general procedure.

[0049] Solvent (MIBK), maleic anhydride, and a portion of the radical initiator (tert-butyl peroxy-2-ethylhexanoate) were added to the reaction vessel. The mixture was heated to a temperature of 90° C. to dissolve the reactants. A feed solution of alkyl methacrylate and a further portion of the radical initiator in MIBK was added to the reaction vessel over a period of 6 hours, while stirring. The total amount of MIBK was 12.5 wt-%, based on the total mass of the monomers and the solvent. An additional dose of initiator was added 2 hours after the feed solution had been completely added. The copolymerization mixture was stirred over night before the reaction was stopped. The copolymerization mixture was then diluted with additional MIBK to reach a final MIBK content of 50 wt-%.

[0050] Copolymer 1 was prepared from a monomer mixture comprising 10.8 wt-% HODMA, 61.2 wt-% LMA, and 28 wt-% MSA, based on the total amount of monomers. The amount of initiator used was 0.3 wt-% in the initial reaction solution, 0.5 wt-% in the second feed solution, and 0.2 wt-% in the solution of the final additional initiator dosage, based on the total amount of monomers.

[0051] Copolymer 2 was prepared from a monomer mixture comprising 56.9 wt-% SMA, 21.1 wt-% BeMA, and 22 wt-% MSA, based on the total amount of monomers. The amount of initiator used was 0.4 wt-% in the initial reaction solution, 0.6 wt-% in the second feed solution, and 0.2 wt-% in the solution of the final additional initiator dosage, based on the total amount of monomers.

[0052] Copolymer 3 was prepared from a monomer mixture comprising 82 wt-% IDMA and 18 wt-% MSA, based on the total amount of monomers. The amount of initiator used was 0.4 wt-% in the initial reaction solution, 0.7 wt-% in the second feed solution, and 0.2 wt-% in the solution of the final additional initiator dosage, based on the total amount of monomers.

[0053] Copolymer 4 was prepared from a monomer mixture comprising 22.1 wt-% LMA, 62.9 wt-% SMA, and 15 wt-% MSA, based on the total amount of monomers. The amount of initiator used was 0.5 wt-% in the initial reaction solution, 0.9 wt-% in the second feed solution, and 0.2 wt-% in the solution of the final additional initiator dosage, based on the total amount of monomers.

[0054] Copolymer 5 was prepared from a monomer mixture comprising 70 wt-% LMA and 30 wt-% MSA, based on the total amount of monomers. The amount of initiator used was 0.28 wt-% in the initial reaction solution, 4.2 wt-% in the feed solution, and 0.2 wt-% in the solution of the final additional initiator dosage, based on the total amount of monomers.

[0055] Copolymer 6 was prepared from a monomer mixture comprising 70 wt-% LMA and 30 wt-% MSA, based on the total amount of monomers. The amount of initiator used was 0.24 wt-% in the initial reaction solution, 3.5 wt-% in the feed solution, and 0.2 wt-% in the solution of the final additional initiator dosage, based on the total amount of monomers.

[0056] Copolymer 7 was prepared from a monomer mixture comprising 70 wt-% LMA and 30 wt-% MSA, based on the total amount of monomers. The amount of initiator used was 0.19 wt-% in the initial reaction solution, 2.8 wt-% in the feed solution, and 0.2 wt-% in the solution of the final additional initiator dosage, based on the total amount of monomers.

[0057] Copolymer 8 was prepared from a monomer mixture comprising 70 wt-% LMA and 30 wt-% MSA, based on the total amount of monomers. The amount of initiator used was 0.14 wt-% in the initial reaction solution, 2.1 wt-% in the feed solution, and 0.2 wt-% in the solution of the final additional initiator dosage, based on the total amount of monomers.

[0058] Copolymer 9 was prepared from a monomer mixture comprising 70 wt-% LMA and 30 wt-% MSA, based on the total amount of monomers. The amount of initiator used was 0.17 wt-% in the initial reaction solution, 2.5 wt-% in the feed solution, and 0.2 wt-% in the solution of the final additional initiator dosage, based on the total amount of monomers.

[0059] Copolymer 10 was prepared from a monomer mixture comprising 75 wt-% IDMA and 25 wt-% MSA, based on the total amount of monomers. The amount of initiator used was 0.19 wt-% in the initial reaction solution, 2.8 wt-% in the feed solution, and 0.2 wt-% in the solution of the final additional initiator dosage, based on the total amount of monomers.

[0060] The crude reaction product containing the copolymers of alkyl methacrylate and maleic anhydride was analyzed by gel permeation chromatography (GPC) against poly (methyl methacrylate) to determine the number average molecular weight Mn and the weight average molecular weight Mw. A mixture of 0.2 wt-% trifluoroacetic acid in tetrahydrofuran (THF) is used as eluent. To determine the conversion rate of maleic anhydride, the residual amount of maleic anhydride in the crude reaction product was determined by high pressure liquid chromatography (HPLC). The residual amount of alkyl methacrylate was also determined by HPLC. HPLC was carried out using tetrahydrofuran as solvent and a Nucleosil 100-7 C.sub.18 column (125×4.6 mm). The eluent was 0.06 to 5 M phosphate buffer at a pH of 2.

[0061] The following table 1 shows the number average molecular weight data of several copolymers (see Copolymers No. 1 to 10 in Table 1), and the residual alkyl methacrylate and maleic anhydride contents of the crude reaction products prepared using different alkyl methacrylates and comonomer molar ratios in the monomer mixture.

TABLE-US-00002 TABLE 1 Residual maleic anhydride Residual alkyl [weight %, methacrylates based on Alkyl [weight %, the total Comonomer methacrylate based on the weight of molar ratio composition total weight of the (alkyl based on C Mn Mw the reaction reaction Yield methacrylate:maleic No. alkyl chain [g/mol] [g/mol] PDI solution (*)] solution (*)] [%] anhydride) 1 C6, C8, C10, 14600 50400 3.46 0.01 0.15 99.7 1:1 C12, C14, C16 linear 2 C14, C16, 13700 48800 3.56 0.04 0.02 99.9 C18, C20, C22 linear 3 C10 15800 64900 4.10 0.38 0.02 99.2 2:1 branched 4 C12, C14, 14500 63600 4.39 0.45 0.006 99.1 C16, C18 linear 5 C12, C14, 4510 13300 2.95 1.20 0.003 97.6 1:1 C16 linear 6 C12, C14, 4840 15400 3.17 1.11 0.007 97.8 1:1 C16 linear 7 C12, C14, 5820 19300 3.31 0.56 0.02 98.8 1:1 C16 linear 8 C12, C14, 6650 20000 3.02 0.88 0.03 98.2 1:1 C16 linear 9 C12, C14, 6030 21300 3.53 0.91 0.01 98.2 1:1 C16 linear 10 C10 5280 16100 3.05 0.90 0.02 98.2 1:1 branched (*) the total weight of the reaction solution corresponds to total weight of the initial reaction solution, the feed solution and the solution of the final initiator dosage

[0062] Table 1 shows that by using the claimed process, it is possible to prepare sulfur-free copolymers of alkyl methacrylate and maleic anhydride with very high reaction yields and with excellent monomer conversions of both monomers, namely, maleic anhydride and different alkyl methacrylates.

[0063] As shown in Table 1, the claimed process for the specific preparation of maleic anhydride-alkyl methacrylate copolymers gives excellent conversions of both monomers maleic anhydride and alkyl methacrylate. Indeed, the residual amount of maleic anhydride according to the claimed process is never higher than 0.15 weight % and the residual amount of alkyl methacrylate according to the claimed process is never higher than 1.20 weight %, based on the total weight of the reaction solution (see Table 1 above). Consequently, the compositions of the copolymers obtainable by the claimed process nearly correspond to the compositions of the respective monomers in the reaction mixture.

[0064] Furthermore, the copolymers obtained according to the claimed process have the desired number average molecular weights (all below 18 000 g/mol) and are obtained with excellent yields of minimum 97.6%.

Example 2 (Comparative Example)

[0065] The following example illustrates a method for a solution polymerization according to U.S. Pat. No. 5,721,201 A.

[0066] A solution of maleic anhydride in toluene was fed into a reaction vessel and heated to the reaction temperature of 80° C. When the maleic anhydride had dissolved, a radical initiator (AIBN) in toluene was introduced into the reaction vessel. A solution of alkyl methacrylate or alkyl acrylate was added to the reaction vessel over a period of 4 hours.

[0067] Using this general procedure, examples 1, 2 and 3 of U.S. Pat. No. 5,721,201 A were reproduced to prepare eight different copolymers.

[0068] Copolymer 1 was prepared from 72.7 wt-% DPMA and 27.3 wt-% MSA, based on the total amount of monomers.

[0069] Copolymer 2 was prepared from 73.1 wt-% DPA and 26.9 wt-% MSA, based on the total amount of monomers.

[0070] Copolymer 3 was prepared from 73.7 wt-% DPMA and 26.3 wt-% MSA, based on the total amount of monomers.

[0071] Copolymer 4 was prepared from 76.1 wt-% SA and 23.9 wt-% MSA, based on the total amount of monomers.

[0072] Copolymer 5 was prepared from 76.9 wt-% SMA and 23.1 wt-% MSA, based on the total amount of monomers.

[0073] Copolymer 6 was prepared from 70 wt-% IDMA and 30 wt-% MSA, based on the total amount of monomers.

[0074] Copolymer 7 was prepared from 78.7 wt-% BeA and 26.3 wt-% MSA, based on the total amount of monomers.

[0075] Copolymer 8 was prepared from 78.2 wt-% BeMA and 21.8 wt-% MSA, based on the total amount of monomers.

[0076] The copolymers thus obtained were analyzed using the procedures described above for example 1. The results are shown in the following table 2 (see the results for Copolymers No. 1 to 8 in Table 2 below).

TABLE-US-00003 TABLE 2 Residual maleic Residual alkyl anhydride methacrylates [weight %, Alkyl [weight %, based on Comonomer (meth)acrylate based on the the total molar ratio composition total weight of weight of Reaction (alkyl based on C Mn Mw the reaction the reaction Yield methacrylate:maleic No. alkyl chain [g/mol] [g/mol] PDI solution (*)] solution (*)] [%] anhydride) 1 C12, C13, 17500 61700 3.53 0.22 3.22 85.5 1:1 C14, C15 linear methacrylate (example 1) 2 C12, C13, 11400 20300 1.79 4.20 5.36 60.3 C14, C15 linear acrylate (example 1) 3 C12, C13, 26800 54100 2.02 1.09 4.29 78.2 C14, C15 linear methacrylate (example 1) 4 C14, C16, C18 16600 28100 1.69 6.48 5.44 56.1 linear acrylate (example 1) 5 C14, C16, C18 28100 61000 2.17 1.08 4.31 80.8 linear methacrylate (example 1) 6 C10 branched 17800 64100 3.61 0.04 4.06 25.6 methacrylate (example 2) 7 C18, C20, C22 45700 92000 2.01 0.01 4.08 89.2 linear acrylate (example 3) 8 C18, C20, C22 18100 32500 1.80 3.07 5.04 78.2 linear methacrylate (example 3) (*) the total weight of the reaction solution corresponds to total weight of the reaction mixture (solvent, monomers, initiator)

[0077] The data shown in Table 2 demonstrate that the copolymerization of alkyl methacrylate or alkyl acrylate and maleic anhydride according to the process described in U.S. Pat. No. 5,721,201 A results in a higher residual amount of maleic anhydride as compared to the process of the present invention. Indeed, in the particular case of maleic anhydride-alkyl methacrylate copolymers, the amount of residual maleic anhydride is in the range of 3.22 to 5.04 weight %, based on the total weight of the reaction solution, according to the process of U.S. Pat. No. 5,721,201 A, whereas the amount of residual maleic anhydride according to the claimed process is never higher than 0.15 weight %, based on the total weight of the reaction solution (see Table 1 above). The conversion of maleic anhydride according to the claimed process for the specific preparation of maleic anhydride-alkyl methacrylate copolymers has thus been drastically improved in comparison to the conversions obtained with the prior art process.

[0078] Furthermore, in the process of U.S. Pat. No. 5,721,201 A it can be observed that some alkyl (meth)acrylate monomers remain unreacted as shown in Table 2 with the values of residual alkyl (meth)acrylate. When an equimolar amount of maleic anhydride and alkyl acrylate or methacrylate is used in the process of U.S. Pat. No. 5,721,201 A, it is observed that the resulting copolymers of all examples given in Table 2 have a higher molar amount of alkyl methacrylate or acrylate incorporated than of maleic anhydride. Thus the resulting copolymers prepared according to the process of U.S. Pat. No. 5,721,201 A are not equimolar copolymers.

[0079] Furthermore, the overall reaction yields of the comparative examples 1 to 8 reproduced according to the process in U.S. Pat. No. 5,721,201 A are low with values ranging from 25.6% to 89.2%, whereas the claimed process results in yields well above 97% (see Table 1).

Example 3 (Comparative Example)

[0080] In the following comparative example, copolymers of methacrylate and maleic anhydride are prepared under the reaction conditions of the solution copolymerization process disclosed in CN 1302031 C.

[0081] A mixture of maleic anhydride in toluene was charged into a reaction vessel and heated to a reaction temperature of 60° C. The reaction mixture was purged with nitrogen gas for 30 minutes. When the maleic anhydride was completely dissolved, alkyl methacrylate was added and the reaction was started by addition of radical initiator. Instead of AIBN, the radical initiator 2,2′-Azobis-(2-methylbutyronitrile) (AMBN) was used. Both initiators are azo compounds having a similar half-life period.

[0082] Two different copolymers were prepared. Copolymer 1 was prepared from 53.3 wt-% LMA; 21.7 wt-% SMA, and 26 wt-% MSA, based on the total amount of monomers. Copolymer 2 was prepared from 56.9 wt-% SMA, 21.1 wt-% BeMA, and 22 wt-% MSA, based on the total amount of monomers.

[0083] The results are given in the following Table 3 (see Copolymers No. 1 and 2 in Table 3).

TABLE-US-00004 TABLE 3 Residual maleic anhydride [weight Residual alkyl %, based methacrylates on the Alkyl [weight %, total Comonomer methacrylate based on the weight of molar ratio composition total weight of the Reaction (alkyl based on C Mn Mw the reaction reaction Yield methacrylate:maleic No. alkyl chain [g/mol] [g/mol] PDI solution (*)] solution*] [%] anhydride) 1 C12, C14, C16, 402000 729000 1.82 21.90 5.65 19.2 1:1 C18 linear 2 C14, C16, C18, 370000 796000 2.15 9.20 6.59 53.7 C20, C22 linear (*) the total weight of the reaction solution corresponds to total weight of the reaction mixture (solvent, monomers, initiator)

[0084] The results show that under the reaction conditions of the polymerization process according to CN 1302031 C, the copolymerization reaction has low reaction yields and low monomer conversions (as reflected in the high residual amounts of maleic anhydride monomer and alkylmethacrylate monomer left at the end of the reaction). Furthermore, the resulting copolymers 1 and 2 of Table 3 have a very high number average molecular weight.

[0085] Copolymer No. 2 of Table 3 was prepared according to CN 1302031 C from exactly the same monomer composition as copolymer No. 2 in Table 1, which was synthesized according to the claimed process. In case of the claimed process, a number average molecular weight of 13 700 g/mol was obtained versus a number average molecular weight of 370 000 g/mol in case of the process according to CN 1302031 C. Furthermore, the residual amounts of monomers are very low in case of copolymer 2 prepared according to the claimed process with values of 0.04% residual alkyl methacrylate and 0.02% maleic anhydride, whereas in case of copolymer 2 prepared according to the process of CN 1302031 C, the residual amounts of monomers were high with values of 9.20% residual alkyl methacrylate and 6.59% maleic anhydride. This is also reflected in the yields: copolymer 2 of Table 1, prepared according to the claimed process, was obtained in a yield of 99.9%, whereas copolymer 2 of Table 3, prepared according to CN 1302031 C, was obtained in a yield of 53.7%.

Example 4 (Comparative Example)

[0086] The following example represents a solution polymerization process according to CN 1328392 C.

[0087] A solution of maleic anhydride in xylene was heated to a reaction temperature of 140° C. Subsequently, two separate solutions of radical initiator in xylene and alkyl methacrylate in xylene were added dropwise within 3 hours. The alkyl methacrylate solution also contained n-dodecyl mercaptan as change transfer agent. The mixture was then continuously refluxed for 2 to 4 hours to obtain the alkyl methacrylate/maleic anhydride copolymer. The resulting copolymer composition as analyzed as described above.

[0088] Six different copolymers were prepared. Copolymer 1 was prepared from 70 wt-% IDMA and 30 wt-% MSA, based on the total amount of monomers. Copolymer 2 was prepared from 52.3 wt-% LMA, 21.7 wt-% SMA, and 26 wt-% MSA, based on the total amount of monomers. Copolymer 3 was prepared from 19.8 wt-% LMA, 56.2 wt-% SMA, and 24 wt-% MSA, based on the total amount of monomers. Copolymer 4 was prepared from 56.9 wt-% SMA, 21.1 wt-% BeMA, and 22 wt-% MSA, based on the total amount of monomers. Copolymer 5 was prepared from 85 wt-% IDMA and 15 wt-% MSA, based on the total amount of monomers. Copolymer 6 was prepared from 22.5 wt-% LMA, 64 wt-% SMA, and 13.5 MSA, based on the total amount of monomers.

[0089] The results are given in the following Table 4 (see results for Copolymers No. 1 to 6 in Table 4 below).

TABLE-US-00005 TABLE 4 Residual Residual alkyl maleic methacrylates anhydride [weight %, [weight %, Alkyl based on the based on the Comonomer methacrylate total weight total weight molar ratio composition of the of the (alkyl based on C Mn Mw reaction reaction Reaction methacrylate:maleic No. alkyl chain [g/mol] [g/mol] PDI solution (*)] solution (*)] Yield [%] anhydride) 1 C10 1450 2730 2.13 0.25 0.0001 99.4 1:1 branched 2 C12, C14, 1740 3440 1.98 0.80 0.0002 98.1 C16, C18 linear 3 C12, C14, 2270 4950 2.18 1.10 0.0009 97.4 C16, C18 linear 4 C14, C16, 1990 3780 2.88 0.56 0.0002 98.7 C18, C20, C22 linear 5 C10 1620 3550 2.19 3.20 0.0001 92.5 2:1 branched 6 C12, C14, 2000 5040 2.52 0.54 0.0002 98.7 C16, C18 linear (*) the total weight of the reaction solution corresponds to total weight of the reaction mixture (solvent, monomers, initiator)

[0090] As these results show, the process according to CN 1328392 C results in an excellent conversion rate of maleic anhydride. However, the copolymers do not have the desired number average molecular weight and contain sulfur due to the presence of n-dodecyl mercaptan in the polymerization reaction.

[0091] Copolymer No. 4 of Table 4 was prepared according to CN 1328392 C from exactly the same monomer composition as copolymer No. 2 in Table 1, which was synthesized according to the claimed process. In case of the claimed process, a number average molecular weight of 13700 g/mol was obtained versus a number average molecular weight of 2000 g/mol in case of the process according to CN 1328392 C. The residual amounts of monomers are very low both cases with values of 0.04% residual alkyl methacrylate and 0.02% maleic anhydride in case of the claimed process and 0.54% residual alkyl methacrylate and 0.0002% maleic anhydride in case of the process according to CN 1328392 C.

[0092] Therefore, the reaction conditions according to CN 1328392 C do not allow controlling the number average molecular weight of the copolymer to produce the copolymer with the required number average molecular weight range, while maintaining high conversion of maleic anhydride into the copolymer. The resulting copolymers are also not sulfur-free.

Example 5 (Comparative Example)

[0093] The following example represents the polymerization process according to EP 0484773 A1.

[0094] According to the process disclosed in EP 0484773 A1, a solution of alkyl acrylate and maleic anhydride in solvent naphtha 150 was heated upon stirring to the reaction temperature in nitrogen flow. After reaching the target reaction temperature, the radical initiator solution was added continuously to the reaction mixture within four hours. Subsequently, a further portion of the radical initiator was added, and the reaction mixture was kept stirring for 1 hour.

[0095] Five different copolymers were prepared according to the above-indicated process of EP 0484773 A1, using respectively alkyl methacrylate or alkyl acrylate together with maleic anhydride.

[0096] Copolymers 1 to 5 were prepared using the reaction conditions of example 1 in EP 0484773 A1, involving a reaction temperature of 80° C. and AIBN as initiator.

[0097] Copolymer 1 was prepared from 72.7 wt-% LA and 27.3 wt-% MSA, based on the total amount of monomers.

[0098] Copolymer 2 was prepared from 71.6 wt-% LMA and 28.4 wt-% MSA, based on the total amount of monomers.

[0099] Copolymer 3 was prepared from 86.3 wt-% LA and 13.7 wt-% MSA, based on the total amount of monomers.

[0100] Copolymer 4 was prepared from 87.1 wt-% LMA and 12.9 wt-% MSA, based on the total amount of monomers.

[0101] Copolymer 5 was prepared from 89.0 wt-% SA and 11.0 wt-% MSA, based on the total amount of monomers.

[0102] The results are given in the following table 5 (see results for each copolymer No. 1 to 5 in Table 5).

TABLE-US-00006 TABLE 5 Residual maleic anhydride Residual alkyl [weight %, Alkyl (meth)acrylates based on (meth)acrylate [weight %, the total Comonomer composition based on the weight of molar ratio based on total weight of the Reaction (alkyl average C Mn Mw the reaction reaction yield methacrylate:maleic No. alkyl chain [g/mol] [g/mol] PDI solution (*)] solution*] [%] anhydride) 1 C12, C14 21300 71700 3.37 0.02 6.84 84.0 1:1 linear acrylate 2 C12, C14 8370 17400 2.08 0.58 6.97 82.1 linear methacrylate 3 C12, C14 21700 55100 2.54 2.20 2.73 90.1 2.5:1   linear acrylate 4 C12, C14 64400 324000 5.04 0.01 1.47 97.1 linear methacrylate 5 C14, C16, C18 25900 84800 3.28 1.74 1.57 94.2 linear acrylate (*) the total weight of the reaction solution corresponds to total weight of the reaction mixture (solvent, monomers, initiator)

[0103] The results show that all copolymers prepared according to the process of EP 0484773 A1 do not comprise the full amount of each monomer used in the reaction mixture. For example, in the case of equimolar monomer ratios among alkyl acrylate or alkyl methacrylate versus maleic anhydride as exemplified with copolymers 1 and 2, a very high amount of residual maleic anhydride remains in the product mixture and the yield therefore is low when using the polymerization process according to EP 0484773 A1.

[0104] Furthermore, taking into account, on the first hand, the conversion of maleic anhydride, and on the other hand, the residual amount of alkyl acrylate or alkyl methacrylate (0.02 and 0.58 weight % for copolymers 1 and 2, respectively), it can be derived that the composition of the polymer obtained by the process described in EP 0484773 A1 is totally different from the copolymers obtained by the claimed process. Indeed, the alkyl methacrylate monomers nearly fully react during the polymerization reaction, whereas the second maleic anhydride monomers only partially react (as shown by the residual amount of maleic anhydride at the end of the reaction). Therefore, the copolymers obtained by the process described in EP 0484773 A1 do not comprise an equimolar composition of both repeating units, maleic anhydride versus alkyl acrylate or alkyl methacrylate, whereas the copolymers obtained by the claimed process do.

[0105] Furthermore, the yields obtained with the process of EP 0484773 A1 are lower than the yields obtained with the claimed process.