the range from 3 to 5 mol per mol of the maleic acid monoester this is because the yield of the reaction is reduced at a molar ratio of less than 2 while a molar ratio of more than 10 often causes side reactions the reaction temperature ranging from 20 to 110 u00b0 c and the reaction time ranging from 1 to 6 hours are preferred this is because the reaction proceeds slowly when the temperature is lower than this range while the side reactions tend to occur when the temperature is higher than this range after fumaric acid monoester chloride has thus been obtained excess thionyl chloride is eliminated if necessary from the reaction system by distillation such as vacuum distillation subsequently in order to introduce the other substituent the silicon containing alkyl group an alcohol having silicon containing alkyl group is added which is provided for reacting with the acid chloride specific examples of such an alcohol having silicon containing alkyl group includes in addition to 2 trimethylsilylethanol 3 trimethylsilylpropanol 3 pentamethyldisiloxanylpropanol 3 heptamethyltrisiloxanylpropanol 3 bis trimethylsiloxy silylpropanol 3 tris trimethylsiloxy silylpropanol 4 tris trimethylsiloxy silylbutanol 5 tris trimethylsiloxy silylpentanol 3 tris trimethylsiloxy silylpropyl 3 phenol and 3 tris trimethylsiloxy silylpropyl 3 cyclohexanol compounds having a terminal hydroxyl group at the 3 tris trimethylsiloxy silylpropyl group via the u2014 ch 2 ch 2 o o u2014 ch 2 ch 2 ch 2 u2014 group o is an integer from 1 to 10 or a group represented.