Continuous process for preparing methylenebisiminodiacetonitrile

Claim 2

The process of claim 2 in which the washed crystalline methylenebisiminodiacetonitrile is dried in a drying zone at about 30*-60*C. at about 5-760 millimeters of mercury absolute pressure until the crude crystalline methylenebisiminodiacetonitrile is substantially free of moisture, the thus dried methylenebisiminodiacetonitrile having a purity of about 98-99.9 percent and a melting point of about 84*-86*C.

Claim 3

The process of claim 1 in which the aqueous formaldehyde solution analyzes about 20-50 percent HCHO.

Claim 4

The process of claim 1 in which the ammonia source is an aqueous hexamethylenetetramine solution analyzing about 25-55 percent hexamethylenetetramine.

Claim 5

The process of claim 1 in which the strong mineral acid is sulfuric acid.

Claim 6

The process of claim 1 in which the residence time in the reaction zone is about 0.3-15 minutes.

Claim 7

A fully continuous process for preparing methylenebisiminodiacetonitrile comprising: a. charging into a cooled agitated mixing zone, and mixing therein to form an aqueous reaction mixture, reactants consisting essentially of; (i) an aqueous solution of an ammonia source selected from the group consisting of ammonium sulfate and hexamethylenetetramine, the hexamethylenetetramine being both an ammonia source and a formaldehyde source, said aqueous solution analyzing about 45-75 percent water; (ii) an aqueous formaldehyde solution analyzing about 20-50 percent formaldehyde; (iii) a strong mineral acid; (iv) concentrated mother liquor recycled from later recited separating, concentrating, and cooling steps; and (v) liquid anhydrous HCN while maintaining the temperature of the reactants in the mixing zone within the range of about 10*-40*C., the mole ratio of ammonia:formaldehyde:HCN in the aqueous reaction mixture being about 1:2.5-3:2-3, the weight ratio of ammonia to water in the aqueous reaction mixture being about 1:2-20, and the pH of the aqueous reaction mixture being about 1-3; B. passing the aqueous reaction mixture through a heated reaction zone, residence time in the reaction zone being about 0.1-30 minutes, while maintaining the temperature of the aqueous mixture in the reaction zone within the range of about 20*-90*C. to form a reacted mixture; c. adjusting the temperature of the reacted mixture to about 5*-50*C. if it is not already within this temperature range to form crude precipitated crystalline methylenebisiminodiacetonitrile and a mother liquor; d. passing the precipitated crude crystalline methylenebisiminodiacetonitrile and the mother liquor through a separating zone while maintaining the temperature of the crude methylenebisiminodiacetonitrile and mother liquor in said zone within the range of about 5*-50*C. to separate the crude crystalline methylenebisiminodiacetonitrile from the mother liquor; e. passing at least a portion of the separated mother liquor into an evaporating and concentrating zone while maintaining the temperature and pressure within said zone at about 50*-95*C. and 75-630 millimeters absolute pressure, respectively, to evaporate about 20-80 percent of the water present in the mother liquor therefrom to prepare a concentrated mother liquor; f. passing the concentrated mother liquor through a cooling zone wherein the temperature of the concentrated mother liquor is adjusted to about 10*-30*C.; g. recycling at least a portion of the cooled concentrated mother liquor to the cooled agitated mixing zone; h. washing the separated crude crystalline methylenebisiminodiacetonitrile in a washing zone to free the crystalline methylenebisiminodiacetonitrile of mother liquor; i. drying the washed crystalline methylenebisiminodiacetonitrile in a drying zone at about 30*-60*C. to form substantially dry crystalline methylenebisiminodiacetonitrile; and j. recovering the substantially dry crystalline methylenebisiminodiacetonitrile, the recovered methylenebisiminodiacetonitrile having a purity of about 98-99.9 percent, and a melting point of about 84*-86*C.

Claim 8

The process of claim 8 in which the aqueous formaldehyde solution analyzes 30-40 percent HCHO.

Claim 9

The process of claim 8 in which the ammonia source is an aqueous hexamethylenetetramine solution analyzing about 30-50 percent hexamethylenetetramine.

Claim 10

The process of claim 8 in which the residence time in the reaction zone is about 0.3-15 minutes.

Claim 11

The process of claim 8 in which the pH of the reaction mixture is about 1.1-2.5.

Claim 12

The process of claim 8 in which the separated crude crystalline methylenebisiminodiacetonitrile is washed with water, the temperature of the wash water being about 10*-30*C., the wash water being applied at the rate of about 0.1-2.0 parts per part of crude crystalline methylenebisiminodiacetonitrile.

Claim 13

The process of claim 8 in which the washed crystalline methylenebisiminodiacetonitrile is dried in the solid state in a stream of air fed into the drying zone at a temperature of about 30*-60*C. and a relative humidity of about 0-30 percent, the pressure within the drying zone being about 5-760 millimeters of mercury absolute.