Process for preparing continuously variable-composition copolymers

Claim 1

A process for preparing continuously variable-composition copolymers comprising: (a) forming a first reaction mixture comprising a monomer-containing phase in which two or more copolymerizable monomers are present in a weight percent ratio from X 1 /Y 1 to Y 1 /X 1 ; (b) forming one or more additional reaction mixtures comprising a monomer-containing phase in which two or more copolymerizable monomers are present in a weight percent ratio from X n /Y n to Y n /X n ; (c) initiating a free-radical addition polymerization by gradual addition of the first reaction mixture or a mixture of the first reaction mixture with the one or more additional reaction mixtures to a reactor under polymerization conditions; (d) continuing the polymerization by gradual addition of the one or more additional reaction mixtures (i) to the reactor or (ii) to the first reaction mixture being added to the reactor at a point prior to where the first reaction mixture is added to the reactor; and (e) maintaining polymerization conditions until at least 90% of the two or more copolymerizable monomers has been converted to copolymer; wherein X 1 and Y 1 represent weight percents of any two X and Y monomers of the two or more copolymerizable monomers in the first reaction mixture; X n and Y n represent weight percents of any two X and Y monomers of the two or more copolymerizable monomers in the one or more additional reaction mixtures; X 1 , X n , Y 1 and Y n have values from zero to 100 percent; n represents successive integers from 2 to 10 corresponding to each of the one or more additional reaction mixtures containing the analogous X n and Y n weight percents; the maximum value of n represents the total number of reaction mixtures used in the process; wherein the gradual addition of the one or more additional reaction mixtures in step (d) is conducted such that at least one of [X i -X T ] or [Y i -Y T ] absolute values in the reactor is at least 5 percent and X i , X T , Y i and Y T represent instantaneous weight percents of any two X and Y monomers added to the reactor initially (X i and Y i ) and at some time later in the polymerization (X T and Y T ).