Stabilized gamma-irradiated polypropylene and sterilizable articles thereof

Claim 1

A method for imparting improved strength and discoloration resistance to a stabilized, gamma-irradiated polypropylene polymer article which comprises incorporating into said polypropylene polymer, which is essentially free of an antioxidant, an effective amount from 20 ppm to 2% of a hindered amine stabilizer containing a polysubstituted piperazin-2-one (PSP) moiety having the structure ##STR3## wherein, R 1 represents hydrogen, oxygen, C 1 -C 18 alkyl, C 1 -C 6 hydroxyalkyl, C 2 -C 12 acyl, C 3 -C 8 alkenyl, C 3 -C 8 alkynyl, C 7 -C 12 aralkyl which is unsubstituted or substituted in the alkyl moiety by hydroxyl, or C 1 -C 8 alkanoyl or C 3 -C 5 alkenoyl; R 2 , R 3 , R 4 and R 5 independently represent hydrogen, C 1 -C 24 alkyl, C 1 -C 12 hydroxyalkyl, C 1 -C 12 haloalkyl, C 1 cyanoalkyl, C 2 -C 12 aminoalkyl or iminoalkyl, C 3 -C 18 ether groups, C 4 -C 18 hydroxyalkyl ether or cyanoalkyl ether groups, C 7 -C 14 alkenyl or aralkyl, C 2 -C 7 alkylene, and optionally containing a phosphite, ester, or hindered phenol group, and which in combination, one with another, represent C 5 -C 14 cycloalkyl at least four of which C atoms are cyclized, and, optionally containing a keto, ester, amide, ether, thio or hydroxy groups; but, only one of R 2 and R 3 , and only one of R 4 and R 5 may be hydrogen; and, R 6 represents a free valency through which the PSP moiety is connected to the remaining structure of the stabilizer; said hindered amine stabilizer being selected from the group consisting of (i) a bis-compound consisting of a C 2 -C 12 alkylene connecting two PSP moieties, and (ii) a polyalkylene polyamine having a pendant triazine ring with a PSP substituent; said effective amount being sufficient to attenuate oxidative degradation of said polypropylene polymer.

Claim 2

A method for imparting improved strength and discoloration resistance to a stabilized, gamma-irradiated polypropylene polymer article which comprises incorporating into said polypropylene polymer, which is essentially free of an antioxidant, an effective amount from 20 ppm to 2% of a hindered amine stabilizer containing a polysubstituted piperazin-2-one (PSP) moiety having the structure ##STR3## wherein, R 1 represents hydrogen, oxygen, C 1 -C 18 alkyl, C 1 -C 6 hydroxyalkyl, C 2 -C 12 acyl, C 3 -C 8 alkenyl, C 3 -C 8 alkynyl, C 7 -C 12 aralkyl which is unsubstituted or substituted in the alkyl moiety by hydroxyl, or C 1 -C 8 alkanoyl or C 3 -C 5 alkenoyl; R 2 , R 3 , R 4 and R 5 independently represent hydrogen, C 1 -C 24 alkyl, C 1 -C 12 hydroxyalkyl, C 1 -C 12 haloalkyl, C 1 cyanoalkyl, C 2 -C 12 aminoalkyl or iminoalkyl, C 3 -C 18 ether groups, C 4 -C 18 hydroxyalkyl ether or cyanoalkyl ether groups, C 7 -C 14 alkenyl or aralkyl, C 2 -C 7 alkylene, and optionally containing a phosphite, ester, or hindered phenol group, and which in combination, one with another, represent C 5 -C 14 cycloalkyl at least four of which C atoms are cyclized, and, optionally containing a keto, ester, amide, ether, thio or hydroxy groups; but, only one of R 2 and R 3 , and only one of R 4 and R 5 may be hydrogen; and, R 6 represents a free valency through which the PSP moiety is connected to the remaining structure of the stabilizer; said hindered amine stabilizer being selected from the group consisting of (i) a bis-compound consisting of a C 2 -C 12 alkylene connecting two PSP moieties, and (ii) a polyalkylene polyamine having a pendant triazine ring with a PSP substituent; said effective amount being sufficient to attenuate oxidative degradation of said polypropylene polymer.

Claim 5

A method for sterilizing a shaped article made from polypropylene polymer, which method comprises, subjecting said shaped article to gamma radiation in an amount sufficient to sterilize the article; said polypropylene polymer being essentially free of an antioxidant, and having incorporated therein from 20 parts per million (ppm) to about 2.0%, based upon the weight of the propylene polymer in the article, of a hindered amine stabilizer containing a polysubstituted piperazin-2-one (PSP) moiety having the structure ##STR4## wherein, R 1 represents hydrogen, oxygen, C 1 -C 18 alkyl, C 1 -C 6 hydroxyalkyl, C 2 -C 12 acyl, C 3 -C 8 alkenyl, C 3 -C 8 alkynyl, C 7 -C 12 aralkyl which is unsubstituted or substituted in the alkyl moiety by hydroxyl, or C 1 -C 8 alkanoyl or C 3 -C 5 alkenoyl; R 2 , R 3 , R 4 and R 5 independently represent hydrogen, C 1 -C 24 alkyl, C 1 -C 12 hydroxyalkyl, C 1 -C 12 haloalkyl, C 1 -C 12 cyanoalkyl, C 2 -C 12 aminoalkyl or iminoalkyl, C 3 -C 18 ether groups, C 4 -C 18 hydroxyalkyl ether or cyanoalkyl ether groups, C 7 -C 14 alkenyl or aralkyl, C 2 -C 7 alkylene, and optionally containing a phosphite, ester, or hindered phenol group, and which in combination, one with another, represent C 5 -C 14 cycloalkyl at least four of which C atoms are cyclized, and, optionally containing a keto, ester, amide, ether, thio or hydroxy group; but, only one of R 2 and R 3 , and only one of R 4 and R 5 may be hydrogen; and, R 6 represents a free valency through which the PSP moiety is connected to the reamining structure of the stabilizer; said hindered amine stabilizer being selected from the group consisting of (i) a bis-compound consisting of a C 2 -C 12 alkylene connecting two PSP moieties, and (ii) a polyalkylene polyamine having a pendant triazine ring with a PSP substituent.

Claim 6

A method for sterilizing a shaped article made from polypropylene polymer, which method comprises, subjecting said shaped article to gamma radiation in an amount sufficient to sterilize the article; said polypropylene polymer being essentially free of an antioxidant, and having incorporated therein from 20 parts per million (ppm) to about 2.0%, based upon the weight of the propylene polymer in the article, of a hindered amine stabilizer containing a polysubstituted piperazin-2-one (PSP) moiety having the structure ##STR4## wherein, R 1 represents hydrogen, oxygen, C 1 -C 18 alkyl, C 1 -C 6 hydroxyalkyl, C 2 -C 12 acyl, C 3 -C 8 alkenyl, C 3 -C 8 alkynyl, C 7 -C 12 aralkyl which is unsubstituted or substituted in the alkyl moiety by hydroxyl, or C 1 -C 8 alkanoyl or C 3 -C 5 alkenoyl; R 2 , R 3 , R 4 and R 5 independently represent hydrogen, C 1 -C 24 alkyl, C 1 -C 12 hydroxyalkyl, C 1 -C 12 haloalkyl, C 1 -C 12 cyanoalkyl, C 2 -C 12 aminoalkyl or iminoalkyl, C 3 -C 18 ether groups, C 4 -C 18 hydroxyalkyl ether or cyanoalkyl ether groups, C 7 -C 14 alkenyl or aralkyl, C 2 -C 7 alkylene, and optionally containing a phosphite, ester, or hindered phenol group, and which in combination, one with another, represent C 5 -C 14 cycloalkyl at least four of which C atoms are cyclized, and, optionally containing a keto, ester, amide, ether, thio or hydroxy group; but, only one of R 2 and R 3 , and only one of R 4 and R 5 may be hydrogen; and, R 6 represents a free valency through which the PSP moiety is connected to the reamining structure of the stabilizer; said hindered amine stabilizer being selected from the group consisting of (i) a bis-compound consisting of a C 2 -C 12 alkylene connecting two PSP moieties, and (ii) a polyalkylene polyamine having a pendant triazine ring with a PSP substituent.