Stabilized polyolefin compositions

Abstract

Polyolefin compositions comprising a particular hindered phenolic antioxidant selected from the group consisting of tris(3,5-di-tert-butyl-4-hydroxybenzyl)isocyanurate, 1,3,5-tris-(3,5-di-tert-butyl-4-hydroxybenzyl)-2,4,6-trimethylbenzene and the calcium salt of the monoethyl ester of 3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid, an oligomeric sterically hindered amine light stabilizer, a hydroxylamine stabilizer or trialkylamine N-oxide stabilizer, and, optionally, an organic phosphorus stabilizer, are effectively stabilized against degradation upon melt processing, long term heat aging, and exposure to combustion products of natural gas.

1 . A polyolefin composition of improved discoloration resistance comprising 
 a polyolefin which has incorporated therein a stabilizer system sufficient to attenuate the deleterious effects of melt processing, long term heat aging, and exposure to combustion products of natural gas, said stabilizer system comprising    i) at least one hindered phenolic antioxidant selected from the group consisting of tris(3,5-di-tert-butyl-4-hydroxybenzyl)isocyanurate, 1,3,5-tris-(3,5-di-tert-butyl-4-hydroxybenzyl)-2,4,6-trimethylbenzene and the calcium salt of the monoethyl ester of 3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid,    ii) at least one compound selected from the group consisting of the oligomeric sterically hindered amine light stabilizers having a molecular weight above about 1000 g/mole,    iii) at least one compound selected from the group consisting of the hydroxylamine stabilizers; and    optionally,    iv) at least one compound selected from the group consisting of the organic phosphorus stabilizers,    where    the phenolic antioxidants i) are incorporated from about 0.01% to about 5% by weight, the oligomeric hindered amine stabilizers ii) are incorporated from about 0.05% to about 5% by weight,    the hydroxylamine stabilizers iii) are incorporated from about 0.0005% to about 2% by weight, and    optionally    the organic phosphorus stabilizers iv) are incorporated from about 0.01% to about 5% by weight, 
 each based on the weight of the polyolefin.  
   
   
   
       2 . A polyolefin composition according to  claim 1  wherein the polyolefin is polypropylene or polyethylene.  
   
   
       3 . A polyolefin composition according to  claim 2  wherein the polyolefin is a polypropylene homopolymer or impact (heterophasic) copolymer.  
   
   
       4 . A polyolefin composition according to  claim 1  wherein the hindered phenolic antioxidant is tris(3,5-di-tert-butyl-4-hydroxybenzyl)isocyanurate.  
   
   
       5 . A polyolefin composition according to  claim 1  wherein the oligomeric sterically hindered amine stabilizers contain at least one group of the formula (I)  
     
       
         
         
             
             
         
       
       in which R x  is hydrogen or methyl.  
     
   
   
       6 . A polyolefin composition according to  claim 5  in which the oligomeric sterically hindered amine stabilizers are selected from the group consisting of  
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     wherein m and n are integers such that the total molecular weight is above about 1000 g/mole.  
   
   
       7 . A polyolefin composition according to  claim 1  in which the hydroxylamine stabilizers of are of the formula (II)  
       R 1 R 2 N—OH  (II)  where    R 1  is alkyl of 1 to 36 carbon atoms, cycloalkyl of 5 to 12 carbon atoms or aralkyl of 7 to 9 carbon atoms; or R 1  is said alkyl, cycloalkyl or aralkyl substituted by one to six alkyl of 1 to 12 carbon atoms, perfluoroalkyl of 1 to 12 carbons atoms, halogen, cyano, E 1 O—, E 1 CO—, E 1 OCO—, E 1 COO—, E 1 S—, E 1 SO—, E 1 SO 2 —, —NH 2 , —NHE 1 , —NE 1 E 2 , —PO(OE 1 )(OE 2 ) or —OPO(OE 1 )(OE 2 ) groups;    R 2  is hydrogen or independently has the same meaning as R 1 , where at least one of R 1  and R 2  contains a hydrogen alpha to the —NOH moiety; or    R 1  and R 2  together form a C 2-12 heterocyclic ring which contains at least one carbon substituted hydrogen alpha to the —NOH moiety, where said C 2-12 heterocyclic ring is unsubstituted or is substituted by one to three three alkyl of 1 to 12 carbon atoms, perfluoroalkyl of 1 to 12 carbon atoms, halogen, cyano, E 1 O—, E 1 CO—, E 1 OCO—, E 1 COO—, E 1 S—, E 1 SO—, E 1 SO 2 —, —NH 2 , —NHE 1 , —NE 1 E 2 , —PO(OE 1 )(OE 2 ) or —OPO(OE 1 )(OE 2 ) groups; or where said C 2-12 heterocyclic ring is interrupted by one to three —O—, —NE 1 -, —CO—, —CONE 1 -, —S—, —SO—, —SO 2 —, —COO—, —PO 3 — or —PO 4 E 1  groups; or where said heterocyclic ring is both substituted and interrupted by said groups;    E 1  and E 2  independently are hydrogen, alkyl of 1 to 8 carbon atoms or alkyl of 1 to 8 carbon atoms substituted by one to three hydroxyl groups; or E 1  and E 2  independently are an oligomer of poly(ethylene glycol) or poly(propylene glycol) terminated by hydroxyl, methoxy, acetate or propionate, where the oligomer has a molecular weight up to about 500.    
   
   
       8 . A polyolefin composition according to  claim 7  in which the hydroxylamine stabilizers are selected from the group consisting of N,N-dibenzylhydroxylamine, N,N-diethylhydroxylamine, N,N-dioctylhydroxylamine, N,N-dilaurylhydroxylamine, N,N-didodecylhydroxylamine, N,N-ditetradecylhydroxylamine, N,N-dihexadecylhydroxylamine, N,N-dioctadecylhydroxylamine, N-hexadecyl-N-tetradecylhydroxylamine, N-hexadecyl-N-heptadecylhydroxylamine, N-hexadecyl-N-octadecylhydroxylamine, N-heptadecyl-N-octadecylhydroxylamine, N-methyl-N-octadecylhydroxylamine and N,N-di(hydrogenated tallow)hydroxylamine.  
   
   
       9 . A polyolefin composition according to  claim 8  in which the hydroxylamine stabilizer iii) is the N,N-di(alkyl)hydroxylamine produced by the direct oxidation of N,N-di(hydrogenated tallow)amine.  
   
   
       10 . A polyolefin composition according to  claim 1  comprising iv) at least one organic phosphorus stabilizer of the formulae (I), (2), (3), (4), (5), (6) and (7)  
     
       
         
         
             
             
         
       
       in which the indices are integral and  
       n is 2, 3 or 4; p is 1 or 2; q is 2 or 3; r is 4 to 12; y is 1, 2 or 3; and z is 1 to 6;  
       A 1 , if n is 2, is C 2 -C 18  alkylene; C 2 -C 12 alkylene interrupted by oxygen, sulfur or —NR 4 —; a radical of the formula  
       
         
           
           
               
               
           
         
       
       phenylene;  
       A 1 , if n is 3, is a radical of the formula —C r H 2r-1 —;  
       A 1 , if n is 4, is  
       
         
           
           
               
               
           
         
       
       A 2  is as defined for A 1  if n is 2;  
       B is a direct bond, —CH 2 —, —CHR 4 —, —CR 1 R 4 —, sulfur, C 5 -C 7 cycloalkylidene, or cyclohexylidene which is substituted by from 1 to 4 C 1 -C 4  alkyl radicals in position 3, 4 and/or 5;  
       D 1 , if p is 1, is C 1 -C 4  alkyl and, if p is 2, is —CH 2 OCH 2 —;  
       D 2 , if p is 1, is C 1 -C 4 alkyl;  
       E, if y is 1, is C 1 -C 18  alkyl, —OR 1 , or halogen;  
       E, if y is 2, is —O-A 2 -O—,  
       E, if y is 3, is a radical of the formula R 4 C(CH 2 O—) 3  or N(CH 2 CH 2 O—) 3 ;  
       Q is the radical of an at least z-valent alcohol or phenol, this radical being attached via the oxygen atom to the phosphorus atom;  
       R 1 , R 2  and R 3  independently of one another are C 1 -C 18  alkyl which is unsubstituted or substituted by halogen, —COOR 4 , —CN or —CONR 4 R 4 ; C 2 -C 18  alkyl interrupted by oxygen, sulfur or —NR 4 —; C 7 -C 8  phenylalkyl; C 5 -C 12  cycloalkyl, phenyl or naphthyl; naphthyl or phenyl substituted by halogen, 1 to 3 alkyl radicals or alkoxy radicals having a total of 1 to 18 carbon atoms or by C 7 -C 8  phenylalkyl; or a radical of the formula  
       
         
           
           
               
               
           
         
       
       in which m is an integer from the range 3 to 6;  
       R 4  is hydrogen, C 1 -C 18  alkyl, C 5 -C 12  cycloalkyl or C 7 -C 8  phenylalkyl,  
       R 5  and R 6  independently of one another are hydrogen, C 1 -C 8  alkyl or C 5 -C 6  cycloalkyl,  
       R 7  and R 8 , if q is 2, independently of one another are C 1 -C 4  alkyl or together are a 2,3-dehydropentamethylene radical; and  
       R 7  and R 8 , if q is 3, are methyl;  
       R 14  is hydrogen, C 1 -C 9  alkyl or cyclohexyl,  
       R 15  is hydrogen or methyl and, if two or more radicals R 14  and R 15  are present, these radicals are identical or different,  
       X and Y are each a direct bond or oxygen,  
       Z is a direct bond, methylene, —C(R 16 ) 2 — or sulfur, and  
       R 16  is C 1 -C 8 alkyl.  
     
   
   
       11 . A polymer composition according to  claim 10  in which the organic phosphorus stabilizers are selected from the group consisting of triphenyl phosphite, tris(nonylphenyl)phosphite, trilauryl phosphite, trioctadecyl phosphite, distearyl pentaerythritol diphosphite, tris(2,4-di-tert-butylphenyl)phosphite, diisodecyl pentaerythritol diphosphite, bis(2,4-di-tert-butylphenyl) pentaerythritol diphosphite, bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphite, bisisodecyloxypentaerythritol diphosphite, bis(2,4-di-tert-butyl-6-methylphenyl)pentaerythritol diphosphite, bis(2,4,6-tri-tert-butylphenyl)pentaerythritol diphosphite, tristearyl sorbitol triphosphite, tetrakis(2,4-di-tert-butylphenyl) 4,4′-biphenylene-diphosphonite, 6-isooctyloxy-2,4,8,10-tetra-tert-butyl-dibenzo[d,f][1,3,2]dioxaphosphepin, 6-fluoro-2,4,8,10-tetra-tert-butyl-12-methyl-dibenzo[d,g][1,3,2]dioxaphosphocin, bis(2,4-di-tert-butyl-6-methylphenyl)methyl phosphite, bis(2,4-di-tert-butyl-6-methylphenyl)ethyl phosphite and 2,2′,2″-nitrilo[triethyltris(3,3′5,5′-tetra-tert-butyl-1, 1′-biphenyl-2,2′-diyl)phosphite],  
     
       
         
         
             
             
         
       
     
   
   
       12 . A polyolefin composition according to  claim 1  in which the organic phosphorus stabilizer iv) is tris(2,4-di-tert-butylphenyl)phosphite.  
   
   
       13 . A polyolefin composition according to  claim 1  which additionally has incorporated therein at least one coadditive selected from the group consisting of UV absorbers, thiosynergists, metal stearates, nucleating agents, fillers, reinforcing agents, lubricants, emulsifiers, dyes, pigments, optical brighteners, flame retardants, antistatic agents, blowing agents, polyethylene oxide waxes and mineral oil.  
   
   
       14 . An article of manufacture comprising a polyolefin composition according to  claim 1  which is selected from the group consisting of woven fibers, non-woven fibers, films and molded articles.