53  US 6,391,949 B2  54  Pigmented polypropylene pellets are prepared from pure  pigment or pigment concentrates, stabilizers, co-additives  and commercially available polypropylene by mixing the  components in a Superior/MPM 1" single screw extruder  with a general all-purpose screw (24:1 LID) at 475°  F. (250°  C.), cooled in a water bath and pelletized. The resulting  pellets are molded into 60 mil (0.06 inch thick) 2"x2"  plaques at about 475°  F. (250°  C.) on a BOY 30M Injection  Molding Machine.  Molded test specimens are prepared by injection molding  polypropylene pellets containing pigments, a phosphite, a  phenolic antioxidant or hydroxylamine, a metal stearate,  ultraviolet light absorbers or a hindered amine stabilizers or  a mixture of UV absorbers and hindered amine stabilizers.  Stabilization of Polypropylene Molded Articles  The light stable formulations are painted with one-pack  paint systems and tested for TPO/paint interactions. Before  painting, the test specimens are first washed in accordance  with GM998-4801 and dried for 15 minutes at 200°  F. (94°  Molded test specimens are prepared by injection molding  thermoplastic olefin  (TPO)  pellets containing the instant  compounds, pigments and other coadditives as described in  Example 76.  Paintable  TPO  In all cases, the light stabilized formulations show much  greated resistance to photodegradation than unstabilized  specimens which fail quickly under the UV exposure con› ditions outlined above.  Polymer blends containing an unsaturated ternary  component, such as EPDM blends, are especially benefited  with the more efficient instant light stabilizer systems  described above.  The compound of Example 73 present in test plaques  NOR-2 specifically shows greatly improved gloss retention  compared to the less effective control system and in fact is  also more effective that a related hindered amine compound  (TINUVINfi 123) present in test plaques NOR-1. Resis› tance to color change upon UV exposure is also enhanced.  The data in the table indicate that, although formulation A  failed in both the Taber Scuff and Aggressive Adhesion  Tests, both formulations B and C passed both paint adhesion  tests. However, as inspection of the  pKa  values attests, the  lower the  pKa  value (less basic) for the test hindered amine  compound the less paint loss results in this Aggressive  Adhesion Test. The instant compound of Example 73 having  the hydroxyl moiety present has the lowest  pKa  value and  also the least paint loss even better than the close prior art  compound where no hydroxyl moiety is present.  C also contains 0.2% of 1-(2-hydroxy-2-methylpropoxy)-4- octadecanoy loxy-2,2,6,6-tetramethy lpiperidine ( compound  of Example 73,  pKa  of 4.0)  B  also contains 0.2% of bis(l-octyloxy-2,2,6,6- tetramethylpiperidin-4-yl) sebacate  (TINUVINfi  123,  pKa  of 4.6).  A  also contains 0.2% of bis(2,2,6,6-tetramethylpiperidin-4- yl) sebacate  (TINUVINfi  770,  pKa  of 9.1).  Formulations  B  and C contain 0.2%  CHIMASSORBfi  119,  0.2%  TINUVINfi  328, 500 ppm calcium stearate and 750  ppm N,N-dialkylhydroxylamine in reactor-grade  TPO.  Formulation A contains 0.2%  CHIMASSORBfi  944, 0.2%  TINUVINfi  328, 500 ppm calcium stearate and 750 ppm  N,N-dialkylhydroxylamine in reactor-grade  TPO.  0.2%  CHIMASSORB  944, Ciba [polycondensation prod› uct of 4,4’-hexamethylene-bis(amino-2,2,6,6- tetramethylpiperidine) and 2,4-dichloro-6-tert-octylamino› s-triazine].  The two test plaques (NOR-1 and NOR-2) each contain  0.05% N,N,-dialkylhydroxylamine;  NOR-1  additionally contains  0.2%  TINUVINfi  770, Ciba [bis(2,2,6,6- tetramethylpiperidin-4-yl) sebacate ];  Samples are tested to evaluate the TPO/paint interactions  as follows:  Paint adhesion is measured by Aggressive Adhesion Test› ing (proprietary test procedure conducted at Technical  Finishing, Inc.) and Taber Scuff. Painted panels which retain  greater than 80% of the paint finish are considered accept› able. After Aggressive Adhesion Testing, samples with less  than 5% paint loss are deemed acceptable.  C.). Adhesion promoter is applied to the dry film thickness  of 0.2-0.4 mils. The samples are dried for five minutes  before a 1 K basecoat is applied to a film thickness of  1.2-1.4 mils. The painted panels are dried for three minutes,  a clearcoat is then applied to a dry film thickness of 1.2-1.5  mils followed by ten minutes flash drying and a 30 minute  oven bake at 250°  F. (121 °  C.).  0.1 %  IRGANOXfi  B225 (50:50 blend of  IRGANOXfi  1010, Ciba (neopentanetetrayl tetrakis(4-hydroxy-3,5-di› tert-butylhydrocinnamate) and  IRGAFOSfi  168, Ciba [tris› (2,4-di-tert-butylphenyl) phosphite;  The Control plaques additionally contain  Polymer substrate is commercially available polyolefin  blend POLYTROPEfi TPP 518-01 supplied by  A Schulman  Inc. Akron, Ohio)  Color package is 0.025% Red 3B -Pigment Red 177, C.I.  #65300.  Each plaque contains:  0.2% TINUVINfi 328;  0.1 % calcium stearate; and  15% talc.  0.2% of  CHIMASSORBfi  119; and  0.2% of  TINUVINfi  123, Ciba, [bis(l-octyloxy-2,2,6,6- tetramethylpiperidin-4-yl) sebacate].  NOR-2  additionally contains  0.2% of  CHIMASSORBfi  119; and  0.2% of the compound of Example 73.  The results of the UV testing are given in the table below.  EXAMPLE 78  EXAMPLE 77  DE*  Gloss Value  % Gloss Value  0  3000  0  3000  0  3000  Sample  Kj/m 2  Kj/m 2  Kj/m 2  Kj/m 2  Kj/m 2  Kj/m 2  control  0.0  4.7  66.6  5.4  100  8.1  NOR-1  0.0  4.0  65.5  16.9  100  25.8  NOR-2  0.0  3.8  64.9  45.3  100  69.8  Aggresive  HALS  Formulation*  Taber Scuff Test  Adhesion Test  pK,  A  100% removed  6% Loss (fail)  9.1  B  0% removed  4% Loss (pass)  4.6  C  0% removed  3% Loss (pass)  4.0 