Abstract:
Homopolymers and copolymers of 1-olefins are protected against the deleterious effects of oxygen, heat and ultraviolet light by incorporating therein an additive system comprising a hindered amine component and a metal phosphonate component, optionally, containing a phenolic antioxidant, an organic phosphite, a lubricant and pigments in an amount sufficient to prevent such deterioration.

Description:
This application is a continuation application of my copending application, Ser. No. 82,391, filed Oct. 5, 1979, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to polyolefin stabilization. In accordance with another aspect, this invention relates to the stabilization of 1-olefin polymers by the incorporation of a stabilizing system comprising a hindered amine component and a metal phosphonate component. In accordance with another aspect, this invention relates to stabilized olefin polymers containing a stabilizing system comprising a hindered amine component and a metal phosphonate component, optionally, containing a phenolic antioxidant, an organic phosphite, a lubricant and pigments. In accordance with a further aspect, this invention relates to articles produced from polyolefins that are protected from the deleterious effects of oxygen, heat and UV light by admixture with a minor amount of the stabilizing system of this invention. In accordance with a further aspect, this invention relates to a stabilizer system for olefin polymers comprising a mixture of a hindered amine component and a metal phosphonate component. 
     The importance of protecting 1-olefin polymers against the degradative effects of oxygen, heat and sunlight is well-known. Numerous additives have been found to be effective, to varying degrees, for certain polymer compositions to provide this protection. 
     Accordingly, an object of this invention is to provide an oxygen, heat and ultraviolet light stabilizing system for polyolefins. 
     It is another object of this invention to provide polyolefins stabilized against the degradative effect of ultraviolet light. 
     Other objects, aspects and the several advantages of this invention will become apparent to one skilled in the art upon the study of this disclosure and the appended claims. 
     STATEMENT OF THE INVENTION 
     In accordance with the present invention, there is provided a polyolefin composition stabilized against the effects of oxygen, heat and ultraviolet light degradation comprising a normally solid polymer of an aliphatic 1-olefin having incorporated therein a stabilizing amount of a stabilizer system comprising a hindered amine component and a metal phosphonate component. 
     In accordance with another embodiment of the invention, polyolefins, such as polymers of propylene, are stabilized against the deleterious effects of oxygen, heat and UV light by admixture with a minor amount of the stabilizing system of the invention which, optionally contains a phenolic antioxidant, an organic phosphite, a lubricant, e.g., calcium stearate, and a pigment. 
     In accordance with another embodiment of the invention, articles such as fibers, film, injection molded objects, blow molded objects, and the like, produced from polyolefins are protected from the deleterious effects of oxygen, heat and UV light by admixture with a minor amount of the stabilizing system of this invention. 
     DETAILED DESCRIPTION 
     The term &#34;polyolefin&#34; as used herein is intended to include the normally solid homopolymers and co- and terpolymers of aliphatic 1-olefins having from 2 to about 10 carbon atoms per molecule and blends thereof. Specific examples include polyethylene, polypropylene, poly(1-butene), copolymers of ethylene/propylene, ethylene1-hexene, ethylene/1-decene, propylene/ethylene, propylene/ethylene/1-butene, and the like. Presently preferred polymers include polypropylene and propylene/1-olefin copolymers containing at least about 90 mole % propylene and from about 0.1 to about 10 mole % of a 1-olefin comonomer, particularly ethylene, Processes for preparing the polymers are well-known, e.g. U.S. Pat. No. 2,825,725 which issued Mar. 26, 1956, to Hogan et al and U.S. Pat. No. 3,502,632 which issued Mar. 24, 1970, to Stedefeder et al. 
     The hindered amine component can be shown by the formula ##STR1## where R, R 1 , R 2  are the same or different and each is an alkyl group having from 1 to 6 carbon atoms such as methyl, n-propyl, n-butyl, t-butyl, t-pentyl, t-hexyl, R 3  is an alkyl group having from 1 to 12 carbon atoms, and n is an integer of 1 to 4. 
     Specific hindered amine compounds that can be used according to the invention include: 
     di-(1,2,2,6,6-pentamethyl-4-piperidyl)-2-n-butyl-2-(4-hydroxy-3,5-di-t-butylbenzyl)malonate, presently, preferred 
     di-(1-dodecyl-2,2,6,6-tetramethyl-4-piperidyl)-2-methyl-2-(4-hydroxy-3,5-di-t-hexylbenzyl)malonate, and 
     di-(1-n-propyl-2,2,6,6,-tetramethyl-4-piperidyl)-2-ethyl-2-(4-hydroxy-3,5-di-t-butylphenylpropyl)malonate and the like, and mixtures thereof. 
     The metal phosphonate can be shown by the formula: ##STR2## where R is as before, R 4  is hydrogen or alkyl having from 1 to 6 carbon atoms, R 5  is an alkylene radical having from 1 to 4 carbon atoms, R 6  is hydrogen or alkyl having from 1 to 30 carbon atoms, M is a metal selected from among aluminum, barium, cadmium, calcium, chromium, cobalt, nickel, sodium, tin, and zinc and m is 1, 2 or 3. Of the metals, nickel and calcium are presently preferred. 
     Specific metal phosphonate compounds that can be used according to the invention include: nickel bis(O-ethyl-3,5,-di-t-butyl-4-hydroxybenzylphosphonate), cobalt bis(O-n-octadecyl-3,5-di-t-hexyl-4-hydroxybenzylphosphonate), barium bis[O-triacontyl(3,5-di-t-pentyl-4-hydroxyphenyl)propylphosphonate], calcium bis[O-methyl(3,5-di-t-butyl-4-hydroxybenzyl)butylphosphonate], aluminum tris(O-n-butyl-3,5-di-t-butyl-4-hydroxybenzylphosphonate), sodium [O-dodecyl-(3-t-butyl-4-hydroxyphenyl)ethylphosphonate], zinc 3,5-di-t-butyl-4-hydroxybenzylphosphonate, chromium tris(O-n-hexyl-3,5-di-t-butyl-4-hydroxybenzylphosphonate), cadmium bis(O-octadecyl-3-methyl-4-hydroxy-5-t-butylbenzylphosphonate), and tin bis(O-n-butyl-3,5-di-t-butyl-4-hydroxybenzylphosphonate), and the like, and mixtures thereof. 
     In a presently preferred embodiment, the stabilized compositions of this invention are also admixed with a phenolic heat stabilizer, a colorant(s), and optionally, an organic phosphite. 
     The phenolic heat stabilizer that can be used according to the invention is preferably a hydroxyphenylalkenyl isocyanurate such as tris-(3,5-di-t-butyl-4-hydroxybenzyl)isocyanurate. The isocyanurates are more fully described in U.S. Pat. No. 3,531,483 which issued Sept. 29, 1970 to J. C. Gilles. However, other conventional heat stabilizers such as 2,6-di-t-butyl-4-methylphenol (BHT), n-octadecyl[3-(3,5-di-t-butyl-4-hydroxybenzyl)]propionate, di-n-octadecyl(3,5-di-t-butyl-4-hydroxybenzyl) phosphonate, tetrakis[methylene(3,5-di-t-butyl-4-hydroxyhydrocinnamate)]methane, and 2,4,6-tris(3,5-di-t-butyl-4-hydroxybensyl)benzene, and the like, and mixtures thereof, can also be employed. 
     The organic phosphites contemplated, when used include aryl phosphites such as tris(nonylphenyl)phosphite, tris(2,4-di-t-butylphenyl) phosphite, alkyl phosphites such as trioctyl phosphite, dilauryl phosphite, and the like. More preferably, the organic phosphite is a diphosphite such as the pentaerythritol derivatives disclosed in U.S. Pat. Nos. 3,047,608 which issued July 31, 1962, to Friedman et al and 3,053,873 which issued Sept. 11, 1962, to Friedman et al. A particularly preferred compound is 3,9-di(octadecyloxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5,5]undecane, more commonly known as distearly pentaerythritol diphosphite. 
     Suitable colorants for use in the inventive compositions are those having sufficient thermal stability to be conventionally employed with polyolefins and can be of inorganic or organic nature. Mixtures can be used. Such colorants are commercially available in powder and concentrate form and can include, for example, titanium dioxide, carbon black, cadmium sulfide, phthalocyanine green, ultramarine blue, chelating dyestuffs including those described in U.S. Pat. No. 3,357,783 which issued Dec. 12, 1967, to Wunderlich et al, and the like. 
     Other suitable additives can be included in the formulations of the invention providing the improved results of this invention are not adversely affected. These additives include fillers, antistatic agents, lubricating or processing agents such as calcium stearate, and the like. 
     Each stabilizer component is used in a small but effective amount sufficient to provide the desired degree of stabilization. The hindered amine component and the metal phosphonate component each can be employed in an amount ranging from about 0.05 to about 5 wt. % based on the weight of the total composition, preferably from about 0.05 to about 2 wt. %. The weight ratio of these components, amine/phosphonate generally lies in the range from about 0.1:1 to about 10:1. 
     The amounts of each of the heat stabilizer and processing aids, when employed, can range from about 0.01 to about 1 wt. %, preferably from about 0.05 to about 0.5 wt. %. 
     The amount of organic phosphite, when employed, can range from about 0.02 to about 1 php, preferably from about 0.05 to about 0.2 php. 
     The amount of colorant(s), when employed, can range from about 0.0005 to about 5 wt. % so as to provide the desired shade of color required. 
     The stabilizing systems of the present invention can be incorporated into the polymer in any conventional manner such as by dry blending the additive system directly with polymer pellets or fluff by means of tumble mixers, Henschel blenders, and the like. Solutions or slurries of the stabilizers can be sprayed onto or admixed with a granular polymer. Stabilizers can also be blended with a molten polymer by means of a Banbury mixer, Brabender mixer, roll mill, screw extruder, and the like. 
    
    
     EXAMPLE 1 
     A series of compositions was prepared by admixing the stated quantities of the specified hindered amine, when employed, specified nickel phosphonate, when employed, and 0.1 wt. % tris (2,4-di-t-butylphenyl) phosphite with a commercially available polypropylene having a nominal melt flow of 12 as determined by ASTM D 1238-65T, condition L, and a melting point of about 170° C. Each blend was initially mixed together in a Henschel blender by combining the additive(s) with the polypropylene powder (fluff). The resulting blend was extruded at about 245° C. into strands and pelletized. The resulting pellets were then reextruded and repelletized as before to produce each final composition. The compositions were then melt spun at about 260° C. into an eight strand multifilament. Four such strands were plied together and drawn 5X at about 135° C. to produce a 17 denier per filament yarn. The yarn was then knitted into a sleeve about 5 cm in diameter from which samples of convenient lengths for test purposes were later cut. 
     The UV stability of the samples was determined in a [GMC] twin carbon arc Weatherometer at a black panel temperature averaging about 88° C. Periodic water spraying also occurs in this test. Each sample was mounted on a black backed Altas mounting fadeometer card. Each sample was periodically examined for degradation, usually about every 20 hours. Degradation (time to failure) was arbitrarily taken as the number of exposure hours required to weaken the fabric so that it was observed to flake when gently scratched with a finger nail or plastic needle. 
     The quantity and nature of each stabilizer employed and the results obtained are given in Table 1. 
     
                                           TABLE 1__________________________________________________________________________Degradation Results   Hindered     Nickel   WeightRun   Amine (A)     Phosphonate (B)              Ratio                  Hours to Failure                             ImprovementNo.   Wt. Percent     Wt. Percent              A:B Actual                      Expected (C)                             %__________________________________________________________________________1  0      0        --   80 -- (D) --2  0.2    0        --  240 --     --3  0.4    0        --  260 --     --4  0.6    0        --  340 --     --5  0      0.2      --  160 --     --6  0      0.4      --  360 --     --7  0      0.6      --  440 --     --8  0.2    0.2      1:1 540 320    699  0.2    0.4      0.5:1                  640 520    2310 0.2    0.6      0.3:1                  780 600    3011 0.4    0.2      2:1 780 340    12912 0.4    0.4      1:1 840 540    5613 0.4    0.6      0.67:1                  920 620    4814 0.6    0.2      3:1 900 420    11415 0.6    0.4      1.5:1                  1220                      620    97                      average                             71__________________________________________________________________________ (A) di(1,2,2,6,6-pentamethyl-4-piperidyl)-2-n-butyl-2-(4-hydroxy-3,5-di-t-butlbenzyl) malonate. (B) nickel bis(O--ethoxy3,5-di-t-butyl-4-hydroxybenzyl phosphonate) (C) Expected hous are calculated by adding hours to time of failure of control fiber (80 hours) plus time to failure of appropriate sample containing hindered amine less 80 hours plus time to failure of appropriate sample containing nickel phosphonate less 80 hours. (D) A dash signifies no entry is needed. 
    
     Examination of the data given in Table 1 shows that the total amount of the stabilizer mixtures employed varied from 0.4 to 1.0 wt. % based on the total weight of the compositions and that the weight ratio of hindred amine to nickel phosphonate varies from 0.3:1 to 3:1. In these ranges, the test results clearly show that the actual hours to failure (degradation) are substantially greater than the predicted hours to failure based on the additive effect of each stabilizer alone. This is particularly evident at weight ratios of 1:1 or higher. 
     EXAMPLE 2 
     Following the procedure described in the first example, a series of compositions was prepared by mixing individual portions of the 12 melt flow polypropylene fluff with a specified amount of the hindered amine, when employed, with a specified amount of the nickel phosphonate, when employed, with 0.1 wt. % of distearyl pentaerythritol diphosphite, with 0.08 wt. % of tris-(3,5-di-t-butyl-4-hydroxybenzyl)isocyanurate, and with an amount of a color concentrate containing Pigment Red 194 (Color Index 71100) sufficient to provide about 1 wt. % pigment in the final composition. 
     Each composition was formed into knitted sleeves, cut into lengths, and tested for UV stability in the twin carbon arc weatherometer as before. 
     A curve was constructed from the results obtained with the series 20 compositions (hindered amine, no nickel phosphonate) and a curve was constructed from the results obtained with the series 30 compositions (nickel phosphonate, no hindered amine). 
     With the remaining compositions containing varying amounts of both hindered amine and nickel phosphonate, the expected contribution of each is determined by consulting the appropriate curve, summing the results, and subtracting 80 hours to get the expected time to failure for that particular combination. A composition containing neither hindered amine nor nickel phosphonate has a time to degradation of about 80 hours in the test employed. In calculating the expected time to degradation of an invention composition, the expected time to degradation of a control containing either hindered amine (no phosphonate) or nickel phosphonate (no hindered amine) is determined by inspection of the proper curve and 80 hours is subtracted from the summed results so that the basic 80 hours is counted only once. The final result thus gives the expected (predicted) time to failure for that particular combination. 
     The quantities of the stabilizers employed and the results obtained are given in Table 2. 
     
                                           TABLE 2__________________________________________________________________________Degradation Results, Red Samples__________________________________________________________________________          Composition          A               B               CStabilizer.sup.a          Stab.           Stab.           Stab.      Wt..sup.c          Wt.             Hours to Failure                      Impr.                          Wt.                             Hours to Failure                                      Impr.                                          Wt.                                             Hours to                                                      Impr.reSeriesComponent      Ratio          %  Actual                 Expected                      %   %  Actual                                 Expected                                      %   %  Actual                                                 Expected                                                      %__________________________________________________________________________20   HA    1   0.17            0.34            0.51NF    0   0  500 --.sup.b                      --  0  740 --   --  0  940 --   --30   HA    0   0               0               0NF    1   0.33             160 --   --  0.66                             180 --   --  0.99                                             340 --   --40   HA    4   0.16            0.30            0.45NF    1   0.04             540 480  12  0.08                             820 700  17  0.11                                             920 885  3.950   HA    3   0.15            0.29            0.44NF    1   0.05             540 470  15  0.10                             880 690  27  0.15                                             940 885  6.260   HA    2   0.14            0.27            0.41NF    1   0.07             400 455  -12 0.14                             820 690  19  0.20                                             1080                                                 870  2478   HA    1   0.11            0.22            0.34NF    1   0.11             480 405  48  0.22                             720 625  15  0.34                                             880 820  7.380   HA    0.5 0.08            0.17            0.25NF    1   0.17             540 365  19  0.33                             460 580  -21 0.50                                             880 755  1790   HA    0.3 0.07            0.13            0.20NF    1   0.20             260 350  -26 0.40                             480 530  -9.4                                          0.60                                             700 705  -0.7100  HA    0.25          0.06            0.11            0.17NF    1   0.22             180 335  -46 0.45                             380 500  -24 0.67                                             680 690  -1.4__________________________________________________________________________                           Composition                           D               E                 Stabilizer.sup.a                           Stab.           Stab.                       Wt..sup.c                           Wt.                              Hours to Failure                                       Impr.                                           Wt.                                              Hours to                                                       Impr.re             Series                 Component                       Ratio                           %  Actual                                  Expected                                       %   %  Actual                                                  Expected                                                       %__________________________________________________________________________             20  HA    1   0.68            0.85                 NF    0   0  1080                                  --   --  0  1000                                                  --   --             30  HA    0   0               0                 NF    1   1.32                               440                                  --   --  1.65                                               540                                                  --   --             40  HA    4   0.60            0.75                 NF    1   0.15                              1100                                  1045 5.3 0.19                                              1220                                                  1080 13             50  HA    3   0.58            0.73                 NF    1   0.19                              1160                                  1035 12  0.24                                              1320                                                  1120 18             60  HA    2   0.54            0.68                 NF    1   0.27                              1140                                  1020 12  0.34                                              1340                                                  1160 16             78  HA    1   0.45            0.56                 NF    1   0.45                              1180                                  975  21  0.56                                              1320                                                  1120 18             80  HA    0.5 0.34            0.42                 NF    1   0.67                              1040                                  910  14  0.84                                              1100                                                  1060 3.8             90  HA    0.3 0.27            0.34                 NF    1   0.81                               880                                  875  0.6 1.01                                              1100                                                  1010 8.9             100 HA    0.25                           0.22            0.28                 NF    1   0.89                               760                                  815  -6.7                                           1.11                                              1400                                                   965 45__________________________________________________________________________ .sup.a HA is hindered amine, di(1,2,2,6,6-pentamethyl-4-piperidyl)-2-n-butyl-2(4-hydroxy-3,5-di-t-butybenzyl) malonate. NF is nickel phosphonate, nickel bis (O--ethoxy3,5-di-t-butyl-4-hydroxybenzyl phosphonate). .sup.b A dash signifies no entry required. These are control runs. .sup.c HA/NF weight ratio. 
    
     Inspection of the results of Table 2 reveals that the fibers containing the hindered amine and nickel phosphonate in combination with the red pigment, the organic phosphite and the substituted isocyanurate antioxidant generally exhibit good resistance to UV light. Some of the fibers exhibit outstanding resistance, particularly those where the hindered amine/nickel phosphonate weight ratio varies from about 0.5:1 to about 4:1 and the concentration of both stabilizers ranges from about 0.2 wt. % to about 1.2 wt. %. Some of the values obtained, particularly those of series 60, Composition A, and series 80, Composition B, appear too low and out of line with the other results. This is believed to reflect possible errors in compounding the samples thus giving samples lower in stabilizer content than specified. 
     EXAMPLE 3 
     A series of compositions similar to those of the second example except that an amount of a color concentrate containing Pigment Blue 15 (Color Index 74160) sufficient to provide about 1 wt. % pigment in the final composition was used as the colorant in place of the red pigment. 
     As before, each composition was converted into knitted sleeves and tested for UV stability in the twin carbon arc weatherometer. 
     Curves were constructed as described before for the degradation results obtained for the control runs, e.g., Series 110 and 120 compositions. Based on the curves and the actual test results obtained, the improvement in degradation resistance for the invention compositions was determined as well as the expected values. 
     The quantities of stabilizers employed and the results obtained are presented in Table 3. 
     
                                           TABLE 3__________________________________________________________________________Degradation Results, Blue Samples__________________________________________________________________________          Composition          F               G               HStabilizer.sup.a          Stab.             Hour to Failure                          Stab.                             Hours to Failure                                          Stab.                                             Hours to Failure      Wt..sup.c          Wt.         Impr.                          Wt.         Impr.                                          Wt.         Impr.SeriesComponent      Ratio          %  Actual                 Expected                      %   %  Actual                                 Expected                                      %   %  Actual                                                 Expected                                                      %__________________________________________________________________________110  HA    1   0.17            0.34            0.51NF    0   0  360 --.sup.b                      --  0  660 --   --  0   800                                                 --   --120  HA    0   0               0               0NF    1   0.33             480 --   --  0.66                             860 --   --  0.99                                              920                                                 --   --130  HA    4   0.16            0.30            0.45NF    1   0.04             400 410  -2.4                          0.08                             780 670  16  0.11                                             1100                                                  890 24140  HA    3   0.15            0.29            0.44NF    1   0.05             460 410  12  0.10                             880 680  29  0.15                                             1140                                                  930 23150  HA    2   0.14            0.27            0.41NF    1   0.07             400 410  -2.4                          0.14                             1020                                 700  46  0.20                                             1220                                                  960 27160  HA    1   0.11            0.22            0.34NF    1   0.11             600 410  46  0.22                             1200                                 720  67  0.34                                             1380                                                 1030 34170  HA    0.5 0.08            0.17            0.25NF    1   0.17             580 430  35  0.33                             1180                                 770  53  0.50                                             1320                                                 1040 27180  HA    0.3 0.07            0.13            0.20NF    1   0.20             520 450  16  0.40                             1000                                 760  32  0.60                                             1320                                                 1040 27190  HA    0.25          0.06            0.11            0.17NF    1   0.22             740 460  61  0.45                             860 770  12  0.67                                             1160                                                 1050 10Average Improvement, %     52              55              40__________________________________________________________________________                           Composition                           I               J                 Stabilizer.sup.a                           Stab.                              Hours to Failure                                           Stab.                                              Hours to Failure                       Wt..sup.c                           Wt.         Impr.                                           Wt.         Impr.             Series                 Component                       Ratio                           %  Actual                                  Expected                                       %   %  Actual                                                  Expected                                                       %__________________________________________________________________________             110 HA    1   0.68            0.85                 NF    0   0   900                                  --   --  0  1040                                                  --   --             120 HA    0   0               0                 NF    1   1.32                              1020                                  --   --  1.65                                              1140                                                  --   --             130 HA    4   0.60            0.75                 NF    1   0.15                              1140                                  1080 5.6 0.19                                              1480                                                  1220 21             140 HA    3   0.58            0.73                 NF    1   0.19                              1120                                  1100 1.8 0.24                                              1440                                                  1270 13             150 HA    2   0.54            0.68                 NF    1   0.27                              1440                                  1160 24  0.34                                              1460                                                  1350 8.1             160 HA    1   0.45            0.56                 NF    1   0.45                              1660                                  1250 33  0.56                                              1860                                                  1450 28             170 HA    0.5 0.34            0.42                 NF    1   0.67                              1960                                  1300 51  0.84                                              1800                                                  1510 19             180 HA    0.3 0.27            0.34                 NF    1   0.81                              1700                                  1300 31  1.01                                              1900                                                  1500 27             190 HA    0.25                           0.22            0.28                 NF    1   0.89                              1400                                  1270 10  1.11                                              1780                                                  1600 11             Average Improvement, %    31              26__________________________________________________________________________ .sup.a HA is hindered amine, di(1,2,2,6,6-pentamethyl-4-piperidyl)-2-n-butyl-2(4-hydroxy-3,5-di-t-butybenzyl) malonate. NF is nickel phosphonate, nickel bis(O--ethoxy3,5-di-t-butyl-4-hydroxybenzyl phosphonate). .sup.b A dash signifies no entry needed. These are control runs. .sup.c HA/NF weight ratio. 
    
     Examination of the results of Table 3 shows that the fibers containing the hindered amine and nickel phosphonate in combination with the blue pigment, the organic phosphite and the substituted isocyanurate antioxidant also generally exhibit good resistance to UV light. In fact, better results are obtained in the presence of this pigment than in the presence of the red pigment. With the blue pigment, the weight ratio of hindered amine to nickel phosphonate, can vary from at least 0.25:1 to at least 4:1 and the concentration of the two stabilizers can range from about 0.2 wt. % to about 1.2 wt. %. Some anomolous results were obtained as before, particularly those in Series 130, Composition F, Series 140 Composition I, and Series 150, Composition F. As stated before, such results are believed to result from possible compounding errors in preparing the compositions. 
     In summation, the specific examples show that the hindered amine/metal phosphonate stabilizing system is effective in natural and in colored compositions to provide unexpected resistance to UV light compared to either stabilizer alone at comparable concentrations. When a colorant is employed, optimum results can be obtained by adjusting the level of the stabilizer as required to compensate for the effect of the colorant on the system as is known in the art.