MXPA98010496A - Ductile composition of polyolephine resistant to gamma laradiation and articles produced from the im - Google Patents

Abstract

A ductile, gamma-radiation-resistant olefin polymer composition that includes (a) an olefin polymer, (b) an amount of N, N-dialkylhydroxylamine that is effective to increase the ductility of the composition, and (c) a polysiloxane containing sterically hindered piperidino groups and present in an amount effective to increase the gamma radiation resistance of the composition. The combination of N, N.dialkylhydroxylamine and the polysiloxane imparts superior ductility, resistance to discoloration and resistance to oxidation to an olefin polymer. The composition can be used to manufacture sterilizable articles including food packaging and medical articles, such as syringe barrels, syringe plungers, tubing, tube assemblies, forceps, surgical staples, tissue culture tubes and surgical gown fibers.

Description

DIATIC COMPOSITION OF POLYMYPHINE RESISTANT TO GAMMA RADIATION AND ITEMS PRODUCED FROM THE SAME It is known to incorporate additives into articles made of olefin polymers to prevent fading and brittleness over time due to exposure to UV radiation. For example, European Patent Publication No. 343,717 discloses the use of polysiloxanes containing sterically hindered piperidino groups to stabilize polyolefins against ultraviolet radiation and heat. There is no exposure related to stabilization against gamma radiation, which has a wavelength of 10"10 to 10 ~ 12 meters and is thus significantly more energetic than ultraviolet radiation having a wavelength of 10" 6 a 10"7 meters It is also known as sterilizing polyolefin items with 2.5 to 5.0 megarads of high energy gamma radiation, however, polymeric articles exposed to such radiation typically suffer from discoloration and brittleness, which may make them unsuitable for intended use U.S. Patent No. 5,371,124 provides a good summary of the various additives that have been proposed to improve the radiation resistance of propylene polymer compositions prior to molding or configuration of the polymer towards a useful article. See also the U.S. Patent. No. 4,888,369. However, any additive must be compatible with the other components of the polymer composition, and may cause other problems, including objectionable odor and / or color, processing difficulties, bleeding of the additive from the article during the time, etc. See, for example, example, the US Patent No. 4,710,524, which suggests that the inclusion of a mobilization additive as described in US Patents. Nos. 4,110,185 and 4,274,932 produce undesirable handling and printing problems. The syringe grade material made from polypropylene is typically viscose peroxide from a polymer having a low melt flow rate (MFR) to obtain a narrower molecular weight distribution and contains oil as a mobilizer to improve the free radical scavenging ability of a hindered amine light stabilizer additive. The polypropylene material typically contains a sorbitol-based additive as a nucleator. The Patent of E.U.A. No. 4,876,300 discloses that long chain N, -dialkylhydroxylamines can used as process stabilizers for polyolefin compositions in order to minimize discoloration and increase the rate of melt flow due to extrusion. However, there is no recognition that such long chain N-dyalkylhydroxylamines can also improve the ductility of a polyolefin composition that has been subjected to high energy gamma radiation. The Patent of E.U.A. No. 4,668,721 broadly discloses that the hydroxylamine derivatives can be used to stabilize polyolefin compositions against degradation due to extrusion, exposure to natural gas combustion products, gamma radiation or during storage for extended periods. The hydroxylamine derivative can have a chemical structure that conforms to one of fourteen structural formulas. even when data is presented for processing stability, resistance to gas fading and resistance to discoloration due to aging in the furnace, there is no data related to the gamma ratio. Additionally, almost all data are directed to polyolefin compositions stabilized with N, -dibenzylhydroxylamine, the only dialkylhydroxylamma evaluated was N, N-di-n-octylhydroxylamine.

Recently, European Patent Publication No. 664,315 proposed the use of mobilization oil and a hindered piperidine polysiloxane ether to stabilize the polypropylene against sterilization radiation. There is no exposure regarding the addition of an N, N-dialkylhydroxylamine to improve the ductility of the propylene composition. It is an object of the present invention to provide a ductile polymer composition that can be easily injection molded into flexible, substantially transparent articles. Another object of the present invention TS provides a polymeric composition resistant to gamma radiation that is particularly resistant to yellowing. In one aspect, the present invention relates to an olefin polymer composition, comprising: (a) an olefin polymer, (b) an amount of N, N-dialkylhydroxylamine which is effective to increase the ductility of the composition, and (c) a polysiloxane containing sterically hindered piperidino groups and which is present in an effective amount to increase the resistance to the gamma radiation of the composition. In another aspect, the present invention relates to a sterilizable article wherein at least part of the material construction thereof comprises an olefin polymer composition comprising: (a) an olefin polymer, (b) an amount of N, -dialkylhydroxylame which is effective to increase the ductility of the composition, and (c) a polysiloxane containing spherically hindered piperidino groups and which is present in an amount effective to increase the gamma radiation resistance of the composition. Figures 1-3 are plots of ductility values of different polyolefin film samples measured after different periods of oven aging at 60aC after being exposed to 0, 3 and 5 Mrad of cobalt gamma radiation 60, respectively. Figure 4 is a graph of the yellowness index of various granule and polyolefin sheet samples that have been exposed to gamma radiation of cobalt 60 of 0, 3 and 5 Mrad. As summarized in the foregoing, this invention relates to an olefin polymer composition which includes: (a) an olefin polymer, (b) an amount of N, N-dialkylhydroxylamine which is effective to increase the ductility of the composition, and (c) a polysiloxane which contains sterically hindered piperidino groups and which is present in an amount effective to increase the gamma radiation resistance of the composition. the inventor has unexpectedly discovered that a combination of N, -dialkylhydroxylamine and the polysiloxane imparts superior ductility, resistance to discoloration and resistance to oxidation to an olefin polymer. The N, -dialkylhydroxylamine must have a hydroxyl group attached to the nitrogen atom, and is preferably conformed to the formula: RiRz OH wherein R, and R 2 are independently C 1-36 alkyl, which is unsubstituted or substituted by hydroxyl. Exemplary hydroxylamines remaining within the above form include N, N-distearylhydroxylamine and di (hydrogenated bait) amine.

A di (hydrogenated bait) amine has the following distribution of alkyl substituents: C16 c16 12. 4 another 4. 0 The di (hydrogenated bait) amine that originates from animal sources may very well vary somewhat in the specific distribution of alkyl substituents, but the di (hydrogenated bait) amine contains higher amounts of N, N-dihexadecylamine, N, N-dioctadecylamine and N-hexadecyl-N-octadecylamine. The individual components of the mixture can be separated by distillation under high vacuum. However, for the purposes of this invention there is no need to carry out said separation and the hydroxylamine prepared from the di (hydrogenated bait) amine is a preferred embodiment of the present invention. The long chain N-dyalkylhydroxylamines can be prepared by a number of methods. These include (a) oxidation of the corresponding secondary amine with aqueous hydrogen peroxide to directly form the desired N, N-dialkylhydroxylamine; (b) the addition of the -amine secondary to an alpha, beta unsaturated compound such as an alkyl acrylate to form a Michael addition product, which in turn is oxidized to the corresponding tertiary amine oxide using aqueous hydrogen peroxide, and followed by removing the fa, -beta-unsaturated compound by the Cope reaction to provide the N, -dialkylhydroxylamine; (c) the metathesis reaction between an alkyl halide and a hydroxylamine in the presence of an alkali such as sodamide, and (d) the reaction of an amine with a peroxy compound, such as benzoyl peroxide, followed by saponification of the intermediate The N, -dialkylhydroxylamine should be present in an amount that is effective to increase the ductility of the olefin polymer.For polypropylene, the N, -dialkylhydroxylamine is typically present in an amount of 0.01 to 5". 0 percent by weight, of 0.1 to 0.5 weight percent preference, based on the weight of the olefin polymer. The polysiloxane containing spherically hindered piperidino groups preferably conforms to the formula: wherein Ri and R3 are linear or branched independent C1-10 alkyl radicals, cycloalkyl radicals of C3-u or phenyl radicals; R2 is a radical that conforms to one of the following formulas I-IV: (II) wherein: R4 is hydrogen or methyl-or benzyl; R5 is a linear or branched alkyl radical of Cj-CV; z is a group selected from: -0-; -N-; I R7 wherein R7 is a linear or branched C? -C3 alkyl group or hydrogen; R6 is hydrogen or methyl; q is zero or one; n is an integer; m and p, which may be the same or different, are zero or integers, with the proviso that n + p + m is an integer less than or equal to 50; A is a group that corresponds to the formula: Rr - - (III) wherein R, has the above-mentioned meaning B is a group corresponding to the formula: where Rx has the above mentioned meaning; or A and B together represent a direct link, giving rise to a cyclical structure. The polysiloxane stabilizers corresponding to the formula (I) are polymers having random distribution of the monomer units and a linear or cyclic structure. In particular, they assume a linear structure when a and B are groups corresponding to formulas (III) and (IV), while assuming a cyclic structure when A and B together represent a direct link. A preferred polysiloxane that falls within the above formula is polymethyl propyl 3-oxy- (4- (2,6,6,6-tetramethyl) piperidinyl) siloxane, which is commercially available under the trademark Uvasil 299 from Great Lakes Chemical Corporation . The olefin polymer is derived from monoolefins, such as polyethylene, which may be crosslinked, polypropylene, polyisobutylene, polybutene-1, poly-3-methylbutene-1 and poly-4-methylpentene-1. Polyethylene, for example, can be polyethylene medium density, high density or linear density low density. Mixtures of the aforementioned homopolymers, for example mixtures of polypropylene and polyethylene, polypropylene and polybutene-1, or polypropylene and polyisobutylene and the like, can also be used. Copolymers of monoolefins can also be used in the present compositions, for example, ethylene / propylene copolymers, propylene / butene-1 copolymers, propylene / octene-1 copolymers, ethylene / butene-1 copolymers, ethylene / octene-copolymers 1, as well as ethylene / vinyl acetate copolymers. The saturated olefin polymer is preferably a propylene polymer, more preferably either a crystalline propylene homopolymer having an isotactic index greater than 90 or a random copolymer, crystalline propylene and either ethylene or 1-olefins of C4. -C? O? The propylene polymer is preferably visbroken at an MFR of 11-15 g / 10 minutes. These propylene polymers are commercially available from Montell North America Inc. The polymer composition may also include a second stabilizing additive in an effective amount to increase the resistance of the olefin polymer to yellowing. The second stabilizing additive is preferably at least one stabilizer selected from the group consisting of a phosphite, a phosphonite and a hindered amine. Exemplary phosphites include tris (2,4-di-tert-butyl phenyl) phosphite; 2, 2 ', 2"-nitrile triethyltris (3, 3', 5 ', 5" -tetra-tert-butyl l.l'-biphenyl 2,2 dil) phosphite; and bis (2,4-bis (1, 1-dimetilet.il) -6-methylphenyl) ethyl ester of phosphorous acid. Illustrative hindered amines include bis (2,2,6,6-tetramethylpiperin-4-yl) sebacate, the polycondensation product of l- (2-hydroxyethyl) -2,6,6-tetramethyl-4-hydroxypiperidine and succinic acid, the polycondensation product of 2, -dichloro-6-tert-octylamino-s-triazine and 4,4'-hexamethylenebis- (amino-2, 2,6,6,6-tetramethylpiperidine) or N, ', N ", N1"-tetraquis- ((4,6-bis (butyl- (2,2,6,6-tetramethyl-pipe idin-4-yl) amino) -s-triazine-2-yl) -l, 10-diamino 4,7-diazadecane The polymer composition can also include at least one acid neutralizing agent selected from the group consisting of metal soaps, hydrocalcites, lactates, aluminum silicate, calcium and oxides and hydroxides of Group metals. II Calcium stearate and sodium stearate are preferred.The polymer composition may also include at least one sorbitol-based nucleator selected from the. a group consisting of bis- (3,5-dimethylbenzylidene) sorbitol; (1, 3) 2,4-di) p-methylbenzylidene) sorbitol; p-ethylenebenzylidene sorbitol; and 2,4-dimethylbenzylidene sorbitol. The polymeric composition of the present invention can be prepared by mixing an olefin polymer in flake or particle form, the tertiary amine substituted with hydroxyl and the propyl-3-oxy- (- (2, 2, 6,6-tetramethyl) piperidinyl) polymethyl siloxane in a conventional mixer. The polymer composition of the present invention is particularly suitable for injection molding into articles that will be sterilized by gamma irradiation, including food and medical packaging articles, such as syringe barrels, syringe plungers, tubing, tube assemblies, forceps, staples. surgical, tissue culture tubes, and fibers for surgical gowns.

EXAMPLES The following Examples describe preferred embodiments of the ductile, gamma-radiation-resistant propylene polymer composition of the invention, and are presented for illustrative purposes only. TO unless otherwise specified, all amounts of ingredients are in pph of the propylene polymer material except, of course, by the propylene polymer material. The following procedures were used to prepare and evaluate the compositions set forth in the following Examples. The components of each sample composition, which were in finely divided condition, were mixed in a Henschel mill for one minute and low speed and 30 seconds at high speed. Lupersol 101 was added to all batches to achieve a melt flow rate of 11-15 dg / m-inuto. The mixture was then extruded at 260eC and 125 rpm in a Haake counter-rotating double inter-spinner extruder in an air atmosphere. The resulting mixture was extruded as a strand, cooled in water and granulated. The sample granules were then extruded at 204SC and 75 rpm through a 2286 centimeter wide die at 218aC to a 1.02 millimeter thick sheet. The extruded sheet was cut into 8.89 cm x 8.89 cm squares, which were then tested for melt flow rate, radiation resistance, and high impact resistance as described below.

The melt flow rate of all samples (granule and sheet, non-irradiated and irradiated) was determined in accordance with ASTM D1238, Condition L. The melting stability of the samples was determined in a Kayeness plastometer. The radiation resistance of the leaf samples was tested by packing samples in plastic bags, with pieces of paper inserted between the individual sheets to allow air circulation. These samples were then irradiated either with a dose of gamma radiation of cobalt 60 of 3 or 5 megarad at an exposure rate of approximately 1.0 megarad / hour in air. The discoloration suffered by the samples was measured in accordance with the Yellowness Index in accordance with ASTM D 1925 using a Hunter Lab Colorimeter. All the leaf samples, which have a radiation exposure of 0, 3 or 5 megarads, were aged in a forced air oven at 60aC,. After specified periods of aging, the samples were removed and tested for impact resistance by means of a Rheometrics high-speed impact test discussed below, if a complete sample-set suffered catastrophic failure before the end of the test period, HE removed from the oven and the test for that sample was discontinued. The impact strength of the sample sheet frames were tested in accordance with ASTM D3673 using a Rheometrics RIT-8000 High Rhythm Impact Tester. Samples were tested at 0.01 m / sec using an arrow of 12.7 mm and a rear ring of 6.35 cm at "temperature ambient. The energy and force required to drill the sample and the distance (millimeters) traveled by the hub. The shape of the break was recorded as either ductile or brittle. The ductility value is the ductility ratio (the total energy reading divided by the final energy reading) multiplied by the ductility factor (the value assigned to the number of ductile breaks in each batch). The ductility factor in turn depends on the number of "total plates tested in each batch for each period of time; that is, if 4 plates are tested, and all are ductile, the ductility factor is "10". These ductile breaks, the factor is "7.5", two ductile breaks, "5.0", a ductile break, "2.5". If there are no ductile breaks, the ductility factor is "0", which also gives a ductility value of "0". (Two readings "0" in consecutive tests for a batch means total failure and no additional test is performed).

Traditionally, the test has been based solely on the ductility ratio, "in which a value of" 1"was considered to show the sample as fragile.Three years of testing in this way has shown, however, that the ductility ratio may be misdirected and not true for the actual ductility or brittleness of a particular sample.The ductility value compensates for this by taking the actual physical evidence of the shape of the break to the equation - the higher the value, the The more ductile the sample, the point of total brittleness is also defined "clearly - when the ductility value is" 0", the sample is considered fragile, despite what the ductility ratio alone indicates.

Example 1 A polypropylene base formulation was used to prepare all sample compositions. The base formulation comprised PH 180 propylene polymer commercially available from Montell North America, Inc. and 0.05 pph calcium stearate, and mixed with different amounts of the additives listed below, viscera with Lupersol 101, extruded to sheet and evaluated for ductility value, both initially and after 1 week of aging in oven at 60 aC.

Table 1 Ductility Value at 0 Megarads No Initial Additive 1 Week 1-4 0.1 pph FS-042 15.9 13.3 0.125 pph Uvasil 299 1-2 0.3 pph FS-042 18.4 14.3 1-3 0.5 pph FS-042 18.7 17.5 1-5 0.5 pph FS-042 19.2 13.4 0.125 pph Uvasil 299 1-6 0.5 pph FS-042 19.7 15.9 0.125 pph Uvasil 299 4.7 pph oil 1-7 0.5 pph FS-042 19.8 14, 6 0.2 pph Chimassorb 944 1-8 PF-091B - 15.7 12.8 1-1 0.1 pph FS-042 16.5 14.95 Notes: FS-042 is a trademark for a product that contains N, N-di (stearyl) hydroxylamine that is commercially available from Ciba. Uvasil 299 is a trademark for a product containing polymethylpropyl 3-oxy (4- (2,6,6,6-tetramethyl) -piperidinyl) -iloxane, which is commercially available from Great Lakes Chemical Corporation. Chimassorb 944 is a brand name for a product containing poly (6 - ((1, 1, 3, 3-tetramethylbutyl) amino-s-triazine 2,4-yl)) 2, 2, 6, 6-tetramethyl-4 -piperidinyl) - imino) hexamethi len (2, 2,6,6-tetramethyl-4-pip idyl) imino), which is commercially available from Ciba. PF-019B has the following formulation: PH 180 visroto, 0.12 pph Tinivin 770 hindered amine stabilizer 0.05 pph of sodium stearate, Lupersol 101 peroxide to the desired MFR. The ductility results listed in Table 1 above are illustrated graphically in Figure 1. An increase in initial ductility (Week 0) is seen in Samples Nos. 1-1 to 1-3 as the amount of N, distearylhydroxylamine. An additional increase in initial ductility is achieved by the addition of polymethylpropyl 3-oxy- (4- (2, 2, 6,6-tetramethyl) piperidinyl) siloxane alone (Sample 1-5), and together with a hydrocarbon oil (Sample 1-6), The combination of N, -distearylhydroxylamine and the siloxane results in decreased ductility after one week of oven aging.Other leaves of the above formulations were exposed to 3 megarads of gamma radiation, and were measured to determine the ductility value after various periods of aging in the oven at 60 ° C.

Table 2 Ductility Value at 3 Megarads No. Initial Additive 2 Sem. 4 Sem, 8 Sem, 1-4 0.1 pph FS-042 14.0 18.6 6.4 5.2 0.125 Uvasil 299 1-2 0.3 pph FS-042 17.1 10.3 14.0 7.1 1-3 0.5 pph FS-042 • 12.8 7.8 10.8 8.7 1-5 0.5 pph FS-042 18.8 14.1 12.9 15 0 125 Uvasil 299 1-6 0.5 pph FS-042 18.2 14.0 14.0 0.125 pph Uvasil 299 4.7 pph oil 1-7 0.5 pph FS-042 18.7 15.7 13.9 15.7 0.2 pph Chimassorb 944 1-8 PF-091B 12.3 0 0 1-1 0.1 pph FS-042 14.8 11.6 8.0 0 The ductility results listed in Table 2 above are illustrated graphically in Figure 2. The combination of N, N-distearylhydroxylamine and the siloxane (Sample 1-5) exhibits the highest initial ductility and maintains one of the highest ductility values at weeks 2, 4 and 8 of oven aging. Other sheets of the formulations were subjected to 5 megarads of gamma radiation, and were measured for ductility value after various periods of oven aging at 60aC.

Table 3 Ductility value at 5 Megarads No Initial Additive 2 Sem. 4 Sem. 8 Sem. 1-4 0.1 pph FS-042 13.1 0 0 0 0.125 pph Uvasil 299 1-2 0.3 pph FS-042 17.6 2.8 5.9 0 1-3 0.5 pph FS-042 18.0 15.5 10.5 14.1 1-5 0.5 pph FS-042 18.8 11.3 13.8 10.3 0.125 pph Uvasil 299 1-6 0.5 pph FS-042 16.6 13.7 14.1 13.4 0.1215 pph Uvasil 299 4.7 pph oil 1-7 0 5 pph FS-042 7 3 16.3 16 5 14 2 0.2 pph Chimassorb 944 1-8 PF-091B 5.65 0 0 0 1-1 0.1 pph FS-042 13.57 0 0 0 The ductility results listed in Table 3 above are illustrated graphically in Figure 3. The combination of N, -tetearylhydroxylamine and the siloxane (Sample 1-5) exhibits the highest initial ductility and maintains one of the highest ductility values in weeks 2, 4 and 8 of oven aging Example 2 The yellowness index of the above formulations was measured after extrusion to sheet, and after the extruded sheet was cut into samples of 8.89 cm x 8.89 cm and exposed to 3 and 5 Mrad of radiation cobalt gamma 60 Table 4 Yellowing index No. Initial Additive 3Mrad 5Mrad 1-1 0.1 pph FS-042 2.1 2.6 2.6 1-2 0.3 pph FS-042 2. 2.8 2.9 1-3 0.5 pph FS-042 2.4 3.1 3.2 1-5 0.5 pph FS-042 2.3 2.9 2.97 0.125 pph Uvasil 299 1-6 0.5 pph FS-042 2.4 3.1 3.2 0.125 pph Uvasil 299 4.7 pph oil 1-7 0.5 pph FS-042 2.7 2.9 3.2 0.2 pph Chimassorb 944 1-8 PF-091B 1.8 2.2 2.65 1-4 0.1 pph FS-042 2.2 2.9 2.70 0.125 pph Uvasil 299 The yellowness index data listed in Table 4 above are illustrated graphically in Figure 4. The composition containing a combination of polysiloxane and N, -tetearylhydroxylamine (Sample 1-5) exhibited less yellowing than a corresponding composition containing only N, N-distearylhydroxylamine (Sample 1-3), or a composition containing N, -distearylhydroxylamine and a light stabilizer of conventional hindered amine (Sample 1-7).

Example 3 A base polypropylene formulation was used to prepare a comparison sample composition discussed below. The base formulation comprised of PH 180 propylene polymer commercially available from Montell North America, Inc. and 0.05 pph calcium stearate. The base formulation was mixed with 0.05 pph of calcium stearate, 0.50 pphr of FS-042 N, N-distearylhydroxylamine and 0.125 pph of a conventional hindered amine (non-polysiloxane), and visbroiled with sufficient Lupersol 101 to raise the melt flow of the composition at 12 g / 10 min. The formulation was extruded to sheet and evaluated for ductility values at 3 and 5 Mrads: Table 5 Ductility Value Initial Formulation 3Mrad 5Mrad 100 PH 180 20.04 18.76 18.40 0. 50 pph FS-042 0.125 pph Chimassorb 044 As required Lupersol-101 Other features, advantages and embodiments of the invention described herein will be easily evident to those who exercise ordinary experience after reading previous expositions. In this regard, even when specific embodiments of the invention have been described in considerable detail, variations and modifications of these embodiments may be made without departing from the spirit and scope of the invention as described and claimed.

Claims (17)

1. A composition of olefin polymer resistant to gamma, ductile radiation, comprising: (a) an olefin polymer, (b) an amount of N, N-dialkylhydroxylamine which is effective to increase the ductility of the composition, and ( c) a polysiloxane containing spherically hindered piperidino groups and which is present in an amount effective to increase the gamma radiation resistance of the composition.

2. The polymer composition of claim 1, wherein the N, -dialkylhydroxylamine is formed to the formula R1R2NOH wherein Ri and R2 are independently C? -36 alkyl. which is unsubstituted or substituted with hydroxyl.

3. The polymer composition of claim 2, wherein the N, -dialkylhydroxylamine is N, -distearylhydroxylamine.

4. The polymer composition of claim 2, wherein the N, -dialkylhydroxylamine comprises di (hydrogenated bait) hydroxylamine, 5 - The polymer composition of the

claim 1, wherein the N, -dialkylhydroxylamine is present in an amount of 0.01 to 5.0 percent by weight, based on the weight of the olefin polymer.

6. The polymer composition of claim 5, wherein the N, -dialkylhydroxylamine is present in an amount of 0.1 to 0.5 weight percent, based on the weight of the olefin polymer.

7. The polymer composition of claim 1, wherein the polysiloxane is conformed to the formula:

wherein Ri and R3 are independent linear or branched C rad _ rad alkyl radicals, C5-u cycloalkyl radicals or phenyl radicals; R2 is a radical that conforms to one of the following formulas I-IV:

wherein: R4 is hydrogen or methyl or benzyl; R5 is an alkyl radical of Ci-C? linear or branched; z is a group selected from: -o- -N-; I R7 wherein R7 is a linear or branched C? -C3 alkyl group or hydrogen; R6 is hydrogen or methyl; q is zero or one; n is an integer; m and p, which may be the same or different, are zero or integers, with the proviso that n + p + m is an integer less than or equal to 50; A is a group corresponding to the formula:

where Ri has the aforementioned meaning;

B is a group corresponding to the formula:

where Ri has the aforementioned meaning; or A and B together represent a direct link, giving rise to a cyclical structure.

8. The polymer composition of claim 7, wherein the polysiloxane is polymethylpropyl 3-oxy- (4- (2,2,6,6-tetramethyl) piperidinyl) i loxane.

9. The polymorphic composition of claim 1, wherein the olefin polymer is a crystalline propylene homopolymer having an isotactic index greater than 90 or a random, crystalline, propylene copolymer and either ethylene or 1-olefins of

C4-Cio • 10.- The polymer composition of claim 1, wherein the olefin polymer has a melt flow rate of 11-15 g / 10 minutes.

11.- The polymer composition of the

claim 1, further comprising a second stabilizing additive in an amount effective to increase the resistance of the olefin polymer to yellowing, the second stabilizer comprising at least one light stabilizer selected from the group consisting of a phosphite, a phosphonite and a hindered amine.

12. The polymer composition of claim 11, wherein the phosphite is at least one member of the group consisting of tris (2,4-di-tert-butyl-phenyl) phosphite; 2, 2 ', 2"nitrile triethyltris (3, 3', 5 ', 5" -tetra-tert-butyl l.l'-biphenyl 2,2 dil) phosphite; and bis (2,4-bis (1, 1-dimethylethyl) -6-methylphenyl) ethyl ester of phosphorous acid.

13. The polymorphic composition of claim 11, wherein the hindered amine is at least one member of the group consisting of bis (2, 2,6,6,6-tetramethylpiperidin-4-yl) sebacate, the product of polycondensation of 1- (2-hydroxyethyl) -2,6,6-tetramethyl-4-hydroxypiperidine and succinic acid, the polycondensation product of 2,4-dichloro-6-ter-octylamino-s-triazine and 4, -hexethylenebis- (amino-2, 2, 6, 6-tetramethylpiperidine) or N, ', ",'" -tetrakis ((, 6-bis- (butyl- (2,2,6, -tetramethyl-pipe idin-4-yl) amino) -s- triazin-2-yl) -l, 10-diamino-4,7-diazadecane.

14. - The polymer composition of claim 1, further comprising at least one acid neutralizing agent selected from the group consisting of metal soaps, hydrotalcites, aluminum silicate, calcium and oxides and hydroxides of Group II metals.

15. The polymer composition of claim 1, further comprising a sorbitol-based compound selected from the group consisting of bis- (3,5-dimethyl-ylbenzylidene) sorbitol; (1, 3) 2,4-di) p-methylbenzyldene) sorbium; p-et ilbenciliceno sorbitol; and 2,4-dimethylbenzylidene sorbitol. 16.- A ductile gamma radiation resistant olefin polymer composition prepared by mixing: (a) an olefin polymer, (b) an amount of tertiary amine substituted with hydroxy which is effective to increase the ductility of the composition, (c) ) an amount of polymethylpropi 1 3-oxy- (4- (2, 2, 6, -tetramethyl) piperidinyl) siloxane which is effective to increase the gamma radiation resistance of the composition. 17.- A sterilizable article in which when

less part of the material construction thereof comprises the polymer composition of claim 1. The sterilizable article of claim 17, wherein the article is selected from the group consisting of syringe barrels, syringe plungers , tubing, tube sets, forceps, surgical staples, tissue culture tubes, and fibers for surgical gowns. 19. A sterilized article in which at least part of the material construction thereof comprises the polymer composition of claim 1.