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3,022,267 United States Patent h?ce Patented Feb. 20, 1962 2 11 HardnessRockwell' ASTNI D;-7 85-5 1 3,022,267 R-sca'le ____________________ __ 815-925. STABILIZED ISO'FACTIC POLYPROPYLENE Melting point, ° F; __r.-.._- ______ __» 330-350. AND METHOD Speci?c heat-K ca1./gm., ‘’ C. _'__-__.0.4'6; David- W.‘ Young, Homewood; IlL, assi'gnor to Sinclair 5 X-ray diffraction pattern of isotactic polypropylene in Re?ning Company, New. York, N.Y., a corporation of terms of Bragg spacings‘ (d/n.) and intensities} arne I d./n. 631 A. _ Filed. May 14,1953, Ser. No. 735,130 No Drawing. Filed-May; 14,1958, Se'r. N0.v 735,130‘ 6 Claims. (Cl; 260-453) int. 10 5.26 10 ' Fun-meac 4.81 This‘ invention concerns a novel composition which 4.22 comprises a major amount of isotactic polypropylene and 4.08’. 3.51 3;l2 2.12 a minor amount of a high molecular weight amide, in par ticular N-stearoyl p-amino phenol. Isotactic polymers are head-tail-connected linear poly 15 mers, the monomer units of which ('CH2=CHR) are dis Natta, in 37, La Chimica and Industri'a (-Milan')’, 8'8'-8 tinguished by a simple,’ regular structure incapable of stereoisomerism. Their chains consist of sections which 900v (19551), attributes’ to the isotactic structure certain properties which‘ had previously not been found" in By; tertiary C atoms of‘equal steric con?guration. In iso 20 drocarbons'. At ambient temperatures; these high-molecu lar-weight polymers are actually hard, crystalline solids. tactic polypropylene, the “R” group of'the formula is a The low-molecular-weight isotactic polymers exhibit- like} CH3 group. The structure of this polymer is illustrated‘ wise ahigh degree‘ of crystallinity; For example, isotactic inl97, Scienti?c American, number 3, pages 102 and 103 polypropylene specimens with a molecular weight of (September 1957). about 2,500 present the‘ same crystalline polymeric‘ struc-_ The advantages of isotactic polymers have been cited ture as those polymers which have weights of several’ by Natta in 68, Angewandte Chemie, 393—403. (1956). hundreds of thousands. The isotactic polymers‘ are of These high-melting thermoplastic polymers, obtained from great resistivity towards isomerization'eifects', which would low-priced starting materials, yield ?bers of' great tensile modify the con?guration of‘ the branched methyl group‘, strength, which are useful as- textile raw materials. Iso exhibit a uniform reiteration of monomer units with tactic polypropylene threads have a tear strength up to 30 even in the presence of catalysts‘ which act by an: ionic) mechanism. Prolonged heating to 300450" C. in the absence of‘ catalysts (or else to lower temperatures‘, but in the presence of various reagents which‘ act’ by‘ a free more than 7 g./den. (.70 kg./ sq. mm.), comparableto the strengthof steel, but witha speci?c gravity of one-eighth as,- high as that of iron. Isotactic polypropylene sur passes polyethylene in many properties. This polypropyl 35 radical mechanism), may cause a depolymeri'z'ation of the macromolecules, although not to a very largev extent. ene has an averagemolecular weight. generally of from There are noteworthy differences in the- degrees of about 100,000 to 1,500,000Staudinger. The CH3 groups solubility between isotactic and‘ non-isotactic polymers, are. located onthe same side of, the carbon chain inv a which contain irregularly’ distributed carbonium atoms of helical structure, characterized by an identity period gen diverse steric con?gurations, as shown-in Table I. erally of from about 6.5 .to 6.6 A. along the axis of the TABLE“ r ' l-order Intrinsic Polymer Experim. ~‘transition viscosl spec. 100 ccJg. gravity I Soiubilityinv 2 Initial - a temp, fusion _ ‘’ O. temp; - Ether ; High-gnolecular-weight crystalline polypropylpolypropyli ens.‘ . 0. 92' 158-160- . _______ _. -Insol'__-- -Insol-.._- S011 0.17 0391 I49E ........ __ ‘Insulin. Sol ____ .. Sol; . 1 Amorphous polypropylene .4 ____________________ -.‘ ' 0.55 . 0.85- . ......... .- . 75 I p Toluene 2.40 . crystalline ~ tame 0116. Low-nalolecular-weight 1 v n-Hep- . ‘S01 ____ __ ' . . .1 .. . Sol ____ -_ ,Highly sol. rDeterminedat‘135""0: using tetralin as asolveut;v 2‘isotactic. 3 Made by depolymerizingv the hlgli-molecular-weight. crystallinematerialist-335? C. lntattetra'lin solution-ands nitrogen atmosphere. 4 Atactic-mode according to'conventlonal procedures. A product‘ which is insoluble in‘ boiling n-heptane is principal: chain. It has: a- high melting point v(e.g. 346° practically completely‘ crystalline.“ An‘ ether-extracted polypropylene product. is‘co'mpletelly amorphousv and’ has‘ and: is-"assolid'; highlytcrystalline substance with; for‘v instance, the. following ‘physical. properties: Speci?c.gravity‘..__._e___.g_.. ____ _, 0.90.4092. 60 Tensile strength ASTM Dl638052T presents elastomer-like properties; lbs./ in. 2 _.., _________ __,..___..._.._ 4,600 to 5,400‘. Stiffness (?evual) ASTM D-747-50 lbs/in."z .._____ ______ __, ____ _____ 130,000 65 1/2.” x. 1/2.” bar ASTM D—256~54T ft. lb./in. ________ -F _________ __ 19.. Fusiontemperature, ° F. _____ -_,_.._ 31.6.4 to 3.38. Compressive strengthvASTM D‘—695— 54 lb./in. 3 _________________ __ 9,500-1.1,00.0. Dielectric constant sec.) (106 These isotactic polypropylenes can be‘ prepared‘ from‘. propylene with Ziegler type catalysts inclu'dingcomplexes‘ to 170,000 Impactstrength Izod test unnot'ched. cycles/ __._.. ____________________ __ 2,0---2.1. a much lower transistion temperature. After' sulfochlo rination andvulcanization treatments, the amorphous'type' consisting of'several substances; for‘ instance, the chloridev of a metal with an un?lled electron shell,‘ and: an‘organo? metallic co‘mpoun'cl‘, under‘polymerizationconditions in cluding temperatures" above‘ ambient‘ temperatures; ezg; from about 68°‘to 302° F. and‘pres'sures‘ from about at mospheric or less up tov about 30satmo'splieresj o'r'mo're'; 7.0 With catalysts ofjihigh selectivity‘; very'h‘igh yields of isotactic ‘polymers maybe obtained.‘ The" formation of 3,022,267 3 4 . Natta has found that the production of isotactic poly merizates of alpha-ole?ns requires the presence of solid This invention consists in mixing with the isotactic polypropylene 0.005 percent to 5 percent of a high molecular weight amide which is soluble in the polymer, that is, N-stearoyl p-ann'no phenol to produce an oxygen catalysts which are chemically bound to the growing stabilized product. amorphous, non-crystalline polymers may be almost com pletely prevented. polymer chain. It is probable that such stereospeci?c N-stearoyl p-amino phenol is sold under the trade name catalytic processes are based on the chemisorption of the “Suconox-IS.” It is a white solid which melts at 131 134° C. (268—273° F.) and can, be heated'to above 250° monomer-molecules on the surface of the solid catalyst, and that the adsorbed molecule presents itself always in C. (482° F.) without any detectable evidence of decom position, and appears to be non-toxic. In “Suconox-l8” a de?nite orientation on the growing chain. the “stearoyl” group is a mixture derived from com This type of catalyst is characterized by the presence of compounds of a metal of the fourth to the eighth group of the transition elements in a lower stage of oxida tion. The structure of their atomsjis characterized by mercial stearic acid and is, theoretically, primarily C117H35CO. N-stearoyl p-amino phenol is prepared in general by the incompleteness of the d-shell. Their compounds, in 15 reacting an approximately equimolar amount of stearic anhydride or dry stearic acid with the amino-phenol in a lower stage of oxidation, can enter into associations with metal hydrides or with metal alkyls, whereby com plexes are formed in which metal-hydrogen or metal-alkyl linkages are found in a highly polarized form. In practical operation, the best catalysts are obtained 20 from Ti, V, Cr and Zr. The polymerization catalysts arerproduced by reacting compounds of these metals with alkyls or hydrides of Na, Li, Ba or Al. Compounds of a lower stage of oxidation, such as VCl2 and TiCl2, enter into combinations with the metal hydrides or metal alkyls. This results in the formation of catalysts which act by an anionic mechanism. These catalysts are heterogene ous, due to the presence of a solid phase, which may be colloidal in dimension or microcrystalline. the presence of a solvent or water-entraining agent such as benzene, toluene or xylene. The solid product is then dehydrated by evaporation and the product is ob tained in relatively pure form. . The N-stearoyl p-amino phenol can be used in iso tactic polypropylene over the concentration range of 0.005 percent to 5 percent. However, best results are obtained at about 0.01 to 0.25 percent by weight. It is important ' to obtain adequate dispersion of the N-stearoyl p-amino phenol in the polypropylene and this can be done by mixing the N-stearoyl p-amino phenol with the polymer isotactic polypropylene at a temperature about 5 to 10° F. above the crystalline'melting point of the polymer and Typical catalysts with an anionic mechanism-activity 30 holding this temperature for about 2 to 5 minutes, then removing the heat and letting the temperature drop to cool the mixture at the rate of about 15 to 30° F. in alkyls, solid crystalline lower halides of metals of the about 7 to 10 minutes. The polymer and anti-oxidant preferred transition element group. The quantity of are agitated together as the system is cooled and the metal alkyl required for accomplishing maximum catalytic activity, is relatively small: e.g. 0.1 mol. AlRa per mol. 35 mixture reverts from a liquid to a solid. When the isotactic polypropylene with 0.1 percent N of the halide of the transition element. Natta found it stearoyl p-arnino phenol is placed in a watch glass and advantageous to operate with an excess of this metal held for 15 days in a circulating air oven in the dark alkyl compound, to exert a protective activity by destroy at 150° F. the product shows no change in color. An ing oxygen and moisture which may be present in trace amounts. Otherwise, these substances might poison the 40 isotactic control with no anti-oxidant present gave a are those which are obtained by treating, with metal catalysts. Using the terminology developed for cationic product in the same type test at the same time that was catalysis, Natta hypothesizes that in this type of anionic dark brown in color. The results are recorded in Table H. TABLE II catalysis‘ the transition element compound may be re garded as the catalyst and the other compound, alumi num trialkyl or aluminum dialkylhydride, for instance, as the co-catalyst. Isotactic polypropylene Natta'also found (69, Angewandte Chemie, 213-219 ) that the ?nal reaction velocity after an initial adjustment period is a linear function of the amount of the crystalline constituents of the catalyst and remains constant for a long period of time, sometimes more than Property 50" Original Original after 15 days at 150° F. thirty hours, when the concentration of the catalyst is Original plus 0.1% N-stearoyl p-amino phenol after 15 days at 150° F. 'su?iciently low. The rate of reaction is also a linear M.Pt., ° F .................... __ 330 384 332 function of the‘ propylene partial pressure. The energy Mo]. weight __________________ __ 159, 000 47, 000 144, 000 of activation of the over-all process lies at approximately 55 12,000-14,000 kcal./kmol., a value which is lower than Isotactic, polypropylene has found uses as an addi that found in most of the radical-activated polymeriza tive in wax, white oil, soap and other compositions. This tion processes. The number of active centers created by invention provides a means whereby the isotactic poly the interaction between aluminum triethyl and titanium propylene may be stabilized when admixed with other tnichloride surfaces does not vary markedly with time, 60 materials as well as when it is used asthe major con if the catalyst has attained the ?nal state. stituent of ?ber, ?lm or other materials, along with suit As has been pointed out above, isotactic polypropylene able amounts of other additives such as plasticizers, etc. made according to the process outlined by Natta has valu Although N-acyl p-amino phenols have been suggested able properties for use as a synthetic ?lm or ?ber. How in US. Patent No. 2,654,722, as a suitable stabilizer for ever, it has been found that exposure of this material to various conventional polymers and elastomers of the more light and air causes a darkening of such ?lm and ?ber 65 or less highly cross-linked type, these materials are ap products which seriously a?ects their marketability. Since parently attacked by oxygen in a di?erent manner from these polymers are essentially paraf?nic in nature, and the attack by oxygen on isotactic polypropylene, since since the linearity of them is due to the absence of any few materials which will stabilize cross-linked polymers active centers along the polymer chain, it is hypothe 70 have any stabilizing e?ect on isotactic polypropylene, and sized that the polymer molecule is attacked at its end, since N-stearoyl p-amino phenol has a better stabilizing: since Natta theorizes that a vinylidene group appears at the end of the molecule when it breaks away from the polypropylene. effect on isotactic polypropylene than on non-isotactic “growing surface” of the catalyst. This invention, how ever, is not to be limited by this theory. I claim: 75 ' 1. A composition of matter consisting essentially of 3,022,267 5 solid, crystalline isotactic polypropylene and 0.005 to 5 percent of N-stearoyl p-amino phenol. 2. The composition of claim 1 Which contains 0.01 to 6 , 6., The method of claim 4 which includes cooling the mixture at the rate of about 15 to 30° ‘F. in about 7 to 10 minutes, after the holding step. 0.25 percent of N-stearoyl pqamino phenol. 3. The composition of claim 2 resulting from mixing 5 the ingredients at about 5 to 10° F. above'the melting References Cited in the ?le of this patent UNITED STATES PATENTS point of the polymer. 4. A method of stabilizing a solid, crystalline isotac tic polypropylene composition which comprises mixing the polypropylene and 0.005 to 5 percent by weight of N 10 stearoyl p~amino phenol at a temperature about 5 to 10° F. above the crystalline melting point of the polypropyl ene and holding the mixture at this temperature for about 2,654,722 2,705,227 2,824,089 2,843,577 2,908,670 Young et a1. ___________ __ Oct. 6, 1953 Stamatoff ___________ _.. Mar. 29, 1955 Peters et a1. __________ __ Feb. 18, 1958 Friedlander et a1 _______ __ July 15, 1958 Hagemeyer et a1 _______ __ Oct. 13, 1959 2,921,048 Bell et al ______________ __ J an. 12, 1960 5. The composition of claim 1 in which the isotactic 15 polyropylene has an average molecular weight of from 2,925,400 Tholstrup et a1 ________ __ Feb. 16, 1960 2,939,860 Schramm ______________ __ June 7, 1960 about 100,000 to 1,500,000 Staudinger. 2,957,849 Kennedy _____________ __ Oct. 25, 1960 2 to 5 minutes.