Patented Jan. 20, 1948 UNITED smug-mew0mm f - POLYETHYLENE STABILIZED WITH BIS (HYDROXYPHENYL) PROPANES ' Georgev H. Latham, and Daniel E. Strain, Wil mington, -Del., assignors to du Pont de Nemourssdr'company, Wilmington, Del._, a cor poration ofDelaware ' " ' ' ' \ No Drawing. ApplioationFebruary3,1944, ; _ ' Serial No. 520,954 - 5 Claims. ‘(01. 260-94) This invention relates to new compositions of matter and particularly to new compositions of matter comprising normally solid polymers from . 2 , » oughly distribute .itv throughout the polymer...v \ This-‘can .be accomplished in any machine suit,-, \ able for mixing solids, as by millingthe ethylene ethylene. This application is in part a continua polymer on heated rolls,‘such as are used-inthe' . tion of our copending application S. N. 474,850 5 compounding of rubber, or other suitableymillin'g . filed February 5, 1943. ' equipment, and adding agent theretal Instead In the practice of this invention any normally of adding the agent to the polymer in the'solid or‘ solid polymer of ethylene made either by the molten state it can be addedto a solution or processes of U. S. Patents 2,153,553 or 2,188,465 suspension of polymer in an organic Solvent ,01‘ 0r by contacting ethylene with water and a 10 to an aqueous dispersion thereof. Thepolymer Deroxy compound catalyst, preferably a diacyl containing the agent. or the Solution. emulsion, peroxide or a dlalkyl dioxide, at temperatures of or dispersion of polymer containing added agent from 40° to 350° C. and at pressures in excess of can be formed into any desired'shape atmospheric, preferably in the range of 50 to Through the use of the agents described here 1500 atmospheres, can be used_ The polymers of 15 in it has been found that three kinds of‘stabiliza ethylene correspond in composition substantially tion can be brought about, namely, stabiliza to (CH2) I, have molecular weights in excess 01' tion against heat-degradation, against light 4000, and soften 0r melt between about 100° c, degradation, and against degradation upon out and about 120° C. and their melting point is subdoor exposure. stantially independent of their molecular weight, 20 In general, the amount of agent to be added to On the basis of their known structure it wguld the ethylene polymer depends upon the agent be expected that these ethylene polymers would used, and upon the degree and kind of stabiliza show unusual stability to oxidative and other tion desired. The amount of agent added can degradative agencies. It has been found, howvery up to 50% on the weight of the ethylene D01 ever, that when 'these ethylene polymers are ex- 25 ymer but as a rule it is preferred to use the mini posed for prolonged periods to weathering agenmum amount required to achieve the desired re cles, light or heat in contact with air, they Show sults. The amount commonly used will vary from severe degradation, as evidenced by loss in ten0.1 to 5 parts by weight per hundred parts eth sile strength, elongation, and tear resistance. ylene polymer It is accordingly an object of this invention 30 In one form of practicing the invention the eth to provide compositions comprising ethylene polylene polymer is dissolved in a hot organic hydro~ ymers, including its interpolymers, which have carbon solvent, e. g., xylene, and to this solution improved stability. Another object is to provide is added the agent in amount sufficient to give 1% compositions comprising ethylene polymers which thereof on the polymer. These solutions are cast in the form of self-supporting ?lms, molded arti- 35 on steel plates, the thickness of the ?lm is ad cles, ?bers. or coatings have improved heat and justed so as to give a dry ?lm of about 1 'mil in light stability and improved durability upon outthickness, the solvent is removed by evaporation, door exposure. Still another object is to provide and, after drying, the ?lm is stripped from the new compositions comprising ethylene polymers plate and as a minor component a substituted phenol, a 40 The examples which follow illustrate the utility polyhydric phenol, an aryl amine, a long chain and the outstanding advantages of this invention. aliphatic amine, a heterocyclic compound conExample 1.—A solution of a polymer of ethyl taining annular nitrogen, or a polymeric amino one having an intrinsic viscosity of 0.55 (meas nitrogen containing substance. Other objects tired as a 0.125% solution in Xylene at 85° (3-) will appear hereinafter, ' , The above objects are accomplished according to this invention by incorporating into a normal- 45 and a calculated molecular weight of about 9,200 was prepared by dissolving 10 parts of the poly mer in 90 parts of hot xylene. To this solution ly solid ethylene polymer a small amount of an was added a su?lcient amount of the agents list agent such as a substituted phenol, a polyhydric ed in Table I, to give 1% thereof, based on the phenol, in any suitable'manner that will thor- 50 polymer. These solutions were poured over steel 2,434,602 3 4 plates and the ?lm thicknesses adjusted so as to give a dry ?lm of about 1 mil in thickness. After evaporation of the solvent the films were stripped from the plate and exposed to heat. light, and outdoor conditions. These ?lms were tested for tear resistance both before and after various pe riods of exposure. Typical results are shown be low: Table I slot in the edge of the dim. Values are expressed in units of grams to tear 2" of ?lm 1 mil in thick ness, and represent the average or duplicate or triplicate measurements. In place 01' the substituted phenols oi’ the ex amples there can be used bls(4-hydroxyphenyl) dimethyl methane (diphenylol propane), bis(4 hydroxy - 3 - methylphenyl) propane), bis(4-hydroxy-3-chloro phenylidimethylmethane, bis(4-hydroxyphenyl; methyiethylmethane, None .......................... .. Bis(2-hydroxy-4,6-dimethyl , 1,000 500 hrs. hrs. 67 64 23 57 63 33 bis(4 - hydroxyphenyl) phenylmethane, bis(4-hydroxyphenyl) dipropyl methaneI bis(4-hydroxy-3,5-dimethylphenyl) di Stabilizer inal dimethyl methane 10 (dicresylol Tea: Resistance Alter iade-ometer Orig , pies and starting the tear from the end of a 115" 1,500 hrs. methylmethane, 4-hydroxyphenyldimethylbutyl ~methane, 4-hydroxyphenyltriethylmethane, 4 hydroxyphenyldimethylisoamylmethane, and the like. Polyhydric phenols, in addition to hydro The fade-ometer in which the above exposures 20 quinone, useful in the practice of this invention were obtained was operated at approximately include catechol, resorcinol, pyrogallol (1,2,3-tri phony ) propyl methane ..... _. hydroxybenzene), phloroglucinol (symmetrical trihydroxybenzene), p,p'-dihydroxydiphenyl and 100° C. and 100% relative humidity. Example 2.—-A polymer of ethylene‘was pre pared by contacting ethylene containing 60 parts the like. per million of oxygen with water at a tempera 26 Aryl amines, in addition to those of the ex ture of approximately 200° C. and at a pressure amples, which are useful include octyl-phenyl of 1,000 atmospheres. The polymer had a melt amine, octadecylphenylamine, p,p'-diaminodi viscosity of 0.02. One batch of the polymer was phenylmethane, triphenylamine, alpha- and untreated, a second milled with 2% phenyl-beta beta-naphthylamines, decyl - beta - naphthyla naphthylamine, and a third with 2% of hydro 30 mine, dodecyl-alpha-naphthylamine, octadecyl quinone. Each batch was rolled into sheets of ap proximately 1 mil in thickness and placed in an beta-naphthylamine, symmetrical phenyl-naph thyl-ethylene-diamine, symmetrical dinaphthyl oven maintained at 100° C. An atmosphere of air surrounded the products during the treat ment. At the end of 4 weeks the products were removed from the oven, moldings prepared, and tensile and elongation measurements were made. Original and ?nal values are given in Table II. mine, and the like. Long chain aliphatic amines useful in the prac tics of this invention are those containing at least Table II 2'7 Hydro (fuinone Orig. 4 Wks. Orig. 4 Wks. Orig. 4 Wks. lbs. q. strength, ‘ ...... _. 2,(XX] Elongation at rea .......... -. 525 Melt viscoslty..... 0.02 8 carbon atoms. Typical members of this class of compounds include dioctylamine, octadecylamine, 40 2'7 nhenyl-betr No stamina 'iaophthylarninr Tensile ethylenediamine, diphenyl paraphenylenedia 850 1,800 l, 950 1,800 1,375 25 500 400 500 125 0.02 0.01 0.02 0.002 1 Inlusible. Example 3.—A sample of polythene was milled didodecylamine. octyldecylamine, dodecylamine, dodecyltetradecylamine, dihexadecylamine, tri butylamlne, and the like. Heterocyclic compounds containing annular nitrogen include the pyridines, dipyridyl, quino line, melamine, and nitrogen bases extractable 45 from petroleum, those obtained from shale, or obtainable by pyrolysis of cottonseed meal. These nitrogen bases are complex mixtures of com pounds and may be classi?ed in a general way into aromatic bases, e. g., methylated quinolines and hydroaromatic bases, e. g.. the pyrindacine base CIBHZSN. The polymeric amino nitrogen-containing‘ sub stances are derived from ammonia or from mono for one hour on a small rubber mill, the rolls of meric amino nitrogen-containing compounds and which were heated to 150° C. This operation was repeated with the addition in one case of 0.1% 55 are characterized by being substantially insoluble dicresylol propane to the polythene at the start of the milling period and in the second case with the addition of .01% 0t diphenylol propane. Suit able samples for determining power factor were prepared from the milled material. The power factor at 3000 me. was .0011’! for polythene milled in the absence oi.’ stabilizer, 00076 when dicresylol propane was present during the one-hour milling period and .00064 when diphenylol propane had been added. The tensile strength and elongation measure in water and soluble in 2% aqueous acetic acid ments described in Examples 2 and 3 were meas ured on samples 1" long and 1/4" wide, and all (2) Resinous reaction products oi’ amino ‘al cohols and a substance from the group of acrylic measurements were made in triplicate or more on and alkacrylic acids. and/or organic solvents. The amino nitrogen can be primary, secondary or tertiary and can be part of an open chain or of a cyclic structure. These polymeric amino nitrogen-containing sub stances can be divided into sub-groups as fol lows: (1) Resinous reaction products of phenols, aldehydes, and a material from the group con sisting of ammonia, primary amines, and sec ondary amines, 8. Scott pendulum type tester using a stretching 70 (3) Resinous reaction products of amino’ phenols with aldehydes. rate of 20 inches/min. Results of tensile strength are given in lbs./sq, in. and elongations are in per (4) Reslnous reaction products of alkyl ke cent to break. tones with formaldehyde and a substance selected Tear resistances were measured on an from the group of ammonia. primary amines. Elmendort type tear tester, using 1" square sam 76 secondary amines. and tertiary amines. 2,434,662 5 (5i Resinous reaction products of diaryl guani dines with aldehydes, especially formaldehyde. (6) Resinous reaction products of diaryl guanidines with aldehydes, especially formalde ' hyde, and either a primary or a secondary amine. (7) Resinous reaction products of aryl amines with aldehydes or ketones. - (8) Resinous reaction products of vinyl ketones with either ammonia or primary or secondary amines. ‘ (9) Resinous reaction products of phenols} piperazine, and aldehydes, especially formalde hyde. (10) Resinous reaction products of dimethylol urea dimethyl ether with amines. (11) Resinous reaction products of polyvinyl chloroacetate with secondary aliphatic amines. (12) Resinous reaction products of urea, formaldehyde, and aliphatic primary or second The compositions of this invention can be extruded about wire orother electrical conduc tors, or they can be formed into tapes or ribbons and applied about the wire or other electrical conductor. ' In the above electrical use the compositions of this invention can be employed as such or they can be modi?ed with such materials as pigments, ?llers, para?in wax, or polymeric materials such 10 as rubber, hydrogenated rubber, polyisobutylene, polystyrene, polybutadiene, etc. The remarkable stability against heat ofthe compositions of this invention renders them more suitable than unstabilized ethylene polymers for melt extrusion of ?lms, ?bers, ?laments, and coatings, or for other melt manipulations. The physical properties of objects prepared from ethylene polymers by melt manipulation are in ary amines containing less than» 5 carbon atoms. 20 ?uenced by the temperature used. Tempera tures above 185° C. are preferred, providing that (13) Reaction products of phenol-lignln with degradation of the polymer can be avoided. Un dimethylamine and formaldehyde. (14) Resinous reaction products obtained by stabilized compositions suffer serious degrada tion at such temperatures, even when practical precautions to exclude oxygen from the polymers 25 have been taken. However, the stabilized, com containing resins. positions of this invention are resistant to Combinations of two or more of the agents degradation under these conditions. Such ?lms can be added to the ethylene polymer, particu the catalytic hydrogenation, in the presence of , ammonia or a primary amine, of ketone group are useful as unsupported ?lms or in coatings or laminations, while the ?bers or ?laments can be 30 knitted or woven into valuable fabrics, tubings, The agents of the invention are effective in etc. larly when stabilization against more than one degradative agency is desired. protecting the ethylene polymers against degrada We claim: tion catalyzed by copper and its compounds. 1. A composition of matter comprising a nor Because of their excellent stability the ethylene polymers containing the agents of this invention 35 mally solid ethylene homopolymer and from 0.01 to 5 parts by weight of a compound selected from are advantageously used as binders, coatings, and the group consisting of diphenylol propane and . impregnating agents in the manufacture of elec dicresylol propane. ' trical insulating materials. In sheet form the 2. A composition of matter comprising a nor~ compositions of this invention can be used as condenser plate separators, as separators in stor 40 mally solid ethylene homopolymer and 0.1% by weight of dicresylol propane based on the age batteries, and as separators for the layers ethylene polymer. _ of coils in transformers, and also as external insulation on all sorts of coils such as are used 3. A composition of matter comprising a nor mally solid ethylene homopolymer and 0.1% by in electrical machinery, radio, telephone, tele of diphenylol propane based on the graph, and miscellaneous electrical and elec 45 weight ethylene polymer. tronic apparatus. 4. A composition of matter comprising a nor In the form of sheets the compositions of this invention are valuable as so-called slot insula tion in dynamo electrical machines such as mo tors and generators. In dynamos the connect 50 ing coils are positioned in slots which are formed in the magnetic core and which are lined with suitable insulation. Machines of this type are mally solid ethylene homopolymer and from 0.01 to 5 parts by weight of diphenylol propane per 100 parts of polymer. 5. A composition of matter comprising a nor mally solid ethylene homopolymer and from 0.01 to 5 parts by weight of dicresylol propane per 100 parts of polymer. improved when the coil insulations, the slot lin ing, or both, comprise the compositions of this 55 GEORGE H. LATHAM. invention. The connections between the coils DANIEL E. STRAIN. ‘and the so-called end-windings are preferably insulated with the compositions of this inven REFERENCES crrnn tion. The connections between the coils may be The following references are of record in the Q covered 'by a sleeve which is preferably composed of the compositions of this invention in order 00 file of this patent: ‘ that the sleeve may have the desired ?exibility, UNITED STATES PATENTS insulating properties, and permanence. Sheets Number Name Date may be punched into segments of the proper 2,270,959 Murke __________ __ Jan. 27, 1942 shape as spacers between commutator bars of Hop? __________ __ Nov. 16, 1943 automotive, aero and like motors and generators 65 2,334,195 2,336,195 Sparks _____ _______ __. Dec. 7, 1943 for direct current and for alternating frequency currents. Motors of this kind are particularly OTHER REFERENCES . useful in devices and locations where the ma chines are exposed to conditions abnormally de stru'ctive to conventional insulation. Swallow, Endeavour, vol, 3, pages 26-31 (Jan. 70 1944).