Патент USA US2406191код для вставки
Patented Aug. 20, 1946 ' UNITED 2,406,191 STATES .PATENT OFFICE 2,406,191 ‘MANUFACTURE OF ELASTIC COMPOSITION SUITABLE FOR ELECTRICAL CABLE IN SULATION Hugh J. Cameron, Gary, Ind., assignor to Edgar F. Seifert, Chesterton, Ind. - No Drawing. Application January 11, 1943. > ‘Serial No. 472,071 6 Claims. (Cl. 260—42) 1 2 The present invention relates to the produc the mixture made into a ?lm or foil with two tion of compounds or compositions having some of the desirable physical characteristics of rub ber, and in particular to‘ such which are useful like rubber for extrusion over a centered strand, rolls running at the same speed, but not with rolls‘ running at different speeds, otherwise such as an electric wire conductor, to effect an bined with a solvent such as carbon tetrachloride. electrical insulating covering. In such extrusion the temperature of the ma The present invention is particularly directed trouble is experienced. The product of g the kneader so made, may be extruded when com chine should be below 80.” C., while the nozzle to a composition which is a mixture, and which should be above 100° C. The solvent is used to derives its properties from its two essential com 10 render the material plastic for the'purpose of ponents. One of these is polystyrene. The other _ is polyisobutylene. It is a general object of the invention to com pound polystyrene and polyisobutylene to form a rubber substitute. It is a particular object of the invention to compound polystyrene and polylsobutylene in such a way that the resulting composition acts‘ extrusion. ' ' Others have attempted to secure mixtures op erative for hot extruding processes, and contain ing- polystyrene and polyisobutylene, but resort 15 ing to a different method to achieve a product capable of extrusion. Instead of combining the said two ingredients, 3, mixture is ?rst made of styrene monomer and polyisobutylene, and this as a homogeneous mixture capable of being ex mixture is treated'to effect polymerization of ‘the truded while hot and under high pressure to pro 20 styrene to polystyrene. The results so obtained vide a rigid non-tacky body, such as a sheath on are not comparable to those attained by the pres a wire, which sheath presents resistance to sof - ent invention, and the differences are attributed tening and ?ow at temperatures “likely to be en in part to the fact that the polymerization of styrene in the presence of polyisobutylene as a countered in use, and presents valuable elec trical properties for use with high tension and 25 diluent therefor, gives a different type‘iof molec high frequency currents in an‘ electrical conduc ular structure to the polystyrene which results. tor insulated therewith. The catalyst for the polymerization is not readily Various other and ancillary objects and ad eliminated. ' vantages of the invention will appear from the The present invention provides a product following description and explanation of the in 30 which is a physical mixture of one polymer con vention. _ sisting of polymerized styrene or polystyrene, with another polymer consisting of polymerized In one instance British Patent No; 534,464, accepted June 6, 1939, states that it is impossible isobutylene or polyisobutylene. It is a type of to mix the two ingredients on mixing ‘rolls. This mixture which the art has not heretofore at.- . is true for some conditions, but not for all con tained, and, contrary to the teachings of the art, ditions, as will be explained hereinafter. it may be subjected .to the action of two mixing The initial objective giving rise to the present rolls of differential speed, under certain condi invention was the provision of a rubber substitute tions. In fact the mixture may be ' initially for insulating electric conductors by the extru effected by use of such rolls, contrary to the sion procedure. In attaining this objective it has, been discovered how polystyrene and polyiso butylene may be successfully combined to give 40 tachings of the art. ' The conventional practice in use of differential rolls, as used in the rubber industry, and as used elastic compositions, some ‘of which are suitable in the art of rubber substitutes, is to use cored for the more exacting requirements of electrical rolls, or hollow rolls, having cooling water run insulation, and others of which‘ have uses other 45 ning through them to carry away the heat of fric tion. Such use of cooled rolls applied to the mix wise. Attempts heretofore have been made to com ture produced by the present invention, ruins-the product, causing it to crumble. bine polystyrene and polyisobutylene, but failures In experiments leading to the present inven and difficulties have been encountered, and prod 50 tion it was discovered that <dispensing with the ucts of only limited value have been attained. Also, British Patent No. 506,855, accepted June cooling water did not overcome the dif?culty, or permit mixing the two ingredients to e?ect a 6, 1939, teaches that polystyrene and polyisobutyl ene may be combined in a kneader in proportions from 1 to 9 parts of any one with the other at uniform mixture. It was also discovered that the ‘introduction of steam into the rolls did not ef temperatures from 100° C. to 200°C" and then 55 fect any new result, until the roll temperature 2,400,191 3 '4 - . ' I with heating. ‘It is commercially defined by mo attained at least 300° F. Below this point a non lecular weight, as calculated from viscosity by uniform mixture merely passes through the rolls and discharges as a non-uniform mixture. But the Staudinger vequation. , It is believed that the following is the equation ‘at and above this temperature for the differen tial mixing rolls, the non-uniform mixture be- 5 soemployed: ‘ gins to smooth out, to lose its shortness, and mu- Ur- l=KMC = ‘tually to combine the ingredients to produce a wherein V smooth plastic elastic composition having many ' _ viscosity of solution of polymer physical properties of rubber, including .that of 0 Ur_ viscosity of solvent ‘extrudability while hot. j K =constant The softness of the‘ resulting uniform mixture when normally cold, and its degree of tackiness, " . C -'—_gram unit groups per liter in solution M =molecular weight of polymer or the lack of it, depend upon both the propor-' tions of the two polymers used, and upon the In carrying out the present invention it is nec degree of Polymerization of each of the poly" 15 essary, in producing the desired mixture of any polystyrene and any solid polyisobutylene, to use For the purpose‘ of providing a suitable elec-' /'mechanical means to effect both a mixing and 1trical insulation, which is su?iciently non-tacky, masticating action, and in so doing to have a and suiliciently resistant to softening and ?ow contact mechanical means at a temperature of at temperatures encountered practically in use of 20 at least 300» R The term “masticating” as used mers. , . ‘electrical conductors insulated with it, de?nite ‘herein, is de?ned as a frictional or shearing ac tion on a mass containing the unmixed materials, wherebythere is a stretching of the mass, as will occur when a relatively thin mass is pinched be lower limits of degrees of polymerization have been determined for each polymer, and‘limitjng ‘proportions of such polymers have also been de jtermined. However, for other uses, and for less 25 tween two. parts moving relatively to each other whereby to effect a tearing and shearing of one" [drastic conditions of exposure of insulated con ductors, polymers and proportions outside of ‘such layer of the material from an adjacent layer speci?cations, may be employed. Polystyrene while said material is in contact at-the point of such mastication with physical means having a ‘30 temperature of at least 300° F, These moving Polystyrene, as the product referred toin the present invention, is a product of polymerizing styrene in the absence of diluents. As ‘the degree of polymerization increases the molecular ‘weight increases. Polystyrene is at normal tem ‘perature a transparent brittle solid, capable of ‘becoming plastic at an elevated softening tem perature, and of ?owing as a plastic mass, es pecially under high pressure. The higher the ' parts may be the nip of heated rolls running at' different speeds in opposite directions, as in con ' ventional rubber-mixing differential rolls: Being' highly viscous and plastic, the masticating action pulls one layer from an , adjacent layer and stretches the mass locally, effecting an ac tion which produces the desired uniform mutual incorporation of the two polymers. The temper; ature of the mass under such action may actually :degree of polymerization, the less is the plasticity 40 be higher than the contact temperature of. the mechanical means, due to friction within them ' or ?ow for a given temperature and applied pres sure. In fact, polystyrene is commercially speci fied by this property, in terms of time of ?ow at locally being masticated. . . - It has been determined that a mass having the polymers unmixed, must be raised in temperature a given temperature under'a given pressure in a ‘speci?ed type of plastometer. such an instm- 45 by contact at the point of mastication with means having a temperature of at least 300° F., in order ‘ment is the Rossi-Peekes plastometer (U; S. Pat to impart to it the property of responding to the ,ent No. 2,066,016), and it is commonly used at mastication for mixing to uniformity. In fact, it has been shown by experience that a product Testing Machine Company, Philadelphia, Penm 50 already mixed to uniformity in accordancerwith the present invention, and in process of mastica sylvania. The method is referred to by the Amer;v 130° C. under 1000 lbs. pressure per sq. in. Such a plastometer is manufactured by 'I‘inius Olsen ican Society of Testing Materials publication ‘ tion between di?’erential rolls at 300° F. or above, will become short and crumble if the temperature of the rolls drops below 300° F. The mixture is value for speci?cations, because polystyrene-is a 55.110‘? thereby destroyed, for each crumb remains as a particle of the mixture. However, the im ‘mixture of higher and lower polymers, and a mo portant point is that conditions which. crumble lecular weight identi?cation is merely an average. ‘the mixture are insu?icient to produce the mix The distribution of all the polymers,-rather than. ture from a non-uniform mixture of the constitu the average molecular weight of the composition ‘predetermines the plasticity or ?ow-time, which 60 ems“ D569-41T. g . The molecular weight of polystyrene is, a poor In producing the composition the preferred ‘are the important properties pertinent to the presentinvention for vdefining polystyrene to be used within the prescribed compositions for high ‘frequency electrical insulation. First, polystyrene is fed to the rolls in quantity " Polyisobutylene a portion of the nip with‘ a mobile mass thereof. method is to use differential rolls heated to at least 300° F., preferably by steam ‘within the rolls. . c5 peripherally to cover the slower roll and to ?ll To this, preferably at the hip, is added a smaller amount of solid polyisobutylene. The latter is, ‘the present invention, is provided by polymerizing preferably in particle form, the smaller the par ‘isobutylene at a temperature below —50° C. and through the use of an amphoteric halide catalyst. 70- ticles, the more speedy the incorporation. 'Con tinuation of the masticating action carries the A low degree of polymerization provides a polymer which is liquid at normal temperature of 70° F. _ added material as a plastic unincorporated sub- stance continually around one roll and through ,As the degree of polymerization increases, a poly- _ Polyisobutylene, as the product referred to in the nip, gradually e?ecting its distribution uni ‘70° F. is attained, which polymer becomes plastic 75 formly into the polystyrene base‘ or the mixture ' mer which-is solid .at a normal temperature of 5 .which results. More polyisobutylene is added uh-r . ' ous products may be made without departing til any desired proportion has been assimilated. from the spirit and scope o1’v the invention as ex vAll th desired polyisobutylene may be added at pressed in the appended claims. , = _ once, i the ?rst instance, or it may be added in I claim: , stages, or it may be added gradually at a uniform 1. The method which comprises subjecting rate. The quickest results are obtained by add polystyrene consisting of a polymerized mass o'rig- ' ing it throughout a period of time as it is seen inally consisting substantially entirely of styrene that the mass is becoming smooth and uniform and characterized by a ?ow-time of at least 120 from the assimilation of that previously added. seconds for a flow of 1.5 inches as tested in a. In the end, a mastic, elastic, rubber-likev sheet Rossi-Peekes plastometer at 130° C. with 1,000 _ may be removed from the slower roll around lbs. pressure per sq. in., to the masticating mix which it forms, as in conventional rubber prac ing action of two adjacent parallel mixing rolls tice, the di?erence being that the material is at having a plastieizing temperature for the poly- ' Y a higher temperature than in the case of using styrene of at least 300° F. and rotating in oppo such mixing rolls with other materials. site directions at different speeds, whereby the For the purpose of. desirable extrudable elec polystyrene is rendered plastic and capable of as trical insulation, which is suitably resistant to softening and ?ow with heat, and substantially similating polyisobutylene, continuing the vmasti cating action and gradually adding to\ the mass being masticated a polymer consisting of poly non-tacky, a polystyrene is used having a ?ow time of at least 120 seconds for a ?ow‘of 1.5 20 isobutylene characterized by a normally solid inches in a Rossi-Peekes plastometer at ‘130° C. state at 70° F. and by a molecular weight of at and at 1000 lbs. pressure per sq, inch. A poly least 60,000, as determined by viscosity using isobutylene is used having a molecular weight of the Staudinger equation, until a quantity of from at least 60,000 as determined by viscosity by the 1 to 9,)parts of polyisobutylene has been added to ‘ Staudinger equation. > Having selected such polymers the proportions 25 1 part of polystyrene, whereby the added poly isobutylene is gradually incorporated into a re used are from 1 to 9 parts by weight of polyisoé sulting uniform ‘mixture of said polystyrene and butylene to 1 part by weight of polystyrene. This said polyisobutylene, and after the addition of gives limiting compositions of one mixture hav the last of the polyisobutylene continuing the ing equal parts of each polymer, and another 30 mastication until the last added material is uni ‘mixture having 10% by weight of polystyrene. formly incorporated into the mixture. Mixtures within this range are substantially non 2. The method which comprises subjecting tacky, are extrudable by heat, suitably resistant polystyrene consisting of a polymerized mass orig to softening and flow under heat below 300° F., inally consisting substantially entirely of styrene and of varying degrees of softness when cold, the 85 and characterized by a ?ow-time of at least 120 equal-part mixture being the least soft. seconds for a flow of 1.5 inches as tested in a Such a mixture may be placed in a rubber .Rossi-Peekes plastometer at 130° C. with 1,000 extruding machine having a moving conductor lbs. pressure per sq. in., to the masticating mix centered in the ori?ce or nozzle, and having high ing action of two, adjacent parallel mixing rolls mechanical pressure active on the mixture. The 40 having a plasticizing temperature for the poly mixture must have a temperature of at least 300° styrene of at least 300° F. and rotating in oppo F, in the body behind the ori?ce, but where a site directions at different speeds, whereby the nozzle of uniform cross-section may lead from the initial ori?ce, the nozzle may be colder than 300° F., and preferably is colder, whereby the dis 4 charged extruded mass is chilled to a rubber-like solid sheath over the conductor. . ' Such a sheathed conductor may be bent to polystyrene is rendered plastic and capable vof assimilating polyisobutylene, continuing the mas ticating action and gradually adding to the mass being masticated a polymer consisting of poly isobutylene characterized by a normally solid state at 70° F., until a quantity of from 1 to 9 parts of polyisobutylenehas been added to 1 part of poly small angles without breaking, due 'to the clas ticity of the ‘mass, and in mechanical respects 50 styrene, whereby the added polyisobutylene is acts like a vulcanized rubber covering. gradually. incorporated into a resulting uniform Where a product of the invention is mixed mixture of said polystyrene and 'said ‘polyiso as described‘above, it may be sheeted in calender butylene, and after the addition of the last of rolls running at the same'speed, provided they are heated to 300° For higher. Any pressure molding operation effecting a material tempera_ ture of 300° F. or higher may be employed. Tacki the polyisobutylene continuing the mastication until the last added material is uniformly incor porated into the mixture. 3. The method which comprises subjecting poly ness of a composition, as for example result styrene consisting of a polymerized mass origi ing from use of a solid polyisobutylene having a nally consisting substantially entirely of styrene molecular weight value lower than the speci?ed 60 and characterized by a ?ow-time of at least 120 ‘ 60,000 is permissible, depending upon the use to which the product is put. Even tackiness of a seconds for a ?ow of 1.5 inches as tested in a Rossi-Peekes plastometer at 130° C. with 1,000 lbs. sheath on a conductor is permissible, where other pressure per sq. in., tov the masticating mixing ac covering, such as fabric or metal is placed over tion of two adjacent parallel mixing rolls having a sheath consisting of a mixture of independently 65 a plasticizing temperature for the polystyrene polymerized styrene and independently polymer- ‘ of at least 300° F.‘ and rotating in opposite di ized isobutylene, characterizing the present inven rections at different speeds, whereby the poly tion. styrene is rendered plastic and capable of as ' Tackiness of a layer calendered at 300° F. or over, as onto a fabric, is advantageous, as for ex ample in making an adhesive or friction tape. For such a purpose, ‘paper, cloth, Cellophane and the like may be adopted as the base. 'similating polyisobutylene, continuing the mas 70 ticating action and gradually adding to the mass being masticated a polymer consisting of poly isobutylene characterized by a normally solid state , at 70° F. and by a molecular weight‘ of at least From the foregoing it will be appreciated that 60,000 as determined by viscosity using the ‘Staud numerous variations of the process, and numer 75 lnger equation, until a quantity of from 1. to 9 ' 2,406,191 7 A ' _ parts of polyisobutylene has been added to 1v part of polystyrene. whereby the added polyisobutylene ' opposite directions at different speeds. whereby the polystyrene is rendered plastic and capable of assimilating polyisbbutylene, continuing the masticating action and gradually adding to the l is gradually incorporated into a resulting uni " form mixture of said polystyrene and said poly ‘ isobutylene, and after the addition of the last of mass being masticated a polymer consisting of polyisobutylene characterized by a normally solid the polyisobutylene continuins the mastication state ‘at 70° F. and by a molecular weight of at 3 until the last added material is uniformly incorii porated' into the mixture, and sheeting the re: least 80,000 as determined byviscosity ‘using the -j suiting uniform mixture between rolls operating . Btaudinger equation, until a ._uantity of from 1 ‘ at the same speed and having a'plasticizing tem 10 to"9 parts of polyisobutylene has been added to 1. part of polystyrene, whereby the added polyiso ‘ perature for the mixture of at least 300° F. butylene is gradually incorporated into a result 4. The method which comprises subjecting ing uniform mixture of said polystyrene and said 3 polystyrene consisting of a polymerized mass orig , inally consisting substantially entirely of styrene ' polyisobutylene, and after the addition of the last and characterized by a flow-time of at least 120 15 of the polyisobutylene continuing the masticaq tion until the last added material is uniformly seconds for a ?ow of 1.5 inches ‘as tested in a ‘ nossil-Peelies plastometer at 130° C.'wi_th 1,000 . . incorporated into the mixture, and extruding the resulting mixture by. applied mechanical pressure lbs. pressure per sq. in., to the-masticating mix while saidimaterial is softened and extrudable at 1 ing action of two adjacent parallel mixing rolls having a plasticizing temperature for the poly-' 20 a temperature of at least 300° F. . 6. The method which comprises subjecting styrene or at least 300° F. and-rotating in oppo ~ site directions at different speeds, whereby the polystyrene consisting of a polymerized mass orig 1 polystyrene is rendered plastic and capable of assimilating polyisobutylene, continuing the mas and characterized by a ?ow-time of at least 120 inally consisting substantially entirely of styrene ‘ ticating action and gradually adding to the mass being masticated a polymer consisting of poly isobutylene' characterized by a ‘normally solid‘ 1 state at 70° F. until a quantity of from 1 to 9 ‘ parts of polyisobutylene ‘has been added to 1 part of polystyrene, whereby the added polyisobutylene 3 is gradually incorporated into a resulting uniform I mixture of said polystyrene and said polyisobu- 1, seconds for. a‘?ow of 1.5 inches as tested in a Rossi-Peekes plastometer at 130° C. with 1,000 lbs. pressure per sq. in., to the masticating mixing action of two adjacent parallel mixing rolls hav ing a plasticizing temperature for the polystyrene of at least 300° F. and rotating in opposite direc tions at di?érent speeds, whereby the polystyrene is rendered plastic and‘ capable of assimilating polyisobutylene, continuing the masticating action ‘ tylene, and after the addition of the last of the and gradually adding to the mass being masti . the last added material is uniformly incorporated as cated ‘a polymer consisting of polyisobutylene characterized by a. normally solid state at 70°F. 1 into the mixture} and sheeting the resulting uni until _a quantity of from 1 to 9 parts of‘polyiso form mixture between rolls operating at the same ‘ butylene has been added to 1 part of polystyrene, ‘ speed and having a plasticizing temperature for polyisobutylene continuing the mastication until whereby the added polyisobutylene is gradually ' the mixture'of at least 300° F. 5. The method which comprises subjecting polystyrene consisting ‘of a polymerized inass 5 originally consisting substantially entirely of 40 incorporated into a resulting uniform mixture of styrene and characterized by a ?ow-time of at said polystyrene and said polyisobutylene, and after the addition‘ of the last of the polyisobu tylene continuing the mastication until the last ; least 120 seconds for a ?ow of 1.5 inches as tested ' , added material is uniformly incorporated into the f in. a Rossi-Reekes plastometer at 130° C. with 1,000 lbs. pressure per sq. in., to the'masticatins mixing actiongof two adjacent'parallel mixing . rolls having a plasticizing temperature for the ~ ‘ polystyrene of at least 300° F. and rotating in > mixture, and extruding the resulting mixture by applied mechanical pressure while said material is softened and extrudable at a temperature of atleast 300° F. . ' Y , v p . HUGH J. CAMERON.