Патент USA US2406837код для вставки
Patented Sept. 3, 1946 2,406,837 UNITED ‘STATES. PATENT OFFICE, STABILIZED POLYVIINYL FLUORIDE ‘Frederick L. Johnston, Claymont, Del., assig‘nor V to E. I. du Pont ‘de Nemours & Company, Wil- ’ . mington, Del., a corporation of ‘Delaware No Drawing. Application ‘November 19, 1943, Serial No. 510,962 2Claims. . V ' 1 (01. 260-88) ' _ softening temperature of polyvinyl ?uoride. Best This invention relates to compositions compris ing polyvinyl ?uoride of improved heat stability, results are obtained by using dicyclohexylamine as the stabilizing compound. Polyvinyl ?uoride‘ containing the stabilizers of this invention can and more particularly to new and valuable mold ing compositions comprising polyvinyl ?uoride. The polymeric vinyl halides and their copoly be heated in a molding press for 5 minutes at 250° mers are subject to discoloration and decomposi tion under the‘ influence of heat. For'example, polyvinyl chloride shows marked evidence of de composition at temperatures as low as 135° C. C. without any discoloration or decomposition, whereas in the absence of stabilizer polyvinyl ?uoride darkens at 225°C. in 5 minutes and de-. composes explosively ‘at 235° C. after 5 minutes The ‘minimum decomposition temperatures. of 10 in a moldingpress. ‘ , " The invention in the examples givenpherein has been illustrated in connection with orientable polyvinylv ?uoride from which the most valuable agents which areeffective for polyvinyl chloride products are obtained for the reasons previously are not effective in the‘case of polyvinyl ?uoride. A successful method forinjection molding of the 15 given. This invention, however, by reason of the vinyl chloride polymers can be raised to some de gree by the addition of stabilizers. Many of these orientable; high molecular weight polyvinyl ?uo markedly greater heat stability conferred, is also ride wouldin particular be desirable because of the high tensile strength and ?exibility of this polymer. In spite of the fact‘that polyvinyl fluo ride is a high softening polymer, it cannot, with ride as ordinarily prepared. The orientable poly vinyl ?uoride can .beprepared by heating vinyl out modi?cation as described herein, be suitably injection molded withoutevidences of decomposi pheres and at a temperature above thes‘decom useful in enhancing ‘the utility of polyvinyl ?uo ?uoride in the presence of an organic peroxy compound. under‘ a pressure above 150 atmos-. position point of the peroxycompound and below that of the vinyl ?uoride. In contrast with the ing press after 5 minutes‘ heating; ~Gradual de 25 non-orientable polymer which breaks after a stretching of a few per cent, a fused sample of composition also occurs even at 200° C. after 15 tion. For example, even at235° C.‘ polyvinyl'?uo ride decomposes explosivelyiin an injection mold or ‘20 minutes heating. - . l the orientable‘ polymer in the form ‘of a ?lm or l ?lament ‘when subjected toilongitudinal stress in the solid state will permanently elongate at least . This invention has as anobject theprepara tion of polyvinyl‘ ?uoride compositions of im proved heat stability.” A further object is the production of polyvinyl ?uoride molding‘ compo sitions comprising polyvinyl ?uoride which are of especial-‘value in the manufacture of polyvinyl ?uoride articles by; injection molding. Other ob-_ jects will appear hereinafter. V . \ - s The above objects ‘are accomplished by incor porating with- a“ polyvinyl ?uoride a stabilizing agent comprising a small amount-of a formalde hyde-reactive compound of the/kind described hereinafter, and in the case of compositions par ticularly adaptedfor molding, by preparing an intimate mixturev of the ?nely divided polymer and the stabilizing agent. ‘ _ The formaldehyde-reactive compounds most advantageously usedsin the practice of this in vention are nitrogen-containing compounds hav ing a replaceable hydrogen attached to the nitro gen, e. _g., primary and secondary amines and amides,~ and in particular ‘the primary and sec ondary aliphatic amines and amides. 1n the preferredl'practiceof this invention poly vinyl ?uoride is powdered and uniformly mixed by grinding with from 0.5% to 2% by weight 100% and up to 400% or more. Before orienta tion it shows an X-ray diffraction pattern charac teristic of a crystalline powder, and after orienta tion it shows the pattern characteristic of an oriented ?ber. 35 ' The invention is further illustrated by the fol lowing examples in which the parts are by weight. Example 1 One hundred parts of orientable polyvinyl ?uoride are ground with 2 parts of urea‘ until a uniformly’ mixed powder is obtained. A sample of this composition is tested ,for heat stability by pressing between aluminum foils in a Carver laboratory press (supplied by Fred S. Carver, New York city), at 250° C. for 5 minutes under 10,000 lbs;/sq_ in. pressure.“ When the vsample is re; moved from‘ the press and cooled, there is ob tamed a water-white ?lm 0.025” thick which is completely fused by the molding ‘process. ‘ There 50 is no evidence of decomposition or discoloration. .A sample of the same polyvinyl fluoride con taining no stabilizer heated in the molding press based on the polyvinyl ?uoride of a primary‘or under the same conditions as above decomposes violently after 2 minutes leaving a charred black _ secondary. amine or amide which boils above ‘the friable residue. 2,406,837 4 3 Example II One hundred parts of orientable polyvinyl pheres. After 15 hours the reaction is complete, 80% of the polymerization having occurred dur aluminum foils in a Carver laboratory press at orientable polyvinyl ?uoride after washing and ing the ?rst '7 hours. The reactor is cooled, pres ?uoride is ground with 1/2 part of dicyclohexyl sure is released, and the product is discharged. amine until a uniform powder is obtained. A sample of this powder is then pressed between O1 It is a friable white cake consisting of 62 parts of drying. 250° C. ‘for 5' minutes under 10,000 lbs/sq. in. In addition to the stabilizing agents mentioned pletely fused by the molding process is obtained. 10 in the examples formaldehyde-reactive com pounds containing phenol groups can be em The product shows no decomposition or discolora ployed, e. g., para-aminophenol. Other phenols tion. can be used although those which do not contain Similarly, when 2 parts of the following com a nitrogen having a replaceable hydrogen are not pounds were uniformly mixed with 100 parts of as effective as are nitrogen containing compounds. polyvinyl ?uoride, no decomposition or discolora The stabilizers are used in amounts from 0.25% tion of the product occurred when molded for 5 15 to 2% by weight for best results. The proportions minutes at 250° C. under 10,000 lbs/sq. in.‘pres-, are usually within 0.1% to 5% since lower pro sure: Hexamethylene-bis-urea, biuret, mono portions give insu?icient stabilizing effect for most acetylurea, monobenzylurea, cyanamide, dicyan purposes and with higher proportions compat diamide, diethylenetriamine, melamine, and pressure. A water-white ?lm of the product com 20 furylamine. Example III ibility with polyvinyl ?uoride decreases and the molded products become weaker. The stabilizers can be incorporated in the polyvinyl ?uoride by dissolving both the polyvinyl ?uoride and the sta .One hundred parts of orientable polyvinyl ?uoe ride is ground with 2 parts of urea until a uniform bilizer in a mutual solvent and evaporating off the then chopped to pass a %" screen. The product is injection molded in a De Mattia, one ounce corporation into polyvinyl ?uoride and to avoid powder is obtained. .This powder is pelleted by 25 solvent. The stabilizer may also be incorporated by grinding it and the polyvinyl ?uoride together, cold pressing at 15,000 lbs/sq. in. pressure and capacity vertical injection molding machine (sup plied by the De Mattia Machine and Tool Com or they may be mixed on a mill. For ready in volatilization during'the molding process, the sta 30 bilizers should have a boiling point above the pany, Clifton, New Jersey). The injection mold softening point of the polyvinyl ?uoride. ing machine is ?tted with a die capable of mold ing test pieces 5" x 1/2" x 1/8”. With an injection cylinder wall temperature of 250° C. and at a pres The stabilizers which are effective fOr polyvinyl ?uoride are unsatisfactory when applied to poly vinyl chloride. For example, polyvinyl chloride sure of 23,500 lbs/sq. in. on the injection piston, 35 pressed between aluminum foils for 5 minutes at tough molded objects are obtained which are faithful reproductions of the die cavity and which showno discoloration or decomposition in com shows a medium brown discoloration indicating a certain amount of decomposition. In this same parison with the original molding powder. Orientable poly-vinyl ?uoride containing no sta bilizer and subjected to the same molding condi tions decomposes violently when it comes in con tact with the heating zone at 250° C. Example IV One hundred parts of orientable polyvinyl ?uo ride is ground with 1/2 part of dicyclohexylamine. 175° C. under 10,000 lbs/sq. in. yields a ?lm which test polyvinyl chloride containing 2 parts per hundred of magnesium stearate, a known stabil izer for polyvinyl chloride, remains light colored. When heated at 175° C. polyvinyl chloride con taining 2 parts per hundred of hexamethylene bis-urea gives a dark maroon, opaque ?lm and polyvinyl chloride containing 2 parts per hundred The polyvinyl ?uoride containing the dicyclo of dicyclohexylamine heated in a press at this temperature gives a dark reddish-brown ?lm ?ecked with black areas of complete decomposi hexylamine stabilizer is injection molded in a De Mattia machine as in Example III under a pres sure of 25,300 lbs/sq. in. on the injection piston tion illustrating that even at the lower tempera tures these compounds, which are excellent heat stabilizers for polyvinyl ?uoride, do not satis and with an injection cylinder Wall temperature factorily stabilize polyvinyl chloride against the of 210° C. By this procedure tough molded ob in?uence of heat. Conversely, many compounds which are effective heat stabilizers for polyvinyl chloride, e. g., magnesium stearate, sodium carbo J'ects of excellent appearance are obtained. A_ method for obtaining the polyvinyl ?uoride : used in the foregoing examples is as follows: A silver-lined reactor is swept with oxygen-free nitrogen and charged with 120 parts of deoxy nate and maleic anhydride are of no value in raising the temperature at which polyvinyl ?uo ride is subject to decomposition. Stabilized polyvinyl ?uorides of this invention genated water, 80 parts of pure methanol, and 0.2 part of benzoyl peroxide. It is then closed, nitro 60 ?nd particular use in molded products since their gen is removed by evacuation, and 100 parts of decomposition temperature is sufficiently raised to vinyl ?uoride containing 20 P. P. M. of oxygen and enable them to be successfully injection and com a trace of acetylene (less than 50 P. P. M.) is ad mitted. The reactor is placed in a reciprocating pression molded without discoloration or decom position. These Products are also useful in melt agitator, ?tted with temperature and pressure re cording and controlling instruments, and connect spinning of polyvinyl ?uoride and in calendering operations where temperatures above 200° C. are ed through a valve to a source of additional mono used. meric vinyl ?uoride of the same purity. Heating and agitation are begun, and when the tempera ments of this invention may be made without ture within the reactor reaches 78° C. additional vinyl ?uoride is injected to raisethe pressure in the system to 250 atmospheres. Reaction sets in and the temperature is maintained at 80° C. Monomeric vinyl ?uoride is injected as rapidly as necessary to maintain the pressure at 250 atmos As many apparently widely different embodi~ departing from the spirit and scope thereof, it is to be understood that I do not limit myself to the speci?c embodiments thereof except as de?ned in the appended claims. ' I claim; 1. A composition of matter comprising poly 2,406,837 ‘ vinyl ?uoride which is stable against discoloration and decomposition when heated 5 minutes at 225° C., said composition comprising polyvinyl ?uoride having dieyclohexylamine intimately dispersed therethrough in amount of 0.1% to 5% by weight of the polyvinyl ?uoride. 2. A molding powder comprising ?nely divided 6 orientable polyvinyl ?uoride having dicyclohexyl amine ‘intimately dispersed therethrough in amount of 0.1% to 5% by weight of the polyvinyl ?uoride, said polyvinyl ?uoride being character ized in that it is capable of being permanently elongated at least 100% under longitudinal stress. FREDERICK L. JOHNSTON.