Document Vj8Xyk1ovLO0qJYJad66zy6oq

i.3iEHAL IBB CO, Patented Oct. 4, 1949 2,483,469 UNITED STATES PATENT OFFICE 2,483,469 BASIC LEAD PHOSPHITE PIGMENTS Leonard M, Kebrlch, Brooklyn, N. I, assignor to National Lead Company, New York, N. Y., a corporation of New Jersey No Drawing. Application February 14,1947, i Serial No. 728,721 4 Claims. (CL 106--297) 1 This invention relates to basic lead phosphite compositions useful as pigments and more par 2 tion catalyst, namely lead acetate, to facilitate the reaction. ticularly to the preparation and use of dibasic When the dilute phosphorous acid Is added to lead phosphite and combinations of this com the aqueous suspension which has a pH value of pound with monobasic lead phosphite. approximately 9.3, no change in the pH value Monobasic lead phosphite is known and has occurs until, on the addition of sufficient phos been previously prepared by prolonged digestion phorous acid the suspension turns white. At of normal lead phosphite with ammonium hy this point a lowering of the pH value to 6.9 droxide and by reacting a solution of basic lead place and the white solid phase is found to con acetate with ammonium phosphite. The prod 10 tain on analysis 90.17% PbO, 4.18% P and 2.43% ucts thus obtained by the prior art methods have HsO, corresponding to the compound dibasic lead been identified as monobasic phosphites and were phosphite, 2PbO.PbHPCh.l/2HjO. This com found to contain a maximum of 85.9% lead oxide pound is constituted of well defined aclcular crys PbO, corresponding approximately to the formula tals which are anisotropic in character. Due to for monobasic lead phosphite hemi-hydrate, 15 the difficulties of obtaining proper optical orien Pb0PbHP03.1/2H30. Other basic lead phos tation, the several indices of refraction were not phite compounds have not been described previ easily determined, but one of the refractive in ously, so far as is known. dices was found to be about 2.25. The tinting A principal object of this invention is to pro strength of this pigment was found to be un vide a white basic lead phosphite composition 20 usually high, approaching a value of 300 in com useful for pigment purposes containing more parison to 100 for Dutch process white lead, than 85.9% PbO. Another object of this inven when tested by the method described in "Exami tion is to provide a new chemical compound, di nation of Paints, Varnishes, Lacquers and Colors," basic lead phosphite, corresponding to the for by H. A. Gardner, 6th edition, p. 65. mula 2Pb0JPbHP03. 1/2Hj O. Another object of 25 On further treatment with phosphorous acid, this invention is to provide basic lead phosphite the dibasic lead phosphite is converted to mono pigments characterized by high tinting strength basic lead phosphite, PbOPbHP03.1/2HjO, dur and opacity. A further object is to provide sur ing which conversion the pH value of the sus face coating compositions containing basic lead pension remains constant at about 6.9. Thus, by phosphite having excellent opacity and covering 30 maintaining the pH value of the suspension at power and further characterized by excellent re about 6.9, it is possible, by using calculated sistance to weathering. A still further object of amounts of materials, to produce mixtures of di this invention is to provide white rust inhibiting basic and monobasic lead phosphite. These pig surface coating compositions especially valuable ments are insoluble In water and desirable from for protection of metal surfaces against corro the standpoint of their pigment properties. sion. These and other objects will be apparent For the purpose of being more clearly under from the following description of the invention. stood, the preparation of dibasic lead phosphite This invention in its broadest aspects contem and mixtures of the dibasic and monobasic lead plates the preparation of a new chemical com pound, dibasic lead phosphite, and also coalesced in phosphite will be illustrated by the following ex- ""P181 Ex a mp l e I mixtures of this compound with monobasic lead phosphite, in finely divided form, adapted for Dibasic lead phosphite use as a pigment. The primary product of this invention, dibasic lead phosphite, represented by the formula 2PbO.PbHPC>3.1/2HjO, is in the form of fine aclcular crystals, is of good white color, and possesses high tinting strength and covering 43 1200 grams of finely powdered litharge were suspended in 6 liters of water containing 1.2 grams of glacial acetic acid. The suspension was heated to about 50* C. and vigorously agitated while 507.1 grams of a 29% phosphorous acid power. A general method for preparing dibasic lead phosphite is first to prepare a finely powdered suspension of lead monoxide or litharge in warm water containing a rnan quantity of lead acetate and then while agitating, slowly adding dilute phosphorous acid, using amounts sufficient to pro 50 solution was slowly added over a period of 5% hours. The white solid obtained on filtration was found on analysis to contain 89.9% lead oxide, 7.30% phosphorous trioxide and 2.8% com bined water corresponding to the formula 2PbOPbHPOj.l/2HjO. duce the dibasic salt. It will be noted that the 55 Ex a mp l e n process of this invention differs from the proc esses of the prior art in that lead oxide and phos Equimolecular mixture of dibasic and monobasic lead phosphites 3,483,489 of glacial acetic acid. The suspension was heated proper drying after each coat. The panels were to about 50 C. and while stirring, 113.1 grains of a 29% phosphorous acid solution was gradu exposed to natural weather conditions on ver tical test fences with a southern exposure. After ally added over a 5% hour period. The white 33 months the relative ratings of the two paints, product after being filtered and dried, was found with 10 the optimum, were as follows: to contain 88.4% lead oxide and 8.70% phos phorous trioxide and 2.9% combined water. The methods described in the preceding ex 1 amples are convenient for laboratory procedures. A method more adapted to commercial practice, however, Is to mix the components in their proper rihflclring 8 7 10 1 proportions with water and to grind them to 10 8 gether in a- ball mill or other conventional grind ing mill for several hours In which case a com It is thus evident that outside white paints plete reaction Is effected at normal room tempera 15 prepared from dibasic lead phosphite are ap ture. Such a procedure is Illustrated by the fol proximately the equivalent, in respect to weath lowing example: Ex ampl e HI ering, of those prepared from basic carbonate white lead which has long been recognized as the standard pigment for exterior paints. Dibasic lead phosphite 20 That dibasic lead phosphite is also suitable as A mixture consisting of 1200 grams litharge, 507.1 grams of a 29% phosphorous acid solution, a rust inhibiting or anti-corrosion paint as illus trated by the following: 1.2 grams of glacial acetic acid and 6 liters of Ex amp l e V water was placed in a 5 gallon porcelain lined ball 25 The following paints were prepared in the mill with 14 lbs. of flint pebbles. The mill was usual manner. sealed and rotated for several hours at room temperature. The reaction product, a suspen sion of fine acicular crystals, was transferred to a 34 tray and dried at about 60 C. The dried product was found to be dibasic lead phosphite, compara ble to the product of Example I. Lead phosphite pigments prepared as outlined above may be made into surface coating compo 34.1 Iron oxide.-___7.____-............................................. do----- Cuinarone-Indeiie coal tar resin............................ do___ Coal tar naphtha.....................................................do------ 7.1 10.6 25.6 22.6 42.4 6.9 10.3 24.9 15.5 sitions, such as paint, by ordinary well known methods. The physical and chemical properties, 35 These paints were equivalent in composition useful for compounding paint formulations, for on a volume basis when corrected for the volatile both dibasic and monobasic lead phosphite are thinner content. tabulated below. Compositions consisting of They were applied to hot-rolled steel panels, coalesced mixtures of the dibasic and monobasic salts will show properties dependent on the pro 40 both sides, two coats being employed. A cover coat of a suitable anti-fouling paint was then portionate amount of each present in the com applied. The panels were tested by immersion position. in marine waters. After 13 months immersion the two paints were examined. The results are Dibasic Lead Phosphite Monobasic Lead Phosphite noted below, where a rating of 10 indicates opti45 mum resistance to the type of failure under question. Percent PbO___ Specific gravitycrystal Habit... Tintinz strength. Oil absorption .. Solubility in water. 2PbO.PbHPOi.l/2HjO.. 90.2%................................. 6.95-'-.-................ ............ 250-300.............................. 17 .............................. PbO.PbHPO.l/2HtO. 85.9% 6.95. acicular. white, about 220. 15. Insoluble. Paint No. 50 General appearance--blistering Peeling from metal base. ....... General rusting________ ______ The paint containing dibasic lead phosphite By way of illustration of the utility of dibasic 55 has shown superior resistance to the corrosive lead phosphite in coating compositions, the fol effects of sea water immersion, as shown by these lowing examples are cited. tests. Ex amp l e IV The lead phosphite compositions of this inven tion may be used generally for applications where The following paints were prepared in the 8 lead pigments are valuable. These will include usual manner. use in surface coating compositions, printing inks of various kinds, pigmentation of rubber, plastics 12 and other materials. Also the lead phosphite products of this invention will be found to be use 1,437.5 65 ful in applications where finely divided lead com Alkali refined linssed oil...............................do___ Acid refined linseed ofl ................................do___ Heat bodied linseed oil (Q)........................... do-- Liquid drier.,...................... -......................... do.... Mineral spirits................................................. do___ Yield..................................................... gallons.. 102.0 288.0 32.5 15.5 65.0 103.73 1,483.7 192.0 288.0 pounds are used because of certain chemical or physical properties, such, for instance, as high 32.5 15.5 65.0 PbO content and high specific gravity. Such in clude use in ceramics, rubber compounding, heat 103.73 70 stabilization of vinylite resins, and other applica tions which will become apparent from the chem These paints were applied to wooden panels of ical and physical properties shown. four different woods, white pine, yellow pine, The basic phosphite pigments of this invention cedar and cypress. have several advantages over previously known Three coats of each paint were applied with 75 lead compounds used as pigments. The excep- * 0000-NLI-000018997