US3057813A

US3057813A - Styrene polymer composition containing butyl stearate and a metal compound

Info

Publication number: US3057813A
Application number: US611752A
Authority: US
Inventors: Russell H Fay
Original assignee: Dow Chemical Co
Current assignee: Dow Chemical Co
Priority date: 1956-09-24
Filing date: 1956-09-24
Publication date: 1962-10-09
Anticipated expiration: 1979-10-09

Description

United States Patent Ofifice 3,057,813 Patented Oct. 9, 1962 STYRENE POLYMER COMPOSITION CONTAIN- ING BUTYL STEARATE AND A METAL COM- POUND Russell H. Fay, Midland, Mich., assignor to The Dow Chemical Company, Midland, Mich., a corporation of Delaware No Drawing. Filed Sept. 24, 1956, Ser. No. 611,752

8 Claims. (Cl. 26031.2)

This invention relates to a discoloration-inhibiting treatment for butyl stearate and like fatty acid esters which are commonly employed as internal lubricants for polymeric compositions, particularly polystyrene and the like, to facilitate their fabrication during extrusion, molding and similar operations. It has particular reference to polymeric compositions in which the treated ester lubricant is incorporated.

Although butyl stearate and like fatty acid esters are extremely beneficial internal lubricants for polystyrene and similar polymeric compositions, they frequently tend to decompose at elevated temperatures, particularly in the presence of certain ferrous metals such as mild steel,

and cause discoloration in the polymeric composition. The discoloration usually occurs in the form of objectionable black specks which are believed to consist predominantly of the degraded free fatty acid, such as stearic acid, from the ester. The conditions which seem to promote discoloration of the butyl stearate are ordinarily present during fabrication of polymeric compositions which are commonly extruded or molded at elevated temperatures, frequently in the presence of such deleterious, discoloration-promoting ferrous alloys as mild steel.

It would be advantageous if butyl stearate and like fatty acid esters could be employed as lubricants in polymeric compositions without occasioning the discoloration that may occur from the decomposition of the ester lubricant when the composition is exposed to heat at elevated temperatures, especially when the exposure occurs in the presence of mild steel and the like ferrous metal alloys.

To the accomplishment of this and related ends, butyl stearate and like fatty acid esters may be treated to overcome their tendency to decompose and cause discoloration at elevated temperatures by incorporating in the ester lubricant a minor proportion of a compound selected from the group consisting of the sulfites, sulfates, oxides and hydroxides of the group I}, and II, metals of the periodic system and aluminum. The metal compound that is incorporated in the ester lubricant saponifies or neutralizes the free fatty acid that forms upon its thermal decomposition and prevents the discoloration that may occur when the fatty acids, such as stearic acid, are permitted to remain in a free acid form. The treated fatty acid ester lubricant may be handled and incorporated in polymeric compositions according to conventional techniques, taking care that the metal compound is uniformly dispersed throughout the fatty acid ester. Polymeric compositions, particularly polystyrene, that are lubricated internally with fatty acid esters, particularly butyl stearate, treated in accordance with the present invention, are not discolored or contaminated with black specks due to decomposition of the fatty acid ester even when they are exposed to heat at elevated extrusion or molding temperatures in the presence of mild steel alloys. Further, the metal salts of the fatty acids that are formed do not exert an undesirable influence on the composition. To the contrary, they frequently contribute beneficial lubricating characteristics of their own.

Ordinarily, the fatty acid esters may be suitably treated by the incorporation of less than a stoichiometric quantity of the metal compound, based on the weight of the treated ester. In most cases, satisfactory results may be achieved when between about 10 and 25 percent by weight of a stoichiometric quantity of the metal compound is employed. Preferably, calcium hydroxide is utilized as the basic metal compound for treating the fatty acid ester lubricant although it is also advantageous to employ the oxides and hydroxides of the other alkaline earth metals, barium and strontium. Excellent results may also be obtained with the oxides and hydroxides of the alkali metals such as sodium and potassium and aluminum hydroxide.

By way of further illustration, about 20 percent by weight of the stoichiometric equivalent quantities of several metal compounds for treating butyl stearate in accordance with the invention Were separately added to 200 milliliter samples of butyl stearate in sealed, evacuated glass cylinders. Each of the samples was maintained at a temperature of about 240 C. for four days, after which they were observed for evidence of discoloration. The treating compounds that were employed and the results that were obtained are set forth in the following tabulation.

Treating Compound Results Remarks Calcium hydroxide.-. No discoloration Excellent. Calcium sulfate No discoloration-about 20 per- Good.

cent creamy white solid, remainder pale yellow liquid. Magnesium oxide No diseolorationercamy white Do. solid formed. Sodium sulfite Very slight darkening-mo black Satisfactory.

speck formation-about 5 percent white solid, remainder yellow liquid. Sodium sulfate ..do Do. Aluminum hydroxide. N0 discolorationvery little Excellent.

white solid, remainder pale yellow liquid. Aluminum oxide Very slight darkeningno solid, Suitable.

relatively dark yellow liquid. Zinc oxide About 25 percent solidremain- Poor.

der dark liquid.

Analogous results were obtained when the refluxing was conducted in the presence of mild steel. In contrast, plain butyl stearate tested in the same manner in glass discolored to an intolerable degree within a day. This effect was noted in much less than a day when the plain untreated ester was refluxed in the presence of mild steel. Polystyrene that contains butyl stearate as an internal lubricant which is treated in accordance with the invention, especially with calcium hydroxide, magnesium' oxide, aluminum hydroxide and the indicated alkali metal compounds, does not develop black specks or other color impurities even when it is passed through a mild steel devolatilizing extruder at elevated extruding temperatures.

What is claimed is:

1. A styrene polymer composition containing butyl stearate as an internal lubricant which has incorporated therein a metal compound selected from the group consisting of the sulfites, sulfates, oxides and hydroxides of the group I, and II metals of the periodic system and aluminum, in a proportion up to about a stoichiometric quantity for neutralization of the free fatty acid available from the butyl stearate, based on the quantity of butyl stearate in the composition.

2. The polymeric composition of claim 1, wherein the butyl stearate contains an amount of the metal compound that is between about 10 and 25 percent by weight of a stoichiometric quantity for neutralization of the free fatty acid available from the butyl stearate, based on the weight of the butyl stearate in the composition.

3. The composition of claim 1, wherein the metal compound is a calcium hydroxide.

4. The composition of claim 1, wherein the metal compound is a sodium hydroxide.

5. The composition of claim 1, wherein the metal compound is a potassium hydroxide.

6. The composition of claim 1, wherein the metal compound is a magnesium hydroxide.

7. The composition of claim 1, wherein the metal compound is an aluminum hydroxide.

8. The composition of claim 2 wherein the styrene polymer is polystyrene.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Condensed Chemical Dictionary, 5th Edition, Reinhold ublishing Co., New York, N.Y., page 966.

UNITED STATES. PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,057,813 October 9, 1962 Russell H. Fay

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3, line 11,

for the claim ref 11 read l erence numeral 2 Signed and sealed this 14th day of May 1963,

(SEAL) Attest:

ERNEST w. SWIDER DAVID LADD Attesting Officer Commissioner of Patents

Claims

1. A STYRENE POLYMER COMPOSITION CONTAINING BUTYL STEARATE AS AN INTERNAL LUBRICANT WHICH HAS INCORPORATED THEREIN A METAL COMPOUND SELECTED FROM THE GROUP CONSISTING OF THE SULFITES, SULFATES, OXIDES AND HYDROXIDES OF THE GROUP IA AND IIA METALS OF THE PERIODIC SYSTEM AND ALUMINUM, IN A PROPORTION UP TO ABOUT A STOICHIOMETRIC QUANTITY FOR NEUTRALIZATION OF THE FREE FATTY ACID AVAILABLE FROM THE BUTYL STEARATE, BASED ON THE QUANTITY OF BUTYL STEARATE IN THE COMPOSITION.