Bromination of poly(arylene sulfides)

#This invention relates to the production of aromatic sulfide polymers having improved physical properties. In accordance with another aspect, this invention relates to a process for the bromination of arylene sulfide polymers by contacting with an oxygen-containing gas and a catalyst system containing a copper ion, an alkali metal ion, and a bromide ion. In accordance with another aspect, the bromination of arylene sulfide polymers with a free oxygen-containing gas and a catalyst system containing a copper ion, an alkali metal ion, and a bromide ion is carried out in the presence of a diluent having substantial oxidative stability such as carboxylic acids. In accordance with a further aspect, bromination of arylene sulfide polymers such as poly(phenylene sulfide) is carried out by contacting particulate polymer with an oxygen-containing gas in the presence of the above-defined catalyst system, preferably in a diluent having oxidative stability.

#Aromatic sulfide polymers ranging in consistency from viscous liquids to crystalline solids are known. While such polymers exhibit desirable properties for many applications, considerable research has been expended to find methods of improving the properties and versatility of arylene sulfide polymers for various applications. The present invention is directed to a process for brominating arylene sulfide polymers to yield a brominated polymeric product having reduced flammability characteristics which has utility as a flame retardant additive as well as an ultraviolet stabilizer.

#Accordingly, an object of this invention is to improve the physical properties of poly(arylene sulfide) resins.

#A 250 ml Fisher-Porter aerosol compatibility bottle equipped with magnetic stirring means was charged with 6.5 grams (75 millimoles) of lithium bromide, 4.8 grams (24 millimoles) of cupric acetate monohydrate, 50 ml of acetic acid, 25 ml of acetic anhydride, and 11.1 grams (0.1 mole equivalent) of an uncured poly(phenylene sulfide) powder having a melt flow of about 6,000 as determined by the previously described modified ASTM-D-1238 method. The reaction bottle was placed in an oil bath, pressured to 30 psig (206.7 kPa) with oxygen, and heated to 140.degree. C (284.degree. F). About 45 minutes was required to reach the reaction temperature, and the reaction was continued for about four hours with repressuring the vessel to about 80 to 100 psig (551.2 to 689 kPa) with oxygen at about 15 to 25 minute intervals. It was calculated that about 0.092 moles of oxygen was consumed during the reaction. The reaction bottle was vented, and the product was collected on a sintered glass funnel and washed with acetic acid until the washing liquid was colorless. The solid material was then thoroughly washed with water, with methanol, and finally with acetone. The recovered product was dried in the air to a weight of 14.1 grams. Infrared analysis of the recovered polymer showed that very little, if any, oxidation of the sulfide group to sulfoxide or sulfone had occurred. Analysis of the polymer sample for bromine content found 9.68% and 9.72% in two determinations. It was calculated that one bromine per repeat unit of the poly(phenylene sulfide) would have given a bromine content of 40.61%; thus, the values shown above correspond to about one bromine atom per 4.18 repeat units in the brominated poly(phenylene sulfide).

#The above result demonstrates operability for the instant invention in providing a bromination sytem for poly(arylene sulfides).

#Another run was conducted by charging a 250 ml Fisher-Porter aerosol compatibility bottle equipped with a magnetic stirrer with 6.5 grams (75 millimoles) of lithium bromide, 9.6 grams (48 millimoles) of cupric acetate monohydrate, 50 ml of acetic acid, 25 ml of acetic anhydride, and two 3/4 inch .times. 1/4 inch pieces (weight 1.3 grams ) of a molded poly(phenylene sulfide) material previously utilized in a tensile strength test. The material was molded from an unfilled poly(phenylene sulfide) which had a melt flow of about 35. The reaction bottle was placed in an oil bath and pressured to 30 psig (206.7 kPa gage) with oxygen and heated to 140.degree. C (284.degree. F). About one hour and ten minutes was required to reach the reaction temperature and the reaction was then continued for four hours with intermittent repressuring of the reaction bottle to 100 psig (689 kPa gage) at about 15 to 25 minute intervals. However, after about two hours into the reaction period, essentially no more oxygen uptake appeared to occur. At the end of the reaction period, the bottle was vented and the poly(phenylene sulfide) slabs were recovered, washed with water, and air dried. Weight of the dried poly(phenylene sulfide) slabs indicated no weight change had taken place during the reaction. Infrared analysis of a ground-up portion of the treated poly(phenylene sulfide) showed that some oxidation had occurred but was not very extensive. Analysis of the treated polymer slabs for bromine content was not carried out. It is believed that very little bromination or oxidation of the sulfide group in the polymer had occurred under the conditions described. This result indicates the desirability of utilizing the poly(arylene sulfide) polymer in a finely divided form such as the powdered form utilized in Example I above.