PREPARATION OF A HIGH MOLECULAR WEIGHT POLY (ARYLENE SULFIDE KETONE)

Abstract: A process, and product produced therefrom, for preparing a high molecular weight (poly(arylene sulfide ketone) from the reaction product of an alkali metal bisulfide with an alkali metal hydroxide, employing molar excess of alkali metal bisulfide with respect to the alkali metal hydroxide. A process, and product produced therefrom, for preparing a high molecular weight poly(arylene sulfide ketone) employing an alkali metal sulfide and an alkali metal hydrosulfide, wherein the alkali metal sulfide is added in a molar excess with respect to the alkali metal hydrosulfide.

Description: The invention relates to a method for preparing poly(arylene sulfide ketone)s. The invention further relates to poly(arylene sulfide ketone)s prepared from the reaction product of an alkali metal hydrosulfide with an alkali metal hydroxide. The invention further relates to poly(arylene sulfide ketone)s prepared employing an alkali metal sulfide and an alkali metal hydrosulfide. The invention also relates to fibers and other articles of manufacture prepared from these poly(arylene sulfide ketone)s. Poly(arylene sulfide ketone)s, PASK, are an important class of engineering thermoplastics. (Poly(arylene sulfide ketone)s are of commercial interest for film, fiber, moldings and composite applications because of their high melting points. One process for producing poly(arylene sulfide ketone)s involves the reaction of a dihalobenzophenone such as a dichlorobenzophenone with an alkali metal sulfide. The alkali metal sulfide is prepared by the reaction of an alkali metal hydrosulfide with an alkali metal hydroxide using virtually precise equimolar amounts (stoichiometric amounts) of the alkali metal hydrosulfide with respect to the alkali metal hydroxide, since an excess of either component has been considered undesirable. However, a major disadvantage with the poly(arylene sulfide ketone)s has been a relatively low molecular weight. It would be most desirable to be able to produce poly(arylene sulfide ketone)s having a relatively high molecular weight. The high molecular weight poly(arylene sulfide ketone)s would exhibit improved impact strength and toughness when compared to low molecular weight poly(arylene sulfide ketone)s. It is an object of the invention to provide a process for preparing a high molecular weight poly(arylene sulfide ketone). It is a further object of the invention to prepare high molecular weight poly(arylene sulfide ketone)s. Summary of the Invention I have discovered that relatively high molecular weight poly(arylene sulfide ketone)s are prepared by contacting in a reaction mixture, preferably in a polar solvent, a polyhalobenzophenone and an alkali metal hydrosulfide present in a small but important closely defined amount over the stoichiometric amount of alkali metal sulfide needed in the condensation polymerization. In a first embodiment, presently preferred, the alkali metal sulfide is prepared by bringing together an alkali metal hydrosulfide with an alkali metal hydroxide at a molar ratio of 1.004:1 to 1.038:1 so as to have the defined slight excess of alkali metal hydrosulfide. In a further embodiment, I have discovered that high molecular weight poly(arylene sulfide ketone)s are prepared by contacting in a reaction mixture a polyhalobenzophenone, an alkali metal sulfide and an alkali metal hydrosulfide, preferably in a polar solvent, wherein an alkali metal hydro sulfide is brought together with an alkali metal sulfide at a molar ratio of 0.004:1 to 0.038:1 under polymerization conditions effective for producing the poly(arylene sulfide ketone), again so as to have the defined slight excess of alkali metal hydrosulfide. In either embodiment, or combination thereof, desired is 0.004 to 0.038 molar excess of alkali metal hydrosulfide relative to the polyhalobenzophenone, that is in addition to the alkali metal sulfide added or formed in situ. Poly(arylene sulfide ketone)s having an inherent viscosity of at least 0.48 are obtained by my processes for producing the poly(arylene sulfide ketone)s. This is unexpected in my experience when considering how important stoichiometry is for condensation polymerizations. FIGURE 1 is a graphical representation of the inherent viscosity of poly(phenylene sulfide ketone)s prepared in the condensation polymerization reaction employing a slight amount of sodium bisulfide (sodium hydrosulfide) (NaSH) in a reaction mixture containing 4,4′dichlorobenzophenone, sodium sulfide (Na₂S), and N-methyl-2-pyrrolidone (NMP). The graph indicates by the portion between the larger dashed lines that poly(phenylene sulfide ketone)s having an inherent viscosity of at least 0.55 are obtained when a slight molar excess of NaSH of 1 to 3.5 mole percent over that needed to form Na₂S was employed in the reaction mixture. The graph indicates by the portion between the shorter dashed lines that poly(phenylene sulfide ketone)s having an inherent viscosity of at least 0.65 are obtained when a molar excess of NaSH of 1.5 to 3.3 mole percent was employed in the reaction mixture. These results are in sharp contrast to poly(phenylene sulfide ketone)s having an inherent viscosity of less than 0.45 prepared employing an alkali metal bisulfide with an alkali metal hydroxide at a stoichiometric molar ratio of 1:1, thus no excess NaSH, and at a higher ratio of 1.05:1. Only the narrow ratio was effective. In accordance with the invention, poly(arylene sulfide ketone)s are prepared by contacting in a reaction mixture (a) at least one polyhalobenzophenone, (b) at least one alkali metal sulfide either added as such or the equivalent in situ from an alkali metal hydrosulfide and alkali metal hydroxide or both, and (c) alkali metal hydrosulfide, preferably in a polar solvent. In one embodiment, the alkali metal sulfide employed in the process of my invention can be prepared from an alkali metal hydrosulfide and an alkali metal hydroxide in an aqueous solution using defined ratios. In a further embodiment, the alkali metal sulfide can be employed with the alkali metal hydrosulfide in an aqueous solution. In either embodiment the amount of the hydrosulfide is critical to the production of poly(arylene sulfide ketone)s of high inherent viscosity. In the first embodiment, the reaction of a dihalobenzophenone, such as 4,4' dichlorobenzophenone, with an alkali metal sulfide, prepared from an alkali metal hydrosulfide and an alkali metal hydroxide, such as sodium hydrosulfide and sodium hydroxide, in a polar solvent, such as N-methyl-2-pyrrolidone (NMP), so as to form a poly(phenylene sulfide ketone) of repeating units of poly(phenylene sulfide ketone), can be represented by: In the further embodiment, the polymerization employs a dihalobenzophenone, such as 4,4' dichlorobenzophenone, with an alkali metal sulfide, such as sodium sulfide, and an alkali metal hydrosulfide, such as sodium hydrosulfide, in a polar solvent, such as NMP, to form a poly(phenylene sulfide ketone) of repeating units of poly(phenylene sulfide ketone), which can be represented by: In the invention, a slight but essential molar excess of alkali metal hydrosulfide is employed with respect to the dihalobenzophenone or alkali metal sulfide. Although the molar excess of alkali metal hydrosulfide to alkali metal hydroxide can vary somewhat, generally when alkali metal hydrosulfide is employed with alkali metal hydroxide, it will be within the range of 0.4 to 3.8 mole percent, preferably within the range of 1 to 3.5 mole percent over the stoichiometric amount calculated to form alkali metal sulfide. The corresponding molar ratio of alkali metal hydrosulfide to alkali metal hydroxide will be in the range of 1.004:1 to 1.038:1, preferably within the range of 1.01:1 to 1.035:1. In a further embodiment of the invention, an alkali metal hydrosulfide and an alkali metal sulfide are employed in a range of 0.4 to 3.8 mole percent, preferably within the range of 1 to 3.5 mole percent, relative to the alkali metal sulfide amount as 100, again to assure a slight but essential excess of alkali metal hydrosulfide. The corresponding molar ratio of alkali metal hydrosulfide to alkali metal sulfide is in the range of 0.004:1 to 0.038:1, preferably in the range of 0.01:1 to 0.035:1. The poly(arylene sulfide ketone)s prepared according to my processes will to have an inherent viscosity of at least 0.48, preferably from 0.55 to 0.77. The polymers have wide utility for film, fiber, moldings, and composite applications because of this high melting point and high molecular weight. FIGURE 1 is a graphical representation of the inherent viscosity of poly(phenylene sulfide ketone)s as representative of poly(arylene sulfide ketone)s prepared from the condensation reaction of a molar excess of NaSH with respect to NaOH of 0 to 5 mole percent in a polymerization mixture containing 4,4'dichlorobenzophenone and NMP. The graph indicates by the portion between the longer dashed line that poly(phenylene sulfide ketone)s having an inherent viscosity of at least 0.55 are obtained when a molar excess of NaSH of 1 to 3.5 mole percent was employed. The shorter dashed lines indicate that poly(phenylene sulfide ketone)s having an inherent viscosity of at least 0.65 are obtained when a molar excess of NaSH versus NaOH of 1.1 to 3.3 mole percent was employed. This is in sharp contrast to the poly(arylene sulfide ketone)s having an inherent viscosity of less than 0.45 obtained by bringing together a dihalobenzophenone, an alkali metal bisulfide, and an alkali metal hydroxide at a stoichiometric molar ratio of 1:1:1 and at a higher ratio of 1:1.05:1. The process employs a polyhalobenzophenone, preferably a dihalobenzophenone. The dihalobenzophenones can be represented by the formula: wherein each X is selected from the group consisting of chlorine, bromine, fluorine, and iodine. Among the polyhalobenzophenones which can be employed are 4,4'dichlorobenzophenone, 4,4'difluorobenzophenone, 4,4'dibromobenzophenone, 4,4'diiodobenzophenone, 2,4'dichlorobenzophenone, 2,4,4'trichlorobenzophenone, 2,4,4'triiodobenzophenone, 2,4,4'trifluorobenzophenone, 2,4,4'tribromobenzophenone, and the like, and mixtures thereof. The presently preferred dihalobenzophenone, due to its effectiveness and commercial availability, is 4,4' dichlorobenzophenone. The alkali metal sulfides include lithium sulfide, sodium sulfide, potassium sulfide, rubidium sulfide, cesium sulfide, and mixtures thereof. The alkali metal hydrosulfides (sometimes called bisulfides) include lithium hydrosulfide, sodium hydrosulfide, potassium hydrosulfide, rubidium hydrosulfide, cesium hydrosulfide, and mixtures thereof. The alkali metal hydroxides include lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide, and mixtures thereof. The preferred alkali metal sulfide, due to its effectiveness, is sodium sulfide (Na₂S). The preferred alkali metal hydrosulfide, due to its effectiveness, is sodium hydrogen sulfide (NaSH). The preferred alkali metal hydroxide, due to its effectiveness, is sodium hydroxide (NaOH). The molar ratio of dihalobenzophenone: alkali metal sulfide should be held as close to stoichiometric ratio of 1:1 as possible in the condensation polymerization. The solvents useful in the process of my invention are polar organic solvents which can be used with a dihalobenzophenone and an alkali metal sulfide in the production of poly(arylene sulfide ketone)s. These polar organic solvents include such as the amides and sulfones. Specific examples of such polar organic solvents include hexamethyl phosphoramide, tetramethylurea, N,N'-ethylenedipyrrolidone, N-methyl-2-pyrrolidone (NMP), pyrrolidone, caprolactam, N-ethylcaprolactam, sulfolane, N,N'-dimethylacetamide, diphenyl sulfone, and the like, and mixtures thereof. The preferred polar organic solvent, due to its effectiveness and commercial availability, is NMP. The amount of solvent can vary, as is known in the art. The order of addition of the ingredients used to prepare the poly(arylene sulfide ketone)s can be varied as desired. Generally, the alkali metal sulfide (such as Na₂S), and the alkali metal hydrosulfide (such as NaSH), or the alkali metal hydroxide (such as NaOH) and the alkali metal hydrosulfide (such as NaSH), and the dihalobenzophenone, (such as 4,4' dichlorobenzophenone), can be added to a reactor vessel in any order. The polar organic solvent, (such as NMP), will generally be added to the reaction mixture following the addition of the aforementioned ingredients. Although the reaction temperature at which the polymerization is conducted can vary over a wide range, generally it will be within the range of 125°C to 450°C, preferably 175°C to 350°C, most preferably 225°C to 275°C. The reaction time can vary widely, depending in part on the reaction temperature, but generally will be within the range of 10 minutes to 72 hours, preferably 1 hour to 20 hours. The pressure should be sufficient to maintain the the reaction mixture substantially in the liquid phase. The pressure will generally be within the range of 0 psig to 2,17 MPa gauge (300 psig), preferably 1,14 to 1,83 MPa gauge (150 to 250 psig). The polymer can be recovered as desired, preferably by removing the polymer and solvent from a cooled reactor and recovering the polymer by filtration. The polymer can be subsequently washed with water and dried in a vacuum oven. Examples Examples provided are intended to assist in a further understanding of the invention. Particular materials employed, species, conditions, are intended to be further illustrative of my invention and not limitative of the reasonable scope thereof. Example I In this example the preparation of a poly(phenylene sulfide ketone) (PPSK) resin with equimolar amounts of NaSH and NaOH is described. To a 1-liter stainless steel reactor fitted with a double helical stirrer, nitrogen inlet tube, and rupture disc were charged: 41.63 grams of sodium hydrogen sulfide flakes (containing 58.17 weight-% NaSH, 0.35 weight-% Na₂S, and 41.4 weight-% H₂O), 17.58 grams of sodium hydroxide pellets (98.2 weight-% NaOH, provided by Mallinckrodt, Inc., St. Louis, Mo), 108.48 grams of 4,4′-dichlorobenzophenone (DCBP, provided by Aldrich Chemical Company, Milwaukee, Wisconsin), and 343 grams (3.46 moles) of N-methyl-2-pyrrolidone (NMP). Thus an equal number of moles (0.432) of each of NaSH, NaOH, and DCBP were charged, and the molar H₂O: NaSH ratio was 2.2:1. The reactor was sealed, alternately pressured with 100 psig N₂ and then vented so as to remove air. The reactor mixture was then stirred and heated to 250°C (during a one hour period). This temperature was maintained for about 3 hours, while a pressure of 1,34 MPa gauge (180 psig) was established. The reactor was then cooled to 200°C, and 3 grams of DCBP plus 100 grams of NMP were charged for end-capping the formed PPSK polymer with DCBP. The reactor contents were again heated to 250°C and kept at that temperature for about 1 hour. The polymer of this run (Run 1) was removed from the cooled reactor, recovered by filtration through a Buchner funnel, washed seven times with 2.5 liter aliquots of hot deionized water (about 70°C), and dried in a vacuum oven at 80°C. The inherent viscosity (IV) of the PPSK polymer, measured at 30°C in a #200 viscometer using a 0.5 weight-% solution in concentrated H₂SO₄ as solvent, was 0.45. Polymer yield was 73.6 grams. In a second run (Run 2) , an equimolar mixture of NaSH, NaOH, and DCBP in NMP was polymerized at essentially the same process conditions as described above, except that the mixture of NaSH, NaOH, H₂O, and NMP was first allowed to dehydrate at 0 psig and 160-205°C before all DCBP was added to the cooled reactor (105°), and no end-capping with DCBP was carried out. Then the reactor was sealed and heated at 250°C/1,0 MPa gauge (130 psig) for 3 hours. The inherent viscosity of the washed and dried PPSK polymer was 0.28. Runs 3-8 reflect the preparation of PPSK employing increased molar ratios of NaSH relative to NaOH, otherwise essentially in accordance with the procedure of Run 1 (no dehydration; polymerization of 250°C for 3 hours; end-capping with DCBP at 250°C for 1 hour; molar H₂O: NaSH ratio of about 2.2:1). Results are summarized in Table I: Runs 3-8 demonstrate that when a small defined molar excess of alkali metal hydrosulfide is used, the IV of the resultant polymer product will be equal to or greater than the IV of polymer products resulting from the use of a stoichiometric amount of alkali metal hydrosulfide NaSH (Runs 1 or 2) or the use of a larger excess (Run 9) of alkali metal hydrosulfide. The data, plotted in Figure 1, show that PPSK polymers having an inherent viscosity of at least 0.45 were obtained when a molar excess of NaSH (versus NaOH) of 0.4% to 3.8% was employed in the reaction mixture. Thermal transitions were measured for the PPSK resin produced in Run 5 employing a Perkin-Elmer DAC-2C differential scanning calorimeter equipped with a computerized data system and a Perkin-Elmer TADS-1 plotter. The polymer sample was heated at a rate of 20°C/minute. Results obtained were: glass transition temperature Tg = 144°C; crystallization temperature Tc = 191°C; melting temperature Tm = 340°C; melt crystallization temperature (upon cooling of the melt) Tmc = 291°C. Example II In this example, the preparation of PPSK, essentially in accordance with the procedure for Run 1 (Example I), employing Na₂S flakes (rather than NaSH and NaOH) is described. 56.88 grams of sodium sulfide flakes (containing about 59.3 weight-% Na₂S, 1.3 weight-% NaSH, and 39.4 weight-% H₂O, equal to 0.432 moles of Na₂S, 0.013 moles of NaSH and 1.25 moles of water), were reacted with 0.432 moles of DCBP in the presence of 3.46 moles of NMP. The presence of NaSH was equivalent to a molar NaSH excess of about 3%. The IV of the formed PPSK resin (89 grams yield) was 0.58. Therefore, the use of an alkali metal sulfide such as Na₂S, plus a defined slight excess of alkali metal hydrosulfide, such as NaSH, clearly is effective and within the scope of this invention. Example III This example illustrates the curing of PPSK so as to further increase its molecular weight. The dark-colored resin prepared in Run 6 was placed in an air oven heated to 316°C. The inherent viscosity of the polymer increased from an initial value of 0.68 to 0.84 after 30 minutes, and to 0.97 after 60 minutes. After heating for about 120 minutes, the polymer was no longer soluble in H₂SO₄. Degassing of the polymer during curing, especially during the first hour, was observed.

Claims: A method for preparing a poly(arylene sulfide ketone) comprising subjecting to polymerization in a reaction mixture equimolar amounts of polyhalobenzophenone and alkali metal sulfide characterized by conducting said polymerization in the presence of a small stoichiometric excess of alkali metal hydrosulfide over the alkali metal sulfide wherein the mole ratio of alkali metal hydrosulfide to alkali metal sulfide is from 0.004:1 to 0.038:1. The method of claim 1, wherein said alkali metal sulfide is prepared in situ from (a) alkali metal hydrosulfide and (b) alkali metal hydroxide and said small stoichiometric excess of alkali metal hydrosulfide is provided by utilizing a mole ratio of (a) to (b) from 1.004:1 to 1.038:1. The method of claim 1 or 2, characterized in that the polyhalobenzophenone comprises a dihalobenzophenone, and the reaction mixture includes a polar reaction medium. The method of claim 1 or 3, characterized by employing the alkali metal hydrosulfide in a ratio of 0.01:1 to 0.035:1 relative to said alkali metal sulfide. The method of claim 2 or 3, employing a mole ratio of (a) to (b) from 1.01:1 to 1.035:1. The method of any of claims 1 to 5 characterized in that the dihalobenzophenone comprises 4,4'-dichlorobenzophenone and the polar reaction medium comprises N-methyl-2-pyrrolidone. The method of any of the preceding claims characterized in that the poly(arylene sulfide ketone) is represented by repeating units of the structural formula: The method of any of the preceding claims characterized in that the poly(arylene sulfide ketone) comprises poly(phenylene sulfide ketone). The method of claim 6, characterized in that the poly(phenylene sulfide ketone) exhibits an inherent viscosity of at least 0.48 dl/g measured at 30°C in a No, 200 viscometer using an 0.5 weight percent solution in concentrated H₂SO₄; in particular wherein the poly(phenylene sulfide ketone) exhibits an inherent viscosity of 0.55 to 0.77 dl/g. The method of any of the preceding claims characterized in that the polymerization conditions include a temperature range of 175°C to 350°C, a pressure range of 0 to 2,17 MPa gauge and a reaction time of 1 to 72 hours. The use of the poly(arylene sulfide ketone) as obtained by the method of any of claims 1 to 10 for making shaped articles, in particular fibers and films.

Inventors: GAUGHAN, ROGER GRANT
Applicants: PHILLIPS PETROLEUM COMPANY
Application year: 1987
Main classification: C08G75
IPC codes: C08G75