The invention relates to blends of a copoly(arylene sulfide) and a polyphenylene ether. Poly(arylene sulfide) resins are thermoplastic polymeric materials with good thermal stability, unusual insolubility, resistance to chemical environments and inherent flame resistance. Poly(arylene sulfide) resins additionally have good electrical insulative properties which make them ideal for electrical and electronic applications. Their excellent resistance to chemical degradation makes them ideal for use in chemical environments which involve organic solvents and strong mineral acids, such as coatings for pipes, tanks, pumps and other equipment. These polymers can be prepared by reacting p—dichloro—benzene with sodium sulfide in a polar organic solvent to produce poly(phenylene sulfide) and the by¬ product sodium chloride in accordance with U.S. 2,513,188 and U.S. 2,538,941. An improvement on this procedure involves adding N—haloamides as catalysts.

Recently copoly(arylene sulfides) have been discovered. These polymers can be described as having repeating units corresponding to the structure

[(-A-SJ^-A-S-S-),.] _n

wherein x is in the range of 0.5 to 0.001, A is a divalent aromatic radical and n is at least 200 and is preferably in the range of 500 to 5,000.

It has now been discovered that this copoly(arylene sulfide) can be blended with a polyphenylene ether. This blend can be broadly described as an admixture of

(A) from 99 to l weight percent, based on the weight of the admixture, of a copoly(arylene sulfide) corresponding to the structure

[ (-A-S-J^-A-S-S-),, ] _n

wherein A is a divalent substituted or unsubstituted aromatic radical, x is in the range of 0.5 to 0.001 and n is at least 25, and

(B) from 1 to 99 weight percent, based on the weight of the admixture, of a polyphenylene ether. The copoly(arylene sulfide) polymers useful in this invention are identical to the copoly(arylene sulfide) polymers disclosed in U.S. 4,786,713 and U.S. 4,855,393, herein incorporated by reference, except that the minimum value of n of the copoly(arylene sulfide) polymers useful in this invention is lower than the minimum value of n for the copoly(arylene sulfide) polymers which is disclosed in these references. The copoly(arylene sulfide) polymers useful in this invention are therefore inherent in the disclosure of these references because as the molecular weight builds up toward the minimum value of n of at least 200 which is disclosed in these references the molecular weight passes through a molecular weight associated with the lower minimum value of n of 25 of the copoly(arylene sulfide) polymers of this invention. The copoly(arylene sulfide) polymers useful in this invention can be prepared by those skilled in the art by following the teachings of these references and controlling the stoichiometry, time, temperature and other variables of the reaction to achieve a molecular weight associated with a value of n which is at least 25. The diiodoaro atic compounds which can be utilized to prepare the copoly(arylene sulfide) useful in this invention, include unsubstituted or substituted aromatics which have two iodine substituents. Preferred

diiodoaromatic compounds are the diiodobenzenes, diiodonaphthalenes and diiodobiphenyls which may be unsubstituted or substituted. More preferably the diiodoaromatic compounds suitable for the present invention include p—diiodobenzene, m—diiodobenzene, p,p'— diiodobiphenyl, p,p ^, -diiodobiphenyl, p,p'-diiododiphenyl ether and 2,6-diiodonaphthalene. Most preferably the diiodo compound is p—diiodobenzene.

The polyphenylene ethers useful in this invention and the method of their preparation are well known in the art.

The polyphenylene ethers correspond to the structure

wherein R _lf R ₂ , R ₃ and R are selected from the group consisting of a hydrogen atom, a halogen atom, an aryl group containing 6 to 12 carbons, an alkyl group containing 1 to 4 carbons, an alkoxy group containing 1 to 6 carbons, a haloalkyl group containing 1 to 6 carbons in which at least 2 carbon atoms are present between a halogen atom and the phenyl ring and a haloalkoxy group containing 1 to 6 carbons in which at least 2 carbon atoms are present between a halogen atom.

The intrinsic viscosity of the polyphenylene ether is at least 0.35 dl/g as measured in chloroform at 25°C. In a preferred embodiment the polyphenylene ether corresponds to the structure

and is..often.called poly(2,6 dimethyl-1,4—phenylene) ether.

The polyphenylene ether useful in this invention can be prepared by methods well know in the art such as disclosed in U.S. 3,306,874 and 3,236,807. The blends of this invention can be prepared by known techniques for blending polymers. For example, the polymers can be coextruded in convention twin screw extrusion equipment. Also, polymers of both polymers may be admixed and the admixed powders extruded in a single screw extruder. Preferably, an admixture of powdered polymer is prepared and the admixture powder is extruded in a single screw extruder.

The amount of copoly(arylene sulfide) is in the range of 99 to 1 weight percent, preferably 95 to 5 weight percent, based on the weighty of the composition. The amount of polyphenylene ether is in the range of 1 to 99 weight percent, preferably 5 to 95 weight percent, based on the weight of the composition.

The compositions of this invention can be used for preparation of various shaped articles such as pellets, fibers and molded articles. The polymer can be prepared into these shaped articles by conventional processes, such as injection molding, melt spinning, and melt extrusion. The compositions of this invention can additionally contain fillers, nucleating agents and reinforcing materials in the form of fibers, minerals, powders or mats. For example, the compositions can contain glass fibers, aluminum oxide, calcium oxide, silicon dioxide, Titanium dioxide, copper, kaolin, and the like.

The compositions of this invention are normally solid in the sense that at typical room temperatures and pressures the compositions are in a solid state as compared to a liquid state. The solid character of the composition results from both polymers having a sufficiently high molecular weight to be a solid.

The blends of this invention are characterized by extremely desirable interfacial adhesion between the copoly(phenylene sulfide) and polyphenylene ether. Interfaced adhesion is an important property of a blend of two polymers because it governs the strength of the blended material. When the interfacial adhesion is high, the blends can withstand higher stress before failure for any given morphology.

Example 1 This example illustrates the enhanced interfacial adhesion associated with the admixtures of this invention. A copoly(phenylene sulfide) was prepared by the melt phase reaction of sulfur and p-di—iodobenzene, as described in U.S. Patents 4,786,713 and 4,792,600. The value of x was estimated to be 0.10 as determined by elemental analysis.

The melt viscosity of copoly(phenylene sulfide) at 300°C at 25 Sec ^-1 shear rate was 5000 poise. Properties of the product included a melt viscosity of 5000 poise at 300°C and 25 rad/sec, a glass transition temperature of 89°C and an estimated disulfide content of 10 mol percent.

An admixture was prepared which contained 95 weight percent of the copoly(phenylene sulfide) and 5 weight percent of a poly(2,6—dimethyl—1,4—phenylene) ether having an intrinsic viscosity of 0.48 dl/g as measured at 25°C in chloroform. The two polymers were cryogenically micropulverized to a particle size less than 1.0 mm. A physical blend of 0.75 g of the polyphenylene ether and 14.25 g of copoly(phenylene sulfide) was made and well mixed. The powdered mixture of the above two polymers, 15 g by weight, was dried for at least 12 hours at 90°C in a vacuum oven. The dried polymer mixture was melt extruded into a film at 615°F. The film was cryogenically fractured in liquid nitrogen and the fracture surface morphology was determined using a scanning electron microscope. A scanning

electron micrograph of the cryogenically fractured surface clearly shows good interfacial adhesion between the two phases. The particle sizes are quite small and only a few particles are seen separate from the polyphenylene ether matrix.

Example 2

This example illustrates the composition of the invention containing different amounts of copoly(phenylene sulfide) and polyphenylene ether. Example 1 is repeated except that the amount of copoly(phenylene sulfide) is 90 weight percent and the amount of polyphenylene ether is 10 weight percent.

The scanning electron micrograph of the cryogenically fractured surface clearly shows good interfacial adhesion between the two phases.

Example 3

This example illustrates the poor interfacial adhesion associated with admixtures of poly(phenylene sulfide) and polyphenylene ether. Example 1 was repeated except that a poly(phenylene sulfide) was used instead of the copoly(phenylene sulfide) . The poly(phenylene sulfide) had a melt shear viscosity of 11,700 poise at 300°C and 25 sec ^-1 shear rate. The admixture of 95 percent poly(phenylene sulfide) and 5 percent polyphenylene ether was prepared the same way as in Example l. A scanning electron photomicrograph of the fractured surface of the admixture clearly indicates very poor interfacial adhesion between the two phases.