Process for the preparation of vinyl aromatic-modified polyphenylene ethers

A complex of polyphenylene ether resin and methylene chloride obtained by polymerizing a phenol in methylene chloride and then cooling the mixture to cause the complex to precipitate, is mixed with a vinyl aromatic compound, e.g., styrene monomer, heated to decompose the complex and remove methylene chloride from the blend, and thereafter the vinyl aromatic compound is polymerized. The products are useful as molding resins and the like.

This invention relates to an improved method to prepare resinous 
compositions and to the composition themselves. More particularly, it 
concerns the formation of compositions of polyphenylene ether resins and 
vinyl aromatic resins by decomposing a polyphenylene ether-methylene 
chloride complex (obtained as the reaction product of the oxidation of a 
suitable phenol in methylene chloride solution) in a vinyl aromatic 
compound and, after removal of the methylene chloride, polymerizing the 
vinyl aromatic compound. 
BACKGROUND OF THE INVENTION 
Polyphenylene ethers are known and described in numerous publications 
including Hay, U.S. Pat. Nos. 3,306,874 and 3,306,875. Polyphenylene 
ethers can be combined with vinyl aromatic resins, e.g., styrene resins, 
to provide thermoplastic compositions having many properties improved over 
those of either polyphenylene ether resin or styrene resin alone. See 
Cizek, U.S. Pat. No. 3,393,435. Polyphenylene ether-vinyl aromatic resin 
compositions can be made by forming a mixture of polyphenylene ether resin 
and the vinyl aromatic compound, see, for example, Fox, U.S. Pat. No. 
3,356,761; Bostick and Hay, U.S. Pat. No. 3,522,326; and U.K. Pat. No. 
1,264,889. 
In a copending application (Attorney's Docket GE-429 (8CH-2122/2154)), 
filed concurrently herewith by applicants herein, is described an improved 
process to make a polyphenylene ether-methylene chloride solid complex. In 
the process, methylene chloride is used as a combined solvent for 
polymerization and as a precipitant for the polyphenylene ether product. 
Typically, 2,6-xylenol is oxidatively coupled to produce a resin at 
elevated temperature (&lt;40.degree. C.) under oxygen pressure, the 
polymerization catalyst is extracted from the hot solution with aqueous 
acid or a chelating agent, and then the mixture is cooled. The polymer 
precipitates as a complex with methylene chloride and is removed by 
filtration or centrifugation. In the application above-mentioned, the 
polymer complex is washed with methylene chloride to remove quinones and 
other low molecular weight reaction products, and sometimes with water to 
complete removal of the catalyst. The wet cake is then heated to break up 
the complex and drive off methylene chloride and water--producing dry, 
amorphous polyphenylene ether powder suitable for blending, e.g., with 
other ingredients, such as styrene resins, glass fiber fillers, flame 
retardant agents, stabilizers, pigments and other conventional molding 
resin components. 
It has now been discovered, and is the subject matter of the present 
invention, that the drying step can be eliminated and compositions 
comprising polyphenylene ethers and vinyl aromatic resins can be prepared 
from the wet cake by suspending it in monomeric vinyl aromatic compounds 
and heating gently to break the complex and distill off methylene chloride 
(and water). After the methylene chloride (and water) has been removed, 
the temperature of the mixture may be increased to bring about 
polymerization of the vinyl aromatic compound. Of course, catalysts can be 
added, if desired, to increase the polymerization rate. When enough of the 
monomer has been polymerized to provide the desired composition ratio, the 
composition of two resins is isolated by crumbing in hot water, spray 
drying, devolatizing in an extruder, or other conventional procedures, and 
any excess of vinyl aromatic compound can be recovered for recycling. 
In comparison with conventional coextrusion techniques, the compositions 
provided by the present process are made without costly blending and 
compounding equipment, and high extrusion temperatures--and the 
possibility of polymer degradation, color formation, and the like--are 
avoided. 
The process of this invention can be used with the polymer-methylene 
chloride complex produced by washing the cake with methylene chloride to 
remove low molecular weight impurities. Altenatively, it can be used with 
the "crude" wet cake, i.e., the highly colored polyphenylene 
ether-methylene chloride complex prepared by washing the cake with water 
to remove catalyst--but not colored impurities. In the latter case, the 
final product is a light colored composition of polyphenylene ether and 
poly (vinyl aromatic), because of a considerable reduction in color which 
occurs during polymerization of the vinyl aromatic component. 
DESCRIPTION OF THE INVENTION 
This invention provides in a process for the preparation of a composition 
comprising a polyphenylene ether resin and a vinyl aromatic resin which 
comprises heating a mixture comprising a polyphenylene ether resin and a 
vinyl aromatic compound under polymerization conditions until the vinyl 
aromatic compound has at least partially polymerized, the improvement 
which comprises forming said mixture from (i) a polyphenylene 
ethermethylene chloride complex obtained by polymerizing a phenol in 
methylene chloride and then cooling to precipitate the complex and (ii) 
said vinyl aromatic compound, heating said mixture to decompose said 
complex and to remove the methylene chloride from the mixture, and 
thereafter continuing said heating until the vinyl aromatic compound has 
at least partially polymerized. 
The products prepared by the process, as defined, are also contemplated by 
this invention. 
The preferred polyphenylene ethers are of the formula: 
##STR1## 
wherein the oxygen ether atom of one unit is connected to the benzene 
nucleus of the next adjoining unit; n is an integer of at least 50; and R 
and R.sub.1 are monovalent substituents selected from hydrogen, halogen, 
hydrocarbon radicals, halohydrocarbon radicals having at least two carbon 
atoms between the halogen atom and the phenyl nucleus, hydrocarbonoxy and 
halohydrocarbonoxy radicals having at least two carbon atoms between the 
halogen atom and the phenyl nucleus. Especially preferred as the 
polyphenylene ether is poly(2,6-dimethyl-1,4-phenylene)ether. 
The vinyl aromatic compound can be a sytrene or substituted styrene, a 
vinyl naphthalene or substituted vinyl naphthalene, or the like. The 
preferred vinyl aromatic compounds will fall within the formula: 
##STR2## 
wherein R is hydrogen, lower alkyl or halogen, Z is hydrogen, lower alkyl, 
chloro or vinyl and p is a whole integer of from 1 to 5. "(Lower) alkyl" 
means alkyl of from 1 to 6 carbon atoms. Typically, the vinyl aromatic 
compounds will be styrene, .alpha.-methyl styrene, vinyl toluene, and the 
like. Especially preferred is styrene. 
Polymerization of the vinyl aromatic compound in admixture with the 
polyphenylene ether resin can be carried out by conventional techniques, 
such as suspension, bulk, bead, etc., techniques with and without 
agitation, with and without the addition of conventional modifiers, such 
as natural or synthetic resins or rubbers, etc., and using a catalyst, if 
desired. Preferably, polymerization will be by a bulk technique. 
The ratio of polyphenylene ether resin to vinyl aromatic compound is not 
critical, and can vary between 1 to 60 parts of the former to 40 to 99 
parts of the latter, by weight, preferably, 20 to 50 and 80 to 50, 
respectively. 
The polyphenylene ether-complex forming reaction is carried out under a 
wide variety of well known process conditions. Merely be way of 
illustration, a copper halide can be mixed with an aliphatic amine in 
methylene chloride, then oxygen or an oxygen-containing gas is pressured 
into the closed system containing the appropriate phenol, e.g., 
2,6-xylenol. The mixture is agitated at a temperature of at least about 
40.degree. C. The degree of polymerization is primarily controlled by the 
reaction time, although catalyst activity, promoters, temperature, oxygen 
pressure (or partial pressure) and other parameters have known effects. 
At the point where the polymerization reaction reaches the desired degree 
of polymerization or molecular weight, the reaction solution will comprise 
polyphenylene ether, typically from 1 to 50% by weight and usually from 5 
to 30% by weight, metal and amine (from the catalyst), typically from 
0.005 to 1.5% of metal and from 0.5 to 2% of amine, by weight, as well as 
minor amounts of other materials, such as various promoters, byproducts, 
unreacted monomer, and the like. The catalyst components are extracted 
from the hot solution, if desired, by contacting with an aqueous solution 
of an acid, or of a chelating agent, such as a salt of 
ethylenediaminetetraacetic acid. Cooling down to about 25.degree. C. or 
below then causes the precipitation of a polyphenylene ether-methylene 
chloride complex, which is used as the starting material herein. 
In one manner of proceeding, the wet cake, recovered by filtration or 
separation, comprising polyphenylene ether-methylene chloride is suspended 
in vinyl aromatic compound and the mixture is heated gently, e.g., to 
40.degree. to 50.degree. C., to break the complex and to distill off the 
methylene chloride (and water). The methylene chloride comes off readily, 
first, because of its low boiling point and will be admixed with water, if 
present. The distillate then will comprise water and vinyl aromatic 
compound, as the temperature is further increased. After the distillate 
becomes essentially vinyl aromatic compound, the temperature is further 
increased, e.g., to 85.degree. C. and higher, closing the system, if 
necessary, and adding a catalyst, etc., if desired, to start the 
polymerization. Rubber or other modifiers may be added at this point if 
desired. When at least enough of the vinyl aromatic compound has 
polymerized to provide the desired ratio of polyphenylene ether resin to 
vinyl aromatic resin, heating is discontinued and the product is isolated 
in any desired manner, e.g., by crumbing in boiling water, by spray 
drying, by concentrating the passing through a devolatilizing extruder, 
and the like. 
It can be seen that expensive drying equipment is avoided. It is 
advantageous that dry polyphenylene ether resin is obtained without 
exposing the resin to the high temperatures necessary to drive off water 
in a conventional dryer. Exposure of the polyphenylene ether to the high 
temperatures of conventional drying may cause degradation of the polymer, 
leading to an increase in color and some deterioration of physical 
properties. In essence, the total process provides a path from the two 
monomers to the blend of the two polymers without ever exposing the 
product to the high temperatures of drying or extrusion.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The following examples are for the purpose of illustration and are not to 
be construed as limiting the invention. 
EXAMPLE 1 
A solution of 1.23 grams of cupric bromide and 0.42 grams of 
methyltrioctylammonium chloride in 20 ml. of methanol is added to 32.7 
grams of di-n-butyl amine in 100 ml. of methylene chloride. The catalyst 
solution is transferred to a one gallon stirred reactor with 1300 ml. of 
methylene chloride. Oxygen is introduced to a pressure of 30 psig and a 
solution of 210 grams of 2,6-xylenol in 246 ml. of methylene chloride is 
added through a pump over a period of 10 minutes, followed by 100 ml. of 
methylene chloride. The temperature of the reaction mixture is allowed to 
increase slowly to 44.degree. C. and the pressure maintained at 30 psig. 
At 105 minutes after the beginning of reacting a solution of 5.5 grams of 
38% aqueous trisodium salt of ethyelendiaminetetraacetic acid in 15 ml. of 
water is added and the mixture stirred for 10 minutes. The hot solution is 
drawn off and cooled for three hours in an ice bath. The precipitate is 
filtered off and washed throughly with water to remove cooper. A small 
sample, approximately one gram, is removed and dried in vacuum; the 
poly(2,6-dimethyl-1,4-phenylene)ether has an intrinsic viscosity of 0.54 
dl.g. measured in chloroform at 30.degree. C. 
The crude wet cake of polymer-methylene chloride complex, intensely yellow 
in color, is added to 400 grams of styrene in a round bottom flask. A slow 
stream of nitrogen is introduced and the mixture is heated to drive off 
methylene chloride and water. After seven hours, the distillate no longer 
consists of two phases--and the temperature of the mixture in the pot is 
85.degree. C. Styrene, 160 grams, is added to the mixture and a portion of 
the solution is heated for 14 hours at 130.degree. C. in a pressure 
bottle. The product contains 85% polymer, in the proportion of 62 parts of 
poly(2,6-dimethyl-1,4-phenylene)-ether to 38 parts of polystyrene, by 
weight. The composition is light ivory color, much lighter than a 
composition prepared by coextrusion of the two homopolymers. After 
devolatilization under a vacuum at 150.degree. F., compression molding of 
the composition at 500.degree. C. yields transparent, almost colorless 
films. 
EXAMPLE 2 
Example 1 is repeated, except that some of the volatiles are removed from 
the wet cake of polyphenylene ethermethylene chloride complex under vacuum 
at room temperature (23.degree. C.) before heating with styrene. After 
four hours, the mixture is diluted with 100 grams of styrene and a portion 
of the mixture heated under nitrogen for 14 hours at 130.degree. C. The 
product, a light amber colored solid, contains 72% polymer in the 
proportion of 41 parts of poly(2,6-dimethyl-1,4-phenylene)-ether to 59 
parts of polystrene, by weight. 
EXAMPLE 3 
Cupric bromide, 2.46 grams, and 0.82 grams of methyltrioctylammonium 
chloride are dissolved in 30 ml. of methanol and added to 65.4 grams of 
dibutylamine in 200 ml. of methylene chloride. The catalyst is transferred 
to a one gallor reactor with 1100 ml. of methylene chloride. The reactor 
is filled with oxygen to a pressure of 30 psig and 420 grams of 
2,6-xylenol in 446 ml. of methylene chloride is added over a period of 20 
minutes. The temperature is held at 44.degree. C. and the pressure at 30 
psig. After 65 minutes, the polymerization is terminated by addition of a 
38% aqueous solution of the trisodium salt of ethylenediaminetetraacetic 
acid and the mixture is cooled for three hours in an ice bath to cause 
precipitation of the polymer-methylene chloride complex. The complex is 
filtered off, washed on the filter with 2000 ml. of cold methylene 
chloride and then with water. The wet cake is transferred to a five liter 
flask equipped with a high speed stirrer, a reflux condenser, and a 
Dean-Stark trap. 1200 ml of styrene is added, a slow current of nitrogen 
is introduced and the mixture is heated. The first portion of the 
distillate consists of a lower phase of methylene chloride with a trace of 
styrene, and an upper phase of water. Both phases are withdrawn from the 
Dean-Stark trap. When the temperature of the mixture reaches approximately 
70.degree. C., the character of the distillate change, and the upper phase 
consists of styrene, with water as the lower phase. The water is drawn off 
as it accumulates in the trap. When the temperature reaches 90.degree. C., 
distillation of water ceases and the temperature is increased rapidly to 
100.degree. C. Ethylbenzene, 400 ml., is added and the temperature is 
adjusted to 100.degree. C. and the mixture held overnight at this 
temperature. The temperature is then increased to 120.degree. C. for four 
hours. A sample of the mixture is withdrawn, diluted with toluene, and the 
polymer is precipitated with methanol. Analysis shows that it consists of 
96% poly(2,6-dimethyl-1,4-phenylene)ether and only 4% polystyrene. The 
temperature is slowly increased to approximately 135.degree. C., and held 
at 135.degree. to 140.degree. C. for one hour, then for four hours at 
120.degree. C. The mixture is diluted to approximately five liters with 
toluene and the polymer composition is isolated by spraying the solutions 
under nitrogen pressure into vigorously stirred hot water, kept hot with 
steam. The polymer composition, a light tan powder, is filtered off, 
washed with water, and dried under vacuum. Analysis shows that it consists 
of 57% poly(2,6-dimethyl-1,4-phenylene)ether and 43% polystyrene. 
One hundred parts by weight of this product is mixed with 10 parts by 
weight of Kraton 1101, a sytrenebutadiene copolymer manufactured by the 
Shell Chemical Company, and five parts by weight of titanium dioxide and 
extruded at 450.degree. F. in a twin screw extruder. The extruded pellets 
are injection molded into test pieces of very light color with 26% 
elongation, a tensile strength of 7400 psi., and notched Izod impact 
strength of 1.1 ft.lbs./in. of notch. 
Other modifications and variations of the present invention are possible in 
the light of the above teachings. It is, therefore, to be understood that 
changes may be made in the particular embodiments described which are 
within the full intended scope of the invention as defined by the appended 
claims.