Polyphenylene Ether-Polyamide Copolymers From Epoxytriazine-Capped Polyphenylene Ethers

To a mechanically stirred solution of 220.8 g. (1.2 moles) cyanuric chloride in 1500 ml. chloroform, cooled to 0-10.degree. C., was added 266.4 g. (3.6 moles) glycidol in one portion. Aqueous sodium hydroxide (50% solution; 192 g.) was added to the mixture dropwise with stirring over about 3 hours maintaining the reaction temperature below 10.degree. C. and preferably around 0.degree.-5.degree. C. The reaction mixture was allowed to warm slowly to room temperature. The chloroform layer was washed with distilled water until neutral and dried over magnesium sulfate. The reaction product was found by carbon-13 nuclear magnetic resonance to be 2-chloro-4,6-diglycidoxy-1,3,5-triazine (DGCC). Analysis by liquid chromatography showed about 95% (by weight) chlorodiglycidoxytriazine. The reaction mixture also was found to contain small amounts of triglycidoxytriazine and dichloroglycidoxytriazine.

To a magnetically stirred solution of 250 g. (1.125 moles) n-butyl dichlorocyanurate in 757 ml. chloroform, cooled to 0.degree.-10.degree. C., was added 250 g. (3.375 moles) glycidol in one portion. Aqueous sodium hydroxide (50% solution; 90 g.) was added to the mixture dropwise with stirring over about 2 hours, maintaining the reaction temperature below 10.degree. C. and preferably around 0.degree.-5.degree. C. The reaction mixture was allowed to warm to room temperature over 30 minutes. The chloroform layer was washed with distilled water until neutral and dried over magnesium sulfate. Proton nuclear magnetic resonance analysis indicated a 95% yield of 2-chloro-4-(n-butoxy)-6-glycidoxy-1,3,5-triazine (BGCC).

To a mechanically stirred solution of 50 g. (0.175 mole) 2,4,6-trimethylphenyl dichlorocyanurate (prepared by the reaction of equimolar amounts of mesitol and cyanuric chloride) in 170 ml. methylene chloride, cooled to 0.degree.-10.degree. C., was added 26.38 g. (0.356 mole) glycidol in one portion. Aqueous sodium hydroxide (50% solution; 14.26 g.) was added to the mixture dropwise with stirring over about 25 minutes maintaining the reaction temperature between 0.degree. and 10.degree. C. and preferably around 0.degree.-5.degree. C. After stirring an additional 30 minutes, the reaction mixture was allowed to warm to room temperature. The methylene chloride layer was washed with distilled water until neutral and dried over magnesium sulfate. The reaction product was found by proton nuclear magnetic resonance to be 2-chloro-4-(2,4,6-trimethylphenoxy)-6-glycidoxy-1,3,5-triazine (MGCC).

Various options are available for the reaction of the polyphenylene ether with the epoxychlorotriazine. In one method, the reaction is conducted in solution in a non-polar organic liquid, typically at a temperature in the range of about 80-150.degree. C. and preferably about 100.degree.-125.degree. C. The basic reagent employed in this method should be soluble in the organic liquid and is generally a tertiary amine. Its identity is not otherwise critical, provided it is sufficiently nonvolatile to remain in the reaction mixture at the temperatures employed. Pyridine is often preferred.

The amount of epoxychlorotriazine employed in this option is generally in the range of about 1-20% by weight, based on polyphenylene ether. The amount of basic reagent is an effective amount to promote the reaction; in general, about 1.0-1.1 equivalent thereof per mole of chloroepoxytriazine is adequate.

The epoxytriazine-capped polyphenylene ethers made in solution by the above-described process are generally found to contain rather high proportions (e.g., at least about 0.4% by weight) of chemically combined chlorine, principally covalently bound. It is believed that the covalently bound chlorine is the result of epoxy groups competing with the organic base as a hydrogen chloride acceptor, with the formation of chlorohydrin moieties. This may be followed by condensation of said chlorohydrin moieties with additional epoxy groups to produce such molecular species as polyphenylene ether-epoxytriazine block copolymers and homopolymeric epoxytriazine oligomers.

Upon molding, compositions containing polyphenylene ether copolymers prepared from products containing such species form articles which are ductile but have impact strengths somewhat lower than desired under certain conditions. This is particularly true of copolymers with polyesters.

A second, preferred method of preparation produces epoxytriazine-capped polyphenylene ethers with little or no covalently bound chlorine. In this method, the reaction is conducted interfacially in a medium comprising water and an organic liquid as previously described. The basic reagent is a water-soluble base, typically an alkali metal hydroxide and preferably sodium hydroxide. It may added to the mixture of epoxychlorotriazine and polyphenylene ether, or may initially react with the polyphenylene ether to form a salt which is then contacted with the epoxychlorotriazine There is also employed a phase transfer catalyst. Any of such catalysts which are stable and effective under the prevailing reaction conditions may be used; those skilled in the art will readily perceive which ones are suitable. Particularly preferred are the tetraalkylammonium chlorides wherein at least two alkyl groups per molecule, typically 2 or 3, contain about 5-20 carbon atoms.

In this method, reaction temperatures in the range of about 20.degree.-100.degree. C. may be employed. The amount of epoxychlorotriazine is frequently lower than in the previously described method, typically in the range of about 1-6% and preferably about 2-6% by weight based on polyphenylene ether, since the reaction of the epoxychlorotriazine with the polyphenylene ether apparently proceeds more nearly to completion. Most often, the ratio of equivalents of base to moles of epoxychlorotriazine is about 0.5-1.5:1 and the weight ratio of phase transfer catalyst to polyphenylene ether is about 0.01-5.0:1.

Still another method utilizes an organic liquid and a solid base, typically a solid alkali metal hydroxide or an anion exchange resin in the free base form. Chloride salts may be removed by methods known in the art, including water washing when a hydroxide is employed and filtration when an anion exchange resin is employed.

Regardless of which method of preparation is used, the epoxytriazine-capped polyphenylene ether may be isolated by conventional methods, typically by precipitation with a non-solvent. Among the non-solvents which may be employed are methanol, 1-propanol, acetone, acetonitrile and mixtures thereof.

When the non-solvent is an alcohol, and especially methanol, it may undergo base-promoted reaction with the epoxytriazine moieties on the capped polyphenylene ether, usually resulting in a loss of epoxide groups. Either or both of two operations may be employed to suppress this reaction. The first is to neutralize the reaction mixture with any convenient acidic compound; carbon dioxide, in gaseous, liquid or solid form, is often preferred. The second is to remove alcohol from contact with the product as rapidly and completely as possible by conventional means, typically including a subsequent drying step.

In the following examples which illustrate the preparation of epoxytriazine-capped polyphenylene ethers, proportions of epoxychlorotriazine are expressed as a percentage of polyphenylene ether. The following polyphenylene ethers were employed:

PPE - a poly(2,6-dimethyl-1,4-phenylene ether) having an intrinsic viscosity in chloroform at 25.degree. C. of 0.40 dl./g.

VV - PPE which had been extruded on a twin screw extruder within the temperature range of about 260.degree.-320.degree. C., with vacuum venting to a maximum pressure of about 20 torr.

LN - a poly(2,6-dimethyl-1,4-phenylene ether) having an intrinsic viscosity of 0.57 dl./g., having a low proportion of nitrogen as a result of preparation with a catalyst containing no primary or secondary amine.

Percentages of epoxytriazine in the capped polymer were determined from the relative areas of peaks in the nuclear magnetic resonance spectrum attributable to hydrogen atoms in the epoxy and aromatic moieties. Chlorine percentages were determined by quantitative X-ray fluorescence.

To solutions of 400 grams of polyphenylene ether in 2500 ml. of toluene were added, with stirring, various quantities of pyridine followed by various quantities of epoxychlorotriazines, added in portions. The ratio of equivalents of pyridine to moles of epoxychlorotriazine was 1.04:1. The solutions were heated under reflux for various periods of time, after which the products were precipitated with methanol in a blender, filtered, washed with methanol and vacuum dried. The relevant parameters and analytical results are given in Table I.

To solutions of 400 grams of polyphenylene ether in 2500 ml. of toluene were added various quantities of epoxychlorotriazines dissolved in a small amount of methylene chloride. There were then added 48 grams of a 10% solution in toluene of a commercially available methyltrialkylammonium chloride in which the alkyl groups contained 8-10 carbon atoms, and 10% aqueous sodium hydroxide solution in the amount of 1.3 equivalents of sodium hydroxide per mole of epoxychlorotriazine. The mixtures were stirred vigorously for various periods at 25.degree.-40.degree. C., after which the products were precipitated with methanol in a blender and rapidly filtered, washed with methanol and vacuum dried.

The results are given in Table II. Chlorine proportions were less than 200 ppm., the minimum detectable by quantitative X-ray fluorescence.

Any polymer (other than a polyphenylene ether) containing amine end groups may be employed in the present invention. Polyamides are particularly preferred. Included are those prepared by the polymerization of a monoamino-monocarboxylic acid or a lactam thereof having at least 2 carbon atoms between the amino and carboxylic acid group, of substantially equimolar proportions of a diamine which contains at least 2 carbon atoms between the amino groups and a dicarboxylic acid, or of a monoaminocarboxylic acid or a lactam thereof as defined above together with substantially equimolar proportions of a diamine and a dicarboxylic acid. (The term "substantially equimolar" proportions includes both strictly equimolar proportions and slight departures therefrom which are involved in conventional techniques for stabilizing the viscosity of the resultant polyamides.) The dicarboxylic acid may be used in the form of a functional derivative thereof, for example, an ester or acid chloride.

Examples of the aforementioned monoamino-monocarboxylic acids or lactams thereof which are useful in preparing the polyamides include those compounds containing from 2 to 16 carbon atoms between the amino and carboxylic acid groups, said carbon atoms forming a ring containing the --CO--NH-- group in the case of a lactam. As particular examples of aminocarboxylic acids and lactams there may be mentioned .epsilon.-aminocaproic acid, butyrolactam, pivalolactam, .epsilon.-caprolactam, capryllactam, enantholactam, undecanolactam, dodecanolactam and 3- and 4-aminobenzoic acids.

Diamines suitable for use in the preparation of the polyamides include the straight chain and branched chain alkyl, aryl and alkaryl diamines. Illustrative diamines are trimethylenediamine, tetramethylenediamine, pentamethylenediamine, octamethylenediamine, hexamethylenediamine (which is often preferred), trimethylhexamethylenediamine, m-phenylenediamine and m-xylylenediamine.

The dicarboxylic acids may be represented by the formula

wherein Y is a divalent aliphatic or aromatic group containing at least 2 carbon atoms. Examples of aliphatic acids are sebacic acid, octadecanedioic acid, suberic acid, glutaric acid, pimelic acid and adipic acid.

Both crystalline and amorphous polyamides may be employed, with the crystalline species often being preferred by reason of their solvent resistance. Typical examples of the polyamides or nylons, as these are often called, include, for example, polyamide-6 (polycaprolactam), 66 (polyhexamethylene adipamide), 11, 12, 63, 64, 6/10 and 6/12 as well as polyamides from terephthalic acid and/or isophthalic acid and trimethylhexamethylenediamine; from adipic acid and m-xylylenediamines; from adipic acid, azelaic acid and 2,2-bis(p-aminophenyl)propane or 2,2-bis-(p-aminocyclohexyl)propane and from terephthalic acid and 4,4'-diaminodicyclohexylmethane. Mixtures and/or copolymers of two or more of the foregoing polyamides or prepolymers thereof, respectively, are also within the scope of the present invention. Preferred polyamides are polyamide-6, 46, 66, 11 and 12, most preferably polyamide-66.

For the preparation of copolymer compositions according to this invention, a blending method which results in the formation of an intimate blend is required. Suitable procedures include solution blending, although such procedures are of limited applicability to many polyamides by reason of their insolubility in most common solvents. For this reason and because of the availability of melt blending equipment in commercial polymer processing facilities, melt reaction procedures are generally preferred. Conventional melt blending procedures and equipment may be employed, with extrusion often preferred because of its relative convenience and particular suitability. Typical reaction temperatures are in the range of about 175.degree.-350.degree. C.

The necessity for intimate blending is particularly strong when the epoxytriazine-capped polyphenylene ether is one in which X has formula II; that is, in the case of diepoxide-capped polymers. It is still stronger when a "low chlorine" capped polymer, as described hereinabove, is employed. In those cases, such properties as impact strength may be adversely affected by less than extremely efficient blending methods.

Those skilled in the art will be familiar with blending methods and apparatus capable of intimately blending resinous constituents, especially by kneading. They are exemplified by disc-pack processors and various types of extrusion equipment. Illustrations of the latter are continuous mixers; single screw kneading extruders; counterrotating, non-intermeshing twin screw extruders having screws which include forward-flighted compounders, cylindrical bushings and/or left-handed screw elements; corotating, intermeshing twin screw extruders; and extruders having screws which include at least one and preferably at least two sections of kneading block elements. As previously mentioned, vacuum venting may also be advantageous at this stage.

It is within the scope of the invention to include in the blending step elastomeric impact modifiers compatible with either or both of the polyphenylene ether and the polyamide.

Impact modifiers for polyphenylene ether-polyamide compositions are well known in the art. They are typically derived from one or more monomers selected from the group consisting of olefins, vinyl aromatic monomers, acrylic and alkylacrylic acids and their ester derivatives as well as conjugated dienes. Especially preferred impact modifiers are the rubbery high-molecular weight materials including natural and synthetic polymeric materials showing elasticity at room temperature. They include both homopolymers and copolymers, including random, block, radial block, radial block, graft and core-shell copolymers as well as combinations thereof.

Polyolefins or olefin-based copolymers employable in the invention include low density polyethylene, high density polyethylene, linear low density polyethylene, isotactic polypropylene, poly(1-butene), poly(4-methyl-1-pentene), propylene-ethylene copolymers and the like. Additional olefin copolymers include copolymers of one or more .alpha.-olefins, particularly ethylene, with copolymerizable monomers including, for example, vinyl acetate, acrylic acids and alkylacrylic acids as well as the ester derivatives thereof including, for example, acrylic acid, ethyl acrylate, methacrylic acid, methyl methacrylate and the like. Also suitable are the ionomer resins, which may be wholly or partially neutralized with metal ions.

A particularly useful class of impact modifiers are those derived from the vinyl aromatic monomers. These include AB and ABA type block and radial block copolymers and vinyl aromatic conjugated diene core-shell graft copolymers.

An especially preferred subclass of vinyl aromatic monomer-derived resins is the block copolymers comprising monoalkenyl arene (usually styrene) blocks and conjugated diene (e.g., butadiene or isoprene) or olefin (e.g., ethylenepropylene, ethylene-butylene) blocks and represented as AB and ABA block copolymers. The conjugated diene blocks may be partially or entirely hydrogenated, whereupon the properties are similar to the olefin block copolymers.

Suitable AB type block copolymers are disclosed in, for example, U.S. Pat. Nos. 3,078,254; 3,402,159; 3,297,793; 3,265,765 and 3,594,452 and UK Pat. No. 1,264,741, all incorporated herein by reference. Examples of typical species of AB block copolymers include:

polystyrene-polybutadiene (SBR),

polystyrene-polyisoprene and

ha-methylstyrene)-polybutadiene.

Such AB block copolymers are available commercially from a number of sources, including Phillips Petroleum under the trademark SOLPRENE.

Additionally, ABA triblock copolymers and processes for their production as well as hydrogenation, if desired, are disclosed in U.S. Pat. Nos. 3,149,182; 3,231,635; 3,462,162; 3,287,333; 3,595,942; 3,694,523 and 3,842,029, all incorporated herein by reference.

Examples of triblock copolymers include:

polystyrene-polybutadiene-polystyrene (SBS),

polystyrene-polyisoprene-polystyrene (SIS),

poly(.alpha.-methylstyrene)-polybutadiene-poly(.alpha.-methylstyrene) and

poly(.alpha.-methylstyrene)-polyisoprene-poly(.alpha.-methylstyrene).

Particularly preferred triblock copolymers are available commercially as CARIFLEX.RTM., KRATON D.RTM. and KRATON G.RTM. from Shell.

Another class of impact modifiers is derived from conjugated dienes. While many copolymers containing conjugated dienes have been discussed above, additional conjugated diene modifier resins include, for example, homopolymers and copolymers of one or more conjugated dienes including, for example, polybutadiene, butadiene-styrene copolymers, isoprene-isobutylene copolymers, chlorobutadiene polymers, butadiene-acrylonitrile copolymers, polyisoprene, and the like. Ethylene-propylene-diene monomer rubbers may also be used. These EPDM's are typified as comprising predominantly ethylene units, a moderate amount of propylene units and up to about 20 mole percent of non-conjugated diene monomer units. Many such EPDM's and processes for the production thereof are disclosed in U.S. Pat. Nos. 2,933,480; 3,000,866; 3,407,158; 3,093,621 and 3,379,701, incorporated herein by reference.

Other suitable impact modifiers are the core-shell type graft copolymers. In general, these have a predominantly conjugated diene rubbery core or a predominantly cross-linked acrylate rubbery core and one or more shells polymerized thereon and derived from monoalkenylarene and/or acrylic monomers alone or, preferably, in combination with other vinyl monomers. Such core-shell copolymers are widely available commercially, for example, from Rohm and Haas Company under the trade names KM-611, KM-653 and KM-330, and are described in U.S. Pat. Nos. 3,808,180; 4,034,013; 4,096,202; 4,180,494 and 4,292,233.

Also useful are the core-shell copolymers wherein an interpenetrating network of the resins employed characterizes the interface between the core and shell. Especially preferred in this regard are the ASA type copolymers available from General Electric Company and sold as GELOY.TM. resin and described in U.S. Pat. No. 3,944,631.

In addition, there may be employed the above-described polymers and copolymers having copolymerized therewith or grafted thereon monomers having functional groups and/or polar or active groups. Finally, other suitable impact modifiers include Thiokol rubber, polysulfide rubber, polyurethane rubber, polyether rubber (e.g., polypropylene oxide), epichlorohydrin rubber, ethylene-propylene rubber, thermoplastic polyester elastomers and thermoplastic ether-ester and ether-amide elastomers.

The proportion of impact modifier or other resinous material is subject to wide variation. Impact modifiers such as diblock or triblock copolymers are usually present in an amount up to about 50 parts per 100 parts of polyphenylene ether.

Provided the necessity for intimate blending is strictly observed, the order of blending may be varied. It is often found advantageous to employ an extruder which has at least two ports for introduction of ingredients, one such port being downstream from the other. The capped polyphenylene ether and at least a portion of the impact modifier are introduced through the first port and extruded. This portion of the extruder is often preferably vacuum vented.

The polyamide and any additional impact modifier are introduced through the downstream port and extrusion is continued, preferably at a lower temperature to minimize degradation of the impact modifier. By this method, optimum dispersion may be achieved, with either polyphenylene ether or polyamide being the continuous phase depending on proportion and method of blending.

The principal reaction which takes place between the epoxytriazine-capped polyphenylene ether and a polyamide generally involves amine end groups of the latter, which are highly nucleophilic and open the epoxide rings to form amino alcohol groups. Thus, a preferred embodiment of the invention is compositions comprising polyphenylene ether-polyamide copolymers comprising molecules containing at least one polyphenylene ether-polyamide linkage of the formula ##STR8## wherein Q.sup.1, Q.sup.2 and R.sup.1 are as previously defined; Z.sup.1 is an alkyl, cycloalkyl or aromatic radical (most often lower alkyl

or aromatic hydrocarbon) or ##STR9## and Z.sup.2 is OH and Z.sup.3 is --NH--, or Z.sup.2 is --NH-- and Z.sup.3 is OH.

Another possible reaction is between carboxylic acid end groups of the polyamide and the epoxy groups of the capped polyphenylene ether. Thus, the compositions of the invention are not limited to compounds containing linkages of formula IX but may include compounds with linkages of similar structures containing carboxylate moieties replacing the amino moieties of Z.sup.2 or Z.sup.3.

The proportions of polyphenylene ether and other polymer employed for the preparation of the compositions of this invention are not critical; they may be widely varied to provide compositions having the desired properties. Most often, each polymer is employed in an amount in the range of about 5-95%, preferably about 30-70%, of the composition by weight.

In addition to polyphenylene ether-polyamide copolymer, the compositions of this invention also contain unreacted polyphenylene ether. This will include any polyphenylene ether molecules having only hydrogen bonded end groups (i.e., the aminoalkyl-substituted end groups of formula IV), as well as other polyphenylene ether which is unfunctionalized as a result of incomplete capping or which is functionalized but fails to react with polyamide. Said compositions may also contain unreacted polyamide. In any event, molded parts produced from said compositions are generally ductile and have higher impact strengths than those produced from simple polyphenylene ether-polyamide blends, which are incompatible and often exhibit brittleness or delamination as previously described.

Experimental data suggest that certain other factors are of importance in preparing compositions of maximum impact strength. One of these is the proportion of chlorine in the epoxytriazine-capped polyphenylene ether. Compositions of this invention prepared from high chlorine capped polyphenylene ethers, obtained by the solution method previously described, often have lower impact strengths than those prepared from the low chlorine materials obtained by the interfacial method.

Another factor is the proportion of unneutralized amino nitrogen in the polyphenylene ether. High proportions may cause side reactions, including opening of epoxide rings, displacement of epoxide groups from the cyanurate moiety and cleavage of ester linkages. Such side reactions can be minimized by vacuum venting the polyphenylene ether and/or the composition of this invention as previously described. A third factor is the molecular structure of the copolymer, which may vary with the molecular structure of the capping agent used (BGCC or MGCC as contrasted with DGCC) and its proportion.

It also appears that compositions containing "high chlorine" capped polyphenylene ethers have a greater tendency toward ductility and high impact strength when a polyphenylene ether containing a low proportion of unneutralized amino nitrogen is employed, while the opposite is true for "low chlorine" materials. The reason for this is not presently understood.

There may also be present in the compositions of this invention conventional ingredients such as fillers, flame retardants, pigments, dyes, stabilizers, anti-static agents, crystallization aids, mold release agents and the like, as well as resinous components not previously discussed.

The invention is illustrated by the following examples. All parts and percentages are by weight. The impact modifier used in each example, unless otherwise specified, was a commercially available triblock copolymer with polystyrene end blocks having weight average molecular weights of 29,000 and a hydrogenated butadiene midblock having a weight average molecular weight of 116,000.

Mixtures of 49% epoxytriazine-capped polyphenylene ether, 41% of a commercially available polyamide-66 and 10% impact modifier were dry blended and extruded on a 20-mm. counterrotating, non-intermeshing twin screw extruder, at temperatures from 120.degree. C. to 290.degree. C. or 320.degree. C. The extrudates were quenched in water, pelletized, dried for 2-4 hours at 100.degree.-120.degree. C. and molded into test specimens which were tested for notched Izod impact strength and tensile properties (ASTM procedures D256 and D638, respectively) and heat distortion temperature at 0.455 MPa. (ASTM procedure D648). The results are given in Table III. No delamination was observed.

A mixture of 49% of the epoxytriazine-capped polyphenylene ether of Example 18, 41% of the polyamide used in Examples 26-28 and 10% of a commercially available diblock copolymer with polystyrene and hydrogenated butadiene blocks, having a weight average molecular weight of about 164,000, was dry blended, extruded in a 28-mm. corotating, intermeshing twin screw extruder at temperatures from 150.degree. C. to 260.degree. C. using a screw having two sections of kneading block elements, and molded into test specimens which were tested as described in Examples 26-28. The test results were as follows:

Izod impact strength - 678 joules/m.

Tensile strength at yield - 52.1 MPa.

Tensile strength at break - 58.7 MPa.

Tensile elongation - 139%

Heat distortion temperature - 188.degree. C.

No delamination was observed.

The improved impact strength of this composition as compared with the compositions of Examples 26-28 is believed to be primarily the result of more intimate mixing, although the employment of a different epoxytriazine-capped polyphenylene ether and impact modifier may have had some effect.

The epoxytriazine-capped polyphenylene ethers employed in these examples were MGCC-capped products similar to that of Example 25, but prepared employing 3.7% or 5% MGCC.

Compositions were prepared from 49% epoxytriazine-capped polyphenylene ether, 41% nylon-6 (Example 30) or nylon-66 (Example 31) and 10% impact modifier, by the procedure of Example 26. The relevant parameters and properties are listed in Table IV. No delamination was observed.

Following the procedure of Example 31, a blend was prepared from 49% polyphenylene ether capped with MGCC at a reactant level of 3.5%, 10% impact modifier and 41% of a commercially available amorphous polyamide prepared from hexamethylenediamine and a 67:33 mixture of isophthalic and terephthalic acids. It had an Izod impact strength of 85 joules/m., as compared to 21 joules/m. for a control sample in which PPE was substituted for the capped polyphenylene ether. Moreover, the control exhibited delamination which was not observed in the composition of the invention.