CA2057147A1 - Thermally stable blends of polyphenylene ether and diene based rubber - Google Patents

Abstract

RD - 20,514 THERMALLY STABLE BLENDS OF POLYPHENYLENE

ETHER AND DIENE BASED RUBBER

Abstract of the Disclosure There are provided melt extruded blends of polyphenylene ether and diene based rubber containing an effective amount of a dialkylamine which has been found effective as a stabilizer for the diene based rubber.
Additional diene based rubber stability can be achieved by using preextruded polyphenylene ether. The resulting melt extruded blends have been found to enjoy increased resistance to change in impact values when recycled in the molded state.

Description

2g~3 7~

RD - 20,514 THERMALLY STABLE BLENDS OF POLYPHENYLENE

ETHER AND DIENE BASED RUBBER

Background of the Invention The present invention relates to blends comprising polyphenylene ether and diene based rubber which exhibit improved resistance to loss of impact strength upon thermal recycling after being molded. More particularly, the present invention relates to blends comprising diene based rubber, and preextruded polyphenylene ether end capped with salicylic acid and diene rubber, polyphenylene ether and an effective amount of a dialkylamine having a boiling point of at least 150C, such as dioctylamine.
As shown in United States Patent No. of Richards et al, issued , the use of metal deactivator/antioxidants have been used as stabilizers for ;~
polyphenylene ethers, while metal deactivators and/or antioxidants have often been used to reduce metal catalyzed degradation in unsaturated rubber. Commercially available stabilizers have been used with butadiene copolymers, such as Kraton KD1102 manufactured by Shell Chemical company, which is a styrene butadiene styrene (SBS) block copolymer. Antioxidants also have been folmd to minimize crosslinking in butadiene based -, ':
:- . . .: , .:

~5~7 RD 20,514 rubber resulting from oxidation during high temperature processing. The use of metal deactivator/antioxidants, along with the prior extrusion of polyphenylene ether for blending with diene based rubber, provided moldable materials which exhibited improved resistance to loss of impact strength after thermal aging or upon thermal recycling after being molded.
Although metal deactivators and/or antioxidants have been effective for stabilizing diene based rubber, it has been found that blends of such stabilized diene based rubber and polyphenylene ether and after they have been molded often experience a reduction in toughness when thermally recycled as compared to their toughness when initially molded. One possible explanation is that crosslinking in the diene block results during the subsequent melt extrusion of the recycled thermoplastic and the effectiveness of the diene based rubber as an impact modifier is reduced. Metal residues, such as copper in the polyphenylene ether, can catalyze the crosslinking of he unsaturated diene. Accordingly, in order to maintain the impact properties of molded blends of polyphenylene ether and diene based rubber which are subject to recycling, additional methods to improve the thermal stability of diene based rubber are constantly being sought.

SummarY of the Invention The present invention is based on the discovery that the thermal stability of diene based rubber subject to thermal aging or thermal recycling, as part of a molded blend with polyphenylene ether, can be substantially improved by the incorporation of an effective amount of a dialkylamine, such as dioctylamine. In an alternate embodiment the blend can be improved if polyphenylene ether is used having polysalicylate terminal groups, and the polysalicylate capped polyphenylene ether is melt extruded prior to being blended with the diene 2 ~

RD 20,514 based rubber. Based on impact studies shown hereinafter and in U.S. Patent , any improvement in the thermal stability of diene based rubber automatically can be translated into improved resistance to loss of impact upon the thermal recycling or aging of molded blends of such improved diene based rubber with polyphenylene ether. While some improvement is shown when the dialkylamine is simply added to the polyphenylene ether and diene based rubber blend during initial processing, significantly greater advantages have been obtained by either extruding the polyphenylene ether with the dialkylamine prior to blending with the diene based rubber, or when using preextruded polyphenylene ether in combination with the dialkylamine during the melt extrusion with the butadiene based rubber. The incorporation of the dialkylamine or any matrix materials such as polyamide as described hereinafter, can include "down stream feeding" where the matrix material and/or the diene based rubber can be added to the extruder following the earlier melt extrusion of the polysalicylate capped polyphenylene ether.

Statement of the Invention There is provided by the present invention, a polyphenylene ether composition which has enhanced impact strength when initially molded and which resists loss of impact strength upon being thermally recycled at temperatures in the range of 250C-350C, or thermally aged at a temperature of 50C-200C, comprising by weight, from about 5 to about 400 parts of a diene based rubber, per 100 parts of a polyphenylene ether or a preextruded salicylic acid ester capped polyphenylene ether, which blend of polyphenylene ether and diene based rubber is an extrudate of a mixture selected from the class consisting of, . , .
.

,- ., :` : : :
.

~3 RD 20,514 (a) a blend of polyphenylene ether, a diene based rubber and an effective amount of a dialkylamine haviny a boiling point of at least 150C, (b) a blend of a diene based rubber, a preextruded polyphenylene ether and an effective amount of a dialkylamine having a boiling point of at least 150DC, (c) a blend of a diene based rubber and a preextruded mixture of polyphenylene ether and an effective amount of a dialkylamine havinq a boiling point of at least 150C, and (d) a blend of a diene based rubber and a preextruded salicylic acid ester capped polyphenylene ether.
The polyphenylene ethers which are employed in the practice of the present invention are widely used in industry, especially as enginesring plastics in applications requiring toughness and heat resistance. Since their discovery, they have given rise to numerous variations and modifications all of which are applicable to the present invention, including but not limited to those described hereinafter.
The polyphenylene ethers comprise a plurality of structural units having the formula, ~ Ql ~0~ (1) ,~
~r Q
where in each of said units, each Ql is a primary or secondary lower alkyl (i.e., alkyl containing up to 7 carbon atoms), phenyl or hydrocarbonoxy ancl each Q2 is independently hydrogen, halogen, primary or secondary lower alkyl, phenyl or hydrocarbonoxy as clefined by Ql. Examples of suitable primary lower alkyl groups are methyl, ethyl, n-propyl, n-butyl, isobutyl, n-amyl, isoamyl~ 2-methylbutyl, n-hexyl, 2,3-dimethylbutyl, 2-,3- or 4-methylpentyl and the corresponding heptyl groups. Examples of secondary lower alkyl groups are isopropyl, sec-butyl and 3-pentyl. Preferably, any alkyl 2 ~ 3 ~ J

RD 20,514 radicals are straight chain rather than branched. Most often, each Ql is alkyl or phenyl, especially C1_4 alkyl, and each Q2 is hydrogen.
Both homopolymer and copolymer polyphenylene ethers are included. Suitable homopolymers are those containing, for example, 2,6-dimethyl-1,4-phenylene ether units.
The polyphenylene ethers can have a number average molecular weight within the range of about 3,000-40,000 and a weight average molecular weight within the range of about 20,000-80,000, as determined by gel permeation chromatoyraphy.
Their intrinsic viscosities are most often in the range of about 0.2-0.6 dl./g., as measured in chloroform at 25C.
The po]yphenylene ethers are typically prepared by the oxidative coupling of at least one corresponding monohydroxyaromatic compound. Particularly useful and ~eadily available monohydroxyaromatic compounds are 2,6-xylenol (wherein each Ql is methyl and each Q2 is hydrogen), whereupon the polymer may be characterized as a poly(2,6-dimethyl-1,4-phenylene ether), and 2,3,6-trimethylphenol (wherein each Ql and one Q2 is methyl and the other Q2 is hydrogen).
A variety of catalyst systems are known for the preparation of polyphenylene ethers by oxidative coupling.
There is no particular limitation as to catalyst choice and any of the known catalysts can be used. For the most part, they contain at least one heavy metal compound such as a copper, manganese or cobalt compound, usually in combination with various other materials.
A first class of preferred catalyst systems consists of those containing a copper compound. Such catalysts are disclosed, for example, in U.S. Pat. Nos. 3,306,874; 3,306,875;

3,914,266 and 4,028,341. They are usually combinations of cuprous or cupric ions, halide (i.e., chl~ride, bromide or iodide) ions and at least one amine.
Catalyst systems containing manganese compounds constitute a second preferred class. They are generally alkaline systems in which divalent manganese is combined with - ~

RD 20,514 such anions as halide, alkoxide or phenoxide. Most often, the manganese is present as a complex with one or more complexing and/or chelating agents such as dialkylamines, alkanolamines, alkylenediamines, o-hydroxyaromatic aldehydes, o-hydroxyazo compounds,~ -hydroxyoximes (monomeric and polymeric), o-hydroxyaryl oximes and ~-diketones. Also useful are known cobalt-containing catalyst systems. Suitable manganese and cobalt-containing catalyst systems for polyphenylene ether preparation are also known in the art.

Particularly useful polyphenylene ethers are those which comprise molecules having at least one of the end groups of the formulas l ~R2 ~ C~

- O ~ OH
~ Ql (2) _o~O~I, 1;22 Ql (3) wherein Ql and Q2 are as previously defined; each R1 is independently hydrogen or alkyl, with the proviso that the total number of carbon atoms in both Rl radicals is 6 or less; and each R2 is independently hydrogen or a C1_6 primary alkyl radical. Preferably, each R1 is hydrogen and each R2 is alkyl, especially methyl or n-butyl.

RD 20,514 Polymers containing the aminoalkyl-substituted end groups of formula 2 may be obtained by incorporating an appropria~e primary or secondary monoamine as one of the constituents of the oxidative coupling reaction mixture, especially when a copper- or manganese-containing catalyst is used. Such amine~, especially the dialkylamines and preferably di-n-butylamine and dimethylamine, frequently become chemically bound to the polyphenylene ether, most often by replacing one of the ~-hydrogen atoms on one or more radicals. The principal site of reaction is the radical adjacent to the hydroxy group on the terminal unit of the polymer chain. During further processing and/or blending, the aminoalkyl-substituted end groups may undergo various reactions, probably involving a quinone methide-type intermediate of the formula ~0, (4) ~ Ql with numerous beneficial effects often including an increase in impact strength and compatibilization with other blend components, Reference is made to U.S. Pat. Nos. 4,054,553;
4,092,294; 4,477,649; 4,477,651 and 4,517,34 . Polymers with 4-hydroxybiphenyl end groups of formula (3) are typically obtained from reaction mixtures in which a byproduct diphenoquinone of the formula, Ql ~ ~ Ql O=~eO

~ (5) .' ~
: ' ' '. : ' , .
" ' ' . '.' :' ~ ' . ~ .
- . . . ~ ~ :. -.

2 ~

RD 20,514 in present, especially in a copper-halide-secondary or tertiary amine system. In this regard, the disclosure of U.S. Pat. No.
~,~77,649 is again pertinent as are those of U.S. Pat. No.s 4,234,70~ and 4,482,697. In mixtures of this type, the dipilenoquinone is ultimately incorporated into the polymer in substantial proportions, largely as an end group.
In many polyphenylene ethers obtained undex the above-described conditions, a substantial proportion of the polymer molecules, typically constituting as much as about 90%
by weight of the polymer, contain end groups having one or frequently both of formulas (2) and (3). It should be understood however, that other end groups may be present and that the invention in its broadest sense may not be dependent on the molecular structures of the polyphenylene ether end groups.
The salicylic acid ester capped polyphenylene ethers and method for making which can be used in the practice of the present invention are shown in U.S. Patent 4,760,118, White et al. The capping method can be achieved by melt extruding a mixture of a polyphenylene ether with at least one ester of salicylic acid or a substituted derivative thereof.
Particularly useful polyphenylene ethers are poly(2,6-dimethyl-1,4-phenylene ethers) having a number average molecular weight within a range of about 3,000-40,000 and a weight average molecular weight within a range of about 20,000-80,000 as determined by gel permeation chromatography. The intrinsic viscosity is most often in the range of about 0.2-0.6 dl/g as measured in chloroform at 25C. The polyphenylene ether can be reacted in the melt with at least one ester of salicylic acid, or anthranilic acid, or a substituted derivative thereof. The term "ester of salicylic acid" hereinafter means compounds in which the carboxy group, the hydroxy group or both have been esterified.
The capping agents which are generally found to give the best yields of the capped polyphenylene ethers of this invention are aryl salicylates such as phenyl salicylate, aspirin (i.e. acetylsalicylic acid), salicylic carhonate and .' , . ~

t i RD 20,514 _g_ polysalicylates, including both linear polysalicylates and cyclic compounds such as disalicylide and trisalicylide. Such compounds as phenyl salicylate and aspirin react to form acidic by-products (phenol and acetic acid), which may be undesirable.
Therefore, the most preferred capping agents are salicylic carbonate and the polysalicylates, especially linear polysalicylates.
Of the capping agents whic:h may be used according to the invention, such compounds as phenyl salicylate, aspirin and isatoic anhydride are commercially available. Salicylic carbonate is a known compound which may be prepared, for example, by the reaction of salicylic acid with phosgene.
Disalicylide and trisalicylide are also known, as is their preparation by pyrolysis of aspirin; Baker et al., J.Chem.Soc.
1951, 201.
Linear polysalicylates may be prepared by anionic polymerization of salicylic carbonate; Saegusa et al., Polym.
Bull. 1,341 (1979). They have also been found to be the product (rather than the reported disalicylide) of the treatment of salicylic carbonate with a catalytic amount of triethylamine;
Dean et al., J.Chem.Soc., Perkin I, 1972, 2007. Linear polysalicylates are additionally obtainable by reacting salicylic acid with acetic anhydride or thionyl chloride, or by pyrolysis of aspirin at somewhat lower temperatures. Finally, the reaction of salicylic acid with phosgene in the presence of a tertiary amine such as triethylamine affords linear polysalicylates in high yield.
The polyphenylene ether can be heated in the melt with the capping agent. Typical reaction temperatures are in the range of about 225-325~C. The capping reaction can be conveniently conducted in an extruder or similar equipment.
Under certain circumstances, it may be advantageous to extrude the polyphenylene ether with vacuum venting, thus removing a substantial proportion of any amines present in the catalyst.
The capping agent may then be advantageously introduced downstream from the polyphenylene ether feed.

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~ rf~J j J ~ l ~ J

RD 20,514 The proportion of salicylic acid ester capping agent used should generally be sufficient to react with substantially all hydroxy end groups, including those with aminoalkyl substituents. In addition, it is generally beneficial to employ enough capping agent to react with any amine generated. There can be used about 1-12%, and preferably about 2-7% by weight of the salicylic acid ester capping agent, based on polyphenylene ether.
The term "diene based rubber", as used hereinafter, means rubber having unsaturated double bonds and includes, for example, butadiene based rubber which is preferred, and isoprene based rubber.
Diene based rubber impact modifiers for polyphenylene ether 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 in combination with 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, graft and core-shell copolymers as well as combinations thereof.
In combination with diene based rubber there can be used polyolefins or olefin-based copolymers employable in the invention include poly(l-butene), poly(4-methyl-1-pentene), propylene-ethylene copolymers and the like.
A particularly useful class of impact modifiers are those derived from the vinyl aromatic monomers. These include, for example, modified polystyrenes, ABS type graft copolymers, AB and ABA type block and radial block copolymers and vinyl aromatic conjugated diene core-shell graft copolymers. Modified polystyrenes include rubber modified polystyrenes, such as butadiene rubber-modified polystyrene (otherwise referred to as high impact polystyrene or HIPS). Additional useful polystyrenes include copolymers of styrene and various monomers, , -' . . .

c ~

RD 20,514 including, for example, poly(styreneacrylonitrile) (SAN), styrene-butadiene copolymers as well as the modified alpha- and para-substituted styrenes and any of the styrene reslns disclosed in U.S. Patent 3,383,435. ABS types of graft copolymers are typified as comprising a rubbery polymeric backbone derived from a conjugated cliene alone or in combination with a monomer copolymerizable therewith having grafted thereon at least one monomer, and preferably two, selected from the group consisting of monoalkenylarene monomers and substituted derivatives thereof as well as acrylic monomers such as acrylonitriles and acrylic and alkylacrylic acids and their esters.
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) blocks and represented as AB and ABA block copolymers.
Suitable A~ type block copolymers are disclosed in, for example, U.S. Patents 3,07~,254; 3,402,159; 3,297,793; 3,265,765 and 3,594,452 and UK Patent 1,264,741. Examples of typical species of AB block copolymers are polystyrene-polybutadiene ~SBR), polystyrene-polyisoprene and poly(alphamethyl-styrene)-polybutadiene. Such AB block copolymers are available commercially from a number of sources, including Phillips Petroleum under the trademark SOLPRENE.
Examples of triblock copolymers include polystyrene-polybutadiene-polystyrene (SBS), polystyrene-polyisoprene-polystyrene (SIS), poly(~-methylstyrene)-polybutadiene-poly-(~-methlylstyrene) and poly(~-methylstyrene)-polyisoprene-poly-(~-methylstyrene).
Particularly preferred triblock copolymers are available commercially under the trademarks CARIFLEX, and KRATON D from Shell. Referenc~ also is made to Kambour, U.S. Patent 3,639,508.
Another c]ass of impact modifiers is derived from conjugated dienes. While many copolymers containing conjugated ~ ~ r~ Y;t RD 20, 514 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, butadiene-glycidyl methacrylate 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.
Patents ~,933,480; 3,000,866; 3,407,158; 3,093,621 and 3,379,701.
Other suitable impact modifiers are the core-shell type graft copolymers. In general, these have a predominantly conjugated diene 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.
The preferred impact modifiers are block (typically diblock, triblock or radial telebloc~) copolymers of alkenylaromatic compounds and dienes or a mixture of dienes and olefins. Most often, at least one block is derived from styrene and at least one other block from at least one of butadiene, or isoprene. Especially preferred are the triblock copolymers with polystyrene end blocks and diene-derived midblocks. The average molecular weights of the impact modifiers are typically in the range of about 50,000-300,000. Block copolymers of this type are commercially available from Shell Chemical Company under the trademark KRATON, and include KRATON D1101, and D1102.
Dialkylamines which can be used in the practice of the invention are characterized by having a boiling point of at least 150C. The dialkylamines are included within the formula, ~r~ f RD 20,514 H

(6) where R3 and R4 are selected from C~ ) organic radicals selected from alkyl radicals, cycloalkyl radicals and alkaryl radicals, where the sum of the tota] number of carbon atoms in R3 and R4 iS sufficient to provide clialkylamines having volatility characteristics allowing for polyphenylene ether extrusion conditions of at least 150C or greater. There are included within the dialkylamines of formula ~6), dibutylamine, dioctylamine, dihexylamine, dioctadecylamine, methyloctadecylamine, methyldodecylamine, dicyclohexylamine, n-butylbenzylamine and dibenzylamine.
The thermally stable blends of polyphenylene ether and diene based rubber can be made by melt blending, and preferably melt extruding, the ingredients at temperatures of from 250C to 350C. The resulting blend can be pelletized and thereafter blended with an organic polymeric matrix material, such as a polyamide, polystyrene, a polyetherimide, or a polyester, for example, polyalkyleneterephthalate and preferably polybutyleneterephthalate. Dry blending followed by melt extrusion at the aforementioned melt extrusion temperatures also will provide effective results. Additional procedures can include "down stream feeding" where the matrix material and/or the diene based rubber can be added to the extruder following the earlier melt extrusion of the polyphenylene ether.
A proportion of from 60 to 200 parts of the matrix material, per 100 parts of the polyphenylene ether will provide effective results.
Polyamicles suitable as matrix material in the preparation of the compositions of this invention may be made by any known method, including the polymerization of a monoanino-monocarboxylic acid or a lactam thereof having at least 2 carbon atoms between the amino and carboxylic acid group, of substant:ially equimolar proportions of a diamine which ' '' ` ~

- ~

2 ~3 RD 20,51 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 with the -CO-NH- group in the case of a lactam. Particular examples of aminocarboxylic acids and lactams are ~-aminocaproic acid, butyrolactam, pivalolactam, ~-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. Such diamines include, for example, those represented by the general formula H2N(CH2)nNH2 wherein n is an integer of from 2 to 16. Illustrative diamines are trimethylenediamine, tetramethylenediamine, pentamethylene-diamine, octamethylenediamine, hexamethylenediamine (which is often preferred), trimethylhexamethylenediamine, m-phenylenediamine and m-xylylenediamine.
The dicarboxylic acids may be represented by the formula HOOC-Y-COOH

.,. ". .
'' :' '~ ` ' ':

7 1 ~

RD 20,514 wherein Y is a divalent aliphatic or aromatic group containlng at least 2 carbon atoms. Examples of aliphatic acids are sebacic acid, octadecanedioic acid, suberic acid, glutaric acid, pimelic acid and adipic acid. Aromatic acids, such as isophthalic and terephthalic acids, are preferred.
In addition to polyamides, other matrix material which can be used are polystyrene and polyesters, such as poly-alkyleneterephthalates and preferably polybutyleneterephthalate.
In addition, polyetherimides are included which are shown by Heath et al, U.S. Pat. 3,847,867.
Polyesters which can be used as matrix material, generally have number average molecular weights in the range of about 20,000-70,Q00, as determined by intrinsic viscosity (IV) at 30C in a mixture of 60% (by weight) phenol and 40 1,1,2,2-tetrachloroethane. When resistance to heat distortion is an important factor the polyester molecular weight should be relatively high, typically above about 40,000.
The polyesters are ordinarily prepared by the reaction of at least one diol such as ethylene glycol, 1,4-butanediol or 1,4-cyclohexanedimethanol with at least one aromatic dicarboxylic acid such as isophthalic or terephthalic acid, or lower alkyl ester thereof. Poly(ethylene terephthalate) and poly(butylene terephthalate), and especially the latter are preferred.
In order that those skilled in the art will be better able to practice the present invention, the following examples are given by way of illustration and not by way of limitation.
All parts are by weight.

~xample Blends of poly(2,6-dimethyl-1,4-phenylene ether) having an intrinsic viscosity of about 0.4 dl/g in chloroform at 25C and a styrene butadiene styrene block copolymer (Kraton KDl102 manufactured by the Shell Chemical Company) were prepared using a 20 mm Welding Engineers twin screw extruder at a set ~37 1~7 RD 20,514 temperature of 295C and a screw speed of 400 rpm. A weight ratio of 80/20 of the polyphenylene ether to the styrene butadiene styrene block copolymer was used for the blends. In producing the polysalicylate end capped polyphenylene ether, there was added 6.5 weight ~ of polysalicylate to a polyphenylene ether having an intrinsic viscosity of about 0.4 dl/g in chloroform at 2SC during melt extrusion using a twin screw extruder in accordance with the teaching of U.S. Patent 4,760,118.
In addition to the polysalicylate end capped polyphenylene ether blends, additional blends were prepared utilizing 80 parts of polyphenylene ether free of polysalicylate end capping and 20 parts of the styrene butadiene styrene copolymer. Further blends were prepared utili~ing commercial stabilizers and some of the blends of polyphenylene ether free of the polysalicylate end capping with the styrene butadiene styrene copolymer. In instances where dioctylamine was used it was employed at a level of either 1~ or 2% by weight, based on the weight of the blend. Two different molding procedures were used to simulate mild and severe thermal recycling histories.
For a mild thermal recycling, a temperature of 240C was used and the molded extrudate held for 1 minute prior to quenching.
Quenching was effected by introducing the sample in the molding press having platens at a temperature of about 20C.
A more severe thermal recycling history was used when the samples were heated to 300C and held for 20 minutes prior to quenching after the initial molding procedure.
Rubber stability was determined by using dynamic mechanical analysis to measure the temperature of the loss peak associated with the glass transition temperature of the butadiene based rubber. An increase in the glass transition temperature would indicate an increase in the crosslink density.
The following results were obtained, where PPE is polyphenylene ether, and the components in square brackets were extruded prior to being blended with KD 1102, impact modifier:

. .
-~ ~ 3 RD 20,514 Table I

Rubber Transitions (C) Mild Processing Severe Processing Blends1 min at 240C 20 min at 300OC
.
1. KDl102 -80 -54 2. PPE/KDl102 -62 to -51 15 to 45 3. PPE/KD1102/Seenox 412S(1%)/
Ultranox 257 (1%~-61 5 4. PPE/KD1102/Dioctylamine (1%) -62 13 5. PPE/KD1102/Dioctylamine (2%) -67 -5 6. [PPE]/XD1102 -81 to -71 -27 to 2 7. [PPE]/KD1102/Dioctylamine (1%) -81 -55 8 [PPE/Seenox 412S(1%)/
Ultranox 257(1%)] KD1102 -80 -33, -42 9. [PPE/Dioctylamine (2%)]/KD1102 -84 -46 10. [PPE/Polysalicylate (6.5%)]/ -82 -44 11. [PPE/Polysalicylate (6.5%)/ -86 -35 Irganox 1024 (1.5%)] KD1102 12. [PP~/Polysalicylate (6.5%)/
Seenox 412 (1%)/Ultranox 257 (1%)]/

The above results show that the stability of the SBS
is much worse in polyphenylene ether blends than whell the SBS is processed alone. One possible explanation is that there are components in the polyphenylene ether resin which catalyze the polybutadiene cross linking reaction. The addition of a stabilizer consisting of a hindered phenol (Ultranox 257 provided by GE Speciality Chsmicals and Seenox 412S supplied by Argus Chemical Co,, a thioester found to have synergistic effects when used with hindered phenols), provide some - ... .

. . , -RD 20,514 improvement in rubber stability. However, the Tg of the rubber still increases sufficiently during processing to eliminate this blend as material which can be satisfactorily recycled during high thermal conditions. The addition of dioctylamine at 1~
provides a rubber stability substanl;ially equivalent to the use of conventional stabilizers, while further improvement is shown using dioctylamine at a 2% weight level.
Further improvements in polybutadiene stability can be achieved by using extruded polyphenylene ether resin which is shown by polyphenylene ether in the square brackets. The addition of 1~ or 2% by weight of dioctylamine in combination with the preextruded polyphenylene ether reduces the polybutadiene Tg to a value substantially equivalent to the polybutadiene when processed alone. A possible explanation is that the dioctylamine is effectively neutralizing the components in the polyphenylene ether resin that are responsible for accelerating the polybutadiene crosslinking reaction. These results show that enhanced resistance to loss in impact upon thermal recycling of molded blends of such polyphenylene ether, KD1102, and dioctylamine can be predicted.
The use of preextruded polysalicylate capped PPE, as shown in 10, ll and 12 provides further improvement in rubber stability as compared to the preextruded PPE alone.
Additional evaluation of particular samples shown in Table I was made to determine their Notched Izod value under Mild Processing and Severe Processing conditions. Izod bars for impact testing were produced on an Engel 28 ton injection molding machine. For the mild process history, the samples were molded at 300C using an average residence time in the barrel of 2.2 minutes. For the severe process history, the samples were also molded at 300C, but the residence time in the barrel was increased to 15 minutes by enlarging the cushion in front of the screw. The following results were obtained:

.

, ' ~-~ ~ 7;~

RD 20,514 Table II

Impact Performance of PPE/KD1102 Blends Mild Processing Transition Notched Izod (ft-lb/in~
Material Temperature(C)_ -29C -23C
PPE/KD1102 -34 - 3.2 PPE/KD1102 -41 1.0 2.8 [PPE]/XD1102 -70 1.9 4.4 ~PPE/Polysalicylate -75 2.3 5.4 (2~)]/KD1102 Severe Processing Transition Notched Izod (ft-lb/in) Material Temperature(C~ _ -29C -23C
PPE/KD1102 17 - 2.5 PPE/KD1102 -7 0.7 2.8 [PPE]/KD1102 -26 0.6 2.8 [PPE/Polysalicylate -42/18 0.9 3.4 (2%)~/KD1102 Although the above examples are directed to only a few of the very many variables which can be used in the practice of the present invention, it should be understood that the present invention is directed to the use of a much broader variety of polyphenylene ethers, polysalicylate end capped polyphenylene ethers, diene based rubber and dialkylamines as set forth in the description preceding these examples.

.
- - ; - ~ ~

.

Claims (21)

1. A polyphenylene ether composition which has enhanced impact strength when initially molded and which resists loss of impact strength upon being thermally recycled at temperatures in the range of 250°C-:350°C, or thermally aged at a temperature of 50°C-200°C, comprising by weight, from about 5 to about 400 parts of a diene based rubber, per 100 parts of a polyphenylene ether, which blend of polyphenylene ether and diene based rubber is an extrudate of a mixture selected from the class consisting of, (a) a blend of polyphenylene ether, a diene based rubber and an effective amount of a dialkylamine having a boiling point of at least 150°C, (b) a blend of a diene based rubber, a preextruded polyphenylene ether and an effective amount of a dialkylamine having a boiling point of at least 150°C, and (c) a blend of a diene based rubber and a preextruded mixture of polyphenylene ether and an effective amount of a dialkylamine having a boiling point of at least 150°C.

2. A polyphenylene ether composition in accordance with claim 1, where the polyphenylene ether is poly(2,6-dimethyl -1,4-phenylene ether).

3. A polyphenylene ether composition in accordance with claim 1, which is an extrudate of a styrene-butadienestyrene copolymer, a polyphenylene ether and dioctylamine.

RD 20,514

4. A polyphenylene ether composition in accordance with claim l, where the polyphenylene ether has been preextruded prior to blending with the diene based rubber and the dialkylamine.

5. A polyphenylene ether composition in accordance with claim 1, which is an extrudate of a blend of polyphenylene ether, a diene based rubber, and an effective amount of a dialkylamine and 60 to 200 parts by weight of a matrix organic polymer, per 100 parts of the polyphenylene ether.

6. A polyphenylene ether composition in accordance with claim 5, where the polyphenylene ether and the dialkylamine is utilized in the blend as a preextruded mixture.

7. A polyphenylene ether composition in accordance with claim 5, where the matrix material is a polyamide.

8. A polyphenylene ether composition in accordance with claim 5, where the matrix material is a polyester.

9. A polyphenylene ether composition in accordance with claim 5, where the matrix material is a polyetherimide.

10. A polyphenylene ether composition in accordance with claim 5, where the matrix material is a polystyrene.

11. A polyphenylene ether composition which has enhanced impact strength when initially molded and which resists loss of impact strength upon being subjected to thermal recycling conditions at a temperature in the range of 250°C-350°C, or exposed to thermal aging conditions over a temperature in the range of 50°C-200°C, which comprises by weight from about 5 to about 400 parts of a diene based rubber, per 100 parts of a preextruded salicylic acid ester capped polyphenylene ether.

RD 20,514

12. A polyphenylene ether composition in accordance with claim 11, where the polyphenylene ether is a salicylic acid ester capped poly(2,6-dimethyl-1,4-phenylene ether).

13. A polyphenylene ether composition in accordance with claim 11, which is an extrudate of a styrene-butadienestyrene copolymer and preextruded salicylic acid ester capped polyphenylene ether.

14. A polyphenylene ether composition in accordance with claim 11, which is an extrudate of a diene based rubber, and 60 to 200 parts by weight of a matrix organic polymer, per 100 parts of the preextruded salicylic acid ester capped polyphenylene ether.

15. An extrudate in accordance with claim 14, which utilizes a polyamide as a matrix material.

16. An extrudate in accordance with claim 14, which utilizes a polyester as a matrix material.

17. An extrudate in accordance with claim 14, which utilizes a polyetherimide as a matrix material.

18. An extrudate in accordance with claim 14, which utilizes polystyrene as a matrix material.

19. A polyphenylene ether composition in accordance with claim 12, where the preextruded polyphenylene ether is capped with about 1-12% by weight of salicylic acid ester.

20. A polyphenylene ether composition in accordance with claim 19, capped with about 2-7% by weight of salicylic acid ester.

-23- RD - 20,514

21. The invention as defined in any of the preceding claims including any further features of novelty disclosed.