EP0097152A4

EP0097152A4 - Polyphenylene ether phosphites.

Info

Publication number: EP0097152A4
Application number: EP19820900463
Authority: EP
Inventors: David John Galicchia; Philip Langdon Kinson
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1981-12-18
Filing date: 1981-12-18
Publication date: 1984-04-17
Also published as: JPS58502150A; AU8085582A; WO1983002117A1; EP0097152A1

Abstract

The softening points, intrinsic viscosities, and impact strength values of hydroxyl-terminated thermoplastic polyphenylene ether resins are improved when the resins are "capped" (i.e., reacted) with a triaryl phosphite. The reaction proceeds rapidly to a useful extent in the normal time the components pass through an extrusion press or molding machine.

Description

Polyphenylene Ether Phosphites

The present invention relates to capped Thermoplastic polyphenylene ether resins, molding compositions containing said resins, and mixtures of materials and processes for the preparation of the resins.

Background of the Invention - The polyphenylene ether resins (also termed "polyphenylene oxide resins" and "phenoxy polyphenylenoxy phenol resins") are a well-known large and constantly expanding family of linear thermoplastic engineering resins having the theoretical formulas

wherein X and X' independently represent a substituent or hydrogen, Y and Y' each independently represent an inert substituent, and n represents a number (usually above 50) which is sufficiently large so that the polymer possesses a desirably high softening point. The resins themselves were discovered by Dr. A. S. Hay, and a wide variety of these resins and a number of methods for their preparation are disclosed in Hay U.S. Patent Nos. 3,306,874 and 3,306,875 as well as in Stamatoff U.S. Patent Nos. 3,257,357 and 3,256,358. The substituents designated by X, X', Y and Y' are not critical so long as they are inert, and a variety of lower alkyl, cycloalkyl, halohydrocarbon, hydrocarbonoxy and halohydrocarbonoxy substituents have been found to be generally useful.

The polymer molecules are hydroxyl-terminated, and it has recently been found that these subεtitueπts impart certain properties to the resin, which can be improved by "capping" the resin, that is, by esterifying the hydroxyl groups with a monocarboxylic acid, monoacyl halide, or the equivalent, prefer ably after the resins have been reacted with a diphenoquinone; see Hay U.S. Patent No. 4,048,143 and White U.S. Patent No. 4,165,422. These resins, after being capped, when molded alone or in admixture with customary additives, provide articles which possess outstandingly useful physical properties. The compositions are used for the molding of radio and television cabinets, hand tool and household appliance housings, medical and surgical instruments, films, sheets, etc.

The discovery has now been made that the stability of the polyphenylene ether resins and the impact resistance and elasticity of molded .articles prepared therefrom are significantly improved, without need for a preliminary diphenoquinone reaction or other preliminary step, when at least part of the resin is present in capped condition, that is, when the resin is present in the composition or alone as an ester of phosphorous acid, that is, as a phosphite, as is more particularly set forth below. Blends of phosphates and polyphenylene ethers are described in Lee, Jr., U.S. 4,166,055.

The further discovery has been made that the capping reaction proceeds rapidly at normal extrusion or molding temperature, and that a substantial improvement in the properties mentioned can be effected by merely uniformly mixing the polyphenylene ether resin with an appropriate triaryl phosphite and then feeding the mixture into a commercial thermoplastic extrusion or molding machine having a chamber temperature which is higher than the transesterification point of the mixture and preferably in the range of 400οF.-700^οP. In this range the capping reaction proceeds rapidly without significant degradation of the resin. The capping reaction proceeds while the mixture is passing through the machine, and the fact that a transesterification reaction is taking place is evident from the phenolic odor which is released. Also confirmatory are chromatographic and spectral data.

The invention thus provides a capped thermoplastic polyphenylene ether resin having the theoretical formula :

wherein R represents the residue of a polyphenylene ether resin, and A and A' independently represent R or a thermostable aryl substituent containing not more than 10 carbon atoms. The polyphenylene ether resin residue has the theoretical formula:

wherein X, X', Y, Y' and n have the meanings assigned to them above. Preferably X and X' represent hydrogen and Y and Y' represent methyl, so that the residue is derived from a poly (2,6-dimethyl-1,4-p-ienylene) ether resin prepared by the catalyzed oxidative polymerization of 2,6-xylenol by the method of said Hay patents and having an intrinsic viscosity in the range of about 0.2 to 0.8 dl./g.

Preferably also at least one of the substituents A or A' represents R, so that the molecular weight of residue R is in effect doubled.

The polyphenylene ether resin itself is useful for molding purposes, but more advantageously it is present as a component (and preferably as a predominant component) of a thermoplastic molding composition in particulate free-flowing form. The invention further provides a thermoplastic blend of the polyphenylene ether resin in uncapped state and a triaryl phosphite, of the type described below, the molar ratio of the resin to the triaryl phosphite being between about 1:10 and 9:1. The resin and the phosphite can be present as separate particles, or the phosphite can be in solution in the resin. The latter solution is prepared by dissolving the uncapped polyphenylene ether resin and the triaryl phosphite in a volatile mutual solvent to form a homogeneous solution of the two materials, evaporating the solvent, and comminuting the product. If desired, other compatible and soluble resins can be present in the solution.

The invention still further provides a method for capping a thermoplastic polyphenylene ether resin which comprises forming a homogeneous melt of the resin and a triaryl phosphite of the type mentioned below and heating the melt at a transesterification temperature until evolution of phenolic matter has substantially ceased. In the instance where the triaryl phosphite is triphenyl phosphite, the phenolic matter is phenol. The capping occurs rapidly when the melt has a temperature between 400°F. and 700°F. in most instances, and in other instances a suitable temperature can be found by laboratory trial.

The capped resins of the present invention possess a decreased proportion of reactive hydroxyl substituents, and if desired they need possess substantially none o'f these substituents. As a result, the capped resins possess improved chemical stability, particularly to oxidants, without added disadvantage. This in turn improves the life of molded articles which contain the resin under adverse conditions of service. The capped resins are compatible with the widely-used resins of the Noryl type, as well as with polystyrene and copolymers of styrene with butadiene.

In the capping process, the extent to which, the polyphenylene ether resin should be reacted with the triaryl phosphite depends in part on the extent of the improvement in stability and strength which is desired, and in the time which is available for the reaction. Thus, theoretically in the initial reaction mixture "the molar ratio of resin to the triaryl phosphite need not be larger than 3:1, as this ratio provides a sufficient amount of the triaryl phosphite(which contains three functional groups) for esterification of substantially all of the hydroxyl substituents of the resin. The ratio thus provides a capped resin having the theoretical formula:

wherein the R's represent the polyphenylene ether resin residue, as is shown above. Capped resins of this formula generally possess all the benefits of the present invention.

However, the ratio of the polyphenylene ether resin to the triaryl phosphite can be decreased considerably without more than a slight loss of benefit. Thus the resin:phosphite molar ratio can be as low as about 2:1. With this ratio the capped resin has the theoretical formula:

wherein the R's represent the polyphenylene ether resin residue and Ar represents one of the substituents of the starting triaryl phosphites. This ratio provides an effective doubling of the molecular weight of the starting resin as well as a substantial increase in stability.

If further desired, the molar ratio of the resin to the triaryl phosphite can be decreased still further, to the range of about 1:1. This ratio provides a capped polyphenylene ether resin which hasthe theoretical formula:

wherein the substituents have the meanings set forth above, and which therefore possesses substantially improved stability.

Surprisingly, however, it has been found that the reaction of even a small amount of a triaryl phosphite (.i.e., at a resin:phosphite molar ratio of less than 1:1) results in a very perceptible improvement in the properties noted above. The reason for this appears to be that a certain proportion of the triaryl phosphite reacts with the resin to the extent of all three of its functionalities and that a further proportion of the triaryl phosphite reacts with the resin to the extent of two of its functionalities. These portions of the triaryl phosphite thus provide the benefits stated above.

Because of the speed with which the transesterification reaction takes place, it is practical to supply the polyphenylene ether resin and the triaryl phosphite as an unreacted blend to the molding or extrusion machine. The capping reaction proceeds to a satisfactory extent in the brief time during which these components are in molten state in the molding machine. The conditions required for a substantially complete transesterification reaction are an adequately long time at a sufficiently high temperature, and usually these conditions are easily met within a commercial extrusion or molding machine. It is advantageous in some cases to provide a substantial excess of the triaryl phosphite so as to force the transesterification reaction in the desired direction, an excess of 10 to 50 mol percent being preferred. The preferable proportion of triaryl phosphite which need be added in any instance depends, in addition to the variables mentioned above, on the chain length or molecular weight of the polyphenylene ether resin, short chain length resins requiring a larger weight percent of the triaryl phosphite, than the longer chain length resins. The preferable proportion in any instance can be rapidly found by making a series of laboratory trials along the lines shown in the examples below.

Suitable triaryl phosphites for capping the polyphenylene ether resins are the phosphorus acid triesters of phenols which contain not more than 10 carbon atoms. Phosphites of this group are non-volatile at temperatures at which the polyphenylene ether resins are molten but below their decomposition points, yet the phenolic components, when released, are volatile in this temperature range and so cause the transesterification reaction to proceed in the desired direction. Suitable phosphites include tri (p-aminothiophenyl) phosphite, tri- (o-bromo- phenyl) phosphite, tri (o-chlorophenyl) phosphite, tri-o-iso- propylphenyl phosphite, triguaiacyl phosphite, tricresyl phosphite, tri (dimethoxyphenyl) phosphite, tri-(2,4-dichlorophenyl) phosphite, tri-(2,6-diidophenyl) phosphite, tri-o-isopropyl- phenyl phosphite, and tri (thibphenyl) phosphite. Triphenyl phosphite is preferred because this ester has a sufficiently high boiling point (245^οC, 473^οF.) to permit it to remain in a polyphenylene ether resin melt without more than negligible volatilization, and yet the transesterifcation product (phenol) has a sufficiently low boiling point (approximately 182°C.) so that it volatilizes rapidly and completely as soon as it is formec. With triphenyl phosphite, the transesterification can be performed within a few minutes in an open reaction vessel at about the minimum temperature at which preferred polyphenylene ether resins form a fluid mix. The capped polyphenylene ethers of the present invention can be molded alone to provide useful articles, or they can be and preferably are molded in admixture with any of the modifying polymers, plasticizers, stabilizers, fire retardants, fillers, strengthening agents and pigments which have been used in the past in conjunction with thermoplastic molding resins. Thus the capped polyphenylene ether resins can be molded in admixture with polystyrene, styrene-butadiene, copolymers, polyethylene, zinc oxide, zinc sulfide, asbestos fibers, glass fibers, carbon whiskers, ground walnut shells, carbon black, titanium dioxide pigment, etc., in any of the customary proportions. The polyphenylene ether resin's which can be used as the starting materials of the present invention may be of customary engineering molecular weight, usually expressed as an intrinsic viscosity in the range of 0.20 to 0.80 dl./g. as determined in CHCI₃ at 30^οC. it is an important feature of the invention, however, that the polyphenylene ether resins which have a molecular weight which is too low to permit them to be used for structural purposes, i.e., resins which have intrinsic viscosities in the range of about 0.20 to 0.40 dl./g., can be rendered suitable for structural purposes by the present invention. Thus if it is desired to prepare a capped resin which has a higher molecular weight than the starting resin, a sufficient proportion of the triaryl phosphite is used so that the diester or triester is formed from substantially all of the resin, as is shown above. This permits the conversion of a comparatively low molecular weight starting polyphenylene ether resin into a capped product which has about twice the original molecular weight and which therefore possesses a much higher softening point and so provides a molded article having a higher impact resistance and greater elasticity. If the starting polyphenylene ether resin is of engineering molecular length, the capping procedure, performed to best advantage as described, provides resin which is of still better quality.

The existence of capped resin can be determined directly by conventional analytical techniques, for example, by ³¹p and ¹³C nuclear magnetic resonance spectra, by determining the amount of increase in the intrinsic viscosity of the resin, and by the use of GPC data. In addition, the proportion of the polyphenylene ether resin which is esteri fied in any instance can be determined by recovering the evolved phenol or other released component of the triaryl phosphite and calculating therefrom the number of aryl groups of the phosphite which have reacted. These data in turn will permit determination of the percentage of the hydroxyl substituents of the resin which have undergone esterification.

The capped polymer can be recovered in high yield from the crude reaction product by dissolving the reaction product in a sufficiently large amount of toluene to form a fluid solution and then adding cold methanol. The capped polymer precipitates and can be recovered by filtration, centrifugation, etc., followed by a washing with methanol.

The invention is further illustrated by the examples which follow. These examples are specific embodiments of the invention and are not to be construed in limitation thereof. Parts are by weight unless otherwise stated. EXAMPLE I

The following illustrates the preparation of a capped polyphenylene ether resin by transesterification of the resin with a triaryl phosphite, showing the effectiveness of a preferred triaryl phosphite in comparison with other phosphites.

A. 50 parts of a powdered polyphenylene ether resin ("PPO", of General Electric Co.) having an intrinsic viscosity of 0.48 dl./g. (determined in CHCl₃ at 30^οC.), 50 parts of polystyrene (Dylene 8G) as modifying resin, and 1 part of triphenyl phosphite are dry blended in a Henschel mixer until a homogeneous blend is obtained. The blend is fed into a 28-mm. Warner-Pfleiderer twin-screw extruder working at 600°F. and the resulting composition is extruded and chopped into pellets. The intrinsic viscosity of the extruded composition is 0.80 dl./g.

B. (control). Procedure A is repeated except that the triphenyl phosphite is omitted. The intrinsic viscosity of the product is 0.67 dl./g.

C. (control). Procedure A is repeated except that the triphenyl phosphite is replaced by 1 part of decyldiphenyl phosphite. The intrinsic viscosity of the product is 0.69 dl./g.

D. (control). Procedure A is repeated except that the triphenyl phosphite is replaced by 1 part of triisoctyl phosphite. The intrinsic viscosity of the product is 0.65 dl./g.

The products of the above runs A-D are separated into their polyphenylene ether resin and polystyrene components. The intrinsic viscosity of the polystyrene is substantially constant. The increases in intrinsic viscosity are due to increases in the intrinsic viscosities of the polyphenylene ether resin, resulting from the capping reaction.

EXAMPLE 2 The following illustrates the preparation of a molding composition having a substantial content of a polyphenylene ether resin capped by reaction with a triaryl phosphite and the properties of a test piece molded therefrom, in comparison with a test piece molded from a similar composition prepared by use of a polyphenylene ether resin containing a trialkyl phosphite.

A. The following are dry blended in powdered form: Polyphenylene ether resin (high molecular weight; intrinsic viscosity 0.45 dl.g.) 50 parts Polystyrene-butadiene copolymer (high impact type, Foster-Grant Co. No. 834) 50 Triphenyl phosphite 0.83 Polyethylene 1.5 Triphenyl phosphate (plasticizer) 3.0 Zinc oxide 0.15 Zinc sulfide 0.15 Titanium dioxide pigment 3.0 The resulting free-flowing particulate composition is extruded and molded into test bars by the procedure of Example 1. The pieces have a notched Izod impact strength of 3.8 ft.-lb./in. and a 62% elongation at break.

B. (control). Procedure A is repeated except that the triphenyl phosphite is replaced by 1.12 parts (an equimolecular amount) of triisooctyl phosphite. The test pieces exhibit a notched Izod strength of 3.5 ft.-lb./in. and an elongation at break of 54%. EXAMPLE 3

The following illustrates the effectiveness of the process of the present invention in producing an engineeringgrade resin from a resin having too low a molecular weight to be of practical utility for structural purposes.

A. The procedure of Example 2 is repeated, except that the high molecular weight polyphenylene ether resin is replaced by an equal weight of a low molecular weight polyphenylene ether resin (intrinsic viscosity = 0.37 dl./g.). The molded product has a notched Izod impact strength of 3.3 ft.-lb./in.

B. (control). Procedure A is repeated except that the triphenyl phosphite is replaced by 1.00 part of decyldiphenyl phosphite (equimolar amount). The product has a notched Izod impact strength of 2.2 ft.-lb./in.

EXAMPLE 4

The following illustrates the preparation of a homogeneous polyphenylene ether resin-triaryl phosphite blend by the solution method.

To a laboratory reaction flask fitted with thermometer, nitrogen gas inlet tube and gas vent tube leading to a dry-ice trap are placed a solution of polyphenylene ether in toluene and triphenyl phosphite. The solution is stirred and heated to 60-80^οC., and evolution of phenol is observed by chromatography. The polymer is precipitated with an excess of methanol and dried. Extrusion and molding into test bars is carried out. The Izod impact strength is acceptable. The above mentioned patents and/or publications are incorporated herein by reference. Obviously, 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 embodimenrs of the invention described which are within the full intended scope of the invention as defined by the appended claims.

Claims

Claims 1. A capped thermoplastic polyphenylene ether resiii having the theoretical formula:

wherein R represents the residue of a thermoplastic polyphenylene ether resin, and Ar and Ar' independently represent R or a thermostable aryl substituent containing not more than 10 carbon atoms.

2. A capped resin according to Claim 1 wherein

R represents the residue of a poly (2, 6-dirsethy1-1,4-phenylene) ether resin.

3. A capped resin according to Claim 1 wherein Ar represents R.

4. A capped resin according to Claim 1 wherein Ar and Ar' both represent R.

5. A capped resin according to Claim 1 wherein Ar represents phenyl.

6. A capped resin according to Claim 1 wherein Ar and Ar' both represent phenyl.

7. A capped resin according to Claim 1 wherein Ar and Ar' both represent the residue of a poly(2,6-dimethyl- 1,4-phenylene) ether resin.

8. A capped resin according to Claim 1 wherein said thermoplastic polyphenylene ether resin from which said residue is derived has an intrinsic viscosity between 0.2 and 0.8 dl./g.

9. A thermoplastic molding composition in particulate free-flowing form comprising a capped polyphenylene ether resin according to Claim 1.

10. A thermoplastic molding composition in particulate free-flowing form comprising a capped polyphenylene ether resin according to Claim 7.

11. A thermoplastic blend in particulate free-flowing form comprising a polyphenylene ether resin and a triaryl phosphite, the aryl substituents of said phosphite containing notmore than 10 carbon atoms each, and the molar ratio of said resin to said phosphite being between about 1:10 and 9:1.

12. A blend according to Claim 11 wherein said resin is a poly (2, 6-dimethylphenylene-1,4-phenyl) ether resin.

13. A blend according to Claim 1 wherein the triaryl phosphite is triphenyl phosphite.

14. A blend according to Claim 13 wherein said resin is poly (2,6-dimethylphenylene-1,4-phenyl) ether.

15. A blend according to Claim 10 wherein said resin and said phosphite are present as separate particles.

16. A blend according to Claim 10 wherein said phosphite is in solution in said resin.

17. A method of 'capping a thermoplastic polyphenylene ether resin which comprises forming a homogeneous melt of said resin and a triaryl phosphite in molar ratio between about 1:10 and 9:1, the aryl substitutents of said phosphite containing not more than 10 carbon atoms each, and heating said melt at a transesterification temperature until at least a part of said resin has esterified with said phosphite.

18. A method according to Claim 17 wherein the molar ratio of said resin to said phosphite is about 1:1 to 3:1.

19. A process according to Claim 17 wherein said resin has an intrinsic viscosity between 0.2 and 0.8 dl./g.

20. A process according to Claim 17 wherein said phosphite is triphenyl phosphite and said melt is heated to a temperature between 400^οC. and 700°C.