IMPACT STRENGTH IMPROVED POLYPHENYLENE ETHER RESIN COMPOSITIONS

Abstract: The impact resistance of articles produced from a composition rich in polyphenylene ether resin alone or in combination with conventional additives is stabilized when the starting polyphenylene ether resin (or a composition containing the resin) includes a small but effective content of a hindered phenolic compound.

Description: IMPACTSTRENGTHIMPROVEDPOLYPHENYLENEETHERRESIN COMPOSITIONS The present invention relates to polyphenylene ether resin compositions of improved impact resistance. More particularly the invention relates to polyphenylene ether resins alone and in admixture with conventional additives together with an agent which inhibits degradation of the resin at molding temperatures, and to filled and/or plasticized compositions. Background of the Invention The polyphenylene ether resins (also termed "poly¬ phenylene oxide resins") are a well-known family of linear thermoplastic engineering resins having the repeating formul : wherein X and X' independently represent inert substituents, Y and Y' each independently represent an inert substituent, and n represents a number (usually 50 or more) which is sufficiently large so that the poly- ether possesses a softening point which is sufficiently high to satisfy engineering requirements. A wide variety of these resins and a number of methods for their preparation are disclosed in Kay U.S. Patent Nos. 3,306, 874 and 3,306,875* as well as in Stamatoff U.S. Patent Nos. 3,257,357 and 3,257,358. The substituents designated by X, X' , Y and Y' are not critical so long as they are inert and thermostable, and a variety of lower alkyl cycloalkyl, halohydrocarbon, hydrocarbonoxy and halo- hydrocarbonoxy substituents have been found to be O PI generally useful. The resins wherein X and X' represent hydrogen and Y and Y* represent methyl have long been in large-scale commercial production, the preferred polymer being poly(2,6-dimethyl-l,4-phenylene)ether, prepared by the catalyzed oxidative polymerization of 2,6-xylenol. Molding compositions containing relatively high amounts of said resins, e.g., from 70 to 90 or even 100 parts per hundred of the total resin are very difficult to process (because of their otherwise excellent high heat properties) and this is reflected in poorer impact strength than is desired. It has now been found that the impact resistance of moldings prepared compositions rich in the polyphenylene ether resins of the type described is stabilized or increased, and in preferred instances is very greatly increased, when the polyphenylene ether resin is supplied to the molding machine in admixture with a hindered phenolic compound. The improvement occurs.when the resins are molded alone in admixture only with the phenolic co - pound, and also when the resins are molded in admixture - .. : with one or more of the customary added materials, and is more fully disclosed below. Impact resistance is a very important physical property of a molded thermoplastic article, and even a slight increase in this property is of commercial importance. Moreover, the resins can be molded in admixture with an organic plasticizer (typically a triaryl phosphate) and a mineral filler (typically clay) and neither of these materials inhibits the impact strength improving action of the above-mentioned phenolic compound. The invention thus provides useful compositions high in polyphenylene ether resin content with over a small but effective amount of-a hindered phenolic compound as an impact strength stabilizer or enhancer for the resin. The invention further provides such thermoplastic molding compositions of improved properties, which also include a triaryl phosphate as plasticizer and/or clay as filler. The present invention is applicable to the engineering grade thermostable polyphenylene ether resins, as a family. • )' Illustrative of the hindered phenolic compounds which can be in the compositions of the present invention are 5 a well-known and large group of agents known in this art and. listed among others, for example, in the Encyclopedia of Polymer Science and Technology, Volume 2, pages 190- 194, Interscience, New York,.1965. Specific mention is made of 4-methoxy-2-t-butylphenpl, 2,6-t-butyl-p-cresol, 10 2,6-di-t-butyl-4-methoxyphenol. Preferred are 2,2'- methylenebis-(6-methyl-2-t-butylρhenol) , available from Catalin as CAO-14 and tetrakis [methylene-3-(3'5-di-t- butyl-4*-hydroxy-phenyl)propionate] methane, available from Geigy as IRGANOX 1010. 15 The foregoing compounds are effective for the purposes of the present invention in very small proportions. In the case of the preferred phenolic compounds as little as 0.1 part per hundred based on the weight of the poly-..„ phenylene ether resin provides a significant improvement, 20 and up to 5 parts per hundred on the same basis, and even more can be present. In practice between about 0.5 parts and 2 parts of the phenolic compound on the same basis, provides satisfactory mpact strength retention and/or improvement while avoiding over- or under-use of the 25 agent. The composition of the hindered phenolic compound and the polyphenylene ether resin (or mixture of such resin with one or more of the usual additives which are employed to form a molding composition) can be prepared by any 30 of the methods therefor which have been used in the past. Thus the components, each in granular or powder form, can be dry blended to form a free-flowing particulate mix. If preferred, a-mixture of the polyphenylene ether resin and the phenolic ςo pound (or mixture of phenolic compounds) 35 can be melted and the resulting homogeneous solution can be cooled until solid and then comminuted to for a free- flowing particulate product. ' Alternatively, when feasible the antioxidant can be mixed into a plasticizer or into any supplementary resin which may be present, for example the styrene-butadiene-styrene block copplymer which is often included as an agent for improving the properties of articles made from the compositions. The invention does not depend on which method is adopted. A variety of materials can be present which do not affect the essential character of the resin-phenolic mixture. Thus the mixture can contain: resins which are intended to improve the properties of articles coming from the molding machine, such as the rubbery styrene- butadiene-styrene copolymer resin referred to above; a plasticizer (for example, 5% to 15% by weight of triphenyl or other similar triaryl phosphate) ; glass or asbestos fibers, or graphite "whiskers" as reinforcing fillers, halogen, and/or phosphorus compounds as fire-retardants; non-reinforcing fillers (for example 5% to 50% of clay) ; one or more dyes; and one or more pigments (for example carbon black, phthalocyanine blue and titanium dioxide white) . The polyphenylene ether resins tolerate large proportions of these supplementary agents, so the weight of the polyphenylene ether resin can vary within broad ranges. Generally, however, for filled and/or plasticized molding compositions the composition of polyphenylene ether and hindered phenolic compounds should be between 40 and 80 parts by weight per 100 parts by weight of the molding composition. The compositions which have been described above can be successfully molded in the same ways as polyphenylene ether resin molding compositions have been molded in the past. Blow, injection and extrusion processes can be employed in molding machines working in the conventional temperature range of 450°F-650°F. The invention is further illustrated by the examples which follow. These examples are preferred embodiments of the invention, and are not to be construed in. limitation thereof. Parts are by weight unless otherwise stated. EXAMPLES I AND '11 The following illustrates the comparative effect of two preferred phenolic compounds maintaining or enhancing the impact strength of a commercial polyphenylene ether resin in admixture with customary additives. The antioxidants used are: A. - 2,2'-Methylenebis-(4-methyl-6-t-butylρhenol) (CAO-14, catalin) ; and B. tetrakis [methylene 3-(3' ,5'-di-t-butyl-4- hydrσxy-phenyDpropionate] methane. (IRGANOX 1010, Geigy) in a standard laboratory test composition. A control composition is prepared by dry blending: Poly (2,6-dimethyl-l,4-phenylene)ether resin (PPO, polymeric material, General Electric Co.) 91 " Parts Styrene-butadiene-styrene block copolymer (Kraton G-1651, Shell Chemical Co.) 8 Parts Triaryl phosphate ( ronitex 50, FMC Corp.) 9 Parts Run 1. Test compositions are prepared by blending 1 part of the respective hindered phenolic compound shown above into 109 parts of the control composition prepared as described above. All compositions are melt blended in a laboratory Warner-Pfleiderer extrusion molding machine working at 600°F and test bars were molded in a 3 oz. Newbury injection molding machine. The molded test bars are used to determine tensile yield, tensile strength and tensile elongation, and also their impact resistance by the Izod and Gardner methods. Run 2. The procedures of Run 1 are repeated except with a new batch of the control composition. The phenolic compounds used are identified in the table below by the designating letters shown above. Control. The foregoing procedure is repeated with the control composition (which contains no phenolic compound) . The tensile yield and Gardner impact strength, values of all the bars (including the control bars) are substantially the same. The phenolic compound does not significantly improve or harm these properties. The other results are as follows: T e n s i I e ' ' Izod Antioxidant Strength Elongation Impact Used (p.s.i.) % (ft.-lb./in.n) Desig.* Parts Run 1 Run 2 Run 1 Run 2 Run 1 Run 2 Control None 9,175 9,030 75 53 . 2.7 3.1 A(I) 1 9,700 9,770 80 79 4.2 4.0 B(II) 1 9,470 9,000 69 57 3.9 3.7 * See text above. The data show that the present invention is capable of increasing tensile strength by 8.2%, elongation by 49%, and Izod impact resistance by 56%. 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. For example, the following hindered phenolic compounds may be substituted: o-t-butylanisole and 2,6-di-t-butyl-4- cresol. In addition, up to 125 parts of clay filler per 100 parts of polyphenylene ether resin can be included. The block copolymer and the phosphate plasticizer can be omitted, and the like. It is therefore, to be understood that changes may be made in the particular embodiments of the invention described which are within the full intended scope of the invention as defined by the appended claims.

Claims: • ' CLAIMS . 1. A composition comprising a polyphenylene ether resin and a small but effective amount of- a hindered phenolic compound as impact strength stabilizer for said resin, the polyphenylene ether comprising at. least 70 5 parts by weight per.100 parts, by weight of the total resin components of the composition. 2. A composition according to Claim.1 wherein said resin is a poly(2,6-dimethyl-l,4-phenylene) ether resin. 3. A composition according to Claim 1 wherein said phenolic compound is 2,2'-methylenebis-(4-methyl-6-t- butylphenol) . 4. A composition according to Claim 1 wherein said phenolic compound is tetrakis [methylene-3-(3' ,5'-di-t- butyl-4'-hydroxy-phenyl) propionate] methane. 5. A composition according to Claim 1 wherein the weight of said phenolic compound is between about 0.1 and 5 parts by weight per 100 parts by weight of said polyphenylene ether resin. 6. A filled thermoplastic molding composition comprising from 40 to 80 parts by weight of a composition according to Claim 1 per 100 parts by weight of said .. molding composition. 7. A filled thermoplastic molding composition comprising at least 40 parts by weight of a composition according to Claim 1 and at least 5 parts by weight of a clay filler per 100 parts by weight of said molding 5 compositions. 8. A plasticized thermoplastic molding composition V. comprising at least 40 parts by weight of a composition according to Claim 1 and at least 5 parts by weight of a triaryl phosphate plasticizer per 100 parts by weight of 5 said molding composition.

Inventors: LEE GIM FUN JR
Applicants: GEN ELECTRIC
Application year: 1982
Main classification: C08K5
IPC codes: C08K5, C08L71