WO1981002020A1

WO1981002020A1 - Improve polyphenylene plasticizer blends

Info

Publication number: WO1981002020A1
Application number: PCT/US1981/000044
Authority: WO
Inventors: W Haaf; G Lee
Original assignee: Gen Electric
Priority date: 1980-01-14
Filing date: 1981-01-13
Publication date: 1981-07-23
Also published as: EP0043836A1; BR8105866A; EP0043836A4; JPS57500152A; AU6777981A

Abstract

Thermoplastic molding compositions having high impact resistance and good processing characteristics comprise, in admixture, (a) a composition comprising (i) a polyphenylene ether resin and (II) a polymer selected from the group consisting of hydrogenated A-B-A1 block copolymers and unsaturated A-B-A1 block copolymers, and (b) a plasticizer composition in an amount at least sufficient to provide improved processing characteristics.

Description

IMPROVED POLYPHENYLENE PLASTICIZER BLENDS

This invention relates to novel thermpoplastic molding compositions which have good processing characteristics and are moldable into finished articles having good impact resistance. More particularly, the invention is concerned with thermoplastic compositions of a polyphenylene ether resin, a polymer selected from hydrogenated A-B-A¹ block copolymer and unsaturated A-B-A¹ block copolymers, and a plasticizer composition which is present in an amount sufficient to provide improved processing characteristics to the resultant molded article while, at the same time, rendering the total composition food compatible.

Background of the Invention

The polyphenylene ether resins are well known in the art as a class of thermoplastics which possess a number of outstanding physical properties. They can be prepared by oxidative and non-oxidative methods, such as are disclosed, for example, in Hay, U.S. Patents Nos. 3,306,874 and 3,306,875 and Stamatoff U.S. Patents Nos. 3,257,357 and 3,257,358.

It has been found that many of the properties of polyphenylene ether resihs, e.g., ease of processing, impact strength and solvent resistance, can be improved by combining these resins with other resins, such as for example, polystyrene. Examples of polyphenylene ether resin-polystyrene compositions are disclosed in Cizek, U.S. Patent No. 3,383,435.

More recently, it has been found that polyphenylene ether resins can also be combined with block copolymers of the A-B-A¹- type, e.g., polystyrene-polybutadiene-polystyrene, and with acrylic resin modified diene rubber containing resins, to provide compatible compositions characterized by a number of excellent physical properties in the resulting molded articles. These discoveries are described in Abolins et al., U.S. Patents Nos. 3,833,688 and 3,792,123 and in copending application Serial No. 387,588 filed April 13, 1973, and assigned to the same assignee as in the present application.

It is known in the art that the polyphenylene ehters by themselves have excellent flame retardant properties and are classified self-extinguishing and non-dripping according to ASTM Test Method D635 and Underwriters Laboratories Bulletin No. 94. On the other hand, when polyphenylene ethers are combined with other polymers such as the abovementioned A-B-A¹- block copolymers, many of the resulting compositions have poor flame retardancy and are not self-extinguishing, but rather burn slowly upon ignition. Consequently, many compositions of polyphenylene ether resin and A-B-A¹ block copolymers are unable to meet the minimum requirements established by various testing laboratories such as the Underwriters Laboratories. This restricts the use of such compositions for many commercial applications.

Flame retardant additives for thermoplastics are also known. In general, these are either blended physically with the thermoplastic or are used to unite chemically with the plastics and to modify it. For instance, self-extinguishing blends of a polyphenylene ether resin and a styrene resin using a combination of an aromatic phosphate and an aromatic halogen for flame retardancy are disclosed by Haaf in U.S. Patent No. 3,693,506. Other self-extinguishing polyphenylene etherpolystyrene compositions are disclosed by Reinhard in U.S. Patent No. 3,809,729, wherein aromatic halogens combined with antimony compounds are used as flame retardant additives. Still other flame retardant compositions of a polyphenylene ether resin and a styrene resin which include various phosphorus-containing and halogen-containing flame retardant agents, are described by Haaf et al. in U.S. Serial No. 647,981 filed December 27, 1975, and assigned to the same assignee as herein. However, as is also well known, the inclusion of flame retarding compounds in thermoplastic materials not only affects burning characteristics, it frequently changes other physical properties as well, such as color, flexibility, tensile strength, electrical properties, softening point, and moldability characteristics. Thus, for example, aromatic phosphates such as triphenyl phosphate have been added to blends of polyphenylene ethers and styrene resins, with flame retardant properties being improved to the point where the compositions can be classified as self-extinguishing and non dripping according to the above-noted ASTM Test Method D635 and U.L. Bulletin No. 94.

It has also been found that molded compositions consisting of polyphenylene ether or various combinations of polyphenylene ether and certain polymeric modifiers, and aromatic phosphare compounds exhibit excellent self-extinguishing behavior, Impact strength and acceptable surface gloss. Such compositions are disclosed by Haaf et al. in copending application Serial No. 870,984, filed January 20, 1978, and assigned to the same assignee as the present invention.

While the aforementioned compositions achieve a combination of high heat distortion, good impact strength and good self-extinguishing properties, they encounter some difficulty in processing and yield a product which has surface gloss characteristics which, while good, has deficiencies which can be improved upon via the utilization of minor amounts of low molecular weight polystyrene, as has been disclosed by Lee et al. in copending application Serial No. 84,746, filed October 15, 1979, which application is also assigned to the same assignee as the present invention.

As noted the aforementioned developments achieve compositions vhich exhibit a combination of high heat distortion, good impact strength, good self-extinguishing properties and in some instance ease of processability and high surface gloss characteristics in the resultant molded articles, such results are achieved via the utilization of compositions as flame retardant plasticizers and the like vhich are not compatible with FDA requirements controlling the use of such compositions in contact with edible food products, thereby rendering these compositions unsuitable for use as packaging materials and the like. In addition, such compositions, as have been disclosed in the art, suffer from additional limitations in the physical characteristics of the- resultant molded articles, such as to render them inappropriate for use in a number of specialized applications as will be apparent to those skilled in the art.

It has now been discovered that molded compositions consisting of polyphenylene ether, or various combinations of polyphenylene ether and polystyrene, together with certain polymeric modifiers and a particular class of plasticizer compounds exhibit a superior combination of physical properties in the resultant molded product while, at the same time, avoid the deficiencies in such products which are inherent with similar prior art molding compositions incorporating various flame retardant plasticizers and the like. The commercial benefit of avoiding the limitations which are inherently imposed when the various flame retardant plasticizers of the prior art are employed serves to widen the field of effective utilization of the subject modified polyphenylene ether compositions especially since such compositions find utility and are acceptable as food packaging materials and in similar applications where they have been heretofore considered inappropriate due to their incompatibility with prevailing FDA standards.

DESCRIPTION OF THE INVENTION

According to the present invention, there are provided thermoplastic molding compositions which have improved processing characteristics and, after molding, have improved impact resistance, comprising an intimate admixture of:

(a) a composition comprising (i) a polyphenylene ether resin and (ii) a polymer selected from the group consisting of hydrogenated A-B-A-¹ block copolymers, and unsaturated A-B-A¹ block copolymers, and

(b) a plasticizer composition in an amount at least sufficient to provide improved processing characteristics.

The polyphenylene ether resins of (a) are preferably of the type having the structural formula:

wfaerein the oxygen ether atom of one unit is connected to the benzene nucleus of the next adjoining unit, n is a positive integer and is at least 50, and each Q is a monovalent substituent selected from the group consisting of hydrogen, halogen, hydrocarbon radicals free of a tertiary alpha carbon atom, halohydrocarbon radicals having at least two carbon atoms between the halogen atom and the phenyl nucleus , hydrocarbonoxy radicals and halohydrocarbonoxy radicals having at least two carbon atoms between the halogen atom and the phenyl nucleus.

An especially preferred class of polyphenylene ether resins for the compositions of this invention includes those of the above formula wherein each Q is alkyl, most preferably having from 1 to 4 carbon atoms . Illustratively, members of this class include poly(2, 6-dimethyl-l, 4-ρheιiylene) ether; poly (2, 6-diethyl-l,4-phenylene) ether ; poly(2-methyl-6-ethyl-l,4- pheny lene) ether; poly (2-methyl-6-propyl-l, 4-phenylene) ether; poly (2 , 6- dipropyl- 1 , 4-pheny lene) ether; poly (2- ethyl- 6 -propyl-1 ,

4-phenylene) ether; and the like. Most preferred is poly(2 , 6- dimfithyl-l ,4-phenylene) ether , preferably having an intrinsic viscosity of about 0. 45 deciliters per gram (dl. /g. ) as measured in chloroform at 30 ºC.

The A-B-A¹ block copolymers of component (a) (ii) are well known. In general , these are block copolymers of the A-B-A¹ type in which terminal blocks A and A¹ are the same or different and, prior to hydrogenation , comprise homo polymers of copolymers derived. from vinyl aromatic hydrocarbons and, especially, vinyl aromatics vhaxein the aromatic moiety can be either monocyclic or polycyclic. Examples of the monomers are styrene, alpha methyl styrene, vinyl xylene, ethyl vinyl xylene, vinyl naphthalene, and the like. Center block B will always be derived from a conjugated diene, e.g., butadiene, isoprene, 1,3-pentadiene, and the like. Preferably, center block B will be comprised of polybutadiene or polyisoprene.

It is preferred to form terminal blocks A and A¹ having average molecular weights of 4,000 to 115,000 and center block B having average molecular weights of 20,000 to 450,000. Still more preferably, the terminal blocks will have average molecular weights of 8,000 to 60,000 while the center block has an average molecular weight between about 50,000 and 300,000. The terminal blocks will preferably comprise from 2 to 331 by weight, and more preferably, 5 to 30% by weight of the total block copolymer. Especially preferred axe A-B-A¹ type block copolymers having a polybutadiene center block wherein 35 to 55%, or more preferably, 40 to 50% of the carbon atoms present in the butadiene polymer block are in the form of dependent vinyl side chains.

The A-B-A¹ block copolymers will have an unsaturation in the center block B reduced to less than 10% and more preferably, less than 5%, of its original value. The hydrogenated block copolymers are formed by techniques which are well known to those skilled in the art. For instance, the preparation of these materials is described in detail in Jones, U.S. Patent No. 3,431,323, the disclosure of which is incorporated herein by reference.

Hydrogenation can be carried out with a variety of hydrogenation catalysts, such as nickel on Kieselguhr, Raney nickel, copper chromate, molybdenum sulfide and finely divided platinum or other noble metals on a low surface area catalyst.

Hydrogenation can be conducted at any desired temperature or pressure, e.g., from atmospheric to 3,000 p.s.i.g., the usual range being between 100 and 1,000 p.s.i.g., and at temperatures from about 75º to 600ºF., for times between 0.1 and 24 hours, preferably 0.2 to 8 hours.

Particular preferred block copolymers are Kraton 1101, an unsaturated polystyrene-polybutadiene-polystyrene block copolymer commercially available from Shell Chemical Company and Kraton G 1652, a hydrogenated polystyrene-polybutadiene-polystyrene block copolymer commercially available from Shell Chemical Company.

The plasticizers of the present invention are compositions selected from the group consisting essentially of the alkyl adipates, alkyl phthalates and paraffinic oils amongst which the most preferred compositions are dioctyl adipate, trimellitate ester, butyl phthaly butyl glycolcate, dioctyl phthalate, mineral oil and extra heavy mineral oil. Dioctyl adipate, trimellitate ester (as Santicizer 79TM), butyl phthaly butyl glycolate (as Santicizer B-16) and dioctyl phthalate are all commercially available from Monsanto Chemical Company. Mineral oil (as Shellflex 371) is commercially available from Shell Chemical Company and extra heavy mineral oil (as KAYDOL^®) is commercially available from Witco Chemical Company.

The respective amounts of the major components in the present compositions can vary broadly, e.g., from 60 to 99 parts by weight of polyphenylene ether resin to 40 to 1 parts by weight of A-B-A¹ block copolymer. With respect to the compositions containing A-B-A¹ block copolymers, the most preferred such compositions contain no less than about 65% by weight of polyphenylene ether, based on the total weight of the resinous components in the composition. With respect to the plasticizer compositions, amounts of from 1 to 40 parts by weight of the total composition can be employed to yield a good combination of properties in the resultant product with from 10 to 25 parts by weight being preferred. Particular amounts will, of course, vary depending on the needs of the specific composition.

The compositions of the invention can also further include glass fibers as a reinforcing filler, especially preferably, fibrous glass filaments comprised of lime-altaainum borosilicate glass which is relatively soda free, known as "E" glass. However, other glasses are useful where electrical properties are not so important, e.g., the low soda glass known as "C" glass. The filaments are made by standard processes, e.g., by steam or air blowing, flame blowing and mechanical pulling. The preferred filaments for plastics reinforcement are made by mechanical pulling. The filament diameters range from about

0.000112 to 0.00075 inch, but this is not critical to the present invention.

In general, best properties will be obtained if the sized filamentous glass reinforcement comprise from about 1 to about 80% by weight based on the combined weight of glass and polymers and preferably, from about 10 to about 50% by weight. Especially preferably, the glass will comprise from about 10 to about 40% by weight based on the combined weight of glass and resin. Generally, for direct molding use, up to about 50% of glass can be present without causing flow problems. However, it is useful also to prepare the compositions containing substantially greater quantities, e.g., up to 70 to 80% by weight of glass. These concentrates can then be custom blended with blends of resins that are not glass reinforced to provide any desired glass content of a lower value.

Other ingredients, such as stabilizers, pigments, plasticizers, antioxidants, and the like, can be added for their conventionally employed purposes The compositions of this invention can be prepared conventionally by tumbling the components to form a preblend, extruding blend into a continuous strand, cutting the strand into pellets or granules, and molding the pellets or granules into the desired shape. These techniques are well known to those skilled in the art and further elaboration herein is notnecessary.

DESCRIPTIOH OF THE PREFERRED EMBODIMENTS

The following examples illustrate compositions accordingto the invention. They are set forth for illustrative purposes only, and are not to be construed as limiting.

EXAMPLES I-VI

The compositions shown in Table 1, were prepared by preblending the components, extruding the blend and molding the extrudate into test pieces. All amounts are in parts by weight. The values for Izod impact strength are in units of ft.1bs./in.n., and the values for Gardner impact strength are in units of in.-1bs. Tensile yield, tensile break, flexural yield and flexural modulus values are each in units of p.s.i. x 10-³. Tensile elongation values are in percent (Z) ; Heat Distortion Temperature (HDT) in ºF., and melt viscosity in poise.

Although the above examples illustrate various modifications of the present invention, other vaxiations will suggest themselves to those skilled in the art in the light of the above disclosure. It is to be understood, therefore, that changes may be made in the particular embodiments described above which axe within the full intended scope of the invention as defined in the appended claims.

Claims

1. A thermoplastic molding composition having high impact resistance and good processing characteristics comprising, in admixture,

(a) a composition comprising (i) a polyphenylene ether resin and (ii) a polymer selected from the group consisting of hydrogenated A-B-A¹ block copolymers and unsaturated A-B-A¹ block copolymers, and

2. A thermoplastic molding composition having high impact resistance and good processing characteristics comprising, in admixture,

(b) a minor amount of a plasticizer composition selected from the group consisting essentially of alkyl adipates, alkyl phthalates and paraffinic oils.

3. A thermoplastic molding composition as defined in claim 1 wherein the polyphenylene ether resin (a) (i) is of the formula:

wherein the oxygen ether atom of one unit is connected to the benzene nucleus of the next adjoining unit, n is a positive integer and is at least 50, and each Q is a monovalent substituent selected from the group consisting of hydrogen, halogen, hydrocarbon radicals free of a tertiary alpha-carbon atom, halohydrocarbon radicals having at least two carbon atoms between the halogen atom and the phenyl nucleus, hydrocarbonoxy radicals and halohydrocarbonoxy radicals having at least two carbon atomsbetween the halogen atom and the phenyl nucleus.

4. A thermoplastic molding composition as defined in claim 3 wherein in said polyphenylene ether resin (a)(i). each Q is alkyl having from 1 to 4 carbon atoms.

5. A thermoplastic molding composition as defined in claim 4 wherein in said polyphenylene ether resin (a)(i), each Q is methyl.

6. A thermoplastic molding composition as defined in claim 1 wherein the A-B-A¹ block copolymer of component (a) (ii), prior to hydrogenation, is characterized as follows:

(1) each A is a polymerized mono alkenyl aromatic hydrocarbon block having an average molecular weight of about 4,000 to 115,000; (2) B is a polymerized butadiene hydrocarbon block having an average molecular weight of about 20,000 to 450,000;

(3) the blocks A constituting 2 to 33 weight percent of the copolymer;

(4) 35 to 55% of the butadiene carbon atoms in block B being vinyl side chains;

(5) and the unsaturation of block B having been reduced to less than 10% of the original unsaturation.

7. A thermoplastic molding composition as defined, in claim 6 wherein the A-B-A¹ block copolymer of component (a) (ii),prior to hydrogenation, is characterized as follows:

(1) each A is a polymerized styrene block having an average molecular weight of about 8,000 to 60,000;

(2) B is a polymerized butadiene block having an average molecular weight of about 50,000 to 300,000; 40 to 50% of the butadiene carbon atoms in the block being vinyl sidechains;

(3) the blocks A comprising 5 to 30% by weight of the copolymer; the unsaturation of block B having been reduced by hydrogenation to less than 10% of its original value.

8. A thermoplastic molding composition according to claim 2 wherein the plasticizer composition is selected from the group consisting essentially of dioctyl adipate, trimellitate ester, butyl phthaly butyl glycolate, dioctyl phthalate, mineral oil and extra heavy mineral oil.

9. A thermoplastic molding composition according to claim 2 wherein the plasticizer composition is dioctyl adipate.

10. A thermoplastic molding composition according to claim 2 wherein the plasticizer composition is trimellitate ester.

11. A thermoplastic molding composition according to claim 2 wherein the plasticizer composition is butyl phthaly butyl glycolate.

12. A thermoplastic molding composition according to claim 2 wherein the plasticizer composition is dioctyl phthalate.

13. A thermoplastic molding composition according to claim 2 wherein the plasticizer composition is mineral oil.

14. A thermoplastic molding composition according to claim 2 wherein the plasticizer composition is extra heavy mineral oil.

15. A thermoplastic molding composition according to claim 2 wherein the plasticizer is present in an amount from

1 to about 40 parts by weight of the total composition.

16. A thermoplastic molding composition according to claim 2 wherein the plasticizer is present in an amount from 10 to 25 parts by weight of the total composition.

17. A thermoplastic molding composition having high impact resistance and good processing characteristics comprising, in admixture,

(a) a composition comprising (i) a polyphenylene ether resin and (ii) an unsaturated A-B-A¹ block copolymer and a hydrogenated A-B-A¹ block copolymer, and

(b) plasticizer composition in an amount at least sufficient to provide improved processing characteristics.

18. A thermoplastic molding composition having high impact resistance and good processing characteristics comprising, in admixture,

19. A composition as defined in claim 17 wherein the polyphenylene ether resin (a) (i) is of the formula:

wherein the oxygen ether atom of one unit is connected to the benzene nucleus of the next adjoining unit, n is a positive integer and is at least 50, and each Q is a monovalent substituent elected from the group consisting of hydrogen, halogen, hydrocarbon radicals free of a tertiary alpha-carbon atom, halohydrocarbon radicals having at least two carbon atoms between the halogen atom and the phenyl nucleus, hydrocarbonoxy radicals and halohydrocarbonoxy radicals having at least two carbon atoms between the halogen atom and the phenyl nucleus.

20. A composition as defined is claim 19 wherein in said polyphenylene ether resin (a) (i), each Q is alkyl having from 1 to 4 carbon atoms.

21. A composition as defined in claim 20 wherein in said polyphenylene ether resin (a) (i), each Q is methyl.

22. A composition as defined in claim 17 wherein the A-B-A¹ block copolymer of component (a) (ii), prior to hydrogenation, is characterized as follows:

(1) each A is a polymerized mono alkenyl aromatic hydrocarbon block having an average molecular weight of about 4,000 to 115,000;

(2) B is a polymerized butadiene hydrocarbon block having an average molecular weight of about 20,000 to 450.000 ;

(3) the blocks A constituting 2 to 33 weight percent of the copolymer;

(4) 35 to 55% of the butadiene carbon atoms in block B being vinyl side chains;

(5) aad the unsaturation of block B having been reduced to less than 10% of the original unsaturation

23. A composition as defined in claim 22 wherein the A-B-A¹ block copolymer of component (a) (ii), prior to hydrogenation, is characterized as follows:

(2) B is a polymerized butadiene block having an average molecular weight of about 50, 000 to 300,000; 40 to 50% of the butadiene carbon atoms in the block being vinyl sidechains;

24. A thermoplastic composition according to claim 18 wherein the plasticizer composition is selected from the group consisting essentially of dioctyl adipate, trimellitate ester, butyl phthaly butyl glycolate, dioctyl phthalate, mineral oil and extra heavy mineral oil.

25. A composition according to claim 18 wherein the plasticizer composition is dioctyl adipate.

26. A composition according to claim 18 wherein the plasticizer composition is trimellitate ester.

27. A composition according to claim 18 wherein the plasticizer composition is butyl phthaly butyl glycolate.

28. A composition according to claim 18 wherein the plasticizer composition is dioctyl phthalate.

29. A composition according to claim 18 wherein the plasticizer composition is mineral oil.

30. A composition according to claim 18 wherein the plasticizer composition is extra heavy mineral oil.

31. A composition according to claim 18 wherein the plasticizer is present in an amount from 1 to about 40 parts by weight of the total composition.

32. A composition according to claim 18 wherein the plasticizer is present in an amount from 10 to 25 parts by weight of the total composition.