GB1575457A

GB1575457A - Polyphenylene ether compositions

Info

Publication number: GB1575457A
Application number: GB51974/77A
Authority: GB
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1976-12-21
Filing date: 1977-12-14
Publication date: 1980-09-24
Also published as: AU3179277A; FR2375293A1; CA1101579A; DE2751496A1; BR7708512A; NL7713133A; DD134538A5; FR2375293B1; MX146037A; IT1088919B; DE2751496C2; JPS5379945A; AU517478B2

Description

(54) IMPROVEMENTS IN POLYPHENYLENE ETHER COMPOSITIONS (71) We, GENERAL ELECTRIC COMPANY, a corporation organized and existing under the laws of the laws of the State of New York, United States of America, of 1 River Road, Schenectady 12305, State of New York, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates. to flame retardant, flexibilized thermoplastic polyphenylene ether compositions.The compositions of this invention comprise the polyphenylene ether, an aromatic phosphate and a thermoplastic elastomer comprising an A-B-A' block copolymer, e.g. polystyrene-polybutadiene-polystyrene, and optionally, a halogenated hydrocarbon resin, alumina trihydrate and/or elemental red phosphorus.

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, in general, by oxidative and non-oxidative methods, such as are disclosed, for example, in Hay, U.S. Patents No. 3,306,874 and 3,306,875 and Stamatoff, U.S. Patents No.

3,257,357 and 3,257,358.

It is known that the polyphenylene ether resins alone are somewhat difficult to fabricate because of their high temperature themoplastic molding characteristics and this has limited their use in applications where flexibility, such as the need to calender into relatively thin sheets, without cracking or crazing, is desirable.

In recent years, there has also been increasing concern about the performance and safety of thermoplastic materials, including the afore-mentioned polyphenylene ether compositions during real-life fire situation.

Of particular interest would be a polyphenylene ether composition which is both flexibilized and flame retardant without loss of desirable properties.

It is known that flexible polyphenylene ether blends have been made with fairly high loadings of plasticizers. It has now been found that the capabilities and alternatives in making such blends can be greatly expanded by incorporating rubber in the form of a block copolymer into such blends, and further that if the flexibilizer is predominately an aromatic phosphate, good self-extinguishing properties are obtained.

Based on the foregoing discovery, it has also been found possible to further modifiy the blends to make them somewhat less costly, without loss of other beneficial properties, by replacing some of the aromatic phosphate with a halogenated hydrocarbon resin, e.g., chlorinated paraffin. Complete replacement of the aromatic phosphate is not possible, however, without loss of flame resistance.

Furthermore, based on the foregoing discovery, it has also been found possible to decrease the cost of the formulation, without introducing a halogen source, and at the same time, improve the self-extinguishing properties. This discovery comprises including alumina trihydrate in the composition.

Finally, based on the foregoing discovery, it has also been found possible to use higher levels of thermoplastic elastomer without disrupting flame retardant properties and still keeping a halogen-free system by the addition to the composition of elemental red phosphorus.

In addition to being useful by themselves, the new compositions are useful in blends with other resins and elastomers to improve flame retardancy. Of course, conventional additives such as pigments, fillers, and stabilizers, can be used with the new compositions of this invention.

Accordingly, the present invention provides in its broadest aspects, a flame retardant flexibilized thermoplastic composition which comprises, in admixture: (a a normally flammable polyphenylene ether resin; (b) a flame retardant aromatic phosphate plasticizer in an amount at least sufficient to provide a flexibilized composition after molding; and (e) a thermoplastic elastomer comprising an A-B-A' block copolymer wherein terminal blocks A and A' are polymeric units of a vinyl aromatic compound and center block B is a polymer of a conjugated diene.

As employed herein, the term "flexibilized" is used in its art-recognized sense to define compositions which are calenderable into relatively thin sheets, e.g., 1/4 inch or less in thickness, which can be bent without causing cracking or crazing. Such thermoplastic compositions are suitable, in appropriately thin forms, for products such as shower curtains, wall coverings, and automobile upholstery.

The term "normally flammable" as used herein, describes compositions which do not meet the V-0 and V-l requirements of the Underwriters' Laboratories Bulletin No. 94 test.

In a preferred feature, the new compositions will also include: (d) a minor proportion of flame retardant halogenated plasticizer based on the amount of aromatic phosphate component (b). Especially preferred halogenated hydrocarbons are chlorinated paraffins. The amount can vary, but up to equal parts by weight, 50:50, based on the aromatic phosphate are preferred, and 50:50 is most economical. A useful chlorinated paraffin is available from ICI America, Inc., under the designation Cereclor S-45, ("Cereclor" is a Registered Trade Mark).

Another preferred feature is the new composition which also includes: (e) a minor proportion of alumina trihydrate, sufficient to enhance the flame retardant capability of aromatic phosphate component (b). The amount can vary widely within these limits but preferably, the amount of alumina trihydrate (which is a standard item of commerce), comprises from 5 to 40 parts by weight per 100 parts by weight of components (a) and (b) combined.

Still another preferred feature is the new composition which also includes: (f) a minor proportion of elemental red phosphorus, sufficient to enhance the flame retardant capability of aromatic phosphate component (b). Elemental red phosphorous can be used in fairly broad ranges in amount but preferably, it will comprise from 1 to 10 parts by weight per 100 parts by weight of components (a), (b) and (c) combined.

The normally flammable polyphenylene ether resin (a) is preferably of the type having the structural 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 hydrogen or a monovalent substituent selected from halogen, hydrocarbon radicals free of a tertiary alpha-carbon atom, halohydrocarbon and haloghydrocarbonoxy radicals having at least two carbon atoms between the halogen atom and the phenyl nucleus, and hydrocarbonoxy radicals.

A more 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- 1, 4-phenylene)ether; poly-(2,6-diethyl- 1, 4-phenylene)ether; poly(2-methyl-6 ethyl-l, 4-phenylene)ether; poly(2-methyl-6-propyl- 1, 4-phenylene)ether; poly(2,6dipropyl-1, 4-phenylene)ether and poly(2-ethyl-6-propyl-1, 4-phenylene ether.

Especially preferred is poly(2,6-dimethyl-l, 4-phenylene)ether, preferably, having an intrinsic viscosity of about 0.45 deciliters per gram (dl./g.) as measured in chloroform at 30"C.

The choice of an aromatic phosphate plasticizer can vary broadly.

The phosphate plasticizer is preferably a compound of the formula:

wherein Rl, R2 and R3 are the same or different and are aryl, alkyl substituted aryl, or hydroxyalkyl. To keep the amount of halogen low, it is preferred that no halogen be present in component (b).

Examples include cresyl diphenyl phosphate, tricresyl phosphate, triiosopropylphenyl phosphate, triphenyl phosphate, cresyl diphenyl phosphate, or mixtures thereof. Especially preferred is triphenyl phosphate.

Commercially available aromatic phosphates which have been found to be particularly useful are FMC Corporations's Kronitex 50 and Kronitex 300, which are isopropylated triphenyl phosphate compounds.

The plasticizer (b) is added in amounts which will be sufficient to provide a flexibilized composition within the meaning of the term described above. In general, the plasticizer is present in amounts ranging from at least 10 to 100, preferably from 15 to 65 parts by weight of plasticizer, per 100 parts of resin component (a).

The present compositions also include thermoplastic elastomers (c), which are A-B-A, block copolymers. In general, these resins comprise a polymerized center block B which is derived from a conjugated diene, e.g., butadiene, isoprene, and 1,3-pentadiene, and polymerized terminal blocks A and A' which are derived from vinyl aromatic, e.g., styrene, compounds, such as styrene, a-methyl styrene, vinyl toluene, vinyl xylene and vinyl naphthalene. Preferably, the A-B-A' block copolymer will have terminal blocks A and A comprised of polystyrene and a center block comprises of polybutadiene.

The linear A-B-A' block copolymers are made by an organometallic initiated polymer ization process using, for example, sodium or lithium metal or can organic derivative thereof. The diene monomers can be polymerized with a monofunctional or difunctional initiator, as is described in Kennedy et al, Interscience Publishers, Vol. 23, Part It(1969), pages 553-449. Other methods of preparing these block copolymers are described in Zelinski, U.S. Patent No. 3,251,905 and Holden et al, U.S. Patent No. 3,231,635.

Commercially available A-B-A' block copolymers include Kraton X4119, poly(styrenebutadiene-styrene) with 20% mineral oil, and the Kratons designated as K-1101 (polystyrene-polybutadiene-polystyrene), K-1102 (polystyrene-polybutadienepolystyrene), and K-1107 (polystyrene-polyisoprene-polystyrene), all from Shell Chemical Company, Polymers Division.

Hydrogenated A-B-A' block copolymers can also be used as thermoplastic elastomers in the present compositions. These are prepared by techniques which are well known in the art. See, for instance, the disclosure in Jones, U.S. Patent No. 3,431,323. A preferred commercially available copolymer of this type is Shell Chemical's KG-6521 resin.

The thermoplastic elastomer (c) can vary broadly in amount, but generally is present in amounts from 10 to 100, more preferably from 15 to 65 parts by weight of thermoplastic elastomer per 100 parts of polyphenylene ether (a). Alternatively, a preferred amount of thermoplastic elastomer is from 5 to 100 parts by weight, most preferaly 15 to 50 parts by eight, per 100 parts by weight of components (a) and (b) combined.

Other ingredients, such as fillers, reinforcements, pigments, stabilizers, lubricants, may be added for their conventional purposes.

The manner in which the present compositions are prepared is not critical and conventional methods can be employed. Preferably, however, each of the ingredients is added as part of a blend premix, and the latter is passed through an extruder, e.g., a 28 mm. WP twin screw extruder, at an extrusion temperature of from 350 to 550"F., dependent on the needs of the particular composition. The strands emerging from the extruder may be cooled, chopped into pellets, and molded or calendered to any desired shape.

The following examples are illustrative of the compositions of this invention. They are not intended to limit the invention in any manner.

EXAMPLES 1-10 The following blends were prepared in a 28 mm Werner Pfleiderer twin screw extruder and tested for physical properties and flame retardancy by the Underwriters' Laboratory U.L. 94 test and the GE Oxygen Index Test, with results set forth in Table 1: Table 1. Flexibilized Polyphenylene Styrene Compositions Comp Aromatic Phosphates and A-B-A 1 Block Copolymers Example Aa 1 2 3 4 5 6 7 8 9 10 Composition(parts by weight) (a) poly(2,6-dimethyl-1,4phenylene)ether 60 60 60 60 60 60 60 55 55 55 55 (b) aromatic phosphateb - - - - - - - 45 45 45 45 aromatic phosphatec 40 40 40 40 40 40 40 - - - (c) thermoplastic elastomer block copoly(styrene-butadienestyrene)d - 20 40 60 80 100 - 25 - - block copoly(styrene-butadienesytrene)e - - - - - - 100 - 25 - block copoly(styrene-sioprenestyrene)f - - - - - - - - - 25 hydrogenated block copoly (styrene-butadiene styrene)g - - - - - - - - - - 25 Properties Tensile yeild, psi 6300 3700 3000 2100 2000 1800 700 2000 1300 1600 1500 Elongation, % 66 60 71 74 51 59 135 65 67 71 77 U.L. flame self-extinguishing times, sec/sec. 1/drip 1/1 10/10 12/24 35/15 drip drip 1/2 1/4 1/3 2/3 Oxygen index,% - - - - - - - 34 31 31 31.5 a Control Experiment b FMC's Kronitex 50 c FMC's Kronitex 300 d Shell Chemical's Kraton 1101 e Shell Kraton 1102 f Shell Kraton 1107 g Shell Kraton G6521 It is of particular interest to note that in the above flexible blends which contain an aromatic phosphate as the plasticizer, good self-extinguishing properties are obtained.

Thus, the present compositions, particularly those containing between 20 and 80 parts by weight of A-B-A1 block copolymer per 100 parts by weight of polyphenylene ether and aromatic phosphate, are flame retardant without the change to produce toxic and corrosive halogen-derived products on incineration.

EXAMPLES 11 and 12 Following the procedure of Examples 1-10, the list compositions are prepared, having the properties set forth in Table 2: Table 2. Compositions Comprising Polyphenylene Ethers, Aromatic Phosphates, A-B-A 1 Block Copolymer and Halogenated Hydrocarbon Resin Example 11a 12 Be Composition(parts by weight) (a) poly(2,6-dimethyl-1,4phenylene)ether 60 60 60 (b) aromatic phosphatea 40 20 (c) thermoplastic elastomer block copoly(styrene-butadienestyrene)b 43 43 43 (d) chlorinated paraffind - 20 40 Properties Tensile yield, psi 1700 2200 2000 Elongation, % 70 156 160 U.L. flame self-extinguishing times, sec/sec. 19/24 28/26 41 drips flaming resin Oxygen index,% 32 30.5 21 a Control Experiment in the sense that all flame retardancy is conferred by aromatic phosphate (b).

b FMC's aromatic phosphate Kronitex 50, which is an isopropylated triphenyl phosphate.

c Shell Chemical's Kraton 1102.

d ICI America Inc's Cereclor S-45, which is a chlorinated paraffin.

e Control Experiment It is noteworthy that in these compositions, complete replacement of the aromatic phosphate by chlorinated paraffin is catastrophic to the flame resistance, whereas up to 50% replaccment is only slightly detrimental.

EXAMPLES 13 - 15 Following the procedure of Examples 1-10, the listed compositions are prepared, having the properties set forth in Table 3: Table 3. Compositions Comprising Polyphenylene Ethers, Aromatic Phosphates, A-B-A 1 Block Copolymer and alumina Trihydrate Example 11a 13 14 15 Composition(parts by weight) (a) poly(2,6-dimethyl-1,4phenylene)ether 60 60 60 60 (b) aromatic phosphateb 40 40 40 40 (c) thermoplastic elastomer block copoly(styrene-butadienestyrene)c 43 43 43 43 (d) alumina trihydrate - 10 20 30 Properties Tensile yield, psi 1700 2200 2000 1700 1700 Elongation, % 70 53 57 51 U.L. flame self-extinguishing times, sec/sec. 19/24 11/11 3/11 2/6 Oxygen index,% 32 29 30 31 a Control Experiment in the sense that no alumina trihydrate is used.

c Shell Chemical's Kraton 1102.

It is seen that the properties can be retained with significant cost advantages by addition of alumina trihydrate.

EXAMPLES 16- 17 Following the procedure of Examples 1-10, the listed compositions are prepared, having the properties set forth in Table 4: Table 4. Compositions Comprising Polyphenylene Ethers, Aromatic Phosphates, A-B-A t Block Copolymer and Elemental Red Phos phorus Example Ca 16 17 Composition(parts by weight) (a) poly(2,6-dimethyl- 1,4 phenylene)ether 30 30 30 (b) aromatic phosphateb 30 30 30 (c) thermoplastic elastomer block copoly(styrene-butadiene- styrene) C 40 40 40 (d) elemental red phosphorus - 2 5 Properties Tensile strength, psi 1700 1700 1600 Elongation, % 106 127 126 U.L. flame self-extinguishing time, sec./sec. 18/25 4/4 1/8 a Control Experiment in the sense that no elemental red phosphorus is present.

c Shell Chemical's Kraton 1102.

It is seen that red phosphorus permits the incorporation of high amounts of rubber, while maintaining good flame retardant characteristics. These compositions also have the desirable feature of being free of halogen.

WHAT WE CLAIM IS: 1. A flame retardant, flexibilized thermoplastic composition which comprises, in admixture: a) a normally flammable polyphenylene ether resin: b) a flame retardant aromatic phosphate plasticizer and c) a thermoplastic elastomer comprising an A-B-A' block copolymer wherein terminal blocks A and A' are polymeric units of a vinyl aromatic compound and center block B is a polymer of a conjugated diene.

2. A composition as claimed in claim 1 which also includes a flame retardant halogenated hydrocarbon plasticizer.

3. A composition as claimed in claim 2 wherein said halogenated hydrocarbon is a chlorinated paraffin and is present in amount up to 100% by weight of said aromatic phosphate.

4. A composition as defined in any one of the preceding claims which also includes an amount of alumina trihydrate, sufficient to enhance the flame retardant capability of the aromatic phosphate component.

5. A composition as claimed in any one of the preceding claims wherein the amount of alumina trihydrate is from 5 to 40 parts by weight per 100 parts of the total weight of components (a) and (b).

6. A composition as claimed in any one of claims 1 to 3 which also includes an amount of elemental red phosphorus, sufficient to enhance the flame retardant capability of the aromatic phosphate component.

7. A composition as claimed in claim 6 wherein the amount of elemental red phosphorus is 1 to 10 parts by weight per 100 parts of the total weight of components (a), (b) and (c).

8. A composition as claimed in any one of the preceding claims wherein the polyphenylene ether resin has the formula:

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. It is seen that the properties can be retained with significant cost advantages by addition of alumina trihydrate. EXAMPLES 16- 17 Following the procedure of Examples 1-10, the listed compositions are prepared, having the properties set forth in Table 4: Table 4. Compositions Comprising Polyphenylene Ethers, Aromatic Phosphates, A-B-A t Block Copolymer and Elemental Red Phos phorus Example Ca 16 17 Composition(parts by weight) (a) poly(2,6-dimethyl- 1,4 phenylene)ether 30 30 30 (b) aromatic phosphateb 30 30 30 (c) thermoplastic elastomer block copoly(styrene-butadiene- styrene) C 40 40 40 (d) elemental red phosphorus - 2 5 Properties Tensile strength, psi 1700 1700 1600 Elongation, % 106 127 126 U.L. flame self-extinguishing time, sec./sec. 18/25 4/4 1/8 a Control Experiment in the sense that no elemental red phosphorus is present. b FMC's aromatic phosphate Kronitex 50, which is an isopropylated triphenyl phosphate. c Shell Chemical's Kraton 1102. It is seen that red phosphorus permits the incorporation of high amounts of rubber, while maintaining good flame retardant characteristics. These compositions also have the desirable feature of being free of halogen. WHAT WE CLAIM IS:

1. A flame retardant, flexibilized thermoplastic composition which comprises, in admixture: a) a normally flammable polyphenylene ether resin: b) a flame retardant aromatic phosphate plasticizer and c) a thermoplastic elastomer comprising an A-B-A' block copolymer wherein terminal blocks A and A' are polymeric units of a vinyl aromatic compound and center block B is a polymer of a conjugated diene.

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 hydrogen or a monovalent substituent selected from halogen, hydrocarbon radicals free of a tertiary alpha-carbon atom, halohydrocarbon and halohydrocarbonoxy radicals having at least two carbon atoms between the halogen atom and the phenyl nucleus, and hydrocarbonoxy radicals.

9. A composition as claimed in any one of the preceding claims wherein the polyphenylene ether resin is poly(2,6-dimethyl-1, 4-phenylene)ether.

10. A composition as claimed in any one of the preceding claims wherein the flame retardant aromatic phosphate plasticizer is a compound of the formula:

wherein Rl, R2 and R3 are the same or different and are aryl, alkyl substituted aryl or hydroxyaryl.

11. A composition as claimed in any one of the preceding claims wherein said aromatic phosphate is triphenylphosphate.

12.. A composition as claimed in any one of the preceding claims wherein the amount of the aromatic phosphate component is 10 to 100 parts by weight per 100 parts by weight of component (a).

13. A composition as claimed in any one of the preceding claims wherein the amount of the aromatic phosphate component is 15 to 65 parts by weight per 100 parts of component (a).

14. A composition as claimed in any one of the preceding claims wherein said A-B-A1 block copolymer is an unhydrogenated or hydrogenated styrene-butadiene-styrene block copolymer.

15. A composition as claimed in any one of the preceding claims wherein the amount of the thermoplastic elastomer is 5 to 100 parts by weight per 100 parts by weight of components (a) and (b) combined.

16. A composition as claimed in any one of the preceding claims wherein the amount of the thermoplastic elastomer component is 15 to 50 parts by weight per 100 parts by weight of components (a) and (b).

17. A flame retardant flexibilised thermoplastic composition as claimed in claim 1 substantially as hereinbefore described in any one of the Examples.