GB1591137A - Self-extinguishing polyphenylene ether moulding compositions - Google Patents

Description

(54) SELF-EXTINGUISHING POLYPHENYLENE ETHER (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: This invention relates to self-extinguishing polyphenylene ether molding compositions which are self-extinguishing and are moldable to finished articles of good impact resistance and high surface gloss.More particularly, the invention is concerned with thermoplastic compositions of a polyphenylene ether resin, a polymer selected from hydrogenated A-B-A' block copolymers - and certain acrylic resin modified diene rubber containing resins, and an aromatic phosphate which is present in amounts sufficient to provide, in addition to flame resistance to the thermoplastic impurities, impact resistance and good surface gloss to the resulting molded articles.

The polyphenylene ether resins are well known in the art as a class of therino- plastics which possess a number of outstanding physical properties. They can be prepared by oxidative and non-oxidative methods, such as are disposed, 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 has been found that many of the properties of polyphenylene ether resins, 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--BB-A' 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 No. 3,833,688 and 3,792,123 and in British Patent 1,477,706.

It is known in the art that the polyphenylene ethers 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--BB-A1 block copolymers and acrylic resin modified diene rubber containing resins, 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-A' block copolymers or acrylic resin modified diene rubber containing resins 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 known. In general, these are either blended physically with the thermoplastic or are used to unite chemically with the plastic 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.

3,639,506. Other self-extinguishing polyphenylene ether-polystyrene 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 German Application 2,554,324.

However, as is 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 a 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 now been surprisingly discovered that molded compositions consisting of polyphenylene ether, certain polymeric modifiers, and aromatic phosphate compounds exhibit excellent self-extinguishing behaviour, impact strength and surface gloss.

The commercial benefits of flame retardancy, good impact resistance and high surface gloss in the composition of this invention are most unexpected, generally in view of the physical properties frequently exhibited by flame retardant compositions of the prior art.

According to the present invention, there is provided a self-extinguishing thermoplastic molding composition comprising: (1) a resin component consisting of (a) from 60 to 99% by weight, based on (a) plus (b), of a polyphenylene ether resin, and correspondingly (b) from 40 to 1% by weight, based on (a) plus (b), of a polymer selected from a hydrogenated A-B-A' block copolymer and an acrylic resin modified diene rubber resin which is (i) a poly(alkylmethacrylate) grafted on to a butadiene styrene or an acrylonitrile-butadiene-styrene backbone, or (ii) a mixture of a poly(alkylmethacrylate) and a butadiene-styrene copolymer or an acrylonitrile butadiene-styrene terpolymer; and (2) from 1 to 40% by weight, based on (1) plus (2) of an aromatic phosphate compound.

These compositions are self-extinguishing, and provide impact resitant moldings having a high surface gloss.

The polyphenylene ether resins of (a) are 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 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 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 for example poly(2,6-dimethyl- 1,4-phenylene)ether; poly(2,6-diethyl-1,4phenylene)ether; poly(2-methyl-6-ethyl- 1,4-phenylene)ether; poly(2-methyl-6-propyl1,4-phenylene)ether; poly(2,6-dipropyl- 1,4-phenylene)ether; poly(2-ethyl-6-propyl- 1,4- phenylene)ether. Most preferred is poly(2,6-dimethyl- 1 ,4-phenylene)ether, preferably having an intrinsic viscosity of about 0.45 decililiters per gram (dl./g.) as measured in chloroform at 300C.

The hydrogenated A-B-A' block copolymers of component (b) are well known.

In general, these are block copolymers of the A-B-A' type in which terminal blocks A and Al are the same or different and, prior to hydrogenation, comprise homopolymers or copolymers derived from vinyl aromatic hydrocarbons and, especially, vinyl aromatics wherein 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. Center block B will always be derived from a conjugated diene, e.g., butadiene, isoprene or 1,3-pentadiene. Preferably, center block B will be comprised of polybutadiene or polyisoprene.

It is preferred to form terminal blocks A and A' 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 50,000 and 300,000. The terminal blocks will preferably comprise from 2 to 33% by weight, and more preferably, 5 to 30% by weight of the total block copolymer. Especially preferred are A-B-A' 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-A' 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.

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 750 to 6000F., for times between 0.1 and 24 hours, preferably 0.2 to 8 hours.

The acrylic resin modified diene rubber resin of component (b) is as indicated above, a poly(alkyl-methacrylate) grafted onto a butadiene-styrene backbone or an acrylonitrile-butadiene-styrene backbone, or a mixture of a poly(alkyl-methacrylate) and a butadiene styrene copolymer or an acrylonitrile-butadiene-styrene terpolymer.

The graft polymerization product of an acrylic monomer and a diene rubber of component (b) preferably comprises (1) from 20 to 80% by weight of a backbone copolymer of butadiene and styrene or a backbone terpolymer of acrylonitrile, butadiene and styrene, wherein the butadiene units are present in quantities of at least 40% by weight of the backbone polymer; (2) 80 to 20% by weight of an acrylic monomer graft polymerized to (1), said acrylic monomer units being selected from the group consisting of lower alkyl methacrylates, alicyclic methacrylates and alkyl acrylates, and (3) O to 60% by weight of a styrene monomer graft polymerized to (1).

The graft polymerization product of an acrylic monomer alone or with styrene monomer and the rubbery diene polymer or copolymer may be prepared by known techniques, typically by emulsion polymerization. They may be formed from a styrene-butadiene copolymer latex and a monomeric material such as methyl methacrylate alone or with another compound having a single vinylidene group copolymerizable therewith, e.g., styrene.For example, in the preparation of a representative material, 85 to 65 parts by weight of monomeric methyl methacrylate or monomeric methyl methacrylate to the extent of at least 55%, and preferably as much as 75% by weight, in admixture with another monomer which copolymerizes therewith, such as ethyl acrylate, acrylonitrile, vinylidene chloride, styrene, and similar unsaturated compounds containing a single vinylidene group, is added to 15 to 35 parts by weight of solids in a styrene-butadiene copolymer latex. The copolymer solids in the latex comprise 10 to 50% by weight of styrene and about 90 to 50 S, by weight of butadiene and the molecular weight thereof is within the range of 25,000 to 1,500,000. The copolymer latex of solids in water contains a dispersing agent, such as sodium oleate to maintain the copolymer in emulsion.Interpolymerization of the monomer or monomeric mixture with the copolymer solids emulsified in water is brought about in the presence of a free-radical generating catalyst and a polymerization regulator which serves as a chain transfer agent, at a temperature in the range between 15 C. and 800C. Coagulation of the interpolymerized product is then effected with a calcium chloride solution, for instance, whereupon it is filtered, washed and dried.

Other graft copolymers which differ from the above only in the ratio of monomeric material comprised solely or preponderantly of methyl methacrylate to the butadiene styrene copolymer latex extend from 85 to 25 parts by weight of the former to 15 to 75 parts by weight of the latter. These materials can vary in physical properties from relatively rigid compositions to rubbery compositions. A preferred commercially available material is Acryloid KM 611, which is sold by Rohm & Haas Company ("Acryloid" is a Registered Trade Mark). Additional information on the preparation of these materials is contained in U.S. Patents No. 2,943,074 and 2,857,360. A preferred material is described in U.S. Patent No. 2,943,074, Column 4, preparation "D" with conversion to emulsified polymer "B" described therein.

The aromatic phosphate compound of the compositions of the invention is a compound of the formula:

where R', R2 and R3 can be the same or different and are alkyl, cycloalkyl, aryl, alkyl substituted aryl, halogen substituted aryl aryl substituted alkyl, halogen, hydrogen and combinations of any of the foregoing, provided that at least one of Rl, R2 and R3 is aryl.

Typical examples include phenylbisdodecyl phosphate, phenylbisneopentyl phosphate, phenylethylene hydrogen phosphate, phenyl-bis(3,5,5 '-trimethylhexyl phosphate), ethyl-diphenyl phosphate, 2-ethyl-hexyldi(p-tolyl) phosphate, di-phenyl hydrogen phosphate, bis (2-ethylhexyl) p-tolylphosphate, tri-tolyl phosphate, bis (2-ethylhexyl)phenyl phosphate, tri-(nonyl-phenyl) phosphate, phenylmethyl hydrogen phosphate, di(dodecyl) p-tolyl phosphate, tricresyl phosphate, triphenyl phosphate, dibutylphenyl phosphate, 2-chloroethyldiphenyl phosphate, p-tolyl bis (2,5,5'-trimethylhexyl) phosphate, 2-ethylhexyl-diphenyl phosphate and diphenyl hydrogen phosphate. The preferred phosphates are those where each R is aryl. Especially preferred is triphenyl phosphate.

The respective amounts of the components in the present compositions can vary broadly within the above-stated range from 60 to 99% by weight of polyphenylene ether resin to, correspondingly, 40 to 1% by weight of A-B-A' block copolymer or acrylic resin modified diene rubber containing resin (these percentages being based on the total of (a) and (b)). With respect to the compositions containing A-B-A' block copolymers, the most preferred such compositions contain no less than 65% by weight of polyphenylene ether, based on the total weight of the resinous components in the composition. With respect to the aromatic phosphate flame retarding agent, amounts of from 1 to 40% by weight of the total composition (i.e. (1) and (2)) are employed to impart flame retardancy.Particular amounts will, of course, vary within this range, depending on the needs of the specific composition.

The composition of the invention can also further include glass fibers as a reinforcing filler, especially preferably, fibrous glass filaments comprised of limealuminum 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 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 1 to 80% by weight, based on the combined weight of glass and polymers, and preferably from 10 to 50% by weight. Especially preferably, the glass will comprise from 10 to 40% by weight, based on the combined weight of glass and resin. Generally, for direct molding use, up to 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, and antioxidants, 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 not necessary.

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

EXAMPLES 1-10.

The compositions shown in Table I, below, 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. Ibs./in.n., and the values for Gardner impact strength are in units of in.-lbs. Tensile yield, tensile break, flexural yield and flexural modulus values are each in units of p.s.i. X 10-J. The gloss values are 450 surface gloss expressed as relative dimensionless units.

TABLE I Poly(2,6-dimethyl- Hydrogenated A-B-A1 Triphenyl U.L. 94 Example 1,4-phenylene ether)a Block Copolymerb Phosphate 1/16" % Elongation 1 95 5 0 8/10, 12/37, 9/16 45 4/8,10/35 2 95 5 5 3/3,4/7,4/3 64 3 95 5 10 3/2,3/4,10/7 75 4 95 5 15 5/5,1/6,3/7 92 5 90 10 20 1/1,1/1,0/1 28 6 90 10 30 1/5,1/1,1/1 96 7 90 10 40 1/1,1/1,1/3 89 8 80 20 20 1/2,1/2,2/3 60 9 80 20 30 1/1,1/1,1/2 62 10 80 20 40 1/3,1/1,1/2 76 a) PPO, General Electric Company, intrinsic viscosity of about 0.5 in CHCl3 at 25 C.

b) Kraton G, Shell Chemical Co., an hydrogenated styrene-butadiene-styrene blocck copolymer.

TABLE I (Continued) Tensile Flexural Izod Impact Gardner Heat Deflection Strength Impact Strength Example Temp. ( F.) Yield Break Yield Modulus Gloss 1 373 10.1 8.0 15.0 323 54.8 4.8 283 2 329 10.6 8.9 15.4 308 60.1 3.9 298 3 300 10.4 9.1 15.0 339 62.3 4.1 343 4 267 10.2 9.2 14.3 323 61.8 3.2 262 5 248 8.3 7.1 11.0 261 58.2 10.2 260 6 200 7.8 6.9 10.5 261 66.5 3.6 260 approx. 2.47 156 6.3 5.5 8.8 237 64.9 4.3 230 8 222 6.2 6.3 8.6 221 64.7 13.8 190 9 174 5.4 5.6 7.5 208 - 12.7 175 10 140 4.6 4.6 6.8 200 60.4 13.5 180 EXAMPLES 11-18.

Additional compositions according to the invention were prepared and tested as in Examples 1 to 10. The formulations and test results for the additional compositions are listed in Table II. Unless shown otherwise, units are as in Table I.

TABLE II Poly(2,6-dimethyl- Triphenyl Acrylic Graft Tensile Example 1,4-phenylene ether)a Phosphate Copolymer Yield % Elongation 11 75 25 - 9.5 77 12 75 25 10 9.9 91 13 75 25 15 8.7 90 14 80 20 - 10.6 77 15 80 20 10 11.2 86 16 83 17 - 11.5 89 17 83 17 10 11.7 83 18 85 17 15 10.4 71 a) A in Table 1.

b) Acryloid KM 611, Rohm & Maas Co., an acrylic resin modified graft copolymer of styrene and styrene-butadiene.

TABLE II (Continued) Heat Deflection Temp. 1/16" Example Izod Impact Strength Gardner Impact Strength ( F.) U.L.-94 11 1.0 125 208 1/1, 1/2 1/2, 1/1 12 2.8 340 240 1/2, 3/5, 1/3,1/3 13 10.0 292 222 1/9, 2/13, 2/10 14 0.9 122 250 0/2, 1/5, 1/3, 1/3 15 1.3 125 267 2/3, 7/3, 4/6, 2/5 16 1.1 100 280 4/3, 1/3, 1/4, 2/7 17 1.0 20 283 2/7, 7/5, 6/8, 2/1 18 3.8 197 - -

Claims (10)

WHAT WE CLAIM IS:

1. A self-extinguishing thermoplastic molding composition comprising: (1) a resin component consisting of (a) from 60 to 99% by weight, based on (a) plus (b), of a polyphenylene ether resin, and correspondingly (b) from 40 to 1% by weight, based on (a) plus (b), of a polymer selected from a hydrogenated A-B-A' block copolymer and an acrylic resin modified diene rubber resin which is (i) a poly(alkylmethacrylate) grafted on to a butadiene styrene or an acrylonitrile-butadiene-styrene backbone, or (ii) a mixture of a poly(alkylmethacrylate) and a butadiene-styrene copolymer or an acrylonitrile butadiene-styrene terpolymer; and (2) from 1 to 40% by weight, based on (1) plus (2) of an aromatic phosphate compound.

2. A composition as claimed in Claim 1 wherein the polyphenylene ether resin has the formula:

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

3. A composition as claimed in Claim 1 or 2 wherein said polyphenylene ether resin is poly (2,6-dimethyl-1,4-phenylene) ether.

4. A composition as claimed in any one of the preceding Claims wherein the A-B-A1 block copolymer prior to hydrogenation, is as follows: (1) each A is a polymerized mono alkenyl aromatic hydrocarbon block having an average molecular weight of 4,000 to 115,000; (2) B is a polymerized butadiene hydrocarbon block having an average molecular weight of 20,000 to 450,000; (3) the blocks A constitute 2 to 33 weight percent of the copolymer; (4) 35 to 55% of the butadiene carbon atoms in blocks B are in vinyl side chains.

5. A composition as claimed in Claim 4 wherein the unsaturation of block B has been reduced to less than 10% of the original unsaturation.

6. A compositon as claimed in Claim 4 or 5 wherein the A-B-A' block copolymer prior to hydrogenation, is as follows: (1) each A is a polymerized styrene block having an average molecular weight of 8,000 to 60,000; (2) B is a polymerized butadiene block having an average molecular weight of 50,000 to 300,000, 40 to 50% of the butadiene carbon atoms in the block being vinyl side-chains; (3) the blocks A comprising 5 to 30% by weight of the copolymer.

7. Composition as claimed in any one of the precedmg Claims wherein component (b) is present in an amount of 10 to 40% by weight, based on (a) plus (b).

8. A composition as claimed in any one of the preceding Claims wherein the aromatic phosphate compound has the formula:

wherein R', R2 and R" are the same or different, and are alkyl, cycloalkyl, aryl, alkyl substituted aryl, halogen substituted aryl, aryl substituted alkyl, halogen, hydrogen or combinations of any of the foregoing, provided that at least one of R', R2 and R3 is aryl.

9. A composition as claimed in any one of the preceding Claims, which includes a reinforcing amount of a fibrous glass reinforcing filler.

10. A self extinguishing thermoplastic moulding composition as claimed in Claim 1 substantially as hereinbefore described in any one of the Examples.