GB2042560A - Non-blooming flame retardant thermoplastic compositions - Google Patents

Abstract

Normally flammable polyester resins (a) are rendered flame-retardant without blooming or plate out problems and without loss in toughness or other properties by combination with (b) a flame retardant amount of a polybrominated diphenyl ether having from 5 to 8 bromine atoms per molecule and (c) a flame-retardant synergist compound. The compositions, which are useful per se for molding, extrusion, and the like, are, in addition, described in impact modified resin compositions and filled and/or reinforced modifications. <IMAGE>

Description

SPECIFICATION Non-blooming flame retardant thermoplastic compositions The present invention relates to novel flame retardant thermoplastic compositions. More particularly it is concerned with non-blooming compositions of high molecular weight polyesters in combination with flame retardant amounts of Br5-Br8 brominated diphenyl ether.

The use of high molecular weight polyesters in thermoplastic molding compositions is well known to those skilled in the art. Such polyesters provide compositions with excellent moldability and molded articles therefrom having smooth and glossy surface appearance, high strength, stiffness, temperature resistance and other desirable properties.

However, a major short-coming in the use of such polyesters in molding compositions is their normally highly flammable nature. The flammability of polyesters has been reduced by using halogen-, phosphorus- or nitrogen-containing additives, and such compositions are described in various patents and publications. Flame retarded thermoplastic polyester compositions are desired for many fields of use such as in home construction, automobile and aircraft manufacture, packaging, electrical equipment and the like.

With particular reference to polyesters of the poly-(alkylene dicarboxylate) family and related copolyesters, it has been difficult to adequately render such materials flame retardant without sacrificing their inherent superior toughness properties.

Specifically, the use of conventional flame retardant additives in conventional amounts causes decreases in toughness, e.g., impact strength, elongation and deflection temperature under load, especially in glass filled embodiments.

A highly useful family of flame retardant agents has been reported to comprise polybrominated diphenyl ether compounds of the formula

wherein the total of x andy ranges from 2 to 10.

Patents describing such flame retardants are U.S.

3,624,024; 3,751,396; 3,873,491; 3,971,752; 4,010,219; and 4,070,332, the disclosures of which are incorporated herein by reference. Although diphenyl ethers having from 2 to 10 bromines are disclosed to be useful, e.g., in U.S. 4,010,219, and a preference is stated for the Br6, Br8 and Br10 analogs (in combination with decabromodiphenyl), dripping during burning is a problem. Furthermore, the decabromodiphenyl ether analog, which has become the flame-retardant agent of the polybrominated diphenyl ether family of commercial choice in poly(1 ,4-butylene terephthalate) resin compositions, has the undesirable habit of migrating to the surface of articles molded from compositions containing it.

This habit, known as "blooming" or plate-out", not only is visually unacceptable, but also causes breakdown in surface electrical characteristics of parts molded from compositions in which decabromodiphenyl ether is the flame-retardant agent.

It has now been discovered that if polybrominated diphenyl ethers ranging from pentabromodiphenyl ether to octabromodiphenyl ether are employed, flame-retardant compositions without any tendency to bloom when subjected to high temperatures over a period of time are obtained. Furthermore, such compositions are provided without sacrificing the other desirable traits, such as toughness, of the polyester resin molding compositions of the prior art.

By way of illustration, the addition of a Brs-Br8 diphenyl ether additive provides compositions which are flame retardant to the point where they meet stringent Underwriter's Laboratory requirements for self-extinguishing compositions, but which at the same time do not "bloom" or "plate out" on the surface of molded parts when subjected to oven aging at 100, 140 and 1700C for about 1 hours, 24 hours and 168 hours. In contrast, under the same conditions, decabromodiphenyl ether forms a powder by blooming to the surface, jeopardizing electrical properties.

It is, accordingly, a principal object of this invention to provide a family of bloom-resistant, flame retardant polyester compositions.

It is another object of this invention to provide flame retardant polyester compositions with excellent moldability and which, after oven aging, retain smooth and glossy surfaces, high flexural strength and superior surface electrical properties.

Other objects and advantages of the invention will become apparent from the following detailed description.

According to this invention there are provided non-blooming improvements in flame retardant thermoplastic compositions comprising (a) a normally flammable high molecular weight polyester; (b) a flame retardant amount of a polybrominated diphenyl ether compound of the formula

wherein x + y is from 2 to 10, and (c) an effective amount of an organic or inorganic flame retardant synergist compound in which the improvement consists of using as component (b) a compound or mixture of compounds wherein the sum of x andy for each compound is not less than 5 nor more than 8 whereby a composition is obtained from which the polybrominated flame retardant does not bloom or plate out after molding.

The term "normally flammable high molecular weight polyester" includes, in general, linear saturated condensation products of diols and dicarboxylic acids, or reactive derivatives thereof. Preferably, they will comprise condensation products of aromatic dicarboxylic acids and aliphatic diols. It is to be understood that is also possible to use polyesters such as poly(1,4-dimethylol cyclohexane dicarboxy lates, e.g., terephthalates). In addition to phthalates, small amounts of other aromatic dicarboxylic acids such as naphthalene dicarboxylic acid, or aliphatic dicarboxylic acids, such as adipic acid, can also be present in preferred compositions. The diol constituent can likewise be varied, in the preferred embodiments, by adding small amounts of cycloaliphatic diols.In any event, the preferred polyesters are well known as film and fiber formers, and they are provided by methods outlined in Whinfield, U.S. 2,465,319 and Pengilly, U.S. 3,047,539, and elsewhere. The preferred polyesters will comprise a poly(alkylene terephthalate, isophthalate or mixed isophthalate-terephthalate, e.g., up to 30 mole percent isophthalate), said alkylene groups containing from 2 to 10 carbon atoms, e.g., poly(ethylene terephthalate) or poly(1 ,4-butylene terephthalate).

Because of its rapid crystallization from the melt, it is preferred to use poly(1 ,4-butylene terephthalate) as the normally flammable polyester resin component of the present compositions.

The molecular weight of the polyester component should be sufficiently high to provide an intrinsic viscosity of about 0.6 to 2.0 deciliters per gram, preferably 0.7 to 1.6 dl./g., measured for example, as a 1% solution in a 60:40 mixture of phenol and tetrach loroethane at 25"C.

In preferred embodiments, the polyester component (a) will be poly(1 4-butylene terephthalate) either straight chain or branched and it is present alone or in further combination with poly(ethylene terephthalate) or in the form of a block copolyester with an aromatic-aliphatic or aliphatic-aliphatic polyester or in the form of a blended composition with such a copolyester, or in the form of a blended composition with a resin selected from an aromatic polycarbonate, a polyacrylate, a vinyl-aromatic compound-modified polyacrylate, a copolymer comprising a vinyl aromatic compound and a diene, a polyolefin or copolymer of an olefin with a vinyl ester or a mixture of any of the foregoing. Such combinations and methods of making them are known to those skilled in this art.

As has been mentioned, there will be used in the flame retardant compositions of this invention a conventional flame-retardant synergist component (c), such as organic or inorganic antimony, aluminum or molybdenum compound, or mixture thereof. Such compounds are widely available or can be made in known ways. In preferred embodiments, the synergist will comprise an organic or inorganic antimony compound, and the type of antimony compound used is not critical, being a choice primarily based on economics. For example, as inorganic antimony compounds there can be used antimony oxide, (Sb2Oa); antimony phosphate; KSb(OH)6; NH4SbF6; SbS3; and the like. A wide variety of organic antimony compounds can also be used, such as antimony esters with organic acids, cyclic alkyl antimonites; aryl antimonic acids, and the like.Illustrative of the organic antimony compounds, including inorganic salts of such compounds are: KSb tartrate; Sb caproate; Sb(OCH2CH3)3; Sb(OCH(CH3)CH2CH3)3; Sb polymethylene glycolate; triphenyl antimony; and the like. Especially preferred is antimony oxide.

The flame retardant component (b) can be made in known ways and/orthey are commercially available.

If less than 5 bromine atoms per molecule are present, the high level of flame retardant needed will lower the physical properties of the product, e.g., flexural modulus and deflection temperature under load. If more than 8 bromine atoms per molecule are present, "bloom" and loss of surface electrical properties becomes a problem. A mixture comprising primarily octabromodiphenyl ether has a melting range of 70-140"C., a theoretical bromine content of 79.8%, and is commercially available from Great Lakes Chemical Corporation, West Lafayette, Indiana 47906, U.S.A., under the trade designation DE-79.

This product has small amounts of decabromodiphenyl ether and non-abromodiphenyl ether, causing a slight degree of bloom on aged molded parts. More suitable is a brominated diphenyl ether having slightly lower theoretical bromine content, 77.4%, and melting range 58-129"C. This product, available from Great Lakes under designation DE-77 has a vapour phase chromatograph distribution weighted toward Br6. As will be shown hereinafter, DE-77 produces no bloom on elevated temperature oven aging in polyester compositions, in contrast to the Bur10 analog. Moreover, the Bq, analog must be entirely absent from the flame retardant component (b) to achieve the advantageous results of this invention.

The amount of polybrominated diphenyl ether used as flame retardant component (b) is not critical to the invention so long as it is present in a minor proportion based on said composition -- major proportions are uneconomical and may detract from moldability, gloss and the like. However, at least an amount sufficient to render the thermoplastic polyester resin flame retardant, non-burning or self-extinguishing will be used, as the case may be.

Those skilled in the art are well aware that the amount of component (b) will vary with the nature of the flammable resin(s) and the relative efficiency of the additive. In general, however, the amount of additive will be from 0.5 to 50 parts by weight per 100 parts by weight of the resinous components. A preferred range will comprise from about 5 to about 25 parts of component (b) per 100 parts of resinous components in the composition. The amount of synergist component (c) likewise can vary over a fairly wide range but, in general, there is used from about 0.5 to about 20 parts by weight per 100 parts of combined resinous components in the composition and preferably from about 1 to about 12 parts by weight.

It is specifically contemplated by this invention to provide compositions which also include (d) an effective amount of a conventional filler and/or reinforcing agent. Among the fillers and/or reinforcing agents which may be used are glass, talc, mica, clay or a mixture of any of the foregoing. The amounts used are conventional and will, in general range from about 1 to about 80 parts by weight per 100 parts by weight of the total composition. Especially preferably, the filler and/or reinforcing component (d) will comprise glass fibers. Preferably the glass will comprise from about 5.0 to about 40 parts by weight per 100 parts by weight of the total composition.

It is also regarded to be among the features of this invention to include in the compositions other ingredients such as mold release agents, pigments, stabilizers, nucleating agents, and the like, in conventional amounts for their conventionally employed purposes.

The manner of adding the flame retardant additives to the thermoplastic polyester resin is not critical; it is conventional and will be obvious to those skilled in the art. Preferably, however, each ingredient is added as part of a blend premix and the latter is mixer, e.g., by passage through an extruder, or by fluxing on a mill, at a temperature dependent on the needs of the particular composition. The mixed composition can be cooled and cut up into any desired shape. Typical processing and molding techniques will be illustrated hereinafter.

It is to be understood that the compositions of this invention can be used in many different ultimate shapes. They may be molded into three-dimensional articles, or formed into films, or be extruded into rods, tubes, etc., or shaped into fibers, by conventional techniques.

The following examples illustrate the preparation of certain compositions within the scope of this invention. They are not to be contrued to limit the scope of the invention in any manner whatsoever.

EXAMPLE 1 In a Prodex extruder operated at 540"F. are blended poly(1 ,4-butylene terephthalate), octabromodiphenyl ether, (Great Lakes Chemical Corporation DE-79) antimony oxide, and small amounts of a stabilizer combination. The blended composition is injection molded in a van Dorn molding machine at 500"F. into test pieces which are subjected to physical, elevated temperature oven aging and flame retardance measurements. For purposes of comparison, a composition substituting a bromineequivalent amount of decabromodiphenylether is mixed, molded and tested. The formulations and the results are set forth in Table 1.

Table 1 Composition Comprising Polyester, Brominated Diphenylether and Antimony Oxide Example 1 lA* Composition (percent) Poly(1 ,4-butylene terephthalate) 82.3 83.8 Octabromodiphenyl ether 11.5 Decabromodiphenyl ether - 10.0 Antimony oxide 6.0 6.0 Stabilizer (to make 100) Properties Deflection Temp. Under Load, "F., 66 psi 322 283 Deflection Temp. Under Load, "F., 264 psi 104 122 Oven Aging, 100, 140, 1700C., 168 hrs. no bloom" bloom Notched Izod impact, ft.lbs./in. 0.67 0.68 Unnotched Izod impact,ft.lbs./in 8.3 10.2 Flexural strength, psi 15,000 13,400 Flexural modulus, psi 411,000 414,000 Tensile strength, psi 8,900 9,000 % Elongation 27 57 Specific gravity 1.41 1.43 Flammability, U.L.Standard 94,30 mils. V-2 V-2 ASTM D495 Arc Resistance as molded seconds 14.6 10.1 ASTM D495 Arc Resistance after 24 hrs.

at 170 C., sec. 14.3 2.5 * Control ** onedgesonly The substantial improvement in bloom resistance and retention of electrical properties can readily be seen.

EXAMPLE2 The general procedure of Example 1 is repeated, but this time glass fibers are added to produce a reinforced molded composition. The formulations used and the results obtained are set forth in Table 2.

Table 2 Reinforced Compositions Comprising Polyester, Brominated Diphenyl Ether, Antimony Oxide and Glass Fiber Example 2 2A* Composition (percent) Poly(1 ,4-butylene terephthalate) 54.4 55.4 Octabromodiphenyl ether 8.0 Decabromodiphenyl ether - 7.0 Antimony oxide 7.2 7.2 Glass fiber reinforcement 30 30 Stabilizers (to make 100) Polytetrafluoroethylenea 0.2 0.2 Properties Deflection Temp. Under Load, "F., 66 psi 401 410 Deflection Temp.Under Load, "F., 264 psi 382 384 Oven Aging, 100, 140, 1700C., 168 hrs. no bloom bloom Notched Izod impact, ft.lbs./in. 1.8 1.9 Unnotched Izod impart, ft.lbs./in. 10.9 11.7 Flexural strength psi 27,300 26,200 Flexural modulus, psi 1,160,000 1,120,000 Tensile strength, psi 17,300 17,600 % Elongation 10 11 Specific Gravity 1.66 1.66 Flammability, U.L. Standard 94,30 mils. V-2 V-2 ASTM D995 Arc Resistance, As molded, sec. 8.7 16.5 ASTM D495 Arc Resistance after 24 hrs.

at 1700C., sec. 50.6 12.5 * Control a duPont,Teflon6 Again, the surprising lack of blooming in articles molded from the composition according to this invention is observed.

EXAMPLE3 The procedure of Example 1 is repeated, substitut ing for the octabromodiphenyl ether 12.5% of a polybrominated diphenyl ether having a melting range of 58-129"C. and 18.0 /O < Br6; 50.0% Br6; 27.0% Br,; 4.8% Br8; and 0.3% Brig. The color is 73 (%T), acidity is 0.12 mg. KOH/gm. and theoretical % bromine is 77.4. The product is free of decabromodiphenyl ether and is designated DE-77 by its supplier Great Lakes Chemical Corporation. After extrusion, molding and oven aging at 100, 140 and 1700C. for 1 hr., 24 hrs., and 168 hrs., no bloom is seen. The formulation used and properties obtained are set forth in Table 3.

Table 3 Composition Comprising Polyester And Polybrominated Diphenyl Ether Example 3 Composition (percent) Poly(1,4-butylene terephthalate) 81.35 DE-77 (polybrominated diphenyl ether) 12.5 Antimony Oxide 6.0 Stabilizers (to make 100) Properties Deflection Temp. Under Load F., 66 psi 294 Deflection Temp. Under Load "F., 264 psi 124 Oven aging, 100, 140, 1700C., 168 hrs. no bloom Notched Izod impact, ft.lbs./in. 0.52 Unnotched Izod impact, ft.lbs./in. 9.5 Flexural Strength, psi 14,600 Flexural Modulus, psi 408,000 Tensile Strength, psi 7,700 % Elongation 242 Specific Gravity 1.47 Flammability, U.L. Standard 94,30 mils. V-0 EXAMPLES 4-8 In a Prodex extruder are blended DE-77, antimony oxide, stabilizers, fillers and resins as shown in Table 4.These examples illustrate the utility of DE-77 in formulations containing copolymers, polymer blends, and various fillers. In all cases bloom was absent and the materials were V-0 by the U.L. standard 94 test. The properties obtained are set forth in Table 4.

Table4 Compositions of Polyesters and Polybrominated Diphenyl Ether Example 4 5 6 7 8 Poly(1,4-butylene terephthalate) - 60.85 43.0 20.35 48.15 Poly(ethyleneterephthalate) - - - 20 20 Bisphenol-Apolycarbonate 10 11 - Ethylene-vinyl acetate copolymer - - - 7 Acrylate-methacrylate copolymer - 10 - - Polyethylene - - - 2 Copolyester 81.85 - - - - DE-77 12 13 9 9 9 Antimony Oxide 6 6 6.6 - 7.2 Thermogard CPA - - - 5 Glass Fibers - - 30 11 15 Mica - - - 25 Stabilizers )to make 100) Polytetrafluoroethylene - - 0.1 0.5 0.5 Properties Deflection Temp. Under Load, "F., 264 psi 120 134 372 360 365 Oven aging, 100, 140, 1700C., 168 hrs. no bloom no bloom no bloom no bloom no bloom Notched Izod impact, ft.lbs./in. 0.6 2.3 1.5 0.9 1.0 Unnotched Izod impact, ft.lbs./in. > 16 > 16 10 5 9 Flexural Strength, psi 7,100 12,500 28,100 16,700 24,000 Flexural modulus, psi 169,000 342,000 1,240,000 1,140,000 833,000 Tensile Strength, psi 4,900 7,200 17,50 9,600 15,300 % Elongation 460 137 - - Specific Gravity 1.43 1.41 1.69 1.75 1.61 Flammability, U.L., Standard 94,30 mils. V-0 V-0 V-0 V-0 V-0 All obvious variations are within the full intended scope of the appended claims.

Claims (12)

1. Aflame retardant thermoplastic composition which comprises: (a) a normally flammable high molecular weight polyester; (b) a flame retardant amount of a polybrominated diphenyl ether compound of the formula

wherein x + y is from 5 to 8, and (c) an effective amount of an organic or inorganic flame retardant synergist compound.

2. A composition as claimed in Claim 1 which comprises from 3 to 25 parts by weight of component (b) and the amount from 1 to 12 parts by weight of component (c) per 100 parts by weight of said composition.

3. A composition as claimed in Claim 1 or2 wherein polyester component (a) is poly(1 ,4- butylene terephthalate) either straight chain or branched, alone or in further combination with poly(ethylene terephthalate), or in the form of a block copolyester with an aromatic-aliphatic or aliphaticaliphatic polyester, or in the form of a blended composition with such a copolyester, or in the form of a blended composition with a resin selected from an aromatic polycarbonate, a polyacrylate, a vinylaromatic compound-modified polyacrylate, a copolymer of a vinyl aromatic compound and a diene, a polyolefin, or a copolymer of an olefin with a vinyl ester, or a mixture of any of the foregoing.

4. A composition as claimed in any preceding Claim wherein, in component (b), the total of x andy is8.

5. A composition as claimed in any of Claims 1 to 3 wherein, in component (b), the total of x andy is primarily in the range of 5 to 7, with substantially 50% of component (b) having x + y = 6.

6. A composition as claimed in any preceding Claim wherein component (c) comprises an organic or inorganic antimony, aluminum or molybdenum compound.

7. A composition as claimed in any preceding Claim which also includes 0.01 to 1.0% by weight of polytetrafluoroethylene.

8. A composition as claimed in any preceding Claim which also includes (d) an effective amount of a filler and/or reinforcing agent.

9. A composition as claimed in Claim 8 wherein the filler and/or reinforcing agent component (d) comprises glass, talc, mica, clay, or a mixture of any of the foregoing.

10. A composition as claimed in Claim 9 wherein component (d) comprises glass fibres.

11. A composition as claimed in Claim 10 wherein the glass fibres comprise from 5 to 40 parts by weight, per 100 parts by weight of said composition.

12. A composition as claimed in Claim 1 and substantially as hereinbefore described with reference to any of Examples 1 to 8.