Document ykaevJpG6Q7yORRaNzVxO1BY4

United States Patent m Hochberg et al. [li] Patent Number: 4,732,921 [45] Date of Patent: Mar. 22, 1988 [54] FLAME RETARDANT POLYBUTYLENE TEREPHTHALATE [75] Inventors: Arie Hochberg, Montclair; Nancy C. Eickman, Mountainside; Frank Haimbach, IV, Montclair, all of NJ. [73] Assignee: Hoechst Celanese Corporation, Chatham, N.J. [21] Appl. No.: 938,198 [22] Filed: Dec. 5,1986 [51] Int Cl.........................C08K 3/22; C08K 67/02 [52] U.S. CL................................... 523/460; 524/410; 524/411; 525/438 [58] Field of Search............... 525/438; 524/410, 411; 523/460 [56] References Cited U.S. PATENT DOCUMENTS 3,909,485 3,912,792 3,929,908 3,957,905 3,965,212 4,221,893 4,222,926 4,548,964 4,562,216 9/1975 Hongo et al......................... 260/40 R 10/1975 Touval ................................. 260/863 12/1975 Orlando et al........................ 260/620 5/1976 Sumoto et al......................... 260/860 6/1976 Kamada et al........................ 260/835 9/1980 Behar et al............................ 525/438 9/1980 Mizuno et al....................... 260/40 R 10/1985 Yoshida et al........................ 523/455 12/1985 Kishida et al......................... 523/433 FOREIGN PATENT DOCUMENTS 149190 2757557 58-118849 59-149954 7/1985 European Pat Off. . 6/1978 Fed. Rep. of Germany . 7/1983 Japan . 8/1984 Japan . OTHER PUBLICATIONS "A New Brominated Polymeric Additive for Flame Retardant Glass-Filled Polybutylene Terephthalate", Journal of Fire Retardant Chemistry, vol. 9, (Aug. 1982), p. 181. Primary Examiner--Veronica P. Hoke Attorney, Agent, or Firm--Depaoli & O'Brien [57] ABSTRACT A flame-resistant polybutylene terephthalate molding composition has vastly improved fatigue strength and improved melt flow by incorporating therein a halogenated epoxy flame retardant represented by the general formula: ch2---- ch--ch2-- (X)l CH3(X)t \=/--\_/ --CH2--^H_CHr ch3 oh Wi ch3 POi ----ch--ch2 ch3 o wherein an n is the degree of polymerization and the halogenated epoxy resin has a molecular weight of at least about 20,000 to 40,000; X is a chlorine or bromine atom, and i is an integer of from 1-4. 20 Claims, No Drawings 4,732,921 12 ester resins including polybutylene terephthalate are FLAME RETARDANT POLYBUTYLENE disclosed in U.S. Pat. Nos. 3,873,491 and 3,936,400. TEREPHTHALATE Recently, it has been suggested to incorporate a bro minated epoxy resin as a flame retardant for polybutyl BACKGROUND OF THE INVENTION 5 ene terephthalate molding compositions. A useful bro The present invention relates to flame retardant addi minated epoxy resin is one formed by reacting tetratives to be used in conjunction with polyalkylene tere- bromobisphenol-A and epichlorohydrin. This is exem phthalate molding resins. More particularly, the present plified in U.S. Pat. No. 3,965,212 wherein tetrainvention relates to flame resistant polybutylene tere- bromobisphenol-A, optionally non-brominated bisphthalate molding resins having improved toughness 10 phenol-A and epichlorohydrin are reacted to form a containing, as a flame retardant, a high molecular glycidyi ether-end capped brominated resin useful as a weight halogenated epoxy resin and an antimony-con flame retardant for polybutylene terephthalate. A flame taining flame retardant synergist retardant synergist such as antimony trioxide is also Polybutylene terephthalate and reinforced polybutyl added. The epoxy resins which are disclosed in U.S. ene terephthalate molding resins have been found to be 15 Pat. No. 3,965,212, however, are of relatively low mo surprisingly superior to polyethylene terephthalate in lecular weight having at most about 11 repeating units many important processing and performance character of the bisphenol-A-containing ether. Other patents istics. For example, polybutylene terephthalate can be which teach improving the flame resistance of polybu molded and otherwise processed at lower temperatures, tylene terephthalate with the brominated epoxy resins have a shorter cycle time in the mold and do not re- 20 described above together with other brominated aro quire, as does polyethylene terephthalate, the presence matic compounds include U.S. Pat Nos. 3,909,485; of a nucleating agent to induce crystallinity. Further 4,548,964; and 4,562,216. more, reinforced polybutylene terephthalate molding In European Patent Application No. 0149190, pub resins have correspondingly higher tensile strength, lished July 24,1985, it is suggested to add a brominated lower water absorption and better creep (flexural) prop- 25 aromatic flame retardant including tetrabromobis- erties than does similarly reinforced polyethylene tere phenol-A bisdiglycidyl ethers to a co-polyetherester phthalate. As a direct result, these polybutylene tere resin which comprises long-chain ester units derived phthalate molding resins which were first disclosed, from dicarboxylic acids and polyalkylene oxide glycols along with polyethylene terephthalate in U.S. Pat. No. having a molecular weight of from about 400 to 6,000 2,465,319 to Whinfield and Dickson, have been found to solve processing problems long associated with poly ethylene terephthalate and believed, by those skilled in the art to be equally associated with all polyalkylene 30 and short-chain ester units derived from a dicarboxylic acid and low molecular weight diols. The brominated epoxies are described as having an epoxy equivalent of terephthalates Equally as significant, these molding from about 1,700 to about 2,100 g/eq and a molecular resins present a noticeably improved balance of perfor- 35 weight of from about 2,000 to 30,000. Especially pre mance properties which those skilled in the art, did not ferred are the F-2300 diglycidyl-type polymers having believe to exist. Consequently, the superior processing requirements and physical properties of polybutylene about 50% aromatic bound bromine as produced by Makhtashim Chemical Works, Ltd., Beer Sheba, Israel. terephthalate molding resins makes them more com The F-2300 flame retardant is described in the Journal mercially desirable, with a wider area of applicability 40 ofFire Retardant Chemistry, Volume 9 (August, 1982), than polyethylene terephthalate. These molding resins do, however, have one consid pp. 181-7. In this journal article, glass-filled polybutyl ene terephthalate is mixed with the F-2300 flame retar erable drawback-they are flammable. Quite signifi dant brominated epoxy which is described as having a cantly, the presence of many important reinforcing molecular weight of from 3,800 to 4,000. It is believed agents, such as glass, enhances rather than deters the 45 the F-2300 flame retardant is marketed by M & T burning rate of these molding resins. Since the reinforc Chemicals under the tradename Thermoguard 230. ing agents have a direct effect on the desirable physical Highly brominated bisphenol-A epoxy resins are also and mechanical properties of these molding resins, sev described in U.S. Pat. No. 4,221,893 assigned to Makh eral commercially advantageous applications are pre tashim. The brominated bisphenol-A epoxy resins dis cluded. 50 closed therein are produced by reacting epichlorohy It is well known in general that halogen-substituted drin with the residue remaining after the formation of aromatic compounds are effective as flame retardants tetrabromobisphenol-A. These resins are described as for thermoplastic resins, particularly those which are flame retardant additives for polymers including ther required to be molded at elevated temperatures. Thus, a mosetting polyester resins. variety of halogen-substituted aromatic compounds and 55 It has been found that many of the aforementioned polymers have been suggested as flame retardants for brominated flame retardants have the drawback that polyalkylene terephthalates, including polybutylene when the same are added to polybutylene terephthalate terephthalate. For example, tetrabromophthalic anhy and the mixture subjected to molding, the resulting dride, tetrabromobisphenol ether, decabromobiphenol molded articles are greatly deteriorated in mechanical ether, hexabromobiphenol and brominated bisphenol-A 60 properties, particularly toughness. The brominated as well as brominated polycarbonates formed from bro epoxy resins disclosed in U.S. Pat No. 3,965,212, how minated bisphenol-A and phosgene have all been sug ever, are described in the patent as imparting excellent gested as flame retardants for polybutylene terephthal mechanical properties to polybutylene terephthalate. ate. Typically, the fire retardant package for the ther Unfortunately, applicants have recently discovered that moplastic polyester molding compositions includes a 65 polybutylene terephthalate compositions containing the halogenated aromatic fire-retardant such as listed above brominated epoxy resin disclosed in U.S. Pat. No. and a flame retardant synergist, most notably antimony 3,965,212 show a marked decrease in melt flow relative trioxide. Brominated aromatic fire retardants for poly- to the polyester without the flame retardant. It is theo- 4,732,921 rized that the low molecular weight brominated epoxy the same or different for each aromatic substituent and flame retardant is involved in intermolecular crosslink is an integer of 1 to 4. ing with the polybutylene terephthalate. In accordance with the invention, there is provided a In molding large articles or articles with complicated flame resistant resin composition comprising 40 to 90 structures, it is important that the melt flow of the ther- 5 parts by weight polybutylene terephthalate, 0 to 50 moplastic polyester be sufficient so as to allow the mol parts by weight glass fibers, 5 to 20 parts by weight of ten resin to uniformly fill the mold cavities without the the halogenated bisphenol-A diglycidyl ether polymer need of substantially increased pressure and/or of modi as set forth in general formula I, and 1 to 10 parts by fying the molding equipment with consequent added weight of an antimony-containing flame retardant syn expense to accommodate highly viscous molding com- 10 ergist. The flame resistant polybutylene terephthalate positions. Excessive molding pressure to accomodate highly viscous molding compositions may also lead to localized areas of frozen-in stress in the formed article since it is unlikely that the pressure will even itself out in a filled mold and, thus, excessive pressure is to be 15 molding composition of the present invention has vastly improved fatigue strength relative to other flame resis tant PBT molding compositions utilizing other haloge nated aromatic flame retardants and has improved melt avoided. Obviously, the lower the viscosity of the plas flow characteristics relative to fire resistant PBT mold tic melt, the less will be the pressure needed to convey ing compositions which contain as the flame retardant the molding resin into the mold fully and evenly. Ac therefor lower molecular weight, brominated epoxy cordingly, it is a distinct disadvantage that the incorpo resins. ration of additives including the flame retardant addi- 20 tives sacrifice the melt flow of the molding resin com position. Accordingly, it is a primary objective of the present DETAILED DESCRIPTION OF THE INVENTION The molding resins of this invention are based on a invention to provide a flame resistant polybutylene polybutylene terephthalate polymer. This polymer is of terephthalate molding composition having improved 25 the general type described in U.S. Pat. No. 2,465,319 to toughness. Whinfield and Dickson, and can be produced from the It is another object of the present invention to pro reaction product of a dibasic acid, such as terephthalic vide a flame resistant polybutylene terephthalate mold acid or a dialkyl ester of terephthalic acid (especially ing composition of improved melt flow characteristics. dimethyl terephthalate), and diols having 4 carbon It is still another object of the present invention to 30 atoms. Suitable diols include 1,4-butanediol, 1,3- provide a brominated epoxy resin as a flame retardant butanediol, 1,2-butanediol, 2,3-butanediol and the like. which when added to polybutylene terephthalate mold As is well known in the art, in the production of ing compositions does not degrade the toughness of the polybutylene terephthalate, the appropriate bis (hy- molded article or disadvantageous^ affect the melt droxyalkyl) terephthalate is produced as the intermedi flow characteristics of the molding composition. 35 ate. The bis (hydroxyalkyl) terephthalate can be pre These and other objects and aspects of the present pared by reacting the dialkyl ester of terephthalic acid invention will be readily understood by those of ordi in which the alkyl radicals can contain from 1 to 7 nary skill in the art upon consideration of the following description of the invention together with the appended -claims. 40 carbon atoms with about two molecular proportions of the diols described above. It is preferred to use higher proportions of the diol, i.e., in excess of 1.5 moles of the SUMMARY OF THE INVENTION diol per mole of the terephthalate derivative, since by In accordance with the present invention, polybutyl using such proportions, the initial transesterification is ene terephthalate (PBT) is successfully made flame caused to take place more rapidly and completely. resistant without deteriorating the excellent mechanical 45 The reaction for the esterification is conducted under properties, particularly toughness, inherent thereto and conditions of elevated temperatures and atmospheric, without adversely effecting the other resin characteris subatmospheric or superatmospheric pressure. Nor tics such as melt flow by adding thereto a flame retar mally, the desired temperatures of the reaction can dant represented by general formula I. range from about the boiling temperature of the reac O /\ tion mixture to as high as 250 C., if desired. fl) 50 The molding composition of the present invention is preferably based on polybutylene terephthalate which CH2------ CH--CH2-- will be present in amounts of about 40 to about 90 wt. % of the composition. The intrinsic viscosity of the poly 55 butylene terephthalate is preferably in the range of 0.4 to 5.0 dl/g, and more preferably in the range of from 0.6 to 3.0 dl/g. The balance of the composition will comprise the brominated epoxy resin flame retardant, flame retardant 60 synergist, fillers and other additives which are used to promote stability and moldability of the composition. Further, the molding composition may contain a polyal- kylene terephthalate other than polybutylene tere phthalate. Preferably, the additional polyester will be wherein n is an integer describing the degree of poly- 65 polyethylene terephthalate. Accordingly, 0-40 wt. % of merization and is sufficient to provide a molecular the molding composition can comprise polyalkylene weight of from about 20,000 to about 40,000, e.g., at terephthalate such as polyethylene terephthalate in ad least 32; X is a bromine or chlorine atom; and i may be dition to polybutylene terephthalate. 4,732,921 The flame retardant which is added to the polybutyl tive to the total polybutylene terephthalate molding ene terephthalate molding composition has the struc composition. If the amount of flame retardant is too ture represented by general formula I above and is ob small, a sufficient flame resistance cannot be attained tained, for example, by the condensation of epichloro- while if the amount thereof is too large, the beneficial hydrin with tetrabromobisphenol-A. The epoxy resin characteristics of the molding resin is undesirably dete flame retardant preferably comprises about 50 percent riorated. aromatically bound halogen, preferably, bromine. Ac Along with the halogenated epoxy resin flame retar cordingly, referring to general formula I, preferably, X dant which has been discussed above, there is added to is bromine, and i is the same for each aromatic substitu the composition a flame retardant synergist comprising ent and is equal to about 2. In formula I, n indicates the 10 antimony. Preferably, antimony trioxide is used in com average degree of polymerization and is an integer of at bination with the flame retardant of formula I. The least about 32 to 65 such that the molecular weight of flame retardant synergist is preferably added in amounts the flame retardant epoxy resin is at least about 20,000 ranging from about 1 to 10% by weight relative to the to 40,000. total polybutylene terephthalate molding composition. The molecular weight of the epoxy resin flame retar 15 In preparing the composition of the present inven dants of this invention is a critical feature as it has been tion, there may be adopted such a procedure that a found that articles molded from polybutylene tere flame retardant of the formula I and antimony trioxide phthalate containing the higher molecular weight flame are added to a molten polybutylene terephthalate dur retardants of the present invention are not only im ing or after polymerization reaction, or added to chips parted with vastly improved toughness as shown by 20 of the polybutylene terephthalate. For example, suffi impact and tensile strengths as compared to molded ciently dried polybutylene terephthalate in the form of PBT articles containing other halogenated aromatic chips, a flame retardant of formula I and antimony tri flame retardants, but, the compositions are also pro oxide can be blended together and the resulting mixture vided with a sufficient melt flow. On the other hand, then kneaded by means of an extruder or the like. PBT molding compositions containing halogenated 25 Optionally, reinforcing agents can be intimately epoxy resins of lower molecular weight such as set forth blended with the polybutylene terephthalate by either in U.S. Pat. No. 3,965,212, have decreased melt flow, dry blending or melt blending, blended in extruders, especially when the compositions are allowed to stand heated rolls or other types of mixers. If desired, the for even short periods of time. The intennolecular reinforcing agents can be blended with monomers in the crosslinking between the lower molecular weight epoxy 30 polymerization reaction as long as the polymerization resins of U.S. Pat. No. 3,965,212 and the PBT which is reaction is not effected. Alternatively, the reinforcing believed to reduce the melt flow of such compositions is agent can be added after polymerization and prior to not found when the high molecular weight halogenated extrusion. The types of reinforcing agents which can be epoxy flame retardants of the present invention are used include among others glass fibers (chopped or used. 35 continuous rovings) asbestos fibers, cellulosic fibers, The molecular weight of the brominated epoxy resin cotton fabric paper, synthetic fibers, metallic powders can be regulated by the molar ratio of reactants which and the like. The amount of reinforcing agent can range are used in the condensation reaction to form the resin. from about 0 to about 50 weight percent, preferably Thus, increasing the amount of epichlorohydrin relative from about 5 to about 40 weight percent based on the to the tetrabromobisphenol-A, tends to reduce the mo 40 total molding composition. Glass fibers are the pre lecular weight of the epoxy resin which is formed and ferred reinforcing agent. likewise decreasing the relative amount of epichlorohy Glass reinforced polybutylene terephthalate resins drin results in increasing the molecular weight of the have important advantages over the equivalent glass epoxy resin. An alternative method of forming a bromi reinforced polyethylene terephthalate. Compared to nated epoxy resin useful in the present invention is set 45 polyethylene terephthalate, polybutylene terephthalate forth in U.S. Pat. No. 4,221,893 where the residue from can be processed at much lower temperatures, at a sig the formation of tetrabromobisphenol-A is reacted with nificantly lower cycle time and with a lower mold tem epichlorohydrin. This residue is substantially tetra perature. In addition they have noticeably higher bromobisphenol-A but may include other impurities notched Izod and tensile impact, less shrinkage and such as brominated bisphenol-A at various stages of 50 lower water absorption than does polyethylene tere bromination, brominated phenols resulting from the phthalate. All of these improved processing and physi cleavage of bisphenol and other small amounts of bro cal characteristics of the glass reinforced polybutylene mine containing oxidation products produced by side terephthalate resins are highly desirable having direct reactions during the bromination process. The men commercial ramifications, when compared to equiva tioned patent is herein incorporated by reference. 55 lent glass reinforced polyethylene terephthalate resin. Again, molecular weight can be regulated by control In addition to the components discussed here and ling the relative molar amount of epichlorohydrin con above, the blends of this invention may contain addi tained in the reaction medium. In accordance with this tives commonly employed with polyester resins, such as invention, molar epichlorohydrin levels below those colorants, mold release agents, antioxidants, toughen- described in U.S. Pat. No. 4,221,893 would be appropri 60 ers, ultra violet light and heat stabilizers, plasticizers, ate. Commercial brominated epoxy resin flame retar and the like. dants are available including the Thermoguard series The resin composition of the present invention has from M&T Chemicals, including Thermoguard 240 excellent mechanical properties, thermal properties, which has a molecular weight of 40,000. and moldability, and has excellent flame resistance. In The amount of the flame retardant to be added to the 65 particular, the flame retardant PBT composition of this molding composition is properly determined according invention has greatly improved toughness relative to to the desired extent of flame resistance, and is prefera flame retardant PBT compositions containing other bly added in a range of about 5 to 20% by weight rela halogenated aromatic flame retardants. Importantly, 4,732,921 8 the PBT molding composition of the present invention yield stress. The testing was continued until the sample has an improved melt flow relative to PBT composi failed or 1X 106 cycles were imposed on the sample. tions which contain brominated epoxy resins having up to 10 or 11 repeating units such as disclosed in U.S. Pat. EXAMPLE 1 No. 3,965,212 which are of relatively low molecular 5 Five flame retardant PBT blends were mixed and weight. The melt flow of the molding resin is an impor extruded into samples for testing mechanical and flame tant characteristic allowing for the precise molding of resistant properties according to standardized test pro relatively large components or small components of cedures. The compositions of blends A-E are shown in variegated configuration. An adequate melt flow allows Table 1 below along with the results of the evaluations. the mold cavity to be fully and uniformly filled. The use 10 In particular, the flame retardant brominated epoxy of the lower molecular weight brominated epoxy flame resin within the scope of the present invention was retardants as disclosed in U.S. Pat. No. 3,965,212 have compared with a brominated phenoxy compound flame been found to drastically reduce melt flow of the PBT retardant composition. Compounding of all composition blends was per The following examples illustrate the improved flame 15 formed on a 21 inch Egan extruder (2-stage vented, 30:1 resistance, toughness and melt flow properties which L/D screw). Conditions used were about 500 F. on all are obtained utilizing the high molecular weight haloge- zones and 80 rpm screw speed, with vacuum on vent to nated epoxy resin flame retardant set forth in the de remove volatiles during extrusion. scription of the invention. The following tests were Molding into the test bars was done on a 4 oz. Cincin performed on the sample compositions and molded 20 nati Milicron. Molding conditions used were as follows: samples therefrom. In order for a material to attain the self-extinguishing grades V-0 and V-l regulated in the flammability test according to Underwriters' Laboratories Bulletin 94 (hereinafter abbreviated to "UL-94"), the material is 25 required to have a short combustion time and not to ignite cotton placed below the material due to dripping Melt Temperature Mold Temperature Screw Speed Injection Pressure 470`-490* F. 180' F. 100 rpm 6.000-8,000 psi. caused at the time of combustion. Accordingly, not only the combustion time but also the shape variation TABLE 1 and dripping when the material is exposed to flame 30 Composition wt. % A BCD E should sufficiently be taken into consideration. For example, when a material is exposed to flame, ifa part of PBT0 PBT/Teflon K (10/1) 48.3 5.J 49.3 5.5 51.2 52.2 5.5 5.5 49.2 the material in the neighborhood of the ignition place Antimony oxide 5.5 5.5 5.5 5.5 falls down as a chunk, the cotton placed below the Acrowax C material tends to ignite, and if the material fuses owing 35 Phenoxy stabilizer to the flame before extinguishment drips, the cotton also Brominated epoxy resin1 tends to ignite. In order to prevent such a spread of Tetradecabroraodi- flame, it is necessary to impart to the material such a phenoxy benzene2 0.3 0.3 0.3 0.3 1.0 -- 1.0 -- 9.0 9.0 6.5 6.5 0.3 1.0 property as not to drip even when exposed to flame or Phosphite stabilized such a property as not to ignite the cotton even when 40 Phenolic stabilizer4 Brominated epoxy allowed to drip. resin1 -f antimony The ease of flow of the molding composition can be oxide 0.2 0.2 0.2 0.2 0.2 0.2 13.6 determined by its melt index. Melt index is determined Glass fibers by heating a sample of a polymer in a standard cylinder Properties to a standard temperature of 250 C. and forcing it 45 Color under a standard load of 2.160 kg. through a standard Tensile strength, psi Unnotched Izod, orifice of 0.0825 inch diameter and 0.315 inch long for a ft-lb/in standard period and weighing the polymer passing Flexural Strength, psi through the orifice during this period. The results are Flexural modulus, recorded in grams per 10 minutes. The test is described 50 psi X 106 Notched Izod ft-lb/in in detail in ASTM D-1238-57T. Flame resistance A further test to determine the melt flow of the mold UL-94 (1/32 inch bar) ing composition is the method of spiral flow molding. Average burn time 30.0 30.0 30.0 30.0 gray 18,022 12.54 gray 17,440 12.10 white 17,310 12.82 white 16,650 11.67 28,760 27,730 28,100 26,540 1.35 1.32 1.35 1.31 1.24 1.15 1.33 1.30 V-0 V-0 V-2 V-2 .91 .96 .99 .91 30.0 white 18,940 13.80 29,420 1.33 1.30 v-0 1.03 This test involves molding into an open-ended channel (seconds) marked off in centimeters or inches, and arranged, for 55 UL-94 (1/64 inch bar) Average burn time V-0 .93 V-0 .94 V-2 3.31 V-2 1.43 convenience, in the form of an archimedean spiral. The (seconds) results are shown in the amount of inches the molding 'Thennoguard 240. M & T Chemicals, Molecular Weight = 40,000 resin flows at specified temperature and pressure. 2Saytex - 120, Ethyl Corporation Tensile strength and elongation were measured on JUllranox 626, Borg-Wamer 4Irganox 1010, Ciba-Geigy injection molded bars by ASTM method D638. 60 "0.7 I.V. V-0 1.01 Flex strength and flex modulus were tested by ASTM method D790. As can be seen from Table 1, the PBT compositions The notched izod impact strength was determined by containing the brominated epoxy resin flame retardant ASTM method D256. within the scope of the present invention had improved Heat Distortion Temperature (HDT) was determined 65 physical properties, in particular, tensile and flexural by ASTM method D-648. strength as compared to PBT compositions containing Fatigue testing of the sample was accomplished in the comparative brominated flame retardant. Impor tension at IHZ and 80% of the original ASTM D638 tantly, the compositions containing the flame retardant 4,732,921 10 of the present invention had vastly improved flame resistance. EXAMPLE 2 TABLE 3-continued FATIGUE STRENGTH Load (lbs) % of In this example, various unfilled PBT flame retardant 5 Sample Low High compositions were evaluated for mechanical and flame resistant properties. Samples F, G, H and I represent substantially the same compositions with the only dif ference being the particular flame retardant tested. F G G H H 50 460 50 443 50 443 50 429 50 429 Samples G and H tested brominated epoxy resins. Sam- 10 pie H contained a brominated epoxy resin having a molecular weight within the scope of the present inven H H H I 50 429 50 429 50 429 50 409 tion whereas in Sample G, the brominated epoxy resin I 50 409 had a molecular weight of up to about 4,000. The com positions of each molding sample and the evaluation of IS I I 50 409 50 409 the properties are shown in Table 2. Compounding of Test terminated at 1,000,000 cycles Yield 80 so 80 80 80 80 80 80 80 80 80 80 Cycles to Failure 11,000 454,800 552,100 53,200 1,000,000* 1,000 1,200 1,800 3,600 2,500 3,100 4,500 all composition blends was done as in Example 1. TABLE 2 As can be seen from Table 3, the PBT compositions containing the brominated epoxy resin flame retardants Composition wt. % PBT6 PBT/Teflon K (10/1) Decabromodiphenyl ether Brominated epoxy resin1 Brominated epoxy resin2 Tetradecabromodiphenoxy benzene3 Antimony oxide Acrowax Phosphite stabilizer4 Phenolic stabilizer5 Properties Tensile strength at yield, psi Tensile strength at break, psi % elongation Notched izod Unnotched izod. Gardner Impact 2" discs, in-lbs (pass/fail) Flame resistance UL-94 (1/32) Average Bum time (sec.) FGH 82.7 80.3 80.3 3.0 3.0 3.0 10.0 12.0 12.0 4.0 4.0 4.0 0.3 0.3 0.3 0.2 0.2 0.2 0.2 9,280 8,779 8,410 8,789 7,844 7,830 84 0.48 8.1 1.4 10/12.5 21 2 0.54 22 9 25/30 11 10 0.78 32 3 35/40 V-2 1.86 V-0 1.90 V-0 1.89 I 82.7 3.0 10.0 4.0 0.3 7,922 7,510 68 0.66 0.13 94 5/7.5 V-0 1.08 20 had vastly improved fatigue strength over the compara tive compositions. It should be noted that the diversity of the results obtained in Sample H containing the epoxy resin flame retardant within the scope of the present invention is not uncommon in this type of test 25 since even small nonhomogenities within the sample bar have a large effect on the fatigue properties. Accord ingly, a single high value in the fatigue test is indicative of the improved fatigue properties of a given sample. It is important to note that the base PBT has a fatigue 30 strength of at least about 2,000 cycles, but never exceeds 5,000 cycles. Thus, the results shown in the fatigue test of the PBT compositions containing the epoxy resin flame retardant indicate vastly improved PBT fatigue strength. 35 EXAMPLE 4 The spiral flow molding of various PBT composi tions was examined. Samples J and K were identical to samples A and B, respectively, except that the epoxy 40 resin flame retardant utilized was Thermoguard 230 having a molecular weight of 4,000. Sample L was equivalent to Sample J with the only difference being in the brand of glass fibers utilized in the composition. 'Thermoguard 230, MAT Chemicals, molecular weight -- 4,000 2Thermoguard 240. MAT Chemicals, molecular weight = 40,000 'Saytex 120, Ethyl Corporation 4Ultranox 626, Borg Warner 'Irganox 1010, Ciba-Geigy *1.0 l.V. Sample M had the equivalent composition as Sample K. 45 Sample N was a 30% glass filled PBT containing a decabromodiphenyl ether flame retardant. Sample O was a 30% glass filled PBT containing a brominated polystyrene flame retardant. Sample P was a commer Again, the PBT composition containing the bromi- 5Q nated epoxy resin flame retardant within the scope of cial PBT composition from G.E. comprising a 30% glass filled PBT. The results are shown in Table 4. the present invention had improved tensile strength and TABLE 4 improved impact strength relative to the comparative compositions. The flame resistance of the unfilled com Sample SPIRAL FLOW MOLDING1 Inches2 at 6,000 psi Inches2 at 12,000 psi positions containing the invention was excellent. flame retardant of the present 55 A C EXAMPLE 3 J K The unfilled PBT compositions of Example 2 were L M tested for fatigue strength. The results strength testing are shown in Table 3. of the fatigue 60 N O P TABLE 3____________________ '475* F. FATIGUE STRENGTH ~ ^Average of 10 cycles 25 0.2 23 0.5 10 -- 6 15 1 15 -- 5 14 0.3 31 1 33 1 23 1 32 [ 43 2 10 -- 6 25 1 84 -- 7 24 0.2 40 1 48 1 34 0.7 Sample F F F Load (lbs) Low High 50 460 50 460 50 460 % of Yield 80 80 80 Cycles to Failure 13,400 4,100 6,100 65 As can be seen in comparing samples A and J, the PBT composition containing the higher molecular weight epoxy resin flame retardant had substantially improved melt flow. Moreover, melt flow of samples J 4,732,921 11 12 and L actually began to decrease as the melt composi tion was allowed to stand. EXAMPLE 5 Composition wt. % TABLE 6-continued AA BB CC DD EE FF Melt Index 5 epoxy* Brominated Unfilled PBT composition samples G and H were compared for melt index. Results are shown in Table 5. epoxv3 PBT" Irganox 1010 Arcawax-C Sample TABLE 5io Dwell Time M.W. of Epoxy F.R. Melt Index Properties Color Spiral Flow It. gray It. gray G 5 min. 4,000 10.0 finches) G 15 min. 4,000 8 4,000 psi 12.8 21.2 G 30 min. 4,000 0.0 12,000 psi 34.2 37.9 H 5 min. 40,000 15.0 , c Tensile 17,301 18,085 H 15 min. H 30 min. 40,000 40,000 18 strength 20.0 Flex strength 25,748 27,500 Notched izod 1.18 1.28 As can be seen in Table 5, the melt index of the PBT Unnotched izod 8.8 9.5 sample composition containing the low molecular weight brominated epoxy resin flame decreases as the 20 Flex modulus % Elong. Flame 1.42 1.42 melted composition sits prior to injection into the test Resistance cylinder. It is believed that the lower molecular weight UL-94 (1/32) V-0 V-0 epoxy resin flame retardant crosslinks with the PBT. UL-94 (1/64) V-2 V-0 All samples tested in following Examples 6 and 7 were blended on a 2 inch Johnson Extruder having 25 "0.7 I.V. 41.0 I.V. substantially the same configuration as the Egan used in 'Molecular Weight = 4,000 ^Molecular Weight =* 40,000 the previous examples. Mixing conditions as well as the ^Molecular Weight = 10,000 9.0 white 17.9 40.4 18,100 27,366 1.233 11.3 1.423 V-0 V-2 79.0 0.2 0.3 17.8 27.0 8,192 14,353 0.54 5.4 2.3 V-2 V-2 79.0 0.2 0.3 18.6 32.9 8,804 13,330 0.83 19.1 7.8 V-0 V-0 12.0 79.0 0.2 0.3 19.3 32.2 8,898 13,488 0.670 16.5 6.3 V-0 V-0 molding conditions on a 6 oz. HPM molding machine were substantially identical to mixing and molding con ditions used in Examples 1 and 2. 30 From Table 6, it can be seen there is significantly improved flow of those glass filled PBT samples con EXAMPLE 6 taining epoxy resin flame retardants with molecular weights of 10,000 and 40,000 over the samples contain Various glass filled and unfilled PBT compositions ing the low molecular weight epoxy resin flame retar were compounded and tested for toughness and flow properties. The samples compared PBT compositions 35 dant, e.g. 4,000. The spiral flow molding showed small differences in unfilled PBT samples DD, EE, and FF. containing brominated epoxy resin flame retardants in Thus, the greatest advantage obtained with respect to which the epoxy resins had varying molecular weights. melt flow upon using the higher molecular weight bro The results are shown in Table 6. minated epoxy resin as flame retardant is seen clearly in TABLE 6_________________________th__e_g_l_a_s_s_r_e_in__forced40sam` ples. This has the greater signif icance inasmuch as the glass filled samples are more Composition wt. % AA BB CC DD EE FF difficult to form into the desired molded article. The impact strength of PBT samples containing brominated PBT" 49.5 49.5 49.5 epoxy resins within the scope of the invention is higher Glass fiber 30.0 30.0 30.0 PBT/Teflon 5.5 5.5 5.5 3.3 3.3 3.3 45 than the comparative samples. (10/1) Brominated 9.0 12.0 EXAMPLE 7 Epoxy1 Antimony Oxide 5.5 5.5 5.5 5.0 5.0 5.0 Unfilled PBT samples were evaluated for mechanical properties and fire resistance. The results are shown in Ultranox 626 0.2 0.2 0.2 0.2 0.2 Lubricant 0.3 0.3 0.3 0.2 50 Table 7. The samples were pigmented in order to deter mine whether brominated epoxy resin flame retardants Brominated 9.0 12.0 deteriorate pigmented PBT samples. TABLE 7 Composition Wt. % PBT PBT/Teflon (10/1) Thermoguard 230 Thermoguard 240 Antimony Oxide Acrawax C Ultranox 626 Irganox 1010 Lubricant Blue Pigment Blue Pigment Gray Pigment Red Pigment Properties HDT at 264 (PSI) Tensile break GG HH II JJ 79.3 79.3 79.3 79.3 3.0 3.0 3.0 3.0 12.0 12.0 12.0 12.0 5.0 5.0 5.0 5.0 0.3 0.3 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.3 0.3 62 8,854 65 9,008 8,981 9,189 KK 72.6 3.0 12.0 5.0 0.3 0.2 0.2 6.7 LL 72.6 3.0 12.0 5.0 0.3 0.2 0.2 6.7 MM 74.3 3.0 12.0 5.0 0.3 0.2 0.2 5.0 8,621 9,365 9,215 NN 72.6 3.0 12.0 5.0 0.3 0.2 0.2 6.7 9,270 Composition Wt. % % Elongation Flea strength Flex modulus Notched izod Unnotched izod Gardner Impact Ln-ibs 2" discs pass fail Flame Resistance UL-94 (1/32) UL-94 (1/64) 4,732,921 13 TABLE 7-continued GG HH 2.8 14,241 4.15 0.60 12.1 10.8 13,749 . 4.21 0.77 20.7 II 5.7 13,313 4.06 0.69 19.1 JJ 3.66 13,594 4.04 0.68 13.6 KK LL 2.546 14,269 4.28 0.66 11.0 3.92 13,965 4.28 0.63 13.6 MM 3.99 13,914 4.16 0.65 14.8 5.0 13 7.5 25.0 15.0 10.0 10 13.0 5.0 7.5 7.5 10.0 15.0 18.0 V-0 V-2 V-0 V-0 V-0 V-2 V-0 V-0 V-0 V-0 V-0 V-0 V-0 V-0 NN 3.28 14,000 4.28 0.63 9.2 5.0 7.5 V-0 V-0 14 15 3. The molding composition of claim 2 wherein said flame retardant synergist is antimony trioxide. 4. The molding composition of claim 1 further includ EXAMPLE 8 ing glass fibers. The melt index of GG and HH were compared to determine if the molecular weight of the brominated 20 5. The molding composition of claim 1 comprising 40 to by weight polybutylene terephthalate, 0 to 50% by epoxy resin flame retardant effected the melt flow of the weight glass fibers, 5 to 20% by weight said haloge resin. The results are shown in Table 8. nated epoxy resin flame retardant and 1 to 10% by weight of an antimony-containing flame retardant syn TABLE 8 ergist. Sample ID GG GG GG HH HH HH Dwell Time 5 min. 15 min. 30 min. 5 min. 15 min. 30 min. M.W. of BR. Epoxy 4,000 4,000 4,000 40,000 40,000 40,000 Melt Index 16.4 11.1 0.0 11.4 21.4 35.2 25 6. The molding composition of claim 1 comprising 40 to 90% by weight polybutylene terephthalate, 0 to 50% by weight polyethylene terephthalate, 5 to 40% by weight glass fibers, and 5 to 20% by weight of said halogenated epoxy resin. 30 7. The molding composition of claim 6 further includ ing a 1 to 10% by weight of an antimony-containing flame retardant synergist. From Table 8, it can clearly be seen that the melt 8. The molding composition of claim 7 wherein said index of the material containing the lower molecular flame retardant synergist is antimony trioxide. weight brominated epoxy resin had decreased melt flow the longer the sample melt sat prior to injection into the 35 9. The molding composition of claim 1 wherein X is bromine. testing cylinder. These results are consistent with those 10. The molding composition of claim 1 wherein said obtained in Example 5 and indicate that there is cross- halogenated epoxy resin has a molecular weight of linking between the lower molecular weight epoxy about 40,000. resin and PBT. What is claimed is: 40 11. The molding composition of claim 4 wherein said halogenated epoxy resin has a molecular weight of 1. A molding composition comprising a polybutylene about 40,000. terephthalate and a halogenated flame retardant com 12. A molded article formed from the composition of prising a halogenated epoxy resin having the general claim 1. structure of formula I 45 13. The molded article of claim 12 wherein said mold ing composition comprises 40 to 90% by weight poly O /\ CH2------ CH--CH2-- (D butylene terephthalate, 0 to 50% by weight glass fibers, 5 to 20% by weight said halogenated epoxy resin flame retardant and 1 to 10% by weight of an antimony-con (X)i ch3 Wi 50 taining flame retardant synergist. 14. The molded article of claim 12 wherein said mold O--C--/"y--O--CH2--CH--CH2- ing composition comprises 40 to 90% by weight poly ch3 OH butylene terephthalate, 0 to 50% by weight polyethyl ene terephthalate, 5 to 40% by weight glass fibers, 5 to POl CHj TOl 55 20% by weight of said halogenated epoxy resin. 15. The molded article of claim 14 wherein said mold --\_/--CH2_CH---- CH2 ing composition includes 1 to 10% by weight antimonycontaining flame retardant synergist. CH3 O 16. The molded article of claim 12 wherein X is bro- mine. wherein n is an integer describing the degree of poly merization and is sufficient to provide said brominated 17. The molded article of claim 12 wherein said epoxy resin has a molecular weight of about 40,000. epoxy resin with a molecular weight of at least about 18. The molded article of claim 14 wherein said 20,000 to about 40,000; X is a chlorine or bromine atom; epoxy resin has a molecular weight of about 40,000. and i is the same or different for each aromatic substitu- 19. A film formed from the molding composition of ent and is an integer of from 1-4. claim 1. 2. The molding composition of claim 1 further includ ing a flame retardant synergist comprising antimony. 20. The film of claim19 *whe*rei*n X is bromine.