GB1569230A - Flame retardant compositions comprising block copolyesters of polybutylene terephthalate - Google Patents

Description

(54) FLAME RETARDANT COMPOSITIONS COMPRISING BLOCK COPOLYESTERS OF POLYBUTYLENE TEREPHTHALATE (71) We, GENERAL ELECTRIC COMPANY, a corporation organised and existing under 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 flame retardant compositions comprising a thermoplastic block copolyester prepared by the transesterification of (a) straight or branched chain poly(l,4-butylene terephthalates) and (b) a polyester of a linear aliphatic dicarboxylic acid and, optionally, aromatic dibasic acids such as isophthalate or terephthalic acid with one or more straight or branched chain dihydric aliphatic glycols, and a flame retardant agent. The compositions are useful as molding resin components.

Poly(l,4-butylene terephthalate) is a widely used molding resin because of its rapid crystallization and also because of its rigidity, good dimensional stability, low water absorption and good electrical properties. The resin also has high heat resistance, inherent lubricity and excellent chemical resistance. One restriction on the use of this valuable resin, however, is the fact that the impact strengths of moldings tend to be somewhat inadequate for applications where the molded part is likely to be subjected to severe service conditions. This has led to work to upgrade this property of poly(l,4-butylene terephthalate) because, both in straight and branched chain modifications, it is so superior to many other molding materials, especially with respect to its surface gloss when molded.

It has been discovered that if a poly(l,4-butylene terephthalate) resin is chemically modified by being segmented in a copolyester in which a portion, preferably the major portion, of the repeating units are poly(l,4-butylene terephthalate) blocks, and a portion, preferably the minor portion, of the repeating units are blocks of a polyester of a linear aliphatic dicarboxylic acid with one or more straight or branched chain dihydric aliphatic or cycloaliphatic glycols, and, optionally, an aromatic dibasic acid, such as isophthalic or terephthalic acid, then the resulting block copolyesters will have enhanced impact resistance, compared to the resin itself. The improvement in impact resistance is achieved with minimal loss of other physical properties and is accompanied with a measurable increase in toughness. It is believed that the presence of the internal blocks of other polyesters modifies the rate at which poly(l,4-butylene terephthalate) crystallizes from the melt in a very desirable manner.

In particular, if certain aliphatic, or partially aliphatic/aromatic, polyesters, are added to the reactor during the preparation of poly(l,4-butylene terephthalate) after ester interchange between dialkyl terephthalate and 1 ,4-butanediol, there is caused a most desirable modification in the properties of the resulting polyester molding resins.

By way of illustration, poly(neopentyl - adipate), poly(l,4 - hexylene neopentyl - adipate - isophthalate), poly(l,6 - hexylene - (0.7)adipate (0.3)isophthalate); poly(l,4 - hexylene(0.5)adipate) - (0.5)isophthalate) and poly(l,6 - hexylene - (0.7) - azelate - (0.3)isophthalate), each having a hydroxyl number in the range of 32 to 38, corresponding to a number average molecular weight of 3000 to 3500, are used as the source of blocks. These polyesters are added, respectively, to a reactor after the ester interchange between 1 ,4-butanediol and dimethyl terephthalate is complete and any excess of butanediol has been removed by distillation under a mild vacuum.

After completion of the reaction and molding the block copolyesters, the moldings are improved in toughness and reduced in notch sensitivity as compared to bars molded from unmodified poly(lP-butylene terephthalate). There is insubstantial loss in flex modulus and strength. Even at only 10% of the aliphatic/aromatic polyester content, the increase in impact strength is so marked that some of the samples cannot even be broken.

The effect on crystallization behavior is also noteworthy. The copolyester block components significantly reduce the crystallization rate of the molding resin.

This is desirable, since it allows longer time for the polymer melt to flow through thin walled sections of a mold before the cooling product solidifies.

In addition to their use in injection molding applications, the polyester coreactants have also been found to be beneficial in improving the properties of poly(l,4-butylene terephthalate) resins used in other applications, such as profile extrusion, extrusion- and injection blow molding, thermoforming, foam molding; in these cases small amounts of ester-forming branching agents may be added to enhance the melt elasticity properties of the products for easier processing.

The block copolyester products have also been converted to valuable modifications by adding reinforcing fillers, such as glass fibers, and talc.

Surprisingly, the increased toughness of the block copolyesters compensates for the greater brittleness usually induced by the incorporation of such non-soluble additives and fillers.

It has now been discovered that the block copolyesters can be converted to a particularly valuable family of flame retardant compositions by adding a flame retardant agent, such as monomolecular and polymeric halogenated atomatic compounds, with or without flame retardant synergists, such as antimony compounds, or phosphorus compounds.

Sumoto, Imanaka and Shirai, Japanese Patent Publication 49-99150, dated September 19, 1974, disclose flame retardant compositions comprising block copolyesters which, however, are different from those used herein. The methods of preparation in Sumoto et al. will give high randomization of the blocks because all ingredients, dimethyl ester of aromatic dicarboxylic acid, diol and the polymer for producing "soft polymer segment" are mixed together and heated with a transesterifications catalyst. In contrast, the copolyesters employed according to the present invention are not highly randomized because the coreactant is not added until the ester interchange has been completed and the excess butanediol has been removed. This reaction is a transesterification between a poly(l,4- butylene terephthalate), prepolymer or polymer, and the coreactant polyester. The other methods in Sumoto et al give segmented copolyesters joined through linking compounds such as diisocyanates or lactone monomers, i.e., there is no connection by linkages consisting essentially of ester linkages.

According to this invention, there are provided flame retardant compositions comprising a thermoplastic copolyester which consists essentially of blocks derived from: (a) a terminally-reactive straight chain or branched poly( 1 4-butylene terephthalate); and (b) (i) a terminally-reactive aromatic/aliphatic copolyester of a dicarboxylic acid selected from terephthalic acid, isophthalic acid, naphthalene dicarboxylic acids, phenyl indane dicarboxylic acid and compounds of the formula:

in which X is alkylene or alkylidene having from 1 to 4 carbon atoms, carbonyl, sulfonyl, oxygen or a bond between the benzene rings and an aliphatic dicarboxylic acid having from 6 to 12 carbon atoms in the chain, with one or more straight or branched chain dihydric aliphatic or cycloaliphatic glycols having from 4 to 10 carbon atoms in the chain, said copolyester having at least 10 mole% and preferably 35 mole% of aliphatic units being derived from an aliphatic dicarboxylic acid; or (ii) a terminally-reactive aliphatic polyester of a straight chain aliphatic dicarboxylic acid having from 4 to 12 carbon atoms in the chain and one or more straight or branched chain dihydric aliphatic glycol, said blocks being connected by interterminal ester linkages, and (b) a flame retardant amount of a flame retardant agent.

It is essential that the copolyester component be prepared by the reaction of terminally-reactive poly(butylene terephthalate), preferably low molecular weight, and a terminally-reactive copolyester or polyester as defined in paragraph (b), in the presence of a catalyst for transesterification, such as zinc acetate, manganese acetate, or titanium esters. The terminal groups can comprise hydroxyl, carboxyl, or carboalkoxy, including reactive derivatives thereof. The result of reaction between two terminally reactive groups, of course, must be an ester linkage. After initial mixing, polymerization is carried out under standard conditions, e.g. 220 to 2800C, in a high vacuum, e.g., 0.1 to 2 mm Hg, to form the block copolymer of minimum randomization in terms of distribution of chain segments.

The copolyester component (b) (i) is preferably prepared from terephthalic acid or isophthalic acid or a reactive derivative thereof and a glycol, which may be a straight or branched chain aliphatic or cycloaliphatic glycol. Illustratively, the glycol will be 1,4-butanediol; 1,5-pentanediol; 1,6-hexanediol; 1,9-nonanediol; 1, l0-decanediol; neopentyl glycol; 1 ,4-cyclonexanediol; 1 ,4-cyclohexane dimethanol; or a mixture of any of the foregoing. Illustrative of suitable aliphatic dicarboxylic acids are suberic, sebacic, azelaic, and adipic acids.

The copolyester component (b) (i) may be prepared by ester interchange in accordance with standard procedures. The polyesters designated (b) (i) are most preferably derived from an aliphatic glycol and a mixture of aromatic and aliphatic dibasic acids in which the mole ratio concentration of aromatic to aliphatic acids is at most 9:1 and preferably between 1 to 9 and 9 to 1, with an especially preferred range being from 3 to 7 to 7 to 3.

The aliphatic polyester component (b) (ii) will contain substantially stoichiometric amounts of the aliphatic diol and the aliphatic dicarboxylic acid, although hydroxy-containing terminal groups are preferred.

In addition to their ease of formulation by well-known procedures, both the aromatic/aliphatic copolyesters (b) (i) and the aliphatic polyesters (b) (ii) are commercially available. One source for such materials is the Ruco Division/Hooker Chemical Company, Hicksville, New York, U.S.A. which designates its compounds as "Rucoflex".

The block copolyesters used in the compositions of this invention preferably comprise from 95 to 50 parts by weight of the segments of poly(l,4-butylene terephthalate). The poly(1,4-butylene terephthalate) blocks, before incorporation in the block copolyesters, will preferably have an intrinsic viscosity of above 0.1 dl/g and preferably, between 0.1 and 0.5 dVg, as measured in a 60:40 mixture of phenoVtetrachloroethane at 300 C. The balance, 5 to 50 parts by weight of the copolyester will comprise blocks of component (b).

As will be understood by those skilled in this art, the poly(l,4-butylene terephthalate) block (a) can be straight chain or branched, e.g., by use of a branching component, e.g., 0.05 to 3 mole%, based on terephthalate units, of a branching component which contains at least three ester-forming groups. This can be a polyol, e.g., pentaerythritol, or trimethylolpropane, or a polybasic acid compound, e.g., trimethyl trimesate.

A wide variety of flame retardant agents can be used in intimate admixture with the block copolyesters, with or without reinforcing agents, to produce the flame retardant compositions of this invention. Illustrative flame retardant agents are disclosed in U.S. Patents No. 3,833,685; 3,341,154; 3,915,926;3,671,487; 3,681,281; 3,557,053, and 3,830,771 and British Patent No. 1,358,080.

In general, the flame retardant agents useful in this invention comprise a family of chemical compounds well known to those skilled in the art. Generally speaking, the more important of these compounds contain chemical elements employed for their ability to impart flame resistance, e.g., bromine, chlorine, antimony, phosphorus and nitrogen. It is preferred that the flame retardant additive comprises a halogenated organic compound (brominated or chlorinated); a halogen-containing organic compound in admixture with antimony oxide; elemental phosphorus or a phosphorus compound; a halogen-containing compound in admixture with a phosphorus compound or compounds containing phosphorus-nitrogen bonds or a mixture of two or more of the foregoing.

The amount of flame retardant agent used is not critical to the invention, so long as it is generally present in a minor proportion based on said composition- major proportions will detract from physical properties-but at least sufficient to render the block polyester resin (and any additional flammable resin component) non-burning or self-extinguishing. Those skilled in the art are well aware that the amount will vary with the nature of the resin and with the efficiency of the additive.

In general, however, the amount of additive will be from 0.5 to 50 parts by weight per 100 parts of resin. A preferred range will be from about 3 to 40 parts and an especially preferred range will be from 8 to 40 parts of additive per 100 parts of resin. Smaller amounts of compounds highly concentrated in the elements responsible for flame retardance will be sufficient, e.g., elemental red phosphorus will be preferred at 0.5 to 2.0 parts by weight per 100 parts of resin, while phosphorus in the form of triphenyl phosphate will be used at 25 parts of phosphate per 100 parts of resin. Halogenated aromatics will be used at 8 to 40 parts and synergists, e.g., antimony oxide will be used at about 2 to 10 parts by weight per 100 parts of resin.

Among the useful halogen-containing compounds are those of the formula:

wherein R is alkylene or substituted alkylene, alkylidene or cycloaliphatic linkage, e.g., methylene, ethylene, propylene, isopropylene, isopropylidene, butylene, isobutylene, amylene, cyclohexylene, or cyclopentylidene; an ether; carbonyl or amine linkage; a sulfur-containing linkage, e.g., sulfide, sulfoxide or sulfone; or a phosphorus-containing linkage. R can also consist of two or more alkylene or alkylidene linkages connected by such groups as aromatic, amino, ether, carbonyl, sulfide, sulfoxide, sulfone, or a phosphorus-containing linkage. Other groups which are represented by R will occur to those skilled in the art.

Ar and Ar' are mono- or polycarbocyclic aromatic groups, such as phenylene, biphenylene, terephenylene, or naphthylene. Ar and Ar' may be the same or different.

Y is an organic, inorganic, or organometallic radical. The substituents represented by Y include (1) halogen, e.g., chlorine, bromine, iodine, or fluorine or (2) ether groups of the general formula OE, wherein E is a monovalent hydrocarbon radical as defined for X', or (3) monovalent hydrocarbon groups, e.g., alkyl, substituted alkyl or cycloalkyl, or (4) other substituents, e.g., hydroxy, nitro or cyano, said substituents being essentially inert, provided there be at least one and preferably two halogen atoms per aryl, e.g., phenyl nucleus.

X' is a monovalent hydrocarbon group exemplified by the following: alkyl, such as methyl, ethyl, propyl, isopropyl, butyl, and decyl; aryl groups, such as phenyl, naphthyl, biphenyl, xylyl, and tolyl; aralkyl groups, such as benzyl, and phenethyl; cycloaliphatic groups such as cyclopentyl, and cyclohexyl; as well as monovalent hydrocarbon groups containing inert substituents therein. It will be understood that where more than one X' is used, they may be alike or different.

The letter d represents a whole number ranging from 1 to a maximum equivalent to the number of replaceable hydrogens substituted on the aromatic rings comprising Ar or Ar'. The letter e represents a whole number ranging from 0 to a maximum controlled by the number of replaceable hydrogens on R. The letters a, b and c represent 0 or whole numbers. When b is not 0, neither a or c may be 0.

Otherwise either a or c, but not both, may be 0. Where b is 0, the aromatic groups are joined by a carbon-carbon bond.

The Y substituents on the aromatic groups, Ar and Ar' can be varied in the ortho, meta or para positions on the aromatic rings.

Included within the scope of the above formula are biphenyls of which the following are representative: 2,2-bis(3 , 5-dichlorophenyl)propane bis-(2-chlorophenyl)methane bis-(2,6-dibromophenyl)methane 1,1 -bis-4(4-iodophenyl)ethane 1,2-bis(2,4-dichlorophenyl)ethane 1,1 -bis-(2-chloro-4-iodophenyl)ethane 1,1 -bis42-chloro-4-methylphenyl)ethane 1, 1-bis-(3,5-dichlorophenyl)ethane 2 2-bis43-phenyl-4-bromophenyl)ethane 2,6-bis(4,6-dichloronaphthyl)propane 2,2-bis2,6dichlornphenyl)pentane 2,2-bis-(3,5-dichlorophenyl)hexane bis-(4-chlorophenyl)phenylmethane bis-(3 ,5-dichlorophenyl)cyclohexylmethane bis43-nitro-4-bromophenyl)methane bis-(4-hydroxy-2,6-dichloro-3-methoxyphenyl)methane 2,2-bis-(3, 5-dichloro-4-hydroxyphenyl)propane 2,2-bis43-bromo-4-hydroxyphenyl)propane 2,2-bis-(3,5-dibromo4-hydroxyphenyl)propane.

The preparation of these and other applicable biphenyls are known in the art.

In place of the divalent aliphatic group in the above examples may be substituted, for example, sulfide, or sulfoxy.

Included within the above structural formula are substituted benzenes exemplified by 1 ,3-dichlorobenzene, 1 ,4-dibromobenzene, 1,3-dichloro-4hydroxybenzene, hexachlorobenzene, hexabromobenzene, and biphenyls such as 2,2'-dichlorobiphenyl, 2,4'-dibromobiphenyl, and 2,4'-dichlorobiphenyl.

Preferred flame retardant additives consist of aromatic carbonate homopolymers having repeating units of the formula:

wherein R' and R2 are hydrogen, (lower)alkyl or phenyl, X' and X2 are bromine or chlorine and m and r are from 1 to 4. These materials may be prepared by techniques well known to those skilled in the art. Also preferred are aromatic carbonate copolymers in which from 25 to 75 weight percent of the repeating units comprise chloro- or bromo-substituted dihydric phenol, glycol or dicarboxylic acid units. See, e.g., U.S. Patent No. 3,915,926.

In addition, preferred are aromatic halogen compounds such as chlorinated benzene, brominated benzene, chlorinated biphenyl, chlorinated terphenyl, brominated biphenyl, brominated terphenyl, or a compound comprising two phenyl radicals separated by a divalent alkylene or oxygen group and having at least two chlorine or bromine atoms per phenyl nucleus, and mixtures of at least two of the foregoing.

In general, the preferred phosphorus compounds are selected from elemental phosphorus or organic phosphonic acids, phosphonates, phosphinates, phosphonites, phosphinites, phosphine oxides, phosphines, phosphites or phosphates. Illustrative are triphenyl phosphine oxide. This can be used alone or mixed with hexabromobenzene or a chlorinated biphenyl and, optionally, antimony oxide.

Typical of the preferred phosphorus compounds to be employed in this invention would be those having the general formula:

in which X=S or 0, and n=0 or 1, Y', Y" and Y"' are the same or different and represent alkyl, cycloalkyl, aryl, alkyl substituted aryl, halogen substituted aryl, aryl substituted alkyl, alkyloxy, cycloalkyloxy, halogen substituted alkyloxy, aryloxy, halogen substituted aryloxy, or halogen. Two of the Y's may be combined into a cyclic structure, or one or two of the Y's may be difunctional in which case the compounds consists of short or long chain compounds containing a plurality of P atoms per molecule. Typical examples of suitable phosphorus compounds include: triphenyl phosphate, diphenyl phenyl phosphonate, phenyl diphenyl phosphinate, triphenyl phosphine, triphenyl phosphine oxide, tris(p-bromophenyl) phosphate, neopentyl phenyl phosphonate, tris(dibromopropyl) phosphate, dibenzyl phenyl phosphonate, poly(l,4 cyclohexylene dimethylene) phenyl phosphonate, and pentaerythritol bis(p-bromophenyl) phosphonate. A preferred flame retardant is tris(tribromophenyl) phosphate.

Also suitable as flame retardant additives for this invention are compounds containing phosphorus-nitrogen bonds, such as phosphonitrilic chloride, phosphorus ester amides, phosphoric acid amides, phosphonic acid amines, phosphinic acid amides, (tris(aziridinyl)phosphine) oxide. These flame retardant additives are commercially available.

The compositions may be employed as such in the fabrication of molded articles or they may be blended with other polymers, especially preferably poly(l,4butylene terephthalate) straight chain or branched (as described), and with stabilizers, and reinforcing agents.

In one feature of the invention, the flame retardant compositions may be combined with a normally flammable high molecular weight poly(l,4-butylene terephthalate), i.e., having an intrinsic viscosity of at least 0.7 dUg, as measured in a 60:40 mixture of phenoVtetrachloroethane at 300 C. These compositions can vary broadly, but, preferably, will contain from 5 to 95 parts by weight of the block copolyester and from 95 to 5 parts by weight of the high molecular weight poly(l ,4butylene terephthalate), straight chain or branched. Of course, a sufficient amount of flame retardant additive will be present to ensure that the entire combination is flame retardant.

The present invention contemplates reinforced flame retardant compositions, too. Suitable reinforcing agents are well known but, illustratively, they may be metals, such as aluminum, iron or nickel particles, or non-metals, such as carbon filaments, silicates, such as acicular calcium silicate, asbestos, titanium dioxide, potassium titanate and titan ate whiskers, wollastonite, glass flakes and fibers. It is also to be understood that unless the filler adds to the strength and stiffness of the composition, it is only a filler and not a reinforcing filler as contemplated herein.

Although it is only necessary to have at least a reinforcing amount of the reinforcement present, in general the reinforced compositions will comprise from 1 to 80% by weight of the total composition of the reinforcing agent.

In particular, the preferred reinforcing fillers are of glass, and it is usually preferred to employ fibrous glass filaments comprised of lime-aluminum borosilicate glass that is relatively soda free. This is known as "E" glass. However, other glasses are useful where electrical properties are not 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 filament diameters range from 0.00012 to 0.00075 inch, but this is not critical to the present invention. Glass fibers may be surface coated in accordance with standard procedures to improve their reinforcing performances. In general, best properties will be obtained from reinforced compositions that contain from 20 to 30 percent by weight of the glass reinforced composition.

The length of glass filaments and whether or not they are bundled into fibers and the fibers bundled in turn to yarns, ropes or rovings, or woven into mats, are also not critical to the practice of the invention. In preparing the present compositions, it is convenient to use the filamentous glass in the form of chopped strands of from 1/8 inch to 1 inch long, preferably, less than 1/4 inch long. In articles that are molded from the compositions of the invention, even shorter lengths will be encountered because, during compounding, considerable fragmentation will occur. This is desirable, however, because the best properties are exhibited by thermoplastic injection molded articles in which the filament lengths lie between 0.000005 inch and 0.12 (1/8 inch).

Compositions of this invention can be prepared by a number of procedures. In one way, the flame retardants and any other additives, e.g., reinforcement, e.g., fillers or fibers, pigments, and stabilizers, are put into an extrusion compounder with the resinous components to produce molding pellets. The additives are dispersed in a matrix of the resin in the process. In another procedure, the flame retardant additive(s) and resin are dry blended then either fluxed on a mill and comminuted, or they are extruded and chopped. The additives can also be mixed with the resin(s) and directly molded, e.g., by injection or transfer molding techniques.

It is always important to thoroughly free all of the ingredients: resin, flame retardant, reinforcement, and other additives from as much water as possible.

In addition, compounding should be carried out to ensure that the residence time in the machine is short; the temperature is carefully controlled; the friction heat is utilized; and an intimate blend between the resin, the flame retardant and the reinforcement and/or other additives is obtained.

Although it is not essential, best results are obtained if the ingredients are precompounded, pelletized and then molded. Pre-compounding can be carried out in conventional equipment. For example, after carefully pre-drying the copolyester, and polyester resins, the flame retardant and the additives, e.g., reinforcing agent, e.g., under vacuum at 1000C for 12 hours, a single screw extruder is fed with a dry blend of the ingredients, the screw employed having a long transition section to ensure proper melting. On the other hand, a twin screw extrusion machine, e.g., a 28 mm Werner Pleiderer machine can be fed with resin and additives at the feed port and reinforcement downstream. In either case, a generally suitable machine temperature will be about 450 to 4600 F.

The pre-compounded composition can be extruded and cut up into molding compounds such as conventional granules, or pellets, by standard techniques.

The composition can be molded in any equipment conventionally used for thermoplastic compositions.

The following procedures illustrate the preparation of certain copolyesters which are used to prepare compositions within the scope of this invention.

Procedure A Into a 500 ml, 3-neck flask is weighed 110 grams (0.5 moles) of a poly(l,4butylene terephthalate) prepolymer, containing residue of tetraoctyl titanate transesterification catalyst, having an intrinsic viscosity of about 0.1 dl/g, as measured in a 6040 mixture of phenoVtetrachloroethane at 300 C. After evacuating the flask and purging with nitrogen, the flask is submerged in an oil bath heated to 2350C. The agitator is turned on and stirring maintained at low speed while the prepolymer melts. Upon completion of the melting, 54 grams of poly(neopentyladipate) (number average molecular weight 3000) is added to the stirred melt while maintaining a nitrogen bleed. Since the addition of the poly(neopentyl-adipate) causes some solidification of the mass, a few minutes are spent re-melting the mixture. Aspirator vacuum is applied and the temperature is raised to 252 to 2550C.

A vacuum of 12 to 13 mm is attained and a slow, steady distillation commenced.

After about 20 minutes full vacuum is applied via pump and maintained at 0.3 to 0.4 mm of mercury throughout the polycondensation. Approximately one hour later, the vacuum is shut off and the system brought to equilibrium. The material is soft and elastic and adheres to aluminum foil tenaciously. The block copolymer consists of 34% poly(neopentyl-adipate) and 66% polybutylene terephthalate, and has an intrinsic viscosity of 0.66 dVg, as measured in a 60:40 mixture of phenyPtetrachloroethane at 300 C.

Procedure B Into a 500 ml, 3-neck flask is weighed 110 grams (0.5 moles) of the poly(l,4butylene terephthalate) prepolymer employed in Example 1. After successive evacuations and nitrogen purges, the flask is immersed in an oil bath at 2350C.

After melting, 10.3 grams (0.48 moles) of poly(neopentyl-adipate) is added.

Aspirator vacuum of about 10 mm of mercury is commenced and the temperature was raised to 2550C over a six-hour period. Fifteen minutes later, pump vacuum is applied to raise the vacuum to about 0.2 mm of mercury. The reaction is continued for one hour after removal of vacuum, the polymer is removed according to the method of Procedure A.

Procedure C A reactor is charged with 35.3 Ibs of dimethyl tetephthalate, a stoichiometric excess of 1 ,4-butanediol and 8.0 grams of tetrai terephthalate) is transferred to another reactor and polymerization is carried out at about 250"C and at a pressure of about 0.2 mm of mercury. After two hours, the vacuum is released and the polymer is obtained in band form by hand and is chopped after it is cooled to room temperature. The block copolyester has the following properties: IV=0.81 as measured in a 60:40 mixture of phenoVtetrachloroethane at 300C Melting Range 175 to 1970C Composition-9% poly(neopentyl-adipate) Notched Izod ft Ibs/in 1.21 Tensile strength, psi at yield 5632 Elongation, % 350 Flexural strength, psi 7900 Flexural modulus 226,000 Procedure D A low molecular weight poly(l,4-butylene terephthalate) (110 grams) having an intrinsic viscosity of about 0.1 dVg, as measured in a 60:40 mixture of phenoVtetrachloroethane is placed in a 3-neck, 300 ml flask; the flask is purged three times with nitrogen and dipped into a 2500C oil bath. Upon melting, 33.17 grams of poly(l,6-hexylene-(0.5)adipate-(0.5) isophthalate), with an approximate number average molecular weight of 1600, is added and the aspirator is started and is run for 23 minutes before the pump is started. The reaction is run under full pump vacuum for 135 minutes at an average pressure of 0.2 mm and temperature of 2500C. A soft, milky white product (105.3 grams) is obtained having the following analysis: IV= 0.71 dUg, as measured in a 60:40 mixture of phenoVtetrachloroethane at 300C Melting Range 133 to 1640C Flexural strength, psi 1700 Flexural modulus, psi 38,270 Tensile strength, psi at yield 2930 Elongation, % 386 Procedure E The general procedure of Procedure D is followed in preparing a block copolyester of poly(l,4-butylene terephthalate) (110.4 grams) and poly(l,6hexylene-(0.5) adipate-(0.5) isophthalate) (33.3 grams) (number average molecular weight 3000). There is obtained 110.75 grams of a soft, creamy white product that has the following physical properties: Poly(1,6-hexylene adipate isophthalate) content 23 ,; IV=0.91 dUg, as measured in a 60:40 mixture of phenoVtetrachloroethane at 30"C Melting Range 124 to 1620C Flexural strength, psi 1430 Flexural modulus, psi 30,520 Tensile strength, psi at yield 2630 Elongation, % 436 Procedure F Into a 3-neck, 300 ml flask is placed 110 grams of the poly(l,4-butylene terephthalate) employed in Procedure E. This is melted at 2350C (after nitrogen purging) and 33.2 grams of poly(1 ,4butylene-adipate) (number average molecular weight 1600) is added. After complete melting, the aspirator vacuum is applied for about 20 minutes. Then full vacuum via pump is started, the temperature is raised to 2500C and the reaction continued. A vacuum of 0.3 mm is attained for a short period but rises to 5 mm because of a leak. After finding the leak, 0.3 mm is restored and vacuum is maintained for about three hours. An off white material is collected which has the following physical properties: Poly(l,4-butylene adipate) content 23% IV=0.90 dUg, as measured in a 60:40 mixture of phenoVtetrachloroethane at 30"C Melting Range 165 to 188"C Flexural strength, psi ~ 2440 Flexural modulus, psi 56,080 Tensile strength, psi at yield 3530 Elongation, % 348 Procedure G Into a 3-neck flask is weighed 110 grams of poly(l 4-butylene terephthalate) (it=0.1 dUg, as measured in a 60:40 mixture of phenoVtetrachloroethane at 300C).

After purging with nitrogen, and melting the polymer at 2350C, 34 grams of poly(ethylene - co - 1,4 - butylene - adipate) (number average molecular weight 3000) is added; and vacuum is applied as the temperature is raised to 2500C. After two hours, a flesh-colored polymer is recovered that has the following properties: Poly(ethylene-co-butylene adipate) content 23.6% IV=0.92 dUg, as measured in a 60:40 mixture of phenoVtetrachloroethane at 30"C I Melting Range 138 to 1710C Flexural strength, psi 1980 Flexural modulus, psi 43,540 Tensile strength, psi at yield 2900 psi at break 3400 Elongation, % 410 Procedure H Into a 3-neck flask is weighed 110 grams of poly(l,4-butylene terephthalate) (IV of about 0.1 dUg, as measured in a 60:40 mixture of phenoVtetrachloroethane at 300C). After purging with vacuum and N2 and melting at 2350C with stirring, 32.9 grams of a copolyester of adipic acid, ethylene glycol and 1,4-butanediol is added.

Stirring is continued until melting is complete. Then the vacuum aspirator is applied and the temperature is raised to 250"C over a 50-minute period. Twenty minutes later, the vacuum pump is turned on and full vacuum (0.3 mm Hg) is maintained for one hour and 25 minutes. The polymer has an off white color having the following properties: Poly(ethylene-butylene adipate) content 23% IV=0.81 dUg, as measured in a 60:40 mixture of phenoVtetrachloroethane at 30"C Melting Range 145 to 1740C Flexural strength, psi 2085 Flexural modulus, psi 47,475 Tensile strength, psi at yield 3170 Elongation, % 30 Procedure I A block copolyester of poly(l,4-butylene terephthalate) IV=0.1 dVg, as measured in a 60:40 mixture of phenoVtetrachloroethane at 300 C) and poly(neopentyl-adipate) (number average molecular weight 2700) is prepared according to the general procedure of Procedure H. The block copolyester has the following properties: , IV=0.94 dUg, as measured in a 60:40 mixture of phenoVtetrachloroethane at 300C Melting Range 105 to 1520C Flexural strength, psi 1100 Flexural modulus, psi 24,130 Tensile strength, psi at yield 2100 psi at break 2045 Elongation, % 250 Procedure J A 20-gallon reactor is charged with 35.3 Ibs of dimethylterephthalate, 32.6 Ibs of 1 ,4-butanediol (stoichiometric excess) and 8.0 grams of tetraisopropyl titanate.

Because the theoretical charge of methanol is not recovered, an additional 7.7 Ibs of 1 ,4-butanediol is added. The methanol finally distills and it is assumed that a pluggage has held it up. The poly(l,4-butylene tetephthalate) is found to have an IV of 0.2 dUg, as measured in a 60:40 mixture of phenol/tetrachloroethane at 300 C. At this point, 9.5 Ibs of a poly(neopentyl-adipate) (number average molecular weight 3500) is added and the polycondensation is run for two hours and 50 minutes. A ribbon the block copolymer having the following physical properties is collected by hand for future dicing: Poly(neopentyl adipate) content 19% IV=0.68 dUg, as measured in a 60:40 mixture of phenoVtetrachloroethane at 30"C Melting Range 154 to 1760C Specific gravity=1.263 (before drying) Specific gravity=1.271 (after drying) Procedure K A 10-gallon polyesterification reactor is charged with 30 Ibs of dimethyl terephthalate, 24 Ibs of 1,4-butanediol and 11 grams of tetra(2-ethylhexyl)titanate.

The mixture is gradually heated with stirring to 220 to 2250C while methanol distills off (approximately I 1/2 hours). Subsequently, a vacuum is applied to the vessel and the excess butanediol is distilled (approximately 1 hour required). Then 1.54 Ibs of poly(neopentyl-adipate), MW 3200--3500, is added. The temperature is raised to 250 to 2550C and the vacuum increased to 0.2 to 0.4 mm Hg until the product reaches a melt viscosity of 6100 poises*. The vacuum is released with nitrogen and the product cast onto a chilled roll through a slide valve in the bottom of the reactor. The resulting band is granulated in a dicer into approximately 1/8" cubes.

The cubes are extruded, chopped and molded into test bars that have the following physical properties: Gardner Impact in/lbs 300 Notched Izod, ft Ibs/in 1.0 Tensile strength, 103 psi 7.3 Tensile elongation, % 304 Flexural strength, 103 psi 12.1 Flexural modulus, 103 psi 329 Deflection Temp., "F 264 psi 127 Crystallization rates, 200"F time to initial crystallization, Ti 2.0 Time to 50% crystallisation 0.6 DCS Data Tm AHf Tc AHc "C caVg "C caUg 215 7.0 163 10.8 Procedures L-P Using the same procedure as Procedure K, the following block copolyesters are prepared with poly(l,4-butylene terephthalate) blocks and blocks comprising the listed aliphatic polyesters or aliphatic/aromatic copolyesters and using 11 grams of tetra(2-ethylhexyl)-titanate as a transesterification catalyst: Example Components Weight (Ibs) L dimethylterephthalate 27 1,4-butanediol 25 poly( 1 ,6-hexylene-(0.7) azelate (0.3 isophthalate) 3 M dimethyl terephthalate 27 1,4-butanediol 25 polyneopentyl-adipate 3 *MV=melt viscosity in poises at 2500C using melt index procedure with 21,600 g weight and .042x.615" orifice.

Example Components Weight (Ibs) N dimethyl terephthalate 27 1 ,4-butanediol 25 poly(l,4-hexyleneX0.5) adipate (0.5 isophthalate) 3 0 dimethyl terephthalate 27 1,4-butanediol 25 poly(l ,6-hexylene-(0.7) adipate (0.3 isophthalate) 3 P dimethyl terephthalate 27 I ,4-butanediol 25 poly( 1 ,6-hexylene-co-neopentyl adipate-co-isophthalate) 3 The following examples illustrate the present invention.

EXAMPLES 1-2 A polybutylene terephthalate homopolymer (for comparison) and a block copolymer prepared by procedure L with (1 ,6-hexylene-(0.7) azelate-(0.3) isophthalate (PHAI) are used to prepare flame retarded polymer blends. The blends are prepared by extrusion and the physical data are determined on molded test specimens: Example (parts by weight) A* 1 2 PHAI content of the block 0 8.5 12 copolymer Block copolymer content 69 69 69 Copolycarbonate of BPA and tetrabromo BPA (27% bromine)** 26 26 26 Antimony trioxide 5 5 5 Properties Flammability (UL-94) V 0 V-0 V-0 Notched Izod, ft Ibs/in .74 1.4 1 2 Tensile strength, psi 9100 7900 6700 Tensile elongation, % 31 138 206 Flexural strength, psi 15,800 14,000 11,700 Flexural modulus, psi 409,000 366,000 307,000 *Comparative Example.

**Procedure A, U.S. 3,936,400, modified.

EXAMPLES 3-4 Similar blends as in Examples 1--2 are made up, which contain, in addition, glass fiber reinforcement: Example (parts by weight) B* 3 4 PHAI content of the block copolymer 0 8.5 12 Block copolymer content 52 52 52 Copolycarbonate of BPA** and tetrabromo BPA (27% bromine) 13 13 13 Antimony trioxide 5 5 5 Glass fibers 30 30 30 Properties Flammability (UL-94) V-0 V-0 VX Notched Izod, ft Ibs/in 1.4 1.7 1.8 Tensile strength, psi 18.5 16.7 15.4 Flexural strength, psi 28,300 26,200 24,400 Flexural modulus, psi 1,219,000 1,146,000 1,011,000 Deflection Temp., 264 psi 399 347 336 *Comparative Example.

**Procedure A, U.S. 3,936,400.

Compositions according to this invention will be obtained if the teachings of the examples are followed, and the following substitutions are made: for the block copolyesters of poly(l,4-butylene terephthalate) with poly(l,4 hexylene - (0.7) azelate - (0.3) isophthalate, substituted block copolyesters prepared in Procedures A-K and M-P, respectively, or one in which the poly( 1,4- butylene terephthalate) has been made in the presence of a small amount of pentaerythritol or trimethylolpropane as a branching agent; for the copolycarbonate of tetrabromobisphenol-A and bisphenol-A, substitute, respectively, 2,2 - bis - (3,5 - dibromo - 4 - hydroxyphenyl)propane, decabromodiphenyl ether, hexabromobenzene, triphenyl phosphine oxide, or tris(tribromophenyl)phosphate, as flame retardant additives; and for glass as a reinforcing agent, substitute talc, mica or- kaolin as a reinforcing agent.

Having regard to the provisions of Section 9 of the Patents Act 1949, attention is directed to the claims of our British Patent Application No. 51741/77, (Serial No.

1,569,229).

WHAT WE CLAIM IS: 1. A flame retardant composition which comprises: (A) a thermoplastic copolyester which comprises blocks derived from: (a) a terminally-reactive straight chain or branched poly(l,4-butylene terephthalate); and (b) (i) a terminally-reactive aromatic/aliphatic copolyester of a dicarboxylic acid selected from terephthalic acid, isophthalic acid, naphthalene dicarboxylic acids, phenyl indane dicarboxylic acid, compounds having the formula:

in which X is alkylene or alkylidene having from 1 to 4 carbon atoms, carbonyl, sulfonyl, oxygen or a bond between the benzene rings, and an aliphatic dicarboxylic acid having from 6 to 12 carbon atoms in the chain, with one or more straight or branched chain dihydric aliphatic or cycloaliphatic glycols having from 4 to 10 carbon atoms in the chain, said copolyester having at least 10 mole% of units derived from an aliphatic dicarboxylic acid; or (ii) a terminally-reactive aliphatic polyester of a straight chain aliphatic dicarboxylic acid having from 4 to 12 carbon atoms in the chain and one or more straight or branched chain aliphatic glycols; said blocks being connected by interterminal ester linkages, and (B) a flame retardant amount of a flame retardant agent.

2. A composition as claimed in Claim 1 wherein the flame retardant agent (B) comprises a halogenated organic compound, a halogen-containing organic compound in admixture with antimony oxide; elemental phosphorus or a phosphorus compound; a halogen-containing compound in admixture with a phosphorus compound a compound containing phosphorus-nitrogen bonds, or a mixture of two or more of the foregoing.

3. A composition as claimed in Claim 1 or 2 wherein the amount of flame retardant agent is from 0.5 to 50 parts by weight per 100 parts of flammable resinous components, including said block polyester, in said composition.

4. A flame retardant composition as claimed in any preceding claim wherein block (a) is branched.

5. A flame retardant composition as claimed in Claim 4 wherein block (a) includes from 0.05 to 3 mole%, based on the terephthalate units, of a branching component which contains at least three ester-forming groups.

6. A flame retardant composition as claimed in Claim 5 wherein the branching component is a polyol.

7. A flame retardant composition as claimed in Claim 6 wherein the polyol is pentaerythritol or trimethylolpropane.

8. A flame retardant composition as claimed in any preceding claim wherein block (b) is a copolyester of isophthalic acid and a straight chain aliphatic dicarboxylic acid having from 6 to 12 carbon atoms in the chain, with one or more straight or branched chain dihydric aliphatic glycols having from 4 to 10 carbon atoms in the chain.

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

Claims (20)

**WARNING** start of CLMS field may overlap end of DESC **. Compositions according to this invention will be obtained if the teachings of the examples are followed, and the following substitutions are made: for the block copolyesters of poly(l,4-butylene terephthalate) with poly(l,4 hexylene - (0.7) azelate - (0.3) isophthalate, substituted block copolyesters prepared in Procedures A-K and M-P, respectively, or one in which the poly( 1,4- butylene terephthalate) has been made in the presence of a small amount of pentaerythritol or trimethylolpropane as a branching agent; for the copolycarbonate of tetrabromobisphenol-A and bisphenol-A, substitute, respectively, 2,2 - bis - (3,5 - dibromo - 4 - hydroxyphenyl)propane, decabromodiphenyl ether, hexabromobenzene, triphenyl phosphine oxide, or tris(tribromophenyl)phosphate, as flame retardant additives; and for glass as a reinforcing agent, substitute talc, mica or- kaolin as a reinforcing agent. Having regard to the provisions of Section 9 of the Patents Act 1949, attention is directed to the claims of our British Patent Application No. 51741/77, (Serial No. 1,569,229). WHAT WE CLAIM IS:

1. A flame retardant composition which comprises: (A) a thermoplastic copolyester which comprises blocks derived from: (a) a terminally-reactive straight chain or branched poly(l,4-butylene terephthalate); and (b) (i) a terminally-reactive aromatic/aliphatic copolyester of a dicarboxylic acid selected from terephthalic acid, isophthalic acid, naphthalene dicarboxylic acids, phenyl indane dicarboxylic acid, compounds having the formula:

in which X is alkylene or alkylidene having from 1 to 4 carbon atoms, carbonyl, sulfonyl, oxygen or a bond between the benzene rings, and an aliphatic dicarboxylic acid having from 6 to 12 carbon atoms in the chain, with one or more straight or branched chain dihydric aliphatic or cycloaliphatic glycols having from 4 to 10 carbon atoms in the chain, said copolyester having at least 10 mole% of units derived from an aliphatic dicarboxylic acid; or (ii) a terminally-reactive aliphatic polyester of a straight chain aliphatic dicarboxylic acid having from 4 to 12 carbon atoms in the chain and one or more straight or branched chain aliphatic glycols; said blocks being connected by interterminal ester linkages, and (B) a flame retardant amount of a flame retardant agent.

2. A composition as claimed in Claim 1 wherein the flame retardant agent (B) comprises a halogenated organic compound, a halogen-containing organic compound in admixture with antimony oxide; elemental phosphorus or a phosphorus compound; a halogen-containing compound in admixture with a phosphorus compound a compound containing phosphorus-nitrogen bonds, or a mixture of two or more of the foregoing.

3. A composition as claimed in Claim 1 or 2 wherein the amount of flame retardant agent is from 0.5 to 50 parts by weight per 100 parts of flammable resinous components, including said block polyester, in said composition.

4. A flame retardant composition as claimed in any preceding claim wherein block (a) is branched.

5. A flame retardant composition as claimed in Claim 4 wherein block (a) includes from 0.05 to 3 mole%, based on the terephthalate units, of a branching component which contains at least three ester-forming groups.

6. A flame retardant composition as claimed in Claim 5 wherein the branching component is a polyol.

7. A flame retardant composition as claimed in Claim 6 wherein the polyol is pentaerythritol or trimethylolpropane.

8. A flame retardant composition as claimed in any preceding claim wherein block (b) is a copolyester of isophthalic acid and a straight chain aliphatic dicarboxylic acid having from 6 to 12 carbon atoms in the chain, with one or more straight or branched chain dihydric aliphatic glycols having from 4 to 10 carbon atoms in the chain.

9. A flame retardant composition as claimed in Claim 8 wherein component

(b) is poly(l,6 - hexylene - azelate - co - isophthalate).

10. A flame retardant composition as claimed in Claim 9 wherein component (b) is poly(l,6 - hexylene - (0.7) - azelate - co - (0.3) - isophthalate).

I I. A flame retardant composition as claimed in Claim 8 wherein component (b) is poly(l,6 - hexylene - adipate - co - isophthalate).

12. A flame retardant composition as claimed in Claim 11 wherein component (b) is poly(l,6 - hexylene - (0.5) - adipate - co(0.5) - isophthalate), or poly(l,6 hexylene - (0.7) - adipate - co - (0.3) - isophthalate).

13. A flame retardant composition as claimed in Claim 8 wherein component (b) is poly(l,6 - hexylene - co - neopentyl - adipate - co - isophthalate).

14. A flame retardant composition as claimed in any of Claims 1 to 7 wherein block (b) is a polyester of a straight chain aliphatic dicarboxylic acid having from 6 to 12 carbon atoms and a straight or branched chain aliphatic glycol.

15. A flame retardant composition as claimed in Claim 14 wherein component (b) is poly(neopentyl-adipate), poly( 1,4 - butylene - adipate), or poly(ethylene co - 1,4 - butylene - adipate).

16. A flame retardant composition as claimed in any preceding claim which also includes a thermoplastic poly(l,4 - butylene terephthalate) resin.

17. A flame retardant composition as claimed in Claim 16 wherein said resin component comprises from 95 to 50 parts by weight of said composition of a poly(l,4-butylene terephthalate) having an intrinsic viscosity of at least 0.7 dVg, as measured in a 60:40 mixture of phenoVtetrachloroethane at 300 C.

18. A flame retardant composition as claimed in any of the preceding claims which comprises a reinforcing amount of a reinforcing filler.

19. A flame retardant composition as claimed in Claim 18 wherein the reinforcing agent comprises filamentous glass.

20. A flame retardant composition as claimed in Claim 1 and substantially as hereinbefore described with reference to any of Examples 1 to 4.