FIELD OF THE INVENTION

The present invention relates to a flame retardant polymer composition and a process of making thereof. More particularly, the invention relates to a polyethylene terephthalate (PET) masterbatch with improved flame retardant properties and a process of manufacturing thereof.

BACKGROUND OF THE INVENTION

Generally, the flammability of polymers can be decreased either by altering the products of thermal decomposition in such a way that the amount of nonflammable combustion products is increased at the expense of flammable volatiles (solid-phase retardation), or by inhibiting oxidation reactions in the gas phase through trapping of free- radical species (gas-phase retardation), or by a combination of these mechanisms.

The technology related to various aspects of polymer flammability, of flame-retardant compounds for polymers, and of possible improvements in the fire safety of our environment has undergone explosive growth in last few decades.

Retardant is defined as a material that has been chemically treated to self-extinguish. There are many textiles that can be "treated". For example, treated cotton is sometimes used on garments since it will self-extinguish and will typically not melt or drip. Polyester is a textile that is frequently used and potentially causes the greatest harm. Polyester will also melt and drip molten polymers which is also hazardous. It is the melting and dripping that also causes safety concern. Flame retardant material has been used to reduce the flammability in polymeric materials. Flame retardants play a vital role in a system in: generation of non-combustible gases, which dilutes the oxygen supply at the surface of the burning polymer; endothermic reactions of degradation products from the flame retardants with species present in the flame or substrate; endothermic decomposition of the flame retardant; formation of nonvolatile char or glassy film barrier, which minimizes diffusion of oxygen to the polymer substrate and also reduces heat transfer from flame to polymer

Flame-retardant compounds, in order to be useful, must fulfill complex sets of requirements, many of which are specific for each product. A flame retardants added to a polymer should, reduce flammability as compared to unmodified polymer to a level specified for the products in terms of product performance in a specific flammability test; reduce smoke generation under specified condition of testing, reduce smoke generation, under specified conditions of testing: not increase the toxicity of combustion products from the modified polymer as compared to the unmodified polymer; be retained in the product through normal use (including exposure, cleaning, aging, etc.); and have acceptable or minimal effect on other performance properties of the product in use.

Polyesters have considerable potential utility as molded components in the automotive field, in appliance manufacture, and in the electrical industry. Additionally, fibers and yarns of polyesters have been very popular in carpeting and upholstery applications. In view of the nature of the applications in which this polymer is usually employed, must have good flame resistance and flame retardancy. Considerable research efforts have been extended toward the goal of improving the flame retardancy of the polyesters. To be acceptable in commercial formulations, flame retardancy additives must be effective at low concentrations, must be stable at polymer processing temperatures and must not contribute excessively to polymer degradation at processing temperatures. Furthermore, such flame retardant polyesters should be developed in cost effective and environment friendly approach to reduce their flammability and to improve their physical properties.

US 2005/0154099 relates to flame resistant polyester resin compositions comprising 30 to 90 weight percent thermoplastic polyester; 1 to 30 weight percent oligomeric aromatic phosphate ester; 1 to 25 weight percent phenolic polymer; 1 to 35 weight percent of at least one melamine flame retardant selected from melamine pyrophosphate, melamine phosphate, melamine polyphosphate, melamine cyanurate, and mixtures thereof; and optionally inorganic reinforcing agents. Likewise, EP 1578856 discloses flame resistant, laser weldable polyester resin compositions comprising melt-mixed blends of polyester, phosphorus containing flame retardant, phenolic polymer, and acrylic polymer and articles made therefrom. In last few years, a significant progress has been made in the development of halogen- free flame retardant polyester in textile and packaging industry. The polymers or reactive monomers that are inherently flame retarding usually contain phosphorous (P), silicon (Si), Boron (B), Nitrogen (N) and other miscellaneous elements. Such flame retardants can be used on their own or added to current bulk commercial polymers to enhance flame retardancy of the base polymer.

EP 1425340 discloses a polyester composition that includes a poly (butylene terephthalate), a nitrogen-containing flame retardant, and a phosphorus -containing flame retardant, such that the weight ratio of the total of the nitrogen-containing flame retardant and the phosphorus-containing flame retardant to poly (butylene terephthalate) is at least about 0.70, and the weight ratio of the phosphorus-containing flame retardant to the nitrogen- containing flame retardant is at least about 1.0.

Many types of fire-retardants are used in poly(ethylene terephthalate), PET, formulations, but the most common are additive phosphorus species like ammonium polyphosphate which enhances charring, or halogenated products used for their gas-phase action, inhibiting the ignition of the volatile pyrolysis products. Halogenated species are amongst the most effective fire-retardant species known, but they are gradually being abandoned for environmental and safety reasons. Attention is therefore turned to phosphorus compounds, mostly under the form of reactive fire-retardants copolymerised with the polymer.

EP 2588531 discloses a thermoplastic polyester composition comprising, based on the total weight of the composition, a chlorine- and bromine-free combination of: from 40 to 60 wt% of a polyester; from 25 to 35 wt% of a reinforcing filler; from 2 to 8 wt% of a flame retardant synergist selected from the group consisting of melamine polyphosphate, melamine cyanurate, melamine pyrophosphate, melamine phosphate, and combinations thereof; from 5 to 15 wt% of a phosphinate salt flame retardant; from more than 0 to less than 5 wt% of an impact modifier component comprising a poly(ether-ester) elastomer and a (meth)acrylate impact modifier; from more than 0 to 5 wt% poly(tetrafluoroethylene) encapsulated by a styreneacrylonitrile copolymer; from more than 0 to 2 wt% of a stabilizer; wherein the thermoplastic polyester composition contains less than 5 wt% of a polyetherimide. However, a masterbatch of such halogen free flame-retardant polyester has not been developed in the industry so far. The process of the present invention incorporates one or more phosphorous based flame retardant additives or combination of long chain molecules containing phosphorous atom in polyethylene terephthalate during the melt phase polymerization reaction. The flame retardant additive reacts with unreacted monomers or other reactive end groups of monomers, oligomers, or pre-polymers during esterification in the reactor. Thus the FR additive is uniformly distributed in the polymer chain rendering permanent flame retardancy and enables better processing of polymers by extrusion blow moulding process. The polyester modified from such phosphorous based additives shows the improved properties, e.g. high crystallinity, low moisture contents, low oligomer contents, high glass transition temperature (T _g ) and high melting point (T _m ). Such masterbatch gives flexibility of inventory management whereby-it can be incorporated in any PET chips (super-bright, semi- dull, full dull, etc.) and RPET; it can also be used in film & sheets. The contents of phosphorous used in the PET can be varied as per the requirement.

The oxygen index, or limiting oxygen index (LOI), is the minimum percentage of oxygen that is required to maintain flaming combustion of a specimen under specified laboratory conditions. Highly flammable materials are likely to have a low LOI. The FR polyester disclosed in the present disclosure has high LOI and because of that the polyesters have very low tendency to burn. The LOI of the polyester is geneally at a level > 22. The content of the phosphorous in the finished polyester can be adjusted to achieve the required LOI of the polyester. The masterbatch can further be blended with the normal polyester to prepare homogeneous flame-retardant polyester as per the requirement of the industry and application in prevailing countries.

The flame-retardant polyester obtained in accordance to the process of the present disclosure also meets the health, safety and recycling standards in textile and packaging industry. Moreover, the polyester composition contains reactive flame retardants which makes the polyester thermally stable due to permanent bonding between the flame-retardant comonomer and the polyester. Such modified flame-retardant PET grades have permanent FR properties which are not lost on washing. OBJECTIVE OF THE INVENTION

Some of the objects of the present invention which at least one embodiment is adapted to provide, are described herein below: It is an object of the present invention to provide a modified polyethylene terephthalate (PET) polyester masterbatch in crystallized form which can be blended with PET/RPET to get polyester with improved flame retardant properties.

It is another object of the present invention to provide a process of modified polyethylene terephthalate (PET) polyester masterbatch composition.

It is yet another object of the present invention to provide a halogen-free and phosphorous based flame retardant polyethylene terphthalate polyester masterbatch. It is yet another object of the present invention to provide a flame retardant PET masterbatch composition for textile and packaging applications.

It is yet another object of the present invention to provide a flame retardant polyethylene polyester masterbatch with improved flame retardancy in crystallized form so that it can be dried and processed like normal PET.

It is still another object of the present invention to provide a polyethylene terephthalate (PET) polyester masterbatch for extrusion or molding applications to obtain flame retardant finished products.

Other objects and advantages of the present invention will be more apparent from the following description when read in conjunction with the accompanying figures, if any, which are not intended to limit the scope of the present invention. SUMMARY OF THE INVENTION

In one aspect methods of making flame retardant polyester masterbatch are provided. The methods provide a phosphorus based flame retardant polyester that is capable of imparting permanent flame retardance in normal polyethylene terephthalate and the masterbatch can also be melt blended in required quantity with other polyesters and nylon to impart the flame retardance to them. The methods includes polymerizing monomers, oligomers or pre-polymers obtained from esterification of one or more dicarboxylic acids and at least one diol with one or more additives and at least one phosphorus based flame retardant additive to obtain the amorphous polyester, and crystalizing the amorphous polyethylene terephthalate to form the FR masterbatch of the polyester.

In some embodiments, the methods for the preparation of a flame retardant polyester include, preparing slurry of pure terephthalic acid (PTA) and ethylene glycol (MEG) along with sodium acetate anhydrous and pentaerythritol in presence of catalyst; preparing oligomers, pre-polymers along with low molecular weight oligomers by esterification of slurry at inert atmosphere; polymerizing the oligomers, pre-polymers in presence of phosphorus based flame retardant additive and one or more catalysts or combinations thereof to extrude strands of molten polymer; preparing amorphous chips from strands obtained; crystallizing the amorphous chips obtained so obtained at temperature of about 120 °C to 150 °C for 2 to 6 hours to obtain crystalline polymer; solid state polymerization at temperature of about 190 °C to 210 °C of said crystallized polymer until the required intrinsic viscosity (IV) is achieved. In yet another aspect, provided is a flame retardant polyester composition for use in fiber and yarn manufacturing, said polyester product characterized by low limiting oxygen index (LOI) having value greater than 22.

In some embodiments, a melt blend of the FR polyester with polyethylene terephthalate exhibits a greater flame retardance of the target polymer than a non-blended polyethylene terephthalate and the required LOI of the target polymer can be achieved by adding requisite phosphorus content in the target polymer. In other embodiments, a blend of the FR PET with other polyesters and nylon exhibits improved flame retardant properties compared to non-blended polyesters and nylon. DETAILED DESCRIPTION OF THE INVENTION

Various embodiments are described hereinafter. It should be noted that the specific embodiments are not intended as an exhaustive description or as a limitation to the broader aspects discussed herein. One aspect described in conjunction with a particular embodiment is not necessarily limited to that embodiment and can be practiced with any other embodiment(s). As used herein, "about" will be understood by persons of ordinary skill in the art and will vary to some extent depending upon the context in which it is used. If there are uses of the term which are not clear to persons of ordinary skill in the art, given the context in which it is used, "about" will mean up to plus or minus 10% of the particular term. The use of the terms "a" and "an" and "the" and similar referents in the context of describing the elements (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., "such as") provided herein, is intended merely to better illuminate the embodiments and does not pose a limitation on the scope of the claims unless otherwise stated. No language in the specification should be construed as indicating any non-claimed element as essential.

In general, "substituted" refers to an alkyl, alkenyl, alkynyl, aryl, or ether group, as defined below (e.g., an alkyl group) in which one or more bonds to a hydrogen atom contained therein are replaced by a bond to non- hydrogen or non-carbon atoms. Substituted groups also include groups in which one or more bonds to a carbon(s) or hydrogen(s) atom are replaced by one or more bonds, including double or triple bonds, to a heteroatom. Thus, a substituted group will be substituted with one or more substituents, unless otherwise specified. In some embodiments, a substituted group is substituted with 1, 2, 3, 4, 5, or 6 substituents. Examples of substituent groups include: halogens (i.e., F, CI, Br, and I); hydroxyls; alkoxy, alkenoxy, alkynoxy, aryloxy, aralkyloxy, heterocyclyloxy, and heterocyclylalkoxy groups; carbonyls (oxo); carboxyls; esters; urethanes; oximes; hydroxylamines; alkoxy amines; aralkoxyamines; thiols; sulfides; sulfoxides; sulfones; sulfonyls; sulfonamides; amines; N-oxides; hydrazines; hydrazides; hydrazones; azides; amides; ureas; amidines; guanidines; enamines; imides; isocyanates; isothiocyanates; cyanates; thiocyanates; imines; nitro groups; nitriles (i.e., CN); and the like.

As used herein, Cm-Cn, such as C1-C12, C1-C8, or C1-C6 when used before a group refers to that group containing m to n carbon atoms.

As used herein, "alkyl" groups include straight chain and branched alkyl groups having from 1 to about 20 carbon atoms (i.e., C1-C20 alkyl), and typically from 1 to 12 carbon atoms (i.e., C1-C12 alkyl) or, in some embodiments, from 1 to 8 carbon atoms (i.e., C1-C8 alkyl). As employed herein, "alkyl groups" include cycloalkyl groups as defined below. Alkyl groups may be substituted or unsubstituted. This term includes, by way of example, linear and branched hydrocarbyl groups such as methyl (CH3-), ethyl (CH3CH2-), n-propyl (CH3CH2CH2-), isopropyl ((CH3)2CH-), n-butyl (CH3CH2CH2CH2-), isobutyl ((CH3)2CHCH2-), sec-butyl ((CH3)(CH3CH2)CH-), t-butyl ((CH3)3C-), n-pentyl (CH3CH2CH2CH2CH2-), and neopentyl ((CH3)3CCH2-). Representative substituted alkyl groups may be substituted one or more times with, for example, amino, thio, hydroxy, cyano, alkoxy, and/or halo groups such as F, CI, Br, and I groups. As used herein the term haloalkyl is an alkyl group having one or more halo groups. In some embodiments, haloalkyl refers to a per-haloalkyl group.

Cycloalkyl groups are cyclic alkyl groups such as, but not limited to, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl groups. In some embodiments, the cycloalkyl group has 3 to 8 ring members, whereas in other embodiments the number of ring carbon atoms range from 3 to 5, 6, or 7. Cycloalkyl groups may be substituted or unsubstituted. Cycloalkyl groups further include polycyclic cycloalkyl groups such as, but not limited to, norbornyl, adamantyl, bornyl, camphenyl, isocamphenyl, and carenyl groups, and fused rings such as, but not limited to, decalinyl, and the like. Cycloalkyl groups also include rings that are substituted with straight or branched chain alkyl groups as defined above. Representative substituted cycloalkyl groups may be mono-substituted or substituted more than once, such as, but not limited to: 2,2-; 2,3-; 2,4-; 2,5-; or 2,6- disubstituted cyclohexyl groups or mono-, di-, or tri-substituted norbornyl or cycloheptyl groups, which may be substituted with, for example, alkyl, alkoxy, amino, thio, hydroxy, cyano, and/or halo groups.

As used herein, "aryl", or "aromatic," groups are cyclic aromatic hydrocarbons that do not contain heteroatoms. Aryl groups include monocyclic, bicyclic and polycyclic ring systems. Thus, aryl groups include, but are not limited to, phenyl, azulenyl, heptalenyl, biphenylenyl, indacenyl, fluorenyl, phenanthrenyl, triphenylenyl, pyrenyl, naphthacenyl, chrysenyl, biphenyl, anthracenyl, indenyl, indanyl, pentalenyl, and naphthyl groups. In some embodiments, aryl groups contain 6-14 carbons, and in others from 6 to 12 or even 6-10 carbon atoms in the ring portions of the groups. The phrase "aryl groups" includes groups containing fused rings, such as fused aromatic-aliphatic ring systems (e.g., indanyl, tetrahydronaphthyl, and the like). Aryl groups may be substituted or unsubstituted.

The term "includes" is used to mean "includes but not limited to", "include" and "include but not limited to", "Including" and "including but not limited to" are used interchangeably. The polyester obtained in accordance with the method of the present invention is herein also referred to as "Flame Retardant Polyester" or "FR Polyester" or "FR PET" or "Modified Polyester" and are used interchangeably.

The terms "Flame Retardant Polyester" and "Flame Retardant Polyester Masterbatch" or "FR Polyester" and "FR Polyester Masterbatch" or "FR PET" and "FR PET Masterbatch" or "Modified Polyester" and "Modified Polyester Masterbatch", "Polyester" and "Flame Retardant Polyester" are used interchangeably.

The term "flame retardant additive" refers to additives used to impart flame retardant properties in polymers

The term "target polymer" is a polymer in which FR polyester masterbatch is blended to achieve the required LOI of the polymer. Ratios, concentrations, amounts, and other numerical data may be presented herein in a range format. It is to be understood that such range format is used merely for convenience and brevity and should be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. For example, 5 to 40 mole % should be interpreted to include not only the explicitly recited limits of 5 to 40 mole %, but also to include sub-ranges, such as 10 mole % to 30 mole %, 7 mole % to 25 mole %, and so forth, as well as individual amounts, including fractional amounts, within the specified ranges, such as 15.5 mole %, 29.1 mole %, and 12.9 mole %, for example.

The term "intrinsic viscosity" (I.V.) as used herein is a measure of the molecular mass of the polymer and is measured by dilute solution viscosimetry (DSV) in a 3:2 mixture of phenol, 1,2 dichlorobenzene solution, at 25 °C.

The term "Limiting Oxygen Index (LOI)" is the minimum concentration of oxygen, expressed as a percentage that will support combustion of a polymer.

In one aspect, methods are provided preparing flame retardant polyesters and a masterbatch thereof for industrial applications such as textile, apparel, carpet, plastics etc. which can impart improved permanent flame retardancy. In one aspect methods of making flame retardant polyester masterbatch are provided. The methods provide a halogen free flame retardant polyester that is capable of imparting permanent flame retardance in normal polyethylene terephthalate and the masterbatch thereof can also be melt blended in required quantity with other polyesters and nylon to impart the flame retardance to them. The methods includes polymerizing monomers, oligomers or pre-polymers obtained from esterification of one or more dicarboxylic acids and at least one diol with at least one phosphorus based flame retardant additive to obtain the amorphous polyester, and crystalizing the amorphous polyethylene terephthalate to form the FR masterbatch of the polyester. In some embodiments, the methods for the preparation of a flame retardant polyester include, preparing slurry of pure terephthalic acid (PTA) and ethylene glycol (MEG) along with sodium acetate anhydrous and pentaerythritol in presence of catalyst; preparing oligomers, pre-polymers along with low molecular weight by esterification of slurry at inert atmosphere; polymerizing the oligomers, pre-polymers in presence of at one or more flame retardant additive, wherein at least one flame retardant additive contains phosphorus atom and one or more catalysts or combinations thereof to extrude strands of molten polymer; preparing amorphous chips from strands obtained; crystallizing the amorphous chips obtained so obtained at temperature of about 120 °C to 150 °C for 2 to 6 hours to obtain crystalline polymer; solid state polymerization at temperature of about 190 °C to 210 °C of said crystallized polymer until the required intrinsic viscosity (IV) is achieved.

In one aspect, a method of preparing a crystallized flame retardant polyester is provided wherein the crystallized FR polyester exhibits an intrinsic viscosity greater than about 0.75 dL/g, greater than about 0.5 dL/g, greater than about 0.3 dL/g, greater than about 0.25 dL/g, greater than about 0.2 dL/g, greater than about 0.15 dL/g, or greater than about 0.10 dL/g. In some embodiments, the crystallized FR polyester exhibits an intrinsic viscosity from about 0.1 dL/g to about 10 dL/g, about 0.2 dL/g to about 1 dL/g, about 0.3 dL/g to about 0.75 dL/g, about 0.4 dL/g to about 0.5 dL/g, and ranges between and including any two of these values. In some embodiments, the crystallized FR polyester exhibits an intrinsic viscosity greater than 0.25 dL/g.

In one aspect, a method of preparing a crystallized flame retardant polyester is provided wherein the crystallized FR polyester can be blended with target polymer to achieve higher Limiting Oxygen Index (LOI) of the target polymer. In some embodiments the LOI of the target polymers can be achieved greater than 22, greater than 25, greater than 28, greater than 31, greater than 35, greater than 38. In some embodiments, the target polymer exhibits LOI from about 21 to 24, about 23 to 27, about 26 to 30, about 29 to 34, about 33 to 40, and ranges between and including any two of these values. In some embodiments, the target polymer exhibits an LOI greater than 25.

Examples of the target polymer is, but not limited to, polyesters and polyamides. In some embodiments the, the target polyesters is, but not limited to, PET, PBT, PTT, PEN, PCDT, or combination thereof. In some embodiments the target polyamide is, but not limited to nylon 6, nylon 66, or combination thereof.

The method further includes subjecting the crystallized FR polyester to solid state polymerization (SSP). The SSP leads to an increase in the molecular weight and/or intrinsic viscosity of the polyester product. In another aspect, the amorphous polyester can be pre-crystallized using known methods, e.g. using fluid bed crystallizer. The amorphous polyester can be further crystallized to form a crystallized and further upgraded by solid state polymerization. The crystallized FR polyester can then be used as a masterbatch sample to produce polymer compositions such as polyesters and polyamides.

In one aspect, the method includes preparation of the oligomer, pre-polymer in the esterification reaction and then polymerizing the oligomers with at least one phosphorus based flame retardant additive. In one embodiment, the pre-polymer or oligomer is produced by the esterification of a dicarboxylic acid, or an ester thereof, with an alkylene diol. Suitable dicarboxylic acids or esters thereof are disclosed herein and include, but are not limited to an aliphatic dicarboxylic acid, aliphatic dicarboxylate, a cycloaliphatic dicarboxylic acid, cycloaliphatic dicarboxylate, an aromatic dicarboxylic acid, aromatic dicarboxylate, or a combination thereof.

The FR polyester can be prepared from two or more dicarboxylic acid residues. The dicarboxylic acid residue is selected from the group as consisting of aliphatic dicarboxylic acid, an aliphatic dicarboxylate, a cycloaliphatic dicarboxylic acid, a cycloaliphatic dicarboxylate, an aromatic dicarboxylic acid, or an aromatic dicarboxylate and combinations thereof. Examples of aromatic dicarboxylic diacids include terephthalic acid, isophthalic acid, 2, 6-napthalene dicarboxylic acid, and ester derivatives thereof. Examples of aliphatic diacids include adipic acid, glutaric acid, succinic acid, azelaic acid, and ester derivatives thereof.

In one embodiments, the dicarboxylic acid residue is selected from the group consisting of terephthalic acid, dimethyl terephthalate, dimethyl isophthalate, dimethyl-2,6- naphthalate, 2,7-naphthalenedicarboxylic acid, dimethyl-2,7-naphthalate, 3,4'-diphenyl ether dicarboxylic acid, dimethyl- 3, 4 'diphenyl ether dicarboxylate, 4,4'-diphenyl ether dicarboxylic acid, dimethyl-4,4'-diphenyl ether dicarboxylate, 3,4'-diphenyl sulfide dicarboxylic acid, dimethyl-3,4'-diphenyl sulfide dicarboxylate, 4,4'-diphenyl sulfide dicarboxylic acid, dimethyl-4,4'-diphenyl sulfide dicarboxylate, 3,4'-diphenyl sulfone dicarboxylic acid, dimethyl-3,4'-diphenyl sulfone dicarboxylate, 4,4'-diphenyl sulfone dicarboxylic acid, dimethyl-4,4'-diphenyl sulfone dicarboxylate, 3,4'-benzophenonedicarboxylic acid, dimethyl- 3,4'-benzophenonedicarboxylate, 4,4'-benzophenonedicarboxylic acid, dimethyl-4,4'- benzophenonedicarboxylate, 1,4-naphthalene dicarboxylic acid, dimethyl- 1,4-naphthalate, 4,4'-methylene bis(benzoic acid), dimethyl-4,4'-methylenebis(benzoate), dimethyl oxalate, malonic acid, dimethyl malonate, dimethyl succinate, methylsuccinic acid, 2-methylglutaric acid, 3-methylglutaric acid, dimethyl adipate, 3-methyladipic acid, dimethyl azelate, sebacic acid, 1,11-undecanedicarboxylic acid, 1,10-decanedicarboxylic acid, undecanedioic acid, 1,12-dodecanedicarboxylic acid, hexadecanedioic acid, docosanedioic acid, tetracosanedioic acid, dimer acid, dimethyl- 1,4-cyclohexanedicarboxylate, dimethyl- 1,3- cyclohexanedicarboxylate, 1,1-cyclohexanediacetic acid, metal salts of 5-sulfo- dimethylisophalate, maleic anhydride, and combinations thereof.

Some non-limiting examples of dicarboxylic acid residue are isophthalic acid, 2,6- napthalene dicarboxylic acid, oxalic acid, maleic acid, succinic acid, glutaric acid, dimethyl glutarate, adipic acid, 2,2,5,5-tetramethylhexanedioic acid, pimelic acid, suberic acid, azelaic acid, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,1- cyclohexanediacetic acid, fumaric acid, maleic acid, hexahydrophthalic acid, and phthalic acid.

The flame retardant polyester can be prepared using suitable methods known in the art. For example, the dicarboxylic acid or ester thereof can be reacted with an alkylene diol at a suitable temperature and pressure for a sufficient amount of time to obtain the oligomers or pre-polymer having end groups. Suitable esterification conditions can be employed for the preparation of the FR polyester. For example, the reaction can be conducted at a temperature of about 300 °C or below, about 200 °C or below, about 100 °C or below, at about 80 °C or below, at about 50 °C or below, at about 45 °C or below, at about 40 °C or below, at about 35 °C or below, at about 30 °C or below, at about 25 °C or below or at about 20 °C or below, and ranges between and including any two of these values. The reaction can be conducted for a pressure of about 1 bar to about 30 bars, about 2 bars to about 20 bars, about 3 bars to about 10 bars, about 4 bars to about 5 bars, and ranges between and including any two of these values.

In some embodiments, the reaction pressure is up to about 20 bars, up to about 10 bars, up to about 5 bars, up to about 3 bars, up to about 2 bars, up to about 1 bar, and ranges between and including any two of these values. The reaction can be conducted for a period of about 1 min to about 60 min, about 1 h to about 5 h, about 5 h to about 8 h, about 8 h to about 15 h, about 15 h to about 25 h, about 25 h to about 40 h, and ranges between and including any two of these values. In some embodiments, the reaction of dicarboxylic acid or ester thereof with an alkylene diol is conducted at a temperature of about 240 °C to about 260 °C and at a pressure of up to about 4 bars for about 2 h to about 3 h.

The phosphorus based flame retardant additive is selected from the group consisting of 2-Carboxyethyl(phenyl) phosphinic acid or 3-hydroxyphenylphosphinyl-propanoic acid), 9,10-dihydro-10-[2,3-di(hydroxyl carbonyl) propyl] 10-phosphaphenanthrene-lO-oxid, 2,2- Bis(chloromethyl)trimethylene bis[bis (2-chloroethyl) Phosphate, Chlorendic acid, tetrakis (2-chloroethyl) dichloroisopentyldiphosphate, Tris(2-chloroethyl) phosphate, tris(l-chloro-2- propyl)phosphate, tris(2,3-dichloro- l-propyl)phosphate, hexachlorocyclopentadienyl- dibromocyclooctane,tetrakis(2-chloroethyl)dichloroisopentyld iphosphate, tris(2-chloroethyl) phosphate, Poly(2,6-dibromo-phenylene oxide), tetra-decabromo-diphenoxy-benzene, 1,2- Bis(2,4,6-tribromo-phenoxy) ethane, 3,5,3,5-Tetrabromo-bisphenol A (ΤΒΒΑ),ΤΒΒΑ, unspecified, TBBA-epichlorhydrin oligomer, TBBA-TBBA-diglycidyl-ether oligomer, TBBA carbonate oligomer, TBBA carbonate oligomer, phenoxy end capped, TBBA carbonate oligomer, 2,4,6-tribromo-phenol terminated, TBBA-bisphenol A-phosgene polymer, brominated epoxy resin end-capped with tribromophenol, TBBA-(2,3-dibromo- propyl-ether), TBBA bis-(2-hydroxy-ethyl-ether), TBBA-bis-(allyl-ether), TBBA-dimethyl- ether, Tetrabromo-bisphenol S, TBBS-bis-(2,3-dibromo-propyl-ether), 2,4-dibromo-phenol, 2,4,6-tribromo-phenol, pentabromo-phenol, 2,4,6-Tribromo-phenyl-allyl-ether, tribromo- phenyl-allyl-ether, bis(methyl)tetrabromo-phtalate, Bis(2-ethylhexyl)tetrabromo-phtalate, 2- Hydroxy-propyl-2-(2-hydroxy-ethoxy)-ethyl-TBP, TBPA, glycol-and propylene-oxide esters, Ν,Ν-Ethylene -bis-(tetrabromo-phthalimide), ethylene-bis(5,6-dibromo-norbornane-2,3- dicarboximide), 2,3-Dibromo-2-butene-l,4-diol, Dibromo-neopentyl-glycol, Dibromo- propanol, tribromo-neopentyl-alcohol, poly tribromo-styrene and combination thereof.

Examples of the phosphorus based flame retardant additive used in the method include, but are not limited to, 2-carboxyethyl (phenyl) phosphinic acid [also known as 3- (hydroxyphenylphosphinyl) propanoic acid], and/or 9,10-dihydro-10-[2,3- di(hydroxylcarbonyl)propyl] 10-phosphaphenanthrene-10-oxide, or combination thereof. In some embodiments, the alkylene diols include C4-C5 branched aliphatic diols. Examples of branched diols include, but are not limited to, 2-methyl-l, 3 -propanediol, 2, 2- dimethyl-1, 3 -propanediol, 2-butyl-2-ethyl-l, 3 -propanediol, trimethylpentanediol, and the like. The diol may be a cyclo aliphatic diol having between 6-20 carbon atoms, with the proviso that if a cyclohexane diol is used, it is included with at least one additional cyclic or branched diol. For example, isosorbide or a mixture of (cis, trans) 1, 3- cyclohexanedimethanol and (cis, trans) 1, 4 cyclohexanedimethanol may be used. Examples of aromatic diol may include xylene glycol, and hydroquinone. In one embodiment the diol may be 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, 1,12-dodecanediol, 1,14-tetradecanediol, 1,16-hexadecanediol, dimer diol, 1,4- cyclohexanedimethanol, di(ethylene glycol), tri(ethylene glycol), poly(ethylene ether) glycols, poly(butylene ether) glycols, 2- methyl- 1,3-propanediol, 2,2-dimethyl- 1,3- propanediol, 2-butyl-2-ethyl- 1,3-propanediol, trimethylpentanediol, isosorbide or a mixture of (cis, trans) 1,3-cyclohexanedimethanol and (cis, trans) 1,4 cyclohexanedimethanol, xylene glycol, and hydroquinone.

The alkylene diol can be a straight chain or a branched diol having 2 to 12 carbon atoms per molecule. Examples of suitable diols include, but are not limited to, ethylene glycol, propanediol, butanediol, cyclohexanedimethanol, hexane diol, octanediol, decanediol, dodecanediol, and combinations thereof. In some embodiments, the preferred alkylene diol is ethylene glycol.

The FR polyester masterbatch may be produced by suitable polymerization techniques known in the art. In some embodiments, the flame retardant polyester is produced by any of the conventional melt or solid state polycondensation techniques. The melt polycondensation method can be carried out in either batch, semi-continuous or continuous mode. In another embodiment, the melt polycondensation method can be carried out in either batch reaction, or continous polymerization line. The method is best carried out in a reactor equipped with a distillation column and a stirrer or other means for agitation. The distillation column separates the volatile product of reaction (water and/or alkanol) from volatile reactants (e.g., ethylene glycol). Use of a distillation column allows for operation at a lower molar ratio of ethylene glycol to terephthalic acid, which serves to suppress the formation of DEG. Melt polycondensation can be carried out in conventional method like PTA, DMT and PCR PET glycolysis. When terephthalic acid is used in the polymerization method, the volatile reaction product will be water; when an ester such as dimethyl terephthalate is used, the volatile reaction product will be the corresponding alkanol (such as methanol), together with smaller amounts of water. Continuous polymerization method may be used to prepare polyesters. In one aspect, the method further includes crystallizing the amorphous polyester to form a crystallized FR polyester. Suitable crystallization techniques known in the art may be used to produce the crystallized FR polyester. The crystallization reaction can be conducted by heating the amorphous FR polyester at a suitable temperature for a suitable period of time. For example, the crystallization can be conducted at a temperature of about 10 °C to about 300 °C, about 30 °C to about 200 °C, about 50 °C to about 250 °C about 80 °C to about 200 °C and about 100 °C to about 150 °C, and ranges between and including any two of these values. In some embodiments, the amorphous FR polyester is crystallized at a temperature in the range of about 110 °C to about 150 °C to produce a crystallized FR polyester. The reaction of producing of flame retardant polyester may further include addition of one or more additives. In some embodiments, the additive is selected from the group consisting of a nucleating agent, branching agent, chain extender, antioxidant, plasticizers, stabilizing agent, a coloring agent and other additives. Additives may also be added before or during or after the polymerization reaction to impart requisite property to the resulting co- polyester. Such additives include but are not limited to dyes; pigments; flame retardant additives such as decabromodiphenyl ether and triarylphosphates, such as triphenylphosphate; reinforcing agents such as glass fibers; thermal stabilizers; ultraviolet light stabilizers methoding aids, impact modifiers, flow enhancing additives, ionomers, liquid crystal polymers, fluoropolymers, olefins including cyclic olefins, polyamides and ethylene vinyl acetate copolymers.

The additives described herein, for example, the plasticizer, anti-oxidizing agent, stabilizing agent, and end-capped oligomer, if present, can be incorporated for example, at a concentration in the range of about 0.001 wt%, about 0.01 wt%, about 0.02 wt%, about 0.05 wt%, about 0.1 wt%, about 0.5 wt%, about 1.0 wt%, about 2 wt%, about 5 wt%, about 10.0 wt%, about 15.0 wt%, about 20.0 wt%, about 30.0 wt%, and ranges between any two of these values or less than any one of these values. Other additives, such as for example, nucleating agent and the branching agent, if present, can be incorporated for example, at a concentration in the range of about 0.1 ppm to about 10,000 ppm, about 2 ppm to about 5000 ppm, about 5 ppm to about 7500 ppm, about 10 ppm to about 2000 ppm, about 20 ppm to about 1000 ppm, or about 50 ppm to about 500 ppm, and ranges between any two of these values or less than any one of these values. In one aspect, the flame retardant polyester obtained by the methods described herein is provided, wherein the polyester includes up to about 30 to about 90 wt% of the dicarboxylic acid, up to about 10 wt% to 70% of the alkylene diol, up to about 0.01 wt% to about 10 wt% of one or more flame retardant additives, and one or more reagents selected from the group consisting of a liquid plasticizer, a nucleating agent, a branching agent, an anti-oxidizing agent, and a stabilizing agent.

Examples of additives useful for the purpose of the present disclosure is at least one selected from the group consisting of a liquid plasticizer, a nucleating agent, a branching agent, an anti-oxidizing agent, a stabilizing agent and an end-capped oligomer. In some embodiments, the additives useful for the purpose of the present disclosure is at least one selected from the group consisting of branching agent in an amount of 10 ppm to 2000 ppm, nucleating agent in an amount of 10 ppm to 2000 ppm and liquid plasticizer in an amount of 0.5 to 2 wt%, at least one stabilizing agent and at least one anti-oxidizing agent in an amount ranging from 0.1 to 5 wt%. Other agents useful for the purpose of the present disclosure include at least one end-capped oligomer in an amount from 1 to 20 wt%.

The branching agent useful for the purpose of the present disclosure includes but is not limited to 1,2,4-benzenetricarboxylic acid (trimellitic acid); trimethyl- 1,2,4- benzenetricarboxylate; 1,2,4-benzenetricarboxylic anhydride (trimellitic anhydride); 1,3,5- benzenetricarboxylic acid; 1,2,4, 5-benzenetetracarboxylic acid (pyromellitic acid); 1,2,4,5- benzenetetracarboxylic dianhydride (pyromellitic anhydride); 3, 3 ',4,4'- benzophenonetetracarboxylic dianhydride; 1,4,5,8-naphthalenetetracarboxylic dianhydride; citric acid; tetrahydrofuran-2,3, 4,5-tetracarboxylic acid; 1,3,5-cyclohexanetricarboxylic acid;pentaerythritol, 2-(hydroxymethyl)-l,3-propanediol; 2,2-bis(hydroxymethyl) propionic acid; sorbitol; glycerol and combinations thereof. Particularly, branching agents such aspentaerythritol, trimellitic acid, trimellitic anhydride, pyromellitic acid, pyromellitic anhydride and sorbitol are used. The nucleating agent improves the crystallinity and increases heat deformation temperature of the polyester product. The nucleating agent can be organic or inorganic. Examples of inorganic nucleating agent include, but are not limited to, calcium silicate, nano silica powder, talc, microtalc, aclyn, kaolinite, montmorillonite, synthetic mica, calcium sulfide, boron nitride, barium sulfate, aluminum oxide, neodymium oxide and a metal salt of phenyl phosphonate. The inorganic nucleating agent can be modified by an organic material to improve its dispersibility in the polyester product of the present disclosure.

Examples of organic nucleating agent include, but are not limited to, carboxylic acid metal salts such as sodium benzoate, potassium benzoate, lithium benzoate, calcium benzoate, magnesium benzoate, barium benzoate, lithium terephthalate, sodium terephthalate, potassium terephthalate, calcium oxalate, sodium laurate, potassium laurate, sodium myristate, potassium myristate, calcium myristate, sodium octacosanoate, calcium octacosanoate, sodium stearate, potassium stearate, lithium stearate, calcium stearate, magnesium stearate, barium stearate, sodium montanate, calcium montanate, sodium toluoylate, sodium salicylate, potassium salicylate, zinc salicylate, aluminum dibenzoate, potassium dibenzoate, lithium dibenzoate, sodium β-naphthalate and sodium cyclohexane carboxylate; organic sulfonates such as sodium p-toluene sulfonate and sodium sulfoisophthalate; carboxylic acid amides such as stearic acid amide, ethylene bis-lauric acid amide, palmitic acid amide, hydroxystearic acid amide, erucic acid amide and tris(t- butylamide) trimesate; phosphoric compound metal salts such as benzylidene sorbitol and derivatives thereof, sodium-2,2'-methylenebis(4,6-di-t-butylphenyl)phosphate, and 2,2- methylbis(4,6-di-t-butylphenyl)sodium, and the like, or combinations thereof. Examples of liquid plasticizer useful for the purpose of the present disclosure include, but are not limited to, N-isopropyl benzene sulfonamide, N-tert-butyl benzene sulfonamide, N-pentyl benzene sulfonamide, N-hexyl benzene sulfonamide, N-n-octyl benzene sulfonamide, N-methyl-N-butyl benzene sulfonamide, N-methyl-N-ethyl benzene sulfonamide, N-methyl-N-propyl benzene sulfonamide, N-ethyl-N-propyl benzene sulfonamide, N-ethyl p-ethylbenzenesulfonamide, N-ethyl p-(t-butyl)benzene sulfonamide, N-butyl p-butyl benzene sulfonamide, N-butyl toluene sulfonamide, N-t-octyl toluene sulfonamide, N-ethyl-N-2-ethylhexyl toluene sulfonamide, N-ethyl-N-t-octyl toluene sulfonamide and tri-octyltrimellitate, and the like, or combinations thereof. Examples of anti-oxidizing agent include, but are not limited to, irganox 1010, irganox 1076, irgafos 126 and irgafos 168. Similarly, copper nitrate (up to 150 ppm) along with Potassium Iodide &/or Potssium bromides (up to 1000 ppm ) or any other Light & UV Stabilizers which can be added to enhance weatherability of the polymers.

Examples of stabilizing agent include, but are not limited to, ortho-phosphoric acid, trimethylphosphate (TMP), triphynylphosphate (TPP) and triethylphosphono acetate (TEPA). In some embodiments, ortho-phosphoric acid is used as stabilizing agent. Examples of end-capped oligomer include, but are not limited to, oligomers of polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polytreimethylenenaphthalate and polybutylenenaphthalate, and the like, or combinations thereof. The methods and products described herein may include other suitable additives known in the art, which include but are not limited to, pigments such as decabromodiphenyl ether and triarylphosphates, such as triphenylphosphate, reinforcing agents such as glass fibers, thermal stabilizers, ultraviolet light stabilizers methoding aids, impact modifiers, flow enhancing additives, ionomers, liquid crystal polymers, fluoropolymers, olefins including cyclic olefins, polyamides and ethylene vinyl acetate copolymers.

In an embodiment of the invention, the catalysts may be selected from the group consisting of antimony trioxide, antimony triacetate, Ti compounds, germanium dioxide, tin compounds or combinations thereof.

In one embodiment, the method further includes subjecting the crystallized FR polyester to solid state polymerization conditions. This will increase the molecular weight and the intrinsic viscosity of the polyester. The solid state polymerization is conducted under a vacuum or in the presence of a stream of an inert gas. Suitable inert gases include, but are not limited to, nitrogen, carbon dioxide, helium, argon, neon, krypton, xenon, and the like. Suitable solid state polymerization temperatures can range from a temperature at or above the polymerization reaction temperature up to a temperature below their melting point. For example, the solid state polymerization reaction can be conducted at a temperature of about 400 °C or below, about 300 °C or below, about 200 °C or below, about 100 °C or below, at about 80 °C or below, at about 50 °C or below, at about 45 °C or below, at about 40 °C or below, at about 35 °C or below, at about 30 °C or below, at about 25 °C or below or at about 20 °C or below, and ranges between and including any two of these values. In some embodiments, the solid state polymerization is conducted at a temperature of about 50 °C to about 400 °C, about 80 °C to about 350 °C, about 100 °C to about 300 °C, about 150 °C to about 250 °C, about 180 °C to about 200 °C, and ranges between and including any two of these values. The FR polyester can be solid state polymerized for a time sufficient to increase its molecular weight or IV to the desired value. For example, the solid state polymerization reaction can be conducted for a period of about 1 min to about 60 min, about 1 h to about 5 h, about 5 h to about 8 h, about 8 h to about 15 h, about 15 h to about 25 h, about 25 h to about 40 h, and ranges between and including any two of these values.

In some embodiments, dicarboxylic acid used in the methods of the present invention are used in an amount ranging from about 0.01% to about 99% by weight of the total weight of the flame retardant polyester. This includes embodiments in which the amount ranges from about 10% to about 99%, from about 20% to about 95%, from about 30% to about 92%, from about 40% to about 90 %, from about 50 % to about 80% and from about 60% to about 75% of the total weight of the FR polyester composition, and ranges between any two of these values or less than any one of these values. In some embodiments, the alkylene diol may constitute from about 0.01 wt%, about 10 wt%, about 20 wt%, about 30 wt%, about 40 wt%, about 50 wt%, about 60 wt%, about 70 wt%, and ranges between any two of these values or less than any one of these values. In some embodiments, the flame retardant additives used is ranging from about 0.01 wt%, about 4 wt%, about 8 wt%, about 10 wt%, about 12 wt%, about 15 wt%, about 20 wt%, about 30 wt%, about 40 wt%, about 50 wt%, about 60 wt%, about 70 wt%, about 80 wt%, and ranges between any two of these values or less than any one of these values. However, other amounts are possible. The particular amount depends upon the desired properties of the polyester composition. In some embodiments, the organic phosphonic acid includes about 0.01 wt% to about 15 wt% of the flame retardant polyester masterbatch.

In one embodiment, the crystallized co-polyester is subjected to solid state polymerization by placing the pelletized or pulverized polymer into a tumble drier of an inert gas, such as nitrogen, or under a vacuum of 1 torr, at an elevated temperature, above 150 °C but below the melting temperature, for a period of about 4 to about 16 h. In some embodiments, the solid state polymerization is carried out at a temperature of about 180 °C to about 200 °C which results in an increase in inherent viscosity to about 1 dl/g.

In another aspect, provided is a flame retardant polyethylene terephthalate (FR PET) polyester masterbatch obtained by the method described herein. The FR PET includes 30 to 90 wt% of one or more aromatic dicarboxylic acid or ester thereof; and 10 to 70 wt% of one or more alkylene diol; 0 to 10 wt% of at least one phosphorus based flame retardant additive; one or more reagents selected from the group consisting of liquid plasticizer in an amount of 0.5 to 2 wt%; at least one nucleating agent in an amount of 10 ppm to 2000 ppm; at least one branching agent in an amount of 10 ppm to 2000 ppm; at least one anti-oxidizing agent in an amount ranging from 0.1 to 5 wt%; at least one stabilizing agent; at least one additive and optionally, at least one end-capped oligomer in an amount of 1 to 20 wt%, wherein the polyester has characterized by LOI having value greater than 25 (LOI>25). In one aspect, the method further includes melt blending the FR polyester masterbatch with normal polyamide or normal polyester, extruding a filament, and spinning the filament into a fiber or yarn. In some embodiments the FR polyester masterbatch can be melt blended with normal nylon ("Target Polymer") or normal polyethylene terephthalate ("Target Polymer") in suitable amounts to adjust the Phosphorus content of the polyester or polyamide composition with desired limiting oxygen index (LOI). Suitable melt blending conditions are known in the art.

The FR polyester has an inherent viscosity of at least 0.250 dL/g and lower oligomer content less than 1.2 wt% after up gradation of intrinsic viscosity in solid state polymerization. In one embodiment, the inherent viscosity of the FR polyester is in the range of 0.30 to 0.50 dL/g. The FR PET masterbatch can be blended with polyester or polyamides to extruded and/or molded to fibers and other articles. The fibers obtained from blending polyester (PET) have superior flame retardant property. The fibers obtained from blending of FR polyester and nylons have improved flame retardancy of the fiber.

In one aspect, provided are flame retardant polyesters which can be used in fiber or yarn applications. The FR polyester includes at least one polyester; and at least one flame retardant additive and optionally one or more additives. The FR polyester is obtained from the polymerization reaction of at least one dicarboxylic acid or ester thereof, alkylene diol, and phosphinic acid. The phosphorus based FR additive is preferably added to the esterification reactor, after formation of oligomers or pre-polymers, for uniform distribution of the FR additive in the polyester chain. The phosphinic acid is useful for obtaining the flame retardant polymer include, but are not limited to, 2-Carboxyethyl(phenyl) phosphinic acid or 3-hydroxyphenylphosphinyl- propanoic acid), 9,10-dihydro-10-[2,3-di(hydroxyl carbonyl) propyl] 10- phosphaphenanthrene-10-oxid, 2,2-Bis(chloromethyl)trimethylene bis[bis (2-chloroethyl) Phosphate, Chlorendic acid, tetrakis (2-chloroethyl) dichloroisopentyldiphosphate, Tris (2- chloroethyl) phosphate, tris (l-chloro-2-propyl) phosphate, tris (2, 3-dichloro-l -propyl) phosphate, hexachlorocyclopentadienyl-dibromocyclooctane, tetrakis(2- chloroethyl)dichloroisopentyldiphosphate, tris(2-chloroethyl) phosphate, Poly(2,6-dibromo- phenylene oxide), tetra-decabromo-diphenoxy-benzene, l,2-Bis(2,4,6-tribromo-phenoxy) ethane, 3,5,3,5-Tetrabromo-bisphenol A (ΤΒΒΑ),ΤΒΒΑ, unspecified, TBBA-epichlorhydrin oligomer, TBBA-TBBA-diglycidyl-ether oligomer, TBBA carbonate oligomer, TBBA carbonate oligomer, phenoxy end capped, TBBA carbonate oligomer, 2,4,6-tribromo-phenol terminated, TBBA-bisphenol A-phosgene polymer, brominated epoxy resin end-capped with tribromophenol, TBBA-(2,3-dibromo-propyl-ether), TBBA bis-(2-hydroxy-ethyl-ether), TBBA-bis-(allyl-ether), TBBA-dimethyl-ether, Tetrabromo-bisphenol S, TBBS-bis-(2,3- dibromo-propyl-ether), 2,4-dibromo-phenol, 2,4,6-tribromo-phenol, pentabromo-phenol, 2,4,6-Tribromo-phenyl-allyl-ether, tribromo-phenyl-allyl-ether, bis(methyl)tetrabromo- phtalate, Bis(2-ethylhexyl)tetrabromo-phtalate, 2-Hydroxy-propyl-2-(2-hydroxy-ethoxy)- ethyl-TBP, TBPA, glycol-and propylene-oxide esters, Ν,Ν-Ethylene -bis-(tetrabromo- phthalimide), ethylene-bis(5,6-dibromo-norbornane-2,3-dicarboximide), 2,3-Dibromo-2- butene-l,4-diol, Dibromo-neopentyl-glycol, Dibromo-propanol, tribromo-neopentyl-alcohol, poly tribromo-styrene, and combination thereof.

The alkylenediol used for obtaining the phosphorus containing polymer include, but are not limited to, ethylene glycol, propanediol, butanediol, cyclohexanedimethanol, hexane diol and combinations thereof. Suitable additives useful for obtaining the FR polyester include, but are not limited to, nucleating agent, branching agent, chain extender, antioxidant, plasticizers, stabilizing agent etc. In one aspect, provided is a crystallizable FR polyester masterbatch containing greater than about 10 wt% phosphorus so that it can be upgraded in solid state polymerization to required I.V. level and lower oligomer contents. In some embodiments, the polyester exhibits superior flame retardant properties to polyester (PET). The FR polyester can be made by the melt condensation method described above to have an inherent viscosity of at least about 0.25 dl/g, and often as high as about 0.35 dl/g or greater, without further treatment. The product made by melt polymerization, after extruding, cooling, and pelletizing, is in amorphous state (non- crystalline). The product can be made semi-crystalline by heating it to a temperature in the range of about 110 °C to about 150 °C for an extended period of time (about 4h to about 8 h). This induces crystallization so that the product can then be heated up to below melting temperature of polyester to raise the molecular weight and obtain the desired intrinsic viscosity. Suitable coloring agents for use in fibers are known in the art and may include, but are not limited to dyes, inorganic or organic pigments, or mixtures of these. In some embodiments, the coloring agents include dyes selected from the group consisting of azo, azomethine, methine, anthraquinone, phthalocyanine, dioxazine, flavanthrone, indanthrone, anthrapyrimidine and metal complex dyes. In one embodiment the coloring agent is selected from the group consisting of metal oxides, mixed metal oxides, metal sulfides, zinc ferrites, sodium alumino sulfo-silicate pigments, carbon blacks, phthalocyanines, quinacridones, nickel azo compounds, mono azo coloring agents, anthraquinones and perylenes. In some embodiments, the coloring agent is selected from the group consisting of Solvent Blue 132, Solvent Yellow 21, Solvent Red 225, Solvent Red 214 and Solvent Violet 46, Carbon Black, Titanium Dioxide, Zinc Sulfide, Zinc Oxide, Ultramarine Blue, Cobalt Aluminate, Iron Oxides, Pigment Blue 15, Pigment Blue 60, Pigment Brown 24, Pigment Red 122, Pigment Red 147, Pigment Red 149, Pigment Red 177, Pigment Red 178, Pigment Red 179, Pigment Red 202, Pigment Red 272, Pigment Violet 19, Pigment Violet 29, Pigment Green 7, Pigment Yellow 119, Pigment Yellow 147 and Pigment Yellow 150, or a combination thereof.

Depending on the desired color, any number of different coloring agents in varying proportions may be used. In some embodiments, the coloring agent may constitute from about 0.001 wt%, about 0.01 wt%, about 0.1 wt%, about 0.5 wt%, about 1 wt%, about 2 wt%, about 5 wt%, about 8 wt%, about 10 wt%, about 15 wt%, about 20 wt%, about 25 wt%, about 30 wt%, about 40 wt%, about 50 wt% of the total composition, and ranges between any two of these values or less than any one of these values. However, other amounts are possible. The particular amount depends upon the desired color of the fiber composition. In some embodiments, the composition includes about 0.01 wt% to about 10 wt% of the coloring agent.

The flame retardant polyester and polymer compositions described herein can be utilized for various applications. Typical end-use applications include, but are not limited to, extruded and non-extruded fibers and yarns for various applications such as for example, apparel fabric, drapery, upholstery, wall coverings, heavy industrial fabrics, ropes, cords, shoe laces, nettings, carpets and rugs.

In one aspect, there is provided a flame retardant polyester masterbatch composition comprising: at least one dicarboxylic acid; at least one diol; up to 10 wt.% of one or more flame-retardant additives or combination thereof containing phosphorous atom, wherein the flame-retardant additives is, but not limited to, 2-Carboxyethyl(phenyl) phosphinic acid or 3- (Hydroxyphenylphosphinyl) propanoic acid), 9,10-dihydro-10-[2,3-di(hydroxyl carbonyl) propyl] 10-phosphaphenanthrene-lO-oxide, or combination thereof. In some embodiments, 60-98 mol% of dicarboxylic acid is used in the methods of the present invention. The dicarboxylic acid of this embodiment is purified terephthalic acid (PTA) or dimethyl terephthalate (DMT). In another embodiment, 2-40 mol% of dicarboxylic acid other than the terephthalic acid can also be used. The dicarboxylic acid of this embodiment is selected from the group consisting of isophthalic acid (IP A), 2, 6-napthalene dicarboxylic acid (NDA), adipic acid, sebacic acid, succinic acid, azelic acid etc.

In some embodiments, the diol used in the methods of the present invention is mono ethylene glycol (MEG). Preferably, about 80 mol% to about 99 mol% of mono ethylene glycol (MEG) is used as a glycol.

In one another aspect of the present invention, Post-Consumer Recycled (PCR) PET flakes can be used as starting raw material instead using PT A/DMT. In some embodiments, the recycling route can be mechanical extrusion or glycolysis with required filtration scheme. In some embodiments, the flame retardant used in the methods of the present invention are 2-carboxyethyl (phenyl) phosphinic acid [also known as 3- (hydroxyphenylphosphinyl) propanoic acid] and/or 9, 10-dihydro-10-[2, 3-di (hydroxyl carbonyl) propyl] 10-phosphaphenanthrene-lO-oxide or combination thereof.

In some embodiments of the present invention, 2-carboxyethyl(phenyl) phosphinic acid is used in an amount ranging from about 0.01 wt% to about 10 wt%, about 5 wt% to 30 wt%, about 8 wt% to 50 wt%, about 12 wt% to 70 wt%, and ranges between and includes any two of these values. The weight percent (wt%) is calculated based on the total weight of the flame retardant polyester.

In some embodiments of the present invention, the flame retardant polyester comprises up to about 60 wt. % of the flame retardant additive. In a preferred embodiment the flame retardant is selected from the group consisting of 2-carboxyethyl (phenyl) phosphinic in an amount from about 2 wt% to about 10 wt%, preferably up to 5 wt%, more preferably 2.5 wt%. The weight percent is calculated based on the total weight of the flame retardant polyester.

In some embodiments, 9,10-dihydro-10-[2,3-di(hydroxyl carbonyl) propyl] 10- phosphaphenanthrene-10-oxide is used in an amount up to 1 wt% to 5 wt%, preferably in amount of 2 wt%, more preferably in amount of 1.5 wt%.

The flame retardant additive reacts with monomer or other reactive end groups of monomers, oligomers, or pre-polymers during esterification process in the reactor. Thus the FR additive is uniformly distributed in the polymer chain rendering permanent flame retardancy and enables better processing of the polymer by extrusion blow moulding process. The other polymeric properties will remain unaffected due to incorporation of the flame retardant additive. The presence of additional functional group in the phosphoric acid encourage reaction with oligomer, pre-polymers, and unreacted monomers.

In some embodiments, there can be incorporated some co-monomers e.g. isophthalic acid, or plasticizers for easy dispersibilty of masterbatch. In some embodiments, there can be added multifunctional additive e.g. maleic anhydride. In some embodiments, the phosphorous content in the flame retardant polyester masterbatch can be achieved up to about 60,000 ppm, up to about 45,000 ppm, up to about 30,000 ppm up to about 15,000 ppm, preferably up to about 10,000 ppm, preferably about up to 5,000 ppm, preferably up to about 1000 ppm, or in any range falling between above value.

In some embodiments, the flame retardant polyester can be melt blended, in required proportion, with target polymers e.g. PET, PEN, PBT, PTT, PBN, Nylon, or polypropylene for further extrusion or spinning purposes. The phosphorus content in the target polymer can be adjusted by controlled use of FR PET masterbatch in a manner so as to achieve the required level of Low Limiting Oxygen Index (LOI).

In some embodiments of the present invention there can be incorporated some compatibilizers e.g. SIPA, DMSIP. In some embodiments the flame retardant additive can be added before, during or after esterification reaction in the reactor. In some embodiments the flame retardant additive can be added before, during or after polymerization reaction. In a preferred embodiment the flame retardant additive is added after esterification and before polymerization reaction in the esterification reactor. In some embodiments the flame retardant additive reacts with monomers, oligomers or pre-polymers in the esterification reactor.

In some embodiments the FR polyethylene terephthalate masterbatch is preferably used to impart permanent flame retarding properties in carpet, textiles, fibers, yarns, and sheets comprising polyester or nylon.

In melt phase polymerization polymer granules of I.V. up to 0.40 to 0.50 dL/gm can be manufactured that further can be upgraded solid state polymerization to get the required intrinsic viscosity (I.V.). The polyester masterbatch produced in this manner have improved flame retardant properties, good color (L* > 55%, a* of -1.0 & b* of -1.0), transparency and good processability.

The polyester masterbatch obtained from use of such phosphorous based additives shows the improved properties, e.g. high crystallinity, low moisture contents, low oligomer contents, high glass transition temperature (T _g ) and high melting point (T _m ). Such masterbatch gives flexibility of inventory management whereby-it can be incorporated in any PET chips (super bright, semi-dull, full-dull, etc.) and RPET; it can also be used in film & sheets. The contents of phosphorous used in the PET can be varied as per the requirement. The flame-retardant polyester obtained in accordance to the process of the present disclosure also meets the health, safety and recycling standards in textile and packaging industry. Moreover, the polyester composition contains reactive flame retardants which makes the polyester thermally stable due to permanent bonding between the flame-retardant comonomer and the polyester. Such modified flame-retardant PET grades have permanent FR properties which are not lost on washing.

The products manufactured from the flame retardant polyester masterbatch can be blended with PET or RPET including other polymers in textile, wires, cables, consumer electronic housings, office electronics housing, printed circuit boards, appliances, applications, vehicle seats, in electrical engineering and electronics, carpet, flooring, thermal insulation for roofs, facades, walls, ducting and conduit etc. The polyester masterbatch is preferably used in textile applications.

The present invention, thus generally described, will be understood more readily by reference to the following examples, which are provided by way of illustration and are not intended to be limiting of the present invention.

Quality Parameters In the examples below as well as throughout the application, the following abbreviations have the following meanings. If not defined, the terms have their generally accepted meanings.

PET: Polyethylene terephthalate,

PTA: Purified terephthalic acid,

PCR: Post-consumer recycled,

MEG: Mono ethylene glycol,

DEG: Diethylene glycol,

N.A.: Nucleating Agent, PBT: Polybutylene terephthalate,

PTN: Polytrimethylene terephthalate,

SSP: Solid state polymerization,

dL/gm: deciliters per gram,

meg/kg: mill equivalents/kilogram,

wt %: weight percentage,

I. V.: intrinsic viscosity,

T _g : glass transition temperature,

T _Ch : crystallization temperature,

T _m : melting temperature

LOI: Limiting Oxygen Index

FR: Flame Retardant

FR PET: Flame retardant polyester

FR Polyester: Flame retardant polyester

Intrinsic Viscosity

Intrinsic viscosity (I.V.) is a measure of the molecular mass of the polymer and is measured by dilute solution using an Ubbelohde viscometer. All intrinsic viscosities are measured in a 60:40 mixture of phenol and s-tetrachloroethane with 0.5 % concentration. The flow time of solvent and solution are checked under I.V. water bath maintained at temperature bout 25 °C. The I.V., η, was obtained from the measurement of relative viscosity, nr, for a single polymer concentration by using the Billmeyer equation: IV = [r|] = 0.25[(RV-l) + 3 1n RV] / c

Wherein η is the intrinsic viscosity, RV is the relative viscosity; and c is the concentration of the polymeric solution (in g/dL). The relative viscosity (RV) is obtained from the ratio between the flow times of the solution (t) and the flow time of the pure solvent mixture (to).

RV = n _re i = Flow time of solution (t) / Flow time of solvent (to) I. V. must be controlled so that process ability and end properties of a polymer remain in the desired range. Class 'A' certified burette being used for IV measurement for more accuracy. Color

The color parameters were measured with a Hunter Lab Ultrascan VIS instrument. D65 illuminant and 10° angle is being used for color measurement. Both Amorphous and Solid State Polymerized (SSP) were used to check by reflectance mode of Hunter Color Scan. Generally, the changes measured could also be seen by eyes. The color of the transparent amorphous/SSP chips was categorized using the Hunter Scale (L / a / b) & CIE Scale (L* / a* / b*) values which are based on the Opponent-Color Theory. This theory assumes that the receptors in the human eyes perceive color as the following pairs of opposites. · L / L* scale: Light vs. Dark where a low number (0-50) indicates dark and a high number (51-100) indicates light.

• a / a* scale: Red vs. Green where a positive number indicates red and a negative number indicates green.

• b / b* scale: Yellow vs. Blue where a positive number indicates yellow and a

negative number indicates blue.

The L* values after SSP are higher because of whitening caused by spherulitic crystallization of the polymer. DEG/EG/IPA/BDO content:

To determine the diethylene glycol (DEG), ethylene glycol (EG), isophthalic acid (IPA) and butanediol (BDO) in the modified polyester, polymer sample is trans-esterified with methanol in an autoclave at 200 °C temperature for 2.5 hours with zinc acetate as a catalyst.

During methanolysis, the polymer sample is depolymerized and the liquid is filter through Whatman 42 filter paper. After filtration, 1 micro liter of the liquid was injected in Agilent Gas Chromatography (GC) under controlled GC configuration. Based on the RT (Retention Time), DEG / EG / IPA/BDO are calculated with Internal Standard ISTD (tetraethylene glycol dimethyl ether) and results are declared as wt. %. COOH End groups:

The Polymer was dissolved in a mixture of phenol and chloroform (50: 50 w/v) under reflux conditions. After cooling to room temperature, the COOH end groups were determined using titration against 0.025 N Benzyl alcoholic KOH solution with bromophenol blue as an indicator. Run a blank simultaneously along with sample and the final end point is at the color change from blue from yellow. COOH groups are calculated based on the below calculation and the results are expressed in meq of COOH/kg. In the equation, TR is the volume of benzyl alcoholic KOH consumed for the sample, N is the normality of benzyl alcoholic KOH, and the blank is the volume of benzyl alcoholic KOH consumed for sample solution.

[(TR- Blank) x N x 1000] = COOH end groups (meq/kg)

DSC analysis The Differential Scanning Calorimeter (DSC) is a thermal analyzer which can accurately and quickly determine the thermal behavior of Polymers such as glass transition temperatures (T _g ), crystallization exothermic peak temperatures (T _Ch ), peak endotherm temperatures (T _m ), heats of crystallization (ΔΗ) and heats of fusion for all materials. A Perkin-Elmer model Jade DSC was used to monitor thermal properties of all polymer samples at heating and cooling rates of 10 °C per minute. A nitrogen purge was utilized to prevent oxidation degradation.

Crystallinity by DSC and DGC: The Differential Scanning Calorimeter (DSC) and Density Gradient Column (DGC) are used to calculate the crystallinity of polymer samples.

By DSC, the crystallinity is calculated by heat of fusion ((ΔΗ) of Tml (Heat 1 cycle) with specific heat of polymer. By DGC (Density Gradient Column), the crystallinity is calculated with the help of known standard balls floating at the Lloyds densitometer. Oligomer Content:

The oligomer content in the polymer samples was determined by Soxhlet reflux methods. Polymer samples were refluxed with 1, 4-dioxane for 2 hours in a mantle heater. After 2 hours, the refluxed sample is filtered through Whatmann 42 filter paper and the filtrate was transferred to a clean, dry, pre-weighed 100 ml glass beaker. The filtrate was then heated to dryness on a hot plate at 180°C. After drying, the beaker was kept in an air oven at 140°C for 30 minutes. Finally, the oligomer content wt. %) was calculated according to the following: { [(Beaker with Residue (g)) - (Empty Beaker (g))]/ sample weight (g)} x 100.

The following examples are given for the purpose of illustrating various embodiments of the invention and are not meant to limit the present invention in any fashion. The present examples, along with the methods described herein are presently representative of preferred embodiments, are exemplary, and are not intended as limitations on the scope of the invention. Changes therein and other uses which are encompassed within the spirit of the invention as defined by the scope of the claims will occur to those skilled in the art.

Examples

The following examples are given for the purpose of illustrating various embodiments of the invention and are not meant to limit the present invention in any fashion. The present examples, along with the methods described herein are presently representative of preferred embodiments, are exemplary, and are not intended as limitations on the scope of the invention. Changes therein and other uses which are encompassed within the spirit of the invention as defined by the scope of the claims will occur to those skilled in the art. The flame retardant polyester is generally prepared from a process comprising following four steps. Step 1: Preparation of Raw Material Slurry: A slurry of pure terephthalic acid (PTA) and ethylene glycol (MEG) in the ratio of about 70:30 wt. % was prepared in a paste preparation vessel along with the required concentration of sodium acetate anhydrous and of pentaerythritol. The polymerization catalysts, e.g. antimony trioxide (Sb ₂ 0 ₃ ), germanium oxide (Ge0 ₂ ), was added to the paste preparation vessel along with Cobalt Acetate (CoAc) as a color toner along with additional red and/or blue toners if required in the range up to 40 ppm.

Step 2: Esterification Process: An esterification reactor equipped with agitator, internal heating coils, and external heating limpet coils. The esterification reaction is maintained under the inert atmosphere by nitrogen supplied through a separate system attached to the reactor. The reaction is, as known in the art, carried out under pressure in the range of 2 to 3.5 kg/cm2 and at the temperature ranging from 260 °C to 285 °C for 4 to 5 hours. The slurry made in step 1 was transferred into the esterification reactor and the esterification reaction was carried out at temperature between 240 to 260 °C, under 3 kg nitrogen pressures. The esterification reaction results to the formation of diester, e. g. bis (2- hydroxyethyl) terephthalate including other low molecular weight esters. The low molecular compounds, e.g. low oligomers, have the degree of polymerization (DP) between 5 to 10.

Byproducts, e.g. water or alkanol, formed during the esterification reaction was separated so as to push forward the reaction.

Step 3: Polycondensation Reaction: Like the esterification reactor, the polycondensation reactor used in the process is also equipped with an agitator, external heating, limpet coils, condenser and fine vacuum system. Polymerization was processed by gradually reducing the pressure from 5 to 20 mbar and increasing the temperature from 260 °C to 285 °C. The polymerization takes place in the presence of one more catalysts or combination thereof. During the polymerization reaction various oligomers react each other leading to larger molecules with increased degree of polymerisation (DP) of 150 -170 under low pressure up to 0.2 mbar and at temperature about 245 °C to 288 °C. The polycondensation reaction was monitored based on agitator's power consumption, and subsequently the reaction was terminated once the intrinsic viscosity (I.V.) is achieved about 0.62 dL/gm. eventually, the molten polymer was extruded out as strands and cut under the cold water and collected as amorphous chips.

Step 4: Solid state polymerization: The amorphous chips obtained from the above step 3, were crystallized to obtain the crystallized polymer at a temperature about 120 °C to 150 °C for an extended period of time (about 2 to about 6 hours) in tumble drier. The crystallized polymer was further subjected to solid state polymerization (SSP) in the same tumble drier against the inert gas current, usually nitrogen, or under a vacuum of 1 Torr, at an elevated temperature about 150 °C, but below the melting temperature, for a period of about 4 to about 16 hours. The solid state polymerization was preferably carried out at temperature about 190 °C to about 210 °C. The SSP, in results, increases the inherent viscosity level of the polymer up to about 0.95 dL/g or higher.

Example 1: preparation of flame retardant polyethylene terephthalate polyester

In an esterification reactor equipped with a stirrer, condenser, pressurizing and vacuum system, 8.66 kg of PTA and 3.75 kg of MEG in molar ratio 1: 1.16 for a 15 kg batch size were made into a paste and fed into the esterification reactor for charging. In addition, 60 ppm of sodium acetate anhydrous, 700 ppm of pentaerythritol, 7.17 gm (400ppm as Sb) of antimony trioxide catalyst, 0.65 gm (30 ppm as Ge) Ge02 catalyst, 2.53 gm (40 ppm as Co) of Cobalt Acetate powder were added to the esterification reactor. Esterification was carried out at temperature ranging from about 240°C to 260°C. Subsequently, 2.69 gm (50 ppm as P) of orthophosphoric acid and 2.60 gm (2.5 wt %) of 2-Carboxyethyl(phenyl) phosphinic acid were added to the esterified resin, and the reaction mixture was kept on hold for half an hours at a temperature between 252 to 255 °C and then 4.59 gm (1.5 wt. %) of 9,10-dihydro- 10-[2,3-di(hydroxyl carbonyl) propyl] 10-phosphaphenanthrene-lO-oxide to obtain pre- polymers. The pre-polymers formed along with all the additives was transferred to the polycondensation reactor through 10 micron filter, and the polymerization of the pre- polymers was conducted at temperature ranging from about 270 °C and 285°C with a peak temperature of 284° C. The polycondensation reaction was monitored based on reactor agitator power consumption and the reaction was terminated to get I.V. of about 0.62 dL/gm, the melt polyester resin was extruded out as strands, quenched under cold water, and cut into amorphous chips. These amorphous chips were then dried and pre-crystallized before subjecting to solid state polymerization (SSP) for increasing the I.V. up to 0.95 dl/gm. Example 2: preparation of flame retardant polyethylene terephthalate polyester

A paste of 9.75 kg of PTA and 4.23 kg of MEG, in molar ratio 1: 1.16, was fed into an esterification reactor equipped with a stirrer, condenser, pressurizing and vacuum system. Then, 60 ppm of sodium acetate anhydrous, 700 ppm of pentaerythritol, 7.17 gm (400ppm as Sb) of antimony trioxide catalyst, 0.65 gm (30 ppm as Ge) Ge02 catalyst, 2.53 gm (40 ppm as Co) of Cobalt Acetate powder were added to the esterification reactor. Subsequently the esterification was carried out at temperature ranging from about 240 °C and 260 °C. After esterification when some oligomers, pre-polymers are formed, 2.69 gm (50 ppm as P) of orthophosphoric acid and 4.17 gm (4 wt %) of 2-Carboxyethyl(phenyl) phosphinic acid was added to the esterified resin and kept the reaction mixture on hold for half an hours at a temperature between 252 to 255 °C, thereafter the pre-polymers including the additives was transferred to the polycondensation reactor through 10 micron filter for polymerization conducted at temperature between 270 and 285°C with a peak temperature of 284° C. The polycondensation reaction was monitored based on reactor agitator power consumption and reaction was terminated to get I.V of about 0.62 dL/gm, the amorphous polyester resin melt was extruded out as strands, quenched under cold water and cut under water into chips. These amorphous chips were further dried and pre-crystallized before subjecting them to solid state polymerization (SSP) for increasing the I.V up to 0.95 dL/gm.

Example 3: preparation of flame retardant polyethylene terephthalate polyester

To an esterification reactor equipped with a stirrer, condenser, pressurizing and vacuum system, 7.85 kg of pure terephthalic acid (PTA) and 3.40 kg of monoethylene glycol (MEG) for a 15 kg of FR PET batch were made into a paste and then fed into the esterification reactor. The molar ratio of PTA: MEG is 1: 1.16. Further, 7.17 gm (400ppm as Sb) of antimony trioxide catalyst, 0.65 gm (30 ppm as Ge) Ge02 catalyst, 2.53 gm (40 ppm as Co) of Cobalt Acetate powder, 60 ppm of sodium acetate anhydrous and 700 ppm of pentaerythritol calculated on the basis of 15kg FR PET, were added to the esterification reactor. Thereafter esterification was carried out at temperature between about 240 to 260° C to obtain the low molecular weight pre-polymers/oligomers. The pre-polymers/oligomers then, reacted with 2.69 gm (50 ppm as P) of orthophosphoric acid and 3.65 gm (3.5 wt %) of 2-Carboxyethyl(phenyl) phosphinic acid in the esterification reactor to obtain the esterified resin, then the reaction mixture was kept on hold for about half an hours at a temperature between about 252 to 255 °C and then 4.59 gm (1.5 wt%) of 9,10-dihydro-10- [2,3-di(hydroxyl carbonyl) propyl] 10-phosphaphenanthrene-lO-oxide added to the reaction mixture. The reaction mixture comprising pre-polymers was transferred via a 10 micron filter to the polycondensation reactor for polymerization thereof. The polymerization was conducted at temperature about 270 °C to about 285°C. with a peak temperature of 284° C. The polycondensation reaction was monitored based on reactor agitator power consumption and reaction was terminated as the IV reaches about 0.6 dL/gm, the amorphous melt polyester resin so obtained was extruded out as strands and cut under cold water to get amorphous chips. These amorphous chips were then dried and pre-crystallized before subjecting to solid state polymerization (SSP) for increasing the I.V up to 0.95 dL/gm.

Example 4: preparation of flame retardant polyethylene terephthalate polyester In an esterification reactor equipped with a stirrer, condenser, pressurizing and vacuum system, 154.5 kg of PTA, 50 kg of IPA, and 80.5 kg of MEG in molar ratio 1: 1.16 for a 15 kg batch size were made into a paste and fed into the esterification reactor for charging. In addition, 60 ppm of sodium acetate anhydrous, 700 ppm of pentaerythritol, 7.17 gm (400ppm as Sb) of antimony trioxide catalyst, 0.65 gm (30 ppm as Ge) Ge02 catalyst, 2.53 gm (40 ppm as Co) of Cobalt Acetate powder were added to the esterification reactor. Esterification was carried out at temperature ranging from about 240°C to 260°C. Subsequently, 2.69 gm (50 ppm as P) of orthophosphoric acid and 57.5 kg of 2- Carboxyethyl(phenyl) phosphinic acid were added to the esterified resin, and the reaction mixture was kept on hold for half an hours at a temperature between 252 to 255 °C and then 383.3 kg of 9,10-dihydro-10-[2,3-di(hydroxyl carbonyl) propyl] 10-phosphaphenanthrene-lO- oxide to obtain pre-polymers. The pre-polymers formed along with all the additives was transferred to the polycondensation reactor through 10 micron filter, and the polymerization of the pre-polymers was conducted at temperature ranging from about 270 °C and 285°C with a peak temperature of 284° C. The polycondensation reaction was monitored based on reactor agitator power consumption and the reaction was terminated to get I.V. of about 0.58 dL/gm, the melt polyester resin was extruded out as strands, quenched under cold water, and cut into amorphous chips. These amorphous chips were then dried and pre-crystallized before subjecting to solid state polymerization (SSP) for increasing the I.V. up to 0.95 dl/gm. Example 5: preparation of flame retardant polyethylene terephthalate

In an esterification reactor equipped with a stirrer, condenser, pressurizing and vacuum system, 76.75 kg of PTA, 25 kg of IPA, and 40 kg of MEG in molar ratio 1: 1.16 for a 15 kg batch size were made into a paste and fed into the esterification reactor for charging. In addition, 60 ppm of sodium acetate anhydrous, 700 ppm of pentaerythritol, 7.17 gm (400ppm as Sb) of antimony trioxide catalyst, 0.65 gm (30 ppm as Ge) Ge02 catalyst, 2.53 gm (40 ppm as Co) of Cobalt Acetate powder were added to the esterification reactor. Esterification was carried out at temperature ranging from about 240°C to 260°C. Subsequently, 2.69 gm (50 ppm as P) of orthophosphoric acid and 28.75 kg of 2- Carboxyethyl(phenyl) phosphinic acid were added to the esterified resin, and the reaction mixture was kept on hold for half an hours at a temperature between 252 to 255 °C and then 191 kg of 9,10-dihydro-10-[2,3-di(hydroxyl carbonyl) propyl] 10-phosphaphenanthrene-lO- oxide to obtain pre-polymers. The pre -polymers formed along with all the additives was transferred to the polycondensation reactor through 10 micron filter, and the polymerization of the pre-polymers was conducted at temperature ranging from about 270 °C and 285°C with a peak temperature of 284° C. The polycondensation reaction was monitored based on reactor agitator power consumption and the reaction was terminated to get I.V. of about 0.59 dL/gm, the melt polyester resin was extruded out as strands, quenched under cold water, and cut into amorphous chips. These amorphous chips were then dried and pre-crystallized before subjecting to solid state polymerization (SSP) for increasing the I.V. up to 0.95 dl/gm.

anhydrous

(ppm)

Pentaerythrit

700 700 700 700 700

ol

AD01* 2.60 kg 4.17 kg 3.65 57.5 28.75

AD02* 4.59 kg - 4.59 kg 383.3 191

P lysical Properties of Amorphous Polyester

I.V.(dL/gm) 0.663 0.558 0.468 0.586 0.595

Ecooh

60 112 115 36 33

(meq/kg)

Color L* 47.7 54 42.4 33.5 34.1

Color a* -3.3 -1.3 2 -1.3 -1.6

Color b* 18 22.9 22 6.5 6.8

DEG wt% 2.85 5.85 4.22 5.82 5.32

IPA wt% Nil Nil Nil 9.46 9.48

Tg (°C) 55.3 - - 52.3 53.1

P Content

38557 39,176 50,104 51,035 50,918

(ppm)

The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.

The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein. The use of the expression "at least" or "at least one" suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results.

Any discussion of documents, acts, materials, devices, articles and the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application. While considerable emphasis has been placed herein on the particular features of this disclosure, it will be appreciated that various modifications can be made, and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other modifications in the nature of the disclosure or the preferred embodiments will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.