WO2001025325A2

WO2001025325A2 - Improved pct formulations containing halogenated imides, sodium antimonate, and reinforcing fibers

Info

Publication number: WO2001025325A2
Application number: PCT/US2000/024376
Authority: WO
Inventors: Gerald Timothy Keep; Bruce Connard Bell
Original assignee: Eastman Chemical Company
Priority date: 1999-09-23
Filing date: 2000-09-05
Publication date: 2001-04-12
Also published as: JP2003511504A; WO2001025325A3; BR0014132A; CN1374980A; EP1228130A2

Abstract

This invention relates to a polymer composition comprised of: (A) a polyester comprising: (1) terephthalic acid in the amount of 85 to 100 mole % based on the mole percentages of the dicarboxylic acid component equaling a total of 100 mole %. (2) a glycol compnent comprising from about 60 to 100 mole % 1,4-cyclohexanedimethanol; (B) one or more halogenated imides; (C) sodium antimonate; and (D) reinforcing fiber.

Description

IMPROVED PCT FORMULATIONS CONTAINING

HALOGENATED IMIDES, SODIUM ANTIMONATE,

AND REINFORCING FIBERS

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority upon provisional application Serial No. 60/155,723 filed September 23, 1999, and the 60/155,723 application is herein incorporated by this reference in its entirety.

FIELD OF THE INVENTION

This invention relates to an improvement in melt stability of a fiber reinforced, flame retardant (FR) poly(cyclohexylenedimethylene terephthalate) (PCT) formulation.

BACKGROUND OF THE INVENTION

Certain electronics must be soldered at high temperatures and require high heat deflection temperatures (HDT) materials. Such materials typically have high melting points and thus must be melt processed at relatively high temperatures. PCT is a high-melting polyester with a melting point of about 290°C and, consequently, is very challenging to formulate while retaining good molecular weight. In addition to good melt stability, good dimensional stability and flammability characteristics are important. United States Patent No. 4,338,243 by Hecht et al discloses the use of an antimonate to stabilize a PET/flame retardant system that also contains glass fiber, an ionic hydrocarbon salt, and a plasticizer. This system, being based on PET, could not achieve the high HDT required for soldering in high temperature electronics applications, nor is it mentioned in the patent. Also, the effectiveness of NaSbO₃ in PET is shown to be equal in examples based on brominated polystyrene as well as brominated phthalimides. There is no criticality shown in the use of NaSbO₃ in combination with brominated phthalimides in a PET system. United States Patent 4,313,903 by Bier discloses the use of high melting imides with PET in order to improve crystallization, and to achieve flammability targets. Such a system, based on PET, would not achieve good dimensional stability/HDT, especially given that absence of glass fiber reinforcement is recited as being preferred.

United States Patent 4,399,244 by Bier also discloses the use of high melting imides with PET in order to improve crystallization, and even achieve flammability targets, but this one requires the presence of glass fibers to improve HDT. Again, a PET based system has too low a melting point to be useful in high temperature soldering operations.

United States Patent 4,880,860 by Blocker et al discloses the use of low melting point imides (less than 200°C) to improve crystallization in any polyester, preferably PET.

United States Patent 4,778,820 by Minnick discloses the use of PCT with a halogenated flame retardant and elemental antimony metal as a synergist. This was shown to give superior physical properties to either Sb₂O₃ or NaSbO₃, though the examples were based on poly dibromophenylene oxide. This is recognized as a valid but different route to achieving a useful material for high temperature electronics. However, the cost, safety, and environmental factors associated with use of elemental antimony metal illustrate the need for alternative methods.

United States Patent 5,021,495 by Minnick broadly discloses use of a halogenated species and an antimony compound to flame retard PCT or PBT formulations that have an olefin with either acidic or epoxy functional groups to improve flame retardancy. The examples cited are based on sodium antimonate and brominated polystyrene, and none of them achieve an HDT as high as 260°C. Minnick's invention does not recognize the superior HDT but greater challenge of using brominated phthalimides as flame retardants. United States Patent 4,837,254 by Minnick discloses the use of PCT, a halogenated flame retardant, a mixture of elemental antimony metal and Sb₂O_3l and phenoxy. The invention is based on the synergistic effects of antimony metal and phenoxy. This patent mentions that sodium antimonate gives inadequate HDT in the cited system.

United States Patent 5,371 , 123 by Gallucci et al discloses use of glass fibers with specific coatings (olefin or epoxy) to improve the color of a polyester with a halogenated bis-imide flame retardant. This choice of glass fiber coating is not relevant to the current invention. Sb₂O₃ is preferred in Gallucci's invention.

United States Patent 3,624,024 by Caldwell et al discloses the use of Sb₂O₃ as flame reinforced synergist in a PBT formulation including talc and various flame retardant synergist. The HDT obtained with PBT is not useful for high temperature soldering applications. United States Patent 4,467,062 by Hornbaker et al discloses compositions based on PET or its copolymers, a bis-imide flame retardant, and optionally an inorganic FR synergist. Sb₂O₃ is said to be preferred and no special mention of stability is made. The HDT obtained with PET and its copolymers is not useful for high temperature soldering applications.

BRIEF SUMMARY OF THE INVENTION

This invention relates to a polymer composition comprised of:

(A) a polyester comprising:

(1 ) terephthalic acid in the amount of 85 to 100 mole % based on the mole percentages of the dicarboxylic acid component equaling a total of 100 mole %.

(2) a glycol component comprising from about 60 to 100 mole % 1 ,4-cyclohexanedimethanol;

(B) one or more halogeated imides; (C) sodium antimonate; and (D) reinforcing fiber

A preferred embodiment of this invention comprises one or more phosphorous based compounds.

The polymer composition of this invention has improved dimensional stability, improved melt stability, and improved flammability characteristics that are particularly useful in high temperature electronics.

DETAILED DESCRIPTION

Specifically, this formulation simultaneously achieves good dimensional stability (as demonstrated by Heat Deflection Temperature above 260°C) and good melt stability (as demonstrated by molecular weight retention upon melt processing). At the same time, formulations must have acceptable flammability characteristics to be useful. This is typified by UL- 94 flammability testing. Also, the relative hazard or environmental load of the metallic synergist can be considered in evaluating the usefulness of the invention. It is preferred in this invention that the polyester comprise 90 mole % or more of terephthalic acid based on the mole percentages of the dicarboxylic acid component of the polyester equaling a total of 100 mole %. By terephthalic acid, suitable synthetic equivalents, such as dimethyl terephthalate, are included. The polyester useful in this invention comprises 0 to 15 mole %, preferably 0 to 10 mole %, of dicarboxylic acids other than terephthalic acid, based on the mole percentages of the dicarboxylic acid component of the polyester equaling a total of 00 mole %. The other dicarboxylic acids include, but are not limited to, aromatic dicarboxylic acids preferably having 4 to 40 carbon atoms, more preferably, 8 to 14 carbon atoms; aliphatic dicarboxylic acids having, preferably 4 to 40 carbon atoms more preferably 4 to 12 carbon atoms or cycloaliphatic dicarboxylic acids having 4 to 40 carbon atoms, more preferably, 8 to 12 carbon atoms

Particularly preferred examples of other dicarboxylic acids useful in forming the copolyester useful in the invention include, but are not limited to, isophthalic acid, naphthalenedicarboxylic acid, cydohexanedicarboxylic acid, 1 ,4-cyclohexanedιacetιc acid, dιphenyl-4,4'-dιcarboxylιc acid, naphthalenedicarboxylate, succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, and the like Of these, isophthalic acid, naphthalenedicarboxylic acid cydohexanedicarboxylic acid and naphthalenedicarboxyate are preferred, either singly or in combination

When cydohexanedicarboxylic acid is used as a comonomer in the context of the invention, trans-, cis-, or cis/trans mixtures may be used Any of the naphthalenedicarboxylic acid isomers or mixtures of isomers may be used Some preferred naphthalenedicarboxylic acid isomers include 2,6-, 2,7- 1 ,4- and 1 ,5- isomers

It should be understood that "dicarboxylic acids", includes the corresponding acid anhydrides, esters, and acid chlorides of these acids In the acid component of this invention, the mole percentages of the acids of the polyester referred to herein equal a total of 100 mole %

In the glycol component of this invention, the mole percentages of the glycols referred to herein equal a total of 100 mole %

In the invention, it is preferred that the glycol component of the copolyester of the invention contain from about 80 to 100 mole %, preferably 90 to 100 mole %, of one or more of the isomers of 1 ,4- cyclohexanedimethanol

Preferably, the copolyesters of this invention may be based on trans-, or cis/trans mixtures of 1 ,4-cyclohexanedιmethanol For example, a 30/70 cis/trans mixture of the isomers may be readily used The glycol component may comprise up to 20 mole %, and more preferably, up to 10 mole %, of one or more other aliphatic or alicyclic glycols.

Such additional diols include cycloaliphatic diols preferably having 6 to 20 carbon atoms or aliphatic diols preferably having 2 to 20 carbon atoms. Examples of such diols are: ethylene glycol, diethylene glycol, triethylene glycol, propane-1 ,3-diol, butane-1 ,4-diol, pentane-1 ,5-diol, hexane-1 ,6-diol, 3-methylpentanediol-(2,4), 2-methylpentanediol-(1 ,4), 2,2,4-trimethylpentane-diol-(1 ,3), 2-ethylhexanediol-(1 ,3), 2,2- diethylpropane-diol-(1,3), hexanediol-(1 ,3), 1 ,4-di-(hydroxyethoxy)-benzene,

2,2-bis-(4-hydroxycyclohexyl)-propane, 2,4-dihydroxy-1 ,1 ,3,3-tetramethyl- cyclobutane, 2,2-bis-(3-hydroxyethoxyphenyl)-propane, decalin diol and 2,2-bis-(4-hydroxypropoxyphenyl)-propane. Copolyesters may be prepared from the above diols in addition to the 1 ,4-cyclohexanedimethanol. It is more preferred that the one or more glycols are selected from ethylene glycol, diethylene glycol, triethylene glycol, propanediol, butanediol, pentanediol, hexanediol, and tetramethylcyclobutanediol.

When the copolyester contains ethylene glycol, it is preferable that the ethylene glycol be present in an amount less than 20 mole %, more preferably, less than 10 mole %.

Copolyesters containing substantially only 1 ,4-cyclohexanedimethanol and terephthalic acid or substantially only 1 ,4- cyclohexanedimethanol, isophthalic and terephthalic acid are preferred. The polyester resins useful in the blend of this invention are well known and are commercially available. By the term "polyester", copolyesters are also intended. Methods for their preparation are described, for example, in United States Patents 2,465,319 and 3,047,539. For example, the polyesters can be prepared by direct condensation of terephthalic acid or ester interchange using dimethyl terephthalate with the selected glycol. Typical catalysts which may be used to make these copolyesters include titanium alkoxides, dibutyl tin dilaurate, combinations of zinc, manganese, or magnesium acetates or benzoates with antimony oxide or antimony triacetate. The polyesters of the invention preferably have an inherent viscosity of 0.1 to 2.0 dL/g, more preferably 0.3 to 1.5 dUg, and even more preferably, 0.4 to 1.2 dL/g as measured at a temperature of 25°C for a 0.5 gram sample in 100 ml of a solvent consisting of 60% by weight phenol and 40% by weight tetrachloroethane. It is preferred that the copolyester useful herein have a melting point of greater than 260°C, more preferably greater than 270°C. In some embodiments, the copolyester has a melting point of 260°C to 310°C.

Melting points for the polyester resins and halogenated imides of the invention are measured by DSC (differential scanning calorimetry) analysis The invention is meant to incorporate all melt processing methods known in the art.

As used herein, the term "melt processing" refers to any processing step commonly used in the art for polyesters or copolyesters which occurs after the polyesters or copolyesters are heated to their melting temperature or melting point. This includes, but is not limited to, injection molding, calendering, extrusion and rotational molding.

It is also preferred within the context of this invention that the polymer composition of the invention undergoes less than a 50%, preferably 25%, and more preferably 15% loss in number average molecular weight as determined by gel permeation chromatography when melt processed at 25°C above the crystalline melting temperature (Tm) for 10 minutes.

The second component of the composition is a halogenated organic compound containing at least one imide group and having a melting point greater than 240°C Useful families of imide-group containing compounds include N,N'-arylenediphthalιmιdes wherein the arylene group includes phenylene, diphenylene, naphthylene and sulfone bridged bisphenyls, tetrabrominated phthalimides, N, N'bιs(dιbromocyclohexane dicarboxyimides) with various bridging groups, and N,N'- alkylenebis(tetrahalophthalimides).

Preferred imide group containing compounds are those corresponding to the following formula:

wherein both n and m may be 1 or 0, X may be halogen, particularly chlorine or bromine, or hydrogen, and

R is a Ci to Cε alkyl group, a single bond, a phenylene group, a toluene group, a cyclohexylene group, a bis phenyl methane group, a bis cyclohexylmethane group, or a naphthylene group.

The N,N'-alkylenebis(tetrahalophthaiimides) suitable in the present invention and a process for their production are described in U.S. Pat. No. 4,087,441 , incorporated herein by reference. The preferred N,N'- alkylenebis(tetrahalophthalimides) are represented by the formula:

wherein R represents a C-|-C₆ alkyl group, preferably a C₂-C₆ alkyl group, and most preferably an ethyl group, and

Hal which may be the same or different, represents a halogen atom, preferably Br or Cl, and most preferably Br.

The most particularly preferred N,N'- alkylenebis(tetrahalophthalimide) is

N,N'-ethylenebis(tetrabromophthalimide) (R is an ethyl group and Hal is a Br atom). These types of imide group containing components are described in United States Patent Nos. 3,624,024 and 3,873,567 and British Pat. No.

1 ,287,934.

Other suitable imide group containing compounds include 1 ,4,5,6- tetrabromo-2,3-phthaloimide; N methylol-tetrabromophthalimide; N,N-bis- (1 ,4,5,6-tetrabromo-2,3-phthaloimide); N,N'-p-phenylene-diphthalimide; N,N'-di-phthalimidodiphenyl; bis-(N phenyl-phthalimido)sulphone; N,N'-p- phenylene-di-tetrachlorophthalimide; 4,4'-di-tetrachlorophthalimidodiphenyl; N-(tetrachlorophthalimido)-tetrachlorophthalimide, N,N'-p-phenylene-di- tetrabromophthalimide; N.N'-di-tetrabromophthalimidodiphenyl; N- (tetrabromophthalimido)-tetrabromophthalimide; N,N'-bis-(5,6- dibromocyclohexane-2,3-dicarboximide); and N,N'-(1 ,2ethane)-bis-(5,6 dibromocyclohexane-2,3-dicarboximide).

Further suitable imide containing compounds are disclosed in U.S. Pat. Nos 3,868,388; 3,873,567; 3,915,930; 3,923,734; 4,001 ,179 and 4,003,862. Suitable imides are also disclosed in British Pat. No. 1 ,287,934 and are incorporated herein by reference.

Preferred imides have a melting point above 240°C, preferably above 300°C, including bis-imides made from aromatic or aliphatic diamines, including ethylene diamine, or hydrazine, and tetrabromophthallic anhydride or acid are preferred. Again, the most preferred flame retardant is the imide from reacting tetrabromo phthallic acid (anhydride) with ethylene diamine. This is sold commercially as Saytex BT-93 and BT-93W. This flame retardant has a high bromine content. It is thermally stable to processing temperatures characteristic of PCT, and does not soften below the PCT melting point. This class of phthalimides has an advantage over other high temperature bromine sources like decabromodiphenyl in that they are not singled out as having the same environmental concerns (dioxins/furans).

It is preferred that the sum of all flame retardants used in this invention is 5-30%, preferably 10-20%, by weight of the total composition. One or more flame retardants may be used within the context of this invention.

Brominated phthalimides are high melting materials, in contrast to other brominated flame retardants, and provide superior HDT. However, the combination of PCT and BPI is especially challenging from a melt stability standpoint. The preferred FR synergists with PCT/BPI system are not the same as with lower melting point materials like PBT (Tm=220°C) or PET (Tm=250°C).

A number of patents describe processes for preparing brominated phthalimides, for example, United States Patents 4,997,953; 5,076,970; 5,290,945; 5,137,948; and 5,317,048, all of which are incorporated herein by reference.

The polymer composition of this invention achieves good dimensional stability and good melt stability due, at least in part, to use of the flame retardant synergist. Antimony compounds are preferred. Sodium antimonate is more preferred. Even more preferred is NaSbO₃ that is substantially free of Sb⁺³ or less than 1 mole % of Sb⁺³ based on the total mole percentages of antimony in the sodium antimonate.

Sodium antimonate is normally described in the art as being a sodium-neutralized version of Sb₂O₃ but the importance of Sb⁺³ level and the desire to reduce rather than increase the amount of synergist suggest this different mechanism, reducing catalytic activity of the Sb species

It is even more preferred that the ratio of flame retardant halogenated imide(s), preferably, brominated phthalimide(s), to flame retardant synergist (sodium antimonate) is optimized at a much higher weight ratio (5:1 to 10:1 , preferably 8:1 ) than is commonly practiced in the art (3:1 to 4:1 ).

In effect, the sodium antimonate stabilizes the halogenated imide system. It can also be shown that melt stability of the composition of the invention can be further improved by addition of a phosphorous-based compound. The phosphorous-based compounds include, but are not limited to, one or more phosphites or phosphonites wherein at least one of the P-O bonds is attached to an aryl radical. Such compounds may be represented by the formulas

R,0 — P Phosphite

OR₃

where at least one of Rι, R₂ and R₃ is an aryl radical of 6 to 30 carbon atoms and any other(s) of R-i, R₂ and R₃ are H or alkyl of 1 to 30 carbon atoms, or R₄0

Phosphonite

R₅0^* OR_e

where at least one of R , R₅ and Rε is an aryl radical of 6 to 30 carbon atoms. Phosphites are preferred within the context of this invention.

Even more preferred are, for example, commonly available symmetrical triaryl esters of phosphorous acid which may be used are triphenyl phosphite; tris(nonylphenyl) phosphite; and tris(2,4-di-t- butylphenyl) phosphite (Irgafos 168). The most preferred symmetrical ester of phosphorous acid is bis(2,4-di-t-butylphenyl) pentaerythritol diphosphite

(Ultranox® 626 - a trademark of General Electric Co.).

Examples of phosphorous-based compounds which may be used include, but are not limited to, Ultranox® 633 phosphite, (General Electric Chemicals), lrgafos®168 phosphite (Ciba-Geigy Corporation), Ethanox® 398 phosphonite (Ethyl Corporation) and Sandostab® P-EPQ phosphonite (Sandoz Chemicals).

The phosphorous compounds may be functioning by inhibiting the metal catalyst system present in the PCT. While much is known about use of phosphorous compounds in stabilizing polyester systems, it is not generally recognized as a way to stabilize flame retardants.

Without limiting the invention, it is suggested that all these changes may function by reducing the catalytic activity of the blend to a much lower level than is required for lower melting polyesters. This is in contrast to the usual concern of buffering the system from acidic HBr release which can directly attack the polyester. It is understood that other additives such as other stabilizers other flame retardants (FR), flame retardant synergists, tougheners, epoxy compounds, branching agents, mold release agents nucleating agents reinforcing agents such as reinforcing fibers, fillers, antioxidants and colorants such as carbon black, might also be desirable in such formulations These may be added either during or after polymerization to form a copolyester composition, depending on the chemical structure of the additive

Such additives are generally present at 0 1 to about 40 weight %, preferably 0 1 to about 20 weight %, based on the total weight of the copolyester composition

It is also preferable that 0 1 to 5 0 weight %, preferably less than 2 0 weight %, of one or more branching agents is included within the context of this invention, including but not limited to, trimellitic acid, trimellitic anhydride, pyromellitic anhydride, multifunctional epoxy compounds and multi-functional phenoxy compounds, and the like If the branching agent is a phenoxy compound, 2 0 to 5 0 weight % is preferred

Examples of reinforcing agents useful in the invention mica, clay, talc, wollastonite, and calcium carbonate Examples of reinforcing fibers are carbon fibers and glass fibers

A particularly preferred reinforcing fiber is glass fiber It is preferable that the glass fibers be present in the polyester composition at from 0 1 to 45%o, preferably 10 to 40%, by weight based on the total weight of said polyester composition Glass fibers suitable for use in the polyester compositions of the invention may be in the form of glass filaments, threads, fibers, or whiskers, etc , and may vary in length from about 1/8 inch to about 2 inches Chopped glass strands having a length of about 1/8 inch to about 1/4 inch are preferred Such glass fibers are well known in the art Of course the size of these glass fibers may be greatly diminished depending on the blending means employed, even to lengths of 300 to 700 microns or lower. It is preferred that the glass fibers are coated with polyurethane. The polyester compositions of the invention may be reinforced with a mixture of glass and other reinforcing agents as described above, such as mica or talc, and/or with other additives.

The components of the copolyester composition of the invention may be blended and/or mixed by any suitable technology known in the art. Compounding temperatures must be at least the melting point of the polyester. For example, the polyester can be mixed dry in any suitable blender or tumbler with the other components and the mixture melt- extruded. The extrudate can be chopped. If desired the reinforcing material can be omitted initially and added after the first melt extrusion, and the resulting mixture can then be melt extruded. The copolyester of this invention may be melt processed and extruded, injection molded or compression molded into a variety of shapes and forms including fibers, molded parts, bottles, pellets, containers, sheeting, film and the like. Preferably, the molded or shaped articles are formed through either injection molding or extrusion molding. The product is especially suitable as an injection molding material for produdng molded articles. Examples of shaped articles are extruded sheets or injection molded articles. The shaped articles may include electronic components, which include, but are not limited to, sheet for circuit boards, connectors, circuit breaker housing, computer components, sockets, and switches. Unless otherwise specified, all parts, percentages, ratios, etc., are by weight. Weight of reinforcing glass fibers is based on total composition weight.

This invention can be further illustrated by the following examples of preferred embodiments thereof, although it will be understood that these examples are included merely for purposes of illustration and are not intended to limit the scope of the invention unless otherwise specifically indicated. The starting materials are commercially available unless otherwise indicated.

The following definitions of terms are applicable throughout this invention unless otherwise specified:

Dimensional Stability - judged by observation of the dimensions of molded electronic parts after being subjected to typical Infrared Reflow Soldering time - temperature profiles used for Surface Mount Electronics, preferably while stressed by loading with contact pins. Also, the retention of pull-out resistance force of the inserted contact pins is measured after exposure to soldering temperatures;

Flammability Measurement - UL 94 - Flammability tests were performed following the procedure of Underwriter's Laboratory Bulletin 94 entitled 'Tests for Flammability of Plastic Materials, UL94". A rating of

"V0" means that a flame will self-extinguish within 10 seconds after each ignition without dripping molten polymer. A rating of "V2" means that a flame will self-extinguish within 30 seconds after each ignition and may have flaming drips which ignite dry absorbent surgical cotton; Flame Retardant 1 - (FR1 ) - N,N'- ethylenebis(tetrabromophthalimide) which is reaction product of ethylene diamine and tetrabromophthalic anhydride; flame retardant of the invention;

Flame Retardant 2 - (FR2) - brominated polystyrene; comparative flame retardant; Flame Retardant 3 - (FR3) - decabromodiphenylether); comparative flame retardant;

Flame Retardant Synergist 1 - (FRS1 ) - sodium antimonate, 5 μm, has about 3% Sb⁺³;

Flame Retardant Synergist 2 - (FRS2) - sodium antimonate, 5 μm, has less than 1 % Sb⁺³ ; Glass Fibers Type 1 - (GF1 ) - 14 microns diameter, amino silane coupler, and thermoset epoxy coating;

Glass Fibers Type 2 - (GF2) -10 micron diameter, amino silane coupler, and thermoplastic polyurethane coating; Glass Fibers Type 3 - (GR3) - 10 micron diameter, amino silane coupler, and thermoplastic polyurethane coating; GPC - gel permeation chromatography;

HDT - heat deflection temperature as determined according to ASTM Method D648 at 264 psi loading; Inherent viscosity or "IN." - refers to inherent viscosity expressed in dL/g measured as described herein;

Melting Point - determined by DSC (differential scanning calorimeter);

Molecular Weight (Mn) - number average molecular weight unless otherwise specified;

Melt stability was determined on these blends by drying a small sample of the compounded pellets. Adequate drying can be obtained by drying in a vacuum oven overnight at 80°C, or by drying for 4 hours at 125°C in a hot air circulating oven. The dried pellets were then loaded into a Tinius Olsen melt indexer or capillary rheometer and held for 10 minutes at 305°C melt temperature, then analyzed by gel permeation chromatography. The melt stability of these blends was shown by the retention of number average molecular weight (Mn) and weight average molecular weight (Mw) after 10 minutes at 305°C. Good melt stability is characterized by a loss of less than about 15% of the original Mn and Mw, after exposure for 10 minutes, the original molecular weights being defined as that at zero time. Blends with less than this degree of melt stability may still be useful, but are correspondingly inferior;

PCT - poly(cyclohexyienedimethylene terephthalate); PCTA - poly(cyclohexylenedimethylene terephthalate modified with 5 mole% isophthalic acid;

Plasticizer A - (PL A) - epoxided soybean oil; Plasticizer B - (PL B) - triethyleneglycol-di-2-ethylhexanoate; Plasticizer C - (PL C) - polyethyleneglycol-di-2-ethylhexanoate;

Plasticizer D - (PL D) - 1 ,4-cyclohexanedimethanol-di-2- ethylehexanoate;

Plasticizer E - (PL E) - trioctyltrimellitate; Plasticizer F - (PL F) - dioctylterephthalate; Plasticizer G - (PL G) - diundecylphthalate;

Plasticizer H - (PL H) - triisononyltrimellitate; Plasticizer I - (PL I) - quaterphenyl; Plasticizer J - (PL J) - pentaerythritol tetrabenzoate Plasticizer K - (PL K) - polymeric neopentyl adipate/glutarate; Plasticizer L _ (PL L) - (polyethylene glycol dilaurate);

Stabilizer 1 - (ST 1 ) - polyethyleneglycol with epoxy functional end- caps

Stabilizer 2 - (ST 2) - multifunctional bisphenol F epoxy; Stabilizer 3 - (ST 3) - epoxy resin (polymer of tris(4- glycidyloxyphenyl) methane);

Stabilizer 4 - (ST 4) - tetrakis -[methylene -(3,5-di-tert-butyl-4- hydroxyhydro-cynnamate)]; and

Stabilizer 5 - (ST 5) - [bis(2,4-di-t-butylphenyl)pentaerythritol diphosphite

All percentages expressed herein refer to weight percentages unless otherwise specified.

EXAMPLES The fiber reinforced PCT blends of this work were prepared by extrusion compounding using a twin screw extruder at temperatures of 305°C. The resulting pellets were injection molded into tensile and flexural bars for use in mechanical and flammability property testing. Melt stability was determined on these blends by drying a small sample of the compounded pellets Adequate drying can be obtained by drying in a vacuum oven overnight at 80°C, or by drying for 4 hours at 125°C in a hot air circulating oven. The dried pellets were then loaded into a Tinius Olsen melt indexer or capillary rheometer and held for 10 minutes at 305°C melt temperature, then analyzed by gel permeation chromatography. The melt stability of these blends was shown by the retention of number average molecular weight (Mn) and weight average molecular weight (Mw) after 10 minutes at 305°C.

The blends in the Examples below are described as follows. Percentages are by weight of the total composition.

EXAMPLE 1

Blends A-D in Table I are described as follows:

Blend A is described as follows: 49.3% PCT 30.0% GF1 13.0% FR1

4.0% FRS1

3.7% ST1

Blend B is described as follows:

Same as Blend A except that FR1 is replaced by FR2

Blend C is described as follows:

Same as Blend A except that ST1 is replaced by ST2

Blend D is described as follows:

Same as Blend B except that ST1 is replaced by ST2

TABLE I

Table 1 illustrates the fact that compositions of the invention containing brominated phthalimides (FR1 ) have a higher heat deflection temperature than brominated polystyrene (FR2) but have inferior melt stability compared to the brominated polystyrene (FR2).

EXAMPLE 2

The compositions used in Table 2 all consist of the following: 48.8% PCT 30.0%) Glass Fibers Type 1

4.0% FRS1

0.5% ST3 13.0% of a flame retardant selected from FR1 or FR2

3.7% of a plasticizer as described in Table 2

TABLE 2

In Table 2, FR1 is N,N'-ethylenebis(tetrabromophthalimide; FR2 is brominated polystyrene; FR1-2 is the difference between FR1 & FR2.

The data in Table 2 shows that the relative difference between halogenated imides (FR1 ) (for example, brominated phthalimides) and brominated polystyrene (FR2) varies with choice of plasticizer systems but still shows similar behavior.

EXAMPLE 3

Blends E-F in Table 3 are described as follows:

Blend E is described as follows: 30.0% GF2 14.0% FR2

3.5% FRS1

3.7% PL C

0.5% Stabilizer 3

1.0% Talc

0.3%) Stabilizer 4, and PCT in an amount sufficient for the composition to total 100 weight%

Blend F is described as follows:

Same as Blend E except that the 14.0% FR2 is replaced by 10.5% FR3

TABLE 3

*m 305° equals minutes at 305°C The data in Table 3 shows that another common flame retardant

(FR3) behaves similarly to brominated polystyrene (FR2).

EXAMPLE 4

Blends G-l in Table 4 are described as follows Blend G is described as follows

30.0% GF2 14.0% FR2 3.5% FRS1 3.7% PL C 0.5% ST3

1.0% Talc 0.3% ST4, and a 50:50 ratio by weight of PCT and PCTA in an amount sufficient for the composition to total 100 weight%; PCTA is PCT modified with 5 mole%> isophthalic acid;

Blend H is described as follows:

Same as Blend G except that the 14.0% FR2 is replaced by 10.5% FR3;

Blend I is described as follows:

Same as Blend G except that the 14.0% FR2 is replaced by 12.0% FR1 ;

TABLE 4

Table 4 illustrates the fact that compositions of the invention containing halogenated imides (FR1) (for example, brominated phthalimides) have a higher heat deflection temperature than those with brominated polystyrene (FR2) but have inferior melt stability compared to the brominated polystyrene (FR2) compositions. EXAMPLE 5

Blends J-0 in Table 5 are described as follows Blend J is described as follows:

20.0% FR1 , and 80.0% PCT

Blend K is described as follows: 20.0% FR1

70.0% PCT 10.0% Antimony oxide

Blend L is described as follows: 20.0% FR1

70.0% PCT 10.0% FRS1

Blend M is described as follows: 20.0% FR2, and

80.0% PCT

Blend N is described as follows: 20.0% FR2 70.0% PCT

10.0%) Antimony oxide

Blend O is described as follows: 20.0% FR2 70.0% PCT

10.0% FRS1

TABLE 5

Table 5 shows that, with FR1 (brominated phthalimide), any antimony compound harms stability whereas, with FR2 (polystyrene), the oxide harms stability but the sodium salt helps stability. EXAMPLE 6

Blends P-Q in Table 6 are described as follows:

Blend P is described as follows: 30.0% GF2 14.0% FR1 3.5% FRS1 3.8% PL L 0.5% ST3

0.5% polyethylene wax 0.25% ST4 0.25% ST5, and

PCT in an amount sufficient for the composition to total 100 weight%.

Blend Q is described as follows:

Same as Blend P except that the FR1 is increased to 16.0% and FRS1 is decreased to 2.0%

TABLE 6

Table 6 shows that stability can be improved by increasing the ratio of flame retardant to synergist while maintaining desired flammability characteristics.

EXAMPLE 7

Blends R-S in Table 7 are described as follows:

Blend R is described as follows: 30.0% GF3 16.0% FR1 2.0% FRS2 4.0% PL L 3.0%) Phenoxy 0.5%) polyethylene wax 0.25% ST4 0.25% ST5, and

PCT in an amount sufficient for the composition to total 100 weight%.

Blend S is described as follows:

Same as Blend R except that ST5 is omitted.

TABLE 7

Table 7 shows the benefit of using a phosphite.

EXAMPLE 8

Blends T-U in Table 8 are described as follows: Blend T is described as follows:

30.0% GF3 16.0% FR1 2.0% FRS1 4.0% PL L 3.0%) Phenoxy

0.5%) polyethylene wax 0.25% ST4 0.25% ST5 PCT in an amount sufficient for the composition to total 100 weight%.

Blend U is described as follows:

Same as Blend T except that ST5 is present in the amount of 0.75%.

TABLE 8

*Rheological properties measured by Kayeness rheometer *Delta is change

Table 8 shows the benefit of increasing the amount of the phosphite beyond the level normally used to stabilize against degradation.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

Claims

We claims:

1. A polymer composition comprised of: (A) a polyester comprising: (1 ) terephthalic acid in the amount of 85 to 100 mole % based on the mole percentages of the dicarboxylic acid component equaling a total of 100 mole %. (2) a glycol component comprising from about 60 to 100 mole % 1 ,4-cyclohexanedimethanol; (B) one or more halogenated imides;

(C) sodium antimonate; and

(D) reinforcing fiber.

2. The composition of Claim 1 wherein said one of said dicarboxylic acids comprises terephthalic acid in an amount of 90 to 100 mole %.

3. The composition of Claim 1 wherein said acid component comprises repeat units of from 0 to 15 mole % or less of one or more other dicarboxylic acids.

4. The composition of Claim 3 wherein said one or more dicarboxylic acids is selected from cydohexanedicarboxylic acid, isophthalic acid, 1 ,4-cyclohexanediacetic acid, diphenyl-4,4'-dicarboxylic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, naphthalenedicarboxylic acid, or sebacic acid.

5. The composition of Claim 4 wherein said one or more dicarboxylic acid is selected from isophthalic acid, naphthalenedicarboxylic acid, cydohexanedicarboxylic acid or naphthalene dicarboxylate.

6. The composition of Claim 5 wherein said one or more dicarboxylic acid is selected from isophthalic acid and naphthalenedicarboxylic acid.

7. The composition of Claim 6 wherein said dicarboxylic acid comprises isophthalic acid.

8. The composition of Claim 3 wherein said acid component comprises cydohexanedicarboxylic acid.

9. The composition of Claim 6 wherein said acid component comprises naphthalenedicarboxylic acid.

10. The composition of Claim 1 wherein said glycol component comprises 80 to 100 mole % 1 ,4-cyclohexanedimethanol.

11. The composition of Claim 10 wherein said glycol component comprises 90 to 100 mole % 1 ,4-cyclohexanedimethanol.

12. The composition of Claim 10 wherein said glycol component comprises up to 20 mole % of one or more other aliphatic or alicyclic glycols.

13. The composition of Claim 12 wherein said glycol component comprises up to 10 mole % of one or more other aliphatic or alicyclic glycols.

14. The composition of Claim 12 wherein said one or more other glycols is selected from the group consisting of cycloaliphatic diols having 6 to 20 carbon atoms and aliphatic diols having 2 to 20 carbon atoms.

5. The composition of Claim 14 wherein said one or more other glycols is selected from the group consisting of ethylene glycol, diethylene glycol, triethylene glycol, propane-1 ,3-diol, butane-1 ,4-diol, pentane- 1 ,5-diol, hexane-1 ,6-diol, 3-methylpentanediol-(2,4), 2- methylpentanediol-(1 ,4), 2,2,4-trimethylpentane-diol-(1 ,3), 2-ethylhexanediol-(1 ,3), 2,2-diethylpropane-diol-(1 ,3), hexanediol- (1 ,3), 1 ,4-di-(hydroxyethoxy)-benzene, 2,2-bis-(4- hydroxycyclohexyl)-propane, 2,4-dihydroxy-1 ,1 ,3,3-tetramethyl- cyclobutane, 2,2-bis-(3-hydroxyethoxyphenyl)-propane, decalin diol and 2,2-bis-(4-hydroxypropoxyphenyl)-propane.

16. The composition of Claim 15 wherein said one or more other glycols is selected from the group consisting of ethylene glycol, diethylene glycol, triethylene glycol, propanediol, butanediol, pentanediol, hexanediol, and tetramethylcyclobutanediol.

17. The composition of Claim 12 wherein said one or more other glycols comprises ethylene glycol in an amount less than 20 mole %.

18. The composition of Claim 17 wherein said one or more other glycols comprises ethylene glycol in an amount less than 10 mole %.

19. The composition of Claim 1 wherein said copolyester has a melting point of 260°C or more.

20. The composition of Claim 19 wherein said copolyester has a melting point of 270°C or more.

21 . The composition of Claim 19 wherein said copolyester has a melting point of 260°C to 310°C.

22. The composition of Claim 1 wherein said polymer composition undergoes less than a 50% loss in number average molecular weight as determined by gel permeation chromatography when melt processed at about 25°C above the crystalline melting temperature for 10 minutes.

23. The composition of Claim 22 wherein said polymer composition undergoes less than a 25% loss in number average molecular weight as determined by gel permeation chromatography when melt processed at about 25°C above the crystalline melting temperature for 10 minutes.

24. The composition of Claim 1 comprising one or more additives selected from the group consisting of stabilizers, flame retardants, flame retardant synergists, tougheners, epoxy compounds, mold release agents, nucleating agents, reinforcing agents and branching agents.

25. The composition of Claim 1 wherein said organic compounds containing at least one imide group have a melting point above 240°C.

26. The composition of Claim 25 wherein said organic compounds containing at least one imide group have a melting point above 7 The composition of Claim 25 wherein said organic compounds containing at least one imide group comprise N,N'- arylenediphthalimides wherein the arylene group includes phenylene, diphenylene, naphthylene and sulfone bridged bisphenyls; tetrabrominated phthalimides;

N,N'bis(dibromocyclohexanedicarboxyimides) with bridging groups, and N,N'-alkylenebis(tetrahalophthalimides).

28. The composition of Claim 25 wherein said imide group containing compounds have the following formula:

wherein both n and m are either 1 or 0; X is selected from halogen, and hydrogen, and

R is selected from the group consisting of one or more of a Ci to C₆ alkyl group, a single bond, a phenylene group, a toluene group, a cyclohexylene group, a bis phenyl methane group, a bis cyclohexylmethane group, and a naphthylene group.

29. The composition of Claim 27 wherein said imide group containing compounds are N,N'-alkylenebis(tetrahalophthalimides) having the formula:

wherein R is a Ci-Cβ alkyl group, and Hal represents a halogen atom.

30. The composition of Claims 28 or 29 wherein said halogen atom is selected from the group consisting of chlorine and bromine.

31. The composition of Claim 30 wherein said halogen or halogen atom is bromine.

32. The composition of Claim 29 wherein R is ethyl.

33. The composition of Claim 29 wherein said imide group containing compounds are brominated phthalimides made from aromatic or aliphatic diamines and from tetrabromophthalic anhydride or tetrabromophthalic acid.

34. The composition of Claim 33 wherein said diamines are selected from the group consisting of ethylene diamine and hydrazine.

35. The composition of Claim 33 wherein said imide group containing compound is N, N'-ethylenebis(tetrabromophthalimide).

36. The composition of Claim 1 wherein said sodium antimonate is substantially free of Sb+3.

37 The composition of Claim 1 wherein said sodium antimonate contains less than 1 mole percent of Sb+3 based on the total mole % of antimony present in the sodium antimonate.

38. The composition of Claim 1 wherein the amount of halogenated phthalimide(s) and sodium antimonate in the composition results in a weight ratio of 5: 1 to 10: 1.

39. The composition of Claim 38 wherein the amount of halogenated phthalimide(s) and sodium antimonate present in said composition results in a weight ratio of 8:1 of brominated phthalimide(s):sodιum antimonate.

40. The composition of Claim 24 additionally comprising one or more phosphorous based compounds.

41. The composition of Claim 40 wherein said phosphorous based compounds are selected from the group consisting of phosphites and phosphonites.

42. The composition of Claim 41 wherein said phosphorous based compounds are one or more phosphites.

43. The composition of Claim 42 wherein said one or more phosphites is bis(2,4-di-t-butylphenyl)pentaerythritol diphosphite.

44. The composition of Claim 24 wherein said reinforcing agents are selected from the group consisting of mica, clay, talc, wollastonite, and calcium carbonate.

45 The composition of Claim 1 wherein said reinforcing fiber is selected from the group consisting of carbon fibers and glass fibers

46. The composition of Claim 45 wherein said reinforcing fiber is glass fiber.

47. The composition of Claim 46 wherein said glass fibers are present at from 0.1 to 45% by weight based on the total weight of the polymer composition.

48. The composition of Claim 46 wherein said glass fibers are chopped glass strands having a length of from about 1/8 inch to about 2 inches.

49. The composition of Claim 48 wherein said glass fibers are chopped glass strands having a length of from about 1/8 inch to about 1/4 inch.

50. The composition of Claim 46 wherein said glass fibers are coated with polyurethane.