WO2011120686A1

WO2011120686A1 - Thermally oxidatively stable carbonate phosphite copolymer

Info

Publication number: WO2011120686A1
Application number: PCT/EP2011/001600
Authority: WO
Inventors: Günter A. JÜPTNER
Original assignee: Styron Europe Gmbh
Priority date: 2010-03-31
Filing date: 2011-03-30
Publication date: 2011-10-06
Also published as: TW201144356A

Abstract

The present invention relates to carbonate phosphite copolymers having an effective amount of a phosphorous compound copolymerized therein to render the carbonate phosphite copolymer thermally oxidatively stabile and methods to make said copolymer. A preferred carbonate copolymer is the polymerization product resulting from the phosgenation of the comonomers bisphenol A and tris(4-hydroxy-2, 2- diphenylpropane)phosphite.

Description

THERMALLY OXIDATTVELY STABLE CARBONATE PHOSPHITE COPOLYMER

FIELD OF THE INVENTION

The present invention relates to carbonate polymers having an effective amount of a phosphorous compound, preferably tris(4-hydroxy-2, 2-diphenylpropane)phosphite, copolymerized therein to render the carbonate phosphite copolymer thermally oxidatively stabile resin with low plate-out behavior and methods to make said copolymer.

BACKGROUND OF THE INVENTION

Polycarbonate resins offer an excellent balance of properties with respect to transparency, toughness, dimensional stability and heat resistance. These properties make polycarbonate an ideal choice for the preparation of many types of molded, shaped or otherwise fabricated articles, especially including electronic storage applications (CDs, DVDs, and the like), medical applications, sheeting or other structures and parts to be used in glazing and other outdoor applications. However, polycarbonates, like most organic polymers, are subject to oxidation, especially thermal oxidation. Typical manifestations of thermal oxidation in polycarbonate are yellowing, loss of impact strength, and elongation which can result in loss of transparency and undesired affects to surface appearance such as cracking and gloss changes. Since polycarbonates derive much of their value and utility from their excellent optical properties, i.e., low color and high clarity and their toughness, protection against thermal oxidation is vital.

Various methods have been attempted to stabilize polycarbonate to thermal oxidation, including (1) addition of antioxidant compounds and (2) structural modification of the carbonate backbone by copolymerizing therein an antioxidant compound.

The conventional approach used in all commercial polycarbonate products is the addition of an antioxidant stabilizer, e.g., the additive approach. Phosphite compounds have been found to be an especially effective family of compounds for oxidative stabilization of polycarbonates. For examples of phosphite stabilizers, see 3,305,520; 4,066,611;

4,073,769; 4,088,709; 4,427,813; and 4,254,014; or in combination with other stabilizers, see EP 825,226, JP 10-044,356; JP 10-044,357; and JP 10-044,358; JP 04-103,626; JP 04- 159,354 and JP 10-138,435.

However, during the processing of polycarbonates, antioxidant additives are prone to leaching from or migrating out of the carbonate polymer and collecting on the

extrusion/molding equipment and/or mold and/or the molded article. This loss of the antioxidant is referred to as juicing and/or mold sweat during injection molding or fuming, blooming, and or plate-out in sheet extrusion. Plate-out is objectionable because it is a coating which gradually forms on the metal surfaces of molds during the processing of plastics. The coating is a result of the migration and deposition of one or more resin components, such as a lubricants, stabilizers, plasticizers and short chain polycarbonate oligomers, onto the mold and/or processing equipment. Plate-out from the commonly used antioxidant additives, specifically low molecular weight phosphite additives, is difficult to remove for a variety of reasons including partial hydrolysis of the phosphite group forming phosphoric acidic groups, which in turn attack or etch the metallic surfaces of the mold and afford mechanical binding sights between the metal and partially hydrolyzed phosphite additives. These kinds of deposits are strongly bound on the surface metal surface and are difficult to remove.

These effects have several detrimental effects: Manufacturing costs increase because of (1) reduced production rates due to frequent, necessary cleaning operations of the equipment and (2) higher reject rates because of build-up of the antioxidant on the molded or extruded article. Furthermore, the reduced level of antioxidant in the polycarbonate increases the susceptible to yellowing, loss of impact strength, and elongation in the molded/extruded article.

Attempts to reduce the juicing/plate-out problem by copolymerization of a phosphite compound into backbone of a carbonate polymer have met with limited technical success and no commercial success. For an example of the latter, US 3,578,634 discloses copolymerization of phosphorous trichloride into the backbone of a polycarbonate by solution polymerization process. On the small scale disclosed in the patent, the products of this process showed limited color stability improvement. However, the disclosed solution process to manufacture said polycarbonate is only useful as a lab scale process; it has not been extrapolated to a viable commercial scale polycarbonate manufacturing process primarily because in the common commercial interfacial processes, the phosphorous trichloride is hydrolyzed to phosphoric acid.

Methods to overcome the undesired hydrolysis of phosphorous trichloride have been devised wherein attempts to copolymerize aryl substituted phosphonic dichlorides or aryl substituted dichloro phosphines have been disclosed, see USP 4,444,978. While low levels of phosphorous has been shown to make it into the backbone of the carbonate copolymer, the resultant products demonstrate significantly more initial color and subsequent color generation upon heat aging than the controls. USP 4,444,978 further discloses exotic di- or tri- substituted phosphite oligomers with up to 200 monomeric units wherein the color stability of the carbonate copolymer is improved. However, the '978 patent is completely silent as to what effects these exotic comonomers have on the other properties (i.e., mechanical, thermal, Theological, and physical properties) of the resulting carbonate copolymers.

It would be desirable to have a carbonate phosphite copolymer that can be produced in commercial polycarbonate manufacturing processes, which demonstrates good thermal oxidative stability without detrimental effects to other key properties, while further demonstrating good viscosity properties with a reduced level of juicing/plate-out to equipment, molds, and molded and/or extruded articles.

SUMMARY OF THE INVENTION

The present invention is a method to produce such a thermally oxidatively stable carbonate phosphite copolymer comprising the steps of:

(a) polymerizing a dihydric phenol and a carbonate precursor in the presence of an organo phosphite of the formula:

P-(0-Z-OH)₃ wherein Z is a xylene glycol radical, a resorcinol radical, a hydroquinone radical, a catechol radical or has the formula:

where X is a single bond, a divalent hydrocarbon radical containing 1-15 carbon atoms, or o o o

II II II

-S- , -S- , -S- , -O- , or -C- ,

O

and

Y is independently hydrogen, chlorine, bromine, fluorine, or a monovalent hydrocarbon radical such as an alkyl group of 1-4 carbons, an aryl group of 6-8 carbons such as phenyl, tolyl, xylyl, an oxyalkyl group of 1-4 carbons or an oxyaryl group of 6-8 carbons and

n is independently an integer from 1 to 4,

and

(b) recovering the carbonate copolymer, preferably having a weight average molecular weight of from 16,000 g/mole to 45,000 g/mole,

wherein the carbonate copolymer has an elemental phosphorous content of from about 5 ppm to about 5000 ppm, more preferably from 10 ppm to 500 ppm based on the total weight of the copolymer, and preferably Z is a bisphenol A radical.

In an alternative embodiment of the process of the present invention disclosed herein above, the organo phosphite in step (a) has the formula:

(R,-0)_m-P-(0-Z-OH)„ 6 wherein m is 1 or 2 and n is 1 or 2 with the proviso that m + n equal 3, Ri is independently phenyl, p-tert-butyl phenyl, nonyl-phenyl or octyl phenyl group, preferably Z is a bisphenol A radical, n equals 1, m equals 2, and both Ri are p-tert-butyl phenol. In one embodiment of the process of the present invention the organo phosphite is an isolated solid in greater than 85 percent by weight purity.

In another embodiment of the present invention, the organo phosphite is an insitu product not isolated from its reaction by-products and is present in the reaction mixture in an amount of at least 60 weight percent based on the weight of all the reaction products.

BRIEF DESCRIPTIONS OF THE DRAWINGS FIG. 1 shows the structures and weight percents for the reaction products of Example 1.

FIG. 2 is a plot comparing oven aging color stability for carbonate (co)polymers. FIG. 3 is a plot comparing viscosity for carbonate (co)polymers.

FIG. 4 is a plot comparing the ratio of the viscous modulus versus the elastic modulus (tan delta) for carbonate (co)polymers.

DETAILED DESCRIPTION OF THE INVENTION

Useful dihydric phenols employed in the practice of the present invention are of the general formula HO-M-OH, wherein M comprises a mono- or poly-aromatic diradical of 6- 30 carbon atoms, to which the phenolic oxygen atoms are directly linked. Preferably, both phenolic hydroxy groups in the dihydric phenol HO-M-OH are arranged in para-positions on the aromatic ring(s). The dihydric phenols employed in the process of the present invention include the bis(aryl-hydroxy-phenyl)alkylidenes including their aromatically and aliphatically substituted derivatives, such as disclosed in USP 2,999,835; 3,038,365;

3,334,154 and 4,299,928; and aromatic diols such as described in USP 3,169,121. Among the most preferred dihydric phenol suitable for production of polycarbonate in the present invention are bisphenol A, bisphenol A P, bisphenol F, tetrabromo bisphenol A, and tetramethyl bisphenol A. The most preferred dihydric phenol is bisphenol A.

A suitable carbonate precursor for use in the present is a carbonyl halide or an acyl halide, of which, the most preferred is phosgene. Phosgene is contacted with the dihydric phenol compound in the aqueous alkaline solution and can be added as a solution in the water-immiscible non-reactive organic solvent and thoroughly mixed with the aqueous phase or can be bubbled into the reaction mixture in the form of a gas and preferentially dissolve and locate in the organic phase. The carbonate copolymers of the present invention comprise a small, but effective amount of phosphorous copolymerized into the carbonate copolymer backbone. Preferably, the comonomer is an organo phosphite of the formula:

1

P-(0-Z-OH)₃ wherein Z is a divalent residue (derived from a dihydric phenol) bonded to phosphorous and a hydroxyl group. The dihydric phenol from which Z is derived is selected from the dihydric phenols listed hereinabove. The dihydric phenol from which Z is derived may be the same as M (HO-Z-OH = M) or different from M (HO-Z-OH≠ M).

Z comprises a mono- or poly-aromatic diradical of 6-30 carbon atoms, to which phenolic oxygen atoms are directly linked. Z may be the diradical derivative of a dihydric mononuclear phenol, preferably xylene glycol, resorcinol, hydroquinone, or catechol.

Alternatively, Z may be a dihydric polynuclear phenol having the formula:

where X is a single bond, a divalent hydrocarbon radical containing 1-15 carbon atoms, or

O II

-S- , -S- , - -SS-- , -O- , or -C- ,

II

O

and

Y is independently hydrogen, chlorine, bromine, fluorine, or a monovalent hydrocarbon radical such as an alkyl group of 1-4 carbons, an aryl group of 6-8 carbons such as phenyl, tolyl, xylyl, an oxyalkyl group of 1-4 carbons or an oxyaryl group of 6-8 carbons and n is independently an integer from 1 to 4. Preferably Z is a bisphenol A radical and the organo phosphite is tris(4-hydroxy-2, 2- diphenyl-propane)phosphite:

The carbonate phosphite copolymers of the present invention have the following formula:

p_(0_Z-R)₃ wherein Z is defined herein above and R is a polycarbonate backbone derived from an above described dihydric phenol and carbonate precursor, preferably bisphenol A and phosgene.

In a preferred embodiment of the present invention, dihydric phenol diradical of the organo phosphite (Z) is derived from the same dihydric phenol (M) that comprises the backbone of the carbonate polymer R (i.e., HO-Z-OH = M), the carbonate phosphite copolymer can be represented by the following formula:

P-(0-R)₃. 5

A preferred carbonate phosphite copolymer of the present invention comprises a carbonate copolymer from the polymerization reaction of bisphenol A and tris(4-hydroxy-2, 2-diphenyl-propane)phosphite 3 in the presence of phosgene.

In another embodiment the comonomer is an organo phosphite of the formula:

D

(R,-0)_m-P-(0-Z-OH)„ wherein m is 1 or 2 and n is 1 or 2 with the proviso that m + n equal 3 and

Ri is (independently if m equal 2) a phenolic radical, preferably phenyl, p-tert-butyl phenyl, nonyl-phenyl or octyl phenyl group. These phosphite esters with mixed phenyl groups can be prepared by using a mixture of the bifunctional and monofunctional phenols, as e.g. phenol, p-tert-butyl phenol, butyl phenol, nonyl-phenol, or octyl phenol. The phosphite comonomer is copolymerized into the carbonate copolymer of the present invention to give an amount of elemental phosphorous in the copolymer backbone equal to or greater than about 1 parts per million (ppm), preferably 5 ppm, preferably 10 ppm, and more preferably 20 ppm, wherein ppm are based on the total weight of the carbonate copolymer. The phosphite comonomer is copolymerized into the carbonate copolymer of the present invention to give an amount of elemental phosphorous in the copolymer backbone equal to or less than about 10,000 ppm, preferably 5,000 ppm, preferably 1,000 ppm, preferably 500 ppm, preferably 100 ppm, and more preferably 50 ppm, wherein ppm are based on the total weight of the carbonate copolymer.

Any process to manufacture the organo phosphite to be used in the present invention is acceptable and the process is not particularly limited. The organo phosphite may be made in a non-continuous (batch) process or a continuous process. The organo phosphite may be isolated as relatively pure component (i.e., in solid form which has been separated from solvents, unreacted reactants, and/or reaction byproducts of it synthesis and comprising greater than 85 percent by weight of the desired phosphite, preferably greater than 90 percent, preferably greater than 95 percent, and more preferably greater than 99 percent by weight of the desired phosphite) or used as an intermediate insitu product. An insitu product is not isolated from its typical reaction by-products (notably mono-, di-, cyclic- and/or oligomeric-phosphite esters and/or phosphate esters) which will, once copolymerize into the carbonate copolymer backbone, also provide thermal oxidative stability to the copolymer and, since bound in the polymer's backbone, are resistant to juicing/plate-out. Preferably, if the phosphite is added as an insitu product, the desired phosphite is present in the reaction mixture in an amount of equal to or greater than about 60 weight percent, preferably equal to or greater than about 70 weight percent, preferably equal to or grater than about 75 weight percent, preferably equal to or grater than about 80 weight percent, preferably equal to or grater than about 85 weight percent, preferably equal to or grater than about 90 weight percent, preferably equal to or grater than about 95 weight percent, and more preferably equal to or grater than about 98 weight percent, wherein weight percent is based on the total weight of the reaction products.

In one embodiment, the organo phosphites for use in the present invention are prepared in a non-contiunoius batch method using bisphenol A and phosphorus trichloride. Bisphenol-A (bis A) is added to solution of dichloromethane (MeCl₂) and triethyl amine (TEA). To this solution a mixture of phosphorous trichloride (PC1₃) in MeCl₂ is added. This mixture is reacted for typically up to 120 minutes, but more preferably up to 30 minutes and the desired organo phosphite may be isolated or used unisolated along with any by products in the form of the reaction mixture. The temperature during the reaction for ambient pressure is between 0°C to 40°C, preferably 25°C to 35°C. At elevated pressures, the temperature may be increase too as much as 100°C.

Suitable molar ratios of TEA:PC1₃ are between 1: 10, preferably from 2.5:4, and more preferably from 3.5:4.0. Suitable molar ratios of bis A:PC1₃ are from 1:50, preferably from 3: 10, and more preferably from 2.5:6. Suitable weight ratios of MeCl₂:bisA are from 1 : 100, preferably from 5:30, and more preferably from 10: 15. Suitable molar ratios of TEA:bisA from 0.1:5, more preferably 0.5:1.5.

For example, suitable feeds for making an organo phosphite mixture from bis A is: 20.2 mumole bis A, 24.7 mmole TEA, and 6.85 mmole PC1₃ which results in the following molar ratios (mole/mole): BisA:PCl₃of 2.95, TEA:bis A of 1.22, and TEA/PC1₃ of 3.61.

In one embodiment of the process of present invention, the organo phosphite is made by a continuous process using the above given ratios of raw materials by continuously adding bis A to a mixture of MeCl₂ and TEA in a stirred reactor, this mixture is then continuously pumped to a second reactor (vessel or pipe) containing PC1₃ dissolved in MeCl₂ (or optionally pure PC1₃) and allowed an adequate reaction time to form the desired phosphite ester intermediate(s) then the reaction mixture is fed into the carbonate polymerization process.

In another embodiment of the process of present invention, the organo phosphite is made by a continuous process using the above given ratios of raw materials by continuously adding TEA to a solution or slurry of bis A in MeCl₂ in a stirred reactor, this mixture is then continuously pumped into a second reactor (vessel or pipe) containing a solution of PC1₃ in MeCl₂ (or optionally pure PCI₃) and allowed an adequate reaction time to form the desired phosphite ester intermediate(s) then the reaction mixture is fed into the carbonate polymerization process.

In yet another embodiment of the process of present invention, the organo phosphite is made by a continuous process using the above given ratios of raw materials by continuously adding a solution or a slurry of bis A in MeCl₂ from a first stirred vessel continuously into a second vessel or a pipe system, where pure TEA or preferably a TEA/MeCl₂ solution is added, to dissolve the bis A. This solution is pumped into a second stirred vessel or a pipe, where a solution of PC1₃ in MeCl₂ (or optionally pure PCI3) is added. After an adequate residence time to form the desired phosphite ester intermediate(s) then the reaction mixture is fed into the carbonate polymerization process.

Organo phosphite reaction mixtures may be analyzed using a combination of high performance liquid chromatography (HPLC) combined with a mass spectrometer (MS). The MS analysis defines phosphite/phosphate structures which are correlated to HPLC peaks/retention times. Once the residence time versus structure calibration is completed, reaction mixtures may be analyzed on a second HPLC operating under similar conditions equipped with a UV detector. Quantitative analysis of each species is based on the size of the signals.

Suitable types and amounts of chain terminators for use in the process of the present invention can be employed to obtain the desired molecular weight and branching degrees in the carbonate copolymer. Preferred chain terminators useful for the production of carbonate copolymers in the present invention are phenol and the derivatives thereof, for example phenol, para-t-butyl phenol (PTBP), p-cumyl phenol and para-t-octyl phenol (4-(l, 1, 2, 2- tetramethylbutyl)-phenol or PTOP).

In addition to polymerizing phosphorous into the backbone of the carbonate copolymer, the organo phosphite comonomer acts as a branching agent. If a higher degree of branching is desired optionally branching agents such as phloroglucin; phloroglucid; l,l,l-tri(4-hydroxyphenyl)ethane; trimellitic acid; trimellitic trichloride; pyromellitic acid; benzophenonetetracarboxylic acid and acid chlorides thereof; 2,6-bis(2-hydroxy-5- methylbenzyl)-4-methylphenol and l,3,5-tri(4-hydroxyphenyl)benzene can be used. If used the carbonate copolymer of the present invention these branching agents may be used in the range of from about 0.0005 to about 0.1 mole branching agent per mole of dihydroxy compound, preferably from about 0.001 to about 0.01, and more preferably from about 0.002 to about 0.005 mole branching agent per mole of dihydroxy compound.

Suitable coupling catalyst for use in the carbonate copolymers of the present invention are tertiary amines including trimethylamine, tributylamine, 4-N,N- dimethylaminopyridine, with triethylamine being most preferred, for example see USP 6,225,436; 5,321 ,116; and 5,412,064, all of which are incorporated herein in their entirety.

Suitable coupling catalyst for use in the carbonate copolymers of the present invention are tertiary amines including trimethylamine, tributylamine, 4-N,N- dimethylaminopyridine, with triethylamine being most preferred, for example see

USP 6,225,436; 5,321,116; and 5,412,064, all of which are incorporated herein in their entirety.

Polycarbonate resins may be produced by the transesterification process or by the interfacial polymerization process. The carbonate copolymers of the present invention are preferably made by a standard interfacial process which can be done either batchwise or continuously. As is known, a standard interfacial process (also referred to as phase boundary process) for aromatic carbonate polymer polymerization involves the reaction of the dihydric phenol such as a bisphenol A, and the carbonate precursor such as phosgene. The initial stage of the interfacial process is the monomer preparation. The bisphenol A is at least partially dissolved and deprotonated in an aqueous alkaline solution to form a bisphenolate A (phenate). The phosgene is supplied to the process, optionally dissolved in an inert organic solvent which forms the second of the two phases which initially serves as a solvent for the phosgene passed in, but in the course of the reaction also acts as a medium for the arylchlorocarbonates and oligocarbonates formed during the oligomerization process.

The aqueous alkaline solution can be formed in water by adding base such as caustic soda, NaOH. Base is typically used over the course of the interfacial polymerization and further added to the reaction mixture where appropriate to maintain the proper pH. The caustic soda is added to the reaction mixture to adjust the pH of the mixture to a level at which the dihydric phenol compound is at least partially converted to dianionic form. A reducing agent such as sodium sulfite or sodium dithionite can also be advantageously added to the reaction mixture as well.

The other phase of the two phase mixture is a non-reactive organic solvent immiscible with water and in which the carbonate precursor and polycarbonate product are typically soluble. Representative solvents include chlorinated hydrocarbons with methylene chloride, 1,2-dichloroethane, tetrachloroethane, chlorobenzene, and chloroform preferred.

Both phases are mixed in a manner which is sufficient to disperse or suspend droplets of the solvent containing the carbonate precursor in or otherwise contact the precursor with the aqueous alkaline mixture. Reaction between the carbonate precursor and the phenate reactant in the aqueous phases yields primarily the bis-ester of the carbonate precursor with the dihydric phenol compound which can further react with more dihydric phenol units to form longer chain oligomers.

With the addition of the coupling catalyst, the coupling reactions occur between ester moieties to couple/polymerize the oligomers into the carbonate polymer. Typically, the catalyst is added during or at a point after phosgenation. The desired molecular weight of the polycarbonate is dictated by the ratio of monomer to chain terminator.

A chain terminator is typically used and can be added to with or after the monomer preparation, during or after phosgenation or during or after the oligomerization and/or condensation steps.

The final stage of the interfacial process comprises obtaining the finished carbonate copolymer. Upon completion of polymerization, the organic and aqueous phases are separated to allow purification of the organic phase and recovery of the polycarbonate product therefrom. The organic phase is washed as needed with dilute acid, water and/or dilute base until free of unreacted monomer, residual process chemicals such as the coupling catalyst and/or other electrolytes. Recovery of the carbonate copolymer product can be affected by spray drying, steam devolatilization, direct devolatilization in a vented extruder, precipitation by use of an anti-solvent. The finished carbonate copolymer of the present invention may be recovered in a flake or pellet form.

In general, by whatever production technique it is prepared and whichever type or types it is, the carbonate copolymer of the present invention should have a molecular weight that provides the desired balance of processing features (melt flow rate, melt strength, shear sensitivity, and the like) and physical properties (toughness, surface properties, and the like) according to the known trade-offs between these.

In general, desirable weight average molecular weights for the carbonate copolymer of the present invention are equal to or greater than about 10,000 gram per mole (g/mole), preferably equal to or greater than about 16,000 g/mole, more preferably equal to or greater than about 18,000, more preferably equal to or greater than about 20,000 g mole, more preferably equal to or greater than about 22,000 g/mole, and even more preferably equal to or greater than about 25,000 g/mole. In order to obtain polymer with minimized levels of gels and other beneficial effects, it has been found that the weight average molecular weight of a polymer should be equal to or less than about 100,000 g/mole, preferably equal to or less than about 80,000 g mole, preferably equal to or less than about 60,000 g mole, preferably equal to or less than about 45,000 g/mole, preferably equal to or less than about 40,000 g/mole, and more preferably equal to or less than about 35,000 g/mole. Unless otherwise noted, weight average molecular weight is intended when referring to molecular weight.

In this range it has been found that the carbonate copolymer of the present invention should have a melt flow rate (MFR) determined according to ASTM D 1238 under conditions of 300°C and 1.2 kilograms mass (300°C/1.2 kg) of equal to or greater than about 1.5 grams per 10 minutes (g/10 min), preferably equal to or greater than about 2 g/10 min, preferably equal to or greater than about 2.5 g/10 min, and most preferably equal to or greater than about 3.0 g/10 min. It has been found that the carbonate copolymer of the present invention should have a melt flow rate preferably equal to or less than about 100 g/10 min, preferably equal to or less than about 80 g/10 min, preferably equal to or less than about 45 g/10 min, preferably equal to or less than about 30 g/10 min, preferably equal to or less than about 22 g/10 min, preferably equal to or less than about 15 g/10 min and more preferably equal to or less than about 12 g/10 min.

If an additional branching agent is employed in the process of the present invention, in general, it can be indirectly determined whether there is a sufficient degree of branching in the carbonate copolymer by measuring the change in shear sensitivity due to the incorporation of the branched carbonate polymer in a carbonate polymer blend composition. These measurements of shear sensitivity can be done by standard techniques with dynamic mechanical spectroscopy (DMS) or by capillary rheometry.

It is understood that for the carbonate copolymer of the present invention, the carbonate copolymer comprise both a branched carbonate copolymer component (from the copolymerization of the organo phosphite) and a non-branched linear homopolymer component (containing no organo phosphite). It is further understood that the carbonate copolymer according to the present invention may be a single component carbonate copolymer directly obtained from a polymerization process. It may also be blended with a one or more carbonate homopolymer (not the non-organo phosphite containing component described herein above), branched carbonate homopolymer, or combinations thereof. On the other hand, the carbonate copolymer can also be based on a combination of two components of the same type of carbonate copolymer with differing molecular weights and melt flow rates and/or levels of elemental phosphorous that are blended to obtain the desired intermediate melt flow rate/phosphorous level product.

The carbonate copolymer of the present invention may further comprise other known additives and/or stabilizers in amounts commonly used in carbonate polymer compositions of this type, for example pigments, dyes, UV stabilizers, X-ray stabilizers, light stabilizers, mold releases, charring agents, flame retardants, or processing stabilizers which are described, for example, in USP 5,288,778.

The types and amounts of the additive(s) to be included in the carbonate copolymer according to the present invention will vary depending upon the desired balance of combinations of properties and cost. In general, to provide noticeable stabilizing effects and benefits, the additive(s) should be used at levels of at least about 5 ppm based on weight of carbonate copolymer into which the compound is being incorporated, preferably at least about 25 ppm, more preferably at least about 50 ppm and most preferably at least about 100 ppm. In general, at higher concentration levels there is diminishing benefit and levels of these compounds should not be greater than about 5000 ppm, preferably not greater than about 3000 ppm, and most preferably not greater than about 2000 ppm.

EXAMPLES

Example 1 is the procedure for the preparation tris(4-hydroxy-2, 2-diphenyl- propane)phosphite an organo phosphite of the present invention which is used in the succeeding Examples. The organo phosphite is tris(4-hydroxy-2, 2-diphenyl- propane)phosphite is prepared in a batch method using bisphenol A and phosphorus trichloride and is used as an unisolated intermediate. 4.6 g (20.2 mmole) bisphenol A is added to solution of 2.5 g 3.42 ml (24.2 mmole) triethylamine in 60 ml of dichloromethane in a 200 ml round bottom flask. To this solution a mixture is added 0.94 g/0.6 ml (6.8 mmole) of phosphorous trichloride in 10 ml dichloromethane. This mixture is reacted for 30 minutes starting at -2°C and warming to 24°C. The tris(4-hydroxy-2, 2-diphenyl- propane)phosphite is not isolated but added, along with any reaction by products, as a solution in methylene chloride to the carbonate polymerization process. Typically, the tris(4-hydroxy-2, 2-diphenyl-propane)phosphite (C45H₄5O7P) is present in the reaction mixture at about 75 weight percent as determined by HPLC MS analysis (FIG. 1).

Examples 2 and 3 and Comparative Examples A and B are (co)polymerized in a temperature controlled, agitated, 15-litre, jacketed glass reactor. The supplies of water, caustic, dichloromethane, tertiary-butyl-phenol solution and triethylamine solution are connected with a CAMELE™ control system to provide proper feed rates and are padded with nitrogen to prevent oxidation of the described raw materials. A pH electrode in the reactor allows the addition of additives at a controlled pH level during phosgenation. For the polymerizations described below the following raw material amounts and conditions are used:

Bisphenol-A (BP A): 0.700kg (3 moles);

Water : 3.870 kg;

Caustic solution (30 weight percent NaOH in water): 0.9 kg;

Methylene chloride: 2.000 kg;

Phosgene flow: 0.06 g/s (0.6 mmole/s);

Total phosgene feed: 405 g (4.1 mole);

Reaction temperature: between 20°C and 40°C, normally 25°C;

Agitator speed: 250 rpm;

Tertiary-butyl phenol (PTBP): 200 mmoles in 550 grams methylene chloride);and Triethyl amine (TEA): 6.6g TEA (65 mmol TEA) in 80 ml methylene chloride.

The bisphenol-A (0.70 kg/3 moles) is deoxygenated in a glass flask under vacuum for 10 minutes. Then it is kept under nitrogen to remove traces of oxygen. The

deoxygenated bisphenol-A is added into the constantly stirred 20-litre double wall glass reactor which is purged with nitrogen. To dissolve the bisphenol-A, argon purged water (3.87 kg) and the caustic (0.9 kg of 30 weight percent sodium hydroxide) are added.

During dissolution nitrogen is blanketed above the mixture to exclude oxygen. After all the bisphenol-A is dissolved, 2.0 kg dichloromethane is added, the reactor is closed and stirred for 20 minutes under an argon atmosphere and then phosgenation is started. During phosgenation, and throughout the rest of the polymerization reaction, the reaction mixture is constantly stirred.

After the phosgenation, for Examples 2 and 3 the reaction product of Example 1 is added in to achieve a specified phosphorous content in the final carbonate copolymer, for Comparative Example A no phosphite comonomer or additive is added. For Example 2 5.45 ml of the intermediate phosphite ester mixture of Example 1 is added to the

polymerization. For Example 3, 9.5 ml of the intermediate phosphate ester mixture is added. Then a solution of the TEA dissolved in MeCl₂ is added to the polymerization. After 20 minutes the polymerization is finished. The organic phase comprising the polymer is separated from the aqueous phase. The polymer solution is washed two times with 10 weight percent of hydrochloric acid, followed by a four fold wash with pure water. For Comparative Example B a phosphite additive (not a comonomer) is added to the polymer solution and mixed to achieve a specified phosphorous content in the carbonate polymer. After that, the solvent dichloromethane is removed by steam precipitation and the

(co)polymer is obtained as flakes. Each of the (co)polymers has a target weight average molecular weight of about 40,000 g/mole.

The resulting carbonate (co)polymer flakes are dried 24hours at 80°C under vacuum, extruded, and commuted to pellets. The extrusion is performed on a Brabender 19/25 single screw extruder having a compression ratio of the screw was 1:3, the extrusion temperature 280°C for all five heating zones. The screw speed was limited to 40-45 rpm. In Table 1 the source of phosphorous and amount in Examples 2 and 3 and Comparative Examples A and B are given.

Table 1

For property analysis, each of the carbonate (co)polymers is compression molded into discs having diameters of 40mm and thicknesses of 3mm. The compression molding test specimens are molded from pellets using a Thermo Mini- Jet compression molding machine. About 7g of the pellets are filled into the heated barrel and moulded for 7 minutes at 320°C. After 7 minutes the molten polymer is molded for 30 seconds underl200 bar pressure. The backpressure after moulding is 600 bars for 30 seconds. The resulting discs have a diameter of 40mm and a thickness of 3 mm. Thermal Aging Testing

Compression molded samples are oven aged in a Hereaus 6060 oven at 140°C for up to 500 hours. Yellowness index (YI) is determined prior to aging and periodically up to 500 hours. YI is determined according to ASTM D 1925 on a Hunterlab Colour Quest machine. The resulted were normalized by following equation:

Normalized YI = YI ( at tite beginning [O hrs.]) The results are plotted and shown in FIG. 2. As can be seen, carbonate copolymers of the present invention, Examples 2 and 3 show improved YI and reduced thermal oxidative degradation over the Comparative Examples A without any phosphorous or with

phosphorus or Comparative Example B comprising phosphorous from a phosphite additive. The data showed for the carbonate phosphite copolymer of the present invention

demonstrate the same, or better, thermo oxidative behavior as compared to the additive phosphite.

Plate-Out Migration of phosphorous containing component(s), or plate-out, is preformed by

GC-MS / Pyrolysis (WEB EDMS Method A020708) using a PY-2020iD unit of a Shimadzu GC-MS machine. Testing is performed by placing pellets weighing about 0.5mg in the pyrolyzing unit, purging with nitrogen and then heating for 60 minutes at 325°C, 350°C and 375°C and migrated products are then analyzed by the Gas Chromatography - Mass

Spectroscopy (GC-MS).

The following molar masses are identified for P-168: 57g/mole, 191g mole and 206 g mole. P-168 starts to sublimate out of the carbonate polymer below 325°C.

The following molar masses are for Example 1 : 65 g mole, 165 g mole and

231 g/mole. Migration of phosphorous compounds for carbonate copolymer compositions of the present invention are not observed before 375°C, which is 50°C higher than carbonate polymers comprising P-168 stabilized material. The qualitative plate-out results are summarized in Table 2, none = no detectable plate-out, low minimal and acceptable amount of plate-out, and high = excessive and unacceptable levels of plate-out.

Table 2

Rheological Characterization

Viscosities for the carbonate (co)polymers are determined on a Physica MCR 300

Dynamic Mechanical Spectrometer (DMS). A frequency sweep with an angular frequency from 0.1 -100 ^1/s at est temperature of 300°C was performed. The total amount of

complex viscosity (η) which is expressed in Pa*s, is measured and shown in FIG. 3. The viscose modulus (G") and the elastic modulus (G') and the resulting ratio (tan delta δ, G'VG') is measured and is shown in FIG. 4.

Phosphorous content

The phosphorous content of the polymers is determined by a spectroscopic method which measures the light absorption of a blue phosphate-molybdate complex at a wavelength of 675 nm. For this purpose, a certain amount of polymer is covered with a layer of magnesium oxide and burned in a muffle oven at 900°C. The solid body is dissolved in 20 wt% aqueous sulphuric acid. Subsequently, ammonium molybdate and ascorbic acid are added and the solution is heated. After that, the light absorption of the blue solution is measured in a quartz cuvette. The concentration is calculated by means of a coefficient of extinction of 0.0027 mL/(cm*mg P).

Weight average molecular weight

The weight average molecular weight of the polymers is determined by gel permeation chromatography employing tetrahydrofurane (THF) as fluid phase at a flow rate of 1 mL/min. 5μπι mixed D columns are used for the preparation. The detector is a UV DAD device (diode array detector). The calibration is performed by a polystyrene standard.

Claims

CLAIMS:

1. A method for producing a thermally oxidatively stable carbonate copolymer comprising the steps of:

(a) polymerizing a dihydric phenol and a carbonate precursor in the presence of an organo phosphite of the formula: l

-S- , -S- , -S- , -O- , or -C- ,

O

and

n is independently an integer from 1 to 4,

and

(b) recovering the carbonate copolymer,

wherein the carbonate copolymer has an elemental phosphorous content of from about 5 ppm to about 5000 ppm based on the total weight of the copolymer.

2. A method for producing a thermally oxidatively stable carbonate copolymer comprising the steps of:

(R,-0)_m-P-(0-Z-OH)_n ⁶ wherein m is 1 or 2 and n is 1 or 2 with the proviso that m + n equal 3,

Ri is independently phenyl, p-tert-butyl phenyl, nonyl-phenyl or octyl phenyl group, and

Z is a xylene glycol radical, a resorcinol radical, a hydroquinone radical, a catechol radical or has the formula:

o o o

II II II

-S- , -S- , -S- , -O- , or -C- ,

II

o

and

n is independently an integer from 1 to 4,

and

(b) recovering the carbonate copolymer,

3. The process of Claim 1 wherein Z is a bisphenol A radical.

4. The process of Claim 2 wherein Z is a bisphenol A radical, n equals 1, m equals 2, and both R are p-tert-butyl phenol.

5. The process of Claims 1 or 2 wherein the organo phosphite is an isolated solid in greater than 85 percent by weight purity.

6. The process of Claims 1 or 2 wherein the organo phosphite is an insitu product not isolated from reaction by-products and is present in the reaction mixture in an amount of at least 60 weight percent based on the weight of all the reaction products.

7. The process of Claims 1 or 2 wherein the carbonate polymer comprises from 10 ppm to 500 ppm elemental phosphorous.

8. The process of Claims 1 or 2 wherein the carbonate polymer comprises a weight average molecular weight of from 16,000 g/mole to 45,000 g/mole.