CA1161990A - Process for preparing polycarbonates using amino guanidine or amino amidine catalysts - Google Patents

Abstract

PROCESS FOR PREPARING POLYCARBONATES USING
AMINO GUANIDINE OR AMINO AMIDINE CATALYSTS
Abstract of the Disclosure An interfacial polymerization process for preparing high molecular weight aromatic polycarbonates by reacting a dihydric phenol with a carbonate precursor in the presence of a catalytic amount of an amino amidine or amino guanidine.

Description

116~ CL-1775 This invention is directed to an interfacial poly-merization process for preparing high molecular weight aromatic polycarbonates which comprises reacting, under interfacial polycarbonate- forming conditions, a dihydric phenol and a carbonate precursor in the presence of a catalytic amount of an amino amidine or amino guanadine.
BACKGROUND OF THE INVENTION
Polycarbonates are well known thermoplastic materials finding a wide range of uses, particularly for injection molding applications and as glazing sheet for replacement of window glass. The interfacial polymerization technique, which is one of the methods employed in preparing a poly-carbonate, in general comprises reacting a dihydric phenol and a carbonate precursor in the presence of an aqueous caustic solution containing an alkali or alkaline earth metal hydroxide and an inert organic solvent medium which is a solvent for the polycarbonate as it is formed. While the interfacial polymerization process is generally effective in producing polycarbonates, it suffers from two general disadvantages. Firstly, the rate of reaction is relatively slow. Secondly, there is difficulty in producing high molecular weight aromatic polycarbonates; i.e., those having a weight average molecular weight of about 15,000 or greater. Many techniques, such as those employing ultrasonic waves during the reaction, have been employed to ` remedy these two disadvantages. These techniques have not always proved to be entirely effective and involve the use of cumbersome and expensive equipment. It is advantageous economically to speed up the reaction and to produce high molecular weight aromatic polycarbonates without having to employ extra equipment or more severe reaction conditions.

One such method is the use of catalysts in the i~ter-_._~ , t 1~6~9g~ gC:L-1775 facial polymexization process.
However, relatively little is known about effective catalysis of polycarbonate reactions. The prior art discloses that certain compounds such as tertiary and quanternary amines and their salts (U.S. Patent 3,275,601 to Schnell et al dated September 27, 1966), guanidine compounds (U.S. Patent 3,763,099 to Jaquiss dated October 2, 1973) and ammonia and ammonium compounds (U.S. Patent 4,055,544 to Baggett dated October 25, 1977) are effective catalysts for the interfacial polymerization process for producing polycarbonates.
However, the prior art also teaches that certain organic nitrogen compounds function as molecular weight regulators or chain terminators in the polycarbonate reactions. Thus, the afore-mentioned U.S. Patent 3,275,601 discloses that aniline and methyl aniline function as chain termlnators in the polycarbonate reaction, while U.S. Patent 4,001,184 to Scott dated January 4, 1977 discloses that primary and secondary amines are effective molecular weight regulators.
Furthermore, U.S. Patent 4,111,910 to Baggett dated September 5, 1978 discloses that ammonia, ammonium compounds, primary amines, and secondary amines function as chain terminators in the formation of polycarbonates via the interfacial polymerization process, and U.S. Patent 3,223,678 to Bolgiano dated December 14, 1965 discloses that monoethanolamine and morpholine act to break the polycarbonate chain thereby re-sulting in lower molecular weight polycarbonates.
SUMMARY OF THE [N~ENTION
, This invention is directed to an interfacial poly-merization process for producing high molecular weight aromatic carbonate polymers wherein a dihydric phenol is reacted with a carbonate precursor in the presence of an aqueous caustic solution containing an alkali metal or ' ~ ~9~ 8CL-1775 alkaline earth metal hydroxide and a catalyst which is an amino amidine or amino guanidine.
The reaction of a dihydric phenol such as 2,2~bis (4-hydroxyphenyl) propane with a carbonate precursor such as phosgene results in a high molecular weight aromatic polycarbonate polymer consisting of dihydric phenol derived units bonded to one another through carbonate linkages. The reaction is carried out in the presence of an aqueous caustic solution containing an alkali or alkaline earth metal hydroxide as the acid acceptor and an inert organic solvent medium which is a solvent for the polycarbonate as it is formed. Generally, a molecular weight regulator is also present to control the molecular weight of the polycarbonate polymer. In the process of the present invention, an amino amidine or amino guanidine is present and acts as an effective catalyst to speed up the reaction between the carbonate precursor and the dihydric phenol.
The high molecular weight aromatic carbonate polymers produced in accordance with the practice of this invention include carbonate homopolymers of dihydric phenols or carbonate copolymers of two or more different dihydric phenols. Additionally, the production of high molecular weight thermoplastic randomly branched poIycarbonates and copolyester-polycarbonates are included within the scope of this invention. The randomly branched polycarbonates are prepared by coreacting a polyfunctional organic compound with the afore-described dihydric phenol and carbonate precursor.
The dihydric phenols that can be employed in the practic of this invention are known dihydric phenols in which the sole reactive groups are the two phenolic hydroxyl groups. Some of these are represented by the ~ 08CL-1775 general formula /x /x ~ )n ~ O OH

X X
herein A is a divalent hydrocarbon radical containing 1-15 O O
carbon atoms, -S-, -S-S, -S-, -S-, -O , or -C-, X is o independently selected from the group consisting of hydrogen, halogen, or a monovalent hydrocarbon radical such as alkyl ` ~roup of 1-4 carbons, an aryl group of 6 10 carbons such as phenyl, tolyl, xylyl, naphthyl, an oxyalkyl group of 1-4 carbons or an oxyaryl group of 6-10 carbons and n is 0 or 1.
Typical of some of these dihydric phenols are bis-phenols such as bis(4-hydroxyphenyl) methane, 2,2-bis (4-hydroxyphenyl) propane (also known as bisphenol-A), 2,2 -bis(4-hydroxy-3-methylphenyl)propane, 4,4-bis(4-hydroxyphenyl) heptane, 2,2-bis(4-hydroxy-3,5-dichlorophenyl)propane,2,2-bis(4-hydroxy-3,5-dibromophenyl)propane, etc., dihydric phenol ethers such as bis(hydroxyphenyl) ether, bis(3,5-dichloro-4-hydroxyphenyl)ether, etc.; dihydroxydiphenyls such as p,p'-dihydroxydiphenyl, 3,3'-dichloro-4.4'-dihydroxydiphenyl, etc.; dihydroxyaryl sulfones such as bis(4-hydroxyphenyl) sulfone, bis(3,5-dimethyl-4-hydroxyphenyl)sulfone, etc., dihydroxy benzenes, resorcinol, hydroquinone, halo-and alkyl-substituted dihydroxy benzenes such as 1,4-dihydroxy-

2,5-dichlorobenzene, 1,4-dihydroxy-3-methylbenzene, etc., and dihydroxy diphenyl sulfides and sulfoxides such as bis (4-hydroxypherlyl) sulfide and bis(4-hydroxyphenyl) sulfoxide, bis (3,5-dibromo-4-hydroxyphenyl)sulfoxide, etc. A variety of additional dihydric phenols are also available and ~re also available and are disclosed in U.S. Patent Nos.

2,999,835 to ~oldberg dated September 12, 1961, 3,028,3~5 to Schnell et al dated April 3, 1962 and 3,153,008 -to Fox dated October 13, 1964.
It is, of course, possible to employ two or more dif-ferent dihydric phenols or a copolymer of a dihydric phenol with glycol or with hydroxy or acid-terminated polyester, or with a dibasic acid in the event a polycarbonate copolymer or interpolymer rather than a homopolymer is desired for use in the preparation of the polycarbonate polymers of this invention. Blends of any of the above dihydric phenols can also be employed, the preferred dihydric phenol being bisphenol-A.
The polyfunctional organic compounds which may be included within the scope of this invention are set forth in U.S. Patent Nos. 3,635,895 to Kramer dated January 18, 1972 and 4,001,184 to Scott dated January 4, 1977. These polyfunctional aromatic compounds contain at least three functional groups which are carboxyl, carboxylic anhydride, haloformyl or mixtures thereof. Examples of these poly-functional aromatic compounds include trimellitic anhydride, trimellitic acid, trimellityl trichloride, 4-chloroformyl phthalic anhydride, pyromellitic acid, pyromellitic dianh-ydride, mellitic acid, mellitic anhydride, trimesic acid, benzophenonetetracarboxylic acid, benzophenonetetracar-boxylic anhydride, and the like. The preferred poly-functional aromatic compounds are trimellitic anhydride or trimellitic acid or their haloformyl derivatives.
Also included herein are blends of a linear polycarbonate and a branched polycarbonate.

The carbonate precursor can be ei-ther a carbonyl halide or a bishalo~ormate. The carbonyl halides include car~
bonyl bromide, carbonyl chloride, and mixtures thereof.

gC:L-1775 The bishaloformates suitable for use include the bis-haloformates oE dihydric phenols such as bischloxoformates of 2,2-bis(4-hydroxyphenyl) propane, 2,2~bis(4-hydroxy-3,5-dichlorophenyl) propane, hydroquinone, and the like, or bishaloformates of glycols such as bishaloformates of ethylene glycol, and the like. While all of the above carbonate precursors are useful, carbonyl chloride, also known as phosgene, is preferred.
By adding monofunctional compounds with are capable reacting with phosgene or with the end groups of the poly-carbonates consisting of the chlorocarbonic acid ester group and which terminate the chains, such as the phenols, e.g., phenol, tertbutylphenyl, cyclohexylphenol, and 2,2-(4,4-hydroxyphenylene-4'-methoxyphenylene)propane, aniline and methylaniline, it is possible to regulate the molecular weight of the polycarbonates.
As mentioned hereinabove, the acid acceptor can be an alkali or alkaline earth metal hydroxide. Illustrative of these acid acceptors are sodium hydroxide, lithium hydroxide, potassium hydroxide, calcium hydroxide, and the like. The amount of acid acceptor present should be sufficient to maintain the pH of the aqueous caustic solution above about 9.
Illustrative of the inert organic solvents which are present during the reaction and which dissolve the poly-carbonate as it is formed are aromatic hydrocarbons and halogenated hydrocarbons such as benzene, toluene, xylene, chlorobenzene, orthodichlorobenzene, chloroform, methylene chloride, càrbon tetrachloride, trichloroethylene and dichloroethane. The solvent is present in an amount effective to solubilize or dissolve substan-tially all of the polycarbonate as it is formed.

; One of the catalytic compounds within the scope of the instant invention are the amino amidines which are represented by the general formulae R N -- N = C ---- N ~ I .
R \ R3 and R N N = C N Z II.

, wherein R and R2 are independently selected from hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, cycloalkyl, substituted cycloalkyl, aryl, substituted aryl, alkaryl and aralkyl radicals; Rl iS selected from alkyl, substituted alkyl, alkenyl, substituted alkenyl, cycloalkyl, substituted cycloalkyl, aryl, substituted aryl, alkaryl, aralkyl, acyl radicals represented as R-C (O) - wherein R iS
as defined above, and substituted acyl radicals; R3 is selected from alkyl, substituted alkyl, alkenyl, sub-stituted alkenyl, cycloalkyl, substituted cycloalkyl, aryl, substituted aryl, aralkyl and alkaryl radicals; and Z is a divalent aliphatic hydrocarbon radical containing from 2 to 7 carbon atoms completing a 3 to 8 membered ring, preferably Z is a divalent saturated aliphatic hydrocarbon radical containing from 2 to 7 carbon atoms completing, in conjunction with the nitrogen, a 3 to 8 membered ring.
The amino guanidine catalyst compounds of the .invention are represented by the general formulae III, IV and V

1~3 - 7 -~CL,- 1775 l I 1 3 R N - N = _ C N _R III.

R N - N = C _ _ N Z
R N _ R3 and R _ N N = C -_ N Z V.

z wherein R-R and Z are as defined above.
Preferred alkyl radicals are those containing from l to about 20 carbon atoms such as methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl, tert-butyl, n-pentyl and various positional isomers thereof, as well as -the straight and branched chain positional isomers of hexyl, heptyl, octyl, nonyl, decyl and the like.
Preferred alkenyl radicals are those containing from 2 to about 20 carbon atoms such as vinyl, propenyl, al~yl, butenyl, 2-methylpropenyl, 3-octenyl, and the like.
Preferred cycloalkyl radicals are those containing from 3 to about 14 carbon atoms as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, dimethylcyclohexyl, propylcyclohexyl, and the like.
Preferred aryl radicals are those containing from 6 to 18 carbon atoms such as phenyl, naphthyl and an-th-racyl.
Preferred aralkyl radicals are those containing from 7 to abou-t 20 carbon atoms such as benzyl, 2-phenylethyl, - scr~ll7s 2-phenylpropyl, cumyl, phenylbutyl, naphthylmethyL, and the like.
Preferred alkaryl radicals are those con~aining from 7 to about 20 carbon atoms such as tolyl, 2,3-xylyl, 2,4-xylyl, pethylphenyl, 2-methyl-1-naphth~l, and the like.
Preferred acyl radicals are those containing from 1 to about 20 carbon atoms such as formyl, acetyl, propanoyl, dodecanoyl, benzoyl, l-naphtoyl, 2-naphtoyl, pivaloyl, and the li]ce.
When substituent groups are present on the afore-described radicals, they are preferably selected from the group consisting of alkyl, hydroxyl, and alkoxy radicals.
Illustrative amino amidines represented by formulae I and II are set forth in Table I below:

TABLE I
(CH3)2N-N=I-N(CH3) 2 (C2H5) 2N-N ~ N(C2H5)2 C3H 7 O -~HN-N=C-NH- O

~ I l 3 O IC 3 0 (~-C(O)-HN-N=C-N~
O f2H5 (~
CH3-N-N=CI-N (CH2CH=CH2)2 C2H5-N-N=C-N O
CH(CH3) 2 H

~ 99 ~ ~CL-1775 The amino amidines employed can 3e o~epared from the a7~ro-priate hydrazines by ~e general me'hods used .or the sy..thesis of amidines as discussed in Open-Chain N_.rosen Compounds, by P.A.S. Smith, W.A. Benjamin Publishers, lg6~, ?~. 177-124, and in the survey article by R.L. Schriner and F.W. .~Je~,ann in Cr.emicai ' Reviews, Vol. 35, p~. 351-425 (1944).
Illustrative amino suanidines represented by formulae III-V
are set forth in Table II below:
, TABLE II
10 G N-C-~ ~ (C~3)2N~ (CH3)2 C2H5-N-C2H5 H~

C2H5 C2H; CH3 C~3 N-C-N N-~-N
'' / 11 \ / 11 \
C2~5 ~ C2H5 H .

H-~-C(O)- ~ C4Hg-~-C4~9 N-C-~ ~ CH~
-' ~ J C~-c~ ' , ~0 C:i3-N- ~ ~ CH3 - c~3-~-C~3 The amino guaniaines employe~ can be p.epared 'rom _he app-o-priate hydrazines by the general met:,oas used or the svn.hesis o~
guanidines, as discussed by P.A.S. Smith in Open-Ch_in Nitro~en Compounds, Vol. 1, pp. 281-2, (1965), W.A. Benjamin Publishers.
The amount of the amino amidine or amino guanidine catalyst present during the reaction is a catalytic amount. By catalytic amount is meant that amount which is effective to catalyze the reaction between the dihydric phenol and the carbonate precursor - to produce the high molecuIar weight polycarbonate. Generally, this amount ranges from about 0.01 to about 10 weight percent based on the weight of the dihydric phenol present, e.g., ~ C~.-177S

bisphenol-A.
The temperature at which this reaction proceeds can vary from below 0C to about 100C. The reaction proceeds satisfactorily at temperatures ranging from about room temperature (25C) to about 50C. Since the reaction is exothermic, the rate of carbonate precursor addition can be used to control the reaction temperature. The amount of carbonate precursor, such as phosgene, required will generally depend upon the amount of dihydric phenol pxesent. Generally, one mole of the carbonate precursor will react with one mole of dihydric phenol to provide the polycarbonate. When a carbonyl halide, such as phosgene, is used as the carbonate precursor, two moles of hydrohalic acid such as HCl are produced by the above reaction.
These two moles of acid are neutralized by the alkali or alkaline earth metal hydroxide acid acceptor present. The foregoing are heréin referred to as stoichiometric or theoretical amounts.
PREFERRED EMBODIMENT OF THE INVENTION
The following examples are set forth to more fully and clearly illustrate the present invention. Although they represent the best mode currently known for carrying out the process of the invention, these examples should be considered as being illustrative rather than limiting the invention. In the examples, all parts and percentages are by weight unless otherwise specified.

This example illustrates an unsuccessful attempt to prepare a high molecular weight aromatic polycarbonate polymer via the interfacial polymerization technique without the presence of a catalyst.
To a reactor fitted with a reflux xondenser and a g ~ ~CL~1775 mechanical agi.tator, there was charyed 57 parts of 2,2-bis (4-hydroxyphenyl) propane, 57 parts of water, 325 parts of methylene chloride, and 1.2 parts of para-tertiarybutylphenol.
Phosgene was then added to the reaction mixture at a rate o 0.65 part per minute for a period of 30 minutes while maintaining the pH at 9 by the addition of a 15% aqueous sodium hydroxide solution. After 30 minutes, the pH was raised to 11.0 by the use of additional amounts of sodium hydroxide solution. Phosgenation was continued for a further 10 minutes at this pH. The material recovered from the reaction was found to have an intrinsic viscosity of 0.12 dl/g. This indicated that the degree of poly-merization was not sufficient for practical applications, the I.V. being measured in methylene chloride at 25C.

This example illustrates the use of one of the catalysts of the invention following the process of Example 1.
To a reactor fitted with a reflux condenser and a mechanical agitator there was charged 57 parts of 2,2-bis (4-hydroxyphenyl) propane, 157 parts of water, 325 parts of methylene chloride, 1.2 parts of para-tert-butylphenol and 0.8 part of 2-(dimethyl)amino-1,1,3,3-tetramethyl-guanidine. Phosgene was then added to this reaction mixture at a rate of 0.65 part per minutes for a period-of 30 minutes while maintaining the pH at 9 by the addition of a 15%
aqueous sodium hydroxide solution. After 30 minutes, the pH
was raised to 13.0 by the use of additional amounts of sodium hydroxide solution. Phosgenation was continued for an ad-ditional 10 minutes at this pH.
The polycarbonate recovered from solution was dried and was found to have an intrinsic viscosity of 0.46 dl/g. This ~6~ 8CI,-1775 indicated the formation of a hiyh molecular weight aromatic polycarbonate.

The procedure of Example 2 was substantially repeated for each of the examples of 3-6 except that the amino-guanidine catalysts listed in Table III were substituted, in the amounts shown, for the catalyst of Example 2.
The intrinsic viscosities of the recovered polycarbonates are also displayed in Table III.
TABLE III

Example Parts by Intrinsic No Aminoguanidine Catalyst Weight Viscosity dl/g

3 2-Anilino-1,1,3,3-bis 1.0 0.43 (pentamethylene)guani-dine

4 2-Benzoylimino 1,1,3,3- 0.8 0.37 tetramethylguanidine 2-Anilino-1,1,3,3-tetra- 0.8 0.41 methylguanidine 6 2-(N-methylcyclohexyl- 1.0 0.44 amino)-1,1,3,3-tetra-ethylguanidine EXAMPLES_7-14 The procedure of Example 2 was substantially repeated for each of the examples 7-14, except that the aminoamidine catalysts listed in Table IV were substi-tuted, in the amounts shown, for the catalyst of Example 2. The in-trinsic viscosities of the recovered polycarbonates are also shown in Table IV.

T~BLE IV

Parts by Intrinslc ENxOample Aminoamidine Catalyst Weight Viscosity dl/q 7 N,N,N'-Trimethyl-N'- 0.8 0.38 phenylmethanehydrazon-amide 8 N,NI,N'-Trimethylben-zenecarbohydrazonamide 1.2 0.40 9 N,N'-Dimethyl-N'-phenyl- 1.3 0.36 benzenecarbohydrozonamide N,N,N',N'-Tetramethyl-benzenecarbohydrazon- 1.2 0.43 amide 11 N,N,N',N'-Tetraethyl ethanehydrazonamide 0.8 0.48 12 N,N,N',N'-Tetramethyl- 0.7 0.48 propanehydrazonamide 13 N'-Formyl-N,N-dimethyl- 1.0 0.32 N'-phenylmethanehydra-zonamide 14 N'-Benzyl-N'-formyl-N,N- l.l 0.38 dimethylmethanehydrazon-amide As can be seen by comparision of Example l with Examples 2-14, the use of the amidine catalysts of the invention generally results in the relatively rapid production of high molecular weight aromatic polycarbonates via the interfacial polymerization technique while, in the absence of a catalyst (Example l), the interfacial polymerization technique is generally ineffective in producing high molecular weight aromatic polycarbonates under substan-tially identical reaction conditions.

Claims (5)

The embodiments of the invention in which an exclu-sive property or privilege is claimed are defined as follows:

1. An interfacial polymerization process for preparing a high molecular weight aromatic polycarbonate which comprises reacting, under interfacial polycarbonate-forming conditions, a dihydric phenol and a carbonate precursor in the presence of an aqueous caustic solution containing an alkali metal or an alkaline earth metal hydroxide and a catalyst which is an amino amidine or an amino guanidine.

2. The process of claim 1 wherein said amino amidine is represented by the general formulae and wherein R and R2 are independently selected from the group consisting of hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, cycloalkyl, substituted cycloalkyl, aryl, substituted aryl, alkaryl, and aralkyl radicals, R1 is selected from the group consisting of alkyl, substituted alkyl, alkenyl, substituted alkenyl, cycloalkyl, substituted cycloalkyl, aryl, substituted aryl, alkaryl, aralkyl; acyl radicals represented by R-C(O)- wherein R is as defined above, and substituted acyl radicals; R3 is selected from the group consisting of alkyl, substituted alkyl, alkenyl, substituted alkenyl, cycloalkyl, substituted cycloalkyl, aryl, substituted aryl, aralkyl and alkaryl radicals; and, Z is a divalent aliphatic hydrocarbon containing from 2-7 carbon atoms completing a 3-8 membered ring in conjunction with said nitrogen.

3. The process of claim 1 wherein said amino guanidine is represented by the general formulae and wherein R and R2 are independently selected from the group consisting of hydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl, cycloalkyl, substituted cycloalkyl, aryl, substituted aryl, alkaryl, and aralkyl radicals, R1 is selected from the group consisting of alkyl, substituted alkyl, alkenyl, substituted alkenyl, cycloalkyl, substituted cycloalkyl, aryl substituted aryl, alkaryl, aralkyl; acyl radicals represented by R - C(O) wherein R is as defined above, and substituted acyl radicals; R3 is selected from the group consisting of alkyl, substituted alkyl, alkenyl, substituted alkenyl, cycloalkyl, substituted cycloalkyl, aryl, substituted aryl, aralkyl and alkaryl radicals; and Z is a divalent aliphatic hydrocarbon containing from 2-7 carbon atoms completing a 3-9 membered ring in conjunction with said nitrogen.

4. The process of claim 1 wherein said dihydric phenol is bisphenol-A and said carbonate precursor is phosgene.

5. The process of claim 4 wherein said amino amidine is present in an amount from about 0.01 to about 10 weight percent based on the weight of bisphenol-A.