Method of polycarbonate preparation

Details Method of polycarbonate preparation Method of polycarbonate preparation

2001-07-24

2003-04-15

Boykin, Terressa M. (Department: 1711)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

From phenol, phenol ether, or inorganic phenolate

C528S198000

Reexamination Certificate

active

06548623

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to the preparation of polycarbonates by the melt reaction of a bisphenol with an ester-substituted diaryl carbonate. More particularly, the instant invention relates to the formation under mild conditions of polycarbonates having extremely low levels of Fries rearrangement products and possessing a high level of endcapping.
Polycarbonates, such as bisphenol A polycarbonate, are typically prepared either by interfacial or melt polymerization methods. The reaction of a bisphenol such as bisphenol A (BPA) with phosgene in the presence of water, a solvent such as methylene chloride , an acid acceptor such as sodium hydroxide and a phase transfer catalyst such as triethylamine is typical of the interfacial methodology. The reaction of bisphenol A with a source of carbonate units such as diphenyl carbonate at high temperature in the presence of a catalyst such as sodium hydroxide is typical of currently employed melt polymerization methods. Each method is practiced on a large scale commercially and each presents significant drawbacks.
The interfacial method for making polycarbonate has several inherent disadvantages. First it is a disadvantage to operate a process which requires phosgene as a reactant due to obvious safety concerns. Second it is a disadvantage to operate a process which requires using large amounts of an organic solvent because expensive precautions must be taken to guard against any adverse environmental impact. Third, the interfacial method requires a relatively large amount of equipment and capital investment. Fourth, the polycarbonate produced by the interfacial process is prone to having inconsistent color, higher levels of particulates, and higher chloride content, which can cause corrosion.
The melt method, although obviating the need for phosgene or a solvent such as methylene chloride requires high temperatures and relatively long reaction times. As a result, by-products may be formed at high temperature, such as the products arising by Fries rearrangement of carbonate units along the growing polymer chains. Fries rearrangement gives rise to undesired and uncontrolled polymer branching which may negatively impact the polymer's flow properties and performance.
Some years ago, it was reported in U.S. Pat. No. 4,323,668 that polycarbonate could be formed under relatively mild conditions by reacting a bisphenol such as BPA with the diaryl carbonate formed by reaction phosgene with methyl salicylate. The method used relatively high levels of transesterification catalysts such as lithium stearate in order to achieve high molecular weight polycarbonate. High catalyst loadings are particularly undesirable in melt polycarbonate reactions since the catalyst remains in the product polycarbonate following the reaction. The presence of a transesterification catalyst in a the polycarbonate may shorten the useful life span of articles made therefrom by promoting increased water absorption, polymer degradation at high temperatures and discoloration.
It would be desirable, therefore, to minimize the amount of catalyst required in the for the melt preparation of polycarbonate from bisphenols and ester substituted diaryl carbonates such as bis-methyl salicyl carbonate.
BRIEF SUMMARY OF THE INVENTION
The present invention provides a method for preparing polycarbonate comprising heating a mixture comprising a catalyst; at least one diaryl carbonate having structure I
wherein R
1
and R
2
are independently C
1
-C
20
alkyl radicals, C
4
-C
20
cycloalkyl radicals, or C
4
-C
20
aromatic radicals, R
3
and R
4
are independently at each occurrence a halogen atom, cyano group, nitro group, C
1
-C
20
alkyl radical, C
4
-C
20
cycloalkyl radical, C
4
-C
20
aromatic radical, C
1
-C
20
alkoxy radical, C
4
-C
20
cycloalkoxy radical, C
4
-C
20
aryloxy radical, C
1
-C
20
alkylthio radical, C
4
-C
20
cycloalkylthio radical, C
4
-C
20
arylthio radical, C
1
-C
20
alkylsulfinyl radical, C
4
-C
20
cycloalkylsulfinyl radical, C
4
-C
20
arylsulfinyl radical, C
1
-C
20
alkylsulfonyl radical, C
4
-C
20
cycloalkylsulfonyl radical, C
4
-C
20
arylsulfonyl radical, C
1
-C
20
alkoxycarbonyl radical, C
4
-C
20
cycloalkoxycarbonyl radical, C
4
-C
20
aryloxycarbonyl radical, C
2
-C
60
alkylamino radical, C
6
-C
60
cycloalkylamino radical, C
5
-C
60
arylamino radical, C
1
-C
40
alkylaminocarbonyl radical, C
4
-C
40
cycloalkylaminocarbonyl radical, C
4
-C
40
arylaminocarbonyl radical, or C
1
-C
20
acylamino radical; and b and c are independently integers 0-4; and at least one dihydroxy aromatic compound, said catalyst comprising at least one source of alkaline earth ions or alkali metal ions, and at least one quaternary ammonium compound, quaternary phosphonium compound, or a mixture thereof, said source of alkaline earth ions or alkali metal ions being present in an amount such that between about 10
−5
and about 10
−8
moles of alkaline earth metal ions or alkali metal ions are present in the mixture relative per mole of dihydroxy aromatic compound employed, said quaternary ammonium compound, quaternary phosphonium compound or mixture thereof being present in an amount between about 2.5×10
−3
and about 1×10
−6
moles per mole of dihydroxy aromatic compound employed.
The present invention further relates to a method for forming polycarbonates by reaction of an ester-substituted diaryl carbonate in which the level of Fries rearrangement product in the product polycarbonate is less than about 1000 parts per million (ppm) and the level of internal ester carbonate linkages in the product polycarbonate is less than about 1 percent of the total number of moles of dihydroxy aromatic compound employed and the level of terminal hydroxy ester groups in the product polycarbonate is less than about 1 percent of the total number of moles of dihydroxy aromatic compound employed.
DETAILED DESCRIPTION OF THE INVENTION
The present invention may be understood more readily by reference to the following detailed description of preferred embodiments of the invention and the examples included therein. In the following specification and the claims which follow, reference will be made to a number of terms which shall be defined to have the following meanings:
The singular forms “a”, “an” and “the” include plural referents unless the context clearly dictates otherwise.
“Optional” or “optionally” means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where the event occurs and instances where it does not.
As used herein the term “polycarbonate” refers to polycarbonates incorporating structural units derived from one or more dihydroxy aromatic compounds and includes copolycarbonates and polyester carbonates.
As used herein, the term “melt polycarbonate” refers to a polycarbonate made by the transesterification of a diaryl carbonate with a dihydroxy aromatic compound.
“BPA” is herein defined as bisphenol A or 2,2-bis(4-hydroxyphenyl)propane.
“Catalyst system” as used herein refers to the catalyst or catalysts that catalyze the transesterification of the bisphenol with the diaryl carbonate in the melt process.
The terms “bisphenol”, “diphenol” and “dihydric phenol” as used herein are synonymous.
“Catalytically effective amount” refers to the amount of the catalyst at which catalytic performance is exhibited.
As used herein the term “Fries product” is defined as a structural unit of the product polycarbonate which upon hydrolysis of the product polycarbonate affords a carboxy-substituted dihydroxy aromatic compound bearing a carboxy group adjacent to one or both of the hydroxy groups of said carboxy-substituted dihydroxy aromatic compound. For example, in bisphenol A polycarbonate prepared by a melt reaction method in which Fries reaction occurs, among the Fries products within the product polycarbonate are those structural units, for example structure VIII below, which afford 2-carboxy bisphenol A upon complete hydrolysis of the product polycarbo

Affiliated with

Also associated with

Rating

Method of polycarbonate preparation does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Method of polycarbonate preparation, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of polycarbonate preparation will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3105366