Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
1999-02-22
2001-01-23
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
C528S176000, C528S198000
Reexamination Certificate
active
06177536
ABSTRACT:
This application relates to the manufacture of polycarbonates via a melt polycondensation reaction, and in particular to an improved method for finishing such compositions through the addition of a quenching agent to neutralize the alkaline condensation catalyst.
Aromatic polycarbonates are useful in a great many applications because of their desirable physical properties, including strength and optical clarity. There are three processes known for the production of aromatic polycarbonates, which are illustrated in FIG.
1
. The conventional interfacial process and the phosgene-based melt process start with the reaction of phosgene with carbon monoxide. The “no phosgene” melt process was developed to eliminate the use of highly toxic phosgene in the reaction process.
Both types of melt processes make use of a diarylcarbonate such as diphenylcarbonate (DPC) as an intermediate, which is polymerized with a dihydric phenol such as bisphenol A (BPA) in the presence of an alkaline catalyst to form a polycarbonate in accordance with the general reaction shown in FIG.
2
. This polycarbonate may be extruded or otherwise processed, and may be combined with additives such as dyes and UV stabilizers. In many cases, however, the presence of residual catalyst has a detrimental effect on the quality of the product, leading to poor color, molecular weight or rheological properties. Residual catalyst may also interact with additives, detracting from their efficacy. Thus, it is desirable to reduce the levels of residual catalyst to minimize these interactions. Such reduction is referred to as “quenching.”
In the production of optical quality polycarbonates, several reactors are used in sequence to prepare the final product. The fourth and final reactor in this sequence subjects the reaction mixture to both high temperature and high vacuum. This treatment assists in the removal of unreacted monomer and short oligomers, and improves the overall quality of the final product. For optical quality (OQ) products, this is also the phase of the reaction at which quencher is added. Because of the very small amount of actual quencher which is required, the quencher is conventionally added in a solvent. For example, the assignee company has made use of toluene as a solvent for the delivery of n-butyl tosylate as a quencher. Unfortunately, this system negatively impacts on the process for the continuous production of OQ polycarbonates, because decomposition occurs in the nozzle, which results in fluctuating flow rates.
It would therefore be desirable to have an alternative system for quenching polycarbonate reactions that occur at high temperature and vacuum, which does not suffer from this drawback. It is an object of the present invention to provide such a system.
SUMMARY OF THE INVENTION
The present invention provides a method for quenching alkaline catalyst present in the product of a melt polycondensation reaction, comprising adding to the product a sulfonic acid ester quencher in a carrier. The carrier comprises a first carrier component effective to solubilize the quencher and having a lower boiling point than the quencher, and a second carrier component soluble in the first carrier component and having a higher boiling point than the quencher. An exemplary carrier composition contains equal parts of diphenylcarbonate and toluene.
REFERENCES:
patent: 5403878 (1995-04-01), Ishiwa et al.
patent: 5418269 (1995-05-01), Ishiwa et al.
patent: 5606007 (1997-02-01), Sakashita et al.
Anamizu Takayoshi
Kanezawa Akio
Mestanza Raphael
Shimoda Tomoaki
Boykin Terressa M.
General Electric Company
LandOfFree
Method for quenching of catalyst in the production of low... 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 for quenching of catalyst in the production of low..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for quenching of catalyst in the production of low... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2531428