CA1189240A - Decolorization of polycarbonate resins - Google Patents
Decolorization of polycarbonate resinsInfo
- Publication number
- CA1189240A CA1189240A CA000420976A CA420976A CA1189240A CA 1189240 A CA1189240 A CA 1189240A CA 000420976 A CA000420976 A CA 000420976A CA 420976 A CA420976 A CA 420976A CA 1189240 A CA1189240 A CA 1189240A
- Authority
- CA
- Canada
- Prior art keywords
- acid anhydride
- anhydride
- titanate
- polycarbonate resin
- amount
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G64/00—Macromolecular compounds obtained by reactions forming a carbonic ester link in the main chain of the macromolecule
- C08G64/40—Post-polymerisation treatment
- C08G64/406—Purifying; Drying
Abstract
ABSTRACT OF THE DISCLOSURE
Polycarbonate resins which have been polymerized employing titanates as polymerizing agents generally have characteristic undesirable color. Removal of this color is accomplished by treatment of the polycarbonate resin with a quantity of an organic acid anhydride, optionally employing a smaller amount of a mineral acid, in addition for lower temperature decolorization.
Polycarbonate resins which have been polymerized employing titanates as polymerizing agents generally have characteristic undesirable color. Removal of this color is accomplished by treatment of the polycarbonate resin with a quantity of an organic acid anhydride, optionally employing a smaller amount of a mineral acid, in addition for lower temperature decolorization.
Description
12, 773 1~929~0 DECOLORIZATION OF POLYCARBONATE RESINS
.. .... . _ .
BACKGROUND OF THE INVENTION
Several processes for the production of polycarbonate resins by transesterification reactions have been proposed.
In these reactions, the catalyst employed is frequently a titanate ester, which is quite effective in catalyzing the reaction; however,-residues from the titanate esters in tr.e polycarbonate resin result in an obvious color in the resin.
Since commercially desirable polycarbonate resins aye expected to be colorless, polycarbonate resins produced by the transes~erification reaction employing titanate catalysts art at a disadvantage because of the color, regardless of the effectiveness or economy of the transesterification process.
.4ccordingly, a method for effectively decolorizing such titanate catalyzed polycarbonate resins has been sought.
CROS S - REFEREN CE T O RELATED APPLI CAT ION
15One transesterification reaction employing titanate ester catalysts is shown in Canadian application Serial No.
I, 9~ filed ~o~e~nber /9~ filed and assigned to he same Assignee as the present invention. As pointed out in that disclosure, the titanate ester is an effective catalyst fo-formation of the polymer, but the resulting polymer does have an undesirable color.
SI~IMARY OF THE INVENTIOII
- In accordance wlth the present invention, it has unexpectedly been discovered that the discoloration of a poly-25 carbonate resin caused by the use of a titanate ester as 2 RD-12,773 transesterification catalyst can be eliminated by treatment of the resin wi-th an organic aeid anhydride. The resulting oxy-titanium sal-ts are soluble in -the resin and colorless. Thus, separa-tion of the end produet is not neeessary, resulting in an extremely faeile method of deeolorizing.
Speeifically, depending on its molecular weight and in the absence ox a mineral acid, the polyearbona-te resin ean be heated with an organie aeid anhydride to from about 250C to 325C. The aeid anhydride and titanate ester react according -to -the following equa-tion using an aryl ti-tanate as an example.
2Ti(OAr)4 -I 7(RCO)2O
Ti2O(o2CR)6 8RCO2Ar (1), where Ar is an aroma-tie group seleeted from -the class eonsis-ting ,_ of phenyl, tolyl, xylyl, - O C(CH3)2 H, e-tc. R is seleeted from the elass consisting of Cl 20 alkyl radieals, e.g., me-thyl ethyl, propyl, bu-tyl, hexyl, dodeeyl, ete.; phenyl, tolyl, ete. Preferred are phthalic anhydride, substituted phthaLie anhydrides, aeetie anhydride, ete.
In addition, -the aeid anhydride represelltecl by the formula (RCO)2O ean be:
O O
Il il < CH3 / X / A
O
RD-12,773
.. .... . _ .
BACKGROUND OF THE INVENTION
Several processes for the production of polycarbonate resins by transesterification reactions have been proposed.
In these reactions, the catalyst employed is frequently a titanate ester, which is quite effective in catalyzing the reaction; however,-residues from the titanate esters in tr.e polycarbonate resin result in an obvious color in the resin.
Since commercially desirable polycarbonate resins aye expected to be colorless, polycarbonate resins produced by the transes~erification reaction employing titanate catalysts art at a disadvantage because of the color, regardless of the effectiveness or economy of the transesterification process.
.4ccordingly, a method for effectively decolorizing such titanate catalyzed polycarbonate resins has been sought.
CROS S - REFEREN CE T O RELATED APPLI CAT ION
15One transesterification reaction employing titanate ester catalysts is shown in Canadian application Serial No.
I, 9~ filed ~o~e~nber /9~ filed and assigned to he same Assignee as the present invention. As pointed out in that disclosure, the titanate ester is an effective catalyst fo-formation of the polymer, but the resulting polymer does have an undesirable color.
SI~IMARY OF THE INVENTIOII
- In accordance wlth the present invention, it has unexpectedly been discovered that the discoloration of a poly-25 carbonate resin caused by the use of a titanate ester as 2 RD-12,773 transesterification catalyst can be eliminated by treatment of the resin wi-th an organic aeid anhydride. The resulting oxy-titanium sal-ts are soluble in -the resin and colorless. Thus, separa-tion of the end produet is not neeessary, resulting in an extremely faeile method of deeolorizing.
Speeifically, depending on its molecular weight and in the absence ox a mineral acid, the polyearbona-te resin ean be heated with an organie aeid anhydride to from about 250C to 325C. The aeid anhydride and titanate ester react according -to -the following equa-tion using an aryl ti-tanate as an example.
2Ti(OAr)4 -I 7(RCO)2O
Ti2O(o2CR)6 8RCO2Ar (1), where Ar is an aroma-tie group seleeted from -the class eonsis-ting ,_ of phenyl, tolyl, xylyl, - O C(CH3)2 H, e-tc. R is seleeted from the elass consisting of Cl 20 alkyl radieals, e.g., me-thyl ethyl, propyl, bu-tyl, hexyl, dodeeyl, ete.; phenyl, tolyl, ete. Preferred are phthalic anhydride, substituted phthaLie anhydrides, aeetie anhydride, ete.
In addition, -the aeid anhydride represelltecl by the formula (RCO)2O ean be:
O O
Il il < CH3 / X / A
O
RD-12,773
2~
The treatment of the polycarbonate resin containing the titanate ester can be carried out with molten polycarbonate resin, at an elevated temperature, but below the temperatures at which the polycarbonate resin decomposes, generally from 250C to 325~C, in the absence of solvent, or the polycarbonate resin can be dissolved in a carbona-te monomer (e.g., diphenyl carbonate, dimethyl carbonate, etc.) which constitutes one of the raw materials for its production, prior to separation of the polycarbonate resin from the carbona-te.
While the acid anhydrides jus-t described are ex-tremely effective in reacting with the titanate and removing the undesirable color, even faster reactions can often be achieved by employing additionally a small quantity of a mineral acid, particularly phosphoric or sulfuric acids, e.g., 15 from 0.001 to 0.5%, by weight, mineral acid per 100 parts, by weight, polymer. The use of the mineral acid permits -the decolorization to take place rapidly at room temperature.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
.. _ . . . . . . ...... .. _ . . .
In one embodiment, a polycarbonate resi.n which has been made by transesterification or ester carbonate in-te:r-change using a titanate catalyst is decolorized by treating -the molten resin, or while the resin is dissolvecl in a sol-vent of a monomeric carbonate, with an acid anhydride in the manner described above, so as to convert the color produc-ing titanate ester to a colorless titanium compound, solublein the polycarbonate resin.
Thus, the acid anhydride employed in -the decoloriza-tion of polycarbonate resins in accordance with the present RD-12,773 invention may be selected from the class consisting of acetic anhydride, propionic anhydride, benzoic anhydride, phthalic anhydride, chlorophthalic anhydrides, a dianhydride of formula A, etc.
In order to effect the decolorization of -the poly-carbonate resin, it is merely heated with the anhydride un-til it is molten, to at least about 250C. It may be heated as high as 325C in carrying ou-t the decolorization process in accordance with the present invention. Preferably, -the tem-10 pera-ture is maintained be-tween 275C and 300C.
The polycarbonate resin may be treated in the absence of any solvent, or it may be treated before separation from the monomers from which the resin is formed. Thus, for example, the polycarbonate resin may be contained in a dimethyl or diphenyl carbonate monomer, where that monomer remains from -the original reactants. The conditions of -treatment remain the same.
While stirring the heated polycarbonate resirl, a quantity of an acid anhydride, as described above, i5 aclded.
Preferably, from the s-tandpoint of cost and ease of reaction, the preEerred anhydride is acetic anhydride or ph-thalic anhydride. The anhydride concentration should be stoichiometric, as far as -the titanate ester is concerned, as illus-trated in accordance with equation (1). A 5% stoichiometric excess of the acid anhydride is permitted, based upon the amount of titanate ester employed in the polymerization reac-tion.
Decolorization employing the acid anhydride, as just disclosed, is generally accomplished in about 2 to 5 minutes. Even faster decolorization can be ob-tained at much RD-12,773 29~
lower temperatures, however, by including with the acid anhydride a trace of a mineral acid, particularly phosphoric or sulfuric acid. The amount of mineral acid employed can be varied widely, and generally, About 10~ of the stoichiome-tric amount of acid anhydride employed, -though an amoun-t up to stoichiometric equivalence is permissible. When the mineral acid is used in conjunction with the acid anhydride, decolori-zation is accomplished almost immediately at around room temperature (15 -to 35C).
While the resin being treated for decolorization has a significant orange color prior to -the treatment, it is colorless, at least by visual inspection, subsecluent to the treatment. further, resins decolorized in accordance wi-th the present invention were investigated by ultra viole-t transmission at 350 to 400 nanometers and showed an optical density of 0.1 absorbance unit maximum.
'rhe examples se-t forth below should not be con-sidered as limiting, in any way, the full scope of -the invention. All parts in the examples, unless otherwise indicated, are by weight.
Example 1 A reaction vessel, equipped with a s-tainless s-teel stirrer, was charged with 5 parts of an in-tensely orange colored polycarbonate resin having a molecular weight of 102,000. The resin had been prepared via an ester-carbonate (dime-thyl car-bonate and bisphenol-A diacetate) interchange reaction with a tetraphenyl titanate catalyst in an amount of 72 ppm calculated at TiO2. The reaction vessel was flushed with nitrogen ~2~ RD--12, 7 7 3 and the contents then heated to 300C. After the polycarbonate resin had melted, a quantity of 0.0024 part of phthalic anhydride was added, and stirring continued for 2 minutes.
After the 2 minutes of stirring, the orange color had disappeared and the mixture was cooled to room temperature. The resulting resin was transparent and nearly colorless and virtually no change in molecular weight was observed. By yel permeation chromotography, the molecular weight of the decolorized material was 103,500.
Example 2 Into a reaction vessel equipped with a stixrer was charged 15 parts of -the polycarbonate resin employed in Example 1 dissolved in approximately 100 parts of dimethyl carbonate.
To this was added 0.0048 part of acetic anhydride and 0.0001 part of phosphoric acid. Within a stirring time ox 2 minutes at room temperature (e.g. from 15 to 35C), -the orange color disappeared, and a colorless solution remained.
Results equivalent to those of Example 1 were obtained when phthalic anhydride was replaced by acetic anhydride, propionic anhydride, and Pl 1l ~d~--~\ / /
or when the phosphoric acid in Example 2 is replaced with sulfuric acid using acetic anhydride.
V RD-12,773 Whiie specific examples of the invention have been shown and described, the invention should be consldered only as limited by the appended claims.
The treatment of the polycarbonate resin containing the titanate ester can be carried out with molten polycarbonate resin, at an elevated temperature, but below the temperatures at which the polycarbonate resin decomposes, generally from 250C to 325~C, in the absence of solvent, or the polycarbonate resin can be dissolved in a carbona-te monomer (e.g., diphenyl carbonate, dimethyl carbonate, etc.) which constitutes one of the raw materials for its production, prior to separation of the polycarbonate resin from the carbona-te.
While the acid anhydrides jus-t described are ex-tremely effective in reacting with the titanate and removing the undesirable color, even faster reactions can often be achieved by employing additionally a small quantity of a mineral acid, particularly phosphoric or sulfuric acids, e.g., 15 from 0.001 to 0.5%, by weight, mineral acid per 100 parts, by weight, polymer. The use of the mineral acid permits -the decolorization to take place rapidly at room temperature.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
.. _ . . . . . . ...... .. _ . . .
In one embodiment, a polycarbonate resi.n which has been made by transesterification or ester carbonate in-te:r-change using a titanate catalyst is decolorized by treating -the molten resin, or while the resin is dissolvecl in a sol-vent of a monomeric carbonate, with an acid anhydride in the manner described above, so as to convert the color produc-ing titanate ester to a colorless titanium compound, solublein the polycarbonate resin.
Thus, the acid anhydride employed in -the decoloriza-tion of polycarbonate resins in accordance with the present RD-12,773 invention may be selected from the class consisting of acetic anhydride, propionic anhydride, benzoic anhydride, phthalic anhydride, chlorophthalic anhydrides, a dianhydride of formula A, etc.
In order to effect the decolorization of -the poly-carbonate resin, it is merely heated with the anhydride un-til it is molten, to at least about 250C. It may be heated as high as 325C in carrying ou-t the decolorization process in accordance with the present invention. Preferably, -the tem-10 pera-ture is maintained be-tween 275C and 300C.
The polycarbonate resin may be treated in the absence of any solvent, or it may be treated before separation from the monomers from which the resin is formed. Thus, for example, the polycarbonate resin may be contained in a dimethyl or diphenyl carbonate monomer, where that monomer remains from -the original reactants. The conditions of -treatment remain the same.
While stirring the heated polycarbonate resirl, a quantity of an acid anhydride, as described above, i5 aclded.
Preferably, from the s-tandpoint of cost and ease of reaction, the preEerred anhydride is acetic anhydride or ph-thalic anhydride. The anhydride concentration should be stoichiometric, as far as -the titanate ester is concerned, as illus-trated in accordance with equation (1). A 5% stoichiometric excess of the acid anhydride is permitted, based upon the amount of titanate ester employed in the polymerization reac-tion.
Decolorization employing the acid anhydride, as just disclosed, is generally accomplished in about 2 to 5 minutes. Even faster decolorization can be ob-tained at much RD-12,773 29~
lower temperatures, however, by including with the acid anhydride a trace of a mineral acid, particularly phosphoric or sulfuric acid. The amount of mineral acid employed can be varied widely, and generally, About 10~ of the stoichiome-tric amount of acid anhydride employed, -though an amoun-t up to stoichiometric equivalence is permissible. When the mineral acid is used in conjunction with the acid anhydride, decolori-zation is accomplished almost immediately at around room temperature (15 -to 35C).
While the resin being treated for decolorization has a significant orange color prior to -the treatment, it is colorless, at least by visual inspection, subsecluent to the treatment. further, resins decolorized in accordance wi-th the present invention were investigated by ultra viole-t transmission at 350 to 400 nanometers and showed an optical density of 0.1 absorbance unit maximum.
'rhe examples se-t forth below should not be con-sidered as limiting, in any way, the full scope of -the invention. All parts in the examples, unless otherwise indicated, are by weight.
Example 1 A reaction vessel, equipped with a s-tainless s-teel stirrer, was charged with 5 parts of an in-tensely orange colored polycarbonate resin having a molecular weight of 102,000. The resin had been prepared via an ester-carbonate (dime-thyl car-bonate and bisphenol-A diacetate) interchange reaction with a tetraphenyl titanate catalyst in an amount of 72 ppm calculated at TiO2. The reaction vessel was flushed with nitrogen ~2~ RD--12, 7 7 3 and the contents then heated to 300C. After the polycarbonate resin had melted, a quantity of 0.0024 part of phthalic anhydride was added, and stirring continued for 2 minutes.
After the 2 minutes of stirring, the orange color had disappeared and the mixture was cooled to room temperature. The resulting resin was transparent and nearly colorless and virtually no change in molecular weight was observed. By yel permeation chromotography, the molecular weight of the decolorized material was 103,500.
Example 2 Into a reaction vessel equipped with a stixrer was charged 15 parts of -the polycarbonate resin employed in Example 1 dissolved in approximately 100 parts of dimethyl carbonate.
To this was added 0.0048 part of acetic anhydride and 0.0001 part of phosphoric acid. Within a stirring time ox 2 minutes at room temperature (e.g. from 15 to 35C), -the orange color disappeared, and a colorless solution remained.
Results equivalent to those of Example 1 were obtained when phthalic anhydride was replaced by acetic anhydride, propionic anhydride, and Pl 1l ~d~--~\ / /
or when the phosphoric acid in Example 2 is replaced with sulfuric acid using acetic anhydride.
V RD-12,773 Whiie specific examples of the invention have been shown and described, the invention should be consldered only as limited by the appended claims.
Claims (11)
1. A process for decolorizing a polycarbonate resin containing a titanate ester of formula Ti(OAr)4, where Ar is an aryl group, comprising (1) reacting said titanate ester with at least a stoichiometric amount of an organic acid anhydride.
2. The process as in claim 1 where the acid anhydride is selected from the class consisting of acetic acid anhydride, propionic acid anhydride, phthalic acid anhydride, substituted phthalic acid anhydrides and and (2) isolating the decolorized polycarbonate resin.
3. The process of claim 1 wherein the titanate ester is tetraphenyl titanate.
4. The process of claim 1 wherein the acid anhydride is acetic anhydride or phthalic anhydride.
5. The process of claim 1 wherein the temperature is from 275° to 300°C.
6. The process of claim 1 wherein the polycarbonate resin is dissolved in a carbonate monomer.
7. The process of claim 1 wherein the amount of acid anhydride added is from stoichiometric based upon the amount of titanate ester, to an excess of 5% excess, based on the stoichiometric amount of the titanate.
8. The process of claim 1 wherein an amount of a mineral acid of from 10% of the stoichiometric amount to the stoichiometric amount, based on the amount of acid anhydride, selected from the class consisting of phosphoric and sulfuric acids, is stirred with the polycarbonate resin and acid anhydride at around room temperature.
9. The process of claim 8 wherein the titanate ester is tetraphenyl titanate.
10. The process of claim 8 wherein the acid anhydride is acetic anhydride.
11. The process of claim 8 wherein the polycarbonate resin is dissolved in a carbonate monomer.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/346,667 US4377684A (en) | 1982-02-08 | 1982-02-08 | Decolorization of polycarbonate resins |
| US346,667 | 1982-02-08 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1189240A true CA1189240A (en) | 1985-06-18 |
Family
ID=23360494
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000420976A Expired CA1189240A (en) | 1982-02-08 | 1983-02-04 | Decolorization of polycarbonate resins |
Country Status (2)
| Country | Link |
|---|---|
| US (1) | US4377684A (en) |
| CA (1) | CA1189240A (en) |
Families Citing this family (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4921940A (en) * | 1988-08-15 | 1990-05-01 | Xerox Corporation | Process for the purification of Ti containing polycarbonate with solvent, complexing agent and water |
| US7256241B2 (en) * | 2000-01-21 | 2007-08-14 | Cyclics Corporation | Methods for polymerizing macrocyclic polyester oligomers using catalyst promoters |
| US6906147B2 (en) * | 2002-03-20 | 2005-06-14 | Cyclics Corporation | Catalytic systems |
| US7767781B2 (en) | 2000-09-01 | 2010-08-03 | Cyclics Corporation | Preparation of low-acid polyalkylene terephthalate and preparation of macrocyclic polyester oligomer therefrom |
| US7750109B2 (en) | 2000-09-01 | 2010-07-06 | Cyclics Corporation | Use of a residual oligomer recyclate in the production of macrocyclic polyester oligomer |
| WO2002018476A2 (en) * | 2000-09-01 | 2002-03-07 | Cyclics Corporation | Methods for converting linear polyesters to macrocyclic oligoester compositions and macrocyclic oligoesters |
| US7071291B2 (en) * | 2001-06-27 | 2006-07-04 | Cyclics Corporation | Isolation, formulation and shaping of macrocyclic oligoesters |
| US7304123B2 (en) * | 2001-06-27 | 2007-12-04 | Cyclics Corporation | Processes for shaping macrocyclic oligoesters |
| US6787632B2 (en) * | 2001-10-09 | 2004-09-07 | Cyclics Corporation | Organo-titanate catalysts for preparing pure macrocyclic oligoesters |
-
1982
- 1982-02-08 US US06/346,667 patent/US4377684A/en not_active Expired - Fee Related
-
1983
- 1983-02-04 CA CA000420976A patent/CA1189240A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| US4377684A (en) | 1983-03-22 |
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Legal Events
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|---|---|---|---|
| MKEC | Expiry (correction) | ||
| MKEX | Expiry |