Organic compounds -- part of the class 532-570 series – Organic compounds – Heavy metal containing
Reexamination Certificate
2000-05-09
2002-04-16
Nazario-Gonzalez, Porfirio (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heavy metal containing
C556S174000, C556S182000, C502S162000
Reexamination Certificate
active
06372929
ABSTRACT:
The invention concerns esterification catalysts and in particular esterification catalysts which comprise novel organotitanium, organozirconium or organoaluminium compounds.
Organotitanium compounds and, in particular, titanium alkoxides or orthoesters are known as catalysts for esterification processes. During the esterification, these compounds are frequently converted to insoluble compounds of titanium which result in a hazy product The presence of a haze is a particular disadvantage in polyesters which have a high viscosity and/or high melting point and are therefore difficult to filter. Furthermore, many organotitanium compounds which are effective catalysts in the manufacture of polyesters such as polyethylene terephthalate are known to produce unacceptable yellowing in the final polymer. Our co-pending application, published as GB 2 314 081 relates to an esterification process in which these problems are partially solved but there is still a need for a catalyst which induces little or no yellowing in a polyester produced using the catalyst.
It is an object of the present invention to provide an improved catalyst for process for preparing esters.
According to the invention, an organometallic compound suitable-for use as a catalyst for the preparation of an ester comprises the reaction product of an orthoester or condensed orthoester of titanium, zirconium or aluminium, an alcohol containing at least two hydroxyl groups, an organophosphorus compound containing at least one P—OH group and a base.
Also according to the invention, a process for the preparation of an ester comprises carrying out an esterification reaction in the presence of a catalyst comprising the reaction product of an orthoester or condensed orthoester of titanium, zirconium or aluminium, an alcohol containing at least two hydroxyl groups, an organophosphorus compound containing at least one P—OH group and a base.
In a further embodiment the organometallic compound suitable for use as a catalyst in an esterification process comprises the reaction product of an orthoester or condensed orthoester of titanium, zirconium or aluminium, an alcohol containing at least two hydroxyl groups, an organophosphorus compound containing at least one P—OH group, a base and a 2-hydroxy carboxylic acid.
The organometallic compound of the invention is the reaction product of a titanium, zirconium or aluminium orthoester or condensed orthoester, an alcohol containing at least two hydroxyl groups, an organophosphorus compound containing at least one P—OH group and a base. Preferably, the orthoester has the formula M(OR)
4
or AJ(OR)
3
where M is titanium or zirconium and R is an alkyl group. More preferably R contains 1 to 6 carbon atoms and particularly suitable orthoesters include tetraisopropoxy titanium, tetra-n-butoxy titanium, tetra-n-propoxy zirconium, tetra-n-butoxy zirconium and tetra-iso-butoxy aluminium.
The condensed orthoesters suitable for preparing the compounds of this invention are typically prepared by careful hydrolysis of titanium, zirconium or aluminium orthoesters. Titanium or zirconium condensed orthoesters are frequently represented by the formula
R
1
O[M(OR
1
)
2
O]
n
R
1
in which R
1
represents an alkyl group and M represents titanium or zirconium. Preferably, n is less than 20 and more preferably is less than 10. Preferably, R
1
contains 1 to 12 carbon atoms, more preferably, R
1
contains 1 to 6 carbon atoms and useful condensed orthoesters include the compounds known as polybutyl titanate, polyisopropyl titanate and polybutyl zirconate.
Preferably, the alcohol containing at least two hydroxyl groups is a dihydric alcohol and can be a 1,2-diol such as 1,2-ethanediol or 1,2-propanediol, a 1,3-diol such as 1,3-propanediol, a 1,4-diol such as 1,4-butanediol, a diol containing non-terninal hydroxyl groups such as 2-methyl-2,4pentanediol or a dihydric alcohol containing a longer chain such as diethylene glycol or a polyethylene glycol. Preferred dihydric alcohols are 1,2-ethanediol and diethylene glycol. The organometallic compound can also be prepared from a polyhydric alcohol such as glycerol, trimethylolpropane or pentaerythritol.
Preferably, the organometallic compound useful as a catalyst is prepared by reacting a dihydric alcohol with an orthoester or condensed orthoester in a ratio of from 1 to 16 moles of dihydric alcohol to each mole of titanium, zirconium or aluminium. More preferably, the reaction product contains 2 to 12 moles of dihydric alcohol per mole of titanium, zirconium or aluminium and most preferably 4 to 8 moles dihydric alcohol per mole of titanium, zirconium or aluminium.
The organophosphorus compound which contains at least one P—OH group can be selected from a number of organophosphorus compounds including phosphates, pyrophosphates, phosphonates, phosphinates and phosphites.
Preferably, the organophosphorus compound is a substituted or unsubstituted alkyl phosphate, a substituted or unsubstituted aryl phosphate or a phosphate of an alkylaryl glycol ether or an alkyl glycol ether. Preferred compounds include monoalkyl acid phosphates and dialkyl acid phosphates and mixtures of these. Particularly convenient organophosphorus compounds are the compounds commercially available as alkyl acid phosphates and containing, principally, a mixture of mono- and di-alkyl phosphate esters. When an alkyl phosphate is used, the organic group preferably contains up to 20 carbon atoms, more preferably up to 8 carbon atoms and, most preferably, up to 6 carbon atoms. When alkylaryl or alkyl glycol ether phosphates are used the carbon chain length is preferably up to 18 carbon atoms and, more preferably, 6 to 12 carbon atoms. Particularly preferred organophosphorus compounds include butyl acid phosphate, polyethylene glycol phosphates and aryl polyethylene glycol phosphates.
The amount of organophosphorus compound present in the reaction product of the invention is usually in the range 0.1 to 4.0 mole of phosphorus to 1 mole of metal (titanium, zirconium or aluminium), preferably in the range 0.1 to 2.0 mole phosphorus to 1 mole metal and most preferably in the range 0.1 to 1.0 mole phosphorus to 1 mole metal.
A base is also used in preparing the reaction product of the invention. The base is generally an inorganic base and suitable bases include sodium hydroxide, potassium hydroxide and ammonium hydroxide, but organic bases such as tetrabutyl ammonium hydroxide or choline hydroxide [trimethyl-(2-hydroxyethyl)ammonium hydroxide] can also be used. Usually, the amount of base used is in the range 0.1 to 4.0 mole base per mole of metal (titanium, zirconium or aluminium). The preferred amount is in the range 0.1 to 2.0 mole base per mole of metal and, frequently, the amount of base present is in the range 0.1 to 1.0 mole base per mole of titanium, zirconium or aluminium.
When 2-hydroxy carboxylic acids are used to prepare the products of the invention, preferred acids used include lactic acid, citric acid, malic acid and tartaric acid. Some suitable acids are supplied as hydrates or as aqueous mixtures and can be used in this form. When a 2-hydroxy acid is present, the preferred molar ratio of acid to titanium, zirconium or aluminium in the reaction product is 0.5 to 4 moles per mole of titanium, zirconium or aluminium. More preferably the catalyst contains 1.0 to 3.5 moles of 2-hydroxy acid per mole of titanium, zirconium or aluminium.
The organometallic compound can be prepared by mixing the components (orthoester or condensed orthoester, alcohol containing at least two hydroxyl groups, organophosphorus compound and base) with removal, if desired, of any by-product, (e.g. isopropyl alcohol when the orthoester is tetraisopropoxytitanium), at any appropriate stage. In one preferred method the orthoester or condensed orthoester and a dihydric alcohol are mixed and, subsequently, a base is added, followed by the organophosphorus compound. When a 2-hydroxy carboxylic acid is also present in the reaction product, this is usually added to the orthoester or condensed orthoester before
Hepplewhite Iain Wesley
Ridland John
ACMA Limited
Nazario-Gonzalez Porfirio
Pillsbury & Winthrop LLP
LandOfFree
Esterification catalysts does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Esterification catalysts, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Esterification catalysts will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2856130