Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acid esters
Reexamination Certificate
1999-09-23
2002-08-13
Killos, Paul J. (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acid esters
Reexamination Certificate
active
06433217
ABSTRACT:
The present invention relates to a process for the preparation of glycidylesters of branched monocarboxylic acids.
More in particular the present invention relates to a multistep process for the preparation of glycidylesters of &agr;-branched monocarboxylic acids containing from 5 to 20 carbon atoms and preferably from 9 to 13 carbon atoms.
Glycidylesters of &agr;-branched monocarboxylic acids are useful for the preparation of epoxy, acrylic polyester and alkyd resins, either directly or via intermediate products such as adducts with (meth)acrylic acid amines, polyols and polyacids or as reactive diluents for the preparation of thermoset acrylic, epoxy polyester and/or urethane paints and coatings.
Of particular interest are glycidylesters of aliphatic monocarboxylic acids represented by the formula
wherein R
1
, R
2
and R
3
each represent the same or different alkyl radicals of normal or branched structure containing 1-20 carbon atoms, and R
4
through R
8
each represent hydrogen or a hydrocarbyl group containing 1-3 carbon atoms. A more preferred product is one where R
1
through R
3
are alkyl groups containing a sum total of 3-20 carbon atoms and where R
4
through R
8
are each hydrogen, e.g. the reaction product of neodecanoic acid (R
1
+R
2
+R
3
=C
8
) and epichlorohydrin.
Glycidylesters of this general type and their method of preparation are disclosed in U.S. Pat. Nos. 3,075,999, 3,178,454, 3,275,583 and 3,397,176, the complete disclosures of each of which are incorporated herein by reference.
Such glycidylesters can be made by reacting an alkali salt of the carboxylic acid with a halo-substituted monoepoxide such as an epihalohydrin, e.g., epichlorohydrin (1-20 molar excess). The mixture is heated (50-150° C.) in the presence of a catalyst forming glycidylester plus alkali salt and water. The water and excess epihalohydrin are removed by azeotropic distillation, and the salt by-product, e.g., NaCl, is removed by filtration and/or washing. The glycidylesters can also be made by reacting the carboxylic acid directly with epichlorohydrin under similar process conditions. The chlorohydrin ester intermediate formed during this reaction is subsequently treated with an alkaline material, e.g., sodium or potassium hydroxide, which yields the desired glycidylester. By-product salt is removed by washing and/or filtration, and water is removed by drying.
Investigations of these reactions have revealed that several heavier by-products are produced during the reactions to varying degrees, and that species which add colour to the main product are contained within the heavier by-products. The heavier by-products include the reaction products of the glycidylester product and/or the chlorohydrin ester intermediate with either unreacted epichlorohydrin, unreacted monocarboxylic acid or salt and/or water at various stages of the synthesis process, and have been depicted hereinafter:
The heavier by-products may also include further reaction products of initially formed compounds with the glycidylester product and other species present. Generally speaking, one or a combination of these or other unidentified heavies are present in the glycidylester reaction product at levels of from 8 wt % to 12 wt %.
Because glycidylesters are thermally and chemically reactive molecules, separation of these by-products from glycidylesters is not easily accomplished. Standard atmospheric distillation techniques have been found to increase the amount of by-products as well as the degree of colour of the esters. It is known that this increase in colour is caused by the reaction at elevated temperatures, as encountered during distillation, of the glycidyl functionality present in the desired product with functionalities present in the by-products, thereby forming additional by-products, which are not separable from the glycidylester and which are extremely sensitive to discoloration upon heating.
One of the remedies for solving this problem of said present by-products, has been disclosed in WO 97/44335.
In said application has been clearly suggested that standard vacuum distillation is ineffective in reducing the initial or aged colour of the glycidylesters and tends to worsen the colour problem.
In said patent application a process for the distillation of the glycidylester reaction product is proposed, which uses a thin film, short pass distillation apparatus and provides a light fraction which after recovery shows a Pt-Co colour value of less than 100 after 20 days storage in contact with air at 125° C. when measured according to ASTM D1209.
Although said distillation process has provided glycidylesters of branched chain saturated monocarboxylic acids, showing an significantly reduced initial colour and a improved colour stability after periods of storage, it will be appreciated that such distillation process will cause a significant cost price increase of the final product, since the reported purity increases are only achieved by discarding about 8% of the intake for obtaining a 96% pure product and up to 30% of the intake for obtaining a 99% pure product. Moreover, said process leads to significant production of chlorinated waste, which is disadvantageous from an environmental point of view
It will be appreciated that there is still a need for an improved manufacturing process for glycidylesters of branched monocarboxylic acids, which may lead to the purity and/or colour performance of the product aimed at but at a lower cost price.
As object of the present invention therefor is to provide a process for the manufacture of glycidylesters of branched monocarboxylic acids, with improved initial colour, heat stability and colour stability and/or higher purity, which must be reached at a reduced cost price per product unit.
As a result of extensive research and experimentation, such a process has been surprisingly found now.
Accordingly, the invention relates to a process for the manufacture of glycidylesters of &agr;-branched monocarboxylic acids, comprising
(a) the reaction of the &agr;-branched monocarboxylic acid with a halo substituted monoepoxide such as an epihalohydrin (e.g. epichlorohydrin) in a 2-20 molar excess and preferably 3-20, optionally in the presence of water and water-miscible solvent and preferably an aqueous alkanol as solvent, and in the presence of a catalyst in an amount of at most 45 mol % of the molar amount of the monocarboxylic acid, and preferably at most 20% and more preferably of at most 10%, at a temperature in the range of from 30 to 110 (and preferably from 65 to 95° C.), during a period in the range of from 0.5 to 2.5 hr,
(b) addition of additional alkali metal hydroxide or alkali metal alkanolate up to a total molar ratio as to the monocarboxylic acid in the range of from 0.9:1 to 1.2:1 and preferably from 0.95:1 to 1.10:1 and reaction at a temperature of from 0 to 80° C. (and preferably from 20 to 70° C.),
(c) distillation of the obtained reaction mixture to remove the excess halo substituted monoepoxide and the solvent and water formed, and
(d) removal of alkali metal halide salt, e.g. by washing the obtained glycidylester with water, after optionally treating the residual product with a concentrated aqueous alkali metal hydroxide solution, in order to complete the dehydrohalogenation (and preferably a dehydrochlorination).
It will be appreciated that the glycidylester obtained after step (d), can be dried in addition e.g. by distillation or treating with water absorbers.
The process according to the present invention can be carried out either as batch process or as a continuous process. The process preferably uses saturated &agr;-branched monocarboxylic acid.
The preferred reaction time in step (a) is in the range of from 0.9 to 1.5 hours.
The catalyst to be used in step (a) may be selected from alkalimetal hydroxides, alkalimetal carbonates, alkaline earth hydroxides, alkalimetal or alkaline earth metal alcoholates of the formula X
n+
(OR
−
)
n
, wherein X represents the alkali metal or alkaline earth metal ion and R represents C
1
-C
Heymans Denis Marie Charles
Rosenbrand Gerrit Gerardus
Stichter Hendrik
Calve John N.
Killos Paul J.
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