Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acid esters
Reexamination Certificate
2002-08-21
2003-11-18
Rotman, Alan L. (Department: 1625)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acid esters
C528S297000, C560S199000, C560S200000
Reexamination Certificate
active
06649786
ABSTRACT:
This invention relates to an ester-forming addition reaction product which is useful for the manufacture of low-solvent or non-solvent articles in the field of paint, ink, adhesive, etc., and which is excellent both in compatibility with curing agent and in curability. This invention also relates to a process for the production of said product.
From environmental concerns, the manufacture of low-solvent articles has recently been being promoted in the field of paint, ink, adhesive, etc. As one of the means to achieve this purpose, the utilization of reactive diluent is being considered. Furthermore, paint and ink which comprise, as main components, low-molecular compounds such as reactive diluent or oligomer are also being studied with a view to attaining much lower-solvent or non-solvent articles.
For instance, U.S. Pat. No. 4,314,918 discloses an idea of blending, with a coating composition, a reactive diluent which has a functionality of at least 2.0, an acid number of less than 50 mgKOH/g, a non-volatile content of greater than about 85% and a Gardner-Holdt viscosity of less than Z
10
. U.S. Pat. No. 5,952,452 and U.S. Pat. No. 6,069,203 exemplify a hydroxyl group-containing oligomer (polyesterpolyol oligomer, oligoether) to be blended with a high solids coating composition, which oligomer is manufactured from a reaction of branched fatty glycidyl ester.
The reactive diluent and oligomer which are disclosed in the above-mentioned U.S. patents have, owing to their production process, no selectivity in reacting with a number of functional groups, and, therefore, components are formed more than intended from the reaction, and the polydispersibility (ratio of weight average molecular weight to number average molecular weight) of molecular weight distribution increases, and, resultantly, the viscosity of products increases, which is disadvantageous for the manufacture of low-solvent articles.
In detail, (1) in a combination of polyol and glycidylester or glycidylether (hereinafter referred to as glycidylester/ether), hydroxyl group in polyol has no selectivity, and, therefore, there are formed undesirable components from a reaction of polyol with a number of glycidylester/ether; (2) in a combination of polyol and acid anhydride, hydroxyl group in polyol has similarly no selectivity, and, therefore, there are formed undesirable components from a reaction of polyol with a number of acid anhydrides; and (3) in a combination of oxyacid which has a high melting point and glycidylester/ether, a reaction needs to be conducted at a high temperature, and, therefore, a reaction between hydroxyl group and carboxyl group partially occurs in addition to the intended reaction between glycidyl group and carboxyl group, and, thus, there are formed undesirable high-molecular components.
As for polyether polyol and polycaprolactone polyol which are known well as reactive diluent, they have a problem that the hardness of cured matters decreases, and that they are inferior in compatibility with curing agent, as well as the above-mentioned problem that high-molecular components are formed.
The objective of this invention is to provide a hydroxyl group-containing ester-forming addition reaction product which contains almost no undesirable high-molecular components, which is excellent in reactivity and compatibility, and which is useful for the manufacture of low-solvent or high-solid articles such as paint, ink, adhesive, etc., and to provide a process for the production of said hydroxyl group-containing ester-forming addition reaction product.
The inventors studied assiduously for the purpose of attaining the above-mentioned objectives, and have now found that a product of an ester-forming addition reaction between 2,2-dimethylolalkanoic acid having 6 to 8 carbon atoms which is an oxyacid having comparatively low melting point and alkanoic acid monoglycidylester having a hydrophobic group is not only useful for the manufacture of low-solvent or high-solid articles, but also is a material which is excellent in curability and compatibility. The inventors have further found an efficient process for the production of said product, and have thus completed this invention.
This invention provides a product of ester-forming addition reaction between 2,2-dimethylolalkanoic acid of the following formula (I):
wherein R
2
is an alkyl group having 2 to 4 carbon atoms, and alkanoic acid monoglycidylester of the following formula (II):
wherein R
1
is an alkyl group having 4 to 20 carbon atoms, which product has an acid value of 20 mgKOH/g or less.
This invention also provides a process to produce the above-mentioned ester-forming addition reaction product, which process is characterized in that an ester-forming addition reaction is conducted between 2,2-dimethylolalkanoic acid of the following formula (I):
wherein R
2
is an alkyl group having 2 to 4 carbon atoms, and alkanoic acid monoglycidylester of the following formula (II):
wherein R
1
is an alkyl group having 4 to 20 carbon atoms, until the acid value of the resultant reaction product becomes 20 mgKOH/g or less.
In the following, this invention is explained in more detail.
One of the characteristic features of this invention is to use 2,2-dimethylolalkanoic acid having 6 to 8 carbon atoms such as 2,2-dimethylolbutanoic acid. This compound has, in a molecule, plural functional groups which are different in reactivity, i.e., two hydroxyl groups and one carboxyl group. By an ester-forming addition reaction between this carboxyl group of dimethylolalkanoic acid and alkanoic acid monoglycidylester, any desired hydroxyl group-containing ester-forming addition reaction product can easily be synthesized.
There has been publicly known (see, e.g., U.S. Pat. No. 4,314,918 and U.S. Pat. No. 5,693,723) a process per se for producing polyol by a reaction between oxyacid having, in a molecule, hydroxyl group and carboxyl group, and alkanoic acid monoglycidylester.
Oxyacids which have conventionally been used are, however, glycolic acid, lactic acid, hydroxy pivalic acid, 12-hydroxy stearic acid, malic acid, citric acid, tartaric acid, 2,2-dimethylolpropionic acid, etc. Among these oxyacids, glycolic acid, lactic acid, hydroxy pivalic acid and 12-hydroxy stearic acid have only a single hydroxyl group in a molecule, and, therefore, diol is formed from an ester-forming addition reaction with alkanoic acid monoglycidylester. As a result, there occurs a problem that, when the product from said ester-forming addition reaction is used in a large amount, curability decreases. Furthermore, for instance, malic acid, citric acid and tartaric acid have plural carboxl groups, which fact causes a problem of selectivity in reaction. Besides, 2,2-dimethylolpropionic acid has a melting point as high as 150° C., which gives rise to a problem that, during an ester-forming addition reaction with glycidyl group at a high temperature, there are liable to occur, as a subsidiary reaction, a reaction between carboxyl group and hydroxyl group and a reaction between hydroxyl group and glycidyl group.
In this invention, 2,2-dimethylolalkanoic acid having 6 to 8 carbon atoms and having low melting point which is represented by 2,2-dimethylolbutanoic acid having a melting point of 110° C. is subjected, as a starting material, to ester-forming addition reaction with alkanoic acid monoglycidylester. When, for instance, 2,2-dimethylolbutanoic acid is used, it can be made to react with glycidyl group even without solvent at a comparatively low temperature of about 110° C. or higher. In a reaction at such low temperature, subsidiary reactions such as a reaction between carboxyl group and hydroxyl group and a reaction between hydroxyl group and glycidyl group are hard to occur, and molecular weight distribution comes near to monodispersion infinitely, and, thus, there can be formed a hydroxyl group-containing ester-forming addition reaction product which is very useful for the manufacture of low-solvent or high-solid articles.
As examples of 2,2-dimethylolalkanoic acid of formula (I), there can be
Kansai Paint Co. Ltd.
Reyes Hector M.
Rotman Alan L.
Wenderoth, Lind&Ponack LLP
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