Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acids and salts thereof
Reexamination Certificate
2001-01-03
2002-06-11
Killos, Paul J. (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acids and salts thereof
C560S056000
Reexamination Certificate
active
06403827
ABSTRACT:
TECHNICAL FIELD
The present invention provides a crystalline 2-hydroxynaphthalene-3-carboxylic acid having significantly suppressed dusting tendency, and a process for preparing the same.
BACKGROUND ART
2-hydroxynaphthalene-3-carboxylic acid is important as an intermediate for pigments or dyes. Generally, it is prepared by reacting &bgr;-naphthol with sodium hydride to give sodium &bgr;-naphtholate, reacting the resulting compound with carbon dioxide under pressure to give sodium 2-hydroxynaphthalene-3-carboxylate and then, isolating the desired compound by means of acid precipitation i.e. by adding a mineral acid to the salt.
For a long time, the Kolbe-Schmitt reaction, a solid-gas phase reaction, had been employed for the reaction between sodium &bgr;-naphtholate and carbon dioxide. Said reaction, however, had some problems, such as more than 50 hours of long reaction time was required, high amount of &bgr;-naphthol was wasted because of thermal heterogeneity at the high reaction temperature, controlling the reaction was difficult due to the phase conversion and a stable yield was hardly obtained. In order to solve those problems, a number of methods including a method using reaction media had been proposed.
One of the present inventors had invented a process comprising the step of reacting a liquid mixture consisting of light oil or kerosene, sodium &bgr;-naphtholate and &bgr;-naphthol, with carbon dioxide (Japanese Patent Publication (KOKOKU) No. 53296/1981) and said process has been industrially used at present. This process can be carried out successively and can provide 2-hydroxynaphthalene-3-carboxylic acid with very low amount of impurities and with highly stable quality. According to said method, 2-hydroxynaphthalene-3-carboxylic acid with high quality, such as those having 220-221° C. of melting point and 99.5% of purity and containing only 0.03% of sodium &bgr;-naphtholate, can be obtained. In the process, 2-hydroxynaphthol-3-carboxylic acid is isolated from the mother liquid by means of acid precipitation, filtration, centrifugation and the like, washed with water, dried and then, is used as an intermediate for pigments or dyes.
Crystalline composition of 2-hydroxynaphthalene-3-carboxylic acid usually comprises very fine particles and, therefore, is highly dusty. In addition to the dusting tendency, due to the severe mucosal irritativeness of 2-hydroxynaphthalene-3-carboxylic acid, handling of the compound is highly obstructed. For example, when 2-hydroxynaphthalene-3-carboxylic acid is added into a reaction tank as an intermediate for a pigment or dye, fine particles of 2-hydroxynaphthalene-3-carboxylic acid fly in the air as powdery dust. The fine particles of 2-hydroxynaphthalene-3-carboxylic acid flown in the air are hardly precipitated, disperse widely, pollute the environment, and stimulate the skin and mucosa of the operators to make them uncomfortable. In order to diminish the problems concerning workability and safety in the feeding step, operators wear dust-proof glasses and masks and the reactor is mounted a vacuum at a position other than the supply port to deaerate the fine particles and a filter to trap the same. However, they are not enough.
The reason why 2-hydroxynaphthalene-3-carboxylic acid dusts significantly is believed that said compound consists of very fine crystalline particles, and that said compound is hardly dissolved in water and, therefore, hardly uptakes moisture; and therefore, each crystalline particles do not agglomerate or bind together through the free water. As a consequence, the fine crystalline particles move individually upon an external impact. In order to suppress the dusting tendency of the material having the above-described characteristics, Japanese patent Application Laid Open No. 196841/1983 discloses a method for granulating 2-hydroxynaphthalene-3-carboxylic acid particles. Although thus obtained granulated 2-hydroxynaphthalene-3-carboxylic acid particles exhibited suppressed dusting tendency, said process is highly complicated, that is, comprises the steps of adding a determined amount of water to 2-hydroxynaphthalene-3-carboxylic acid and controlling the water content of acid precipitated 2-hydroxynaphthalene-3-carboxylic acid by centrifugation and therefore was not suitable for mass production.
Further, Japanese Patent Application Laid Open NO. 212533/1986 discloses a process for preparing granule comprising the step of granulating 2-hydroxynaphthalene-3-carboxylic acid together with an aqueous mixture containing a hydrophilic organic solvent having lower boiling point such as a lower alcohol. In this process, the step to add the organic solvent is required and therefore, the whole process becomes longer.
Accordingly, the object of the present invention is to solve the above-mentioned problems and to provide crystalline 2-hydroxynaphthalene-3-carboxylic acid with well-suppressed dusting tendency.
DISCLOSURE OF INVENTION
The present invention provides a crystalline composition of 2-hydroxynaphthalene-3-carboxylic acid with a extremely suppressed dusting tendency, having an average particle size of equal to or more than 175 &mgr;m and the proportion of the particles of which particle size are equal to or less than 74 &mgr;m is equal to or less than 14%.
In the present specification and claims, each “%” represents weight % except for indicated particularly.
In the present specification and claims, the average particle size means the value determined as below:
The sample material is weighted and then is sequentially screened with sieves having aperture of 710 &mgr;m, 297 &mgr;m, 170 &mgr;m, 106 &mgr;m, 74 &mgr;m and 45 &mgr;m in this order. The residue on the respective sieves and the amount of passed the 45 &mgr;m sieve were weighed. The average particle size is calculated as follows:
average particle size (&mgr;m)=(710×residue on the 710 &mgr;m sieve (wt %)/100)+(297×residue on the 297 &mgr;m sieve
(wt %)/100)+(170×residue on the 170 &mgr;m sieve (wt %)/100)+(106×residue on the 106 &mgr;m sieve (wt %)/100)+
(74×residue on the 74 &mgr;m sieve (wt %)/100)+(45×residue on the 45 &mgr;m sieve (wt %)/100)+(25×passed the 45 &mgr;m sieve (wt %)/100).
The crystalline particles of 2-hydoroxynaphthalene-3-carboxylic acid having the characteristics recited in the present invention are more than 2-4.5 times as large as the conventional crystalline 2-hydoroxynaphthalene-3-carboxylic acid particles. The crystalline composition of the present invention exhibits significantly suppressed dusting tendency, and therefore, is easy for handling with significantly reduced risk to environment and human beings. Further, said crystalline particles of the present invention can easily be pulverized into fine particles and exhibit the dissolution rate comparative to the conventional small size (50-90 &mgr;m) crystalline particles. That is, the crystalline composition of the present invention may preferably be used as intermediate of pigments or dyes.
The large-size crystalline 2-hydroxynaphthalene-3-carboxylic acid of the present invention preferably possesses chromaticity of, 38-69 of lightness and 4.6-18.0 of whiteness.
“Chromaticity” used herein means a property of a color stimulus determined by chromaticity coordinates or by combination of dominant wavelength or complementary wavelength and purity (JIS Z 8120).
“Lightness” means an attribute of a color in respect of relative contrast of the surface of an object, which is classified on the basis of white surface that is illuminated by same condition (JIS Z 8105). In the present specification and claims, “lightness” represents L value of the “Lab” color representation system, which is well known in the art. The Lab values are calculated by the following formula from tristimulus values (X, Y, Z) measured according to JIS Z 8722:
L=
10(
Y
)
½
a=
17.5(1.02
X−Y
)/(
Y
)
½
b=
7.0(
Y−
0.847
Z
)/(
Y
)
½
“Whiteness” is a number of one-dimensional value representing the
Izumichi Nobutaka
Kato Hiroyuki
Kitayama Masaya
Ueno Ryuzo
Kabushiki Kaisha Ueno Seiyaku Oyo K.
Killos Paul J.
Sughrue & Mion, PLLC
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