Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acid esters
Reexamination Certificate
2002-03-25
2004-03-23
Acquah, Samuel A. (Department: 1711)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acid esters
C524S174000, C210S633000, C560S234000
Reexamination Certificate
active
06710204
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a decreasing method of an N-oxyl compound contained in an easily polymerizable material. More specifically, the present invention relates to a decreasing method of an N-oxyl compound contained in (meth)acrylic acid or a (meth)acrylic acid ester. Further, the present invention relates to a decreasing method of an organic titanium group compound further contained in the easily polymerizable material.
BACKGROUND OF THE INVENTION
With respect to an improving method of characteristics of an ester plasticizer, JP-A-50-145449 discloses a process for producing an ester plasticizer, which comprises the step of allowing an alcohol having a specific carbon atom number to react with an aromatic acid or an aliphatic acid having a specific carbon atom in the presence of a catalyst, thereby obtaining an ester, and the step of contacting the obtained ester with a combination of an activated clay and at least one of a magnesium oxide and a calcium oxide in the presence of water. In the literature, it is disclosed that according to said process, impurities such as unreacted acids, monoesters, the catalyst and by-products, which cause to deteriorate characteristics of the plasticizer, are removed, and as a result, the characteristics can be improved. In the literature, it is further disclosed that a titanium compound such as a tetraalkyl titanate is enumerated as the catalyst used for the production of such an ester. Further, in the literature, there is disclosed a process comprising the step of adding an activated clay, at least one of MgO and CaO and water to the obtained ester at the same time, or adding an activated clay thereto, followed by successive addition of at least one of MgO and CaO and water, and the step of filtering the resulting mixture. It is also disclosed that a water content is suitably from 0.1 to 1% by weight based on the weight of the ester.
JP-A-10-36319 discloses a process for producing an ester, which comprises the step of contacting an ester obtained by reaction between an alcohol and an acid with a compound having both a solid acid and a solid base in the molecule. In the literature, it is disclosed that in producing the ester, the ester, namely a final product is desired to be small in a metal ion content, colorless and low in its acid value, and for that purpose, the ester obtained by reaction between an alcohol and an acid in the presence of an acid catalyst or a metal compound catalyst is treated with an adsorbent, thereby removing various impurities such as impurities contained in the raw materials for the production, by-products produced at the time of production and purification and catalyst residues, and an active carbon, an activated clay and the like can be used as the adsorbent. Further, in the literature, it is disclosed that in the case where an activated clay is used in a manner as proposed in JP-B-59-38254 (corresponding to JP-A-50-145449), there has been left a problem such that physical adsorption and electrostatic adsorption mainly proceed, so that a cation exchange is caused between the activated clay and the metal ion remained in the ester, thereby discharging a proton, and as a result, an acid value of the ester increases to deteriorate a stability.
JP-A-11-222462 discloses a process for producing a high purity (meth)acrylic acid ester, according to which in producing the (meth)acrylic acid ester by the reaction between methyl (meth)acrylate and an alcohol having a specific carbon atom number, tetramethyl titanate and a specific N-oxyl compound are used as a catalyst and a polymerization inhibitor, respectively.
While, JP-A-1-258642 discloses a process comprising the step of using a titanium alkoxide and a steric hindrance phenol as the catalyst and the polymerization inhibitor, respectively, in carrying out a transesterification between a carboxylic acid ester and an alcohol and a direct esterification between a carboxylic acid and an alcohol. Further, JP-A-4-66555 discloses a process comprising the step of using a titanium alkoxide as the catalyst, whose alkoxide is derived from the same alcohol as that used as the material.
Furthermore, with respect to a separating method of such a titanium alkoxide from a reaction product by a means other than distillation, JP-A-8-259498 (corresponding to U.S. Pat. No. 5,760,265) discloses a process, according to which a titanium group metal carboxylate used in the direct esterification between a carboxylic acid and an alcohol is made soluble in water with use of a chelating agent, and then extracted.
SUMMARY OF THE INVENTION
An easily polymerizable material such as various monomers used as materials for producing a polymer can be usually obtained from a petroleum material. Such an easily polymerizable material polymerizes itself due to heat or light or the like, and therefore a polymerization inhibitor is usually added during a production or purification process. The polymerization inhibitor is usually contained also to the easily polymerizable material itself after the production thereof. There are known many compounds to be added to monomers as the polymerization inhibitor. Of these, an N-oxyl compound has a superior polymerization inhibiting ability.
However, when a lot of the polymerization inhibitor is contained in the monomer, a lot of a polymerization initiator is needed when carrying out the polymerization to produce a polymer. A problem of such a polymerization obstruction is remarkable particularly when the monomer contains an N-oxyl compound having a high polymerization inhibiting ability.
As a decreasing method of the polymerization inhibitor contained in the monomer before polymerization, there is known a process for separating the polymerization inhibitor from the monomer by means of distillation. However, according thereto, there is left a problem such that a loss of the monomer is large, a recovery rate is low, and moreover the N-oxyl compound cannot be sufficiently separated or decreased. Further, there is a possibility of polymerization because the monomer is necessarily heated.
As a catalyst used for a transesterification between a carboxylic acid ester and alcohols and a direct esterification between a carboxylic acid and alcohols, there are known a metal catalyst such as an organic titanium group compound and an organic tin based catalyst; an acid catalyst such as p-toluene sulfonic acid, sulfuric acid and a strongly acidic ion exchange resin; and a base catalyst such as a solid base and a strongly basic ion exchange resin.
Of these, an organic titanium group compound, whose typical example is a titanium alkoxide, is extremely high in reaction activity and selectivity, and therefore of extensively wide use as a catalyst in the transesterification and direct esterification.
However, since the catalyst of the organic titanium group compound per se generally dissolves in a reaction liquid, it is necessary to separate the catalyst from the reaction product.
With respect to the separation operation of the catalyst, it is general to carry out the separation by distillation. However, the distillation inevitably causes a loss of a product (a desired product), requires a lot of energy and time and greatly increases costs for apparatus or the like. Moreover, there is a possibility of polymerization during distillation, in the case where the desired product is an unsaturated carboxylic acid ester.
Still, according to the method other than distillation as disclosed in the above-mentioned JP-A-8-259498, there is left a problem such that a lot of waste water is produced, thereby placing a severe load on the environment.
The present invention has been accomplished in the light of these problems. It is an object of the present invention to provide a superior decreasing method of an N-oxyl compound, according to which the N-oxyl compound contained in an easily polymerizable material can be sufficiently decreased with a little loss of the easily polymerizable material.
It is another object of the present invention to economically and industrially an
Doi Junichi
Oh-Kita Motomu
Tokuda Masanori
Yoshida Yasukazu
Acquah Samuel A.
Mitsubishi Rayon Co. Ltd.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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