Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acid esters
Reexamination Certificate
2001-12-19
2002-10-15
Rotman, Alan L. (Department: 1625)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acid esters
C560S129000, C560S205000
Reexamination Certificate
active
06465681
ABSTRACT:
BACKGROUND OF THE INVENTION
A. Technical Field
The present invention relates to a production process for a hydroxyalkyl(meth)acrylate, which comprises the step of carrying out a reaction between (meth)acrylic acid and an alkylene oxide.
B. Background Art
When a hydroxyalkyl(meth)acrylate is produced by carrying out a reaction between (meth)acrylic acid and an alkylene oxide, impurities, such as a diester (for example, alkylene glycol di(meth)acrylate) and a monoester (for example, dialkylene glycol mono(meth)acrylate), are formed as by-products. Therefore, a problem of lowering the reaction selectivity of the hydroxyalkyl(meth)acrylate is hitherto caused.
This diester promotes the polymerization of the aimed hydroxyalkyl(meth)acrylate and causes a trouble such as clogging of apparatuses. In addition, when a (co)polymer was produced by using a hydroxyalkyl(meth)acrylate including a diester as a raw material, the resultant polymer might have “turbidity” or be gelled in the polymerization. Furthermore, the vapor pressure of this diester approximate that of the hydroxyalkyl(meth)acrylate. Therefore, once the diester is formed, it is very difficult to separate them.
It is known that the diester is formed by an esterification or disproportionation reaction as a side-reaction when a reaction liquid obtained by the reaction between (meth)acrylic acid and an alkylene oxide is heated to higher temperature (JP-A-133227/1976). Therefore, if the reaction temperature is lowered, the formation of the diester is suppressed. However, if the reaction temperature is lowered, the productivity is not only lowered because the reaction process time is extremely lengthened but also a portion of the resultant product may be denatured or decomposed because of the reaction for a long time.
In addition, methods for adding an inhibitor for forming the diester are proposed (JP-A-133227/1976, JP-A-23019/1977, JP-A-237021/1998, and JP-A-237022/1998). However, the sufficient effect is not obtained.
In addition, as to the monoester, methods for suppressing its formation are proposed (JP-B-6182/1989). However, the sufficient effect is not obtained.
In a production process of a hydroxyalkyl(meth)acrylate by carrying out a reaction between (meth)acrylic acid and an alkylene oxide, the following modes are generally employed: a mode of adding the (meth)acrylic acid, the alkylene oxide and a catalyst all at once to a reactor (addition of all at once); or a mode of beforehand charging a reactor with the (meth)acrylic acid and a catalyst, and then adding the alkylene oxide to the reactor (addition of one after another).
When the addition of all at once is carried out, the formation of the impurities is suppressed. Therefore, it is a favorable mode in the respect that the reaction selectivity of the hydroxyalkyl(meth)acrylate can be raised. However, when the alkylene oxide exists together with oxygen and a certain condition is satisfied, an explosive (mixed) gas is formed. Therefore, the addition of all at once, which causes a concentration of the alkylene oxide of the gas phase in the reaction system to rise when the raw alkylene oxide is charged or at the start of adding the alkylene oxide, has a problem of high danger of explosion.
When the addition of one after another is carried out, it is a favorable mode in the respect that the above-mentioned problem is decreased and the hydroxyalkyl(meth)acrylate can safely be produced, and further the formation of the impurities can be suppressed by selecting an appropriate reaction temperature and controlling it.
In the addition of one after another, the alkylene oxide is generally supplied at a constant speed hitherto. This is because the following is thought: it is easy to control an appropriate reaction temperature for suppressing the side-formation of the impurities; and the supply of the alkylene oxide is favorably carried out at a constant speed in consideration for difficulty of handling the alkylene oxide.
In order to raise productivity in the addition of one after another, it is necessary to increase the supplying speed of the alkylene oxide and to shorten the supplying time of the alkylene oxide. In addition, it is desired to shorten the supplying time of the alkylene oxide in order also to suppress the side-formation of the impurities (for example, the diester or the monoester) that have a bad influence on product quality. However, a conventionally general method, which involves supplying with simply increasing the supplying speed in a definite amount, causes the concentration of the residual alkylene oxide to increase, and causes a problem of danger of explosion.
SUMMARY OF THE INVENTION
A. Object of the Invention
Accordingly, an object of the present invention is to provide: a production process for a hydroxyalkyl(meth)acrylate, which can raise productivity together with avoiding danger of explosion, and further produces the hydroxyalkyl(meth)acrylate with high purity for a short time while the side-formation of impurities such as a diester or a monoester is suppressed wherein the impurities have a bad influence on product quality.
B. Disclosure of the Invention
The present inventors diligently studied in order to solve the problems. As a result, they found that the problems can be solved by varying a supplying speed of the alkylene oxide so as to adjust to specific conditions during a supplying period.
In addition, they found that the temperature-dependency of the formation amount of the diester or the monoester is varied by the reaction conversion of the (meth)acrylic acid in a reaction liquid. Then, they found that: if the alkylene oxide was added to the (meth)acrylic acid, the temperature-dependency was high at the initial reaction stage when the reaction conversion of the (meth)acrylic acid was low, but the temperature-dependency was low at the latter reaction stage when the reaction conversion of the (meth)acrylic acid was high.
According to the above findings, the present inventors reached an idea that the problems of the present invention could be solved by varying the supplying speed of the alkylene oxide during the supplying period and/or by: suppressing the formation of the diester or the monoester by controlling the reaction temperature in the range of a low temperature while the reaction conversion of the (meth)acrylic acid is low; and elevating the reaction temperature when the reaction conversion of the (meth)acrylic acid was high to a certain extent. Then, they completed the present invention.
That is to say, a production process for a hydroxyalkyl(meth)acrylate, according to the present invention, comprises the step of carrying out a reaction between (meth)acrylic acid and an alkylene oxide in the presence of a catalyst in order to produce the hydroxyalkyl(meth)acrylate, wherein: when the time from the start of adding the alkylene oxide till the end of supplying the entirety of the alkylene oxide is defined as T (hour), the amount of more than 50% of the entirety of the alkylene oxide is supplied before T/2 (hour) has passed since the start of adding the alkylene oxide.
In addition, another production process for a hydroxyalkyl(meth)acrylate, according to the present invention, comprises the step of carrying out a reaction between (meth)acrylic acid and an alkylene oxide in the presence of a catalyst in order to produce the hydroxyalkyl(meth)acrylate, wherein: when the total amount of the alkylene oxide as supplied and the time from the start of adding the alkylene oxide till the end of supplying the entirety of the alkylene oxide are defined as W (mol) and T (hour) respectively, the supply of the alkylene oxide is started at a supplying speed V0 (mol/hour) that is faster than the average supplying speed V (=W/T) (mol/hour), and thereafter the supplying speed of the alkylene oxide is decreased at least once, and then the supply of the entirety of the alkylene oxide is completed for T (hour) from the start of adding the alkylene oxide.
Furthermore, yet another production process for a hydroxyalkyl(meth)acrylate, according to the present i
Ishida Tokumasa
Kajihara Tetsuya
Kawashima Tadayoshi
Shingai Yasuhiro
Uemura Masahiro
Nippon Shokubai Co. , Ltd.
Reyes Hector
Roylance Abrams Berdo & Goodman L.L.P.
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