JPH01258643A - Production of polyfunctional (meth)acrylic acid ester - Google Patents

Abstract

PURPOSE:To easily obtain the subject compound having high purity and transparency and light color, by reacting (meth)acrylic acid with a polyhydric alcohol under blowing a molecular O2-containing gas in the presence of an acid catalyst and pyrogallol and subjecting the reaction product to a specific treatment. CONSTITUTION:The objective compound useful as a crosslinking agent or a modifier for synthetic resins, synthetic fibers, coatings, etc., e.g. trimethylolpropane trimethacrylate, can be produced by reacting (meth)acrylic acid with a polyhydric alcohol such as trimethylolpropane in a solvent forming an azeotropic mixture with formed water (e.g. siloxane) in the presence of an acid catalyst (e.g. p-toluenesulfonic acid) and pyrogallol at 80-130 deg.C for 5-12h while blowing a gas containing molecular O2 (preferably air), adding water to the reaction mixture to extract and remove the acid catalyst and treating with an alkaline aqueous solution of NaOH, etc., having a concentration of 5-20wt.% to neutralize, wash and remove excess (meth)acrylic acid.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing a polyfunctional ester of acrylic acid or methacrylic acid ester (hereinafter abbreviated as (meth)acrylic acid) which is light in color and has good transparency.

[Prior art and problems]

In general, when producing polyfunctional (meth)acrylic acid esters, there are drawbacks such as a distillation purification step that causes polymerization and a decrease in yield, so a water washing method or the like is employed. Polyfunctional (meth)acrylic acid esters are widely used as crosslinking agents and modifiers for synthetic resins, synthetic fibers, paints, etc., and products with high transparency are desired, but they cannot be colored by simply washing with water. It has been extremely difficult to obtain products with low color, light color, and high transparency.

According to Japanese Patent Publication No. 48-11084, a method of coexisting a hypophosphorous acid compound during the synthesis reaction is known as a method for obtaining a highly transparent polyfunctional (meth)acrylic acid ester. Since this is insufficient, it has been proposed to further treat with activated carbon after removing the solvent. Furthermore, JP-A No. 49-26227 describes a method in which a copper compound and a polyhydroxy compound are used together as polymerization inhibitors in the synthesis reaction of polyfunctional (meth)acrylic acid; ) A large amount of luenesulfonic acid catalyst etc. must be used, and as a result, a large amount of neutralizing agent is required, which is economically disadvantageous.

Moreover, in Japanese Patent Publication No. 60-42777, polyfunctional (meth)
A method has been proposed in which ferrous sulfate or copper sulfate is used as a polymerization inhibitor in the synthesis of acrylic acid ester, and the reaction solution is treated with activated carbon. Furthermore, JP-A-61-165
No. 349 uses /'t hydroquinone or hydroquinone monomethyl ether or copper chloride as a polymerization inhibitor, and a solid decolorizing agent (activated carbon and/or activated clay).
It has been proposed to cause the activated carbon to coexist and react, to separate most of the activated carbon after the reaction, and then to add celite as a filter aid and perform suction filtration. However, with either method, it is extremely difficult to obtain a light-colored product with an APIIA of 30 or less using only ordinary alkali and water washing, and both require the use of activated carbon, activated clay, etc., and a filter aid such as Celite. , the operation process is complicated and it is economically disadvantageous.

An object of the present invention is to provide an industrially advantageous method for producing a highly pure, light-colored, and highly transparent polyfunctional (meth)acrylic ester.

The present invention relates to a method for producing a polyfunctional (meth)acrylic acid ester by reacting (meth)acrylic acid and a polyhydric alcohol, in which the reaction is performed while blowing a molecular oxygen-containing gas in the presence of an acid catalyst and pyrogallol. , production of a polyfunctional (meth)acrylic acid ester characterized by adding water after the reaction to extract and remove the acid catalyst, and then neutralizing, washing, and removing excess (meth)acrylic acid with an aqueous alkaline solution. It is the law.

In the present invention, the polyhydric alcohol used as a raw material is a compound having two or more alcoholic hydroxyl groups. For example, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, 1°3-phthylene gelicol, 1.6
-hexanediol, neopentyl glycol, hydrogenated bisphenol Δ, trimethylolethane, trimethylolpropane, pentaerythritol, dipentaerythritol, and the like.

As the acid catalyst, one containing heavy metals (particularly containing iron, copper, tin, lead, etc.) of 50 ppm or less is usually used. If the heavy metal component in the acid catalyst exceeds 50 ppm, it is not preferable in terms of an increase in the amount of polymerization inhibitor required and the number of colors of the product.

The pyrogallol used in the present invention has a purity of 98% by weight or more,
It is preferable to have a melting point of 132 to 137°C, a loss on drying of 1% or less, and a heavy metal content (particularly including iron, copper, tin, lead, etc.) of 1100 pp or less. The amount of pyrogallol used is 0.01 to 3% by weight based on (meth)acrylic acid, especially 0.1 to 3% by weight.
0.5% by weight is preferred. If it is less than 0.011% by weight, the effect of preventing polymerization will be small, and if it is more than 3% by weight, it will become a burden on the subsequent purification process.

In the reaction, an azeotropic solvent with the produced water, such as benzene, toluene, n-hexane, cyclohexane, etc., is usually used.

The reaction temperature is usually 80 to 130°C. During the reaction, a molecular oxygen-containing gas (preferably air) is blown into the reaction solution. It is preferable to start blowing the molecular oxygen-containing gas when the temperature of the reaction solution reaches 60°C. If a molecular oxygen-containing gas is not blown, a portion of the (meth)acrylic acid polymerizes at 80° C. or higher, causing cloudiness and a decrease in yield.

The reaction time is determined by determining the degree of progress of the reaction based on the amount of water produced, and is selected so that the reaction is completed at an appropriate time according to the required purity of the reaction product. Usually, the amount of water produced is 97% or more of the theoretical amount of water produced. so that it becomes The reaction time is usually
It is in the range of 5 to 12 hours.

After the reaction is completed, the amount of the target product is usually 0.5 to 1.
Further add 5 times the amount of azeotropic solvent by weight, and cool to 60° C. or lower if necessary. Next, usually 10 to 3
0% by weight of water is added, and after stirring, the mixture is allowed to stand, and the acid catalyst is extracted, separated, and recovered as an aqueous solution.

This operation typically recovers 85% or more of the catalyst.

Further, unreacted (meth)acrylic acid added in excess is also recovered at the same time, and the recovery rate is usually 15 to 20%. The recovered catalyst solution can be reused as it is or after being purified separately. If this catalyst separation step is omitted, floating matter will be generated at the interface during the next alkaline washing, causing a decrease in yield, and a light-colored product will not be obtained.

An aqueous alkaline solution is added to the reaction solution after removing the catalyst. The concentration of the alkaline aqueous solution is usually 5 to 20% by weight, and the alkali is preferably caustic soda. The amount added is 0.5 to 2 times the weight of the target product. After addition, 40℃
The mixture is stirred at the following temperature and allowed to stand, and unreacted (meth)acrylic acid and the remainder of the catalyst are separated as an alkali salt, and pyrogallol is separated as an aqueous alkali solution. It is preferable to repeat this alkaline washing operation two to three times. With this cleaning,
A solution of a polyfunctional (meth)acrylic acid ester with high transparency (color number APIIA 15 or less in the case of a 50% solution) is obtained. After that, water washing is usually performed once or twice. After washing, the (meth)acrylic acid ester is obtained by distilling off the solvent under reduced pressure, usually at a temperature of 80° C. or lower.

According to the present invention, a highly pure, light-colored, and highly transparent polyfunctional (
meth)acrylic acid esters can be obtained.

〔Example〕

Examples will be given and explained below.

Example 1 313 g (3.3 mol) of methacrylic acid, 148 g (1.1 mol) of trimethylolpropane, 34 g (0.18 mol) of p-)luenesulfonic acid, 0.1 g (0.18 mol) of pyrogallol.
6 g of cyclohexane and 130 g of cyclohexane were placed in a 1J2 glass flask equipped with a reflux condenser, water separator, thermometer, stirrer, and dropping funnel, and reacted while blowing air at a rate of 20 ml/min. Water produced during the reaction was azeotroped with cyclohexane, and after cooling and separation, cyclohexane was returned to the reaction solution, and water was taken out of the reaction system. After 61.5 g of produced water was obtained in a reaction time of 10 hours, 242 g of cyclohexane was added and the mixture was cooled to 60°C. Next, add 100g of water and add 20g of water.
After stirring for 10 minutes, leave to stand still for 10 minutes to form the lower layer aqueous solution I]-
Toluenesulfonic acid was separated. Next, neutralization cleaning was performed three times with 372 g of a 15% caustic soda aqueous solution, and then twice with 372 g of water. Next, 0.01 g of toluhydroquinone was added to this cyclohexane solution, and 6
Cyclohexane was distilled off by heating to 0 to 80°C, and 350 g of trimethylolpropane trimethacrylate (yield 9) was obtained.
5.4%). The number of colors of this product was APHA20.

Example 2 261 g (3.3 mol) of acrylic acid, 148 g (1.1 mol) of trimethylolpropane, 34 g (0.18 mol) of p4 luenesulfonic acid, 0.5 g of pyrogallol,
130 g of cyclohexane was reacted in the same manner as in Example 1. The amount of produced water obtained was 61.3 g. After the reaction,
Add 195g of cyclohexane and cool to 60°C,
100 g of water was added to separate p-toluenesulfonic acid as an aqueous solution. Next, neutralization washing was performed three times with 325 g of a 15% caustic soda aqueous solution, followed by washing twice with 325 g of water. Next, 0.0% toluhydroquinone was added to this cyclohexane solution. 305 g (yield: 94.0%) of trimethylolpropane triacrylate was obtained by adding Olg and heating the mixture to 60 to 80° C. under reduced pressure to distill off cyclohexane. The number of colors of this product was APIIA20.

Example 3 378 g (4.4 mol) of methacrylic acid, 124 g (2.2 mol) of ethylene glycol, 20 g (0.11 mol) of p-toluenesulfonic acid, 0.8 g of pyrogallol,
130 g of cyclohexane was reacted in the same manner as in Example 1. The reaction was carried out for 8.5 hours, and the product water obtained was 64
．． It was 3g. After the reaction, 302 g of cyclohexane was added and the mixture was cooled to 60° C., and 100 g of water was added to separate p-toluenesulfonic acid as an aqueous solution. Then,
After performing neutralization washing three times with 216 g of a 15% caustic soda aqueous solution, washing was performed twice with 216 g of water. Next, 0.0% toluhydroquinone was added to this cyclohexane solution. When cyclohexane is distilled off by adding Olg and heating to 60 to 80°C under reduced pressure, ethylene glycol dimethacrylate 279
g (yield 70.4%) was obtained. The number of colors of this product is A
It was PI + AIO.

Comparative Example 1 Methacrylic acid 313g (3.3 mol), trimethylolpropane 148g (1.1 mol), p-toluenesulfonic acid 34g (0.18 mol), hydroquinone 0.
6 g and 130 g of cyclohexane were reacted in the same manner as in Example 1.

The reaction was run for 9.5 hours. The product water obtained was 3 g of 6C. After the reaction, add 242g of Katasan to the cyclo
The mixture was cooled to 0° C., and 100 g of water was added to separate p-toluenesulfonic acid as an aqueous solution. Then 37
After performing neutralization washing three times with 2 g of 15% caustic soda aqueous solution, washing was performed twice with 372 g of water. Next, 0.01 g of toluhydroquinone was added to this cyclohexane solution, and the cyclohexane was distilled off by heating to 60 to 80°C under reduced pressure, resulting in trimethylolpropane trimethacrylate 3.
57 g (yield 96.0%) was obtained. The number of colors of this product was AI'11A60.

Comparative Example 2 The synthesis reaction and purification were carried out under the same conditions as in Comparative Example 1, except that 0.6 g of catechol was used instead of 0.6 g of hydroquinone as a polymerization inhibitor. As a result, 350 g of trimethylolpropane trimethacrylate (yield 94.1
%)was gotten. The color number of this product was 300 or more.

Comparative Example 3 The synthesis reaction and purification were carried out under the same conditions as in Comparative Example 1, except that 1.2 g of hydroquinone monomethyl ether was used instead of 0.6 g of hydroquinone as a polymerization inhibitor. As a result, trimethylolpropane trimethacrylate 3
40 g (yield 91.4%) was obtained. The number of colors of this product is A
It was PIlA90.

Comparative Example 4 A synthesis reaction was carried out under the same conditions as in Comparative Example 1, and after the reaction was completed, 242 g of cyclohexane was added, and after cooling to 60°C, a 15% caustic soda aqueous solution of 37 g was added without recovering the catalyst with water.
After adding 2 g and stirring for 20 minutes, the mixture was allowed to stand for 10 minutes, but precipitates were generated in the water layer, and a large amount of suspended matter was generated near the interface, making it impossible to separate the liquid.

Comparative Example 5 Under the same preparation conditions as in Example 1, nitrogen gas was blown into the reaction solution instead of air to raise the temperature. Reaction liquid temperature is 82
When the temperature reached ℃, reflux started, so the reaction was considered to have started and the reaction was continued. After 5 minutes, a colored precipitate was formed and continued to increase as time progressed. After reacting for 10 hours at 90°C or lower, the reaction solution was cooled to 40°C and passed through a glass filter (17
When filtered with G4), the solid matter in the wet state was 95.2
g was obtained. After washing this pox solution with 100 g of water, washing with alkali three times and washing with water twice, cyclohexane was distilled off.

As a result, 270 g (yield 72.5%) of trimethylolpropane trimethacrylate was obtained. The number of colors of this product was APIIA25.

Patent applicant: Mitsubishi Gas Chemical Co., Ltd. Agent: Patent attorney Sadafumi Kohori

Claims (1)

[Claims] In a method for producing a polyfunctional (meth)acrylic ester by reacting (meth)acrylic acid and a polyhydric alcohol, the reaction is carried out while blowing molecular oxygen-containing gas in the presence of an acid catalyst and pyrogallol, and after the reaction, water is After extracting and removing the acid catalyst by adding
A method for producing a polyfunctional (meth)acrylic acid ester, which comprises neutralizing, washing, and removing meth)acrylic acid.