KR0161528B1 - Process for the preparation of esters of (meth)-acrylic acid and polyfunctional alcohols - Google Patents

Abstract

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Description

Method for preparing (meth) acrylic acid ester of polyhydric alcohol (IV)

The present invention reacts acrylic acid and / or methacrylic acid with polyhydric alcohols in the presence of an acid esterification catalyst with the addition of a synthetic inhibitor to the reaction mixture, hereinafter referred to as (meth) acrylic acid ester. It relates to a method of manufacturing). The method according to the invention is particularly

The reaction zone is rinsed with a stream of oxygen-containing gas to operate by an additional way to enhance the effect of the inhibitor and to promote the release of water from the reaction zone that accumulates as condensation products from the esterification reaction.

Polyhydric alcohols, especially (meth) acrylic acid esters of dihydric to tetrahydric aliphatic saturated alcohols and their alcoholylated products, are increasingly used as highly reactive components in radiotherapy systems. Multifunctional (meth) acrylic acid esters of this type are, for example, as paint components for curing with an electron beam or as components for UV-curing printing inks or the corresponding paint, surface treatment, molding or coating compounds or Among the adhesives, in particular, it may be used as an anaerobic adhesive. However, there are many problems with these productions. The final product needs to be especially colorless with a low acid value, high storage stability, few specific odors. The (meth) acrylic acid esters of the present invention generally cannot be purified by distillation because of their high molecular weight and high reactivity.

Therefore, it is going to accumulate a product directly as a colorless product of esterification reaction. The esterification reaction requires the presence of a high performance inhibitor, a high performance inhibitor that does not start in the form of a particular second reaction, which in other words does not win, for example a decolorization reaction. In addition to protecting the liquid reaction product from causing unwanted polymerization during esterification, it may also be necessary to adequately suppress the entire reaction zone, including the inner gas space and the wall surface in contact with the inner gas space. . This mitigates the risk of undesired polymer formation, for example, if the wall surface is not protected, the polymer may be washed off into the reaction product, causing an undesirable increase in the viscosity of the final product or producing unwanted poorly soluble particles.

The preparation of such polyfunctional (meth) acrylic acid esters of polyhydric alcohols can be found in extensive literature, in particular in JP 29 13 218 and the related literature cited therein.

That is, the polyfunctional (meth) acrylic acid ester can be prepared by an azeotropic esterification reaction of (meth) acrylic acid with a polyhydric alcohol in the presence of an acid catalyst and a polymerization inhibitor such as phenol, phenol derivative, copper copper compound or phenothiazine. Yes, it is known from Federal Republic of Germany Patent Publication No. 1267547 and Chem, and Ind. 18 (1970), 597. Inorganic or organic acids or acid ion exchangers may be used as the acid catalyst, with p-toluene sulfonic acid and sulfuric acid being preferred. The esterification reaction is carried out under azeotropic conditions using, for example, an entraining agent to remove water in the reaction, for example at a temperature in the range from 40 to 120 ° C. Suitable covalent agents are, for example, aliphatic or cycloaliphatic or aromatic hydrocarbons having a boiling point within the above temperature range or mixtures thereof.

The above-mentioned JP 29 13 218 mentions azeotropic esterification by adding a phenol-based inhibitor in the presence of at least one phosphoric acid organic ester to improve the esterification reaction and not distillation purification. It is proposed to obtain (meth) acrylic acid esters in the form. Such phosphite-based inhibitors are especially designed to be added by carrier gas and are believed to be used in particular to promote the inhibition of internal reaction zones filled with gas or vapor phase and to reduce color concentration. In other words, the patent document includes blowing air or nitrogen rich or saturated with organic phosphites to remove residual solvents, residues of reactive components and volatile by-products from esterification products, especially after azeotropic esterification reactions. Is proposed.

Problems addressed by the present invention include not only effectively stabilizing the reactive liquid phase by a polymerization inhibitor, but also protecting the entire interior of the reactor from undesirable polymerization reactions. However, the present invention seeks to consider ways to eliminate the need for a gas phase combined inhibitor system in this regard. More specifically, the problem addressed by the present invention is that the same inhibitor can be used to protect the reactive liquid phase and also to protect the gas- or vapor-filled interior and the solid surface inside the reactor in contact with these parts. It is. Another problem to be dealt with by the present invention is that the application inhibitors actually required for highly reactive systems can be used simultaneously as reaction inhibitors in the synthesis of multifunctional (meth) acrylic acid esters. The problem to be dealt with by the present invention is solved by the new process technology described below.

Accordingly, the present invention provides a method for producing a (meth) acrylic acid ester of a polyalcohol by adding a polymerization inhibitor to a reaction mixture and washing the reaction zone with an oxygen-containing gas stream to react the reactants in the presence of an acid esterification catalyst. And a fine liquid droplet containing a polymerization inhibitor in a portion of the reactor filled with a gas phase.

In a preferred aspect of the present invention, the presently dispersed inhibitor-containing liquid phase finely dispersed in the reactor containing the gas phase is injected in an amount such that all internal solid surface in contact with the gas phase is preferably wetted with the continuous inhibitor-containing liquid film. do. It is also desirable to inject the inhibitor-containing liquid phase into the reactor containing the gas phase while in other words allowing the entire internal gas phase space to be filled with particulate droplets such that no prominent shaded space is formed. In one particularly industrially important embodiment, the inhibitor-containing liquid phase is injected in a finely dispersed state by spraying.

Thus, a description of the new technology according to the invention is as follows:

Instead of inhibiting the gas- or vapor-filled interior and the inner wall surface in contact with it with the inhibitor injected in gaseous form, a previously finely dispersed inhibitor-containing liquid phase is injected into the gas space. These droplets condense on the wall surface in contact with the gas phase.

The amount of inhibitor-containing dispersed liquid phase injected in a batch or preferably continuously into the internal gas space is determined to such an extent that a continuous liquid film containing a polymerization inhibitor can be formed on the inner wall surface. In this way, the possibility of undesired polymerization being initiated is defended by the inhibitor-containing liquid phase, thus ensuring the optimum inhibitory effect of the reaction mixture throughout the entire reaction phase.

In a particularly important aspect, this new principle is carried out as follows: a portion of the liquid reaction mixture containing the polymerization inhibitor in a particulate form in the reactor, more specifically inside the reactor packed with gas or vapor phase or By injection continuously, the reactor interior is filled with particulate inhibitor-containing liquid phase. The amount of the reaction mixture injected in this way is determined so that a continuous liquid film is formed on the inner wall of the reactor, and as the reaction proceeds, it flows down the wall into the pond portion of the reactor and recombines with the main amount of the reaction mixture.

The advantages of this approach are obvious. The new inhibitor-containing particulate liquid phase is injected continuously or batchwise into the internal gas space. This dispersed phase can be fused by droplet agglomeration, in particular condensation on the reactor inner wall, thus returning to the reaction mixture. At the same time, the entire inner wall of the reactor is washed vigorously with an inhibitor-containing liquid phase.

The reaction mixture portion can be particularly easily sprayed by separating a limited amount of liquid reaction mixture batchwise, or preferably continuously, from the pool portion of the reactor and returning it to the gas phase filled reactor through a spray nozzle. have.

Technically, several models can be applied to this. That is, a single spray nozzle or multiple spray nozzles can be used. A liquid circuit may be provided inside the reactor, or the liquid phase portion to be sprayed may be removed by a pump located outside the reactor and returned to the reactor by a spray nozzle. The size of the liquid and the degree of spraying of the liquid phase in the gas-filled reactor greatly influences the design of the spray nozzle and its manner of operation.

When the liquid phase is circulated as described above, it is preferable to inject at least a part of the free oxygen-containing gas stream into the partial stream of the removed liquid and return it to the inside of the reactor with the partial stream. Undesired containment of the circulating liquid phase is known to be avoided in this way. In another important aspect, the liquid phase is drawn inside the reactor by drawing the liquid phase portion into the reactor and rapidly transporting it into the gas-filled reactor in finely dispersed form using, for example, a rotator immersed in the liquid reaction mixture. Disperse It is also possible to provide a plurality of the above rotary devices.

In a particularly important aspect of the present invention, the gas phase is at least partially recovered from the inside of the reactor and returned to the liquid reaction mixture, whereby a portion of the liquid phase is distilled together by a recycle gas stream into the gas-filled reactor. If this method is adopted, the esterification reaction will be more vigorous and accelerated if the circulating gas phase is further dried, ie removing the absorbed condensate.

In one particularly preferred embodiment, the reaction mixture is liquid at room temperature and contains at least substantially no solvents and / or azeotropic agents. In practical application of this aspect of the process of the present invention, it is effective to discharge the reaction water generated during the esterification reaction only by the gas flow injected into the reaction zone. Depending on the process conditions, an air or oxygen-deficient gas mixture, for example a nitrogen / air mixture, can be used as the gas stream. In general, however, it will be desirable to have some free oxygen in such a gas phase that is conveyed to the reaction mixture. These limited amounts of oxygen activate the inhibitor in a known manner during the reaction.

Through the method according to the invention in which the polymerization inhibitor is dispersed throughout the reactor by partial spraying of the liquid inhibitor-containing reaction mixture, application inhibitors necessary for the practical use of the reaction product can be used as inhibitors of the esterification reaction itself. Relatively high volatility inhibitor components for proper protection of gas- or steam-filled reactor interiors and corresponding wall surfaces, which have typically been used up to now, are no longer needed. Thus, the present invention allows a substantially nonvolatile and highly effective inhibitor system or appropriately selected substantially nonvolatile individual inhibitors to be effectively used from the beginning of the reaction to the final practical use of the reaction product. It is no longer necessary to replace the reaction inhibitors used in the manufacturing process with application inhibitors for practical use.

Suitable polymerization inhibitors are inhibitor systems containing certain individual inhibitor compounds selected and various components. Particular preference is given to using relatively low volatility compounds based on monovalent or polyhydric phenols, particularly suitable polyhydric phenol compounds are dihydric phenols in the form of hydroquinone or hydroquinone derivatives.

According to the invention there is particular significance in the three selected forms of the process for the preparation of the above-mentioned forms, in particular substantially colorless, high purity radio-therapeutic (meth) acrylic acid esters. Although specific conditions are required in order to use hydroquinone itself in esterification reaction as mentioned below, the best among these inhibitors is hydroquinone.

There is almost no problem with the use of steric hindrance hydroquinone, ie di-t-butylhydroquinone. The third important polymerization inhibitors are phenolic compounds in which the tocopherol form is steric hindrance, among which α-tocopherol is particularly important.

By using di-t-butyl hydroquinone, a pale, hypotonic (meth) acrylic acid ester of the desired form can be obtained. In this case, if the lightening of the reaction product takes place during the manufacturing process, especially in the absence of solvent and under vigorous esterification conditions, it may be easily removed by post-treatment, for example with aluminum oxide.

Solvent esterification reactions according to the invention using hydroquinone as polymerization inhibitors cause relatively more serious color problems. In this case, the absence of an auxiliary means results in relatively severe decolorization of the esterified product, which cannot be easily removed by post-treatment of the reaction product. In one particular aspect, the present invention proposes to resolve this style by co-adding activated carbon to the reaction mixture in which hydroquinone is used as a polymerization inhibitor. Surprisingly, while the combination of hydroquinone and activated carbon inhibits undesirable and undesirable decolorization of the reaction product even under severe esterification conditions, the inhibitory effect of hydroquinone is not significantly affected by the presence of activated carbon. Found. Upon completion of the esterification reaction, simply purifying the reaction mixture, for example by filtration, yields a substantially colorless reaction product. The inhibitor is typically added to the reaction mixture in an amount of 200 to 10,000 ppm, preferably about 300 to 2,000 ppm, based on the weight of the reaction mixture consisting of (meth) acrylic acid and polyhydric alcohol.

When hydroquinone is used in combination with activated carbon as an inhibitor system, the amount of activated carbon does not significantly exceed the amount of hydroquinone in the preferred embodiment. Activated carbon is used in an amount of about 10 times or more, preferably 10 to 100 times, more preferably about 20 to 60 times the weight of the hydroquinone.

Preferred embodiments of the use of the inhibitors referred to herein include three patents in which the invention, which is filed as the same, is a method for preparing a (methyl) acrylic acid ester of polymethyl alcohol (I), (II), (III) D8492, D8493, D8494). Although it is specified in the application, the content described therein applies equally to the present invention.

Polyhydric alcohols suitable for esterification are, for example, ethylene glycol, propylene glycol, butane-1, 4-diol, hexane-1, 6-diol, neopentyl glycol, diethylene glycol, triethylene glycol, dimethylolpropane , Glycerol, trimethylolpropane, trimethylolhexane, trimethylolethane, hexane-1, 5-triol and pentaerythritol.

However, particularly suitable polyhydric alcohols in the present invention are the alcohol silylation products of such polyhydric alcohols, of particular importance in this regard are the ethoxylated products and / or propoxylated products. This type of chain-extending polyalcohol may contain a significant amount of polyalkoxide groups, for example 1 to 50 moles, preferably about 1 to 20 moles of ethylene oxide per gram-equivalent hydroxyl group.

Suitable esterification catalysts for the process of the present invention are commercially available organic or inorganic acids or acid ion exchangers are also possible, particularly important are the corresponding compounds which are often used in practice, ie p-toluenesulfonic acid and sulfuric acid. The esterification catalyst is used, for example, in an amount of 0.1 to 5% by weight, based on the esterification mixture.

The reactants may be reacted under relatively vigorous conditions in the absence of solvents or diluents. A sump temperature of at least about 90 ° C., preferably at least about 100 ° C., is preferred for the esterification reaction, with a temperature range of about 150 ° C. or less being particularly suitable. Although it is suitable to carry out the reaction under reduced pressure, it can be carried out under normal pressure. When the reaction is carried out under reduced pressure, in one embodiment the pressure can be reduced stepwise or continuously to low pressure.

Since it can be carried out under relatively vigorous esterification conditions and at the same time under reduced pressure, the reaction time is considerably shortened compared to the methods known so far. Thus, the theoretical yield obtained in the process of the present invention carried out for a reaction time of about 10 hours or less, preferably about 8 hours or less, in the temperature range of about 100 to 140 ° C. may be at least 90%, preferably at least about 94%. have. Despite these conditions, the reaction product is obtained in the form of a light lump or a stable mass which can be effectively purified by simple workup.

The crude reaction product containing the acid esterification catalyst is then neutralized. This neutralization step can be carried out under known wet conditions using, for example, an aqueous solution containing sodium carbonate and optionally sodium chloride. In one preferred embodiment, however, the crude reaction product containing the acid catalyst is dried to neutralize. Suitable dry neutralizing agents are oxides and / or hydroxides of alkali metals, alkaline earth metals, in particular magnesium or calcium and / or aluminum.

(Meth) acrylic acid and alcohol may be used in equivalent amounts in the esterification reaction.

However, when dihydric or higher alcohols are used, there is a high possibility of only partially esterifying hydroxyl groups. For complete esterification, it is most suitable to use the acid component in slightly excess than the stoichiometric amount required for esterification of the hydrosil group.

This slight excess may be at least about 10 mole percent. In some cases, the inhibitor may be further added to the reaction product upon completion of the reaction.

Example 1

14.53 kg of acrylic acid, 14.18 kg of ethoxylated trimethylol propane (OH value: 665 mg KOH / g material), 1.01 kg of p-toluenesulfonic acid and 0.047 kg of 2,5-di-t-butylhydroquinone (polymerization inhibitor) 2,000 ppm by weight of product) was quantified and injected into a 30 1 reactor. Air (100 1 / h) was passed through the reaction mixture during the esterification and water was removed. Injection of the reaction mixture containing the polymerization inhibitor in the form of particulate droplets is carried out by spraying the reaction mixture containing the polymerization inhibitor inside the reactor containing no polymerization inhibitor through the compressed-air diaphragm pump and the upper one-component nozzle. It was. The flow rate of the product was chosen to the extent of wetting with the product containing the polymerization inhibitor of all parts of the reactor (40 1 / h). To avoid undesired polymer formation, the inner wall of the pipe was coated with Teflon and further air was injected into the pressurized portion of the product circuit (60 1 / h). According to another way of suppressing the condensation part of the reactor, further suppressed distillate was circulated and sprayed in the condenser zone. Maximum reaction temperature of 105 ° C. and reduced pressure distribution 2h / 400 mbar; 1 h / 300 mbar; 0.5 h / 200 mbar; At 1 h / 100 mbar and 0.5 h / 23 mbar, the esterification time was 5 hours.

Crude product:

Acid value: 17.3 mg KOH / g

OH value: 12.6 mg KOH / g

Yield: 96.9%

Gardner Color Standard Number: 1

Viscosity: 150 mPa.s

H2O content: 0.09%

0.53 kg Ca (OH) ₂ was added and stirred at 80 ° C./50 mbar for 2 hours to neutralize the crude product, which was then filtered through a pressure filter.

Product:

Acid value: 1 mg KOH / g

OH value: 14 mg KOH / g

Gardner Color Standard Number: 1

Comparative Example 1

The process of Example 1 was followed except that no product or distillate was sprayed during the esterification reaction. Even after only 30 minutes of esterification, polymer formation was clearly observed in both the cover region and the condensation zone of the reactor.

Crude product:

Acid value: 39.2 mg KOH / g

OH value: 18 mg KOH / g

Yield: 95.4%

Gardner Color Standard Number: 1

H ₂ O content: 0.13%

1.5 kg Ca (OH) ₂ was added and stirred at 80 ° C./50 mbar for 2 hours to neutralize the crude product, which was then filtered through a pressure filtration apparatus.

Product:

Acid value: 1 mg KOH / g

OH value: 21 mg KOH / g

Gardner Color Standard Number: 1

H ₂ O content: 0.17%

Example 2

12.97 kg of acrylic acid, 15.82 kg of propoxylated neopentylglycol (OH value: 509 mg KOH / g substance), 1.01 kg of p-toluenesulfonic acid and 47 kg of 2.5-di-t-butylhydroquinone (polymer weight) 2,000 ppm) was quantified and injected into a 30 1 reactor. Air (100 1 / h) was passed through the reaction mixture during the esterification and water was removed. Compression-injecting the reaction mixture containing the polymerization inhibitor in the form of particulate droplets by spraying the reaction mixture containing the polymerization inhibitor into the reactor containing no polymerization inhibitor through the air diaphragm pump and the upper one-component nozzle. It was. The flow rate of the product was chosen to the extent that all parts of the reactor were wetted with the product containing the polymerization inhibitor (40 1 / h). In order to avoid unwanted polymer formation, the inner wall of the pipe was coated with Teflon and further air was injected into the pressurized portion of the product circuit (60 1 / h). According to another way of suppressing the condensation part of the reactor, further suppressed distillate was circulated and sprayed in the condenser zone. Maximum reaction temperature 105 ° C. and reduced pressure distribution 2 h / 400 mbar; 1 h / 300 mbar; 0.5 h / 200 mbar; At 1 h / 100 mbar and 0.5 h / 30 mbar, the esterification time was 5 hours.

Crude product:

Acid value: 34 mg KOH / g

OH value: 17 mg KOH / g

Yield: 94.4%

Gardner Color Standard Number: 1

1.3 kg Ca (OH) ₂ was added and stirred at 80 ° C./50 mbar for 2 hours to neutralize the crude product, which was then filtered through a pressure filtration apparatus.

Product:

Acid value: 1 mg KOH / g

OH value: 20 mg KOH / g

Gardner Color Standard Number: 1

Comparative Example 2

The process of Example 2 was followed except that no product or distillate was sprayed during the esterification reaction. After only 40 minutes of esterification, polymer formation was clearly observed both in the cover region and the condensation zone of the reactor.

Crude product:

Acid value: 20 mg KOH / g

OH value: 20 mg KOH / g

Yield: 95.0%

Gardner Color Standard Number: 1

0.63 kg Ca (OH) ₂ was added and stirred at 80 ° C./50 mbar for 1.5 hours to neutralize the crude product, which was then filtered through a pressure filtration apparatus.

Product:

Acid value: 1 mg KOH / g

OH value: 23 mg KOH / g

Gardner Color Standard Number: 1

Example 3

14.53 kg of acrylic acid, 14.18 kg of ethoxylated trimethylol propane (OH value: 665 mg KOH / g substance) and 1.01 kg of p-toluenesulfonic acid were quantified and injected into a 30 1 reactor, and 52.6 kg of α- as a polymerization inhibitor. Tocopherol (HENKEL; 2,000 ppm by product weight) was added to inhibit polymerization. Air (100 1 / h) was passed through the reaction mixture during the esterification reaction and water was removed. Injecting the reaction mixture containing the polymerization inhibitor in the form of particulate droplets by spraying the reaction mixture containing the polymerization inhibitor into the reactor containing no polymerization inhibitor through the compressed-air diaphragm pump and the upper one-component nozzle. It was. The flow rate of the product was chosen to the extent that all parts of the reactor were wetted with the product containing the polymerization inhibitor (40 1 / h).

To avoid unwanted polymer formation, the inner wall of the pipe was coated with Teflon and further air was injected into the pressurized portion of the product circuit (60 1 / h). According to another way of suppressing the condensation part of the reactor, further suppressed distillate was circulated and sprayed in the condenser zone. Maximum reaction temperature of 105 ° C. and reduced pressure distribution 2h / 400mbar; 1 h / 300 mbar; 0.5 h / 200 mbar; At 1 h / 100 mbar and 0.5 h / 25 mbar, the esterification time was 5 hours.

Crude product:

Acid value: 17.0 mg KOH / g

OH value: 33.6 mg KOH / g

Yield: 91.4%

Gardner Color Standard No.: 7-8

H ₂ O content: 0.16%

0.52 kg Ca (OH) ₂ was added and stirred at 80 ° C./50 mbar for 1.5 hours to neutralize the crude product, which was then filtered through a pressure filtration apparatus.

Product:

Acid value: 1 mg KOH / g

OH value: 43 mg KOH / g

Gardner Color Standard No.: 5-6

H ₂ O content: 0.42%

For bleaching, the neutralized and filtered product was stirred with 2.5 kg of basic Al ₂ O ₃ at 80 ° C. for 2 hours and then filtered with a pressure filtration device.

Product:

Acid value: 1 mg KOH / g

OH value: 42 mg KOH / g

Gardner Color Standard Number: 1

H ₂ O content: 0.08%

Comparative Example 3

The process of Example 3 was followed except that no product or distillate was sprayed during the esterification reaction. After only 30 minutes of esterification, polymer formation was clearly observed both in the cover region and the condensation zone of the reactor.

Crude product:

Acid value: 23 mg KOH / g

OH value: 19 mg KOH / g

Yield: 95.3%

Gardner Color Standard Number: 8

0.71 kg Ca (OH) ₂ was added and stirred at 80 ° C./50 mbar for 1 hour to neutralize the crude product, which was then filtered through a pressure filter.

Neutralization product:

Acid value: 1 mg KOH / g

OH value: 20 mg KOH / g

Gardner Color Standard Number: 6

For decolorization, the neutralized and filtered product was stirred with 2.5 kg of basic Al ₂ O ₃ at 80 ° C. for 2 hours and then filtered with a pressure filtration device.

Product:

Acid value: 1 mg KOH / g

OH value: 22 mg KOH / g

Gardner Color Standard Number: 1

Example 4

12.97 kg of acrylic acid, 15.82 kg of propoxylated neopentyl glycol (OH value: 509 mg KOH / g substance) and 1.01 kg of p-toluene sulfonic acid were quantified and injected into a 30 1 reactor, and 47 g of α- polymerization inhibitor, Polymerization was inhibited with tocopherol (HENKEL; 2,000 ppm by product weight). Air (40 1 / h) was passed through the reaction mixture during the esterification and water was removed. The reaction mixture containing the polymerization inhibitor is sprayed into the reactor free of polymerization inhibitor through a compressed-air diaphragm pump and an upper one-component nozzle, thereby injecting the reaction mixture containing the polymerization inhibitor in the form of fine droplets. It was. The flow rate of the product was chosen to the extent that all parts of the reactor were wetted with the product containing the polymerization inhibitor (40 1 / h). In order to avoid unwanted polymer formation, the inner wall of the pipe was coated with Teflon and further air was injected into the pressurized portion of the product circuit (60 1 / h). According to another way of suppressing the condensation part of the reactor, further suppressed distillate was circulated and sprayed in the condenser zone. Maximum reaction temperature of 105 ° C. and reduced pressure distribution 2h / 400mbar; 1 h / 300 mbar; 0.5 h / 200 mbar; At 1 h / 100 mbar and 0.5 h / 25 mbar, the esterification time was 5 hours.

Crude product:

Acid value: 24 mg KOH / g

OH value: 20 mg KOH / g

Yield: 94.4%

Gardner Color Standard No.: 7-8

0.72 kg Ca (OH) ₂ was added and stirred at 80 ° C./50 mbar for 1 hour to neutralize the crude product, which was then filtered through a pressure filtration apparatus.

Neutralization product:

Acid value: 1 mg KOH / g

OH value: 22 mg KOH / g

Gardner Color Standard Number: 6

For decolorization, the neutralized and filtered product was stirred with 2.5 kg of basic Al ₂ O ₃ at 80 ° C. for 2 hours and then filtered through a pressure filtration apparatus.

Product:

Acid value: 1 mg KOH / g

OH value: 24 mg KOH / g

Gardner Color Standard Number: 1

[Comparative Example 4]

The process of Example 4 was followed except that no product or distillate was sprayed during the esterification reaction. After only 30 minutes of esterification, polymer formation was clearly observed both in the cover region and the condensation zone of the reactor.

Crude product:

Acid value: 35.1 mg KOH / g

OH value: 25.2 mg KOH / g

Yield: 92.6%

Gardner Color Standard No.: 7-8

1.09 kg Ca (OH) ₂ was added and stirred at 80 ° C./50 mbar for 1 hour to neutralize the crude product, which was then filtered through a pressure filtration apparatus.

Neutralization product:

Acid value: 1 mg KOH / g

OH value: 28 mg KOH / g

Gardner Color Standard Number: 5

For decolorization, the neutralized and filtered product was stirred with 2.5 kg of basic Al ₂ O ₃ at 80 ° C. for 2 hours and then filtered through a pressure filtration apparatus.

Product:

Acid value: 1 mg KOH / g

OH value: 28 mg KOH / g

Gardner Color Standard Number: 1

Example 5

1559.5 g of acrylic acid, 1521.0 g of ethoxylated trimethylol propane (OH value: 665 mg KOH / g substance), 107.8 g of p-toluenesulfonic acid and 124.4 g (5% by weight based on acrylic acid + polyol) were quantified Was injected into a 3 1 reactor equipped with a stirrer and inhibited with 2.5 g of hydroquinone (1,100 ppm by weight of product).

Air (40 1 / h) was passed through the reaction mixture during the esterification and water was removed. The reaction mixture containing the polymerization inhibitor was stirred at a stirrer speed of 500 r.p.m. Particles of the polymerization inhibitor-containing reaction mixture formed by spinning at the front cover portion of the reactor were wetted to prevent unwanted polymer formation. Maximum reaction temperature of 105 ° C. and reduced pressure distribution 2h / 400mbar; 1 h / 300 mbar; 1 h / 150 mbar; The esterification time at 1 h / 40 mbar was 5 hours. The mixture was cooled to 80 ° C. and filtered through a pressure filtration device.

Crude product:

Acid value: 24.8 mg KOH / g

OH value: 23.8 mg KOH / g

Yield: 94.1%

Gardner Color Standard Number: 1

82 g Ca (OH) ₂ was added and stirred at 80 ° C./50 mbar for 1 hour to neutralize the crude product, which was then filtered through a pressure filtration apparatus.

Product:

Acid value: 1 mg KOH / g

OH value: 29 mg KOH / g

Gardner Color Standard Number: 1

[Comparative Example 5]

The same process as in Example 5 was carried out except that the stirrer speed was 150 r.p.m.

Since the reactor cover was not wetted with the inhibitory product, polymer formation was clearly observed on the non-wetted portion of the reactor.

Crude product:

Acid value: 28 mg KOH / g

OH value: 17 mg KOH / g

Yield: 95.8%

Gardner Color Standard Number: 1

92 Ca (OH) ₂ was added and stirred at 80 ° C./50 mbar for 1 hour to neutralize the crude product, which was then filtered through a filtration apparatus.

Product:

Acid value: 1 mg KOH / g

OH value: 23 mg KOH / g

Gardner Color Standard Number: 1

Example 6

1559.5 g of acrylic acid, 1521.0 g of ethoxylated trimethylol propane (OH value: 665 mg KOH / g substance) and 107.8 g of p-toluene sulfonic acid were quantified and injected into a 3 1 reactor, and 4.96 g of 2,5-di Polymerization was inhibited with -t-butylhydroquinone (2,000 ppm by product weight). Air (40 1 / h) was passed through the reaction mixture during the esterification and water was removed. The reaction mixture containing the polymerization inhibitor was stirred at a stirrer speed of 500 r.p.m. The front cover portion of the reactor was wetted with the particulates of the polymerization inhibitor-containing reaction mixture formed by spinning in order to prevent unwanted polymer formation. Maximum reaction temperature 105 ° C. and reduced pressure distribution 2 h / 400 mbar; 1 h / 300 mbar; 1 h / 150 mbar; At 1 h / 40 mbar, the esterification time was 5 hours.

Crude product:

Acid value: 32 mg KOH / g

OH value: 21 mg KOH / g

Yield: 94.8%

Gardner Color Standard Number: 1

105 g Ca (OH) ₂ was added and stirred at 80 ° C./50 mbar for 1 hour to neutralize the crude product, which was then filtered through a pressure filtration apparatus.

Product:

Acid value: 1 mg KOH / g

OH value: 25 mg KOH / g

Gardner Color Standard Number: 1

Comparative Example 6

The stirrer speed is 150 r.p.m. And the same procedure as in Example 6 was conducted except that the reactor cover was not wetted with the inhibitory product. Polymer formation was clearly observed on the non-wet part of the reactor.

Crude product:

Acid value: 15 mg KOH / g

OH value: 14 mg KOH / g

Yield: 96.5%

Gardner Color Standard Number: 1

46 g Ca (OH) ₂ was added and stirred at 80 ° C./50 mbar for 1 hour to neutralize the crude product, which was then filtered through a filtration apparatus.

Product:

Acid value: 1 mg KOH / g

OH value: 18 mg KOH / g

Gardner Color Standard Number: 1

Example 7

1297 g of acrylic acid, 1582 g of propoxylated neopentyl glycol (OH value of 509 mg KOH / g material) and 101 g p-toluene sulfonic acid were quantified and injected into the 3 1 reactor and inhibited with 4.79 g of α-tocopherol (HENKEL). . Air (40 1 / h) was passed through the reaction mixture during the esterification and water was removed. The reaction mixture containing the polymerization inhibitor was stirred at a stirrer speed of 500 r.p.m. The particulates of the polymerization inhibitor-containing reaction mixture formed by spinning with wetted the front cover portion of the reactor so that unwanted polymer formation did not occur. Maximum reaction temperature of 105 ° C. and reduced pressure distribution 2h / 400mbar; 1 h / 300 mbar; 1 h / 150 mbar; At 1 h / 40 mbar, the esterification time was 5 hours.

Crude product:

Acid value: 15 mg KOH / g

OH value: 10 mg KOH / g

Yield: 97.0%

Gardner Color Standard No.: 7-8

47 g Ca (OH) ₂ was added and stirred at 80 ° C./50 mbar for 1 hour to neutralize the crude product, which was then filtered through a pressure filtration apparatus.

Neutralization product:

Acid value: 1 mg KOH / g

OH value: 12 mg KOH / g

Gardner Color Standard Number: 6

For bleaching, the neutralized and filtered product was stirred at 80 ° C. with 240 g of basic Al ₂ O ₃ and then

Filtration was carried out with a pressure filtration device.

Product:

Acid value: 1 mg KOH / g

OH value: 12 mg KOH / g

Gardner Color Standard Number: 1

Comparative Example 7

The same process as in Example 7 was carried out except that the stirrer speed was 150 r.p.m and the reactor cover was not wetted with the product containing the polymerization inhibitor. Polymer formation was clearly observed on the non-wet part of the reactor.

Crude product:

Acid value: 25 mg KOH / g

OH value: 25 mg KOH / g

Yield: 92.6%

Gardner Color Standard No.: 7-8

79 g Ca (OH) ₂ was added and stirred at 80 ° C./50 mbar for 1.5 hours to neutralize the crude product, which was then filtered through a pressure filtration apparatus.

Neutralization product:

Acid value: 1 mg KOH / g

OH value: 30 mg KOH / g

Gardner Color Standard Number: 5

For decolorization, the neutralized and filtered product was stirred at 80 ° C. with 240 g of basic Al ₂ O ₃ and then filtered through a pressure filtration apparatus.

Product:

Acid value: 1 mg KOH / g

OH value: 29 mg KOH / g

Gardner Color Standard Number: 1

Claims (27)

A process for preparing a (meth) acrylic acid ester of a polyhydric alcohol by adding a polymerization inhibitor to a reaction mixture and washing the reaction zone with an oxygen-containing gas stream while reacting the reactants in the presence of an acid esterification catalyst. A method of producing a (meth) acrylic acid ester of a polyhydric alcohol, characterized by injecting liquid droplets containing a polymerization inhibitor into a part of the reactor. The method of claim 1, wherein the inhibitor-containing microdispersed liquid phase is injected into the gas phase-containing reactor in an amount that wets all internal solid surface surfaces in contact with the gas phase. The liquid reaction mixture portion of claim 1 or 2, wherein the portion of the liquid reaction mixture containing the polymerization inhibitor is atomized continuously or batchwise to fill the gas phase filled reactor, and the inner wall of the reactor is washed with a liquid membrane so that the liquid membrane flows along the inner wall of the reactor. How to get off. The process according to claim 1 or 2, characterized in that the reaction mixture is liquid at room temperature and contains at least no solvents or azeotropic entraining agents. The method according to claim 1 or 2, characterized in that a polymerization inhibitor (application inhibitor) itself necessary for the practical use of the reaction product is used as a reaction inhibitor for the esterification reaction. The process according to claim 1 or 2, wherein the phenolic compound is used as a polymerization inhibitor, wherein the steric hindrance phenolic compound is used with activated carbon during the esterification reaction or only steric hindrance phenol is used without adding activated carbon. The method according to claim 1 or 2, wherein tocopherol is used as a steric hindrance phenolic compound. The process according to claim 1 or 2, characterized in that the esterification reaction is carried out batchwise at a residual temperature of at least 90 ° C., at least under reduced pressure. The process of claim 1 or 2, wherein the inside of the reactor is cleaned with air or a mixture of nitrogen and air. The process according to claim 1 or 2, characterized in that the inhibitor is used in an amount of 200 to 10,000 ppm based on the weight of the reaction mixture. The process according to claim 1 or 2, wherein the reaction is continued with a reaction time of 10 hours or less until the yield is at least 90% of the theoretical value. 3. Process according to claim 1 or 2, characterized in that the reaction crude is dry neutralized. 3. Process according to claim 1 or 2, characterized in that the reaction product obtained initially is subjected to a final treatment with a bleaching agent. 3. The method of claim 2, wherein all internal solid surfaces in contact with the gas phase are wetted with a continuous inhibitor-containing liquid film. 4. The process of claim 3, wherein the portion of the reaction mixture is remixed with the continuous liquid phase. 7. A method according to claim 6, wherein hydroquinone is used as steric hindrance phenol. 8. Process according to claim 7, characterized in that at least partially use a-tocopherol or di-t-butyl hydroquinone as the steric hindrance phenolic compound. The process according to claim 8, wherein the esterification reaction is carried out at a residual temperature of at least 100 ° C. The process according to claim 8, wherein the esterification reaction is carried out at a residual temperature of 150 ° C. or less. The method of claim 8, wherein the process is carried out under pressure which is gradually reduced in stages. The process according to claim 10, wherein the inhibitor is used under reaction conditions in an amount of 300 to 2,000 ppm based on the weight of the reaction mixture. The method of claim 10, wherein a low volatility inhibitor is used under reaction conditions. The method of claim 11, wherein the reaction is continued until the yield is at least 94% of theory. The process according to claim 11, wherein the reaction is carried out in a temperature range of 100 to 140 ° C. The method of claim 11, wherein the reaction is performed under vacuum. The method of claim 11, wherein the reaction time is 8 hours or less. 13. The process of claim 12, wherein the reaction crude is dry neutralized using one or more oxides, hydroxides or mixtures thereof selected from alkaline earth metals or aluminum.