JPH0137388B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing methacrylic acid chloride by reacting methacrylic acid and phosphorus trichloride. More specifically, when reacting methacrylic acid and phosphorus trichloride, (1) while adding phosphorus trichloride to methacrylic acid,
(2) distill off the methacrylic acid chloride produced from the reaction mixture; (3) separate and remove the lower phosphorus compound layer of the resulting bottom liquid; (4) remove the resulting upper layer. Process the unreacted methacrylic acid layer
Methacrylic acid chloride is produced by reusing in (1) and using phosphorus trichloride in a molar range of 1/3 to 1/4 times the total methacrylic acid used in the reaction. .

Methacrylic acid chloride is useful as an acylating agent, and can be used in reactions that replace hydrogen in hydroxyl groups, amino groups, aromatic nuclei, etc. with acyl groups, and at the same time introduce highly reactive double bonds. Products resulting from acylation reactions are important mainly as raw materials for various functional polymers and raw materials or intermediates for pharmaceuticals, agricultural chemicals, fungicides, and the like.

Methods for synthesizing carboxylic acid chlorides by reacting aliphatic carboxylic acids with various phosphorus compounds, thionyl chloride, or phosgene have been known. (Synthetic Organic Chemistry,
Edited by Wagner & Zook, John Wiley & Sons Inc.546
(pages 557 to 557) However, in the thionyl chloride method, processing of by-product hydrogen chloride and sulfur dioxide gas is costly, and contamination of sulfur compounds into the product is unavoidable. In addition, the phosgene method requires the use of expensive catalysts such as dimethylformamide due to its low reactivity, and there is also the problem of the toxicity of phosgene itself, so although both methods are industrially superior, sea bream. On the other hand, the phosphorus trichloride method is inexpensive in terms of raw material costs, and by-product phosphorus compounds can be converted and reused into useful inorganic phosphorus compounds relatively easily, making it a preferable method from the standpoint of effective resource utilization. There are also prior documents regarding the phosphorus trichloride method, such as the Journal of American Chemical Society,
Vol. 67, p. 208-210 (1945), CERehberg et al. reported that methacrylic acid chloride could be obtained with a yield of 75-80%, but even if the reaction was carried out under their experimental conditions, the above No yield was obtained, and even after various examinations of surrounding reaction conditions, it was found that the yield was only about 60% at most, and in order to produce it industrially,
It turns out that there are still many issues that need to be resolved.

Under these circumstances, the present inventors developed a phosphorus compound,
In particular, the present invention has been completed as a result of intensive research aimed at producing methacrylic acid chloride from phosphorus trichloride and methacrylic acid with high yield and efficiency.

That is, in the present invention, when producing methacrylic acid chloride by reacting methacrylic acid and phosphorus trichloride, (1) while adding phosphorus trichloride to methacrylic acid,
The reaction is carried out at a temperature in the range of 90°C (2) the methacrylic acid chloride produced from the reaction mixture is distilled off (3) the lower phosphorus compound layer of the resulting bottom liquid is separated and removed, (4) the upper layer Process the unreacted methacrylic acid layer
A method for producing methacrylic acid chloride, which is reused in (1) and is characterized in that phosphorus trichloride is used in a mole range of 1/3 to 1/4 times the total amount of methacrylic acid used in the reaction. .

In the present invention, a suitable method for reacting methacrylic acid with phosphorus trichloride is a method in which phosphorus trichloride is added dropwise to methacrylic acid. The yield is lower than when using the above method, either by dropping methacrylic acid into phosphorus trichloride or by charging phosphorus trichloride and methacrylic acid all at once. The reaction temperature may be any temperature between 40 and 90°C, but 50 to 60°C is more preferable. At temperatures below 40°C, the reaction is very slow, and at temperatures above 90°C, polymerization increases.

The method of adding phosphorus trichloride to methacrylic acid can be carried out in a continuous or continuous manner. usually,
The dropping time is preferably 0.5 to 2 hours. Dripping time
If it is shorter than 0.5 hours, the improvement in yield will be small;
Even if the time is increased by 2 hours or more, no further improvement in yield is obtained, and there is no need to further increase the dropping time.

There is no problem in distilling methacrylic acid chloride immediately after dropping phosphorus trichloride, but since a large amount of unreacted phosphorus trichloride may be mixed into the product,
It is preferable to allow a maturing time of 4 to 2 hours.

After the reaction is complete, when the reaction solution is allowed to stand still, it separates into two layers: an upper layer containing methacrylic acid chloride and a lower layer containing phosphorous acid. However, the methacrylic acid chloride is distilled off without separating and removing this lower layer. It is preferable to let If the lower layer containing phosphorous acid is separated and only the upper layer is distilled, the yield will be low. Although the method of distilling off methacrylic acid chloride does not require a special distillation column,
A mist separator or simple distillation column may be used. When methacrylic acid chloride is distilled off, normal pressure may be used, but it is preferably carried out under reduced pressure of 400 mmHg or less in order to reliably reduce yield loss due to polymerization, etc. In a preferred embodiment, start at around 200mmHg and eventually reach 30mmHg.
An example is a method of distilling off at the Hg position.

After the methacrylic acid chloride has been distilled off, the liquid can be left to stand and separate into two layers: an upper layer containing unreacted methacrylic acid and a lower layer containing phosphorous acid. Although the reason is not clear, the present inventors have found that the yield of methacrylic acid chloride can be further improved by reusing this upper layer liquid for the reaction with phosphorus trichloride. In order to obtain a liquid containing unreacted methacrylic acid for reuse, the amount of phosphorus trichloride charged must be 1/3 times the mole or less relative to methacrylic acid. If phosphorus trichloride is used in an amount exceeding 1/3 mole, the residual liquid will be difficult to separate into two layers, and therefore unreacted methacrylic acid cannot be recycled and reused, and methacrylic acid chloride Since the boiling points of phosphorus trichloride and phosphorus trichloride are close to each other and it is difficult to separate them cleanly, a large amount of phosphorus trichloride will be mixed into the product, significantly reducing the purity of the product.

Furthermore, in consideration of industrial productivity, the amount of phosphorus trichloride used is preferably 1/4 or more times the mole of methacrylic acid. When phosphorus trichloride is used in an amount less than 1/4 times the mole of methacrylic acid, less phosphorus trichloride is mixed into the product, but unreacted methacrylic acid increases, which is economically disadvantageous. That is, in carrying out the present invention, the amount of phosphorus trichloride used is 1/3 to 1/3 of the total amount of unreacted methacrylic acid contained in the upper layer of the distillation residue to be reused and methacrylic acid newly charged. A range of 4 times the mole is preferred.

When reusing the upper layer liquid containing unreacted methacrylic acid obtained as described above, an advantageous industrial production method is to keep the amount of unreacted methacrylic acid approximately constant in each subsequent reaction. This is desirable. Therefore, the amount of phosphorus trichloride used is 85 to 1/3 times the mole of all methacrylic acid used in the reaction, including the newly charged methacrylic acid.
A range of 95% is particularly preferred. The molar ratio of phosphorus trichloride and methacrylic acid that can maintain a substantially constant amount of unreacted methacrylic acid within this range is appropriately determined.

Furthermore, the layer containing phosphorous acid after reactive distillation can be converted into a useful inorganic phosphorus compound and reused.

If methacrylic acid chloride is produced by the method described above according to the present invention, a product of high purity can be obtained industrially efficiently and continuously with high yield.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Reference Example 1 After stirring, add 100 g (1.162 mol) to a 300 ml flask equipped with a thermometer, reflux condenser, and dropping funnel.
of methacrylic acid and 0.1 g of phenothiazine were heated to 53° C. with rotational stirring at 500 rpm.
While maintaining the same temperature, 53.2 g (0.387 mol) of phosphorus trichloride was added dropwise over 80 minutes. 100 at the same stirring rotation speed and temperature
Stirring was continued for a minute, and when the mixture was left to stand after stirring, the reaction solution was separated into two layers. After the reaction is complete, remove the reflux condenser and dropping funnel from the flask, and add the phenothiazine.
Added 0.02g. A distillation thermometer, a Liebig condenser, a suction port, and a simple cooling device with a distillation receiver were installed, and the condenser and receiver were cooled with a -10℃ refrigerant.
Slow suction was applied while stirring at ~100 rpm.
The degree of vacuum, stirring speed, and temperature were gradually increased, and finally, reactive distillation was carried out under conditions of a degree of vacuum of 35 mmHg, a stirring speed of 700 rpm, and a solution temperature of 70° C. until no more distillation occurred. Contains less than 0.5% by weight of phosphorus trichloride
87.4 g (0.836 mol, yield 71.9% based on the charged methacrylic acid) of methacrylic acid chloride was obtained.

Comparative Example 1 The method described in Reference Example was followed except that 53.2 g (0.387 mol) of phosphorus trichloride was charged into a flask, and a mixture of 100 g (1.162 mol) methacrylic acid and 0.1 g of phenothiazine was added dropwise. Ivy. 78.7g of methacrylic acid chloride obtained by distillation
(0.753mol, yield based on charged methacrylic acid
64.8%) and contained less than 0.5% by weight of phosphorus trichloride.

Comparative Example 2 In the Reference Example, 100 g
g (1.162 mol) of methacrylic acid, 53.2 g
The method described in Reference Example was followed except that (0.387 mol) of phosphorus trichloride and 0.1 g of phenothiazine were charged. The methacrylic acid chloride obtained by distillation is 76.7
g (0.734 mol, yield 63.1% based on the charged methacrylic acid), and contained less than 0.5% by weight of phosphorus trichloride.

Comparative Example 3 A 300 ml flask equipped with a stirrer, thermometer, reflux condenser, and dropping funnel was charged with 100 g (1.162 mol) of methacrylic acid and 0.1 g of phenothiazine. The mixture was heated to 53° C. with rotational stirring at 500 rpm. While maintaining the same temperature, 53.2 g (0.387 mol) of phosphorus trichloride was added dropwise over 80 minutes. Stirring was continued for 100 minutes at the same stirring speed and temperature, and when the stirring was completed and left to stand, the reaction solution was separated into two layers. After the reaction was completed, only the upper layer of the solution was transferred to a 200 ml flask and distilled under reduced pressure. The distillation equipment, degree of vacuum, and distillation temperature were the same as those described in the reference example, but a capillary was used instead of a stirring bar. The methacrylic acid chloride obtained by distillation is
It was 67.7 g (0.648 mol, yield 55.7% based on the charged methacrylic acid) and contained 0.5% by weight or less of phosphorus trichloride.

Example 1 After reaction and distillation according to the method described in Reference Example,
The distillation residue remaining in the flask was separated into two layers. Of these, only the upper layer (18 g) was transferred to another flask. The same apparatus as shown in the reference example was attached to this flask, and 100 g (1.162 mol) of methacrylic acid and 0.1 g of phenothiazine were added.
58.0 g (0.422 mol) of phosphorus trichloride was added dropwise and reacted according to the method described in Reference Example. The resulting methacrylic acid chloride was 97.2g (0.930mol,
Yield 80.0 based on freshly charged methacrylic acid
%) and contained less than 0.5% by weight of phosphorus trichloride.
The residue at this time was also separated into two layers, and the upper layer weighed 18g.
The amount was the same as the upper layer of the residue from the first time. The same reaction was repeated again using this upper layer. The resulting methacrylic acid chloride was 98.0g.
(0.937 mol, yield 80.7% based on freshly charged methacrylic acid), and contained less than 0.5% by weight of phosphorus trichloride. The upper layer of residue was also 18g, the same amount as last time. Thereafter, methacrylic acid chloride was consistently obtained at a yield of about 80%.

Comparative Example 4 After reaction and distillation according to the method described in Reference Example,
The distillation residue remaining in the flask was separated into two layers. Of these, only the upper layer (18 g) was transferred to another flask. The same apparatus as shown in the reference example was attached to this flask, and 100 g (1.162 mol) of methacrylic acid and 0.1 g of phenothiazine were added.
46.7 g (0.340 mol, 1/4 mol or less based on the total amount of methacrylic acid charged) of phosphorus trichloride was added dropwise and reacted according to the method described in Reference Example. The resulting methacrylic acid chloride was 79.8g (0.763mol, yield 65.7% based on newly charged methacrylic acid)
and contained less than 0.4% by weight of phosphorus trichloride. The residue at this time was also separated into two layers, and the upper layer weighed 37 g. The same operation as before was carried out using this upper layer. The obtained methacrylic acid chloride was 78.8g.
(0.754 mol, yield 64.9% based on freshly charged methacrylic acid) and contained 0.4% by weight of phosphorus trichloride. The amount of residue in the upper layer increased to 58g.

Comparative Example 5 In the reference example, 100g (1.162mol) of methacrylic acid and 0.1g of phenothiazine were charged, and 79.8g
The method described in Reference Example was followed except that phosphorus trichloride (0.581 mol, 1/2 mole relative to the methacrylic acid used) was added dropwise. The amount of methacrylic acid chloride obtained by distillation was 109.0 g (1.043 mol, yield 89.7% based on the charged methacrylic acid), and contained 10.2% by weight of phosphorus trichloride.

Comparative Example 6 This comparative example is based on the Journal of American Chemical
This is a re-examination of the method described in Society Vol. 67, p. 208 (1945).

A 300 ml flask equipped with the same equipment as in the reference example except that the dropping funnel was not attached was filled with 100
g (1.162 mol) of methacrylic acid and 53.2 g
(0.387 mol) of phosphorus trichloride was charged all at once. After slowly heating to 70℃ and keeping it at 70℃ for 15 minutes,
Stirring was continued for 120 minutes at room temperature. Separate the upper and lower layers,
1 g of cuprous chloride was added only to the upper layer, and vacuum distillation was performed in the same manner as in Comparative Example 3. The obtained methacrylic acid chloride weighed 71.9 g (0.688 mol, yield 59.2% based on the charged methacrylic acid) and contained 0.5% by weight or less of phosphorus trichloride.

Claims (1)

[Claims] 1. When producing methacrylic acid chloride by reacting methacrylic acid and phosphorus trichloride, (1) while adding phosphorus trichloride to methacrylic acid,
The reaction is carried out at a temperature in the range of 90°C. (2) The methacrylic acid chloride produced from the reaction mixture is distilled off. (3) The lower phosphorus compound layer of the resulting bottom liquid is separated and removed. (4) The resulting upper layer is removed. Process the reaction methacrylic acid layer
A method for producing methacrylic acid chloride, which is reused in (1) and is characterized in that phosphorus trichloride is used in a mole range of 1/3 to 1/4 times the total amount of methacrylic acid used in the reaction.