JPH02193944A - Production of (meth)acrylic acid ester - Google Patents

Abstract

PURPOSE:To readily suppress polymerization to a less extent than that of a single polymerization inhibitor and obtain the subject compound useful as a monomer for polymers by carrying out ester interchange reaction of a lower alcohol with methyl (meth)acrylate using two kinds of polymerization inhibitors. CONSTITUTION:Ester interchange reaction of a lower alcohol expressed by the formula ROH (R is 2-4C alkyl) with methyl (meth)acrylate expressed by formula I (R' is H or CH3) is carried out in the presence of a catalyst, such as sodium methylate, preferably dissolved in a solvent and a polymer polymerization inhibitor using phenothiazine(PTZ) and hydroquinone monomethyl ester (MEHQ) together at 50-100 deg.C for 5-20hr under ordinary or reduced pressure according to reaction distillation in a batch form to afford the objective compound, expressed by formula II and useful as a monomer for (meth)acrylic acid ester resins. The afore-mentioned polymerization inhibitor is preferably used by charging the PTZ into a reactor before starting the reaction and then charging the MEHQ from the column top of a distillation column during the reaction and purification.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for producing (meth)acrylic ester.

(Meth)acrylic acid ester is a typical monomer used as a raw material for (meth)acrylic resin.

Poly(
Meth)acrylic acid ester resin has excellent weather resistance, transparency, and gloss. Additionally, this resin has excellent electrical insulation, chemical resistance, and processability.

Ethyl methacrylate, butyl methacrylate, etc. are used in paints,
It is a useful substance used in fiber treatment agents, adhesives, etc.

Acrylic acid esters such as methyl acrylate, ethyl acrylate, and butyl acrylate are also used in acrylic fibers, fiber processing, paints, paper processing, adhesives, leather processing, acrylic rubber, and the like.

[Conventional technology]

and [Problem U to be solved by the invention] When producing (meth)acrylic ester from methyl (meth)acrylate and lower alcohol by the transesterification method, the raw material and the target ester tend to polymerize, so There is a time period U when the rate decreases.

Polymerization inhibitors are used to reduce this polymerization, but when synthesizing low-grade (meth)acrylic acid esters, using only one type of polymerization inhibitor cannot sufficiently inhibit polymerization. Can not do it.

In view of the above-mentioned situation, the inventor of the present invention has conducted intensive studies and has found 2.
The present invention has been completed.

(Means for Solving the Problems) In other words, the present invention is directed to lower alcohols and (meth) represented by the general 2 ROM.
1. A method for producing (meth)acrylic acid ester, characterized in that phenothiazine and hydroquinone monomethyl ether are used together as polymerization inhibitors when methyl acrylate is subjected to a transesterification reaction (wherein, R is a straight carbon atom containing 2 to 4 carbon atoms). is a chain or branched alkyl group).

The method for producing (meth)acrylic acid ester of the present invention will be explained in detail below.

-m, the reaction formula for synthesizing (meth)acrylic acid ester from methyl (meth)acrylate and lower alcohol by the transesterification method is expressed as follows.

CH=C0C-CH3+ROH CH=C0C-R+CH30H However, R is a linear or branched alkyl group containing 2 to 4 carbon atoms.

Further, Ro is a hydrogen atom or a methyl group.

The (meth)acrylic esters used in the method of the present invention are methyl acrylate and methyl methacrylate.

Methyl acrylate is usually synthesized by an acrylonitrile alcoholysis method or a propylene direct oxidation method, and methyl methacrylate is usually synthesized by an acetone cyanohydrin method.

Moreover, the lower alcohol used in the present invention is ethyl alcohol, n-propyl alcohol, is.

-propyl alcohol, n-butanol, 5ec-butanol, tert-butanol, 1so-butanol, etc.

Using these as raw materials, the corresponding (meth)acrylic esters can be produced.

As a means to overcome the above-mentioned problem that polymerization tends to occur when synthesizing (meth)acrylic acid ester, the present inventors have found a method in which two types of polymerization inhibitors are purposely used in combination.

In other words, compared to the conventional case of using only one type of polymerization inhibitor, using two types of polymerization inhibitors together can achieve a higher yield of reaction. be.

As a polymerization inhibitor for (meth)acrylic acid ester, -
droquinone, hydroquinone monomethyl ether,
T-butylcatechol, di-t-butylcatechol, phenothiazine, methylene blue, hydrosulfide, P-phenylenediamine, copper acetate, iron acetate, etc. are known, but among these, when combined with a polymerization inhibitor, We also examined whether the greatest effect could be obtained. As a result, phenothiazine (hereinafter referred to as PT2) and hydroquinone monomethyl ether (hereinafter referred to as MB
It was found that the combination of (denoted as HQ) had the greatest effect.

PTZ and MEHQ can be charged in solid form or as a solution in any organic solvent.

As for how to use it, it is possible to use it in the following combinations.

Preferably, PTZ is charged into the reactor before the reaction starts, and MEHQ is charged from the top of the distillation column during the reaction and purification.

The polymerization inhibitor charged into the reactor before the start of the reaction has a polymerization ratio of 200 to 2,000 E) l) l to the total raw materials charged in the reaction vessel.
Also, during reaction and purification, the polymerization inhibitor charged from the top of the column should be used at a polymerization ratio of 300 to 3,500 pD during reaction, and at a polymerization ratio of 2,000 to 8°0001) pI relative to the reaction crude liquid during purification. .

When PTZ and MEHQ are charged together into the reactor, or when both are charged from the top of the column, their combined amount is adjusted to the above amount.

The manufacturing method will be explained below.

In the method of the present invention, catalysts known as catalysts for transesterification reactions, such as sodium methylate, lithium methylate, sodium hydroxide, lithium hydroxide, tetraalkoxytitanium, calcium ceracetonate, etc. can be used. .

The amount of catalyst added is 300 molar ratio to the total number of moles of methyl (meth)acrylate and lower alcohol in the charging solution.
~3. OOOppm is preferred.

Although the reaction proceeds even if the amount is less than 300 ppm, there is a drawback that the reaction rate becomes slow.

In addition, 3. If it is used in an amount of OOOppm or more, secondary reactions are likely to occur, resulting in the formation of compounds or polymers in which a methoxy group or ethoxy group is added to a double bond.

Preferably, only 1,200 to 1,800 ppm of catalyst is used.

At this time, sodium alcoholade can be added in a solid state, but in order to further enhance the activity and reduce the amount used, it is preferable to dissolve it in a solvent and add it.

The catalyst may be charged either intermittently or continuously, but it is preferably charged continuously to minimize side reactions.

The molar ratio of methyl (meth)acrylate and lower alcohol used is methyl (meth)acrylate/alcohol = 11.
The ratio should be in the range of 5 to 5, preferably 1/2 to 2.

The reaction time varies depending on the amount of raw materials used, humidity, amount of catalyst, etc., but is usually 5 to 20 hours.The reaction can be carried out under normal pressure or reduced pressure.

The reaction temperature is in the range of 50 to 150°C, but in order to further reduce the polymerization of (meth)acrylic ester,
It is preferable to keep the temperature below 00°C; if it is too low, the reaction will be difficult to proceed.

In the present invention, the reaction is carried out by batchwise reactive distillation, in which the methanol produced by transesterification is converted into (meth)
By azeotropically extracting methyl acrylate from the top of the column, the equilibrium is significantly shifted and the reaction proceeds.

On the other hand, purification can be carried out under reduced pressure or normal pressure.

The temperature of the reaction vessel during distillation can be 50 to 200"C.! To reduce the number of tables, adjust the pressure so that the temperature of the reaction vessel at the end of distillation is below 100"C. is preferable.

In fact, using the method of the present invention, polymerization can be suppressed to a lower level than when using only a single polymerization inhibitor.

Hereinafter, the method of the present invention will be explained more specifically using Examples. However, the polymerization rate referred to in the examples is the number of moles of the (meth)acrylic ester monomer lost relative to the charged (meth)acrylic ester monomer.

[Example 1] Internal volume 2.0 equipped with a thermometer, dropping funnel and fractionating column
00ml flask, 989.1 methyl methacrylate
g (9.88 mol), ethanol 682.5
g (14.8 mol), phenothiazine o, 845 g
(0,004 mo 1) was charged and heated at normal pressure.

When the inside of the system was stable, 7.1 g of a 28% by weight methanol solution of sodium methylate was added as a catalyst intermittently from the dropping funnel over a period of 4 hours.

At the same time, 2.03 g of hydroquinone monomethyl ether was continuously added as a polymerization inhibitor from the top of the column.

After the reaction started, the produced methanol was distilled out together with ethyl methacrylate.

The reaction temperature was 74 to 88°C, and the polymerization rate during the zero reaction, which was carried out for 5 hours and 30 minutes, was 3.7%.

After the reaction was completed, 2.77 g of 5% aqueous phosphoric acid 85'M solution was added, and vacuum distillation was carried out at 150 mmHg for 6 hours to obtain the desired ethyl methacrylate (G, C, purity 99.
0% or more) was obtained.

Throughout the distillation, 81.2 g of a 10% solution of hydroquinone monomethyl ether in ethyl methacrylate was added.

The yield based on methyl methacrylate was 62%.
The polymerization rate during distillation was 0.4%. [Example 2] Using the same apparatus as in Example 1, methyl methacrylate 9
02.1g <9゜Olmol), n-butanol 44
4.8g (6,OOmol), phenothiazine 0.6
Prepare 72g (0,003mol), 200~4
The reaction was carried out at 00 mm Hg.

During the reaction, in the same manner as in Example 1, 4.34 g of a 28% by weight methanol solution of sodium methylate was added in 2.5 hours and 16.9 g of a 10% methacrylic acid n-butanol solution of hydroquinone monomethyl ether was added in 4 hours. Added in time.

Methanol was distilled out together with methyl methacrylate. The reaction temperature was 55 to 112°C, and the polymerization rate during the 9 reactions, which were reacted for 4.5 hours, was 3.3%.

After the reaction, 1.69 g of an 85% by weight aqueous phosphoric acid solution was added and vacuum distillation was performed at 100 mmHg for 7.3 hours, resulting in n-butyl methacrylate (G, C).

777.8 g of the product (purity of 99.5% or higher) was obtained.

Throughout the distillation, 19.1 g of a 10% solution of hydroquinone monomethyl ether in Mn-butyl methacrylate was added.

The yield based on n-butanol was 86%.

Moreover, the polymerization rate during distillation was 1.7%.

[Example 3] Using the same apparatus as in Example 1, methyl acrylate 12
9.1g (1.5mol), n-butanol 74.1
g (1,0 mol), hydroquinone monomethyl ether O, l1 g (0,0009 mo1) were charged, and 300 m
The reaction was carried out at mHg.

During the reaction, 28f! of sodium alcoholade was added in a manner similar to Example 1. 3. 72g of % methanol solution.
In 5 hours, 1 of hydroquinone monomethyl ether
4.71 g of 0% acrylic fin-butyl solution was added over 5 hours.

Methanol was distilled off together with methyl acrylate.

The reaction temperature was 65 to 88°C, and the polymerization rate during the 5.5 hour reaction was 3.5%.

After reaction, 1/2 N<7)tM! 7.9 ml was added and distilled under reduced pressure at 100 mmHg for 6 hours.
n-Butyl acrylate (G, C, purity 99.0% or more)
83.3g of was obtained.

Throughout the distillation, 10% acrylic v of hydroquinone
6.2 g of in-butyl solution was added.

The yield based on n-butanol was 65%, and the polymerization rate during distillation was 1.2%.

[Comparative Example 1] (When only PTZ is used) In Example 1, MBHQ'? When the reaction and purification were carried out in the same manner except for changing to PTZ, the polymerization rate during the reaction was 10.0%, the polymerization rate during purification was 5.2%, and the yield was 5.
It was 8%.

[Comparative Example 2] <When using only MEHQ) When reaction and purification were carried out using the same method as in Example 1 except that PTZ was changed to MEHQ, the polymerization rate during the reaction was 10.2%, and the polymerization rate during purification was 10.2%. rate is 6.2%, yield is 55
%Met.

Claims (1)

[Claims] A method for producing (meth)acrylic acid ester, characterized in that phenothiazine and hydroquinone monomethyl ether are used together as polymerization inhibitors when transesterifying a lower alcohol represented by the general formula ROH and methyl (meth)acrylate (provided that , R is a straight or branched alkyl group containing 2 to 4 carbon atoms).