JPS5814416B2 - Process for producing zinc salt of acrylic acid or methacrylic acid - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing zinc salts of acrylic or methacrylic acid.

Specifically, the present invention provides a high-yield, highly pure, substantially water-free powder solid by reacting acrylic acid or methacrylic acid with a zinc compound to form a zinc acrylic acid or methacrylate salt. The present invention relates to a method for producing zinc acrylic acid or methacrylic acid salt.

Zinc salts of acrylic acid or methacrylic acid (hereinafter referred to as (meth)acrylic acid) are compounds useful as crosslinking agents, and are used, for example, as modifiers for synthetic resins and co-vulcanizing agents for rubber.

In particular, the zinc (meth)acrylate salt used as an additive to these base resins and rubbers is required to be in the form of a highly pure powder that does not contain substantially water.

The present inventors investigated various methods for producing a powdery solid with high purity and substantially no water content of zinc salt of (meth)acrylate, and discovered that the method for producing an alkali metal salt of (meth)acrylate is known as It was discovered that the spray drying method and concentration crystallization method that have been proposed cannot be used as a method for producing zinc (meth)acrylate salt.

That is, when (meth)acrylic acid and a zinc compound are reacted using acidic water or a lower alcohol in which zinc (meth)acrylate is dissolved as a solvent, and the homogeneous solution is directly applied to a momme spray dryer, (meth)acrylate is dissolved. Zinc acrylate powder has adhesive properties when heated due to the presence of a small amount of water, and is easily thermally polymerized by hot air, causing fire or solidified lumps, and the reaction solution must be concentrated and crystallized in a concentrator. When the product was subjected to heating, the crystals adhered firmly to the inner wall of the heated surface in the form of a lump, and the resulting product had a high water content and was of low quality, containing basic salts and polymers.

After various studies on the causes of this, it was found that zinc (meth)acrylate is thermally unstable, and even in solid form it has a
It has the property of thermally polymerizing and igniting at ℃, and when concentrating and crystallizing, the crystals tend to adhere to heated surfaces (particularly metal surfaces), and it also hydrolyzes when it comes into contact with moisture when heated. It was found that the crystals attached to the heated surface tend to become basic salts, and that some of the crystals attached to the heated surface become polymers even at relatively low temperatures. It has been found that it is very difficult to remove water from and obtain a powder of high purity.

When (meth)acrylic acid and zinc compound are reacted, 1 to 1 mole of zinc (meth)acrylate, the target product, is
2 moles of water are produced as a by-product.

A small amount of water may also be present in the raw material (meth)acrylic acid or zinc compound.

Therefore, it is necessary to remove these waters from the reaction product.

The present inventors conducted various studies on this dehydration method and found that the neutralization reaction was carried out in a solvent that is mutually insoluble with water and has the property of being azeotropic with water, and that methane was also produced within the reaction system. ) It was found that the desired high-purity powdery solid can be obtained by reaction and dehydration drying at a temperature of 40 to 100°C while maintaining the water content to such an extent that zinc acrylate does not coagulate and precipitate. It was completed.

Thus, the present invention provides an extremely industrially advantageous method for producing zinc (meth)acrylic acid salt powder that overcomes the drawbacks of conventional methods, is extremely easy to operate and control, and has a high yield. The present invention provides a method for producing substantially anhydrous (meth)acrylic acid zinc salt powder with high yield and purity.

That is, the present invention involves producing a zinc salt of acrylic acid or methacrylic acid by reacting acrylic acid or methacrylic acid with a zinc oxide, hydroxide, carbonate, bicarbonate, or a mixture thereof. Using a hydrocarbon compound that is mutually insoluble with water and capable of forming an azeotrope with water as a solvent in the substantial absence of water, and at a temperature of 40 to 1
The present invention provides a method for producing highly pure acrylic acid or zinc methacrylate, which is characterized in that the reaction is carried out in the range of 00°C, water produced together with the solvent is azeotropically removed, and the process is further dried.

A method of azeotropic dehydration using an organic solvent, similar to the method of the present invention, is described in the specification of JP-A-47-11365.

However, this method relates to a method for producing an alkali metal salt of (meth)acrylic acid in the step of synthesizing glycidyl ester, and as is clear from the specification, potassium and sodium salts of (meth)acrylic acid are The reactions and physical properties are fundamentally different from zinc salts, and the reaction conditions are also essentially different.

That is, in the case of alkali metal salts, the presence of water in the reaction system is an essential condition, but in the synthesis of zinc (meth)acrylate of the present invention, the reaction proceeds even in the absence of water. Preferably, substantially no water is present.

Further, in the method disclosed in the above-mentioned publication, dehydration is performed by azeotropic distillation of the solvent and water, but dehydration is not sufficient with this operation alone, and a solid desiccant must be used.

In the method of the present invention, there is no need to further use a desiccant after azeotropic dehydration, and it is sufficient to simply carry out the drying treatment.

These synthetic differences between potassium and sodium salts and zinc salts are thought to be due to differences in their reactivity, binding strength with water, and ease of hydrolysis, and zinc salts of (meth)acrylic acid It is clear that even if the above-mentioned method is used to react and dehydrate the product in the presence of water, a product with high purity and substantially free of water and basic salts cannot be obtained.

The solvent used in the present invention is a hydrocarbon compound that is azeotropic with water and is not mutually soluble with water when cold, and has a boiling point of 50 to 160°C, preferably 8.0 to
Organic compounds within the range of 140°C are preferred, and specific examples include benzene, toluene, xylenes, cyclohexane, methylcyclohexane, n-heptane, and n-hexane.

The (meth)acrylic acid used in the present invention is ordinary glacial (meth)acrylic acid that is not diluted with water, but it may contain some amount of water.

Furthermore, the presence of polymerization inhibitors such as hydroquinone and hydroquinone monomethyl ether contained in (meth)acrylic acid does not cause any problem.

Further, as the raw material zinc compound, a normal powdery solid is used.

If it is in powder form, it is convenient to charge it into the reactor, and it is also easily stirred and dispersed in the solvent, so it can be added (meta).
The reaction with acrylic acid can be made uniform.

Although it is preferable that the raw material zinc compound does not contain water, there is no problem even if it contains some amount of water.

However, it is of course necessary that the water contained in the raw material zinc compound and (meth)acrylic acid be within a range that does not cause coagulation and precipitation of zinc (meth)acrylate produced when the water contained in the raw material zinc compound and (meth)acrylic acid are combined with the reaction product water.

If the raw material contains a large amount of water, the amount of solvent used may be increased.

Zinc compounds include zinc oxide, zinc hydroxide, zinc carbonate and zinc bicarbonate.

The reason why the water present in the reaction system has a great effect on the quality of the produced zinc (meth)acrylate salt in the present invention is considered to be as follows.

First, 1 to 2 mol of reaction water is generated per 1 mol of zinc (meth)acrylate by the reaction.

This produced water and the water coming from the raw materials adhere to the produced salt crystals.

At this time, the more water there is, the more crystals that are formed will be dissolved, forming a solution that will surround the surface of the crystal, and as a result, the hydrocarbons in the solvent will no longer wet the surface of the crystal, resulting in agglomeration of the crystals, which will form a large lump and precipitate. I end up.

These precipitated crystals tend to adhere strongly to the inner walls of the reactor, such as the heated surface, and during the reaction and dehydration/drying process, these hydrated crystals are hydrolyzed and become basic salts, and some of these adhering crystals are becomes a polymer and causes quality deterioration,
Moreover, since it becomes a large lump, it becomes difficult to remove water in the dehydration and drying process.

In view of this, in the most preferred embodiment of the present invention, it is preferable to use substantially anhydrous raw material (meth)acrylic acid and zinc compound for reaction.

Next, specific embodiments of the present invention will be described.

A sufficiently stirrable reactor is filled with a solvent, the zinc compound powder is stirred and dispersed, and then (meth)acrylic acid is added dropwise for reaction.

Alternatively, (meth)acrylic acid is mixed in advance in the above solvent, and the zinc compound powder is added and reacted with stirring.

The ratio of the zinc compound and (meth)acrylic acid is from 10 to 10 salt-forming equivalents of (meth)acrylic acid to the zinc compound.
It is advisable to use an excess of about %.

The amount of solvent used is based on the amount of water present in the reaction system (reaction water and raw materials (
total amount of water coming from meth)acrylic acid and zinc compounds)
There is no restriction as long as the amount is at least the amount that can be azeotropically removed, but usually it is about 2 to 15 moles per mole of (meth)acrylic acid.

Within this range, the raw material zinc compound will be uniformly dispersed in the reaction system, heat can be conveniently removed without locally reacting with (meth)acrylic acid, and the (meth)acrylic acid zinc salt produced by the reaction This improves the dispersion of zinc compounds and prevents unreacted raw material zinc compounds from being encapsulated.

The reaction temperature is preferably 40 to 100°C. This temperature is regulated by a cooler or heater installed in the reactor.

If the reaction temperature is below 40°C, the reaction rate will be slow and it will take too much time, and if the reaction temperature is above 100°C, polymerization reaction will easily occur and the purity of the product will decrease.

Water present in the reaction system is removed by azeotropic distillation with the solvent, which may be carried out during the reaction or after completion of the reaction.

When performing azeotropic distillation during the reaction, it is better to separate the distilled solvent into two layers from water and then return it to the reaction system.

Otherwise, the amount of solvent in the reaction system will decrease, resulting in poor dispersion of the raw material zinc compound and zinc (meth)acrylate salt, which is disadvantageous.

At this time, since unreacted (meth)acrylic acid is present in the reaction system, a separation column is required to prevent (meth)acrylic acid from distilling off during azeotropic distillation.

In this case, after the reaction and azeotropic dehydration, the solvent is mechanically separated using a filter, centrifuge, etc., and the resulting zinc salt of (meth)acrylate is dried to remove the solvent at a temperature of 40 to 100°C. It can be done.

When performing azeotropic dehydration after the completion of the reaction, the reaction solution is transferred to a kneader, blender, etc. equipped with a stirrer with scraping blades, and heated at a temperature of 40 to 100°C and a pressure of 5 to 500 mmHg.
Dry under reduced pressure.

In this case, a mechanical separator and a separation column for separating the solvent and zinc (meth)acrylic acid salt are not necessary, and this is a more preferred embodiment of the present invention.

If the dehydration and drying temperature is below 40°C, the water of crystallization contained in zinc (meth)acrylate cannot be sufficiently removed, and basic salts and polymers may be present in powders that are expected to exceed 100°C. It will be included.

Example 1 407 g of zinc oxide was suspended in 2.5 liters of toluene, 756.6 g of acrylic acid was added dropwise over 20 minutes while stirring, and the mixture was reacted at 50 to 55° C. for 3.5 hours.

Put the leaked slurry into a jacketed kneader and
Under a reduced pressure of 20 to 80 mmHg, hot water at 50°C was passed through the jacket and heated for 2 hours to distill out the produced water and toluene, and the drying operation was continued to produce 100% zinc acrylate powder.
I gained 4g.

The produced zinc acrylate did not adhere to the kneader at all.

The zinc acrylate thus obtained contained no basic salts or polymers, had a water content of 0.1% by weight, and a purity of 99.5% by weight.

Example 2 151 g of acrylic acid was dissolved in 900 cc of benzene, 81 g of powdered zinc oxide was added over 15 minutes while stirring, and the mixture was reacted at 60° C. for 3 hours.

Put the obtained slurry into a kneader and mix it with 160~100gH.
g, and heated in 50° C. hot water for 2 hours to obtain 200 g of zinc acrylate powder.

The analysis results of this product were the same as in Example 1.

Example 3 3.66 kg of zinc oxide was suspended in 19.5 liters of toluene, and 6.49 kg of acrylic acid was added dropwise over 25 minutes while stirring, followed by a reaction at 65 to 70°C for 4 hours.

After the reaction was completed, the resulting slurry was heated in a blender at 55°C for 1
Drying was performed at 40-30 mmHg for 7 hours.

There was no product adhesion to the blender. The resulting product had a moisture content of 0.09%, a purity of 98.5%, and no contamination of polymers or basic salts.

In this case, the yield reached 99.0% (theoretical yield based on acrylic acid).

Example 4 81 g of zinc oxide was suspended in 400 cc of toluene and heated to 75°C.
While stirring at high speed, 178.5 g of methacrylic acid was added dropwise over 15 minutes, followed by stirring at 75 to 80° C. for 4 hours to complete the reaction.

Put the obtained slurry into a kneader and kneader to a thickness of 120 to 70 mm.
Drying was carried out for 2 hours while heating with Hg and hot water at 50° C. to obtain 224 g of zinc methacrylate powder.

The water content was 0.05% and the purity was 99.5%.

There was no powder adhesion to the kneader.

Example 5 99 g of zinc hydroxide, 600 cc of toluene, 1 acrylic acid
Using 51 g, reaction and drying were carried out in the same manner as in Example 1 to obtain 197 g of zinc acrylate dry powder having a moisture content of 0.2% and a purity of 98%.

Claims (1)

[Claims] 1. When producing a zinc salt of acrylic acid or methacrylic acid by reacting acrylic acid or methacrylic acid with a zinc oxide, hydroxide, carbonate, bicarbonate, or a mixture thereof, substantially no water is added. Using a hydrocarbon compound that is mutually insoluble with water and capable of forming an azeotrope with water in the absence of water as a solvent, the reaction is carried out within a temperature range of 40 to 100°C, and the water produced together with the solvent is A method for producing a zinc salt of acrylic acid or methacrylic acid, which comprises azeotropic removal and further drying.