JPS5914017B2 - Method for producing polyfunctional acrylate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing high-quality polyfunctional acrylate (hereinafter referred to as PETA) containing pentaerythritol triacrylate as a main component by an esterification reaction between pentaerythritol and acrylic acid.

related. This so-called "PETA" is highly reactive,
A compound with high boiling point and low volatility, used in solvent-free paints, inks, etc.
It is used in adhesives, cross-linking agents, and molding materials, and is particularly effective in improving chemical resistance, especially solvent resistance.It is also practical in handling as it is less irritating to the skin. This is a compound that is expected to have a wide range of applications in the future.

Conventionally, PETA has been produced by direct esterification or transesterification using the above-mentioned raw material compounds.

The resulting reaction product, PETA, usually contains not only pentaerythritol monoacrylate, diacrylate, triacrylate, and tetraacrylate, but also an oligomer mixture such as dipentaerythritol polyacrylate produced by the dehydration condensation reaction of alcohol. It is known that the amount of tetraacrylate produced tends to be relatively large, and as the amount of tetra-acrylated products and oligomers increases, the product becomes solid or semi-solid even at room temperature, which may cause difficulties in handling. become. The above PETA is extremely easily polymerized and easily hydrolyzed, and is also easily colored, making it difficult to produce colorless and transparent high-quality PETA in a good yield. . That is, according to the findings of the present inventors, when pentaerythritol and acrylic acid are directly subjected to an esterification reaction, the alcohol group of cidaerythritol and the carboxylic acid group of acrylic acid undergo a sequential esterification reaction. However, in order to obtain the target PETA with a high content of pentaerythritol triacrylate and to complete the reaction rate as much as possible, that is, free
If the reaction conditions are chosen so that pentaerythritol and acrylic acid are eliminated, the amount of tetrahydride produced will inevitably increase, and furthermore, the production of oligomers due to the dehydration condensation reaction as a side reaction will be unavoidable, and the reaction will not be completed soon. Is the viscosity increasing? 5 It was observed that this caused difficulties in production, and furthermore, the coloring of the reaction solution became significant, leading to a decrease in the quality of the resulting product. Furthermore, even if the above reaction is carried out using an aromatic hydrocarbon such as benzene or toluene as a solvent, which easily dissolves the reaction products, the formation of a tetrahydride or polypentaerythritol polyacrylate oligomer will occur. It also turned out to be extremely difficult to reduce the amount.

The object of the present invention is to provide an improved method for producing PETA to overcome the above-mentioned drawbacks.

Specifically, the object of the present invention is to increase the reaction rate significantly compared to the conventional method, and at the same time, to obtain a P that has a substantially increased triacrylate content and a low content of the above-mentioned tetra compounds and oligomers.
The purpose of this method is to obtain ETA, and the obtained PETA is characterized by a marked improvement in the degree of coloration. More specifically, when pentaerythritol and acrylic acid are esterified using an acidic catalyst and a polymerization inhibitor, the esterification rate is 85 to 95 in the presence of molecular oxygen in a chain or cyclic alkane having 6 to 8 carbon atoms. This is a method for producing a polyfunctional acrylate, characterized in that the reaction is carried out within a range of 50%. In the present invention, after separating the solvent alkane from the esterification reaction mixture, PHL2
The present invention also provides a method for obtaining high-quality product PETA at a higher yield by washing with an alkaline aqueous solution adjusted to a pH of 14.

The chain or cyclic alkane having 6 to 8 carbon atoms used in the present invention has the property of being a poor solvent for the above-mentioned PETA,
In particular, those with low solubility for mono-, di-, and triacrylates are preferred.

Specifically, n-hexane, heptane, isoheptane,
Examples include isooctane, cyclohexane, and methylcyclohexane, and these solvents may be used alone or in combination. The amount used is preferably in the range of 20 to 60% by volume of the total amount of the reaction solution, and if the aromatic hydrocarbon is mixed in the alkanes up to about 10%, there will be no substantial effect. As the polymerization inhibitor, known acrylic acid polymerization inhibitors such as hydroquinone, hydroquinone monomethyl ether, and copper acrylate can be used, but hydroquinone and hydroquinone monomethyl ether are preferably used because of ease of removal in the subsequent purification step.

The amount of polymerization inhibitor used is 0 based on the acrylic acid used.
．． 01-1% by weight, preferably 0.02-0.2% by weight
is within the range of The acidic catalyst used is sulfuric acid, P-toluenesulfonic acid, benzenesulfonic acid, methanesulfonic acid,
Examples include ion exchange resins and mixtures thereof, and sulfonic acid catalysts, particularly P-toluenesulfonic acid, are preferred.

The amount used may be in a range corresponding to 4 to 20 mol% based on the raw material pentaerythritol. Molecular oxygen may be present at a concentration below the explosive limit of the amount of solvent vapor in the reactor, and is usually added in a volumetric range of 0.001 to 1.0%, preferably 0.01 to 1.0%, by volume within the reactor while being vented into the reaction solution. 0%, more preferably 0.01-0
．． It is sufficient if it exists in 5%.

The method of the present invention is specifically carried out as follows.

The raw materials, pentaerythritol and acrylic acid, are added to the above solvent at a molar ratio of 1:2 to 4, preferably 1:3.0 to 3.6, and are thoroughly dispersed and mixed.
Add a polymerization inhibitor and an acidic catalyst, heat to a temperature of 50 to 150°C, preferably 60 to 100°C, and add a small amount of air to the reaction solution as a source of molecular oxygen while adding the ester under atmospheric pressure or reduced pressure. Perform the chemical reaction. Water produced by the esterification reaction is distilled off alone or azeotropically with the solvent and removed from the system. The reaction is thus stopped after 5 to 15 hours. The obtained esterification reaction mixture is separated into two layers, so the solvent layer is removed and the ester layer is separated into two layers.
Cool to 0-30°C.

In this solvent layer, the raw materials acrylic acid and pentaerythritol are hardly dissolved, and the dissolved amount of the product is also very small. This recovered solvent can be used again for the esterification reaction as it is, and the trace amount of the product contained therein will not have any adverse effect on the subsequent reaction. The cooled ester layer is either directly neutralized with an alkaline aqueous solution to neutralize the unreacted acid and the acid catalyst, and then washed with an alkaline aqueous solution adjusted to pH 2 to 14 after removing the neutralized waste water, or washed with an alkaline aqueous solution adjusted to a pH of 2 to 14, or a good solvent for the ester. After diluting with a halogenated hydrocarbon or aromatic hydrocarbon such as trichloroethylene, trichloroethane, benzene or toluene, the solution is similarly subjected to neutralization and washing. In addition, in order to promote the separation of the two layers of the obtained esterification reaction mixture, it is also possible to newly add alkanes, and to increase the relative solubility of the alkane by adding new alkanes to the obtained ester layer. It is also possible to separate and remove the large amount of acrylate.The alkaline aqueous solution used for alkaline neutralization cleaning contains hydroxides of alkali metals and alkaline earth metals such as sodium hydroxide, potassium hydroxide, sodium carbonate, and slaked lime. diacrylates and triacrylates in the reaction products are relatively easily soluble in water, so to prevent this, 5% is added to the alkaline aqueous solution.
It is preferable to add up to 20% by weight of salt, calcium chloride, etc., as this will increase the yield.

The neutralized and washed ester can be dried with a conventional drying agent such as anhydrous sodium sulfate or activated alumina, or it can be made into a product as it is, and if desired, it can be dried at 70°C under reduced pressure to remove light boiling components such as solvents. Purified polyfunctional acrylate can also be obtained by stripping at a low temperature below.

The method of the present invention makes it possible to achieve high esterification rates as described above. That is, the esterification reaction proceeds as a sequential reaction as shown in FIG. 1, but Comparative Example 1 using toluene as a solvent (B in FIG. 1)
This is clear even when comparing Reference Example 1 (indicated by the dotted line) and Reference Example 1 (indicated by the solid line A in FIG. 1) using n-hexane. The composition of the reaction product changes as the esterification rate progresses, but with a good solvent such as toluene, the tetraacrylate content exceeds the triacrylate content when the esterification rate reaches 50 to 55%. Since then, as the esterification rate has progressed, the content of tetraacrylate has increased from 43% to 5%.
3%, and triacrylate changes significantly from 43% to 31%. On the other hand, when a poor solvent such as n-hexane is used, the esterification rate of tetraacrylate remains at a level of 33% even after reaching 95%, and the triacrylate content targeted by the present invention is at a high level of 46%. Maintained. Thus, the PETA obtained by the method of the present invention contains a high level of triacrylate content and has a high esterification rate of 85 to 95%.

Furthermore, when molecular oxygen is supplied to the reaction solution during the esterification reaction and allowed to coexist, PETA obtained by the method of the present invention unexpectedly contains peroxides, which were previously thought to be generated during the reaction due to oxygen. It was found that there was a significant reduction in the amount of colored substances and colored substances. This can be said to be an advantage due to the method of the present invention identifying the catalyst. This is because, by allowing molecular oxygen to coexist, the amount of polymerization inhibitor used in the reaction is greatly reduced, and the subsequent purification operation is extremely easy. In particular, when the esterification reaction is carried out in the absence of molecular oxygen in the method of the present invention, the amount of polymerization inhibitor used must be significantly increased, and the degree of coloration of the resulting product increases. This became clear. The ability to overcome these drawbacks is due to the effect of using alkanes as a solvent as a poor solvent for acrylic acid, pentaerythritol, and their esterified products, especially mono-, di-, and triacrylates, which are specified in the present invention. This can be said to be an advantage not found in good solvents such as benzene and toluene.

Thus, the PETA obtained by the present invention is a product with a high triacrylate content and low tetraacrylate and oligomer content, and has the advantage of having a low freezing point and being extremely easy to handle.

The present invention will be further explained below with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

In the present invention, the esterification rate refers to the dehydration rate relative to the theoretical value when pentaerythritol triacrylate is produced by the esterification and dehydration reaction of pentaerythritol and acrylic acid, and is expressed by the following formula.

Example 1 Pentaerythritol 500
V1 acrylic acid 8757 (containing 200 ppm hard-mouthed quinone monomethyl ether), P-toluenesulfonic acid 707, hydroquinone 0.175y and n-hexane 5307 were added and air 1.51 (NTP)/Hr was bubbled into the reaction mixture. The reaction mixture was heated and stirred, and the n-hexane-water azeotrope produced by the reaction and distilled out was separated using a water separator, water was taken out of the reaction system, and n-hexane was returned to the reaction system.

After 6 hours of reaction, produced water 94.6% of the theoretical value 187.67
was distilled out.

During this time, the reaction temperature was 67.5-69°C. The resulting reaction mixture was cooled to room temperature and separated into two layers, of which n
- The hexane layer was decanted (removed) and the ester layer was diluted with trichlorethylene to a concentration of approximately 50%.

Then, it was neutralized with 1,370 ml of a mixed aqueous solution of sodium hydroxide and sodium chloride (prepared so that the concentrations of each component were 5% and 10%, respectively) (the neutralized aqueous solution had a pH of 8.
5), and then sequentially with 600 ml of the same alkaline mixed aqueous solution (prepared as above so that the component concentrations were 0.5% and 10%, respectively, PHL 2.8) and 600 ml of 5% sodium chloride solution. Washed. The ester solution containing the solvent was allowed to stand, and when it became clear, the solvent was distilled off at 50° C. under reduced pressure (achieved vacuum degree of 5 mmHg). After stripping (solvent distillation), 1% by weight based on the ester
A filter aid (Radiolite, Showa Kagaku Kogyo) was added and filtered to remove the "cloudiness" of the ester. The ester yield was 9007, and its composition (by Hitachi 635 type column, Hitachi Gel 3050 liquid chromatography) was as follows: traces of pentaerythritol monoacrylate, 7% of diacrylate, 54% of triacrylate, 34% of tetraacrylate, dipentaerythritol. Erythritol polyacrylate (polyacrylate) and the like were 5% (each % by weight, hereinafter the same), color tone (APHA) 501, viscosity (B-type viscometer) 700 cps/25°C, and residual solvent 0.3%.

Moreover, it did not solidify even at -20°C. In addition, 3.07 tetraacrylates were contained in the inclined n-hexane.

Comparative Example 1 The reaction was carried out using the apparatus and method of Example 1, except that 530 tons of toluene was used instead of n-hexane as the solvent.
However, the reaction temperature was maintained at 68-70°C under reduced pressure (18°C).
2 to 185 m71 LHg).

). The reaction was continued for 5 hours until the amount of water produced by the reaction reached 187.6 tons. Since the reaction mixture was a homogeneous layer, the toluene content was adjusted to about 50%, and then as in Example 1,
After neutralization, washing, and purification, the yield of ester was 800 tons, and its composition was 4% diacrylate, 24% triacrylate, 56% tetraacrylate, and 16% polyacrylate.It was a product that solidified at room temperature and had a viscosity of 16 at 45℃.
It showed 0 cps. The appearance was yellow-orange, and the residual solvent content was 0.3%. In the attached FIG. 1, the reaction products in the reaction mixture according to the progress of the esterification rate of this comparative example were analyzed, and diacrylate, triacrylate, tetraacrylate, and polyacrylate were shown.

Reference Example 1 The apparatus and method of Example 1 were used except that the process was carried out until the produced water reached 1987 (corresponding to 100% esterification rate).The obtained ester yield was 9207, and its composition was diacrylate. 3.2% triacrylate, 33.3% triacrylate, 46.9% tetraacrylate, and 12.6% polyacrylate, and the product solidified at room temperature.

The attached FIG. 1 shows diacrylate, triacrylate, tetraacrylate, and polyacrylate by analyzing the reaction mixture as the esterification rate progressed in this reference example.

Example 2 Using the same apparatus as in Example 1, pentaerythritol 500
7. Add acrylic acid 8357 (contains 200 ppm of hydroquinone monomethyl ether), P-toluenesulfonic acid 41.7y1, hydroquinone 0.35f7 and cyclohexane 650t, and air 2.5f! The esterification reaction was carried out while aerating /Hr.

The reaction temperature was 79 to 80°C, and the reaction was carried out for 6 hours, and 180.2 tons of produced water (corresponding to an esterification rate of 90.9%) was distilled out. The resulting reaction mixture was cooled to room temperature, separated into two layers, the cyclohexane layer was decanted (removed), and the ester layer was diluted with benzene to a concentration of about 50%.

Next, a mixed aqueous solution of sodium carbonate and sodium chloride (prepared to have a concentration of 5% and 10% for each component) was neutralized with 1350a (pH 9), and then a mixed aqueous solution of sodium hydroxide and sodium chloride (each with a concentration of 1%) was neutralized (pH 9).
% and 10% PHL3) and 600 d of 5% aqueous sodium chloride solution. The ester solution containing the solvent was poured into an activated alumina packed bed (Nippon Siebel, A
After passing the solution through a column packed with ctalAlOOml, the solvent was distilled off at 50° C. under reduced pressure (ultimate vacuum level: 5 mmHg). After stripping, 0.5% by weight based on the ester
Nosawa filter aid (Radiolite) was added and filtered to remove suspended solids. The ester yield was 8757, and its composition was 7% diacrylate, 53% triacrylate, 32% tetraacrylate, 8% polyacrylate, and the color (AP
HA) 601 viscosity 760 cps/25°C, residual solvent content 0
．． It was 2%. This product did not solidify even at -20°C. Comparative Example 2 Benzene 7007 was used instead of cyclohexane, the reaction temperature was 81 to 82°C, and the reaction was carried out for 4 hours and 10 minutes, and 149.7 produced water (equivalent to esterification rate of 75.5%) was distilled out. The reaction was otherwise carried out using the same apparatus and method as in Example 2.

Since a small amount of unreacted pentaerythritol remains in the reaction mixture, it is filtered before neutralization and washing to remove about 5% of benzene.
The concentration was adjusted to 0%. A product was obtained in the same manner as in Example 2. The yield of ester was 705y, and its composition was almost the same as in Example 2, with a color (APHA) of 120, a viscosity of 720 cps/25°C, and a residual solvent content of 0.3%.

[Brief explanation of the drawing]

FIG. 1 shows the esterification rate and product composition of pentaerythritol acrylate.

Claims (1)

[Claims] 1. When pentaerythritol and acrylic acid are esterified using an acidic catalyst and a polymerization inhibitor, the reaction occurs at an esterification rate of 85 to 95% in the presence of molecular oxygen in a chain or cyclic alkane having 6 to 8 carbon atoms. 1. A method for producing a polyfunctional acrylate, the method comprising: