JPH0249752A - Method for crystallizing and purifying beta-crystal of tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionyloxymethyl)methane - Google Patents

Abstract

PURPOSE:To crystallize excellent white granular beta-crystals of the subject compound by melt mixing a reaction mixture containing the subject compound once in a solvent while refluxing, injecting and mixing the resultant molten mixture in a specific cooled solvent, quenching the mixture and carrying out crystallization and purification from a heterogeneous solution. CONSTITUTION:A reaction mixture containing tetrakis[3-(3,5-di-tert-butyl-4- hydroxyphenyl)propionyloxymethyl]methane obtained by ester interchange reaction of pentaerythritol with a lower alkyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate is melt mixed with a water-soluble solvent while being refluxed. A cooled solvent consisting of a water-soluble solvent in an amount of 0.2-1.5 times based on the above-mentioned reaction mixture and water in an amount of 0.06-0.09 based on the water-soluble solvent is then mixed to carry out crystallization and purification. Water is further added to afford beta-crystals of the objective compound, having the stabilized beta-crystal structure and useful as an antioxidant for polyolefins, etc.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention provides tetrakis(3-(3,5-ditertiary-butyl-4-hydroxyphenyl)propionyloxymethyl) useful as an antioxidant for polyolefins and the like. The present invention relates to a crystallization purification method for industrially stably obtaining methane as β crystals.

[Problems to be solved by conventional technology and invention] Tetrakis (3
-(3,5-ditert-butyl-4-hydroxyphenyl)propionyloxymethylcomethane (hereinafter, compound I
It is also sometimes called. ) is produced by transesterifying 3-(3,5-ditertiary-butyl-4-hydroxyphenyl)propionic acid lower alkyl ester and pentaerythritol in the presence of a base catalyst such as an alkali metal lower alkoxide. U.S. Patent No. 364
It is known from specification No. 4482.

Recent research on the crystal structure of Compound I has revealed that Compound II has four types: α crystal, β crystal, T crystal, and δ crystal (US Pat. No. 4,405,807).
No. Specification). Among these, α-crystals can only be obtained from crystals with poor purity and color, as the conventional method turns the crystals into fine powder during crystallization, making stirring impossible, as described in the same US patent specification. Therefore, from the viewpoint of manufacturing process problems and handling as a product, the β-crystal structure is suitable.

In producing β-crystals, 2 to 10% by weight of water is added to a water-soluble solvent such as methanol or ethanol, the transesterification product is dissolved, and if necessary, the product is clarified and filtered, and then cooled. A method of gradually lowering the temperature is known from European Patent Publication No. 244361.

However, in this method, if the crystallized liquid is gradually cooled,
As mentioned above, the crystal structure may partially change to alpha crystals, which is undesirable from the viewpoint of handling as a product, or if the slurry is kept stirring even after crystallization, the crystal structure changes from beta crystals to alpha crystals over time. changes progress. Like this, the same?
- It is extremely difficult to obtain β-crystals industrially and stably with good reproducibility using the crystallization method described in Rosova's published patent application. In addition, considering the fact that if β crystals are stored in a wet state at room temperature, their crystal structure changes to α crystals, β
It is extremely difficult to produce crystals stably industrially.

The object of the present invention is to provide an industrially advantageous method for stably obtaining Compound I in the form of β crystals.

[Means to solve the problem]

In order to solve the above problems, as a result of intensive research, the present inventors found that in order to stably produce β-crystals on an industrial scale, -tan compound I was melt-mixed in a solvent under reflux, and then cooled. The present inventors have discovered that the desired objective can be achieved by a crystallization purification method in which the mixture is poured into a liquid and rapidly cooled, and the present invention has been completed.

That is, the present invention provides pentaerythritol and 3-(3,
Tetrakis[3-(3,5-ditert-butyl-4-hydroxyphenyl)propionyloxymethyl] obtained by transesterification reaction with lower alkyl ester of 5-ditert-butyl-4-hydroxyphenylpropionic acid. The methane-containing reaction mixture is melt-mixed with a water-soluble solvent G under reflux, and then a water-soluble solvent of 0.2 to 1.5 times the weight of the reaction mixture is mixed with a water-soluble solvent of 0.06 to 1.5 times the weight of the water-soluble solvent.
Tetrakis (3 -(35-ditert-butyl-4-
The present invention relates to a method for crystallizing and purifying hydroxyphenyl)propionyloxymethylcomethane.

The reaction mixture containing Compound I used in the present invention may be used as the transesterified product, or it may be a residue (often candy-like) obtained by concentrating and removing the solvent used to improve fluidity in the catalyst removal step. ) may be used.

According to the method of the present invention, a water-soluble solvent (such as methanol, ethanol or a mixed solvent thereof, etc. ) and melt-mix under reflux, and if necessary, seed crystals of β crystals are added to the transesterification reaction product into a cooled solvent consisting of a water-soluble solvent (methanol, ethanol, or a mixed solvent thereof, etc.) and water. , preferably 0.05 to 1% by weight, and the above-mentioned melt-mixed liquid is mixed with oil and crystallized, and further water is added to stabilize the generated β crystals, and the resulting crystals are β by isolating, washing and drying if necessary.
Compound I having a single crystal structure can be obtained.

The amount of the water-soluble solvent used in the melt-mixing under reflux is 0.1 to 1 times the weight of the reaction product containing Compound I, preferably 0.4 to 0.6 times by weight.

The temperature at which mixing is started may be the temperature at which the reaction product containing compound (1) melts in the water-soluble solvent, and is usually 100-150°C.
°C1 Preferably it is 120-130 °C. After mixing, the solution is kept at a temperature where the solvent refluxes.The holding time is the time until it dissolves, which is within 2 hours.If the solution is held for a longer time, a small amount of α crystals will precipitate. After oiling and mixing, it becomes a seed crystal and causes α crystal to be mixed in.

The recrystallization solvent used, that is, the solvent consisting of a water-soluble solvent and water, has a concentration of 0.2 to 1
．． It is preferably composed of 5 times the weight of the water-soluble solvent and 0.06 to 0.099 weight of water relative to the water-soluble solvent, and the temperature is usually 0 to 30°C, preferably 15 to 25°C.
Keep cool. The liquid obtained by melting and mixing the water-soluble solvent obtained above under reflux is added to this recrystallization solvent, and the mixture is heated to 10 to 50°C, preferably 35 to 45°C, to precipitate crystals. Further, by adding water to the crystallization solution of the β-crystals thus obtained, the β-crystals of Compound I can be obtained industrially stably without changing the crystal structure. The advantage of adding water is that in addition to increasing the stability of the six-component structure, the solubility is lower than the original solubility of the solvent, which improves the crystallization yield, and furthermore, as a result of mixing with water, ignition and explosion may occur. It is industrially preferable because it can improve the safety against. The amount of water to be mixed is usually 0.2% of the total amount of water-soluble solvent used.
Not more than twice the weight, preferably 0.1 to 0.2 times the weight,
When the amount exceeds 0.2 times by weight, product quality such as purity and hue tends to deteriorate significantly. Water may be added temporarily, or may be added continuously or intermittently.

(Actions and Effects of the Invention) The method of the present invention is a crystallization purification method from a heterogeneous solution,
According to the method of the present invention, granular β-crystals can be stably produced industrially without changing the crystal structure of Compound I.

The granular compound (1) obtained by the method of the present invention is a white granular compound having excellent properties such as high bulk specific gravity and high fluidity. In addition, analysis using differential scanning calorimetry (DSC) (in analysis using differential scanning calorimetry, absorption of α crystals!
The center of the melting peak is 121-123°C, and the β crystal is 1
13 to 115°C, the change in crystal structure is
This can be clearly seen from the line diffraction spectrum. ), it exhibits an endothermic melting peak with a single center at 113-115°C, and its X-ray (α to Cu-) diffraction spectrum is described as a β-crystal feature in U.S. Pat. No. 4,405,807. As shown in the figure, it was confirmed that it had a single β-crystal structure, as it had five peaks in the range of diffraction angle 2θ of 5° to 10.6°. The three products obtained stably maintain their crystal structures. In conventional methods, it was difficult to produce industrially because the compound (■) was colored or the β-crystalline structure changed to the α-product structure, but this method is difficult to manufacture industrially by scaling the equipment and pulverizing the compound. Easily and stably produce three compounds on an industrial scale as white crystals with excellent hue and with sufficient purity for practical purposes, without causing operational inconveniences such as inability to stir. It became possible to do so.

〔Example〕

The present invention will be specifically explained below using reference examples, working examples, and comparative examples. However, the present invention is not limited to what is illustrated here.

Reference Example 1 50 equipped with a stirrer, cooler, thermometer and nitrogen inlet pipe
Methyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate 182 to 40 flasks of 0Id
．． 7 g (0,625 mol) and 18.9 g (0,139 mol) of pentaerythritol and 0.73 g (0,0035 mol) of monobutyltin oxide,
The temperature was raised to 185°C, the reaction was carried out for 1 hour, and the methanol produced was distilled off. Vt is dead.

Nitrogen gas was bubbled into the liquid (2NL/HV) under a pressure of 60 to 70 mHg to complete the reaction for 13 hours. [
The amount of unesterified trisubstituted product (A) in the mixture at the end of the reaction is 5% or less (HPLC (S/S)). excessive 3-
(3,5-ditertiary butyl-4-hydroxyphenyl)
Methyl propionate 150-185"C10,5-0
．． It was distilled off in 1 hour by thin film distillation under the condition of 2 mmHg. The distillate was 19.5 g, and the distillation rate was 97.
%. This product can be used as is in the next reaction.

Thereafter, the reaction mixture was cooled to 115°C, returned to atmospheric pressure by introducing nitrogen gas, and uniformly dissolved in toluene.

This toluene solution was mixed with 5% oxalic acid in ice water at 400 ml (0,1
6 mol), followed by repeated aqueous separation twice with 40 g of water at 60°C, and the toluene layer was washed at 125°C with 13Qa
*H@, when concentrated in 1 hour, tetrakis(3-(3,
A pale yellow candy-like substance consisting of 5-ditert-butyl-4-hydroxyphenyl)propionyloxymethylcomethane was obtained.

Example 1 50 g of methanol was added to 100 g of the candy-like substance obtained in Reference Example 1.
g was gradually added from 125°C and heated under reflux (68°C).
Melt mixed. Subsequently, a recrystallization solvent consisting of 92.5 g of methanol and 7.5 g of water was cooled to 20 to 25°C, 0.1 g of seed crystals were added, and then the above melt was separated while stirring, and the internal temperature was The temperature was 42°C. Then, after stirring for 1 hour at an internal temperature of 35 to 45°C to precipitate crystals, 17.6 g of water was added, and after stirring for 1 hour, the mixture was stirred at 20°C.
The mixture was cooled to C, stirred and maintained for 48 hours, and centrifuged to dry the nine separated products to obtain 83 g of granular white crystals with a bulk specific gravity of 0.57. In DSC analysis, this compound has a center of 1
It showed only one endothermic melting peak at 14.5°C. This supports the fact that the crystal is a single β-crystal (Fig. 1). In addition, the β-crystal structure was confirmed by X-ray (Cu-Kα) diffraction spectrum (Figure 2), and the melting point measured using a melting point measuring device with a microscope was 111-115'C, and liquid chromatography The crystal purity analyzed by the method was 98% or more.

Example 2 Using 50 g of the candy-like substance obtained in Reference Example 1, the solvent was changed to ethanol, and the amounts of the solvent and water used were the same as in Example 1.
72, the same operation as in Example 1 was carried out, and the bulk specific gravity was 0.
41 g of 52 granular crystals were obtained.

This compound showed a single endothermic melting peak centered at 114°C in DSC analysis. This supports the fact that the crystal is a single β crystal. In addition, X-rays (
It was confirmed by Cu-α) diffraction spectrum that it was a β crystal structure. It has a melting point of 112-115°C and a crystal purity of more than 98% as analyzed by liquid chromatography.

Example 3 11-4 equipped with a stirrer, cooler, thermometer, and nitrogen inlet tube
0 flask, 671.6 g of methyl 3-(3,5-ditertiary-butyl-4-hydroxyphenyl)propionate (
2.3 mmol), pentaerythritol 68.0 g (
0.50 mol), monobutyltin oxide 2.25 g (
10.9 mmol), monobutyltin trichloride 0.
16 g (0.57 mmol) (the total amount of catalyst corresponds to 0.5 mol% of the methyl propionate compound) and 100 g of toluene were charged and heated at 170 to 175° while stirring.
The reaction was carried out at C for 12 hours. During the reaction, 500 g of toluene was added dropwise and distilled off together with the generated methanol. After the reaction was completed, 200 g of toluene was added and dissolved, 200 g of 5% by weight iced water was added, stirred for 1 hour, and allowed to stand, and the aqueous layer was separated and removed. After washing the organic layer twice with 200 g of water, toluene was distilled off under reduced pressure and tetrakis(3-(3,5-
590 g of a candy-like substance containing ditert-butyl-4hydroxyphenyl)propionyloxymethyl)methane was obtained.

The same operation as in Example 1 was performed on 100 g of this candy-like substance to obtain 81 g of white granular crystals with a bulk specific gravity of 0.55. This compound showed a single endothermic melting peak centered at 114°C in DSC analysis. This supports the fact that the crystal is a single β crystal. In addition, X-rays (Cu
- It was confirmed by α) diffraction that it had a β crystal structure, and the melting point was 110 to 114°C, and the crystal purity (analysis by liquid chromatography) was 98% or more.

Table 1 below shows the 3-(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyloxymethylcomethanes) obtained in Examples 1.2 and 3.
The bulk specific gravity and angle of repose of the product are shown in comparison with commercially available products.

From the above Table 1, it can be seen that the products obtained by the present invention have better fluidity than commercially available products.

Comparative Example 1 The candy obtained in Reference Example 1! 50g and 25g of methanol
was gradually added from 125°C and melt-mixed under reflux (68°C). Then methanol 46.3g, water 3.8g
The recrystallization solvent adjusted to 0.0 g was cooled to 20-25°C.
When 1 g of seed crystals were added and the solution was stirred, the internal temperature became 43°C. After that, internal temperature 3
The crystals were precipitated by stirring at 5-45"C for 1 hour, immediately cooled to 20°C, and stirring continued. After 4-5 hours, the crystals became pulverized and stirring became impossible.・Filter with a lath filter, wash with methanol cooled to 20°C, dry and measure the melting point: 121-123°
DSC analysis showed an endothermic melting peak (centered at 123.0°C) of α crystals (Fig. 3), and X-ray (
It was confirmed by the Cu-α) diffraction spectrum that it had seven crystal structures (Fig. 4).

Comparative Example 2 Methyl 3-(35-ditert-butyl-4-hydroxyphenyl)propionate 2 was placed in a 1000d40 flask equipped with a stirrer, distillation condenser, thermometer, and toluene inlet tube.
00g (0.68 mol) and pentaerythritol 21.
2 g (0.15 mol) and di-butyltin oxide 1
g and heated to 170°C. Toluene was continuously added dropwise, and the resulting methanol was distilled off while the reaction was maintained for 12 hours to complete the reaction. After the reaction was completed, diluted with toluene and treated to remove di-butyltin oxide.
toluene? We get 8'/&. Toluene was distilled off to obtain 201 g of a pale yellow candy-like substance. The resulting candy-like substance tto.

Regarding g, the same procedure as in Comparative Example 1 was carried out to precipitate crystals, which were immediately cooled to 20°C and stirring was continued. After 1 hour, the crystals became fine and stirring became impossible. The obtained crystals were filtered through a glass filter, washed with methanol cooled to 20°C, and dried, resulting in a melting point of 121-12.
At 4.3°C, DSC analysis showed an endothermic melting peak (centered at 123.2'C) of α crystals. In addition, X-rays (Cu
- and α) Diffraction spectra confirmed that it had an α-crystalline structure.

Comparative Example 3 71 g of methanol was added to 50 g of the candy-like substance obtained in Reference Example 1.
3g was gradually added from 125°C and heated under reflux (6B”C).
) melt mixed. Then, 3.8 g of water was added dropwise and the mixture was gradually cooled to precipitate crystals at an internal temperature of around 55°C. Stirring was continued for 3 hours with further cooling. The obtained crystals were filtered, washed with methanol, and dried, and the melting point was measured to be 110 to 124°C. Also DSC
The analysis results showed two endothermic melting peaks (α-crystal peak center: 122.4°C; β-crystal peak center: 113.8°C), and the ratio of the seven products to the β-crystal was 28:72 based on the area ratio. Ta.

Comparative Example 4 The same operation as Comparative Example 3 was performed except that the stirring time in Comparative Example 3 was changed from 3 hours to 5 hours. When the melting point of the obtained crystal was measured, it was found to be 111-125°C. X-ray (C
The u- to α) diffraction spectrum is shown in FIG. In the DSC analysis, two endothermic melting peaks (7 products peak center 122
．． 2” C1β crystal peeling center 113.8°C),
The ratio of α and β crystals was 50:50 based on the area ratio (
Figure 5).

Comparative Example 5 The same operation as Comparative Example 3 was performed except that the stirring time in Comparative Example 3 was changed from 3 hours to 10 hours.

The precipitated crystals were pulverized and could no longer be stirred. When the melting point of the obtained crystals was measured, it was found to be 121-124°C.

The results of DSC analysis showed only one endothermic melting peak (centered at 122.8°C), indicating a single α-crystal crystal structure. In addition, it was confirmed by X-ray (Cu-α) diffraction that it was a compound with an α-crystal structure.

Comparative Example 6 Using 50 g of candy-like substance obtained in Example 3, Comparative Example 5
When the same operation was performed as in Comparative Example 5, the precipitated crystals were pulverized and could no longer be stirred. The obtained crystals were filtered, washed with methanol, and dried, and the melting point was measured to be 119 to 123°C, and DSC analysis showed an endothermic melting peak (centered at 122.5°C) of α crystals. Ta. In addition, it was determined by X-ray (α to Cu-) diffraction that it is a compound with an α-crystal structure. Approved.

Comparative Example 7 The same operation as in Example 1 was carried out except that the operation of melt-mixing under reflux (68°C) in Example 1 was performed at a temperature lower than the reflux temperature (63 to 65°C).

When the melting point of the obtained crystal was measured, it was found to be 110-125°C. In addition, the results of DSC analysis showed two endothermic melting peaks (α crystal peak center 123.0'C, β crystal peak center 114.0°C), and the ratio of α crystals and β crystals was 2o from the area ratio. :So it was.

Comparative Example 8 The same procedure as in Example 1 was carried out, except that the mixture was melt-mixed under reflux (68°C) and held at that temperature for 4 hours. The melting point of the obtained crystals was measured to be 111-124°C.
showed that. In addition, the results of DSC analysis showed two endothermic melting peaks (α crystal peak center 123, 1°C, β crystal peak center 114.2°C), and the ratio of α crystal and β crystal was 35:65 from the area ratio. Met.

[Brief explanation of the drawing]

Figures 1 and 2 show the differential scanning calorimetry analysis pattern and X-ray (Cu-
Figures 3 and 4 show the analysis pattern and X-ray (Cu- α) diffraction spectrum of the product of Comparative Example 1 by differential scanning calorimetry, respectively, and Figures 5 and 6 show the diffraction spectrum of the product of Comparative Example 1. The figures show the differential scanning calorimetry analysis pattern and the X-ray (Cu-α) diffraction spectrum of the product of Comparative Example 4, respectively.

Claims (6)

[Claims] (1) Tetrakis [3-(3,5-ditertiary butyl) obtained by transesterification reaction of pentaerythritol and 3-(3,5-ditertiary butyl-4-hydroxyphenyl)propionic acid lower alkyl ester The reaction mixture containing butyl-4-hydroxyphenyl)propionyloxymethyl]methane is melt-mixed in a water-soluble solvent under reflux, and then 0.2 to 1.5 times the weight of the water-soluble solvent and its water-soluble A cooled solvent consisting of water in an amount of 0.06 to 0.09 times the weight of the solvent is mixed with the above molten mixture to crystallize it, and further water is added to stabilize the generated β-crystal structure. A method for crystallizing and purifying tetrakis[3-(3,5-ditert-butyl-4-hydroxyphenyl)propionyloxymethyl]methane, which comprises: (2) The method according to claim 1, characterized in that the water-soluble solvent is used in an amount of 0.1 to 1 times the weight of the reaction mixture. (3) Tetrakis(3-(3,5-di-tert-butyl-4)
-Hydroxyphenyl)propionyloxymethyl]methane-containing reaction mixture is melt-mixed with the water-soluble solvent under reflux, the method according to claim 1, characterized in that the resulting molten mixture is maintained at a temperature at which the solvent used is refluxed. . (4) The method according to claim 3, characterized in that the time during which the molten mixture is held under reflux of the solvent is within 2 hours. (5) The method according to claim 1, wherein the temperature at which the cooled solvent and the molten mixture are mixed is 10 to 50°C. (6) The method according to claim 1, characterized in that 0.1 to 0.2 times the weight of water is added to the total water-soluble solvent used.