JP2005145857A - Method for purifying 1,2-diphenoxyethane and method for producing its solid matter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for stably purifying high-purity 1,2-diphenoxyethane in a high yield, which has no solvent recovery process to cause a problem in a solvent cleaning process or a recrystallization process and with which a waste occurring in solvent recovery is reduced and a method for producing a product, with which the purified product obtained by the purification method is used and which leads also to solution of a dust problem. <P>SOLUTION: The method for purifying high-purity 1,2-diphenoxyethane comprises subjecting a crude reaction product of 1,2-diphenoxyethane to vacuum distillation to ≤2.0% impurity. The method for producing 1,2-diphenoxyethane comprises spraying 1,2-diphenoxyethane in a melt state obtained by the purification method or feeding to a flaker and cooling to give a granule or a flake-like material. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an industrially advantageous purification method for obtaining 1,2-diphenoxyethane having a low impurity content, and purified 1,2-diphenoxyethane in the form of granules or flakes. It is related with the manufacturing method to obtain.

  As a method for producing 1,2-diphenoxyethane widely used as a sensitizer for heat-sensitive recording materials, for example, 1,2-diphenoxyethane may be prepared by reacting a disulfonic acid ester of an alkylene diol with an aromatic alcohol. Is discharged into water to precipitate crystals and washed with methanol-water (see Patent Document 1).

  Furthermore, there is known a method in which dihalogenated alkane and phenol are heated and condensed in an aqueous medium in the presence of alkali to produce 1,2-diphenoxyethane and recrystallized with isopropanol (see Patent Document 2). It has been.

  Since the 1,2-diphenoxyethane reaction crude product obtained by these production methods contains impurities, it needs to be further purified in order to obtain a high-purity product. Incidentally, as a purification method for the 1,2-diphenoxyethane reaction crude product, a washing method using a solvent and a recrystallization method are known.

  However, since these purification methods all use a solvent, the number of steps such as a solvent recovery step is increased, and a waste solvent treatment operation is required, which increases the manufacturing cost. Furthermore, there were problems with air pollution and the like. As a purification method other than the washing method or the recrystallization method, Patent Document 2 merely describes “vacuum distillation” and does not describe the specific formulation.

Moreover, although the powder form is known also about the form of refine | purified 1, 2- diphenoxyethane, what was described about the method of manufacturing in forms other than a powder form is not found. Incidentally, 1,2-diphenoxyethane produced by the method described in the above-mentioned patent documents and the like is in a powdery form, so there is a problem that dust is generated during handling, and problems to be solved Was left as.
JP 61-260036 A Japanese Patent Publication No.6-21083

  The object of the present invention is to eliminate the solvent recovery step that has been a problem in the conventional washing method or recrystallization method as a purification method of 1,2-diphenoxyethane, and to dispose of the solvent during recovery. An object of the present invention is to provide an industrially advantageous purification method for solving high-quality 1,2-diphenoxyethane in a stable and high yield, which solves the problem of product generation and has a low impurity content.

  Another object of the present invention is to provide a method for producing purified 1,2-diphenoxyethane in the form of granules or flakes that is easier to handle and also helps to solve the dust problem. is there.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have obtained a 1,2-diphenoxyethane reaction crude product for the purification method of 1,2-diphenoxyethane, which is the first problem. It was found that high-purity 1,2-diphenoxyethane equivalent to the recrystallization method can be obtained in high yield by vacuum distillation under reduced conditions under specific conditions, and the present invention has been completed. .

  Furthermore, the inventors of the present invention are concerned with a method for producing purified 1,2-diphenoxyethane, which is the second problem, in the form of granules or flakes, in a molten state obtained by vacuum distillation. A method of forming droplets of 1,2-diphenoxyethane and cooling it, or bringing molten 1,2-diphenoxyethane into contact with a cooling flaker to form flakes, has led to the completion of the present invention. It is a thing.

  The present invention collectively includes the following inventions.

  (1) The 1,2-diphenoxyethane reaction crude product is 2.0% or less of impurities under vacuum under the condition that the temperature at the top of the column (the upper position of the rectifying column installed in the distillation kettle) is 250 ° C. or less. A method for purifying high-purity 1,2-diphenoxyethane, which is distilled until

  (2) For distillation purification of the 1,2-diphenoxyethane reaction crude product, the distillation conditions are as follows: the number of distillation stages is 2 or more, the degree of vacuum is 5 mmHg or less, the reflux ratio is 1 or more, and the column top temperature is 145 ° C to 170 ° C. The method for purifying 1,2-diphenoxyethane as described in (1) above, wherein the distillation is carried out until the impurities become 1.0% or less.

  (3) When the 1,2-diphenoxyethane reaction crude product is purified by distillation, the distillation conditions are as follows: the number of distillation stages is 4 or more, the degree of vacuum is 3 mmHg or less, the reflux ratio is 3 or more, and the top temperature is 135 ° C to 170 ° C. The method for purifying 1,2-diphenoxyethane as described in (1) above, wherein the distillation is conducted until the impurities are 0.5% or less.

  (4) By cooling the molten 1,2-diphenoxyethane obtained by the purification method described in (1), (2) or (3) above, a granular material having an average particle size of 5 mm or less or a size of 5 cm square Hereinafter, a process for producing 1,2-diphenoxyethane, characterized in that the flake is 2 cm or less in thickness.

(5) The molten 1,2-diphenoxyethane obtained by the purification method described in the preceding (1), (2) or (3) is nitrogen of 5.0 kg / cm ² or less in a molten state of 200 ° C. or less. Before spraying through a disk with a hole in an atmosphere, and dropping the molten material into a cooled nitrogen or air space to cool it down to a granular material having an average particle diameter of 5 mm or less (before 4) A process for producing 1,2-diphenoxyethane as described above.

  (6) The molten 1,2-diphenoxyethane obtained by the purification method described in the preceding (1), (2) or (3) was supplied to a cooling flaker in a molten state at 200 ° C. or less and solidified by contact. The method for producing 1,2-diphenoxyethane as described in (4) above, wherein the flakes are obtained by peeling off.

  According to the method of the present invention, a highly purified 1,2-diphenoxyethane purified product useful as a sensitizer for a heat-sensitive recording material is obtained industrially advantageously in a small number of steps and in a high yield and high quality. be able to. In addition, since the product form is produced as a granular or flaky product, it is easy to handle, has no dust, and can be easily pulverized by a pulverizer when used.

First, the 1,2-diphenoxyethane reaction crude product subjected to vacuum distillation according to the present invention is intended to be a 1,2-diphenoxyethane reaction crude product containing a large amount of impurities that have been synthesized and not yet purified. Of course, for example, the present invention can be applied to the purification of a 1,2-diphenoxyethane reaction crude product obtained by the known production method (described in Patent Documents 1 and 2).
Among them, the simplest method to be applied in the method for producing 1,2-diphenoxyethane described in Patent Document 2 is to heat-condense dihalogenated ethane and phenols in the presence of alkali in an aqueous medium. In terms of yield, waste, etc.

  As a specific example, 1,2-diphenoxyethane is synthesized by heat-condensing dichloroethane and phenol in the presence of sodium hydroxide in water to synthesize 1,2-diphenoxyethane, and the salt formed after completion of the reaction is removed by filtration, or water is added to the reaction mixture. Is added to dilute the salt concentration, separate the aqueous layer, and use the resulting oil layer as the reaction crude product.

  First, the present inventors distillatively purify the 1,2-diphenoxyethane reaction crude product under vacuum at a column top temperature of 250 ° C. or lower to obtain 1, It was confirmed that 2-diphenoxyethane was obtained.

  In order to obtain 1,2-diphenoxyethane having an impurity content of 2.0% or less by the distillation purification method, in the present invention, it is essential to distill and purify the column top temperature at 250 ° C. or less. However, during distillation purification, the number of distillation (theoretical) plates, the degree of vacuum, the reflux ratio, and the like are also related to the degree of purification, so that the column top temperature is 250 ° C. or lower, and these conditions are appropriately combined.

  For example, when the number of distillation (theoretical) plates is one theoretical plate, it is difficult to adjust the content of impurities to 2.0% or less, and it is desirable that the number is at least two or more.

  The degree of vacuum is also related to the desired tower top temperature. When the tower top temperature is high, the degree of vacuum can be appropriately reduced in relation to the temperature at that time. It is also possible to increase the degree of distillation purification by increasing the degree.

  Therefore, the present inventors distilled and purified the 1,2-diphenoxyethane reaction crude product under the conditions of a theoretical plate number of 2 or more, a degree of vacuum of 5 mmHg or less, a reflux ratio of 1 or more, and a top temperature of 145 ° C to 170 ° C. As a result, 1,2-diphenoxyethane having an impurity of 1.0% or less is obtained, and the performance equivalent to 1,2-diphenoxyethane obtained by the recrystallization method is used as a sensitizer for the thermal recording material. Confirmed to have.

  The present inventors further purified the 1,2-diphenoxyethane reaction crude product by distillation under the conditions of a theoretical plate number of 4 or more, a degree of vacuum of 3 mmHg or less, a reflux ratio of 3 or more, and a mounting temperature of 135 ° C to 170 ° C. As a result, it was confirmed that 1,2-diphenoxyethane having impurities of 0.5% or less was obtained.

  In addition, when the distillation is performed under conditions other than the above distillation conditions, for example, at a column top temperature higher than 250 ° C., there is a problem that 1,2-diphenoxyethane is partially sublimated and decomposed and the purification efficiency is lowered. is there.

  Furthermore, conditions outside the above distillation conditions, for example, 1,2-diphenoxyethane purified with a theoretical plate number of 1 and a reflux ratio of 0, contain more than 2.0% impurities and are obtained by recrystallization. Compared to the 1,2-diphenoxyethane obtained, the melting point is low, and the performance as a sensitizer of the heat-sensitive recording material is compared, and the initial value of the background rash is conspicuous, and the background and recorded image in moisture resistance and heat resistance (printing) It was also confirmed that the storage stability was inferior.

  In addition, the low boiling point substance and initial distillation obtained at the stage of distillation purification can be reused as a reaction raw material.

  The distillation purification method can be carried out either by a batch process or by continuous purification distillation, and the same highly purified 1,2-diphenoxyethane purified product can be obtained.

  The high-purity 1,2-diphenoxyethane obtained by the distillation purification method of the present invention can be stored in a molten state in a storage tank heated to the melting point or higher and taken out and used when necessary. is there. In addition, when storing at a temperature higher than the melting point, 1,2-diphenoxyethane may be oxidized, and therefore a device such as sealing with nitrogen is required.

  For this reason, it is preferable to shift the purified 1,2-diphenoxyethane obtained by the above-mentioned distillation purification to a solidification step for making a granular or flaky product. We propose a solidification method by such a method.

  In the present invention, as a granulation method for granulating 1,2-diphenoxyethane obtained by distillation and purification, pressure is applied to the molten 1,2-diphenoxyethane liquid to form droplets, An ejection-type granular method is adopted in which this is passed through a cooling environment and solidified.

More specifically, while maintaining the molten 1,2-diphenoxyethane liquid at a temperature of 200 ° C. or lower, preferably 100 ° C. to 150 ° C., more preferably 120 ° C. to 140 ° C., 5.0 kg / cm ² or less Te, preferably by applying a nitrogen pressure of 1.5~3kg / cm ^2, and injected through a disk with a hole, dropping the melt cooled nitrogen or cooling air that liquid droplets It is made to cool and granulate.

  When the molten 1,2-diphenoxyethane liquid is heated to a temperature higher than 200 ° C., decomposition and sublimation of 1,2-diphenoxyethane occur, and the temperature is maintained at 200 ° C. or lower. It is important to spray in a state and form droplets.

  The particle diameter of the obtained granular material is a hole diameter of the disc so that the average particle diameter is 5 mm or less, preferably 1 to 2 mm in order to prevent dusting during handling and facilitate pulverization with a pulverizer. It is desirable to adjust setting conditions such as nitrogen pressure.

  In addition, as a flaking method for flaking 1,2-diphenoxyethane obtained by distillation purification, the present invention adopts a method of bringing 1,2-diphenoxyethane in a molten state into contact with a cooled flaker and solidifying it. To do.

  More specifically, the molten 1,2-diphenoxyethane liquid is supplied to a cooled flaker while keeping the molten liquid at 200 ° C. or lower, preferably 100 ° C. to 150 ° C., more preferably 120 ° C. to 140 ° C. It is then solidified by contact and flakes.

  When the molten 1,2-diphenoxyethane liquid is heated to a temperature higher than 200 ° C., decomposition and sublimation of 1,2-diphenoxyethane occur, and the temperature is maintained at 200 ° C. or lower. It is important that the supply is brought into contact with the flaker cooled in the state.

  As the above-mentioned flaker, a cooled steel belt flaker, a chilled drum flaker, or the like is used, and a molten 1,2-diphenoxyethane liquid is supplied to the surface of the belt or the drum so as to be contact-solidified. It flakes by scraping with an edge.

  The size and thickness of the flakes are 5 cm square or less, preferably 0.5 to 1 cm square, and the thickness is 2 cm in order to prevent dust during handling and facilitate pulverization with a pulverizer. In the following, it is desirable to adjust the rotational speed of the belt and the drum used so as to be preferably 0.1 to 0.5 cm.

  When using the obtained 1,2-diphenoxyethane granules or flakes as a sensitizer for heat-sensitive recording materials, use a grinder such as a ball mill, attritor or sand grinder at the time of use. It can be used after being pulverized and dispersed.

  EXAMPLES Next, although an Example demonstrates this invention concretely, of course, this invention is not limited to these Examples.

[Synthesis of 1,2-diphenoxyethane]
A reactor was charged with 95 g (0.96 mol) of ethylene dichloride, 174 g (1.85 mol) of phenol and 35 ml of water, and 106 g of 49% (by weight) sodium hydroxide aqueous solution was added dropwise over 20 minutes while stirring in a nitrogen gas atmosphere. did. Next, after heating for 3 hours under gentle reflux, 77 g of a 49% aqueous sodium hydroxide solution was added dropwise over 8 hours. Thereafter, the reflux condenser was switched to the outflow condenser with an oil / water separator, the aqueous layer of the condensate was removed from the system, and the oil layer was returned to the reactor to continue the condensation reaction. After 4 hours, the effluent amount was 95 ml, and the temperature in the reactor reached 120 ° C. Thereafter, 185 ml of water was added, and the mixture was stirred at 100 ° C. and allowed to stand, and then the aqueous layer was separated.

[Example 1]
When the obtained oil layer (reacted crude product) was simply distilled under the condition of a vacuum degree of 25 mmHg, when the tower top temperature reached 50 ° C., unreacted low-boiling substances began to distill, Distillation removal was continued. Next, under the distillation conditions with a theoretical plate number of 2 and a degree of vacuum of 5 mmHg and a reflux ratio of 1, the removal of the first fraction was continued until the top temperature reached 150 ° C., and 9 g of the first fraction was removed.

  Next, under the distillation conditions with a theoretical plate number of 3, a vacuum of 4 mmHg, and a reflux ratio of 2, the main distillation was started from 150 ° C., and distilled until reaching 180 ° C., yielding 78.0% (with respect to phenol) ), 174.6 g of 1,2-diphenoxyethane having a purity of 99.2% (by gas chromatography, the same shall apply hereinafter) and a melting point of 97.5 ° C.

[Example 2]
From the oil layer (reaction crude product) obtained by the synthesis method, 9 g of the first fraction was removed under the same distillation conditions as in Example 1. Next, under distillation conditions with a theoretical plate number of 5 and a degree of vacuum of 2 mmHg and a reflux ratio of 3, the main distillation was started from the top temperature of 140 ° C. and distilled until reaching 170 ° C., yield 78% (vs. phenol), 174.6 g of 1,2-diphenoxyethane having a purity of 99.6% (according to gas chromatography, the same shall apply hereinafter) and a melting point of 97.5 ° C. was obtained.

[Example 3]
From the oil layer (reaction crude product) obtained by the synthesis method, 9 g of the first fraction was removed under the same distillation conditions as in Example 1. Next, under the distillation conditions with a theoretical plate number of 2, a vacuum of 15 mmHg and a reflux ratio of 1, the main distillation was started from the top temperature of 180 ° C., and distilled until reaching 230 ° C., yield 77% (vs. phenol), 172.4 g of 1,2-diphenoxyethane having a purity of 98.5% (according to gas chromatography, the same shall apply hereinafter) and a melting point of 97.3 ° C. was obtained.

Analysis of 1,2-diphenoxyethane Gas chromatograph: Shimadzu GC-14B (FID detector)
Column: Inner diameter 3 mm × 1.1 mm Glass column Filler: Silicone OV-17 3% / Uniport HP (60-80 mesh) (manufactured by GL Sciences Inc.)
Column temperature: 70 → 280 ° C. (12 ° C./min temperature increase)
[Example 4]
A disk having a hole diameter of 1 mm while maintaining a state in which a nitrogen pressure of 2.0 kg / cm ² is applied to 1,2-diphenoxyethane in a molten state (120 ° C.) obtained by the purification method described in Example 1. And then dropped for 15 m in air at 10 ° C. to obtain 1,2-diphenoxyethane granules having an average particle diameter of 3 mm. The obtained granule of 1,2-diphenoxyethane did not generate dust during handling, and could be easily pulverized when applied to a pulverizer.

[Example 5]
Contact is made by supplying 1,2-diphenoxyethane in a molten state (120 ° C.) obtained by the purification method described in Example 1 so as to form a thin film on a rotating metal drum flaker cooled to 25 ° C. After solidifying, scraping with a knife edge resulted in 1,2-diphenoxyethane flakes having an average size of 1 cm square and a thickness of 1 mm. The obtained 1,2-diphenoxyethane flakes did not generate dust during handling, and could be easily pulverized when applied to a pulverizer.

[Comparative Example 1]
In the same manner as in Example 1, after removing unreacted low-boiling substances from the oil layer (reacted crude product) by simple distillation, the top temperature was reduced under the distillation conditions of 1 theoretical plate, 5 mmHg vacuum and 1 reflux ratio. The initial distillation was continuously removed until the temperature reached 140 ° C., and 9 g of the initial distillation was removed.

  Subsequently, under the conditions of 1 theoretical plate, 100 mmHg vacuum, and 0 reflux ratio, the main distillation was started from the top temperature of 260 ° C., and distilled until reaching 310 ° C., yield 60% (vs. phenol), 134.3 g of 1,2-diphenoxyethane having a purity of 95% (by gas chromatography, the same shall apply hereinafter) and a melting point of 96 ° C. was obtained. Analysis of 1,2-diphenoxyethane and high-boiling substances remaining after the distillation with a gas chromatograph confirmed that a part of 1,2-diphenoxyethane was decomposed and a part was polymerized. It was.

[Comparative Example 2]
The molten 1,2-diphenoxyethane obtained by the purification method described in Example 1 was subjected to a nitrogen pressure of 6.0 kg / cm ² under a condition of 210 ° C. and passed through a disk having a hole with a diameter of 1 mm at 10 ° C. When 1,2 diphenoxyethane was partially sublimated, it was dropped 15m into the air, but the solidification of the granular material was slow, and the dropped granular material adhered to each other. As a result, re-agglomeration occurred, resulting in a dispersed granular material having a particle diameter of 1 cm or more. This granular material has a particle size that is too large to be used for pulverization with a pulverizer (ball mill, attritor, sand grinder).

[Comparative Example 3]
The molten 1,2-diphenoxyethane obtained by the purification method described in Example 1 was supplied so as to form a thin film on a rotating metal drum flaker cooled to 25 ° C. under a condition of 210 ° C. As a result of flaking, 1,2-diphenoxyethane partially sublimated, and the solidification of the melt was slow, so that it could not be made into a flaky material.

[Comparative Example 4]
To the oil layer (reaction crude product) obtained by the synthesis example, 580 ml of isopropanol was added and dissolved at 85 ° C. to 90 ° C., followed by hot filtration, cooling, crystallization, filtration, washing with isopropanol, and drying, yield 72.8. % (Vs. phenol), purity 99.6%, melting point 97.7 ° C. As a result, 163 g of 1,2-diphenoxyethane was obtained.

  Subsequently, 1,2-diphenoxyethane obtained in Examples 1, 2 and 3, 1,2-diphenoxyethane obtained in Comparative Example 1 and 1,2-diphenoxyethane obtained in Comparative Example 4 Was used to test the quality of the thermal recording material when used as a sensitizer.

(Production of sensitizer dispersion)
(1) 1,2-diphenoxyethane obtained in Examples 1, 2, and 3, 1,2-diphenoxyethane obtained in Comparative Example 1, and 1,2-diphenoxy obtained in Comparative Example 4 Ethane was preliminarily pulverized with a pulverizer (manufactured by Nippon Seiki Seisakusho, ZM1 type) using a wire mesh (wire mesh hole: one side of 1.5 mm).

  Next, sieving was carried out with a sieve (made by IIDASEISAKUSHO, TESTING SIEVE (opening: 0.85 mm)), and the passed powdery sample was used for the next pulverization.

  (2) The pulverization was performed using a three-stage blade type pulverizer (manufactured by Igarashi Machinery Co., Ltd., TSG4H type) under the following conditions.

  In a pot with a jacket of 300 ml capacity, powdered sample 33.4 g, 5% Metroze (manufactured by Shin-Etsu Chemical Co., Ltd., dispersant, 60SH-03), 27.5 g, defoaming agent (manufactured by San Nopco, Nopco 1407) -K, 5% aqueous solution) 0.2g, Perex (manufactured by KAO, dispersing agent, Perex TR) 0.4g and 22.0g of water for dispersion were charged, and the powder composition was well infiltrated into the water for dispersion with a spatula. Then, it was left for 1 hour.

  While charging 200 g of grinding media beads (beads manufactured by AS ONE, product number BZ-1, bead diameter 1 mm) into the above-mentioned pulverizer and circulating water at 20 to 25 ° C. through the pot jacket at a rotation speed of 1000 rpm, Grinding started.

  Sample compositions are collected at any time during the pulverization step, and the particle size is measured over time by a particle size measuring device (Shimadzu SALD-2000J, manufactured by Shimadzu Corporation), and is executed until the average particle size becomes 1 μm. A desired sensitizer dispersion was obtained.

(Manufacture of thermal recording media)
<Adjustment of coating solution for undercoat layer>
Baked kaolin (trade name: Ancilex, manufactured by EC) 80 g, calcium carbonate (trade name: Univers 70), 20 g, polyvinyl alcohol (trade name: PVA-117, 5% aqueous solution, manufactured by Kuraray Co., Ltd.) 140 g Then, 15 g of styrene-butadiene latex (48% emulsion), 2 g of sodium polyacrylate (20% aqueous solution), and 30 g of water were mixed and stirred to obtain an undercoat layer coating solution.

<Adjustment of thermal recording layer coating solution>
(Adjustment of developer dispersion)
30 g of 4-hydroxy-4′-isopropoxy-diphenylsulfone was pulverized in 70 g of a 5% aqueous methylcellulose solution using a sand grinder to prepare an aqueous dispersion of a developer having an average particle size of 1.0 μm.

(Adjustment of dye dispersion)
30 g of 3-N, N-dibutylamino-6-methyl-7-anilinofluorane was pulverized in 70 g of 5% aqueous polyvinyl alcohol (PVA-117) using a sand grinder, and the average particle size was 1 An aqueous dispersion of 0.0 μm dye was prepared.

(Adjustment of sensitizer dispersion)
To 40 g of the sensitizer dispersion, 13.3 g of water was added to prepare a 30% aqueous dispersion.

(Adjustment of pigment dispersion)
30 g of calcium carbonate (Univers 70), 69 g of water, and 1.0 g of 40% sodium hexametaphosphate aqueous solution are stirred for 5 minutes at a rotation speed of 5000 rpm with a homogenizer (manufactured by Tokushu Kika Co., Ltd., TK homodisper type L) to disperse the pigment. The liquid was adjusted.

(Adjustment of thermal recording layer coating solution)
As described above, the developer dispersion 7.2 g, the dye dispersion 3.6 g, the sensitizer dispersion 7.2 g, the pigment dispersion 7.2 g, and zinc stearate 30% as a lubricant dispersion were prepared. 1.8 g of an emulsion (manufactured by Chukyo Yushi Co., Ltd., trade name: Hydrin Z-7) and 21.6 g of polyvinyl alcohol (manufactured by Kuraray Co., Ltd., PVA-117, 5% aqueous solution) are mixed to obtain a coating solution for a thermosensitive recording layer. Obtained.

<Preparation of thermal recording material>
On one surface of woodfree neutral paper 64 g / m ^2, an undercoat layer coating solution and a heat-sensitive recording layer coating liquid, as the coating amount after drying of respectively ^{10g / m 2, 3g / m} 2, sequentially A heat-sensitive recording material was obtained by coating and drying. In addition, after forming the undercoat layer and the heat-sensitive recording layer, it was smoothed by supercalendering.

<Performance comparison test>
The thermal recording paper composed of the 1,2-diphenoxyethane obtained in Examples 1, 2, and 3, Comparative Example 1 and Comparative Example 4 was used as a thermal paper color test device (manufactured by Okura Electric Co., Ltd., TH-PMD). ) Using a thermal head (KYOSERA, TYPE KJT-256-8MGFI-ASH) 1653Ω, a printing test was performed at a printing voltage of 24 V, a printing cycle (heating time) of 0.7 msec, and 1.4 msec. A performance test was conducted. The results are shown in Table 1.

(1) Background and printing density It measured using the Macbeth densitometer (Macbeth company make, RD-948 type | mold).

(2) Moisture resistance test The thermal recording paper after printing was measured with a Macbeth densitometer after being left for 24 hours in an atmosphere of 45 ° C. and 85% humidity. Note that “background” refers to the whiteness of an unprinted portion of the recording paper.

(3) Heat resistance test The fog and print density of the background after being left at a temperature of 60 ° C. for 24 hours were measured with a Macbeth densitometer in the same manner as described above.

  From Table 1, the 1,2-diphenoxyethane obtained in Comparative Example 4 was used as the thermal recording material using 1,2-diphenoxyethane obtained in Examples 1, 2, and 3 of the present invention. As apparent from the comparison with the heat-sensitive recording material, there is no discoloration in the background rash and color development at the initial value, and there is no discoloration in the preservation of the background and the recorded image (printing) in moisture resistance and heat resistance. Further, as is clear from Comparative Example 1, 1,2-diphenoxyethane distilled at a position outside the purification distillation conditions specified in the present invention is the initial value in the performance as a thermal recording paper body. It can be seen that the background rash is conspicuous and the storage stability of the background and the recorded image (printing) is poor in moisture resistance and heat resistance. That is, 1,2-diphenoxyethane obtained by the distillation purification method of the present invention has the excellent properties as a sensitizer possessed by conventional 1,2-diphenoxyethane without any loss. I understand that. Further, the heat-sensitive recording material obtained in Examples 1 and 2 is not inferior to the heat-sensitive recording material obtained in Example 3.

  The 1,2-diphenoxyethane purification method and the solid production method of the present invention can be applied to the purification of 1,2-diphenoxyethane used as a sensitizer for heat-sensitive recording materials. The 1,2-diphenoxyethane obtained by the distillation purification method of the present invention was used as a sensitizer for heat-sensitive recording materials even when compared with 1,2-diphenoxyethane obtained by the recrystallization method. In this case, there is no inferiority in the background rash and color development, and in the preservation of the background and the recorded image (printing) in moisture resistance and heat resistance.

Claims (6)

  1,2-diphenoxyethane reaction crude product is distilled under vacuum at a column top temperature of 250 ° C. or less until impurities are 2.0% or less. Purification method of diphenoxyethane.   When distilling and purifying the 1,2-diphenoxyethane reaction crude product, the distillation conditions are as follows: the number of distillation stages is 2 or more, the degree of vacuum is 5 mmHg or less, the reflux ratio is 1 or more, and the top temperature is 145 ° C to 170 ° C. 2. The method for purifying 1,2-diphenoxyethane according to claim 1, wherein the distillation is performed until the water content becomes 1.0% or less.   For distillation purification of the 1,2-diphenoxyethane reaction crude product, the distillation conditions are as follows: the number of distillation stages is 4 or more, the degree of vacuum is 3 mmHg or less, the reflux ratio is 3 or more, and the top temperature is 135 ° C to 170 ° C. 2. The method for purifying 1,2-diphenoxyethane according to claim 1, wherein the distillation is carried out until the impurities become 0.5% or less.   By cooling 1,2-diphenoxyethane in a molten state obtained by the purification method according to claim 1, 2 or 3, a granular material having an average particle size of 5 mm or less or a size of 5 cm square or less and a thickness of 2 cm or less A process for producing 1,2-diphenoxyethane, characterized in that it is made into a flaky product. The molten 1,2-diphenoxyethane obtained by the purification method according to claim 1, 2 or 3 is passed through a disk having a hole in a nitrogen atmosphere of 5.0 kg / cm ² or less in a molten state of 200 ° C. or less. 5. The 1,2-diene according to claim 4, wherein the melted material is sprayed and cooled while being dropped in a cooled nitrogen or air space to form a granular material having an average particle diameter of 5 mm or less. A method for producing phenoxyethane.   By melting the 1,2-diphenoxyethane in a molten state obtained by the purification method according to claim 1, 2 or 3 in a molten state at 200 ° C. or less, supplying it to a cooling flaker and solidifying it after contact, The method for producing 1,2-diphenoxyethane according to claim 4, wherein the product is a flake.