JP2007161636A - 4-hydroxybutyl acrylate and method for producing purified 4-hydroxybutyl acrylate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide 4-hydroxybutyl acrylate which gives the final objects such as a resin, having a viscosity excellent in workability and no fear of producing a gel substance and capable of obtaining a desired molecular weight distribution, when used as a material. <P>SOLUTION: The 4-hydroxybutyl acrylate has ≤1000 ppm content of a diacrylate form represented by structural formula (1). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to 4-hydroxybutyl acrylate, and specifically relates to 4-hydroxybutyl acrylate suitable as a raw material for various products such as copolymers and photosensitive resin compositions.

  Since 4-hydroxybutyl acrylate (hereinafter abbreviated as “4HBA”) shares a hydrophobic alkyl group and a hydrophilic hydroxyl group in the molecule, it is particularly practically interesting with appropriate flexibility and hydrophilicity. It is useful as a raw material for polymers or copolymers having physical properties. In particular, depending on the length of the alkyl group chain, it exhibits desirable flexibility not found in other acrylates, and the hydroxyl group in the molecule is highly reactive, so that it can be used as a crosslinkable polymer or copolymer as a building material, automobile. It is attracting attention for paint applications. Furthermore, recently, it has attracted attention as a raw material for various photosensitive resin compositions.

  As an industrial production method of 4HBA, direct esterification or transesterification reaction of acrylic acid or acrylic acid ester with an excess amount of 1,4-butanediol with respect to each of these components is known.

  By the way, when it is going to manufacture a coating material and photosensitive resin using said 4HBA as a raw material, malfunctions, such as a deterioration of workability | operativity by a viscosity increase and the production | generation of resin from which molecular weight distribution differs, may arise.

For example, in the case of producing a self-crosslinking resin in which 4HBA is added to a part of the isocyanate group of a vinyl polymerizable substance having two or more isocyanate groups in one molecule (for example, see Patent Document 1), the crosslinking cannot be controlled. However, there is a problem that a resin having the expected physical properties cannot be obtained.
JP-A-4-275319

  The present invention has been made in view of the above circumstances, and its purpose is that when used as a raw material, the resin or the like that is the final target product has a viscosity with excellent workability and is concerned about the formation of a gel-like substance. The object of the present invention is to provide a 4HBA that has no molecular weight and can obtain a desired molecular weight distribution.

  As a result of intensive studies to achieve the above object, the present inventors have obtained the following knowledge.

(1) The generally used 4HBA contains a specific diacrylate as described below. In particular, when 4HBA is produced from acrylic acid or an acrylic ester and 1,4-butanediol, the above diacrylate is used. Body generation is essential.

(2) In the distillation method generally used as a purification method, the boiling point of 4HBA is 230 ° C., the boiling point of diacrylate is 235 to 275 ° C., and the boiling points of both are very close. Is virtually impossible. Further, although a purification method using activated carbon (Japanese Patent Laid-Open No. 8-53392) has been proposed, the effect is small for removing the diacrylate body. In the separation and purification method by extraction, due to the physical properties of diacrylate dissolved in 4HBA, 4HBA with less diacrylate cannot be obtained unless a large excess of solvent is used and extraction is repeated. Under such circumstances, 4HBA currently contains 2000-10000 ppm of diacrylate.

(3) In addition, when a crosslinkable resin composition is produced using 4HBA as a raw material, an operation of adding a diacrylate body to 4HBA is sometimes performed to adjust physical properties. The problem caused by the situation has never been studied.

(4) However, as a result of the study by the present inventors, in the production of the crosslinkable resin composition, the above-mentioned diacrylate body has physical properties due to an increase in viscosity due to an increase in crosslink density and a difference in molecular weight distribution due to a change in polymerization rate. It was found to be the cause of various problems on the work surface. That is, except for special cases, the diacrylate content of 4HBA is desirably as low as possible.

  The present invention has been achieved based on the above findings, and the first gist thereof is characterized in that the content of a diacrylate compound represented by the following structural formula (1) is 1000 ppm or less 4 -In hydroxybutyl acrylate.

  The second gist of the present invention is that acrylic acid or an acrylic ester and 1,4-butanediol are reacted to obtain 4-hydroxybutyl acrylate, and the obtained reaction product is purified by a synthetic adsorbent. The feature resides in a method for producing purified 4-hydroxybutyl acrylate.

  According to the 4HBA of the present invention, it is possible to control crosslinking, and as a result, increase in viscosity can be suppressed, and in the production of a resin using 4HBA as a raw material, a resin having excellent physical properties and workability and having a desired molecular weight distribution can be obtained. I can do it. Moreover, according to the manufacturing method of this invention, the refinement | purification 4-hydroxybutyl acrylate from which the diacrylate body was removed highly is obtained.

  Hereinafter, the present invention will be described in detail. However, the present invention is not limited to the following description, and various modifications can be made within the scope of the gist of the present invention.

  A feature of 4HBA of the present invention is that the content of the diacrylate compound represented by the structural formula (1) is 1000 ppm or less, preferably 500 ppm or less, more preferably 300 ppm or less. If the content of diacrylate exceeds 1000 ppm, the object of the present invention cannot be achieved.

  As above-mentioned, 4HBA obtained by the conventional manufacturing method contains about 2000-10000 ppm diacrylate body. Therefore, the object of the present invention can be achieved by separating such a diacrylate body. However, it is virtually impossible to make the diacrylate body zero by any purification method, and if it is about 1000 ppm as defined in the present invention, the influence can be minimized.

  In addition, the density | concentration of said diacrylate body in this invention says the value measured on condition of the following Table 1 using the gas chromatography method.

  In the present invention, as a method for producing 4HBA, direct esterification or transesterification reaction using acrylic acid or acrylic ester and 1,4-butanediol is preferably used. In this method, an excess of 1,4-butanediol is used. And although it is possible to reduce the production amount of diacrylate by selection of reaction conditions, it is impossible to make the content of the diacrylate body required by the present invention. For example, according to the results of experiments by the present inventors, when 0.9 mol of methyl acrylate and 1.0 mol of 1,4-butanediol are used, the diacrylate form is 0 with respect to 0.5 mol of 4HBA as the target product. .2 mol is formed.

  Further, for example, in Japanese Patent Application Laid-Open No. 2003-155263, 4HBA obtained by the above method is used as a raw material, and 4HBA purified by an extraction purification method and extraction / distillation purification is obtained. And content of the diacrylate body is reduced to 2000-10000 ppm with respect to 4HBA. However, 4HBA having a diacrylate content of 2000 ppm cannot achieve the object of the present invention.

  In the present invention, 4HBA having a diacrylate content of 1000 ppm or less is obtained by employing a purification method different from the conventional one.

  By the way, as a purification method, it is an extraction method described in the above-mentioned document, and in order to remove a diacrylate body, a method of employing a continuous extraction tower having a further theoretical plate is conceivable. Furthermore, the purification efficiency can be slightly improved by greatly reducing the concentration of the charged raw materials. According to the study by the present inventors, it can be reduced to 1000 to 2000 ppm. However, the content of the diacrylate body required by the present invention is not always sufficient. Moreover, these operations may result in an increase in cost.

  In this invention, there is no problem of the said cost increase, and the following methods are recommended as a method of reducing a diacrylate body.

  For example, as a method for reducing the diacrylate content by an extraction method, crude 4HBA produced by a conventional method is dissolved in water and extracted with an aliphatic hydrocarbon (preferably n-hexane, n-heptane, etc.). To do. Extraction may be either batch type or continuous type. The extraction temperature is preferably in the range of 30-50 ° C. When the extraction temperature is less than 30 ° C., the extraction efficiency is poor and the expected result cannot be obtained, and if it is attempted to obtain, the number of extractions is increased, and the recovery rate of 4HBA is greatly deteriorated. On the other hand, when the extraction temperature exceeds 50 ° C., the operation becomes difficult due to the boiling point of the extraction solvent, which is not preferable. Usually, 1 to 5 L of water is used for 1 L of crude 4HBA, and extraction is performed using 0.1 to 0.5 L of aliphatic hydrocarbon. When the amount of water is too small, there is a lot of loss in hexane, and when it is too large, the concentration is lowered and there is a problem in extraction efficiency. The amount of aliphatic hydrocarbon relative to the amount of water is preferably about 0.01 to 0.1 times the amount. The number of extractions is usually 1 to 5 times. It can be reduced to the target content by extraction about twice. Distillation of water to recover 4HBA from the aqueous phase is not preferable from the viewpoint of energy cost. Therefore, salting out with salts such as salt, back extraction with toluene, and toluene distillation are preferred.

  Further, as another method for reducing the diacrylate body, a method for purifying 4HBA using a synthetic adsorbent can be mentioned. For purification with a synthetic adsorbent, a batch type or a flow type is generally employed. As the synthetic adsorbent, a styrene-divinylbenzene-based, aromatic porous resin, a synthetic adsorbent into which a hydrophobic substituent is introduced, or the like is used. For example, aromatic HP series (HP10, HP20, etc.) and aromatic SP series (SP800, SP850, etc.) manufactured by Mitsubishi Chemical Corporation can be exemplified.

  An example of the batch processing method is as follows. First, the synthetic adsorbent is taken in a beaker or the like and washed with a solvent. As the solvent, alcohol such as methanol and ethanol, water and the like can be used, and methanol is preferred. The amount of the cleaning solvent is preferably 1 to 4 times the amount of the synthetic adsorbent capacity, and it is effective not to wash at once but to wash several times. At this time, since the synthetic adsorbent may bring in bubbles, it is preferable to remove the bubbles with an ultrasonic cleaner or the like.

  After the washing is completed, the synthetic adsorbent is transferred to a flask or the like, and a diacrylate body or the like is adsorbed. Although the usage-amount of a synthetic adsorbent can be selected arbitrarily, it is 0.01-10 times amount normally with respect to 4HBA to process, Preferably it is 0.05-5 times amount. Processing temperature is 20-40 degreeC normally. The adsorption time is usually 0.1 to 10 hours. Further, it is preferable in view of the adsorption effect that excess solvent is removed by decantation as much as possible. Further, after the treatment, if necessary, the solvent is distilled off.

  The adsorbed synthetic adsorbent can be regenerated. Regeneration is possible with an alcohol such as methanol, and the adsorbing power is restored to the initial level by washing with 1 to 10 times the amount of methanol with respect to the synthetic adsorbent. The diacrylate content of 4HBA obtained by this purification method is usually 1000 ppm or less.

  4HBA of the present invention with a reduced diacrylate content is superior in workability when used in photosensitive resins and paints used in the information technology field, compared to the case of using normal products that are not purified. In addition, a resin having uniform physical properties can be obtained.

  EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited to a following example, unless the summary is exceeded. In the following description, “%” means mass%.

<Production of crude 4HBA>
(Transesterification reaction)
A rectification tower, temperature measurement tube, air introduction tube, and catalyst introduction tube were attached to the reactor, and the rectification column was filled with 1/4 (inch) McMahon-type packing material at a height of 60 cm. Using a reactive distillation apparatus, the components shown in Table 2 below were charged, n-hexane was added, and the ester exchange reaction was carried out while distilling off methanol produced by reactive distillation together with hexane.

(Extraction purification)
Using 8.08 kg of the reaction solution obtained above as a raw material, liquid-liquid extraction was performed in a continuous extraction tower using 12.15 kg of n-hexane and 11.5 kg of pure water, and diacrylate was added to the hexane layer. 4HBA and unreacted 1,4 butanediol were recovered. From the obtained aqueous layer, unreacted 1,4 butanediol was separated into an aqueous layer and 4HBA was separated into a toluene layer by continuous extraction tower using toluene. Toluene was distilled off under reduced pressure to recover 4HBA. The composition of 4HBA was as shown in Table 3 below.

Example 1:
Into a 5 L reactor equipped with a thermometer, a cooling device, and a stirring device, 1 L of the above composition solution was charged, 3 L of water was added, and the mixture was stirred and dissolved while heating at 40 ° C. Here, 0.3 L of n-hexane was added and stirred for 30 minutes. Then, stirring was stopped and it left still and isolate | separated for 1 hour. An aqueous layer was extracted from the bottom of the reactor. After repeating the above operation twice, about 200 g of sodium chloride was added to the aqueous layer, and extraction was performed 3 times with 3 L of toluene at room temperature to extract 4HBA. The composition after distillation under reduced pressure in toluene was as shown in Table 4 below. The recovery rate of 4HBA was 94.8%.

Example 2:
First, 100 ml of synthetic adsorbent (“Separbeads SP850” manufactured by Mitsubishi Chemical Corporation) was placed in a 300 ml beaker, 200 ml of methanol was added, and the mixture was washed with gentle stirring for 5 minutes. This operation was repeated twice to complete the cleaning of the synthetic adsorbent.

  Next, it was introduced together with methanol from the upper part of the 30 mm diameter column while paying attention to air bubbles. The height of the synthetic adsorbent was 148 mm. Unnecessary methanol was removed. And 4HBA was distribute | circulated from the column upper part by 100 g (1v) liquid flow rate of 30 g / h (cavity speed SV = 0.31). Methanol was removed from the resulting methanol solution. The composition of 4HBA before and after purification was as shown in Table 5 below.

Example 3:
In Example 2, the same operation as in Example 2 was performed except that the cavity speed SV was set to 0.15. As a result, purified 4HBA having the composition shown in Table 6 below was obtained.

Example 4:
Methanol was passed through the synthetic adsorbent used in Example 2 at a cavity velocity (SV = 1) to regenerate the synthetic adsorbent. Then, the same operation as in Example 2 was performed using the regenerated synthetic adsorbent. For 4HBA, the cavity velocity SV was 0.31. As a result, purified 4HBA having the composition shown in Table 7 below was obtained. The same adsorption effect as that of a new product was confirmed by regeneration.

Reference example 1:
In a 1 L separable flask equipped with a water-cooled tube and a gas inlet, 315.0 g of methyl ethyl ketone, 35.0 g of isopropyl alcohol, 75.0 g of methyl methacrylate, 60.0 g of n-butyl acrylate, and 800 ppm of 4-hydroxy containing diacrylate 15.0 g of butyl acrylate (4HBA) was charged, the liquid temperature was kept at 70 ° C., and nitrogen was passed. 1.5 g of azobisisobutyronitrile (AIBN) was added to initiate polymerization, and 1.5 g of AIBN was added twice every 1 hour, polymerized for 6 hours, solid content 30%, viscosity 2000 mP · s / An acrylic copolymer solution at 25 ° C. was obtained. This is suitably used as a coating agent raw material.

Comparative Reference Example 1:
In Reference Example 1, an acrylic monomer was polymerized in the same manner as Reference Example 1 except that 4HBA containing 2000 ppm of diacrylate was used. The viscosity of the copolymer solution was as high as 18000 mP · s / 25 ° C. and was unsuitable as a coating agent raw material.

Comparative Reference Example 2:
In Reference Example 1, an acrylic monomer was polymerized in the same manner as in Reference Example 1 except that 4HBA containing 5000 ppm of diacrylate was used. About 1 hour after the completion of AIBN addition, the reaction solution markedly increased in viscosity and became a gel.

Claims (5)

Content of the diacrylate body shown by the following structural formula (1) is 1000 ppm or less, 4-hydroxybutyl acrylate characterized by the above-mentioned.

  The 4-hydroxybutyl acrylate according to claim 1, which is obtained by purifying a reaction product of acrylic acid or an acrylic ester and 1,4-butanediol.   The 4-hydroxybutyl acrylate according to claim 2, wherein the purification of the reaction product is performed by dissolving the reaction product in water and then extracting with an organic solvent.   The 4-hydroxybutyl acrylate according to claim 2, wherein the reaction product is purified by using a synthetic adsorbent.   A 4-hydroxybutyl acrylate is obtained by reacting acrylic acid or an acrylic ester with 1,4-butanediol to obtain 4-hydroxybutyl acrylate, and purifying the obtained reaction product with a synthetic adsorbent. Production method.