JP2008137972A - Method for purifying phenyl (meth)acrylate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for obtaining purified phenyl (meth)acrylate containing less phenol by removing the phenol from the phenyl (meth)acrylate containing the phenol, in good efficiency. <P>SOLUTION: This method for purifying the phenyl (meth)acrylate is provided by crystallizing the crude phenyl (meth)acrylate containing ≤30 mass% phenol, and obtaining the precipitated crystal of the phenyl (meth)acrylate. It is preferable to present at least one compound selected from the group consisting of benzene, toluene, xylene, cumene, ethylbenzene, hexane, octane, decane, methacrylic acid and acrylic acid in the crude phenyl (meth)acrylate on crystallizing the same. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for purifying phenyl (meth) acrylate which is a kind of phenyl group-containing monomer and is useful as a raw material for a homopolymer or copolymer having a high glass transition temperature and refractive index.

  Phenyl (meth) acrylate is unstable compared to other (meth) acrylic acid esters. Therefore, it is generally synthesized by a reaction between expensive (meth) acrylic acid chloride or (meth) acrylic anhydride and phenol (Non-patent Document 1). Moreover, as a method of synthesizing phenyl (meth) acrylate by esterification reaction of free (meth) acrylic acid and phenol, for example, trifluoroacetic anhydride (Non-patent Document 2) or trifluoromethanesulfonic acid as a catalyst. A method using an anhydride (Non-Patent Document 3), a method using dicyclohexylcarbodiimide or the like as a condensing agent (Non-Patent Document 4), and a method using polyphosphoric acid as a dehydrating agent (Non-Patent Document 5) are known. Furthermore, as a method for synthesizing phenyl (meth) acrylate by dehydration esterification reaction of (meth) acrylic acid and phenol, the reaction is performed at 110 ° C. or higher in a solvent such as xylene using sulfuric acid or a sulfuric acid / boric acid mixture. A method (Patent Document 1) is also known.

  In the above synthesis method, the conversion rate of the raw material is not necessarily 100%. Therefore, when producing (meth) acrylic acid phenyl on an industrial scale, the product (phenyl) (meth) acrylate is obtained from the reaction product. In many cases, an unreacted (meth) acrylic acid and / or phenol and solvent are separated by providing a purification step. At that time, since phenyl (meth) acrylate is liquid at room temperature, a method of distillation under reduced pressure is employed in the purification step. However, since phenol and phenyl (meth) acrylate are azeotroped, phenyl (meth) acrylate obtained by ordinary distillation means still contains a trace amount of phenol. There was a problem that a high-stage purification tower was required and the cost increased.

On the other hand, as a method for separating phenol in phenyl (meth) acrylate, the reaction solution is diluted with a large amount of a low-polar hydrocarbon solvent such as hexane or octane and then washed with an alkaline aqueous solution or the like ( Patent document 2) is known.
J. et al. Chem. Soc. , 1931, 2495 J. et al. Chem. Soc. , 1949, 2976 J. et al. Chem. Soc. , 1957, 4069 Tetrahedron, 1965, 21, 3531 J. et al. Am. Chem. Soc. , 75, 5416 (1953) JP 60-258144 A JP-A 63-77841

  However, the method of Patent Document 2 is low in productivity because the (meth) acrylic acid phenyl reaction solution is diluted with a large amount of solvent, and chemically unstable phenyl (meth) acrylate is hydrolyzed by alkali. There was a problem that the yield was low.

  Accordingly, an object of the present invention is to provide a method capable of efficiently removing phenol from phenyl (meth) acrylate containing phenol and obtaining purified phenyl (meth) acrylate with less phenol.

  The present invention is a method for purifying phenyl (meth) acrylate that crystallizes crude phenyl (meth) acrylate containing 30% by mass or less of phenol and obtains precipitated crystals of phenyl (meth) acrylate.

  In the present invention, at least one compound selected from the group consisting of benzene, toluene, xylene, cumene, ethylbenzene, hexane, octane, decane, methacrylic acid and acrylic acid is present in the crude phenyl (meth) acrylate. It is preferable to conduct analysis. In that case, it is preferable that the density | concentration of the said compound in crude phenyl (meth) acrylate is 0.1-30 mass%.

  In the present invention, it is preferable to perform crystallization by adding one or more compounds to the crude phenyl (meth) acrylate and setting the concentration of the compound to 0.1 to 30% by mass. More preferably, the freezing point of the crude phenyl (meth) acrylate is lowered by −10 to 10 ° C. by addition. The compound to be added is preferably at least one compound selected from the group consisting of benzene, toluene, xylene, cumene, ethylbenzene, hexane, octane, decane, methacrylic acid and acrylic acid.

  The crude phenyl (meth) acrylate to be purified in the present invention is phenyl (meth) acrylate containing 30% by mass or less of phenol. The crude phenyl (meth) acrylate may contain other raw materials used in the synthesis reaction, solvents such as a dehydrating solvent, additives such as a polymerization inhibitor, and the like.

  Phenyl (meth) acrylate containing more than 30% by mass of phenol has a higher freezing point of phenol than phenyl (meth) acrylate, so when crystallized, it precedes the crystals of phenyl (meth) acrylate. Since the crystal | crystallization of a phenol may precipitate, it is not preferable. However, even if the amount of phenol exceeds 30% by mass, the amount of phenol can be reduced to 30% by mass or less in advance to be a purification target of the present invention. The method for reducing the amount of phenol in advance to 30% by mass or less is not particularly limited, and various purification means including distillation and crystallization can be employed.

  Crude (meth) acrylate phenyl, for example, esterification method of phenol and (meth) acrylic acid using an acid catalyst, esterification method of phenol and (meth) acrylic anhydride, phenol and (meth) acrylic acid Examples include those produced by various production methods such as esterification with chloride, esterification of phenol and (meth) acrylic acid using a dehydrating agent such as dicyclohexylcarbodiimide, and transesterification of methyl methacrylate with diphenyl carbonate. The manufacturing method is not particularly limited.

  In the present invention, crude phenyl (meth) acrylate is crystallized to obtain precipitated phenyl (meth) acrylate crystals. In that case, for example, a known apparatus described in “Chemical Engineering Handbook, Revised 5th Edition (1988)” can be used. The crystallization operation may be either a batch method or a continuous method. Purified phenyl (meth) acrylate is obtained by separating crystals of phenyl (meth) acrylate precipitated by crystallization operation from the mother liquor. The method for separating the crystal and the mother liquor is not particularly limited as long as it is a method that can separate the solid and the liquid. For example, a solid-liquid separation method such as a filtration method, a centrifugal separation method, or a decantation is used. Can do. A specific example of an apparatus for performing such separation includes a Kureha continuous crystal purification apparatus (KCP manufactured by Kureha Engineering Co., Ltd.). The separation operation may be either a batch method or a continuous method.

  In the method of the present invention, at least one compound selected from the group consisting of benzene, toluene, xylene, cumene, ethylbenzene, hexane, octane, decane, methacrylic acid and acrylic acid in crude phenyl (meth) acrylate (hereinafter, It is preferable to perform crystallization in the presence of the second component). The concentration of the compound present in the crude phenyl (meth) acrylate is preferably 0.1 to 30% by mass, and more preferably 0.5 to 20% by mass.

  In the method of the present invention, one or more compounds (hereinafter also referred to as a second component) are added to crude phenyl (meth) acrylate, and the concentration of the second component is preferably 0.1 to 30% by mass. More preferably, the crystallization may be carried out at 0.5 to 20% by mass.

  The higher the concentration of the second component, the lower the concentration of phenol contained in the crystals of phenyl (meth) acrylate obtained. The lower the concentration of the second component, the higher the recovery rate of phenyl (meth) acrylate crystals.

  The second component to be added is not particularly limited as long as it is an organic compound or an inorganic compound that hardly forms a solid solution with phenyl (meth) acrylate during crystallization. Examples of such a second component include benzene, chlorobenzene, naphthalene, toluene, xylene, cumene, ethylbenzene, hexane, octane, decane, chloroform, and cyclohexane. The compound which can be used as raw materials of esterification reaction, such as an acid and acrylic acid, is mentioned.

  The present invention can be applied to purification of crude phenyl (meth) acrylate obtained by, for example, an esterification method using phenol and (meth) acrylic acid. By leaving the reaction solvent used in the esterification step in the crude phenyl (meth) acrylate, it can be a second component that is present during the crystallization of the present invention. In the present invention, most of the second component present or added during crystallization is finally contained in the mother liquor. The mother liquor containing the reaction solvent can be used effectively by returning to the esterification step. For these reasons, when the present invention is carried out in combination with the esterification method, the second component includes benzene, toluene, xylene, cumene, ethylbenzene, hexane, octane, decane suitable as a reaction solvent for esterification. Is preferred.

  Further, the present invention can be applied to purification of crude phenyl (meth) acrylate obtained through a production process for synthesizing phenyl acrylate using (meth) acrylic acid as a raw material, for example. By leaving the raw material (meth) acrylic acid in the crude phenyl (meth) acrylate, the second component to be present during the crystallization of the present invention can be obtained. In the present invention, most of the second component present or added during crystallization is finally contained in the mother liquor. The mother liquor containing (meth) acrylic acid, which is a raw material for the synthesis reaction of this phenyl (meth) acrylate, can be used effectively by returning to the process for producing phenyl (meth) acrylate. For this reason, when the present invention is carried out together with a reaction for synthesizing phenyl (meth) acrylate using (meth) acrylic acid as a raw material, (meth) acrylic acid is preferred as the second component.

  From the above, the second component is preferably at least one compound selected from the group consisting of benzene, toluene, xylene, cumene, ethylbenzene, hexane, octane, decane, methacrylic acid and acrylic acid. As the second component, these substances can be used alone, or two or more kinds can be mixed and used.

  In crystallization, it is preferable that the seed crystal is present in the crude phenyl (meth) acrylate, for example, by adding a seed crystal to the cooled crude phenyl (meth) acrylate. The seed crystal is not particularly limited as long as it is a small crystal for inducing crystallization, but a small crystal of purified phenyl (meth) acrylate is preferable because it does not cause contamination by impurities.

  The crystal of phenyl (meth) acrylate obtained by carrying out the present invention may be further subjected to a washing treatment. By washing, the content of phenol and the second component can be further reduced. For example, toluene or the like can be used as the cleaning solvent. The temperature of the cleaning solvent is preferably about the same as or lower than that of the crystal.

  The crude phenyl (meth) acrylate, which is the purification target of the present invention, may be colored by impurities in the raw materials used for the synthesis reaction or by-products generated during the synthesis reaction. When phenyl (meth) acrylate is used as a polymer raw material for optical applications, it is preferable that the pigment is less colored, but such colored crude phenyl (meth) acrylate is purified by the method of the present invention. In some cases, impurities that cause coloring may not be sufficiently removed. In addition, other impurities (excluding phenol) may not be sufficiently removed by the method of the present invention. In such a case, it is preferable to purify crude phenyl (meth) acrylate obtained by further distilling an organic solvent and a part of the raw material from the reaction solution by simple distillation in advance by the method of the present invention. .

  In the present specification, “phenyl (meth) acrylate” means phenyl methacrylate and / or phenyl acrylate, and “(meth) acrylic acid” means methacrylic acid and / or acrylic acid.

  The present invention will be described in more detail below with reference to examples and comparative examples, but these examples do not limit the scope of the present invention.

  The content of phenol, methacrylic acid, xylene, toluene and hexane in the phenyl methacrylate crystals was measured by GLC analysis of the crystals dissolved. In addition, the content rate of 0 mass% means that it was below the detection limit.

  Further, purified phenyl methacrylate crystals were used as seed crystals to be added during crystallization.

<Example 1>
20 parts of crude phenyl methacrylate containing 5% by weight of phenol and 0.2% by weight of methacrylic acid was placed in a sample bottle and cooled to 5 ° C. Next, a small amount of seed crystal was added to the sample bottle, and the crystal was precipitated by leaving it at 5 ° C. for 2 hours, and the mother liquor was separated by decantation to obtain 13.9 parts of phenyl methacrylate crystal. The contents of phenol and methacrylic acid in the obtained crystals were 2.3% by mass and 0% by mass, respectively.

<Example 2>
150 parts of crude phenyl methacrylate containing 5% by mass of phenol and not containing methacrylic acid was placed in an Erlenmeyer flask and cooled to 5 ° C. Next, a small amount of seed crystal was added to the Erlenmeyer flask, and the crystal was precipitated by leaving it at 5 ° C. for 2 hours, and the mother liquor was separated by decantation to obtain 122.5 parts of phenyl methacrylate crystal. The contents of phenol and methacrylic acid in the obtained crystals were 1.6% by mass and 0% by mass, respectively.

  The obtained crystals are dissolved, cooled again to 5 ° C. in an Erlenmeyer flask, a small amount of seed crystals are added, and left at 5 ° C. for 3 hours to precipitate crystals, and the mother liquor is separated by decantation and methacrylic. Crystals of phenyl acid were obtained. The contents of phenol and methacrylic acid in the obtained crystals were 1.1% by mass and 0% by mass, respectively.

<Comparative Example 1>
150 parts of crude phenyl methacrylate containing 32% by mass of phenol and not containing methacrylic acid was placed in an Erlenmeyer flask and cooled to -20 ° C. Next, a small amount of seed crystal was added to the Erlenmeyer flask and left at −20 ° C. for 2 hours, but phenyl methacrylate crystals did not precipitate.

<Example 3>
After adding 0.1 part of xylene to 20 parts of crude phenyl methacrylate containing 5% by mass of phenol and not containing methacrylic acid, the mixture was stirred well, then placed in a sample bottle and cooled to 5 ° C. Next, a small amount of seed crystal was added to the sample bottle, and the crystal was precipitated by leaving it at 5 ° C. for 2 hours. The mother liquor was separated by decantation to obtain 10.4 parts of phenyl methacrylate crystal. The contents of phenol, methacrylic acid, and xylene in the obtained crystal were 2.1 mass%, 0 mass%, and 0.2 mass%, respectively.

<Example 4>
After adding 0.1 part of xylene to 20 parts of crude phenyl methacrylate containing 5% by mass of phenol and not containing methacrylic acid, the mixture was stirred well, then placed in a sample bottle and cooled to 5 ° C. Next, a small amount of seed crystal was added to the sample bottle, and the crystal was precipitated by leaving it at 5 ° C. for 3 hours, and the mother liquor was separated by decantation to obtain phenyl methacrylate crystals. The obtained crystals were washed with toluene at 2 ° C. to obtain 8 parts of washed crystals. The contents of phenol, methacrylic acid, and xylene in the obtained washed crystals were 0.8% by mass, 0% by mass, and 0.1% by mass, respectively.

<Example 5>
20 parts of crude phenyl methacrylate containing 2.5% by weight of phenol and 5% by weight of methacrylic acid was placed in a sample bottle and cooled to 5 ° C. Next, a small amount of seed crystal was added to the sample bottle, and the crystal was precipitated by leaving it at 5 ° C. for 2 hours, and the mother liquor was separated by decantation to obtain 14.8 parts of phenyl methacrylate crystals. The contents of phenol and methacrylic acid in the obtained crystals were 1.1% by mass and 1.8% by mass, respectively.

<Example 6>
20 parts of crude phenyl methacrylate containing 2.5% by mass of phenol, 5% by mass of methacrylic acid, and 5% by mass of toluene was placed in a sample bottle and cooled to 0 ° C. Next, a small amount of seed crystal was added to the sample bottle, and the crystal was precipitated by leaving it at 0 ° C. for 2 hours. The mother liquor was separated by decantation to obtain 9.4 parts of phenyl methacrylate crystals. The contents of phenol, methacrylic acid, and toluene in the obtained crystal were 0.5% by mass, 0% by mass, and 2.4% by mass, respectively.

<Example 7>
20 parts of crude phenyl methacrylate containing 5% by mass of phenol, 5% by mass of methacrylic acid, and 10% by mass of hexane was placed in a sample bottle and cooled to -5 ° C. Next, a small amount of seed crystal was added to the sample bottle, and the crystal was precipitated by leaving it at −5 ° C. for 2 hours, and the mother liquor was separated by decantation to obtain 10.8 parts of phenyl methacrylate crystal. The contents of phenol, methacrylic acid and hexane in the obtained crystals were 0.9% by mass, 0.5% by mass and 2% by mass, respectively.

<Example 8>
20 parts of crude phenyl methacrylate containing 2.5% by weight of phenol, 5% by weight of methacrylic acid and 20% by weight of hexane was placed in a sample bottle and cooled to -5 ° C. Next, a small amount of seed crystal was added to the sample bottle, and the crystal was precipitated by leaving it at −5 ° C. for 2 hours, and the mother liquor was separated by decantation to obtain 9.0 parts of phenyl methacrylate crystal. The contents of phenol, methacrylic acid, and hexane in the obtained crystals were 0.7% by mass, 0.2% by mass, and 3.4% by mass, respectively.

Claims (6)

  A method for purifying phenyl (meth) acrylate, which crystallizes crude phenyl (meth) acrylate containing 30% by mass or less of phenol and obtains precipitated crystals of phenyl (meth) acrylate.   Crystallization of crude phenyl (meth) acrylate in the presence of at least one compound selected from the group consisting of benzene, toluene, xylene, cumene, ethylbenzene, hexane, octane, decane, methacrylic acid and acrylic acid. The method of claim 1 wherein:   The method according to claim 2, wherein the concentration of the compound present in the crude phenyl (meth) acrylate is 0.1 to 30% by mass.   The method according to claim 1, wherein the crystallization is performed by adding one or more compounds to the crude phenyl (meth) acrylate so that the concentration of the compound is 0.1 to 30% by mass.   The method according to claim 4, wherein the freezing point of crude phenyl (meth) acrylate is lowered by -10 to 10 ° C by addition of the compound.   The method according to claim 4 or 5, wherein the compound to be added is at least one compound selected from the group consisting of benzene, toluene, xylene, cumene, ethylbenzene, hexane, octane, decane, methacrylic acid and acrylic acid.