JP2004027160A - Method for producing methylene-crosslinked polyphenylene polyisocyanate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for the production of a methylene-crosslinked polyphenylene polyisocyanate to efficiently and effectively decrease the hydrolyzable chlorine content and acid content. <P>SOLUTION: The method for the production of a methylene-crosslinked polyphenylene polyisocyanate comprises the condensation of aniline with formaldehyde in the presence of an acid catalyst and the phosgenization of the produced methylene-crosslinked polyphenylene polyamine. In the production of a crude product by reacting the methylene-crosslinked polyphenylene polyamine with phosgene in an organic solvent, hydrogen chloride gas is blown into the solution of the obtained crude product and an inert gas is blown into the system under heating to decrease the hydrolyzable chlorine content and the acid content in the crude product. The contents of hydrolyzable chlorine and acid in the methylene-crosslinked polyphenylene polyisocyanate can be decreased in high efficiency with a smaller amount of hydrogen chloride gas than conventional processes. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing a methylene-crosslinked polyphenylene polyisocyanate. More specifically, the present invention relates to a method for producing a methylene-crosslinked polyphenylene polyisocyanate having reduced hydrolyzable chlorine content and acid content.
[0002]
[Technical Background of the Invention]
Methylene cross-linked polyphenylene polyisocyanate is an extremely reactive substance and is used in a wide range of production of polyurethane foams, elastomers, adhesives and paints.
As a method for producing such a methylene-crosslinked polyphenylene polyisocyanate, methylene-crosslinked polyphenylene is obtained by phosgenation of a methylene-crosslinked polyphenylenepolyamine (hereinafter abbreviated as polyMDA) produced by condensing aniline and formaldehyde in the presence of an acid catalyst. A method for producing polyisocyanate (hereinafter abbreviated as polyMDI) is well known.
[0003]
However, in the case of producing poly-MDI through phosgenation of poly-MDA, the production of hydrolyzable chlorine (hereinafter abbreviated as HC) and acid cannot be avoided, and impurities such as these are present. It is known that when the amount is too large, the reactivity at the time of urethane production deteriorates.
Numerous patent applications have been filed as a method for reducing the HC content and the acid content, including a method of treating polyMDI with an organometallic compound at a high temperature, and a method involving simultaneous use of a part of diphenylmethane diisocyanate in polyMDI. There is known a method of extracting by distillation. However, the method using an organometallic compound has a problem that a metal component remains in poly MDI or that tarification by heat is promoted. In addition, the method of extracting by distillation also involves extracting diphenylmethane diisocyanate with an HC content or the like. There is a problem that secondary treatment is necessary because the acid content is high, and none of these methods can be said to be industrially satisfactory.
[0004]
Japanese Patent Application Laid-Open No. 6-234724 discloses a method in which hydrogen chloride gas is blown into a reaction solution containing polyMDI under heating conditions to reduce HC content and acid content. However, in this method, the amount of hydrogen chloride gas used is large, and it has been desired to reduce the amount of gas and reduce equipment and cost related to gas supply and exhaust gas treatment.
In view of the above circumstances, the present inventors have intensively studied a method for efficiently and effectively reducing a hydrolyzable chlorine content and an acid content in a method for producing a methylene-crosslinked polyphenylene polyisocyanate. By combining the subsequent step of blowing hydrogen chloride gas into the crude product solution containing poly-MDI and the step of blowing nitrogen gas under heating conditions, hydrolyzable chlorine and acid are added under industrially advantageous conditions. The present inventors have found that it is possible to efficiently reduce the amount, and have completed the present invention.
[0005]
[Object of the invention]
An object of the present invention is to provide a method for producing a methylene-crosslinked polyphenylene polyisocyanate, which efficiently and effectively reduces hydrolyzable chlorine and acid.
[0006]
Summary of the Invention
The method for producing a methylene-crosslinked polyphenylene polyisocyanate according to the present invention is a method for producing a methylene-crosslinked polyphenylene polyisocyanate by phosgenation of a methylene-crosslinked polyphenylene polyamine produced by condensing aniline and formaldehyde in the presence of an acid catalyst,
In producing the crude product by reacting the methylene-crosslinked polyphenylene polyamine with phosgene in an organic solvent, hydrogen chloride gas is blown into the obtained crude product solution, and then an inert gas is blown under heating conditions. , Characterized in that the hydrolyzable chlorine content and acid content in the crude product are reduced.
[0007]
Here, the hydrolyzable chlorine component means a compound that hydrolyzes at a water boiling point to release hydrochloric acid, and its value is shown as chlorine. The acid content refers to an acid component released by reacting with an alcohol at room temperature, and indicates the value as hydrochloric acid. Therefore, the acid content is included in the hydrolyzable chlorine content.
In the present invention, the hydrogen chloride gas is preferably supplied in an amount of 0.5 to 3 parts by weight based on 100 parts by weight of the crude product solution.
[0008]
In the present invention, the inert gas is preferably supplied in an amount of 0.1 to 6 parts by weight based on 100 parts by weight of the crude product.
In the method for producing a methylene-crosslinked polyphenylene polyisocyanate according to the present invention, it is preferable to blow an inert gas under a heating condition of 180 ° C to 240 ° C.
[0009]
In the present invention, the inert gas is preferably a nitrogen gas.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described specifically.
Poly MDA used in the phosgenation reaction is a methylene-bridged polyphenylene polyamine formed by the condensation of aniline and formaldehyde in the presence of an acid catalyst such as hydrochloric acid. Although the composition of the poly MDA varies depending on the ratio of aniline / formaldehyde / acid catalyst and the condensation reaction temperature during the condensation reaction, poly MDA having any composition can be used as a raw material of the present invention.
[0011]
As the organic solvent used in the phosgenation of poly-MDA, any organic solvent may be used as long as it is an inert solvent generally used in the production of organic isocyanates, for example, aromatic hydrocarbons such as toluene and xylene. And halogenated aromatic hydrocarbons such as chlorotoluene, chlorobenzene and dichlorobenzene, esters such as butyl acetate and amyl acetate, and ketones such as methyl isobutyl ketone. The amount of the organic solvent used is not uniform because the solubility of the raw material poly MDA varies depending on the type of the organic solvent used, but it is appropriately selected within a range where the concentration of the poly MDA is approximately 1% by weight to 50% by weight. Can be used.
[0012]
The method of phosgenation is not particularly limited as long as it is a generally known method irrespective of a continuous method or a batch method. Examples thereof include a hydrochloride method, a two-stage cold / hot method, a pressurized phosgene method, and a liquefied phosgene method. Any method can be applied, including the method.
After the completion of the phosgenation reaction, residual phosgene is removed as necessary. As a method for removal, a common method such as a method of charging an inert gas such as nitrogen, helium, or argon at a temperature of 160 ° C. or less, preferably 140 ° C. or less, or a method of heating to the boiling point of a solvent under reduced pressure is used. Method can be appropriately selected and used.
[0013]
After removing residual phosgene as needed, a treatment step of blowing hydrogen chloride gas into the crude product solution containing poly-MDI is performed. By this hydrogen chloride gas blowing step, the phosgene adduct, which is a by-product impurity in the phosgenation present in the crude product solution, is converted into a hydrochloric acid adduct and decomposed.
At this time, the hydrogen chloride gas is usually 0.5 to 3 parts by weight, preferably 0.5 to 0.98 parts by weight, more preferably 0.6 to 0.95 parts by weight with respect to 100 parts by weight of the crude product solution. The composition is supplied to the biological solution in an amount in the range of parts. As described above, in the present invention, by combining the blowing of the hydrogen chloride gas and the blowing of the inert gas under the heating conditions described later, the amount of the hydrogen chloride gas used can be reduced as compared with the related art.
[0014]
The effect of the treatment with the hydrogen chloride gas increases as the concentration of hydrogen chloride in the solution increases and as the temperature increases. In order to increase the concentration of hydrogen chloride in the solution, it is preferable to carry out the reaction at a temperature as low as possible, but when the temperature is lower than 60 ° C., the processing efficiency tends to decrease. Also, when the temperature exceeds 160 ° C., the concentration of hydrogen chloride in the solution may decrease and the efficiency may decrease. For this reason, the processing temperature is usually in the range of 60 ° C to 160 ° C, and preferably in the range of 100 ° C to 140 ° C.
[0015]
The treatment with hydrogen chloride gas can be performed under normal pressure conditions or under pressurized conditions. In this case, the higher the processing pressure, the more the amount of hydrogen chloride gas used and the shorter the processing time can be. However, from the viewpoint of industrial equipment, the pressure is usually 5 MPa or less, preferably 2 MPa or less.
The processing time varies depending on the processing temperature, the pressure, and the amount of hydrogen chloride gas blown, but is usually desirably 2 minutes to 60 minutes, preferably 5 minutes to 30 minutes.
[0016]
The injection of the hydrogen chloride gas may be performed in a reaction tank or by using a bubble column or the like. When the reaction is carried out in a reaction tank, a nozzle or the like can be provided at or near the bottom of the reaction tank. For example, a normal tubular nozzle is used, or a ring is formed so that the tip of the nozzle is adjacent to the inner periphery of the reaction tank, and a hydrogen chloride gas blowing hole is provided in the ring to blow hydrogen chloride gas. Can be implemented.
[0017]
In particular, when the treatment with the hydrogen chloride gas is performed continuously, it is preferable to install a blowing nozzle so that the hydrogen chloride gas is not generated from the treatment liquid extracting portion so that a short pass is not generated at the time of the treatment.
After the hydrogen chloride gas treatment step is completed, a second treatment step of blowing an inert gas under heating conditions is performed. The second treatment step can be performed on the crude product solution which has been subjected to the treatment step with hydrogen chloride gas.However, if necessary, the crude product solution is desolvated to obtain a crude product solution. (Crude poly MDI). In consideration of thermal efficiency and equipment efficiency, it is preferable to perform the second processing step after removing the solvent after the processing step using the hydrogen chloride gas is completed.
[0018]
Examples of the inert gas used in the second treatment step include nitrogen, helium, and argon. Industrially, it is preferable to use nitrogen gas. The inert gas is supplied in an amount of usually 0.1 to 6 parts by weight, preferably 0.1 to 3 parts by weight, based on 100 parts by weight of the crude product after the solvent is removed.
The temperature at which the inert gas is blown is usually in the range of 180C to 240C, preferably in the range of 200C to 230C. In this treatment step, at least a part of the HC component and the acid component is decomposed by heating, and the generated decomposition gas is removed out of the system by blowing an inert gas to thereby remove the HC component and the acid component in the crude product. The purpose is to reduce, but at a temperature lower than 180 ° C., the efficiency of thermal decomposition may be reduced. On the other hand, when the temperature exceeds 240 ° C., the influence of undesired side reactions such as decomposition of the poly-MDI and a self-polymerization reaction increases, and the quality of the poly-MDI may deteriorate.
[0019]
The second treatment step of blowing an inert gas under heating conditions can be performed under reduced pressure in addition to normal pressure conditions. The pressure can be appropriately selected depending on the processing temperature and the amount of the inert gas to be blown, but is generally 1 kPa or more. When the reaction is performed under reduced pressure, the removal efficiency of the decomposed gas increases, so that the amount of the inert gas used can be reduced as compared with the normal pressure condition.
[0020]
The processing time of the second processing step varies depending on the processing temperature, the pressure, and the blowing amount of the inert gas, but is usually preferably in the range of 2 minutes to 60 minutes, preferably 5 minutes to 30 minutes.
The method of blowing the inert gas is not particularly limited, and examples thereof include a method of directly blowing the gas into the reaction tank and a method of using a bubble column. When the reaction is carried out in a reaction tank, a nozzle or the like can be provided at or near the bottom of the reaction tank. For example, a normal tubular nozzle may be used, or a ring may be formed such that the tip of the nozzle is adjacent to the inner periphery of the reaction tank, and an inert gas blowing hole may be provided in the ring to blow the inert gas. Can be implemented.
[0021]
The treatment step of blowing hydrogen chloride gas of the present invention and the subsequent second treatment step by blowing inert gas under heating conditions can be carried out in any mode of a continuous method, a batch method, or a combination of a continuous method and a batch method. It is.
As described above, the present invention provides a hydrogen chloride gas blowing treatment step for decomposing phosgene adduct, which is a by-product impurity during phosgenation, and a subsequent inertization under heating conditions for decomposing HC and acid components. By combining with the second processing step by gas injection, the HC content and the acid content in poly MDI are efficiently reduced with a smaller amount of hydrogen chloride gas than before, and It is intended to provide a method for producing poly-MDI which is advantageous to
[0022]
【Example】
Hereinafter, the present invention will be described more specifically based on examples, but the present invention is not limited to these examples. In the following Examples and Comparative Examples, all parts and ratios are by weight unless otherwise specified.
<Method for measuring HC content and acid content of poly MDI>
In Examples and Comparative Examples, the HC content and acid content of poly MDI were measured and indicated as follows.
[0023]
HC content measuring method: About 0.4 g of a sample is precisely weighed, dissolved in 100 ml of a solution of acetone: methanol (volume ratio) = 1: 1, and heated on an electric heating plate. When boiling starts, 60 ml of distilled water is added, and the mixture is further hydrolyzed for 2 hours, and then titrated with a 0.01 N silver nitrate aqueous solution. The values are expressed in weight percent as chlorine.
Acid content measuring method: About 2 g of a sample is precisely weighed, dissolved in 150 ml of a 1: 1 solution of acetone: ethanol (volume ratio), stirred at room temperature for 60 minutes, and then titrated with a 0.01 N potassium hydroxide / methanol solution. . Values are expressed as weight percent as HCl.
[0024]
[Reference Example 1] <Production of poly MDA>
Poly MDA used in the following Examples and Comparative Examples was produced by the following method.
22.7 kg of aniline (purity 97%) and 7.9 kg of 37% formaldehyde aqueous solution are subjected to a condensation reaction in the presence of 10.9 kg of 35% hydrochloric acid at a temperature of 30 to 120 ° C., and the obtained reaction solution is mixed with a 32% aqueous sodium hydroxide solution. 16.5 kg was added for neutralization, and the oil layer was taken out. Subsequently, after the oil layer was washed with hot water, water and excess aniline were distilled off under reduced pressure to obtain 16.9 kg of crude poly MDA.
[0025]
Embodiment 1
Using the reactor shown in FIG. 1, 9.1 kg / h of a 20 wt% solution of poly-MDA in orthodichlorobenzene (hereinafter abbreviated as ODCB) and phosgene (recycled from the gas separator 8) were placed in the first reactor 1. 7.8 kg / h (including phosgene) and 6.9 kg / h (including recycled ODCB from the cooler 10) were supplied. The reaction liquid extracted from the first reaction tank by overflow was supplied to the second reaction tank 2.
[0026]
The reaction temperature was maintained at 80 ° C. in the first reactor and 140 ° C. in the second reactor by a jacket and an external heater, and the pressure was maintained at 0.5 MPa-G (gauge pressure) in both reactors.
17.9 kg / h of the reaction solution was returned to the atmospheric pressure in the flash tank 3, and the phosgene concentration was reduced to 3.0%. This liquid was supplied to the degassing column 4 at a pressure of 16.4 kg / h, heated to 120 ° C. under a reduced pressure of 15.3 kPa, and the residual phosgene was completely removed with a residence time of 5 minutes.
[0027]
Next, the dephosgene solution was fed into the hydrogen chloride treatment tank 5. 0.11 kg / h of hydrogen chloride was supplied to the treatment tank 5, the treatment was performed at a temperature of 110 ° C. and a residence time of 10 minutes, and excess hydrogen chloride was recovered through a gas separator 9. ODCB was distilled off from the reaction solution obtained by the treatment in the desolvation tower 6. The ODCB distilled off was collected via the cooler 10. The obtained crude poly-MDI is supplied to the inert gas treatment tank 7 at 2.3 kg / h, and at the same time, while supplying nitrogen gas at 0.02 kg / h, under a reduced pressure of 13.3 kPa, at a temperature of 220 ° C., and a residence time. Processing was performed in 10 minutes.
[0028]
The acid content in the poly-MDI obtained after the treatment was 110 ppm, and the HC content was 950 ppm.
[0029]
Embodiment 2
Using the reactor of Example 1, the supply amount of hydrogen chloride in the hydrogen chloride treatment tank 5 was 0.15 kg / h, and the supply amount of nitrogen gas in the inert gas treatment tank 7 was 0.025 kg / h. The same operation as in Example 1 was performed except that the degree of pressure reduction in the gas treatment tank 7 was 34.7 kPa. The acid content in the obtained poly-MDI was 95 ppm, and the HC content was 900 ppm.
[0030]
Embodiment 3
The same operation as in Example 1 was performed, and crude poly-MDI from which ODCB was distilled off in the desolvation tower 6 was prepared. A tank-type reactor equipped with a stirrer and a heating jacket was used as a batch-type inert gas treatment tank, and 3.5 kg of the crude poly-MDI was charged therein, heated, and heated to 215 ° C. While maintaining the temperature at 215 ° C., a process was performed by supplying 0.1 kg of nitrogen gas over 20 minutes. After the treatment, the mixture was cooled and the poly-MDI was taken out. The acid content in the obtained poly-MDI was 55 ppm, and the HC content was 700 ppm.
[0031]
[Comparative Example 1]
The same operation as in Example 1 was performed using the reactor of Example 1 except that the liquid was directly sent from the vacuum degassing tower 4 to the desolvation tower 6 without operating the hydrogen chloride treatment tank 5. The acid content in the obtained poly-MDI was 140 ppm, and the HC content was 1550 ppm.
[0032]
[Comparative Example 2]
The same operation as in Example 1 was performed using the reactor of Example 1 except that the treatment was terminated at the outlet of the desolvation tower 6 without operating the inert gas processing tank 7. The acid content in the obtained poly-MDI was 160 ppm, and the HC content was 1500 ppm.
[0033]
【The invention's effect】
According to the present invention, in a method for producing poly-MDI by phosgenation of poly-MDA, a hydrogen chloride gas blowing treatment step is combined with a second treatment step by blowing inert gas under heating conditions. Thereby, the HC content and the acid content in the poly-MDI can be efficiently reduced with a smaller amount of hydrogen chloride gas than before.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of a continuous reaction apparatus in Example 1.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 First reaction tank 2 Second reaction tank 3 Flash tank 4 Decompression degassing tower 5 Hydrochloride treatment tank 6 Desolvation tower 7 Inert gas treatment tank 8 Gas separator 9 Gas separator 10 Cooler

Claims (5)

A method for producing a methylene-bridged polyphenylene polyisocyanate by phosgenation of a methylene-bridged polyphenylene polyamine produced by condensing aniline and formaldehyde in the presence of an acid catalyst,
In producing the crude product by reacting the methylene-crosslinked polyphenylene polyamine and phosgene in an organic solvent, by blowing hydrogen chloride gas into the obtained crude product solution, and then blowing an inert gas under heating conditions, And a method for producing a methylene-crosslinked polyphenylene polyisocyanate, which comprises reducing a hydrolyzable chlorine content and an acid content in a crude product. The method for producing a methylene-crosslinked polyphenylene polyisocyanate according to claim 1, wherein the hydrogen chloride gas is supplied in an amount of 0.5 to 3 parts by weight based on 100 parts by weight of the crude product solution. The method for producing a methylene-crosslinked polyphenylene polyisocyanate according to claim 1 or 2, wherein the inert gas is supplied in an amount of 0.1 to 6 parts by weight based on 100 parts by weight of the crude product. The method for producing a methylene-crosslinked polyphenylene polyisocyanate according to any one of claims 1 to 3, wherein an inert gas is blown under a heating condition of 180C to 240C. The method for producing a methylene-crosslinked polyphenylene polyisocyanate according to any one of claims 1 to 4, wherein the inert gas is a nitrogen gas.

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