JP2000119240A - Method for producing polyfunctional polyisocyanate composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject stable compound having a specific polynuclear body easily by making a polymeric MDI mixture continuously in contact with a separating solvent in a super critical state and mixing in the presence of a cyclic carbonic acid ester as a compatible agent. SOLUTION: This method for producing a multi-functional polyisocyanate composition is to make (A) an aromatic polyisocyanate composition as a mixture of polymethylenepolyphenylenepolyisocyanates (hereinafter a polymeric MDI) continuously in contact with (C) a separating solvent in a super critical state of which temperature and pressure exceed critical values specific to a substance (especially preferably a carbon dioxide gas of 31 deg.C critical temperature and 7.38 MPa critical pressure) in the presence of (B) a cyclic carbonic acid ester [preferably the cyclic carbonic acid ester of formula I [R1 to R4 are each H or a 1-6C alkyl; and (n) is 1 or 2] as a compatible agent for obtaining a multi- functional aromatic polyisocyanate composition selectively containing 3-nuclides and 4-nuclides. The composition A is preferably a polymeric MDI of formula II [(n) is 1-8] and a mixture containing the same.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing a polyfunctional aromatic polyisocyanate composition. More specifically, in the presence of a separation solvent in a supercritical state where the temperature and pressure exceed a critical value inherent to the substance and a cyclic carbonate as a compatibilizer, the aromatic polyisocyanate composition is continuously contact-mixed. The present invention relates to a method for producing a high-performance and stable polyfunctional aromatic polyisocyanate composition which is easily produced and has excellent compatibility with other resins.

[0002]

2. Description of the Related Art Conventionally, the composition of a polyisocyanate to be formed is determined by the composition of a raw material polyamine, but it is known that isolation of binuclear isocyanate can be relatively easily obtained by distillation or crystallization. It is difficult to isolate a polynuclear isocyanate having three or more nuclei by an ordinary distillation method and cannot be adjusted freely. Thus, relatively high molecular weight resin components, substantially non-volatile chlorine or iron containing compounds and other impurities which particularly have an adverse effect on color cannot be removed by distillation, so that a light product having a stable appearance can be obtained. There is no present. Therefore, the method of polyfunctionalization of a stable aromatic polyisocyanate is as follows:
Various modifications have been made in known ways for various applications.

For example, as disclosed in JP-A-63-309512, a polymethylene polyphenylene polyisocyanate having an increased polynuclear content (hereinafter abbreviated as polymeric MDI) has flame resistance and low surface brittleness. Polyurethane foam has been manufactured. In addition, JP-A-3-20322 and JP-B-8-32759 describe:
It is described that a product obtained by a method for producing a modified aromatic polyisocyanate having an isocyanurate ring provides a polyurethane foam having heat resistance, flame retardancy, rigidity, toughness, and the like. Also, JP-A-7-3
No. 16123, a method for producing an aromatic polyisocyanate by extracting a specific polynuclear component by a solvent extraction method utilizing a difference in solubility parameter between an isocyanate and an extraction solvent is disclosed.

However, this method requires a complicated process of distilling off the solvent from the extract and a long distillation time in order to obtain a desired specific component. Further, a long distillation time at a high temperature causes an increase in coloring of the obtained product, which is not preferable from the viewpoint of quality stability. In addition, in recent years, it has been desired to select an environmentally friendly raw material due to VOC regulations and the like. In the solvent extraction method, if a large amount of solvent remains in the concentrated polyisocyanate mixture, it may be used as a raw material for paints, adhesives, elastomers, and foams. When used, the quality of the product is reduced due to the influence of the residual solvent. In addition, it is necessary to reduce the amount of the remaining solvent as much as possible to cause unfavorable factors such as deterioration of the working environment and flammability, which further complicates the working process.

[0005] In recent years, as a method for extracting low molecular compounds, a supercritical fluid extraction separation method using a supercritical fluid as a solvent has attracted attention, and an application example of purification of a polyisocyanate compound has been reported. ing.
For example, Japanese Patent Application Laid-Open No. 2-758 discloses a method of separating toluene diisocyanate from the residue from the production process of toluene diisocyanate by treating with supercritical carbon dioxide gas. In this method, since the extract has a high viscosity, an aromatic solvent which may adversely affect the environment is used as a diluent.

[0006]

As described above, the heat resistance, which is influenced by the reactivity and the molecular structure during urethane molding,
In order to obtain a stable polyisocyanate composition having high strength, enhanced surface properties, excellent storage stability and reduced coloring, the diisocyanate content and the high molecular weight polyisocyanate content are reduced, and the polymer having a high tri- or tetraisocyanate content is obtained. MDI compositions are highly desired.

[0007]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have conducted intensive studies on a method for producing an aromatic polyisocyanate composition having a specific polynuclear compound, and as a result, have found that a polymer MDI as a raw material is obtained. To selectively separate and extract specific components by continuously contacting and mixing the mixture with a separation solvent in a supercritical state where the temperature and pressure exceed the intrinsic value of the substance in the presence of a cyclic carbonate as a compatibilizer As a result, a stable polyfunctional aromatic polyisocyanate composition was obtained, and the present invention was achieved.

That is, the present invention relates to a method for preparing an aromatic polyisocyanate composition, which is a mixture of polymethylene polyphenylene polyisocyanate, in a supercritical state in which the temperature and the pressure exceed the critical values inherent to the substance in the presence of a cyclic carbonate as a compatibilizer. And a method for producing a polyfunctional aromatic polyisocyanate composition selectively containing trinuclear and tetranuclear compounds, characterized by continuously contacting and mixing with a separation solvent described in (1).

Further, the present invention provides the above-mentioned cyclic carbonate,
2. The method according to claim 1, wherein the formula is represented by the following general formula (1).
A method for producing the polyfunctional polyisocyanate composition described above.

[0010]

Embedded image

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The polymeric MDI mixture used in the present invention may be a polyisocyanate mixture obtained by phosgenation of a polyamine mixture formed by condensation of aniline and formaldehyde in the presence of an acid catalyst, or a binuclear compound obtained by distillation or crystallization from this mixture. Examples include a polyisocyanate mixture from which a part of diphenylmethane diisocyanate (hereinafter abbreviated as MDI) has been removed.

Particularly useful polyisocyanates include polymeric MDI represented by the following general formula (2) and mixtures containing them.

[0013]

Embedded image In an extraction operation using a supercritical fluid, the dissolving power of the supercritical gas determines its efficiency, and the controlling factor of the dissolving power is density, and the dissolving power increases as the density of the supercritical gas increases. For this reason, the feature of the supercritical gas extraction method is that the density governing the dissolving power can be controlled by changing the pressure and temperature, so that the extraction conditions can be selected easily and arbitrarily, and a wide range of selective separation is possible. is there.

The supercritical fluid used in the present invention is not limited as long as it is inert to isocyanate groups.
For example, carbon dioxide, nitrogen, methane, ethylene, propane, propylene, butane, isobutane, pentane, monochlorotrifluorocarbon, dichlorodifluorocarbon, trichlorofluorocarbon, monochlorodifluorohydrocarbon, dichlorofluorohydrocarbon, dichlorotetrafluorodicarbon, trichlorotetracarbon Examples include fluorodicarbon, octafluorocyclobutane, methyl ether, ethyl methyl ether, ethyl ether, acetone hexanes and the like, and mixtures thereof. A particularly preferred supercritical fluid for the present invention is carbon dioxide having a critical temperature of 31 ° C. and a critical pressure of 7.38 MPa. Also, since supercritical carbon dioxide gas has a low critical temperature,
It can be operated at low temperatures, is tasteless, odorless, harmless, non-flammable, chemically stable, inexpensive, and has the advantages of leaving no solvent in the product.

In the method of the present invention, the extraction temperature and pressure required for separation and extraction differ depending on the critical temperature and critical pressure of the supercritical fluid, and are usually carried out at a temperature above the critical point. Accordingly, the separation and extraction amount of the polynuclear polyisocyanate can be achieved by changing the temperature and pressure during the separation.

The contact condition between the polyisocyanate mixture and the supercritical fluid in the present invention can be arbitrarily determined according to the purpose, and is not particularly limited. 10 of the critical temperature of the fluid
A range of 0 to 300% is preferable, and a range of 100 to 200% is particularly preferable. On the other hand, the pressure condition is preferably in the range of 100 to 600% of the critical pressure (MPa) of the supercritical fluid, and particularly preferably in the range of 100 to 400%.

In the case of carbon dioxide (CO ₂ ), which is the most preferred supercritical fluid in the present invention, the temperature conditions
The temperature is preferably in the range of 31 to 80 ° C.
A range of 40 MPa is preferred. 80 ℃ or more and 40MP
a under the above conditions, the storage stability of the extracted product decreases,
It is not preferable because the color stability and the like adversely affect the quality stability, and furthermore, the apparatus becomes complicated due to high temperature and high pressure, so that efficient separation control cannot be performed. The most preferred separation conditions are 31 to
A temperature of 50 ° C. and a pressure of 7.38 to 40 MPa.

The contact time between the polyisocyanate mixture and the supercritical fluid is not particularly limited because it is set arbitrarily according to the required polynuclear content of the desired polyfunctional polyisocyanate. From the viewpoint, it is generally preferable to carry out in the range of 1 minute to 24 hours. The mixing amount of the separation solvent with respect to the polyisocyanate mixture depends on the dissolution of the separation solvent to be used. When CO ₂ is used, the mixing amount is 1 to 10 times the weight of the polyisocyanate, preferably Considering the efficiency, it is 1 to 5 times by weight. Naturally, the amount of solvent /
The feed ratio also affects the polynuclear MDI content. Solvent amount /
As the raw material ratio increases, the content of dinuclear MDI increases, and at the same time, the content of trinuclear MDI increases. However, to increase the P-MDI content of 3,4 nuclei is achieved by changing the pressure during extraction rather than by changing the amount of solvent.

The separation of a liquid mixture by supercritical fluid extraction is a phenomenon due to distribution and mass transfer at the interface between the supercritical fluid and the liquid phase. Conventionally known methods, for example, an extraction separation method in which a polymerization mixture is charged into an extractor, an extraction solvent in a supercritical state is poured into the extractor from above, below, or from the side to cause contact with the polymerization mixture. When used, the removal of the low molecular weight compound from the mixture has a small surface area because the mixture is unlikely to be formed into droplets, and the surface is unlikely to be renewed. Furthermore, the fluid in the supercritical state hardly diffuses into the mixture, and the mass transfer does not effectively occur, so that the removal of the low molecular weight compound is insufficient. Therefore, in the method of the present invention, in order to increase the extraction efficiency, that is, in order to increase the surface contact efficiency at the liquid interface between the supercritical fluid and the raw material liquid in the vessel, by using a specific compatibilizer in combination, the supercritical It is possible to increase the separation efficiency by smoothing the gas-liquid equilibrium with the fluid.

The compatibilizer used in the present invention includes a cyclic carbonate compound represented by the following general formula (1).

[0021]

Embedded image

Examples of the cyclic carbonate include, for example, ethylene carbonate, propylene carbonate and the like. The amount of the cyclic carbonate used is preferably 0.5% by weight or more based on the polyisocyanate. A particularly preferred amount is 0.5 to 5% by weight based on the polyisocyanate. Further, it is preferable that the compatibilizer is previously mixed with the polyisocyanate mixture before coming into contact with the separation solvent.

On the other hand, in the present invention, as the contacting device between the polyisocyanate mixture and the supercritical fluid, a conventionally known device can be applied as it is, and for example, a device of a distribution type, a semi-batch type, a batch type or the like can be used. It is possible to arbitrarily select and produce a separated polynuclear-containing mixture as needed. In order to contact the polymerization mixture with the supercritical fluid and produce an efficiently separated polyfunctional mixture, the mixture should be as fine as possible, thin-film, or highly porous. Is a particularly preferred method in the production method of the present invention.

The continuous contact mixing of the polyisocyanate mixture with the separating solvent and the compatibilizer may be carried out in a mixing tank equipped with a stirrer or in a pipe. Mixing in piping is advantageous in that it does not have large equipment. In this case, simple pipe mixing may be used, but for more uniform mixing, a line mixer is installed, or a supercritical fluid or polyisocyanate is ejected from a fine-diameter nozzle and mixed. desirable. This causes some preliminary extraction even in the piping. Preliminarily contacting and mixing the polyisocyanate mixture with the separation solvent is an effective method for increasing extraction efficiency because fine droplets are easily formed and uniformly dispersed. The separation solvent in the extractor can be either countercurrent or cocurrent with the polyisocyanate mixture discharged into the extractor, but in order to effectively cause fluid contact and mass transfer. Is preferably countercurrent.

In the present invention, since the dissolving power of the supercritical fluid is smaller than that of the liquid solvent, a simplified separation process can be performed only in the extraction step. That is, selective extraction is possible without dissolving the extra components. In addition, since the substance to be extracted in the present invention is a non-volatile substance, the solvent can be completely separated after extraction by a reduced pressure operation. As a method of separating the supercritical gas from the target component extracted by the supercritical gas, the pressure in the separation tank is appropriately reduced to a critical pressure or less to reduce the solubility of the target component in the supercritical gas, and the temperature of the separation tank is extracted. A method of changing the temperature of the tank to lower the solubility of the target component in the supercritical gas, a method of loading an adsorbent into a separation tank, and adsorbing and separating the target component can be used. In the present invention, a method of separating a supercritical gas and a target extraction component by reduced pressure is most preferable. There is no problem if the supercritical gas recovered by distillation is used again for extraction without performing new purification.

Immediately after extraction, the compatibilizer is present in the extracted components and the extraction residue. This compatibilizer may be removed as needed. As a removing method, a known method such as heating under reduced pressure is used.

[0027]

The polyfunctional aromatic isocyanate composition obtained according to the present invention has a high trinuclear or higher content, so that a cross-linking reaction occurs and the possibility of designing the resin on the isocyanate side comes out. Furthermore, since it has a stable quality without solvent, it is widely useful as a raw material for paints, adhesives, as well as plastic foams and elastomers, and the product obtained by reaction with an active hydrogen compound is: Excellent performance in flame retardancy, heat resistance, water resistance, toughness, etc. In addition, supercritical carbon dioxide as a separation solvent as compared with conventional liquid solvent extraction of hexanes is excellent in diffusivity and permeability, thereby simplifying the pretreatment step of the raw material and improving the extraction speed, and Aromatic polyisocyanate produced in a large amount and continuously produced industrially in a large amount because the target component can be obtained in high purity because the dissolving power can be adjusted by temperature or pressure operation and the selectivity at the time of extraction is large. This is a useful method for producing a composition.

[0028]

EXAMPLES The present invention will be described below with reference to examples.
The present invention is not limited to the embodiments unless departing from the spirit of the present invention.

Example 1 Using a supercritical extraction apparatus shown in FIG. 1, 38% by weight of 2% by weight was added to an extraction tank equipped with a supercritical carbon dioxide gas nozzle and kept at 40 ° C.
Core (2,4'-MDI: 4,4'-MDI = 15: 8
5), 36% by weight trinuclear, 12% by weight tetranuclear, 14
1% by weight of a polyisocyanate containing at least 5 nuclei
After the addition of 00 g, 5 g of propylene carbonate was further added as a compatibilizer, and a supercritical carbon dioxide gas having a pressure of 25 MPa was supplied at a rate of 1 liter / min by a bubbling method for 2 hours. The extract containing carbon dioxide and the compatibilizer was sent to the respective collecting devices from the upper part of the extractor, and the extraction residue containing the carbon dioxide gas and the compatibilizer was sent from the lower part of the extractor to the respective collecting devices. Next, the carbon dioxide gas was removed by returning each recovery unit to normal pressure, and the compatibilizing agent was removed by a heating and depressurizing device to obtain an extract and an extraction residue. Table 1 shows the results of gel permeation chromatography (GPC) analysis of the obtained aromatic polyisocyanate.

Example 2 The procedure was as in Example 1, except that the compatibilizer was ethylene carbonate. Table 1 shows GPC analysis values of the obtained aromatic polyisocyanate.

Example 3 Except that the pressure of the supercritical carbon dioxide gas was 15 MPa,
Performed in the same manner as in Example 1. Table 1 shows the results of GPC analysis of the obtained aromatic polyisocyanate.

Example 4 Binucleate (2,4'-MDI: 4,4'-MDI = 2: 98) 3 in which the composition of the starting polyisocyanate is 40% by weight
The procedure was performed in the same manner as in Example 1 except that the polyisocyanate contained 0% by weight of a trinuclear body, 10% by weight of a tetranuclear body, and 22% by weight of a pentanuclear body. Table 1 shows the results of GPC analysis of the obtained aromatic polyisocyanate.

Example 5 The temperature of the supercritical carbon dioxide gas extraction tank was 32 ° C. and the extraction pressure was 20
Except having been MPa, it carried out similarly to Example 1. Table 1 shows the results of GPC analysis of the obtained aromatic polyisocyanate.

[0034]

[Table 1]

[Brief description of the drawings]

FIG. 1 is a preferred process flow diagram used in the manufacture of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Propylene carbonate storage tank 2 Raw material storage tank 3 Carbon dioxide gas cylinder 4 Propylene carbonate supply pump 5 Raw material supply pump 6 Supercritical fluidization device 7 Pressure pump 8 Extractor 9 Extraction recovery device 10 Extract residue recovery device 11 Heat decompression device 12 Heat decompression device

Claims (2)

[Claims] 1. A separation solvent in which a polymethylene polyphenylene polyisocyanate mixture is an aromatic polyisocyanate composition in a supercritical state in which temperature and pressure exceed critical values inherent to a substance in the presence of a cyclic carbonate as a compatibilizer. And a method for producing a polyfunctional aromatic polyisocyanate composition selectively containing trinuclear and tetranuclear compounds, which is characterized by continuously contacting and mixing the same. 2. The method for producing a polyfunctional polyisocyanate composition according to claim 1, wherein the cyclic carbonate is represented by the following general formula (1). Embedded image