JPH11335344A - Production of organic isocyanate excellent in heat stability - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a simple method for producing an organic isocyanate excellent in heat stability at slight risk and provide a method for improving heat stability of the organic isocyanate. SOLUTION: This method for producing an organic isocyanate comprises the step of bringing a raw material organic isocyanate into contact with a metal oxide. This method for improving heat stability of the organic isocyanate comprises bringing the raw material isocyanate into contact with the metal oxide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing an organic isocyanate having excellent thermal stability and a method for improving the thermal stability of an organic isocyanate.

[0002]

2. Description of the Related Art A general method for producing an organic isocyanate is a method in which a corresponding amine is phosgenated and then, if necessary, purified by extraction or distillation. The organic isocyanate thus obtained is further used as a raw material for a so-called "modified isocyanate" or a raw material for a high-molecular-weight "urethane resin" through a reaction such as prepolymerization or isocyanuration. Furthermore, this "modified isocyanate" is used for curing agents such as paints and adhesives, various foams, two-component cured resins, etc.
"Urethane resin" refers to paints, adhesives, coatings,
Used in various binders, thermoplastic elastomers, etc.

[0003] Commercially available organic isocyanates are often colored when heated, and various studies have been made to solve this problem. For example, JP-A-7-2
No. 78087 proposes a method in which after phosgenation, a shell-type catalyst having a specific range of size and a specific range of surface area is used and brought into contact with hydrogen. JP-A-10-9
No. 5763 proposes a method of contacting hydrogen after phosgenation and before the solvent is completely removed. JP-A-5-65264 discloses a bisphenol A-based phosphite, 2,6-di-tert-butyl-
A method of adding an additive such as 4-methylphenol and triphenyl phosphite has been proposed. JP-A-2-6
No. 454 proposes a method of venting nitrogen gas. JP-A-4-211641 proposes a method of adding a low molecular weight alkanol and / or a polyhydric alcohol to a phosgene-containing isocyanate solution. British Patent Publication GB-2207671 discloses bifunctional methylenebis (phenylisocyanate) (hereinafter referred to as
As a method for removing impurities causing coloring from MDI), contacting the MDI with anhydrous metal silicate, silica, or a mixture thereof at about 190 ° C. is described. It is alleged that white thermoplastic polyurethane was obtained from the MDI thus produced.

[0004]

However, in the method using hydrogen, since the explosion limit of hydrogen is wide, skill and considerable care are required for the handling. In addition, in the method using an additive, since the additive is present in the isocyanate, the quality such as reactivity may be affected. The method using nitrogen gas requires an exhaust system, and an insufficient exhaust system risks suffocation due to a decrease in oxygen concentration in the air. Also, the method of GB-2207671 requires energy to heat the diisocyanate to about 190 ° C.

An object of the present invention is to provide a method for producing an organic isocyanate which has a low degree of danger, is simple, consumes less energy, and has excellent heat stability.

[0006]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above problems, and as a result, after converting an amino group into an isocyanate group using a corresponding amine as a starting material, a specific process was carried out. It has been found that the above-mentioned object can be achieved by providing, and the present invention has been completed.

That is, the present invention is a method for producing an organic isocyanate having excellent thermal stability, which comprises a step of bringing a raw material organic isocyanate into contact with a metal oxide.

Further, the present invention is a method for improving the thermal stability of an organic isocyanate, which comprises contacting a raw material organic isocyanate with a metal oxide.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, the organic isocyanate which can be used includes 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate,
Xylene-1,4-diisocyanate, xylene-1,
3-diisocyanate, 4,4'-differmethane diisocyanate, 2,4'-differmethane diisocyanate, 4,4'-diphenyl ether diisocyanate, 2-nitrodiphenyl-4,4'-diisocyanate, 2,2'-diphenyl Propane-4,4'-diisocyanate, 3,3'-dimethyldiphenylmethane-
4,4'-diisocyanate, 4,4'-diphenylpropane diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, naphthylene-
1,4-diisocyanate, naphthylene-1,5-diisocyanate, 3,3'-dimethoxydiphenyl-4,
Aromatic diisocyanates such as 4'-diisocyanate,
Aliphatic diisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate, 3-methyl-1,5-pentane diisocyanate, lysine diisocyanate, isophorone diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated xylene diisocyanate, hydrogenated diphenylmethane diisocyanate, tetramethyl xylene diisocyanate And the like, alicyclic diisocyanates, polymeric products thereof, and mixtures thereof. The present invention is a preferred method for obtaining a non-yellowing diisocyanate particularly used for paints such as aliphatic diisocyanates and alicyclic diisocyanates, and is also a preferred method for producing hexamethylene diisocyanate.

The method of converting an amino group into an isocyanate group (isocyanation reaction) includes, for example, (1) a method of reacting an inorganic salt of an amine (such as a hydrochloride) with phosgene. (2) A method in which an amine is directly reacted with phosgene. (3) A method in which an amine is directly reacted with carbon monoxide. (4) A method in which an amine is directly reacted with oxayl chloride. And other known methods.

The organic isocyanate of the present invention is obtained by converting the amino group of the corresponding amine into an isocyanate group, and bringing the resulting reaction product into contact with a metal oxide. If necessary, a purification step such as extraction or distillation can be provided, and this step may be performed at any place after completion of the isocyanation reaction. The reaction between the amine and phosgene is usually performed in a solvent, and after the reaction is completed, the solvent is removed. The contact with the metal oxide may be before the solvent is removed. The present invention is more effective for organic isocyanates after removal of the solvent, which have been purified and distilled once. Furthermore, by contacting a commercially available organic isocyanate with a metal oxide, the thermal stability of the organic isocyanate can be further improved.

The metal in the metal oxide used in the present invention includes alkaline earths such as magnesium, calcium and barium, aluminum, iron, zinc, lead, copper and the like.
Known materials such as titanium, manganese, and tin are exemplified. In the present invention, silicon is not considered a metal. Preferred metal oxides in the present invention are oxides of metals selected from magnesium, aluminum, calcium, and titanium. The shape of the metal oxide is preferably powder, and the particle size is more preferably 200 mesh or less.

The specific method of bringing the metal oxide into contact with the organic isocyanate is not particularly limited. For example, a method in which the metal oxide is charged into a reactor or a vessel filled with the organic isocyanate and brought into contact with the organic isocyanate, And a method in which an organic isocyanate is poured into a material filled with a metal oxide. The temperature of the contact is not limited, but is preferably a temperature that does not require heating or cooling in terms of energy consumption. Specifically, it is in the range of 5 to 50 ° C.

The weight ratio of the organic isocyanate to the metal oxide in the contacting step between the organic isocyanate and the metal oxide is preferably 0.1 to 20 parts by weight, more preferably 0.1 to 20 parts by weight, based on 100 parts by weight of the organic isocyanate. 5 to 5 parts by weight are more preferred. When the amount of the metal oxide is too small, the thermal stability of the isocyanate after the contact treatment tends to be insufficiently improved. If the amount of the metal oxide is too large, it becomes difficult to remove the metal oxide.

The metal oxide having a reduced activity can be reactivated by, for example, a heat treatment or a washing treatment, so that it is more advantageous in terms of cost and environment than the conventional method.

In the step of contacting with a metal oxide, an organic solvent inert to isocyanate groups can be used. As this organic solvent, toluene, xylene,
Aromatic organic solvents such as monochlorobenzene and dichlorobenzene, aliphatic organic solvents such as hexane and heptane, ketone organic solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, and ester organic solvents such as methyl acetate and ethyl acetate Solvents, ether organic solvents such as tetrahydrofuran and dioxane, glycol ether ester organic solvents such as ethylene glycol monomethyl ether acetate and propylene glycol monoethyl ether acetate, and glycol ether organic solvents such as ethylene glycol dimethyl ether and propylene glycol diethyl ether acetate And mixtures thereof.

The organic isocyanate obtained by the present invention has less coloring after heating and is excellent in thermal stability. For this reason, even if various modifications such as heat history, such as urethane modification, urea modification, biuret modification, allophanate modification, carbodiimide modification, uretdione modification, isocyanurate modification, etc., the subsequent coloring will be small. Conceivable.

Thereafter, if necessary, an emulsifier, a surfactant, an antioxidant,
UV absorber, filler, flame retardant, plasticizer, pigment / dye,
Known various additives and auxiliaries such as antibacterial agents and antifungal agents may be added.

[0019]

The organic isocyanate obtained by the production method of the present invention has little coloring upon heating and has improved thermal stability as compared with the conventional one. In addition, the processing steps are safer than the conventional method, and the procedure itself is simplified. Further, the obtained organic isocyanate can be omitted or reduced in the amount of additives and stabilizers. For this reason, the organic isocyanate obtained by the present invention is most suitable as a raw material for various urethanes or a modified polyisocyanate.

[0020]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto. In Examples and Comparative Examples, “parts” indicates “parts by weight” and “%” indicates “% by weight”.

[Synthesis of crude hexamethylene diisocyanate] Raw materials used Hexamethylene diamine: Special grade reagent Monochlorobenzene: Special grade reagent Dry hydrogen chloride gas: Filled cylinders Phosgene: Filled cylinders Magnesium oxide powder: Light, special grade titanium oxide powder: Reagent Special grade aluminum oxide powder: Special grade reagent

Synthesis Example A reactor equipped with a stirrer, thermometer, gas inlet pipe, gas outlet pipe, reflux condenser, and gas absorption pipe was charged with 300 parts of hexamethylenediamine (HDA) and monochlorobenzene (MC).
B) 3100 parts were charged and stirred uniformly. Then, at 60 ° C
When dry hydrogen chloride gas was blown in at a flow rate of 1690 ml / min for 1 hour, HDA hydrochloride precipitated in MCB. Thereafter, the water was removed from the reaction system by azeotropic distillation with MCB (flow rate: about 100 ml). Then, the reaction was carried out at 130 ° C. while blowing phosgene at a flow rate of 220 ml / min for 12 hours. Thereafter, the inside of the reactor was purged with dry nitrogen gas, cooled to room temperature, and filtered, and then monochlorobenzene was removed from the reaction solution by a rotary evaporator. Thereafter, the product is further purified by distillation under reduced pressure to obtain hexamethylene diisocyanate (hereinafter referred to as HD).
(Identified as I-0). HDI-0 had an isocyanate content of 50%.

Example 1 A reactor equipped with a stirrer, a thermometer, a gas inlet tube, a gas outlet tube, and a reflux condenser was charged with 100 parts of HDI-0 and 1 part of magnesium oxide powder as a metal oxide. Stir for 15 hours. Thereafter, magnesium oxide powder was removed by filtration to obtain HDI-1. HDI-1 had an isocyanate content of 50% and a color number of 10 APHA. HDI
-1 was heated at 130 ° C. for 24 hours. HDI after heating
-1 isocyanate content 50%, color number 100 AP
HA.

Examples 2 to 4 and Comparative Example 1 As shown in Table 1, the kinds and amounts of metal oxides were varied, and the mixture was stirred at room temperature for 24 hours to obtain HDI-2 to HDI-2. All the metal oxides used were powdery ones of 400 mesh or less. The HDI-2 to 4 were heated at 130 ° C. for 24 hours. All isocyanate contents were 50%. Comparative Example 1 measured the thermal stability of untreated HDI-0. Table 1 shows the color number measurement results.

[0025]

[Table 1]

As shown in Table 1, the thermal stability of HDI contacted with the metal oxide was smaller than that of untreated HDI, and the thermal stability was better.

Claims (2)

[Claims] 1. A method for producing an organic isocyanate having excellent thermal stability, comprising a step of bringing a raw material organic isocyanate into contact with a metal oxide. 2. A method for improving the thermal stability of an organic isocyanate, comprising contacting a raw material organic isocyanate with a metal oxide.