JPS59172450A - Quality improvement of organic isocyanate - Google Patents

Abstract

PURPOSE:To obtain the titled compound having a low content of hydrolyzable chlorine and improved tint, by blending a specific zinc salt of saturated fatty acid with a hindered phenol antioxidant, heating it to give a liquid material, adding it to crude organic isocyanate, treating the blend at a specific temperature, distilling it. CONSTITUTION:A zinc salt of 6-9C saturated fatty acid (especially zinc octylate which is liquid at room temperature and obtainable industrially easily is preferable) or zinc octylate is blended with a hindered phenol antioxidant such as 2,6-di-t-butyl-4-methylphenol at >=70 deg.C, preferably at 70-130 deg.C, made into a liquid state, the liquid material is added to an organic isocyanate compound containing a hydrolyzable chlorine compound, treated at 100-220 deg.C with stirring for 0.5-2hr, distilled at about the same temperature under reduced pressure to distill the organic isocyanate compound, and the treated hydrolyzable chlorine compound together with a molten distillation residue is taken out from the bottom of the column.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a purification method for producing an organic incyanate containing less hydrolyzable chlorine and having a good color.

Organic isocyanates, such as tolylene diisocyanate (TDI) and diphenylmethane diisocyanate (CMDI), are extremely reactive substances and are used in a wide range of manufacturing processes such as polyurethane foams, elastomers, adhesives, and packaging materials. ing.

Industrially, most of these organic isocyanates are manufactured by reacting raw material amines with phosgene. For example, tolylene diisocyanate is produced by reacting tolylene diamine (TDA) in the presence of an inert solvent. to synthesize crude TDI by reacting it with phosgene, and then degassing it.
It is obtained by collecting the molten tm and subjecting it to purification as required, such as a step of removing tar. The isocyanate produced in this manner contains an impurity called acid and hydrolyzable chlorine (hereinafter abbreviated as hydrolyzable chlorine HC). Such impurities have a significant effect on the reactivity in the production of polyurethane. For example, in the production of polyurethane foam, if the He content is high, a standard product cannot be obtained, so it is very important to reduce the acid content and HC component.

Conventionally, methods to reduce the HC components contained in organic isocyanates have been proposed, such as repeated rectification and heat treatment by adding metal compounds. The HC is reduced to a permissible range depending on each application, for example, in the case of TDI polyurethane foam, it is about 0.002 to 0.000s%.

In the HC treatment, the method of repeating rectification to obtain purified isocyanate with a low He content results in a poor yield of purified incyanate, and the additive treatment method leaves problems in post-treatment.

H due to addition treatment of organic isocyanate with metal compounds
As a C reduction method, a treatment method using a zinc compound is known. For example, heat treatment using zinc oxide (%
Kosho 41-21. ．． 611 J, a method of heat treatment using zinc acetate (Japanese Patent Publication No. 42-17887J), or a method of heat treatment using saturated fatty acid zinc at a relatively low temperature (Japanese Patent Publication No. 54-44613), etc.・、
Although these HC treatment methods using zinc compounds are certainly highly effective among metal compounds, a common and important problem with these is that even if they are used in small amounts, scaling will occur in the processing equipment.

For example, according to additional tests by the present inventors, JP-A-54-44
The treatment method as described in Publication No. 613, i.e. TD
About 0.05% by weight of zinc stearate was added to I (mixing ratio of 2,4 bodies/2.6 bodies 80:20), and after stirring at 50°C for 3 hours, 140 to 1 G O-(3, / 30
The purified TDI obtained by distilling off the purified TDI from the top of the distillation column under reduced pressure distillation of vmH1/m2 did have a slightly lower HC, but it did not form a viscous powder on the walls of the reaction tank, the stirrer, or the distillation column. If the pipes in the treatment process become clogged due to scaling, which is caused by the accumulation of stiffness during repeated treatments, the heat transfer efficiency of the treatment tank, distillation column revoir, etc. will deteriorate, making treatment operations difficult. It happened.

A similar phenomenon also occurred when TDI was treated with zinc oxide or zinc acetate.

Regarding this problem, the present inventors found that the added zinc compound
Completely dissolved in the TDI treatment solution in the treatment process, H,C
It has been found that scaling occurs if the reactant that completely reacts with the compound and is produced in the treatment process is not present in liquid form in the treatment tank and distillation purification process, and we have previously filed an application regarding this issue. (Japanese Patent Application No. 57-217843) This invention discloses that among zinc saturated fatty acids, zinc saturated fatty acids having a relatively large number of carbon atoms, such as zinc octyl, zinc laurate, and zinc stearate, are highly compatible with isocyanates. 1. Therefore, select the temperature at which the saturated fatty acid zinc of Kowara completely dissolves in TDI, and pre-heat the HC in this temperature range.
When the treatment is completed and the reaction is completed, the added saturated fatty acid zinc and HC compound will completely react, and the reactant can be maintained in a liquid state in the system, thereby preventing skate song. The application was filed based on the following.

However, it has been found that when a metal salt of a saturated fatty acid having a large number of carbon atoms, such as zinc stearate, is used, the following disadvantages occur.

The crude organic isocyanate obtained by the phosgenation reaction of amines is degassed and then subjected to distillation purification as necessary, such as a detarring step. The isocyanate-responsive amine is recovered. In that case, if zinc stearate or the like is used in the step before the HC treatment, and if it remains unreacted and remains attached in a trace amount, it will act as a surfactant, so in the amine recovery step of hydrolysis, Foaming occurs and operation becomes difficult.

Further, in the above invention, in order to prevent scaling, it is necessary to carry out the HC treatment reaction at a relatively high temperature, and the bent refined isocyanate becomes colored over time due to thermal history.

In order to solve these problems, the method of the present invention has been completed. In other words, the present invention has been developed to use zinc saturated fatty acids having 6 to 9 carbon atoms among zinc saturated fatty acids, or zinc naphthenate.
: Used as a HC treatment agent, mixed with a hindered phenol antioxidant and heated to 70°C or higher to make it liquid, then added to an organic isocyanate compound containing HC and heated at 100 to 220°C. After treatment at this temperature, it is subjected to distillation at this temperature and the treated IC component is removed as a liquid reactant, thereby preventing scaling in the treatment tank and distillation column, and eliminating the resulting purified isocyanate. Moreover, in the recovery of isocyanates and amines from the distillation residue after HC treatment, water is added to the HC processing power method.

The hindered phenol compound used in the present invention is known as an antioxidant, and ordinary antioxidants have traditionally been added to compounds that easily polymerize, such as organic incyanates, to prevent discoloration. However, surprisingly, when mixed with the saturated fatty acid zinc or zinc naphthenate according to the present invention and heated and melted, the compatibility is good, and these zinc salts alone in the liquid or molten state are It has been found that the viscosity can be significantly lowered and the hue of purified isocyanate obtained by HC treatment can also be improved.

Although zinc naphthenate is a viscous liquid at room temperature, it remains relatively highly viscous even when heated to high temperatures;
Even if it is heated to 0° C. or higher and used as an HC processing agent, it exists in the processing solution in the form of an emulsion and is not completely dissolved in the isocyanate solution.

In addition, caproic acid, enanthic acid, and solid saturated fatty acid zinc cannot be melted unless heated to high temperatures, and moreover, they remain highly viscous.

On the other hand, if a hindered phenol antioxidant is added to the zinc salt according to the present invention and then heated and melted, a homogeneous liquid mixture with low viscosity is obtained, so this is not necessary for the HC treatment reaction.
It is sufficient to add a small amount of these at a relatively low temperature, and a complete treatment reaction can be carried out. Therefore, processing reactants can also be removed from the system in liquid form, and there is no scaling. Furthermore, these zinc salts have almost no effect as a surfactant after the HC treatment, and do not cause foaming during the amine recovery step. Furthermore, the hindered phenol compound mixed with the zinc salt does not participate in the reaction during the HC treatment, but only acts as a solvent for the zinc salt, and is distilled out to the refined isocyanate fraction by distillation after the HC treatment. Therefore, it was found that it has the effect of acting as a storage coloring prevention stabilizer for refined isocyanate without loss.

The present invention was invented based on these findings, and is carried out, for example, as follows.

As the saturated fatty acid zinc used in the present invention, zinc caproate, zinc nanthate, zinc octylate, zinc nonanoate, etc. can be used, but zinc octylate is particularly preferred because it is liquid at room temperature and is easily available industrially. It is a zinc salt.

In the present invention, these zinc salts or zinc naphthenate,
The mixing ratio of hindered phenol antioxidant was 1:05.
Used in the range of ~05:1, and heated at 70°C after mixing.
or higher temperature is necessary and preferably (required 7o~130''
Heat to C. If the temperature is higher than 130°C, the liquid becomes slightly colored, which is not preferable. When using zinc octylate,
Heating at 80P-90"C is sufficient. For example, if the same amount of antioxidant powder is mixed and heated, zinc octylate, which is starch syrup-like at room temperature, will gradually increase its fluidity as the temperature rises and reach 70℃. At around this temperature, the antioxidant will also melt and the mixed liquid will become a fluid liquid mixture with a viscosity of 5QOCP or less, so it can be easily added if maintained at this temperature and charged into the HC treatment tank.

The amount added varies depending on the HC component content in the isocyanate treatment solution, but usually 7
The above may be used, and in the case of TDI obtained by a conventional method,
It is sufficient to use 50 to 2,000 ppm relative to TDI. The liquid to be treated may be an isocyanate solution produced by phosgenation of an amine in the presence of an inert organic solvent, an isocyanate solution after desolvation, or inocyanate after detarring distillation. However, since it is preferable to use as small a quantity as possible, the incyanate after detaring is introduced into the treatment tank, maintained at a temperature of 100 to 220'Q, and stirred for about 30 minutes to 2 hours. It is better to set a residence time for this purpose. If the temperature is below 100°C, the reaction with the HC component will not be complete, and if it is above 220°C, by-products will increase and coloring will increase, which is not preferable.

In the case of TDI, the treatment can be carried out at a high temperature of about 200°C, but especially in the case of MDI, polymerization by-products such as dimers increase rapidly if the process is carried out at a high temperature, so it is necessary to carry out the process at around 100°C.

In this way, HC treatment 31! After the reaction is completed, the temperature may be slightly lower, but the reaction solution is placed in a vacuum distillation tower at the same temperature as the treatment temperature, and the HC components that have been cured and fixed are distilled from the molten distillate. It is extracted in liquid form along with the residue.

The organic isocyanates used in the present invention include aromatic isocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, and polymethylene polyphenyl polyisocyanate, hexamethylene diisocyanate, and undecane methylene diisocyanate. and alicyclic isocyanates such as isoborone diisocyanate and tricyclodecane diisocyanate.

In addition, as hindered phenol antioxidants, 2.
6-tert-butyl-4-methylphenol (B
IT), 2.6-tert-butyl-4-ethylphenol, etc., or 2.2'
Hindered phenolic compounds such as bisphenols such as -methylenebis(4-ethyl-6-tert-butylphenol) can be used. These are readily available under trade names such as Swanox, with BHT being a particularly preferred It is an oxidizing agent.

Furthermore, zinc octylate, zinc naphthenate, and the like are commercially available for use in paints, printing inks, and the like, and can be easily obtained.

Examples are shown below.

Example 1 2.6-tert-butyl-4-methylphenol (BHT) 1oo,! Add 7 ml and add 85 ml under nitrogen stream.
When stirred at °C, the fluidity gradually increased and became a uniform liquid with a viscosity of 450 CP. Meanwhile, 31 four-loaf flasks equipped with a stainless steel stirrer were equipped with hydrolyzable chlorine (HC).
) was added to 2 to 9 times the TDI containing 0.01% of zinc octylate (200 ppm (
04, S'J was added, and the treatment reaction was carried out with stirring at 200° C. for 40 minutes, and the HCfi portion treatment reaction was completed. Subsequently, remove the stirrer from this flask, fill it with a 1° glass container, attach a t-tower, and use it for 40 to 60 m.
Distillation was carried out under reduced pressure of mHH until the internal temperature rose to 170° C. to obtain distilled TDI of 1920I. The distilled TDI contains 2,6-di-tert-butyl-4
- 190 ppm of methylphenol, which means that 91% of the charge was detected. Also, HC&X in distilled TDI was 0.0030%. This distillate TI)I was left in the dark and under illumination around the mouth for 5 days, but the hue remained clear and colorless and did not change.

Further, the distillation residue was liquid, and no insoluble matter was observed, and no scaling was observed on the stirrer or flask wall, probably because the treatment was repeated three times.

Example 2 100g of zinc naphthenate instead of zinc octylate,
B) 2,2'-methylene-bis(4-ethyl-6tert-butylpheno-/l/) in place of IT 1001
A homogeneous liquid mixture was prepared in exactly the same manner as in Example 1 except that 1'It was used at 120°C. This was mixed with 2 kg of 4', l-diphenylmethane diisocyanate containing 0:005% hydrolyzable chlorine (HC).
400 ppm of zinc naphthenate was added to the same four-loaf flask used in Example 1 charged with
After stirring for a period of time, 0.5 to 1 ma was prepared in the same manner as in Example 1.
Distillation was carried out at 200°C under reduced pressure of Hg to obtain 1.6 kg of purified 4,4'-diphenylmethane diisocyanate. The hue was colorless and its HC content was o,oos%.

Also, no scratches or rings on the stirrer or flask wall were observed.

Example 3 All <
The same treatment as in Example 1 was performed. After treatment, 30mIII
1 g of transparent, colorless hexamethylene diinocyanate 1.9 kl containing 0.01% HC, distilled under 50-16 o-0 liters under reduced pressure. I got it.

Patent applicant: Mitsui Toatsu Chemical Co., Ltd.

Claims (3)

[Claims] (1) Mix saturated fatty acid zinc having 6 to 9 carbon atoms or zinc naphthenate with a hindered phenol antioxidant, heat it to 70°C or higher to make it liquid, and add hydrolyzable chlorine. It is characterized by adding the compound to an organic isocyanate compound containing the compound, treating it at a temperature of 100 to 220°C, and then subjecting it to distillation at this temperature to remove the treated hydrolyzable chlorine compound as a liquid reactant. A method for improving the quality of organic isocyanates. (2) The method according to claim 1, wherein the saturated fatty acid zinc is zinc octylate. (3) Mixing with hindered phenolic antioxidant;
2. The method according to claim 1, wherein the heating is carried out at 70-130<0>C.