JP2634877B2 - Method for producing polyisocyanate - Google Patents

Description

The present invention relates to a method for producing an aliphatic / alicyclic polyisocyanate.

[Prior art] Polyisocyanates derived from aliphatic and alicyclic diisocyanates represented by hexamethylene diisocyanate (hereinafter referred to as HDI), isophorodiisocyanate (IPDI), etc. Utilizing yellowing, it is widely applied in fields such as paints, coatings, casting materials, and foams.

Among them, polyisocyanates having a buret structure obtained by reacting an excess of an aliphatic / alicyclic diisocyanate with an active hydrogen-containing compound and then removing the excess diisocyanate (for example, see 49-13
No. 4629) and polyisocyanates having a urethane structure (for example, Japanese Patent Publication No. 45-11146, Japanese Patent Application Laid-Open No. 55-3).
No. 4234, JP-A-56-159212, JP-A-61-2851
No. 8 is highly evaluated for its excellent performance.

[Problems to be solved by the invention]

However, these polyisocyanates have the drawback that the polyisocyanate formed during the reaction between the diisocyanate and the active hydrogen compound is liable to be colored. is there.

Therefore, in the art, the appearance of a method for producing a polyisocyanate obtained by reacting a diisocyanate with an active hydrogen compound and having a low degree of coloration has been expected.

[Means to solve the problem]

The present inventors have conducted intensive studies in view of these points, and as a result, overcoming the above disadvantages by performing a reaction between a diisocyanate and an active hydrogen compound under conditions in which a specific compound coexists with a raw material diisocyanate. After finding out what can be done, they have completed the present invention.

That is, the present invention reacts an excess of an aliphatic / alicyclic diisocyanate with an active hydrogen-containing compound, and then removes excess diisocyanate to produce a polyisocyanate. When two or more substituents are present on the aromatic ring, and at least one of the substituents is a 2-position (6
The present invention is a process for producing a polyisocyanate, characterized in that a phenolic compound present in the above (ii) is allowed to coexist with an aliphatic / alicyclic diisocyanate.

As used in the present invention, the aromatic ring has two or more substituents, and at least one of the substituents is present at the 2-position (6-position) when the carbon atom having a hydroxyl group is at the 1-position. The phenolic compound is a compound generally referred to as a hindered phenolic compound, and includes, for example, a compound having the following structure. Of these, 2,6-di-tert-butyl-4-methylphenol represented by the structural formula is most preferably used.

The amount of the phenolic compound to be used is 0.1 to 1000 ppm, more preferably 1 to 1000 ppm based on the aliphatic / alicyclic diisocyanate.
300 ppm is used. If the amount is less than the above range, the effect is poorly expressed. If the amount is too large, it is economically undesirable.

As the aliphatic / alicyclic diisocyanate used in the present invention, in addition to the HDI and IPDI, for example, 2,4,4- or
2,2,4-trimethylhexamethylene diisocyanate,
Dodecamethylene diisocyanate, 2.6-diisocyanatomethyl caproate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, 4,
4'-methylenebis (cyclohexyl isocyanate), methyl-2,4-cyclohexanediisocyanate, methyl-2,6-cyclohexanediisocyanate,
1,3-bis (isocyanatomethyl) cyclohexane, 1,4
-Bis (isocyanatomethyl) cyclohexane, m- or p-xylylene diisocyanate (XDI), and 1,3- or 1,4-tetramethylxylene diisocyanate. These diisocyanate monomers can be used as a mixture of two or more kinds.

These diisocyanate monomers are arbitrarily selected depending on the purpose of use of the final product, but HDI, IPDI and XDI are particularly preferably used.

As the active hydrogen compound to be reacted with the diisocyanate, when a polyisocyanate having a burette structure is intended, a so-called buret agent, for example, water,
Tertiary butyl alcohol, methylamine, hexamethylenediamine and the like are used, and when a polyisocyanate having a urethane structure is intended, ethylene glycol, 1,3-butanediol, neopentyl glycol, 2-ethyl- 1,3-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, low molecular weight polyhydric alcohols such as trimethylolpropane, for example, polyester polyol, polyether polyol, polycaprolactone polyol, polycarbonate polyol, polyolefin Examples include high molecular weight polyhydric alcohols such as polyols and acrylic polyols.

The equivalent ratio of NCO group / active hydrogen group in the reaction is usually 3 to 5
It is selected in the range of 0, preferably in the range of 5 to 30.

The reaction may or may not use a solvent. When a solvent is used, a solvent having no reaction activity for the isocyanate group should be selected.

The reaction temperature is generally selected from the range of 20 to 250 ° C, preferably 40 to 200 ° C.

After completion of the reaction, excess diisocyanate and solvent are removed to obtain a product. The removal of the diisocyanate and the solvent is performed by, for example, a thin film evaporator or a solvent extraction method.

〔The invention's effect〕

The polyisocyanate having a burette or urethane structure obtained by the method of the present invention has a very low degree of coloring, and is used for, for example, polyurethane resins such as paints, adhesives, coating materials, casting materials, elastomers, and foam materials. Very useful as a curing agent.

〔Example〕

Hereinafter, the present invention will be further described with reference to examples, but the present invention is not limited to the examples.

The APHA used as an evaluation of the degree of product coloring in the examples
The index was in accordance with ASTM D-1209.

Example 1 To a four-necked flask equipped with a stirrer, thermometer and reflux condenser was added 1000 g of HDI and 50 mg of 2,6-di-tert-butyl-4-methylphenol, and 300 g of methyl cellosolve acetate was added as a solvent. Was reacted with 12 g of water at 160 ° C. for 1 hour.

The reaction mixture was used for the first time using a falling film evaporator.
The solvent and unreacted HDI were removed and recovered under the conditions of 0.8 mmHg / 160 ° C and 0.1 mmHg / 160 ° C for the second time, and the product polyisocyanate was obtained as the bottom liquid of the can.

The viscosity of the obtained product at 25 ° C. is 2200 mpa.s, NCO
The content was 23.1%.

The obtained polyisocyanate having a buret structure is an almost colorless transparent liquid, and its coloring degree is
APHA30.

Example 2 The reaction and purification were carried out in the same manner as in Example 1, except that 150 mg of 2,5-di-tert-butylhydroquinone was used instead of 50 mg of 2,6-di-tert-butyl-4-methylphenol. .

The physical properties of the obtained product were the same as those in Example 1, and the coloring degree was APHA30.

Example 3 In the same apparatus as in Example 1, 1000 g of HDI added with 20 mg of 2,6-di-tert-butyl-4-methylphenol and 67 g of HDI were added.
Was reacted at 160 ° C. for 1 hour, and unreacted HDI was recovered in the same manner as in Example 1 to obtain a polyisocyanate.

The viscosity of the obtained polyisocyanate having a urethane structure was 2300 mpa.s / 25 ° C., the NCO content was 17.9%, and the degree of coloring was APHA 30 or less.

Comparative Example 1 The reaction and purification were carried out in the same manner as in Example 1 except that 50 mg of 2,6-di-tert-butyl-4-methylphenol was not added.

The physical properties of the obtained product were the same as those of Example 1, but the coloring degree was APHA100 and was yellowish.

Comparative Example 2 The reaction and purification were carried out in the same manner as in Example 3, except that 20 mg of 2,6-di-tert-butyl-4-methylphenol was not added.

The physical properties of the obtained product were the same as those of Example 3, but the coloring degree was APHA70, which was yellowish.

Claims (1)

(57) [Claims] 1. A method for producing a polyisocyanate by reacting an excess of an aliphatic or alicyclic diisocyanate with an active hydrogen compound and removing excess diisocyanate. A branched alkyl group having 4 or more carbon atoms, which is present at the 2-position (6-position) when the carbon atom having a hydroxyl group is 1-position, having the above substituents on an aromatic ring, and at least one of the substituents is 1-position A method for producing a polyisocyanate, wherein the phenolic compound is coexisted with an aliphatic / alicyclic diisocyanate.