JP5183025B2 - Method for producing polyisocyanate composition - Google Patents

Description

  The present invention relates to a polyisocyanate composition excellent in storage stability, particularly moisture stability, used for paints, adhesives, pressure-sensitive adhesives, and the like, and a two-component polyurethane coating composition using the same.

Polyisocyanates obtained from aliphatic and / or alicyclic diisocyanates are excellent in weather resistance, chemical resistance, and adhesion, so they can be used in a wide range of urethanes, such as for automobile repairs, bridges and buildings, plastics, and woodwork. It is used as a curing agent for paints, adhesives, and adhesives. Among them, polyisocyanates having an isocyanurate structure are known to be particularly excellent in weather resistance and durability because the chemical stability of the isocyanurate structure is high.
Thus, since the polyisocyanate having an isocyanurate structure has extremely excellent characteristics, it is desired to be used for a wider range of industrial applications. However, when this polyisocyanurate having an isocyanurate structure is used as a paint, when diluted with an organic solvent, or when stored after dilution, moisture from the organic solvent, etc. may cause a phenomenon such as cloudiness or solidification. It happened.

Various methods have been proposed to increase moisture resistance stability. For example, Non-Patent Document 1 shows that the addition of iminooxadiazinedione is good in moisture resistance stability, but expensive fluorine is contained in order to synthesize iminooxadiazinedione. It is necessary to adjust the catalyst, and since multistage adjustment of the catalyst is necessary, it is economically disadvantageous and the reaction is difficult to control. Furthermore, thermal stability is also low.
There is also a method of increasing the moisture resistance stability by adding orthoformate ester or monofunctional monoisocyanate and preferentially reacting with moisture, but the adduct that reacts with water remains in the polyisocyanate to reduce the final physical properties. Much.
Congr FATIPEC, Vol. 24th, D PAGE. D. 131-D. 145, 1998

  An object of the present invention is to provide a polyisocyanate composition having excellent storage stability, in particular, stability to moisture, and a two-component polyurethane coating composition using the same, by using a specific polyisocyanate. And

As a result of studies to solve the above problems, the present inventors have completed the present invention by using a method for producing a specific polyisocyanate composition.
That is, the present invention is as follows.
1) A method for producing a polyisocyanate composition obtained from an aliphatic and / or alicyclic diisocyanate, after the biuretization reaction is carried out without removing the unreacted diisocyanate after the isocyanuration reaction. The content of unreacted diisocyanate is removed to 1% by mass or less. The number of moles of biuret bonds (A) and the number of moles of isocyanurate bonds (B) are (A) / (B) = 1 / 99-60 / A method for producing a polyisocyanate composition having a biuret structure and an isocyanurate structure, which is 40.
2) The process for producing a polyisocyanate composition according to 1), wherein the diisocyanate is hexamethylene diisocyanate.

  According to the present invention, by using a specific polyisocyanate, it is possible to provide a polyisocyanate composition having excellent storage stability, in particular, moisture stability, and a two-component polyurethane coating composition using the same. .

The present invention will be specifically described below.
The diisocyanate used in the present invention is aliphatic and / or alicyclic. In particular, aromatic diisocyanates can be used unless the weather resistance is required.
The aliphatic diisocyanate preferably has 4 to 30 carbon atoms, and the alicyclic diisocyanate preferably has 8 to 30 carbon atoms. For example, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 2,2, Examples include 4-trimethyl-1,6-diisocyanatohexane, lysine diisocyanate, isophorone diisocyanate, 1,3-bis (isocyanatomethyl) -cyclohexane, 4,4′-dicyclohexylmethane diisocyanate, and the like. Of these, hexamethylene diisocyanate and isophorone diisocyanate are preferred from the viewpoint of weather resistance and industrial availability, and may be used alone or in combination.

  Moreover, the preliminary urethanation reaction product of these diisocyanate monomers and 1-3 functional alcohols can also be used suitably as a raw material. Examples of the 1-3 functional alcohol used here include, for example, methanol, ethanol, various butanols, 2-ethyl-hexanol, ethylene glycol, 1,2- or 1,3-propylene glycol, 1,3- Or 1,4- or 2,3-butylene glycol, 1,6-hexanediol, neopentyl glycol, neopentyl glycol hydroxypivalate, 2-ethyl-1,3-hexanediol, trimethylolpropane, glycerin, 1 And low molecular weight compounds such as 2,6-hexanetriol and polyester polyols, polyether polyols, polycarbonate polyols and the like having a molecular weight of about 200 to 10,000. The NCO / OH equivalent ratio during the preliminary reaction of alcohol and diisocyanate monomer is selected according to the purpose from a value of about 5 to 100, preferably about 10 to 50, and more preferably about 10 to 30.

The reaction temperature during the synthesis is usually selected from the range of 40 to 120 ° C. for the isocyanurate reaction and 60 to 180 ° C. for the biuret reaction. The progress of the reaction can be traced by measuring the isocyanate content (NCO%) of the reaction solution or measuring the refractive index.
The polyisocyanate composition of the present invention is a polyisocyanate composition having a biuret structure and an isocyanurate structure in which the unreacted diisocyanate is substantially removed after the biuretization reaction is performed before or after the isocyanurate formation reaction, The number of moles of biuret bonds (A) and the number of moles of isocyanurate bonds (B) are preferably (A) / (B) = 1/99 to 60/40. (A) / (B) = 3/97 to 50/50 is more preferable. Most preferably (A) / (B) = 3/97 to 30/70. It is preferable that (A) / (B) = 1/99 to 60/40 because a polyisocyanate composition having excellent storage stability, particularly excellent stability to moisture, can be obtained.

In the present invention, substantially removing unreacted diisocyanate means that the unreacted diisocyanate content in the polyisocyanate composition, which is a reaction product, is 1% by mass or less.
The polyisocyanate of the present invention refers to one having only one biuret structure or isocyanurate structure in one molecule and / or one having both a biuret structure and isocyanurate structure in one molecule.

  It is generally said that the isocyanuration reaction is accompanied by a uretdione structure which is a cyclic dimer with low thermal stability. Therefore, when the reaction is stopped at a low conversion rate, the uretdione concentration in the product tends to be high. Therefore, in order to suppress the uretdione content in the product, it is preferable to select a catalyst having a small amount of uretdione residue. Suitable catalysts for such conditions include: a) for example, tetraalkylammonium hydroxides and organic weak acid salts such as tetramethylammonium, tetraethylammonium and tetrabutylammonium; b) for example trihydroxypropylammonium, trimethylhydroxyethylammonium, Hydroxyalkylammonium hydroxides and organic weak acid salts such as triethylhydroxypropylammonium and triethylhydroxyethylammonium, c) Alkali metal salts of alkylcarboxylic acids such as acetic acid, caproic acid, octylic acid, myristic acid, and d) above Metal salts of alkylcarboxylic acids such as tin, zinc and lead; e) aminosilyl group-containing compounds such as hexamethyldisilazane.

  The catalyst concentration varies depending on the catalyst used and the reaction concentration, but is usually selected from the range of 10 to 1000 ppm relative to the diisocyanate. Further, if the isocyanuration reaction proceeds too much, the viscosity of the product increases and the content of the isocyanurate cyclic trimer decreases, so that a product having the desired physical properties cannot be obtained. Therefore, the conversion rate of the reaction is approximately 25. It is preferable to stop at% or less. However, since the initial reaction rate of the isocyanuration reaction is very fast, it is difficult to stop the progress of the reaction at the initial stage, and the reaction conditions, particularly the addition amount and addition method of the catalyst, should be carefully selected. Is preferred. For example, it is recommended that a catalyst addition method at regular intervals is suitable.

  When the reaction reaches the target conversion rate, for example, a catalyst deactivator such as sulfuric acid, phosphoric acid, or phosphoric acid ester is added to stop the isocyanuration reaction. If necessary, after removing the deactivated catalyst, excess diisocyanate and solvent are removed to obtain a product. The diisocyanate and the solvent are removed by, for example, thin film distillation or solvent extraction.

  Next, the biuretization reaction is described. The biuretization reaction uses water, tert-alcohol, preferably tert-butanol. As an organic solvent during the reaction, diisocyanate and water or tert-alcohol can be dissolved respectively to form a homogeneous phase under the reaction conditions, and a sufficient amount necessary to achieve a homogeneous phase is added. Also good. If water is taken as an example, those having low water solubility must be added in such a large amount, and this is not preferable because the solvent is separated and recovered after the completion of the reaction. The solubility of water is preferably 0.5% or more. For example, generally, solvents such as phosphoric acid trialkyl esters, alkylene glycols, ethers, esters and the like can be mentioned. On the other hand, benzene, toluene, monochlorobenzene, dichlorobenzene and the like are not preferable. Since isocyanates are generally highly reactive functional groups, they react with many. Accordingly, it is not preferable to react with isocyanate even if it is hydrophilic. For example, amines, alcohols, carboxylic acids, phosphoric acids, and diketones are not preferred.

Further, those which can promote coloring by coexisting with isocyanate are not preferable, and are preferably chemically stable as much as possible.
In order to obtain the polyisocyanate composition of the present invention, the biuretization reaction is performed before or after the isocyanurate formation reaction. To perform the biuretization reaction before the isocyanurate reaction is to perform the isocyanurate reaction after the biuretization reaction described above. Moreover, performing a biuretization reaction after an isocyanurate formation reaction is performing a biuretization reaction continuously after performing the above-mentioned isocyanurate formation reaction.
By obtaining a polyisocyanate composition by the method of the present invention, one having an isocyanurate bond and a biuret bond in the same molecule is obtained, rather than simply mixing the polyisocyanate composition obtained by reacting alone. Excellent durability and weather resistance.

The two-component polyurethane coating composition referred to in the present invention is a coating composition that is used by mixing the polyisocyanate composition of the present invention and a prepolymer having a hydroxyl group. Examples of the prepolymer having a hydroxyl group include polyols known in the art, such as polyether polyols, polyester polyols, acrylic polyols, and polycarbonate polyols, which may be used alone or in combination of two or more.
As a polyurethane coating composition, additives such as solvents, pigments, colorants, dispersants, ultraviolet absorbers, light stabilizers and antioxidants known in the art can be added without any problem.

Next, the present invention will be described more specifically with reference to examples. The part and% in an Example are a mass part and mass%, respectively.
[Viscosity Measurement Method] JIS K5600-2-3
[Isocyanate content measurement method] ASTM D2572
[Gas chromatography measurement method]
Equipment used GC-8A manufactured by Shimadzu Corporation
Column Silicone OV-17 manufactured by Shinwa Kako Co., Ltd.
Detection method FID
Measurement conditions Injection / detector temperature 160 ° C
Column temperature 120 ° C constant [Infrared absorption spectrum measurement method]
Equipment used JASCO Corporation FT / IR-600
[13C-NMR measurement method]
Equipment used JEM-LA400 manufactured by JEOL Ltd.

[Example 1]
610 parts of hexamethylene diisocyanate was charged into a 2 L four-necked flask equipped with a cooling tube, a nitrogen introducing tube and a thermometer, a dropping funnel, and a stirrer, and heated to 60 ° C. in a nitrogen stream, and then tetramethylammonium capryate. Of 45.7% was added in 4 portions over 2 hours. Furthermore, after reacting at 60 ° C. for 1 hour, 0.9 part of 85% phosphoric acid was added, the temperature was raised to 90 ° C., and the mixture was reacted for 1 hour. Subsequently, 210 parts of trimethyl phosphoric acid in which 0.48 part of water was dissolved was added and reacted at 90 ° C. for 1 hour and at 160 ° C. for 1 hour. The mixture was cooled to room temperature, filtered, and unreacted hexamethylene diisocyanate was removed by operating twice with a falling film distiller. The conditions of this flow-down type thin film distillation were 0.5 Torr / 150 ° C. for the first time and 0.1 Torr / 160 ° C. for the second time to obtain polyisocyanate 1.

The resulting polyisocyanate 1 is a yellow, transparent liquid having a viscosity at 25 ° C. of 1640 mPa.s. s, isocyanate content (hereinafter abbreviated as NCO%) 22.0%, residual hexamethylene diisocyanate was 0.2%.
The viscosity was measured according to JIS K5600-2-3, and the NCO% was measured according to ASTM D2572. The amount of residual hexamethylene diisocyanate was determined by gas chromatography using an FID detector. The infrared absorption spectrum of the obtained polyisocyanate was measured, biuret of characteristic absorption in 1770 cm ^-1, characteristic absorption of the isocyanurate was observed in 1690 cm ^-1. From the measurement of ¹³ C-NMR, the biuret / isocyanurate molar ratio was 11/89.

[Example 2]
A polyisocyanate 2 was obtained in the same manner as in Example 1 except that trimethyl phosphoric acid in which 0.6 part of water was dissolved was used.
The resulting polyisocyanate 2 is a yellow, transparent liquid having a viscosity of 1800 mPa.s at 25 ° C. s, isocyanate content (hereinafter abbreviated as NCO%) 21.2%, residual hexamethylene diisocyanate was 0.2%. When IR measurement was carried out, absorption of isocyanurate at 1690 cm ⁻¹ and biuret absorption at 1770 cm ⁻¹ were confirmed. From the measurement of ¹³ C-NMR, the biuret / isocyanurate molar ratio was 16/84.

[Example 3]
A polyisocyanate 3 was obtained in the same manner as in Example 1 except that trimethyl phosphoric acid in which 0.38 part of water was dissolved was used.
The resulting polyisocyanate 3 is a yellow, transparent liquid having a viscosity at 25 ° C. of 1550 mPa.s. s, isocyanate content (hereinafter abbreviated as NCO%) 22.5%, residual hexamethylene diisocyanate was 0.2%. When IR measurement was carried out, absorption of isocyanurate at 1690 cm ⁻¹ and biuret absorption at 1770 cm ⁻¹ were confirmed. From the measurement of ¹³ C-NMR, the biuret / isocyanurate molar ratio was 8/92.

[Example 4]
610 parts of hexamethylene diisocyanate was charged into a 2 L four-necked flask equipped with a cooling tube, a nitrogen introducing tube and a thermometer, a dropping funnel, and a stirrer, and heated to 60 ° C. in a nitrogen stream, and then tetramethylammonium capryate. Of 45.7% was added in 4 portions over 2 hours. Furthermore, after reacting at 60 ° C. for 1 hour, 0.9 part of 85% phosphoric acid was added, the temperature was raised to 90 ° C., and the mixture was reacted for 1 hour. Subsequently, 2.0 parts of tert-butanol was added and the temperature was raised to 180 ° C. After reacting at 180 ° C. for 2 hours, the reaction mixture was cooled to room temperature and filtered, and the unreacted hexamethylene diisocyanate was removed by operating twice with a falling film distiller. The conditions of this flow-down type thin film distillation were 0.5 Torr / 150 ° C. for the first time and 0.1 Torr / 160 ° C. for the second time to obtain polyisocyanate 4.

The resulting polyisocyanate 1 is a yellow, transparent liquid having a viscosity at 25 ° C. of 1640 mPa.s. s, isocyanate content (hereinafter abbreviated as NCO%) 22.0%, residual hexamethylene diisocyanate was 0.2%. When IR measurement was carried out, absorption of isocyanurate at 1690 cm ⁻¹ and biuret absorption at 1770 cm ⁻¹ were confirmed. From the measurement of ¹³ C-NMR, the biuret / isocyanurate molar ratio was 10/90.

[Comparative Example 1]
A four-necked flask equipped with a stirrer, thermometer, and reflux condenser was charged with 1000 parts of hexamethylene diisocyanate and 300 parts of xylene, and at 60 ° C with stirring, 0.3 parts of tetramethylammonium capryate was divided into four parts. Added every 30 minutes.
The reaction was continued at 60 ° C, and after 4 hours, the reaction was stopped by adding 0.2 part of phosphoric acid when the conversion of hexamethylene diisocyanate reached 21% by NCO% titration and refractive index measurement of the reaction solution. did. Thereafter, heating was further continued at 90 ° C. for 1 hour, then cooled to room temperature, and the reaction solution was filtered. Then, using a thin film evaporator, the first time was 0.8 Torr / 160 ° C., the second time was 0.1 Torr / Under the condition of 160 ° C., the solvent and unreacted hexamethylene diisocyanate were removed and recovered to obtain polyisocyanate 5.
The resulting polyisocyanate 5 is a slightly yellow, transparent liquid with a viscosity at 25 ° C. of 1300 mPa.s. s, NCO% was 23.5%, and the residual hexamethylene diisocyanate was 0.2%.

[Example 5]
A mixed solvent of 30 parts of n-butyl acetate containing 30 parts of polyisocyanate 1 obtained in Example 1 and 0.2 part of water and 30 parts of xylene was mixed. The sample was left in a room kept at a temperature of 20 ° C., and the number of days until the appearance became cloudy was visually observed. The results are shown in Table 1.

[Examples 6 to 7]
A visual appearance test was performed in the same manner as in Example 4 except that the solvent containing water shown in Table 1 was used. The results are shown in Table 1.

[Comparative Example 2]
The appearance was observed in the same manner as in Example 4 except that polyisocyanate 5 was used alone and the solvent containing water shown in Table 1 was used. The results are shown in Table 1.

[Example 8]
A visual appearance test was performed in the same manner as in Example 4 except that the polyisocyanate 2 obtained in Example 2 was used. The results are shown in Table 2.

[Examples 9 to 10]
A visual appearance test was performed in the same manner as in Example 7 except that the solvent containing water shown in Table 2 was used. The results are shown in Table 2.

[Example 11]
A visual appearance test was performed in the same manner as in Example 4 except that the polyisocyanate 3 obtained in Production Example 3 was used. The results are shown in Table 3.

[Examples 12 to 13]
A visual appearance test was performed in the same manner as in Example 10 except that the solvent containing water shown in Table 3 was used. The results are shown in Table 3.

[Example 14]
A mixed solvent of 30 parts of n-butyl acetate and 30 parts of xylene containing 40 parts of polyisocyanate 4 obtained in Example 4 and 0.2 parts of water was mixed. The sample was left in a room kept at a temperature of 20 ° C., and the number of days until the appearance became cloudy was visually observed. The results are shown in Table 4.

[Example 15]
A visual appearance test was performed in the same manner as in Example 14 except that the solvent containing water shown in Table 4 was used. The results are shown in Table 1.

[Example 16]
50 parts of the polyisocyanate solution after the appearance test was carried out in Example 5, Acrydic A-801 which is an acrylic polyol as a polyol (OH value 50 mg KOH / g, solid content 50%, manufactured by Dainippon Ink & Chemicals, Inc.) , Trade name) 110 parts. The blended solution was applied with an applicator to a thickness of 50 μm and baked at 120 ° C. for 30 minutes. The appearance was visually observed to confirm that the film was clear.

[Comparative Example 3]
50 parts of the polyisocyanate solution after the appearance test in Comparative Example 2 was performed, and Acrydic A-801, which is an acrylic polyol as a polyol (acid value 50 mg KOH / g, solid content 50%, manufactured by Dainippon Ink & Chemicals, Inc.) , Trade name) 110 parts. The blended solution was applied with an applicator to a thickness of 50 μm and baked at 120 ° C. for 30 minutes. The appearance was visually observed to confirm that the film was cloudy.

[Example 17]
40 parts of Polyisocyanate 1 and 0.1 part of Tinuvin 292 as a UV absorber were mixed, and Acrydic A-801 (OH value 50 mgKOH / g, solid content 50%, Dainippon Ink & Chemicals, Inc.) 251 parts of a product name). The blended solution was coated with an applicator to a thickness of 50 μm, baked at 120 ° C. for 30 minutes, and then subjected to a weather resistance test with a sunshine weather meter. The results are shown in Table 5. However, the gloss retention is (Gloss of coating after weathering test) / (Gloss of initial coating) x 100. The blended solution was applied with an applicator to a thickness of 50 μm and baked at 120 ° C. for 30 minutes.

[Comparative Example 4]
Polyisocyanate 6: A mixed solution containing 6700 parts of hexamethylene diisocyanate, 1000 parts of trimethyl phosphate and 2300 parts of ethylene glycol monomethyl ether acetate was placed in a reactor equipped with a reflux condenser, and 50 parts of water was stirred well under a nitrogen atmosphere. In addition, the temperature was raised to 160 ° C. over 20 minutes, and further reacted at 160 ° C. for 60 minutes at normal pressure. After the reaction, no precipitation of polyurea or the like was observed in the solution, and this reaction solution was unreacted hexamethylene diisocyanate and trimethyl phosphate, ethylene glycol monomethyl ether acetate in a thin film evaporator under the condition of 0.2 Torr / 180 ° C. Was recovered to obtain 1190 parts of polyisocyanate.

The resulting polyisocyanate is a yellow, transparent liquid having a viscosity of 1200 mPa.s at 25 ° C. s, isocyanate content (hereinafter abbreviated as NCO%) 23.9%, residual hexamethylene diisocyanate was 0.2%.
When the infrared absorption spectrum of the obtained polyisocyanate was measured, characteristic absorption of biuret was observed at 1770 cm ⁻¹ .
Polyisocyanate 7: A four-necked flask equipped with a stirrer, a thermometer, and a reflux condenser was charged with 1000 parts of hexamethylene diisocyanate and 300 parts of xylene, and stirred at 60 ° C, 0.3 parts of tetramethylammonium capryate as a catalyst. Was added in half portions every 30 minutes.

The reaction was continued at 60 ° C, and after 4 hours, the reaction was stopped by adding 0.2 part of phosphoric acid when the conversion of hexamethylene diisocyanate reached 21% by NCO% titration and refractive index measurement of the reaction solution. did. Thereafter, heating was further continued at 90 ° C. for 1 hour, then cooled to room temperature, and the reaction solution was filtered. Then, using a thin film evaporator, the first time was 0.8 Torr / 160 ° C., the second time was 0.1 Torr / Under the condition of 160 ° C., the solvent and unreacted hexamethylene diisocyanate were removed and recovered.
The resulting polyisocyanate is a slightly yellow, transparent liquid, the yield is 210 parts, and the viscosity at 25 ° C. is 1300 mPa.s. s, NCO% was 23.5%, and the residual hexamethylene diisocyanate was 0.2%.

When the infrared absorption spectrum of the obtained polyisocyanate was measured, characteristic absorption of isocyanurate was observed at 1690 cm ⁻¹ .
4 parts of polyisocyanate 6, 36 parts of polyisocyanate 7, 0.1 part of tinuvin 292 as an ultraviolet absorber were mixed, and Acrydic A-801 (acid value 50 mgKOH / g, solid content 50%, Dainippon Ink as a polyol) Using the chemical industry Co., Ltd., a brand name), it mix | blended in the weight part shown in Table 5. The blended solution was coated with an applicator to a thickness of 50 μm, baked at 120 ° C. for 30 minutes, and then subjected to a weather resistance test with a sunshine weather meter. The results are shown in Table 5.

  The coating composition of the present invention is useful for uses such as urethane paints, adhesives, pressure-sensitive adhesives, and casting agents.

Claims (2)

  A method for producing a polyisocyanate composition obtained from an aliphatic and / or alicyclic diisocyanate, wherein after the isocyanuration reaction, the biuretization reaction is performed without removing the unreacted diisocyanate. The number of moles of biuret bond (A) and the number of moles of isocyanurate bond (B) are (A) / (B) = 1/99 to 60/40. A method for producing a polyisocyanate composition having a biuret structure and an isocyanurate structure.   The method for producing a polyisocyanate composition according to claim 1, wherein the diisocyanate is hexamethylene diisocyanate.