JP3985260B2 - Process for producing modified polyisocyanate for paint - Google Patents

Description

【００３４】
表１、実施例１〜３、比較例１〜４において

【００３５】
〔塗料ポリイソシアネートの評価〕
応用実施例１〜３、応用比較例１〜４
・貧溶剤希釈試験
得られたポリイソシアネートをソルベントＡ（日石三菱製貧溶剤）にて希釈して、トレランスを測定した。結果を表２に示す。
【００３６】
【表２】

【００３７】
【表３】

応用実施例４〜６、応用比較例５〜８
・耐揮発油性（主剤用樹脂との相溶性）
得られたポリイソシアネート、アクリディックＡ−８２３（アクリルポリオール溶液、固形分＝５０％、水酸基価＝３０ｍｇＫＯＨ／ｇ、大日本インキ化学工業製）、ソルベントＡを表３に示す配合で混合して、固形分＝５０％のクリヤー塗料を調製した。その後、調製した塗料を鋼板上に塗布し、２０℃、６５％ＲＨの条件で１週間静置して、乾燥膜厚３０〜４０μｍの塗膜を形成させた試験片を得た。得られた試験片を２５℃のソルベントＡに４時間浸漬し、その後の外観を確認した。結果を表３に示す。
【００３８】
表２、３より、実施例のポリイソシアネートは、貧溶剤への溶解性、耐揮発油性は良好であったが、比較例のポリイソシアネートは貧溶剤への溶解性、耐揮発油性の両方とも良好となったものはなかった。
【００３９】
【発明の効果】
以上説明した通り、本発明によって得られたポリイソシアネートは低粘度であり、貧溶剤への溶解性も良好であった。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a polyisocyanate for paint. More specifically, the present invention relates to a method for producing a polyisocyanate for paint having a low viscosity and good solubility in a poor solvent.
[0002]
[Prior art]
Polyisocyanate curing agents are widely used as curing agents for paints and adhesives. Among these, polyisocyanates having an isocyanurate group are known to be excellent in weather resistance, heat resistance and durability.
[0003]
However, polyisocyanates having an isocyanurate group are not highly soluble and often have high viscosity. For this reason, when used as a curing agent, it is necessary to dilute with an organic solvent such as ethyl acetate, butyl acetate, and methyl ethyl ketone, which have strong dissolving power and strong toxicity. Such an organic solvent has a risk of odor and erosion of the substrate. Further, in order to improve workability, it is necessary to lower the solid content.
[0004]
In order to solve such problems, it has been proposed to use an allophanate group-containing polyisocyanate. For example, JP-A-8-325516 proposes a polyisocyanate having an isocyanurate group and an allophanate group. Japanese Patent Laid-Open No. 10-168155 proposes a polyisocyanate having an allophanate group obtained from a polyol having a specific molecular weight and an organic diisocyanate.
[0005]
[Problems to be solved by the invention]
However, since the polyisocyanate actually produced in JP-A-8-325516 has an isocyanurate group, the viscosity is still too high. In JP-A-10-168155, since the polyol has a large molecular weight, the resulting polyisocyanate has a low isocyanate content.
[0006]
An object of this invention is to provide the manufacturing method of the polyisocyanate for coating materials which is low-viscosity, is soluble in a poor solvent, and has sufficient isocyanate content in view of the said subject.
[0007]
[Means for Solving the Problems]
As a result of intensive studies, the present inventors have found that a method for producing an allophanate group-containing polyisocyanate obtained without using a co-catalyst solves the above problems, and has completed the present invention.
[0008]
That is, the present invention contains substantially no organic solvent, urethane group, uretdione group, isocyanurate group, a viscosity at 25 ° C. of 5,000 mPa · s or less, and an isocyanate content of 6.1 to 9.3 mass%. A polyisocyanate- modified product for paint is produced by the following steps.
(1) Hexamethylene diisocyanate (a) and a poly (oxypropylene) polyol (b) having a number average molecular weight of 1,000 to 3,000 are charged in an amount in which the isocyanate group is excessive with respect to the hydroxyl group, and 20 to 120. A first step of urethanization reaction at 70 ° C., followed by allophanatization reaction at 70 to 150 ° C. in the presence of an allophanate catalyst until substantially no urethane group is present.
(2) A second step of removing unreacted hexamethylene diisocyanate (a) from the reaction product until the free hexamethylene diisocyanate content is 1% by mass or less.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
The raw material used for this invention is demonstrated.
Examples of the organic diisocyanate (a) used in the present invention include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 2,2'- Diphenylmethane diisocyanate, 4,4'-diphenyl ether diisocyanate, 2-nitrodiphenyl-4,4'-diisocyanate, 2,2'-diphenylpropane-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 ' Aromatic isocyanates such as dimethoxydiphenyl-4,4'-diisocyanate; aliphatic isocyanates such as hexamethylene diisocyanate, 1,4-tetramethylene diisocyanate, 2-methylpentane-1,5-diisocyanate, lysine diisocyanate; xylylene-1, Aroaliphatic diisocyanates such as 4-diisocyanate and xylylene-1,3-diisocyanate; alicyclic diisocyanates such as isophorone diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated xylene diisocyanate, hydrogenated diphenylmethane diisocyanate, and hydrogenated tetramethylxylene diisocyanate Is mentioned. These organic diisocyanates may be used alone or in the form of a mixture of two or more.
[0010]
Among the above organic diisocyanates, hexamethylene diisocyanate, which is a non-yellowing isocyanate, is suitable in consideration of weather resistance and the like.
[0011]
The poly (oxypropylene) polyol (b) used in the present invention has a number average molecular weight of 1,000 to 3,000. When the number average molecular weight is too large, the isocyanate content of the resulting polyisocyanate becomes small, and when this is used as a curing agent for paints, the physical properties of the coating film are hardly exhibited. Moreover, when a number average molecular weight is too small, the obtained polyisocyanate becomes difficult to dissolve in a poor solvent.
[0012]
Examples of the allophanatization catalyst used in the present invention include metal salts of carboxylic acids. Examples of the carboxylic acid include acetic acid, propionic acid, butyric acid, caproic acid, octylic acid, lauric acid, myristic acid, palmitic acid, stearic acid, 2-ethylhexanoic acid and other saturated aliphatic carboxylic acids, cyclohexanecarboxylic acid, and cyclopentane. Saturated monocyclic carboxylic acids such as carboxylic acids, saturated polycyclic carboxylic acids such as bicyclo (4.4.0) decane-2-carboxylic acid, mixtures of the above carboxylic acids such as naphthenic acid, oleic acid, linoleic acid, linolenic acid Examples thereof include unsaturated aliphatic carboxylic acids such as acids, soybean oil fatty acids and tall oil fatty acids, aromatic aliphatic carboxylic acids such as diphenylacetic acid, and aromatic carboxylic acids such as benzoic acid and toluic acid. The metal constituting the metal salt of the carboxylic acid includes alkali metals such as lithium, sodium and potassium, alkaline earth metals such as magnesium, calcium and barium, transitions such as manganese, iron, cobalt, nickel, copper and zinc. Examples thereof include metals, boron group such as aluminum, and carbon group metals such as tin and lead. Of these, metal salts of alkylcarboxylic acid such as tin, zinc and lead are preferred.
[0013]
Next, specific steps will be described.
In the first step, the above-mentioned organic diisocyanate (a) and poly (oxypropylene) polyol (b) having a number average molecular weight of 1,000 to 3,000 are charged in an amount that makes the isocyanate group excessive with respect to the hydroxyl group, In this process, after urethanization reaction at 20 to 120 ° C., allophanatization reaction is carried out at 70 to 150 ° C. in the presence of the allophanatization catalyst until substantially no urethane group is present.
[0014]
Here, the “amount of isocyanate group in excess with respect to the hydroxyl group” means that the isocyanate group becomes excessive with respect to the hydroxyl group when the raw material is charged, and the molar ratio of isocyanate group to hydroxyl group is isocyanate group / hydroxyl group. = 8 or more is preferable, and 10 to 50 is particularly preferable.
[0015]
The reaction temperature of the urethanization reaction is 20 to 120 ° C, preferably 50 to 100 ° C. In the urethanization reaction, a known so-called urethanization catalyst can be used. Specific examples thereof include organic metal compounds such as dibutyltin dilaurate and dioctyltin dilaurate, organic amines such as triethylenediamine and triethylamine, and salts thereof.
[0016]
The reaction time for the urethanization reaction varies depending on the presence or absence of the catalyst, the type thereof, and the reaction temperature.
[0017]
When the urethanization reaction is completed, an allophanate reaction is performed. The allophanatization reaction is carried out by adding the above-mentioned allophanate catalyst and setting the reaction temperature to 70 to 150 ° C, preferably 80 to 130 ° C. When the reaction temperature is too low, the reaction reaches the formation of urethane groups, and the average number of functional groups of the resulting polyisocyanate decreases. When such a polyisocyanate is used in a coating material, the physical properties of the coating film tend to be insufficient. If the reaction temperature is too high, the resulting polyisocyanate is unnecessarily given a thermal history, which not only wastes energy during production but also damages the polyisocyanate. The average number of functional groups of polyisocyanate is the average number of isocyanate groups present in one molecule.
[0018]
The amount of catalyst used during the allophanatization reaction varies depending on the type, but is preferably 0.0005 to 1% by mass, and 0.001 to 0.1% by mass with respect to the total amount of the above (a) and (b). More preferred. When the amount of the catalyst used is less than 0.0005% by mass, the reaction is substantially delayed and takes a long time. On the other hand, when the amount of the catalyst used exceeds 1% by mass, it is difficult to control the reaction, and the obtained poly Problems such as shortening the pot life of a two-component paint containing isocyanate as a curing agent may occur.
[0019]
The reaction time varies depending on the type of catalyst, the amount added, and the reaction temperature, but is usually within 10 hours, preferably 1 to 5 hours.
[0020]
At this time, an organic solvent can be used as necessary. Examples of the organic solvent include aliphatic hydrocarbon organic solvents such as n-hexane and octane, alicyclic hydrocarbon organic solvents such as cyclohexane and methylcyclohexane, ketone organics such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone. Solvents, ester organic solvents such as methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, ethylene glycol ethyl ether acetate, propylene glycol methyl ether acetate, 3-methyl-3-methoxybutyl acetate, ethyl-3-ethoxypropionate Glycol ether ester organic solvents such as diethyl ether, tetrahydrofuran, dioxane and other organic solvents such as methyl chloride, methylene chloride, chloroform, carbon tetrachloride, methyl bromide, methylene iodide, Halogenated aliphatic hydrocarbon organic solvents chloroethane, etc., N- methylpyrrolidone, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, polar aprotic solvents such as hexamethylphosphoric phosphonyl amides. The said solvent can be used 1 type, or 2 or more types.
[0021]
The second step is a step of removing unreacted organic diisocyanate (a) from the reaction product until the free organic diisocyanate content is 1% by mass or less.
[0022]
Examples of the method for removing free organic diisocyanate include known methods such as distillation, reprecipitation, and extraction. Distillation, particularly thin-film distillation, can be performed without using a solvent or the like, which is preferable. Further, preferable conditions for thin film distillation are pressure: 0.1 kPa or less, temperature: 100 to 200 ° C., and particularly preferable conditions are pressure: 0.05 kPa or less and temperature: 120 to 180 ° C.
[0023]
It is more preferable to add a catalyst poison after the allophanate reaction to stop the allophanate reaction. The catalyst poisoning time is not particularly limited as long as it is after the allophanate reaction. However, when the thin film distillation method is used to remove the free organic diisocyanate, the catalyst poison should be added after the allophanate reaction and before the thin film distillation. It is preferred to do so. This is to prevent side reactions from occurring due to heat during thin film distillation.
[0024]
As the catalyst poison, known acids such as inorganic acids such as phosphoric acid and hydrochloric acid, organic acids having a sulfonic acid group, a sulfamic acid group and the like, esters thereof, acyl halides and the like can be used.
[0025]
The addition amount of the catalyst poison varies depending on the type and the type of the catalyst, but an amount that is 0.5 to 2 equivalents of the catalyst is preferable, and 0.8 to 1.5 equivalents is particularly preferable. When there is too little catalyst poison, the storage stability of the polyisocyanate obtained tends to fall. When there are too many, the obtained polyisocyanate may color.
[0026]
The viscosity of the polyisocyanate for paints thus obtained at 25 ° C. (solid content = 100% conversion) is 5,000 mPa · s or less, preferably 500 to 3,000 mPa · s. Moreover, isocyanate content (solid content = 100% conversion) is 5-15 mass%, Preferably it is 6-12 mass%.
[0027]
To the polyisocyanate obtained by the present invention, for example, an antioxidant such as 2,6-di-tert-butyl-4-methylphenol, an ultraviolet absorber, a pigment, a dye, a solvent, a flame retardant, Additives such as hydrolysis inhibitors, lubricants, plasticizers, fillers, storage stabilizers and the like can be appropriately blended.
[0028]
【Example】
The present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited thereto. In Examples and Comparative Examples, “%” means “% by mass”.
[0029]
[Manufacture of paint polyisocyanate]
Example 1
A volume of 1 L reactor equipped with a stirrer, a thermometer, a cooler, and a nitrogen gas introduction tube was charged with 750 g of HDI and 250 g of polyol-1 and subjected to urethanization reaction at 90 ° C. for 2 hours. When the reaction product was analyzed by FT-IR, the hydroxyl group had disappeared. Next, 0.2 g of lead 2-ethylhexanoate was charged and reacted at 90 ° C. for 3 hours. When the reaction product was analyzed by FT-IR and ¹³ C-NMR, the urethane group had disappeared. Furthermore, 0.1 g of phosphoric acid was added and a stop reaction was carried out at 50 ° C. for 1 hour. The isocyanate content of the product was 33.0%. This reaction product was subjected to thin-film distillation under the conditions of 130 ° C. and 0.04 kPa, a polyisocyanate having an isocyanate content of 9.5%, a viscosity at 25 ° C. of 920 mPa · s, and a free HDI content of 0.2%. P-1 was obtained. When P-1 was analyzed by FT-IR and ¹³ C-NMR, the presence of urethane group was not recognized, and the presence of allophanate group was confirmed. Further, traces of uretdione groups and isocyanurate groups were observed.
[0030]
Examples 2 and 3, Comparative Examples 1 and 2
Using the raw materials shown in Table 1, polyisocyanates P-2 to 5 were obtained in the same manner as in Example 1. The results are shown in Table 1.
[0031]
Comparative Example 3
The same reactor as in Example 1 was charged with 800 g of HDI and 200 g of monool-1 and subjected to urethanization reaction at 90 ° C. for 2 hours. When the reaction product was analyzed by FT-IR, the hydroxyl group had disappeared. After the liquid temperature was adjusted to 50 ° C., 0.2 g of potassium caprate was charged and reacted at 50 ° C. for 6 hours. Furthermore, 0.1 g of phosphoric acid was added and a stop reaction was carried out at 50 ° C. for 1 hour. The isocyanate content of the product was 31.3%. This reaction product was subjected to thin-film distillation under the conditions of 130 ° C. and 0.04 kPa, a polyisocyanate having an isocyanate content of 13.2%, a viscosity at 25 ° C. of 200 mPa · s, and a free HDI content of 0.2%. P-6 was obtained. When P-6 was analyzed by FT-IR and ¹³ C-NMR, the presence of a uretdione group was not recognized, and the presence of a urethane group, an allophanate group and an isocyanurate group was confirmed.
[0032]
Comparative Example 4
Polyisocyanate P-7 was obtained in the same manner as in Comparative Example 3 using the raw materials shown in Table 1. The results are shown in Table 1.
[0033]
[Table 1]

[0034]
In Table 1, Examples 1-3 and Comparative Examples 1-4

[0035]
[Evaluation of paint polyisocyanate]
Application Examples 1-3, Application Comparative Examples 1-4
-Poor solvent dilution test The obtained polyisocyanate was diluted with Solvent A (Niseki Mitsubishi-made poor solvent), and the tolerance was measured. The results are shown in Table 2.
[0036]
[Table 2]

[0037]
[Table 3]

Application Examples 4-6, Application Comparative Examples 5-8
・ Volatile oil resistance (compatibility with main resin)
The resulting polyisocyanate, Acrydic A-823 (acrylic polyol solution, solid content = 50%, hydroxyl value = 30 mg KOH / g, manufactured by Dainippon Ink and Chemicals), Solvent A were mixed in the formulation shown in Table 3, A clear paint having a solid content of 50% was prepared. Then, the prepared coating material was apply | coated on the steel plate, and it left still for one week on 20 degreeC and 65% RH conditions, and obtained the test piece which formed the coating film with a dry film thickness of 30-40 micrometers. The obtained test piece was immersed in Solvent A at 25 ° C. for 4 hours, and the subsequent appearance was confirmed. The results are shown in Table 3.
[0038]
From Tables 2 and 3, the polyisocyanate of the example had good solubility in a poor solvent and resistance to volatile oil, but the polyisocyanate of the comparative example had both good solubility in poor solvent and resistance to volatile oil. There was nothing that became.
[0039]
【The invention's effect】
As described above, the polyisocyanate obtained by the present invention has a low viscosity and good solubility in a poor solvent.

Claims (1)

Polyisocyanate for paints substantially free of organic solvent, urethane group, uretdione group and isocyanurate group, having a viscosity at 25 ° C. of 5,000 mPa · s or less and an isocyanate content of 6.1 to 9.3 mass% The manufacturing method characterized by performing a modified body in the following processes.
(1) Hexamethylene diisocyanate (a) and a poly (oxypropylene) polyol (b) having a number average molecular weight of 1,000 to 3,000 are charged in an amount in which the isocyanate group is excessive with respect to the hydroxyl group, and 20 to 120. A first step in which allophanatization reaction is carried out at 70 to 150 ° C. in the presence of the allophanatization catalyst until substantially no urethane group is present after urethanization reaction at ° C.
(2) A second step of removing unreacted hexamethylene diisocyanate (a) from the reaction product until the free hexamethylene diisocyanate content is 1% by mass or less.