JPS598284B2 - Method for producing thermosetting polyisocyanate partial adduct - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a partial adduct of an organic polyisocyanate that can be self-cured by heat.

More specifically, the present invention provides that a part of the isocyanate groups of the aliphatic or alicyclic polyisocyanate having an average isocyanate group content of 2.5 or more are at least one group selected from hydroxyl groups, amino groups, and carboxyl groups. The present invention relates to a method for producing a polyisocyanate partial adduct, which undergoes an addition reaction with a compound having active hydrogen-containing groups. Such a polyisocyanate partial adduct is characterized by self-curing by heat and forming a chemically and physically stable coating film. In general, organic polyisocyanates are widely used, particularly in the field of urethane paints, by taking advantage of the reactivity of their isocyanate groups.

Among them, aliphatic or alicyclic polyisocyanates have excellent physical properties such as weather resistance and yellowing resistance, and therefore their demand is rapidly increasing. By the way, polyurethane paints are generally classified into one-component type and two-component type, and those belonging to the former include modified oil type, moisture curing type, and block type, and those belonging to the latter include polyol curing type and catalyst type. Each curing type can be mentioned.

The one-component type does not require mixing of raw materials during painting, so it is easy to handle, but the physical properties of the coating are slightly inferior to the two-component type, and the modified oil type and moisture-curing type have poor storage stability. For example, if they are stored, they will gel in a few days to a few months, so their pot life is limited, and the block type needs to be heated to 180°C or higher to form a coating, and furthermore, it will dissociate during this process. The drawback is that the protective agent such as phenol is not used for coating film formation and is scattered into the atmosphere, causing a large amount of air pollution. In addition, while the two-component type has good physical properties of the coating, it is troublesome because it requires mixing two components, organic polyisocyanate and polyol, when painting, and the mixed solution has a certain pot life. There is the administrative hassle of having to work within a limited time. The present inventors have made extensive research to improve the drawbacks of the conventional one-component and two-component types while making use of their advantages, and as a result, the inventors have found a new product with an average isocyanate group content of 2.5 or more. We have discovered that this objective can be achieved by reacting a portion of the isocyanate groups of aliphatic or alicyclic polyisocyanate with alcohols, amines, or carboxylic acids to form a partial adduct, and based on this knowledge, The present invention has now been accomplished.

Conventional polyurethane paints form a coating film by reacting organic polyisocyanate with water or a curing agent such as a polyol, but the partial adduct obtained by the method of the present invention does not require a curing agent and can be used alone. Can be hardened.

That is, since the partial adduct of the present invention has an imino group produced by a partial addition reaction with an isocyanate group in one molecule, the isocyanate group in the molecule can be removed at a temperature below the dissociation temperature of the partial adduct or by using a catalyst. By reacting with the active hydrogen of the imino group, it polymerizes and self-cures, forming a coating film with good chemical and physical properties. In other words, by setting the equivalent ratio of the isocyanate group and the group that reacts with the isocyanate group within an appropriate range, a coating film with a well-balanced crosslinking density can be obtained, and the hardness and solvent resistance can be significantly improved. . Furthermore, from a structural standpoint, it is an aliphatic or alicyclic polyisocyanate, so it has flexibility,
It has the advantage of providing a coating film with good bending resistance, adhesion resistance, and weather resistance. In addition, the polyisocyanate partial adduct obtained by the method of the present invention is a type of one-component paint, and it has the characteristics of a one-component paint such as easy handling, as well as physical properties that are considered to be disadvantageous to one-component paints. In particular, it has improved the poor solvent resistance and has the further advantage of unlimited pot life. Furthermore, since it is cured at a temperature below the dissociation temperature of conventional blocking agents, it has the advantage that the blocking agent does not dissociate, that is, it does not scatter into the atmosphere. When an organic polyisocyanate, in which some of the isocyanate groups have not undergone an addition reaction with the active hydrogen group-containing compound, forms a coating, the balance between the excess isocyanate groups and the active hydrogen present in the molecule to be reacted cannot be maintained. Celsius on the board, blistering due to air bubbles,
Phenomena such as shrinkage of the film occur, and a practical coating film cannot be produced.

It is known that the reaction rate of aliphatic or alicyclic polyisocyanates is extremely slow compared to aromatic polyisocyanates.

This suggests that the reaction does not proceed at room temperature but proceeds due to heat or catalysts, and as mentioned above, the partial adduct obtained by the method of the present invention does not undergo gelation even when stored for a long period at room temperature. The fact that it can be cured by heat or catalyst is well supported. It is clear that the slow reaction rate of aliphatic or alicyclic polyisocyanates greatly contributes to the usefulness of the partial adducts of the present invention. On the contrary,
Aromatic polyisocyanates have an extremely fast reaction rate, so when preparing a partial adduct, gelation may occur and the desired product may not be produced, or even if a partial adduct is formed, it may take several hours or several hours if left at room temperature. It gels within a few days and becomes practically unusable.

According to the method of the present invention, the desired partial adduct comprises an aliphatic or cycloaliphatic polyisocyanate and a compound having at least one active hydrogen-containing group selected from hydroxyl, amino and carboxylic acid groups. It is obtained by reacting so that the equivalent ratio of isocyanate groups is preferably 0.05 to 0.8.

If the equivalence ratio is less than 0.05, the proportion of partial addition is low, and phenomena such as shrinkage of the coating film, blistering due to air bubbles, and repellency on the substrate are observed, which is undesirable from a practical standpoint. On the other hand, if the equivalent ratio is 0.8 or more, the number of isocyanate groups in the molecule becomes too small, the degree of crosslinking of the coating film does not increase, the physical properties are adversely affected, and a practically preferable coating film cannot be obtained. The equivalent ratio is preferably in the range of 0.1 to 0.4. This reaction may or may not use a solvent or catalyst, but
It is preferable to use them for the purpose of homogenizing the reaction and shortening the reaction time. The solvent or catalyst used in the reaction is not removed after the reaction, but is used as a diluting solvent during coating film formation.
Alternatively, it has the advantage that it can be used as is as a catalyst.
Solvents that are generally used as paint diluents and do not react with isocyanate groups are often benzene, xylene,
Toluene, ethyl acetate, butyl acetate, cellosolve acetate,
Volatile and low viscosity materials such as methyl ethyl ketone can be used. As the catalyst, a catalyst generally used in urethane production reactions is used, such as dibutyltin dilaurate, tin chloride, etc. The amount added varies depending on the activity, but the amount is 0.001 to 0.1% by weight; anything outside this range has disadvantages such as slow reaction or rapid gelation. Preferably it is 0.01 to 0.1% by weight.
The reaction temperature is 0 to 150°C, and the reaction is slow below 0°C.
If the temperature is 150°C or higher, side reactions may occur, which is not preferable.

Preferably it is in the range of 50 to 120°C. Typical aliphatic or alicyclic polyisocyanates having 2.5 or more isocyanate groups include ethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, isoborone diisocyanate, water, trimethylolpropane, hexanetriol, etc. There are adducts with polyhydric alcohols such as , glycerin, and pentaerythritol.

In addition, the above diisocyanate and tertiary butyl alcohol,
Polyisocyanates obtained by reaction with formic acid, hydrogen sulfide, etc. can also be used. Alternatively, a polyisocyanate containing a uretdione group or an isocyanurate group obtained by polymerizing the above diisocyanate in the presence of a catalyst such as tributylphosphine may be used. Polyisocyanates containing a large amount of uretdione groups have difficulty balancing the reaction between active hydrogen-containing compounds and isocyanate groups.
Furthermore, the ring opening of the uretdione group causes a decrease in molecular weight, and no improvement in the physical properties of the coating film can be obtained. On the other hand, since isocyanurate groups affect the physical properties of the coating film, the physical properties of the coating film vary depending on the content ratio of uretdione groups/isocyanurate groups, and the preferable content ratio of uretdione groups/isocyanurate groups is in the range of 60/40 to 10/90. It is. Among these polyisocyanates, polyisocyanates obtained from hexamethylene diisocyanate are preferred because they are easily available industrially and have excellent coating film properties.
Among the active hydrogen-containing compounds suitable for the present invention, hydroxyl group-containing compounds include methynol, ethanol, n-propanol, isopropanol, n-butanol, n-hexanol, n-decanol, n-octadecanol, stearyl alcohol, cyclohexanol, Monohydric alcohols such as benzyl alcohol, phenol, ethylphenol, and kydylenol; ethylene glycol, propylene glycol, butylene-1,4- and 2,3-glycol, hexane-1,6-diol, and octane-1,8-diol;
-diol, neopentyl glycol, 1,4 bis-hydroxymethylcyclohexane, tetraethylene glycol, dipropylene glycol, butylene glycol,
glycerin, trimethylolpropane, hexane-1,
2,6-triol, butane-1,2,4-triol, trimethylolethane, pentaerythritol, catechol, resorcinol, hydroquinone, pyrogallol, acrylic A-801,813 (acrylic polyol, manufactured by Dainippon Ink), molecular weight 500~ A polyhydric alcohol such as 5000 epoxy alcohol is used. Examples of amino group-containing compounds include monovalent compounds such as methylamine, ethylamine, n-butylamine, n-hexylamine, dimethylamine, diethylamine, ethylmethylamine, di-n-butylamine, morpholine, pyrrolidine, piperazine, aniline, and toluidine. Amines, ethylenediamine, triethylenediamine, tetraethylenediamine, hexamethylenediamine, N,N'-dithythylethylenediamine, N,N'-dimethyltriethylenediamine, N,N'-dimethyltetraethylenediamine,
Polyamines such as N,N'-dimethylhexamethylene diamine and tolylene diamine are used. Furthermore, compounds containing carboxylic acid groups include monovalent carboxylic acids such as acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, lauric acid, stearic acid, benzoic acid, toluic acid, malonic acid, succinic acid, glutaric acid, Polycarboxylic acids such as adipic acid, sebacic acid, phthalic acid, and isophthalic acid are used. In addition, active hydrogen-containing compounds having different functional groups in one molecule include ethanolamine, N-methylethanolamine, N-ethylethanolamine, diethanolamine, triethanolamine, 3-amino-
Propanol, tris-propanol-amine, glycolic acid, salicylic acid, aminoacetic acid, etc. are used. Among these active hydrogen-containing compounds, those having two or more groups that react with isocyanate groups are preferable, and the obtained partial adducts can be coated uniformly on the substrate without running out of liquid during coating, and are easy to coat. It is preferable to use ethylene glycol, diethylene glycol, glycolic acid, epoxy polyol, etc. because they have good properties as well as good physical properties of the coating film. The partial adduct of the present invention can be sufficiently hardened by conventional heating baking equipment and methods. The curing temperature and time vary slightly depending on the working conditions, required physical properties of the coating film, etc., and are preferably 60-180°C, preferably 80-140°C.
Generally, the dissociation temperature of the partial addition reaction product of an aliphatic polyisocyanate is higher than that of an aromatic polyisocyanate, and is 180° C. or higher.

Since the partial adduct obtained by the method of the present invention is cured at a temperature below this dissociation temperature, it has the advantage that the compound having an active hydrogen-containing group subjected to the partial addition reaction can be effectively used without disappearing. The partial adduct obtained by the method of the present invention has a different shape depending on the compound having an active hydrogen-containing group subjected to the partial addition reaction, and is either solid or viscous liquid, and can be used in solvents used in paints, such as ethyl acetate, butyl acetate, etc. Soluble in toluene, xylene, etc. Further, it can be confirmed that this partial adduct can be obtained almost quantitatively by confirming the isocyanate group using an infrared spectrophotometer, measuring the isocyanate content by titration, and measuring the molecular weight. The partial adducts obtained by the method of the present invention include iron, aluminum, copper,
It can be applied to ceramics, paper, rubber, leather, synthetic leather, cloth, textile products, wood, synthetic wood, plastic products, glass, etc. It has a wide range of applications and is very useful like general polyurethane paints. The present invention will be explained in more detail with reference to Examples below.

Example 1 100 parts by weight of a polyisocyanate obtained from hexamethylene diisocyanate and water with an isocyanate content of 23.8% by weight and a viscosity at 30°C of 1400 cp, 7.4 parts by weight of diethyl glycol, and 5 parts by weight of ethyl acetate.
0 parts by weight of dibutyltin dilaurate and 0.05 parts by weight were mixed (equivalent ratio of CO to O = 0.25) at 700C for 1 hour.

The solution viscosity of the partial adduct thus obtained was 240
cp, and the isocyanate content was 28.2% by weight in terms of pure partial adduct. This solution is extremely stable for long periods of time at room temperature. When this was applied to a mild steel plate with a thickness of 5 mils and left in a constant temperature dryer at 120°C to force dry it, it hardened within 10 minutes and the JlSK54O
The pencil hardness according to l was H, and the pencil hardness after drying at 120° C. for 1 hour was 2H. 6.35mT1L15009 by JISK54Ol impact deformation tester
The results of the load test showed that no scars remained even after a drop distance of 50 cm, and the Erichsen extrusion test was 8u1 or higher. This coating film has excellent gloss, smoothness, transparency, and adhesion, and has acid resistance, alkali resistance, and
It was excellent with no change in the volatile oil resistance test. Table 1 shows examples in which the polyisocyanate used in this example was used in other different partial adducts.

Example 2 Obtained from hexamethylene diisocyanate and water, the viscosity of 30 was 150 at an isocyanate content of 23.4% by weight.
A solution prepared by dissolving 18.0 parts by weight of di-n-butylamine in 10 parts by weight of ethyl acetate was added dropwise to a solution prepared by dissolving 100 parts by weight of polyisocyanate (0 cp) in 40 parts by weight of ethyl acetate while stirring at room temperature over 1 hour. An adduct was obtained.

(NH/NCO equivalent ratio = 0.25) The solution viscosity of this product was 175 cp, and the isocyanate content calculated as pure partial adduct was 13.6% by weight. When this was applied to a thickness of 5 mil on a mild steel plate and kept at 120°C, the temperature was 30.
It cured in minutes and the pencil hardness according to JIS K54Ol was F-H. In addition, no scars were produced in the impact deformation test using JISK54Ol, and the Erichsen extrusion test was good at 8 ml or more. Example 3 Polyisocyanate obtained from hexamethylene diisocyanate and water (isocyanate content 23.4% by weight)
) and 20 parts by weight of ethyl acetate was stirred at 10°C, and 4 parts of monoethanolamine was added to it.
．． A solution prepared by dissolving 3 parts by weight in 5 parts by weight of ethyl acetate was added dropwise over 1 hour, the temperature was raised to 50°C, and the reaction was continued for 20 hours. The solution viscosity was 210 cp at 30°C, and the isocyanate content was 7.5% by weight ( A partial adduct polyisocyanate solution (in terms of pure partial adduct) is obtained.

(H/NCO equivalent ratio = 0.25) This was coated on a mild steel plate and a glass plate to a thickness of 5 mils and dried at 140°C, whereupon it cured in 30 minutes. The pencil hardness according to JIS54Ol is H, and in the impact deformation test under the same conditions as Example 1, it was 50.
It was better than mine, and the Erichsen extrusion test also showed an excellent coating film of 8 ml or more. Further, no change was observed in the acid resistance, alkali resistance, and volatile oil resistance tests, and the coating film had excellent physical properties. Example 4 100 parts by weight of a uretdione group-containing polyisocyanate (uretdione group/isocyanurate group content ratio 60/40) of hexamethylene diisocyanate obtained using tributylphosphine as a catalyst with an isocyanate content of 21.5% by weight was mixed with ethyl acetate. / xylene C (weight ratio)) and 45 parts by weight of a solvent was mixed with 0.0% dibutyltin dilaurate as a catalyst.
While stirring the mixture at 50°C, a solution of 15.2 parts by weight of n-butyl alcohol dissolved in 5 parts by weight of ethyl acetate/xylene was added dropwise over 1 hour to obtain an adduct containing a uretdione group. Ta.

(0H/NCO equivalent ratio = 0.4) The solution viscosity of this product was 125 cp at 30°C, and the isocyanate content calculated as pure partial adduct was 9.0% by weight. This solution is extremely stable at room temperature, and when applied to a mild steel plate with a thickness of 5 mils and kept in a constant temperature dryer at 140°C,
It hardened within minutes and had a pencil hardness of F according to JIS K54Ol. This is probably because the uretdione ring was cleaved by heating and the isocyanate group was regenerated, resulting in a higher-than-expected crosslinking density. This product has excellent gloss and transparency, and as a result of measurement with a 6.35 mm 5009 load using a JISK54Ol impact deformation tester, no scars remain even at a drop distance of 50 CTrL, and it also shows over 8 mm in the Erichsen extrusion test, and has acid resistance, alkali resistance, It was also excellent in the volatile oil resistance test with no change at all. Example 5 100 parts by weight of a polyisocyanate containing uretdione groups (uretdione group/isocyanurate group content ratio 60/40) with an isocyanate content of 21.5% by weight was dissolved in 50 parts by weight of butyl acetate. Adding 6.3 parts by weight of ethylene glycol (0H/NCO equivalent ratio = 0.4) and 0.1 part by weight of dibutyltin dilaurate and reacting at 50°C for 1 hour, the resulting partial adduct had a solution viscosity of 140 cp at 30°C. The isocyanate content in terms of pure partial adduct was 4.9% by weight.

This solution was stable for long periods at room temperature. When this solution was applied to a thickness of 5 mils on a mild steel plate and dried at 140°C, it hardened in 30 minutes, the pencil hardness according to JISK54Ol was H, and the impact deformation test was 50CrfL or more under the same conditions as Example 1. Erichsen extrusion test is also 81! The coating film had excellent physical properties as described above, and other physical properties were also good. Example 6 Isocyanurate group-containing polyisocyanate obtained by polymerizing hexamethylene diisocyanate using a conventional trimerization catalyst (uretdione group/isocyanurate group content ratio 30)
/70 Isocyanate content 22.5 weight 01))10
0 parts by weight, 75 parts by weight of butyl acetate/xylene (kidney weight ratio), and 6.2 parts by weight of ethanol, and 0.05 parts by weight of dibutyltin dilaurate as a catalyst were added and reacted at 70°C for 1 hour with stirring. The solution viscosity of the obtained isocyanurate group-containing polyisocyanate partial adduct was 220 cp1, and the isocyanate content was 15.1% by weight in terms of pure partial adduct.

(0H/NCO equivalent ratio = 0.25) This solution is stable even when stored at room temperature for long periods of time. When this solution was applied to a thickness of 5 mils on a mild steel plate and dried at 120°C, it hardened within 15 minutes, and the pencil hardness according to JIS K54Ol was 2H.
It was hot. This coating film has excellent gloss, transparency, and adhesion, and has a 6.
The test result at 35mm 15009 load is 50CTIL
There was no change in the drop distance, and the Erichsen extrusion test was also excellent with a score of 8 or more. The chemical resistance is also excellent as in the above examples, and it also has heat resistance.
The coating film was stable even at temperatures around 300°C. Example 7 100 parts by weight of the polyisocyanate used in Example 6 was dissolved in 50 parts by weight of ethyl acetate, and 14.2 parts by weight of diethylene diglycol and 0.0 parts by weight of dibutyltin dilaurate were added thereto.
05 parts by weight (0H/NCO equivalent ratio 20.25)
When stirred at 70°C for 1 hour, the solution viscosity was 245 cp and the isocyanate content was 7.5% by weight in terms of pure partial adduct.
A partial adduct solution of .

Claims (1)

[Scope of Claims] 1. An aliphatic or alicyclic polyisocyanate having an average isocyanate group content of 2.5 or more, at least one active hydrogen-containing group selected from hydroxyl, amino, and carboxyl groups. A method for producing a thermosetting polyisocyanate partial adduct, which comprises reacting a compound having an active hydrogen-containing group/isocyanate group at a ratio such that the equivalent ratio of active hydrogen-containing group to isocyanate group is in the range of 0.05 to 0.8. 2 The equivalent ratio of active hydrogen-containing group/isocyanate group is 0.
1 to 0.4, the method for producing a partial adduct according to claim 1. 3. The method for producing a partial adduct according to claim 1, wherein the polyisocyanate is a polyisocyanate obtained from hexamethylene diisocyanate and water. 4. The method for producing a partial adduct according to claim 1, wherein the polyisocyanate is a polyisocyanate containing a uretdione group and an isocyanurate group obtained by polymerizing hexamethylene diisocyanate. 5 The content ratio of uretdione group/isocyanurate group is 6
The method for producing a partial adduct according to claim 4, wherein the ratio is 0/40 to 10/90. 6. The method for producing a partial adduct according to claim 1, wherein the active hydrogen-containing compound is glycolic acid. 7. The method for producing a partial adduct according to claim 1, wherein the active hydrogen-containing compound is ethylene glycol. 8. The method for producing a partial adduct according to claim 1, wherein the active hydrogen-containing compound is diethylene glycol. 9. The method for producing a partial adduct according to claim 1, wherein the active hydrogen-containing compound is an epoxy alcohol having a molecular weight of 500 to 5,000.