JP3419596B2 - Polyisocyanate curing agent and coating composition using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates to hexamethylene diisocyanate (hereinafter abbreviated as HDI) alone or H.
The present invention relates to a curing agent containing a modified polyisocyanate in which a portion of a mixture of DI and isophorone diisocyanate (hereinafter abbreviated as IPDI) is urethanized and then isocyanurate, and a coating composition using the same. .

[0002]

2. Description of the Related Art In the field of paints and coatings and adhesives, aliphatic diisocyanates such as HDI and IPDI,
Non-yellowing polyisocyanates derived from alicyclic diisocyanates are excellent in weather resistance, but among them, polyisocyanate type containing isocyanurate (hereinafter abbreviated as trimer) group (ring structure) is chemically ,
Since it has high thermal stability, particularly excellent weather resistance, and also excellent heat resistance and durability, it is widely used according to its application, and further development of applications is expected in the future.

The type containing a trimer group is more excellent in solvent solubility (hereinafter referred to as tolerance) than the bullet type or urethane type, and is soluble in nonpolar aromatic hydrocarbon solvents such as toluene and xylene. However, since ordinary solvents such as toluene and xylene have strong solubility enough to attack plastics, there are practical limitations in terms of solvent selectivity, such as coating cannot be repeated until the base is cured in the coating process. Is the current situation. As a method for solving these problems of the prior art, for example, Japanese Patent Publication No. 62-51968 and Japanese Patent Laid-Open No.
A method of modifying a diisocyanate with a dihydric alcohol as in the method of JP-A-2-215662, and JP-A-2-
As disclosed in JP-A-250872 and JP-A-4-306218, there has been proposed a method for improving the tolerance to a non-polar organic solvent by using a trimer type urethane-modified polyisocyanate obtained by modifying diisocyanate with a monohydric alcohol. There is. Furthermore, from the viewpoint of preventing malodor, non-polar organic solvents are not preferable because they have a pungent odor, and in the future there is a tendency to use odorless solvents such as paraffin hydrocarbons, which have good solubility. At present, no curing agent has been obtained.

[0004]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
As in the method proposed in Japanese Patent Application No. 968 and Japanese Patent Application Laid-Open No. 62-215662, diisocyanate is converted to C _{10 to} C _40.
When modified with a dihydric alcohol, the resulting modified polyisocyanate has a large molecular weight and thus has a high viscosity, and a non-polar organic solvent, especially a solvent with a high aniline point, which has no solubility, and an odorless solvent. And the tolerance is lowered, which is not preferable. In addition, the above-mentioned JP-A-
Similarly in the case of denaturing with a short monohydric alcohol such as C _{6 to} C ₉ as in the method of JP-A-306218.
The tolerance for the solvent is insufficient. Further, in the case of modification with a long monohydric alcohol such as C _{10 to} C ₅₀ as in the method of JP-A-2-250872, the tolerance to the solvent is higher than that in the method of JP-A-4-306218. Although it is improved, it is difficult to obtain a sharp molecular weight distribution effective for improving the tolerance because the urethanization reaction and the trimerization reaction by the monohydric alcohol simultaneously proceed, and the high molecular weight is easily obtained, and the tolerance to the solvent is also insufficient. In addition, the effect of an internal plasticizer due to the long monohydric alcohol is exhibited, and the hardness and the drying property of the resin itself are inevitably lowered.

All of the techniques disclosed in the above publications are aimed only at improving the tolerance to a non-polar organic solvent, and the long-chain modifier is used to improve the tolerance. Regarding the composition and the hardness when used as an adhesive composition, the drying property tends to be inferior because the long chain modifier is used as compared with the existing curing agent which is easily dissolved in a normal polar solvent. However, it was not a technique that considered dryness. That is, a non-polar organic solvent,
In particular, it is the current situation that a trimer type curing agent having a high aniline point, which has no solubility, and a high tolerance to an odorless solvent, and which has excellent hardness and dryness, has not been obtained. In the field of paints and adhesives, a decrease in hardness leads to a decrease in physical properties, and a decrease in drying property leads to a decrease in workability, which is generally regarded as a disadvantage, which is not preferable.

[0006]

Therefore, the present inventors have
Through intensive studies, we worked on the development of a trimer type that dissolves in non-polar organic solvents as well as odorless solvents, achieving "tolerance improvement" for these solvents compared to the conventional technology, and at the same time compatible with "hardness and dryness". In order to achieve the above, as a result of diligent research on its production, first, it was found that a part of the diisocyanate can be urethanized with a mixture of specific monohydric alcohols, and then the reaction can be carried out in the order of trimerization to solve the above problems, The present invention has been completed.

That is, the polyisocyanate curing agent of the present invention has a molar ratio of HDI to IPDI of 10: 0 to 4: 6.
Diisocyanate of 4-18 of all isocyanate groups
In the range of mol%, urethanized with a mixture of one monohydric alcohol having 8 to 12 carbon atoms and one or more monohydric alcohol having 13 to 20 carbon atoms, and then the trimer group molar concentration /
A modified polyisocyanate containing a modified polyisocyanate having a content of 0.5% by weight or less by removing unreacted diisocyanate after trimerization with a urethane group molar concentration in the range of 0.8 to 1.4. To do.

The polyisocyanate curing agent solution of the present invention is characterized by containing the above-mentioned polyisocyanate curing agent and a nonpolar organic solvent and / or odorless solvent.

The polyurethane coating composition of the present invention is a polyurethane coating composition comprising the above polyisocyanate curing agent or the above polyisocyanate curing agent solution and a polyhydric hydroxyl compound, which comprises a polyisocyanate group and a polyisocyanate group of a modified polyisocyanate. The molar ratio of the hydroxyl groups of the valent hydroxyl compound is in the range of 9: 1 to 1: 9.

[0010]

DETAILED DESCRIPTION OF THE INVENTION

In order to improve the tolerance to a non-polar organic solvent, it is necessary to lower the molecular weight and to sharpen the molecular weight distribution. For that purpose, it is necessary to limit the high molecular weight in trimerization, and for that purpose, prior to trimerization. The diisocyanate is converted to a urethane with a monohydric alcohol to reduce the number of functional groups. After that, dryness improvement,
It is better to trimmer to improve hardness and weather resistance,
By using a two-step reaction in this manner, JP-A-2-25
As in the method of Japanese Patent No. 0872, the molecular weight distribution does not become wide and the "tolerance" can be improved, and the "tolerance" and "hardness and hardness" can be controlled by controlling the molar concentration of the trimer group and the urethane group. It is possible to achieve both "dryability".

The diisocyanate used to synthesize the modified polyisocyanate in the present invention is HDI alone or a mixture of HDI and IPDI. That is, diisocyanate of HDI / IPDI = 10/0 to 4/6 (molar ratio) is used. When the HDI / IPDI molar ratio is smaller than 4/6 (for example, HDI / IPDI molar ratio = 3/7), the effect of IPDI becomes large in the obtained modified polyisocyanate, resulting in too high hardness and brittleness. Further, since IPDI has a lower reactivity than HDI, the reactivity as a curing agent decreases.

In the synthesis of the modified polyisocyanate of the present invention, a mixture of one monohydric alcohol having 8 to 12 carbon atoms and at least one monohydric alcohol having 13 to 20 carbon atoms is used to reduce the functionality of diisocyanate. In addition, the monohydric alcohol having a branched hydrocarbon group is particularly preferable among these, in order to further improve the tolerance to the nonpolar organic solvent and the odorless solvent. Examples include 2-ethylhexanol, ethyldimethyl-
1-hexanol, methyl-1-nonanol, dimethyl-1-octanol, tetramethyl-1-hexanol, 3-ethyl-4,5,6-trimethyloctanol, 4,5,6,7-tetramethylnonanol, 4 ，
5,8-trimethyldecanol, 4,7,8-trimethyltridecanol, tridecanol, tetradecanol, 2-hexyldecanol, 2-octyldodecanol, 2-decyltetradecanol, 2-hexadecyloctadecane Examples include Nol. If the monohydric alcohol has less than 8 carbon atoms, the tolerance tends to be insufficient (decreased). If the number of carbon atoms exceeds 20, the modified polyisocyanate tends to have a low isocyanate content (hereinafter, referred to as NCO content) or solidify at a low temperature in the case of stearyl alcohol.

The urethane conversion rate by diisocyanate is
It is necessary to be 4 to 18 mol% based on all isocyanate groups. When the urethanization rate is less than 4 mol%, the effect of introducing a urethane group is not obtained, and the tolerance to nonpolar organic solvents and odorless solvents is poor, and the phase with the solvent and the polyvalent hydroxyl compound when used as a coating composition Problems such as poor solubility and formation of a partially gelled product during the synthesis of the modified polyisocyanate occur. If the urethanization rate exceeds 18 mol%, the number of functional groups of the trimer body formed will decrease, and the features of the trimer group formed thereafter cannot be fully exerted, resulting in a hardness as a coating composition, The improvement in drying property and weather resistance cannot be achieved.

A mixture of one monohydric alcohol having 8 to 12 carbon atoms and one or more monohydric alcohol having 13 to 20 carbon atoms is used in order to increase only the tolerance to nonpolar organic solvents and odorless solvents. It is preferable to introduce a urethane group, but it is essential to introduce a trimer group in order to improve the hardness, drying property and weather resistance of a coating composition, and the trimer group molar concentration / urethane group molar concentration ( Ratio of 0.8 to 1.4 is necessary, and preferably 1.
It is 0 to 1.3. Specifically, this ratio is obtained by subtracting the NCO content (molar concentration) at the start of trimerization from the NCO content (molar concentration) at the start of trimerization, and the NCO content (molar concentration) consumed by the urethanization. It is the value divided by. By setting such a ratio, it becomes possible to show good tolerance not only to nonpolar organic solvents but also to odorless solvents such as paraffin hydrocarbons.

If the ratio (molar concentration of trimer group / molar concentration of urethane group) is less than 0.8, the reaction product obtained by the first step of urethanization has a low number of functional groups, and the hardness and dryness are also improved by subsequent trimerization. However, it becomes difficult to improve weather resistance. Since the number of functional groups of the modified polyisocyanate to be generated does not increase, when the coating composition is combined with a polyvalent hydroxyl compound, the cross-linking point decreases,
Hardness, durability, and physical properties of various coating films deteriorate, which is not preferable. Further, if this ratio is larger than 1.4, the number of functional groups of the modified polyisocyanate produced by trimerization, and further, the viscosity becomes too large and the molecular weight becomes large,
Not only the tolerance to the non-polar organic solvent and odorless solvent aimed at by the present invention is lowered, but also when the coating composition is combined with a polyvalent hydroxyl compound, the compatibility with the polyvalent hydroxyl compound is deteriorated and the coating composition is deteriorated. The function as a thing cannot be exhibited.

Usually, the trimerization catalyst is used in an amount of preferably 100 to 4000 ppm, more preferably 300 to 3000 ppm, based on the diisocyanate. Examples of effective trimerization catalysts in the present invention include:
Triethylamine, N-ethylpiperidine, N, N'-
Dimethylpiperazine, N-ethylmorpholine, tertiary amines such as Mannich bases of phenolic compounds, tetraalkylammonium hydroxides such as tetramethylammonium, tetraethylammonium, tetrabutylammonium and organic weak acid salts such as trimethylhydroxypropylammonium, Hydroxyalkyl ammonium hydroxides such as trimethylhydroxypropylammonium and triethylhydroxyethylammonium and weak organic acid salts such as acetic acid, propionic acid, butyric acid, caproic acid, capric acid, valeric acid, octylic acid, myristic acid and naphthenic acid. Examples thereof include alkali metal salts of acids. The trimerization temperature is usually selected from the range of 50 to 90 ° C.

After reaching the desired reaction rate, for example, phosphoric acid,
The trimerization reaction is stopped by adding a terminating agent such as methyl paratoluenesulfonate, and the free unreacted diisocyanate (monomer) present in the reaction mixture is extracted with, for example, n-hexane or 0.01 ~ 0.1
0.5% by weight at most by suitable means such as thin film distillation at 120-140 ° C. under high vacuum of Torr.
The residual modified polyisocyanate is removed to obtain the target modified polyisocyanate. In the modified polyisocyanate of the present invention, a part of all the isocyanate groups of the diisocyanate is urethanized so that the trimerization reaction is partially gelled due to the catalytic effect of the urethane group (polymer).
Proceed smoothly without generating.

Although the solvent that can be used in the polyisocyanate curing agent solution of the present invention is an inert solvent,
Of these, House (Shell Chemical, aniline point 15 ° C),
Swazol 310 (Maruzen Sekiyu, aniline point 16 ° C),
Essonaphtha No. 6 (exon chemical, aniline point 4
3 ° C), Loose (Shell Chemical, aniline point 43 ° C),
Examples of the solvent include isopentane, isohexane, isooctane, and isododecane, which are nonpolar organic solvents such as A solvent (manufactured by Nippon Oil Co., Ltd., aniline point: 44.5 ° C.) and / or odorless solvents. These may be used alone or in combination of two or more. The present invention also includes practical use in a state where these are mixed with a polar organic solvent.

The polyvalent hydroxyl compound used in the coating composition of the present invention is a polyvalent hydroxyl compound having two or more hydroxyl groups in the molecule and is soluble in a nonpolar organic solvent and / or an odorless solvent. Alternatively, those having a certain degree of affinity and dispersibility are preferable. Specifically, saturated or unsaturated polyester polyol, polycaprolactone polyol, saturated or unsaturated oil-modified or fatty acid-modified alkyd polyol, aminoalkyd polyol, polycarbonate polyol, acrylic polyol, polyether polyol, epoxy polyol,
Fluorine-containing polyol, further saturated or unsaturated polyester resin, polycaprolactone resin, saturated or unsaturated oil-modified or fatty acid-modified alkyd resin, aminoalkyd resin, polycarbonate resin, acrylic resin,
Polyether resin, epoxy resin, polyurethane resin,
Examples thereof include cellulose acetate butyrate resin and fluorine-containing resin. Among these, in terms of coating properties such as gloss, texture, hardness, flexibility and durability, workability such as drying property and curability, and economical efficiency, saturated or unsaturated polyester resin, saturated or unsaturated polyester resin, etc. Unsaturated oil-modified or fatty acid-modified alkyd resin and acrylic resin are preferable as the polyvalent hydroxyl compound used in the coating composition.

In the coating composition of the present invention, the molar ratio of the isocyanate group in the modified polyisocyanate to the hydroxyl group in the polyhydric hydroxyl compound is 9: 1 to 1: 9, preferably 6: 4 to 4: 6. It is a range. The composition of the present invention may contain, in addition to the solvent, various pigments and various additives commonly used in the lacquer industry. Furthermore, the composition of the present invention can be coated by a conventional coating method which has been conventionally performed, and for coating, an airless spray machine, an air spray machine, an electrostatic coating machine, dipping, a roll coater, a knife coater, a brush. Etc. can be used.

[0022]

The modified polyisocyanate according to the present invention comprises one monohydric alcohol having 8 to 12 carbon atoms and 1 carbon atom.
Since a part of the diisocyanate is urethanized by a mixture with one or more monohydric alcohols of 3 to 20 and then trimerized, the polyisocyanate curing agent of the present invention containing the diisocyanate has a low viscosity and a solvent or a polyhydric alcohol. Good compatibility with hydroxyl compounds. By using this polyisocyanate curing agent, it is possible to obtain a low-viscosity type polyurethane coating composition which has both tolerance to non-polar organic solvent and / or odorless solvent and curability, drying property, and weather resistance. , Metal, plastic, concrete,
It can be applied to a wide range of objects such as wood with good workability. When using the coating composition of the present invention, compared to when using a conventional polar solvent, lifting of the coating film when overcoating or repairing a coating film that is easily attacked by the polar solvent. It is possible to obtain a coating film having a good appearance without being generated.

[0023]

EXAMPLES 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, all "parts" mean "parts by weight", and "%" means "% by weight" unless otherwise specified.

[0024]Examples 1, 2 and Comparative Examples 1, 2, and 6-
8 Four-necked hood with stirrer, thermometer and reflux condenser
HDI (manufactured by Nippon Polyurethane Industry Co., Ltd .;
NCO content = 49.9%, solid content = 100%) or H
DI and IPDI (Huls Japan KK; NCO
Charge a mixture of content = 37.8%, solid content = 100%)
And then add monohydric or dihydric alcohol
I see. Heat this to 50-60 ° C with stirring and aim
The urethanization reaction proceeded until the NCO content of was reached. So
Then, as a trimerization catalyst, 2-
Add potassium ethylhexanoate to proceed the trimerization reaction,
When the specified NCO content (NCO content when the reaction was stopped) was reached
At the time of
In addition, the reaction was stopped and a pale yellow transparent reaction product solution was obtained.
It was Unreacted HDI and IPDI at 120-140 ° C,
Removed by thin film distillation at 0.01-0.05 Torr,
A product (modified polyisocyanate) was obtained. Each original used
Table 1, 2
Are shown together. Examples 1, 2 and Comparative Examples 6, 8 are products
A solvent because of its high viscosity (Nippon Oil Co., Ltd. non-polar
Diluted with a polar organic solvent). In addition, residual free HDI,
The IPDI content is determined by gas chromatography analysis.
I have

[0025]

[Table 1]

[0026]

[Table 2]

[0027]Comparative Examples 3 and 4 Four-necked hood with stirrer, thermometer and reflux condenser
HDI (manufactured by Nippon Polyurethane Industry Co., Ltd .;
NCO content = 49.9%, solid content = 100%)
And then 2-ethylhexanoic acid as a trimerization catalyst
Potassium and monohydric alcohol were charged. Do not stir this
Heat to 50-60 ° C to reach the target NCO content
Up to the urethane and trimerization simultaneous reactions. So
To reach the prescribed NCO content (NCO content at the time of stopping the reaction)
When it reaches, the termination agent, paratoluene sulfonic acid methyl ester
Is added to stop the reaction, and a pale yellow transparent reaction product solution is added.
Obtained. Unreacted HDI at 120-140 ° C, 0.01-
Removal by thin film distillation at 0.05 Torr to obtain product
It was Each raw material used, the amount charged, and the properties of the product
Table 1 shows them together. In addition, residual free HDI included
The rate was determined by gas chromatography analysis.

[0028]Comparative Example 5 Four-necked hood with stirrer, thermometer and reflux condenser
HDI (manufactured by Nippon Polyurethane Industry Co., Ltd .;
NCO content = 49.9%, solid content = 100%) 2,000
0 part and potassium trimerization catalyst 2-ethylhexanoate
Charge 1.4 parts and heat to 50-60 ° C with stirring.
When the NCO content = 44.4% was reached,
Add 0.6 parts of methyl paratoluenesulfonate and add
The reaction was stopped, and a pale yellow reaction product solution was obtained. Unreacted H
DI at 120 to 140 ° C., 0.01 to 0.05 Torr
Was removed by thin film distillation to obtain a reaction product (yield = 2
0%). The reaction product has an NCO content = 23.3%,
Free HDI content = 0.3% (gas chromatography
It was a pale yellow transparent liquid (from analysis). And the opposite
300 parts of the reaction product was added to 2-octane under the condition of 70 to 80 ° C.
Urethane with 15 parts of chilled decanol, NCO content =
21.5%, viscosity = 1,500 cSt / 25 ° C pale yellow
A product which is a transparent liquid is obtained. Note that the product
Conversion rate is 3 mol%, trimer group molar concentration / urethane group
The concentration (ratio) is 38. This product is Comparative Example 5.
The raw materials used, the amount charged, and the properties of the product.
Table 2 shows them.

[Tolerance] 5 g of the products obtained in Examples 1 and 2 and Comparative Examples 1 to 8 were added little by little with various solvents shown in Tables 3 and 4 using a buret, and the mixture was shaken well to become cloudy. End point,
The required number of ml of the solvent at that time was determined. Then, the tolerance (solvent dilutability) corresponding to various solvents was calculated by the following formula. Tolerance = number of ml of solvent required / sample volume (5
g). The larger this value, the better the solvent dilutability. The results are shown in Tables 3 and 4.

[0030]

[Table 3]

[0031]

[Table 4]

[0032]Examples 3 and 4, Comparative Examples 9 to 16 Products obtained in Examples 1 and 2 and Comparative Examples 1 to 8 (modified poly
(Isocyanate), and coatings shown in Tables 5 and 6
A composition was obtained. For example, the polyisocyanate of Example 1
When combined with Acridic A-825 using
An example of the coating composition is Example 3. Table 5 and Table
In 6, Acridic A-825 is
Non-polar organic with acrylic polyol manufactured by Ki Kagaku Kogyo Co., Ltd.
It is a type that is soluble in solvents. Hydroxyl value = 30mgKOH
/ G, solid content = 50%.

[0033]

[Table 5]

[0034]

[Table 6]

[Coating Film Test] A steel sheet (JIS G3141 <3141−) obtained by degreasing the above composition thus obtained with trichlorethylene.
SB>, specification: PF-1077, manufactured by Nippon Test Panel Industry Co., Ltd., hereinafter abbreviated as Bonde steel plate. ) And left for 1 week in an environment of 20 ° C. and 65% RH to form a coating film having a dry film thickness = 40 to 50 μm. Then, the coating film appearance, drying property, pencil hardness, adhesion and impact resistance of the formed coating film were measured according to the prescription of JIS K5400. The adhesive property was determined by the cross-cut tape method, and the impact resistance was determined by 1/2 inch and 500 g. The results are shown in Tables 7 and 8.

[0036]

[Table 7]

[0037]

[Table 8]

─────────────────────────────────────────────────── --- Continuation of front page (56) References JP-A-4-306218 (JP, A) JP-A-6-157709 (JP, A) JP-A-7-330860 (JP, A) JP-A-7- 268059 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C08G 18/78-18/79 C09D 175/04-175/10 C09J 175/04-175/10

Claims (3)

(57) [Claims] 1. A diisocyanate having a molar ratio of hexamethylene diisocyanate to isophorone diisocyanate of 10: 0 to 4: 6, which is one monohydric alcohol having 8 to 12 carbon atoms in the range of 4 to 18 mol% of all isocyanate groups. And urethanization with a mixture of one or more monohydric alcohols having 13 to 20 carbon atoms, and then isocyanurate-forming in the range of isocyanurate group molar concentration / urethane group molar concentration of 0.8 to 1.4. A polyisocyanate curing agent, characterized in that it contains a modified polyisocyanate having a content of 0.5% by weight or less by removing the diisocyanate in the reaction. 2. A polyisocyanate curing agent solution containing the polyisocyanate curing agent according to claim 1 and a non-polar organic solvent and / or an odorless solvent. 3. A polyurethane coating composition comprising the polyisocyanate curing agent according to claim 1 or the polyisocyanate curing agent solution according to claim 2 and a polyvalent hydroxyl compound, which comprises a polyisocyanate curing agent and a polyisocyanate curing agent. The polyurethane coating composition, wherein the molar ratio of the hydroxyl groups of the valent hydroxyl compound is in the range of 9: 1 to 1: 9.