JPH06206978A - Polyisocyanate curing agent, polyurethane coating composition and polyurethane adhesive composition using the same - Google Patents

Abstract

PURPOSE:To provide a low-viscosity polyisocyanate curing agent excellent in low-temperature stability, compatibility and reactivity, useful for coatings, adhesives, etc., containing a modified polyisocyanate formed by isocyanurate modification of part of a specific diisocyanate mixture. CONSTITUTION:The curing agent containing a modified polyisocyanate formed by isocyanurate modification of part of a mixture composed of (A) 10-90wt.% of a diphenylmethane diisocyanate mixture comprising (1) 10-90wt.% of 2,4'- diphenylmethane diisocyanate and (2) 90-10wt.% of 4,4'-diphenylmethane diisocyanate and (B) 90-10wt.% of tolylene diisocyanate. The second objective polyurethane coating composition can be obtained by blending this curing agent and a polyhydric hydroxyl compound.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyisocyanate curing agent excellent in low-temperature stability and compatibility with polyhydric hydroxyl compounds and solvents, and a composition useful as a coating and an adhesive using the same. Is.

[0002]

2. Description of the Related Art When various isocyanate compounds are used as a curing agent, for example, in the fields of metals, plastics, paints for woodworking, paints for magnetic recording media, and adhesives, the drying property and reaction of the coating film can be mentioned. Sex and low temperature stability are important factors. Therefore, aromatic isocyanates typified by tolylene diisocyanate (hereinafter abbreviated as TDI) and diphenylmethane diisocyanate (hereinafter abbreviated as MDI) are more preferable than aliphatic isocyanates typified by hexamethylene diisocyanate and isophorone diisocyanate. Mainly used.
Among these isocyanates, in the case of thick film type paints such as heavy anticorrosion paints and automobile chipping prevention paints,
Alternatively, in the case of a hot melt adhesive, MDI is generally used because MDI has a higher reactivity of isocyanate groups than TDI.

[0003]

[Problems to be Solved by the Invention] However, MDI
Is slower to dry than TDI. In addition, 4,4'-MDI, which is a typical MDI, lacks low temperature stability due to its strong crystallinity. In order to improve the insufficient drying property and low temperature stability of this MDI, various modifications such as urethanation and isocyanurate modification make MDI highly reactive, making it difficult to control the reaction and increasing the molecular weight to increase the viscosity. Cheap. Currently available MDI-based curing agents with good low temperature stability used for paints and adhesives
4,4'-MDI polymerization type, eg Millionate M
R-100 (Nippon Polyurethane Industry) or 4,4'-
There is an uretonimine carbodiimide type of MDI, for example, Millionate MTL (manufactured by Nippon Polyurethane Industry Co., Ltd.), but since both are 4,4′-MDI type, foaming easily occurs during thick film coating due to their high reactivity, The appearance of the coating film tended to be inferior. On the other hand, as a currently available TDI-based low temperature stable curing agent used for paints and adhesives, there is a urethane oligomer of TDI polyol such as Coronate L (manufactured by Nippon Polyurethane Industry Co., Ltd.), but it is TDI-based. Still MD
The reaction tended to be slower than that of system I.

[0004]

The inventors of the present invention have found that the curing agent has low temperature stability, compatibility with polyvalent hydroxyl compounds and solvents, viscosity when an isocyanate group is modified, reactivity,
Further, in order to improve the performance, workability, adhesiveness, etc. of paints or adhesive coatings using the same, as a result of repeated studies on MDI and TDI, 2,4'-MDI and 4,4'- The inventors have found that the improvement can be achieved by using a mixture of an MDI mixture containing MDI in a specific ratio and TDI in a specific ratio and modifying the mixture, and arrived at the present invention.

That is, the present invention relates to a polyisocyanate curing agent containing a modified polyisocyanate obtained by isocyanurate-forming a part of a mixture of 10 to 90% by weight of MDI mixture and 90 to 10% by weight of TDI. The mixture contains 10% to 90% by weight of 2,4'-MDI and 4,4'-
The polyisocyanate curing agent is characterized by comprising 90 to 10% by weight of MDI.

The present invention is based on 10 to 90% by weight of MDI mixture.
A polyisocyanate curing agent comprising a modified polyisocyanate obtained by isocyanurate-forming and uretonimine-ized and / or carbodiimidated part of a mixture of 90 to 10% by weight of TDI, wherein the MDI mixture is 2,4 '. -MDI 10-90% by weight and 4,4'-M
The polyisocyanate curing agent is characterized by comprising DI of 10 to 10% by weight.

The present invention comprises 10-90% by weight of MDI mixture.
A polyisocyanate curing agent comprising a modified polyisocyanate in which a part of a mixture of 90% by weight and TDI of 90 to 10% by weight is urethanized and isocyanurate with a polyol, wherein the MDI mixture is 2,4'-MDI1.
The polyisocyanate curing agent comprises 0 to 90% by weight and 4,4'-MDI of 90 to 10% by weight.

The present invention comprises 10-90% by weight of MDI mixture.
A polyisocyanate curing agent comprising a modified polyisocyanate urethanized with a polyol, and isocyanurate, and uretoniminated and / or carbodiimidated, a part of a mixture of 90 to 10% by weight of TDI with MDI mixture is 2,4'-
MDI 10 to 90% by weight and 4,4'-MDI 90 to 10
The above-mentioned polyisocyanate curing agent is characterized in that it is comprised by weight%.

The present invention is also a polyurethane coating composition or polyurethane adhesive composition containing a polyhydric hydroxyl compound and each of the above polyisocyanate curing agents.

For the preparation of the modified polyisocyanates contained in the polyisocyanate curing agent according to the invention, a mixture of 10 to 90% by weight of MDI mixture and 90 to 10% by weight of TDI, preferably 20 to 80% by weight of MDI mixture and TDI.
A mixture with 80 to 20% by weight is used. As an MDI mixture, 2,4'-MDI 10 to 90% by weight and 4,4 '
-MDI 90 to 10 wt% mixture, preferably 2,
20% to 80% by weight of 4'-MDI and 4,4'-MDI80
~ 20 wt% mixture is used. The glass transition temperature (Tg) affects the drying property of the coating film, and the higher the Tg, the faster the drying property of the coating film tends to be. The TDI type has a high glass transition temperature (Tg), is excellent in drying property, and has good compatibility with a polyvalent hydroxyl compound and a solvent. On the other hand, the MDI type has a structure in which the methylene group between the two aromatic rings easily rotates, so it has a lower Tg and slower drying than the TDI type, but it has high reactivity, durability of the coating film, and chemical resistance. It has excellent properties and solvent resistance. Therefore, by using the MDI type and the TDI type together, it is possible to obtain a curing agent having a balance of various properties such as reactivity, compatibility with polyvalent polyhydroxyl compounds and solvents, and drying properties and appearance of the coating film. it can. Furthermore M
Of the DI mixtures, 2,4'-MDI is considered to be able to improve the low temperature stability because it becomes difficult to form an agglomerated structure due to urethane bonds due to its non-linear structure. Also, due to the effect of steric hindrance, the isocyanate group at the 2-position is slower than the isocyanate group at the 4-position, so that the isocyanurate-forming reaction can be easily controlled, and at the same time,
In the modified polyisocyanate obtained, the isocyanate group at the 2-position, which has a relatively slow reaction, is present at the terminal. Therefore, compared with the modified polyisocyanate obtained only from 4,4′-MDI, the field of wood coatings is particularly high. It is considered that foaming due to a reaction with water, which is a problem in the field of heavy-duty anticorrosive paints, is less likely to occur, and an effect of improving the appearance is obtained. Therefore, if the weight ratio of the MDI mixture to TDI is more than 90% by weight, the compatibility with the polyvalent hydroxyl compound and the solvent becomes poor. When the weight ratio of the MDI mixture to TDI is less than 10% by weight,
As the reactivity with polyvalent hydroxyl compounds slows down,
The appearance is poor, such as lack of a long-awaited feeling that can be said to be a thick coating feeling of the coating film. Also, for 4,4'-MDI, 2,
When the weight ratio of 4'-MDI is less than 10% by weight and 90
When the content is more than 10% by weight, the effect of 4,4'-MDI or 2,4'-MDI becomes too large, and the polyisocyanate curing agent excellent in low temperature stability aimed at by the present invention cannot be obtained. Further, when the weight ratio of 2,4'-MDI to 4,4'-MDI is more than 90% by weight, the non-linear structure makes it difficult to form an agglomerated structure due to hydrogen bond of urethane bond, resulting in hardness of the coating film. Run out.
When the weight ratio of 2,4'-MDI is less than 10% by weight, it is difficult to control the reaction due to the high reactivity of 4,4'-MDI, and the resulting curing agent is compatible with polyvalent hydroxyl compounds and solvents. Becomes worse. As TDI, TD
Either the I isomer alone or a mixture of them in any proportion can be used. As a TDI isomer,
Specific examples include 2,4-TDI and 2,6-TDI.

When an isocyanurate bond is introduced into isocyanate, Tg becomes higher and the drying property tends to be faster than when a urethane bond is introduced. In order to improve the drying property of the coating film, the low temperature stability, etc., tetramethylammonium hydroxide, phenyltrimethylammonium hydroxide, and some of the isocyanate groups of the mixture of MDI and TDI can be converted into isocyanurate bonds. Quaternary ammonium salts such as β-hydroxypropylmethylammonium formate or fatty acid metal salts such as potassium octylate, potassium naphthenate and magnesium naphthenate, and 1,3,5-tris (dimethylaminopropyl) -S-hexa A known isocyanurate-forming catalyst such as a triazine compound such as hydrotriazine, and an amine compound such as triethylamine, dimethyloctylamine, diazabicycloundecene, or the like is used. It is preferable to use a cocatalyst for the isocyanurate-forming reaction, and as such a cocatalyst, phenol which is a phenolic hydroxyl compound, cresol, and the like,
Examples thereof include alcoholic hydroxyl compounds such as ethanol and cycloethanol. The isocyanurate-forming catalyst was 0.0 based on the mixture of MDI and TDI.
It is preferable to use 0.01 to 1.0% by weight, particularly 0.01 to 0.3% by weight, and the isocyanurate-forming cocatalyst is 0.01 to 0.3% by weight, particularly 0.1 to 0. Three
It is preferred to use weight percent. The reaction temperature for isocyanurate formation is preferably about 50 to 120 ° C. When the isocyanurate-forming reaction proceeds too much, the viscosity of the product increases, and a composition excellent in compatibility with the polyvalent hydroxyl compound or the solvent, which is a feature of the present invention, cannot be obtained. The isocyanurate-forming reaction is terminated by adding a strong acid such as phosphoric acid or sulfuric acid when the target NCO content is reached.

In the modified polyisocyanate contained in the polyisocyanate curing agent of the present invention, if further low temperature stability is desired, it is effective to further introduce a uretonimine bond and / or a carbodiimide bond. If more compatibility with the polyvalent hydroxyl compound or solvent is desired, it is effective to introduce a urethane bond. In addition, the modified polyisocyanate, together with the isocyanurate bond and the urethane bond,
Introducing a uretonimine bond and / or a carbodiimide bond is more preferable because it is possible to obtain a type which is particularly excellent in compatibility with polyvalent hydroxyl compounds and solvents and stability at low temperature. As the uretonimine carbodiimidization catalyst, any catalyst having a function of causing an isocyanate group to undergo an aggregation reaction to form a uretonimine bond and / or a carbodiimide bond can be used. For example, phosphorene oxide derivatives such as 1-phenyl-3-methyl-2-phospholen-1-oxide and ethylmethylphosphorene oxide are particularly preferable.
The amount of uretonimine carbodiimidization catalyst used is M
0.001 to the mixture of DI mixture and TDI
1.0% by weight is preferred, especially 0.01-0.3% by weight
Is preferred. The reaction temperature for the uretonimine carbodiimidization is preferably about 40 to 120 ° C. When the uretonimine carbodiimidization reaction proceeds too much, the viscosity of the product increases, and a composition excellent in compatibility with the polyvalent hydroxyl compound and the solvent, which is a feature of the present invention, cannot be obtained. The uretonimine carbodiimidization reaction is stopped by tracking the content by measuring the content, and when the target NCO content is reached, for example, trichlorosilane is added.

In producing the modified polyisocyanate contained in the polyisocyanate curing agent of the present invention, the polyol for introducing a urethane bond preferably has a molecular weight of 62 to 5,000. For example, ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6
-Hexanediol, 2-ethyl-1,3-hexanediol, neopentyl glycol, 1,3,5-trimethyl-1,3-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, 2 , 2-diethyl-
1,3-propanediol, 2-n-butyl-2-ethyl-1,3-propanediol, diethylene glycol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, or ethylene oxide or propylene oxide of bisphenol A Examples thereof include glycols such as adducts. The temperature of the urethanization reaction is usually selected from the range of 50 to 90 ° C. A catalyst for the urethanization reaction is not particularly required, but in some cases, a catalyst of dibutyltin dilaurate, naphthex calcium, or an amine compound such as triethylamine, dimethyloctylamine, or diazabicycloundecene may be used. It is effective. If the urethanization reaction proceeds too much, the viscosity of the product increases, and a composition excellent in compatibility with the polyvalent hydroxyl compound and the solvent, which is the feature of the present invention, cannot be obtained. Follow the measurement and stop the reaction when the target NCO content is reached.

The urethanization rate of the modified polyisocyanate contained in the polyisocyanate curing agent of the present invention is preferably 20 mol% or less, more preferably 18 mol% or less, based on all isocyanate groups. However, this ratio depends on the NCO content (mol) at the start of the reaction and the NCO content at the end of the urethanization reaction.
The value obtained by subtracting the content (mol) is divided by the NCO content (mol) at the start of the reaction and multiplied by 100. When the urethanization rate exceeds 20 mol%, the amount of isocyanurate bond formed thereafter becomes relatively small, and the advantage cannot be fully utilized. Uretonimine and /
Alternatively, the carbodiimidization rate is preferably 1 to 25 mol%, and particularly preferably 2 to 20 mol% based on all the isocyanate groups for the same reason as in the urethane conversion rate. This ratio is 100 times the value obtained by subtracting the NCO content (mol) at the end of the uretonimine and / or carbodiimidization reaction from the NCO content (mol) at the start of the reaction, divided by the NCO content (mol) at the start of the reaction. It is the value. The isocyanurate conversion rate is preferably from 15 to 70 mol%, and more preferably from 20 to 65 mol%, based on all isocyanate groups. If the isocyanurate conversion rate is lower than 15 mol%, unreacted MDI will remain, which may cause storage stability, especially crystal precipitation over time at low temperature. The molecular weight of the product, the number of functional groups increase, the solubility in solvents, the compatibility with polyvalent hydroxyl compounds deteriorates,
Either case is not preferable. The above ratio is a value obtained by dividing the value obtained by subtracting the NCO content (mol) at the start of the reaction from the NCO content (mol) at the start of the reaction by 100 times the NCO content (mol) at the start of the reaction. When the modified polyisocyanate has an isocyanurate bond, a urethane bond, and / or a uretonimine bond and / or a carbodiimide bond, the total modification ratio is preferably 80 mol% or less of all isocyanate groups.

In these reactions, an inert solvent commonly used in the polyurethane industry, for example, an aromatic solvent such as toluene and xylene, a ketone solvent such as methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, ethyl acetate,
Ester solvents such as butyl acetate and isobutyl acetate, ethylene glycol ethyl ether acetate, propylene glycol methyl ether acetate, 3-methyl-3
-Glycol ether ester solvents such as methoxybutyl acetate and ethyl-3-ethoxypropionate,
Ether solvents such as tetrahydrofuran and dioxane may be used alone or in combination of two or more. By selecting the solvent to be used, the viscosity can be adjusted according to the usage conditions.

The polyhydric hydroxyl compound used in the coating composition and adhesive composition of the present invention preferably has a molecular weight of 500 to 100,000 having two or more hydroxyl groups in the molecule. For example, 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, polyurethane polyol,
Examples thereof include cellulose acetate butyrate polyol and fluorine-containing polyol. Among these, in terms of coating film performance (gloss, texture, hardness, flexibility, durability, etc.), workability (dryability, reactivity, etc.), cost, etc., saturated or unsaturated polyester polyols, saturated polyester polyols, etc. Alternatively, unsaturated oil-modified or fatty acid-modified alkyd polyols and acrylic polyols are preferable. In the coating composition of the present invention, the compounding ratio (molar ratio) of the polyisocyanate curing agent and the polyvalent hydroxyl compound is isocyanate group / active hydrogen group =
The range of 0.5 to 2.0 is preferable, the range of 0.8 to 1.7 is particularly preferable, and the range of 0.8 to 1.3 is the most preferable. In the adhesive composition of the present invention, the compounding ratio (molar ratio) of the polyisocyanate curing agent and the polyvalent hydroxyl compound is as follows: isocyanate group / active hydrogen group = 0.5 to 1
The range of 2.0 is preferable, and the range of 0.8 to 10.0 is particularly preferable. The coating composition and adhesive composition of the present invention include a curing accelerator, a retarder, and a curing accelerator commonly used in the lacquer industry.
It may contain various additives such as an ultraviolet absorber, an antioxidant, a leveling agent, various pigments and the like. Furthermore, this paint or adhesive can be applied by a conventional coating method which has been conventionally used. For coating, an airless spray machine, an air spray machine, an electrostatic coating machine, dipping, a roll coating machine, a brush, etc. Can be used.

[0017]

INDUSTRIAL APPLICABILITY According to the present invention, a mixed polyisocyanate curing agent of MDI and TDI having a relatively low viscosity, excellent stability at low temperature, compatibility with polyhydric hydroxyl compounds and solvents, reactivity, etc. Can be provided. The polyurethane coating composition and polyurethane adhesive composition of the present invention comprising this curing agent and a polyhydric hydroxyl compound can be applied thicker in one time than conventional paints and adhesives, and the limit of sagging and sagging can be achieved. And the workability such as the coating performance such as the appearance of the coating and the drying property are good, or the adhesiveness is excellent. Therefore, it can be applied to a wide range of fields such as metals, plastics, concrete, wood, audio tapes, video tapes, magnetic recording media such as floppy disks, etc., and can widely contribute to the industrial world.

[0018]

Next, the present invention will be further described with reference to Examples and Comparative Examples. "Parts" and "%" in Examples and Comparative Examples mean "parts by weight" and "% by weight" unless otherwise specified. Examples 1 to 10 and Comparative Examples 1 to 9 A four-necked flask equipped with a stirrer, a thermometer, and a reflux condenser was charged with various raw materials shown in Table 1, Table 2, Table 3, and Table 4. That is, in Examples 1 to 5, isocyanate was dissolved in a solvent, an isocyanurate-forming catalyst was added, and an isocyanurate-forming reaction was carried out. Examples 6-8
In, the isocyanate was dissolved in a solvent, the polyol was charged, and the urethanization reaction (2 to 5 hours at 50 to 90 ° C.) was proceeded until the target NCO content was reached, and then isocyanurate as in Examples 1 to 5. An isocyanurate-forming reaction was carried out by adding a chlorination catalyst. In Example 9,
Isocyanate is dissolved in a solvent, a polyol is charged, and a urethanization reaction (50
After advancing at ~ 90 ° C for 2-5 hours), uretonimine
The carbodiimidization catalyst was added to proceed the uretonimine carbodiimidization reaction (1 to 5 hours at 40 to 90 ° C.) until the target NCO content was reached, and then the terminating agent was added to stop the reaction, and then Examples 1 to Similarly to 5, an isocyanurate-forming catalyst was added to carry out an isocyanurate-forming reaction. In Example 10, the isocyanate was dissolved in a solvent, and a uretonimine carbodiimidization catalyst was added to the uretonimine carbodiimidization reaction (40-
90 ° C. for 1 to 5 hours) until the target NCO content is reached, the reaction is stopped by adding the terminating agent, and then an isocyanurate-forming catalyst is added in the same manner as in Examples 1 to 5. The chemical reaction was carried out. When the reaction was carried out at 50 to 60 ° C. for about 7 to 8 hours to reach the target NCO content, an isocyanurate-stopping agent was added to stop the reaction, and a pale yellow reaction product was obtained. The properties of those reaction products are shown in Tables 1 and 2. In Comparative Examples 1 to 9 as well, the reaction was performed in the same manner as in Examples 1 to 10 to obtain reaction products. However, in Comparative Example 3, the reaction system of the modified isocyanurate-modified polyisocyanate was gelled and synthesis was impossible. The properties of those reaction products are shown in Tables 3 and 4.

[0019]

[Table 1]

[0020]

[Table 2]

[0021]

[Table 3]

[0022]

[Table 4]

Low temperature stability Various reaction products obtained in Table 1, Table 2, Table 3 and Table 4 were judged by the appearance state after standing for 2 months at -20 ° C. The results are shown in Table 5, Table 6 and Table 7. Compatibility with polyhydric hydroxyl compounds The various reaction products obtained in Table 1, Table 2, Table 3 and Table 4 were mixed with the polyvalent hydroxyl compounds shown in Table 5, Table 6 and Table 7 in a weight ratio of 1/1. After mixing and applying the obtained mixed liquid to a glass plate, the solvent was completely scattered over 120 ° C./1 hour, and the appearance of the obtained coating film was judged. The results are shown in Table 5, Table 6 and Table 7. Tolerance 5 g of each reaction product obtained in Table 1, Table 2, Table 3 and Table 4 was added little by little with various solvents listed in Table 5, Table 6 and Table 7 in a buret, and the mixture was shaken well to become cloudy. The number of m1 required at that time was calculated with the standing point as the end point. Then, the tolerance (solvent dilutability) corresponding to various solvents was calculated by the following formula. Tolerance = required m1 number / sample amount (5 g) The results are shown in Tables 5, 6 and 7.

[0024]

[Table 5]

[0025]

[Table 6]

[0026]

[Table 7] In Table 5, Table 6 and Table 7, Nipporan 133 is
Polyester polyol manufactured by Nippon Polyurethane Industry. Epicoat 1001 is an epoxy polyol manufactured by Yuka Shell.
CELNOVA BTH1 / 2 is nitrified cotton manufactured by Asahi Kasei.

Examples 11 to 20, Comparative Examples 10 to 18 Reaction products (modified polyisocyanate solutions) obtained in Examples 1 to 10 and Comparative Examples 1 to 9 as polyisocyanate curing agents, and Niprolane as polyvalent hydroxyl compounds. 1
Using 33 (polyester polyol manufactured by Nippon Polyurethane Industry, hydroxyl value 200, solid content 60%) and butyl acetate as a solvent, coating compositions and adhesive compositions having the compositions shown in Tables 8 and 9 were obtained.

[0028]

[Table 8]

[0029]

[Table 9]

Coating film test Steel sheets obtained by degreasing the coating compositions of Examples 11 to 20 and Comparative Examples 10 to 18 with trichlorethylene (JIS G3141).
<3141-SB>, specification: PF-1077, manufactured by Nippon Test Panel Industry Co., Ltd .; Bonde steel plate), and applied at 20 ° C., 65
Leave for 1 week in the environment of% RH, dry film thickness = 40-50
A μ coating film was formed. Then, the physical properties of the formed coating film were examined by the JIS K5400 test method. The results are shown in Tables 10 and 11. Presence or absence of foaming, presence or absence of fleshness ... Adhesiveness: Performed by a cross-cut tape method. Flexibility: Measured with a mandrel diameter of 2 mmφ. Impact resistance: Performed under the conditions of 1/2 inch and 1 kg. Reactivity: A plate (sample) on which a coating film was formed was set in a Soxhlet extractor, extraction operation was performed for 2 hours under reflux of acetone, and the gel fraction was determined by comparing the weights of the samples before and after extraction. Gel fraction = weight of sample after extraction × 100 / weight of sample before extraction

[0031]

[Table 10]

[0032]

[Table 11]

Adhesion Test Using the adhesive compositions of Examples 11 to 20 and Comparative Examples 10 to 18, an adhesion test was conducted as follows. That is, 3 mm thick polyurethane RIM (reactive injection molding) molded product, FRP, AB
S and Bonde steel plates were degreased with trichlorethylene, and the adhesive composition was applied thereon so that the dry film thickness was 40 to 50 μm. Then, it is pre-dried at 50 ° C. for 5 minutes to evaporate the solvent in the coating film, stack the above-mentioned plates of the same kind so that air bubbles do not enter, press-bond at 25 kg / cm ² , and press at 20 ° C., 65 ° C. Leave it in the environment of% RH for 1 week,
A dry coating film was obtained. After that, the sample was cut into a width of 25 mm, and in accordance with JIS K6854, Tensilon UTM-500 manufactured by Oriente Co., Ltd. was used and the adhesive strength (unit: kg / min) was set under the condition that the tensile speed was 100 mm / min.
25 mm) was measured. The results are shown in Table 12 and Table 13.
Shown in.

[0034]

[Table 12]

[0035]

[Table 13] In Tables 12 and 13, A indicates material failure and B indicates cohesive failure.

Example 21, Comparative Example 19 In combination with an adhesive resin Nipporan 2301 (a polyurethane resin manufactured by Nippon Polyurethane Industry Co., Ltd., a hydroxyl value = 1.6) which is also used as a resin for a magnetic tape binder, Example 6, Comparative Example 9 For each curing agent, an adhesive composition (binder) was prepared in the same manner as in Example 11 at a compounding ratio of Nipolan 2301 / curing agent = 15/1 (weight), and used as a base film of a magnetic tape. An adhesion test was performed on the used PET (polyethylene terephthalate) and RIM, FRP, ABS, or Bonde steel plate (unit of adhesive strength: kg / 25 mm). This compounding ratio (weight) corresponds to the isocyanate group of the curing agent / active hydrogen group of Nipolan 2301 = 9.7 (molar ratio) for both the curing agents of Example 6 and Comparative Example 9 in terms of molar ratio. The results are shown in Table 14.

[0037]

[Table 14]

Claims (6)

[Claims] 1. Diphenylmethane diisocyanate mixture 10-90% by weight and tolylene diisocyanate 90-
A polyisocyanate curing agent comprising a modified polyisocyanate obtained by isocyanurate-forming a part of a mixture with 10% by weight, wherein the diphenylmethane diisocyanate mixture is 2,
10 to 90% by weight of 4'-diphenylmethane diisocyanate and 4,4'-diphenylmethane diisocyanate 9
The polyisocyanate curing agent is characterized by comprising 0 to 10% by weight. 2. A diphenylmethane diisocyanate mixture of 10 to 90% by weight and tolylene diisocyanate of 90 to 90% by weight.
A polyisocyanate curing agent comprising a modified polyisocyanate obtained by isocyanurate-forming, and uretonimine-forming and / or carbodiimidating a part of a mixture with 10% by weight, wherein the diphenylmethane diisocyanate mixture is 2,
10 to 90% by weight of 4'-diphenylmethane diisocyanate and 4,4'-diphenylmethane diisocyanate 9
The polyisocyanate curing agent is characterized by comprising 0 to 10% by weight. 3. 10 to 90% by weight of diphenylmethane diisocyanate mixture and 90 tolylene diisocyanate.
A polyisocyanate curing agent comprising a modified polyisocyanate in which a part of the mixture with 10% by weight is urethanized and isocyanurate with a polyol, wherein the diphenylmethane diisocyanate mixture is 2,
10 to 90% by weight of 4'-diphenylmethane diisocyanate and 4,4'-diphenylmethane diisocyanate 9
The polyisocyanate curing agent is characterized by comprising 0 to 10% by weight. 4. Diphenylmethane diisocyanate mixture 10-90% by weight and tolylene diisocyanate 90-
A polyisocyanate curing agent comprising a modified polyisocyanate which is urethane-modified, isocyanurate-modified, and uretoniminated and / or carbodiimidated with a polyol to a part of a mixture with 10% by weight, wherein the diphenylmethane diisocyanate mixture is used. Is 2,
10 to 90% by weight of 4'-diphenylmethane diisocyanate and 4,4'-diphenylmethane diisocyanate 9
The polyisocyanate curing agent is characterized by comprising 0 to 10% by weight. 5. A polyhydric hydroxyl compound and claim 1,
A polyurethane coating composition comprising the polyisocyanate curing agent described in 2, 3, or 4. 6. A polyhydric hydroxyl compound and claim 1,
A polyurethane adhesive composition comprising the polyisocyanate curing agent described in 2, 3, or 4.