JPH0324508B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a one-component thick film type polyurethane paint, and more specifically, a blocking isocyanate compound (hereinafter abbreviated as blocking isocyanate) containing 60% by weight or more of polyphenylmethane polyisocyanate as an organic polyisocyanate, and an alicyclic compound as a curing agent. The present invention relates to a one-component thick-coating type polyurethane paint that uses a diamine, an alkylphenol, and/or a hydroxyl group-containing polyol, and/or an amine compound having a spiroacetal ring. Conventionally, as a one-component technology for polyurethane paints, isocyanate groups are partially reacted with an active hydrogen-containing compound, and then unreacted isocyanate groups are blocked (inactivated) to synthesize blocked isocyanate, which is then mixed with polyols, polyamines, etc. It is mixed to form a one-component paint that is stable at room temperature, and when heated during the baking process during use, a dissociation reaction occurs.
A method for producing a polyurethane paint is known that utilizes the principle of a so-called reversible reaction in which the original active isocyanate groups are regenerated. A typical example of blocked isocyanate is Coronate AP, which is a prepolymer obtained from 1 mol of trimethylolpropane (hereinafter abbreviated as TMP) and 3 mol of tolylene diisocyanate (hereinafter abbreviated as TDI) to which 3 mol of phenol is added. Stable (manufactured by Nippon Polyurethane Industries) is widely used as a paint for coating electric wires. This is an example of using phenols as a blocking agent to dissociate at a relatively low temperature of 140°C or higher, but since phenols dissociate during baking and are released into the atmosphere, they are toxic. There are environmental health problems such as odors and odor. Therefore, there is a demand for blocking agents with low toxicity and odor, and blocking isocyanates using alcohols, lactams, etc. are being researched and developed. However, blocked isocyanates based on TDI using these blocking agents have a high dissociation temperature.
It has the disadvantage of requiring high temperatures of 170°C or higher.
In this case, even if a phenol or oxime is used as a blocking agent and an amine compound is used as a curing agent in order to dissociate at a low temperature, this has the disadvantage that storage stability, workability, etc. are reduced. . In addition, polyol-curing one-component paints are made using non-yellowing isocyanate prepolymers made from alicyclic diisocyanates such as isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate, and low-temperature dissociation blocking agents such as oximes and ethyl acetoacetate. is also commonly seen, but the reaction is slower than the TDI type, and it is only used for limited thin-film applications. Also, as a curing agent for blocked isocyanate,
If aliphatic primary or secondary amines are selected from amines, they may cause skin damage to the human body, are difficult to handle due to their hygroscopic properties, and the heat resistance of the cured coating film is low. However, satisfactory results have not been obtained in terms of flexibility, adhesion, etc. In the case of aromatic amines, many of them are solid or viscous liquid at room temperature, making them inconvenient to handle, and have drawbacks such as lower low-temperature dissociation ability than alicyclic amines, and yellowing during baking. In addition, acid amides synthesized by the reaction of fatty acids and aliphatic polyamines generally have a low vapor pressure and, as a result, are low in toxicity. Furthermore, because the acid amide itself is highly colored, its uses are limited and it has drawbacks such as poor storage stability. Therefore, as a result of intensive research, the present inventors reacted an organic polyisocyanate containing 60% by weight or more of polyphenylmethane polyisocyanate with an active hydrogen-containing compound to form an isocyanate group-terminated prepolymer. Blocked isocyanate with blocked isocyanate groups, 25 to 90% by weight of alicyclic diamine as a curing agent, and
A one-component thick-coat polyurethane paint that uses 10 to 75% by weight of alkylphenol and/or hydroxyl group-containing polyol and/or spiroacetal ring-containing amine compound.It has good storage stability and can be cured at a low temperature during baking. It is smooth and has no heat yellowing during baking or wrinkles at high film thickness (flakes are a phenomenon that causes wrinkles on the paint film after painting, and generally the thicker the film, the more likely it is to occur). The present invention was completed by discovering a one-component thick-coating polyurethane paint that can form a coating film. That is, the present invention provides: 1. In a one-component polyurethane paint, (A) polyphenylmethane polyisocyanate.
A blocked isocyanate obtained by reacting an organic polyisocyanate containing 60% by weight or more with an active hydrogen-containing compound to obtain an isocyanate group-terminated prepolymer, and blocking the terminal isocyanate groups with a lactam blocking agent, and (B) an alicyclic diamine as a curing agent. 25-90% by weight
and corresponds to 10-75% by weight. The present invention relates to a one-component thick-coating polyurethane paint characterized by using an alkylphenol and/or a hydroxyl group-containing polyol and/or an amine compound having a spiroacetal ring. The blocked isocyanate that can be used in the present invention can be obtained by reacting an organic polyisocyanate with an active hydrogen-containing compound to obtain an isocyanate group-terminated polypremer, and reacting the prepolymer with a blocking agent. The organic polyisocyanate that can be used in the present invention may be any polyisocyanate containing polyphenylmethane polyisocyanate alone or 60% by weight or more, such as carbodiimide-modified diphenylmethane diisocyanate,
Examples include TDI, xylylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, lysine diisocyanate, trimethylhexamethylene diisocyanate, hydrogenated TDI, and hydrogenated diphenylmethane diisocyanate. There are also isocyanate group-terminated prepolymers obtained by addition reaction with low molecular weight glycols such as ethylene glycol, diethylene glycol, 1,3-butylene glycol, dipropylene glycol, neopentyl glycol, glycerin, and TMP, such as Coronate L. (manufactured by Nippon Polyurethane Industries, NCO content 13.2%), Coronate
HL (manufactured by Nippon Polyurethane Industries, NCO content 12.8
%), HL-100 (Nippon Polyurethane Industries, NCO
There are polyisocyanates containing Biuret bonds, allophanate bonds, carbodiimide bonds, etc. in the molecule, and Coronate EH (manufactured by Nippon Polyurethane Industries, Ltd.).
Trimers such as NCO21.2%) can also be used, and one or a mixture of two or more of these can also be used. As the polyphenylmethane polyisocyanate used in the present invention, for example, Millionate MR-100 manufactured by Nippon Polyurethane Industries, Millionate
There are MR-200, Millionate MR-300, Millionate MR-400, etc. Examples of active hydrogen-containing compounds that can be used in the present invention include polyester polyols, polyether polyols, etc., which have a molecular weight of 150 to 5000 and a hydroxyl value of 30.
Molecular weight in castor oil and its derivatives ~500
900~2000, hydroxyl value 160~370, acrylic polyol with molecular weight 3000~10000, hydroxyl value 15~
100, and others such as epoxy resins, butyral resins, polybutadiene polyols, etc.
Moreover, the above-mentioned low molecular weight glycols can be used alone or in combination. The reaction of the isocyanate group-terminated prepolymer that can be used in the present invention involves the reaction of an organic polyisocyanate and an active hydrogen-containing compound at 60 to 80°C for 3 to 30 minutes.
It can be obtained by reacting for 6 hours.
It is necessary to keep the content in the range of 3 to 10%, preferably 3.5 to 9%. This is to make the effective NCO content of the blocking isocyanate 2 to 8%, and the effective NCO content of the blocking isocyanate has a large effect on the underside of the paint film.
When the NCO content is less than 2%, the viscosity increases, resulting in poor workability and poor compatibility with other resins.On the other hand, as the NCO content exceeds 8%, Since the amount of blocking agent required to be added increases, this blocking agent scatters during baking, resulting in a lowered edge limit and a tendency to make it difficult to obtain a high film thickness. A catalyst can be added to the reaction of the isocyanate group-terminated polypremer as necessary. As a catalyst, dibutyltinjilaunaut (hereinafter referred to as
DBTDL), zinc naphthenate, calcium octenoate, etc. are 0.001 to 1% by weight based on the resin content.
used. The reaction for obtaining the blocked isocyanate that can be used in the present invention is accomplished by reacting the isocyanate group-terminated prepolymer with the blocking agent at 70 to 150°C for 4 to 10 hours.
Blocking agents used in blocking isocyanates include, for example, methanol, ethanol, n-
Particularly preferred blocking agents include alcohol-based blocking agents such as butanol, lactam-based blocking agents such as ε-caprolactam, β-propiolactam, γ-butyrolactam, and δ-valerolactam, and active methylene-based blocking agents such as diethyl malonate and methyl acetoacetate. It is a lactam type. The catalyst used in the synthesis of the isocyanate group-terminated polypremer can be used in the reaction, if necessary. Further, the reaction of the isocyanate group-terminated polypremer or the prepolymer to a blocked isocyanate can be carried out in the presence or absence of a solvent. Examples of solvents include ester-based solvents such as ethyl acetate, butyl acetate, and cellosolve acetate (hereinafter abbreviated as cello-acetate); aromatic solvents such as toluene and xylene;
Ketones such as methyl ethyl ketone and methyl isobutyl ketone are typically used, but ether alcohols such as butyl cellosolve can also be used as diluents. Examples of the curing agent that can be used in the present invention include alkylphenols and/or hydroxyl group-containing polyols and/or amine compounds having spiroacetal rings corresponding to 25 to 90% by weight of alicyclic diamine and 10 to 75% by weight. There is. When the amount of alicyclic diamine exceeds 90% by weight, yellowing (burning) due to the diamine and coating film hardness increase, resulting in poor processing properties (DuPont impact, Erichsen,
bending test, etc.) becomes inferior. If the amount of alicyclic diamine is less than 25% by weight, the reaction slows down, so the curing temperature must be set as high as 170 to 200°C. Therefore, at around 140°C, curing will be insufficient and physical properties (resistance) will deteriorate. Solvent resistant, hot water resistant,
(chemical resistance, etc.) will decrease. As the alicyclic diamine, for example, 1.3
-Diaminocyclohexane, 1,4-diaminocyclohexane, 4,4'-diaminodicyclohexylmethane, 4,4'-diaminocyclohexylpropane, 3-aminomethyl-3,5,5-trimethyl-1-cyclohexylamine, 3,3 '-Dimethyl-4,4'-diaminodicyclohexylmethane (manufactured by BASF Corporation, trade name Laromin C-260), also manufactured by BASF Corporation, trade name Laromin Z-172 (this is a cured product consisting of Laromin C-260 and an alkyl phenol). Calculating the alicyclic diamine from the amine value using the agent is approximately 35%.
Corresponds to inclusion. ) etc. are used. Examples of alkylphenols include those in which the alkyl group has 3 to 12 carbon atoms, such as P-isopropylphenol, P-tert-butylphenol,
P-tert-amylphenol, P-tert-octylphenol, P-nonylphenol, etc. are used. Examples of hydroxyl group-containing polyols include glycol,
There are monomolecular compounds such as triols, polyester polyols, polyether polyols, castor oil and its derivatives, epoxy resins and those containing nitrogen in their structure.Glycols and triols include ethylene glycol, propylene glycol, 1・3-Butylene glycol, diethylene glycol, dipropylene glycol,
TMP, glycerin, etc. are used. As polyester polyols, ethylene glycol, diethylene glycol, triethylene glycol, 1-2-propylene glycol, trimethylene glycol, 1-3 or 1-4 butylene glycol, hexamethylene glycol, decamethylene glycol, glycerin, TPM, pentaerythritol, sorbitol One or two monomolecular compounds having two or more hydroxyl groups such as
one or more monomolecular compounds having two carboxyl groups such as adipic acid, succinic acid, malonic acid, maleic acid, tartaric acid, pimelic acid, sebacic acid, phthalic acid, terephthalic acid, isophthalic acid, trimellitic acid, etc. Those obtained by a condensation reaction with two or more species, and lactone esters obtained by ring-opening polymerization such as ε-caprolactone and ε-valerolactone are used. As polyether polyols, ethylene glycol, propylene glycol, diethylene glycol, 1,3-butylene glycol, TMP,
Those obtained by addition polymerization of one or more polyhydric alcohols such as glycerin, hexanetriol, pentaerythritol, and sorbitol with alkylene oxides such as ethylene oxide, propylene oxide, and butylene oxide are used. In addition, castor oil and derivatives thereof, epoxy resins, etc. can also be used. In addition, as a substance containing nitrogen in its structure, N・N・N′・N′-tetrakis(2-hydroxypropyl)ethylenediamine (manufactured by Asahi Denka Kogyo, trade name: Quadrol,
EDP-450, EDP-650, BM-54, etc.) are used. As an amine compound having a spiroacetal ring, 3,9-bis(3-aminopropyl)-
2,4,8,10-tetroxaspiro[5.5]undecane (manufactured by Ajinomoto Co., Ltd., product name ATU, manufactured by Yuka Ciel Co., Ltd., product names Epomate N-001, Epomate N-002, Epomate B-001, Epomate B-
002 etc.). The appropriate amount of the curing agent to be used is a curing agent:blocking isocyanate equivalent ratio of 7/10 to 15/10, particularly preferably 8/10 to 12/10. When the equivalent ratio is less than 7/10, the coating film tends to foam, and when it is greater than 15/10, the coating film tends to be difficult to cure. In the one-component thick coating type polyurethane paint according to the present invention, colorants, extenders, solvents, plasticizers, etc. can all be applied, and various additives,
A thickener and the like can be made into a paint using a known mixing device (three-roll, pot mill, sand grind mill, etc.). The baking coating of the paint prepared as described above is carried out at a relatively low temperature of 90°C or higher, particularly preferably 100 to 170°C, and usually within 120 minutes, particularly preferably 60°C.
It can be done within minutes. In addition, it has characteristics such as being able to obtain a smooth coating film that does not cause wrinkles or yellowing due to heating even if it is applied to a high film thickness of 300μ or more in one coat and cured, and it is free from chipping. In addition to being suitable as a protective coating, it can also be used in a wide range of applications, including precoating for metals, coatings for electric wires, and coatings for plastics. The present invention will be explained below with reference to Examples. Parts and percentages in the examples are parts by weight unless otherwise specified.
Weight%. Examples 1 to 14 In a reactor equipped with a thermometer, a reflux condenser, a nitrogen seal tube, and a stirrer, organic polyisocyanates were added in the proportions shown in Table 1 (Examples 1 to 10). Examples 1 to 7 and 10 were solvents, In Examples 2 to 4 and 7 to 10, a catalyst was added, the temperature was raised to 45°, and a predetermined amount of polyol was added dropwise with stirring at the same temperature to react under the conditions shown in the table to obtain isocyanate-terminated prepolymers. Next, a predetermined amount of blocking agent shown in Table 2 (Examples 1 to 10) was added to the prepolymer, followed by a catalyst and reacted under the conditions shown in the same table to obtain blocked isocyanate. Furthermore, a curing agent was added to the blocked isocyanate in the proportions shown in the same table (Examples 1 to 14), and after mixing, a one-component paint was prepared.

【table】

【table】

【table】

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[Table] Comparative Examples 1 to 3 Blocked isocyanate was synthesized and a one-component paint was formulated in the same reactor as in the example using the formulations shown in Tables 3 and 4 and in the same manner as in the example.

【table】

【table】

[Table] Comparative Examples 4 to 9 The blocked isocyanates of each example shown in Table 5 were used in the same reactor as in the example, and a curing agent was mixed to formulate a one-component paint.

[Table] Storage stability test One-component paints of Examples 1 to 14 and Comparative Examples 1 to 9
The product was placed in a 500 ml glass bottle, sealed tightly, and stored at 45°C for 12 months, and the appearance, NCO content, viscosity, etc. were tested and comprehensively evaluated. The results are shown in Table 6. Application example: Test of paint film armpit limit The one-component paints of Examples 1 to 14 and Comparative Examples 1 to 9 were diluted with vinegar cello to a solid content of 65%, and filmed using airless spray (primary pressure 5.0 Kg/cm ² ). Thickness 100, 150, 200, 250,
300, 350, 400, 500 (μ) on a tin plate (100mm x 300mm x 0.2mm) at room temperature.
After being allowed to stand for 10 minutes, the coating was cured at 140°C for 20 minutes, and the coating film was tested for its peeling limit. The results are shown in Table 6. Paint film performance test (including the limit after coating) For the one-component paints of Examples 1 to 14 and Comparative Examples 1 to 9, baryta BC (manufactured by Sakai Chemical, barium sulfate) and CR 90 (manufactured by Ishihara Sangyo, titanium oxide) was added at a weight ratio of 4:1 to 50% and mixed with a desolver, and then dispersed with a grind gauge using a triple roll so that the particle size was 40 to 50 μm. Adjust the application solids of these paints to 65-70% with a mixture of vinegar cello: xylene = 1:1, and dry them to 300-400μ with an airless spray (primary pressure 4Kg/cm ² , pressure ratio 1:30). Apply it on a tin plate (100mm x 300mm x 0.2mm) to a film thickness of 10
After being left at room temperature for a minute, it was cured in an oven at 140°C for 30 minutes to obtain a test piece. The test results are shown in Table 6.

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Claims (1)

[Scope of Claims] 1. In a one-component polyurethane paint, (A) polyphenylmethane polyisocyanate is
An isocyanate group-terminated prepolymer is obtained by reacting an organic polyisocyanate containing at least % by weight with an active hydrogen-containing compound, and a blocked isocyanate whose terminal isocyanate groups are blocked with a lactam blocking agent and (B) alicyclic diamine 25 as a curing agent. 1. A one-component thick-coating polyurethane paint characterized by using an alkylphenol and/or a hydroxyl group-containing polyol and/or an amine compound having a spiroacetal ring in an amount of ~90% by weight and 10~75% by weight.