JPS6342648B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to cationic water-soluble blocked isocyanate compounds useful as curing agents or crosslinking agents for water-based paints and the like. It is well known in the art to use blocked isocyanate compounds in place of free polyisocyanate compounds as curing agents in coatings and other applications. By using such blocked isocyanate compounds, it is not affected by moisture, there are no problems with pot life, the paint is easy to store, there is no change in viscosity during work, and solvent selectivity is improved. Advantages such as low pigment dispersibility and good pigment dispersibility can be obtained. However, these blocked isocyanate compounds are generally used as a thermosetting resin solution prepared by mixing and dissolving a solvent-type blocked isocyanate compound in a solvent-type polyol resin solution. Many examples have been reported in which the aqueous block polyisocyanate compounds in the prior art are used as crosslinking components of water-soluble resins using water as a medium. However, there are no examples of completely dissolved aqueous solutions being formed. In addition, a major feature of an aqueous dispersion of a block polyisocyanate compound is that water can be used as a medium, but it is difficult to form a uniform system by combining an aqueous dispersion of a block polyisocyanate compound with an emulsion or suspension of a resin. For example, when these water-based resin mixtures are used as paints, the coating film that is formed may have low gloss because the blocking isocyanate compound and resin are in a non-uniform system, or the curing reaction may not be sufficient and the coating may fail. There are drawbacks such as insufficient membrane performance. On the other hand, for example, there are methods in which a blocked isocyanate compound is dissolved in a resin dispersed in water, or methods in which a part of the resin composition is premixed with a block compound and then dispersed in water. It is difficult to obtain a homogeneous system in the method of dispersing in water. The water-soluble blocked isocyanate compound of the present invention is a completely new compound that has improved the above-mentioned drawbacks. That is, the compound of the present invention has the general formula (1) [In the formula, A represents a residue of a polyisocyanate compound, and R and R' may be the same or different,
represents a divalent hydrocarbon group having 2 to 6 carbon atoms (an oxygen atom may be present in the C-C bond of the main chain), Z represents a residue of an isocyanate group blocking agent, And n represents an integer from 1 to 6. ] It is a water-soluble blocked isocyanate compound obtained by neutralizing the compound represented by the following with an acidic substance. The compound represented by the general formula (1) can be obtained by reacting a hydroxyhydrocarbon disubstituted piperazine with an excess polyisocyanate compound and a blocking agent. In this case, the excess ratio (mole ratio) of the polyisocyanate compound is preferably within the range of 2 to 1.16, and the product obtained with the excess ratio (mole ratio) within such a range is actually the product of the present invention. Polyisocyanate skeleton as a characteristic part of the target compound: piperazine inside

[Formula] This corresponds to the degree of polymerization (n) of the structure, that is, when n in the above general formula (1) is 1 to 6. Here, if the excess ratio of the polyisocyanate compound exceeds 2, the amount of the block polyisocyanate compound that does not contain the above-mentioned piperazine structure will be too large, resulting in a water-solubilized block polyisocyanate compound, which is the object of the present invention. It will not be possible to obtain polyisocyanate compounds and, on the contrary, 1.16
If it is lower than this, the molecular weight of the target compound becomes large, and as a result, the active functional group concentration of the polyisocyanate compound becomes low, which is not preferable. Therefore, in order to obtain a good crosslinkable resin in the present invention, it is necessary that the excess ratio of the polyisocyanate compound be within the range of 2 to 1.16. The hydroxyhydrocarbon disubstituted piperazine has the general formula (2) It is a compound represented by, in the formula, R and
R' can be the same or different, for example -
CH ₂ - _{CH 2} -,

[Formula] -CH ₂ - CH ₂ -CH ₂ -, -CH ₂ -CH ₂ -O-CH ₂ -CH ₂
--,

【formula】

[Formula] ―CH ₂ ―CH ₂ ―O ―CH ₂ ―CH ₂ ―O―CH ₂ ―CH ₂ ― etc. 2 or more carbon atoms
6 represents a divalent hydrocarbon group, and the piperazine ring is substituted with a halogen atom such as Cl or Br, an alkyl group such as methyl or ethyl, an alkenyl group such as allyl, or an alkoxy group such as methoxy. It's okay. The compound of general formula (2) is not only available as a commercial product, but also easily synthesized, for example, by adding 2 moles or more of alkylene oxide to 1 mole of piperazine. Polyisocyanate compounds that can be used include, for example, 1,6-hexamethylene diisocyanate,
1,8-octamethylene diisocyanate, 1,
2-dodecamethylene diisocyanate, 2,2,
alkylene diisocyanates such as 4-trimethylhexamethylene diisocyanate, 3,
3'-Diisocyanate dipropyl ether, 3-
Isocyanate methyl-3,5,5-trimethylcyclohexyl isocyanate, cyclopentylene-1,3-diisocyanate, cyclohexylene-1,4-diisocyanate, methyl-2,6
-Diisocyanate caproate, bis(2-isocyanate ethyl) fumarate, 4-methyl-
1,3-Diisocyanate cyclohexane, transvinylene diisocyanate and similar unsaturated isocyanates, 4,4'-methylene-bis(cyclohexyl isocyanate), methane diisocyanate, N,N',N''-tris(6-isocyanate hexamethylene) biuret , screw (2-
aliphatic or cycloaliphatic polyisocyanates such as carbonate (ethyl isocyanate) carbonate and similar diisocyanates, toluene diisocyanate, xylylene diisocyanate, dianisidine diisocyanate, 4,4'-diphenylmethane diisocyanate, 1-ethoxy-2, 4-diisocyanatebenzene, 1-chloro-2,4-
Diisocyanate benzene, tris (4-isocyanate phenyl) methane, naphthalene diisocyanate, phleolein diisocyanate, 4,
Aromatic polyisocyanates such as 4'-biphenyl diisocyanate, phenylene diisocyanate, 3,3'-dimethyl-4,4'-biphenyl diisocyanate, p-isocyanate-benzyl isocyanate, tetrachloro-1,3-phenylene NCO which is a reaction product of diisocyanate and the above organic polyisocyanate with a small amount of low molecular weight polyhydroxy compound or polyamine compound
Examples include terminal prepolymers. Examples of low molecular weight polyhydroxy compounds include ethylene glycol,
propylene glycol, diethylene glycol,
Examples include polyester polyols such as dipropylene glycol, polyethylene glycol, polypropylene glycol, 1,4-butanediol, hexamethylene glycol, neopentyl glycol, polyethylene adipate glycol, and polybutylene adipate glycol, glycerin, trimethylolpropane, and pentaerythritol. Examples of the low molecular weight polyamine compound include ethylene diamine, propylene diamine, hexamethylene diamine, and the like. On the other hand, examples of blocking agents for active isocyanate groups include alcohols such as methanol, ethanol, n-propanol, n-butanol, n-pentanol, and isopropanol, phenol, n-cresol, isooctylphenol, and 4-hydroxybifurol. phenols such as enyl, n-nitrophenol, p-nitrophenol, o-nitrophenol, p-chlorophenol, catechol, chloroglucinol, acetylacetone, ethyl acetoacetate, dimethyl malonate,
Active methylene compounds such as diethyl malonate, mercaptans such as butyl mercaptan, thiophenol, and tertiary dodecyl mercaptan, acid amides such as acetanilide, acetanisidide, acetamide, and benzamide, and imides such as succinimide and maleic imide. , diphenylamine, phenylnaphthylamine, aniline, amines such as carbazole, imidazoles such as imidazole, 2-ethylimidazole, carbamates such as phenyl N-phenylcarbamate, 2-oxazolidone, and ethyleneimines such as ethyleneimine. , formaldoxime, acetaldoxime, methyl ethyl ketoxime, cyclohexanone oxime and other oximes, β-methyl-β-butyrolactam, α,β-dimethylbutyrolactam, α,α′,β-trimethylbutyrolactam, β
-Carbomethoxy-β-butyrolactam, β-phenyl-β-propiolactam, β-methyl-β
-Caprolactam, β-methyl-β-valerolactam, β-ethyl-β-valerolactam, 2-pyrrolidrine, 6-methyl-2-piperidone, 3-
Methyl-ε-caprolactam and 7-methyl-
Lactams such as ε-caprolactam, as well as oxazolidine, ketimine, acetohydroxamic acid ester, benzhydroxamic acid ester,
Hydroxamic acid esters such as benzyl methacryloyl hydroxamate are used. The blocked isocyanate compound of the present invention can be produced in the same manner as in the case of conventional blocked isocyanate compounds. In this case, it is advantageous for production to carry out the reaction in a solvent-free system, but in some cases, a solvent such as toluene or dimethylformamide may be used for synthesis. However, when a solvent is used, it is preferable to use a low boiling point solvent such as methyl ethyl ketone or ethyl acetate that is inert to isocyanate groups and that can be easily removed after synthesis. The reaction temperature for the reaction to obtain the isocyanate-terminated prepolymer before blocking and the reaction temperature for blocking the terminal isocyanate generally ranges from room temperature to
A temperature of about 120°C is employed, and a temperature of about 50°C to 80°C is particularly preferred. Although these reactions can be carried out satisfactorily without a catalyst, triethylamine, dibutyltin dilaurate,
Conventional urethanization catalysts such as stannous octoate can also be used. To the isocyanate-terminated prepolymer thus prepared from piperazine and a polyisocyanate compound of general formula (2), a blocking agent in an amount equivalent to the free isocyanate group is added, and the resulting blocked isocyanate compound is then added to acetic acid, lactic acid, crotonic acid, formic acid, etc. The water-solubilized blocked isocyanate compound of the present invention can be obtained by neutralizing with an acidic substance such as , propionic acid, malonic acid, tartaric acid, citronic acid, or phosphoric acid. This material has excellent water dilutability,
Gives a stable clear aqueous solution at any amount of water added. One of the major features of the compounds of the present invention is that their water solubility is not impaired by the type of blocking agent, and they can be selected from a wide variety of known blocking agents. The compound of the present invention can be mixed and used as a crosslinking agent for cationic water-soluble resins and nonionic water-soluble resins in any ratio, and by baking at or above the block dissociation temperature of the blocking agent, A high level of coating performance can be obtained. This new water-soluble blocked isocyanate compound is stable at room temperature and is therefore particularly useful as a crosslinking agent for one-component water-based polyurethane resin coatings. Hereinafter, the present invention will be specifically explained using Examples. Example 1 N,N'-bishydroxyisopropyl-2-
108 parts by weight of methylpiperazine was heated to 50°C.
Thereafter, 168 parts by weight of 1,6-hexamethylene diisocyanate was gradually added dropwise over 5 hours with sufficient stirring. After the dropwise addition was completed, the reaction was carried out at 60°C for 4 hours, and an isocyanate-terminated prepolymer having an average degree of polymerization of 1 was obtained. This prepolymer
NCO% was 7.3%. Then, 43 parts by weight of methyl ethyl ketoxime was added and the mixture was reacted at the same temperature for 5 hours to obtain a blocked isocyanate compound. This was dissolved in 95 parts of isopropyl alcohol and neutralized with 65% acetic acid to obtain the blocked isocyanate compound of the present invention. This was a clear solution soluble in water with a non-volatile content of 71.2% and a pH of 6.3. Example 2 N,N'- in place of N,N'-bishydroxyisopropyl-2-methylpiperazine in Example 1
Bishydroxyethyl-2-methylpiperazine96
parts by weight, 1342 parts by weight of "polyisocyanate with an NCO content of 16.7% which is an adduct of 1 mol of trimethylolpropane and 3 mol of 1,6-hexamethylene diisocyanate" is used instead of 1,6-hexamethylene diisocyanate, and An isocyanate-terminated prepolymer having an average degree of polymerization of 1 was obtained in the same manner as in Example 1, except that 447 parts by weight of ethyl acetate and 75 parts by weight of methyl ethyl ketone were used as the solvent. The NCO content of this prepolymer was 5.7%. Then, 112 parts by weight of ε-caprolactam was added and reacted at 70°C for 2 hours to obtain a blocked isocyanate compound. After removing the solvent under reduced pressure, this material was dissolved in 664 parts of isopropyl alcohol, neutralized with lactic acid,
A water-soluble blocked isocyanate compound of the present invention was obtained. This was a clear solution soluble in water with a non-volatile content of 69.1% and a pH of 6.6. Example 3 222 parts by weight of isophorone diisocyanate at 60°C
While heating and stirring, 90 parts by weight of methyl ethyl ketoxime was gradually added dropwise over 5 hours. After completion of the dropwise addition, the mixture was allowed to react at the same temperature for 4 hours to obtain a partially blocked isocyanate. The temperature was lowered to 50°C, and 96 parts by weight of N,N'-bishydroxyethyl-2-methylpiperazine was gradually added dropwise over 2 hours. After the dropwise addition was completed, the reaction was allowed to proceed at the same temperature for 4 hours. The product was dissolved in 90 parts by weight of isopropyl alcohol and then neutralized with 65% acetic acid to obtain a blocked isocyanate compound of the present invention having an average degree of polymerization of 1. This is non-volatile content
It was a clear solution soluble in water with a pH of 70.4% and pH 6.5. Examples 4 to 12 NCO content is 7.3% and average degree of polymerization is 1
Example 1 was repeated in the same manner as in Example 1, except that various blocking agents as shown in the following table were used in predetermined amounts for 276 parts by weight of the isocyanate-terminated prepolymer. A clear solution of the blocked isocyanate compound was obtained.

[Table] Example 13 99 of 1,6-hexamethylene diisocyanate
Heat the weight part to 50℃ and add N, while stirring thoroughly.
108 parts by weight of N'-bishydroxyisopropyl-2-methylpiperazine was gradually added dropwise over 5 hours. After the dropwise addition was completed, the temperature was raised to 60°C and the reaction was continued at the same temperature for 4 hours to obtain an isocyanate-terminated prepolymer having an average degree of polymerization of 6. The NCO content of this prepolymer was 1.6%. Next, methyl ethyl ketoxime is added here.
7.3 parts by weight was added and reacted for 5 hours to obtain a blocked isocyanate compound. Thereafter, the blocked isocyanate compound thus obtained was diluted with 100% isopropyl alcohol.
The target blocked isocyanate compound was obtained by dissolving in parts by weight and then neutralizing with 65% acetic acid. This has a non-volatile content of 67.0% and a pH of 6.4.
It was a clear solution soluble in water.

Claims (1)

[Claims] 1. General formula [In the formula, R and R' are divalent hydrocarbon groups having 2 to 6 carbon atoms, which may be the same or different (the C--C bond in the main chain has an oxygen atom intervening). ). ] A hydroxy hydrocarbon disubstituted piperazine represented by the above formula is reacted with an excess of a polyisocyanate compound, and then the isocyanate-terminated prepolymer thus obtained is reacted with a blocking agent, and then neutralized with an acidic substance. , the general formula [In the formula, A represents a residue of a polyisocyanate compound, and R and R' may be the same or different,
Represents a divalent hydrocarbon group having 2 to 6 carbon atoms (an oxygen atom may be present in the C--C bond of the main chain), and Z represents a residue of an isocyanate group blocking agent. , and n represents an integer from 1 to 6. ] A method for producing a water-soluble blocked isocyanate compound.