JP5060757B2 - Weak solvent soluble isocyanate - Google Patents

Description

  The present invention relates to a polyisocyanate curing agent, and more particularly to a polyisocyanate curing agent suitably used for curing a fluorine-containing copolymer.

  Conventionally, a fluororesin has been known as a coating resin having excellent weather resistance, and is used, for example, as a heavy-duty anticorrosive topcoat or a cement-based topcoat.

  In addition, if the coating resin containing such a fluororesin contains a strong solvent (strong polar solvent) such as toluene or xylene, a coating film such as synthetic resin blended paint, chlorinated rubber paint, lacquer, etc. However, when a coating resin is directly applied to an old paint film that has changed over time for the purpose of repairing, there may be a problem that shrinkage or swelling occurs, or adhesion deteriorates.

  In addition, when a coating resin containing such a fluororesin is used as a two-component curable coating in combination with a polyisocyanate curing agent in order to improve hardness and stain resistance, the coating resin is Since a hydroxyl group for reacting with an isocyanate group is introduced, it is difficult to dissolve in a weak solvent (weak polar solvent) and contains a strong solvent. However, when a strong solvent is contained in the coating resin, the old coating film may be damaged in the repair of the old coating film as described above.

  Therefore, as a fluororesin that is soluble in a weak solvent and can be used as a coating resin for a two-component curable coating, for example, a fluoroolefin and a double bond-containing monomer copolymerizable with the fluoroolefin It is a copolymer, the fluorine content based on the fluoroolefin is 10% by mass or more, and among the double bond-containing monomers, 5 to 30 mol% contains a hydroxyl group, and 10 to 50 mol% has 3 carbon atoms. A weak solvent-soluble fluorine-containing copolymer containing the above branched alkyl group has been proposed (for example, see Patent Document 1).

As for the polyisocyanate curing agent, as a polyisocyanate curing agent that dissolves in a nonpolar solvent and is excellent in compatibility with a fluororesin, for example, a diisocyanate compound and a monoalcohol having 10 to 50 carbon atoms are combined with isocyanurate. There has been proposed a polyisocyanate having an isocyanurate ring obtained by reacting in the presence of an oxidization catalyst and then removing an unreacted diisocyanate compound (see, for example, Patent Document 2).
JP 2004-277716 A JP-A-2-250872

  However, in the case where the fluorine-containing copolymer described in Patent Document 1 is combined with the polyisocyanate described in Patent Document 2 and used as a two-component curable coating, the fluorine-containing copolymer and the polyisocyanate are used as weak solvents. When it dissolves, it initially completely dissolves once, but after that, there arises a problem that it precipitates again as the amount of weak solvent increases.

  The objective of this invention is providing the polyisocyanate hardening | curing agent which is excellent in the solubility with respect to a weak solvent, and is excellent also in the coating-film physical property after hardening a fluorine-containing copolymer.

In order to achieve the above object, the polyisocyanate curing agent of the present invention is obtained by the reaction of 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate and dodecyl alcohol, and has an allophanate / isocyanurate composition ratio. 50/50 to 100/0.

Also, the polyisocyanate curing agent of the present invention, the following dilutions against mineral spirits, it is preferable that at least 500%.
Dilutability: When the mineral spirit is added to the polyisocyanate curing agent Xg at 0 ° C. until it becomes cloudy, it is expressed by the following formula from the blending amount Yg of the mineral spirit at the time of cloudiness.
Dilutability (%) = Yg / Xg × 100

  The polyisocyanate curing agent of the present invention is a copolymer of a fluoroolefin and a double bond-containing monomer copolymerizable with the fluoroolefin, and the fluorine content based on the fluoroolefin is 10% by mass or more. Among the double bond-containing monomers, 5-30 mol% contains a hydroxyl group, and 10-50 mol% contains a branched alkyl group having 3 or more carbon atoms. Therefore, it is preferably used.

  The polyisocyanate curing agent of the present invention is excellent in solubility in a weak solvent, and is excellent in weather resistance and physical properties of the coating film obtained by curing the fluorinated copolymer. Furthermore, it is excellent in workability such as pot life. Therefore, it is possible to form a coating film excellent in coating film properties without damaging the coating object in various fields that are easily damaged by the strong solvent.

  The polyisocyanate curing agent of the present invention can be obtained by reacting 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate with a monoalcohol having at least 10 to 50 carbon atoms.

  In the present invention, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate is isophorone diisocyanate (hereinafter abbreviated as IPDI), and is available as a polyurethane raw material.

  In the present invention, examples of the monoalcohol having 10 to 50 carbon atoms include n-decanol, n-undecanol, n-dodecanol, butylhexanol, trimethylnonyl alcohol, n-tridecanol, n-tetradecanol, 5-ethyl- 2-nonanol, n-pentadecanol, n-hexadecanol, 2-hexyldecanol, n-heptadecanol, 3,9-diethyl-6-decanol, n-octadecanol, 2-isoheptylisoundecanol N-nonadecanol, eicosanol, 2-octyldodecanol, ceryl alcohol, 2-decyltetradecanol, 2-cetylstearyl alcohol, melyl alcohol and the like. Preferably, the monoalcohol having 10 to 30 carbon atoms, more preferably, the monoalcohol having 10 to 16 carbon atoms, more specifically, n-decanol (n-decyl alcohol), n-dodecanol (n-dodecyl alcohol). , N-hexadecanol (n-hexadecyl alcohol). These monoalcohols can be used alone or in combination of two or more.

  Moreover, as long as these monoalcohols have one hydroxyl group in the molecule, other molecular structures are not particularly limited as long as they do not inhibit the excellent effects of the present invention. For example, in the molecule, It can also have an ester group, an ether group, a cyclohexane ring, an aromatic ring and the like.

  In the present invention, IPDI and monoalcohol having 10 to 50 carbon atoms in the obtained polyisocyanate curing agent have an allophanate / isocyanurate composition ratio of 50/50 to 100/0 (mass ratio), preferably Is reacted so as to be 60/40 to 95/5 (mass ratio). That is, the allophanate composition (IPDI allophanate) is reacted so as to be equal to or higher than the isocyanurate composition (IPDI isocyanurate).

  The allophanate / isocyanurate composition ratio is the mass ratio of the IPDI allophanate to the IPDI isocyanurate in the resulting polyisocyanate curing agent, for example, gel permeation equipped with a differential refractive index detector (RID). The molecular weight distribution of the polyisocyanate curing agent was measured by an association chromatograph (GPC). From the obtained chromatogram (chart), a peak corresponding to the IPDI allophanate and a peak corresponding to the IPDI isocyanurate Can be calculated by obtaining the ratio (area ratio). For convenience, in the chromatogram measured by GPC, peaks other than those corresponding to IPDI allophanate are regarded as peaks corresponding to IPDI isocyanurate (provided that unreacted IPDI remains). The peak corresponding to the unreacted IPDI is excluded.) The area ratio of the peak corresponding to the allophanate of IPDI to all peaks is calculated as the allophanate composition ratio (the remainder is the isocyanurate composition ratio). can do.

  In the obtained polyisocyanate curing agent, the IPDI allophanate body can improve the weak solvent solubility (dilutability), and the IPDI isocyanurate body can improve the physical properties of the coating film. Therefore, in the obtained polyisocyanate curing agent, if the allophanate / isocyanurate composition ratio is in the above range, both weak solvent solubility and physical properties of the coating film can be achieved.

  In the obtained polyisocyanate curing agent, in order to react IPDI with a monoalcohol having 10 to 50 carbon atoms so that the allophanate / isocyanurate composition ratio falls within the above range, in the presence of a specific reaction catalyst, React with specific reaction conditions.

  As such a reaction catalyst, one that can easily control the reaction, has little reaction product coloration, and can reduce the formation of a dimer having poor heat stability, such as tetramethylammonium and tetraethylammonium, is used. Tetraalkylammonium hydroxide and its organic weak acid salts, for example, trialkylhydroxyalkylammonium hydroxide and its organic weak acid salts such as trimethylhydroxypropylammonium and triethylhydroxypropylammonium, for example, acetic acid, caproic acid, octylic acid, myristic Alkali metal salts of alkyl carboxylic acids such as acids, for example, metal salts of the above alkyl carboxylic acids such as tin, zinc and lead, for example, gold of β-diketone such as aluminum acetylacetone and lithium acetylacetone Chelate compounds, such as Friedel-Crafts catalysts such as aluminum chloride and boron trifluoride, various organometallic compounds such as titanium tetrabutyrate and tributylantimony oxide, and aminosilyl group-containing compounds such as hexamethylsilazane Etc. Preferred examples include quaternary ammonium compounds such as tetraalkylammonium hydroxide and organic weak acid salts thereof, and trialkylhydroxyalkylammonium hydroxide and organic weak acid salts thereof. These reaction catalysts can be used alone or in combination of two or more.

  The addition ratio of the catalyst is, for example, 0.1 parts by mass or less, preferably 0.01 parts by mass or less, with respect to 100 parts by mass of IPDI. In order to prevent the polyurethane compound from becoming polymerized, it is desirable to use as little catalyst as possible.

  As such reaction conditions, for example, under an inert gas atmosphere such as nitrogen gas, under normal pressure (atmospheric pressure), the reaction temperature is, for example, a temperature exceeding 80 ° C., preferably 90-100 ° C. The time is, for example, 0.1 to 2.0 hours, preferably 0.2 to 0.5 hours.

  In this reaction, the IPDI and the monoalcohol having 10 to 50 carbon atoms have an equivalent ratio (NCO / OH) of the isocyanate group of IPDI to the hydroxyl group of the monoalcohol having 10 to 50 carbon atoms, for example, 5-50. The blending ratio is preferably 15-30.

  In this reaction, if necessary, a known reaction solvent may be added, and a known catalyst deactivator may be added at an arbitrary timing.

  More specifically, this reaction is performed, for example, by charging IPDI and a monoalcohol having 10 to 50 carbon atoms into the reaction vessel substituted with an inert gas at the above blending ratio. The reaction is carried out at a temperature exceeding 80 ° C., preferably at 85-90 ° C. for 2-6 hours, and then added with a reaction catalyst, for example, at 70-90 ° C., preferably at 75-85 ° C. The reaction is allowed to proceed for 1-2 hours, after which a catalyst deactivator is added to stop the reaction.

  After completion of the reaction, unreacted IPDI is removed by a known removal method such as distillation, if necessary.

  Further, after completion of the reaction, the obtained polyisocyanate curing agent is reacted with a polyol having a number average molecular weight of, for example, 400-2000, preferably 700-1000, to obtain the obtained polyisocyanate curing agent. It can also be modified with a polyol.

  Examples of such polyols include polyoxyalkylene polyols such as polyoxyethylene diol, polyoxyethylene triol, polyoxypropylene diol, polyoxypropylene triol, polyoxyethylene oxypropylene diol, polyoxyethylene oxypropylene triol, and the like. Etc. These polyols can be used alone or in combination of two or more.

  The blending ratio of the polyol is, for example, 1-20 parts by mass, preferably 5-15 parts by mass with respect to 100 parts by mass of the polyisocyanate curing agent.

  Further, the polyisocyanate curing agent and the polyol are not particularly limited and can be reacted under known reaction conditions.

  As described above, the polyisocyanate curing agent thus obtained preferably has an allophanate / isocyanurate composition ratio of 50/50 to 100/0 (mass ratio), and more preferably 60/40 to 95 / 5 (mass ratio), the conversion rate (reaction rate) is, for example, 30-50%, further 35-45%, and the isocyanate content is, for example, 10-20%, further 12-18. The unreacted IPDI content is, for example, 1.0% by mass or less, and further 0.5% by mass or less.

  Moreover, the dilutability with respect to mineral spirit of the obtained polyisocyanate curing agent is preferably 500% or more, more preferably 700% or more, and usually 1000% or less.

  The dilutability is an index (dilution rate) indicating how much the polyisocyanate curing agent can be diluted with a weak solvent. For example, at 0 ° C., until the mineral spirit becomes cloudy with respect to the polyisocyanate curing agent Xg. From the blending amount Yg of the mineral spirit at the time of the cloudiness when added, it is represented by the following formula.

Dilutability (%) = Yg / Xg × 100
If the dilutability is 500% or more, the solubility of the polyisocyanate curing agent in the weak solvent is very good, and the polyisocyanate curing agent can be sufficiently dissolved in the weak solvent in its use.

  The polyisocyanate curing agent of the present invention is not particularly limited. For example, it is used as a curing agent for a coating composition, preferably as a curing agent for a fluororesin having a hydroxyl group. Used as a curing agent for solvent-soluble fluorine-containing copolymers.

  The polyisocyanate curing agent of the present invention is excellent in solubility in a weak solvent, and is excellent in weather resistance and physical properties of the coating film obtained by curing the fluorinated copolymer. Furthermore, it is excellent in workability such as pot life. Therefore, it is possible to form a coating film excellent in coating film properties without damaging the coating object in various fields that are easily damaged by the strong solvent.

  Such a fluorine-containing copolymer is, for example, a copolymer of a fluoroolefin and a double bond-containing monomer copolymerizable with the fluoroolefin, and the fluorine content based on the fluoroolefin is 10% by mass or more. Yes, among the double bond-containing monomers, mention is made of a weak solvent-soluble fluorine-containing copolymer in which 5 to 30 mol% contains a hydroxyl group and 10 to 50 mol% contains a branched alkyl group having 3 or more carbon atoms. It is done. As such a fluorine-containing copolymer, for example, a fluorine-containing copolymer for paint described in JP-A No. 2004-277716 can be mentioned.

  The fluoroolefin is preferably a fluoroolefin having a fluorine addition number of 2 or more, and further 3 to 4 from the viewpoint of weather resistance. Specifically, for example, tetrafluoroethylene, chlorotrifluoroethylene, fluorine Vinylidene chloride, hexafluoropropylene and the like, and tetrafluoroethylene and chlorotrifluoroethylene are preferable. These fluoroolefins can be used alone or in combination of two or more.

The double bond-containing monomer is a vinyl monomer having a carbon-carbon double bond represented by CH ₂ ═CH— other than a fluoroolefin copolymerizable with a fluoroolefin, and as such a vinyl monomer Includes alkyl vinyl ethers and alkyl vinyl esters containing linear, branched or cyclic alkyl groups.

  The double bond-containing monomer includes a double bond-containing monomer containing a hydroxyl group (hereinafter referred to as a hydroxyl group-containing monomer) and a double bond-containing monomer containing a branched alkyl group having 3 or more carbon atoms (hereinafter, Both of which are referred to as branched alkyl group-containing monomers). The hydroxyl group-containing monomer may contain a branched alkyl group having 3 or more carbon atoms, and the branched alkyl group-containing monomer may contain a hydroxyl group.

  Moreover, 5-30 mol% contains a hydroxyl group among double bond containing monomers. When the content of the hydroxyl group-containing monomer is 5 mol% or more, a coating film having a high hardness can be obtained, and when the content of the hydroxyl group-containing monomer is 30 mol% or less, Sufficient solubility can be maintained.

  The number of carbon atoms of the hydroxyl group-containing monomer is not particularly limited, but is preferably 2 to 10, more preferably 2 to 6, and particularly preferably 2 to 4.

  Examples of such a hydroxyl group-containing monomer include hydroxyalkyl vinyl ethers such as 4-hydroxybutyl vinyl ether (HBVE), 2-hydroxyethyl vinyl ether (HEVE), and cyclohexanedimethanol monovinyl ether, such as hydroxyethyl allyl ether, cyclohexane dimethyl ether. Examples thereof include hydroxyalkyl allyl ethers such as methanol monoallyl ether, and (meth) acrylic acid hydroxyalkyl esters such as hydroxyethyl (meth) acrylate.

  From the viewpoint of excellent copolymerizability and improving the weather resistance of the formed coating film, hydroxyalkyl vinyl ethers are preferable. In particular, from the viewpoint of excellent solubility in a weak solvent, hydroxyalkyl vinyl ethers having 2 to 4 carbon atoms are preferable, and HBVE is more preferable. These hydroxyl group-containing monomers can be used alone or in combination of two or more.

  Of the double bond-containing monomers, 10 to 50 mol% contains a branched alkyl group having 3 or more carbon atoms. If the branched alkyl group-containing monomer is 10 to 50 mol%, solubility in a weak solvent can be ensured even if the hydroxyl group-containing monomer is blended in the above proportion.

  The number of carbon atoms of the branched alkyl group in the branched alkyl group-containing monomer is not particularly limited as long as it is 3 or more, but is preferably 4 to 15, more preferably 4 to 10.

  Examples of such branched alkyl group-containing monomers include vinyl ethers, allyl ethers or (meth) acrylic acid esters containing a branched alkyl group. Examples of the branched alkyl group include isopropyl group, isobutyl group, sec-butyl group, tert-butyl group, 2-ethylhexyl group, 2-methylhexyl group and the like. The branched alkyl group-containing monomer is preferably a vinyl ether such as 2-ethylhexyl vinyl ether (2-EHVE) or tert-butyl vinyl ether (t-BuVE), more preferably from the viewpoint of excellent copolymerizability. Includes 2-EHVE. These branched alkyl group-containing monomers can be used alone or in combination of two or more.

  As the double bond-containing monomer, other double bond-containing monomers other than the hydroxyl group-containing monomer and the branched alkyl group-containing monomer may be contained as long as the above-described excellent effects are not inhibited.

  The other double bond-containing monomer preferably includes a monomer containing an alkyl group, and the alkyl group includes a linear, branched or cyclic alkyl group. The carbon number of the alkyl group is preferably 2 to 8, more preferably 2 to 6. In particular, if a double bond-containing monomer containing a cyclic alkyl group is blended, the glass transition temperature (Tg) of the fluorinated copolymer can be increased, and the hardness of the coating film can be further increased.

  Examples of such a double bond-containing monomer containing a cyclic alkyl group include cyclic alkyl vinyl ethers such as cyclohexyl vinyl ether and cyclohexyl methyl vinyl ether, cyclohexyl (meth) acrylate, and 3,3,5-trimethylcyclohexyl (meth) acrylate. And (meth) acrylic acid cyclic alkyl esters. These other double bond-containing monomers can be used alone or in combination of two or more. The ratio of the other double bond-containing monomer is preferably 70 mol% or less, more preferably 30 to 60 mol%, based on the total amount of the double bond-containing monomer.

  The ratio of the polymer unit based on the fluoroolefin and the polymer unit based on the double bond-containing monomer is preferably 30 to 70 mol%, more preferably 40 to 60 mol%, based on the fluoroolefin. The polymerized units based on the double bond-containing monomer are preferably 70 to 30 mol%, more preferably 60 to 40 mol%. If the proportion of the polymer units based on fluoroolefin is 70 mol% or less, the solubility of the fluorinated copolymer in a weak solvent becomes sufficient, and if it is 30 mol% or more, sufficient weather resistance can be secured. it can.

  The fluorine-containing copolymer is obtained by blending a fluoroolefin and a double bond-containing monomer including a hydroxyl group-containing monomer and a branched alkyl group-containing monomer, and in the presence or absence of a polymerization medium, It can be obtained by adding a polymerization initiation source such as ionizing radiation and copolymerizing. This copolymerization reaction is a known radical copolymerization reaction, and reaction conditions such as reaction temperature, reaction time, and reaction pressure are appropriately selected.

  In the copolymerization reaction, the blending ratio of the fluoroolefin and the double bond-containing monomer is the same as the ratio of the polymer unit based on the fluoroolefin and the polymer unit based on the double bond-containing monomer in the fluorinated copolymer. .

  Examples of the polymerization medium include ketones such as methyl ethyl ketone and methyl isobutyl ketone, esters such as ethyl acetate and n-butyl acetate, aromatic hydrocarbons such as xylene and toluene, such as cyclohexanone, and solvent naphtha. , Mineral terpenes, mineral spirits, aliphatic hydrocarbons such as petroleum naphtha, for example, ethyl 3-ethoxypropionate, methyl amyl ketone, tert-butyl acetate, 4-chlorobenzotrifluoride, benzotrifluoride, monochlorotoluene, 3 , 4-dichlorobenzotrifluoride and the like.

  Examples of the polymerization initiator include 2,2′-azobisisobutyronitrile, 2,2′-azobiscyclohexane carbonate nitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2 Examples include azo initiators such as' -azobis (2-methylbutyronitrile). Also, for example, ketone peroxides such as cyclohexanone peroxide, hydroperoxides such as tert-butyl hydroperoxide, diacyl peroxides such as benzoyl peroxide, eg di-tert-butyl peroxide, etc. Dialkyl peroxides such as, for example, peroxyketals such as 2,2-di- (tert-butylperoxy) butane, for example, alkyl peresters such as tert-butyl peroxypivalate, such as diisopropyl And peroxide initiators such as percarbonates such as peroxydicarbonate.

  The fluorine-containing copolymer has a fluorine content based on fluoroolefin of 10% by mass or more, preferably 20-30% by mass, based on the total amount of the fluorine-containing copolymer. The weather resistance of a coating film can be improved as content of a fluorine is 10 mass% or more.

  The fluorine-containing copolymer contains a hydroxyl group for reacting with the isocyanate group of the polyisocyanate curing agent, and the hydroxyl value (hereinafter referred to as OHV) is preferably 30 to 55 mgKOH / g, Preferably, it is 35-50 mgKOH / g. If OHV is 30 mgKOH / g or more, the hardness of the coating film can be increased. Moreover, if OHV is 55 mgKOH / g or less, a fluorine-containing copolymer can fully be melt | dissolved with respect to a weak solvent.

  The fluorine-containing copolymer preferably has a number average molecular weight (Mn) measured by GPC based on a standard polystyrene calibration curve of 5000 to 10,000. When Mn is 5000 or more, the weather resistance is excellent, and when Mn is 10,000 or less, the solubility in a weak solvent is excellent.

  Moreover, the glass transition point (henceforth Tg) of a fluorine-containing copolymer becomes like this. Preferably it is 25 degreeC or more, More preferably, it is 30-40 degreeC. The hardness of a coating film can be raised as Tg is 25 degreeC or more.

  The fluorine-containing copolymer preferably contains a carboxyl group. By containing a carboxyl group, the dispersibility of the pigment can be improved. The acid value (hereinafter referred to as AV) of the fluorinated copolymer is, for example, 0.5 to 5 mgKOH / g, preferably 2 to 5 mgKOH / g.

  A carboxyl group can be introduce | transduced by making polyhydric carboxylic acid or its anhydride react with the hydroxyl group which a fluorine-containing copolymer has after the copolymerization reaction of a fluoro olefin and a double bond containing monomer, for example. Further, in the copolymerization reaction, a double bond-containing monomer having a carboxyl group can be directly copolymerized by including it as a double bond-containing monomer together with a hydroxyl group-containing monomer and a branched alkyl group-containing monomer. Examples of such polyvalent carboxylic acid or anhydride thereof include maleic anhydride. Examples of the double bond-containing monomer having a carboxyl group include acrylic acid and methacrylic acid.

  And when using the polyisocyanate hardening | curing agent of this invention as a hardening | curing agent of a weak solvent soluble fluorine-containing copolymer, it contains the polyisocyanate hardening | curing agent of this invention, a fluorine-containing copolymer, and a weak solvent, for example. A coating composition is prepared.

Weak solvents are weak polar solvents, that is, poor solvents for polar solutes. Specifically, those classified as Type 3 organic solvents in the classification of organic solvents by the Industrial Safety and Health Act. And corresponds to any one of the following a) to c).
B) Gasoline, coal tar naphtha (including solvent naphtha), petroleum ether, petroleum naphtha, petroleum benzine, turpentine oil, mineral spirit (including mineral thinner, petroleum spirit, white spirit and mineral turpentine),
B) A mixture consisting only of a)
C) Mixtures other than a) and b) containing a) in excess of 5% by mass.

  If such a third type organic solvent is used as the weak solvent, the second type organic solvent corresponding to the strong solvent is not contained in excess of 5% by mass of the total solvent, and damage to the object to be coated is prevented. be able to.

  The weak solvent is preferably mineral spirit from the viewpoint that the flash point is room temperature or higher.

  And a coating composition can be obtained by mix | blending a polyisocyanate hardening | curing agent, a fluorine-containing copolymer, and a weak solvent.

  In the coating composition, the blending ratio of the fluorine-containing copolymer is, for example, 20 parts by mass or more, preferably 30 parts by mass or more, and more preferably 40 parts by mass with respect to 100 parts by mass of the solid content of the coating composition. That is above, and usually 50 parts by mass or less.

  The blending ratio of the polyisocyanate curing agent is blended in such a ratio that the equivalent ratio (NCO / OH) of the isocyanate group of the polyisocyanate curing agent to the hydroxyl group of the fluorine-containing copolymer is approximately 1 (equivalent). Specifically, it is 1-100 mass parts with respect to 100 mass parts of fluorine-containing copolymers, Preferably, it is 1-50 mass parts. When the polyisocyanate curing agent is 1 part by mass or more, the solvent resistance and hardness of the coating film are sufficient, and when it is 100 parts by mass or less, processability and impact resistance are excellent.

  The blending ratio of the weak solvent is the remaining amount of the polyisocyanate curing agent and the fluorine-containing copolymer in the coating composition, taking into consideration the solubility of the fluorine-containing copolymer, the appropriate viscosity at the time of coating, the coating method, etc. It is determined as appropriate. Specifically, considering the excellent solubility of the fluorinated copolymer in a weak solvent, it is, for example, 10 to 30% by mass with respect to the total amount of the coating composition.

  Further, in the coating composition, it is best that the total amount of solid content contained is dissolved in a weak solvent, but some insolubles are allowed.

  The coating composition is preferably used as a two-component curable coating. Specifically, first, a main component is prepared by dissolving a fluorine-containing copolymer in a weak solvent. An isocyanate curing agent is prepared. Immediately before use, a main component and a polyisocyanate curing agent are mixed to prepare a coating composition, and the coating composition is applied to an object to be coated.

  In addition to the above components, the coating composition can contain other functional compounding agents depending on the purpose and application.

  As such a functional compounding agent, for example, in order to improve the drying property of the coating film, CAB (cellulose acetate butrate), NC (nitrocellulose) and the like may be contained. In order to improve the hardness and workability of the paint, a polymer or polyester made of acrylic acid or its ester can be contained.

  Examples of other functional compounding agents include coloring pigments, dyes, silane coupling agents for improving adhesion of coating films, ultraviolet absorbers, curing accelerators, light stabilizers, and matting agents.

  Examples of color pigments and dyes include inorganic pigments such as carbon black and titanium oxide having good weather resistance, for example, organic pigments such as phthalocyanine blue, phthalocyanine green, quinacridone red, indanthrene orange, and isoindolinone-based yellow, And dyes.

  Examples of the silane coupling agent include 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, ureidopropyltriethoxysilane, vinyltri Ethoxysilane, vinyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane , 3-mercaptopropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, methyltriethoxysilane, methyltrimethoxysilane and the like.

  Examples of the ultraviolet absorber include benzophenone-based, benzotriazole-based, triazine-based, and cyanoacrylate-based ultraviolet absorbers.

  Examples of the curing accelerator include dibutyltin dilaurate.

  Examples of the light stabilizer include hindered amine light stabilizers, and more specifically, for example, ADK STAB LA62, ADK STAB LA67 (trade name, manufactured by Adeka Argus Chemical Co., Ltd.), Tinuvin 292, Tinuvin 144, Tinuvin 123, Tinuvin 440 (above, manufactured by Ciba Specialty Chemicals, Inc., trade name) and the like can be mentioned.

  Examples of the matting agent include ultra fine powder synthetic silica. If a matting agent is blended, an elegant semi-gloss and matte finish film can be formed.

  These functional compounding agents are blended into the coating composition at an appropriate blending ratio depending on the purpose and application. Further, the functional compounding agent may be blended in advance with the above-described main agent and / or polyisocyanate curing agent, or may be blended with the coating composition after the blending of the main agent and polyisocyanate curing agent.

  And according to such a coating composition, it is excellent in the solubility with respect to a weak solvent, and is excellent also in coating-film physical properties, such as a weather resistance, hardness, and impact resistance. Furthermore, it is excellent in workability such as pot life. Therefore, it is possible to form a coating film excellent in coating film properties without damaging the coating object in various fields that are easily damaged by the strong solvent.

  The coating composition is not particularly limited with respect to the object to be coated. For example, the coating composition is applied by any coating method such as spray coating, air spray coating, brush coating, dipping method, roll coater, or flow coater. be able to.

  Further, the material to be coated is not particularly limited, and for example, inorganic materials such as concrete, natural stone, and glass, for example, metals such as iron, stainless steel, aluminum, copper, brass, and titanium, such as plastic, rubber, and adhesive And organic materials such as wood. In particular, it is suitable for repainting the surface of a coating film that has already been formed. It is also suitable for coating of organic and inorganic composite materials such as FRP, resin reinforced concrete, and fiber reinforced concrete.

  More specifically, transportation equipment such as automobiles, trains and aircraft, civil engineering members such as bridge members and steel towers, industrial materials such as waterproof sheets, tanks and pipes, building exteriors, doors, window gate members, monuments, poles Building materials such as, road median strips, road rails such as guardrails and sound barriers, communication equipment, electrical and electronic parts.

  Next, although this invention is demonstrated based on an Example and a comparative example, this invention is not limited by the following Example.

Synthesis Example 1 (Synthesis of curing agent A)
A 500 mL four-necked flask equipped with a stirrer, thermometer, nitrogen gas inlet tube and Dimroth condenser tube was charged with IPDI 521.7 g and dodecyl alcohol 44.4 g in a nitrogen gas atmosphere and heated to 90 ° C. for 2 hours. Retained.

  Thereafter, 0.02 g of trimethyl-N-2-hydroxypropylammonium 2-ethylhexanoate was added as a reaction catalyst, and the reaction was continued for 2 hours while adjusting the reaction temperature to 90 ± 5 ° C. Thereafter, 0.02 g of o-toluenesulfonic acid amide was added as a catalyst deactivator to deactivate the reaction catalyst, and the reaction was stopped.

  Unreacted IPDI was removed from the resulting reaction liquid to obtain 237.7 g (conversion rate, 42%) of a light yellow transparent polyisocyanate curing agent A.

  This polyisocyanate curing agent A is almost in a solid state at 25 ° C., has an allophanate / isocyanurate composition ratio of 73/27, an isocyanate content of 14.6%, and an unreacted IPDI content of 0. As a result of NMR measurement, substantially no urethane group was observed.

  Further, a solution obtained by diluting the polyisocyanate curing agent A with mineral spirit A (manufactured by Nippon Oil Corporation) to a solid content of 80% by mass has a viscosity of 3600 mPa · s at 25 ° C. and is cloudy even at 0 ° C. And maintained a uniform transparent state.

Synthesis Example 2 (Synthesis of curing agent B)
Polyisocyanate curing agent B was obtained by the same method as in Synthesis Example 1 except that the temperature to be heated was changed from 90 ° C. to 60 ° C.

  This polyisocyanate curing agent B has an allophanate / isocyanurate composition ratio of 10/90, an isocyanate content of 19.9%, an unreacted IPDI content of 0.5% by mass, and an NMR measurement. As a result, urethane groups were not substantially recognized.

Synthesis Example 3 (Synthesis of curing agent C)
Polyisocyanate curing agent C was obtained by the same method as in Synthesis Example 1 except that isobutyl alcohol was used instead of monodecyl alcohol instead of monodecyl alcohol.

  This polyisocyanate curing agent C has an allophanate / isocyanurate composition ratio of 73/27, an isocyanate content of 17.3%, an unreacted IPDI content of 0.5% by mass, and an NMR measurement. As a result, urethane groups were not substantially recognized.

Synthesis Example 4 (Synthesis of curing agent D)
A polyisocyanate curing agent H was obtained in the same manner as in Synthesis Example 1 except that the polyisocyanate was replaced with IPDI and replaced with HDI.

  This polyisocyanate curing agent D has an allophanate / isocyanurate composition ratio of 72/28, an isocyanate content of 17.9%, an unreacted HDI content of 0.5% by mass, and an NMR measurement. As a result, urethane groups were not substantially recognized.

Synthesis Example 5 (Synthesis of curing agent E)
A polyisocyanate curing agent E was obtained in the same manner as in Synthesis Example 1 except that the polyisocyanate was replaced with IPDI and replaced with HDI, and the monoalcohol was replaced with dodecyl alcohol and replaced with 2-ethylhexyl alcohol. .

  This polyisocyanate curing agent E has an allophanate / isocyanurate composition ratio of 60/40, an isocyanate content of 20.0%, an unreacted HDI content of 0.5% by mass, and an NMR measurement. As a result, urethane groups were not substantially recognized.

Preparation Example 1 (Preparation of main agent)
Lumiflon LF800 (mineral spirit soluble fluorine-containing copolymer, manufactured by Asahi Glass Co., Ltd.) 41.5 g, D-918 (white pigment, manufactured by Sakai Chemical Co., Ltd.) 100 g, mineral spirit A 108.5 g, and 2 hours in a bead mill By forced stirring, 250 g of mill base was obtained.

  Next, 250 g of mill base and 342.9 g of Lumiflon LF800 were mixed, and then mineral spirit A was added so that the resin solid content was 35% by mass to prepare the main agent.

Example 1 and Comparative Examples 1 to 4 (Preparation of coating composition, formation of coating film)
Polyisocyanate curing agents A to E are blended so that the equivalent ratio of the isocyanate group of the curing agent and the hydroxyl group of the main agent is 1/1 with respect to 100 parts by mass of the main agent, and the non-volatile content (solid) in mineral spirit A After diluting so that the component was 50% by mass, 0.01 parts by mass of dibutyltin dilaurate was added as a curing accelerator to prepare coating compositions of Examples and Comparative Examples shown in Table 1.

  Each coating composition was applied to the surface of a chromate-treated aluminum plate so as to have a film thickness of 25 μm to form a coating film, and was cured in a thermostatic chamber at 23 ° C. for 1 week.

表１中、アロファネート／イソシアヌレート組成比は、各ポリイソシアネート硬化剤を、ＲＩＤを装備したＧＰＣにて分子量分布測定し、すべてのピークに対するアロファネート体に相当するピークの面積比率をアロファネート体の組成比とし、その残余をイソシアヌレート体の組成比として算出した。

In Table 1, the composition ratio of allophanate / isocyanurate is the molecular weight distribution measurement of each polyisocyanate curing agent by GPC equipped with RID, and the ratio of the area of the peak corresponding to the allophanate body to all the peaks is the composition ratio of the allophanate body. The remainder was calculated as the composition ratio of the isocyanurate body.

Evaluation 1) Dilutability The polyisocyanate curing agents A to E 100 g obtained above were diluted at 0 ° C. with mineral spirit A (manufactured by Shin Nippon Oil Co., Ltd.) until white turbidity, and dilution of mineral spirit A at the time of white turbidity The amount Y (g) was defined as dilutability (%). The results are shown in Table 1.

In addition, although each polyisocyanate hardening | curing agent melt | dissolved completely in the mineral spirit A initially, it became cloudy again as the dilution amount of the mineral spirit A increased.
2) Physical properties of coating film 2-1) Pot life Viscosity was measured with an E-type viscometer at 25 ° C. from the time of preparation of the coating composition, and the time until it reached 450 mPa · s was defined as the pot life time (minutes). The results are shown in Table 1.
2-2) In accordance with Erichsen JIS K 5600-5-6 (2002), a 1/4 inch diameter center punch is applied to the coating surface (back), and the periphery of the paint plate is firmly fixed, Extrusion length (mm) when a punch was extruded on the coated plate at a predetermined speed and a crack occurred on the coating film surface was evaluated as Eriksen (mm). The results are shown in Table 1.

  From the above results, it can be seen that the polyisocyanate curing agent using IPDI as the polyisocyanate exhibits excellent dilutability and good coating film properties. On the other hand, when the carbon number of the monoalcohol is less than 10, it can be seen that the dilutability is remarkably lowered.

  Further, it can be seen that the polyisocyanate curing agent using HDI has good elixir but poor dilutability.

Claims (3)

Polyisocyanate obtained by reaction of 3-isocyanatomethyl-3,5,5-trimethylcyclohexylisocyanate with dodecyl alcohol and having an allophanate / isocyanurate composition ratio of 50/50 to 100/0, Isocyanate curing agent. Following dilution against mineral spirit, characterized in that it is 500% or more, the polyisocyanate curing agent of claim 1.
Dilutability: When the mineral spirit is added to the polyisocyanate curing agent Xg at 0 ° C. until it becomes cloudy, it is expressed by the following formula from the blending amount Yg of the mineral spirit at the time of cloudiness.
Dilutability (%) = Yg / Xg × 100 It is a copolymer of a fluoroolefin and a double bond-containing monomer copolymerizable with the fluoroolefin, the fluorine content based on the fluoroolefin is 10% by mass or more, and among the double bond-containing monomers, A weak solvent-soluble fluorine-containing copolymer in which 30 mol% contains a hydroxyl group and 10-50 mol% contains a branched alkyl group having 3 or more carbon atoms,
The polyisocyanate curing agent according to claim 1, wherein the polyisocyanate curing agent is used for curing.