JP2001064344A - Heat-curable urethane composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a urethane composition excellent in storage stability before being heated and curability and adhesion after being heated by mixing a urethane prepolymer with a normally solid latent curing agent being a salt of an amine with an acid and epoxy resin. SOLUTION: It is desirable that this composition further contains calcium oxide. The urethane prepolymer is the one formed from a polyol compound being one kind of a polyhydroxyl compound and a polyisocyanate compound. The polyol compound is the polyadduct of at least one alkylene oxide such as ethylene oxide with a compound having at least two active hydrogen atoms, is exemplified by polytetramethylene glycol or polyethylene glycol, and is desirably the one having a weight-average molecular weight of 100 to about 10,000. The polyisocyanate compound is desirably the one in which all or a part of the isocyanate groups of a polyisocyanate compound are blocked with oxime groups.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a heat-curable urethane composition having excellent storage stability.

[0002]

2. Description of the Related Art In a production line of an automobile, a refrigerator, or the like, when a press-formed steel plate is assembled by partial welding such as spot welding, a joint portion and a gap portion are sealed to provide airtightness.
In order to maintain water tightness, a thermosetting sealing material is used. The structure assembled by partial welding such as spot welding is subjected to electrodeposition coating for the purpose of rust prevention, a thermosetting sealing material is applied to a predetermined part, and then an undercoat used for aesthetic purposes etc.・ The intermediate and top coats are baked. The sealing material is hardened by heating at the time of baking the paint. For such use, it is preferable to use a one-pack type thermosetting sealing material which does not require measurement and mixing and has no limitation on pot life.

[0003] This one-part type thermosetting sealing material includes:
Conventionally, a polyvinyl chloride (PVC) powder is dispersed in a plasticizer, and an adhesive, a stabilizer, a filler and the like are blended in the PVC.
A paste composition, that is, a so-called PVC plastisol-based sealing material is used. However, since polyvinyl chloride causes the generation of dioxin, development of an alternative is desired, and research on a heat-curable urethane composition or a sealing material using an acrylic sol has been actively conducted in recent years.

[0004] When a one-part heat-curable urethane composition is used for the above-mentioned sealing material, it is required that curing does not take place before heating, but that curing takes place only by heating. Since the curing of the urethane composition is caused by the reaction between the isocyanate group of the urethane prepolymer and the functional group of the curing agent, the curing is sufficiently performed by heating, and a method that does not cause a curing reaction in a state before heating, in other words, Then, various methods for obtaining excellent storage stability have been studied. For example, a method using a polyamine that is solid at room temperature as a curing agent has been proposed (Japanese Patent No. 2734238). This is a technique that aims to significantly reduce the contact area with the prepolymer by suppressing the curing reaction during storage by making the curing agent a solid, but as described in the publication. However, curing actually occurs during storage, and storage stability is not sufficient. Further, a method of suppressing the curing reaction by coating the surface of a solid amine as a curing agent with a fine powder (WO 95/26374), a urethane prepolymer having an isocyanate group blocked by a blocking agent and a fine powder A method has been proposed in which a curing reaction is suppressed by combining a coating amine (Japanese Patent Application Laid-Open No. H10-158353). However, even with these methods, storage stability that can be practically used has not been obtained.

When a one-pack type heat-curable urethane composition is used as a sealing material, after the urethane composition is applied,
Before being heated and baked at a high temperature, the urethane composition has a problem that it hardens by moisture and a sufficient pot life cannot be secured.

There is a need for a heat-curable urethane composition which has the property of softening when baked at a high temperature, for example, 160 ° C. or higher, and which does not soften even when baked at a high temperature.

Further, if the one-part heat-curable urethane composition is baked at a high temperature of about 150 ° C. after absorbing the moisture in the air, the moisture absorbed by the urethane composition evaporates rapidly. . For this reason, there is a problem that the urethane composition foams and the sealing effect is impaired.

[0008]

SUMMARY OF THE INVENTION The present invention solves the above problems of storage stability, foaming during baking, and pot life, and further provides a heat-curable urethane composition which does not soften even when baked at a high temperature. As an issue.

[0009]

That is, the present invention relates to a heat-curable urethane composition containing a urethane prepolymer, a latent curing agent which is a salt of an amine and an acid and is solid at room temperature, and an epoxy resin. I will provide a.

[0010] Further, it preferably contains calcium oxide.

The present invention also provides a urethane prepolymer,
Provided is a latent curing agent which is a salt of an amine and an acid and is solid at ordinary temperature, and a heat-curable urethane composition containing calcium oxide.

It is preferred that some or all of the isocyanate groups contained in the urethane prepolymer are blocked by oximes.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. The urethane prepolymer used for the heat-curable urethane composition of the present invention is generally a urethane prepolymer produced from a polyol compound and a polyisocyanate compound, which are a kind of polyhydroxyl compound,
There is no particular limitation.

[0014] The polyol compound is a general term for alcohols in which a plurality of hydrogens of a hydrocarbon are substituted with hydroxyl groups.
For example, ethylene oxide, propylene oxide,
It is a product obtained by addition polymerization of one or more alkylene oxides such as butylene oxide and tetrahydrofuran to a compound having two or more active hydrogens. Here, examples of the compound having two or more active hydrogens include polyhydric alcohols, amines, alkanolamines, and polyhydric phenols. Polyhydric alcohols include ethylene glycol, propylene glycol, butanediol, diethylene glycol, glycerin, hexanetriol, trimethylolpropane,
Pentaerythritol and the like, and amines,
Ethylenediamine, hexamethylenediamine, etc., as alkanolamines, ethanolamine, propanolamine, etc., and as polyhydric phenols,
Resorcinol, bisphenols and the like can be mentioned.

Specifically, polyether polyols such as polytetramethylene glycol, polyethylene glycol, polypropylene glycol, polyoxypropylene glycol and polyoxybutylene glycol, polyolefin polyols such as polybutadiene polyol and polyisoprene polyol, and other adipate polyols Polyols such as polyols, lactone-based polyols and castor oils are preferred. These compounds may be used alone or in combination of two or more, but preferably have a weight average molecular weight of about 100 to 10,000.
Those having about 0 to 7000 are more preferable.

As the polyisocyanate compound, there are various compounds used for producing ordinary polyurethane resins. Specifically, 2,4-tolylene diisocyanate,
2,6-tolylene diisocyanate, diphenylmethane-4,4′-diisocyanate and modified products thereof,
Examples thereof include 1,5-naphthalene diisocyanate, ethylene diisocyanate, propylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, and triphenylmethane triisocyanate. These polyisocyanate compounds may be used alone or in combination of two or more.

The ratio of the amount of the polyol compound to the amount of the polyisocyanate compound in the production of the urethane prepolymer is determined based on one isocyanate group in the polyisocyanate compound.
Although the ratio is such that the number of hydroxyl groups in the polyol compound is one or less, it is preferably 0.95 to 0.75. The production conditions for the urethane prepolymer may be the ordinary production conditions for the urethane prepolymer. That is, the above-mentioned polyol compound and polyisocyanate compound are reacted at a reaction temperature of 50.
What is necessary is just to make it react under normal pressure at about 100 degreeC.

In the present invention, those in which all or a part of the isocyanate groups of the polyisocyanate compound are blocked by oximes are preferred. Examples of the oximes include formamidoxime, acetamidooxime, acetoxime, methylethylketoxime, diacetylmonooxime, benzophenone oxime, and cyclohexanone oxime. Of these, methyl ethyl ketoxime is particularly preferred.
These blocking agents may be used alone or in combination of two or more. These blocked polyisocyanate compounds generate isocyanate groups when heated.

In a urethane composition using a urethane prepolymer prepared from a polyisocyanate compound in which an isocyanate group is not blocked, the unblocked isocyanate group contained in the urethane prepolymer reacts with moisture in the atmosphere. Causes a cross-linking and curing reaction,
Not enough pot life. If the isocyanate group of the urethane prepolymer is blocked by oximes, the moisture curing reaction of the urethane composition is hindered, and a sufficient pot life (or so-called open time from application to curing) can be secured, After applying the sealant, the sealant can be modified at any time. In addition, since the oximes are unblocked at a relatively low temperature (about 120 ° C.) as compared with other blocking agents, the urethane composition can be cured at a low temperature, which is preferable. It is preferable that all the isocyanate groups of the polyisocyanate compound are blocked.

The latent curing agent used in the present invention (hereinafter, referred to as the latent curing agent)
The latent curing agent of the present invention) is a salt of an amine and an acid. Heating releases a certain amount of amino groups. The amine is not particularly limited as long as it is a polyamine, and is preferably a diamine, and 4,4′-diaminodiphenylmethane,
4'-diaminodiphenylmethane, 3,3'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 2,2'-diaminobiphenyl, 3,3'-diaminobiphenyl, 2,4-diaminophenol, 2,5-
Diaminophenol, o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, 2,3-
Tolylenediamine, 2,4-tolylenediamine, 2,5
-Tolylenediamine, 2,6-tolylenediamine, 3,
Aromatic diamines such as 4-tolylenediamine; ethylenediamine, 1,3-propanediamine, 1,4-butanediamine, 1,5-pentanediamine, 1,6-hexanediamine, 1,7-heptanediamine, 8-octanediamine, 1,9-nonanediamine, 1,10-decanediamine, 1,12-dodecanediamine, 1,14-
Aliphatic diamines such as tetradecanediamine and 1,16-hexadecanediamine; and polyamines such as various triamines can be used. Among them, 1,3-propanediamine, 1,6-hexanediamine and 1,12-dodecanediamine are preferable in view of performance and availability. These may be used alone or in combination of two or more.

The average number of amino groups in one molecule is 1
If it exceeds the range, one or more monoamines can be used in combination. Monoamines include, for example, methylamine, ethylamine, propylamine, isopropylamine, butylamine, hexylamine, heptylamine,
Octylamine, nonylamine, decylamine, undecylamine, dodecylamine, tridecylamine, tetradecylamine, pentadecylamine, cetylamine,
Stearylamine, dimethylamine, diethylamine,
Dipropylamine, diisopropylamine, dibutylamine, diamylamine, trimethylamine, triethylamine, tripropylamine, tributylamine, triamylamine, allylamine, diallylamine, triallylamine, cyclopropylamine, cyclobutylamine, cyclopentylamine, cyclohexylamine, aniline, methyl Aniline, dimethylaniline, ethylaniline, diethylaniline, o-toluidine, m-toluidine, p-toluidine, benzylamine, dibenzylamine, tribenzylamine, diphenylamine, triphenylamine, α-naphthylamine, β-naphthylamine. .

The acid is not particularly limited as long as it reacts with an amine to form a salt, and various organic acids and inorganic acids can be used. Organic acids include, for example, carboxylic acids,
Sulfonic acid and sulfinic acid are exemplified. Examples of the inorganic acid include hydrochloric acid, hydrofluoric acid, sulfuric acid, nitric acid, phosphoric acid, carbonic acid, and perchloric acid. Among these, carboxylic acids are preferred in that the acid liberated by the melting of the salt hardly affects the steel plate, coating and the like. Carboxylic acids include, for example, formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, undecylic acid, lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid , Heptadecylic acid, stearic acid, nonadecanoic acid, arachinic acid, behenic acid, lignoceric acid, cerotic acid, heptacosanoic acid,
Saturated fatty acids such as montanic acid, melicic acid, lacceric acid;
Unsaturated fatty acids such as acrylic acid, crotonic acid, isocrotonic acid, undecylenic acid, oleic acid, elaidic acid, setleic acid, erucic acid, brassic acid, sorbic acid, linoleic acid, linolenic acid, arachidonic acid, propiolic acid, and stearolic acid Aliphatic saturated dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid and sebacic acid; aliphatic unsaturated dicarboxylic acids such as maleic acid and fumaric acid; cyclohexane Carboxylic acid; phenylacetic acid; benzoic acid, o
-Toluic acid, m-toluic acid, p-toluic acid, o-
Chlorobenzoic acid, m-chlorobenzoic acid, p-chlorobenzoic acid, o-bromobenzoic acid, m-bromobenzoic acid, p-
Bromobenzoic acid, o-nitrobenzoic acid, m-nitrobenzoic acid, p-nitrobenzoic acid, phthalic acid, isophthalic acid,
Terephthalic acid, salicylic acid, p-hydroxybenzoic acid,
Anthranilic acid, m-aminobenzoic acid, p-aminobenzoic acid, o-methoxybenzoic acid, m-methoxybenzoic acid,
and aromatic carboxylic acids such as p-methoxybenzoic acid and nicotinic acid. Above all, benzoic acid, toluic acid, and lauric acid are preferable because they show excellent storage stability when a latent curing agent is used in a heat-curable urethane composition or the like.
In particular, benzoic acid is preferred because it can act as a rust inhibitor. These may be used alone or in combination of two or more.

The salt used for the latent curing agent of the present invention is
One or more of the above-mentioned amines and one or more of the above-mentioned acids can be obtained in any combination, and the amine and the acid may be solid or liquid, respectively. It is solid. Here, solid at room temperature means
It is solid at 25 ° C. and normal pressure. In consideration of storage stability, the melting point of the salt is preferably 50 ° C. or more, more preferably 80 ° C. or more, and the baking temperature of the coating, for example,
It is particularly preferred that the temperature be in the range of 100 to 140 ° C.

The latent curing agent of the present invention includes, in addition to salts,
A plasticizer and the like can be contained. By making the latent curing agent contain a plasticizer or the like to form a slurry, the latent curing agent containing a salt that is solid at normal pressure can be mixed well with the urethane prepolymer described below. Examples of the plasticizer include dioctyl phthalate (DOP), dibutyl phthalate (DBP), dilauryl phthalate (DLP), butylbenzyl phthalate (BBP), diisodecyl phthalate (DIDP), and diisononyl phthalate (DIN).
P), dioctyl adipate (DOA), diisononyl adipate (DINA), diisodecyl adipate, trioctyl phosphate, tris (chloroethyl) phosphate, tris (dichloropropyl) phosphate, tributyl trimellitate (TBTM), Trioctyl trimellitate (TOTM), propylene glycol adipate polyester, butylene glycol adipate polyester, alkyl epoxy stearate,
Epoxidized soybean oil.

The method for producing the latent curing agent of the present invention is not particularly limited. For example, an amine and an acid are mixed so that the equivalent of an amino group is equal to or less than the equivalent of an acid, and a plasticizer or the like is added as necessary. After adding, pulverized by stirring using a ball mill or the like,
It is obtained by slurrying. In the course of such mixing and stirring, the amine and the acid react to form a salt.

From the viewpoint of storage stability, the mixing ratio of the amine to the acid is, for example, the case where a carboxylic acid is used as the acid, the equivalent ratio of the COOH group to the active hydrogen of the NH ₂ group (C
OOH group equivalent / NH ₂ group active hydrogen equivalent) of 0.9
It is preferable to be from 5 to 1.05, more preferably a = 0.98 to 1.03 (COOH equivalent of active hydrogen equivalents / NH ₂ groups of the group), eq / NH ₂ groups of (COOH group It is particularly preferable to set the equivalent of active hydrogen to 0.98 or more and less than 1.00. It is not necessary that all of the mixed amine and acid react to form a salt, and it is sufficient that the amino group is reacted to such an extent that a curing reaction does not occur when mixed with the urethane prepolymer. Therefore, the latent curing agent of the present invention, in addition to the salt,
It may contain unreacted amines and acids. Preferably, the amino group blocking rate is 95 to 105%, more preferably 98 to 103%, and still more preferably 98% or more.
It should be less than 00%.

The epoxy resin used in the heat-curable urethane composition of the present invention may have at least two epoxy resins per molecule.
It is not particularly limited as long as it is a polyepoxy compound having individual epoxy groups. Examples thereof include glycidyl ether type epoxy resin of bisphenol A and its derivatives, glycidyl ether type epoxy resin of glycerin, glycidyl ether type epoxy resin of polyalkylene oxide, and phenol novolak. Glycidyl ether type epoxy resin, dimer acid glycidyl ester type epoxy resin, bisphenol F glycidyl ether type epoxy resin and the like can be used. Among them, the glycidyl ether type epoxy resin of bisphenol A is preferably used because it is easily available.

The heat-curable urethane composition of the present invention containing an epoxy resin is cured by heating and is heated to a high temperature, for example, 16
Even when baked and cured at 0 ° C. or higher, the degree of softening is lower than when heated and cured at a lower temperature, for example, 120 ° C. In addition, storage stability is excellent before heating. As described above, since the baking temperature can be set to a high temperature, the curing time can be shortened and workability is improved.

The content of the epoxy resin in the heat-curable urethane composition of the present invention is preferably 1 to 20 parts by weight, and more preferably 3 to 20 parts by weight based on 100 parts by weight of the urethane prepolymer.
10 parts by weight is more preferred.

When the heat-curable polyurethane composition of the present invention does not contain an epoxy resin, the content of the latent curing agent is as follows: isocyanate groups (including blocked ones) of the urethane prepolymer; When all the salts are decomposed, the molar ratio of the amino group of the latent curing agent (mol number of isocyanate group / mol number of amino group) is
(Mol number of isocyanate group / mol number of amino group) = 1
/0.7 to 1 / 1.5 is preferable.

When the heat-curable polyurethane composition of the present invention contains a urethane prepolymer and an epoxy resin, the content of the latent curing agent is in addition to the compounding amount when the epoxy resin is not contained. The amount for curing the epoxy resin is also added. Further, the compounding amount of the curing agent to be added is a molar ratio of the epoxy group in the epoxy resin to the amino group of the latent curing agent when all the salts are decomposed (moles of epoxy group / moles of amino group). Is preferably 1.5 to 3.0.

The heat-curable urethane composition of the present invention may contain calcium oxide. When the urethane composition is applied, the urethane composition, particularly calcium carbonate or the like contained as a filler in the composition, easily absorbs moisture in the air, and after being cured by moisture, is rapidly heated to a high temperature (about 150 ° C.). When the baking step is performed, the moisture absorbed in the composition rapidly evaporates, the sealing material foams, and the sealing effect is impaired. In the heat-curable polyurethane composition of the present invention containing calcium oxide, moisture reacts with calcium oxide, and after moisture curing, even if heated to a high temperature for baking, moisture absorbed immediately is lost. It does not evaporate and foaming is prevented.

The content of calcium oxide in the heat-curable urethane composition of the present invention is preferably 2 to 10% by weight, more preferably 3 to 7% by weight in the heat-curable urethane composition of the present invention. This is because in this range, foaming of the urethane composition can be sufficiently suppressed.

The heat-curable urethane composition of the present invention may contain, if necessary, a filler, a plasticizer, an antioxidant, a silane coupling agent, a dispersant, a solvent, a catalyst,
Thixotropic agents, ultraviolet absorbers, dyes, pigments, flame retardants and the like may be contained.

Examples of the filler include carbon black, calcium carbonate, clay, talc, titanium oxide, quicklime, kaolin, zeolite, diatomaceous earth, and glass balloon.

As the plasticizer, those described above as the plasticizer used for the latent curing agent can be similarly used. The amount of the plasticizer as the whole composition is the sum of the amount added as the plasticizer contained in the latent curing agent.

As the silane coupling agent, for example,
Epoxy silane, vinyl silane, amino silane, mercapto silane, phenyl silane are exemplified. this house,
Amino silane, mercapto silane, isocyanate silane and epoxy silane are preferred.

Examples of the solvent include aromatic hydrocarbons, mineral spirits, and methyl ethyl ketone.

As the catalyst, for example, dioctyltin dilaurate (DOTL), dibutyltin dilaurate (DB)
TL), zinc octylate, organic bismuth compounds and the like, and amine catalysts such as triethylenediamine and morpholine amine.

The method for producing the heat-curable urethane composition of the present invention is not particularly limited. Preferably, the above-mentioned components are sufficiently kneaded under reduced pressure using a stirring device such as a mixing mixer and uniformly dispersed. It may be a composition.

Since the heat-curable urethane composition of the present invention is cured by heating and has excellent storage stability before heating, it is suitably used as a thermosetting sealing material used in the production of automobiles, refrigerators and the like. Can be In addition, PVC plastisol-based sealing materials, which are currently used as thermosetting sealing materials, and acrylic sol-based sealing materials, which are being developed as substitutes, are sols, so they are produced under strict quality control. Need to do
It also has the advantage of relatively easy production management. Further, in the heat-curable urethane composition of the present invention containing an epoxy resin, the composition is cured by heating, and is cured by baking at a high temperature, for example, 160 ° C. or more;
The degree of softening is smaller than when heated and cured at 20 ° C. In addition, storage stability is excellent before heating. In this way, the baking temperature can be set to a high temperature,
The curing time can be shortened and workability is improved.

In the heat-curable urethane composition of the present invention containing calcium oxide, the moisture absorbed by the composition is absorbed by the calcium oxide, and after the moisture curing, the high temperature (1%) is obtained.
Even when baked at about 50 ° C.), foaming of the urethane composition is prevented. The heat-curable urethane composition of the present invention using a urethane prepolymer in which isocyanate groups are blocked by oximes has a sufficiently long pot life and can be modified with a spatula or the like for a long time after application. preferable. In addition, relatively low temperature (about 12
(0 ° C.). Therefore, the heat-curable urethane composition of the present invention is suitably used as a thermosetting sealing material used for production of automobiles, refrigerators and the like. When the heat-curable urethane composition of the present invention is used as a sealing material, it is preferable to use a one-pack type, but it is also possible to use another hardener component to form a two-pack type.

[0043]

EXAMPLES The present invention will be specifically described below with reference to examples. <Preparation of urethane prepolymer> 80 parts by weight of polypropylene triol having an average molecular weight of 5,000 and 20 parts by weight of polypropylene diol having an average molecular weight of 2,000 were placed in a reaction vessel, and diphenylmethane-4,4'-diisocyanate (MDI) was converted into OH group / NCO group = The mixture was further stirred at 80 ° C. for 6 hours, and reacted to obtain a urethane prepolymer having a terminally active NCO group.

<Preparation of Curing Agent> 14 parts by weight of 1,12-diaminododecane and 17 parts by weight of benzoic acid (COOH / NH
₂ = 0.996) and diisodecyl phthalate (DI
DP) 100 parts by weight was stirred and ground using a ball mill for 12 hours to obtain a slurry-like latent curing agent.

(Examples 1-1 to 1-3, Comparative Example 1-1)
The raw materials shown below were mixed and dispersed using a stirrer at the weight ratios shown in Table 1 to obtain urethane compositions shown in Table 1. (Mole number of NCO group / Mole number of NH ₂ group) in each composition was 1/1. (1) The above urethane prepolymer (2) The above curing agent (3) Filler: Surface-treated calcium carbonate: Searets 200, manufactured by Maruo Calcium Heavy calcium carbonate: Super S, manufactured by Maruo Calcium (4) Epoxy resin : Bisphenol A type epoxy resin YD-128, manufactured by Toto Kasei Co., Ltd.

<Performance Test> The obtained urethane composition was subjected to a performance test for softening property. (1) Softening property The obtained urethane composition was electrodeposited on a steel plate (25 mm ×
50 mm x 2 mm), and then applied at 120 ° C for 60 minutes.
Heating was performed at 160 ° C. under two conditions for 60 minutes, and the hardness (JIS-A, JIS K6301) of the formed cured film was measured. The results are shown in Table 1.

[0047]

As is clear from Table 1, the heat-curable urethane compositions of the present invention containing an epoxy resin (Examples 1-1, 1-2 and 1-3) are obtained by baking at 160 ° C. The hardness of the cured product is the same or almost the same as the hardness of the cured product obtained by baking at 120 ° C. On the other hand, when no epoxy resin was contained (Comparative Example 1-1), the cured product obtained by baking at 160 ° C. was 120 ° C.
And became extremely softer than the cured product obtained by baking.

<Preparation of urethane prepolymer> A polypropylene triol having an average molecular weight of 5,000 was placed in a reaction vessel, and tolylene diisocyanate (TDI) was converted to OH group / N.
In addition, the mixture was stirred at 80 ° C. for 6 hours, and reacted to obtain a urethane prepolymer having a terminally active NCO group.

<Preparation of curing agent> 9 parts by weight of 1,6-hexanediamine and 19 parts by weight of benzoic acid were stirred and ground with a ball mill together with 30 parts by weight of diisodecyl phthalate to obtain a slurry-like latent curing agent. .

(Examples 2-1 and 2-2, Comparative Examples 2-1 and 2-2)
2-2) The raw materials shown below were mixed and dispersed at a weight ratio shown in Table 2 using a stirrer to obtain each urethane composition shown in Table 2. (1) Urethane prepolymer described above (2) Filler Surface-treated calcium carbonate: Sealets 200, manufactured by Maruo Calcium Co., Ltd. Heavy calcium carbonate: Super S, manufactured by Maruo Calcium Co. (3) Plasticizer: diisononyl adipate (DINA) (4) ) Epoxy resin: bisphenol F type epoxy resin YDF-170, manufactured by Toto Kasei Co., Ltd. (5) The above curing agent (6) Calcium oxide: CML-31, manufactured by Omi Chemical Industry Co., Ltd.

<Performance Tests> Various performance tests were performed on the obtained urethane compositions. (1) Foamability Each of the obtained urethane compositions was moisture-cured at 35 ° C. and 85% RH for 3 days, and then baked at 160 ° C. for 60 minutes. (2) Storage stability Each of the obtained urethane compositions was sealed and stored at 35 ° C for 7 days, and the rate of increase in viscosity was measured. Under these conditions, the viscosity increase rate is 1
If the value is less than 0%, it is shown as ○, and if it is more than 0%, it is shown as x in the table. The results are shown in Table 2.

[0053]

[Table 1]

<Preparation of urethane prepolymer> Unblocked urethane prepolymer A polypropylene triol having an average molecular weight of 5,000 was put in a reaction vessel, and tolylene diisocyanate (TDI) was
H group / NCO group = 0.5 and stirring reaction at 80 ° C. for 6 hours to obtain an unblocked urethane prepolymer (urethane prepolymer) containing an active isocyanate group (terminal isocyanate group) at a molecular terminal. A) was obtained. Methyl ethyl ketoxime block urethane prepolymer To the unblocked urethane prepolymer obtained by the above-mentioned method, methyl ethyl ketoxime of the same mole number as the isocyanate group contained is further added, and the mixture is stirred at 80 ° C. for 6 hours, and the terminal isocyanate group is methyl ethyl ketoxime. A blocked urethane prepolymer (urethane prepolymer B) was obtained. ε-caprolactam-blocked urethane prepolymer The unblocked urethane prepolymer obtained by the above-mentioned method has the same mole number of ε-
Add caprolactam, stir at 80 ° C. for 6 hours, and urethane prepolymer in which terminal isocyanate groups are blocked with ε-caprolactam (urethane prepolymer C)
I got Phenol-blocked urethane prepolymer To the unblocked urethane prepolymer obtained by the above-mentioned method, phenol of the same mole number as the isocyanate group contained was further added, and the mixture was stirred at 80 ° C. for 6 hours to block the terminal isocyanate group with phenol. A urethane prepolymer (urethane prepolymer D) was obtained.

<Preparation of Curing Agent> 9 parts by weight of 1,6-hexanediamine and 19 parts by weight of benzoic acid were stirred with a ball mill together with 30 parts by weight of diisodecyl phthalate to obtain a slurry-like latent curing agent. .

(Example 3-1 and Comparative Examples 3-1 to 3-3)
The raw materials shown below were mixed and dispersed using a stirrer at the weight ratios shown in Table 3 to obtain the respective urethane compositions shown in Table 3. In the table, the unit of the compound is part by weight. (1) The urethane prepolymer (2) The curing agent (3) Plasticizer: diisononyl adipate (DINA) (4) Filler Surface-treated calcium carbonate: Sealets 200, Maruo Calcium Co., Ltd. Heavy calcium carbonate: Super S, (5) Epoxy resin: bisphenol F type epoxy resin YDF-170, manufactured by Toto Kasei Co., Ltd. (6) Calcium oxide: CML-31, manufactured by Omi Chemical Industry Co., Ltd.

<Performance Tests> Various performance tests were performed on each of the obtained urethane compositions. (1) Spatula-modifying properties Each of the obtained urethane compositions was applied to an electrodeposition coated steel sheet (25 mm ×
(50 mm x 2 mm), left for 3 days in an atmosphere of 35 ° C and 85% RH, and then confirmed whether it could be corrected with a spatula. ○ indicates that the correction was possible with a spatula, and x indicates that moisture was hardened to such an extent that the spatula could not be corrected. (2) Curability Each of the obtained urethane compositions was electrodeposited on a steel plate (25 mm ×
50 mm x 2 mm), and 1 minute at 120 ° C for 60 minutes.
Heating was performed at 60 ° C. for 60 minutes under two conditions, and the hardness (JIS-A, JIS K6301) of the formed cured film was measured. The results are shown in Table 3.

[0058]

As is evident from the results, when the isocyanate group contained in the urethane prepolymer was not blocked (Comparative Example 3-1), the film was left to stand at 35 ° C. and 85% RH for 3 days and then moisture cured. I couldn't fix it with a spatula. When the isocyanate groups contained in the urethane prepolymer were blocked with ε-caprolactam and phenol (Comparative Example 3-2 and Comparative Example 3, respectively)
In the case of -3), curing at 120 ° C was insufficient.

[0060]

The heat-curable urethane composition of the present invention comprises:
It has excellent storage stability before heating, and has excellent curability and adhesiveness after heating. Further, by containing an epoxy resin, it has a characteristic that it does not soften even when baked at a high temperature. In addition, the heat-curable urethane composition of the present invention containing calcium oxide does not foam even when baked at a high temperature after application and moisture curing. The heat-curable urethane composition of the present invention using a urethane prepolymer blocked with oximes can ensure a sufficiently long pot life and can be easily cured at low temperatures.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C09K 3/10 C09K 3/10 D Z // (C08L 75/04 63:00) F-term (Reference) 4H017 AA04 AA24 AA25 AB03 AB08 AC03 AC16 AD05 AE05 4J002 CD012 CD052 CD062 CD102 CK031 CK041 CK051 DE086 EN027 EN037 EN067 EN077 FD010 FD016 FD020 FD050 DAFD FD070 FD090 FD130 FD147 FD200 CC03 4 DF01 DF11 DF20 DF27 DG03 DG04 DG06 DG08 DG14 DP19 HA01 HA07 HA08 HA11 HC03 HC12 HC13 HC17 HC46 HC52 HC61 HC67 HC71 HC73 HD12 JA42 KB02 KC08 KC17 KC23 KD12 KE02 MA03 MA24 QB03 QB12 RA07 RA08

Claims (4)

[Claims] 1. A heat-curable urethane composition comprising a urethane prepolymer, a latent curing agent which is a salt of an amine and an acid and is solid at ordinary temperature, and an epoxy resin. 2. The heat-curable urethane composition according to claim 1, further comprising calcium oxide. 3. A heat-curable urethane composition comprising a urethane prepolymer, a latent curing agent which is a salt of an amine and an acid and is solid at ordinary temperature, and calcium oxide. 4. The heat-curable urethane composition according to claim 1, wherein a part or all of the isocyanate groups contained in the urethane prepolymer are blocked by oximes.