JP6911404B2 - Thermosetting urethane resin compositions, films and articles - Google Patents

Description

The present invention relates to a thermosetting urethane resin composition, a film, and an article using the same.

Thermosetting urethane resin compositions are currently used in various applications such as automobile parts, home appliance parts, packaging materials, leather-like sheets, and printing rolls.

A hard coat layer has been provided on the surface of conventional articles such as plastic members and metal members for the purpose of preventing scratches (improving durability) and maintaining aesthetic appearance. However, while the hard coat layer is not easily scratched, once it is scratched, the scratch is not restored, and dirt adheres to the scratch, and the contamination tends to spread from the scratch, and the appearance of the article is aesthetically pleasing. It was the cause of damaging.

Furthermore, since the hard coat layer with high hardness as described above is hard and brittle, (1) the surface is liable to be cracked or scratched by long-term use, and (2) the scratch once on the surface is restored. If the base material to be coated is a soft material such as polycarbonate, the target level of high hardness will not be exhibited and durability at the outermost layer cannot be ensured. There was a problem such as that.

Therefore, in recent years, a thermosetting resin composition having a function of naturally recovering a scratch once made on the surface (hereinafter referred to as "self-healing property") has been proposed. (See, for example, Patent Documents 1 and 2.). Such a self-healing thermosetting resin composition is flexible and highly elastic, and even if it has a dent such as a scratch, it can be restored to its original state in a few seconds to a few minutes, so that it can be restored to its original state for a long period of time. There was an advantage that the initial good scratch resistance could be maintained.

However, the conventional thermosetting composition having self-healing property has a problem that the workability is not sufficient because the viscosity is high and the pot life is short.

Therefore, there has been a demand for a thermosetting resin composition having excellent workability (pot life) having a long pot life and capable of forming a coating film having excellent self-repairing property and elongation.

Japanese Unexamined Patent Publication No. 2-74540 Japanese Unexamined Patent Publication No. 2016-147416

The problem to be solved by the present invention is a thermosetting urethane resin composition having a long pot life and excellent curability, and a cured coating film of the thermosetting urethane resin composition. It is to provide a film excellent in self-healing property and elongation, and an article having the film.

As a result of diligent research to solve the above problems, the present inventors have added an isocyanate group at the molecular terminal, which is a reaction product of a polyol having no aromatic ring structure and a polyisocyanate having no aromatic ring structure. We have found that the above problems can be solved by using a thermosetting urethane resin composition containing a urethane prepolymer, a specific chain extender, a main agent containing an organic solvent, and a curing agent, and completed the present invention. I let you.

That is, the present invention is a urethane prepolymer (A) having an isocyanate group at the molecular end, which is a reaction product of a polyol (a1) having no aromatic cyclic structure and a polyisocyanate (a2) having no aromatic cyclic structure. ), A chain extender (B), a main agent (i) containing an organic solvent (C), and a thermosetting urethane resin composition containing a curing agent (ii). ) Contains the branched diol (b1), and the content of the branched diol (b1) in the main agent (i) is 2% by mass or less, which is a thermosetting urethane resin composition. It relates to a thing, a film having a cured coating film thereof, and an article using the film.

The heat-curable urethane resin composition of the present invention can form a film having a coating film having excellent workability (pot life) and curability, self-healing property and elongation, which has a long pot life, for example. , Automobiles, home appliances, mobile phones, OA equipment, galvanized steel sheets used for automobile parts, plated steel sheets such as aluminum-zinc alloy steel sheets, aluminum plates, aluminum alloy plates, electromagnetic steel sheets, copper plates, stainless steel sheets, etc. It can be suitably used for applications such as metal base materials.

The thermosetting urethane resin composition of the present invention contains a urethane prepolymer (A) having an isocyanate group at the molecular terminal, a chain extender (B), a main agent (i) containing an organic solvent (C), and a curing agent. It is characterized by containing (ii).

As the main agent (i), one containing a urethane prepolymer (A) having an isocyanate group at the molecular terminal, a chain extender (B), and an organic solvent (C) is used. The "main agent" in the present invention means a composition exceeding 50% by mass with respect to the total amount of the composition.

As the urethane prepolymer (A), a reaction product of a polyol (a1) having no aromatic cyclic structure and a polyisocyanate (a2) having no aromatic cyclic structure is used.

Examples of the polyol (a1) having no aromatic cyclic structure include an aliphatic polyol.

Examples of the aliphatic polyol include an aliphatic polyester polyol, an aliphatic polyether polyol, and an aliphatic polycarbonate polyol.

Examples of the polyester polyol include a polyester polyol obtained by reacting a low molecular weight polyol with a polycarboxylic acid; a polyester polyol obtained by a ring-opening polymerization reaction of a cyclic ester compound such as ε-caprolactone; Examples thereof include polyester polyols obtained by polymerization. These polyester polyols can be used alone or in combination of two or more. Further, a polyester polyol having an aliphatic cyclic structure can also be used.

Examples of the low molecular weight polyol include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, and 1,2-butane. Diol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 1,5-hexanediol, 1,6-hexanediol, 2,5-hexanediol , 1,7-Heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 2-methyl-1,3 -Propanediol, neopentyl glycol, 2-butyl-2-ethyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2-ethyl-1,3-hexanediol, 2-methyl-1 , 8-octanediol, glycerin, trimethylolpropane, ditrimethylolpropane, trimethylolpropane, pentaerythritol and other aliphatic polyols, 1,4-cyclohexanedimethanol, hydrogenated bisphenol A and other aliphatic polyols having an aliphatic cyclic structure. Can be mentioned.

As the polycarboxylic acid, one having no aromatic ring structure can be used, and for example, an aliphatic poly such as succinic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, dodecandicarboxylic acid, and dimer acid. Examples thereof include polycarboxylic acids having an aliphatic ring structure such as carboxylic acids, 1,4-cyclohexanedicarboxylic acids and cyclohexanetricarboxylic acids.

Examples of the polyether polyol include polytetramethylene glycol obtained by ring-opening polymerization of tetrahydrofuran. In addition, a compound obtained by addition polymerization of an alkylene oxide using one or more compounds having two or more active hydrogen atoms as an initiator can be mentioned. Examples of the compound having two or more active hydrogen atoms include propylene glycol, trimethylolglycol, 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, glycerin, and di. Examples thereof include glycerin, trimethylolethane, trimethylolpropane, water and hexanetriol. Examples of the alkylene oxide include propylene oxide, butylene oxide, styrene oxide, epichlorohydrin, and tetrahydrofuran. These polyether polyols can be used alone or in combination of two or more. Further, a polyether polyol having an aliphatic cyclic structure can also be used.

Examples of the polycarbonate polyol include those obtained by esterifying a carbonic acid and a carbonic acid ester with a polyhydric alcohol. Examples of the carbonic acid ester include methyl carbonate, dimethyl carbonate, ethyl carbonate, diethyl carbonate, cyclocarbonate, diphenyl carbonate and the like. Examples of the polyhydric alcohol include 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol and the like. These polycarbonate polyols can be used alone or in combination of two or more. Further, a polycarbonate polyol having an aliphatic cyclic structure can also be used.

The polycarbonate polyol is obtained by subjecting carbonic acid and carbonic acid ester to an esterification reaction with a polyhydric alcohol. Examples of the polyhydric alcohol include 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol and the like. These polycarbonate polyols can be used alone or in combination of two or more.

Examples of the polyisocyanate (a2) include polyisocyanates having an alicyclic structure such as cyclohexane diisocyanate, dicyclohexylmethane diisocyanate, and isophorone diisocyanate; and fats such as hexamethylene diisocyanate, lysine diisocyanate, xylylene diisocyanate, and tetramethylxylylene diisocyanate. Group polyisocyanates can be mentioned. Among these, the use of dicyclohexylmethane diisocyanate provides a thermosetting urethane resin composition that has a long pot life and can form a coating film having excellent self-healing properties and elongation. preferable. Further, these polyisocyanates (a2) can be used alone or in combination of two or more.

The isocyanate group equivalent of the urethane prepolymer (A) is 1000 to 4000 g / eq. Since a thermosetting urethane resin composition having a long pot life and excellent curability can be obtained. The range is preferably 1500 to 1800 g / eq. The range of is more preferable.

As the chain extender (B), a branched diol (b1) is indispensably used. As a result, an alkyl group can be introduced into the side chain of the urethane prepolymer (A), and the urethane prepolymer (A) can be made of a high molecular weight while preventing resin aggregation. Therefore, it has a long pot life and is excellent. A thermosetting urethane resin composition having a curable property can be obtained.

Examples of the branched diol (b1) include 2-methylpropanediol, neopentyl glycol, 1,3-butanediol, 1,2-butanediol, 1,4-pentanediol, 1,5-hexanediol, and 2, , 2,4-trimethyl-1,3-pentanediol, 2-butyl-2-ethyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2-ethyl-1,3-hexanediol , 2-Methyl-1,8-octanediol, and the like. Among these, 2-methylpropanediol, neopentyl glycol, 2,2,4-trimethyl-1,3-pentanediol, 2-butyl-2-ethyl-1,3-propanediol, 3-methyl-1, Diols in which all hydroxyl groups such as 5-pentanediol, 2-ethyl-1,3-hexanediol, and 2-methyl-1,8-octanediol are primary hydroxyl groups have a long pot life and excellent curability. It is preferable because a thermocurable urethane resin composition capable of forming a coating film having excellent self-healing properties and elongation can be obtained. Further, these branched diols (b1) can be used alone or in combination of two or more.

Further, the content of the branched diol (b1) in the chain extender (B) is 2% by mass or less because a thermosetting urethane resin composition having a long pot life and excellent workability can be obtained. Is preferable.

Further, as the chain extender (B), a low molecular weight diol having a molecular weight of 500 or less other than the branched diol (b1) and / or a low molecular weight triol having a molecular weight of 500 or less can be used.

The low molecular weight diol having a molecular weight of 500 or less means a diol having two hydroxyl groups, for example, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, and the like. 1,4-Butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1, , 11-Undecanediol, 1,12-dodecanediol and the like. Among these, a thermosetting urethane resin composition in which 1,4-butanediol has a long pot life and excellent curability, and can form a coating film having excellent self-healing property and elongation. It is preferable because it can be obtained. Further, these low molecular weight diols can be used alone or in combination of two or more. The molecular weight is a value calculated from the chemical formula.

Examples of the low molecular weight triol having a molecular weight of 500 or less include those having three hydroxyl groups, and examples thereof include glycerin, trimethylolpropane, and oxyethylene adducts of trimethylolpropane. These low molecular weight triols can be used alone or in combination of two or more. In the oxyethylene adduct of trimethylolpropane, the number of moles of oxyethylene added is not particularly limited, but is preferably 6 mol or less with respect to one molecule of trimethylolpropane. Among these, a thermosetting urethane resin composition in which trimethylolpropane has a long pot life and excellent curability, and can form a coating film having excellent self-healing property and elongation can be obtained. More preferred from. The molecular weight is a value calculated from the chemical formula.

Examples of the organic solvent (C) include ketone solvents such as acetone and methyl ethyl ketone; ether solvents such as tetrahydrofuran and dioxane; acetate solvents such as ethyl acetate and butyl acetate; nitrile solvents such as acetonitrile; dimethylformamide and N-methyl. Examples thereof include an amide solvent such as pyrrolidone. These organic solvents can be used alone or in combination of two or more.

In addition, the organic solvent is a part of the organic solvent (C) or a part of the organic solvent (C), for example, by distilling under reduced pressure during or after the production of the urethane prepolymer (A) in order to reduce the load on safety and the environment. You may remove all.

The curing agent (ii) contains an isocyanate group-reactive compound.

The isocyanate group-reactive compound refers to a compound having a functional group capable of reacting with an isocyanate group in the present invention.

The content of the isocyanate group-reactive compound in the curing agent (ii) in the range of 10 to 100% by mass has a long pot life and excellent self-healing property and elongation. It is preferable because a thermosetting urethane resin composition capable of forming a coating film having a coating film can be obtained, and a range of 15 to 50% by mass is more preferable.

Examples of the isocyanate group-reactive compound include the above-mentioned low molecular weight diol having a molecular weight of 500 or less and the low molecular weight triol having a molecular weight of 500 or less. These can be used alone or in combination with the low molecular weight diol and the low molecular weight triol. As a mixing method in the case of mixing and using, stirring by hand, stirring by a flask, stirring by a large shaft machine and the like can be used, but the mixing method does not matter as long as it can be mixed uniformly.

When the low molecular weight diol and the low molecular weight triol are mixed and used, the mass ratio [low molecular weight diol / low molecular weight triol] of the low molecular weight diol and the low molecular weight triol is in the range of 40/60 to 95/5. Is preferable.

Further, as the curing agent (ii), a reaction delaying agent can be used if necessary.

In the thermosetting urethane resin composition of the present invention, for example, the main agent (i) and the curing agent (ii) are charged in separate tanks of a two-component mixing and casting machine, and the main agent (i) and the curing agent (i) are charged. Examples thereof include a method of obtaining a thermosetting urethane resin composition by mixing each of the curing agents (ii) at room temperature with a mixing casting machine.

The excellent elongation is such that the equivalent ratio (NCO / OH) of the hydroxyl group (OH) of the curing agent (ii) to the isocyanate group (NCO) of the main agent (i) is in the range of 0.9 to 1.5. It is preferable because a thermosetting urethane resin composition capable of forming a coating film having the above can be obtained, and 1.0 to 1.2 is more preferable.

Further, the thermosetting urethane resin composition of the present invention may contain an additive, if necessary, and the additive includes, for example, a tackifier, a leveling agent, a catalyst, a plasticizer, a stabilizer, and the like. Various conventionally known additives such as fillers, pigments, dyes, and flame retardants can be used as long as the effects of the present invention are not impaired.

Examples of the tackifier include a rosin resin, a rosin ester resin, a hydrogenated rosin ester resin, a terpene resin, a terpene phenol resin, a hydrogenated terpene resin, and a C5 aliphatic resin as a petroleum resin. , C9-based aromatic resin, C5-based and C9-based copolymer resin, and the like can be used.

Examples of the catalyst include a tertiary amine catalyst and an organometallic catalyst.

Examples of the plasticizer include dibutyl phthalate, dioctyl phthalate, dicyclohexyl phthalate, diisooctyl phthalate, diisodecyl phthalate, dibenzyl phthalate, butyl benzyl phthalate, trioctyl phosphate, epoxy plasticizer, toluene-sulfoamide, chloroparaffin and adipate. Acid esters, castor oil and the like can be used. Examples thereof include methyl acid phosphate (AP-1) and an acrylic surface conditioner (BYK-361N).

Examples of the stabilizer include hindered phenol-based compounds, benzotriazole-based compounds, and hindered amine-based compounds.

Examples of the filler include silicic acid derivatives, talc, metal powder, calcium carbonate, clay, carbon black and the like.

The film of the present invention has a cured coating film of the thermosetting urethane resin composition on a base material.

Examples of the base material include polyethylene terephthalate (PET) and polyvinyl chloride (PVC).

As a method for producing the film of the present invention, for example, the thermosetting urethane resin composition is applied to the surface of the base material by a slit coater method such as a curtain flow coater method or a die coater method, a knife coater method, a roll coater method, or the like. Examples thereof include a method of coating, drying if necessary, and then heating and curing. The drying may be natural drying at room temperature, but it may also be heat-dried. The heat drying is usually preferably performed at 40 to 250 ° C. for a time of about 1 to 1000 seconds. Further, as a secondary curing step, heat drying may be performed at 40 to 100 ° C. for about 1 to 10 hours.

Further, the tan δ peak temperature (loss coefficient peak temperature) measured by dynamic viscoelastic analysis according to JIS K 0129 using the film is preferably in the range of 10 to 40 ° C. because excellent self-repairing property can be exhibited. The range of 20 to 35 ° C. is more preferable.

However, when the tan δ peak temperature of the film exceeds 45 ° C., the elasticity of the film is poor, and it may take a long time to heal the scratches, or the scratches once made may not be sufficiently healed. On the other hand, when the tan δ peak temperature of the film is less than -8 ° C., the strength of the cured product is insufficient and the self-healing property becomes insufficient, or the surface of the film tends to become sticky and the surface of the article. It may not be possible to use it by contacting it.

Examples of the article of the present invention include galvanized steel sheets used for automobiles, home appliances, mobile phones, OA equipment, automobile parts, etc., plated steel sheets such as aluminum-zinc alloy steel sheets, aluminum plates, aluminum alloy plates, etc. It can be suitably used for applications such as electromagnetic steel plates, copper plates, and metal base materials such as stainless steel plates.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.

(Preparation Example 1: Preparation of main agent (1))
35 parts by mass of ethyl acetate was placed in a 1-liter 4-necked round-bottom flask equipped with a nitrogen introduction tube, a thermometer, and a stirrer. 12.5 parts by mass of 4,4'-dicyclohexylmethane diisocyanate was added thereto, and stirring was started. Next, 17.5 parts by mass of polyoxytetramethylene glycol (“PTMG-1000” manufactured by Mitsubishi Chemical Corporation) that had been previously heated to 50 ° C. and melted was added. After raising the internal temperature to 60 ° C. while paying attention to heat generation, the mixture was stirred for 3 hours while maintaining the temperature, and it was confirmed that the equivalent weight of the non-volatile isocyanate groups reached 500. Next, the internal temperature was adjusted to 50 ° C., and 0.6 parts by mass of 1,4-butanediol, 0.6 parts by mass of 1,3-butanediol, and 0.6 parts by mass of trimethylolpropane were added. After raising the internal temperature to 60 ° C. while paying attention to heat generation, the mixture was stirred for 3 hours while maintaining the temperature, and it was confirmed that the equivalent weight of the non-volatile isocyanate groups reached 1630. Finally, 35 parts by mass of methyl ethyl ketone, 0.1 parts by mass of a light-resistant agent (“Tinubin 765” manufactured by BASF Japan Ltd.), and 0.15 parts by mass of an antioxidant (“Irganox 245” manufactured by BASF Japan Ltd.) were added. Then, the main agent (i-1) was obtained by stirring for 30 minutes.

(Preparation Examples 2 to 5: Preparation of main agents (i-2) to (i-5))
Main agents (i-2) to (i-5) were obtained in the same manner as in Example 1 except that the type and / or amount of the chain extender was changed as shown in Table 1.

(Comparative Preparation Examples 1 to 6: Preparation of Main Agents (i-6) to (i-11))
Main agents (i-6) to (i-11) were obtained in the same manner as in Example 1 except that the type and / or amount of the chain extender was changed as shown in Table 1.

Table 1 shows the compositions of the main agents (i-1) to (i-11) obtained in Preparation Examples 1 to 5 and Comparative Preparation Examples 1 to 6.

(Manufacturing Example 1: Production of curing agent)
0.71 parts by mass of 1,4-butanediol / trimethylol propane prepared at a ratio of 65:35 and 3 parts by mass of reaction retarder in a 1-liter 4-neck round-bottom flask equipped with a nitrogen introduction tube, a thermometer, and a stirrer. A curing agent was obtained by adding parts and 0.06 parts by mass of the catalyst and stirring at room temperature for 30 minutes.

(Example 1: Preparation of thermosetting urethane resin composition (1))
In the liquid A tank of the elastomer casting machine, 100 parts by mass of the main agent (i-1) obtained in Preparation Example 1 and 0.2 parts by mass of the leveling agent (“BYK-394” manufactured by Big Chemie Japan Co., Ltd.) were placed in B. 4.0 parts by mass of the curing agent obtained in Production Example 1 was charged into the liquid tank. Both the A liquid system and the B liquid system were operated at room temperature, and the two liquids were mixed with a mixing head at an NCO / OH ratio of 1.10 to obtain a thermosetting urethane resin composition (1).

(Examples 2 to 5: Preparation of thermosetting urethane resin compositions (2) to (5))
Thermosetting urethane resin compositions (2) to (5) were obtained in the same manner as in Example 1 except that the type of the main agent and the amount of the curing agent were changed as shown in Table 2.

(Comparative Example 1: Preparation of Thermosetting Urethane Resin Composition (C1))
In the liquid A tank of the elastomer casting machine, 100 parts by mass of the main agent (i-6) obtained in Comparative Preparation Example 1 and 0.2 parts by mass of the leveling agent (“BYK-394” manufactured by Big Chemie Japan Co., Ltd.) were placed. 4.0 parts by mass of the curing agent obtained in Production Example 1 was charged into the liquid B tank. Both the A liquid system and the B liquid system were operated at room temperature, and the two liquids were mixed with a mixing head at an NCO / OH ratio of 1.10 to obtain a thermosetting urethane resin composition (C1).

(Comparative Examples 2 to 6: Preparation of Thermosetting Urethane Resin Compositions (C2) to (C6))
Thermosetting urethane resin compositions (C2) to (C6) were obtained in the same manner as in Comparative Example 1 except that the type of the main agent and the amount of the curing agent were changed as shown in Table 3.

The following evaluations were carried out using the thermosetting urethane resin compositions obtained in the above Examples and Comparative Examples.

[Evaluation method of pot life]
The thermosetting urethane resin compositions obtained in Examples and Comparative Examples were put into a mayonnaise bottle, and the viscosity (25 ° C.) was measured. Based on the viscosity, the mixed solution was allowed to stand at 25 ° C., and the time until the viscosity was increased by 20% was measured and evaluated as follows.
⊚: 20 hours or more 〇: 10 hours or more and less than 20 hours Δ: 6 hours or more and less than 10 hours ×: less than 6 hours

[Evaluation method of curability]
The thermosetting urethane resin compositions obtained in Examples and Comparative Examples were coated on a PET film with a knife coater to a thickness of 30 μm, and then cured with a dryer to allow time for the tactile sensation to disappear. It was measured and evaluated as follows.
〇: No tack at 110 ° C x 2 minutes Δ: No tack at 110 ° C x 4 minutes x: No tack at 110 ° C x 6 minutes

[Production of film]
The thermosetting urethane resin compositions obtained in Examples and Comparative Examples were coated on a mold-released polyethylene terephthalate film with a knife coater to a thickness of 30 μm, and then tacked at 110 ° C. in an oven. A film was prepared by heating and curing until there was no more.

[Evaluation method of self-healing property]
A brass brush was pressed against the coating film with a load of 500 g and moved back and forth 10 times, and then the presence or absence of scratches was visually confirmed and evaluated as follows.
⊚: Wound heals within 5 minutes 〇: Wound heals within 10 minutes △: Wound heals within 1 hour ×: Wound does not heal after 1 hour

[Evaluation method of elongation]
The film was cut into strips having a width of 1 cm and a length of 5 cm, and the film was pulled using "Autograph AG-I" manufactured by Shimadzu Corporation, and the elongation rate was measured.
⊚: 220% or more 〇: 180% or more and less than 220% Δ: 150% or more and less than 180% ×: less than 150%

Table 2 shows the compositions and evaluation results of the thermosetting urethane resin compositions (1) to (5) obtained in Examples 1 to 5.

Table 3 shows the compositions and evaluation results of the thermosetting urethane resin compositions (C1) to (C6) obtained in Comparative Examples 1 to 6.

From the evaluation results of Examples 1 to 5 shown in Table 2, it was confirmed that the thermosetting urethane resin composition of the present invention was excellent in pot life and curability. Further, it was confirmed that the film formed by using the thermosetting urethane resin composition of the present invention has excellent self-healing property and elongation, and is also excellent in the appearance of the film.

On the other hand, from the evaluation results shown in Table 3, Comparative Examples 1 and 3 to 6 are examples in which the branched diol is not used as the chain extender used as the main agent, but the heat obtained in Comparative Examples 1 and 3 to 6 is obtained. It was confirmed that the curable urethane resin composition had a remarkably insufficient pot life.

Further, Comparative Example 2 is an example in which the content of the branched diol in the non-volatile content of the main agent is more than 2% by mass, but the thermosetting urethane resin composition obtained in Comparative Example 2 is the example of Comparative Example 1 and It was confirmed that the pot life was remarkably insufficient, as in the thermosetting urethane resin compositions obtained in 3 to 6.

Claims (7)

A urethane prepolymer (A) having an isocyanate group at the molecular end, which is a reaction product of a polyol (a1) having no aromatic cyclic structure and a polyisocyanate (a2) having no aromatic cyclic structure, and a chain extender ( A thermosetting urethane resin composition containing a main agent (i) containing B) and an organic solvent (C) and a curing agent (ii).
The chain extender (B) contains a branched diol (b1) and a low molecular weight triol having a molecular weight of 500 or less.
A thermosetting urethane resin composition characterized in that the content of the branched diol (b1) in the non-volatile content of the main agent (i) is 2% by mass or less. The chain extender (B) is further said branch diol (b1) other than the molecular weight of 500 or lower molecular weight Jio those containing Le claim 1 thermosetting urethane resin composition. The thermosetting urethane resin composition according to claim 1 or 2, wherein all the hydroxyl groups of the branched diol (b1) are primary hydroxyl groups. The isocyanate group equivalent in the non-volatile component of the main agent (i) is 1,000 to 4,000 g / eq. The thermosetting urethane resin composition according to any one of claims 1 to 3, which is in the range of. Any 1 of claims 1 to 4 in which the peak temperature of tan δ measured by the dynamic viscoelastic spectrum of the cured coating film made of the thermosetting urethane resin composition at a frequency of 1 Hz is in the range of 10 to 40 ° C. The thermosetting urethane resin composition according to the above item. A film comprising a cured coating film of the thermosetting urethane resin composition according to any one of claims 1 to 5. An article comprising the film according to claim 6.