KR20090111720A - Cycloalkane dicarboxamide compounds, their preparation and application - Google Patents

Abstract

PURPOSE: A cycloalkane dicarboxamide compound is provided to improve mechanical strength and heat resistance when used as a hardener of polyester powder resin. CONSTITUTION: A cycloalkane dicarboxamide compound is represented by formula 1. In formula 1, R1~R4 are independently linear or branched C1-C7 alkyl groups of which one or more hydroxyl groups are substituted; R9 and R10 are independently hydrogen, hydroxyl group, or hydroxyl-substituted or non-substituted C1-C7 alkyl groups; and m and n are independently integers between 1 and 3.

Description

CYCLOALKANE DICARBOXAMIDE COMPOUNDS, THEIR PREPARATION AND APPLICATION

The present invention relates to a novel cycloalkane dicarboxamide compound used as a curing agent for polyester powder coating, a preparation method thereof, and a polyester powder coating composition comprising the same as a main component of the curing agent.

The present invention relates to a curing agent for low-toxic polyester powder coating, and more particularly, a problem of triglycidyl isocyanurate (TGIC) mainly used as a curing agent of a conventional polyester. It relates to a curing agent and a method for producing the same having improved performance and excellent performance.

Powder coatings are 100% solids paints, which can achieve thicker coatings and superior coating performance compared to liquid coatings with one-time coating, as well as problems resulting from liquid coatings such as environmental pollution, fire hazard, toxicity and odor. As it can be solved, usage is steadily increasing.

The powder coating is composed of a polymer resin, a curing agent, a pigment, and ordinary additives, and since the polymer resin and the curing agent occupy most of the powder coating composition, the main physical properties of the powder coating depend on the polymer resin and the curing agent. Polyester resin is used as the main resin constituting the thermosetting powder coating, and is the second most used after the epoxy resin. In addition, polyester resins can be colored in various colors and have excellent aesthetic and decorative properties. The physical and chemical properties are inferior to epoxy resins, but the heat and ozone resistance and weather resistance are excellent, so the amount of use is gradually increasing. Triglycidyl isocyanurate (1,3,5-triglycidylisocyanurate, TGIC) is mainly used as a curing agent for polyester powder coatings having such carboxyl groups, and has been an industrial standard for high weatherability powder coating since the 70s. have. Polyester resin-triglycidyl isocyanurate powder coating is widely used as ceiling and building exterior materials because of its excellent weatherability and mechanical properties.The gel time is long during the curing process, so the viscosity is correspondingly high. Because of the increased curing rate control is relatively easy compared to other curing agents. However, since the hardening reaction occurs at a high temperature (near 250 ° C.), energy consumption is very high during the hardening reaction, and it is difficult to apply to materials that are concerned about deformation due to heat, that is, wood or plastic materials. In addition, the toxicity of triglycidyl isocyanurate poses a big problem of import regulation in developed countries.

The problem of import regulation caused by the toxicity of triglycidyl isocyanurate resulted in low-toxic beta-hydroxyalkylamide (β-HAA) in Rohm & Haas in 1972; Patent Publication No. 0957082, US Patent No. 4,076,917, US Patent No. 4,101,606, International Publication No. 0055266, and European Patent Publication No. 1203763). These beta hydroxyalkylamides are less toxic than triglycidyl isocyanurate, and have the advantages of simple process and low manufacturing cost. However, beta hydroxyalkyl amide has higher mechanical strength and overbake resistance than triglycidyl isocyanurate. Falling has the disadvantage. In this regard, a study of replacing the alkyl chain of the beta hydroxyalkylamide main chain with an unsaturated alkyl group (ie, alkenylene) (US Pat. No. 4,101,606) has been attempted. Although the physical properties are poor to commercialize, attempts to improve heat resistance by controlling the carbon number of the main chain or by increasing the alkyl number of the side chain (US Pat. No. 6,235,933) have been made, but this situation is also difficult to commercialize because the reaction is not easy.

Therefore, there is still a need for the development of a curing agent for powder coating having excellent mechanical strength and heat resistance as compared to the conventional beta hydroxyalkylamide.

An object of the present invention is to provide a novel polyester powder coating curing agent that can improve the low mechanical strength and heat resistance problems of beta hydroxyalkylamide (β-HAA) mainly used as a conventional low toxicity curing agent.

More specifically, by replacing the non-cyclic main chain of betahydroxyalkylamide, a curing agent for polyester powder coating, with a cyclic chain, that is, cycloalkane, it improves the heat resistance of the curing agent itself and when applied to powder coating, mechanical strength and It is an object to provide a novel cycloalkane dicarboxamide compound with improved overbake resistance.

Another object of the present invention is to provide a method for preparing the novel cycloalkane dicarboxamide compound.

It is another object of the present invention to provide a carboxyl group-containing polyester resin powder coating composition comprising the cycloalkane dicarboxamide compound as a main component of a curing agent.

The present inventors conducted extensive research to improve the heat resistance and mechanical strength, which is a problem of the conventional beta hydroxyalkyl amides used as a curing agent for polyester resins, as described above. As a result of replacing the cyclic chain, that is, cycloalkylene, it was surprisingly found that the heat resistance and the curing property with the polyester resin were remarkably improved as compared with the conventional beta hydroxyalkylamide, thereby completing the present invention.

Accordingly, the present invention provides a cycloalkane dicarboxamide compound represented by Chemical Formula 1, a method for preparing the same, and a polyester resin powder coating composition containing the same.

[Formula 1]

[In Formula 1, R ¹ to R ⁴ are independently selected from a linear or branched (C 1 -C 7) alkyl group having one or more hydroxy groups substituted, and R ⁹ and R ¹⁰ are independently hydrogen, a hydroxy group, or A hydroxy group is selected from a substituted or unsubstituted (C1-C7) alkyl group, and m and n are independently integers of 1 to 3.]

Hereinafter, the present invention will be described in more detail.

At this time, if there is no other definition in the technical terms and scientific terms used, it has a meaning commonly understood by those of ordinary skill in the art. In addition, repeated description of the same technical configuration and operation as in the prior art will be omitted.

The present invention provides a cycloalkane dicarboxamide compound represented by the following formula (1).

[Formula 1]

[In Formula 1, R ¹ to R ⁴ are independently selected from a linear or branched (C 1 -C 7) alkyl group having one or more hydroxy groups substituted, and R ⁹ and R ¹⁰ are independently hydrogen, a hydroxy group, or A hydroxy group is selected from a substituted or unsubstituted (C1-C7) alkyl group, and m and n are independently integers of 1 to 3.]

The compound represented by Formula 1 may be a pure cis-isomer, a pure trans-isomer, or a mixture of two stereoisomers.

Specifically, the compound of Formula 1 may be selected from the compound of Formula 2.

[Formula 2]

[In Formula 2, R ⁵ to R ⁸ are independently selected from linear or branched (C 1 to C 7) alkylene, and m and n are independently integers of 1 to 3.

In Formula 2, when m + n is 2 to 6, the main chain introduced between the dicarboxamides is cyclobutylene, cyclopentylene, cyclohexylene, cycloheptylene or cyclooctylene group, and more specifically, A compound in which cyclohexylene having m + n of 4 is introduced into the main chain, and the compound in which the cyclohexylene group is introduced may be more specifically N ¹ , N ¹ , N ⁴ , and N ⁴ -tetra of Formula 3 It may be kiss (2-hydroxyethyl) cyclohexane-1,4-dicarboxamide.

[Formula 3]

The compound of Chemical Formula 1 according to the present invention may be prepared by the same method as in Scheme 1 below.

Scheme 1

[In Scheme 1, R ¹ to R ⁴ are independently selected from a straight or branched chain (C 1 -C 7) alkyl group having one or more hydroxy groups substituted, and R ⁹ and R ¹⁰ are independently hydrogen, hydroxy group or hydroxy. The group is selected from a substituted or unsubstituted (C1-C7) alkyl group, R ¹¹ and R ¹² are independently selected from straight or branched chain (C1-C4) alkyl, m and n are independently an integer from 1 to 3 to be.]

In Scheme 1, a carboxyl group may be protected or deprotected by an appropriate protecting group, and Scheme 1 may prepare an amide compound having a structure in which different types of secondary amines are bonded to both sides. It is illustrated as a reaction.

In the present invention, the cycloalkane dicarboxamide compound of Formula 4, formed by combining the same secondary amine, is represented by the following formula: Dialkyl cycloalkane dicarboxylate represented by Formula 5 and Formula 6 below: It can be prepared from the reaction of secondary amines.

[Formula 4]

[Formula 5]

[Formula 6]

[In Formulas 4 to 6, R ⁹ and R ¹⁰ are independently selected from hydrogen, a hydroxy group, or a (C1-C7) alkyl group having a substituted or unsubstituted hydroxy group, and R ¹¹ and R ¹² are independently a straight chain. Or branched (C 1 -C 4) alkyl, R ¹³ and R ¹⁴ are independently selected from a straight or branched chain (C 1 -C 7) alkyl group having one or more hydroxy groups substituted, and m and n are independently Is an integer of 1 to 3.]

The reaction for preparing the amide compound of Formula 4 from the ester compound of Formula 5 and the secondary amine compound of Formula 6 may be performed without a catalyst, but it is more preferable to proceed under a base catalyst. The base catalyst is selected from sodium hydroxide or sodium (C1-C4) alkoxide, and the sodium (C1-C4) alkoxide includes sodium methoxide, sodium ethoxide, sodium i-propoxide or sodium t-butoxide The side is mentioned.

The reaction temperature and the reaction time may vary depending on the catalyst component and the starting material, but the reaction temperature is 80 to 150 ° C., and the reaction time is suitably in the range of 1 hour to 24 hours. If the reaction temperature is less than 80 ℃ reaction rate is too slow to produce an unreacted material, if the reaction temperature is too high exceeding 150 ℃ there is no increase in further effects and some decomposition reactions proceed economically disadvantageous can do. If the reaction time is less than 1 hour, unreacted matter may occur, and if the reaction time is too long for more than 24 hours, discoloration of the product may be caused, which is disadvantageous.

The present invention also provides a polyester resin powder coating composition containing the cycloalkane dicarboxamide compound of Chemical Formulas 1 to 4 as a main component of the curing agent. The cycloalkane dicarboxamide compound according to the present invention is contained in an amount of 1 to 20% by weight, more preferably 5 to 15% by weight, based on the total weight of the powder coating composition, and may be used in combination with other curing agent components. When the content of the curing agent component is less than 1% by weight, the curing rate is too slow and sufficient curing does not occur, so that the coating film may not be easily formed. When the content of the curing agent component is more than 20% by weight, the mechanical properties of the coating film may be too high. Physical properties and heat resistance may be lowered.

The powder coating is prepared by uniformly mixing 80 to 99% by weight of the carboxyl group-containing polyester resin and 1 to 20% by weight of the curing agent in a grinder, and then extruded through a melt extruder, the extruded material is cooled again and then regrind. In addition to the polyester resin and the curing agent, an additive for improving the physical properties of the coating film may be additionally added. As the additive, polyacrylate as a smoothing agent, benzoin as a pinhole inhibitor, barium sulphate as a filler, and the like may be added. Carbon black, titanium oxide or other various pigments can be added to develop the color of the pigment.

Coating film formation using the powder coating may be achieved by spraying the powder coating powder on the coating object using a spray gun or the like and then heating the coating material to a constant temperature.

Since the cycloalkane dicarboxamide compound according to the present invention contains a cycloalkane ring structure in its skeleton, its molecular structure is relatively strong compared to the conventional beta hydroxyalkylamide having an acyclic alkyl chain. (rigid) When used as a curing agent of the polyester resin powder coating, there is an effect of increasing the mechanical strength and heat resistance of the coating film compared to the case of using a conventional beta hydroxyalkylamide as a curing agent.

The present invention will be described in more detail with reference to the following Examples. However, the following examples are merely examples of the present invention, and the claims of the present invention are not limited thereto.

Preparation Example 1 Preparation of Dimethyl Cyclohexane-1,4-Dicarboxylate

In a 100 ml flask equipped with a reflux apparatus, cyclohexane-1,4-dicarboxylic acid (3.5 g, 20.3 mmol), 50 ml of methanol, and 1 to 2 drops of concentrated sulfuric acid were added and reacted at 85 to 90 ° C for 10 hours. The residual methanol was removed using a rotary evaporator, the obtained residue was dissolved in ethyl ether again, washed several times with an aqueous NaHCO ₃ solution, dried over anhydrous MgSO ₄ , the solvent was distilled off under reduced pressure, and the resulting product was dried in vacuo. Dimethyl cyclohexane-1,4-dicarboxylate was obtained (colorless liquid, 4.10 g, 99%).

¹ H NMR (CDCl ₃ ) δ 3.64-3.50 (6H), 2.29-2.27 (2H), 1.91-1.88 (4H), 1.38-1.31 (4H).

Preparation Example 2 Preparation of Diethyl Cyclohexane-1,4-Dicarboxylate

In a 100 ml flask equipped with a reflux apparatus, cyclohexane-1,4-dicarboxylic acid (4.0 g, 23.2 mmol), 50 ml of ethanol, and 1-2 drops of concentrated sulfuric acid were added and refluxed for 6 hours. The residual ethanol was removed using a rotary evaporator, the obtained residue was dissolved in ethyl ether again, washed with an aqueous NaHCO ₃ solution, dried over anhydrous MgSO ₄ , the solvent was distilled off under reduced pressure, and the resulting product was dried again in vacuo. Diethyl cyclohexane-1,4-dicarboxylate was obtained (colorless liquid, 5.19 g, 98%).

¹ H NMR (CDCl ₃ , 300 MHz) δ 4.13-4.10 (4H), 2.30-2.25 (2H), 1.93-1.90 (4H), 1.40-1.32 (4H), 1.30 (6H).

Example 1 Preparation of N ¹ , N ¹ , N ⁴ , N ⁴ -tetrakis (2-hydroxyethyl) cyclohexane-1,4-dicarboxamide

Dimethyl 1,4-cyclohexane-1,4-dicarboxylate (1.04 g, 5.19 mmol) and diethanolamine (1.09 g, 10.38 mmol) prepared in Preparation Example 1 were equipped with a 25 ml reaction flask equipped with a cooler. After stirring and adding 2 wt% of sodium methoxide, the reaction was carried out at 110 ° C. for about 10 hours. The reaction was terminated when the product gradually solidified to produce a solid. The product was dried in vacuo to give N ¹ , N ¹ , N ⁴ , N ⁴ -tetrakis (2-hydroxyethyl) cyclohexane-1,4-dicarboxamide (white solid, 1.76 g, 98% ).

¹ H NMR (DMSO-d ₆ , 300 MHz) δ 3.52-3.28 (16H), 2.60-2.50 (2H), 1.67-1.65 (4H), 1.43-1.40 (4H).

¹³ C NMR (DMSO-d ₆ , 75 MHz) δ 175.9, 59.9-59.5, 50.9, 48.9, 39.2, 29.2-28.7.

3369, 3186, 2935, 2862, 1595, 1458, 1427, 1165, 1053 cm^-1 .FT-IR / ATR

3369, 3186, 2935, 2862, 1595, 1458, 1427, 1165, 1053 cm ^-1 .

ESI-MS: calculated 346.23 [M] ⁺ ; Found 347.24 [M + H] ⁺ .

1 is a thermogravimetric spectrum comparison diagram of a compound prepared in Example 1 with conventional β-HAA [ N ¹ , N ¹ , N ⁶ , N ⁶ -tetrakis (2-hydroxyethyl) adipamide]

Figure 2 is a differential scanning calorimetry spectra of the conventional β-HAA [ N ¹ , N ¹ , N ⁶ , N ⁶ -tetrakis (2-hydroxyethyl) adipamide] and the compound prepared in Example 1. As can be seen in FIG. 1, the conventional β-HAA starts to lose weight at 150 ° C., whereas N ¹ , N ¹ , N ⁴ , N ^4- (2-hydroxyethyl) cyclohexane-1,4-dica In the case of voxamide, the weight loss starts at 200 ° C, indicating that the thermal properties are superior to the existing β-HAA. Also, as can be seen from the differential scanning calorimetry comparison of FIG. 2, the conventional β-HAA has a melting point of about 125 ° C., whereas N ¹ , N ¹ , N ⁴ , N ^4- (2-hydroxyethyl) cyclo according to the present invention is used. Hexane-1,4-dicarboxamide was found to be about 190 ° C., indicating that the heat resistance of the compound itself was very good.

Example 2

Diethyl 1,4-cyclohexane-1,4-dicarboxylate (1.5 g, 6.57 mmol) and diethanolamine (1.38 g, 13.14 mmol) prepared in Preparation Example 2 were added to a 25 ml reaction flask equipped with a cooler. After stirring and adding 2 wt% of sodium ethoxide, the reaction was carried out at 110 ° C. for about 10 hours. To remove unreacted product, the product was washed with THF and the residue dried in a vacuum pump to give N ¹ , N ¹ , N ⁴ , N ⁴ -tetrakis (2-hydroxyethyl) cyclohexane-1,4- Dicarboxamide was prepared (2.16 g, 95%).

The nuclear magnetic resonance spectrum of the tetrakis (2-hydroxyethyl) cyclohexane-1,4-dicarboxamide thus prepared is the same as the spectrum value described above in Example 1 above.

Example 3

The carboxyl group-containing polyester resin (manufacturer UCB group, weight average molecular weight = 7000 to 9000, viscosity = 7 to 16 poise (P) / 200 ° C, acid value = 25 to 40) and the curing agent prepared in Example 1 Disperse evenly for 1 minute in a grinder (Henschel FM-10 Premixer) at a weight ratio of 8, and extruded using a melt extruder (Werner & Pfleiderer ZSK-30) at 100 ℃ (Zone 1: 100 ℃, Zone 2: 100 ℃, Screw Speed: 300 RPM, Torque: 30 ~ 50%). After cooling the extruded material again at room temperature, the powder of 140 mesh obtained by regrinding twice with Paudal K2-1 type hammer mill is sprayed on the workpiece (steel plate) with a spray gun (Nordson Versa-Spray 100, applied at -80 kV). After the spraying, the thickness was 40 μm based on the dry coating thickness. The coating film was formed by baking for 200 minutes by applying heat of 200 ° C. in an oven in which a constant temperature was maintained. The photograph of the coated specimen is as shown in Figure 3, the photograph according to the heat resistance test is as shown in Figure 4, Figure 3 is a compound of Example 1 and the conventional β-HAA [ N ¹ , N ¹ , N ⁶ , N ^6- As a test result comparing the performance as a curing agent between tetrakis (2-hydroxyethyl) adipamide], the photograph (a) is a specimen immediately after powder coating with a mixture of the curing agent and polyester resin of Example 1 of the present invention. Photograph (b) is a specimen immediately after powder coating using a conventional β-HAA [ N ¹ , N ¹ , N ⁶ , N ⁶ -tetrakis (2-hydroxyethyl) adipamide] as a curing agent. Is a photo of.

4 is an experimental result comparing heat resistance as a curing agent between the compound of Example 1 and conventional β-HAA [ N ¹ , N ¹ , N ⁶ , N ⁶ -tetrakis (2-hydroxyethyl) adipamide] Photograph (a) is a photograph of the specimen after 1 hour at 210 ℃ after powder coating with a mixture of the curing agent and the polyester resin of Example 1 of the present invention, photograph (b) is a conventional β-HAA [ N ¹ , N ¹ , N ⁶ , N ⁶ -tetrakis (2-hydroxyethyl) adipamide] is a photograph of specimens which have been elapsed at 210 ° C. for 1 hour after polyester powder coating using a curing agent. The heat resistance test results showed that δE (color difference) = 1.2 when using the curing agent of Example 1 of the present invention, and δE (color difference) = 2.0 when using conventional β-HAA. Therefore, the heat resistance of the N ¹ , N ¹ , N ⁴ , N ⁴ -tetrakis (2-hydroxyethyl) cyclohexane-1,4-dicarboxamide of the present invention was better.

1 is a thermogravimetric spectrum comparison diagram of a compound prepared in Example 1 with conventional β-HAA [ N ¹ , N ¹ , N ⁶ , N ⁶ -tetrakis (2-hydroxyethyl) adipamide]

Figure 2 is a differential scanning calorimetry spectra of the conventional β-HAA ([ N ¹ , N ¹ , N ⁶ , N ⁶ -tetrakis (2-hydroxyethyl) adipamide] and the compound prepared in Example 1 .

3 is an experimental result comparing the performance as a curing agent between the compound of Example 1 and the conventional β-HAA [ N ¹ , N ¹ , N ⁶ , N ⁶ -tetrakis (2-hydroxyethyl) adipamide]

(a) is a photograph of a specimen immediately after powder coating with a mixture of a curing agent and a polyester resin of Example 3 of the present invention,

(b) is a photograph of the specimen immediately after coating the polyester powder using the existing β-HAA N ¹ , N ¹ , N ⁶ , N ⁶ -tetrakis (2-hydroxyethyl) adiamide as a curing agent.

4 is an experimental result comparing heat resistance as a curing agent between the compound of Example 3 and conventional β-HAA ( N ¹ , N ¹ , N ⁶ , N ⁶ -tetrakis (2-hydroxyethyl) adipamide),

Photograph (a) is a photograph of the specimen after 1 hour at 210 ℃ after powder coating with a mixture of the curing agent and the polyester resin of Example 1 of the present invention (δE (color difference) = 1.2),

Photograph (b) shows polyester powder coating using conventional β-HAA N ¹ , N ¹ , N ⁶ , N ⁶ -tetrakis (2-hydroxyethyl) adiamide as a curing agent, A photograph of a specimen that has elapsed (δE (color difference) = 2.0).

Claims (7)

The cycloalkane dicarboxamide compound represented by the following formula (1). [Formula 1]

[In Formula 1, R ¹ to R ⁴ are independently selected from a linear or branched (C 1 -C 7) alkyl group having one or more hydroxy groups substituted, and R ⁹ and R ¹⁰ are independently hydrogen, a hydroxy group, or A hydroxy group is selected from a substituted or unsubstituted (C1-C7) alkyl group, and m and n are independently integers of 1 to 3.] The method of claim 1, The compound of Formula 1 is a cycloalkaine dicarboxamide compound selected from the compound of Formula 2. [Formula 2]

[In Formula 2, R ⁵ to R ⁸ are independently selected from linear or branched (C 1 -C 7) alkylene, and m and n are each independently an integer of 1 to 3. The method of claim 2, Cycloalcaine dicarboxamide compound, characterized in that m + n is 4 in the formula (2). The method of claim 3, wherein The compound of Formula 2 is a cycloalkaine dicarboxamide compound selected from the compound of Formula 3. [Formula 3]

To prepare a cycloalkane dicarboxamide compound of the formula (4) from the reaction of a dialkyl cycloalkane dicarboxylate represented by the formula (5) and a secondary amine represented by the formula (6) Method of producing a cycloalkaine dicarboxamide compound. [Formula 4]

[Formula 5]

[Formula 6]

[In Formulas 4 to 6, R ⁹ and R ¹⁰ are independently selected from hydrogen, a hydroxy group, or a (C1-C7) alkyl group having a substituted or unsubstituted hydroxy group, and R ¹¹ and R ¹² are independently a straight chain. Or branched (C 1 -C 4) alkyl, R ¹³ and R ¹⁴ are independently selected from a straight or branched chain (C 1 -C 7) alkyl group having one or more hydroxy groups substituted, and m and n are independently Is an integer of 1 to 3.] The method of claim 5, The reaction is a method for producing a cycloalkane dicarboxamide compound formed under a base catalyst selected from sodium hydroxide or sodium (C1-C4) alkoxide. The polyester resin powder coating composition containing the cycloalkane dicarboxamide compound of any one of Claims 1-4 as a hardening | curing agent.

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