KR100967697B1 - 2-hydroxy amide compounds, their preparation and their application - Google Patents

Abstract

The present invention relates to a 2-hydroxy amide compound useful as a curing agent for low-toxic polyester powder coatings, a method for preparing the same, and a polyester powder coating composition comprising the same as a main component of the curing agent.

Powder coating, low toxicity, polyester, curing agent, β-HAA, 2-hydroxy-N, N, N ', N'-tetrakis (2-hydroxyethyl) alkylamide, 2-hydroxy amide

Description

2-hydroxy amide compound, preparation method and use thereof {2-HYDROXY AMIDE COMPOUNDS, THEIR PREPARATION AND THEIR APPLICATION}

The present invention relates to a novel 2-hydroxy amide 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.

Powder coatings are 100% solid paints, which can be used to obtain thicker coatings and superior coating performance compared to liquid coatings, and also provide problems 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 (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. . Polyester resin-triglycidyl isocyanurate powder coating is widely used as ceiling and building exterior materials because of its excellent weatherability and mechanical properties, and the gel time is long during the curing process so that the viscosity increases accordingly. Since the 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. In 1972, by Rohm & Haas, beta-hydroxyalkylamide (β-HAA, for example, European Patent Publication No. 0957082, U.S. Patent 4,076,917, US Patent 4,101,606, International Publication No. 0055266, and European Patent Publication No. 1203763). Beta hydroxyalkylamide is low toxicity compared to triglycidyl isocyanurate, has the advantages of a simple process and low manufacturing cost. However, compared with triglycidyl isocyanurate, the mechanical strength and overbake resistance are inferior. In the case of triglycidyl isocyanurate, the molecular structure is cyclic and the ring opening reaction of three epoxides results in the formation of a solid and multidimensional structure with polyester, while beta hydroxyalkylamide is structurally linear and Since the reaction site is divided into two sides, the formation of a multidimensional network is rather difficult. In addition, polyester-betahydroxyalkylamide causes water (H ₂ O) produced during the curing reaction to cause pinholes on the surface of the paint during drying, and some of them even at temperatures lower than the appropriate curing temperature. As the curing proceeds, the surface smoothness, that is, the leveling is inferior to that of triglycidyl isocyanurate.

Therefore, it is easy to form a multi-dimensional network structure with polyester resins compared to the existing beta hydroxyalkyl amide, and the development of a curing agent for powder coating having excellent mechanical strength and heat resistance is required.

An object of the present invention to provide a new curing agent for polyester powder coating that can suppress the generation of micropores according to the use of the existing curing agent beta hydroxyalkylamide (β-HAA) and further improve the mechanical strength and heat resistance It is. In other words, as a curing agent for polyester powder coating, a new structure having a structure capable of easily forming a multidimensional network structure with polyester by additionally introducing a hydroxy group into an intermediate alkyl chain of an existing beta hydroxyalkylamide. It is to provide a 2-hydroxy amide compound.

Another object of the present invention is to provide a method for preparing the novel 2-hydroxy amide compound.

Still another object of the present invention is to provide a polyester powder coating composition comprising the 2-hydroxy amide compound as a main component of a curing agent.

The present inventors conducted extensive research to solve the problems of the conventional beta hydroxyalkylamides used as polyester curing agents as described above, as a result of using the 2-hydroxy amide compound of the formula (1) according to the present invention as a curing agent In this case, it was confirmed that the curing properties are superior to the existing beta hydroxyalkylamides, and that the mechanical strength and heat resistance can be improved, and thus, the present invention has been completed.

Accordingly, the present invention provides a 2-hydroxy amide compound represented by the following Chemical Formula 1, a preparation method thereof, and a polyester powder coating composition containing the same.

[Formula 1]

[In Formula 1, A is a straight or branched chain (C1-C7) alkylene,

R ¹ to R ⁴ are independently selected from linear or branched (C 1 -C 7) alkyl having one or more hydroxyl groups substituted.]

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 2-hydroxy amide compound represented by the following formula (1).

[Formula 1]

[In Formula 1, A is a straight or branched chain (C1-C7) alkylene,

R ¹ to R ⁴ are independently selected from linear or branched (C 1 -C 7) alkyl having one or more hydroxyl groups substituted.]

delete

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

[Formula 2]

[In Formula 2, A is a straight or branched chain (C1-C7) alkylene,

R ⁵ to R ⁸ are independently selected from linear or branched (C 1 -C 7) alkyl.]

In more detail, the compound of Formula 1 may be selected from a compound of Formula 3 below.

(3)

[N is an integer of 1 to 5 in Formula 3]

Specifically, the compound of Formula 3 is 2-hydroxy-N, N, N ', N'-tetrakis (2-hydroxyethyl) succinimide (2-hydroxy-N, N, N', N'- tetrakis (2-hydroxyethyl) succinamide], 2-hydroxy-N, N, N ', N'-tetrakis (2-hydroxyethyl) glutaramide (2-hydroxy-N, N, N', N ' -tetrakis (2-hydroxyethyl) glutaramide], 2-hydroxy-N, N, N ', N'-tetrakis (2-hydroxyethyl) adipamide (2-hydroxy-N, N, N', N'-tetrakis (2-hydroxyethyl) adipamide].

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, A, R ¹ to R ⁴ are as defined in Formula 1, and R ¹¹ and R ¹² are independently selected from linear or branched (C 1 -C 7) alkyl.]

In the reaction scheme 1, the hydroxyl group may include a process of being protected or deprotected with an appropriate protecting group, and the carboxyl group may be protected or deprotected depending on the reaction conditions. Scheme 1 is exemplified as a reaction capable of producing a compound having a structure in which different types of secondary amines are bonded to both sides.

The present invention is a 2-hydroxy amide compound represented by the following formula (4) formed by combining the same secondary amine is represented by the dialkyl 2-hydroxy dicarboxylate (dialkyl 2-hydroxydicarboxylate) represented by the formula (5) It can be prepared by reacting a secondary amine compound.

[Formula 4]

[Chemical Formula 5]

[Formula 6]

[In Formulas 4 to 6, A is a straight or branched chain (C1 ~ C7) alkylene,

R ¹¹ and R ¹² are independently selected from linear or branched (C 1 -C 7) alkyl,

R ¹³ and R ¹⁴ are independently selected from straight or branched chain (C 1 -C 7) alkyl having one or more hydroxyl groups substituted.]

The compounds of Formula 4 and Formula 5 may be pure (S) -stereoisomers, pure (R) -stereoisomers or a mixture of two stereoisomers.

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 preferably 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 The reaction rate may be too high and a large amount of reaction byproducts may occur. If the reaction time is less than 1 hour, unreacted substances may be generated. If the reaction time is too long for more than 24 hours, discoloration of the product may be caused, which is disadvantageous.

In another aspect, the present invention provides a polyester powder coating composition containing the 2-hydroxy amide compound of Formula 1 to Formula 4 as a main component of the curing agent. The 2-hydroxy amide compound according to the present invention contains 1 to 15% by weight, more preferably 5 to 10% 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 curing agent component is less than 1% by weight, the curing rate is too slow and sufficient curing does not occur, so that the mechanical properties and heat resistance of the coating film may be lowered, and when the curing agent component is more than 15% by weight, it is easy to form a coating film. You can't.

The powder coating is prepared by mixing 75 to 99% by weight of the polyester resin and 1 to 15% by weight of the curing agent evenly in a grinder, and then extruded through a melt extruder, and after cooling the extruded material again and regrind. In addition to the polyester resin and the curing agent, an additive for improving the physical properties of the coating film may be further 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 pigments can be added for color.

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.

The 2-hydroxy amide compound according to the present invention is easier to form a polyester resin and a multi-dimensional network structure than the conventional beta hydroxyalkyl amide in which the hydroxy group is not substituted at the 2-position of the alkyl chain. When used as a paint hardener, the curing time is fast and the mechanical strength and heat resistance of the powder paint can be improved and the formation of micropores can be suppressed.

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.

The structure of the material according to the present embodiment was confirmed using a nuclear magnetic resonance analyzer (Bruker, 300 MHz ARX-R300 spectrometer) and infrared spectroscopy (Shimadzu, IRPrestige-21). Molecular weight measurement of the main product according to the invention was confirmed using a mass spectrum analyzer (PerSeptive Biosystems, 4700 Proteomics Analyzer, MAlLDI-TOF}.

Preparation Example 1 Preparation of Dimethyl 2-hydroxysuccinate

1.2 g (40.8 mmol) of 2-hydroxysuccinic acid and 50 ml of methanol were mixed in a round flask, and 10.22 ml (163.2 mmol) of thionyl chloride were added dropwise under a stream of nitrogen at 0 ° C. Thereafter, the mixture was further stirred at the same temperature for about 1 hour, and stirred at room temperature for about 12 hours to terminate the reaction. At this time, the remaining solvent and unreacted material were removed using a rotary evaporator and the residue was dried in vacuo to give dimethyl 2-hydroxysuccinate (yield 99%).

¹ H-NMR (CDCl ₃ ) δ 4.49 (dq, 1H) 3.79 (s, 3H) 3.69 (s, 3H) 2.86 (dd, 1H) 2.77 (dd, 1H)

¹³ C-NMR (DMSO) δ 173.5, 170.9, 67.2, 51.8, 51.6, 39.0

Preparation Example 2 Preparation of Diethyl 2-Hydroxysuccinate

After mixing 1.2 g (40.8 mmol) of 2-hydroxysuccinic acid and 50 ml of ethanol in a round flask, about 2 drops of concentrated sulfuric acid was added and refluxed under nitrogen stream for about 1 hour, and then the solvent was distilled off. The residue was dissolved in 50 ml of ethyl ether, washed with sodium carbonate solution, dried over anhydrous sodium sulfate (Na ₂ SO ₄ ), and the organic layer was concentrated on a rotary evaporator. Nate (yield 99%) was obtained.

¹ H-NMR (CDCl ₃ ) δ4.50 (dq, 1H), 4.22 (q, 2H), 4.10 (q, 2H), 2.85 (dd, 1H), 2.77 (dd, 1H), 1.30 (t, 3H ), 1.29 (t, 3 H).

Example 1

1 g (6.17 mmol) of dimethyl 2-hydroxysuccinate and 1.36 g (12.34 mmol) of ethanolamine prepared in Preparation Example 1 were placed in a reactor equipped with a distillation apparatus, respectively. 1 wt% of sodium methoxide was added and stirred under nitrogen stream at 120 ° C. for 6 hours. Methanol produced from the reaction was distilled off during the reaction. The resulting product was dried under vacuum to yield 2-hydroxy-N, N, N ', N'-tetrakis (2-hydroxyethyl) succinimide (2-hydroxy-N, N, N', N'-tetrakis ( 2-hydroxyethyl) succinamide) was obtained (yield 98%). Infrared spectroscopy and mass spectrometry spectra of the prepared compounds are shown in FIGS. 1 and 2, respectively.

¹ H-NMR (CDCl ₃ ) δ5.18 (br s, 2H), 4.85 (br s, 2H), 4.69 (m, 1H), 3.55-3.25 (m, 16H), 2.74 (m, 2H)

¹³ C-NMR (DMSO) 172.8, 171.0, 69.2, 59.54, 59.40, 59.14, 59.04, 50.90, 50.23, 48.84, 48.69

[Example 2]

1 g (6.17 mmol) of diethyl 2-hydroxysuccinate and 1.36 g (12.34 mmol) of diethanolamine were placed in a reactor equipped with a distillation unit, and sodium corresponding to 1% by weight of diethyl 2-hydroxysuccinate was added. Ethoxide was added and reacted under nitrogen stream at 120 ° C. for 6 hours. Ethanol produced from the reaction was distilled off. The resulting product was dried under vacuum to yield 2-hydroxy-N, N, N ', N'-tetrakis (2-hydroxyethyl) succinimide (2-hydroxy-N, N, N', N'-tetrakis ( 2-hydroxyethyl) succinamide] (yield 98%).

The nuclear magnetic resonance spectrum of the 2-hydroxyalkylamide thus prepared is the same as the spectrum value described above in Example 1 above.

Example 3

Polyester resin (UCB group, weight average molecular weight = 7000 ~ 9000, viscosity = 7 ~ 16 Poise (P) / 200 ℃, acid value = 25 ~ 40) and the curing agent prepared in Example 1 weight of 92: 8 Disperse evenly for 1 minute in a grinder (Henschel FM-10 Premixer) at a ratio, and extrude 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 spraying, the thickness is 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 specimen thus painted is shown in FIG. 3, and the photograph according to time is shown in FIG. 4, (a) in FIG. 4 is a photograph of the specimen one week after painting and (b) is a photograph of the specimen one month after painting. (C) is a photograph of a specimen one month after powder coating using the conventional β-HAA curing agent N, N, N ', N'-tetrakis (2-hydroxyethyl) adipamide in the same manner as above. . As shown in the photo (c) of FIG. 4, the formation of pinholes was found in part, but when the curing agent of the present invention was used, there was no formation of pinholes on the surface of the coating film as shown in FIG. After a while (photo c in Fig. 4), no discoloration or deformation of the coating film occurred.

1 is an infrared spectroscopy spectrum of the compound prepared in Example 1,

2 is a mass spectrometry spectrum of the compound prepared in Example 1,

Figure 3 is a photograph of the polyester powder coating specimens carried out using the compound prepared in Example 1 as a curing agent,

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

(a) is a photograph of the specimen after one week after powder coating with a mixture of polyester resin using the compound of Example 1 of the present invention as a curing agent,

(b) is a photograph of one month after the polyester powder coating using the compound of Example 1 of the present invention as a curing agent,

(c) is a photograph of one month after the polyester powder coating using the existing β-HAA N, N, N ', N'-tetrakis (2-hydroxyethyl) adiamide as a curing agent. .

Claims (7)

2-hydroxy amide compound represented by the formula (1). [Formula 1]

[In Formula 1, A is a straight or branched chain (C1-C7) alkylene, R ¹ to R ⁴ are independently selected from linear or branched (C 1 -C 7) alkyl having one or more hydroxyl groups substituted.] delete The method of claim 1, The compound of Formula 1 is a 2-hydroxy amide compound selected from the compound of Formula 2. [Formula 2]

[In Formula 2, A is a straight or branched chain (C1-C7) alkylene, R ⁵ to R ⁸ are independently selected from linear or branched (C 1 -C 7) alkyl.] The method of claim 3, wherein The compound of Formula 2 is a 2-hydroxy amide compound selected from the compound of Formula 3. (3)

[N is an integer of 1 to 5 in Formula 3] To prepare a 2-hydroxy amide compound of Formula 4 by reacting a dialkyl 2-hydroxy dicarboxylate represented by the formula (5) and a secondary amine compound represented by the formula (6) Method for producing a 2-hydroxy amide compound. [Formula 4]

[Chemical Formula 5]

[Formula 6]

[In Formulas 4 to 6, A is a straight or branched chain (C1 ~ C7) alkylene, R ¹¹ and R ¹² are independently selected from linear or branched (C 1 -C 7) alkyl, R ¹³ and R ¹⁴ are independently selected from straight or branched chain (C 1 -C 7) alkyl having one or more hydroxyl groups substituted.] The method of claim 5, The reaction is a method for producing a 2-hydroxy amide compound formed under a base catalyst selected from sodium hydroxide or sodium (C1-C4) alkoxide. A polyester powder coating composition comprising the 2-hydroxy amide compound of any one of claims 1, 3 and 4 as a curing agent.

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