KR20080105313A - Thermosetting powder paint composition for coating of pipe - Google Patents

Abstract

A thermosetting powder paint composition for coating a pipe is provided to improve adhesion, corrosion resistance and impact resistance and to be allow it to be wetted and cured to a base by melting. A thermosetting powder paint composition for coating a pipe comprises 20-60 wt% of a bisphenol A epoxy resin as a thermosetting epoxy resin; 1-30 wt% of a novolac modified bisphenol A epoxy resin or a urethane modified bisphenol A epoxy resin; 5-15 wt% of a phenol-based curing agent; 0.1-2 wt% of an amine-based accelerating latent curing agent; 0.5-1 wt% of a curing accelerator; 10-20 wt% of a phosphate-based pigment; and 5-30 wt% of a pigment other than a phosphate-based pigment.

Description

Thermosetting powder paint composition for coating of pipes

The present invention relates to a thermosetting powder coating composition for pipe coating, and more particularly, to a thermosetting powder coating composition for pipe coating that can be melted at a low temperature and can improve adhesion, corrosion resistance and impact resistance.

Looking at the powder coating method for the conventional pipe coating, there are a melt bonding method, a double steel pipe coating method and a triple steel pipe coating method, etc. All these coating methods are applied to a high temperature preheating method of 230 ℃ or more.

That is, all of the above coating methods preheat the substrate at a high temperature of 230 ° C. or higher, and after the powder coating is deposited or sprayed on the substrate, the powdery powder coating can be attached to the substrate while the temperature of the substrate is maintained at a constant temperature. By forming the coating film in a molten state, it becomes possible to secure the adhesion and mechanical properties to the substrate required for the coating film.

As such, preheating the substrate at a high temperature of 230 ° C. or higher causes an increase in raw material costs such as excessive use of energy for preheating the substrate, and cooling of the substrate does not occur even after curing of the paint. In order to facilitate handling, there is a disadvantage in that inconvenience is derived from workability and work stability, such as accompanied by a water cooling process.

In order to overcome the above problems, it is possible to consider a method of proceeding the curing of the coating film having a holding temperature of 160 ~ 170 ℃ low temperature, when forming a coating film using the existing paint in this way, holding temperature It was a disadvantage that the paint could not be sufficiently melted due to the low temperature, and the cooling rate of the substrate was increased to ensure sufficient time for the coating to be formed.

In addition, in order to improve this problem, when using a powder coating material for fast curing type pipe coating having a compounding composition capable of speeding up the reaction rate of powder coating material, adhesion to the substrate in boiling water, cathode peeling, etc., which is represented by the molten and cured coating film It was a problem that it could not be secured or the mechanical properties such as impact and flexibility could not be satisfied.

Looking at the thermosetting epoxy powder coating applied in the existing epoxy powder coating for pipe coating, US Pat. It is disclosed to react with dicyandiamide or with phenol resin using an epoxy resin in which polyisocyanate is added to form an isocyanurate with oxazolidone in the process of polymerizing an epoxy resin. US Patent No. 3,882,064 uses bisphenol A type epoxy resins and dicyandiamide as a curing agent, and US Patent No. 3,819,564 uses bisphenol A type epoxy resins, acid anhydrides, and hydroxyl curing agents. A method is disclosed. In addition, Japanese Patent No. 92-20605 proposes a method in which diphenol is used as a curing agent while mixing a novolak epoxy resin with a bisphenol type epoxy resin.

As described above, it can be seen that the thermosetting epoxy powder coating method for applying to inside and outside the pipe uses various systems. However, such systems, as mentioned above, applies a method of preheating the pipe and curing after coating, wherein the preheating temperature should be 230 ° C. or higher, and this is an epoxy powder coating for pipe coating. It can be said that the limit.

An object of the present invention is to solve the problems described above, by changing the combination system of the epoxy resin and the curing agent, it can be melted at a low temperature, and the thermosetting powder coating composition for pipe coating which can improve the adhesion, corrosion resistance and impact resistance To provide.

The thermosetting powder coating composition for pipe coating of the present invention is 20 to 60% by weight of a bisphenol A type epoxy resin, 1 to 30% by weight of a novolak modified bisphenol A type epoxy resin or a urethane modified bisphenol A type epoxy resin, as a thermosetting epoxy resin, 5 to 15% by weight of a phenol-based curing agent, 0.1 to 2% by weight of an amine-based accelerator latent curing agent, 0.5 to 1% by weight of a curing accelerator, 10 to 20% by weight of a phosphate-based pigment, and 5 to 30% by weight of a pigment other than the phosphate-based Characterized in that.

As the thermosetting epoxy resin used in the present invention, it is preferable that the equivalent weight of the bisphenol A epoxy resin is 400 to 1200, and more preferably 500 to 1000. When the equivalent weight of the bisphenol A epoxy resin is less than 400, the powder coating Although the viscosity is low and the wettability with resin is improved, it is unfavorable because it is inferior in flexibility and the storage property of a paint falls, and when the equivalent of bisphenol-A epoxy resin exceeds 1200, the flexibility of a coating film improves, but it is wettability with resin. This lowers the adhesion force, which leads to a significant decrease in boiling water and corrosion resistance.

The content of the bisphenol A epoxy resin is preferably used 20 to 60% by weight, more preferably 25 to 50% by weight, when the content is less than 20% by weight is not preferable because the flexibility is reduced, on the other hand When it exceeds 60% by weight, the flexibility of the powder coating composition is increased, but it is not preferable because the desired desired curability is not obtained.

In addition, as another thermosetting epoxy resin used in the present invention, the novolak-modified bisphenol-A epoxy resin is equivalent to 500 to 900, an epoxy resin modified with a phenol novolak resin or cresol novolak resin 5 to 15% by weight. Another compatible urethane modified bisphenol-A epoxy resin is equivalent to 380-700, and is an epoxy resin modified with 20-30% by weight of monoisocyanate or di-isocyanate, the content of which is 1-30% by weight. Preferably, it is more preferable to use 5-25 weight%. When the modified bisphenol-A epoxy resin is used in less than 1% by weight, an appropriate degree of curing cannot be obtained when applied to paint, and when used in excess of 30% by weight, the resin synthesis stability is lowered and gelled, which is not preferable. .

The curing agent used in the present invention may be used by mixing a phenolic curing agent and an amine accelerator latent curing agent, and the phenolic curing agent may be a cresol novolac epoxy phenol curing agent or a novolak epoxy phenol curing agent having a hydroxyl equivalent of 200 to 300. It is preferable to use 5 to 15% by weight, and it is preferable to use 0.1 to 2% by weight of the amine-based accelerated latent curing agent having an active hydrogen equivalent of 30 to 50 as the amine-based accelerated latent curing agent.

When the hydroxyl equivalent of the phenolic curing agent is out of the range of 200 to 300, sufficient reactivity cannot be obtained, and thus the flexibility is poor, which is not preferable. In addition, when the amount of the phenolic curing agent used is less than 5% by weight, the physical properties of the coating film are too hard, and the flexibility is lowered. When the amount of the phenol-based curing agent is more than 15% by weight, the softness is too soft and the flexibility is good. not.

The amine-based accelerated latent curing agent can be used known without limitation, preferred examples are 2-cyanoguanidine, adipic acid dihydrazide, sebacic acid dihydrazide, hexamethylenetetraamine, imidazole derivatives, And amine complexes of dichlorophenyl-1,1-dimethyl urea and boron trifluoride. If the active hydrogen equivalent weight of the amine-promoting latent curing agent is less than 30, sufficient crosslinking density cannot be obtained, and if it exceeds 50, the crosslinking density becomes too dense, which may adversely affect the flexibility or cause side reactions to cure in an undesired direction. Is not preferable because there is a possibility to proceed. In addition, when less than 0.1% by weight of the amine-based curing agent is used, it is difficult to produce a structure having a flexible and constant curing density at almost the catalyst or additive level, and when used in excess of 2% by weight, unreacted amine and moisture It is undesirable because it may react and cause discoloration of the coating and serious blisters.

By mixing the phenol-based curing agent and the amine-based curing agent, it is possible to maintain the appropriate flexibility and strength during crosslinking by low-temperature curing to ensure mechanical properties such as impact and flexural properties. In the case where the phenolic curing agent is used alone, the coating film is flexible and the flexibility is improved, but the impact property is poor, and when the amine curing agent is used alone, the flexibility is poor, which is not preferable.

The curing accelerator used in the present invention may be a known one without particular limitation on the kind thereof, and examples thereof include triphenylphosphine, benzyltriphenylphosphonium chloride, butyltriphenylphosphonium chloride, and tetraphenyl phosphonium chloride. Quaternary ammonium, 1-methylimidazole, 2-methylimidazole, 1,2-dimethylimidazole, 1,5-dimethylimidazole, 2-butyl-5-chloro-1H-imidazole-4 -Carbaldehyde, vinylimidazole, climbazole, 1,1-carbonyldiimidazole, tert-butyl dimethylsilylchloride, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2- It is preferable to use 0.5-1 weight% of those selected from imidazoles, such as ethylimidazole, 1-benzyl-2-methylimidazole, and 2-butylimidazole. If the amount of use exceeds the above range, an appropriate gelling time cannot be obtained, and thus, in the present invention where the reaction rate and the degree of crosslinking at a low temperature are required, the workability and the stability of the coating film properties are greatly deteriorated.

In the coating composition of the present invention, in order to achieve fast curing at low temperature, the coating composition should have a gel time of 10 to 50 seconds at 160 ~ 180 ℃. However, this rapid reactivity may be a detrimental factor that degrades sufficient wetting with the resin and degrades the adhesion performance.

In order to improve the deterioration of adhesion performance during such low temperature curing, phosphate-based pigments are used in the present invention. Examples of the structural formulas include X ₃ (PO ₄ ) ₂ , XHPO _{4 ,} X (H ₂ PO ₄ ) ₂ , X ₁₀ (PO ₄ ) ₆ (OH) ₂ (herein, X = Zn, Ca, K or Na) or a hydrate thereof, and the PO ₄ content in the pigment is preferably 30 to 55% by weight, 40 to 50 It is more preferable that it is weight%, and it is preferable that oil absorption is 30 to 40%. If the content of PO _{4 in the} pigment is less than 30% by weight, it is difficult to expect an adhesion effect. If the content is more than 55% by weight, the adhesion is improved but the corrosion resistance tends to be somewhat poor, which is not preferable. In addition, when the oil absorption amount is less than 30%, the compatibility with the epoxy resin is poor, not only dispersibility but most of the physical properties are poor, and when the oil absorption exceeds 40%, the inertness of the pigment itself is canceled, which is not preferable. Preferred phosphate-based pigments are zinc phosphates. It is preferable that the phosphate pigment is used in an amount of 10 to 20% by weight. If the content is less than 10% by weight, the effect of increasing adhesion with the resin cannot be expected. It may cause.

Pigments other than the phosphate-based pigments used in the present invention may include at least one of titanium dioxide, barium sulfate, calcium carbonate, silica and small amounts of known organic pigments and inorganic pigments for color, the content of which is 5 to 30 When the content is less than 5% by weight, it is preferable that the content is less than 5% by weight, and the content of the resin is relatively high, resulting in poor boiling water and corrosion resistance. Since the dispersion becomes poor due to the excess of the pigment, the coating film does not express the performance, which is not preferable.

In addition, examples of the organic pigments and inorganic pigments, color pigments such as ultramarine blue, phthalocyanine blue, phthalocyanine green, carbon black, and the like, which are commonly used for color in powder coating, and control the physical properties and strength of the powder coating And various kinds of inorganic pigments.

The powder coating composition of the present invention may further include additives for conventional powder coating compositions, and examples of such additives include a flow improver and a pinhole for preventing pinholes in the coating, which are typically used in the manufacture of powder coating to lower the surface tension of the coating. And adhesion promoters for enhancing adhesion of the inhibitor and the coating film.

Thermosetting powder coating composition for pipe coating according to the present invention can be prepared by the following manufacturing process.

First, in a one-step process, the raw materials such as epoxy resins, curing agents, curing accelerators, pigments, and additives are uniformly mixed, followed by dry premixing for about 100 to 600 seconds at 2,000 to 5,000 rpm using a Henschel mixer. A premixing process is performed to dry mix to maintain uniform physical properties.

In a two-step process, the raw material pre-dispersed through the first step process using a disperser (eg, PLK46, Booth) to perform melt mixed dispersion at a temperature of 90 ~ 120 ℃. The melt-mixed raw materials are passed through a cooling roll and a cooling belt to produce chips having a size of 50 to 100 mm and a thickness of 1 to 5 mm.

In the three-step process, the melt-dispersed chip through the two-step process using a pulverizer (for example, hammer mill, ACM mill, turbo mill, etc.) having a mechanically constant powder particle size (average particle size 40 ~ 60μ) The thermosetting powder coating for pipe coating of the present invention is prepared by carrying out a pulverization process for preparing a paint.

The present invention is explained in more detail by the following examples and comparative examples. The following examples are merely examples for illustrating the present invention and are not intended to limit the protection scope of the present invention.

Example  And Comparative example

After mixing each component in the blending ratio (wt%) shown in Table 1 to prepare a thermosetting powder coating for pipe coating, based on the CAN / CSA Z245.20 standard, a physical property evaluation test was carried out by the following method, and The results are shown in Table 2 below.

                                                                 (Unit: weight%) Example Comparative example One 2 3 One 2 3 4 5 6 CNE80408 ^{1 )} 36.50 35.90 37.30 20.80 51.00 26.40 23.70 24.50 13.20 CNE00336 ^{2 )} 15.60 - 16.00 32.70 2.70 - 35.60 18.30 - CNE00400 ^{3 )} - 15.80 - - - 30.00 - 18.30 35.20 Phenol Curing Agent ^{4 )} 8.30 8.60 6.40 6.20 5.90 6.80 7.30 7.00 6.50 DICY Hardener ^{5 )} 0.30 1.00 0.50 - - - - - - DICY Hardener ^{6 )} - - - 0.50 0.40 0.50 0.50 0.50 0.50 Curing accelerator ^{7 )} - - - - 0.50 - 1.80 - 0.50 Curing accelerators ^{8 )} 1.00 1.00 1.00 0.50 0.50 0.60 0.60 0.60 0.60 Additives1 ^{9 )} 0.30 0.30 0.30 0.30 0.30 0.30 0.30 0.30 0.30 Additives2 ^{10 )} 0.30 0.30 0.30 0.30 0.30 0.30 0.30 0.30 0.30 TiO ₂ ^{11 )} 2.60 2.60 2.60 2.60 2.60 2.60 2.60 2.60 2.60 Pigments2 ^{12 )} 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 Pigments3 ^{13 )} 20.00 18.00 24.00 35.40 35.10 31.20 26.60 27.20 39.60 Pigments4 ^{14 )} 14.40 15.40 10.90 - - - - - - Additives3 ^{15 )} 0.60 1.00 0.60 0.60 0.60 1.20 0.60 0.30 0.60 sum 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0

week)

1) Bisphenol A type epoxy resin, epoxy equivalent 850 ~ 950 (Keumgang Korea Chemical)

2) Novolac modified bisphenol A type epoxy resin, epoxy equivalent 450 ~ 550 (Kumkang Korea Chemical)

3) Urethane modified bisphenol A epoxy resin, epoxy equivalent 450 ~ 550 (Kumkang Korea Chemical)

4) Cresol novolac epoxy phenol curing agent KD-420 (Kukdo Chemical)

5) amine-based accelerated latent curing agent, EH-3842 (ASAHI DENKA)

6) amine latent curing agent, DMPF (THOMAS SWAN)

7) Hardening accelerator, MIA-5 (DEGUSSA HULLS)

8) Hardening accelerator, 2-MI (SIKOKU)

9) Flow improver, PLP100 (KS Chemicals)

10) Pinhole preventive agent, BENZOIN (Miwon)

11) Colored Pigment, CR-80 (ISHIHARA)

12) Colored Pigment, MA-100 (MITSUBISHI)

13) Constitution Pigment, HB-400 (Korea Semiconductor)

14) Constitutional Pigment, ZINC PHOSPHATE (SB Chemical)

15) Adhesion Promoter, Organosilane, KBM-403 (SHINETSU)

<Measurement of physical properties>

* Flexibility: Test at 6˚ angle at room temperature

          Poor-if a crack has occurred

          Pass-if no crack

          Δ-cracks can be observed when viewed under a microscope,

               If not observed with the naked eye

* Impact: Check whether the specimen is cracked when the specimen is struck with constant force at room temperature. The value shown in Table 2 is the strength of the force exerted when a crack occurred.

The greater the strength, the better the impact.

* Navability: Classified as Rating 1 ~ Rating 5 (R1 ~ R5),

              Typical pass levels are R1 to 3, and excellent in R1 to R2.

* Cathode peelability: After exposing the specimen for 65 ℃ * 48 hours at constant voltage, put the blade on the exposed part and lift the coating to rank with the distance from the center of the coating. The smaller the number, the better.

Test Items Exam conditions Example Comparative example One 2 3 One 2 3 4 5 6 Gel time @ 160 39 seconds 40 seconds 39 seconds 36 seconds 37 seconds 40 seconds 39 seconds 38 seconds 40 seconds Flexibility 6 ° C Pass Pass Pass Bad △ △ Pass Pass Pass Impact Room temperature 6J 6J 6J 5J 4J 6J 6J 3J 6J Boiling water resistance 24 hours @ 95 ℃ R2 R2 R1 R4 R3 R3 R4 R5 R2 Cathode Peelability 5V × 48 hours @ 65 ℃ 3.5mm 3.0mm 2.0mm Bad Bad Bad 7.0mm 6.0mm Bad

According to the present invention, even after coating at a low temperature preheating of 160 to 170 ° C., wetting and curing with the base material due to melting on the substrate are possible, and the coating properties of the film have the flexibility, impact resistance, boiling resistance and boiling resistance of the high temperature preheating film of 230 ° C. The thermosetting powder coating composition for pipe coating excellent in peelability etc. can be provided.

Claims (6)

As a thermosetting epoxy resin, 20-60 weight% of bisphenol-A epoxy resins, 1-30 weight% of novolak-modified bisphenol-A epoxy resins or urethane modified bisphenol-A epoxy resins, 5-15 weight% of phenolic hardening | curing agents, and amine promotion 0.1-2 wt% of latent curing agent, 0.5-1 wt% of curing accelerator, 10-20 wt% of phosphate pigment, 5-30 wt% of pigment other than phosphate-based thermosetting powder coating composition for pipe coating . The equivalent weight of the bisphenol A type epoxy resin is 400-1200, the equivalent weight of the novolak-modified bisphenol A type epoxy resin is 500-900, and the equivalent weight of the urethane-modified bisphenol A type epoxy resin is 380-700. Thermosetting powder coating composition for pipe coating, characterized in that. According to claim 1, wherein the phenolic curing agent is a cresol novolac epoxy phenol curing agent or novolak epoxy phenol curing agent having a hydroxyl equivalent of 200 ~ 300, the amine-based promoting latent curing agent is 30 to 50 active hydrogen equivalent A thermosetting powder coating composition for coating a pipe. The method of claim 1, wherein the curing accelerator is triphenylphosphine, benzyltriphenylphosphonium chloride, butyltriphenylphosphonium chloride, tetraphenyl phosphonium chloride, 1-methylimidazole, 2-methylimidazole , 1,2-dimethylimidazole, 1,5-dimethylimidazole, 2-butyl-5-chloro-1H-imidazole-4-carbaldehyde, vinylimidazole, klimbazole, 1,1- Carbonyldiimidazole, tert-butyl dimethylsilylchloride, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-ethylimidazole, 1-benzyl-2-methylimidazole and 2 -Thermosetting powder coating composition for pipe coating, characterized in that selected from butylimidazole. The method of claim 1, wherein the phosphate-based pigment is a structural formula X ₃ (PO ₄ ) ₂ , XHPO ₄ , X (H ₂ PO ₄ ) ₂ or X ₁₀ (PO ₄ ) ₆ (OH) ₂ (where X = Zn , Ca, K or Na) compound or a hydrate thereof, the thermosetting powder coating composition for pipe coating. According to claim 1, wherein the pigment other than the phosphate-based thermosetting powder coating composition for pipe coating, characterized in that at least one selected from titanium dioxide, barium sulfate, silica, ultramarine blue, phthalocyanine blue, phthalocyanine green and carbon black. .