KR20110112965A - Thermosetting powder coating composition for pipe coating with excellent high temperature corrosion resistant - Google Patents

Abstract

The present invention relates to a thermosetting powder coating composition for steel pipes, and more particularly, characterized in that it includes a thermosetting epoxy resin, a curing agent, a curing accelerator, a pigment and a silicone-based additive, and has excellent long-term boiling water adhesion and high temperature long-term corrosion resistance. It relates to a thermosetting powder coating composition for use.

Description

Thermosetting powder coating composition for pipe coating with excellent high temperature corrosion resistant}

The present invention relates to a thermosetting powder coating composition for steel pipes, and more particularly, to high-temperature long-term boiling water adhesion, corrosion resistance and bendability, including a high molecular weight epoxy resin and a sieving pigment capable of maximizing a barrier effect. It relates to a thermosetting powder coating composition.

In general, powder coating methods performed to prevent corrosion of steel pipes include a melt bonding method, a double steel pipe coating method, and a triple steel pipe coating method, and these coating methods have long-term physical properties of 48 hours or more, particularly high temperature boiling water attachment. Resistance and corrosion resistance were not required separately. Recently, the specifications required by the original government building or steel pipe coating companies have been strengthened, and the boiling water properties at 56 days of deposition at 75 ° C and 95 ° C for more than 3 grades, and after 56 days of cathode peeling test at 65 ° C and 95 ° C The peeled distance is required to be 15 mm or less.

     Therefore, in order to meet these demands, the degree of crosslinking is excellent, chemical resistance is excellent, and moisture absorption, which causes corrosion, is suppressed, thereby requiring powder coating having excellent boiling water adhesion and negative electrode peelability at high temperatures.

In general, the following three methods are most commonly used for steel pipe coating.

The first is a single layer melt adhesive thermosetting epoxy powder coating, and in order to transfer the contents of 90 ° C or less, a coating film having a glass transition temperature of 100 ° C or more should be formed in a single coating and at the same time, it should have excellent adhesion with steel pipe materials such as iron.

The second is a two-layer melt adhesive thermosetting epoxy powder coating, and the powder coating coated on the undercoat is for realizing adhesion and corrosion resistance with steel pipe material, and the top coat coating exposed to the outside has impact and bendability to protect the steel pipe from the outside. An excellent coating film should be formed.

The third is a three-layer extruded coated steel pipe coating method, which is coated with a melt-bonding method on a steel pipe preheated with a thermosetting powder coating for the undercoat, and then a polyolefin-based adhesive is wrapped around it, and then a polyethylene or polypropylene film is combined with the adhesive. Therefore, it is the most important factor because the thermosetting powder coating applied to the bottom in the manner that the coating is completed realizes corrosion resistance.

The present invention relates to a powder coating composition for steel pipes excellent in high temperature long-term corrosion resistance, boiling water adhesion, it is applicable to not only single-coated steel pipe coating method, but also multiple coating methods such as two layers, three layers.

Looking at the thermosetting epoxy powder coating applied in the existing epoxy powder coating for steel pipes, US Pat. No. 5,407,978 discloses the use of an aliphatic polyol-modified epoxy resin and a phenol curing agent, US Pat. No. 5,112,932 It is disclosed to react with dicyandiamide or with phenol resin using an epoxy resin in which polyisocyanate is added to form an oxazolidone and an isocyanurate ring in the process of polymerizing the epoxy resin. This method has the possibility that the polyisocyanate consumes a secondary hydroxyl group of epoxy-based, thereby reducing the functional group capable of hydrogen bonding with the iron-based hydroxyl group, and consequently hinder boiling water adhesion.

US Pat. No. 3,882,064 uses bisphenol A type epoxy resins and dicyandiamide as curing agents. US Pat. No. 3,819,564 uses bisphenol A type epoxy resins and acid anhydrides and hydroxypyridine curing agents. Is disclosed. This method is capable of producing a powder coating having excellent flexibility, but the acid anhydride reacts with moisture in the air, resulting in poor manufacturing stability, which may cause a disadvantage of deterioration of negative electrode peeling and impact.

As discussed above, various methods for improving boiling water adhesion and corrosion resistance have been discussed. However, in order to realize powder coating that satisfies the recently demanded long-term and high temperature tests, it is necessary to apply a high equivalent resin and maximize the barrier effect. The introduction of the pigment can be said to require improved corrosion resistance and improved flexibility.

U.S. Patent 5,407,978

U.S. Patent 5,112,932

U.S. Patent No. 3,882,064

U.S. Patent No. 3,819,564

An object of the present invention is to solve the above problems, by applying a high equivalent epoxy resin and a special anti-corrosive pigment, thermosetting powder coating composition for steel pipe that can improve the excellent boiling water adhesion, corrosion resistance and flexibility even in high temperature environment To provide.

The thermosetting powder coating composition for steel pipes of this invention is 25 to 60 weight% of bisphenol-A epoxy resins, 1 to 30 weight% of modified bisphenol-A epoxy resins, 0.1 to 10 weight% of phenolic hardening | curing agents, and an amine as a thermosetting epoxy resin. 0.1 to 2% by weight of the latent curing agent, 0.1 to 1% by weight of the curing accelerator, 3 to 20% by weight of the zinc pigment, 5 to 40% by weight of the non-zinc pigment, and 0.1 to 1% by weight of the silicone additive. do.

As the thermosetting epoxy resin used in the present invention, it is preferable that the equivalent weight of bisphenol A epoxy resin is 600 to 1300, and more preferably 800 to 1200. When the equivalent weight of the bisphenol A type epoxy resin is less than 600, the powder coating Although the viscosity is low, the adhesion to the substrate is improved, but the flexibility is poor, and the storage property of the paint is deteriorated, which is not preferable. When the equivalent of the epoxy resin exceeds 1300, the flexibility of the coating film is improved, but the adhesion with the substrate is deteriorated. As a result, the boiling water and corrosion resistance are significantly reduced. The content of the bisphenol-A epoxy resin is preferably used in an amount of 25 to 60% by weight based on the total weight of the composition, and more preferably in the range of 30 to 50% by weight. On the other hand, in the case of more than 60% by weight, the flexibility of the powder coating composition increases, but due to the increase in the organic content in the cured coating film, proper heat resistance and chemical resistance cannot be expected.

Moreover, the modified bisphenol-A epoxy resin as another thermosetting epoxy resin used by this invention is cresol novolak-modified bisphenol-A epoxy resin, a urethane-modified bisphenol-A epoxy resin, or an isocyanate-modified bisphenol-A epoxy resin. Cresol novolac modified bisphenol A type epoxy resin has an equivalent weight of 500 to 900, and an urethane modified bisphenol A type epoxy resin modified with 5 to 15% by weight of epoxy phenol novolac resin or cresol novolac resin has an equivalent weight of 380 to 700, The isocyanate modified bisphenol-A epoxy resin which modified 20 to 30 weight% of monoisocyanate or di-isocyanate is 400-850 equivalent. The modified bisphenol A epoxy resin is preferably used in an amount of 1 to 30% by weight, more preferably 5 to 25% by weight. When the modified bisphenol-A epoxy resin is used at less than 1% by weight, sufficient adhesion cannot be obtained when applied to paint, and when used in excess of 30% by weight, high temperature heat resistance is lowered, which is not preferable.

The curing agent used in the present invention may be used alone or mixed with a phenolic curing agent and an amine curing agent, as a phenolic curing agent is a cresol novolak epoxy phenol curing agent or novolak epoxy phenol curing agent having a hydroxyl equivalent of 200 ~ 300 It is preferable to use 0.1 to 10 weight%, and it is preferable to use 0.1 to 2 weight% of amine type accelerated latent hardener whose active hydrogen equivalent is 20-50 as an amine hardener. When the hydroxyl equivalent of the phenol-based curing agent is outside the range of 200 to 300, the flexibility is improved, but the adhesion with the base is poor, which is not preferable. In addition, when using more than 2% by weight of the amine-based curing agent may react with the unreacted amine and water may cause discoloration of the coating film and severe blister.

By mixing the phenol-based curing agent and the amine-based curing agent, it is possible to maintain the appropriate flexibility and strength to ensure mechanical properties such as impact and flexibility. When the phenolic curing agent is used alone, the coating film is flexible to improve the flexibility, but the impact resistance, long-term high temperature corrosion resistance and boiling resistance decrease, and when the amine curing agent is used alone, the surface blister and the unreacted amine are used. It is not preferable because it shows a phenomenon of surface appearance deterioration.

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 0.1-1 weight% of those chosen 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 secure high-temperature long-term corrosion resistance and boiling resistance, a relatively high equivalent epoxy resin is used. Such a high equivalent resin application has a bad effect of lowering viscosity and lowering adhesion performance. It could be

Zinc-based pigments are used in the present invention to improve the deterioration of adhesion performance due to such high-equivalent resin applications, for example, Zn, ZnX (here, X = O, CO ₃ or CrO ₄ ), Zn ₂ Y ( Wherein Y = SiO ₄ , Sn ₂ O ₄ or P ₂ O ₇ ) or Zn ₃ (Z) ₂ (wherein Z = PO ₄ , BO ₃ or C ₁₈ H ₃₅ O ₂ ), such zinc-based pigments may contain from 3 to 20% by weight. If the content is less than 5% by weight, it is not desirable to increase the adhesion with the base material. If the content is more than 20% by weight, the appearance becomes poor and there is a concern that the flexibility may be reduced. have.

Pigments other than zinc-based pigments used in the present invention include at least one of titanium dioxide, barium sulfate, silicon dioxide, calcium carbonate, calcium silicate and known organic pigments and inorganic pigments for color, the content of which is 5 It is preferable that it is -40 weight%. If the content is less than 5% by weight, the resin content is relatively increased and the heat resistance is deteriorated, and if it is more than 30% by weight, the flexibility is poor, and the dispersion becomes poor due to the excess pigment during dispersion. The coating film is not preferable because it does not express the expected performance.

In addition, examples of the organic pigments and inorganic pigments, the physical properties and strength of the color pigments and powder coatings, such as ultramarine blue, phthalocyanine blue, phthalocyanine green, carbon black, etc. And various kinds of inorganic pigments.

Silicone additives used as additives include 2- (3,4 epoxycyclohexyl) -ethyltrimethoxysilane (2- (3,4 epoxycyclohexyl) -ethyltrimethoxysilane) and 3-glycidoxypropyltrimethoxysilane (3- glycidoxypropyltrimethoxysilane), N-2 (aminoethyl) 3-aminopropylmethyldimethoxysilane (N-2 (aminoethyl) 3-aminopropylmethyldimethoxysilane), 3-aminopropyltrimethoxysilane, N-phenyl-3- Aminopropyltrimethoxysilane (N-phenyl-3-aminopropyltrimethoxysilane) or 3-mercaptopropyltrimethoxysilane (molecular weight: 150-300), preferably used in an amount of 0.1 to 2% by weight. Do. If the content of the additive is less than 0.1% by weight can not be expected to improve the adhesion of the body, more than 2% by weight is the cause of poor dispersion and storage stability in the manufacture of the paint.

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. An inhibitor etc. are mentioned.

The thermosetting powder coating composition for steel pipes 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 steel pipes of the present invention is prepared by performing a grinding process for preparing a paint.

At this time, the particle size of the powder has a very close relationship with the workability of the powder coating. Among the particle size conditions of US Patent No. 5319001, which is appropriate powder particles, the average particle size is 15 to 45 microns, and particles of 250 microns or more are present within 0.3% by weight. Adjust the particle size to

According to the present invention, a mixture of a high equivalent epoxy resin and a low equivalent or modified epoxy resin and an anti-corrosive pigment may be used to provide long-term boiling water and corrosion resistance, and to provide a thermosetting powder coating composition having excellent corrosion resistance at high temperatures. have.

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 mixing ratio (wt%) shown in Table 1 to prepare a thermosetting powder coating material for steel pipe, a physical property evaluation test was carried out by the following method, the results are shown in Table 2 below.

week)

1) Bisphenol A epoxy resin, epoxy equivalent 1750-2100 (Kukdo Chemical)

2) Bisphenol A type epoxy resin, epoxy equivalent 900-1000 (KCC)

3) Bisphenol A epoxy resin, epoxy equivalent 780 ~ 840 (KCC)

4) Cresol novolac modified bisphenol A epoxy resin, epoxy equivalent 500-900 (KCC)

5) Urethane modified bisphenol A epoxy resin, epoxy equivalent 380-700 (KCC)

6) cresol novolac epoxy phenol curing agent (KCC)

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

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

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

10) Curing accelerator, 2-MI (SIKOKU)

11) Surface Adjuster, PLP-100 (KS Chemical)

12) Pinhole preventive agent, BENZOIN (Miwon)

13) Colored Pigment, CR-80 (ISHIHARA)

14) Colored Pigment, MA-100 (MITSUBISHI)

15) Constitution Pigment, HANSIL C-15J (Korea Semiconductor Material)

16) Constitutional Pigment, SWA-90 (Sungshin)

17) Antirust Pigment, ZnO (Hanchang Industry)

Organic Silane, KBM-403 (SHINETSU)

As can be seen in Table 2, the thermosetting powder coating composition according to the present invention, by containing a mixture of a high equivalent epoxy resin and a low equivalent or modified epoxy resin and rust preventive pigment, high temperature long-term boiling water adhesion, corrosion resistance and All exhibit excellent physical properties in flexibility.

Claims (9)

25 to 60% by weight of bisphenol A type epoxy resin and 1 to 30% by weight of modified bisphenol A type epoxy resin, 0.1 to 10% by weight of phenol-based curing agent, 0.1 to 2% by weight of amine-based latent curing agent and curing accelerator as thermosetting epoxy resin A thermosetting powder coating composition for steel pipes, comprising 0.1 to 1% by weight, 3 to 20% by weight of zinc-based pigments, 5 to 40% by weight of non-zinc-based pigments, and 0,1 to 1% by weight of silicone-based additives. The thermosetting powder coating composition for steel pipe according to claim 1, wherein the modified bisphenol A type epoxy resin is a cresol novolac modified bisphenol A type epoxy resin, a urethane modified bisphenol A type epoxy resin or an isocyanate modified bisphenol A type epoxy resin. . The equivalent weight of the bisphenol A type epoxy resin is 600 to 1300, the equivalent weight of the cresol novolac-modified bisphenol A type epoxy resin is 500 to 900, and the equivalent weight of the urethane modified bisphenol A type epoxy resin is 380 to 700. The isocyanate-modified bisphenol A epoxy resin is equivalent to 400 ~ 850 thermosetting powder coating composition for steel pipes. The phenolic curing agent according to claim 1 or 2, wherein the phenolic curing agent is a cresol novolac epoxy phenol curing agent or a novolak epoxy phenol curing agent having a hydroxyl equivalent of 200 to 300, and the amine-based promoting latent curing agent has an active hydrogen equivalent of 20 Thermosetting powder coating composition for steel pipes, characterized in that ~ ~ 50. The method of claim 1, wherein the curing accelerator is triphenylphosphine, benzyltriphenylphosphonium chloride, butyltriphenylphosphonium chloride, tetraphenyl phosphonium chloride, 1-methylimidazole, 2-methyl Midazole, 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-ethylimidazole, 1-benzyl-2-methylimidazole And 2-butylimidazole. Thermosetting powder coating composition for steel pipes, characterized in that selected from the group consisting of. The method of claim 1 or 2, wherein the zinc-based pigment is Zn, ZnX (here, X = O, CO ₃ or CrO ₄ ), Zn ₂ Y (here, Y = SiO ₄ , Sn ₂ O ₄ or P ₂ O ₇ ) or Zn ₃ (Z) ₂ (wherein Z = PO ₄ , BO ₃ or C ₁₈ H ₃₅ O ₂ ) It is a thermosetting powder coating composition for steel pipes. The steel pipe according to claim 1 or 2, wherein the non-zinc-based pigment is at least one member selected from the group consisting of titanium dioxide, barium sulfate, silicon dioxide, calcium carbonate, calcium silicate and organic or inorganic pigments. Thermosetting powder coating composition. 8. The thermosetting powder coating composition for steel pipe according to claim 7, wherein the organic or inorganic pigment is at least one selected from the group consisting of ultramarine blue, phthalocyanine blue, phthalocyanine green and carbon black. 3. The silicone additive according to claim 1, wherein the silicone additive is 2- (3,4 epoxy cyclohexyl) -ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, N-2 (aminoethyl) 3- Aminopropylmethyldimethoxysilane, 3-aminopropyltrimethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane or 3-mercaptopropyltrimethoxysilane, molecular weight 150-300, 0.1-2 weight Thermosetting powder coating composition for steel pipes, characterized in that used in an amount of%.