KR20110113394A - Powder paint composition having a high glass transition temperature - Google Patents

Abstract

The present invention relates to a powder coating composition having a high glass transition temperature and excellent in acid resistance, boiling water resistance, and negative electrode peelability under high temperature / high pressure conditions, and more particularly, tri- or more functional cresol novolac epoxy resin 10 It relates to a powder coating composition comprising from 60% by weight to 60% by weight, aromatic amine curing agent 1-30% by weight, pigment 1-20% by weight and filler 20-40% by weight.

Description

Powder paint composition having a high glass transition temperature

The present invention relates to an epoxy resin powder coating composition having a high glass transition temperature and excellent physical properties such as acid resistance, boiling resistance and negative electrode peeling resistance, and more particularly, trisol or more cresol novolac epoxy resin, aromatic amine curing agent. The present invention relates to a powder coating composition comprising a pigment and a filler. Powder coating according to the present invention has a high glass transition temperature and a dense crosslinked structure, the structure of the coating film is maintained even in high temperature corrosion and acidic environment and excellent durability in bonding to the coating material.

Conventional epoxy resin powder coating mainly comprises a thermosetting epoxy resin containing a bisphenol A-type epoxy resin, a urethane substituted or novolac-modified epoxy resin, high molecular weight polyhydric phenol curing agent, dicyanamide type Co-curing agent and acid anhydride are included as a curing agent, and additives are included.

Conventional epoxy resin powder coatings of steel pipes or pipelines buried underground or undersea due to the thermal properties of the coating film having a glass transition temperature of 100 ℃ and the adhesive strength and chemical resistance, mechanical strength and battery insulation properties of the epoxy resin It has been used to prevent corrosion and improve durability. However, as the environment of subsea or buried pipes for mining and transporting fluid becomes increasingly severe, there is a need for improvements in the thermal, chemical and physical properties of epoxy coatings to protect the pipes from corrosion.

Gases and oils stored underground go through various environments such as storage and refinery, and are transported through steel pipes and pipes from drilling to storage and refinery, thereby accelerating the corrosion of metal pipes depending on the transport environment.

Oil inside the earth's crust is a gas containing 5 to 40 hydrocarbons, nitrogen and sulfur, as water, at high temperatures and pressures, depending on the depth and location of the well, and also buried underground. The oil has a high content of sulfur. Sulfur does not affect corrosion on its own, but compounds such as hydrogen sulfide and sulfuric acid create an acidic environment to promote corrosion of steel pipes. Sulfur oxides have excellent reducing power to stimulate hydrogenation reactions, penetrating into linkages of general polymers as well as metals, weakening the bonds of polymers, and causing cracks and cracks on the surface of polymers.

Drilling pipes in direct contact with oil wells, which are used to raise the oil present at high temperatures and pressures to the ground, must be able to protect the pipes and coatings themselves from these high temperatures and pressures and sulfur compounds, and have high viscosity. It must be possible to protect the pipe from corrosion due to the hydraulic pressure caused by contact with the internal pipe surface while the oil moves to the ground.

Commonly used drilling pipe paints use a coating method that is melt-bonded at a temperature of about 200 ° C., and has a fast curing time of less than 10 minutes. The excellent mechanical properties and corrosion resistance of epoxy paints can prevent corrosion of pipes from underground and marine environments.However, due to the rapid curing speed, the crosslinked structure in the hardened coating film is not dense. When dissolved by, and exposed to an environment of 150 ° C / 300 atm or above, a change occurs in the coating film, and a blister phenomenon occurs in which the coating film and the substrate are separated by the influence of gas and moisture contained in the coating film, or due to high heat Softening occurs and the body cannot be protected.

Therefore, the powder coating used in the drilling pipe should be excellent in resistance to acidic environments such as sulfides first, and should form a coating film having a glass transition temperature of 150 ° C or higher because of contact with petroleum of 150 ° C or higher. It should have a cross-linked structure that does not cause mutations. Therefore, the powder coating used in the drilling pipe is difficult to apply as a general-purpose coating product and there is a need to apply a special coating that maximizes the glass transition temperature.

On the other hand, the method of increasing the flow rate in order to move the crude oil on the ground quickly and heated and transported to reduce the viscosity has been applied. There is a need for a paint that has a high glass transition temperature and at the same time satisfies the properties as a basic powder coating for pipes.

U.S. Patent No. 5,112,932 is a glass of 166 DEG C prepared by reacting an epoxy resin, in which oxazolidone and isocyanurate is formed by adding polyisocyanate to polymerize a low equivalent epoxy resin, with dicyanamide. It describes about the paint which has a transition temperature. However, in this case, the heat resistance is excellent due to the high glass transition temperature, but blister occurs when exposed to high pressure of about 300 atm due to the large volume and weak bonding force of the oxazolidone ring.

US 5,686,185 and US 5,077,355 describe bisphenol A type epoxy resins and methods of using diphenol derivatives as curing agents. However, in this case, the flexibility and cathodic peeling property are excellent, but the glass transition temperature of the coating film is 100 ° C. When the film is exposed to sulfuric acid, the coating film dissolves, and when exposed to an environment of 150 ° C / 300 atmospheres, the coating film changes and swelling occurs. Done.

As described above, even if the coating film after curing has a high glass transition temperature of 150 to 170 ° C., when the structure in the coating film becomes bulky and the crosslinking density is not high, the bonding strength of the coating film is affected by high pressure, and the coating film is dense. Even if it has a low glass transition temperature, there is a problem in that the bond is changed by heat and swelling occurs in the coating film.

U.S. Patent 5,112,932 U.S. Patent 5,686,185 U.S. Patent 5,077,355

The present invention is to solve the problems existing in the prior art as described above, an object of the present invention to improve the glass transition temperature of the coating film after curing of the powder coating to 120 to 220 ℃, in a low paint viscosity and high temperature environment It has a durability of the oil coating environment does not occur even in high temperature / high pressure oil drilling environment, to provide a powder coating composition that can be applied to the drilling pipe for corrosion protection.

The present invention provides a powder coating composition comprising 10 to 60% by weight of a cresol novolac epoxy resin having at least three functional groups, 1 to 30% by weight of an aromatic amine curing agent, 1 to 20% by weight of a pigment, and 20 to 40% by weight of a filler.

이고, 에폭시기는

인 바, 실질적으로 관능성을 가진 부분이 에폭시 부분이므로, 글리시딜기로 관능기를 더 구체한정할 이유가 없다고 사료되어 에폭시기로 변경하였습니다. 이에 대한 확인부탁드립니다.)Creole novolac epoxy resin of the tri- or more functional group is contained 10 to 60% by weight, when the content is less than 10% by weight of the reaction cross-link density is difficult to maintain a high glass transition temperature, the content exceeds 60% by weight In this case, agglomeration phenomenon occurs in the paint due to the deterioration of the storage property of the resin after the paint is produced, or easily broken even in a small impact due to dense hardening density after the coating film is formed. In the cresol novolac epoxy resin, a functional group means an epoxy group. Glycidyl is

And epoxy group

In fact, since the functional part is an epoxy part, it is considered that there is no reason to further define the functional group with glycidyl group, so it was changed to the epoxy group. Please confirm this.)

The aromatic amine-based curing agent is contained 1 to 30% by weight, the content of which is directly related to the content and the curing degree of the cresol novolac epoxy resin of the tri- or more functional groups, the powder of the present invention if out of the range of the content It is not preferable in the storage property of a coating composition and formation of a dense reaction structure.

The pigment may be a general pigment used in the powder coating for drilling pipes, titanium dioxide is preferred. The content is preferably 1 to 20% by weight, but beyond the range of the above content, the hiding power of the coating film by the powder coating composition of the present invention is not sufficiently secured.

The filler may be commonly used barium sulfate, calcium carbonate, silica, alumina hydroxide, mica and zinc oxide, it is preferable to use 20 to 40% by weight. If the filler is less than 20% by weight, the hiding power of the coating film is lowered. If the filler is more than 40% by weight, problems in the appearance of the coating film may occur.

Existing epoxy resins used in powder coatings include bisphenol epoxy resins and novolac modified epoxy resins, which have two functional groups at the sock end. The cresol novolac epoxy resin having three or more functional groups of the present invention has cresol functional groups in each novolak reactor, not at both ends, so that the number of reaction bonds increases, the crosslinking density is high, and the structure itself is also high due to the presence of methyl groups. When applied, not only has a very high glass transition temperature of 150 to 220 ℃, but also the bonding strength is improved after the formation of the coating film due to the uniform repeat arrangement of the structure, the flowability of the paint is improved due to the low viscosity, the adhesion to the coating and coating This is improved. Therefore, it is effective in use even at high temperature and high pressure conditions such as oil drilling.

In one embodiment of the present invention. The composition further provides a powder coating composition comprising bisphenol A type epoxy resin in an amount of 50% by weight or less (eg, 1 to 50% by weight).

When the composition is applied in combination with a conventional general purpose bisphenol A-type epoxy resin or a novolac modified epoxy resin, etc., it has a considerable high glass transition temperature of about 110 to 150 ℃ while satisfying the properties of the conventional powder coating for pipes It can be used as a paint.

In another embodiment of the present invention, the cresol novolac epoxy resin having at least three functional groups is an ortho-group cresol novolac epoxy resin polymerized using a phenol-based meta carbon, and an epoxy equivalent of 300 to 500, and a softening point. It provides the powder coating composition which is 70 to 130 ℃.

If the epoxy equivalent of the tri- or more functional cresol novolac epoxy resin is less than 300, the molecular weight is difficult to maintain a solid phase, if more than 500 is polymerized to change to a level similar to the equivalent of the general-purpose epoxy resin does not exhibit its properties. In addition, if the softening point of the cresol novolac epoxy resin of the trifunctional or more than trifunctional group is less than 70 ° C., agglomeration phenomenon occurs in the paint due to the deterioration of the storage property of the resin after the production of the paint. It is so high that it does not mix well with other raw materials, so that the physical properties of the paint cannot be sufficiently exhibited.

In another embodiment of the present invention, the aromatic amine-based curing agent is selected from the group consisting of diamino diphenyl methane (DDM), metaphenylene diamine (MDP) and diphenyl diamino sulfone (DDS) It provides a powder coating composition. Among these, diphenyl diamino sulfone (DDS) is preferable. Diphenyl diamino sulfone is a curing agent with four functional groups with a molecular weight of 248 and a melting point of 175 ° C. Due to the strong electronegativity of sulfone groups of O = S = O in the structure, the side chains may react with the cresol novolac epoxy. When forming a hydrogen bond with the hydroxyl group of the epoxy resin, the crosslinking force becomes strong, and as a result, a coating film having high heat resistance and high pressure resistance is formed.

In another embodiment of the present invention, 30 wt% or less (eg, 1 to 1) of the phenol curing agent, bisphenol A-type novolac curing agent, a hydrol novolak phenol curing agent having a cresol group, or a mixture thereof, in addition to the composition, is added. It provides a powder coating composition comprising an amount of 30% by weight).

In the present invention, the curing agent may be used in combination with an aromatic amine curing agent, a phenolic curing agent having a trifunctional group or more, a bisphenol A-type novolac curing agent, and a hydric novolac phenol curing agent having a cresol group depending on the application.

The phenolic curing agent having a tri- or more functional group is characterized by being made by reacting a phenol curing agent on the sock end using carbon linkage rings such as ethane and butane groups, and may have 3 to 5 functional groups depending on the degree of reaction. Ethane has the most preferable structure, for example, Kolon KCE-F3110, etc. can be used. The trifunctional or higher phenolic curing agent is included in 30% by weight or less (eg, 1 to 30% by weight), when the content exceeds 30% by weight, the glass transition temperature of the coating film is improved by increasing the number of cross-linking, but acid resistance And resistance to pressure falls. In the phenolic curing agent, a functional group means a hydroxy group.

Bisphenol A type novolak curing agent refers to a curing agent in which a bisphenol novolak reactor is polymer-chained in a bond of bisphenol A type, and is characterized by containing two phenol curing agents for each single structure, for example, Kolon's KBE-F4113 , KBE-F4123, KBE-F4127, etc. can be used. When a bisphenol A novolac curing agent is used, its hydroxyl equivalent is from 150 to 350 and its content is up to 30% by weight (eg 1 to 30% by weight). When the hydroxyl equivalent weight is 150 or less, the molecular weight is hard to maintain a solid phase, and when it is 350 or more, it is polymerized and the bond with the epoxy resin is physically limited during the reaction. If the content of the bisphenol A novolac curing agent exceeds 30% by weight, there is a problem in the initial adhesion due to the increase in the paint viscosity.

As the hydronic novolak phenol curing agent having a cresol group, a known one can be used without limitation, and a structure having one methyl group and one phenol group in one novolak structure is preferable. For example, KOL-2020, KCE-2118, KCE-2123 from Kolon, Resicure3100 from David Chemical, etc. may be used. When a hydric novolac phenol curing agent having a cresol group is used, the content thereof is preferably 30% by weight or less (eg, 1 to 30% by weight). When the content exceeds 30% by weight, the glass transition temperature of the coating film is improved by increasing the number of crosslinking bonds, but the acid resistance and resistance to pressure are lowered.

In addition to the above components, the coating composition of the present invention may further use a conventional additive depending on the purpose of use and environment of the powder coating.

For example, as an additive for improving the appearance of the paint, an acrylic flow improver (eg, FV-5, FV88: manufactured by Estrone, AKRON 4F: BASF) 1 to 1.5% by weight of a manufactured, modapro: Monsanto Co., Ltd. and a silicone-based flow improver (for example, PEL-200: Estrone Co., Ltd.) can be added, and pinholes used for ordinary powder coating 2-hydroxy-1,2-dipentanone (e.g., benzoin: DSM Co., Ltd.), which contributes to the prevention of gelation and the efficient release of bubbles generated during the reaction in the paint as a retardant on the surface as an inhibitor. ) Can be added from 1 to 1.5% by weight.

In addition to the above additives, amide-based, polypropylene-based, olefin-based, Teflon-based waxes and dispersants, which may be conventionally added during powder coating, may be further added. In order to improve the workability of the coating during coating, Propylene-based waxes and hydrophilic or hydrophobic silicas may be further added in conventional amounts.

In another aspect of the present invention, there is provided a coated steel pipe coated with one to three layers of the powder coating composition.

The coating film provided by the powder coating composition of the present invention is, for example, after coating the phenol-based undercoat on a steel pipe which has been blasted in advance, and then allowed to stand on air to volatilize a diluent, and then 160 to 190 ° C in the steel pipe. Heat the furnace to cure the undercoat, while preheating the steel pipe, coating the powder coating composition of the present invention on the undercoat with an electrostatic spray coater at a thickness of 200 to 500 microns, and then heating to 200 to 230 ° C. to post-heat coating film. After forming, it can be obtained by standing on air.

The painting may be overpainted according to the environment of the pipe, but in consideration of the increase in cost, one to three overlapping paint is preferable.

When using a trifunctional or higher cresol novolac epoxy resin as in the present invention, it has acid resistance even in a glass transition temperature of 180 ° C. or higher and a high temperature and high pressure environment such as 150? / 300 atm, which is significantly higher than a bifunctional epoxy resin coating material. It is excellent in boiling water resistance and cathodic peeling resistance to protect pipe steel pipe without any change in appearance. In addition, it is possible to control the glass transition temperature of the coating film by applying a mixture of tri- or more functional cresol novolac epoxy resin and bi-functional epoxy resin, depending on the application and environment (petroleum drilling: more than 180 ℃, underground underground for transport: 110 To 150 ° C., etc.) It is possible to form a powder coating composition having excellent high temperature glass transition temperature of 110 ° C. or more while being excellent in other coating film properties such as impact resistance and flex resistance.

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

Each component was blended according to the composition shown in Table 1 below, and then uniformly mixed using a container mixer (CMS). The uniformly mixed composition was melt mixed at a temperature of 85 to 120 ° C. through a kneader (PK-46: manufactured by Booth Co., Ltd.), and then pulverized using a pulverizer and classified into an average particle size of 30 to 80 microns to prepare a powder coating. did.

[Table 2] Comparison of physical properties of powder coatings of Comparative Examples 1 and 2 and Comparative Examples

1) YDC 500-90P; manufactured by Kukdo Chemical Co., Ltd. (Polyglycidyl ether of ortho-cresol formaldehyde novolac = ortho cresol novolac epoxy resin)

2) CN00105; manufactured by KC Corporation (BP epoxy = di (4-hydroxyphenol) isopropylidine diglycidyl ether-di (4-hydroxyphenol) isopropylidine copolymer)

3) KCC 2118; manufactured by Kolon Corporation (Cresol Noblec)

4) KFFF 3110; manufactured by Kolon Corporation (tetraphenylolethane)

5) HT 976; manufactured by Hertzmann (diphenyldiaminosulfone)

6) KBF 4113; Kolon Co., Ltd. (Bisphenol A Noble Resin)

7) flow improvers; Fib-5; Estrone (acrylic polymer)

8) pinhole inhibitor; manufactured by DSM Corporation (benzoin)

9) pigments; Color pigments for general powder coatings other than carbon black

10) fillers; Filler pigments for general powder coatings, including calcium carbonate and barium sulfate

Each of the powder coating compositions prepared according to the Examples and Comparative Examples as described above was preheated at 230 ° C. for 1 hour, coated with a thickness of 400 micrometers by electrostatic spray coating, and then heated at 230 ° C. for 3 minutes. Was added, followed by immersion cooling with water to prepare a coating film specimen.

The physical properties of the coating film specimens prepared above are shown in Table 2 below.

[Table 2] Comparison of physical properties of powder coatings of Comparative Examples 1 and 2 and Comparative Examples

◎: Excellent, X defectiveness.

In Table 2, the acid resistance evaluation was performed by leaving the coating material formed by coating the powder coating composition according to the Examples and Comparative Examples on the autoclave test equipment containing sulfuric acid, which can maintain high temperature and high pressure in an acid state, under the above conditions. It was performed by visually confirming whether swelling and discoloration occurred on the surface.

When the result of Table 2 is examined, in the present invention, when a cresol phenol curing agent, a trifunctional or higher phenol curing agent, an aromatic amine curing agent, or a bisphenol A-type novolak curing agent is used in a cresol novolak epoxy resin having a trifunctional or higher functional group, It can be seen that the glass transition temperature of the coating film is improved to 180 ° C. or higher, the coating film does not change even at 150 ° C./300 atm, and blisters do not occur, thereby forming a coating film capable of protecting the coating from corrosion. In addition, the coating film can be confirmed that the result is much better than the general powder coating in the high temperature (95 ℃) negative electrode peeling test and boiling water test.

Table 3 Physical properties of Example 3, 4 powder coating

◎: Excellent, X defectiveness.

In the case of the physical properties of Example 3 and 4 powder coating, which reduced the content of the cresol novolac epoxy resin of the trifunctional group or more and increased the content of the bisphenol A type epoxy resin, the glass transition temperature of the coating film was 110-150 ° C. as shown in Table 3. It can be seen that while maintaining the high temperature of the level, it is possible to form a coating film that can satisfy the bending resistance and impact resistance characteristics of the general powder coating material for pipes. The high temperature (95 ℃) negative electrode peeling test and boiling water proof test also showed much better results than general powder coating.

Claims (9)

Powder coating composition comprising 10 to 60% by weight of cresol novolac epoxy resin of at least trifunctional group, 1 to 30% by weight of aromatic amine curing agent, 1 to 20% by weight of pigment and 20 to 40% by weight of filler The powder coating composition of claim 1, further comprising a bisphenol A-type epoxy resin in an amount of 50% by weight or less. The cresol novolac epoxy resin of claim 1, wherein the cresol novolac epoxy resin having at least three functional groups is an ortho-group cresol novolac epoxy resin polymerized by linking a phenol-based meta carbon, and has an epoxy equivalent of 300 to 500 and a softening point of 70. Powder coating composition, characterized in that from 130 ℃. The powder coating composition of claim 1, wherein the aromatic amine curing agent is selected from the group consisting of diamino diphenyl methane (DDM), metaphenylene diamine (MDP), and diphenyl diamino sulfone (DDS). . The powder coating composition according to claim 1, further comprising a tri- or higher functional phenol curing agent, a bisphenol A-type novolac curing agent, a hydric novolac phenol curing agent having a cresol group, or a mixture thereof in an amount of 30% by weight or less. . The powder coating composition according to claim 5, wherein the phenol curing agent having at least three functional groups is made by reacting a phenol curing agent at the sock end using a carbon linkage ring. 6. The powder coating composition of claim 5, wherein the bisphenol A type novolac curing agent is a polymer chain curing agent of a bisphenol novolak reactor in a bisphenol A type bond, and contains two phenol curing agents for each single structure. 6. The powder coating composition according to claim 5, wherein the hydrol novolak phenol curing agent having a cresol group has a methyl group and a phenol group each in one novolak structure. A coated steel pipe coated with one to three layers of the powder coating composition according to any one of claims 1 to 8.