HK1254539B - Foaming refractory coating composition - Google Patents

Description

Foamable refractory coating composition

Technical Field

The present invention relates to a foamable fire-resistant coating composition.

Background Art

Oil fires in offshore structures and workshops are characterized by a rapid rise in temperature to approximately 945°C within five minutes. Curing epoxy fire-resistant coatings are the primary fire-resistant coatings used in areas where oil fires are likely to occur. However, existing fire-resistant coatings have the disadvantage of releasing large amounts of harmful gases when the coating expands.

The following three U.S. patents represent recent technologies for epoxy-based refractory coatings.

The solvent-free epoxy refractory coating proposed in U.S. Patent No. 4,529,467 proposes that during a fire, as the coating expands, zinc (Zn) burns to form a microporous foam layer. This foam layer improves thermal insulation and adhesion to the substrate. However, excessive use of zinc prevents the coating from expanding, potentially reducing thermal insulation performance.

U.S. Patent No. 5,108,832 proposes an epoxy-based fire-resistant coating with excellent flexibility by synthesizing an epoxy resin having excellent flexibility. In this U.S. patent, an epoxy resin is synthesized using an epoxy monomer having a chain structure, and a fire-resistant coating is prepared using this epoxy resin. The flexibility is predicted through low-temperature cycle testing.

US Patent No. 6,096,812 proposes using hydrophobic fumed silica to reduce the density of a coating film, thereby reducing the amount of coating material used while ensuring fire resistance.

These US patents all disclose a foaming mechanism for refractory coatings using boric acid and ammonium polyphosphate. Boric acid undergoes a dehydration reaction at around 170°C, releasing gas that causes the coating to expand. However, this foaming mechanism also poses the problem of releasing harmful gases during foaming.

Meanwhile, U.S. Patent Application No. 1997-999536 discloses a fire-resistant coating material that uses hydrophobic fumed silica in an epoxy resin-based coating to reduce the density of the applied coating film, thereby reducing the amount of coating material used and still achieving fire-resistant properties. However, the phosphorus-based flame retardant used in this invention contains TPP (triphenylphosphate) at a content of 21% by weight or more, and has a thermal decomposition temperature of less than 250°C. TPP vaporizes at a lower temperature than epoxy resins cured with low-molecular-weight substances. While this improves initial foaming, a high TPP content increases the toxicity of the gas and reduces long-term fire resistance.

Therefore, there is still a demand for a foamable fire-resistant coating composition that can save the TPP content of the phosphorus-based flame retardant to reduce gas harmfulness and improve long-term fire resistance.

Summary of the Invention

Technical issues

The technical problem of the present invention is to provide a foamable refractory coating composition, which includes an epoxy resin, a curing resin, a flame retardant, a foaming agent, an acid catalyst and fibers. In particular, a flame retardant with a triphenyl phosphate content of less than 20% by weight and a thermal decomposition temperature of more than 250°C is used to reduce the harmfulness of the gas, impart flexibility to the foaming layer, prevent cracks from occurring in the carbonized layer, and thus improve long-term fire resistance.

Technical Solution

The foamable fire-resistant coating composition of the present invention comprises, based on a total of 100 weight percent, 10 to 25 weight percent of an epoxy resin, 10 to 15 weight percent of a curing resin, 10 to 20 weight percent of a flame retardant, 3 to 10 weight percent of a foaming agent, 20 to 40 weight percent of an acid catalyst, and 3 to 10 weight percent of a fiber. The flame retardant is a flame retardant having a triphenyl phosphate content of 20 weight percent or less and a thermal decomposition temperature of 250° C. or higher.

Effects of the Invention

The foamable fire-resistant coating composition of the present invention has a low TPP content, which reduces gas toxicity. Its thermal decomposition temperature is above 250°C, imparting flexibility to the foamed layer and preventing cracks in the carbonized layer, thereby improving long-term fire resistance. The composition exhibits gas toxicity of at least 12 minutes when measured using the Gas Toxicity Test Method (KSF 2271). Furthermore, the composition exhibits fire resistance of at least three hours when measured using the Fire Resistance Test Method (UL 1709), even without the use of a separate reinforcement (net).

DETAILED DESCRIPTION

The present invention is described in more detail below.

The foamable refractory coating composition of the present invention comprises, based on a total of 100 weight percent, 10 to 25 weight percent of an epoxy resin, 10 to 15 weight percent of a curing resin, 10 to 20 weight percent of a flame retardant, 3 to 10 weight percent of a foaming agent, 20 to 40 weight percent of an acid catalyst, and 3 to 10 weight percent of a fiber. The content of triphenyl phosphate in the flame retardant is less than 20 weight percent, and the thermal decomposition temperature is above 250°C.

The epoxy resin used in the composition of the present invention allows the coating to adhere to the substrate, and the cured coating exhibits durability at room temperature. Furthermore, during a fire, exposure to high-temperature heat causes the coating to fluidize, generating gas that allows the coating to expand appropriately, acting as a framework for the foamed carbonized layer.

As such epoxy resins, bisphenol A epoxy resins, bisphenol F epoxy resins, flame-retardant epoxy resins, novolak epoxy resins, multifunctional amine epoxy resins, and alicyclic epoxy resins can be used. Preferably, at least one selected from bisphenol A epoxy resins and bisphenol F epoxy resins can be used.

The epoxy resin has a weight average molecular weight of 150 to 900, preferably 200 to 800, and an equivalent weight of 75 to 450 g/eq, preferably 100 to 400 g/eq.

The foamable fire-resistant coating composition of the present invention may contain 10 to 25 weight percent of epoxy resin, for example, 15 to 23 weight percent. If the epoxy resin content is less than 10 weight percent, the adhesion of the coating film may be reduced due to insufficient resin content. If the epoxy resin content exceeds 25 weight percent, the foaming rate of the coating film may be hindered during a fire, thereby failing to fully demonstrate fire-resistant performance.

The curing resin used in the composition of the present invention is used to cure epoxy resins. While not particularly limited, the curing resin may be an amide or aminoamine resin having a viscosity of 200 to 800 cps, an amine value of 300 to 600 mgKOH/g, and an active hydrogen equivalent of 50 to 200 g/eq, obtained by polymerizing polyvinylamine, a fatty acid dimer, and a fatty acid monomer.

The synthesis method of the corresponding resin is as follows. First, a mixture of polyvinylamine, fatty acid dimer, and fatty acid monomer is heated to 200°C for polycondensation until the acid value of the corresponding reactants reaches 1 to 5. Preferably, the reaction is carried out in this step so that the amine/acid molar ratio is 1.2 to 2.0. If the molar ratio is less than 1.2, the viscosity is high, making it difficult to apply the coating. If the molar ratio is greater than 2.0, unreacted amine is present, and the desired physical properties are difficult to achieve when the coating is applied.

More specifically, the polyvinylamine can be one of ethylenediamine, diethylenetriamine, triethylenetetramine, and tetraethylenepentamine, or a mixture thereof. The fatty acid dimer and monomer are monomers and dimers prepared from the group consisting of soybean oil fatty acid, tall oil fatty acid, castor oil fatty acid, rice bran oil fatty acid, linseed oil, coconut oil fatty acid, lauric acid, and linoleic acid. More than one selected one of these can be used in combination. Preferably, tall oil fatty acid monomers and dimers can be used.

If the acid value of the corresponding reactant reaches 1 to 5 or less, heating is terminated to obtain the generated amide or amidoamine resin. Preferably, the obtained resin has a viscosity of 200 cps to 800 cps, an amine value of 300 KOH/g to 600 mgKOH/g, and an active hydrogen equivalent of 50 g/eq to 200 g/eq. The curing property can be maximized within the above physical property range.

The foamable fire-resistant coating composition of the present invention includes 10 to 15 weight percent of a curable resin, for example, 11 to 14 weight percent. If the curable resin content is less than 10 weight percent, the adhesion of the coating film may be reduced. If the curable resin content exceeds 15 weight percent, the curable resin content may be excessive, resulting in coating film defects such as amine blushing.

The phosphorus-based flame retardant used in the composition of the present invention regulates the thermal decomposition rate of the cured coating, thereby imparting flexibility to the early foaming carbonized layer. Conventional phosphorus-based flame retardants used in foamable fire-resistant coating compositions contain 21% TPP (Triphenyl phosphate) by weight, with a thermal decomposition temperature of less than 250°C. Compared to epoxy resins cured with low-molecular-weight substances, TPP vaporizes at lower temperatures, improving early foaming. However, high TPP content increases gas toxicity and reduces long-term fire resistance. Therefore, in the present invention, the amount of this phosphorus-based flame retardant used is reduced to half the previous level, thereby reducing the TPP content and thereby minimizing gas toxicity. In addition, an additional phosphorus-based flame retardant with a thermal decomposition temperature of 250°C or above (i.e., a heating loss of less than 5% at 250°C) is applied to slow down the thermal decomposition rate of the cured coating, impart flexibility to the foaming layer, and prevent cracks in the carbonized layer, thereby ensuring long-term fire resistance even without the use of a reinforcing material (mesh).

The phosphorus-based flame retardant contained in the foamable fire-resistant coating composition of the present invention may be a flame retardant having a triphenyl phosphate (TPP) content of 20 wt% or less and a thermal decomposition temperature of 250°C or above (ie, a heating loss of less than 5% at 250°C).

More specifically, the phosphorus-based flame retardant used in the present invention can be at least one selected from aryl phosphates such as triphenyl phosphate (TPP), isopropylated triphenyl phosphate, tricresyl phosphate, butylated triphenyl phosphate, cresyl diphenyl phosphate, and isopropyl phenyl diphenyl phosphate; and diphosphates such as resorcinol bis(diphenyl phosphate) (RDP) and bisphenol-A bis(diphenyl phosphate) (BDP).

In a specific example, as the aryl phosphate, isopropylated triphenyl phosphate having a TPP content of 5% to 10% can be used, and as the diphosphate, RDP (Resorcinol bis(diphenyl phosphate)) or BDP (Bisphenol-A bis(diphenylphosphate)) having a TPP content of less than 5% can be used.

Preferably, it can be a mixture of aryl phosphate and diphosphate, and the mixing weight ratio thereof is 1:0.5 to 1:3, preferably, 1:0.5 to 1:1.5, but not limited thereto.

The foamable fire-resistant coating composition of the present invention includes a flame retardant in an amount of 10 to 20% by weight, for example, 13 to 18% by weight. When the amount is less than 10% by weight, the coating film has insufficient flame retardancy and burns readily, failing to fully demonstrate fire resistance. When the amount exceeds 20% by weight, the coating film's melt viscosity decreases, and the carbonized layer easily breaks due to excessive foaming, failing to demonstrate thermal insulation properties. The TPP content increases, making it impossible to achieve the desired level of gas toxicity reduction and fire resistance.

The foaming agent used in the composition of the present invention decomposes and generates a large amount of gas when the cured coating film is softened and liquefied by exposure to high-temperature heat, forming a carbonized layer. This causes the carbonized layer to expand (foam) with fine pores, thereby providing thermal insulation properties. While not particularly limited, the foaming agent can be selected from the group consisting of melamine, urea, glycine, and combinations thereof.

The foamable refractory coating composition of the present invention includes a foaming agent in an amount of 3 to 10% by weight, for example, 5 to 10% by weight. If the foaming agent content is less than 3% by weight, the coating will not expand, thereby reducing thermal insulation performance. If the content exceeds 10% by weight, the coating will expand excessively, causing cracks in the carbonized layer and reducing strength, thereby reducing thermal insulation performance.

The acid catalyst used in the composition of the present invention decomposes when the cured coating film softens due to exposure to high-temperature heat, thereby promoting the formation of a carbonized layer. Simultaneously, the gas generated by the decomposition acts to expand (foam) the carbonized layer. While not particularly limited, the acid catalyst may be selected from the group consisting of ammonium phosphate, melamine polyphosphate, melamine monophosphate, melamine diphosphate, and combinations thereof.

The foamable fire-resistant coating composition of the present invention may include 20 to 40 weight percent of the acid catalyst, for example, 27 to 35 weight percent. If the acid catalyst is less than 20 weight percent, insufficient carbonized layer is generated, and fire-resistant performance cannot be ensured. If the acid catalyst exceeds 40 weight percent, the carbonized layer is easily broken due to excessive foaming, thereby reducing thermal insulation performance.

The fibers used in the composition of the present invention perform the following functions: (1) they have a high specific surface area, thereby imparting thixotropy to the coating and preventing it from flowing during application; (2) the thin and long fibers are evenly distributed in the cured coating film, acting as a reinforcing material, thereby preventing cracks from occurring during normal times; and (3) in the event of a fire, when the cured coating film softens and foams due to heat, the fibers regulate the foaming rate, react with the acid catalyst, and strengthen the foamed carbonized layer, thereby preventing cracks from occurring, thereby maintaining thermal insulation properties even at high temperatures.

Although not particularly limited, the fibers may be selected from the group consisting of ceramic fibers, mineral wool, carbon fibers, Kevlar, and combinations thereof. For example, the ceramic fibers may be aluminosilicate fibers or magnesium silicate fibers, the mineral wool may be synthetic glass (silicate) fibers, the carbon fibers may be PAN-based carbon fibers, and the Kevlar fibers may be para-aramid synthetic fibers.

The foamable refractory coating composition of the present invention may include 3 to 10% by weight of fiber, for example, 3 to 8% by weight. If the fiber content is less than 3% by weight, the fiber ratio is too low to exhibit the effect of preventing cracks in the carbonized layer. If the fiber content exceeds 10% by weight, the excessive fiber content may increase the viscosity of the coating, resulting in reduced coating workability, reduced coating expansion, and decreased thermal insulation performance.

The foamable fire-resistant coating composition of the present invention may further contain one or more additives selected from the group consisting of dispersants, defoamers, toners, thickeners, pigments and curing catalysts in order to achieve optimal coating and film performance.

The foamable refractory coating composition of the present invention may include 5 to 15 weight percent of the additive. If the additive is less than 5 weight percent, the coating will not disperse smoothly and bubbles will occur in the coating film. If the additive exceeds 15 weight percent, the adhesion performance of the coating film will decrease.

As for the foaming fire-resistant coating composition of the present invention, when measured by the gas toxicity test method (KSF 2271), the gas toxicity is more than 12 minutes, and when measured by the fire resistance test method (UL 1709), even without using additional reinforcing materials (net), the fire resistance performance is more than 3 hours. The release of harmful gases when the coating film expands during a fire is improved, thereby reducing the risk of suffocation during a fire. Therefore, it is effective not only as a fire-resistant coating for equipment such as offshore structures or workshops for handling oil or gas, but also in confined spaces such as tunnels and underground.

The present invention will be described in more detail below by way of examples. However, these examples are only intended to aid understanding of the present invention, and the scope of the present invention is not limited by these examples in any sense.

[Example]

The foamable fire-resistant coating compositions of Examples 1 to 3 and Comparative Examples 1 to 3 were prepared with the compositions shown in Table 1 below, and their fire-resistant properties and gas toxicity were evaluated.

[Table 1]

(weight%)

Epoxy resin: bisphenol A type resin, equivalent weight 182-192 g/eq, viscosity 11,000-14,000 cps, color maximum 25 APHA, maximum hydrolyzable chlorine content 300 ppm, weight average molecular weight 100-400

Curing resin: amide resin, viscosity 300-600 cps, color (#G) maximum 11, amine value 400-500 mgKOH/g, active hydrogen equivalent 50-150 g/eq

Foaming agent: melamine

Acid catalyst: ammonium polyphosphate

Phosphorus-based flame retardant #1 (liquid): Isopropylated triphenyl phosphate (TPP content > 21 wt%, thermal decomposition temperature less than 250°C (TGA heating loss less than 5%))

Phosphorus flame retardant #2 (liquid): Isopropylated triphenyl phosphate (TPP content 10 wt% or less, thermal decomposition temperature 250°C or higher (TGA heating loss 5% or less), viscosity 60-80 cps)

Phosphorus flame retardant #3 (liquid): RDP (TPP content less than 5% by weight, thermal decomposition temperature above 250°C (TGA heating loss less than 5%), viscosity 600 cps)

Fiber #1: Aluminum silicate fiber (diameter 1-2.5 μm, length approximately 5,000 μm, melting point 1,760°C)

Fiber #2: Magnesium silicate fiber (diameter 2-3 μm, melting point 1,500-1,550°C)

Fiber #3: Mineral wool (diameter 6 μm (digital average), length 650 ± 150 μm, melting point 1,000°C)

Fiber #4: Carbon fiber (7 μm diameter, 3 mm length, specific gravity 1.8)

Curing catalyst: tris-(dimethylaminomethyl)phenol

Pigment: Titanium dioxide

Thickener: Alkyl quaternary ammonium clay

Dispersant: Unsaturated polyamine amide salt and acid polyester solution

Defoaming agent: polymethyl alkylsiloxane

- Fire resistance (UL1709) evaluation

The fire resistance performance test used the Rapid Heating Oil Fire Test Standard (UL1709, Rapid Rise Fire Tests of Protection Materials for Structural Steel) which simulates the heating temperature of oil fires on steel structures. This heating curve is characterized by a temperature increase to 1,093°C within 5 minutes and is an internationally used standard heating temperature chart for oil fire tests on steel structures. The evaluation method is based on the temperature of the test body. If the average temperature of each section is less than 538°C and the maximum temperature of each sensor is less than 649°C at the end of the test, the performance as a fire-resistant structure can be ensured. The results of comparing the fire resistance performance of a test body (W10×49, ANSI Designation) coated with paint without using reinforcement materials (Mesh free) are shown in Table 1 above.

-Evaluation of gas toxicity (time of mouse activity cessation, minutes)

The gas toxicity test was conducted according to the KSF 2271 test method. The test involved applying heat to a fire-resistant coating test piece, burning it. The resulting fumes were captured and introduced into a room containing live rats, where the average time it took for the rats to cease activity was measured. As the toxicity of the gas improved, the average time it took for the rats to cease activity increased. The benchmark for this evaluation was a minimum of nine minutes.

As can be seen from Table 1 above, Examples 1 to 3 of the foamable fire-resistant coating composition of the present invention use a liquid phosphorus-based flame retardant having a TPP content of 20% by weight or less and a thermal decomposition temperature of 250°C or more, thereby confirming that even without the use of a reinforcing material (net), excellent gas toxicity characteristics are exhibited while meeting the fire resistance performance benchmark. In contrast, Comparative Examples 1 and 2, which use a phosphorus-based flame retardant having a TPP content of 21% or more, confirm that the fire resistance performance is poor or the gas toxicity is less than 9 minutes. In addition, as shown in Comparative Example 3, when the TPP content is less than 20% by weight and the content of the liquid phosphorus-based flame retardant having a thermal decomposition temperature of 250°C or more exceeds 20% by weight, it can also be confirmed that poor fire resistance and gas toxicity are exhibited compared to Examples 1 and 2.

Claims (3)

1. A foamed refractory coating composition, comprising, based on the total weight of the foamed refractory coating composition, 10% to 25% by weight of epoxy resin, 10% to 15% by weight of curing resin, 10% to 20% by weight of phosphorus-based flame retardant, 3% to 10% by weight of foaming agent, 20% to 40% by weight of acid catalyst, and 3% to 10% by weight of fiber, wherein, The phosphorus-based flame retardant is a mixture of aryl phosphates and diphosphates, wherein the aryl phosphates are composed of triphenyl phosphate and compounds selected from the group consisting of isopropyltriphenyl phosphate, tricresyl phosphate, butylated triphenyl phosphate, cresol diphenyl phosphate, and isopropylbenzene diphenyl phosphate and combinations thereof, and the diphosphates are composed of compounds selected from the group consisting of resorcinol bis(diphenyl phosphate), bisphenol A bis(diphenyl phosphate), and combinations thereof. The content of triphenyl phosphate in the phosphorus-based flame retardant is less than 20% by weight, and the thermal decomposition temperature of the phosphorus-based flame retardant is above 250°C. The weight ratio of the aryl phosphate ester to the diphosphate ester in the phosphorus-based flame retardant is from 1:0.5 to 1:3. The epoxy resin has an equivalent weight of 75 g/eq to 450 g/eq, and The cured resin is an amide resin or an amide resin having an amine value of 300 mg KOH/g to 600 mg KOH/g and an active hydrogen equivalent of 50 g/eq to 200 g/eq. 2. The foamed refractory coating composition according to claim 1, wherein, The epoxy resin has a weight average molecular weight of 150 to 900, and the epoxy resin is selected from the group consisting of bisphenol A type epoxy resin, bisphenol F type epoxy resin, flame retardant epoxy resin, linear phenolic varnish type epoxy resin, multifunctional amine epoxy resin, alicyclic epoxy resin, and combinations thereof. 3. The foamed refractory coating composition according to claim 1, wherein, The cured resin is an amide resin or an amino amine resin with a viscosity of 200 cps to 800 cps.