Heat exchanger fin material

Abstract

To provide a heat exchanger fin material capable of further suppressing frost formation than one using a conventional technique.SOLUTION: The heat exchanger fin material includes a metal plate, and a coat arranged on at least one face of the metal plate, the coat including a portion inherent to a first compound having polyalkylene glycol groups and alkoxysilyl groups, and a portion inherent to a second compound having fluoroalkyl groups and alkoxysilyl groups.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a fin material for a heat exchanger. [Background technology]

[0002] Condensation can form on the fins of an air conditioner's heat exchanger during heating operation. The condensation freezes and turns into frost, reducing the performance of the heat exchanger. In addition, defrosting is required to remove the frost from the fins, which increases the energy consumed by the heat exchanger.

[0003] In order to solve the above problem, Patent Document 1 discloses a technique for reducing frost formation by applying paint containing synthetic silica to a metal plate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 55-164264 Summary of the Invention [Problem to be solved by the invention]

[0005] However, even with the conventional technology disclosed in Patent Document 1, the frost formation suppression effect may be insufficient, and further improvement is required.

[0006] The present invention has been made in view of the above circumstances, and one of its objects is to provide a fin material for a heat exchanger that can suppress frost formation more effectively than conventional techniques. [Means for solving the problem]

[0007] Aspect 1 of the present invention is a metal plate and a coating disposed on at least one surface of the metal plate; The coating is a heat exchanger fin material that includes a portion derived from a first compound having a polyalkylene glycol group and an alkoxysilyl group, and a portion derived from a second compound having a fluoroalkyl group and an alkoxysilyl group.

[0008] Aspect 2 of the present invention is Aspect 1 is a heat exchanger fin material according to aspect 1, having an intermediate layer containing hydroxyl groups between the metal plate and the coating.

[0009] Aspect 3 of the present invention is In the heat exchanger fin material according to aspect 1 or 2, the first compound is represented by the following general formula (1), and the second compound is represented by the following general formula (2): X-SiR 1 3-a (OR 2 ) a ···(1) Y-SiR 3 3-b (OR 4 ) b ···(2) In formulas (1) and (2), X is a monovalent organic group containing a polyalkylene glycol group, Y is a monovalent organic group containing a fluoroalkyl group, and R 1 , R 2 , R 3 and R 4 is independently in each occurrence an alkyl group having 1 to 10 carbon atoms, and a and b are integers of 1 to 3. [Effects of the Invention]

[0010] According to an embodiment of the present invention, it is possible to provide a fin material for a heat exchanger that can suppress frost formation more effectively than conventional techniques. DETAILED DESCRIPTION OF THE INVENTION

[0011] The inventors conducted extensive research to develop a heat exchanger fin material that can suppress frost formation more effectively than conventional techniques. As a result, they discovered that forming a coating on at least one surface of a metal plate, which includes a portion derived from a first compound having a polyalkylene glycol group and an alkoxysilyl group and a portion derived from a second compound having a fluoroalkyl group and an alkoxysilyl group, can suppress frost formation more effectively than conventional techniques. This is believed to be because the highly hydrophilic polyalkylene glycol group and the highly hydrophobic fluoroalkyl group make it difficult for water molecules adhering to the fin material to aggregate, thereby suppressing the formation of ice nuclei. Furthermore, the alkoxysilyl groups contained in each compound bond the compounds together to form a dense coating, ensuring adhesion between the metal plate and the coating. They also discovered that frost formation can be suppressed continuously (e.g., even when multiple cycles of frosting evaluation are performed). As a result, it has been possible to realize a heat exchanger fin material that can suppress frost formation more effectively than conventional techniques. Note that the above mechanism does not limit the technical scope of the embodiments of the present invention.

[0012] The following provides details of each requirement stipulated by the embodiment of the present invention.

[0013] A heat exchanger fin material according to an embodiment of the present invention includes a metal plate and a coating disposed on at least one surface of the metal plate, the coating including a portion derived from a first compound having a polyalkylene glycol group and an alkoxysilyl group and a portion derived from a second compound having a fluoroalkyl group and an alkoxysilyl group. This allows for suppression of frost formation compared to conventional techniques.

[0014] Examples of metal sheets used in embodiments of the present invention include aluminum sheets, aluminum alloy sheets, steel sheets, plated steel sheets, copper sheets, and titanium sheets. Among these, aluminum sheets or aluminum alloy sheets are preferred, and 1000 series aluminum sheets specified in JIS H 4000:2014 are more preferred due to their excellent thermal conductivity and processability. More specifically, aluminum sheets with alloy numbers 1050, 1070, and 1200 are more preferred. The sheet thickness is preferably about 0.05 to 0.3 mm.

[0015] In an embodiment of the present invention, a coating is formed on one or both sides of the metal plate. When a coating is formed on both sides of the metal plate, the coatings on both sides may be the same or different.

[0016] The coating according to the embodiment of the present invention includes a portion derived from a first compound having a polyalkylene glycol group and an alkoxysilyl group, and a portion derived from a second compound having a fluoroalkyl group and an alkoxysilyl group. The first compound and the second compound may each be one or more types.

[0017] In the embodiments of the present invention, the "moiety derived from a first compound having a polyalkylene glycol group and an alkoxysilyl group" refers to a reaction product of the first compound and / or a portion of the alkoxysilyl groups of the first compound. The "moiety derived from a second compound having a fluoroalkyl group and an alkoxysilyl group" refers to a reaction product of the second compound and / or a portion of the alkoxysilyl groups of the second compound. The reaction product of a partially reacted alkoxysilyl group may be, for example, a reaction product in which at least a portion of the alkoxysilyl group is hydrolyzed to form a silanol group, or the silanol group may be a reaction product of a dehydration condensation reaction with another silanol group or a hydroxyl (OH) group, etc.

[0018] The first compound having a polyalkylene glycol group and an alkoxysilyl group can be represented by the following general formula (1). X-SiR1 3-a (OR 2 ) a ···(1) In formula (1), X is a monovalent organic group containing a polyalkylene glycol group, and R 1 and R 2 is independently in each occurrence an alkyl group having 1 to 10 carbon atoms, and a is an integer of 1 to 3. The first compound may contain at least one compound represented by the above formula (1), or may be a mixture of two or more compounds.

[0019] R 1 is preferably an alkyl group having 1 to 5 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms, and even more preferably a methyl group or an ethyl group. R 2 is preferably a methyl group or an ethyl group from the viewpoint of ease of hydrolysis. From the viewpoint of film formation and adhesion to the metal sheet, a is preferably 2 or more, and more preferably 3.

[0020] The number of alkylene glycol units in the polyalkylene glycol group contained in X can be, for example, 2 to 20. X may contain a structure other than a polyalkylene glycol group, and may be, for example, one represented by the following general formula (3). R 5 -O-(R 6 -O) n -R 7 -···(3) In formula (3), R 5 represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and R 6 is an alkylene group having 1 to 10 carbon atoms, n is an integer of 2 to 20, and R 7 is an alkylene group having 1 to 10 carbon atoms.

[0021] R 5is preferably an alkyl group having 1 to 10 carbon atoms, more preferably an alkyl group having 1 to 5 carbon atoms, even more preferably an alkyl group having 1 to 3 carbon atoms, and even more preferably a methyl group or an ethyl group. 6 is preferably an alkylene group having 1 to 5 carbon atoms, and more preferably an alkylene group having 1 to 3 carbon atoms. 7 is preferably an alkylene group having 1 to 5 carbon atoms.

[0022] In an embodiment of the present invention, the fluoroalkyl group in the second compound may be an alkyl group in which at least one hydrogen atom has been substituted with a fluorine atom, and is preferably a perfluoroalkyl group in which all hydrogen atoms in the alkyl group have been substituted with fluorine atoms.

[0023] The second compound having a fluoroalkyl group and an alkoxysilyl group can be represented by the following general formula (2). Y-SiR 3 3-b (OR 4 ) b ···(2) In formula (2), Y is a monovalent organic group containing a fluoroalkyl group, and R 3 and R 4 is independently in each occurrence an alkyl group having 1 to 10 carbon atoms, and b is an integer of 1 to 3.

[0024] R 3 is preferably an alkyl group having 1 to 5 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms, and even more preferably a methyl group or an ethyl group. R 4 is preferably a methyl group or an ethyl group from the viewpoint of ease of hydrolysis. From the viewpoint of film formation and adhesion to the metal sheet, b is preferably 2 or more, and more preferably 3.

[0025] The number of fluorines contained in Y may be, for example, 1 or more, or 2 or more, and may be 41 or less, 29 or less, or 27 or less. Y may contain a structure other than a fluoroalkyl group, and may be, for example, one represented by the following general formula (4). R f -R 8 - (4) In formula (4), R f is a fluoroalkyl group having 1 to 41 fluorines and 1 to 20 carbon atoms, and R 8 is an alkylene group having 1 to 10 carbon atoms.

[0026] R f is preferably a perfluoroalkyl group, and the number of fluorines therein may be 3 to 41. 8 is preferably an alkylene group having 1 to 5 carbon atoms.

[0027] In the coating according to the embodiment of the present invention, it is preferable that the portions derived from the first compound and the portions derived from the second compound are large. For example, the total of the portions derived from the first compound and the portions derived from the second compound in the coating is preferably 50% by mass or more, and more preferably 60% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more in that order.

[0028] In embodiments of the present invention, the compound may contain other moieties in addition to the moieties derived from the first compound and the moieties derived from the second compound. For example, the compound may contain a moiety derived from a third compound having an alkoxysilyl group, which is different from the first compound and the second compound. Examples of the third compound include compounds having an amino group and an alkoxysilyl group. For example, the compound may be co-condensed with the second compound to impart good water solubility to the second compound. The mass of the moiety derived from the third compound is preferably less than the mass of the moiety derived from the second compound. Here, the "moiety derived from the third compound having an alkoxysilyl group" refers to the third compound and / or a portion of the alkoxysilyl group of the third compound that has reacted. Examples of a partially reacted alkoxysilyl group include, for example, at least a portion of the alkoxysilyl group may be hydrolyzed to form a silanol group, and the silanol group may further undergo a dehydration condensation reaction with another silanol group or a hydroxyl (OH) group. The third compound may be one or more types.

[0029] In an embodiment of the present invention, the mass ratio of the portion derived from the first compound to the portion derived from the second compound contained in the coating (i.e., [mass of the portion derived from the first compound] / [mass of the portion derived from the second compound]) is preferably 0.1 to 10, and more preferably 0.2 to 5. Furthermore, when a portion derived from a third compound is contained, the mass ratio of the portion derived from the first compound to the total mass of the portion derived from the second compound and the portion derived from the third compound (i.e., [mass of the portion derived from the first compound] / [mass of the portion derived from the second compound + mass of the portion derived from the third compound]) is 0.1 to 10, and preferably 0.2 to 5.

[0030] In an embodiment of the present invention, the ratio of the number of moles of the portion derived from the first compound to the number of moles of the portion derived from the second compound in the coating is preferably 0.1 to 10, more preferably 0.2 to 5, and even more preferably 0.5 to 1.5.

[0031] In an embodiment of the present invention, the molar ratio of alkylene glycol units to the number of fluorine atoms in the coating (i.e., [number of moles of alkylene glycol units] / [number of moles of fluorine]) is preferably 0.05 to 5, more preferably 0.1 to 2, and even more preferably 0.3 to 0.8.

[0032] The thickness of the coating is not particularly limited, and may be, for example, 0.001 to 1.0 g / m 2 It could be.

[0033] The heat exchanger fin material according to the embodiment of the present invention may include other layers to achieve the object of the present invention. From the viewpoint of adhesion, it is preferable to have an intermediate layer containing hydroxyl groups between the metal plate and the coating. Examples of the intermediate layer containing hydroxyl groups include a metal oxide or inorganic oxide layer such as silica (the surface of which is terminated with hydroxyl groups), or a polymer layer containing hydroxyl groups. Examples of polymers containing hydroxyl groups include polyvinyl alcohol and cellulose. The thickness of the intermediate layer is not particularly limited, but may be 0.1 μm or more and 10 μm or less.

[0034] The heat exchanger fin material according to the embodiment of the present invention can be obtained, for example, by applying a composition obtained by mixing predetermined amounts of the first compound and the second compound (and the third compound) onto a metal plate and then heating and drying. It is advisable to add an acid or the like and stir and mix the mixture before application to hydrolyze the alkoxysilyl groups of the first compound, etc. The solids concentration and pH of the composition can be appropriately adjusted taking into account the applicability, hydrolysis property, etc. The heating temperature and time are not particularly limited, but can be, for example, 100 to 200°C for 10 seconds to 10 minutes. If the heat exchanger fin material has an intermediate layer, the intermediate layer can be formed on the metal plate by a known method before applying the composition, and then the composition can be applied to form a coating. [Example]

[0035] The following examples are provided to more specifically describe the embodiments of the present invention. The embodiments of the present invention are not limited to the following examples, and may be modified as appropriate within the scope of the above-described and below-described aims, and all such modifications are within the technical scope of the embodiments of the present invention.

[0036] The metal plate was prepared by treating an aluminum plate (0.1 mm thick) conforming to alloy number 1070 specified in JIS H 4000:2014 with phosphate chromate and then cutting it into a length of 20 cm and width of 10 cm. An intermediate layer (0.5 μm thick) was formed on the metal plate by crosslinking a polyvinyl alcohol (PVA) resin (PVA-117, manufactured by Kuraray Co., Ltd.) with a melamine resin (Beckamine M-3, manufactured by DIC Corporation). Then, 0.06 parts by mass of first compound A (methoxy PEG-10 propyltrimethoxysilane, Dynasylan 4150, solids concentration 100% by mass), 0.43 parts by mass of second compound B1 (aqueous solution of modified fluoroalkylsiloxane, Dynasylan F8815, solids concentration 14% by mass), and 0.05 parts by mass of 10% acetic acid solution were added to 4.45 parts by mass of ion-exchanged water and stirred overnight to prepare a composition. It is believed that the above treatment causes at least a portion of the alkoxysilyl groups in the first compound A and the second compound B1 to be hydrolyzed to form silanol groups. The composition was then applied onto the intermediate layer and dried by heating at 150°C for 1 minute, resulting in a coating thickness of 0.06 g / m 2 Thus, a heat exchanger fin material of Test No. 1 was obtained. Note that, by the above treatment, it is believed that at least a portion of the silanol groups formed by the above treatment undergoes a dehydration condensation reaction with other silanol groups or hydroxyl (OH) groups, etc. Heat exchanger fin materials of Test Nos. 2 to 10 were obtained by changing the compounds and additive amounts, etc., from Test No. 1 as shown in Table 1. For Test No. 6, 0.19 parts by mass of the first compound A, 0.19 parts by mass of the second compound B2 (trimethoxy(1H,1H,2H,2H-heptadecafluorodecyl)silane, solids concentration 100% by mass), 10 parts by mass of ethanol, and 0.05 parts by mass of a 10% acetic acid solution were added to 0.75 parts by mass of ion-exchanged water, and a coating was formed using the composition stirred overnight. For Test Nos. 5, 9, and 10, a paint containing synthetic silica was applied to form an intermediate layer. In Table 1, the numbers in the "Coating" row indicate the amount (parts by mass) of each material added to the film-forming composition, a "-" in the "Coating" row indicates that the film-forming composition does not contain the corresponding material, and a "←" in the "Intermediate layer" row indicates that it is the same as the one on the left.

[0037] [Table 1]

[0038] The fin materials for heat exchangers of Test Nos. 1 to 10 were evaluated for frost formation as follows. A copper plate equipped with a refrigerant flow path, a Peltier element, and an air flow path was placed at the top of the inside of an acrylic cylinder, and this was left standing for 3 hours in an environment with a temperature of 2°C and a relative humidity of 85%. The surface temperature of the copper plate was then adjusted to 10°C, and heat exchanger fin materials Nos. 1 to 10 were placed on the copper plate in a position that was in contact with the air inside the cylinder. Air was then blown into the cylinder at a speed of 1.5 m / s, and the plate was left standing for 2 minutes. The copper plate was then cooled to a surface temperature of -7.5°C while continuing to blow air into the cylinder at the same speed. The temperature was maintained at -7.5°C from the start of cooling until frost formed on the heat exchanger fin material. After frost formation, the temperature was raised to 40°C and held for 5 minutes to dry the heat exchanger fin material, followed by defrosting by lowering the temperature to 10°C, holding for 1 minute, and then cooling to -7.5°C. The time from the start of cooling at -7.5°C until frost formed was taken as the frost delay time, and the average value was calculated from 10 or more repeated measurements. Meanwhile, as a comparison sample, a paint containing synthetic silica was applied to the metal plates used in Tests Nos. 1 to 10, as in the conventional technology. Heat exchanger fin materials with an average frost delay time 1.5 times or more longer than the comparison sample were evaluated as being able to suppress frost formation more effectively than the conventional technology (◯), while heat exchanger fin materials with an average frost delay time less than 1.5 times longer were evaluated as being unable to suppress frost formation more effectively than the conventional technology (×). The evaluation results are shown in Table 2.

[0039] [Table 2]

[0040] The results in Table 2 can be considered as follows: All of the heat exchanger fin materials of Test Nos. 1 to 6 satisfied the requirements defined in the embodiments of the present invention, and were able to suppress frost formation more than the prior art. On the other hand, the heat exchanger fin materials of Test Nos. 7 to 10 had coatings that did not include either the portion derived from the first compound or the portion derived from the second compound, and were unable to suppress frost formation as well as the prior art.

Claims

1. a metal plate and a coating disposed on at least one surface of the metal plate; The coating is a fin material for a heat exchanger, which is made of a mixture including a portion derived from a first compound having a polyalkylene glycol group and an alkoxysilyl group, and a portion derived from a second compound having a fluoroalkyl group and an alkoxysilyl group.

2. The heat exchanger fin material according to claim 1, further comprising an intermediate layer containing hydroxyl groups between the metal plate and the coating.

3. The heat exchanger fin material according to claim 1 or 2, wherein the first compound is represented by the following general formula (1), and the second compound is represented by the following general formula (2): X-SiR １ ３－ａ (OR ２ ) ａ ・・・(1) Y-SiR ３ ３－ｂ (OR ４ ) ｂ ・・・(2) In formulas (1) and (2), X is a monovalent organic group containing a polyalkylene glycol group, Y is a monovalent organic group containing a fluoroalkyl group, and R １ , R ２ , R ３ and R ４ is independently in each occurrence an alkyl group having 1 to 10 carbon atoms; and a and b are integers from 1 to 3. is.

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