JP4455913B2 - Latent heat recovery type heat exchanger member, latent heat recovery type heat exchanger and heat exchange device - Google Patents

Description

  The present invention relates to a latent heat recovery type heat exchanger suitable for a heat exchange device using combustion gas such as a water heater, its members, and a heat exchange device using the heat exchanger.

  In a heat exchange device using combustion gas such as a water heater, sensible heat of the combustion gas is mainly used for heat exchange. Heat that has not been used for heat exchange has been discarded as low-temperature exhaust heat. However, in recent years, from the viewpoint of improving energy efficiency, the low-temperature exhaust heat has been recovered and used. This type of heat exchanger that recovers low-temperature exhaust heat is called a latent heat recovery heat exchanger.

  For example, a high-efficiency water heater that also uses low-temperature exhaust heat was heat-exchanged between a sensible heat recovery heat exchanger that recovers sensible heat from combustion gas at about 1300 ° C. and a sensible heat recovery heat exchanger. It is composed of a latent heat recovery type heat exchanger that recovers latent heat from the combustion gas whose temperature has been lowered to about 200 ° C. later.

  By the way, a sensible heat recovery type heat exchanger has excellent thermal conductivity, good workability, and is inexpensive, so copper or an alloy thereof (hereinafter referred to as “copper metal”), aluminum or an alloy thereof ( Hereinafter, “aluminum-based metal”) is used.

  On the other hand, in the latent heat recovery type heat exchanger, it is difficult to apply copper-based metal or aluminum-based metal for the following reasons.

The latent heat recovery type heat exchanger condenses water vapor in the combustion gas and recovers the latent heat at that time to achieve heat exchange, but the water generated by the condensation of water vapor is latent heat recovery type heat exchange. It adheres as drain water to the outer surface of the vessel. Since this drain water is dissolved in NO _x , SO _x , and CO ₂ in the combustion gas, it usually shows an acidity with a pH of 4 or less. Further, when the water heater is operated intermittently, the acid drain water adhering to the outer surface of the latent heat recovery type heat exchanger is heated to evaporate the water, whereby the acid concentration gradually increases. Copper-based metals and aluminum-based metals corrode when contacted with such acidic drain water.

For example, the following technologies (1) to (3) have been proposed as countermeasures against corrosion by acidic drain water in the latent heat recovery type heat exchanger.
(1) A method using a corrosion-resistant material such as ceramics, stainless steel, or titanium (Patent Documents 1 to 3);
(2) A heat exchanger is configured by combining a copper-based metal pipe and an aluminum-based metal fin, and the aluminum-based metal fin acts as a sacrificial anode (Patent Documents 4 and 5), and the pipe and the fin are both made of copper. A method of increasing the thickness of the fin and causing it to act as a sacrificial anode (Patent Document 6);
(3) A method of improving corrosion resistance by forming an anticorrosion film on copper (Patent Documents 7 to 11).

For the anticorrosion film of (3), an epoxy resin, a silicone resin, a perfluoro type fluororesin (polytetrafluoroethylene, etc.) or the like generally known as a resin excellent in anticorrosion is used. .
JP 2000-161788 A (Claims etc.) JP 2002-71213 A (Claims etc.) JP 2002-106970 A (Claims etc.) JP 2000-146304 A ([0007] etc.) JP 2000-292010 A (Claims etc.) JP2003-185388 (Claims, [0022]), etc.) JP-A-11-148720 ([0026]) JP-A-11-148723 (Claims, [0028]) JP 2000-88355 A (Claims, [0016]) JP 2003-161527 (Claims, [0018]) JP 2003-161595 (Claims, [0017])

  However, the above-mentioned various techniques proposed as means for avoiding corrosion by acidic drain water in the latent heat recovery type heat exchanger have the following problems.

  The corrosion resistant material (ceramics, stainless steel, titanium, etc.) used in the technique (1) has sufficient resistance to acidic drain water. However, these materials have poor workability compared to copper-based metals and aluminum-based metals. Ceramics and titanium are more expensive than copper-based metals and aluminum-based metals. Furthermore, ceramics, stainless steel, and titanium have lower thermal conductivity than copper-based metals and aluminum-based metals, so for example, to ensure the same heat exchange rate as a latent heat recovery type heat exchanger using copper, Since a larger heat transfer area is required, the heat exchange device must be enlarged or its shape complicated. Under these circumstances, there is a problem that the manufacturing cost is increased in the heat exchange device having a latent heat recovery type heat exchanger using ceramics, stainless steel or titanium.

  Among (2), the techniques of Patent Documents 4 and 5 require joining of dissimilar metals, so the price is likely to be high, and from the viewpoint of resource recycling, they are joined at the time of disposal of the heat exchange device. There is also the problem that special measures must be taken to separate these metals. Furthermore, in order for the aluminum-based metal fin to act as a sacrificial anode, it is necessary to remove a considerable amount of corrosion, and in addition, the corrosion product of the aluminum-based metal eluted by the adhesion of acidic drain water is clogged between the fins. This may reduce the heat exchange efficiency.

  Also, in the technique of Patent Document 6, as in the technique of Patent Document 5, it is necessary to make the fin corrosive margin considerable, and the corrosion product of copper eluted by the adhesion of acidic drain water is The problem is that the heat exchange efficiency may be reduced due to clogging.

  Among the techniques of (3), in an anticorrosion film using an epoxy resin, an epoxy resin containing an aromatic group such as a bisphenol type epoxy resin or a phenol novolac type epoxy resin is generally used as the epoxy resin (for example, In Patent Document 10 and Patent Document 11, it is described as “epoxyphenol water-based paint”).

  However, under the environment where the latent heat recovery type heat exchanger is used, since it is constantly exposed to acidic drain water and high-temperature (for example, about 200 ° C.) combustion gas, the oxidative decomposition of the aromatic groups in the film gradually proceeds. Since the anticorrosion performance deteriorates, the long-term anticorrosive effect is insufficient.

  Silicone resins are commonly used as corrosion-resistant and heat-resistant coating materials, but even with anti-corrosion coatings that use them, mineralization due to oxidation of the organosiloxane portion in the coating is possible in the environment where the latent heat recovery heat exchanger is used. Since it progresses gradually and its anticorrosion performance deteriorates, the long-term anticorrosion effect is still insufficient.

  On the other hand, perfluoro type fluororesins have high molecular structure stability and good acid resistance of the material itself. Therefore, even under the environment where the latent heat recovery type heat exchanger is used, the film itself is less deteriorated but has the following drawbacks.

  Perfluoro type fluororesins represented by polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), etc. are solvents. Therefore, it is necessary to form an anticorrosive film by a powder coating method. In addition, since these fluororesins have poor adhesion to metal substrates, the surface of members (fins, pipes, etc.) is roughened by shot blasting or the like as a pretreatment for coating, thereby improving adhesion by the anchor effect. There is a need. A general heat exchanger has a fin-pipe shape, and the fin pitch is usually about several mm. It is difficult to uniformly perform surface treatment (shot blasting) or powder coating over such a complicated shape or the entire surface of a narrow part.

  In addition, even if the shape of the heat exchanger is devised so that surface treatment and powder coating are possible, in order to obtain a dense film without pinholes that can exhibit a sufficient long-term anticorrosion effect, It is required to make the thickness of about 100 μm or more by repeating the coating. For this reason, even if it uses a copper-type metal and aluminum-type metal with favorable heat conductivity for a base material, the fall of a heat exchange rate cannot be avoided.

  Furthermore, since these fluororesins have high crystallinity, the flexibility of the film is poor. Therefore, the anticorrosion film cannot follow the thermal deformation of the base material due to the heat cycle in the intermittent operation of the water heater, and the adhesion strength between the base material and the film may gradually decrease.

  In addition, since these fluororesins employ a film forming method based on a powder coating method, it is necessary to heat and bake the fluororesin above the softening point at the time of film formation, and the temperature is usually as high as 200 to 400 ° C. It is very hot. When firing at such a temperature, particularly in the case of a copper metal base material, a thick oxide layer is formed due to oxidation of the surface of the base material, which causes deterioration of the adhesion of the anticorrosive film. For this reason, prior to firing, it is necessary to devise such as plating (Ni plating or the like) on the substrate surface. However, when plating is performed on the surface of the base material, it is necessary to take special measures for separating the plated portion from the viewpoint of resource recycling when the heat exchange device is discarded.

  In addition, some liquid paints used for corrosion-resistant coatings are called modified fluororesins. This is a liquid composition in which perfluoro type fluororesin fine particles are dispersed in a thermosetting resin binder. Although it is conceivable to use this modified fluororesin for the corrosion resistant coating of latent heat recovery type heat exchangers, the thermosetting resin applied to the modified fluororesin generally has an aromatic group in the molecule. Under the environment where the latent heat recovery type heat exchanger is used, there is a problem of film deterioration due to decomposition of the aromatic group. Furthermore, when forming a film, it is usually necessary to heat to a temperature of 180 ° C. or higher, and similarly to the case of firing the fluororesin, there arises a problem of reduced adhesion due to the formation of an oxide layer.

  The present invention has been made in view of the above circumstances, and its purpose is to recover latent heat excellent in resistance to corrosion by acidic drain water while having a copper-based or aluminum-based metal base material excellent in thermal conductivity. An object of the present invention is to provide a mold heat exchanger member, a latent heat recovery type heat exchanger using the member, and a heat exchange device using the latent heat recovery type heat exchanger.

  The latent heat recovery type heat exchanger member of the present invention that can achieve the above object is made of a copper-based or aluminum-based metal in which a film containing a polymer having a methylene chain containing a fluorine substituent is formed on the outer surface. The polymer has a gist in that the number ratio is 5 to 50 fluorine atoms with respect to 100 carbon atoms and does not substantially contain an aromatic group.

The coating, when performing infrared absorption spectrum analysis, the area of the characteristic absorption peak derived from C-H stretching vibration of aromatic group wave number may appear in 3000～3100Cm ^-1, wave number in 2800 to 3000 cm ^-1 It is preferable that the ratio with the area of the characteristic absorption peak derived from C—H stretching vibration of the appearing aliphatic chain is 10/100 or less.

  The film includes a composition comprising a fluoroethylene and a copolymer obtained by polymerizing a monomer component that essentially includes one or more compounds selected from the group consisting of vinyl ethers, vinyl esters, and acrylate esters. It is desirable to be formed from a product. Monochlorotrifluoroethylene and / or tetrafluoroethylene are recommended as the fluoroethylenes.

  Moreover, the latent heat recovery type heat exchanger having the latent heat recovery type heat exchanger member of the present invention and the heat exchange apparatus having the latent heat recovery type heat exchanger are also included in the present invention.

  The latent heat recovery type heat exchanger member of the present invention has a copper base material or an aluminum base material surface excellent in thermal conductivity, and the film excellent in acid resistance and heat resistance, regardless of the shape of the member, It is uniformly and well formed. Therefore, in the latent heat recovery type heat exchanger using the latent heat recovery type heat exchanger member of the present invention, a high heat exchange rate and resistance to acidic drain water can be secured. Therefore, in the latent heat recovery type heat exchanger of the present invention and the heat exchange apparatus of the present invention using the same, the service life can be extended while ensuring a high heat exchange rate.

  The member for latent heat recovery type heat exchanger of the present invention (hereinafter sometimes simply referred to as “member”) has the greatest feature in that a film having a specific composition is provided. Hereinafter, the present invention will be described in detail in the order of a member, a latent heat recovery type heat exchanger (hereinafter sometimes simply referred to as “heat exchanger”), and a heat exchange device.

<Latent heat recovery type heat exchanger member>
[Base material]
The base material which concerns on the member of this invention is comprised with a copper-type metal or an aluminum-type metal. These metals are excellent in thermal conductivity, and, for example, a heat exchanger excellent in heat exchange efficiency can be configured as compared with base materials such as stainless steel, titanium, and ceramics adopted for the purpose of ensuring corrosion resistance. In addition, the moldability is excellent as compared with these corrosion-resistant materials, and it is easy to form a substrate having a complicated shape. For these reasons, a more compact heat exchanger (heat exchange device) can be provided.

  The copper-based metal is a metal containing copper, such as a copper simple substance or a copper alloy (for example, oxygen-free copper, phosphorous deoxidized copper, tough pitch copper, Cu-Fe-P, Cu-Mn-P, Cu- Ni-Si, Cu-Sn-P, Cu-Zn, etc.). Among these, copper alone, particularly phosphorous deoxidized copper, is preferable because it is excellent in thermal conductivity, workability, and heat resistance and is advantageous in terms of cost.

  An aluminum-based metal is a metal containing aluminum, such as an aluminum simple substance or an aluminum alloy [for example, pure Al (1000 series), Al-Cu (2000 series), Al-Mn (3000 series), Al-Si. (4000 series), Al-Mg (5000 series), Al-Mg-Si (6000 series), Al-Zn-Mg (7000 series), etc.]. Among these, aluminum alloys of 3003, 3004, 5052, 5083, 5086, 5454, 6061, and 6063 are preferable because they are excellent in thermal conductivity, workability, and heat resistance and are advantageous in terms of cost.

  The shape and size of the base material are not particularly limited. Pipes used in ordinary latent heat recovery type heat exchangers [pipes for passing materials (such as water) heated by heat exchange], heat exchange efficiency There is a shape such as a fin for enhancing, and a shape in which a pipe and a fin are integrated is also included. The size may be the size required for the latent heat recovery type heat exchanger.

[Coating]
As described above, in the member of the present invention, a copper-based metal or an aluminum-based metal excellent in thermal conductivity and formability is adopted as a material for the base material. However, since these metals have poor resistance to acidic drain water, they are corroded by the use of heat exchange devices. The coating film according to the member of the present invention plays a role as a protective layer that enhances the color resistance of the member and suppresses corrosion by acidic drain water.

  The film according to the present invention includes a polymer having a methylene chain containing a fluorine substituent in the main chain, and the polymer has 5 to 50 fluorine atoms per 100 carbon atoms in terms of number ratio. And does not substantially contain an aromatic group. Hereinafter, in the polymer according to the film and the fluororesin for forming the film, the number ratio of fluorine atoms to carbon atoms 100 is simply referred to as “fluorine atom ratio”.

  If the fluorine atomic ratio in the polymer contained in the film is too small, the corrosion resistance of the film becomes insufficient, and corrosion of the member due to acidic drain water may not be sufficiently suppressed. A more preferable fluorine atom ratio is 8 or more, and further preferably 10 or more.

  On the other hand, if the fluorine atom ratio in the polymer contained in the film is too large, a good film cannot be obtained particularly when the shape of the substrate is complicated, for example, when the interval between fins is narrow.

  As described above, a latent heat recovery type heat exchanger member having a fluororesin film has also been provided. This fluororesin film is formed by a powder coating method using a perfluoro type fluororesin. . For this reason, it is difficult to form a good film, and sufficient resistance to acidic drain water cannot be ensured.

  Therefore, in the present invention, the film is formed using a liquid composition (liquid paint) containing a fluororesin. That is, by selecting a fluororesin that can be made into a liquid composition and using this liquid composition, for example, uniform and good film formation substantially free of pinholes and the like has been achieved.

  The polymer contained in the formed film is derived from the fluororesin contained in the liquid composition. Therefore, when the fluorine atomic ratio related to the polymer is too large, the solvent solubility of the fluororesin related to the liquid composition is low, so that the liquid composition cannot be formed or is unstable, and there is a pinhole in the formed film. A uniform and good film cannot be obtained due to contamination. Furthermore, the adhesion of the film to the substrate and the flexibility of the film are inferior, and the total durability as a corrosion-resistant film is deteriorated. The fluorine atomic ratio related to the polymer is more preferably 40 or less, and further preferably 30 or less.

  The number ratio of carbon atoms and fluorine atoms in the polymer contained in the coating is determined by the energy dispersive X-ray analyzer (EDX) after gold deposition (thickness: about 30 nm) is performed to impart electrical conductivity to the coating surface. ). First, the relative intensities of the characteristic X-rays of carbon atoms and fluorine atoms are obtained, and from the relative intensities, using a conversion factor determined based on PTFE data in which the number ratio of the number of carbon atoms to the number of fluorine atoms is known, carbon The number ratio between the number of atoms and the number of fluorine atoms is calculated. At this time, it is desirable that the acceleration voltage is 15 kV and the observation magnification is about 100 times.

  As will be described later, in the member of the present invention, a primer layer may be provided on the surface of the substrate, and the film may be formed on the primer layer. In this case, when the above measurement by EDX is performed in a state having the primer layer, characteristic X-rays derived from the components contained in the primer layer are also observed at the same time, and the number of carbon atoms may increase apparently.

  Therefore, in order to correctly measure the fluorine atomic ratio of the film, for example, by examining the thickness of the film, the presence / absence of the primer layer, the thickness of the primer layer by the following method, when it is found that the primer layer exists Use the microtome or the like to scrape only the film and perform the above analysis. As a method for examining the thickness of the film, the presence or absence of the primer layer, and the thickness of the primer layer, for example, the cut surface in the thickness direction of the film (and the primer layer) obtained by using a microtome or the like is scanned with an optical microscope or an electron microscope (scanning). Observation with a scanning electron microscope, etc.), determining the presence or absence of the interface between the film and the primer layer, and measuring the thickness of the film (primer layer). If the interface is clear, it can be judged visually, but if it is unclear, EDX may be used together, and the constituent atoms of the cross section may be judged by performing a line analysis in the direction perpendicular to the coating surface.

  In addition, the polymer contained in the film is substantially free of aromatic groups. When the latent heat recovery type heat exchanger is used, the film is exposed to acidic drain water and high-temperature combustion gas. Therefore, when the polymer contains an aromatic group, the oxidative decomposition of the aromatic group occurs. Since it progresses gradually and the performance of the film tends to deteriorate, the corrosion resistance of the member of the present invention may not be ensured over a long period of time.

  The aromatic group referred to in the present invention is a group having an aromatic ring. The aromatic ring includes a non-benzene aromatic ring; a benzene ring; a condensed aromatic ring such as a naphthalene ring, an anthracene ring, and a pyrene ring; Heteroaromatic ring (pyrrole ring, pyridine ring, thiophene ring, furan) in which one or more carbon atoms of benzene aromatic ring, aromatic ring or condensed aromatic ring are replaced by hetero atom such as oxygen atom, nitrogen atom, sulfur atom Ring, etc.); The aromatic group as used in the present invention includes not only those bonded to the main chain of the resin forming the polymer as a substituent, but also aromatic rings constituting the main chain.

  Further, the phrase “the polymer does not substantially contain an aromatic group” means that, for example, in the present invention, the use of an additive having an aromatic group in the film is not completely excluded. The aspect in which the polymer inevitably contains an aromatic group as in the case where the aromatic group derived from the additive is bonded to the polymer during film formation is not excluded from the present invention. It is.

The fact that the polymer does not substantially contain an aromatic group means that, for example, when an absorption spectrum is obtained by performing infrared absorption spectrum analysis, characteristic absorption derived from C—H stretching vibration of the aromatic group may appear. : in the context of 3000~3100cm ^-1, it can be maximum value that exceeds the absorbance at 3000 cm ^-1 is confirmed by the absence. In addition, about the method and conditions of infrared absorption spectrum analysis, it is set to be the same as the method and conditions employ | adopted when calculating | requiring the ratio of the area (A) and (B) of the specific absorption peak mentioned later.

From the viewpoint of suppressing film deterioration based on aromatic groups under the use environment of the latent heat recovery type heat exchanger, when infrared absorption spectrum analysis is performed on the above film, the fragrance that can appear at a wave number of 3000 to 3100 cm ^−1. Area of characteristic absorption peak (A) derived from C—H stretching vibration of group and area of characteristic absorption peak (B) derived from C—H stretching vibration of aliphatic chain appearing in wave number of 2800 to 3000 cm ⁻¹ The ratio [(A) / (B) ratio] is preferably 10/100 or less. The ratio (A) / (B) is more preferably 6/100 or less, and most preferably 0/100.

The ratio (A / B ratio) of the area (A) and (B) of the characteristic absorption peak is a Fourier transform infrared spectrophotometer (for example, “JIR-100 type” manufactured by JEOL Ltd.). Is used to perform infrared absorption spectrum analysis by a transmission method using a beam condenser (resolution: 4 cm ⁻¹ , number of integrations: 100 times), and obtained according to the following procedure.
(1) the horizontal axis wavenumber, the vertical axis to obtain an infrared absorption spectrum chart of absorbance, draw a straight line connecting the location of points and 3100 cm ^-1 in 2700 cm ^-1 of the spectrum curve of the chart.
(2) The region surrounded by the straight line and the spectrum curve of (1) above is cut, and the cut chart pieces are further cut into (A) 3000 to 3100 cm ⁻¹ and (B) 2800 to 3000 cm ⁻¹ . Cut.
(3) The mass of the chart pieces (A) and (B) in (2) above is measured, and these are regarded as the areas (A) and (B) of the characteristic absorption peak, and (A) / (B) Calculate the ratio.

  That is, when the (A) / (B) ratio in the film exceeds the upper limit, the amount of aromatic groups present in the film is large, so the film in the environment where the latent heat recovery type heat exchanger is used. Deterioration is more likely to proceed. In the above film, since the polymer does not substantially contain an aromatic group, the aromatic group that can be present in the film (detected by the above measurement method) is a composition used for forming the film. It originates from the solvent residue of (liquid paint), additives having aromatic groups, and the like.

  Here, when the film is formed on the primer layer provided on the substrate surface, only the film is scraped with a microtome or the like, and the areas (A) and (B) of the characteristic absorption peaks are measured. do it.

  The film is formed of a liquid composition containing a specific fluororesin. The fluororesin for forming a film has a methylene chain containing a fluorine substituent and has a fluorine atom ratio of 5 or more, preferably 8 or more, more preferably 10 or more, and 50 or less, preferably 40 or less. More preferably, it is 30 or less and does not contain an aromatic group.

  More preferable fluororesins include, for example, a copolymer obtained by polymerizing a monomer component that essentially contains fluoroethylenes and one or more compounds selected from the group consisting of vinyl ethers, vinyl esters, and acrylic esters. Examples of the polymer include those having a fluorine atomic ratio within the above range. Among these copolymers, those having a fluorine atomic ratio within the above range can be prepared as follows. For example, the monomer composition ratio is calculated and charged so that the fluorine atomic ratio is within the above range, copolymerization is performed according to a conventional method, and the obtained copolymer is obtained from the fragment peak area ratio by pyrolysis gas chromatography. Quantify the fluorine atomic ratio by the calibration curve method. When the fluorine atom ratio of the copolymer is not within the above range, the monomer charge composition is appropriately changed according to the fluorine atom ratio, copolymerization is performed again, and the fluorine atom ratio of the obtained copolymer is changed to the above value. Repeat a series of operations that are quantified and confirmed by the method.

  In the above copolymer, vinyl ethers copolymerizable with fluoroethylenes include alkyl vinyl ethers (methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, n-butyl vinyl ether, t-butyl vinyl ether, 2-ethylhexyl vinyl ether, n- Aliphatic alkyl vinyl ethers such as nonyl vinyl ether, lauryl vinyl ether, stearyl vinyl ether; alicyclic alkyl vinyl ethers such as cyclohexyl vinyl ether, cyclohexyl methyl vinyl ether, 4-methylcyclohexyl methyl vinyl ether, etc .; alkoxyalkyl vinyl ethers (methoxyethyl vinyl ether, ethoxy Ethyl vinyl ether, butoxyethyl vinyl ether, methoxy et Hydroxyethyl vinyl ethers (2-hydroxyethyl vinyl ether, 2-hydroxypropyl vinyl ether, 4-hydroxybutyl vinyl ether, 4-hydroxymethylcyclohexyl methyl vinyl ether, etc.); carboxyalkyl vinyl ethers; glycidyl Vinyl ethers; and the like.

  In the above copolymer, vinyl esters copolymerizable with fluoroethylenes include vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl laurate, vinyl stearate, vinyl 2-ethylhexanoate. And vinyl cyclohexanecarboxylate. In these vinyl esters, it is also preferred that a part of the hydrogen of the alkyl group bonded to the vinyl group via an ester bond is substituted with a hydroxyl group or a carboxyl group.

  In the above copolymer, the acrylic acid ester copolymerizable with fluoroethylenes is methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, s-butyl acrylate, t-butyl acrylate, 2-ethylhexyl. Examples include acrylic acid alkyl esters such as acrylate and lauryl acrylate; acrylic acid cycloalkyl esters such as cyclohexyl acrylate; 4-siloxybutyl acrylate; and the like. In these acrylic acid esters, it is also preferred that part of the hydrogen of the alkyl group or cycloalkyl group bonded to the vinyl group via an ester bond is substituted with a hydroxyl group, a carboxyl group or a silyl group.

  Moreover, as fluoroethylenes, monochlorotrifluoroethylene and tetrafluoroethylene are suitable.

  In addition, the copolymer may be copolymerized with another copolymerizable monomer as long as the effects of the present invention are not impaired. Such other monomers are not particularly limited, but olefins (ethylene, propylene, butylene, pentene, etc.) can be exemplified as typical examples.

  In the case where the fluororesin for forming the film is each of the above exemplified copolymers, the corrosion resistance (acid resistance) and heat resistance are good due to the action of fluorine atoms present in the molecule. In addition, by introducing a copolymer component having a bulky group such as vinyl ethers, vinyl esters, and acrylates, the crystallinity of the fluororesin is lowered and the solvent solubility and flexibility are improved. Furthermore, by introducing polar parts such as ether bonds and ester bonds of these copolymer components into the fluororesin, pigment dispersibility when pigments are added to the film and substrate adhesion of the film are improved. The fluororesin can be dissolved in a more polar solvent.

  In addition, when vinyl ethers, vinyl esters, acrylic acid esters, or other monomers that are copolymerization components have a hydroxyl group, the fluororesin also has a hydroxyl group. Therefore, in such a fluororesin, a cross-linked structure can be introduced by reacting a hydroxyl group with a cross-linking agent, so that the film can be densified and strengthened. For example, it can be made very thin.

  In addition, when the vinyl ethers, vinyl esters, acrylic acid esters or other monomers that are copolymerization components have a carboxyl group, the fluororesin also has a carboxyl group. The carboxyl group possessed by the fluororesin can contribute to improving the stability of the liquid composition and improving the adhesion between the substrate and the film.

  Furthermore, in the vinyl ethers, the vinyl esters, and the acrylate esters, it is desirable that the number of carbon atoms of the group (side chain) bonded to the vinyl group carbon atom is 3 or more. By introducing such a bulky group (side chain) into the copolymer, the hydrolysis resistance of the cross-linked portion is improved due to the steric hindrance, so that a film having higher durability can be obtained.

  In each of the above-mentioned copolymers, vinyl ethers, vinyl esters, and acrylic acid esters are used as copolymerization components because of the above-mentioned fragment peak by pyrolysis gas chromatography and characteristic absorption by infrared absorption spectrum measurement. This can be confirmed by analyzing the peak.

  Examples of the crosslinked structure when introducing a crosslinked structure into the film using a fluororesin having a hydroxyl group include ether crosslinking including an ether bond, ester crosslinking including an ester bond, urethane crosslinking including a urethane bond, and siloxane crosslinking including a siloxane bond. Is mentioned. Therefore, the crosslinking agent may be appropriately selected from known resin crosslinking agents that can form such bonds.

  Among these crosslinked structures, for example, urethane crosslinking and siloxane crosslinking are recommended. This is because the isocyanate compounds and silyl compounds, which are crosslinking agents used for forming these crosslinks, have good compatibility with the fluororesin, and thus have an advantage that a stable liquid composition can be obtained. As a crosslinking agent for forming urethane crosslinking, polyisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, transcyclohexane-1,4-diisocyanate; adducts of these polyisocyanates and polyols; dimers of these polyisocyanates; Isocyanate compounds such as trimers of polyisocyanates (isocyanurates); The isocyanate group of these isocyanate compounds may be blocked with a known blocking agent (alcohol, oxime, active methylene, etc.). In such a blocked isocyanate compound, the blocking agent is desorbed by the action of heat or a catalyst and becomes active.

  Examples of crosslinking agents for forming siloxane crosslinking include organosilicates (tetraalkoxysilanes such as tetramethoxysilane and tetraethoxysilane; methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane and ethyltriethoxysilane). Trialkoxysilanes; dialkoxysilanes such as dimethyldimethoxysilane, dimethyldiethoxysilane, diethyldimethoxysilane, and diethyldiethoxysilane), and silyl isocyanate (such as methyltriisocyanate).

  In addition, as a crosslinking agent for introducing such a crosslinked structure, a compound that does not contain an aromatic group in the molecule is selected.

In the above film, the introduction of the urethane cross-linked structure means that the wave number of the infrared absorption spectrum is around 1680 to 1750 cm ⁻¹ , and the introduction of the siloxane cross-linked structure means that the wave number of the infrared absorption spectrum is: Since strong characteristic absorption appears in the vicinity of 1000 to 1200 cm ⁻¹ , it can be easily confirmed.

  The film is formed using a liquid composition (liquid paint) containing a fluororesin that satisfies the fluorine atomic ratio. Therefore, this composition also includes a solvent for dissolving the fluororesin. Usable solvents include those that do not have a functional group capable of reacting with a hydroxyl group, a carboxyl group, or an isocyanate group. For example, aromatic hydrocarbons such as toluene, xylene, and ethylbenzene; esters such as butyl acetate; ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; glycol ethers such as ethyl cellosolve; Or a mixture of two or more.

  The composition of the liquid composition for film formation is 20 parts by mass or more, more preferably 40 parts by mass or more and 350 parts by mass or less, more preferably 100 parts by mass of the fluororesin. It is desirable to be 250 parts by mass or less. If the amount of the solvent is too small, the viscosity of the liquid composition may become too high. If the viscosity of the liquid composition is too high, it will be difficult to apply to the details, or cross-linking will proceed before the solvent evaporates at the time of heat curing, resulting in an increase in the amount of residual solvent and impair film performance. Sometimes. On the other hand, when the amount of the solvent is too large, shrinkage of the film accompanying evaporation of the solvent during heat curing becomes large, and residual stress, cracks, micropores, etc. are likely to occur.

  Moreover, when using the said crosslinking agent, it is 5 mass parts or more with respect to 100 mass parts of fluororesins, More preferably, it is 10 mass parts or more, Comprising: It shall be 50 mass parts or less, More preferably, it shall be 40 mass parts or less. Is recommended. If the amount of the crosslinking agent is too small, the effect of using the crosslinking agent may not be sufficiently ensured. On the other hand, if the amount of the crosslinking agent is too large, the film becomes too hard and may become brittle.

  Furthermore, you may add various well-known additives to the liquid composition for film formation as needed. For example, various additives (such as antifoaming agents, viscosity modifiers, leveling agents, anti-gelling agents), antioxidants, coloring pigments, curing accelerators (organometallic compounds and tertiary amines) ) And the like. In addition, when using what has an aromatic group as these additives, it is desirable to adjust the usage-amount so that (A) / (B) ratio may become below the said upper limit. The use amount of the additive having an aromatic group is, for example, a series of (A) / (B) ratios measured for the formed film, and when this exceeds the upper limit, the amount used is reduced to create a film. It can be determined by repeating the operation.

  In order to form a film using the above liquid composition, the liquid composition is applied to the base material, or the base material is immersed (dipped) in a bath of the liquid composition, and then the solvent in the liquid composition is removed. A method of drying and removing and forming a crosslink as necessary can be employed. The solvent removal and cross-linking may be performed simultaneously.

  There is no particular limitation on the coating method used when the liquid composition is applied to the substrate, and a method capable of forming a more uniform coating film may be selected from various known coating methods according to the shape of the substrate.

  The temperature at the time of solvent removal and cross-linking formation is preferably, for example, room temperature to around 100 ° C. By such treatment, a corrosion-resistant film having good characteristics can be formed. In particular, when a liquid composition containing a crosslinking agent is used, the characteristics become better.

  In addition, in the member of this invention, since the adhesiveness of a base material and a membrane | film | coat is favorable, the special ground treatment (for improving adhesiveness by an anchor effect) which is generally implemented in the case of fluororesin coating. Surface roughening by shot blasting, etc.) is not particularly necessary, but if oil or deposits remain on the surface of the base material, the film adhesion at that part will decrease and cause defects. Therefore, it is desirable to degrease and clean the substrate before forming the film (before forming the primer layer if a primer layer is provided).

  The thickness of the film is desirably 80 μm or less, more preferably 60 μm or less. The thickness here refers to an average value of thicknesses measured at arbitrary five locations. The thickness of each part is the method of subtracting the thickness of the base material from the value obtained by measuring the thickness of the member itself with a micrometer, etc. You may measure with. Moreover, what is necessary is just to measure the thickness of a film | membrane by the same method as the thickness measuring method of the primer layer mentioned above, when a member has a primer layer. If the thickness of the film is too large, heat conduction is hindered, so that the heat exchange efficiency of the heat exchanger tends to be reduced. On the other hand, as the lower limit of the thickness of the film, it is desirable that the thickness of the thinnest part is 5 μm or more when the above-mentioned film thickness measurement is performed. If the thickness of the thinnest part is too small, the ability to block the penetration of acid ions in the acid drain water tends to be inferior, so the long-term durability may be insufficient.

  As will be described later, in the member of the present invention, a primer layer may be provided on the surface of the substrate, and the film may be formed on the primer layer. In this case, it is preferable that the total thickness of the primer layer and the coating is not more than the upper limit of the thickness of the coating. However, the lower limit value of the thickness of the film (the “thickness of the thinnest portion”) means the thickness of only the film even when a primer layer is provided.

[Other configurations]
In the member of the present invention, the film may be formed on a primer layer provided on the substrate surface. The primer layer is generally provided for the purpose of improving the adhesion between the substrate and the film. In the present invention, the adhesion between the substrate and the film is good, and the primer layer is not an essential component, but by providing the primer layer, the adhesion between the substrate and the film can be maintained for a longer period of time. For example, when applying to heat exchangers used in heat exchangers such as commercial water heaters that require longer-term durability, it is recommended to provide such a primer layer. The In addition, even if a defect occurs in the film during use of the heat exchange device, there is an advantage that further progress of the film defect becomes gentle due to the presence of the primer layer.

  Examples of the material for the primer layer include various materials conventionally used as a primer for resin-coated metal products such as epoxy resin and silicone resin. It is also preferable to add a known rust preventive pigment such as zinc phosphate to the primer layer. In addition, since the said film | membrane is formed on the surface, a primer layer does not contact acidic drain water directly. Therefore, the material forming the primer layer may contain an aromatic group in the molecule.

  As described above, the upper limit of the thickness of the primer layer may be such that the total thickness with the film is not more than the upper limit. There is no restriction | limiting in particular about the minimum of the thickness of a primer layer, What is necessary is just a thickness (for example, 0.1 micrometer or more) of the grade which can fully exhibit the function as a primer layer.

  The method for forming the primer layer is not particularly limited. Usually, a method is adopted in which a liquid composition containing a resin or the like as a material for the primer layer is applied to the substrate surface and dried, and a resin crosslink is formed as necessary.

<Heat exchanger and heat exchange device>
The heat exchanger of the present invention only needs to include the above-described heat exchanger member of the present invention, and there is no particular limitation on other configurations, and the same configuration as a conventionally known latent heat recovery type heat exchanger can be adopted.

  Further, the heat exchange apparatus of the present invention is only required to include the heat exchanger of the present invention, and there is no particular limitation on other configurations, and the configuration of a conventionally known heat exchange apparatus including a latent heat recovery type heat exchanger Can be adopted.

  Examples of such a heat exchange device of the present invention include a water heater equipped with a sensible heat recovery type heat exchanger and a heat exchanger used for exhaust heat recovery of a gas turbine or a gas heat pump.

  Hereinafter, the present invention will be described in detail based on examples. However, the following examples are not intended to limit the present invention, and all modifications made without departing from the spirit of the preceding and following descriptions are included in the technical scope of the present invention. In addition, the measurement implemented in the present Example is as follows.

(1) Measurement of fluorine atomic ratio by EDX Gold was deposited to a thickness of about 30 nm in order to give electrical conductivity to the surface of the film. With respect to this sample, the relative intensity of the characteristic X-rays of carbon atoms and fluorine atoms was obtained using an electron beam apparatus “ESEM-2700” manufactured by Nikon Corporation. From this relative intensity, PTFE having a known fluorine atom ratio value was obtained. The fluorine atomic ratio was calculated using a conversion factor determined in advance from the above data. The measurement conditions were acceleration voltage: 15 kV and magnification: 100 times.

  In addition, about the member for heat exchangers which provided the primer layer (after-mentioned Example 2), while using a microtome, it measures by scraping the outermost layer of a film about 5 micrometers, and also has a primer layer as a reference value. The measurement was performed as is.

(2) Measurement of (A) / (B) ratio Using a Fourier transform infrared spectrophotometer “JIR-100 type” manufactured by JEOL Ltd., transmission method with beam condenser (resolution: 4 cm ⁻¹ , integration The number of times was 100), and the infrared absorption spectrum analysis was performed, and the ratio of the characteristic absorption peak area (A) to (B) [(A) / (B) ratio] was calculated according to the following procedure.
(I) and the vertical axis to obtain an infrared absorption spectrum chart of absorbance, draw a straight line connecting the location of points and 3100 cm ^-1 in 2700 cm ^-1 of the spectrum curve of the chart.
(II) The region surrounded by the straight line and the spectrum curve of (I) is cut out, and the cut chart pieces are further divided into (A) 3000 to 3100 cm ⁻¹ and (B) 2800 to 3000 cm ⁻¹ . Cut.
(III) The masses of the chart pieces (A) and (B) of (II) above are measured, and these are regarded as the areas (A) and (B) of the characteristic absorption peaks, and (A) / (B) Calculate the ratio.

  In addition, about the member for heat exchangers which provided the primer layer (after-mentioned Example 2), while using a microtome, it measures by scraping the outermost layer of a film about 5 micrometers, and also has a primer layer as a reference value. The measurement was performed as is.

(3) Film thickness The thickness of the member was measured at five locations using a micrometer, the thickness of the substrate was subtracted from the obtained value to determine the film thickness at each measurement location, and the average value was taken as the average film thickness. The thickness of the thinnest part was defined as the minimum film thickness. In addition, in the member provided with the primer layer (described later in Example 2), when the primer layer was formed, the thickness of the base material and the primer layer was measured at five locations with a micrometer, and the thickness of the base material was determined from the obtained value. The primer layer thickness at each measurement location was obtained by subtracting and the average value was calculated as the primer layer thickness. Then, after forming the film, the thickness of the member was measured at five points by the same method as above, and the film thickness at each measurement point was obtained by subtracting the base material thickness and the primer layer thickness from the obtained values. Thickness and minimum film thickness were calculated.

(4) Evaluation of heat resistance The film was peeled from the heat exchanger member, and thermogravimetric analysis was performed when the temperature was increased from room temperature at a constant rate of 20 ° C./min. The temperature when the temperature was reduced by 5% from the above was regarded as the heat resistant temperature, and was evaluated according to the following criteria. Evaluation criteria are: A: heat resistant temperature of 300 ° C or higher, ○: heat resistant temperature of 200 ° C or higher and lower than 300 ° C, Δ: heat resistant temperature of 100 ° C or higher and lower than 200 ° C, x: heat resistant temperature of lower than 100 ° C, ○ was accepted.

(5) Adhesion evaluation The heat exchanger member was immersed in boiling water for 2 hours, and then a tape peeling test was conducted on a grid of 1 mm square and 100 squares in accordance with JIS 5600-5-6. Adhesion was evaluated. Evaluation criteria are: ◎: no peeling, ○: peeling for less than 10% of the total mass, Δ: peeling for 10% or more and less than 30% of the total mass, x: peeling for 30% or more of the total mass , And ◎ and ○ were accepted.

(6) Corrosion resistance evaluation The film of the heat exchanger member was cut using a cutter to reach the substrate. There were two cuts, each 10 mm long, and intersecting each other at an angle of 30 °. The base material for heat exchanger into which this cut was made was immersed in 50 mL of 15% nitric acid aqueous solution so that the cut portion was completely immersed, and the lid was loosely covered so that the water did not rapidly evaporate and left at room temperature. The corrosion resistance was evaluated by the number of days until the blue coloration by the copper ions eluted from the base material was sufficiently visually confirmed with a white paper background under normal fluorescent lighting. The evaluation criteria are as follows: ◎: can endure for 14 days or more, ○: abnormality occurs from 7 days to less than 14 days, △: abnormality occurs from 2 days to less than 7 days, ×: abnormality occurs after less than 2 days, ◎ and ○ were accepted.

(7) Durability evaluation (simulation test under actual machine conditions)
A liquid having a pH of about 2 (artificial drain water) was prepared using a commercially available reagent for nitric acid, sulfuric acid and hydrochloric acid as a test liquid simulating drain water generated in the latent heat recovery section of the combustion heat exchanger. The composition of the artificial drain water was nitrate ion: about 680 mg / L, sulfate ion: about 80 mg / L, chloride ion: about 10 mg / L. In this artificial drain water (temperature: room temperature), a member for a heat exchanger obtained by forming a film on a U-bent copper tube was immersed with the bent portion down. The immersion in artificial drain water and drying were repeated every 2 minutes. A dryer was used for drying at the time of pulling up. The surface temperature of the heat exchanger member during drying is about 80 ° C. Durability was evaluated by the time until film breakage occurred. Evaluation criteria are: A: 1600 hours or longer, ○: 1000 hours to less than 1600 hours, film breakage occurred: Δ: 400 hours to less than 1000 hours, film breakage: ×: less than 400 hours film breakage occurred , And ◎ and ○ were accepted.

Experiment <Production of heat exchanger components>
A phosphorous deoxidized copper plate (20 × 100 mm, thickness: 0.3 mm) or a U-shaped bent phosphorous deoxidized copper tube (outer diameter: 12 mm, length: 170 mm, thickness: 0.57 mm) was used as the substrate. A film was formed on the surface of the base material using a liquid composition containing the resin shown in Table 1. Film formation is a method in which a solvent-degreased base material is dipped in a liquid composition bath (liquid temperature: 25 ° C.), pulled up, and heated and cured at 100 to 120 ° C. for 30 minutes. Adopted. In addition, in the heat exchanger member of Example 2 provided with the primer layer, the base material previously degreased by solvent was dipped in a liquid composition bath (liquid temperature: 25 ° C.) for forming the primer layer, After pulling up the substrate, a primer layer was formed by heating and curing at 100 ° C. for 15 minutes, and a film was formed on the surface of the primer layer in the same manner as other heat exchanger members. The evaluation results of each heat exchanger member are also shown in Table 1.

In Table 1, 1 is a resin [a copolymer having a copolymer composition of monochlorotrifluoroethylene: cyclohexyl vinyl ether: lauryl vinyl ether: 4-hydroxy vinyl ether = 100: 10: 80: 20 (molar ratio)], a crosslinking agent ( Hexamethylene diisocyanate cyclic trimer, content is 10 parts by mass with respect to 100 parts by mass of resin), and solvent (xylene and methyl isobutyl ketone 5: 1 (mass ratio) mixed solvent, content is 100 parts by mass of resin 100 parts by weight with respect to]
2 is a resin [a copolymer having a copolymer composition of tetrafluoroethylene: cyclohexyl vinyl ether: lauryl vinyl ether: 4-hydroxy vinyl ether = 100: 10: 80: 20 (molar ratio)], a cross-linking agent (hexamethylene diisocyanate cyclic three And a solvent [xylene and methyl isobutyl ketone 5: 1 (mass ratio) mixed solvent, content is 100 parts by mass with respect to 100 parts by mass of the resin. A composition having
3 is a resin [a copolymer having a copolymer composition of monochlorotrifluoroethylene: 2-ethylhexyl acrylate: 4-siloxybutyl acrylate = 100: 200: 150 (molar ratio)], a crosslinking agent (tetraethoxysilane, content Is 20 parts by mass with respect to 100 parts by mass of resin), and a solvent [5: 1 (mass ratio) mixed solvent of xylene and methyl isobutyl ketone, content is 100 parts by mass with respect to 100 parts by mass of resin]. ,
4 is a resin [a copolymer having a copolymer composition of tetrafluoroethylene: 2-ethylhexyl acrylate: 4-siloxybutyl acrylate = 100: 200: 150 (molar ratio)], a crosslinking agent (tetraethoxysilane, content: 20 parts by mass with respect to 100 parts by mass of the resin) and a solvent [5: 1 (mass ratio) mixed solvent of xylene and methyl isobutyl ketone, 100 parts by mass with respect to 100 parts by mass of the resin]
5 is a resin [a copolymer having a copolymer composition of monochlorotrifluoroethylene: vinyl 2-ethylhexanoate: 2-ethylhexyl acrylate = 100: 30: 70 (molar ratio)], a cross-linking agent (hexamethylene diisocyanate cyclic three And a solvent [xylene and methyl isobutyl ketone 5: 1 (mass ratio) mixed solvent, content is 100 parts by mass with respect to 100 parts by mass of the resin. A composition having
6 is a resin [a copolymer having a copolymer composition of tetrafluoroethylene: vinyl 2-ethylhexanoate: 2-ethylhexyl acrylate = 100: 30: 70 (molar ratio)], a crosslinking agent (hexamethylene diisocyanate cyclic trimer). Body, content is 5 parts by mass with respect to 100 parts by mass of resin), and solvent [5: 1 (mass ratio) mixed solvent of xylene and methyl isobutyl ketone, content is 100 parts by mass with respect to 100 parts by mass of resin] A composition having
7 is “Polyflon TC-7408” manufactured by Daikin Industries, Ltd. (perfluoro fluororesin fine particles dispersed in an epoxy resin heat resistant binder),
8 is “Epicoat 152” (bisphenol type epoxy resin, amine cured type) manufactured by Japan Epoxy Resin Co., Ltd.
9 is “ES1023” (epoxy-modified silicone resin, heat-curing type) manufactured by Shin-Etsu Chemical Co., Ltd.,
10 is “Silicotect AC” (acrylic silicone resin paint) manufactured by Kansai Paint Co., Ltd.
Means each.

  In addition, each liquid composition of 1-6 of Table 1 contains "BYK-322" by Big Chemie Japan Co., Ltd. as a leveling agent in 1 mass% or less in a liquid composition whole quantity.

  Moreover, the primer layer of Example 2 used a primer containing an epoxy resin rust preventive pigment (“Nippe Power Bind” manufactured by Nippon Paint Co., Ltd.). Further, the parentheses in the columns of “fluorine atomic ratio” and “(A) / (B) ratio” of Example 2 in Table 1 indicate reference values measured in the presence of the primer layer. The brackets in each column indicate the thickness of only the primer layer.

  As can be seen from Table 1, in each heat exchanger member of Examples 1 to 8 in which a good film is formed, each evaluation result of heat resistance, adhesion, corrosion resistance and durability is good, and the performance is very high. Is an excellent one. In Examples 1 to 8, the resin for forming the film does not contain an aromatic group, but the ratio (A) / (B) is not 0/100 because the leveling agent and the residual solvent (xylene ).

  In contrast, in the heat exchanger members of Comparative Examples 1 to 3, the polymer in the film contains an aromatic group, and the amount of the aromatic group in the film is large. Moreover, in the member for heat exchangers of Comparative Examples 2 and 3, the fluorine atom ratio in the film is also small. In particular, since the aromatic group in the film is easily oxidized by acidic drain water, these heat exchanger members have poor corrosion resistance and durability. Moreover, in the member for heat exchangers of Comparative Example 4, the fluorine atom ratio in the film was small, the corrosion resistance and durability were poor, and the heat resistance and adhesion were not good.

Claims (6)

A copper-based or aluminum-based latent heat recovery type heat exchanger member in which a film containing a polymer having a methylene chain containing a fluorine substituent is formed on the outer surface,
The film includes a copolymer formed by polymerizing a monomer component containing essentially fluoroethylenes and one or more compounds selected from the group consisting of vinyl ethers, vinyl esters, and acrylate esters. It is formed from a liquid composition,
The polymer is characterized in that it has 5 to 50 fluorine atoms with respect to 100 carbon atoms and has substantially no aromatic group and is derived from the copolymer. Member for latent heat recovery type heat exchanger. The coating, when performing infrared absorption spectrum analysis, the area of the characteristic absorption peak derived from C-H stretching vibration of aromatic group wave number may appear in 3000～3100Cm ^-1, wave number in 2800 to 3000 cm ^-1 2. The member according to claim 1, wherein the ratio of the area of the characteristic absorption peak derived from C—H stretching vibration of the appearing aliphatic chain is 10/100 or less. The member according to claim 1 or 2, wherein the film is formed from a liquid composition containing a crosslinking agent that forms urethane crosslinking or siloxane crosslinking in addition to the copolymer. The fluoro ethylenes are monochloro trifluoro ethylene and / or member according to any one of claims 1 to 3 which is a tetrafluoroethylene.   It has a member for latent-heat-recovery type heat exchangers in any one of Claims 1-4, The latent-heat-recovery type heat exchanger characterized by the above-mentioned.   A heat exchange apparatus comprising the latent heat recovery type heat exchanger according to claim 5.