JP5006758B2 - Metal surface treatment agent - Google Patents

Description

  The present invention relates to a hydrophilic metal surface treatment agent that forms a film having corrosion resistance and hydrophilicity on a metal surface such as aluminum.

  In recent years, air conditioning combined with air conditioning, dehumidification, and air conditioning has become widespread, and heat exchange parts of these air conditioners are generally lightweight and have excellent workability and thermal conductivity. Is used.

  During the cooling operation of the air conditioner, moisture in the air adheres to the fin surface as condensed water. Aluminum and its alloys are inherently excellent in corrosion resistance, but if condensed water stays on the fin surface for a long time, an oxygen concentration cell is formed, and as a result of gradually concentrating pollutants in the atmosphere, the corrosion reaction is accelerated. . Corrosion products generated thereby accumulate not only on the surface of the fins, but also impair heat exchange characteristics, and in the winter heating operation, they become white fine powder and are discharged together with warm air from the blower to contaminate indoor air.

In order to prevent such a problem, a metal surface treatment agent that forms a film having corrosion resistance and hydrophilicity on the fin surface has been proposed. For example, Patent Document 1 below discloses a hydrophilic metal surface treatment agent in which a vinyl compound is Michael-added to a modified polyvinyl alcohol having an anionic and / or nonionic group. In Patent Document 2, a water-soluble organic compound having a polyoxyethylene chain, a hydrophilic polymer having a sulfonic acid group and the like, polyvinyl alcohol, a water-soluble derivative of polyvinyl alcohol, and a metal material containing a specific water-soluble polymer An aqueous treatment agent for hydrophilization is described.
JP 10-36757 A JP-A-9-316434

  However, the conventional metal surface treatment technique described above has not obtained a film having sufficient hydrophilicity and corrosion resistance and further generating no odor.

  The present invention has been made in view of such problems, and forms a hydrophilic film that can be suitably used for heat exchanger fins that have good hydrophilicity, corrosion resistance, and water resistance and do not generate unpleasant odors. An object of the present invention is to provide a metal surface treatment agent.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that a polymer obtained by grafting vinylpyrrolidone to polyvinyl alcohol is extremely useful in producing the intended surface treatment agent. It came to be completed.

  That is, the present invention is a metal surface treatment agent characterized by containing a polymer obtained by graft polymerization of polyvinyl pyrrolidone to polyvinyl alcohol.

  In the present invention, the metal surface treatment agent preferably contains a crosslinking agent.

  Further, the metal surface treatment agent contains a polymer having a K value of 12 to 150 obtained by graft polymerization of vinyl pyrrolidone to polyvinyl alcohol having a polymerization degree of 100 to 4000 and a saponification degree of 70 to 100 mol%. It is preferable.

  In the metal surface treatment agent according to the present invention, the polymer obtained by graft polymerization of polyvinyl pyrrolidone on the polyvinyl alcohol is blended with vinyl pyrrolidone in the polyvinyl alcohol solution, and hydrogen peroxide, an organic peroxide or an azo compound is used as an initiator. Can be obtained by polymerization.

  According to the surface treatment agent of the present invention, when applied to the surface of a metal material, particularly an aluminum-containing metal material, not only has good hydrophilicity and water resistance, but also the odor is remarkably suppressed and the corrosion resistance is also good. A hydrophilic film can be formed on the metal surface.

  The polymer contained in the metal surface treatment agent of the present invention may be expressed as polyvinyl pyrrolidone (N-vinyl-2-pyrrolidone) (hereinafter referred to as VP) to polyvinyl alcohol (hereinafter also referred to as PVA). ).

  PVA used as a raw material for the graft polymer used in the present invention preferably has a degree of polymerization of 100 to 4000, and more preferably 100 to 3000. When the degree of polymerization is less than 100, sufficient film strength cannot be obtained, and when it exceeds 4000, the viscosity becomes high and workability decreases.

  The degree of saponification of PVA is preferably 70 to 100 mol%. If the degree of saponification is less than 70 mol%, the strength of the film may be weakened.

  The K value of the graft polymer is preferably 12 to 150. The K value is a constant representing the degree of polymerization proposed by the German chemist Fikencher. When the K value is less than 12, the strength of the film becomes weak, and when it exceeds 150, the viscosity becomes high and the workability decreases.

  The amount of VP in the graft polymer is preferably 5 to 900% by weight with respect to PVA. If it is less than 5% by weight, sufficient hydrophilicity cannot be obtained, and if it exceeds 900% by weight, the strength of the film tends to be lowered.

  The surface treatment agent of the present invention preferably contains 5% by weight or more of the graft polymer when formed into a film. If it is less than 5% by weight, it is difficult to obtain the intended effect of the present invention.

  The graft polymer can be obtained by a production method in which VP is blended into a PVA solution in a polymerization reactor and VP is graft-polymerized to a PVA chain using an appropriate radical polymerization initiator.

  As the polymerization initiator, hydrogen peroxide, an organic peroxide, an azo initiator, or the like that is usually used for radical polymerization can be used. Examples of the organic peroxide include tert-butyl hydroperoxide, di-tert-butyl peroxide, benzoyl peroxide and the like. As the azo compound, 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), 2,2′-azobis (2,4-dimethylvaleronitrile), 2, And 2'-azobis (4-methoxy-2,4-dimethylvaleronitrile). What is necessary is just to select the reaction method and reaction conditions according to the example of general radical polymerization.

  In the metal surface treatment agent of the present invention, a crosslinking agent is preferably used for the purpose of improving water resistance. As the crosslinking agent, epichlorohydrin, glyoxal, urea compound, melamine compound, glycidyl compound, isocyanate compound, formalin, aldehydes, boric acid compounds such as boric acid and borax, aluminum chloride, aluminum sulfate, aluminum acetate, Examples thereof include inorganic metal salts such as zinc sulfate. Among these, an isocyanate compound is preferable in terms of reactivity, film strength, and water resistance. Among these, a blocked isocyanate blocked with a blocking agent that dissociates by heating is preferable.

  These usually exist stably in a state of being dissolved or dispersed in water, and when applied to the surface of the heat exchanger fins, when heated, the blocking agent is dissociated and there is a crosslinking reaction with the graft polymer. A film having hydrophilicity and water resistance is formed.

  The addition amount of the crosslinking agent is 0.1 to 50% by weight, preferably 1.0 to 30% by weight, based on the solid content of the graft polymer. If the content is less than 0.1%, sufficient water resistance may not be obtained. On the other hand, if it exceeds 50%, the hydrophilicity may decrease.

  The metal surface treating agent of the present invention may contain a surfactant, an antifungal agent, an antiseptic, and the like in addition to the above components.

  As the surfactant, there are a nonionic type, a cationic type and an anionic type, and an anionic type is preferable from the viewpoint of hydrophilic durability and coating workability. As an anionic surfactant, sodium alkylbenzenesulfonate, sodium alkyldiphenyl ether disulfonate, sodium alkylnaphthalenesulfonate, sodium salt of naphthalenesulfonic acid-formalin condensate and the like can be used. The addition amount of the anionic surfactant is 1 to 10 parts by weight, and if it is less than 1 part by weight, the effect of addition cannot be sufficiently obtained, and if it exceeds 10 parts by weight, the water resistance is lowered.

  Antifungal agents and antiseptics include quaternary ammonium salts, nitrogen-containing sulfur compounds, halogen-containing nitrogen sulfur compounds, 1,2-benzisothiazolin-3-one (BIT), organic iodine compounds, benzimidazole compounds, etc. Can be used. The addition amount is preferably 0.15 to 1.5 parts by weight.

  There are no restrictions on the type, size, shape, etc. of the metal material to which the metal surface treatment agent of the present invention is applied, but generally heat exchangers and aluminum-containing metal materials (plate materials, rods, pipes, etc.), especially aluminum-containing materials It is preferable to apply to a metal material. The aluminum-containing metal material can be selected from aluminum and aluminum alloy (Al-Mn, Al-Mg, Al-Si alloy, etc.) materials.

  Although the surface treatment method by the metal surface treating agent of this invention is not specifically limited, For example, the following method can be illustrated.

  First, before the surface treatment agent is applied, a ground treatment is performed. As the ground treatment, a degreasing treatment is performed using a solvent or an alkaline solution. Examples of the solvent include trichloroethylene, perchlorethylene, gasoline, and normal hexane. Examples of the alkaline solution include solutions of sodium hydroxide, sodium carbonate, sodium silicate, sodium phosphate, and the like.

  After the degreasing treatment, a corrosion resistant film is formed by chemical conversion treatment. The corrosion resistant film can be obtained by chromate treatment. In the chromate treatment, a treatment solution prepared by adding an additive to chromic anhydride and sulfuric acid, nitric acid, hydrofluoric acid, phosphoric acid or the like is used.

  Or you may perform the process by a zirconium type processing agent. Examples of the zirconium-based treatment agent include a mixture of polyacrylic acid and zircon fluoride.

  Furthermore, better corrosion resistance can be imparted by applying a phenol-based primer coating after the degreasing treatment. As the phenol-based primer, a resol-type water-soluble phenol resin (initial polymerized product of phenol and formalin under an alkali catalyst) is preferable.

A surface treatment agent is applied on the aluminum material that has been subjected to the above-described base treatment. For coating, a roll coating method, a dipping method, a spray method, a brush coating method, or the like can be used as appropriate. For example, in the case of a roll coating method, a hydrophilic film can be obtained by drying at 150 to 240 ° C. for 10 seconds to 1 minute after coating. The thickness of the hydrophilic film is preferably 0.05 to 0.5 g / m ² . 0.05 g / m is a no sufficient hydrophilicity is obtained less than ^2, whereas when it exceeds 0.5 g / m ² becomes costly, yet not preferable for improvement of the effect corresponding thereto is not obtained.

  Hereinafter, the present invention will be specifically described by way of examples, but the scope of the present invention is not limited thereto.

  Graft polymers 1 to 4 according to Examples 1 to 4 of the present invention were prepared by the following method. Using the obtained polymers 1 to 4 and the polymers 5 and 6 according to Comparative Examples 1 and 2, a surface treatment film was formed on an aluminum plate, and the following performance evaluation was performed.

  Polymer 1: Dissolved 190 g of PVA (polymerization degree 200, saponification degree 98-99 mol%) in 800 g of pure water, then added and mixed VP 10 g (vs. PVA 5.26 wt%), and deoxygenated by nitrogen purge. . Subsequently, the temperature of the reaction system was adjusted to 70 ° C. To this, 10 mg of 1 wt% copper sulfate, 1.0 g of 28 wt% aqueous ammonia and 1.5 g of 30 wt% aqueous hydrogen peroxide were added to initiate polymerization. During polymerization, the temperature is maintained at 70 to 80 ° C. and pH 5.5 to 6.5 with ammonia, and 1.5 g of 30% by weight hydrogen peroxide solution is added 6 times every 15 minutes so that the polymerization rate is 90% or more. It became. Subsequently, 4 g of 30 wt% aqueous hydrogen peroxide was added as a residual VP treatment step and reacted for a total of 210 minutes while maintaining the pH at 5 or higher with aqueous ammonia to obtain a 20% aqueous solution of polymer 1 having a K value of 23.

Polymer 2: Polymer having a K value of 31 in the same manner as the preparation of Polymer 1 except that PVA (polymerization degree 2400, saponification degree 98-99 mol%) and VP (vs. PVA 42.9 wt%) were used. A 20% aqueous solution of 2 was obtained.
Polymer 3: PVA (polymerization degree 500, saponification degree 72.5-74.5 mol%) and VP (vs. PVA 150 wt%) were used in the same manner as the preparation method for polymer 1, and a K value of 40 A 20% aqueous solution of polymer 3 was obtained.

  Polymer 4: A PVA (polymerization degree 3500, saponification degree 87-89 mol%) and VP (vs. PVA 900 wt%) were used in the same manner as the preparation of polymer 1 except that polymer 4 having a K value of 94 A 20% aqueous solution was obtained.

  Polymer 5: PVA (polymerization degree 3500, saponification degree 87-89 mol%) powder.

  Polymer 6: Polyvinylpyrrolidone (K-30, K value 30) powder.

[Formation of hydrophilic surface treatment film]
After degreasing the aluminum plate, a zirconium-based surface treatment agent (“Allodyne 1690/1691”, manufactured by Nippon Paint Co., Ltd.) is applied by the bar coating method, dried at 150 ° C. for 15 seconds, and the corrosion resistance of zirconium is 5 mg / m ² . A film was formed. Next, a surface treatment agent containing 10% by weight of the above polymer and 1% by weight of a cross-linking agent (Elastoron H-38: manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was applied by a bar coating method at 240 ° C. A hydrophilic film was formed by drying for 30 seconds. The film thickness of the hydrophilic film was 0.2 g / m ² . In the surface treatment agent, sodium alkyldiphenyl ether disulfonate as a surfactant is 5 parts with respect to a total of 100 parts of the above components, and benzimidazole compound and nitrogen-containing sulfur compound are 0.25 parts as a fungicide. Each of them was previously contained at a ratio of

[Performance evaluation]
Each of the obtained hydrophilic films was subjected to an odor test, a water resistance test, a hydrophilicity test, and a corrosion resistance test as follows. The results are shown in Table 1.

(1) Odor test An odor test was performed by directly sniffing each hydrophilic film-formed aluminum plate (hereinafter simply referred to as a sample). The evaluation criteria are as follows.
A: No odor is felt at all. B: Almost no odor is felt. Δ: An odor is clearly felt. X: A strong odor is felt.

(2) Water resistance test Each sample was immersed in tap water for 24 hours, and the water dissolution rate was determined by the following equation from the coating amount (weight) before and after immersion.
Water dissolution rate (%) = [(initial film amount−film amount after immersion for 24 hours) ÷ initial film amount] × 100
The evaluation criteria for water resistance are as follows.
A: Water solubility of less than 10% B: Water solubility of 10% or more but less than 30% Δ: Water solubility of 30% or more but less than 50% x: Water solubility of 50% or more.

(3) Hydrophilic test Each sample was exposed to running water (flowing amount 5 liters / hour, tap water) for 17 hours, and then dried at 80 ° C. for 7 hours. The contact angle of water droplets was measured. The contact angle of the water droplet was measured by a solid-liquid interface analyzer (Drop Master 500: manufactured by Kyowa Interface Chemical Co., Ltd.). The evaluation criteria for hydrophilicity are as follows.
A: Contact angle of less than 20 ° B: Contact angle of 20 ° or more and less than 30 ° Δ: Contact angle of 30 ° or more and less than 40 ° ×: Contact angle of 40 ° or more.

(4) Corrosion resistance test Each sample was subjected to a salt spray test based on JIS-Z-2371 for 500 hours, and the corrosion resistance was evaluated by the area ratio of occurrence of white rust in the flat portion. The evaluation criteria are as follows.
A: White rust does not occur. B: White rust generation area ratio of over 0% and less than 10%. Δ: White rust generation area ratio of 10% or more and less than 50%. X: White rust generation area ratio of 50% or more.

  The present invention can greatly contribute to solving the problem of a decrease in heat exchange efficiency due to the condensed water adhering to the fin surface, and is suitable for the surface treatment of a metal fan such as aluminum or aluminum alloy in a heat exchange part of an air conditioner combined with an air conditioner. It is.

Claims (4)

  A metal surface treatment agent comprising a polymer obtained by graft polymerization of vinyl pyrrolidone to polyvinyl alcohol.   The metal surface treatment agent according to claim 1, further comprising a crosslinking agent.   2. A polymer having a K value of 12 to 150, which is obtained by graft polymerization of vinylpyrrolidone to polyvinyl alcohol having a polymerization degree of 100 to 4000 and a saponification degree of 70 to 100 mol%. 2. The metal surface treatment agent according to 2.   A polymer obtained by graft-polymerizing vinyl pyrrolidone with polyvinyl alcohol is obtained by blending vinyl pyrrolidone with a polyvinyl alcohol solution and polymerizing using hydrogen peroxide, an organic peroxide or an azo compound as an initiator. The metal surface treating agent according to any one of claims 1 to 3.