JP2009255549A - Resin-coated metal plate having high coating peeling resistance during roll forming - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resin-coated metal plate having characteristics required of a resin-coated metal plate, such as corrosion resistance, and capable of preventing troubles during roll forming. <P>SOLUTION: The resin-coated metal plate having high coating peeling resistance during roll forming and provided with a resin coating obtained from a surface treated composition is characterized in that Sward rocker hardness of the resin coating is 35 or more and an indentation depth of an indenter in nano-scratch test is less than 0.3 μm. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a resin-coated metal plate used for automobiles, home appliances, building materials, and the like, and particularly relates to a resin-coated metal plate particularly excellent in corrosion resistance and film peeling resistance during roll forming.

  From the viewpoint of corrosion resistance, zinc-based plated steel sheets such as electrogalvanized steel sheets and hot-dip galvanized steel sheets are used for building materials. Conventionally, chromate treatment has been applied to zinc-based plated steel sheets for the purpose of further improving corrosion resistance. However, due to the recent increase in environmental awareness, demand for steel sheets not subjected to chromate treatment is increasing.

  For example, Patent Document 1 proposes a surface treatment composition containing an olefin, an α, β-ethylenically unsaturated carboxylic acid, a copolymer emulsion, and a crosslinking agent as a means for improving the corrosion resistance in place of the chromate treatment. Yes.

  By the way, the resin-coated metal plate is processed and molded according to the application. For example, the roll forming method suitable for the production of long cross-section materials is to pass a metal plate continuously between a plurality of sets of rolls arranged in a row, and sequentially perform the forming process, from the flat plate to the desired cross-sectional shape It is a method of processing into a molded product. In roll forming, a coolant is supplied to the surface of the metal plate in order to ensure lubricity and to cool the processing heat. This coolant liquid is removed by wiping the surface of the metal plate with a draining pad before the step of cutting the molded product (draining step).

  When performing severe processing with high surface pressure such as the above roll forming (molding speed of about 20 to 70 m / min), if the processability of the resin film of the resin-coated metal plate is inferior, the resin film is removed from the surface of the metal plate. May peel off a little. Although this film residue is introduced into the coolant tank, the resin film has a specific gravity as low as about 1 and therefore floats in the liquid without sinking to the bottom of the coolant tank. The coolant circulation system is usually equipped with a filter, but the filter is designed to catch galvanized strips, so the filter is fine enough to catch the resin film residue. In other words, the film residue accompanies the coolant liquid that is repeatedly used. As a result, film residue gradually accumulates on the surface of the draining pad in the draining process, and friction is generated between the deposited film residue and the surface of the molded product, or abnormal noise is generated, or the molded product uniformly distributes the drained pad portion. There was a problem that it was impossible to pass through at the traveling speed, the shape and dimensions of the product were distorted, and the yield deteriorated.

  In order to solve the above problems, it was considered to increase the hardness of the film by making an inorganic component present in the resin film. However, as the amount of the inorganic component increases, the resin film becomes brittle, and the peel resistance of the film decreases instead. Therefore, there is a need to form a resin film that is reasonably hard and does not have brittleness.

JP 2007-269018 A

  Accordingly, the present invention provides a resin-coated metal plate that has the characteristics required for a resin-coated metal plate such as corrosion resistance, and that has less film peeling at the time of roll forming as described above, and that does not cause trouble at the time of roll forming. As an issue.

  The resin-coated metal plate excellent in peel resistance at the time of roll forming of the present invention is a resin-coated metal plate provided with a resin film obtained from the surface treatment composition, and the rocker hardness of the resin film is 35 or more. And the indenter penetration depth in the nano-scratch test is less than 0.3 μm. The details of the method for measuring the pseudo rocker hardness and the nano scratch test will be described later.

  The surface treatment composition includes a resin component composed of an olefin-α, β-unsaturated carboxylic acid copolymer, an α, β-unsaturated carboxylic acid polymer and an oxazoline group-containing copolymer, and colloidal silica. Of the total 100 parts by mass of the resin component and colloidal silica, the resin component is preferably 70 to 90 parts by mass and the colloidal silica is preferably 10 to 30 parts by mass. At this time, the resin component contains 1 to 9 mass of the oxazoline group-containing copolymer with respect to a total of 100 mass parts of the olefin-α, β-unsaturated carboxylic acid copolymer and the α, β-unsaturated carboxylic acid polymer. It is preferable to include a part. Moreover, it is preferable that the surface area average particle diameter of colloidal silica is 4-20 nm.

  The aspect which further contains 0.1-10 mass parts of glycidyl group containing silane coupling agents with respect to a total of 100 mass parts of the said resin component and colloidal silica, or also contains 0.5-6 mass parts of metavanadate. Any of these embodiments is a preferred embodiment of the present invention.

  The resin film is preferably formed by applying the surface treatment composition to a metal plate and then heating it at a plate temperature (attainable temperature) of 120 to 180 ° C.

  In the present invention, since a tough resin film having a good balance between hardness and brittleness could be formed, the film peeling resistance during roll forming could be improved. In particular, the hardness of the resin film is represented by the pseudo rocker hardness, the brittleness of the resin film is represented by the depth of penetration of the indenter in the nano-scratch test, and these suitable ranges could be grasped. It was possible to increase the correlation with the amount of film peeling. As a result, almost no film residue is deposited on the surface of the draining pad during roll forming, and roll forming can be performed at a high yield for a long period of time.

It is a front view of a suedo locker. It is a rear view of a pseudo rocker. It is a side view of a pseudo rocker. It is a front view of a pseudo rocker value measuring apparatus. It is explanatory drawing of the test method when evaluating the film residual rate at the time of surface sliding.

  The present inventors have succeeded in forming a hard film by suppressing the ratio of the inorganic component in the resin film in the resin-coated metal plate to be considerably larger than the organic component and suppressing film peeling, and have already filed applications. (Japanese Patent Application No. 2007-229395). As a result of intensive studies aimed at further improving roll formability, the present inventors have reached the present invention. Hereinafter, the present invention will be described in detail.

  The present invention relates to a resin-coated metal plate provided with a resin film obtained from a surface treatment composition. The feature of the present invention is that the hardness of the resin film is 35 or more in terms of sword rocker hardness, and the resin film is not brittle. The depth of penetration of the indenter in the scratch test is less than 0.3 μm. This is because the present inventors have found that the pseudo rocker hardness accurately represents the hardness of the resin film, and the indenter penetration depth in the nano scratch test accurately represents the brittleness of the resin film. Like roll forming, the toughness of the film is improved by balancing the hardness and brittleness of the film during severe processing that contacts the surface of the film at a high surface pressure and repeatedly slides with a multistage roll. It is important to let Brittleness is manifested only by imparting hardness to the film, and therefore the film is easily scraped when repeatedly slid. Resin film with Sword rocker hardness and indenter penetration depth in the above range balances the hardness and brittleness of the film and has a tough film, so it has excellent film peel resistance during roll forming. ing.

  Sword rocker hardness is a hardness specified in ASTM D2134-93, and is based on a Sword rocker hardness meter (manufactured and sold by numerous foreign companies in addition to Ueshima Seisakusho (currently discontinued) and Tester Sangyo). Measured. It was also specified in JIS K 5400-1959 (currently abolished). Briefly, a pendulum (sword rocker) is shaken on a sample on which a resin film or the like is formed, and the number of swings until the pendulum reaches a certain swing width is counted to obtain the hardness. In the case of a hard material, the vertical force (self-weight of the rocker) acting downward on the film and the repulsive force (upward) of the film against the rocker balance and do not disturb the left and right repetitive movements, so the number of times until the pendulum stops is increased. In a soft material, since the repulsive force is smaller than the normal force, the left and right repetitive motions are prevented, and the number of times until the pendulum stops is reduced.

  The pseudo rocker has a structure as shown in FIGS. 1 to 3 and is configured to be able to roll and reciprocate between two parallel wheels of the same shape and size. FIG. 4 shows a side view during measurement. A concave portion is formed in a rectangular parallelepiped shape at the center portion of the test plate of the test plate fixing device, and the test plate is placed on the bottom surface of the concave portion, and the sword rocker can be rolled thereon.

  A specific measurement method based on JIS K 5400-1959 will be described. First, place the pseudo rocker on a horizontal surface and adjust with the weight for vertical stabilization so that the vertical axis is vertical. Set a standard glass plate on the test plate fixing device, fix it with the test plate fixing device, place a level on the plate surface, and adjust the height with the adjusting feet of the fixing device so that it is horizontal in the vertical and horizontal directions. Adjust. Place a rock rocker on the test plate, apply a rolling motion, cover with a windshield, and observe the state of the level from outside the windshield. The time when the hour of Sudoku rocker's level B is hidden behind B's oyster is not counted as 0 (start). Thereafter, the count is incremented by 1 for each reciprocation of the rolling motion, and is counted until the millet of the level C is hidden behind the oil and disappears for the first time, and this value is used as the pseudo rocker value. Since the standard glass plate has a pseudo rocker value of 50, the inclination of each of the spirit levels B and C is adjusted so that the pseudo rocker value becomes 50 ± 1 after five measurements. Also, the vertical position of the period adjusting weight is adjusted so that the time required for 50 ± 1 reciprocation is 60 ± 5 seconds. Next, the test plate is changed to a standard methacryl methyl plate (polymethyl methacrylate), and the inclination of each of the level levels B and C is adjusted so that the five rocker lock values are 20 ± 1. This is repeated, and when the measured values of both standard plates satisfy the above-mentioned standard, the spirit levels B and C are fixed. The ambient temperature is 20 to 23 ° C., and the humidity is 20 to 40% RH. The test plate is changed to a sample for which the pseudo rocker is to be measured, and the pseudo rocker value is measured in the same manner as described above. With n = 5, the pseudo rocker value is measured for each, and the average of three of the five pseudo rocker values is determined as the final value. The final value as it is is the Sword Rocker value of the sample, and the value obtained by doubling this is the Sword Rocker hardness. The ambient temperature is 20 to 23 ° C., and the humidity is 20 to 40% RH.

  Next, the nano scratch test will be described. The nano scratch test correlates with the brittleness of the resin film, and also correlates with the film peeling resistance during roll forming. In the present invention, a nano-scratch test was performed using a high-load microindenter (“High Load Tribo Indenter” manufactured by Hysitron). The working indenter is a spherical indenter (tip radius 84.5 μm, made of diamond). Applying a load of 0.1 mN to the indenter and fixing it vertically on the measurement sample, the depth of penetration of the indenter into the resin film when the indenter is horizontally moved by 100 μm at a scratch speed of 10 μm / second while maintaining the load. Was measured. The ambient temperature is 20 to 23 ° C., and the humidity is 20 to 40% RH. In the present invention, the indentation depth of the nano scratch test must be less than 0.3 μm. A film having this value exceeding 0.3 μm is brittle even if the Sword rocker hardness is high, and therefore the film is easily peeled off during roll forming. Therefore, it is inappropriate in terms of film peeling resistance.

  Below, each component of a surface treatment composition suitable in order to obtain the resin film which satisfies the requirements for the above-mentioned pseudo rocker hardness and the requirements for the indentation depth in the nano scratch test will be described.

[Resin component]
The surface treatment composition used in the present invention comprises an olefin-α, β-unsaturated carboxylic acid copolymer (hereinafter sometimes abbreviated as “olefin-acid copolymer”), α, β-unsaturated. It includes a resin component comprising a saturated carboxylic acid polymer (hereinafter sometimes abbreviated as “carboxylic acid polymer”) and an oxazoline group-containing copolymer capable of crosslinking with these. The “α, β-unsaturated carboxylic acid” in the present invention also includes “α, β-unsaturated carboxylic acid salts” in which a part of the carboxyl group is neutralized with a neutralizing agent described later.

  The “olefin-α, β-unsaturated carboxylic acid copolymer” or “olefin-acid copolymer” in the present invention is a copolymer of an olefin and an α, β-unsaturated carboxylic acid, Means that the constituent unit derived from the copolymer is 50% by mass or more (that is, the constituent unit derived from α, β-unsaturated carboxylic acid is 50% by mass or less); The “acid polymer” or “carboxylic acid polymer” is a polymer (including a copolymer) obtained using an α, β-unsaturated carboxylic acid as a monomer, and is an α, β-unsaturated carboxylic acid. It means that the derived structural unit is 90% by mass or more in the polymer.

  The exact mechanism by which the corrosion resistance of the resin-coated metal sheet is improved by surface treatment with a composition containing both an olefin-acid copolymer and a carboxylic acid polymer is unknown, but both of these are described below as oxazoline groups. By using together with the containing copolymer, it can be presumed that a dense resin film was formed and the permeation of water and oxygen was effectively suppressed. However, the present invention is not limited to this estimation.

  The olefin-acid copolymer used in the present invention can be produced by copolymerizing an olefin and an α, β-unsaturated carboxylic acid by a known method, and is commercially available. In the present invention, one or more olefin-acid copolymers can be used.

  Although there is no limitation in particular in the olefin which can be used for manufacture of an olefin-acid copolymer, ethylene, propylene, etc. are preferable and ethylene is more preferable. As the olefin-acid copolymer, any one in which the olefin structural unit is derived from only one olefin or from two or more olefins can be used.

  The α, β-unsaturated carboxylic acid that can be used for the production of the olefin-acid copolymer is not particularly limited, and examples thereof include monocarboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, and isocrotonic acid, maleic acid, and fumaric acid. Examples thereof include dicarboxylic acids such as acid and itaconic acid. Among these, acrylic acid is preferable. As the olefin-acid copolymer, the constituent unit of α, β-unsaturated carboxylic acid is derived from only one kind of α, β-unsaturated carboxylic acid, or two or more kinds of α, β-unsaturated carboxylic acid. Any of those derived from acids can be used.

  The olefin-acid copolymer used in the present invention may have structural units derived from other monomers as long as they do not adversely affect the corrosion resistance and the like, which are the effects of the present invention. In the olefin-acid copolymer, the amount of structural units derived from other monomers is preferably 10% by mass or less, more preferably 5% by mass or less, and the most preferable olefin-acid copolymer is an olefin. And an α, β-unsaturated carboxylic acid alone. A preferred olefin-acid copolymer is an ethylene-acrylic acid copolymer.

  The α, β-unsaturated carboxylic acid in the olefin-acid copolymer is used to improve the adhesion between the resin film and the metal plate, and to secure the amount of carboxyl groups that are reactive groups for crosslinking. . The amount of α, β-unsaturated carboxylic acid in the copolymer is preferably 5% by mass or more, more preferably 10% by mass or more. However, if the α, β-unsaturated carboxylic acid is excessive, the corrosion resistance and alkali resistance may be lowered. Therefore, the amount is preferably 30% by mass or less, more preferably 25% by mass or less.

  The mass average molecular weight (Mw) of the olefin-acid copolymer used in the present invention is preferably 1,000 to 100,000, more preferably 3,000 to 70,000, and still more preferably 5,000 to 3, in terms of polystyrene. Ten thousand. This Mw can be measured by GPC using polystyrene as a standard.

  As the carboxylic acid polymer, either a homopolymer or copolymer of one or more α, β-unsaturated carboxylic acids, or a copolymer obtained by copolymerizing another monomer is used. can do. Such carboxylic acid polymers can be produced by known methods and are commercially available. In the present invention, one or more carboxylic acid polymers can be used.

  Examples of the α, β-unsaturated carboxylic acid that can be used for the production of the carboxylic acid polymer include the α, β-unsaturated carboxylic acids exemplified as those that can be used for the synthesis of the olefin-acid copolymer. It can be used. Among these, acrylic acid and maleic acid are preferable, and maleic acid is more preferable.

  The carboxylic acid polymer may contain a constitutional unit derived from a monomer other than the α, β-unsaturated carboxylic acid, but the amount of the constitutional unit derived from the other monomer is contained in the polymer. A carboxylic acid polymer composed of only an α, β-unsaturated carboxylic acid is more preferably 10% by mass or less, preferably 5% by mass or less.

  Preferred carboxylic acid polymers include, for example, polyacrylic acid, polymethacrylic acid, acrylic acid-maleic acid copolymer, polymaleic acid and the like. Among these, coating film adhesion, resin film adhesion, and corrosion resistance viewpoints Therefore, polymaleic acid is more preferable. Although the exact mechanism by which the corrosion resistance is improved by using polymaleic acid is unknown, the adhesion between the resin film and the metal plate is improved due to the large amount of carboxyl groups. It is done. However, the present invention is not limited to this estimation.

  Mw of the carboxylic acid polymer used in the present invention is preferably 500 to 30,000, more preferably 800 to 10,000, still more preferably 900 to 3,000, and most preferably 1,000 to 2,000 in terms of polystyrene. It is. This Mw can be measured by GPC using polystyrene as a standard.

  The content ratio of the olefin-acid copolymer and the carboxylic acid polymer in the surface treatment composition is 1,000: 1 to 10: 1, preferably 200: 1 to 20: 1, more preferably 100: 1. 100: 3. When the content ratio of the carboxylic acid polymer is too low, the effect of combining the olefin-acid copolymer and the carboxylic acid polymer is not sufficiently exhibited. Conversely, when the content ratio of the carboxylic acid polymer is excessive, This is because the olefin-acid copolymer and the carboxylic acid polymer are phase-separated in the surface treatment composition, so that a uniform resin film may not be formed, and the alkali resistance may be lowered.

  The resin component includes an oxazoline group-containing copolymer. In the oxazoline group-containing copolymer, since the oxazoline group undergoes a crosslinking reaction with the carboxyl group of the olefin-acid copolymer or carboxylic acid polymer, the resins are crosslinked to form a dense network structure. This improves the toughness of the coating.

  As the oxazoline group-containing copolymer, “Epocross (registered trademark)” manufactured by Nippon Shokubai Co., Ltd. whose main chain is styrene / acryl is suitable. A very hard film is formed and the brittleness of the film is improved. In particular, the emulsion type “Epocross (registered trademark) K” series is preferable, and the grades are K-2010E (Tg: −50 ° C.), K-2020E (Tg: 0 ° C.) and K-2030E (Tg: 50 ° C.). ) Epocros K-2030E is most preferable for obtaining a hard film. These “Epocross (registered trademark) K” series have a merit that the pot life of the surface treating agent composition is long because the functional group is blocked and hardly causes a crosslinking reaction at room temperature.

  In the resin component, in order to improve the hardness of the resin film, the oxazoline group-containing copolymer is preferably 1 to 9 parts by mass with respect to 100 parts by mass in total of the olefin-acid copolymer and the carboxylic acid polymer. . When the amount of the oxazoline group-containing copolymer is less than 1 part by mass, the improvement of the toughness of the film may be insufficient. A more preferred lower limit is 2 parts by mass, and a more preferred lower limit is 3 parts by mass. On the other hand, when the amount of the oxazoline group-containing copolymer exceeds 9 parts by mass, the resin is sufficiently crosslinked, and not only further improvement in brittleness and improvement in corrosion resistance is observed, but also the number of carboxyl groups remaining in the resin decreases. This is not preferable because the paintability (adhesion with the top coat film) may be deteriorated. A more preferred upper limit is 6 parts by mass, and a more preferred upper limit is 5 parts by mass.

  As described above, the resin component includes an olefin-acid copolymer, a carboxylic acid polymer, and an oxazoline group-containing copolymer. The amount of these resin components is preferably 70 to 90 parts by mass for the resin component and 10 to 30 parts by mass for the colloidal silica when the total amount with the colloidal silica described later is 100 parts by mass. In order to improve the hardness of the film, it is effective to use a large amount of colloidal silica, which is an inorganic substance and has a hard nano-order size, but if the amount of colloidal silica is excessively increased, the resin component in the film When the amount is reduced, the film-forming property is lowered, and the film is brittle. As a result, not only peeling of the film is likely to occur, but also corrosion resistance and paintability are deteriorated. On the other hand, if the amount of colloidal silica is too small, the hardness of the film is insufficient, and the corrosion resistance is low because the rust prevention effect is small. When the amount of the resin component and colloidal silica is within the above range, a resin film having an excellent balance between the hardness and brittleness of the film and excellent corrosion resistance and paintability can be obtained.

  Of the total 100 parts by mass of the resin component and colloidal silica, the resin component is preferably 75 parts by mass or more. The upper limit of the resin component is more preferably 85 parts by mass and even more preferably 80 parts by mass.

[Colloidal silica]
When colloidal silica is present in the film, it dissolves and elutes at the film defects in a corrosive environment, and the dissolution / elution of the metal plate is suppressed by the pH buffering action and the passive film forming action, thereby improving the corrosion resistance. However, the state of dispersion in the film changes depending on the surface area (particle diameter) of the colloidal silica, which greatly affects mechanical properties such as hardness and brittleness of the film. In order to form a dense film and improve the toughness of the film, it is desirable to uniformly disperse colloidal silica having a small particle diameter in the film. In this respect, colloidal silica has a surface area average particle diameter of 4 It is preferably ˜20 nm. When it is larger than 20 nm, the surface area itself becomes small, and the dispersibility tends to decrease. For this reason, there is a possibility that a dense film cannot be formed, and the toughness of the film is insufficient, or the corrosion resistance improving effect is lowered. On the other hand, if the thickness is less than 4 nm, the storage stability of the surface treatment composition may be deteriorated and gelation may occur. As for the surface area average particle diameter of colloidal silica, 4-6 nm is more preferable. The surface area average particle diameter of silica can be measured by the Sears method when the average particle diameter is about 1 to 10 nm and by the BET method when it is about 10 to 100 nm.

  Colloidal silica is commercially available. For example, if it has a surface area average particle diameter of 4 to 6 nm, “Snowtex (registered trademark) XS” manufactured by Nissan Chemical Industries, Ltd. can be used. Also, "Snowtex (registered trademark) 40", "Snowtex (registered trademark) N", "Snowtex (registered trademark) SS", "Snowtex (registered trademark) O", etc., also manufactured by Nissan Chemical Industries, "Adelite (registered trademark) AT-30", "Adelite (registered trademark) AT-30A" manufactured by ADEKA, etc. can be used. When the surface treatment composition used for forming the resin film is aqueous, it is preferable to select the type of colloidal silica according to the pH of the surface treatment composition in order to disperse the colloidal silica well.

[Glycidyl group-containing silane coupling agent]
The surface treatment composition of the present invention may further contain a glycidyl group-containing silane coupling agent. When a silane coupling agent is used, the adhesion between the metal and the resin film is improved, and the corrosion resistance is also improved accordingly. Moreover, there exists an effect which improves the bond strength of a resin component and colloidal silica, and the toughness of a film | membrane improves. In particular, a glycidyl group-containing silane coupling agent has high reactivity and has a large effect of improving corrosion resistance and alkali resistance.

  Glycidyl group-containing silane coupling agents include γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxymethyldimethoxysilane, β- (3,4-epoxycyclohexyl) Examples include ethyltrimethoxysilane.

  The amount of the silane coupling agent in the surface treatment composition is preferably 0.1 to 10 parts by mass with respect to 100 parts by mass in total of the resin component and colloidal silica. If the amount is less than 0.1 parts by mass, the adhesion between the metal plate and the resin film and the bonding force between the resin component and colloidal silica may be insufficient, and the toughness and corrosion resistance of the film may be insufficient. However, even if it exceeds 10 parts by mass, the effect of improving the adhesion between the metal plate and the resin film is saturated, and the coatability may be reduced because the functional groups in the resin are reduced. Moreover, silane coupling agents cause a hydrolysis condensation reaction, stability of a surface treatment composition falls, and there exists a possibility of causing gelatinization and precipitation of colloidal silica. A more preferable amount of the silane coupling agent is 3 to 9 parts by mass, and further preferably 5 to 7 parts by mass.

[Metavanadate]
The surface treatment composition of the present invention may further contain metavanadate. Metavanadate is also eluted like colloidal silica, thereby suppressing the dissolution / elution of the metal plate and improving the corrosion resistance. In the surface treatment composition, metavanadate also exhibits an effect of suppressing the hydrolysis condensation reaction of the silane coupling agent. As a result, the adhesion between the metal plate and the resin film and the bonding force between the resin component and the colloidal silica are improved, and the toughness is improved by forming a dense film. In order to exhibit these effects effectively, it is good to use 0.5-6 mass parts of metavanadates with respect to 100 mass parts in total of a resin component and colloidal silica. When the amount is less than 0.5 parts by mass, the above effect is not sufficiently exhibited. However, even when the amount exceeds 6 parts by mass, the above effect is saturated and the stability of the surface treatment composition is deteriorated. As for the amount of metavanadate, 1-5 mass parts is more preferable, and 3-4 mass parts is further more preferable. In addition, the suitable amount of this metavanadate is a V element conversion amount.

Examples of the metavanadate include ammonium metavanadate (NH ₄ VO ₃ ), sodium metavanadate (NaVO ₃ ), and potassium metavanadate (KVO ₃ ). One or more of these can be used. These metavanadates are commercially available and can be easily obtained.

[Carbodiimide group-containing compound]
The surface treatment composition of the present invention may further contain a carbodiimide group-containing compound. A carbodiimide group reacts with a carboxyl group in an olefin-acid copolymer and a carboxylic acid polymer. Therefore, by using a carbodiimide group-containing compound, the amount of carboxyl groups in the resin film can be reduced and the alkali resistance can be improved. In the present invention, one or more carbodiimide group-containing compounds can be used.

  Carbodiimide group-containing compounds include isocyanates such as hexamethylene diisocyanate (HDI), xylylene diisocyanate (XDI), hydrogenated xylylene diisocyanate (HXDI), 4,4-diphenylmethane diisocyanate (MDI), and tolylene diisocyanate (TDI). Can be produced by heating in the presence of a carbodiimidization catalyst, and can be made aqueous (water-soluble, water-emulsifiable or water-dispersible) by modification. When the surface treatment composition is aqueous, an aqueous carbodiimide group-containing compound is preferable. A compound containing a plurality of carbodiimide groups in one molecule is preferable. When a plurality of carbodiimide groups are contained in one molecule, corrosion resistance and the like can be further improved by a crosslinking reaction with a carboxyl group in the resin component.

  Examples of commercially available polycarbodiimide compounds include N, N-dicyclohexylcarbodiimide, N, N-diisopropylcarbodiimide and the like, and polycarbodiimides (polymers having a plurality of carbodiimide groups in one molecule). Mention may be made of the “Carbolite®” series. The grades of “Carbolite (registered trademark)” include water-soluble “SV-02”, “V-02”, “V-02-L2”, “V-04” and emulsion type “E-01”. , “E-02” and the like are preferable.

  The amount of the carbodiimide group-containing compound is set according to the amounts of the olefin-acid copolymer and carboxylic acid polymer which are crosslinking partners. That is, when the total of the olefin-acid copolymer and the carboxylic acid polymer is 100 parts by mass, the amount is preferably 0.3 parts by mass or more, more preferably 0.5 parts by mass or more, more preferably 100 parts by mass. Preferably it is 8 mass parts or more. On the other hand, when the amount of the carbodiimide group-containing compound is excessive, the effect of the combination of the olefin-acid copolymer and the carboxylic acid polymer is lowered. Further, when an aqueous carbodiimide group-containing compound is excessively used in an aqueous surface treatment composition, it may adversely affect water resistance and corrosion resistance. From such a viewpoint, the amount of the carbodiimide group-containing compound is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and further preferably 16 parts by mass or less with respect to 100 parts by mass.

  The surface treatment composition of the present invention is a wax, a cross-linking agent, a diluent, an anti-skinning agent, a surfactant, an emulsifier, a dispersant, a leveling agent, an antifoaming agent, and a penetrating agent as long as the effects of the present invention are not impaired. , Film-forming aids, dyes, pigments, thickeners, lubricants and the like can also be contained.

  The surface treatment composition of the present invention may be either a solvent-based composition or an aqueous composition that can be applied to the surface of a metal plate, but is preferably an aqueous composition from the viewpoint of environmental problems. The surface treatment composition may be an organic solvent (in the case of a solvent-based composition) or water, preferably deionized water (in the case of an aqueous composition), an olefin-acid copolymer, a carboxylic acid polymer, colloidal silica, or a silane coupling. It can be prepared by mixing a predetermined amount of an agent, a metavanadate, an oxazoline group-containing copolymer, and, if necessary, a carbodiimide group-containing compound or other components and stirring.

  When preparing a surface treatment composition, a part of a silane coupling agent and a carbodiimide group-containing compound are added to an emulsion (emulsion) of an olefin-acid copolymer and a carboxylic acid polymer, and these mixtures are added. It is preferable to prepare and add colloidal silica, the remaining glycidyl group-containing silane coupling agent, metavanadate, and oxazoline group-containing copolymer in this order. When an oxazoline group-containing copolymer is directly added to and mixed with an olefin-acid copolymer and a carboxylic acid polymer, gelation may occur, and when a metavanadate is added prior to the silane coupling agent, The reaction of the ring agent may be suppressed. The silane coupling agent is preferably added in two or more portions as described above. The silane coupling agent added first contributes to the refinement of the emulsion particles and the resulting improvement in the density of the resin film. The silane coupling agent added later ensures adhesion to the metal plate and film characteristics. It is because it contributes to the improvement of.

  You may heat at the time of stirring the said component. In particular, when the olefin-acid copolymer is emulsified in the presence of a carboxylic acid polymer, it is preferably heated. However, it is better not to heat after blending the oxazoline group-containing copolymer. This is to avoid the gelation of the surface treatment composition due to the reaction of the oxazoline group-containing copolymer, the olefin-acid copolymer, and the carboxylic acid polymer.

  When producing an aqueous surface treatment composition, it is preferable to emulsify the olefin-acid copolymer which is the main component of the resin component. The olefin-acid copolymer can be emulsified by using an emulsifier or neutralizing a carboxyl group in the copolymer. If an emulsifier is used, the average particle diameter of the aqueous emulsion of an olefin-acid copolymer can be reduced, and the film-forming property and thereby the density of the resin film can be improved.

  However, it is preferable to neutralize and emulsify the carboxyl group in the olefin-acid copolymer. By neutralizing and emulsifying carboxyl groups, the amount of emulsifier used can be reduced, or no emulsifier can be used, and the adverse effect of the emulsifier on the water resistance and corrosion resistance of the resin film can be reduced or eliminated. It is. When neutralizing the carboxyl group in the olefin-acid copolymer, a base of preferably about 0.5 to 0.95 equivalent, more preferably about 0.6 to 0.8 equivalent is used with respect to the carboxyl group. It is preferable. If the degree of neutralization is too small, the emulsifying property will not be improved so much. On the other hand, if the degree of neutralization is too large, the amount of carboxyl groups that react with the oxazoline group-containing copolymer will decrease, resulting in an adverse effect on corrosion resistance and the like. In some cases, the viscosity of the composition containing the olefin-acid copolymer may be too high.

As a base for neutralization, for example, a strong base composed of a group consisting of hydroxides of alkali metals and alkaline earth metals (for example, NaOH, KOH, Ca (OH) ₂ etc., preferably NaOH), aqueous ammonia, There may be mentioned primary, secondary and tertiary amines (preferably triethylamine). If a strong base such as NaOH is used, the emulsifying property is improved, but if it is too much, the corrosion resistance of the resin film may be lowered. On the other hand, an amine having a low boiling point (preferably an amine having a boiling point of 100 ° C. or lower under atmospheric pressure; for example, triethylamine) does not significantly reduce the corrosion resistance of the resin film. The reason for this may be that the low boiling point amine volatilizes when a resin film is formed by heating and drying after applying the surface treatment composition. However, since an amine has a small effect of improving emulsifiability, it is preferable to neutralize by combining the strong base and the amine. The optimal combination is a combination of NaOH and triethylamine. When a strong base and an amine are used in combination, the strong base is used in an amount of about 0.01 to 0.3 equivalents and the amine is used in an amount of 0.4 to 0.8 equivalents relative to the amount of carboxyl groups of the olefin-acid copolymer. It is preferable to use a degree.

  When an aqueous surface treatment composition is used, a small amount of an organic solvent may be added in order to reduce the interfacial tension and improve the wettability to the metal plate. Examples of the organic solvent for this purpose include methanol, ethanol, isopropanol, butanols, hexanol, 2-ethylhexanol, ethylene glycol ethyl ether, ethylene glycol butyl ether, diethylene glycol, propylene glycol and the like.

  There is no limitation in particular in solid content of a surface treatment composition, What is necessary is just to adjust according to the application | coating method of the surface treatment composition to a metal plate. The solid content of the surface treatment composition is generally about 5 to 20% by mass. For example, when the surface treatment composition is applied by a spray ringer method (an application method in which the surface treatment composition is sprayed on the surface of the metal plate and then squeezed with a roll), 10 About -18 mass% is suitable.

  There is no limitation in particular in the metal plate used by this invention, For example, a non-plating cold-rolled steel plate, hot-dip galvanized steel plate (GI), hot-dip galvanized steel plate (GA), electrogalvanized steel plate (EG), an aluminum plate, and A titanium plate etc. can be mentioned. Among these, it is preferable to apply this invention to the hot dip galvanized steel plate (GI) and the hot galvannealed steel plate (GA) which are not chromated.

  In the present invention, the method and conditions for forming the resin film on the metal plate are not particularly limited, and the surface treatment composition is applied to one or both surfaces of the metal plate surface by a known coating method, followed by heating and drying. A resin-coated metal plate can be manufactured. Examples of the method for applying the surface treatment composition include a curtain flow coater method, a roll coater method, a spray method, and a spray ringer method. Among these, the spray ringer method is preferable from the viewpoint of cost and the like.

  Heating and drying after applying the surface treatment composition is performed so that the metal plate arrival temperature is 120 to 180 ° C. This is because the crosslinking reaction of the resin is accelerated by a higher drying temperature, and a resin film that is hard and not brittle is obtained. The chemical change in the resin structure due to the increase in the heating temperature could not be confirmed by FT-IR, but heating at less than 120 ° C. resulted in insufficient film-forming properties and the degree of cross-linking, and the film was not strong. Insufficient film peeling resistance is not fully exhibited. However, heating at a temperature exceeding 180 ° C. is not preferable because the film becomes too hard and brittle, cracks are generated on the surface of the film, the peel resistance of the film is lowered, and the corrosion resistance is also deteriorated.

The adhesion amount of the resin film on the resin-coated metal plate is preferably 0.1 to 1 g / m ² , more preferably 0.3 to 0.6 g / m ² in terms of dry mass. If the adhesion amount is too small, the hardness itself approaches the original plate, but it becomes difficult to cover the surface of the metal plate, and there is a possibility that the film peeling resistance due to roll forming may deteriorate. On the other hand, if the amount of adhesion increases, the film hardness decreases due to the repulsive force of the resin component, and the amount of film peeled off during roll molding may increase, which is not preferable.

  EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited by the following examples, and appropriate modifications are made within a range that can meet the purpose described above and below. Of course, it is possible to implement them, and they are all included in the technical scope of the present invention.

  The characteristic evaluation method used in the examples is as follows.

[Sword rocker hardness]
It measured by the said method based on JISK5400-1959.

[Indentation depth (μm) in nano scratch test]
Measurement was performed by the method described above.

[Surface sliding test]
A surface sliding test was performed as an indirect evaluation method for roll formability. As shown in FIG. 5, a resin-coated metal plate cut to 40 mm × 300 mm is set vertically on a tensile tester, and a SUS-projected die having a convex portion with a tip radius R = 1 mm is brought into contact (line contact). And a flat plate die was brought into contact with the back surface of the metal plate. The metal plate was pulled upward while applying a load of 1960 N to the protruding die in the horizontal direction. The metal plate was reset every time it was pulled out, and pulled out a total of five times. The length (sliding portion) in contact with the protrusion was 150 mm, and the upper and lower ends were not in contact with the protrusion. The speed at the time of sliding was 300 mm / min. A portion not in contact with the protrusion (non-sliding portion) and a sliding portion were each punched out to 50 mm and subjected to fluorescent X-ray analysis, and the amount of Si in the film was quantified. The residual film rate (%) was calculated by dividing the amount of Si in the sliding portion by the amount of Si in the non-sliding portion.
A: The film remaining rate is over 80% to 100%.
○: Residual rate of film exceeds 60% to 80%
Δ: Residual rate of film over 40% to 60%
×: film remaining rate of 40% or less

[Flat corrosion resistance]
A salt spray test was carried out based on JIS Z2371, and the time until the white rust occurrence rate (100 × area where white rust occurred / total area of the test material) reached 5% was measured. If this flat plate corrosion resistance is 120 hours or more, there is no practical problem.

[Corrosion resistance in JASO cycle test]
A JASO cycle test was conducted based on JIS H8502. 1 cycle is salt spray (temperature 35 ° C. × 2 hours) → drying (temperature 35 ° C. × humidity 30% or less × 4 hours) → wetting (temperature 50 ° C. × humidity 95% or more × 2 hours) (each transition time) including.). After carrying out 15 cycles, the white rust occurrence rate was evaluated according to the following criteria.
◎: White rust occurrence rate of less than 5% ○: White rust occurrence rate of 5% to less than 10% △: White rust occurrence rate of 10% to less than 20% ×: White rust occurrence rate of 20% or more

[Paintability]
A resin-coated metal plate was bar-coated with an acrylic paint (top coat) so that the coating thickness after drying was 20 μm, and baked at 160 ° C. for 20 minutes for post-coating. Subsequently, after immersing this test material in boiling water for 1 hour, taking it out and leaving it to stand for 1 hour, 100 mm of a 1 mm square grid was cut with a cutter knife, and a tape peeling test was carried out on this. The coating film adhesion was evaluated according to the following criteria based on the number of remaining squares.
A: Coating film remaining rate 100%
○: Coating film remaining rate of less than 100% to 90% or more Δ: Coating film remaining rate of less than 90% to 80% or more ×: Coating film remaining rate of less than 80%

Experimental example 1
To an autoclave having an emulsification facility with an internal capacity of 1.0 L equipped with a stirrer, a thermometer and a temperature controller, an ethylene-acrylic acid copolymer ("Primacol (registered trademark) 5990I" manufactured by Dow Chemical Co., Ltd.), derived from acrylic acid Structural unit: 20% by mass, mass average molecular weight (Mw): 20,000, melt index: 1300, acid value: 150) 200.0 g, polymaleic acid aqueous solution (Non-Paul (registered trademark) PMA-50W manufactured by NOF Corporation) , Mw: about 1100 (polystyrene conversion), 50% by mass product) 8.0 g, triethylamine 35.5 g (0.63 equivalent to the carboxyl group of the ethylene-acrylic acid copolymer), 6.9 g of 48% NaOH aqueous solution (0.15 equivalent to the carboxyl group of the ethylene-acrylic acid copolymer), tall oil fatty acid (harima Narusha made "HARTALL FA3") 3.5 g, and sealed with ion exchange water 792.6G, after 3 hours stirred at high speed 0.99 ° C. and 5 atm, and cooled to 30 ° C.. Next, 10.4 g of glycidyl group-containing silane coupling agent (Momentive Performance Materials (former name: GE Toshiba Silicone) “TSL8350”, γ-glycidoxypropyltrimethoxysilane), carbodiimide group-containing compound (Nisshinbo Co., Ltd.) “Carbodilite (registered trademark) SV-02” manufactured by Polycarbodiimide, Mw: 2,700, solid content 40 mass%) 31.2 g and ion-exchanged water 72.8 g were added and stirred for 10 minutes. 1 (solid content 20.3% by mass, measured according to JIS K6833).

  Emulsion No. 1 and colloidal silica (“Snowtex (registered trademark) XS” manufactured by Nissan Chemical Industries, Ltd., surface area average particle size (catalog value): 4 to 6 nm) were variously changed as shown in Table 1, After mixing, glycidyl group-containing silane coupling agent (“KBM403” manufactured by Shin-Etsu Silicone Co., Ltd., γ-glycidoxypropyltrimethoxysilane) 7 parts by mass, and then sodium metavanadate (new) 3 parts by mass of “Sodium Metavanadate” manufactured by Kagaku Kogyo Co., Ltd. is added, and an oxazoline group-containing copolymer (“Epocross (registered trademark) K-2030E” manufactured by Nippon Shokubai Co., Ltd., solid content: 40% by mass) is added. Treatment composition no. 1 was prepared. The amount of the resin component in Table 1 is the emulsion No. 1 corresponds to the total amount of the resin (solid content) in 1 and the oxazoline group-containing copolymer. The oxazoline group-containing copolymer was added to 5 parts by mass with respect to 100 parts by mass of the total amount of the ethylene-acrylic acid copolymer and polymaleic acid.

As the metal plate, an alkali degreased hot dip galvanized steel plate (Zn adhesion amount 45 g / m ² ) was used. 1 was applied with a bar coat (bar No. 3) and dried by heating at a plate temperature of 150 ° C. for about 12 seconds to produce a resin-coated metal plate having a resin film adhesion amount of 0.5 g / m ² .

Experimental example 2
Emulsion No. As shown in Table 2, the amount of the oxazoline group-containing copolymer relative to 100 parts by mass (solid content) of the ethylene-acrylic acid copolymer and polymaleic acid in 1 was changed. The ratio of the resin component to colloidal silica was constant at 80 parts by mass: 20 parts by mass. Otherwise, a resin-coated metal plate was produced in the same manner as in Experimental Example 1. The evaluation results are shown in Table 2.

Experimental example 3
Resin in the same manner as in Experimental Example 1 except that the ratio of the resin component to colloidal silica was constant at 80 parts by mass: 20 parts by mass, and the surface area average particle diameter (nm) of colloidal silica was changed as shown in Table 3. A painted metal plate was produced. The colloidal silica of Invention Example 12 is “Snowtex (registered trademark) 20” manufactured by Nissan Chemical Industries, Ltd. The colloidal silica of Comparative Example 8 is “Snowtex (registered trademark) XL” manufactured by the same company, and Comparative Example 9 The colloidal silica is “Snowtex (registered trademark) ZL” manufactured by the same company.

Experimental Example 4
The ratio of the resin component to colloidal silica is constant at 80 parts by mass: 20 parts by mass, and the glycidyl group-containing silane coupling agent added afterwards to 100 parts by mass (solid content) of both (“KBM403” manufactured by Shin-Etsu Silicone Co., Ltd.) A resin-coated metal plate was produced in the same manner as in Experimental Example 1 except that the amount of was changed as shown in Table 4. The evaluation results are shown in Table 4.

Experimental Example 5
The ratio of the resin component and colloidal silica was fixed at 80 parts by mass: 20 parts by mass, and the type and amount of metavanadate relative to the total of 100 parts by mass (solid content) were changed as shown in Table 5. A resin-coated metal plate was produced in the same manner as in Experimental Example 1. The evaluation results are shown in Table 5.

Experimental Example 6
The experiment was conducted except that the ratio of the resin component to colloidal silica was constant at 80 parts by mass: 20 parts by mass, and the drying temperature (metal plate arrival temperature) after applying the surface treatment composition was changed as shown in Table 6. In the same manner as in Example 1, a resin-coated metal plate was produced. The evaluation results are shown in Table 6.

Experimental Example 7
A resin-coated metal plate was produced in the same manner as in Experimental Example 1, except that the ratio of the resin component to colloidal silica was constant at 80 parts by mass and 20 parts by mass, and the amount of the resin film deposited was changed as shown in Table 7. did.

  As is clear from Tables 1 to 7, in the examples of the present invention, a tough resin film excellent in the balance between hardness and brittleness was obtained, corrosion resistance was good, and paintability was also excellent.

  The resin-coated metal sheet of the present invention has a resin film with improved film peel resistance at the time of roll molding, and is excellent in corrosion resistance and paintability, so it is suitable for use in automobiles, home appliances, building materials, etc. Can do.

Claims (7)

  A resin-coated metal plate provided with a resin film obtained from the surface treatment composition, wherein the resin film has a Sword rocker hardness of 35 or more and an indenter penetration depth in a nano scratch test is less than 0.3 μm A resin-coated metal plate having excellent film peeling resistance during roll forming.   The surface treatment composition comprises a resin component comprising an olefin-α, β-unsaturated carboxylic acid copolymer, an α, β-unsaturated carboxylic acid polymer and an oxazoline group-containing copolymer, and colloidal silica, 2. The resin-coated metal sheet according to claim 1, wherein the resin component is 70 to 90 parts by mass and the colloidal silica is 10 to 30 parts by mass, out of a total of 100 parts by mass of the resin component and colloidal silica.   The resin component contains 1 to 9 parts by mass of an oxazoline group-containing copolymer with respect to 100 parts by mass in total of the olefin-α, β-unsaturated carboxylic acid copolymer and the α, β-unsaturated carboxylic acid polymer. The resin-coated metal plate according to claim 2, which is a waste.   The resin-coated metal plate according to claim 2 or 3, wherein the colloidal silica has a surface area average particle diameter of 4 to 20 nm.   The resin-coated metal plate according to any one of claims 2 to 4, further comprising 0.1 to 10 parts by mass of a glycidyl group-containing silane coupling agent with respect to 100 parts by mass in total of the resin component and colloidal silica.   The resin-coated metal plate according to any one of claims 2 to 5, further comprising 0.5 to 6 parts by mass of metavanadate with respect to a total of 100 parts by mass of the resin component and colloidal silica. The resin-coated metal plate according to any one of claims 1 to 6, wherein the resin film is formed by applying the surface treatment composition to a metal plate and then heating at a plate temperature of 120 to 180 ° C. .

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