JPH08323283A - Heat-sensitive adhesive resin-coated metal sheet and its preparation - Google Patents

Abstract

PURPOSE: To perform heat bonding at a low temp. and in a short time by specifying build-up of a partially crosslinked coating film at a resin coating film stage before heat bonding, in a coated metal sheet coated with a coating liq. contg. a thermoplastic resin with a functional group exhibiting thermocrosslinking reactivity in its molecule and a heat-sensitive crosslinking agent. CONSTITUTION: This coated metal sheet applicable for automobiles and electric appliances is obtd. by applying and drying a coating liq. S contg. a thermoplastic resin A with a functional group X exhibiting thermocrosslinking reactivity in its molecule and a heat-sensitive crosslinking agent B as essential components on the surface of a metal sheet. In this case, at a resin coating film stage before heat bonding, processing is performed in such a way that a coating film in which the functional group X in the thermoplastic resin A and the heat-sensitive crosslinking agent B are partially crosslinked is formed at least on one face of the metal sheet with a build-up of 0.5-30g/m<2> in terms of solid content. In addition, a part of the thermoplastic resin A is made to be a thermoplastic resin A' which is partially crosslinked in advance with such a heat-sensitive crosslinking agent B as a blocked isocyanate group-contg. compd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive adhesive type resin-coated metal sheet and a method for producing the same. The heat-sensitive adhesive resin-coated metal sheet exhibits excellent adhesiveness by heating, At the stage of, good processability and chemical resistance are exhibited, and corrosion resistance and solvent resistance after adhesion are also excellent. Therefore, it can be applied as an outer plate material for automobiles, household electric appliances, metal furniture, etc., or for building materials, etc., without the need for welding or joining means such as an adhesive, and at the time of molding / assembling. It can be used to bond plates to each other or metal and non-metal plates (including plywood plates, plastic plates, rubber plates, cloths, etc.).

[0002]

2. Description of the Related Art Conventionally, as a method of joining metal plates, a welding method including brazing, a mechanical joining method using bolts / nuts, rivets, etc., a method using an adhesive and the like have been widely used. On the other hand, for joining non-metal materials such as plastics and cloths to metal plates, a bonding method using an adhesive or a double-sided adhesive tape is used in most cases. It is classified into thermoplastic resin, thermosetting resin and elastomer depending on the physical properties.

In the joining method using these adhesives, the adhesive is applied to one surface or both surfaces of the surface to be joined, and the components of the resin contained in the adhesive that contribute to the adhesion are reacted,
Alternatively, heat treatment of the adherends and / or pressure bonding treatment of the adherends is performed in order to melt the resin and develop the tackiness (hot melt method).

However, in the method of applying an adhesive as described above, prior to joining, a metal plate is first punched into a desired shape or sheared, and then a desired forming process is performed, and then the surface of a portion to be joined is joined. Since it is necessary to apply an adhesive to each individual component, the work efficiency is extremely poor, resulting in a disadvantage in terms of productivity and manufacturing cost. As a solution for solving such a problem, for example, in the field of magnetic steel sheets for lamination, a steel sheet coated with a water-based emulsion type resin has been proposed as shown below.

First, Japanese Examined Patent Publication No. 52-8998 discloses a resin liquid obtained by diluting and mixing a thermoplastic resin and a thermosetting resin with an organic solvent as an electromagnetic steel sheet for laminated iron cores of electric products and using an emulsifier as an aqueous emulsion. , An organic resin-coated electromagnetic steel sheet applied to the surface of a steel sheet and dried.

[0006] In this organic resin-coated steel sheet, the electromagnetic steel sheets can be joined simply by laminating, pressurizing and heating, and since it is not necessary to separately apply an adhesive agent, the adhesive application step on the user side is not required. It has the advantage that it can be omitted.

In this method, the adhesive strength is insufficient with a resin coating made of only a thermoplastic resin, and especially when the laminated iron core is heated to a high temperature and used, the bonding agent is plasticized and the adhesive strength is rapidly increased. In order to solve the problem of decrease in temperature, it is possible to increase the heat resistance after joining by mixing a thermosetting resin with a thermoplastic resin, and also to prevent the softening point from decreasing due to the addition of an emulsifier. It prevents the decrease of the adhesive strength. However, as long as the thermoplastic resin is present in the final coating film, it is unavoidable that the adhesive strength is reduced at high temperatures and in a wet environment, and that the solvent resistance is insufficient.

In addition, in the above-mentioned organic resin-coated steel sheet, the joining work requires a long time, so the work efficiency is poor, and such an organic resin-coated steel sheet for iron core is used for the structure of automobiles, home electric appliances, metal furniture, building materials and the like. It is not appropriate to apply it to the joining of materials.

Further, as a similar type of organic resin-coated steel sheet for laminated iron cores, Japanese Patent Publication No. 52-8999, a water-based acrylic resin emulsion coated with a water-soluble phenol resin or a water-soluble melamine resin is applied, A method of obtaining an organic resin-coated electromagnetic steel sheet by performing incomplete baking is disclosed.

The resin-coated steel sheet obtained by this method also has the advantage that it can be joined without applying an adhesive,
In this case, since the thermoplastic resin component is present in the coating film after final adhesion, a decrease in the adhesive strength when exposed to high temperature conditions above the plasticizing temperature of the resin or a wet environment is unavoidable, It also has poor solvent resistance.

Further, since the incomplete baking treatment for forming the coating film for adhesion is a short time treatment at a high temperature exceeding 250 ° C., if heating unevenness occurs in this baking, the resin is locally heated. There is a problem that not only deterioration of adhesive strength occurs due to deterioration, but also control of baking temperature during bonding is very difficult.

Therefore, applying the resin coating film of the organic resin-coated steel sheet for laminated iron core described in this publication as it is to join automobiles, home appliances, steel furniture or building materials has both performance and construction workability. From lacking aptitude.

Further, as disclosed in Japanese Patent Publication No. 52-8999, the temperature range and time at the time of incomplete baking, which are pointed out in the coated steel sheet, are expanded to improve the performance and make the workability easier. No. 55-9815,
Aqueous emulsion of acrylic resin with water-soluble styrene
An organic steel sheet coated with an organic resin for adhesion is disclosed in which a treatment liquid containing a maleic acid copolymer is applied to the surface of a steel sheet and dried.

However, even with this organic resin-coated steel sheet, the adhesive strength at high temperature is slightly improved, and basically the thermoplastic resin is contained in the final coating film. The adhesive strength in a wet environment is insufficient and the solvent resistance is also poor.

Further, in this publication, it is described that the adhesive strength is increased by the cross-linking bond between the acrylic resin and the water-soluble styrene-maleic acid copolymer. The bond with the carboxyl group is not so strong, and since the styrene-maleic acid copolymer becomes a huge polymer, the fluidity becomes worse, and the bonding opportunity (crosslinking point) with the acrylic resin decreases, No significant effect can be expected in improving the adhesive strength. Moreover, the time required for laminated joining is long,
The problem of poor work efficiency during bonding remains unsolved.

In order to solve these problems of the prior art,
The inventors of the present invention are capable of completely eliminating the thermoplasticity of a coating film after heat-bonding and performing heat-bonding at low temperature in a short time, and are useful for automobiles, home appliances, metal furniture, building materials, etc. Developed a heat-sensitive self-adhesive coated steel sheet and filed a patent application earlier.

This heat-sensitive self-adhesive coated steel sheet has a temperature of 80 ° C.
What is coated with a coating film containing a urethane resin which is plasticized at the above temperature and shows crosslinking reactivity at a temperature above it, the coating film before bonding does not cause stickiness or blocking at room temperature, Moreover, it can be said to be very useful since it loses thermoplasticity by a crosslinking reaction after heat bonding and can exhibit excellent adhesiveness, adhesive durability, high temperature adhesiveness, solvent resistance, corrosion resistance and the like.

However, in this heat-sensitive self-adhesive resin-coated steel sheet, since the base resin, which is the main constituent material of the coating film, is entirely a thermoplastic resin, the coating film as it is formed by coating and drying is used. However, there is still room for improvement in that the crosslinking reaction with the crosslinking agent does not occur at all, and the water resistance of the coating film itself before bonding or the chemical resistance to an organic solvent is insufficient.

Further, the coating film before the heat-crosslinking treatment does not have sufficient film hardness, and therefore, the adhesive resin coating film may be flawed during the punching process or the pressing process performed before the heat-bonding. There is a slight problem with the property, and the corrosion resistance after processing tends to be insufficient in the part where the resin coating film has been mechanically damaged.For example, when the metal plate to be coated is a galvanized steel plate, etc., the coating film damaged part Therefore, it causes a problem that white rust is easily generated due to corrosion of zinc plating.

[0020]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and its purpose is not limited by the type and thickness of the metal plate, and brazing or bonding. An excellent joining force can be obtained by bringing the surfaces to be joined into close contact with each other and then heating and baking at a relatively low temperature for a short time without requiring a joining means such as coating with a coating agent. The film has excellent processability, corrosion resistance after processing, and chemical resistance, and heat sensitivity that can exhibit excellent adhesion, adhesion durability, heat resistant adhesion, corrosion resistance, solvent resistance, etc. after joining by heating and baking. An adhesive resin-coated metal plate and a method for manufacturing the same are provided.

[0021]

The constitution of the heat-sensitive adhesive resin-coated metal plate according to the present invention, which has been able to solve the above-mentioned problems, is a thermoplastic resin having a functional group (X) exhibiting thermal crosslinking reactivity in the molecule. In a heat-sensitive adhesive resin-coated metal plate obtained by coating and drying a resin (A) and a coating liquid (S) containing a heat-sensitive crosslinking agent (B) as essential components on a metal plate surface, before heating and bonding. The coating film in which the functional group (X) in the thermoplastic resin (A) and the thermosensitive crosslinking agent (B) are partially crosslinked in the resin coating film stage is 0.5 to 30 g / solid basis. m ²
The gist is that it is formed on at least one surface of the metal plate with the amount of adhered.

In the heat-sensitive adhesive resin-coated metal plate, a part of the thermoplastic resin (A) in the coating liquid (S) is partially cross-linked with the heat-sensitive crosslinking agent (B) in advance. '), A thermosensitive crosslinking agent (B) is a blocked isocyanate group-containing compound or an aziridinyl group-containing compound, and a functional group (X which is present in the molecule of the thermoplastic resin (A) and exhibits thermal crosslinking reactivity. ), A hydroxyl group, an amino group, a carboxyl group, or two or more thereof, and the thermoplastic resin (A), one or more of a polyethylene-based, polyester-based, polyurethane-based resin. It is preferable to use a water-soluble or water-dispersible resin as the thermoplastic resin (A), because the performance and handleability thereof can be further improved.

As a method for producing the coated metal plate, a coating liquid (S) containing a thermoplastic resin (A) and a heat-sensitive crosslinking agent (B) as essential components on the surface of the metal band whose surface has been cleaned. When a heat-sensitive adhesive resin-coated metal plate is manufactured by applying and drying, a low-temperature heat treatment is performed in advance before or after the application of the coating solution (S) and before the joining step, and the thermoplastic resin (A) It can be easily produced by partially crosslinking the heat-sensitive crosslinking agent (B). At this time,
It is a preferable means from the viewpoint of productivity and manufacturing cost to carry out the above-mentioned low temperature heating treatment simultaneously with the drying treatment for forming a film after coating the coating liquid (S).

[0024]

The metal plate coated with the heat-sensitive adhesive resin of the present invention is a coating liquid containing a thermoplastic resin (A) having a functional group exhibiting heat-crosslinking reactivity in the molecule and a heat-sensitive crosslinking agent (B) as essential components. (S) is applied on a metal surface and dried, and this coating film is utilized as a heat-sensitive adhesive layer.

Considering the application of the present invention, the resin-coated metal plate, which is often provided as a cut plate product or a coil product, is formed into a predetermined shape by a customer's desired slit processing, punching processing, press processing, or the like. It is molded, and if necessary, washed with an organic solvent or an alkaline aqueous solution to be cleaned, and thereafter, bonding (adhesion) by heat baking treatment is performed.

Upon processing or handling by such a consumer, the heat-sensitive adhesive resin-coated metal sheet of the present invention does not cause stickiness or blocking on the coating film surface before the joining (adhesion) step, and It has excellent workability, corrosion resistance after processing, and chemical resistance, and when joining, it is firm by performing heat baking treatment with the coating surfaces or the coating surface and the adherend surface in close contact. Not only can be adhered to, but the coating film that has lost its thermoplasticity in the heating and joining step has solvent resistance, corrosion resistance, adhesion durability,
Exhibits excellent performance in all, including high-temperature adhesive strength. Hereinafter, the respective reasons for limitation and preferred embodiments defined by the resin-coated metal plate will be described in detail.

[Selection of Thermoplastic Resin as Resin (A)] After the coating surfaces of the resin-coated metal sheet according to the present invention are brought into close contact with each other or between the coating surface and the surface of the adherend, heating and baking are carried out to obtain a high degree. In order to obtain adhesive strength, it is necessary that the resin coating film itself softens and exhibits fluidity during the initial process of heating and baking.

That is, when the resin (A) is once softened in the initial stage of heating and baking, in the case of joining the coating film surfaces, the adhesive interface layer becomes smooth by the leveling action of the coating film, and the adhesive interfaces are fused and integrated. To do. When the coating surface and the adherend surface are joined, the resin (A) that has been softened by heating enters into the surface irregularities of the adherend surface, so that the contact area (joint area) between the coating surface and the adherend surface Increase. Thus, in the initial stage of the heating and baking process for joining, the entire joining interface is utilized as an effective joining surface by the plasticizing action of the resin (A), and the subsequent cross-linking reaction ensures uniform and strong adhesiveness at the joining interface. In order to exert such effects effectively, the resin (A) which is the main component of the coating film must be a thermoplastic resin which is once plasticized in the initial process of heating and baking. The thermoplastic development temperature of the thermoplastic resin (A) is not particularly limited, but is preferably in the range of 80 ° C to 200 ° C for the following reasons.

That is, in the baking and adhering process for various home electric appliances and building materials, which are the main applications of the heat-sensitive adhesive resin-coated metal sheet according to the present invention, the metal sheet itself is usually 80 ° C. or higher, more generally 80 to 250. Although it is heated to about ℃, in order to obtain sufficient bonding strength under such heating and baking conditions, it is necessary that the resin coating film is once plasticized and softened in the initial stage of the heating and baking process as described above. is there. Further, if the thermoplastic expression temperature of the resin (A) is too low, the coating film tends to become sticky or blocking during storage, transportation or handling. Therefore, the lower limit of the thermoplastic expression temperature is 80 ° C or higher, preferably 100 ° C. The above is good. However, if the plasticizing temperature becomes too high, the resin may be thermally decomposed during superheat-baking bonding, resulting in deterioration of strength. Therefore, it is desirable to keep the thermoplasticizing temperature at about 230 ° C. or lower.
From such a viewpoint, the more preferable thermoplastic temperature of the resin (A) is in the range of 100 ° C to 200 ° C.

As will be described later, in the heating and baking step for joining, it is necessary to heat the cross-linking agent (B) to the cross-linking reactivity developing temperature (T _B ) or higher in order to obtain a desired adhesive strength. When the thermoplasticity development temperature of the resin (A) is higher than the heating and baking temperature, the resin (A) is heated by the cross-linking agent (B) in the initial stage of heating and baking without causing plasticization of the resin (A). As the cross-linking reaction proceeds, as a result, the fluidity and leveling property of the coating film described above are not sufficiently expressed, and the contact area (bonding effective area) at the bonding interface becomes insufficient, resulting in satisfactory adhesive strength. You won't get it. Therefore, the temperature at which the resin (A) develops the thermoplasticity is preferably lower than the temperature at which the crosslinking reactivity (B) develops the crosslinking reactivity (T _B ).

Specific examples of the thermoplastic resin (A) used in the present invention include polyethylene resin, polyurethane resin, polyester resin, epoxy resin, acrylic resin, vinyl acetate resin, phenol resin, Urea-based resins, vinyl chloride-based resins, melamine-based resins and the like can be mentioned, and each of them can be used alone or in combination of two or more kinds, but the thermoplastic expression temperature of these resins (A) is It can be easily controlled by appropriately adjusting the molecular weight, the degree of branching, or the degree of polymerization of the resin.

By the way, a usual thermoplastic resin is generally an organic compound having a linear structure, and since an organic resin having such a structure is easily dissolved in various organic solvents, a film is formed by coating and drying. As it is, the organic solvent resistance is poor.For example, when cleaning with various organic solvents is performed before baking and joining on the user side, the coating film dissolves in the organic solvent and the coating film is chemically damaged. It becomes easy to receive. In general, the uncrosslinked thermoplastic resin coating does not have sufficient coating hardness, and the coating is susceptible to mechanical damage when subjected to strong processing, and its surface may be flawed or partially damaged. The coating film may decrease or disappear. When the coating film is chemically or mechanically damaged in this way, not only cannot sufficient bonding strength be obtained at that portion, but
Corrosion resistance of the damaged portion also deteriorates.

The problems of organic solvent resistance (chemical resistance), workability, and post-processing corrosion resistance deficiency due to chemical or mechanical damage of the thermoplastic resin are three-dimensionally determined by a cross-linking agent or the like between resins (A). This can be easily improved by crosslinking, but if most or all of the resin (A) is crosslinked in the film-forming step by coating and drying, the thermoplasticity of the coating film itself will be almost All of them will be lost, so at the initial stage of baking during bonding, not only the effect of expanding the effective bonding interface due to the leveling function of the coating film at the bonding interface as described above will not be exhibited, but also the function at the time of heating and baking. Since a crosslinking reaction due to a group can hardly be expected, a high level of adhesiveness is not expressed, and the heat-sensitive adhesiveness intended by the present invention is impaired.

That is, at the stage of degreasing with an organic solvent or the like, which is carried out before heating and baking, and various molding processes, the coating film is free from stickiness and blocking properties, and is excellent in chemical resistance, workability and post-processing corrosion resistance. In addition, thermoplasticity (however, only necessary in the initial stage of heating and baking) and thermal crosslinking reactivity are required in the heating and baking process step for bonding.

In order to satisfy the properties required at each of these stages, as the thermoplastic resin (A), a resin having a functional group exhibiting thermal crosslinking reactivity in its molecule is used as the thermoplastic resin (A), as will be described later. In order to further improve the coating film characteristics, a thermoplastic resin (A ') in which a thermoplastic resin (A) and a cross-linking agent (B) are partially cross-linked in advance in the resin coating film before the heating and baking step for joining. Is preferably contained in the coating film.

That is, a part of the cross-linking agent (B) is applied in the film-forming step by coating and drying, or in the low-temperature heat treatment step thereafter when the drying temperature cannot be sufficiently obtained, in the thermoplastic resin (A).
When the resin (A ') is partially reacted with the resin (A') to be included in the coating film, the coating film has excellent chemical resistance, processability and processing even before heating and baking. The post-corrosion resistance can be exhibited.

At this stage, since the resin (A) is only partially crosslinked so as not to lose the thermoplasticity,
In the initial stage of heating and baking, the plasticity of the coating film is expressed,
The fluidization of the coating film at the bonding interface and the leveling action associated therewith are exhibited, and a uniform and coherent bonding interface can be secured. Moreover, in the subsequent heating and baking step, the residual unreacted crosslinking agent (B) causes a thermal crosslinking reaction at the bonding interface, and as a result, a high bonding strength can be obtained.

For the above reasons, the coating film of the heat-sensitive adhesive resin-coated metal sheet according to the present invention is preliminarily partially crosslinked with the thermoplastic resin (A) and the crosslinking agent (B) before heating and baking for joining. It is desirable to include the thermoplastic resin (A ′).

The role of the cross-linking agent (B) functions as a partial cross-linking agent of the resin (A) for improving the chemical resistance, workability and post-processing corrosion resistance of the coating film before baking and joining. , Which functions as a thermal cross-linking reaction agent in the joining step by heating and baking, and when the content of the cross-linking agent (B) in the coating film is extremely low, the step of film formation by coating / drying or after film formation All or most of the crosslinking agent (B) may be consumed in the low-temperature heat treatment step of, and if so, the thermal crosslinking reaction may hardly occur at all in the heating and baking step. Therefore, as described below, The mixing ratio (blending ratio) of the thermoplastic resin (A) and the cross-linking agent (B) in the coating liquid (S) is within a range that does not cause a large excess or deficiency in the equivalent conversion ratio of each functional group for the cross-linking reaction. It is desired to do.

As described above, in order to exhibit excellent heat-sensitive adhesiveness, high-temperature bonding strength, corrosion resistance, solvent resistance, etc., to the coating film, crosslinking between the coating film surfaces or between the coating film surface and the adherend surface is performed. The cross-linking points necessary for causing no reaction, that is, the functional group (X) must be present in the resin (A), and there are many combinations thereof, but the cross-linking that reacts with the functional group (X). As a preferred combination of the agent (B), the crosslinking agent (B) is a blocked isocyanate group-containing compound or an aziridinyl group-containing compound, and the functional group (X) contained in the resin (A) is the above-mentioned crosslinking agent (B). Those having an active hydrogen group such as a hydroxyl group, an amino group and a carboxyl group which are reactive with

The crosslinking reaction between the resin (A) and the crosslinking agent (B) when a blocked isocyanate group-containing compound or an aziridinyl group-containing compound is used as the crosslinking agent (B) will be described below.

[When an isocyanate group-containing compound is used as the crosslinking agent (B)] When an isocyanate group-containing compound is used as the crosslinking agent (B), the functional group in the resin (A) for crosslinking reaction with the isocyanate group Specific preferred examples of (X) include a functional group having active hydrogen, such as a hydroxyl group (—OH), a carboxyl group (—COOH),
Amino group (-NH _2), and the like.

Each of these active hydrogen-containing functional groups (X) is an active isocyanate group (-) produced by the dissociation of the blocking agent from the blocked isocyanate group.
It easily reacts with (NCO group) to cause a crosslinking reaction, and the specific reaction is as follows. Isocyanate group Active hydrogen group Crosslinking -NCO + -OH → -NH-COO- -NCO + -COOH → -NH-CO- + CO ₂ -NCO + -NH ₂ → -NH-CO-NH-

Among the functional groups (X) having reactivity with the above-mentioned isocyanate group, the most preferable is an amino group.
However, the amino group has a higher crosslinking reaction rate with the isocyanate group than the hydroxyl group and the carboxyl group, and high bonding strength can be obtained in a shorter time or at a lower baking temperature.

By the way, the active isocyanate group easily reacts with the active hydrogen-containing functional group (X) such as hydroxyl group, carboxyl group and amino group at room temperature. Therefore, if the active isocyanate group is mixed and coexisted with the resin (A) as it is, the cross-linking reaction progresses in the coating layer over time without heat treatment, and the cross-linking point gradually disappears. The required coating film thermoplasticity is lost in the initial stage.

As described above, the coating film in which the crosslinking reaction has sufficiently proceeded before the heating and baking is plasticized even if the coating surfaces are subsequently adhered to each other by heating and baking. Since a uniform and smooth bonding interface cannot be obtained and a crosslinking reaction hardly occurs, the heat-sensitive adhesiveness intended by the present invention cannot be exhibited.

Therefore, in the state before heat-baking and joining, the isocyanate group-containing compound as the crosslinking agent (B) spontaneously reacts with the resin (A) containing the functional group (X) exhibiting crosslinking reactivity with the isocyanate group. In order to prevent this, the isocyanate group in the cross-linking agent (B) is blocked in advance with a blocking agent such as phenol, alcohol, oxime, active methylene, etc., and is in an inactive state that does not cross-link with the resin (A) at room temperature. It is necessary to coexist with the resin (A).

At this time, it is possible to adjust the dissociation temperature of the blocking agent from the isocyanate group by appropriately selecting the type of the blocking agent, whereby the temperature at which the isocyanate group-containing compound exhibits the thermal crosslinking reactivity. Can be adjusted.

[When an Aziridinyl Group-Containing Compound is Used as the Crosslinking Agent (B)] When an aziridinyl group-containing compound is used as the crosslinking agent (B), the functional group (X) in the resin (A) for the crosslinking reaction with the aziridinyl group is used. Specific examples of () include a functional group having active hydrogen, for example, a hydroxyl group (—OH), a carboxyl group (—COOH), an amino group (—NH ₂ ), and the like.

Examples of the aziridinyl group-containing compound include trimethylolpropane tris (β-
Aziridinyl propionate),

[0051]

Embedded image

Tris-2,4,6- (1 represented by the following equation:
-Aziridinyl) -1,3,5-triazine,

[0053]

Embedded image

Tris [1- (2-methyl) aziridinyl] phosphine oxide represented by the following formula:

[0055]

Embedded image

And the like, or glycidylamine type epoxy resin available as a commercial product is preferably used.

Such an organic compound having an aziridinyl group undergoes a crosslinking reaction with an active hydrogen group-containing compound as shown by the following formula to form a resin film having a high crosslinking density. Crosslinking agent (B) Thermoplastic compound (A) Aziridinyl group-containing compound Active hydrogen group-containing compound Crosslinking bond

[0058]

[Chemical 4]

Of the functional groups having reactivity with the aziridinyl group, the carboxyl group is most preferred. However, a carboxyl group has a higher crosslinking reaction rate with an aziridinyl group than a hydroxyl group or an amino group, and a high bonding strength can be obtained in a shorter time or at a lower baking temperature.

The thermoplastic resin (A) and the cross-linking agent (B) can be prepared by appropriately selecting the combination of the type of aziridinyl group-containing compound and the type of functional group (X) in the thermoplastic resin (A). It becomes possible to adjust the crosslinking reactivity development temperature.

[The temperature at which the crosslinking agent (B) exhibits the thermal crosslinking reactivity]
The thermal crosslinking reactivity expression temperature (T _B ) of the crosslinking agent (B) is not particularly limited, but it is desirable to set it to the thermoplasticity development temperature of the resin (A) or higher for the following reasons. That is, in order to obtain a high level of adhesive strength by heat-baking treatment and to exhibit excellent high-temperature adhesiveness, corrosion resistance, solvent resistance, etc. after joining, the coating surfaces or the coating surface and the adherend surface may be It is necessary to temporarily plasticize the coating film at the initial stage of heating / baking after combining, to secure a uniform joint interface layer and a sufficient joint area, and then to carry out a crosslinking reaction between functional groups. .

However, if most or all of the cross-linking reaction by the cross-linking agent (B) occurs below the thermoplastic development temperature of the resin (A), the resin (A) will be heated in the initial stage of heating for bonding. The cross-linking reaction is completed without obtaining a uniform joint interface layer and a sufficient joint area due to the plasticization, and high joint strength cannot be obtained. Therefore, the thermal crosslinking reactivity expression temperature (T _B ) of the crosslinking agent (B) contained in the coating film
Is preferably higher than the thermoplastic development temperature of the resin (A). Considering a general production process, the crosslinking agent (B)
The thermal crosslinking reactivity developing temperature (T _B ) should be 80 ° C. or higher, and more preferably 100 ° C. or higher.

[0063] However, the crosslinking reactivity expression temperature of the crosslinking agent _(B) (T B) is a high temperature exceeding 230 ° C., will heat the baking temperature at the time of joining MUST to high temperatures above 250 ° C., heated baking At the same time, not only the resin constituting the coating film is thermally decomposed but sufficient bonding strength cannot be obtained, but also the appearance quality may be deteriorated due to yellowing in the non-bonded portion. The crosslinking reactivity expression temperature (T _B ) is 200 ° C. or lower, more preferably 18
It is desired to keep the temperature below 0 ° C.

As described above, as the thermoplastic resin (A), one or a mixture of two or more kinds of polyethylene resin, polyurethane resin and polyester resin is mentioned as a preferable one, but they are selected. The reason for this is as follows. That is, the heat-sensitive adhesive resin-coated metal plate according to the present invention is generally subjected to some processing prior to the joining step as described above, but at this time, the resin coating film itself is also processed together with the metal plate base material. become. Therefore, at the time of processing, the coating film itself along with the metal plate base material is appropriately spread and deformed,
It is desired that no flaws or defects occur on the surface of the coating film. Therefore, in the present invention, considering the workability of the coating film before such baking and joining, as a preferable resin base showing excellent spreadability and resistance to processing flaws, polyethylene resin, polyurethane resin, polyester resin One kind or a mixture of two or more kinds is mentioned.

As described above, in carrying out the production method of the present invention, in order to more reliably suppress mechanical damage and chemical damage to the coating film in the processing step and the cleaning step before baking and joining, the coating film The resin (A) and the cross-linking agent (B) therein should be partially cross-linked in advance to enhance the chemical resistance, workability, and post-processing corrosion resistance of the coating film. Next, specific examples of the thermoplastic resin (A) preferably used in the present invention will be described in detail.

[Thermoplastic Polyurethane Resin (A ₁ )]
When a polyurethane resin is used as the thermoplastic resin (A), as the resin, two functional groups (X) exhibiting crosslinking reactivity with a crosslinking agent (for example, an isocyanate group-containing compound) are contained in one molecule. The thermoplastic polyurethane resin (A ₁ ) contained above is used.

Such a thermoplastic polyurethane resin (A
₁ ) Is a functional group (X
₁ ) Two or more organic compounds and an isocyanate group
(Y ₁ ) Two or more organic polyisocyanate compounds
It is manufactured by reacting with
In addition, the isocyanate group (Y₁ )
Shows reactivity with isocyanate groups for contained compounds
Functional group (X₁ ) When the excess amount of the contained compound is reacted,
Reaction functional group (X₁ ) Polyurethane system where
Resin (A₁ ), The unreacted functional group (X
₁ ) Is a functional group showing a crosslinking reaction with the crosslinking agent (B).
It

[Thermoplastic polyester resin (A ₂ )]
When a polyester resin is used as the thermoplastic resin (A), as the resin, two functional groups (X) showing crosslinking reactivity with a crosslinking agent (for example, an isocyanate group-containing compound) are contained in one molecule. The thermoplastic polyester resin (A ₂ ) having the above is used.

This thermoplastic polyester resin (A ₂ )
Is a compound containing two or more hydroxyl groups (X ₂ ) in one molecule and two or more carboxyl groups (Y ₂ ) in one molecule
It is produced by reacting with a compound containing OH. At that time, the hydroxyl group (X
₂ ) The compound containing a carboxyl group (Y ₂ ) is reacted with an excess amount of the compound containing a carboxyl group (Y ₂ )
₂ ) When a compound containing a hydroxyl group (X ₂ ) is reacted in excess with respect to a compound containing ₂ ), an unreacted functional group (X ₂ ) or (Y
₂₎ it is possible to obtain a polyester resin remaining in the molecule (A _2).

Examples of such thermoplastic polyester resin (A ₂ ) include glyptal resin; aromatic or aliphatic polyester resin containing terephthalic acid, isophthalic acid, maleic acid or the like as an acid component; and oxy acid. Examples thereof include polyester resins as raw materials, and the unreacted functional groups (X ₂ ) or (Y ₂ ) in these polyester resins (A ₂ ) are functional groups that show a crosslinking reaction with the crosslinking agent (B). Will be the basis.

[Thermoplastic Polyethylene Resin (A ₃ )]
When a polyethylene resin is used as the thermoplastic resin (A), as the resin, two functional groups (X) exhibiting crosslinking reactivity with a crosslinking agent (for example, an isocyanate group-containing compound) are contained in one molecule. The thermoplastic polyethylene resin (A ₃ ) having the above is used.

These thermoplastic polyethylene resins (A
₃ ) can be obtained by reacting ethylene with an ethylenically unsaturated carboxylic acid having a carboxyl group, and the carboxyl group in the polyethylene resin (A ₃ ) is crosslinked with the crosslinking agent (B). It becomes a functional group showing the property.

Incidentally, in order to improve the strength of the resin coating film in order to improve the performance such as abrasion resistance, punching workability, and film blackening resistance in the press working and punching carried out before the heat baking joining, As the polyethylene-based resin (A ₃ ), it is also possible to use a copolymerizable monomer such as an acrylic ester or styrene in addition to both ethylene and an ethylenically unsaturated carboxylic acid to prepare an ethylene copolymer resin. Also included in the preferable thermoplastic polyethylene-based resin (A ₃ ).

[A mixture of two or more thermoplastic resins (A
₄ )] As described above, in the present invention, as the thermoplastic resin (A), two or more kinds of the above-mentioned polyurethane resin (A ₁ ), polyester resin (A ₂ ) and polyethylene resin (A ₃ ) are mixed. It is also possible to use this mixed resin (A
_{As 4} ), those having two or more functional groups showing cross-linking reactivity with a cross-linking agent (for example, an isocyanate group-containing compound) in one molecule are used.

As a concrete combination of them,
Polyurethane resin (A₁ ) And polyester resin (A
₂ ), A polyester resin (A₂ ) And Polyech
Len resin (A₃ ) Mixture, polyethylene resin (A
₃ ) And polyurethane resin (A ₁ ) Mixture, polyuret
Tan resin (A₁ ) And polyester resin (A₂ ) And po
Polyethylene resin (A₃ ) And a mixture thereof.

[Details of Crosslinking Agent (B)] In the present invention,
As a preferable cross-linking agent (B) used for the cross-linking reaction with the thermoplastic resin (A), there may be mentioned a blocked isocyanate group-containing compound, which is obtained by reacting an organic polyisocyanate compound with a known blocking agent. Obtainable. At this time, the thermal dissociation temperature of the blocking agent from the isocyanate group can be appropriately adjusted by appropriately selecting the types of the organic polyisocyanate compound and the blocking agent.

In selecting the blocking agent, it is preferable to select a blocking agent having a boiling point higher than the thermal crosslinking reaction temperature so that the blocking agent dissociated during the thermal crosslinking reaction does not boil and foam.

Specific preferred examples of such a blocking agent include phenols such as phenol and cresol; alcohols such as methanol, ethanol and butyl cellosolve; lactams such as ε-caprolactam; oximes such as methylethylketoxime and cyclohexanone oxime. Known blocking agents such as active methylene type such as dimethyl malonate and ethyl acetoacetate. Next, the raw materials for producing the resin (A) and the cross-linking agent (B) that compose the resin coating film in the present invention will be described in detail below.

[0079] crosslinking agent [raw material of thermoplastic polyurethane resin _{(A 1)] (B)} ( for example, an isocyanate group-containing compound) thermoplastic polyurethane resin (A ₁ having a functional group (X) having reactivity with the As a raw material for producing), a known polyvalent hydroxyl compound (2 in 1 molecule)
Compounds having two or more hydroxyl groups), polyvalent amino compounds (compounds having two or more amino groups in one molecule), polyvalent aminohydroxyl compounds (compounds having two or more hydroxyl groups and amino groups in one molecule) ) And the like.

As the polyvalent hydroxyl compound, ethylene glycol, diethyl glycol, butanediol,
Polyhydric alcohols such as propylene glycol, hexanediol, polypropylene glycol, 3-methyl-1,5-pentanediol, 1,4-cyclohexanedimethanol, dihydroxyethyl terephthalate, hydroquinone dihydroxyethyl ether trimethylolpropane, glycerin and pentaerythritol. An alkylene derivative synthesized from the above polyhydric alcohols and bisphenol A, bisphenol S, hydrogenated bisphenol A, dibromobisphenol A, etc .; the above polyhydric alcohols or their alkylene derivatives and polyvalent carboxylic acid, polycarboxylic anhydride Compounds, ester compounds synthesized from polycarboxylic acid esters; polycarbonate polyols, polytetramethylene glycols, polycaprolactone polyols, and polycarboxylic acid esters. Butadiene polyols, polythioether polyols, polyacetal polyols, polyol compounds such as castor oil polyols, and the like.

Examples of the polyvalent amino compound include ethylenediamine, propylenediamine, diethylenetriamine, hexylenediamine, triethylenetetramine, tetraethylenepetamine, isophoronediamine, xylylenediamine, diphenylmethanediamine and hydrogenated diphenylmethanediamine. Examples of the polyvalent aminohydroxyl compound include diethanolamine and 3-aminopropanol.

[0082] crosslinking agent [raw material of the thermoplastic polyester-based resin _{(A 2)] (B)} ( for example, an isocyanate group-containing compound) thermoplastic polyester resin having a functional group (X) having a reactivity with (A ₂ As a raw material for producing), a known polyvalent hydroxyl compound (2 in 1 molecule)
And a polybasic acid (a compound having two or more carboxyl groups in one molecule) or an anhydride thereof.

Examples of polybasic acids and anhydrides include phthalic anhydride, phthalic acid, terephthalic acid, isophthalic acid, tetrachlorophthalic anhydride, succinic acid, adipic acid, sebacic acid, azelaic acid and hexahydrophthalic anhydride. To be It is also possible to share an intramolecular condensate of an oxyacid, an unsaturated polybasic acid, etc., and also use a small amount of a monobasic acid (for example, benzoic acid etc.) together in order to adjust the hardness and molecular weight of the coating film. You can also

As the polyhydric hydroxyl compound, ethylene glycol, propylene glycol, diethylene glycol, glycerin, 1,3-butylene glycol, neopentyl glycol, trimethylolpropane, pentaerythritol, sorbitol, butanediol, 4-
Examples thereof include hydroxyethoxyphenol propane and glycerin monoallyl.

[0085] Production of Thermoplastic polyethylene resin (A ₃₎ of the raw material] crosslinking agent (B) (for example, an isocyanate group-containing compound) thermoplastic polyethylene resin having a functional group reactive with (A ₃₎ As a raw material for this, ethylene and one or more ethylenically unsaturated carboxylic acids such as (meth) acrylic acid, maleic acid and itaconic acid are used.

Further, together with the ethylenically unsaturated carboxylic acid, for example, (meth) acrylate such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, etc.
Acrylic ester; Styrene-based monomers such as styrene, vinyltoluene and chlorostyrene; Hydroxyethyl (meth) acrylate, Hydroxyalkyl (meth) acrylate such as hydroxypropyl (meth) acrylate; N-Methylol (meth ) N-substituted (meth) acrylamides such as acrylamide; epoxy group-containing (meth) acrylates such as glycidyl (meth) acrylate;
It is also possible to use one type or two or more types together such as (meth) acrylonitrile.

[Raw Material of Blocked Isocyanate Group-Containing Compound] The organic polyisocyanate-based compound which is a raw material for producing the blocked isocyanate group-containing compound suitably used as the cross-linking agent (B) includes aromatic compounds and fatty compounds. A group-type or alicyclic-type isocyanate compound may be used alone or in combination of two or more, and specific examples thereof include tolylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, naphthylene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, hydrogen. Isocyanates such as added diphenylmethane diisocyanate, hydrogenated toluene diisocyanate, and tetramethylene xylylene diisocyanate; burette compounds and iso compounds of the above isocyanates Cyanurate products; the isocyanates of the compound by addition reaction of a polyhydric hydroxy compound such as trimethylol propane.

[Method for Providing Water-Solubility (Hydrophilicity) to Resin (A) and Crosslinking Agent (B)] The polyurethane resin (A
₁ ), a thermoplastic resin (A) such as a polyester resin (A ₂ ) or a polyethylene resin (A ₃ ), or a crosslinking agent (B) such as a blocked isocyanate group-containing compound or an aziridinyl group-containing compound By introducing an anionic hydrophilic group, a cationic hydrophilic group, a nonionic hydrophilic group or the like by a known method or by adding a surfactant to the reaction system, the thermoplastic resin (A) or the crosslinking agent ( B) can be made hydrophilic, and coating workability can be improved by making the coating liquid water-soluble or water-dispersible.

[Blending Ratio of Thermoplastic Resin (A) and Crosslinking Agent (B)] Functional group (X) showing crosslinking reactivity with the crosslinking agent (B).
The preferred blending ratio of the thermoplastic resin (A) and the cross-linking agent (B) is, in terms of the equivalent ratio of the functional groups of both, the functional group (X) in the resin (A) and the cross-linking agent (B). The equivalent ratio to the functional group is 1: 0.5 to 1: 2, more preferably 1 :.
The range of 0.8 to 1: 1.5 is preferable.

The reason for this is that if the equivalent ratio range in terms of functional groups is outside the above range, even after the coating film obtained by coating and drying is heated and baked, it remains in the resin (A) or the crosslinking agent (B) in the coating film. This is because a large amount of unreacted functional groups remain in () and heat resistance and solvent resistance after heating and baking are insufficient.

When the addition amount of the cross-linking agent (B) is extremely small, the partial cross-linking reaction of the resin (A) can be sufficiently performed at the film-forming step by coating / drying or the low-temperature heat treatment after drying. It may not occur, and the chemical resistance and workability of the coating film before heating and baking or the corrosion resistance after processing may be insufficient,
On the contrary, when the amount of the crosslinking agent (B) added is excessive, the total amount of the compounded crosslinking agent (B) is crosslinked with the resin (A) in the film-forming step by coating / drying or low-temperature heat treatment after drying. When reacted, the chemical resistance and workability of the coating film before baking and joining, and the corrosion resistance after processing are improved, but not only the thermoplasticity does not develop at the initial stage of baking and joining, but also high bonding due to the crosslinking reaction. It becomes difficult to obtain strength, and the heat-sensitive adhesiveness intended in the present invention cannot be effectively exhibited.

The preferable blending ratio of the resin (A) and the crosslinking agent (B) is as described above, but the resin (A) in the case where these are preliminarily reacted (partially crosslinked) in the coating film. The degree of partial cross-linking between the cross-linking agent (B) and the cross-linking agent (B) is such that a sufficient amount of a functional group capable of causing a sufficient cross-linking reaction between the resin (A) and the cross-linking agent (B) remains in the heating and baking step for bonding. Should be considered.

[Regarding Adhesion of Resin Coating] The adhesion of the resin coating formed on the surface of the metal plate varies slightly depending on the type of adherend, and therefore cannot be determined unconditionally. 0.5 g / m in terms of solid content after drying in order to ensure sufficient adhesive strength per unit area
² or more, preferably it is desirable to 1 g / m ² or more. However, when the coating film adhesion amount is less than 0.5 g / m ² , the surface of the metal plate cannot be sufficiently covered with the coating film, and there is a tendency that defective bonding is partially caused. .

On the other hand, the upper limit value of the coating amount of the resin coating film is not particularly limited from the viewpoint of the adhesive strength, but an excessively large coating amount is a factor of coating material cost per unit treated area. Not only does this lead to an increase, but the drying time after application of the treatment liquid becomes longer, and the line speed is forced to decrease in the continuous coating line process that is preferably adopted for practical use, which results in a decrease in productivity and a corresponding increase in manufacturing costs. Problems arise. From such a point, the amount of the resin coating film deposited is 30 g / m ² or less, more preferably 10 g / m ² or less.
It is preferable to set it to g / m ² or less.

[Allowable Additives to Coating Liquid (S) and Modification of Resin (A)] Preparation of coating liquid (S) containing thermoplastic resin (A) and crosslinking agent (B) as essential components Is a diluent solvent, an anti-skinning agent, a leveling agent, within a range that does not impair various performances such as adhesiveness intended in the present invention.
Various additives such as defoaming agents, penetrants, film-forming aids, color pigments, thickeners, etc., or finely divided silica, colloidal silica, silane coupling agents, etc. for improving adhesion and corrosion resistance are added as appropriate and applied. It is also possible to further enhance the membrane performance or add a new function.

Further, in order to further improve the weather resistance, hardness, shear strength, etc. of the coating film, a part of the resin (A) may be modified with acrylic resin or epoxy resin, and the cost of the resin (A) may be reduced. For the purpose, various resins such as polyvinyl alcohol resin, SBR resin, chloroprene resin, NBR resin, acrylic resin, vinyl chloride resin, vinyl acetate resin, ethylene / vinyl acetate resin are appropriately mixed within a range not impairing the original characteristics of the present invention. It is also possible to do so. Next, a method for producing the heat-sensitive adhesive resin-coated metal plate according to the present invention will be described.

The resin-coated metal plate is coated with the coating solution (S) containing the above-mentioned thermoplastic resin (A) and crosslinking agent (B) as essential components on the surface of the metal plate by an arbitrary coating method.・
It can be obtained by drying and forming a film on the surface of a metal plate.

The drying temperature at this time is set to a temperature slightly lower than the temperature at which the crosslinking reactivity of the crosslinking agent (B) develops, and the crosslinking agent (B) and the resin (A) are appropriately partially crosslinked. It does not cause stickiness or blocking on the surface of the coating after coating and drying, and it does not easily scratch the coating in various processing steps before baking and bonding, and it has excellent processability, and it is degreased with various organic solvents. Even if
It is possible to form a coating film that is hard to dissolve in an organic solvent and has excellent chemical resistance.

As described above, by making the coating film before baking and joining less susceptible to chemical or mechanical damage,
It is possible to maintain a healthy coating film that has excellent corrosion resistance after processing and does not cause defective bonding.

However, if the cross-linking reaction between the thermoplastic resin (A) and the cross-linking agent (B) is excessively advanced in the coating / drying step (that is, cross-linking is advanced beyond the stage of partial cross-linking),
The resulting coating film has no stickiness or blocking problems and has better chemical resistance, workability, and post-processing corrosion resistance, but loses thermoplasticity and is heated at the time of heating for subsequent bonding. Such a leveling effect and the effect of enlarging the effective bonding area cannot be exhibited, and since there are no crosslinking points for the crosslinking reaction that should proceed during baking, it becomes difficult to obtain a high level of bonding strength.

Therefore, the drying temperature after coating of the coating liquid (S) containing the thermoplastic resin (A) and the crosslinking agent (B) is the temperature at which the crosslinking agent (B) exhibits the thermal crosslinking reactivity for partial crosslinking. Although it is necessary that the temperature is not less than the above, it is necessary to appropriately adjust the drying temperature and the drying time to keep the crosslinking reaction within the range of partial crosslinking, and a preferable drying temperature therefor is a thermoplastic resin ( Since it varies depending on the type of A) and the cross-linking agent (B), it cannot be uniformly determined, but it is about 80 to 120 ° C. if shown as a standard range.

When the coating film drying temperature after coating cannot be raised to a temperature higher than the crosslinking reactivity developing temperature of the crosslinking agent (B) due to constraints on the manufacturing line, manufacturing process, etc., coating / drying is performed. After the film formation by (1), heat treatment is carried out for a short time at a temperature higher than the crosslinking reactivity expression temperature of the crosslinking agent (B) to cause partial crosslinking between the resin (A) and the crosslinking agent (B). It is possible to prevent blocking between each other and ensure chemical resistance, workability, and corrosion resistance after processing of the coating film, and such a method is also included in the technical category of the present invention.

Furthermore, in the coating / drying process, the above-mentioned temperature required for the partial crosslinking reaction cannot be obtained, and further, the equipment which cannot perform the low temperature heat treatment required for the partial crosslinking even after the film formation is used. In the case of applying, the resin (A) and the cross-linking agent (B) are previously prepared at the stage of the coating liquid (S) before coating on the surface of the metal plate.
It is also possible to obtain the resin-coated metal plate of the present invention by partially cross-linking and, and applying and drying the coating liquid (S) containing the partially cross-linked thermoplastic resin (A ′). It is included in the category of.

When such a partially cross-linked coating solution (S) is used, the cross-linking agent (B) and the resin (A) are used in the coating / drying process.
It is not necessary to partially crosslink and, therefore, it is also possible to dry at a temperature lower than the temperature at which the crosslinking reactivity of the crosslinker (B) develops, the drying conditions are less restricted, and there is no need to perform a separate low temperature heat treatment. Therefore, it is recommended as one of the preferred means.

[Heat Baking Treatment for Joining] The heat-sensitive adhesive resin-coated metal sheet according to the present invention is punched into a predetermined shape as described above, and the portions to be joined are overlapped and joined by heating and baking. However, in that case, the heating and baking temperature is not less than the thermoplasticizing temperature of the resin (A) and not less than the crosslinking reactivity developing temperature of the crosslinking agent (B), and preferably under the temperature condition of 250 ° C. or less. By doing so, high bonding strength can be obtained.

That is, at a heating and baking temperature lower than the thermoplastic development temperature of the resin (A), the softening and fluidity of the resin in the initial step of heating and baking are poor, and the leveling effect at the bonding interface is not effectively exerted, so that it is uniform. Therefore, a high level of adhesive strength intended by the present invention cannot be obtained. Further, when the heating and baking temperature is lower than the crosslinking reactivity manifestation temperature of the crosslinking agent (B) [for example, when the crosslinking agent (B) is a blocked isocyanate group-containing compound, the blocking agent dissociation temperature], Cross-linking reaction between the cross-linking agent (B) contained in the coating film and the resin (A) does not occur [for example, when the cross-linking agent (B) is a blocked isocyanate group-containing compound, The dissociation of the blocking agent does not occur and the active isocyanate group does not occur, so that the crosslinking reaction with the resin (A) does not occur], and the desired high level of bonding strength cannot be obtained.

On the other hand, at a heating and baking temperature above 250 ° C., the crosslinking reaction between the crosslinking agent (B) and the resin (A) proceeds sufficiently and quickly, while the thermal decomposition of the resin (A) proceeds. As a result, the coating film components may be deteriorated and the adhesive strength and the like may be rather lowered, and further, the yellowing due to the decomposition of the resin (A) may progress to deteriorate the appearance.

For the above reasons, the heating and baking temperature for joining is not less than the thermoplasticizing temperature of the resin (A) and not less than the temperature at which the crosslinking agent (B) exhibits the thermal crosslinking reactivity, and preferably 2
It is recommended that the temperature is 50 ° C. or lower, more preferably 200 ° C. or lower.

[Specific Example of Heating and Baking Method] The heat-sensitive adhesive resin-coated metal sheet of the present invention can be widely applied as, for example, automobiles, household electric appliances, outer panel materials for metal furniture, building materials and the like. However, in its practical application, various paints (for example, acrylic paints, melamine paints, polyester paints, fluorine paints, etc.) are applied to parts other than the joining surface at any time before or after heat baking joining.
Various coating methods (for example, spray method, electrostatic coating method,
It is also possible to apply the coating by an electrodeposition method or the like) and simultaneously carry out the baking treatment of these coating films and the cross-linking joining by heating and baking the joint surfaces of the coating films.

For example, the resin-coated metal plate according to the present invention is punched into a predetermined shape, and after caulking two of them,
Various topcoat paints as described above are applied to the surface, and the heat of heat treatment for baking and curing the paint is used to simultaneously cause a crosslinking reaction on the joint surface of the heat-sensitive adhesive resin coating film,
It is also possible to develop a high degree of adhesive strength at the joint.

By adopting such a method, the baking treatment of the top coat film and the joining by the crosslinking reaction of the heat-sensitive adhesive coat film can be carried out at the same time, which has an advantage that the manufacturing process can be further simplified.

By the way, as described above, the coating liquid for forming the heat-sensitive adhesive resin coating film in the present invention is preferably water-dispersible or water-soluble. It is as follows.

First, in the case of the water-based resin, it is not necessary to provide special exhaust treatment equipment for exhausting the organic solvent component gas, which is necessary when using the solvent-based resin liquid in the resin coating line, and the equipment cost is reduced. It Further, when a resin solution is applied, for example, when a plated metal plate or a chemical conversion treatment metal plate is used as the original plate, the resin coating equipment is provided in the existing plating treatment line or chemical conversion treatment line to make the production continuous. And productivity is increased.

When the coating liquid is of an organic solvent type, the solid content and viscosity of the coating liquid change with time due to the volatilization of the solvent, which not only causes uneven coating, but also makes it difficult to control the coating amount of the coating. . However, if the coating liquid is water-dispersible or water-soluble, the amount of water volatilized from the coating liquid is extremely small, so there is little change in solid content or viscosity over time, stable coatability is obtained, and adhesion Quantity control is also easy.

There is no particular limitation on the method of applying the above resin-containing coating liquid to the surface of a metal plate, but as a general method, for example, the surface is cleaned or pretreatment (for example, phosphate treatment, chromate treatment). As a preferred method, the coating solution is continuously applied to one surface or both surfaces of the metal plate surface using a roll coater method, a spray method, a curtain flow coater method, etc. Can be mentioned. Among them, the method of applying by a roll coater is most practically preferable in consideration of the uniformity of the thickness of the coating film in the longitudinal direction and the width direction of the metal strip, the coating treatment cost, the coating efficiency, and the like.

The type of the base metal plate used in the present invention is not limited at all, and various alloy steel plates such as the most common mild steel plates and stainless steel plates, as well as Al and Al alloy plates, Cu and Cu alloy plates are used. , Ti and Ti alloy plates,
Plated metal plate (zinc and zinc alloy-based plated steel plate, Al
And Al alloy-based plated steel sheets, copper-based plated steel sheets, Ni-based plated steel sheets, Cr-based plated steel sheets, various plated metal sheets such as zinc-based plated Al and Al alloy sheets), chemical conversion treatment (phosphate treatment, chromate treatment, etc.) A wide variety of metal plates and coated metal plates can be applied.

[0117]

EXAMPLES Examples of the present invention will now be described. However, the present invention is not limited by the following examples, and the present invention may be carried out with appropriate modifications within a range compatible with the gist of the preceding and the following. Of course, it is possible, and all of them are included in the technical scope of the present invention. In preparing various resin coating solutions for coating a metal plate, as shown in Table 1, a thermoplastic resin (A) having various functional groups and physical properties and a crosslinking agent (B) were used, and the solid content concentration was 30%. A coating solution (S) of ˜50% aqueous dispersion was prepared.

[0118]

[Table 1]

Among the coating solutions shown in Table 1, No.
A to F are mixed so that a functional group present in the thermoplastic resin (A) and an isocyanate group or an aziridinyl group present in the cross-linking agent (B) in an equivalent conversion ratio; B / A are suitable ratios. Adjusted ratio, coating liquid No. G to I are those in which the thermoplastic resin (A) has no functional group capable of reacting with the crosslinking agent (B), and the coating liquid No. J to L respectively represent those in which the cross-linking agent (B) was not blended.
The thermoplastic expression temperature of the resin (A) and the thermal crosslinkability expression temperature of the crosslinking agent (B) shown in Table 1 were measured by the following methods.

[Method for Measuring Thermoplastic Development Temperature] A film obtained by applying a resin solution on a Teflon plate and drying it at 60 ° C. is placed on a hot plate heated to a predetermined temperature, and the temperature at which the resin film melts is set. It measured and made it the thermoplasticity development temperature.

[Measurement Method of Thermal Crosslinking Development Temperature] The film obtained by applying the resin solution on a Teflon plate and drying at 60 ° C. was subjected to differential thermal analysis to measure the dissociation temperature of the blocking agent to reveal the thermal crosslinking property. Temperature. On the other hand, electro-pure Zn-plated steel plate (coating weight: 20 g / m ² , plate thickness 0.6 mm)
Chromate treatment on the surface of (the amount of chromate adhered: 4
0 mg / m ² ) was used as a metal plate, and each of the coating solutions A to L shown in Table 1 was applied to the surface of the metal plate by a roll coater to give a predetermined film thickness. Each resin-coated steel sheet obtained by drying at a temperature shown in Tables 2 to 5 while being transferred in a hot air drying furnace was subjected to the following performance evaluation test.

[Performance Evaluation after Coating / Drying (Before Heating and Baking for Bonding)] (1) Workability (Scratch resistance; Coating hardness) The coating film hardness of the coated metal plate after coating / drying is determined by JIS. -K5
It was measured by a pencil hardness test specified by 400 to evaluate the scratch resistance of the coating film surface. For the determination, the coating film surface was scratched a total of 5 times with a pencil of each hardness, and the pencil hardness one rank below with two or more scratches was defined as the coating film hardness. The evaluation criteria are as follows. ◎ Excellent: Pencil hardness H or higher ○ Good: Pencil hardness HB to F × Poor: Pencil hardness B or lower

(2) Chemical resistance The coated metal plate after coating and drying is cut into a size of 70 mm × 150 mm as a test material, and the surface of each test material is slid 10 times with gauze containing toluene. Then, the deterioration state of the coating film was evaluated according to the following criteria. ◎ Excellent: No abnormality ○ Good: Slightly swelled × Poor: Dissolved coating film

(3) Corrosion resistance after processing (white rust resistance after processing) The coated metal plate after coating and drying was processed with an Erichsen tester to a height of 6 mm, and the corrosion resistance after processing was measured by JI.
It was evaluated by the 5 wt% salt spray test shown in SZ-2371. Corrosion resistance is based on the electrical pure Z in the lower layer of the coating.
The 1% white rust generation time due to corrosion of the n-plated layer was measured, and the white rust resistance was evaluated according to the following criteria. ◎ Excellent: White rust occurred at 240 h or more. ○ Good: White rust occurred at 120 to 240 h. △ Slightly inferior: White rust occurred at 48 to 120 h. × Inferior: White rust occurred within 48 h.

[Performance Evaluation after Heat Baking Treatment] (4) Adhesion between Coating Films (Heat Sensitive Self-Adhesive Strength) After coating and drying the coated metal plate into a size of 25 mm × 100 mm, the coating film surfaces were cut off from each other. 25 mm x 12 mm
A simple lapping material (single lap joint) is produced by superimposing it in the area of. This laminated material is shown in Table 2
2 at the temperature shown in 5 (bonding temperature) with a hot press machine.
After pressurizing for 0 minutes (3 kgf / cm ² ), cooling, subjecting each test piece to a uniaxial tensile test according to JIS K-6850, the maximum load until the test piece breaks at room temperature Was measured and this value was divided by the shear cross-sectional area to obtain the shear adhesive strength. The evaluation criteria are as follows. ◎ excellent: the adhesive strength 150 kgf / cm ² or more ○ Good: adhesion strength 80~150kgf / cm ² △ slightly inferior: adhesive strength 50~80kgf / cm ² × poor: less than the adhesive strength 50 kgf / cm ²

(5) Adhesion with cloth (90 ° peel strength) After coating and drying, the coated metal plate was cut into a size of 70 mm × 150 mm, and then 25 mm × 12 of cotton cloth was applied to the surface of the coating film.
Overlap with an area of 0 mm. This laminated material is shown in Table 2.
After pressurizing (3 kgf / cm ² ) for 20 minutes with a heating press device at the temperatures (adhesion temperature) shown in 5 to 5, it is cooled.

The test piece thus obtained was held horizontally in a uniaxial tensile tester, and 3 from the joining end of the cotton canvas attached to the test piece.
After the length of 0 mm was previously peeled off by hand, the average load until the cotton cloth peeled from the test piece was measured at room temperature while maintaining the angle between the cloth and the test piece to be always vertical. Two
The peel adhesion strength per 5 mm was determined. The evaluation criteria are as follows. ◎ Excellent: Adhesive strength 10 kgf / 25 mm or more ○ Good: Adhesive strength 8 to 10 kgf / 25 mm △ Slightly inferior: Adhesive strength 5 to 8 kgf / 25 mm × Inferior: Adhesive strength less than 5 kgf / 25 mm

(6) Adhesion durability (deterioration of adhesiveness over time) After coating and drying, the coated metal plate was cut into a size of 30 mm × 75 mm, and the coating film surfaces were overlapped with each other in an area of 30 mm × 10 mm. A simple laminated material (single lap joint) was produced. This laminated material is shown in Table 2
As shown in FIG. 5, a heating press was used to apply pressure (3 kgf / cm ² ) for 20 minutes at a predetermined temperature (bonding temperature), and then cooled.

The obtained test piece was tested according to JIS K-6857.
In accordance with the above, a constant temperature and humidity test is performed under the following conditions, and then a uniaxial tensile test similar to that described in (4) above is performed to obtain durability of adhesive strength (deterioration of adhesive property with time). ) Was investigated. [Constant temperature and humidity test] -Temperature: 25 ° C-Relative humidity: 90% RH-Test time: 720h The evaluation criteria are as follows.

◎ Excellent: Adhesive strength 130 kgf / cm ² or more ○ Good: Adhesive strength 70 to 130 kgf / cm ² △ Slightly inferior: Adhesive strength 40 to 70 kgf / cm ² × Inferior: Adhesive strength less than 40 kgf / cm ^2.

(7) Heat Resistant Adhesion After coating and drying, the coated metal plate is cut into a size of 30 mm × 75 mm, and the coating film surfaces are overlapped with each other in an area of 30 mm × 10 mm. ) Was produced. This laminated material is shown in Table 2
As shown in 5, a heating press device having a predetermined temperature (adhesion temperature) was used to apply pressure (3 kgf / cm ² ) for 20 minutes and then cooled.

The obtained test piece was subjected to a uniaxial tensile test in the atmosphere of 60 ° C. in the same manner as in the above (4) to examine the adhesive strength (heat resistant adhesiveness) in a high temperature environment. The evaluation criteria are as follows. ◎ Excellent: Adhesive strength of 80 kgf / cm ² or more ○ Good: Adhesive strength of 50 to 80 kgf / cm ² × Poor: Adhesive strength of less than 50 kgf / cm ^2.

(8) Corrosion resistance (white rust resistance) In order to evaluate the corrosion resistance after baking, first, the coated metal plate after coating and drying was cut into a size of 70 mm × 150 mm, and a predetermined temperature as shown in Tables 2-5. After heat-baking, the end face and the back face were tape-sealed, and then subjected to a 5 wt% salt spray test defined by JIS Z-2371 in the same manner as (3) above.

The corrosion resistance was evaluated by the white rust resistance, that is, the time until 1% white rust was generated by the corrosion of the electric pure Zn plating layer under the coating film. The evaluation criteria are as follows. ◎ Excellent: White rust occurred at 240 h or more. ○ Good: White rust occurred at 120 to 240 h. △ Slightly inferior: White rust occurred at 48 to 120 h. × Inferior: White rust occurred within 48 h.

(9) Chemical resistance In order to evaluate the chemical resistance of the resin coating film after baking, first the coated metal plate after coating and drying was cut into a size of 70 mm × 150 mm, and as shown in Tables 2-5. Bake at a predetermined temperature. The surface of the obtained test piece was slid 20 times with gauze containing toluene, and the deterioration state of the coating film was visually evaluated. The evaluation criteria are as follows. ◎ Excellent: No abnormality ○ Good: Slightly swelling degree × Inferior: Dissolution of coating film The above performance evaluation test results are shown in Tables 2 to 5.

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[Table 2]

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[Table 3]

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[Table 4]

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[Table 5]

From these results, the following can be considered. Coating liquids A to F having functional groups for cross-linking defined in the present invention in a suitable equivalent ratio are used, and the coating liquids are formed on the surface of the steel sheet under conditions that satisfy the preferable amount of adhesion, drying temperature and baking temperature. The coated steel sheet of the present invention obtained as described above has excellent workability in a state after coating and drying, corrosion resistance after processing, and chemical resistance, and has excellent inter-coating adhesiveness and a cloth in a state after heating and baking. It can be seen that it has adhesiveness, adhesive durability, heat resistant adhesiveness, corrosion resistance, and chemical resistance.

On the other hand, even when the coating liquids A to F satisfying the preferable conditions defined by the present invention are used, the amount of coating film adhered is extremely small, and a large number of coating film defects occur, or bonding is performed. Insufficient coating thickness can be obtained: -The heating and baking temperature is lower than the thermal crosslinking reactivity manifesting temperature of the crosslinking agent (B), and the crosslinking agent (B) and the resin (A) are crosslinked in the heating and baking step. The reaction has not progressed, -The heating and baking temperature is very high, and the coating film is thermally deteriorated.-The drying temperature is low and the resin (A) and the cross-linking agent (B) are used in the coating and drying process. No partial cross-linking reaction has occurred.-The drying temperature is extremely high, and the cross-linking reaction between the resin (A) and the cross-linking agent (B) has progressed too much in the coating / drying process. At least one of corrosion resistance after processing, chemical resistance, and various types of adhesion It has become insufficient.

Particularly, in the case where the drying temperature is excessively high in the step of coating and drying the coating film, the blocking agent of the blocked isocyanate group is dissociated during the drying, or the reaction with the aziridinyl group-containing compound causes the coating. The crosslinking reaction between the resin (A) and the crosslinking agent (B) in the film actively proceeds,
Since the thermoplasticity disappears due to the curing reaction of the coating film, in the subsequent heat-baking joining step, the integration and cross-linking reaction of the adhesive surfaces between the coating film surfaces hardly occur, and the heat-sensitive adhesiveness which is the maximum object of the present invention is You won't get it.

Further, as to the coating liquids G to I, since the thermoplastic resin (A) in the coating liquid does not have a functional group exhibiting crosslinking reactivity with an isocyanate group or an aziridinyl group as described above, -The workability of the coating film after drying, the corrosion resistance after processing, and the chemical resistance are extremely poor. Moreover, even if the coating film is heated and baked, only the effect of increasing the adhesive strength can be obtained due to the fusion and integration of the joining surfaces brought about by the thermoplasticity, and the coating surface surfaces and the coating surface and the adherend surface are cross-linked. Since the effect of enhancing the adhesive strength due to the reaction is not exhibited, and the coating film remains thermoplastic even after heating and baking,
It can be seen that performances such as high temperature adhesiveness and solvent resistance are insufficient.

With respect to the coating solutions J to L, since the coating solution does not contain the crosslinking agent (B), the resin (A) is also used.
As with the case of using the coating liquids G to I, no cross-linking reaction occurs with the processability of the coating film after coating and drying, the corrosion resistance after processing,
Not only has poor chemical resistance, but even after heating and baking
Since the thermoplasticity is maintained, it can be seen that performances such as high temperature adhesiveness and solvent resistance are insufficient.

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EFFECTS OF THE INVENTION Since the present invention is constituted as described above, it does not cause stickiness or blocking in a coated / dried state, and has workability of a film during slitting or punching, corrosion resistance after processing, and an organic solvent. It is also excellent in chemical resistance against heat, etc., and after heat baking for bonding, it is a heat-sensitive adhesive that can exhibit excellent adhesiveness, adhesive durability, high temperature adhesiveness, chemical resistance, corrosion resistance, etc. It has become possible to provide a metal plate coated with a transparent resin.

Claims (8)

[Claims] 1. A metal plate comprising a coating solution (S) containing a thermoplastic resin (A) having a functional group (X) exhibiting thermal crosslinking reactivity in the molecule and a heat-sensitive crosslinking agent (B) as essential components. In a heat-sensitive adhesive resin-coated metal plate obtained by coating and drying on the surface, the thermoplastic resin (A) at the resin coating stage before heat bonding
The coating film in which the functional group (X) therein and the heat-sensitive crosslinking agent (B) are partially crosslinked has a solid content of 0.5 to 30 g / m 2.
A heat-sensitive adhesive resin-coated metal plate, characterized in that it is formed on at least one side of the metal plate with an adhesion amount of ² . 2. The thermoplastic resin (A) in the coating liquid (S) is partly a thermoplastic resin (A ′) which has been partially cross-linked in advance with the heat-sensitive crosslinking agent (B). Thermosensitive adhesive resin coated metal plate. 3. The thermosensitive crosslinking agent (B) is a blocked isocyanate group-containing compound, and the thermoplastic resin (A).
Functional group (X) present in the molecule of the compound and exhibiting thermal crosslinking reactivity
Is one or two of a hydroxyl group, an amino group and a carboxyl group
The heat-sensitive adhesive resin-coated metal plate according to claim 1 or 2, which comprises at least one kind. 4. The thermosensitive crosslinking agent (B) is an aziridinyl group-containing compound, and the functional group (X) present in the molecule of the thermoplastic resin (A) and exhibiting thermal crosslinking reactivity is a hydroxyl group or an amino group. The heat-sensitive adhesive resin-coated metal sheet according to claim 1 or 2, which comprises one or more of carboxyl groups. 5. A thermoplastic resin (A) selected from the group consisting of a polyethylene resin, a polyester resin, and a polyurethane resin having a functional group (X) showing a thermal crosslinking reactivity with a heat-sensitive crosslinking agent (B). The heat-sensitive adhesive resin-coated metal plate according to any one of claims 1 to 4, which is one kind or two or more kinds. 6. The heat-sensitive adhesive resin-coated metal plate according to claim 1, wherein the thermoplastic resin (A) is a water-soluble or water-dispersible resin. 7. A metal plate containing a coating solution (S) containing, as essential components, a thermoplastic resin (A) having a functional group (X) exhibiting thermal crosslinking reactivity in its molecule and a heat-sensitive crosslinking agent (B). In the method for producing a heat-sensitive adhesive resin-coated metal plate by coating and drying on the surface, low-temperature heat treatment is performed before or after coating of the coating liquid (S) and before heat-bonding to obtain a thermoplastic resin (A). And a part of the heat-sensitive crosslinking agent (B) are subjected to a partial crosslinking reaction, and a method for producing a heat-sensitive adhesive resin-coated metal plate. 8. The method for producing a heat-sensitive adhesive resin-coated metal plate according to claim 7, wherein the low-temperature heat treatment is performed simultaneously with the drying treatment for forming a film after coating the coating liquid (S).