JPH091730A - Heat-sensitive-adhesive-resin coated metal plate and manufacture thereof - Google Patents

Abstract

PURPOSE: To obtain a metal plate having the excellent bonding strength at a relatively low temperature and heating in a short time by forming a painted film, which has the functional group indicating cross-linking reactivity and the main components comprising a thermoplastic resin, whose thermoplasticity revelation temperature is specified, and two kinds of heat sensitive cross-linking agents, wherein the cross-linking reactivity revelation temparature satisfies a specified requirement, on one surface of the metal plate. CONSTITUTION: The heat-sensitive-adhesice-resin painted metal plate is formed by coating at least one surface of a metal plate with a coating film, wherein a thermoplastic resin A having 80 deg. of the thermoplastic revelation temperature or more and heat sensitive agents B1 and B2 of two kinds having the different corss-linking- reactivity revelation temparatured are main components. Here, the cross-linking- reaction revelation temperatures TB1 and TB2 for the two kinds of heat sensitive cross-linking agents B1 and B2 are selected so as to satisfy the requirement for TB1 <TB2 , and the thermoplastic revelation temperature TA of the thermoplastic resin A is selected so as to satisfy the requirement for TB1 <TB2 . The heat-sensitive-adhesive- resin painted metal plate is obtained by painting and drying the surface coating liquid containing the component on the surface of the metal plate.

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 plate and a method for producing the same. The heat-sensitive adhesive resin-coated metal plate exhibits excellent adhesiveness by heating and is good in a stage before being bonded. It exhibits excellent workability and has excellent corrosion resistance and solvent resistance after adhesion. 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 a non-metallic material such as plastic or cloth to a metal plate, a bonding method using an adhesive or a double-sided adhesive tape is used in most cases. , Thermoplastic resins, thermosetting resins, and elastomers according to their thermal 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, a metal plate is first punched or sheared into a desired shape and then a desired forming process is performed prior to the joining, and then the surfaces of the portions to be joined are 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 electromagnetic steel sheets for lamination, a steel sheet coated with a water-based emulsion type resin has been proposed as shown below.

First, Japanese 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 appliances 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.

This organic resin-coated steel sheet can be joined together by simply laminating, pressurizing and heating the electromagnetic steel sheets, 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. Particularly, when the laminated iron core is heated and becomes high in temperature, 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 the resin coating film of such an organic resin-coated steel sheet for iron core is used for automobiles, home electric appliances,
It is not appropriate to apply it to structural materials such as metal furniture or building materials.

Further, as a steel sheet coated with an organic resin of the same kind for laminated cores, Japanese Patent Publication No. 52-8999 discloses a water-based acrylic resin emulsion coated with a water-soluble phenol resin or a water-soluble melamine resin, 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 adhesive coating film 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 the deterioration of the adhesive strength occurs and the variation of the adhesive strength occurs, but also it is very difficult to control the baking temperature at the time of joining.

Therefore, applying the organic resin-coated steel sheet for laminated iron core described in this publication as it is to automobiles, home electric appliances, steel furniture, building materials, etc. lacks suitability in terms of both performance and construction workability. .

Further, the temperature range and time at the time of incomplete baking, which is pointed out in the resin-coated steel sheet disclosed in Japanese Patent Publication No. 52-8999, is expanded to improve performance and make workability easier. JP-A-55-9815 discloses a magnetic steel sheet coated with an organic resin for adhesion, which is obtained by applying a treatment liquid prepared by mixing a water-soluble emulsion of an acrylic resin with a water-soluble styrene-maleic acid copolymer to the surface of the steel sheet and drying it. .

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, but the acrylic acid group or the acrylic acid ester group is described. The bond between the carboxylic acid and the carboxyl group is not so strong, and the larger the styrene-maleic acid copolymer becomes, the poorer the fluidity and the less chance of bonding with the acrylic resin (crosslinking point). However, no significant effect can be expected in improving the adhesive strength. Moreover, the disadvantage that the time required for lamination and bonding is long and the work efficiency at the time of bonding is poor 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. We developed a new heat-sensitive self-adhesive resin coated steel sheet and completed a patent application.

This heat-sensitive self-adhesive resin-coated steel sheet is 8
A coating film containing a urethane-based resin which is plasticized at a temperature of 0 ° C. or higher and exhibits crosslinking reactivity at a temperature of 0 ° C. or higher, and the coating film before bonding may be sticky or blocking at room temperature. Moreover, it is very useful since it does not have thermoplasticity due to 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, the base resin, which is the main constituent material of the coating film, is a thermoplastic resin, so the coating film in the as-formed state by coating and drying is not 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 organic solvents is insufficient.

Further, the coating film before the heat-crosslinking treatment does not have sufficient film hardness, so that 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.

[0022]

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 bonding force can be obtained by bringing the surfaces to be joined into close contact and then heating and baking at a relatively low temperature for a short time without the need for joining means such as application of a coating agent. Shows excellent workability, post-processing corrosion resistance and chemical resistance, and also heat-sensitive adhesive that can exhibit excellent adhesion, adhesion durability, heat-resistant adhesion, corrosion resistance, solvent resistance, etc. after joining by heating and baking. The present invention aims to provide a metal plate coated with a resin and a method for producing the same.

[0023]

The constitution of the heat-sensitive adhesive resin-coated metal sheet according to the present invention, which has been able to solve the above-mentioned problems, has a functional group exhibiting a cross-linking reactivity in the molecule and has a thermoplasticity developing temperature. Thermoplastic resin (A) having T _A of 80 ° C or higher
And a coating film containing, as a main component, thermosensitive crosslinking agents (B ₁ ) and (B ₂ ) satisfying the following crosslinking reactivity expression temperature is formed on at least one side of a metal plate. Have T _B1 <T _B2 , T _A ≦ T _B2 [where T _B1 and T _B2 are heat-sensitive crosslinking agents (B ₁ ), (B ₂ ).
The cross-linking reactivity developing temperature (° C.) and T _A represent the thermoplasticity developing temperature (° C.) of the thermoplastic resin (A). ]

The thermoplastic resin (A) used in the above has a thermoplastic temperature T _A of 80 to 200.
It is preferably in the range of ℃, and the heat-sensitive crosslinking agent (B
₂ ) preferably has a crosslinking reactivity expression temperature T _B2 of 200 ° C. or lower, and further, the thermosensitive crosslinking agent (B ₁ ) or (B _1
When the crosslinking reactivity developing temperatures T _B1 and T _B2 of ₂ ) satisfy the requirements of the following formula, a heat-sensitive adhesive resin-coated metal plate having further excellent performance can be obtained. T _B2- T _B1 ≧ 30 ℃

Further, the heat-sensitive crosslinking agent (B
Particularly preferred as ₁ ) and (B ₂ ) are both blocked isocyanate group-containing compounds, and particularly preferred as the thermoplastic resin (A) are functional groups showing crosslinking reactivity with isocyanate groups (among others, Preferred is
A resin having in its molecule one or more selected from the group consisting of a hydroxyl group, an amino group and a carboxyl group), and a preferable base resin used as the thermoplastic resin (A) is a polyethylene resin or a polyester. Resins and polyurethane resins can be used alone or in combination of two or more if necessary.
The thermoplastic resin (A) is more effective if it is water-soluble or water-dispersible in consideration of handling properties and the like. Furthermore, in order to effectively exhibit the heat-sensitive adhesiveness and the like of the coating film, the preferable coating amount of the coating film is 0.5 to 30 g / solid basis.
It is in the range of m ² .

The above-mentioned heat-sensitive adhesive resin-coated metal plate is a coating liquid containing the above-mentioned thermoplastic resin (A) and heat-sensitive crosslinking agents (B ₁ ) and (B ₂ ) as main components. Can be easily produced by applying at least one surface of a metal plate and then performing low-temperature heat treatment at a temperature Z (° C.) that satisfies the following conditions. T _B1 ≤Z <T _B2 [where T _B1 and T _B2 have the same meanings as described above]. ]

[0027]

The heat-sensitive adhesive resin-coated metal sheet of the present invention is a thermoplastic resin containing at least one surface of the metal sheet having a thermoplastic temperature T _A of 80 ° C. or higher and a functional group for a crosslinking reaction in the molecule. 2 which has a different cross-linking reactivity expression temperature from (A)
_One of the above two types of heat-sensitive crosslinking agents (B ₁ ) and (B ₂ ) is coated with a coating film containing _two types of heat-sensitive crosslinking agents (B ₁ ) and (B ₂ ) as main components. The crosslinking reactivity expression temperatures T _B1 and T _B2 are selected so as to satisfy the requirements of T _B1 <T _{B2 and} the thermoplastic expression temperature T _A ≦ T _B2 of the thermoplastic resin (A). It More preferably, the thermoplastic resin (A) has a thermoplastic temperature of 80 to 200 ° C.
And the expression temperature of the crosslinking reactivity expression temperature T _B2 of the heat-sensitive crosslinking agent (B ₂ ) is 200 ° C. or lower.

As a preferred specific example of the coating film constituent, one of polyethylene, polyurethane and polyester resins having a functional group exhibiting cross-linking reactivity with isocyanate groups such as hydroxyl group, amino group and carboxyl group, or A thermoplastic resin (A) composed of two or more kinds, and a cross-linking agent (B ₁ ) composed of a blocked isocyanate group-containing compound,
A coating film containing (B ₂ ) as a main component may be mentioned.

The resin-coated metal plate according to the present invention can be obtained by applying a coating solution containing the above components to the surface of the metal plate and drying it. The resin-coated metal plate is in the state of a cut plate product or a coil product. Has no stickiness or blocking property on the surface of the coating film, and has excellent solvent resistance and moderate film hardness despite the fact that the coating film remains thermoplastic, so it is also excellent in scratch resistance. In addition, there is no processing flaw on the coating film surface during slitting, punching, or forming before the joining process.

Furthermore, after that, the resin (A) exhibits thermoplasticity and the cross-linking agents (B ₁ ) and (B ₂ ) are thermally cross-linked in the state where the coating film surfaces are adhered to each other or the coating film surface and the adherend surface are brought into close contact with each other. By heating at a temperature T _B1 , T _B2 or higher at which reactivity is exhibited, a mutual cross-linking reaction between the resin (A) and the cross-linking agent (B ₁ , B ₂ ) or a functional group in the coating film and deposition A binding reaction occurs between the functional groups in the material, and the coating surfaces can be firmly bonded to each other or the coating surface and the adherend surface can be firmly bonded. Further, the coating film after heating and baking loses thermoplasticity, and exhibits excellent properties in solvent resistance, corrosion resistance, high temperature adhesive strength and the like. Hereinafter, the reasons for limitation and preferred embodiments of the heat-sensitive adhesive resin-coated metal sheet according to the present invention 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 the adhesive strength, it is necessary that the resin coating film itself softens and exhibits fluidity in the initial stage of heating and baking.

That is, the resin (A) is used in the initial stage of heating and baking.
Once softened, the adhesive interface layer becomes smooth and the adhesive interfaces are fused and integrated by the leveling action of the coating film when the coating film surfaces are joined. When the coating surface and the adherend surface are joined, the softened resin (A) enters the surface irregularities of the adherend surface, so that the contact area between the coating surface and the adherend surface (bonding effective area) 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 adhesion 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 expression temperature T _{A of the} thermoplastic resin (A) is 80 ° C. or higher, preferably 80 to 200 ° C. for the following reasons.

That is, in the baking and joining process of 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, and more generally 80 to 250. Although it is heated to about 0 ° C., in order to obtain sufficient bonding strength after heating and baking, it is necessary that the resin coating film is once plasticized and softened in the initial stage of the main heating and baking as described above. If the thermoplastic temperature T _{A of the} resin (A) is too low, the coating film tends to become sticky or blocking during storage, transportation or handling.
Thermoplastic development temperature T _A is 80 ° C. or higher, preferably 100
It is good to be more than ° C. However, if the plasticization temperature becomes too high, the resin may be thermally decomposed at the time of heat-baking and joining, which may lead to strength deterioration.
It is desirable to keep _A at 200 ° C. or lower, more preferably 180 ° C. or lower.

As will be described later, in the heating and baking step for joining, in order to obtain a desired adhesive strength, the crosslinking reactivity developing temperature T of the crosslinking agent (B ₂ ) having a crosslinking reactivity developing temperature on the higher temperature side is obtained. _Although heating to _B2 or higher is an essential condition,
When the thermoplasticity development temperature T _A of the resin (A) is higher than this heating and baking temperature, the crosslinking agent (B ₂ )
As a result, the thermal cross-linking reaction due to the above progresses, and as a result, the fluidity and leveling action of the coating film as described above are not sufficiently exerted, the effect of enlarging the effective bonding area becomes insufficient, and a satisfactory adhesive strength cannot be obtained. Therefore, the thermoplastic expression temperature T _A of the resin (A) is not more than the crosslinking reactivity expression temperature T _B2 of the crosslinking agent (B ₂ ) and not more than 200 ° C., more preferably 18
It is recommended that the temperature be 0 ° C or lower.

The thermoplastic temperature T _A of the resin (A) is
It can be easily controlled by appropriately adjusting the molecular weight, the degree of branching or the degree of polymerization of the polyethylene-based, polyurethane-based, polyester-based resin or the like that is the resin base.

[Thermosensitive Crosslinking Agents (B ₁ ) and (B ₂ )] As described above, a high degree of adhesiveness is exhibited by heating and baking the coating film, and excellent high-temperature adhesiveness, corrosion resistance, and In order to exert solvent resistance, the resin (A) is once plasticized in the initial process of heating and baking after the coating surfaces have been joined together or the coating surface and the adherend surface have been joined together, and sufficient bonding is effective. It is necessary to secure an area, and for that purpose, it is necessary that the coating film itself exhibits thermoplasticity before the heating and baking.

However, a normal thermoplastic resin is an organic compound having a linear structure, and since an organic resin having such a structure is easily dissolved in various organic solvents, it is applied as it is by coating and drying. When the film is washed with an organic solvent as a pretreatment for bonding or the like, the coating film may dissolve into the organic solvent and be chemically damaged. Furthermore, since the normal thermoplastic resin coating film which is not crosslinked has insufficient hardness, its surface is easily scratched when subjected to strength processing, and the coating film partially decreases or disappears. In some cases, sufficient bonding strength cannot be exhibited at that part.

The problem of chemical or mechanical damage of the coating film due to the lack of solvent resistance and scratch resistance of the thermoplastic resin is that the resins (A) are three-dimensionally cross-linked by a cross-linking agent or the like. Although it can be easily improved by doing so, if most or all of the resin (A) is cross-linked in the film-forming step by coating and drying, the thermoplasticity of the coating film is lost at this point and heating and baking At the initial stage, not only the leveling action at the bonding interface as described above is not effectively exhibited, but also the crosslinking reaction does not occur during heating and baking, so that a high level of adhesiveness cannot be obtained.

That is, the coating film is required to have solvent resistance and scratch resistance at the stages of degreasing with an organic solvent and various forming processes before heating and baking, and at the heating and baking stage for bonding, the leveling action is effectively performed. Although it is required to have thermoplasticity to exert the effect and thermal crosslinking reactivity to improve the bonding strength,
In the present invention, two kinds of crosslinking agents (B ₂ ) and (B ₂ ) having different thermal crosslinkability developing temperatures are used together as the coating film constituents in order to satisfy the properties required in each of these stages.

Then, on the lower temperature side, the thermal crosslinking property development temperature T
Apply a part or all of the crosslinking agent (B ₁ ) having _B1
Before heating and baking by reacting with the thermoplastic resin (A) in the film-forming step by drying (the low-temperature heat treatment step thereafter when the drying temperature cannot be sufficiently taken) to partially crosslink the resin (A). Ensures solvent resistance and scratch resistance required for degreasing of organic solvents and various molding processes. In this film forming step, the resin (A) is only partially crosslinked to the extent that the thermoplasticity is not lost. Therefore, the resin (A) shows plasticity in the initial stage of heating and baking for joining, and fluidization and leveling of the coating film. The effect is exerted, and a uniform and close bonding interface can be secured, and after that, the rest of the cross-linking agent (B ₁ ) remains (when it is completely consumed in the coating / drying process, it remains. In some cases, the thermal cross-linking reaction at the bonding interface by the cross-linking agent (B ₂ ) having the cross-linking reactivity developing temperature T _B2 on the higher temperature side proceeds, and a high level of bonding strength is exhibited.

For the above reasons, in the present invention, two kinds of cross-linking agents (B ₁ ) and (B ₂ ) having different thermal cross-linking reactivity developing temperatures T _B1 and T _{B2 in} the coating film, provided that T _B1 <T _B2 ] Is included as an essential requirement.

That is, the role of the cross-linking agent (B ₁ ) mainly functions as a partial cross-linking agent for the resin (A) in order to improve the solvent resistance and the scratch resistance of the coating film before heat-baking and joining. Depending on the case, it functions as a thermal crosslinking reaction agent at the joining stage by heating and baking. However, when a very small amount of the cross-linking agent (B ₁ ) is mixed in the coating film, most of it is consumed in the cross-linking reaction in the film-forming step by coating / drying or the low-temperature heat treatment step after film-forming, Although it may hardly contribute to the thermal crosslinking reaction in the heating and baking step for joining, such an embodiment does not depart from the spirit of the present invention. On the other hand, the role of the cross-linking agent (B ₂ ) is to obtain a high degree of bonding strength as a thermal cross-linking reaction agent in the bonding step by heating and baking, and the function of the resin (A) as a partial cross-linking reaction agent before bonding is I do not expect.

When the temperature difference between the cross-linking reactivity developing temperatures T _B1 and T _B2 of the cross-linking agents (B ₁ ) and (B ₂ ) is too small, the cross-linking agent (B ₁ ) is applied at the film-forming stage by coating and drying. When a partial crosslinking reaction of the resin (A) by the
_{Even 2} ) there is a risk of cross-linking reaction, and in that case,
At the initial stage of heating and baking for joining, plasticization of the coating film
Not only will the leveling function not be exhibited, but also the crosslinking reaction for bonding will be reduced and satisfactory bonding strength will not be obtained.

Therefore, it is preferable that there is a certain temperature difference between the thermal crosslinking reactivity developing temperatures T _B1 and T _B2 of the cross-linking agents (B ₁ ) and (B ₂ ), and [T _B2- T _B1 ] is desirable. It is preferable to select a combination of two kinds of cross-linking agents (B ₁ ) and (B ₂ ) having a temperature of 30 ° C. or higher.

When a blocked isocyanate group-containing compound is used as the cross-linking agent (B ₁ ) or (B ₂ ), the heat of the blocking agent can be adjusted by appropriately selecting the type of the blocking agent that blocks the active isocyanate group. It is preferable because the dissociation temperature can be controlled, and thereby the crosslinking reactivity expression temperatures T _B2 and T _B1 can be arbitrarily adjusted.

In the above, the crosslinking agents (B ₁ ) and (B
₂ ) The crosslinking reactivity expression temperatures T _B1 and T _B2 are set to T _B1 <T _B2 ,
The reason why (T _B2 −T _B1 ) ≧ 30 ° C. is preferably determined for the above-mentioned reason, but the crosslinking reactivity expression temperature T _B2 of the crosslinking agent (B ₂ ) is set to the thermoplastic expression of the resin (A). The reason for setting the temperature T _A or higher is as follows.

That is, in order to obtain a high degree of adhesive strength by heat-baking treatment for joining and to exhibit excellent high temperature adhesiveness, corrosion resistance, solvent resistance and the like after joining,
The coating film is once plasticized at the initial stage of the heating / baking process after the coating film surfaces are combined or the coating film surface and the adherend surface are aligned.
It is necessary to carry out the cross-linking reaction between the functional groups after securing a sufficient effective bonding area by the leveling action or the like.

However, if most or all of the cross-linking reaction by the cross-linking agent (B ₂ ) occurs below the thermoplastic development temperature T _{A of the} resin (A), the resin ( This is because the crosslinking reaction is completed without the effect of expanding the effective bonding area due to the thermoplasticization of A) being achieved, and a satisfactory bonding strength cannot be obtained. Therefore, it is essential that the thermal crosslinking reactivity developing temperature T _B2 of the crosslinking agent (B ₂ ) in the coating film is equal to or higher than the thermoplasticity developing temperature T _A of the resin (A).

Considering a general production process, it is desirable that the crosslinking reactivity developing temperature T _B2 of the crosslinking agent (B ₂ ) is 100 ° C. or higher, more preferably 130 ° C. or higher. However, the crosslinking reactivity expression temperature T _B2 of the crosslinking agent (B ₂ ) is 20.
When the temperature is higher than 0 ° C, the heating and baking temperature at the time of joining in a general production line needs to be as high as 250 ° C or higher, and the resin constituting the coating film is thermally decomposed during the heating and baking to cause strength deterioration. The cross-linking reactivity developing temperature T _B2 is 20 because the coating quality of the non-bonded portion may be yellowed or the like and the appearance quality may be deteriorated.
It is desired to suppress the temperature to 0 ° C or lower, more preferably 180 ° C or lower.

[0050] Incidentally, the crosslinking reaction expression temperature T _B1 of the crosslinking agent (B _1), the street it is previously mentioned that the cross-linking reaction expression should be lower than the temperature T _B2 of the crosslinking agent (B ₂₎ However, the crosslinking reactivity expression temperature T _B1 of the crosslinking agent (B ₁ ) and the resin (A)
The relationship with the thermoplastic development temperature T _A is not particularly specified in the present invention. Next, preferred specific examples of the thermoplastic resin (A) used in the present invention will be described.

Specific examples of the thermoplastic resin (A) used as a main component of the resin coating for heat-sensitive bonding in the present invention include polyethylene resins, polyurethane resins and polyester resins, and these are preferable. These resins can be used alone or in combination of two or more, but the reason for selecting these resins is as follows.

That is, the resin-coated metal plate according to the present invention is subjected to some processing prior to joining as described above, but at this time, the resin coating film itself is also processed together with the metal plate base material. Therefore, at the time of the processing, it is required that the coating film itself as well as the metal plate base material are easily spread and deformed and that the surface of the coating film is unlikely to have a flaw or a defect. From such a point, in the present invention, considering the workability of the coating film before joining, polyethylene resin, polyurethane resin and polyester resin are preferable as the resin exhibiting excellent spreadability and scratch resistance. Listed.

In order to more effectively suppress mechanical damage and chemical damage to the coating film due to the processing often performed before joining and the degreasing process using an organic solvent, the resin (A) in the coating film
As described above, it is preferable to partially cross-link the above and the cross-linking agent (B ₁ ) in advance.

[Crosslinking agents (B ₁ ), (B ₂ ) and resin (A)]
Cross-linking reaction with] As described above, the heat-sensitive adhesive coating has excellent heat-sensitive adhesiveness, high-temperature bonding strength,
In order to exhibit corrosion resistance, solvent resistance, etc., a crosslinking point necessary for a crosslinking reaction between the coating film surfaces or between the coating film surface and the adherend surface, that is, a functional group exists in the resin (A). And a cross-linking agent (B ₁ ) which reacts with the functional group, (B _{1
As 2} ), a blocked isocyanate group-containing compound is preferably used, and therefore these crosslinking reactions will be described.

When an isocyanate group-containing compound is used as the crosslinking agent (B ₁ ) or (B ₂ ), specific examples of the functional group in the resin (A) which undergoes a crosslinking reaction with the isocyanate group include a functional group having active hydrogen. A group such as a hydroxyl group (-O
H), carboxyl group (-COOH), amino group (-N)
H ₂ ) and the like.

Each of these active hydrogen-containing functional groups is an active isocyanate group (--NCO) formed by the dissociation of the blocking agent from the blocked isocyanate group.
Group) to cause a crosslinking reaction, and the specific reaction is as follows. -NCO + -OH → -NH-COO- -NCO + -COOH → -NH-CO- +
CO ₂ -NCO + -NH ₂ → -NH-CO-NH-

Of the functional groups having reactivity with the above-mentioned isocyanate group, the most preferred is an amino group. That is, the amino group has a higher crosslinking reaction rate with the isocyanate group than other hydroxyl groups and carboxyl groups, and in a shorter time,
Alternatively, high bonding strength can be obtained at a lower baking temperature.

By the way, since the active isocyanate group easily reacts with a functional group containing active hydrogen such as a hydroxyl group, a carboxyl group and an amino group at room temperature, if the active isocyanate group is mixed and coexisted with the resin (A), The crosslinking reaction progresses within the coating layer over time without heat treatment, and the crosslinking points gradually disappear, and the thermoplasticity of the coating film required in the initial stage of heating and baking disappears or is diminished, which is satisfactory. Bonding strength will not be exhibited. That is, a coating film in which the crosslinking reaction has proceeded excessively before heating and baking does not plasticize even if the coating surfaces are subsequently brought into close contact with each other and heating and baking are performed, so that a uniform and smooth bonding interface is obtained. Is not obtained, and the crosslinking reaction hardly occurs, so that the heat-sensitive adhesiveness intended in the present invention is not expressed.

Therefore, in the coating film state after coating and drying, that is, at the time before bonding, the isocyanate group-containing compounds of the crosslinking agents (B ₁ ) and (B ₂ ) spontaneously react with the functional groups in the resin (A). To avoid this, it is necessary to block the isocyanate groups in the cross-linking agents (B ₁ ) and (B ₂ ) with a blocking agent such as phenol, alcohol, oxime and active methylene in advance. By appropriately selecting the type of the blocking agent, it is possible to adjust the dissociation temperature of the blocking agent from the isocyanate group, whereby the crosslinking reactivity expression temperatures T _B1 , T 2 of the isocyanate group-containing compound can be adjusted.
_B2 can be adjusted arbitrarily. Next, preferred specific examples of the thermoplastic resin (A) used as the base resin of the heat-sensitive adhesive coating film 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 (A), two or more functional groups exhibiting crosslinking reactivity with a crosslinking agent (for example, an isocyanate group-containing compound) are contained in one molecule. The thermoplastic polyurethane-based resin (A ₁ ) having is preferable, and as a method for producing the thermoplastic polyurethane-based resin (A ₁ ), an organic compound having two or more functional groups (X ₁ ) showing reactivity with an isocyanate group is used. ,
Examples thereof include a method of reacting with an organic polyisocyanate compound having two or more isocyanate groups (Y ₁ ).
At that time, if the functional group (X ₁ ) -containing compound having reactivity with the isocyanate group is reacted in excess with respect to the isocyanate group (Y ₁ ) -containing compound in terms of the equivalent ratio of the functional group, unreacted functional group A polyurethane resin (A ₁ ) having a group (X ₁ ) remaining in the molecule can be obtained, and the unreacted functional group (X ₁ ) is crosslinked with a crosslinking agent (B ₁ ), (B ₂ ). It becomes a functional group showing the property.

<Thermoplastic polyester resin (A ₂ )>
When a polyester resin is used as the thermoplastic resin (A), as the resin (A), two or more functional groups exhibiting crosslinking reactivity with a crosslinking agent (for example, an isocyanate group-containing compound) are contained in one molecule. The thermoplastic polyester-based resin (A ₂ ) having is preferable, and the production method of the thermoplastic polyester-based resin (A ₂ ) includes a compound containing two or more hydroxyl groups (X ₂ ) in one molecule and a compound in one molecule. A method of reacting with a compound containing two or more carboxyl groups (Y ₂ ) can be mentioned. At that time, in terms of the equivalent ratio of the functional group, the hydroxyl group (X ₂ ) -containing compound is converted to the carboxyl group (Y ₂ )
When the contained compound is reacted in an excessive amount or the compound containing a hydroxyl group (X ₂ ) is reacted with the compound containing a carboxyl group (Y ₂ ) in an excessive amount, the unreacted functional group (X ₂ ) or (Y ₂ ) becomes a molecule. Polyester resin remaining inside (A
₂ ) You can get

Such a thermoplastic polyester resin (A
Specific preferred examples of ₂ ) include glyptal resin, terephthalic acid resin, isophthalic acid resin, maleic acid resin,
Aliphatic polyester resins, oxyacid resins and the like,
The unreacted functional group (X ₂ ) or (Y ₂ ) in the polyester resin (A ₂ ) becomes a functional group exhibiting crosslinking reactivity with the crosslinking agents (B ₁ ) and (B ₂ ).

<Thermoplastic polyethylene resin (A ₃ )>
When a polyethylene-based resin is used as the thermoplastic resin (A), the thermoplastic polyethylene has two or more functional groups in one molecule that exhibit crosslinking reactivity with a crosslinking agent (for example, an isocyanate group-containing compound) as the resin. Resin (A
₃ ) is preferable, and the thermoplastic polyethylene resin (A
Examples of the production method of ₃ ) include a method of reacting ethylene with an ethylenically unsaturated carboxylic acid having a carboxyl group. Then, the carboxyl group in the polyethylene resin (A ₃ ) becomes a functional group exhibiting crosslinking reactivity with the crosslinking agents (B ₁ ) and (B ₂ ).

In press working and punching before heating and baking, abrasion resistance, punching workability,
In order to further improve the coating blackening resistance and other properties, the polyethylene-based resin (A ₃ ) is produced in addition to ethylene and an ethylenically unsaturated carboxylic acid in order to further improve the coating strength. It is also effective to use acrylic acid ester, styrene, etc. together to prepare a copolymer resin.

<A mixture of two or more thermoplastic resins (A
₄ )> In the present invention, as the thermoplastic resin (A),
It is also possible to use a mixed resin (A ₄ ) of two or more of the above-mentioned polyurethane resin (A ₁ ), polyester resin (A ₂ ) and polyethylene resin (A ₃ ). As the mixed resin (A ₄ ), a thermoplastic mixed resin (A ₄ ) having two or more functional groups in one molecule showing crosslinking reactivity with a crosslinking agent (for example, an isocyanate group-containing compound)
Is used. As a specific combination, a polyurethane resin (A ₁ ) and a polyester resin (A ₂ )
Mixture of polyester resin (A ₂ ) and polyethylene resin (A ₃ ), polyethylene resin (A ₃ ).
And a polyurethane resin (A ₁ ) or a mixture of a polyurethane resin (A ₁ ), a polyester resin (A ₂ ) and a polyethylene resin (A ₃ ).

[0066] [crosslinking agent _{(B 1), (B 2} ) about] crosslinking agent used in the present invention (B _1), particularly preferred are include blocked isocyanate group-containing compound as (B _2), This product can be obtained by reacting an organic polyisocyanate compound with a known blocking agent. At that time, the thermal dissociation temperature of the blocking agent from the isocyanate group, that is, the crosslinking reactivity expression temperatures T _B1 and T _B2 can be arbitrarily adjusted by appropriately selecting the types of the organic polyisocyanate compound and the blocking agent. .

In selecting the blocking agent,
It is desirable to select a blocking agent having a boiling point higher than the temperature of the thermal crosslinking reaction so that the blocking agent dissociated during the thermal crosslinking reaction does not boil and foam. Examples of such blocking agents are 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; dimethyl malonate and acetoacetic acid. Known blocking agents such as active methylene type such as ethyl are exemplified. Next, materials such as the above resin components will be described.

<Raw Material of Thermoplastic Polyurethane Resin (A ₁ )> Thermoplastic Polyurethane Resin Having Functional Group Reactive with Crosslinking Agents (B ₁ ) and (B ₂ ) (for example, Isocyanate Group-Containing Compound) As a raw material for producing (A ₁ ), known polyvalent hydroxyl compounds (compounds having two or more hydroxyl groups in one molecule) as shown below, polyvalent amino compounds (two in one molecule) Examples of the compound having the above amino group) and polyvalent aminohydroxyl compounds (compounds having two or more hydroxyl groups and amino groups in one molecule).

Polyhydric hydroxyl compound: ethylene glycol, diethyl glycol, butanediol, propylene glycol, hexanediol, polypropylene glycol, 3-methyl-1,5-pentanediol, 1,
Polyhydric alcohols such as 4-cyclohexanedimethanol, dihydroxyethyl terephthalate, hydroquinone dihydroxyethyl ether trimethylolpropane, glycerin and pentaerythritol; the above polyhydric alcohols and bisphenol A, bisphenol S, hydrogenated bisphenol A, dibromobisphenol A An alkylene derivative such as; an ester compound synthesized from the above polyhydric alcohol or its alkylene derivative and a polycarboxylic acid, a polycarboxylic anhydride, or a polycarboxylic ester;
Further, polyol compounds such as polycarbonate polyol, polytetramethylene glycol, polycaprolactone polyol, polybutadiene polyol, polythioether polyol, polyacetal polyol, castor oil polyol and the like can be mentioned.

Polyvalent amino compounds: ethylenediamine, propylenediamine, diethylenetriamine, hexylenediamine, triethylenetetramine, tetraethylenepetamine, isophoronediamine, xylylenediamine, diphenylmethanediamine, hydrogenated diphenylmethanediamine and the like. Polyvalent aminohydroxyl compound: diethanolamine,
3-aminopropanol etc. are mentioned.

<Raw Material of Thermoplastic Polyester Resin (A ₂ )> Thermoplastic Polyester Resin Having Functional Group Reactive with Crosslinking Agents (B ₁ ) and (B ₂ ) (for example, Isocyanate Group-Containing Compound) As a raw material for producing (A ₂ ), known polyvalent hydroxyl compounds (compounds having two or more hydroxyl groups in one molecule) as shown below, polyvalent carboxylic acids (two in one molecule) The above-mentioned compounds having a carboxyl group) and their anhydrides can be mentioned.

Polybasic acid used here (2 in 1 molecule)
Compounds having one or more carboxyl groups) and anhydrides include phthalic anhydride, phthalic acid, terephthalic acid, isophthalic acid, tetrachlorophthalic anhydride, succinic acid, adipic acid, sebacic acid, azelaic acid, and hexahydrophthalic anhydride. Is mentioned.

Besides, an intramolecular condensate of an oxyacid, an unsaturated polybasic acid, etc. may be used in common. In addition, a small amount of monobasic acid (for example, benzoic acid) to control film hardness and molecular weight.
Can also be used in combination.

Examples of the polyvalent hydroxyl compound (compound having two or more hydroxyl groups in one molecule) include ethylene glycol, propylene glycol, diethylene glycol, glycerin, 1,3-butylene glycol, neopentyl glycol, trimethylolpropane and penta. Examples thereof include erythritol, sorbitol, butenediol, 4-hydroxyethoxyphenol propane, glycerin monoallyl and the like.

<Raw Material of Thermoplastic Polyethylene Resin (A ₃ )> Thermoplastic Polyethylene Resin Having Functional Group Reactive with Crosslinking Agents (B ₁ ) and (B ₂ ) (for example, Isocyanate Group-Containing Compound) As raw materials for producing (A ₃ ), ethylene and an ethylenically unsaturated carboxylic acid are used, and as the ethylenically unsaturated carboxylic acid,
For example, one or more of (meth) acrylic acid, maleic acid, itaconic acid and the like are used.

In addition to the ethylenically unsaturated carboxylic acid, (meth) acrylates 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 such as hydroxyethyl (meth) acrylate and hydroxypropyl (meth) acrylate; N-
N-substituted (meth) acrylamides such as methylol (meth) acrylamide; epoxy group-containing (meth) acrylic acid esters such as (meth) acrylic glycidyl; (meth)
It is also possible to use one kind or a combination of two or more kinds such as acrylonitrile.

<Raw Materials for Blocked Isocyanate Group-Containing Compounds> Examples of the organic polyisocyanate-based compound which is a starting material for producing the blocked isocyanate group-containing compounds preferably used as the crosslinking agents (B ₁ ) and (B ₂ ): Aromatic, aliphatic, and alicyclic isocyanate compounds can be used, and these can be used alone or in combination of two or more as required.

Specifically, tolylene diisocyanate,
Diphenylmethane diisocyanate, xylylene diisocyanate, naphthylene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate,
Isocyanates such as hydrogenated diphenylmethane diisocyanate, hydrogenated tolylene diisocyanate, and tetramethylene xylylene diisocyanate; and buret compounds and isocyanurates of the above isocyanates, and the above isocyanates were added to a polyvalent hydroxyl compound such as trimethylolpropane. A compound etc. are mentioned.

In carrying out the present invention, it is effective to impart water solubility or water dispersibility (hydrophilicity) to the resin in order to improve the coating workability, etc., as described above. , Thermoplastic polyurethane resin (A
₁ ), a thermoplastic polyester-based resin (A ₂ ), a thermoplastic polyethylene-based resin (A ₃ ), a blocked isocyanate group-containing compound or the like thermosensitive crosslinking agent (B ₁ ), (B ₂ ) 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
₁ ), (A ₂ ), (A ₃ ) and cross-linking agent (B ₁ ), (B
It is possible to impart hydrophilicity to ₂ ), which makes the coating solution water-soluble or water-dispersible.

[The thermoplastic resin (A) and the cross-linking agent (B ₁ ),
Mixing ratio of (B ₂ )] A thermoplastic resin (A) having a functional group showing a cross-linking reactivity with a cross-linking agent (B ₁ ) or (B ₂ ) including an isocyanate group-containing compound, and a cross-linking agent (B
₁ ) and (B ₂ ) (for example, a blocked isocyanate group-containing compound) are preferably mixed and mixed in terms of the equivalent ratio of the functional groups, the functional group in the resin (A) and the crosslinking agent (B
₁ ) and (B ₂ ) in an equivalent ratio to the functional group (in the case where the crosslinking agent is a blocked isocyanate group-containing compound, the active isocyanate group), 1: 0.5 to 1: 2, and more preferably 1 It is preferable to mix them in a ratio of 0.8 to 1: 1.5.

The reason for this is that if the equivalent ratio range in terms of functional groups is out of the above range, the unreacted functional groups that have not participated in the crosslinking reaction will remain in the coating film even after heating and baking the coating film obtained by coating and drying. Inside the resin (A) or cross-linking agent (B ₁ ),
This is because a large amount remains in (B ₂ ) and adversely affects the heat-resistant adhesion and solvent resistance of the resin-coated metal sheet after the heat-baking treatment.

The mixing ratio of the cross-linking agent (B ₁ ) and the cross-linking agent (B ₂ ) is not particularly limited, and may be changed depending on the restrictions on the manufacturing conditions of the resin-coated metal sheet, the processing conditions, the baking joining conditions, etc. A suitable blending ratio may be selected.

However, when the addition amount of the cross-linking agent (B ₁ ) is extremely small, the partial cross-linking reaction of the resin (A) may occur at the film-forming step by coating / drying or by the low-temperature heat treatment after drying. It may not occur sufficiently, and the solvent resistance and scratch resistance of the coating film before the joining process may be insufficient, while the crosslinking agent (B ₁ )
When the addition amount of is too large, when the total amount of the crosslinking agent (B ₁ ) added in the film-forming step by coating / drying or the low-temperature heat treatment after drying is cross-linked with the resin (A). Although the solvent resistance and scratch resistance of the coating film before the bonding process are improved, the thermoplasticity of the coating film is not exhibited at the initial stage of bonding, and it is difficult to obtain high bonding strength due to the thermal crosslinking reaction. Become. Therefore, it is desired that the addition amount (blending ratio) of the crosslinking agent (B ₁ ) is appropriately selected after fully considering the ratio of partial crosslinking with the resin (A). In particular,
The ratio in terms of the equivalent ratio of functional groups is B ₁ : B ₂ = 0.
A range of 1: 1 to 1: 1 is recommended.

The preferable addition amount (compounding ratio) of the cross-linking agent (B ₂ ) is such that the cross-linking reaction necessary for obtaining a high adhesive strength is sufficiently performed during heating and baking for joining. It may be decided in consideration. In this joining step, the unreacted cross-linking agent (B ₁ ) remaining in the coating film before joining also contributes to the thermal cross-linking reaction, so that the cross-linking agent (B ₁ ) and the cross-linking agent (B ₂ ) The addition amount of each cross-linking agent (B ₂ ) should not be considered individually, and the necessary addition amount of the cross-linking agent (B ₂ ) should be determined in consideration of the amount of the unreacted cross-linking agent (B ₁ ) remaining before joining. Is desirable.

[Regarding Adhesion Amount of Resin Coating Film] The adhesion amount of the resin coating film is a coating film adhesion amount in terms of solid content after drying in order to sufficiently secure the adhesive strength per unit area on the joint surface. 0.5 g / m ² or more, preferably 1 g / m ²
It should be over. Then, the adhesion amount is 0.5 g /
When it is less than m ² , the surface of the metal plate cannot be sufficiently covered with the coating film, so that the resin coating film is difficult to be uniform and smooth at the time of baking, and the defective bonding is likely to occur partially. Therefore, the performance as an adhesive resin-coated metal plate may be insufficient. On the other hand, the upper limit of the coating amount of the resin coating is not particularly limited from the viewpoint of adhesive strength, but if the coating amount becomes too thick, the cost of coating material costs per unit treated area increases. In addition to the above, the time required for drying after applying the treatment liquid becomes long, the line speed must be reduced in the continuous production process in the continuous coating line, and the productivity is reduced, resulting in an increase in the production cost.

[0086] Thus the upper limit of the resin coating film adhesion amount, when considering the cost due characteristics obtained and the film thickness increases, 30 g / m ² or less, and more preferably preferably 10 g / m ² or less.

[Sub-additives allowed to be added to the coating solution and modification allowed to the resin (A)] The thermoplastic resin (A) and the crosslinking agents (B ₁ ) and (B ₂ ) are essential. In the preparation of the coating liquid containing as a component, in the range that does not hinder the various properties such as adhesiveness obtained in the present invention, a diluent solvent, an anti-skinning agent, a leveling agent, a defoaming agent, a penetrating agent, a film-forming aid. , Color pigments, various additives such as thickeners, and further, finely divided silica for improving adhesion and corrosion resistance, colloidal silica, silane coupling agent, etc. are appropriately added to further enhance coating film performance and It is also possible to add a function.

Further, for the purpose of improving the weather resistance, hardness and shear strength of the coating film, a part of the resin (A) is acrylic-modified or epoxy-modified, and further, the cost of the resin is reduced, and the like. Properly mix 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, etc. within a range not impairing the original characteristics of the present invention. Is also possible.

Next, a method of manufacturing the heat-sensitive adhesive resin-coated metal plate according to the present invention will be described. The heat-sensitive adhesive resin-coated metal sheet of the present invention is prepared by applying a coating liquid containing the thermoplastic resin (A) and the crosslinking agents (B ₁ ) and (B ₂ ) as essential components as described above, by a metal by an arbitrary method. It can be obtained by applying and drying on the surface of the plate. At this time, after the coating and drying, the drying temperature is set to a temperature range not less than the crosslinking reactivity developing temperature T _B1 of the crosslinking agent (B ₁ ) and less than the crosslinking reactivity developing temperature T _{B2 of the} crosslinking agent (B ₂ ). No cross-linking agent (B ₁ ) without stickiness or blocking on the coating film surface of
By forming an appropriate partial cross-linking of the resin (A) by a part or all of the above, a coating film with excellent scratch resistance which is hard to be scratched in various processing steps before the bonding step, and Even when a degreasing step with various organic solvents is performed before joining, it is possible to form a coating film having excellent solvent resistance that hardly dissolves in the organic solvent.

In this coating / drying process, crosslinking on the higher temperature side
Crosslinking agent (B _Two ) Thermal crosslinkability
Temperature T_B2Drying the coating at a temperature above
Less stickiness and blocking of the coating and scratch resistance
The coating film has excellent texture and solvent resistance, but the coating film
Crosslinking agent (B₁ ), (B_Two ) Both
Will cause a crosslinking and curing reaction with the resin (A)
Therefore, when the film is heated and baked thereafter, the coating film may not be plasticized.
And no thermal crosslinking reaction for joining
Therefore, it becomes difficult to obtain high bonding strength.

For these reasons, the drying temperature after coating of the coating liquid containing the thermoplastic resin (A) and the crosslinking agents (B ₁ ) and (B ₂ ) is at least the crosslinking reactivity of the crosslinking agent (B ₂ ). It is required to be less than the expression temperature T _B2 [when the crosslinking agent (B ₂ ) is a blocked isocyanate group-containing compound, less than the thermal dissociation temperature of the blocking agent). A general drying temperature therefor is 30 to 100 ° C., preferably 50 to 80 ° C.

When the coating film drying temperature after coating cannot be raised to the cross-linking reactivity developing temperature T _B1 of the cross-linking agent (B ₁ ) or higher due to restrictions on the production line or the production process,
After film formation by coating / drying, the cross-linking agent development temperature T _B1 of the cross-linking agent (B ₁ ) or more and less than the cross-linking reactivity development temperature T _B2 of the cross-linking agent (B ₂ ) in a state where the coating film surfaces do not contact each other. If a heat treatment is performed for a short time at the temperature of, the resin (A) in the coating film
And partial crosslinking with the crosslinking agent (B ₁ ) occur, and solvent resistance and scratch resistance of the coating film before bonding can be secured.
The drying temperature during coating / drying may be higher than or lower than the thermoplastic temperature T _{A of the} resin (A).

When the resin (A) is dried at the thermoplasticity development temperature T _A or higher, it is sufficiently cooled after film formation and then wound up as a coil product or laminated as a cut plate product so that blocking does not occur. On the other hand, in the case of drying at a temperature lower than the thermoplasticity developing temperature T _A , it may be wound sufficiently as a coil product after being sufficiently dried so as not to cause stickiness, or laminated as a cut plate product.

[Heating and Baking Conditions for Joining] When the heat-sensitive adhesive resin-coated metal sheet of the present invention is processed into a predetermined shape and the portions to be joined are superposed and joined by heating and baking, By setting the heating and baking temperature to a temperature at which the resin (A) exhibits the thermoplasticity T _A or higher and a temperature at which the crosslinking agent (B ₂ ) develops the crosslinking reactivity T _B2 or higher, and preferably 250 ° C. or lower, High bonding strength can be obtained.

That is, the thermoplastic temperature T of the resin (A)
_When the heating and baking temperature is less than _A, the softening and fluidity of the resin in the initial heating and baking process is poor, and the leveling effect at the bonding interface is not exhibited, so a uniform adhesive layer is not formed and the desired high adhesive strength is obtained. I can't. Further, the heating and baking temperature is the cross-linking reactivity developing temperature T _B2 of the cross-linking agent (B ₂ ).
If it is less than the above range, the crosslinking reaction between the crosslinking agent (B ₂ ) contained in the coating film and the resin (A) does not occur, and the desired high bonding strength cannot be obtained. Furthermore, when baking is performed at an excessively high temperature exceeding 250 ° C., the crosslinking reaction between the crosslinking agent and the resin (A) proceeds sufficiently and quickly,
On the other hand, not only the thermal decomposition of the resin progresses and the coating film components deteriorate, but the adhesive strength and the like may rather decrease, and the yellowing due to the decomposition of the resin progresses and the appearance deteriorates.

For these reasons, the heating and baking temperature for joining is a temperature not lower than the thermoplastic temperature T _{A of the} resin (A) and not _lower than the temperature T _{B2 of the} crosslinking agent (B ₂ ). It should satisfy the conditions, preferably 250 ° C or lower, more preferably 200 ° C or lower.

[Advantages of Selectively Using Water-Soluble or Water-Dispersible Resin] In carrying out the present invention, if the coating solution for forming the heat-sensitive adhesive layer is water-soluble or water-dispersible, It is preferable because such advantages can be obtained. That is, with the water-based resin liquid, it is not necessary to provide a special exhaust treatment facility for exhausting the organic solvent component gas required when using the solvent-based resin liquid in the coating line, so that the facility cost can be suppressed. Moreover, for example, when using a plated metal plate or a chemical conversion treatment metal plate as the original plate,
Continuation can be easily achieved by installing the resin liquid coating equipment in the existing plating treatment or chemical conversion treatment line, and compared with the case of manufacturing with a dedicated resin coating line equipped with special exhaust treatment equipment. , Productivity can be improved.

When the coating solution is of an organic solvent type, the solid content and viscosity of the coating solution are liable to change with time due to evaporation of the solvent during coating, resulting in uneven coating and control of coating film adhesion. However, if the coating liquid is water-based, the amount of solvent volatilized from the coating liquid is extremely small, so there is almost no change in solid content or viscosity over time, and stable coating is possible. It is possible to easily control the adhesion amount under the condition.

The method of applying the above resin solution to the surface of the metal plate is not particularly limited, but as a general method, for example, cleaning the surface or pretreatment for coating (for example, phosphate treatment, chromate treatment), etc. Examples of the method include a method of coating the surface of a long metal band subjected to the above-mentioned treatment with a roll coater method, a spray method, a curtain flow coater method or the like on one surface or both surfaces of the metal plate surface. The method of coating with a roll coater is the most practically preferable in view of the uniformity of coating film thickness in the longitudinal direction and width direction of the metal strip, the coating treatment cost, the coating efficiency, and the like.

There is no limitation on the type of the base metal plate used in the present invention, 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. , Ti and Ti alloy plates, plated metal plates (zinc and zinc alloy-based plated steel plates, Al and Al alloy-based plated steel plates, copper-based plated steel plates, Ni-based plated steel plates, Cr-based plated steel plates, zinc-based plated Al and Al alloy plates Various plated metal plates such as), chemical conversion treatment (phosphate treatment, chromate treatment, etc.) metal plates, and further coated metal plates can be widely applied.

The heat-sensitive adhesive resin-coated metal plate of the present invention thus obtained can be widely applied as an outer plate material for automobiles, household electric appliances, metal furniture, etc., and also as a building material, etc. At the time of heat-baking and joining, various paints (for example, acrylic paints, melamine paints, polyester paints, fluorine paints, etc.) can be applied to various parts before and after heat-baking. For example, it is possible to apply a coating method such as a spray method, an electrostatic coating method, an electrodeposition method, etc.) and match the baking treatment of the coating with the heating and baking joining of the coating film joint surface according to the present invention. For example, the heat-sensitive adhesive resin-coated metal plate of the present invention is punched into a predetermined shape, two sheets are caulked, and then the above various topcoat paints are applied to the surface, and heat is applied when baking the paint. It is also effective to simultaneously perform heat bonding on the bonding surface of the heat-sensitive adhesive resin coating film according to the present invention, and if such a method is adopted, the baking treatment step of the top coating film and the heat-sensitive adhesive property of the present invention are performed. Since the joining process by the cross-linking reaction of the coating film can be performed at the same time, the processing or joining work is further simplified.

[0102]

EXAMPLES Hereinafter, the structure and operation and effect of the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples, and the present invention is applicable to the above and following points. It is, of course, possible to carry out the present invention with appropriate modifications within the scope of the invention, and all of them are included in the technical scope of the present invention.

Example As shown in Tables 1 and 2, various resin coating solutions for coating a metal plate were prepared by using resins or compounds having various crosslinking reactive functional groups and physical properties. Among the various coating solutions shown in Tables 1 and 2, No. For A to F,
Equivalent conversion ratio of various active hydrogen functional groups present in the thermoplastic resin (A) and isocyanate groups present in the cross-linking agent (B ₁ + B ₂ ); (B ₁ + B ₂ ) / A is a suitable ratio. The blending ratio is adjusted.

On the other hand, the coating liquid No. Heat is acceptable for G to I
Active hydrogen functional group capable of reacting with a crosslinking agent in the plastic resin (A)
Does not exist, the resin (A) and
(B ₁ , B_Two ) Does not occur. Also, the coating liquid
No. For J and K, there is only one cross-linking agent,
Crosslinking reaction with resin (A) occurs rapidly at low temperature
The cross-linking reaction between the example (coating liquid No. J) and the resin (A) is high.
Example that occurs only when heated (coating liquid No. K), coating liquid N
o. L and M are thermoplastic resin (A) or crosslinking agent (B
₁ , B_Two ) Is an example that does not include any one. The table
Thermoplastic development temperature T of resin (A) shown in 1_A And the bridge
Agent (B₁ , B_Two) Crosslinking reaction expression temperature T_B1, T_B2Is below
It was measured by the method described above.

(Measurement Method of Thermoplastic Development Temperature) A film obtained by drying a resin solution on a Teflon plate at 60 ° C. is placed on a hot plate heated to a predetermined temperature, and the temperature at which the resin melts is measured. Then, it was set as the thermoplastic development temperature T _A. (Measurement Method of Crosslinking Reactivity Development Temperatures T _B1 and T _B2 ) The film obtained by drying the resin solution on a Teflon plate at 60 ° C. is used to measure the dissociation temperature of the blocking agent by differential thermal analysis and crosslink. The reactive expression temperatures T _B1 and T _B2 were used.

[0106]

[Table 1]

[0107]

[Table 2]

Next, coating type chromate treatment (chromate adhesion amount: 50 mg / m ² ) was applied to the surface of the electric pure Zn plated steel plate (plating adhesion amount: 20 g / m ² , plate thickness 0.6 mm).
Then, this was used as a treated metal plate for resin coating. After coating various coating solutions A to M shown in Tables 1 and 2 on the surface of the metal plate to be treated with a roll coater to a predetermined film thickness,
The resin coating film was dried at a predetermined plate temperature (drying temperature) while being transferred in a hot air drying furnace, and the various resin-coated steel sheets obtained were subjected to the following performance evaluation tests.

1. Performance evaluation after coating-drying (before heating and baking for joining) (1-1) Scratch resistance (film hardness) The coating film hardness of the coated metal plate after coating-drying is JIS-K5.
It was measured according to the pencil hardness test specified in 400, and the scratch resistance of the coating film surface was evaluated according to the following criteria. The judgment is
The coating film surface was scratched 5 times in total with pencils of various hardness, and the pencil hardness one rank below with two or more scratches was defined as the coating film hardness. ◎ Excellent: Pencil hardness H or higher ○ Good: 〃 HB to F × Poor: 〃 B or less

(1-2) Solvent resistance Coating-dried resin coated metal plate 70 mm x 150 mm
The size of the test piece was cut, and the surface of the test piece was slid 10 times with gauze containing toluene, and the solvent resistance was evaluated according to the following criteria in the deteriorated state of the coating film. ◎ Excellent: No abnormality ○ Good: Slightly swelling degree × Inferior: Dissolution of coating film

(1-3) Corrosion resistance (white rust resistance) The corrosion resistance of the coated metal plate after coating and drying is determined by JIS-Z237.
It was subjected to the 5 wt% salt spray test shown in No. 1 and the corrosion resistance was evaluated according to the following criteria depending on the white rust generation state. That is, it was evaluated by the time until the occurrence of 1% white rust due to the corrosion of the electric pure Zn plating layer under the coating film. ◎ 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.

[0112] 2. Performance evaluation after heating and baking treatment (2-1) Adhesion between coating films (heat-sensitive self-adhesive strength) After coating and drying, the coated metal plate is cut into a size of 25 mm × 100 mm, and the coating film surfaces are 25 mm × 12 mm.
A simple lapping material (single lap joint) is produced by superposing with the area of. This laminated material was pressed (3 kgf / cm ² ) for 20 minutes using a heating press device at a predetermined temperature (adhesion temperature) and then cooled, and the obtained test piece was measured according to JIS K-6850. The maximum load until the test piece broke at room temperature was measured with an axial tensile tester, and the shear load was determined by dividing the maximum load by the shear cross-sectional area. ◎ excellent: the adhesive strength 150 kgf / cm ² or more ○ Good: 〃 80~150kgf / cm ² △ slightly inferior: 〃 50~80kgf / cm ² × poor: 〃 50 kgf / cm less than ²

(2-2) Adhesion with cloth (90 ° peeling strength) After coating and drying, the coated metal plate was cut into a size of 70 mm × 150 mm, and then a cotton canvas was placed on the surface of the coating film with 25 mm × 12.
They are superposed in an area of 0 mm, and the superposed material is pressurized (3 kgf / cm ² ) for 20 minutes using a heating press device at a predetermined temperature (bonding temperature) and then cooled. The obtained test piece was held horizontally in a uniaxial tensile tester, and the cotton cloth attached to the test piece was peeled off by hand for a length of 30 mm in advance, so that the angle between the cloth and the test piece was always vertical. While maintaining, measure the average load until the cotton canvas peels from the test piece at room temperature,
The peeling adhesive strength per cotton sail width of 25 mm was obtained. ◎ Excellent: Adhesive strength 10 kgf / 25 mm or more ○ Good: 〃 8 to 10 kgf / 25 mm △ Somewhat inferior: 〃 5 to 8 kgf / 25 mm × Inferior: 〃 less than 5 kgf / 25 mm

(2-3) Adhesion durability (deterioration of adhesiveness over time) After coating and drying, the coated metal plate is cut into a size of 30 mm × 75 mm, and the coating film surfaces are overlaid with an area of 30 mm × 10 mm. Then, a simple laminated material (single lap joint) is prepared. This laminated material was pressurized (3 kgf / cm ² ) for 20 minutes using a heating press device at a predetermined temperature (adhesion temperature) and then cooled, and the obtained test piece was subjected to JIS K-6857 according to JIS K-6857. The test piece was subjected to a constant temperature and humidity test under the conditions shown below, and then the same uniaxial tensile test as in (2-1) above was performed to examine the durability of the adhesive strength (deterioration of the adhesive property over time).

[Constant temperature and humidity test] Temperature: 25 ° C., relative humidity: 90% RH, test time: 72
The 0h evaluation standard is as follows. ◎ Excellent: Adhesive strength of 130 kgf / cm ² or more ○ Good: 〃 70 to 130 kgf / cm ² △ Slightly inferior: 〃 40 to 70 kgf / cm ² × Inferior: 〃 less than 40 kgf / cm ²

(2-4) Heat Resistant Adhesiveness 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. Lap joint). This laminated material was pressed (3 kgf / cm ² ) for 20 minutes using a heating press device at a predetermined temperature (bonding temperature) and then cooled, and the obtained test piece was placed in an atmosphere of 60 ° C. It was subjected to the same uniaxial tensile test as in (2-1) above, and evaluated according to the following criteria by the adhesive strength (heat resistant adhesiveness) in a high temperature environment. ◎ Excellent: Adhesive strength of 80 kgf / cm ² or more ○ Good: 〃 50 to 80 kgf / cm ² × Poor: 〃 less than 50 kgf / cm ²

(2-5) Corrosion resistance (white rust resistance) In order to evaluate the corrosion resistance after baking, first, the coated-dried coated metal plate is cut into a size of 70 mm × 150 mm, and then the predetermined temperature shown in Table 2 is obtained. After baking, and tape-sealing the end and back surfaces, perform JI in the same manner as (1-3) above.
It was subjected to a 5 wt% salt spray test shown in S-Z2371, and the corrosion resistance was evaluated according to the following criteria by the 1% white rust generation time due to the corrosion of the electric pure Zn plating layer under the coating film. ◎ 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.

(2-6) Solvent Resistance Coating-After drying, the coated metal plate is cut into a size of 70 mm × 150 mm, and heated and baked at the temperature shown in Table 2.
The surface of the obtained test piece was slid 20 times with gauze containing toluene, and the deterioration state of the coating film was evaluated according to the following criteria. ◎ Excellent: No abnormality ○ Good: Slightly swelling degree × Inferior: Dissolution of coating film The above performance evaluation test results are shown in Tables 3 to 7.

[0119]

[Table 3]

[0120]

[Table 4]

[0121]

[Table 5]

[0122]

[Table 6]

[0123]

[Table 7]

From Tables 1 to 7, the following can be considered. As defined in the present invention, coating liquids A to F containing a thermoplastic resin (A) having a cross-linking functional group and a cross-linking agent (B ₁ , B ₂ ) in a predetermined equivalent ratio are used, and a preferable coating film is used. The coated steel sheet obtained by treating the coating amount and the drying temperature has excellent scratch resistance, solvent resistance and corrosion resistance in the coating film state after coating and drying, and the coating film after heating and baking is excellent. Adhesion between coatings,
It can be seen that it has adhesiveness with cloth, adhesive durability, heat resistant adhesiveness, corrosion resistance, and solvent resistance.

On the other hand, even when the coating liquids A to F satisfying the requirements of the component composition defined in the present invention are used, if the drying temperature or the heating / baking temperature is not appropriate as described below,
It can be seen that either the performance before heat baking or the performance after heat baking joining is insufficient.

No. 5,13,21,29,37,4
5: The heating and baking temperature is lower than the thermal crosslinking reactivity development temperature T _{B2 of the} crosslinking agent (B ₂ ), and the crosslinking agent (B
No. ₂ ) and the resin (A) are not cross-linked. No. 7, 15, 23, 31, 39, 47: When the drying temperature is low and a partial crosslinking reaction between the resin (A) and the crosslinking agent (B ₁ ) does not occur in the coating / drying process, No. 8, 16, 24, 32, 40, 46: Drying temperature is very high, and the resin (A) and the cross-linking agent (B
_When the crosslinking reaction with ₁ ) and (B ₂ ) has proceeded excessively.

That is, when the drying temperature in the coating / drying step of the coating film is high, the resin (A) and the crosslinking agent (crosslinking agent) in the coating film are dissociated by the dissociation of the blocking agent of the blocked isocyanate group during the drying. The crosslinking reaction with B ₁ ) and (B ₂ ) excessively progresses, the thermoplasticity disappears due to the progress of the curing reaction in the coating film, and even after the heat baking treatment for bonding, the coating surface Satisfactory heat-sensitive adhesiveness cannot be obtained because the integration of the adhesive surfaces between them and the crosslinking reaction hardly occur.

No. 4, 12, 20, 28, 36,
In No. 44, since the amount of coating film adhering tends to be insufficient, it is considered that the coating film becomes non-uniform and a coating film defect is partially generated, and the heat-sensitive adhesiveness and the adhesive durability are not sufficient. No.
Nos. 6, 14, 22, 30, 38, and 46 have extremely high temperatures during heating and baking, and thus the adhesiveness and adhesion durability are deteriorated due to the heat deterioration of the coating film, and the yellowing of the coating film occurs. Was recognized.

Next, since the thermoplastic resins (A) in the coating liquids do not have a functional group exhibiting a crosslinking reactivity with the isocyanate group contained in the crosslinking agent, the coating liquids G to I are
Poor scratch resistance and solvent resistance of the coating film after drying. In addition, even in the heating and baking treatment, the adhesive strength is obtained only by the fusion and integration effect of the joint surfaces due to the thermoplasticization of the resin, and the strength is improved by the cross-linking reaction between the coating surfaces and between the coating surface and the adherend surface. It can be seen that performances such as high-temperature adhesiveness and solvent resistance are insufficient because the effect cannot be obtained.

Further, in the coating liquids J to K, only one kind of the crosslinking agent is contained in the coating liquid, and in the case of only the crosslinking agent having a low crosslinking reactivity developing temperature, the coating liquids J to K are treated with the resin (A) at the time of coating and drying. The cross-linking reaction of (1) does not proceed sufficiently so that sufficient adhesion performance is not exhibited by heat baking, or if the drying temperature is too low, the partial cross-linking reaction does not proceed during drying, so the scratch resistance of the coating film before heat baking and The solvent resistance becomes poor. On the other hand, in the case of only a crosslinking agent having a high crosslinking reactivity expression temperature, the crosslinking reaction with the resin (A) does not proceed during coating and drying, so the scratch resistance and solvent resistance of the coating film before heating and baking are poor. Has become.

The coating liquids L to M are comparative examples in which only the thermoplastic resin (A) or only the cross-linking agent (B ₁ , B ₂ ) is blended in the coating liquid, and the coating films obtained are The performance intended by the present invention is hardly exhibited even after drying and after baking by heating.

[0132]

EFFECTS OF THE INVENTION Since the present invention is constituted as described above, it does not cause stickiness or blocking properties in the film-forming / drying state, and furthermore, the film has scratch resistance and organic property during slitting and punching. It also has excellent solvent resistance to solvents, and when heated and baked for bonding, it exhibits excellent adhesion, adhesion durability, high temperature adhesion, solvent resistance, corrosion resistance, etc. in a short heat treatment. It has become possible to provide a heat-sensitive adhesive resin-coated metal plate that can be processed.

Claims (9)

[Claims] 1. _A thermoplastic resin (A) having a functional group exhibiting crosslinking reactivity in a molecule and having a thermoplastic expression temperature T _A of 80 ° C. or higher, and a thermosensitive resin satisfying the following crosslinking reactivity expression temperature. The coating film containing the type cross-linking agents (B ₁ ) and (B ₂ ) as the main components,
A heat-sensitive adhesive resin-coated metal plate, which is formed on at least one surface of a metal plate. T _B1 <T _B2 , T _A ≦ T _B2 [where T _B1 and T _B2 are heat-sensitive crosslinking agents (B ₁ ), (B ₂ ).
The cross-linking reactivity developing temperature (° C.) and T _A represent the thermoplasticity developing temperature (° C.) of the thermoplastic resin (A). ] 2. The thermoplastic resin (A) has a thermoplastic expression temperature T _A of 80 to 200 ° C., and a thermosensitive crosslinking agent (B).
The heat-sensitive adhesive resin-coated metal sheet according to claim 1, wherein the crosslinking reactivity developing temperature T _B2 of ₂ ) is 200 ° C or lower. 3. The heat-sensitive cross-linking agent according to claim 1, wherein the cross-linking reactivity developing temperatures T _B1 and T _B2 of the heat-sensitive cross-linking agents (B ₁ ) and (B ₂ ) satisfy the requirements of the following formula. Adhesive resin coated metal plate. T _B2- T _B1 ≧ 30 ℃ 4. The heat-sensitive crosslinking agents (B ₁ ) and (B ₂ ) are both blocked isocyanate group-containing compounds,
The thermoplastic resin (A) is a resin having in the molecule thereof a functional group exhibiting crosslinking reactivity with an isocyanate group.
The heat-sensitive adhesive resin-coated metal plate according to any one of 3 above. 5. The thermoplastic resin (A), wherein the functional group showing cross-linking reactivity with the isocyanate group is a hydroxyl group, an amino group,
One or two selected from the group consisting of carboxyl groups
The heat-sensitive adhesive resin-coated metal plate according to claim 4, which comprises at least one kind. 6. A polyethylene resin, a polyester resin or a polyurethane resin, wherein the thermoplastic resin (A) contains a functional group exhibiting cross-linking reactivity with an isocyanate group.
The heat-sensitive adhesive resin-coated metal plate according to claim 4 or 5, which is one kind or two or more kinds. 7. 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. 8. A thermoplastic resin (A) and a heat-sensitive crosslinking agent (B
The heat-sensitive adhesive resin-coated metal according to any one of claims 1 to 7, wherein the coating amount of ₁ ) or (B ₂ ) as a main component is 0.5 to 30 g / m ² in terms of solid content. Board. 9. A method for producing the heat-sensitive adhesive resin-coated metal sheet according to claim 1, which comprises a thermoplastic resin (A), a heat-sensitive crosslinking agent (B ₁ ), and (B). ₂ ) A method for producing a heat-sensitive adhesive resin-coated metal plate, which comprises applying a coating liquid containing as a main component to at least one surface of a metal plate and then performing low-temperature heat treatment at a temperature Z (° C) that satisfies the following conditions. . T _B1 ≤Z <T _B2 [where T _B1 and T _B2 have the same meanings as described above]. ]