JPS59148657A - High-workability precoated steel plate - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a highly workable precoated steel plate. In recent years, in addition to conventional outdoor building materials, the industry that manufactures home appliances, interior building materials, utensils, and other high-end products has been gaining momentum to adopt prepainted steel sheets in more fields. Coaters are also making efforts to meet these needs, but the required coating film performance is extremely high. There are even examples of good processability. From the perspective of pre-painted steel sheet manufacturing,
This is extremely difficult, and various studies are being conducted, including pre-treatment of the steel plate, materials such as paint, electron beam curing, heat curing, ultraviolet curing, and other coating film curing methods. Currently, there are no products that have coating film properties comparable to postcoats and can be processed freely.

One possible way to solve this problem is to stop the hardening of the coating at a stage where it can withstand processing, process it into the desired shape, and then heat it again to completely cure it. JP-A-55-85827 is an invention based on this idea, but it is based on a very specific coating material, namely, an epoxy resin and an allyl etherified methylolphenol as the main components, and if necessary, acetal. The key point is that polyvinyl alcohol, cellulose derivatives, resol type phenolic resins, amine resins, etc. can be added, and the amounts used of each component are also limited.

Moreover, as stated in the detailed explanation of the invention in the above-mentioned publication, stopping the thermosetting reaction at the desired stage is
In practice, there were many cases where the coating was hard due to insufficient hardening, and the processability was poor due to excessive hardening.

As a result of many years of study, the inventors of the present invention intended to develop a pre-coated steel sheet having a semi-cured coating film that overcomes the drawbacks of the prior invention, and succeeded in that purpose. The present invention uses a resin system (component A) having an unsaturated carbon double bond that is active to electron beams in its molecules, which completely cures the coating film by heating after shaping into a desired shape. The main component is a resin system (component B) that has a functional group that reacts with the resin, or a lacquer-type horse chestnut resin system that does not have unsaturated carbon bonds in the molecule. It is a pre-coated steel plate made by coating a hardened coating film, and this steel plate (d1 is processed into the desired shape by the user,
It is heated and completely cured to be used as home appliances, building materials, and other products.

While comparing the features of the present invention, the contents of the above-mentioned Japanese Patent Application Laid-open No. 56-85827, which is an example of the prior art, will be described and examined in more detail. In other words, the specification of this publication states that (1) it is important to set the conditions for curing to be stopped at what degree the coating film is in a semi-cured state, and an inappropriate semi-cured state may result in unsatisfactory results; is difficult to obtain, and also (
2) For ordinary thermosetting paints, this optimum semi-curing condition range is narrow, and it is stated that it is difficult to put it into practical use when considering the fluctuations in drying conditions that can occur in ordinary industrial paint drying equipment. In Japanese Patent Application Laid-open No. 53-85827, it is thought that this problem was solved by the use of a paint that uses a very limited resin system and has a specific composition ratio.

The greatest feature of the present invention is that, in a pre-coated steel sheet in which the paint is coated onto a single sheet and then coated with a semi-hardened coating, the semi-hardening method utilizes radical polymerization for the curing reaction of the paint polymer. It is something.

More specifically, when electron or wire curing methods are used as the drying and curing method, it is possible to freely select the conditions for semi-curing the paint film.In other words, compared to ordinary thermosetting paints, it is possible to select the optimum semi-curing conditions. Furthermore, the range of drying conditions that can occur in thermosetting industrial paint drying equipment can be greatly expanded, and even when applied to a practical line, the use of the Yoshiko-Katsu accelerator can be greatly reduced. It has been experimentally discovered that it can be reduced. Here, the paint that can be used is one that contains a radically polymerizable C11 bond in its molecule.

When semi-curing the coating film, 7 defects, subdivisions, and
When using a curing reaction such as a heavy separation reaction, 1)! ]
The difficulty of overcoming the problems described in Jōdō 85827, 1973 is considered to be extremely difficult from the viewpoint of controlling the curing reaction of paint resin and the curing equipment using heat. It will be done. When semi-curing a paint film, an example of a method of thermosetting is a hot air drying oven, which is the most common industrial method, and a small precision drying oven used in a laboratory.
Even if the curing conditions (eg, temperature, time) are set, there are many difficulties in applying it to an actual industrial line.

First, regarding the temperature setting of the drying oven in an industrial line, even if the temperature is set to a certain level, it is unavoidable to see a fluctuation of ±5°C or more when looking at the ambient temperature meter. Furthermore, fluctuations in hot air speed, air volume, etc. cannot be avoided, and the initial board temperature during threading, the movement of the board due to the catenary during threading, etc., may have a synergistic effect with the conditions mentioned above. Coupled with this, it is difficult to set the state at the time of leaving the drying oven, for example, the final plate temperature (-set value of curing conditions) within a very small range.

Furthermore, due to changes in line speed due to line troubles before the baking process (d), it is impossible to suddenly change the baking conditions. Even if the coating film is completely cured,
Since the painted surface is heated, it is soft and in order to prevent blocking, it is rapidly cooled and wound in the case of a coil, and wire-layered in the case of a cut plate, but in this case,
While the purpose is only to cool a hardened coated steel plate, in the case of semi-hardening, even this cooling condition poses a problem in that the degree of hardening varies. Furthermore, in addition to the factors mentioned above, the influence of plate thickness also plays a large role.

As mentioned above, from the equipment point of view, as long as thermosetting equipment is used, stopping the curing reaction at an intermediate stage involves many extremely unstable factors.

From the viewpoint of paint curing reactions, most of the curing reactions by heating belong to sequential reactions among the polymerization reactions shown in Table 1 below, and are typical of ordinary thermosetting paint films. Taking the polycondensation reaction (crosslinking reaction) as an example of a reaction, the relationship between the reaction time (I-tl at the time of curing) and the molecular weight of the product (degree of crosslinking or degree of curing) is shown in Figure 1 (Kyoritsu Zenyō " It appears schematically as in Organic Electron Theory Ill, p. 281, published in 1960).

Table 1 Classification of polymerization reactions of polymers ("Organic Electronics Theory ■" written by Minoru Imoto) Kyoritsu Zensho (published in 1988)
(Page 296) Here, the degree of curing of a normal thermosetting coating film is usually controlled at a point exceeding the reaction time TA and the molecular weight point, as explained using the example of FIG.

That is, in other words, the coating film is cured in a region where the relationship between the curing time and the degree of curing is relatively gradual.

In this region, the coating film has been completely cured, so it has good hardness, stain resistance, chemical resistance, etc., but as a matter of course, processability is poor.

In the case of semi-curing, the reaction is suppressed below the TA1MA point in Figure 1, but coupled with the equipment factors mentioned earlier, it is extremely difficult to stably obtain the desired degree of curing. It's difficult.

The greatest feature of the present invention is that the paint applied to steel plates is
A resin made by adding a fat (component B) having a functional group that reacts with heating to a fat (component A) that has an unsaturated carbon double bond that is active to electron beams in the molecule. It is a system in which a catalyst is added to the composition to enable radical polymerization by thermal decomposition as the case requires, and the curing process utilizes a radical polymerization reaction by electron beam as a first-stage semi-curing reaction. After processing into the form (), a condensation reaction of the I3 structure by heating and a radical polymerization reaction of the A component are carried out as a complete curing reaction.

Here, in the first stage of semi-curing, using radical polymerization for the curing reaction makes it much easier to control the degree of ionization and expands the range of curing conditions, compared to sequential reactions.
In particular, the degree of reaction can be controlled extremely easily using the electronic assembly curing method, and from an equipment perspective, an electron beam irradiation machine can significantly narrow the range of fluctuations in physical conditions compared to a heating oven (experimental results show that This discovery is the key to the present invention.

The content of the present invention will now be described in more detail. Component A of the resin constituting the paint used in the present invention is an unsaturated carbon bond in the molecule that is active to electron beams. There are those introduced by an esterification reaction and those having a double bond in the molecule such as a diene type, and one or two of these can be used.

Component B is a resin that has a functional group that reacts with heating (d, for example, a carfoquinol group, a hytrogynol group, an iso/ai group, a -+- group, a lyricidyl group, a methylol group, a notoki/group, It must contain one or more functional groups that enable thermal reaction, such as ethoxymethyl group, butoquinomethyl group, amide group, imide group, etc., and one or more of these can be used.Both components A and B. If the surface layer system satisfies the conditions mentioned above, polyester, acrylic, epoxy, urethane, flexible silicone, melamine, alkyd, etc.
Good too. What is important here is the amount of unsaturated carbon double bonds in component A and the total amount of functional groups that enable thermal reaction in component B.

Since the first stage semi-curing reaction is based on an electron beam, the amount of unsaturated double bonds involved in the reaction is important.
According to experiments conducted by the present inventors, it is appropriate that there be 01 to 10 (meth)acryloyl groups, preferably 04 to 6, per molecular weight i'ooo.

That is, if the amount of unsaturated double bonds is more than 10 parts per molecular weight of 1000, there will be too many crosslinking points and the curability of the coating film will be too high, causing problems such as cracking during processing after semi-curing. In this case, it is possible to loosen the half-if condition, that is, to reduce the electron beam irradiation dose, but the degree of curing with respect to the dose is suddenly too high, and even if electron beam curing is used, Curability may not be easily controlled. Also,
If the double bond content is less than 0.01 per molecular weight of 1000, the number of crosslinking points will be too small and the film will be too soft to be used as a semi-cured coating, making it unsuitable for use as a pre-coated steel sheet, or a thick coating will be required for semi-curing. , not industrially useful.

Next, regarding the number of functional groups that react in the second stage of heating, the molecular weight is 0.05 to 50, preferably D1 to 40, per 1 0'O. If the amount is too low, the performance of the coating film will not be sufficient even if it is cured by heating, for example, the hardness, stain resistance, chemical resistance, etc. will be poor. Sword 5
If it is 0 or more, the crosslinking density after heating will be too different,
As a result, it is unclear whether this is due to an increase in internal stress or not, but cracks and cracks occur in the machined portion over time.

Furthermore, the molecular weights of component A and component B will be discussed.

Regarding component A, the number average molecular weight is 200 to 200.00.
0 suitable size is 300 to 100,000. Regarding component B, the number average molecular weight is 60-200,000, preferably 100-500,000. In this case, when the resin system consisting of both components A and B is semi-cured with an electron beam, if the lower limit of each is below or below, the coating film will generally have
There is no elongation and workability is insufficient. On the other hand, if the upper limit is exceeded, the viscosity increases and a large amount of solvent must be added at the time of coating, and it is necessary to heat the coating to a considerably high temperature in the solvent evaporation process, which impairs economic efficiency.

Furthermore, in this case, one lacquer-type l1tJ resin that does not induce unsaturated carbon bonds can be added to the molecule. This lacquer-type resin can be made of (polymer) acrylic, polyester, urethane, acrylamide, diene, melamine, or rubber, but in this case, the main purpose is to impart flexibility to the coating film. Since no curing reaction is expected during the first stage of semi-curing and the second stage of complete curing, free functional groups such as hydroxyl groups, carboxyl groups, ynonaneate groups, amide groups, etc. Contamination/Chemical Resistance, Refill Water] It is better to have zero or as little as possible for substances that may have a negative effect on raw materials, etc., and increase affinity with pigments or other resins without causing roughening. The amount necessary for this purpose is fine, and even if there is, it is sufficient that it is less than a few molar proportions. The viscosity of this resin is preferably solid or close to solid, and the viscosity of the resin is preferably 10,000 centipoise or more, and the elongation of the resin is preferably 100% or more. The purpose of adding this resin is to compensate for the lack of flexibility and elongation of resins that have active unsaturated carbon double bonds in their molecules when they are semi-cured by Kame beam irradiation. This is to relieve internal shrinkage stress during semi-curing.

Here, a catalyst that enables radical polymerization by thermal decomposition may be added as necessary, but this is because when the coating film is semi-cured by the electron beam in the first step, the two Ij bonds are sufficiently reacted. It is added in advance to prevent the coating film from being completely cured by heating after processing into the desired shape in the second step, since there is a possibility that the coating film may remain uncoated.

Examples of catalysts that enable radical polymerization through thermal decomposition include the following. That is, examples thereof include ketone peroxide, peroxyketanol, hydroperoxide, dialkyl peroxide, dianrubber oxide, peroxy dicarbonate, peroxy ester type, and the like. However, due to longevity, the decomposition temperature of these catalysts must be at least 50°C or higher, preferably 70°C or higher. This is because after the first stage of semi-curing of the coating film, the pre-coated; This is because the inventors conducted a follow-up experiment on the coating film performance during the first stage of semi-curing (for 12 months), and found that It has been found that in the f-1 fat system, it is preferable that the decomposition temperature of the catalyst is 50°C or higher.

However, even if the temperature of the catalyst increases by 1, even if it does not cause any problem from the viewpoint of membrane performance, it is inappropriate from the viewpoint of energy saving and cost, and the temperature should be set at 20
A temperature of at least °C is desirable.

Since both the A component and the B component can be cured by heating, a catalyst may be added in advance as needed to accelerate the reaction.

In addition, the following additives may be added when the above resin system is made into a paint. That is, polyhydric alcohol (meth)acrylates for controlling crosslinking degree and viscosity, such as ethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, trimethylolprobanto(meth)acrylate, penta Erythritol tetra or methacrylate or □ monofunctional methacrylate, such as phenylglycidyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenylcalpitol (meth)acrylate, nonylphenoxylate ethyl (meth)acrylate, nonylphenol/ethylene oxide adduct (meth)acrylate, benzoyloxyethyl (meth)acrylate, nonylphenol/ethylene oxide adduct (meth)acrylate, cresol glycidyl ether (meth)acrylate, cresol/
Added propylene oxide! These include V/J (meth)acrylate, styrenated cresol/ethylene glycol (meth)acrylate, butanol/propylene oxide adduct (meth)acrylate, dialkylethanol (meth)acrylate, and the like. Furthermore, examples of q4 agents include butylphthale-1, dioctyl phthale-1,
/Octyl terephthalate, zontyl terephthalate-1.
You may also use the blue 7-tal 1' limb type or the phosphate type. Still, of course, pigments, in some cases
Ordinary non-two-(may be added).In addition, when /ner is added, MiJ (C1) which irradiates electron 7 warabi or /et air or hot air, far (near) infrared j1,5 magnetic wave induction Either it is necessary to scatter the nonner by heating, etc., or even if heat is applied, it is essential to keep the decomposed residue of the radical polymerization catalyst below 1 degree. Conditions must be carefully set to prevent reactions from occurring.

The above-depleted paint is applied to a steel plate and semi-cured with an acid beam, and in this case, the degree of conversion to 4Jq requires that it be painted or tank-free. In addition, the glass transition point (peak value of loss tangent tan δ in viscoelasticity measurement) of Hiromei is 90°C or less, preferably 70°C.
°C or less and the dynamic bullet 1 vitality E' is 1X 10 dyn at the processing temperature during post-processing by the user.
e/C1n2 or less w-i or 9 X 109a y
It has been experimentally found that the object of the present invention is achieved when ne/cm2 or less.

As a further supplement, the glass transition point of the coating film after semi-curing is desirably 98% or less compared to that at the time of heat curing after the second stage of processing (first complete curing) when expressed in terms of absolute quality. must be 95% or less.

Hell, the glass transition point of the paint film after complete curing is 70.
°C or higher, the dynamic elastic modulus E' is 1010d y n
e 10n2 or more preferably 2 X 10 dyn
It was also experimentally discovered that e must be 7 cm2 or more.

The original plate to be coated in the present invention is, for example, a steel plate, an electrolytic galvanized steel plate, a hot-dip galvanized steel plate, or those whose surfaces have already been subjected to a chemical conversion treatment such as chromic acid or phosphoric acid in the steel plate manufacturing process, stain-free steel, or frigid steel plate. , aluminum plate, stainless steel plate, etc. can be used. In addition, as a pretreatment method to be performed on the gold 11β plate as necessary, the well-known 4.1! It can be done in various ways.
] E, if the metal plate is a u1iIj plate that has already been subjected to a chemical conversion treatment during its manufacturing process, it may be pretreated with only a cleaning treatment; Items are treated using chemical conversion treatment agents appropriate for their materials.
Pretreatment can be performed. Furthermore, in the present invention, it is preferable to apply a brimer to the original plate, which has good adhesion to the painted original plate, and which is applied to the paint coated on the base plate.
You can use anything that doesn't have 1~te l/rahul. For example, epoxy, epoxy/acrylic)
)Heat-curing type, UV-curing type, such as epoxy polyester, polyester, acrylic, vinyl phenol yarn,
'Any electron beam curing type paint may be used, and it is cured by the respective curing means.

As a reminder, a setting and flask-off step may be included in the polymerization process in which a solvent is contained in the ultraviolet or electronic curing type brimer (d). These primers can be applied by conventional methods such as natural roll coating, reverse roll coating, curtain flow coating, and spray coating, and the coating thickness is approximately 1 to 10 μm. Preferably, it is around 6 coats.As a method for applying the paint system in the present invention, common methods such as o-ru coat, curtain flow coat, and spray coat are used, and even if the paint viscosity is very high, , may be applied by heating.

To explain the electron beam irradiation method, any known device can be used, and currently developed and commercially available accelerating voltages range from 150 kV to several M.
Any of V can be used. To set the acceleration voltage,
Film thickness, coating film specific gravity and known knowledge (Dep th -1)
For example, 3001ζ
(2) A 20-unit ITIA accelerator is sufficient.

Generally, when curing a coating film by irradiating it with an electron beam,
It is known that ozone or ozone acts as a polymerization inhibitor, so it is desirable to block this, and the oxygen concentration in the electron beam irradiation atmosphere should be set to 5% or more. 0.05% or less.

It is also possible to print on the coating of this product.
Furthermore, it is desirable to laminate a protective film to protect the surface of the thread membrane.

Note that this product can also be printed, and the same printing ink as that used for the above-mentioned Kui Yarn is suitable. As the protective film, those made of polyvinyl chloride, polypropylene, polyethylene or oil are used.

Example 1 As the component A, the molar ratio of φ-mers of 1 diaphragm obtained by adding acrylic to ethyl acrylate, methyl methacrylate, and tutacryl late Grin/L was 65:30:5, Number average molecular weight is approximately i o, o o o, molecular weight 100
To 100 parts of acrylic cutting (by weight, the same shall apply hereinafter) which has about 0.48 acrylic groups in the mouth, as component B, Toyobo Iron P-300'' (molecular weight 2
0,000, OH value: 100-150eq, / 106
．． ';') 100 sound L day - < sz urethane +
l Ko.

126 parts of L-75' (i.e., in component B,
NC'O/0I-1-6), titanium white 210
Add sonic μ, use 200 parts of Kijiroll as a solvent, and disperse with three rolls to form a paint.

Apply this paint to a heat-cured epoxy acrylate.

Limer (film thickness: 2 μm) was applied to a hardened galvanized steel sheet to a dry film thickness of 25 μm using a coater, and pheasants were scattered using jet air. This coated sheet was coated under a nitrogen atmosphere. (oxygen concentration 0.1%), voltage 3
00 kV, two accelerators with a current of 25 mA, and a dose of 5 Mr.
A coated steel plate having a semi-cured coating film was obtained by irradiating the steel plate with ad electron beam.

The hardness of this painted female j board is F, and the hardness of this painted board is 90 with a bending machine.
0 (R=O), but no cracks were observed and the workability was good. This same board was subjected to a stain resistance test. Magic, Nki (red, black, blue)
After applying it and keeping it at room temperature for 24 hours, I tried wiping it with gauze soaked in Etasyl, but it left a strong mark (Rating × - △)
In addition, ``sparkling'' occurred in areas where the marker ink was not applied.

Next, this processed board was held in an atmosphere of 230" O for 3 minutes, and then taken out from the oven and the eruption degree was measured. It was 31-1, and there were no changes such as cracks in the processed part. As before, we conducted a stain resistance test and found that the stain traces were easily wiped away (rating: g).
), gappa and sink' did not occur.

Reference example 1 ``Drowsiness i+t+lead plating;! Instead of Qj board, use soot foil (
Apply the same paint as in Example 1 (25μ thick), add a tin foil with the same diameter to form a half-width W1 film, and melt the tin foil using the amalgam method to obtain a free film. the law of nature.

When this film was examined for viscoelastic behavior using a Vibrono V-111-EA test tube manufactured by Toyo Paul J. Winn Co., Ltd., the dynamic elastic modulus E' was 6, OX
10 dyne 70m2 (20'C), loss, rh
The temperature showing contact fan δ111aX was 35°C.

Furthermore, when the viscoelastic behavior of the semi-cured coating film was examined under the same heating conditions as in Example 1, E' was 3.
．． Ox 1 010d y n e /cTL2(2
0′O), t””maX temperature was 90°C.

Example 2 The monomer molar ratio of phthalic acid, trimethylolpropane, and acrylic acid was 1:2:4, and the number average molecular weight was about 6.
A coated board having a semi-cured coating film was obtained by using a polyester oligomer having 0 units and about 6 double bonds per 1000 molecules as component A, and using component B and other conditions exactly as in Example 1.

The hardness of this painted board is F+, and the hardness is 90' with a bending machine.
(R=0), but no cracks were observed and the workability was good. When we conducted a stain resistance test on this board, we applied marker ink (red, black, blue) and lipstick, kept it at room temperature for 24 hours, and then wiped it with gauze soaked in ethanol, but strong marks remained. (Rating △)
.

Next, this processed plate was held in an atmosphere of 250°C for 6 minutes, and then taken out from the oven and its hardness was measured to be H, and there were no changes such as cracks in the processed area. As before, a stain resistance test was carried out, and traces of staining were easily wiped off (score 0).

Reference Example 2 'Instead of an electrogalvanized plate, the same material as in Example 2 was applied on a tin foil (25μ thick), and a tin foil with a semi-quaternized coating was applied under the same conditions. A free film was obtained by decomposing tin using the amalgam method. When the viscoelastic behavior of this film was investigated (Toyo Baldwin Co., Ltd.: Vibron DDXf-III-EA type testing machine), the dynamic elastic modulus E' was 9.5x109dyne/C1n.
2 (20'Q), and the temperature at which the loss tangent tan'max was 60°C.

When we investigated the viscoelastic behavior of the semi-cured coating film after heating it under the same heating conditions as in Example 1, we found that E' was 2.8.
X 1010dyne/v+2 (20”Q), fa
The temperature of nδ111aX was 85''C.

Example 6 All the same procedures as in Example 1 except that hexamethine methylolmelamine (molecular weight 390, 15 methoxy groups per molecular weight 1000) was used as component B in Example 1.
A coated steel plate with a semi-cured coating film was obtained under the same conditions as above.

The hardness of this painted steel plate is HB, and the hardness of this painted steel plate is 90
The same plate was subjected to impact bending at an angle of 1% = 0, but no cracks were observed and the workability was good.3 This same plate was subjected to a stain resistance test. After applying magic ink (red, black, and blue) and keeping it in a room for 24 hours, I tried wiping it with gauze soaked in ethanol, but it left a strong mark (rating: ×-). The parts that are not polished will have a ``loss of shine''.

Next, this processed steel plate was kept in an atmosphere of 230"C for 6 minutes, then taken out from the oven and its hardness was measured to be 31-1, and there were no changes such as cracks in the processed part. Still the same as before. Then, when a stain resistance test was conducted, traces of contamination were easily detected (scored 1), and no smearing or fading was observed.

Comparative Example 1 In Example 1, a paint containing only component B was prepared by omitting component A, and a coated copper plate was obtained by irradiating the paint with a dose of 5 Mrad under exactly the same conditions and procedures.

However, this coated copper plate had only 1 tack and a hardness of 4 B or less, making it unsuitable for use as a pre-coated α1114 plate.

Example 4 In the resin system of Example 1, a lacquer type resin having a monomer mole ratio of ethyl acrylate and methyl methacrylate of 60:40 and a 9-number average molecular weight of about 50,000 (solid) was added.
A further 100 parts were added, and titanium white was added so as to have the same normal phase to prepare a paint.

This paint system was applied under exactly the same conditions as in Example 1, and then irradiated with an electron beam to obtain a coated steel plate with a homemade coating film.

The hardness of the steel plate for the hall is HB, and the hardness of the steel plate is 1.
No impact bending or cracking at 80° (R=0) was observed, and workability was good.

This same steel plate was subjected to a stain resistance test. After applying magic ink (red, black, blue) and keeping it in the room for 24 hours,
I tried wiping it with gauze soaked in ethanol, but it left a strong mark (rating: ×-△), and the areas where the marker ink was applied were ``glossy''.

Next, this processed 1Qlii board was placed in an atmosphere of 260°C.
After being kept in the oven for 5 minutes, it was taken out of the oven and its hardness was measured, and there was no change in the hardness or hardness rank of 2I-1.

As before, when we conducted a stain resistance test, traces of contamination were easily wiped away (scored ◎), and there was no "shininess".

[Brief explanation of drawings]

FIG. 1D is a schematic diagram illustrating the relationship between the reaction time and the molecular weight of the product in a polymer reaction.

Claims (1)

[Claims] Adding a resin system with a functional group that reacts when heated to a resin system that has unsaturated carbon double bonds that are active to electron beams in its molecules, where the coating film is completely cured by heating after processing into the desired shape. A highly formable pre-coated steel sheet made of a lacquer-type resin system containing no unsaturated carbon bonds in the molecule, and coated with a semi-hardened coating film by electron beams. .