JPS61148046A - Surface-treated metallic plate and manufacture thereof - 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 Field of Industrial Application The present invention relates to a surface-treated metal plate used in the architectural field or general industrial field and a method for manufacturing the same. It is a surface-treated metal plate that has three laminated resin layers: an adhesive layer made of modified polyolefin and a protective layer made of polyolefin, and has excellent corrosion resistance, workability, and especially outdoor durability.

2. Description of the Related Art Techniques for directly laminating a polyolefin, such as a polyethylene film or a polypropylene sheet, onto a metal plate have been disclosed.

However, although the surface-treated metal plates obtained using these techniques generally have good initial adhesion and are sufficient for processing such as simple bending, they may be exposed to the outdoors for a long time, exposed to high temperature and humidity, or Metals corrode and the film easily peels off in wet tests and salt spray tests that simulate environments near the coast, and in Sunshine Weatherometer and Due Cycle Weatherometer tests, which are weather resistance tests. There is a phenomenon in which cracks occur in the film and it must be repaired, which is a defect when considering outdoor use.

Problems to be Solved by the Invention In order to improve the weather resistance of surface-treated metal plates, the present inventors
First, we decided to make the polyethylene and polypropylene resins themselves that are laminated on the surface to be high molecular weight, without double bonds or branches, and to be stable against ultraviolet rays and thermal deterioration. It was also determined that it would be effective to add colored pigments to these resins to further prevent UV deterioration.

However, although attempts were made to impart adhesive properties to this resin,
There is a phenomenon that weather resistance deteriorates when adhesion is imparted, and it was determined that it would be quite difficult to satisfy both adhesion and weather resistance at the same time, so it was decided to divide the film into two layers: an adhesive layer and a protective layer.

Furthermore, when a surface-treated metal plate is subjected to OT bending, it is required to have an elongation rate that does not cause cracks in the processed portion. The fact that there are no cracks in the processed area means that ordinary colored steel sheets (surface-treated metal sheets) do not crack when processed.
The disadvantage is that the metal is exposed in that area, resulting in poor corrosion resistance, but if this problem can be solved, a dramatic improvement in performance can be seen.

Moreover, this elongation rate, preferably OT crack-free, is not temporary, and if it is outdoors, etc., it must not be such that it will crack due to heat shrinkage even if exposed to heat.
From this point of view, it is meaningless to temporarily obtain something close to crack-free using ordinary colored steel plates. In other words, it is necessary to maintain an OT crack-free state for a long period of time. It was confirmed that the film thickness also needs to be within a certain range in terms of weather resistance.

Generally known methods for improving adhesiveness include treating polyethylene with corona discharge and applying flame at about 2000°C. All of these methods oxidize the film surface to generate carbonyl groups, but not only do they require large-scale equipment, but the adhesive strength obtained is still insufficient.

The present inventor has studied a method of extruding heated and melted resin from a T-die, but in this case, the lower the melt viscosity, the higher the adhesive force. However, the adhesive strength is still insufficient when simply T-die extruded, and the adhesive strength is such that the film will peel off if subjected to drawing processing, for example, and is not practical.

In contrast, the present inventor focused on the good adhesive strength of polyethylene modified with maleic acid, acrylic acid, methacrylic acid, phthalic acid, itaconic acid, etc., and after conducting studies, found that these modified polyethylene It was found that those bonded using the same method had poor corrosion resistance to steel plates.

Therefore, an attempt was made to add zinc chromate and strontium chromate to this modified polyethylene to increase its antirust effect. However, tests of bonding steel sheets and modified polyethylene with anti-corrosion pigments revealed that the bond strength was unstable and, contrary to expectations, there was little improvement in corrosion resistance.

Therefore, in order to provide corrosion resistance to resin-laminated steel sheets, a rust-preventing resin layer containing anti-corrosion pigments is provided on the steel sheet, and a modified polyethylene layer is placed on top of this, which provides excellent properties that combine adhesive strength, corrosion resistance, and processability. I was able to get

In other words, attempts to add anti-rust pigments to polyolefins
Since polyolefins have a characteristic of being difficult for water to pass through, this has the opposite effect, and soluble chromates are hardly eluted, so it was confirmed that they have no effect. Since such unexpected results were obtained, we decided to further increase the amount of rust preventive pigment and provide a rust preventive layer based on the idea that it would be necessary to add the rust preventive pigment to the resin that allows water to pass through easily.

Generally, paint films are designed to be impermeable to moisture, moisture, ions, and corrosive gases. However, the ease with which water passes through is determined by the properties of the resin, and even though this idea exists, in reality, nothing is perfect.For example, even if the coating film is easily permeable to water, it is difficult for gas to pass through. There is a phenomenon called.

If a large amount of anti-corrosion pigment is added to stiff resins in order to improve the corrosion resistance of the bent parts, blisters will occur on the flat parts in salt spray tests and wet tests. The current situation is that the design maintains a balance with the flat surface at the expense of corrosion resistance, resulting in poor overall corrosion resistance.

However, even such resins (for example, epoxy resins) are effective when combined with polyolefins. This is because polyolefin has the property of being difficult for water to pass through but easy for gas to pass through, so that moisture can be blocked by the olefin layer and corrosive gas can be blocked by the rust-preventing resin layer.

In addition, the olefin layer is not used by diluting it with a solvent like paints, but by heating and melting the raw materials to form a coating film, so pinholes do not occur even during heat drying, so the coating film does not form. Since there are no defects, its moisture barrier properties are excellent.

For general pre-coated metal plates, there is a paper section or.

There is a problem with corrosion starting from the edges. This is because, as mentioned above, the amount of antirust pigment added is limited to a small amount.

However, when combined with an olefin layer, the anticorrosion resin layer does not need to have moisture resistance.

Rather, it is more important to increase the amount of chromium, which is a rust-preventing pigment, eluted.

Corrosion resistance of the processed part is satisfied with an olefin layer capable of OT crack-free, and it is sufficient to consider rust-preventing resin layers mainly for the edges and paper parts.

In order to confirm the corrosion resistance of the product of the present invention, a polyolefin laminated metal sheet that cannot be combined with a conventional epoxy resin layer, and a general pre-coated steel sheet, the results of a salt spray test time and
The relationship between the amount of Cr6+ elution when immersed in PHII buffer was compared using samples with crosscuts. For a general pre-coated metal plate, the preferable range of C,64 elution amount when immersed in a buffer solution for one day is 0.02 to 0.
．． 05 p, g/cra, and above that,
In the salt spray test, blistering occurred on the flat surface, and below that, rust appeared on the crosscuts. In the OT processed part, the occurrence of rust is noticeable both within and outside the range of this Cr6+ elution amount.

On the other hand, the polyolefin laminated metal plate combined with the epoxy resin layer maintained a good condition with no blistering in the salt spray test, even with a large elution amount of 0.02 to 0.18 gg/c■. . Cru elution amount is 0.18 g
Even if it exceeds g/cm, elution seems to be simply wasted, and no further effect is observed, and some blistering is observed. On the other hand, in the case of an olefin laminated metal plate that does not have a rust prevention layer, the film peels off from the cross-cut portions, and rust occurs significantly.

That is, in the present invention, a large amount of rust-preventing pigment can be added to the rust-preventing resin layer, and as a result, the corrosion resistance of the paper portion and edges can be improved.
They discovered that it can be significantly improved compared to conventional pre-coated metal sheets.

The present invention was completed based on the above findings.

Means for Solving the Problems The present invention provides: (1) A rust preventive resin layer containing a rust preventive pigment with a dry film thickness of 2 to 20μ on one or both sides of a metal plate with a thickness of 0.2 to 2.0 mm. on which is an adhesive layer made of modified polyolefin with a dry film thickness of 2 to 30 p, and on top of which an adhesive layer with a dry film thickness of 2 to 30 p.
A surface-treated metal plate having a protective layer made of a polyolefin of 0 to 400 ml, and (2) a plate thickness of 0.2 to 2. (A rust preventive resin layer containing a rust preventive pigment is applied to one or both sides of a 1+us steel plate with a dry film thickness in the range of 2 to 20 μm, then heated, and a layer of dry film thickness in the range of 2 to 30 μm is applied. An adhesive layer made of a modified polyolefin heated and melted is applied, and at the same time or on top of this, a protective layer made of a heated and melted polyolefin is applied to a dry film thickness of 20 to 400!, and this is bonded to a mounting plate. After that, the melting point of the modified polyolefin used for the adhesive layer ~250
The present invention relates to a method of manufacturing a surface-treated metal plate by reheating in the temperature range of °C.

action The structure of the present invention will be explained below along with its operation.

In the present invention, first, the metal plate serves as a natural material and a supporting reinforcement, and includes a cold rolled steel plate, a galvanized iron plate, a galvanized steel plate, and a zinc alloy plated steel plate with a plate thickness of 0.2 to 2.0 mm. ,
A lead-plated steel sheet, a lead alloy-plated steel sheet, an aluminum-plated steel sheet, an aluminum alloy-plated steel sheet, a stainless steel sheet, or the like is used. The surface of this metal plate is preferably degreased in order to obtain adhesive strength, and in addition,
Also included are those having a chemical conversion treatment layer of about 0.1 to 5. Chemical conversion treatment is performed as a surface treatment for metal plates in order to improve their corrosion resistance, oxidation resistance, and adhesion.For example, it is performed by zinc phosphate treatment, iron phosphate treatment, or chromate treatment. .

The rust-preventing resin layer has the effect of preventing corrosion from the ends of the resin laminated steel plate or the paper portion of the surface layer. As the resin, synthetic resins, particularly epoxy resins are most suitable, and epoxy resins also include polyester resins modified with epoxy resins, urethane resins, and acrylic resins.

To these resins, anti-rust pigments such as zinc chromate and strontium chromate are added to 100 parts by weight of the resin.
It is optimal to add about 5-35 parts by weight, and the film thickness range is preferably 2-20μ.

The reason why 5 to 35 parts by weight is preferable is that if it is less than 5 parts by weight, almost no rust prevention effect can be expected by passivating the steel plate, and if it exceeds 35 parts by weight, the rust prevention effect will not improve and it is meaningless. . If the amount of anti-rust pigment is close to the lower limit, the film thickness is increased, and if the amount of anti-rust pigment is close to the upper limit, the film thickness is decreased.
The appropriate combination is selected and used depending on the application of the product, painting/drying workability, etc. 111 thickness range from 2 to
The reason for setting the value at 20 μl is that if it is less than 21 μL, almost no effect on corrosion resistance can be expected, and if it exceeds 20 μm, no significant improvement in corrosion resistance can be expected, which increases the cost, and also causes the solvent to volatilize during dry e-baking. This is because the phenomenon of blistering may also occur.

Next, the polyolefin of the present invention is typically polyethylene and polypropylene. When using polyolefin as a protective layer, the dry film thickness is preferably 20 to 400 microns.

The reason for setting the film thickness in the range of 20 to 400 mm is that less than 20 mm is insufficient to obtain a beautiful appearance through coloring and to have weather resistance to maintain the OT crack-free processing state for a long period of time. It is.

Moreover, even if the number exceeds 400, there is hardly any improvement in performance, and the cost simply increases.

The protective layer can be colored with an appropriate pigment.
Coloring prevents the transmission of ultraviolet rays, further improving weather resistance. At the same time, in order to improve corrosion resistance, the coating film is OT crack-free (JIS G 3312
According to a test method similar to . ) It is preferable to select a polyolefin that has processability of:

The modified polyolefin of the present invention is a polyolefin modified with maleic acid, acrylic acid, methacrylic acid, phthalic acid, itaconic acid, or the like.

The reason why the film thickness range is 2 to 30#L is that if it is less than 2L,
This is because a satisfactory adhesive force cannot be obtained and the quality becomes unstable. Moreover, even if it exceeds 30 hiro, no improvement in adhesive strength is observed and the cost simply increases.

In the resin used for the protective layer and the adhesive layer, the polyolefin of the protective layer has a low MFR1, for example 0.05 to i, o.
It is preferable to appropriately select a combination of resins in which the modified polyolefin of the adhesive layer has a high MFR1, for example, from 1.0 to 20.0.

It is known that in injection molding, a higher MFR (melt flow rate) is preferable because the resin flows better.

However, in the present invention, when flowing out from a T-die, a high MFR material tends to shrink at both ends and cause necking. As a result, the film width becomes narrower, and the film thickness at both ends becomes thicker than at the center, resulting in uneven product quality.

In order to prevent this, it is possible to reduce the distance between the T-die outlet and the adherend, but the distance between the T-die and the adherend may be reduced to 0.
It is almost impossible to achieve this in terms of equipment.Also, lowering the resin temperature and increasing the melt viscosity can be considered, but due to insufficient melting of the resin, it is not possible to obtain a film with a uniform thickness and the film is uneven. Air tends to get mixed in between the film and the adherend, resulting in variations in adhesive strength and blistering of the film due to air.

On the other hand, although resins with low MFR have features such as excellent weather resistance, they do not have to worry about necking if they leak out from the T-die, but they have the disadvantage that the film is easily cut, and they may sacrifice weather resistance. It may be necessary to take measures such as modifying the MFR value so that it is appropriate for the T-die.

In the present invention, from the T-die, high MFR (adhesive layer) and low MF
By extruding the R (protective layer) resin in two batches, necking caused by the high MFR resin can be reduced within an appropriate temperature range, and low MFR resin can be used without breaking the film.

For high MFR layers, the lower limit of the film thickness is just the amount necessary to obtain adhesion, maintain a balance with the low MFR layer, and prevent film breakage.
The lower limit is the amount needed to prevent calendar necking.

On the other hand, the upper limit has the advantage that a thicker high MFR layer eliminates film breakage, but it is not particularly limited and can be determined based on economics since the effect will be saturated. From this point of view, the dry film thickness is particularly preferably 20 to 400 μm for the protective layer and 2 to 30 μm for the adhesive layer.

Now, we confirmed the conditions for producing the surface-treated metal plate laminated with the above polyolefin on a continuous high-speed line.

First, a rust-preventing resin layer is provided, which is applied in an appropriate amount using a roll coater or the like, and dried in an oven.

Next, an adhesive layer and a protective layer are applied separately or simultaneously. The method involves laminating a resin heated and melted at 120 to 250°C on a steel plate with a rust-preventing resin layer, and even if the adhesive layer and the protective layer are extruded from separate T-dies, they can be extruded from the same T-die. Although they may be extruded simultaneously from the die, the latter is recommended from the viewpoint of labor saving and fewer cuts of the film.

Both resins are extruded by two extruders, and immediately after being extruded inside or outside the T-die, they are superimposed in a molten state to form two layers.

When the thus obtained polyolefin laminated metal sheet was tested, a phenomenon in which the film peeled off was observed in an outdoor exposure test and a long-term salt spray test. The cause of this is not entirely clear, but it seems to be because the surface of the rust-preventing resin layer with epoxy groups has microscopic irregularities, and the adhesive layer is not completely embedded inside the irregularities. . In other words, when the adhesive layer extruded from the T-die is continuously applied, the adhesive layer is forcibly pulled down, so that stress exists in the adhesive layer that causes it to shrink. Moreover, in order to manufacture continuously, a temporary adhesion method such as roll pressure bonding is required. For this reason, we believe that this is the result of the adhesive layer not being completely embedded into the irregularities of the rust-preventing resin layer.

Therefore, this problem was solved by reheating.

It was confirmed that the reheating temperature must be higher than the melting point of the adhesive layer resin (the temperature at which the resin starts melting), and the upper limit is 250° C. or lower to prevent deterioration of the resin.

For example, a reheating temperature of 110 to 250°C is recommended for polyethylene and 130 to 250°C for polypropylene. The baking time varies depending on the relationship between the oven capacity of the line and the line speed, but may be 20 to 300 seconds, and from the viewpoint of productivity, 20 to 80 seconds is recommended. Thus, the obtained surface-treated metal sheet is very useful in alleviating the stress existing in the resin extruded from the T-die and preventing the occurrence of cracks due to long-term harsh external conditions. .

Furthermore, by reheating, the adhesive strength is improved without the film peeling off from the edges, etc., and more stable performance is obtained.This not only improves the initial adhesive strength, but also provides stable performance even in harsh environments with high temperatures and humidity. A product with good adhesive strength and long-term durability was obtained. Furthermore, in order to enhance the design of the product, the heated film can be embossed by reheating.

For example, in the case of polyethylene, the reheating temperature is 110 to 2.
The temperature was set at 50°C because temperatures below 110°C are close to the melting point of modified polyethylene, requiring a long baking time, and the adhesive strength is unstable, making it unsuitable for high-speed, continuous mass production lines. It is. The same applies to polypropylene. Further, even if the temperature exceeds 250° C., no significant improvement in adhesive strength is observed, but rather causes thermal deterioration of polyethylene, etc., which is not preferable.

In this case, reheating using a hot press method is not excluded from the present invention, but it is inferior in workability and is disadvantageous for continuous production. The presence or absence of press pressure during reheating is
No effect on adhesion was observed. Moreover, it is more preferable that the reheating is performed once after being cooled after coating.

Example 1 After degreasing the surface of a galvanized iron plate with a thickness of 0.3 mm, a chromium treatment was applied, and 6 parts by weight of an epoxy resin solution containing anti-rust pigment was applied to 100 parts by weight of the resin to a dry film thickness. The anti-corrosive resin layer was applied by applying the resin to a 3-glycide finish and curing with heat.

Three tiles were coated with maleic acid-modified polyethylene that had been heated and melted so that the temperature at the time of adhesion was 120° C. to form an adhesive layer on this rust-preventing resin layer. On top of this adhesive layer, heat-melted polyethylene is applied so that the temperature at the time of bonding is 120℃.
140 l was applied to form a protective layer. This resin laminated steel plate was heated at a temperature of 130° C. for 50 seconds to produce a product.

Examples 2 to 7 and Comparative Example 1 are as follows under the conditions listed in Table 1.
Table 1 shows the results of preparing and testing surface-treated metal plates of ~1O.

Example 8 Difference in rust prevention properties of surface-treated metals depending on the presence or absence of a rust prevention resin layer,
Table 2 shows the difference in rust prevention between the steel sheet and general colored steel sheets.

Note that the middle part of the table indicates parts by weight, and * indicates points outside the scope of the present invention.

Example 9 Table 3 shows the combination effect of low MFR and high MFR.

The test conditions for Examples and Comparative Examples were as follows. The test result of 0 is excellent, and Δ is poor. × indicates an inferior result.

(1) Cylindrical deep drawing test The presence or absence of peeling of the resin was examined under the following conditions: die diameter 42φ, punch diameter 40φ, punch shoulder 8R1 drawing depth 20■■.

(2) Forming test Using the forming machine of the processing department IR, the presence or absence of peeling of the resin was examined.

(3) Vise OT bending test: OT bending was performed with the coating surface facing outward, and the presence or absence of cracks was determined.

(4) Peeling test 180 degree peeling, 10mm during peeling, peeling speed 100mm/
Adhesion strength was measured using ll1n.

(5) Salt water spray test Spray 5% salt solution at 500°C under the condition of 35°C internal temperature.
After spraying for 3,000 hours, the presence or absence of white rust and red rust from the OT processed parts and cross-cut parts, and the presence or absence of blistering and peeling of the resin were determined.

(6) #Weather Test The test was conducted for 5,000 hours using a Standard, Sunshine, and Weather-O-meter machine, and the presence or absence of peeling of the resin and occurrence of cracks was determined.

(7) Chemical resistance test Place a glass ring in the center of the product, add 20% HCi,
Fill the ring with 0% Na0)1 and leave it for 100 hours.
The presence or absence of resin blistering was determined.

(8) Outdoor exposure test 28 force moons were carried out facing south at a 45 degree angle (at Funabashi cloth).

Effects of the Invention According to the present invention, a surface-treated metal plate having excellent weather resistance, rust prevention, adhesiveness, and workability can be obtained. In other words, (1) Although conventional olefin laminated metal sheets have some degree of excellent weather resistance and workability, they do not contain a large amount of rust-preventing pigment, and it is difficult for water to pass through, making it difficult for the rust-preventing pigment to function. Once surface flaws occur, there is a limit to rust prevention, and
Adhesion was also not sufficient. This point has been improved in the present invention.

(2) Conventional epoxy resin laminated metal plates are easily compatible with anti-corrosion pigments, but if a large amount is added, even if the corrosion resistance of the bent areas is improved, water may easily penetrate from the processed areas or allow moisture to pass through. Therefore, blistering occurs on flat surfaces, and if a balanced design is carried out, the overall durability is not sufficient.6 In the present invention, moisture is absorbed by an olefin layer, and corrosive gas is absorbed by an anti-rust resin layer. The overall durability is sufficient because it is blocked by .

(3) In addition to the present invention, the intermediate coating can be hot-melt coated by heating and melting, so there are few pinholes, so the coating film is free from defects, and from this point as well, it has excellent moisture barrier properties.

(4) The processed part is an olefin layer that allows no OT cracks, and the paper part is mainly a rust-preventing resin layer, which can each provide corrosion resistance, so the total corrosion resistance is greatly improved.

(5) Long-term durability was significantly improved by reheating.

(6) By combining a low MFR resin for the protective layer and a high MFR resin for the adhesive layer, there is less necking, no film tearing, and a good balance of weather resistance, adhesion, and surface condition. A surface-treated metal plate can be obtained.

As described above, the industrial value of the present invention is significant.

Claims (1)

[Scope of Claims] 1. A metal plate having a thickness of 0.2 to 2.0 mm has a rust-preventing resin layer containing a rust-preventing pigment on one or both sides of the metal plate having a dry film thickness of 2 to 20 μm; It has an adhesive layer made of modified polyolefin with a dry film thickness of 2 to 30 μm, and on top of that an adhesive layer with a dry film thickness of 20 μm
A surface-treated metal plate having a protective layer made of ~400μ polyolefin. 2. The rust-preventing resin layer contains a rust-preventing pigment and is made of epoxy resin, one or both of the protective layer or adhesive layer is colored, and has OT crack-free processability. A surface-treated metal plate according to claim 1. 3. The surface-treated metal sheet according to claim 2, wherein the olefin of the adhesive layer and the protective layer is polyethylene and modified polyethylene, or polypropylene and modified polypropylene. 4. The surface-treated metal plate according to claim 3, wherein the modified polyolefin of the adhesive layer has a high MFR, and the polyolefin of the protective layer has a low MFR. 5. Apply a rust preventive resin layer containing a rust preventive pigment to a dry film thickness of 2 to 20 μm on one or both sides of a metal plate with a thickness of 0.2 to 2.0 mm, then heat it and apply it on top. 2 in dry film thickness
An adhesive layer made of a heat-melted modified polyolefin with a thickness of ~30μ is applied, and at the same time or on top of this, a protective layer made of a heat-melted polyolefin with a dry film thickness of 20~400μ is applied. After gluing
A method of producing a surface-treated metal plate by reheating the modified polyolefin used for the adhesive layer in a range from the melting point to 250°C. 6. The rust-preventing resin layer contains a rust-preventing pigment and is made of epoxy resin, the adhesive layer is a layer made of a modified polyolefin with a high MFR, and the protective layer is made of a polyolefin with a low MFR, and is colored. 6. The method for producing a surface-treated metal sheet according to claim 5, wherein the surface-treated metal sheet has OT crack-free workability.