JPH0866986A - Manufacture of laminate - Google Patents

Abstract

PURPOSE: To provide a laminate of superior resistance to corrosion and resistance to hot water without generating rust on a steel surface for a long period of time even when used under severe conditions such as temperature difference between the inner side of hot water and the inner face of outer face. CONSTITUTION: A hot rolled steel sheet is heated up to the surface temperature of 150 deg.C-550 deg.C to form an oxide film of 10μthickness, and then 60wt.% isopropanol solution of di-1 propoxy.bis(acetylacetonate) titanium is applied by using a brush and drying by wind, and then heated to form a a primer sintered layer of 15μm thickness. Vinyl trimethoxysilane of 1wt.% and di-t-butyl peroxide of 0.01 wt.% to straight chain-shaped low-density polyurethane of 100wt.% is added to the surface and kneaded at 190 deg.C, and modified silane graft polyethylene is extruded and fusion bonded to form a silane graft straight chain-shaped low-density polyethylene coated layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a laminate, and more particularly to a method for producing a steel / silane-grafted polyolefin laminate excellent in corrosion resistance and hot water resistance.

[0002]

2. Description of the Related Art In order to improve the corrosion resistance of a metal plate, a laminate having a synthetic resin layer formed on the surface of the metal plate has been conventionally known. Such a laminate is a roof material, a wall material, an automobile. It is used for materials, resin-coated metal pipes, etc. For example, in Japanese Unexamined Patent Publication No. 5-169585, an organic titanate is baked on the surface of a metal body in order to provide a laminate excellent in corrosion resistance and hot water resistance even under severe conditions such as repeated immersion in hot water and cold water. A laminate in which a synthetic resin layer (silane-grafted polyolefin layer) is formed on the bonded primer layer has been proposed.

However, even the laminated body described in the above publication cannot be said to have sufficient corrosion resistance and hot water resistance in a harsh environment where there is a temperature difference between hot water and the inner and outer surfaces. . That is, when used in the above harsh environment, water diffuses and permeates in the synthetic resin to reach the interface with the primer layer, and further water gradually diffuses and permeates into the organic titanate primer layer, and eventually the interface with the metal. In some cases, the metal was rusted, and the adhesive strength of the synthetic resin layer to the metal body was reduced, resulting in peeling from the metal body layer.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the problems of the prior art as described above, and is intended for use in hot water of high temperature or in a severe environment where there is a temperature difference between the inner and outer surfaces. Another object of the present invention is to provide a method for producing a laminate, which is excellent in corrosion resistance and hot water resistance and in which the synthetic resin layer does not peel off from the surface of the metal body for a long period of time.

[0005]

[Means for Solving the Problems] The present inventor has found that even when an organic titanate primer is applied to a so-called "scale" steel sheet with an iron oxide film, the primer is likely to be peeled off from the steel substrate. I found it. In addition, the present invention was completed based on the finding that an oxide film that can contribute to durability is formed when heat treatment is performed on steel such that the surface temperature is 150 ° C. or higher and 550 ° C. or lower. Let

The method for producing a laminate of the present invention uses steel as the metal body and silane-grafted polyolefin as the synthetic resin in the above description.
It is characterized in that after heat treatment so that the surface temperature is 150 ° C. to 550 ° C., a primer sintered layer of organic titanate is provided on the surface, and a silane-grafted polyolefin coating layer is further formed on the surface. The above object is achieved.

The types of steel used in the present invention are:
Without being particularly limited, ordinary steel plates and steel pipes such as hot rolled steel plates, cold rolled steel plates, carbon steel pipes for piping, etc. are widely used, and the shapes are not limited to plate-like or tubular ones, but rod-shaped and other shapes. May be. Usually, a scale is formed on the surface of commercially available steel plates and steel pipes (especially hot rolled steel plates, carbon steel pipes for piping, etc.), so before heating the steel surface,
In some cases, it is preferable to remove the scale by degreasing treatment with sodium silicate or the like and acid treatment with hydrochloric acid, nitric acid, sulfuric acid or the like, including sand blasting treatment.

Thereafter, the surface temperature of the steel is 150 ° C. or higher,
The steel is heated to 550 ° C or lower, preferably 300 ° C or higher and 500 ° C or lower. This is because when heat treatment forms an iron oxide film on the surface of steel (it is considered that the structure is different from that of conventional scales), the laminate can be used under severe conditions such as in a steam atmosphere or in hot water. In such a case, even if water reaches the surface of the oxide film, the steel will not easily rust. If the surface temperature during the heat treatment is less than 150 ° C., an oxide film that exerts a sufficient effect in the present invention cannot be obtained. Further, when the temperature exceeds 550 ° C., the surface layer peels off from the steel base material due to the embrittlement of the oxide film, or the carbon component contained in the steel accumulates on the surface and adheres to the primer sintered layer that is further formed on the oxide film surface. Reduce sex.

The thickness of the oxide film formed by the above heat treatment is preferably about 5 to 50 μm. this is,
This is because it is difficult to obtain a sufficient effect on the adhesion durability in the present invention even if it is less than 5 μm or exceeds 50 μm. The organic titanate primer in the present invention means an organic group capable of binding to an inorganic substance in the molecule (for example, a hydrolyzing group such as isopropyl group) and an organic group having an affinity for the organic substance (for example, stearoyl group, N-aminoethyl- An organic titanate compound having an aminoethyl group and an organic group such as dodecylbenzenesulfonyl group), and examples of commercially available products include “Planeact” manufactured by Ajinomoto Co., Inc. and “Citacoat” manufactured by Nippon Soda Co., Ltd.

A typical example of such an organic titanate primer is isopropyl (N-aminoethyl-
Aminoethyl) titanate, ethyl tri (N-aminoethyl-aminoethyl) titanate, diisopropyldi (N-aminoethyl-aminoethyl) titanate, butyl tri (N-aminoethyl-aminoethyl) titanate, dibutyldi (N-aminoethyl-amino) Ethyl) titanate, tetra-n-butoxy titanium, tetra (2-
Examples include ethylhexyloxy) titanium and tetra-i-propoxy titanium.

Above all, it is preferable that two of the above-mentioned hydrolyzable groups and two organic groups having an affinity for organic substances are bonded to a Ti atom, and di-i-propoxy bis (acetylacetonato) is preferable.
Titanium and di-n-butoxy bis (triethanolaminato) titanium are particularly preferred in this respect.

These organic titanates are mainly diluted with an alcoholic solvent and applied onto the surface of the above steel by a usual application means such as a roll, brush, brush, coating rod, and spray. The coating is preferably performed after the surface temperature of the steel reaches 100 ° C. or lower after the above heat treatment.
This is because if the coating is carried out at a temperature higher than 100 ° C, the solvent used to dilute the organic titanate will volatilize rapidly, and it will be difficult to obtain a uniform organic titanate layer. This is because it is not preferable.

Further, the coating film is heated at 200 to 450 ° C., preferably 2 by burner heating, hot air blowing, induction heating or the like.
A primer sintered layer is formed by sintering at a temperature of 30 to 420 ° C. The thickness of the primer sintered layer is usually
The thickness is 0.01 to 100 μm, preferably 5 to 50 μm. If it is less than 0.01 μm, a sufficient effect of suppressing water diffusion cannot be obtained, and if it exceeds 100 μm, cracks or cracks are likely to occur when the laminate is processed such as bending,
This is because the effects of the present invention may not be sufficiently obtained. .

In the present invention, a silane-grafted polyolefin coating layer is formed on the surface of the primer sintered layer. The reason is that it has good adhesiveness with the organic titanate sintered layer and has excellent long-term adhesion durability even in the state of being immersed in high temperature hot water. The silane-grafted polyolefin is obtained by, for example, mixing a silane coupling agent and an organic peroxide with polyolefin, heating and melting the mixture, and graft-modifying the polyolefin. As the polyolefin, known materials such as high density polyethylene, medium density polyethylene, low density polyethylene, linear low density polyethylene and the like, polypropylene, polybutene and the like are used, and polyethylene, and particularly linear low density polyethylene is preferably used.

As the silane coupling agent, a hydrolyzable alkoxy group (methoxy group, ethoxy group,
An example is a compound that has a β-methoxyethoxy group, etc.), a chloro group, etc., and has a double bond site that reacts with the free radical site generated in the polyolefin such as vinyl group, acryl group, methacryl group, etc. in the same molecule. To be done.

Having a hydrolyzable functional group in the molecule is necessary for bonding, that is, adhesion with the organic titanate sintered layer, and having a double bond site is the fact that the polyolefin is heated together with the organic peroxide. This is because it easily reacts with the radical site generated by the reaction to cause a graft reaction. Examples of such silane coupling agents include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriacetoxysilane, γ-methacryloxypropyltrimethoxysilane, and the like.

Preferred examples of organic peroxides include dimethyl peroxide, di-t-butyl peroxide, dicumyl peroxide, dipropionyl peroxide, benzoyl peroxide, t-butyl hydroperoxide and cumene hydro. There are peroxides and the like.

The thickness of the silane-grafted polyolefin coating layer in the present invention is not particularly limited, but it is 5 m in order to prevent cracks from occurring when the laminate is bent.
It is desirable to be m or less. Further, an antioxidant, an ultraviolet absorber, a colorant and the like may be converted into the silane-grafted polyolefin layer within a range that does not impair the effects of the present invention.

The method for forming the silane-grafted polyolefin coating layer on the surface of the steel on which the primer sintered layer has been formed includes a method of coating the silane-grafted polyolefin heated and melted using an extruder, and a powdery silane-grafted polyolefin. Examples of the method include a method in which heated steel is immersed in the fluidized bed to adhere and melt a resin, and a method in which a silane-grafted polyolefin sheet is heat-pressed with or without an adhesive.

[0020]

For example, hot-rolled steel sheets are produced by heating at a high temperature of 800 ° C. to 1000 ° C. and hot rolling, and most of various steel sheets are called “scale” on the surface due to the heat history in the manufacturing process. An oxide film is formed, but this "scale" is a brittle oxide film and cannot enhance the corrosion resistance of steel. Although the detailed composition of such a scale is unknown, it is considered that Fe2 O3, Fe3 O4, and FeO are combined or mixed in a predetermined ratio. In the present invention, the surface temperature of steel is 1
By heat treatment so that the temperature becomes 50 ° C to 550 ° C,
Although details are unknown, it is presumed that an oxide film having a structure different from that of the conventional scale is formed.

Since the organic titanate primer sintered layer is provided after the heat treatment, the primer sintered layer firmly bonded to the oxide film having a new structure is formed, and further firmly adhered and formed on the surface thereof. The above-mentioned silane-grafted polyolefin coating layer completes a laminate having high corrosion resistance. That is, even if water penetrates and permeates the silane-grafted polyolefin layer having strong water repellency with time in a harsh environment, and further penetrates and permeates into the primer sintered layer that is firmly bonded to both the resin and the oxide film. Since the novel oxide film prevents or delays the arrival at the steel surface, rust is extremely unlikely to occur.

[0022]

[Examples] In the following examples and comparative examples, the thickness of the oxide film was measured by using an EPMA (Electron Probe of
Micro Analysis) concentration mapping analyzer
Mapping was performed by using a different color to represent the oxygen concentration distribution at each location, and the distribution in the thickness direction was examined before measurement. Also, the peel adhesion strength between the sintered primer layer and the silane-grafted polyethylene in the laminate is determined by JIS
The measurement was carried out in accordance with K6854 "Peeling Adhesive Strength Testing Method of Adhesive" (however, carried out with "T-type peeling test piece" having a width of 10 mm).

(Example 1) 60 hot-rolled steel sheets (SPHC)
℃ sodium phosphate degreaser (manufactured by Nippon Parkerizing,
Immerse in P-3,5% aqueous solution for 1 minute (degreasing treatment), wash with water, then soak in 25% 10% nitric acid for 1 minute (etching)
Then, rinse it with water and put it in an oven set to 400 ° C. 1
Heat treatment was performed for 0 minutes. In the measurement result by the thermocouple,
The surface temperature of the steel sheet was 395 ° C. The thickness of the oxide film formed on this surface was 10 μm.

After the surface temperature of the steel plate has dropped to 25 ° C.,
A 60 wt% isopropanol solution of di-i-propoxy bis (acetylacetonato) titanium was applied to one surface with a brush, air-dried, and then placed in an oven again for 10 minutes for heat treatment to 395 ° C. The thickness of the primer sintered layer thus obtained was 15 μm. Furthermore, linear low-density polyethylene 100 is formed on the surface of the primer sintered layer.
1 part by weight of vinyltrimethoxysilane, di-
Add 19 parts by weight of t-butyl peroxide to obtain 19
The modified silane-grafted polyethylene was kneaded at 0 ° C., and the modified silane-grafted polyethylene was extruded and fused to form a silane-grafted linear low-density polyethylene (G-LLDPE) coating layer having a thickness of 2 mm to obtain a target laminate.

The peel adhesion strength between the primer sintered layer and the silane-grafted polyethylene coating layer of this laminate was 36.0.
It was kgf / 2cm. Then, a heating-cooling test was performed in which the laminate was immersed in hot water at 85 ° C. for 5 minutes and then immersed in cold water at 20 ° C. for 5 minutes to repeat 20000 cycles. After completion of the test, as a result of observing peeling of each layer and occurrence of other abnormalities, no abnormality such as peeling between the layers, floating, swelling, discoloration due to rust, etc. was observed. The adhesive strength after repeated cold heat was 31.8 kgf / 2 cm 2.

(Example 2) A steel sheet having a thickness of 1 was prepared in the same manner as in Example 1 except that the steel sheet was placed in an oven set at 300 ° C and heat-treated for 10 minutes to change the surface temperature to 297 ° C.
Sintered 5 μm primer layer and 2 mm thick G-LLDP
A laminate having the E coating layer was obtained. The film thickness of the oxide film formed after the heat treatment was 10 μm.

The peel adhesion strength between the primer sintered layer and the G-LLDP coating layer measured in the same manner as in Example 1 was 35.7.
It was kgf / 2cm. As a result of the same cold-heat repeated test as in Example 1, no abnormality such as peeling between each layer, floating, swelling, discoloration due to rust, etc. was observed, and the adhesive strength after repeated heat-cooling was:
It was 29.8 kgf / 2 cm.

(Embodiment 3) A steel sheet having a thickness of 1 was prepared in the same manner as in Embodiment 1 except that the steel sheet was placed in an oven set to 200 ° C. and heat-treated for 10 minutes to change the surface temperature to 198 ° C.
Sintered 5 μm primer layer and 2 mm thick G-LLDP
A laminate having the E coating layer was obtained. The thickness of the oxide film formed on the surface by heating was 8 μm. Primer sintered layer and G-LL measured in the same manner as in Example 1
The peel adhesion strength between the DP coating layers was 35.0 kgf / 2 cm. As a result of the same repeated heat and cold test as in Example 1, no abnormalities such as peeling, floating, swelling and discoloration due to rust between the layers were observed, and the adhesive strength after repeated heat and cold was 27.9 kgf / 2 cm.

(Example 4) A primer burner having a thickness of 15 µm was prepared in the same manner as in Example 1 except that the steel sheet was placed in an oven set at 500 ° C and heat-treated for 10 minutes to change the surface temperature to 479 ° C. Layer and 2mm thick G-LLD
A laminate having a PE coating layer was obtained. The thickness of the oxide film formed on the surface by heating was 20 μm.
The primer sintered layer and G- which were measured in the same manner as in Example 1
The peel adhesion strength between the LLDP coating layers was 35.6 kgf / 2 cm 2. The result of the cold heat repetition test similar to that in Example 1 was as follows.
No abnormalities such as peeling between layers, floating, swelling, discoloration due to rust, etc. were observed, and the adhesive strength after repeated cooling and heating was 30.9 kgf / 2 cm.
Met.

(Example 5) In the same manner as in Example 1, a steel plate surface temperature was set to 395 ° C and an oxide film having a thickness of 10 µm was obtained. Next, a 10 wt% isopropanol solution of di-i-propoxy bis (acetylacetonato) titanium was applied to one surface of the steel sheet with a brush, air-dried, and then again placed in an oven set at 400 ° C. and heat-treated for 4 minutes. . This process consisting of coating, air drying, and heating is performed 3 times to obtain a thickness of 1
A 0 μm primer sintered layer was formed. Further, the same G-LLDPE as in Example 1 was extruded and fused on this surface in the same manner to obtain a laminate having a G-LLDPE coating layer having a thickness of 2 mm. The peel adhesion strength between the primer sintered layer and the G-LLDP coating layer measured in the same manner as in Example 1 was 3
It was 9.0 kgf / 2 cm. As a result of the same repeated heat and cold test as in Example 1, no abnormalities such as peeling, floating, swelling, discoloration due to rust between the layers were observed, and the adhesive strength after repeated heat and cold was 34.8 kgf / 2 cm.

(Example 6) Rolled steel for general structure (SS4
After degreasing and etching the socket type pipe joint consisting of 1) in the same manner as in Example 1, the steel plate surface temperature was set to 395 ° C. in the same manner as in Example 1 to obtain an oxide film having a thickness of 10 μm. After that, the primer was uniformly applied to the inner surface of the joint in the same manner as in Example 1, and heating was performed at 400 ° C. for 10 minutes to give a thickness of 1
A 7 μm primer sintered layer was provided. This pipe fitting 20
It was heated to 0 ° C. and connected to a powder coating device, and the same G-LLDPE as in Example 1 was laminated on the inner surface by jetting. At this time, the thickness of G-LLDPE was 2.0 mm. A hot and cold repeated test was conducted by passing hot water at 85 ° C for 5 minutes to this joint and then passing water at 20 ° C for 5 minutes.
After 000 cycles, the metal body on the inner surface of the joint
No abnormalities such as peeling between resins and rust on the metal layer were observed. Also, the adhesive strength before and after this cold heat repeating test was cut out from a part of the pipe joint and carried out by a T-type peeling test. It was

Example 7 A G-LLDPE coating layer having a thickness of 2 mm was formed in the same manner as in Example 3 except that the heating conditions of the steel sheet were 200 ° C. for 30 minutes and the surface temperature was 199 ° C. A laminated body was obtained. The peel adhesion strength between the primer sintered layer and the G-LLDP coating layer measured in the same manner as in Example 1 was 32.6 kgf / 2 cm 2. As a result of the same repeated heat and cold test as in Example 1, no abnormalities such as peeling, floating, swelling, and discoloration due to rust between the layers were observed, and the adhesive strength after repeated heat and cold was 31.9 kgf / 2 cm.

(Embodiment 8) In this example, the present invention is applied to a tube. A carbon steel pipe for piping (SGP) having an outer diameter of 114 mm and a length of 2.5 m was degreased and etched in the same manner as in Example 1, and then heated at 400 ° C. for 10 minutes to a surface temperature of 395 ° C. and a thickness of 10 μm. An oxide film of was obtained. Thereafter, the same primer solution as in Example 1 was uniformly applied to the inner surface of the steel pipe and heated at 400 ° C. for 10 minutes to bring the surface temperature to 395 ° C. The thickness of the primer sintered layer is 17
was μm. On this inner surface, the same G-LLDPE as in Example 1 obtained by the same method as in Example 1 was laminated at a temperature of 190 ° C. and a pressure of 100 kg / cm ² . At this time, G-LLD
The PE coating layer had a thickness of 2.0 mm.

A hot / cold heat cycle test was conducted by passing hot water at 85 ° C. for 5 minutes and then passing water at 20 ° C. for 5 minutes to this steel pipe for 20000 cycles. No abnormality such as rust on the body layer was observed. In addition, the steel pipe was cut into strips to measure the adhesive strength before and after this cold heat repeated test and measured by the T-type peeling test. Before the cold heat repeated test, 35.3 kgf / 2
cm, and 31.6 kgf / 2 cm after the test.

Comparative Example 1 A primer sintered layer having a thickness of 10 μm and a G-LLDPE coating layer having a thickness of 2 mm were formed in the same manner as in Example 1 except that the steel sheet was not heat-treated. A laminated body was obtained. The peel adhesion strength between the primer sintered layer and the G-LLDP coating layer measured in the same manner as in Example 1 was 37.3 kgf / 2 cm. After the same thermal cycling test as in Example 1, the presence or absence of abnormalities such as peeling between layers was observed, and a large number of swellings due to peeling were observed between the primer layer and the silane-grafted polyethylene layer. In addition, the surface of the steel sheet had a discoloration that appeared to be black rust. Further, when the adhesive strength was measured, it was 12.6 kgf / 2 cm 2.

(Comparative Example 2) A primer sintered layer was not provided,
20 sheets of G-LLDP obtained by the same method as in Example 1 were used.
A laminate in which an oxide film having a thickness of 10 μm and a G-LLDPE coating layer having a thickness of 2 mm were formed in the same manner as in Example 1 except that the layers were heated and laminated at 0 ° C. The peel adhesion strength between the steel and the G-LLDP coating layer measured according to the method of Example 1 was 33.3 kgf / 2 cm 2. After the same thermal cycling test as in Example 1, the presence or absence of abnormalities such as peeling between layers was observed, and a large number of blisters were observed between the steel plate-silane graft polyethylene layer. In addition, the surface of the steel sheet had a discoloration that appeared to be black rust. Further, when the adhesive strength was measured, it was 14.6 kgf / 2 cm 2.

(Comparative Example 3) A thickness of 10 μm was obtained in exactly the same manner as in Example 1 except that the heating condition for the steel sheet as pretreatment was 100 ° C. for 60 minutes to form an oxide film having a thickness of 2 μm.
Thus, a laminated body in which a primer sintered layer of m and a G-LLDPE coating layer having a thickness of 2 mm were formed was obtained. The peel adhesion strength between the primer sintered layer and the G-LLDP coating layer measured in the same manner as in Example 1 was 33.5 kgf / 2 cm 2. After the same thermal cycling test as in Example 1, the presence or absence of abnormalities such as peeling between layers was observed, and a large number of blisters were observed between the primer layer and the silane-grafted polyethylene layer. In addition, the surface of the steel sheet had a discoloration that appeared to be black rust. Further, the adhesive strength was measured and found to be 15.6 kgf / 2 cm.

(Comparative Example 4) The same procedure as in Example 1 was carried out except that the heating condition for the steel sheet as the pretreatment was 600 ° C. for 10 minutes, the surface temperature was 575 ° C., and an oxide film having a thickness of 2 μm was formed. As a result, a laminated body in which a primer sintered layer having a thickness of 10 μm and a G-LLDPE coating layer having a thickness of 2 mm were once formed was obtained. In the same manner as in Example 1, the primer sintered layer and G
-An attempt was made to measure the peeling adhesive strength between the LLDP coating layers, but the oxide film was brittle and the primer sintered layer was easily peeled off.

[0039]

According to the method for producing a laminate of the present invention, the steel is heat-treated so that the surface temperature is 150 ° C to 550 ° C. Therefore, an oxide film having a novel structure is present on the surface of the steel. Since the organic titanate primer sintered layer is further provided and the silane-grafted polyolefin coating layer is formed, according to the present invention, when there is a temperature difference between hot water and the inner and outer surfaces, or when hot water-cold water is repeatedly used. It is possible to provide a laminate excellent in corrosion resistance and hot water resistance that does not cause rust on the steel surface for a long period of time even under such severe conditions as described above.

Claims (1)

[Claims] 1. The surface temperature of steel is 150 ° C. to 550.
A method for producing a laminate, which comprises heat-treating at a temperature of 0 ° C., providing an organic titanate primer sintered layer on the surface thereof, and further forming a silane-grafted polyolefin coating layer on the surface thereof.