JP3302167B2 - Method for producing resin-coated metal body - Google Patents

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 resin-coated metal body having excellent durability.

[0002]

2. Description of the Related Art In general, in order to improve the corrosion resistance of a metal body, a surface of the metal body is coated with a synthetic resin. Inexpensive and chemically stable polyethylene resins are widely used as synthetic resins.

[0003] Polyethylene resin has poor adhesion to a metal body.
No. 76960 proposes a resin-coated metal body obtained by extrusion-coating the surface of a steel pipe with a silane-modified polyethylene resin, and extruding and coating the polyethylene resin thereon.

[0004]

In the resin-coated metal body proposed above, the adhesion between the metal body and the polyethylene resin coating layer is considerably improved by using a silane-modified polyethylene resin as a primer. It is not yet satisfactory in terms of durability.

That is, the resin-coated metal body proposed above is
If used over a long period of time under severe conditions such as the transfer of hot water or high-temperature chemicals, the adhesion between the metal body and the polyethylene resin coating layer will decrease due to the deterioration of the primer and repeated shear stress, etc. There is a problem that rust and corrosion occur on the metal body due to peeling.

[0006] The present invention solves the above-mentioned problems, and an object of the invention is to reduce the decrease in adhesion between a metal body and a polyethylene resin coating layer even when used under severe conditions for a long period of time. An object of the present invention is to provide a method for producing a resin-coated metal body having excellent durability.

[0007]

According to the method for producing a resin-coated metal body of the present invention, a short-glass-fiber-containing silane-modified polyethylene resin powder having a concentration of 5 to 40% by weight is added to a surface of a metal material. Weight% of the primer, and heated to 200 to 250 ° C. to form a sintered layer of the primer. The above operation is repeated a plurality of times to form a silane-modified polyethylene resin coating layer thereon. Thus, the above object can be achieved.

In the present invention, the metal body may be iron,
What was shape | molded by metal, such as steel, aluminum, etc. into arbitrary shapes, such as a tubular shape, a rod shape, and a plate shape, is used. The surface of these metal bodies is generally subjected to blasting, degreasing with an alkali or the like, and pickling with hydrochloric acid, nitric acid, sulfuric acid or the like in order to improve the adhesion to the primer.
Further, if necessary, a chemical conversion treatment with zinc phosphate, iron phosphate, or the like may be performed.

On the surface of the metal body, a primer obtained by mixing a short glass fiber-containing silane-grafted polyethylene resin powder with an organic titanate solution is applied. As a method for applying the primer, a known primer method such as a roll, a brush, a brush, or a coating rod is employed. The surface of the metal body to be applied may be the inner surface, the outer surface, or both the inner and outer surfaces.

The organic titanates include tetra-iso.
-Propoxytitanium, tetra-n-butoxytitanium, tetrakis (2-ethylhexyloxy) titanium, tetrastearyloxytitanium, di-iso-propoxybis (acetylacetonato) titanium, di-n-butoxy.
Bis (triethanolaminato) titanium, dihydroxybis (lactato) titanium and the like can be mentioned.

These organic titanates are diluted with an organic solvent such as iso-propanol, n-hexane, benzene, toluene, and the like.
Preferably it is adjusted to 10 to 30% by weight.

When the solution concentration of the organic titanate is 5% by weight
If it is less than 1, the workability at the time of application is poor, and the number of operation steps for forming a sintered layer of the primer increases due to the relationship with the thickness of the primer layer, and therefore, the silane-modified polyethylene resin powder contained therein is heated. Deterioration is likely due to the history, which adversely affects adhesion durability. Conversely, if the concentration exceeds 40% by weight, the workability during coating is poor, and the heating temperature may be relatively low, so that the size of cracks becomes small and the adhesion durability is adversely affected.

The short glass fiber-containing silane-modified polyethylene resin powder is a mixture of 95 to 70% by weight, preferably 90 to 80% by weight of polyethylene resin and 5 to 30% by weight, preferably 10 to 20% by weight of short glass fibers. Silane compound, melt-knead it with an extruder or a roll in the presence of a radical generator, graft the silane compound to the polyethylene resin by the action of the radical generator, and finely pulverize this with a freezing mill or the like. Can be obtained by

In the case where the short glass fiber and the silane-modified polyethylene resin powder are separately used without using the short glass fiber-containing silane-modified polyethylene resin powder as described above, and these are mixed with the organic titanate solution, good results are obtained. No result.

Here, as the polyethylene resin, ordinary low density, medium density, high density polyethylene and linear low density polyethylene are used. The silane compound is used in an amount of 0.1 to 1 with respect to 100 parts by weight of the polyethylene resin.
0 parts by weight, preferably 0.25 to 3 parts by weight,
The radical generator is used in an amount of 0.001 to 2 parts by weight, preferably 0.0015 to 100 parts by weight, based on 100 parts by weight of the polyethylene resin.
0.1 part by weight is blended.

The particle size of the short glass fiber-containing silane-modified polyethylene resin powder is preferably in the range of 5 to 30 μm, more preferably 10 to 20 μm. If the particle size of the resin powder is too small, the dispersibility in the organic titanate solution will be poor and the resin powder will aggregate and a uniform primer cannot be obtained. Conversely, if the particle size of the resin powder is too large, it becomes difficult for the resin powder to enter cracks formed in the sintered layer of the primer, and a sufficient anchor effect cannot be obtained. Of the adhesive decreases.

The silane compound contains a hydrolyzable alkoxy group (eg, methoxy group, ethoxy group, butoxy group) and is an unsaturated hydrocarbon group (eg, vinyl group, allyl group, butenyl group, especially vinyl group). Groups are preferable), and typical examples thereof include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriacetoxysilane, and vinylmethyldiethoxysilane.

Examples of the radical generator include organic peroxides such as dicumyl peroxide, dibutyl peroxide, and 2,5-di-methyl-2,5-di (t-butyl peroxide) hexane, and azobis. Organic azo compounds such as isobutyronitrile and dimethylazoisobutyrate are used.

The silane-modified polyethylene resin powder containing short glass fibers thus obtained has a concentration of 5 to 40% by weight.
From 1 to 8% by weight, preferably from 2 to
A primer is mixed in the range of 5% by weight.

When the content of the short glass fiber-containing silane-modified polyethylene resin powder in the organic titanate solution is less than 1% by weight,
Cracks hardly occur in the sintered layer of the primer, and a sufficient anchor effect cannot be obtained. Conversely, if the silane-modified polyethylene resin powder containing short glass fibers exceeds 8% by weight, cracks formed in the sintered layer of the primer become too large, and the sintered layer of the primer is broken, thereby achieving the object. Can not be done.

The above-mentioned primer is applied to the surface of the metal body, and then at 200 to 250 ° C., preferably 220 to 24 ° C.
Heated to 0 ° C., thereby forming a sintered layer of the primer on the surface of the metal body. Then, this operation is repeated a plurality of times. Usually, it is repeated a few times, and it is preferable that the thickness of the sintered layer is finally 10 to 50 μm. As the heating method, a known heating method such as a heating method using hot air, a heating method using a burner, or an induction heating method is employed.

A coating layer of a silane-modified polyethylene resin is formed on the thus-sintered primer layer. The silane-modified polyethylene resin constituting the coating layer can be obtained by the same method using the same polyethylene resin, silane compound, and radical generator as those used for preparing the primer.

For example, 0.1 to 10 parts by weight of a silane compound and 0.001 to 2 parts by weight of a radical generator are added to 100 parts by weight of a polyethylene resin, and the mixture is extruded with an extruder or a roll in the presence of the radical generator. It can be obtained by melt-kneading and grafting a silane compound to a polyethylene resin by the action of a radical generator.

As a method of forming a coating layer of a silane-modified polyethylene resin on the sintered layer of the primer, known methods such as a melt extrusion method, a powder coating method, and a sheet pressing method are employed. . The thickness of the coating layer of the silane-modified polyethylene resin is generally about 0.05 to 3 mm.

Incidentally, the silane-modified polyethylene resin is used for the purpose of reducing linear expansion coefficient and suppressing molding shrinkage.
If necessary, known fillers such as short glass fiber, talc, mica, potassium titanate, and whiskers may be contained. If necessary, known additives such as a coloring agent such as carbon black, an antioxidant, and an ultraviolet absorber may be contained.

[0026]

The surface of the metal body is coated with a primer obtained by mixing 1 to 8% by weight of a silane-modified polyethylene resin powder containing short glass fibers with an organic titanate solution having a concentration of 5 to 40% by weight. When heated to form a sintered layer of the primer, titanium oxide is mainly produced by the action of organic titanate, which is strongly chemically bonded to the metal body and improves the adhesion between the metal body and the sintered layer of the primer. I do.

When the sintered layer of the primer is observed with an electron microscope, countless small cracks (cracks) are generated on the surface thereof, and the operation of forming the sintered layer of the primer is repeated a plurality of times. Since the location of occurrence is shifted, even if moisture enters from the resin coating layer, the moisture does not reach the metal surface.

When a coating layer of a silane-modified polyethylene resin is formed on the sintered layer of the primer thus formed, the resin of the coating layer enters into countless small cracks on the surface of the sintered layer. An anchor effect is generated, and the sintered layer of the primer and the coating resin are firmly bonded to each other by the anchor effect and the adhesive force due to the siloxane bond of the silanol group due to the hydrolysis of the silane compound in the coating layer.

Moreover, since the sintering layer of the primer contains a silane-modified polyethylene resin, the compatibility with the coating resin is improved, the adhesive strength of both resins by heat fusion is increased, and the sintering of the primer is also performed. Since the tie layer contains short glass fibers, the molding shrinkage of the sintered layer is reduced, and a decrease in the adhesive strength between the metal body and the coating layer is suppressed.

Further, the primer is heated to 200 to 250 ° C. to form a sintered layer of the primer. Since this temperature is relatively low, the silane-modified polyethylene resin in the primer is less likely to be carbonized, so that a good primer A tie layer is formed and is firmly heat-sealed to the silane-modified polyethylene resin of the coating layer.

[0031]

EXAMPLES Examples and comparative examples of the present invention will be described below. Example 1 As an organic titanate solution, di-iso-propoxy.
A 30 wt% i-propanol solution of bis (acetylacetonato) titanium (T-50: manufactured by Nippon Soda Co., Ltd.) was prepared.

As a silane-modified polyethylene resin powder containing short glass fibers, polyethylene resin (density 0.935 g)
/ Cm ³ , melt index 5g / 10min) 80% by weight
And 20% by weight of glass short fiber (silane-treated chopped strand, cut length 3 mm, filament diameter 13 μm) were mixed by a tumbler, and 100 parts by weight of this mixture, 1 part by weight of vinyltrimethoxysilane and 0.04% by weight of dibutyl peroxide The mixture was melt-kneaded at 190 ° C. with an extruder, pelletized by a pelletizer, and then freeze-pulverized to prepare a powder having an average particle diameter of 20 μm.

Then, 95 parts by weight of the above-mentioned organic titanate solution and 5 parts by weight of a short glass fiber-containing silane-modified polyethylene resin powder were placed in a container, and stirred well to prepare a primer.

As the silane-modified polyethylene resin used for the coating layer, the same polyethylene resin as described above (density 0.935 g / cm ³ , melt index 5 g / 10
Min) 100 parts by weight, 1 part by weight of vinyltrimethoxysilane and 0.04 part by weight of dibutyl peroxide,
This was melt-kneaded at 190 ° C. by an extruder and pelletized by a pelletizer.

Steel plate (120 mm long x 120 mm wide x 2 m thick)
m) is subjected to alkali degreasing and pickling treatment with nitric acid, the primer is applied to the treated surface with a brush, and heated at 240 ° C. for 10 minutes in a hot-air drier to form a sintered layer of the primer on the surface of the steel sheet. Was formed.

Next, the primer-treated steel sheet is allowed to cool at room temperature for 5 minutes, and the primer is again applied by brush on the sintered layer of the primer-treated steel sheet, and this is heated at 240 ° C. in a hot air dryer. By heating for 10 minutes, a similar sintered layer of the primer was formed on the first sintered layer of the steel sheet. The thickness of the sintered layer thus obtained (total thickness of the sintered layers) was 40 μm.

A spacer having a thickness of 2 mm is placed around the sintered layer of the steel sheet, and the silane-modified polyethylene resin for forming a coating layer is extruded in a molten state at 190 ° C. in the center of the spacer. 2mm thick by pressing
To form a resin-coated steel sheet.

[0038] This resin-coated steel sheet is described in JIS K-
According to 6854, the peel adhesion strength between the steel plate and the coating layer (T-peel adhesion strength of 10 mm width) was measured.
The peel adhesion was strong at 25.8 kg / 10 mm width.

The resin-coated steel sheet was immersed in hot water of 90 ° C. for 5 minutes, immersed in cold water of 20 ° C. for 5 minutes, and this hot water-cold water immersion operation was repeated 10,000 cycles. As for, observation was made of shrinkage and peeling of the coating resin layer at the end, generation of a gap between the coating and the steel plate, and the like, but no abnormality was found at all. For the resin-coated steel sheet after this hot water / cold water immersion test, the peel adhesion strength of the coating layer was measured.
2.2 kg / 10 mm width, excellent in adhesive durability.

EXAMPLE 2 A steel pipe (outer diameter 114 mm × length 5 m) was subjected to alkali degreasing and pickling treatment with nitric acid, and the inner surface of the steel pipe was treated as in Example 1.
The same primer as that used in 1 was applied by a rotating brush, and this was heated by induction heating at 230 ° C. for 5 minutes to form a sintered layer of the primer on the inner surface of the steel pipe.

Next, the primer-treated steel pipe was left standing at room temperature for 5 minutes to cool, and the above-mentioned primer was applied again on the sintered layer of the primer-treated steel pipe by a rotating brush, and this was heated at 230 ° C. by induction heating. By heating for 5 minutes, a similar sintered layer of the primer was formed on the first sintered layer on the inner surface of the steel pipe. The thickness of the sintered layer thus obtained (the total thickness of the sintered layers) was 30 μm.

On the sintered layer on the inner surface of the steel pipe, the same silane-modified polyethylene resin as that used in Example 1 was used.
The resin-coated steel pipe was manufactured by forming a coating layer of a silane-modified polyethylene resin having a thickness of 2.5 mm by melt extrusion coating at a temperature of 200 ° C.

Hot water of 90 ° C. was placed in the resin-coated steel pipe for 5 minutes.
After passing for 000 hours, no shrinkage and peeling of the coating resin layer and no cracking of the sintered layer of the primer were observed at all with respect to this resin-coated steel pipe, and the adhesion durability was excellent.

Example 3 A resin-coated steel sheet was produced in the same manner as in Example 1 except that the heating temperature after the application of the primer was changed to 220 ° C.

The peel strength of the resin-coated steel sheet between the steel sheet and the coating layer was as strong as 25.3 kg / 10 mm width.
Also, in the hot water-cold water 10,000 cycle immersion test,
No abnormalities such as shrinkage and peeling of the coating resin layer and generation of a gap between the steel sheet were observed. The peel adhesive strength after this hot water / cold water immersion test was 21.4 kg / 10 mm width, and was excellent in adhesive durability.

Example 4 The concentration of the organic titanate solution was changed to 10% by weight, the average particle size of the short glass fiber-containing silane-modified polyethylene resin powder was changed to 10 μm, and the operation of forming a sintered layer of the primer was repeated three times. Repeated (total thickness of sintered layer is 40μ)
m). Otherwise in the same manner as in Example 1, a resin-coated steel sheet was manufactured.

The peel strength of the resin-coated steel sheet between the steel sheet and the coating layer was as strong as 24.9 kg / 10 mm width.
Also, in the hot water-cold water 10,000 cycle immersion test,
No abnormalities such as shrinkage and peeling of the coating resin layer and generation of a gap between the steel sheet were observed. The peel adhesive strength after the hot water / cold water immersion test was 21.1 kg / 10 mm width, and the adhesive durability was excellent.

Example 5 The concentration of the organic titanate solution was changed to 10% by weight, the average particle size of the short glass fiber-containing silane-modified polyethylene resin powder was changed to 10 μm, and the operation of forming a sintered layer of the primer was repeated three times. Repeated (total thickness of sintered layer is 40μ)
m). Otherwise in the same manner as in Example 2, a resin-coated steel pipe was manufactured.

Into this resin-coated steel pipe, hot water of 90 ° C. was added for 5 hours.
After passing for 000 hours, no shrinkage and peeling of the coating resin layer and no cracking of the sintered layer of the primer were observed at all with respect to this resin-coated steel pipe, and the adhesion durability was excellent.

Example 6 The procedure of Example 1 was repeated, except that 93 parts by weight of the organic titanate solution and 7 parts by weight of the silane-modified polyethylene resin powder containing short glass fibers were mixed to prepare a primer.
A resin-coated steel sheet was manufactured.

The peel strength of the resin-coated steel sheet between the steel sheet and the coating layer was as strong as 25.2 kg / 10 mm width.
Also, in the hot water-cold water 10,000 cycle immersion test,
No abnormalities such as shrinkage and peeling of the coating resin layer and generation of a gap between the steel sheet were observed. The peel adhesive strength after the hot water-cold water immersion test was 21.6 kg / 10 mm width, and was excellent in adhesive durability.

Embodiment 7

A resin-coated steel sheet was manufactured in the same manner as in Example 1 except that a primer was prepared by mixing 98 parts by weight of the organic titanate solution and 2 parts by weight of a short glass fiber-containing silane-modified polyethylene resin powder.

The peel strength of the resin-coated steel sheet between the steel sheet and the coating layer was as strong as 25.5 kg / 10 mm width.
Also, in the hot water-cold water 10,000 cycle immersion test,
No abnormalities such as shrinkage and peeling of the coating resin layer and generation of a gap between the steel sheet were observed. The peel adhesive strength after the hot water / cold water immersion test was 22.1 kg / 10 mm width, and the adhesive durability was excellent.

Comparative Example 1 A resin-coated steel sheet was manufactured in the same manner as in Example 1 except that the application of the primer was omitted and the sintered layer of the primer was not formed.

The peel strength of the resin-coated steel sheet between the steel sheet and the coating layer was 18.1 kg / 10 mm width. Also,
In the hot water-cold water 10,000 cycle immersion test, the coating resin layer of the entire circumference peels off from the end of the coating resin layer for about 5 mm, and shrinks to the coating resin layer of the entire circumference from about 1 to 2 mm from the end. Admitted. The peel adhesive strength after the hot water / cold water immersion test was 3.8 kg / 10 mm width, and the adhesive durability was poor.

Comparative Example 2 A resin-coated steel sheet was manufactured in the same manner as in Example 1 except that the concentration of the organic titanate solution was changed to 3% by weight and the total thickness of the sintered layers was changed to 15 μm.

The peel strength of the resin-coated steel sheet between the steel sheet and the coating layer was 20.4 kg / 10 mm width. Also,
In the hot water-cold water 10000 cycle immersion test, no abnormalities such as shrinkage and peeling of the coating resin layer and the generation of a gap between the steel sheet were observed, but the peel adhesion strength after this hot water-cold water immersion test Had a width of 11.5 kg / 10 mm and had poor adhesion durability.

Comparative Example 3 A resin-coated steel sheet was manufactured in the same manner as in Example 1 except that the concentration of the organic titanate solution was changed to 50% by weight.

The peel strength of the resin-coated steel sheet between the steel sheet and the coating layer was 21.1 kg / 10 mm width. Also,
In the hot water-cold water 10000 cycle immersion test, no abnormalities such as shrinkage and peeling of the coating resin layer and the generation of a gap between the steel sheet were observed, but the peel adhesion strength after this hot water-cold water immersion test Had a width of 10.2 kg / 10 mm and poor adhesion durability.

Comparative Example 4 A resin-coated steel pipe was manufactured in the same manner as in Example 2 except that the application of the primer was omitted and the sintered layer of the primer was not formed.

The hot water of 90 ° C. was placed in the resin-coated steel pipe for 5 minutes.
After passing for 000 hours, in the resin-coated steel pipe, peeling was observed in the coated resin layer of the entire circumference over about 50 mm from the pipe end, and the adhesive durability was poor.

Comparative Example 5 A resin-coated steel sheet was manufactured in the same manner as in Example 4 except that the heating temperature after the application of the primer was changed to 180 ° C.

The peel adhesion strength between the steel sheet and the coating layer of the resin-coated steel sheet was 11.5 kg / 10 mm width. Also,
In the 10,000 cycle immersion test of hot water and cold water, the coating resin layer peeled off during the test, and the adhesion durability was poor.

Comparative Example 6 A resin-coated steel sheet was manufactured in the same manner as in Example 4 except that the heating temperature after the application of the primer was changed to 300 ° C.

The peel adhesion strength between the steel sheet and the coating layer of the resin-coated steel sheet was 21.6 kg / 10 mm width. Also,
In the hot water-cold water 10000 cycle immersion test, no abnormalities such as shrinkage and peeling of the coating resin layer and the generation of a gap between the steel sheet were observed, but the peel adhesion strength after this hot water-cold water immersion test Was 11.4 kg / 10 mm in width and had poor adhesion durability.

Comparative Example 7

A resin-coated steel sheet was manufactured in the same manner as in Example 1 except that a primer was prepared by mixing 85 parts by weight of the organic titanate solution and 15 parts by weight of a short glass fiber-containing silane-modified polyethylene resin powder.

The peel strength of the resin-coated steel sheet between the steel sheet and the coating layer was 18.5 kg / 10 mm width. Also,
In the hot water-cold water 10,000 cycle immersion test, the coating resin layer on the entire circumference peels off from the end of the coating resin layer for about 3 mm, and shrinks to the coating resin layer on the entire circumference about 1 mm or less from the end. Admitted. The peel strength after the hot water / cold water immersion test was 4.0 kg / 10 mm width.
The adhesion durability was poor.

Comparative Example 8

A resin-coated steel sheet was prepared in the same manner as in Example 1, except that 99.5 parts by weight of an organic titanate solution and 0.5 part by weight of a short glass fiber-containing silane-modified polyethylene resin powder were mixed to prepare a primer. Was manufactured.

The peel adhesion strength between the steel sheet and the coating layer of the resin-coated steel sheet was 21.9 kg / 10 mm width. Also,
In the hot water-cold water 10000 cycle immersion test, no abnormalities such as shrinkage and peeling of the coating resin layer and the generation of a gap between the steel sheet were observed, but the peel adhesion strength after this hot water-cold water immersion test Had a width of 13.6 kg / 10 mm and had poor adhesion durability.

[0073]

As described above, according to the method for producing a resin-coated metal body of the present invention, the surface of the metal body is coated with an organic titanate solution having a concentration of 5 to 40% by weight in a short glass fiber-containing silane-modified polyethylene resin powder of 1 to 8% Weight% of the primer, and heated to 200 to 250 ° C. to form a sintered layer of the primer. The above operation is repeated a plurality of times to form a silane-modified polyethylene resin coating layer thereon. According to such a production method, even when used under severe conditions for a long period of time, a resin-coated metal body excellent in durability with little decrease in adhesion between the metal body and the polyethylene resin coating layer is obtained. Obtainable.

Therefore, the resin-coated metal body obtained according to the present invention can be suitably used for various applications requiring corrosion resistance and durability.

────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ identification symbol FI B05D 7/24 303 B05D 7/24 303G 303K (56) References JP-A-6-166140 (JP, A) JP-A-5-166 329982 (JP, A) JP-A-6-143451 (JP, A) JP-A-7-232402 (JP, A) JP-A-5-169585 (JP, A) JP-A-62-264940 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) B32B 15/08 B05D ⁷ /14-7/24

Claims (1)

(57) [Claims] 1. A primer comprising a mixture of an organic titanate solution having a concentration of 5 to 40% by weight and a powder of a silane-modified polyethylene resin containing short glass fibers containing 1 to 8% by weight is applied to the surface of a metal body. A method for producing a resin-coated metal body, comprising heating to 250 ° C. to form a sintered layer of a primer, repeating the above operation a plurality of times, and forming a coating layer of a silane-modified polyethylene resin thereon.