JPH0749550B2 - Primer for polyolefin coated steel with excellent hot water resistance - Google Patents

Description

TECHNICAL FIELD The present invention relates to a polyolefin-coated steel primer composition. More specifically, it relates to a primer for a polyolefin-coated steel material, which is interposed between a steel material and a polyolefin and has excellent hot water resistance and high-temperature cathode peeling resistance.

PRIOR ART Steel materials often corrode considerably when exposed to the atmosphere, the ground, or seawater without taking measures to prevent corrosion from the surrounding environment. As a countermeasure against this corrosion, a polyolefin coating such as polyethylene or polypropylene having excellent chemical stability is applied. In recent years, as the development of resources such as petroleum, heavy oil and geothermal oil in the sea floor and polar regions has become active due to the increase in energy demand, the durability of polyolefin coatings on steel structures and line pipes under high temperature wetted environments Is a problem.

Generally, polyolefin resin is non-polar due to its scientific structure,
It is difficult to directly adhere to the surface of a steel material, and a method of coating a polyolefin resin with an adhesive polyolefin modified with an unsaturated carboxylic acid or an acid anhydride thereof is used. However, when immersed in an environment containing electrolytes such as seawater or salt water or in a wet soil environment, the adhesive strength is reduced in a short period of time at a temperature near room temperature, and rust occurs between the steel material and the coating.
Further, in an environment where cathodic protection is also used, there is a defect that the coating is easily peeled off from the coating defect as a starting point due to over-corrosion current (cathode peeling).

Therefore, in order to solve these drawbacks, a method of further subjecting the corrosion-resistant steel material and the adhesive polyolefin to a chromate-type chemical conversion treatment (JP-A-52-143934, JP-A-54-120681)
Alternatively, a method of interposing a thermosetting epoxy primer (JP-A-56-143223, JP-A-59-222275) and the like have been proposed, and there is a remarkable effect in improving water-resistant adhesiveness at around room temperature. However, it is difficult to maintain adhesive strength for a long period of time in a water contact environment exceeding 60 ° C, and a polyolefin having excellent water resistance in hot water or hot salt water exceeding 60 ° C, that is, hot water resistance and high temperature cathode peeling resistance. The development of coated steel is desired.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention An object of the present invention is to provide a primer for a polyolefin-coated steel material which is excellent in hot water resistance and high-temperature cathode peeling resistance.

Means for Solving the Problems The present inventors
As a result of diligent studies to eliminate the drawbacks related to high-temperature cathode peeling resistance, an alkyl glycidyl ether was added to a condensate of m-xylylenediamine and epichlorohydrin as a specific epoxy resin and an inorganic pigment between the steel to be protected and the adhesive polyolefin. The inventors have found that the above-mentioned problems can be solved by interposing a primer composition containing a modified polyamine curing agent, and have completed the present invention.

That is, the present invention is a primer for laminating a steel material and a polyolefin, which contains the following three components (A), (B) and (C) as essential components.

(A) An epoxy resin composed of a bisphenol A type epoxy resin, a bisphenol AD type epoxy resin or a mixture thereof.

(B) One or more of butyl glycidyl ether, phenyl glycidyl ether, o-cresyl glycidyl ether, and ethylhexyl glycidyl ether in a proportion of 0.2 to 0.6 mol per 1 mol of a condensate of m-xylenediamine and epichlorohydrin. Modified polyamines added by reaction with.

(C) An inorganic pigment.

Action First, in the present invention, the steel material is a generic name for steel pipes, shaped steels, steel strips, steel bars, etc., which are widely used outdoors, in the ground, on the sea, on the seabed and the like.

Next, the structure of the laminate of the steel material and the polyolefin of the present invention will be described.

FIG. 1 is a schematic view showing one embodiment of a laminate of steel material and polyolefin. What is a laminate? The surface of the steel 1 to be protected is sequentially coated with an epoxy-based primer layer 2, a modified polyolefin adhesive layer 3, and a polyolefin anticorrosive layer 4, which essentially include the three components (A), (B), and (C). It was done.

Further, in order to further improve the adhesiveness and corrosion resistance at the boundary between the epoxy-based primer layer 2 and the corrosion-resistant steel material 1, a phosphate treatment film,
It is effective to provide a chemical conversion treatment layer such as a chromate treatment film.

Further, in order to improve the strength and heat deformability of the polyolefin anticorrosion layer 4, the anticorrosion layer may have a two-layer structure, a polyolefin layer containing a fibrous substance or scale-like substance as an upper layer, and a polyolefin resin layer as a lower layer. Good.

Next, the epoxy primer composition of the present invention will be described.

An epoxy primer composition used for a polyolefin laminated steel material as shown in FIG. 1 is a butyl glycidyl ether based on 1 mol of a condensate of an epoxy resin as a component (A) and m-xylenediamine as a component (B) and epichlorohydrin. , Phenyl glycidyl ether, o-cresyl glycidyl ether, ethylhexyl glycidyl ether, or a modified polyamine-based curing agent obtained by oppositely adding one or more of them in a proportion of 0.2 to 0.6 mol as a vehicle,
The epoxy primer is characterized by containing 3 to 45% of PWC as the component (C) pigment.

The epoxy resin as the component (A) is bisphenol A.
Type glycidyl ether or bisphenol AD type glycidyl ether alone or as a mixture, and the epoxy equivalent is preferably in the range of 170 to 2150 from the viewpoint of hot water resistance.

The bisphenol A type diglycidyl ether typically has the following molecular structure, and commercially available ones correspond to, for example, the trade names in Table 1.

The bisphenol AD type diglycidyl ether has a molecular structure as shown below, and for example, Epomic R-710 and R-710 commercially available from Mitsui Petrochemical Co., Ltd.
It is equivalent to H.

An epoxy resin containing less than 0.05% of hydrolyzable chlorine such as Epomic R-140p in Table 1 may be used.

The modified polyamine curing agent obtained by adding alkyl glycidyl ether to the condensate of m-xylenediamine and epichlorohydrin, which is the component (B), is With respect to 1 mol of a condensate of m-xylenediamine and epichlorohydrin having a structure of n = 1 to 4 (for example, gascamine G328 manufactured by Mitsubishi Gas Chemistry Co., Ltd.), And the R group is a butyl group, a phenyl group, o
A curing agent obtained by addition reaction of glycidyl ether, which is either a cresyl group or an ethylhexyl group, in a ratio of 0.2 to 0.6 mol.

When the R group is other than the above-mentioned groups, the hot water dipping property is poor and the object of the present invention cannot be achieved.

The addition ratio of the glycidyl ether is preferably in the range of 0.2 to 0.6 mol of the glycidyl ether with respect to 1 mol of the condensate of m-xylenediamine and epichlorohydrin. When this ratio is less than 0.2 mol, the hot water dipping property is deteriorated, and when it exceeds 0.6 mol, the viscosity increases greatly during the synthesis, and the compound becomes a hard solid substance, which is difficult to put into practical use. The method for producing these curing agents is disclosed in JP-A-59-33321.

From the viewpoint of hot water resistance, the compounding ratio of the epoxy resin (A) and the modified polyamine (B) should be the equivalent number of epoxy groups / the equivalent number of active hydrogen of the modified polyamine = 1/1, that is, the equivalent reaction equivalent ratio. Is desirable.

The inorganic pigment as the component (C) is, for example, a constitution such as alumina, silica, titanium oxide, talc (hydrous magnesium silicate), kaolin clay, scaly mica (biotite, muscovite, suzolite), micaceous iron oxide. Pigment, Synthetic iron oxide red, Synthetic iron oxide yellow, Cobalt blue, Cobalt green, Cobalt purple, Strontium yellow, Manganese purple, Chromium oxide, Red iron oxide, Carbon black, Coloring pigments such as aluminum powder, Alkaline earth metal phosphate ( For example, zinc phosphate), aluminum phosphate (for example, aluminum tripolyphosphate), alkaline earth metal chromate (for example, basic zinc chromate), phosphomolybdic acid compound, silicomolybdic acid compound, tungstic acid compound, silicotungstic acid compound, One kind of anti-corrosion pigment such as barium sulfate, red lead, etc. A mixture of two or more.

Further, in order to improve the wettability with the epoxy resin, the surface of the above pigment may be subjected to chemical treatment such as silane treatment, aluminum-silica treatment, phosphoric acid treatment, etc. The compounding amount of the inorganic pigment is the epoxy resin 100 which is the component (A).
It is desirable to mix 3 to 45 parts by weight with respect to parts by weight.

In addition to these components (A), (B) and (C), in order to adjust the curing time of the epoxy primer coating, 2-ethyl-4-methylimidazole, 2,4,6-tris (dimethylaminomethyl) It is also possible to add additives such as accelerators such as phenol, reactive diluents and viscosity modifiers.

The primer of the present invention is produced, for example, as follows.

For each of the epoxy resin (main component) which is the component (A) or the curing agent which is the component (B), the pigment and the additive are appropriately proportioned from the compounding amounts, premixed, and then roll-dispersed. Dispersions of a base material and a curing agent having a particle size of the pigment of 5 to 40 µ are obtained.

The main agent and curing agent are mixed by stirring at the time of use to form a uniform paint,
A steel material is appropriately selected from conventionally known methods such as airless spray, roll coating, and ironing coating.

This coating film thickness, that is, the film thickness of the epoxy primer layer after heat curing in Fig. 1 is 20μ in view of hot water resistance and coating cost
~ 300μ is preferred. If the particle size of the dispersed pigment is less than 5μ, the surface area of the pigment becomes large and the paint viscosity becomes extremely high, making it difficult to paint. If it exceeds 40μ, the spray nozzle is clogged and the surface of the epoxy primer coating film becomes rough. , The adhesive strength is reduced.

Further, as the polyolefin resin in the present invention, low density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene, conventionally known polyolefin such as polypropylene, and ethylene-propylene block or random copolymer, polyamide -A conventionally known polyolefin copolymer such as a propylene block or a random copolymer can be used.

As the modified polyolefin resin, a conventionally known modified polyolefin such as one obtained by modifying the above-mentioned polyolefin resin with an unsaturated carboxylic acid such as maleic acid, acrylic acid or methacrylic acid, or one obtained by appropriately diluting the modified product with a polyolefin resin. Can be used.

The details will be described below based on examples.

EXAMPLES First, in order to specifically explain the present invention, Table 2 shows Examples 1 to 41 of the primer composition according to the present invention.

Further, as comparative examples, Comparative Examples 1 to 4 of primer compositions corresponding to JP-A-56-143223, Comparative Examples 5 to 31 of primer compositions corresponding to JP-A-60-245544, and primer compositions other than the above Comparative Examples 32 to 40 are shown in Table 2.

The epoxy resins used in Examples and Comparative Examples shown in Table 2 are shown in Table 3, the curing agent is shown in Table 4, and the inorganic pigment is shown in Table 5.
Each is shown in the table.

In addition, the compounding amounts of the curing agent and the inorganic pigment shown in Table 2 are shown in parts by weight per 100 parts by weight of the epoxy resin. The amount of the solvent added is parts by weight per 100 parts by weight of the primer.
In the examples and comparative examples in Table 2, the inorganic pigments were premixed in proportion to the compounding ratio of the epoxy resin and the curing agent, and the particle size was 40 μm or less in a paint roll mill. Dispersed into range.

An epoxy resin in which the above inorganic pigment is dispersed and a curing agent are mixed so that the epoxy groups of the epoxy resin and the active hydrogen of the curing agent have equal chemical equivalent values, and when the viscosity of the mixture is high, a solvent is added to the mixture. Added and diluted.

Next, a method for producing a high-density polyethylene-coated steel sheet using the primer shown in Table 2 will be described.

A grit blasted steel plate (100 mm width × 300 mm length × 9 mm thickness) was preheated to a surface temperature of 190 ° C. Then
Using a spray coater, apply a primer of Table 1 to a film thickness of 100μ
It was painted and cured so that Then, powdery maleic anhydride-modified linear low-density polyethylene was electrostatically coated on the surface so that the film thickness was 200 μ, and was melted.
Then, a high-density polyethylene sheet (100 mm width × 300 mm length × 2.5 mm thickness sheet obtained by press molding, which was preheated to 200 ° C.) was pressure-bonded to the surface thereof, and a high-density polyethylene-coated steel sheet It was created.

In addition, phosphoric acid-
Silica-based chromate treatment agent (PO ₄ ^3- / total chromium weight ratio = 1.
16 and silica / total chromium weight ratio = 1.29) was applied by roll coating so that the total chromium adhesion amount was 520 mg / m ² , preheated and baked, and the surface temperature was set to 190 ° C. Density polyethylene-coated steel sheets were prepared and compared.

Adhesion test (measurement temperature 90 ° C, peeling angle 90 °, peeling speed 50mm / min), hot water immersion test (immersion temperature 95 ° C, immersion time 4000 hours, adhesive strength test after immersion) for the above high density polyethylene coated steel sheet ), Cathode peel test [(initial holiday diameter 5m
mφ, electrolytic solution 3% NaCl, voltage -1.5V (Cu / CuSO ₄ , standard electrode), test temperature 90 ° C, test time 2000 hours), and peeling distance of coating after the test [(x-5) / 2mm , X is the coating peeling diameter after the test] is shown in Table 6.

As is clear from the results of Table 6, as the base treatment of the steel material, bisphenol A diglycidyl ether or bisphenol AD diglycidyl ether alone or in a mixture, m-xylenediamine and epichlorohydrin condensate with butylglycidyl ether, If a primer composed of a modified polyamine to which any one of phenyl glycidyl ether, o-cresyl glycidyl ether, and ethylhexyl glycidyl ether is added and an inorganic pigment is applied, an adhesion test at high temperature, a hot water immersion test and a high temperature cathode In the peel test, extremely good results that have never been obtained can be obtained. Further, when the primer treatment according to the present invention and the conventionally known chromate treatment are used together for the base treatment of the steel material, the high temperature cathode peeling resistance can be improved.

Effects of the Invention As is clear from the examples, the polyolefin-coated steel material primer according to the present invention forms a primer layer having excellent hot water resistance as compared with the conventional polyolefin-coated steel material primer. It dramatically improves adhesiveness, hot water resistance, and high temperature cathode peeling resistance.

[Brief description of drawings]

FIG. 1 is a sectional view of a polyolefin-coated steel material using a primer according to the present invention. 1 ... Corrosion-resistant steel material, 2 ... Epoxy-based primer layer, 3
…… Modified polyolefin adhesive layer, 4 …… Polyolefin anticorrosion layer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hirotada Kato 1 Kimitsu, Kimitsu-shi, Chiba Nippon Steel Stock Co., Ltd. Inside the Kimitsu Works, Inc. (72) Makoto Kaga 4-chome, Minamishinagawa, Shinagawa-ku, Tokyo No. Nippon Paint Co., Ltd. Tokyo Office (72) Inventor Mitsuo Kuze 4-15 Minami-Shinagawa, Shinagawa-ku, Tokyo Japan Paint Co., Ltd. Tokyo Office (72) Inventor Hideo Takeshima 4-chome Minami-Shinagawa, Shinagawa-ku, Tokyo No. 15 Japan Paint Co., Ltd. Tokyo office (56) Reference JP-A-59-33321 (JP, A) JP-A-61-162564 (JP, A) JP-A-61-163971 (JP, A) JP-A 63-301264 (JP, A) JP-A-59-222275 (JP, A)

Claims (1)

[Claims] 1. A primer for laminating a steel material and a polyolefin, which contains the following three components (A), (B) and (C) as essential components. (A) An epoxy resin composed of a bisphenol A type epoxy resin, a bisphenol AD type epoxy resin or a mixture thereof. (B) Reaction addition of at least one selected from butyl glycidyl ether, phenyl glycidyl ether, o-cresyl glycidyl ether, and ethylhexyl glycidyl ether in a proportion of 0.2 to 0.6 mol per 1 mol of a condensate of m-xylenediamine and epichlorohydrin. Modified polyamine. (C) An inorganic pigment.