JPS6018537B2 - Polyolefin coated metal products - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to polyolefin metal products, and more specifically, a polyester resin containing an epoxy compound is interposed between a metal and a polyolefin, and an unsaturated fatty acid or an anhydride thereof is interposed between a metal and a polyolefin. This product relates to polyolefin-coated metal products that have excellent properties necessary for corrosion protection of metals, such as a smooth coated surface and good adhesion and salt water resistance by using a modified polyolefin modified by It is.

Polyolefin is well known as a general-purpose resin that has excellent thermal stability, heat resistance, chemical resistance, water resistance, etc., and is used in a wide range of fields such as blow molding, injection molding, films, and fibers.

However, since polyolefin does not have a functional group in its molecule and is nonpolar, it has poor adhesive properties and is difficult to coat onto metals and the like. For this reason, many attempts have been made to improve adhesion. For example, there is a method of oxidizing the surface of polyolefin using flame or the like, but with this method it is difficult to obtain the desired adhesive strength. This method was not put to practical use because the excellent properties of polyolefin were impaired by exposure to the atmosphere.

Further, polyolefin-coated metal products are also known, which are coated with modified polyolefins obtained by graft polymerization of unsaturated fatty acids or their anhydrides in order to improve the adhesion of polyolefins to metals.

However, although the adhesive strength of the coating on these metal products is good, when they come alongside an electrolyte aqueous solution such as salt water, the adhesive strength of the modified polyolefin decreases in a short period of time, and the coating layer peels off more easily than metal, making it resistant to salt. The water content was not sufficient. Furthermore, polyolefin-coated metal products have been known that are coated with the modified polyolefin by interposing various substances between the polyolefin and the metal.

As the substance interposed between the polyolefin and the metal, ethylene-vinyl acetate copolymer, adhesive resin such as epoxy resin, pressure-sensitive adhesive such as rubber, etc. are often used. However, when ethylene monovinyl acetate copolymer is used, it has disadvantages such as poor water resistance, and adhesives such as rubber have poor low-temperature properties and poor adhesive strength at low temperatures, so it is not satisfactory. There wasn't. Furthermore, as a method using epoxy resin, there is a method shown in Tsubaki Sekisho 50-182184, but in this method, the polyolefin is baked at a relatively high temperature and for a long time, resulting in "deterioration of physical properties due to thermal deterioration of the polyolefin itself." There are drawbacks etc. The present inventors have
As a result of intensive research with the aim of obtaining practical polyolefin-coated metal products that satisfy not only adhesive strength but also various properties required for anticorrosive coating of metals, such as salt water resistance, we found that polyester resins including epoxy resins were combined with unsaturated fatty acids or To obtain a practical polyolefin-coated metal product having the above-mentioned anticorrosion performance by interposing a polyolefin modified with an anhydride and a metal and heat-welding the modified polyolefin while curing the polyester resin or afterward. This made it possible.

That is, an object of the present invention is to provide a metal product coated with a polyolefin film modified with an unsaturated fatty acid or its anhydride or a polyolefin film containing the modified polyolefin, in which the coating with the polyolefin film is applied via a cured polyester resin layer. It is an object of the present invention to provide a polyolefin-coated metal product characterized in that it is made of a polyolefin-coated metal product. In the present invention, when heat-welding a polyolefin to a metal surface to obtain a polyolefin-coated metal product, a polyester resin as described below is interposed between the polyolefin and the metal, and a polyolefin made of the modified polyolefin described above is used as the polyolefin. For example, sufficient adhesive strength can be obtained by curing the polyester resin and heat welding the polyolefin at a temperature close to the melting temperature of the polyolefin and in a relatively short time, thereby reducing thermal deterioration of the polyolefin. It is something that can be done.

In addition, although metal products coated with core polyester resin and the polyolefin alone have poor salt water resistance, metal products coated with polyolefin in which the polyester resin is interposed between the core polyolefin and the metal have good salt water resistance and adhesive strength. This was based on the knowledge that the results were good. Further, when coating the polyolefin, it may be coated by a powder coating method using powder made of the modified polyolefin and unmodified polyolefin, or a coating layer of unmodified polyolefin may be further formed on the coated layer of the modified polyolefin. If this is done, a practical polyolefin-coated metal product with a good coated surface appearance can be obtained. The polyester resin used in the present invention is obtained by mixing 5 to 15 wt% of an epoxy compound to the polyester resin. Polyester resins include aromatic dicarboxylic acids such as phthalic acid, terephthalic acid and isophthalic acid, aliphatic dicarboxylic acids such as succinic acid and adipic acid, or aromatic dicarboxylic acids such as p-oxybenzoic acid and p-oxyethoxybenzoic acid. It can be obtained by polycondensing a group oxyacid as an acid component and an aliphatic diol such as ethylene glycol, propane diol, or neobentyl glycol as an alcohol component. Epoxy compounds contain two or more epoxy groups in the molecule, such as bisphenol A diglycidyl ether, neobentyl diglycidyl ether, phthalate diglycidyl ester, or condensates thereof. be. The epoxy compound is mixed to impart thermosetting properties and adhesive properties to the polyester resin, and if the amount is less than 5 to 15% by weight based on the polyester resin, it will not thermoset, and if it is too much, the resulting coating will deteriorate. It is undesirable because its anticorrosive properties such as salt water resistance are inferior. Furthermore, the polyester resin containing the epoxy resin of the present invention can be used as a solution by uniformly dispersing or dissolving it in a suitable solvent such as methyl ethyl ketone or methyl isoptyl ketone, or the polyester resin and the epoxy compound can be mixed using a roll or the like. Powdered powder can be used.

When used as a solution, the solid content concentration can be arbitrarily determined depending on the desired dry film thickness, etc. The application method is as follows.

Coating and curing conditions include dry film, curing time, and curing temperature, and the dry film has 5 to 50 r of the polyester resin, preferably 71 to 15 m.

If it is too thin, it will not adhere well, and if it is too thick, the resin itself will become brittle. The curing temperature is 150 DEG C. to 300 DEG C., preferably 180 DEG C. to 240 DEG C. If it is too low, it will not cure, and if it is too high, problems such as deterioration as mentioned above will occur. Curing time is 6
minutes to 9 G minutes, preferably 1 d minutes to 6 nights. The polyolefins used in the present invention are low density polyethylene, medium density polyethylene, high density polyethylene, polypropylene, polypuden-1, copolymers thereof, and blends thereof.

The unsaturated fatty acids grafted onto these include monobasic unsaturated fatty acids such as acrylic acid and methacrylic acid, and dibasic unsaturated fatty acids such as maleic acid and itaconic acid, which also include their anhydrides. . Among these, maleic anhydride can be easily modified, and the obtained modified polyolefin has good physical properties, so maleic anhydride is preferred.
Appropriate. Methods for modifying polyolefins with unsaturated fatty acids include adding a predetermined amount of the unsaturated fatty acids to polyolefins and modifying them, or mixing some polyolefins with unsaturated fatty acids at a high concentration under conditions that do not cause any reaction, and then modifying polyolefins from all over the country. There is a so-called masterbatch method in which the mixture is mixed with other substances and reacted.

Furthermore, when reacting an unsaturated fatty acid with a polyolefin, a radical generator such as dicumyl peroxide, ditertiary butyl peroxide, or tertiary butyl perbenzoate may be present. The heating reaction can be carried out by using an extruder, or by using a kneading machine such as a Banbury mixer, ribbon mixer, or roll.Also, the reaction can be carried out without a solvent or in a solvent, but from the viewpoint of post-processing steps, etc. , it is desirable to carry out without a solvent.

The amount of unsaturated fatty acid or its bran water to be added is 0.01 to 2 parts by weight, preferably 0.05 to 1 part by weight, per 100 parts by weight of the polyolefin. Addition amount is 0.
If it is less than 0.01 parts by weight, the desired adhesive strength cannot be obtained, and if it is more than 2 parts by weight, side reactions such as excessive crosslinking and decomposition reactions become significant, making it impossible to obtain desired results. The modified polyolefin is applied and fused onto the polyester resin during or after curing of the polyester resin. Methods for coating metal with polyolefin resin include an extrusion coating method, a method of heat-pressing a molded sheet, and a powder coating method.

Among these, the powder coating method allows easy adjustment of coating thickness,
Moreover, the performance of the obtained coating is also good, so it is preferable. When adding unsaturated fatty acids to polyolefins, a cross-linking reaction between the polyolefins occurs simultaneously, resulting in poor fluidity, so methods are being explored to melt the powder and adhere it to metal. In this method, the surface of the modified polyolefin does not become smooth, and furthermore, when additives such as pigments are added to the modified polyolefin, the adhesive strength tends to decrease. For this reason, when the polyolefin is coated by a powder coating method, a practical polyolefin-coated metal product with a smooth surface can be obtained if the powder is a mixture of the modified polyolefin and unmodified polyolefin.

That is, the modified polyolefin:
/ unmodified polyolefin with MI higher than 20
If a coating method using a powder coating method using a powdered polyolefin mixed with .about.8% is used, a practical polyolefin-coated metal product with a smooth coated surface can be obtained.

The modified polyolefin and the unmodified polyolefin may be mixed in advance by making each powder into powder by an appropriate method, such as mechanically pulverizing or precipitating it from a solvent. Alternatively, the modified polyolefin and the terminally modified polyolefin may be melt-mixed and then powdered.

When coating with a mixture of powdered modified polyolefin and unmodified polyolefin, the unmodified polyolefin, which has good resin fluidity, fills in the irregularities on the surface of the polyolefin coating and makes the surface smooth. Further, when the modified polyolefin and the unmodified polyolefin are melt-mixed and then powdered and coated, the coated surface becomes smooth because the fluidity of the modified polyolefin itself is improved.

Furthermore, if the modified polyolefin is coated and then coated with an unmodified polyolefin, there is little decrease in adhesive strength even when it is necessary to add pigments, etc., and corrosion resistance such as smooth coating surface and salt water resistance are improved. Excellent polyolefin coated metal products are obtained.

That is, in the present invention, the polyolefin coating layer is made of two of the modified polyolefin and unmodified polyolefin, in which the layer in contact with the polyester resin is the modified polyolefin.
If it is made into a layer, a polyolefin-coated metal product with a smooth surface and good anticorrosion performance such as salt water resistance can be obtained.If it is necessary to coat with polyolefin to which pigments have been added, unmodified polyolefin can be used. If a pigment or the like is added, this is preferable because it reduces the decrease in adhesive strength.

The metal materials to which the anticorrosion coating used in the present invention is applied include:
Iron, such as steel, titanium, aluminum, nickel, copper, zinc, tin, etc., and alloys containing these, which can be molded into tubes, hollows, wires, plates, and various other shapes. .

Next, the present invention will be explained in more detail with reference to the following examples and comparative examples. Note that parts represent parts by weight. Examples 1 to 4 Dimethyl terephthalate, ethylene glycol, neobentyl glycol, 100M each, were placed in a reactor and 150~
After performing a transesterification reaction at 250 qo to remove a theoretical amount of methanol, a polycondensation reaction was performed under reduced pressure at 270 qo to obtain a polyester resin.

Next, 1 part by weight of bisphenol A dicrycidyl ether as an epoxy compound was mixed with 1 part by weight of this polyester resin 9 and dissolved in a methyl ethyl ketone solvent to obtain a solution with a solid content of 30%. Next, medium density polyethylene (MI
Add 10 parts by weight of I〇density 0.925), 0.1 parts by weight of dicumyl peroxide, and parts by weight of maleic anhydride shown in Table 1, resin temperature 220°C, residence time in extruder 10q.
A bran water maleic acid-modified polyethylene was obtained using an extruder of 500 ml under suitable conditions. This modified polyethylene was dissolved in a solvent and then precipitated to obtain a modified polyethylene powder. Steel plate treated with zinc phosphate in advance (material SP
The above polyester resin solution was brushed onto a CC-D steel plate (CC-D steel plate) and preliminarily heated and dried in an oven for 150 minutes.

Next, after heating for 4 times at 20 mm, sprinkle the above powdered modified polyethylene while heating at the same temperature.
Polyolefin coating was performed by heating for the time shown in the table. The thickness of the resulting coating was approximately 10 mm for the polyester resin and 500 mm for the polyolefin layer. Next, the adhesive strength of the coating layer was measured by a 1800 peel test (pulling speed: 50 side/min).

In addition, the salt water resistance is determined by adding a steel plate with a knife cut into the coating layer up to the steel surface of 1 ㎇ angle to 3% NaCI aqueous solution.
The steel plate was immersed in a groove for 10 days, and measurements were taken from the inside (rib) where salt water entered the surface of the steel plate from the notch. Examples 5 to 7 Polyethylene of Example 1 was treated with maleic anhydride 0
．． A modified polyethylene containing 5 parts by weight was obtained.

The skin of this modified polyethylene was 0.5. This was melt-mixed with the unmodified polyethylene of Example 1 in the proportions shown in Table 2, and then powdered in the same machine as Example 1 to obtain a powdered polyolefin in which modified polyethylene and unmodified polyethylene were mixed. Next, a polyester resin solution was applied to a steel plate in the same manner as in Example 1, and then the polyolefin powder was coated. The adhesive strength and salt water resistance of the obtained polyolefin-coated steel sheets were measured, and the appearance of the coated surface was also observed. Examples 8 to 13 Modified polyethylene to which maleic anhydride was added in the proportions shown in Table 3 was produced and powdered in the same manner as in Example 1.

The modified polyethylene powder described above was coated on the polyester resin layer using the same machine as in Example 1, and then the unmodified polyethylene used in Example 1 was further coated thereon.

In Example 13, unmodified polyethylene to which 0.2% of carbon black was added was coated. The coating appearance, adhesive strength, and salt water resistance of the obtained polyethylene-coated steel plate were measured.

Comparative Examples 1 to 3 In Comparative Example 1, unmodified polyethylene was used in place of the modified polyethylene in Example 1.

In Comparative Examples 2 and 3, only the polyester resin and modified polyethylene used in Example 1 were individually coated in the same manner. The test results are shown in Table 4. Comparative Example 4 35 parts of Epicoat 1007 (epoxy resin manufactured by Shell Co., Ltd., molecular weight approximately 3000) and 30 parts of Yuban 1$ (manufactured by Mitsui Tosho Co., Ltd., urea formaldehyde resin, solid content 50%) were dissolved in a solvent containing methyl ethyl ketone to reduce the solid content. A 30% epoxy resin solution was obtained.

Next, coating was carried out in the same manner as in Example 1 except that the above epoxy resin solution was used instead of the polyester resin solution to obtain a polyolefin-coated steel plate, and the adhesive strength and salt water resistance were measured. The results are shown in the table below. Note that the thickness of the epoxy resin layer was also approximately 10 mm. From the above table, it can be seen that metal products coated with two layers of an epoxy resin layer and a polyolefin layer have poor salt water resistance.

As can be seen from the results of the above Examples and Comparative Examples, the polyolefin-coated metal products of the present invention have high adhesion strength of the coating, excellent long-term salt water resistance, etc., and a good appearance of the coated surface. This is a polyolefin coated metal product.

Table 1 Table 2 Table 3 Table 4

Claims (1)

[Scope of Claims] 1. A metal product coated with a polyolefin coating modified with an unsaturated fatty acid or its anhydride or a polyolefin coating containing the modified polyolefin, in which the coating with the polyolefin coating is applied via a cured polyester resin layer. A polyolefin coated metal product characterized by: 2. In a metal product coated with two layers, the upper layer being a terminally modified polyolefin layer and the lower layer being a modified polyolefin layer modified with an unsaturated fatty acid or its anhydride, the coating by the modified polyolefin coating is a cured polyester resin. A polyolefin-coated metal product characterized by being made through layers.