JPH0569870B2 - - Google Patents

Description

[Detailed description of the invention]

(Prior technology) Fluorine resin has properties such as heat resistance, corrosion resistance, non-adhesiveness, and low friction, so it is coated on a substrate such as a steel plate and the excellent properties of fluorine resin are applied to the surface of the substrate. is being granted.
However, since fluororesin has non-adhesive properties and is difficult to flow, it has poor adhesion to the substrate. As a result, paint films made from fluororesin paints tend to have pinholes, peeling, and blisters after long-term use. Fluorine resin itself has a low hardness, so it has the disadvantage that the painted film surface is easily scratched and easily abraded. In order to improve the adhesion between the fluororesin and the substrate, modified fluororesin paints are also manufactured by blending organic binders such as phenolic resins, acrylic resins, and epoxy resins with the fluororesin. Such an organic binder has no physicochemical interaction with the fluororesin, and is simply mixed together.
Therefore, the chemical resistance and heat resistance of the paint as a whole does not come from the excellent chemical resistance and heat resistance inherent to fluororesin, but from the low level chemical resistance and heat resistance of the organic binder. Become something to do. JP-A-50-126735 discloses a method of coating a substrate with polyvinylidene fluoride. According to this, in order to improve adhesion, a small amount of polytetrafluoroethylene powder is mixed with polyvinylidene fluoride powder along with a small amount of surfactant, and this is coated on the substrate to form a ground coat layer; - It has been shown that a final coating of polyvinylidene fluoride powder is applied on top of the coating layer. Providing such a base layer (ground coat layer) improves the adhesion of polyvinylidene fluoride to the substrate due to the anchor effect, but the adhesion improves as the polyvinylidene fluoride itself undergoes chemical changes. Therefore, the adhesion is not sufficient. Generally, the coefficient of thermal expansion of the coated resin is much larger than that of the metal substrate. If the coating film is a single layer, it is likely to be strained and peeled off due to temperature changes, so a base layer as in the above-mentioned known technique is often provided. However, coating in two layers is complicated in terms of operation, and at the same time, since a surfactant is used, the formed coating film has poor water resistance. (Problems to be Solved by the Invention) The present invention is intended to solve the above-mentioned conventional drawbacks, and its purpose is to provide a fluorocarbon paint film that has excellent adhesion to the substrate and is free from peeling. An object of the present invention is to provide a resin composition for coating. Another object of the present invention is that the painted surface has the inherent properties of fluororesins such as heat resistance, corrosion resistance, chemical resistance, non-adhesiveness, and low friction, and also has excellent scratch resistance. An object of the present invention is to provide a fluorine-based coating resin composition that can form a durable coating film. (Means for Solving the Problems) The coating resin composition of the present invention is irradiated with ionizing radiation of 0.1 to 50 Mrad in advance and
It contains a fluororesin having a melt viscosity of 10 ⁸ poise or less at 380°C and a thermosetting polyimide, and the polyimide is contained in a proportion of 0.5 to 100 parts by weight per 100 parts by weight of the fluororesin. This achieves the above objective. The fluororesin used is a homopolymer or copolymer of monomers such as vinyl fluoride, vinylidene fluoride, ethylene tetrafluoride, propylene hexafluoride, perfluoroalkyl vinyl ether, and ethylene chloride-trifluoride. be. They may be single polymers, copolymers, or a mixture thereof.
Thermosetting polyimide polymerizes to a high degree when heated, forming a network structure and exhibiting excellent heat resistance. Thermosetting polyimide is 0.5 to 100 parts by weight of fluororesin.
It is contained in an amount of 100 parts by weight, preferably 5 to 80 parts by weight. If the content exceeds 100 parts by weight, a continuous coating film of fluororesin will not be obtained, and a coating film with the excellent properties inherent to fluororesin, such as non-adhesion, will not be formed. If the content is too small, the effects derived from the properties of the thermosetting polyimide described below cannot be fully exhibited. The ionizing radiation irradiated to the fluororesin refers to electron beams or gamma rays. When irradiated with such ionizing radiation, the main chain of the fluororesin is severed,
Fluidity improves due to lower molecular weight. Improved fluidity improves wetting with the substrate and improves compatibility with thermosetting polyimide.
At the same time, physical properties such as heat resistance and mechanical strength deteriorate. These drawbacks are overcome by the thermosetting polyimide present in the composition. When the main chain of the fluororesin irradiated with ionizing radiation is severed,
A reactive site is generated at the cut site. When the resin composition is heated, these active sites react, and a crosslinking reaction between the fluororesins and a crosslinking reaction between the fluororesin and the thermosetting polyimide proceed. At the same time, the thermosetting polyimide is crosslinked to form a network structure and harden. Therefore, the fluororesin and thermosetting polyimide are compatible, and the two are intertwined with each other.
It hardens with an IPN (Interpenetrating Polymer Networks) structure. Therefore, the formed coating film has excellent adhesion to the substrate, as well as excellent heat resistance and mechanical strength. Scratch resistance is also improved.
Furthermore, it has the properties inherent to fluororesin, such as non-adhesiveness, low friction, and corrosion resistance, and a coating film with excellent durability is formed. The amount of ionizing radiation irradiated to fluororesin is
0.1-50 Mrad, preferably 0.5-20 Mrad.
If it is 50 Mrad or more, the fluororesin main chain will be severed too much, and the degree of deterioration of the resin will increase. Therefore, the mechanical strength of the resulting coating film decreases. If it is less than 0.1 Mrad, the effect of the present invention cannot be obtained because the amount of cleavage of the fluororesin main chain is insufficient. The melt viscosity of the fluororesin irradiated with the above amount of ionizing radiation is 10 ⁸ poise or less at 380°C. If a fluororesin with a viscosity higher than this is used, a continuous coating film of the fluororesin cannot be obtained. In the resin composition,
Various reaction accelerators, retarders, solvents, fillers, etc. may be added as necessary. Such a resin composition is coated on the substrate surface by a general coating method such as a powder coating method such as an electrostatic coating method or a fluidized dipping method; or a dispersion coating method. A desired fluororesin film is formed by heating. The coefficient of thermal expansion of the formed coating film is smaller than that of the original fluororesin, and is close to that of a substrate made of metal such as iron, for example. Therefore, even if the coating film is a single layer, the coating film will not peel off due to the influence of temperature changes. (Example) The present invention will be described below with reference to Examples. Example 1 (A) Formation of coating film: Polyvinylidene fluoride (KF Polymer #1000 manufactured by Kureha Chemical Co., Ltd.; melt viscosity at 200°C: 3×10 ⁴ poise) was used as the fluororesin, and γ-rays were irradiated at 10 Mrad. did. The melt viscosity after γ-ray irradiation was 1×10 ⁴ poise. Bismaleimide triazine resin (BT2400 manufactured by Mitsubishi Gas Chemical Co., Ltd.) is used as a thermosetting resin for 100 parts by weight of this γ-ray irradiated polyvinylidene fluoride.
50 parts by weight were added and mixed at 180°C for 1 minute. The resulting mixture was pulverized using a pulverizer to form a powder with a particle size of approximately 50 μm. A sanded steel plate is used as a substrate, and this is heated to about 200℃,
Powder coat the above powder on the surface and heat at 200℃.
A coated steel plate was obtained by firing for a period of time. The thickness of the coating film is 500 μm. (B) Evaluation of paint film: The adhesion of the obtained paint film to the substrate (initial adhesion) was examined. An attempt was made to remove the paint film using a cutter knife. The results are shown in the table below. In the table below, ○ indicates that the coating cannot be removed with a cutter knife, △ indicates that it can be removed, and × indicates that the coating has peeled off. next
Another sample obtained in section (A) was immersed in water and heated at 150°C for 300 hours using an autoclave. The adhesion state of the paint film was observed after 300 hours.
Furthermore, this coated steel plate was bent to peel off the coating film, and the substrate surface was visually observed. The respective results are shown in the table below. Example 2 (A) Formation of paint film: Same as Example 1 (A) except that the γ-ray irradiation dose was 3 Mrad. (B) Evaluation of paint film: Same as Example 1 (B). Example 3 (A) Formation of paint film: Same as Example 1 (A) except that the γ-ray irradiation dose was 20 Mrad. (B) Evaluation of paint film: Same as Example 1 (B). Example 4 (A) Formation of paint film: Same as Example 1 (A) except that the γ-ray irradiation dose was 50 Mrad. (B) Evaluation of paint film: Same as Example 1 (B). Comparative Example 1 (A) Formation of coating film: Same as Example 1 (A) except that polyvinylidene fluoride was not irradiated with gamma rays. (B) Evaluation of paint film: Same as Example 1 (B). Comparative Example 2 (A) Formation of paint film: Same as Example 1 (A) except that the γ-ray irradiation dose was 70 Mrad. Example 5 (A) Formation of coating film: Example 1 (A) except that 100 parts by weight of bismaleimide triazine resin was used.
Same as section. (B) Evaluation of paint film: Same as Example 1 (B). Example 6 (A) Formation of coating film: Same as Example 1 (A) except that 50 parts by weight of bismaleimide prepolymer (Kelimide 601 manufactured by Mitsui Petrochemicals) was used as the thermosetting resin. (B) Evaluation of paint film: Same as Example 1 (B). Comparative Example 3 (A) Formation of coating film: Same as Example 1 (A) except that 120 parts by weight of bismaleimide triazine resin was used. (B) Evaluation of paint film: Same as Example 1 (B). Comparative Example 4 (A) Formation of coating film: Same as Example 1 (A) except that no thermosetting resin was used. (B) Evaluation of paint film: Same as Example 1 (B). Comparative Example 5 (A) Formation of coating film: Kelimide as thermosetting resin
It is the same as Comparative Example 1 (A) except that 601 was used. (B) Evaluation of paint film: Same as Example 1 (B). Comparative Example 6 (A) Formation of paint film: Only thermosetting resin BT2400 was powder coated onto a substrate and fired to form a paint film in accordance with Example 1 (A). (B) Evaluation of paint film: Same as Example 1 (B). Comparative Example 7 (A) Formation of coating film: Only the thermosetting resin Kelimide 601 was powder coated onto a substrate and fired to form a coating film in accordance with Example 1 (A). (B) Evaluation of paint film: Same as Example 1 (B). Example 7 (A) Formation of coating film: Tetrafluoroethylene-hexafluoropropylene copolymer (manufactured by Daikin Industries, Ltd.; melt viscosity at 380°C: 3 × 10 ⁵
This was irradiated with 10 Mrad of gamma rays. For 100 parts by weight of this fluororesin
A powdered resin composition was obtained by mixing 50 parts by weight of BT2400. Steel plate with sanded surface
It was heated to 350°C, and the above resin composition was applied as a powder onto its surface. 350 more steel plates
It was baked at ℃ for 1 hour. (B) Evaluation of paint film: Same as Example 1 (B). Comparative Example 8 (A) Formation of paint film: Same as Example 7 (A) except that γ-rays were not irradiated. (B) Evaluation of paint film: Same as Example 1 (B). Comparative Example 9 (A) Formation of coating film: Example 7 (A) except that only the powder of tetrafluoroethylene-hexafluoropropylene copolymer was used and no thermosetting resin (BT-2400) was used. ) is the same as the item. (B) Evaluation of paint film: Same as Example 1 (B).

【table】

[Table] (Effects of the invention) As described above, the coating resin composition of the present invention can easily form a fluorine-based resin film on a substrate such as metal, and there is a risk of pinholes occurring during coating/film formation. There is no. The coating film has excellent adhesion to the substrate. Furthermore, the inherent properties of the fluororesin, such as heat resistance, corrosion resistance, chemical resistance, non-adhesiveness, and low friction, are not impaired. The surface hardness of the paint film is also improved and it has excellent water resistance. Since the coefficient of thermal expansion of the painted surface is close to that of the metal used for the substrate, such as iron, the paint film will not peel off due to distortion due to temperature changes. In this way, by forming a relatively thin coating film without requiring a base layer, a coating film with excellent durability can be obtained. The composition of the present invention can be used in a wide range of applications such as coating steel plates and steel pipes.

Claims (1)

[Scope of Claims] 1. Ionizing radiation of 0.1 to 50 Mrad has been irradiated in advance and the melt viscosity at 380°C after irradiation is 10 ⁸
A coating resin composition containing a fluororesin and a thermosetting polyimide, wherein the thermosetting polyimide is in a proportion of 0.5 to 100 parts by weight per 100 parts by weight of the fluororesin. Painting resin composition contained. 2. The resin composition according to claim 1, wherein the fluororesin is polyvinylidene fluoride or a copolymer containing vinylidene fluoride as a constituent component. 3. The resin composition according to claim 1, wherein the polyimide contains bismaleimide represented by the following general formula: [Formula] Here, R represents a group containing a phenyl group.