JPS6134474B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a primer used for polyethylene powder coating. Generally, when applying polyethylene powder to various metal surfaces, the adhesion of polyethylene to metal surfaces is poor, so the object to be coated must be heated to a high temperature before painting, or the polyethylene powder must be mixed with wood that has good adhesion. Painting is done in this state. However, it is difficult to obtain a coating film with sufficient adhesion using these methods. In addition, in order to further improve adhesion, a method is used in which a primer such as a rubber adhesive is applied to the object to be coated in advance, and then polyethylene powder is applied. Even if an excellent coating film is obtained, there is a drawback that the adhesion decreases significantly when immersed in room temperature water or hot water. Both of these factors made it difficult to obtain an excellent coating film. The present invention has been made with the aim of eliminating the drawbacks of conventional polyethylene powder coatings as described above and providing a polyethylene coating film that is also excellent in hot water resistance and other properties. A primer for polyethylene powder coating is characterized in that it contains an alkoxy titanate coupling agent and a solvent capable of dissolving the coupling agent. The monoalkoxy titanate coupling agent used in the present invention has the general formula RO-Ti(-X) ₃ (wherein R represents an alkyl group, and X is -O-CH ₂ R ₁ Y, -O-CO- R ₁ Y -O-SO ₂ -R1Y

【formula】

[Formula] or

[Formula] In the above, R ₁ represents a divalent hydrocarbon group, and Y represents a hydrogen atom, a hydroxyl group, or an amino group. and multiple Xs present in the same compound,
Each of R ₁ and Y may be the same or different. ) is a compound represented by In the above formula, R is, for example, a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a bentyl group,
Examples include octyl group. Also, as R ₁ (−CH ₂
)-n,

[Formula] (where n=1 ~31), -CH=CH-,

Examples include aliphatic divalent hydrocarbon groups and aromatic divalent hydrocarbon groups such as [Formula]. Further, specific examples of the monoalkoxy titanate coupling agent used in the present invention include isopropyl triisostearoyl titachite,
Isopropyl tri(lauryl-myristyl)
Titanate, isopropyl-isostearoyl (dimethacrylic)-titanate, isopropyl-isostearoyl (diaryl)-titanate,
Isopropyl-trimethacrylate-titanate, Isopropyl-triacryl-titanate, Isopropyl-isostearoyl (di-4-aminobenzoyl)-titanate, Isopropyl-tri(dodecylbenzenesulfonyl)-titanate, Isopropyl-didotecylbenzenesulfonyl (4-aminobenzene) Sulfonyl)-titanate, Isopropyl-tri(dioctylphosphate)-titanate, Isopropyl-tri(dioctylpyrophosphate)-titanate, Isopropyl-tri(dioctylphosphate)-titanate, Isopropyl-tristearoyl-titanate, Isopropyroudi(lauryl-) myristyl) methacrylic titanate, isopropyl (lauryl myristyl) dimethacrylic titanate, isopropyl diisostearoyl (acrylic) titanate, isopropyl trianthrunyl titanate, isopropyl diisostearoyl (cumyl phenyl) titanate, isopropyl root Examples include liquemylphenyl titanate, isopropyl lysinoyl titanate, and the like. Therefore, among the monoalkoxy titanate coupling agents used in the present invention, in the structural formula -O-CO,

【formula】

[Formula] and

Those having the structure of the following formula are preferred because they have particularly excellent adhesion. The monoaloxytitanate coupling agent is usually in the form of a viscous liquid or wax, and in the present invention, the coupling agent is dissolved in an appropriate solvent to form a primer composition. . Suitable solvents used in the present invention include ethyl alcohol, isopropyl alcohol, butyl alcohol, toluene, xylene, trichloroethane, trichloroethylene, hexane, cyclohexane, pentane, ethyl cellosolve, butyl cellosolve, methyl ethyl ketone, acetone, ethyl acetate, acetic acid. Examples include butyl. And the concentration of the coupling agent when made into solution is 0.5
Preferably, the amount is 50% by weight. Further, viscosity modifiers, fillers, dispersion stabilizers, etc. may be added to the primer of the present invention as necessary. In addition, the polyethylene powder coating targeted in the present invention includes not only unmodified polyethylene powder commonly used, but also ethylene copolymers mainly composed of ethylene monomers, such as ethylene-vinyl acetate copolymers, Also included are powders of ethylene-acrylic acid copolymer, ethylene-acrylic acid-vinyl acetate copolymer, etc., and polyethylene powder modified to improve adhesiveness. Next, in order to perform polyethylene powder coating using the primer of the present invention, the primer is first applied to the surface of the object to be coated and allowed to dry. For this coating, ordinary coating methods such as dipping, spraying, and brushing may be appropriately employed. A polyethylene powder coating is then applied onto the primer coating film formed as described above. Conventional coating methods such as spraying, fluidized dipping, electrostatic coating, and thermal spraying may be used for this coating, and the object to be coated is usually heated to a temperature higher than the melting temperature of the polyethylene powder coating. The polyethylene powder coated as described above is heated and melted and adheres closely to the surface of the object to be coated. The polyethylene coating film obtained in the above manner has excellent adhesion, especially water-resistant adhesion and hot water-resistant adhesion, as well as excellent corrosion resistance due to the action of the monoalkoxy titanate coupling agent interposed between the object to be coated and the coating film. It becomes something. As mentioned above, since the primer of the present invention contains a monoalkoxy titanate coupling agent, by using the primer of the present invention,
It is possible to form a polyethylene coating film with excellent not only normal adhesion but also water-resistant adhesion and hot water-resistant adhesion on the surface of objects to be coated, such as metals, and also provides excellent corrosion resistance to the surface of objects to be coated. It is possible. Therefore, the primer of the present invention can be effectively used for coating the inner and outer surfaces of steel pipes, coating steel plates, etc. by polyethylene powder coating. Next, examples of the present invention will be described. Note that in the following, parts mean parts by weight. Example 1 A primer solution was obtained by dissolving 3 parts of isopropyl-triisostearoyl-titanate in 97 parts of isopropyl alcohol. The above primer was applied with a brush to a steel plate that had been cleaned with trichlene and thoroughly dried. The thickness of the primer layer thus formed was approximately 5 microns. Next, the above steel plate was preheated to 200℃, and powdered polyethylene (melt index 20, density 0.920g/cm ³ , particle size 100
~150 microns) and heated at 200°C for 20 minutes to obtain a coating film approximately 300 microns thick. The polyethylene coating thus obtained was subjected to a cross-cut test and a cross-cut test, and the results shown in Table 1 were obtained. The cross-cut test is a test in which cuts are made vertically and horizontally at 2 mm intervals in the paint film and the peeling status is observed for two types of samples: a normal sample without any treatment and a sample immersed in hot water at 100℃ for 24 hours. I went. or,
In the cross-cut test, a cross-cut is inserted into the coating of a normal sample without any treatment to observe the peeling condition, and then it is immersed in 100℃ hot water for 24 hours and the peeling condition and rusting condition after immersion is observed. That's what I did. Example 2 A primer solution was obtained by dissolving 5 parts of isopropyl-tri(dioctylphosphate)-titanate in 95 parts of xylene. Using this primer, primer coating was performed on a steel plate in the same manner as in Example 1, preheated to 200℃, and powdered polyethylene (melt index 14, density 0.925g/
^cm3 , particle size 200-300 microns) and at 220℃.
Heating was performed for 20 minutes to obtain a coating film of approximately 300 microns. The coating film thus obtained was subjected to the same tests as in Example 1, and the results shown in Table 1 were obtained. Example 3 A film with a thickness of approximately 250 microns was prepared in the same manner as in Example 2, except that adhesive polyethylene powder (trade name Admar P, manufactured by Mitsui Petrochemicals) was used as the powder polyethylene, and the heating temperature of the polyethylene coating was 210°C. A coating film was obtained. The above coating film was subjected to the same test as in Example 1, and the results shown in Table 1 were obtained. Example 4 5 parts of isopropyl-tri(dioctylpyrophosphate)-titanate was dissolved in 95 parts of hexane to obtain a primer solution, and powder polyethylene coating was performed in the same manner as in Example 1. The test results for the resulting coating film are shown in Table 1. Example 5 A primer solution was obtained by dissolving 3 parts of isopropyl-didodecylbenzenesulfonyl (4-aminobenzenesulfonyl)-titanate in 97 parts of toluene. Using this primer, a 5-micron-thick primer layer was formed on a steel plate that had been cleaned with Triclean, and this was preheated to 200°C and painted using adhesive polyethylene powder (same as in Example 3) using the sprinkle method. , heated to 210℃ for 20 minutes to a thickness of about 250℃
A micron coating was obtained. The test results for this coating film are shown in Table 1. Comparative example: A steel plate cleaned with Triclean is preheated to 300℃,
The same powdered polyethylene as used in Example 1 was coated by the sprinkle method and heated at 200° C. for 20 minutes to obtain a coating film with a thickness of about 400 microns. The test results for the resulting coating film are shown in Table 1.

【table】

Claims (1)

[Scope of Claims] 1. A primer for polyethylene powder coating, comprising a monoalkoxy titanate coupling agent and a solvent capable of dissolving the coupling agent. 2. The primer according to claim 1, wherein the concentration of the monoalkoxy titanate coupling agent is 0.5 to 50% by weight.