JP4760007B2 - Method for forming fluororesin coating - Google Patents

Description

  The present invention relates to a method for forming a fluororesin coating on the surface of a metal substrate and a metal substrate having the coating on the surface.

  Fluororesin is excellent in heat resistance, slidability, weather resistance, chemical resistance, non-adhesiveness, water repellency, oil repellency, etc., and is therefore used in various industrial products. In addition, it is also practiced to form a fluororesin film on the surface of various articles to impart excellent properties of the fluororesin.

  In particular, a molded body having a metal substrate surface such as a pipe, a container, a plate, a tank, a jig, a valve, a stirring blade, or a tank lorry (hereinafter referred to as a metal molded body) that handles a corrosive fluid or contacts a chemical. In other cases, chemical coating, corrosion resistance, non-adhesiveness, heat resistance, etc. are imparted to the surface by forming a fluororesin film on the surface by a method such as powder coating or rotational molding. The However, since the fluororesin generally has low adhesion to a metal substrate, the adhesion durability with the fluororesin coating may not be sufficient, and it is important to improve the adhesion between the fluororesin and the metal molded body. It is a problem.

  In Patent Document 1, a fluororesin having melt adhesiveness is formed on a covering member that is previously matched to the shape of the metal molded body, the surface of the metal molded body is covered with the coating member, and then heated and melted, A method for improving the adhesion between the molded body and the fluororesin coating is described. This method is not sufficiently applicable to a complex shaped metal molded body.

  In Patent Document 2, a fluoropolymer primer layer and a fluororesin outermost layer are provided on a metal substrate, and the fluoropolymer primer layer comprises a metal oxide polycondensate and a functional group-containing fluoroethylenic polymer. A multilayer coating consisting of: Since this method uses an aqueous dispersion of a functional group-containing fluorine-containing ethylenic polymer, the dispersibility of the primer is not sufficient, and the primer workability is not sufficient.

JP 2001-121606 A JP 2002-19052 A

  The present invention improves the conventional method as described above, and has a method of forming a fluororesin film excellent in adhesiveness to a metal substrate and also excellent in primer application workability, and a metal substrate having the film. provide.

The present invention relates to a method of forming a fluororesin film on the surface of a metal substrate, the surface of the metal substrate being roughened, and then the surface of the metal substrate at 200 to 600 ° C. in an atmosphere containing oxygen. Then, a primer composed of a silane coupling agent having an amino group on the surface, a partial hydrolyzate thereof, or a mixture thereof is applied to form a primer layer, and then a fluororesin is formed on the primer layer. A method for forming a fluororesin film is provided .

  According to the method for forming a fluororesin film of the present invention, it is possible to form a fluororesin film having excellent workability and excellent adhesion to a metal substrate. In addition, the formed fluororesin film has excellent adhesion to the metal substrate and excellent durability.

  In the method for forming a fluororesin film of the present invention, the heat treatment of the surface of the metal substrate is performed at 200 to 600 ° C. in an atmosphere containing oxygen. In both cases where the temperature is lower than this range and when the temperature is higher, the adhesion between the fluororesin coating and the metal substrate is not sufficient. Preferably it is 300-500 degreeC. The time for the heat treatment is preferably 10 minutes to 5 hours, more preferably 30 minutes to 2 hours. The atmosphere containing oxygen is preferably air because no special equipment is required.

The primer in the present invention comprises a silane coupling agent having an amino group and a partial hydrolyzate thereof, or a mixture thereof. Specific examples of the silane coupling agent having an amino group include a general formula, R ⁴ R ⁵ N—R ¹ —Si (R ² ) _n (OR ³ ) _{3 -n} (where R ¹ has 2 to 2 carbon atoms) 8 alkylene group, phenylene group, R ² is an alkyl group having 1 to 6 carbon atoms, phenyl group, R ³ is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, phenyl group, R ⁴ and R ⁵ are each independently , A hydrogen atom, an organic group having 1 to 6 carbon atoms, n represents 0 or 1. The same shall apply hereinafter), and R ⁷ R ⁸ N—R ⁶ —NR ⁴ —R ¹ —Si (R ² ) _n ( OR ³ ) _3-n (wherein R ⁶ represents an alkylene group having 2 to ⁶ carbon atoms, and R ⁷ and R ⁸ each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms). And silane coupling agents.

R ¹ is preferably an alkylene group, more preferably (CH ₂ ) ₂ , (CH ₂ ) ₃ , (CH ₂ ) ₄ , and most preferably (CH ₂ ) ₃ . R ² is preferably a methyl group or a phenyl group, and more preferably a methyl group. The R ^3, preferably an alkyl group having 1 to 3 carbon atoms, more preferably a methyl group or an ethyl group. n is 0 or 1, and 0 is more preferable. R ⁴ or R ⁵ is preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. R ⁶ is preferably an alkylene group, more preferably (CH ₂ ) ₂ , (CH ₂ ) ₃ , (CH ₂ ) ₄ , and most preferably (CH ₂ ) ₂ . R ⁷ or R ⁸ is preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and more preferably a hydrogen atom.

Specific examples include the following. 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, N-methyl-3-aminopropyltrimethoxysilane, N-methyl-3 -Aminopropyltriethoxysilane, N-methyl-3-aminopropylmethyldiethoxysilane, N, N'-dimethyl-3-aminopropylmethyldimethoxysilane, N, N'-dimethyl-3-aminopropylmethyldiethoxysilane ,
2-aminoethyl-3-aminopropyltrimethoxysilane, 2-aminoethyl-3-aminopropyltriethoxysilane, 2-aminoethyl-3-aminopropylmethyldimethoxysilane, 2-aminoethyl-3-aminopropylmethyldi Ethoxysilane, (N-methyl-2-aminoethyl) -3-aminopropyltrimethoxysilane, (N-methyl-2-aminoethyl) -3-aminopropyltriethoxysilane, (N-methyl-2-aminoethyl) ) -3-Aminopropylmethyldiethoxysilane, (N, N′-dimethyl-2-aminoethyl) -3-aminopropyltrimethoxysilane, (N, N′-dimethyl-2-aminoethyl) -3-amino Propyltriethoxysilane, (N, N′-dimethyl-2-aminoethyl) -3-aminopropy Methyl diethoxy silane, 3-aminoethyl trimethoxysilane, aminoethyl triethoxy silane,
4-aminobutyltrimethoxysilane, 6-aminohexyltriethoxysilane, 8-aminooctyltriethoxysilane, 4-aminophenyltrimethoxysilane.
Among them, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, 2-aminoethyl-3-aminopropyltrimethoxysilane, 2 -Aminoethyl-3-aminopropyltriethoxysilane, 2-aminoethyl-3-aminopropylmethyldimethoxysilane and 2-aminoethyl-3-aminopropylmethyldiethoxysilane are preferred. The silane coupling agent having an amino group and a partial hydrolyzate thereof may be used alone or in combination of two or more.

A partial hydrolyzate of an amino group-containing silane coupling agent can be easily produced by reacting an amino group-containing silane coupling agent with a predetermined amount of water in the presence of a catalyst such as an acid. The molecular weight of the partial hydrolyzate produced can be controlled by the amount of water used.
The silane coupling agent having an amino group, a partial hydrolyzate thereof, or a mixture thereof is preferably used after diluted with a solvent such as water or alcohol. The concentration is preferably 0.1 to 10% by mass, more preferably 0.5 to 7% by mass, and most preferably 1 to 5% by mass. When the concentration is smaller than this range, the adhesiveness of the fluororesin coating is low, and when the concentration is larger than this range, the dispersibility of the primer is insufficient and the coating workability is low.

For the primer, a silane coupling agent not having an amino group, tetraalkoxysilanes, Ti or Al alkoxides may be mixed and used, and co-hydrolyzed with an amino group-containing silane coupling agent, It may be used as a cohydrolyzate.
For the primer layer, a solution of a silane coupling agent having an amino group, a partial hydrolyzate thereof, or a mixture thereof was applied to the surface of a metal substrate by a method such as dipping, spin coating, spraying, brushing, or roll coating. After that, it is formed by drying. Drying is performed at room temperature to 150 ° C, preferably at room temperature to 130 ° C. The drying time is preferably 0 to 60 minutes, and more preferably 10 to 40 minutes.

Although it does not specifically limit as a fluororesin in this invention, The homopolymer or copolymer of a fluorine-containing monomer is used. Examples of the fluorine-containing monomer include fluoroethylenes such as tetrafluoroethylene (hereinafter referred to as TFE), CF ₂ = CFCl, CF ₂ = CH ₂ (hereinafter referred to as VdF), CF ₂ = CFCF ₃ (hereinafter referred to as HFP). .) hexafluoropropylene such _{as, CH 2 = CHCF 2 CF 3} , CH 2 = CHCF 2 CF 2 CF 2 CF 3, CH 2 = CFCF 2 CF 2 CF 2 H, CH 2 = CFCF 2 CF 2 CF 2 CF 2 (perfluoroalkyl) ethylenes of 2-8 carbon atoms in the perfluoroalkyl group such as _{^{H, R f (OCFXCF 2)}} m OCF = CF 2 ( wherein ^{R f} perfluoroalkyl group having 1 to 6 carbon atoms, X Represents a fluorine atom or a trifluoromethyl group, m represents an integer of 0 to 5, and the like; ₂ = CFOCH partially fluorinated vinyl ethers, such as ₂ CF ₃ and the like. A fluorine-containing monomer may be used individually by 1 type, and may use 2 or more types together. The fluorine-containing monomer alone or a copolymer is preferably a TFE homopolymer or a copolymer with a comonomer. Examples of the comonomer include olefins such as ethylene, propylene, and isobutylene, vinyl esters such as vinyl acetate, and the like in addition to the above-described fluorine-containing monomers.

  Specific examples of the fluororesin include polytetrafluoroethylene (hereinafter referred to as PTFE), TFE / ethylene copolymer (hereinafter referred to as ETFE), TFE / perfluoro (alkyl vinyl ether) copolymer (hereinafter referred to as PFA). TFE / HFP copolymer (hereinafter referred to as FEP), TFE / HFP / VdF copolymer, chlorotrifluoroethylene / ethylene copolymer, VdF polymer, HFP / VdF copolymer Examples include coalescence. PFE is preferably a TFE / perfluoro (propyl vinyl ether) copolymer. The fluororesin is preferably at least one selected from PTFE, ETFE, PFA and HFP, and more preferably ETFE. ETFE is excellent in formability and mechanical properties of the coating.

  It is also preferable that the fluororesin in the present invention contains 1 to 50% by mass of fluororubber such as TFE / propylene copolymer rubber, VdF / HFP copolymer rubber, VdF / HFP / TFE copolymer and the like. When the fluororesin contains fluororubber, the adhesion to the metal substrate and the impact resistance of the fluororesin coating are excellent. The fluorine content of the fluororubber is preferably 35 to 74 mass%, more preferably 50 to 74 mass%, and most preferably 55 to 74 mass%.

  The fluororesin in the present invention preferably contains an inorganic filler. Inorganic fillers include silica, clay, talc, calcium carbonate, mica, diatomaceous earth, alumina, zinc oxide, titanium oxide, calcium oxide, magnesium oxide, iron oxide, tin oxide, antimony oxide, calcium hydroxide, magnesium hydroxide, water Aluminum oxide, basic magnesium carbonate, magnesium carbonate, zinc carbonate, barium carbonate, dosonite, hydrotalcite, calcium sulfate, barium sulfate, calcium silicate, montmorillonite, bentonite, activated clay, sepiolite, imogolite, sericite, glass fiber, glass Examples include beads, silica-based balloons, carbon black, graphite, carbon fibers, fullerenes, wood flour, and zinc borate. When an inorganic filler is contained, it is excellent in wear resistance, slidability and the like. An inorganic filler may be used individually by 1 type, and may use 2 or more types together. As for content of an inorganic filler, 1-100 mass% is preferable with respect to a fluororesin.

  The fluororesin in the present invention preferably contains 0.1 to 2% by mass of an antistatic agent. When it contains an antistatic agent, it is excellent in antistatic properties. Examples of the antistatic agent include surfactants such as nonionic surfactants, anionic surfactants, cationic surfactants, and zwitterionic surfactants.

  In the present invention, the thickness of the fluororesin coating and the primer layer can be appropriately selected depending on the application. The thickness of the primer layer is preferably from 0.01 to 500 μm, more preferably from 0.1 to 100 μm. The thickness of the fluororesin coating is preferably 5 to 5000 μm, more preferably 5 to 3000 μm, and most preferably 5 to 1000 μm.

  The fluororesin coating in the present invention is usually preferably formed by the following steps (1) to (5). (1) a step of roughening the surface of the metal substrate on which the fluororesin film is to be formed by blasting or the like, (2) a step of washing with a solvent such as alcohol and washing the surface, (3) oxygen (4) a silane coupling agent having an amino group on the surface at a temperature of room temperature to 100 ° C., a partial hydrolyzate thereof, or their Applying a primer composed of a mixture and drying to form a primer layer; (5) forming a fluororesin film on the primer layer;

  The method for forming the fluororesin film is preferably at least one selected from the group consisting of a rotational molding method, a blow molding method, an electrostatic coating method and a fluidized immersion coating method. Rotational molding methods are pipes, tubes, rolls, containers, tanks, autoclaves, distillation towers, jigs, tank trucks, pump and blower casings, centrifuges, etc., blow molding is pipes, tubes, rolls, containers, Suitable for tanks, autoclaves, jigs, valves, tank trucks, etc.

  The electrostatic coating method is suitable for pipes, tubes, rolls, containers, plates, tanks, autoclaves, heat exchangers, distillation towers, jigs, valves, stirring blades, tank trucks, pump and blower casings, centrifuges, etc. . The fluidized dip coating method is suitable for rolls, containers, plates, heat exchangers, distillation towers, jigs, valves, stirring blades, pump and blower casings, centrifuges, and the like.

The metal substrate in the present invention is not particularly limited, and examples thereof include iron, stainless steel, aluminum, brass, copper, titanium, and tin.
The metal substrate may be a substrate formed on the surface by plating, laminating a metal foil on a film, or the like. As the metal substrate, articles having various shapes can be used. Specific examples thereof include plates, films, pipes, tubes, tanks, elbows, and vessels. Specific examples of the metal molded body include rolls, containers, tanks, autoclaves, heat exchangers, distillation towers, jigs, valves, stirring blades, tank trucks, casings for pumps and blowers, and centrifuges.

  Although the mechanism by which the metal base material and the fluororesin film have excellent adhesiveness is not necessarily determined by the method for forming a fluororesin film of the present invention, the metal base material is heated at 200 to 600 ° C. in an oxygen-containing atmosphere. By causing some change on the surface of the metal substrate, the adhesion between the primer layer and the metal substrate is improved, and as a result, the adhesion between the fluororesin coating and the metal substrate is improved. it is conceivable that.

  The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto. Examples 1 to 4 are examples, and examples 5 and 6 are comparative examples. In addition, adhesive evaluation and the electrostatic coating method followed the method as described below.

  [Adhesion Evaluation] A 50 mm × 100 mm, 2 mm-thick metal base specimen with a fluororesin coating formed on the surface, and a width of 10 mm from the end with a cutter knife between the fluororesin coating and the metal base A cut was made and peeled off. The peeled end was fixed to the chuck, and the fluororesin coating and the metal substrate were peeled from the end in the length direction of the test piece to a position of 50 mm using a tensile tester. The tensile speed was 50 mm / min, the metal substrate and the fluororesin film were peeled 90 degrees, and the maximum load was the peel strength (N / 10 mm). It shows that it is excellent in adhesiveness, so that peeling strength is large.

  [Electrostatic coating method] Using a powder spray gun, powder was sprayed onto the metal surface at an applied voltage of -60 kV and fired in an oven at a predetermined temperature and time. The coating was repeated until a predetermined film thickness was obtained.

[Example 1]
As a metal substrate, an SS400 iron plate 1 having a size of 50 mm × 100 mm and a thickness of 2 mm was used. After blasting the surface, the blast powder was removed with an air gun and immersed in ethanol for 30 minutes. Then, it heat-processed at 400 degreeC in the air for 1 hour. Next, 3 g of 2-aminoethyl-3-aminopropyltrimethoxysilane, 3 g of distilled water, and 94 g of methanol were placed in a beaker and stirred at 23 ° C. for 1 hour to obtain a primer solution. The primer solution was applied to the surface of the iron plate 1 at room temperature so that the dry film thickness was 1 μm, air-dried, and then dried at 120 ° C. for 30 minutes to form a primer layer. The primer solution was uniform and excellent in coating workability. On the primer layer, ETFE1 (Fullon ETFE / TL-081 manufactured by Asahi Glass Co., Ltd.) was electrostatically coated to a thickness of 600 μm to form a coating of ETFE1. The peel strength between the ETFE1 film and the iron plate 1 was 68.6 N / 10 mm, indicating a sufficient adhesive force.

[Example 2]
A primer layer is formed on the surface of the metal substrate in the same manner as in Example 1 except that a 50 mm × 100 mm, 2 mm thick SuS304 stainless steel plate 2 is used as the metal substrate, and an ETFE1 film is formed on the primer layer. did. The peel strength between the ETFE 1 coating and the stainless steel plate 2 was 55.0 N / 10 mm, indicating a sufficient adhesive strength.

[Example 3]
A primer layer was formed on the surface of the iron plate 1 in the same manner as in Example 1 except that ETFE2 (Fullon LM-ETFE / LM-2150 manufactured by Asahi Glass Co., Ltd.) was used as the fluororesin, and an ETFE2 film was formed on the primer layer. . The primer solution was uniformly dispersed and was excellent in workability during coating. The peel strength between the ETFE2 coating and the iron plate 1 was 107.8 N / 10 mm, indicating a sufficient adhesive strength.

[Example 4]
A primer layer was formed on the surface of the stainless steel plate 2 in the same manner as in Example 3 except that the stainless steel plate 2 was used as the metal substrate, and an ETFE2 film was formed thereon. The peel strength between the ETFE2 coating and the stainless steel plate 2 was 60.8 N / 10 mm, indicating a sufficient adhesive strength.

[Example 5 (comparative example)]
The surface of the stainless steel plate 2 was blasted and the blast powder was removed with an air gun and immersed in ethanol for 30 minutes. Without heating the stainless steel plate 2, 3 g of 2-aminoethyl-3-aminopropyltrimethoxysilane, 3 g of distilled water, and 94 g of methanol were placed in a beaker and stirred at 23 ° C. for 1 hour to obtain a primer solution. . The primer solution was applied to the surface of the stainless steel plate 2 at room temperature so that the dry film thickness was 1 μm, air-dried, and then dried at 120 ° C. for 30 minutes to form a primer layer. The primer solution was uniform and excellent in coating workability. On the primer layer, ETFE2 was electrostatically coated to a thickness of 600 μm to form a coating of ETFE2. The peel strength between the ETFE2 coating and the stainless steel plate 2 was 27.7 N / 10 mm, and the adhesion was insufficient.

[Example 6 (comparative example)]
The surface of the iron plate 1 was blasted, and then the blast powder was removed with an air gun and immersed in ethanol for 30 minutes. Without heating the iron plate 1 and without forming a primer layer, ETFE1 was electrostatically coated to a thickness of 600 μm to form a coating of ETFE1 on the iron plate 1. The peel strength between the ETFE 1 coating and the iron plate 1 was 19.6 N / 10 mm, and the adhesion was insufficient.

[Example 7 (comparative example)]
A ETFE1 film was formed in the same manner as in Example 5 except that the stainless steel plate 2 was used as the metal substrate. The peel strength between the ETFE 1 coating and the stainless steel plate 2 was 14.7 N / 10 mm, and the adhesion was insufficient.

[Example 8 (comparative example)]
Stainless steel 1 was prepared in the same manner as in Example 1 except that 27 g of tetraethoxysilane, 23 g of methyltriethoxysilane, and 50 g of ethanol were placed in a beaker and stirred at 23 ° C. for 1 hour. A primer layer was formed on the surface, and an ETFE1 film was formed on the primer layer. The peel strength between the coating of ETFE1 and stainless steel 1 was 107.5N / 10mm and showed a sufficient adhesive force, but the primer solution was not uniform and contained particles with poor dispersibility. Solution application workability was poor.

The metal substrate having a fluororesin coating formed by the method of the present invention has a fluororesin coating in the outermost layer, and thus has excellent characteristics such as chemical resistance, corrosion resistance, non-adhesiveness, and heat resistance. Moreover, it is excellent also in durability. Specific examples include plates, films, pipes, tubes, pipes, containers, plates, tanks, jigs, valves, stirring blades, tank trucks, cooking equipment, and the like.

Claims (5)

A method of forming a fluororesin film on a surface of a metal substrate , wherein the metal substrate is roughened, and then the surface of the metal substrate is heated at 200 to 600 ° C. in an atmosphere containing oxygen. Then, a primer layer comprising a silane coupling agent having an amino group, a partial hydrolyzate thereof, or a mixture thereof is formed on the surface to form a primer layer, and then a fluororesin film is formed on the primer layer. A method for forming a fluororesin film, comprising:   The fluororesin is at least one selected from a tetrafluoroethylene / ethylene copolymer, a tetrafluoroethylene / perfluoro (alkyl vinyl ether) copolymer, a tetrafluoroethylene / hexafluoropropylene copolymer, and polytetrafluoroethylene. The method for forming a fluororesin film according to claim 1, which is a seed.   The method for forming the coating film is one or more selected from the group consisting of a rotational molding method, a blow molding method, an electrostatic coating method, and a fluidized immersion coating method. Method. The method for forming a fluororesin film according to any one of claims 1 to 3, wherein the fluororesin film is formed by the following steps (1) to (5).
(1) a step of roughening a surface on which a fluororesin coating film is formed on the surface of the metal substrate;
(2) washing with a solvent and washing the surface;
(3) a step of heat-treating the surface at 200 to 600 ° C. in an oxygen-containing atmosphere;
(4) A step of applying a primer comprising a silane coupling agent having an amino group on the surface at room temperature to 100 ° C., a partial hydrolyzate thereof, or a mixture thereof, and drying to form a primer layer;
(5) A step of forming a fluororesin film on the primer layer. The method for forming a fluororesin film in the step (5) is at least one selected from the group consisting of a rotational molding method, a blow molding method, an electrostatic coating method, and a fluidized dip coating method. A method for forming a fluororesin film.