JP5652989B2 - Repair method of old paint film - Google Patents

Description

  The present invention is a binder for various types of steel structures such as road guardrails, bridges, tunnels, etc., old paints that have been painted on plants, ships, etc. and exposed for a long period of time, that is, thermoplastic resins exposed to sunlight or wind and rain. It relates to the repair coating method of the old paint film.

  Conventionally, as an anti-corrosion and aesthetic countermeasure for outdoor steel structures, a paint using a thermoplastic resin as a binder that has good water resistance and weather resistance, can be dried quickly, and can be coated with a thick film, such as a chlorinated rubber-based paint And vinyl paints are widely applied.

  When repairing old chlorinated rubber-based or vinyl-based old paint films that have been deteriorated by long-term exposure, the part of the old paint film that has not deteriorated (active film part) is utilized and the part that has deteriorated (dead film part) A so-called three-type kelen, which is removed with kelen, is used to repair the portion removed with kelen, and then the entire surface is painted. In this case, chlorinated rubber-based and vinyl-based old paint films, etc., are essentially made of a thermoplastic resin having no cross-linking component as a binder. If an epoxy resin-based paint or urethane resin-based paint is applied, the solvent in the repair paint partially dissolves or swells the chlorinated rubber-based old film or vinyl-based old paint film, or the solvent in the repair paint After volatilization, the old chlorinated rubber coating film, the old vinyl coating film, etc. contracted, and this caused problems such as wrinkles, cracks, peeling, etc. in the repair coating film.

  Furthermore, since the chlorinated rubber coating film is easy to follow the expansion and contraction due to the repeated action of heating and cooling of the object to be coated, if an inorganic coating material with excellent weather resistance and fire resistance is used as a repair coating material, Since it is not flexible, cracks are likely to occur. Therefore, it was considered impossible to use an inorganic coating having excellent characteristics as a repair coating for a chlorinated rubber-based old coating film. Therefore, conventionally, the chlorinated rubber-based old coating film is peeled off entirely and newly coated, and therefore, there is a problem that a lot of man-hours and costs are required.

  It is not necessary to peel the entire surface of the chlorinated rubber-based coating film, and on top of that, as a repair coating method for the chlorinated rubber-based old coating film that can be repaired without causing blemishes and cracks, There has been proposed a method of using an undercoating paint containing a solvent that does not dissolve or swell a rubber-based coating film (for example, see Patent Document 1).

In addition, as a method of avoiding problems caused by partial dissolution or swelling of the chlorinated rubber-based old paint film or vinyl-based old paint film by the solvent in the repair paint, the solvent contains a solvent that does not dissolve or swell the old paint film, and There has been proposed a method of applying an undercoating paint for forming a coating film having an elongation of 3 to 200% so that the dry film thickness is 50 to 300 μm (for example, see Patent Document 2).
JP 2000-334375 A JP 2005-334759 A

  In the method of using an undercoat paint containing a scaly filler and containing a solvent that does not dissolve or swell the chlorinated rubber-based coating film, the formed coating film is poor in flexibility, and thus tends to crack. It was not always satisfactory. Moreover, in the method using an undercoat paint containing a solvent that does not dissolve or swell the old paint film, the anticorrosion property, the adhesive force, and the thermal cycle property are not always satisfactory.

  The present invention eliminates the need to completely peel off an old paint film made of a thermoplastic resin as a binder, such as a chlorinated rubber-based paint or a vinyl-based paint, and prevents corrosion, cracks, peeling, etc. Repair method of old paint film, which can be used for repair painting of undercoat film with excellent adhesion, thermal cycle performance, flexibility or internal stress relaxation, and can be applied with thick film type paint or finish paint. The purpose is to provide.

As a result of intensive studies to achieve the above object, the inventors of the present invention contain a solvent that dissolves or swells the old coating film on the surface of the old coating film using a thermoplastic resin as a binder. A thick film type paint that forms a coating film having a specific elongation by coating an undercoating paint that forms a coating film having an elongation rate to a specific dry film thickness , dissolving or swelling the old coating film The present invention has been completed by finding that the above-mentioned object can be achieved by painting to have a specific dry film thickness.

That is, the repair coating method for an old paint film of the present invention comprises a solvent for dissolving or swelling the old paint film on the surface of the old paint film containing a chlorinated rubber resin or a vinyl resin as a binder, and an elongation rate. Is coated with an epoxy resin-based or urethane resin-based undercoating material that forms a 5-150% coating film so that the dry film thickness is 50-300 μm, and the old coating film is dissolved or swollen, and then the elongation percentage Is characterized in that an epoxy resin-based, urethane resin-based, vinyl resin-based or polyester resin-based thick film-type paint that forms a 2 to 200% coating film is applied to a dry film thickness of 200 to 1000 μm. .

  According to the repair coating method of the old paint film of the present invention, it is not necessary to completely peel off the old paint film made of a paint using a thermoplastic resin as a binder, and it is free from corrosion, cracks, peeling, etc. It is possible to repair the undercoat film with excellent adhesion, thermal cycle performance, flexibility, internal stress relaxation, etc., and it can be applied with thick film paint or finish paint to improve long-term durability. I can do it.

  The old coating film using a thermoplastic resin to which the repair coating method of the present invention is applied as a binder is, for example, a coating film made of a resin such as chlorinated rubber or vinyl. The chlorinated rubber-based coating film constituting the chlorinated rubber-based old coating film is a chlorinated resin such as chlorinated rubber or chlorinated polyolefin specified in JIS K 5639, or an alkyd resin or an acrylic resin is blended with these resins. It is an old paint film formed from a paint having a resin as a binder. The vinyl-based coating film constituting the vinyl-based old coating film is, for example, an old coating film formed from a paint mainly composed of polyvinyl chloride defined in JIS K 5581.

  In addition, about the old coating film with which the repair coating method of this invention is applied, an active film part is a part which has the adhesive force of 1.0 Mpa or more in an adhesive test (JISK5600-5-7), and a dead film part Is a part having an adhesion less than that, and when repairing, it is desirable to remove the dead film part from the old paint film with kelen.

Next, the repair paint used in the present invention will be described.
The undercoating paint used in the present invention is required to be able to follow the expansion and contraction of the article to be coated and the old coating film, so that the elongation is 5 to 150%, preferably 20 to 100%. More preferably, it is necessary to apply an undercoat paint for forming a 30 to 80% coating film in a dry film thickness of 50 to 300 μm, preferably 70 to 280 μm, more preferably 90 to 250 μm. The elongation percentage of the coating film can be expressed, for example, as the elongation at break measured with a tensile strength tester (Autograph AG2000B manufactured by Shimadzu Corporation).

  When the elongation percentage of the undercoat coating film is smaller than 5%, such a coating film hardly follows the expansion and contraction of the article to be coated or the old coating film, and causes cracks and cracks later. Further, when the elongation ratio of the undercoat coating film exceeds 150%, such a coating film has a low cross-linking density and increases the permeability of the solvent, which causes a blur. Moreover, when the dry film thickness of an undercoat coating film is thinner than 50 micrometers, such a coating film becomes inadequate in durability (corrosion resistance). Moreover, when the dry film thickness of an undercoat coating film exceeds 300 micrometers, such a coating film becomes bad in drying property, workability | operativity, and adhesiveness.

  Examples of suitable film forming resins used for such undercoat paints include epoxy resin-based, urethane resin-based, and oil-modified alkyd resins. In particular, an epoxy resin system or a urethane resin system is preferable because of its excellent adhesion to an old coating film. Among the epoxy resin-based synthetic resins, a synthetic resin capable of forming a coating film having excellent flexibility is preferable, and examples of suitable commercially available products include “FLEP-50” and “FLEP-60” manufactured by Toray Rethiol Co., Ltd. "Adeka Resin" EPU-4-75 "manufactured by Asahi Denka Kogyo Co., Ltd. In addition, as a typical curing agent for the epoxy resin, known epoxy resin curing agents such as aliphatic polyamines, aromatic polyamines, alicyclic polyamines, polyamide amine compounds, and modified products thereof may be exemplified. be able to. Specifically, “Sanmide 308D-65”, “Sanmide 301D”, “Sanmide i-544” manufactured by Sanwa Chemical Industry Co., Ltd. and the like can be mentioned as preferable ones.

  Among urethane resin-based synthetic resins, a synthetic resin capable of forming a coating film excellent in flexibility is preferable. For example, as a commercially available product, “Acridic A-801” manufactured by Dainippon Ink and Chemicals, Ltd. ”, Polyester polyols such as“ Haripol F-209 ”manufactured by Harima Chemical Co., Ltd., and“ Duranate E-405-80T ”or“ Duranate E ”manufactured by Asahi Kasei Kogyo Co., Ltd. as curing agents. -402-90T "etc. can be mentioned.

  The undercoating paint used in the present invention is a coating film-forming resin, a solvent, and pigments such as colored pigments, extender pigments, rust preventive pigments, fillers, curing agents, curing accelerators and wetting agents. And various additives such as a dispersant and a thickener.

  The solvent blended in the primer coating used in the present invention is a solvent for dissolving or swelling the old coating film. When evaluating whether the solvent dissolves or swells the old coating film, it can be evaluated, for example, by attaching the solvent to be used to the fingertip and bringing the finger into contact with the old coating film. For example, if the fingertip adheres to the old paint film when it comes into contact with the old paint film, the solvent can be evaluated as dissolving the old paint film. In addition, the fingertip does not adhere to the old paint film when it comes into contact with the old paint film, but if the back of the finger remains on the old paint film, the solvent can be evaluated to swell the old paint film. . Such a solvent can be easily selected by those skilled in the art depending on the type of thermoplastic resin used in the old coating film.

  When the old coating film using a thermoplastic resin as a binder is composed of a chlorinated rubber resin or a vinyl resin, xylene can be used as a solvent for dissolving or swelling the old coating film. In addition to the above solvents, strong solvents such as ester solvents, ketone solvents, and ether solvents can also be used.

  The undercoat paint used in the present invention preferably contains a scaly pigment as a pigment. The scale-like pigment blocks the penetration of the solvent in the thick film paint and prevents the old paint film from being impregnated when the thick film paint described below is applied on the undercoat film. It has the function of mitigating the propagation of expansion and contraction of the object to be coated and the old coating film to the thick film coating film and preventing the occurrence of cracks in the coating film.

  Regarding the size of the scaly pigment, the average thickness is usually 0.3 to 10 μm, preferably 2 to 8 μm in consideration of its strength, coating workability, etc. while exhibiting the above-described effects. The average major axis (maximum length in the surface direction) is 1 to 1700 μm, preferably 2 to 500 μm. Suitable scaly pigments include scaly iron oxide (MIO), scaly talc, glass flakes and the like.

  A pigment can be arbitrarily blended in the undercoat paint for the purpose of increasing the thickness of the undercoat paint, coloring, improving anticorrosion, and the like. Specifically, coloring pigments such as titanium dioxide, iron oxide, and carbon black, extender pigments such as silica, calcium carbonate, and barium sulfate, zinc phosphate, aluminum phosphate, zinc molybdate, barium metaborate, hydro A typical example is a rust preventive pigment such as calumite.

  The undercoat paint used in the present invention is 30 to 90% by mass, preferably 35 to 70% by mass, preferably 5 to 70% by mass of a pigment, based on the solid content of the paint. It is preferably contained in an amount of 65% by mass, preferably 25-60% by mass, and 20-100% by mass (based on the mass of the pigment), preferably 30-80% by mass, of the pigment.

In the repair coating method of the present invention, the thick film type paint applied on the undercoat film after forming the undercoat film needs to be able to follow the expansion and contraction of the undercoat film, A thick film-type coating material that forms a coating film having an elongation of 2 to 200%, preferably 3 to 200%, more preferably 5 to 150% in terms of dry film thickness is 200 to 1000 μm, preferably 250 to 900 μm, more preferably. It is necessary to paint so that it may become 300-800 micrometers.

  When the elongation rate of the thick film-type coating film is smaller than 2%, such a coating film hardly follows the expansion and contraction of the undercoat coating film, and causes cracks and cracks later. Further, when the elongation rate of the undercoat coating film exceeds 200%, such a coating film has a low cross-linking density, increases the permeability of the solvent, causes blemishes, and further reduces the corrosion resistance. Moreover, when the dry film thickness of a thick film type coating film is thinner than 200 micrometers, such a coating film becomes inadequate in durability (anticorrosion property). Moreover, when the dry film thickness of a thick film type coating film exceeds 1000 micrometers, such a coating film becomes bad in drying property, workability | operativity, and adhesiveness.

  Examples of the coating film forming resin used in such a thick film type paint include epoxy resin, urethane resin, vinyl resin, polyester resin, fluororesin, and inorganic.

  The thick film-type paint used in the present invention includes the above-mentioned coating film-forming resin, solvent, and pigments such as coloring pigments, extender pigments, rust preventive pigments, fillers, curing agents, and curing accelerators. And various additives such as a wetting agent, a dispersing agent and a thickener. As additives such as pigments to be blended as necessary, the same additives as those described in connection with the undercoat paint can be preferably used.

  As a solvent blended in the thick film type paint used in the present invention, any solvent such as an ester solvent, a ketone solvent, an alcohol solvent, an ether solvent, or a strong solvent or a weak solvent commonly used for paints is used. Even things can be used.

  The thick film type paint used in the present invention contains 30 to 90% by mass, preferably 35 to 70% by mass of a binder (including a curing agent when a curing agent is used), preferably 35 to 70% by mass, based on the solid content of the coating. 5 to 65% by mass, preferably 25 to 60% by mass is preferable. Of course, a scale-like pigment can also be contained as a pigment.

Next, the repair coating method for the old coating film of the present invention will be described.
First, if there is a deteriorated part such as rusting, blistering, or cracking in the old paint film, or if there is a deteriorated part (dead film part) where the adhesion of the old paint film is extremely low, those deteriorated parts Is removed with kelen. When choking is generated on the surface, or when dirt is adhered to the surface of the old coating film, it is preferable to roughen the surface by a polishing process using a sandpaper or the like in advance. Apply the above-mentioned undercoat on the surface of the old coating film thus surface-treated by means of spray coating, roller coating, brush coating, etc. to a dry film thickness of 50 to 300 μm and let it air dry. To form an undercoat.

  Next, a thick film type paint is applied to the surface of the undercoat film by means of spray coating, roller coating, brush painting, etc., so that the dry film thickness is 200 to 1000 μm, and then naturally dried to form a thick film coating film. Form.

  In the repair coating method of the old coating film of the present invention, it is preferable that after the thick film coating film is formed, a finish paint is further coated thereon. The purpose of applying the finish paint is to impart weather resistance, water resistance, stain resistance, design properties, and the like to the repair coating film.

  The finish paint arbitrarily used in the present invention is preferably a paint such as urethane resin, vinyl resin, acrylic resin, polyester resin, fluororesin, and inorganic. In addition, any solvent such as ester solvents, ketone solvents, alcohol solvents, ether solvents, or other strong or weak solvents that are commonly used for paints can be used as the solvent solvent in the finish paint. It is. As the finish coating, an intermediate coating or top coating is applied to the surface of the thick film coating by means of spray coating, roller coating, brush coating or the like, and is naturally dried to form a finished coating.

Below, this invention is demonstrated based on an Example and a comparative example. In the examples and comparative examples, “parts” and “%” are based on mass unless otherwise specified.
Examples 1-6 and Comparative Examples 1-5
<Composition of undercoat paint and thick film type paint>
Table 1 shows the compositions (parts) of the undercoat paint and the thick film paint used in Examples and Comparative Examples.

  In Table 1, the flexible epoxy resin varnish A is FLEP-50 (epoxy equivalent: 330, solid content: 100%) manufactured by Toray Rethiocol Co., Ltd., and the flexible epoxy resin varnish B is manufactured by Toray Rethiocol Co., FLEP. -60 (epoxy equivalent 280, solid content 100%), epoxy resin varnish C is manufactured by Japan Epoxy Resin Co., Ltd., Epicoat 828 (epoxy equivalent 190, solid content 100%), and the polyamidoamine solution is Sanwa Chemical. Sanmide 308D-65 (active hydrogen equivalent 177, solid content 65%) manufactured by Kogyo Co., Ltd., and modified alicyclic polyamine compound is Sanmide 301D (active hydrogen equivalent 380, solid content 100) manufactured by Sanwa Chemical Industry Co., Ltd. %), And the elongation percentage of the coating film was measured by an autograph AG2000B (tensile strength tester) manufactured by Shimadzu Corporation. Is the growth rate.

<Preparation of test piece>
For Examples and Comparative Examples, an epoxy resin base coat ("Epoall # 40 base coat" manufactured by Dainippon Paint Co., Ltd.) and a chlorinated rubber intermediate coat (Dainippon) were applied to the inner and outer surfaces of a 1L round can polished with # 240 sandpaper. Paint Co., Ltd. “Rubber Tight # 100 Intermediate Coat”) and Chloride Rubber Top Coat (“Dai Nippon Paint Co., Ltd.“ Rubber Tight # 100 Top Coat ”) in a constant temperature room at 23 ° C. and 50% relative humidity for 24 hours After repeated coating at intervals, drying in the same room for 1 week, forced drying at 50 ° C. for 5 days, [−20 ° C. × 2 hours] → [50 ° C. × 2 hours] (transition time: 1 hour each, 4 cycles / day) were subjected to 100 cycles of the cooling / heating cycle test and used as test pieces of the old coating film.

  After polishing the test piece of the old coating film with # 240 sandpaper, each of the above primer coatings (A to E) was applied with a brush so that the dry film thickness was a predetermined thickness, 23 ° C., 50% relative humidity. It was naturally dried for 2 days in a constant temperature room. Next, each thick film type paint (X) was applied with a brush so that the dry film thickness was a predetermined thickness, and dried in the same room for 2 days. This was further cured for one week in a thermostatic chamber at room temperature of 23 ° C. and a relative humidity of 50% to obtain a test piece.

  Table 2 shows the types of undercoat paint used for each test piece, the elongation rate and dry film thickness of the undercoat film, and the type of thick film paint, the elongation rate and dry film thickness of the thick film paint film. It was.

About the test piece of Examples 1-6 and Comparative Examples 1-5, the following characteristic was tested with the following method, and the following evaluation criteria evaluated. The evaluation results are also shown in Table 2.
<Cooling cycle test>
The obtained test piece was subjected to a cooling / heating cycle test of [−20 ° C. × 2 hours] → [50 ° C. × 2 hours] (transition time: 1 hour, 4 cycles / day), and applied to the coating film of the test piece. The number of cycles until cracks and cracks occurred was measured.

<Moisture resistance test>
Evaluation was performed according to the following evaluation criteria in accordance with “Evaluation of coating film deterioration” and “Bulding density” “Grading by numerical value of blister density” of JIS K 5600-8-2.
◎: Bulge density numerical grade 0
◯: Grades based on numerical values of swelling density 1-2
△: Bulge density numerical grade 3
X: Grade 4-5 based on numerical value of swelling density

<Adhesive strength test after moisture resistance test and cohesive fracture peel position in adhesive strength test>
Based on the classification of the test results in Table 1 of “Mechanical properties of coating film” and “Adhesiveness (cross-cut method)” of JIS K 5600-5-6, evaluation was performed according to the following evaluation criteria.
○: Classification of test results 0-1
Δ: Classification of test results 2-3
X: Classification of test results 4-5

  As is clear from the data in Table 2, the repair coating method of the present invention of Examples 1 to 6 can provide a repair coating film excellent in moisture resistance and adhesive force and excellent in thermal cycle performance. On the other hand, in Comparative Examples 1 and 2 using a solvent that does not dissolve the old coating film as the solvent for the undercoat paint, the moisture resistance and the adhesive strength were insufficient. In the case of Comparative Example 3 where the film thickness of the thick film coating film is thinner than the thickness defined in the present invention, the moisture resistance and the adhesive strength are insufficient, and the film thickness of the thick film coating film is defined in the present invention. In the case of the comparative example 4 thicker than the thickness, the cooling cycle performance was insufficient. Moreover, in the case of the comparative example 5 in which the film thickness of an undercoat coating film is thinner than the thickness prescribed | regulated by this invention, the thermal cycle property was inadequate.

Claims (5)

Epoxy resin system that contains a solvent that dissolves or swells the old paint film on the surface of the old paint film using a chlorinated rubber resin or a vinyl resin as a binder, and forms a paint film with an elongation of 5 to 150%. Alternatively, an epoxy resin system in which a urethane resin-based undercoating material is applied so as to have a dry film thickness of 50 to 300 μm, the old coating film is dissolved or swollen, and then a coating film having an elongation of 2 to 200% is formed. A method for repairing an old paint film, characterized in that a thick film type paint of urethane resin type, vinyl resin type or polyester resin type is applied to a dry film thickness of 200 to 1000 μm. Epoxy resin system containing a solvent for dissolving or swelling the old coating film on the surface of the old coating film using a chlorinated rubber resin or a vinyl resin as a binder, and forming a coating film having an elongation of 20 to 100%. Alternatively, an epoxy resin system in which a urethane resin-based undercoating material is applied so as to have a dry film thickness of 70 to 280 μm, the old coating film is dissolved or swollen, and then a coating film having an elongation of 3 to 200% is formed. A method for repairing an old paint film, characterized in that a urethane resin-based, vinyl resin-based or polyester resin-based thick film-type paint is applied so as to have a dry film thickness of 280 to 900 μm.   Furthermore, the repair coating method of the old coating film of Claim 1 or 2 which coats a finishing coating on the coating film of the said thick film type coating material.   The repair coating method of the old paint film according to any one of claims 1 to 3, wherein the undercoat paint is an epoxy resin-based or urethane resin-based paint and contains a scaly pigment.   The repair coating method of the old coating film according to claim 4, wherein the scaly pigment is scaly iron oxide (MIO), scaly talc, or glass flakes.