JP4949757B2 - Undercoat material composition and coating method using the same - Google Patents

Description

  The present invention relates to a primer composition that can be preferably applied to a metal surface having rust, and a coating method using the same.

Rust generated in metal members used in buildings, civil engineering structures, etc. not only impairs aesthetics, but may cause a reduction in strength of the metal members. For this reason, some rust prevention process is needed with respect to the member which rusted.
As such a rust prevention treatment, a method is generally employed in which rust is removed to some extent with keren and the like, and then a rust preventive primer is applied, and a top coat is further applied.
Patent Document 1 (Japanese Patent Application Laid-Open No. 2000-140746) discloses a coating method for a metal surface having rust. As a rust preventive primer, an epoxy resin is used as a base, and a phosphoric acid compound and an organic chelating agent are used. It contains a rust-proof primer.

JP 2000-140746 A

However, when a primer such as that described in the above publication is applied to a metal surface on which rust has remarkably generated, the paint is sucked into the rust layer, so that the sealing property is required unless applied many times. There is a problem that it cannot be secured. If the sealing property is insufficient, it is disadvantageous in terms of rust prevention, and the finish and adhesion of the top coating material may be reduced.
Many of such rust-preventing primer materials are strong solvent-type paints using aromatic hydrocarbon solvents such as toluene and xylene as a medium. A strong solvent-type paint is not very preferable in view of toxicity to the human body, work safety, and influence on air pollution. Recently, there has been an increasing trend to suppress the use of such aromatic hydrocarbon solvents, and there has been a demand for a shift to weak solvent-type paints mainly composed of aliphatic hydrocarbon solvents.

  The present invention has been made in view of such points, and has a high sealing property against a rust surface, a weak solvent-type primer composition capable of exhibiting excellent rust prevention properties, top coat compatibility, and the like, and An object of the present invention is to provide a coating method using the primer composition.

  In order to solve such problems, the present inventors have conducted extensive research, and as a result, urethane-modified soluble epoxy resins and amine compounds obtained by reacting specific polyisocyanates with hydroxyl group-containing soluble epoxy resins. And an undercoat material composition containing an antirust pigment as an essential component, and the present invention has been completed.

That is, the present invention has the following characteristics.
1. A polyisocyanate (p) having an allophanate structure obtained by a reaction between a monoalcohol having 1 to 12 carbon atoms and an isocyanate compound, and a hydroxyl group-containing soluble epoxy resin (q), obtained on a metal surface having rust . A urethane-modified soluble epoxy resin (A), an amine compound (B), which is obtained by reacting such that the NCO / OH equivalent ratio is 0.02 to 0.5 and the number average molecular weight is 500 to 10,000, and A coating method comprising applying an undercoat after applying an undercoat composition containing an anticorrosive pigment (C) .

  The undercoat material composition of the present invention is excellent in film forming performance, and can form an undercoat film excellent in sealing properties with a relatively small coating amount even on a rust layer having a large suction. It is also advantageous in terms of finish and adhesion after painting.

  Hereinafter, the present invention will be described in detail based on the embodiments.

  The undercoat material composition of the present invention comprises a urethane-modified soluble epoxy resin (A), an amine compound (B), and a rust preventive pigment (C) as essential components. Among these, urethane-modified soluble epoxy resin (A) (hereinafter referred to as “component (A)”) is a polyisocyanate having an allophanate structure obtained by reaction of a monoalcohol having 1 to 12 carbon atoms with an isocyanate compound ( p) (hereinafter referred to as “component (p)”) and a hydroxyl group-containing soluble epoxy resin (q) (hereinafter referred to as “component (q)”).

  In the present invention, by using such a component (A) as an essential component, an undercoat material composition having excellent performance in sealing properties, rust prevention properties, top coat compatibility and the like can be obtained. The reason for such an effect is not clear, but the (p) component having a specific chemical structure is appropriately polymerized by the (q) component, so that it can be dissolved in an aliphatic hydrocarbon solvent. It is presumed that the film forming property can be improved while ensuring the property, and as a result, the sealing property can be expressed with a relatively small coating amount, and the rust prevention property is improved. In addition, it is presumed that adhesion and the like are increased by adding a structure via a urethane bond by the reaction of the component (p) and the component (q).

  (P) A component is obtained by reaction of a C1-C12 monoalcohol and an isocyanate compound. Of these, the monoalcohol can be used without particular limitation as long as it has 1 to 12 carbon atoms. Specifically, methanol, ethanol, n-propanol, isopropyl alcohol, n-butyl alcohol, n-amyl alcohol, n-hexyl alcohol, 2-ethyl-1-hexanol, n-heptanol, isoheptyl alcohol, n-octanol , 2-octanol, n-nonanol, n-decanol, n-undecyl alcohol, n-dodecyl alcohol and the like.

  As the isocyanate compound in the component (p), diisocyanate is usually used. Among these, aliphatic diisocyanate and alicyclic diisocyanate are preferable. Specifically, for example, ethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, undecamethylene diisocyanate, 1,3-diisocyanatocyclobutane, 1,3-diisocyanatocyclohexane, 1,3-diisocyanatomethylcyclohexane And isophorone diisocyanate. Among these isocyanate compounds, one or more selected from hexamethylene diisocyanate, 1,3-diisocyanatomethylcyclohexane, and isophorone diisocyanate are particularly preferable.

  The component (p) can be obtained by a known method. Specifically, for example, a method in which a part or all of the hydroxyl group of the monoalcohol is reacted with a part of the isocyanate group in the isocyanate compound to form an allophanate by the presence of an allophanate catalyst. In addition, according to a method in which a part or all of the hydroxyl group of the monoalcohol is reacted with a part of the isocyanate group in the isocyanate compound to urethanize and then isocyanurated in the presence of a catalyst, Allophanatization can be performed simultaneously. As the component (p) in the present invention, those having an isocyanurate structure in addition to the allophanate structure are suitable.

Component (q) is a compound having both an epoxy group and a hydroxyl group. For example, a compound in which a hydroxyl group is generated by ring opening of an epoxy group of an epoxy resin, or a reaction product of an epoxy resin and a hydroxyl group-containing compound is used. it can. Specifically, a reaction product of an epoxy resin and an amine compound, a reaction product of an epoxy resin and a fatty acid, a reaction product of an epoxy resin and an acrylic resin, a reaction product of a phenol compound and an epoxy resin, a phenol compound and a dibasic acid And a reaction product of epoxy resin and the like. Examples of the epoxy resin include bisphenol type epoxy resins such as bisphenol A type epoxy resin and bisphenol F type epoxy resin, as well as novolac type epoxy resins and phenol resin glycidyl ether compounds. When a reaction product of a phenol compound, a dibasic acid, and an epoxy resin is used as the component (q), it is particularly advantageous in terms of improving flexibility.
The hydroxyl value of the component (q) is usually 10 to 300 KOHmg / g, preferably 50 to 200 KOHmg / g. The epoxy equivalent of the component (q) is usually about 100 to 5000 g / eq.

  (A) component is obtained by making the above-mentioned (p) component and (q) component react. At this time, the mixing ratio of the (p) component and the (q) component is such that the NCO / OH equivalent ratio is 0.02 to 0.5, preferably about the NCO group of the (p) component and the OH group of the (q) component. Prepare to be 0.05-0.3. If it is such a ratio, while ensuring the solubility to an aliphatic hydrocarbon-type solvent, a sealing performance, rust prevention property, etc. can be improved. When the NCO / OH equivalent ratio is too small, the sealing property becomes insufficient, which adversely affects rust prevention, finish after top coating, adhesion, and the like. On the other hand, when it is too large, the solubility in an aliphatic hydrocarbon solvent is lowered, and it is difficult to design a weak solvent type paint. In addition, storage stability may be reduced.

  (A) The number average molecular weight of a component is 500-10000, Preferably it is 800-8000, More preferably, it is 1000-5000. In the present invention, by using the component (A) having such a molecular weight, advantageous effects can be obtained in sealing properties, adhesion properties, impregnation reinforcing properties, solubility properties, finish properties, and the like. When the number average molecular weight is too smaller than the above value, the sealing property becomes insufficient, which adversely affects the finish properties, adhesion, etc. after top coating. When the number average molecular weight is too large, it is difficult to obtain sufficient performance in impregnation reinforcement and the like, and the solubility in an aliphatic hydrocarbon solvent is also lowered. In addition, the number average molecular weight in this invention is a value measured by gel permeation chromatography.

  The amine compound (B) (hereinafter referred to as “component (B)”) in the composition of the present invention serves as a curing agent for the component (A). As the component (B), commercially available or known materials can be used. For example, aliphatic polyamines, alicyclic polyamines, aromatic polyamines, polyamides, polyamidoamines, heterocyclic amines, or modified products thereof can be used.

  As the rust preventive pigment (C) in the composition of the present invention, commercially available or known materials can be used. Specifically, for example, phosphate-based rust preventive pigments such as zinc phosphate, iron phosphate, and aluminum phosphate, and phosphite-based rust preventive pigments such as zinc phosphite, iron phosphite, and aluminum phosphite. , Anti-molybdates such as calcium molybdate, aluminum molybdate, barium molybdate, vanadium anti-rust pigments such as vanadium oxide, strontium chromate, zinc chromate, calcium chromate, potassium chromate, barium chromate anti-chromate Examples include rust pigments, water-dispersed silica, fine silica such as fumed silica, and the like, and one or more of these can be used.

  The undercoat material composition of the present invention uses a non-aqueous solvent as a solvent and contains an aliphatic hydrocarbon solvent as a main component as the non-aqueous solvent. Such an aliphatic hydrocarbon solvent has characteristics that it is less toxic than an aromatic hydrocarbon solvent, has high safety in operation, and has little influence on air pollution. Furthermore, since the aliphatic hydrocarbon solvent has an appropriate evaporation rate, it is advantageous for impregnation and reinforcement of the primer composition of the present invention. The ratio of the aliphatic hydrocarbon solvent may be 50% by weight or more in the total solvent.

  Examples of the aliphatic hydrocarbon solvent include n-hexane, n-pentane, n-octane, n-nonane, n-decane, n-undecane, n-dodecane, terpin oil, mineral spirit, and the like. . In addition to such aliphatic hydrocarbon solvents, it is possible to use non-aqueous solvents that are usually used in paints as necessary. In the present invention, however, it does not contain toluene or xylene, and has a flash point of 21. Those that fall under the Fire Service Act Type 4 and Type 2 Petroleum above ℃ are preferred for safety and health.

  In the composition of the present invention, in addition to the above-described components, if necessary, coloring pigment, extender pigment, plasticizer, preservative, antifungal agent, antialgae, antifoaming agent, leveling agent, pigment dispersant, antisettling agent, dripping An inhibitor, a matting agent, a catalyst, a curing accelerator and the like can be mixed within a range in which the effect of the present invention is not inhibited.

  The solid content of the composition of the present invention is usually 5 to 60% by weight, preferably 10 to 50% by weight. If the solid content is set within such a range, the balance between the impregnation reinforcing property and the sealing property is improved, and the coating workability can be further improved.

The composition of the present invention can be used for coating a rust surface. The objects to be painted are mainly rust surfaces in buildings, civil engineering structures and the like. Specifically, for example, building steel frames, iron doors, handrails, fences, gates, mounts, lightweight steel frames, guard rails, bridges, steel towers, and the like can be given.
In addition, the rust surface in this invention is a metal surface of the state in which rust has generate | occur | produced in part thru | or the whole. Even after the treatment with keren or the like, any remaining rust is included in the rust surface of the present invention.
For example, cold rolled steel, aluminum steel, stainless steel, copper steel, hot dip galvanized steel, hot dip galvanized aluminum alloy steel, electrogalvanized steel, electroalloy plated steel, alloy plating Examples thereof include metal substrates such as steel, copper-plated steel, and tin-plated steel, or metal substrates obtained by subjecting these metal substrates to a surface treatment such as phosphate or chromate. These metal substrates may have various coatings such as alkyd resin paint, chlorinated rubber paint, acrylic resin paint, urethane resin paint, acrylic silicon resin paint, and fluororesin paint. Good.

As a method for applying the undercoat material, various methods such as brush coating, roller coating, and spray coating can be used. The coating amount at the time of coating is usually 50 to 500 g / m ² , preferably 80 to 300 g / m ² .
The number of times of applying the undercoat material may be appropriately set depending on the surface state of the surface to be coated, but is usually 1 to 2 times. With the undercoat material of the present invention, a coating film having excellent sealing properties can be formed even with such a small number of coatings.
The drying time of the primer is usually 3 hours or longer.

In the present invention, after the undercoat material is dried, various topcoat materials can be applied.
The top coating material is not particularly limited as long as it has a cosmetic property, and various materials can be used. Specific examples include alkyd resin paints, acrylic resin paints, urethane resin paints, acrylic silicon resin paints, fluororesin paints, and the like. These topcoat materials are preferably weak solvent paints or water-based paints.
The top coating material may be finished with one layer, or two or more layers may be laminated and finished.

  Examples and Comparative Examples are shown below to clarify the features of the present invention.

Example 1
As a polyisocyanate, a polyisocyanate containing an isocyanurate structure and an allophanate structure (reaction product of hexamethylene diisocyanate and n-butyl alcohol, non-volatile content: 100% by weight, NCO content: 21% by weight) is prepared. Soluble epoxy resin (reaction product of phenol novolac resin, bisphenol A type epoxy resin and dimer acid, solid content: 60 wt%, hydroxyl value: 100 KOH mg / g, epoxy equivalent: 1200 g / eq, number average molecular weight: 2010, (Solvent: mineral spirit). At this time, the mixing ratio of the polyisocyanate and the hydroxyl group-containing soluble epoxy resin was such that the NCO / OH equivalent ratio was 0.15. The number average molecular weight of the urethane-modified soluble epoxy resin obtained by the above method was 2500.

100 parts by weight of the urethane-modified soluble epoxy resin is mixed with 8 parts by weight of aluminum phosphate, 30 parts by weight of titanium dioxide, 115 parts by weight of mineral spirits, and 0.1 part by weight of a silicone-based antifoaming agent, and then an amine compound. (Composition: polyamidoamine, amine value: 100 KOH mg / g, solid content: 40% by weight) 70 parts by weight were mixed to obtain an undercoat material.
The following tests were performed on the obtained primer.

(Test method)
(1) Sealing properties A coating amount of 150 g is applied to a steel plate that has been rusted by exposing the steel plate SPCC-SB specified in JIS G3141 “Cold-rolled steel plate and strip” outdoors for 3 months. Brush applied at / m ² . After curing for 7 days in a standard state (temperature 23 ° C., humidity 50%), 1 ml of water was spotted on the surface of the test body, and the portion was covered with a watch glass, and the state until 24 hours after standing was confirmed. The evaluation criteria were “◯” when the spot did not decrease, “Δ” when the spot decreased, and “X” when the spot disappeared.

(2) Adhesion test Amount of primer applied to steel plate that has been rusted by exposing steel plate SPCC-SB specified in JIS G3141 “Cold rolled steel plate and steel strip” outdoors for 3 months After brushing at 150 g / m ² and curing for 7 days in a standard state (temperature 23 ° C., humidity 50%), adhesion to the rust layer was evaluated by a cross-cut tape method (4 × 4 mm · 25 mass). The evaluation criteria were “◯” when the rupture in the rust layer was less than 2/25, “△” when the rupture in the rust layer was 2/25 or more and less than 5/25, and 5 in the rust layer. What was / 25 or more was taken as "x".

(3) Topcoat compatibility test Coat the primer to the steel plate that has been rusted by exposing the steel plate SPCC-SB specified in JIS G3141 “Cold rolled steel plate and steel strip” outdoors for 3 months. The brush was applied in an amount of 150 g / m ² . After curing for 3 hours in the standard state, a top coating material (trade name “Clean Mild Urethane”; manufactured by SK Kaken Co., Ltd.) was applied with a brush at a coating amount of 200 g / m ² .
After curing for 7 days in the standard state, the top coat compatibility was evaluated by measuring the specular gloss (measurement angle: 60 degrees) of the coating film surface. In the evaluation, a mirror glossiness of 70 or more was “◯”, a mirror glossiness of 60 or more and less than 70 was “Δ”, and a mirror glossiness of less than 60 was “x”.

  The test results are shown in Table 1. In Example 1, good results could be obtained in any test.

(Example 2)
Undercoating material in the same manner as in Example 1 except that the isocyanurate structure / allophanate structure combined polyisocyanate and the hydroxyl group-containing soluble epoxy resin were mixed at an NCO / OH equivalent ratio of 0.10. Manufactured. The number average molecular weight of the urethane-modified soluble epoxy resin in Example 2 was 2380. The obtained primer was subjected to the same test as in the example. The test results are shown in Table 1.

(Comparative Example 1)
In place of the urethane-modified soluble epoxy resin, an unmodified hydroxyl group-containing soluble epoxy resin was used, and a primer was produced in the same manner as in Example 1. The obtained primer was subjected to the same test as in the example. The test results are shown in Table 1.

(Comparative Example 2)
Undercoating material in the same manner as in Example 1 except that the isocyanurate structure / allophanate structure combined polyisocyanate and the hydroxyl group-containing soluble epoxy resin were mixed at an NCO / OH equivalent ratio of 0.01. Manufactured. The number average molecular weight of the urethane-modified soluble epoxy resin in Comparative Example 1 was 2020. The obtained primer was subjected to the same test as in the example. The test results are shown in Table 1.

(Comparative Example 3)
The mixing ratio of the isocyanurate structure / allophanate structure combined polyisocyanate and the hydroxyl group-containing soluble epoxy resin was changed to the same as in the examples except that the NCO / OH equivalent ratio was 0.55. Tried to manufacture. However, in Comparative Example 3, aggregates were generated in the reaction product of the polyisocyanate and the hydroxyl group-containing soluble epoxy resin.

Claims (1)

A polyisocyanate (p) having an allophanate structure obtained by a reaction between a monoalcohol having 1 to 12 carbon atoms and an isocyanate compound, and a hydroxyl group-containing soluble epoxy resin (q), obtained on a metal surface having rust . A urethane-modified soluble epoxy resin (A), an amine compound (B), which is obtained by reacting such that the NCO / OH equivalent ratio is 0.02 to 0.5 and the number average molecular weight is 500 to 10,000, and A coating method comprising applying an undercoat after applying an undercoat composition containing an anticorrosive pigment (C) .