JP2013163855A - Polyaniline-containing rust preventing composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyaniline-containing composition showing a high rust preventive effect.SOLUTION: A rust preventing compositional medicine contains a phosphate-doped polyaniline or polyaniline derivative and a hydroxypropyl cellulose.

Description

  The present invention relates to a polyaniline-containing rust preventive composition and a rust preventive paint containing the composition.

  Conventionally, chromate treatment, plating treatment, and the like have been used as metal surface treatment methods for the purpose of rust prevention. In recent years, it has been discovered that by coating a metal surface with a conductive polymer compound typified by polyaniline, which has a low environmental impact and is relatively inexpensive, corrosion of the metal is suppressed, and it is possible to protect coated steel sheets and the like. Application as a rust pigment is expected.

  As a rust prevention method using polyaniline, Patent Document 1 describes a method in which powdered polyaniline is dispersed in a polymer compound and the obtained paste-like mixture is applied to a metal surface. According to this method, the powdered polyaniline is dispersed non-uniformly in the solution, and a uniform polyaniline mixture cannot be prepared, so that a sufficient rust prevention effect cannot be obtained.

  Patent Document 2 describes a method of dispersing polyaniline in water by applying ultrasonic waves to a mixture containing a conductive polymer such as polyaniline and a water-soluble polymer partially soluble in polyaniline. .

  Patent Document 3 describes a method in which polyaniline is solubilized in water by introducing a sulfone group into polyaniline.

JP-A 63-199884 Japanese Patent Laid-Open No. 61-16931 JP 2001-354765 A

  As described above, various attempts have been made to solubilize polyaniline. However, the composition containing solubilized polyaniline has a problem that rust is generated when it is exposed to a corrosive environment for a long time. It has become.

  Then, an object of this invention is to provide the water-soluble polyaniline containing composition which hold | maintains a high rust prevention effect, especially a high rust prevention effect over a long period of time.

  As a result of intensive research to solve the above-mentioned problems, the present inventors have found that a rust-proof composition comprising polyaniline or polyaniline derivative doped with phosphoric acid and hydroxypropyl cellulose has a high rust-preventive effect, particularly for a long period of time. The present inventors have found that a high rust prevention effect is exhibited over a long period of time, and have completed the present invention.

That is, the present invention includes the following inventions.
[1] A rust preventive composition comprising polyaniline or polyaniline derivative doped with phosphoric acid and hydroxypropylcellulose.
[2] The composition according to [1], wherein polyaniline and hydroxypropylcellulose are present in a weight ratio of 1: 1.5 to 1: 2.5.
[3] A rust-proof paint containing the composition according to [1] or [2].
[4] The rust preventive paint according to [3], further containing polyurethane.

  According to this invention, the water-soluble polyaniline containing composition which shows the high rust prevention effect which is not obtained conventionally, especially a high rust prevention effect over a long period of time is provided.

It is the figure which showed the time-dependent change of the corrosion potential regarding the coating material containing 2 weight% of compositions containing polyaniline and various water-soluble polymers. It is the figure which showed the time-dependent change of the corrosion potential regarding the coating material containing 4 weight% of compositions containing polyaniline and various water-soluble polymers. It is the figure which showed the time-dependent change of the corrosion potential regarding the coating material containing 2 weight% of the composition containing polypyrrole or polyethylenedioxythiophene and various water-soluble polymers.

  Hereinafter, the present invention will be described in detail.

  The polyaniline or polyaniline derivative of the present invention is not particularly limited, but a polymer of a compound represented by the following formula (I) is preferably used.

In said formula (I), n shows the integer of 0-5. R ¹ may be the same or different from each other, and is not particularly limited. However, hydrogen, C _1-6 alkyl group, C _2-6 alkenyl group, C _1-6 alkoxy group, C _1-6 acyl group, C _1-6 alkylthio group, aryloxy group, C _1-6 alkylsulfinyl group, aryl group, C _1-6 alkyl-aryl group, aryl-C _1-6 alkyl group, C _1-6 alkoxy-C _1-6 alkyl _{group, C 1-6} alkylsulfonyl group, a carboxyl group, a halogen group, a cyano _{group, C 1-6} haloalkyl _{group, C 1-6} nitroalkyl _group, selected from among _{C 1-6} cyanoalkyl group.

  Specifically, for example, aniline, o-toluidine, m-toluidine, o-ethylaniline, m-ethylaniline, m-butylaniline, o-ethoxyaniline, m-hexylaniline, m-octylaniline, 2,3 -Dimethylaniline, 2,5-dimethylaniline, 2,5-dimethoxyaniline, o-cyanoaniline, 2,5-dichloroaniline, 5-chloro-2-methoxyaniline, 2-bromoaniline, 3-phenoxyaniline, etc. Can be mentioned.

  The polyaniline or polyaniline derivative of the present invention may be a polymer using one of these monomers or a copolymer using two or more. In addition to the above monomers, other monomers may be used as long as the object of the present invention is not impaired. However, the polymerized polyaniline has four different structures depending on the redox state: leucoemeraldine (reduced state), emeraldine base (semi-oxidized state), pernigranin (oxidized state) and emeraldine salt (emeraldine base as protons). However, it preferably has an emeraldine salt structure (see, for example, Yamagata University Bulletin (Engineering) Vol. 29, No. 2, page 99, February 2007).

  The hydroxypropyl cellulose used in the present invention is not particularly limited, but preferably has a viscosity of 6 to 10 mPa · s (20 ° C., B-type viscometer).

  The polyurethane of the present invention is not particularly limited as long as it is usually used for rust prevention, but water-soluble polyurethane is preferably used. The water-soluble polyurethane is a water-soluble resin obtained by copolymerizing a monomer with a urethane bond formed by condensation of an isocyanate group and a hydroxyl group, and can be produced by a known method.

  In the rust preventive composition of the present invention, the polyaniline and hydroxypropyl cellulose are preferably present in a weight ratio of 1: 1.5 to 1: 2.5.

  In the anticorrosive paint of the present invention, the composition containing polyaniline and hydroxypropylcellulose is usually contained in an amount of 1 to 5% by weight, preferably 2 to 4% by weight. Further, the polyurethane can be contained in an amount of 99 to 90% by weight.

  The manufacturing method of the polyaniline or its derivative of this invention is not specifically limited, A well-known manufacturing method can be used. Usually, it is obtained as a black-green powder by dropping an oxidizing agent solution such as ammonium persulfate into an aqueous solution of aniline or a derivative thereof and hydroxypropylcellulose in the presence of a protonic acid. For polymerization, usual polymerization conditions are applied. For example, the reaction temperature is between −10 ° C. and 40 ° C., the reaction time is within the range of 30 minutes to 48 hours, and the reaction mixture is stirred under normal pressure.

  Although it does not specifically limit as an oxidizing agent, Ammonium persulfate, hydrogen peroxide, ferric chloride, etc. are mentioned, Preferably ammonium persulfate is used.

  The dopant for which the present invention is used is an acceptor-type dopant that is generally used, and examples thereof include phosphoric acid or a salt thereof.

Phosphoric acid is most preferably orthophosphoric acid (H ₃ PO ₄ ). For example, in addition to orthophosphoric acid, phosphorous acid, polyphosphoric acid, and salts thereof such as zinc, iron, cobalt, calcium, and aluminum are sometimes used. Can be used.

  As for the dope method, as described in the above-mentioned production method of polyaniline, a method in which the polyaniline is previously dissolved or dispersed in the paint in a form doped with polyaniline, or the polyaniline is dissolved or dispersed in the paint in an undoped state. An optimal method such as a method of dope after coating and drying can be arbitrarily selected. In the present invention, a method of dissolving or dispersing in a paint in a pre-doped polyaniline form is preferable.

  The dopant is added in a reaction aqueous solution containing a monomer, preferably at 0.8 to 1.2M. Excess dopant is undesirable because it can induce corrosion.

  The anticorrosive paint in the present invention includes a curing agent, a leveling agent, a dispersant, a pigment, a catalyst, a plasticizer, an auxiliary agent, a thickener, an antioxidant, a light stabilizer and the like that are widely used in preparing the paint. Additives may be included.

  The method for forming a coating film on the surface of the substrate is not particularly limited, and the substrate is immersed in a paint containing polyaniline, applied by a known method such as brush coating, roller coating, spray coating, or the like, and dried. Thus, a coating film can be formed.

  Although the said base material is a base material from which at least one part of a surface consists of metal, it is not specifically limited, Steel, iron, aluminum, etc. are mentioned. Specifically, it can apply | coat to surfaces, such as a motor vehicle, an electrical appliance outer plate, a bicycle, a roof, a park playground equipment, metal fittings.

  Although the thickness of a coating film is not specifically limited, 0.01-100 micrometers is preferable from the point which is excellent in rust prevention property.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the scope of the present invention is not limited to these examples.

[Example 1] Synthesis of water-soluble polyaniline, preparation of coating film and evaluation of rust prevention After dissolving 98.0 g (1 mol) of phosphoric acid and 10 g of aniline in 900 g of distilled water, 20 g of hydroxypropylcellulose ( HPC) (manufactured by Tokyo Chemical Industry Co., Ltd.) was added to an aniline aqueous solution while adding an oxidizing aqueous solution of phosphoric acid in which 64.4 g of ammonium persulfate (APS) was dissolved in 102 g of distilled water as an oxidizing agent. For 24 hours. After the reaction, when the polymerization solution was heated to 50 ° C. or higher, a layer containing polyaniline and hydroxypropylcellulose was separated. Except for the supernatant layer, the layer containing polyaniline was recovered by decantation. This operation was repeated three times for purification.

  Similarly, 20-30 cps methylcellulose (MC) (manufactured by Tokyo Chemical Industry Co., Ltd.), polyvinyl alcohol (PVA) having a weight average molecular weight of 31,000-50,000 (manufactured by Wako Pure Chemical Industries, Ltd.) or 35, Water-soluble polyaniline was synthesized using 20 g of polyvinylpyrrolidone (PVP) (manufactured by Wako Pure Chemical Industries, Ltd.) having a weight average molecular weight of 000.

  Next, water-soluble polyurethane HUX-320 (ADEKA) was added to and mixed with the various water-soluble polyanilines obtained so that the weight ratio of water-soluble polyaniline and polyurethane paint was 2:98 or 4:96. A paint was prepared. The prepared coating was cured at 150 ° C. for 1 hour so that the coating thickness was 20 μm, and a coating was formed on the iron surface.

  The coated iron substrate was immersed in a 3% NaCl solution, and the corrosion potential and the corrosion current were evaluated by a Tafel plot based on polarization measurement (Tables 1-2 and FIGS. 1-2). During the measurement, when the occurrence of rust was confirmed by appearance observation, the subsequent measurement was not continued.

  From Tables 1-2 and FIGS. 1-2, in Pani-HPC / HUX320, it turns out that a corrosion potential falls in the initial stage to about two weeks after a test start. This shift is attributed to the progress of corrosion and the elution of iron ions due to the influence of oxygen, water and chlorine ions. The corrosion potential gradually increased about 2 weeks after the start of the test, and the corrosion potential was maintained 90 days after the start of the test. On the other hand, in the case of using other water-soluble polymers such as methylcellulose, the corrosion potential decreased after the start of the test and increased after a certain period of time, but the corrosion did not occur even after 90 days from the start of the test. None of the potentials were maintained. From these results, it was found that a coating containing polyaniline and hydroxypropylcellulose has a higher protective effect against iron corrosion by forming a stable oxidation protective film over a relatively long period of time.

[Comparative Example 1] Rust prevention evaluation for a composition containing other conductive polymer and various water-soluble polymers As a conductive polymer different from polyaniline, polypyrrole (PPy) or polydiethyloxythiophene (PEDOT) , A polymer containing hydroxypropyl cellulose (HPC) or polyvinyl alcohol (PVA) was synthesized under the conditions shown in Table 3 below in the same manner as in Example 1 and mixed with water-soluble polyurethane HUX-320, respectively. Prepared. The prepared paint was applied to an iron substrate, and the corrosion potential and the corrosion current were evaluated by Tafel plot in the same manner as in Example 1 (Table 4, FIG. 3).

  From Table 4 and FIG. 3, in the case of using polypyrrole or polyethylenedioxythiophene, as in the case of using polyaniline and hydroxypropyl cellulose, rust does not occur over a relatively long period, and the increased corrosion potential is obtained. It was never maintained.

Claims (4)

  A rust preventive composition comprising polyaniline or polyaniline derivative doped with phosphoric acid and hydroxypropylcellulose.   The composition of claim 1, wherein the polyaniline and hydroxypropyl cellulose are present in a weight ratio of 1: 1.5 to 1: 2.5.   A rust preventive paint containing the composition according to claim 1.   Furthermore, the antirust paint of Claim 3 containing a polyurethane.

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