JP4871556B2 - Water-based paint - Google Patents

Description

  The present invention relates to a water-based paint for facilitating removal of graffiti stains, etc. on public and private building outer walls, inner walls, bridge piers such as railway viaducts, bridge girders, underground cross-wall walls, automobile soundproof walls, etc. .

In recent years, graffiti has been made with spray cans regardless of public buildings such as railway piers, viaducts, bridge girders, outer walls of expressways, and walls of underground crossing passages. Traces and develops into social problems.
There have been several methods for repairing graffiti damage. One way is to erase the graffiti. There are two ways to do this: 1) repaint 2) drop the paint 1) Repainting the graffiti on the graffiti is very costly It will not return to the state. To remove the paint of 2), it takes time and effort because the paint cannot be removed easily with organic solvents. For this reason, there are two ways to drop paint. One is a means of dropping, which uses a special machine, uses a special cleaning agent, is expensive, or contains a volatile solvent, which is harmful to the environment. Or Another means to remove is that the graffiti can be easily dropped by coating or processing the graffiti-preventing paint on the base beforehand, but fluororesin-based and silicon-based ones can be painted on it again , There are problems such as repelling and inability to draw cleanly, and paints coming off (see Non-Patent Document 1).
For this reason, there is a need for graffiti-removing water-based paints that do not contain organic solvents in consideration of the earth and work environment, are excellent in completely water-based graffiti removal, and can be repainted by peeling off the paint film even after coating. It has been.

  Patent Document 1 describes a paste-like polishing agent in which a wax is dispersed in water in the presence of a surfactant obtained by addition polymerization of ethylene oxide to a long-chain aliphatic primary alcohol. Because of the use of organic solvents, there were problems with safety and health.

Current status and future prospects for 2003 edition of functional paints and coatings (Fuji Chimera Research Institute, Ltd.) JP-A-9-310046

  It is possible to wash off dirt and graffiti with water without using an organic solvent like conventional stain removers and graffiti-preventing paints. To provide a water-based paint that can be repainted.

In the present invention, paraffin wax is dispersed in water in the presence of a surfactant having an HLB value of 7 to 13 obtained by addition polymerization of ethylene oxide to a long-chain aliphatic primary alcohol having 25 to 61 carbon atoms in the alkyl chain. It relates to a water-based paint.

  The present invention also relates to the water-based paint in which the wax has a melting point of 52 to 69 ° C.

  Moreover, this invention relates to the said water-based coating material whose alkyl group of surfactant is C30-55.

  The present invention also relates to the water-based paint, wherein the surfactant is 7 to 45 parts by weight with respect to 100 parts by weight of the wax.

  The present invention also relates to the water-based paint, wherein the dispersed particles have an average particle size of 5 μm or less.

  The present invention also relates to a water-based paint comprising 5 to 100 parts by weight of an aqueous wax dispersion having an acid value based on 100 parts by weight of the water-based paint.

  The present invention also relates to the water-based paint, wherein the wax having an acid value has a molecular weight of 400 to 2000 and an acid value of 10 to 100 mgKOH / g or less.

  Since the water-based paint of the present invention is completely water-based and does not volatilize the solvent in the atmosphere, it does not adversely affect the environment, while pre-coating on the outer wall etc. while flowing the graffiti written on it It can be easily removed by rubbing with a metal scrubber or by attaching an adhesive tape and peeling it off. In the case of re-coating, it is possible to provide a water-based paint that can be re-painted by simply removing the paint film of the water-based paint.

  The aqueous paint of the present invention is an aqueous paint obtained by dispersing wax in water in the presence of a surfactant having an HLB value of 7 to 13 obtained by addition polymerization of ethylene oxide to a long-chain aliphatic primary alcohol.

  In the present invention, the wax includes petroleum wax such as paraffin wax and microcrystalline wax, and synthetic wax such as polyethylene wax, propylene wax and Fischer-Tropsch wax. The melting point of the wax is 52 to 69 ° C, preferably 60 to 66 ° C. If it is less than 52 ° C. or higher than 69 ° C., the average particle size of the dispersed particles becomes large, and the graffiti removal effect decreases. The melting point of the wax is measured by the method defined in JIS K 2235-5.3.

The molecular structure of the surfactant includes those having a branched structure of a long-chain aliphatic primary alcohol, but a linear structure is more preferable. If the branched structure is used, the ability to disperse the wax decreases, and the average particle size of the dispersed particles increases.
Further, the alkyl group of the surfactant has 30 to 55 carbon atoms. If the number of carbons is smaller or larger than this, the average particle size of the dispersed particles becomes large and the graffiti removal effect is lowered, which is not preferable.

  In the present invention, the molecular weight of the surfactant is measured by an osmotic pressure method and expressed as a number average molecular weight Mn. When the HLB value of the surfactant is smaller than 7 or larger than 13, the average particle diameter of the dispersed particles made of wax is increased, and the graffiti removal effect is inferior.

  The surfactant used in the present invention is preferably used in an amount of 7 to 45 parts by weight per 100 parts by weight of the wax. When the weight ratio of the surfactant is less than 7, the dispersibility of the wax is lowered, the average particle diameter of the dispersed particles is increased, the dispersion stability is lowered, the water and the active ingredient are separated, and the graffiti removing effect is lowered. . On the other hand, when the weight ratio of the surfactant is more than 45, the particles are atomized, the fluidity is lowered, the state of the coating is deteriorated, and the handling is lowered.

  Further, the water-based paint obtained in the present invention preferably has an average particle size of wax dispersed particles of 5 μm or less. When the average particle diameter is larger than 5 μm, the dispersion stability is lowered, the water and the active ingredient are separated, and the graffiti removing effect is lowered.

  Furthermore, additives such as preservatives and pH adjusters can be added to the graffiti drop paint of the present invention in addition to wax and surfactant.

  The graffiti dropping paint of the present invention can be applied and used on areas where graffiti damage is caused by paint, such as pier wall surfaces and soundproof wall surfaces such as concrete, mortar, and metal plates.

  The graffiti drop paint of the present invention may be formulated by blending 5 to 100 parts by weight of an aqueous dispersion of wax having an acid value with respect to 100 parts by weight of the aqueous paint. The wax having an acid value has a molecular weight of 400 to 2000. An acid value of 10 to 100 mgKOH / g, preferably 15 to 45 mgKOH / g is preferred.

  Specific examples of the wax having oxidation include an oxidized wax, an acid-modified wax or an acid copolymer wax. Examples of the acid-modified wax and the acid copolymer wax include ethylene acrylic acid, ethylene methyl methacrylate, ethylene ethyl acrylate, There are copolymer waxes such as ethylene methyl acrylate and ethylene methacrylic acid. The molecular weight of the wax having an acid value is represented by the number average molecular weight Mn measured by the osmotic pressure method.

  By using an aqueous dispersion of a wax having an acid value in combination, the coating on the concrete or metal plate during coating is enhanced and a coating film resistant to erosion is formed. This improves the water resistance, and there is no problem when it is not directly exposed to water, such as in a tunnel, but even when exposed to rain outdoors, the coating is not affected by water and is resistant to erosion. It is a good-looking coating film that does not whiten the film. If the combined use amount is less than 5 parts by weight, the water resistance effect cannot be obtained, and if it exceeds 100 parts by weight, the graffiti removal effect decreases.

  Preferred examples of the present invention will be given below to specifically describe the present invention, but these examples do not limit the scope of the present invention in any way.

In the present invention, various characteristic values were measured by the following methods.
(1) Measurement of average particle diameter (μm) Measurement with a laser diffraction / scattering particle size distribution measuring apparatus LA-920 manufactured by Horiba, Ltd., and the median diameter was defined as the average particle diameter.

(2) State evaluation of water-based paint The state of water-based paint is determined. The condition is judged according to the following criteria, and normal or higher can be used.
Good: Excellent fluidity.
Normal: Flows when the container is tilted.
Bad: Does not flow.

(3) Evaluation of aging stability of water-based paint Aqueous paint is put in a glass bottle, sealed and allowed to stand at room temperature, and the state after 6 months is determined. Judgment is based on the following criteria, and normal or higher can be used.
Good: Does not separate or aggregate.
Normal: Separates but becomes uniform when shaken.
Poor: Separation or aggregation occurs and does not return even if shaken.

(4) Evaluation method of water resistance Substrate on which a water-based paint is applied: Large plate coating substrate preparation method:
1) Apply a water-based paint diluted with water twice to the base material.
2) Leave to dry at room temperature for 1 day.
3) Soak the coated substrate in a container filled with water for 3 days.
4) Evaluation The surface condition of the paint film is judged. Evaluation is performed in three stages according to the following criteria. ○ The above can be used.
A: No change in coating state.
○: The surface turns slightly white.
Δ: The surface turns white.

(5) Evaluation method of graffiti removal effect Base material to which water-based paint is applied: Large plate graffiti removal effect evaluation method:
1) Apply a water-based paint diluted with water twice to the base material.
2) Leave to dry at room temperature for 1 day.
3) Apply various paints the next day.
4) Evaluation One week after the paint is applied, scrape it off with a gold scissor and compare the unpainted part with the coated part to compare the degree of graffiti removal. Evaluation is performed in five stages according to the following criteria.
5: Paint completely falls with light force.
4: Completely falls due to strong rubbing of paint.
3: There is a part where paint cannot be removed.
2: The paint can be partially removed.
1: No paint at all.
Judgment: 4 or more is set as the pass in the above evaluation.

Method for producing surfactant A long-chain aliphatic primary alcohol and potassium hydroxide are placed in a heat-resistant pressure-resistant container and sealed, and oxygen in the container is replaced with nitrogen to completely expel it. Then, it dissolves completely with stirring and heating. Thereafter, water generated along with the formation of potassium alcoholate is removed by reducing the pressure with a vacuum pump. A cylinder filled with ethylene oxide is connected thereto, and ethylene oxide is gradually added while paying sufficient attention to an increase in pressure while stirring the inside of the container. After the target amount has been added, the mixture is further heated and stirred to complete the reaction. The contents were taken out and impurities were adsorbed with an adsorbent and then removed with a filter to obtain the desired surfactant.
The long-chain aliphatic primary alcohols used are as shown in Table 1.

Method for producing water-based paint 40 parts of paraffin wax and 10 parts of a surfactant are weighed into a stainless beaker. It is dissolved by heating and sufficiently stirred with a stirrer to 110 ° C. Weigh 50 parts of water in another stainless steel container and heat to 90 ° C. The molten mixture of the wax and the surfactant is slowly dropped there. At this time, the stainless beaker containing water at 90 ° C. is dropped while slowly stirring. After completion of the dropping, the heating is stopped, the heating medium is removed, and the mixture is gradually cooled at room temperature. The target water-based paint is obtained after cooling to 50 ° C. or lower.
Table 2 shows the formulation of the obtained water-based paint. Even if the number of parts, the melting point, the molecular weight, etc. of the paraffin wax and the surfactant are different, it was prepared under the above conditions.

Method for producing aqueous dispersion In a pressure resistant vessel, 25 parts of oxidized wax having a molecular weight of 2000 and an acid value of 20, 25 parts of dimethylethanolamine, 3 parts of oleic acid and 70 parts of water are added, sealed and heated to 130 ° C. After stirring with heating for a period of time, the mixture was cooled with stirring and cooled to 60 ° C. in about 30 minutes to obtain the desired aqueous dispersion.
The aqueous dispersion and the aqueous paint were weighed as necessary to obtain an aqueous paint intended for mixing.
Also, for oxidized wax having a molecular weight of 1000 and an acid value of 40, 25 parts of oxidized wax, 3 parts of dimethylethanolamine, 3 parts of oleic acid, and 70 parts of water were added to the pressure vessel and sealed. Got.

Paraffin wax 1 Melting point 49 ° C
2 Melting point 54 ℃
3 Melting point 68 ℃
4 Melting point 71 ℃

Surfactant 1 Molecular weight 1420 HLB value 8
2 Molecular weight 1170 HLB value 8
3 Molecular weight 1150 HLB value 12
4 Molecular weight 940 HLB value 12

Aqueous dispersion 1 Oxidized wax Molecular weight 2000 Acid value 20 mgKOH / g
2 Oxidized wax Molecular weight 1000 Acid value 40mgKOH / g

Claims (7)

A water-based paint obtained by dispersing paraffin wax in water in the presence of a surfactant having an HLB value of 7 to 13 by addition polymerization of ethylene oxide to a long-chain aliphatic primary alcohol having an alkyl chain carbon number of 25 to 61 . The water-based paint according to claim 1, wherein the melting point of the paraffin wax is 52 to 69 ° C. The water-based paint according to claim 1, wherein the alkyl chain of the surfactant has 30 to 55 carbon atoms.   The water-based paint according to any one of claims 1 to 3, wherein the surfactant is 7 to 45 parts by weight with respect to 100 parts by weight of the wax.   The water-based paint according to any one of claims 1 to 4, wherein the dispersed particles have an average particle size of 5 µm or less. Furthermore, 5 to 100 parts by weight of an aqueous dispersion of an oxidized wax having an acid value of 10 to 100 mgKOH / g or less is used in combination with 100 parts by weight of the aqueous paint according to any one of claims 1 to 5. Water-based paint. The water-based paint according to claim 6 , wherein the molecular weight of the oxidized wax is from 400 to 2,000.