JP2000026844A - Coating material for water-repellent coating film and coating film obtained therefrom - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating material for giving a water-repellent coating film enhanced in the difficulty with which it is covered with ice or frost upon the icing or frosting of very fine water drops such as dew and retaining its high water repellency even when used under immersed conditions for a long term and to provide a coating film made therefrom. SOLUTION: There are provided a coating material for a water-repellent coating film and a coating film made therefrom each of which contains a fluororesin powder or at least one inorganic powder with its surface being hydrophobized (water-repellent microparticles), a silicone resin binder 3, and at least one oil selected among silicone oils and fluorosilicone oils. By adding the silicone oil or fluorosilicone oil having a surface free energy lower than that of the water-repellent microparticles 2, the fine irregularities on the surface of the coating film are covered with the oils 1 to enable the film to retain high water repellency.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-repellent coating paint in which a water-repellent fluororesin powder or an inorganic fine powder whose surface has been subjected to a hydrophobic treatment is dispersed in a binder, and oil is added thereto, and a coating film thereof. About. The coating film is a product obtained by applying a coating material to an object to be coated, drying and curing the organic solvent after volatilization.

A coating film formed by using the coating material of the present invention has water repellency, so that it can be applied to many articles that require water repellency, snow-repelling property, ice-repelling property, and frost-repelling property. Can be used. Examples of articles that require water repellency include rain gear such as umbrellas, and articles that require low snow and ice resistance, such as roofs, bridges, wireless communication antennas, and heat exchangers of buildings in heavy snow areas. Is mentioned.

[0003]

2. Description of the Related Art Conventional fluororesin paints are used in the fields of construction, automobiles and the like as paints having excellent weather resistance and stain resistance. These are one-component paints utilizing copolymers of fluoroolefins and various hydrocarbons.
None of them has high water repellency, and the contact angle of water of the formed coating film is about 80 °. Low snow and hard icing.

[0004] Further, in a paint obtained by mixing a fluororesin fine powder or a surface-hydrophobized inorganic fine powder with a fluororesin binder, or a paint to which a perfluoroalkyl polyether is added, the water contact angle of the formed coating film. Is 15
It realizes high water repellency of about 0 ° and is being put to practical use. However, in any case, fine irregularities due to the water-repellent powder are formed on the surface of the conventional coating film which achieves the contact angle of 115 ° or more. These fine irregularities are difficult to land,
When seeking hard-to-reach snow, it becomes a source of anchor effect and hinders hard-to-ice and hard-to-snow. In addition, even if the initial water repellency is excellent, there is a problem that the water repellency and the difficulty in snow and ice accretion are lowered by long-term water immersion.

FIG. 2 is a schematic cross-sectional view of a coating film formed by using a conventional water-repellent fine particle such as a fluororesin binder and a fine powder of a fluororesin or a fine powder of SiO _{2 having a} hydrophobic surface. A fluorine-based resin binder 6 containing a large amount of water-repellent fine particles 2 is applied on a substrate 4, and an additive 5 such as perfluoroalkyl polyether is used on the surface of the binder 6. 2 has a structure in which the head is exposed. With such a coating film, it is possible to obtain a coating surface with high apparent water repellency, but it is difficult to form ice and frost due to dew condensation. Is not fully exhibited. In addition, a decrease in water repellency is observed due to long-term water immersion. When the cause is investigated, when fine water droplets are generated due to dew condensation or the like due to fine irregularities on the coating film surface 5 formed by the water-repellent fine particles 2, and when this freezes and causes icing and frosting phenomenon, The effect of water repellency is not exhibited, and the effect of hard ice and hard frost is small. In addition, it is considered that water penetrates into the gap 7 formed between the water-repellent fine particles and the binder, and thereafter, water does not escape from the gap and causes a decrease in water repellency.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a water-repellent coating composition and a coating film which solve the above-mentioned problems of the prior art. That is, icing generated from extremely fine water droplets such as dew condensation, hard icing property against frosting phenomenon, improved hard frosting property, and can maintain high water repellency even when used under long-term water immersion. An object of the present invention is to provide a paint for an aqueous coating and a coating film thereof.

[0007]

In order to solve the above-mentioned problems, the water-repellent coating composition and the coating film according to the present invention are one type of fluororesin powder or inorganic fine powder whose surface has been subjected to a hydrophobic treatment. Or a mixed powder of a plurality of types, a silicone resin binder, and one or a plurality of mixed oils of silicone oil and fluorosilicone oil.

FIG. 1 is a schematic sectional view of a coating film according to the present invention formed on a substrate. The present invention has a structure in which a silicone resin binder 3 containing a large amount of water-repellent fine particles 2 is applied on a substrate 4 and the head of the water-repellent fine particles 2 is exposed from the surface of the silicone resin binder 3. By using a silicone oil or fluorosilicone oil having a smaller surface free energy than the fine particles 2 as the additive oil 1, the additive oil 1 covers the surface of the fine unevenness of the coating film surface, and maintains the high water repellency while maintaining the high water repellency. The lubricity of the surface can be improved. Silicone oil or fluorosilicone oil is dissolved in an organic solvent such as n-heptane and toluene, unlike additives such as perfluoroalkylpolyethers of the prior art.
It is possible to effectively reduce the generation of the gap 7 between the water-repellent fine particles and the binder without settling in the paint.

For the above reasons, the coating film formed by using the coating material of the present invention has remarkably improved icing and frosting resistance to icing and frosting caused by extremely fine water droplets such as condensation. Can be done. Even in long-term immersion in water, it is possible to prevent a decrease in water repellency over details of the entire coating film.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The water-repellent coating composition of the present invention and its coating film are made of a fluororesin powder or one kind of inorganic fine powder whose surface has been subjected to a hydrophobic treatment, or a mixture of a plurality of kinds of powders, It is characterized by containing a resin binder, one kind of oil among silicone oil and fluorosilicone oil or a mixed oil of plural kinds. Further, effective configuration requirements in the present invention are listed below.

(1) Fluororesin powder is ethylene tetrafluoride resin powder (PTFE), ethylene tetrafluoride-propylene hexafluoride copolymer resin powder (FEP), ethylene tetrafluoride-perfluoroalkyl vinyl ether copolymer Among the resin powders (PFA), one kind of powder or a mixed powder of plural kinds is preferable. All of these powders are materials capable of obtaining high water repellency.

(2) As the inorganic fine powder whose surface has been subjected to a hydrophobic treatment, one or a plurality of mixed powders of SiO ₂ and Al ₂ O ₃ are preferable. The hydrophobic treatment is performed by coating the surface of the powder with a hydrophobic material such as dimethyl silicone oil. SiO ₂ and Al ₂ O ₃ themselves are hydrophilic, but if the surface of the powder is coated with a hydrophobic material, they can be fine, hard, and hard to break water-repellent fine particles.

(3) The binder is not particularly limited as long as it has a small surface free energy. A fluorinated alkyl group or a silicone resin modified with an alkyl group is suitable, and may be used alone or in a mixture thereof. A hydrophilic group such as a hydroxyl group or a carbonyl group may be mixed in a chain of the silicone resin. Since the presence of such a hydrophilic group deteriorates the water repellency, it is preferable that the hydrophilic group be substituted with a hydrophobic group such as a fluorinated alkyl group or an alkyl group, that is, modified.

In general, the surface free energy of the binder is larger than the surface free energy of the water-repellent fine powder, and the smaller the difference between the surface free energies, the better the wettability. Therefore, the smaller the surface free energy of the binder, the better. is there. The surface free energy can be evaluated by the surface tension, and the surface tension of general water-repellent fine powder is 21.5.
dyne / cm, the surface tension of the high-purity PTFE according to the present invention is about 18.5 dyne / cm or less, and the surface tension of the silicone resin binder is 22.2.
It is quite low at about dyne / cm, and it can be said that the surface free energy of the silicone resin binder is small.

(4) It is desirable that the silicone oil or fluorosilicone oil has a smaller surface free energy than the powder and the binder. The smaller the surface free energy is, the more easily it comes out to the surface, and can cover the surfaces of the powder and the binder. The surface tension of fluorosilicone oil is about 18.3 dyne / cm and high purity PTFE
It can be smaller than the surface free energy of the powder and the silicone resin binder. A fluorosilicone oil having a small surface free energy can be obtained, for example, by introducing a long-chain fluoroalkyl group into the molecule of the silicone oil.

Fluorine silicone oils are not usually dissolved in organic solvents, but oils obtained by introducing long-chain fluoroalkyl groups into the molecules of silicone oils include oils such as ethyl alcohol, n-heptane and toluene. Dissolve in organic solvents. As the organic solvent, any one of alcohols, aromatics, and aliphatics or a mixed organic solvent thereof can be used.

Among the above-mentioned fluorosilicone oils, particularly preferred examples include those represented by the chemical structural formula 1.

Embedded image In the chemical formula, the fluoroalkyl group contains 4 carbons, but 3 or more carbons are suitable.

(5) The paint is prepared by removing the non-volatile content of the above (1) to (4) by using any of alcoholic, aromatic and aliphatic organic solvents such as ethyl alcohol, n-heptane and toluene, or any of these. It is prepared by mixing with a mixed organic solvent.

[0019]

Example 1 A fluororesin powder having an average molecular weight of 5,000 and a particle size of 0.8 μm was prepared by mixing a tetrafluoroethylene resin powder with a volume fraction of 4
5%, a binder was 55% by volume of silicone resin, and a fluorosilicone oil was prepared by mixing three components having a weight ratio of 1% with respect to the nonvolatile content of the coating using a ball mill to prepare a coating. This fluororesin silicone resin fluorosilicone oil mixed paint was spray-coated on a slide glass and an aluminum substrate to form a coating film, and a sample for confirming the effect of the present invention was produced.

In order to compare the performance of the sample of Example 1, samples of Comparative Examples 1 to 4 were prepared. (Comparative Example 1) As a comparative example, the same two components of the same ethylene tetrafluoride resin powder as in Example 1 were mixed in a volume fraction of 45% and a fukavinylidene resin binder in a volume fraction of 55% using a ball mill. A paint was prepared. This paint was spray-coated on a slide glass and an aluminum substrate to form a coating film, and a comparative sample was prepared. The resin binder is different from that of Example 1, and no fluorosilicone is used.

Comparative Example 2 As a comparative example, the same ethylene tetrafluoride resin powder as in Example 1 was used in a volume fraction of 45%, the volume ratio of a fukkavinylidene resin binder was 55%, and the perfluoroalkyl polyether was The three components having a weight ratio of 1% to the non-volatile content of the paint were mixed using a ball mill to prepare a paint. This paint was spray-coated on a slide glass and an aluminum substrate to form a coating film, and a comparative sample was prepared. Example 1 differs from Example 1 in the resin binder and the oil.

(Comparative Example 3) As a comparative example, the same two components as in Example 1 were used, using a ball mill consisting of 80% by volume fraction of a tetrafluoroethylene resin powder and 20% by volume fraction of a fukavinylidene resin binder. To prepare a coating. This paint was spray-coated on a slide glass and an aluminum substrate to form a coating film, and a comparative sample was prepared. The resin binder is different from that of Example 1, and no fluorosilicone is used.

COMPARATIVE EXAMPLE 4 As a comparative example, the same ethylene tetrafluoride resin powder as in Example 1 was used in a volume fraction of 80%, the volume ratio of a fukkavinylidene resin binder was 20%, and the perfluoroalkyl polyether was used in a comparative example. The three components having a weight ratio of 1% to the non-volatile content of the paint were mixed using a ball mill to prepare a paint. This paint was spray-coated on a slide glass and an aluminum substrate to form a coating film, thereby preparing a comparative sample. Example 1 differs from Example 1 in the resin binder and the oil.

Table 1 summarizes the main components of Example 1 and Comparative Examples 1 to 4. In Example 1 and Comparative Examples 1 to 4, PTFE was used for the water-repellent fine particles.

[Table 1]

The performance of the coating films of Example 1 and Comparative Examples 1 to 4,
That is, Table 2 shows the initial water repellency, the water repellency 200 days after immersion in water, and the initial hard-to-ice property.

[Table 2]

First, the hard landing characteristics will be described below.
In order to compare the easiness of ice adhesion, ice was adhered on the coating film at −15 ° C., and the icing shear force was measured using an icing force tester. FIG. 3 shows the configuration of the icing power tester. The icing force tester pulls ice 10 surrounded by a cylindrical tube 9 having an inner diameter of 32 mm adhered onto the coating film 8 at a constant speed in a direction 13 parallel to the coating film 8 using a stainless steel wire 11, This is a device for reading a load change until the ice is detached by the load cell 12. The maximum load was the icing shear force.

Example 1 of the present invention and Comparative Examples 1, 2, 3,
The icing shear force of the coating No. 4 was measured. The measured value is 5
The average value of the points was used. The icing shear force of the coating film was 83 g / cm @ 2 in Example 1 of the present invention, whereas those of Comparative Examples 1, 2, 3, and 4 were 552 g / cm @ 2, 392 g / cm @ 2, and 381.
g / cm2, 154 g / cm2. FIG. 4 shows a comparison of these icing shear forces. In the embodiment of the present invention, a remarkable improvement in characteristics can be obtained as compared with the related art.

The water repellency of the samples of Examples and Comparative Examples will be described below. FIG. 5 is a schematic diagram in which water droplets are dropped on the coating film 8 on the substrate 4. Further, the contact angle θ is measured from the water droplet 14 on the coating film 8. The contact angle θ of water is best known as a measure of water repellency, and the larger the angle, the higher the water repellency. The water repellency was evaluated using a contact angle meter manufactured by Kyowa Interface Science Co., Ltd. About 4μl (4 × 10-9m3) on the paint surface
Was dropped, and the contact angle of water was measured. Measurement at room temperature 2
The measurement was performed at 3 ° C., and an average value of five measurement points was used.

The contact angle between the coating film of Example 1 and water was 148 °. The contact angles of the coating films of Comparative Examples 1, 2, 3, and 4 with water were 128 °, 139 °, 152 °, and 152 °, respectively. Comparative Example 3, the amount of the water-repellent fine particles added to the coating film of Example 1 was 45 vol%.
The addition amount of the water-repellent fine particles of No. 4 was 80 vol%, and their contact angles were almost the same. It can be seen that higher water repellency was obtained with a smaller amount of the water-repellent powder than in the conventional case.

FIG. 6 shows Example 1 and Comparative Examples 1, 2,
The relationship between the number of days of water immersion and the water repellency of the coating films 3 and 4 is shown. The water repellency was evaluated by the contact angle with water. It can be seen that the coating film of Example 1 shows less decrease in water repellency with time than the comparative example, and has long-term durability to water.

[0031]

Example 2 15% by volume fraction of SiO2 fine powder having a particle diameter of 0.2 .mu.m, which had been subjected to surface hydrophobization treatment with dimethyl silicone oil, the binder was 85% by volume of polyorganosiloxane resin, and the non-volatile content of the coating material was 85%. 1 by weight
% Fluorosilicone oil was mixed using a ball mill to prepare a coating. This fluororesin silicone resin fluorosilicone oil mixed paint was spray-coated on a slide glass and an aluminum substrate to form a coating film, and a sample for confirming the effect of the present invention was produced.

In order to compare the performance of the sample of Example 1, samples of Comparative Examples 5 to 7 were prepared. (Comparative Example 5) A coating material was prepared by mixing two components of the same SiO ₂ fine particles as in Example 2 with a volume fraction of 15% and a fucavinylidene resin binder with a volume fraction of 85% using a ball mill. The paint was spray-coated on a slide glass and an aluminum substrate to form a coating film, and a sample for confirming the effects of the invention was produced. Example 2 differs from Example 2 in the binder resin.

(Comparative Example 6) A coating material was prepared by mixing two components of the same SiO ₂ fine particles as in Example 2 with a volume fraction of 50% and a fucavinylidene resin binder with a volume fraction of 50% using a ball mill. . The paint was spray-coated on a slide glass and an aluminum substrate to form a coating film, and a sample for confirming the effects of the invention was produced. Example 2 differs from Example 2 in the binder resin.

(Comparative Example 7) The same SiO ₂ fine particles as in Example 2 were used in a volume fraction of 50%, a fukavinylidene resin binder in a volume fraction of 50%, and a weight ratio of 1% to the nonvolatile content of the paint. The three components of perfluoroalkyl polyether were mixed using a ball mill to prepare a paint. This paint was spray-coated on a slide glass and an aluminum substrate to form a coating film, and a sample for confirming the effects of the invention was produced. Example 2 differs from Example 2 in the binder resin and oil.

Table 3 summarizes the main components of Example 2 and Comparative Examples 5 to 7. Example 2 and Comparative Examples 5 to 7 use SiO2 fine particles having a particle diameter of 0.2 [mu] m which have been subjected to a surface hydrophobic treatment with dimethyl silicone oil.

[Table 3]

Table 4 shows the coating properties of Example 2 and Comparative Examples 5 to 7, that is, the initial water repellency, the water repellency after 200 days of immersion in water, and the initial hard-to-ice property.

[Table 4]

The icing shear force of the coating films of Example 2 of the present invention and Comparative Examples 5, 6, and 7 was measured in the same manner as in Example 1. Example 2 of the present invention was 57 g / cm 2, whereas Comparative Examples 5, 6, and 7 were 576 g / cm 2 and 283 g.
/ Cm2 and 203 g / cm2. FIG. 4 shows a comparison of these icing shear forces. In the coating film of Example 2, a remarkable improvement in characteristics was obtained as compared with the prior art.

The contact angles of water on the coating films of Example 2 and Comparative Examples 5, 6, and 7 were measured in the same manner as in Example 1.
In the case of Example 2, the contact angle of water was 155 °. The contact angles of Comparative Examples 5, 6, and 7 were 111 °, 155 °, 1
55 ゜. The amount of the water-repellent fine particles added to the coating film of Example 2 was 15 vol%, and the amount of the water-repellent fine particles of Comparative Examples 6 and 7 was 5%.
Since these contact angles are almost equal at 0 vol%, it can be seen that high water repellency can be obtained with a smaller amount of the water repellent powder added than before.

In Example 2, the relationship between the number of days of water immersion and the water repellency for Comparative Examples 5, 6, and 7 is not shown, but as in Example 1, the water repellency over time was lower than that of the comparative example. The decrease is small, and it can be said that it has long-term durability to water.

In Examples 1 and 2, the case where one type of powder was used as the water-repellent fine particles was described. Similar results were confirmed with a plurality of types of powder. The fluororesin powder, the inorganic fine powder, the binder, and the additive oil were also examined for combinations other than those shown in the examples. However, they have high initial water repellency, long-term resistance to water, and excellent ice-freeness. It was confirmed that.

[0041]

As described above, according to the present invention,
A fluororesin powder having water repellency or an inorganic fine powder whose surface has been subjected to a hydrophobic treatment is dispersed in a silicone resin binder, and further a silicone oil, a coating film is formed using a paint to which fluorosilicone oil is added. As a result, it is possible to prevent a decrease in hard-to-ice properties due to the occurrence of fine irregularities on the surface, which is indispensable for achieving a contact angle of 115 ° or more,
Further, a high contact angle can be maintained. The gap between the fluororesin powder and the binder can be reduced, and water can be prevented from penetrating into the coating film, so it retains high water repellency for a long time even when used outdoors where it is exposed to water. it can. In other words, according to the present invention, icing generated from extremely fine water droplets such as dew condensation, hardly icing property against frosting phenomenon, improved hard frosting property, and high even when used under long-term water immersion It is possible to provide a water-repellent coating paint capable of maintaining water repellency and a coating film thereof.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a coating film according to the present invention.

FIG. 2 is a schematic cross-sectional view of a conventional coating film.

FIG. 3 is a diagram showing a configuration of an icing power tester.

FIG. 4 is a graph showing the icing shear force of the coating films of Examples and Comparative Examples.

FIG. 5 is a schematic diagram in which water droplets are dropped on a coating film.

FIG. 6 is a diagram showing the relationship between the number of days of water immersion and the water repellency of the coating films of Example 1 and Comparative Examples 1, 2, 3, and 4.

[Explanation of symbols]

 1: additive oil 2: water-repellent fine particles 3: silicone resin binder 4: substrate 5: conventional additive 6: fluorine-based resin binder 7: gap 8: coating film 9: Teflon ring 10: ice 11: stainless steel wire 12: load cell 13: Direction parallel to the coating 14: Water drop

 ────────────────────────────────────────────────── ─── Continued on front page (72) Inventor Yasuhiro Tsukamoto 1-3-1 Gotenyama, Musashino-shi, Tokyo F-term in NTT Advanced Technology Co., Ltd. 4H020 BA32 BA36

Claims (10)

[Claims] 1. One type or a mixture of plural types of powders of fluororesin powder or inorganic fine powder whose surface has been subjected to a hydrophobic treatment, a silicone resin binder, and one type of oil of silicone oil or fluorosilicone oil Alternatively, a paint for a water-repellent coating, comprising a plurality of types of mixed oils. 2. The method according to claim 1, wherein the fluororesin powder is one of ethylene tetrafluoride resin powder, ethylene tetrafluoride-propylene hexafluoride copolymer resin powder, and ethylene tetrafluoride-perfluoroalkyl vinyl ether copolymer resin powder. The water-repellent coating paint according to claim 1, which is a powder of a kind or a mixed powder of a plurality of kinds. 3. The method according to claim 1, wherein the inorganic fine powder is SiO ₂ , Al ₂ O ₃
The water-repellent coating paint according to claim 1, wherein the paint is one kind of powder or a mixed powder of a plurality of kinds. 4. The coating material for water-repellent coating according to claim 1, wherein said silicone resin binder is modified with a fluorinated alkyl group or an alkyl group. 5. The silicone oil or the fluorosilicone oil has a surface free energy smaller than that of a powder and a binder, and is dissolved in an alcohol-based, aromatic-based, or aliphatic-based organic solvent or a mixed organic solvent thereof. The coating material for a water-repellent coating according to any one of claims 1 to 4, wherein: 6. A powder of at least one of a fluororesin powder or an inorganic fine powder whose surface has been subjected to a hydrophobic treatment or a mixed powder of a plurality thereof, a silicone resin binder, and one of a silicone oil and a fluorosilicone oil. Water-repellent coating film, characterized by containing an oil or a mixed oil of a plurality of types. 7. The fluororesin powder is one of ethylene tetrafluoride resin powder, ethylene tetrafluoride-propylene hexafluoride copolymer resin powder, and ethylene tetrafluoride-perfluoroalkyl vinyl ether copolymer resin powder. The coating film for water-repellent coating according to claim 6, wherein the coating film is a powder of a kind or a mixed powder of a plurality of kinds. 8. The method according to claim 1, wherein the inorganic fine powder is SiO ₂ based, Al ₂ O ₃
7. The water-repellent coating film according to claim 6, wherein the powder is one kind of powder or a mixed powder of plural kinds. 9. The water repellent coating according to claim 6, wherein the silicone resin binder is modified with a fluorinated alkyl group or an alkyl group. 10. The silicone oil or the fluorosilicone oil has a smaller surface free energy than a powder and a binder, and is dissolved in an alcohol-based, aromatic-based, or aliphatic-based organic solvent or a mixed organic solvent thereof. The paint for a water-repellent coating according to any one of claims 6 to 9, wherein: