JPH0693225A - Composition for forming water repellent coating film - Google Patents

Abstract

PURPOSE:To obtain a composition for forming water repellent coating film, capable of preventing residence of drops of water and excellent in corrosion resistance. CONSTITUTION:This composition for forming water repellent coating film is characterized by including a fluorine-containing thermosetting resin having >=10wt.% fluorine content and particles having <=5mum average particle diameter.

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 film-forming composition containing a fluorine-containing thermosetting resin and granules as main components.

[0002]

2. Description of the Related Art As water-repellent materials, for example, hydrocarbon-based polymer materials such as polyethylene, fluorine-containing resin-based polymer materials such as polytetrafluoroethylene, and silicon-based polymer materials are known. this house,
Polytetrafluoroethylene has a water droplet contact angle of 115 °.
It is up to 120 °, and it is a material with high hydrophobicity, but depending on the purpose for which it is used, higher water repellency is required,
Development of materials with high water repellency is desired.

In response to such a demand, a composition containing an acrylic copolymer containing a silicon-containing weight unsaturated monomer as an essential component and a granular material as main components has been proposed (JP-A-2- No. 8263), the coating is cured by hydrolysis of an alkoxysilane group, which is a so-called moisture curing method. Therefore, when the composition is stored for a long period of time, viscosity increase or gelation occurs due to moisture in the air. However, it lacked storage stability. Furthermore, the physical and chemical performance of the formed (cured) coating film may be insufficient.

[0004]

As a result of intensive studies to solve these problems, the present inventors have found that this time, the contact angle of water droplets is 140 ° or more, and compared with polytetrafluoroethylene. , The contact angle with paraffin is large,
Moreover, they have developed a water-repellent composition capable of forming a coating film having excellent water repellency. That is, the present invention provides a water-repellent coating film-forming composition comprising, as a main component, a fluorine-containing thermosetting resin having a fluorine content of 10% by weight or more and a granular material having an average particle diameter of 5 μm or less. It is a thing.

The composition of the present invention contains two components, a fluorine-containing thermosetting resin and a granular material, as a main component, and the fluorine-containing thermosetting resin is composed of a base resin and a curing agent. The base resin is a resin having fluorine and a hydroxyl group in the main chain and / or side chain, and the curing agent is a cross-linking agent for curing the above-mentioned hydroxyl group-containing fluororesin. Including) etc.

Specific examples of the base resin include the following copolymers (a) and (b). (A) A copolymer containing a fluoroolefin (A) and a hydroxyl group-containing vinyl monomer (B) as main components. (B) A copolymer containing a fluorinated alkyl (meth) acrylate and a hydroxyl group-containing vinyl monomer as main components.

Regarding the copolymer (a) , examples of the fluoroolefin (A) include hexafluoropropene, tetrafluoroethylene, monochlorotrifluoroethylene, dichlorodifluoroethylene,
1,2-difluoroethylene, vinylidene fluoride, monofluoroethylene and the like can be mentioned. Of these, vinylidene fluoride, tetrafluoroethylene, monofluoroethylene and monochlorotrifluoroethylene are particularly preferable from the viewpoint of copolymerizability.

The hydroxyl group-containing vinyl monomer (B) comprises a double bond copolymerizable with the fluoroolefin and a hydroxyl group.
One or more in the molecule, for example, hydroxyethyl vinyl ether, hydroxypropyl vinyl ether, hydroxybutyl vinyl ether, hydroxyhexyl vinyl ether, hydroxypentyl vinyl ether and other hydroxyl group-containing vinyl ethers; 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, Examples thereof include hydroxyl group-containing (meth) acrylates such as hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, and hydroxybutyl methacrylate.
Of these, hydroxyl group-containing vinyl ethers, especially vinyl ethers having a hydroxyalkyl ether group having 2 to 6 carbon atoms are particularly preferable from the viewpoint of copolymerizability with fluoroolefins.

Further, in (a), another monomer (C) copolymerizable with the above-mentioned both monomers may be used in combination, if necessary, and examples of such a monomer include methyl,
Vinyl ether having an alkyl group such as ethyl, propyl, n-butyl, isobutyl, hexyl, octyl, decyl and lauryl, or an alicyclic group such as cyclobutyl, cyclopentyl, cyclohexyl; having an alkyl group having 1 to 18 carbon atoms (meth) Acrylic acid alkyl ester; vinyl acetate such as vinyl acetate vinyl propionate, vinyl butyrate, vinyl caproate, and vinyl laurate, and the like.

The proportion of each of the above-mentioned components in the copolymer (a) can be arbitrarily selected according to the fluorine content, the surface tension and the chemical and physical properties of the target formed coating film. (A): hydroxyl group-containing vinyl monomer (B): other monomer (C) in a mole% ratio of 20 to 20
The range of 90: 1 to 80:79 to 0 is preferable.

On the basis of (a), the weight average molecular weight of the hydroxyl group-containing fluororesin is usually 2,000 to 100,000, preferably 5,000 to 60,000. When the molecular weight is smaller than the above range, the water resistance and physical properties of the cured coating film tend to be deteriorated, and when it is larger than the above range, the viscosity when dissolved tends to be high. The hydroxyl value of the resin is in the range of 20 to 400 mgKOH / g, more preferably 40 to 300 mgKOH / g. When the hydroxyl value is smaller than the above range, the curability is insufficient and crosslinking of the coating film is insufficient, while when it is larger than the above range,
The water resistance and physical properties of the coating film are reduced.

In the copolymerization reaction for synthesizing the above-mentioned (a) copolymer, a polymerization catalyst is usually added in a total amount of 1 monomer in an organic solvent.
Usually, about 0.01 to 5 parts by weight is added to 00 parts by weight, the temperature is about -20 to 150 ° C., and the pressure is normal pressure or 3
It is carried out under pressure up to about 0 kg / cm ² G.

Regarding the copolymer (b), examples of the fluorinated alkyl (meth) acrylate (D) include 2,2-difluoroethyl (meth) acrylate,
2,2,2-trifluoroethyl (meth) acrylate, 2,2,3,3-tetrafluoropropyl (meth)
Acrylate, 2,2,3,3,3-pentafluoropropyl (meth) acrylate, 2,2,3,3,4,4
-Hexafluorobutyl (meth) acrylate, 2,
2,3,3,4,4,5,5-octafluoropentyl (meth) acrylate, 1,1-di (trifluoromethyl) 2,2,2-trifluoroethyl (meth) acrylate, 2,2 3, 3, 4, 4, 5, 5, 6, 6, 7,
7-dodecafluoropentyl (meth) acrylate,
3,3,4,4,5,5,6,6,7,7,8,8,
Examples include 9,9,10,10,10-heptadecafluorodecanyl (meth) acrylate.

The hydroxyl group-containing vinyl monomer (E) may be any one having a hydroxyl group and a double bond copolymerizable with the fluorinated alkyl (meth) acrylate (D), for example, 2-hydroxyethyl (meth). ) Acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate and the like.

Further, in (b), another monomer (F) copolymerizable with the above-mentioned both monomers (D) and (E) may be optionally used in combination. As such a monomer, , For example, a lower alkyl (meth) acrylate having 1 to 10 carbon atoms, a lower alkoxy (meth) acrylate having 1 to 6 carbon atoms, cyanoethyl (meth) acrylate, acrylamide, acrylic acid, methacrylic acid, etc. The preferred form is styrene, alkyl-substituted styrene, acrylonitrile, methacrylonitrile and the like.

The proportion of each of the above-mentioned components in the copolymer (b) can be arbitrarily selected according to the fluorine content, the surface tension and the chemical / physical properties of the target formed coating film. The alkyl (meth) acrylate (D): hydroxyl group-containing vinyl monomer (E): other monomer (F) is preferably in the range of 20 to 80: 1 to 80:79 to 0 in mol% ratio. The weight average molecular weight and hydroxyl value of the copolymer are preferably within the ranges shown in the copolymer (a).

An amino resin and / or a polyisocyanate compound is used as a cross-linking agent for the hydroxyl group-containing fluororesin.

Specific examples of the amino resin include a methylolated amino resin obtained by reacting an amino component such as melamine, benzoguanamine, acetoguanamine, steroganamin, spiroguanamine and dicyandiamide with an aldehyde. Examples of arshydrides include formaldehyde, paraformaldehyde, acetaldehyde, and pentaldehyde. Further, an etherified product of this methylolated amino resin with an appropriate alcohol can be used, and examples of the alcohol used for modification include methyl alcohol, ethyl alcohol, n-propyl alcohol, i-propyl alcohol, n-butyl alcohol, Examples thereof include i-butyl alcohol, 2-ethylbutanol, 2-ethylhexanol and the like.

Commercial products of such amino resins include Cymel 303 (full methoxylated melamine resin, manufactured by Mitsui Cyanamid), Uban 20SE-60 (butylated melamine resin, manufactured by Mitsui Toatsu Co., Ltd.), and Nicalac MS-95 (methyl Amino resins that are commercially available under the trade names of isobutylated melamine resin and Sanwa Chemical Co., Ltd. can be used.

The mixing ratio of the hydroxyl-functional fluorine-containing resin and the amino resin is 10 to 100 parts by weight, preferably 20 to 70 parts by weight, based on 100 parts by weight of the hydroxyl-functional fluorine-containing resin. . Outside this range, the curability and physical performance of the coating film will deteriorate.

The polyisocyanate compound is a compound having at least two isocyanate groups in one molecule. Specifically, aliphatic diisocyanates such as hexamethylene diisocyanate or trimethylhexamethylene diisocyanate: xylylene diisocyanate or isophorone. Cycloaliphatic diisocyanates such as diisocyanates; organic diisocyanates themselves such as tolylene diisocyanates or aromatic diisocyanates such as 4,4'-diphenylmethane diisocyanate, or these organic diisocyanates and polyhydric alcohols, low molecular weight polyester resins Alternatively, an adduct with water or the like, a polymer of the above organic diisocyanates, or an isocyanate biuret body may be mentioned.

As the polyisocyanate compound,
A block type polyisocyanate compound in which an isocyanate group is blocked with a suitable blocking agent can also be used. By using such a block-type polyisocyanate, a one-pack type water-repellent treatment composition having excellent storability can be obtained. As the blocking agent, a volatile low-molecular active hydrogen compound is used, and examples thereof include known compounds such as aliphatic or aromatic monoalcohols, hydroxy tertiary amines, oximes, active methylene compounds, lactams and phenols. You can

The mixing ratio of the hydroxyl group-containing fluororesin and the polyisocyanate compound is based on the molar ratio of the hydroxyl group in the hydroxyl group-containing fluororesin and the isocyanate group in the polyisocyanate compound, and OH / NCO = 0.5-2. 5,
A suitable range is 0.7 to 2.0.

Further, as a fluorine-containing thermosetting resin, a self-crosslinking resin obtained by copolymerizing the above monomer with a vinyl monomer such as N-methylolacrylamide and Nn-butoxymethylacrylamide (a crosslinking agent is required). Not) is also useful.

In the present invention, the fluorine content is based on the total weight of the hydroxyl group-containing fluororesin and the crosslinking agent, and the self-crosslinking resin is based on the resin itself.

The content of fluorine atoms in the fluorine-containing thermosetting resin is preferably 10% by weight or more, more preferably 15% by weight or more. By adjusting the fluorine content within this range, the contact angle of water droplets (angle from the water droplet side) on the surface of the formed and cured film can be 95 ° or more (particularly preferably 98 to 110 °).

The particles used together with the fluorine-containing thermosetting resin are particles having an average particle size of 5 μm or less, preferably 3 μm or less, more preferably 1 μm or less, and the particles are either organic fine particles or inorganic fine particles. It may be present, but it is necessary that it be present as a granular material in the coating film after the coating film is formed. Examples of such particles include:
Examples thereof include fine silica powder, fine fluorocarbon powder, and carbon black. Among them, fine silica powder is preferable, and especially silazane [(CH ₃ ) ₃ Si-
NH-Si- (CH ₃₎ silica fine powder hydrophobized by _3] are preferred. Further, by adding fine spherical silica particles, the smoothness of the obtained coating film surface can be improved. As a granular material, the average particle size is 5 μm
When a coating film having a thickness of more than 10 is used, microscopically, the surface roughness of the coating film becomes large and the water repellency tends to decrease.

In the present invention, the mixing ratio of the fluorine-containing thermosetting resin and the granular material is not particularly limited, but the granular material is generally 15 to 300 per 100 parts by weight of the fluorine-containing thermosetting resin solid content. Parts by weight, preferably 30-1
It is preferable to mix it in the range of 50 parts by weight from the viewpoint of water repellency and physical properties of the coating film obtained.

In the present invention, the fluorine-containing thermosetting resin having the adjusted fluorine content is used in combination with the granular material having an average particle diameter of 5 μm or less, so that the water droplet contact angle is 140 °.
A cured coating film as described above can be obtained. In addition to the fluorine-containing thermosetting resin and the components of the granular material, the composition of the present invention may be appropriately blended with an additive that is usually used in paints, such as a solvent, a coloring agent such as a pigment, and a surfactant. , Obtained by mixing. As the mixing means,
A commonly used stirring method or dispersion method can be adopted, and for example, a dissolver, a steel ball mill, a bevel mill, a sand mill, an attritor, or the like can be used.

The water-repellent coating film-forming composition of the present invention can be directly applied to the surface of a substrate such as metal, plastic, glass or wood material, and a coating film previously formed on these substrates can be applied. It is also possible to apply it as an overcoat on top. Further, the composition of the present invention can be used as a molded product by laminating it on the surface of an object.

As the method for applying the water-repellent composition of the present invention onto the above-mentioned substrate, for example, spraying, brushing, roller coating, dipping and the like known coating means can be used. I can. The composition of the present invention usually has a film thickness of 0.5 to 50 μm, preferably 5 to 30 μm.
Paint and cure so that it is within the range of μm. When a non-blocking type polyisocyanate compound is used as a curing agent, the coating film is cured by separating it from the hydroxyl group-containing fluororesin in advance into a two-component type, mixing immediately before coating, and at room temperature to 200 ° C. It can be dried and cured in a temperature range. Further, when a block type polyisocyanate compound, an amino resin is used as a curing agent, and when a self-crosslinking resin is used as a thermosetting resin, the paint can be a one-pack type, and curing in that case It is carried out by baking at 120 to 200 ° C. for 10 to 30 minutes.

[0032]

FUNCTION AND EFFECT On the surface of the coating film formed from the composition of the present invention, irregularities on the order of microns are observed on a micrograph, and ESCA analysis shows that C-F bonds are distributed in a large amount on the surface. It turns out. Further, the surface energy γ calculated from the contact angle is expressed by the following formula: γ = γp + γd (mN / m) where:

[Equation 1] γd = 32.8 (1 + COSθp) / 4 θw: contact angle of water θp: calculated by the contact angle of paraffin, the surface energy of the coating film formed using the composition of the present invention is 5 mN / m or less. Yes, the value is much lower than that of Teflon (γ is 21 mN / m). On a surface having such low surface energy, the amount of water droplets attached is very small, and since the water droplets are spherical, they are quickly released.

Since the surface of the coating film and the like formed from the composition of the present invention has the above-mentioned characteristics, the composition of the present invention is waterproof, anti-frost, anti-snow, anti-ice ice and water It is very useful in fields such as short circuit prevention. Moreover, the storage stability of the composition is excellent, and the physical and chemical performance of the formed coating film is also good. Examples and comparative examples are shown below. These examples are for illustrating the present invention in more detail, and do not limit the present invention in any way. "Parts" and "%" are "parts by weight"
And "% by weight" are shown.

Production of Fluorine Resin Containing Hydroxyl Group (1) A 1000 ml glass autoclave was charged with 20 parts of hydroxypropyl vinyl ether, 64.3 parts of xylene, 21.4 parts of methyl isobutyl ketone and 0.36 parts of N-dimethylbenzylamine. After replacing the space portion with nitrogen, 80 parts of vinylidene fluoride was added and heated to 65 ° C. The pressure when the temperature became stable was 6.2 kg / cm 2 G. Then, xylene / methyl isobutyl ketone (0.9% by weight of azobisisobutyronitrile) (3 / by weight)
14.3 parts of the mixture of 1) was added to initiate polymerization. Hold at 65 ° C. for 20 hours with stirring. The pressure of the autoclave after 20 hours was 0.2 kg / cm ² G. The resulting varnish containing hydroxyl group-containing fluororesin (1) had a solid content of about 50% and a hydroxyl value (resin solids) of about 1%.
10 mgKOH / g, the weight average molecular weight was 15,000, and the fluorine content was 47%.

Production of hydroxyl group-containing fluororesins (3) to (5)
A hydroxyl group-containing fluororesin varnish was obtained in the same manner as in Production Example 1, except that the composition and the number of parts of the polymerizable monomer were as shown in Table 1.

[0036]

[Table 1]

Example 1 200 parts of the hydroxyl group-containing fluororesin (1) varnish having a solid content of 50% obtained in Production Example 1 was mixed with 20 parts of granules A (* 3) and dispersed with a shaker, and then solidified. Minute 75%
Tis module BL3175 (manufactured by Sumitomo Bayer Urethane Co., Ltd., methyl ethyl ketone oxime block adduct type hexamethylene diisocyanate, isocyanate group content 11.5%) (curing agent A) 96 parts (molar ratio of hydroxyl group and isocyanate group OH / NCO = 1.0)
Is added under stirring, and further diluted with a mixed organic solvent (toluene / butyl acetate / ethylene glycol monoethyl ether acetate = 3/1/1) to give a water-repellent coating film forming composition (A) having a solid content of 15%. Obtained.

An aluminum plate (A-1050, plate thickness) obtained by degreasing the water-repellent composition (A) with an alkaline degreasing agent (manufactured by Nippon CB Chemical Co., Ltd., trade name "Chemic Cleaner 561B"), washing with water and drying. 0.8mm), film thickness 6-8
It is applied so that it becomes μm (as a cured coating film), 140 ℃
And baked for 30 minutes to form a water-repellent coating film. The test results are shown in Table 2.

Example 2 Hydrofluoric acrylic copolymer AS having a hydroxyl content of 50% solids
-1301 [Mitsubishi Rayon Co., Ltd., fluorine content 1
7.5% (to polymer), hydroxyl value 52, weight average molecular weight 20,000] (hydroxyl group-containing fluororesin (2)) 20
50 parts of the granular material (B) (* 3) was blended with 0 part and dispersed by a shaker, and then Nikarac MS-95 (methyl / isobutyl mixed etherified melamine resin, manufactured by Sanwa Chemical Co., Ltd.) (hardening agent (B)) 40 parts, Cure5
225 (KING INDUSTRIES, dodecylbenzene sulfonic acid amine block catalyst) (1.5 parts) was added with stirring, and further mixed organic solvent (toluene / butyl acetate / ethylene glycol monoethyl ether acetate = 3/1/1) was added. Diluted to obtain a water-repellent coating film forming composition (B) having a solid content of 15%.

Then, in the same manner as in Example 1, an aluminum plate having a thickness of 6 after being degreased with an alkaline degreasing agent, washed with water and dried
It was applied so as to have a thickness of ˜8 μm, and baked at 140 ° C. for 30 minutes to form a water repellent coating film. The test results are shown in Table 2.

Examples 3 to 12 and Comparative Examples 1 to 6 The formulations and methods shown in Table 2 were carried out according to Example 1 to obtain a water repellent coating film forming composition having a solid content of 15%. A water-repellent coating film was formed in the same manner. The blending amounts in Table 2 are solid contents, and the test results of the obtained test plates are also shown in Table 2.

[0042]

[Table 2]

In Table 2, (* 1) Hydroxyl group-containing fluororesin (1), (3), (4) and (5): See the above Production Example. (2): Explained in Example 2. (6): Hydroxyl group-containing fluorinated acrylic copolymer AS-13
03 [Mitsubishi Rayon Co., Ltd., fluorine content 30% (relative to polymer), hydroxyl value 52, weight average molecular weight 20,000
0] (7): Hydroxyl group-containing fluorinated acrylic copolymer AS-66
12 (Mitsubishi Rayon Co., Ltd., fluorine content 30%, N
-N-Butoxymethylacrylamide functional self-crosslinking resin)

(* 2) Curing agents (A) and (B): As described in Examples 1 and 2. (C): Takenate B-815N (Takeda Pharmaceutical Co., Ltd.)
(Trade name, block type of methyl ethyl ketone oxime of isophorone diisocyanate, isocyanate group content 12.6%) (D): Cymel 303 (full methoxylated melamine resin manufactured by Mitsui Cyanamid) (E): Takenate D-160N ( Takeda Pharmaceutical Co., Ltd.
Made, trade name, trimethylolpropane adduct hexamethylene diisocyanate, isocyanate group content 1
2.8%)

(* 3) Granules (A): Hydrophobic silica fine powder having an average particle size of about 0.1 μm.
Product name "Cabogil TS-53" manufactured by Cabot Corporation of the United States
0 ”(B): True spherical hydrophobic silica fine powder having an average particle size of about 2 μm, trade name“ TOSPEARL ”manufactured by Toshiba Silicone Co., Ltd. (C): Untreated silica fine powder having an average particle size of 0.1 μm. (D): Fluorocarbon fine powder having an average particle size of 0.3 μm. (E): Carbon black fine powder having an average particle size of 0.3 μm. (F): Untreated silica fine powder having an average particle size of 7 μm (manufactured by Fuji Devison Co., Ltd., trade name “Cyroid 308”)

The test method shown in Table 2 was carried out by the following method. Gel fraction: A free film having a film thickness of 10 to 20 μ is immersed in acetone, boiled under reflux for 8 hours, and then sufficiently dried,
The weight loss of the film was calculated and the gel fraction was calculated by the following formula.

[0050]

[Equation 2]

Solvent resistance: Three layers of gauze were soaked with xylene, and the flatness of the test plate was rubbed back and forth 10 times. ○: No abnormality is observed. Δ: Scratches occur. X: The coating film melts and the base material is exposed. Water drop contact angle: Approximately 0.03 cc of deionized water drops are formed on the coated surface of the test plate immediately after baking, and the contact angle of the water drop is measured at 20 ° C with a contact tangle meter DCAA type manufactured by Kyowa Scientific Co., Ltd. did. Furthermore, the test plate is placed in running tap water for 12 hours.
After soaking for 0 hours, after washing with tap water, 20 ℃, 75%
Each test plate left in the RH environment for 24 hours was also tested. Sliding property of water droplets: 0.03 cc of deionized water was dropped on the coated surface of the test plate with a syringe to form water droplets. Then, the test plate was tilted to read the tilt angle of the test plate where the water droplets slip off. a: Drop at less than 20 ° b: Drop at less than 20 ° to 40 ° c: Drop at 40 ° to 60 ° d: Do not fall even at 60 °

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁵ Identification number Internal reference number FI Technical indication location C09D 161/20 PHK 8215-4J 175/04 PHR 8620-4J (72) Inventor Koichi Tamura Hiratsuka, Kanagawa Kanagawa Paint Co., Ltd. 4-17-1, Higashi-Hachiman, City (72) Inventor Naoya Haruta 4-17-1, Higashi-Hachiman, Hiratsuka-shi, Kanagawa Kansai Paint Co., Ltd.

Claims (3)

[Claims] 1. A composition for forming a water-repellent coating film, which comprises a fluorine-containing thermosetting resin having a fluorine content of 10% by weight or more and particles having an average particle diameter of 5 μm or less. 2. The composition according to claim 1, wherein the particulate matter is silica fine particles having an average particle diameter of 3 μm or less. 3. 15 to 300 particles having an average particle size of 5 μm or less are added to 100 parts by weight of a fluorine-containing thermosetting resin.
The composition according to claim 1 or 2, which comprises parts by weight.