JPS5833267B2 - Sonoto Souhouhou - Google Patents

Description

Detailed Description of the Invention The present invention is a fluororesin coating composition, particularly a novel fluororesin coating composition that does not contain chromic acid and is used to improve the adhesion, hot water resistance, and hot oil resistance of fluororesin coatings. Regarding.

Recently, food utensils coated with fluororesin on the surfaces of aluminum, aluminum die-cast, iron, etc.
It is becoming increasingly popular due to its heat resistance.

Therefore, fluororesin coatings are required not only to be food hygienic safe but also to have stable performance over a long period of time.

On the other hand, although a large number of fluororesin undercoating compositions have been known, the fluororesin undercoating compositions that are currently widely used are particularly polytetrafluoroethylene (hereinafter referred to as "PT").
It is abbreviated as "FE".

) Primer compositions include those consisting of PTFE and chromic acid and those consisting of PTFE, phosphoric acid and chromic acid, as described in U.S. Pat. Nos. 2,562,117 and 2,562,118. There is.

Although these PTFB undercoating compositions have excellent adhesion to substrates, they are not preferred in terms of handling because they contain chromic acid.

Recently, a chromic acid-free fluororesin basecoat composition was proposed in US Pat. No. 3,489,595.

This composition consists of a fluororesin, phosphoric acid, and an oxide of aluminum or boron, and another consists of a fluororesin, phosphoric acid, and aluminum phosphate.

Although these undercoat compositions are excellent in that they do not contain chromic acid, it has been found that they are not necessarily fully satisfactory in terms of adhesion to substrates, the condition of the coating film, etc.

Further, U.S. Pat. No. 3,644,260 discloses a fluororesin undercoat composition using an alkyl silicate, and Japanese Patent Application Publication No. 49-5434 discloses a colloidal silica sol stabilized with ammonia. A fluororesin basecoat composition is disclosed.

However, in the former case, it is preferable to use water or an organic liquid as the liquid carrier.

This is thought to be due to the fact that alkyl silicate easily changes in quality in water, which has a negative effect on the adhesive function, but in order to use an organic liquid as a carrier, a fluororesin organosol must be prepared through a complicated process. First, attention must be paid to the occurrence of pollution problems during painting.

Furthermore, the latter method still cannot be said to be sufficient in terms of long-term stability of the fluororesin coating.

As a result of intensive research aimed at overcoming the drawbacks of the prior art, the present inventors have found that they have not only been able to form a coating film that has excellent performance by itself, but also have excellent properties as a fluororesin undercoat composition. We have completed a new fluororesin coating composition that has the following properties.

The present invention is characterized in that (a) fluororesin (b) general formula % formula % () [wherein R is a chlorine atom, an amino group, an aminoalkyl group,
an alkyl group having 1 to 10 carbon atoms and having at least one functional atom or group selected from a ureido group, a glycidoxy group, an epoxycyclohexyl group, an acryloyloxy group, a methacryloyloxy group, a mercapto group, and a vinyl group, or Vinyl groups R1 and R2 are each a chlorine atom, a hydroxyl group, an alkoxy group having 1 to 10 carbon atoms, an alkoxy-substituted alkoxy group having 2 to 15 carbon atoms, or a 2 to 15 carbon atoms
4 hydroxyalkyloxy groups and 2 to 15 carbon atoms
an atom or group selected from acyloxy groups, y is 0.
Indicates an integer of 1 or 2.

]; (c) at least one of an organic acid, an inorganic acid, an amine, ammonia, and an inorganic hydroxide; and (d) a liquid carrier. By applying the composition as a fluororesin paint or its undercoat composition to a substrate, drying it, and then baking it at a temperature higher than the melting point of the fluororesin, it has excellent adhesion to the substrate, hot water resistance, A fired fluororesin coating film with good oil resistance and base coating properties can be obtained.

Such excellent effects of the present invention can be achieved by applying the composition according to the present invention to a substrate, drying it, and then firing the fluororesin to a temperature higher than that at which the fluororesin is melted.

According to the inventor's estimation, the silane compound in the composition is easily decomposed and condensed by the above baking, resulting in a three-dimensional network structure consisting of units represented by the formula: This is thought to be due to the formation of a fluororesin, which is effectively entangled with the molten fluororesin in molecular units to form a physically strongly integrated composite structure.

In particular, the addition of component (c) promotes the decomposition and condensation reaction of the silane compound, and when it reacts with the functional groups of the silane compound, it forms a three-dimensional network structure that is desirable for fixing the fluororesin, and forms a bond with the base material. It is effective in further improving the adhesion of fluororesin and other properties of fired fluororesin coatings.

In addition, component (c) has a viscosity regulating effect and also has the effect of improving the handling of the composition of the present invention during coating.

The fact that a liquid homogeneous dispersion of a fluororesin containing the specific silane compound represented by the above general formula forms an excellent baked coating film of the fluororesin on the surface of a substrate such as metal is a completely new finding. be.

The component (a) used in the present invention, that is, the fluororesin, includes PTFE, tetrafluoroethylene, and ethylenically unsaturated compounds copolymerizable therewith (for example, olefins such as ethylene and propylene, hexafluoropropylene, and vinylidene fluoride). , chlorotrifluoroethylene, vinyl chloride, halogenated olefins such as perfluoroalkyl vinyl ether, etc.), polychlorotrifluoroethylene, polyvinylidene fluoride, and the like.

Specific examples of particularly preferred fluororesins include: PTFE, copolymers of tetrafluoroethylene and hexafluoropropylene, copolymers of tetrafluoroethylene and perfluoromethyl vinyl ether, and tetrafluoroethylene and perfluoropropyl. Copolymers of vinyl ether, copolymers of tetrafluoroethylene and ethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, etc.

The form of fluororesin is powder or dispersion.
Aqueous dispersions are usually used.

In some cases, a dispersion using an organic liquid as a carrier is also used.

As an aqueous dispersion, the emulsion polymerization dispersion itself obtained by emulsion polymerization, the polymer obtained by suspension polymerization, bulk polymerization, etc. are crushed and finely powdered, and dispersed in a liquid using a surfactant as necessary. things are used.

For example, the PTFE aqueous dispersion is an aqueous dispersion of PTFE colloidal particles with an average particle size of 0.1 to 0.5 microns obtained by emulsion polymerization of tetrafluoroethylene in an aqueous medium containing a fruit surfactant. Usually, a commercially available PTFE aqueous dispersion is used as it is, or it is concentrated or diluted as appropriate, and the above PTFB particles are added to a concentration of 10 to 70% by weight, or 30 to 70% by weight.
It is used as an aqueous dispersion having a weight content of 60% by weight.

Usually, pigments and surfactants are added to these aqueous dispersions.

Further, the aqueous dispersion of tetrafluoroethylene-hexafluoropropylene copolymer is obtained by emulsion polymerization of tetrafluoroethylene and hexafluoropropylene in an amount of 30 molar or less, preferably 20 or less molar relative to tetrafluoroethylene. , can be used as a colloidal dispersion with an average particle size of 0.5 microns or less.

In the component (b) used in the present invention, that is, the silane compound [I], R is a functional alkyl group, and preferable examples include β-aminoethyl group, γ
-aminopropyl group, N-(β-aminoethyl)-γ-
Aminopropyl group, r-ureidopropyl group, γ-glycidoxypropyl group, β-(3,4-epoxycyclohexyl)ethyl group, r-acryloyloxypropyl group, γ-methacryloyloxypropyl group, γ-mercapto Examples include propyl group, β-chloroethyl group, γ-chloropropyl group, and γ-vinylpropyl group.

Further, R may be a vinyl group. Specific examples of the silane compound [I] that are preferably used are as follows: γ-aminopropyltriethoxysilane, N-(β
-aminoethyl)-γ-aminopropyltrimethoxysilane, γ-ureidopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, β-(3,4
-epoxycyclohexyl)ethyltrimethylsilane,
γ-methacryloyloxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, vinyltriethoxysilane, vinyltrichlorosilane, vinyltriacetoxysilane, etc.

In the present invention, organic acids used as component (c) include formic acid, acetic acid, propionic acid, butyric acid, acrylic acid,
Aliphatic carboxylic acids such as oxalic acid, malonic acid, succinic acid, maleic acid, and fumaric acid; alkyl sulfates such as methyl sulfate and ethyl sulfate; mono- or dialkyl phosphates such as monoethyl phosphate and diethyl phosphate. Inorganic acids include hydrochloric acid, hydrofluoric acid, sulfuric acid, nitric acid, phosphoric acid, carbonic acid, etc.
Examples of amines include aliphatic amines such as methylamine, ethylamine, propylamine, ethanolamine, dimethylamine, diethylamine, trimethylamine, triethylamine, triethanolamine, ethylenediamine, propylene diamine, 1,2,3-triaminopropane, and hexamethylenetetramine. Preferred examples of the inorganic hydroxide include monovalent or divalent metal hydroxides such as sodium, potassium, lithium, calcium, magnesium, and barium.

Among these, nitric acid is preferred.

The liquid carrier used as component (d) in the present invention is preferably water, but in some cases an organic solvent may be used alone or in combination with water.

There are several possible ways to obtain the coating composition of the present invention. For example, in a dispersion of component (d) containing a fluororesin as the main component (a), component (b) and (c) are added. Method of adding ingredients and stirring and mixing uniformly, (b)
ff and component (c) are diluted in advance to an appropriate concentration with water or organic liquid as component (d), and this is added to (a).
There is a method of adding and mixing the fluororesin as component (d) to a dispersion of component (d).

When preparing the coating composition according to the present invention, the types of fluororesin, silane compound [I], organic acid, inorganic acid, ammonia, amine, or inorganic hydroxide, and liquid carrier to be used are selected as appropriate. You can.

Furthermore, various additives may be added for the purpose of reaction with the functional groups of the silane compound [I].

For example, aminosilanes such as γ-aminophyltrimethylsilane are alkaline in themselves, so PTF
When added to an aqueous dispersion, the resulting coating composition exhibits alkalinity as a whole and can be suitably used.

However, since r-glycidoxypropyltrimethylsilane is neutral, it is more preferable to add an acid or an alkali to it.

Inorganic fillers such as titanium oxide, red iron oxide, carbon, cadmium oxide, and chromium trioxide can usually be added to the coating composition of the present invention.

Additionally, various surfactants, viscosity modifiers, etc. can be added to improve coating workability.

The coating composition of the present invention usually has a weight fraction content of 2 to 60 parts by weight, more preferably 20 to 550 to 55 parts by weight.

The amount of the fluororesin as component (a) is usually 40 to 980 to 98 parts by weight, preferably 60 to 90 parts by weight based on the solid content.
0 to 90 parts by weight The mixing ratio of the fluororesin-based dispersion as component (a) and the silane compound CI as component (b) is 100 for the former and 0.1 to 5 for the latter by weight.
0. More preferably, it is between 1 and 30 mm.

Although the amount of component (c) to be used cannot be specifically defined depending on the type thereof, it is usually 800 parts by weight or less, preferably 0.1 to 50 parts by weight relative to the fluororesin that is component (a).

These mixing ratios are appropriately selected within the above range depending on the type of fluororesin used, the type of silane compound CI), the type of liquid carrier, etc.

The amount of inorganic filler added is usually 60% relative to the fluororesin.
0 parts by weight, preferably 4 to 20 parts by weight.

The coating composition of the present invention can be applied to base materials made of materials that can sufficiently withstand the firing temperature of fluororesin, such as metals such as iron and aluminum, alloys such as stainless steel, and composite materials such as Altite. .

The base material can usually be simply degreased, but it can also be roughened by methods such as sandblasting or etching, sprayed with metal ceramics, sprayed with frit, baked, anodized, etc. A surface-treated material is used.

Note that the coating composition of the present invention can be sufficiently applied to substrates that are not subjected to these surface treatments, and can provide coatings with good adhesion.

The coating composition of the present invention is applied to the surface of the substrate according to a normal coating method, dried at around 100°C, and then heated to a temperature higher than the melting point of the fluororesin (for example, 327-40°C for PTFE).
A fluororesin coating film can be obtained by firing at a temperature of 0°C.

Furthermore, after the coating composition of the present invention is similarly applied as an undercoat, a fluororesin topcoat enamel coating can be applied.

The coating film coated, dried, and baked in this manner has excellent adhesion to the substrate and coating properties, and has the excellent properties of a fluororesin.

In addition, since the coating composition of the present invention does not contain chromic acid, it is preferable from the viewpoint of safety and health in coating operations and the working environment.

Next, specific embodiments of the present invention will be described by way of examples.

Note that parts and parts represent parts by weight, respectively.

Examples 1 to 8 and Comparative Examples 1 to 2 After uniformly mixing the first liquid, second liquid, and third liquid shown in Table 1, the mixture was purified door-to-door using a 200-mesh wire mesh to obtain a coating composition. .

On the other hand, an aluminum plate having a length of 100 mm, a width of 5011 LrIL, and a thickness of 1 plate was heated to 380° C. for about 30 minutes to degrease it, and then one side was roughened by blasting using 100 mesh alumina powder.

Masking half of the long sides of this degreased and blasted aluminum plate, the above composition was evenly applied to a film thickness of 10 microns, dried at 80 to 90°C for 10 minutes, and then
Primer coating was performed by baking in an electric furnace at 80° C. for 15 minutes and then cooling.

Next, remove the mask and apply Polyflon enamel EK-11080Y to the entire surface, including the unprimed surface.
(PTFE enamel manufactured by Daikin Industries, Ltd. (solid content: 45%, including about 4% TiO2 and carbon as inorganic fillers) was applied uniformly to a film thickness of 20 microns, and dried at 80 to 90°C for 20 minutes. Thereafter, it was baked in an electric furnace at 380° C. for 15 minutes, cooled, and then overcoated.

Further, the same top coating was repeated seven times to obtain a fired coating film with a thickness of about 150 microns.

Each of the obtained test pieces was cut into strips along the lengthwise direction, with the boundary line between the primer coated area and the non-primer coated area in the horizontal direction, at right angles to the boundary line, to the extent that the aluminum base material with a width of 1011t7IL was scratched. It was cut into 507 Wffl/mi using a universal tensile tester from the edge of the non-primer coated part.
The peel strength was measured by pulling at a speed of n.

Separately, an aluminum plate was coated with a primer in the same manner as above, and then the above-mentioned top coat was applied only once to prepare two coated test pieces for each composition.

One of the test pieces obtained was immersed in hot water at 90°C for 4 days, and the coating film properties were measured according to JISK-6894.

The results are shown in Table 1.

Examples 9 to 12 and Comparative Examples 3 to 6 A coating composition having the formulation shown in Table 2 was coated with a primer to a thickness of 10 microns on an aluminum plate in the same manner as in Example 1, and then polyflon enamel EK4108 was applied.
GY (PTFE enamel manufactured by Daikin Industries, Ltd., solid content: 41 parts, including about 5 parts of TiO2 and carbon as inorganic fillers.

), and two coated test pieces were prepared for each composition.

One of the sheets was left as is, and the other was immersed in hot water at 90° C. for 4 days, and then the coating film properties were measured.

The results are shown in Table 2.

Examples 13 to 20 and Comparative Examples 7 to 8 Using a coating composition having the formulation shown in Table 3, an undercoat with a film thickness of 10 microns was applied on an aluminum plate in the same manner as in Example 1, and then Polyflon enamel EK
A film thickness of 2 was prepared in the same manner as in Example 1 using 1108GY or PTFE aqueous dispersion (solids content 41%).
A top coat of 0 micron was applied.

That is, Examples 13 to 17 and Comparative Example 7 use Polyflon Enamel EK1108GY containing an inorganic filler as a topcoat and undercoat coating composition,
Examples 18 to 20 and Comparative Example 8 used Polyflon Enamel EK-11080Y as the top coat composition and P containing no inorganic filler as the undercoat composition (first liquid).
A TFE aqueous deaqueous dispersion type is used.

In addition, Examples 13 to 20 are examples in which the coating film was fired at 380°C, and Comparative Examples 7 and 8 were fired at 380°C instead of firing.
This is an example in which drying was performed at 0° C. for 20 minutes.

Three paint test pieces were prepared for the same composition, one of which
One sheet was left as it was, and the other two sheets were immersed in hot water at 90° C. for 4 days and in hot lard oil at 260° C. for 15 hours, and then the coating properties were measured.

The results are shown in Table 3.

When baking was not carried out at a temperature higher than the melting point of PTFE as in Comparative Examples 7 and 8, the resulting coating film had extremely poor adhesion to the substrate, and moreover, a tough coating film was formed. When rubbed with a fingernail, the film easily came off in pieces.

Claims (1)

[Claims] 1(a) Fluororesin (b) General formula % Formula % [In the formula, R is a chlorine atom, an amino group, an aminoalkyl group,
an alkyl group having 1 to 10 carbon atoms and having at least one functional atom or group selected from a ureido group, a glycidoxy group, an epoxycyclohexyl group, an acryloyloxy group, a methacryloyloxy group, a mercapto group, and a vinyl group, or The vinyl group, R1 and R2 are each a chlorine atom, a hydroxyl group, an alkoxy group having 1 to 10 carbon atoms, an alkoxy-substituted alkoxy group having 2 to 15 carbon atoms, and a 2 to 15 carbon atoms
4 hydroxyalkyloxy groups and 2 to 15 carbon atoms
an atom or group selected from acyloxy groups, y is 0.
Indicates an integer of 1 or 2. ] A silane compound represented by A fluororesin coating composition comprising (c) at least one of an organic acid, an inorganic acid, an amine, ammonia, and an inorganic oxide, and (d) a liquid carrier.