JP2008179719A - Coating material composition and method for forming film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To more stably disperse and dissolve a fluorine atom-containing polymer having an ether bond in a molecule, a polysiloxane having a polyether structure, the fluorine atom-containing polymer, and a crosslinking agent of the fluorine atom-containing polymer. The object is to obtain a coating composition.
A fluorine atom-containing polymer having an ether group in a molecule, a polysiloxane having a polyether structure, a cross-linking agent for the fluororubber polymer, a ketone-based or ester-based solvent, and an alcohol. The coating composition characterized by the above-mentioned.
[Selection figure] None

Description

  The present invention relates to a coating composition for obtaining a film in which polysiloxane is finely dispersed in a fluororubber matrix and a film forming method using the same.

A film made of fluororubber is excellent in heat resistance and mechanical strength in addition to excellent flexibility, and is therefore used for exterior coating of articles in various fields.
Since the fluororubber has a very high viscosity even before being crosslinked, it is necessary to prepare a coating material in which the fluororubber before crosslinking is dissolved in a solvent for film formation. Here, as the solvent, a ketone-based or ester-based solvent is known (see Non-Patent Document 1).
“Fluorine Resin Handbook” Nikkan Kogyo, p. 591 (1.4.7 Coating)

  The inventors of the present invention have made various studies in order to improve the surface characteristics of the above-described film made of fluororubber. As a result, by dispersing polysiloxane in the fluororubber matrix finely, a film having a surface property capable of uniformly holding an oily substance such as wax on the surface while maintaining the original flexibility of the fluororubber. Successfully developed.

  Such a film can be obtained by crosslinking a coating film of a paint containing a fluorine atom-containing polymer having an ether bond in the molecule, a polysiloxane having a polyether structure, and a crosslinking agent for the fluorine atom-containing polymer. The film thus obtained has a structure in which polysiloxane having a polyether structure is uniformly dispersed in a fine island shape in a fluororubber matrix having an ether bond. Such a film is uniformly dispersed in the surface of the oily substance due to the polysiloxane finely dispersed in the fluororubber matrix and having a high affinity with the oily substance. Moreover, it has excellent flexibility by including fluororubber. Such a film is considered to be applicable to, for example, a film for rust prevention or a film for exterior materials having excellent antifouling properties.

  The present inventors have described the above non-solvent as a solvent for preparing a paint containing a fluorine atom-containing polymer having an ether bond in the molecule, a polysiloxane having a polyether structure, and the fluorine atom-containing polymer. Based on Patent Document 1, methyl isobutyl ketone was used.

  A coating film of a paint obtained using such a solvent is formed on a substrate by a spray coating method, and the coating film is cross-linked to obtain a polymer having a polyether structure in a fluororubber matrix having an ether bond. A film having a structure in which siloxane is uniformly dispersed in fine islands can be obtained. However, when a method such as a dipping method is employed as a coating method, a film having a structure in which polysiloxane is finely dispersed in a fluororubber matrix may not always be obtained. This is presumed that the instability of the dissolved state or the dispersed state of each component of the coating material was manifested by adopting the dipping method in which the drying of the coating film was slower than the coating film by the spray method.

  Therefore, even when a dipping method or the like having a higher paint utilization efficiency than the spray coating method is adopted, a film having a structure in which polysiloxane is uniformly dispersed in a fine island shape in the fluororubber matrix can be obtained. It came to the recognition that it is necessary to obtain such a coating composition excellent in stability.

  Therefore, an object of the present invention is to more stably disperse a fluorine atom-containing polymer having an ether bond in the molecule, a polysiloxane having a polyether structure, the fluorine atom-containing polymer, and a crosslinking agent of the fluorine atom-containing polymer. In the point which obtains the coating composition which is melt | dissolving.

  Another object of the present invention is to form a film having a structure in which polysiloxane having a polyether structure is uniformly dispersed in a fine island shape in a fluororubber matrix having an ether bond, regardless of the coating method. It is in the point of obtaining the film formation method which can be performed.

The coating composition according to the present invention is:
(1) a fluorine atom-containing polymer having an ether group in the molecule;
(2) a polysiloxane having a polyether structure;
(3) a crosslinking agent for the fluororubber polymer;
(4) a ketone-based or ester-based solvent;
(5) It contains alcohol.

  A film forming method in which polysiloxane is dispersed in islands in a fluororubber matrix according to the present invention includes a step of forming a coating film of the coating composition on the surface of a substrate, and the coating method. And a step of cross-linking the fluororubber polymer in the film.

  According to the present invention, the components (1) to (3), which are constituents of the membrane, are stable in dispersion and dissolution, and each of the components (1) to (3) is phase-separated even when left for a long time. It is possible to obtain a coating composition that is difficult to perform.

  Although the detailed mechanism by which this effect is obtained by the present invention is still being elucidated, phase separation is difficult due to the interaction of the ether part of the fluorine atom-containing polymer, the ether part of the polysiloxane, and the hydroxyl group of the alcohol. It is thought that a coating composition is obtained. For example, these components are phase-separated only with a ketone-based or ester-based solvent having no hydroxyl group.

<About a film in which polysiloxane is dispersed in an island shape in a fluororubber matrix>
The film | membrane concerning this invention contains the fluororubber which has an ether bond, and the polysiloxane which has a polyether structure.

  A film made of fluororubber generally has low affinity with oily substances such as wax. As a means for improving the affinity of the film surface with the oily substance, a method of dispersing polysiloxane (dimethylpolysiloxane or the like) having a relatively high affinity with the oily substance in the fluororubber can be considered.

  However, since the fluororubber and polysiloxane have low affinity, their dispersion state tends to be non-uniform. In this case, the adhesion of the oily substance to the film surface tends to be non-uniform.

  On the other hand, by cross-linking a coating film of a coating containing a fluorine atom-containing polymer having an ether bond in the molecule and a polysiloxane having a polyether bond, a surface layer having a structure in which polysiloxane is finely dispersed in a fluororubber matrix Can be obtained. That is, a fluorine atom-containing polymer having an ether bond in the molecule and capable of crosslinking is used as a raw material for fluororubber. At the same time, polysiloxane having a polyether structure is used as polysiloxane. When these coexist in the paint of the present invention, the fluorine atom-containing polymer and the polysiloxane are excellent in affinity, and the polysiloxane can be finely dispersed in the fluorine atom-containing polymer.

  When such a paint film is crosslinked, a film having a structure in which fluorosiloxane having an ether bond is used as a matrix and polysiloxane having an ether structure is uniformly finely dispersed in an island shape in the matrix is obtained. Can do.

  An oily substance can be uniformly attached to the surface of such a film.

  Here, the average particle diameter based on the number of island portions made of polysiloxane in the surface layer is preferably 0.1 μm or more and 2.0 μm or less. This is because the oily substance can be uniformly and reliably held on the surface of the surface layer.

  In the present invention, the average particle size of the island portion can be measured using an electron microscope or a video microscope. Randomly select 20 islands and measure the major axis of the islands. Among the measured values, an average value of 14 measured values obtained by removing three values from the largest side value and the smallest side is defined as the average particle size of the island portion.

<About paint composition>
Next, the coating composition according to the present invention which gives the film as described above will be described.
The coating composition according to the present invention includes the following (1) to (5).
(1) a fluorine atom-containing polymer having an ether group in the molecule;
(2) polysiloxane having a polyether structure;
(3) a crosslinking agent for the fluororubber polymer;
(4) a ketone-based or ester-based solvent; and
(5) Alcohol.

The materials (1) to (5) will be sequentially described below.
(1) a fluorine atom-containing polymer;
As an example of the raw material of the fluororubber constituting the surface layer, there can be mentioned a fluorine atom-containing polymer having an ether bond in the molecule, which can be crosslinked. Specific examples include terpolymers of vinylidene fluoride having an ether group, tetrafluoroethylene and perfluoroalkyl vinyl ether.

  Such a terpolymer can be synthesized by a known method using, for example, vinylidene fluoride containing iodine or bromine in the molecule, tetrafluoroethylene, and perfluoromethyl vinyl ether. Examples of the known method include block, vinylidene fluoride, tetrafluoroethylene, perfluoromethyl vinyl ether which is a component of a copolymer, and a monomer having iodine or bromine which is a crosslinking site, There are known polymerization methods such as emulsion polymerization.

  Such terpolymers are commercially available. For example, Daikin Industries, Ltd. is marketed under the trade name “DAIEL LT-302”. DuPont Dow Elastomer Japan Co., Ltd. has trade names “Viton GLT”, “Viton GLT-305”, “Viton GLT-505”, “Viton GFLT”, “Viton GFLT-300”, “Viton GFLT-301”. "Viton GFLT-501" and "Viton GFLT-600".

(2) polysiloxane;
The polysiloxane preferably has a dialkylpolysiloxane structure as a hydrophobic group, more preferably a dimethylpolysiloxane structure. The hydrophilic group is preferably a nonionic surfactant having a polyether structure, more preferably a polyoxyalkylene structure.
The polysiloxane surfactant can be classified mainly into three types of structures by taking dimethylpolysiloxane as an example.

That is,
A side chain-modified type having a structure in which polyoxyalkylene is bonded to a side chain of a dimethylpolysiloxane skeleton represented by the following formula (1):
A terminal-modified type having a structure in which polyoxyalkylene is bonded to the terminal of a dimethylpolysiloxane skeleton represented by the following formula (2), and dimethylpolysiloxane and polyoxyalkylene represented by the following formula (3) are alternately repeated. It is a copolymer type consisting of a bonded structure. In particular, the copolymer type represented by the following formula (3) is more preferable in that the dispersibility with respect to the fluororubber is most excellent.

（上記式（１）〜（３）中、ａ及びｂは０または整数であり、ｎ及びｍは整数であり、Ｒ及びＲ´は飽和炭化水素鎖または不飽和炭化水素鎖である）。

(In the above formulas (1) to (3), a and b are 0 or an integer, n and m are integers, and R and R ′ are a saturated hydrocarbon chain or an unsaturated hydrocarbon chain).

  As a compounding quantity of polysiloxane, it is preferable that it is 20-60 mass parts with respect to 100 mass parts of fluororubber, especially 40-60 mass parts. By using within the above range, the effect of improving the lipophilicity can be sufficiently obtained, and the mechanical strength of the fluororubber can be maintained in a favorable range.

  The polysiloxane having a polyether structure is not particularly limited, but a copolymer type of dimethylpolysiloxane and polyalkylene oxide is preferable.

(3) a crosslinking agent;
The aforementioned fluorine atom-containing polymer and polysiloxane have a structure in which polysiloxane having a polyether structure is finely dispersed in a fluororubber matrix as a result of the crosslinking reaction of the fluorine atom-containing polymer. Furthermore, it has a structure in which at least a part of the polysiloxane is fixed to the fluororubber.

  Here, as a crosslinking agent used for crosslinking, an organic peroxide is preferable. When crosslinked with an organic peroxide, the mixture of the fluororubber and the polysiloxane surfactant having a polyether structure can be effectively crosslinked.

  That is, most of the blended silicone surfactant can be reacted with the fluororubber and fixed in the fluororubber matrix. Therefore, the durability of the toner releasability on the surface layer can be further improved.

Examples of such crosslinkers include the following:
・ Benzoyl peroxide;
-Bis (2,4-dichlorobenzoyl) peroxide;
・ Dicumyl peroxide;
2,5-dimethyl-2,5-di (t-butylperoxy) hexane.

  In particular, benzoyl peroxide having a low evaporation loss at room temperature and a low decomposition temperature is preferable.

In addition, the use of a crosslinking agent other than the above is not excluded.
When the fluorine atom-containing polymer has iodine or bromine at the molecular chain terminal or side chain, crosslinking with an organic peroxide includes an extraction reaction of iodine or bromine atoms and a radical reaction to the allyl group of the crosslinking aid. It will be performed more efficiently.

Therefore, when using the organic peroxide as a crosslinking agent, it is preferable to use triallyl cyanurate, triallyl isocyanurate, or the like as a crosslinking aid.
Triaryl isocyanurate is particularly preferable from the viewpoint of crosslinking efficiency.

  When the polysiloxane having a polyether structure has a vinyl group or an allyl group as a reactive group, the crosslinking with the organic peroxide is performed by a radical reaction to the vinyl group or the allyl group.

(4) ketone-based or ester-based solvents;
The ketone-based or ester-based solvent is preferably a good solvent for the crosslinking agent of the fluorine atom-containing polymer (1) and the fluororubber polymer (3). Specific examples include acetone, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, butyl acetate, and isobutyl acetate.

(5) alcohol;
As the alcohol, an alcohol which is excellent in compatibility with the above (4) and is a good solvent of the above (1) is preferably used. Specifically, methanol can be mentioned, for example.

Moreover, as a preferable blending ratio of each of the above components,
For 100 parts by mass of the fluorine atom-containing polymer (1) above,
100 parts by weight or more and 300 parts by weight or less of the alcohol of (5) above,
40 parts by weight or more and 60 parts by weight or less of the polysiloxane (2) above,
The ketone or ester solvent of the above (4) may be 1/10 or more and 3/10 or less by mass ratio (total amount of ketone or ester solvent / alcohol) to the alcohol of (5). preferable.

Thereby, the coating composition which is excellent in stability and suitable for coating can be obtained.
The stability of the coating composition according to the present invention is considered to be achieved by the interaction between the ether moiety of the fluorine atom-containing polymer, the ether moiety of the polysiloxane surfactant, and the hydroxyl group of the alcohol.

  And according to the said composition, it is thought that the balance of each component is good and the effect | action of stabilization becomes large.

<Method for forming a film in which polysiloxane is dispersed in an island shape in a fluororubber matrix>
As a method for forming a film in which polysiloxane is dispersed in islands in a fluororubber matrix according to the present invention, a step of forming a coating film of the coating composition on the surface of the substrate, Cross-linking the fluororubber polymer.

  The method for forming the coating film on the substrate is not particularly limited, and examples thereof include known methods such as spray coating, cast coating, slit coating, die coating, roll coating, knife coating, dip coating, and spin coating. It can be illustrated. In particular, coating methods such as cast coating, slit coating, die coating, roll coating, knife coating, dip coating, and spin coating tend to be slower in drying the coating film than spray coating. Therefore, when phase separation of each component occurs in the coating film in the drying process, it may be difficult to form a film having uniform surface characteristics. However, the coating composition according to the present invention is excellent in stability, and phase separation of each component hardly occurs even after standing for a long time. Therefore, a film with excellent uniformity in which polysiloxane is finely dispersed in the fluororubber matrix can be obtained even when a coating method in which the coating film is slowly dried is employed or when the coating film is thick. Therefore, the method for drying the coating film is not particularly limited. Well-known methods, such as natural drying, ventilation drying, and heat drying, can be illustrated.

  Although the thickness of a coating film can be suitably adjusted as needed, it is 1 micrometer or more and 1 mm or less normally. Further, as a method for performing the peroxide crosslinking reaction after drying the coating film, a known means can be used, but a means for carrying out the crosslinking reaction by heating in a nitrogen purged inert gas oven is preferable. . The crosslinking conditions are 100 ° C. or more and 200 ° C. or less and 30 minutes or more and 30 hours or less.

  Furthermore, the base material is not particularly limited, and examples thereof include metals such as SUS, plastics, glass, concrete, and wood.

(Example 1)
The following (1) and the following (5) were mixed and mixed using a mix rotor (trade name: MR-5; manufactured by ASONE Co., Ltd.) to obtain a mixture thereof.
(1) Fluorine atom-containing polymer (ternary copolymer of vinylidene fluoride, tetrafluoroethylene and perfluoromethyl vinyl ether (trade name: Daiel LT-302, manufactured by Daikin Industries, Ltd.))
: 100 parts by mass
(5) Methanol: 100 parts by mass The following (2) to (4) and (6) were added to the above mixture and mixed again with a mix rotor to obtain a coating composition.
(2) Polysiloxane surfactant having a dimethylpolysiloxane structure and a structure containing polyoxyalkylene (trade name: FZ2207; manufactured by Toray Dow Corning Co., Ltd.): 40 parts by mass,
(3) Benzoyl peroxide (25% water-containing product, manufactured by Kishida Chemical Co., Ltd.): 4 parts by mass
(4) Methyl isobutyl ketone: 10 parts by mass (6) Triallyl isocyanurate (crosslinking aid) (trade name: TAIC; manufactured by Nippon Kasei Co., Ltd.): 4 parts by mass

(Example 2 to Example 5)
The coating composition concerning each Example was prepared like Example 1 except having changed the compounding quantity of each structural component of the coating composition concerning Example 1 as shown in the following Table 1.

(Comparative Examples 1-3)
A coating composition according to each comparative example was prepared in the same manner as in Example 1 except that the amount of each constituent component of the coating composition according to Example 1 was changed as shown in Table 1 below.

  The coating compositions according to Examples 1 to 5 and Comparative Examples 1 to 3 were allowed to stand at room temperature for 6 hours, and the state of the coating composition was visually observed. The results are shown in Table 1 below.

  This result shows that the coating composition concerning Examples 1-5 has shown sufficient stability. On the other hand, in the coating compositions according to Comparative Example 1 and Comparative Example 2, phase separation of the constituent components was observed when the amount of methanol was too small or too large.

  In Comparative Example 3, since methyl isobutyl ketone was not blended, the crosslinking agent was precipitated, and the stability as a coating was insufficient.

  Further, the coating compositions of Examples 1 to 4 were left for 24 hours and visually observed for the state of the coating composition. As a result, phase separation of these coating compositions was not confirmed even after 24 hours. From this, it was confirmed that the coating composition which concerns on Examples 1-4 has very favorable stability.

  Next, the coating composition according to Example 1 was cast-coated on a slide glass so as to have a thickness of about 500 μm, and air-dried at room temperature. Then, it is put into an inert gas oven (trade name: INL-60; manufactured by Koyo Thermo System Co., Ltd.), purged with nitrogen gas at a flow rate of 90 L / min, heated to 200 ° C. after 15 minutes, and heated at 200 ° C. for 1 hour. Hold and take out after cooling. Subsequently, it heated at 180 degreeC for 24 hours in normal hot-air oven, and the fluorine atom containing polymer was bridge | crosslinked. The surface of the coat film was observed at a magnification of 2000 using a video microscope (trade name: VH200, manufactured by Keyence Corporation). As a result, an aggregation state larger than at least 1 μm was not confirmed, and it was confirmed that the island portion of the polysiloxane dispersed in an island shape in the fluororubber matrix had an average particle diameter of 1 μm or less.

  On the other hand, a film was formed in the same manner as described above using the coating composition according to Comparative Example 1 that was not phase-separated. As a result, an aggregated state having a size of about 10 to 100 μm was confirmed, and the particle size of the island portion made of polysiloxane in the obtained film varied widely. This is considered to be due to the result of phase separation in the drying process of the coating film of the coating composition.

Claims (6)

(1) a fluorine atom-containing polymer having an ether group in the molecule;
(2) a polysiloxane having a polyether structure;
(3) a crosslinking agent for the fluororubber polymer;
(4) a ketone-based or ester-based solvent;
(5) A coating composition comprising alcohol. The fluorine atom-containing polymer is a terpolymer of vinylidene fluoride, tetrafluoroethylene and perfluoromethyl vinyl ether,
The coating composition according to claim 1, wherein the polysiloxane includes a dimethylpolysiloxane structure and a polyoxyalkylene structure, and the crosslinking agent crosslinks the fluororubber polymer by a peroxide crosslinking reaction.   The crosslinking agent is at least one selected from benzoyl peroxide, bis (2,4-dichlorobenzoyl) peroxide, dicumyl peroxide, and 2,5-dimethyl-2,5-di (t-butylperoxy) hexane. The coating composition according to claim 1 or 2, wherein The alcohol is methanol;
The coating composition according to any one of claims 1 to 3, wherein the ketone-based or ester-based solvent is at least one selected from acetone, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, butyl acetate, and isobutyl acetate. For 100 parts by mass of the fluorine atom-containing polymer,
100 parts by weight or more and 300 parts by weight or less of the alcohol,
40 parts by mass or more and 60 parts by mass or less of the polysiloxane, and the mass ratio of the ketone-based or ester-based solvent to the alcohol (total amount of the ketone-based or ester-based solvent / alcohol) is 1/10 or more. The coating composition according to any one of claims 1 to 4, which is 3/10 or less.   A step of forming a coating film of the coating composition according to any one of claims 1 to 5 on a substrate surface, and a step of crosslinking a fluororubber polymer in the coating film, A method of forming a film in which polysiloxane is dispersed in an island shape in a fluororubber matrix.