JPH07268275A - Water-based coating material comprising core/shell fluorocopolymer and production of the same copolymer dispersed in aqueous medium - Google Patents

Abstract

PURPOSE:To obtain a water-based coating material excellent in film-forming properties, water resistance and staining resistance by dispersing a specified core/shell fluorocopolymer in an aqueous medium. CONSTITUTION:The material is prepared by dispersing in an aqueous medium a core/shell fluorocopolymer having a core/shell weight ratio of 20/1 to 1/2 and a two-layer structure composed of a core comprising a fluorocopolymer mainly consisting of repeating units derived from a fluoroolefin monomer and repeating units derived from a vinyl carboxylate monomer and having a Tg of 40 deg.C or above and a shell comprising a fluorocopolymer mainly consisting of repeating units derived from a fluoroolefin monomer and repeating units derived from a vinyl carboxylate monomer and having a Tg of 5-30 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-dispersible coating composition comprising a fluorine-containing copolymer and a method for producing a water-dispersible fluorine-containing copolymer, which is excellent in water resistance and stain resistance and has a wide range of applications. And a water-dispersible coating which is particularly useful as a substitute for an organic solvent-based fluororesin coating, and a method for efficiently producing a fluorine-containing copolymer useful in the resin content of the coating and other fields. is there.

[0002]

2. Description of the Related Art Organic solvent-based paints have problems such as air pollution due to organic solvents and harmfulness to the human body. Therefore, recently, water-based paints replacing organic solvent-based paints have been demanded. There is. As a typical example of water-based paint, there is a water-based emulsion paint by water-based emulsion polymerization,
Regarding the fluororesin paint, many proposals have been made regarding an aqueous resin dispersion that can be used as an aqueous emulsion paint.

That is, JP-A-2-225550 proposes an aqueous resin dispersion obtained by emulsion polymerization of a fluoroolefin, a vinyl monomer having a polyoxyethylene group and a hydroxyl group-containing monomer. JP-A-3-33148 proposes a method for producing an aqueous dispersion of a fluorinated copolymer by an emulsion polymerization method using a reactive emulsifier capable of copolymerizing with a monomer such as a fluoroolefin. In the invention described in the above publication, in order to solve the problem of poor water resistance of a coating film common to water-based paints, a technical means for stably performing emulsion polymerization without using an emulsifier, or a polymer emulsion. A technical means of copolymerizing the emulsifier at the time of polymerization is adopted so that the low molecular weight emulsifier does not remain therein.

As described above, the conventional studies on the fluororesin-based water-based emulsion paint have been to avoid leaving the emulsifier as much as possible in the emulsion. However, the aqueous dispersion of the fluorocopolymer according to the invention described in the above publication is still inferior in film-forming property and water resistance as compared with the organic solvent type fluororesin coating material, and there is a limitation in use.

An object of the present invention is to provide an aqueous coating composition having a fluorine-containing copolymer dispersed in an aqueous medium, which has excellent film-forming properties, water resistance and stain resistance, and a technique for producing the fluorine-containing copolymer. .

[0006]

Means for Solving the Problems As a result of intensive studies for solving the above problems, the present inventors have found that a core layer formed of a fluorocopolymer having a specific glass transition temperature (hereinafter referred to as Tg). It was found that a core / shell type fluorinated copolymer comprising a shell layer and a shell layer can easily provide an aqueous dispersion of the fluorinated copolymer having excellent film-forming properties and water resistance, and completed the present invention. It was

The gist of the present invention is as set forth in the claims, and the present invention will be described in more detail below.

In the present invention, as described above, the core /
A shell type fluorine-containing copolymer is used. The core / shell type polymer is a polymer having a two-layer structure synthesized by two-step emulsion polymerization, as is well known in, for example, an aqueous emulsion of an alkyl acrylate copolymer system. The core / shell type fluorinated copolymer in the present invention comprises a core made of a fluorinated copolymer mainly composed of a fluoroolefin monomer unit and a vinyl carboxylate monomer unit, and a similar monomer unit. Main component is Tg (glass transition temperature)
Is composed of a shell made of a fluorinated copolymer having a Tg lower than that of the core. Preferred T of each fluorine-containing copolymer
g has a core portion of 40 ° C. or higher and a shell portion of 5 to 30 ° C.

The essential monomers constituting the fluorine-containing copolymer of the core portion and the shell portion are fluoroolefin and vinyl carboxylate, and hydrophilic vinyl monomer or other copolymerizable monomers can be added to these, if desired. The monomers are copolymerized. First, examples of fluoroolefins include chlorotrifluoroethylene, tetrafluoroethylene, and hexafluoropropylene. Next, the vinyl carboxylate is preferably a vinyl ester of a linear aliphatic carboxylic acid having 2 to 18 carbon atoms, specifically, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl caproate, vinyl caprylate, Examples thereof include vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate and vinyl stearate.

Further preferred vinyl carboxylate is a vinyl ester composed of a linear aliphatic carboxylic acid having 3 to 8 carbon atoms, and vinyl propionate and vinyl caproate are particularly preferred.

Vinyl monomers of branched carboxylic acids having 4 to 15 carbon atoms are also suitable monomers, and specific examples thereof include vinyl isobutyrate, vinyl pivalate, vinyl 2-ethylhexanoate and carbon. Examples thereof include vinyl versatate having 9 carbon atoms and vinyl versatate having 10 carbon atoms. Vinyl pivalate and vinyl versatate are more preferable, and vinyl versatate is most preferable, from the viewpoint of effectively increasing the Tg of the fluorine-containing copolymer.

As the hydrophilic vinyl monomer, a monomer having a hydrophilic group such as a carboxylic acid group, a sulfonic acid group, a hydroxyl group or an amino group and having an olefinically unsaturated double bond is used. Specific examples of the monomer having a carboxylic acid group include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, vinylacetic acid and salts thereof. Examples of the monomer having a sulfonic acid group include vinyl sulfonic acid, styrene sulfonic acid, allyl sulfonic acid, and 2 acrylamido 2-methylpropane sulfonic acid. A reactive emulsifier having a sulfonic acid group can also be used, and as commercially available products that can be used, for example, Latemur S-180 series (manufactured by Kao Corporation), Aqualon HS series (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), Eleminor JS-2 (Manufactured by Sanyo Kasei Co., Ltd.), which may be used as a salt with ammonia, amine, metal ion or the like. Examples of the monomer having a hydroxyl group include hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxybutyl methacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, hydroxybutyl vinyl ether, hydroxyethyl allyl ether, hydroxyethyl crotonate, N-methylol acrylamide. Are exemplified. Examples of the monomer having an amino group include methacrylamide, acrylamide, diethylaminoethyl methacrylate, dimethylaminoethyl acrylate,
Aminopropyl vinyl ether and the like are exemplified. From the viewpoint of stability of the aqueous dispersion of the fluorine-containing copolymer, a monomer containing a carboxylic acid or a sulfonic acid is preferable, more preferably acrylic acid, methacrylic acid, 2-acrylamido-2-methylpropanesulfonic acid or a salt thereof. is there.

In the present invention, the other monomers to be optionally copolymerized are halogenated olefins such as vinylidene fluoride, vinyl fluoride, vinylidene chloride and vinyl chloride, and α such as ethylene, propylene and isobutylene. Olefins, vinyl ethers such as ethyl vinyl ether, butyl vinyl ether, methyl (meth) acrylate, cyclohexyl (meth) acrylate, (meth) acrylates such as diethylene glycol mono (meth) acrylate, allyl acetate, allyl butyrate, ethyl allyl ether, etc. Examples include allyl compounds and styrene. Preferred monomers are α-olefins and (meth) acrylates.

The preferred proportion of each monomer unit in the fluorinated copolymer is 30-60 mol% of fluoroolefin and 2 to 18 carbon atoms in the core portion based on the total amount of all the monomers. Vinyl ester of chain carboxylic acid 0
˜30 mol%, vinyl ester of branched carboxylic acid having 4 to 15 carbon atoms 20 to 60 mol%, hydrophilic vinyl monomer 0.01 to 5 mol%, and other copolymerizable monomer 0 to It is 30 mol%. On the other hand, in the shell portion, the fluoroolefin is 30 to 60 mol% and the carbon number is 2 to 18
20 to 60 mol% of linear carboxylic acid vinyl ester, 0 to 20 mol% of branched carboxylic acid vinyl ester having 4 to 15 carbon atoms, and hydrophilic vinyl monomer 0.01 to 5
Mol% and 0 to 30 mol% of other copolymerizable monomers.

A more preferable copolymerization ratio is 40 to 55 mol% of fluoroolefin in the core portion, and 0 to 1 of vinyl ester of linear carboxylic acid having 2 to 18 carbon atoms.
5 mol%, 35 to 50 mol% of vinyl ester of branched carboxylic acid having 4 to 15 carbon atoms, 0.1 to 3 mol% of hydrophilic vinyl monomer, and 0 to other copolymerizable monomers It is 20 mol%. In the shell portion, 40 to 55 mol% of fluoroolefin, 35 to 50 mol% of vinyl ester of linear carboxylic acid having 2 to 18 carbon atoms,
Vinyl ester of branched carboxylic acid having 4 to 15 carbon atoms 0 to 15 mol%, hydrophilic vinyl monomer 0.1 to 3 mol%
And 0 to 20 mol% of other copolymerizable monomers.

In the fluorine-containing copolymer in the core part, if the amount of fluoroolefin units is too large, the stability of the aqueous dispersion is lowered, and if it is too small, the weather resistance is lowered and the carbon number is 2-18.
When the amount of the vinyl ester unit of the linear carboxylic acid is too large, the Tg and stain resistance of the copolymer decrease. Further, if the number of vinyl ester units of a branched carboxylic acid having 4 to 15 carbon atoms is too large, the coating becomes brittle, and if it is too small, the T of the copolymer is reduced.
If the amount of hydrophilic vinyl monomer units is large, the hydrophilicity is high and the water resistance of the coating film is low, and if it is low, the stability of the dispersion is low during polymerization.

In the fluorine-containing copolymer of the shell part, if the amount of the fluoroolefin unit is too large, the stability of the aqueous dispersion is lowered, and if it is too small, the weather resistance is lowered. 2 to 1 carbon atoms
When the amount of the vinyl ester unit of the linear carboxylic acid of 8 is too large, the Tg and stain resistance of the copolymer are lowered, and when it is too small, the film-forming property during coating is lowered. If there are too many vinyl ester units of a branched carboxylic acid having 4 to 15 carbon atoms, the film-forming property at the time of coating is deteriorated. Further, if the hydrophilic vinyl monomer unit is large, the hydrophilicity becomes large and the water resistance of the coating film is lowered, and if it is small, the stability of the dispersion during polymerization is lowered.

In the core / shell type fluorinated copolymer of the present invention, there is no means for quantitatively analyzing only the fluorinated copolymer in the shell part to confirm the composition ratio of the constituent monomer units. In the present invention, the amount of the core portion fluorine-containing copolymer to be subjected to the second-stage polymerization step and the composition ratio of the constituent monomer units, and the core / shell type fluorine-containing copolymer weight obtained in the same step The value calculated from the combined amount and the composition ratio of the constituent monomer units is the composition ratio of the constituent monomer units of the fluorine-containing copolymer in the shell part.

The Tg of the fluorine-containing copolymer in the core part is preferably 40 ° C. or higher, more preferably 50 ° C. or higher. Four
If the temperature is lower than 0 ° C, the effect on the stain resistance of the core part is reduced, the coating film is softened at high temperature in summer, and the adherence of contaminants is increased. On the other hand, Tg of the fluorine-containing copolymer in the shell part is preferably 5 to 30 ° C, more preferably 20 ° C or less. If it is higher than 30 ° C, the film-forming property is lowered. Tg is 5
Sufficient stain resistance cannot be expected unless the temperature is above ℃.

Examples of the types and ratios of the constituent monomer units and Tg in the fluorine-containing copolymer are as follows. In the following, CTFE is an abbreviation for chlorotrifluoroethylene, which is one type of fluoroolefin monomer, and the proportion of each monomer unit is mol%.

Fluorine-containing copolymer having Tg of 40 ° C. or higher suitable for the core part: CTFE / vinyl versatic acid / acrylic acid = 48.
5 / 48.5 / 3 (Tg = 67 ° C.) CTFE / vinyl pivalate / acrylic acid = 48.5 /
48.5 / 3 (Tg = 69 ° C.) CTFE / vinyl benzoate / acrylic acid = 48.5 / 4
8.5 / 3 (Tg = 64 ° C.) CTFE / vinyl cyclohexylcarboxylate / acrylic acid = 48.5 / 48.5 / 3
(Tg = 54 ° C.) CTFE / vinyl versatic acid / vinyl caproate /
Acrylic acid = 48.5 / 36.4 / 12.1 / 3
(Tg = 52 ° C.) CTFE / vinyl versatic acid / vinyl laurate /
Acrylic acid = 48.5 / 42.5 / 6.0 / 3
(Tg = 46 ° C)

Fluorine-containing copolymer having a Tg of 5 to 30 ° C. suitable for the shell part: CTFE / vinyl caproate / acrylic acid = 48.5 /
48.5 / 3 (Tg = 9 ° C.) CTFE / vinyl propionate / acrylic acid = 48.5
/48.5/3 (Tg = 22 ° C) CTFE / Vinyl caprylate / Vinyl versatic /
Acrylic acid = 48.5 / 24.2 / 24.3 / 3
(Tg = 11 ° C.) CTFE / vinyl isobutyrate / acrylic acid = 48.5 / 4
8.5 / 3 (Tg = 16 ° C) CTFE / vinyl caproate / vinyl versatic acid /
Acrylic acid = 48.5 / 36.4 / 12.1 / 3
(Tg = 23 ° C.) CTFE / vinyl laurate / vinyl versatate /
Acrylic acid = 48.5 / 19.4 / 29.1 / 3
(Tg = 9 ° C)

In the core / shell type fluorine-containing copolymer of the present invention, the weight ratio of core / shell is 20/1 to 1 /.
2 is preferable and 10/1 to 2/3 is more preferable. If the ratio of the shell portion is too small, the film-forming property at the time of coating is deteriorated, and if it is too large, the stain resistance is deteriorated.

A preferred method for producing the fluorine-containing copolymer of the present invention is a two-stage seed emulsion copolymerization in the presence of a radical-generating type polymerization initiator. As the emulsifier, an anionic emulsifier and a nonionic emulsifier are used. Combined use is preferred.

Examples of the anionic emulsifier include potassium and ammonium salts of perfluorooctanoic acid,
Fluorine-based anionic emulsifiers such as sodium and ammonium salts of perfluorooctane sulfonic acid, ammonium lauryl sulfate, sodium dodecylbenzene sulfonate, sodium alkylnaphthalene sulfonate, sodium dialkyl sulfosuccinate, sodium polyoxyethylene alkyl ether sulfate, sodium alkane sulfonate Hydrocarbon-based anionic emulsifiers such as Among these, a fluorinated anionic emulsifier is preferable from the viewpoint of the fineness of the particle size of the obtained aqueous dispersion.

As the nonionic emulsifier, polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene alkyl allyl ether, polyoxyethylene sorbitan fatty acid ester,
Polyoxyethylene sorbitol fatty acid ester, glycerin fatty acid ester, polyoxyethylene fatty acid ester, etc. are hydrocarbon type nonionic emulsifiers, perfluoroalkylethylene oxide adducts, monohydropolyfluoroalkylethylene oxide adducts, etc. fluorine type nonionic emulsifiers, aqualon A reactive emulsifier such as RN series (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) can be used. Among the above, hydrocarbon nonionic emulsifiers are preferable, and polyoxyethylene alkyl ether and / or polyoxyethylene alkylphenyl ether are particularly preferable, from the viewpoint of fineness of the particle diameter of the aqueous dispersion and cost. The above-mentioned emulsifier is mainly used in the first stage polymerization step for the purpose of forming the core part, and in the second stage polymerization step for the purpose of obtaining the shell part, new emulsifier is not added or added. In this case, it is desirable to suppress the content of the particles of the copolymer so that they are not newly formed.

The radical-generating type polymerization initiator is used in each of the first and second stage polymerization steps. For example, diisopropyl peroxydicarbonate, tertiary butyl peroxypivalate, benzoyl peroxide, lauroyl peroxide, and succinate. Peroxides such as nick acid peroxide, or azo compounds such as azobisisobutyronitrile, azobisisovaleronitrile, azobisamidinopropane hydrochloride, ammonium persulfate,
Inorganic peroxides such as potassium persulfate can be used. When performing redox polymerization, it is preferable to use sodium bisulfite, sodium sulfite, rongalite, ascorbic acid, etc. in combination as a reducing agent.

Each of the first-stage and second-stage polymerization steps is carried out in an aqueous medium at a polymerization temperature of about 20 to 100 ° C. and a pressure of 1 to 200 kg / cm ² in a pressure-resistant autoclave for 3 to 40 hours. It can be carried out for the reaction time. All the monomers to be supplied to each step may be initially charged in a batch manner, or a part of the monomers or a pre-emulsion of the monomers and the emulsifier may be sequentially added as the polymerization proceeds. If necessary, a pH adjusting agent such as potassium carbonate, sodium hydrogen carbonate, ammonium hydrogen carbonate or disodium phosphate may be added. As the polymerization medium, in addition to water, a water-soluble or hydrophilic organic solvent may be used in combination with water according to a conventional method in this type of technical field.

When shifting from the first-stage polymerization step for obtaining the core part to the second-stage polymerization step for obtaining the shell part,
Once the emulsion is removed from the first stage polymerization step,
Re-polymerization may be carried out by adding the monomer in the second stage, or after confirming the completion of the reaction by detecting the consumption amount of the monomer in the first stage by gas chromatography or the like, A monomer may be charged and polymerized as it is. After the completion of the polymerization, usually, unreacted fluoroolefin monomer remains in the polymerization system, so that it is purged. At this time, it is preferable to carry out an operation of further substituting nitrogen and degassing under reduced pressure and allowing to stand, and repeat this operation until the internal pressure of the autoclave becomes stable at -500 mmHg or less. The purged unreacted fluoroolefin monomer can be recovered and subjected to polymerization again according to a conventional method.

In the present invention, the molecular weight of each fluorine-containing copolymer forming the core part and the shell part is GP.
The polystyrene-equivalent number average molecular weight of C is 1,000.
Is preferably up to 5,000,000, more preferably 5000
It is 0 to 1,000,000. When the molecular weight is lower than this, the resin becomes brittle, and when the molecular weight is higher, the film-forming property deteriorates.

When the core / shell type fluorine-containing copolymer according to the present invention is used as a coating material, pigments such as titanium oxide, iron oxide, phthalocyanine blue, benzidine yellow, quinacridone, etc., stainless powder and aluminum are added to the aqueous dispersion. Powders, metal powders such as bronze powder, pigment dispersants, ultraviolet absorbers, surface modifiers, thickeners, fungicides, rust preventives and film forming aids may be added.

The coating material thus obtained can be applied to a base material such as steel plate, stainless steel, aluminum, concrete, mortar, plastic and wood by a spray, brush, roll, bar coater or the like. Examples will be given below.
This will be specifically described.

[0033]

【Example】

Example 1 A first stage polymerization for obtaining a core part was performed. In a 2 liter autoclave equipped with a stirrer, 534 g of pure water, 7.7 g of perfluorooctanoic acid ammonium salt as an anionic emulsifier, and polyoxyethylene nonylphenyl ether Emulgen 910 and Emulgen 930 which are polyoxyethylene nonylphenyl ether as a nonionic emulsifier. 1 each
7.3 g, vinyl versatate as a monomer (vinyl ester of branched carboxylic acid having 9 carbon atoms, manufactured by Shell Chemical Co., Ltd., sold under the trade name of Veova 9)
319 g (hereinafter abbreviated as V-9), 7.4 g of acrylic acid (hereinafter abbreviated as AA), and 12.6 g of ammonium hydrogencarbonate as a pH adjusting agent were charged, and deaeration and nitrogen substitution were repeated 3 times, followed by deaeration. Then, 405 g of chlorotrifluoroethylene (hereinafter abbreviated as CTFE) was charged.
After the temperature was raised to 40 ° C. and well stirred for 1 hour, an aqueous solution of a polymerization initiator in which 3.4 g of ammonium persulfate was dissolved in 20 g of water and 0.64 g of sodium hydrogen sulfite were added to 1 part of water.
A reducing agent aqueous solution dissolved in 0 g was injected under pressure to initiate polymerization.
After that, both of them had the same concentration of the polymerization initiator solution as described above.
Polymerization was carried out for 8 hours by adding 7 g and 5.32 g of the reducing agent aqueous solution every 3 hours. Subsequently, unreacted CTFE was purged, nitrogen substitution and vacuum degassing were performed until the internal pressure of the autoclave reached −500 mmHg, and then the autoclave was opened to give a solid content of 49% (weight% when simply indicated as%). The same shall apply hereinafter) to obtain an aqueous dispersion of a fluorinated copolymer.

At this time, no aggregate of the aqueous dispersion of the fluorocopolymer was observed. The polymerization conversion rate of V-9 and AA by gas chromatography is 99% or more,
When the particle size of the dispersion was measured, the particle size distribution was monodisperse and the average particle size was 0.10 μm. A part of the obtained dispersion was put into methanol, washed and dried to obtain a copolymer for analysis. The polystyrene reduced number average molecular weight of this copolymer measured by GPC was 120,000, and the glass transition temperature (hereinafter Tg) was 68 ° C.
Moreover, when the fluorine content of this copolymer was analyzed, it was 1
It was 9.0%, and from ¹ H-NMR and ¹³ C-NMR, the composition of the constituent monomer units was CTFE / V-9 / AA.
= 48.6 / 48.5 / 2.9 (mol%).

Next, a second stage polymerization was carried out to obtain a shell part. Into a 1 liter autoclave equipped with a stirrer, 640 g of the above-prepared aqueous dispersion, 15 g of vinyl caproate (hereinafter abbreviated as VCp) and 0.15 g of AA as monomers were charged, and deaeration and nitrogen substitution were repeated 3 times. After degassing, 25 g of CTFE was charged. After heating up to 40 ° C. and stirring well for 1 hour, an aqueous solution of a polymerization initiator in which 1.0 g of ammonium persulfate was dissolved in 10 g of water and an aqueous solution of a reducing agent in which 0.38 g of sodium hydrogen sulfite were dissolved in 5 g of water were prepared. It was pressed in and the polymerization was started. Thereafter, an aqueous solution of a polymerization initiator in which 0.5 g of ammonium persulfate was dissolved in 5 g of water and an aqueous solution of a reducing agent in which 0.07 g of sodium hydrogen sulfite were dissolved in 5 g of water were added every 3 hours, and polymerization was performed for 8 hours. . Then, the unreacted CTFE was purged, and the internal pressure was -500 mmHg as in the case of the first stage polymerization.
After purging with nitrogen and degassing under reduced pressure, the autoclave was opened to obtain 683 g of an aqueous dispersion of a fluorocopolymer having a solid content of 50%. At this time, no aggregate of the fluorocopolymer aqueous dispersion was observed. The polymerization conversion rate of VCp and AA by gas chromatography is 99.
% Or more. When the particle size of the dispersion was measured, the particle size distribution was monodisperse, and the average particle size was 0.10 μ.

The particles of the core / shell type fluorinated copolymer obtained above were observed with a transmission electron microscope. As a result, the particle size distribution was monodisperse, as in the case of the fluorinated copolymer particles of the core. The particle size is uniform, and this core / shell type fluorine-containing copolymer has two Tg's as described later. From these facts, the particles of the fluorine-containing copolymer produced by the above-mentioned two-step polymerization method are the two types of different fluorine-containing copolymers obtained by carrying out the first-stage polymerization and the second-stage polymerization separately. It is clearly different from just a blend of particles.

The resulting core / shell type fluorinated copolymer had a polystyrene-equivalent number average molecular weight (hereinafter the same) of 120,000 as measured by GPC, a Tg of 68 ° C. and a small peak of 11 ° C. I confirmed one. As a result of analyzing the fluorine content of this core / shell type fluorine-containing copolymer, it was 19.0%, and ¹ H-NMR and ¹³ C-
From NMR, the composition of the constituent monomer units is CTFE / VC
p / V-9 / AA = 48.8 / 4.5 / 44.0 / 2.
It was 7 (mol%). From the results of the amount of the aqueous dispersion, the solid content concentration, and the composition analysis of the copolymer obtained in the above first-stage polymerization and second-stage polymerization, the core / shell ratio was 1
It is 0/1 (weight ratio), and the composition of the constituent monomer units of the fluorine-containing copolymer of the shell part is CTFE / VCp / A.
A was 50.8 / 48.2 / 1.0 (mol%).

The stability of the core / shell type fluorine-containing copolymer aqueous dispersion obtained above was evaluated as follows.
The method for evaluating the stability of the aqueous dispersion in each of the following examples is also the same. Mechanical stability: 100 g of the aqueous dispersion was stirred with a homodisper at 5000 rpm for 5 minutes, and the amount of aggregation after standing for 1 day was measured. Chemical stability: 1 g of calcium chloride in 10 g of aqueous dispersion
10 g of 0% aqueous solution was added, and the amount of aggregation after standing for 1 day was measured. Freezing stability: The aqueous dispersion was allowed to stand for 1 day in a thermostatic chamber at -5 ° C, and the amount of aggregation was measured. High temperature stability: The aqueous dispersion was allowed to stand at 50 ° C., and the number of days until aggregation started was measured. The results are shown in Table 1, and all were good.

Example 2 530 g of the core portion fluorocopolymer aqueous dispersion prepared by the same method as in Example 1 was used, 35 g of water was added, and a monomer for obtaining the shell portion fluorocopolymer was used. As CTFE / VCp / AA 91g / 56g / 0.6
Polymerization was performed in the same manner as in Example 1 except that g was changed to g to obtain 708 g of a core / shell type fluorocopolymer aqueous dispersion having a solid content of 51%. At this time, no aggregate of the fluorocopolymer aqueous dispersion was observed. The polymerization conversion rate of VCp and AA by gas chromatography is 9
It was 9% or more. When the particle size of the dispersion was measured, the particle size distribution was monodisperse and the average particle size was 0.11μ. The number average molecular weight of the obtained core / shell type fluorinated copolymer was 130000, and Tg was 68 ° C and 11 ° C. The fluorine analysis value of this copolymer was 19.6%, and when analyzed in the same manner as in Example 1, the composition of the constituent monomer units was CTFE / VCp / V-9 / AA = 48.8 /
15.5 / 33.4 / 2.3 (mol%), and the amount of the aqueous dispersion obtained in each polymerization step, the solid content concentration, and the composition analysis of the copolymer showed that the core / shell ratio was 2 /. 1
In terms of (weight ratio), the composition of the constituent monomer units of the fluorine-containing copolymer in the shell part is CTFE / VCp / AA = 50.3 /
It was 48.7 / 1.0 (mol%). Table 1 shows the evaluation results of the stability of this core / shell type fluorocopolymer aqueous dispersion.

Example 3 680 g of the core portion fluorocopolymer aqueous dispersion prepared by the same method as in Example 1 was used, 200 g of water was added, and the shell portion fluorocopolymer was used as a monomer. , CTFE / VCp / AA 230g / 122g /
Polymerization was performed in the same manner as in Example 1 except that the amount was changed to 1.75 g, to obtain 1165 g of a core / shell type fluorocopolymer aqueous dispersion having a solid content of 48%. At this time, no aggregate of the fluorocopolymer aqueous dispersion was observed.
The polymerization conversion rate of VCp and AA by gas chromatography was 99% or more. When the particle size of the dispersion was measured, the particle size distribution was monodisperse, and the average particle size was 0.13.
It was μ. The number average molecular weight of the obtained core / shell type fluorocopolymer was 120,000, and Tg was 68 ° C and 11 ° C. The fluorine analysis value of this copolymer was 20.
It was 1%, and when analyzed in the same manner as in Example 1, the composition of constituent monomer units was CTFE / VCp / V-9 / AA = 4.
It was 9.3 / 22.2 / 26.3 / 2. 1 (mol%). As a result of analysis of the amount of the aqueous dispersion, the solid content concentration and the composition of the copolymer obtained in each polymerization step, the core / shell ratio was 1/1 (weight ratio), and the composition of the fluorine-containing copolymer in the shell part was determined. The composition of the monomer unit is CTFE / VCp / A
A was 50.1 / 48.6 / 1.3 (mol%).
Table 1 shows the evaluation results of the stability of this core / shell type fluorocopolymer aqueous dispersion.

Example 4 265 g of the core portion fluorine-containing copolymer aqueous dispersion prepared by the same method as in Example 1 was used, and 155 g of water was added,
In addition, CTFE / VCp / AA of 190 g / 117 g /
Polymerization was performed in the same manner as in Example 1 except that the amount was changed to 1.2 g to obtain 670 g of a core / shell type fluorocopolymer aqueous dispersion having a solid content of 51%. At this time, no aggregate of the fluorocopolymer aqueous dispersion was observed. The polymerization conversion rate of VCp and AA by gas chromatography was 99% or more. When the particle size of the dispersion was measured, the particle size distribution was monodisperse and the average particle size was 0.18μ. The number average molecular weight of the obtained core / shell type fluorinated copolymer was 110000, and Tg was 68 ° C. and 11
It was ℃. Fluorine analysis value of this copolymer is 20.6%
When analyzed in the same manner as in Example 1, the composition of the constituent monomer units was CTFE / VCp / V-9 / AA = 49.
It was 0 / 32.6 / 166.7 / 1.7 (mol%).
As a result of analysis of the amount of the aqueous dispersion, the solid content concentration and the composition of the copolymer obtained in each polymerization step, the core / shell ratio was 1/2 (weight ratio), and the composition of the fluorine-containing copolymer in the shell part was determined. The composition of the monomer unit is CTFE / VCp / AA = 4
It was 9.4 / 49.5 / 1.0 (mol%). Table 1 shows the evaluation results of the stability of this core / shell type fluorocopolymer aqueous dispersion.

Example 5 A core / shell type fluorinated copolymer aqueous dispersion was produced by continuously carrying out the first stage polymerization step and the second stage polymerization step. That is, as the first-stage polymerized monomer,
CTFE / VCp / V-9 / AA 405g / 21g /
Polymerization was carried out in the same manner as in Example 1 using 80 g / 2.5 g, and the consumption amount of the monomer was analyzed by gas chromatography to confirm the completion of the reaction. Then, a part of the dispersion was extracted and the solid content concentration was increased. Was measured, and the composition of the copolymer was analyzed.
As a result, the solid content was 26%, the fluorine analysis value was 19.3%,
Tg is 29 ° C., and the composition of the constituent monomer units of the copolymer is CTFE / VCp / V-9 / AA = 48.5 / 1.
It became 2.2 / 36.4 / 2.8 (mol%). Subsequently, VCp / V-9 / AA was added in an amount of 125 g / 54 g / into the otoclave containing the above-mentioned dispersion and unreacted CTFE.
The second-stage polymerized monomer (1.7 g) was injected under pressure, and then the second-stage polymerization was carried out in the same manner as in Example 1 so that the solid content was 46%.
Core / shell type fluorine-containing copolymer aqueous dispersion 11
79 g were obtained. At this time, no aggregate of the fluorocopolymer aqueous dispersion was observed. The polymerization conversion rate of VCp, V-9 and AA by gas chromatography was 99% or more. When the particle size of the dispersion was measured, the particle size distribution was monodisperse and the average particle size was 0.20 μ. The number average molecular weight of the obtained core / shell type fluorine-containing copolymer is 1
10,000 and Tg was 51 ° C and 29 ° C. The fluorine analysis value of this copolymer was 20.4%. When analyzed in the same manner as in Example 1, the composition of the constituent monomer units was C.
TFE / VCp / V-9 / AA = 48.9 / 28.9 /
It was 20.5 / 1.7 (mol%). As a result of analysis of the amount of the aqueous dispersion, the solid content concentration and the composition of the copolymer obtained in each polymerization step, the core / shell ratio was 1/2 (weight ratio), and the constitutional unit amount of the fluorine-containing copolymer in the shell part was The composition of the body unit is CTFE / VCp / V-9 / AA = 49.4 /
It was 37.4 / 12.3 / 1.0 (mol%). Table 1 shows the evaluation results of the stability of this core / shell type fluorocopolymer aqueous dispersion.

Example 6 CTFE / VPv / VPr / AA is 405 g / 178 g
/ 24 g / 7.5 g of the first stage polymerization monomer,
By the same method as in Example 1, an aqueous fluorocopolymer dispersion having a solid content of 43.3% and an average particle diameter of 0.08μ was obtained. The number average molecular weight of this copolymer is 100,000, Tg
Is 60 ° C., the fluorine analysis value is 20.4%, and the composition of the constituent monomer units is CTFE / VPv / VPr / AA = 50.1 /
It was 40.1 / 6.9 / 2.9 (mol%). 640 g of the above-mentioned aqueous dispersion of the fluorine-containing copolymer for the core part, and CT
FE / VPv / VPr / AA is 25.3g / 12.5g
Polymerization was carried out in the same manner as in Example 1 except that the second-stage polymerized monomer of /2.8 g / 1.5 g was used, and the solid content was 42.9%. 1050 g of a combined aqueous dispersion was obtained. At this time, no aggregate of the fluorocopolymer aqueous dispersion was observed. The polymerization conversion rate of VPv, VPr and AA by gas chromatography was 99% or more. When the particle size of the dispersion was measured, the particle size distribution was monodisperse, and the average particle size was 0.10 μ. The obtained core / shell type fluorocopolymer had a number average molecular weight of 110000 and a Tg of 60 ° C. and 32.
It was ℃. Fluorine analysis value of this copolymer is 23.7%
When analyzed in the same manner as in Example 1, the composition of the constituent monomer units was CTFE / VPv / VPr / AA = 49.
It was 6 / 40.0 / 7.2 / 3.2 (mol%). As a result of analysis of the amount of the aqueous dispersion, the solid content concentration and the composition of the copolymer obtained in each polymerization step, the core / shell ratio was 1
0/1 (weight ratio), the composition of the constituent monomer units of the fluorine-containing copolymer in the shell part is CTFE / VPv / VPr / A.
A = 42.1 / 38.6 / 11.0 / 8.3 (mol%)
Met. Table 1 shows the evaluation results of the stability of this core / shell type fluorocopolymer aqueous dispersion.

Comparative Example 1 In the same autoclave as in Example 1, 290 g of pure water and V were added.
-9 g of 167 g, VCp of 43 g, perfluorooctanoic acid ammonium salt of 2.0 g, Emulgen 910 and Emulgen 930 of 12.4 g each, and ammonium hydrogencarbonate of 9.7 g were charged, and degassing and nitrogen substitution were performed to 3 g. After repeating the process twice, the mixture was degassed and charged with 290 g of CTFE. After heating up to 40 ° C. and stirring well for 1 hour, 2.0 g of ammonium persulfate and 0.3 of sodium bisulfite
Polymerization was initiated by pressing in 8 g. Thereafter, every 3 hours, 1.0 g of ammonium persulfate and 0.
Unreacted CTFE was carried out by adding 19g and polymerizing for 8 hours.
Was purged and the internal pressure of the autoclave was -500 mmHg.
The atmosphere was replaced with nitrogen and deaeration under reduced pressure was performed, and then the autoclave was opened to obtain an aqueous dispersion of a fluorocopolymer having a solid content of 45%. At this time, no aggregate of the fluorocopolymer aqueous dispersion was observed. Polymerization conversion rate of VCp and V-9 by gas chromatography is 99%
When the particle size of the dispersion was measured, the particle size distribution was monodisperse and the average particle size was 0.28μ. The number average molecular weight of the obtained fluorocopolymer was 100,000, and Tg was 44 ° C. The fluorine analysis value of this copolymer was 21.6%. When analyzed in the same manner as in Example 1, the composition of the constituent monomer units of the copolymer was CTFE / V.
It was found that Cp / V-9 = 54/12/34 (mol%). Table 1 shows the evaluation results of the stability of this fluorocopolymer aqueous dispersion.

[0045]

[Table 1]

Examples 7 to 12 In 100 parts (parts by weight, the same applies hereinafter) of the core / shell type fluorocopolymer aqueous dispersions of Examples 1 to 6, butyl cellosolve acetate as a film forming auxiliary is shown in Table 2 below. Quantity added,
A chromate-treated electrogalvanized steel sheet having a thickness of 0.6 mm was coated with a bar coater so that the film thickness after drying was 30 μ, and dried at room temperature for one week. The appearance of the obtained coating film was visually observed. The results are shown in Table 2.

Comparative Example 2 CTFE / VCp / AA = 290 g / 176 g / monomer was used as the monomer used to obtain the core portion fluorine-containing copolymer.
Only the first-stage polymerization was carried out in the same manner as in Example 1 except that the amount was changed to 5.3 g to obtain a fluorocopolymer aqueous dispersion having a solid content of 49% (hereinafter referred to as aqueous dispersion A). It was
At this time, no aggregate of the fluorinated copolymer dispersion was observed. When the particle size of the dispersion was measured, the particle size distribution was monodisperse and the average particle size was 0.1 μm. The number average molecular weight of the obtained fluorine-containing copolymer was 120,000,
Tg was 10 ° C. When the fluorine analysis of this copolymer was performed, it was 19.8%. When analyzed in the same manner as in Example 1, the composition of the constituent monomer units of the copolymer was C.
It was found that TFE / VCp / AA = 51/46/3 (mol%).

Fluorine-containing copolymer aqueous dispersion obtained by the same method as in the first-stage polymerization step of Example 1 was added to the above aqueous dispersion A, that is, the composition of the constituent monomer units was CTFE / V-9 /.
AA = 48.6 / 48.5 / 2.9 (mol%), Tg
Was blended to prepare an aqueous dispersion B / aqueous dispersion A = 10/1 (weight ratio) by blending an aqueous dispersion of a fluorocopolymer having a temperature of 68 ° C. (hereinafter referred to as an aqueous dispersion B). . To this blend, the amount of butyl cellosolve acetate shown in Table 2 below was blended as a film-forming aid, and Examples 7 to 1 were used.
A coated plate was prepared and tested in the same manner as in 2. The results are shown in Table 2.

Comparative Examples 3 to 5 As shown in Table 2, blends were prepared by changing the ratios of the aqueous dispersion B and the aqueous dispersion, and other conditions were the same as in Examples 7 to 12, and the formulation of the film-forming auxiliary was blended. The coated plate was prepared and tested, and the results shown in Table 2 were obtained.

[0050]

[Table 2] Coating state: ○ Good film-forming property, × Whitening, cracking

Test Examples 7 to 12 and Comparative Test Examples 2 to 5 The coating films of the same coated plates as Examples 7 to 12 and Comparative Examples 2 to 5 were tested by the following method. The results are shown in Tables 3 and 4. The numbers given to the respective test examples and comparative test examples other than comparative test example 6 are, for example, test example 7 which is the test result for the coated plate of Example 7, and comparative test example 2.
Is the test result for the coated plate of Comparative Example 2,
They correspond to the numbers of Examples and Comparative Examples, respectively.

1) Water resistance test Visual evaluation was made by water absorption. Visually, the coating film is 25 ℃
It was judged after dipping in water for 12 hours. Water absorption is AS
According to the TM standard, it was immersed in water at 25 ° C for 12 hours, and the weight increase rate of the coating film was calculated. 2) Contamination resistance test Artificial soil suspension water according to JSM J7602, that is, 5.0 parts of carbon black, 67.5 parts of yellow oak (synthetic loess), 22.5 parts of calcined Kanto loam and 5.0 parts of silica powder. Yes, the concentration is 1 g / L. The coating film was contaminated with the artificial soil suspension water, and dried at 40 ° C. for 10 minutes. This cycle was repeated 10 times, and the color difference (ΔE) before and after the test was measured. 3) Weather resistance Continuous irradiation was performed using QUV (fluorescent ultraviolet weather resistance tester manufactured by Q Panel Co., Ltd.), and ion-exchanged water was sprayed from the back side of the coated surface for 4 hours out of each 8 hours. The 60-degree gloss retention (%) after the 500-hour test was shown.

Comparative Test Example 6 A coated plate was prepared in the same manner as in Test Example 7, except that a commercially available product, Boncoat 818 (manufactured by Dainippon Ink and Chemicals, Inc.) was used as the acrylic copolymer aqueous dispersion. The test was conducted. The results are shown in Table 3.

[0054]

[Table 3] Water resistance: ○ No abnormality △ Whitening × Blistering

[0055]

[Table 4] Water resistance: ○ No abnormality △ Whitening × Blistering

[0056]

EFFECT OF THE INVENTION The fluorine-containing copolymer aqueous dispersion of the present invention has excellent stability and film-forming property as a result of forming the core / shell type copolymer, The resulting coating film has excellent weather resistance, water resistance and stain resistance, and according to the present invention, a core / shell type fluorocopolymer aqueous dispersion can be easily and efficiently produced. be able to.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akihito Iida 1-1 Funami-cho, Minato-ku, Nagoya, Aichi Prefecture Toagosei Chemical Industry Co., Ltd. Nagoya Research Institute (72) Inventor Tatsuo Nishio Nagoya, Aichi Prefecture 1 Toago Synthetic Chemical Industry Co., Ltd., Nagoya Research Institute, Minami-ku Funami-cho (72) Inventor Hiroshi Inukai 1 Touna Synthetic Chemical Industry Co., Ltd. Nagoya Research Institute, Minami-ku, Aichi Prefecture Nagoya City Within

Claims (4)

[Claims] 1. A core made of a fluorocopolymer having a fluoroolefin monomer unit and a vinyl carboxylate monomer unit as main components and having a Tg of 40 ° C. or higher, a fluoroolefin monomer unit and a vinyl carboxylate monolayer. It has a two-layer structure of a shell composed of a fluorocopolymer having a monomer unit as a main component and Tg of 5 to 30 ° C., and a weight ratio of the core to the shell is 20.
A water-based coating obtained by dispersing a core / shell type fluorinated copolymer having a ratio of 1/1 to 1/2 in an aqueous medium. 2. The following polymerization step [1] and polymerization step [2]
A process for producing a core / shell type fluorinated copolymer having a two-layer structure of a core and a shell dispersed in an aqueous medium. Polymerization step [1]: emulsion polymerization of a monomer mixture containing a fluoroolefin monomer, a vinyl carboxylate monomer and a hydrophilic vinyl monomer as essential components in an aqueous medium in the presence of an emulsifier, A step of obtaining fluorine-containing copolymer particles having a hydrophilic vinyl monomer unit content of 0.01 to 5 mol% based on the total amount of the monomer units. Polymerization step [2]: In the presence of the polymer particles obtained in the polymerization step [1], a fluoroolefin monomer, a vinyl carboxylate monomer and a hydrophilic vinyl monomer are essential components in an aqueous medium. Emulsion polymerization of the monomer mixture to have 0.01 to 5 mol% of hydrophilic vinyl monomer units, based on the total amount of all monomer units, and Tg in the polymerization step [1].
A step of forming a fluorine-containing copolymer having a Tg lower than the Tg of the fluorine-containing copolymer obtained in above on the surface of the copolymer particles obtained in the polymerization step [1]. 3. The core / shell type fluorinated copolymer produced by the method according to claim 2 is dispersed in an aqueous medium, and the Tg of the fluorinated copolymer in the core is 40 ° C.
That is, the Tg of the fluorocopolymer in the shell is 5 to 30 ° C., and the weight ratio of the core to the shell is 20.
Water-based paint that is / 1-1 / 2. 4. The fluorine-containing copolymer forming the core comprises a fluoroolefin monomer unit of 30 to 60 mol% and a vinyl ester monomer unit of a linear aliphatic carboxylic acid having 2 to 18 carbon atoms. ˜30 mol%, vinyl ester monomer unit of branched aliphatic carboxylic acid having 4 to 15 carbon atoms 20 to 6
It is a copolymer having a composition of 0 mol%, a hydrophilic vinyl monomer unit of 0.01 to 5 mol%, and another copolymerizable monomer unit of 0 to 30 mol%, and also includes a shell-forming component. The fluorocopolymer is a fluoroolefin monomer unit 30
˜60 mol%, vinyl ester monomer unit of linear carboxylic acid having 2 to 18 carbon atoms 20 to 60 mol%, vinyl ester monomer unit of branched carboxylic acid having 4 to 15 carbon atoms 0 to 20 mol%, hydrophilic vinyl monomer unit 0.01 to
The water-based paint according to claim 1, which is a copolymer having a composition of 5 mol% and 0 to 30 mol% of other copolymerizable monomer units, and the core / shell type fluorine-containing co-polymer according to claim 2. A method for producing a coalescence or the water-based paint according to claim 3.