JPH0931400A - Curable emulsion and coating agent comprising the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an aqueous curable emulsion that has excellent storage stability and can give high-grade physical properties of a coating film. SOLUTION: This emulsion is a curable emulsion obtained by emulsion copolymerization or micro-suspension copolymerization of the following radical- polymerizable components (a) to (b) in an aqueous medium in the presence of a pH buffer; (a) an alkoxysilane having a radical-polymerizable group; (b) a vinyl monomer copolymerizable with the component (a); (c) a polyester or a polyalkylene oxide having a radial-polymerizable group copolymerizable with the component (a) at one end of the molecule and an average degree of condensation of 3 or more; and (d) a radical-polymerizable surfactant represented by the general formula: Z-(AO)n-Y wherein Z denotes a structural unit having a radical-polymerizable double bond copolymerizable with the component (a), AO denotes an oxyalkylene group, (n) is an integer of 2 or more, and Y denotes an ionizable group.

Description

Detailed Description of the Invention

[0001]

The present invention relates to an alkoxysilyl group,
That is, it relates to a curable emulsion composed of a polymer having a group in which a hydrolyzable alkoxy group is bonded to a silicon atom, and the curable emulsion is used as a paint or a coating agent.

[0002]

A polymer obtained by copolymerizing a radical-polymerizable monomer having an alkoxysilyl group represented by γ-methacryloxypropyltriethoxysilane or vinyltriethoxysilane with another monomer is known. ,adhesive,
It is widely used in applications such as sealing materials, paints and coatings. However, in these applications, in order to avoid harm to the human body and environmental pollution due to volatilization of organic solvents,
There is a need for aqueous materials that do not use organic solvents.
Aqueous emulsions composed of polymers containing alkoxysilyl groups have the property that the groups are originally hydrolyzed, so there is a problem with storage stability, and many proposals have been made for the purpose of improving this point. There is.

That is, in JP-A-3-227312, in the aqueous emulsion polymerization of a monomer having an alkyl (meth) acrylate and an alkoxysilyl group, in addition to the above-mentioned monomers, acrylamide, acrylic acid or styrene is used. 0.1 to 5% by weight of a specific water-soluble monomer such as sulfonic acid
A method of copolymerization to some extent has been proposed, and is disclosed in Japanese Patent Laid-Open No.
No. 25354, an alkoxysilyl group-containing monomer is copolymerized with an amineimide group-containing monomer in an alcohol solvent, and then water is added to form an emulsion.
Then, a method of evaporating alcohol is proposed.

Further, in JP-A-59-152972, an aqueous emulsion obtained by aqueous emulsion polymerization of vinylsilane, an acrylic monomer and a polymerizable emulsifier is added.
It is disclosed that by adding a specific amount of colloidal silica, an aqueous emulsion forming a film having excellent water resistance can be obtained. However, the conventionally known curable emulsions have a problem that the storage stability is still insufficient, and in addition to that point, the weather resistance and the acid resistance of the obtained coating are unsatisfactory. The present inventors have studied for the purpose of providing an aqueous emulsion composed of a polymer having an alkoxysilyl group, which has excellent storage stability and can form a film having excellent physical properties. Using an ionic surfactant having an oxyalkylene unit and a radically polymerizable double bond,
It was found that a curable emulsion excellent in both storage stability and film properties can be obtained by copolymerizing a radically polymerizable alkoxysilane and another vinyl monomer in the presence of a pH buffer, and a patent application has been filed. We are doing (Japanese Patent Application No. 7-
49129).

[0005]

As a result of further study after the above patent application, the present inventors have found that when an alkoxysilane having a radically polymerizable group is polymerized with another copolymerizable monomer in an aqueous medium. , An ionic surfactant having a polyoxyalkylene unit and a radically polymerizable double bond together with those monomers, and a polyester or a polyalkylene oxide having a radically polymerizable group at one terminal of the molecule and having an average degree of condensation of 3 or more It was found that an emulsion that gives a film excellent in durability against acid rain (hereinafter referred to as acid resistance) can be obtained by using in combination with the above-mentioned Japanese Patent Application No. 7-49129. The invention was completed.

That is, the present invention provides the following radically polymerizable components (a) to (a) in the presence of a pH buffer in an aqueous medium.
A curable emulsion obtained by copolymerizing (d) by emulsion polymerization or microsuspension polymerization, and further a coating agent comprising the emulsion. (A) Alkoxysilane having a radical polymerizable group (b) Vinyl monomer copolymerizable with the above component (a) (c) Radical polymerizable group copolymerizable with the above component (a) at one end of the molecule Or a polyalkylene oxide having an average degree of condensation of 3 or more (d) a general formula; Z- (AO) n-Y (wherein Z is a radical-polymerizable double bond copolymerizable with the above component (a)) A radical-polymerizable surfactant represented by the following structural unit: AO is an oxyalkylene group, n is an integer of 2 or more, and Y is an ion-dissociative group.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. As described above, the component (a) in the present invention is an alkoxysilane having a radical-polymerizable group (hereinafter referred to as an alkoxysilane monomer), which is vinyltriethoxysilane, vinylmethyldiethoxysilane, γ-methacryloxypropyltri. Ethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, vinyltripropoxysilane, vinylmethyldipropoxysilane,
γ-methacryloxypropyltripropoxysilane, γ-methacryloxypropylmethyldipropoxysilane and the like can be mentioned. Preferred component (a) is an alkoxysilane monomer in which the alkoxy group is a methoxy group or an ethoxy group.

As the vinyl monomer (b) to be copolymerized with the above component (a), methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate,
Cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate,
Alkyl (meth) acrylate such as stearyl (meth) acrylate; 2-hydroxyethyl (meth) acrylate,
2-hydroxypropyl (meth) acrylate, (meth)
Perfluoroalkyl acrylate, glycidyl (meth)
Acrylates, (meth) acrylic acid esters such as N, N-diethylaminoethyl (meth) acrylate; vinyl acetate, vinyl propionate, styrene, and α-methylstyrene. Preferred vinyl monomer (b)
Is a monomer that imparts film-forming properties to the polymer, and specifically, alkyl (meth) acrylate having an alkyl group having 1 to 8 carbon atoms, styrene, and a hydroxyalkyl group having 2 to 3 carbon atoms. Is a hydroxyalkyl (meth) acrylate and glycidyl (meth) acrylate. On the other hand, it accelerates the hydrolysis of the alkoxyl group (meth).
It is desirable not to use acidic monomers such as acrylic acid.

The component (c) in the present invention is a polyester or polyalkylene oxide having a radically polymerizable group copolymerizable with the above component (a) at one terminal of the molecule and having an average degree of condensation of 3 or more (hereinafter, these are respectively It is a polyester monomer and a polyalkylene oxide monomer), and a (meth) acryloyl group is preferable as the radically polymerizable group. Preferred monomer units forming the polyester portion of the polyester monomer are oxycarboxylic acids and lactones, and the average condensation degree of the polyester portion is preferably 3 to 100, more preferably 3
~ 8. The preferred monomer units forming polyalkylene oxide in the polyalkylene oxide monomer are ethylene oxide and propylene oxide, and the preferred average degree of condensation of the polyalkylene oxide is 3 to 200. When the degree of condensation of each monomer unit constituting the polyester monomer or the polyalkylene oxide monomer is 2 or less, a curable emulsion obtained does not provide a film having excellent acid resistance.

In the present invention, a polyester monomer composed of polycaprolactone represented by the following chemical formula 1 or chemical formula 2 and having an average degree of condensation of 3 to 8 is particularly preferable.

[0011]

Embedded image

[0012]

Embedded image

As the polyester monomer, a commercially available product may be used, and examples thereof include Praxel FM3 (n = 3 represented by the above chemical formula 1) and Praxel FA3 (the above chemical formula) manufactured by Daicel Chemical Industries, Ltd. 2 and n = 3), Praxel FM6 (represented by Formula 1 above and n = 6), Praxel FA6 (represented by Formula 2 above and n = 6), Praxel FM8 (represented by Formula 1 above) Represented by n = 8) and Praxel FA8 (represented by the above chemical formula 2 and n = 8)
Stuff) and the like.

Specific examples of the polyalkylene oxide monomer include Blemmer PP-1000 manufactured by NOF CORPORATION.
(Polypropylene oxide having a condensation degree of 5 to 6 with a methacryloyl group bonded to one end), PP-500 (polypropylene oxide having a condensation degree of 9 having a methacryloyl group bonded to one end), PP-800 (methacryloyl group bonded to one end) Polypropylene oxide with condensation degree of 12), PE
-200 (polyethylene oxide having a condensation degree of 4 to 5 with a methacryloyl group bonded to one end) and PE-350
(Polyethylene oxide having a condensation degree of 7 to 9 in which a methacryloyl group is bonded to one end) and the like.

Next, the component (d) in the present invention is a radical polymerizable surfactant containing a polyoxyalkylene group represented by the following general formula (1) and an ion dissociative group. Z- (AO) n-Y (1) (In the formula, Z is a structural unit having a radically polymerizable double bond copolymerizable with the component (a), AO is an oxyalkylene group, and n is 2 or more. An integer, Y represents an ion dissociative group.) Preferred Z in the general formula (1) is a hydrophobic hydrocarbon such as an aromatic hydrocarbon group, an alkyl-substituted aromatic hydrocarbon group, a higher alkyl group or an alicyclic hydrocarbon group. It is a structural unit in which a functional group and a radically polymerizable double bond are combined. further,
The radically polymerizable double bond in Z is (meth)
An allyl group, a propenyl group, a butenyl group and the like are preferable.

The preferred ionicity of component (d) is an anion, and therefore Y is preferably a salt in which an anion is covalently bonded to the group (AO) n side and a cation is ionically bonded thereto. Specific examples of preferable Y include —SO ₃ N
_{a, -SO 3 NH 4, -COONa} , -COONH 4,
-PO ₃ Na ₂ and -PO ₃ (NH _{4) 2} and the like, more preferably -SO ₃ Na or -SO ₃ NH
_{Is 4} . The n in the group (AO) n is preferably 300 or less, more preferably 5 to 50. When n is less than 5, the stability of the alkoxysilyl group in the monomer (a) tends to be insufficient, while when n exceeds 50, the physical properties of the coating film formed from the curable emulsion obtained are deteriorated. Shows the tendency to Further, the unit A in the group (AO) n, that is, the alkylene group, is preferably an ethylene group or a propylene group.

Typical examples of the radically polymerizable surface active agent include compounds represented by the following chemical formulas 3, 4 and 5. In each formula, Y is an ion-dissociable group, and preferred specific examples are as described above.

[0018]

Embedded image As R in Chemical formula 3, a linear or branched alkyl group having 6 to 18 carbon atoms is preferable.

[0019]

Embedded image As R in Chemical formula 4, a linear or branched alkyl group having 6 to 18 carbon atoms is preferable.

[0020]

Embedded image R1 in the chemical formula 5 is a hydrogen atom or a methyl group, and R2 is preferably an alkyl group having 8 to 24 carbon atoms.

In the present invention, the above components (a) to
In polymerizing (d) in an aqueous medium, component (a)
A pH buffer is used for the stability of the alkoxysilyl group in. As the pH buffer, the pH of the aqueous medium is 6
A buffering agent suitable for holding at 10 to 10 is preferable, and examples of the pH buffering agent include sodium hydrogencarbonate, potassium hydrogencarbonate, monosodium phosphate, monopotassium phosphate, disodium phosphate, trisodium phosphate and acetic acid. Examples thereof include sodium, ammonium acetate, sodium formate and the like. These compounds may be used in combination of two or more. A more preferred pH buffering agent is sodium hydrogen carbonate, which has a stable pH with a small amount of addition. The suitable amount of the pH buffer used is 0.01 to 5% by weight with respect to water.
It is.

The preferred copolymerization ratio of the above polymerizable components (a) to (d) is (a) 1 based on the total amount thereof.
-40% by weight, (b) 50-97% by weight, (c) 1-4
0% by weight and (d) 0.2 to 20% by weight, more preferably (a) 3 to 20% by weight, (b) 50 to 9%.
3% by weight, (c) 3 to 30% by weight and (d) 0.5 to
5% by weight. If the copolymerization ratio of the above component (a) is less than 1% by weight, good curability will not be exhibited, while if it exceeds 40% by weight, storage stability tends to decrease. When the copolymerization charge ratio of the component (c) is less than 1% by weight, the acid resistance of the film formed from the curable emulsion obtained is low,
On the other hand, if it exceeds 40% by weight, the weather resistance of the coating tends to decrease.
If the proportion of component (d) is less than 0.2% by weight, the polymerization stability tends to decrease, while if it exceeds 20% by weight, the water resistance of the coating film becomes insufficient. Further, if the proportion of the component (b) is less than 50% by weight, the film-forming property of the curable emulsion obtained and the adhesion of the film to the substrate are poor.

Next, the polymerization method will be described. In the present invention, the polymerization method is not limited, microsuspension polymerization in which the oil-soluble polymerization initiator is used to polymerize in the fine particles of the oil-soluble monomer, or a single amount by the water-soluble polymerization initiator in the micelle by the emulsifier. Emulsion polymerization or the like for polymerizing the body is adopted, but the preferred polymerization method is microsuspension polymerization. The outline of the micro suspension polymerization will be described below. In order to carry out microsuspension polymerization, first, fine particles composed of a monomer and an oil-soluble polymerization initiator are dispersed in an aqueous medium in which a pH buffer is dissolved. In the operation of dispersing the monomer or the like in the aqueous medium, the component (d) of the surfactant may be dissolved in the aqueous medium in advance in the same manner as the pH buffer.
The ratio of the aqueous medium and the monomer to be dispersed is appropriately about 20 to 150 parts by weight of the aqueous medium per 100 parts by weight of the monomer.

For dispersing the above fine particles in an aqueous medium, a dispersion method using a rotary homomixer, a high pressure type emulsification disperser (usually called a homogenizer), a turbine mixer or the like can be adopted. By the above operation,
It is possible to obtain fine particles having a particle size of 1 μm or less. A more preferable particle size is 0.2 to 0.05 μ. The smaller the aqueous dispersion particles of the monomer, the smaller the polymer dispersion particles in the obtained polymer emulsion, and the film formed from the polymer has excellent solvent resistance and water resistance.

An aqueous dispersion of fine particles of a monomer or the like (hereinafter referred to as a monomer emulsion) obtained by the above operation is fed into an aqueous medium heated to a temperature not lower than the decomposition temperature of the polymerization initiator, The components (a) to (d) are copolymerized. The preferable amount of the aqueous medium to be charged in the polymerization vessel in advance is 10 to 50 per 100 parts by weight of the monomer emulsion.
Parts by weight. The polymerization temperature is usually about 40 to 100 ° C, preferably 70 to 90 ° C.

The oil-soluble radical polymerization initiator used for microsuspension polymerization has a solubility of 1 at 20 ° C. in water.
It is preferably 0% by weight or less, such as 2,2′-azobisisobutyronitrile or 2,2′-azobis-2,4.
Azo initiators such as dimethyl valeronitrile, 1-azobis-1-cyclohexanecarbonitrile and dimethyl-2,2′-azobisisobutyrate, lauroyl peroxide, benzoyl peroxide, dicumyl peroxide, cyclohexanone peroxide di- Representative examples are organic peroxides such as n-propyl peroxydicarbonate and t-butyl peroxypivalate. The amount used is preferably 0.1 to 10% by weight, more preferably 0.5 to 5% by weight, based on the total amount of components (a) to (d).

The curable emulsion of the present invention obtained by the above-mentioned microsuspension polymerization or emulsion polymerization has a temperature of 60.degree.
Even after being left for 1 month, it maintains a stable emulsion state and maintains good curing performance. The curable emulsion of the present invention forms a film having excellent physical properties and is suitable as a coating agent. Materials to be applied include the following. Metal base materials such as iron, stainless steel, tin plate, aluminum, nickel, etc. Cement base materials such as concrete, slate, mortar, calcium silicate material, gypsum / slag material, etc. Acrylic resin, vinyl chloride resin, polyester resin,
Polycarbonate resin, ABS, Bakelite, Nylon, Epoxy resin, etc. Resin moldings Wood such as glass cedar, cypress and paper

When the curable emulsion is used as a coating agent for paints or the like, it is preferable to add a catalyst before use in order to accelerate the condensation reaction of silanol groups generated by hydrolysis of alkoxysilyl groups. As such catalysts, organic titanate compounds such as isopropyl triisostearoyl titanate and isopropyl tri (dioctyl pyrophosphate) titanate, or organic tin compounds such as tin dioctylate, dibutyltin dilaurate and dibutyltin malate, or paratoluene sulfonic acid, etc. Organic acids of. The coating can be cured by drying at room temperature or by heat drying, and preferable drying conditions are 3 to 14 days at room temperature and 3 at a temperature of 100 to 150 ° C.
It is about 30 minutes.

When the curable emulsion is used as a coating material, a thickener, a film-forming aid and a pigment can be used in combination, and if necessary, an anti-sagging agent, an anti-settling agent, a defoaming agent or a silane coupling agent. Other paint additives can also be added. Examples of the method for applying the paint to the base material include spray painting, roller painting, and brush painting. Other uses of the curable emulsion include water repellents for inorganic building materials,
Examples thereof include a moisture-proof coating agent for electronic parts, a back coat agent for magnetic tapes, a curing finish agent for fibers, a sealing agent, an adhesive agent, a binder or an adhesive agent.

[0030]

The present invention will be described more specifically below with reference to examples and comparative examples. In addition, "part" showing the compounding quantity in each example is a "weight part." Aqualon HS20 [Daiichi Kogyo Seiyaku Co., Ltd., trade name] used as a radically polymerizable surfactant is a compound represented by the following chemical formula 6.

[0031]

[Chemical 6]

The curable emulsion obtained in each example was coated on an aluminum plate with a bar coder so that the film thickness was 20 to 25 μm, and dried at a temperature of 25 ° C. and a humidity of 60% for 14 days. By doing so, the following test piece for measuring the physical properties of the coating film was prepared. Water resistance: The test piece was immersed in ion-exchanged water at 25 ° C for 7 days, and the degree of whitening of the coating film was observed. (○: no change, △: slightly whitened, ×: completely whitened) Acid resistance: 1 drop of 5% sulfuric acid was dropped on the film, and 1 at 60 ° C
The state of the coating film was evaluated by holding for 0 minute. (○: No change, Δ: Scratch, X: Floating or peeling of coating film) Accelerated weathering test; Forced deterioration of the coating film under the conditions of JIS5400 using a Sunshine Weather Meter manufactured by Suga Test Instruments Co., Ltd. The weather resistance was evaluated by the retention rate (%) of the gloss (60 °) after 3000 hours with respect to the gloss (60 °).

[0033]

Example 1 Monomers, radically polymerizable surfactants and polymerization initiators shown in Table 1 below were added to an aqueous medium in which a pH buffer was dissolved and mixed with a homomixer, and then a homogenizer [Gorin Co. Manufactured] is used.
A monomer emulsion of 2 μm and pH 8.5 was prepared.
A flask equipped with a stirrer, a thermometer and a condenser was charged with 40 parts of deionized water, the liquid temperature was raised to 80 ° C., and the above monomer emulsion was allowed to stand for 2 hours while stirring the aqueous medium at high speed. Was dropped. After the dropping is completed, the temperature is raised to 80 ° C for 2
Hold for time to complete polymerization, then cool to room temperature. During the polymerization, aggregates slightly adhered to the inner wall of the flask, but liquid separation and blocking did not occur, and the polymerization was stably performed. Table 3 shows the evaluation results of the physical properties of the film formed from the obtained curable emulsion.

[0034]

[Table 1]

[0035]

Examples 2 to 4 A curable emulsion was synthesized in the same manner as in Example 1 except that the monomers shown in Table 2 and the radical-polymerizable surfactant were used. The evaluation results of the physical properties of the coating film formed from the obtained curable emulsion are as shown in Table 3.

[0036]

Comparative Examples 1 to 3 A curable emulsion was synthesized in the same manner as in Example 1 except that the monomers shown in Table 2 and the radical polymerizable surfactant were used. In Comparative Example 3, the radical-polymerizable surfactant was replaced with a radical-polymerizable surfactant Rebenol WZ (trade name of Kao Corporation,
Polyoxyethylene alkylphenyl ether sulfate salt] was used. The evaluation results of the physical properties of the coating film formed from the obtained curable emulsion are as shown in Table 3.

[0037]

[Table 2]

[0038]

[Table 3]

[0039]

INDUSTRIAL APPLICABILITY The curable emulsion of the present invention has excellent storage stability, and can form a film having excellent acid resistance and weather resistance.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C09D 133/14 PFY C09D 133/14 PFY 171/02 PLQ 171/02 PLQ // C08F 290/06 MRS C08F 290/06 MRS

Claims (4)

[Claims] 1. A curable emulsion obtained by copolymerizing the following radically polymerizable components (a) to (d) by emulsion polymerization or microsuspension polymerization in the presence of a pH buffer in an aqueous medium. (A) Alkoxysilane having a radical polymerizable group (b) Vinyl monomer copolymerizable with the above component (a) (c) Radical polymerizable group copolymerizable with the above component (a) at one end of the molecule Or a polyalkylene oxide having an average degree of condensation of 3 or more (d) a general formula; Z- (AO) n-Y (wherein Z is a radical-polymerizable double bond copolymerizable with the above component (a)) A radical-polymerizable surfactant represented by the following structural unit: AO is an oxyalkylene group, n is an integer of 2 or more, and Y is an ion-dissociative group. 2. The copolymerization ratio of the radically polymerizable components (a) to (d) is based on the total amount thereof and is from (a) 1 to
40% by weight, (b) 50 to 97% by weight, (c) 1 to 40
% By weight and (d) 0.2-20% by weight.
The curable emulsion described. 3. The radically polymerizable component (b) has 1 carbon atom.
1 to 8 selected from the group consisting of alkyl (meth) acrylate having an alkyl group of -8, styrene, hydroxyalkyl (meth) acrylate having a hydroxyalkyl group having 2 to 3 carbon atoms and glycidyl (meth) acrylate, or The curable emulsion according to claim 1 or 2, which comprises two or more monomers. 4. A coating agent comprising the curable emulsion according to claim 1, claim 2 or claim 3.