JPH09110946A - Curable emulsion and coating material comprising the emulsion - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a curable emulsion which has excellent storage stability and is capable of forming a coating film excellent in weatherability and acid resistance by copolymerizing four specific free radical-polymerizable components by microsuspension polymerization in an aqueous medium in the presence of a pH buffer. SOLUTION: This curable emulsion is formed by polymerizing the following free radical-polymerizable components (a) to (d) by microsuspension polymerization in an aqueous medium in the presence of a pH buffer: (a) an alkoxysilane having a free radical-polymerizable group; (b) a vinyl monomer copolymerizable with the component (a); (c) a macromonomer which comprises a vinyl polymer or a polysiloxane each having at one molecular end a radical-polymerizable group copolymerizable with the component free (a) and has a number-average mol.wt. of 1,000-30,000; and (d) a free radical-polymerizable anionic or cathionic surfactant represented by the formula Z-(AO)n -Y (wherein Z is a structural unit having a free radical-polymerizable group copolymerizable with the component (a); AO is an oxyalkylene; (n) is an integer of 2 or larger; and Y is 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 used for sealants, paints and coatings. In recent years, in these applications, an aqueous material that does not use an organic solvent has been demanded in order to avoid harm to the human body and environmental pollution due to the organic solvent. However, since an aqueous emulsion composed of a polymer containing an alkoxysilyl group originally has a property of hydrolyzing the group, there is a problem in storage stability, and many proposals have been made to improve this point. ing.

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 for copolymerization has been proposed, and JP-A-5-22
No. 5,354, discloses an aqueous method in which a monomer having an alkoxysilyl group is copolymerized with an amineimide group-containing monomer in an alcohol solvent, water is then added to form an emulsion, and then the alcohol is evaporated. Proposed. On the other hand, in JP-A-59-152972, a water-based emulsion prepared by aqueous emulsion-polymerizing vinylsilane, an acrylic monomer and a polymerizable emulsifier is blended with a specific amount of colloidal silica to improve water resistance. Aqueous emulsions have been disclosed that give excellent coatings.

[0004]

[Problems to be solved] However, conventionally known curable emulsions have problems that storage stability is still inadequate, and that weather resistance and acid resistance of the obtained coating film are not good enough. The present inventors have used an ionic surfactant having a polyoxyalkylene unit and a radical-polymerizable double bond to combine a radical-polymerizable alkoxysilane and another vinyl monomer in the presence of a pH buffer. It has been found that a curable emulsion excellent in both storage stability and coating physical properties can be obtained by copolymerization, and a patent application has been filed (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. , With those monomers, an ionic surfactant having a polyoxyalkylene unit and a radical-polymerizable double bond, and a number average molecular weight of 1,
The above-mentioned Japanese Patent Application No. 7-49129 proposed by using a macromonomer having a radically polymerizable group copolymerizable with the above (a) at one end of 000 to 30,000 vinyl polymer or polysiloxane. The present inventors have completed the present invention by finding that an emulsion can be obtained that gives a coating having more excellent durability against acid rain (hereinafter referred to as acid resistance) and weather resistance as compared with a curable emulsion.

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 microsuspension polymerization. (A) Alkoxysilane having a radical-polymerizable group (b) Vinyl monomer copolymerizable with (a) above (c) Vinyl polymer or polysiloxane copolymerizable with (a) above at one end of a polysiloxane molecule Macromonomer having a radical-polymerizable group and a number average molecular weight of 1,000 to 30,000 (d) Radical-polymerizable anion or cation surfactant Z- (AO) n-Y represented by the following general formula (1). (1) [In the formula (1), Z is a structural unit having a radically polymerizable group copolymerizable with the above (a), AO is an oxyalkylene group, n is an integer of 2 or more, and Y is an ion dissociable group. Is]

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. (A) in the present invention, as described above,
It is an alkoxysilane having a radically polymerizable group (hereinafter referred to as an alkoxysilane monomer), vinyltrimethoxysilane, vinylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, vinyltri. Ethoxysilane, vinylmethyldiethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, vinyltripropoxysilane, vinylmethyldipropoxysilane,
γ-methacryloxypropyltripropoxysilane, γ-methacryloxypropylmethyldipropoxysilane and the like can be mentioned. Preferred is an alkoxysilane monomer in which the alkoxy group is a methoxy group or an ethoxy group.

The vinyl monomer (b) to be copolymerized with the above (a) is methyl (meth) acrylate, (meth)
Ethyl acrylate, n-butyl (meth) acrylate, cyclohexyl (meth) acrylate, (meth) acrylic acid 2
-Alkyl (meth) acrylate such as ethylhexyl, lauryl (meth) acrylate, stearyl (meth) acrylate; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, (meth) acrylic acid (Meth) acrylic acid esters such as perfluoroalkyl, glycidyl (meth) acrylate, and N, N-diethylaminoethyl (meth) acrylate; vinyl acetate, vinyl propionate, styrene, and α-methylstyrene. Preferably, it is a monomer that imparts film-forming properties to the polymer, specifically, alkyl (meth) acrylate having an alkyl group having 1 to 8 carbon atoms, styrene, and hydroxyalkyl having 2 to 3 carbon atoms. Hydroxyalkyl (meth) acrylates having groups and glycidyl (meth) acrylates. As (b), it is desirable not to use an acidic monomer such as (meth) acrylic acid that promotes hydrolysis of the alkoxylyl group.

(C) in the present invention, as described above,
It is a macromonomer having a number average molecular weight of 1,000 to 30,000 and having a radically polymerizable group copolymerizable with (a) at one end of a vinyl polymer or polysiloxane molecule, and the radically polymerizable group is: A (meth) acryloyl group is preferred. The number average molecular weight of the macromonomer is
If it is less than 1,000, the acid resistance is poor, while on the other hand it is 30,000.
When it exceeds 0, the copolymerizability with other polymerizable components is poor. The number average molecular weight in the present invention is a polystyrene conversion value by gel permeation chromatography. A preferred vinyl polymer as a constitutional unit of a macromonomer is an alkyl (meth) acrylate such as methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate; 2- (meth) acrylate. It is a homopolymer or copolymer of hydroxyethyl, 2-hydroxypropyl (meth) acrylate, acrylonitrile, vinyl acetate or styrene. In the present invention, either the above vinyl polymer or polysiloxane can be used as the polymer skeleton of the macromonomer, but more preferably, the above vinyl polymer is preferable in that the coating film formed from the obtained curable emulsion has excellent transparency. It is a polymer.

Specific examples of the macromonomer include the following. Each of these has a methacryloyl group as a radically polymerizable group. Macromonomer manufactured by Toagosei Co., Ltd .: AS-6 (polystyrene, number average molecular weight; 6000) AN-6 [copoly (styrene / acrylonitrile), number average molecular weight; 6000] AA-6 (polymethyl methacrylate, number average molecular weight) ;
6000) AA714S [copoly (methyl methacrylate / 2-hydroxyethyl methacrylate), number average molecular weight; 70
00] AX707S [copoly (butyl methacrylate / 2-hydroxyethyl methacrylate), number average molecular weight; 70
00] AK5 (polysiloxane, number average molecular weight; 5000) AK30 (polysiloxane, number average molecular weight; 30,000)
0) Macromonomer manufactured by Chisso Corporation: FM0725 (polysiloxane, number average molecular weight; 10,
000)

Next, (d) in the present invention is a radically polymerizable anion or cation 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 (1), Z is a structural unit having a radically polymerizable group copolymerizable with the above (a), AO is an oxyalkylene group, and n is an integer of 2 or more. , And Y is 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 group and a radically polymerizable group are combined. Further, the radical polymerizable group for Z is preferably a (meth) allyl group, a propenyl group, a butenyl group, or the like.

The preferred ionicity of component (d) is an anion, and specific examples of preferred Y include --SO ₃ Na,
_{-SO 3 NH 4, -COONa, -COONH} 4, -P
O ₃ Na ₂ and -PO ₃ (NH _{4) 2} and the like, more preferably from -SO ₃ Na or -SO ₃ NH _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. To do. As the structural unit A in the group (AO) n, that is, the alkylene group, an ethylene group or a propylene group is preferable.

Typical examples of the radically polymerizable surfactant (d) include compounds represented by the following chemical formulas 1 and 2. In each formula, Y is an ion-dissociable group, and preferred specific examples are as described above.

[0014]

Embedded image As R in Chemical formula 1, a linear or branched alkyl group having 6 to 18 carbon atoms is preferable.

[0015]

Embedded image R1 in the chemical formula 2 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, when the above radical polymerizable components (a) to (d) are polymerized in an aqueous medium,
Due to the stability of the alkoxysilyl group in (a), pH
Use a buffer. As a pH buffer, p of an aqueous medium is used.
A buffer suitable for holding H at 6-10 is preferred,
Examples of the pH buffer include sodium hydrogen carbonate, potassium hydrogen carbonate, monosodium phosphate, monopotassium phosphate, disodium phosphate, trisodium phosphate, sodium acetate, 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.
A suitable amount of the pH buffer used is 0.01 to 5 with respect to water.
% By weight.

The preferred copolymerization ratio of the above-mentioned 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. The copolymerization ratio of the above (a) is 1% by weight.
If it is less than 40% by weight, good curability does not appear, while 40% by weight
If it exceeds, the storage stability tends to decrease. The ratio of (c) is
When it is less than 1% by weight, the acid resistance of the coating film formed from the curable emulsion obtained is low, while when it exceeds 40% by weight, the weather resistance of the coating film tends to be lowered. The ratio of (d) is 0.
If it is less than 2% by weight, the polymerization stability tends to decrease, while 2
If it exceeds 0% by weight, the water resistance of the coating is insufficient. When the proportion of (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, in order to efficiently copolymerize the macromonomer (c) with other components, the radical polymerizable component is copolymerized by a micro suspension polymerization method using an oil-soluble polymerization initiator. 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. Upon aqueous dispersion of the monomer, it is preferable that the surfactant (d) is previously dissolved in an aqueous medium in the same manner as the pH buffer.
The appropriate ratio of the aqueous medium to the monomer is about 20 to 150 parts by weight of the aqueous medium per 100 parts by weight of the monomer.

In the dispersion of the fine particles in the aqueous medium, a dispersion method using a rotary homomixer, a high-pressure 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. The smaller the dispersed particles of the monomer, the smaller the polymer particles in the resulting polymer emulsion, and the film formed from the polymer has excellent solvent resistance and water resistance. A more preferable particle size is 0.2 to 0.05 μ.

An aqueous dispersion of fine particles (hereinafter referred to as a "monomer emulsion") obtained by the above operation and comprising a monomer, an oil-soluble polymerization initiator and the like is heated to a temperature above the decomposition temperature of the polymerization initiator. Supply in the component (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 parts by weight per 100 parts by weight of the monomer emulsion. 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 maintains a stable emulsion state even when it is allowed to stand at a temperature of 60 ° C. for one month, and also has good curing performance. The curable emulsion of the present invention is suitable as a coating agent, and as a coating material, iron,
Metal base materials such as stainless steel, tin plate, aluminum and nickel; cement base materials such as concrete, slate, mortar, calcium silicate material, gypsum / slag material; acrylic resin, vinyl chloride resin, polyester resin, polycarbonate resin, ABS, bakelite,
Examples of the resin molding include nylon and epoxy resin; glass; wood such as cedar and 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 paint, 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.

[0025]

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 3.

[0026]

Embedded image

The curable emulsions obtained in each example were coated on an aluminum plate with a bar coater so as to have a film thickness of 20 to 25 μm and dried at a temperature of 25 ° C. and a humidity of 60% for 14 days. The following test film physical properties were evaluated using the test pieces obtained as described above. a. 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. Evaluation result ─
◯: No change, Δ: slightly whitened, ×: completely whitened b. Acid resistance: One drop of 5% sulfuric acid was dropped on the coating, and the coating was maintained at 60 ° C. for 10 minutes to evaluate the state of the coating. Evaluation result ─
◯: No change, Δ: Marked, ×: Floating or peeling of coating film c. Accelerated weathering test; using a Sunshine weather meter manufactured by Suga Test Instruments Co., Ltd., the film was deteriorated by the method specified in JIS 5400, and the retention rate of gloss (60 °) after 3000 hours with respect to the initial gloss (60 °) ( %) Was used to evaluate the weather resistance.

[0028]

Example 1 The following monomers, radically polymerizable surfactant and polymerization initiator were added to an aqueous medium in which a pH buffer was dissolved and mixed with a homomixer, and then a homogenizer (manufactured by Gorin Co.) was used. With an average particle size of 0.2 μm
A monomer emulsion of H8.5 was prepared. Compounds (parts) Component (a) γ-methacryloxypropyltriethoxysilanemethyl 10 methacrylate 50 Component (b) · n-Butyl acrylate 30 · 2-Hydroxyethyl methacrylate 5 Component (c) AA-6 [Toagosei Co., Ltd. ), Polymethylmethacrylate type 5 macromonomer, number average molecular weight; 6000] Component (d) Aqualon HS20 2 polymerization initiator 2,2′-azobisisobutyronitrile 1 pH buffer sodium bicarbonate 0.2 Aqueous medium deionized 40 parts of deionized water was charged into a flask equipped with a water 100 stirrer, a thermometer and a condenser, the liquid temperature was raised to 80 ° C., and then the above-mentioned monomer emulsion was mixed with 2 while stirring the aqueous medium at high speed. It dripped over time. After the dropping is completed, the temperature is raised to 80 ° C for 2
Hold for time to complete the polymerization, and 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. The evaluation results of the physical properties of the coating film formed from the obtained curable emulsion are shown in Table 2.

[0029]

[Examples 2 to 5] A curable emulsion was synthesized in the same manner as in Example 1 except that the monomers shown in Table 1 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 2.

[0030]

Comparative Examples 1-2 A curable emulsion was synthesized in the same manner as in Example 1 except that the monomers shown in Table 1 and the radical-polymerizable surfactant were used. In Comparative Example 2, in place of the radical-polymerizable surfactant, 2 parts of Lebenol WZ, a surfactant containing no radical-polymerizable group (Kao Corporation trade name, polyoxyethylene alkylphenyl ether sulfate ester salt) was used. used. The evaluation results of the physical properties of the coating film formed from the obtained curable emulsion are as shown in Table 2.

[0031]

[Table 1]

[0032]

[Table 2] * Since the dry film is white and opaque, it cannot be evaluated.

[0033]

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 number Internal reference number FI Technical indication C09D 183/07 PEA C09D 183/07 PEA

Claims (4)

[Claims] 1. A curable emulsion obtained by copolymerizing the following radically polymerizable components (a) to (d) by 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 (a) above (c) Vinyl polymer or polysiloxane copolymerizable with (a) above at one end of a polysiloxane molecule Macromonomer having a radical-polymerizable group and a number average molecular weight of 1,000 to 30,000 (d) Radical-polymerizable anion or cation surfactant Z- (AO) n-Y represented by the following general formula (1). (1) [In the formula (1), Z is a structural unit having a radically polymerizable group copolymerizable with the above (a), AO is an oxyalkylene group, n is an integer of 2 or more, and Y is an ion dissociable group. Is] 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.