JP3355618B2 - Curable emulsion and coating comprising the emulsion - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an alkoxysilyl group,
That is, the present invention relates to a curable emulsion comprising 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]

2. Description of the Related Art A polymer obtained by copolymerizing a radical polymerizable monomer having an alkoxysilyl group with another monomer, represented by γ-methacryloxypropyltriethoxysilane or vinyltriethoxysilane, is ,adhesive,
It is used for applications such as sealing materials, paints and coatings. In recent years, in these applications, in order to avoid harm to the human body and environmental pollution by an organic solvent, an aqueous material not using an organic solvent has been required. However, an aqueous emulsion comprising a polymer containing an alkoxysilyl group has a problem of storage stability because the group originally has a property of hydrolyzing, and many proposals have been made to improve that point. ing.

[0003] That is, JP-A-3-227312 discloses that when a monomer having an alkyl (meth) acrylate and an alkoxysilyl group is subjected to aqueous emulsion polymerization, acrylamide, acrylic acid or styrene may be used in addition to the above monomer. 0.1-5% by weight of a specific water-soluble monomer such as sulfonic acid
A method of copolymerizing has been proposed.
No. 5,354, discloses an aqueous method in which a monomer having an alkoxysilyl group is copolymerized with an amine imide group-containing monomer in an alcohol solvent, water is added to form an emulsion, and then the alcohol is evaporated. Proposed. On the other hand, JP-A-59-152972 discloses an aqueous emulsion obtained by aqueous emulsion polymerization of vinyl silane, an acrylic monomer and a polymerizable emulsifier, and a specific amount of colloidal silica. Aqueous emulsions that give excellent coatings are disclosed.

[0004]

However, the conventionally known curable emulsions have the problem that the storage stability is still insufficient, and the weather resistance and acid resistance of the resulting film are just one step away. The present inventors use a polyoxyalkylene unit and an ionic surfactant having a radical polymerizable double bond to form a radical polymerizable alkoxysilane and another vinyl monomer in the presence of a pH buffer. It has been found that by copolymerization, a curable emulsion excellent in both storage stability and film properties can be obtained, and a patent application has been filed (Japanese Patent Application No. 7-49129).

[0005]

Means for Solving the Problems As a result of further studies after the above-mentioned patent application, the present inventors have found that, when polymerizing an alkoxysilane having a radical polymerizable group with another copolymerizable monomer in an aqueous medium, the present inventors have found that: Ionic surfactant having a polyoxyalkylene unit and a radical polymerizable double bond together with those monomers, and a number average molecular weight of 1,
The use of a macromonomer having a radical polymerizable group copolymerizable with (a) at one end of a vinyl polymer or polysiloxane having a molecular weight of 000 to 30,000 has been proposed in Japanese Patent Application No. 7-49129. The present inventors have found that an emulsion can be obtained which provides a film having more excellent resistance to acid rain (hereinafter referred to as acid resistance) and weather resistance as compared with the curable emulsion, and the present invention has been completed.

That is, the present invention provides the following radically polymerizable components (a) to (a) in an aqueous medium in the presence of a pH buffer.
It is a curable emulsion obtained by copolymerizing (d) by microsuspension polymerization. (A) an alkoxysilane having a radical polymerizable group (b) a vinyl monomer copolymerizable with the above (a) (c) a vinyl monomer copolymerizable with the above (a) at one end of a vinyl polymer or polysiloxane molecule Macromonomer having a radical polymerizable group and having a number average molecular weight of 1,000 to 30,000 (d) Radical polymerizable anionic or cationic surfactant represented by the following general formula (1) Z- (AO) n-Y (1) [In the formula (1), Z is a structural unit having a radical 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,
An alkoxysilane having a radical polymerizable group (hereinafter, referred to as an alkoxysilane monomer), which includes vinyltrimethoxysilane, vinylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, and vinyltrimethoxysilane. Ethoxysilane, vinylmethyldiethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, vinyltripropoxysilane, vinylmethyldipropoxysilane,
γ-methacryloxypropyltripropoxysilane and γ-methacryloxypropylmethyldipropoxysilane. Preferably, it 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) includes methyl (meth) acrylate, (meth)
Ethyl acrylate, n-butyl (meth) acrylate, cyclohexyl (meth) acrylate, (meth) acrylic acid 2
-Alkyl (meth) acrylates such as ethylhexyl, lauryl (meth) acrylate, stearyl (meth) acrylate; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, (meth) acrylic acid (Meth) acrylates 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 a film-forming property to a polymer, and 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) acrylate and glycidyl (meth) acrylate having a group. As (b), it is desirable not to use an acidic monomer such as (meth) acrylic acid which promotes hydrolysis of the alkoxylyl group.

In the present invention, (c) is as described above.
It is a macromonomer having a number average molecular weight of 1,000 to 30,000 having a radical polymerizable group copolymerizable with the above (a) at one end of a vinyl polymer or polysiloxane molecule, and the radical polymerizable group includes: (Meth) acryloyl groups are preferred. The number average molecular weight of the macromonomer is
If it is less than 1,000, it is inferior in acid resistance, while 30,000
If it exceeds 0, the copolymerizability with other polymerizable components will be poor. In addition, the number average molecular weight in the present invention is converted into polystyrene by gel permeation chromatography. Preferable vinyl polymers as the constitutional unit of the macromonomer include alkyl (meth) acrylates such as methyl (meth) acrylate, ethyl (meth) acrylate and n-butyl (meth) acrylate; It is a homopolymer or copolymer of hydroxyethyl, 2-hydroxypropyl (meth) acrylate, acrylonitrile, vinyl acetate or styrene. In the present invention, any of the above-mentioned vinyl polymers or polysiloxanes can be used as the polymer skeleton of the macromonomer, but more preferably, the above-mentioned vinyl polymer is used because a film formed from the obtained curable emulsion has excellent transparency. It is a polymer.

The following are specific examples of the macromonomer. In addition, all of these have a methacryloyl group as a radical polymerizable group. Toagosei Co., Ltd. macromonomer: 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
AK5 (polysiloxane, number average molecular weight; 5000) AK30 (polysiloxane, number average molecular weight; 30,000)
0) Macro monomer manufactured by Chisso Corporation: FM0725 (polysiloxane, number average molecular weight; 10,
000)

Next, (d) in the present invention is a radically polymerizable anionic or cationic surfactant containing a polyoxyalkylene group and an ion dissociable group represented by the following general formula (1). Z- (AO) n-Y (1) [In the formula (1), Z is a structural unit having a radical 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-dissociable group. Preferred Z in the general formula (1) is a hydrophobic group 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 radical polymerizable group are combined. Further, as the radical polymerizable group for Z, a (meth) allyl group, a propenyl group, a butenyl group, or the like is preferable.

The preferred ionicity of component (d) is an anion. 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 are exemplified, and more preferred is —SO ₃ Na or —SO ₃ NH ₄ . 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 reduced. I do. The structural unit A in the group (AO) n, that is, the alkylene group, is preferably an ethylene group or a propylene group.

Representative examples of the radical 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 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,
In order to stabilize the alkoxysilyl group in (a), pH
Use a buffer. Examples of the pH buffer include p of an aqueous medium.
A buffer suitable for holding H at 6 to 10 is preferable,
Examples of such a pH buffer include sodium bicarbonate, potassium bicarbonate, monosodium phosphate, monopotassium phosphate, disodium phosphate, trisodium phosphate, sodium acetate, ammonium acetate, and sodium formate. These compounds can be used in combination of two or more kinds. A further preferred pH buffer is sodium bicarbonate, the pH of which is stable with small additions.
A suitable amount of the pH buffer is 0.01 to 5 with respect to water.
% By weight.

The preferred copolymerization ratio of the 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, and (b) 50 to 9% by weight.
3% by weight, (c) 3-30% by weight and (d) 0.5-
5% by weight. When the copolymerization ratio of the above (a) is 1% by weight
If the amount is less than 40% by weight, good curability is not exhibited.
If it exceeds 300, the storage stability tends to decrease. The ratio of (c) is
If the amount is less than 1% by weight, the acid resistance of the film formed from the curable emulsion obtained is low, while if it exceeds 40% by weight, the weather resistance of the film tends to decrease. (D) is 0.
If the amount is less than 2% by weight, the polymerization stability tends to decrease.
If it exceeds 0% by weight, the water resistance of the coating will be insufficient. If the proportion of (b) is less than 50% by weight, the resulting curable emulsion will have poor film-forming properties and poor adhesion of the coating to the substrate.

Next, the polymerization method will be described. In the present invention, in order to efficiently copolymerize the macromonomer (c) with other components, the above radical polymerizable component is copolymerized by a microsuspension 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. When the monomer is dispersed in an aqueous solution, the surfactant (d) is preferably dissolved in an aqueous medium in advance similarly to the pH buffer.
The ratio of the aqueous medium to the monomer is suitably about 20 to 150 parts by weight of the aqueous medium per 100 parts by weight of the monomer.

In dispersing the fine particles in an aqueous medium, a dispersion method using a rotary homomixer, a high-pressure emulsifier / disperser (usually called a homogenizer), a turbine mixer or the like can be adopted. By the above operation,
Fine particles having a particle size of 1 μ or less can be obtained. The smaller the dispersed particles of the monomer, the smaller the polymer particles in the obtained polymer emulsion, and the coating formed therefrom is excellent in solvent resistance and water resistance. A more preferred particle size is 0.2-0.05μ.

An aqueous dispersion of fine particles comprising a monomer and an oil-soluble polymerization initiator (hereinafter referred to as a monomer emulsion) obtained by the above operation is heated to an aqueous medium heated to a temperature not lower than the decomposition temperature of the polymerization initiator. And the component (a)
To (d) are copolymerized. The preferred amount of the aqueous medium previously charged in the polymerization vessel 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 in microsuspension polymerization has a solubility in water at 20 ° C. of 1
It is preferably 0% by weight or less, for example, 2,2'-azobisisobutyronitrile, 2,2'-azobis-2,4
Azo initiators such as dimethylvaleronitrile, 1-azobis-1-cyclohexanecarbonitrile and dimethyl-2,2'-azobisisobutyrate, lauroyl peroxide, benzoyl peroxide, dicumyl peroxide, cyclohexanone peroxide dioxide; Organic peroxides such as n-propylperoxydicarbonate and t-butylperoxypivalate are typical examples. The amount used is preferably from 0.1 to 10% by weight, more preferably from 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-described microsuspension polymerization maintains a stable emulsion state even when left at a temperature of 60 ° C. for one month, and also maintains good curing performance. The curable emulsion of the present invention is suitable as a coating agent, and as a coating material, iron,
Metal substrate such as stainless steel, tinplate, aluminum, nickel, etc .; Cement-based substrate such as concrete, slate, mortar, calcium silicate-based material, gypsum / slag-based material; acrylic resin, vinyl chloride resin, polyester resin, polycarbonate resin, ABS, Bakelite,
Resin moldings such as nylon and epoxy resin; glass; wood such as cedar and hinoki, paper and the like.

When the curable emulsion is used as a coating material such as a paint, it is preferable to add a catalyst before use in order to promote a condensation reaction of silanol groups generated by hydrolysis of alkoxysilyl groups. Examples of such a catalyst include organic titanate compounds such as isopropyl triisostearoyl titanate and isopropyl tri (dioctyl pyrophosphate) titanate; organic tin compounds such as tin dioctylate, dibutyltin dilaurate, and dibutyltin malate; and paratoluenesulfonic acid Organic acids. The coating can be cured by drying at room temperature or by heating. Preferred drying conditions are 3 to 14 days at normal temperature and 3 to 14 days at 100 to 150 ° C.
It is about 30 minutes.

When the curable emulsion is used as a paint, a thickener, a film-forming aid, a pigment, and the like can be used in combination, and if necessary, an anti-dripping agent, an anti-settling agent, an antifoaming agent, or a silane coupling agent. Paint additives can also be added. Examples of the method of applying the coating to the base material include spray coating, roller coating, and brush coating. Other applications of the curable emulsion include water repellents for inorganic building materials,
Examples include a moisture-proof coating agent for electronic parts, a backcoat agent for magnetic tape, a hardening finish agent for fibers, a sealing agent, an adhesive, a binder or an adhesive.

[0025]

The present invention will be described more specifically below with reference to examples and comparative examples. The “parts” representing the blending amounts in each example are “parts by weight”. Aqualon HS20 [Daiichi Kogyo Seiyaku Co., Ltd., trade name] used as a radical polymerizable surfactant is a compound represented by the following chemical formula (3).

[0026]

Embedded image

The curable emulsion obtained in each example was coated on an aluminum plate with a bar coater so as to have a thickness of 20 to 25 μm, and dried at a temperature of 25 ° C. and a humidity of 60% for 14 days. Using the test pieces obtained as described above, the following coating properties were evaluated. 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 film and kept at 60 ° C. for 10 minutes to evaluate the state of the coating film. Evaluation result─
；: No change, △: a mark is formed, ×: the coating film floats or peels off. C. Accelerated weather resistance test: Using a sunshine weathermeter manufactured by Suga Test Instruments, the coating was deteriorated by the method specified in JIS 5400, and the retention of gloss (60 °) after 3000 hours from initial gloss (60 °) ( %), The weather resistance was evaluated.

[0028]

Example 1 The following monomer, radically polymerizable surfactant and polymerization initiator were added to an aqueous medium in which a pH buffer was dissolved, mixed with a homomixer, and further used with a homogenizer (manufactured by Gorin). And the average particle size is 0.2 μm
A monomer emulsion of H8.5 was prepared. Compounds used (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. ), Polymethyl methacrylate 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 deionization Water 100 Into a flask equipped with a stirrer, thermometer and cooler was charged 40 parts of deionized water, and after raising the liquid temperature to 80 ° C., while stirring the aqueous medium at high speed, 2 parts of the above monomer emulsion were added. It was dropped over time. After dropping is completed, the temperature is
The polymerization was completed by holding for a time, and then cooled 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 2 shows the evaluation results of the physical properties of the film formed from the obtained curable emulsion.

[0029]

Examples 2 to 5 Curable emulsions were synthesized in the same manner as in Example 1 using the monomers and the radical polymerizable surfactants shown in Table 1. The evaluation results of the physical properties of the film formed from the obtained curable emulsion are as shown in Table 2.

[0030]

Comparative Examples 1 and 2 Curable emulsions were synthesized in the same manner as in Example 1 using the monomers and the radical polymerizable surfactants shown in Table 1. In Comparative Example 2, in place of the radical polymerizable surfactant, 2 parts of a surfactant Levenol WZ [trade name of Kao Corporation, polyoxyethylene alkylphenyl ether sulfate] containing no radical polymerizable group was used. used. The evaluation results of the physical properties of the film formed from the obtained curable emulsion are as shown in Table 2.

[0031]

[Table 1]

[0032]

[Table 2] * Cannot be evaluated because the dried film is white and opaque.

[0033]

The curable emulsion of the present invention is excellent in storage stability, and can form a film excellent in acid resistance and weather resistance from the emulsion.

Continuation of the front page (51) Int.Cl. ⁷ identification code FI C09D 155/00 C09D 155/00 (58) Field surveyed (Int.Cl. ⁷ , DB name) C08F 299/00-299/08 C08F 290 / 00-290/14 C09D 1/00-201/10

Claims (4)

(57) [Claims] 1. A curable emulsion obtained by copolymerizing the following radically polymerizable components (a) to (d) by microsuspension polymerization 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 above (a) (c) a vinyl monomer copolymerizable with the above (a) at one end of a vinyl polymer or polysiloxane molecule Macromonomer having a radical polymerizable group and having a number average molecular weight of 1,000 to 30,000 (d) Radical polymerizable anionic or cationic surfactant represented by the following general formula (1) Z- (AO) n-Y (1) [In the formula (1), Z is a structural unit having a radical 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 of the radical polymerizable components (a) to (d).
40% by weight, (b) 50 to 97% by weight, (c) 1 to 40
% By weight and (d) 0.2 to 20% by weight.
A curable emulsion as described. 3. The radical polymerizable component (b) has 1 carbon atom.
One or more selected from the group consisting of alkyl (meth) acrylates having an alkyl group of -8, styrene, hydroxyalkyl (meth) acrylates having a hydroxyalkyl group having 2 to 3 carbon atoms, and glycidyl (meth) acrylate 3. The curable emulsion according to claim 1, which is at least two kinds of monomers. 4. A coating comprising the curable emulsion according to claim 1, 2 or 3.