JP2637955B2 - Aqueous coating composition - Google Patents

Description

The present invention relates to a novel and useful crosslinkable resin composition. More specifically, the present invention relates to a monomer comprising at least one monomer selected from the group consisting of alkyl esters of α, β-ethylenically unsaturated carboxylic acids and alkenylbenzene as essential monomers. The mixture and a water-dispersible resin composition (A) obtained by emulsion-polymerizing 10 to 500 parts by weight of colloidal silica with respect to 100 parts by weight of the monomer mixture in an aqueous system, and a silane coupling agent [B], the solid content weight ratio of [A]: [B] is 95: 5 to 50:50.
An extremely practical aqueous coating composition which forms a coating film having excellent film forming properties, durability, stain resistance, hardness and heat resistance, etc. About things.

[Conventional technology]

Generally, the water-based resin includes a water-soluble resin and a water-dispersible resin, and has respective characteristics.

For example, the former water-soluble resin includes an anion type in which a carboxyl group is neutralized and dissolved with various alkalis such as ammonia or an amine, and a tertiary amino group with an acid with an acid. There is a canion type that dissolves, and both types are excellent in film formability, regardless of the high or low glass transition temperature of the polymer, if a water-soluble solvent flies, a film is formed, for example, A hard polymer excellent in stain resistance due to outdoor exposure and stain resistance such as black feel mark (black heel mark) on floors and roads can be obtained.

However, in the case of a water-soluble resin, in order to impart hydrophilicity, a large amount of acid or alkali is used, so that the so-called durability such as water resistance, alkali resistance and / or acid resistance is inferior. There were drawbacks.

In addition, if the molecular weight is increased, the concentration must be
In addition, from the viewpoint that it is difficult to obtain a low-viscosity resin, the molecular weight has to be low in handling, but the low molecular weight also causes poor durability.

On the other hand, in the case of a water-dispersible resin obtained by emulsion polymerization in the presence of an emulsifier, protective colloid, or the like, or obtained by mechanically dispersing, regardless of the molecular weight, a high concentration can be obtained. Target, low viscosity, and in addition, there is little problem such as pollution because it hardly uses organic solvents and amines.
Due to the effect of the emulsifier and protective colloid used, there is a disadvantage that the water resistance of the coating film and the adhesion to the substrate are poor.

In addition, the water-dispersible resin is different from the water-soluble resin in the film forming mechanism, and if fusion between the resin particles does not occur,
A film cannot be formed, and as the glass transition temperature of the polymer rises and falls, its MFT (minimum film formation temperature) also rises and falls, so that a hard polymer film with excellent stain resistance can be formed at room temperature. Then, there was a disadvantage that it could not be obtained.

In that respect, if the film is dried by heating, a hard polymer film can be obtained, but the disadvantage of practically lacking versatility cannot be wiped out.

Therefore, as a means of obtaining a hard polymer film by curing at room temperature, it is also known to add a large amount of a so-called film-forming aid such as a plasticizer or a water-soluble solvent to a water-dispersible resin of a hard polymer. However, according to such means, there is a drawback that it takes a long time to restore the hardness of the coating film, and during that time, the water resistance and the stain resistance are reduced.

As another means, it is known that colloidal silica is added to a water-dispersible resin having an MFT at about room temperature, but as the amount of such colloidal silica is increased, film formation gradually increases. Thus, a coating film having high hardness was hardly obtained by drying at room temperature (normal drying).

[Problems to be solved by the invention]

However, the present inventors have eagerly started research in view of the above-mentioned various disadvantages or difficulties in the conventional technology.

Therefore, the problems to be solved by the present invention are, in part, water resistance, including durability, such as alkali resistance and acid resistance, among others, in particular, film formation, stain resistance, hardness and An object of the present invention is to provide a highly practical aqueous coating composition capable of forming a coating film having excellent heat resistance and the like.

[Means for solving the problem]

Therefore, the present inventors have focused on the problems to be solved by the invention as described above, and as a result of diligent and repeated studies, that is, having the advantages and disadvantages as described above, As a result of various studies on the resin and the water-dispersible resin, here, in the form of eliminating the disadvantages of each resin, in particular, the film forming property,
Has durability, stain resistance, hardness and heat resistance, etc.
The present invention has been completed by finding an extremely practical aqueous coating composition.

That is, the present invention basically provides a simple method wherein at least one monomer selected from the group consisting of an alkyl ester of α, β-ethylenically unsaturated carboxylic acid and alkenylbenzene is an essential monomer. And a water-dispersible resin composition [A] obtained by subjecting 10 to 500 parts by weight of colloidal silica to emulsion polymerization in an aqueous system with respect to 100 parts by weight of the monomer mixture, and a silane cup. The weight ratio of the solid content of [A]: [B] to the ring agent [B] is 95: 5 to 50:50.
An extremely practical aqueous coating composition which forms a coating film having excellent film forming properties, durability, stain resistance, hardness and heat resistance, etc. They try to provide things.

The water-dispersible resin composition used in the present invention is an acrylic comonomer, that is, at least one monomer selected from the group consisting of α, β-ethylenically unsaturated carboxylic acid alkyl ester and alkenylbenzene. Refers to a water-dispersible composition obtained by subjecting 10 to 500 parts by weight (solid content) of colloidal silica to emulsion polymerization in an aqueous system with respect to 100 parts by weight (solid content).

Here, the aforementioned α, β-ethylenically unsaturated carboxylic acid alkyl ester (hereinafter, also referred to as an acrylic comonomer) and one of the essential raw material components for forming the water-dispersible resin composition, and And / or alkenylbenzene are particularly preferred as α, β
-10 to 500 parts by weight (in terms of solids) of colloidal silica is added to anionic surfactant and / or non-ionic in 100 parts by weight (in terms of solids) of ethylenically unsaturated carboxylic acid alkyl ester and / or alkenylbenzene. A water-dispersible resin composition obtained by emulsion polymerization in an aqueous system in the presence of an ionic surfactant is exemplified.

Here, as the at least one monomer selected from the group consisting of the above-mentioned α, β-ethylenically unsaturated carboxylic acid alkyl ester and alkenylbenzene, the following compounds may be mentioned.

That is, at first, only typical examples of such acrylic comonomers are exemplified, and esters of (meth) acrylic acid and alkanols (monohydric alcohols) having 1 to 18 carbon atoms can be mentioned. But,
Of those, only the most representative ones are to be illustrated, for example, methyl (meth) acrylate,
Ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, decyl (meth) acrylate, (meth) acryl Dodecyl acid or 2-hydroxyethyl (meth) acrylate, and styrene, α
-Methylstyrene or vinyltoluene.

In addition, α, β such as (meth) acrylic acid, maleic acid, maleic anhydride, fumaric acid, crotonic acid or itaconic acid, which are monomers copolymerizable with these ester comonomer and / or alkenylbenzene.
The use of monoethylenically unsaturated carboxylic acids is also possible.

Also, divinyldimethoxysilane, divinylbis-β
A polymerizable unsaturated bond such as a di- or trialkoxysilane-based compound such as -methoxy-ethoxysilane, vinyltriethoxysilane, vinyltris-β-methoxy-ethoxysilane or γ-methacryloxypropyltrimethoxysilane; and an alkoxysilyl group. When a silane monomer having a combination of about 20% by weight (of all monomers) or less is used at the time of emulsion polymerization, the compatibility between the organic polymer and the inorganic polymer is further improved,
Even more, a stable water-dispersible composition can be obtained, and the durability of the obtained coating film is even more.
To improve.

The colloidal silica refers to a dispersion in water containing SiO ₂ as a basic unit and particularly having a particle diameter of 4 to 100 μm (μm). Any of the basic groups can be used, and can be appropriately selected according to various conditions at the time of emulsion polymerization.

Among these, as the acidic colloidal silica,
"Snowtex O" (product of Nissan Chemical Industry Co., Ltd.) is particularly typical. On the other hand, as the colloidal silica on the basic side, "Snowtex 20, 30, 40, C
Or N "(product of the same company) is particularly representative.

The range of the amount of the colloidal silica used is 10 to 5 parts by weight based on 100 parts by weight of the acrylic comonomer described above.
The range within the range of 00 parts by weight is appropriate, and it is appropriate to use at such a ratio.

If the amount of the colloidal silica is less than 10 parts by weight based on 100 parts by weight of the acrylic comonomer, the effect of forming a strong organic-inorganic composite coating is not exhibited, and the durability, hardness, and colloidal silica such as stain resistance are not used. The features to have will be reduced. Conversely, if it exceeds 500 parts by weight, the flexibility of the acrylic polymer will decrease.

On the other hand, the silane coupling agent used in the present invention is not particularly limited, but is in a range generally used. As such a silane coupling agent, for example, a general formula Are included. Examples of commercially available silane coupling agents include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (2-
Methoxyethoxy) silane, N- (2-aminoethyl)
3-aminopropylmethyldimethoxysilane, N- (2
-Aminoethyl) 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2- (3,4-epoxycyclohexyl) Ethyltrimethoxysilane, 3-
Examples include chloropropylmethyldimethoxysilane, 3-chloropropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, and 3-mercaptopropyltrimethoxysilane. The solid component weight ratio of the water-dispersible resin composition obtained by emulsion polymerization in the presence of colloidal silica and the silane coupling agent is desirably in the range of 95: 5 to 50:50. If the ratio exceeds 95, the film formability is reduced, a continuous coating film cannot be obtained, and the crosslinking is insufficient. On the other hand, if the ratio of the silane coupling agent exceeds 50, the addition of the silane coupling agent to the aqueous system and dispersion stability are difficult, and the silane coupling agent bleeds into the obtained coating film, and the desired coating film is formed. Can not be obtained.

The aqueous coating composition obtained in the present invention was found to have good film-forming properties under normal drying conditions and excellent durability, stain resistance, hardness and heat resistance. Although the reason for having the above-mentioned features is not necessarily clear, during the emulsion polymerization, the surface OH group of the colloidal silica reacts with an acid monomer or a silane monomer to form a cross-linking, and as a result, the organic -It is believed that an inorganic hybrid-type water-dispersible composition is formed. Since it is of a hybrid type, it is superior in flexibility, film formability and storage stability as compared with those simply mixed. When the ratio of colloidal silica is high, the coating film itself shrinks and forms a cohesive force during film formation, which may cause cracking.In the present invention, however, the silane coupling agent is hydrolyzed, and the colloidal silica is hydrolyzed. Causes silanol condensation with the surface -OH group of the colloidal silica of the water-dispersible resin composition obtained by emulsion polymerization in the presence, exhibits good film forming properties, and has excellent stain resistance, heat resistance, and durability. It is considered to form a crosslinked film.

In addition, the hydrolysis of the silane coupling agent occurs on both the alkali side and the acid side.
It is recommended to adjust the pH to the acidic side, and use acidic catalysts, Sn-based, Zr-based,
The use of a Ti-based coordination compound catalyst also contributes to crosslinking.

If necessary, pigments (white pigments such as titanium dioxide, calcium carbonate, barium carbonate and kaolin, colored pigments such as redwood, carbon and cyanine blue) and plasticizers which are usually used for paints may be added to the obtained aqueous coating composition, if necessary. Additives used as ordinary components for coatings, such as solvents, dispersants, thickeners, defoamers, and preservatives, may be mixed and used.

The aqueous coating composition of the present invention, as a paint, paper,
Useful for fibers and various coatings (eg, glass, asbestos, plastics, ceramics, etc.).

〔The invention's effect〕

The coating composition of the present invention exhibits excellent film-forming properties by drying at room temperature (normal drying) and, in addition, gives a coating film having excellent durability, stain resistance, hardness and heat resistance. It is.

〔Example〕

Next, the present invention will be described more specifically with reference to Production Examples, Examples and Comparative Examples. In the following, all parts and percentages are by weight unless otherwise specified. I do.

Production Example 1 (Production of water-dispersible resin composition) (1) Polymerizable monomers 2-ethylhexyl acrylate 43 parts Methyl methacrylate 55〃 acrylic acid 2〃 (2) Surfactants sodium lauryl sulfonate 3 parts (3) Colloidal silica "Snowtecs 30" (solid content = 30%) 667 parts (4) Deionized water 88 parts (5) Polymerization initiators Ammonium persulfate 0.5 part Sodium bisulfite 0.2〃 Surfactant in four-necked flask , Charged with colloidal silica and ion-exchanged water and heated to 60 ° C in a nitrogen stream,
Next, polymerization initiators were added, and a mixture of polymerizable monomers was further added dropwise over 3 hours. At this time, the reaction temperature was adjusted to 60 to 70 ° C. The reaction is continued under stirring while maintaining the same temperature range for 2 hours after the completion of the dropwise addition, and then cooled and adjusted to pH 8 to 9 with 14% aqueous ammonia to obtain a stable water dispersibility of 35% in solid content. A resin composition was obtained.

Production Example 2 (Production of the same) (1) Polymerizable monomers 2-ethylhexyl acrylate 43 parts Methyl methacrylate 55〃 Acrylic acid 1 part γ-methacryloxypropyltrimethoxysilane 1〃 (2) Surfactants laurylsulfonic acid Sodium 3 parts (3) Colloidal silica "Snowtecs 30" (solid content = 30%) 667 parts (4) Deionized water 88 parts (5) Polymerization initiators ammonium persulfate 0.5 part Sodium hydrogen sulfite 0.2% In the same manner as in Production Example 1, a stable water-dispersible resin composition having a solid content of 35% was obtained by adjusting the pH to 8 to 9 with 14% aqueous ammonia.

Production Example 3 (Production of the same) (1) Polymerizable monomers 2-ethylhexyl acrylate 43 parts Methyl methacrylate 55〃 acrylic acid 2〃 (2) Surfactants Sodium lauryl sulfonate 3 parts (3) Colloidal silicas Snowtex 30 "(solid content = 30%) 20 parts (4) Deionized water 181 parts (5) Polymerization initiators Ammonium persulfate 0.5 part Sodium bisulfite 0.2〃 By adjusting the pH to 8 to 9 with 14% aqueous ammonia, a stable water-dispersible resin composition having a solid content of 35% was obtained.

Production Example 4 (Production of the same) (1) Polymerizable monomer 2-ethylhexyl acrylate 43 parts Methyl methacrylate 55〃 Acrylic acid 2〃 (2) Surfactants Sodium lauryl sulfonate 3 parts (3) Colloidal silica Snowtex 30 "(solid content = 30%) 2,000 parts (4) Polymerization initiators Ammonium persulfate 0.5 parts Sodium hydrogen sulfite 0.2〃 Produced in the same manner as in Production Example 1 and pH 8-9 with 14% aqueous ammonia To obtain a stable water-dispersible composition having a solid content of 35%.

Production Example 5 (Production of the same) (1) Polymerizable monomers 2-ethylhexyl acrylate 43 parts Methyl methacrylate 55〃 acrylic acid 2〃 (2) Surfactants sodium lauryl sulfonate 3 parts (3) ion-exchanged water 192 Part (4) Polymerization initiators Ammonium persulfate 0.5 Part Sodium bisulfite 0.2〃 Produced in the same manner as in Production Example 1 and adjusted to pH 8-9 with 14% aqueous ammonia to obtain a stable solid content of 35%. A water-dispersible resin composition was obtained.

Examples 1 to 3 and Comparative Examples 1 to 5 A silane coupling agent was added to each of the water-dispersible resin compositions obtained in Production Examples 1 to 5 described above.
Various water-dispersible resin compositions were prepared by adding or not adding at the ratios shown in the table and sufficiently stirring and dispersing with a stirrer.

Next, the pot life of each of these water-dispersible resin compositions themselves is evaluated and determined, and each of these water-dispersible resin compositions is individually applied to a predetermined substrate to be coated. At least, then, for the coating film thus obtained, film formability, hardness, stain resistance,
The water resistance and alkali resistance, the gel fraction with respect to the solvent and the swelling ratio were evaluated and determined. The results of these evaluation determinations are shown in the same table.

 The evaluation method is as follows.

(1) Pot life 100 g of the obtained aqueous coating composition was placed in a 100 cc sample bottle.
Samples were collected and stored at 25 ° C, and thickening-gelation was visually determined.
The number of days when the fluidity of the aqueous coating composition was lost was described as pot life.

(2) Film-forming properties Each aqueous coating composition was applied on a glass plate using a 6-mil applicator, dried at 25 ° C. and 65% RH for 2 days, and visually observed for cracks.

(3) Hardness Measurement of the Empitz hardness (fracture hardness) of the sample on which the film forming property was observed.

(4) Stain resistance A commercially available carbon paper is placed on the sample prepared in the same manner as the sample for evaluating the film forming property, a glass plate is further placed thereon, and a 2 kg weight is placed on the glass plate at 50 ° C. After leaving still in a dryer for 5 minutes, the carbon paper was peeled off, and the state of adhesion of the carbon to the film was visually observed.

(5) Water resistance A sample prepared in the same manner as the sample for evaluating the film forming property was immersed in water for 7 days, and the degree of whitening and swelling of the film was visually observed.

(6) Alkali resistance A sample prepared in the same manner as the sample for evaluating
The film was immersed in an aqueous solution of NaOH and the degree of whitening and swelling of the film was visually observed.

(7) Gel fraction, (8) Swelling ratio The aqueous coating composition is applied on release paper so that the dry film thickness is about 0.8 to 1.0 mm, and dried at 25 ° C. and 65% RH for 7 days. 1. Make a square film sample with a side of 2cm, 50cc
It was immersed in acetone for 48 hours, and the weight and area change were calculated by the following formula.

However, the weight of the film after immersion in acetone is the weight of the film taken out of acetone and dried at 80 ° C. for 1 hour.

However, the area of the film after immersion in acetone was taken out of the acetone and the side length was measured immediately.

Example 4 Vinyltriethoxysilane [“A-151” manufactured by Nippon Unicar Co., Ltd.] was used for 100 parts of the water-dispersible resin composition obtained in Production Example 1. 3.9 parts), and sufficiently stirred and dispersed to prepare an aqueous coating composition.

Next, when the evaluation judgment of this aqueous coating composition was performed, the pot life was 2 days, the hardness was 3H,
Moreover, the film-forming properties, stain resistance, water resistance and alkali resistance were also good.

Example 5 To 100 parts of the water-dispersible resin composition obtained in Production Example 1, 3.9 parts of vinyltrimethoxysilane ("KBM-1003" manufactured by Shin-Etsu Chemical Co., Ltd.) was added, and the mixture was stirred and dispersed to form an aqueous coating composition. Was prepared. When the obtained aqueous coating composition was evaluated, the pot life was 1 day, the hardness was 3H, and the film forming property, stain resistance, water resistance and alkali resistance were also good.

Claims (1)

(57) [Claims] 1. A monomer mixture comprising at least one monomer selected from the group consisting of α, β-ethylenically unsaturated carboxylic acid alkyl ester and alkenylbenzene as an essential monomer, A water-dispersible resin composition [A] obtained by emulsion-polymerizing 10 to 500 parts by weight of colloidal silica with respect to 100 parts by weight of the monomer mixture in an aqueous system, and a silane coupling agent [B] And [A]:
A composition for aqueous coating, characterized in that the composition has a solid content weight ratio of [B] of 95: 5 to 50:50.