JPH0940912A - Aqueous resin composition for paint - Google Patents

Abstract

(57) Abstract: [PROBLEMS] To provide an aqueous resin composition for paints containing a water-dispersible polysiloxane which gives a coating film having excellent stability when an organic solvent is added and good transparency. SOLUTION: A polymer block (A) having dimethyl siloxane as a repeating unit, a polymer block (B) having a vinyl polymerizable monomer as a repeating unit, and the polymer block (A) and the polymer block (A). The graft block copolymer composed of the silicon-containing graft crossing agent unit (C) copolymerized with B) is emulsified and dispersed in an aqueous medium in the presence of a surfactant.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an aqueous resin composition for paint.

[0002]

2. Description of the Related Art Polysiloxane resins have excellent heat resistance, water repellency and weather resistance and are useful as paint resins. However, when polysiloxane resins are used alone, their elastic modulus and strength are too low. Therefore, it is difficult to obtain a tough coating film, and its application is limited to a narrow range. For this reason, conventionally, a combination of a polysiloxane resin and an acrylic resin or a polyester resin has been devised to make the most of its characteristics.

In addition, various types of water-based paints, such as acrylic type and urethane type, have been developed and widely used because the risk of ignition, poisoning and air pollution is extremely small compared with solvent type paints. Some problems still remain in the practical application of an aqueous coating material containing a large amount of polysiloxane resin, and it is the current situation that it has not been widely used for general coating material applications.

For example, Japanese Patent Publication No. 63-23212 discloses a method of obtaining a water-soluble paint by introducing a plurality of alcoholic hydroxyl groups into the side chain of polysiloxane.
Compared with water-dispersed paints, paints that are completely soluble in water have a too high paint viscosity when the resin has a high molecular weight, and a large amount of hydrophilic functional groups remain in the paint film. Then, there are disadvantages such as difficulty in ensuring the water repellency of the coating film.

Further, in JP-A-1-161057, a water-based organic polymer is prepared by mixing a silanol- or alkoxysilane-containing silicone polymer and an organic polymer in the presence of a nonionic surfactant. Have been disclosed, and improvements in corrosion resistance have been observed with the introduction of more than 20% silicone.
However, in this method, it is difficult to obtain a homogeneous resin component due to lack of fluidity and compatibility of the polymer,
It is not suitable for applications that require transparency of the coating film.

On the other hand, water-dispersed paints are inferior to solvent-based paints in film-forming property and drying property, so that it is common to blend organic solvents such as film-forming aids and evaporation promoters to some extent. Since the blending of the organic solvent significantly affects the stability of the water-dispersed paint, the stability at the time of adding the organic solvent has always been a problem.

[0007]

In view of the above-mentioned current situation, the object of the present invention is to provide excellent stability when an organic solvent is added,
Another object of the present invention is to provide an aqueous resin composition for paints containing a water-dispersed polysiloxane that gives a coating film having good transparency.

[0008]

The present invention is directed to a polymer block (A) containing dimethylsiloxane as a repeating unit, a polymer block (B) containing a vinyl polymerizable monomer as a repeating unit, and the polymer block. A graft block copolymer composed of a silicon-containing graft crossing agent unit (C) copolymerized with (A) and the polymer block (B) is emulsified in an aqueous medium in which a surfactant (D) is present. A dispersed resin composition, wherein the content of the silicon-containing graft crossing agent unit (C) is based on the total amount of the polymer block (A) and the silicon-containing graft crossing agent unit (C). Is 1 mol% or more and 50 mol% or less, and the amount of the surfactant (D) is 0.05 wt% or more and 2.0 wt% or less with respect to the graft block copolymer. Providing coating aqueous resin composition characterized by.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The aqueous resin composition for coating of the present invention (hereinafter referred to as a resin composition) comprises a graft block copolymer emulsified and dispersed in an aqueous medium in which a surfactant is present. .

The graft block copolymer constituting the resin composition of the present invention comprises a polymer block (A) having dimethylsiloxane as a repeating unit (hereinafter referred to as polymer block (A)) and a vinyl polymerizable monomer. A polymer block (B) (hereinafter referred to as a polymer block (B)) having a repeating unit of ## STR3 ## and a silicon-containing graft crossing agent unit (C) (hereinafter referred to as a graft crossing agent unit (C)). The drug unit (C) is at least 1
The polymer block (A) is copolymerized through individual siloxane bonds, and the graft crossing agent unit (C) is also copolymerized with the polymer block (B).

The copolymerization of the graft crossing agent unit (C) and the polymer block (B) is carried out by copolymerizing the vinyl polymerizable functional group and the polymer block (B) in the graft crossing agent which is a raw material of the graft crossing agent unit (C). It can be achieved by radical copolymerization with the vinyl polymerizable monomer as the raw material of (1).

The polymer block (A) in the graft block copolymer of the present invention is dimethyldichlorosilane,
It can be synthesized using dimethyl dialkoxy silane, dimethyl siloxane cyclic oligomer and the like as raw materials. Considering the price of the raw material and the performance such as the thermal stability of the obtained resin, the most preferable raw material of the polymer block (A) is a dimethylsiloxane cyclic oligomer (dimethyl cyclics).
It is.

Further, examples of the vinyl polymerizable monomer used for constituting the polymer block (B) include, for example, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate and the like. Alkyl acrylate, methyl acrylate, ethyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, etc. alkyl acrylate, cycloalkyl methacrylate, cycloalkyl acrylate, methacrylic acid, acrylic acid, fumaric acid, maleic acid Acid, methacrylamide,
Examples thereof include styrene and α-methylstyrene.

The graft crossing agent used to form the graft crossing agent unit (C) is one or more silanol groups or alkoxysilyl groups in the molecule for copolymerization with the polymer block (A). Alternatively, those having a functional group such as a chlorosilyl group and a polymerizable group such as a vinyl group, an allyl group, a (meth) acryloyloxy group, and a p-vinylphenyl group for copolymerization with the polymer block (B) are mentioned. However, in the present invention, a vinyl polymerizable functional group-containing alkoxysilane compound is preferably used in view of polymerization reactivity and cost.

Examples of the vinyl-polymerizable functional group-containing alkoxysilane compound include, for example, γ-methacryloyloxypropylmethoxydimethylsilane, γ-methacryloyloxypropyldimethoxymethylsilane, γ-methacryloyloxypropyltrimethoxysilane and γ-methacryloyloxypropyl. Ethoxydiethylsilane, γ-
Examples thereof include methacryloyloxypropyldiethoxymethylsilane and γ-methacryloyloxytriethoxysilane.

Although the amounts of alkoxysilane and silanol contained in the siloxane polymer component can be controlled by the polymerization conditions of the siloxane component, the alkoxysilane and silanol residues are not necessary in the present invention, but rather the resin composition is stored. In order to ensure stability, it is better that these functional groups are few. Therefore, the total amount of alkoxy groups and hydroxy groups on the silicon atom contained in the polymer block (A) and the graft crossing agent unit (C) is determined by the total amount of the polymer block (A) and the graft crossing agent unit (C). It is preferably less than 2 mol% with respect to the total amount of silicon atoms.

The content of the graft crossing agent unit (C) in the graft block copolymer is determined by the polymer block (A).
And 1 mol% or more and 50 mol% or less based on the silicon atom with respect to the total amount of the graft crossing agent unit (C). If it is less than 1 mol%, the transparency of the obtained resin coating film On the other hand, when it exceeds 50 mol%, it is disadvantageous in terms of raw material cost, in addition, by-products such as alcohol released during condensation impair the stability and handleability of the latex, and further The membrane performance will be impaired. The content of the graft crossing agent unit (C) is preferably 1.5 mol% or more and 40 mol% or less, and more preferably 3 mol% or more and 20 mol% or less based on the above criteria. The content of the graft crossing agent unit (C) is 3 mol%
The transparency of the coating film obtained in the above case is extremely good,
When it is 20 mol% or less, the stability of latex during emulsion polymerization becomes good.

The content of the polymer block (B) in the graft block copolymer is based on the total amount of the polymer block (A), the polymer block (B) and the graft crossing agent unit (C). 50% by weight or more 95% by weight
The following is preferred. A coating film formed from a resin composition having a polymer block (B) content of less than 50% by weight tends to have reduced strength, and the polymer block (B) content exceeds 95% by weight. In this case, the water resistance and blocking resistance of the coating film tend to decrease. More preferably, it is 70% by weight or more and 95% by weight or less.

The resin composition of the present invention is provided in the form of an emulsion in which a resin component comprising a graft block copolymer having the above characteristics is emulsified and dispersed in an aqueous medium in which a surfactant (D) is present. However, the particle size of the emulsion can be arbitrarily changed according to the production method, and the average particle size is usually about 0.01 to 0.5 μm.

The content of the resin component in the emulsion can be arbitrarily selected, usually in the range of 50% by weight or less, but it is also possible to further increase the concentration by concentrating. When used for ordinary spray coating, a content of 15 to 45% by weight is preferable in consideration of coatability and coating film performance.

The type of the surfactant (D) used in the present invention is not particularly limited, but from the viewpoint of stability during polymerization, an anionic surfactant is used, or an acidic surfactant is used and then neutralized. Preferably. Examples of the surfactant that can be used include sodium alkylbenzene sulfonate, alkylbenzene sulfonic acid, sodium alkyl sulfate, sodium alkyl sulfonate, alkyl sulfonic acid and the like.

The amount of the surfactant (D) in the resin composition of the present invention is 0.10 with respect to the graft block copolymer.
It is necessary to be from 05% by weight to 2.0% by weight. When the amount of the surfactant is less than 0.05% by weight, it becomes difficult to emulsify and disperse the resin. Further, when the amount of the surfactant exceeds 2.0% by weight, the stability at the time of adding the organic solvent is lowered and the resin is apt to aggregate. The amount of the surfactant is more preferably 0.1% by weight or more and 1.0% by weight or less, and in this range, the emulsification and dispersion of the resin is extremely easy, and the stability upon addition of the organic solvent is further improved Become. A more preferable amount of the surfactant is 0.1% by weight or more and 0.5% by weight or less. Within this range, the stability when an organic solvent is added becomes extremely good.

The surfactant (D) is added to the resin composition of the present invention during the polymerization of the graft block copolymer.
It is performed after completion of the polymerization or at the time of blending the resin composition.

The method for producing the resin composition of the present invention is not particularly limited. For example, a cyclic dimethylsiloxane oligomer which is a raw material of the polymer block (A) and a vinyl polymerizable functional group which is a raw material of the graft crossing agent unit (C). Emulsion polymerization of the contained alkoxysilane in the presence of an acidic emulsifier and neutralization, followed by addition of a vinyl polymerizable monomer which is a raw material of the polymer block (B) and graft polymerization in the presence of a radical polymerization initiator. Can be manufactured in.

The total amount of the cyclic dimethyl siloxane oligomer and the vinyl-polymerizable functional group-containing polyfunctional alkoxysilane and water can be arbitrarily selected, but a weight ratio of 1: 1 to 1: 9 is preferable.

The acidic emulsifier is not particularly limited as long as it can open the cyclic dimethylsiloxane oligomer, but as an example of the acidic emulsifier which is easily available and suitable for polymerization, dodecylbenzenesulfonic acid can be mentioned.
The preferable amount of the acidic emulsifier used varies depending on the particle size of the intended emulsion, the solid content, the polymerization temperature and the combined use of other surfactants, but in order to accelerate the polymerization of the siloxane, the cyclic dimethylsiloxane oligomer and It is preferable to use 0.5% by weight or more based on the total amount of the vinyl-polymerizable functional group-containing polyfunctional alkoxysilane.

The polymerization temperature of the siloxane is not particularly limited, but it is preferable that it undergoes a thermal history of 60 ° C. or higher at least once, and more preferably 75 ° C. or higher.

The particle size of the obtained siloxane polymer emulsion can be controlled by the degree of preliminary dispersion of the raw material, the amount of emulsifier, the polymerization temperature and the method of supplying the raw material. Emulsions having a smaller particle size are prepared by preliminarily emulsifying the raw material and water with a high shear generator such as a homogenizer in the presence of an emulsifier, dropping the raw material or pre-emulsion into water, increasing the emulsifier, or polymerizing. It can be obtained by any method of raising the temperature or by appropriately combining these methods.

The time required for the polymerization of siloxane varies depending on the polymerization conditions, but is usually 0.5 hour or more and 1 month or less. Substantially no unreacted alkoxysilane remains in the siloxane polymer polymerized in the presence of the acidic emulsifier. Since the obtained siloxane polymer emulsion is strongly acidic, it is necessary to neutralize the siloxane after the polymerization is completed.

As the radical polymerization initiator used for the subsequent emulsion polymerization of the vinyl polymerizable monomer, known ones used for emulsion radical polymerization can be used. The method of charging the vinyl-polymerizable monomer is not particularly limited and may be batch charging or dropping.

The resulting emulsion as it is, or diluted with water, is sprayed or applied onto a plastic, a metal plate or a surface-treated base material by a spraying method or another method, and then dried and cured to form a coating film. Can be

The resin composition of the present invention may contain a pigment, a stabilizer, a co-curing agent, a curing aid, etc., if necessary, and further mixed with another emulsion resin, a water-soluble resin or a viscosity control agent. You may use.

[0033]

The present invention will be described in more detail with reference to the following examples. All parts in the examples are parts by weight. In addition, the evaluation of the performance in the examples and comparative examples was performed using the method described below.

(1) Transparency A heat-cured coating film having a thickness of about 100 μm applied on a glass plate was visually evaluated. ◯: No cloudiness is observed. B: Slightly cloudy. X: Clearly cloudy.

(2) Dilution stability with isopropyl alcohol 100 g of the emulsion was added with isopropyl alcohol (IPA) while stirring with a magnetic stirrer.
After standing for 4 hours, formation of aggregated polymer was observed by visual evaluation. Stability was evaluated by the amount of IPA that could be added with little formation of aggregated polymer. ⊚: Aggregate polymer is hardly formed even when IPA is added up to 100 g. ◯: Aggregated polymer is hardly formed even when IPA is added up to 50 g. Δ: Almost no aggregated polymer is formed even when IPA is added up to 20 g. X: A large amount of agglomerated polymer is produced or gelation occurs and the fluidity is lost when less than 20 g of IPA is added.

[Example 1] Dimethyl cyclics (D
MC, cyclic dimethylsiloxane oligomer 3 to 7-mer mixture) 90 parts, γ-methacryloyloxypropyltrimethoxysilane (KBM3) (graft crossing agent) 10
Part, 300 parts of water and 1 part of sodium dodecylbenzenesulfonate (DBSNa) (surfactant) were premixed with a homomixer, then sheared by a homogenizer at a pressure of 200 kg / cm ² , and forcibly emulsified. A silicone raw material emulsion was obtained.

Next, 100 parts of water and 1 part of dodecylbenzenesulfonic acid (DBSA) (acidic emulsifier) were charged into a flask equipped with a stirrer, a condenser, a heating jacket and a dropping pump, while keeping the temperature in the flask at 85 ° C. The above silicone raw material emulsion was added dropwise over 3 hours. After completion of dropping, heating and stirring were continued for another hour, and then the obtained emulsion was cooled to room temperature.
Dodecylbenzene sulfonic acid was neutralized with sodium hydroxide to obtain a silicone polymer emulsion.

Then, the total amount of the obtained silicone polymer emulsion, 820 parts of water and 5 parts of potassium persulfate were charged into a flask equipped with a stirrer, a condenser, a heating jacket and an inert gas inlet, and the temperature was raised to 70 ° C. Then, while stirring under a nitrogen atmosphere, 342 parts of methyl methacrylate (MMA), 540 parts of n-butyl methacrylate (BMA) and 18 parts of methacrylic acid (MAA) were stirred.
Part of the mixture was polymerized dropwise over 4 hours. After dropping,
The temperature was maintained at 70 ° C for 1 hour, the temperature was further raised to 80 ° C, and the temperature was maintained for 1 hour. The reaction solution was cooled to room temperature and neutralized with aqueous ammonia to obtain a silicone-acrylic polymer emulsion. The evaluation results of the obtained emulsion are shown in Table 1.

Example 2 The amount of DBSA used during the polymerization of the silicone polymer emulsion was changed to 4 parts,
Example 1 was repeated except that the amount of DBSNa in the finally obtained silicone-acrylic polymer emulsion was 0.5% by weight (based on the polymer) and the amounts of the respective raw material components were changed as shown in Table 1. A silicone-acrylic polymer emulsion was produced in the same manner. The evaluation results of the obtained emulsion are shown in Table 1.

Example 3 The amount of DBSA used during the polymerization of the silicone polymer emulsion was changed to 2 parts,
Example 1 except that the amount of DBSNa in the finally obtained silicone-acrylic polymer emulsion was 0.3% by weight (based on the polymer) and the amounts of the respective raw material components were changed as shown in Table 1. A silicone-acrylic polymer emulsion was produced in the same manner. The evaluation results of the obtained emulsion are shown in Table 1.

Example 4 The amount of each raw material component was changed as shown in Table 1, and the amount of DBSNa in the finally obtained silicone-acrylic polymer emulsion was 0.4% by weight.
A silicone-acrylic polymer emulsion was produced in the same manner as in Example 1 except that the amount of water charged in the graft copolymerization reaction of the component (B) was changed to 210 parts (to polymer). The evaluation results of the obtained emulsion are shown in Table 1.

Example 5 The silicone-acrylic polymer finally obtained by changing the weight ratio of the component (A) and the component (C) and the component (B) of Example 2 as shown in Table 1. Silicone was prepared in the same manner as in Example 1 except that the amount of DBSNa in the emulsion was set to 1.5% by weight (based on the polymer) and the amount of water charged during the graft copolymerization reaction of component (B) was set to 0 part. -Manufactured acrylic polymer emulsion. The evaluation results of the obtained emulsion are shown in Table 1.

Example 6 The amount of DBSA used during the polymerization of the silicone polymer emulsion was changed to 6 parts,
Example 1 was repeated except that the amount of DBSNa in the finally obtained silicone-acrylic polymer emulsion was 0.7% by weight (based on the polymer) and the amounts of the respective raw material components were changed as shown in Table 1. A silicone-acrylic polymer emulsion was produced in the same manner. The evaluation results of the obtained emulsion are shown in Table 1.

Comparative Example 1 A silicone-acrylic polymer emulsion was produced in the same manner as in Example 1 except that the amount of the graft crossing agent KBM3 was changed as shown in Table 1. The evaluation results of the obtained emulsion are shown in Table 1.

[Comparative Example 2] The amount of DBSA used during the polymerization of the silicone polymer emulsion was changed to 24 parts, and the amount of DBSNa in the finally obtained silicone-acrylic polymer emulsion was 2.5% by weight (based on the polymer). A silicone-acrylic polymer emulsion was produced in the same manner as in Example 1 except that the above was adopted. The evaluation results of the obtained emulsion are shown in Table 1.

Comparative Example 3 The amount of DBSA used during the polymerization of the silicone polymer emulsion was changed to 14 parts, and 25 parts of DBSNa was added before the dropwise polymerization of the component (B) to finally obtain the silicone-acrylic polymer. Silicone was prepared in the same manner as in Example 1 except that the amount of DBSNa in the emulsion was adjusted to 4.0% by weight (based on the polymer) and the amounts of the raw material components were changed as shown in Table 1.
An acrylic polymer emulsion was prepared. The evaluation results of the obtained emulsion are shown in Table 1.

[0047]

[Table 1]

[0048]

EFFECT OF THE INVENTION The resin composition of the present invention provides a coating film with good transparency and has good solvent dilution stability.
It can be used for various paint applications as a resin for an aqueous emulsion paint containing a polysiloxane.

Claims (1)

[Claims] 1. A polymer block (A) having dimethylsiloxane as a repeating unit, a polymer block (B) having a vinyl polymerizable monomer as a repeating unit, and the polymer block (A) and the polymer block. A resin composition in which a graft block copolymer composed of a silicon-containing graft crossing agent unit (C) copolymerized with (B) is emulsified and dispersed in an aqueous medium in which a surfactant (D) is present. The content of the silicon-containing graft crossing agent unit (C) is 1 mol% or more based on the silicon atom with respect to the total amount of the polymer block (A) and the silicon-containing graft crossing agent unit (C). 50 mol% or less, and the amount of the surfactant (D) is 0.05% by weight or more and 2.0% by weight or less with respect to the graft block copolymer, water for paints. Resin composition.