JP3479563B2 - Resin composition for paint and method for producing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating resin composition, and more particularly to a coating resin containing a water-dispersible polysiloxane that provides a coating film having excellent weather resistance and water resistance and an excellent appearance. The present invention relates to a composition and a method for producing the same.

[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, coating films formed by using a polysiloxane resin alone have It is difficult to obtain a tough coating film because its rate and strength are too low, and its use is limited to a narrow range. Therefore, conventionally, by combining polysiloxane resin and acrylic resin or polyester resin,
Ingenuity has been made to make use of these characteristics as a paint.

A so-called emulsion paint, in which a resin component is emulsified and dispersed in water, is more flammable than a solvent-based paint.
Various types of emulsion paints using acrylic resins, urethane resins, etc. have been developed and widely used because of the extremely low risk of poisoning and air pollution, but they contain a large amount of polysiloxane resin. In the practical application of emulsion paints, some problems still remain, and it is the current situation that they have not been widely used for general paint applications.

Japanese Examined Patent Publication No. 63-23212 discloses a method for producing a water-soluble paint using a resin in which a plurality of alcoholic hydroxyl groups are introduced into a side chain of polysiloxane.
However, in the case of a paint using such a completely water-soluble polysiloxane, when the polysiloxane resin is made to have a high molecular weight for the purpose of improving the coating properties, the paint viscosity becomes high and its coating property becomes poor. It has the drawback of decreasing.
Furthermore, since a coating film formed from this coating material has a large amount of hydrophilic functional groups, the water repellency and water resistance of the coating film tend to be low.

In JP-A-1-315451 and JP-A-2-92974, a core composed of a crosslinked polysiloxane obtained by copolymerization of a vinyl-polymerizable monomer and a polyfunctional alkoxysilane containing a vinyl-polymerizable functional group ( Disclosed is an invention of a so-called core / shell type emulsion paint in which a vinyl polymerizable functional group is introduced into a surface layer of a core) by using a graft crossing agent and then a shell of an acrylic polymer having a hydrophilic group is formed. It has been shown that the excellent thixotropic property improves the sagging property. However, if an emulsion paint containing a large amount of polysiloxane is to be produced by this method, it is necessary to use a large amount of an expensive graft crossing agent, which causes a problem of high raw material cost.

In JP-A-1-161057, a water-based organic polymer is modified by mixing a silicone polymer having silanol or alkoxysilane and an organic polymer in the presence of a nonionic surfactant. And a coating with improved corrosion resistance. However, in this method, it is necessary to introduce a large amount of alkoxysilane or silanol groups into the silicone polymer in order to connect the organic polymer and the silicone polymer, and it is generated between the organic polymer and the silicone polymer. The Si-O-C bond has a drawback that it has poor chemical stability. Furthermore, in the case of mixing such heterogeneous polymers, in order to compensate for the lack of fluidity and compatibility of the polymers, it is necessary to add a common good solvent at the time of mixing both, and there is still concern about environmental pollution. Remain.

In Japanese Patent Laid-Open No. 4-202554, a vinyl-polymerizable functional group-containing polyfunctional alkoxysilane and a vinyl-polymerizable monomer are mixed with an alkoxydimethylsilane and emulsion-polymerized to form a flexible coating film. It has been shown that an emulsion paint for concrete exterior wall paint is obtained. However, since the functional group used for crosslinking and curing the coating film formed from the coating material obtained by this method is alkoxysilane or silanol, a large amount of alkoxysilane or silanol is left in the resin in order to obtain a tough coating film. Therefore, it is necessary to use a large amount of expensive alkoxysilane, which causes a problem that the raw material cost becomes high.

[0008]

The present invention has been made to solve the drawbacks of the prior art, and the object of the present invention is to provide an aqueous emulsion paint which gives a cured coating film excellent in appearance and durability. To provide.

[0009]

Means for Solving the Problems As a result of intensive studies in view of the present situation, the present inventors have completed an invention comprising a coating resin composition and a method for producing the same, which can solve the above problems. That is, the gist of the present invention is that a polymer block (A) having dimethylsiloxane as a repeating unit, a polymer block (B) having a vinyl polymerizable monomer as a repeating unit, and a polymer block (A).
A graft block copolymer composed of a silicon-containing graft crossing unit (C) copolymerized with the polymer block (B) is emulsified and dispersed in water in the presence of a surfactant. A resin composition for coatings, wherein the content of the graft crossing unit (C) is 1 mol% or more and 50 mol% or more based on the silicon atom with respect to the total amount in the polymer block (A) and the graft crossing unit (C). Is
In addition, 3 to 30% by weight of the repeating unit constituting the polymer block (B) is constituted by a hydroxyalkyl functional group side chain, and a coating resin composition.
(However, at least 2 mol% of the polymer block (B)
But glycidyl acrylate, glycidyl methacrylic acid
Selected from N-alkoxymethyl acrylamide
Vinyl polymerizable monomer having self-crosslinking functional side chain
Except for those composed of repeating units of) , and,
50 mol% or more and 99 mol% or more based on the amount of silicon atoms
The following cyclic dimethyl siloxane oligomer and a graft crossing agent comprising 1 mol% or more and 50 mol% or less of a vinyl-polymerizable functional group-containing polyfunctional alkoxysilane are emulsion-polymerized and neutralized in the presence of an acidic emulsifier, and further, A vinyl polymerizable monomer having 3 to 30% by weight of a hydroxyalkyl functional side chain and 70 to 97% by weight of another vinyl monomer based on the total amount of the monomer (provided that the total amount of the monomer is To
Glycidyl acrylate, glycidyl methacrylate
Selected from N-alkoxymethyl acrylamide
Vinyl polymerizable monomer having self-crosslinking functional side chain
(Excluding those containing 2 mol% or more) are graft-copolymerized in the presence of a radical polymerization initiator.

In the present invention, the graft block copolymer is obtained by copolymerizing the graft crossing unit (C) with a polymer block (A) having dimethylsiloxane as a repeating unit through at least one siloxane bond. It is necessary that the graft crossing unit (C) is copolymerized with the polymer block (B) composed of a vinyl polymerizable monomer. The graft crossing unit (C) and the polymer block (B) are the vinyl polymerizable functional group in the graft crossing agent which is the raw material of the graft crossing unit (C) and the vinyl which is the raw material of the polymer block (B). It is copolymerized by radically copolymerizing with a polymerizable monomer.

The polymer block (A) has a repeating unit of dimethylsiloxane synthesized from dimethyldichlorosilane, dimethyldialkoxysilane, cyclic oligomer of dimethylsiloxane, etc. as a raw material. Among them, dimethylsiloxane cyclic oligomer (dimethyl cyclics) is preferable as the raw material of the polymer block (A) from the viewpoint of performance such as thermal stability of the obtained resin and cost. The weight average molecular weight of the polymer block (A) is preferably 10,000 or more, more preferably 50,000 or more.

As the graft crossing agent which is a raw material of the graft crossing unit (C), at least one vinyl polymerizable group and one or more silanol groups, alkoxysilane groups or chlorosilane groups such as siloxane bonds can be formed in the molecule. It has various functional groups. Among them, those having an alkoxysilane group as a functional group capable of forming a siloxane bond are preferable from the viewpoint of durability of the obtained resin. Any vinyl-polymerizable monomer unit contained in the graft crossing unit (C) may be used as long as it is copolymerizable with the vinyl-polymerizable monomer constituting the polymer block (B) in ordinary radical polymerization. Well, for example, vinyl group, allyl group, γ-acryloyloxypropyl group, γ-
Examples thereof include a methacryloyloxypropyl group and p-vinylphenyl group, and an example of a vinyl-polymerizable monomer unit having good copolymerizability is a methacryloyloxy group. One of preferred structures as the graft crossing unit (C) is represented by the following formula [1].

[Chemical 1]

Graft crossover units (C) relative to the total amount in the polymer block (A) and graft crossover units (C)
It is necessary that the content of 1 mol% or more and 50 mol% or less based on silicon atoms. This is because when the graft crossing unit content is less than 1 mol%, the transparency of the coating film formed from the obtained emulsion is poor, while when the graft crossing unit content exceeds 50 mol%, In addition to being disadvantageous in terms of cost, by-products such as alcohols that are eliminated during the condensation of the polymer block (A) and the graft crossing unit (C) are likely to impair the stability of the latex, and Handleability,
Furthermore, it is because the performance of the coating film formed from the emulsion is impaired. Preferably, the content of the graft crossing unit (C) is 1.5 mol% or more 4 based on the above criteria.
0 mol% or less, more preferably 3 mol% or more 2
It is 0 mol% or less. When the content of the graft crossing unit (C) is 3 mol% or more, the transparency of the coating film obtained from the obtained emulsion tends to be further improved, and the content of the graft crossing unit (C) tends to be high. When it is 20 mol% or less, the latex stability at the time of emulsion-polymerizing the vinyl polymer tends to be improved.

The number of siloxane bonds generated from the graft crossing unit (C) is 1 to 3, but so-called 3 such as trialkoxysilane which can form 3 siloxane bonds.
When a functional silane is used as the graft crossing agent, a crosslinked structure is formed in the siloxane polymer depending on the amount used, and the emulsion obtained by graft-polymerizing the vinyl polymerizable monomer onto the siloxane polymer is used as a coating agent. The content of the trifunctional silane is preferably 10 mol% or less based on the above criteria, because the compatibility between the two during film formation tends to decrease and the transparency and durability of the coating film may decrease. The inert substituent on the silicon atom introduced into the graft crossing agent comprising a bifunctional or monofunctional silane compound used in the present invention is not particularly limited, but generally, an alkyl group represented by a methyl group, A phenyl group or a derivative thereof.

The amounts of alkoxysilane and silanol contained in the siloxane polymer component can be controlled by the polymerization conditions of the siloxane component, but the alkoxysilane and silanol residues are not necessary in the siloxane polymer component used in the present invention, but rather the resin. In order to ensure the storage stability of the composition, it is preferable that these functional groups are small. Preferably, the total amount of alkoxy groups and hydroxy groups on the silicon atoms contained in the polymer block (A) and the graft crossing unit (C) is the total amount of silicon atoms in the polymer block (A) and the graft crossing unit (C). It is preferably less than 2 mol%.

In the present invention, the polymer block (B) containing a vinyl-polymerizable monomer as a repeating unit may have a hydroxyalkyl functional side chain in an amount of 3 to 30 % by weight of the repeating units constituting the polymer block (B). is necessary. When the amount of the monomer having a hydroxyalkyl functional group side chain is less than 3% by weight, the water resistance of the coating film becomes insufficient, which is not preferable. More preferably, it is in the range of 5 to 20% by weight. The number of carbon atoms of the alkyl group of the hydroxyalkyl functional group is not particularly limited, but the number of carbon atoms of the alkyl group is preferably 16 or less in consideration of ease of emulsion polymerization. Further, taking the water resistance of the resulting coating film into consideration, it is preferable that the hydroxyalkyl group is introduced into the side chain of the methacrylic ester. Examples of monomers having a hydroxyalkyl functional group side chain include hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxybutylethyl methacrylate, hydroxyhexyl methacrylate,
Examples thereof include hydroxyoctyl methacrylate.

The polymer block (B) may further have a side chain of other functional group, for example, by containing a strongly polar functional group such as a carboxyl group or an amide group, the base material of the coating film. Adhesion to is likely to improve. However, in consideration of the stability of emulsion polymerization, it is not preferable to include a large amount of these, and for example, for a carboxyl group, the amount of a monomer containing this is preferably 5% by weight or less. , And more preferably 3% by weight or less.

Examples of the component that constitutes the polymer block (B) and does not contain a polar functional group include alkyl methacrylate, alkyl acrylate, cycloalkyl methacrylate, cycloalkyl acrylate and styrene. 70 at least one
It is preferable that the content is at least wt%. Alkyl acrylate is often used as a component of a coating resin, and among them, ethyl acrylate, butyl acrylate and the like increase the flexibility of the resin and are known as a component that imparts hydrophobicity, but in the silicone-containing emulsion of the present invention,
The content of alkyl acrylate is preferably 20% by weight or less. This is because when the content of alkyl acrylate exceeds 20% by weight, the coating film tends to be whitened when it comes into contact with water. The range is more preferably 10% by weight or less, and further preferably 5% by weight or less.

The content of the polymer block (B) with respect to the total amount of the polymer block (A), the polymer block (B) and the graft crossing unit (C) is preferably in the range of 50 to 95% by weight. . A coating film formed from a resin composition having a content of the polymer block (B) of less than 50% by weight has an increased flexibility, but the strength and durability of the coating film tend to be reduced. This is because if the content of B) exceeds 95% by weight, the water resistance and blocking resistance of the coating film tend to decrease. More preferably, it is in the range of 70 to 95% by weight.

The resin composition of the present invention is provided in the form of an emulsion in which the resin component having the above characteristics is emulsified and dispersed in water in the presence of a surfactant. The particle size of the emulsion can be arbitrarily changed depending on the production method, but the average particle size is usually about 0.01 μm to 0.5 μm.

The content of resin component in the emulsion is usually 5
The content can be arbitrarily selected at a content of 0% by weight or less, but a higher concentration can be obtained by concentrating. When this emulsion is subjected to a usual spray coating method, the resin component content is preferably in the range of 15 to 45% by weight in view of its coatability and the performance of the resulting coating film.

The coating resin composition of the present invention may optionally contain a pigment, a stabilizer, a co-curing agent or a curing aid, and is further mixed with another emulsion resin, a water-soluble resin or a viscosity control agent. You may use. The crosslinked cured coating film obtained from the resin composition of the present invention has smooth and good gloss, and has significantly improved water resistance as compared with the coating film formed from the resin composition having no self-crosslinking functional group. May be included.

The resin composition having the features of the present invention includes, for example, 50 mol% or more and 99 mol% or less of a cyclic dimethylsiloxane oligomer and 1 based on the amount of silicon atoms.
Mol% to 50 mol% of a vinyl polymerizable functional group-containing polyfunctional alkoxy grafting agent consisting of silane emulsion polymerization in the presence of an acidic emulsifier, after neutralization, 3-30 relative to the total amount of the monomers By adding a vinyl polymerizable monomer having a side chain of hydroxyalkyl functional group in weight% and performing graft copolymerization in the presence of a radical polymerization initiator,
It can be suitably manufactured. That is, a polymer comprising the polymer block (A) and the graft crossing unit (C) is obtained by emulsion polymerization, and further, the graft crossing unit (C) and the polymer block (B) are copolymerized by graft copolymerization. The graft block copolymer of the present invention can be obtained.

The ratio of the total amount of the cyclic dimethyl siloxane oligomer and the polyfunctional alkoxysilane containing a vinyl polymerizable functional group to water can be arbitrarily selected, but the weight ratio is 1: 1 to 1.
A range of 1: 9 is preferred. The acidic emulsifier is not particularly limited as long as it can open the cyclic dimethylsiloxane oligomer, but examples of acidic emulsifiers that are readily available and suitable for polymerization include dodecylbenzene sulfonic acid. The preferable amount of the acidic emulsifier used varies depending on the particle size of the resin formed in 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, , Relative to the total amount of cyclic dimethyl siloxane oligomer and polyfunctional alkoxysilane containing vinyl polymerizable functional group
It is preferable to use 0.5% by weight or more.

The polymerization temperature of siloxane is not particularly limited, but it is preferable that the siloxane is subjected to 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. Emulsion having a resin having a smaller particle size is preliminarily emulsified with a high shear generator such as a homogenizer in the presence of a raw material and water, a raw material or a pre-emulsion is dropped into water, or the emulsifier is increased, It can be obtained by any method of raising the polymerization 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 hours or more and 1 month or less. In the siloxane polymer polymerized in the presence of the acidic emulsifier, substantially no unreacted alkoxysilane remains. 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 for charging the vinyl-polymerizable monomer is not particularly limited and may be batch charging or dropping. The polymerization temperature is not particularly limited, but when a self-crosslinking functional group having low stability is used, it is preferable to set the upper limit of the polymerization temperature so that the functional group is not deteriorated.

The resulting emulsion as it is or diluted with water is sprayed or applied onto a plastic, a metal plate or a surface-treated substrate, then dried and cured to form a coating film. Can be The drying and curing temperatures are determined by the type of self-crosslinking functional group, but are preferably 80 ° C to 200 ° C.

Hereinafter, the present invention will be described in more detail with reference to Examples. All "parts" in the examples are parts by weight.

[0029]

Example 1 90 parts of dimethyl cyclics (a mixture of cyclic dimethyl siloxane oligomer 3 to 7 mer), 10 parts of a graft crossing agent (γ-methacryloxypropyldimethoxymethylsilane), 300 parts of water, and sodium dodecylbenzenesulfonate 0 After premixing the composition consisting of 0.5 parts with a homomixer, 2 parts were mixed with a homogenizer.
It was sheared at a pressure of 00 Kg / cm ² and forcedly emulsified to obtain a silicone raw material emulsion.

A flask equipped with a stirrer, a condenser, a heating jacket and a dropping pump was charged with 100 parts of water and 10 parts of dodecylbenzenesulfonic acid, and the above silicone raw materials were taken for 3 hours while keeping the temperature in the flask at 85 ° C. The emulsion was added dropwise. After further heating and stirring for 1 hour, the obtained emulsion was cooled to room temperature and neutralized with sodium hydroxide to obtain a silicone polymer emulsion. The average number molecular weight (Mn) of the silicone polymer measured by GPC was about 100,000.

The obtained silicone polymer emulsion was placed in a flask equipped with a stirrer, a condenser, a heating jacket and an inert gas introduction hole, added with an aqueous solution of EDTA, Rongalit and ferrous oxide and heated to 70 ° C. , 792 parts of butyl methacrylate (BMA), 0 part of n-butyl methacrylate (BA), and hydroxyethyl methacrylate (HEM) with stirring under a nitrogen atmosphere.
A) 90 parts, methacrylic acid (MAA) 18 parts, and cumene hydroperoxide (CHP) 1 as an initiator
Part of the mixture was polymerized dropwise over 3 hours. After the dropping is completed,
The temperature was maintained at 70 ° C for 1 hour, 0.5 parts of CHP was further added, and the temperature was maintained at 80 ° C for 2 hours. Then, the reaction liquid was cooled to room temperature to obtain a silicone-acrylic composite polymer emulsion.

The obtained emulsion had a viscosity suitable for coating. When 5% (to emulsion) of butyl cellosolve was added and coated on a test steel plate with a bar coater and dried at room temperature, a smooth and transparent coating film was obtained. was gotten. The viscosity and coatability of the resulting emulsion did not change for at least 1 week. Furthermore, when this coating film was heated at 120 ° C. for 25 minutes, a smooth, transparent and tough crosslinked coating film was obtained. The 60 ° gloss value of the heat-cured coating film measured by a gloss meter was 90. Further, the 60 ° gloss value measured after immersing the heat-cured coating film in warm water of 40 ° C. for 1 hour was 90, showing that the coating film had good water resistance.

[0033]

Examples 2 to 5 Silicone / acrylic composite polymer emulsions were prepared in the same manner as in Example 1 except that the amounts of the raw materials used in Example 1 were changed as shown in Table 1.
Furthermore, after performing the same coating and heat curing as in Example 1,
The appearance of the coating film and the water resistance test were performed. The results are shown in Table 1.
It was shown to.

[0034]

Example 6 The amount of acrylic monomer component (B) used was 0.
The same procedure as in Example 1 except that the silicone
An acrylic composite polymer emulsion was prepared, and the 60 ° gloss value of the coating film formed as this emulsion was 82. (Table 1).

[0035]

Comparative Example 1 A silicone-acrylic composite polymer emulsion was prepared in the same manner as in Example 1 except that the amount of the graft crossing agent was reduced as shown in Table 1. The transparency of the coating film formed from this emulsion was poor. (Table 1).

[0036]

Comparative Example 2 Of the acrylic monomer components (B), HE
A silicone-acrylic composite polymer emulsion was prepared in the same manner as in Example 1 except that MA was 0 part. It was found that the coating film formed from this emulsion was inferior in water resistance due to the occurrence of blisters after the water resistance test.

[0037]

[Comparative Example 3] Of the acrylic monomer components (B), HE
When a silicone-acrylic composite polymer emulsion was produced in the same manner as in Example 1 except that MA was 18 parts and MAA was 90 parts, the polymerization was slightly unstable and cullet formation was observed. It was very noticeable.
The evaluation results up to this point are also shown in Table 1.

[Table 1]

* Note: Evaluation of transparency In a visual evaluation of a heat-cured coating film having a thickness of about 300 μm applied on a glass plate, ◯: no fog was observed, Δ: slight fog was observed, x: clear white turbidity was observed. To be

[0039]

INDUSTRIAL APPLICABILITY The resin composition of the present invention can be used as a resin for an aqueous emulsion paint containing a polysiloxane and gives a coating film having good appearance and durability, and
Since it has good storage stability, it can be used for various paint applications. Further, the production method of the present invention is extremely useful as a method for producing the polysiloxane-containing resin composition for coating material having the above-mentioned characteristics in a stable and inexpensive manner.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-261454 (JP, A) JP-A-5-209149 (JP, A) JP-A-8-3512 (JP, A) JP-A-3- 126735 (JP, A) Patent 3387633 (JP, B2) (58) Fields investigated (Int.Cl. ⁷ , DB name) C09D 1/00-201/10 C08F 290/00-290/14 C08F 299/00- 299/08

Claims (3)

(57) [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 a copolymer block with the polymer block (A), and , Polymer block (B)
A resin composition obtained by emulsifying and dispersing a graft block copolymer composed of a silicon-containing graft crossing unit (C) copolymerized with, in the presence of a surfactant.
The content of the graft crossing unit (C) with respect to the total amount in the polymer block (A) and the graft crossing unit (C) is 1 mol% or more and 50 mol% or less based on the silicon atom, and the polymer block 3 to 30% by weight of the repeating unit constituting (B) is composed of hydroxyalkyl functional group side chains (at least in the polymer block (B). 2 mol%
But glycidyl acrylate, glycidyl methacrylic acid
Selected from N-alkoxymethyl acrylamide
Vinyl polymerizable monomer having self-crosslinking functional side chain
Excluding those composed of repeating units) . 2. The content of the polymer block (B) with respect to the total amount of the polymer block (A), the polymer block (B) and the graft crossing unit (C) is 50% by weight or more and 95% or more.
The resin composition for coating composition according to claim 1, wherein the resin composition is contained in an amount of not more than 5% by weight. 3. 50 mol% based on the amount of silicon atoms
To 99 mol% or more of a cyclic dimethylsiloxane oligomer, and 1 mol% to 50 mol% of a graft cross-linking agent composed of a vinyl-polymerizable functional group-containing polyfunctional alkoxysilane, are emulsion-polymerized and neutralized in the presence of an acidic emulsifier. Furthermore, 3 to 30% by weight of a hydroxyalkyl group-containing vinyl polymerizable monomer and 70 to 97% by weight of another vinyl monomer based on the total amount of the monomers (provided that the total amount of the monomers is based on the total amount of the monomers).
Glycidyl acrylate, glycidyl methacrylate
Selected from N-alkoxymethyl acrylamide
Vinyl polymerizable monomer having self-crosslinking functional side chain
(Excluding those containing 2 mol% or more of) are graft-copolymerized in the presence of a radical polymerization initiator.