JP2006096950A - Resin composition for water-based coating - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resin composition which has a small evaporable organic compound content and is used for water-based coatings having excellent light resistance, stain resistance and film formability. <P>SOLUTION: This resin composition for water-based coatings is characterized by comprising different phase structure-having polymer particles obtained by a multistage polymerization method, wherein a cycloalkyl group-containing polymerizing monomer is contained in the innermost phases of the polymer particles in an amount of 10 to 50 wt.%. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a resin composition for water-based paints, and more particularly relates to a resin composition for water-based paints having a low VOC (volatile organic compound) content and excellent light resistance, stain resistance, and film-forming properties.

In recent years, water-based paints are widely used in place of solvent-based paints using organic solvents from the viewpoint of pollution-free, good workability, and resource saving. However, even in the case of water-based paints, in order to ensure the film-forming properties of the paint, a film-forming aid, a solvent, or the like that becomes a VOC component is currently added. However, health damage due to indoor air pollutants such as VOC contained in adhesives and paints has become a serious social problem, and it is strongly requested not to contain VOCs or to reduce the content of paints. On the other hand, for example, low VOC resin compositions for water-based paints using an emulsion resin having a heterogeneous structure obtained by multistage polymerization have been proposed (Patent Documents 1 and 2).
JP 2002-371225 A JP 2004-149686 A

  However, the weather resistance, stain resistance, and film formability of the coating film are not always sufficient. Accordingly, an object of the present invention is to provide a resin composition for water-based paints that has a low VOC content and is excellent in light resistance, stain resistance, and film-forming properties.

  In order to solve the above-mentioned problems, the present inventors include a predetermined amount of a polymerizable monomer having a specific functional group in the innermost phase of polymer particles having a heterogeneous structure obtained by multistage polymerization, thereby allowing VOCs to be contained. The present invention has been completed by finding that a resin composition for water-based paints excellent in light resistance, stain resistance and film-forming property can be obtained while suppressing the content of. That is, the resin composition for water-based paints of the present invention contains polymer particles having a heterogeneous structure obtained by multistage polymerization, and a polymerizable monomer containing a cycloalkyl group is contained in the innermost phase of the polymer particles. It is characterized by containing 10 to 50% by weight.

  In the present invention, the polymer particles having a different phase structure obtained by multistage polymerization refer to core-shell type polymer particles, and the innermost phase refers to the core portion. Further, the shell portion is composed of one or more layers, the outermost layer of the shell portion is the outermost phase, and the phase between the innermost phase and the outermost phase is an intermediate phase. According to the present invention, the innermost phase of the polymer particles contains a polymerizable monomer containing a cycloalkyl group in an amount of 10 to 50% by weight, whereby the light resistance of the coating film is suppressed while suppressing the VOC content. It has become possible to improve the property, stain resistance, and film forming property.

  Moreover, in this invention, the outermost phase of the said polymer particle can also be comprised with the ethylenically unsaturated monomer which has a glass transition temperature lower than the glass transition temperature of the polymer which comprises an innermost phase. Thereby, the outermost phases of a large number of polymer particles are easily fused, and the film formability of the coating film can be further improved.

  Moreover, in this invention, the said innermost phase can be comprised with the polymer of the ethylenically unsaturated monomer whose glass transition temperature is 0-50 degreeC. Thereby, the film formability can be further improved.

  Moreover, in this invention, content of a volatile organic compound can be less than 0.1 weight%. Furthermore, the minimum film forming temperature can be 5 ° C. or less.

  ADVANTAGE OF THE INVENTION According to this invention, the resin composition for water-based paints which is excellent in a weather resistance, stain resistance, and film formability with low odor and low VOC can be provided.

Hereinafter, embodiments of the present invention will be described.
(Polymer constituting the innermost phase)
The polymer particles contained in the resin composition of the present invention include a single weight of a polymerizable monomer containing a cycloalkyl group represented by the following general formula (1) in the polymer constituting the innermost phase. A polymer or a copolymer can be used.

_{CH 2 = C (R 1)} -C (= O) -O-X (1)
(In the formula, R ₁ represents a hydrogen atom, a methyl group or an ethyl group, and X represents a cycloalkyl group which may have a substituent.)

  Here, examples of the cycloalkyl group include monocyclic saturated hydrocarbon groups such as a cyclopentyl group, a cyclohexyl group, and a cyclododecyl group. In addition, the substituent of the cycloalkyl group includes an alkyl group having 1 to 7 carbon atoms, that is, a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a t-butyl group, a pentyl group, and a hexyl group. And heptyl group.

  Specific examples of the polymerizable monomer containing a cycloalkyl group include cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, methylcyclohexyl (meth) acrylate, t-butylcyclohexyl (meth) acrylate, and hydroxymethylcyclohexyl (meth). An acrylate, cyclooctyl (meth) acrylate, cyclodecyl (meth) acrylate, cyclododecyl (meth) acrylate, etc. can be mentioned, These 1 type (s) or 2 or more types can be used.

The polymerizable monomer copolymerized with a polymerizable monomer containing a cycloalkyl group includes an acrylic polymerizable monomer, a polymerizable monomer that forms a urethane bond, or a silicon-containing acrylic polymerizable monomer. The glass transition temperature of the copolymer needs to be in the range of 0 to 50 ° C, more preferably 10 to 30 ° C. This is because when the glass transition temperature is lower than 0 ° C., the toughness of the coating film is lowered, and when it is higher than 50 ° C., the film formability is lowered. Here, the glass transition temperature (Tg) of the copolymer can be determined from the glass transition temperature (Tg _n ) of the homopolymer of the component monomer by the following equation.
1 / Tg = W ₁ / Tg ₁ +... + W _n / Tg _n
(Tg 1, ···, _{Tg n} is the glass transition temperature of the homopolymer of component monomers, _{respectively,} W 1, · · · ·, _{W n} is the weight fraction of each monomer.)

  The acrylic polymerizable monomer is not particularly limited. For example, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, t-butyl (meth) acrylate, 2- Alkyl group-containing (meth) acrylic polymerizable monomers such as ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, and the like. Hydroxyl group-containing (meth) acrylic polymerizable monomers such as 2-hydroxyethyl (meth) acrylate, ethylenically unsaturated carboxylic acid polymerizable monomers such as (meth) acrylic acid, dimethylaminoethyl (meth) Amino group-containing (meth) acrylic polymerizable monomers such as acrylate, amide group-containing acrylic polymerizable monomers such as (meth) acrylamide, and nitrile group-containing (meth) acrylic polymerizable compounds such as acrylonitrile And monomers.

  The polymerizable monomer containing a cycloalkyl group includes, in addition to the above-mentioned acrylic polymerizable monomer, α, β-ethylenic monomers such as maleic acid, itaconic acid, crotonic acid and fumaric acid. Monomers such as saturated carboxylic acid, sulfonic acid-containing vinyl monomers such as styrene sulfonic acid and vinyl sulfonic acid, or acid anhydrides such as maleic anhydride can also be copolymerized.

  Further, instead of or in addition to the above acrylic polymerizable monomer, a polymerizable monomer or a silicon-containing polymerizable monomer that forms a urethane bond can be copolymerized.

  As the polymerizable monomer having a urethane bond, hexamethylene diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate, dicyclohexylhetane diisocyanate, or the like can be used. In addition, an aqueous urethane resin having a reactive group, Aerustron BN (Daiichi Kogyo Seiyaku Co., Ltd.) and the like can be reacted.

  Silicon-containing polymerizable monomers include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltripropoxysilane, vinyltributoxysilane, (meth) acryloyloxymethyltrimethoxysilane, (meth) acryloyloxyethyltrimethoxysilane , (Meth) acryloyloxypropyltrimethoxysilane, (meth) acryloyloxypropyltriethoxysilane, (meth) acryloyloxyethyltriethoxysilane, (meth) acryloyloxypropyltributoxysilane, and the like. Species or two or more can be used.

  Moreover, a crosslinked structure can also be introduce | transduced into the polymer of an innermost phase by making the polymerizable monomers which have a reactive group react. Thereby, light resistance and contamination | pollution resistance can be improved further. For example, hydroxyl group and isocyanate compound, epoxy group and carboxylic anhydride, epoxy group and amine, carbonyl group and hydrazide group, carboxylic acid and metal ion, carboxylic acid and oxazoline, organoalkoxysilane and carboxyl group, acetoacetate Combinations such as ketimine can be mentioned.

(Polymer constituting outermost phase)
The polymer constituting the outermost phase includes the above-mentioned acrylic polymerizable monomer, a homopolymer composed of a polymerizable monomer that forms a urethane bond, or a silicon-containing polymerizable monomer, or these three types of single monomers. Although a copolymer composed of two or more of the monomers can be used, the glass transition temperature of the polymer constituting the outermost phase is preferably lower than the glass transition temperature of the polymer constituting the innermost phase, It is preferably in the range of −40 to 10 ° C. By lowering the glass transition temperature of the outermost phase, the polymer particles can be easily self-fused and the film-forming property can be improved. More preferably, the glass transition temperature of the polymer constituting the innermost phase is 10 to 30 ° C, and the glass transition temperature of the polymer constituting the outermost phase is preferably -30 to 0 ° C. This is because if the glass transition temperature of the polymer constituting the outermost phase is lower than −40 ° C., the toughness and stain resistance of the coating film are lowered, and if it is higher than 10 ° C., the film formability is lowered.

  Further, the outermost phase polymer can contain a polymerizable monomer containing a carbonyl group. When polymerizing the outermost phase polymer, the hydrazine compound coexists in the molecule, and the hydrazine compound and the carbonyl group react to form a crosslinked structure, so that the weather resistance, stain resistance, and Water resistance can be further improved.

  In addition to the outermost polymer, the innermost or intermediate phase polymer may contain a polymerizable monomer containing a carbonyl group. In this case, in order to maintain weather resistance and stain resistance, the content of the polymerizable monomer containing a carbonyl group in the polymer of the outermost phase is changed to a polymerizable monomer containing a carbonyl group contained in a phase other than the outermost phase. It is necessary to make it the same or more than the content of the monomer.

(Polymer constituting the intermediate phase)
When the polymer particles used in the present invention have one or more intermediate phases between the innermost phase and the outermost phase, the polymer constituting the intermediate phase includes the above acrylic polymerizable monomer, urethane A homopolymer composed of a polymerizable monomer having a bond or a silicon-containing polymerizable monomer, or a copolymer composed of two or more of these three types of monomers can be used. The glass transition temperature of the polymer constituting the intermediate phase is preferably higher than the glass transition temperature of the polymer constituting the outermost phase. This is because, by lowering the glass transition temperature of the outermost phase, the polymer particles can be easily self-fused and the film-forming property can be improved.

  In the present invention, the polymer constituting the outermost phase has a glass transition temperature of -30 to 0 ° C. and the glass transition temperature of the polymer constituting the innermost phase is 10 to 30 ° C. By making the glass transition temperature lower than the glass transition temperature of the innermost phase, the polymer particles are easily fused. Therefore, the minimum film forming temperature of the resin composition obtained in the present invention is 5 ° C. or lower, more preferably in the range of 0 to 3 ° C.

(Polymerization method)
For the multistage polymerization used in the production of the resin composition of the present invention, a known emulsion polymerization method such as batch emulsion polymerization, monomer-drop polymerization, emulsion monomer-drop polymerization method, or the like can be used in two or more steps.

  As the radical production initiator used in the emulsion polymerization, those used in usual emulsion polymerization can be used. For example, organic peroxides such as benzoyl peroxide, t-butyl hydroperoxide, cumene hydroperoxide, organic azo such as azobiscyanovaleric acid, azobisisobutyronitrile, azobis (2,4-dimethyl) valeronitrile Inorganic water-soluble radical initiators such as compounds, potassium persulfate, ammonium persulfate, sodium persulfate and hydrogen peroxide, as well as these persulfates or metal ions such as peroxide and iron ions and sodium pyrosulfite A known redox initiator that is used in combination with a reducing agent such as L-ascorbic acid can also be used.

  Furthermore, a chain transfer agent can be added to adjust the molecular weight of the polymer particles as necessary. Examples thereof include alkyl mercaptans such as lauryl mercaptan, n-butyl mercaptan, t-butyl mercaptan, octyl mercaptan, n-dodecyl mercaptan, and α-methylstyrene dimer.

  Examples of the emulsifier used in emulsion polymerization include anionic emulsifiers such as sodium alkylallylsulfone succinate, sodium alkylbenzene sulfonate, sodium lauryl sulfate, sodium dioctyl sulfosuccinate, or ammonium salt, ethylene Reactive emulsifiers having ionic unsaturated double bonds, nonionic emulsifiers such as polyoxyethylene alkyl ethers, polyoxyethylene-polyoxypropylene block copolymers, cationic surfactants, amphoteric surfactants, etc. be able to. Further, water-soluble polymers such as polyvinyl alcohol and hydroxyethyl cellulose, and protective colloids such as water-soluble oligomers can also be used.

  Moreover, it is preferable that content of the polymer particle in the resin composition of this invention exists in the range of 40 to 60 weight% in solid content.

  In addition, it is preferable from the viewpoint of stability that the pH of the resin composition is adjusted to a neutral to alkaline range from 6.5 to 11.0 after the completion of the polymerization. As the neutralizing agent, ammonia, trimethylamine, propylamine, diethylamine, morpholine, dimethylethanol, triethanolamine and other amines, sodium hydroxide, potassium hydroxide and the like can be used.

  In addition to the above components, the resin composition of the present invention may contain components such as thickeners, antioxidants, preservatives, and fungicides that do not fall under the VOC component, if necessary.

Hereinafter, embodiments of the present invention will be described in detail with reference to examples and comparative examples.
(Polymerization method)
A four-necked flask equipped with a stirrer, reflux condenser, dropping tank, and thermometer was replaced with nitrogen gas, and then 50 parts of ion-exchanged water was added. In an emulsifying tank, 3 parts of Eleminol JS-2 (reactive emulsifier, manufactured by Sanyo Chemical Co., Ltd.) was dissolved in 25 parts of ion-exchanged water, and a mixture of composition 1 in Table 1 was added to prepare an emulsion. After raising the flask to 80 ° C., 10% of the prepared emulsion was charged into the flask, and then 0.3 g of sodium persulfate was charged. After the reaction was completed, the remaining 90% of the emulsion was added dropwise over 2 hours. After completion of the dropping, the temperature of the flask was raised to 80 ° C. and maintained for 1 hour. Next, 3 parts of Eleminol JS-2 was dissolved in 25 parts of ion-exchanged water in an emulsifying tank, and a mixture of composition 2 in Table 1 was added to prepare an emulsion. After aging for 1 hour, the emulsion was added dropwise over 2 hours. After completion of the dropping, the temperature of the flask was set to 80 ° C., and polymerization was performed for 1 hour. After cooling to room temperature, the pH was adjusted to 8 with an aqueous ammonia solution to obtain the desired resin composition.
In the comparative example, a mixture of composition 1 and a mixture of composition 2 in Table 2 were used.

CHMA：シクロヘキシルメタクリレート
MMA：メチルメタクリレート
nBA：n−ブチルアクリレート
MAA：メチルメタクリレート
DAAM：ジアセトンアクリルアミド
ADH：アジピン酸ジヒドラジド
CS-12：水性樹脂分散剤（チッソ製、２，２，４−トリメチルペンタンジオール−１，３−モノイソブチレート） Table 1.

CHMA: cyclohexyl methacrylate
MMA: Methyl methacrylate
nBA: n-butyl acrylate
MAA: Methyl methacrylate
DAAM: Diacetone acrylamide
ADH: Adipic acid dihydrazide
CS-12: Aqueous resin dispersant (manufactured by Chisso, 2,2,4-trimethylpentanediol-1,3-monoisobutyrate)

ST：スチレン
Table 2.

ST: Styrene

(Test plate production)
The resin compositions obtained in the examples and comparative examples were applied on a slate plate coated with a solvent-based acrylic enamel (white) with a 250 μm applicator, cured at 23 ° C. for 7 days, dried and tested for evaluation tests A plate was made.

(Weather resistance test)
An accelerated weather resistance test was conducted with a sunshine weatherometer using a test plate, and the change in the coating film after 2000 hours was expressed as a gloss retention rate.
○: Gloss retention 80% or more Δ: Gloss retention 60% or more and less than 80% ×: Gloss retention 40% or less

(Contamination resistance test)
Using a test plate, an outdoor exposure test was performed, and the state of dirt after 3 months was visually observed.
○: No difference compared to the standard plate.
(Triangle | delta): There are few stains compared with a standard board.
X: Contamination is remarkable as compared with the standard plate.

(Film formability)
Each resin composition of Examples and Comparative Examples was applied to a glass plate and dried at 5 ° C. for 24 hours to prepare a glass test plate for film formability evaluation. The surface of the coating film of this glass test plate was visually observed. The minimum film-forming temperature was evaluated with a thermal gradient tester (manufactured by Tester Sangyo).
○: No cracking.
Δ: Slightly cracked
X: There is a remarkable crack.

(Odor)
The odor was evaluated by smelling the actual odor.
○: No odor.
Δ: Slight odor.
X: The odor is remarkable.

(VOC content)
The resin compositions obtained in Examples and Comparative Examples were analyzed by gas chromatography.

(result)
As is clear from the results of Examples 1 to 6, the resin composition of the present invention had low odor and low VOC, and was excellent in weather resistance, contamination resistance, and film formability. On the other hand, Comparative Example 1 composed of single particles had a high VOC content and inferior film formability. In addition, even when polymer particles obtained by multistage polymerization are included, a monomer containing a cycloalkyl group is present in the outermost phase, and the outermost phase polymer is compared with the innermost phase polymer. In Comparative Example 3 having a high glass transition temperature, the VOC content was high and the film formability was also poor. Further, Comparative Example 4 having a high glass transition temperature in both the innermost phase and the outermost phase had a high VOC content, and was inferior in weather resistance and stain resistance. In Comparative Example 5, where the glass transition temperature of the innermost phase was high, the film formability was poor and the VOC content was high, despite the low glass transition temperature of the outermost phase. Comparative Example 6 having a low glass transition temperature of the outermost phase was inferior in weather resistance and stain resistance as compared with Examples 1-6. The resin composition obtained from Comparative Example 7 having a small glass transition temperature between the innermost phase and the outermost phase had a high VOC content and poor film formability as in Comparative Example 1 consisting of single particles.

Claims (5)

Water-based paint resin comprising polymer particles having a heterogeneous structure obtained by multistage polymerization, wherein the innermost phase of the polymer particles contains 10 to 50% by weight of a polymerizable monomer containing a cycloalkyl group Composition. 2. The resin for water-based paint according to claim 1, wherein the outermost phase of the polymer particles is composed of an ethylenically unsaturated monomer having a glass transition temperature lower than the glass transition temperature of the polymer constituting the innermost phase. Composition. The resin composition for water-based paints according to claim 1 or 2, wherein the innermost phase is composed of a polymer of an ethylenically unsaturated monomer having a glass transition temperature of 0 to 50 ° C. The resin composition for water-based paints as described in any one of Claim 1 to 3 whose content of a volatile organic compound is less than 0.1 weight%. The resin composition for water-based paints as described in any one of Claim 1 to 4 whose minimum film forming temperature is 5 degrees C or less.