JP2006299193A - Coating agent composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coating agent composition that is capable of forming a coating film excellent in gloss and hiding characteristics and is excellent in pigment dispersibility and adhesion. <P>SOLUTION: The coating agent composition comprises (A) a vinyl copolymer consisting of 0.5-5 mass% acrylic acid unit, 30-99.5 mass% methyl methacrylate unit and 0-69.5 mass% other copolymerizable vinyl monomer units, (B) a benzoyl peroxide, and an organic solvent, wherein the content of the benzoyl peroxide (B) is 0.5-10 pts.mass based on 100 pts.mass of the vinyl copolymer (A); and the vinyl copolymer (A) and the benzoyl peroxide (B) are dissolved in the organic solvent. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an acrylic coating composition that is capable of forming a paint film excellent in gloss and hiding properties, and is excellent in pigment dispersibility and adhesion, for example, used in paints, inks, adhesives, and the like. .

  Acrylic thermoplastic resins are used for various applications such as paints, inks, adhesives and the like because of their excellent durability.

  However, since acrylic thermoplastic resins are inferior in pigment dispersibility, methods for improving pigment dispersibility, such as adding additives such as pigment dispersants or blending other resins such as alkyd resins, have been studied. Various things have been done. For example, Patent Document 1 proposes a method of using a copolymer comprising isobutyl methacrylate and a nitrogen-containing monomer as a pigment dispersion resin.

In addition, since acrylic thermoplastic resins have relatively low adhesion to various metals, particularly aluminum, stainless steel, and tin, various studies have been made to improve adhesion. For example, Patent Document 2 discloses an acrylic copolymer having a weight average molecular weight of 30,000 to 200,000, a calculated glass transition temperature (calculated Tg) of 0 to 100 ° C., and a copolymer of a specific ethylenically unsaturated carboxylic acid monomer. An acrylic coating composition in which a thermoplastic resin is dissolved in an organic solvent is described.
JP-A-60-139712 Japanese Patent Publication No.8-13951

  In patent document 1, other resin is blended and the pigment dispersibility is expressed. Therefore, the compatibility differs depending on the resin to be blended, and it is necessary to use an oil-soluble solvent such as toluene, which is disadvantageous in that it cannot be used for a wide range of paints and inks.

  When the coating composition described in Patent Document 2 is applied to a metal-based substrate, the initial adhesion exhibits good adhesion, but the adhesion after a water resistance test may be reduced. Moreover, the bending resistance of a coating film is not sufficient, and when a bending process is performed as a post-processing of a metal-based substrate, the coating film may be broken or peeled off.

  An object of the present invention is to provide a coating composition that is capable of forming a coating film excellent in gloss and concealment, and that is excellent in pigment dispersibility and adhesion.

  As a result of intensive studies to achieve the above object, the present inventors have found that it is very effective to add benzoyl peroxide to a specific vinyl copolymer, and have completed the present invention. .

  That is, the present invention comprises 0.5 to 5% by mass of acrylic acid units, 30 to 99.5% by mass of methyl methacrylate units, and 0 to 69.5% by mass of other copolymerizable vinyl monomer units. Containing vinyl-based copolymer (A), benzoyl peroxide (B), and organic solvent, the content of benzoyl peroxide (B) is 100 parts by weight of vinyl-based copolymer (A) The coating composition is characterized in that it is 0.5 to 10 parts by mass, and the vinyl copolymer (A) and benzoyl peroxide (B) are dissolved in the organic solvent.

  Since the coating composition of the present invention contains a specific vinyl copolymer (A) and benzoyl peroxide (B), both pigment dispersibility and adhesion are excellent. Moreover, since the content of benzoyl peroxide (B) is within a specific range, it is possible to form a paint film having excellent gloss and hiding properties. The composition exhibiting such excellent characteristics can be suitably used for coatings such as paints, adhesives, and inks, and is extremely useful industrially.

  In the present invention, the vinyl copolymer (A) contains 0.5 to 5% by mass of acrylic acid units, 30 to 99.5% by mass of methyl methacrylate units, and other copolymerizable vinyl monomer units of 0 to 5% by mass. To 69.5% by mass. Specifically, as shown in more detail in the examples described later, the vinyl copolymer (A) having such a composition contains 0.5 to 5% by mass of acrylic acid and 30 to 99.5% by weight of methyl methacrylate. % And other copolymerizable vinyl monomers 0 to 69.5% by mass. Each monomer may be added stepwise as necessary and allowed to undergo a polymerization reaction, or may be added collectively to cause a polymerization reaction.

  In this invention, the film which shows the outstanding adhesiveness can be obtained by using the vinyl copolymer (A) of such a composition. Here, the lower limit of the content range of the other copolymerizable vinyl monomer units is zero. That is, the vinyl copolymer (A) may be a copolymer composed of only acrylic acid units and methyl methacrylate units without containing other copolymerizable vinyl monomer units.

  Further, from the viewpoint of adhesion, the lower limit of the content range of acrylic acid units is preferably 1% by mass or more, and the lower limit of the content range of methyl methacrylate units is preferably 40% by mass or more, and other copolymerization is possible. The lower limit of the content range of the vinyl monomer units is preferably 60% by mass or less.

The vinyl copolymer (A) has the following formula (1) from the viewpoint of adhesion:
1 / Tg = Σ (W _i / Tg _i ) (1)
(W _i represents the mass fraction of monomer i, and Tg _i represents Tg (K) of the homopolymer of monomer i.)
It is preferable that the glass transition temperature (Tg) of the copolymer calculated | required by the formula of Fox shown by is 110 degrees C or less, and it is especially preferable that it is 100 degrees C or less. Moreover, about the lower limit of glass transition temperature, 30 degreeC or more is preferable.

  The weight average molecular weight of the vinyl copolymer (A) is preferably 300000 or less, more preferably 200000 or less, from the viewpoint of pigment dispersibility. Further, the lower limit of the weight average molecular weight is preferably 10,000 or more.

  Examples of other copolymerizable vinyl monomer units constituting the vinyl copolymer (A) include alkyl (meta) other than methyl methacrylate such as methyl acrylate, ethyl (meth) acrylate, and propyl (meth) acrylate. ) Acrylate; hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate; glycol di (meth) such as ethylene glycol di (meth) acrylate and butylene glycol di (meth) acrylate ) Acrylate; alkylamino (meth) acrylate such as dimethylaminoethyl (meth) acrylate; dimethylaminoethyl (meth) acrylate methyl chloride salt, allyl (meth) acrylate, trimethylolpropane tri ( A) acrylate, glycidyl (meth) acrylate; aromatic vinyl compounds such as styrene, α-methylstyrene, p-methylstyrene; vinyl acetate, vinyl propionate, (meth) acrylonitrile, benzyl (meth) acrylate, acrylamide, diacetone Acrylamide; (meth) acrylic acid, itaconic acid, monobutyl itaconate, citraconic acid, maleic acid, monomethyl maleate, monobutyl maleate, 2- (meth) acryloyloxyethyl succinate, 2- (meth) acryloyloxypropyl succinate , 2- (meth) acryloyloxybutyl succinate, 2- (meth) acryloyloxyethyl maleate, 2- (meth) acryloyloxypropyl maleate, 4- (meth) acryloyloxybutyl maleate, etc. And monomer units composed of vinyl monomers such as unsaturated carboxylic acids.

  As a polymerization method of the vinyl copolymer (A), a known polymerization method such as a solution polymerization method, a suspension polymerization method, an emulsion polymerization method, a bulk polymerization method and the like can be employed. In particular, it is preferable to employ a solution polymerization method or a suspension polymerization method because they can be easily mixed and dissolved in an organic solvent and can improve the appearance of the coating film.

  As the polymerization initiator used in the polymerization, various conventionally known initiators, for example, azobis initiators such as azobisisobutyronitrile, benzoyl peroxide, tertiary butyl peroxy-2-ethylhexa Organic peroxide initiators such as nates can be used. In particular, organic peroxide radical polymerization initiators such as benzoyl peroxide and tertiary butyl peroxy-2-ethylhexanate are preferred in terms of improving the appearance of the paint film.

  In the polymerization, a conventionally known chain transfer agent such as normal dodecyl mercaptan or α-methylstyrene dimer may be used for the purpose of adjusting the molecular weight.

  The content of benzoyl peroxide (B) contained in the coating composition of the present invention is 0.5 to 10 parts by mass with respect to 100 parts by mass of the vinyl copolymer (A). When the content of benzoyl peroxide (B) is 0.5 parts by mass or more, preferably 1.0 parts by mass or more with respect to 100 parts by mass of the vinyl copolymer (A), the gloss of the coating film is improved. To do. Moreover, the pigment dispersibility of a coating material improves because content of benzoyl peroxide (B) is 10 mass parts or less with respect to 100 mass parts of a vinyl-type copolymer (A), Preferably it is 9 mass parts or less. .

  In the coating composition of the present invention, the vinyl copolymer (A) and the benzoyl peroxide (B) are dissolved in an organic solvent. As the organic solvent used here, various organic solvents similar to those used in the conventional coating composition can be used. Specific examples thereof include hydrocarbons such as toluene and xylene; esters such as ethyl acetate, butyl acetate and cellosolve acetate; alcohols such as isopropyl alcohol and n-butanol; ketones such as acetone and methyl ethyl ketone; It is done.

  The content of the organic solvent in the coating composition is not particularly limited. What is necessary is just to determine a specific content suitably according to the use of the composition, the coating method, etc. In general, the resin solid content in the coating composition is preferably 20 to 50% by mass, and more preferably 25 to 45% by mass.

  Various known pigments, pigment dispersants, slip agents, and leveling agents can be added to the coating composition of the present invention in order to develop high performance as a coating material.

  Examples of the coating method when the coating composition of the present invention is applied to the surface of various substrates to form a coating include, for example, spray coating, roller coating, bar coating, air knife coating, brush coating, A known method such as a dipping method can be appropriately selected and employed.

  When a coating film is formed using the coating composition of the present invention, a sufficiently dried coating film is usually dried at a temperature in the range of room temperature to about 60 ° C. for about 1 minute to 1 hour. Obtainable.

  Hereinafter, the present invention will be described with reference to examples. In the following description, “part” means part by mass.

[Examples 1-4, Comparative Examples 1-3]
In a polymerization apparatus equipped with a stirrer, a thermometer and a reflux condenser and capable of heating and cooling, the mixture (1) shown in Table 1 for Examples 1 to 4 and Table 2 for Comparative Examples 1 to 3 was added. The stirring was started and the temperature was raised to 90 ° C. After the temperature reached 90 ° C., the mixture (2) was added dropwise over 4 hours, and the mixture (3) was further added dropwise over 1 hour to continue the polymerization reaction. After 10 hours, the mixture (4) was added. Then, it cooled to 50 degrees C or less, and also the mixture (5) was added. The characteristics of each obtained coating composition were measured according to the following method. The results are shown in Tables 1 and 2. In addition, the numerical value of the component of each mixture in a table | surface shows a mass part.

[Weight average molecular weight]
The weight average molecular weight of the polymer in the coating composition was measured by gel permeation chromatography (GPC) method (polystyrene conversion). Specifically, the sample was dissolved in tetrahydrofuran (THF) to prepare a 0.8 mass% THF solution as a resin component, which was filtered through a 0.5 μm membrane filter, and the filtrate was measured under the following conditions.

(Measurement condition)
Apparatus: Tosoh HPLC-8120
Eluent: THF
Flow rate: 1 ml / min Temperature: 40 ° C
Detector: differential refractometer Injection volume: 100 μl.

[Gardner viscosity]
About the Gardner viscosity of the coating composition, the bubble viscosity at 25 ° C. was measured according to ASTM-D1545.

[Examples 5-8, Comparative Examples 4-6]
In the same polymerization apparatus as described above, an aqueous solution of the mixture (1) shown in Table 3 for Examples 5 to 8 and Table 4 for Comparative Examples 4 to 6 was added, and stirring was started. Subsequently, each mixture (2) was added and heated to carry out a polymerization reaction for 3 hours while maintaining the reaction temperature at 75 to 85 ° C, and then heated to 95 ° C and reacted for 1 hour to cool. Thereafter, the obtained suspension was filtered with a mesh having an opening of 30 μm and dried with hot air at 40 ° C. to obtain a granular vinyl polymer. And this vinyl polymer was melt | dissolved with the mixture (3), respectively, and it was set as the coating composition. The results are shown in Table 3 and Table 4.

[Evaluation]
In each of the coating compositions obtained in the above Examples and Comparative Examples, titanium oxide (trade name CR-90, manufactured by Ishihara Sangyo Co., Ltd.) was blended to 40% by mass, and thinner (acetic acid) was added. 60 parts of butyl, 30 parts of ethyl acetate, 10 parts of propylene glycol monomethyl ether), and the paint shaker is adjusted so that the viscosity by Zaan cup (viscosity cup) # 3 after 3 hours of dispersion treatment is 18 seconds. did.

  Using this paint, steel plate (SPCC-B, plate thickness 0.6 mm, manufactured by Dazai Equipment Co., Ltd.), aluminum plate (A1050P, plate thickness 0.8 mm, manufactured by Dazai Equipment Co., Ltd.), copper plate (C1100P, plate thickness) 0.8 mm, manufactured by Dazai Equipment Co., Ltd.), tin plate (SPTE, plate thickness 0.3 mm, manufactured by Dazai Equipment Co., Ltd.), zinc iron plate (SPG, plate thickness 0.3 mm, manufactured by Dazai Equipment Co., Ltd.) Each degreased panel was coated with a bar coater so as to have a film thickness of 30 μm, and the panel was dried in a drying oven at 70 ° C. for 1 hour to prepare an evaluation panel.

  The following A to C were evaluated for the paints, evaluation panels, and resin solutions of each Example and Comparative Example. The results are shown in Tables 5 and 6.

B) Evaluation of pigment dispersibility of paints:
According to JIS K5600-2-5, the degree of dispersion by the linear method was evaluated. As a specific evaluation method, it was confirmed by a tube gauge that the titanium oxide was 15 μm or less and the pigment was well dispersed.

B) Evaluation of coating film appearance:
According to JIS K5600-4-7, the specular gloss of the coating film at an incident angle of 20 degrees and 60 degrees was evaluated.

C) Evaluation of coating film adhesion:
According to JIS K5600-5-6, a tape peeling test was performed by a cross-cut method. Specifically, the coating film was cut to form 100 2 mm × 2 mm wide gobangs, and a tape peeling test was performed. The number of fractional molecules shown in the table indicates the number of cells remaining without being peeled after the peel test.

Claims (1)

A vinyl copolymer composed of 0.5 to 5% by mass of acrylic acid units, 30 to 99.5% by mass of methyl methacrylate units, and 0 to 69.5% by mass of other copolymerizable vinyl monomer units. Including polymer (A), benzoyl peroxide (B), and organic solvent,
The content of benzoyl peroxide (B) is 0.5 to 10 parts by mass with respect to 100 parts by mass of vinyl copolymer (A), and vinyl copolymer (A) and benzoyl peroxide (B). Is a coating composition which is dissolved in the organic solvent.