JP2004010735A - Filler for powder coating and powder coating composition comprising the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a filler for powder coating which gives a powder coating composition for forming a coating film having good external appearance. <P>SOLUTION: The filler for powder coating comprises a surface treated calcium carbonate having a BET specific surface area by the nitrogen adsorption method of 2-15 m<SP>2</SP>/g, and the powder coating is obtained by compounding the calcium carbonate with a thermosetting resin. <P>COPYRIGHT: (C)2004,JPO

Description

【００６２】
実施例１０〜２２、比較例３〜５
実施例１〜９、比較例１〜２によって得られた粉体塗料用充填剤を用いて、下記要領にて各粉体塗料組成物を作成し、その塗料物性試験を行った。
【００６３】

【００６４】

【００６５】

【００６６】
原料として上記成分をスーパーミキサー（日本スピンドル製造社製）にて約３分間混合し、コニーダー（ブス社製）により約１００℃の条件で溶融混練した。室温で冷却し、粗粉砕後にアトマイザー（不二パウダル社製）で粉砕し、１５０メッシュの篩いで分級し、体積平均粒子径３５μｍの粉体塗料を得た。
【００６７】
以上の方法にて製造した各粉体塗料を２００×１００×０．８ｍｍのリン酸亜鉛処理を施した鋼板に、膜厚約６０μｍになるようにコロナ帯電型塗装ガンにより静電吹きつけ塗装し、１８０℃×２０ｍｉｎ、２００℃×２０ｍｉｎの各条件で焼き付けたのち、室温迄放冷した。塗膜性能の評価を下記の方法により行った。
【００６８】
＜外観評価＞
◎　：凹凸が少なく、平滑な塗膜状態である。
○　：凹凸がややあるが、平滑な塗膜状態である。
△　：凹凸がややあり、ブツが僅かにある。
×　：凹凸があり、平滑性にやや劣る。
××：ブツ等があり、平滑性に劣り、試験板の下部エッジ部分にたまりが認められる。
【００６９】
＜ペレットフロー値＞
錠剤成形器を用い、各粉体塗料を３００ｋｇ／ｃｍ^２の圧力で、直径５０ｍｍの円盤状のペレットに加圧形成した。このペレット１を、図１に示すように、２００×１００ｍｍの金属製板に両面テープで固定し、この金属製板２を垂直に吊した状態で、１８０℃×２０ｍｉｎ焼き付け、ペレット１の流動した塗料長さ３を測定した。以上の試験を３回行い、その平均値を評価値とした。
【００７０】
＜光沢値＞
上記した如く、１８０℃×２０ｍｉｎ、２００℃×２０ｍｉｎで焼き付けた各試験板の塗膜面のうち任意の５カ所を選択し、そのグロスメーター（日本電色（株）製）にて６０°光沢、２０°光沢をそれぞれ測定し、その平均値を評価値とした。
【００７１】
【表２】

【００７２】
【発明の効果】
以上のように、本発明の粉体塗料用充填剤は、優れた外観を有する塗膜を形成する粉体塗料組成物を提供することができる。
【図面の簡単な説明】
【図１】ペレットフロー値の測定方法を示す説明図である。
【符号の説明】
１　ペレット
２　金属製板
３　塗料流動長さ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a filler for a powder coating which forms a coating film having a high appearance, and a resin composition for a powder coating obtained by blending the same.
[0002]
[Prior art]
Powder coating is a method in which the powder coating is applied to the object by flying or floating in the air by electrostatic spraying or fluidized bed immersion coating, etc., and then baked, etc. to perform coating. is there. Since powder coating uses solvent-free powder coating, there is no danger of environmental problems and disasters caused by solvents as in the coating method using solvent-based coating, and it occurs in the case of water-soluble coating. There is no wastewater treatment problem, and furthermore, it is possible to collect and reuse the oversprayed paint, so that the loss of the paint can be extremely reduced, so that it is widely used in various coating fields. It has become to.
[0003]
In addition, since it is possible to automate by a complete circulation system with a combination of a recovery device and a coating machine, it is said that efficient coating is possible including that a skilled technician is not required for the coating operation. In powder coating, a coating film is formed on an object to be coated by a method such as electrostatic spray coating or immersion coating in a fluidized bed and baked.
[0004]
However, the conventional powder coating has a drawback that a glossy and smooth coating film cannot be formed and the appearance of the coating film is poor. That is, in the process of forming a powder coating, the powder applied to the object to be coated forms a film through heat melting and subsequent curing. Since the curing proceeds before and after the melt flow at that time, the leveling becomes insufficient, and the appearance of the coating film tends to deteriorate. As a solution, it is necessary to thicken the coating, raise the baking temperature or extend the temperature holding time to sufficiently melt the resin, but completely eliminate the slight irregularities due to the shape of the powder paint particles. It is difficult. In particular, there is a problem that the unevenness is more conspicuous in the coating of a thin film, and the appearance of the coating film is further deteriorated.
[0005]
There is a strong demand for improvement in appearance, and in order to meet this demand, it is necessary to lower the melt viscosity of the resin. For the purpose of lowering the melt viscosity, methods such as lowering the glass transition temperature of the resin and lowering the molecular weight have been proposed, but when the melt viscosity is lowered to achieve a highly smooth coating film with powder, In some cases, sagging occurs during baking, making it impossible to obtain a high-appearance coating film, and also reduces coating workability. Thickening is effective as a method of improving the smoothness of the coating film, but when combined with the resin having a reduced melt viscosity, the sagging phenomenon at the time of baking becomes more remarkable.
[0006]
As a technique for improving such a defect and obtaining a smooth coating film, for example, JP-A-2001-33750 discloses a liquid resin dissolved in a solvent in addition to a liquid resin in addition to a particulate resin component of a powder coating material. Although a coating composition containing the components is disclosed, in addition to the increase in the cost of the coating material, the characteristics of the powder coating that is solvent-free are eliminated, and a problem also arises in equipment cost and solvent recovery cost. . Japanese Patent Application Laid-Open No. 8-41384 discloses that as a powder coating material having excellent transportability and forming a coating film having a high appearance, the volume average particle diameter of the coating film forming resin is set to 20 to 50 μm, and the particle size distribution standard deviation is also set. It is disclosed that a powder coating having a particle size of 20 μm or less is used. However, in order to obtain a powder coating material having a controlled particle size distribution in this way, a classification operation is required as exemplified in the same gazette, and it is inevitable that the production cost increases. The same publication also discloses, as a hybrid powder coating, a powder coating in which a resin having a low glass transition point is coated with a resin having a high glass transition point, and a powder coating having the particle size distribution is used. And the operation becomes complicated, which further increases the cost.
[0007]
[Problems to be solved by the invention]
The present invention solves the above-mentioned disadvantages of the prior art and provides a powder coating composition capable of providing a powder coating composition that forms a coating film having a high appearance, and a powder coating composition containing the filler. To provide.
[0008]
[Means for Solving the Problems]
The present inventors have conducted intensive studies to solve the above problems, and as a result, it has been found that a filler made of calcium carbonate having specific powder physical properties solves the above-mentioned conventional disadvantages as described above and provides a powder having a high appearance coating film. The present inventors have found that a body paint can be provided, and have completed the present invention.
[0009]
The first aspect of the present invention is that the BET specific surface area by the nitrogen adsorption method is 2 to 15 m. ² / G of calcium carbonate. (Claim 1)
[0010]
In a preferred embodiment, the filler for powder coating material according to claim 1, wherein the calcium carbonate has an average particle size of 0.5 to 15 µm (claim 2).
[0011]
In a preferred embodiment, calcium carbonate is a saturated fatty acid, unsaturated fatty acid, aliphatic carboxylic acid, resin acid, (co) polymer of unsaturated carboxylic acid, alkali metal salt thereof, alkaline earth metal salt thereof, surfactant The filler for powder coating material according to claim 1 or 2, which is surface-treated with at least one selected from silane coupling agents (claim 3).
[0012]
In a preferred embodiment, the surface treatment rate is 0.05 to 0.50% by weight / m 2 per unit BET specific surface area of calcium carbonate. ² The filler for powder coating material according to any one of claims 1 to 3, wherein the filler is (claim 4).
[0013]
A second aspect of the present invention is a powder coating composition comprising a filler for powder coating according to any one of claims 1 to 4 mixed with a powder coating resin. Item 5).
[0014]
In a preferred embodiment, the powder coating composition according to claim 5, wherein the powder coating resin is a thermosetting resin (claim 6).
[0015]
In a preferred embodiment, the powder coating composition according to claim 6, wherein the thermosetting resin comprises at least one selected from a polyester resin, an epoxy resin, an epoxy-polyester resin, a fluororesin, and an acrylic resin (claim 7). .
[0016]
As a preferred embodiment, the powder coating composition according to any one of claims 5 to 7, wherein the amount of the filler for the powder coating composition is 1 to 75 parts by weight based on 100 parts by weight of the powder coating resin. (Claim 8).
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
The filler for powder coating of the present invention has a BET specific surface area of 2 to 15 m by a nitrogen adsorption method. ² / G of calcium carbonate.
[0018]
Calcium carbonate is generally classified into two types: heavy calcium carbonate, which is mechanically pulverized from limestone and classified into various grades by classifying the calcium carbonate, and synthetic calcium carbonate, which is prepared by a chemical method. Separated. Furthermore, (1) the limestone is prepared by reacting quicklime obtained by calcining limestone at a high temperature with water to adjust lime milk, and then conduct carbon dioxide gas generated during limestone calcination into lime milk to synthesize calcium carbonate. There are three types: a carbon dioxide compounding process, (2) a lime soda process for reacting sodium carbonate with lime milk, and (3) a solution method for reacting soluble calcium with soluble carbonate.
[0019]
The calcium carbonate constituting the filler of the present invention is not particularly limited, but the above-mentioned heavy calcium carbonate may have a reduced particle size distribution due to its production method because the particle size distribution is broad. Therefore, it is desirable to use calcium carbonate having a certain degree of fineness as a desired particle size distribution by special classification (classification is repeated many times).
[0020]
Regarding synthetic calcium carbonate, the lime soda process of reacting sodium carbonate with lime milk of the above-mentioned (2) and the solution method of reacting soluble calcium with a soluble carbonate of (3) are by-products due to the characteristics of the reaction. NaCl or the like is generated, and the cost for removing the NaCl or the like increases, which is not preferable in some cases.
[0021]
On the other hand, the carbon dioxide compounding process of the above (1) is generally preferable from an economic viewpoint, but synthetic calcium carbonate produced by using the carbon dioxide compounding process has a relatively uniform primary particle shape and is usually used. The primary particles are aggregated or aggregated to form secondary particles (aggregate particles of primary particles). As the calcium carbonate constituting the filler of the present invention, synthetic calcium carbonate (colloidal calcium carbonate) having a uniform primary particle diameter is particularly preferable.
[0022]
The BET specific surface area of the calcium carbonate used in the present invention is 2 to 15 m ² / G, preferably 3 to 13 m ² / G, more preferably 4 to 10 m ² / G. BET specific surface area of calcium carbonate is 2m ² If it is less than / g, the primary particle diameter of the extender itself becomes large, and when the powder coating is used to form a coating film, the smoothness of the coating film surface is impaired, and the appearance, particularly gloss, is impaired. On the other hand, 15m ² / G, the primary particle size of the calcium carbonate becomes small, the cohesiveness becomes strong, and the calcium carbonate is not sufficiently dispersed when blended with the resin, or absorbs the resin or the like more than necessary, and heat-melts the powder coating. The leveling at the time is deteriorated, and the appearance of the finished coating film is impaired.
[0023]
In order for a coating film obtained using a powder coating material to have an excellent appearance (gloss), the coating material is different from a normal coating material, and it is considered that the aggregation energy of the coating powder causes a decrease in physical properties. The smaller the primary particle diameter of the calcium carbonate compounded therein, the higher the BET specific surface area. It is considered that the higher the BET specific surface area is, the larger the cohesive energy of the coating powder is and the poorer the appearance is. On the other hand, if the BET specific surface area is low (primary particles are large below a certain level), it is considered that the smoothness is impaired and the appearance, particularly the gloss, is impaired.
[0024]
In addition, the agglomeration of the powder coating is affected by the particle diameter of the powder particles, and the smaller the particle size, the stronger the cohesive force. Therefore, in order to prevent the agglomeration, the powder coating contains a chemical agent such as a surface conditioner, unlike the ordinary solvent-based coating. When calcium carbonate having a relatively large BET specific surface area is mixed therein, the calcium carbonate adsorbs a drug or the like and does not sufficiently perform functions such as surface adjustment, and the paint powder itself agglomerates. It is considered that a coating film having a high appearance cannot be obtained. Therefore, the BET specific surface area of calcium carbonate needs to be adjusted to the above range.
[0025]
In addition, the calcium carbonate used in the present invention usually has primary particles aggregated or aggregated to form secondary particles (aggregate particles of primary particles). It is preferable to satisfy the average particle size (the particle size configuration as secondary particles), whereby the re-aggregation of the coating powder can be prevented, and an excellent appearance can be obtained when the powder coating is applied.
[0026]
That is, the average particle diameter of the calcium carbonate used in the present invention is preferably 0.5 to 15 μm, more preferably 0.75 to 12 μm, and further preferably 1.0 to 10 μm. If the average particle size is less than 0.5 μm, the cohesiveness is so strong that sufficient dispersion cannot be obtained when compounding the resin, or the resin resin or additives are adsorbed more than necessary, and the powder coating is heated and melted. It is not preferable because the leveling at the time is deteriorated and the appearance of the finished coating film may be impaired. On the other hand, when the thickness exceeds 15 μm, when the powder coating is used to form a coating film, the smoothness of the coating film surface is impaired, and the appearance, particularly gloss, may be impaired, which is not preferable.
[0027]
The average particle diameter was measured under the following conditions.
Particle size distribution measurement conditions: The following ingredients (I) and (II) were weighed into a 140 ml mayonnaise bottle, stirred with a stainless steel spoon until visually dispersed, diluted with the ingredient (III), and then ultrasonically dispersed. The pre-dispersed sample was used as a sample, and the measurement was performed using a laser diffraction type particle size distribution meter (manufactured by Shimadzu Corporation: SALD-2000).
(I) Neutral detergent (5 times diluted with water) 2.0 g
(II) Calcium carbonate sample 0.4 g
(III) 40 g of water
In addition, after adjusting with the above-mentioned composition as a pretreatment, it was preliminarily dispersed under a constant condition of 100 μA for 60 seconds using an ultrasonic dispersing machine US-300T (manufactured by Nippon Seiki Seisakusho). The neutral detergent is not particularly limited and is a general commercial product without any problem. In the present invention, mama lemon (manufactured by Lion Corporation) was used.
[0028]
The calcium carbonate used in the present invention may be, for example, a method of passing a carbon dioxide-containing gas (hereinafter referred to as carbon dioxide gas) to an aqueous suspension of calcium hydroxide (hereinafter referred to as lime milk), or a method of introducing lime milk or calcium hydroxide into carbon dioxide gas. It is manufactured by a known method such as a method of spraying a mixed solution of urea and precipitated calcium carbonate. It is preferable to disperse the calcium carbonate particles as much as possible. For example, as a method, the carbonation reaction is stopped at a pH of 7.5 to 10.0 of the reaction system, the mixture is stirred, and the calcium carbonate particles remain in the calcium carbonate. A method in which the pH of the system is controlled at 9.0 to 12.0 for 5 hours or more by eluting the alkali component to be added, and adding or conducting milk of lime and carbon dioxide as needed in the system.
[0029]
In order to obtain fine heavy calcium carbonate, limestone produced naturally is pulverized by a dry method or a wet method to adjust to fine particles having an average particle diameter of 0.4 to 1.0 μm. In the case of the dry type, it may be pulverized by a micron mill, a vibrating ball mill or the like, and then classified by an air classifier. In the case of the wet type, it may be pulverized by a continuous wet disperser such as a ball mill or a tower mill, and is not particularly limited.
[0030]
The calcium carbonate used in the present invention is preferably subjected to a surface treatment for improving the surface activity and improving the affinity with the powder coating resin.
[0031]
Examples of surface treatment agents include saturated fatty acids, unsaturated fatty acids, alicyclic carboxylic acids, resin acids and their alkali metal salts, alkaline earth metal salts, surfactants, silane coupling agents, and polymer (co) polymers. Products, their alkali metal salts, their alkaline earth metal salts, and the like. Specifically, saturated fatty acids such as caprylic acid, lauric acid, myristic acid, palmitic acid, stearic acid, and aragic acid; unsaturated fatty acids such as oleic acid, elaidic acid, linoleic acid, and ricileic acid; and alicyclic rings such as naphthenic acid Resin acids such as aromatic carboxylic acids, abietic acid, pimaric acid, parastolic acid, and neoabietic acid; and alkali metals, alkaline earth metals, NH ₃ , Al, Zn or the like, or a partially neutralized salt. In addition, dodecylbenzenesulfonic acid, dialkyl sulfosuccinate and sulfonic acid type represented by Na salt thereof, sulfate ester type represented by sodium dodecyl sulfate, sodium monolauryl phosphate, dodecyl polysulfate Anionic surfactants such as phosphate esters represented by oxyethylene and salts thereof, amine salts represented by stearylamine hydrochloride, and quaternary ammonium represented by stearyltrimethylammonium chloride Cationic surfactants such as salt type, ester type typified by glycerin monostearate, ether type typified by polyoxyethylene nonyl phenyl ether, typified by polyethylene glycol oleate Beauty treatment Non-ionic surfactants such as alkanolamides represented by ether type and lauric acid diethanolamide, and silane coupling agents such as vinyl silane, amino silane, epoxy silane, chloroalkyl silane, and methyl triethoxy silane are exemplified. Can be Further, acrylic acid, itaconic acid, unsaturated monocarboxylic acid such as maleic acid, a polymer of a monomer composed of an unsaturated dicarboxylic acid and the like or an alkali metal of a copolymer with a monomer copolymerizable therewith, Alkaline earth metal, NH ₃ , Al, Zn or the like, or a completely neutralized salt. These surface treatment agents may be treated alone or in combination of two or more. Among these, alkali metal salts of saturated fatty acids and alkali metal salts of resin acids are preferred because they have good reactivity with calcium carbonate and are easily available industrially.
[0032]
The treatment amount of the surface treatment agent may be appropriately selected depending on the kind of the powder coating resin to be used, as long as the surface treatment of the calcium carbonate particles can be uniformly performed. It is preferably from 0.5 to 0.50% by weight, more preferably from 0.07 to 0.40% by weight. If the amount is less than 0.05% by weight, the treatment amount per unit BET specific surface area is reduced, and the effect of the surface treatment cannot be sufficiently exhibited, which may be undesirable. If the content exceeds 0.5% by weight, the amount of treatment per unit BET specific surface increases, and the excessive surface treatment agent adversely affects the physical properties of the coating resin, or the excessive surface treatment agent melts during baking during film formation. In some cases, the coating film becomes cloudy, which is not preferable.
[0033]
The method of obtaining the surface-treated calcium carbonate as a powder may be a conventional method. For example, it is added to a calcium carbonate slurry having an average particle diameter of 0.01 to 1.0 μm obtained by the above-described production method, and stirred. After the surface treatment agent is adsorbed on the calcium carbonate particles by mixing more uniformly, the mixture can be obtained by dehydrating, drying and pulverizing with a filter press or the like. Further, the calcium carbonate slurry after completion of carbonation is once dehydrated, the surface treating agent is added to a calcium carbonate press cake, and the mixture is vigorously stirred, and then dried and powdered with a spray drier or the like. Further, as a method of firmly fixing the calcium carbonate on the surface of the calcium carbonate, it is also effective to disperse the calcium carbonate slurry to which the surface treating agent has been added using a continuous wet disperser such as a sand grinder before drying.
[0034]
The powder coating composition of the present invention is obtained by blending the filler for powder coating of the present invention obtained as described above with a powder coating resin. The powder coating resin is not particularly limited, and those commonly used in the field of powder coating can be used. Examples of such a resin include a thermoplastic resin and a thermosetting resin. it can. The thermoplastic resin is not particularly limited, but particularly, a vinyl resin such as a polyvinyl chloride resin, a polyethylene resin, a polyamide resin, a fluororesin, or the like can be suitably used. The thermosetting resin is not particularly limited, but in particular, an epoxy resin, an epoxy-polyester resin, an acrylic resin, a fluororesin, a polyester resin, or the like can be suitably used. When a thermosetting resin is used as the coating resin, the powder coating composition of the present invention preferably contains a curing agent and a curing accelerator.
[0035]
The compounding amount of the filler for powder coating of the present invention is 1 to 75 parts by weight, preferably 5 to 70 parts by weight, more preferably 10 to 50 parts by weight based on 100 parts by weight of the powder coating resin. If the compounding amount of the filler for powder coating is less than 1 part by weight, a sufficient effect cannot be obtained. It is not preferable because the workability is deteriorated due to too high or the coating film itself may not be formed.
[0036]
In the powder coating composition of the present invention, when it is necessary to form a coating film having good weather resistance, it is necessary to form an acrylic resin system, and to form a coating film having good coating properties such as impact resistance. In some cases, it is preferable to use a polyester resin, and when it is necessary to form a coating film having good corrosion resistance, it is preferable to use an epoxy resin. If necessary, two or more resins may be used in combination, such as coating a resin having a low glass transition point with a resin having a high glass transition point.
[0037]
In the present invention, when using an epoxy resin as the powder coating resin, if necessary, for example, phthalic anhydride, an amine compound, an imidazole compound, a curing agent such as dicyandiamide, a curing accelerator can be used, Further, another resin such as an acrylic resin can be used in combination. When using a thermosetting acrylic resin as the powder coating resin, if necessary, for example, use another resin such as an epoxy resin or a melamine resin, or use a curing agent such as a polyvalent carboxylic acid or a blocked isocyanate compound. can do.
[0038]
In the present invention, when using a thermosetting polyester resin as the powder coating resin, if necessary, for example, other resins such as melamine resin, epoxy resin, polybasic acid, blocked isocyanate compound, triglycidyl isocyanate A curing agent such as nurate can be used.
[0039]
The content of the curing agent is preferably 5 to 80 parts by weight per 100 parts by weight of the thermosetting resin used as the powder coating resin. If the amount is less than 5 parts by weight, the curing will be insufficient, and if it exceeds 80 parts by weight, the curing will proceed too much and the physical properties of the coating film will be reduced. The content of the curing accelerator is preferably from 0.1 to 5 parts by weight per 100 parts by weight of the thermosetting resin used as the powder coating resin. If the amount is less than 0.1 part by weight, the curing is insufficient, and if it exceeds 5 parts by weight, the curing is excessively advanced, and the physical properties of the coating film tend to decrease.
[0040]
The powder coating composition of the present invention may contain a pigment and other additives as necessary. Examples of the other additives include other resins, curing agents, curing accelerators or curing catalysts, surface conditioners, plasticizers, ultraviolet absorbers, antioxidants, anti-penetrating agents, pigment dispersants, and the like. . The pigment is not particularly limited, and among them, titanium dioxide, red iron oxide, yellow iron oxide, carbon black, phthalocyanine blue, phthalocyanine green, quinacridone red pigment, and the like can be preferably used. These may be used alone or in combination of two or more as necessary.
[0041]
The content of the pigment is preferably 1 to 60 parts by weight based on 100 parts by weight of the powder coating composition. If the content is less than 1 part by weight, the effect of the pigment such as coloring cannot be obtained, and if it exceeds 60 parts by weight, a high-appearance coating film cannot be obtained. The pigment and other additives may be contained in the powder coating particles together with the powder coating resin or the like, or may be added as particles separate from the powder coating resin.
[0042]
The particles of the powder coating resin can be directly produced, for example, by a method such as emulsion polymerization or suspension polymerization. Alternatively, the resin can be produced by producing a resin by solution polymerization, bulk polymerization, or the like, and pulverizing and classifying the resin.
[0043]
The method for producing the powder coating composition of the present invention is not particularly limited, and it can be carried out by a method generally used in the field of powder coating production. For example, the above-mentioned powder coating resin, and, if necessary, a pigment and other additives are uniformly mixed by a mixer such as a Henschel mixer, a super mixer, a ball mill, and a Banbury mixer, and then the obtained product is obtained. The mixture thus obtained is melt-kneaded with a kneader such as an extruder or a hot roll, components other than the resin are uniformly dispersed in the molten powder coating resin, and the resulting mixture is formed into pellets. The obtained pellets are pulverized by an impact pulverizer such as a hammer mill or an air current pulverizer such as a jet mill, and then classified to obtain the powder coating composition of the present invention.
[0044]
The classification is carried out by using a 170 mesh, preferably 200 mesh Tyler standard sieve, a fluid separator such as a dispersion separator for separating and removing particles larger than 90 μm, preferably 80 μm, a micron separator, and a particle smaller than 1 μm. The separation and removal can be performed using a fluid classifier such as a cyclone, a dispersion separator, or a micron separator.
[0045]
As a method for producing the powder coating composition of the present invention, in addition to the above-described methods, for example, raw materials are mixed in a solvent, and the obtained mixture is dried, finely pulverized, or powdered by a spray dry method. It is also possible to adopt a method of doing so. The obtained powder can be subjected to the above-mentioned pulverization and classification as needed.
[0046]
When such a powder coating material is used, pellets in which a pigment and various additives are uniformly dispersed in a resin component can be obtained. Therefore, the powder coating obtained by pulverizing the pellets contains various raw material components in each particle. Are almost equally included. For this reason, in the coating film forming step, for example, the curing reaction of the resin is likely to occur uniformly, so that a coating film having better appearance such as smoothness can be formed.
[0047]
The application target of the powder coating composition of the present invention is not particularly limited, and includes, for example, steel plates for automobiles, home appliances, building materials, miscellaneous goods, zinc phosphate treated steel plates, aluminum or aluminum alloy materials, and the like. be able to. As a coating method of the powder coating composition of the present invention, for example, the powder coating composition of the present invention is deposited to a desired thickness on the surface of the object to be coated by a known method such as an electrostatic spraying method and a fluid immersion method. And then baking. When a thermosetting resin is used as the resin component, a cured coating film is formed.
[0048]
【Example】
Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.
[0049]
Example 1
Lime milk having a specific gravity of 1.06 was adjusted to 15 ° C., and carbon dioxide gas (30% / min. ₂ ) Was conducted to carry out a carbonation reaction, and after the carbonation reaction was stopped when the pH of the system reached 8.5, the system was stirred at 50 ° C. for 24 hours under the conditions of 10 to 11 to obtain a system. The average primary particle diameter of the aggregate particles is extremely small due to 0.10 μm, and the BET specific surface area is 11 m. ² / G of calcium carbonate was obtained. Lime milk having a specific gravity of 1.06 and a temperature of 16 ° C. is added to the calcium carbonate slurry, and 3 liters / minute of carbon dioxide gas (of which 25% CO 2 is contained) per kg of calcium hydroxide. ₂ ) Was conducted to carry out a carbonation reaction until the pH of the system reached 8.5. Lime milk adjusted in the same manner as described above was further added to the obtained calcium carbonate slurry, and a calcium carbonate slurry was obtained by the same operation. By repeating this operation several times, the BET specific surface area with a very small amount of aggregated particles is 6.5 m. ² / G, and a calcium carbonate slurry having an average particle size of 3.17 µm. This calcium carbonate slurry was treated with a solution of potassium abietate at a concentration of 10% with respect to the solid content of calcium carbonate at a treatment rate of 0.20% / m 2. ² After performing surface treatment, the mixture was dehydrated with a filter press, dried and crushed to obtain a filler for powder coating.
[0050]
Example 2
Lime milk having a specific gravity of 1.06 was adjusted to 15 ° C., and carbon dioxide gas (30% / min. ₂ ) Was conducted to carry out a carbonation reaction, and when the pH of the system was 8.5, the carbonation reaction was stopped. Then, the system was stirred at 50 ° C. for 24 hours under the conditions of 10 to 11 and again. The pH of the system was adjusted to 6.8 by passing carbon dioxide gas. As a result, the average primary particle diameter of the aggregate particles was very small, 0.10 μm, and the BET specific surface area was 11 m. ² / G, an aqueous slurry of calcium carbonate having an average particle diameter of 4 µm was obtained. This calcium carbonate slurry was treated with a solution of potassium abietate at a concentration of 10% with respect to the solid content of calcium carbonate at a treatment rate of 0.25% / m 2. ² After performing surface treatment, the mixture was dehydrated with a filter press, dried and crushed to obtain a filler for powder coating.
[0051]
Example 3
Lime milk having a specific gravity of 1.06 was adjusted to 15 ° C., and carbon dioxide gas (30% / min. ₂ ) Was conducted to carry out a carbonation reaction, and when the pH of the system was 8.5, the carbonation reaction was stopped. Then, the system was stirred at 50 ° C for 15 hours under the conditions of 10 to 11 to obtain a slurry system. When the viscosity reached 2,300 cp, carbon dioxide gas was passed again to adjust the pH of the system to 6.8. Thereby, the average primary particle diameter of the aggregate particles is extremely small, 0.07 μm, and the BET specific surface area is 14 m. ² / G, an aqueous slurry of calcium carbonate having an average particle diameter of 4 µm was obtained. The calcium carbonate slurry was treated with a 10% solution of sodium stearate at a treatment rate of 0.25% / m 2 based on the solid content of calcium carbonate. ² After performing surface treatment, the mixture was dehydrated with a filter press, dried and crushed to obtain a filler for powder coating.
[0052]
Example 4
After limestone produced naturally was pulverized by a micron mill, classification was repeated by an air classifier to obtain particles having an average particle diameter of 2.0 μm. Thereafter, using a Henschel mixer, potassium abietic acid was treated at a treatment rate of 0.25% / m with respect to the solid content of calcium carbonate. ² To obtain a powder coating filler.
[0053]
Example 5
In Example 1, the BET specific surface area was 6.5 m by changing the carbon dioxide gas flow rate from 3 L / min to 10 L / min. ² / G, calcium carbonate having an average particle size of 6.5 μm, and then subjected to the same surface treatment as in Example 1 to obtain a filler for powder coating.
[0054]
Example 6
In Example 1, the BET specific surface area was 5.2 m by changing the flow rate of carbon dioxide gas from 3 L / min to 15 L / min. ² / G, calcium carbonate having an average particle size of 12.5 μm, and the same operation was performed except that the surface treatment agent was changed to sodium stearate, to obtain a filler for powder coating.
[0055]
Example 7
In Example 1, the treatment rate was changed to 0.08% / m by changing the surface treatment agent to sodium stearate. ² The same operation was performed except for changing to the above, to obtain a filler for powder coating.
[0056]
Example 8
In Example 1, the treatment rate was changed to 0.04% / m by changing the surface treatment agent to sodium stearate. ² The same operation was performed except for changing to the above, to obtain a filler for powder coating.
[0057]
Example 9
After limestone produced in nature is pulverized with a micron mill, classification is repeated with an air classifier, and the BET specific surface area is 5.2 m. ² / G, having a mean particle size of 3.7 μm.
[0058]
Comparative Example 1
A BET specific surface area of 18 m was obtained in the same manner as in Example 1, except that the aging time after completion of carbonation was changed to 10 hours. ² / G, an average particle diameter of 2 μm was obtained. Then, potassium abietic acid was treated in the same manner as in Example 1 with respect to the solid content of calcium carbonate at a treatment rate of 0.2% / m 2. ² To obtain a powder coating filler.
[0059]
Comparative Example 2
After limestone produced in nature is crushed with a micron mill, classification is repeated with an air classifier, and the BET specific surface area is 2.5 m. ² / G, calcium carbonate particles having an average particle size of 25 μm. Thereafter, using a Henschel mixer, potassium abietic acid was treated at a treatment rate of 0.25% / m with respect to the solid content of calcium carbonate. ² To obtain a powder coating filler.
[0060]
Table 1 shows the properties of the powder coating fillers obtained in Examples 1 to 9 and Comparative Examples 1 and 2.
[0061]
[Table 1]

[0062]
Examples 10 to 22, Comparative Examples 3 to 5
Using the fillers for powder coatings obtained in Examples 1 to 9 and Comparative Examples 1 and 2, powder coating compositions were prepared in the following manner, and their coating properties were tested.
[0063]

[0064]

[0065]

[0066]
The above components were mixed as a raw material in a super mixer (manufactured by Nippon Spindle Manufacturing Co., Ltd.) for about 3 minutes, and melt-kneaded at about 100 ° C. using a coneder (manufactured by Bus). After cooling at room temperature, the mixture was coarsely pulverized and then pulverized with an atomizer (manufactured by Fuji Paudal), and classified with a 150-mesh sieve to obtain a powder coating having a volume average particle diameter of 35 μm.
[0067]
Each of the powder coatings produced by the above method was applied to a 200 × 100 × 0.8 mm zinc phosphate treated steel sheet by electrostatic spraying with a corona charging type coating gun to a film thickness of about 60 μm. After baking under each condition of 180 ° C. × 20 min and 200 ° C. × 20 min, it was allowed to cool to room temperature. The coating film performance was evaluated by the following method.
[0068]
<Appearance evaluation>
◎: Smooth coating state with little unevenness.
：: Smooth coating film state with some unevenness.
Δ: Slight irregularities and slight bumps.
X: There are irregularities, and the smoothness is slightly inferior.
XX: There are bumps and the like, poor in smoothness, and accumulation at the lower edge portion of the test plate is observed.
[0069]
<Pellet flow value>
Using a tableting machine, each powder coating was 300 kg / cm ² Under pressure to form a disk-shaped pellet having a diameter of 50 mm. As shown in FIG. 1, the pellet 1 was fixed to a metal plate of 200 × 100 mm with a double-sided tape, and the metal plate 2 was baked at 180 ° C. for 20 minutes while being suspended vertically, and the pellet 1 was flowed. Paint length 3 was measured. The above test was performed three times, and the average value was used as the evaluation value.
[0070]
<Gloss value>
As described above, any five places were selected from the coating surface of each test plate baked at 180 ° C. × 20 min and 200 ° C. × 20 min, and the gloss was measured at 60 ° by a gloss meter (manufactured by Nippon Denshoku Co., Ltd.). , 20 ° gloss was measured, and the average value was used as the evaluation value.
[0071]
[Table 2]

[0072]
【The invention's effect】
As described above, the filler for powder coating of the present invention can provide a powder coating composition that forms a coating film having an excellent appearance.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a method of measuring a pellet flow value.
[Explanation of symbols]
1 pellet
2 Metal plate
3 Paint flow length

Claims (8)

A filler for powder coatings, comprising calcium carbonate having a BET specific surface area of ² to 15 m ² / g by a nitrogen adsorption method. The filler for powder coating materials according to claim 1, wherein the average particle size of the calcium carbonate is 0.5 to 15 µm. Calcium carbonate is a saturated fatty acid, unsaturated fatty acid, aliphatic carboxylic acid, resin acid, (co) polymer of unsaturated carboxylic acid, their alkali metal salts, their alkaline earth metal salts, surfactant, silane coupling The filler for powder coating according to claim 1 or 2, which is surface-treated with at least one selected from agents. Powder coating filler according to any one of claims 1 to 3 surface treatment ratio is the unit BET specific surface area per 0.05-0.50 wt% / ^{m 2} of calcium carbonate. A powder coating composition comprising the powder coating resin according to any one of claims 1 to 4 mixed with a powder coating resin. The powder coating composition according to claim 5, wherein the powder coating resin is a thermosetting resin. The powder coating composition according to claim 6, wherein the thermosetting resin comprises at least one selected from a polyester resin, an epoxy resin, an epoxy-polyester resin, a fluororesin, and an acrylic resin. The powder coating composition according to any one of claims 5 to 7, wherein the compounding amount of the powder coating filler is 1 to 75 parts by weight based on 100 parts by weight of the powder coating resin.

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