JPS6136027B2 - - Google Patents

Description

[Detailed description of the invention]

An object of the present invention is to provide a powder coating that can form a multilayer coating film made of different types of resins on the surface of an object by just one application process. The method of forming a coating film on a surface to be coated, such as metal, using a powder coating composition is said to make it easy to form a relatively thick coating film of several hundred microns in one coating. It has been widely used in recent years due to its characteristics of being resource-saving and disaster-free. However, in conventional powder coating methods, even when a film thickness of several hundred microns is formed, the entire coating is coated, from the surface in contact with the surface to be coated to the surface in contact with the outside atmosphere. However, only a compositionally homogeneous coating film was formed.
In general, when a paint composition is used to form a coating film on a surface to be coated such as metal, wood, or plastics to protect and beautify the surface, only a single paint composition is used and as needed. Rather than forming a coating film of the required thickness by applying multiple coats,
A paint composition is used that has functions such as high adhesion depending on its properties and anti-corrosion properties due to electrochemical effects in metal coatings, while the side in contact with the external atmosphere (hereinafter referred to as the "surface layer") is coated with colors, gloss, etc. 2 with differentiated functionality, such as using coating compositions with functionality regarding external factors such as abrasion resistance, photochemical stability, impermeability to chemicals and chemical or physical stability.
It is preferred to use a combination of more than one type of coating composition to form a multilayer coating. In order to form a multilayer coating film by coating with a liquid coating composition, it is necessary to use at least one coating composition for each function to be differentiated, and a single liquid coating composition may not serve the purpose. unattainable. In the case of powder coating, it has generally been impossible to form a multilayer coating film using a single coating composition, but in particular, it has been impossible to form a multilayer coating film using a single coating composition. A technique is known in which a multilayer coating film with good corrosion resistance can be formed by one electrostatic coating by using the following as a coating material. However, in this case, it is necessary to consider not only the chargeability of the resin, but also its specific gravity, particle size, etc., and it is also affected by the properties of the coloring pigment used in combination, so the multilayer formation effect is Adjustment is extremely complex and has not yet reached widespread practical use. The present inventor has developed a multi-layered coating film that has different compositions for each part of the coating film, such as the surface layer and the lower layer, and has highly differentiated functions, through a complicated process of recoating it multiple times. A method was provided for forming the layer by just one powder coating without using the difference in chargeability (see JP-A-51-122137), but the method used a thermosetting addition copolymer resin as the surface layer forming component. The present invention was completed as a result of continued detailed studies on powder coatings that are particularly easy to form multilayer coatings. That is, the present invention relates to (a) a hardening monomer that is a polymerizable ethylenically unsaturated compound that exhibits a glass transition temperature of over 80°C as a homopolymer, and a hardening monomer that exhibits a glass transition temperature of lower than 10°C as a homopolymer; (b) powder of resinous material A, the main component of which is an acrylic thermosetting addition copolymer containing a softening monomer, which is an ethylenically unsaturated compound, as a comonomer; and (b) the resinous material A. is incompatible or poorly compatible with
and a powder of one or more resinous substances having a substantially higher surface tension than the resinous substance A at the same temperature of the melt and having a substantial difference in the multilayer formation composite parameters as the main component. a composition in which the thermosetting addition copolymer contains a hardening monomer and a softening monomer in weight percentages of a% and b%, respectively, a≦6. , and b≦4, or a+b≦50, b≦20, and b≦a≦1.5b. Pertains to. The above-mentioned powder coating of the present invention comprises a powder of a resin-like substance A containing the above-mentioned specific acrylic thermosetting addition copolymer as a main component for forming the surface layer of the coating film; It is composed of at least two types of powder of one or more resin-like substances having the above-mentioned specific properties, and as a result, it is possible to easily and reliably form a multilayer coating film. be. That is, when the powder coating of the present invention is applied to an object to be coated and heated and melted to form a multilayer, the entire coating layer from the lower layer to the surface layer, especially the surface layer. Also, since the phase separation between the resinous material A and the other resinous materials among the components is completely carried out, the coating film can be easily and reliably formed in a single coating process. In order to obtain the above effects, the acrylic thermosetting addition copolymer which is the main component of the resin material A needs to have an appropriate balance between cohesiveness and fluidity. In other words, this copolymer contains monomers that are combined in such a way that the composition of the copolymer is moderate in terms of hardness-imparting properties and softness-imparting properties, and the hardness-imparting monomers are It is necessary to contain the monomer and the softening monomer within the mutually antagonistic range specified in a and b above. The hardness-imparting monomer referred to here refers to the hardness-imparting monomer when it is added-polymerized alone to form a homopolymer.
Refers to a monomer that is a polymerizable ethylenically unsaturated compound exhibiting a glass transition temperature exceeding 80°C, and the glass transition temperature of a homopolymer thereof is illustrated for a few examples, but the present invention is not limited to these. do not have. Hardening monomer Glass transition temperature Styrene 100℃ Methyl methacrylate 105℃ Acrylonitrile 105℃ Methacrylonitrile 120℃ Methacrylic acid 144℃ Acrylic acid 86℃ Indene 85℃ Isobornyl acrylate 94℃ 2-chlorostyrene 119℃ 2-Methyl Styrene 136°C t-Butyl vinyl ether 88°C Vinyl chloride 81°C Acrylamide 153°C In addition, the softening monomer referred to here means 10% when added alone to form a homopolymer.
It refers to a monomer that is a polymerizable ethylenically unsaturated compound exhibiting a glass transition temperature lower than °C, and although a few are exemplified, the present invention is not limited thereto. Softening monomer Glass transition temperature 2-ethylhexyl acrylate -50°C Methyl acrylate 6°C Ethyl acrylate -24°C 2-ethylhexyl methacrylate -10°C Isobutyl acrylate -24°C Acrylic acid -n- Butyl -56℃ 2-hydroxyethyl acrylate -60℃ 2-hydroxypropyl acrylate -60℃ Lauryl methacrylate -27℃ t-butyl acrylate -22℃ P-nonylstyrene -53℃ n-butyl vinyl ether -52℃ Vinyl fluoride -20℃ Isopropyl acrylate -3℃ Excluding these hardening monomers and softening monomers, the main monomers of the comonomer component of the addition copolymer are: The glass transition temperature of the homopolymer is not included in the former two values, such as 2-hydroxyethyl methacrylate (glass transition temperature of homopolymer 55℃), isobutyl methacrylate (glass transition temperature of homopolymer 53℃) , ethyl methacrylate (65℃), glycidyl methacrylate (65℃)
46℃), n-butyl methacrylate (20℃), 2-hydroxypropyl methacrylate (26℃)
℃), cyclohexyl acrylate (16℃), hexadecyl acrylate (35℃), p-octadecylstyrene (32℃), acrylic esters, methacrylate esters, aromatic vinyl compounds, etc. One or more selected from ethylenically unsaturated compounds are used. Regarding the proportion of the hardening monomer and the softening monomer contained in the addition copolymer, if they are in very small amounts, there is no problem even if the ratio between them is not particularly considered. For example, for hardening monomers, 6% (weight%, same hereinafter),
If at least one of the softening monomers exceeds the 4% limit, it is necessary to maintain balance by limiting the ratio of the two within a certain range. That is, in the acrylic thermosetting addition copolymer of the present invention, when the hardening monomer and the softening monomer are a% and b%, respectively, a≦6 and b≦4. It is necessary to include within the range expressed by, or within the range expressed by a+b≦50, b≦20, and b≦a≦1.5b. By setting a and b within the above ranges, the present inventors can easily and reliably form a multilayer coating film, which is the object of the present invention.
Moreover, it has been found that the general coating performance can be adjusted at will, and therefore an ideal powder coating for forming multilayer coatings can be obtained. If a or b is outside the above range, the reliability of forming a multilayer coating will be lost. especially,
When a+b exceeds 50, it becomes difficult to achieve competition between the hardness-imparting monomer and the softness-imparting monomer. In order to reliably form a multilayer coating film, it is necessary that the surface layer components separate during heating, harden through a crosslinking reaction, and lose fluidity. Therefore, the resin material A, which is the surface layer component, should be thermosetting, and the addition copolymer, which is its main component, should be a copolymer of monomers with crosslinkable functional groups. used. Examples of crosslinking functional groups that can be incorporated into the copolymer for this purpose include -OH,

[Formula], -NH ₂ , -COOH, -CO-O-CO-, -NHCR ₂ OR (R represents H or a hydrocarbon group having 1 to 6 carbon atoms), and these functional groups are It may contain any of the hardening monomer, the softening monomer, and other monomers. Specifically, for example, 2-hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, glycidyl (meth)acrylate, (meth)acrylic acid, fumaric acid, maleic anhydride, N-methylolacrylamide, N-butoxymethyl Acrylamide etc. are used. A crosslinkable monomer having such a functional group,
The proportion used as a comonomer in the thermosetting addition copolymer is usually 1 to 30% by weight, particularly preferably 5% by weight.
~25% by weight, and if it is less than 1% by weight, the crosslinked molecular structure cannot be sufficiently developed, so the coating film may lack practical performance in terms of solvent resistance, hardness, etc. If they are used in excess of this range, there is a risk that the coating film will become brittle due to excessive development of the cross-linked molecular structure, or that water resistance may become insufficient due to the hydrophilicity of these monomers. In this way, for thermosetting addition copolymers,
If necessary, additives such as a crosslinking agent, a reaction accelerator, a plasticizer, and a pigment are mixed or dispersed within a range that does not destroy the resin state that can be powdered, and then powdered. The type of crosslinking agent is selected and used according to the type of crosslinkable functional group in the addition copolymer in accordance with ordinary powder coating technology. The degree of powderization can also be determined according to conventional powder coating technology, e.g.
The thickness is preferably 300 microns or less, particularly preferably 100 microns or less. The powder coating for forming a multi-layer coating film of the present invention contains, in addition to the powder of the resinous material A for forming the surface layer, a powder of the resinous material A for forming the lower layer and, if necessary, an intermediate layer. The main component is one or more powders of resin-like substances other than those mentioned above. At least one of these resinous materials is incompatible or poorly compatible with the resinous material A, and the surface tension of the molten material at the same temperature is substantially greater than that of the resinous material A. It is also necessary to have a substantial difference in the multilayer formation composite parameters. If these conditions are satisfied, either thermosetting or non-thermosetting,
Those normally used as components of powder coatings can be used as they are. The degree of incompatibility or poor compatibility of each resinous substance is
Although it is preferable to make the affinity as significant as possible because it can ensure the formation of a multilayer coating film, the degree of poor compatibility is usually determined by the numerical value of the affinity parameter given by the measurement method described later. , standards can be established. That is, when the affinity parameter is a positive number, 0, or a negative number with an absolute value of less than 0.10, the degree of poor compatibility is within a preferable range for the present invention, and it is particularly preferable that the affinity parameter be a positive number. good. When the affinity parameter is a negative number with an absolute value of 0.10 or more, there is a possibility that the formation of a multilayer becomes uncertain. The affinity parameter is measured by observing the mixing state of both types of resins in solution under certain test conditions.The affinity parameter determined by this method is as follows: It is most preferable as an index regarding the degree of affinity between resins, which is an essential element in the present invention. Specifically, each of the test soluble resins was made into a solution with a resin content of 33% by weight using an equal volume mixture of toluene and methyl isobutyl ketone (MIBK) as a solvent, and the solution was obtained at 25°C. Mix equal weights of the two solutions. After stirring the mixture to make it sufficiently homogeneous, look through the 5 cm thick liquid layer with the naked eye under natural daylight and if it is completely transparent, it indicates the affinity of the combination of the two resins. The parameter is 0 or a negative number, and if turbidity is observed, it is a positive number. To find the numerical value of this parameter, add ethylene glycol monomethyl ether acetate (CH ₃ OCH ₂・ CH ₂ OCCCH ₃ ) dropwise to this mixed solution while stirring and if it is a positive number. If it is 0 or a negative number, n-hexane is added dropwise to cause turbidity to occur due to the destabilization of the solute due to the addition of a poor solvent. The numerical value of the affinity parameter P is calculated by the following formula. |P|=△D/A+B+C+△D×K A and B: Weight of each of the two resins in the mixed solution (g) C: Weight of the solvent in the first mixed solution (g) △D : Weight of any of the solvents dropped (g) K : Correction coefficient, 1 when P is a negative number, P
When is a positive number, 100/45 When P does not reach the minimum display unit, P is set to 0. If at least one of the two resins is insoluble in the mixed solvent, it is impossible to determine the affinity parameter by the above method, but the approximate numerical value can be obtained indirectly by another method. be able to. That is, in the case of insoluble or poorly soluble resins such as polyethylene and polyamide, the thickness obtained by molding the resin is 400 to 500 μm.
The straight edges of the sheet are placed on a glass surface in close contact with each other, heated to a temperature sufficient to completely melt both resins, and held for about 30 minutes. If the affinity parameter between both resins is a positive number, 0, or a negative number with an absolute value of less than 0.10, an interface or boundary layer is formed between both molten resins, resulting in discontinuity, but the absolute value is 0.10 or more. When is a negative number, the composition changes continuously due to mutual diffusion, and no discernible interface is formed. The presence or absence of such an interface can be more easily observed with the naked eye by dispersing a coloring pigment or dye such as carbon black into at least one of the two resins to create a color change. . The combination of two types of resins used in combination for the purpose of forming a multilayer coating film not only requires that the affinity parameter observed in the solution state be within the above range, but also that the affinity parameter observed in the solution state must be within the above range. They also need to be incompatible or poorly compatible. That is, the mixed solution prepared when measuring the affinity parameters was applied to a transparent plate to obtain a dry film with a thickness of about 50 microns, and the solvent was evaporated (at room temperature, 24 hours) to form a dry film. It is necessary that turbidity or resin separation be observed when observed under transmitted light and scattered light. When at least one of both resins is insoluble in the mixed solvent,
The fact that the formation of an interface, etc. was observed in the above-mentioned sheet melting test can be considered to indicate incompatibility or apparent compatibility between the two resins. In order to ensure multilayer formation, it is preferable that the resin state for forming the lower layer and the intermediate layer has a melt surface tension as large as possible than that of the resin material A for forming the surface layer, but it is usually 1.0. The purpose of forming a multilayer coating film can be achieved easily enough by setting the amount to be at least dyne/cm, particularly preferably at least 2.0 dyne/cm. This difference in surface tension
If it does not reach 1.0 dyne/cm, there is a risk that phase separation, especially in the surface layer portion, will be incomplete when a coating film is formed. The temperature at which the surface tension is measured is the temperature immediately above the highest melting temperature of each component resin material for each powder coating, that is,
The most accurate heating temperature is to apply the mixture to the surface to be coated and melt it to form a multilayer coating, but in practice, the temperature is constant for any resinous material. For example, it is convenient and convenient to use the value of surface tension at 180°C or 200°C for comparison. There are no particular restrictions on the method for measuring the surface tension σ _L (dyne/cm) of a molten resin material, but for example, from the measured value of the contact angle θ between the molten material and Teflon (tetrafluoroethylene resin), the following method can be used: It is given by the Neumann and Sell equations. σ _s : Surface tension of Teflon (dyne/cm) In the present invention, an approximate value was obtained on the diagram by setting σ _s to 18.6 dyne/cm. Predetermined temperature of resin melt, e.g. 180℃ or 200℃
Regarding the method of measuring the contact angle for Teflon at °C, it can be applied without any particular restriction as long as the advancing contact angle can be determined.
The hemisphere-shaped resin to be measured is placed on a Teflon plate held horizontally with its spherical side facing down, and is melted and cast in a constant temperature chamber maintained at a predetermined temperature to reach equilibrium. At that point, it is enlarged and projected or observed with a telescope. If the melting temperature of the resin to be measured is high and it is not possible to directly calculate the surface tension at this temperature by measuring the contact angle with Teflon at a given temperature, it is possible to calculate the surface tension between the resin, which is solid at 20°C, and water. The surface tension value of the resin at 20°C obtained by measuring the contact angle, and the surface tension value measured and calculated by the same method as above just above the melting temperature of the resin instead of the predetermined temperature. It is requested by the law that is within the scope of the law. In the powder coating of the present invention, in order to separate the mixed powder resinous material by heating and melting and form a complete multilayer coating film, the resinous material for forming the lower layer must be thermosetting for forming the surface layer. It is necessary to be attracted to the coated surface more strongly than resin. Selective attraction of a molten resin material to a coated surface is controlled by a combination of factors such as its melting temperature range, surface tension, viscosity, and specific gravity. The present inventor believes that the "multilayer formation composite parameter" (hereinafter referred to as "multilayer formation composite parameter") measured by the test method described later is an index that quantitatively indicates the extent to which molten resin is attracted to the polar surface of metal, glass, ceramics, etc. It has been clarified that the difficulty of forming a multilayer coating film can be most easily determined by the numerical ratio of this multilayer parameter for each component resin. That is, in the case of the present invention,
It is necessary that the multilayer parameter of the resin for forming the lower layer is substantially larger than the multilayer parameter of the thermosetting resin for forming the surface layer, and specifically, it is desirable that the ratio is 1.3 or more, particularly 1.5. It is preferable that it is above. If this ratio is closer to 1 than 1.3, there is a risk that the separation between the mixed resins will not be sufficient, especially in the lower layer of the coating, resulting in an incomplete multilayer coating with a large degree of irregularity. . To measure the multilayer parameters, as shown in Fig. 1, a fixed amount of 0.15 g of solid resin to be measured is placed inside a heat-resistant glass cylindrical container 1 with an inner diameter of 12 cm, and on top of the solid resin, A Virex glass capillary tube 2 with an outer diameter of 4.0 mm and an inner diameter of 2.53 mm and whose inner surface has been thoroughly cleaned is stood upright so that it is coaxial with the cylindrical container 1 and can freely hang down by gravity.
This thin tube 2 has its lower end surface polished so that it is perpendicular to the axis, and a notch or guide hole 3 is provided in the lower end portion to allow the molten resin to be measured to flow freely. It is. The entire measurement system is stored in a constant temperature chamber maintained at a predetermined measurement temperature (T°C) with the bottom surface of the cylindrical container 1 being horizontal, and the resinous material to be measured is melted, and a layer 4 of the molten material is
to form. The lower end surface of the capillary tube 2, which hangs down as the resinous material to be measured is melted, reaches the bottom surface of the cylindrical container 1, and at the same time, the molten material flows into the capillary tube 2. The liquid surface of the molten resin to be measured not only forms a meniscus inside the capillary tube 2, but also advances on the inner wall surface of the capillary tube 2 by a so-called "creeping" phenomenon. this
The creeping speed indicates the degree to which the resinous material to be measured is attracted to a polar coated surface such as glass, and the creeping speed indicates the degree to which the resinous material to be measured is attracted to a polar coated surface such as glass. Measure the height Ht (cm) from the bottom of the container 1, and use the product ht (g/cm ³ ) obtained by multiplying this Ht by the density of the melt ρ (g/cm ³ ) as the multilayer parameter. is most preferred. It is most preferable and practical to measure the multilayer parameters at a temperature immediately above the highest melting temperature of each component resin material for each powder coating. In the case of other component resinous materials for which it is difficult to measure multi-layer parameters by continuing heating at that temperature for 25 minutes due to decomposition, curing, etc., such difficulty may occur from just above the melting temperature of the resinous material. Measurement is carried out at two or more temperature ranges within a temperature range in which there is no risk of causing damage, and the multilayer parameters at the same predetermined temperature are calculated and compared using the removal method. Alternatively, if the heating duration is shortened to less than 25 minutes and the rising speed of the tip of the creeping portion 5 is uniform, no significant difference will occur. When two or more types of resinous materials for forming the lower layer are used, it is not necessarily necessary that the combination of two of them also satisfy each of the above-mentioned restrictive requirements; If these restrictions are met between the thermosetting resin material and the resin material for forming the lower layer,
In addition to being incompatible or poorly compatible, a multilayer structure with three or more layers can be created by satisfying the above restrictions for only one of the indexes of surface tension and multilayer parameters. Easy to form. In the case of resin materials for forming the lower layer and intermediate layer, if they are thermosetting rather than self-curing, the necessary crosslinking agent, etc., and additives such as pigments as necessary are added. can be mixed and dispersed in advance. The degree to which these resinous substances are turned into powder depends on the desired powder coating method, such as electrostatic method,
It is sufficient to have a particle size that does not interfere with coating by a fluidized bed dipping method, etc., and precise adjustment of particle size distribution is not particularly necessary for the purpose of forming a multilayer coating, but preferably a particle size of 300 microns, In particular, it is desirable not to leave any coarse particles exceeding 100 microns, and by making the particle size of the component resin powder having the maximum multilayer parameter relatively small, it is possible to improve the ease of melting. Due to the relationship, the formation of multiple layers, especially the separation of the components on the lower side, can be further promoted. The ratio of mixing each component powder resin material is less than 10% by weight, particularly preferably 30% by weight of the total amount of each component to be separated by melting to form a multilayer.
It is necessary to ensure that the value is not less than 10.
Components mixed in proportions less than % by weight cannot constitute a complete multilayer. The distribution of each component resinous substance in each part of the multilayer coating film formed by the powder coating of the present invention can be confirmed and quantified by various methods. For example, if colored pigments with different colors for each component are pre-dispersed and mixed as a powder, it is possible to observe the cross section of the cured coating film, or to polish it from the top and observe the sequential changes in color. You can check the changes. In addition, even if it is not possible to distinguish by color, the composition of the powdered resin produced by polishing and grinding the coating film is analyzed by, for example, observing the infrared absorption spectrum. Alternatively, a method such as observing the infrared reflection spectrum of the exposed polished surface may be used. By using the powder coating of the present invention, in a single powder coating process, multiple layers can be divided into parts that require advanced functions such as weather resistance and adhesion depending on the purpose of use. Since the coating film is easily formed, it greatly contributes to streamlining the painting work. Hereinafter, the present invention will be explained in more detail with reference to Examples. Example 1 Methyl methacrylate 9%, styrene 18%, 2-ethylhexyl acrylate 19%, n-butyl methacrylate 39% and glycidyl methacrylate
Number average molecular weight obtained by copolymerizing 15%
100 parts of 12000 acrylic resin and 12.5 parts of dodecanedicarboxylic acid, the maximum particle size does not exceed 74 μ,
Grind to an average particle size of approximately 45μ and add component _A
And so. The multilayer parameters (value at 180℃, the same applies hereafter) of this component _A1 are 0.29g/cm ² , surface tension (value at 180℃
(the same applies hereafter) was 30.7 dyne/cm. Next, Epicote 1007 and Epicote 1007
(both trade names, manufactured by Schiel Kagaku Co., Ltd.) were mixed with 20 parts and 80 parts, respectively, of trimellitic anhydride, and 30 parts of rutile-type titanium oxide, and ground to the same particle size to obtain component _B1 . The multilayer parameter of this component B ₁ was 0.42 g/cm ² and the surface tension was 34.5 dyne/cm. The affinity parameter between component A ₁ and component B ₁ is
It was 0.30. By mixing Component A ₁ and Component B ₁ at a weight ratio of 40:60, a powder coating for forming a multilayer coating film () was completed. The surface of this powder coating was pre-conditioned (Bonderite BN manufactured by Nippon Parkerizing Co., Ltd.).
#144 treatment liquid and Elekron #9000 electrodeposition paint manufactured by Kansai Paint Co., Ltd. were applied under predetermined conditions. ) It was applied to a mild steel plate (0.5 mm thick) using the electrostatic coating method, and was heated at 180°C for 30 minutes to form a film and harden it. As a result, a white epoxy resin layer with a thickness of about 70 μ and A multilayer coating film was obtained, consisting of a transparent acrylic resin layer with a thickness of approximately 50 μm. For each of the following Examples, tests for forming a multilayer coating film were similarly conducted for each completed powder coating, and in each case, acrylic resin was applied to the surface layer with a film thickness configuration corresponding to the mixing ratio of each component. A coating film having the following properties was obtained. Example 2 100 parts of an acrylic resin (number average molecular weight approximately 10,000) copolymerized with 10% styrene, 5% acrylonitrile, 15% 2-hydroxyethyl acrylate and 70% ethyl methacrylate, blocked isocyanate curing agent (ε-caprolactam) Xylylene diisocyanate blocked with NCO group content
By mixing and pulverizing 20 parts of 19%), 5 parts of phthalocyanine blue, and 20 parts of rutile titanium oxide, component A ₂ having the same particle size as each component in Example 1 (the same applies hereinafter) was obtained.
(Multilayer parameter 0.38g/cm ² , surface tension 32.5dyne/
Got cm. Next, 100 parts of Epicote 1004, 30 parts of a blocked isocyanate curing agent (equal weight mixture of xylylene diisocyanate and isophorone diisocyanate blocked with benzyl alcohol, NCO group content 20%) and 30 parts of red iron
By mixing and grinding KNO (trade name, manufactured by Toda Kogyo Co., Ltd.), component B ₂ (multilayer parameter 0.45 g/cm ² ,
A surface tension of 34.6 dyne/cm) was obtained. The affinity parameter between component A ₂ and component B ₂ is
It was 0.26. By mixing the two in a ratio of 40:60, a powder coating for forming multilayer coatings () was completed. Example 3 100 parts of an acrylic resin (number average molecular weight approximately 9000) obtained by copolymerizing 8% styrene, 6% 2-ethylhexyl methacrylate, 66% isobutyl methacrylate and 20% hydroxypropyl methacrylate and a blocked isocyanate curing agent (implemented) Ingredients of example 2
Component A ₃ (multilayer parameter 0.35 g/cm ² , surface tension 29.3 dyne/cm was obtained from 20 parts of the same product as A ₂ ). Next, dimethyl terephthalate 40.7%, isophthalic acid 11.6%, adipic acid 10.2% , 100 parts of a polyester (average molecular weight approximately 8000, acid value 19.5) produced in a conventional manner using 34.2% neopentyl glycol and 3.3% glycerin as condensation components, a blocked isocyanate curing agent (same as component B ₂ of Example 2) component B ₃ (multilayer parameters
0.47 g/cm ² and surface tension of 36.3 dyne/cm). The affinity parameter between component A ₃ and component B ₃ is
It was 0.60. By mixing the two in a ratio of 35:65, a powder coating for forming multilayer coatings () was completed. Example 4 100 parts of an acrylic resin (number average molecular weight approximately 16,000) obtained by copolymerizing 5% styrene, 80% isobutyl methacrylate, and 15% glycidyl methacrylate;
By mixing and grinding with 12.5 parts of dodecanedicarboxylic acid, component A ₄ for surface layer formation (multilayer parameter 0.32
g/cm ² and a surface tension of 27.6 dyne/cm. Next, 25% styrene, 10% methyl methacrylate
%, 100 parts of acrylic resin (number average molecular weight approximately 8000) produced by copolymerization of 20% 2-ethylhexyl methacrylate, 25% n-butyl methacrylate and 20% 2-hydroxyethyl methacrylate, blocking isocyanate curing agent ( ε-Isophorone diisocyanate blocked with caprolactam) 30
By mixing and pulverizing 35 parts of yellow titanium oxide (manufactured by Ishihara Sangyo Co., Ltd., trade name ``Titaniero''), ₄ parts of component B for forming the lower layer (multilayer parameter 0.42) are mixed and crushed.
g/cm ² and a surface tension of 33.1 dyne/cm). The affinity parameter between component A ₄ and component B ₄ is
It was 0.08. By mixing the two in a ratio of 40:60, a powder coating for forming multilayer coatings () was completed. Example 5 2% 2-ethylhexyl methacrylate, 80% isobutyl methacrylate and 2% methacrylate
- Component A ₅ (multilayer parameter 0.31 g) from 100 parts of acrylic resin (number average molecular weight approximately 15,000) copolymerized with 18% hydroxyethyl and 20 parts of blocked isocyanate curing agent (same product as component A ₂ of Example 2) /
cm ² and surface tension of 28.5 dyne/cm). Next, polyester (number average molecular weight approximately 6000,
Acid value approx. 30) 100 parts, cyclohexanol, p-toluenesulfonic acid amide-modified hexamethylolmelamine (manufactured by Sanwa Chemical Co., Ltd., product number PX-
Component B ₅ (multilayer parameter 0.41g/
cm ² and surface tension of 38.2 dyne/cm). The affinity parameter between component A ₅ and component B ₅ is 0.23
It was hot. By mixing equal weights of both, a powder coating for forming a multi-layer coating film (2008) was completed. Example 6 100 parts of acrylic resin (number average molecular weight approximately 12,000) produced by copolymerization of 16% styrene, 6% acrylamide, 16% 2-ethylhexyl methacrylate, 54% isobutyl methacrylate, and 8% 2-hydroxyethyl methacrylate , 20 parts of hexamethylolmelamine curing agent PX-2000 (see Example 5) and 15 parts of "Titanie Yellow" (see Example 4) to component A ₆ (multilayer parameter 0.28 g/cm ² , surface tension
32.2dyne/cm). Next, 100 copies of Epicote 1004, 30 copies of PX―
Component B ₆ (layer parameter 0.37 g/cm ² , surface tension 36.5 dyne/cm) was obtained from 2000 and 20 parts of "Mapico Yellow" (see Example 3). The affinity parameter between component A ₆ and component B ₆ is
It was 0.26. By mixing equal weights of both, a powder coating for forming a multi-layer coating film (2) was completed. Example 4 22% styrene, 18% 2-ethylhexyl methacrylate, 42% isobutyl methacrylate, 16% 2-hydroxyethyl methacrylate and n-butyl etherified N-methylolacrylamide 2
Acrylic resin by copolymerization of % (number average molecular weight approx.
9000) and 20 parts of hexamethylolmelamine curing agent "PX-2000" (see Example 5) to produce component A ₇ (multilayer parameter 0.40 g/cm ² , surface tension 33.0 d)
yne/cm) was obtained. Next, component B ₁ (multilayer parameter 0.53 g/cm ² , surface tension 37.4 dyne/cm The affinity parameter between component A ₇ and component B ₇ is
It was 0.15. By mixing the two in a ratio of 40:60, a powder coating for forming multilayer coatings () was completed. Example 8 100 parts of an acrylic resin (number average molecular weight approximately 14,000) obtained by copolymerizing 14% styrene, 18% 2-ethylhexyl methacrylate, 58% isobutyl methacrylate, 8% acrylic acid, and 2% maleic anhydride and Epicoat 1001 (trade name, epoxy resin manufactured by Ciel Chemical Co., Ltd.) 10 parts to component A ₈ (multilayer parameters
A surface tension of 0.37 g/cm ² and a surface tension of 31.3 dyne/cm were obtained. Next, Component B ₃ was prepared from 100 parts of the same polyester as Component B 3 of Example 3, 30 parts of a blocked isocyanate curing agent (same as Component B ₂ of Example 2), and 30 parts of "Titanier Yellow" (see Example ₄ ). (Multilayer parameter: 0.49 g/cm ² , surface tension: 37.4 dyne/cm). The affinity parameter between component A ₈ and component B ₈ is
It was 0.46. With a 40:60 ratio of both, we completed a powder coating for forming multilayer coatings ().

[Brief explanation of the drawing]

The drawing is a cross-sectional view schematically showing a measurement system used for measuring multilayer parameters.

Claims (1)

[Claims] 1 (a) A hardening monomer which is a polymerizable ethylenically unsaturated compound exhibiting a glass transition temperature exceeding 80°C as a homopolymer;
A resinous material A whose main component is an acrylic thermosetting addition copolymer containing as a comonomer a softening monomer which is a polymerizable ethylenically unsaturated compound exhibiting a glass transition temperature lower than 10°C. Powder and (b) are incompatible or poorly compatible with the resinous material A, and have a surface tension substantially greater than that of the resinous material A at the same temperature of the melt, and are capable of forming a multilayer. A composition comprising a powder of one or more resinous materials having substantial differences in composite parameters as a main component, wherein the thermosetting addition copolymer contains a hardening monomer and a softening monomer. When the weight percentages of monomers are a% and b%, the monomers are included in the range expressed by a≦6 and b≦4, or a+b≦50, b≦20 and b≦a≦1.5b 1. A powder coating for forming a multilayer coating film, characterized in that it contains within the range expressed by: 2 The acrylic thermosetting addition copolymer which is the main component of the resin material A has the following formula: -OH, [Formula] -NH ₂ , -COOH, -CO-O-CO-, or -NHCH ₂ OR(R represents H or a hydrocarbon group having 1 to 6 carbon atoms. A powder coating for forming multilayer coatings. 3. An affinity parameter between the resinous material A and at least one resinous material other than the resinous material A is a positive number, 0, or a negative number with an absolute value of less than 0.10. A powder coating for forming a multilayer coating according to claim 1. 4 At least one of the resinous materials other than the resinous material A exhibits a melt surface tension that is 0.5 dyne/cm or more greater than that of the resinous material A at the same temperature. A powder coating for forming a multilayer coating film according to claim 1, characterized in that: 5. Between the resinous material A and other resinous materials other than resinous material A, the ratio of large to small multilayer formation composite parameters is 1.3 or more. A powder coating for forming a multilayer coating according to claim 1.