JPS6234076B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing paint particles, more specifically,
The present invention relates to a method for producing coating particles useful for preparing powder coatings with improved blocking resistance or slurry coatings with anti-sedimentation and flocculation properties without reducing fluidity during hot melting. In recent years, powder coatings or slurry coatings have become important as coatings for the purpose of preventing pollution of the air, water, and the like. For powder coatings, it is essential that the resin shape be stable in the form of particles, especially the so-called "blocking" phenomenon in which particles fuse together or form agglomerates under high temperatures, during transportation, or storage. Therefore, there is a limit to the hardness of paint particles due to glass transition temperature or molecular weight. That is, the particles that are stable against blocking have poor fluidity when melted, and on the other hand, in order to improve the fluidity and improve the finished state of the coating film, blocking resistance must be sacrificed. For this reason, only unsatisfactory results have been obtained in fields that require a relatively high-quality finish, such as the automobile field and the home appliance field. On the other hand, even in slurry paints, the resin shape needs to be stable in the form of particles.
They have the same problems as powder coatings because they cause "sedimentation" and "agglomeration" phenomena due to particles fusing with each other or clumping together at high temperatures or during transportation or storage. The object of the present invention is to create a powder coating or slurry that simultaneously solves the mutually contradictory problems of such coatings, that is, has good blocking resistance or sedimentation and agglomeration resistance, and has excellent thermal fluidity and provides a good coating film. It is an object of the present invention to provide a method for producing paint particles that can produce paints of various colors. As a result of intensive research to achieve this objective, the present inventors have discovered that a liquid paint composed of a solvent part and a non-solvent part is brought into contact with a liquid that solidifies the paint (hereinafter referred to as a coagulating liquid). Along with urging,
In a method for producing paint particles that undergoes granulation treatment, the liquid paint and coagulating liquid are brought into contact with each other in the presence of a vinyl polymer having a softening point within a specific range and having a carboxyl group at the end. It has been found that coating particles can be obtained which are considered to be coated in a so-called encapsulated manner with the above-mentioned vinyl polymer. That is, since the film formation and the composition of the vinyl polymer in the liquid paint can be appropriately selected and used,
It has been found that the contradictory problems of fluidity during hot melting (i.e., smoothness of the coating film) and blocking or sedimentation agglomeration when used as powder coatings or slurry coatings can be solved at the same time. The present invention was completed based on the above-mentioned findings, and the gist thereof is to bring a liquid paint into contact with a coagulating liquid that is compatible with the solvent portion of the liquid paint and incompatible with the non-solvent portion of the liquid paint. In addition, in the method for producing paint particles that involves granulation, the liquid paint and the coagulating paint are mixed with a vinyl polymer having a softening point higher than that of the film-forming component in the liquid paint and having a carboxyl group at the end. The present invention relates to a method for producing particles for coating material, which comprises contacting particles in the presence of a coating material. In addition, in the present invention, the above-mentioned "film-forming component" refers to a component generally called a color vehicle in paint particles obtained by contacting a liquid paint with a coagulating liquid. refers to resins, crosslinking agents, modifiers, and other additive components. The liquid paint according to the present invention is composed of a solvent portion and a non-solvent portion, and may be prepared according to a conventional method. Specifically, for example, various polymerizable monomers are solution-polymerized in a suitable solvent, or a pre-synthesized solid resin composition (for example, a commercially available powder coating) is dissolved or dispersed in a solvent. The liquid paint can be obtained by the method. In addition, if necessary, ordinary crosslinking agents, modifiers,
Pigments, other additives, etc. may be dispersed and mixed using a conventional method. In this case, in order to obtain a colored liquid paint by blending pigments, it is necessary to disperse and mix in a conventional manner using dispersion equipment used for ordinary paint manufacturing or ink manufacturing. It is desirable to heat-melt it and mix it into the solid resin composition in advance. As a solvent in the above liquid paint, it is important that it has compatibility with the coagulating liquid described later, and generally speaking, it is important to use water as the coagulating liquid from all aspects (economical, pollution prevention, workability, etc.). hydrophilic solvents that are compatible with water are preferred. Specifically, ketones such as acetone, methyl ethyl ketone, and cyclohexanone, ethers such as ethyl ether, ethylene glycol monoethyl ether, and ethylene glycol monobutyl ether, ethyl alcohol, n-butanol, and butyl diglycol, etc.
Examples include hydric or polyhydric alcohols, esters such as ethyl acetate, butyl acetate, and the like. The type of polymerizable monomer used in the above method is not particularly limited, and examples thereof include styrene, α-methylstyrene, vinyltoluene, p-tertiarybutylstyrene, vinyl acetate, vinyl propionate, acrylonitrile, methacrylonitrile, 2-hydroxyethyl acrylate, acrylic acid
2-hydroxypropyl, 1-methyl-2-hydroxyethyl acrylate, 2-methacrylate
Hydroxyethyl, 2-hydroxypropyl methacrylate, 1-methyl-2-hydroxyethyl methacrylate, acrylamide, N-methylolacrylamide, N-alkoxymethylacrylamide (alkyl group has 1 to 15 carbon atoms), acrylic acid, methacrylic Acids, esters of acrylic acid or methacrylic acid and alcohols having an alkyl group of 1 to 15 carbon atoms, crotonic acid, itaconic acid, fumaric acid, dibutyl fumarate, maleic anhydride, monobutyl maleate, methoxyethyl acrylate, acrylic Ethoxyethyl acrylate, butoxyethyl acrylate, glycidyl acrylate, glycidyl methacrylate, adduct of glycidyl acrylate or glycidyl methacrylate with aliphatic, vinylpyrrolidone, vinylpyridine, vinylimidazole, N/N'-dimethyl methacrylate Examples include aminoethyl, divinylbenzene, diallyl phthalate, triallyl isocyanurate, polyethylene glycol dimethacrylate, and one or more of these may be used in an appropriate combination. In the combination of polymerizable monomers used here, when the desired paint particles are to be made into a powder paint or a slurry paint, the intended purpose is to improve the smoothness and blocking resistance of the baked paint. Or, since it is necessary to achieve both sedimentation and flocculation resistance, sufficient consideration must be given to the formulation. That is, the softening point of the film-forming component in the liquid paint and the vinyl copolymer described later, which is considered to cover the film-forming component in a capsule manner, may be set so that the latter has a higher softening point than the former. Therefore, based on this viewpoint, the combination of polymerizable monomers or the monomer composition of the vinyl polymer located in the surface layer should be determined so that the softening points of the two relatively satisfy the above conditions. It is important that the selection is made within In the solid resin composition in the above method,
The resin may be any resin as long as it can be dissolved or dispersed in the solvent portion of the liquid paint and has a softening point lower than that of the vinyl polymer. Examples include acrylic, polyester, epoxy, urethane, and amino resins, and may also be a mixture of these resins and a crosslinking-reactive resin or compound. The coagulating liquid used in the present invention is compatible with the solvent part of the liquid paint and incompatible with the non-solvent part, and in particular, as mentioned above,
It is desirable to use water in correspondence with the case where a hydrophilic solvent is used as a solvent for liquid paint. The vinyl polymer used in the present invention may be any polymer as long as it has a carboxyl group at its terminal and has a softening point higher than that of the film-forming component in the liquid paint. In particular, a comb made of a copolymer of a chain polymer having an unsaturated bond at the terminal and a polymerizable monomer containing at least one carboxyl group-containing polymerizable monomer (hereinafter abbreviated as carboxyl monomer). Graft copolymers are preferred. Such a comb-like graft copolymer is
Specifically, it has a polymer component of the above-mentioned polymer monomer as a base, and the above-mentioned chain polymer is bonded to this in a comb-like manner. An example of its composition and manufacturing procedure will be described in detail below. (1) First, the above-mentioned chain polymer is obtained by, for example, esterifying an acrylic polymer having a carboxyl group at one end with a glycidyl group-containing polymerizable monomer (hereinafter abbreviated as glycidyl monomer). can be manufactured. Furthermore, this acrylic polymer having a carboxyl group at one end can be expressed by, for example, the general formula [Wherein, R represents H, CH ₃ or C ₂ H ₅ , and n represents 1 or 2. ] An initiator (carboxyl group-containing azo compound such as azobiscyanovaleric acid, azobiscyanopropionic acid, etc.) and, if necessary, a chain transfer side (mercapto compound having a carboxyl group such as thioglycolic acid, thiomalic acid, etc.) In the presence of a compound having a mercapto group (such as xantogen disulfide, lauryl mercaptan, etc.), the vinyl monomer is processed by a conventional method such as solution polymerization, bulk polymerization, emulsion polymerization, suspension polymerization, etc. Obtained by polymerization. In this case, by introducing a mercapto compound having a carboxyl group, a carboxyl group is also introduced at the chain transfer terminal, which is more advantageous. Polymerization conditions include a temperature of 50 to 160°C, preferably
A temperature of 80 to 110°C for 0.5 to 10 hours, preferably 1 to 3 hours may be employed. The acrylic polymer obtained in this way usually has an average molecular weight of 300 to
5000 and an acid value of 10 to 300. Examples of the above-mentioned vinyl monomer include ordinary polymerizable monomers such as styrene, α-methylstyrene, alkyl acrylate or alkyl methacrylate (methyl, ethyl, isopropyl, isobutyl, etc. as alkyl), acrylamide, and acrylonitrile. The softening point of the homopolymer or copolymer of vinyl monomers can be used to form a film in a liquid paint that forms the inner layer of the intended paint particles. Set so that it is higher than the softening point of the component. Examples of the glycidyl monomer include glycidyl acrylate, glycidyl methacrylate, and glycidyl methyl methacrylate, and one type or a mixture of two or more of these may be used. The esterification reaction between the acrylic polymer and the glycidyl monomer is carried out by a conventional method in the presence of an esterification catalyst (dimethylbenzylamine, dimethylaminoethyl methacrylate, etc.) and, if necessary, a polymerization inhibitor (hydroquinone, etc.). For example, it can be carried out by a bulk method, a solution method, or the like. The reaction conditions are a temperature of 50 to 160℃.
C., preferably 110 to 130.degree. C. for 2 to 15 hours, preferably 3 to 10 hours. The above-mentioned chain polymer can be obtained by such an esterification reaction, but in addition to this, for example, instead of the above-mentioned acrylic polymer, a fatty acid having a carboxyl group at one end (for example, lauric acid, stearic acid, oleic acid, etc.) may be used. , can also be obtained by esterifying a glycidyl monomer in the same manner as described above. Furthermore, such chain polymers include those obtained by addition reaction of a hydroxyl group-containing polymer and acrylic or methacrylic chloride or vinyl isocyanate, -COOl group-containing polymer and an amino group-containing polymerizable monomer (such as allylamine), or It is also possible to employ those obtained by addition reaction with a hydroxyl group-containing polymerizable monomer. (2) Examples of the above carboxyl monomers include acrylic acid, methacrylic acid, hydroxy compounds having polymerizable unsaturated bonds (2-hydroxyethyl methacrylate, etc.), and carboxylic acid anhydrides (maleic anhydride, etc.). Examples include adducts. These monomers are essential components, and if necessary, styrene, methyl methacrylate,
Any other copolymerizable monomer may be used in combination. (3) Production of the comb-shaped graft copolymer: The above-mentioned chain polymer and a polymerizable monomer containing a carboxyl monomer are combined in the presence of a common initiator (such as azobisisobutyronitrile). , by polymerizing by conventional methods such as solution polymerization method, bulk polymerization method, emulsion polymerization method, suspension polymerization method, etc.
The desired comb-like graft copolymer is obtained.
Polymerization conditions include, for example, temperature in the case of solution polymerization.
A temperature of 70 to 130°C, preferably 80 to 110°C, for 2 to 8 hours, preferably 2 to 5 hours may be employed. The paint particles according to the present invention use the above-mentioned vinyl polymer, particularly the above-mentioned comb-like graft copolymer, and are brought into contact with the liquid paint and a coagulating liquid in the presence of this polymer, and are subjected to a granulation treatment. It can be manufactured by applying In addition, the above
An acrylic polymer having a carboxyl group at one end in (1) can also be advantageously used as the vinyl polymer. Hereinafter, the processing procedure in the above manufacturing will be explained in detail. When the liquid paint and coagulating liquid come into contact with each other, the above-mentioned vinyl polymer may be mixed and dissolved in one of the two components, or it may be separated from both components and the vinyl polymer is present. For example, a method of providing contact in the form of a spray may be adopted. especially,
It is preferable to mix and dissolve this vinyl polymer in the coagulating liquid. In this case, when the coagulating liquid is water, it is preferable to neutralize some or all of the carboxyl groups of the vinyl polymer with an inorganic or organic base. This neutralization treatment allows the vinyl polymer to exist in water in a uniform state. After the vinyl polymer is present in this manner, contact between the liquid paint and the coagulating liquid and granulation treatment are carried out according to a conventional method. Note that this granulation treatment may be performed at the same time as the contact treatment, or before or after the contact treatment. Specific methods for such contact and granulation treatment include, for example, the following. A method of adding liquid paint to a coagulating liquid under stirring, or vice versa. A method of spraying liquid paint onto or into the coagulating liquid, with stirring if necessary. A method in which both the coagulating liquid and the liquid paint are brought into contact in a spray state. Through the above-described contact and granulation treatments, a dispersed suspension containing the intended paint particles is obtained. In such coating particles, as mentioned above, it is thought that the particle surface of the film-forming component in the precipitated liquid coating material is coated in a capsule-like manner with a vinyl polymer having a carboxyl group at the end. When the carboxyl groups of this vinyl polymer are neutralized, the paint particles are treated with an acidic substance (preferably an aqueous solution thereof) such as an organic acid, an inorganic acid, or an acidic gas (carbon dioxide, etc.) to neutralize the carboxyl groups. By using a free carboxyl group as the group, the physical properties of the coating film can be improved. In addition, paint particles with or without the above neutralization treatment may be injected with polyvalent metal ions (Ba ²⁺ , Ca ²⁺ , Al ³⁺ , Sr ^{3+ ,} etc.) substances (preferably their aqueous solutions, such as CaCl ₂ aqueous solution, Ba
(OH) ₂ aqueous solution, etc.) to convert the carboxyl group into a carboxyl group constituting the polyvalent metal salt, it is possible to obtain better blocking resistance or sedimentation and agglomeration resistance. These processes are
Similar to the above-mentioned methods (-), stirring and mixing or spray contact may be used. The coating particles may be separated from the dispersion suspension by a conventional method, such as a filtration method, a sieving method, or a centrifugation method. The obtained paint particles can be made into a powder paint either as they are or by washing and removing adhering impurities as necessary and drying them according to the usual method (hot air drying, spray drying, vacuum drying, etc.). can. Such powder coatings have better blocking resistance (blocking stability at high temperatures) than, for example, commercially available powder coatings used to create the above-mentioned liquid coatings.
It was observed that the coating film applied and baked by the usual fluidized dipping method or electrostatic dipping method showed the same texture and gloss as the coating film of the commercially available powder coating mentioned above. On the other hand, in order to obtain a slurry-like paint, the paint particles may be used as they are, or after being washed, subjected to a pulverization treatment if necessary, and then redispersed in water to a predetermined non-volatile content. The resulting slurry paint also
It has good sedimentation and flocculation resistance and is a uniform and stable slurry dispersion. This slurry paint is applied using a conventional method such as a spray method, and the baked paint film is also produced using a conventional method from a commercially available powder paint used to create a liquid paint, just as in the case of the powder paint described above. It is recognized that the finish is in good condition, showing the same texture and gloss as that of the slurry-type paint film. Next, the present invention will be specifically explained with reference to Reference Examples, Examples, and Comparative Examples. Note that "parts" and "%" in the example sentences mean "parts by weight" and "% by weight." Reference Example 1 Production of an acrylic polymer having a carboxyl group at one end: 50 parts of methyl methacrylate, 25 parts of toluene and 9.2 parts of thioglycolic acid were charged in a Kolben.
The temperature was raised to 90°C while stirring, and then 2.
2'-dimethyl-4,4'-azobiscyanovaleric acid 14
A dispersion mixture consisting of 1 part and 25 parts of isopronol was added dropwise over a period of 1 hour to obtain a polymer solution. This polymer is an acrylic polymer having a number average molecular weight of 950, an acid value of 100, and a carboxyl group at one end. Production of a chain polymer having an unsaturated bond at the end: In a Kolben, the solvent obtained by distilling off the entire amount of the above polymer, 0.6 parts of benzyldimethylamine, and 0.12 parts of hydroquinone were charged, and the mixture was stirred.
The mixture was kept at 110°C, and then 12.0 parts of glycidyl methacrylate was added dropwise over a period of about 2 hours. After completion of the dropwise addition, aging is further performed at the same temperature for 3 hours to obtain a polymer. Such a polymer is a chain polymer having an acid value of about 20 and an ethylenically unsaturated bond at the end. Production of a comb-shaped graft copolymer having a carboxyl group at the terminal: In a Kolben, 172 parts of the above polymer, 30 parts of isopropanol, and 36.4 parts of methacrylic acid were charged.
The mixture was kept at 90° C. with stirring, and then a dispersion mixture consisting of 24.8 parts of azobisisobutyronitrile, 100 parts of toluene and 18.4 parts of thioglycolic acid was added dropwise over 1 hour. After completion of the dropwise addition, the mixture is further aged for 4 hours at the same temperature, and then the solvent in the system is distilled off to obtain a polymer. Such polymers are comb-like graft copolymers having carboxyl groups at the ends. Example 1 A liquid paint was prepared by mixing and dissolving 100 parts of an acrylic powder paint (trade name: "Powdax A40 White" manufactured by Nippon Paint Co., Ltd.) in 200 parts of methyl ethyl ketone. Next, add the polymer obtained in Reference Example 1 to 1000 parts of water.
Three parts of a 50% aqueous solution of KOH neutralized product is dissolved, and the above liquid paint is added dropwise to the solution while stirring with a high-speed lab mixer to form a dispersed suspension. This suspension is subjected to centrifugation to obtain paint particles. The above paint particles are dried as they are to form a powder paint, and the blocking resistance and appearance of the paint film are evaluated as follows.
As shown in the table (in addition, the above commercial product “Powdats A40
(The results for “White” are also listed). Example 2 35 parts of styrene and methyl methacrylate in Kolben
35 parts, n-butyl methacrylate 10 parts, glycidyl methacrylate 20 parts, lauryl mercaptan 4 parts and ethylene glycol monoethyl ether 100 parts
After adding 6 parts of azobisisobutyronitrile with stirring, a polymerization reaction was carried out at a temperature of 120℃ for 5 hours. (measured with a differential thermal scanning calorimeter, the same applies hereafter)). Next, dissolve 3 parts of a 50% aqueous solution of the KOH neutralized product with the polymer obtained in Reference Example 1 (softening point 85°C) in 1000 parts of water, and add the above liquid paint to this while stirring with a high-speed lab mixer. Add dropwise to form a dispersed suspension.
This suspension is subjected to centrifugation to obtain paint particles. The above paint particles are dried as they are to form a powder paint, and the blocking resistance and appearance of the paint film are evaluated as follows.
Shown in the table. Comparative Example 1 While stirring 1000 parts of water with a high-speed lab mixer,
The acrylic resin liquid paint prepared in Example 2 is added dropwise to this to form a dispersed suspension, which is centrifuged to obtain paint particles. The above paint particles are dried as they are to form a powder paint, and the blocking resistance and appearance of the paint film are evaluated as follows.
Shown in the table.

[Table] Example 3 The dispersion suspension of Example 1 was diluted with 1/10N hydrochloric acid 10
After stirring and mixing with a portion of the mixture, the mixture is centrifuged to obtain paint particles. The paint particles were dried as they were to form a powder paint, which was electrostatically coated and baked at 180°C for 20 minutes, and the resulting paint film had a good appearance. In addition, when this was left in an atmosphere of 50° C. and RH=98% or more for 240 hours, the blisters on the surface were better than that of the powder coating of Example 1. Example 4 The dispersion suspension of Example 2 was first stirred and mixed with 50 parts of a 5% calcium chloride aqueous solution, and then centrifuged to obtain paint particles. Such paint particles,
Redisperse in water to make a slurry paint with a solid content of 40%. This slurry paint was heated at 40℃ for 30 minutes.
When stored for several days, it was confirmed that the sedimentation and flocculation resistance was improved compared to the slurry-like paint obtained by the same treatment from the paint particles of Example 2.

Claims (1)

[Scope of Claims] 1. A method for producing particles for paint, in which a liquid paint is brought into contact with a coagulating liquid that is compatible with a solvent portion of the liquid paint and is incompatible with a non-solvent portion, and subjected to granulation treatment. , the above liquid paint and coagulating liquid,
1. A method for producing paint particles, which comprises bringing them into contact in the presence of a vinyl polymer having a softening point higher than that of a film-forming component in a liquid paint and having a carboxyl group at its terminal. 2. A comb-shaped graft obtained by copolymerizing a vinyl polymer with a chain polymer having an unsaturated bond at the end and a polymer monomer containing at least one carboxyl group-containing polymerizable monomer. The manufacturing method according to item 1 above, which is a copolymer. 3. Item 1 or 2 above, where the coagulating liquid is water.
Manufacturing method described in section. 4. A method for producing paint particles in which a liquid paint is brought into contact with water, which is a coagulating liquid that is compatible with the solvent portion of the liquid paint and is incompatible with the non-solvent portion, and subjected to a granulation treatment. Bringing the paint and the coagulating liquid into contact in the presence of a vinyl copolymer that has a softening point higher than that of the film-forming component in the liquid paint and has at least a partially neutralized carboxyl group at the end, Furthermore, a method for producing paint particles, which comprises treating with an acidic substance after granulation. 5 A comb-shaped graft copolymer obtained by copolymerizing a vinyl polymer with a chain polymer having an unsaturated bond at the terminal and a polymerizable monomer containing at least one carboxyl group-containing polymerizable monomer. The manufacturing method according to item 4 above, which is a polymer. 6. A method for producing paint particles in which a liquid paint is brought into contact with water, which is a coagulating liquid that is compatible with the solvent portion of the liquid paint and is incompatible with the non-solvent portion, and subjected to a granulation treatment. The paint and the coagulating liquid are brought into contact with each other in the presence of a vinyl polymer that has a softening point higher than that of the film-forming component in the liquid paint and has a carboxyl group at the end, and after the granulation process, the polyvalent metal is A method for producing paint particles characterized by treatment with an ionic substance. 7. A comb-shaped graft obtained by copolymerizing a vinyl polymer with a chain polymer having an unsaturated bond at the terminal and a polymerizable monomer containing at least one carboxyl group-containing polymerizable monomer. The method for producing a copolymer according to item 6 above.