Resin composite, molded body, method for manufacturing resin composite, and method for manufacturing molded body

Abstract

To provide a thermoformable thermoplastic resin composite containing thermosetting powder coating.SOLUTION: A resin composite 10 includes a powder for coating 20 used in electrostatic coating method or fluidized bed coating method, inorganic alkali 30, and a thermoplastic resin 40. The resin composite is thermoformable.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a resin composite and a molded article, as well as a method for producing a resin composite and a method for producing a molded article. [Background technology]

[0002] With the growing awareness of reducing the environmental burden, there is a demand for replacement with environmentally friendly products, and in the field of coating compositions, attention is being paid to powder coatings that do not contain organic solvents, are low-polluting, have high workability, and have a smaller environmental impact. Such powder coatings, which are used in electrostatic coating methods and fluidized bed coating methods, are relatively inexpensive, and furthermore, powder coatings that are thermosetting are easy to color, have high adhesion to substrates, and form thermosetting films with high rust prevention, weather resistance, and durability, so there is a strong demand for them in electronic parts, office automation equipment, home appliances, building materials, automobile parts, etc.

[0003] The electrostatic coating method is a method in which a voltage is applied between an electrically connected object to be coated and a paint spraying device, forming an electrostatic field between the two, charging the powder paint, and forming a powder paint film on the object to be coated.The fluidized bed method is a method in which the powder paint is stirred up by air or the like, and a powder paint film is formed in this area on the surface of the object to be coated that has been heated in advance.

[0004] Thermosetting powder paints used in such coating methods are basically composed of oligomer or polymer particles that melt and form a film by heating and have crosslinking points, and crosslinking agent particles that are compatible with this polymer, and are fixed to the surface of the object to be coated to perform film formation and curing. Depending on the type of crosslinking method, there are those that utilize the reaction of blocked isocyanate using ε-caprolactam with hydroxyl groups, those that form oxazolidone rings with blocked isocyanate and bisphenol A type epoxy resins that have epoxy groups at both ends and are cured (Non-Patent Document 1), those that crosslink bisphenol A type epoxy resins that also have epoxy groups at both ends with ε-caprolactam (Non-Patent Document 2), those that utilize the bonding reaction of epoxy groups with dicyandiamide (Non-Patent Document 3), those that utilize carboxylic acids at both ends of polyesters and are cured with a multifunctional epoxy compound such as triglycyl isocyanurate (Non-Patent Document 4), and those that utilize esterification reactions.

[0005] However, epoxy-based materials and ε-caprolactam are known to be environmentally toxic because they react with biological components such as proteins. In recent years, with the development of β-hydroxyalkylamides (Patent Document 1) as compounds with a low environmental impact, a method of crosslinking this material with polycarboxylic polyesters by a dehydration condensation reaction (commonly known as the Primid curing type, Non-Patent Document 2) is becoming mainstream.

[0006] Powder paints have many advantages, but although powder particles that do not adhere to the substrate during painting can be reused, the particle size gradually decreases due to collisions between the particles and the object to be coated, and when an appropriate amount of coating cannot be obtained, the particles are discarded. This amount exceeds 10% to 20% of the powder paint that was put in, and this has been a major problem. Furthermore, once the polymer particles and the crosslinker particles are mixed together, it is difficult to separate them again, and the current situation is that there is no known way to use them other than hardening the residue and using it for another purpose as in Patent Document 2.

[0007] On the other hand, general-purpose thermoplastic resins can be molded in a variety of ways, such as injection molding, extrusion molding, and vacuum molding, and are used in a wide range of applications, such as packaging materials for delivery, product display shelves, and simple structures. If powder coatings can be used for such applications, the waste materials that were previously disposed of can be reused. Patent Document 3 describes that thermoplastic resins such as polyethylene, polypropylene, and ABS may be added to powder coatings using polyester, as well as leveling agents and pigments, but the purpose is related to thermosetting films and not to composites that can be thermoformed, that is, to use powder coatings as extenders for thermoplastic resins. However, when powder coatings are compounded with general-purpose thermoplastics such as polyethylene, polypropylene, ABS, and PET, first, the temperature range during kneading is about 180°C to 300°C, so the powder coatings containing crosslinking agents harden by themselves and separate and solidify from the thermoplastic resin, making it difficult to manufacture composites. [Prior art documents] [Non-patent literature]

[0008] [Non-Patent Document 1] Thermosetting resin, vol.6, No.2, p87-93(1985) [Non-Patent Document 2] Network Polymer, vol. 38, No. 2 (2017) [Non-Patent Document 3] Thermosetting resin, vol.8, No.3, p141-151(1987) [Non-Patent Document 4] DNT Coating Technical Report, vol.10, p32-37, (2010) [Patent documents]

[0009] [Patent Document 1] Special Publication No. 2010-508424 [Patent Document 2] Patent No. 6564988 [Patent Document 3] Special Publication No. 62-236870 Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention provides a thermoformable thermoplastic composite containing a thermosetting powder coating. [Means for solving the problem]

[0011] The present invention is characterized in that a thermosetting powder coating material, an inorganic alkali, and a thermoplastic resin are combined together.

[0012] More specifically, it is as follows. The resin composite of the first embodiment contains a paint powder used in electrostatic coating or fluidized bed coating, an inorganic alkali, and a thermoplastic resin, and is thermoformable. A resin composite of a second aspect is the resin composite of the first aspect, wherein the paint powder contains a thermally film-forming resin and a crosslinking agent.

[0013] The molded article of one embodiment contains the resin composite of the second embodiment and has a predetermined shape.

[0014] The method for producing a resin composite of the first embodiment is a method for producing a resin composite of the first or second embodiment, and includes a first step of producing a mixture by mixing a solution in which a water-soluble inorganic alkali is dissolved in water with a paint powder used in an electrostatic coating method or a fluidized bed coating method, and a second step of mixing a thermoplastic resin with the mixture. The method for producing a resin composite of the second embodiment is the method for producing a resin composite of the first or second embodiment, and includes a first step of producing a mixture by mixing a solution in which a water-soluble inorganic alkali is dissolved in water with a paint powder used in an electrostatic coating method or a fluidized bed coating method, a second step of drying the mixture to produce a dried body, and a third step of mixing a thermoplastic resin with the dried body.

[0015] The method for producing a structure of the first embodiment includes the steps of producing a resin composite by the method of the first embodiment, and forming the resin composite produced in the step into a structure having a predetermined shape. The method for producing a structure of the second embodiment includes a step of producing a resin composite by the method of the second embodiment, and a step of forming the resin composite produced in the step into a structure having a predetermined shape.

[0016] Moreover, the resin composite of the third embodiment contains a thermosetting powder coating and an inorganic alkali, and is thermoformable. Furthermore, a resin composite of a fourth aspect is the resin composite of the third aspect, characterized in that the thermosetting powder coating contains a polyester resin having a carboxylic acid. Furthermore, in the third embodiment of the method for producing a resin composite, an aqueous inorganic alkali solution is added to the thermosetting powder coating material, and then the thermosetting powder coating material is composited with a thermoplastic resin. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a diagram of a resin composite according to an embodiment of the present invention (hereinafter, referred to as the present embodiment). [Diagram 2] FIG. 2 is a flow diagram of a method for producing a resin composite according to the present embodiment. [Diagram 3] FIG. 4 is another flow diagram of the method for producing a resin composite according to the present embodiment. [Figure 4] This is a microscope image (photograph) of powder paint before application. [Diagram 5] This is a microscope image (photograph) of powder paint that was discarded after painting. [Figure 6] This is a microscopic image (photograph) of the molded resin composite. [Figure 7] 1 is a photograph of a molded body formed by injection molding. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] The thermoplastic resin composite (resin composite: see reference number 10 in the figure) in this embodiment is a composite of a thermosetting powder paint (an example of a powder for paint: see reference number 20 in the figure) and various thermoplastic resins (see reference number 40 in the figure), such as olefin resins such as polyethylene and polypropylene, aliphatic polyesters having properties such as biodegradability, semi-aromatic polyesters such as PET and PBT, and further aliphatic-aromatic hybrid polyester resins, polystyrene resins, acrylic resins, ABS resins, nylon, and fluororesins.

[0019] The thermosetting powder paint in this embodiment is a paint that does not contain a medium such as a solvent or water, and is heat-cured with a crosslinking agent (see reference number 24 in the figure) that is already contained in the polyester after the polyester is heated to form a film (after the polyester is subjected to a heat-film-forming treatment to form a heat-film-treated polyester (an example of a heat-film-forming resin, see reference number 26 in the figure)), ensuring high durability, weather resistance, adhesion, etc. As a method for forming a crosslinked structure, blocked isocyanate, epoxy, and dehydration condensation type of hydroxyl group and carboxylic acid are known, but since β-hydroxyalkylamide has become known as a crosslinking agent, dehydration condensation type using this is becoming mainstream. In addition to the base agent and crosslinking agent, inorganic particles such as silica, alumina, calcium carbonate, etc., ultraviolet inhibitors such as titanium oxide, and further carbon and various coloring agents may be added to the powder paint. In addition, the reference numeral 22 in the figure denotes a pigment contained in the thermosetting powder paint.

[0020] The polyester in the present embodiment is a dehydration condensation product of an aliphatic diol, such as ethylene glycol, 1,4-butanediol, 1,3-propanediol, 1,6-hexanediol, or neopentyl glycol, and a polycarboxylic acid compound, such as phthalic acid, isophthalic acid, terephthalic acid, phthalic anhydride, 1,4-cyclohexanedicarboxylic acid, adipic acid, sebacic acid, or dodecanedioic acid, and the melting point, crosslink density, and the like are controlled depending on the structure, molecular weight, and number of residual carboxylic acid groups of the selected compound.

[0021] The inorganic alkali (see reference numeral 30 in the figure) used in this embodiment must be water-soluble or hygroscopic, and is preferably a hydroxide of lithium, sodium, potassium, calcium, or the like, or a carbonate or formate of lithium, sodium, or potassium. From the viewpoint of storage and handling, sodium hydroxide, carbonates such as sodium bicarbonate and sodium carbonate are more preferred compounds. Inorganic alkalis suppress the dehydration condensation reaction between hydroxyl groups and carboxylic acids, and can dissociate ester bonds in the presence of water or water vapor at high temperatures to decompose the polymer matrix. On the other hand, organic alkali compounds such as amines are alkalis, but they react with carboxylic acids, and in the case of polyvalent amines, they form amide bonds that are more stable than ester bonds, and are therefore not preferred compounds for the present invention.

[0022] The inorganic alkali is added in the form of a powder or an aqueous solution. As mentioned above, water is essential for inhibiting the hardening of the powder coating, so when using it in powder form, it is preferable to add a small amount of water or use it in a hygroscopic state. The amount of water to be added is 0.1 to 200 parts by mass, more preferably 0.2 to 40 parts by mass, per 100 parts by mass of the inorganic alkali. This method is a method of kneading the powder coating and the inorganic alkali using a small amount of water without producing excess water. Since the powder coating is hydrophobic, a material with high water retention, such as a surfactant, fine cellulose, methyl cellulose, or sodium salt of carboxymethyl cellulose, may be added during kneading.

[0023] When added in the form of an aqueous solution, the concentration is preferably 0.01 to 30 parts by mass per 100 parts by mass of water, and the amount added is preferably 1 to 500 parts by mass per 100 parts by mass of powder paint. If the inorganic alkali concentration is too low, it is difficult to obtain the effect, and if the concentration is too high, workability is poor, so the concentration is more preferably 0.1 to 10 parts by mass. If the amount added is too high, the excess water increases the fluidity and makes handling difficult, so the amount added is more preferably 5 to 50 parts by mass. Since powder paints are hydrophobic, various activators such as sodium salt of dodecylbenzenesulfonic acid may be added to improve wettability.

[0024] The powder coating mixture with added inorganic alkali (one example of a mixture) is thoroughly kneaded and stirred using a powder kneader or mixer, and then kneaded with a thermoplastic resin in a resin kneader to produce a thermoplastic resin composite (see Figure 2). When using inorganic alkali in powder form, a thorough kneading process is required, so if care is taken with regard to excess water, it is easier to work with an aqueous solution. However, if the inorganic alkali concentration is reduced during the work process, the mixture may be heated and dried to remove excess water, although this will increase the number of manufacturing steps (see Figure 3).

[0025] Thermoforming in this embodiment refers to a method of molding the resin composite 10 produced by the above-mentioned production method into a molded body having a specified shape (see reference numeral 50 in FIG. 7 as an example), and is a molding method that uses a general-purpose thermoplastic resin, such as injection molding, blow molding, extrusion molding, vacuum molding, etc. Molding methods that are particularly useful for reuse are injection molding and extrusion molding, which can be processed into trays, panels, tables, chairs, trolley beds, etc. for transportation or display, and these can also be reused if crushed. A molded body is an example of a structure having a predetermined shape. In the above description, the resin composite 10 is molded to form a molded body having a predetermined shape, but a structure including the resin composite 10 may be manufactured by processing the resin composite 10 using a processing method other than molding (adhesion, fusion, cutting, or other processing method). The shapes of trays, panels, tables, chairs, trolley beds, and the like for transportation or display are examples of defined shapes. EXAMPLES

[0026] Preliminary experiment Commercially available powder coatings Nippon Paint Industrial Coatings' Bilyusia (registered trademark) PL7000 (a powder coating in which polyester is cured with β-hydroxyalkylamide) was used as powder coating 1, and the particle state was observed before and after electrostatic coating using a microscope VHX-2000 manufactured by Keyence Corporation. Figure 4 shows the state before electrostatic coating, and Figure 5 shows the state after electrostatic coating.

[0027] Furthermore, when the particle size was measured using an Antpearl dry particle size analyzer PSA1190L / D, the volume average particle size was 33μm before coating, decreasing to 22μm after coating, and similar to the results of the microscope observation, the particle size showed a tendency to decrease. The powder coating after coating is designated as Powder Coating 2.

[0028] The thermoplastic resins used in the examples are as follows: Polypropylene, Japan Polypropylene Corporation, Novatec PP BC-06C ABS Denka Co., Ltd. GR-2000

[0029] Example 1 100 parts by mass of powder coating 2 was taken out, to which 1 part by mass of sodium carbonate powder, 15 parts by mass of water, and 1 part by mass of fine cellulose were added, and thoroughly kneaded in a powder kneader. 20 parts by mass of this kneaded product and 80 parts by mass of polypropylene were kneaded in a resin kneader, and composite 1 could be taken out in good condition. This composite 1 could be molded into a plate-shaped body using an injection molding machine.

[0030] Example 2 100 parts by mass of powder coating 2 was taken out, and 25 parts by mass of an aqueous solution of sodium carbonate adjusted to a concentration of 2% by mass and 4 parts by mass of an aqueous solution of sodium dodecylbenzenesulfonate (abbreviated as DBS) with a concentration of 2% by mass were added and stirred. 20 parts by mass of this mixture was kneaded with 80 parts by mass of polypropylene in a resin kneader, and composite 2 could be taken out in good condition. This composite 2 could be molded into a plate-shaped body using an injection molding machine.

[0031] Example 3 100 parts by mass of powder coating 2 was taken out, and 80 parts by mass of a sodium carbonate aqueous solution adjusted to a concentration of 1% by mass and 4 parts by mass of DBS with a concentration of 2% by mass were added and stirred. The stirred product was dried at 130°C for 2 hours. When 20 parts of the dried product and 80 parts of ABS were kneaded in a resin kneader, composite 3 was obtained in a good condition. Furthermore, this composite 3 could be molded into a plate-shaped body using an injection molding machine.

[0032] Example 4 100 parts by mass of powder coating 1 was taken out, and 25 parts by mass of a sodium carbonate aqueous solution adjusted to a concentration of 2% by mass and 4 parts by mass of a DBS aqueous solution with a concentration of 2% by mass were added and stirred. 20 parts by mass of this mixture and 80 parts by mass of polypropylene were kneaded in a resin kneader, and composite 4 could be taken out in good condition. This composite 4 could be molded into a plate-shaped body using an injection molding machine.

[0033] Example 5 100 parts by mass of powder coating 2 was taken out, and 25 parts by mass of a sodium carbonate aqueous solution adjusted to a concentration of 2% by mass and 4 parts by mass of a DBS aqueous solution with a concentration of 2% by mass were added and stirred. 50 parts by mass of this mixture and 50 parts by mass of polypropylene were kneaded in a resin kneader, and composite 5 could be taken out in good condition. Composite 5 could be molded into a plate-like body using this injection molding machine. Furthermore, a thin piece was taken out of this molded body, and the surface was observed with a microscope VHX-2000. Figure 6 is an image obtained as a result of this observation. As shown in this figure, a break-shaped composite and a spherical polyester were observed after kneading.

[0034] Example 6 Powder paint 3 was prepared by electrostatically applying powder of Bilyusia PL1000 (a powder paint that cures bisphenol A epoxy resin with blocked isocyanate) manufactured by Nippon Paint Industrial Coatings Co., Ltd. 100 parts by mass of this was taken out, and 25 parts by mass of a 2% by mass aqueous sodium hydroxide solution and 4 parts by mass of a 2% by mass DBS were added and stirred. After stirring, 15 parts of the stirred mixture and 85 parts of polypropylene were kneaded in a resin kneader to obtain Composite 6. Composite 6 could be molded into a plate-shaped body using an injection molding machine. Comparative Example

[0035] Comparative Example 1 (When powder coating is mixed directly into polypropylene (1)) When 20 parts by mass of Powder Coating 1 and 80 parts by mass of polypropylene were mixed in a resin mixer, a solidified material separated and precipitated, and a composite could not be taken out.

[0036] Comparative Example 2 (When powder coating is mixed directly into polypropylene (2)) When 20 parts by mass of Powder Coating 2 and 80 parts by mass of polypropylene were mixed in a resin mixer, a solidified material separated and precipitated, and a composite could not be taken out.

[0037] Comparative Example 3 (When powder coating is mixed directly into polypropylene (3)) When 20 parts by mass of Powder Coating 3 and 80 parts by mass of polypropylene were mixed in a resin mixer, a solidified material separated and precipitated, and a composite could not be taken out.

[0038] Comparative Example 4 (When water is added (1)) 100 parts by mass of powder coating 1 was taken out, 25 parts by mass of water and 4 parts of a 2% by mass DBS aqueous solution were added, and the mixture was stirred. When 20 parts of the stirred mixture and 80 parts of polypropylene were kneaded in a resin kneader, a solidified material was precipitated, and it was not possible to take out a composite.

[0039] Comparative Example 5 (When water is added (2)) 100 parts by mass of powder coating 2 was taken out, and 25 parts by mass of water and 4 parts of a 2% by mass DBS aqueous solution were added and stirred. When 20 parts of this mixture and 80 parts of polypropylene were kneaded in a resin kneader, a solidified material was precipitated and it was impossible to take out a composite.

[0040] Comparative Example 6 (When water is added (3)) 100 parts by mass of powder coating 3 was taken out, 25 parts by mass of water and 4 parts of a 2% by mass DBS aqueous solution were added, and the mixture was stirred. When 20 parts of the stirred mixture and 80 parts of polypropylene were kneaded in a resin kneader, a solidified material was precipitated, and it was not possible to take out a composite.

[0041] Comparative Example 7 (When ethylenediamine is used as the organic alkali (1)) 100 parts by mass of powder coating 1 was taken out, and 25 parts by mass of ethylenediamine adjusted to a concentration of 4% by mass and 4 parts by mass of a DBS aqueous solution with a concentration of 2% by mass were added and stirred. When 20 parts by mass of this mixture and 80 parts by mass of polypropylene were kneaded in a resin kneader, a solidified material was precipitated and it was impossible to take out a composite.

[0042] Comparative Example 8 (When ethylenediamine is used as the organic alkali (2)) 100 parts by mass of powder coating 2 was taken out, and 25 parts by mass of ethylenediamine adjusted to a concentration of 4% by mass and 4 parts by mass of a 2% by mass DBS aqueous solution were added and stirred. When 20 parts by mass of this mixture and 80 parts by mass of polypropylene were kneaded in a resin kneader, a solidified material was precipitated and it was not possible to take out a composite.

[0043] Comparative Example 9 (When ethylenediamine is used as the organic alkali (3)) 100 parts by mass of powder coating 3 was taken out, and 25 parts by mass of ethylenediamine adjusted to a concentration of 4% by mass and 4 parts by mass of a DBS aqueous solution with a concentration of 2% by mass were added and stirred. When 20 parts by mass of this stirred product and 80 parts by mass of polypropylene were kneaded in a resin kneader, a solidified product was precipitated and it was impossible to take out a composite.

[0044] (Consideration) In the Examples, inorganic alkali was added to the powder coating, and in each case, a composite and a molded body using the same were obtained. On the other hand, Comparative Examples 1 to 3 are the results of directly compounding the powder coating and the thermoplastic resin, Comparative Examples 4 to 6 are the results of adding only water during kneading, and Comparative Examples 7 to 9 are the results of using an organic alkali, but in all cases, a composite could not be obtained after kneading, and it was made clear that the combined use of inorganic alkali is very effective for the purpose of the present invention, that is, the method of obtaining a thermoplastic resin composite containing a powder coating. [Explanation of symbols]

[0045] 10 Resin Complex 20 Paint powder 22 Pigments 24 Additives 26 Thermally Formable Resin 30 Inorganic Alkali 40 Thermoplastic resin 50 Molded body

Claims

1. A coating powder used in an electrostatic coating method or a fluidized bed coating method; Inorganic alkali, A thermoplastic resin; Including, Thermoformable, Resin complex.

2. The coating powder contains a thermal film-forming resin and a crosslinking agent. The resin composite of claim 1.

3. A resin composite according to claim 2 having a predetermined shape. structure.

4. A first step of preparing a mixture by mixing a solution of a water-soluble inorganic alkali dissolved in water with a paint powder used in an electrostatic coating method or a fluidized bed coating method; A second step of mixing the mixture with a thermoplastic resin; Including, A method for producing the resin composite according to claim 1 or 2.

5. A first step of preparing a mixture by mixing a solution of a water-soluble inorganic alkali dissolved in water with a paint powder used in an electrostatic coating method or a fluidized bed coating method; A second step of drying the mixture to produce a dry body; A third step of mixing the dried material with a thermoplastic resin; Including, A method for producing the resin composite according to claim 1 or 2.

6. producing a resin composite by the method according to claim 4; forming the resin composite produced in the above step into a structure having a predetermined shape; Including, A method for manufacturing a structure.

7. producing a resin composite by the method according to claim 5; forming the resin composite produced in the above step into a structure having a predetermined shape; Including, A method for manufacturing a structure.

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