JPH0466264B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to spherical melamine resin particles having thermosetting properties and excellent storage stability, and a method for producing the same. (Prior art) Melamine resin is produced by heating and curing an initial condensate containing hexamethylol melamine as its main component, which is obtained by reacting melamine and aldehydes in an aqueous medium. The initial condensate as a component has extremely high reactivity, so if water is heated and distilled off to remove the initial condensate from the aqueous medium, the curing reaction proceeds and only a solid melamine resin is obtained. . Therefore, in order to obtain the initial condensate in solid form without curing it, a spray drying method is employed. However, the spray drying method is not only relatively expensive, but also the solids obtained by the spray drying method are
There were problems in that it was difficult to handle because its apparent specific gravity was small and its shape was not necessarily spherical. Furthermore, the initial condensate has a low molecular weight and a low melt viscosity, which makes it impossible to perform injection molding. For this reason, the methods for using the initial condensate are to apply the initial condensate in the form of an aqueous solution, or to impregnate the base material with an aqueous solution of the initial condensate, remove moisture, and then press-form while heating. As such, its uses were relatively limited. For this reason, there has been a desire to develop a thermosetting melamine resin that can be injection molded. In order to make injection molding possible, it is necessary to extract a melamine resin having a certain degree of high molecular weight as a solid thermosetting resin. Japanese Patent Publication No. 1983-45852 discloses a method in which guanamine, which has lower reactivity with aldehydes than melamine, is reacted with melamine in an aqueous medium in the presence of an organic polymer emulsion stabilizer. There is. According to this method, by adding a curing catalyst such as dodecylbenzenesulfonic acid during the reaction and further reacting, cured resin particles can be obtained, but if a curing catalyst is not added, a thermosetting resin cannot be obtained. I can do it. (Problems to be Solved by the Invention) However, since the thermosetting resin obtained in this way exists in the form of a semi-solid paste, it is difficult to filter and extract it, and it is difficult to extract it in solid form. When water is heated and distilled off for this purpose, the curing reaction progresses and only a cured resin is obtained. Furthermore, even if a spray drying method or a method of dehydration at room temperature and reduced pressure is adopted for the purpose of obtaining a solid resin without curing, the cost of the spray drying method is relatively high; However, these methods not only have the problem of requiring a process of pulverizing the lumps, but also the solid resins obtained by these methods fuse together and become lumps when left at room temperature. However, there was a problem of poor storage stability. The object of the present invention is to provide a solid thermosetting melamine resin free from such problems. That is, the first object of the present invention is to provide a solid particulate thermosetting melamine resin that can be injection molded and has excellent moldability and thermosetting properties, and a method for producing the same. A second object of the present invention is to provide a solid particulate thermosetting melamine resin that is easy to handle and has excellent storage stability, and a method for producing the same. A third object of the present invention is to provide a solid particulate thermosetting melamine resin that can be made into a molded article with excellent performance, and a method for producing the same. A fourth object of the present invention is to provide a method for producing thermosetting melamine resin particles that can be obtained by simply filtering solid resin particles that have a uniform particle size distribution and have good storage stability. This is what I am trying to do. (Means for Solving the Problems) In order to solve these problems, the inventors of the present invention have made extensive studies and found that when reacting melamine with aldehydes in an aqueous medium in the presence of guamines, The present invention was achieved by discovering that the desired thermosetting melamine resin in the form of solid particles can be obtained extremely easily by simply using a specific fluorocarbon salt as an emulsion stabilizer. That is, in the present invention, part or all of the surface is coated with a substantially water-insoluble fluorate salt,
Thermosetting spherical melamine resin particles characterized by having a particle size of 500 μm or less, and reacting melamine, guanamines, and aldehydes in an aqueous medium in the presence of substantially water-insoluble fluorates. Abstract: A method for producing thermosetting spherical melamine resin particles, the surface of which is partially or entirely coated with a water-insoluble fluorate salt, and whose particle size is 500 μm or less. That is. The present invention will be explained in detail below. The thermosetting melamine resin particles of the present invention (hereinafter abbreviated as the resin particles of the present invention) are particles in which part or all of the surface of the resin particles is coated with a fluoride salt that is substantially insoluble in water. It is. In the present invention, the substantially water-insoluble fluorates have a solubility in water of 0.2g/25°C.
It refers to the following fluoride salts, such as calcium fluoride, magnesium fluoride, and strontium fluoride. In order to illustrate how substantially water-insoluble fluorates cover part or all of the surface of the resin particles of the present invention, a photomicrograph of the resin particles of the present invention magnified 400 times is shown below. It is shown in Figure 1. This first
From the figure, it can be confirmed that substantially water-insoluble fluorates are deposited in the form of fine particles on the surface of the resin particles of the present invention. As will be described later, coating the surface with particles of substantially water-insoluble fluorates is effective when reacting melamine with aldehydes in the presence of guanamines in an aqueous medium. It is formed by using acid salts as emulsion stabilizers, and the coating amount is
The ratio can be controlled to a desired level by appropriately changing the amount of the substantially water-insoluble fluorates added. The resin particles of the present invention have a spherical shape with a particle size of 500 μm or less. It can be confirmed from Fig. 1 that the resin particles of the present invention have such a particle size and shape, but the micrograph (Fig. 2) magnified 100 times shows that the resin particles of the present invention have a particle size of 500 μm.
It can also be clearly confirmed that the particles are independent spherical particles and have uniform particle sizes (narrow particle size distribution). The resin particles of the present invention are independent particles because
This seems to be because, in the production method described below, the surface is coated with substantially water-insoluble fluorates to prevent particles from adhering to each other during the reaction. The resin particles of the present invention are smooth, non-fused microspherical solid particles, and have extremely good storage stability. This good storage stability is also thought to be largely due to the coating with the substantially water-insoluble fluorates. Furthermore, the resin particles of the present invention have good flow characteristics during melt molding and are excellent in moldability. Furthermore, the resin particles of the present invention have excellent thermosetting properties, a fast gel speed, can be molded in a short time, and the performance of the obtained molded product is also good. Next, a method for producing resin particles of the present invention will be explained. The production method of the present invention involves reacting melamine, guanamines, and aldehydes in an aqueous medium in the presence of a substantially water-insoluble fluoride salt. The gnanamines used in the present invention include hydrogen atom at least one of the amino groups of melamine,
Examples include aliphatic hydrocarbons having 1 to 20 carbon atoms, aromatic hydrocarbons, and compounds in which at least one hydrogen atom is substituted with an aliphatic hydrocarbon halogen atom having 1 to 20 carbon atoms. It will be done. Specific examples of such compounds include, for example,
Examples include formoguamine, acetoguanamine, and benzoguanamine. Guanamines can be used in combination of one or more types. The molar ratio of guanamine to melamine is preferably 0.1 to 20. If the molar ratio of guanamines to melamine is less than 0.1, the reaction rate is fast and the whole solidifies, making it difficult to obtain spherical resin particles. If it exceeds this, the reaction rate becomes slow and it becomes difficult to stably obtain spherical resin particles. The aldehydes used in the present invention are preferably, for example, formaldehyde or acetaldehyde, but in addition to formaldehyde in the form of formalin or paraformaldehyde, compounds that decompose to generate formaldehyde such as furfural may also be used. good. The amount of aldehydes used is 0.5 molar ratio to the total number of moles of melamine and guanamines.
-12, preferably 4-10, particularly preferably 6
~9. If the molar ratio of aldehydes to the total number of moles of melamine and guanamines is less than 0.5, the reaction will be slow, and if it exceeds 12, the reaction will be rapid, making it difficult to control the reaction. The substantially water-insoluble fluorates used in the present invention are those mentioned above, and the amount of such fluorates to be used is 0.2 to 15 % by weight, preferably 0.5-7% by weight. As a method for adding substantially water-insoluble fluorates, fine powder of substantially water-insoluble fluorates may be directly added to the aqueous medium, but a particularly effective method is to add substantially water-insoluble fluorates directly to the aqueous medium. Melamine, a compound that can produce fluorates that are generally insoluble in water by reaction,
It is added to the reaction system of guanamines and aldehydes to produce melamine, guanamines, and aldehydes at the same time. Examples of this include, for example, an aqueous solution of at least one compound selected from the group consisting of sodium fluoride, potassium fluoride, and ammonium fluoride, and chlorides, sulfates, and nitrates of calcium, magnesium, and strontium. Calcium fluoride, magnesium fluoride, An example is given of producing a finely divided solid of strontium fluoride. The aqueous medium in the production method of the present invention may be water alone or water in which a small amount of an organic solvent is dissolved or dispersed. The organic solvent may be methanol, acetone, dioxane, tetrahydrofuran, etc., which have good compatibility with water, or may be a hydrocarbon, which has poor compatibility with water. The proportion of the organic solvent is preferably 40 parts by weight or less per 100 parts by weight of water. The amount of the aqueous medium used is such that the solid content of the resulting resin is 10 to 70% by weight, preferably 20 to 60% by weight.
It is. Examples of reactions in the production method of the present invention include, for example, an aqueous solution of two or more compounds capable of producing substantially water-insoluble fluorates, melamine, guanamines, and aldehydes while vigorously stirring an aqueous medium. After adding at room temperature, 0.5
Raise the temperature to 70-90°C, preferably 75-85°C at a rate of ~1.5°C/min, preferably 0.8-1.2°C/min, and stir at this temperature for 10-60 minutes, preferably 15-40 minutes. An example can be given of the following. The contents are then cooled to below 40°C.
Since the solid melamine resin is obtained in a dispersed state in an aqueous medium, the resin particles of the present invention can be obtained by separating the solid by a method such as filtration or centrifugation, and then washing and drying. can. In the production method of the present invention, the reaction conditions for obtaining a thermosetting melamine resin largely depend on the charging ratio of melamine and guanamines. This is only an example of the conditions, and any reaction conditions can be selected for the production method of the present invention as long as the produced thermosetting melamine resin does not further react and harden. As the manufacturing method of the present invention, either a continuous method or a batch method can be adopted. The resin particles obtained by the production method of the present invention are smooth microspherical solid particles and have excellent storage stability. In addition, the thermosetting melamine resin obtained by the production method of the present invention not only has good flow characteristics when melted, moldability, and thermosetting properties, but also has a fast gelation rate, so the molding time is short. In addition, the properties of the obtained molded product are also good. The resin particles obtained by the production method of the present invention have a particle size of
It is characterized by a particle diameter of 500 μm or less, most of which is 100 μm or less, and a narrow particle size distribution. In the production method of the present invention, in reacting melamine, guanamines and aldehydes in the presence of fluorates, which are substantially insoluble in water, in an aqueous medium, thermoplastic resin, thermosetting resin, heat retardant, etc. Additives such as foaming agents, reinforcing materials, fillers, extenders, stabilizers, antistatic agents, dyes and pigments can be added. The thermoplastic resin is preferably one that is compatible with the thermosetting melamine resin of the present invention,
For example, polyethylene, polypropylene, rubber modified polysterene, AS, ABS, polyvinyl chloride,
Polyolefins such as polymethyl methacrylate and ethylene-vinyl acetate copolymer; polyesters such as polyethylene terephthalate, polybutylene terephthalate, polycarbonate, and polyarylate; polyamides such as polycaprolactam and polyhexamethylene adipamide; polysulfone; and polyphenylene sulfide. etc. Examples of thermosetting resins include phenolic resins, urea resins, furan resins, alkyd resins, unsaturated polyester resins, and the like. Examples of flame retardants include halogen compounds such as decabromodiphenyl ether, inorganic and organic phosphorus compounds, and the like. Examples of reinforcing agents, fillers, extenders, etc.
Examples include talc, glass fiber, asbestos fiber, carbon fiber, metal fiber, quartz, mica, asbestos, kaolin, aluminum oxide, silica, aluminum hydroxide, and antimony trioxide. Other additives include titanium oxide, iron oxide, aluminum powder, iron powder, metal soap, carbon black, wood powder, paper, and the like. The resin particles of the present invention and the resin particles obtained by the production method of the present invention include the above-mentioned thermoplastic resins, thermosetting resins, flame retardants, blowing agents, reinforcing materials, fillers, extenders,
Additives such as stabilizers, antistatic agents, dyes and pigments can be mixed and used. (Example) The present invention will be specifically explained below using examples. Example 1, Comparative Example 1 92 benzoguanamine was added to the three-necked flask of 1.
g, melamine 10g, 37% by weight formalin 370g
After charging 4.2 g of calcium chloride with stirring at room temperature, the mixture was heated to 75° C. over 60 minutes. During this time, the contents went from a slurry to clear.
Then, at this temperature, a 5% by weight aqueous solution of potassium fluoride
60g was added and stirring was continued. 20 minutes and 1 hour after the addition of potassium fluoride, 150 ml of the contents in an emulsion state were collected. Cool each sampled content to 30 °C and then add 0.5 ml of water,
Filter the resin part using filter paper, wash it with water and air dry it for 50~
Particulate resin was obtained by drying at 60°C for 5 hours under reduced pressure (5 mmHg or less). (Hereinafter, the resin particles after 20 minutes are referred to as resin A, and the resin particles after 5 hours are referred to as resin B.) When resins A and B were observed under a microscope, the majority of the particles were observed. It was found that the resin particles were not only spherical and had independent spherical shapes, but also that the surfaces of the resin particles were covered with granular fluorates. Further, the average particle size of each of resins A and B was approximately 50 μm. Example 2, Comparative Example 2 Add benzoguanamine 93 to a three-necked flask.
g, melamine 63 g, 37% by weight formalin 648 g
and calcium chloride 8.4g, potassium fluoride 5.8g
After adding 50 g of water at room temperature while stirring, 60 g
The mixture was heated to 75°C over several minutes. The temperature of the contents is 75℃
After reaching , stirring was continued, and 150 ml of the emulsion-state contents were collected at 25 minutes and 1 hour.
Each sampled content was treated in the same manner as in Example 1 to obtain resin particles. (Hereinafter, the resin particles after 25 minutes are referred to as resin C, and the resin particles after 1 hour are referred to as resin D.) When resins C and D were observed under a microscope, most of the particles were independent of each other. It was found that the surface of the resin particles was not only spherical but also covered with granular fluorates. In addition, the average particle diameters of resins C and D are each approximately
It was 30μm. Example 3, Comparative Example 3 23 benzoguanamine was added to the three-necked flask of 1.
g, melamine 63g, 37% by weight formalin 404g
After charging 4.2 g of calcium chloride with stirring at room temperature, heating and stirring were continued to 75° C. over 60 minutes. During this time, the contents went from a slurry to clear. Then, a solution of 2.9 g of potassium fluoride dissolved in 20 g of water was added. After addition of potassium fluoride, stirring was continued at 75°C, and 150 ml of the emulsion was collected at 30 minutes and 1.5 hours. Each sampled content was treated in the same manner as in Example 1 to obtain resin particles. (Hereafter, the resin particles after 30 minutes are referred to as resin E,
The resin particles after 1.5 hours are referred to as resin F. ) When resins E and F were observed under a microscope, it was found that not only were most of the particles spherical and independent from each other, but the surfaces of the resin particles were covered with granular fluorates. I found out something. Further, the average particle size of each of resins E and F was approximately 40 μm. Comparative Examples 4 and 5 92 benzoguanamine in the three-necked flask of 1
g, melamine 10g, 37% by weight formalin 370g
Then, 2.0 g of gum arabic and 40 g of water were charged at room temperature with stirring, and the mixture was heated to 75° C. over 60 minutes. After the temperature of the contents reached 75° C., stirring was continued at this temperature, and 50 ml of the contents in an emulsion state were collected at 20 minutes and 1 hour. After cooling the contents collected at 20 minutes and 1 hour to 30℃, 0.5% water was added, and when trying to filter the resin part using filter paper, the contents collected at 20 minutes were clogged. could not be filtered out. On the other hand, the resin portion could be filtered out from the emulsion after 1 hour using filter paper. These resin particles are called resin G. ) When resin G was enlarged and observed under a microscope, we found that
Most of the particles were fused together. Comparative Example 6 A resin was produced according to the method described in JP-A-50-45852. That is, 150 g of benzoguanamine, 130 g of 37% by weight formalin, and 10% by weight aqueous sodium carbonate solution were placed in a three-necked flask.
0.52g was charged and the pH was adjusted to 8.0. This mixture was heated to 95° C. with stirring, and stirring was continued at this temperature to obtain a soluble fusible resin with a methanol soaking degree of 60% after 5 hours. Separately, polyvinyl alcohol [Kuraray Poval]
205, manufactured by Kuraray Co., Ltd.] was dissolved in 750 parts by weight of water, this aqueous solution was heated to 95°C, and stirred at this temperature for 1 hour at 7000 rpm using a homomixer. When the above reactants were added to this liquid and stirred for 2 hours, a white emulsion was obtained. When an attempt was made to filter the resin portion from this emulsion using filter paper, it became clogged and could not be filtered out. Regarding resins A to G obtained in Examples 1 to 3, Comparative Examples 1 to 3, and Comparative Example 5, immediately after production and at 30 ° C.
JISK - gelation time and flow characteristics on a hot plate at 150℃ after being left in an 85%RH atmosphere for 3 months
6911, and the angle of repose of the solid resin particles and the state of the solid resin particles were visually observed. For comparison, the same items as possible were also measured for a commercially available solid melamine resin [manufactured by Nippon Carbide Co., Ltd., Nikaresin S-260] (hereinafter, these resin particles are referred to as resin H).These results are shown in Table 1.

[Table] From Table 1, it can be seen that the resin particles of the present invention have thermosetting properties and are excellent in flow characteristics when melted. Furthermore, it can be seen that the resin particles of the present invention have better storage stability and fluidity in a solid state than commercially available melamine resins. Further, from Comparative Examples 1 to 3 and Comparative Example 5, it can be seen that when the manufacturing conditions of the manufacturing method of the present invention are made severe, the resin particles become hardened. Commercially available melamine resins have a somewhat irregular shape, but not only are they very hygroscopic, so when stored in a solid state,
It turns out that there is a problem that requires water blocking. (Effects of the Invention) The resin particles of the present invention enable injection molding of melamine resin, which has been difficult in the past, and have excellent moldability because the resin has good flow characteristics when melted. It has the characteristics required when injection molding thermosetting resins, such as the fact that it can be molded in a short cycle due to its short gelation time. In addition, the resin particles of the present invention do not fuse even if left in a humid atmosphere for a long period of time, so they not only have extremely excellent storage stability, but also have excellent fluidity as a solid particle. Easy to handle in solid state. Furthermore, the resin particles of the present invention are not only fine-grained but also have a uniform particle size, so they are suitable for sintering. The resin particles of the present invention can be used not only in the field of injection molding by taking advantage of the above-mentioned features, but also in fields where melamine-based resins have been conventionally used, such as laminates and binders. Further, the resin particles of the present invention can be used not only in solid form but also as an adhesive or the like in the form of an aqueous emulsion. The production method of the present invention is an extremely excellent production method that allows thermosetting melamine resin particles having the above-mentioned excellent features to be easily obtained.

[Brief explanation of the drawing]

1 and 2 are micrographs showing an example of the particle structure of the thermosetting melamine resin particles of the present invention. The magnification of FIG. 1 is 400 times, and the magnification of FIG. 2 is 100 times.

Claims (1)

[Claims] 1 Part or all of the surface is coated with substantially water-insoluble fluorates, and the particle size is 500 μm.
Thermosetting spherical melamine-based resin particles characterized by having a particle size of m or less. 2. Hydrofluoric acid whose surface is partially or entirely insoluble, characterized by reacting melamine, guanamines and aldehydes in an aqueous medium in the presence of a substantially water-insoluble fluoric acid salt. A method for producing thermosetting spherical melamine resin particles coated with salts and having a particle size of 500 μm or less.