JPS6332827B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an epoxy resin powder coating with good storage stability and curability, and a method for producing the same. Conventionally, epoxy resin powder coatings have been used from the viewpoint of saving resources and energy, and because the coatings formed from them exhibit excellent insulation and corrosion resistance.
It has been used for various purposes. Furthermore, recently, fast-curing type epoxy resin powder coatings using curing accelerators have appeared in order to improve painting workability. However, the above-mentioned fast-curing type powder coatings generally have poor storage stability in powder form and are of little practical use. In addition, there is a method of adjusting the amount of curing accelerator in order to balance fast curing and storage stability, but since the amount of curing accelerator added is originally small, it is difficult to achieve the above balance, and the quality is stable. I had a problem that didn't work. Another method has been attempted in which the active sites of the curing accelerator are chemically trapped in order to reduce the activity of the curing accelerator near room temperature. There is a tendency that the activity of the accelerator is not sufficiently regenerated, so that the desired rapid curing property cannot be obtained. As a result of intensive studies from the above viewpoint, the inventors discovered that when mixing a curing accelerator into an epoxy resin and its curing agent, they first mixed it with a resin having a higher melting point than the epoxy resin and pulverized it into an epoxy resin. He discovered that when a resin and its curing agent are melt-mixed or powder-blended (dry blended), a fast-curing powder coating with excellent storage stability and curing properties can be obtained, which led to the completion of this invention. It is something. That is, this invention consists of the following components a to c: a. A main agent made of an epoxy resin. b. A curing agent made of a compound having a phenolic hydroxyl group or an acid anhydride group. A curing accelerator made of a basic compound and the above-mentioned epoxy resin. The invention consists of a first invention relating to an epoxy resin powder coating characterized by containing a resin powder containing a resin having a higher melting point than a base resin, and a second invention relating to a method for manufacturing the powder coating. The epoxy resin powder coating of the present invention has a base resin made of epoxy resin (hereinafter referred to as epoxy resin base) and a curing accelerator mixed with the curing agent, which is coated with a resin having a higher melting point than the base resin. Therefore, it has excellent storage stability in powder form, and when melted and cured during use, the coating with the high melting point resin is released and rapid contact with the epoxy resin base and curing agent results in good curing. You can get sex. In addition, by using the above-mentioned high melting point resin, the relative amount of curing accelerator to the epoxy resin base resin and curing agent can be increased without deteriorating storage stability, and the amount of curing accelerator can be increased relative to the epoxy resin base resin and curing agent. Since the curing accelerator can be mixed in a uniform manner, this effect of increasing the amount of the curing accelerator can produce very good results in uniform dispersion of the curing accelerator, and these functions further promote the above-mentioned good curing properties. As described above, the present invention has the outstanding effect of providing a fast-curing type epoxy resin powder coating that has excellent storage stability in powder form and curability during use. As the epoxy resin base agent for component a used in this invention, any conventionally known epoxy resin can be used. On the other hand, the curing agent for component b is a compound having a phenolic hydroxyl group such as phenol resin, cresol resin, bisphenol A, modified bisphenol A, hydroquinone, or pyromellitic anhydride, benzophenonetetracarboxylic anhydride, butanetetracarboxylic anhydride. An acid, a compound having an acid anhydride group such as trimellitic anhydride, tetrahydrophthalic anhydride, and phthalic anhydride is used. This curing agent is preferably one that is solid at room temperature. The ratio of the epoxy resin base resin to the curing agent is usually 0.6 to 1.3 per equivalent of the epoxy resin.
It is preferable to set the ratio to be an equivalent, sometimes 0.7 to 1.3 equivalents. The resin powder as the component c mixed with the epoxy resin base material and the curing agent contains a curing accelerator and a resin having a higher melting point than the epoxy resin base material. A basic compound such as an imidazole compound or a tertiary amine compound is used in order to obtain a fast-curing powder coating by a combination of the following. As a resin with a higher melting point than the epoxy resin base resin,
10℃ or more than the melting point of the epoxy resin base material, preferably
Any material having a melting point higher than 15°C, usually 15 to 40°C higher may be used. The melting point range of this high melting point resin is 60 to 140°C, preferably 70 to 120°C. Typical examples that can be used as such high melting point resins include epoxy resins, ethylene-vinyl acetate copolymers, and polyester resins. The resin powder containing the hardening accelerator and high melting point resin is produced by melt-mixing both components, cooling and pulverizing, and the particle size is preferably 60 mesh passes.
It is good that it is 80 metsushiyu pass. If the particle size is too large, it is not preferable because it may cause problems in uniform dispersibility and curability with respect to the epoxy resin main ingredient and curing agent. The blending ratio of this resin powder to the epoxy resin base resin and curing agent is 50 to 92% by weight, preferably 70 to 90% by weight of the total amount of the epoxy resin base and curing agent.
In contrast, the total amount of the curing accelerator and high melting point resin in the resin powder is preferably 50 to 8% by weight, preferably 30 to 10% by weight. In addition, the amount of the curing accelerator at this time is 0.5 to 20% by weight, preferably 0.7 to 15% by weight of the total amount of this and the high melting point resin. The proportion of curing accelerator in the four components consisting of resin and curing accelerator is
The proportion is preferably 0.05 to 10% by weight, preferably 0.1 to 5% by weight. If the amount of resin powder and curing accelerator used is too little or too much, it will be difficult to achieve both storage stability and quick curing properties, and if too much resin powder is used, the original properties of the epoxy resin will be impaired. Undesirable. Next, a method for producing the epoxy resin powder coating of the present invention will be explained. There are two manufacturing methods similar to those used for general powder coatings.
One method is to prepare a resin powder containing an epoxy resin base resin and a curing agent according to a conventional method, and then powder-mix or dry blend the resin powder containing a curing accelerator and a resin with a higher melting point than the epoxy resin base resin. It's a method. This method itself is not particularly different from conventional methods, except that the curing accelerator to be Druid blended is coated with a high melting point resin. The epoxy resin powder coating of the present invention obtained by the above dry blending is made by uniformly dispersing and mixing the epoxy resin base powder and the curing accelerator powder, and the particle size of the epoxy resin base powder is , 60 as in the case of hardening accelerator powder.
The mesh pass is preferably 80 mesh passes. Another way to obtain the epoxy resin powder coating of the present invention is to blend resin powder containing a curing accelerator and a resin with a higher melting point than the epoxy resin base into the epoxy resin base and curing agent, then melt and mix, cool, and then crush. This method involves powdering. Although the melt mixing method itself is known, it is necessary to carry out the melt mixing at a temperature lower than the melting point of the high melting point resin to maintain the powder state even after melt mixing. This method can be said to be completely different from the mixed method. That is, by performing the above melt mixing at a temperature higher than the melting point of the epoxy resin main ingredient and 10°C, preferably 15°C lower than the melting point of the high melting point resin powder, the curing accelerator and epoxy resin during melt mixing are Direct contact with the base agent and curing agent is avoided, thereby making it possible to produce an epoxy resin powder coating with good storage stability and curing properties. The epoxy resin powder coating of the present invention obtained by the above-mentioned melt mixing method is such that resin powder containing a curing accelerator and a resin having a higher melting point than the above-mentioned base resin is uniformly dispersed and mixed inside the epoxy resin base and curing agent. Generally, the particles have a particle size of 40 mesh passes, preferably 60 mesh passes. Here, the curing accelerator is incorporated into the epoxy resin base system, but even in this case, direct contact between the curing accelerator and the epoxy resin base and curing agent is prevented by the high melting point resin. Therefore, as in the case of the dry blend, it also has excellent storage stability and curing properties. In addition, the epoxy resin powder coating of this invention includes:
In addition to the above-mentioned components, ie, the epoxy resin base, curing agent, curing accelerator, and resin with a higher melting point than the epoxy resin base, various known additives such as pigments and fillers may be blended as necessary. These additives may be blended into a system consisting of an epoxy resin base and a curing agent, or may be blended into a resin powder containing a curing accelerator and a high melting point resin formed by an epoxy resin base. In order to form a coating film using the epoxy resin powder coating of this invention, the powder is coated on the object to be coated by a known method, and then the epoxy resin base and the resin component with a higher melting point than the base are both melted and softened. It may be cured by heating at a temperature, generally 150 to 240°C, for 0 to 15 minutes. The formed cured coating film, which usually has a thickness of about 0.1 to 3 mm, exhibits the excellent properties inherent to epoxy resins, such as insulation, corrosion resistance, and heat resistance, due to its good curing properties. EXAMPLES Below, examples of the present invention will be described in more detail. Example 1 98.5 g of bisphenol A type epoxy resin (melting point 97°C) with an epoxy equivalent of 930 and 1.5 g of 2-undecylimidazole were melt-kneaded using a twin-screw extruder.
After cooling, it was pulverized to obtain 80 mesh passes of resin powder A. 20g of this resin powder A, 69.6g of bisphenol A type epoxy resin with an epoxy equivalent of 630 (melting point 81℃)
and 10.4 g of a novolac phenol resin having a hydroxyl equivalent of 120 g/equivalent were melt-mixed at 82° C. in a twin-screw extruder, cooled and pulverized to obtain an 80 mesh pass epoxy resin powder coating. Comparative Example 1 86.7 g of the bisphenol A type epoxy resin with an epoxy equivalent of 630 used in Example 1, 13 g of the novolac phenol resin with a hydroxyl equivalent of 120 g/equivalent used in Example 1, and 2-undecylimidazole
0.3 g was melt-mixed in a twin-screw extruder, cooled and pulverized to obtain an 80 mesh pass epoxy resin powder coating. Example 2 69.6 g of the bisphenol A type epoxy resin used in Example 1 with an epoxy equivalent of 630 and a hydroxyl equivalent of 120
g/equivalent of novolac phenolic resin (10.4 g), cooled and pulverized to obtain resin powder B of 80 mesh passes. Example 1 to 80g of this resin powder B
20 g of the resin powder A containing 2-undecylimidazole obtained in step 1 was dry blended to obtain an epoxy resin powder coating. Comparative Example 2 86.7 g of the bisphenol A type epoxy resin used in Example 1 with an epoxy equivalent of 630 and 13 g of the novolac phenol resin with a hydroxyl equivalent of 120 g/equivalent used in Example 1 were melt-mixed, cooled, and crushed. Resin powder C of 80 mesh passes was obtained. This resin powder
An epoxy resin powder coating was prepared by dry blending 99.7 g of C and 0.3 g of 2-undecyl imidazole. Example 3 0.1 mol of trimethic anhydride and isophthalic acid
90 g of a polyester resin with an acid value of 0.3 meq/g, a hydroxyl value of 1.0 meq/g, and a melting point of 100°C obtained from 0.5 mol and an excess amount of ethylene glycol;
10 g of triethylenediamine were melt-kneaded using a twin-screw extruder, cooled, and pulverized to obtain 60 mesh passes of resin powder D. 30 g of this resin powder D, the bisphenol A type epoxy resin with an epoxy equivalent of 630 used in Example 1.
64.4 g and 5.6 g of anhydrous benzophenonetetracarboxylic acid were melt-mixed at 85°C in a twin-screw extruder,
After cooling, it was crushed to obtain an epoxy resin powder coating of 60 mesh passes. Comparative Example 3 89.2 g of the bisphenol A type epoxy resin with an epoxy equivalent of 630 used in Example 1, 7.8 g of anhydrous benzophenonetetracarboxylic acid, and 3 g of triethylenediamine were melt-mixed in a twin-screw extruder, cooled, and pulverized. It was made into an epoxy resin powder coating with 60 mesh passes. Example 4 64.4 g of the bisphenol A type epoxy resin used in Example 1 with an epoxy equivalent weight of 630 and 5.6 g of anhydrous benzophenonetetracarboxylic acid were melt-mixed, cooled and pulverized to obtain resin powder E of 80 mesh pass. Ta. 70 g of this resin powder E was dry-blended with 30 g of the triethylenediamine-containing resin powder D obtained in Example 3 to obtain an epoxy resin powder coating. Comparative Example 4 89.2 g of the bisphenol A type epoxy resin with an epoxy equivalent of 630 used in Example 1 and 7.8 g of anhydrous benzophenonetetracarboxylic acid were melt-mixed, cooled and pulverized to obtain resin powder F of 80 mesh pass. Ta. 97 g of this resin powder F was mixed with 3 g of triethylene diamine at room temperature to obtain an epoxy resin powder coating. The gelation time, preservability and curing properties of each of the paints of Examples 1 to 4 and Comparative Examples 1 to 4 were examined, and the results were as shown in Table 1 below. In addition, each characteristic was measured as follows. <Gelification time> Gelation time was measured at 150°C and 200°C by the hot plate method. <Storability> After storing the paint at 30℃ for 3 months, a coating film of approximately 0.3mm thickness is formed on the object heated to 150℃.
The case where the smoothness of this coating film was good was judged as (◯), and the case where the appearance was poor was judged as (×). <Curability> When the paint is heated and applied onto the object to be coated and cured at 150°C for 30 minutes to form a coating film approximately 0.3mm thick, the coating surface is rubbed with a cloth impregnated with acetone. If no change in surface gloss is observed (〇),
A case where the gloss decreased significantly was marked as (x).

【table】

[Table] The paints of Examples 1 and 2 and Comparative Examples 1 and 2 used the same amount of 2-undecylimidazole as a curing accelerator, and the paints of Examples 3, 4 and Each of the paints of Comparative Examples 3 and 4 used the same amount of triethylenediamine as a curing accelerator. As is clear from the above results, conventional powder coatings are inferior in either curability or storage stability, and in particular, the melt mixing method in Comparative Examples 3 and 4 using triethylenediamine as a curing accelerator was adopted. In Comparative Example 3, there was almost no flowability immediately after production, and even in Comparative Example 4, which adopted the dry blending method, it was difficult to store for more than one week. In contrast, the powder coating of the present invention had good storage stability and excellent curability in all cases, and could easily achieve both storage stability and curability. . In Examples 3 and 4, when the amount of resin powder D used was reduced to 5 g and the amounts of the epoxy resin base and curing agent were increased accordingly, there was a tendency for the curability to decrease slightly. From this, it was found that reducing the amount of resin powder D too much is undesirable because it results in an absolute shortage of triethylenediamine, which is a curing accelerator.

Claims (1)

[Scope of Claims] 1 The following components a to c: a A main agent made of an epoxy resin b A curing agent made of a compound having a phenolic hydroxyl group or an acid anhydride group C A curing accelerator made of a basic compound and the above-mentioned epoxy resin An epoxy resin powder coating comprising a resin powder having a higher melting point than a base resin. 2. The epoxy resin powder coating according to claim 1, wherein the basic compound as a curing accelerator in component c comprises an imidazole compound or a tertiary amine compound. 3. Claim 1, wherein the resin having a higher melting point than the main resin consisting of an epoxy resin in component c is at least one selected from epoxy resins, ethylene-vinyl acetate copolymers or modified products thereof, and polyester resins. Or the epoxy resin powder coating described in item 2. 4. The epoxy according to any one of claims 1 to 3, wherein the resin powder containing a curing accelerator consisting of a basic compound as component c and a resin having a higher melting point than the main resin consisting of an epoxy resin has a 60 mesh pass. Resin powder paint. 5 The total amount of the main resin consisting of epoxy resin as component a and the curing agent consisting of a compound having a phenolic hydroxyl group or acid anhydride group as component b 50
Claims 1 to 4, wherein the total amount of the curing accelerator made of a basic compound in component c and the resin having a higher melting point than the main resin made of epoxy resin is 50 to 8% by weight relative to 92% by weight. The epoxy resin powder coating described in any of the above. 6. The epoxy resin powder according to claim 5, in which the curing accelerator made of a basic compound in component c accounts for 0.5 to 20% by weight of the total amount of this and the resin having a higher melting point than the main resin made of epoxy resin. paint. 7 a) A main resin consisting of an epoxy resin, b) a curing agent consisting of a compound having a phenolic hydroxyl group or an acid anhydride group, c) a curing accelerator consisting of a basic compound, and a resin having a higher melting point than the main resin consisting of the above epoxy resin. After blending resin powder containing
1. A method for producing an epoxy resin powder coating, which comprises melting and mixing at a temperature above the melting point of the main ingredient made of epoxy resin and below the melting point of the resin powder, cooling, and then pulverizing.