JPS5923581B2 - Method for producing epoxy resin powder coating composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an epoxy resin-based powder coating composition having good performance, and more particularly to an improved production method based on a dry bread method. .

In recent years, the development of solvent-free paints has been actively promoted from the viewpoint of resource saving and pollution-free production, but powder paints that do not contain any organic solvents are the most representative of these. Paints are also becoming more and more popular.

Despite this, one of the reasons why its usage has not increased is probably due to the price.

In other words, powder coatings are much more expensive than conventional solvent-based coatings, but this is due to the difficulty in obtaining suitable raw materials, especially hardeners, as well as solvent-based coatings. This is because the manufacturing cost is inevitably higher than that of mold paint. Manufacturing methods for such powder coatings can be roughly divided into two types: dry manufacturing methods and wet manufacturing methods.

The former includes the so-called melt-blending method, which goes through a melt-kneading process, and the so-called dry bread method, which involves pre-blending raw materials, pulverizing them, and then classifying them in powder form or using them as they are without classifying them. On the other hand, in the latter case, the so-called chemical pulverization method is considered to be the mainstream, but it has not been put into practical use so far.

By the way, when using the dry bread method, compared to the case using the melt blend method, one process of melting and kneading can be omitted, so the manufacturing process can be shortened, but it is possible to shorten the manufacturing process by using the resin, curing agent, and even pigments. At present, this dry blend method is hardly used as a manufacturing method for thermosetting powder coatings because it is impossible to achieve uniform mixing of the powders, and the resulting coating film is generally lackluster and has poor physical properties. Almost all thermosetting powder coatings on the market today are based on the melt-blending process.

The present inventors sought to solve the problem of relatively high manufacturing costs, which is a fatal flaw of the conventional melt blending method, by using a type of dry blending method, and also achieved uniform mixing, which could not be achieved with the conventional dry blending method. The present invention was achieved by discovering an improved method for producing an epoxy resin powder coating composition that can solve the problems of improving physical properties. An object of the present invention is to provide an improved method for producing a powder coating composition that is comparable in performance to the melt-blending method.

The method of the present invention involves separately pulverizing the solid epoxy resin (4) and the solid curing agent (B), and then pulverizing each fine powder in the presence of a filler and finely divided silica as an additive. , in a predetermined ratio, and then thoroughly mixed to obtain a powder coating composition.

Solid epoxy resin (4
) and hardening skewers, both need to be pulverizable, and therefore those with too low melting points are not suitable for the method of the present invention.

Therefore, it is recommended that both the solid epoxy resin (4) and the solid curing agent (B), which are advantageously used in the method of the present invention, have a melting point of at least about 70° C. according to the "ring and ball method" described below.

Here, the "ring and ball method" (melting point measurement method) based on ASTM-36 will be explained.

The measurement is carried out using an automatic softening point measuring device as shown in Fig. 1. First, the sample to be measured is finely ground in a mortar, approximately 50 tons is weighed into a 100 CC beaker, and a heating device (dryer) is used to measure the softening point. ), while avoiding partial overheating, melt the sample at a temperature as low as possible without heating it more than 55°C above the estimated melting point, and without leaving any air bubbles in the sample. Next, the ring 1, which has been heated in advance to approximately the same temperature as the sample, is placed on a flat metal plate, and the bubble-free portion of the sample is immediately poured into the ring 1, with a slight excess. The total sample heating time up to the time of sample injection into this ring must be kept as short as possible, and care must be taken not to require too much time. This sample was then heated at room temperature for 30 to 4
After cooling for 0 minutes, the excess sample on the top surface of the ring 1 is removed along the upper edge of the ring (this step is the preparatory stage, which can also be called a pre-processing).

Now, place this ring 1 on the ring stand 2, and then place the ring 1 on the ring 1 with a diameter of 9.
A copper ball 3 having a length of 53m7ft and a weight of 3.5±0.05t is placed and placed in a 600CC glycerin bath 4.
Soak inside.

After this, the temperature of the glycerin bath 4 is immediately increased at a rate of 5°C/- (at this time, a stirrer 5 is inserted to raise the bath temperature uniformly), and as shown in FIG. The temperature is read when the sample in the bath begins to soften and hangs down to a specified distance.Usually, the temperature is measured by softening the light beam from the light source 6 placed on the side of the bath 4 (at the specified distance above). A melting point indicating thermometer is used that automatically stops displaying the temperature at that time when the dropping sample just intercepts it.

In addition, in the case of a sample with a melting point of 70°C or less, a normal thermometer may be installed in the center of the ring stand 2 instead of the automatic melting point indicating thermometer and the same method as above may be used. Yes, but in this case the person taking the measurement will have to read the scale of the thermometer.

The above is an overview of the melting point measurement method for measuring the melting points of solid epoxy resin (4) and curing agent (B), respectively, used in the method of the present invention. Regarding this melting point, if an epoxy resin with a melting point that is too high (generally 120°C or higher) is used in the melt blend method, uniform dispersion will not be completely achieved under normal kneading conditions during the heating process with hardeners and pigments. If this is not done and the kneading temperature is increased or the kneading time is lengthened, the reaction will proceed too much even with a latent curing agent and the performance as a powder coating will deteriorate.

On the other hand, according to the method of the present invention, even if the epoxy resin has a high melting point or a high molecular weight, there is no problem as long as it can be pulverized, as described above, and in fact, it is advantageous in terms of improving coating film performance. This is often the case.

Thus, the solid epoxy resin (A) suitable for the method of the present invention includes bisphenol A1 bisphenol F
Or diglycidyl ethers such as tetrabromo bisphenol A, polyglycidyl ethers of phenol or cresol novolak, and modified epoxy resins thereof, polyglycidyl ethers of polyhydric alcohols, polyglycidyl esters of polybasic acids, and modified epoxies thereof. Examples include commonly used epoxy resins known as resins.

On the other hand, the curing agent (B) suitable for the method of the present invention includes:
The curing agent is selected from known and commonly used curing agents such as amines, adducts, polyamides, polyamide adducts, acid group-containing polyesters, polyvalent carboxylic acid anhydrides and modified products thereof, and modified dicyandiamides.

In particular, among these curing agents, in order to further improve the uniform dispersibility with the epoxy resin (Al) to be combined, the specific gravity of this curing agent (B) is higher than that of the epoxy resin (A).
The specific gravity is as close as possible to that of the epoxy resin (
It is recommended that the volume mixing ratio with A) be close to 1:1.

Usually, a ratio of at least 20 parts by weight of the curing agent (I) to 100 parts by weight of the epoxy resin (A) is preferred.

Furthermore, in the method of the present invention, there is no heating process involved at all before obtaining the final composition, and moreover, the epoxy resin (A) and the curing agent (B) are always physically in contact with each other in a solid phase. Therefore, low-temperature-reactive or fast-curing curing agents that cannot be used in the melt-blending method can also be advantageously used, and as a result, it is possible to produce low-temperature, fast-curing powder coatings that cannot be obtained using the melt-blending method. It becomes possible.

It goes without saying that in this way, the storage stability of the final composition will also be improved.

Furthermore, as the filler additive, in addition to finely powdered silica, solid bituminous fine powder such as tarpitz can also be used, thereby making it possible to form a tar-epoxy powder coating.

In addition, the surface condition of the paint film, such as orange beer,
Flow control agents may be added, if necessary, to improve leveling and the like. However, such small amounts of additives must be added to the epoxy resin (4) or curing agent (g) in advance.

The features of the method of the present invention can be summarized as follows.

1. The epoxy resin (A) and curing agent (g) are separately finely ground, and then both components are blended at once, with or without a classification operation, and mixed well to produce the desired product. Since it is based on the composition and the method used, the uniform dispersion of the components will not be disrupted by externally applied energy (for example, crushing, classification, etc.) during the manufacturing process.

2. The amount of curing agent (D) relative to the epoxy resin (A) is
By using a certain amount or more, that is, 20 parts by weight or more of (g) per 100 parts by weight of (), epoxy resin (A)
It is possible to advantageously achieve uniform dispersion of 1 J (days) of curing time.

3 In response to the realization of uniform dispersion based on 1 and 2 above,
Although the epoxy resin (4) and the curing agent (B) are physically in contact with each other in a solid phase, the above (5) during baking,
(B) The reaction between the two parties should be carried out smoothly.

Thus, the composition obtained by the method of the present invention maintains the above-mentioned features of the method of the present invention, exhibits excellent performance as a coating material, and has superior performance as a coating material compared to the conventional melt blend method as described above. It has a low manufacturing cost and is advantageous in terms of price, and can be used for a wide range of coating materials such as low-temperature, fast-curing powder coatings and tar/epoxy powder coatings.

Next, the present invention will be specifically explained using examples. Hereinafter, all parts and percentages are based on weight unless otherwise specified. Example 1 "Modaflo 1" (trade name of flow control agent manufactured by Monsanto Company in the United States; "Modaflo 1" is a registered trademark of the company) 0.2%
"Epicron 4050" (trade name of bisphenol A type epoxy resin manufactured by Dainippon Ink and Chemicals Co., Ltd.);
Epoxy equivalent -900~1000; Melting point -96~104
℃; "Epiclon" is a trademark of the company) and diaminodiphenylmethane adduct as a curing agent Diaminodiphenylmethane adduct (active hydrogen equivalent -430
; melting point = 110°C) was used.

] separately from Pindisk Mill (ALPIN, West Germany)
(product of Company E) to obtain a fine powder of 200 mesh.

Next, 100 parts of the fine powder of "Epicron 4050" obtained in this way, 45 parts of fine powder of diaminodiphenylmethane adduct, and further fine powder of silica "Crystallite AA" were added.
(Product of Ryumori Co., Ltd.) and 80 parts of the powder coating were thoroughly mixed in a V-type mixer (Product of Tokuju Kosho Co., Ltd.) to obtain the intended powder coating composition.

For performance testing, this composition was preheated to 230°C on a tagtar cast iron pipe (a tagtar cast iron pipe with an inorganic film mainly composed of iron silicate and iron oxide formed on the surface of the iron pipe through heat treatment). The removed cast iron pipe (hereinafter referred to as a test piece) was electrostatically coated on the inner and outer surfaces to obtain a coating film with a thickness of 300 μm on the inner surface and 100 μm on the outer surface.

Example 2 Example 1 except that 40 parts of metaxylene diamine adduct of "Epicron 2050" was used as the curing agent, and 75 parts of "Crystallite AA" was used.
The same operation as above was repeated to obtain a powder coating composition.

A coating film with a thickness of 300 μm on the inner surface and 100 μm on the outer surface was obtained using this composition in the same manner as in Example 1.

Example 3 4 moles of trimellitic anhydride was used as the acid component,
"Epicron 850" (bisphenol A type liquid epoxy resin manufactured by Dainippon Ink and Chemicals Co., Ltd.; epoxy equivalent =
184-194) 1 mol and “Newcol BA-P
Acid group-containing polyester (acid value =
130K0H instant/f; melting point = 85°C) was used as a curing agent component, and [Epicron 4050] was used as an epoxy resin component, and 100 parts of [Epicron 4050] fine powder obtained by finely pulverizing each in the same manner as in Example 1. 40 parts of acid group-containing polyester fine powder and 75 parts of fine silica powder
The following procedure was carried out in the same manner as in Example 1 to obtain a powder coating composition.

In addition, in order to obtain performance test pieces of this composition, 20
After electrostatically painting the inner and outer surfaces of the test piece preheated to 0℃,
Bake at 200℃ for 20 minutes to obtain a film thickness of 300μ on the inner surface.
A coating film of 100 μm on the outer surface was obtained.

Example 4 In this example, fine powder of "Epicron 4050" obtained in Example 1 was used as the epoxy resin, and on the other hand,
As a curing agent, acid group-containing oil-free polyester "Schiyadonal S-2065" (product of Schiadonal, Netherlands; acid group content = 1.37 meq/7, melting point = 120°C) was ground in a pin disc mill. The obtained 200 mesh fine powder was used, and 100 parts of the fine powder of "Skyadnar S-2065" was mixed with 108 parts of fine powder of silica, and 100 parts of the fine powder of "Epicron 4050" obtained in Example 1 was added. A composition for powder coating was obtained by mixing well in a V-type mixer.

For this composition, test pieces were prepared in the same manner as in Example 3.

Example 5 Bisphenol A type epoxy resin "Epicron 1050" (product of Dainippon Ink & Chemicals Co., Ltd.) was added to polyamide whose main components were triethylenetetramine and dimer acid;
Epoxy equivalent = 450-5001 melting point 64-74℃) The amine value obtained by reacting is 180 and the melting point is 85℃.
A polyamide adduct having the following properties was used as a curing agent, which was first ground in a pin disc mill to form a fine powder of 200 meshes.

Next, 2 parts of this polyamide adduct fine powder was added to 100 parts of the fine powder of "Epicron 4050" obtained in Example 1.
5 parts and 68 parts of finely divided silica were mixed well in a V-type mixer to obtain a powder coating composition.

In order to obtain a test piece from this composition, a coating film having a thickness of 300 μm on the inner surface and 100 μm on the outer surface was obtained by the same procedure as in Example 1.

Example 6 Dimer acid-modified epoxy resin containing 0.2% of "Modaflo" (this modified resin contains 10% of "Epicron 2050")
The epoxy equivalent obtained by heating and reacting 0 part with 15 parts of dimer acid has an epoxy equivalent of 1100 and a melting point of 90°C.

) was ground in a pin disk mill to form a fine powder of 200 mesh, and then 40 parts of the diaminodiphenylmethane adduct obtained in Example 1 and 75 parts of finely powdered silica were blended with 100 parts of this fine powder, This was thoroughly mixed using a V-type mixer to obtain a powder coating composition. This composition was prepared in the same manner as in Example 1, with a film thickness of 300 μm on the inner surface and 1 μm on the outer surface.
A coating film of 00μ was obtained. Example 7 100 parts of the "Epicron 4050" fine powder obtained in Example 1, 45 parts of the diaminodiphenylmethane adduct fine powder, and 100 parts of finely divided silica, respectively, and hard pitch fine powder ground into 200 meshes. (melting point 100°C) is blended,
The mixture was thoroughly mixed using a V-type mixer to obtain a tar epoxy powder coating composition.

In order to obtain a performance test piece from this composition, a coating film having a thickness of 300 μm on the inner surface and 100 μm on the outer surface was obtained using the same procedure as in Example 1.

Comparative Example 1 (Example using melt blend method) 66.2 parts of "Epicron 4050", "Epicron 4050"
3.3 parts of ``B-610'' (modified dicyandiamide manufactured by Dainippon Ink and Chemicals Co., Ltd.), 30 parts of fine powder silica, and 0.3 parts of ``Modaflo'' were added to ``Bus Konida PR-46''.
'' (manufactured by Busu, Switzerland), the mixture was heated and kneaded, pulverized, and then classified to obtain 200 mesh powder coating compositions.

In order to obtain a performance test piece of this composition, the same operation as in Example 3 was carried out to obtain a coating film with a thickness of 300 μm on the inner surface and 100 μm on the outer surface.

Comparative Example 2 (Example using melt blend method) 50 parts of "Epicron 4050", "Scadonal"
The same operation as in Comparative Example 1 was repeated using 50 parts of [S-2065], 50 parts of finely powdered silica, and 0.4 parts of [Modaflo] to obtain 200 meshes of a powder coating composition.

Note that a test piece was prepared using this composition in the same manner as in Example 3.

Comparative example 3 (by dry blending method) “Epicron 4050” containing 0.2% “ModaFloichi”
100 parts of 200 mesh fine powder and "Epicron B-
610'' (200 mesh fine powder) 5 parts and 4 parts fine silica
5 parts were thoroughly mixed in a V-type mixer.

The same operations as in Example 3 were repeated for this fine powder to obtain a coating film with a thickness of 300 μm on the inner surface and 100 μm on the outer surface.

Comparative Example 4 (Dry blend method) In this example, the mixing ratios of the epoxy resin, curing agent, and finely divided silica were the same as in Example 4, except that the order of mixing these components was as follows. This has been changed.

That is, first, "Epicron 4050" and "Schiadonal S-2065" were separately coarsely pulverized (coarsely pulverized product) and finely powdered silica were mixed into Penshell
The mixture was premixed using a Taibe high-speed stirring mixer, then finely pulverized using a pin disc mill, and then classified to obtain a powder coating composition that passed 200 meshes. In the end, all the components of the composition separated.

Note that a test piece of this composition was also prepared in the same manner as in Example 3.

Table 1 summarizes the results of a performance test performed on each test piece obtained in each Example and each Comparative Example.

As is clear from Table 1, the powder coating composition obtained by the method of the present invention has the same effect as that obtained by the melt blend method, and is even more effective than the powder coating composition obtained by the method of the present invention. The difference is so marked that it cannot be compared with that obtained by blending.

[Brief explanation of drawings]

Figures 1 and 2 are longitudinal cross-sectional views showing an apparatus used for melting point measurement called the [ring and ball method], in which Figure 1 shows the state immediately before the start of measurement, and Figure 2 shows the state at the time of measurement. This shows that. In each figure, 1...ring, 2... ring stand, 3...
...Ball, 4...Glycerin bath, 5...
... Stirrer, 6... Light source.

Claims (1)

[Scope of Claims] 1 (a) Each is solid at room temperature, and has a melting point of at least about 70°C according to the "ring and ball method" detailed in the text. (A) The epoxy resin and (B) the curing agent are each pulverized separately, and if necessary, the
The process of classifying into the 0 mesh range, and then (
b) An epoxy resin system comprising the step of blending at least 20 parts by weight of the above (B) to 100 parts by weight of the above (A) in the presence of an extender pigment such as finely divided silica, and then mixing. A method for producing a composition for powder coating.