WO2001024943A1

WO2001024943A1 - Method for applying thermosetting fluororesin powder coating

Info

Publication number: WO2001024943A1
Application number: PCT/JP1999/005487
Authority: WO
Inventors: Keisuke Tano; Ryuji Iwakiri; Ryoichi Fukagawa; Daisuke Tanizawa; Nobuhiko Tsuda
Original assignee: Daikin Industries, Ltd.
Priority date: 1999-10-05
Filing date: 1999-10-05
Publication date: 2001-04-12
Also published as: AU6003599A

Abstract

A method for applying a thermosetting fluororesin powder coating for electrostatic coating which comprises using a recycled powder coating (C) prepared by blending a fresh thermosetting fluororesin powder coating (A) having an average particle diameter of 20 to 50 νm and a particle size distribution of 1 to 4 with a recovered powder coating (B) obtained by recovering the powder coating which has not been adhered upon electrostatic application of the fresh powder coating (A) as an over-sprayed coating. This method of coating utilizes only one type of fresh powder coating and typically uses the recovered powder coating without subjecting it to a special treatment or modification, which lead to easy blending and re-application in the field, and thus results in significant, practical and economical advantages.

Description

Akira Itoda Thermosetting type fluororesin powder coating method

Technical field

The present invention relates to a coating method for recovering and reusing thermosetting fluororesin powder coatings. Background technology

Compared with general solvent-type paints, powder paints have no emission of volatile solvents, are pollution-free, and are easy to manage. In recent years, it has been widely used in metal painting in general in recent years because of its many advantages.

At this time, when painting by the charging method such as the corona method or the friction banding method, the paint is not applied as an overspray. Unused powder coatings are produced. Such unused powder coatings may be collected, blended with the Virgin powder coatings and reused for painting. In addition, the recovery and reuse method (for example, Japanese Patent Application Laid-Open No. 11-1696919) used in the conventional powder coating of general-purpose resin is a thermosetting type. When applied to fluororesin powder coatings, it has the unique properties of fluororesin, such as extremely high chargeability, high specific gravity, and volume-specific resistance. Due to its large properties (approximately 100 to 100 times that of general-purpose resins), the effects achieved with general-purpose resin powder coatings (such as the appearance of the coating film and the efficiency of coating) are low. Etc.) could not be obtained.

Disclosure of the invention That is, the present invention provides a thermosetting fluororesin powder coating for electrostatic coating, which has an average particle diameter of 20 to 50 m and a particle size distribution of 1 to 4 m. Thermosetting fluororesin resin powder coating

(A) and the thermosetting fluororesin resin powder coating (A) were not applied as an overspray when electrostatically applied. Thermosetting fluorine resin powder using recycled powder paint (C) blended with recovered powder paint (B) obtained by collecting powder paint Regarding how to apply paint.

In addition, the particle diameter contained in the virgin powder coating (A) is 7%.

Preferably, the amount of particles above 5 x m is below 20% by weight.

In addition, it is preferable that the collected powder paint (B) is neutralized before blending with the version powder paint (A). It is preferred that the temperature of the paint (B) be maintained at a temperature of 35 or less until the paint is blended with the version powder paint (A).

Preferably, the content of the nodine powder paint (A) in the reclaimed powder paint (C) obtained by blending is at least 35% by weight. Preferably, the average particle size of the regenerated powder coating (C) is 15 to 55 xm and the particle size distribution is 1 to 5.

Further, the present invention relates to a thermosetting fluororesin resin powder having a mean particle size of 20 to 50 m and a particle size distribution of 1 to 4 (A) and the heat-curable fluororesin resin powder (A). Curable fluororesin version Powder coating

Collected powder coating obtained by collecting powder coating that was not applied as an overspray when (A) was electrostatically coated

(B) a thermosetting fluorine resin powder paint, wherein the content of the zonal powder paint (A) is 35% by weight or more. Related to the composition. According to the reclaimed powder paint (C) of the present invention, the reclaimed powder paint (B) and the powdered version paint (A) are collected twice. The coating efficiency of the raw powder coating (C) can be increased to 40% or more, and even to 50% or more. Best form for carrying out the invention The coating method of the present invention is to adjust the average particle diameter and particle size distribution of the preliminary powder coating (A) in advance. As a result, the recovered powder coating (B) is simply blended with the specific version of the powder coating (A), and the regenerated powder coating (C) is merely blended. ) Can be used repeatedly. In other words, do not adjust after collection or after blending, but adjust before painting, so-called feed-through It is de control. According to the method of the present invention, only one type of powder paint is used as the version powder paint, and as a general rule, the powder powder paint is specially applied to the recovered powder paint. Processing and power!].

First, the Virgin Powder Coating (A) will be described. The average particle diameter of the virgin powder coating material (A) is 20 to 50 im, preferably 30 to 40 m. If it is less than 20 zm, the fluidity of the powder coating material will be reduced, and the electrostatic repulsion will be too large, and the average particle of the regenerated powder coating material (C) will be too high. It works in the direction of decreasing the diameter, and the coating efficiency when applying the reclaimed powder coating (C) decreases. As described above, fluororesin has a high chargeability, and particularly remarkable electrostatic repulsion is caused by particles having a small particle size, so that the coating efficiency is improved. It is necessary to reduce the proportion of small-sized particles from the point of raising. On the other hand, if it exceeds 50 / m, the appearance (smoothness, etc.) of the coating film obtained will be reduced, and the average particle size of the regenerated powder coating material (C) will be reduced. big It works in the opposite direction, and reduces the coating efficiency when applying the reclaimed powder coating (C). In addition, if a large number of particles having a relatively large particle size of 75 or more are present, the appearance of the coating film is remarkably reduced, so that the relatively large particle size (75 m or more) is used. ) Is preferably suppressed to 20% by weight or less.

The particle size distribution of the virgin powder coating (A) is expressed as a ratio of volume average particle diameter / number average particle diameter, and is 1 to 4, preferably 1 to 3, and more preferably. 1 to 2, particularly preferably 1 to 1.5. If the particle size distribution is too large, the coating efficiency of the reclaimed powder coating (C) will decrease, making it difficult to reuse and reuse it, and the appearance of the coating will also decrease. .

The recovered powder coating (B) in the present invention is defined as an overspray when the Nitrogen powder coating (A) or the reclaimed powder coating (C) is electrostatically applied. Unused powder coating material that does not adhere to the object to be coated due to its use, such as laying, and is not used for painting, or its properties have changed during storage within a range that does not hinder reuse. Say. Unused powder paint can be collected in a usual manner, for example, in addition to a collection device consisting of a cyclone and a NOGFIEL®, as well as known collection devices. It should be done by

The powder coating (B) thus recovered is blended with the virgin powder coating (A) and becomes a recycled powder coating (C). The blended virgin powder coating (A) is the same as the powder coating (A) described above.

The blend of the recovered powder coating (B) and the virgin powder coating (A) was 35% by weight of the nitrogen powder coating (A) in the regenerated powder coating (C). As described above, the content is preferably 70 to 98% by weight. When the blend amount of the recovered powder coating (B) is increased, the coating rate and It causes the deterioration of the coating film appearance. When the recovered powder paint (B) from the regenerated powder paint (C) is used, the content of the nitrogen powder paint (A) is increased at a high ratio. It is preferable to keep them constant or to increase them sequentially. For example, when using the recovered powder coating (B) after the second recovery, the content of the version powdered coating (A) should be 45% by weight or more. This is preferable because it increases the number of times of repeated use.

Since the recovered powder paint (B) is charged by electrostatic coating, it is necessary to remove static electricity before blending with the version powder paint (A). Is preferred. There are two ways to remove static electricity: a method of giving the opposite charge and a method of leaving it undisturbed. However, the method is not limited to these.

Also, the recovered powder coating (B) may require a certain period of time before it is blended. In this case, it is necessary to keep the recovered powder coating (B) below 35 until the blending is completed. The blocking of the thermosetting fluororesin powder coating is required. It is desirable from the point of prevention. These temperature control conditions are the same for the reclaimed powder coating (C) and the virgin powder coating. The regenerated powder coating (C) prepared in this manner has an average particle size of 15 to 55 ^ m, preferably 20 to 50 xm, and a particle size distribution. Is 1 to 5, preferably 1 to 4.

The coating conditions for the regenerated powder coating (C) are the same as those used for conventional electrostatic coating.

The thermosetting fluorine resin powder paint used in the present invention is basically a thermosetting fluorine resin powder and a curing agent, and if necessary, a pigment and various additives. It is an ordinary thermosetting fluorine resin powder coating.

Thermosetting fluororesin as a resin component There is no particular restriction as long as the polymer has an essential monomer component and a bridging reactive group as essential components.

Examples of the fluorine-containing monomer include tetrafluoroethylen, black mouth trifluorene, trifluorene, and trifluorene. Len, vinylidene fluoride, hexafluoropropylen, pentafluorene mouth propylene, perfluorovinyl One or more species, such as ethers and monofluoroethylen, are given. If necessary, it may be a non-fluorinated monomer-copolymerized product.

Examples of the bridging reactive group include, for example, a hydroxyl group, a carboxyl group, an amino group, an amido group, an epoxy group, and an isocyanate. In addition to bases, halogen atoms such as bromine and iodine are exposed.

In addition to the above-mentioned thermosetting fluororesin as a powder resin component, if necessary, the above-mentioned general-purpose thermosetting resin of non-fluorocarbon type, for example, epoxy resin , Acrylic resin, polyester resin, etc. may be blended.

As the curing agent, those which are conventionally used in thermosetting powder coatings can be used. For example, the blocking agent can be used. Compounds, acid anhydrides, polyamin compounds, dalycidyl compounds, isocyanurate compounds, polybasic acids, and the like can be used.

Examples of pigments include condensed azo compounds, isoindolinone, quinacridone, diketopyrochloride, pyrrole, and intraquinone. Organic pigments such as xanthane; titanium oxide, iron oxide, carbon black, carbon black, lead chromate, white lead, and molybdenum Inorganic oxide pigments such as orange; metal powders such as aluminum powder and stainless steel powder are produced. In addition, various additives commonly used in powder coatings, such as fillers, UV absorbers, leveling agents, and flow regulation Agents, antioxidants, thermal degradation inhibitors, glazing modifiers, charge control agents, etc., may be combined as appropriate.

As a thermosetting type fluororesin powder coating material whose properties can be maintained particularly favorably by the storage method of the present invention, for example, Japanese Patent Publication No. Relatively low glass described in the No. 2 publication, Japanese Patent Laid-Open No. 5-331338, the Japanese patent No. 28782726, etc. Powder coatings using thermosetting fluororesin with a transition temperature are required.

Next, the present invention will be described with reference to an embodiment, but the present invention is not limited to such an embodiment.

Example 1

(Preparation of thermosetting fluororesin resin-based powder coating (A)) Black mouth Trifluorofluoroethylene Xylyl vinyl ether Z Isobutyl vinyl ether hydroxyl hydroxy vinyl ether (weight ratio: approx. 50 Z 16 Z 9/25) Acid value: 120 mg KOH / g, glass transfer temperature: 45, heat loss: less than 2% by weight, measured in tetrahydrofuran at 30 The determined solid viscosity [η]: 0.21) was pulverized with an impact hammer mill to produce a thermosetting fluorine resin powder. This fluororesin powder 44 parts by weight, a filler (titanium dioxide) 30 parts by weight, and a curing agent (Hads' adduct B—153) 0) The 26 parts by weight were uniformly mixed for about 1 minute with a dry blender (Henshierire 3 Mixer manufactured by Mitsui Chemicals, Ltd.). Melting and kneading by an extrusion kneader (Bus Conider PR_46 made by Buss) at a temperature of 80 to; L00, and after cooling, a universal pulverizer (IKA Manufactured by Pulverize at room temperature for 5 minutes, remove the coarse powder with a 200 mesh wire mesh, and use the thermosetting fluororesin resin bar used in the examples. Powder paint (A) was prepared.

The obtained version powder coating (A) is applied to the Nikkaki Co., Ltd. call using a multi-sided caller by a caller-counter method. According to the measurement, the average particle size was 35 m, the particle size distribution was 2.3, and the content of particles having a particle size of 75 m or more was 9 wt%. there were .

(Collection of electrostatic coating and powder coating)

A 0.8 mm thick zinc phosphate treated steel sheet was electrostatically coated with a powdered vinyl powder (A) at an applied voltage of 40 kV. At this time, the coating efficiency (%) [= (total coating amount (g) Z effective discharge amount of powder coating (g)) XI 0 0] was 61%. The powder coating not used for coating was recovered and used as recovered powder coating (B1). Incidentally, the temperature of the recovered powder coating at the time of recovery was 28 ° C.

The painted steel plate was baked at 190 ° C for 20 minutes to produce a coated plate, and the appearance (Mitsuzawa) of the coating film was examined by the following method (reference). Example) The results are shown in Table 1.

Coating appearance (glossy)

The gloss values of the incident angles of 60 degrees and 30 degrees are measured by a gloss meter manufactured by Nippon Denshoku Co., Ltd.

(Preparation of recycled powder coating (C))

The weight ratio of the recovered powder coating (B 1) and the virgin powder coating (A) is 80/20 (A) / (B 1) (Virgin powder coating (A) With a content of 80% by weight) and a dry powder for 5 minutes by a Henschel Mixer (manufactured by Aisha Seisakusho Co., Ltd.). Paint (C1) was prepared. This regenerated powder coating The average particle size of the material (CI) was 38 m, and the particle size distribution was 2.7.

(Electrostatic coating of regenerated powder paint)

The reclaimed powder coating (C) was electrostatically applied to a 0.8 mm thick zinc phosphate treated steel plate at an applied voltage of 40 kV. At this time, the coating efficiency (%) [= (total coating amount (g) Z effective discharge amount of powder coating (g)) XI 0 0] was 58%.

Further, the coated steel plate was baked at 190 t: for 20 minutes to prepare a coated plate, and the appearance (gloss) of the coating film was examined by the method described above. The results are shown in Table 1.

Examples 2 to 7 and Comparative Examples 1 to 2

Except for using the virgin powder coating (A) shown in Table 1, electrostatic coating, collection, and preparation of a regenerated powder coating were performed in the same manner as in Example 1, and coating after coating was performed. The film appearance was examined. Table 1 shows the results.

In Example 3, before the blending, a treatment was performed to apply a positive charge to the recovered powder coating material (B) to remove electricity.

In Example 6, the recovered powder coating (B) and the nitrogen powder coating (A) were blended and then classified with a 90 mesh wire mesh. Was used as a reclaimed powder coating (C).

In Example 7, in order to see the effect of the storage temperature of the recovered powder coating, the recovered powder coating was held for one hour in a 40 blast drying oven. ). Example Example Comparative Example Reference Example

1 3 4 5 6 7 1 2 Virgin powder paint (A)

5 5 5 3 3 5 5 2 Katana ¾Χ. 200 200 166 166 166 140 140 166 120 140

¾ ~--^ ¾-¾ grain ^ ±. Particle size (, " _m ) 35 41 41 41 47 47 41 55 49 Particle size distribution 2.3 2.3 2,5 2.5 2.5 3.2 3.2 2.5 2.8 4.5

Content of particles of 75 am or more (% by weight) 9 Q it? 1 8 18 24 24 18

Special treatment

除除 Lightning strike for powder rest (休) Yes He recovered powder paint (B) (40 ° C) Yes

Re-classification 4m- Yes

Reclaimed powder coating (C)

Virgin powder coating (A) content (% by weight) 80 40 40 30 40 40 40 40 40 Average particle size (μπΐ) 38 46 45 48 58 52 48

Particle size distribution 2.7 3.2 3.2 3.5 5.2 4.6 3.5

61 58 57 65 48 51 53 52 38 39 Appearance of coating film (glossy)

Incident angle 60 degrees 82 81 79 79 76 72 76 77 71 70 Incident angle 30 degrees 56 55 52 54 48 32 41 48 32 29

Example 8

When the regenerated powder coating (C) prepared in Example 1 was electrostatically applied, the unreacted regenerated powder coating was recovered as an overspray. Then, the recovered powder coating (B1) is mixed with the powdered vacuum coating (A) so that the content of the powdered coating is 80% by weight. Then, a reclaimed powder coating (C1) was prepared.

Further, the reclaimed powder paint (C1) is electrostatically coated, and the unreacted reclaimed powder paint is collected as an overspray, and the recovered powder paint (B2) is collected. Then, this and the virgin powder paint (A) are blended so that the content of the virgin powder paint becomes 80% by weight, and the regenerated powder paint (C) is blended. 2) was prepared.

A steel plate on which the reclaimed powder coating (C 2) was electrostatically coated was baked at 19 Ot: for 20 minutes to prepare a coated plate, and the coating rate and the appearance (gloss) of the coating film were determined as described above. According to the above method, the coating rate was 51% by weight, the gloss at an incident angle of 60 ° was 79, and the gloss at an incident angle of 30 ° was 47. Industrial applicability

According to the method of the present invention, only one kind of powder paint is used as the virgin powder paint, and, in principle, special treatment or processing is performed on the recovered powder paint. Because they do not need to be applied, they can be easily blended and repainted at the painting site, and their practicability and economic effect are enormous.

Claims

The scope of the quest

1. As a thermosetting fluororesin powder coating for electrostatic coating, a thermosetting fluororesin resin with an average particle size of 20 to 50 m and a particle size distribution of 4 When the powder coating (A) and the thermosetting fluororesin virgin powder coating (A) are electrostatically applied, do not apply them as an overspray. The use of recycled powder paint (C) blended with the recovered powder paint (B) obtained by recovering the waste powder paint from a thermosetting fluororesin powder paint. Painting method.

2. The method according to claim 1, wherein the content of the vinyl powder coating (A) in the recycled powder coating (C) is 35% by weight or more.

3. Claims 1 or 2 wherein the amount of particles having a particle diameter of 75 / m or more contained in the virgin powder coating material (A) is 20% by weight or less. The method described.

4. Keep the recovered powder coating (B) at 35 ° C or less between the time when the recovered powder coating (B) is collected and the time when it is blended with the baseline powder coating (A). The method according to any one of claims 1 to 3, wherein the temperature is maintained at the temperature.

5. Claims that the collected powder paint (B) should be neutralized before it is collected and then mixed with the vanno powder coating (A). The method described in any of paragraphs 1 to 4 in the range.

6. The method according to any one of claims 1 to 5, wherein the recycled powder coating (C) has an average particle size of 15 to 55 zm and a particle size distribution of 1 to 5. Method.

7. The recovered powder paint (B) and virgin powder that were collected twice The range of claims in which the coating efficiency of the regenerated powder coating (C), which is composed of the body coating (A) and the coating powder is 50% or more, is described in any one of paragraphs 1 to 6 of the claim. How to appear.

8. The average particle size is 20 to 50 Xm, and the particle size distribution is! When the thermosetting fluororesin resin powder coating (A) and the thermosetting fluororesin resin powder coating (A) are electrostatically applied to It is a blend with the recovered powder coating (B) obtained by recovering the powder coating that was not applied as an overspray. A thermosetting type fluororesin powder coating composition, wherein the content of the above-mentioned version powder coating (A) is 35% by weight or more.