JP2005131673A - Powder release agent - Google Patents

Abstract

Disclosed is a powder release lubricant capable of satisfying conflicting properties of mold release and coating adhesion at a high level and ensuring coating adhesion only by a normal degreasing process.
SOLUTION: At least one of an organic compound and graphite is contained in a range of 30 to 70% by weight, and at least one of aluminum hydroxide and zinc oxide is contained as an inorganic amphoteric compound, and the average particle size of the inorganic amphoteric compound is set. 1 to 30 μm.
[Selection] Figure 4

Description

  The present invention relates to a powder mold release agent used for facilitating removal of a cast product from a mold, and in particular, achieves a high level of mold release properties and paint adhesion of the cast product.

When aluminum parts for automobiles are obtained by die casting or thixocasting, the main components are organic compounds and silicon compounds (silicone oil and talc, etc.) for the purpose of improving casting quality. A large amount of liquid mold release agent has been applied to the mold. However, when manufacturing a large die-cast product having a surface area exceeding 1 m ² , there is a problem that the molten aluminum entrains the release agent and the release agent remains on the surface of the cast product. For this reason, when coating a cast product, the mold release agent fixed to the cast product is not removed at all even if ordinary alkaline degreasing is performed. Therefore, application of the liquid release agent to the mold has been a cause of poor coating adhesion of the cast product. In order to improve this poor coating adhesion, it was necessary to clean the cast product with a strong acid or a strong alkali or mechanically polish the cast product before the alkali degreasing step, and there was a big problem in terms of workability.

  In recent years, development of a powder release agent has been actively conducted for the purpose of improving workability of application of a release agent. For example, a powder mold release agent for die casting has been proposed in which both the release agent base material and the organic compound have a powdery or granular form, or the release agent base material is coated with the organic compound. (See Patent Document 1).

  In addition, based on the configuration of Patent Document 1, a powder mold release agent for die casting using at least one of sulfur compounds, fluorides, talc, boron compounds, and phosphorus compounds as inorganic compounds (see Patent Document 2). ), A mold casting release agent used by spraying on the inner surface of the mold in the mold casting operation (see Patent Document 3), and for high pressure casting used by spraying on the inner surface of the mold in high pressure casting operations including molten metal forging A mold release agent (see Patent Document 4) and a powder mold release agent for low pressure casting (see Patent Document 5) used by spraying on the inner surface of a mold in low-pressure casting operations have also been proposed.

  Furthermore, in order to achieve good mold release properties and seizure prevention, inorganic compound gas cushion type release lubricant consisting of gas generation release lubricant components that decompose and generate gas at high temperature during casting operations (patent Reference 6), powder mold release for die casting, which is made of a mixed powder of organic powder and inorganic powder that evaporates or decomposes by heating to generate gas and is excellent in mold release lubrication performance. A powder release lubricant (see Patent Document 8) for mold casting made of an inorganic powder that is thermally decomposed to generate gas by contact with a molten metal (see Patent Document 7) is also proposed. ing.

  The application of such a powder release agent is suitable for improving the coating adhesion of a cast product because the coating amount can be reduced as compared with a liquid release agent. However, the mold release property and paint adhesion of the cast product are contradictory properties. The plurality of inventions described above focus on the castability, and therefore cannot sufficiently satisfy the paint adhesion.

Japanese Patent Publication No. 6-9730 (Claims) Japanese Patent Publication No. 7-59343 (Claims) Japanese Patent Publication No. 7-59344 (Claims) Japanese Patent Publication No. 7-59345 (Claims) Japanese Patent Publication No. 7-59346 (Claims) JP 2001-198649 A (Claims) JP 2001-353550 A (Claims) Japanese Patent Laid-Open No. 2002-97481 (Claims)

  Therefore, the present invention has been made in view of the above circumstances, and is excellent in ensuring coating adhesion even at a normal level of degreasing process by making the contradictory properties of mold release and coating adhesion compatible at a high level. It is an object of the present invention to provide a powder release lubricant capable of realizing high workability.

  The present inventors have achieved a powder release lubricant capable of realizing excellent workability by ensuring both the above-described mold release property and paint adhesion at a high level and ensuring the paint adhesion only by a normal degreasing process. We have earnestly researched. As a result, it was found that all of the above requirements can be satisfied by optimizing the release agent component and optimizing the average particle diameter of the inorganic amphoteric compound in the release agent component. The present invention has been made based on such findings.

  That is, the powder mold release agent of the present invention contains at least one of an organic compound and graphite in the range of 30 to 70% by weight, and contains at least one of aluminum hydroxide and zinc oxide as an inorganic amphoteric compound. The average particle size of the compound is 1 to 30 μm. Here, the inorganic amphoteric compound refers to an inorganic compound that dissolves while forming a salt in both acid and alkali. That is, it means a compound that can be easily removed by alkali degreasing or pickling even when remaining on the surface of the material.

  In such a powder release agent, it is desirable that the inorganic amphoteric compound has an average particle size of 1 to 10 μm.

  In the present invention, the components of the powder release agent are optimized. That is, from the viewpoint of improving the coating performance of a cast product, the powder release agent of the present invention contains at least one of aluminum hydroxide and zinc oxide as an inorganic amphoteric compound. Aluminum hydroxide is suitable because it does not remain on the surface of the material due to gasification at the time of casting, and does not impair coating adhesion. Moreover, since zinc oxide is the same component as zinc phosphate which is a chemical conversion film component, it does not affect chemical conversion properties and corrosion resistance. Moreover, since it is estimated that a chemical conversion film is formed also on zinc oxide, it is suitable, without inhibiting coating adhesion.

  Moreover, in this invention, optimization of the average particle diameter of an inorganic amphoteric compound is aimed at. That is, in the powder release agent of the present invention, the average particle size of the inorganic amphoteric compound is 1 to 30 μm. As described above, since the average particle diameter of the inorganic amphoteric compound is 1 μm or more, the release agent is sufficiently adhered to the mold, and excellent release properties of the cast product can be realized. Moreover, since the average particle diameter is 30 μm or less, excellent heat retention of the release agent film can be realized, and the castability of the cast product is improved. That is, in the mold release agent of the present invention, since a mixed layer composed of an inorganic substance having a low concentration and a gas (organic compound vapor, aluminum hydroxide vapor, air, etc.) is formed, the heat retention is suitable and good. Hot water circulation is realized. In this mixed layer, the gas is thinly confined by the inorganic substance uniformly attached, and thereby the gas is pinned by the inorganic substance (see Patent Document 7). Therefore, in order to form a mixed layer composed of an inorganic material and a gas, it is necessary to make inorganic particles dense. When the inorganic particles are coarse, the gas cannot form a mixed layer with the inorganic material, and the heat retention is reduced. When the average particle diameter is 10 μm or less, the castability of the cast product is further improved.

  Furthermore, when obtaining a cast product using the powder mold release agent of the present invention, it is possible to ensure excellent paint adhesion of the cast product only by a normal degreasing process, resulting in good workability and results. The product can be obtained inexpensively.

Hereinafter, the present invention will be described more specifically with reference to examples.
Aluminum components for automobiles were cast using powder releasing agents (Production Examples 1 to 16) having the main components, the average particle diameters of the inorganic amphoteric compounds, and the mixing ratio shown in Table 1. Thereafter, in the casting product coating process, the casting product was sequentially subjected to alkaline degreasing, water washing, surface conditioning, chemical conversion treatment, water washing, pure water washing, and electrodeposition coating. Here, as the chemical, SD280 manufactured by Nippon Paint is used in the alkaline degreasing, 5N-10 manufactured by Nippon Paint is used in the surface conditioning, and SD6800HM manufactured by Nippon Paint is used in the chemical conversion treatment. For painting, PN150 made by Nippon Paint was used. Table 1 shows the main component of the release agent of each production example, the average particle diameter of the inorganic amphoteric compound, and the blending ratio.

  After the completion of such a coating process, the cast products obtained by using the release agents of Production Examples 1 to 16 were examined for castability, coating adhesion, and corrosion resistance. As for castability, investigations were made on hot water circulation (appearance quality of cast products typified by mold shape reproducibility) and mold releasability (ease of taking out the casting from the mold after opening the casting mold). These results are also shown in Table 1. The evaluation criteria for hot-rollability and mold release are: ◎ if the casting quality is good and the casting temperature control width such as mold temperature control width and injection speed is wide, ◎, if the casting quality is good, ○, casting quality Is satisfied when the control range of the casting conditions is narrow, and Δ is indicated when the castability is poor and impractical.

As for coating adhesion, a test piece of a cast product obtained by using the powder release agent of each production example was painted, then immersed in pure water at 40 ° C., taken out after 240 hours, and a predetermined grid A tape peeling test was conducted to investigate the peeling of a predetermined area of the eyes (the 1 mm pitch dice). The paint adhesion was investigated for both small aluminum (ADC12) die cast parts having a surface area of 0.5 m ² and large aluminum die cast parts having a surface area of 2 m ² . These evaluation criteria were set as ◯ when there was no peeling and x when there was peeling.

  Furthermore, regarding corrosion resistance, salt water spraying was performed for 480 hours using 5% NaCl salt water at 35 ° C., and the swelling of the coating film from the crosscut after spraying was investigated. As shown in Table 1, this evaluation criterion was “good” if the swollen width of the coating film was within 2 mm, and “poor” if it was 2 mm or more. In addition, in FIG. 1, SST means a salt spray test.

  As is apparent from Table 1, when the powder release agents of Production Examples 1 to 5 are used, it can be seen that all show excellent results with respect to castability, coating adhesion, and corrosion resistance. This is because the powder release agents of Production Examples 1 to 5 contain at least one of aluminum hydroxide and zinc oxide as the inorganic amphoteric compound, and the average particle size of the inorganic amphoteric compound is 1 to 30 μm.

  On the other hand, since the main components of the powder release agents of Production Examples 6 to 9 are not aluminum hydroxide or zinc oxide, the release agent component remains on the material surface of the cast product. For this reason, excellent paint adhesion cannot be obtained. In Production Examples 10 to 13, since the average particle size of the inorganic amphoteric compound is not 1 to 30 μm, excellent results with respect to castability, particularly hot water resistance, have not been obtained, and coating adhesion is generally excellent. The result is not obtained. Since Production Examples 14 and 15 are not satisfied that at least one of the organic compound and graphite, which is the premise of the present invention, is included in the range of 30 to 70% by weight, excellent coating adhesion cannot be obtained. A suitable balance between castability and paint adhesion cannot be obtained. Production Example 16 is a mold release agent that has been used for general purposes and uses talc as a main component. However, excellent coating adhesion cannot be obtained for this, and castability and coating adhesion A suitable balance cannot be obtained.

  Next, since it is mainly C (organic compound or carbon) or Si (silicone oil, talc, etc.) that hinders coating adhesion, it is necessary to analyze C and Si. That is, FIG. 1 is a diagram showing the results of EPMA analysis of Si on the surface of the material after alkali degreasing the cast product obtained using the powder release agent of Production Example 16. In the figure, the red portion has a higher Si concentration and the black portion has a lower concentration. As shown in the figure, it can be seen that when the powder release agent of Production Example 16 is used, Si is partially adhered to the surface of the material even after alkaline degreasing. For this reason, an excellent result cannot be obtained for coating adhesion. In addition, about the powder mold release agent of the manufacture example 16, since only SiO is a main component, the analysis of C was abbreviate | omitted and only the analysis of Si was performed.

  FIG. 2 is a surface photograph of a test piece subjected to a tape peeling test after a water resistance test was performed on the test piece obtained using the powder release agent of Production Example 16. In the figure, 0/100 indicates that a 1 mm pitch dice was created on the surface of the test piece, and the coating was peeled from 100 of the 100 squares. That is, in the test piece obtained using the powder release agent of Production Example 16, it can be seen that all the grids were peeled off.

  On the other hand, FIG. 3 is a figure which shows the EPMA analysis result of the surface element of the raw material surface before carrying out alkali degreasing of the casting obtained using the powder mold release agent of manufacture example 2, (a) is C (B) is the result for Si. In these figures, the darker the portion, the lower the concentration of each element. Thus, when the powder mold release agent of Production Example 2 is used, it can be seen that C and Si are hardly adhered to the material surface even before alkaline degreasing. For this reason, the excellent result is obtained about coating adhesiveness. In addition, about the powder mold release agent of manufacture example 2, since both contain C and Si in a main component, both of these were analyzed.

  FIG. 4 is a surface photograph of the test piece subjected to the tape peeling test after the water resistance test was performed on the test piece obtained using the powder release agent of Production Example 2. In the figure, 100/100 indicates that a 1 mm pitch dice was created, and of the 100 squares, all of the squares were not peeled off. That is, it can be seen that in the test piece obtained using the release agent of Production Example 2, the coating of one square is not peeled off.

  As described above, the powder mold release agent of the present invention can not only achieve a high level of conflicting properties such as mold release property and coating adhesion of a cast product, but also includes a degreasing agent included in a normal coating line process. Can be removed only by the process. For this reason, when the release agent of the present invention is used, it is not necessary to separately introduce a release agent removal step, and the surface simultaneously with various materials (iron, galvanized steel sheet, aluminum wrought material and aluminum extruded material). It can be treated and painted, and the workability can be remarkably improved as compared with the prior art. Therefore, the powder mold release agent of the present invention is preferably applied to a mold casting operation that requires a high level of both contradictory properties of mold release property and paint adhesion, and excellent workability. It is.

It is a figure which shows the EPMA analysis result of Si in the raw material surface after carrying out alkali degreasing of the casting obtained using the powder mold release agent of the manufacture example 16. It is the surface photograph of the test piece which performed the tape peeling test, after giving the water resistance test to the test piece obtained using the powder mold release agent of manufacture example 16. It is a figure which shows the EPMA analysis result of the surface element of the raw material surface before alkali degreasing the casting obtained using the powder mold release agent of manufacture example 2, (a) is about C, (b) is about Si Is the result of It is the surface photograph of the test piece which performed the tape peeling test, after giving the water resistance test to the test piece obtained using the powder mold release agent of manufacture example 2.

Claims (2)

  In a powder release agent containing at least one of an organic compound and graphite in the range of 30 to 70% by weight, the inorganic amphoteric compound contains at least one of aluminum hydroxide and zinc oxide, and the average particle size of the inorganic amphoteric compound Is a powder release agent, characterized in that 1 to 30 μm.   The powder release agent according to claim 1, wherein the inorganic amphoteric compound has an average particle size of 1 to 10 µm.

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