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  9. Problems Resulted From ALPASTE In The Paint System (1)
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      2. Each product (Electrical machinery and apparatus)
        1. TOYAL-CARBO®
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        1. Aluminium alloy powder
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        1. Hino Works
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      1. Each application
        1. Automobiles
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      2. Each product
        1. Leafing Alpaste®
        2. Non-leafing Alpaste®
        3. High-gloss Alpaste®
        4. TD Series (for printing inks)
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        6. Alpaste® for water based coating
        7. Colored Alpaste® "FRIEND COLOR"
        8. Interference color aluminium pigment "CHROMASHINE®"
        9. Interference color aluminium pigment "Cosmicolor®"
        10. Aluminium flakes for powder coating
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        15. Metal coated electrically conductive filler
        16. Dummy balls
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      4. Core competencies
        1. Flaking technologies (Shape control, fine powder pulverization)
        2. Surface treatment technologies
        3. Powder plating technologies
        4. Hybrid technologies
        5. Solvent substitution technologies
        6. Blending technologies
      5. Production bases
        1. Shinjo Works
      6. Troubleshooting Guide
        1. For Better Use Of ALPASTE
        2. For Safe Use Of ALPASTE
        3. Problems Resulted From ALPASTE In The Paint System (1)
        4. Problems Resulted From ALPASTE In The Paint System (2)
        5. Recommendation To Treated Type
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      1. Each product
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      2. Production bases
        1. Yao Works
        2. Hino Works
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  5. Research & Development
  6. Toyal Technical Report
  7. Group Company

Problems Resulted From ALPASTE In The Paint System (1)

Leafing mechanism (1)

The leafing is the phenomenon that aluminium flakes float on the coated paint film surface by convection of the solvent evaporated from vehicle.
In view of the vehicle side, the bigger the specific gravity of vehicle is and the faster the evaporation speed of solvent becomes, the more the aluminium flake floats up.
In view of the aluminium flakes, the larger the specific surface area is and the finer the particle size is, the easier the aluminium flakes float up; the smaller the specific surface area is and the coarser the particle size is, the harder the aluminium flakes float up.

fig. Leafing mechanism (1)
Cross section
Coated surface

Leafing mechanism (2)

Provided that a piece of aluminium flake is dropped onto the solvent and it is kept its balance as illustrated, then it is represented as:

SA = SAB+SB COSα (SB is constant in same type of solvent)
When SA > SAB + SB α = 0
When SA < SAB + SB α = 0 to 180°

About 1 molecular thick of stearic acid absorbed layer is formed on the aluminium flake surface and it becomes
SA < SAB + SB, and the contact angle α is generated.
The balance is maintained at this moment and the flake can float up.

fig. Leafing mechanism (2)

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To achieve leafing stability (1)

Surface tension of vehicle required for leafing

The leafing type ALPASTE is absorbed with stearic acid to form a dense monomolecular film (of surface tension:22to25 dyne/cm), the self-lyophobic phenomenon of such film produces a contact angle between the vehicle and the aluminium flake, and then the leafing property is given by the surface tension of vehicle.
It is said that the surface tension of more than 27dyne/cm is required.

To achieve leafing stability (2)

There are some factors to obstruct the leafing property in the composition of vehicle, the process and the storage. In order to stabilize the leafing property, it is required to protect the stearic acid film absorbed on the aluminium flake surface.

Factors to affect the leafing property

  • Mechanical stress (strongly agitated or the like) : Absorbed film is broken
  • Reaction to water, acid, alkali, etc. : As above
  • Reaction to organic acid, etc. (less C6) : Desorption of stearic acid
  • Contact to activator, metallic salt, etc. : Self-lyophobicness is decreased
  • Air containment
  • High temperature storage

To increase the leafing property

  • Lower the acid value of vehicle.
  • Avoid using high molecular weight material.
  • Lower the viscosity of vehicle.
  • Use the aromatic hydrocarbon as solvent.
  • Use the cobalt type drier.

Problems resulted from ALPASTE in the paint system (2)

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