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Green Bond
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Merits in Sand Development
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Merits in sand development
1. Cost reduction due to reduced sand additivies amount
2. Cost reduction due to reduced defective castings
3. Cost reduction due to saving in finishing process
4. Cost reduction due to enhanced yield
1. Cost reduction due to reduced sand additives amount
― Why can Green Bond substantially decrease the quantity of starch used?
a) The water content is low.

Table 1
Moisture in starch and efficiency of use
(compared with our former use)
Name of starch
Green Bond
A (corn starch)
B (wheat starch)
Moisture (%)
Quantity used (%)
*The above table shows the quantities of other starches used when the use quantity of Green Bond is set at 100.
When comparing Green Bond with Starch B, it is possible to decrease by about 8% when the difference of moisture is solely taken into account. The intriguing point is that the quantity used increases in proportion to the moisture ratio. For a starch that has double moisture content, a double use quantity is required. When selecting really useful starch, the moisture content is an important factor.
b) It has high heat resistance and high reclaiming ratio after pouring.

Green Bond is made of corn starch and Starch A is also made of corn starch, but why does Green Bond have less moisture and a good reclaiming ratio?
The reason is that Green Bond is made solely of the outer polymer layer of corn kernel.
c) High-polymer Green Bond starch is apt to remain in the sand against dust inhalation.

Table 2
Specific gravity of starches
Name of starch
Green Bond
A (corn starch)
B (wheat starch)
Specific gravity
2. Cost reduction due to reduced defective castings
― Why can Green Bond decrease the defective ratio?
a) With the cushioning effect of starch, it becomes possible to mull green sand with stripping ability.

Effects:Decrease fallen pockets, mold drops and mold chippings.
*There are two reasons why Green Bond is excellent in cushioning effect when compared with other types of starches.
1.  It does not absorb any excess moisture and remains in the sand as starch particles (there are some starches which are too hydrophilic).
2.  Green Bond, which is hydrophobic, is excellent in retaining any moisture once absorbed, and it remains almost in the same condition at the time of molding or mulling.
Table 3
Water retention characteristics of green sand

Water retention characteristics of green sand
b) Only a small quantity of Green Bond improves surface stability.

Effects:Decrease sand inclusions, mold drops, push-ups, erosions (scabs) and penetrations. The reason that a small quantity of Green Bond can fully works lies in its outstanding water retention characteristics (see Table 4).
Table 4
Quantity of starch used and mold surface stability

Quantity of starch used and surface stability
c)Less sand additives can mean less moisture in sand.

Effects: Decrease pin holes, blow holes and porosities.

*Table 5 shows the comparison of Green Bond and Starch A in terms of moisture necessary to obtain the same CB. Green Bond starch showed a significant effect on moisture suppression though the simultaneous improvement of Bentonite shall be taken into account. There are three reasons why the starch in Green Bend can bring the same CB level at a lower moisture:

Table 5
Relativity between CB and moisture

Relationship between CB and moisture
1.  Green Bond starch retains water well, which allows the mulling with lower moisture level (see Table 3).
2.  Compared with the traditional starches, the required volume (e.g., the starch ratio in the sand) is one-half, making the required moisture one-fourth (see Table 4).
Using starches without swelling ability is out of the question, as is often the case with starches made from tapioca or wheat.
3.  Green Bond starch usually contains less moisture than the traditional starches (see Table 1).
d) Green Bond does not potently absorb any excess moisture. For this reason, it is excellent in high-temperature air permeability.

Effects:Decrease pin holes, blow holes and porosities.
3. Cost reduction due to saving in finishing process
― Why does Green Bond decrease finishing cost?
a) Casting sand that is excellent in surface stability protects against the penetration of molten metal and allows casting without burrs.

b) Casting sand with a lower level of moisture drastically decreases sand burning and resultant repair cost.

*At Matsubara, we have succeeded in the deburring cost reduction of 19,274,000 yen (compared with 1995) owing to the effects described in a) and b).
Table 7 Ratio of castings without burrs Table 7 Ratio of castings without burrs
Table 7 Ratio of castings without burrs
4. Cost reduction due to enhanced yield
― Why does Green Bond result in enhanced yield?

Pattern designers will appreciate good sand with Green Bond, which ensures good moldability.

a) You can reduce the radius of round corner angles along parting lines to 0.5mm or lower.
b) Green Bond is relatively strong against heat and excellent in cushioning effect. Thus it is effective for the prevention of mold thermal expansion, which may lead to downsizing of a gate cross-section area and/or riser volume.
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