| 配方类型： |
PAPER |
| 配方说明： |
Alkaline Casein Solution |
| 配方组成： |
Soda Ash/12-15
It will be noted that trisodium phosphate is not included in these
formulae. This chemical has been used extensively and gives thin
solutions, especially with colors containing satin white. However,
color, foaming tendency, lower paper adhesive strength, and other
difficulties resulted in the elimination of trisodium phosphate from
most coating formulae. Sodium hydroxide can be used, but often is
avoided because of possible excessive alkalinity, with resulting
decomposition of casein, if the quantity is not accurately controlled.
However. some mills have used sodium hydroxide quite successfully.
The use of larger amounts of borax than given in formulae 1 to 4 is
quite desirable in many cases. The use of more borax, with less of such
alkalies as soda ash, phosphate, etc., gives casein with excellent
keeping qualities, but its use is limited by its tendency to thicken
with satinwhite colors and by its slightly higher cost. An |
| 配制方法： |
In work at the University of Michigan, it was indicated that increasing amounts of alkali give a better coating bond (higher wax test). Excess alkali certainly is necessary to take care of minor variations in casein acidity and pigment absorption, to give complete casein solution, to obtain proper color flow, and to give thin colors when satin white is used. However, it has been found that the use of excessive amounts of alkali (for example, to obtain higher wax tests) is not always good practice. Difficulties that might be encountered include: printing trouble, foaming trouble, brittleness of the coating, decomposition of the coating color, and darkening of the sheet color. |
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