Special calcium carbonate for silicon PU (polyurethane) as well as composite modifier and modification method thereof

The invention discloses a special calcium carbonate composite modifier for silicon PU (polyurethane). The special calcium carbonate composite modifier is prepared from gamma-chloropropyltriethoxysilane, a titanate coupling agent and stearic acid. The invention also discloses a modification method of calcium carbonate special for silicon PU, which uses the composite modifier, and comprises the following steps: (1) cleaning and crushing ore raw materials, fully mixing with the first part of composite modifier, and grinding in grinding equipment; and (2) heating the ground calcium carbonate powder, then spraying a second part of composite modifier atomized at high temperature, and carrying out a modification reaction to obtain the modified calcium carbonate powder. The invention also discloses the special calcium carbonate for silicon PU obtained by the modification method. According to the characteristics of organic silicon, different modifiers and modifier combinations are screened through tests, and gamma-chl