The method, process and influence factor of surface change of quartz powder

surface change of quartz powder is one of the most effective ways and most important technologies to optimize its properties, open up new fields of adaptation, and improve industrial value and added value. Generally divided into coating correction and surface chemical change.
1
, quartz powder coating modified
applying modified is the use of polymer or resin on the surface of quartz powder film
"
and achieve surface correction method. Apply quartz sand, such as phenolic resin, to improve the bonding properties of fine cast sand. This applied casting sand can not only obtain high melt casting speed, but also maintain the mold and core production to obtain high anti-roll shell and anti-cracking properties;
application correction is a simple treatment method of powder surface, to apply quartz sand with resin as an example, surface application correction method can be divided into cold method and heat method.
(
1
) cold coating
rinse or scrub and dry quartz sand before applying it. Cold coating sand is prepared at room temperature, first mixed powder resin with sand, and then added solvent (industrial alcohol, acetone or acetaldehyde), solvent addition depends on whether the sand mixer can be closed
; 40%-50%


;
the method uses a large amount of organic solvents and is used only for small quantities of production.
(
2
) thermal coating
thermal coating is to heat the sand for coating, first the quartz sand heated to
140-160 degrees C
, and then mixed with the resin in the sand mixer (wherein the resin amount is
2%-5%
of quartz sand dosing). At this time the resin is softened by hot frying, covered in the sand surface, with the temperature decreases and becomes sticky, at this time added Uloto products distributed on the sand surface, and the sand cooling (Uloto as a catalyst can be formed in the shell mold to cure the resin). Then add calcium stingrate (prevent lumps) mixed for a few seconds after sanding, and then crushed, screened, cooled after the product.
this method is better, suitable for mass production, but the process control is complex, and requires specialized sand mixing equipment.
the main factors affecting surface application are the shape of particles, surface area, porosity rate, type and dosage of coating agent, application treatment process and so on.
2
, Quartz powder surface chemical modified used in plastics, rubber and other resins quartz powder, silicon powder and other forms of silica powder, in order to make its surface compatible with high polymer substate, so that the comprehensive performance and processability of filling materials to improve and improve, it must be surface treatment.crushed quartz powder or other silicon dioxide powders may appear under the effects of water and air
Si-OH
(siliconol-based),
Si-O-Si
(silicon ether-based) and
Si-OH
.
O
(surface adsorption of free water) and other official groups. Therefore, it is easy to accept foreign official energy groups, such as silane amino, epoxy, methyl propylene, trimethyl, methyl and vinyl and other organic energy groups, which for the surface change of silica powder has laid a certain foundation.(
1
) surface modifierquartz powder, silicon micro paste or other silicon dioxide powder surface chemical modifiers mainly use silane coupled agents, including amino, epoxy, methyl propylene, triple methyl, methyl and vinyl and other silicone coupled agents.principle of silane coupled agent modified quartz powder:
-RO
of thesilane coupled agent can hydrolysively produce a siliconol base in water, including free water adsorbed on the filler surface, which can be chemically combined with
SiO2
or combined with the original silicon alcohol base on the surface to form an ether phase system. Thus, both the moisture on the surface of the
SiO2
is removed and the silicon ether bonds are formed with the oxygen atoms in it, so that the organic hydrometric group
-R'
which carries a good affinity with the polymer at the other end of the silicone coupled agent is firmly covered on the surface of quartz or silica particles, forming a reactive coating.Organic energy group
-R'
and epoxy resin and other polymeric materials have a good affinity, it can reduce the surface energy of quartz or silica powder, improve the wetting with high polymer substate, improve the compatible of powder and polymer base material. In addition, the formation of this new interface layer can improve the fluid performance of the filling composite system.addition to silane coupled agents, zirconate coupled agents and polymers can also be used for surface treatment of silica powders. High porosity ultra-fine silicon dioxide for detergents such as coatings, leather products, cosmetics, etc., is generally modified with fatty acids (e.g. stadic acid) and polyethylene wax.cation surfactants, such as ammonium xenane-trimethyl bromide, can also be used for surface changes in silicon dioxide powder. Because the isoelectrent point of silicon dioxide is low, particles usually charge negative electricity in the water medium, and with the increase of
PH
, the charge point increases. After surface treatment with cation surface modifier, the negative charge on the particle surface is gradually reduced and can finally be converted into a positive charge particle.(
2
) surface change factors the main factors affecting the surface treatment effect of quartz powder and other silicon dioxide powders are: the variety, dosage, use method and treatment time, temperature,
pH
value, etc.Because the organic energy group
-R'
of silane is selective for materials such as polymers or resins, the type of resin to be filled with quartz powder should be considered when selecting silane coupled agents.amount of silane coupled agent can be determined according to the surface area of quartz or silica powder, or the optimal dosage can be determined according to the test.(
3
) surface modified processwet process is the use of appropriate diluents and additives mixed with silane coupled agents into a treatment solution, in a mixing reactor or reaction tank to heat or soak quartz powder or silicon dioxide powder, and then dehydrate.the chemical precipitation legal system to prepare a fixed-shaped silicon dioxide powder, often using wet surface treatment process.drying process is to add a small amount of diluent and silane preparation treatment agent, in quartz powder is high-speed stirring dispersion and heating conditions, fog-like injection into the configured silane treatment agent, after a certain period of time after reaction, this method does not need to be dehydrated drying, the process is simple.Dry
-
wet binding process is the first to acidified aqueous solution (when the electrical performance requirements are very high when the selection of deionized water) and the appropriate amount of co-ionizer mixed in a strong mixing device, with a certain concentration of treatment fluid, according to quartz powder feed
8% -10%
add the treatment fluid, then mix
1h
in a small ball grinder with a rigid jade ball or silica ball as an abrasive, dried at
110
degrees C, and finally screened.process, the addition of water and the grinding time have a great influence on the treatment effect. The addition of water is too large, the powder is easy to group, need to mix and grind for a long time, which will increase the powder re-crushing phenomenon and bring in impurity components;, the acidity and alkalinity of the solution directly control the hydrolyzed degree of the couple. The powder quartz treated with this method was tried in resin glue, resin anti-corrosion coating, resin powder coating and
PVC
artificial leather, with good results.
3
, quartz powder surface modified effect silane treatment of silicon dioxide powder is commonly used in epoxy resin-based plastics. This plastic is used in outdoor high-voltage insulation materials, as well as in the manufacture of casings and insulators for die-cast resin transformers and open-air transformers for dashboards and power outputs rated at up to
150kV
). Silane treated quartz powder for high-polymeth-based electrical equipment material fillers, can improve bend strength, obtain a smoother appearance, improve the ability to resist ultraviolet radiation, and because it is not seriously blackened after the knock-through phenomenon, so that its resistance to small leakage performance is good.addition, modified quartz powders are used in anti-corrosion materials because of their chemical inertness and can also be used for lining fillers in chemical pumps. For the same reason and for long-term surface density, surface-coated quartz powder can also be used in floor coatings in nuclear technology laboratories.treatment of precipitated silicon dioxide (white carbon black) with silane can further improve the application performance of white carbon black in rubber. Some high-quality white carbon black products are surface treated. After treatment by silane coupled agent, white carbon black, surface hydrophobic oil, and rubber compatible greatly improved.
。