The selection of equipment and general production process for modifying fillers with titanium ester coupling agents, the influence of moisture content (humidity) of filler powder and the reaction activity of coupling agents with other additives on the selection of titanium ester coupling agents, and a brief introduction to the pretreatment methods and dosage influencing factors of titanium ester coupling agents.
1. Selection of modified equipment:
SLG3/300 powder surface modification machine, high-speed mixer, etc. If a high-speed mixer is selected, the rotational speed>1000r/min, with a volume of 200-500L, the required powder material is rotated at high speed in the mixing chamber. The high-speed rotating material flow collides with the baffle, changing the flow direction and enhancing the mixing and dispersion effect of the material. The aggregated powder is fully dispersed, and the coupling agent covers a layer of molecular film on each powder particle interface.
General process of filler modification:
The amount of powder filler added to the high-speed mixer is 50% to 75% of the mixer's volume. When the temperature reaches 90-100 ℃ under high-speed stirring (frictional heating), water vapor is discharged, and then a diluted solution of coupling agent is added. When the temperature reaches 105 ℃, the machine is stopped and discharged for later use (sealed packaging to prevent moisture absorption). The entire process time depends on the performance of the high-speed mixer
2. The influence of moisture content of powder materials on:
Choose fatty acid monoalkoxytitanate, and the filler moisture content should be less than 0.5%, otherwise the monoalkoxytitanate coupling agent is prone to hydrolysis and failure. Fillers with high moisture content, such as clay, mica, talc powder, etc., can use pyrophosphate type titanium acid ester coupling agents. In addition to reacting with the hydroxyl groups on the surface of the filler to form coupling, pyrophosphate groups can also decompose to form phosphate esters that combine with some water. For water containing polymer systems with high humidity fillers, such as wet process SiO2, clay, talc powder, aluminum silicate, water treated glass fiber, carbon black, as well as phthalocyanine and iron red, chelating titanate coupling agents with excellent hydrolysis stability can be selected for dispersion and anti settling in aqueous solutions.
3. Reaction activity of coupling agents with other additives:
Tetravalent titanium ester coupling agents will undergo ester exchange reactions with ester plasticizers and other ester compounds to varying degrees. In such cases, coordination type titanium ester coupling agents can be selected. Generally, surfactants can affect or counteract the coupling effect between titanium ester coupling agents and inorganic fillers, such as zinc oxide, stearic acid, etc. These materials must be added after the fillers, coupling agents, and polymers are fully mixed to avoid affecting the coupling effect.
4. Pre treatment method (direct treatment of inorganic powder):
The advantage of modifying inorganic fillers and pigments with coupling agents first, and then processing and mixing them with polymers and other additives, is that it is suitable for blending modification of engineering plastics with complex polymer components or plastic alloy systems, as well as some engineering plastics with high processing temperatures, and can prevent unnecessary side reactions.
Specific preprocessing methods: There are two mixed methods: wet and dry. Wet mixing method, monoalkoxy and coordination coupling agents can be diluted with solvents such as gasoline, benzene, ethanol, etc., and then mixed evenly with fillers. The solvents can be removed by heating or reducing pressure. This method has a relatively complete coupling, but it consumes too much and is not cost-effective. The pyrophosphate coupling agent can be added together with the lubricant white oil diluted in the formula; The chelating coupling agent has good water resistance and can be diluted with water. If it does not dissolve in water, amine additives can be used to dissolve it in water, and then mixed with plastics and pigments to remove moisture. The dry mixing method is mainly used for the use of titanium ester coupling agents in plastics. In order to evenly coat the surface of fillers and pigments with a small amount of titanium ester coupling agent, a small amount of diluent (anhydrous solvent and coupling agent in a ratio of 1:1) is generally added.
5. Dosage of titanium ester coupling agent:
It is determined by the total amount of fillers, pigments, and other inorganic additives, as well as the particle size, specific surface area, soft and hard products of the powder. The empirical dosage is 0.5% to 3.0%, and the optimal dosage is ultimately determined by performance.
