The film is mainly made of polyvinyl chloride, polyethylene, polypropylene and other resins. It has softness, ductility, good processing performance and printing performance. It has been widely used in food, medicine, chemical industry and other fields. However, due to the cost of resin production High, the impact on the environment is large, usually need to add fillers to reduce costs. Due to the performance problems of common fillers, the transparency of the film will be affected. As a new type of filler, nano-calcium carbonate has the advantages of small particle size and large specific surface area, which can increase the strength of plastic films, and has the advantages of small specific gravity and low manufacturing cost.
Through the experimental research on the factors affecting the performance of nano calcium carbonate, such as crystal control agent, barium sulfate dosage, surface modifier formulation, etc., and used in the preparation of PE film to carry out application experiments, in order to prepare small specific gravity, good dispersibility, and oil absorption value. Low nano calcium carbonate provides ideas.
1. The effect of crystal shape control agent dosage on film properties
In the process of preparing nano-calcium carbonate, 0%, 0.3%, 0.6%, 1.2%, 2% (according to the dry content of nano-calcium carbonate) sorbitol were added respectively, and the effect of different sorbitol dosages on the properties of nano-calcium carbonate and film was investigated. Influence (2). It can be seen from the table: the blank sample without the crystal control agent sorbitol has a small specific surface area and poor transparency; as the amount of sorbitol increases, the particles become smaller and the specific surface area increases, which is conducive to light diffraction, The transparency rate is improved; but the specific surface area reaches a certain level, the oil absorption value increases, the processing resistance increases, and the force between particles is strong, resulting in a decrease in dispersibility. After comprehensive consideration, the dosage of sorbitol was determined to be 0.6% of nano calcium carbonate.
2. The effect of coating barium sulfate dosage on membrane properties
The nano-calcium carbonate was coated with different amounts of barium sulfate such as 0%, 5%, 10%, 15% (on the dry basis of nano-calcium carbonate), and the effect of the amount of barium sulfate on the film properties was investigated. The shape of nano-calcium carbonate is cubic. The main purpose of adding barium sulfate to coat nano-calcium carbonate is to form a deposition layer with a sponge structure, generate a certain porosity, improve dispersion, increase light transmittance, and then improve transparency. It can be seen from the table: with the increase of the amount of barium sulfate, the nano-calcium carbonate is covered by barium sulfate, and the dispersibility and light transmittance become better. When the amount reaches more than 10%, the light transmittance changes little. Determine the amount of barium sulfate to be 10% of the dry basis of nano-calcium carbonate.
3. The effect of surface treatment formula on film properties
Experiments were conducted by adding 5% to 6% of different surface treatment agents to investigate their effects on nano-calcium carbonate and film properties. As can be seen from the table below, in test 1: the hydrophilic COO- group in stearic acid soap combines with Ca2+ to form calcium stearate, which is coated on the surface of nano-calcium carbonate to form a coating layer, which can improve dispersibility and reduce oil absorption. value. In test 2: Phosphate ester is a coupling agent with phosphorus as the center and alkoxy group, which is composed of a plurality of lipophilic long carbon chain groups. It is coated on the surface of nano calcium carbonate, which can reduce the oil absorption value and improve the dispersibility and light transmittance. In test 3: Tributyl citrate is a good plasticizer with good compatibility with PE masterbatch, high plasticizing efficiency and strong weather resistance. Tributyl citrate is dissolved in stearic acid soap. Adsorbed to the surface of nano-calcium carbonate, improve the compatibility of nano-calcium carbonate and PE, improve dispersibility and light transmittance. In test 4: Phosphate and tributyl citrate are dissolved by stearic acid soap and coated on the surface of nano calcium carbonate. Stearic acid soap can improve the dispersibility, phosphate ester coupling agent has a strengthening effect, and tributyl citrate Increasing the compatibility can reduce the oil absorption value, improve the dispersibility and improve the light transmittance. Taken together, the Experiment 4 formulation has low oil absorption, good dispersion and visible light transmittance.
The dosage of crystal form control agent sorbitol is 0.6% of nano calcium carbonate, 10% of nano calcium carbonate is used as inorganic surface agent, 4% stearic acid soap, 1% ester coupling agent and 1% lemon are used As an organic surface treatment agent, the prepared nano-calcium carbonate has a specific surface area of 30.6m2/g, an oil absorption value of 19.2 gDOP/100g, an average particle size of 40nm in electron microscope test, and a D50 of 0.43μm in laser particle size analyzer test. The film has good dispersibility, and the light transmittance can reach 88.9%.
Nano calcium carbonate has a smaller specific gravity than nano barium sulfate, and is more than 50% smaller than nano barium sulfate masterbatch, and the masterbatch of the same weight can blow a larger area, which can reduce the production cost of masterbatch.