How to use fluorescent whitening agents in plastics (1):
dry whitening and wet whitening
1. Dry whitening
Dry whitening of plastics is to add a certain amount of dry fluorescent whitening agent powder directly to the plastic base material before molding, first mix it with the plastic base material, and when the extruder reaches the plastic melting temperature, squeeze the mixture into The screw is melted to evenly distribute the fluorescent whitening agent in the melt, and finally granulated or pressed.
Dry whitening is mainly used for injection molding whitening of rigid polyvinyl chloride, polyethylene, polypropylene, ABS and other thermoplastic resins. Fluorescent whitening agents used for dry whitening are relatively cheap, but have the disadvantages of large dust scattering and environmental pollution.
2. Wet whitening
In order to improve the dispersion effect, sometimes (such as polycarbonate) it is necessary to add a certain amount (about 500mg/kg resin) of binder, such as butyl stearate, to the fluorescent whitening agent to make the fluorescent whitening agent better Adhere to the surface of materials to reduce dust flying and contamination. The fluorescent whitening agent can also be dispersed in the additive solution and added in batches in the form of additive dispersion. For example, if used in soft polyvinyl chloride (PVC), it can be first formulated into 10% phthalate. After adding the dioctyl formate plasticizer solution, add it in batches.
In wet whitening, the fluorescent whitening agent is in the form of a finely dispersed slurry. Since non-volatile organic solvents are mixed into the plasticizer, it has the disadvantage of being sticky. This method is mainly used for whitening soft polyvinyl chloride.
3. Application examples
Application example 1:
Plastic fluorescent whitening agent FP has a good whitening effect on polyester film, PVC, PP, ABS, organic glass and other raw materials.
Plastic in dry application: FP = 10000: 2 ~ 10000: 5 (mass ratio). Mix the various raw materials first, then add the fluorescent whitening agent FP, stir evenly at 160°C for about 5 minutes, and then roll it into a sheet.
Solvent in wet application: FP = 2:1 ~ 3:1 (mass ratio). The fluorescent whitening agent FP is first dissolved with a plasticizer, and then ground into a suspension to form a mother liquor through a three-roller grinder. Then, the whitening agent suspension is evenly mixed into the mother liquor during the processing, and formed at a certain temperature, usually between 120 and 160 It takes about 0.5h, and it only takes about 1min at 180 to 190 to produce the whitening effect.
Application example 2:
Fluorescent whitening agent OB-1 is used to whiten white polyvinyl chloride (PVC) hard sheets.
Formula (mass fraction):
Octyl tin mercaptide 2. 8% ~ 3. 0%
Epoxy soybean oil octyl ester 1. 0% ~ 1. 5%
Glyceryl fatty acid ester 1. 2%
Butyl stearate 1% ~ 1. 3%
Impact modifier MBS 5% ~ 6%
Processing modifier K-120N 1. 8% ~ 2. 5%
Fluorescent whitening agent OB-1 0. 01% ~ 0. 05%
Calcium carbonate 20% ~ 30%
Whitening process:
PVC resin, additives → Kneading → Cooling and mixing → Screening → Extrusion → Die shaping → Traction → Cooling and shaping → Trimming → Winding → Finished product
Whitening process: According to the above formula, first put PVC resin and calcium carbonate into the kneader, knead at low temperature and low speed, when the temperature rises to 60, add stabilizer, stir for 1 to 2 minutes, and then knead at high speed. Add the modifier when the temperature reaches 80°C, add other additives when the temperature reaches 100°C, end kneading when the temperature reaches 110°C, and switch the kneader from high speed to low speed. Discharge the kneaded materials into the cooling mixer and stir at low speed to cool.
Feed the cooled material into the twin-screw extruder, control the screw temperature to 110°C, the fuselage temperature to be controlled at 190 to 160°C, the die temperature to be controlled at 180 to 175°C, and the traction temperature to be from 120°C, 100°C, 85°C, 45 gradually reduced. The temperature of the cooling roller is 20 ~ 25. The extruded material is shaped into thin sheets by the touch head, and then is pulled by the tube through the edge trimming frame and entered into the winding machine to obtain rolled products.
Application example 3: Mix 0.01 parts of stilbene fluorescent whitening agent with 70 parts of PVC, 30 parts of plasticizer and 2 parts of stabilizer. The mixture can be ground at 150 for 5 minutes to make a film. If a white covering film is to be prepared, 2.5 parts of TiO2 should be added to the material before grinding.
