On the odor of composite products 0

Brief discussion on the odor problem of composite products

1. The cause of odor generation

generally speaking, the odor of composite products is hard, but it still can't cover up the glory it brings. There are two reasons: one is the odor generated by residual solvents; The second is the odor produced by polyethylene resin. The two odors are different

(1) odor generated by residual solvents

a. solvents used in printing inks of composite products generally include ketone, xylene, toluene, butanol and other solvents with high boiling point, odor and toxicity; The pigment particles in the ink are very small. The adsorption capacity is very strong. Although it has been heated and dried during printing, it is complete due to time; Especially for printing materials with large inking volume; It has more residual solvents. If these residual solvents are brought into the compounding process, they will be more difficult to run away after compounding, so they will slowly penetrate out. In the above solvent; Pay special attention to using a small amount of butanone; It's best not to use it. Because generally, butanone is added to the ink when it is prepared. If it is added when it is turned on, it is easy to add too much butanone and leave too much solvent, resulting in more obvious odor

b. residual solvent produced by the adhesive used in the compounding process

residual student solvent brought by agent

(2) odor generated by resin

generally, polyethylene coextruded in t-mold will oxidize into and out of the resin in the molten state at about 300 ℃

2. Measurement method of residual dose

the amount of residual solvent can be determined by gas chromatography or gravimetric method. A gravimetric method is introduced below

take out the sample that has been dried but not compounded from the outlet of the drying channel, and its size is 100mm × 100mm。 Immediately put it on the analytical balance and weigh its mass as W, then put it into a constant temperature oven at 105 ℃ for 1 hour, take it out and cool it to room temperature in the dryer, and then weigh its mass as W2 (at this time, W2 must be a little smaller than W1, because the residual solvent volatilizes), and then follow the following formula to calculate:

r= (W1-W2)/(0.10 × 0.10)

r-residual solvent (g/m2)

residual solvent after domestic composite drying shall be controlled below 10mg/m2; The United States and Japan require it to be controlled below 5mg/m2

3. Ways to eliminate (reduce) odor

(1) ensure the drying quality of products (including drying in printing and drying in compounding). Whether the printing can be dried thoroughly is mainly related to the drying capacity of mechanical equipment, vehicle speed, ink amount, solvent used in the ink and other factors. The slower the vehicle speed, the less the ink amount, and the faster the solvent volatilizes, the more thorough the drying of the printed matter is, on the contrary, it is more difficult to dry thoroughly. In compounding, it is mainly related to the drying capacity of mechanical equipment, vehicle speed, glue concentration, gluing amount and other factors. The slower the vehicle speed, the thinner the glue, and the less the gluing amount, the easier it is to dry thoroughly. On the contrary, it is more difficult to dry thoroughly. Even if it is completely dry, it can only eliminate part of the odor

(2) to completely eliminate odor, do not use high boiling point inks, solvents and adhesives containing toxicity, odor and odor, but only use non-toxic, low toxicity and odor free solvents such as acetic alcohol, alcohol, ketone and isopropanol with low boiling point. Two component high-performance, versatile polyurethane inks do not need to use aromatics. At the moment of discharge, the lamp liner will flash aromatic solvents, and alcohol soluble inks do not have the above shortcomings. If there is no problem with ink and glue, and the amount of residual solvent is very small, there is basically no odor

(3) for the odor generated by the resin, if possible, the melting temperature of polyethylene should be reduced as much as possible, or the distance between the extrusion of the T-shaped die and the pressing roller should be shortened, so that the design of the hydraulic system can minimize the odor by all mechanical design

finally, remind enterprises that sometimes composite product packaging bags can't smell peculiar smell and odor at room temperature, but when it is used to package food with heat (such as cookies just baked from the processing line), When Pu Nai Gu Fen (002225) tasted the food after cooling, there was a strong peculiar smell and odor, which was caused by excessive residual solvents, which promoted the penetration and volatilization of residual solvents when the temperature increased