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2023

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11

Problems in the production of disposable powder-free PVC gloves

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1. The causes of "white spots" on the surface of gloves

The molding process of PVC gloves is made of PVC paste resin, viscosity reducer, stabilizer and other raw materials, which are formed into a film at a high temperature of about 160° after being fully mixed. Among them, the main calcium and zinc organic compounds of the stabilizer are formed During the coating process, since zinc is more active than calcium, a replacement reaction will occur, that is, part of the zinc will replace part of the calcium, so that the calcium element is deposited on the surface of the glove.

The calcium deposited on the surface of the glove will remain in the PU water in the form of calcium ions during the process of passing through the PU water. As time goes on, the concentration of calcium ions in the PU water will become higher and higher. When the PH value of the PU water When it is lower than 8 or lower, it will react with the carboxyl compound R-OO in PU water to form calcium carboxylate organic compound precipitation and form small white particles.

Since the organic compound of calcium carboxylate is relatively light and suspended in PU water, as time goes on, the small particles will become more and more large, and sometimes the diameter can reach about 13mm. When wearing PVC gloves When the hand model is slowly taken out of the PU water, there will be small white particles adsorbed on the surface of the glove to form "white spots"

Phenomenon. This "white spot" will fall off after gently rubbing the surface of the glove.

Two: the solution

Manufacturers of PVC gloves want to completely solve the "white spot"

  phenomenon, and the increase in the amount of stabilizer in the paste will not appear "white spots", the pH value of PU water must be controlled above 9. Because when the pH value of PU water is higher than 8.5, calcium ions in the water will react with hydroxide ions to form calcium hydroxide precipitates, thereby reducing the concentration of calcium ions in PU water, because the particles of calcium hydroxide precipitates are very small It is invisible to the naked eye, and calcium hydroxide is heavier than water, so it will not be suspended in PU water, but will settle at the bottom of the PU tank, so it will not form "white spots" on the surface of the glove

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