PVDF Coating Process Common Problems and Solutions

(1) film transparency and low gloss film transparency and gloss for the sale of packaging is a very important indicator, because they directly affect the effect of packaging on the display of goods, PVDF coated packaging film is used in a large number of various commodities sales loaded, so the transparency and gloss of PVDF coated packaging film is a need to pay attention to the performance of the indicator.
The reasons for low transparency and gloss of the film may be due to problems with the emulsion (formulation) or improper control of the production process conditions.
D Emulsion problems PVDF coated film transparency and low gloss may be PVDF emulsion anti-adhesive agent silica dosage is high, when found low transparency and gloss, first of all should be on the PVDF emulsion formula to check, will ~ silicon oxide amount of control in the range of 1% to 2%; improve the filtration and mixing of SiO2 dispersion to avoid uneven distribution of SiO, is also a solution to the transparency and gloss of the film, but also to improve the film transparency and gloss of the film, and the film transparency and gloss of the film. It is also one of the ways to solve the low transparency and gloss of the film.

2 improper coating process too tightly wound during coating construction is often one of the common causes of low transparency and gloss of PVDF coated film. Winding too tight, will make the film roll of almost no air between each layer of film to stay, and the occurrence of "uneven" coating mechanical embedded, unwinding this embedded separation, thus destroying the smoothness of the surface, resulting in a decline in the finish of the product as well as an increase in haze. Due to the winding too tightly produced by the transparency and low gloss problem, can be solved by appropriate adjustment of the tension value, increase the tension attenuation or appropriate reduction of silver pressure and other measures to be resolved.



(2) Coating lines The presence of coating lines, on the one hand, the appearance of the film performance degradation at the same time the presence of coating lines, but also may cause the coating to produce a weak point, which leads to a substantial decline in the barrier property of the PVDF coated packaging film, therefore, high-quality products are not allowed to have a significant presence of coating lines.
Burrs on the new doctor blade, or used doctor blade there is a dry solid coating, doctor blade has a micro-incision, the coating material itself is dirty, between the doctor blade and the coating roller solid particles as well as the coating want to block the plate, etc., may be in the PVDF coated film on the surface of the coating line can be resolved using the appropriate targeted measures. Such as burrs and micro-port of the doctor blade for grinding and repair, if necessary, replaced with high-quality doctor blade, strict management and filtration of latex to prevent the coating rollers to block the plate (appropriate to reduce the temperature of the cold water, short downtime to keep the plate rollers to turn immediately after the shutdown and thoroughly cleaned, to ensure that the bottom of the dryness of the coating, etc.).
(3) Leakage As the name suggests, the leakage of coating is that part of the surface of the coated film is not covered by the PVDF coating, the harm of leakage is that it will greatly reduce the barrier property of PVDF coated packaging film, thus losing the reliable protection function of the high barrier film for the packaged goods, and thus it is not allowed in the production process of the coated PVDF barrier packaging film.
There are two types of coating leakage, primer leakage and top coating leakage.
Reasons for undercoating leakage
a. Substrate material Small surface tension; small friction coefficient; poor uniformity of base film.
b. Equipment and process The wrapping rubber of Series A is dirty or aged and has lost its elasticity; Series A driving friction discs have failed; the driving friction of Series A rollers is too small; the tension in the oven section is set too small; the guide rolls are not parallel at the bottom coating.
When the bottom coating is found to be defective, the above factors can be adjusted on a trial basis.
2 Surface coating leakage causes
a. Reasons of base film Surface tension <38mN/m; Friction coefficient <0.4; Uniformity is not good; Heat resistance is poor; Deformation of base film produces wrinkles during drying of base coat; Oven tension is too large; Deformation of base film produces wrinkles; Air volume of base coat oven is too large; Wind speed is too high; Base film produces longitudinal wrinkles. b. Reasons of equipment leakage
b. Equipment and process A roller friction is not big enough; A parcel of rubber is dirty or aging loss of elasticity; oven section tension setting is small; a pair of pressure rollers before coating pressure is not enough or rubber pressure roller surface is not smooth, it will cause the tension can not be effectively segmented, that is, the tension "crosstalk and out of control, caused by the bottom and top coating leakage; top coating speed of the clip speed and the speed of the machine does not match, it will also produce Leakage of coating (the better speed ratio is . /u machine-1.0~1.2).

Nanjing Sumino Precision Machinery Co., Ltd. has professional cast film production lines, the company's main cast film manufacturing lines are: TPU hot melt adhesive film production line, CPP/CPE cast film production line, EVA solar encapsulation adhesive film production line, PE hygiene breathable film production line, PVDF cast film production line, PP three-dimensional film production line, medical blood purification film production line, multi-layer co-extrusion barrier film production line, LLDPE winding film production line, etc.