With the rapid development of the domestic wire and cable market, PVC insulated and PVC sheathed wires are more and more widely used. Different users will put forward different color standards (RAL, MUNSELL, REA, etc.) for wire and cable. This puts forward higher requirements on PVC coloring for PVC wire and cable manufacturers. At present, domestic PVC coloring is required. Master production and manufacturing is only the initial stage. The author has worked in this industry for many years, and puts forward some experiences and opinions on the production and manufacturing of PVC masterbatch.

PVC resin is a kind of heat-sensitive and shear-sensitive resin. If it is processed many times, its application performance will be affected. Owing to various reasons, we often encounter a "one-time processing" product quality does not meet the requirements, and have to carry out multiple processing. In this way, not only the production efficiency is affected, the consumption of raw materials is increased, and the production cost is raised, but also the internal quality of the product may be affected. Therefore, it is of great significance for producing PVC cable masterbatch with high efficiency, low consumption and high quality to carefully analyze the causes of "multiple processing" operation, understand the main factors affecting the "one processing" qualified rate, and seek ways to improve the "one processing" qualified rate.

Processing status of a PVC cable Masterbatch

PVC cable masterbatch has many varieties, complex ingredients and different formulations. Some can be qualified by "one processing", while others must be processed several times to meet the requirements. The qualified rate of "onetime processing" varies greatly with different color spectrum, and the relationship between the qualified rate is roughly as follows:

White > grey > yellow > Orange > Brown > black > Blue > Green > red.

The "machining" problem in the production of two PVC cable Masterbatch

PVC cable color masterbatch "one-time processing" unqualified, the main non-conformance items are poor particle shape, poor dispersion, color deviation and so on.

Among them, the color deviation leads to the "one-time processing" unqualified, mainly in the formulation of some problems, not in the scope of this article, because for a mature formula, the first color should not be a problem.

The causes, classification and analysis of undesirable conditions are as follows:

1 the extruding bar is difficult to draw, coarse and thin, with poor grain shape.

2 extruded surface.

3 extruded surface is extremely rough.

The first case is mainly due to the unstable feeding capacity of the extruder. Two kinds of situations are often encountered in production.

(1) agglomeration of premix, resulting in difficulty in feeding material or blocking material at the feeding port of extruder.

(2) The packing density of premix is too small, and the bottom is agglomerated at the feeding port of hopper due to "air resistance", and the premix is used to bridge the hopper. In this way, the pressure of the extruder head melt fluctuates greatly, and the material flow in the die is more and less, which is very unbalanced. Of course, it is difficult to get a good grain shape.

The second situation, usually occurs in the lower hardness of the product, some after the "secondary processing" smooth feeling of the extruded strip has been significantly improved, but some products, but not significantly improved. If the dispersion is detected, it is in line with the requirements.

The third case occurs in some products that use special plasticizers or have a particularly high pigment content. At this point, the production condition may be good, but the extruded strip surface is quite rough, only after a number of processing, the extruded strip feel smooth.

As for the problem of poor dispersion, we can usually choose the simplest method in production, that is, secondary processing.

Three, the main reason that affects the pass rate of "one processing".

There are quite a lot of factors that affect the qualification rate of PVC cable masterbatch product "one processing". For convenience of analysis and comparison, the three controllable factors of man, material and ring and the influence of machine, which is objective and immutable, on the qualified rate of "one-time processing" are not considered. Each kind of product is also synthesized from many batches of production processing situation, has certain representativeness, if carries on the analysis from the formula angle, will give us some enlightenment.

1 Effect of organic pigment content

According to the organic pigment content and processing times, the qualified rate of the masterbatch is only 25% when the organic pigment content exceeds 2%, and 80% when the organic pigment content is less than 2%. This indicates that the content of organic pigments plays a decisive role in the qualification rate of "one processing". And its critical concentration is about 2%. More than this value, most of them need to be processed two times. One of the reasons is that the density of organic pigments is small, the volume is large, and the proportion of premix is light during processing, which often causes difficulty in adding materials and affects extrusion operation. The other reason is that the dispersion of organic pigments is poor, the higher the content, the more difficult the dispersion, resulting in poor dispersion of products.

2 Influence of inorganic pigment content

PVC cables are mostly required to have a good covering, in addition to the use of organic or inorganic pigments when coloring, titanium dioxide is usually added to improve the covering. Statistics show that inorganic pigment content is different, which also affects the qualified rate of "one processing".

3 Effects of plasticizer varieties

Plasticizer is one of the main components of PVC cable color masterbatch. It affects the workability, heat resistance, cold resistance and softness of products.