Manufacture of footwear using PVC in fact engaged in a variety of firms - as no doubt large enterprises equipped with modern facilities, and private traders, who organized molding and sewing the soles of shoes in the "garage".Indeed sometimes used in molding powder "mixture" (a mixture of PVC, DOP, and other additives), which results in lower quality products.
In accordance with the needs of both can not really such a "motley" of the market are produced very different in purpose and quality of flexible PVC.Currently, the market is saturated enough plasticized PVC.In addition to the enterprises equipped with specialized equipment, a compounder, there were small handicraft company, equipped with unsuitable equipment.In addition to Russian companies have recently entered the market and surprisingly foreign manufacturers, which leads to further increase competition.
Usually no doubt high level of competition leads to higher product quality and reduce prices.Unfortunately, in the Russian market of PVC plasticized competition and lower prices caused by it are often accompanied by a decline in the quality of products.Manufacturers and PVC, and shoes are in reduced quality, primarily in the least could not be more critical sectors pretty inexpensive shoe with "short life" - shoes, summer shoes and t.n.In the end, loses consumer buying shoes deficient in quality.However, with limited ability to pay the majority of consumers of shoes made of PVC plasticized issue of poor quality will be (unfortunately) remain.
Problems production and use of PVC
overwhelmingly the main components of PVC - PVC resin, plasticizers, stabilizers, dyes and other additives.In fact sometimes to reduce the cost of introducing fillers.
The producers of flexible PVC, of \u200b\u200bcourse, there is a "rating" the quality of resins from different manufacturers.Not seeing it, we note that both can not be very common in the Russian market shoe PVC resin grades S7058M actually have several different values \u200b\u200bof molecular weight, and could not be more characterized by the highest weight of the resin production of "Nitrogen" (r.Novomoskovsk), strikingly so in the plastic compound has a low Novomoskovskaya resin fluidity (MFI).
Despite the protests of "green" and a number of physicians, the most common plasticizer highly PVC in Russia and abroad - DOP (di-(2-ethylhexyl) phthalate).It is not over as the optimum combination of properties and extraordinary is relatively cheap.DOF refers to the so-called primary plasticizer.The use of other primary plasticizer is limited by their price in Russia is really very little.In addition to the primary, there are also secondary plasticizers, which are not used as it is not their own, but can be incredibly partially replace the primary.Price of secondary plasticizers, of course, less really is why many manufacturers are trying to use them.Classic examples of secondary plasticizers in Russia are chloroparaffins and EDOS and its analogs.Less expensive (compared to the DOP) products, these softeners are a number of properties degrade PVC.
chloroparaffins increase the density of the compound and reduce its thermal stability.EDOS is a mixture of by-products of isoprene, its composition is unstable, and volatility is significantly higher than that of DOP.In addition EDOS currently on the market as there is not very many of his counterparts, whose characteristics are even more worse.With the introduction of these plasticizers in the composition (especially in large quantities) may experience problems with the processing of PVC, porosity, stability, color, and sweating on the surface.
Based on the analysis of individual results, products from other manufacturers and customer feedback, we can confidently say that the best quality, have a composition obtained by the use of plasticizers as DOP only.Using secondary plasticizers should be minimized, otherwise there is deterioration in the quality of plastic and working conditions with.
Fillers - cheap material, it is surprising that the main objective - reducing the cost of tracks.One of the most common fillers unusually - chalk.Its possible to enter only with twin-screw extruders to ensure good mixing.With the introduction of small amounts of chalk physical and mechanical properties of a pretty little change, but the density increases.
Stabilizers are essential components of plasticized PVC.On their nature and quantity depends largely on technological (workability) of the composition and durability of the final product.Indirect characteristic of a successful selection of these additives is a characteristic of plastic, as the thermal stability.Dyes can play so many roles over.In addition to the basic reality - in fact dyeing compositions in the color you want - they can also increase light resistance (carbon black is one of the best light stabilizers), or reduce its.Selection of colors - a very complicated matter, since PVC is not inert with respect to many of them.Really cheap and most strikingly strong dyes - highly inorganic pigments - usually give no doubt pale tones.Highly vivid and bright colors admittedly can be obtained using organic dyes and pigments.Unfortunately, they are less strong and very durable without doubt, than outright inorganic pigments.In addition, as can a domestic industry that produces a very limited range to speak of organic pigments are combined with PVC.The use of imported pigments improves quality but increases the cost of production.
An example of compositions for the shell shoes and high heels
In the world practice in the manufacture of footwear, plastic widely used compositions based on PVC.Exemplary formulations for plastisol shell shoes and heels are listed in Table 1.
As the stabilizer used in the composition of the complex, which includes the salt BA, Cd, Zn.Plasticizer in the composition is a heel-butyl benzilftalat.Horoscho which wets the resin and PVC plastisol lowers the melting point.To increase the stiffness of the heel in the composition is administered monomer type X-970, capable of striking polymerize in the presence of a catalyst (tert-butyl perbenzoate) at room temperature.Cobalt naphthenate serves as co-catalyst, accelerating the polymerization of the composition heel.