Plastisols - this is the dispersion in the plasticizer vinyl resins for special purposes.It is believed that during processing into a finished product in the composition will remain almost the whole of a plasticizer, a volatilization would have little.If the current composition of the solvent helps to add - "plasticizer", which evaporates during processing, such a composition called organosols.The dividing line between these terms is determined by what organosols contains a few percent (eg,> 5%) of the solvent.In fact, the term "solvent" used here is wrong.No one expects that the "solvent" will dissolve the resin;it would increase the viscosity and processing would be advisable to use relatively high for plastisol emulsion resins.Used in the plastisol and organosols "solvents" evoke a very limited swelling of the resin and reduce the viscosity of the dispersion.Therefore, they are in their action in volatile diluents (or thinners).Sometimes, to describe these songs use the term "modified plastisol".Please note that for polymers with lower molecular weight solvents used in the classical sense as a means for dissolving the polymer.
Dispersion resin plastisols have a very small particle size (1-2 microns) compared to the resins by suspension, designed for conventional compounding, which leads to rapid dispersion in the plasticizer.They are often used with small amounts of PVC, which has larger particles, referred to as "resin for blending" (extender).The influence of expanding the distribution of particles of the mixture of resin is to reduce the amount of plasticizer is expended in filling voids between the particles of resin, plasticizer and increasing amounts of variance.The result is a reduced and more stable viscosity as in warehousing, as well as mixing and processing.However, the use of larger particles increases the tendency to precipitate and may reduce the mechanical properties, transparency, gloss and gelation rate.Used as copolymers of vinyl acetate, such plastisols have reduced gelatinisation temperatures and melting in comparison with the homopolymers, but owing to high solubility in the plasticizer may have a higher viscosity.
When designing compositions plastisols most important point is the correct choice of resin and plasticizer.General-purpose plasticizers (OH), such as DOP, provide acceptable viscosity plastisol and its treatment in the whole range of concentrations.Aliphatic diesters, such as adipate and cyclohexane carboxylates and linear phthalates, provide viscosity lower than grade OH.Low volatility plasticizers such as DIDF usually give a higher viscosity than the plasticizers OH.Plasticizers with fast solvation, such as DGF and BBP, lead to the formation plastisol having a high viscosity due to swelling of the resin particles.Secondary hydrocarbon plasticizers provide low viscosity, but their use is limited to small amounts (except organosols) due to low compatibility with the vinyl.As with all formulations of compositions, the type and amount of plasticizer required properties are determined by age and mechanical properties for specific applications.To secure the desired properties, processor must select the right resin and other additives, and processing conditions.
Most-filled PVC compositions (and not only plastisols) contain calcium carbonate.Usually the size of the filler particles is 1-2 microns, and its concentration is equal to or slightly higher concentrations of plasticizer.Filling increases the viscosity of the plastisol suitable for most kinds of processing, generally decreasing with shear rate.Often this does not apply to varieties of calcium carbonate (or other filler) with submicron dimensions.Typically, higher viscosity obtained using a filler with a high oil absorption, smaller particle size and irregular shape.Other fillers include barytes used are used for sound absorption due to their high density;calcined clay - to make the electrical properties;and hydrated fillers - to make fire and dymopodavleniya.Titanium dioxide is used as a pigment and UV absorption, increases the viscosity of the plastisol at a concentration of 2-8 h.100 h.resin, but this increase does not affect the workability.On the other hand, we can expect that the highly dispersed carbon black significantly increase the viscosity.Due to the fact that in any case require a high level of dispersion, merit the use of a plasticizer dispersion pastes.Added flame retardants to be effective require close contact with the resin additives;therefore not surprising that such AP, as antimony oxide and hydrated fillers (TGA and BMS), increase the viscosity and increase its storage.
Most-filled mixing injected mixture of metal stabilizers or other additives powder, which is especially preferable for downloading songs with a high concentration of filler.On the plasticizer is added and mixed organotin stabilizers liquid metal.Due to the fact that heat stabilizers for plasticized PVC are usually surface-active properties, changing the stabilizer can have a noticeable effect on the viscosity of the plastisol.This is also true for the lubricants and related additives.
Usually radically increase the viscosity of the plastisol can be the introduction of polymers of relatively high molecular weight or elastomers, such as the NSC.This is best carried out with mixtures of latex.Typically, a developer of materials should be considered latexes, solutions and compositions plastisols as a broad unified field to be used in various applications.
Additions to regulate the rheological properties
In the development of plastisols and organosols, as well as in the case of vinyl latexes and solutions, processing technology is seen polyphase system to the stages of gelatinization and melting, which occurs when the processing is usually ends.This differs from the development of "dry" tracks, which usually lasts for processing after melting composition;that is forming in the finished product takes place after melting, but not before.
To reduce the viscosity of the plastisol used various additives;referred to as viscosity depressants.Usually, this surface-active substances, which reduce the surface tension of the plasticizer, it may occur selectively at the interface between the polymer and filler.The simplest of these are alcohols, such as 2-ethylhexanol (2-EGS) and izodetsilovy alcohol (IDS).They are usually used with the corresponding ester plasticizers:2-EGS, such as DOP or DOA, IDS with DIDF.At a concentration of 1-3 h.viscosity and, in particular, its growth has slowed.Both of these compounds are volatile and vaporize at the melting point, so they have little negative effect on the properties of the molten composition.On the other hand, they have a pronounced odor, which may be unacceptable for processing.In some cases, there are traces of melting odors that may be unacceptable.At a concentration of 1-3 h.their effectiveness in lowering the viscosity and its growth is higher than that of aliphatic alcohols.Upon melting, surface-active glycol ethers can completely evaporate.After processing, their presence is noticeable odor.
Applied and permanent non-volatile surfactants, typically in an amount of 1-2 h.These include ethoxylated nonylphenol derivatives, such as Tergitol NP-10 (Dow) or Igepal CO-520 (Rhodia) (CAS 127087-87-0).They can be added to the thermal stability of the compositions, stabilized nonilfenolyatami calcium or barium, oversaturated bases.Based surfactants nonyl-phenolates (and stabilizers) are sensitive to bleaching by nitric oxide (sour gas), which must be balanced with efficiency in reducing the viscosity.For better color retention may be preferable to use aliphatic nonionic surfactants based on polyglycols, such as Pegosperse 400 MO (PE glycol monooleate;CAS 9004-96-0) and 400 LM (PE glycol monolaurate;All of these compounds do not evaporate during processing and are useful as tools for processing of filler, as agent for de-aeration and substances that improve the structure of the foam in the foamed plastisol.Sometimes using ionic surfactants, but more often use of surfactants based on sodium salts taurinovoy acid with general formula RCONR'-CH2CH2-SO3H, which are marketed under the brand name (Igepon Rhodia) and Hostapon (Clariant).They are especially useful in getting plastisols, dispersion is difficult when the filler.These may enhance the effectiveness of antistatic surface, which is similar to surfactant-based polyols.The compositions containing substances that reduce the viscosity should be tested for long-term thermal stability and the possibility of exudation.
For substances that reduce the viscosity, can act and foam stabilizers plastisol.For foamed plastisols these factors should be considered together.Conversely, the above substances that reduce the viscosity, and act as agents for deaeration.In all three areas, you can use silicone additives, but care must be taken, if required, even on other lines, to ensure adhesion, printability or decorating.In some applications, to increase the viscosity of plastisols, not a decrease.This, for example, coating the fibers, when necessary and desirable translucence resistance to flow of sealants during cure.In many such cases requires a high viscosity at low shear and low viscosity at higher shear rates.For plastisols with high calcium carbonate content of this effect can be achieved by choosing a variety of calcium carbonate.Varieties with a particle size of 1-2 microns provide a significant increase in viscosity, for example, if the concentration of use is the same as the concentration of ester plasticizer.Varieties with larger particles 8.10 microns with only a slight thickening effect, but the besieged varieties with submicron particle size and high oil absorption (> 20 g/100 g) provide a large increase in viscosity.Therefore, the compositions are usually filled with a certain amount of calcium carbonate with a particle size of 1-2 microns and a large number of larger filler ¬ th, will be useful to include a small fraction of precipitated calcium carbonate.When processing with high shear range of fractional composition also helps to reduce the viscosity under shear.
When filling small, thickened plastisol usually low concentration (1-3 h.) Highly dispersed silica.The most efficient ultra colloidal silica;suitable varieties are Cab-0-Sil (Cabot) and Aerosil (Degussa).Grades of precipitated hydrated silica, such as HiSil (PPG) and Zeothix (Huber), are less effective in thickening and their use in higher concentrations (2-5 h.);but they are also less exposed to low molecular weight additives, are attracted to the surface.For colloidal silica interaction with additives that reduce the viscosity, providing deaeration and stabilizing foam, may reduce the effectiveness of.For details of this effect to a minimum they are often added to the composition after dispersion of other additives;this is not a problem thanks to a highly dispersed colloidal silica.Usually the number of colloidal silica added very little to give a turbidity or scatter light, which is also associated with fine particles and can be used in the compositions translucent.Consumers should consider the possible existence of hazardous dust when using colloidal silica.
There are a number of special-purpose thickener.For example, aluminum distearate (Ferro, Norac) used in concrete pavements as a thickener and binder.When you need transparency, apply at least two classes of organic thickeners.One of them - polyacrylic acid, manufactured under the brand name Carbopol (Noveon).It is useful for the treatment of filler;combination of filler and acrylic acid can eliminate the mutual effect of thickening.Used at a concentration of 0.5-3 h.Another class - calcium sulfonate, sold under the brand name Ircogel 900 by Noveon, which is used at a concentration of 0.5-3 h.Usually none of them is not as effective as colloidal silicon dioxide;but they both provide increased stability during storage, temperature and shear, as well as - transparency.