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27 Jan 2016 
As a total result of changing philosophies towards continuous manufacturing, new equipment is being introduced into pharmaceutical production facilities. The twin-screw extruder can be an exemplory case of such equipment for employ in wet granulation. The authors critique advancements in wet granulation utilizing a twin-screw extruder; construct the presssing problems with wetting in this machine; and introduce a novel technique, foam granulation, that uses the twin-screw extruder to fully satisfy the unique requirements of granulation.

single screw extruder

The twin-screw extruder provides highly consistent granulates due to its continuous operation and closely confined flow path, which requires that particles experience an identical shear history. The intensive combining of the twin-screw extruder allows lower ideal liquid concentration for granulation while generating denser granules for both placebo formulations and highly dosed drugs in comparison to a high-shear batch mixer. As a total result, drying and milling operations may be significantly reduced with use of this machinery in solid oral-dosage production.

The binding liquid in wet granulation includes a profound influence on product granule properties and affects the friction between conveyed powders and the barrel wall inside the extruder, which affects power consumption and the exiting temperature of granules. You can find crucial problems to be solved in regards to introducing liquids into this type of machinery to acquire rapid and uniform wetting of excipients in order that the process exhibits balance in operation, boundaries become lubricated to lessen equipment wear and granule heating immediately, and top quality granulates are obtained.

A general variant of extruder useful for granulation may be the fully intermeshing, co-rotating twin-screw extruder. Differences between vendors are largely based on the available internal volume of the machine plus the screw diameter, both of which can affect granulate real estate in both granule size and intragranular porosity significantly. The machine is highly modular, making it a flexible platform for constant manufacturing of different products during its lifetime of program to a company. The intermeshing area between the two screws creates a self-wiping actions that minimizes materials accumulation within the machine but also provides a complex flow course for powders to combine and consolidate. For wet granulation, the die end of the extruder is open to collect granules without excessive consolidation generally.

Wet granulation inside the co-rotating twin-screw extruder is a starve-fed procedure, meaning that the available internal level of the machine is under no circumstances completely filled with material during operation. This modus operandi is important to extrusion since it minimizes dissipative warmth build-up in conveyed medicine formulations as it limitations compression against the barrel wall, it decouples the parameters of output screw and rate speed to provide formulators more control over their method, and it more readily permits the downstream addition of products because the system is not pressurized aside from small mixing regions. The zones of the screws which are starved experience dominant drag flow, in which powders are pushed by the rotating flights of conveying-type elements downstream. These screw elements have been noticed to contribute small to granule growth. In fact, screw designs using only conveying elements show inadequate distribution of the binding liquid within exiting solids. It is rare, however, a screw design is completely comprised of conveying components or that the complete length of the machine is ever fully starved. Significant granule growth necessitates the inclusion of pressure-driven mixing zones, which are necessarily fully filled as powders are squeezed through these sections. Kneading blocks and comb elements are examples of mixers popular in sparing numbers across the screw length to create granule growth alongside minor attrition. Keeping these mixing elements closer to the end of the extruder reduces attrition.

Powder flow price is one of the most significant parameters influencing the extent of granule growth, with larger outputs producing bigger granules. The result is induced by the bigger volumes of powder that build up in front of pressure-powered mixing zones as stream rate increases, producing bigger axial compressive forces on the contaminants present. In fact, it's been revealed that the dispersion of binder within poorly wetted mass could be improved for granulation if the screw design and flow price are adjusted to provide ideal compressive forces. The influence of flow price on granule growth, however, is not often seen in smaller extruders or highly starved processes. Increasing screw speed has less effect on granule size but generally escalates the number of chopping events supplied by mixing zones to reduce the occurrence of oversized contaminants. For a set flow rate, increasing the screw speed shall reduce the volume of powder that fills the conveying screw elements, leading to lower power consumption by the process.

Among the published research for wet granulation, an essential point that is rarely mentioned, yet widely known to the pharmaceutical industry, is the problems of wetting a formulation within an extruder uniformly. The problem arises because of the earlier mentioned confined space inside the extruder closely, which effects in the liquid injection port becoming in immediate proximity to the powder flow. This confinement prevents atomization of the binder option into micro-sized droplets ahead of contacting the powder solids, as is done in high-shear batch mixers. As a result, parts of the powder become oversaturated while others remain dry virtually. This presssing issue was highlighted in the industrial-oriented document by Shah, who reported procedure surging, though motor overload events are likewise common. Shah demonstrated several strategies linked to screw design and the sequential addition of smaller liquid quantities into the process as means to minimize surging occurrences. Such changes greatly raise the complexity of working the extruder and do not eliminate the root cause of the issue. Alternatively, a fresh solution called foam granulation uses the unique behavior of aqueous foam to cause rapid spreading of the binding liquid over a large section of the powder during wetting.
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26 Jan 2016 
screw extruders manufacturer

Poor stability will affect the complete board, board will become yellow and the foam sheets'brittleness is large. Insufficient melt strength will cause the cell of foamed sheet becoming bigger and the longitudinal section bulbs longer. Probably the most direct way to guage whether the melt strength is insufficient would be to press the sheet wrapped in the channel speed roll together with your fingertips, if the melt durability is excellent, it is possible to look elasticity when pressing. If it's hard to bounce after pressing, then your melt durability is poor. Because there is larger difference between a screw structure and cooling method, it is troublesome to determine a reasonable temperature. To be able to attain uniform pvc foam board in the foam pipe, there is must ensure good financial strength of PVC materials also. Foaming aid is developed to solve this issue of the foamed article and effectively improve the quality of the foam pipe.

Lubricant is divided into external lubricants and internal lubricants, outer slip is conducive to demolding and the top gloss, if the outer slide is fewer, it is not easy to control and easy heating, which in turn causes the temperature of confluence core, and you will see the problems in the center of plate, such as a huge bubble, string bubble, yellow, and other concerns. While if the surface of the plate the precipitation of the external slide isn't smooth; external slide is more, precipitation will become serious. Inner slide is undoubtedly conducive to the fluidity of melt and plasticization, and then it really is difficult to control the thickness of development foam board, if the inner slide is certainly insufficient. If interior slide is too even more sufficient, it prone to the phenomenon of superior confluence core temperature.

Compared with the above fundamental problems, the process temperature control will be much more intuitive, it is the surface problem, if the heat range control is not good, it may bring about the emergence of the fundamental problems. Improving the processing heat range, material stabilization period will be reduced, and the issues of stability can look; the original lubrication balance will be broken, the general performance may be the insufficient the external lubrication, external lubrication in the late period of time especially, there is need to improve the amount of external lubrication; the raising of temperature shall result in melt strength decreased, cell foam sheet increased, the real number of cell sheet reduced, the sheet is brittle and easy to break; raise the heat to lessen the melt strength and reduce the melt viscosity, reducing of the viscosity reduces dispersing ability, for the screw with poor dispersion, the phenomenon of uneven dispersion sometimes.
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25 Jan 2016 
There are many iterations of foam: rigid, plain styrofoam sheets, extruded, and expanded. The after two, extruded and expanded, will be the most popular in terms of home building projects probably, but what’s the difference?

Expanded Often called Beadboard, sheets are created from sturdy beads of polystyrene. These beads happen to be expanded by injecting and dissolving a small amount of pentane gas into the base material during production. Under temperature, the gas expands the beads to form shut cells. These cells approx are. 4o times the volume of the original bead, and can get molded to create insulation boards, blocks, or shapes. While a shut cell structure and resistant to water even now, it isn't as resistant to wetness as XPS is definitely, but that may be splitting hairs. It is generally cheaper than it ‘extruded’ cousin and scientific tests have shown EPS to get a lower result on the environment and can be recycled easier than XPS.

Extruded, this foam begins with sound polystyrene crystals. The crystals, and also other additives happen to be fed into an extruder. Within the extruder itself, high pressure and heat form the mixture right into a plastic fluid. This thick liquid plastic is then forced into a die where it emerges and expands to a foam. This foam is then shaped, cooled, and cut. Due to the extrusion process, XPS has the ability to maintain steadily its thermal and/or physical properties more uniformly than EPS and makes an excellent substitute for corrugated cardboard, thus it gained in level of popularity amongst architectural modelers. Another benefit of XPS is it’s strength: because it put through higher compression during the manufacturing process, it really is slightly extra rigid than EPS. Also, as the closed cell structure is normally finer than that of EPS indeed, XPS resists moisture better. I suppose once this became the defacto amongst these modelers, it migrated to railway modelers. Manufacturers add dye often, which has no influence on the XPS other than identification of the manufacturer.

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So that is better? Well, after reading numerous content it does indeed seem that Extruded foam has a few slight advantages after all. But i want to note the focus on slight. For some railway modelers with straight forward layouts, there probably is not any difference because the foam will be covered anyway by other materials such as plaster. In the end, it seems the three main variances are: Expense, where EPS gets the advantage; Strength, where XPS stacks up a tad better and retains its rigidity, and finally, Moisture resistance, where once again, XPS includes a minor advantage.
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24 Jan 2016 
The aqueous foamed binder used in foam granulation is made up of a high level of gas dispersed within a liquid containing foamable excipients, forming an unstable thus, semi-rigid structure. Effective excipients for pharmaceutical granulation are cellulose-ether species that enhance excessive foaming activity and become binders in the process. Many approved nonionic, polymeric excipients are appropriate foaming agents also. The foam liquid might include additives given that they do not interfere with its preparation. Semirigid foams characteristically exhibit closely loaded bubbles or a polyhedral morphology according to the gas-volume fraction although a minimum of 64% gas is required for the foam to display some degree of rigidity. The volume fraction of gas within foam is often known as its foam quality. For granulation, FQ is normally kept in a variety of 75-95%. Foams which are too wet lack adequate stability to spread well and often simply collapse on the areas of processing equipment. Very dried out foams occupy large volumes of space; exhibit high inherent viscosities; and more collapse in the current presence of shear than wetter foams readily.

co extrusion machine

Continuous foam granulation with a twin-screw extruder was introduced in a research study comparing the strategy to the traditional liquid addition method. An effective methodology to metering such foam in to the machine expected recognizing its solid-like behavior and using approaches commonly employed for feeding bulk solids rather than liquids. An auxiliary unit, known as a relative aspect stuffer to the extrusion industry, was found ideal for feeding foam. The medial side stuffer is easily available commercially, and the physical control and setup software of most extruders could be configured to support it. The side stuffer is definitely a miniature, twin-screw auger that mounts aside of the primary extruder and conveys materials into a specified area of the process. As a result of drag-flow actions of the rotating screws in the relative part feeder, foam is forced into the moving formulation within the primary extruder and partially collapses upon call, as the remaining foam forms a coating between your powder and extruder barrel. The mechanism of foam wetting in the extruder is still under study. A two-stage version proposed in a recent publication was predicated on how foams prepared from liquids of diverse viscosities and having diverse FQ collapsed and drained under varied shear conditions together with how they influenced granule homes from the extruder. A pressure-driven wetting stage is considered to occur at the true point of entry where the foam enters the process, with stiffer foams showing greater level of resistance to collapsing upon contacting the non-wetted formulation immediately. The remaining, uncollapsed foam pushes the powder to form a layer preceding aside. The next shear-driven wetting stage appears governed by the response of foam to shear; layers of stiffer foam collapse more easily under mechanical shear to wet the powder beneath while wetter foams exhibit greater resistant collapse under mechanical shear by establishing extra stable morphologies made up of smaller bubbles.

These observations are thought to be linked to the two-stage wetting mechanism previously described, which causes the powder to become immediately isolated from the barrel wall by a layer of foam, at least until it really is well wetted. The powder in this instance is usually steadily saturated with the binder over a much larger area of get in touch with than in direct liquid addition, which minimizes the binder's local focus in the porous matter. The lubricating feature of foam granulation, in which the foam coating isolates the powders from the barrel wall until uniformly wetted, is an important point to be stressed for extrusion processing. The lubricity of conveyed solids influences both power consumption by the machinery in addition to the exiting temperature of granules.
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23 Jan 2016 
XPS insulation boards get started as a solid granule. The granules will be fed into an extruder where they are melted and critical additives are mixed with the viscous liquid that is formed. After that, a blowing agent can be injected to make the blend foamable . Under properly controlled heat and pressure conditions, the foamable mixture is pressured through a die, at which time shaping and forming occurs. The rigid foam is trimmed to the ultimate product dimensions then.

COMER series production line can produce better top quality of final products is the consequence of the comprehensive understanding of single screw and twin screw extruder and cooling performance of single screw extruder. This provides the guarantee for bigger capacity and better quality of final products.

Automatic uploading units are configured to supply the fully automated solution.

Batch grave metric feeding and premixing resolution is optional also.

USEON regular solution will equip the K-Tron Ioss-in-excess weight feeders for totally systematic solution.

Precise metering and injection systems for CO2, HFC or butane could be configured according to distinct requirement specifically. Other liquid injection as added blowing agent may be equipped.

All the first plasticating extruder will be equipped with USEON’s super powerful modular twin screw profile permits a myriad of physical blowing agent

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Modular structure of the cooling extruder allows the very best cooling condition that could steer clear of the unbalanced cooling condition. Precise temp control is easily guaranteed through such design.

All COMER systems equip the unique static mixer to progress temperature distribution and the future mixing.

USEON as well develops the specialized die for CO2 extrusion system to meet the strict foam condition.

Post units include the calibrator, haul-off, edge trimmer, printer, stacker and autopacking units. These models are optional regarding to buyer’s specific requirements.

Shape relay to PCC(industrial computer system control), we are able to customize the control system according to your unique requirements. We not only consider economical factors, more and more caring styles have been introduced to your control system, making the complete control easier.
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