Overview of polymer masterbatches
Masterbatches are usually use as polymer processing for combination various additives like as color pigments or additives and antimicrobial substances into polymer resin or other liquid. In the other words, masterbatch is a concentrated mixture of colors and additive encapsulated in a polymer carrier such as polyethylene or polypropylene which is obtained via heat treatment and specially in a high shear mixing extruder. Then the mixture is cooled, cut and granulated through a pelletizer. (The carrier is usually a polymer resin in pellet granular shape, but liquid masterbatches are also available for specific materials and applications.)
IT is necessary to say that pigments and additive parts must be completely homogeneously integrated into the base polymer.
Features of polymer masterbatches
Easier combination of additive:
Masterbatches allow for easier adding via extruder add, that in such situation no specialized dozing equipment is required for small amounts of powder. It gives higher accuracy in dozing expensive components.
Product consistency and improved process stability:
Usage of additive masterbatches, also improves product consistency and process stability through better dispersion. The use of masterbatches for more uniform dispersion can result in fewer parts being rejected (or passed) due to inconsistent color or other critical features which has negative effect on quality.
Safer handling of hazardous materials:
Many additives are hazardous or nuisance substances in their pure form. masterbatches encapsulate additives in a polymer or resin or liquid. This encapsulation reduces or in most case eliminates hazardous nature of additive. It also eliminates hazardous on touching powders. These feature leads to reduce engineering controls and reduce personal protective equipment (PPE) requirement.
Cleaner production:
In addition to being safer, Masterbatches additives are also cleaner. There are no colored pigments or any other powder additives to spill or stick statically to the surfaces. As a result, we will have a cleaner production area, reduce pollution and potentially faster transfer between different products.
Increase additive stability and durability:
Encapsulation of additive, also provide advantages in masterbatches for additive. Masterbatches can help protecting additives from moisture, temperature and UV exposure during storage. In this case, this can significantly increase additive useful life and as a result can reduce the cost of lost materials due to the destruction.
Types of masterbatches
Types of masterbatches are include white, black, colored, additive and special effects and will explain in the following. which meet various appearance and application needs.
White masterbatches
White masterbatches have a wide range of applications including application in blow and injection molding process, lamination, coating, pipe, thermal forming, protective films and fibers. The advanced production capacities of these masterbatch include the production of high-quality titanium dioxide (TiO2) grades in outdoor and indoor spaces.
Advantages of white masterbatches:
• Superior comprehensive
• Use thin and thick walls for injection and blow molding processes.
• Extrusion and casting films
• Ease of integration
Black masterbatches
Range of black masterbatches is based on polyethylene and polypropylene. Carbon black inks are specially selected to provide a wide range of properties including UV protection and food contact protection.
Advantages of black masterbatch:
• Superior comprehensive
• Resistant to weather conditions
• Electrostatic conductor
• Products with easy flow and low viscosity
Color masterbatches
Color masterbatches, brings a massive change in plastic resin and various applications. Color masterbatches, are engineering thermoplastics with high efficiency. From industrial equipment to home applicants, textiles to packaging and plastics processors rely on advanced color technology. Thermal stability and color flexibility are two main factors that make color masterbatches an excellent solution for plastic products. This masterbatches are made of high-grade pigments and they use in various processes including insulated cables, injection molding processes, and blow molding of bottles.
Color masterbatch applications:
• Thin layers, thick layers, sheet extrusion
• Side pipes and irrigation
• Injection molding and blow molding processes
• Polyester staple fibers and non-woven fabrics
• PET sheet
Additive masterbatch
Additive masterbatches, prevent deterioration due to heat and cutting during the processing and UV rays and oxidation in the end user environment.
Additive masterbatch applications:
• Packing
• Consumer goods
• Automobiles
• Building construction
• Agriculture
Special effect masterbatches:
Special effect masterbatches has been a growing procedure for high quality plastic products.
Other production masterbatches:
PP Filler masterbatch
PP Filler masterbatch is a combination of calcium carbonate and polypropylene (PP) as the main components and other additive materials. This product is using as a filler which helps to increase the productivity, hardness, modify physical, chemical and thermal surface features, and reduce total price.
Nowadays, almost all Manufacturers of PP woven bags use filler masterbatch as one of the most important materials in the production of PP woven bags and FIBC bag.
Masterbatches production techniques
To produce masterbatches, before starting formulation, we must know about the application of masterbatches.
In general, the following should be considered for production of masterbatches:
1) Carrier:
Masterbatch production can select relevant carrier according to customer needs and application fields. It must quarantine that carrier material has sufficient mixing properties with the colored plastic material. In addition, it is more reasonable that carrier must be 30 degree or less than the heated melting point of raw material. If carrier or plastic isn’t combined with plastic, the plastic will peel off after the formation dyeing process or the performance of the product will be reduced.
2) color matching:
Red, blue and yellow are three primary colors and other colors can be synthetized through these three colors.
Dark red = red + yellow
Orange = red + yellow
Purple = red + blue
Green = blue + yellow
Light green = blue + yellow
Grass green = yellow + blue
Emerald = yellow + blue
Brown = orange + purple
Olive = green + orange
Light brown = yellow + blue + red
Dark brown = yellow + blue + red
Beige = red + yellow + black
Gray = green + purple
Gray green = gray + olive
Black = gray green + dark brown
And…
Usually during the matching color process, some Tio2 will be added. When more TiO2 amount added, the lighter the color, and the less added, the darker the color.
3) Pigment percentage:
As the color number is confirmed according to the product s requirement, the percentage of pigment that is added to make the color masterbatch must also be confirmed. If the color is suitable, but the product color is lighter than the sample, it shows that pigment amount in the product is low. One of the most important issues during the production of color masterbatch is matching the color and then confirming the pigment ratio.
Usually, the golden section method can be used to find the best ratio.
4) Cleaning the extruder:
After producing a masterbatch of a color, cleaning is very important. For instance, if dark blue masterbatch produced and after that dark red or white masterbatch must be produce, the machine must be cleaned afterwards so that it does not affect next color.
An energy effective way to clean extruder machines is that 5 kilograms polyethylene resin will mix with calcium carbonate in the machine. After that, mardon is taken out and clean with brush. The considerable point is that calcium carbonate dose not stick to the calcium carbonate and will falls with a brush, and it can be cleaned quickly, on the other hand carbonate calcium is very cheap.
Mixer cleaning method is very simple. By first removing inner blade and cleaning with steel ball or calcium carbonate. Then they clean mixer bucket with clean calcium carbonate powder, then assemble it and finally put a pack of carbonate calcium powder in it and stir it for 5 minute and let it to come out.
Polymer compound
Polymer compound is one of the polymer products, which is the result of combination of polymer and special additives in order to strengthen polymer structures and prepare them for use in various industries. Polymer compound is also one the most Consumable and practical kind of polymer material in chemical industries which is used for increase the stability and resistance of plastic materials.
In fact, the reason for using polymer compound during the production of polymer products is that manufacturers are face with problems such as physical weakness, reduction of properties, Undesirable color, Prolongation the production process during producing products with polymer base.
In the other words, polymer compound is a mixture of one or more polymers or various additives to increase physical, mechanical, thermal properties for proper shaping via injection plastic and extrusion processes.
Mixing the Thermoplastic compounds and masterbatches
A compound is produced as a complete composition and is ready to use as is. while masterbatch is a pre dispersed color concentrate, which is combined with natural polymer in proportion of 1 to 5 percentage.
There are different methods for mixing Thermoplastic compounds and masterbatches. Selecting kind and size of mixture is depend on different condition, which the most common is high speed mixtures. Depending on the size of mixing vessel, mixes can weigh at least 22 kg. to5 tone. although they are typically between 100 and 500 kg.
On the other hand, masterbatches, because they have up to 70% pigment content and usually are produced with powdered polymers, require high speed mixing to develop and homogenize the pigments within the mix.
Mixing can be done online or offline. For both of them (compound or masterbatch) batch procedures are considered, in with polymer materials (in powder or pallet form) are mixed with additives such as colors and fillers. Of course, depending on the size of production order and the capacity of mixer, they can be just single mixtures or multiple mixtures.
In offline mixing, the ingredients are mixed independently in a suitable mixture far from extruder. As all the ingredients are mixed, it is poured into the other container and after that located into the extruder hooper. The advantage of this method is that you can make several batches and then extrude later in the end of the day or shift. And its disadvantage is that if you leave the mix for a long time, sometimes the heavier ingredients in the mix can start to sift through the mix, resulting in an inconsistent mix.
In online mixing, mixer is placed on top of the extruder. This method ’s benefit is that it is a fresh mixer and without time to settle down. and its disadvantage is that it must be coordinate with extruder and its timing is essential.
Mixing techniques
Normally, it is better to consider the following for compounds:
1) Add all the resin.
2) Add a binding material and mix for 2 minutes if using high speed mixture or 20 minutes normally.
3) Add pigments, additives and dispersing aids. (It may need that some additives added near the end). Close the mixture and mix them again 3 to 5 minutes on high speed or 20 minutes.
4) Compounds are usually processed on a single mardon extruder (unless they are heavily filled) because less cut is needed and also cleaning single mardon extruder is easier and cheaper than twin screw extruders.
It is necessary to explain that some additives such as anti-astatic or slippery additives have a low melting point between 30 to 60 degrees Celsius. Mixing on high speed can generate temperatures above this and if this happens, the mixture can become so lumpy and difficult to feed. Usually, this kind of additives will add after other ingredients and the mixture speed is reduced to prevent excessive heat production.
Normally it is better to consider the following for masterbatches:
1) use a high-speed mixture, but if there are pigments or additives that my damage by high-speed mixing, they can be used.
2) Use powdered polymer and a small amount of pellet feed, usually about 5-10% of the total weight.
3) Add about 50 percent powdered polymer and then all pigments, additives and dispersing aids to the mix. And after that add the rest of the powdered polymer and pellet feed.
4) Close the mixer and beat on high speed, usually for 3-5 minutes.
5) check the mixture, if there are any signs of lumps or inconsistence, it is better to mix them for another 2 or 3 minutes until the inconsistences are disappeared. (However, it should be noted that over mixing can damage special pigments and adversely affect the dispersion of the mixture.) Feed the mixture into the extruder if the color looks consistent and there are no large clumps of dispersed pigments.
6) Most masterbatch formulas require high speed mixing which only can be achieved on a Du Mardon extruder, continues mixer or Banbury mixer.
Differences between Masterbatch and Compound
Both compound and masterbatches are the same in terms of production method, but they are different from the result they create for using the product.
Masterbatch is a granular form of chemical powder that is formed by a mixture of polymers and mineral or organic pigments and According to its various applications, it can be in different colors, that is used as an important additive in plastic production (which provide other properties such as color, shape and performance).
Masterbatches mixed with row materials in specific proportion and formulas are divided into three groups of color, additives and fillers during the production of the final product and finally, they give characteristics such as color, non-flammability, hardness, ….to the product. It is necessary to explain that the performance of used masterbatches as plastic additive or plastic fillers depends on conversion to the final product.
This product is added to the row material when melting and shaping plastic to change its color. So, for example it is used for coloring and creating original mixture in plastic production process. In fact, we can say that masterbatch is a dense granular mix that is used by feeding additives containing different colors and properties to the carrier polymers as a result of thermal operation used in plastic production process. In the other hand, this product protects polymers from changes that my occur as the result of heat and chemical materials during their production and use. So, they increase the product performance and they enable the plastic production in different shapes and features. Totally, masterbatches can be considered as a part of compounds but they have fundamental difference from a technical point of view.
Masterbatch is added to the extruders during the production stage by thermal operation.
Compounds are the other types of additives that give a large scale of mechanical and physical features to the polymers like as masterbatch. In fact, compound is a process that create a new row material with the physical characteristics desired by the client with additive that are added to the original row material. Filler fibers, pigment and added carbon are mixed and bonded to the plastic by thermal operation and pressure. Durability of characteristic improvement such as impact and attraction are achieved through compounds.
Masterbatch is used for some case in industries, while for others cases its necessary to use compound instead of masterbatch. In fact, compound is used in two cases instead of masterbatch. In the first case, in injection extruders and film extruders that mixing masterbatch with polymer base is not possible, compound can be used instead of masterbatch. In the second case, because compound use is easier than masterbatch use, it is used in various industries to facilitate production process. In the other words, the distribution additives and chemical material inside the masterbatch is very important in the final polymer and if this distribution is not done completely, additives may react with the polymers which is used and finally the using the masterbatch will be vain. On the other hand, some of these chemical additives can create dangerous pollutants if used continuously.
Using compound and masterbatch in production of plastic products ultimately provide higher quality and more affordable products.
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