The term liquid color or liquid color concentrate describes to a system consisting of a liquid binder (carrier), dyes or pigments and other additives such as process additives, stabilisers or similar. The liquid colors are mixed into the plastic (raw polymer or recyclat) for coloring or changing the properties. [1]
In general, there are three groups of liquid colors.
So-called liquid colours have been used for colouring plastics since the end of the 1960s / beginning of the 1970s. [2] However, liquid colours are still not used extensively and have a market share of just 7 % in Europe compared to 93 % for masterbatch colouring. This is different in the US, where the market share of liquid colors is about 40 %. [3] This is mainly due to the inadequate dosing technology in the early days and the associated contamination in the production area. As a result, the liquid colorant gained a bad reputation and is still not very popular with processors, although the dosing systems have been adapted to the requirements of users, especially in the last decade, and clean and easy handling is possible. [2]
It is possible to add liquid colors to a variety of thermoplastic and thermoset processing methods, such as
The products obtained from the processing methods are used in the following areas, for example:
Depending on the plastic, the choice of the liquid carrier is decisive due to the processing temperatures, compatibility and the later application. In order to prevent migration of the carrier liquid as far as possible, well-tolerated liquid carriers are used which interact with the polymer.
The typical components are:
Different mixtures of the components are also used.
The pigment preparations are produced in batches. For this the formulation components are distributed into a binder previously selected for the respective application and then dispersed. The most optimal breaking up of agglomerates is crucial to ensure a high effectiveness of the colour concentrates and / or functional process additives. Dissolvers, bead mills and roller mills are usually used here. For transparent, thin film applications, particularly well broken down pigments are required. In practice, particle sizes < 5 μm have proven successful for film applications.
The liquid colours can be dosed in different ways. The simplest possibility is to use a so-called drum. Here the polymer granulate is wetted with the liquid color, homogenized in a mixing device and usually processed further. In large-scale applications, aggregates such as peristaltic pumps, Progressive Cavity Pumps or gear pumps are usually used. Here, the dosing can take place above the hopper or directly into the melt. [5]
Due to batch production, the pigments can be broken down in the liquid carrier medium until they are optimally dispersed. The particles are therefore very finely distributed, which has a positive effect on color intensity and light scattering.
Each batch can be controlled in terms of colour, viscosity and particle size distribution and, if necessary, corrected as a whole.
If the liquid colorant is added to the main hopper together with the raw polymer, the distribution of the liquid colorant is statistically better than that of masterbatch even before melting. Without additional mixing units, a homogeneous, streak-free coloration can be achieved with highly concentrated liquid color from 0.5 % dosage.
Due to the wetting with liquid carrier, the pigments adhere less strongly to the metal components of the processing machines, which results in sometimes significantly reduced color change times. Especially when using hot runner systems, the number of cleaning cycles can be reduced. [4] In addition, it is possible to inject the liquid colorant downstream into the plastic melt with appropriate dosing technology. This means that only part of the production line has to be flushed when changing colors, which saves a considerable amount of material and time. [6]
The production of the liquid colours takes place at room temperature. A maximum of 40 °C is achieved by shearing. This means that heat-sensitive pigments such as fluorescent or daylight pigments are not thermally damaged. Defect patterns such as black specks and streaks are reduced and rejects are minimized. [7] [8]
Liquid colors do not have to be pre-dried, which reduces energy costs and handling effort and also further reduces the thermal preload.
The coloring of bio-based plastics with liquid colors leads to an increase in characteristic values in the notched bar impact test. [4]
The disadvantages are the high cleaning effort without using suitable dosing equipment. When dosing in the feed zone, very high colouring concentrations are not possible, since above a certain colour dosing level, overlubrication of the plasticizing screw can occur system-related. [9] This means an excessive liquid film on the plasticizing screw, which hinders the uniform conveying of the polymer granulate. The maximum color dosage depends heavily on the polymer used (particle size, surface finish and surface energy), the machine configurations and the pigment load of the liquid color. [1] This can cause problems with very thin-walled parts that must be colored as opaque as possible, or even prevent coloring with liquid color altogether.
If the liquid colorants are not sufficiently stabilized, the colorants may settle. This can lead to uncontrolled flocculation, i.e. pigment particles are in direct contact with each other and can only be separated from each other by high shear forces. When suitable additives are used, pigment particles are connected to a network via additive molecules. Thus there is no direct pigment-pigment contact. Such flocculates can be destroyed by low shear forces, such as manual stirring. [10]
A set of primary colors or primary colours consists of colorants or colored lights that can be mixed in varying amounts to produce a gamut of colors. This is the essential method used to create the perception of a broad range of colors in, e.g., electronic displays, color printing, and paintings. Perceptions associated with a given combination of primary colors can be predicted by an appropriate mixing model that reflects the physics of how light interacts with physical media, and ultimately the retina.
Food coloring, or color additive, is any dye, pigment, or substance that imparts color when it is added to food or drink. They come in many forms consisting of liquids, powders, gels, and pastes. Food coloring is used in both commercial food production and domestic cooking. Food colorants are also used in a variety of non-food applications, including cosmetics, pharmaceuticals, home craft projects, and medical devices.
A colourant/colour additive or colorant/color additive is a substance that is added or applied in order to change the colour of a material or surface. Colourants can be used for many purposes including printing, painting, and for colouring many types of materials such as foods and plastics. Colourants work by absorbing varying amounts of light at different wavelengths of its spectrum, transmitting or reflecting the remaining light in straight lines or scattered.
Plastic welding is welding for semi-finished plastic materials, and is described in ISO 472 as a process of uniting softened surfaces of materials, generally with the aid of heat. Welding of thermoplastics is accomplished in three sequential stages, namely surface preparation, application of heat and pressure, and cooling. Numerous welding methods have been developed for the joining of semi-finished plastic materials. Based on the mechanism of heat generation at the welding interface, welding methods for thermoplastics can be classified as external and internal heating methods, as shown in Fig 1.
Carbon black is a material produced by the incomplete combustion of coal and coal tar, vegetable matter, or petroleum products, including fuel oil, fluid catalytic cracking tar, and ethylene cracking in a limited supply of air. Carbon black is a form of paracrystalline carbon that has a high surface-area-to-volume ratio, albeit lower than that of activated carbon. It is dissimilar to soot in its much higher surface-area-to-volume ratio and significantly lower polycyclic aromatic hydrocarbon (PAH) content. However, carbon black can be used as a model compound for diesel soot to better understand how diesel soot behaves under various reaction conditions as carbon black and diesel soot have some similar properties such as particle sizes, densities, and copolymer adsorption abilities that contribute to them having similar behaviours under various reactions such as oxidation experiments. Carbon black is used as a colorant and reinforcing filler in tires and other rubber products; pigment and wear protection additive in plastics, paints, and ink pigment. It is used in the EU as a food colorant when produced from vegetable matter (E153).
Although PET is used in several applications,, as of 2022 only bottles are collected at a substantial scale. The main motivations have been either cost reduction or recycle content of retail goods. An increasing amount is recycled back into bottles, the rest goes into fibres, film, thermoformed packaging and strapping. After sorting, cleaning and grinding, 'bottle flake' is obtained, which is then processed by either:
Wood-plastic composites (WPCs) are composite materials made of wood fiber/wood flour and thermoplastic(s) such as polythene (PE), polypropylene (PP), polyvinyl chloride (PVC), or polylactic acid (PLA).
Powder coating is a type of coating that is applied as a free-flowing, dry powder. Unlike conventional liquid paint which is delivered via an evaporating solvent, powder coating is typically applied electrostatically and then cured under heat or with ultraviolet light. The powder may be a thermoplastic or a thermoset polymer. It is usually used to create a hard finish that is tougher than conventional paint. Powder coating is mainly used for coating of metals, such as household appliances, aluminium extrusions, drum hardware, automobiles, and bicycle frames. Advancements in powder coating technology like UV-curable powder coatings allow for other materials such as plastics, composites, carbon fiber, and MDF to be powder coated due to the minimum heat and oven dwell time required to process these components.
An antistatic agent is a compound used for treatment of materials or their surfaces in order to reduce or eliminate buildup of static electricity. Static charge may be generated by the triboelectric effect or by a non-contact process using a high voltage power source. Static charge may be introduced on a surface as part of an in-mold label printing process.
Plastics extrusion is a high-volume manufacturing process in which raw plastic is melted and formed into a continuous profile. Extrusion produces items such as pipe/tubing, weatherstripping, fencing, deck railings, window frames, plastic films and sheeting, thermoplastic coatings, and wire insulation.
Filler materials are particles added to resin or binders that can improve specific properties, make the product cheaper, or a mixture of both. The two largest segments for filler material use is elastomers and plastics. Worldwide, more than 53 million tons of fillers are used every year in application areas such as paper, plastics, rubber, paints, coatings, adhesives, and sealants. As such, fillers, produced by more than 700 companies, rank among the world's major raw materials and are contained in a variety of goods for daily consumer needs. The top filler materials used are ground calcium carbonate (GCC), precipitated calcium carbonate (PCC), kaolin, talc, and carbon black. Filler materials can affect the tensile strength, toughness, heat resistance, color, clarity, etc. A good example of this is the addition of talc to polypropylene. Most of the filler materials used in plastics are mineral or glass based filler materials. Particulates and fibers are the main subgroups of filler materials. Particulates are small particles of filler that are mixed in the matrix where size and aspect ratio are important. Fibers are small circular strands that can be very long and have very high aspect ratios.
Plastics are a wide range of synthetic or semi-synthetic materials that use polymers as a main ingredient. Their plasticity makes it possible for plastics to be moulded, extruded or pressed into solid objects of various shapes. This adaptability, plus a wide range of other properties, such as being lightweight, durable, flexible, and inexpensive to produce, has led to its widespread use. Plastics typically are made through human industrial systems. Most modern plastics are derived from fossil fuel-based chemicals like natural gas or petroleum; however, recent industrial methods use variants made from renewable materials, such as corn or cotton derivatives.
A gravimetric blender is an item of industrial equipment used in the plastics industry to accurately weigh two or more components and then mix them together prior to processing in an injection molding machine, plastics extrusion, or blow moulding machine.
Masterbatch (MB) is a solid additive used for coloring or imparting other properties to plastic. Masterbatch is a concentrated mixture of pigments and/or additives that is manufactured by encapsulation during a heat process or twin screw extrusion into a carrier matrix resin, which is then cooled and further cut into a granular shape. Masterbatch allows the processor to color raw polymer economically.
Biodegradable additives are additives that enhance the biodegradation of polymers by allowing microorganisms to utilize the carbon within the polymer chain as a source of energy. Biodegradable additives attract microorganisms to the polymer through quorum sensing after biofilm creation on the plastic product. Additives are generally in masterbatch formation that use carrier resins such as polyethylene (PE), polypropylene (PP), polystyrene (PS) or polyethylene terephthalate (PET).
Americhem, Inc. is a global masterbatch manufacturer that specializes in custom color and additive masterbatches, with its global headquarters in Cuyahoga Falls, Ohio. The company manufactures a diverse range of single pigment dispersions, color and additive concentrates and custom compounds. A sister company, Infinity LTL Engineered Compounds, manufactures custom compounded engineered thermoplastics, and has locations in Swedesboro, New Jersey, and Morrisville, Pennsylvania. Vi-Chem, acquired in 2016, is a producer of PVC and elastomeric compounds.
Acrylonitrile styrene acrylate (ASA), also called acrylic styrene acrylonitrile, is an amorphous thermoplastic developed as an alternative to acrylonitrile butadiene styrene (ABS), but with improved weather resistance, and is widely used in the automotive industry. It is an acrylate rubber-modified styrene acrylonitrile copolymer. It is used for general prototyping in 3D printing, where its UV resistance and mechanical properties make it an excellent material for use in fused deposition modelling printers.
Plastic colorants are chemical compounds used to color plastic. Those compounds come in a form of dyes and pigments. The type of a colorant is chosen based on the type of a polymeric resin, that needs to be colored. Dyes are usually used with polycarbonates, polystyrene and acrylic polymers. Pigments are better suited for use with polyolefins.
Laser welding of polymers is a set of methods used to join polymeric components through the use of a laser. It can be performed using CO2 lasers, Nd:YAG lasers, Diode lasers and Fiber lasers.
Cartonplast is a trademark that was first given by Covema spa (Italy) in the early seventies to a specific model of extrusion line manufactured and sold world wide by the aforesaid.
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