5 key points for a comprehensive understanding of masterbatch

Masterbatch is a high-efficiency and high-concentration color resin coloring mixture made of one or more components of a large number of pigments or dyes and carrier resins through strict processing and dispersion processes. The domestic demand for color masterbatch is huge and the development potential is huge. Therefore, the research and development of color masterbatch production technology is necessary.

Let's take a comprehensive look at the color masterbatch, including common classification, basic components, color masterbatch production process and equipment, and finally look at the application and future development of color masterbatch.

1. Masterbatch classification

01. According to different uses

Masterbatch is divided into injection masterbatch, blow molding masterbatch, spinning masterbatch, etc., and each variety can be divided into different grades.

Advanced injection masterbatch is used in cosmetic packaging boxes, toys, electrical enclosures and other advanced products; ordinary injection masterbatch is used in general daily plastic products, industrial containers, etc. Advanced blow molding masterbatch is used for blow molding coloring of ultra-thin products.

Ordinary blow molding masterbatch is used for blow molding coloring of general packaging bags and woven bags. Spinning masterbatch is used for spinning and coloring of textile fibers. The masterbatch pigment has fine particle size, high concentration, strong tinting strength, and good heat resistance and light resistance. Low-grade masterbatches are used to manufacture low-grade products that do not require high color quality.

02. According to different carriers

Divided into PE, PP, PVC, PS, ABS, EVA, PC, PET, PEK, phenolic resin, epoxy resin, acrylic resin, unsaturated polyester resin, polyurethane, polyamide, fluororesin masterbatch, etc.

03. According to the different functions

Divided into anti-static, flame retardant, anti-aging, antibacterial, whitening and brightening, anti-reflection, weather resistance, extinction, pearlescent, imitation marble pattern (flow pattern), wood grain masterbatch, etc.

04. According to the user's usage

Divided into general color masterbatch and special color masterbatch. Low-melting PE masterbatches are often used as general-purpose masterbatches for coloring other resins other than carrier resins. The vast majority of formal color masterbatch enterprises in the world generally do not produce general-purpose color masterbatches. The general-purpose color masterbatches have a very narrow general range, and have poor technical indicators and economic benefits.

Universal masterbatches show different colors in different plastics, and the coloring effect is less predictable. The general color masterbatch affects the strength of the product, and the product is easily deformed and twisted, which is more obvious for engineering plastics. For universal color masterbatch, higher heat-resistant grade pigments are used, which is costly and wasteful.

In the process of product processing, the special color masterbatch has significant advantages such as high concentration, good dispersion and cleanliness. The heat-resistant grade of the special color masterbatch is generally compatible with the plastic used for the product. It can be used with confidence under normal temperature. It will only cause different degrees of discoloration when the temperature exceeds the normal range and the downtime is too long.

05. According to the color

Divided into black, white, yellow, green, red, orange, brown, blue, silver, gold, purple, gray, pink masterbatch, etc.

2. Basic ingredients of masterbatch raw materials

01. Pigment

Pigment is the basic coloring component. It is best to pre-treat the surface of its fine particles with resin to prevent mutual flocculation and make it easy to disperse. In order to coat and mix evenly, a solvent that has affinity for the pigment and can dissolve the resin, such as o-dichlorobenzene, chlorobenzene, and xylene, is used. In the case where the resin is dissolved, the dispersion treatment of the pigment is performed, and then the solvent is recovered or removed.

02. Carrier

The carrier is the matrix of the masterbatch. At present, special color masterbatches use the same resin as the carrier, which can ensure the compatibility of the color masterbatch and the colored resin, which is conducive to better dispersion of the pigment. There are many types of carrier resins, such as polyethylene, random polypropylene, poly-1-butene, low molecular weight polypropylene, etc.

For polyolefin masterbatch, LLDPE or LDPE with high melt index is generally used as the carrier resin, which has good processing fluidity. It is blended with the colored resin to adjust the viscosity of the system to infiltrate and disperse the pigment, minimize the amount of dispersant, and achieve a good dispersion effect even without dispersant, and ensure that the performance of the colored product does not decline. .

03. Dispersant

The dispersant wets and coats the pigment, so that the pigment can be dispersed evenly in the carrier and no longer agglomerate. Its melting point should be lower than that of the resin, and it has good compatibility with the resin and good affinity with the pigment. There are many types of dispersants, such as low molecular weight polyethylene wax, polyester, stearate, white oil, oxidized low molecular weight polyethylene and so on.

04. Additives

In addition to coloring, the masterbatch also adds flame retardants, antioxidants, antistatic agents, light stabilizers, etc., according to various requirements of users, and has various functions at the same time. Sometimes the user does not require it, but the masterbatch company will also suggest adding some additives according to the needs of the product.

3. Masterbatch production process

The production process of masterbatch is strict and can be divided into dry process and wet process.

01. Wet process

The masterbatch is made by grinding, phase inversion, washing, drying and granulation. When grinding and processing pigments, a series of technical tests are required, such as the determination of the fineness of the grinding slurry, diffusion properties, solid content, etc. The wet process has four methods: ink method, flushing method, kneading method and metal soap method.

(1) Ink method

The ink method is the production method of ink color paste. The ingredients are milled by three rolls to coat the surface of the pigment with a low molecular protective layer. The ground ink paste is mixed with the carrier resin, plasticized with a two-roll plasticizer, and finally pelletized by a single-screw or twin-screw extruder.

(2) flushing method

The rinsing method is that the pigment, water and dispersant are sanded to make the particles less than 1 μm, the pigment is transferred into the oil phase by the phase transfer method, evaporated, concentrated and dried. After adding the carrier, the color masterbatch is obtained by extrusion and granulation. The phase inversion requires an organic solvent and a corresponding solvent recovery device, the operation is complicated, and the processing difficulty is increased.

(3) Kneading method

The kneading method is that after mixing the pigment and the oily carrier, the pigment is washed from the water phase into the oil phase by kneading. The oily carrier coats the surface of the pigment to stabilize the dispersion of the pigment and prevent agglomeration. Then extrude and granulate to obtain color masterbatch.

(4) Metal soap method

After the pigment is ground, the particle size reaches about 1 μm, and the soap solution is added at a certain temperature to evenly wet the surface of the pigment particles to form a saponified solution protective layer (such as magnesium stearate), which will not cause flocculation and maintain a certain fineness. Then add the carrier, stir and mix at a high speed, and extrude and granulate to obtain color masterbatch.

02. Dry process

Some enterprises prepare pre-dispersed pigments by themselves when producing high-grade color masterbatches, and then use dry process to granulate them. The production conditions of color masterbatch show a variety of options according to the requirements of the product. High agitation + single screw, high agitation + twin screw is the most common production process. In order to improve the dispersibility of pigments, some companies grind the carrier resin into powder.

Internal mixer + single screw, internal mixer + twin screw are also the technology used to produce high-quality masterbatch. At present, color masterbatch color measurement and color matching technology are more popular, and more high-performance spectrophotometers are introduced to assist in color matching.

4. Production equipment

Masterbatch production equipment includes grinding equipment, high and low speed kneaders, mixers, extrusion granulation equipment, etc. Grinding equipment includes sand mill, cone mill, colloid mill, high shear disperser, etc.

The kneader is exhausted by vacuuming, decompressing, extracting volatiles and dehydrating; In thermal conditions, heat transfer oil, steam heating or water cooling; The discharging method is turning over the cylinder, discharging under the valve and discharging by screw; The kneading paddle adopts the frequency conversion governor to adjust the speed.

The mixer is divided into two types: open type rubber mixer and closed type rubber mixer. Extrusion granulation equipment includes single-screw extruder, twin-screw extruder (Parallel co-rotating twin-screw extruder, Parallel counter-rotating twin-screw extruder, Conical co-rotating twin-screw extruder, Conical counter-rotating twin-screw extruder), multi-screw extruder and non-screw extruder.

5. Application and Development of Color Masterbatch

Masterbatches are used in a wide range of applications, mainly serving the plastics industry, rubber industry and fiber industry.

01. Plastic

The pigment content of color masterbatch for plastics is usually between 10% and 20%. When used, it can be added to the plastic to be colored at a ratio of 1:10 to 1:20 to achieve the coloring resin or product with the designed pigment concentration. The masterbatch plastic and the coloring plastic can be of the same variety or compatible with other plastic varieties.

The masterbatch can be a single color variety or a variety of pigment color matching varieties. The selection of pigments should meet the processing conditions and various quality requirements of plastic products. The application of color masterbatch in the field of plastic products is relatively mature and common. 85% of the colorants in plastic products use color masterbatch, which is easy to use and has no dust flying problem of dry powder pigments. It completely solves the disadvantages of product color point and pigment inconsistency caused by poor pigment dispersion.

Polyethylene, polypropylene, polyvinyl chloride, plexiglass, nylon, polycarbonate, celluloid, phenolic plastics, epoxy resins, amino plastics and other varieties have corresponding masterbatches.

In the plastics industry, the market demand for color masterbatch is concentrated in engineering plastics products (home appliances, automobiles), architectural plastics products (pipes, profiles), agricultural film products, plastic packaging products, etc. Home appliances, automobiles, and construction plastic products industries have high requirements for color masterbatches and a large amount of them, which has a driving effect on the development of color masterbatches.

02. Rubber

The preparation method of color masterbatch for rubber is similar to that of plastic color masterbatch. The selected pigments, plasticizers and synthetic resins should be the varieties that match with the rubber. Pigments are mainly used as reinforcing agents and colorants in rubber. The black pigment is mainly carbon black; White pigments include zinc oxide, titanium dioxide, calcium carbonate, etc.; other pigments include iron oxide, chrome yellow, ultramarine, chrome oxide green, lightfast yellow, benzidine yellow, phthalocyanine green, lake red C, dioxazine violet, etc.

Carbon black is widely used in wires, cables and tires, and the traditional carbon black is all changed to carbon black masterbatch, and its dosage occupies the first position in all color masterbatches. At present, domestic and foreign carbon black enterprises can not fully produce carbon black masterbatch. It is necessary to conduct research on tire carbon black masterbatch to improve the performance of its products, and the market potential is huge.

When processing rubber, the use of rubber masterbatch can avoid dust flying caused by powdery pigments and improve the operating environment. The color masterbatch is easy to disperse evenly, so that the color of rubber products is uniform and the actual consumption of pigments is reduced.

The amount of rubber coloring pigments is usually between 0.5% and 2%, and the amount of inorganic pigments is slightly more. This kind of processing pigment should be matched with the rubber processing technology and quality to meet the needs of the rubber industry. Pigment companies need to do a lot of applied research work to develop and popularize the varieties of such processed pigments.

03. Fiber

Fiber dope coloring is when the fiber is spinning, the color masterbatch is directly added to the fiber viscose or fiber resin, so that the pigment appears in the spinning, which is called internal fiber coloring.

Compared with traditional dyeing, fiber dope dyeing processes resins and masterbatches into colored fibers and directly uses them for spinning, omitting the post-dyeing and finishing process. It has the advantages of small investment, energy saving, no three wastes and low coloring cost, currently accounting for about 5%.

Pigments for fiber coloring masterbatches require bright color, good dispersibility, good thermal stability, light resistance, solvent resistance, acid and alkali resistance, bleach resistance, insoluble in water, and inorganic or organic pigments can be selected.

Nanjing Haisi Extrusion supply professional twin screw extruder for masterbatch making.

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