Firstly, we analyze this problem from the performance of paperboard, and discuss the four most commonly used paperboards in the industry: single bleached sulfate paperboard, coated unbleached kraft paper, coated recycled paperboard and folded carton paperboard.Select Cardboard For Flexographic Packaging

Single bleached phosphate (SBS) paperboard

      SBS paperboard has always been the most expensive kind of paperboard, which is made from bleached chemical pulp of broad-leaved wood (deciduous forest). Select Cardboard For Flexographic Packaging

       These short and fine fibers make the surface of the paperboard very smooth, which is also the guarantee of high-quality printing effect.Select Cardboard For Flexographic Packaging

      Therefore, SBS paperboard is widely used in high-end market, such as cosmetics packaging, pharmaceutical packaging, audio-visual products packaging and tobacco packaging.Select Cardboard For Flexographic Packaging

      At present, 28 paper machines in the world produce SBS paperboard, with a production capacity of about 5 million tons per year, accounting for 15% of the world’s supply of coated paperboard. Select Cardboard For Flexographic Packaging

     Because North America is rich in fast-growing deciduous forests, which can ensure sufficient supply of broad-leaved wood fiber, most SBS paperboard in the world is produced in North America.Select Cardboard For Flexographic Packaging

     All North American factories use fourdrinier paperboard machine to produce single-layer SBS paperboard, that is, single-layer fiber with a thickness of 10-24pts, and then coated on one or both sides.Select Cardboard For Flexographic Packaging

       The stiffness of SBS paperboard can ensure good printing, folding and concave convex performance. Printers are very satisfied with the printability, uniformity and chip free performance of SBS paperboard.Select Cardboard For Flexographic Packaging

Coated unbleached kraft paper (Cuk)

      Coated unbleached kraft paper is also known as coated primary kraft paper (CNK) or single unbleached kraft board (SUS). The price of Cuk board is generally lower than that of SBS board.Select Cardboard For Flexographic Packaging

     The scale of this kind of paperboard is slightly small. Select Cardboard For Flexographic Packaging

      There are 12 paper machines in the world, with an annual output of 3.5 million tons, accounting for 10% of the total supply of coated paperboard in the world.Select Cardboard For Flexographic Packaging

      Cuk paperboard is made by fourdrinier paperboard paper machine. It uses unbleached chemical pulp and is composed of two or more layers of fibers. Select Cardboard For Flexographic Packaging

     The fibers used in Cuk paperboard are mainly coniferous forest fibers. This kind of fiber has very high strength and is more suitable for durable packaging. Select Cardboard For Flexographic Packaging

     The outermost layer of Cuk paperboard adopts a thin layer of broad-leaved forest fiber vermicelli and multi-layer coating to improve the surface 

      smoothness, which can achieve high printing quality through a variety of printing methods, including flexographic printing.Select Cardboard For Flexographic Packaging

      The stiffness of Cuk paperboard is similar to that of SBS paperboard. Both types of paperboard are considered by the U.S. Food and Drug Administration (FDA) as materials that can be in direct contact with food.Select Cardboard For Flexographic Packaging

      Cuk paperboard is generally 14-30pts thick, especially suitable for packaging frozen food. Repeated freezing / thawing will reduce the performance of the paperboard and reduce its barrier and mechanical protection. Select Cardboard For Flexographic Packaging

     Cuk paperboard with high wet strength is more suitable for the packaging of bottles and cans that need to be frozen.Select Cardboard For Flexographic Packaging

Coated recycled paperboard (CRB).Select Cardboard For Flexographic Packaging

     CRB paperboard is also known as clay coated newsprint, double-layer paperboard, gray bottom white paperboard, etc. Select Cardboard For Flexographic Packaging

     CRB paperboard is the largest paperboard in the industry. Select Cardboard For Flexographic Packaging

     The annual output of 265 paper machines in the world reaches 18 million tons, accounting for 55% of the global supply. CRB paperboard and paper machines have different designs. Select Cardboard For Flexographic Packaging

      Most of them are old and slow drum machines. The stiffness of the produced paperboard is high, and the stiffness of the longitudinal strand is 3-4 times that of the horizontal strand. Select Cardboard For Flexographic Packaging

     This also means that the elasticity of this kind of paperboard is slightly poor in flexographic printing.Select Cardboard For Flexographic Packaging

      Some recycled paperboard is made by compound machine or new fourdrinier paperboard paper machine, and its stiffness is similar to that of original paperboard.Select Cardboard For Flexographic Packaging

      CRB paperboard is made by mixing various recycled fibers and then coating them in multiple layers. The general thickness is 14-40pts. The main raw materials used include:Select Cardboard For Flexographic Packaging

     recycled waste newspapers, old corrugated boxes, recycled SBS paperboard, Cuk paperboard and office waste paper. Select Cardboard For Flexographic Packaging

     CRB paperboard is a multi-layer structure, which can be divided into outer veneer, paperboard core layer, back veneer or bottom veneer.Select Cardboard For Flexographic Packaging

      According to different physical properties, the structure of each layer of paperboard can be the same material or different materials, and the back can be brown, white or semi bleached pulp. Select Cardboard For Flexographic Packaging

       The outermost surface is the layer of fiber below the coating, usually recycled bleached hardwood fiber.Select Cardboard For Flexographic Packaging

     Because the waste paper recycling channels used to produce recycled paperboard are different and the quality is also different, the quality of recycled paperboard is not as stable as that of original paperboard. Select Cardboard For Flexographic Packaging

      In the process of papermaking, although the main impurities such as plastic, wax, metal and rubber have been removed, it will inevitably affect the strength, cleanliness and uniformity of paperboard.Select Cardboard For Flexographic Packaging

      CRB paperboard has a low price and is usually only used for packaging with low requirements for printing quality, strength and cleanliness.Select Cardboard For Flexographic Packaging

Folding carton board (FBB)

      This type of paperboard is widely used in Europe and other regions, but it is not very common in North America. FBB paperboard accounts for 20% of the global paperboard supply, and 47 paper machines in the world produce 6.5 million tons per year.Select Cardboard For Flexographic Packaging

       FBB paperboard is mostly made of mechanical pulp with high pulp yield.Select Cardboard For Flexographic Packaging

       This means that the lignin in the fiber is not removed during the pulping process, and finally a slightly yellow pulp is made. Select Cardboard For Flexographic Packaging

      From an economic point of view, paper makers prefer mechanical pulp because the yield of mechanical pulp is twice that of chemical pulp.Select Cardboard For Flexographic Packaging

Of course, this is at the cost of strength. The internal bonding strength of FBB paperboard is low (such as tearing degree, bonding between fiber layers, etc.). According to the quality and type of coating used, a high-quality printing surface can be obtained.Select Cardboard For Flexographic Packaging

      The thickness of FBB paperboard is 14-28pts, which can be used instead of SBS paperboard in areas where SBS paperboard is not very common. Select Cardboard For Flexographic Packaging

     It is suitable for packaging with higher requirements for printing quality and stiffness and lower requirements for durability, such as cosmetic packaging, Select Cardboard For Flexographic Packaging

    pharmaceutical packaging, etc. Due to the high lignin content, FBB paperboard is not suitable for long-term outdoor use, because the quality of paperboard exposed to strong light will decline rapidly.Select Cardboard For Flexographic Packaging

Paperboard Printing Performance requirements

      Let’s see which type of paperboard has the best quality after flexographic printing. The performance parameters to be analyzed here include smoothness, absorbability, uniform and smooth surface, cleanliness, 

       surface strength, internal adhesion, dimensional stability and colorfastness. Finally, let’s look at the cost of various types of paperboard.Select Cardboard For Flexographic Packaging

        Smoothness today’s flexographic printing press adopts closed ink supply system, ceramic anilox roller and photosensitive resin plate, which can print finer and higher resolution pictures and texts than before.Select Cardboard For Flexographic Packaging

      Flexographic printing can use FM screening or hybrid screening technology for illustrations, and the effect can be comparable to offset printing. Select Cardboard For Flexographic Packaging

      The macro smoothness (Sheffield smoothness tester can be used) and micro smoothness (Parker printing surface roughness tester can be used) of paperboard are closely related to flexographic printing. Select Cardboard For Flexographic Packaging

     SBS paperboard and some advanced FBB paperboard have high smoothness. The smoothness of Cuk paperboard is also good, while CRB paperboard is relatively poor.Select Cardboard For Flexographic Packaging

      Absorption is the same as offset printing. In order to ensure the accuracy and fidelity of printing, flexographic printing needs to control the absorption of ink. Select Cardboard For Flexographic Packaging

      The ideal printing surface is porous, which can make water penetrate through, but keep the pigment particles on the surface. Ink with high pigment content requires less surface absorption.Select Cardboard For Flexographic Packaging

      SBS paperboard and some FBB paperboard are suitable for absorption.Select Cardboard For Flexographic Packaging

       Surface uniformity and stability flexographic printing is characterized by light pressure printing. In order to obtain the best image resolution, we must control the dot increase by controlling the printing pressure. Select Cardboard For Flexographic Packaging

       Although dot gain is also affected by anilox roller, printing plate, printing model, parameter setting and ink type (solvent ink or water-based ink), the uniformity of paperboard thickness is also very important.Select Cardboard For Flexographic Packaging

      In this regard, the best paperboard is SBS paperboard, followed by Cuk paperboard and some FBB paperboard.Select Cardboard For Flexographic Packaging

      Cleanliness the flexographic plate is more vulnerable to impurities or other dirty spots than in the past, such as the impression caused by paper wool. Select Cardboard For Flexographic Packaging

      Therefore, the surface strength of the paperboard should be higher and cleaner, so as to reduce the fiber falling off when the paper is bent around the plate cylinder. SBS paperboard and Cuk paperboard are relatively clean.Select Cardboard For Flexographic Packaging

      A recent progress in surface strength flexographic printing is the development of ink with high pigment content. The ink layer printed with this ink is thinner than before, which can greatly reduce the use of ink.Select Cardboard For Flexographic Packaging

      On the other hand, the thin printing ink layer also puts forward requirements for the surface strength of the paperboard. Select Cardboard For Flexographic Packaging

      The surface strength of the paperboard must be large enough to prevent the ink layer from being brought up from the paperboard surface during the printing process. Cuk paperboard, SBS paperboard and some FBB paperboard have high surface strength.Select Cardboard For Flexographic Packaging

       Because the speed of the printing press is very fast, the requirements for paperboard should not only have high surface strength, but also have high internal adhesion, so as to prevent delamination of paperboard in high-speed printing. Select Cardboard For Flexographic Packaging

     The board with good internal adhesion is Cuk board.Select Cardboard For Flexographic Packaging

      Dimensional stability plant fibers are very sensitive to moisture. Fortunately, web materials are not as prone to paper feeding and feeding problems as sheet fed paper in printing and processing. Select Cardboard For Flexographic Packaging

     However, the dimensional stability of materials is very important to obtain good printing quality. In order to maintain dimensional stability, the paperboard shall not change in size due to transverse shrinkage or elongate due to printing and processing.Select Cardboard For Flexographic Packaging

      Relatively speaking, the base pulp paper is generally not very sensitive to moisture, so the dimensional stability is also higher. SBS paperboard, FBB paperboard and Cuk paperboard have high dimensional stability. Select Cardboard For Flexographic Packaging

      Non fading paperboard coating technology has been very mature. Select Cardboard For Flexographic Packaging

     Non fading pigments, synthetic resin adhesives and special additives have been widely used. Select Cardboard For Flexographic Packaging

     Even so, bleached fibers may turn yellow when exposed to UV light.Select Cardboard For Flexographic Packaging

      SBS paperboard and FBB paperboard are most likely to turn yellow over time. However, Cuk paperboard has advantages in this regard.Select Cardboard For Flexographic Packaging

      If we want to say the relationship between paperboard price and printability, there is no doubt that the price of paperboard with good printing performance will be higher.Select Cardboard For Flexographic Packaging

       Although CRB paperboard has the advantage of low price, its quality and printing performance are often not very good. Low price paperboard will reduce production efficiency and instability of printing quality.Select Cardboard For Flexographic Packaging

      Uncoated paperboard uses flexographic printing. Although uncoated kraft paper and recycled paperboard can be printed, the effect is not very ideal. Select Cardboard For Flexographic Packaging

     If the paperboard is uncoated, the surface smoothness can be improved by selecting short and fine fibers, calendering and surface finishing.Select Cardboard For Flexographic Packaging

       In addition, in order to avoid ink infiltration and excessive dot increase, the internal sizing of paperboard is also very important to control the ink absorption.Select Cardboard For Flexographic Packaging

Make the right choice.Select Cardboard For Flexographic Packaging

       Finally, it should be said that various types of coated paperboard are constantly improving the printability to meet the process requirements of common printing methods. It should be emphasized that flexographic printing can meet the requirements of various paperboards. Select Cardboard For Flexographic Packaging

      Of course, if the printing quality is required to be higher, the corresponding cost will be higher. No matter how you choose, you have to choose between printing quality, packaging durability and cost.Select Cardboard For Flexographic Packaging