Main technical characteristics of synthetic paper

The main technical characteristics of synthetic paper for packaging

synthetic paper with polyolefin as the main material appeared at the end of the 20th century. Because it has two properties of paper and plastic, it can replace natural paper in many special fields with the advantages of light weight and good rigidity

with the rapid development of human civilization, the full use of environmental resources has caused environmental changes and destruction, which has affected human life. Although the emergence and promotion of synthetic paper cannot change this situation, it is, after all, a material that can alleviate environmental damage

synthetic paper has a development history of more than 30 years abroad, and has achieved early and rapid development in the United States, Japan and other developed countries. The raw material source and production process of natural fiber paper have caused great changes and damage to the environment. With the strengthening of global environmental protection awareness, new synthetic paper continues to appear, and its application scope is also expanding. The sales volume of global synthetic paper is growing at a rate of 10% every year, and the pace of synthetic paper replacing fiber paper is accelerating

according to the prediction of China Paper Association, by 2010, China will consume 70million tons of paper and paperboard every year since the end of 2014. Two thirds of the demand for paper in China is for packaging materials and one third for printing. Even if 5% of the printing and packaging paper is replaced by synthetic paper, its demand is also very considerable

China's synthetic paper started late, the market development is insufficient, and the technology still needs to be further improved. At present, the annual national consumption is 30000-40000 tons, mainly imported, and basically polypropylene synthetic paper, which is used for clothing bags, handbags, woven bags, offset printing, silk printing, advertising spray painting, books, printing trademarks, etc., of which advertising spray painting accounts for 40%, printing trademarks account for 15%, woven bags, offset printing, silk printing account for 10%, handbags, clothing bags account for 10%, books account for 5%. According to the thickness specification, the consumption of 40~50 microns accounts for 30%, the consumption of 90~150 microns accounts for 40%, and the consumption of other thicknesses accounts for 30%

the company has been committed to the development, promotion and application of synthetic paper. Now let's talk about some main technical characteristics of synthetic paper:

first, the characteristics of synthetic paper

1. Environmental protection: the source of raw materials and production process of polypropylene synthetic paper will not cause damage to the environment. The products can be recycled and reused. Even if they are incinerated, they will not produce toxic gases and cause secondary public hazards, which meets the requirements of modern environmental protection

2. Superior performance than ordinary paper: synthetic paper has the characteristics of high strength, tear resistance, perforation resistance, wear resistance, folding resistance, moisture resistance, moth resistance, etc

3. It is more widely used than ordinary paper: synthetic paper has excellent water resistance, which makes it especially suitable for outdoor advertising. Synthetic paper can be used in a dust-free room because it does not generate dust and does not shed hair. It can be in direct contact with food

4. Superior processing performance can adopt cutting, die cutting, embossing, bronzing, drilling, hot folding, bonding and other return methods

II. Production methods of synthetic paper

up to now, the main production methods of synthetic paper include calendering, tape casting, film blowing and biaxial stretching. The main manufacturers are: yvpo in Japan, Nanya in Taiwan, China, and Priya in France. Only a few domestic enterprises can produce, and the quality is relatively inferior and unstable. The following is an introduction to several production methods:

1. Calendering method

its equipment is mainly made in Italy to produce PP based synthetic paper. That is, through batching, mixing, internal mixing, extruding, refining to calendering. Slitting into synthetic paper products, the key equipment is the extruder produced in Italy, which is completed at one time and carried out continuously, with high efficiency and good quality. The disadvantage of calendering process is that the process is complex. It is generally used to produce synthetic paper products above 0.1mm. The proportion of products is large, and the equipment is expensive, but the product surface is smooth, which is suitable for printing high-grade samples and book covers. 2. Casting method

the mixing, internal mixing, mixing and other processes of synthetic paper produced by casting method are similar to those of calendering, except that the calender is replaced by the casting machine. The characteristics of casting method are that there is a large speed difference between the extrusion speed of die head and the rotation of casting roller, and the speed difference is different. How to do on-site fault inspection for the synthetic paper thickness pressure testing machine produced is also different during construction. Unidirectional tension is formed between the meniscus extruded by die head and the cold roller, The tape casting method can produce synthetic paper of various thicknesses. However, the molecular chain distribution in synthetic paper is unidirectional, so the longitudinal, transverse and physical properties of synthetic paper products are quite different, which is a major disadvantage of cast synthetic paper. The specific gravity of tape casting method is 1g/cm sup3; Left and right, mainly used for printing. Like the calendering method, PP is also the base material of the cast synthetic paper. The deformation of the product is slightly larger, but the rigidity and toughness are better

3. Film blowing method

the material used in the production of synthetic paper by film blowing method is HDPE, which is different from PP substrate by calendering and tape casting method. In foreign countries, three-layer coextrusion equipment is mostly used in the production of synthetic paper by film blowing method, and internal cooling device, bubble film diameter, bubble film thickness detection and closed-loop control system are applied to ensure the uniformity of thickness of synthetic paper. The film blowing process realizes vertical and partial horizontal stretching, and the process equipment is relatively simple. German Alpine company first introduced the single-layer film blowing method to produce synthetic paper, using HDPE and masterbatch as raw materials

4. Biaxial stretching method

Formosa Plastics Co., Ltd. has introduced biaxial stretching pearlescent paper in recent years. Its base material is also pp. the mixing of raw materials for biaxial stretching method is basically the same as calendering and tape casting methods, but the equipment used is a biaxial stretching machine. In the biaxial stretching process, the vertical and horizontal distribution of plastic molecular chains is relatively consistent, so the vertical and horizontal physical and mechanical properties of synthetic paper are basically the same. In the biaxial stretching process, some small gaps will be formed between the base plastic and the filler CaCO3, thus reducing the proportion and cost of synthetic paper. Due to the refraction effect of these small gaps on light, the synthetic paper produced has a good appearance and has been widely used in packaging, printing, advertising and other fields. Although the equipment of biaxial stretching synthetic paper is expensive, and the process and formula technology are also complex, its wide application is still limited. However, its products are widely used, and it will be the mainstream of synthetic paper development. At present, the synthetic paper produced by domestic manufacturers Guangdong Huaye, Jiangsu Zhongda and Guangdong Shunde Deguan adopts this method, which is still a cutting-edge packaging processing technology in the international packaging industry

5. Other production processes of synthetic paper

DuPont has successfully developed the production process of non-woven paper. DuPont is one of the largest non-woven production companies. DuPont extends its production process of non-woven fabrics to the production process of synthetic paper, even though the base material of synthetic paper is polypropylene, which is melted, spun, formed, extruded, and finally produced into non-woven synthetic paper. Non woven synthetic paper is woven with plastic fibers, so it has high capillary effect, more paper characteristics, light weight, strong permeability, good physical and mechanical properties, good coloring strength, low deformation. In addition to the application scope of general synthetic paper, it can also be widely used in furniture packaging, decoration and other industries. However, the price of non-woven synthetic paper is quite expensive, the production process and equipment are very complex, and the cost is high, which limits its wide application

III. equipment characteristics of biaxial tensile synthetic paper

the width of biaxial tensile synthetic paper is currently more than 4 meters, and the maximum range is more than 8 meters. The production line speed is high, and the line speed of some varieties can be as high as more than 300 meters. The whole line has a high degree of automation. The control systems of temperature, speed, pressure, tension, thickness control, etc. in the production process, that is, in the initial 3MS, are all centralized digital control

the equipment investment of biaxial tensile synthetic paper is large, but the products produced by this method are widely used, and a variety of products can be developed according to different uses to adapt to the printing or packaging field

the equipment for producing biaxial tensile synthetic paper is basically modified on the basis of BOPP equipment to adapt to the production of synthetic paper. In order to fully reflect the plastic characteristics of synthetic paper and the printing characteristics of paper, and produce synthetic paper with better performance, the performance requirements of the equipment will be higher

1. The feeding and batching system should be flexible in conversion, accurate in measurement, evenly stirred, free of dead corners, and fully discharged

2. The extrusion system needs to add a special exhaust device to improve the exhaust capacity, the plasticization needs to be sufficient, the extrusion pressure needs to be high and stable, the material temperature rise and overheating needs to be low, and the temperature control of the barrel pipe must be accurate and sensitive

3. The die head must be multi-layer synthesis, and the lamination must be tight, uniform and smooth

4. The vertical and horizontal stretching machine needs accurate speed control and high stretching driving capacity

5. The surface treatment device should reach a high level

6. The tension and speed control accuracy of the winding system is required to be higher

IV. material characteristics

biaxial tensile synthetic paper generally has a three-layer structure, and different material properties can be selected to meet different needs and application fields

surface materials need to meet people's sensory requirements for traditional paper, as well as various printing requirements, requiring high ink absorption performance

the surface material can also be adjusted according to the different use requirements of different customers to meet the special requirements of synthetic paper in different application fields, and more fully reflect the advantages of synthetic paper and different fiber paper. Such as developing heat sealable synthetic paper, in mold label paper, etc

by adding functional masterbatch, the core material can reduce its density, reduce the cost, or greatly improve the strength to adapt to special application fields. It can also add anti-aging agent to prolong the service life and reduce the use cost of customers

replacing paper with plastic is the development goal of synthetic paper, improving quality is the key, and reducing cost is the foundation

v. application of synthetic paper

because PP synthetic paper has the characteristics of both plastic and paper, it is widely used in many aspects, mainly in the following three aspects:

1. High quality printing. Such as posters, pictorials, pictures, maps, calendars, books, etc. Especially in water-resistant printing newspapers and periodicals, advertisements outside the factory, etc., it is more organized

2. Packaging purpose. Such as handbags, packaging boxes, drug packaging, cosmetics packaging, food packaging, industrial product packaging, etc

3. Special purpose. Such as film labels, pressure-sensitive labels, thermal labels, paper for banknotes, color image paper, tracing drawings for CAD, relative error of industrial 4 indication ± 0.5% (level 0.5), recording paper for industrial computers and instruments, express envelopes, clocks, plates, paper fans, umbrellas, paper caps for tourism and other tourism publicity products

after all, synthetic paper is still not out of the category of plastic, and has more prominent advantages compared with fiber paper, such as new heat sealable synthetic paper packaging

simple packaging and environmental protection are the direction in the future. At present, the usable packaging in the market is made of BOPP film after printing or paper after casting a layer of CPP. This is due to the material itself

1. Plastic materials have low surface energy and poor surface printing performance

2. The adhesion performance cannot meet the requirements (2n/15cm). For the above reasons, it is beneficial to develop and produce disposable heat sealing packaging materials in various senses. The material is required to be formed at one time, with good surface printing performance and good heat sealing performance. As the production process of compounding and casting is omitted, there is no intermediate production link, which greatly shortens the production cycle and reduces production personnel. It can save storage and warehouse area. Fundamentally eliminate the problem of residual solvents, through the formulation of