Stretch film is widely used because of its light weight, thin shape, low price, easy to carry and change shape. Especially in the aspects of food and general merchandise packaging, agricultural masking materials, the application quantity and quality of stretch film have been improved continuously, and the functional requirements of new stretch film materials have been added constantly. To improve the quality and function of the stretch film, only relying on the modification of the resin matrix and the improvement of the molding skills can not meet the needs of the market. Adding various functional auxiliaries has become a simple and efficient way to complete the function of the stretch film.
– Biaxial stretching assistant
Biaxially oriented polypropylene (BOPP), polyester (BOPET) and nylon (BOPA) are widely used in stretch film packaging. The traditional PVC stretch film is widely used in the preservation of various vegetables and fruits, long-term frozen food packaging, microwave baking food packaging, electronic components packaging and conductive stretch film. In addition, the output value of products such as cast polypropylene (CPP) and cast polyethylene (CPE) is also large. The auxiliary products cooperating with the above-mentioned packaging stretch film materials mainly include antistatic agents, smooth and anti adhesion agents, stiffening agents, thermal stabilizers, antioxidants and isolators, etc.
– Antistatic agent for stretch film
Industrial antistatic agents are mainly the single compound or compound of nonionic and ionic surfactants. According to whether the hydrophilic group in the molecule can be ionized, it can be divided into ionic type and non-ionic type, while ionic type can be divided into cation type, anion type and amphoteric type. The anti-static principle is to use its hydrophilic base to absorb water vapor in the air on the surface of the plastic, or to form a conductive layer on the surface to reduce the surface resistance.
Cationic antistatic agent has excellent anti-static function, but it usually has poor thermal stability. It is easy to differentiate and cause color change under high temperature processing conditions. It is usually only used in PVC finished products. The anionic antistatic agent can not be used in the finished stretch film because of its influence on the transparency.
The non-ionic antistatic agent has the characteristics of low toxicity, good thermal stability, not easy to cause plastic aging and so on, which makes it become the most important internal antistatic agent in packaging materials. The main types are fatty acid polyol ester, fatty acid, alcohol, amine ethylene oxide adduct.
In the packaging data, the function of antistatic agent should not only be investigated, but also the function of finished product. For this reason, the key technology of antistatic agent development will focus on the structural design and compatibility investigation of various surfactants. At that time, the development of a series of specialized products was a primary development direction of antistatic agents.
Anti adhesion agent for stretch film
The faster the processing speed is, the more likely static electricity will be generated due to the conflict. The simpler the adhesion between the stretched film (plastic finished products) will severely prevent the extrusion of the high speed line. The better the transparency of the stretched film is, the higher the processing temperature is, the simpler the agglomeration and adhesion will be. As a result, high-efficiency smooth agent and anti adhesion agent play an abnormal primary role in plastic production and automatic packaging.
There are many kinds of smooth agents in China, such as amines (oleic amines and Erucic amines), soaps (calcium stearate, etc.) and organosilicon (silicone). The latter is liquid, which is inconvenient to add and use, and expensive. Although soap is cheap, its function is not ideal, and it can not be used in middle and high-grade products. Most of the smooth agents in the package stretch film are amine compounds, such as oleic acid amine used in LDPE stretch film and erucic acid amine used in PP stretch film.
Anti adhesion agent, also known as opening agent, is usually inorganic fine particles, such as silica. However, the traditional inorganic opening agent often affects the haze because of its refractive index different from the base resin. However, the newly developed polymer particles as the opening agents deal with this problem.
–Tensile film stiffening agent
The stiffening agent for packaging materials, also known as stiffening agent, is mainly used in the BOPP heat shrinkable film for tobacco, to improve the stiffness of BOPP stretch film, improve the appearance of the packaged goods, so as to improve the value of the goods. Now, to measure the quality of the stiffening agent is mainly to measure the improvement of the elastic modulus of the tensile film through investigation. As for the BOPP heat shrinkable film for smoke, the manufacturer’s functional requirements for the stiffening agent also include: it shall not affect the haze and other mechanical functions of the stretched film, reduce the heat sealing temperature, etc.
Now, the R & D and development of stiffening agents mainly focus on two areas. One is to select the polymer with rigid chain segment and PP as alloy to improve the elastic modulus of BOPP. The commonly used polymers are: polycyclopentadiene, etc. The other way is to increase the rigidity according to the principle of promoting nucleation. After the existence of fine particles, it shows heterogeneous nucleation, promotes and improves the crystallization of PP, makes its grains uniform and refined, so as to improve the rigidity of the finished product. Under the influence of this idea, the use of organic nucleating agent to complete the application of stiffening will be carried out.
-Tensile film thermal stabilizer
The thermal stabilizers used in PVC packaging materials will concentrate on the development of non-toxic thermal stabilizers to replace heavy metals such as cadmium and lead.
The development of organic thermal stabilizers is one of the most important aspects. Organic Zion stabilizers have significant advantages in transparency and color stability. The development of organotin products will focus on the research and development of methyl tin and sulfur-free organotin. At present, the domestic production of organotin thermal stabilizers has taken shape.
With the further request of environmental protection, the country is continuously restricting the use of organotin, which makes the calcium / zinc thermal stabilizer gradually become the mainstream of non-toxic PVC thermal stabilizer. With the development of domestic calcium / zinc stabilizer technology, its thermal stability efficiency has been improved. High efficiency calcium / zinc thermal stabilizer has been continuously announced, which can replace some or all of the organic tin or barium cadmium zinc thermal stabilizer.
The new green thermal stabilizer – organic thermal stabilizer is the final development direction of non-toxic thermal stabilizer for PVC packaging materials.
-Stretch film antioxidant
Due to the special nature of the packaging materials, such as packaged food, cosmetics, etc., the requirements for the cleanliness of antioxidants are very high. Although many common antioxidants have been tested for toxicity, they are still worrying. The new antioxidant vitamin E has excellent anti-oxidation effect, has no toxic side effects, and is loved by the professional packaging products.
The packaging materials are close to the usual days, and the consumption is endless. The recycling and reuse of plastic packaging wastes is even more outstanding. This has created a great need for various new types of plastic-recycling additives. In the meantime, the special antioxidant can avoid the disadvantages of yellowing of the resin and greatly reduced strength during repeated processing, which is conducive to the recovery operation. However, packaging materials, especially stretch film materials, are often composites of various resins. The usual hindered phenol and phosphite cooperative systems are less than satisfactory for the thermal oxidation resistance of the hybrid system. The development of antioxidants or processing stabilizer system additives to recover packaging materials is becoming a hot topic in this category.
-Stretch film isolating agent
In order to avoid the passage of various gases through the stretch film and extend the storage period of the packaging materials, the need for the new type of insulated stretch film is constantly added. Obtaining new high-isolation packaging materials In addition to the use of excellent insulation and the use of SiOx steam for surface deposition, the addition of a certain amount of isolating agent is also a primary means. At present, the insulating agent is mainly composed of inorganic fillers, such as layered hydrotalcite and sericite, and its shape is often in the form of a sheet, which is dispersed in layers in the finished product, and the gas is dispersed in the resin by the addition of gas and water vapor to reduce the gas. Transmittance rate. With the increasing research on nano data at home and abroad, the use of nano data in packaging materials, especially for the development of stretch film with outstanding isolation has been gradually developed.
Shenzhen World Packing Industrial Ltd
Stretch Film & Packing Tape Specialist , Top China manufacturer
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