Application of additive technology in packaging and printing industry

In the plastics and inks manufacturing process, in addition to the matrix resin as the main raw material, it is necessary to add some substances in the resin that can improve the use properties or processing characteristics of the plastics and inks. Such substances are called additives for plastics or inks. Or additives. With the wide application of high-tech processing technology in the plastics, packaging and ink industries, additive technology as an important part of the technological innovation of the packaging and printing industry has gradually become the focus of innovation in the industry.

First, the classification of additives

1. Classification by purpose of modification

(1) Improve the mechanical physical properties of plastics such as the use of flame retardants to improve heat resistance; add reinforcing agents, fillers to improve the strength and rigidity of the material; add stabilizers, antioxidants, UV absorbers, etc. to improve durability and weather resistance Add lubricants, surface treatment agents, antistatic agents to improve the material's breathability, antistatic properties and so on.

(2) Improve the processing performance of plastics and inks by using lubricants or processing aids to improve the processing performance of plastics and meet the high-speed production requirements; use dispersants, defoamers, antistatic agents to improve the performance of inks.

(3) Improve the film forming properties of the ink. For example, the coupling agent is beneficial to the affinity of the pigment, the filler and the resin, and improves the adhesion and strength of the ink.

(4) To improve environmental performance The use of polymer degradation agents, decomposers, etc. to facilitate the recycling of waste is conducive to environmental protection. The use of non-toxic compounding agents makes plastic materials sanitary and non-toxic.

2. Classification by modification function

(1) To improve the stability of plastics and inks, using heat stabilizers, antioxidants, UV absorbers, anti-mold agents, etc.;

(2) To make plastic materials soft and lightweight, using plasticizers, foaming agents, etc.;

(3) Adding lubricants, processing aids, plasticizers, etc. to improve the processing performance of plastics;

(4) Add antistatic agents to improve the antistatic properties of plastics and inks; add coloring agents to make the material easy to color;

(5) To improve the surface properties of plastics, add lubricants, brighteners, brighteners, anti-blocking agents, slip agents, etc.;

Second, the performance requirements of additives

1. compatibility

Only additives with good compatibility between plastics and ink resins can enable additives to exist in products for a long period of time, stably and evenly, and exert their effects. If the compatibility between the two is poor, the material is prone to “precipitate” or “fight”, which has an adverse effect on the quality of post-processing processes such as printing, dry recycling, extrusion compounding and packaged products.

2. Durability

It is required that the additive be present in the plastic product or ink system as long as possible. Usually the loss of additives in the product is mainly through the three ways of volatilization, precipitation and migration, and is related to the size of the additive molecular weight, the solubility in the medium and the solubility in the plastic or ink resin. Poor durability also affects the quality of the reprocessing process and the quality of the packaged product.

3. Synergy

In the same plastic or ink resin system, if the additives used have good compatibility, they can work together to make the additive system play a long-lasting and effective role. Conversely, if the additives used are poorly coordinated, "antagonism" will occur between the additives of different systems, weakening the function of the additives and even rendering them ineffective. The interaction and coordination between additives must also consider the effect of additives on the processing technology and product quality. If the amount of smoothing contained in the polyethylene particles is too high, although it is advantageous for the blown film process, due to the precipitation of the slip agent, the peel strength of the dry composite is adversely affected.

4. Adaptive

Some of the plastic resin processing conditions are more demanding, requiring that the additive must have good compatibility with it. For example, when the plastic resin has a relatively high glass transition temperature, melting temperature, and the like, the processing temperature is also high, and the temperature adaptability of the additive must be considered when selecting the plastic additive. Whether it will be decomposed or deteriorated during processing; whether the plastic additive has a corrosive effect on extrusion, blow molding equipment, etc. In addition, the scope of use of packaging materials, the use of the environment on the performance of additives such as electrical properties, thermal properties, weather resistance, toxicity, odor, etc. also have certain requirements and limitations. Such as food, medicine, washing cosmetics, seeds and other products packaging, use non-toxic, odorless additives; pharmaceuticals, chemical products, pesticides and other packaging, to use good compatibility with the packaging products additives.

Third, the significance of additive technology for packaging and printing industry

1. Improve the processing and performance of plastics

Additive technology can effectively improve the processing properties of plastics, the mechanical properties of the film (such as shrinkage, rigidity, etc.), electrical properties (such as charge mobility, antistatic properties), optical properties (such as gloss, haze, etc.), weatherability Sex (anti-oxidation, anti-ultraviolet, high and low temperature suitability), etc., as well as the use of packaging materials. For example, in the production process of film and packaging bags, the surface performance of the film - friction coefficient is an important technical indicator. The coefficient of friction of the film is related to the type of additive (mainly anti-blocking agent), the amount of addition, the particle size, the shape, the dispersibility, and the degree of treatment thereof. For example, SiO2, TiO2, CaCO3, AL2O3, MgO, etc. are commonly used as additive for the biaxially stretched polyester film. As the added amount increases, the surface roughness of the film increases and the friction coefficient decreases. The coefficient of friction of the film is reduced to a value in the range of 0.3 to 0.4, and the binding force between the ink and the aluminum layer and the plastic film can be enhanced during the printing and aluminizing process. In order to meet the requirements of high-speed automatic filling machines, some packaging bags should have a certain smoothness on the inner surface of the packaging bag. The smoothness of the film is generally obtained by adding a certain amount of a slip agent such as oleic amide or the like to the inner layer material such as polyethylene particles. Due to the poor compatibility of oleic acid amide and polyethylene, its molecules can easily migrate to the surface of the film, forming a weak interface layer. If the amount of slip agent is too high, the interfacial layer will weaken the adhesion between the ink, the adhesive and the film surface, and affect the quality of the printing and dry reprocessing products. It is generally required that the coefficient of kinetic friction of the inner surface of the polyethylene film be in the range of 0.2 to 0.4. When blowing polyethylene film, adding a very small amount of low-molecular-weight fluoropolymer can effectively improve the processing and film-forming performance of linear low-density polyethylene (LLDPE) and metallocene-catalyzed polyethylene (mPE), and reduce the The viscosity at high temperature and high shear state enhances the self-cleaning property of the melt and reduces the friction between the melt and the screw, barrel, and die (lip); in particular, the surface quality of the film is significantly improved. Antistatic agents can improve the electrical properties of plastic films, enhance the charge mobility, reduce the surface electrostatic charge, facilitate the high-speed processing of plastic films during printing, compounding, etc., improve the efficiency of the process of filling powder products and the packaging bags. Sealing strength. Additives in the process of high-temperature mixing, rapid shear processing, it is easy to produce volatile substances, so that the packaging material odor. Therefore, additives should be selected according to the requirements of the packaging materials used for packaging materials.

2. Give more functionality to plastic materials

The addition of a tackifier to the polyethylene resin can increase the surface tackiness of the film to produce a stretch film. A rust preventive film is prepared by adding a gas phase rust inhibitor to the polyethylene resin to provide a vapor phase rust prevention function, and a vapor phase rust prevention effect is exerted on the packaged metal product. In particular, the addition of degradation accelerators such as biodegradants, photodegradants, and thermal oxygen degradants to plastic packaging materials can effectively reduce the environmental pollution caused by plastic waste, and the social benefits are obvious.

3. Meaning of ink processing and use

Ink is used as an organic system composed of pigments, additives, binders, fillers, and solvents, and other chemical substances of various types and properties. It is necessary to increase the compatibility between various substances and improve the activity of pigments and fillers to make inks. Good performance, good printability, such as consistent color, good gloss, good ink film strength, abrasion resistance, anti-oxidation, etc., the role of additives is particularly important. Although the additive amount of the ink is small, it has an important influence on the viscosity, dryness, and color of the ink. There are many types of additives used in inks, including plasticizers, quick drying agents, slow drying agents, and the like. The chemisorption and physical entanglement of the binder in the ink is more pronounced. The binder facilitates the affinity between pigments, binders and fillers in the printing ink system, improves the adhesion and mechanical strength of the ink, improves the degree of branching of the ink system and reduces the thickness of the ink film, and prevents the printing product from floating. , flowers and other phenomena; put an end to the printing process knife wire, paste quality accidents such as; paste to extend the storage period and so on. Antistatic agents used in inks can improve the antistatic properties of inks, increase the speed of printing lines, and eliminate various types of print quality problems caused by static electricity. The additive and its content should be selected according to the basic properties of the printed substrate such as electrical properties, printability, process conditions, including differences in ambient temperature, humidity, and the like. If the ambient humidity is high, the ink film is not easy to dry under high printing speed conditions, and the film is prone to blocking after printing, the quick-drying agent should be properly added, and the content of the oxidation promoter in the ink should be reduced; otherwise, if the environment is relatively When dry, slow-drying agents should be added appropriately.

No additive can satisfy all conditions such as matrix resin, process conditions, material properties, and technical requirements. In practice, it is often necessary to scientifically select and optimize various additives so that a variety of additives work synergistically. Processing, but also to obtain a more excellent overall performance. In particular, as environmental protection has become increasingly popular, domestic packaging and printing companies are keen to innovate, strengthen the development and application of additive technology that promotes degradable, economical and environmental protection, and promote the industrialization of green packaging.

Reprinted from: China Ink Web