For some resin or film products, their inherent properties do not meet the requirements of the required processing technology, and additives are needed to change their processability; for other materials, the processability is better, but the product performance cannot meet the requirements, so additives should be added to change the product performance.
Requirements of film for additives
Compatibility
If the compatibility is not good, it will cause the phenomenon of "migration", which is manifested as "sweating" in liquid additives and "frost spraying" in solid additives.
Sometimes in the film requirements are not too strict, can allow its lack of compatibility, such as filler and resin compatibility is not good. As long as the particle size of the film is small, it can still meet the basic requirements of the film properties. If it is treated with coupling agent or surfactant, its function can be better developed. However, there are some additives to improve the film surface properties, such as opening agent, antistatic agent, etc., which require it to have a little mobility to make it play a role on the surface of the film.
Durability
It is required that the additives exist in the film for a long time without or little loss, and the loss of additives mainly comes from three ways: volatilization, extraction and migration. This is mainly related to the molecular weight of the additives, the solubility in the medium and the solubility in the resin.
Processing conditions
Some resins have harsh processing conditions, such as high processing temperature, we should consider whether the selected additives will decompose and whether the additives have corrosive effect on the processing equipment.
Application of film
The films with different applications have different requirements on the odor, toxicity, weatherability and thermal properties of the additives. For example, the plastic bags used for food packaging are different from those used in general packaging due to their non-toxic requirements.
Synergism and antagonism in the coordination of auxiliaries
In the same resin system, some two kinds of additives will produce "synergistic effect". If they are not matched properly, some additives may produce "mutual antagonism", which will weaken the function of each auxiliary, or even make them lose their function. For example, the combination of carbon black and phenolic antioxidants will produce antagonism.
Additives that can change the performance of film packaging
Plasticizers and heat stabilizers
Plasticizers and heat stabilizers can improve the compatibility of film materials to a great extent.
Plasticizer, as the name implies, is to increase the plasticity of the material, on the one hand, increase the fluidity of the resin during molding, improve the processability, and on the other hand, increase the flexibility and elasticity of the film.
The heat stabilizer is mainly to improve the thermal stability of the resin.
Light stabilizer
When the polymer materials are exposed to sunlight, they will lose their properties, such as mechanical properties, brittle properties and light properties. In this complex damage process, ultraviolet radiation is the main reason for aging of polymer materials. It is mainly the result of the combined action of ultraviolet rays in sunlight and oxygen in the atmosphere on polymer macromolecules.
The effect of light stabilizer is as follows
It can effectively absorb the ultraviolet ray with the wavelength of 290 ~ 410nm, eliminate or weaken the ultraviolet ray, protect the polymer film from the damage of ultraviolet and oxygen, prolong the service life and improve the light resistance of the material. Since most of the light stabilizers can absorb ultraviolet light, they are also called ultraviolet absorbers.
The addition amount of light stabilizer:
According to the action mechanism of light stabilizers, they can be divided into light shielding agent (pigment), ultraviolet absorber, ultraviolet quenching agent and free radical trapping agent. These four modes of action constitute four levels of light stabilization.

After adding light stabilizer, although the amount of light stabilizer is very small, its anti-aging effect is very significant, generally only 0.1% ~ 0.5% of the weight of polymer is added.

Antioxidants
For most kinds of plastics, they are sensitive to oxidative degradation in the process of manufacturing, processing, storage and application. Oxygen penetration into plastic film can react with most polymers to cause degradation or crosslinking, thus changing the properties of materials. A small amount of oxygen can make the strength, appearance and properties of these polymer materials change dramatically. Under hot working and sunlight, the oxidation rate is faster. Therefore, the oxidation of polymers is usually divided into thermal oxidation and photooxidation. Finally, the result of this reaction is aging. If this kind of reaction is not stopped, the polymer can be oxidized quickly and lose its use value.
The stability of different plastics to oxygen is different, so some plastics do not need to add antioxidant. Some antioxidants must be added. The function of antioxidants is to capture the active free radicals and interrupt the chain reaction, so as to delay the oxidation process and speed of plastics.
Generally speaking, the protective effect of amine antioxidants is higher than that of phenols. However, amines are not suitable for light color, bright color and transparent films due to their discoloration in varying degrees under the action of light and oxygen, so they are seldom used in plastic films.
According to the antioxidant effect, antioxidants are divided into main antioxidant and auxiliary antioxidant. Aniline is mainly used in rubber products because of its good anti oxygen effect but high pollution; phenols are mainly used in plastic film because of its poor anti oxygen effect, low pollution and good comprehensive effect. Generally, mercaptans, thioesters and phosphites are classified as auxiliary antioxidants and used together with main antioxidants to produce synergistic effects and prolong the effectiveness of antioxidants.
lubricant
The polymer usually has a high viscosity after melting. In the process of processing, when the molten polymer passes through the narrow slot, gate and other channels, the polymer melt must have friction with the surface of the processing machine. These frictions will reduce the melt fluidity. At the same time, serious friction will make the surface of the film rough, lack of luster or flow lines. Therefore, it is necessary to add additives for improving lubricity, reducing friction and reducing interfacial adhesion.
In addition to improving the fluidity of lubricants, they can also be used as melting accelerators, anti adhesion and anti-static agents, and smooth agents.
The main function of external lubricant is to improve the friction between polymer melt and hot metal surface of processing equipment. It has poor compatibility with polymer and is easy to migrate from the melt to the outside.
The internal lubricant has good compatibility with polymer, which can reduce the cohesion of polymer molecules in the polymer, so as to improve the internal friction heat generation and melt fluidity of plastic melt.
In fact, each lubricant has the function of achieving a certain requirement. The internal and external lubrication always work together, but it is more prominent in a certain aspect. The same lubricant in different polymers or different processing conditions will show different lubrication effect, such as high temperature, high pressure, the internal lubricant will be squeezed out and become the external lubricant.
In the production of plastic film, we will encounter some adhesion phenomenon. For example, in the production of plastic film, the two films are not easy to separate, which brings difficulties to automatic high-speed packaging. In order to overcome it, a small amount of additives can be added to the resin to increase the external lubricity, which is generally called anti adhesion agent or smooth agent. In the molecular structure of general lubricants, there are two parts of long chain non-polar group and polar group. Their compatibility in different polymers is not the same, which shows different internal and external lubrication effects.
In extrusion molding, the fluidity can be improved, the adhesion between polymer material and barrel and die can be improved, and the retention can be prevented and reduced. In addition, it can improve the appearance and luster of the film. The amount of lubricant is generally 0.5% ~ 1%.
Attention should be paid to:
1. When the fluidity of polymer meets the needs of molding process, the effect of external lubrication is mainly considered to ensure the internal and external balance;
2. Whether the external lubrication is effective depends on whether it can form a complete liquid film on the plastic surface at the molding temperature. Therefore, the melting point of the external lubricant should be close to the molding temperature, but the difference between 10 ℃ and 30 ℃ can form a complete film;
3. The surface gravitation is small, the viscosity is small, the expansibility at the interface is good, and the interface layer is easy to form;
4. It has excellent heat resistance and chemical stability, does not decompose and volatilize in processing, does not corrode equipment, does not pollute film and has no toxicity.
Service characteristics of different types of lubricants:
Natural paraffin wax is often used for external lubrication, and can be used as a lubricant and release agent for various plastics. The general dosage is 0.2 ~ 1 phr, but its compatibility, thermal stability and dispersion are not very good, and the dosage should not be too large, so it is better to use it together with internal lubricant; while white oil is mostly used as internal lubricant of PVC and PS, with good lubricating performance and thermal stability, and the general dosage is 0.5phr. They are non-toxic and can be used in food packaging. Another kind of microcrystalline paraffin: it is also used as a lubricant in plastic processing, the dosage is 1 ~ 2phr, the thermal stability and lubricity are better than ordinary paraffin. Low molecular weight polymers are also widely used as lubricants, such as polyethylene wax and low molecular weight polypropylene, which have good internal and external lubricity and are nontoxic. Polyethylene wax is suitable for extrusion and calendering of PVC and other materials, and the dosage is generally 0.1 ~ 1 phr, which can improve the processing efficiency, prevent film adhesion, improve the dispersion of filler or pigment, and the compatibility and transparency are not very good.
Antifogging agent
Transparent plastic film, sheet or plate, in a humid environment, when the humidity reaches below the dew point, a layer of fine water droplets will condense on its surface, making the surface fuzzy and atomizing, and hindering the transmission of light waves. For example, when packaging products with film, the contents can not be seen due to fogging, and the generated fog drops are also easy to cause decay and damage of the contents.
Classification of antifogging agents:
? the built-in antifogging agent is added to the resin at the time of proportioning. Its characteristics are that it is not easy to lose and its efficiency is long-lasting, but it is difficult to obtain good antifogging property for polymers with high crystallinity;
? the external coating antifogging agent is applied to the surface of plastic film after being dissolved in organic solvent or water. It is easy to use and low cost, but it has poor durability and is easy to be washed off or wiped off. It can only be used when the internal antifogging agent is ineffective or does not require durability.
The effectiveness of antifogging agent can be divided into initial antifogging, long-term antifogging, low-temperature antifogging and high-temperature antifogging. It is difficult for one antifogging agent to have the four effects. It is often used in combination with several antifogging agents according to the requirements of film on antifogging effect.
The antifogging agent shall have the following properties:
1. It has high anti fogging efficiency, quick effect and good durability;
2. The thermal stability is good, and it is not easy to decompose by heating, and the decomposed products do not lead to the degradation of the polymer;
3. It has good compatibility with other auxiliaries and does not hinder the function of other auxiliaries;
4. It does not affect the transparency, electrical properties, adhesion, pollution resistance and other functions of the film.
Several typical antifogging agents:
The white wax of glycermonooleate can be used as an additive antifogging agent with good initial antifogging property and low temperature antifogging property. It is suitable for food packaging film. The general dosage of glycerin monooleate is 1 ~ 1.5 phr in polyethylene and 0.5 ~ 1 phr in polyolefin.
Sorbitol anhydride Monopalmitate is a yellow granular substance, which is an additive antifogging agent with rapid and lasting effect. It is a yellow granular solid with a melting point of about 60 ℃ and a long-lasting effect. It is commonly used in agricultural films and food packaging materials. Its dosage in polyvinyl chloride is generally 1.5 ~ 1.8 phr, and in polyvinyl acetate is 0.7 ~ 1 phr.
Polyethylene oxide (20) glycerol monostearate is also an internal antifogging agent, which takes effect very quickly and has good antifogging properties at early stage and low temperature. It is a light yellow liquid, but also has antistatic effect, suitable for food packaging film.
Dongguan Beite packaging materials Co., Ltd. - located in Dongguan City, a world famous manufacturing city, is a subsidiary company of Beite packaging (China) Co., Ltd
With an area of 6000 square meters, it is a flexible packaging enterprise integrating R & D, production and sales. It has a complete set of advanced production equipment in China
We provide customers with high-quality products and first-class service with the support of the humanized management system and a group of experienced technical personnel.
The company produces composite bags, roll film, fruit bags, aluminum foil bags, suction mouth bags, self-supporting bags, zipper bags, anti-static bags, special-shaped bags, etc., which are suitable for food, daily chemicals, and other special-shaped bags
Electronic, toys, medicine, cosmetics, industrial products and other industries of internal and external packaging.
We uphold the integrity of cooperation, good quality, thoughtful service business philosophy, the industry's recognition, products sold all over the world; welcome to call friends from all walks of life
Consulting, visiting our factory for investigation and guidance and business negotiation.