Product Categories Of Additives For Plastic Film
Additives for plastic film plastic additives are chemicals that are added to improve the processing and performance of resins. Usually used plastic additives have a dozen, with the increase of plastic varieties, the use of expansion and processing technology progress, the type of auxiliaries and varieties are increasing.
In the plastic film processing and use of the process to add plastic additives. Because some resins or thin film products have inherent properties that do not meet the required processing requirements, adding additives is only necessary to change the processing properties, and some materials have better processing performance, and the product performance is not up to our requirements, this also need to add additives to change the performance of its products. These two roles are, of course, mutually reinforcing, sometimes in order to achieve both of these goals.
Here first introduced to be able to change the performance of plastic packaging film additives.
General requirements for Auxiliaries
Generally speaking, the auxiliaries only have good compatibility with the resin, in order to make the assistant long-term, stable and evenly exist in the film, effectively play its function. If the compatibility is not good, it is easy to occur "migration" phenomenon. Performance in the liquid additives for "sweating", manifested in the solid additives for the "spray" phenomenon. But sometimes when the film requirements are not very strict, can still allow the lack of compatibility, such as filler and resin between the compatibility is not good, but as long as the particle size is small, still can basically meet the performance requirements of the film, of course, if the coupling agent or surfactant treatment, it can give full play to its function. But some additives to improve the surface properties of the film, such as opening agent, antistatic agent, etc. require it to have a little mobility, so that it plays a role on the surface of the film.
Durability is required for long-term presence in the film and basic not or very little loss, and the loss of additives mainly through three ways: evaporation, extraction and migration. This is mainly related to the molecular weight of the additive, solubility in the medium and solubility in the resin.
Adaptability to processing conditions
Some resin processing conditions are more stringent, such as high processing temperature, at this time should consider whether the selected auxiliaries will be decomposed, additives on the processing equipment has no corrosive effect.
The restriction of the use of thin films to auxiliaries
The different uses of the film on the additive odor, toxicity, weather resistance, thermal performance and so on have certain requirements. For example, the plastic bags for food, because the requirements of non-toxic, so the use of auxiliaries and general packaging used in plastic bags are different additives.
Synergistic action and phase resistance in auxiliary coordination
In the same resin system, some of the two auxiliaries will produce a "synergistic effect", that is, than the individual use of a certain auxiliary, play a large number of functions. However, if the combination of improper, some auxiliaries may produce "phase resistance", which will weaken the function of each auxiliary, or even make some kind of auxiliaries lose their role, this should pay special attention to, such as carbon black and amine or phenolic antioxidants and use will have a confrontation effect. Common performance auxiliaries for plastic packaging films
Plasticizers and Heat Stabilizers
Plasticizer, as the name implies is to increase the plasticity of the material, that is added to the resin, on the one hand, the resin in the formation of increased fluidity, improve the processing performance, on the other hand, can be made after the film flexibility and flexibility to increase the material.
Heat stabilizer is a additive which is added for the purpose of improving the thermal stability of the resin. Mainly used in the processing of polyvinyl chloride and vinyl chloride copolymer.
Polymer materials in the sun, light and high-energy radiation exposure, will quickly occur aging, yellow, brittle, cracked, surface loss of luster, mechanical properties and electrical properties are greatly reduced, and even eventually lost value. In this complex destructive process, ultraviolet radiation is the main reason for the aging effect of polymer materials. This is mainly the result of the combination of ultraviolet rays in sunlight and oxygen in the atmosphere on polymer macromolecules.
In order to protect the polymer film from the damage of ultraviolet rays and oxygen, prolong their service life, add the light stabilizer to the plastic material so that they can absorb the ultraviolet energy in the resin and convert the absorbed energy into harmless form. To inhibit or weaken the effect of light degradation, improve the light resistance of materials. Because most of the light stabilizer can absorb ultraviolet light, it is also called light stabilizer as ultraviolet absorbent. The evaluation of an ultraviolet absorbent is good or bad, to take into account the efficiency, processing, price, non-toxic, etc., can not emphasize a single one or two effects. These conditions are combined to:
n can effectively absorb the ultraviolet rays with 290~410nm wavelength and absorb the bandwidth, which can effectively eliminate or weaken the damage effect of ultraviolet rays on polymers, but has no effect on the other physicochemical properties of polymers.
n itself has good stability, ultraviolet radiation long-term exposure, absorption capacity does not decline;
N Thermal stability is good, in the process of molding and the use of processes not due to heat and failure, do not change color, not affect the processing properties of polymers;
N and polymer compatibility, in the processing and use of the process is not separated, migration, not easy to be water and solvent extraction, not easy to evaporate;
n non-toxic or low toxicity;
n chemical stability, does not react with other components in the material to damage the material properties;
n Absorption of visible light is low, does not color, does not change color;
n cheap, easy to manufacture and rich in source.
According to the mechanism of light stabilizer, it can be divided into four kinds: ① light shielding agent (pigment), ② ultraviolet absorbent, ③ ultraviolet quenching agent, ④ free radical capture agent. These four modes of action constitute the light stabilization in the gradual deepening of the four levels, each level can inhibit the damage of ultraviolet radiation on the polymer body, in the specific design, is a level or at each level of protection, depending on the requirements of the film and the use of the environment. After adding the light stabilizer, although the dosage is very small, the effect of preventing aging is very significant, generally only need to add polymer weight 0.1%~0.5%.
Many commonly used light stabilizers, according to their different mechanisms and chemical composition, mainly include: ① O-hydroxy benzophenone (such as uv-9,uv-531), ② benzene and triazole (such as Uv-p, UV-327, UV-326, etc.), ② salicylate (bad, TBS, etc.); ④ Triazine class ⑤ substituted acrylonitrile class ⑥ organic nickel complexes; ⑦ hindered amine. The efficiency of these types of absorbents is the best for the Benzotriazole and Triazine classes.
For most plastics varieties, in their manufacture, processing, storage and application process, the oxidation degradation of a certain degree of sensitivity, oxygen infiltration in the plastic film almost with most polymers can react and lead to degradation or cross-linking, thereby altering the properties of the material. A small amount of oxygen can cause drastic changes in the strength, appearance and properties of these polymeric materials. The oxidation rate is faster under hot processing and sunlight. Therefore, the oxidation of polymers is usually divided into thermal oxidation and light oxidation. The final result of this reaction is the aging of the performance. Such reactions, if not prevented, can quickly oxidize the polymer and lose value. Different plastics have different oxygen stability, so there is no need to add antioxidants in some plastics. Some must add antioxidant, the role of antioxidant is to capture the active free radicals, so that the chain reaction interruption, the purpose is to delay the oxidation of plastic process and speed. According to the action mechanism of antioxidant, it is effective for all plastics.
The chemical structure of antioxidant can be divided into: 1. phenols, including: Single phenol, bisphenol, polyphenols, polyphenols, hydroquinone, bisphenol 2. Amine, including: naphthalene Amine, diphenylamine, benzene diamine, quinoline derivative, in addition, phosphite, sulfur ester and other kinds of other species.
In the above categories, phenolic, amine is the main antioxidant, about 90% of the total, in general, the protective effect of amine antioxidants than phenol, but due to the amine in the light, oxygen, different degrees of discoloration, not suitable for light, color and transparent film, so the application in plastic film less.
According to the antioxidant effect, the antioxidant is divided into main antioxidant and auxiliary antioxidant. Aniline has good anti-oxygen effect, but the pollution is large, mainly used in rubber products, phenolic antioxidant effect is slightly poor, but less pollution, comprehensive effect is good, more used in plastic film. Mercaptan or Thio ester and phosphite are usually classified as auxiliary antioxidants and used with the main antioxidant to produce synergistic effect and prolong the effectiveness of antioxidant.
At present, the production and research of antioxidants towards high efficiency, low toxicity, inexpensive direction. Therefore, phenolic antioxidants will gradually exceed the status of amine antioxidants. The compatibility of antioxidants with polyolefin plastics can be improved by replacing some phenyl with alkyl groups. Increasing the molecular weight of antioxidants is also an important way to improve the durability of antioxidants. Most antioxidants are easy to migrate, so that the polymer loses protection, the molecular weight of antioxidants is large enough, the possibility of migration decreased, it can improve the effective life of antioxidants.
The polymers usually have higher viscosity after melting, in the process of processing, the molten polymer through the narrow slit, gate, and other flow channel, polymers must be with the processing of mechanical surface friction, some friction in the processing of polymers is very unfavorable, these friction to reduce melt fluidity, At the same time, serious friction will make the surface of the film become coarse, lack of luster or flow patterns. Therefore, it is necessary to add additives to improve lubrication, reduce friction and reduce interfacial adhesion properties. This is the lubricant. In addition to improving the flow of lubricants, but also can be a melting agent, adhesion and anti-static agents, such as the role of the slip agent.
Lubricants can be divided into two kinds of external lubricants and internal lubricants, the role of external lubricants is mainly to improve the polymer melt and the processing equipment of hot metal surface friction. It is less compatible with polymers and is easy to migrate outward from the molten body, so it can form a thin layer of lubrication on the interface between the plastic melt and the metal. The internal lubricant has good compatibility with polymer, which plays a role in reducing the cohesion of polymer molecules, thereby improving the fluidity of inner friction heat and melt in plastic melt. The common external lubricant is stearic acid and its salts; the inner lubricant is a low molecular weight polymer. Some lubricants have other functions. In fact, each lubricant has the function of achieving a certain requirement, which is always combined with internal and external lubrication, but it is more prominent in some aspect. The same lubricant in different polymers or different processing conditions will show different lubrication, such as high temperature, high pressure, the internal lubricant will be squeezed out to become an external lubricant.
In the production of plastic film, we will also encounter some adhesion phenomenon, such as in the production of plastic film, two layers of film is not easy to separate, which brings difficulties to automatic high-speed packaging. In order to overcome it, add a small amount of additives to the resin to increase the surface lubricity, in order to increase the external lubrication, commonly known as the anti-adhesion agent or a slip agent. The molecular structure of general lubricants, there will be a long chain of non-polar and polar base two parts, their compatibility in different polymers is not the same, so as to show the role of different internal and external lubrication. According to chemical composition, commonly used lubricants can be divided into the following categories: fatty acids and esters, fatty acid amide, metal soaps, hydrocarbons, silicone compounds.
Lubricants in the actual processing of plastics have a variety of performance, such as in mixing, calendering processing, can prevent polymer bonded barrel, inhibit friction heat, reduce mixing torque and load, so as to prevent the thermal degradation of polymer materials. In extrusion molding, it can improve the fluidity, improve the adhesion between polymer material and barrel and die, prevent and reduce the retention of the material. In addition, it can improve the appearance and luster of the film.
From the point of view of processing machinery, in the mixing, calendering, plastic and other molding processing, external lubricants have an important role in extrusion, injection molding, the internal lubricant is more effective.
The dosage of lubricant is generally in 0.5%~1%, should notice when choosing:
The flow performance of N-Polymer has satisfied the need of molding process, the role of external lubrication is mainly considered to ensure internal and external balance;
n external lubrication is effective, should it be in the molding temperature, in the plastic surface of the formation of a complete liquid film, so the melting point of the lubricant should be close to the molding temperature, but to the difference between 10℃~30℃ to form a complete film;
n does not reduce the mechanical strength and other physical properties of the polymer.
When selecting lubricants in production, the following requirements should be met:
n lubrication efficiency is high and durable;
N and resin compatibility of the size of moderate, internal and external lubrication balance, not spray, not easy scaling;
n Surface gravity Small, viscosity small, at the interface of the expansion of good, easy to form interface layer;
N as far as possible not to reduce the polymer's various fine properties, does not affect the plastic two times processing performance;
n its heat resistance and chemical stability is excellent, in the process does not decompose, not volatile;
n non-corrosive equipment, no fouling film, no toxicity.
However, the simple use of a lubricant, often difficult to achieve the goal, a combination of several lubricants to use, in recent years, the development of composite lubrication, in the selection, you can look at the role of lubricant in many ways.
Commonly used lubricants are stearic acid, butyl stearate, oil amide, B-supported double hard amide and so on.
Many paraffin substances can be used as lubricants, such as natural paraffin, liquid paraffin (white oil), microcrystalline paraffin, but the role is different. Natural paraffin is more used as external lubrication, can be used as a variety of plastic lubricants, release agent, the general dosage 0.2~1PHR, but its compatibility, thermal stability and dispersibility is not very good, the dosage can not be too large, preferably with the internal lubricant and use, and white oil used as PVC, PS of the internal lubricant, good lubrication, thermal stability is also very good, General dosage 0.5PHR. They are all drug-free and can be used in food packaging. Another kind of microcrystalline wax: in plastic processing It is also used as lubricants, the dosage of 1~2phr, thermal stability and lubrication than ordinary paraffin better.
Low molecular weight polymers are also widely used as lubricants, such as polyethylene wax, low molecular weight polypropylene, internal and external lubrication is good, and non-toxic. Polyethylene wax is suitable for plastic extrusion of PVC and other materials, calendering processing, the dosage is generally 0.1~1phr, can improve processing efficiency, prevent film adhesion, improve the dispersion of fillers or pigments, compatibility and transparency is not very good; irregular structure low molecular weight polypropylene can be used as a hard pvc,pe lubricant, excellent performance, Can improve the dispersibility of other auxiliaries, dosage in 0.05~0.5phr.