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The research progress about Packaging film smooth and adhesion agent friction resistance control
Release time2014-9-1  viewed673
 
Slip friction control agent
Fatty acid substrate of ammonia slip agents
Added to the polymer between the ammonia slip agents and slip agents interaction
No migratory slip agents and specialized formula
Between the thin film layer anti-blocking agent
Cost-effective inorganic anti-blocking agent
High mobility organic anti-blocking agent
in conclusion
Slip friction control agent
Slippery agent by reducing the friction between the film, the film with the device and makes the downstream processing and packaging operations become convenient and easy. Slippery agent performance is static or dynamic coefficient of friction (static or kinetic Coefficient of Friction, COF) to assay. COF is a dimensionless number, which represents the sliding resistance between two surfaces in contact with each other, which is added to the value equal to one divided by the minimum vertical surface to promote the role of the force required to slide between two surfaces in contact surface force on.
Min / COF = vertical sliding action between the force required to urge the two surfaces in contact surface force
ASTM D 1894-73 is used to determine the plastic film between a standard test method for coefficient of friction COF. Generally, when the friction coefficient is greater than 0.50, it can be considered a non-slip surface; when the friction coefficient is less than 0.20, it is considered a high-slip surface can be used for jarring.
 
Many types of slip agents, including traditional ammonia slip agents and the newly specialized non-migratory slip agent. Before and after the completion of rolling, specialized non-migratory slip agent can be achieved at higher temperatures, with better reliability and stability requirements COF values. Slip agents may be used as suitable for different diffusion rates, end-use temperature, as well as different masterbatch formulation matrix resin, and can be added to different printing inks.
Fatty acid substrate of ammonia slip agents
Conventional type of slip agents is based on the fatty acid amide (primary amides, secondary amides, bis amide) synthesis. Since these materials in the polymer is not completely dissolved, whereby they migrate to the surface and is coated on the surface of the film which will reduce the friction of the surface. An important factor in the choice of ammonia slip agents, to be considered is the effect of reducing agent slip coefficient of friction COF areas, temperature stability and migration rates. Select the amino compound, the matrix polymer, slip agent concentration and temperature will affect the rate of migration. And because more and more polymers are processed at higher temperatures, the heat oxidation stability slippery agent has also become an increasingly important factor. Oxidative degradation behavior of slip agent can lead to performance loss slippery agent, discoloration, stank like. The ammonia compounds having a high thermal stability also less likely to be volatile, and even at elevated processing temperatures can also remain in the polymer.
Primary amides slippery agent: The most widely used is oleic acid amide and erucic acid amide of unsaturated primary amide slippery agent. Such slippery agent has a relatively small molecular weight, can quickly migrate to the polymer surface, having a low coefficient of friction COF value added at low rates, and the price of such slippery agent is also relatively cheaper . Erucamide is extracted from a non-animal fats out, compared with oleic acid amide has good thermal stability. And because it has a higher melting point, higher heat resistance and can be performed at a higher processing temperature processing of important properties, erucamide is gradually replacing oleic acid amide, and has a wider range of applications.
 
Secondary amides and bis amide slippery agent: Compared with primary amides slippery agent, the ammonia compounds having a higher molecular weight has a low migration rate, so that the COF value is more easily controlled, and such smooth agents are likely to be applied to multi-layer film structure to limit the effects of interlayer slip to one of them. For example, similar to palm oil-based amide (XVIII-9-enyl palmitic acid amide) and stearic acid erucamide such secondary amide slippery agent, the migration will occur in the polypropylene copolymer surface, but migration does not occur in the core layer of polypropylene homopolymer. Compared with primary amides slippery agent, secondary amide slippery agent and bis amide slippery agent can also have lower volatility and better thermal stability. This makes secondary amide slippery agent and bis amide slippery agent and more useful in terms of process engineering at higher temperature conditions in the film casting. In the printing and sealing of such secondary operations, the impact of secondary amide slippery agent and bis amide slip agents often generate less than primary amide slippery agent.
Added to the polymer between the ammonia slip agents and slip agents interaction
Ammonia slippery agent class is affected by many factors:
1. Slip concentration: For a given slip agent, the diffusion rate increases with increasing concentration of slip agent in the polymer increases.
2. Resin Type: slip agent having a lower migration rate in the crystalline resin. For example, high density polyethylene (HSPE) and polypropylene (PP) in the slippery agent migration rate lower than the corresponding values ​​in the low-density polyethylene (LDPE) in. Similar to the EVA (ethylene ethyl acrylate) resin is a polar functional group and slip agents react with each other to reduce its rate of migration. Similar to metallocene LLDPE (mLLDPE) the height of such an amorphous polymer and polymer binder, in order to achieve low adhesion and have less amorphous structure of the same polymer the value of the coefficient of friction COF is necessary to apply a higher load slippage.
3. Other Additives: As an antistatic agent, anti-fogging agents and other additives can migrate to the surface of the film, so they will be in the process of diffusion to the surface position of the competition with a slip agent.
4. Downstream processes: by the oxidation resistance of the polymer, corona treatment before printing process will increase the polarity of the surface of the film while the burned surface smoothness agents, so that the film formed on the surface slippery agent concentration gradient. To form a slip agent concentration gradient is so slippery agent has been treated to one side migration, which is likely to cause concurrency problems in the printing process.
5. The winding tension: slip agent tight around the thin film side to side with a lower winding tension at a decreasing rate of occurrence of migration.
6. Film thickness: the thick film type, the slippery agent takes a long time to become balanced, compared with thicker films, in thin films need to add a higher proportion of slip agent can thick COF achieve the same level.
When any of the additives include slip agents, including the assessment of needs to consider the whole recipe, so better to understand the potentially react with each other so that the additive levels can be optimized. Ammonia slippery agent class will also be affected by laminating adhesive and other downstream operations. These downstream operations can change the polarity of the film, and so slippery agent loss from the surface of the film. Whether slip agents and other substances between the unexpected interaction occurred, or formula slippery agent is too large, too much slip agents will lead to the occurrence of powdery residue on the guide rollers and the tensioning device, It can also cause printing problems or wet adhesion problems. The so-called wet adhesion means excessive smoothness agents can cause excessive film surface is smooth, and makes the fusion phenomenon between the layers.
No migratory slip agents and specialized formula
Silicone and other non-migratory slip agent has a very high molecular weight, their molecular weight is 30 times to 50 times the primary amides slippery agent and secondary amide slippery agent. Since the molecular weight of such a large slippery agent, can not be diffused in the polymer matrix, thereby reducing the coefficient of friction of such slippery agent COF value is achieved by polymer extrusion process, the resin surface smoothness agents arrive completed. Such slippery agent material has been used in some specialty areas. Such slippery agent can quickly restore the COF value, and not subjected to high storage temperatures or the use of high temperature effects. Because of the use of such slip additives in the film after extrusion, its COF value is the minimum change, thereby simply slip agent is added in the surface layer of the multilayer film, thereby reducing the associated cost.
 
 
 
Between the thin film layer anti-blocking agent
The so-called adhesive means an adhesive phenomenon between the adjacent film layers. When circumstances occur film bonded under heat, pressure situations, and in film processing, use and storage of course also possible to produce bonded. When such slippery agent for the film to start, as the laminated sheet, and when you open the bag for bond issues are likely to produce. For PE (polyethylene), PP (polypropylene) and other types of film, will produce thin-film layer between this case and the producers in the face of such problems, which will be added to the anti-tack inorganic or organic class caking agent.
 
Adhesion test can be removed from the roll of the latest film by Induced Reblock 'test ASTM D 3354 test method to obtain reproducible results. Specific test method is: first the film has been separated back together, which was stored at a specific temperature (40 or 60 ) and moderate pressure (6.9kPa) environment for 24 hours, and then tested.
 
Anti-caking inorganic mineral particle form dispersed in the film, the film surface becomes rough, the microscopic level to avoid mutual adhesion between the adjacent film layers. It includes mica and silica, including inorganic anti-caking agent has a very wide range of applications in real life. One drawback is that they will reduce the transparency of the film. The organic anti-caking agents include ammonia, stearate, silicone and polytetrafluoroethylene (PTFE), including in some high-end art has a special application.
Cost-effective inorganic anti-blocking agent
In contrast, inorganic anti-blocking agent and the cheap mass production and daily necessities has the most widely used. Mica is one of the most widely used inorganic anti-caking agents, accounting for 40% of global market share; Diatomite is a natural silica minerals, accounting for 25% of global market share; and synthetic silica kaolin, calcium carbonate and the like other minerals accounted for another 25% of the market share; the other 10% of the market share occupied by the mica.
When using a variable inorganic anti-caking agent has to be considered include the particle size, shape, and size-dispersed film. Other important factors are: Hardness, refractive index (RI) and density. Will affect the hardness of mechanical wear, and the refractive index between the inorganic particles and the polymer (RI) is different by an anti-adhesive material to affect the level of transparency. Particle size will also affect the strength of the film. The iron content is also a factor important consideration, because the iron content makes a lot of organic additives decompose downgrade reaction.
 
Mica is usually the lowest cost performance, and diatomaceous earth can be minimized so that the amount of inorganic substances, and so its effect on the optical properties of the film is minimized. Traditional mineral-based anti-adhesive particles in shape and size are often irregular, resulting in poor film optical properties. The transparency of the film is affected by the distribution of the refractive index and the loading level of RI, particle size. When the anti-caking agent refractive index (RI) and resin refractive index (RI) to match it is possible to obtain a high film transparency. The inorganic anti-caking particles the larger the size of film corresponding higher blocking resistance, but at the same time, the smaller the particle size, the better the transparency of the film. Good control of particle size distribution of the particles size and try to maximize the performance of the optical film and the balance of anti-blocking properties are useful.
 
High mobility organic anti-blocking agent
Organic anti-blocking agent may be a natural migration of, and generally considered organic anti-blocking agent may thus preventing adhesion between the adjacent film layers of the film surface crystallization. Under normal circumstances, the cost of such materials are greater than the inorganic anti-caking agent, a number of high value and therefore is mainly used in the field. Organic anti-blocking agent commonly used include: ammonia compounds, organic acid salts, metal stearate compounds and aromatic silicone, polytetrafluoroethylene (PTFE) and other materials.
In the film higher transparency requirements in the field, you can only use ammonia organic anti-blocking agent to meet the requirements, but more commonly, organic anti-blocking agent was added to increase the inorganic anti-blocking agent, anti-adhesion levels. Before blocking resistance and smoothness have an effect, ammonia anti-blocking agent will take some time to migrate to the film surface. Similar to EVA (ethylene ethyl acrylate) such a soft polymer material, ammonia anti-blocking agent than inorganic particles of anti-blocking agent is more effective, and thus get the best application. Among ammonia substances, the anti-blocking properties of the amide acid amide and behan most effective. behan amide effectively applied biaxially oriented polypropylene film, thereby providing good smoothness and blocking resistance while maintaining the transparency of the material.
in conclusion
Slip and anti-blocking agent most commonly used in polyolefin-based compounds, and is also used in PP (polypropylene), PVC (polyvinyl chloride), PS (polystyrene), PA (polyamide), PET (poly ethylene terephthalate) and other polymers. And PP (polypropylene), PVC (polyvinyl chloride), PS (polystyrene), PA (polyimide), PET (polyethylene terephthalate) are generally single-layer film or a composite film the form used in plastic bags and other packaging. In many applications require these additives may be direct or indirect contact with food. Slip and anti-blocking agent can be added directly to the manufacturer by the resin film, but more generally by way of masterbatch processors to join.
 
 

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