Pulp molded tableware, that is, tableware made of the pulp as the main raw material, by adding functional chemicals (such as water repellent, oil repellent, and wet strength agent, etc.), through the main process of vacuum filtration molding, heating, drying,die-cutting, and disinfection. UV Tableware’s pulp molded tableware is made from sugarcane pulp, which is often referred to as compostable bagasse tableware. Many end consumers and distributors used to ask: Does pulp molded biodegradable tableware oil-proof? The answer is of course yes, oil resistance is an important technical indicator of pulp molded tableware.
How do disposable food containers achieve the effect of oil resistance?
How do traditional disposable tableware achieve oil-proof effect?
Traditional oil-resistant paper products (such as tableware made of cardboard) are produced by secondary processing. Treatment methods are coating, spraying, compounding, etc., to overcome the limitations of paper products can not be oil-resistant, waterproof, but the fundamental drawback of these methods is that the process is cumbersome, high cost, the use of a large number of restrictions, especially some of the chemical products used for coating, spraying, compounding still can not solve the problem of waste degradation, resulting in environmental pollution.
How does pulp molded tableware achieve an oil-proof effect?
With the development of paper products additives, the most simple and practical method is to add an additive in the production process of paper products, so that paper products are produced with oil and water resistance. This paper product can be used not only for food packaging but also for industrial packaging, especially the waste after the paper product use, can be recycled, not only conducive to environmental protection, also conducive to ecological balance. The oil-proof performance of pulp molded tableware is achieved by adding an oil-proof agent in the process of pulp mixing, and the oil-proof agent used is a perfluoroalkyl compound.
What are the factors that affect the oil resistance of pulp molded tableware?
There are many factors affecting the oil resistance of molded pulp tableware. The content of fine fiber in bagasse unbleached pulp, the different kappa numbers, and the beating degree of bagasse natural color pulp are all the factors that affect the oil-proof property of paper. The amount of oil repellent, retention aid, and the addition process also has an impact on the paper properties. The water-proof and oil-proof properties of paper with two different treatments are also different. Using the TAPPI Kit Test method, heat-resistant oil method, and contact angle test, it is found that the oil-proof effect of half pulp and half coated paper is better than only pulp or only coated paper.
What is an oil repellent?
The oil repellents added to pulp molded tableware are mainly straight-chain fluorocarbon organic compounds, which are synthetic glues that bond directly to the fibers, thus improving the physical strength of the finished product, increasing the proportion of low-strength fibers in the pulp without reducing the strength of the finished product, and adding other fillers. The anti-oil agent is actually a neutral sizing agent and therefore requires that must be applied under neutral conditions, and must be added to match the retention agent, which is very critical, at present, China’s pulp molded tableware manufacturers basically choose fluoride as an anti-oil agent. The mechanism of action of fluorine anti-grease agent is to use its characteristics of very low surface tension, so that it can be uniformly dispersed on the surface of the product, reducing the surface tension of the product, in order to achieve the surface of the pulp molded products with the performance of repelling oil, hydrocarbon type surfactants and other liquids containing oil, so that the pulp molded products produce oil resistance.
What are the types and characteristics of oil repellents?
The organic fluorine oil repellents used in pulp molding are a class of compounds with unique properties obtained by replacing a large number of hydrogen atoms in the molecules of organic carbon compounds with fluorine atoms. The hydrogen atoms are replaced to obtain a low-energy substance that is incompatible with aqueous solutions and hydrocarbon systems. The general structural formula is as follows: CF3(CF2)XR, By changing the functional group R, a large number of products with different properties can be obtained. If R is a fluorine atom, the compound is inert and neither soluble nor dispersed in aqueous solution or organic solvents, and if R is an anionic, cationic or nonionic functional group, the compound can be a special type of surfactant. In addition, R can also be some monomers with polymerization function, and they can polymerize with other substances to obtain another class of products with a wide range of properties.
Perfluoroalkyl compounds suitable for pulp molded tableware can be broadly divided into three categories: perfluoroalkyl chromium complexes, perfluoroalkyl phosphate esters (salts), and perfluoroalkyl copolymers. Perfluoroalkyl copolymers can be further divided into hydrophilic and hydrophobic types. Due to the color of chromium fluorocarbon complexes can make paper fibers discoloration, poor stability in solution, even at room temperature are easy to hydrolysis, the drying process is easy to make paper fibers brittle and other shortcomings have now been eliminated.
The fluoro oil-repellent used in the production of pulp molded tableware is a perfluoroalkyl organic compound that also includes polymers. It has good chemical stability, thermal stability, and electronic stability. Its surface tension is very low, insoluble in water and organic solvents, this type of grease inhibitor can be made for food packaging, can be used to prevent oil and part of the solvent of various types of pulp molded products. The characteristics of this fluorine type of oil repellents are:
- Can be widely used in water-soluble or solvent media.
- Can be durable on paper pulp molded products, which remain oil resistant after folding.
- It can maintain the printing performance of paper pulp molded products, etc.
- It can make the paper pulp molded products not only oil resistant but also hydrophobic or hydrophilic.
- It can adopt both in-pulp sizing process and surface sizing or coating process.
- Its finished products are widely used, both for food packaging and industrial packaging.
Application technology of oil repellents
The effect of different kinds of pulp on the effectiveness of oil repellents
The effect of fluoride oil-proofing agents, for different pulp species, the effect is not the same. General bleached pulp effect is better than the color pulp; sulfate pulp is slightly better than sulfite pulp; softwood pulp is slightly better than hardwood pulp; the chemical pulp is better than machine wood pulp. China’s production of pulp molded tableware pulp raw materials, mostly grass pulp, reed pulp, bagasse pulp, wheat straw pulp, rice straw pulp, bamboo pulp, etc., the physical properties and chemical composition of different grass pulp is very different. Anti-oil agent oil resistance not only varies depending on the species of wood pulp, is used for these grass pulp is also very different from each other, which makes the application of a good formulation of additives in the replacement of pulp species after the effect will change. Therefore, in the production of a different pulp, the replacement pulp should first do laboratory tests to obtain the best technical parameters, and then develop a new process program before implementation in production.
In addition, the fibers, fillers, and chemical additives that make up the slurry will affect the effectiveness of the fluoride sizing agent through different physical and chemical effects. Physical effects include the presence of lipophilic substances, such as asphalt, lignin, resin acid salts, and the presence of hydrocarbons in the auxiliaries, all of which will weaken the oil resistance of fluoride sizing agents. A special note is the choice of raw materials for the pulpboard, the first thing you must pay attention to is the quality and cleanliness of the pulpboard, because the anionic impurities in the pulpboard will make some cationic additives worse, and may even make the cationic additives completely ineffective. If the pulpboard is not clean after bleaching, too much residual chlorine content, will also greatly affect the effectiveness of the use of chemical additives. According to tests, such as the residual chlorine content of the pulp is greater than 300 to 400ms/kg, which can make AKD sizing agents lose more than 90%.
The effect of water quality on the effectiveness of oil repellents
The use of cationic fluoride oil repellent, because it is not sensitive to the PH of the water, so there is no need to strictly control the PH of the water. Hard water has little effect on cationic oil repellent products. If an anionic fluoride grease preventive agent is added to the ingredients containing low molecular weight retention aid, then the effect of hard water on it is also very small. In this case, the fluoride grease inhibitor will be immediately absorbed by the fiber and will not precipitate in hard water. For anionic oil repellents, the actual PH can be determined according to the properties of other ingredient additives.
The effect of adding method and adding order on the effectiveness of oil repellents
The order of adding fluoride oil repellant is as follows, but if it is used with water-repellant with special function, it can also be used without retention aid, and the order of adding can be changed accordingly.
Fluoride oil repellents are often pre-diluted at a ratio of 1:20 so that the oil repellents can be more evenly distributed between the fibers, and its uniform distribution or not is a major factor affecting the size of their resistance to oil and water.
Although the performance of fluoride oil repellent is extremely stable, it is not advocated to add before grinding, fluoride oil-repellent if added after grinding, can get the best results. This is because if it is added before grinding, some fiber surfaces will not be glued during the grinding process. Anionic fluoride oil-proofing agent should be added diluted in advance, and soft water should be used. If there is no soft water, 0.3% of the sequestering agents can be added to hard water to reduce the hardness of water and prevent the oil-proofing agent from being neutralized and precipitated by cations in hard water. Cationic water repellents can be diluted directly with tap water.
The effect of setting the temperature on the effectiveness of oil repellents
The temperature of drying paper pulp molded products is an important factor that significantly affects the performance of oil repellents, fluoride oil repellents need to be heated to “ripen”, this ripening is not a chemical process but a physical process, heating to soften the polymer chain, and make perfluorocarbon groups in the fiber surface outside the orientation arrangement. The oil resistance of pulp molded tableware depends on the tightness, alignment, or positioning of the perfluoroalkyl groups on the surface of the pulp molded tableware, and temperature is the key factor in determining the formation of the low energy surface. Therefore, the production line must be able to meet the drying temperature requirements of various types of fluorinated oil repellents.
What process parameters should be paid attention to when using oil repellents?
According to the production experience, when using perfluoroalkyl compounds in the pulp molded tableware production line, the following process parameters should be paid attention to in general.
- Stirring speed and interval time. Anti-oil agent and pulp mixing require a certain amount of time and good stirring conditions, stirring speed generally do not exceed 60r / min, additive additive interval time is generally not less than 10min.
- Mixing concentration. In the addition of chemical additives, the concentration of the pulp is best in 3% to 5%, because the pulp in this concentration range, the mixing process can make chemical additives in the pulp fiber extrusion rubbing, better mutual solid adsorption, and finally diluted to 1% concentration on the machine molding. This will not only reduce the amount of additives, increase the role of anti-oil agent, but also save energy.
- Control foaming. As fluoride anti-grease agent is a surfactant, the use of the process will often bring some foam problems. However, if you control the stirring speed (30~60r/min), stirring time, add position, control the slurry outlet, etc., you can effectively control the foaming. If necessary, defoamer can be added.
- The amount of anti-oil agent. Depending on the specific requirements, the general use of fluorocarbons more, in the use of softened water should be added first diluted, the amount of 4% to 7% of the absolute dry fiber. The specific amount depends on the ingredients and other additives.
How to verify the oil-proof performance of bagasse tableware?
UV Tableware’s environmentally friendly bagasse tableware products are tested in the lab for performance after production is complete. For testing the oil resistance of biodegradable pulp molded tableware, end consumers or distributors can use the following convenient method: put 120°C hot oil into bagasse tableware and let it stand for 30 minutes to observe whether the tableware has no negative seepage, no leakage, and no deformation. For special requirements, you can increase the oil temperature and extend the testing time.
For more details, please contact UV Tableware for an in-depth discussion, thank you.
