Select a fungicide to protect the basis of the polymer dispersion

In polymer dispersions, the dispersion phase is made up of collectial polymer particles with particle sizes usually between 1 nanometer and 1 micron. Collate particles are dispersed in a continuous phase (e.g. water)1. Industrial polymer dispersions typically contain 40%-60% polymers. Typical properties associated with industrial polymer dispersions are usually free flow, viscosity, and shear rates, depending on the monomer used. The polymer dispersion developed should meet the needs of the final application. As the water phase evaporates, the dispersion forms a polymer film. Strength, elasticity and solvent stability depend on the chemical composition and molecular weight of the polymer (see Table 1). In order to improve the diversity of polymer dispersions, a variety of monomer copolymers are generated to obtain more performance.
polymers, including various plastics, are widely used because of the different properties that can be obtained through various types of polymerization processes and the selection of different raw materials. The focus of this article is on water-based polymer dispersions.
the production of polymer dispersions 3,9-11
polymer dispersions based on free-form polymerization is a complex process. The emulsion polymerization process consists of several stages and requires at least four main raw materials: water, monosomy, emulsions and triggers. Other raw materials are chain transfer agents, buffers, acids and alkalis and biocides. Chain transfer agents, such as thiols, are used to regulate molar mass and molar mass distribution of polymer chains. Acids, alkalis and buffers are added to control the pH of the production process and the lotion itself. After production, a fungicide is added to the final dispersion to control the microorganism.
all the parts are added together, the polymerization process involves emulsifying the hydrophobic monosome in water by adding emulsifying agents, followed by triggering a reaction through a free-based trigger that is water-soluble or oil-soluble. At the
, the resulting milk-like liquid is called "latex," "synthetic latex," or "polymer dispersion."
in order to start the entire free-base aggregation process, a free-base needs to be generated. For this purpose, a trigger is required. Typical examples of triggers used in emulsion polymerization are persulphate, hydrogen peroxide, organic peroxides, alumina compounds, and persulphate-heavy sulphate. The trigger is activated by heating or according to the redoxing process.
free fundamentals, they react with monosumes containing carbon-carbon unsaturated bonds to trigger polymerization reactions. When free fundamentals react with monomer molecules, they produce larger free fundamentals, which in turn react with another monomer molecule, so that the polymer chain expands. The growing polymer chain eventually terminates when combined with another free agent, chain transfer agent, inhibitor, etc. (i.e., the formation of a free electron pair).
lotion polymerization can be done through intermittent, semi-continuous or continuous production processes. The most common production processes are semi-continuous, due to their greater flexibility in thermal generation, performance and the morphology of polymer particles, resulting in products with more controlled chemical composition and particle size distribution. This results in relatively high-quality polymers, such as uniform chemical composition and particle size distribution, which helps both the fluidity of the polymer and the properties of the film.
temperature is a key factor in the production of polymer dispersions. The process is carried out in a reactor and can reach temperatures of up to 90 degrees C with thermal triggers. When using a redox reaction trigger, it usually needs to be done at a temperature of 40-50 degrees C. Further details about emulsion aggregation can be found in the articles Cherns3 and Yamak10, which are listed in the following references.
today, emulsion polymerization is an industrial process that produces millions of tons of products. It obtains collogenic polymers containing or containing high molecular weights that VOC can ignore. The reaction medium is usually water, which facilitates stirring and mass transmission and is a relatively safe process in itself. The process is more environmentally friendly when converted to a water-like system with or without low VOC.
effects of microbial contamination on polymer dispersions 12-13
polymer dispersions are mostly water-based formulations. Polymer dispersions are used for a variety of purposes, such as adhesives and coatings. High water content, nutrient-rich polymer dispersion composition for microbial growth, reproduction provides a very suitable environment. Biology and its metabolic by-products can lead to degradation of polymer dispersions. Many factors affect the presence of microorganisms and their metabolic by-products.
water
used as a medium for polymer dispersion due to its excellent thermal conductivity and low viscosity. Water is also a fundamental factor in the growth of most microorganisms, most microorganisms need water activity of more than 0.50. Pure water has a water activity of 1.00. Pure water is not found in the natural environment due to the solvent properties of non-polar water molecules. In most industrial plants, water is the main source of microbial contamination.
viscosity
polymer dispersions can thin or thicken due to microbial growth (degradation of surfactants, acidic by-products, etc.), as a result of increased concentrations of acidic by-products. Phase separation occurs when thinner upper layers and thicker layers are formed. Because viscosity is a key performance of the finished product, contaminated polymer dispersions cannot be used in the finished product.
pH changes
as mentioned earlier, metabolic by-products tend to be acidic. A decrease in pH may cause instability of the polymer dispersion. In addition, acidic conditions promote the formation of corrosive environments on the surface of plant equipment.
gas produces
when microorganisms grow and multiply in polymer dispersions, fermented bacterial cells use collocial thickeners (e.g. cellulose, glucose) to produce organic acids and carbon dioxide. The production of gases is not usually found in factory environments, but is found in the storage of polymer dispersions or finished products. Packaging deformation (expansion of plastic bottles or barrels) is usually observed in the warehouse.
the formation of odors or colors
polymer dispersion contaminated with sulfur-lowering bacteria produces a "skunk egg" odor due to the production of hydrogen sulfide gas. Sulfur-lowering bacteria can also blacken polymer dispersions or finished products. Other microorganisms produce odors as a result of bio-chemical reactions.
the formation
biofilms in plant equipment (e.g., piping systems) can lead to the generation of microbial metabolic by-products. In addition to the above results, various microbiomes within the biofilm may affect corrosion of the metal surface in the plant (i.e. microbial-induced corrosion, MIC). It can also limit the flow of device pipes, clog filters, and produce extracellular polymers that produce foam.
environmental problems
when there is a problem of microbial contamination in the plant, operators and plant personnel are exposed to odors and possible pathogenic microorganisms. Microbes are present in most plant environments. Microbial types and densities are affected by temperature, pH, and nutrient types. Hioxybacteria, anaerobic bacteria (e.g. sulphate-lowering bacteria), mold and yeast have been isolated from production facilities of different polymer dispersions.
factors affecting the efficacy of the fungicide 11-15
Redoxion level 13,15
Redoxionity (expressed in millivolts) is a measure of the material's affinity to electrons (electrical negative), compared to the standard hydrogen electrode (SHE set to 0) 12. Freelances generated by redox reactions are typically used to trigger polymerization reactions. The advantages of using this trigger process are short induction period, low activity energy (10-20 kca/mole) and the ability to control polymerization reactions. Commonly used redox triggers are peroxides and reducers, inorganic reducing agents and inorganic oxidants (e.g. potassium persulphate, ammonium persulphate), peroxydiphosphate systems (e.g. polymerization of acrylonitrile) and organic-organic redox pairs (e.g. Ce4 plus alcohols)1. In the polymerization process caused by redox, the conversion rate of the reactant is less than 100%, leaving behind the residual free monosome. In the finished polymer dispersion, the residual free monomer can react with the active biobicide, reducing the efficacy of biological killing. If the polymer dispersion has a positive redox potential, the product is oxidized. Microbicides that are prone to oxidation may degrade (e.g. benzodiaxone BIT). In the presence of essential nutrients, magpies grow. In a negative redoxionality environment, the polymer dispersion is in a reduced state. Fungicides that are susceptible to reducing agents may degrade. In the absence of oxygen and key nutrients, polymer dispersion provides an ideal environment for anaerobic bacteria. Table 2 illustrates the effect of the redox potentiometer on the stability of the mixture of 1,2-benzodialumine-3-ketones (BIT) and 5-chlorine-2-methyl-4-isoprene-3-ketones and 2-methyl-4-isoprene-3-ketones (CMIT/MIT). Changes in the stability of the fungicide can lead to reduced performance.
pH
pH is critical to the production of polymer dispersions. In order to maintain a certain pH value to optimize the production of a particular polymer, a buffer can be added. Most microorganisms encountered in the plant grow and multiply in the pH range of 4-9. Fungal organisms are more prominent at acidic pH, and bacteria are more prominent under neutral to slightly alkaline pH. In general, polymer dispersions in the ideal pH range are more suitable for microbial growth (Table 3).
temperature
temperature during polymerization can be as high as 90 degrees C. However, the effect of most fungicides is reduced at higher temperatures, so fungicides are usually added when the dispersion has cooled to an acceptable temperature after the polymerization reaction. It is important to add fungicides at the earliest point in time after the polymerization reaction is complete and after the free monolith is eliminated. It is also important to add a fungicide until the temperature of the polymer dispersion has cooled to a temperature that does not destroy the fungicide. Since polymer dispersion tanks are usually insulate containers, fungicides with high heat resistance are recommended.
other
some of which further support the growth of microorganisms. Desiccants, metal catalysts and surfactants are food sources for microorganisms. In general, the characteristics of the ideal fungicide is broad-spectrum efficacy (effective resistance to bacteria, mold and yeast), effective in a wide pH range, temperature stability, anti-redox agent, water-soluble, its distribution coefficient is more suitable for the water phase, with other components of the finished product compatible, with good environmental performance, in line with the regulatory scope and good cost-effective.
16-21
past, residual monomers in polymer dispersants have provided some protection against microbial contamination. However, stricter environmental regulations and polymer dispersions as low as no residual monomers provide a suitable environment for microbial growth. Microbicides provide long-term protection against microbial contamination. Some of the preservatives currently in use in polymer dispersions are BIT, BIT/MIT, CMIT/MIT, bromine nitroproglycol, FA-R and MIT (see Table 4).
BIT:1,2-benzodiaxone-3-ketone (BIT) is an effective broad-spectrum fungicide widely used in the polymer dispersion industry. It is stable at temperatures as high as 100 degrees Celsius. BIT provides the efficacy of killing bacteria in a wide pH range (2-14). BIT does have difficulty fighting fake monocytobacteria, which are common in industrially treated water. BIT works by reacting to cell proteins that inhibit breathing and the synthesis of adenosine triphosphate (ATP).
CMIT/MIT: A three-to-one mixture of methyl chloroform ketones (CMIT) and methyl isopyroidone (MIT) is commonly used as fungicides in polymer dispersions. CMIT/MIT is a broad-spectrum fungicide with a pH range of between 3 and 9. CMIT/MIT works by reacting with cytoproteins leading to respiratory suppression and synthesis of adenosine triphosphate (ATP). Alkaline solution degrades CMIT molecules. CMIT has also been identified as causing skin irritation when the concentration exceeds 64 ppm.
BIT/MIT: 1,2-Benzene isoprene-3-ketone (BIT) and methyl isoprene (MIT) can provide a broad-spectrum fungicide for industrial products. Methyl isopycin can narrow the gap with BIT in the fight against fake monocytobacteria. Since BIT and MIT are both chemical series of isoprine, they work in the form of chemicals reacting with cytoproteins leading to respiratory suppression and the synthesis of ATP20.
bromine nitrosol: 2-bromine-2-nitro-1, 3-propylene glycol (bromine nitroglycol) is a fungicide with limited bactericidal effect on fungal microorganisms. Bromine nitrosol is very effective against fake monocytobacteria and can be used in temperature ranges between 5 and 8.8 pH and below 45 degrees C. Brominitol has a complex mode of effect that attacks thiol-based groups in cells, thereby inhibiting breathing and cell metabolism21.
FA-R: The fungicide (FA-R) that releases formaldehyde is an industrial fungicide used in paints, adhesives, and concrete blends. They are primarily a fungicide, but at higher doses they have some effect on resistance to fungal organisms. The role pattern of FA-R is that they release formaldehyde, which reacts with nucleic and amino acids in cells21.
MIT: Methamphetamine (MIT) is an industrial fungicide used in coatings, adhesives and cosmetics. It is an effective fungicide with limited fungicide effectiveness. MIT works by responding to cytoproteins that cause respiratory suppression and atTP synthesis 20.
recently, decane-based hydrochlorides (DGH) have been shown to have a biocide effect on microorganisms in specific polymer emulsions, such as copolymers of ethylene acetate and ethylene, which do not contain anion surfactants. DGH has significant activity against Bacillus laccharide acetate, described in patent US6890969 22.
of microbicides is essential for the stability of polymer dispersants. Contamination from the environment, raw materials, water, poor factory hygiene and storage containers can cause microbiological problems. Polymers that are not adequately corrosion-proof can cause a decrease or increase in viscosity, produce gases, create a foul odor, and become more acidic, disrupting polymer dispersions, changing colors, and losing polymer performance.
Global Regulations/Environmental Issues
As consumers become more aware of the chemicals used in their coatings, adhesives and sealants, stricter regulations (e.g. low VOCs and non-skin allergens) are in place for commercially available products