Manufacture Process of Polyurea Microcapsules - Report Example

Reading Header: MANUFACTURE PROCESS OF POLYUREA MICROCAPSULES Your Institution Your Name Course Name Course Instructor April 7, 2009 The process of making the polyurea microcapsules involves several chemical processes. In the first process of embodiment there is emulsification of a liquid phase of core material and polyisocyanate in an aqueous continuous phase which includes polyhydroxylated stabilizer that is colloidal, to form microdroplet of the hydrophobic phase that is in suspension form. There is the addition of the a polyamine called diethylenetriamine which is capable of reacting with polyhydroxylated and an alkaline base that act as a catalyst and as a result there is the initiation of an interfacial pollyaddition reaction at a pH that is alkaline resulting into the formation of polyurea microcapsules. The varieties of the alkaline base that can be used include LiOH, NaOH, or KOH while the polyisocyanate is either biuretized or isocyanurate which are a modification of the triisocyanate belonging to a lower alkyl diisocyanate. The addition of the polyamine is done in a stoichiometric ratio in relation to isocyanate. There is a second ambodiment which is very similar to the first with the exception of the alkaline base being added a long with a surfactant that has a multiple S which contains substituent groups and there can be use of a non-polyhydrated stabilizer like polyvinylpyrrolidone. Post-treatment of polyurea microcapsule This procedure involves the treatment of polyurea microcapsule with ammonia or amines as a way of reducing the residual isocyanate level. The residual isocyanate is a product that is a compound that results from microcapsules formation process. When the residual isocyanate is reduced the end product is flowable and the storage can be done at a low pH of below 8 with generation of carbon dioxide gas. The process of formation of microcapsules involves the formation of the polyurea capsule around material that are immiscible to water through interfacial polymerization of organic isocyanate that is intermediate aqueous phase water. The generation of carbon dioxide is as a result of the reaction of residual isocyanate with water in storage (Free patents online). The post treatment also has another stage where the polyurea microcapsules are treated with ammonia so as to modify microcapsule wall permeability. This process is important as it brings about success in the employment of capsule and the material that is to be encapsulated in. When there is use of di and tri-functional monomers in the preparation process of the polyurea microcapsules the result could be a high degree of cross linking. Depending on the materials in use the linking in the walls structure could be undesirable as it has a direct effect on the permeability of the core material. To overcome the problem posed by the high cross linking there can be modification of the resulting capsule wall by ammonia or amine post treatment of the wall. With the treatment of the wall with amine or ammonia there is modification on the permeability of the capsule walls and this allows the product to be stored at a pH lower than 8 with no generation of carbon dioxide. The capsules of the above description have a variety of application that includes containing flavoring materials, pharmaceuticals, chemical reagents, inks and dyes. They are also used in encapsulating pesticides, bactericides and fungicides such as herbicides or insecticides. The material that is being encapsultated can be dispersed at a temperature that is above its melting point or it can be dissolved or be dispersed in suitable organic solvents that are water-immiscible. The water immiscible solvents that are being encapsulated can either be organic or inorganic in nature (Free patents online). The liquid or the other forms of materials that has been encapsulated will be preserved till when the relevant instrumentality is used to remove the capsule skin by breaking, crushing, melting or dissolving or diffusion being done under suitable conditions. Two immiscible liquids, the aqueous phase and the organic phase, can be used in effective encapsulation by organic isocyanate. The organic phase has an isocyanate intermediate which is for polyurea capsule enclose or skin. Hydrolysis of an isocyanate monomer is involved in the interfacial polymerization and this result into the formation of amine that in turn reacts with another isocyanate monomer and therefore forming polyurea enclosure. When the isocyanates react with water that is in acidic solution there is the formation of carbon dioxide. There is some uncreative isocyanate groups in the process mentioned above and these are capable of forming carbon dioxide when water is present. Chemical dangers There are risks which are associated with production process of plastic capsules. The use of isocyanate in the manufacturing process is a risk to the factory workers who might be exposed to it in large quantities and this can cause asthma. The other dangerous chemical in use is ammonia. This chemical can be a disaster if the workers are exposed to it at the factory in their normal routine work or when by accident the ammonia happens to spill. There can also be exposure to ammonia to the general population when trucks, train or other transportation system get involved in accidents resulting in massive spill of the chemical. When the chemical happen to combine with chlorine there will be generation of dangerous gases and compounds (Lawrence, 2008). There are several serious health problems that can be caused by exposure to ammonia. It results in irritating and burning nose throat and eyes when there is inhalation and when the concentration is very high it will cause coughing and choking fits. When the exposure to ammonia gas or liquid is prolonged, the eyes and skin can severely be irritated and this could result scarring of the cornea and chemical burns on the skin and lungs that are permanent. It is dangerous to use this chemical in an enclosed area and when mixed with bleach it can lead to production of chlorine gas which is very toxic (Lawrence, 2008) The use of such a chemicals in this process is a great danger to the workers and the immediate surrounding, not forgetting the dangers that is accompanied by the chemical to the factory. There is also the use of the alkalines such as KOH, LiOH and NaOH. These are highly corrosive substances and when inhaled it will have a burning effect on the whole of the gaseous system. They can also corrode the components of the plant leading to early failure. Health and safety measures From the above text it can be seen that the production of the polyurea microcapsules involves the use of several chemicals most of which are very dangerous to human beings and the environment as a whole. All necessary precautions should therefore be to minimize the negative effect this production is posing. The following are some of the measures that can be taken to ensure that the dangers brought about by the manufacturing process are minimized. Proper design and maintenance of the plant There are a lot of accidents which can occur due to improper design of the processing plants. One of the important things that can come under design is the selection of the proper materials to be used. It has been seen that some of the chemicals are very corrosive and this could corrode some of the pipe works that will be in use in the plant. The physical and chemical characteristics of the material should be put into consideration at the design stage. The design should thoroughly calculate the size of the components that are to be used. Under estimating the size of tank used in storage of a chemical could for example cause spillage that is disastrous. There should also be proper maintenance of the plant. This will ensure that worn out components are replaced before total failure occurs. Proper maintenance will also ensure that the plant runs continuously with no incidence of a major breakdown that could cause the need of disposing of the chemicals due to expiry. Proper design will also ensure that the plant is specious and that there is proper natural and artificial ventilation that ensures that dangerous fumes like those of ammonia does not accumulate to dangerous levels. It will also ensure that there is enough escape routes incase of any accident. Plants dealing with production with a lot of chemical process are also supposed to be located at places that are at reasonable distance from high population areas. Training of workers on accident preparedness As a requirement the workers should be trained on various issues that concern emergencies. For example when there is fire outbreak in the plant the workers should be trained on how to respond in an appropriate manner. All the workers should know where the fire extinguishers are located and how they are used. They should also be aware of the fire exit routes and the assembly point which should be within the factory compound. The fire fighting equipment should be checked and satisfied to make sure that it is always in a good working condition. There should be signs at appropriate points to show risky areas like where dangerous chemicals are stored and no an authorized people allowed entering. The containers should also be labeled clearly to show what they contain. When the chemicals are being transported there should be use of routes that pass in areas that are less populated. Use of appropriate gear All the workers should be supplied with appropriate gear. This could include gloves, gas masks, helmets and appropriate foot wear. The workers should always put on the safety gear and in the required manner to ensure its effectiveness. There should be replacement of the safety gear as advised by the manufacturers or other relevant authority. This being a place with high risk of chemical exposure the time spent working in particular areas that could be dangerous to ones life should be minimized. This can be ensured by arranging for shifts and a time table followed strictly. Disposing of waste The operation of the plant will result in generation of solid waste and liquid waste that could be poisonous. This will call for the appropriate disposal measures to minimize their effect on the environment. The liquid part should undergo some form of treatment before the liquid is disposed to water systems like rivers. There should be hiring of private firms to undertake the collection of some of the waste for appropriate disposal. An incinerator should also be constructed to be used in disposal of some of the solid materials. References ABOUT.COM (2008) Aerial spraying Retrieved April 6 2009, from http://sanfrancisco.about.com/od/sfaerialspraying2008/qt/LBAMParticles.htm Free patents online. Post-treatment of polyurea microcapsules Retrieved April 6 2009 from http://www.freepatentsonline.com/4046741.html Free patents online. Process for manufacturing polyurea microcapsules and product therefrom Retrieved April 6 2009 from http://www.freepatentsonline.com/5324584.html GV Casaña (2007). Novel agrochemical formulation containing microcapsules Retrieved April 6 2009 fromwww.freepatentsonline.com/EP1844653.htm Lawrence R. (2008) Pesticide Spraying Health Hazard Alert. London: Cambridge University Press Shirley M (2001) Delivery of biological performance via micro-encapsulation NEW York: Prentice Hall Read More