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A disposable nitrile rubber glove. Nitrile gloves are available in different colours, the most common being blue and purple.
Nitrile rubber, or Buna-N, is a synthetic rubber copolymer of acrylonitrile (ACN) and butadiene. Some trade names are: Nipol, Krynac and Europrene.
Nitrile butadiene rubber (NBR) is a family of unsaturated copolymers of 2-propenenitrile and various butadiene monomers (1,2-butadiene and 1,3-butadiene). Although its physical and chemical properties vary depending on the polymer&#;s composition of nitrile (the more nitrile within the polymer, the higher the resistance to oils but the lower the flexibility of the material), this form of synthetic rubber is generally resistant to oil, fuel, and other chemicals. Its resilience makes NBR a useful material for disposable lab, cleaning, and examination gloves. It is used in the automotive industry to make fuel and oil handling hoses, seals, and grommets. NBR&#;s ability to withstand a range of temperatures from &#;40°C to +120°C makes it an ideal material for extreme automotive applications. Nitrile butadiene is also used to create moulded goods, footwear, adhesives, sealants, sponge,expanded foams, and floor mats. Nitrile rubber is more resistant than natural rubber to oils and acids, but has inferior strength and flexibility. Nitrile gloves are nonetheless three times more puncture-resistant than rubber gloves[1]. Nitrile rubber is generally resistant to aliphatic hydrocarbons. Nitrile, like natural rubber, can be attacked by ozone, aromatic hydrocarbons, ketones, esters and aldehydes.
Production Process
Emulsifier (soap), 2-propenenitrile , various butadiene monomers (including 1,3-butadiene, 1,2-butadiene), radical generating activators, and a catalyst are added to polymerization vessels in the production of hot NBR. Water serves as the reaction medium within the vessel. The tanks are heated to 30°C-40°C to facilitate the polymerization reaction and to promote branch formation in the polymer. Because several monomers capable of propagating the reaction are involved in the production of nitrile rubber the composition of each polymer can vary (depending on the concentrations of each monomer added to the polymerization tank and the conditions within the tank). One repeating unit found throughout the entire polymer may not exist. For this reason there is also no IUPAC name for the general polymer. The reaction for one possible portion of the polymer is shown below:
Monomers are usually permitted to react for 5 to 12 hours. Polymerization is allowed to proceed to ~70% conversion before a &#;shortstop&#; agent (such as dimethyldithioarbamate and diethyl hydroxylamine) is added to react with the remaining free radicals. Once the resultant latex has &#;shortstopped&#;, the unreacted monomers are removed through a steam in a slurry stripper. Recovery of unreacted monomers is close to 100%. After monomer recovery, latex is sent through a series of filters to remove unwanted solids and then sent to the blending tanks where it is stabilized with an antioxidant. The yielded polymer latex is coagulated using calcium chloride, aluminium sulfate, and other coagulating agents in an aluminium tank. The coagulated substance is then washed and dried into crumb rubber.
The process for the production of cold NBR is very similar to that of hot NBR. Polymerization tanks are heated to 5 °C&#;15 °C instead of 30 °C&#;40 °C. Under lower temperature conditions, less branching will form on polymers (the amount of branching distinguished cold NBR from hot NBR).
Miscellaneous
Unlike polymers meant for ingestion, where small inconsistencies in chemical composition/structure can have a pronounced effect on the body, the general properties of NBR are not altered by minor structural/compositional differences. The production process itself is not overly complex; the polymerization, monomer recovery, and coagulation processes require some additives and equipment, but they are typical of the production of most rubbers. The necessary apparatus is simple and easy to obtain. For these reasons, the substance is widely produced in poorer countries where labor is relatively cheap. Among the highest producers of NBR are Taiwan and China. In January the European Commission imposed fines totalling &#; 34,230,000 on the Bayer and Zeon groups for fixing prices for Nitrile Butadiene Rubber, in violation of the EU ban on cartels and restrictive business practices (Article 81 of the EC Treaty and Article 53 of the EEA Agreement).
The applications of nitrile rubber include automotive transmission belts, hoses, oil seals, V belts, synthetic leather, printer's roller, cable jacketing. The NBR latex can also be used to prepare adhesives, impegnation of paper and binder of pigments
See also
Medical gloves Ozone crackingReferences
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External links
MERL - Rubber Selection Guide AAA Acme Rubber Co - Nitrile Rubber http://ecb.jrc.it/DOCUMENTS/Existing-Chemicals/RISK_ASSESSMENT/DRAFT/R019__env_hh.pdf http://www.ec.gc.ca/substances/ese/eng/psap/final/public/butadiene.cfm http://www.lenntech.com/acrylonitrile.htm http://chemistry.gsu.edu/glactone/modeling/Magid/conjug/conjug.html http://europa.eu/rapid/pressReleasesAction.do?reference=IP/08/78&format=HTML&aged=0&language=EN&guiLanguage=enThe method that the present invention is a kind of segmentation cohesion, activity is isolated, wet grinding prepares acrylonitrile-butadiene rubber powder, it is the new technology in China Synthetic Rubber Industry field.
At present, the preparation acrylonitrile-butadiene rubber powder, the main method that adopts has: mechanical crushing method, spray-drying process, expansion drying method, starch-xanthation compound coagulation method, the carbon black precipitator method and dried emulsion method etc.Shortcomings such as suchlike method exists all that energy consumption height, granularity are big, poor water resistance and foreign matter content height.
Acrylonitrile-butadiene rubber powder is compared with block paracril, its rubber powder fine size, and during with other resin alloy, good dispersity, and can directly enter forcing machine, and make course of processing serialization, automatization, therefore, have advantages such as easy to operate, energy-conservation.
Acrylonitrile-butadiene rubber powder and various kinds of resin blend have good consistency, therefore are mainly used in resin modified.In polyvinyl chloride, add elasticity, water tolerance and the oil-proofness that a small amount of acrylonitrile-butadiene rubber powder can improve goods; Also can greatly improve the shock strength of the special-shaped extruded material of rigid polyvinyl chloride; Be used for the artificial leather product and can improve the leather surface cohesive force; Be used for the polyvinyl chloride calendered film, make film have better elasticity; Be used for the polyvinyl chloride electrical wire and cable goods, can improve its toughness and winter hardiness; Acrylonitrile-butadiene rubber powder and resol and usefulness have plastification or the like.
It is different to the object of the present invention is to provide a kind of and existing coacervation to prepare acrylonitrile-butadiene rubber powder, and is furnished with the segmentation cohesion of relevant device, active isolated method.
Coacervation of the present invention prepares acrylonitrile-butadiene rubber powder, adopt the method for segmentation spraying cohesion, with the aqueous solution of monovalence and divalent metal salt be flocculation agent promptly: nitrile rubber is at the soft salt solution, under the effect of three kinds of flocculation agent of high rigidity salt solution and Adlerika (or calcium chloride solution), make latex pre-coagulate, flocculation, micelle nodularization, active isolate and process such as aftertreatment in make acrylonitrile-butadiene rubber powder.
Preparation process of the present invention is: the special-purpose nitrile rubber that will prepare promptly gets acrylonitrile-butadiene rubber powder through condensation powdering, antiseized isolation processing, filtration, dehydration, drying and process such as sieve.
For achieving the above object, now be described in detail the technological process of segmentation cohesion preparation acrylonitrile-butadiene rubber powder of the present invention.
1. latex preparation: with feed intake 6% potassium stearate and potassium oleate of amount of monomer of polymerization is emulsifying agent, under 40&#;60 &#; temperature, carry out letex polymerization, when transformation efficiency is 95% when above, just make cross-linking type butyronitrile latex:, just make high temperature non-crosslinked type nitrile rubber when transformation efficiency is 75% when following.
When if emulsifying agent is selected synthetic fatty acid potassium and potassium oleate for use, its consumption is that polymerization 3% of the amount of monomer that feeds intake is carried out letex polymerization under 5&#;8 &#; temperature, and its transformation efficiency is 75% o'clock, can make low temperature non-crosslinked type nitrile rubber.
More than prepared cross-linking type and non-crosslinked type nitrile rubber, the requirement of root a tree name product grade all can be used as the raw material of agglomeration process.
2. segmentation cohesion: with soft salt solution, high rigidity salt solution and three kinds of flocculation agent of Adlerika (or calcium chloride solution), in still formula equipment, divide three sections sprayings to add, its proportioning is: dried glue: salt: sal epsom (or calcium chloride)=1: 0.3&#;0.7: 0.02&#;0.08, condensation temperature are 30&#;65 &#;.
Under violent stirring, at first spraying adds soft, concentration is the salt solution of 25% (weight), is the pre-process of coagulating; Again with the high rigidity salt solution of concentration 25% (weight), under continuing to stir, add, and control spraying adding speed is carried out second section cohesion and is flocculation process; At last stirring velocity being improved, is that the Adlerika (or calcium chloride solution) of 8&#;10% (weight) carries out the 3rd section spraying cohesion with concentration, is the micelle nodularization process of hardening.As behind the powder, add the potassium stearate solution (or Magnesium Stearate or silicon sol) of 0&#;6% (weight) of dried glue amount again, as a supplement separant.Operation steps by segmentation cohesion of the present invention can reduce cohesion speed, but makes all condensation powderings of multiple latex.
3. active isolation the: in condensed system, the emulsifying agent potassium stearate, perhaps synthetic fatty acid potassium and potassium oleate, all can generate Magnesium Stearate (calcium) with the magnesium calcium ion in salt solution and sal epsom (or calcium chloride) solution, magnesium oleate (calcium), perhaps synthetic fatty acid magnesium (calcium) precipitates, and is in molecularity.When temperature was 50&#;65 &#;, the micelle that cohesion forms was very strong to its adsorption activity, therefore just produced active buffer action, obtained spontaneous separant.
If with cross-linking type or high temperature non-crosslinked type nitrile rubber is raw material, Cheng Fenhou can no longer add separant; If with low temperature non-crosslinked nitrile rubber is raw material,, and there is not potassium stearate because emulsification dosage is less, so as behind the powder, add the potassium stearate solution (or Magnesium Stearate or silicon sol) of 4&#;6% (in dried glue weight), separant all can reach active isolated purpose as a supplement.
4. grind and sieve:, in the adding material-twisting machine grinding is sieved and carry out simultaneously the filter cake of the nitrile rubber powder after centrifuge washing, the dehydration.Be the requirement that is suitable for grinding, be pressed on the filter cake at the rubber claw of adorning a rotation on the shredder, and contact grinding with screen cloth.Sieve through grinding, separant and micelle adhere to tightlyer, and the particle of pulverizing adheres to separant again, better effects if, and particle is thinner.Its particle diameter reaches below the 0.45mm.Adopt the corresponding sieve apparatus that ground of the present invention that powder formation rate is reached more than 95%.
The method that the present invention prepares acrylonitrile-butadiene rubber powder has the following advantages: (1) Production Flow Chart is short, and technology is simple, grinds sieve apparatus and easily makes; (2) the segmentation condensing method has spontaneous buffer action in agglomeration process, and isolation effect is good, the powder formation rate height; (3) particle diameter that adopts the present invention to prepare acrylonitrile-butadiene rubber powder suits, and is widely used, and has tangible economic benefit.
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