NYLON 6,6

Monomers:-O Nylon 6,6 is made from two

monomers adipic acid (IUPAC name hexane dioic acid) [(CH2)4(COOH)2] and hexamethylene diamine [H2N(CH2)6NH2]

Monomers:-O There are 6 carbon atoms forming a

chain in both the monomers hence the name nylon6,6

Type of polymerization:-

O Nylon 6,6 is obtained by the condensation reaction of adipic acid and hexamethylene diamene

O It is an alternating co-polymer

Physical Properties:-O Melting point, Tm:- 268 degrees

CelsiusO Glass Transition Temperature, Tg:- 47

(probably)O Nylon 6,6 is an amorphous solidO Molecular weight of repeating unit :-

226.32 gm/molO Nylon 6,6 has high mechanical strength,

great rigidity and good stability under heat

Physical Properties:-O Nylon 6,6 has a high melting point

and glass transition temperature due to hydrogen bonding between carboxylic oxygen and hydrogen attached on nitrogen

Adipic Acid Manufacture

Hexamethylenediamine Manufacture

1. From Adipic acid

2. From 1,3-Butadiene

The highly exothermic reaction is carried out either in a high or low pressure process

High pressureFe/Co Catalyst at 25-30 MPa and atemperature of 100-150 °C

Low pressureRaney Nickel Catalyst containing Fe/Cr activated by NaOH or KOH in solution at 2-3.5MPa

1. lower cost and fewer waste products as compared to NaCN2. Dinitrile using Anti-markovnikov addition of HCN

Industrial Production

Method of processing

O From chemicals to Nylon saltO Nylon salt to pelletsO Pellets to molten formO Extruded into different shapes or

Extruded through a spinneret to get filaments

Industrial Production

Three Processes are used commonly:-O Two of them starts with nylon 6,6 salt

O Batch or Autoclave processO Continuous polymerization process

O Third is Solid phase polymerization(SPP) which starts with low molecular weight pellets.

Nylon 6,6 SaltO Its made by adding adipic acid to a

solution hexamethylenediamine in water O First hexamethylenediamine is dilluted.O Then excess adipic acid is added.O Now, diamine is added to reach desired

stoichiometric balance.O There are two methods to get dry salt:-

O Addition of methanol.O Using saturated Nylon 6,6 salt solution.

Batch or Autoclave process

O Concentrating the salt solution to 75% in evaporator.

O Conc. Salt is send to an Autoclave where polymerization takes place in two steps:-O Firstly the reactants forms oligomers pressure of

1.75 MPa until equilibrium is reached.O Temperature is raised to 275 oC keeping

pressure constant at 1 atmO Polymer is drained through a die from

autoclave. These dies are fed into a casting machine that cools and solidifies the polymer in water, then cuts it into cylindrical pellets.

Batch or Autoclave process

O AdvantageO Low capital investmentO FlexibilityO Simple operation

O DisadvantageO Low throughput. O High labor costsO Variation in properties from batch to batchO Difficulty in forming high molecular weight

polymer

Continuous polymerization process

O EvaporatorO Pressurized column Reactor

O Feed is given from the bottom of columnO Initial polymerization reaction takes place.O After a suitable residence time high molecular

weight polymer is produced.O Then it is pumped to Flasher which is designed

to lower the pressure. Of the polymer mass.O Separator is used to remove water vapors from

the polymer, which has reached 98% of reaction.

O In Vacuum finisher the final degree of polymerization takes place. It has a pressure of about 40 kPa.

Continuous polymerization process

O AdvantagesO High continuous throughputO Uniform polymer propertiesO Ability to produce high molecular weightO Low cost

O DisadvantagesO High Capital investmentO Complex operationO Investment

Solid Phase Polymerization(SPP)

O For high molecular weight O Two types: Batch and Continuous

O Batch ProcessO Continuous process :

O First heating (100 degree celcius )O Then SPP vesselO Large plug flow reactorO T = 150-200O Hold up time = 6-24 hr

Solid Phase Polymerization(SPP)

O Advantage O High molecular weight without

increasing thermal degradationO Useful for other polymers

O DisadvantageO Long hold uptimeO More capital investment than cp or

autoclaveO Thermo oxidative damage

Applications:-O Having high mechanical strength Nylon

6,6 is used in places where high wear is expected

O It is generally used in the form of fiber to make carpets, zip ties, ropes etc.

O In other forms it is used to make conveyor belts and pipe hose

O Industrially it is used for ball bearing cages, electro-insulating elements, pipes, profiles and various machine parts

Sources:-O www.plasticsintl.com/nylon.htmO www.pslc.ws/macrog/nysyn.htmO polymer.matscieng.sunysb.edu/forms/Nylon.doc

O www.rtpcompany.com/info/guide/descriptions/0200.htm

O www.invista.com/en/nylon-polymer/index.html

O Kirk-Othmer Encyclopedia of Chemical Technology, Volume 19, Pigments to powders handling

Thank you