Rayon: Difference between revisions
(Created page with "{{Fiber | name=Rayon | source= | locality= | kingdom=Synthetic | radius= | length= | immediate_use=no | native_color=white }} 200px|thumb|Cellulose, {{#Chem: C6H7O2(OH)3}}, with the hydroxyl groups underlined Rayon is any fiber made from dissolved cellulose. The cellulose may be chemically modified to become soluble, or solvents produced which can dissolve cellulose, or combinations thereof. Eventually the dissolved ce...") |
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[[File:CelluloseHydroxyls.png|200px|thumb|Cellulose, {{#Chem: C6H7O2(OH)3}}, with the hydroxyl groups underlined]] | [[File:CelluloseHydroxyls.png|200px|thumb|Cellulose, {{#Chem: C6H7O2(OH)3}}, with the hydroxyl groups underlined]] | ||
Rayon is any fiber made from dissolved [[cellulose]]. The cellulose may be chemically modified to become soluble, or solvents produced which can dissolve cellulose, or combinations thereof. Eventually the dissolved cellulose compound is extruded through a '''spinneret''' into an environment which causes the cellulose to solidify. The solidified cellulosic fibers are rayon. | Rayon is any fiber made from dissolved [[cellulose]]. The cellulose may be chemically modified to become soluble, or solvents produced which can dissolve cellulose, or combinations thereof. Eventually the dissolved cellulose compound is extruded through a '''spinneret''' into an environment which causes the cellulose to solidify. The solidified cellulosic fibers are rayon. |
Latest revision as of 22:40, 17 December 2024
Rayon is any fiber made from dissolved cellulose. The cellulose may be chemically modified to become soluble, or solvents produced which can dissolve cellulose, or combinations thereof. Eventually the dissolved cellulose compound is extruded through a spinneret into an environment which causes the cellulose to solidify. The solidified cellulosic fibers are rayon.
Uses
Primary
- Artificial fiber sourced from wood waste
Natural occurrence
- None
Hazards
- Flammable unless treated specially
Production
The input material is cellulose, an insoluble polymer of glucose. Below it is written C6H7O2(OH)3 to emphasize the hydroxyl substitutions.
Cuperammonium
Schweizer's reagent can dissolve cellulose directly, which separates it from the remainder of the methods below.
- Dissolve cellulose in a minimum of Schweizer's reagent
- Extrude the concentrated solution through a spinneret into 10% sulfuric acid solution, breaking down the solvent into copper sulfate and ammonium hydroxide, and solidifying the cellulose.
- Cu(NH3)4(OH)2(H2O)2 + H2SO4 → CuSO4 + 4 NH4(OH)
- Distil the ammonia, recycle
- Recycle copper sulfate
Producing Schweizer's reagent
This chemical tetraaminecopper dihydroxide dihydrate (Cu(NH3)4(OH)2(H2O)2) dissolves cellulose in a way that it can be reconstituted by reaction with sulfuric acid, producing water and copper sulfate
from copper sulfate
This is the recycling path, since copper sulfate is the chemical produced when the dissolved cellulose is acidified with sulfuric acid.
- Combine copper sulfate, sodium hydroxide producing copper hydroxide (metathesis)
- CuSO4(aq) + 2 NaOH(aq) → Cu(OH)2(s) + NaSO4(aq)
- Combine copper hydroxide and ammonia, producing the reagent
- Cu(OH)2 + 4 NH3 + 2 H2O → Cu(NH3)4(OH)2(H2O)2
from malachite
Malachite has the fortunate composition of copper hydroxide and copper carbonate, which eliminates the need for sodium hydroxide above
- Ammonia and malachite are combined directly, producing the reagent and carbon dioxide
- Cu2CO3(OH)2 + 8 NH3 + 5 H2O → 2 Cu(NH3)4(OH)2(H2O)2 + CO2
Cellulose acetate
- Combine acetic anhydride and cellulose, replacing one two or three of the hydroxide moieties with acetate producing cellulose acetate
- C6H7O2(OH)3 + (CH3COO)2O → C6H7O2[(OH)x(CH3COO)3 -x] (x:0..2)
- Dissolve the cellulose acetate in a minimum of propanone
- Extrude the concentrated solution through a spinnerette into warm dry air, allowing the solvent to evaporate (condensed and reused)
Viscose
In this case the cellulose is modified (to sodium cellulose xanthate) but reconstituted completely.
- React wood pulp with aqueous sodium hydroxide, substituting a sodium for a hydrogen, yielding alkali cellulose
- C6H7O2(OH)3 + NaOH → C6H7O2(OH)2ONa + H2O
- React the alkali cellulose with carbon disulfide giving sodium cellulose xanthate.
- C6H7O2(OH)2ONa + CS2 → C6H7O2(OH)2CS2ONa
- Concentrate ("ripen") the solution allowing its viscosity to get to the "right level"
- Expose the ripened solution to dilute sulfuric acid, producing rayon or cellophane. The carbon disulfide may be recyclable.
- 2 C6H7O2(OH)2CS2ONa + H2SO4 → C6H7O2(OH)3 + 2 CS2 + Na2SO4