Ok boys and girls. Lets play nice. Teacher taught us that 'sticks and stones may break my bones but names will never hurt me". Well, teacher was wrong. Much of the now infamous cedar and bleach thread was actually informative and a lot of it was entertaining and fun. A shame it turned mean and nasty...
Yaz, your entry on regurgitating beer all over your monitor and keyboard is the highlight of my writing career and will remain a fond memory!
Enough editorial comment, back to business. Yesterday afternoon I spent a lot of time web researching the lignin - bleach connection, specifically in the pulp processing, paper production industry. When I went to post, the thread had been pulled, and my efforts lost. I'll try and reconstruct my findings in this new thread.
-----------------------------------
First, some definitions. The inexpensive, pervasive strippers used on removing finishes from exterior wood, are sodium hydroxide based or in chemspeak, NaOH. Bleach is a generic name for sodium hypochlorite, or NaOCl.
Bleach (sodium hypochlorite) is used in processing wood pulp into paper. Others have claimed, and I had assumed was true, is that bleach is used to remove or break the bond between the cellulose and lignin wood fibers early in the pulp process. My findings indicate that this assumption is not true.
Bleach (sodium hypochlorite) is the third stage in an up to seven stage process in chemical pulp processing. The first stage (C or substituted CD Stage in the article) is a chlorination step, which is partially quoted below..
"The chlorine reacts with the lignin by:
- substitution
- oxidation
- addition
Oxidation includes reactions with both lignin and carbohydrates. Oxidation of the carbohydrates leads to a decreases cellulose viscosity and decreased pulp strength. Lignin is not removed to a large degree in this stage, and the pulp actually gets darker..."
Key words are "decreases cellulose viscosity and decreased pulp strength".
The second stage (Extraction Stage (E) in the article) involves our old friend, sodium hydroxide (NaOH), that we all use as strippers. Partial quotes from the article as follows:
"The E stage is extraction of degraded lignin compounds, ...", "Chemistry of alkaline extraction
Removal of chlorinated lignin. Chlorination appears to give three types of lignin fragments:...", and further on, "Chlorination and alkaline extraction will remove ~80% of the residual lignin, but the resultant pulp has low brightness due to a relative increase in chromophoric groups. The alkali displaces chlorine and makes the lignin soluble by the reactions such as:
Lignin-Cl + NaOH --------> Lignin-OH + NaCl"
See the NaOH above? That is chemspeak for sodium hydroxide.
The third stage (Hypoclorite Stage (H) in the article) involves sodium hypochlorite or bleach. A few partial quotes...."The H stage consists of bleaching usually with sodium hypochlorite solution (NaClO).", "Since the pH is high, lignin is continuously extracted as it is depolymerized."
I make no claim to being a chemist. Maybe a reader more knowledgeable in the discipline can refute, change, or enlighten us.
To surmise from my admitted limited expertise, I offer the following. Clorination compounds are used to break the cellulose - lignin bond, not bleach. Sodium hydroxide is then used to further breakdown and extract the degraded lignin from the mix. Sodium hypochlorite (bleach) is then used to further extract lignin remaining in the mix, after the lignin has gone through two separate processes that has significantly altered its original composition. I emphasize, extract - not destroy, and at this point in the process the lignin in no way chemically like it is in wood.
Finally, a quote from another web reference..."The paper industry uses the caustic effects of sodium hydroxide on organic materials. Sodium hydroxide breaks down the lignin in wood. Lignin is a binder that holds cellulose fibers together in wood. When the lignin is removed, the freed cellulose fibers can be formed into paper. The digestive effects of sodium hydroxide on organic materials is the principle behind such drain cleaners as Liquid Plumr, which is a concentrated aqueous solution of sodium hydroxide."
Ok boys and girls. Lets play nice. Teacher taught us that 'sticks and stones may break my bones but names will never hurt me". Well, teacher was wrong. Much of the now infamous cedar and bleach thread was actually informative and a lot of it was entertaining and fun. A shame it turned mean and nasty...
Yaz, your entry on regurgitating beer all over your monitor and keyboard is the highlight of my writing career and will remain a fond memory!
Enough editorial comment, back to business. Yesterday afternoon I spent a lot of time web researching the lignin - bleach connection, specifically in the pulp processing, paper production industry. When I went to post, the thread had been pulled, and my efforts lost. I'll try and reconstruct my findings in this new thread.
-----------------------------------
First, some definitions. The inexpensive, pervasive strippers used on removing finishes from exterior wood, are sodium hydroxide based or in chemspeak, NaOH. Bleach is a generic name for sodium hypochlorite, or NaOCl.
Bleach (sodium hypochlorite) is used in processing wood pulp into paper. Others have claimed, and I had assumed was true, is that bleach is used to remove or break the bond between the cellulose and lignin wood fibers early in the pulp process. My findings indicate that this assumption is not true.
Bleach (sodium hypochlorite) is the third stage in an up to seven stage process in chemical pulp processing. The first stage (C or substituted CD Stage in the article) is a chlorination step, which is partially quoted below..
"The chlorine reacts with the lignin by:
- substitution
- oxidation
- addition
Oxidation includes reactions with both lignin and carbohydrates. Oxidation of the carbohydrates leads to a decreases cellulose viscosity and decreased pulp strength. Lignin is not removed to a large degree in this stage, and the pulp actually gets darker..."
Key words are "decreases cellulose viscosity and decreased pulp strength".
The second stage (Extraction Stage (E) in the article) involves our old friend, sodium hydroxide (NaOH), that we all use as strippers. Partial quotes from the article as follows:
"The E stage is extraction of degraded lignin compounds, ...", "Chemistry of alkaline extraction
Removal of chlorinated lignin. Chlorination appears to give three types of lignin fragments:...", and further on, "Chlorination and alkaline extraction will remove ~80% of the residual lignin, but the resultant pulp has low brightness due to a relative increase in chromophoric groups. The alkali displaces chlorine and makes the lignin soluble by the reactions such as:
Lignin-Cl + NaOH --------> Lignin-OH + NaCl"
See the NaOH above? That is chemspeak for sodium hydroxide.
The third stage (Hypoclorite Stage (H) in the article) involves sodium hypochlorite or bleach. A few partial quotes...."The H stage consists of bleaching usually with sodium hypochlorite solution (NaClO).", "Since the pH is high, lignin is continuously extracted as it is depolymerized."
I make no claim to being a chemist. Maybe a reader more knowledgeable in the discipline can refute, change, or enlighten us.
To surmise from my admitted limited expertise, I offer the following. Clorination compounds are used to break the cellulose - lignin bond, not bleach. Sodium hydroxide is then used to further breakdown and extract the degraded lignin from the mix. Sodium hypochlorite (bleach) is then used to further extract lignin remaining in the mix, after the lignin has gone through two separate processes that has significantly altered its original composition. I emphasize, extract - not destroy, and at this point in the process the lignin in no way chemically like it is in wood.
The full article is found at:
http://www.wmich.edu/ppse/pekarovicova/160999b.html
Related information from other web sites as follows:
A relatively easy read on paper and pulping. Note the sodium hydroxide (NaOH) references. No mention of sodium hypochlorite (bleach, or NaOCl).
http://www.tappiphils.com/about_pulp_and_paper.asp
Some good information on sodium hydroxide and sodium hypochlorite can be found here:
http://www.chemicalland21.com/index.html
Finally, a quote from another web reference..."The paper industry uses the caustic effects of sodium hydroxide on organic materials. Sodium hydroxide breaks down the lignin in wood. Lignin is a binder that holds cellulose fibers together in wood. When the lignin is removed, the freed cellulose fibers can be formed into paper. The digestive effects of sodium hydroxide on organic materials is the principle behind such drain cleaners as Liquid Plumr, which is a concentrated aqueous solution of sodium hydroxide."
http://scifun.chem.wisc.edu/CHEMWEEK/Cl2&NaOH/Cl2&NaOH.html
_________________________
Responsible responses are welcomed.
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