Collagen in Papermaking

Abstract: The collagen extraction methods, structure and chemical properties, focusing on the collagen in the paper application.

Keywords: collagen nature of the paper and chemical properties

1 Introduction

Collagen fibers constitute the main component of skin, collagen is the basic unit of the formation of collagen fibers from the three peptide chains intertwined into a spiral structure. Elastic and collagen fibers with micro-high tensile strength, and there are many unique properties such as high wear resistance, thermal insulation, sound absorption and flexibility, etc.

Collagen addition to the general nature of the protein, there are many unique properties, which is determined by its unique composition and structure of the decision of the General of the protein by two peptide chains to form a double helix, while the collagen from the three peptide chain to form triple-helix structure. collagen-specific L-A chain composed of intertwined right-handed complex helix structure of collagen, the most prominent feature is the large number of collagen molecules containing glycyl, prolyl and glycyl to Gan - prolyl than any other amino acid residues, and the cyclical arrangement of which 30% of glycine, proline and hydroxyproline together account for about 25% collagen ionic bond exists between the peptide chain, hydrogen bonds, van der Waals force and non-polar groups such as the force generated by hydrophobic bonds, while, within the collagen molecules and intermolecular aldol condensation, there are cross-linked, cross-linked and aldehyde-ammonia condensation aldol histidine kinds of cross-linked, making collagen 2 of the peptide chain, three peptide chains connected firmly with high tensile strength. collagen molecules staggered by a quarter way to form a stable supramolecular aggregate toughness strong fiber, fiber to further aggregate to form collagen fibers.


2 Extraction of collagen

Collagen protein is currently extracted mainly from leather waste, there are many studies at home and abroad, according to the literature, from chrome shavings are many ways to extract rubber, according to its different treatment agent into the following extraction methods.

2.1 alkali treatment
Alkali treatment of the principle of lye in the OH-ions into the complex inner world, the collagen carboxy-out from the chromium complex to replace, and while the chrome off of collagen degradation, and then dissolved in water, Cr3 + and OH- ions form a precipitate. After pressure filtration or centrifugal separation, the collagen solution and Cr (OH) 3 precipitation. Wu-Yong Chen and other extraction of CaO in the chrome-tanned leather shavings collagen factors were studied to determine the extraction of calcium oxide collagen, the optimum conditions and programs.

2.2 acid treatment method
Acid treatment method is based on the acidic conditions, the chromium complexes dissociate, with the H + concentration increases, the dissociation speed, complex molecules smaller, loss of tanning production use, to de-chrome extracted collagen purposes. Use acid hydrolysis separation of collagen fibers, H2SO4 concentration the greater the hydrolysis time is shorter, but the concentration is greater than 4%, below 70 ℃, chrome-tanned leather shavings (shaving shavings) the time required for the complete hydrolysis of about 2h; and the influence of temperature is also great, higher than 70 ℃, the hydrolysis of time-dependent decrease, but the acid treatment method to a large degree of hydrolysis of collagen, the collagen molecules can only get a small degradation products, and Cr3 + are dissolved in the acidic conditions state, and the collagen is difficult to completely separate.

2.3 Oxidation
The principle of oxidation in weak alkaline conditions, using the oxidant (usually H2 02) the tanning sludge oxidation of Cr3 + Cr6 + (as soluble chromate), the Cr6 + from the protein peptide chain falling off, in order to achieve separation of chromium with collagen, such as in alkaline medium, hydrogen peroxide oxidation of trivalent chromium according to the principles of the use of acid - base - oxidation alternate methods are available to low chromium content of collagen, and maintained the structure of collagen molecules . Yuan-Liang Wang off the chrome and other alkaline agent and oxidizer used in conjunction with the method of removal of chromium, chromium-off effect is remarkable, after the chrome off a low chromium content of collagen. large number of studies show that: with the oxidation off the chrome, speed, structural damage to the collagen small degree, to obtain the product of molecular weight of collagen, good color, de-chrome effect, but in the process will produce toxic Cr6 +.

2.4 enzyme treatment method
Enzyme treatment method is based on enzymatic hydrolysis of chrome shavings used to make one of the chromium complexes with protein de-tanning, isolated chromium salts and partially hydrolyzed collagen. Cabeza improved enzymatic step, two-step enzymatic (first extracted with pepsin, and then alkaline protease extraction) to extract two different collagen hydrolysates. enzymatic method under mild conditions, the composition of the destruction of a small protein, derived from collagen of high purity, water solubility, physical and chemical properties of stability, but If used alone, the reaction process is very slow.

Because of these methods have their advantages and disadvantages, so far in the extraction of collagen, often combine several methods, such as alkaline enzyme treatment method, ie extraction of collagen, first with the base of the chrome shavings for mild processing, then use a second enzyme treatment, which can increase the extraction rate of collagen and reaction efficiency.


3 the chemical properties of collagen

3.1 and the reaction of nitrite
Protein or amino acids and amino nitrite reaction, amino or terminal amino side is broken, and the release of nitrogen, by measuring the amount of nitrogen released from the protein can be calculated off the extent and speed of protein hydrolysis.

3.2 with formaldehyde
Formaldehyde titration method can be used to determine the amino acid content, the principle is the occurrence of formaldehyde in amino addition reaction to form N-hydroxymethyl derivatives continue to react to produce N-bis-hydroxymethyl derivatives, which will free amino closed to protect amino. titration with alkali solution, the number of free carboxyl to calculate the protein content.

3.3 with the ninhydrin reaction
Protein or amino acid solution was added dropwise a few drops of ninhydrin solution and heated to boiling, the solution that was blue and purple, but because it is the proline and hydroxyproline imino. Produce yellow. The reaction of amino acids used in the quantitative colorimetric analysis.

3.4 with acid, alkali effect
Collagen peptide chains and end groups are amino and carboxyl side chain, that there are a number of basic groups and acidic groups, which in solution in combination with acid and alkali. Combination of collagen molecules and ions between the peptide chain crosslinks and hydrogen bonding will be opened. with time, a variety of key and secondary key cross-linking gradually destroyed. occurrence of acid-soluble or alkali-soluble collagen, or even the main-chain degradation may occur when heated to boiling, the collagen gradually hydrolyzed into small peptides by the large peptides, until into amino acids.

3.5 and the role of base
In the salt solution of collagen peptide chains of the ionic bond is the salt to open, thus swelling. Various ions on collagen expansion capacity the size of the effect below. Cations: Ca2 +> Li +> Na +> K +> Rb2 +> Cs2 +; anion: CNS-> I-> NO-> Cl-> CHCOO-> SO32-> tartrate> citrate. neutral salt can cause collagen swelling, and some caused by dehydration. Links to free download http://www.hi138. com 4. collagen in Papermaking

With the development of society, the application of collagen is also increasing due to collagen fibers do not have some of the nature of plant fibers, so it will gradually be applied to the paper industry.

4.1 as a paper reinforcer
Collagen fibers and plant fibers are either natural polymer with many reactive groups and the active site, the treated leather solid waste into collagen fibers in the process of wood pulping process than the reactive groups exposed to more, more reaction, the combination of two fibers to provide a good condition. collagen fibers as an additive for the paper to join the slurry can be enhanced with plant fiber winding, weaving, to hydrogen bonding, ionic bonding, covalent bonding, van der Waals force and electrostatic attraction, etc. combination of these keys into the paper makes the formation of the binding force between fibers increases, bond energy increases, so that the paper's physical strength is improved.

Collagen is composed of many - by the peptide consisting of amino acids polypeptide chain, the side chains of collagen molecules contain many polar groups on the cellulose molecule contains a large number of hydroxyl groups such as carboxyl and a small amount. Adjust the different media can make the collagen fiber and cellulose molecules to hydrogen bond, ionic bond and covalent bond in the form of combination of these keys allows the formation of the binding force between the paper fibers increases, bond energy increases, so that the paper's mechanical strength is increased, so paper, water absorption, permeability, tightness and other physical indicators have improved. In addition, the collagen modified for cationic or anionic, respectively, made of anions (cations) paper reinforcer, can increase the breaking length, tear index increased.

4.2 Adhesive
Collagen as adhesive, can be used as papermaking sizing agent, but its poor water resistance, usually in the collagen adhesives Cadogan paraformaldehyde cross-linking agent for hardening, urea-formaldehyde resin obtained similar results, and increase resistance to water ability to make collagen molecules to form crosslinks between the chains, so that the viscosity increase and strengthen the solidification structure and improve the mechanical properties of collagen.

Collagen as adhesive, can be used gauze, sand paper manufacturing, is also available for the production of adhesive tape would be chemically treated gelatin for the production of cast coated paper, with the original production and products, speed increased by 1, gloss degree from 30% to 39%, while production costs remain basically unchanged.

4.3 Surfactants
Surfactant in the nature of the opposite sub-2 components, namely, hydrophilic and hydrophobic groups, two groups of proportion (HLB value) determines the surfactant hydrophilic and hydrophobic strength. HLB The higher the value, the stronger hydrophilic, hydrophobic weaker. both the molecular structure of collagen, amino, carboxyl another, in different media showed amphiphilic; a variety of different amino acids amino in the structure with asymmetry, it is also to some extent, the surface activity.

Back in the 1960s, some people study the collagen used as a deinking waste paper back to the agent, collagen and other polymers by the mixed use of waste paper pulp brightness significantly improved for example with 3% sodium sulfite, 0.5% TPP (STPP), l% fatty acid salt and 0.295 collagen (relative to points on the quality of 10000 and isoelectric point of 5), after deinking, waste paper pulp whiteness 60% ISO.


References:
[1] Wu-Yong Chen, Zan Huang, scrap shavings extraction of collagen research [J]. China Leather, 2002, 31 (23): 1-5.

[2] Sun Danhong, Bi Shi, chromium oxide waste shavings off the chrome Method [J]. Leather Science and Engineering, 2002, l2 (9): 3l-3.

[3] Yuan-Liang Wang, Huang Xingchun, chrome shaving shavings off the chrome Method [J]. China Leather, 1991, 20 (12): 7-l2.

[4] Cabeza LF, Isolation of protein products L4J from chromium-containing leather wastes using two consecutive product: pilot plant studies [J]. J Soc Leather Tech Chem, 1999 (83): 14-l9.

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