Development of Green Adhesives for Fibreboard Manufacturing, Using Tannins and Lignin from Pulp Mill Residues (original) (raw)
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Molecules
The extraction of condensed tannins from Aleppo pine bark and sumac roots (Brown Rhus tripartitum) was examined in near industrial conditions, using a water medium in the presence of 2% NaHCO3 and 0.5% NaHSO3 at two different temperatures (70 °C and at 100 °C). The tannins extracts were recovered in high yields (~25% of Aleppo pine and ~30% for sumac) with high phenolic contents (>75%). The tannins were characterized by 13C-NMR and MALDI TOF and showed characteristics of procyanidin/prodelphinidin units. The tannins extracted at 100 °C were composed of smaller flavonoid oligomers (DP < 8) compared to those extracted at a lower temperature (DP > 10). Adhesive resin formulations were prepared using Aleppo or sumac tannins and four different cross linkers (hexamine, glutaraldehyde, furfural, and glyoxal). The resins were studied by TMA in bending and tannins-based formaldehyde-free wood particleboards were produced. The panels displayed internal bond strengths > 0.35 MPa wi...
Environmentally friendly wood adhesives based on chestnut (Castanea sativa) shell tannins
European Journal of Wood and Wood Products, 2016
The aim of this work was the formulation of adhesives for particleboards based on tannins extracted from industrial lignocellulosic wastes, namely chestnut shell, chestnut bur and eucalyptus bark. The interest was centred on the possibility of completely removing formaldehyde from adhesive formulations. For this, hardener alternatives to formaldehyde were used: tris(hydroxymethyl)nitromethane (TRIS), glyoxal (GLY) and hexametilentetramine (HEX). The influence of the type and concentration of the hardener and pH on adhesive gel time and pot-life were studied. A comparative structural characterization of the adhesives was performed by 13C-NMR spectroscopy. Thermomechanical analyses (TMA) tests were carried out as an indication of the final strength of the adhesive systems. Particleboards type 2 of interior use (EN 312) were manufactured with adhesives based on chestnut shell tannins alone or mixed with chestnut bur/or eucalyptus bark tannins. Free-formaldehyde was determined, and boards were prepared with TRIS, GLY and HEX tannin adhesives were classified as E0.
Tannins of Deciduous Trees Bark As a Potential Source for Obtaining Ecologically Safe Wood Adhesives
Environment. Technology. Resources. Proceedings of the International Scientific and Practical Conference, 2015
The bark of deciduous trees grown in Latvia: grey alder, black alder, ash tree and goat willow were sequentially extracted using solvents of increasing polarity. The data about total content of both lipophilic and hydrophilic compounds were obtained using sequentially extraction with hexane and ethanol. The highest yields of hydrophilic extractives were found for grey alder and ash tree barks (25.7% and 25.8%, respectively). Hydrophilic extract from the both alder species contained high amount (up to 12% on bark dry mass) of condensed tannins (CT) or oligomeric proanthocyanidins, whereas CT content of extract from ach tree was negligible. The main component of ethanol-water extract from alder bark was identified using 13C NMR and MALDI–TOF MS spectroscopy as a mixture of A- and B-type oligomeric procyanidins with the epicatechin units polymerization degree of 2-7. Ecologically friendly wood adhesives were obtained on the condensed tannin basis.
Synthetic-resin-free wood panel adhesives from mixed low molecular mass lignin and tannin
European Journal of Wood and Wood Products, 2011
Mixed interior wood panel tannin adhesive formulations were developed in which lignin is in considerable proportion, 50%, of the wood panel binder and in which no "fortification" with synthetic resins, such as isocyanates and phenol-formaldehyde resins as used in the past, was necessary to obtain results satisfying relevant standards. A low molecular mass lignin obtained industrially by formic acid/acetic acid pulping of wheat straw was used. Environment-friendly, non-toxic polymeric materials of natural origin constitute up to 94% of the total panel binder. The wood panel itself is constituted of 99.5% natural materials, the 0.5% balance being composed of glyoxal, a non toxic and non volatile aldehyde, and of hexamine already accepted as a non-formaldehyde-yielding compound when in presence of condensed tannin. Both particleboard and two types of plywood were shown to pass the relevant interior standards with such adhesive formulations. Moreover, the much cheaper nonpurified organosolv lignin showed the same level of results as the more expensive purified type.
Materials
Toxic formaldehyde emissions, and the necessity to reduce the consumption of petrochemicals, stimulates the development of environmentally friendly adhesives. The aim of this research was to study, for the first time, the possibility of using condensed tannins (CTs)-rich extracts from grey alder (Alnus incana) and black alder (Alnus glutinosa) bark in the production of particleboards and plywood adhesives. The chemical structure, composition, and molecular weight of the CTs were identified by a 13C-NMR and TOF-MS analysis. Three innovative adhesive systems were studied: CTs-phenol-formaldehyde (CTs-PF) resin; a CTs-polyethyleneimine (PEI) adhesive system; and CTs–PEI combined with an ultra-low emitting formaldehyde resin (ULEFR)—CTs–PEI–ULEFR. The results showed that CTs-PF resin has properties close to commercial PF resin, and the formaldehyde emission was twice lower. CTs–PEI bonded particleboards corresponded to the requirements of the EN 312:2010 standard for particleboards in d...
Characterization of Tunisian Aleppo pine tannins for a potential use in wood adhesive formulation
Industrial Crops and Products, 2014
The phenolic composition of Tunisian Aleppo pine barks was studied. Colorimetric assays, Fourier transformed infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR) were used to examine Aleppo pine tannins. Analyzes showed that Aleppo pine barks are rich in condensed tannins, especially in procyanidin and prodelphinidin tannins. The reactivity to formaldehyde test (Stiasny number) showed the possible use of Aleppo pine tannins in wood adhesive formulation. Thermomechanical analysis (TMA) and strength analysis of Aleppo pine tannin/hexamin based resin showed important bonding properties.
Holz als Roh- und Werkstoff, 1996
The alkaline extraction of tannins from Pinus pinaster bark was studied as regards the influence of solid/liquid ratio, extraction time and NaOH concentration on the yield and Stiasny number of the extracts precipitated at pH 2. The extract with the highest Stiasny number(97) was copolymerized with a previously prepared resol to afford a resin with a 1 : I phenol/tannins ratio. Plywood boards of Eucalyptus globulus bonded with this resin at board humidities of 10 or 16%, temperatures of 130 or 185 ~ and press times of 5 or 8 rain all passed the WBP knife test (with one exception for the longer press time). We conclude that this resin is superior to commercial phenol-formaldehyde resins as regards its tolerance to moisture in plies and adhesive, its press time requirement, and its ability to bond veneers of woods known for their high levels of adhesive-repellent substances. Tanninkleber zum Verleimen sehr feuchter Furnierbh)'tter: EinfluB der Tanninextraktion und der PreBbedingungen Die Alkaliextraktion von Tanninen aus Pinus pinaster wurde untersucht im Hinblick auf den Einflufl des Flottenverh~iltnisses, der Extraktionszeit und der NaOH-Konzentration anf die Ausbeute und die Stiasnyzahl der Extrakte nach Ausflillen bei pH 2. Der Extrakt mit der h/Schsten Stiasnyzahl (97) wurde mit Resol copolymerisiert, so daft sich ein Phenol-Tannin-Verh~ltnis yon 1:1 ergab. Alle Sperrh61zer, die aus Eukalytus-globulus-Furnieren mit Feuchten yon 10 oder 16% mit diesem Harz verleimt waren (Prefltemperaturen 130 oder 185 ~ Preflzeiten 5 oder 8 Minuten), bestanden entsprechende Qualit~itstests. Eine Ausnahme bildeten Sperrh6lzer, die bei l~ingerer Preflzeit hergestellt waren). Dieses Tanninharz erscheint uns kommerzieilen PF-Harzen fiberlegen in Hinsicht auf seine Feuchtetoleranz in Furnier und Harz, die Preflzeit und das BindevermiSgen auch ftir H61zer, die als schwerverleimbar gelten.
Preparation of wood adhesives based on tannins and glycerol esters ( triacetate )
2016
Background: The use of products obtained from gluing of wood can, directly, contributes to the conservation of forest resources, from the point of view of its full use. However, the synthetic resins used in the bonding are obtained by petroleum derivatives, whose price has grown steadily in recent years as a result of the reduction of fossil resources. An alternative would be the use of compounds derived from renewable sources, such as tannins, instead of phenol. Furthermore, driven by energy policies that encourage the use of renewable sources, we are in the midst of a biodiesel production surge. One of the co-products of biodiesel production is glycerin, which corresponding itself to 10% of the total mass of the obtained oil. Glycerin, or more specifically the glycerol, may be converted to glycerol triacetate. Thus, the objective herein was to prepare environmentally friendly adhesives, using glycerol triacetate and tannins. For preparation of the wood adhesives, glycerol triacetate and H2SO4 were mixed at 80°C for one hour. After this procedure, the tannin was added and the material subjected to the curing process. Adhesives A and B were produced with 25 and 40% tannin, respectively. The analysis of the adhesives differed only in solids content and viscosity. The shear strength and rupture percentage values indicate that the prepared adhesives have great potential and can be used commercially in the future.
Effect of Extraction Solvent on Tannin-Formaldehyde Adhesives for Plywood Production
Journal of Energy and Natural Resource Management, 2018
Pine bark is a good source of natural polyphenolic compounds for wood adhesives. The objective of this study was to obtainthe most suitable solvent for extracting pine tannins in the preparation of tannin-formaldehyde plywood adhesives. Aqueousacetone, aqueous ethanol, aqueous NaOH and water as solvents were used to obtain crude tannins from pine bark. Thetannin content, sugar content and Stiasny number of the extracts were determined. Using the extracts from the solventextractions, synthesis of tannin-formaldehyde resin was carried out. Plywood panels were made using the synthesized resinsand the quality of the resins in plywood application determined. The quality of tannin-formaldehyde resins produced from thetannins were generally in close agreement with the chemical characteristics of the extracts obtained from the various solventextractions. The aqueous NaOH extraction although gave very high tannin yield (16.1%), its associated high sugar content(33.8%) and very low Stiasny nu...
The aim of this study was to determined the quality of mahogany (Swietenia mahagony) tannin extract as an adhesive for plywood. The mahogany tannin extract was copolymerized with phenol and formaldehyde became TPF adhesive. Then, the plywood was made from mangium (Acacia mangium) and sengon (Paraseriathes Falcataria) with dimensions 30 × 30 × 0.6 (cm3) in the length, width, and thickness, respectively. Pressing was carried out using the cold press method for 11 minutes and then followed by the hot press method for 10 minutes at a temperature of 110oC with a specific pressure of 1.47 MPa. Phenol formaldehyde and urea formaldehyde adhesives were used as a comparison and 5 replicates were made for each plywood. The physical and mechanical were tested according to JAS 233:2003. The result showed that TPF had an equal quality with the synthetic adhesive in dry conditions. Moreover, all of plywood from sengon wood categorized as F**** the lowest and the best.