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Application of glycerol in
adhesives for wood panels
KATSAMPAS ILIAS
Foggia, Italy , April 2009
CONTENTS
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CHIMAR HELLAS profile
INTRODUCTION
FORMALDEHYDE BASED ADHESIVE RESINS
FORMALDEHYDE BASED ADHESIVE RESINS AND GLYCEROL
NATURAL RESINS AND GLYCEROL
GLYCEROL DERIVATIVES AND WOOD ADHSIVES
CHIMAR R&D on “green” panel resins
CHIMAR HELLAS profile
• Developer and Provider of Industrial Technology for resins
and chemicals for wood-based panels
• Technology licensing, manufacturing support, application
support for: formaldehyde resins, resin additives, field
processes
• Industrial Engineering and Plant Procurement:
formaldehyde, UFC, resins, chemical additives
• Research & Development: develops know-how in house
• Training of client personnel
• Technical support: remotely and on-site
• Product testing: as per international standards
INTRODUCTION
WOOD ADHESIVE
TECHNOLOGY :
•The recorded history of bonded wood dates back
at least 3,000 years to the Egyptians, and adhesive
bonding goes back to early mankind
(Skeist, I. and Miron, J. (1990). Introduction to adhesives. In: Skeist, I.
(Ed.), Handbook of Adhesives. (3rd)
Van Nostrand Reinhold, New York, chap 1.)
•The conventional wood-based composite
products are typically made with a thermosetting
or heat-curing resin or adhesive that holds the
lignocellulosic (wood) fibre together.
•Wood composites are grouped into three general
categories: plywood, particle and fibre composite
•Commonly used resin–binder systems include
phenol-formaldehyde, urea-formaldehyde,
melamine-formaldehyde, and isocyanate.
Examples of various wood
composite products. plywood,
OSB, particleboard, MDF, and
hardboard.
FORMALDEHYDE BASED
ADHESIVE RESINS
FORMALDEHYDE BASED ADHESIVE RESINS REPRESENT BY FAR (>95%) THE
BIGGEST VOLUMES WITHIN THE WOOD ADHESIVES
UF RESIN ADHESIVES: 85%
MELAMINE BASED RESIN ADHESIVES: 10%
PHENOL BASED RESIN ADHESIVES: <5%
Condensation resins based on formaldehyde are formed by the reaction of
formaldehyde with various chemicals like urea, melamine, phenol or combination
of these substances.
FORMALDEHYDE BASED
ADHESIVE RESINS AND
GLYCEROL
•Glycerol in aminoplastic resins
Glycerol is used
a) as flexibilizer into the stiff chain of aminoplastic resins
b) to improve the hydrophobicity
c) to decrease the curing time
Improving the performance of MUF resins, with the use of polyols, glycerol,
1,2,6-hexanetriol, sorbitol and others.
Act as more effective solvents for melamine and higher molecular weight melamine
resin fractions, they disrupt the colloidal state of MUF resins, both of which
facilitate the homogeneous phase reactions and ensure better uniform network
formation during curing.
All of these additives function by addition to the end of the resin after preparation, or
by addition to the glue-mix before resin application
Glycerol derivatives can also be used as "latent", acid liberating hardeners for
curing melamine resins. 3-Chloro-1,2-propanediol is also known as glycerol-αmonochlorohydrin and Glycerol dichlorohydrin (1,3-dichloro-2-propanol)
•Glycerol in impregnation resins
Woodbase materials, especially chipboard, which are coated with aminoplasticimpregnated paper webs are used in the manufacture of, for example, furniture
components and work surfaces.
Compounds containing hydroxyl groups, primarily glycols, or amido- or amino
groups serve as plasticizers for impregnated papers.
Glycerol is used most widely, however, due to the comparatively high cost of
glycerol; it is combined with other cheap substances. One of the most readily
available additives for glycerol based plasticizers is synthetic urea.
• Glycerol as formaldehyde catcher
The addition of glycerol reduces further the formaldehyde emissions by binding
up remaining free volatiles into the polymer matrix and/or reacting with
formaldehyde moieties to produce less volatile cyclic and polymeric formals.
NATURAL RESINS AND
GLYCEROL
•Soy flour (SF) resins
SF resins was found to be brittle, weak and difficult to process into useful binder.
Glycerol has been reported to increase the flexibility and extensibility of soy protein
plastics by reducing the interaction between protein molecules.
The addition of glycerol provides better tensile and flexural properties on the
composites binded with the natural resin.
•Glyoxal/glycerol/ boric acid
Interesting and environmentally friendly mixture suitable for wood dimensional
stabilization.
•Natural tackifying resin
A potential additive in natural wood adhesives could also be the glycerol ester of gum
resin which is made from gum resin or refined gum resin through esterification with
glycerol
GLYCEROL DERIVATIVES AND
WOOD ADHESIVES
• Hyperbranched polyether with hydroxyl end groups
Hyperbranched polyether (HBP) obtained from glycerol blended with ureaformaldehyde improves the hardness (16%) and the compressive shear strength
(17%) of the cured urea - formaldehyde polymer, whereas water absorption remains
unaffected.
Glycerol triacetate (triacetin)
Used as a cure accelerator in various binder formulation such phenol –
formaldehyde and tannin or lignin binder systems.
Poly-glycerol and poly-glycerol ethers and esters
Very interesting compound due to their high content of hydroxyl groups that can
react either with formaldehyde (scavenger) or with urea or melamine to improve
overall resin properties.
•Diglycidyl ether (DGE) and polyglycidyl ether (PGE) type compounds
Due to the reactivity of diglycidyl and polyglycidyl ether compounds with
hydroxylated reactants like Lignin and or Tannin, they can potentially be applied
in the wood adhesives field.
•Polyethyleneglycols (PEGs), polyglycerol methacrylate (PGMA)
Improve the dimensional stability of wood and its hydrophobicity
CHIMAR R&D on “green” panel resins
Resins derived from natural products or by-products:
 Tannin
 Lignin
 Cellulose
 Spent pulping liquor from paper production
 Biomass pyrolysis oil (bio-oil) and its fractions
 Extraction/liquefaction products of agricultural and
forestry residues (cashew nut shell liquid (CNSL),
liquefied wood, liquefied olive stones, vinasse)
 Starch
 Proteins (soy)
Ilias Katsampas
Chemical Engineer, PhD, Msc
R&D department
Chimar Hellas SA
Sofouli 88, 55131 THESSALONIKI
.: +30-2310424167,  +30-2310424149
e-mail: [email protected], [email protected]
www.chimar-hellas.com