Glues from renewable resources for panel board manufacture

Number

201-EN

Section

General Section

Use

Sector

Manufacture of bulk, large scale chemicals (including petroleum products)
Manufacture of wood and wood products
Manufacture of furniture
Building and construction work

Function

Adhesion promotor

Process

Other

Product category

Adhesives, sealants

Application

Wood glue

Abstract

Urea-formol adhesives are largely used in the wood products industries. Construction materials are the main source of formaldehyde emissions in the indoor environment. Therefore, it is necessary to find new natural alternatives to produce wood adhesives. The project allowed developing and validating extraction process for tannins, based on aqueous extraction, and lignin. These extracted compounds were successfully inserted in adhesives to develop a formula without formaldehyde. The mechanical properties of the panel board produced with this new adhesive responded to European standard.

Substituted substances

Formaldehyde

CAS No. 50-00-0 EC No. 200-001-8 Index No. 605-001-00-5

Chemical group

Aldehyde

Classification: hazard statements

H350 May cause cancer
H341 Suspected of causing genetic defects
H331 Toxic if inhaled
H311 Toxic in contact with skin
H301 Toxic if swallowed
H314 Causes severe skin burns and eye damage
H317 May cause an allergic skin reaction

Other adverse effects

The substance is: 1 carcinogen (IARC) as listed in the Substance Database according to SUBSPORT Screening Criteria (SDSC).

Melamine

CAS No. 108-78-1 EC No. 203-615-4 Index No.

Chemical group

Amino compounds; nitrogen heterocycles

Classification: hazard statements

H351 Suspected of causing cancer
H373 May cause damage to organs through prolonged or repeated exposure

Reliability of information

Convergent opinions: conclusions for similar cases are similar to the ones in this case study

Reason substitution

CMR
skin/respiratory sensitizing

Hazard Assessment

Substances to be substituted: Formaldehyde may cause cancer cat. 1B, according to Annex VI of Regulation (EC) No 1272/2008 (CLP Regulation). It fulfils the criteria to be listed in the Substance Database according to SUBSPORTplus Screening Criteria (SDSC). Melamine has no harmonised classificationaccording to Annex VI of Regulation (EC) No 1272/2008 (CLP Regulation). It fulfils the criteria to be listed in the Substance Database according to SUBSPORTplus Screening Criteria (SDSC). Alternative substances: Tannic acid and Lignin are not listed in the SUBSPORTplus Database and have no harmonised classification according to Annex VI of Regulation (EC) No 1272/2008 (CLP Regulation).

Description of Substitution

The French project 'Panneaux verts' (Green panels) was started in order to substitute urea-resin adhesives with new and environmentally friendly adhesives for wood panels. The project developed a wood adhesive based on lignin and tannins. The tannins extraction was performed on barks supplied by French pulp mills from different softwood species (spruce, pines, Douglas fir) and from eucalyptus. After crushing and extraction, the amount of tannin depended on the wood species. The extractives from Douglas fir bark were very rich in tannins (97%) compared to spruce bark (48%), maritime pine (24%) and eucalyptus (25%). The extractives the most abundant in phenols were from Aleppo pine (25%), spruce (18%) and Douglas fir (16%). The condensed tannins content depended also on the wood species. Pilot extraction trials were carried out with barks of spruce, Aleppo pine and Douglas fir in presence of urea-sulphite. The lignins were extracted from black liquors generated by the paper pulping process. Lignin was precipitated in acidic medium. The gluing behaviour of lignins extracted from different industrial mills was measured. The lignins from kraft pulp black liquors had better characteristics and could be used as adhesives. Kraft pulping is a process to for conversion of wood into wood pulp. For being used in adhesive formula, the lignins had to be dissolved in alkaline medium. A lignin from an organosolvent process using cereal straw, Biolignine®, had specific properties (molecular weight, free phenolic OH groups) and was glyoxylated to improve its adhesive power. A pilot plant installed in the North of France was able to produce large batches of this lignin. Formula based on tannins and lignin were developed. The tannins had to be used with hexamine and the lignins glyoxylated. The formula based on 40% lignin and 60% mimosa tannins had good adhesive properties. Panel boards manufactured at pilot scale with kraft softwood glyoxylated lignin and mimosa tannins presented the properties required by the European standards. The formaldehyde emitted by such “green” panel boards was very low: 1.12 mg formaldehyde/kg panel board and was released by the wood itself. The use of such formula could be envisaged at industrial scale. The industrial trial was previously scheduled during the project, but it was not possible to organise it.

Case/substitution evaluation

The case story was provided by the researchers of the project 'Panneaux verts'. The alternative glue for wood panels is not on the market, yet. It does not contain formaldehyde or other substances that are associated with any hazard statements. In the production hexamine and glyoxal are needed. Both substances are classified according to ECHA Annex VI of Regulation (EC) No 1272/2008 (CLP Regulation). with the hazard statement 317, that would not pass the SUBSPORTplus screening criteria.

State of implementation

Pilot study

Date and place of implementation

not yet implemented

Availability of Alternative

Mimosa tannins are available on the market. Biolignine can be produced at pilot scale by the French CIMV company, which is currently building a production unit. A new French project was launched in 2011 for continuing the development of panelboard adhesives from lignins. The name of this project is Néolignocol.

Producer/Provider

www.fcba.fr

Type of information supplier

Research

Contact