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Resins from sustainable sources for composite materials - LK0813

The production of composite materials such as medium and high density fibre board, particle board, plywood and ceramic tiles continues to rely heavily on formaldehyde based resins such as urea-formaldehyde (UF), melamine-urea-formaldehyde (MUF) and phenol-formaldehyde resins. Though formaldehyde free materials such as diiosocyanate and tannin resins have become available, about 85 % of MDF produced today still uses formaldehyde based materials, corresponding to a European market of approximately 2 million tons of resin . Formaldehyde has been established as an irritant of both the respiratory tract and the skin, and may possibly be carcinogenic. Problems exist concerning both high formaldehyde levels in the workplace and with the slow release of formaldehyde from composite materials themselves. Though a reduction in formaldehyde content has been achieved in recent years, this has been at the cost of longer processing times, decreases in internal bond and bending strength and an increase in swelling and water absorption. There is thus a clear place in the market available for new, more environmentally friendly resins which are competitive in price, performance and adaptable to current manufacturing processes.
The resins currently produced or licenced by Advance Enterprises are styrene-acrylate co-polymer water based emulsions containing minor additives for control of hydrophilicity and viscosity according to the requirements of the particular manufacturing process. After application, the resins are thermoset (cross-linked) by application of heat and pressure.
Advance Enterprises is seeking to replace partially or completely the major feedstocks ( styrene, acrylic acid and acrylic esters) with non-petroleum based alternatives. The reasons for this are two-fold:
• To avoid the volatility in price associated with petroleum based materials, particularly styrene
• To provide a technology for export to developing countries to take advantage of indigeneous raw materials. For example, Advance Enterprises is currently in negotiation with the government of Malaysia and the Commonwealth Science Council to develop composite board and tile manufacture using palm oil (a material also high in unsaturates) and palm fibre or other types of biomass.
Rapeseed oil will be developed as a sustainable partial replacement for the acrylic acid/ester components of the current resins. Though non-food crop alternatives are known (for example, lesquerella oil, tung oil, vernonia oil), none are cultivated at the moment in the UK. Lesquerella oil and vernonia oil have iodine values close to that of rapeseed oil (ca. 100), though the polyunsaturated content is higher and the monounsaturated content is lower. The iodine value of Tung oil is slightly higher at 170.
Three main parts in the work are contemplated:

• Transformation of rapeseed oil
Rapeseed oil will be transformed synthetically as shown below ( using the triglyceride of oleic acid 1 as a structural example). Epoxidation to give 2, followed by treatment with acrylic acid yields the α-hydroxyacrylic ester 3 which may be co-polymerised with styrene using a free-radical process previously developed jointly between Keele University and Advance Enterprises with financial support from the Staffordshire and Black Country Business Innovation Centre (PRISTINE Grant for New Product Development). A key scientific challenge is development of a new, greener method for larger scale epoxidation. Though reported in the literature on a laboratory scale, the route shown using m-chloroperbenzoic acid will be problematic for commodity production because of the cost (m-chloroperbenzoic acid), side-product formation (m-chlorobenzoic acid) and separation problems. It is proposed to investigate other catalytic epoxidation routes, particularly that employing MnIII complexes where the stoichiometric oxidizing reagent is NaOCl. Additionally, selective syntheses of free fatty acid and mono- and diglyceride analogues will be performed to assess their performance relative to triglycerides. This assessment will include measurement of relative reactivity ratios in polymerisation.

The results of synthetic experiments will be monitored using
gas chromatography – mass spectrometry (GC-MS) (either Keele based or through EPSRC Central Facilities for high molecular weight compounds), infra-red spectroscopy and 1H and 13C NMR spectroscopy.

• Introduction of surfactant functionality.
The key scientific challenge here is to match the surfactant functionality required for emulsification with desired physical properties of the emulsion ( in terms of viscosity and particle size) required for mechanical application. Since long chain fatty acids form a major class of surfactants, we are hopeful that these resins may make incorporation of additional surfactant unnecessary for satisfactory emulsification. Should additional surfactant functionality be necessary, the free OH group of 3 can be used for coupling of a variety of surfactant groups esterification or etherification to fine tune the properties of the emulsion.

Again, product characterisation will be accomplished through a combination of GC-MS, infrared and NMR techniques.

• Enhancement of cross-linking
The key scientific challenge here is to maximise adhesion through cross-linking through minimal incorporation of the glyceride-based resin. Di- or monoglycerides may be used to provide further free OH content and enhance crosslinking ability. If the tris(epoxy)triglyceride 2 is ring opened with hydroxymethyl acrylic acid, the resulting resin should have about a six-fold molar content of cross-linking groups compared to the present resins, thus lowering considerably the acrylate composition of the resin. Model studies using octadecyl acrylate (stearyl acrylate) show that the long chain hydrocarbon content enhances resin performance in terms of compatibility with wood fibre without affecting the mechanical properties of fibre board produced using the resin. A key scientific objective is to study the interaction between the emulsified resin and the wood fibre after application and the structure of the matrix produced after manufacture using scanning electron microscopy and infra-red spectroscopy in the hope that better understanding may enable a more efficient design of the resin structure and composition..

• The above work involves a tripartite collaboration between Banks Cargill (supply of oil raw materials and component analysis), Keele University (synthetic chemistry and laboratory scale polymerisation) and Advance Enterprises ( small scale preparation and testing of composite materials). Since it is intended that these new resins may be introduced into existing plant facilities, considerable effort will be devoted to ensuring appropriate performance characteristics in terms of viscosity, solids content and adhesive properties.
• Resins which show promise will be produced on a pilot plant scale (10-20 tons) using Advance Enterprise facilities and tested on a full scale plant facility at Kronospan UK (particle board) and Ceramic Prints Limited (ceramic tiles).

Life Cycle Assessment studies will be performed by Boustead Consulting Limited using technical data supplied as required by the other partners. The assessment is concerned with the environmental impact of extended systems (sequences of industrial operations) which may encompass the entire life cycle of the product from raw material extraction to the different end-of-life management alternatives. Results of the assessment may also be used to identify ways to reduce costs, increase market share, improve strategic positioning or modify the constraints on operations, all with the goal of increasing company profitability. Areas identified as important to this study are current MDF/chipboard production, crop growing and processing and modified MDF/chipboard production.
Time-Scale and Cost
From: 2002

To: 2004

Cost: £177,291
Contractor / Funded Organisations
University - Keele, Ceramic Prints Limited, Cargill Industrial Oils & Lubricants, Boustead Consulting Ltd, Advance Enterprises Limited
Arable Farming              
Cereal Production              
Fields of Study
Non-Food Crops