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FAIR-CT95-0837
Novel Polyol Intermediates Derived from Biosustainable Starch for Polymer Technologies - STARPOL |
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Proposal No: | FAIR-CT95-0837 |
| Date Prepared: | July 2001, November 1999, April 1998 | |
| Source: | Final Report Executive Summary Final Report 1999 First Annual Report Summary |
Final Report Executive Summary
Source: Final Report 1999
Consortium: The project was co-ordinated by Degussa AG, Hanau (Germany) in partnership with the Institut de Recherches sur la Catalyse-CNRS, Villeurbanne (France), Decorative Research & Development Resins and Polymers ICI Paints, Slough (UK), Interchem-Hellas, Athens (Greece), ICI Polyurethanes, Everberg (Belgium) and the Polymer Group, FORTH, Heraklion (Crete, Greece).
Introduction
Environmental, economic, energy conservation and technological aspects have determined a move towards greater use of biosustainable resources by the polymer-based industries in Europe. The overall objectives of this project were to develop new polyols derived from starch -a cheap, readily available biosustainable feedstock- and to identify outlets for these polyols in the polymer industry. The most common multi-functional alcohols that are used as starting materials in the production of polyester and alkyd resins are diethylene glycol, propylene glycol, neopentyl glycol (NPG), trimethylolpropane (TMP) and pentaerythritol (PE, used only for alkyd resins). The resins produced are used in the formulation of coatings which have to be chemically and physically stable at ambient or slightly elevated temperatures so that they can be stored for reasonably long periods without loss of reactivity and without sintering or fusing together. The properties of the final product are a strong function of the type of monomers used for the synthesis of the resins.
The overall objective of this project was to generate a range of novel biosustainable polyols that could substitute for the petrochemical-based raw materials. These polyols were derived from starch a cheap, readily available feedstock. Starch sources were potato, wheat or corn. These were used as starting material for applications as alternative intermediates in the production of advanced polymers to be used by European chemical industries. Such a step would enable these industries to offer a sustainable cost-effective future range of products which can compete effectively within the global market.
A wide range of experiments and tests have been carried out and a large number of significant results were obtained throughout the project. However, this final report is aiming to focus only on the most important conclusions that emerged from the survey and highlight all the possible issues that could be the subject for further investigation in the future.
Activities
The work at the beginning of the whole chain from starch to polymers was to investigate the "Chemical modification of starch" and to "Characterise the novel polyols". These two Tasks were conducted and finished simultaneously. From the novel polyols new alkyd and polyester resins as well as polyurethane foams were manufactured. Different new paint systems were prepared.
During the first year of the project many different polyol mixtures were synthesised from starch by batch processing. The polyols generally contain some 50 compounds of which more than 30 could be identified. During the second and third year of the project the main emphasis was placed on the reaction technology of the novel polyol synthesis. The processes were switched from batch to a continuous flow application. Particular attention was paid to the second step in the process, cyclodehydration. For this a reference material (sorbitol) was selected because it is the main product in the hydrogenation step and readily commercially available. From the novel polyols new alkyd and polyester resins were manufactured. Different new paint systems based on these resins were prepared and characterised using various physical methods. During the second year of the project new polymers (polyesters, alkyd resins, latices) based on the novel polyols were synthesised, characterised and their properties were evaluated in order to select suitable polyol mixtures for industrial polymer applications. The main emphasis of the third year was placed on the reaction technology of the novel polyol synthesis, on optimising the formulation and reaction conditions of the polyester and alkyd synthesis, on the analysis and characterisation of the new polymers and on the exploitation of the novel materials.
Polyester (unsaturated and saturated) and alkyd (medium and long oil) resins that were prepared by use of those new polyols, have been characterised and compared to currently available resins, with an eye towards applications in the coating industry. In this project our aim is to examine how The extent to which the properties of the resulting resins and the coatings were affected when biosustainable polyols, were used in place of propylene glycol, TMP, NPG, and pentaerythritol, was investigated. Isosorbide and tetrol mixtures were used for the synthesis of polyester and alkyd resins.
One activity was centred on alkyd polymer synthesis and liquid decorative surface coatings evaluation. Another activity was the examination how the properties of the resins and coatings would be affected if the conventional polyols, like 1,2-propylene glycol or neopentyl glycol are partially or totally replaced by the novel polyols in polyesters. The coating films were physically and chemically characterised using the following techniques: sheer rheology, dynamic mechanical analysis and Raman spectroscopy. The novel tetrol mixture was applied in rigid and flexible polyurathane foams.
Results
New products were developed, using starch as the starting material, in the form of temperature stable novel polyols. The following series of reactions was used to obtain novel polyols from starch:
Starch was hydrolysed to produce glucose, that was then hydrogenated using a ruthenium catalysts giving sorbitol. The sorbitol was then used as substrate to produce cyclic ethers, either by direct cyclodehydration using a palladium catalyst, or from mannitol derived by isomerisation of the sorbitol using the same catalyst. Alternatively, the sorbitol was converted to other polyols using ruthenium, nickel, cobalt or copper catalysts, as appropriate. From this an upscalable two step process for converting starch or sugar to 1,4- and 2,5- anhydroaltitols, named tetrols because of their quaternary alcohol functionality, was developed. The first step involves the hydrogenation of sugar and starch to hexitols and in the second step these hexols are converted to a mixture of tetrols and diols by cyclodehydration. Tetrols and diols can be separated. This process was tested in pilot plant scale and several samples were supplied for formulation work.
These novel polyols were evaluated for use in traditional alkyd formulations and in high solids alkyd formulations. Alkyd processing time and polyol composition were optimised and viscosity profiles of alkyds were also evaluated. Polyester (unsaturated and saturated) and 'long oil' alkyd resins were synthesised by replacing propylene glycol and pentaerythritol respectively, using the novel polyols. The new products were fully characterised and compared to the commercial products.
An acceptable processing time for commercial alkyds using the novel biosustainable polyols was achieved. New alkyd resins were successfully synthesised. Evaluation of the performance of the new alkyds showed that the alkyds and gloss paints formed exhibited acceptable properties. A minor problem with the colour still exists probably due to the currently used catalyst and/or impurities in the novel polyols.
New temperature stable polyol mixtures, derived from starch, were developed. A process to transform starch into these novel polyols was outlined. The process was scaled up to a 20 l size. This size was sufficient to obtain samples for further evaluation.
Unsaturated and saturated polyesters were produced with the new polyols and their suitability in coating formation was examined. Acid index, viscosity, glass transition temperature and molecular weight values of the new resins for low levels of substitution of the polyol (NPG) were comparable to the values of the commercial products. However, higher levels of substitution resulted in resins with increased viscosity and molecular weight. Similar results were obtained for the cured coatings with respect to their mechanical properties (flow, gloss, impact, reverse impact, bending). The coatings exhibited significant ageing resistance and acceptable chemical homogeneity.
Activities relating to paint covered three areas, starch degradation, latex synthesis and alkyd synthesis and led to development of new, patented alkyd technology for the decorative surface coatings market. Other activities included rheological characterisation of modified starch solutions and coatings formulations, dynamic mechanical analysis of coatings films, feasibility of ageing tests and chemical uniformity with Raman, and chemical structure characterisation of films and formulations.
Further work investigated the extent to which isosorbide or tetrols could be a profitable and attractive alternative intermediates for the polymer industry. It was found that in the production of saturated polyester resins for powder coating systems, isosorbide can be a preferable alternative especially for hybrid systems where the weathering resistance is of minor importance. As far as the synthesis of medium and long oil alkyd resins is concerned, biosustainable tetrols offer an acceptable and attractive alternative of pentaerythritol resulting in coatings with excellent properties. For unsaturated polyester resins, with isosorbide's price being, at present, higher than propylene glycol's price, there was less reason to switch towards this novel biosustainable material. However, taking into account the nature of isosorbide as well as PG and NPG, this might not be the case in the future. As it was previously mentioned, isosorbide and tetrols are derived from starch which is a cheap and available biosustainable feedstock. Therefore, there is the possibility, if not the certainty, of significant economic advantages to be gained from the ability to be independent from petroleum-based chemicals the price of which may rise as such commodities become scarcer.
Conclusion
The new polyols can successfully replace petrochemically derived polyols. Hence, the Starpol project created a new chain from starch or sugar to various polymer applications. Within this chain a side product, isosorbide, is produced in high yields. To compete with petrochemically derived polyols it is necessary to find an outlet for this product. Therefore two steps are necessary to reach the production scale:
Interesting issue for future work can be the investigation of any possible modifications in the production of isosorbide in order to reduce its cost that will make isosorbide even more preferable in the near future. The use of alternative catalysts in the production process of isosorbide is another key issue, as the currently used catalysts proved to be the cause of the deficiency in colour of the new resins. Another interesting issue to be investigated further is the behaviour of isosorbide during polymerisation reactions. Rapid increase of molecular weight and viscosity for high levels of substitution with isosorbide might be an indication that, during the reactions, isosorbide (di-functional polyol) undergoes a structural modification giving a mixture of polyols with functionality greater than two. In this way, a number of branches are developed along the polymer chains causing the molecular weight and viscosity to increase.
INTRODUCTION
The principal objective of this project is to generate a range of novel biosustainable polyols for use as
alternative intermediates to the conventional petrochemically derived materials in the production of
advanced polymers for use by a range of European chemical industries. Starch is used as feedstock
for the production of novel polyol intermediates. The process from starch to the polyols is basically
divided into two steps. First starch has to be depolymerised. Second the depolymerised starch has
to hydrogenolysed. The depolymerisation step is carried out by enzymes. These enzymes hydrolyse
starch to an aqueous solutions that is suitable for the second process step. The solution has a low
viscosity and the compound mixture has a low mean molecular weight. The next objective is to evaluate
the polyols obtained in polyesters, alkyds, polyurethanes and acrylic/vinyl lattices for utilisation in a
range of industrial end uses.
OBJECTIVE
The principal objective of the project is to generate a range of novel polyols from starch for use as
alternative intermediates to the conventional petrochemically-derived materials in the production of
specialty polymers. A secondary aim of the project is to develop the science and technology to facilitate
a complete unified chain from the grower (EU farmer) via the processor (EU chemical industry) to the
end user (EU or worldwide consumer). A further aim is to ensure efficient use of all agricultural raw
material that lacks the quality for food consumption and which would otherwise be discarded as having
no use. The proposed work includes:
More specifically, starch will be converted by hydrogenolysis on solid catalysts into C2 C6 polyols which will be used as feedstock for the synthesis of polyesters, alkyd resins, emulsion polymers and polyurethanes used in surface coatings (decorative paints and powder coatings), polyurethane foams and polyester structural materials.
RESULTS
Corn, wheat and potato starch were investigated. The best depolymerisation results were obtained with
potato starch. Corn and wheat starch need more process steps to end up with a good hydrolysate
quality for the second step. Various hydrogenolysis experiments were run using hydrolysates from
the first step. In all cases it was possible to achieve novel polyol mixtures. The best results again were
obtained from the potato starch hydrolysates. All hydrogenolysis experiments gave polyol mixtures
numerous compounds. An analytical method was developed to determine the nature of the 30 most
abundant components, quantitatively in one run. Results from laboratory experiments showed that the
nature of the hydrgenolysis catalyst has the greatest influence on product distribution. A number of
laboratory experiments were successfully scaled up from the gram scale to give kilogram samples of
polyol mixtures. Work has started on task two, to evaluate the use of the polyols obtained in polyester
and alkyd technology, followed by a detailed analysis of the novel polymers formed. Since this Task
was started whilst Task 1 was still underway much of the early work has been carried out using polyols
from the initial activities under Task 1. However, the results indicate that they will have a significant
presence in the final polyol mixture.
Studies on alkyd technology has resulted in two model polyols. These have been characterised and both processed successfully into prototype alkyds using conventional formulating techniques. The formulation was derived from a current commercial alkyd replacing all or, in some cases, part of the petroleum derived polyol normally used. These alkyds were then evaluated in decorative paints and their performance, although not a complete direct match for the current commercial product, were close enough to indicate that the concept behind STARPOL of replacing petroleum derived polyols by biosustainable polyols does indeed have potential.
INTERCHEM, Greece, during the first year of the project focused on examining the suitability of the novel polyols delivered by task I for the production of polyesters with a composition suited to applications in the powder coatings industry. Several different chemical reactions were carried out the resins obtained were characterised in terms of their acid number, viscosity, and molecular weight. In addition, mechanical properties and the cured coatings have been evaluated. The first results were promising.
The contribution of the Cretian group FORTH, consisted of the following main tasks:
Feasibility tests have been successful in all these tasks, and the first results based on the films from modified formulations have been obtained.
FUTURE ACTIVITIES
The main future task related to the hydrogenolysis step is to find ways of influencing the polyol
distribution. The objective is to increase the selectivity towards formation of compounds most suitable
for synthesis of paint and coating components, with studies of alkyds extended to the full polyol mixture
recently produced Task 1.
CONSORTIUM
The work is co-ordinated by Degussa (Hanau Germany), in collaboration with the Decorative
Research and Development section of ICI Paints (Slough, UK); Inst. de Recherche sur la Catalyse
CNRS, (Villeurbanne France), Polymer Group FORTH. (Heraklion, Crete, Greece) and the Resins
and Polymers group of Interchem Hellas (Athens, Greece).
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Updated
by CPL Press:
03/07/2007
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